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For what is Protein A from Staphylococcus aureus used in biochemistry? | Protein A from the bacterium Staphylococcus aureus (SpA) is used as an affinity ligand for purification of immunoglobulin G (IgG). | Affinity chromatography using protein A from Staphylococcus aureus as the ligand
has been widely used for the isolation of immunoglobulin G (IgG) from various
species. Since ligand leakage from the affinity support can occur, time
consuming analytical controls are required to detect the presence of
contamits associated with the isolated IgG prior to its use for therapeutic
purpose in humans. Besides, protein A is an expensive bacterial product, whose
isolation involves complex and labor intensive procedures. Combinatorial
chemistry enables the synthesis of a wide variety of ligands within a short
period of time. Therefore, chemically defined, stable and inexpensive ligands,
which can mimic the action of protein A, have been developed to isolate
immunoglobulins. Two different types of ligands, synthesized following the
techniques of combinatorial chemistry, have been used to isolate
immunoglobulins. One of them is a synthetic peptide (TG 19318) comprising four
identical tripeptide chains linked to a central polylysine core. Immobilized TG
19318 has been used to isolate polyclonal and monoclonal antibodies of different
classes (IgG, IgM, IgA, IgE) from different sources (serum, ascities and cell
supernatants) and species. The ligand has a binding capacity that can reach upto
25mg IgG/mL of the support. It is stable when treated with sanitation agents
such as ethanol and 0.1 M sodium hydroxide. Computer-aided molecular design and
combinatorial chemistry have been used to develop an IgG binding affinity ligand
(22/8), which consists of two organic aromatic amines (3-aminophenol and
4-amino-1-napthol) linked to a scaffold of cyanuric chloride (triazine). Ligand
22/8 displayed wider specificity than protein A, as it isolated IgG from a
number of species, the order of adsorption being human> chicken > cow > rabbit >
pig > horse > rat > goat > sheep > mouse. It showed an apparent binding capacity
of 51.9 mg IgG/g moist gel and can isolate human IgG from plasma in 60% yield
with a purity of 92%. The ligand is stable, as it withstood incubation in 1M
NaOH for a week without loss of binding capacity for IgG. These findings suggest
that synthetic affinity ligands, which are inexpensive, stable and specific can
facilitate the purification of immunoglobulins in a cost-effective manner. Affinity chromatography with protein A from Staphylococcus aureus (SpA) is the
most widespread and accepted methodology for antibody capture during the
downstream process of antibody manufacturing. A triazine based ligand (ligand
22/8) was previously developed as an inexpensive and robust alternative to SpA
chromatography (Li et al. and Teng et al.). Despite the experimental success,
there is no structural information on the binding modes of ligand 22/8 to
antibodies, namely to Immunoglobulin G (IgG) molecules and fragments. In this
work, we addressed this issue by a molecular docking approach allied to
molecular dynamics simulations. Theoretical results confirmed the preference of
the synthetic ligand to bind IgG through the binding site found in the
crystallographic structure of the natural complex between SpA and the Fc
fragment of IgG. Our studies also suggested other unknown "hot-spots" for
specific binding of the affinity ligand at the hinge between V(H) and C(H)1
domains of Fab fragment. The best docking poses were further analysed by
molecular dynamics studies at three different protonation states (pH 3, 7 and
11). The main interactions between ligand 22/8 and the IgG fragments found at pH
7 were weaker at pH 3 and pH 11 and in these conditions the ligand start losing
tight contact with the binding site, corroborating the experimental evidence for
protein elution from the chromatographic adsorbents at these pH conditions. Staphylococcal Protein A (SPA), a cell wall protein of Staphylococcus aureus, is
in high demand because of its ability to bind immunoglobulins. Much of the SPA
that we use today is recombit SPA (rSPA), which is produced in Escherichia
coli. As rSPA is obtained by expressing SPA as an intracellular protein, its
purification is tedious and time consuming. In order to obtain a large amount of
highly purified rSPA with relative ease, we expressed SPA as a secretory form in
the yeast Pichia pastoris. To increase the expression level of SPA and repress
its proteolysis during fermentation, the cell density (OD600), temperature and
pH at which SPA expression was induced as well as the induction time were
optimized. The final yield of SPA obtained was about 8.8 g per liter of culture,
which under the optimized fermentation condition, accounted for 80% of the total
protein in the culture supernatant. The expressed SPA was purified from the
culture supernatant by DEAE ion-exchange chromatography (IEC) after the
supernatant was subjected to a desalting step. The purified SPA was resolved as
a single band by SDS-PAGE and as a single peak by HPLC. Its identity was
confirmed by MALDI-TOF MS and western-blot. Moreover, the protein also exhibited
excellent affinity for IgG when tested with human IgG. The production and
purification of SPA described in this study offers a new method for obtaining
high level of SPA in relatively pure form that is suitable for practical
application. Staphylococcus aureus protein A (SpA) is the most popular affinity ligand for
immunoglobulin G1 (IgG1). However, the molecular basis for the dissociation
dynamics of SpA-IgG1 complex is unclear. Herein, coarse-grained (CG) molecular
dynamics (MD) simulations with the Martini force field were used to study the
dissociation dynamics of the complex. The CG-MD simulations were first verified
by the agreement in the structural and interactional properties of SpA and human
IgG1 (hIgG1) in the association process between the CG-MD and all-atom MD at
different NaCl concentrations. Then, the CG-MD simulation studies focused on the
molecular insight into the dissociation dynamics of SpA-hIgG1 complex at pH 3.0.
It is found that there are four steps in the dissociation process of the
complex. First, there is a slight conformational adjustment of helix II in SpA.
This is followed by the phenomena that the electrostatic interactions provided
by the three hot spots (Glu143, Arg146 and Lys154) of helix II of SpA break up,
leading to the dissociation of helix II from the binding site of hIgG1.
Subsequently, breakup of the hydrophobic interactions between helix I (Phe132,
Tyr133 and His137) in SpA and hIgG1 occurs, resulting in the disengagement of
helix I from its binding site of hIgG1. Finally, the non-specific interactions
between SpA and hIgG1 decrease slowly till disappearance, leading to the
complete dissociation of the SpA-hIgG1 complex. This work has revealed that
CG-MD coupled with the Martini force field is an effective method for studying
the dissociation dynamics of protein-protein complex. Staphylococcal protein A (SpA) plays an important role in Staphylococcus aureus
pathogenesis. The recombit SpA is also widely used in biotechnology to purify
polyclonal and monoclonal immunoglobulin G antibodies. In this study, expression
and secretion of a truncated form of SpA containing five immunoglobulin-binding
domains using its own native signal sequence were optimized in Escherichia coli.
Optimization was carried out using response surface method (RSM), making use of
the interaction between five variables. The initial results revealed that the
signal peptide from S. aureus was recognized in E. coli and the resulting SpA
was expressed and secreted into the medium. Compounds, such as glycine, affected
the secretion of SpA into the culture medium. The central composite design
experiment showed that the optimum conditions for the maximum expression of
recombit truncated SpA in E. coli included 10% (w/v) lactose, 1.77% (w/v)
glycine, induction time of 11 H, an optical density (600) of 1.1, and a
temperature of 33 °C. Optimization using RSM resulted in a fivefold increase in
the secretion of SpA. To date, this is the first study of its kind regarding the
definite influence of glycine concentration and duration of the cultivation
period on the secretion of SpA. Protein A from Staphylococcus aureus plays one key role as an immobilized
affinity ligand for the purification of antibodies. A simple method for its
extracellular expression in Escherichia coli and subsequent purification is
reported herein. The N-terminus of the gene coding for the five IgG binding
domains was fused to a pelB signal peptide which is responsible for periplasmic
localization and which is removed after translocation into the periplasmic space
of E.coli. Different additives, which were added at the same time with the
induction of the protein expression by IPTG, were tested in order to facilitate
the release of the target protein. With help of this optimized release protocol,
more than 380mgL(-1) of protein A were obtained when Tris-HCl pH 8.5 was added
up to a final concentration of 180mM in shaking flask experiments. Based on
these observations, a protocol was developed for the extracellular production of
SpA in a stirred tank bioreactor yielding 5.5gL(-1) of the secreted target
protein. After cell removal by centrifugation, the protein A-containing
supernatant was concentrated and dialyzed by tangential flow filtration. The
target protein was subsequently purified by anion exchange chromatography with a
total process yield of 90% and a final purity of ⩾95% (RP HPLC) was achieved. Staphylococcal protein A (SpA) binds Fcγ and VH3 clan Fab domains of human and
animal immunoglobulin (Ig) with each of its five Ig binding domains (IgBDs),
thereby supporting Staphylococcus aureus escape from opsonophagocytic killing
and suppressing adaptive B cell responses. The variant SpAKKAA cannot bind Ig
yet retains antigenic properties that elicit SpA-neutralizing antibodies and
disease protection in mice, whereas S. aureus infection or SpA-immunization
cannot elicit neutralizing antibodies. As a test for this model, we analyzed
here mAb 358A76, which was isolated from SpA-immunized mice. Unlike
SpAKKAA-derived mAbs, mAb 358A76 binds only the first IgBD (E) but not any of
the other four IgBDs (D-A-B-C) and its binding can neutralize only the E domain
of SpA, which does not provide disease protection in mice. These results are in
agreement with a model whereby wild-type SpA-immunization generates a limited
antibody response without neutralizing and/or disease protective attributes. |
What is the suggested therapy for Mycobacterium avium infection? | The activity of TLC G-65 (a liposomal gentamicin preparation), alone and in combination with rifapentine, clarithromycin, clofazimine and ethambutol, was evaluated in the beige mouse (C57BL/6J--bgj/bgj) model of disseminated Mycobacterium avium infection. TLC G-65 in combination with rifapentine appears to be an attractive regimen for the treatment of infections caused by bacteria in the M. avium complex. Rifampin 10 mg/kg daily, ciprofloxacin 500 mg twice daily, clofazimine 100 mg every day, and ethambutol 15 mg/kg orally daily for 24 weeks, with or without amikacin 10 mg/kg intravenously or intramuscularly 5 days weekly for the first 4 weeks. In vivo phage treatment may also be used in some cases. | The activity of TLC G-65 (a liposomal gentamicin preparation), alone and in
combination with rifapentine, clarithromycin, clofazimine and ethambutol, was
evaluated in the beige mouse (C57BL/6J--bgj/bgj) model of disseminated
Mycobacterium avium infection. TLC G-65 was found to be more active than
amikacin. The combination of rifapentine and TLC G-65 was more active than
either agent alone. The activity of clarithromycin in combination with TLC G-65
was similar to that of either agent alone. Clofazimine improved the activity of
TLC G-65 with respect to the spleen, while ethambutol improved the activity with
respect to the liver. Clofazimine and ethambutol enhanced the activity of TLC
G-65 against bacteria in the lungs. TLC G-65 in combination with rifapentine
appears to be an attractive regimen for the treatment of infections caused by
bacteria in the M. avium complex. The turning point in antimicrobial therapy of Mycobacterium avium infections
came with the development of two new macrolides, clarithromycin and
azithromycin. Controlled clinical trials, the first ever conducted with any
agent among patients with M. avium infection, indicated the high efficiency of
clarithromycin, in either acquired immune deficiency syndrome (AIDS) patients
having a disseminated infection or non-AIDS patients with localized pulmonary
disease. Monotherapy with clarithromycin resulted in elimination of bacteremia
in almost all patients with disseminated infection, which is inevitably followed
by a relapse of bacteremia in patients who survived long enough to reach this
event. The strains susceptible to clarithromycin isolated before therapy
contained 10(-8) or 10(-9) resistant mutants, and the relapses of bacteremia
were caused by multiplication of these pre-existing mutants.
Clarithromycin-resistance was associated with a mutation in the 23S rRNA gene.
Cross-resistance between clarithromycin and azithromycin was confirmed with
laboratory mutants and clinical isolates. At least two methods for determining
the susceptibility of the M. avium isolates to clarithromycin are available: one
is minimum inhibitory concentration (MIC) determination on Mueller-Hinton agar
(pH 7.4) supplemented with 10% Oleic acid-albumin-dextrose catalase, the other
is MIC determination in 7H12 broth, also at pH 7.4. The breakpoints for
'susceptible' for these methods are < or = 8.0 micrograms/ml and < or = 2.0
micrograms/ml, respectively. The breakpoints for 'resistant' are > 128
micrograms/ml for the agar method and > 32.0 micrograms/ml for the broth method.
The predictability value of MIC determination was confirmed by comparing the
test results with the patients' clinical and bacteriological response to
therapy. The remaining major problem in the therapy of the M. avium infections
is a selection of companion drugs to be used in combination with clarithromycin
(or azithromycin) to prevent the emergence of the macrolide-resistance. A number
of clinical trials are now in progress to find a solution to this problem. OBJECTIVE: To determine the clinical and microbiologic benefit of adding
amikacin to a four-drug oral regimen for treatment of disseminated Mycobacterium
avium infection in HIV-infected patients.
DESIGN: A randomized, open-labeled, comparative trial.
SETTING: Outpatient clinics.
PATIENTS: Seventy-four patients with HIV and symptomatic bacteremic M. avium
infection.
INTERVENTIONS: Rifampin 10 mg/kg daily, ciprofloxacin 500 mg twice daily,
clofazimine 100 mg every day, and ethambutol 15 mg/kg orally daily for 24 weeks,
with or without amikacin 10 mg/kg intravenously or intramuscularly 5 days weekly
for the first 4 weeks.
MAIN OUTCOME MEASURE: Clinical and microbiologic response at 4 weeks;
quantitative level of bacteremia with M. avium.
RESULTS: No difference in clinical response was noted with the addition of
amikacin to the four-drug oral regimen, and only 25% in either group had a
complete or partial response at 4 weeks. A comparable quantitative decrease in
bacteremia was noted in both treatment groups, with 16% of patients being
culture-negative at 4 weeks and 38% at 12 weeks. Toxicities were mainly
gastrointestinal. Amikacin was well tolerated. Median survival was 30 weeks in
both groups.
CONCLUSIONS: The addition of amikacin to a four-drug oral regimen of rifampin,
ciprofloxacin, clofazimine, and ethambutol did not provide clinical or
microbiologic benefit. Two hundred and forty-six patients infected with human immunodeficiency virus
(HIV) who also had disseminated Mycobacterium avium complex received either
azithromycin 250 mg every day, azithromycin 600 mg every day, or clarithromycin
500 mg twice a day, each combined with ethambutol, for 24 weeks. Samples drawn
from patients were cultured and clinically assessed every 3 weeks up to week 12,
then monthly thereafter through week 24 of double-blind therapy and every 3
months while on open-label therapy through the conclusion of the trial. The
azithromycin 250 mg arm of the study was dropped after an interim analysis
showed a lower rate of clearance of bacteremia. At 24 weeks of therapy, the
likelihood of patients' developing 2 consecutive negative cultures (46% vs. 56%,
P=.24) or 1 negative culture (59% vs. 61%, P=.80) was similar for azithromycin
600 mg (n=68) and clarithromycin (n=57), respectively. The likelihood of relapse
was 39% versus 27% (P=.21) on azithromycin compared with clarithromycin,
respectively. Of the 6 patients who experienced relapse, none of those
randomized to receive azithromycin developed isolates resistant to macrolides,
compared with 2 of 3 patients randomized to receive clarithromycin [corrected].
Mortality was similar in patients comprising each arm of the study (69% vs. 63%;
hazard, 95.1% confidence interval, 1.1 [0.7, 1.7]). Azithromycin 600 mg, when
given in combination with ethambutol, is an effective agent for the treatment of
disseminated M. avium disease in patients infected with HIV. The emergence of mycobacteria resistant to currently available antimicrobial
agents has become an important problem in modern medicine. Mycobacterium avium
and M. tuberculosis are intracellular pathogens that replicate and survive
within the mononuclear phagocytes. TM4 is a lytic mycobacteriophage that kills
both extracellular M. avium and M. tuberculosis. When delivered by M. smegmatis
transiently infected with TM4, it kills both M. avium and M. tuberculosis within
RAW 264.7 macrophages. To evaluate the treatment of M. avium infection with
phage in vivo, C57 BL/6 mice were infected with M. avium 109 and, 7 days later,
treated either once or twice with TM4 phage (7.9 x 10(10) PFU/ml), M. smegmatis
(4 x 10(8) cFU/ml), or M. smegmatis with TM4 phage delivered intravenously
(i.v.). Treatment with TM4 phage alone or M. smegmatis without TM4 did not show
a significant decrease in number of intracellular bacteria in the spleen
compared with untreated control. In contrast, administration of M. smegmatis-TM4
resulted in a significant decrease in the number of M. avium in the spleen.
However, 23% of bacteria recovered from treated mice were resistant to TM4.
These in vivo studies confirmed the in vitro findings that an avirulent
mycobacterium can be used as a carrier to deliver antimycobacterial phage
intracellularly. The most common presentations of nontuberculous mycobacterial infections in
kidney transplant recipients (KTR) are cutaneous and disseminated diseases.
Pleuropulmonary infection not associated with disseminated disease is rare. Its
diagnosis can be difficult, requiring a combination of clinical, radiological,
and bacteriological criteria. We report on a Mycobacterium avium complex
pulmonary infection in a KTR with underlying chronic obstructive pulmonary
disease. Chest computed tomography showed an excavated lesion of the right upper
lobe, similar to a typical lesion of pulmonary tuberculosis. Evolution was
favorable with multiple-drug therapy including rifampicin, ethambutol, and
clarithromycin, along with a slight reduction in immunosuppression. We review
the literature and discuss the epidemiology, diagnosis, management, and
follow-up of this uncommon post-transplant complication. |
What is the treatment of acute pericarditis? | A multidisciplinary approach is frequently necessary to treat acute pericarditis; the most frequent treatments are: antiinflammatory steroid and non-steroid drugs, antibiotic therapy, pericardial drainage and, less frequently ,intrapericardial irrigation of fibrinolytics; antituberculous chemotherapy in presence of Tuberculous Agent | Acute purulent pericarditis was treated successfully in five children between
the ages of 27 months and 11 1/2 years during the past 5 years. The responsible
organism was Hemophilus influenzae, type b, in two cases and Meningococcus,
Pneumococcus, and coagulase-positive Staphylococcus aureus in one case each. No
primary source of infection could be identified in two patients. A high index of
suspicion, combined with immediate echocardiograms and pericardiocentesis, led
to the diagnosis. Immediate antibiotic therapy was instituted on the basis of
the gram stain of the pericardial fluid. All five patients had a pericardial
window established--four through subxyphoid approach and the fifth, because of a
left pleural effusion, through a left thoracotomy. When the subxyphoid approach
was used, sump drains were left for postoperative suction and irrigation. All
five patients survived without sequalae during follow-up periods of from 18
months to 5 years. We advocate an aggressive approach to the diagnosis and
treatment of this problem. This report documents the safety, ease, and
effectiveness of the subxyphoid approach as a means of drainage. A 9-year-old boy with systemic onset juvenile rheumatoid arthritis (JRA)
presented with fever and chest pain and rapidly developed pericarditis and
cardiac tamponade. Despite corticosteroid treatment and pericardiocentesis,
rapid deterioration necessitated the emergency placement of a pericardial
window. This is the first reported instance of this type of emergency surgical
intervention for JRA. Of 220 children with JRA followed for 12 years (7%
systemic onset), 8 had evidence of acute pericarditis but no other had definite
evidence of tamponade. Two cases of Haemophilus influenzae type B pericarditis are presented which
demonstrate the major clinical features and sequelae of this serious illness.
These cases are analyzed together with 77 others from the literature to
characterize the clinical features, natural history, and optimal therapy. H.
influenzae pericarditis is an increasingly frequent disease of young children. A
mild prodromal illness is often followed by rapid progression of cardiac
compromise until death ensues, unless pericarditis is diagnosed and treated
appropriately. The development of cardiomegaly in a febrile patient with a
Haemophilus infection is an indication for echocardiography, which is diagnostic
of the pericardial effusion. Initial cultures of pericardial aspirates will be
positive in 75% of cases even when antibiotic therapy has been initiated. Use of
appropriate parenterally administered antibiotics, in combination with early
surgical pericardial drainage or partial pericardiectomy, should minimize
morbidity and mortality and prevent acute constrictive sequelae. Acute purulent pericarditis is a well-recognized, though infrequently seen,
manifestation of systemic Haemophilus influenzae type b disease. We recently
studied two pediatric patients who developed signs of this septic complication
during appropriate antibiotic treatment for bacteremia. These case reports
should alert physicians to the possibility that pericarditis may become
clinically evident in patients with systemic H. influenzae infections many days
after initiation of appropriate therapy. The pathophysiology, diagnostic
modalities and therapy are briefly reviewed. Acute febrile juvenile rheumatoid arthritis (JRA) of adult onset is often
diagnosed by ruling out other problems. The classification of JRA is primarily
based on the distinct type of onset, of which there are usually three: (1) acute
febrile or Still's type, (2) polyarticular, and (3) monoarticular pauciarticular
arthritis. Fever of unknown cause is frequently the initial symptom. This type
of arthritis may be characterized by any or all of the following: unexplained
high fever, rash, weight loss, lymphadenopathy, splenomegaly, pericarditis,
pleurisy, pneumonitis, abdominal pain, myalgias, arthralgias, arthritis, sore
throat, leukocytosis, anemia, circulating immune complexes, liver test
abnormalities, and carpal-metacarpal and tarsal-metatarsal fusion. Patients
often respond dramatically to anti-inflammatory agents. Corticosteroids, gold
salts, penicillamine, and cytotoxic drugs have been effective for certain
patients. The prognosis of the disease has been generally favorable. Although
symptoms may recur, remission can be prolonged. Constrictive pericarditis is a complication of tuberculous pericarditis that
necessitates surgical intervention. In this study, we sought to identify
echocardiographic features that could predict the development of constrictive
pericarditis from acute or subacute pericarditis. From January 1988 through May
1998, all patients with a discharge diagnosis of tuberculous pericarditis were
enrolled in the study, and their clinical features, laboratory findings,
sonographic images, treatments, and outcomes were analyzed. Tuberculous
pericarditis was demonstrated on the basis of positive Mycobacterium
tuberculosis cultures from pericardial fluid or tissue in 11 patients;
pericardial biopsy specimens demonstrating caseating granulomas in seven; and
bacteriologic or histologic evidence of active extra-pericardial tuberculosis in
conjunction with major pericardial effusion in four. Seventeen patients had
effusive tuberculous pericarditis and five had constrictive tuberculous
pericarditis as the initial diagnosis. The echocardiographic findings of
effusive pericarditis were classified as shaggy-type effusion (n = 8) and
non-shaggy-type effusion (9). Shaggy effusion was defined as the presence of
multiple fibrin strands or a mass-like exudate coating the pericardium and
bridging the pericardial effusion. Non-shaggy effusion was characterized by an
anechoic pericardial space with or without a thickened pericardium, but no
shaggy exudative coating. The mean duration between the onset of symptoms and
diagnosis was longer in patients with shaggy-type effusion (39.6 +/- 8.7 vs 21.0
+/- 13.9 days, p < 0.05). Prednisolone (20-30 mg/d) was used in addition to
antituberculous chemotherapy in 11 of the 17 patients with effusive
pericarditis. Two of 11 patients (18%) who received steroid therapy, and five of
the six patients (83%) who did not, developed constrictive pericarditis in the
following year. Therefore, we concluded that adjuvant therapy with steroids
significantly decreased the risk of constrictive pericarditis in patients with
non-shaggy, but not shaggy, effusion. Glucose 6-phosphate dehydrogenase deficiency is an important cause of hemolysis.
People with this disease are prone to hemolytic crisis induced by drugs,
including acetylsalicylic acid. Sodium salicylate is the main therapeutic choice
for acute idiopathic pericarditis. In vitro studies have demonstrated the role
played by sodium salicylate in the inhibition of glucose 6-phosphate
dehydrogenase, but, at therapeutic doses, this inhibition is not enough to
explain acetylsalicylic acid-induced hemolysis observed in vivo. We thus treated
a patient affected by acute idiopathic pericarditis and glucose 6-phosphate
dehydrogenase deficiency with sodium salicylate, obtaining complete resolution
of fever and symptoms, without any hemolytic complication. Therapy with sodium
salicylate could thus be a safe and effective alternative for patients with
glucose 6-phosphate dehydrogenase who require anti-inflammatory therapy. A 39-year-old man was admitted for upper abdominal pain and shortness of breath.
The chest roentgenogram demonstrated cardiomegaly and left lower lobe
atelectasis. Echocardiography showed circumferential pericardial effusion with
signs of cardiac tamponade. Pericardial biopsy and fluid analysis were
consistent with fibrino-purulent pericarditis. Despite broad-spectrum
antibiotics, percutaneous and subsequently surgical drainage, pericardial
effusion and tamponade recurred. We report successful treatment of a
non-resolving fibrino-purulent pericardial effusion by combined intrapericardial
irrigation of fibrinolytics and systemic corticosteroids administration as an
alternative to pericardectomy. Purulent pericarditis is rarely the primary site of bacterial infection. It is
usually a complication of an infection originating elsewhere in the body,
arising by contiguous spread or haematogenous dissemination.This paper, however,
describes a previously healthy young man, who developed a purulent streptococcal
pericarditis with no localizable primary focus. Although many possibilities were
investigated, the entry site of the pericarditis remains unknown. The incidence
of purulent pericarditis has decreased considerably since the antibiotic era. It
is typically an acute and potentially lethal disease, necessitating rapid
diagnosis and adequate therapy to improve prognosis. Standard treatment combines
appropriate antibiotic therapy with surgical drainage. However, the exact timing
and type of surgery is still under discussion. Our patient was treated with
antibiotics, subxiphoidal tube drainage of the pericardial fluid and
intrapericardial thrombolysis. After three weeks, he developed tamponade,
requiring partial pericardiectomy. He recovered completely and resumed his
normal activities after a two-month hospitalisation. Recurrent pericarditis is a rare disease in childhood. Nevertheless, it may
represent a challenge to the clinician due to its resistance to
anti-inflammatory treatment. The initial etiology often remains unclear;
specific laboratory parameters predicting the frequency or severity of the
recurrences are lacking. We report on four patients with recurrent pericarditis
in whom antimyolemmal antibodies (AMLAs) were detected. A prolonged persistence
of IgM-type AMLAs was found in three patients: two of them presented with acute
inflammation as the initial event and one with 48 recurrences during 5.5 years.
The fourth patient showed a fast conversion from IgM to IgG-type AMLAs after a
less acute initial presentation and showed 4 mild recurrences during the
48-month follow-up.
CONCLUSION: We were able to detect AMLAs in four children with recurrent
pericarditis. This finding may be attributed to an auto-immunological disease
following a first, acute event. We propose the detection of AMLAs in all
children with unexplained recurrent pericarditis. Pediatric patients with a
persistence of IgM-type AMLAs may face frequent recurrences and should be
monitored therefore more closely. In addition, medical treatment may be changed
in these patients with a slower tapering of the dosage of steroidal and
non-steroidal antiinflammatory drugs. We describe a case of a 56 year old man with myopericarditis complicated with
cardiogenic shock within first 3 days, mimicking on admission acute myocardial
infarction with ST elevation in inferior ECG leads. Additionally, patient
presented hyperthyroidism and totally decompensated diabetes mellitus. He
required during the first 3 days intravenous infusion of inotropic agents.
Cardiac enzymes levels were elevated. Akinesia in mid-inferior and mid-posterior
regions in ECHO was observed. On the 10th day ST segment elevation in I, II,
V3-V6 and ST depression in aVR was observed in ECG. After stabilisation patient
underwent coronarography which showed normal coronary arteries. The final
diagnosis was acute myopericarditis complicated with acute heart failure and
cardiogenic shock. Recurrences develop in up to 20-50% of patients with acute pericarditis.
Although different causes of recurrent pericarditis have been identified, the
etiology remains obscure in most cases which are therefore labelled as
idiopathic. Autoinflammatory syndromes include familial Mediterranean fever
(FMF), due to mutations in the MEFV gene, and tumor necrosis factor
receptor-associated periodic syndrome (TRAPS), due to mutations in the TNFRSF1A
gene. Recurrent pericarditis is a common feature of both conditions, but it
rarely occurs alone. Colchicine is the standard treatment for FMF, while
patients with TRAPS do not respond to colchicine therapy, but are responsive to
corticosteroids. Based on the proven efficacy of colchicine in preventing
polyserositis in FMF, colchicine has been proposed for the treatment of
recurrent pericarditis and is able to decrease the recurrence rate. Our aim was
to investigate the possible involvement of TNFRSF1A mutations in a group of
patients with idiopathic recurrent pericarditis who were refractory to
colchicine treatment. Thirty consecutive patients (17 males, 13 females)
diagnosed with idiopathic recurrent pericarditis, who were characterized by a
poor response to colchicine treatment, were enrolled in the study. Mutations of
the TNFRSF1A gene were searched for by amplifying, using polymerase chain
reaction (PCR), genomic DNA, and direct sequencing. TNFRSF1A mutations were
found in 4 of the 30 patients. None of these 4 patients had a family history of
recurrent inflammatory syndromes or history of pericarditis. One of the 4
patients had a novel heterozygous deletion (DeltaY103-R104) and three patients
carried a heterozygous low-penetrance R92Q mutation. Our data suggest that TRAPS
should be kept in mind in the differential diagnosis of recurrent pericarditis,
and mutation analysis of the TNFRSF1A gene should be considered, in addition to
MEFV analysis, in patients of Mediterranean origin. A poor response to
colchicine treatment and/or a steroid-dependence may be the clue to investigate
TNFRSF1A mutations in patients with idiopathic recurrent pericarditis. |
What is the genetic basis of tuberous sclerosis? | The genetic basis of tuberous sclerosis has been attributed to mutations in one of two unlinked genes, TSC1 and TSC2. The functions of the TSC1 and TSC2 gene products, hamartin and tuberin, respectively, have remained ill defined until recently. Genetic, biochemical, and biologic analyses have highlighted their role as negative regulators of the mTOR signaling pathway. Tuberin, serving as a substrate of AKT and AMPK, mediates mTOR activity by coordinating inputs from growth factors and energy availability in the control of cell growth, proliferation, and survival. Emerging evidence also suggests that the TSC 1/2 complex may play a role in modulating the activity of beta-catenin and TGFbeta. These findings provide novel functional links between the TSC genes and other tumor suppressors. | We have recently identified on rat chromosome 10q a germline mutation in the
tuberous sclerosis gene (Tsc2), the gene predisposing to renal carcinoma (RC) in
the Eker rat. The homozygous mutant condition is lethal at around the 13th day
of fetal life. In heterozygotes, RCs invariably develop in the first year of
life. Histologically, RCs develop through multiple stages from early
preneoplastic lesions (i.e., phenotypically altered tubules) to adenomas. The
wild-type allele mutation has been found even in the earliest preneoplastic
lesions, fitting Knudson's two-hit hypothesis and supporting the hypothesis that
Tsc2 is a tumor suppressor gene. In this study, homozygous deletion of the Ink4
homologue on rat chromosome 5q was observed in 14 of 24 (58%) RC-derived cell
lines. This may represent involvement of a second tumor suppressor gene,
contributing to tumor progression. Considering previous results of studies of
homozygous deletion of the Ifn alpha gene in five of 24 cases (21%) and the Ifn
beta gene in one of 24 cases (4%), the order of the genes may be Ink4-Ifn
alpha-Ifn beta. Microsatellite instability was not observed in 26 Eker rat
tumors. Tuberous sclerosis is a relatively common inherited disease that causes multiple
benign tumours in different organs, frequently leading to skin rashes, seizures
and mental handicap. The disease can be caused by mutations in either of two
genes, TSC2, identified in 1993, and TSC1, only recently identified. Here we
review the current state of knowledge of the molecular genetics of tuberous
sclerosis and the spectrum of mutations seen in and the implications of recent
findings for patients. Although both genes appear to function as tumour
suppressors, the function of their protein products is not understood. A
speculative model of how these proteins might function is briefly described. Lymphangioleiomyomatosis (LAM) is a progressive and often fatal interstitial
lung disease characterized by a diffuse proliferation of abnormal smooth muscle
cells in the lungs. LAM is of unusual interest biologically because it affects
almost exclusively young women. LAM can occur as an isolated disorder (sporadic
LAM) or in association with tuberous sclerosis complex. Renal angiomyolipomas,
which are found in most tuberous sclerosis patients, also occur in 60% of
sporadic LAM patients. We previously found TSC2 loss of heterozygosity in 7 of
13 (54%) of angiomyolipomas from sporadic LAM patients, suggesting that LAM and
TSC could have a common genetic basis. In this study, we report the
identification of somatic TSC2 mutations in five of seven angiomyolipomas from
sporadic LAM patients. In all four patients from whom lung tissue was available,
the same mutation found in the angiomyolipoma was present in the abnormal
pulmonary smooth muscle cells. In no case was the mutation present in normal
kidney, morphologically normal lung, or lymphoblastoid cells. Our data
demonstrate that somatic mutations in the TSC2 gene occur in the angiomyolipomas
and pulmonary LAM cells of women with sporadic LAM, strongly supporting a direct
role of TSC2 in the pathogenesis of this disease. CONTEXT: Lymphangioleiomyomatosis (LAM) is a cystic lung disease that can be
included in the wide group of proliferative lesions named PEComas (perivascular
epithelioid cell tumors). These proliferative tumors are characterized by the
coexpression of myogenic and melanogenesis-related markers. In all these
lesions, genetic alterations related to the tuberous sclerosis complex (TSC)
have been demonstrated. Striking improvements in the understanding of the
genetic basis of this autosomal domit genetic disease are coupled to the
understanding of the mechanisms that link the loss of TSC1 (9q34) or TSC2
(16p13.3) genes with the regulation of the Rheb/m-TOR/p70S6K pathway. These data
have opened a new era in the comprehension of the pathogenesis of LAM and have
also suggested new therapeutic strategies for this potentially lethal disease.
OBJECTIVE: To present and discuss the pathologic and molecular features of LAM
within the spectrum of PEComas, providing a rational approach to their
diagnosis.
DATA SOURCES: The published literature and personal experience.
CONCLUSIONS: The inclusion of LAM within the PEComa category is supported by a
variety of biologic data and can significantly help in providing a comprehensive
view of this interesting and clinically relevant group of lesions. The
demonstration of molecular alterations of the mTOR pathway in LAM and other
PEComas represents a rational basis for innovative therapeutic approaches with
inhibitors of mTOR signaling. |
What is the molecular function of the Chd1 protein? | The ATP-dependent chromatin-remodelling enzyme Chd1 is a 168-kDa protein consisting of a double chromodomain, Snf2-related ATPase domain, and a C-terminal DNA-binding domain. One of the two chromodomains of Chd1 specifically interacts with the methylated lysine 4 mark on histone H3 that is associated with transcriptional activity. Human CHD1 is an ATP-dependent chromatin remodeling protein, as a factor that directly and selectively recognizes histone H3 methylated on lysine 4. | The specific post-translational modifications to histones influence many nuclear
processes including gene regulation, DNA repair and replication. Recent studies
have identified effector proteins that recognize patterns of histone
modification and transduce their function in downstream processes. For example,
histone acetyltransferases (HATs) have been shown to participate in many
essential cellular processes, particularly those associated with activation of
transcription. Yeast SAGA (Spt-Ada-Gcn5 acetyltransferase) and SLIK (SAGA-like)
are two highly homologous and conserved multi-subunit HAT complexes, which
preferentially acetylate histones H3 and H2B and deubiquitinate histone H2B.
Here we identify the chromatin remodelling protein Chd1
(chromo-ATPase/helicase-DNA binding domain 1) as a component of SAGA and SLIK.
Our findings indicate that one of the two chromodomains of Chd1 specifically
interacts with the methylated lysine 4 mark on histone H3 that is associated
with transcriptional activity. Furthermore, the SLIK complex shows enhanced
acetylation of a methylated substrate and this activity is dependent upon a
functional methyl-binding chromodomain, both in vitro and in vivo. Our study
identifies the first chromodomain that recognizes methylated histone H3 (Lys 4)
and possibly identifies a larger subfamily of chromodomain proteins with similar
recognition properties. Defining the protein factors that directly recognize post-translational,
covalent histone modifications is essential toward understanding the impact of
these chromatin "marks" on gene regulation. In the current study, we identify
human CHD1, an ATP-dependent chromatin remodeling protein, as a factor that
directly and selectively recognizes histone H3 methylated on lysine 4. In vitro
binding studies identified that CHD1 recognizes di- and trimethyl H3K4 with a
dissociation constant (Kd) of approximately 5 microm, whereas monomethyl H3K4
binds CHD1 with a 3-fold lower affinity. Surprisingly, human CHD1 binds to
methylated H3K4 in a manner that requires both of its tandem chromodomains. In
vitro analyses demonstrate that unlike human CHD1, yeast Chd1 does not bind
methylated H3K4. Our findings indicate that yeast and human CHD1 have diverged
in their ability to discriminate covalently modified histones and link histone
modification-recognition and non-covalent chromatin remodeling activities within
a single human protein. Nucleosome remodelling complexes play a key role in gene activation in response
to environmental changes by driving promoter chromatin to reach an accessible
configuration. They also mediate genome-wide chromatin organization, although
their role in processes other than activation-related chromatin remodelling are
poorly understood. The Saccharomyces cerevisiae ADH2 gene represents an
excellent model for understanding the role of chromatin structure and
remodelling in gene regulation. Following glucose depletion, highly positioned
promoter nucleosomes are destabilized leading to strictly regulated kinetics of
transcriptional activation. Nevertheless, no chromatin remodelling activities
responsible for establishing or remodelling ADH2 chromatin structure have been
identified to date. Here we show that the absence of the Isw1 and Chd1
ATP-dependent chromatin remodelling activities delays the maximal expression of
ADH2 without impairing the chromatin remodelling that occurs upon activation.
Instead, a destabilized chromatin structure on the ADH2 coding and termination
region is observed in the absence of Isw1 or Chd1 in repressing conditions. The
specific Isw1 complex involved in this nucleosome repositioning is Isw1b because
the deletion of Ioc2 and Ioc4, but not of Ioc3, causes the same phenotype as the
deletion of Isw1. Moreover, the lack of Chd1 combined with the absence of Isw1
and Isw2 impairs nucleosome spacing along the ADH2 gene, and genome-wide in S.
cerevisiae. Thus, the ISWI and Chd1 remodelling factors are not only involved in
transcription-related chromatin remodelling, but also are required to maintain a
specific chromatin configuration across the yeast genome. ISWI proteins form the catalytic core of a subset of ATP-dependent chromatin
remodeling activities in eukaryotes from yeast to man. Many of these complexes
have been found to reposition nucleosomes but with different directionalities.
We find that the yeast Isw1a, Isw2, and Chd1 enzymes preferentially move
nucleosomes toward more central locations on short DNA fragments whereas Isw1b
does not. Importantly, the inherent positioning properties of the DNA play an
important role in determining where nucleosomes are relocated to by all of these
enzymes. However, a key difference is that the Isw1a, Isw2, and Chd1 enzymes are
unable to move nucleosomes to positions closer than 15 bp from a DNA end,
whereas Isw1b can. We also find that there is a correlation between the
inability of enzymes to move nucleosomes close to DNA ends and the preferential
binding to nucleosomes bearing linker DNA. These observations suggest that the
accessibility of linker DNA together with the positioning properties of the
underlying DNA play important roles in determining the outcome of remodeling by
these enzymes. Chromodomain from heterochromatin protein 1 and polycomb protein is known to be
a lysine-methylated histone H3 tail-binding module. Chromo-helicase/ATPase
DNA-binding protein 1 (CHD1) is an ATP-dependent chromatin remodeling factor,
containing two tandem chromodomains. In human CHD1, both chromodomains are
essential for specific binding to a K4 methylated histone H3 (H3 MeK4) peptide
and are found to bind cooperatively in the crystal structure. For the budding
yeast homologue, Chd1, the second but not the first chromodomain was once
reported to bind to an H3 MeK4 peptide. Here, we reveal that neither the second
chromodomain nor a region containing tandem chromodomains from yeast Chd1 bind
to any lysine-methylated or arginine-methylated histone peptides that we
examined. In addition, we examined the structures of the chromodomains from Chd1
by NMR. Although the tertiary structure of the region containing tandem
chromodomains could not be obtained, the secondary structure deduced from NMR is
well conserved in the tertiary structures of the corresponding first and second
chromodomains determined individually by NMR. Both chromodomains of Chd1
demonstrate a structure similar to that of the corresponding part of CHD1,
consisting of a three-stranded beta-sheet followed by a C-terminal alpha-helix.
However, an additional helix between the first and second beta-strands, which is
found in both of the first chromodomains of Chd1 and CHD1, is positioned in an
entirely different manner in Chd1 and CHD1. In human CHD1 this helix forms the
peptide-binding site. The amino acid sequences of the chromodomains could be
well aligned on the basis of these structures. The alignment showed that yeast
Chd1 lacks several key functional residues, which are responsible for specific
binding to a methylated lysine residue in other chromodomains. Chd1 is likely to
have no binding affinity for any H3 MeK peptide, as found in other chromodomain
proteins. Spt4-Spt5, a general transcription elongation factor for RNA polymerase II, also
has roles in chromatin regulation. However, the relationships between these
functions are not clear. Previously, we isolated suppressors of a Saccharomyces
cerevisiae spt5 mutation in genes encoding members of the Paf1 complex, which
regulates several cotranscriptional histone modifications, and Chd1, a chromatin
remodeling enzyme. Here, we show that this suppression of spt5 can result from
loss of histone H3 lysines 4 or 36 methylation, or reduced recruitment of Chd1
or the Rpd3S complex. These spt5 suppressors also rescue the synthetic growth
defects observed in spt5 mutants that also lack elongation factor TFIIS. Using a
FLO8 reporter gene, we found that a chd1 mutation caused cryptic initiation of
transcription. We further observed enhancement of cryptic initiation in chd1
isw1 mutants and increased histone acetylation in a chd1 mutant. We suggest
that, as previously proposed for H3 lysine 36 methylation and the Rpd3S complex,
H3 lysine 4 methylation and Chd1 function to maintain normal chromatin
structures over transcribed genes, and that one function of Spt4-Spt5 is to help
RNA polymerase II overcome the repressive effects of these histone modifications
and chromatin regulators on transcription. The molecular motor protein CHD1 has been implicated in the regulation of
transcription and in the transcription-independent genome-wide incorporation of
H3.3 into paternal chromatin in Drosophila melanogaster. A key feature of CHD1
is the presence of two chromodomains, which can bind to histone H3 methylated at
lysine 4 and thus might serve to recruit and/or maintain CHD1 at the chromatin.
Here, we describe genetic and biochemical approaches to the study of the
Drosophila CHD1 chromodomains. We found that overall localization of CHD1 on
polytene chromosomes does not appreciably change in chromodomain-mutant flies.
In contrast, the chromodomains are important for transcription-independent
activities of CHD1 during early embryonic development as well as for
transcriptional regulation of several heat shock genes. However, neither CHD1
nor its chromodomains are needed for RNA polymerase II localization and H3K4
methylation but loss of CHD1 decreases transcription-induced histone eviction at
the Hsp70 gene in vivo. Chromodomain mutations negatively affect the chromatin
assembly activities of CHD1 in vitro, and they appear to be involved in linking
the ATP-dependent motor to the chromatin assembly function of CHD1. CHD1 is a conserved chromatin remodeling factor that localizes to active genes
and functions in nucleosome assembly and positioning as well as histone
turnover. Mouse CHD1 is required for the maintece of stem cell pluripotency
while human CHD1 may function as a tumor suppressor. To investigate the action
of CHD1 on higher order chromatin structure in differentiated cells, we examined
the consequences of loss of CHD1 and over-expression of CHD1 on polytene
chromosomes from salivary glands of third instar Drosophila melanogaster larvae.
We observed that chromosome structure is sensitive to the amount of this
remodeler. Loss of CHD1 resulted in alterations of chromosome structure and an
increase in the heterochromatin protein HP1a, while over-expression of CHD1
disrupted higher order chromatin structure and caused a decrease in levels of
HP1a. Over-expression of an ATPase inactive form of CHD1 did not result in
severe chromosomal defects, suggesting that the ATPase activity is required for
this in vivo phenotype. Interestingly, changes in CHD1 protein levels did not
correlate with changes in the levels of the euchromatin mark H3K4me3 or
elongating RNA Polymerase II. Thus, while CHD1 is localized to transcriptionally
active regions of the genome, it can function to alter the levels of HP1a,
perhaps through changes in methylation of H3K9. |
Which drugs are included in the FEC-75 regimen? | Fluorouracil, epirubicin, and cyclophosphamide are included in the FEC-75 regimen. This chemotherapy regiment is used for breast cancer treatment. | The French Epirubicin Study Group carried out a randomized trial comparing
epirubicin alone 75 mg/m2 with fluorouracil (5FU) 500 mg/m2, cyclophosphamide
500 mg/m2, and epirubicin 50 mg/m2 (FEC 50) and 5FU 500 mg/m2, cyclophosphamide
500 mg/m2, and epirubicin 75 mg/m2 (FEC 75) as first treatment for advanced
breast cancer patients. Patients were stratified according to whether or not
there were bone metastases only. Four hundred twelve patients entered this
trial; 378 were assessable for tolerability and 365 for efficacy. The overall
response rates were comparable between FEC 50 (44.6%) and FEC 75 (44.7%), but
both were better than the epirubicin alone (30.6%) (P = .04 and P = .0006,
respectively). The complete response rate was better in FEC 75 (15.5%) than in
FEC 50 (7%) (P = .025) or epirubicin (4%) (P = .002). Similar results were
obtained in the group of patients without bone-only metastases. No difference in
the three treatments was observed in the patients with bone metastases only.
Mean durations of response were similar in the three groups, being 412 days, 440
days, and 350 days for FEC 50, FEC 75, and epirubicin, respectively. Patients
without previous adjuvant chemotherapy fared better than those with previous
treatment (without anthracyclines). Tolerability was fair in the three groups.
Overall, the epirubicin-alone group showed better tolerance than the two other
groups, which did not differ significantly. Time to progression and survival
were not different among the three groups, but more early relapses occurred in
the epirubicin and FEC 50 groups; survival seemed to be better during the first
8 months in the FEC 75 group, and the survival difference between the epirubicin
group and the FEC 75 group was of borderline significance. No difference in
survival was observed between epirubicin- and FEC 50-group patients, even though
the response rate was significantly worse in the monochemotherapy group. Anthracyclines are among the most active drugs for the treatment of advanced
breast cancer. Epirubicin has been found to be as effective as doxorubicin at
equimolar doses but significantly better tolerated, especially in terms of
alopecia, leucopenia, and cardiac toxicity. The role of anthracycline-containing
regimens in adjuvant treatment of breast cancer has been studied by only a few
clinical trial teams. In 1986, the French Adjuvant Study Group (FASG) began a
randomised trial aimed to investigate the concept of dose intensity as well as
the optimal duration of treatment in patients with early breast cancer. Between
1986 and 1990, 621 patients were included in the trial, of whom 595 were
evaluable. Patients were randomised to 1 of 3 treatment groups: Group A (n =
207) received FEC 50 (fluorouracil 500 mg/m2, epirubicin 50 mg/m2 plus
cyclophosphamide 500 mg/m2) every 21 days for 6 cycles; Group B (n = 193)
received FEC 50 every 21 days for 3 cycles; Group C (n = 195) received FEC 75
(fluorouracil 500 mg/m2, epirubicin 75 mg/m2 plus cyclophosphamide 500 mg/m2)
every 21 days for 3 cycles. Locoregional radiotherapy was administered after the
third cycle of chemotherapy in all treatment arms. Clinical prognostic factors
were similar between treatment groups. Approximately 62% of all patients had 1
to 3 positive lymph nodes; 50% of patients were hormone receptor positive and
73% were Scarff-Bloom Richardson (SBR) grade 2 to 3. Toxicity was evaluated in
595 patients (207, 193 and 195 patients in Groups A, B and C, respectively), who
received a total of 2301 chemotherapy cycles.(ABSTRACT TRUNCATED AT 250 WORDS) While the use of 5-HT3 receptor antagonists is clearly justified in patients
receiving cisplatin, their role with less emetic drugs is still not defined. The
aim of our randomized study was to verify the efficacy of the single standard
dose of three 5-HT3-receptor-antagonists in moderately emetic chemotherapies.
Sixty chemotherapy-naive breast cancer patients of 30 to 71 years in age, P.S. =
0-1, receiving 5-fluorouracil-epirubicin-cyclophosphamide (FEC 75) q 21 days or
cyclophosphamide-methotrexate-5-fluorouracil (CMF) or 120 mg/m2 epirubicin or
high dose mitomycin-methotrexate-mitoxantrone (MMM) q 14 days (+ G-CSF) or 100
mg/m2 epirubicin (+ G-CSF) were randomized to receive, 15 min before
chemotherapy, 8 mg i.v. bolus of ondansetron or 3 mg i.v. granisetron or 5 mg
i.v. tropisetron and no further antiemetic therapy in the following days. 180
cycles were evaluable. Complete protection, (the absence of vomiting episodes,)
was respectively 75%, 70% and 70% in the acute and 70%, 82%, 72% in the delayed
phases, and an absence of nausea was 56%, 37% and 20% in the acute phase and
50%, 35% and 27% in the delayed, respectively. Complete response, (absence of
vomiting and absence or mild nausea,) was 74%, 58.6% and 50.8% in the acute and
64%, 63.7%, 47.3% in the delayed phases, respectively. At the statistical
analysis no significant differences between the three drugs were found regarding
acute vomiting while ondansetron was superior to granisetron and tropisetron in
acute (p = 0.018; p < 0.05) and delayed nausea (P = 0.104; p < 0.01). This
activity is practically the same as that we reported (Ann Oncol 1994; 6, suppl
8: 204) with a loading dose on day 1 and maintece for the following 2-5 days,
but with a significantly favorable cost-benefit ratio. From May 1991 to December 1996, 326 patients with advanced metastatic breast
cancer were enrolled in a multicentre, randomised, phase III clinical trial with
four arms. Patients were randomised to receive chemotherapy according to the FEC
regimen (5-fluorouracil (5-FU) 500 mg/m2, epidoxorubicin (EPI) 75 mg/m2 and
cyclophosphamide (CFA) 500 mg/m2, intravenously (i.v.). every 3 weeks) or the EM
regimen (EPI 75 mg/m2, i.v. every 3 weeks; mitomycin C (MMC) 10 mg/m2, i.v.
every 6 weeks) or the same regimens with the addition of lonidamine (LND) until
disease progression (orally, thrice daily, 150+150+300 mg); a maximum of eight
chemotherapy cycles were planned. The aim of the trial was 2-fold: to compare
the EM regimen with the commonly used FEC regimen and to evaluate the possible
role of the addition of LND. Patients were eligible if they had histologically
proven breast carcinoma, metastatic or locoregional relapse with measurable
and/or evaluable disease and were aged between 18 and 70 years: 318 patients
were considered eligible. Patients with previous anthracycline-based adjuvant
chemotherapy or those who relapsed within 6 months after any adjuvant
chemotherapy regimen were excluded. Chemotherapy-related toxicity of grade > or
= 3 was manageable and there was no significant difference between the arms in
terms of haematological side-effects. The impact on heart function was mild. No
increased toxicity was observed in the LND arms (apart from myalgias in 27-30%
of the cases). A significant increase in the complete response rate was observed
for the FEC/EM + LND group (20.4%) versus the FEC/EM group (10.8%). The median
survival time and the median time to progression for the overall series were 608
days and 273 days, respectively; EM+/-LND achieved significantly improved
survival and time to progression versus FEC+/-LND (P=0.01). This result was
confirmed also when the analysis was restricted to patients previously treated
with adjuvant CMF schedules. On the basis of these results, we conclude that EM
may represent a valuable alternative to FEC for patients requiring a first-line
regimen for advanced/ metastatic breast carcinoma, especially in patients
previously treated with CMF in an adjuvant setting. Furthermore, we conclude
that, in spite of a better complete response rate in the LND arms, as there was
no clear advantage in time to progression or survival resulting from the
addition of LND to the FEC or EM regimens, the routine use of LND is not
warranted outside a clinical trial. PURPOSE: To determine whether the duration and the dose of epirubicin modify the
long-term outcome of patients with metastatic breast cancer (MBC).
PATIENTS AND METHODS: Four hundred seventeen anthracycline-naive MBC patients
were randomized to receive one of the following regimens: arm A: 11 cycles of
fluorouracil 500 mg/m(2), epirubicin 75 mg/m(2), and cyclophosphamide 500
mg/m(2) (FEC 75) every 21 days; arm B: four cycles of FEC 100 (same regimen but
with epirubicin 100 mg/m(2)) then eight cycles of FEC 50 (epirubicin 50
mg/m(2)); and arm C: four cycles of FEC 100 then restart the same regimen at
disease progression in case of prior response or stabilization.
RESULTS: Hematologic toxicity was similar. Nausea/vomiting and stomatitis were
significantly less frequent in arm A as was left ventricular ejection fraction
decrease in arm C (A = six patients, B = five patients, and C = one patient).
Six patients died of infections (A = four patients and C = two patients). After
four cycles, the objective response rate (ORR) was better with FEC 100 than with
FEC 75 (49.2% v 40%, respectively; P: =.07). The ORR was better with the longer
regimens (arm A, 56.9%; B, 64%; and C, 47.6%; P: =.06) and was 41% after
second-line FEC 100. After a median follow-up of 41 months, the response
duration and time to progression (TTP) were significantly better with arm B, the
longer regimen (P: =.012 and P: < 10(-3), respectively). The median survival
times for arms A, B, and C were similar (17.9, 18.9, and 16. 3 months,
respectively; P: =.49).
CONCLUSION: In MBC, longer epirubicin-based regimens are better in terms of
response duration and TTP. FEC 100 regimens improve the ORR. However, four
initial cycles of FEC 100 and identical retreatment at disease progression
yielded equivalent overall survival to longer regimens. The aim of this study, using a Fleming single-stage design, was to explore the
efficacy and safety of Taxotere 100 x mg x m(-2) docetaxel and FEC 75
cyclophosphamide 500 mg x m(-2), fluorouracil 500 x mg x m(-2) and epirubicin 75
mg x m(-2), in alternating and sequential schedules for the first-line treatment
of metastatic breast cancer. One hundred and thirty-six women were randomly
allocated, to one of three treatment regimens: DTX 100 plus FEC 75, alternated
for eight courses (ALT); four courses of DTX 100 followed by four courses of FEC
75 (SEQ T); or four courses of FEC 75 followed by four courses of DTX 100 (SEQ
F). One hundred and thirty-one women were evaluable for tumour response.
Although the treatment outcome was equivalent in the two sequential arms and the
alternating regimen (P=0.110, not significant), the response rate was less
encouraging in the SEQ F arm (52.3%) than in the other two arms (71.1% for ALT
and 70.5% for SEQ T), in which docetaxel was administered first. Time to
progression was similar in the ALT, SEQ T and SEQ F arms (9.5, 9.3 and 10.4
months respectively). Grade 3-4 neutropenia was observed in nearly all patients;
febrile neutropenia occurred in 9% (ALT), 16% (SEQ T) and 2% (SEQ F) of
patients. Few patients (< or =9%) developed grade 3-4 non-haematological
toxicities. Relative dose intensity was 97-99% for all regimens. All treatment
regimens were active and well tolerated. PURPOSE: To evaluate the duration and dose intensity of epirubicin-based
regimens in premenopausal patients with lymph node-positive breast cancer.
PATIENTS AND METHODS: Between 1986 and 1990, 621 patients with operable breast
cancer were randomly assigned to receive fluorouracil (Roche SA, Basel,
Switzerland) 500 mg/m2, epirubicin (Pharmacia SA, Milan, Italy) 50 mg/m2, and
cyclophosphamide (Asta Medica AG, Frankfurt, Germany) 500 mg/m2 every 21 days
(FEC 50) for six cycles (6 FEC 50); FEC 50 for three cycles (3 FEC 50); or the
same regimen with epirubicin 75 mg/m2 (FEC 75) for three cycles (3 FEC 75). All
patients in the three arms received chest wall irradiation at the end of the
third cycle.
RESULTS: After a 131-month median follow-up, the 10-year disease-free survival
(DFS) was 53.4%, 42.5%, and 43.6% (P =.05) in the three arms, respectively.
Pairwise comparisons demonstrate that 6 FEC 50 was superior both to 3 FEC 50 (P
=.02) and to 3 FEC 75 (P =.05). The 10-year overall survival (OS) for the 6 FEC
50 arm was 64.3%, for the 3 FEC 50 arm it was 56.6%, and for the 3 FEC 75 arm,
it was 59.7% (P =.25), respectively. Pairwise comparisons demonstrate that 6 FEC
50 was more effective than 3 FEC 50 (P =.10). Cox regression analysis
demonstrates that OS was significantly better in the 6 FEC 50 than in the 3 FEC
50 arm (P =.046). No severe infections (grade 3 to 4), acute cardiac toxicity,
or deaths from toxicity have been observed. Only five patients developed delayed
cardiac dysfunctions, and three patients developed acute myeloblastic leukemia.
CONCLUSION: After a long-term follow-up in an adjuvant setting, the benefit of
six cycles of FEC 50 compared with three cycles, whatever the dose, is highly
significant in terms of DFS. As regards OS, the group receiving six cycles of
FEC 50 has significantly better results than the group receiving three cycles of
FEC 50. Recently, high-dose FEC (fluorouracil, epirubicin, and cyclophosphamide) has
been increasingly used in adjuvant chemotherapy for breast cancer in Japan.
However, the safety and tolerability of high-dose FEC are not well evaluated in
Japanese breast cancer patients. We studied the feasibility of FEC (75)
(fluorouracil: 500 mg/m(2), epirubicin: 75 mg/m(2), and cyclophosphamide:500
mg/m(2), q 3 w, 6 cycles) as adjuvant chemotherapy for 59 primary breast cancer
patients. Out of these patients, 56 (94.9%) finished 6 cycles-FEC. The mean
epirubicin dose received was 431.7 mg/m(2) (95.9% of the intended dose of 450
mg/m(2)). Forty-five (76.2%) of 59 patients experienced neutropenia of grade 3
or 4, while the rates of febrile neutropenia (grade 3) and infection (grade 2)
were 3.4% and 10.2%, respectively. Anemia (88.2%), fatigue (42.4%), nausea
(40.6%), liver dysfunction (40.7%), and vomiting (18.7%) occurred, however most
of them were mild and categorized into grade 1 or 2. No patients developed any
cardiac failure symptoms. This study shows FEC (75) is well tolerable as
adjuvant chemotherapy for Japanese breast cancer patients. BACKGROUND: FEC (5-FU+epirubicin+cyclophosphamide) therapy has been used as
adjuvant chemotherapy for breast cancer patients with nodes positive. The aim of
this study was to evaluate host immunity and side effects of the FEC therapy.
The effect of oral administration of Lentinus edodes mycelia (LEM) was also
observed.
METHODS: Ten patients were enrolled in this study. The treatment with 5-FU (500
mg/m2), epirubicin (75 mg/m2) and cyclophosphamide (500 mg/m2) was administered
every 21 days for 2 cycles, and LEM (9 g/day po) was administered during the 2nd
cycle.
RESULTS: NK cell activity and the number of white blood cells decreased on the
7th day after the therapy, and they recovered on the 21st day. However, this NK
cell activity and the number of white blood cells didn't decrease when the FEC
therapy was used with LEM po.
CONCLUSIONS: FEC 75 therapy has made some impacts on host immunity, and LEM with
the FEC 75 therapy might have prevented host immunity. BACKGROUND: The authors evaluated the long-term efficacy and side effects in
patients with nonmetastatic, unilateral, inflammatory breast cancer (IBC) who
received homogeneous treatment with intensive induction chemotherapy followed by
a maintece regimen.
METHODS: One hundred twenty patients were randomized to receive high-dose
fluorouracil, epirubicin, and cyclophosphamide (FEC-HD) (fluorouracil 750
mg/m(2) on Days 1 to 4, epirubicin 35 mg/m(2) on Days 2 to 4, and
cyclophosphamide 400 mg/m(2) on Days 2 to 4 for 4 cycles every 21 days) with or
without lenograstim. Locoregional treatment consisted of surgery and/or
radiotherapy. Maintece chemotherapy was FEC 75 (fluorouracil 500 mg/m(2),
epirubicin 75 mg/m(2), and cyclophosphamide 500 mg/m(2) on Day 1 every 21 days
for 4 cycles). No hormone treatment was allowed.
RESULTS: The safety of the FEC-HD regimen was described previously. Among 102
patients who underwent surgery, a pathologic complete response (pCR) was
achieved by 23.5% of patients with breast tumors and by 31.4% of patients with
involved axillary lymph nodes. The overall pCR rate was 14.7%. One hundred nine
patients received FEC 75. After a median 10 years of follow-up, the disease-free
survival (DFS) and overall survival (OS) rates were 35.7% and 41.2%,
respectively. The median DFS was 39 months (95% confidence interval [95% CI],
25-53 months), and the median survival was 61 months (95% CI, 43-79 months).
Five patients developed a temporary decrease in left ventricular ejection
fraction without congestive heart failure. In the lenograstim group, 1 patient
developed acute myeloblastic leukemia M2, and 1 patient developed
myelodysplastic syndrome.
CONCLUSIONS: FEC-HD induction chemotherapy followed by FEC 75 maintece
regimen had moderate and acute long-term toxicities and lead to high DFS and OS
rates in patients with IBC. BACKGROUND: A previously published prospective randomized phase 3 trial showed
that administration of 24 weeks of primary systemic chemotherapy (PST) with
paclitaxel and FEC(75) (fluorouracil, epirubicin, cyclophosphamide) concurrently
with trastuzumab in patients with HER2-positive primary breast cancer resulted
in a 60% pathologic complete response rate (PCR) with no associated severe
cardiac toxicity. The purpose of this study was to review the efficacy and
safety of a similar regimen outside the setting of a clinical trial.
METHODS: Patients with HER2-positive breast cancer (defined as either
immunohistochemical 3+ or fluorescence in situ hybridization-positive) that had
received 24 weeks of neoadjuvant trastuzumab concurrently with taxane and
anthracycline-based chemotherapy between 2004 and 2006 were included in the
analysis. PST chemotherapy consisted of paclitaxel (80 mg/m(2)) weekly for 12
weeks followed by 4 cycles of FEC(75) (500 mg/m(2), 75 mg/m(2), and 500 mg/m(2),
respectively).
RESULTS: Forty patients were identified. The median age was 48 years (range,
29-81). In all, 60% of patients had stage III disease and 4 had inflammatory
breast cancer. The PCR rate was 55% (95% confidence interval [CI], 38.5%-70.7%).
At a median follow-up of 19 months. 5 patients had a recurrence, of which 4 did
not achieve a PCR. No severe cardiac events were observed.
CONCLUSIONS: Stage II and III HER2-positive breast cancer patients achieved a
high rate of PCR with trastuzumab given concurrently with paclitaxel and FEC(75)
chemotherapy. No severe cardiac events were observed with the regimen. The data
concur with the results of a previously published trial. |
Between which probes does the recurrent translocation breakpoint on chromosome 22 of neuroepithelioma lie? | The recurrent translocation breakpoint on chromosome 22 of neuroepithelioma has been localized between two probes, D22S1 and D22S15, by both in situ hybridization and somatic cell hybrids | The recurrent translocation breakpoint on chromosome 22 of neuroepithelioma has
been localized between two probes, D22S1 and D22S15, by both in situ
hybridization and somatic cell hybrids. These two probes have further been shown
to be genetically linked at theta = 0.0 and a lod score of 5.3. The two probes
were unaffected by a partial deletion of the chromosome 22 long arm of a
meningioma, showing that the meningioma locus is distal to that of the
neuroepithelioma. |
Does administration of triiodothyronine improve outcome following coronary artery bypass grafting? | Perioperative administration of synthetic thyroid hormone therapy have positive hemodynamic effects (consisting of increases cardiac output, lowered systemic vascular resistance) determining improved postoperative ventricular function, reduced the need for treatment with inotropic agents and mechanical devices, in the absence of relevant effects on outcome ad exception of lower incidence of atrial fibrillation. | BACKGROUND: Thyroid hormone has many effects on the cardiovascular system.
During and after cardiopulmonary bypass, serum triiodothyronine concentrations
decline transiently, which may contribute to postoperative hemodynamic
dysfunction. We investigated whether the perioperative administration of
triiodothyronine (liothyronine sodium) enhances cardiovascular performance in
high-risk patients undergoing coronary-artery bypass surgery.
METHODS: We administered triiodothyronine or placebo to 142 patients with
coronary artery disease and depressed left ventricular function. The hormone was
administered as an intravenous bolus of 0.8 microgram per kilogram of body
weight when the aortic cross-clamp was removed after the completion of bypass
surgery and then as an infusion of 0.113 microgram per kilogram per hour for six
hours. Clinical and hemodynamic responses were serially recorded, as was any
need for inotropic or vasodilator drugs.
RESULTS: The patients' preoperative serum triiodothyronine concentrations were
normal (mean [+/- SD] value, 81 +/- 22 ng per deciliter [1.2 +/- 0.3 nmol per
liter]), and they decreased by 40 percent (P < 0.001) 30 minutes after the onset
of cardiopulmonary bypass. The concentrations in patients given intravenous
triiodothyronine became supranormal and were significantly higher than those in
patients given placebo (P < 0.001). However, the concentrations were once again
similar in the two groups 24 hours after surgery. The mean postoperative cardiac
index was higher in the triiodothyronine group (2.97 +/- 0.72 vs. 2.67 +/- 0.61
liters per minute per square meter of body-surface area, P = 0.007), and
systemic vascular resistance was lower (1073 +/- 314 vs. 1235 +/- 387
dyn.sec.cm-5, P = 0.003). The two groups did not differ significantly in the
incidence of arrhythmia or the need for therapy with inotropic and vasodilator
drugs during the 24 hours after surgery, or in perioperative mortality and
morbidity.
CONCLUSIONS: Raising serum triiodothyronine concentrations in patients
undergoing coronary-artery bypass surgery increases cardiac output and lowers
systemic vascular resistance, but does not change outcome or alter the need for
standard postoperative therapy. OBJECTIVE: The purpose of this study was to investigate any potential
hemodynamic effect of intravenously administered triiodothyronine in patients
undergoing coronary artery bypass surgery.
EXPERIMENTAL DESIGN: Thirty patients were randomized in this single-blind,
placebo-controlled trial. Hemodynamic parameters including heart rate, stroke
volume index, cardiac index, pulmonary wedge pressure, pulmonary vascular
resistances, systemic vascular resistances, and mean blood pressure, were
compared between the two groups preoperatively, before the initiation of
cardiopulmonary bypass (CPB), 5 minutes after the end of CPB, and 2, 4, 10, 16,
and 22 hours thereafter.
INTERVENTION: Triiodothyronine was administered as a bolus infusion over a 1 min
period after removal of the aortic cross-clamp, (0.15 microgram/kg), before the
end of CPB (0.1 microgram/kg), 4 hours after the end of CPB (0.1 microgram/kg),
9 hours after CPB (0.1 microgram/kg), and 14 hours after CPB (0.1 microgram/kg).
Patients received inotropes, vasodilators, and diuretics only if specifically
indicated.
RESULTS: Plasma FT3 levels were higher in the T3 group, but within the normal
range. No significant differences were noted in the pre and post CPB
hemodynamics between the two groups for the most part of the study except that
heart rate was increased in T3 group. A greater number of patients in the
control group received vasodilators. No adverse reactions were noted with
triiodothyronine administration.
CONCLUSION: Triiodothyronine administration in patients undergoing
cardiopulmonary bypass surgery is safe, may lessen the need for pharmacological
(vasodilator) therapy, but may increase heart rate. A controversy persists as to whether cardiopulmonary bypass (CPB) decreases
plasma levels of triiodothyronine (T3), thereby justifying peri-operative
administration of T3 to improve haemodynamic recovery. To examine the effects of
T3 therapy on post-CPB haemodynamics and to determine whether the potential
inotropic effects of T3 are mediated by an increase in beta-adrenergic
responsiveness, a prospective, randomized, double-blind, placebo-controlled
study was performed in 20 patients undergoing cardiac surgery with CPB. T3 or
placebo solution (10 patients in each group) was given intravenously at the time
of aortic unclamping and 4, 8, 12 and 20 h thereafter. End points included (1)
thyroid hormone levels measured by radioimmunoassay (2) standard haemodynamic
parameters (3) the density of lymphocyte beta-adrenoceptors measured by a
radioligand (125I-iodocyanopindolol) binding technique. Post-CPB values (cross
clamp removal) of T3 (pg.ml-1) were not significantly decreased compared with
pre-CPB values: 3.3 +/- 0.2 vs 3.1 +/- 0.2 in controls and 3.3 +/- 0.4 vs 3.7
+/- 0.6 in T3-treated patients, respectively. The haemodynamic parameters were
no different between the two groups at any postoperative time point. Likewise,
density and affinity of lymphocyte beta-adrenoceptors were not significantly
different from pre-operative values in either group. Thus, there seems to be no
sound justification for a routine use of T3 in patients undergoing open-heart
procedures. OBJECTIVE: To test the hypothesis that triiodothyronine (T(3)) administration
improves hemodynamic variables and decreases inotropic drug requirements in
cardiac surgery patients.
DESIGN: Prospective, randomized, double-blind, placebo-controlled trial.
SETTING: Tertiary care medical center.
PATIENTS: A total of 211 patients undergoing coronary artery surgery at high
risk for requiring inotropic drug support.
INTERVENTION: At release of aortic cross-clamp, patients were randomized to an
intravenous infusion of T(3) (0.8 microg/kg followed by 0.12 microg.kg(-1).h(-1)
for 6 hours), dopamine (positive control, 5 microg.kg(-1).min(-1) for 6 hours)
or placebo.
MAIN OUTCOME MEASURES: Perioperative hemodynamic variables, inotropic support
requirements, and serum T(3) concentrations.
RESULTS: Mean+/-SEM free T(3) serum concentrations decreased significantly
during cardiopulmonary bypass in all groups (from 0.0035+/-0.0001 nmol/L
[0.23+/-0.01 ng/dL] to 0.001+/-0.0001 nmol/L [0.7+/- 0.00 ng/dL]; P=.001) and
increased to 0.0133+/-0.0004 nmol/L [0.87+/-0.03 ng/dL] (twice normal range;
P<.001) following initiation of intravenous T(3). Intravenous T(3) did not
change hemodynamic variables or inotropic drug requirements; however, heart rate
increased (P<.001), and a trend toward decreased use of inotropic agents was
demonstrated in the dopamine group.
CONCLUSIONS: Triiodothyronine administration prevents decreases in serum thyroid
hormone concentrations associated with cardiopulmonary bypass. Intravenous T(3)
does not have dramatic effects on hemodynamic variables in this setting as has
been previously suggested. Although mild effects on myocardial performance may
exist, we cannot recommend at this time the routine use of intravenous T(3) as
an inotropic agent in patients undergoing coronary artery bypass graft surgery. A prospective randomized and double-blind study was performed to evaluate
whether perioperative triiodothyronine administration has any effect on
cardiovascular performance after coronary artery bypass surgery. Sixty patients
were assigned to 2 groups of 30 each. When crossclamping ended, group A received
an intravenous bolus of triiodothyronine, followed by infusion for 6 hours.
Group B received a placebo. Serum triiodothyronine levels and hemo-dynamic
parameters were serially measured. Mean postoperative cardiac index was
slightly, but not significantly, higher in group A, whereas systemic vascular
resistance was significantly lower in group A. Compared with preoperative
values, serum triiodothyronine levels dropped significantly in group B at the
end of cardiopulmonary bypass and remained low 12 hours postoperatively, while
levels rose significantly in group A. No significant differences were detected
between the groups in the incidence of arrhythmia, the need for inotropic
support, intensive care unit stay, mortality, and morbidity. Perioperative
administration of triiodothyronine increased cardiac output slightly and
decreased systemic vascular resistance, but it had no effect on operative
outcome. Routine use after coronary surgery is thus not recommended. BACKGROUND: Both glucose-insulin-potassium (GIK) and tri-iodothyronine (T3) may
improve cardiovascular performance after coronary artery surgery (CABG) but
their effects have not been directly compared and the effects of combined
treatment are unknown.
METHODS AND RESULTS: In 2 consecutive randomized double-blind placebo-controlled
trials, in patients undergoing first time isolated on-pump CABG between January
2000 and September 2004, 440 patients were recruited and randomized to either
placebo (5% dextrose) (n=160), GIK (40% dextrose, K+ 100 mmol.L(-1), insulin 70
u.L(-1)) (0.75 mL.kg(-1) h(-1)) (n=157), T3 (0.8 microg.kg(-1) followed by 0.113
microg.kg(-1) h(-1)) (n=63) or GIK+T3 (n=60). GIK/placebo therapy was
administered from start of operation until 6 hours after removal of aortic
cross-clamp (AXC) and T3/placebo was administered for a 6-hour period from
removal of AXC. Serial hemodynamic measurements were taken up to 12 hours after
removal of AXC and troponin I (cTnI) levels were assayed to 72 hours. Cardiac
index (CI) was significantly increased in both the GIK and GIK/T3 group in the
first 6 hours compared with placebo (P<0.001 for both) and T3 therapy (P=0.009
and 0.029, respectively). T3 therapy increased CI versus placebo between 6 and
12 hours after AXC removal (P=0.01) but combination therapy did not. Release of
cTnI was lower in all treatment groups at 6 and 12 hours after removal of AXC.
CONCLUSIONS: Treatment with GIK, T3, and GIK/T3 improves hemodynamic performance
and results in reduced cTnI release in patients undergoing on-pump CABG surgery.
Combination therapy does not provide added hemodynamic effect. The question addressed in this review is whether supplementation with thyroid
hormones during the perioperative period improves the outcome of patients
undergoing coronary artery bypass surgery. Altogether 88 relevant papers were
identified using the below mentioned search, seven papers represented the best
evidence to answer the question. The author, journal, date and country of
publication, patient group studied, study type, relevant outcomes, results, and
study weaknesses were tabulated. We conclude that although widespread interest
has been shown on the use of thyroid hormones in the perioperative period, and
the effect of cardiopulmonary bypass on thyroid hormone metabolism widely
studied, there is no substantial evidence to justify routine use of thyroid
hormones in patients undergoing coronary artery bypass grafting. OBJECTIVE: Cardiopulmonary bypass (CPB) is associated with thyroid hormone
changes consistent with euthyroid sick syndrome. Similar changes have been
observed after general surgical operations. Thyroid hormone changes and their
association with global oxygen consumption were studied in low-risk patients
undergoing coronary artery bypass grafting (CABG) with and without CPB.
METHODS: Fifty-two patients undergoing primary CABG by the same surgeon were
randomised into either on-pump (ONCAB, n=26) or off-pump (OPCAB, n=26) groups.
Thyroid-stimulating hormone (TSH), free thyroxine (fT4) and free
triiodothyronine (fT3) levels were measured at sequential time-points using
chemiluminescence assays. Global oxygen consumption was measured at sequential
time-points using a continuous cardiac output Swan-Ganz catheter.
RESULTS: In both groups TSH and fT4 remained within normal range throughout the
study. There was a similar and progressive decline in fT3 levels with no
significant difference between the groups over time (p=0.42). Mean fT3 levels at
24h were below the normal range and significantly lower than baseline values
(ONCAB, 3.3+/-0.69 pmol/L vs 5.1+/-0.41 pmol/L, p<0.001; OPCAB, 3.3+/-0.51
pmol/L vs 5.0+/-0.46 pmol/L, p<0.001). There was a significant inverse
relationship between fT3 levels and global oxygen consumption.
CONCLUSIONS: Off-pump surgery is associated with thyroid hormone changes similar
to conventional surgical revascularisation. The data suggest that further
studies into T3 administration during OPCAB may be warranted. BACKGROUND: Overt thyroid dysfunction, hypothyroidism in particular, may lead to
coronary artery disease (CAD). Whether more subtle anomalies of thyroid hormone
metabolism influence the progression of CAD remains a matter of speculation.
HYPOTHESIS: The occurrence of CAD and long-term prognosis in patients without a
history of either primary thyroid disease, myocardial infarction, or chronic
heart failure is related to serum levels of biologically active free
triiodothyronine (fT3).
METHODS: The cohort consisted of 1047 clinically and biochemically euthyroid
patients (median age 65.6 y and 69% male) who underwent coronary angiography in
our institute for suspected CAD.
RESULTS: Lower fT3 levels were predictive of both single-vessel (p = 0.012) and
multivessel (p = 0.009) CAD. Through a multivariate logistic regression
analysis, fT3 was still linked to the presence of CAD (hazard ratio [HR]: 0.48,
95% confidence interval [CI]: 0.34-0.68, p < 0.001). After a mean follow-up of
31 months, the survival rate was 95% and total mortality (log-rank 6.75, p =
0.009), as well as cardiac mortality (log-rank 8.26, p = 0.004), was greater
among patients with low T3 (fT3 < 2.10 pg/mL) syndrome. At subsequent
multivariate Cox regression analysis, the association between low T3 syndrome
and survival was maintained (total mortality HR: 1.80, 95% CI: 1.05-3.10, p =
0.034; cardiac mortality HR: 2.58, 95% CI: 1.13-5.93, p = 0.025).
CONCLUSIONS: In this selected population, fT3 levels were inversely correlated
to the presence of CAD and low T3 syndrome conferred an adverse prognosis, even
after adjusting for traditional coronary risk factors. |
Which are the most widely used computational methods for the identification of CRMs (cis-regulatory modules)? | Computational methods attempting to identify instances of cis-regulatory modules (CRMs) in the genome face a challenging problem of searching for potentially interacting transcription factor binding sites while knowledge of the specific interactions involved remains limited. When discriminating CRMs from non-coding regions, those methods considering evolutionary conservation have a stronger predictive power than methods designed to be run on a single genome. Furthermore, most methods appear to be sensitive to the composition and structure of the genome to which they are applied. CisMiner allows to perform a blind search of CRMs without any prior information about target CRMs nor limitation in the number of motifs. | Transcription regulation is controlled by coordinated binding of one or more
transcription factors in the promoter regions of genes. In many species,
especially higher eukaryotes, transcription factor binding sites tend to occur
as homotypic or heterotypic clusters, also known as cis-regulatory modules. The
number of sites and distances between the sites, however, vary greatly in a
module. We propose a statistical model to describe the underlying cluster
structure as well as individual motif conservation and develop a Monte Carlo
motif screening strategy for predicting novel regulatory modules in upstream
sequences of coregulated genes. We demonstrate the power of the method with
examples ranging from bacterial to insect and human genomes. MOTIVATION: Identifying transcription factor binding sites (TFBSs) encoding
complex regulatory signals in metazoan genomes remains a challenging problem in
computational genomics. Due to degeneracy of nucleotide content among binding
site instances or motifs, and intricate 'grammatical organization' of motifs
within cis-regulatory modules (CRMs), extant pattern matching-based in silico
motif search methods often suffer from impractically high false positive rates,
especially in the context of analyzing large genomic datasets, and noisy
position weight matrices which characterize binding sites. Here, we try to
address this problem by using a framework to maximally utilize the information
content of the genomic DNA in the region of query, taking cues from values of
various biologically meaningful genetic and epigenetic factors in the query
region such as clade-specific evolutionary parameters, presence/absence of
nearby coding regions, etc. We present a new method for TFBS prediction in
metazoan genomes that utilizes both the CRM architecture of sequences and a
variety of features of individual motifs. Our proposed approach is based on a
discriminative probabilistic model known as conditional random fields that
explicitly optimizes the predictive probability of motif presence in large
sequences, based on the joint effect of all such features.
RESULTS: This model overcomes weaknesses in earlier methods based on less
effective statistical formalisms that are sensitive to spurious signals in the
data. We evaluate our method on both simulated CRMs and real Drosophila
sequences in comparison with a wide spectrum of existing models, and outperform
the state of the art by 22% in F1 score.
AVAILABILITY AND IMPLEMENTATION: The code is publicly available at
http://www.sailing.cs.cmu.edu/discover.html.
SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics
online. Computational methods attempting to identify instances of cis-regulatory modules
(CRMs) in the genome face a challenging problem of searching for potentially
interacting transcription factor binding sites while knowledge of the specific
interactions involved remains limited. Without a comprehensive comparison of
their performance, the reliability and accuracy of these tools remains unclear.
Faced with a large number of different tools that address this problem, we
summarized and categorized them based on search strategy and input data
requirements. Twelve representative methods were chosen and applied to predict
CRMs from the Drosophila CRM database REDfly, and across the human ENCODE
regions. Our results show that the optimal choice of method varies depending on
species and composition of the sequences in question. When discriminating CRMs
from non-coding regions, those methods considering evolutionary conservation
have a stronger predictive power than methods designed to be run on a single
genome. Different CRM representations and search strategies rely on different
CRM properties, and different methods can complement one another. For example,
some favour homotypical clusters of binding sites, while others perform best on
short CRMs. Furthermore, most methods appear to be sensitive to the composition
and structure of the genome to which they are applied. We analyze the principal
features that distinguish the methods that performed well, identify weaknesses
leading to poor performance, and provide a guide for users. We also propose key
considerations for the development and evaluation of future CRM-prediction
methods. Computationally retrieving biologically relevant cis-regulatory modules (CRMs)
is not straightforward. Because of the large number of candidates and the
imperfection of the screening methods, many spurious CRMs are detected that are
as high scoring as the biologically true ones. Using ChIP-information allows not
only to reduce the regions in which the binding sites of the assayed
transcription factor (TF) should be located, but also allows restricting the
valid CRMs to those that contain the assayed TF (here referred to as applying
CRM detection in a query-based mode). In this study, we show that exploiting
ChIP-information in a query-based way makes in silico CRM detection a much more
feasible endeavor. To be able to handle the large datasets, the query-based
setting and other specificities proper to CRM detection on ChIP-Seq based data,
we developed a novel powerful CRM detection method 'CPModule'. By applying it on
a well-studied ChIP-Seq data set involved in self-renewal of mouse embryonic
stem cells, we demonstrate how our tool can recover combinatorial regulation of
five known TFs that are key in the self-renewal of mouse embryonic stem cells.
Additionally, we make a number of new predictions on combinatorial regulation of
these five key TFs with other TFs documented in TRANSFAC. |
Which enzyme does MLN4924 inhibit? | MLN4924 is an investigational small molecule inhibitor of NEDD8-activating enzyme (NAE). | The NEDD8-activating enzyme (NAE) initiates a protein homeostatic pathway
essential for cancer cell growth and survival. MLN4924 is a selective inhibitor
of NAE currently in clinical trials for the treatment of cancer. Here, we show
that MLN4924 is a mechanism-based inhibitor of NAE and creates a covalent
NEDD8-MLN4924 adduct catalyzed by the enzyme. The NEDD8-MLN4924 adduct resembles
NEDD8 adenylate, the first intermediate in the NAE reaction cycle, but cannot be
further utilized in subsequent intraenzyme reactions. The stability of the
NEDD8-MLN4924 adduct within the NAE active site blocks enzyme activity, thereby
accounting for the potent inhibition of the NEDD8 pathway by MLN4924.
Importantly, we have determined that compounds resembling MLN4924 demonstrate
the ability to form analogous adducts with other ubiquitin-like proteins (UBLs)
catalyzed by their cognate-activating enzymes. These findings reveal insights
into the mechanism of E1s and suggest a general strategy for selective
inhibition of UBL conjugation pathways. Brownell et al. (2010) elucidate the mechanism of action of MLN4924, a
NEDD8-activating enzyme inhibitor. MLN4924 requires the activity of the enzyme
to generate a NEDD8-adenylate analog that potently and selectively shuts down
this posttranslational modification system. MLN4924 is a potent and selective small molecule NEDD8-activating enzyme (NAE)
inhibitor. In most cancer cells tested, inhibition of NAE leads to induction of
DNA rereplication, resulting in DNA damage and cell death. However, in
preclinical models of activated B cell-like (ABC) diffuse large B-cell lymphoma
(DLBCL), we show that MLN4924 induces an alternative mechanism of action.
Treatment of ABC DLBCL cells with MLN4924 resulted in rapid accumulation of
pIkappaBalpha, decrease in nuclear p65 content, reduction of nuclear
factor-kappaB (NF-kappaB) transcriptional activity, and G(1) arrest, ultimately
resulting in apoptosis induction, events consistent with potent NF-kappaB
pathway inhibition. Treatment of germinal-center B cell-like (GCB) DLBCL cells
resulted in an increase in cellular Cdt-1 and accumulation of cells in S-phase,
consistent with cells undergoing DNA rereplication. In vivo administration of
MLN4924 to mice bearing human xenograft tumors of ABC- and GCB-DLBCL blocked NAE
pathway biomarkers and resulted in complete tumor growth inhibition. In primary
human tumor models of ABC-DLBCL, MLN4924 treatment resulted in NF-kappaB pathway
inhibition accompanied by tumor regressions. This work describes a novel
mechanism of targeted NF-kappaB pathway modulation in DLBCL and provides strong
rationale for clinical development of MLN4924 against NF-kappaB-dependent
lymphomas. MLN4924 is a first-in-class experimental cancer drug that inhibits the
NEDD8-activating enzyme, thereby inhibiting cullin-RING E3 ubiquitin ligases and
stabilizing many cullin substrates. The mechanism by which MLN4924 inhibits
cancer cell proliferation has not been defined, although it is accompanied by
DNA rereplication and attendant DNA damage. Here we show that stabilization of
the DNA replication factor Cdt1, a substrate of cullins 1 and 4, is critical for
MLN4924 to trigger DNA rereplication and inhibit cell proliferation. Even only 1
hour of exposure to MLN4924, which was sufficient to elevate Cdt1 for 4-5 hours,
was found to be sufficient to induce DNA rereplication and to activate apoptosis
and senescence pathways. Cells in S phase were most susceptible, suggesting that
MLN4924 will be most toxic on highly proliferating cancers. Although
MLN4924-induced cell senescence seems to be dependent on induction of p53 and
its downstream effector p21(Waf1), we found that p53(-/-) and p21(-/-) cells
were even more susceptible than wild-type cells to MLN4924. Our results
suggested that apoptosis, not senescence, might be more important for the
antiproliferative effect of MLN4924. Furthermore, our findings show that
transient exposure to this new investigational drug should be useful for
controlling p53-negative cancer cells, which often pose significant clinical
challenge. MLN4924 (1), which is in clinical trials as an anticancer agent, was
stereoselectively synthesized from d-ribose via a route involving
stereoselective reduction, regioselective cleavage of an isopropylidene moiety,
and selective displacement of a cyclic sulfate moiety as key steps. Cullin-RING ubiquitin ligase (CRL), with its founding member of
SKP1-Cullins-F-box proteins (SCF) E3 ubiquitin ligase, is the largest family of
E3 ligases, which requires cullin neddylation for its activation. Recently, an
inhibitor of NEDD8 activating enzyme (NAE), MLN4924, was reported to block
cullin neddylation and inactivate CRL/SCF E3, resulting in apoptosis induction
and tumor suppression both in vitro and in vivo. We report here that apoptosis
is not the sole mechanism by which MLN4924 suppresses tumor cell growth because
apoptosis is moderately induced by the drug in some cancer cell lines and
drug-induced growth suppression is only partially blocked by a pan-caspase
inhibitor, z-VAD. MLN4924 treatment induces the characteristics of senescence
phenotypes as evidenced by enlarged and flattened cellular morphology and
positive staining of senescence-associated β-Gal. MLN4924-induced senescence is
associated with cellular response to DNA damage, triggered by accumulation of
DNA-licensing proteins CDT1 and ORC1, as a result of inactivation of CRL/SCF
E3s. The senescence occurs in the manner independent of pRB/p16 and p53, but
dependent on p21, a known substrate of CRL/SCF E3s and a mediator of senescence,
which accumulates on CRL/SCF inactivation by MLN4924. Furthermore,
MLN4924-induced senescence is irreversible and coupled with persistent
accumulation of p21 and sustained activation of DNA damage response. Our study
reveals a novel mechanism of MLN4924 action and showed that MLN4924 could be
further developed as an effective anticancer agent by inducing apoptosis and
irreversible senescence. TNF-related apoptosis-inducing ligand (TRAIL) is a tumor-selective cytokine with
potential anticancer activity and is currently under clinical testing. Head and
neck squamous cell carcinoma (HNSCC), like other cancer types, exhibits varied
sensitivity to TRAIL. MLN4924 is a newly developed investigational small
molecule inhibitor of NEDD8-activating enzyme with potent anticancer activity.
This study reveals a novel function of MLN4924 in synergizing with TRAIL to
induce apoptosis in HNSCC cells. MLN4924 alone effectively inhibited the growth
of HNSCC cells and induced apoptosis. When combined with TRAIL, synergistic
effects on decreasing the survival and inducing apoptosis of HNSCC cells
occurred. MLN4924 decreased c-FLIP levels without modulating death receptor 4
and death receptor 5 expression. Enforced expression of c-FLIP substantially
attenuated MLN4924/TRAIL-induced apoptosis. Thus c-FLIP reduction plays an
important role in mediating MLN4924/TRAIL-induced apoptosis. Moreover, MLN4924
decreased c-FLIP stability, increased c-FLIP ubiquitination, and facilitated
c-FLIP degradation, suggesting that MLN4924 decreases c-FLIP levels through
promoting its degradation. MLN4924 activated c-jun-NH(2)-kinase (JNK) signaling,
evidenced by increased levels of phospho-c-Jun in MLN4924-treated cells.
Chemical inhibition of JNK activation not only prevented MLN4924-induced c-FLIP
reduction, but also inhibited MLN4924/TRAIL-induced apoptosis, suggesting that
JNK activation mediates c-FLIP downregulation and subsequent enhancement of
TRAIL-induced apoptosis by MLN4924. Because knockdown of NEDD8 failed to
activate JNK signaling and downregulate c-FLIP, it is likely that MLN4924
reduces c-FLIP levels and enhances TRAIL-induced apoptosis independent of NEDD8
inhibition. Ubiquitin-activating enzyme (UAE or E1) activates ubiquitin via an adenylate
intermediate and catalyzes its transfer to a ubiquitin-conjugating enzyme (E2).
MLN4924 is an adenosine sulfamate analogue that was identified as a selective,
mechanism-based inhibitor of NEDD8-activating enzyme (NAE), another E1 enzyme,
by forming a NEDD8-MLN4924 adduct that tightly binds at the active site of NAE,
a novel mechanism termed substrate-assisted inhibition (Brownell, J. E.,
Sintchak, M. D., Gavin, J. M., Liao, H., Bruzzese, F. J., Bump, N. J., Soucy, T.
A., Milhollen, M. A., Yang, X., Burkhardt, A. L., Ma, J., Loke, H. K., Lingaraj,
T., Wu, D., Hamman, K. B., Spelman, J. J., Cullis, C. A., Langston, S. P.,
Vyskocil, S., Sells, T. B., Mallender, W. D., Visiers, I., Li, P., Claiborne, C.
F., Rolfe, M., Bolen, J. B., and Dick, L. R. (2010) Mol. Cell 37, 102-111). In
the present study, substrate-assisted inhibition of human UAE (Ube1) by another
adenosine sulfamate analogue,
5'-O-sulfamoyl-N(6)-[(1S)-2,3-dihydro-1H-inden-1-yl]-adenosine (Compound I), a
nonselective E1 inhibitor, was characterized. Compound I inhibited UAE-dependent
ATP-PP(i) exchange activity, caused loss of UAE thioester, and inhibited E1-E2
transthiolation in a dose-dependent manner. Mechanistic studies on Compound I
and its purified ubiquitin adduct demonstrate that the proposed
substrate-assisted inhibition via covalent adduct formation is entirely
consistent with the three-step ubiquitin activation process and that the adduct
is formed via nucleophilic attack of UAE thioester by the sulfamate group of
Compound I after completion of step 2. Kinetic and affinity analysis of Compound
I, MLN4924, and their purified ubiquitin adducts suggest that both the rate of
adduct formation and the affinity between the adduct and E1 contribute to the
overall potency. Because all E1s are thought to use a similar mechanism to
activate their cognate ubiquitin-like proteins, the substrate-assisted
inhibition by adenosine sulfamate analogues represents a promising strategy to
develop potent and selective E1 inhibitors that can modulate diverse biological
pathways. Radiotherapy is used in locally advanced pancreatic cancers in which it can
improve survival in combination with gemcitabine. However, prognosis is still
poor in this setting in which more effective therapies remain needed. MLN4924 is
an investigational small molecule currently in phase I clinical trials. MLN4924
inhibits NAE (NEDD8 Activating Enzyme), a pivotal regulator of the E3 ubiquitin
ligase SCF (SKP1, Cullins, and F-box protein), that has been implicated recently
in DNA damage and repair. In this study, we provide evidence that MLN4924 can be
used as an effective radiosensitizer in pancreatic cancer. Specifically, MLN4924
(20-100 nmol/L) effectively inhibited cullin neddylation and sensitized
pancreatic cancer cells to ionizing radiation in vitro with a sensitivity
enhancement ratio of approximately 1.5. Mechanistically, MLN4924 treatment
stimulated an accumulation of several SCF substrates, including CDT1, WEE1, and
NOXA, in parallel with an enhancement of radiation-induced DNA damage,
aneuploidy, G(2)/M phase cell-cycle arrest, and apoptosis. RNAi-mediated
knockdown of CDT1 and WEE1 partially abrogated MLN4924-induced aneuploidy,
G(2)/M arrest, and radiosensitization, indicating a causal effect. Furthermore,
MLN4924 was an effective radiosensitizer in a mouse xenograft model of human
pancreatic cancer. Our findings offer proof-of-concept for use of MLN4924 as a
novel class of radiosensitizer for the treatment of pancreatic cancer. MLN4924 is an investigational small-molecule inhibitor of NEDD8-activating
enzyme (NAE) in clinical trials for the treatment of cancer. MLN4924 is a
mechanism-based inhibitor, with enzyme inhibition occurring through the
formation of a tight-binding NEDD8-MLN4924 adduct. In cell and xenograft models
of cancer, we identified treatment-emergent heterozygous mutations in the
adenosine triphosphate binding pocket and NEDD8-binding cleft of NAEβ as the
primary mechanism of resistance to MLN4924. Biochemical analyses of NAEβ mutants
revealed slower rates of adduct formation and reduced adduct affinity for the
mutant enzymes. A compound with tighter binding properties was able to potently
inhibit mutant enzymes in cells. These data provide rationales for patient
selection and the development of next-generation NAE inhibitors designed to
overcome treatment-emergent NAEβ mutations. Inhibition of NEDD8-activating enzyme (NAE) has emerged as a highly promising
approach to treat cancer through the adenosine sulfamate analog MLN4924. Here,
we show that selective pressure results in HCT116 colorectal carcinoma cells
with decreased MLN4924 sensitivity and identify a single-nucleotide transition
that changes alanine 171 to threonine (A171T) of the NAE subunit UBA3. This
reduces the enzyme's affinity for MLN4924 and ATP while increasing NEDD8
activation at physiological ATP concentrations. Expression of UBA3 A171T is
sufficient to decrease MLN4924 sensitivity of naive HCT116 cells, indicating
that it is a domit suppressor of MLN4924-mediated cell death. Our data
suggest that the on-target potency of MLN4924 selects for a point mutation in
NAE that overcomes the molecule's inhibitory effects, allowing cancer cell
survival. The multiunit Cullin (CUL)-RING E3 ligase (CRL) controls diverse biological
processes by targeting a mass of substrates for ubiquitination and degradation,
whereas its dysfunction causes carcinogenesis. Post-translational neddylation of
CUL, a process triggered by the NEDD8-activating enzyme E1 subunit 1 (NAE1), is
required for CRL activation. Recently, MLN4924 was discovered via a
high-throughput screen as a specific NAE1 inhibitor and first-in-class
anticancer drug. By blocking CUL neddylation, MLN4924 inactivates CRL and causes
the accumulation of CRL substrates that trigger cell cycle arrest, senescence
and/or apoptosis to suppress the growth of cancer cells in vitro and in vivo.
Recently, we found that MLN4924 also triggers protective autophagy in response
to CRL inactivation. MLN4924-induced autophagy is attributed partially to the
inhibition of mechanistic target of rapamycin (also known as mammalian target of
rapamycin, MTOR) activity by the accumulation of the MTOR inhibitory protein
DEPTOR, as well as reactive oxygen species (ROS)-induced stress. Moreover, the
blockage of autophagy response enhances apoptosis in MLN4924-treated cells.
Together, our findings not only reveal autophagy as a novel cellular response to
CRL inactivation by MLN4924, but also provide a piece of proof-of-concept
evidence for the combination of MLN4924 with autophagy inhibitors to enhance
therapeutic efficacy. MLN4924, a newly discovered small molecule inhibitor of NEDD8-activating enzyme
(NAE), inactivates Cullin-RING E3 ubiquitin Ligases (CRLs) by blocking cullin
neddylation. As a result, MLN4924 causes accumulation of several key substrates
of CRLs and effectively suppresses tumor cell growth by inducing apoptosis and
senescence. However, the role of MLN4924 in induction of autophagy and its
biological significance are totally unknown. Here we showed that MLN4924
effectively induces autophagy in both time- and dose-dependent manners in
multiple human cancer lines, indicating a general phenomenon. Mechanistically,
by inactivating CRLs, MLN4924 causes accumulation of DEPTOR and HIF1α. The siRNA
knockdown and gene KO studies showed that DEPTOR and the HIF1-REDD1-TSC1 axis
are responsible for MLN4924-induced autophagy via inhibiting mTORC1.
Biologically, autophagy is a survival signal to tumor cells, and blockage of
autophagy via siRNA knockdown, gene KO and small molecule inhibitor remarkably
enhanced MLN4924-induced apoptosis. Our study reveals an uncharacterized
mechanism of MLN4924 action and provides the proof-of-concept evidence for
strategic drug combination of MLN4924 with an autophagy inhibitor for maximal
killing of tumor cells via enhancing apoptosis. Multiple myeloma (MM) displays an NFκB activity-related gene expression
signature and about 20% of primary MM samples harbor genetic alterations
conducive to intrinsic NFκB signaling activation. The relevance of blocking the
classical versus the alternative NFκB signaling pathway and the molecular
execution mechanisms involved, however, are still poorly understood. Here, we
comparatively tested NFκB activity abrogation through TPCA-1 (an IKK2
inhibitor), BAY 11-7082 (an IKK inhibitor poorly selective for IKK1 and IKK2),
and MLN4924 (an NEDD8 activating enzyme (NAE)-inhibitor), and analyzed their
anti-MM activity. Whereas TPCA-1 interfered selectively with activation of the
classical NFκB pathway, the other two compounds inhibited classical and
alternative NFκB signaling without significant discrimination. Noteworthy,
whereas TPCA-1 and MLN4924 elicited rather mild anti-MM effects with slight to
moderate cell death induction after 1 day BAY 11-7082 was uniformly highly toxic
to MM cell lines and primary MM cells. Treatment with BAY 11-7082 induced rapid
cell swelling and its initial effects were blocked by necrostatin-1 or the ROS
scavenger BHA, but a lasting protective effect was not achieved even with
additional blockade of caspases. Because MLN4924 inhibits the alternative NFκB
pathway downstream of IKK1 at the level of p100 processing, the quite discordant
effects between MLN4924 and BAY 11-7082 must thus be due to blockade of
IKK1-mediated NFκB-independent necrosis-inhibitory functions or represent an
off-target effect of BAY 11-7082. In accordance with the latter, we further
observed that concomitant knockdown of IKK1 and IKK2 did not have any major
short-term adverse effect on the viability of MM cells. Cellular effects of a Nedd8-activating enzyme (NAE) inhibitor, MLN4924, using
the AlphaScreen format were explored. MLN4924 acts as a substrate-assisted
inhibitor of NAE by forming a tight binding Nedd8-MLN4924 adduct. The inhibited
enzyme can no longer transfer Nedd8 downstream to modify and activate the E3
cullin-RING ligases. This results in the stabilization of proteins regulated by
the proteasome, leading to cell death. These studies monitored the endogenous
cellular changes to NAE∼Nedd8 thioester, the formation of the Nedd8-MLN4924
adduct, and the reduction in the Cul1-Nedd8. Lysates derived from
MLN4924-treated HCT116 cells showed that whereas the β-subunit of NAE remained
constant, reductions of both NAE∼Nedd8 thioester and Cul1-Nedd8 levels occurred
with a concomitant rise of the adduct. Moreover, the formation of the
Nedd8-MLN4924 adduct was approximately stoichiometric with the concentration of
NAEβ. Higher density 384-well cell-based assays illustrated the kinetics of
enzyme inactivation across a wider range of MLN4924 concentrations, showing a
rapid loss of NAE∼Nedd8 thioester and Cul1-Nedd8. The reduction of NAE∼Nedd8
thioester precedes the loss of Cul1-Nedd8 at twice the rate. Finally, these
results clearly demonstrate the utility of the homogeneous assay for
quantitative assessment of these endogenous cellular components in a 384-well
plate in response to inhibition of NAE by MLN4924. The deoxynucleoside triphosphohydrolase SAMHD1 restricts retroviral replication
in myeloid cells. Human immunodeficiency virus type 2 (HIV-2) and a simian
immunodeficiency virus from rhesus macaques (SIVmac) encode Vpx, a
virion-packaged accessory protein that counteracts SAMHD1 by inducing its
degradation. SAMHD1 is thought to work by depleting the pool of intracellular
deoxynucleoside triphosphates but has also been reported to have exonuclease
activity that could allow it to degrade the viral genomic RNA or viral
reverse-transcribed DNA. To induce the degradation of SAMHD1, Vpx co-opts the
cullin4a-based E3 ubiquitin ligase, CRL4. E3 ubiquitin ligases are regulated by
the covalent attachment of the ubiquitin-like protein Nedd8 to the cullin
subunit. Neddylation can be prevented by MLN4924, a drug that inhibits the
nedd8-activating enzyme. We report that MLN4924 inhibits the neddylation of
CRL4, blocking Vpx-induced degradation of SAMHD1 and maintaining the
restriction. Removal of the drug several hours postinfection released the block.
Similarly, Vpx-containing virus-like particles and deoxynucleosides added to the
cells more than 24 h postinfection released the SAMHD1-mediated block. Taken
together, these findings support deoxynucleoside triphosphate pool depletion as
the primary mechanism of SAMHD1 restriction and argue against a nucleolytic
mechanism, which would not be reversible. MLN4924 is a first-in-class cancer drug that inhibits the Nedd8-activating
enzyme (NAE). Herein, we report that MLN4924 inhibits Vpx/Vpr-induced SAMHD1
degradation by inhibiting the neddylation of E3 ubiquitin ligase and blocks
macaque simian immunodeficiency virus (SIVmac) replication in myeloid cells.
SAMHD1 is required for MLN4924-mediated SIVmac inhibition. Our findings indicate
the potential efficacy of inhibiting neddylation as an antiretroviral strategy
and identify the readily available anticancer drug MLN4924 as a candidate agent
for that purpose. Author information:
(1)1] Cancer Institute, Fudan University Shanghai Cancer Center; Collaborative
Innovation Center of Cancer Medicine; Department of Oncology, Shanghai Medical
College, Fudan University, Shanghai, China [2] Department of Immunology, School
of Basic Medical Sciences, Fudan University, Shanghai, China [3] Department of
Pancreas and Hepatobiliary Surgery, Fudan University Shanghai Cancer Center,
Shanghai Medical College, Fudan University, Shanghai, China.
(2)1] Cancer Institute, Fudan University Shanghai Cancer Center; Collaborative
Innovation Center of Cancer Medicine; Department of Oncology, Shanghai Medical
College, Fudan University, Shanghai, China [2] Department of Immunology, School
of Basic Medical Sciences, Fudan University, Shanghai, China.
(3)Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical
Sciences and School of Life Sciences, East China Normal University, Shanghai,
China.
(4)State Key Laboratory of Pharmaceutical Biotechnology, Department of
Biochemistry, Nanjing University, Nanjing, China.
(5)Cancer Institute, Fudan University Shanghai Cancer Center; Collaborative
Innovation Center of Cancer Medicine; Department of Oncology, Shanghai Medical
College, Fudan University, Shanghai, China.
(6)Department of Pancreas and Hepatobiliary Surgery, Fudan University Shanghai
Cancer Center, Shanghai Medical College, Fudan University, Shanghai, China.
(7)College of Pharmacy, Seoul National University, Seoul, Korea.
(8)AntiCancer Biotech Beijing Co. Ltd, Beijing, China.
(9)Department of Immunology, School of Basic Medical Sciences, Fudan University,
Shanghai, China.
(10)Department of Genomic Medicine, University of Texas MD Anderson Cancer
Center, Houston, TX, USA.
(11)1] Department of Surgery, University of California, San Diego, CA, USA [2]
AntiCancer, Inc., San Diego, CA, USA. MLN4924 is an investigational small-molecule inhibitor of the Nedd8-activating
enzyme currently in phase I clinical trials. MLN4924 induces DNA damage via
rereplication in most cell lines. This distinct mechanism of DNA damage may
affect its ability to combine with standard-of-care agents and may affect the
clinical development of MLN4924. As such, we studied its interaction with other
DNA-damaging agents. Mitomycin C, cisplatin, cytarabine, UV radiation, SN-38,
and gemcitabine demonstrated synergy in combination with MLN4924 in vitro. The
combination of mitomycin C and MLN4924 was shown to be synergistic in a mouse
xenograft model. Importantly, depletion of genes within the ataxia
telangiectasia and Rad3 related (ATR) and BRCA1/BRCA2 pathways, chromatin
modification, and transcription-coupled repair reduced the synergy between
mitomycin C and MLN4924. In addition, comet assay demonstrated increased DNA
strand breaks with the combination of MLN4924 and mitomycin C. Our data suggest
that mitomycin C causes stalled replication forks, which when combined with
rereplication induced by MLN4924 results in frequent replication fork
collisions, leading to cell death. This study provides a straightforward
approach to understand the mechanism of synergy, which may provide useful
information for the clinical development of these combinations. PURPOSE: New therapies are urgently needed for patients with acute myelogenous
leukemia (AML). The novel NEDDylation inhibitor MLN4924 (pevonedistat) has
demonstrated significant preclinical antileukemic activity and preliminary
efficacy in patients with AML in a phase I trial. On the basis of its
antimyeloid and DNA-damaging properties, we investigated the ability of MLN4924
to augment conventional cytarabine (ara-C) therapy.
EXPERIMENTAL DESIGN: The effects of MLN4924/ara-C on viability, clonogenic
survival, apoptosis, DNA damage, and relevant pharmacodynamic targets were
determined. The efficacy and pharmacodynamics of MLN4924/ara-C were assessed in
an AML xenograft model.
RESULTS: Cotreatment of AML cell lines and primary patient specimens with
MLN4924 and ara-C led to diminished clonogenic survival, increased apoptosis,
and synergistic levels of DNA damage. RNAi demonstrated that stabilization of
CDT-1, an event previously shown to mediate the DNA-damaging effects of MLN4924,
was not a key regulator of sensitivity to the MLN4924/ara-C combination. Global
metabolic profiling revealed that MLN4924 disrupts nucleotide metabolism and
depletes intracellular nucleotide pools in AML cells. Subsequent experiments
showed that MLN4924 promoted increased incorporation of ara-C into the DNA of
AML cells. This effect as well as the therapeutic benefit of the MLN4924/ara-C
combination was antagonized by supplementation with the nucleotide building
block ribose. Coadministration of MLN4924 and ara-C to mice bearing FLT3-ITD(+)
AML xenografts stably inhibited disease progression and increased DNA damage in
vivo.
CONCLUSIONS: Our findings provide strong rationale for clinical investigation of
the MLN4924/ara-C combination and establish a new link between therapeutic
inhibition of NEDDylation and alterations in nucleotide metabolism. Clin Cancer
Res; 21(2); 439-47. ©2014 AACR. MLN4924, a small molecule inhibitor of NEDD8 activating enzyme (NAE), has been
reported to elicit an anti-tumor effect on various maligcies. In this study,
we investigated the anti-tumor effect of MLN4924 in human urothelial carcinoma
(UC) in vitro and in vivo by using three human UC cell lines of various grading
(T24, NTUB1 and RT4). The impact of MLN4924 on UC cells was determined by
measuring viability (MTT), proliferation (BrdU incorporation), cell cycle
progression (flow cytometry with propidium iodide staining) and apoptosis (flow
cytometry with annexin V-FITC labeling). The cell cycle regulatory molecules,
apoptosis-related molecules, and cell stress-related proteins were examined by
Western blotting. The influence of tumor cell migration and invasion was
analyzed by Transwell and wound healing assays. We also evaluated the effects of
MLN4924 on tumor growth by a SCID xenograft mouse model. The data show that
MLN4924 induced dose-dependent cytotoxicity, anti-proliferation, anti-migration,
anti-invasion and apoptosis in human UC cells, accompanied by activations of
Bad, phospho-histone H2A.X, caspase-3, 7 and PARP, decreased level of
phospho-Bcl2, and caused cell cycle retardation at the G2M phase. Moreover,
MLN4924 activated endoplasmic reticulum stress-related molecules (caspase-4,
phospho-eIF2α, ATF-4 and CHOP) and other stress responses (JNK and c-Jun
activations). Finally, we confirmed MLN4924 inhibited tumor growth in a UC
xenograft mouse model with minimal general toxicity. We concluded that MLN4924
induces apoptosis and cell cycle arrest, as well as activation of cell stress
responses in human UC. These findings imply MLN4924 provides a novel strategy
for the treatment of UC. |
Which protein has been found to interact with phospholamban (PLN) and is also an anti-apoptotic protein? | Phospholamban interacts with HAX-1, a mitochondrial protein with anti-apoptotic function.The discovery of the PLN/HAX-1 interaction therefore unveils an important new link between Ca(2+) homeostasis and cell survival, with significant therapeutic potential. | Phospholamban (PLN) is a key regulator of Ca(2+) homeostasis and contractility
in the heart. Its regulatory effects are mediated through its interaction with
the sarcoplasmic reticulum Ca(2+)-ATPase, (SERCA2a), resulting in alterations of
its Ca(2+)-affinity. To identify additional proteins that may interact with PLN,
we used the yeast-two-hybrid system to screen an adult human cardiac cDNA
library. HS-1 associated protein X-1 (HAX-1) was identified as a PLN-binding
partner. The minimal binding regions were mapped to amino acid residues 203-245
for HAX-1 and residues 16-22 for PLN. The interaction between the two proteins
was confirmed using GST-HAX-1, bound to the glutathione-matrix, which
specifically adsorbed native PLN from human or mouse cardiac homogenates, while
in reciprocal binding studies, recombit His-HAX-1 bound GST-PLN. Kinetic
studies using surface plasmon resoce yielded a K(D) of approximately 1 muM as
the binding affinity for the PLN/HAX-1 complex. Phosphorylation of PLN by
cAMP-dependent protein kinase reduced binding to HAX-1, while increasing
concentrations of Ca(2+) diminished the PLN/HAX-1 interaction in a
dose-dependent manner. HAX-1 concentrated to mitochondria, but upon transient
co-transfection of HEK 293 cells with PLN, HAX-1 redistributed and co-localized
with PLN at the endoplasmic reticulum. Analysis of the anti-apoptotic function
of HAX-1 revealed that the presence of PLN enhanced the HAX-1 protective effects
from hypoxia/reoxygenation-induced cell death. These findings suggest a possible
link between the Ca(2+) handling by the sarcoplasmic reticulum and cell survival
mediated by the PLN/HAX-1 interaction. Intracellular calcium is a major coordinator of numerous aspects of cellular
physiology, including muscle contractility and cell survival. In cardiac muscle,
aberrant Ca(2+) cycling has been implicated in a range of pathological
conditions including cardiomyopathies and heart failure. The sarco(endo)plasmic
reticulum Ca(2+) transport adenosine triphosphatase (SERCA2a) and its regulator
phospholamban (PLN) have a central role in modulating Ca(2+) homeostasis and,
therefore, cardiac function. Herein, we discuss the mechanisms through which
SERCA2a and PLN control cardiomyocyte function in health and disease. Emphasis
is placed on our newly identified PLN-binding partner HS-1-associated protein
X-1 (HAX-1), which has an anti-apoptotic function and presents with numerous
similarities to Bcl-2. Recent evidence indicates that proteins of the Bcl-2
family can influence ER Ca(2+) content, a critical determit of cellular
sensitivity to apoptosis. The discovery of the PLN/HAX-1 interaction therefore
unveils an important new link between Ca(2+) homeostasis and cell survival, with
significant therapeutic potential. Phospholamban (PLN) is a phosphoprotein in cardiac sarcoplasmic reticulum (SR)
that is a reversible regulator of the Ca(2) (+)-ATPase (SERCA2a) activity and
cardiac contractility. Dephosphorylated PLN inhibits SERCA2a and PLN
phosphorylation, at either Ser(16) by PKA or Thr(17) by Ca(2)
(+)-calmodulin-dependent protein kinase (CaMKII), reverses this inhibition.
Through this mechanism, PLN is a key modulator of SR Ca(2) (+) uptake, Ca(2) (+)
load, contractility, and relaxation. PLN phosphorylation is also the main
determit of β1-adrenergic responses in the heart. Although phosphorylation of
Thr(17) by CaMKII contributes to this effect, its role is subordinate to the
PKA-dependent increase in cytosolic Ca(2) (+), necessary to activate CaMKII.
Furthermore, the effects of PLN and its phosphorylation on cardiac function are
subject to additional regulation by its interacting partners, the anti-apoptotic
HAX-1 protein and Gm or the anchoring unit of protein phosphatase 1. Regulation
of PLN activity by this multimeric complex becomes even more important in
pathological conditions, characterized by aberrant Ca(2) (+)-cycling. In this
scenario, CaMKII-dependent PLN phosphorylation has been associated with
protective effects in both acidosis and ischemia/reperfusion. However, the
beneficial effects of increasing SR Ca(2) (+) uptake through PLN phosphorylation
may be lost or even become deleterious, when these occur in association with
alterations in SR Ca(2) (+) leak. Moreover, a major characteristic in human and
experimental heart failure (HF) is depressed SR Ca(2) (+) uptake, associated
with decreased SERCA2a levels and dephosphorylation of PLN, leading to decreased
SR Ca(2) (+) load and impaired contractility. Thus, the strategy of altering
SERCA2a and/or PLN levels or activity to restore perturbed SR Ca(2) (+) uptake
is a potential therapeutic tool for HF treatment. We will review here the role
of CaMKII-dependent phosphorylation of PLN at Thr(17) on cardiac function under
physiological and pathological conditions. |
Is long QT syndrome a cause for sudden cardiac death in athletes? | One of several causes of sudden cardiac death in athletes is long QT syndrome | Sudden death is rare in the young athlete. The causes may vary. In the US,
hypertrophic cardiomyopathy plays the predomit role whereas in Europe right
ventricular arrhythmogenic dysplasia and atherosclerosis of the coronary
arteries are more frequent. Other causes such as congenital anomalies of the
coronary vessels, myocarditis, Marfan's disease, the long QT, the Brugada and
the Wollf-Parkinson-White syndromes exist, but are rare. Attentive
preparticipation screening (clinical history and medical examination) is
mandatory in all future young athletes. Cardiac arrhythmias are the reason of the most sudden deaths in athletes. The
annual risk of sudden death at athletes is between 5 to 10 per one million.
Benign arrhythmia including bradyarrhythmias, atrial and ventricular premature
contractions are common in the athletes. Supraventricular arrhythmias such as
atrial fibrillation, nodal reciprocal entrant tachycardia and
Wolff-Parkinson-White syndrome are less common. Perhaps the rarest and the most
dangerous arrhythmias are ventricular arrhythmias, among them arrhythmias
secondary to hypertrophic cardiomyopathy, arrhythmogenic right ventricular
dysplasia, long QT syndrome, and anomalous origin of coronary arteries.
Asymptomatic bradyarrhythmias (if the heart rate in bradyarrhythmia appropriate
increases with exercise), supraventricularis tachycardias, and atrial premature
contractions without structural heart disease are not the contraindication to
sports Athletes with premature ventricular contraction, nonsustained ventricular
tachycardia and non structural heart disease are without athletic restrictions
as long as the arrhythmias do not worsen and they not cause dyspnea or
presyncope during exertion. Frequent or multiform premature ventricular
contraction or sustained ventricular tachycardia indicate a higher risk, and all
participation in athletic should be restricted. The congenital long QT syndrome (LQTS) is caused by cardiac ion channel
mutations, which predispose young individuals to sudden cardiac death often
related to exercise. The issue of LQTS and sports participation has received
significant publicity due to reports of sudden death in young competitive
athletes. This article reviews the pathophysiology, clinical characteristics,
and management of LQTS in the physically active and athletic population. In athletes under the age of 35 years the incidence of sudden death is low, most
causes to be due to ventricular arrhythmias, usually provoked by exertion, and
nearly always occur in the presence of structural heart disease or abnormalities
in the conduction system. The most common structural disease is hypertrophic
cardiomyopathy followed by coronary artery anomalies, idiopathic dilated
cardiomyopathy, arrhythmogenic right ventricular dysplasia, aortic stenosis,
myocarditis, the Wolff-Parkinson-White syndrome, and long QT syndrome. The
evaluation of athletes with symptoms of cardiac arrhythmias, syncope, family
history of sudden death require a complete cardiac workup. If they have
documented hypertrophic cardiomyopathy, arrhythmogenic right ventricular
dysplasia, idiopathic dilated cardiomyopathy, long QT syndrome, family history
presentation with sudden death, and septal thickness greater than 20 mm
competitive athletics are generally prohibited. In athletes with asymptomatic
bradyarrhythmia, supraventricular tachycardias and atrial premature contractions
without structural heart disease all competitive sports are allowed if heart
rate in bradyarrhythmia appropriately increases with exercise. Athletes with
premature ventricular contraction, nonsustained ventricular tachycardia and non
structural heart disease are without athletic restriction as long as the
arrhythmia does not worsen on exertion and cause dyspnea, presyncope or syncope. INTRODUCTION: Sudden cardiac death in athletes is a growing problem, despite the
huge existing knowledge in medicine and sports.
EFFECTS OF VIGOROUS PHYSICAL ACTIVITY: In response to vigorous physical
activity, the body undergoes profound morphologic and functional changes. These
changes are usually healthy, but sometimes may gravitate to some cardiac
diseases. But still, most saudden cardiac deaths are due to previous unknown
diseases.
CAUSES OF SUDDEN CARDIAC DEATH: The most common cause of sudden cardiac death in
athletes is hypertrophic cardiomyopathy. Other reasons are congenital coronary
artery anomalies, nivocarditis, dilatative cardiomyopathy, arrhythmogenic
cardiomyopathy of the right ventricle, sarcoidosis, mitral valve prolapse,
aortic valve stenosis, atherosclerosis, long QT syndrome, and blunt impact to
the chest.
CONCLUSION: Bearing in mind the above mentioned, more frequent physical
examinations of athletes are recommended. Cardiovascular diseases account for 40% of all deaths in the Western countries,
and nearly two thirds of them occur suddenly. Young people (<35 years) are not
spared from sudden death (SD) with a rate of 1/100,000 per year. Effort is a
trigger with a threefold risk in athletes vs. nonathletes, and sports
disqualification is by itself life-saving in people with underlying concealed
cardiovascular diseases. Several culprits of cardiac SD may be identified at
postmortem and atherosclerotic coronary artery disease is the leading cause (25%
of SD cases in the young), mostly consisting of a single obstructive plaque with
fibrocellular intimal proliferation. However, the spectrum of cardiovascular
substrates is wide and include also congenital diseases of the coronary arteries
(mainly anomalous origin), myocardium (arrhythmogenic and hypertrophic
cardiomyopathies, myocarditis), valves (aortic stenosis and mitral valve
prolapse), and conduction system (ventricular preexcitation, accelerated
atrioventricular conduction and block). In up to 20% of cases, the heart is
grossly and histologically normal at autopsy (unexplained SD or "mors sine
materia"), and inherited ion channel diseases have been implicated (long and
short QT syndromes, Brugada syndrome, catecholaminergic polymorphic ventricular
tachycardia). Targets to treat and prevent SD in the young consist of the
following: (a) avoid triggers like effort or emotion, (b) inhibit the onset of
arrhythmias with drugs or ablation, (c) switch off arrhythmias with
defibrillator, and (d) hinder the recurrence of the disease with genetic
counseling and/or therapy. In vivo detection of cardiomyopathies is nowadays
feasible by electrocardiogram and/or echocardiography, which resulted in a sharp
decline of SD in the athletes in Italy, thanks to obligatory preparticipation
screening for sport activity. Genetic screening could play a pivotal role in
early detection of asymptomatic mutation carriers of cardiovascular diseases at
risk of SD. Sudden cardiac death (SCD) in young athletes is generally caused by inherited
cardiac disorders. While these events are relatively few compared to other
cardiac deaths, they are tragic in that death occurs in a young, otherwise
healthy person. The genetic abnormalities most associated with SCD are
hypertrophic cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy,
long QT syndrome, Brugada syndrome, and catecholaminergic polymorphic
ventricular tachycardia. As a result of growing awareness that these deaths can
be prevented, guidelines have been issued in both Europe and the United States
to help screen and determine qualification for young persons who want to
participate in competitive athletics. There remains debate on the how extensive
screening should be, in particular over the use of the 12-lead electrocardiogram
(ECG), with European guidelines mandating ECG and United States guidelines not
recommending routine use of the ECG. Sudden death in the young is rare. About 25% of cases occur during sports. Most
young people with sudden cardiac death (SCD) have underlying heart disease, with
hypertrophic cardiomyopathy and coronary artery anomalies being commonest in
most series. Arrhythmogenic right ventricular dysplasia and long QT syndrome are
the most common primary arrhythmic causes of SCD. It is estimated that early
cardiopulmonary resuscitation and widespread availability of automatic external
defibrillators could prevent about a quarter of pediatric sudden deaths. Sudden cardiac death is the leading cause of mortality among young athletes with
an incidence of 1-2 per 100,000 athletes per annum. It is described as 'an event
that is non-traumatic, non-violent, unexpected, and resulting from sudden
cardiac arrest within six hours of previously witnessed normal health'. Most
predisposed athletes have no symptoms and there is no warning for the impending
tragic event. The majority of cases are caused by an underlying structural
cardiac abnormality, most commonly hypertrophic cardiomyopathy. More recently,
the understanding of non-structural causes such as long QT syndrome and Brugada
syndrome has grown and diagnostic criteria have been developed. This review
presents the known aetiologies of sudden cardiac death among athletes and
outlines their identification and management including implications for future
sporting participation as laid out in the consensus documents produced by the
European Society of Cardiology and the 36th Bethesda Conference. Athletic activity is associated with an increased risk of sudden death for
individuals with some congenital or acquired heart disorders. This review
considers in particular the causes of death affecting athletes below 35 years of
age. In this age group the largest proportion of deaths are caused by diseases
with autosomal domit inheritance such as hypertrophic cardiomyopathy,
arrhythmogenic right ventricular cardiomyopathy, long QT-syndrome, and Marfan's
syndrome. A policy of early cascade-screening of all first-degree relatives of
patients with these disorders will therefore detect a substantial number of
individuals at risk. A strictly regulated system with preparticipation screening
of all athletes following a protocol pioneered in Italy, including school-age
children, can also detect cases caused by sporadic new mutations and has been
shown to reduce excess mortality among athletes substantially. Recommendations
for screening procedure are reviewed. It is concluded that ECG screening ought
to be part of preparticipation screening, but using criteria that do not cause
too many false positives among athletes. One such suggested protocol will show
positive in approximately 5% of screened individuals, among whom many will be
screened for these diseases. On this point further research is needed to define
what kind of false-positive and false-negative rate these new criteria result
in. A less formal system based on cascade-screening of relatives, education of
coaches about suspicious symptoms, and preparticipation questionnaires used by
athletic clubs, has been associated over time with a sizeable reduction in
sudden cardiac deaths among Swedish athletes, and thus appears to be worth
implementing even for junior athletes not recommended for formal
preparticipation screening. It is strongly argued that in families with
autosomal domit disorders the first screening of children should be carried
out no later than 6 to 7 years of age. |
What is the clinical value of MammaPrint? | MammaPrint has a prognostic value for distant metastasis and death, as well as predictive value for response to adjuvant chemotherapy in patients with breast cancer. However, the EGAPP Working Group found no evidence regarding the clinical utility of the MammaPrint. | PURPOSE: The clinical and economic data for the two currently available
gene-expression assays are reviewed.
SUMMARY: Two gene-expression assays, used to determine the risk of breast cancer
recurrence in patients with stage I or II node-negative breast cancer, are
currently available. Oncotype DX is an assay performed on RNA extracted from
paraffin-embedded tumor tissue. It analyzes the expression of 21 genes: 16
cancer-related genes and 5 reference genes. The results are used to calculate a
recurrence score to identify the likelihood of cancer recurrence in patients
treated with tamoxifen. The results of two studies evaluating the ability of
Oncotype DX to predict the risk of breast cancer recurrence suggest that
patients with ER-positive, node-negative breast cancer and a low recurrence
score may need only adjuvant treatment with tamoxifen, while intermediate- and
high-risk patients may require additional treatment with adjuvant chemotherapy.
MammaPrint, an oligonucleotide microassay performed on fresh-frozen tumor
samples, analyzes the expression of 70 genes. Studies have found that MammaPrint
allows young patients (<61 years) with early-stage breast cancer to be
categorized as having a high or low risk of distant metastasis. High-risk
patients may then be managed with more aggressive therapy.
CONCLUSION: Two gene-expression assays, Oncotype DX and MammaPrint, have been
developed to determine the risk of breast cancer recurrence in patients with
stage I or II node-negative breast cancer. In the future, these tests may be
useful in determining the need for systemic adjuvant therapy in such patients. The 70-gene signature (MammaPrint) is a prognostic tool used to guide adjuvant
treatment decisions. The aim of this study was to assess its value to predict
chemosensitivity in the neoadjuvant setting. We obtained the 70-gene profile of
stage II-III patients prior to neoadjuvant chemotherapy and classified the
prognosis-signatures. Pathological complete remission (pCR) was used to measure
chemosensitivity. Among 167 patients, 144 (86%) were having a poor and 23 (14%)
a good prognosis-signature. None of the good prognosis-signature patients
achieved a pCR (0/23), whereas 29/144 patients (20%) in the poor
prognosis-signature group did (P = 0.015). All triple-negative tumors (n = 38)
had a poor prognosis-signature. Within the non triple-negative subgroup, the
response of the primary tumor remained associated with the classification of the
prognosis-signature (P = 0.023). A pCR is unlikely to be achieved in tumors that
have a good prognosis-signature. Tumors with a poor prognosis-signature are more
sensitive to chemotherapy. BACKGROUND: The majority of breast cancer patients are postmenopausal women who
are increasingly being offered adjuvant chemotherapy. Since the beneficial
effect of chemotherapy in postmenopausal patients predomitly occurs in the
first 5 years after diagnosis, a prognostic marker for early events can be of
use for adjuvant treatment decision making. The aim of this study was to
evaluate the prognostic value of the 70-gene prognosis signature for early
events in postmenopausal patients.
METHODS: Frozen tumor samples from 148 patients aged 55-70 years were selected
(T1-2, N0) and classified by the 70-gene prognosis signature (MammaPrint) into
good or poor prognosis. Eighteen percent received hormonal therapy.
RESULTS: Breast cancer-specific survival (BCSS) at 5 years was 99% for the
good-prognosis signature versus 80% for the poor-prognosis signature group (P =
0.036). The 70-gene prognosis signature was a significant and independent
predictor of BCCS during the first 5 years of follow-up with an adjusted hazard
ratio of 14.4 (95% confidence interval 1.7-122.2; P = 0.01) at 5 years.
CONCLUSION: The 70-gene prognosis signature can accurately select postmenopausal
patients at low risk of breast cancer-related death within 5 years of diagnosis
and can be of clinical use in selecting postmenopausal women for adjuvant
chemotherapy. OBJECTIVE: van't Veer and colleagues developed a 70-gene prognosis profile known
as MammaPrint to identify breast cancer patients who were at low risk of
developing metastases. We evaluated the prognostic value of the 70-gene
MammaPrint profile in Japanese women with node-negative breast cancer.
METHODS: Frozen tumour samples from 102 eligible node-negative breast cancer
patients aged 70 or younger were characterized with the MammaPrint array. The
patients were treated with breast-conserving therapy or mastectomy with axillary
lymph node dissection between December 1998 and August 2001. About 73 percent
received adjuvant hormonal therapy and 28 percent received adjuvant
chemotherapy. The gene expression profiles obtained by MammaPrint classified the
patients as high- or low-genomic risk. The median follow-up was 7.1 years.
RESULTS: Among the 102 patients, 20 (20%) were classified as low-genomic risk
and 82 (80%) were classified as high-genomic risk. The probability of distant
metastasis-free survival at five years was 100% for the low-risk group and 94%
for the high-risk group.
CONCLUSIONS: The 70-gene MammaPrint prognosis profile accurately identified
Japanese breast cancer patients at low risk of developing recurrences. In fact,
100% of the individuals in the low-risk category remained metastasis-free for
the duration of the observation period. Recommendation of systemic adjuvant therapy and choice of optimal agents for
early-stage breast cancer remains a challenge. Adjuvant therapy is indicated on
the assumption of residual micrometastatic disease. Adjuvant assessment tools
for prognosis and prediction of treatment benefit, including Adjuvant! Online,
the St Gallen Consensus, Oncotype DX(®) and MammaPrint(®), aid clinical decision
making. However, all of these tools have limitations that must be considered in
their judicious application. Clinicopathological based tools are critically
dependent on accurate, standardized measurement of parameters. Multigene tools
are appealing for their objectivity and reproducibility, particularly regarding
analysis of proliferation, but these approaches still overlook the biological
heterogeneity within tumors evidenced by distinct cell subpopulations with
different genomic patterns and function. The greatest treatment challenge
remains for patients assessed as intermediate risk of relapse, a problem not
overcome by multigene tools. Remarkable diversity in breast cancer dictates that
adjuvant management must be biologically driven. Future identification of
predictive biomarkers for specific chemotherapy sensitivity may allow targeted
use of available agents, including anthracyclines, taxanes and DNA damaging
agents. The presence of drug targets and targetable signaling pathways, rather
than molecularly defined subgroups, may ultimately drive treatment decisions. PURPOSE: A 70-gene prognostic signature has prognostic value in patients with
node-negative breast cancer in Europe. This diagnostic test known as
"MammaPrint™ (70-gene prognostic signature)" was recently validated and
implementation was feasible. Therefore, we assessed the 70-gene prognostic
signature in Korean patients with breast cancer. We compared the risk predicted
by the 70-gene prognostic signature with commonly used clinicopathological
guidelines among Korean patients with breast cancer. We also analyzed the
70-gene prognostic signature and clinicopathological feature of the patients in
comparison with a previous validation study.
METHODS: Forty-eight eligible patients with breast cancer (clinical T1-2N0M0)
were selected from four hospitals in Korea. Fresh tumor samples were analyzed
with a customized microarray for the 70-gene prognostic signature. Concordance
between the risk predicted by the 70-gene prognostic signature and risk
predicted by commonly used clinicopathological guidelines (St. Gallen
guidelines, National Institutes of Health [NIH] guideline, and Adjuvant! Online)
was evaluated.
RESULTS: Prognosis signatures were assessed in 36 patients. No significant
differences were observed in the clinicopathological features of patients
compared with previous studies. The 70-gene prognosis signature identified five
(13.9%) patients with a low-risk prognosis signature and 31 (86.1%) patients
with a high-risk prognosis signature. Clinical risk was concordant with the
prognosis signature for 29 patients (80.6%) according to the St. Gallen
guidelines; 30 patients (83.4%) according to the NIH guidelines; and 23 patients
(63.8%) according to the Adjuvant! Online. Our results were different from
previous validation studies in Europe with about a 40% low-risk prognosis and
about a 60% high-risk prognosis. The high incidence in the high-risk group was
consistent with data in Japan.
CONCLUSION: The results of 70-gene prognostic signature of Korean patients with
breast cancer were somewhat different from those identified in Europe. This
difference should be studied as whether there is a gene disparity between Asians
and Europeans. Further large-scale studies with a follow-up evaluation are
required to assess whether the use of the 70-gene prognostic signature can
predict the prognosis of Korean patients with breast cancer. HINTERGRUND: Ziel dieser Arbeit war die Evaluierung der 70-Gen-Prognose-Signatur
MammaprintTM bei Patientinnen ≥ 60 Jahre mit einem invasiven Mammakarzinom.
PATIENTEN UND METHODEN: 60 Patientinnen wurden für diese prospektive Studie
rekrutiert. Einschlusskriterien waren: pT1c-3, pN0–1a, Grading 2/3,
Hormonrezeptor-Positivität und HER2-negativer Tumor. Das klinische Risikoprofil
wurde mit dem Programm Adjuvant! Online (AOL) eingeschätzt.
ERGEBNISSE: 38 Frauen (63%) wurden durch die 70-Gen-Signatur als
Niedrigrisiko-Patienten eingestuft; demgegenüber stehen 22 (37%) in der
Hochrisiko-Gruppe. Beim Vergleich zwischen den Niedrigund Hochrisiko-Gruppen
wurde kein statistisch signifikanter Unterschied für die konventionellen
Prognoseparameter gefunden, insbesondere nicht für Ki-67. In der AOL-Analyse
wurden 33 Patientinnen (55%) als Hochrisiko-Patienten eingestuft, von denen 20
ein diskordantes 70-Gen-Signaturergebnis hatten. Eine Diskordanz zwischen der
70-Gen-Signatur und dem AOL-Ergebnis wurde bei 48% der Patientinnen ermittelt.
Diese Rate liegt höher als in früheren Publikationen. Die Kombination von
klinisch-pathologischer Risikoeinstufung und Gensignatur führte bei 11
Patientinnen (18%) zu einer Änderung der adjuvanten systemischen
Therapieempfehlung.
SCHLUSSFOLGERUNGEN: Die 70-Gen-Signatur könnte bei älteren Frauen mit einem
mittleren Risiko ein Zusatzkriterium für bzw. gegen eine adjuvante
Chemotherapieempfehlung sein. Die konventionellen klinischpathologischen
Parameter korrelierten nicht mit der 70-Gen-Signatur für diese Patientinnen. |
Is protein M3/6 a dual specificity phosphatase? | M3/6 (DUSP8) is a dual-specificity phosphatase implicated in the dephosphorylation and inactivation of JNK and, to a lesser extent, p38 MAPKs. | Treatment of leukemic cells with phorbol 12-myristate 13-acetate (PMA) induces a
short-lived phosphorylation and activation of stress-activated protein kinase
(SAPK) and cellular differentiation. To investigate whether the rapid
deactivation of SAPK results from dephosphorylation by dual-specificity
phosphatases (DSPs), we studied regulation of the DSP hVH5 and its murine
orthologue M3/6 in K562 human leukemia cells. PMA treatment rapidly induced hVH5
transcripts in these cells, and induced expression of M3/6 completely inhibited
PMA-stimulated phosphorylation of SAPK, suggesting a feedback loop to control
SAPK activity. Using both stable cell lines and transient transfection we
demonstrate that activation of SAPK rapidly stimulated phosphorylation of M3/6.
This phosphorylation did not regulate the half-life of total cellular M3/6. hVH5
and M3/6 shares with all sequenced mammalian DSPs an amino acid motif, XILPXLXL,
located approximately 80 amino acids from the active site. The hVH5-M3/6
sequence, RILPHLYL, shares significant homology with the SAPK binding site of
the c-Jun protein, called the delta domain. This motif was found to be important
for DSP function, because deletion of RILPHLYL inhibits SAPK-mediated
phosphorylation of M3/6, and deletion of this sequence or mutation of the LYL
portion blocks the ability of this phosphatase to dephosphorylate SAPK. Cells respond to stresses such as osmotic shock and heat shock by activating
stress-activated protein kinases (SAPKs), including c-Jun N-terminal kinase
(JNK) [1]. Activation of JNK requires phosphorylation of threonine and tyrosine
residues in the TPY activation loop motif [2, 3] and can be reversed by the
removal of either phosphate group. Numerous JNK phosphatases including
dual-specificity phosphatases [4, 5], have been identified. Many stimuli
activate JNK by increasing its rate of phosphorylation; however, JNK
dephosphorylation is inhibited in cells after heat shock [6], suggesting that a
JNK phosphatase(s) is inactivated. M3/6 is a dual-specificity phosphatase
selective for JNK [7, 8]. We have previously expressed M3/6 in the mouse bone
marrow cell line BAF3 in order to show that JNK activation by IL-3 is necessary
for cell survival and proliferation [9]. Here we report that M3/6 dissociates
from JNK and appears in an insoluble fraction after heat shock. These data
identify M3/6 as a JNK phosphatase that is inactivated by heat shock and provide
a molecular mechanism for the activation of JNK by heat shock. Stress signals elicit a wide variety of cellular responses, many of which
converge on the phosphorylation of JNK and p38 kinases, the activation of which
has been well-characterized. How these kinases are switched off by
dephosphorylation is not well understood. Here we describe how diverse cellular
stresses affect differently the stability and activity of a JNK-inactivating
dual-specificity threonine-tyrosine phosphatase M3/6. Both anisomycin and
arsenite activate the JNK pathway and, in addition, inactivate the M3/6
phosphatase. However, while anisomycin treatment of cells leads to M3/6 protein
degradation, arsenite appears to inactivate M3/6 directly. These results might
have implications for the mechanism of tumour promotion by arsenic. The c-Jun N-terminal kinase (JNK) group of mitogen-activated protein kinases
(MAPKs) are activated by pleiotropic signals including environmental stresses,
growth factors, and hormones. A subset of JNK can bind to distinct scaffold
proteins that also bind upstream kinases of the JNK pathway, allowing sequential
kinase activation within a signaling module. The JNK-interacting protein-1
(JIP-1) scaffold protein specifically binds JNK, MAP kinase kinase 7, and
members of the MLK family and is essential for stress-mediated JNK activation in
neurones. Here we report that JIP-1 also binds the dual-specificity phosphatases
MKP7 and M3/6 via a region independent of its JNK binding domain. The C-terminal
region of MKP7, homologous to that of M3/6 but not other DSPs, is required for
interaction with JIP-1. When MKP7 is bound to JIP-1 it reduces JNK activation
leading to reduced phosphorylation of the JNK target c-Jun. These results
indicate that the JIP-1 scaffold protein modulates JNK signaling via association
with both protein kinases and protein phosphatases that target JNK. Polyglutamine diseases, including Huntington's disease, designate a group of
nine neurodegenerative disorders characterized by the presence of a toxic
polyglutamine expansion in specific target proteins. Using cell and mouse
models, we have shown that expanded polyglutamine led to activation of the
stress kinase JNK and the transcription factor AP-1, which are implicated in
neuronal death. Polyglutamine expansion-induced stress shared common features
with protein-damaging stress such as heat shock, because activation of JNK
involved inhibition of JNK phosphatase activities. Indeed, expanded
polyglutamine impaired the solubility of the dual-specificity JNK phosphatase
M3/6. Aggregation of M3/6 by polyglutamine expansion appeared to be indirect,
because M3/6 was not recruited into polyglutamine inclusions. The heat shock
protein HSP70, which is known to inhibit JNK during the heat shock response,
suppressed polyglutamine-mediated aggregation of M3/6 and activation of JNK.
Interestingly, levels of HSP70 were down-regulated by polyglutamine expansion.
We suggest that reduction of HSP70 by expanded polyglutamine is implicated in
aggregation and inhibition of M3/6 and in activation of JNK and AP-1. JNK scaffold proteins bind JNK and upstream kinases to activate subsets of JNK
and localize activated JNK to specific subcellular sites. We previously
demonstrated that the dual specificity phosphatases (DSPs) MKP7 and M3/6 bind
the scaffold JNK-interacting protein-1 (JIP-1) and inactivate the bound subset
of JNK (1). The G protein-coupled receptor (GPCR) adaptor beta-arrestin 2 is
also a JNK3 scaffold. It binds the upstream kinases ASK1 and MKK4 and couples
stimulation of the angiotensin II receptor AT1aR to activation of a cytoplasmic
pool of JNK3. Here we report that MKP7 also binds beta-arrestin 2 via amino
acids 394-443 of MKP7, the same region that interacts with JIP-1. This region of
MKP7 interacts with beta-arrestin 2 at a central region near the JNK binding
domain. MKP7 dephosphorylates JNK3 bound to beta-arrestin 2, either following
activation by ASK1 overexpression or following AT1aR stimulation. Initial AT1aR
stimulation causes a rapid (within 5 min) dissociation of MKP7 from
beta-arrestin 2. MKP7 then reassociates with beta-arrestin 2 on endocytic
vesicles 30-60 min after initial receptor stimulation. This dynamic interaction
between phosphatase and scaffold permits signal transduction through a module
that binds both positive and negative regulators. Specific outcomes upon activation of the c-Jun N-terminal kinase (JNK) pathway
critically depend on the intensity and duration of signal transmission.
Dual-specificity phosphatases (DUSPs) play a very important role in these events
by modulating the extent of JNK phosphorylation and activation and thus
regulating cellular responses to stress. M3/6 (DUSP8) is one of the
dual-specificity protein phosphatases with distinct specificity towards JNK. It
has been shown that M3/6 itself is phosphorylated by JNK upon stimulation with
arsenite, but the role of this phosphorylation has not been investigated. In
this study, we mapped JNK-induced phosphorylation sites on M3/6 using mass
spectrometry. Phosphorylated residues Ser 515, Thr 518 and Ser 520 were
identified and site-directed mutagenesis was employed to investigate their role.
Upon arsenite stimulation, M3/6 mutated at these sites exhibited decreased
phosphorylation compared to the wild-type protein. No difference was observed in
terms of the enzyme's in vitro phosphatase activity, its substrate specificity
towards JNK isoforms, its interactions with JNK and the scaffold family of
JNK-interacting proteins (JIPs), its stability or its subcellular localization.
Interestingly, expression of M3/6 phosphorylation mutants delayed the
time-course of JNK phosphorylation and activation by arsenite. We propose that
phosphorylation of the M3/6 phosphatase by JNK in response to stress stimuli
results in attenuation of phosphatase activity and acceleration of JNK
activation. Mitogen-activated protein kinase (MAPK) cascades are involved in the regulation
of cellular proliferation, differentiation, survival, apoptosis, as well as in
inflammatory responses. Signal intensity and duration have been recognized as
crucial parameters determining MAPK signaling output. Phosphatases play a
particularly important role in this respect, by tightly controlling MAPK
phosphorylation and activation. M3/6 (DUSP8) is a dual-specificity phosphatase
implicated in the dephosphorylation and inactivation of JNK and, to a lesser
extent, p38 MAPKs and is found in a complex with these kinases, along with other
pathway components, held together by scaffold proteins. The JNK family consists
of three genes, giving rise to at least ten different splice variants. Some
functional differences between these gene products have been demonstrated, but
the underlying molecular mechanisms and the roles of individual splice variants
are still incompletely understood. We have investigated the interaction of M3/6
with JNK isoforms, as well as scaffold proteins of the JNK interacting protein
(JIP) family, in order to elucidate the contribution of M3/6 to the regulation
of distinct JNK signaling modules. M3/6 exhibited stronger binding towards JNK1β
and JNK2α isoforms and this was reflected in higher enzymatic activity towards
JNK2α2 when compared to JNK1α1 in vitro. After activation of the pathway by
exposure of cells to arsenite, the interaction of M3/6 with JNK1α and JNK3 was
enhanced, whereas that with JNK1β or JNK2α decreased. The modulation of binding
affinities was found to be independent of JNK-mediated M3/6 phosphorylation.
Furthermore, arsenite treatment resulted in an inducible recruitment of M3/6 to
JNK-interacting protein 3 (JIP3) scaffold complexes, while its interaction with
JIP1 or JIP2 was constitutive. The presented data suggest an isoform-specific
role for the M3/6 phosphatase and the dynamic targeting of M3/6 towards distinct
JNK-containing signaling complexes. The c-Jun N-terminal kinase (JNK) undergoes complete inactivation following the
intense activation induced by cerebral ischemia and reperfusion in rat
hippocampi. This study examines the molecular mechanism underlying JNK
dephosphorylation and inactivation evoked by dual-specificity phosphates
following cerebral ischemia. The results revealed upregulation of
dual-specificity phosphatase M3/6 (DUSP8) activity at 4 h of reperfusion in rat
hippocampi. This was accompanied by the dephosphorylation of JNK. The M3/6
inhibitor, anisomycin, was found to enhance JNK activity following postischemic
reperfusion, suggesting that M3/6 is closely associated with JNK inactivation
following cerebral ischemia. Cerebral ischemia also induced an increase in heat
shock protein (HSP70) levels, which is involved in the upregulation of soluble
cytoplasmic M3/6 levels. The inhibition of HSP70 using quercetin resulted in an
elevation of JNK activity by decreasing the cytoplasmic solubility of M3/6. The
findings of the current study suggest that M3/6 is implicated in the
inactivation of JNK in response to cerebral ischemia, which requires the
molecular chaperone HSP70 to facilitate the correction of folding defects. |
Are there focused databases from which you can retrieve gene expression data on renal disease? | Biological databases are used to store and edit large amount of data, created from genomics data. In the most of the cases the data are stored according to their type but there are cases of focused databases that store database on a specific disease. In the case of renal disease there are plenty of databases, for example KUPKB a collection of omics datasets, Nephromine a renal genome-wide gene expression dataset based in transcriptomics, CDKD and Proteomics Database in Chronic Kidney Disease. | BACKGROUND: Although molecular pathway information and the International HapMap
Project data can help biomedical researchers to investigate the aetiology of
complex diseases more effectively, such information is missing or insufficient
in current genetic association databases. In addition, only a few of the
environmental risk factors are included as gene-environment interactions, and
the risk measures of associations are not indexed in any association databases.
DESCRIPTION: We have developed a published association database (PADB;
http://www.medclue.com/padb) that includes both the genetic associations and the
environmental risk factors available in PubMed database. Each genetic risk
factor is linked to a molecular pathway database and the HapMap database through
human gene symbols identified in the abstracts. And the risk measures such as
odds ratios or hazard ratios are extracted automatically from the abstracts when
available. Thus, users can review the association data sorted by the risk
measures, and genetic associations can be grouped by human genes or molecular
pathways. The search results can also be saved to tab-delimited text files for
further sorting or analysis. Currently, PADB indexes more than 1,500,000 PubMed
abstracts that include 3442 human genes, 461 molecular pathways and about
190,000 risk measures ranging from 0.00001 to 4878.9.
CONCLUSION: PADB is a unique online database of published associations that will
serve as a novel and powerful resource for reviewing and interpreting huge
association data of complex human diseases. BACKGROUND: Magnaporthe oryzae, rice blast fungus, is the most devastating
pathogen of rice. It has emerged as a model phytopathogen for the study of
host-pathogen interactions. A large body of data has been generated on different
aspects of biology of this fungus and on host-pathogen interactions. However,
most of the data is scattered and is not available as a single resource for
researchers in this field.
DESCRIPTION: Genomic Resources of Magnaporthe oyzae (GROMO), is a specialized,
and comprehensive database for rice blast fungus, integrating information from
several resources. GROMO contains information on genomic sequence, mutants
available, gene expression, localization of proteins obtained from a variety of
repositories, as primary data. In addition, prediction of domains, pathways,
protein-protein interactions, sumolyation sites and biochemical properties that
were obtained after computational analysis of protein sequences have also been
included as derived data. This database has an intuitive user interface that
shall prompt the user to explore various possible information resources
available on a given gene or a protein, from a single source.
CONCLUSION: Currently, information on M. oryzae is available from different
resources like BROAD MIT Magnaporthe database, Agrobacterium
tumefaciens-mediated transformation (ATMT) M. oryzae database, Magnaporthe
grisea--Oryza sativa (MGOS) and Massive Parallel Signature Sequencing (MPSS)
databases. In the GROMO project, an effort has been made to integrate
information from all these databases, derive some new data based on the
available information analyzed by relevant programs and make more insightful
predictions to better understand the biology of M. oryzae. The database is
currently available at: http://gromo.msubiotech.ac.in/ BACKGROUND: In the post-genomic era, the development of high-throughput gene
expression detection technology provides huge amounts of experimental data,
which challenges the traditional pipelines for data processing and analyzing in
scientific researches.
RESULTS: In our work, we integrated gene expression information from Gene
Expression Omnibus (GEO), biomedical ontology from Medical Subject Headings
(MeSH) and signaling pathway knowledge from sigPathway entries to develop a
context mining tool for gene expression analysis - GEOGLE. GEOGLE offers a rapid
and convenient way for searching relevant experimental datasets, pathways and
biological terms according to multiple types of queries: including biomedical
vocabularies, GDS IDs, gene IDs, pathway names and signature list. Moreover,
GEOGLE summarizes the signature genes from a subset of GDSes and estimates the
correlation between gene expression and the phenotypic distinction with an
integrated p value.
CONCLUSION: This approach performing global searching of expression data may
expand the traditional way of collecting heterogeneous gene expression
experiment data. GEOGLE is a novel tool that provides researchers a quantitative
way to understand the correlation between gene expression and phenotypic
distinction through meta-analysis of gene expression datasets from different
experiments, as well as the biological meaning behind. The web site and user
guide of GEOGLE are available at:
http://omics.biosino.org:14000/kweb/workflow.jsp?id=00020. Because of its availability, ease of collection, and correlation with physiology
and pathology, urine is an attractive source for clinical
proteomics/peptidomics. However, the lack of comparable data sets from large
cohorts has greatly hindered the development of clinical proteomics. Here, we
report the establishment of a reproducible, high resolution method for peptidome
analysis of naturally occurring human urinary peptides and proteins, ranging
from 800 to 17,000 Da, using samples from 3,600 individuals analyzed by
capillary electrophoresis coupled to MS. All processed data were deposited in an
Structured Query Language (SQL) database. This database currently contains 5,010
relevant unique urinary peptides that serve as a pool of potential classifiers
for diagnosis and monitoring of various diseases. As an example, by using this
source of information, we were able to define urinary peptide biomarkers for
chronic kidney diseases, allowing diagnosis of these diseases with high
accuracy. Application of the chronic kidney disease-specific biomarker set to an
independent test cohort in the subsequent replication phase resulted in 85.5%
sensitivity and 100% specificity. These results indicate the potential
usefulness of capillary electrophoresis coupled to MS for clinical applications
in the analysis of naturally occurring urinary peptides. Databases which are useful for proteomic analysis of human kidney tissue and
urine have been discussed in this article. Integration of the gene-centric and
protein-centric general databases with those of human kidney tissue and urine
proteomes may open a new window for research in nephrology. Proteins present in
the kidney and urine provide basic tools for investigation of kidney function
and disease. By comparing such databases between the healthy and diseased
populations, we may be able to identify the following: proteins involved in the
development of renal disease, proteins involved in progression of CKD, or new
biomarker candidate proteins for either the development of renal disease or the
progression of CKD. BACKGROUND: Understanding the biomedical implications of data from high
throughput experiments requires solutions for effective cross-scale and
cross-domain data exploration. However, existing solutions do not provide
sufficient support for linking molecular level data to neuroanatomical
structures, which is critical for understanding high level neurobiological
functions.
RESULTS: Our work integrates molecular level data with high level biological
functions and we present results using anatomical structure as a scaffold. Our
solution also allows the sharing of intermediate data exploration results with
other web applications, greatly increasing the power of cross-domain data
exploration and mining.
CONCLUSIONS: The Flex-based PubAnatomy web application we developed enables
highly interactive visual exploration of literature and experimental data for
understanding the relationships between molecular level changes, pathways, brain
circuits and pathophysiological processes. The prototype of PubAnatomy is freely
accessible at:
[http://brainarray.mbni.med.umich.edu/Brainarray/prototype/PubAnatomy]. The International Cancer Genome Consortium (ICGC) is a collaborative effort to
characterize genomic abnormalities in 50 different cancer types. To make this
data available, the ICGC has created the ICGC Data Portal. Powered by the
BioMart software, the Data Portal allows each ICGC member institution to manage
and maintain its own databases locally, while seamlessly presenting all the data
in a single access point for users. The Data Portal currently contains data from
24 cancer projects, including ICGC, The Cancer Genome Atlas (TCGA), Johns
Hopkins University, and the Tumor Sequencing Project. It consists of 3478
genomes and 13 cancer types and subtypes. Available open access data types
include simple somatic mutations, copy number alterations, structural
rearrangements, gene expression, microRNAs, DNA methylation and exon junctions.
Additionally, simple germline variations are available as controlled access
data. The Data Portal uses a web-based graphical user interface (GUI) to offer
researchers multiple ways to quickly and easily search and analyze the available
data. The web interface can assist in constructing complicated queries across
multiple data sets. Several application programming interfaces are also
available for programmatic access. Here we describe the organization,
functionality, and capabilities of the ICGC Data Portal. Glomerular podocytes are highly differentiated epithelial cells that are key
components of the kidney filtration units. Podocyte damage or loss is the
hallmark of nephritic diseases characterized by severe proteinuria. Recent
studies implicate that hormones including glucocorticoids (ligand for
glucocorticoid receptor) and vitamin D3 (ligand for vitamin D receptor) protect
or promote repair of podocytes from injury. In order to elucidate the mechanisms
underlying hormone-mediated podocyte-protecting activity from injury, we carried
out microarray gene expression studies to identify the target genes and
corresponding pathways in response to these hormones during podocyte
differentiation. We used immortalized human cultured podocytes (HPCs) as a model
system and carried out in vitro differentiation assays followed by dexamethasone
(Dex) or vitamin D3 (VD3) treatment. Upon the induction of differentiation,
multiple functional categories including cell cycle, organelle dynamics,
mitochondrion, apoptosis and cytoskeleton organization were among the most
significantly affected. Interestingly, while Dex and VD3 are capable of
protecting podocytes from injury, they only share limited target genes and
affected pathways. Compared to VD3 treatment, Dex had a broader and greater
impact on gene expression profiles. In-depth analyses of Dex altered genes
indicate that Dex crosstalks with a broad spectrum of signaling pathways, of
which inflammatory responses, cell migration, angiogenesis, NF-κB and TGFβ
pathways are predomitly altered. Together, our study provides new information
and identifies several new avenues for future investigation of hormone signaling
in podocytes. |
What systems have been developed for the numbering of antibody residues? | The most prevalent antibody numbering systems are the Kabat system, the Chothia system as well as the IMGT numbering system. | On the basis of comparative studies of known antibody structures and sequences
it has been argued that there is a small repertoire of main-chain conformations
for at least five of the six hypervariable regions of antibodies, and that the
particular conformation adopted is determined by a few key conserved residues.
These hypotheses are now supported by reasonably successful predictions of the
structures of most hypervariable regions of various antibodies, as revealed by
comparison with their subsequently determined structures. The CH1 domains of antibodies belonging to the following five murine
immunoglobulin (Ig) classes IgG1, IgG2a, IgG2b, IgG3 and IgA have been compared.
The IgG CH1 domain structures are, as would be expected, similar overall, but
show local conformational variations. When compared with IgG CH1 domain
structures, the IgA CH1 domain displays several significant structural
differences, which are a consequence of insertions/ deletions and specific
structural constraints. In regions of structural differences in the IgG CH1
domains, the spatial correspondence of residues is not reflected by conventional
(Kabat) sequence number. Thus the sequence alignment and numbering for CH1
domains has been revised to be consistent with the three-dimensional alignments. A comparative analysis of the main-chain conformation of the L1, L2, L3, H1 and
H2 hypervariable regions in 17 immunoglobulin structures that have been
accurately determined at high resolution is described. This involves 79
hypervariable regions in all. We also analysed a part of the H3 region in 12 of
the 15 VH domains considered here. On the basis of the residues at key sites the
79 hypervariable regions can be assigned to one of 18 different canonical
structures. We show that 71 of these hypervariable regions have a conformation
that is very close to what can be defined as a "standard" conformation of each
canonical structure. These standard conformations are described in detail. The
other eight hypervariable regions have small deviations from the standard
conformations that, in six cases, involve only the rotation of a single peptide
group. Most H3 hypervariable regions have the same conformation in the part that
is close to the framework and the details of this conformation are also
described here. IMGT, the international ImMunoGeneTics information system http://imgt.cines.fr,
was created in 1989 by the Laboratoire d'ImmunoGénétique Moléculaire (LIGM)
(Université Montpellier II and CNRS) at Montpellier, France. IMGT is a high
quality integrated knowledge resource specialized in immunoglobulins (IG), T
cell receptors (TR), major histocompatibility complex (MHC) of human and other
vertebrates, and related proteins of the immune system (RPI) of any species
which belong to the immunoglobulin superfamily (IgSF) and to the MHC superfamily
(MhcSF). IMGT consists of five databases, ten on-line tools and more than 8,000
HTML pages of Web resources. IMGT provides a common access to standardized data
from genome, genetics, proteome and three-dimensional structures. The accuracy
and the consistency of IMGT data are based on IMGT-ONTOLOGY, a semantic
specification of terms to be used in immunogenetics and immunoinformatics.
IMGT-ONTOLOGY comprises six main concepts: IDENTIFICATION, CLASSIFICATION,
DESCRIPTION, NUMEROTATION, ORIENTATION and OBTENTION. Based on these concepts,
the controlled vocabulary and the annotation rules necessary for the
immunogenetics data identification, classification, description and numbering
and for the management of IMGT knowledge are defined in the IMGT Scientific
chart. IMGT is the international reference in immunogenetics and
immunoinformatics for medical research (repertoire analysis of the IG antibody
sites and of the TR recognition sites in autoimmune and infectious diseases,
AIDS, leukemias, lymphomas, myelomas), veterinary research (IG and TR
repertoires in farm and wild life species), genome diversity and genome
evolution studies of the adaptive immune responses, biotechnology related to
antibody engineering (single chain Fragment variable (scFv), phage displays,
combinatorial libraries, chimeric, humanized and human antibodies), diagnostics
(detection and follow up of residual diseases) and therapeutical approaches
(grafts, immunotherapy, vaccinology). IMGT is freely available at
http://imgt.cines.fr. IMGT/V-QUEST is the highly customized and integrated system for the standardized
analysis of the immunoglobulin (IG) and T cell receptor (TR) rearranged
nucleotide sequences. IMGT/V-QUEST identifies the variable (V), diversity (D)
and joining (J) genes and alleles by alignment with the germline IG and TR gene
and allele sequences of the IMGT reference directory. New functionalities were
added through a complete rewrite in Java. IMGT/V-QUEST analyses batches of
sequences (up to 50) in a single run. IMGT/V-QUEST describes the V-REGION
mutations and identifies the hot spot positions in the closest germline V gene.
IMGT/V-QUEST can detect insertions and deletions in the submitted sequences by
reference to the IMGT unique numbering. IMGT/V-QUEST integrates
IMGT/JunctionAnalysis for a detailed analysis of the V-J and V-D-J junctions,
and IMGT/Automat for a full V-J- and V-D-J-REGION annotation. IMGT/V-QUEST
displays, in 'Detailed view', the results and alignments for each submitted
sequence individually and, in 'Synthesis view', the alignments of the sequences
that, in a given run, express the same V gene and allele. The 'Advanced
parameters' allow to modify default parameters used by IMGT/V-QUEST and
IMGT/JunctionAnalysis according to the users' interest. IMGT/V-QUEST is freely
available for academic research at http://imgt.cines.fr. BACKGROUND: Standard numbering schemes for families of homologous proteins allow
for the unambiguous identification of functionally and structurally relevant
residues, to communicate results on mutations, and to systematically analyse
sequence-function relationships in protein families. Standard numbering schemes
have been successfully implemented for several protein families, including
lactamases and antibodies, whereas a numbering scheme for the structural family
of thiamine-diphosphate (ThDP) -dependent decarboxylases, a large subfamily of
the class of ThDP-dependent enzymes encompassing pyruvate-, benzoylformate-,
2-oxo acid-, indolpyruvate- and phenylpyruvate decarboxylases, benzaldehyde
lyase, acetohydroxyacid synthases and
2-succinyl-5-enolpyruvyl-6-hydroxy-3-cyclohexadiene-1-carboxylate synthase
(MenD) is still missing.Despite a high structural similarity between the members
of the ThDP-dependent decarboxylases, their sequences are diverse and make a
pairwise sequence comparison of protein family members difficult.
RESULTS: We developed and validated a standard numbering scheme for the family
of ThDP-dependent decarboxylases. A profile hidden Markov model (HMM) was
created using a set of representative sequences from the family of
ThDP-dependent decarboxylases. The pyruvate decarboxylase from S. cerevisiae
(PDB: 2VK8) was chosen as a reference because it is a well characterized enzyme.
The crystal structure with the PDB identifier 2VK8 encompasses the structure of
the ScPDC mutant E477Q, the cofactors ThDP and Mg(2+) as well as the substrate
analogue (2S)-2-hydroxypropanoic acid. The absolute numbering of this reference
sequence was transferred to all members of the ThDP-dependent decarboxylase
protein family. Subsequently, the numbering scheme was integrated into the
already established Thiamine-diphosphate dependent Enzyme Engineering Database
(TEED) and was used to systematically analyze functionally and structurally
relevant positions in the superfamily of ThDP-dependent decarboxylases.
CONCLUSIONS: The numbering scheme serves as a tool for the reliable sequence
alignment of ThDP-dependent decarboxylases and the unambiguous identification
and communication of corresponding positions. Thus, it is the basis for the
systematic and automated analysis of sequence-encoded properties such as
structural and functional relevance of amino acid positions, because the
analysis of conserved positions, the identification of correlated mutations and
the determination of subfamily specific amino acid distributions depend on
reliable multisequence alignments and the unambiguous identification of the
alignment columns. The method is reliable and robust and can easily be adapted
to further protein families. |
Are there any DNMT3 proteins present in plants? | Yes. The plant DOMAINS REARRANGED METHYLTRANSFERASE2 (DRM2) is a homolog of the mammalian de novo methyltransferase DNMT3. DRM2 contains a novel arrangement of the motifs required for DNA methyltransferase catalytic activity. | Chromodomains are thought to mediate protein-protein interactions between
chromatin components. We have detected a chromodomain embedded within the
catalytic region of a predicted Arabidopsis DNA methyltransferase that is
diverged from other eukaryotic enzymes. The 791 residue "chromomethylase" (CMT1)
is encoded by a floral transcript that is spliced from 20 exons and is present
at only approximately 1/10(-7) of total mRNA. Genomic sequencing reveals an
ancient haplotype split at CMT1 between Col-0 + Metz and the other ecotypes
examined. In the Col-0 + Metz haplotype, alternative mRNA processing at intron
13 truncates the coding region. In Ler, RLD, and No-0, similar truncation is
caused by insertion of an intact retrotransposon, Evelknievel, which is present
as a single copy in Ler and RLD and is currently methylated and inactive.
Evelknievel is found at this site on a single branch that connects the Ler, RLD,
and No-0 ecotypes but is absent from the genomes of all other ecotypes examined.
A stop codon within exon 6 of the Metz ecotype confirms that CMT1 is
nonessential. Nevertheless, comparison to CMT1 of Cardaminopsis arenosa, an
outcrossing relative, indicates conservation for DNA methyltransferase function.
We discuss how allelic diversity of CMT1 may reflect loosened selective
constraints in a self-fertilizing species such as Arabidopsis thaliana. DNA methylation plays a critical role in controlling states of gene activity in
most eukaryotic organisms, and it is essential for proper growth and
development. Patterns of methylation are established by de novo
methyltransferases and maintained by maintece methyltransferase activities.
The Dnmt3 family of de novo DNA methyltransferases has recently been
characterized in animals. Here we describe DNA methyltransferase genes from both
Arabidopsis and maize that show a high level of sequence similarity to Dnmt3,
suggesting that they encode plant de novo methyltransferases. Relative to all
known eukaryotic methyltransferases, these plant proteins contain a novel
arrangement of the motifs required for DNA methyltransferase catalytic activity.
The N termini of these methyltransferases contain a series of
ubiquitin-associated (UBA) domains. UBA domains are found in several ubiquitin
pathway proteins and in DNA repair enzymes such as Rad23, and they may be
involved in ubiquitin binding. The presence of UBA domains provides a possible
link between DNA methylation and ubiquitin/proteasome pathways. Plants maintain cytosine methylation at CG and non-CG residues to control gene
expression and genome stability. In a screen for Arabidopsis mutants that alter
methylation and silencing of a densely methylated endogenous reporter gene, we
recovered 11 loss-of-function alleles in the CMT3 chromomethylase gene. The cmt3
mutants displayed enhanced expression and reduced methylation of the reporter,
particularly at non-CG cytosines. CNG methylation was also reduced at repetitive
centromeric sequences. Thus, CMT3 is a key determit for non-CG methylation.
The lack of CMT homologs in animal genomes could account for the observation
that in contrast to plants, animals maintain primarily CG methylation. A cytosine DNA methyltransferase containing a chromodomain, Zea
methyltransferase2 (Zmet2), was cloned from maize. The sequence of ZMET2 is
similar to that of the Arabidopsis chromomethylases CMT1 and CMT3, with
C-terminal motifs characteristic of eukaryotic and prokaryotic DNA
methyltransferases. We used a reverse genetics approach to determine the
function of the Zmet2 gene. Plants homozygous for a Mutator transposable element
insertion into motif IX had a 13% reduction in methylated cytosines. DNA gel
blot analysis of these plants with methylation-sensitive restriction enzymes and
bisulfite sequencing of a 180-bp knob sequence showed reduced methylation only
at CpNpG sites. No reductions in methylation were observed at CpG or asymmetric
sites in heterozygous or homozygous mutant plants. Our research shows that
chromomethylase Zmet2 is required for in vivo methylation of CpNpG sequences. Proper DNA methylation patterning requires the complementary processes of de
novo methylation (the initial methylation of unmethylated DNA sequences) and
maintece methylation (the faithful replication of preexisting methylation).
Arabidopsis has two types of methyltransferases with demonstrated maintece
activity: MET1, which maintains CpG methylation and is homologous to mammalian
DNMT1, and CHROMOMETHYLASE 3 (CMT3), which maintains CpNpG (N = A, T, C, or G)
methylation and is unique to the plant kingdom. Here we describe
loss-of-function mutations in the Arabidopsis DOMAINS REARRANGED METHYLASE (DRM)
genes and provide evidence that they encode de novo methyltransferases. drm1
drm2 double mutants retained preexisting CpG methylation at the endogenous FWA
locus but blocked de novo CpG methylation that is normally associated with FWA
transgene silencing. Furthermore, drm1 drm2 double mutants blocked de novo CpNpG
and asymmetric methylation and gene silencing of the endogenous SUPERMAN (SUP)
gene, which is normally triggered by an inverted SUP repeat. However, drm1 drm2
double mutants did not show reactivation of previously established SUPERMAN
epigenetic silenced alleles. Thus, drm mutants prevent the establishment but not
the maintece of gene silencing at FWA and SUP, suggesting that the DRMs
encode the major de novo methylation enzymes affecting these genes. BACKGROUND: Going from a gene sequence to its function in the context of a whole
organism requires a strategy for targeting mutations, referred to as reverse
genetics. Reverse genetics is highly desirable in the modern genomics era;
however, the most powerful methods are generally restricted to a few model
organisms. Previously, we introduced a reverse-genetic strategy with the
potential for general applicability to organisms that lack well-developed
genetic tools. Our TILLING (Targeting Induced Local Lesions IN Genomes) method
uses chemical mutagenesis followed by screening for single-base changes to
discover induced mutations that alter protein function. TILLING was shown to be
an effective reverse genetic strategy by the establishment of a high-throughput
TILLING facility and the delivery of thousands of point mutations in hundreds of
Arabidopsis genes to members of the plant biology community.
RESULTS: We demonstrate that high-throughput TILLING is applicable to maize, an
important crop plant with a large genome but with limited reverse-genetic
resources currently available. We screened pools of DNA samples for mutations in
1-kb segments from 11 different genes, obtaining 17 independent induced
mutations from a population of 750 pollen-mutagenized maize plants. One of the
genes targeted was the DMT102 chromomethylase gene, for which we obtained an
allelic series of three missense mutations that are predicted to be strongly
deleterious.
CONCLUSIONS: Our findings indicate that TILLING is a broadly applicable and
efficient reverse-genetic strategy. We are establishing a public TILLING service
for maize modeled on the existing Arabidopsis TILLING Project. DNA methylation of cytosine residues, catalyzed by DNA methyltransferases, is
suggested to play important roles in regulating gene expression and plant
development. In this study, we isolated four wheat cDNA fragments and one cDNA
with open reading frame encoding putative DNA methyltransferase and designated
TaMET1, TaMET2a, TaMET2b, TaCMT, TaMET3, respectively. BLASTX searches and
phylogenetic analysis suggested that five cDNAs belonged to four classes (Dnmt1,
Dnmt2, CMT and Dnmt3) of DNA methyltransferase genes. TaMET2a encoded a protein
of 376 aa and contained eight of ten conserved motifs characteristic of DNA
methyltransferase. Genomic sequence of TaMET2a was obtained and found to contain
ten introns and eleven exons. The expression analysis of the five genes revealed
that they were expressed in developing seed, during germination and various
vegetative tissues, but in quite different abundance. It was interesting to note
that TaMET1 and TaMET3 mRNAs were clearly detected in dry seeds. Moreover, the
differential expression patterns of five genes were observed between wheat
hybrid and its parents in leaf, stem and root of jointing stage, some were
up-regulated while some others were down-regulated in the hybrid. We concluded
that multiple wheat DNA methyltransferase genes were present and might play
important roles in wheat growth and development. Tomato fruit cells are characterized by a strong increase in nuclear ploidy
during fruit development. Average ploidy levels increased to similar levels
(above 50C) in two distinct fruit tissues, pericarp and locular tissue. However,
ploidy profiles differed significantly between these two tissues suggesting a
tissue-specific control of endoreduplication in tomato fruit. To determine
possible relationships between endoreduplication and epigenetic mechanisms, the
methylation status of genomic DNA from pericarp and locular tissue of tomato
fruit was analysed. Pericarp genomic DNA was characterized by an increase of CG
and/or CNG methylation at the 5S and 18S rDNA loci and at gyspsy-like
retrotransposon sequences during fruit growth. A sharp decrease of the global
DNA methylation level together with a reduction of methylation at the rDNA loci
was also observed in pericarp during fruit ripening. Inversely, no major
variation of DNA methylation either global or locus-specific, was observed in
locular tissue. Thus, tissue-specific variations of DNA methylation are unlikely
to be triggered by the induction of endoreduplication in fruit tissues, but may
reflect tissue-specific ploidy profiles. Expression analysis of eight putative
tomato DNA methyltransferases encoding genes showed that one chromomethylase
(CMT) and two rearranged methyltransferases (DRMs) are preferentially expressed
in the pericarp during fruit growth and could be involved in the locus-specific
increase of methylation observed at this developmental phase in the pericarp. During embryogenesis there is a major switch from dependence upon
maternally-deposited products to reliance on products of the zygotic genome. In
animals, this so-called maternal-to-zygotic transition occurs following a period
of transcriptional quiescence. Recently, we have shown that the early embryo in
Arabidopsis is also quiescent, a state inherited from the female gamete and
linked to specific patterns of H3K9 dimethylation and TERMINAL FLOWER2 (TFL2)
localization. We also demonstrated that CHROMOMETHYLASE 3 (CMT3) is required for
H3K9 dimethylation in the egg cell and for normal embryogenesis during the first
few divisions of the zygote. Subsequent analysis of CMT3 mutants points to a key
role in egg cell reprogramming by controlling silencing in both transposon and
euchromatic regions. A speculative model of the CMT3-induced egg cell silencing
is presented here, based on these results and current data from the literature
suggesting the potential involvement of small RNAs targeted to the egg cell, a
process conceptually similar to the division of labor described in the male
gametophyte for which we show that H3K9 modifications and TFL2 localization are
reminiscent of the female gametophyte. Eukaryotic DNA cytosine methylation can be used to transcriptionally silence
repetitive sequences, including transposons and retroviruses. This silencing is
stable between cell generations as cytosine methylation is maintained
epigenetically through DNA replication. The Arabidopsis thaliana Dnmt3 cytosine
methyltransferase ortholog DOMAINS rearranged methyltransferase2 (DRM2) is
required for establishment of small interfering RNA (siRNA) directed DNA
methylation. In mammals PIWI proteins and piRNA act in a convergently evolved
RNA-directed DNA methylation system that is required to repress transposon
expression in the germ line. De novo methylation may also be independent of RNA
interference and small RNAs, as in Neurospora crassa. Here we identify a clade
of catalytically mutated DRM2 paralogs in flowering plant genomes, which in
A.thaliana we term domains rearranged methyltransferase3 (DRM3). Despite being
catalytically mutated, DRM3 is required for normal maintece of non-CG DNA
methylation, establishment of RNA-directed DNA methylation triggered by repeat
sequences and accumulation of repeat-associated small RNAs. Although the
mammalian catalytically inactive Dnmt3L paralogs act in an analogous manner,
phylogenetic analysis indicates that the DRM and Dnmt3 protein families diverged
independently in plants and animals. We also show by site-directed mutagenesis
that both the DRM2 N-terminal UBA domains and C-terminal methyltransferase
domain are required for normal RNA-directed DNA methylation, supporting an
essential targeting function for the UBA domains. These results suggest that
plant and mammalian RNA-directed DNA methylation systems consist of a
combination of ancestral and convergent features. De novo DNA methylation in Arabidopsis thaliana is catalyzed by the
methyltransferase DRM2, a homolog of the mammalian de novo methyltransferase
DNMT3. DRM2 is targeted to DNA by small interfering RNAs (siRNAs) in a process
known as RNA-directed DNA Methylation (RdDM). While several components of the
RdDM pathway are known, a functional understanding of the underlying mechanism
is far from complete. We employed both forward and reverse genetic approaches to
identify factors involved in de novo methylation. We utilized the FWA transgene,
which is methylated and silenced when transformed into wild-type plants, but
unmethylated and expressed when transformed into de novo methylation mutants.
Expression of FWA is marked by a late flowering phenotype, which is easily
scored in mutant versus wild-type plants. By reverse genetics we discovered the
requirement for known RdDM effectors AGO6 and NRPE5a for efficient de novo
methylation. A forward genetic approach uncovered alleles of several components
of the RdDM pathway, including alleles of clsy1, ktf1, and nrpd/e2, which have
not been previously shown to be required for the initial establishment of DNA
methylation. Mutations were mapped and genes cloned by both traditional and
whole genome sequencing approaches. The methodologies and the mutant alleles
discovered will be instrumental in further studies of de novo DNA methylation. In mammals, cadmium is widely considered as a non-genotoxic carcinogen acting
through a methylation-dependent epigenetic mechanism. Here, the effects of Cd
treatment on the DNA methylation patten are examined together with its effect on
chromatin reconfiguration in Posidonia oceanica. DNA methylation level and
pattern were analysed in actively growing organs, under short- (6 h) and long-
(2 d or 4 d) term and low (10 μM) and high (50 μM) doses of Cd, through a
Methylation-Sensitive Amplification Polymorphism technique and an
immunocytological approach, respectively. The expression of one member of the
CHROMOMETHYLASE (CMT) family, a DNA methyltransferase, was also assessed by
qRT-PCR. Nuclear chromatin ultrastructure was investigated by transmission
electron microscopy. Cd treatment induced a DNA hypermethylation, as well as an
up-regulation of CMT, indicating that de novo methylation did indeed occur.
Moreover, a high dose of Cd led to a progressive heterochromatinization of
interphase nuclei and apoptotic figures were also observed after long-term
treatment. The data demonstrate that Cd perturbs the DNA methylation status
through the involvement of a specific methyltransferase. Such changes are linked
to nuclear chromatin reconfiguration likely to establish a new balance of
expressed/repressed chromatin. Overall, the data show an epigenetic basis to the
mechanism underlying Cd toxicity in plants. DNA methylation and histone modification exert epigenetic control over gene
expression. CHG methylation by CHROMOMETHYLASE3 (CMT3) depends on histone H3K9
dimethylation (H3K9me2), but the mechanism underlying this relationship is
poorly understood. Here, we report multiple lines of evidence that CMT3
interacts with H3K9me2-containing nucleosomes. CMT3 genome locations nearly
perfectly correlated with H3K9me2, and CMT3 stably associated with
H3K9me2-containing nucleosomes. Crystal structures of maize CMT3 homolog ZMET2,
in complex with H3K9me2 peptides, showed that ZMET2 binds H3K9me2 via both bromo
adjacent homology (BAH) and chromo domains. The structures reveal an aromatic
cage within both BAH and chromo domains as interaction interfaces that capture
H3K9me2. Mutations that abolish either interaction disrupt CMT3 binding to
nucleosomes and show a complete loss of CMT3 activity in vivo. Our study
establishes dual recognition of H3K9me2 marks by BAH and chromo domains and
reveals a distinct mechanism of interplay between DNA methylation and histone
modification. |
What is the number of protein coding genes in the human genome? | The number of protein coding genes in the human genome is currently estimated between 20,000 and 25,000 | Although the Human Genome Project was completed 4 years ago, the catalog of
human protein-coding genes remains a matter of controversy. Current catalogs
list a total of approximately 24,500 putative protein-coding genes. It is
broadly suspected that a large fraction of these entries are functionally
meaningless ORFs present by chance in RNA transcripts, because they show no
evidence of evolutionary conservation with mouse or dog. However, there is
currently no scientific justification for excluding ORFs simply because they
fail to show evolutionary conservation: the alternative hypothesis is that most
of these ORFs are actually valid human genes that reflect gene innovation in the
primate lineage or gene loss in the other lineages. Here, we reject this
hypothesis by carefully analyzing the nonconserved ORFs-specifically, their
properties in other primates. We show that the vast majority of these ORFs are
random occurrences. The analysis yields, as a by-product, a major revision of
the current human catalogs, cutting the number of protein-coding genes to
approximately 20,500. Specifically, it suggests that nonconserved ORFs should be
added to the human gene catalog only if there is clear evidence of an encoded
protein. It also provides a principled methodology for evaluating future
proposed additions to the human gene catalog. Finally, the results indicate that
there has been relatively little true innovation in mammalian protein-coding
genes. The GENCODE Consortium aims to identify all gene features in the human genome
using a combination of computational analysis, manual annotation, and
experimental validation. Since the first public release of this annotation data
set, few new protein-coding loci have been added, yet the number of alternative
splicing transcripts annotated has steadily increased. The GENCODE 7 release
contains 20,687 protein-coding and 9640 long noncoding RNA loci and has 33,977
coding transcripts not represented in UCSC genes and RefSeq. It also has the
most comprehensive annotation of long noncoding RNA (lncRNA) loci publicly
available with the predomit transcript form consisting of two exons. We have
examined the completeness of the transcript annotation and found that 35% of
transcriptional start sites are supported by CAGE clusters and 62% of
protein-coding genes have annotated polyA sites. Over one-third of GENCODE
protein-coding genes are supported by peptide hits derived from mass
spectrometry spectra submitted to Peptide Atlas. New models derived from the
Illumina Body Map 2.0 RNA-seq data identify 3689 new loci not currently in
GENCODE, of which 3127 consist of two exon models indicating that they are
possibly unotated long noncoding loci. GENCODE 7 is publicly available from
gencodegenes.org and via the Ensembl and UCSC Genome Browsers. |
Has vitamin D has been shown to reduce incidence of falls in older people in clinical trials? | The rate of falls and the number of fallers was significantly reduced in two studies evaluating the effect of medication on preventing falls; one study (85 participants) compared vitamin D versus placebo in institutionalised women after stroke with low vitamin D levels, and the other study (79 participants) evaluated alendronate versus alphacalcidol in hospitalised people after stroke.
Two studies testing vitamin D versus placebo and alendronate versus alphacalcidol found a significant reduction in falls and the number of people falling.
Overall, vitamin D did not reduce rate of falls (RaR 1.00, 95% CI 0.90 to 1.11; seven trials; 9324 participants) or risk of falling (RR 0.96, 95% CI 0.89 to 1.03; 13 trials; 26,747 participants), but may do so in people with lower vitamin D levels before treatment.
We found 26 eligible trials of moderate quality that enrolled 45,782 participants, the majority of which were elderly and female. Vitamin D use was associated with statistically significant reduction in the risk of falls (odds ratio for suffering at least one fall, 0.86; 95% confidence interval, 0.77-0.96) | Increasing data suggest that many or most adults in the United States and Europe
would benefit from vitamin D supplements. This review summarizes the benefits of
vitamin D with the strongest evidence today from randomized controlled trials
for fall and fracture prevention. Beyond fall and fracture prevention, vitamin D
may also reduce overall morbidity by multiple mechanisms. Prospective
epidemiological studies supported by strong mechanistic evidence suggest a
reduction of cardiovascular disease (incident hypertension and cardiovascular
mortality) and colorectal cancer, extending to weaker evidence on
immune-modulatory and anti-inflammatory benefits of vitamin D. OBJECTIVE: To test the effectiveness of using a full-time project nurse to
assist residential aged care facilities in using evidence-based approaches to
falls injury prevention.
DESIGN, SETTING AND PARTICIPANTS: Cluster randomised controlled trial involving
5391 residents in 88 aged care facilities in the Hunter and Lower Mid North
Coast areas of New South Wales. Residents were followed for 545 days or until
death or discharge. Data were collected from July 2005 to June 2007.
INTERVENTION: Employment of a project nurse to encourage best-practice falls
injury prevention strategies during the 17-month intervention period.
MAIN OUTCOME MEASURES: Monthly data about falls, falls injury and falls injury
prevention programs; audit of hospitalisation for fractured neck of femur.
RESULTS: Despite significant increases in the provision of hip protectors and
use of vitamin D supplementation in both intervention and control facilities,
there was no difference in the number of falls or falls injuries between the
intervention and control groups, nor a reduction in falls overall. There was
also no difference between the 7-month pre-intervention period and the
intervention period in the number of falls or falls injuries. Factors related to
residents having an increased risk of falls with fractured neck of femur
included being ambulant, having dementia, increasing age, and having a high
falls risk assessment score.
CONCLUSION: It is difficult to change falls risk among high-risk populations,
including people with dementia. The use of important strategies such as hip
protectors and vitamin D and calcium supplementation increased during the study,
probably with contamination of control facilities. Longer follow-up may be
required to measure the impact on falls outcomes of the strategy of using a
facilitating nurse.
TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry
ACTRN12605000540617. Studies of vitamin D and calcium for fracture prevention have produced
inconsistent results, as a result of different vitamin D status and calcium
intake at baseline, different doses and poor to adequate compliance. This study
tries to define the types of patients, both at risk of osteoporosis and with
established disease, who may benefit from calcium and vitamin D supplementation.
The importance of adequate compliance in these individuals is also discussed.
Calcium and vitamin D therapy has been recommended for older persons, either
frail and institutionalized or independent, with key risk factors including
decreased bone mineral density (BMD), osteoporotic fractures, increased bone
remodelling as a result of secondary hyperparathyroidism and increased
propensity to falls. In addition, treatment of osteoporosis with a
bisphosphonate was less effective in patients with vitamin D deficiency. Calcium
and vitamin D supplementation is a key component of prevention and treatment of
osteoporosis unless calcium intake and vitamin D status are optimal. For primary
disease prevention, supplementation should be targeted to those with dietary
insufficiencies. Several serum 25-hydroxyvitamin D (25(OH)D) cut-offs have been
proposed to define vitamin D insufficiency (as opposed to adequate vitamin D
status), ranging from 30 to 100 nmol/l. Based on the relationship between serum
25(OH)D, BMD, bone turnover, lower extremity function and falls, we suggest that
50 nmol/l is the appropriate serum 25(OH)D threshold to define vitamin D
insufficiency. Supplementation should therefore generally aim to increase
25(OH)D levels within the 50-75 nmol/l range. This level can be achieved with a
dose of 800 IU/day vitamin D, the dose that was used in successful fracture
prevention studies to date; a randomized clinical trial assessing whether higher
vitamin D doses achieve a greater reduction of fracture incidence would be of
considerable interest. As calcium balance is not only affected by vitamin D
status but also by calcium intake, recommendations for adequate calcium intake
should also be met. The findings of community-based clinical trials with vitamin
D and calcium supplementation in which compliance was moderate or less have
often been negative, whereas studies in institutionalized patients in whom
medication administration was supervised ensuring adequate compliance
demonstrated significant benefits. CONTEXT: Vitamin D affects bone and muscle health and likely reduces the risk of
falls in the elderly.
OBJECTIVE: The aim of this systematic review is to summarize the existing
evidence on vitamin D use and the risk of falls.
DATA SOURCES: We searched electronic databases from inception through August
2010.
STUDY SELECTION: Eligible studies were randomized controlled trials in which the
intervention was vitamin D and the incidence of falls was reported.
DATA EXTRACTION: Reviewers working in duplicate and independently extracted
study characteristics, quality, and outcomes data.
DATA SYNTHESIS: Odds ratio and associated 95% confidence interval were estimated
from each study and pooled using the random effects model.
RESULTS: We found 26 eligible trials of moderate quality that enrolled 45,782
participants, the majority of which were elderly and female. Vitamin D use was
associated with statistically significant reduction in the risk of falls (odds
ratio for suffering at least one fall, 0.86; 95% confidence interval,
0.77-0.96). This effect was more prominent in patients who were vitamin D
deficient at baseline and in studies in which calcium was coadministered with
vitamin D. The quality of evidence was low to moderate because of heterogeneity
and publication bias.
CONCLUSIONS: Vitamin D combined with calcium reduces the risk of falls. The
reduction in studies without calcium coadministration did not reach statistical
significance. The majority of the evidence is derived from trials enrolling
elderly women. BACKGROUND: Approximately 30% of people over 65 years of age living in the
community fall each year. This is an update of a Cochrane review first published
in 2009.
OBJECTIVES: To assess the effects of interventions designed to reduce the
incidence of falls in older people living in the community.
SEARCH METHODS: We searched the Cochrane Bone, Joint and Muscle Trauma Group
Specialised Register (February 2012), CENTRAL (The Cochrane Library 2012, Issue
3), MEDLINE (1946 to March 2012), EMBASE (1947 to March 2012), CINAHL (1982 to
February 2012), and online trial registers.
SELECTION CRITERIA: Randomised trials of interventions to reduce falls in
community-dwelling older people.
DATA COLLECTION AND ANALYSIS: Two review authors independently assessed risk of
bias and extracted data. We used a rate ratio (RaR) and 95% confidence interval
(CI) to compare the rate of falls (e.g. falls per person year) between
intervention and control groups. For risk of falling, we used a risk ratio (RR)
and 95% CI based on the number of people falling (fallers) in each group. We
pooled data where appropriate.
MAIN RESULTS: We included 159 trials with 79,193 participants. Most trials
compared a fall prevention intervention with no intervention or an intervention
not expected to reduce falls. The most common interventions tested were exercise
as a single intervention (59 trials) and multifactorial programmes (40 trials).
Sixty-two per cent (99/159) of trials were at low risk of bias for sequence
generation, 60% for attrition bias for falls (66/110), 73% for attrition bias
for fallers (96/131), and only 38% (60/159) for allocation
concealment.Multiple-component group exercise significantly reduced rate of
falls (RaR 0.71, 95% CI 0.63 to 0.82; 16 trials; 3622 participants) and risk of
falling (RR 0.85, 95% CI 0.76 to 0.96; 22 trials; 5333 participants), as did
multiple-component home-based exercise (RaR 0.68, 95% CI 0.58 to 0.80; seven
trials; 951 participants and RR 0.78, 95% CI 0.64 to 0.94; six trials; 714
participants). For Tai Chi, the reduction in rate of falls bordered on
statistical significance (RaR 0.72, 95% CI 0.52 to 1.00; five trials; 1563
participants) but Tai Chi did significantly reduce risk of falling (RR 0.71, 95%
CI 0.57 to 0.87; six trials; 1625 participants).Multifactorial interventions,
which include individual risk assessment, reduced rate of falls (RaR 0.76, 95%
CI 0.67 to 0.86; 19 trials; 9503 participants), but not risk of falling (RR
0.93, 95% CI 0.86 to 1.02; 34 trials; 13,617 participants).Overall, vitamin D
did not reduce rate of falls (RaR 1.00, 95% CI 0.90 to 1.11; seven trials; 9324
participants) or risk of falling (RR 0.96, 95% CI 0.89 to 1.03; 13 trials;
26,747 participants), but may do so in people with lower vitamin D levels before
treatment.Home safety assessment and modification interventions were effective
in reducing rate of falls (RR 0.81, 95% CI 0.68 to 0.97; six trials; 4208
participants) and risk of falling (RR 0.88, 95% CI 0.80 to 0.96; seven trials;
4051 participants). These interventions were more effective in people at higher
risk of falling, including those with severe visual impairment. Home safety
interventions appear to be more effective when delivered by an occupational
therapist.An intervention to treat vision problems (616 participants) resulted
in a significant increase in the rate of falls (RaR 1.57, 95% CI 1.19 to 2.06)
and risk of falling (RR 1.54, 95% CI 1.24 to 1.91). When regular wearers of
multifocal glasses (597 participants) were given single lens glasses, all falls
and outside falls were significantly reduced in the subgroup that regularly took
part in outside activities. Conversely, there was a significant increase in
outside falls in intervention group participants who took part in little outside
activity.Pacemakers reduced rate of falls in people with carotid sinus
hypersensitivity (RaR 0.73, 95% CI 0.57 to 0.93; three trials; 349 participants)
but not risk of falling. First eye cataract surgery in women reduced rate of
falls (RaR 0.66, 95% CI 0.45 to 0.95; one trial; 306 participants), but second
eye cataract surgery did not.Gradual withdrawal of psychotropic medication
reduced rate of falls (RaR 0.34, 95% CI 0.16 to 0.73; one trial; 93
participants), but not risk of falling. A prescribing modification programme for
primary care physicians significantly reduced risk of falling (RR 0.61, 95% CI
0.41 to 0.91; one trial; 659 participants).An anti-slip shoe device reduced rate
of falls in icy conditions (RaR 0.42, 95% CI 0.22 to 0.78; one trial; 109
participants). One trial (305 participants) comparing multifaceted podiatry
including foot and ankle exercises with standard podiatry in people with
disabling foot pain significantly reduced the rate of falls (RaR 0.64, 95% CI
0.45 to 0.91) but not the risk of falling.There is no evidence of effect for
cognitive behavioural interventions on rate of falls (RaR 1.00, 95% CI 0.37 to
2.72; one trial; 120 participants) or risk of falling (RR 1.11, 95% CI 0.80 to
1.54; two trials; 350 participants).Trials testing interventions to increase
knowledge/educate about fall prevention alone did not significantly reduce the
rate of falls (RaR 0.33, 95% CI 0.09 to 1.20; one trial; 45 participants) or
risk of falling (RR 0.88, 95% CI 0.75 to 1.03; four trials; 2555
participants).No conclusions can be drawn from the 47 trials reporting
fall-related fractures.Thirteen trials provided a comprehensive economic
evaluation. Three of these indicated cost savings for their interventions during
the trial period: home-based exercise in over 80-year-olds, home safety
assessment and modification in those with a previous fall, and one
multifactorial programme targeting eight specific risk factors.
AUTHORS' CONCLUSIONS: Group and home-based exercise programmes, and home safety
interventions reduce rate of falls and risk of falling.Multifactorial assessment
and intervention programmes reduce rate of falls but not risk of falling; Tai
Chi reduces risk of falling.Overall, vitamin D supplementation does not appear
to reduce falls but may be effective in people who have lower vitamin D levels
before treatment. BACKGROUND: Falls are one of the most common medical complications after stroke
with a reported incidence of 7% in the first week after stroke onset. Studies
investigating falls in the later phase after stroke report an incidence of up to
73% in the first year post-stroke.
OBJECTIVES: To evaluate the effectiveness of interventions aimed at preventing
falls in people after stroke.
SEARCH METHODS: We searched the trials registers of the Cochrane Stroke Group
(November 2012) and the Cochrane Bone, Joint and Muscle Trauma Group (May 2012),
the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane
Library 2012, Issue 5, MEDLINE (1950 to May 2012), EMBASE (1980 to May 2012),
CINAHL (1982 to May 2012), PsycINFO (1806 to May 2012), AMED (1985 to May 2012)
and PEDro (May 2012). We also searched trials registers, checked reference lists
and contacted authors.
SELECTION CRITERIA: Randomised controlled trials of interventions where the
primary or secondary aim was to prevent falls in people after stroke.
DATA COLLECTION AND ANALYSIS: Review authors independently selected studies for
inclusion, assessed trial quality, and extracted data. We used a rate ratio and
95% confidence interval (CI) to compare the rate of falls (e.g. falls per person
year) between intervention and control groups. For risk of falling we used a
risk ratio and 95% CI based on the number of people falling (fallers) in each
group. We pooled results where appropriate.
MAIN RESULTS: We included 10 studies with a total of 1004 participants. One
study evaluated the effect of exercises in the acute and subacute phase after
stroke but found no significant difference in rate of falls (rate ratio 0.92,
95% CI 0.45 to 1.90, 95 participants). The pooled result of four studies
investigating the effect of exercises on preventing falls in the chronic phase
also found no significant difference for rate of falls (rate ratio 0.75, 95% CI
0.41 to 1.38, 412 participants).For number of fallers, one study examined the
effect of exercises in the acute and subacute phase after stroke but found no
significant difference between the intervention and control group (risk ratio
1.19, 95% CI 0.83 to 1.71, 95 participants). The pooled result of six studies
examining the effect of exercises in the chronic phase also found no significant
difference in number of fallers between the intervention and control groups
(risk ratio 1.02, 95% CI 0.83 to 1.24, 616 participants).The rate of falls and
the number of fallers was significantly reduced in two studies evaluating the
effect of medication on preventing falls; one study (85 participants) compared
vitamin D versus placebo in institutionalised women after stroke with low
vitamin D levels, and the other study (79 participants) evaluated alendronate
versus alphacalcidol in hospitalised people after stroke.One study provided
single lens distance glasses to regular wearers of multifocal glasses. In a
subgroup of 46 participants post-stroke there was no significant difference in
the rate of falls (rate ratio 1.08, 95% CI 0.52 to 2.25) or the number of
fallers between both groups (risk ratio 0.74, 95% CI 0.47 to 1.18).
AUTHORS' CONCLUSIONS: There is currently insufficient evidence that exercises or
prescription of single lens glasses to multifocal users prevent falls or
decrease the number of people falling after being discharged from rehabilitation
following their stroke. Two studies testing vitamin D versus placebo and
alendronate versus alphacalcidol found a significant reduction in falls and the
number of people falling. However, these findings should be replicated before
the results are implemented in clinical practice. CONTEXT: Public health authorities around the world recommend widely variable
supplementation strategies for adults, whereas several professional
organizations, including The Endocrine Society, recommend higher
supplementation.
METHODS: We analyzed published randomized controlled clinical trials to define
the optimal intake or vitamin D status for bone and extraskeletal health.
CONCLUSIONS: The extraskeletal effects of vitamin D are plausible as based on
preclinical data and observational studies. However, apart from the beneficial
effects of 800 IU/d of vitamin D3 for reduction of falls in the elderly,
causality remains yet unproven in randomized controlled trials (RCTs). The
greatest risk for cancer, infections, cardiovascular and metabolic diseases is
associated with 25-hydroxyvitamin D (25OHD) levels below 20 ng/mL. There is
ample evidence from RCTs that calcium and bone homeostasis, estimated from serum
1,25-dihydroxyvitamin D and PTH, calcium absorption, or bone mass, can be
normalized by 25OHD levels above 20 ng/mL. Moreover, vitamin D supplementation
(800 IU/d) in combination with calcium can reduce fracture incidence by about
20%. Such a dose will bring serum levels of 25OHD above 20 ng/mL in nearly all
postmenopausal women. Based on calculations of the metabolic clearance of 25OHD,
a daily intake of 500-700 IU of vitamin D3 is sufficient to maintain serum 25OHD
levels of 20 ng/mL. Therefore, the recommendations for a daily intake of
1500-2000 IU/d or serum 25OHD levels of 30 ng or higher for all adults or
elderly subjects, as suggested by The Endocrine Society Task Force, are
premature. Fortunately, ongoing RCTs will help to guide us to solve this
important public health question. |
What is the indication for prophylactic use of antibiotics in COPD? | In a subset of patients with severe disease and prone to developing infections prophylactic use of antibiotics may reduce number of exacerbations and improve social and health care costs. | Exacerbations of chronic obstructive pulmonary disease (COPD) are an important
cause of morbidity and healthcare expenditure. In hospitalized patients,
antibiotics decrease treatment failure and reduce mortality. There is also
evidence for the effectiveness of antibiotics in treating COPD exacerbations in
the community, but this is most convincing in patients with severe airflow
obstruction and there is uncertainty regarding the value of antibiotics in
patients with mild airflow obstruction. Treatment with antibiotics is usually
recommended for patients who have an increase in sputum volume, sputum purulence
and breathlessness, but the most important determit of bacterial infection
appears to be purulence. There is some evidence to suggest that the decision to
use antibiotics can be guided by the use of procalcitonin, although this needs
to be confirmed in further studies. Newer broad-spectrum antibiotics may be more
effective than older antibiotics but, because of concerns regarding antibiotic
resistance, it may be appropriate to reserve them for patients at highest risk
of treatment failure. A number of studies suggest that antibiotic courses of 5
days in duration may be as effective as those for 7 days or more in patients
with mild-to-moderate exacerbations of COPD. Guidelines do not recommend the use
of prophylactic antibiotics in COPD but there is preliminary evidence to suggest
that they may reduce the number of exacerbations. Until the full results of
these studies are published, it will not be clear if they should be used. Limiting antibiotic use is one of the most important measures to prevent and
control emergence of antibiotic resistance. Therefore, antibiotics should
usually only be prescribed for infection. Yet recent well-designed studies have
demonstrated that prophylactic antibiotic use is of significant benefit to
patients prone to developing infections. Study patients suffered from recurrent
urinary tract infections, COPD or were mechanically ventilated in intensive care
units. In the first 2 populations, use of antibiotics was associated with an
increase in carriage of antibiotic-resistant bacteria, but in intensive care
patients the opposite was documented. These studies demonstrate that antibiotics
do more than cause resistance. The pros and cons of prophylactic antibiotic use
must therefore be carefully considered. |
Has depression been shown to be a predictor of frailty? | Yes | BACKGROUND: Confounding of depression with somatic illness and anxiety, a
problem in any age group, may be especially troublesome in frail older persons.
This paper examined this problem in a factor analytic study of the structure of
depressive symptomatology, identifying affective and somatic symptom clusters
and relating those clusters to health and functional variables cross-sectionally
and prospectively over a 1-year interval.
METHODS: The factor structure of a DSM-IV symptom checklist was examined among
1,245 elderly long-term care residents. Regression analyses examined the
association of resulting factors with cognition, functional disability, self-
and physician-rated health, and pain at baseline and a year later. One-year
mortality was also examined.
RESULTS: Factor analysis revealed three unique symptom clusters: depressed mood,
somatic symptoms, and psychic anxiety. Depressed mood and somatic symptoms were
associated cross-sectionally with all functional health variables, but psychic
anxiety was associated only with pain. Longitudinally, depressed mood was the
only independent predictor of decline in cognition, functional ability,
physician-rated health, and mortality; the last effect, however, did not
withstand control for baseline health and functioning. Somatic symptoms at
baseline predicted decrement in self-rated health a year later. Effects varied
as a function of cognitive status.
CONCLUSIONS: These data suggest that concerns about the confounding role of
somatic symptoms in the association of depression with physical health are
unfounded. Although somatic symptoms of depression and anxiety were associated
with health and functional status cross-sectionally, depressed mood was by far
the stronger predictor of health declines over time. In this chapter we have reviewed the evidence for physiological anorexia of
aging and stressed that its pathophysiology involves both central and peripheral
mechanisms. Early satiation in the older person appears to involve signals
predomitly arising in the stomach. The increased feeling of satiety in older
persons is mainly related to changes in the central feeding drive, in particular
a decrease in the opioid rewarding properties for fatty foods. Increased
cytokines, secondary to inflammatory conditions which are common in old age, may
further increase the anorexia seen in older persons. Leptin, the fat hormone, is
an excellent indicator of fat mass in women, in whom leptin concentrations
correlate with the MNA. In men, testosterone inhibits leptin, and the fall in
testosterone with age results in an increase in leptin concentrations. In males
the MNA is not related to leptin concentrations. Finally, we have examined the
interrelation of two nutritional screening indices, MNA and SCALES. The two
indices were well correlated and were both predictive of poor basic function. We
conclude that the MNA is an excellent predictor of nutritional status. These
findings suggest that malnutrition is a major predictor of frailty or the
"failure to thrive" syndrome in older persons. Depression is a major cause of
poor nutritional status in older persons. INTRODUCTION AND OBJECTIVES: Heart failure patients have high levels of frailty
and dependence. Our aim was to determine the impact of frailty and depressive
symptoms on the 1-year mortality rate and the rate of hospitalization for heart
failure during a follow-up period of 1 year.
METHODS: All patients underwent geriatric evaluation, and frailty and depressive
symptoms were identified. The study included 622 patients (72.5% male; median
age, 68 years; 92% in New York Heart Association class II or III; and median
ejection fraction, 30%).
RESULTS: During follow-up, 60 patients (9.5%) died and 101 (16.2%) were
hospitalized for heart failure. Overall, 39.9% of patients exhibited frailty,
while 25.2% had depressive symptoms. There were significant associations between
mortality at 1 year and the presence of frailty (16.9% vs. 4.8%; P< .001) and
depressive symptoms (15.3% vs. 7.7%; P=.006). There was also a significant
relationship between heart failure hospitalization and the presence of frailty
(20.5% vs. 13.3%; P=.01). No relationship was found between heart failure
hospitalization and depressive symptoms. Frailty was an independent predictor of
mortality but not of hospitalization.
CONCLUSIONS: Univariate analysis demonstrated significant relationships between
frailty and depressive symptoms and mortality at 1 year. In addition, there was
a significant relationship between frailty and the need for heart failure
hospitalization. However, only frailty showed prognostic value to predict
mortality, which was independent of other variables strongly associated to
outcome. OBJECTIVE: This study aimed to examine the cross-sectional and longitudinal
relationships between physical frailty at baseline and depressive symptoms at
baseline and at follow-up.
DESIGN: Four-year prospective study.
SETTING: Communities in the South East Region of Singapore.
PARTICIPANTS: We analyzed data of 1827 older Chinese adults aged 55 and above in
the Singapore Longitudinal Aging Study-I.
MEASUREMENTS: The frailty phenotype (based on Fried criteria) was determined at
baseline, depressive symptoms (Geriatric Depression Scale ≥ 5) at baseline and
follow-ups at 2 and 4 years.
RESULTS: The mean age of the population was 65.9 (standard deviation 7.26). At
baseline, 11.4% (n = 209) had depressive symptoms, 32.4% (n = 591) were prefrail
and 2.5% (n = 46) were frail. In cross-sectional analysis of baseline data, the
adjusted odds ratios (OR)s and 95% confidence intervals controlling for
demographic, comorbidities, and other confounders were 1.69 (1.23-2.33) for
prefrailty and 2.36 (1.08-5.15) for frailty, (P for linear trend <.001). In
longitudinal data analyses, prospective associations among all participants
were: prefrail: OR = 1.86 (1.08-3.20); frail: OR = 3.09 (1.12-8.50); (P for
linear trend = .009). Among participants free of depressive symptoms at
baseline, similar prospective associations were found: prefrail OR = 2.26
(1.12-4.57); frail: OR = 3.75 (1.07-13.16); (P for linear trend = .009).
CONCLUSION: These data support a significant role of frailty as a predictor of
depression in a relatively younger old Chinese population. Further observational
and interventional studies should explore short-term dynamic and bidirectional
associations and the effects of frailty reversal on depression risk. |
What is the generic name of Gliolan? | 5-aminolevulinic acid (or 5-ALA) is the generic name of Gliolan. It is approved for fluorescence-guided resections of adult malignant gliomas. | ALA-induced protoporphyrin IX (PpIX) is used for fluorescence diagnosis (ALA-FD)
and for fluorescence-guided resection of both (pre)maligt and non-maligt
diseases. ALA is also applied in photodynamic therapy (ALA-PDT) of superficial
(pre)maligt lesions in dermatology, urology, neurosurgery,
otorhinolaryngology, gynecology and gastroenterology. Today, ALA is approved as
Levulan for actinic keratoses, the ALA-methyl ester Metvix for actinic keratoses
and basal cell carcinoma, the ALA-hexyl ester Hexvix for the diagnosis of
bladder cancer and Gliolan for maligt glioma. The use of ALA for PDT and FD
was established around 25 years ago, with most of the fundamental knowledge
gained at the "bench" and implemented at the "bedside" due to the diligence of a
few researchers within the first 10 years of research. After 1993 ALA research
was taken up by many groups. For patient treatment, several factors are
relevant. Administered mainly in a topical or oral form, ALA penetrates tissue
in a sub-optimal way, which is currently improved by special techniques and the
use of ALA-esters. PpIX accumulation is elevated in many maligt tissues,
several tissue abnormalities, and in mucosa. It is also found at elevated levels
in macrophages, dendritic cells and activated lymphocytes. Following sufficient
PpIX accumulation in the target cells, irradiation is carried out which may be
accompanied by a burning sensation at the treatment site. Due to a saturation
process of PpIX formation and rapid photobleaching during irradiation the risk
of overtreatment is relatively low. Pharmacokinetical studies have demonstrated
a low systemic photosensitivity and excretion of PpIX via natural routes. INTRODUCTION: Maligt gliomas remain associated with a poor prognosis despite
both surgical treatment and radiochemotherapy.Previous studies have shown that
complete resection of contrast-enhancing tumours is achieved in less than 20-30%
of patients. 5-aminolevulinic acid (5-ALA) is a pro-drug that leads to
accumulation of fluorescent protoporphyrins in maligt gliomas. The
fluorescence can be visualized intraoperatively by use of a modified microscope.
The Department of Neurosurgery at Aalborg Hospital has recently adopted this new
technique as the first centre in Denmark. Our preliminary results are presented
as a retrospective case series.
MATERIAL AND METHODS: All patients who had undergone 5-ALA fluorescence-guided
surgery due to suspected maligt glioma were included. Patients received a
standard preoperative dose of Gliolan. All patients had a postoperative cerebral
magnetic resoce imaging scan done within 72 hours to determine their
postoperative resection status.
RESULTS: To date, 13 patients have undergone fluorescence-guided surgery. Total
resection was achieved in 54-70% of the patients depending on the inclusion
criteria. Total or near total resection was achieved in 92% of patients.
CONCLUSION: The small numbers in our case series do not allow for direct
comparison to be made, but show that our results on postoperative resection
status fall within the range reported in other studies on the efficacy of 5-ALA.
The literature offers mounting evidence in support of the role of aggressive
cytoreductive surgery in patients with maligt gliomas.
FUNDING: not relevant.
TRIAL REGISTRATION: not relevant. OBJECTIVE: To assess effectiveness of 5-aminolevulinic acid (5-ALA, Gliolan(®))
in patients treated for maligt glioma under typical daily practice conditions
in Spain, using complete resection rate (CR) and progression free survival at 6
months (PFS6).
MATERIAL AND METHODS: Retrospective review of data from 18 neurosurgery
departments that were categorised as either using or not using 5-ALA. The study
included adult patients with suspected maligt gliomas for whom the intended
treatment plan included complete resection followed by radiotherapy and
chemotherapy with temozolomide. Postoperative MRI and clinical data representing
at least 6 months were required for inclusion. Rates of CR and PFS6 were
compared between patients with 5-ALA treatment and those without.
RESULTS: The study included 251 evaluable cases. CR and PFS6 rates were
significantly higher in the group of patients treated surgically with 5-ALA: CR,
67% versus 45%, p=.000; PFS6 for patients with grade IV tumours, 69% versus 48%;
p=.002. The differences retained their significance and magnitude after
adjusting for all covariates including age, functional status, and whether
gliomas were located in eloquent areas.
CONCLUSIONS: In this retrospective series, use of 5-ALA during habitual surgical
procedures in Spain was associated with a higher complete resection rate for
maligt glioma and increased PFS6 for grade iv glioma. OBJECTIVE: This study evaluates the cost-effectiveness of 5-aminolevulinic acid
(5-ALA, Gliolan®) in patients undergoing surgery for maligt glioma, in
standard clinical practice conditions in Spain.
MATERIAL AND METHODS: Cost-effectiveness ratios were determined in terms of
incremental cost per complete resection (CR) and incremental cost per additional
quality-adjusted life year (QALY), based on data collected in the VISIONA
observational study.
RESULTS: Incremental cost with 5-ALA versus conventional surgery using white
light only amounts to € 4550 per additional CR achieved and € 9021 per QALY
gained. A sensitivity analysis shows these results to be robust.
CONCLUSION: Maligt glioma surgery guided by 5-ALA fluorescence entails a
moderate increase in hospital costs compared to current surgical practice and
can be considered a cost-effective innovation. BACKGROUND: Five-aminolevulinic acid (Gliolan, medac, Wedel, Germany, 5-ALA) is
approved for fluorescence-guided resections of adult maligt gliomas. Case
reports indicate that 5-ALA can be used for children, yet no prospective study
has been conducted as of yet. As a basis for a study, we conducted a survey
among certified European Gliolan users to collect data on their experiences with
children.
METHODS: Information on patient characteristics, MRI characteristics of tumors,
histology, fluorescence qualities, and outcomes were requested. Surgeons were
further asked to indicate whether fluorescence was "useful", i.e., leading to
changes in surgical strategy or identification of residual tumor. Recursive
partitioning analysis (RPA) was used for defining cohorts with high or low
likelihoods for useful fluorescence.
RESULTS: Data on 78 patients <18 years of age were submitted by 20 centers.
Fluorescence was found useful in 12 of 14 glioblastomas (85 %), four of five
anaplastic astrocytomas (60 %), and eight of ten ependymomas grades II and III
(80 %). Fluorescence was found inconsistently useful in PNETs (three of seven;
43 %), gangliogliomas (two of five; 40 %), medulloblastomas (two of eight, 25 %)
and pilocytic astrocytomas (two of 13; 15 %). RPA of pre-operative factors
showed tumors with supratentorial location, strong contrast enhancement and
first operation to have a likelihood of useful fluorescence of 64.3 %, as
opposed to infratentorial tumors with first surgery (23.1 %).
CONCLUSIONS: Our survey demonstrates 5-ALA as being used in pediatric brain
tumors. 5-ALA may be especially useful for contrast-enhancing supratentorial
tumors. These data indicate controlled studies to be necessary and also provide
a basis for planning such a study. |
Is there any association between Jarid2 and miR-155 in Th17 cells? | Yes. Activation-induced miR-155 targets the chromatin protein Jarid2 to regulate proinflammatory cytokine production in T helper 17 cells. | Specification of the T helper 17 (Th17) cell lineage requires a well-defined set
of transcription factors, but how these integrate with posttranscriptional and
epigenetic programs to regulate gene expression is poorly understood. Here we
found defective Th17 cell cytokine expression in miR-155-deficient CD4+ T cells
in vitro and in vivo. Mir155 was bound by Th17 cell transcription factors and
was highly expressed during Th17 cell differentiation. miR-155-deficient Th17
and T regulatory (Treg) cells expressed increased amounts of Jarid2, a
DNA-binding protein that recruits the Polycomb Repressive Complex 2 (PRC2) to
chromatin. PRC2 binding to chromatin and H3K27 histone methylation was increased
in miR-155-deficient cells, coinciding with failure to express Il22, Il10, Il9,
and Atf3. Defects in Th17 cell cytokine expression and Treg cell homeostasis in
the absence of Mir155 could be partially suppressed by Jarid2 deletion. Thus,
miR-155 contributes to Th17 cell function by suppressing the inhibitory effects
of Jarid2. In this issue of Immunity, Escobar et al. (2014) bring microRNAs and chromatin
together by showing how activation-induced miR-155 targets the chromatin protein
Jarid2 to regulate proinflammatory cytokine production in T helper 17 cells. |
What is enCHIP? | Engineered DNA-binding molecule-mediated chromatin immunoprecipitation (enChIP) is a novel method for purification of specific genomic regions retaining molecular interactions. EnChIP using the CRISPR system efficiently isolates specific genomic regions. In this form of enChIP, specific genomic regions are immunoprecipitated with antibody against a tag(s), which is fused to a catalytically inactive form of Cas9 (dCas9), which is co-expressed with a guide RNA (gRNA) and recognizes endogenous DNA sequence in the genomic regions of interest. enChIP-mass spectrometry (enChIP-MS) targeting endogenous loci identified associated proteins. enChIP using the CRISPR system would be a convenient and useful tool for dissecting chromatin structure of genomic regions of interest. | Isolation of specific genomic regions retaining molecular interactions is
necessary for their biochemical analysis. Here, we established a novel method,
engineered DNA-binding molecule-mediated chromatin immunoprecipitation (enChIP),
for purification of specific genomic regions retaining molecular interactions.
We showed that enChIP using the CRISPR system efficiently isolates specific
genomic regions. In this form of enChIP, specific genomic regions are
immunoprecipitated with antibody against a tag(s), which is fused to a
catalytically inactive form of Cas9 (dCas9), which is co-expressed with a guide
RNA (gRNA) and recognizes endogenous DNA sequence in the genomic regions of
interest. enChIP-mass spectrometry (enChIP-MS) targeting endogenous loci
identified associated proteins. enChIP using the CRISPR system would be a
convenient and useful tool for dissecting chromatin structure of genomic regions
of interest. Biochemical analysis of molecular interactions in specific genomic regions
requires their isolation while retaining molecular interactions in vivo. Here,
we report isolation of telomeres by engineered DNA-binding molecule-mediated
chromatin immunoprecipitation (enChIP) using a transcription activator-like
(TAL) protein recognizing telomere repeats. Telomeres recognized by the tagged
TAL protein were immunoprecipitated with an antibody against the tag and
subjected to identification of telomere-binding molecules. enChIP-mass
spectrometry (enChIP-MS) targeting telomeres identified known and novel
telomere-binding proteins. The data have been deposited to the ProteomeXchange
with identifier PXD000461. In addition, we showed that RNA associated with
telomeres could be isolated by enChIP. Identified telomere-binding molecules may
play important roles in telomere biology. enChIP using TAL proteins would be a
useful tool for biochemical analysis of specific genomic regions of interest. Isolation of specific genomic regions retaining molecular interactions is
essential for comprehensive identification of molecules associated with the
genomic regions. Recently, we developed the engineered DNA-binding
molecule-mediated chromatin immunoprecipitation (enChIP) technology for
purification of specific genomic regions. Here, we developed a retroviral
expression system for enChIP using CRISPR. We showed that the target genomic
locus can be purified with high efficiency by using this system. We also showed
that contamination of potential off-target sites is negligible by using this
system if the guide RNA (gRNA) for the target site has a sufficiently long
unique sequence in its seed sequence. enChIP combined with stable isotope
labeling using amino acids in cell culture (SILAC) analysis identified proteins
whose association with the interferon (IFN) regulatory factor-1 (IRF-1) promoter
region increases in response to IFNγ stimulation. The list of the associated
proteins contained many novel proteins in the context of IFNγ-induced gene
expression as well as proteins related to histone deacetylase complexes whose
involvement has been suggested in IFNγ-mediated gene expression. Finally, we
confirmed IFNγ-induced increased association of the identified proteins with the
IRF-1 promoter by ChIP. Thus, our results showed that the retroviral enChIP
system using CRISPR would be useful for biochemical analysis of genome functions
including transcription and epigenetic regulation. |
How many genes does the human hoxD cluster contain? | The human HOXD complex contains nine genes: HOXD1, HOXD3, HOXD4, HOXD8, HOXD9, HOXD10, HOXD11, HOXD12 and HOXD13, which are clustered from 3′ to 5′ in an approximately 100-kb stretch on chromosome 2q31.1 with HOXD1 at the 3' end and HOXD13 the 5′ end. | Vertebrates have four clusters of Hox genes (HoxA, HoxB, HoxC, and HoxD). A
variety of expression and mutation studies indicate that posterior members of
the HoxA and HoxD clusters play an important role in vertebrate limb
development. In humans, mutations in HOXD13 have been associated with type II
syndactyly or synpolydactyly, and, in HOXA13, with hand-foot-genital syndrome.
We have investigated two unrelated children with a previously unreported pattern
of severe developmental defects on the anterior-posterior (a-p) limb axis and in
the genitalia, consisting of a single bone in the zeugopod, either monodactyly
or oligodactyly in the autopod of all four limbs, and penoscrotal hypoplasia.
Both children are heterozygous for a deletion that eliminates at least eight
(HOXD3-HOXD13) of the nine genes in the HOXD cluster. We propose that the
patients' phenotypes are due in part to haploinsufficiency for HOXD-cluster
genes. This hypothesis is supported by the expression patterns of these genes in
early vertebrate embryos. However, the involvement of additional genes in the
region could explain the discordance, in severity, between these human
phenotypes and the milder, non-polarized phenotypes present in mice hemizygous
for HoxD cluster genes. These cases represent the first reported examples of
deficiencies for an entire Hox cluster in vertebrates and suggest that the
diploid dose of human HOXD genes is crucial for normal growth and patterning of
the limbs along the anterior-posterior axis. Retinoic acid (RA) can induce growth arrest and neuronal differentiation of
neuroblastoma cells and has been used in clinic for treatment of neuroblastoma.
It has been reported that RA induces the expression of several HOXD genes in
human neuroblastoma cell lines, but their roles in RA action are largely
unknown. The HOXD cluster contains nine genes (HOXD1, HOXD3, HOXD4, and
HOXD8-13) that are positioned sequentially from 3' to 5', with HOXD1 at the 3'
end and HOXD13 the 5' end. Here we show that all HOXD genes are induced by RA in
the human neuroblastoma BE(2)-C cells, with the genes located at the 3' end
being activated generally earlier than those positioned more 5' within the
cluster. Individual induction of HOXD8, HOXD9, HOXD10 or HOXD12 is sufficient to
induce both growth arrest and neuronal differentiation, which is associated with
downregulation of cell cycle-promoting genes and upregulation of neuronal
differentiation genes. However, induction of other HOXD genes either has no
effect (HOXD1) or has partial effects (HOXD3, HOXD4, HOXD11 and HOXD13) on
BE(2)-C cell proliferation or differentiation. We further show that knockdown of
HOXD8 expression, but not that of HOXD9 expression, significantly inhibits the
differentiation-inducing activity of RA. HOXD8 directly activates the
transcription of HOXC9, a key effector of RA action in neuroblastoma cells.
These findings highlight the distinct functions of HOXD genes in RA induction of
neuroblastoma cell differentiation. |
Is it safe to take isotretinoin during pregnancy? | No. The isotretinoin has severe teratogenic effects and it is not safe to use during pregnancy. | Isotretinoin is a potent retinoic acid used in the treatment of skin disorders.
Though very effective, it is teratogenic if administered during pregcy, and
its teratogenic effect may be related to the normal activity of retinoids as
signalling molecules in the embryo. Although its exact mechanism of action is
unknown, it has been suggested that it causes its characteristic pattern of
defects that includes heart defects, by inhibiting the migration of neural crest
cells. However, other effects on cells are known. We studied early cardiac cell
proliferation using incorporation of bromodeoxyuridine (BrdU) and detection with
a monoclonal anti-BrdU. Proliferation in heart tissue of whole embryo cultures
was inhibited in medium with 10(-6) M isotretinoin to 62% of the control level
in myocardium. We studied its effects in culture on precardiac explant
development in the absence of the neural crests. Culture of precardiac
mesodermal-endodermal explants revealed that development of heart vesicles from
the mesoderm was little affected, but the development of heartbeat was inhibited
depending on dose in the 10(-5) to 10(-7) M range. The effect on development of
contractions was augmented in the presence of serum; it could be duplicated by
all-trans-retinoic acid, and it was reversible. Synthesis of the alpha-actin
isotype, analyzed by isoelectric focusing, was found to be inhibited or delayed.
The results suggest multiple effects of retinoids on growth, morphogenesis, and
differentiation of early cardiac tissue, and are discussed in relation to the
potential role of retinoids in early embryogenesis. Oral administration of 400 mg/kg of 13-cis retinoic acid to 9 day pregt mice
gives rise to important maxillofacial malformations. The first manifestation of
teratogenic effect is an increase of density of cell death arising in the dorsal
part of the first two branchial arches at day 9.5. These two arches become
hypoplastic at days 10 and 11, and the preskeletal anlagen appear too late in
comparison to control embryos. Meckel's cartilage is too curvilinear and
medially situated. Pre-ossicular and pre-mandibular blastemata develop with
spatial distortions which are well analyzable at days 16 and 17. They give some
arguments to discuss several features of normal early development of this area. Isotretinoin (13-cis-retinoic acid, Accutane) increases the risk of major
congenital malformations in infants exposed to isotretinoin during pregcy.
However, there have been no epidemiologic reports to date on the effect of a
subsequent pregcy after discontinuation of isotretinoin. This article
describes our analysis of pregcy case reports from patients in whom
conception occurred after isotretinoin treatment had been discontinued. Based on
the 88 prospectively ascertained cases, the incidence rate of both spontaneous
and missed abortions from all pregcies was 9.1% (eight patients), and the
incidence rate of congenital malformation among the live births was 5.0% (four
patients). The incidence rates for both these outcomes were not significantly
different from the rates reported for women of reproductive age in the general
population. In addition, the malformations reported were not characteristic of
retinoic acid-induced congenital anomalies. Retinoic acid, an analogue of vitamin A, is known to be teratogenic in
laboratory animals and has recently been implicated in a few clinical case
reports. To study the human teratogenicity of this agent, we investigated 154
human pregcies with fetal exposure to isotretinoin, a retinoid prescribed for
severe recalcitrant cystic acne. The outcomes were 95 elective abortions, 26
infants without major malformations, 12 spontaneous abortions, and 21 malformed
infants. A subset of 36 of the 154 pregcies was observed prospectively. The
outcomes in this cohort were 8 spontaneous abortions, 23 normal infants, and 5
malformed infants. Exposure to isotretinoin was associated with an unusually
high relative risk for a group of selected major malformations (relative risk =
25.6; 95 per cent confidence interval, 11.4 to 57.5). Among the 21 malformed
infants we found a characteristic pattern of malformation involving
craniofacial, cardiac, thymic, and central nervous system structures. The
malformations included microtia/anotia (15 infants), micrognathia (6), cleft
palate (3), conotruncal heart defects and aortic-arch abnormalities (8), thymic
defects (7), retinal or optic-nerve abnormalities (4), and central nervous
system malformations (18). The pattern of malformation closely resembled that
produced in animal studies of retinoid teratogenesis. It is possible that a
major mechanism of isotretinoin teratogenesis is a deleterious effect on
cephalic neural-crest cell activity that results in the observed craniofacial,
cardiac, and thymic malformations. Keratolenticular dysgenesis (Peters' anomaly) was induced in mice by exposure to
the human teratogens, ethanol or 13-cis retinoic acid (isotretinoin, Accutane).
Acute teratogen exposure on the seventh day of gestation (corresponding to the
third week of human gestation) resulted in an eye malformation incidence of 46%
to 100% in day 14 fetuses. Of the abnormal eyes, 10% to 29% demonstrated failure
of detachment of the lens from the surface ectoderm. Delayed lens detachment was
seen as anterior lenticonus in 33% to 35% of the abnormal eyes. Abnormal lens
detachment appeared to result in mechanical interference with neural crest
migration to form the corneal stroma and endothelium, and iris stroma. This
secondary effect on neural crest derivatives is exhibited in the adult animals
as corneal opacities associated with defects in Descemet's membrane and
endothelium, and anterior polar cataracts. Recent evidence has demonstrated that 13-cis-retinoic acid (13-cis-RA, or
isotretinoin) is responsible for various craniofacial malformations in the
rodent and human embryo. Our studies have been directed toward understanding
this effect using mouse whole embryo and primary cell cultures. In whole embryo
culture, 13-cis-RA caused significant overall embryonic growth retardation,
especially in the primary and secondary palatal processes. In embryos explanted
on day 10 of gestation and exposed for 24 or 48 hr, the mesenchyme beneath the
epithelium of the nasal and maxillary processes contained pyknotic nuclei as
well as a dramatically reduced number of nuclei incorporating 3H-thymidine. The
secondary palatal processes and the roof of the oral-nasal cavity had fewer
mesenchymal cells than control embryos. The incorporation of 3H-thymidine into
TCA-insoluble macromolecules was 30% less in the retinoid-treated heads. In
primary cell cultures from day-12 mouse secondary palatal mesenchyme, subsequent
cell growth was decreased at concentrations of 13-cis-RA greater than 1 X 10(-5)
M. After a 40-hr treatment period, labeling indices in retinoid-treated cells
were significantly lower than control values (25% compared with 40%). Retinoic
acid also caused a significant, concentration-dependent decrease in 3H-thymidine
incorporation. The inhibitory effect of 13-cis-RA on proliferation of oral-nasal
mesenchymal cells appears to be related to the production of craniofacial
malformations. Recent clinical observations strongly suggest that isotretinoin [13-cis-retinoic
acid (cis RA)] is a human teratogen causing primarily heart and craniofacial
malformations including ear and palatal defects. The purpose of the present
study was to determine if cis RA could induce similar craniofacial malformations
in mouse embryo culture. Day 8 CD-1 mouse embryos were cultured for 48 hours in
rat serum in the presence or absence of various concentrations of cis RA
dissolved in DMSO. DMSO by itself had no effect on embryonic development;
however, cis RA at 2 X 10(-5) M (6 micrograms/ml) was clearly toxic. At 2 X
10(-6) M cis RA, growth retardation was minimal, and approximately one-third of
the embryos exhibited very specific defects including a dramatic reduction in
the size of the first and second visceral arches, which eventually give rise to
the maxilla, mandible, and ear. Similar observations were also made with
4-oxo-13-cis RA, which is a major metabolite of cis RA in the mouse and human.
These malformations would be expected to result in defects similar to those
observed in the human, and preliminary observations suggest these defects are
due to cis RA-induced inhibition of cranial neural crest cell migration. Using
day-10 mouse embryos cultured for 48 hours in Waymouth's medium containing 50%
fetal calf serum, we observed that cis RA at 2 X 10(-5) M produced a high
percentage of embryos with limb defects and median cleft lip. Our results
demonstrate that labeled cis RA enters the tissues of the embryo both in vivo
and in vitro. Cis RA inhibited proliferation of the frontonasal mesenchyme cells
in primary culture with 31% inhibition occurring at 2 X 10(-5) M cis RA. BACKGROUND: Although topically applied all-trans-retinoic acid (tretinoin)
undergoes minimal absorption and adds negligibly to normal endogenous levels,
its safety in humans is occasionally questioned because oral ingestion of
retinoids at therapeutic levels is known to entail teratogenic risks.
OBJECTIVE: To assess the actual potential for developmental toxicity from
treatment with topical tretinoin.
METHODS: Risk assessments were conducted on four known human developmental
toxicants (valproic acid, methotrexate, thalidomide, and isotretinoin) and a
potential developmental toxicant (acetylsalicylic acid). The margin of safety
for each chemical was calculated from the ratio of animal no-observed adverse
effect levels to human lowest-observed adverse effect levels or estimated
exposure doses.
RESULTS: The derived safety margin of more than 100 for topical tretinoin (with
2% absorption) contrasted sharply with the near unity values for valproic acid,
methotrexate, thalidomide, and isotretinoin and was larger than that for
acetylsalicylic acid.
CONCLUSION: These data support other epidemiologic and animal data that topical
tretinoin is not a potential human developmental toxicant. Teratogenicity of vitamin A was firstly detected in experimental animals in
1953. Nearly 30 years later, teratogenicity of vitamin A analogue-isotretinoin
was reported in humans. Isotretinoin induces serious birth defects of
craniofacial and central nervous system, cardiovascular system and thymic
malformations--in about 25% of babies exposed during the first trimester of
their prenatal development. The biological interconversion of isotretinoin to
vitamin A is known. That is why later epidemiological studies focused on high
vitamin A intake in pregt woman: Women who use daily vitamin A supplements
during early pregcy have approximately a two-fold increased risk of giving
birth to a malformed baby. On the basis of these data, replacement of vitamin A
has been recommended with its natural precursor B-carotene which is supposed to
be more safe for pregt woman due to its limited absorption from intestine.
Aim of the present paper was to test a possible direct embryotoxic effect (i.e.
lethality + teratogenicity) of B-carotene in chick embryos and to compare these
results with known embryotoxicity of vitamin A in the same experimental model.
Single subgerminal or intaamniotic injection of vitamin A or B-carotene within
day 2-5 of incubation was used for estimation of the beginning of the
embryotoxicity range determining the minimal embryotoxic doses. Vitamin A
started to affect development between doses 0.3-0.3 microm [corrected] per
embryo. Malformations of head, extremities and heart were detected similarly
like in laboratory mammals and in man. B-carotene exhibited such an effect
neither after injection of the highest tested doses-100 microm [corrected] per
embryo. The results documented the strong difference in embryotoxicity between
vitamin A and B-carotene. After theoretical extrapolation of the results
achieved in the chick embryo, the minimal embryotoxic doses of vitamin A in
mammals were estimated to be between 0.1-1 mg/kg of maternal weight and those of
B-carotene to be more than 1000 mg/kg of maternal weight. Human epidemiological
studies have proved teratogenicity of vitamin A after daily doses 25,000
i.u.-8.3 mg (0.13 mg/kg)- and reduction of its maximum intake has been
recommended to 10,000 i.u. per day (0.05 mg/kg). The results about
teratogenicity of vitamin A achieved in the chick embryo are in agreement with
such a recommendation. Intake of vitamin A in the food is sufficient for
pregt woman in common Czech population. Therefore, an artificial
supplementation of vitamin A brings risk of overdosage. If supplementation by
vitamin A is unavoidable during pregcy, B-carotene should be preferred. Vitamin A and its derivatives, retinoic acid, tretinoin and isotretinoin, are
currently used in dermatological treatments. The administration of high doses of
this vitamin provokes congenital malformations in mice: cleft palate, maxillary
and mandibular hypoplasia and total or partial fusion of the maxillary incisors.
This study compares the tooth germs of the first maxillary and mandibular molars
of fetal mice submitted to isotretinoin during organogenesis. Twelve 60-day-old
female Mus musculus were divided into two groups on the 7th day of pregcy:
treated group--1 mg isotretinoin per kg body weight, dissolved in vegetable oil,
was administered from the 7th to the 13th day of pregcy; control
group--vegetable oil in equivalent volume was administered orally for the same
period. On the 16th day of pregcy, the females were sacrificed, the fetuses
were removed and their heads amputated. After standard laboratory procedures,
6-micron thick serial slices were stained with hematoxylin and eosin for optical
microscopy examination. The results showed that both groups had closed palates
with no reminiscence of epithelial cells; however, the first molar germs of the
isotretinoin-treated animals showed delayed development compared to the control
animals. BACKGROUND: Topical antibiotics, isotretinoin or systemic antibiotics are
usually used for acne therapy. However, isotretinoin cannot be used during
pregcy because it can cause significant birth defects while systemic
antibiotics can have adverse side effects such as gastrointestinal irritation,
photosensitivity and tetracycline sensitivity. Describe here is a
high-intensity, narrow-band, blue light (ClearLight) system, and its therapeutic
clinical effect is investigated on acne using cutaneous measurements, bacterial
observations and ultrastructural changes.
MATERIALS AND METHODS: A total of 28 adult healthy volunteers with facial acne
(mean age 28.1 years, range 16-56 years) were recruited for this study. They
were treated with a total of eight serial biweekly 15-minute treatment sessions.
Clinical counts of acne, as well as moisture, sebum and pH measurements were
taken between each session. Nine of the 28 patients were followed for 2-3 months
after the last treatment. Detection of bacteria in acne pustules was analyzed by
culture and by polymerase chain reaction (PCR). Ultrastructural changes were
examined in eight patients after four sessions of the light therapy.
RESULTS: All patients completed the study. Overall, there was a 64.7%
improvement in acne lesions. There were no bacterial changes before or after the
therapy, although damaged Propionibacterium acnes were observed at the
ultrastructural level.
CONCLUSIONS: ClearLight performed eight times over 4 weeks can be useful in the
treatment of acne. Further investigation will be needed to elucidate the
mechanism of action of ClearLight. AIMS: To estimate the population-based incidence rates of pregcy, spontaneous
and elective abortions, and birth defects associated with isotretinoin use, and
to determine predictors of pregcy while on isotretinoin.
METHODS: Using the RAMQ (medical and pharmaceutical data), MED-ECHO
(hospitalizations) and ISQ (births and deaths) databases for the period
1984-2002, a cohort of 8609 women between 13 and 45 years of age and with a
first prescription for isotretinoin (date of entry in the cohort) was
identified. Women were eligible if they were insured by RAMQ for their
medications at least 12 months before entry in the cohort and until 1 month
after the end of their isotretinoin treatment. Pregcies, spontaneous and
elective abortions, and birth defects were identified using procedure codes and
medical diagnoses.
RESULTS: Of the 8609 women included, 90 became pregt, an annual incident
pregcy rate during isotretinoin treatment of 32.7 per 1000 person-years of
treatment (95% confidence interval 26.6, 40.1). Of the 90 women who became
pregt while on the drug, 76 terminated the pregcy (84%), three had a
spontaneous abortion (3%), two had trauma during delivery resulting in neonatal
deaths (2%) and nine had a live birth (10%). Among the live births, only one had
a congenital anomaly of the face and neck (11%). Adjusting for potential
confounders, predictors of becoming pregt while on isotretinoin were lower
socio-economic level, one or more visits to the doctor or to the emergency
department, or one or more hospitalization while on isotretinoin; concomitant
isotretinoin and oral contraceptive use had a preventive effect.
CONCLUSIONS: This first non-interventional population-based study generated
incidence rates of pregcy while on isotretinoin four times greater than what
has been reported in the literature thus far; elective abortion rates were also
much higher in our study. This shows the importance of using population-based
data for public health purposes. Clindamycin phosphate 1.2% together with tretinoin 0.025% as a gel (CTG) is a
topical formulation of a fixed and stable combination approved by the FDA for
the treatment of acne vulgaris in patients 12 years of age or older. The main
indication of CTG is the management of moderate comedonal and mild-to-moderate
papulopustular acne, an acne form which is present in more than 50% of acne
patients. CTG can also be combined with systemic antiacne therapy, such as
systemic isotretinoin, in nodulocystic acne. The product combines the
anti-inflammatory and antibacterial properties of clindamycin with the well
proven and beneficial comedolytic and anticomedogenic effects of tretinoin
(all-trans retinoic acid). The addition of clindamycin to tretinoin enhances the
comedolytic efficacy of tretinoin in moderate-to-severe acne of the face. The
comedolytic activity of tretinoin and the anti-inflammatory efficacy of
clindamycin accelerate resolution of all types of acne lesions without affecting
the safety of both compounds. Discontinuation rates due to adverse events
related to this formulation were found to be low (</= 1%). Safety of CTG use in
pregcy has not been established. The combination formulation is mainly
designed to enhance effectiveness and minimize irritation. The once daily use of
CTG, its rapid and dual effect and good tolerability have a positive impact on
the duration of disease, patients' compliance and overall costs of therapy. The isotretinoin, a 13-cis-retinoic acid, has revolutionized the management of
severe treatment-resistant acne and it has been widely used for a range of
dermatological conditions, in 90% of the time in young women between 13 and 45
years of age. This agent has severe teratogenic effects, as serious
craniofacial, cardiovascular, thymic and central nervous system malformations.
The baseline population risk of malformations is 3-5%, but it increases to
almost 30% in women exposed to isotretinoin during the first trimester of
pregcy. Generally, patients in treatment with isotretinoin avoid eventual
pregcy during assumption and, after its stopping, fertility and foetal
development are normal once circulating isotretinoin levels return to normal.
There are no known deleterious effects on male fertility and on long-term
teratogenic effect of isotretinoin. In this report, we suppose the possibility
to develop a foetal malformations after a long-term wash out from isotretinoin
therapy. A 32 year-old healthy nullipara pregt woman, with an uneventful past
gynaecological history, was admitted in Hospital, with a severe depressive
syndrome in a 18 weeks malformed pregcy for thoraco-omphalopagus conjoined
twins. She only assumed isotretinoin, at dose of 1 mg/kg a day, for a severe and
scarring acne for 7 months. After 3 months of pharmacological wash out, patient
become pregt and manifested this severe malformation. Woman interrupted
gestation, by labour induction. |
Which protein is the E3-ubiquitin ligase that targets the tumor suppressor p53 for proteasomal degradation? | The p53 tumour suppressor protein is tightly controlled by the E3 ubiquitin ligase, mouse double minute 2 (MDM2). The RING domain E3 ubiquitin ligase Mdm2 is the master regulator of the tumor suppressor p53. It targets p53 for proteasomal degradation, restraining the potent activity of p53 and enabling cell survival and proliferation. p53 is inactivated in many human malignancies through missense mutations or overexpression of the human homologue of Mdm2 (Hdm2), an E3 ubiquitin ligase that ubiquitinates p53, thereby promoting its proteasomal degradation. | The Mdm2 proto-oncogene is amplified and over-expressed in a variety of tumors.
One of the major functions of Mdm2 described to date is its ability to modulate
the levels and activity of the tumor suppressor protein p53. Mdm2 binds to the
N-terminus of p53 and, through its action as an E3 ubiquitin ligase, targets p53
for rapid proteasomal degradation. Mdm2 can also bind to other cellular proteins
such as hNumb, E2F1, Rb and Akt; however, the biological significance of these
interactions is less clear. To gain insight into the function of Mdm2 in vivo,
we have generated a transgenic Drosophila strain bearing the mouse Mdm2 gene.
Ectopic expression of Mdm2, using the UAS/GAL4 system, causes eye and wing
phenotypes in the fly. Analysis of wing imaginal discs from third instar larvae
showed that expression of Mdm2 induces apoptosis. Crosses did not reveal genetic
interactions between Mdm2 and the Drosophila homolog of E2F, Numb and Akt. These
transgenic flies may provide a unique experimental model for exploring the
molecular interactions of Mdm2 in a developmental context. Mdm2 is a RING finger E3 ubiquitin ligase, which promotes ubiquitination and
proteasomal degradation of the p53 tumor suppressor protein. Acetylation of p53
regulates p53's transcriptional activity and inhibits Mdm2-mediated p53
ubiquitination and degradation. We now report that Mdm2 is also a target for
acetylation. Mdm2 is acetylated in vitro by CREB-binding protein (CBP) and to a
lesser extent by p300, but not by p300/CPB-associated factor. Acetylation occurs
primarily within the RING finger domain of Mdm2. In vivo acetylation of Mdm2 was
detected easily with CBP but not p300. Efficient in vivo acetylation required
the preservation of the RING finger. An Mdm2 mutant (K466/467Q) mimicking
acetylation is impaired in its ability to promote p53 ubiquitination, as well as
Mdm2 autoubiquitination. Moreover, K466/467Q is defective in promoting p53
degradation in living cells. We thus suggest that acetyltransferases may
modulate cellular p53 activity not only by modifying p53, but also by
inactivating Mdm2. p53 is a critical coordinator of a wide range of stress responses. To facilitate
a rapid response to stress, p53 is produced constitutively but is negatively
regulated by MDM2. MDM2 can inhibit p53 in multiple independent ways: by binding
to its transcription activation domain, inhibiting p53 acetylation, promoting
nuclear export, and probably most importantly by promoting proteasomal
degradation of p53. The latter is achieved via MDM2's E3 ubiquitin ligase
activity harbored within the MDM2 RING finger domain. We have discovered that
MTBP promotes MDM2-mediated ubiquitination and degradation of p53 and also MDM2
stabilization in an MDM2 RING finger-dependent manner. Moreover, using small
interfering RNA to down-regulate endogenous MTBP in unstressed cells, we have
found that MTBP significantly contributes to MDM2-mediated regulation of p53
levels and activity. However, following exposure of cells to UV, but not
gamma-irradiation, MTBP is destabilized as part of the coordinated cellular
response. Our findings suggest that MTBP differentially regulates the E3
ubiquitin ligase activity of MDM2 towards two of its most critical targets
(itself and p53) and in doing so significantly contributes to MDM2-dependent p53
homeostasis in unstressed cells. The p53 tumor suppressor protein has a major role in protecting genome
integrity. Under normal circumstances Mdmx and Mdm2 control the activity of p53.
Both proteins inhibit the transcriptional regulation by p53, while Mdm2 also
functions as an E3 ubiquitin ligase to target both p53 and Mdmx for proteasomal
degradation. HAUSP counteracts the destabilizing effect of Mdm2 by direct
deubiquitination of p53. Subsequently, HAUSP was shown to deubiquitinate Mdm2
and Mdmx, thereby stabilizing these proteins. The ATM protein kinase is a key
regulator of the p53 pathway in response to double strand breaks (DSBs) in the
DNA. ATM fine-tunes p53's response to DNA damage by directly phosphorylating it,
by regulating additional post-translational modifications of this protein, and
by affecting two p53 regulators: Mdm2 and Mdmx. ATM directly and indirectly
induces Mdm2 and Mdmx phosphorylation, resulting in decreased activity and
stability of these proteins. We recently provided a mechanism for the reduced
stability of Mdm2 and Mdmx by showing that ATM-dependent phosphorylation lowers
their affinity for the deubiquitinating enzyme HAUSP. Altogether, the emerging
picture portrays an elaborate, but fine-tuned, ATM-mediated control of p53
activation and stabilization following DNA damage. Further insight into the
mechanism by which ATM switches the interactions between HAUSP, Mdmx, Mdm2 and
p53, to favor p53 activation may offer new tools for therapeutic intervention in
the p53 pathway for cancer treatment. MDM2 is an E3 ubiquitin ligase that regulates the proteasomal degradation and
activity of proteins involved in cell growth and apoptosis, including the tumor
suppressors p53 and retinoblastoma and the transcription factor E2F1. Although
the effect of several MDM2 targets on cardiomyocyte survival and hypertrophy has
already been investigated, the role of MDM2 in these processes has not yet been
established. We have, therefore, analyzed the effect of overexpression as well
as inhibition of MDM2 on cardiac ischemia/reperfusion injury and hypertrophy.
Here we show that isolated cardiac myocytes overexpressing MDM2 acquired
resistance to hypoxia/reoxygenation-induced cell death. Conversely, inactivation
of MDM2 by a peptide inhibitor resulted in elevated p53 levels and promoted
hypoxia/reoxygenation-induced apoptosis. Consistent with this, decreased
expression of MDM2 in a genetic mouse model was accompanied by reduced
functional recovery of the left ventricles determined with the Langendorff ex
vivo model of ischemia/reperfusion. In contrast to cell survival, cell
hypertrophy induced by the alpha-agonists phenylephrine or endothelin-1 was
inhibited by MDM2 overexpression. Collectively, our studies indicate that MDM2
promotes survival and attenuates hypertrophy of cardiac myocytes. This
differential regulation of cell growth and cell survival is unique, because most
other survival factors are prohypertrophic. MDM2, therefore, might be a
potential therapeutic target to down-regulate both cell death and pathologic
hypertrophy during remodeling upon cardiac infarction. In addition, our data
also suggest that cancer treatments with MDM2 inhibitors to reactivate p53 may
have adverse cardiac side effects by promoting cardiomyocyte death. Mdm2 has been thought to regulate the tumor suppressor p53 in two ways: by
masking p53's access to transcriptional machinery, and by ubiquitinating p53,
targeting it for proteasomal degradation. This dogma was recently challenged by
data generated from knockin mice in which Mdm2's RING E3 ubiquitin ligase
activity was abrogated by a single point mutation. The RING mutant Mdm2 is fully
capable of binding with p53, yet cannot suppress p53 activity, suggesting that
Mdm2 cannot block p53 by binding alone, without ubiquitination. Data from the
RING knockin mice also revealed that endogenous Mdm2 does not, as previously
thought, regulate its own stability by self-ubiquitination. In this review, we
will discuss these findings and their relevance to the field, including
potential reasons for the discrepancies between previous data and that generated
by our knockin mice, as well as the feasibility of targeting Mdm2's E3 ubiquitin
ligase activity in cancer. We will also discuss additional research questions
that may be addressed using our mouse model. The p53 tumour suppressor protein is tightly controlled by the E3 ubiquitin
ligase, mouse double minute 2 (MDM2), but maintains MDM2 expression as part of a
negative feedback loop. We have identified the immunophilin, 25kDa FK506-binding
protein (FKBP25), previously shown to be regulated by p53-mediated repression,
as an MDM2-interacting partner. We show that FKBP25 stimulates
auto-ubiquitylation and proteasomal degradation of MDM2, leading to the
induction of p53. Depletion of FKBP25 by siRNA leads to increased levels of MDM2
and a corresponding reduction in p53 and p21 levels. These data are consistent
with the idea that FKBP25 contributes to regulation of the p53-MDM2 negative
feedback loop. PURPOSE: p53 is inactivated in many human maligcies through missense
mutations or overexpression of the human homologue of Mdm2 (Hdm2), an E3
ubiquitin ligase that ubiquitinates p53, thereby promoting its proteasomal
degradation. The cis-imidazoline nutlin-3 can disrupt the p53-Hdm2 interaction
and activate p53, inducing apoptosis in vitro in many maligcies, including
multiple myeloma (MM).
EXPERIMENTAL DESIGN: We hypothesized that suppression of Hdm2-mediated p53
ubiquitination may augment sequelae of p53 accumulation caused by proteasomal
inhibition. We compared the response of MM cells versus several epithelial
cancer models to the proteasome inhibitor bortezomib in combination with
nutlin-3.
RESULTS: The combination of sublethal concentrations of bortezomib plus nutlin-3
induced additive cytotoxicity against bortezomib-sensitive MM cell lines.
Importantly, however, in breast, prostate, colon, and thyroid (papillary,
follicular, anaplastic, and medullary) carcinoma cell lines, this combination
triggered synergistic cytotoxicity, and increased expression of p53, p21, Hdm2,
Bax, Noxa, PUMA, and cleavage of caspase-3 and poly ADP ribose polymerase.
Coculture with bone marrow stromal cells attenuated MM cell sensitivity to
nutlin-3 monotherapy and was associated with evidence of suppression of p53
activity in MM cells, whereas combined bortezomib-nutlin-3 treatment maintained
cytotoxicity even in the presence of bone marrow stromal cells.
CONCLUSIONS: This differential response of MM versus epithelial carcinomas to
combination of nutlin-3 with bortezomib sheds new light on the role of p53 in
bortezomib-induced apoptosis. Concurrent Hdm2 inhibition with bortezomib may
extend the spectrum of bortezomib applications to maligcies with currently
limited sensitivity to single-agent bortezomib or, in the future, to MM patients
with decreased clinical responsiveness to bortezomib-based therapy. Murine double minute (MDM2) is an E3 ligase that promotes ubiquitination and
degradation of tumor suppressor protein 53 (p53). MDM2-mediated regulation of
p53 has been investigated as a classical tumorigenesis pathway. Here, we
describe TRIAD1 as a novel modulator of the p53-MDM2 axis that induces p53
activation by inhibiting its regulation by MDM2. Ablation of TRIAD1 attenuates
p53 levels activity upon DNA damage, whereas ectopic expression of TRIAD1
promotes p53 stability by inhibiting MDM2-mediated ubiquitination/degradation.
Moreover, TRIAD1 binds to the C-terminus of p53 to promote its dissociation from
MDM2. These results implicate TRIAD1 as a novel regulatory factor of p53-MDM2. p53 levels and activity are controlled in large part through regulated
ubiquitination and subsequent destruction by the 26S proteasome.
Monoubiquitination of p53 is mediated primarily by the RING-finger E3 ubiquitin
ligase MDM2 and impacts p53 activity through modulation of p53 localization and
transcription activities. Recently, several E4 ubiquitin ligases (E4s) have been
identified which serve to extend these monoubiquitin chains. The ubiquitin
ligase activity of these factors toward p53, and their contribution to p53
degradation, can be studied using a variety of in vitro and in vivo methods and
reagents which will be described in this chapter. These methods include in vivo
ubiquitination of p53 using HA-ubiquitin or his-ubiquitin; the in vitro E3
ubiquitin ligase assay, in which ubiquitin reaction components (URC) are
incubated with a purified E3 or E4 ligase; a one-step E4 assay, in which URC are
incubated with a substrate, E3, and E4; and a two-step E4 assay in which p53 is
monoubiquitinated in an E3 reaction, and subsequently purified and incubated
with an E4. Finally, we will describe an in vitro degradation assay in which
ubiquitinated p53 is incubated with purified 26S proteasomes. Together, these
assays can be used to provide insight into the biochemical nature of p53
ubiquitination and degradation. The RING domain E3 ubiquitin ligase Mdm2 is the master regulator of the tumor
suppressor p53. It targets p53 for proteasomal degradation, restraining the
potent activity of p53 and enabling cell survival and proliferation. Like most
E3 ligases, Mdm2 can also ubiquitinate itself. How Mdm2 auto-ubiquitination may
influence its substrate ubiquitin ligase activity is undefined. Here we show
that auto-ubiquitination of Mdm2 is an activating event. Mdm2 that has been
conjugated to polyubiquitin chains, but not to single ubiquitins, exhibits
substantially enhanced activity to polyubiquitinate p53. Mechanistically,
auto-ubiquitination of Mdm2 facilitates the recruitment of the E2
ubiquitin-conjugating enzyme. This occurs through noncovalent interactions
between the ubiquitin chains on Mdm2 and the ubiquitin binding domain on E2s.
Mutations that diminish the noncovalent interactions render auto-ubiquitination
unable to stimulate Mdm2 substrate E3 activity. These results suggest a model in
which polyubiquitin chains on an E3 increase the local concentration of E2
enzymes and permit the processivity of substrate ubiquitination. They also
support the notion that autocatalysis may be a prevalent mode for turning on the
activity of latent enzymes. The HDM2-p53 loop is crucial for monitoring p53 level and human pathologies.
Therefore, identification of novel molecules involved in this regulatory loop is
necessary for understanding the dynamic regulation of p53 and treatment of human
diseases. Here, we characterized that the ribosomal protein L6 binds to and
suppresses the E3 ubiquitin ligase activity of HDM2, and subsequently attenuates
HDM2-mediated p53 polyubiquitination and degradation. The enhanced p53 activity
further slows down cell cycle progression and leads to cell growth inhibition.
Conversely, the level of p53 is dramatically decreased upon the depletion of
RPL6, indicating that RPL6 is essential for p53 stabilization. We also found
that RPL6 translocalizes from the nucleolus to nucleoplasm under ribosomal
stress, which facilitates its binding with HDM2. The interaction of RPL6 and
HDM2 drives HDM2-mediated RPL6 polyubiquitination and proteasomal degradation.
Longer treatment of actinomycin D increases RPL6 ubiquitination and destabilizes
RPL6, and thereby putatively attenuates p53 response until the level of L6
subsides. Therefore, RPL6 and HDM2 form an autoregulatory feedback loop to
monitor the level of p53 in response to ribosomal stress. Together, our study
identifies the crucial function of RPL6 in regulating HDM2-p53 pathway, which
highlights the importance of RPL6 in human genetic diseases and cancers. |
Can DNA intercalators function as topoisomerase inhibitors? | The DNA unwinding suggests DNA intercalation, which could explain the inhibition of topoisomerase II. Among its many properties, amiloride is a DNA intercalator and topoisomerase II inhibitor. Amsacrine, a DNA intercalator and topoisomerase II inhibitor, is efficacious as an antileukemogenic agent. AQ4N (1,4-bis[[2-(dimethylamino)ethyl] amino]-5,8-dihydroxyanthracene-9, 10-dione bis-N-oxide dihydrochloride) is a prodrug which is selectively activated within hypoxic tissues to AQ4, a topoisomerase II inhibitor and DNA intercalator. Amonafide is a DNA intercalator and topoisomerase II inhibitor in clinical development for the treatment of neoplastic diseases. | Accumulation of gadd153 mRNA is strongly stimulated in mammalian cells by
treatments which arrest growth or damage DNA (A. J. Fornace, Jr. et al., Mol.
Cell. Biol., 9: 4196-4203, 1989). In previous studies, we demonstrated that the
increased expression of gadd153 following treatment with several DNA-damaging
agents was mediated transcriptionally (J. D. Luethy et al., J. Biol. Chem., 265:
16521-16526, 1990). To better define the specificity of this response, we have
established a sensitive reporter system in which we have stably integrated a
chimeric gene containing the gadd153 promoter linked to the coding region of the
chloramphenicol acetyltransferase (CAT) gene into the genome of HeLa cells.
Transcriptional activation from the gadd153 promoter was monitored by
determining levels of CAT activity in cellular lysates prepared from
gadd153CAT/HeLa cells treated with a variety of agents. The gadd153 promoter was
strongly activated by a broad spectrum of genotoxic agents including UV-mimetic
agents, DNA-cross-linking and alkylating agents, DNA intercalators, and
topoisomerase inhibitors. Of the DNA-damaging agents tested, only X-irradiation
and bleomycin treatments failed to induce gadd153 promoter activity. Agents
which inhibit replication and cell division and agents which otherwise result in
cytotoxicity or growth arrest also had little influence on gadd153 promoter
activity. Expression of the gadd153CAT chimeric gene in xeroderma pigmentosum
Group A cells, which are deficient in nucleotide excision DNA repair of
pyrimidine dimers, was maximally induced at UV doses at least 6-fold lower than
those required for similar induction in repair-proficient HeLa cells. However,
the methyl methanesulfonate-induced gadd153 promoter activities were similar in
both cell lines. Novobiocin pretreatment inhibited both UV- and methyl
methanesulfonate-induced gadd153CAT expression. Collectively, these data
indicate that: (a) the gadd153 promoter is activated rapidly and specifically by
DNA damage; (b) the altered DNA structure is the inducing signal for the
activation of the signal transduction pathway responsible for enhanced gadd153
expression; and (c) regulation of gadd153 by growth arrest is distinct from that
of DNA damage. Thus, the gadd153CAT/HeLa cells are a useful model for examining
the molecular mechanisms associated with the response to DNA damage and provide
a reporter system for the screening of potential genotoxic agents. A mutant murine cell line has previously been reported to be resistant to the
AT-specific DNA minor groove ligand 2',5'-bi-1H-benzimidazole,
2',(4-ethoxyphenyl)-5-(4-methyl-1-piperazinyl), trichloride (Ho33342), due to an
enhanced capacity to remove ligand molecules from cellular DNA via a pathway
which can be blocked by DNA topoisomerase poisons. We have studied the
relationship between ligand resistance and DNA topoisomerase II activity. The
cross-sensitivity patterns of the mutant were examined for covalently
(anthramycin) and non-covalently (distamycin A) binding minor groove ligands,
and DNA intercalating [adriamycin, mitoxantrone and
4'-(9-acridinylamino)methanesulphon-m-anisidide (mAMSA)] and non-intercalating
(VP16-213) topoisomerase II poisons. The mutant was cross-resistant to
distamycin A alone. The mutant showed no abnormality in: (i) the in vitro
decatenation activity of topoisomerase II, (ii) VP16-213 or mAMSA induced
protein-DNA cross-linking activities in nuclear extracts, (iii) 'cleavable
complex' generation (or DNA strand scisson) in intact cells exposed to
topoisomerase poisons. Ho33342 and the topoisomerase II inhibitor novobiocin
were found to disrupt both the in vitro binding of nuclear extracted proteins,
from mutant and parental cells, to plasmid DNA and the formation of drug-induced
cleavable complexes in vitro. Unexpectedly, Ho33342 induced significant levels
of DNA-protein crosslinking in both parental and mutant cells. We conclude that:
(i) resistance of the mutant is limited to non-covalently binding minor groove
ligands, (ii) Ho33342 can block the trapping of DNA topoisomerase II by enzyme
poisons in vitro, (iii) Ho33342 can induce a novel form of DNA-protein
cross-link in intact cells, and (iv) the resistance of the mutant is not
dependent upon some abnormality in topoisomerase II function. The effect of cyanomorpholinyldoxorubicin, morpholinyldoxorubicin, doxorubicin,
and Actinomycin D were studied on purified mouse leukemia (L1210) DNA
topoisomerases I and II. DNA unwinding and cross-linking were also studied. It
was found that 1) morpholinyldoxorubicin, cyanomorpholinyldoxorubicin, and
Actinomycin D (but not doxorubicin) stimulated DNA topoisomerase I-induced
cleavage at specific DNA sites; 2) only doxorubicin and Actinomycin D stimulated
DNA cleavage by DNA topoisomerase II; 3) at higher drug concentrations, DNA
intercalators suppressed enzyme-mediated DNA cleavage induced by DNA
topoisomerase I, as well as topoisomerase II; 4) only
cyanomorpholinyldoxorubicin produced DNA-DNA cross-links; no DNA unwinding could
be observed; and 5) DNA intercalation (unwinding) potency of
morpholinyldoxorubicin was about 2-fold less than that of doxorubicin. The data
indicate that some DNA intercalators are not only inhibitors of DNA
topoisomerase II but act also on DNA topoisomerase I. The stabilization of
cleavage intermediates by intercalators may have a common mechanism for DNA
topoisomerase I and DNA topoisomerase II. The cytotoxic actions of several classes of antitumor DNA intercalators are
thought to result from some disturbance to DNA metabolism following trapping of
the nuclear enzyme DNA topoisomerase II as a covalent complex on DNA. Here we
have studied topoisomerase II trapping and DNA synthesis patterns in relation to
the acute cytotoxic actions of 4'-(9-acridinylamino)methanesulfon-m-anisidide
(mAMSA) or mitoxantrone on SV40 transformed human fibroblasts. These two DNA
intercalators differed significantly in their cytotoxic potential, mitoxantrone
being 24-fold more toxic than mAMSA when assayed by the inhibition of
clonogenicity. Although both drugs induced G2 delay at cytotoxic concentrations,
mAMSA-treated cells recovered normal cell cycle phase distributions within 24 h
of removal of drug, while mitoxantrone-treated cells continued to accumulate in
G2 up to 48 h following drug treatment with evidence of complete inhibition of
entry into mitosis. Compared with mAMSA, mitoxantrone showed a similar capacity
to induce cleavable complexes in cellular DNA, and only a 2-fold greater ability
to inhibit DNA synthesis. Within a 4-h posttreatment period, mAMSA-treated cells
recovered normal rates of DNA synthesis, whereas a continued depression of DNA
synthesis was observed in mitoxantrone-treated cells. The recovery patterns of
DNA synthesis correlated with the rapid disappearance of mAMSA-induced complexes
(less than 27% lesions remaining 2 h after drug removal) and the persistence of
mitoxantrone-induced complexes during a 4-h posttreatment period. This
difference in complex longevity was observed in other human transformed
fibroblast cell lines irrespective of differences in the absolute levels of
complexes induced by either agent. We suggest that the results provide evidence
that DNA intercalators may differ in the forms of complexes induced and that the
comparatively high cytotoxicity of mitoxantrone relates to the ability of the
drug to trap topoisomerase II complexes in a form which effects a long-term
inhibition of DNA replication and G2 traverse. Among its many properties, amiloride is a DNA intercalator and topoisomerase II
inhibitor. Previous work has indicated that the most stable conformation for
amiloride is a planar, hydrogen-bonded, tricyclic structure. To determine
whether the ability of amiloride to intercalate into DNA and to inhibit DNA
topoisomerase II was dependent on the ability to assume a cyclized conformation,
we studied the structure-activity relationship for 12 amiloride analogs. These
analogs contained structural modifications which could be expected to allow or
impede formation of a cyclized conformation. Empirical assays consisting of
biophysical, biochemical, and cell biological approaches, as well as
computational molecular modeling approaches, were used to determine
conformational properties for these molecules, and to determine whether they
intercalated into DNA and inhibited topoisomerase II. Specifically, we measured
the ability of these compounds to 1) alter the thermal denaturation profile of
DNA, 2) modify the hydrodynamic behavior of DNA, 3) inhibit the catalytic
activity of purified DNA topoisomerase II in vitro, 4) promote the topoisomerase
II-dependent cleavage of DNA, and 5) inhibit functions associated with DNA
topoisomerase II in intact cells. Results indicated that only those analogs
capable of cyclization could intercalate into DNA and inhibit topoisomerase II.
Thus, the ability of amiloride and the 12 analogs studied to intercalate into
DNA and to inhibit topoisomerase II appears dependent on the ability to exist in
a planar, hydrogen-bonded, tricyclic conformation. Abnormal expression of the nuclear-associated enzyme DNA topoisomerase II
(topoisomerase II) has been implicated in the in vitro phenotype of radiation
hypersensitive ataxia-telangiectasia (A-T) cells and in modifying sensitivity of
eukaryotic cells to topoisomerase II-inhibitor drugs [e.g., the DNA intercalator
amsacrine (mAMSA)]. To study such relationships, various SV40- and Epstein-Barr
Virus-transformed human cell lines derived from normal, A-T, or UV-sensitive
xeroderma pigmentosum donors have been assayed for their sensitivity to mAMSA
together with direct and indirect measurements of topoisomerase II expression.
We report on the identification of an SV40-transformed A-T fibroblast cell line
with abnormally high levels of topoisomerase II in nuclear protein extracts as
determined by immunoblotting, measurement of kinetoplast DNA decatenation
activity, and mAMSA-dependent DNA-protein cross-linking activity in a filter
binding assay. Using a flow cytometric assay for the analysis of reactivity of
nuclei with a polyclonal antitopoisomerase II antibody, overproduction was found
to occur in all phases of the cell cycle. High levels of topoisomerase II were
associated with hypersensitivity (5-10-fold) to mAMSA-induced cell cycle delay,
cell kill, and DNA strand breakage (assayed under protein-denaturing
conditions). Xeroderma pigmentosum (group A) cells demonstrated normal responses
to mAMSA. The results provide evidence that cellular potential for the
generation of topoisomerase II-dependent DNA damage is a major factor in
governing the sensitivity to mAMSA. Furthermore, underexpression of
topoisomerase II does not appear to be a primary factor in describing the in
vitro A-T phenotype. The findings also relate to how changes in chromatin
structure and function may either reflect or dictate the expression of
topoisomerase II in human cells. Interest in DNA-intercalating ligands as anti-cancer drugs has developed greatly
since the clinical success of doxorubicin. However, despite a great deal of
'rational design' of synthetic DNA-intercalators, only a few such compounds have
proved clinically useful. This review briefly surveys the history of
DNA-intercalators as clinically-used anti-cancer drugs, summarizes the known
structure-experimental activity relationships and modes of action, and concludes
that a factor in the slow progress is that much of the work on these compounds
has been carried out by chemists, who were generally more interested in
ligand/DNA interactions than drug development. Future development of the class
rests on a careful consideration of the biochemical reasons behind the common
limitations of the present drugs. The most important are: the inherent
resistance of non-cycling cells, the rapid development (even by cycling cells)
of resistance by the expression of both P-glycoprotein and altered topoisomerase
II, limitations on drug distribution to and transport into tumours, low
extravascular pH in tumours and the cardiotoxic side-effects of quinonoid
chromophores. These considerations provide a set of constraints on
physicochemical properties which must be considered in future design. However,
within these constraints, there are useful future avenues for the development of
DNA-intercalators as anti-cancer drugs. These include: (i) the production of
improved topoisomerase inhibitors (by consideration of drug/protein as well as
drug/DNA interactions); (ii) the development of reductively-activated
chromophores as hypoxia-selective agents; and (iii) the use of DNA-intercalators
of known DNA binding orientation as 'carriers' for the delivery of other
reactive functionality specifically (sequence-, regio- and site-specifically) to
DNA. Amiloride is capable of inhibiting DNA synthesis in mammalian cells in culture.
Recent evidence indicates that the enzyme, DNA topoisomerase II, is probably
required for DNA synthesis to occur in situ. In experiments to determine the
mechanism of inhibition of DNA synthesis by amiloride, we observed that
amiloride inhibited both the catalytic activity of purified DNA topoisomerase II
in vitro and DNA topoisomerase II-dependent cell functions in vivo. Many
compounds capable of inhibiting DNA topoisomerase II are DNA intercalators.
Thus, we performed studies to determine if and how amiloride bound to DNA.
Results indicated that amiloride 1) shifted the thermal denaturation profile of
DNA, 2) increased the viscosity of linear DNA, and 3) unwound circular DNA, all
behavior consistent with a DNA intercalation mechanism. Furthermore,
quantitative and qualitative measurements of amiloride fluorescence indicated
that amiloride (a) bound reversibly to purified DNA under conditions of
physiologic ionic strength, and (b) bound to purified nuclei in a highly
cooperative manner. Lastly, amiloride did not promote the cleavage of DNA in the
presence of DNA topoisomerase II, indicating that the mechanism by which
amiloride inhibited DNA topoisomerase II was not through the stabilization of a
"cleavable complex" formed between DNA topoisomerase II, DNA, and amiloride. The
ability of amiloride to intercalate with DNA and inhibit topoisomerase II is
consistent with the proposed planar, hydrogen-bonded, tricyclic nature of
amiloride's most stable conformation. Thus, DNA and DNA topoisomerase II must be
considered as new cellular targets of amiloride action. Several new pyridoacridine alkaloids, dehydrokuanoniamine B (1), shermilamine C
(2), and cystodytin J (3), in addition to the known compounds cystodytin A (4),
kuanoniamine D (5), shermilamine B (6), and eilatin (7), were isolated from a
Fijian Cystodytes sp. ascidian. Their structures were determined by analyses of
spectroscopic data. These compounds along with a previously reported
pyridoacridine, diplamine (8), showed dose-dependent inhibition of proliferation
in human colon tumor (HCT) cells in vitro. All compounds inhibited the
topoisomerase (TOPO) II-mediated decatenation of kinetoplast DNA (kDNA) in a
dose-dependent manner. The pyridoacridines' ability to inhibit TOPO II-mediated
decatenation of kDNA correlated with their cytotoxic potencies and their ability
to intercalate into calf thymus DNA. These results suggest that disruption of
the function of TOPO II, subsequent to intercalation, is a probable mechanism by
which pyridoacridines inhibit the proliferation of HCT cells. Incorporation
studies show that pyridoacridines disrupt DNA and RNA synthesis with little
effect on protein synthesis. It appears that DNA is the primary cellular target
of the pyridoacridine alkaloids. These results are consistent with those for
known DNA intercalators. Pulse field gel electrophoresis using a contour-clamped homogeneous electric
field was applied for the analysis of DNA-fragmenting activity of antitumor
agents towards human uterine cervix carcinoma HeLa S3 cells. Duocarmycins
(DUMs), novel antitumor antibiotics with ultrapotent cell growth-inhibitory
activities, caused DNA fragmentation at 10 times their IC50 values at 2 h
exposure. At 100 times their IC50 values, the size of the smallest fragments was
about 245 kilobase pairs (kbp). DUMA, DUMB1 and DUMB2 exhibited similar DNA
fragmentation patterns, suggesting similar action mechanisms. DNA fragmentation
was also detected in cells treated with radical producers, intercalators and
topoisomerase inhibitors. Two bands of about 1800 and 1500 kbp were commonly
detected in the cells treated with DUMs and these agents. In addition, fragments
of about 900 kbp were detected in the cells treated with a topoisomerase
inhibitor, 4'-(9-acridinylamino)methane-sulfon-m-anisidine, and fragments in the
broad size range between 700 and 245 kbp in the cells treated with radical
producers, bleomycin and neocarzinostatin. DUMs showed a characteristic DNA
fragmentation pattern, since both types of fragments induced by the
topoisomerase inhibitor and the radical producers were simultaneously detected,
suggesting a novel mode of interaction with DNA. DNA-crosslinking agents and
mitotic inhibitors did not induce DNA fragmentation under these conditions. The
pulse field gel electrophoresis is potentially useful for characterizing
DNA-cleaving activity of various antitumor agents at the cellular level. Amsacrine, a DNA intercalator and topoisomerase II inhibitor, is efficacious as
an antileukemogenic agent. This study was conducted to assess the subchronic
toxicity of amsacrine in rats following a cyclic clinical dosing regimen and as
a range-finding experiment for a subsequent carcinogenicity bioassay. Groups of
30 male Wistar rats were administered drug intravenously at doses of 0, 0.25,
1.0, and 3.0 mg/kg daily for 5 days followed by 23 days without treatment. This
cycle of dosing and recovery was repeated six times to simulate human clinical
usage of the drug. Assessments of hematology, clinical chemistry, and gross and
microscopic pathology were conducted 3 and 21 days following completion of
dosing in the first, third, and sixth cycles. There were no deaths during the
study. Hair loss, diarrhea, tail injuries, chromodacryorrhea, and rhinorrhea
were observed primarily in animals administered 3 mg/kg. Hair loss and diarrhea
occurred during periods of dosing and generally resolved during the recovery
phase of each cycle. Both of these signs became progressively more severe during
the latter half of the study. Body weight loss and reduced food consumption also
occurred in the 3 mg/kg group during each week of dosing. At study termination,
mean body weight and food consumption of the 3 mg/kg group were significantly
less than those of controls by approximately 20 and 50%, respectively. Marked,
reversible leukopenia associated with reductions in both neutrophil and
lymphocyte counts occurred in cycles one and three in animals administered 1 and
3 mg/kg, respectively. Reversible neutropenia was also observed in the 3 mg/kg
group in cycle 6. Similar effects on platelet counts were seen in the 3 mg/kg
group in all three cycles analyzed. Absolute and relative testes weights of the
3 mg/kg group were significantly less than the vehicle controls at all time
points in the third and sixth cycles. Relative testes weights were also
decreased in the 1 mg/kg group in cycle 6. Reversible decreases in absolute
relative spleen weights occurred in all drug-treated groups in cycle 1 and for
the 3 mg/kg group in cycle 3. Lymphoid depletion (spleen, thymus, lymph node),
marked hypocellularity of bone marrow, segmental degeneration of seminiferous
tubules, and intestinal epithelial cell degeneration were observed at 3 mg/kg.
With the exception of testicular changes which remained evident at the end of
cycle 6, pathologic lesions were reversible during the 23-day recovery period of
each cycle. The results show that the subchronic toxicity of amsacrine is
consistent with a cytotoxic mechanism and that target organs are generally
tissues with the highest rates of cell turnover. The doses administered in this
study induced a range of effects which were minimal at 0.25 mg/kg and
dose-limiting at 3 mg/kg and therefore were considered appropriate for use in
the subsequent carcinogenicity bioassay. Cytotoxicity of several classes of antitumor DNA intercalators is thought to
result from disturbance of DNA metabolism following trapping of the nuclear
enzyme DNA topoisomerase II as a covalent complex on DNA. Here, molecular
interactions of the potent antitumor drug amsacrine (m-AMSA), an inhibitor of
topoisomerase II, within living K562 cancer cells have been studied using
surface-enhanced Raman (SER) spectroscopy. The work is based on data of the
previously performed model SER experiments dealing with amsacrine/DNA,
drug/topoisomerase II and drug/DNA/topoisomerase II complexes in aqueous buffer
solutions. The SER data indicated two kinds of amsacrine interactions in the
model complexes with topoisomerase II alone or within ternary complex:
non-specific (via the acridine moiety) and specific to the enzyme conformation
(via the side chain of the drug). These two types of interactions have been both
revealed by the micro-SER spectra of amsacrine within living K562 cancer cells.
Our data suppose the specific interactions of amsacrine with topoisomerase II
via the side chain of the drug (particular feature of the drug/topoisomerase II
and ternary complexes) to be crucial for its inhibitory activity. Germline mutations in the breast cancer susceptibility genes BRCA1 and BRCA2
have been linked to the development of breast cancer, ovarian cancer, and other
maligcies. Recent studies suggest that the BRCA1 and BRCA2 gene products may
function in the sensing and/or repair of DNA damage. To investigate this
possibility, we determined the effects of various DNA-damaging agents and other
cytotoxic agents on the mRNA levels of BRCA1 and BRCA2 in the MCF-7 and other
human breast cancer cell lines. We found that several agents, including
adriamycin (a DNA intercalator and inhibitor of topoisomerase II), camptothecin
(a topoisomerase I inhibitor), and ultraviolet radiation induced significant
decreases in BRCA1 and BRCA2 mRNA levels. Decreased levels of BRCA1 and BRCA2
mRNAs were observed within 6-12 h after treatment with adriamycin and persisted
for at least 72 h. Adriamycin also induced decreases in BRCA1 protein levels;
but these decreases required several days. U.V. radiation induced dose-dependent
down-regulation of BRCA1 and BRCA2 mRNAs, with significant decreases in both
mRNAs at doses as low as 2.5 J/m2, a dose that yielded very little cytotoxicity.
Adriamycin-induced down-regulation of BRCA1 and BRCA2 mRNAs was first observed
at doses that yielded relatively little cytotoxicity and little or no apoptotic
DNA fragmentation. Adriamycin and U.V. radiation induced distinct dose- and
time-dependent alterations in the cell cycle distribution; but these alterations
did not correlate well with corresponding changes in BRCA1 and BRCA2 mRNA
levels. However, the adriamycin-induced reduction in BRCA1 and BRCA2 mRNA levels
was correlated with p53 functional status. MCF-7 cells transfected with a
domit negative mutant p53 (143 val-->ala) required at least tenfold higher
doses of adriamycin to down-regulate BRCA1 and BRCA2 mRNAs than did parental
MCF-7 cells or control-transfected MCF-7 clones. These results suggest that
BRCA1 and BRCA2 may play roles in the cellular response to DNA-damaging agents
and that there may be a p53-sensitive component to the regulation of BRCA1 and
BRCA2 mRNA expression. Naturally occurring 1,8-dihydroxyanthraquinones are under consideration as
possible carcinogens. Here we wanted to elucidate a possible mechanism of their
genotoxicity. All three tested anthraquinones, emodin, aloe-emodin, and
danthron, showed capabilities to inhibit the non-covalent binding of
bisbenzimide Hoechst 33342 to isolated DNA and in mouse lymphoma L5178Y cells
comparable to the topoisomerase II inhibitor and intercalator m-amsacrine. In a
cell-free decatenation assay, emodin exerted a stronger, danthron a similar and
aloe-emodin a weaker inhibition of topoisomerase II activity than m-amsacrine.
Analysis of the chromosomal extent of DNA damage induced by these anthraquinones
was performed in mouse lymphoma L5178Y cells. Anthraquinone-induced mutant cell
clones showed similar chromosomal lesions when compared to the topoisomerase II
inhibitors etoposide and m-amsacrine, but were different from mutants induced by
the DNA alkylator ethyl methanesulfonate. These data support the idea that
inhibition of the catalytic activity of topoisomerase II contributes to
anthraquinone-induced genotoxicity and mutagenicity. Inhibitors of topoisomerase I constitute a novel family of antitumor agents. The
camptothecin derivatives topotecan and irinotecan represent new weapons in our
arsenal for battling human cancer. These two drugs act specifically at the level
of the topoisomerase I-DNA complex and stimulate DNA cleavage. This mechanism of
action is not restricted to the camptothecins. Numerous topoisomerase I poisons
including DNA minor groove binders such as Hoechst 33258 and DNA intercalators
such as benzophethridine alkaloids and indolocarbazole derivatives have been
discovered and developed. Another important group of topoisomerase I inhibitors
contains drugs which prevent or reverse topoisomerase I-DNA complex formation.
Many of these topoisomerase I suppressors are natural products (beta-lapachone,
diospyrin, topostatin, topostin, flavonoids) which are believed to interact
directly with the enzyme. This review is concerned with the different families
of topoisomerase I poisons and suppressors. Their origin, chemical nature and
mechanism of action are presented. The relationships between drug binding to DNA
and topoisomerase I inhibition are discussed. The action of the anticancer drug amsacrine appears to involve molecular
interactions with both DNA and topoisomerase II. It has been shown previously
that DNA intercalators can inhibit the action of amsacrine and several other
topoisomerase II poisons, presumably as a result of interference with the DNA
binding sites for the enzyme. We show here that drug molecules such as
N-phenylmethanesulfonamide, which mimic the anilino side chain of amsacrine,
inhibit the cytotoxicity against cultured Lewis lung murine carcinoma of
amsacrine, amsacrine analogues including asulacrine and DACA
(N-[2-(dimethylamino)-ethyl]acridine-4-carboxamide dihydrochloride), and
etoposide. In contrast, the cytotoxicity of doxorubicin was slightly increased
by co-incubation with N-phenylmethanesulfonamide. The cytotoxicity of amsacrine
was also modulated in human Jurkat leukemia, HCT-8 colon, and HT-29 colon cell
lines. Because o-AMSA, an amsacrine analogue containing a methoxy group in the
ortho rather than in the meta position, is known to be inactive as an antitumor
drug, the abilities of the ortho and meta methoxy-substituted derivatives of
methyl-N-phenylcarbamate to reverse the cytotoxicity of amsacrine, asulacrine,
and DACA were compared. The ortho substitution decreased activity while meta
substitution slightly increased it, suggesting that the side chains were binding
to a similar site to that occupied by amsacrine. To determine whether the side
chain variants actively inhibited the formation of DNA-topoisomerase II covalent
complexes, cultured cells were treated with amsacrine or asulacrine, harvested,
and lysed directly on acrylamide gels before electrophoresis and Western
blotting to identify non-DNA-bound topoisomerase II. Extractable topoisomerase
II was depleted in cells incubated with amsacrine but partially restored by
coculture with methyl-N-phenylcarbamate. The findings are consistent with the
hypothesis that low molecular weight molecules can modulate the effects of
topoisomerase II poisons by directly interacting with the enzyme. N-Benzyladriamycin (AD 288) is a highly lipophilic, semi-synthetic congener of
doxorubicin (DOX). Unlike DOX, which stimulates double-stranded DNA scission by
stabilizing topoisomerase II/DNA cleavable complexes, AD 288 is a catalytic
inhibitor of topoisomerase II, capable of preventing topoisomerase II activity
on DNA. The concentration of AD 288 required to inhibit the topoisomerase
II-catalyzed decatenation of linked networks of kinetoplast DNA was comparable
to that for DOX. However, AD 288 did not stabilize cleavable complex formation
or stimulate topoisomerase II-mediated DNA cleavage. In addition, AD 288
inhibited the formation of cleavable complexes by etoposide in a
concentration-dependent manner. Human CCRF-CEM cells and murine J774. 2 cells
exhibiting resistance against DOX, teniposide, or
3'-hydroxy-3'-deaminodoxorubicin through reduced topoisomerase II activity
remained sensitive to AD 288. These studies suggest that AD 288 inhibits
topoisomerase II activity by preventing the initial non-covalent binding of
topoisomerase II to DNA. Since AD 288 is a potent DNA intercalator, catalytic
inhibition is achieved by prohibiting access of the enzyme to DNA binding sites.
These results also demonstrate that specific substitutions on the aminosugar of
DOX can alter the mechanism of topoisomerase II inhibition. The aporphine alkaloids (+)-dicentrine and (+)-bulbocapnine are non-planar
molecules lacking features normally associated with DNA binding by intercalation
or minor groove binding. Surprisingly, dicentrine showed significant activity as
a topoisomerase II (EC 5.99.1.3) inhibitor and also was active in a DNA
unwinding assay. The DNA unwinding suggests DNA intercalation, which could
explain the inhibition of topoisomerase II. Bulbocapnine, which differs from
dicentrine only by the presence of a hydroxyl group at position 11 and the
absence of a methoxyl group at position 9, was inactive in all assays. Molecular
modeling showed that dicentrine can attain a relatively planar conformation,
whereas bulbocapnine cannot, due to steric interaction between the 11-hydroxyl
group and an oxygen of the methylenedioxy ring. These observations suggest that
dicentrine is an "adaptive" DNA intercalator, which can bind DNA only by
adopting a somewhat strained planar conformation. The requirement of a
suboptimal conformation to achieve DNA binding appears to make dicentrine a
weaker topoisomerase II inhibitor than the very planar oxoaporphine alkaloid
liriodenine. These results suggest that it may be possible to modulate DNA
binding and biologic activity of drugs by modifications affecting their ability
to adopt planar conformations. Indenoisoquinolines are topoisomerase (Top) I inhibitors developed to overcome
some of the limitations of camptothecins and expand their anticancer spectrum.
Bis-1,3-{(5,6-dihydro-5,11-diketo-11H-indeno[1,2-c]isoquinoline)-6-propylamino}-propane
bis(trifluoroacetate) (NSC 727357) is a novel dimeric indenoisoquinoline
derivative with potent antiproliferative activity in the NCI-60 cell line panel,
promising hollow fiber activity (score of 32) and activity against xenografts.
Submicromolar concentrations of the bisindenoisoquinoline NSC 727357 induce Top1
cleavage complexes at specific sites in biochemical assays. At higher
concentrations, inhibition of Top1 catalytic activity and DNA intercalation is
observed. NSC 727357 also induces a limited number of Top2-DNA cleavage
complexes. In contrast to the effect of other Top1 inhibitors, cells treated
with the bisindenoisoquinoline NSC 727357 show an arrest of cell cycle
progression in G(1) with no significant inhibition of DNA synthesis after a
short exposure to the drug. Moreover, unlike camptothecin and the
indenoisoquinoline MJ-III-65 (NSC 706744,
6-[3-(2-hydroxyethyl)aminopropyl]-5,6-dihydro-5,11-diketo-2,3-dimethoxy-(methylenedioxy)-11H-indeno[1,2-c]isoquinoline
hydrochloride), the cytotoxicity of bisindenoisoquinoline NSC 727357 is only
partially dependent on Top1 and p53, indicating that this drug has additional
targets besides Top1 and Top2. In the context of the design and synthesis of minor groove binding and
intercalating DNA ligands some new oligopyrrole carboxamides were synthesized.
These hybrid molecules (combilexins) possess a variable and conformatively
flexible spacer at the N-terminal end. As intercalating tricyclic systems
acridone, acridine, anthraquinones and in a special case iminostilbene terminate
the N-terminal end of the pyrrole chain. The cytotoxicity was examined by the
NCI antitumor screening, furthermore, biophysical as well as biochemical studies
were performed in order to get some information about the DNA binding properties
and topoisomerase inhibition effect of this new series of molecules. BACKGROUND: AQ4N (1,4-bis[[2-(dimethylamino)ethyl]
amino]-5,8-dihydroxyanthracene-9, 10-dione bis-N-oxide dihydrochloride) is a
prodrug which is selectively activated within hypoxic tissues to AQ4, a
topoisomerase II inhibitor and DNA intercalator.
PATIENTS AND METHODS: In the phase I study, 22 patients with oesophageal
carcinoma received an i.v. infusion of AQ4N (22.5-447 mg/m(2)) followed, 2 weeks
later, by further infusion and radiotherapy. Pharmacokinetics and lymphocyte
AQ4N and AQ4 levels were measured after the first dose. At 447 mg/m(2), biopsies
of tumour and normal tissue were taken after AQ4N administration.
RESULTS: Drug-related adverse events were blue discolouration of skin and urine,
grade 2-3 lymphopenia, grade 1-3 fatigue, grade 1-2 anaemia, leucopenia and
nausea. There were no drug-related serious adverse events (SAEs). Three patients
had reductions in tumour volume >50%, nine had stable disease. Pharmacokinetics
indicated predictable clearance. Plasma area under the curve (AUC) at 447
mg/m(2) exceeded AQ4N concentrations in mice at therapeutic doses and tumour
biopsies contained concentrations of AQ4 greater than those in normal tissue.
Tumour concentrations of AQ4 exceeded in vitro IC(50) values for most cell lines
investigated.
CONCLUSIONS: No dose-limiting toxic effects were observed and a maximum
tolerated dose was not established. Tumour AQ4 concentrations and plasma AUC at
447 mg/m(2) exceeded active levels in preclinical models. This dose was chosen
for future studies with radiotherapy. Amonafide is a DNA intercalator and topoisomerase II inhibitor in clinical
development for the treatment of neoplastic diseases. Amonafide contains a free
arylamine, which causes it to be metabolized in humans by N-acetyl transferase-2
(NAT2) into a toxic form. To eliminate the NAT2 acetylation of amonafide while
retaining the anticancer properties, we have synthesized nine derivatives that
are structurally similar to amonafide that should not be acetylated. Eight
derivatives have arylamines at the 6-position (vs. 5-position of amonafide) and
one derivative completely lacks the arylamine. The derivative with a free amine
in the 6-position and one with a substituted amine in the 6-position are not
acetylated, whereas amonafide is extensively acetylated as determined by an NAT2
assay. The biological activities of these compounds were evaluated to determine
whether they behaved similarly to amonafide in purified systems and in vitro. We
found that three compounds had similar cancer cell-selective growth inhibition
to amonafide, while retaining similar subcellular localization, DNA
intercalation and topoisomerase II inhibition activities. In addition, these
compounds were able to eliminate a marker of metastatic potential, the
perinucleolar compartment. These three compounds (named numonafides) might thus
allow for better patient management than those treated with amonafide; hence,
they should be developed further as potential clinical replacements for
amonafide or as novel anticancer drugs. Quinoline alkaloids are abundant in the Rutaceae, and many have exhibited
cytotoxic activity. Because structurally related antitumor alkaloids such as
camptothecin and fagaronine are known to function as intercalative topoisomerase
poisons, it is hypothesized that cytotoxic Stauranthus alkaloids may also serve
as intercalative topoisomerase inhibitors. To test this hypothesis
theoretically, ten Stauranthus quinoline alkaloids were examined for potential
intercalation into DNA using a molecular docking approach. Four of the alkaloids
(stauranthine, skimmianine, 3',6'-dihydroxy-3',6'-dihydrostauranthine, and
trans-3',4'-dihydroxy-3',4'-dihydrostauranthine) were able to intercalatively
dock consistently into DNA. In order to probe the intermolecular interactions
that may be responsible for intercalation of these quinoline alkaloids, density
functional calculations have been carried out using both the B3LYP and M06
functionals. M06 calculations indicated favorable pi-pi interactions between
either skimmianine or stauranthine and the guanine-cytosine base pair.
Furthermore, the lowest-energy face-to-face orientation of stauranthine with
guanine is consistent with favorable dipole-dipole orientations, favorable
electrostatic interactions, and favorable frontier molecular orbital
interactions. Likewise, the lowest-energy face-to-face orientation of
stauranthine with the guanine-cytosine base pair reveals favorable electrostatic
interactions as well as frontier molecular orbital interactions. Thus, not only
can quinoline alkaloids dock intercalatively into DNA, but the docked
orientations are also electronically favorable. To discover novel drugs for neuroblastoma treatment, we have previously screened
a panel of drugs and identified 30 active agents against neuroblastoma cells.
Here we performed microarray gene expression analysis to monitor the impact of
these agents on a neuroblastoma cell line and used the connectivity map (cMAP)
to explore putative mechanism of action of unknown drugs. We first compared the
expression profiles of 10 compounds shared in both our dataset and cMAP database
and observed the high connectivity scores for 7 of 10 matched drugs regardless
of the differences of cell lines utilized. The screen of cMAP for
uncharacterized drugs indicated the signature of Epoxy anthraquinone derivative
(EAD) matched the profiles of multiple known DNA targeted agents (topoisomerase
I/II inhibitors, DNA intercalators, and DNA alkylation agents) as predicted by
its structure. Similar result was obtained by querying against our internal
NB-cMAP (http://pob.abcc.ncifcrf.gov/cgi-bin/cMAP), a database containing the
profiles of 30 active drugs. These results suggest that Epoxy anthraquinone
derivative may inhibit neuroblastoma cells by targeting DNA replication
inhibition. Experimental data also demonstrate that Epoxy anthraquinone
derivative indeed induces DNA double-strand breaks through DNA alkylation and
inhibition of topoisomerase activity. Our study indicates that Epoxy
anthraquinone derivative may be a novel DNA topoisomerase inhibitor that can be
potentially used for treatment of neuroblastoma or other cancer patients. DNA has a strong affinity for many heterocyclic aromatic dyes, such as acridine
and its derivatives. Lerman in 1961 first proposed intercalation as the source
of this affinity, and this mode of DNA binding has since attracted considerable
research scrutiny. Organic intercalators can inhibit nucleic acid synthesis in
vivo, and they are now common anticancer drugs in clinical therapy. The covalent
attachment of organic intercalators to transition metal coordination complexes,
yielding metallointercalators, can lead to novel DNA interactions that influence
biological activity. Metal complexes with σ-bonded aromatic side arms can act as
dual-function complexes: they bind to DNA both by metal coordination and through
intercalation of the attached aromatic ligand. These aromatic side arms
introduce new modes of DNA binding, involving mutual interactions of functional
groups held in close proximity. The biological activity of both cis- and
trans-diamine Pt(II) complexes is dramatically enhanced by the addition of
σ-bonded intercalators. We have explored a new class of organometallic
"piano-stool" Ru(II) and Os(II) arene anticancer complexes of the type
[(η(6)-arene)Ru/Os(XY)Cl](+). Here XY is, for example, ethylenediamine (en), and
the arene ligand can take many forms, including tetrahydroanthracene, biphenyl,
or p-cymene. Arene-nucleobase stacking interactions can have a significant
influence on both the kinetics and thermodynamics of DNA binding. In particular,
the cytotoxic activity, conformational distortions, recognition by DNA-binding
proteins, and repair mechanisms are dependent on the arene. A major difficulty
in developing anticancer drugs is cross-resistance, a phenomenon whereby a cell
that is resistant to one drug is also resistant to another drug in the same
class. These new complexes are non-cross-resistant with cisplatin towards cancer
cells: they constitute a new class of anticancer agents, with a mechanism of
action that differs from the anticancer drug cisplatin and its analogs. The
Ru-arene complexes with dual functions are more potent towards cancer cells than
their nonintercalating analogs. In this Account, we focus on recent studies of
dual-function organometallic Ru(II)- and Os(II)-arene complexes and the methods
used to detect arene-DNA intercalation. We relate these interactions to the
mechanism of anticancer activity and to structure-activity relationships. The
interactions between these complexes and DNA show close similarities to those of
covalent polycyclic aromatic carcinogens, especially to N7-alkylating
intercalation compounds. However, Ru-arene complexes exhibit some new features.
Classical intercalation and base extrusion next to the metallated base is
observed for {(η(6)-biphenyl)Ru(ethylenediamine)}(2+) adducts of a 14-mer
duplex, while penetrating arene intercalation occurs for adducts of the
nonaromatic bulky intercalator
{(η(6)-tetrahydroanthracene)Ru(ethylenediamine)}(2+) with a 6-mer duplex. The
introduction of dual-function Ru-arene complexes introduces new mechanisms of
antitumor activity, novel mechanisms for attack on DNA, and new concepts for
developing structure- activity relationships. We hope this discussion will
stimulate thoughtful and focused research on the design of anticancer
chemotherapeutic agents using these unique approaches. Amsacrine (m-AMSA) is an anticancer agent that displays activity against
refractory acute leukemias as well as Hodgkin's and non-Hodgkin's lymphomas. The
drug is comprised of an intercalative acridine moiety coupled to a
4'-amino-methanesulfon-m-anisidide headgroup. m-AMSA is historically significant
in that it was the first drug demonstrated to function as a topoisomerase II
poison. Although m-AMSA was designed as a DNA binding agent, the ability to
intercalate does not appear to be the sole determit of drug activity.
Therefore, to more fully analyze structure-function relationships and the role
of DNA binding in the action of m-AMSA, we analyzed a series of derivatives for
the ability to enhance DNA cleavage mediated by human topoisomerase IIα and
topoisomerase IIβ and to intercalate DNA. Results indicate that the 3'-methoxy
(m-AMSA) positively affects drug function, potentially by restricting the
rotation of the headgroup in a favorable orientation. Shifting the methoxy to
the 2'-position (o-AMSA), which abrogates drug function, appears to increase the
degree of rotational freedom of the headgroup and may impair interactions of the
1'-substituent or other portions of the headgroup within the ternary complex.
Finally, the nonintercalative m-AMSA headgroup enhanced enzyme-mediated DNA
cleavage when it was detached from the acridine moiety, albeit with 100-fold
lower affinity. Taken together, our results suggest that much of the activity
and specificity of m-AMSA as a topoisomerase II poison is embodied in the
headgroup, while DNA intercalation is used primarily to increase the affinity of
m-AMSA for the topoisomerase II-DNA cleavage complex. Indoloquinoline alkaloids represent an important class of antimalarial,
antibacterial and antiviral compounds. Indolo[2,3-b]quinolines are a family of
DNA intercalators and inhibitors of topoisomerase II, synthetic analogs of
neocryptolepine, an alkaloid traditionally used in African folk medicine. These
cytotoxic substances are promising anticancer agents. Active representatives of
indolo[2,3-b]quinolines affect model and natural membranes. The distinct
structure and hydrophobicity of the compounds leads to marked differences in the
disturbing effects on membrane organization and function. Our results also
indicated a strong relationship between the presence of the chain and the Poct
of the molecule as well as the capacity for incorporation into
carboxyfluorescein-trapped liposomes in the 0.02-0.06 mM range. Moreover, a
correlation between binding to neutral dimyristoylphosphatidylcholine (DMPC) or
negative charged dimyristoylphosphatidylcholine:dimyristoylphosphatidylglycerol
(DMPC:DMPG, 9:1 w/w) liposomes, as well as to erythrocyte ghosts and pKa, was
also found. All the compounds cause hemolysis in isotonic conditions with
concentration causing 50% hemolysis (HC50) in the 0.12-0.88 mM range. The
concentration-dependent inhibitory effect of the tested agents on erythrocyte
ghosts' acetylcholinesterase activity was also studied. To investigate the relationship between the molecular structure and biological
activity of polypyridyl Ru(II) complexes, such as DNA binding, photocleavage
ability, and DNA topoisomerase and RNA polymerase inhibition, six new
[Ru(bpy)(2)(dppz)](2+) (bpy=2,2'-bipyridine;
dppz=dipyrido[3,2-a:2,',3'-c]phenazine) analogs have been synthesized and
characterized by means of (1)H-NMR spectroscopy, mass spectrometry, and
elemental analysis. Interestingly, the biological properties of these complexes
have been identified to be quite different via a series of experimental methods,
such as spectral titration, DNA thermal denaturation, viscosity, and gel
electrophoresis. To explain the experimental regularity and reveal the
underlying mechanism of biological activity, the properties of energy levels and
population of frontier molecular orbitals and excited-state transitions of these
complexes have been studied by density-functional theory (DFT) and time-depended
DFT (TDDFT) calculations. The results suggest that DNA intercalative ligands
with better planarity, greater hydrophobicity, and less steric hindrance are
beneficial to the DNA intercalation and enzymatic inhibition of their complexes. |
Which diseases is microRNA 132 (miR-132) implicated in? | Several targets for for miR-132 have been described and it is implicated in many diseases such as:
neurodegenerative disease,
epilepsy,
schizophrenia,
Huntington's disease (HD),
Alzheimer's disease (AD),
neuroinflammation,
osteosarcoma,
chronic lymphocytic leukemia (CLL),
angiogenesis,
eye disease,
alcoholic liver disease,
progressive supranuclear palsy (PSP taupathy),
mild cognitive impairment. | Micro-RNAs constitute a family of small noncoding ribonucleic acids that are
posttranscriptional regulators of messenger RNA activity. Although micro-RNAs
are known to be dynamically regulated during neural development, the role of
micro-RNAs in brain aging and neurodegeneration is not known. This study
examined micro-RNA abundance in the hippocampal region of fetal, adult and
Alzheimer's disease brain. The data indicate that micro-RNAs encoding miR-9,
miR-124a, miR-125b, miR-128, miR-132 and miR-219 are abundantly represented in
fetal hippocampus, are differentially regulated in aged brain, and an alteration
in specific micro-RNA complexity occurs in Alzheimer hippocampus. These data are
consistent with the idea that altered micro-RNA-mediated processing of messenger
RNA populations may contribute to atypical mRNA abundance and neural dysfunction
in Alzheimer's disease brain. Huntington's disease (HD) is a genetic neurodegenerative disease caused by
abnormal CAG expansion. MicroRNAs (miRNAs) are short RNA molecules regulating
gene expression, and are implicated in a variety of diseases including HD.
However, the profiles and regulation of miRNAs in HD are not fully understood.
Here, we analyzed the miRNA expression and miRNA regulators in two transgenic
models of HD, YAC128 and R6/2 mice, and in a 3-nitropropionic acid (3NP)-induced
striatal degeneration rat model. After characterizing the phenotypes by
behavioral tests and histological analyses, we profiled striatal miRNAs using a
miRNA microarray and we measured the key molecules involved in miRNA biogenesis
and function. YAC128 mice showed upregulation-domit miRNA expressions at 5
months and downregulation-domit expressions at 12 months. Concomitantly, the
expressions of Drosha-DGCR8, Exportin-5, and Dcp1 were increased at 5months, and
the expression of Dicer was decreased at 12 months. In 10-week-old R6/2 mice,
downregulation was domit in the miRNA expressions and the level of Drosha
decreased concomitantly. Nine miRNAs (miR-22, miR-29c, miR-128, miR-132,
miR-138, miR-218, miR-222, miR-344, and miR-674*) were commonly down-regulated
in both the 12-month-old YAC128 and 10-week-old R6/2 mice. Meanwhile, 3NP rats
showed dynamic changes in the miRNA profiles during disease development and a
few miRNAs with altered expression. Our results show that transgenic HD mice
have abnormal miRNA biogenesis. This information should aid in future studies on
therapeutic application of miRNAs in HD. The α-synuclein has been implicated in the pathophysiology of Parkinson's
disease (PD), because mutations in the alpha-synuclein gene cause
autosomal-domit hereditary PD and fibrillary aggregates of alpha-synuclein
are the major component of Lewy bodies. Since presynaptic accumulation of
α-synuclein aggregates may trigger synaptic dysfunction and degeneration, we
have analyzed alterations in synaptosomal proteins in early symptomatic
α-synuclein(A30P)-transgenic mice by two-dimensional differential gel
electrophoresis. Moreover, we carried out microRNA expression profiling using
microfluidic chips, as microRNA have recently been shown to regulate synaptic
plasticity in rodents and to modulate polyglutamine-induced protein aggregation
and neurodegeneration in flies. Differentially expressed proteins in
α-synuclein(A30P)-transgenic mice point to alterations in mitochondrial
function, actin dynamics, iron transport, and vesicle exocytosis, thus partially
resembling findings in PD patients. Oxygen consumption of isolated brain
mitochondria, however, was not reduced in mutant mice. Levels of several
microRNA (miR-10a, -10b, -212, -132, -495) were significantly altered. One of
them (miR-132) has been reported to be highly inducible by growth factors and to
be a key regulator of neurite outgrowth. Moreover, miR-132-recognition sequences
were detected in the mRNA transcripts of two differentially expressed proteins.
MicroRNA may thus represent novel biomarkers for neuronal malfunction and
potential therapeutic targets for human neurodegenerative diseases. Tauopathies represent a large class of neurological and movement disorders
characterized by abnormal intracellular deposits of the microtubule-associated
protein tau. It is now well established that mis-splicing of tau exon 10,
causing an imbalance between three-repeat (3R) and four-repeat (4R) tau
isoforms, can cause disease; however, the underlying mechanisms affecting tau
splicing in neurons remain poorly understood. The small noncoding microRNAs
(miRNAs), known for their critical role in posttranscriptional gene expression
regulation, are increasingly acknowledged as important regulators of alternative
splicing. Here, we identified a number of brain miRNAs, including miR-124,
miR-9, miR-132 and miR-137, which regulate 4R:3R-tau ratios in neuronal cells.
Analysis of miRNA expression profiles from sporadic progressive supranuclear
palsy (PSP) patients, a major 4R-tau tauopathy, showed that miR-132 is
specifically down-regulated in disease. We demonstrate that miR-132 directly
targets the neuronal splicing factor polypyrimidine tract-binding protein 2
(PTBP2), which protein levels were increased in PSP patients. miR-132
overexpression or PTBP2 knockdown similarly affected endogenous 4R:3R-tau ratios
in neuronal cells. Finally, we provide evidence that miR-132 is inversely
correlated with PTBP2 during post-natal brain development at the time when
4R-tau becomes expressed. Taken together, these results suggest that changes in
the miR-132/PTBP2 pathway could contribute to the abnormal splicing of tau exon
10 in the brain, and sheds light into the potential role played by miRNAs in a
subset of tauopathies. Schizophrenia is characterized by affective, cognitive, neuromorphological, and
molecular abnormalities that may have a neurodevelopmental origin. MicroRNAs
(miRNAs) are small noncoding RNA sequences critical to neurodevelopment and
adult neuronal processes by coordinating the activity of multiple genes within
biological networks. We examined the expression of 854 miRNAs in prefrontal
cortical tissue from 100 control, schizophrenic, and bipolar subjects. The
cyclic AMP-responsive element binding- and NMDA-regulated microRNA miR-132 was
significantly down-regulated in both the schizophrenic discovery cohort and a
second, independent set of schizophrenic subjects. Analysis of miR-132 target
gene expression in schizophrenia gene-expression microarrays identified 26 genes
up-regulated in schizophrenia subjects. Consistent with NMDA-mediated
hypofunction observed in schizophrenic subjects, administration of an NMDA
antagonist to adult mice results in miR-132 down-regulation in the prefrontal
cortex. Furthermore, miR-132 expression in the murine prefrontal cortex exhibits
significant developmental regulation and overlaps with critical
neurodevelopmental processes during adolescence. Adult prefrontal expression of
miR-132 can be down-regulated by pharmacologic inhibition of NMDA receptor
signaling during a brief postnatal period. Several key genes, including DNMT3A,
GATA2, and DPYSL3, are regulated by miR-132 and exhibited altered expression
either during normal neurodevelopment or in tissue from adult schizophrenic
subjects. Our data suggest miR-132 dysregulation and subsequent abnormal
expression of miR-132 target genes contribute to the neurodevelopmental and
neuromorphological pathologies present in schizophrenia. Early stages of many neurodegenerative diseases, such as Alzheimer's disease,
vascular and frontotemporal dementia, and Parkinson's disease, are frequently
associated with Mild Cognitive Impairment (MCI). A minimally invasive screening
test for early detection of MCI may be used to select optimal patient groups in
clinical trials, to monitor disease progression and response to treatment, and
to better plan patient clinical care. Here, we examined the feasibility of using
pairs of brain-enriched plasma microRNA (miRNA), at least one of which is
enriched in synapses and neurites, as biomarkers that could differentiate
patients with MCI from age-matched controls. The identified biomarker pairs fall
into two sets: the "miR-132 family" (miR-128/miR-491-5p, miR-132/miR-491-5p and
mir-874/miR-491-5p) and the "miR-134 family" (miR-134/miR-370,
miR-323-3p/miR-370 and miR-382/miR-370). The area under the Receiver-Operating
Characteristic curve for the differentiation of MCI from controls using these
biomarker pairs is 0.91-0.95, with sensitivity and specificity at 79%-100%
(miR-132 family) and 79%-95% (miR-134 family), and p〈0.001. In a separate
longitudinal study, the identified miRNA biomarker pairs successfully detected
MCI in majority of patients at asymptomatic stage 1-5 years prior to clinical
diagnosis. The reported biomarker pairs also appear useful for detecting
age-related brain changes. Further testing in a larger study is necessary for
validation of these results. Osteosarcoma is the most common human primary maligt bone tumor in children
and young adults. Sensitive and non-invasive biomarkers that can facilitate
disease detection at early stage are highly desirable to improve survival rate
and help to determine optimized treatment for osteosarcoma. The small non-coding
RNAs, microRNAs (miRNAs), have recently been identified as critical regulators
for various diseases including cancer and may represent a novel class of cancer
biomarkers. In this study, we aimed to detect the potential of circulating
miRNAs as biomarkers for osteosarcoma. Levels of six candidate miRNAs (miR-21,
miR-199a-3p, miR-143, miR-34, miR-140, and miR-132) that were previously
demonstrated to be regulated in osteosarcoma were examined in plasma of 40
osteosarcoma patients and 40 matched healthy controls by quantitative
reverse-transcription polymerase chain reaction assays. The results showed that
circulating levels of miR-21 were significantly higher in osteosarcoma patients
than controls, while miR-199a-3p and miR-143 were decreased in osteosarcoma
patients. We replicated the findings in an independent study of 40 osteosarcoma
patients and 40 matched controls and confirmed the results. Receiver operating
characteristics curve analysis of the combined populations demonstrated that the
three-miRNA signature could discriminate cases from controls with an area under
the curve of 0.953 (95 % CI 0.924-0.984). In addition, circulating miR-21 and
miR-143 were correlated with both metastasis status and histological subtype of
the patients, while miR-199a-3p only correlated with histological subtype. Our
data suggest that altered levels of circulating miRNAs might have great
potential to serve as novel, non-invasive biomarkers for osteosarcoma. MicroRNA (miRNA) is a class of small non-coding RNA which regulates
post-transcriptional gene expression by repressing and thereby fine-tuning
protein production, mainly via sequence-specific binding within the
3'untranslated region of mRNA transcripts. Although in humans there are only
∼1600 miRNAs, bioinformatics, systems studies and advanced quantitative
proteomics reveal miRNA regulation of over half of all protein-coding genes and
that each miRNA can regulate multiple proteins. Epilepsy is a common, serious
neurologic disorder characterized by recurring unprovoked seizures that result
from abnormal firing of populations of neurons in the brain. The brain expresses
several unique miRNAs which control dendritic morphology as well as ion channel
levels, neuronal migration and glial function. There is an emerging view that
the patho-mechanisms underlying the process of epileptogenesis, as well as
maintece and progression of the epileptic state, involve miRNAs that control
multiple genes and proteins on a systems level. Expression profiling studies
reveal select changes to brain miRNA levels following prolonged seizures (status
epilepticus) in animal models. Inflammation, stress signaling and neuronal
excitation are among the pathways most impacted. Analysis of miRNA expression in
human epilepsy has also been performed, where again neuroinflammatory processes
were prominent. These studies suggest that miRNAs may regulate certain key
processes but are not necessarily broadly altering all patho-mechanisms in
epilepsy. Functional studies employing antagomirs have identified contributions
from miR-34a and miR-132 to seizure-induced neuronal death whereas silencing
miR-134 potently reduced status epilepticus, seizure-damage and the later
occurrence of spontaneous seizures. Efforts to identify the in vivo target(s) of
epilepsy-regulated miRNAs, is now a priority. Last, miRNAs are stable,
information-carrying (paracrine) signals. Profiling miRNA in biofluids may
represent a novel source of disease biomarkers in epilepsy. In summary, miRNA is
emerging as a critical new layer of gene expression control with implications
for the cause and treatment of epilepsy. |
Which are the human glutamate transporters? | Glutamate/aspartate transporter (GLAST) and glutamate transporter-1 (GLT-1) are the most abundant subtypes and are essential for the functioning of the mammalian CNS, but the contribution of the EAAC1 subtype in the clearance of synaptic glutamate has remained controversial, because the density of this transporter in different tissues has not been determined. Using immunofluorescence and postembedding immunogold labeling, we investigated the distributions of the glutamate-aspartate transporter (GLAST or excitatory amino acid transporter 1), vesicular glutamate transporter (VGLUT1), and the AMPA receptor glutamate receptor 4 (GluR4) along the spiral. | Glutamate transporters serve the important function of mediating removal of
glutamate released at excitatory synapses and maintaining extracellular
concentrations below excitotoxic levels. Excitatory amino acid transporter
subtypes EAAT1 and EAAT2 have a high degree of sequence homology and similar
predicted topology and yet display a number of functional differences. Several
recombit chimeric transporters were generated to identify domains that
contribute to functional differences between EAAT1 and EAAT2. Wild-type
transporters and chimeric transporters were expressed in Xenopus laevis oocytes,
and electrogenic transport was studied under voltage clamp conditions. The
differential sensitivity of EAAT1 and EAAT2 to transport blockers, kainate,
threo-3-methylglutamate, and (2S, 4R)-4-methylglutamate as well as
L-serine-O-sulfate transport and chloride permeability were employed to
characterize chimeric transporters. One particular region, transmembrane domains
9 and 10, plays an important role in defining these functional differences. The
intracellular carboxyl-terminal region may also play a minor role in conferring
an effect on chloride permeability. This study provides important insight into
the identification of functional domains that determine differences among
glutamate transporter subtypes. We have investigated the functional impact of a naturally occurring mutation of
the human glutamate transporter GLT1 (EAAT2), which had been detected in a
patient with sporadic amyotrophic lateral sclerosis. The mutation involves a
substitution of the putative N-linked glycosylation site asparagine 206 by a
serine residue (N206S) and results in reduced glycosylation of the transporter
and decreased uptake activity. Electrophysiological analysis of N206S revealed a
pronounced reduction in transport rate compared with wild-type, but there was no
alteration in the apparent affinities for glutamate and sodium. In addition, no
change in the sensitivity for the specific transport inhibitor dihydrokainate
was observed. However, the decreased rate of transport was associated with a
reduction of the N206S transporter in the plasma membrane. Under ionic
conditions, which favor the reverse operation mode of the transporter, N206S
exhibited an increased reverse transport capacity. Furthermore, if coexpressed
in the same cell, N206S manifested a domit negative effect on the wild-type
GLT1 activity, whereas it did not affect wild-type EAAC1. These findings provide
evidence for a role of the N-linked glycosylation in both cellular trafficking
and transport function. The resulting alteration in glutamate clearance capacity
likely contributes to excitotoxicity that participates in motor neuron
degeneration in amyotrophic lateral sclerosis. Glutamate is the major neurotransmitter of the brain, whose extracellular levels
are tightly controlled by glutamate transporters. Five glutamate transporters in
the human brain (EAAT1-5) are present on both astroglia and neurons. We
characterize the profile of three different human astroglial progenitors in
vitro: human glial restricted precursors (HGRP), human astrocyte precursors
(HAPC), and early-differentiated astrocytes. EAAT 1, EAAT3, and EAAT4 are all
expressed in GRPs with a subsequent upregulation of EAAT1 following
differentiation of GRPs into GRP-derived astrocytes in the presence of bone
morphogenic protein (BMP-4). This corresponds to a significant increase in the
glutamate transport capacity of these cells. EAAT2, the transporter responsible
for the bulk of glutamate transport in the adult brain, is not expressed as a
full-length protein, nor does it appear to have functional significance (as
determined by the EAAT2 inhibitor dihydrokainate) in these precursors. A splice
variant of EAAT2, termed EAAT2b, does appear to be present in low levels,
however. EAAT3 and EAAT4 expression is reduced as glial maturation progresses
both in astrocyte precursors and early-differentiated astrocytes and is
consistent with their role in adult tissues as primarily neuronal glutamate
transporters. These human glial precursors offer several advantages as tools for
understanding glial biology because they can be passaged extensively in the
presence of mitogens, afford the potential to study the temporal changes in
glutamate transporter expression in a tightly controlled fashion, and are
cultured in the absence of neuronal coculture, allowing for the independent
study of astroglial biology. Neuronal and glial glutamate transporters play a central role in the termination
of synaptic transmission and in extracellular glutamate homeostasis in the
mammalian central nervous system. They are known to be multimers; however, the
number of subunits forming a functional transporter is controversial. We studied
the subunit stoichiometry of two distantly related glutamate transporters, the
human glial glutamate transporter hEAAT2 and a bacterial glutamate transporter
from Escherichia coli, ecgltP. Using blue native polyacrylamide gel
electrophoresis, analysis of concatenated transporters, and chemical
cross-linking, we demonstrated that human and prokaryotic glutamate transporters
expressed in Xenopus laevis oocytes or in mammalian cells are assembled as
trimers composed of three identical subunits. In an inducible mammalian cell
line expressing hEAAT2 the glutamate uptake currents correlate to the amount of
trimeric transporters. Overexpression and purification of ecgltP in E. coli
resulted in a homogenous population of trimeric transporters that were
functional after reconstitution in lipid vesicles. Our results indicate that an
evolutionarily conserved trimeric quaternary structure represents the sole
native and functional state of glutamate transporters. Transport of L-cystine across the cell membrane is essential for synthesis of
the major cellular antioxidant, glutathione (gamma-glutamylcysteinylglycine). In
this study, uptake of L-[14C]cystine by three of the high affinity
sodium-dependent mammalian glutamate transporters (GLT1, GLAST and EAAC1)
individually expressed in HEK cells has been determined. All three transporters
display saturable uptake of L-[14C]cystine with Michaelis affinity (K(m))
constants in the range of 20-110 microM. L-glutamate and L-homocysteate are
potent inhibitors of sodium-dependent L-[14C]cystine uptake in HEK(GLAST),
HEK(GLT1) and HEK(EAAC1) cells. Reduction of L-[14C]cystine to L-[14C]cysteine
in the presence of 1mM cysteinylglycine increases the uptake rate in HEK(GLT1),
HEK(GLAST) and HEK(EAAC1) cells, but only a small proportion (<10%) of
L-[14C]cysteine uptake in HEK(GLT1) and HEK(GLAST) cells occurs by the high
affinity glutamate transporters. The majority (>90%) of L-[14C]cysteine
transport in these cells is mediated by the ASC transport system. In HEK(EAAC1)
cells, on the other hand, L-[14C]cysteine is transported equally by the ASC and
EAAC1 transporters. L-homocysteine inhibits L-[14C]cysteine transport in both
HEK(GLAST) and HEK(GLT1) cells, but not in HEK(EAAC1) cells. It is concluded
that the quantity of L-[14C]cyst(e)ine taken up by individual high affinity
sodium-dependent glutamate transporters is determined both by the extracellular
concentration of amino acids, such as glutamate and homocysteine, and by the
extracellular redox potential, which will control the oxidation state of
L-cystine. Glutamate is the major excitatory neurotransmitter in the CNS that is cleared
from the extracellular space by a family of high-affinity glutamate
transporters. The astroglial glutamate transporter EAAT2 is thought to carry out
the uptake of the vast quantity of glutamate, and dysregulation of EAAT2
expression is involved in the pathogenesis of neurological disorders with marked
excitotoxic components. Here, we present a novel epigenetic mechanism by which
the human EAAT2 gene is kept in a silent state. Sequence inspection identified a
classical CpG island at the EAAT2 promoter. Bisulfite analysis of the DNA
methylation profile revealed that lack of EAAT2 expression in human glioma cell
lines was associated with a densely methylated EAAT2 promoter. In contrast,
EAAT2 positive normal human brain tissue used as reference displayed
hypomethylation of the same promoter regions. In vitro methylation of EAAT2
promoter sequences indeed altered the binding properties of nuclear factors to
the respective DNA sites as illustrated by electrophoretic mobility shift assay.
Moreover, we observed a reduced activity of a methylated EAAT2 promoter
construct as compared to the unmethylated control, both in a human glioma cell
line and rodent primary astrocytes. Further supporting a role of DNA methylation
for EAAT2 silencing, inhibition of DNA methyltransferases robustly enhanced
EAAT2 mRNA transcription in several cell lines tested. In conclusion, the idea
is put forward of an epigenetic mode of EAAT2 regulation based on the
differential methylation of the gene promoter. (c) 2007 Wiley-Liss, Inc. Excitatory amino acid transporters (EAATs) are the primary regulators of
extracellular glutamate concentrations in the central nervous system. Their
dysfunction may contribute to several neurological diseases. To date, five
distinct mammalian glutamate transporters have been cloned. In brain, EAAC1
(excitatory amino acid carrier 1) is the primary neuronal glutamate transporter,
localized on the perisynaptic membranes that are near release sites. Despite its
potential importance in synaptic actions, little is known concerning the
regulation of EAAC1 trafficking from the endoplasmic reticulum (ER) to the cell
surface. Previously, we identified an EAAC1-associated protein, GTRAP3-18, an ER
protein that prevents ER exit of EAAC1 when induced. Here we show that RTN2B, a
member of the reticulon protein family that mainly localizes in the ER and ER
exit sites interacts with EAAC1 and GTRAP3-18. EAAC1 and GTRAP3-18 bind to
different regions of RTN2B. Each protein can separately and independently form
complexes with EAAC1. RTN2B enhances ER exit and the cell surface composition of
EAAC1 in heterologous cells. Expression of short interfering RNA-mediated
knockdown of RTN2B decreases the EAAC1 protein level in neurons. Overall, our
results suggest that RTN2B functions as a positive regulator in the delivery of
EAAC1 from the ER to the cell surface. These studies indicate that transporter
exit from the ER controlled by the interaction with its ER binding partner
represents a critical regulatory step in glutamate transporter trafficking to
the cell surface. Glutamate transport is coupled to the co-transport of 3Na(+) and 1H(+) and the
countertransport of 1 K(+). However, the mechanism of how this process occurs is
not well understood. The crystal structure of an archaeal homolog of the human
glutamate transporters, Glt(Ph), has provided the framework to begin to
understand the mechanism of transport. The glutamate transporter EAAT2 is
different from other subtypes in two respects. First, Li(+) cannot support
transport by EAAT2, whereas it can support transport by the other excitatory
amino acid transporters, and second, EAAT2 is sensitive to a wider range of
blockers than other subtypes. We have investigated the relationship between the
cation driving transport and whether the glutamate analogues,
l-anti-endo-3,4-methanopyrrolidine-dicarboxylic acid (MPDC) and
(2S,4R)-4-methylglutamate (4MG), are substrates or blockers of transport. We
have also investigated the molecular basis for these differences. EAAT2 has a
Ser residue at position 441 with hairpin loop 2, whereas the corresponding
residue in EAAT1 is a Gly residue. We demonstrate that if the transporter has a
Ser residue at this position, then 4MG and MPDC are poor substrates in Na(+),
and Li(+) cannot support transport of any substrate. Conversely, if the
transporter has a Gly residue at this position, then in Na(+) 4MG and MPDC are
substrates with efficacy comparable with glutamate, but in Li(+) 4MG and MPDC
are poor substrates relative to glutamate. This Ser/Gly residue is located
between the bound substrate and one of the cation binding sites, which provides
an explanation for the coupling of substrate and cation binding. Glutamate transport via the human excitatory amino acid transporters is coupled
to the co-transport of three Na(+) ions, one H(+) and the counter-transport of
one K(+) ion. Transport by an archaeal homologue of the human glutamate
transporters, Glt(Ph), whose three dimensional structure is known is also
coupled to three Na(+) ions but only two Na(+) ion binding sites have been
observed in the crystal structure of Glt(Ph). In order to fully utilize the
Glt(Ph) structure in functional studies of the human glutamate transporters, it
is essential to understand the transport mechanism of Glt(Ph) and accurately
determine the number and location of Na(+) ions coupled to transport. Several
sites have been proposed for the binding of a third Na(+) ion from electrostatic
calculations and molecular dynamics simulations. In this study, we have
performed detailed free energy simulations for Glt(Ph) and reveal a new site for
the third Na(+) ion involving the side chains of Threonine 92, Serine 93,
Asparagine 310, Aspartate 312, and the backbone of Tyrosine 89. We have also
studied the transport properties of alanine mutants of the coordinating residues
Threonine 92 and Serine 93 in Glt(Ph), and the corresponding residues in a human
glutamate transporter, EAAT1. The mutant transporters have reduced affinity for
Na(+) compared to their wild type counterparts. These results confirm that
Threonine 92 and Serine 93 are involved in the coordination of the third Na(+)
ion in Glt(Ph) and EAAT1. The ASCTs (alanine, serine, and cysteine transporters) belong to the solute
carrier family 1 (SLC1), which also includes the human glutamate transporters
(excitatory amino acid transporters, EAATs) and the prokaryotic aspartate
transporter GltPh. Despite the high degree of amino acid sequence identity
between family members, ASCTs function quite differently from the EAATs and
GltPh. The aim of this study was to mutate ASCT1 to generate a transporter with
functional properties of the EAATs and GltPh, to further our understanding of
the structural basis for the different transport mechanisms of the SLC1 family.
We have identified three key residues involved in determining differences
between ASCT1, the EAATs and GltPh. ASCT1 transporters containing the mutations
A382T, T459R, and Q386E were expressed in Xenopus laevis oocytes, and their
transport and anion channel functions were investigated. A382T and T459R altered
the substrate selectivity of ASCT1 to allow the transport of acidic amino acids,
particularly l-aspartate. The combination of A382T and T459R within ASCT1
generates a transporter with a similar profile to that of GltPh, with preference
for l-aspartate over l-glutamate. Interestingly, the amplitude of the anion
conductance activated by the acidic amino acids does not correlate with rates of
transport, highlighting the distinction between these two processes. Q386E
impaired the ability of ASCT1 to bind acidic amino acids at pH 5.5; however,
this was reversed by the additional mutation A382T. We propose that these
residues differences in TM7 and TM8 combine to determine differences in
substrate selectivity between members of the SLC1 family. Glutamate receptors and transporters, including T1R1 and T1R3 (taste receptor 1,
subtypes 1 and 3), mGluRs (metabotropic glutamate receptors), EAAC-1 (excitatory
amino acid carrier-1), GLAST-1 (glutamate-aspartate transporter-1), and GLT-1
(glutamate transporter-1), are expressed in the gastrointestinal tract. This
study determined effects of oral administration of monosodium glutamate [MSG; 0,
0.06, 0.5, or 1 g/kg body weight (BW)/day] for 21 days on expression of
glutamate receptors and transporters in the stomach and jejunum of sow-reared
piglets. Both mRNA and protein levels for gastric T1R1, T1R3, mGluR1, mGluR4,
EAAT1, EAAT2, EAAT3, and EAAT4 and mRNA levels for jejunal T1R1, T1R3, EAAT1,
EAAT2, EAAT3 and EAAT4 were increased (P < 0.05) by MSG supplementation. Among
all groups, mRNA levels for gastric EAAT1, EAAT2, EAAT3, and EAAT4 were highest
(P < 0.05) in piglets receiving 1 g MSG/kg BW/day. EAAT1 and EAAT2 mRNA levels
in the stomach and jejunum of piglets receiving 0.5 g MSG/kg BW/day, as well as
jejunal EAAT3 and EAAT4 mRNA levels in piglets receiving 1 g MSG/kg BW/day, were
higher (P < 0.05) than those in the control and in piglets receiving 0.06 g
MSG/kg BW/day. Furthermore, protein levels for jejunal T1R1 and EAAT3 were
higher (P < 0.05) in piglets receiving 1 g MSG/kg BW/day than those in the
control and in piglets receiving 0.06 g MSG/kg BW/day. Collectively, these
findings indicate that dietary MSG may beneficially stimulate glutamate
signaling and sensing in the stomach and jejunum of young pigs, as well as their
gastrointestinal function. Glutamate transport is a critical process in the brain that maintains low
extracellular levels of glutamate to allow for efficient neurotransmission and
prevent excitotoxicity. Loss of glutamate transport function is implicated in
epilepsy, traumatic brain injury, and amyotrophic lateral sclerosis. It remains
unclear whether or not glutamate transport can be modulated in these disease
conditions to improve outcome. Here, we show that sirtuin (SIRT)4, a
mitochondrial sirtuin, is up-regulated in response to treatment with the potent
excitotoxin kainic acid. Loss of SIRT4 leads to a more severe reaction to kainic
acid and decreased glutamate transporter expression and function in the brain.
Together, these results indicate a critical and novel stress response role for
SIRT4 in promoting proper glutamate transport capacity and protecting against
excitotoxicity. We previously reported that Neisseria meningitidis internalization into human
brain microvasocular endothelial cells (HBMEC) was triggered by the influx of
extracellular L-glutamate via the GltT-GltM L-glutamate ABC transporter, but the
underlying mechanism remained unclear. We found that the ΔgltT ΔgltM invasion
defect in assay medium (AM) was alleviated in AM without 10% fetal bovine serum
(FBS) [AM(-S)]. The alleviation disappeared again in AM(-S) supplemented with
500 μM glutamate. Glutamate uptake by the ΔgltT ΔgltM mutant was less efficient
than that by the wild-type strain, but only upon HBMEC infection. We also
observed that both GltT-GltM-dependent invasion and accumulation of ezrin, a key
membrane-cytoskeleton linker, were more pronounced when N. meningitidis formed
larger colonies on HBMEC under physiological glutamate conditions. These results
suggested that GltT-GltM-dependent meningococcal internalization into HBMEC
might be induced by the reduced environmental glutamate concentration upon
infection. Furthermore, we found that the amount of glutathione within the ΔgltT
ΔgltM mutant was much lower than that within the wild-type N. meningitidis
strain only upon HBMEC infection and was correlated with intracellular survival.
Considering that the L-glutamate obtained via GltT-GltM is utilized as a
nutrient in host cells, l-glutamate uptake via GltT-GltM plays multiple roles in
N. meningitidis internalization into HBMEC. |
What are the functions of sorting nexin 27? | Sorting nexin 27 (SNX27) regulates endocytic sorting/recycling and intracellular trafficking of ion channels and receptors. | The 5-hydroxytryptamine type 4 receptor (5-HT4R) is involved in learning,
feeding, respiratory control and gastrointestinal transit. This receptor is one
of the G-protein-coupled receptors for which alternative mRNA splicing generates
the most variants that differ in their C-terminal extremities. Some 5-HT4R
variants (a, e and f) express canonical PDZ ligands at their C-termini. Here, we
have examined whether some mouse 5-HT4R variants associate with specific sets of
proteins, using a proteomic approach based on peptide-affinity chromatography,
two-dimensional electrophoresis and mass spectrometry. We have identified ten
proteins that interact specifically with the 5-HT4(a)R and three that only
associate with the 5-HT4(e)R. Most of them are PDZ proteins. Among the proteins
that associated specifically with the 5-HT4(a)R variant, NHERF greatly modified
its subcellular localization. Moreover, NHERF recruited the 5-HT4(a)R to
microvilli, where it localized with activated ezrin, consistent with the role of
5-HT4(a)R in cytoskeleton remodelling. The 5-HT4(a)R also interacted with both
the constitutive and inducible (upon methamphetamine treatment) forms of the
recently cloned sorting nexin 27 (SNX27a and b, respectively). We found that
SNX27a redirected part of 5-HT4(a)R to early endosomes. The interaction of the
5-HT4R splice variants with distinct sets of PDZ proteins might specify their
cellular localization as well as their signal transduction properties. Diacylglycerol kinase zeta is a member of the diacylglycerol kinase family of
enzymes, which generate phosphatidic acid through diacylglycerol
phosphorylation. In addition to the catalytic and cysteine-rich domains found in
all diacylglycerol kinases, diacylglycerol kinase zeta has a MARCKS domain as
well as a C-terminal region containing four ankyrin repeats and a PDZ-binding
motif. Previous reports demonstrated that diacylglycerol kinase zeta interaction
with several proteins is an important mechanism for modulating the localization
and activity of this enzyme. Here we used a proteomics approach to search for
novel diacylglycerol kinase zeta-interacting proteins and identified sorting
nexin 27 (SNX27), a recently described member of a protein family involved in
intracellular trafficking, which has a PDZ domain in addition to the phox
homology domain characteristic of SNX proteins. Co-immunoprecipitation studies
and two-hybrid analysis confirmed physical, PDZ-dependent association between
SNX27 and diacylglycerol kinase zeta. Because diacylglycerol kinase zeta is
expressed abundantly in T lymphocytes, we characterized SNX27 expression and
subcellular localization in these cells. SNX27 co-localized with transferrin
receptor-positive vesicles, pointing to its participation in T cell endocytic
recycling. Expression of deletion mutants revealed that in addition to the phox
homology domain the SNX27 PDZ domain contributed to vesicle localization of this
protein, suggesting that interaction with diacylglycerol kinase zeta regulates
SNX27 localization. Analysis of cells with RNA interference-mediated knockdown
of diacylglycerol kinase zeta showed accelerated transferrin receptor exit from
the lymphocyte endocytic recycling compartment back to the plasma membrane,
further confirming diacylglycerol kinase zeta-dependent control of vesicle
trafficking. These data support a previously unreported role for diacylglycerol
kinase zeta in the modulation of membrane trafficking, which may also help to
define SNX27 function. CASP is a small cytokine-inducible protein, primarily expressed in hematopoetic
cells, which associates with members of the Cytohesin/ARNO family of guanine
nucleotide-exchange factors. Cytohesins activate ARFs, a group of GTPases
involved in vesicular initiation. Functionally, CASP is an adaptor protein
containing a PDZ domain, a coiled-coil, and a potential carboxy terminal
PDZ-binding motif that we sought to characterize here. Using GST pulldowns and
mass spectrometry we identified the novel interaction of CASP and sorting nexin
27 (SNX27). In lymphocytes, CASP's PDZ-binding motif interacts with the PDZ
domain of SNX27. This protein is a unique member of the sorting nexin family of
proteins, a group generally involved in the endocytic and intracellular sorting
machinery. Endogenous SNX27 and CASP co-localize at the early endosomal
compartment in lymphocytes and also in transfection studies. These results
suggest that endosomal SNX27 may recruit CASP to orchestrate intracellular
trafficking and/or signaling complexes. Polarization is a critical mechanism for the proper functioning of many cell
types. For lymphocytes, it is essential in a variety of processes, including
migration from the blood to other tissue sites and vice versa. In NK cells and
CTLs, the cytotoxic granule delivery mechanism requires polarization for granule
movement to the immunological synapse (IS), in killing tumor and virus-infected
cells. Recently, it has become apparent that endosomes are also involved in the
cytotoxic mechanism. Using an in vitro conjugation approach, we show that in
NK-92 cells, endosomal Sorting Nexin 27 (SNX27) polarizes to the IS during tumor
cell engagement in a distinct compartment adjacent to the cytotoxic granules. We
also show that SNX27 polarizes to the apical membrane, opposite the uropod,
during NK cell migration. These previously unreported results indicate that
SNX27 is a participant in NK cell polarization, as a mediator or target of the
mechanism. G protein-gated potassium (Kir3) channels are important for controlling neuronal
excitability in the brain. Using a proteomics approach, we have identified a
unique rodent intracellular protein, sorting nexin 27 (SNX27), which regulates
the trafficking of Kir3 channels. Like most sorting nexins, SNX27 possesses a
functional PX domain that selectively binds the membrane phospholipid
phosphatidylinositol-3-phosphate (PI3P) and is important for trafficking to the
early endosome. SNX27, however, is the only sorting nexin to contain a PDZ
domain. This PDZ domain discriminates between channels with similar class I
PDZ-binding motifs, associating with the C-terminal end of Kir3.3 and Kir3.2c
(-ESKV), but not with that of Kir2.1 (-ESEI) or Kv1.4 (-ETDV). SNX27 promotes
the endosomal movement of Kir3 channels, leading to reduced surface expression,
increased degradation and smaller Kir3 potassium currents. The regulation of
endosomal trafficking via sorting nexins reveals a previously unknown mechanism
for controlling potassium channel surface expression. G protein-gated inwardly rectifying potassium (Kir3) channels are involved in
regulating membrane excitability in the brain. Kir3 channels have been shown to
play a role in learning, analgesia and drug addiction. Little is known about the
cell surface regulation of Kir3 channels. Using a proteomics approach, we
recently discovered that sorting nexin 27 (SNX27) associates with a subset of
Kir3 channels. Sorting nexins have been implicated in trafficking of proteins
through endosomal compartments. The single PDZ domain of SNX27 binds directly to
the PDZ binding motif of Kir3 channels leading to their downregulation. Here, we
examined the functional effect of SNX27b expression on different subunit
combinations of the Kir3 family. Our results show that regulation of Kir3
channels by SNX27 depends critically on the combination of Kir3 subunits. This
type of subunit-specific regulation could be important for determining the
extent of Kir3 inhibition in normal as well as diseased states, such as drug
addiction. Postsynaptic density 95/discs large/zonus occludens-1 (PDZ) domain-interacting
motifs, in addition to their well-established roles in protein scaffolding at
the cell surface, are proposed to act as cis-acting determits directing the
molecular sorting of transmembrane cargo from endosomes to the plasma membrane.
This hypothesis requires the existence of a specific trans-acting PDZ protein
that mediates the proposed sorting operation in the endosome membrane. Here, we
show that sorting nexin 27 (SNX27) is required for efficient PDZ-directed
recycling of the beta(2)-adrenoreceptor (beta(2)AR) from early endosomes. SNX27
mediates this sorting function when expressed at endogenous levels, and its
recycling activity requires both PDZ domain-dependent recognition of the
beta(2)AR cytoplasmic tail and Phox homology (PX) domain-dependent association
with the endosome membrane. These results identify a discrete role of SNX27 in
PDZ-directed recycling of a physiologically important signaling receptor, and
extend the concept of cargo-specific molecular sorting in the recycling pathway. Phox (PX) domain-containing sorting nexins (SNXs) are emerging as important
regulators of endocytic trafficking. Sorting nexin 27 (SNX27) is unique, as it
contains a PDZ (Psd-95/Dlg/ZO1) domain. We show here that SNX27 is primarily
targeted to the early endosome by interaction of its PX domain with PtdIns(3)P.
Although targeted ablation of the SNX27 gene in mice did not significantly
affect growth and survival during embryonic development, SNX27 plays an
essential role in postnatal growth and survival. N-Methyl-d-aspartate (NMDA)
receptor 2C (NR2C) was identified as a novel SNX27-interacting protein, and this
interaction is mediated by the PDZ domain of SNX27 and the C-terminal
PDZ-binding motif of NR2C. Increased NR2C expression levels, together with
impaired NR2C endocytosis in SNX27(-/-) neurons, indicate that SNX27 may
function to regulate endocytosis and/or endosomal sorting of NR2C. This is
consistent with a role of SNX27 as a general regulator for sorting of membrane
proteins containing a PDZ-binding motif, and its absence may alter the
trafficking of these proteins, leading to growth and survival defects. Sorting nexin 27 (SNX27) belongs to the sorting nexin family of proteins, which
participate in vesicular and protein trafficking. Similarly to all sorting nexin
proteins, SNX27 has a functional PX domain that is important for endosome
binding, but it is the only sorting nexin with a PDZ domain. We identified SNX27
as a partner of diacylglycerol kinase ζ (DGKζ), a negative regulator of T cell
function that metabolises diacylglycerol to yield phosphatidic acid. SNX27
interacts with the DGKζ PDZ-binding motif in early/recycling endosomes in
resting T cells; however, the dynamics and mechanisms underlying SNX27
subcellular localisation during T cell activation are unknown. We demonstrate
that in T cells that encounter pulsed antigen-presenting cells, SNX27 in transit
on early/recycling endosomes polarise to the immunological synapse. A fraction
of SNX27 accumulates at the mature immunological synapse in a process that is
dependent on vesicular trafficking, binding of the PX domain to
phosphatidylinositol 3-phosphate and the presence of the PDZ region.
Downmodulation of expression of either SNX27 or DGKζ results in enhanced basal
and antigen-triggered ERK phosphorylation. These results identify SNX27 as a
PDZ-containing component of the T cell immunological synapse, and demonstrate a
role for this protein in the regulation of the Ras-ERK pathway, suggesting a
functional relationship between SNX27 and DGKζ. Sorting nexin 27 (SNX27) is a 62-kDa protein localized to early endosomes and
known to regulate the intracellular trafficking of ion channels and receptors.
In addition to a PX domain, SNX27 is the only sorting family member that
contains a PDZ domain. To identify novel SNX27-PDZ binding partners, we
performed a proteomic screen in mouse principal kidney cortical collecting duct
cells using a GST-SNX27 fusion construct as bait. We found that β-Pix
(p21-activated kinase-interactive exchange factor), a guanine nucleotide
exchange factor for the Rho family of small GTPases known to regulate cell
motility directly interacted with SNX27. The association of β-Pix and SNX27 is
specific for β-Pix isoforms terminating in the type-1 PDZ binding motif (ETNL).
In the same screen we also identified Git1/2 as a potential SNX27 interacting
protein. The interaction between SNX27 and Git1/2 is indirect and mediated by
β-Pix. Furthermore, we show recruitment of the β-Pix·Git complex to endosomal
sites in a SNX27-dependent manner. Finally, migration assays revealed that
depletion of SNX27 from HeLa and mouse principal kidney cortical collecting duct
cells significantly decreases cell motility. We propose a model by which SNX27
regulates trafficking of β-Pix to focal adhesions and thereby influences cell
motility. Sorting nexin 27 (SNX27), a brain-enriched PDZ domain protein, regulates
endocytic sorting and trafficking. Here we show that Snx27(-/-) mice have severe
neuronal deficits in the hippocampus and cortex. Although Snx27(+/-) mice have
grossly normal neuroanatomy, we found defects in synaptic function, learning and
memory and a reduction in the amounts of ionotropic glutamate receptors (NMDA
and AMPA receptors) in these mice. SNX27 interacts with these receptors through
its PDZ domain, regulating their recycling to the plasma membrane. We
demonstrate a concomitant reduced expression of SNX27 and CCAAT/enhancer binding
protein β (C/EBPβ) in Down's syndrome brains and identify C/EBPβ as a
transcription factor for SNX27. Down's syndrome causes overexpression of
miR-155, a chromosome 21-encoded microRNA that negatively regulates C/EBPβ,
thereby reducing SNX27 expression and resulting in synaptic dysfunction.
Upregulating SNX27 in the hippocampus of Down's syndrome mice rescues synaptic
and cognitive deficits. Our identification of the role of SNX27 in synaptic
function establishes a new molecular mechanism of Down's syndrome pathogenesis. G protein-gated inwardly rectifying potassium (GIRK) channels play an important
role in regulating neuronal excitability. Sorting nexin 27b (SNX27b), which
reduces surface expression of GIRK channels through a PDZ domain interaction,
contains a putative Ras-association (RA) domain with unknown function. Deleting
the RA domain in SNX27b (SNX27b-ΔRA) prevents the down-regulation of
GIRK2c/GIRK3 channels. Similarly, a point mutation (K305A) in the RA domain
disrupts regulation of GIRK2c/GIRK3 channels and reduces H-Ras binding in vitro.
Finally, the domit-negative H-Ras (S17N) occludes the SNX27b-dependent
decrease in surface expression of GIRK2c/GIRK3 channels. Thus, the presence of a
functional RA domain and the interaction with Ras-like G proteins comprise a
novel mechanism for modulating SNX27b control of GIRK channel surface expression
and cellular excitability. |
Do orphan and gene related CpG islands follow power-law-like distributions? | Yes. Orphan and gene related CpG Islands follow power-law-like distributions in several genomes. The observed distributional pattern is independent of the analogous pattern that protein coding segments were reported to follow. | CpG Islands (CGIs) are compositionally defined short genomic stretches, which
have been studied in the human, mouse, chicken and later in several other
genomes. Initially, they were assigned the role of transcriptional regulation of
protein-coding genes, especially the house-keeping ones, while more recently
there is found evidence that they are involved in several other functions as
well, which might include regulation of the expression of RNA genes, DNA
replication etc. Here, an investigation of their distributional characteristics
in a variety of genomes is undertaken for both whole CGI populations as well as
for CGI subsets that lie away from known genes (gene-unrelated or "orphan"
CGIs). In both cases power-law-like linearity in double logarithmic scale is
found. An evolutionary model, initially put forward for the explanation of a
similar pattern found in gene populations is implemented. It includes segmental
duplication events and eliminations of most of the duplicated CGIs, while a
moderate rate of non-duplicated CGI eliminations is also applied in some cases.
Simulations reproduce all the main features of the observed inter-CGI
chromosomal size distributions. Our results on power-law-like linearity found in
orphan CGI populations suggest that the observed distributional pattern is
independent of the analogous pattern that protein coding segments were reported
to follow. The power-law-like patterns in the genomic distributions of CGIs
described herein are found to be compatible with several other features of the
composition, abundance or functional role of CGIs reported in the current
literature across several genomes, on the basis of the proposed evolutionary
model. |
What is the proportion of non canonical splice sites in the human genome? | Between 1% and 2% of human splice sites do not contain the canonical GT-AG dinucleotides | A set of 43 337 splice junction pairs was extracted from mammalian GenBank
annotated genes. Expressed sequence tag (EST) sequences support 22 489 of them.
Of these, 98.71% contain canonical dinucleotides GT and AG for donor and
acceptor sites, respectively; 0.56% hold non-canonical GC-AG splice site pairs;
and the remaining 0.73% occurs in a lot of small groups (with a maximum size of
0.05%). Studying these groups we observe that many of them contain splicing
dinucleotides shifted from the annotated splice junction by one position. After
close examination of such cases we present a new classification consisting of
only eight observed types of splice site pairs (out of 256 a priori possible
combinations). EST alignments allow us to verify the exonic part of the splice
sites, but many non-canonical cases may be due to intron sequencing errors. This
idea is given substantial support when we compare the sequences of human genes
having non-canonical splice sites deposited in GenBank by high throughput genome
sequencing projects (HTG). A high proportion (156 out of 171) of the human
non-canonical and EST-supported splice site sequences had a clear match in the
human HTG. They can be classified after corrections as: 79 GC-AG pairs (of which
one was an error that corrected to GC-AG), 61 errors that were corrected to
GT-AG canonical pairs, six AT-AC pairs (of which two were errors that corrected
to AT-AC), one case was produced from non-existent intron, seven cases were
found in HTG that were deposited to GenBank and finally there were only two
cases left of supported non-canonical splice sites. If we assume that
approximately the same situation is true for the whole set of annotated
mammalian non-canonical splice sites, then the 99.24% of splice site pairs
should be GT-AG, 0.69% GC-AG, 0.05% AT-AC and finally only 0.02% could consist
of other types of non-canonical splice sites. We analyze several characteristics
of EST-verified splice sites and build weight matrices for the major groups,
which can be incorporated into gene prediction programs. We also present a set
of EST-verified canonical splice sites larger by two orders of magnitude than
the current one (22 199 entries versus approximately 600) and finally, a set of
290 EST-supported non-canonical splice sites. Both sets should be significant
for future investigations of the splicing mechanism. |
List protein gel staining methods visualizing the entire protein set. | Several staining protocols for the visualization of proteins separated by SDS-PAGE have been described in literature:
fluorescence
Sypro Ruby
Colloidal Coomassie Blue
Coomassie Blue
Silver staining
Coomassie Brilliant Blue | Silver staining is widely used to detect protein in polyacrylamide gels when
high sensitivity is required. A simple and rapid protocol for silver staining of
proteins following PAGE was developed in the present study. The number of steps
was reduced compared to conventional protocol by combining fixing, rinsing, and
soaking into a single impregnating step, thus achieving detection of proteins in
20 min. The present method is as sensitive as current protocols with the
advantage of saving time and costs. Gel-based proteomics are the most useful method for protein separation, even
when compared with gel-free proteomics. Proteomic analysis by 2D gel
electrophoresis (2-DE) with immobilized pH gradients is in turn the best
approach to large-scale protein-expression screening. Spots visualization is
pivotal for protein identification by mass spectrometry. Commonly used staining
methods with excellent mass spectrometry compatibility are coomassie brilliant
blue (CBB) or fluorescent dyes. In this study, an implementation of 'blue
silver' colloidal CBB staining, characterized by high sensitivity and immediate
low background, is discussed. The sensitivity of classical, colloidal and 'blue
silver' CBB staining methods was compared on monodimensional and 2-DE gels. The
implementation of the 'blue silver' method performs better, provided the
physical state of the micelles is respected. An example of a 2-DE of human urine
treated with combinatorial peptide ligand libraries demonstrates that
implemented 'blue silver' can evidence the complexity of the sample. The gel-based proteomics approach is a valuable technique for studying the
characteristics of proteins. This technique has diverse applications ranging
from analysis of a single protein to the study of the total cellular proteins.
Further, protein quality and to some extent distribution can be first assessed
by means of one-dimensional gel electrophoresis and then more informatively, for
comparative analysis, using the two-dimensional gel electrophoresis technique.
Here, we describe how to take advantage of the availability of fluorescent dyes
to stain for a selective class of proteins on the same gel for the detection of
both phospho- and total proteomes. This enables the co-detection of
phosphoproteins as well as total proteins from the same gel and is accomplished
by utilizing two different fluorescent stains, the ProQ-Diamond, which stains
only phosphorylated proteins, and Sypro Ruby, which stains the entire subset of
proteins. This workflow can be applied to gain insights into the regulatory
mechanisms induced by signaling molecules such as cyclic nucleotides through the
quantification and subsequent identification of responsive phospho- and total
proteins. The CyDye family of fluorescent dyes is currently the overwhelming choice for
applications in proteomic analysis, using two-dimensional difference gel
electrophoresis (2D-DIGE). Protein labeling with CyDyes is hampered by protein
precipitation and gel smearing when used above minimal labeling. The solubility
of labeled protein may be improved by introducing water solubilizing groups on
the dye such as cysteic acids. However, addition of a negatively charged
functionality will have the undesired effect of shifting the pI in relation to
the unlabeled protein. These limitations have been addressed through the
synthesis of highly water-soluble and pI balancing zwitterionic CyDye
fluorophores (Z-CyDyes). The new dyes feature a cysteic acid motif, a titratable
amine functionality and a NHS activated ester group. In side by side 2D-DIGE
comparisons of Z-CyDyes and CyDyes, the new dyes significantly enhanced protein
spot volume and the number of spots that were detected. Z-CyDyes have the
potential to enhance the depth of proteome coverage and provide a general
strategy for improving the performance of protein tagging reagents. Quantitative proteome analyses suggest that the well-established stain colloidal
Coomassie Blue, when used as an infrared dye, may provide sensitive,
post-electrophoretic in-gel protein detection that can rival even Sypro Ruby.
Considering the central role of two-dimensional gel electrophoresis in top-down
proteomic analyses, a more cost effective alternative such as Coomassie Blue
could prove an important tool in ongoing refinements of this important
analytical technique. To date, no systematic characterization of Coomassie Blue
infrared fluorescence detection relative to detection with SR has been reported.
Here, seven commercial Coomassie stain reagents and seven stain formulations
described in the literature were systematically compared. The selectivity,
threshold sensitivity, inter-protein variability, and linear-dynamic range of
Coomassie Blue infrared fluorescence detection were assessed in parallel with
Sypro Ruby. Notably, several of the Coomassie stain formulations provided
infrared fluorescence detection sensitivity to <1 ng of protein in-gel, slightly
exceeding the performance of Sypro Ruby. The linear dynamic range of Coomassie
Blue infrared fluorescence detection was found to significantly exceed that of
Sypro Ruby. However, in two-dimensional gel analyses, because of a blunted
fluorescence response, Sypro Ruby was able to detect a few additional protein
spots, amounting to 0.6% of the detected proteome. Thus, although both detection
methods have their advantages and disadvantages, differences between the two
appear to be small. Coomassie Blue infrared fluorescence detection is thus a
viable alternative for gel-based proteomics, offering detection comparable to
Sypro Ruby, and more reliable quantitative assessments, but at a fraction of the
cost. Although proteomists working with gel-free methods are considering the gels as
coming from the past, proteomics based on gels has still a lot of opportunities
to offer and acquisition of images on which thousands of spots may be resolved
is still largely performed. Nowadays, two-dimensional electrophoresis remains a
powerful tool to explore the plant proteome and to unravel changes in protein
abundance between samples. Some weak points can be pointed out, as for any
method, as for example the lack of reproducibility, or the detection of
low-abundance proteins. The use of the technique called "difference gel
electrophoresis" or "DIGE" can help to overcome or at least to reduce these
inconveniences. DIGE requires the labelling of proteins by fluorochromes prior
to their separation on 2DE gels. This technique may be applied to a wide array
of plant stress studies, among others to trees. Accurate quantitative results
can then be obtained and proteins presenting an interest in the studied stress
are subsequently subjected to an enzymatic digestion (usually with trypsin) and
identified using electrospray ionization, matrix-assisted laser
desorption/ionization-time-of-flight-MS, and/or tandem MS. |
What clinical use aptamers may have? | In the clinic, aptamers may be used to enhance the antigenicity of disseminated tumors, leading to their immune recognition and rejection; to target HPV16 E7 oncoprotein, inhibiting cell proliferation and activating apoptosis of infected cells; to act as inhibitors for targets such as VEGF, in age-related macular degeneration, and thrombin, or von Willebrand factor, in patients with acute coronary syndromes; to target the RNase H domain of the HIV-1 reverse transcriptase and inhibit viral replication; to transfect and activate B cells in human chronic lymphocytic leukemia (CLL); or finally, to be used as probes in CD4-cell phenotyping. | In vitro selection is a technique for the isolation of nucleic acid ligands that
can bind to proteins with high affinity and specificity, and has potential
applications in the development of new pharmaceuticals. This review summarizes
the protein targets that have successfully elicited nucleic acid binding species
(also known as "aptamers") and explores examples of how they might be developed
for clinical use. In particular, the use of aptamers for the alleviation of
blood clotting and the treatment of AIDS are considered. This article reviews pegaptanib sodium, a compound developed by Eyetech
Pharmaceuticals Inc. and Pfizer Inc., for the treatment of neovascular
age-related macular degeneration (AMD). Traditional treatment approaches to
neovascular AMD have included destructive therapies such as thermal laser
photocoagulation and photodynamic therapy; the use of pegaptanib sodium heralds
a new treatment approach that is a non-destructive therapy based on the
inhibition of vascular endothelial growth factor activity in the eye. This
diminishes the neovascular drive in the pathologically hyperpermeable state of
the diseased eye. Pegaptanib sodium is one of the first therapeutics belonging
to the class of compounds known as aptamers. The chemistry, mechanism of action,
pharmacokinetics and rationale for the clinical use of the drug are reviewed.
The article highlights and summarises the results of the multi-centre,
randomised, sham-controlled clinical trials with pegaptanib sodium to treat
subfoveal choroidal neovascularisation in AMD. In addition, the safety profile
is reviewed. Cancer cells, by releasing pro-angiogenic factors, stimulate the growth of the
thick capillary net necessary for the nourishment of the tumor mass. The battle
to defeat cancer uses today different approaches based on the inhibition of
pathological angiogenesis: several compounds, either synthetic or biotech, aimed
at this complex process, are under development. Vascular endothelial growth
factor (VEGF) is considered the main target for an anti-cancer therapy based on
angiogenesis inhibition; the goal is to block the interaction between this
cytokine and its receptors in order to stop the intracellular signaling pathways
leading to endothelium remodeling. FDA recently approved two drugs specifically
aimed at VEGF, bevacizumab, a humanized monoclonal antibody, and pegaptinib, a
pegylated aptamer with application in ophthalmic pathologies. These two
approvals validate anti-VEGF therapy for clinical use, and show how biotech
companies are investing on angiogenesis using different approaches, i.e.
exploiting protein drugs and oligonucleotide-based therapeutics. Monoclonal
antibodies, as well as other high molecular weight products like cytokine-traps,
aptamers and short interfering RNA (siRNA), are designed to target VEGF and its
receptors. Their design, production and clinical advancement in cancer and other
pathological conditions linked to angiogenesis will be specifically addressed in
this review. BACKGROUND: ARC1779 is a therapeutic aptamer antagonist of the A1 domain of von
Willebrand Factor (vWF), the ligand for receptor glycoprotein 1b on platelets.
ARC1779 is being developed as a novel antithrombotic agent for use in patients
with acute coronary syndromes.
METHODS AND RESULTS: This was a randomized, double-blind, placebo-controlled
study in 47 healthy volunteers of doses of ARC1779 from 0.05 to 1.0 mg/kg.
Pharmacodynamic effects were measured by an ELISA for free vWF A1 binding sites
and by a platelet function analyzer. In terms of pharmacokinetics, the
concentration-time profile of ARC1779 appeared monophasic. The observed
concentration and area under the curve were dose proportional. The mean apparent
elimination half-life was approximately 2 hours, and mean residence time was
approximately 3 hours. The mean apparent volumes of distribution (at steady
state and during terminal phase) were approximately one half the blood volume,
suggesting that ARC1779 distribution is in the central compartment. The mean
clearance ranged from approximately 10% to approximately 21% of the glomerular
filtration rate, suggesting that renal filtration may not be a major mechanism
of clearance of ARC1779. Inhibition of vWF A1 binding activity was achieved with
an EC(90) value of 2.0 mug/mL (151 nmol/L) and of platelet function with an
EC(90) value of 2.6 mug/mL (196 nmol/L). ARC1779 was generally well tolerated,
and no bleeding was observed. Adverse events tended to be minor and not dose
related.
CONCLUSIONS: This is the first-in-human evaluation of a novel aptamer antagonist
of vWF. ARC1779 produced dose- and concentration-dependent inhibition of vWF
activity and platelet function with duration of effect suitable for the intended
clinical use in acute coronary syndromes. The main reason why tumours are not controlled by the immune system is that,
unlike pathogens, they do not express potent tumour rejection antigens (TRAs).
Tumour vaccination aims at stimulating a systemic immune response targeted to,
mostly weak, antigens expressed in the disseminated tumour lesions. Main
challenges in developing effective vaccination protocols are the identification
of potent and broadly expressed TRAs and effective adjuvants to stimulate a
robust and durable immune response. Here we describe an alternative approach in
which the expression of new, and thereby potent, antigens are induced in tumour
cells by inhibiting nonsense-mediated messenger RNA decay (NMD). Small
interfering RNA (siRNA)-mediated inhibition of NMD in tumour cells led to the
expression of new antigenic determits and their immune-mediated rejection. In
subcutaneous and metastatic tumour models, tumour-targeted delivery of NMD
factor-specific siRNAs conjugated to oligonucleotide aptamer ligands led to
significant inhibition of tumour growth that was superior to that of vaccination
with granulocyte-macrophage colony-stimulating factor (GM-CSF)-expressing
irradiated tumour cells, and could be further enhanced by co-stimulation.
Tumour-targeted NMD inhibition forms the basis of a simple, broadly useful, and
clinically feasible approach to enhance the antigenicity of disseminated tumours
leading to their immune recognition and rejection. The cell-free chemically
synthesized oligonucleotide backbone of aptamer-siRNAs reduces the risk of
immunogenicity and enhances the feasibility of generating reagents suitable for
clinical use. Aptamers have emerged as a new class of small molecule ligands. These short,
single-stranded oligonucleotides can be produced through simple chemical
synthesis, making them easier and less costly to produce than antibodies. We
synthesized an RNA aptamer probe specific for human CD4 using a reported
sequence and investigated the potential use of this probe in cell phenotyping.
Studies in cultured cells demonstrated that the synthetic CD4 aptamer had a
nearly identical cell-binding specificity as the standard CD4 antibody.
Fluorescent microscopy confirmed that the aptamer and antibody generated the
same CD4 staining pattern in cells without competing with one another.
Multicolored flow cytometry analysis revealed that the CD4 aptamer could be
combined with antibodies to phenotype cells from bone marrow, lymph nodes, and
pleural fluid, suggesting that the aptamer probe has value for clinical use. Aptamers are a special class of nucleic acid molecules that are beginning to be
investigated for clinical use. These small RNA/DNA molecules can form secondary
and tertiary structures capable of specifically binding proteins or other
cellular targets; they are essentially a chemical equivalent of antibodies.
Aptamers have the advantage of being highly specific, relatively small in size,
and non-immunogenic. Since the discovery of aptamers in the early 1990s, great
efforts have been made to make them clinically relevant for diseases like
cancer, HIV, and macular degeneration. In the last two decades, many aptamers
have been clinically developed as inhibitors for targets such as vascular
endothelial growth factor (VEGF) and thrombin. The first aptamer based
therapeutic was FDA approved in 2004 for the treatment of age-related macular
degeneration and several other aptamers are currently being evaluated in
clinical trials. With advances in targeted-therapy, imaging, and otechnology,
aptamers are readily considered as potential targeting ligands because of their
chemical synthesis and ease of modification for conjugation. Preclinical studies
using aptamer-siRNA chimeras and aptamer targeted oparticle therapeutics have
been very successful in mouse models of cancer and HIV. In summary aptamers are
in several stages of development, from pre-clinical studies to clinical trials
and even as FDA approved therapeutics. In this review, we will discuss the
current state of aptamers in clinical trials as well as some promising aptamers
in pre-clinical development. Aptamers, or nucleic acid ligands, have gained clinical interest over the past
20 years due to their unique characteristics, which are a combination of the
best facets of small molecules and antibodies. The high binding affinity and
specificity of aptamers allows for isolation of an artificial ligand for
theoretically any therapeutic target of interest. Chemical manipulations of
aptamers also allow for fine-tuning of their bioavailability, and antidote
control greatly expands their clinical use. Here we review the various methods
of antidote control of aptamer therapeutics--matched oligonucleotide antidotes
and universal antidotes. We also describe the development, recent progress, and
potential future therapeutic applications of these types of aptamer-antidote
pairs. BACKGROUND: Human papillomavirus 16 (HPV16) is a high-risk DNA tumour virus,
which is a major causative agent of cervical cancer. Cellular transformation is
associated with deregulated expression of the E6 and E7 oncogenes. E7 has been
shown to bind a number of cellular proteins, including the cell cycle control
protein pRb. In this study, RNA aptamers (small, single-stranded
oligonucleotides selected for high-affinity binding) to HPV16 E7 were employed
as molecular tools to further investigate these protein-protein interactions.
METHODOLOGY/PRINCIPAL FINDINGS: This study is focused on one aptamer (termed
A2). Transfection of this molecule into HPV16-transformed cells resulted in
inhibition of cell proliferation (shown using real-time cell electronic sensing
and MTT assays) due to the induction of apoptosis (as demonstrated by Annexin
V/propidium iodide staining). GST-pull down and bead binding assays were used to
demonstrate that the binding of A2 required N-terminal residues of E7 known to
be involved in interaction with the cell cycle control protein, pRb. Using a
similar approach, A2 was shown to disrupt the interaction between E7 and pRb in
vitro. Furthermore, transfection of HPV16-transformed cells with A2 appeared to
result in the loss of E7 and rise in pRb levels, as observed by immunoblotting.
CONCLUSIONS/SIGNIFICANCE: This paper includes the first characterisation of the
effects of an E7 RNA aptamer in a cell line derived from a cervical carcinoma.
Transfection of cells with A2 was correlated with the loss of E7 and the
induction of apoptosis. Aptamers specific for a number of cellular and viral
proteins have been documented previously; one aptamer (Macugen) is approved for
clinical use and several others are in clinical trials. In addition to its role
as a molecular tool, A2 could have further applications in the future. The main reason why tumors are not controlled by the immune system of the cancer
patient is that tumors do not express potent tumor antigens that can be
recognized by the immune system as "foreign." The current focus in developing
immune-based modalities is to potentiate an immune response against the
existing, albeit weak, antigens expressed in the tumor. An alternative approach
is to express new, and hence potent, antigens in tumor cells in situ. To this
end, we have developed an approach to generate new antigenic determits in
tumor cells using siRNA technology to inhibit nonsense-mediated mRNA decay
(NMD), a surveillance mechanism which prevents the expression of mRNAs
containing a premature termination codon. Targeting siRNA inhibition to tumor
cells--an essential requisite because of the constitutive nature and
physiological roles of the NMD process--is accomplished by using a novel
targeting technology based on using oligonucleotide aptamer ligands. Aptamers or
aptamer-targeted siRNA conjugates, unlike antibodies, can be synthesized in a
chemical process providing a more straightforward and cost-effective
manufacturing and regulatory approval process to generate clinical-grade
reagents. In murine tumor models, the aptamer-targeted siRNA-mediated NMD
inhibition in tumor cells led to significant inhibition of tumor growth, which
was superior to best-in-class "conventional" cancer vaccination protocols.
Tumor-targeted NMD inhibition forms the basis of a simple, broadly useful, and
clinically feasible approach to enhance the antigenicity of disseminated tumors
leading to their immune recognition and rejection. The cell-free chemically
synthesized oligonucleotide backbone of aptamer-siRNAs reduces the risk of
immunogenicity and enhances the feasibility of generating reagents suitable for
clinical use. |
What is the causative agent of the "Panama disease" affecting bananas? | Panama disease of banana is caused by the fungus Fusarium oxysporum f. sp. cubense. | Panama disease of baa, caused by the fungus Fusarium oxysporum f. sp.
cubense, is a serious constraint both to the commercial production of baa and
cultivation for subsistence agriculture. Previous work has indicated that F.
oxysporum f. sp. cubense consists of several clonal lineages that may be
genetically distant. In this study we tested whether lineages of the Panama
disease pathogen have a monophyletic origin by comparing DNA sequences of
nuclear and mitochondrial genes. DNA sequences were obtained for translation
elongation factor 1alpha and the mitochondrial small subunit ribosomal RNA genes
for F. oxysporum strains from baa, pathogenic strains from other hosts and
putatively nonpathogenic isolates of F. oxysporum. Cladograms for the two genes
were highly concordant and a partition-homogeneity test indicated the two
datasets could be combined. The tree inferred from the combined dataset resolved
five lineages corresponding to "F. oxysporum f. sp. cubense" with a large
dichotomy between two taxa represented by strains most commonly isolated from
baas with Panama disease. The results also demonstrate that the latter two
taxa have significantly different chromosome numbers. F. oxysporum isolates
collected as nonpathogenic or pathogenic to other hosts that have very similar
or identical elongation factor 1alpha and mitochondrial small subunit genotypes
as baa pathogens were shown to cause little or no disease on baa. Taken
together, these results indicate Panama disease of baa is caused by fungi
with independent evolutionary origins. Using an authentic sample of 2-hydroxy-9-(p-hydroxyphenyl)-phenalen-1-one, a
baa phenalenone-type phytoalexin, we studied its dynamic of accumulation
during pathogenesis of baa plants (Musa acuminata (AAA), Grand Nain)
inoculated with Fusarium oxysporum f.sp. cubense (FOC), Race 4, the causal agent
of Panama disease. The results obtained demonstrate that baa plants treated
prior inoculation with menadione sodium bisulfite (MSB), an inducer of plant
defenses, are capable of changing the dynamic of accumulation (higher amount and
speed of biosynthesis) of this baa phytoalexin, biosynthesized by the baa
plant during pathogenesis. ABSTRACT Fusarium wilt of baa (also known as Panama disease) is caused by
Fusarium oxysporum f. sp. cubense. Where susceptible cultivars are grown,
management is limited to the use of pathogen-free planting stock and clean
soils. Resistant genotypes exist for some applications, but resistance is still
needed in other situations. Progress has been made with this recalcitrant crop
by traditional and nontraditional improvement programs. The disease was first
reported in Australia in 1876, but did the greatest damage in export plantations
in the western tropics before 1960. A new variant, tropical race 4, threatens
the trades that are now based on Cavendish cultivars, and other locally
important types such as the plantains. Phylogenetic studies indicate that F.
oxysporum f. sp. cubense had several independent evolutionary origins. The
significance of these results and the future impact of this disease are
discussed. Intercropping and rotating baa (Musa spp.) with Chinese chive (Allium
tuberosum Rottler) has been used as an effective method to control Panama
disease (Fusarium wilt) of baa in South China. However, the underlying
mechanism is unknown. In this study, we used aqueous leachates and volatiles
from Chinese chive to evaluate their antimicrobial activity on Fusarium
oxysporum f. sp. cubense race 4 (FOC), the causal agent of Panama disease in
baa, and identified the antifungal compounds. Both leaf and root leachates of
Chinese chive displayed strong inhibition against FOC, but the concentrated
leachates showed lower inhibition than the original leachates. In a sealed
system volatiles emitted from the leaves and roots of Chinese chive inhibited
mycelial growth of FOC. Volatile compounds emitted from the intact growing roots
mimicking natural environment inhibited spore germination of FOC. We identified
five volatiles including 2-methyl-2-pentenal and four organosulfur compounds
(dimethyl trisulfide, dimethyl disulfide, dipropyl disulfide, and dipropyl
trisulfide) from the leaves and roots of Chinese chive. All these compounds
exhibited inhibitory effects on FOC, but 2-methyl-2-pentenal and dimethyl
trisulfide showed stronger inhibition than the other three compounds.
2-Methyl-2-pentenal at 50-100 μl/l completely inhibited the mycelial growth of
FOC. Our results demonstrate that antifungal volatiles released from Chinese
chive help control Panama disease in baa. We conclude that intercropping and
rotating baa with Chinese chive can control Panama disease and increase
cropland biodiversity. BACKGROUND: Cavendish, the most widely grown baa cultivar, is relatively
resistant to Race 1 of Fusarium oxysporum f. sp. cubense (Foc1) which caused
widespread Panama disease during the first half of the 20th century but is
susceptible to Tropical Race 4 of Foc (Foc TR4) which is threatening world
baa production. The genome of the diploid species Musa acuminata which is the
ancestor of a majority of triploid baa cultivars has recently been sequenced.
Availability of baa transcriptomes will be highly useful for improving baa
genome annotation and for biological research. The knowledge of global gene
expression patterns influenced by infection of different Foc races will help to
understand the host responses to the infection.
RESULTS: RNA samples from different organs of the Cavendish cultivar were pooled
for deep sequencing using the Illumina technology. Analysis of the baa
transcriptome led to identification of over 842 genes that were not annotated by
the Musa genome project. A large number of simple nucleotide polymorphisms
(SNPs) and short insertions and deletion (indels) were identified from the
transcriptome data. GFP-expressing Foc1 and Foc TR4 were used to monitor the
infection process. Both Foc1 and Foc TR4 were found to be able to invade baa
roots and spread to root vascular tissues in the first two days following
inoculation. Digital gene expression (DGE) profiling analysis reveal that the
infection by Foc1 and Foc TR4 caused very similar changes in the global gene
expression profiles in the baa roots during the first two days of infection.
The Foc infection led to induction of many well-known defense-related genes. Two
genes encoding the ethylene biosynthetic enzyme ACC oxidase and several
ethylene-responsive transcription factors (ERF) were among the strongly induced
genes by both Foc1 and Foc TR4.
CONCLUSIONS: Both Foc1 and Foc TR4 are able to spread into the vascular system
of baa roots during the early infection process and their infection led to
similar gene expression profiles in baa roots. The transcriptome profiling
analysis indicates that the ethylene synthetic and signalling pathways were
activated in response to the Foc infection. The aim of the present study was to scrutinize the response of baa (Grand
Naine variety) plants when interacting with dead or live pathogen, Fusarium
oxysporum f.sp. cubense, a causative agent of Panama disease. Response of plants
was evaluated in terms of induction of defense-related marker enzyme activity,
namely, peroxidase (POX), polyphenol oxidase (PPO), β-1,3 glucanase, chitinase,
and phenolics. Plant's interaction with live pathogen resulted in early
induction of defense to restrain penetration as well as antimicrobial
productions. However, pathogen overcame the defense of plant and caused disease.
Interaction with dead pathogen resulted in escalating defense response in
plants. Later on plants inoculated with dead pathogen showed resistance to even
forced inoculation of live pathogen. Results obtained in the present study
suggest that dead pathogen was able to mount defense response in plants and
provide resistance to Panama disease upon subsequent exposure. Therefore,
preparation from dead pathogen could be a potential candidate as a biocontrol
agent or plant vaccine to combat Panama disease. |
What is the mechanism of action of Nalmefene? | Nalmefene shows opioid receptor antagonism, binds the μ-opioid receptor (MOR1) and modulates opioidergic transmission in the CNS. | Hepatic fibrosis is characterized by excess type I collagen deposition and
exacerbated inflammatory response. Naltrexone, an opioid receptor antagonist
used for treating alcohol abuse, attenuates hepatocellular injury in fibrotic
animal models, which can be accompanied by deleterious side effects.
Additionally, opioid neurotransmission is upregulated in patients with
inflammatory liver disease. Several derivatives of Naltrexone, Nalmefene (Nal)
and JKB-119, exert immunomodulatory activity; however, unlike Nal, JKB-119 does
not show significant opioid receptor antagonism. To delineate the potential
hepatoprotective effects of these compounds, we investigated if JKB-119 and Nal
could modulate activation of hepatic stellate cells (HSCs), primary effector
cells that secrete type I collagen and inflammatory mediators during liver
injury. Our results demonstrated that Nal or JKB-119 treatment decreased smooth
muscle α-actin, a marker of HSC activation, mRNA and protein expression. Despite
decreased collagen mRNA expression, both compounds increased intracellular
collagen protein expression; however, inhibition of collagen secretion was
observed. To address a possible mechanism for suppressed collagen secretion or
retention of intracellular collagen, endoplasmic (ER) protein expression and
matrix metalloproteinase (MMP) activity were examined. While no change in ER
protein expression (Grp78, PDI, Hsp47) was observed, MMP13 mRNA expression was
dramatically increased. In an acute LPS inflammatory injury animal model,
JKB-119 treatment decreased liver injury (ALT), plasma TNFα and PMN liver
infiltration. Overall, these results suggest that JKB-119 can directly inhibit
HSC activation attributed to anti-inflammatory activity and may, therefore,
attenuate inflammation associated with HSC activation and liver disease. INTRODUCTION: Studies have shown that opioid antagonists like naltrexone are
efficient in reducing heavy drinking. The neurobiological mechanism by which
opioid modulators affect drinking behavior is based on the strong connection
between the endogenous opioid system, the dopamine system and the influence of
the CNS stress response.
AREAS COVERED: This review provides an overview of the pathophysiological role
of the opioid system in alcohol dependence and the neurobiological mechanisms of
possible pharmacological interventions. An extensive Medline and Internet
research was performed to retrieve information on existing and currently
investigated opioid modulators. The findings were assessed critically and
interpreted with regard to an individualized therapy for alcohol dependence.
EXPERT OPINION: The opioid system is of crucial importance in the genesis and
maintece of alcohol dependence. Naltrexone- and to a lesser extent nalmefene-
is an agent that modulates opioidergic transmission in the CNS and it shows a
limited but well-studied efficacy in treating alcohol dependence. Several agents
(LY2196044, ALKS-29, ALKS-33) that are currently undergoing Phase II and Phase
III studies are of interest but first their efficacy must be proved in clinical
practice. Opioids that stimulate the μ-opioid receptor (MOR1) are the most frequently
prescribed and effective analgesics. Here we present a structural model of MOR1.
Molecular dynamics simulations show a ligand-dependent increase in the
conformational flexibility of the third intracellular loop that couples with the
G protein complex. These simulations likewise identified residues that form
frequent contacts with ligands. We validated the binding residues using
site-directed mutagenesis coupled with radioligand binding and functional
assays. The model was used to blindly screen a library of ∼1.2 million
compounds. From the 34 compounds predicted to be strong binders, the top three
candidates were examined using biochemical assays. One compound showed high
efficacy and potency. Post hoc testing revealed this compound to be nalmefene, a
potent clinically used antagonist, thus further validating the model. In
summary, the MOR1 model provides a tool for elucidating the structural mechanism
of ligand-initiated cell signaling and for screening novel analgesics. |
Synostosis of which cranial structures are characteristic to the Mercedes Benz syndrome? | Synostosis of sagittal and lambdoid structures are characteristic to the Mercedes Benz syndrome. | A consistent pattern of craniosynostosis in the sagittal and bilateral lambdoid
sutures is described in three patients. The external cranial ridging associated
with fusion of these sutures produces a characteristic triradiate, or "Mercedes
Benz," appearance to the posterior skull. Locally marked growth restriction is
evident in the posterior fossa with compensatory secondary expansion of the
anterior fossa manifesting a degree of frontal bossing which mimics bicoronal
synostosis. Although this appearance could lead to inadvertent surgery in the
frontal region, attention to the occipital region with wide early suture
excision and vault shaping is indicated. |
Can valproic acid act as an activator of AMPK? | Yes, valproic acid canact as an activator of AMPK. | BACKGROUND: The close relationship between epileptic seizure and Alzheimer's
disease (AD) has been demonstrated in the past decade. Valproic acid, a
traditional first-line antiepileptic drug, exerted protective effects in
transgenic models of AD. It remains uncertain whether new antiepileptic drugs
could reverse neuropathology and behavioral deficits in AD transgenic mice.
AIMS: APPswe/PS1dE9 transgenic mice were used in this study, which over express
the Swedish mutation of amyloid precursor protein together with presenilin 1
deleted in exon 9. 7-month-old APPswe/PS1dE9 transgenic mice were treated daily
with 20 mg/kg topiramate (TPM) and 50 mg/kg levetiracetam (LEV) for 30 days by
intraperitoneal injection to explore the effects of TPM and LEV on the
neuropathology and behavioral deficits.
RESULTS: The results indicated that TPM and LEV alleviated behavioral deficits
and reduced amyloid plaques in APPswe/PS1dE9 transgenic mice. TPM and LEV
increased Aβ clearance and up-regulated Aβ transport and autophagic degradation.
TPM and LEV inhibited Aβ generation and suppressed γ-secretase activity. TPM and
LEV inhibited GSK-3β activation and increased the activation of AMPK/Akt
activation. Further, TPM and LEV inhibited histone deacetylase activity in vivo.
CONCLUSIONS: Therefore, TPM and LEV might have the potential to treat AD
effectively in patient care. |
Which signaling pathways have been associated with medulloblastoma formation and growth? | Medulloblastoma comprises approximately 20% of all primary pediatric brain tumors. Multiple signaling pathways have been associated with disease formation and growth. These include the developmental pathways Hedgehog, Notch, and Wnt, as well as pathways in which the receptor tyrosine kinases (RTK) c-Met, erbB2, IGF-R and TrkC, and the oncoprotein Myc are involved. | Elevated expression of the neurotrophin-3 (NT-3) receptor TrkC by childhood
medulloblastomas is associated with favorable clinical outcome. Here, we provide
evidence that TrkC is more than simply a passive marker of prognosis. We
demonstrate that: (a) medulloblastomas undergo apoptosis in vitro when grown in
the presence of NT-3; (b) overexpression of TrkC inhibits the growth of
intracerebral xenografts of a medulloblastoma cell line in nude mice; and (c)
trkC expression by individual tumor cells is highly correlated with apoptosis
within primary medulloblastoma biopsy specimens. TrkC-mediated NT-3 signaling
promotes apoptosis by activating multiple parallel signaling pathways and by
inducing immediate-early gene expression of both c-jun and c-fos. Considered
collectively, these results support the conclusion that the biological actions
of TrkC activation affect medulloblastoma outcome by inhibiting tumor growth
through the promotion of apoptosis. The Hedgehog-Gli signaling pathway is involved in the regulation of the
proliferation of precursors in different organs of the normal vertebrate embryo.
These cells express Gli1 and may be the target of cancer-causing agents. Many
tumor types derived from organs that contain Gli1+ precursors appear to
consistently express Gli1, indicating their origin and/or the presence of an
active pathway. Inappropriate pathway activation in a variety of precursor cells
in model organisms leads to tumor formation while inhibition of the pathway in
human tumor cells leads to a decrease in their proliferation. In the brain we
have documented the expression of Gli1 in germinative zones, and a variety of
brain tumors express GLI1, including medulloblastomas of the cerebellum and a
number of gliomas of the cerebral cortex. The requirement for SHH-Gli signaling
in the growth of the mouse brain, together with the ability of inappropriate
pathway activation in the cerebellum to cause medulloblastomas, and the
inhibition of the growth of a number of brain tumors with cyclopamine, a SHH
signaling inhibitor, underscores the critical role of the SHH-GLI pathway in
brain growth and tumor formation. Moreover, they highlight the components of
this pathway as prime targets for drug development, with special emphasis on the
GLI proteins. Such reagents would allow a rational therapeutic approach to
highly intractable diseases. Medulloblastoma is a maligt tumor that arises in the cerebellum in children,
presumably by transformation of granule neuron precursor cells. In vivo models
of medulloblastoma in genetically engineered mice have shown that activation of
signal transduction pathways that stimulate proliferation and inhibit
differentiation of neural progenitor cells during cerebellar development
initiate medulloblastoma formation. Activation of the Sonic hedgehog
(Shh)/Patched signaling pathway in the postnatal cerebellum is sufficient to
induce medulloblastoma in mice. Activation of the phosphatidylinositol 3-kinase
(PI3K) signaling pathway by insulin-like growth factor-II, inactivation of the
p53 tumor suppressor protein, loss of DNA damage repair mechanisms, and ectopic
expression of Myc oncoproteins cooperate with Shh/Patched signaling to enhance
tumor formation in mice. Ectopic expression of alpha and beta interferons in the
developing brain also induces Shh-mediated medulloblastoma formation, suggesting
a possible role for antiviral response in the genesis of medulloblastoma. By
revealing which cell signaling proteins can initiate medulloblastoma formation,
mouse models have enabled investigators to identify molecular targets for
designing new therapies. Small-molecule inhibitors of the Shh/Patched and PI3K
pathways are potential chemotherapeutic agents for patients with
medulloblastoma. PURPOSE: Medulloblastomas represent the most frequent maligt brain tumors of
childhood. They are supposed to originate from cerebellar neural precursor
cells. Recently, it has been shown that Sonic Hedgehog-induced formation of
medulloblastoma in an animal model is significantly enhanced by activation of
the phosphatidylinositol 3'-kinase (PI3K) signaling pathway.
EXPERIMENTAL DESIGN: To examine a role for PI3K/AKT signaling in the molecular
pathogenesis of human medulloblastoma, we did an immunohistochemical study of
the expression of Ser473-phosphorylated (p)-AKT protein in 22 medulloblastoma
samples: All samples displayed p-AKT expression. To investigate if an activated
PI3K/AKT pathway is required for medulloblastoma cell growth, we treated five
human medulloblastoma cell lines with increasing concentrations of the PI3K
inhibitor LY294002 and analyzed cellular proliferation and apoptosis. The
antiproliferative effect could be antagonized by overexpressing constitutively
active AKT. As the activation of PI3K/AKT signaling may be associated with
alterations of the PTEN gene located at 10q23.3, a chromosomal region subject to
frequent allelic losses in medulloblastoma, we screened PTEN for mutations and
mRNA expression.
RESULTS: Proliferation of all of the medulloblastoma cell lines was dependent on
PI3K/AKT signaling, whereas apoptosis was not prominently affected. Allelic loss
was detected in 16% of the cases. One medulloblastoma cell line was found to
carry a truncating mutation in the PTEN coding sequence. Even more important,
PTEN mRNA and protein levels were found to be significantly lower in
medulloblastomas compared with normal cerebellar tissue of different
developmental stages. Reduction of PTEN expression was found to be associated
with PTEN promoter hypermethylation in 50% of the tumor samples.
CONCLUSIONS: We conclude that activation of the PI3K/AKT pathway constitutes an
important step in the molecular pathogenesis of medulloblastoma and that
dysregulation of PTEN may play a significant role in this context. Medulloblastoma is the most common brain tumor of childhood. Multiple signaling
pathways have been associated with medulloblastoma formation and growth. These
include the developmental pathways Hedgehog, (Hh) Notch, and Wnt as well as the
receptor tyrosine kinases (RTK) c-Met, erbB2, IGF-R and TrkC, and the
oncoprotein Myc. Here we review the involvement of these pathways in
medulloblastoma maligcy with a focus on their mode of deregulation,
prognostic value, functional effects, cellular and molecular mechanisms of
action, and implications for therapy. During development, proliferation of cerebellar granule neuron precursors
(CGNP), candidate cells-of-origin for the pediatric brain tumor medulloblastoma,
requires signaling by Sonic hedgehog (Shh) and insulin-like growth factor (IGF),
the pathways of which are also implicated in medulloblastoma. One of the
consequences of IGF signaling is inactivation of the mammalian target of
rapamycin (mTOR)-suppressing tuberous sclerosis complex (TSC), comprised of TSC1
and TSC2, leading to increased mRNA translation. We show that mice, in which TSC
function is impaired, display increased mTOR pathway activation, enhanced CGNP
proliferation, glycogen synthase kinase-3 alpha/beta (GSK-3 alpha/beta)
inactivation, and cytoplasmic localization of the cyclin-dependent kinase
inhibitor p27(Kip1), which has been proposed to cause its inactivation or gain
of oncogenic functions. We observed the same characteristics in wild-type
primary cultures of CGNPs in which TSC1 and/or TSC2 were knocked down, and in
mouse medulloblastomas induced by ectopic Shh pathway activation. Moreover,
Shh-induced mouse medulloblastomas manifested Akt-mediated TSC2 inactivation,
and the mutant TSC2 allele synergized with aberrant Shh signaling to increase
medulloblastoma incidence in mice. Driving exogenous TSC2 expression in
Shh-induced medulloblastoma cells corrected p27(Kip1) localization and reduced
proliferation. GSK-3 alpha/beta inactivation in the tumors in vivo and in
primary CGNP cultures was mTOR-dependent, whereas p27(Kip1) cytoplasmic
localization was regulated upstream of mTOR by TSC2. These results indicate that
a balance between Shh mitogenic signaling and TSC function regulating new
protein synthesis and cyclin-dependent kinase inhibition is essential for the
normal development and prevention of tumor formation or expansion. Medulloblastoma is a cerebellar tumor affecting children and young adults, and
accounts for approximately one fifth of all pediatric brain tumors. Despite
multimodal therapy that includes surgery, radiotherapy and chemotherapy,
recurrence is frequent and overall mortality rate remains relatively high.
Moreover, radiation therapy results in severe effects on intellect, and younger
age of treatment correlates with larger deficits. Improvements in therapy of
this childhood tumor will focus increasingly on the clarification of the exact
cellular origin and the genetic mechanisms contributing to tumor formation, and
on new targeted therapeutic options. Aberrant activation of the Hedgehog (Hh)
and Wnt developmental pathways is associated with medulloblastoma, but
deregulation of other molecular pathways, including insulin-like growth factor
(IGF) signaling, has also been implicated in the pathogenesis of the tumor.
Recent observations in mouse models have demonstrated the importance of genome
surveillance, as defects in DNA repair pathways in animals can lead to genomic
instability in neural progenitor cells, resulting in medulloblastoma. The
current review will focus on the most recent findings on the molecular pathology
of medulloblastoma and discuss their potential contribution to treatments
directed by the molecular alterations. BACKGROUND: Medulloblastoma comprises approximately 20% of all primary pediatric
brain tumors. Despite recent advances, the survival rate for high-risk patients
and the morbidity associated with these treatments remains suboptimal. To
improve outcomes and decrease morbidity, more targeted therapy is required. One
possible target is the Aurora Kinase family. The objective of this study was to
evaluate the impact of Aurora Kinase A inhibition in medulloblastoma cell lines.
PROCEDURE: Cell proliferation was measured using an MTS assay after adding an
Aurora Kinase inhibitor (C1368) at different concentrations. Cell cycle analysis
was carried out by Flow Cytometry using propidium iodide (PI). RNAi experiments
were performed using siRNA oligonucleotides. Luciferase experiments were carried
out using the Cignal Finder 10 Pathway Reporter Arrays.
RESULTS: Inhibition of Aurora Kinase A induces cell death in medulloblastoma
cells and lowers the IC(50) of other chemotherapeutic agents (etoposide and
cisplatin) used in medulloblastoma treatment. Cell arrest at G2/M phase was
significantly increased in medulloblastoma cell lines treated with C1368 Sigma
at IC(30) or transfected siRNA. Inhibition of Aurora Kinase A resulted in
decreased activity of pro-proliferative signaling pathways including Wnt, Myc,
and RB as measured by luciferase reporter assays.
CONCLUSIONS: These data indicate that inhibition of Aurora Kinase A inhibits
cell growth in medulloblastoma through inhibition of pro-proliferative signaling
pathways Wnt, Myc, and RB. Additionally, combining Aurora Kinase A inhibition
with other chemotherapeutic agents significantly lowers their IC(50), which make
it a promising small molecule target for medulloblastoma therapy. Hedgehog (Hh) signaling is an important factor in growth and patterning during
embryonic development. A mutation in Patched, Smoothened or Gli1, which regulate
the Hh signaling pathway, might lead to the onset of glioblastoma, basal cell
carcinoma, medulloblastoma and rhabdomyosarcoma. Recently, Hh signaling has been
reported to be activated in a ligand-dependent manner, contributing to
carcinogenesis and cancer progression. Hedgehog signaling is reactivated in
various types of cancer, and this contributes to cancer progression by
facilitating proliferation, invasion and cell survival. Moreover, Hh signaling
is associated with several other signaling pathways that contribute to cancer
progression. These observations indicate that controlling Hh signaling might
become a target for novel molecular targeting therapy. The primary cilium is a well-established target in the pathogenesis of numerous
developmental and chronic disorders, and more recently is attracting interest as
a structure relevant to cancer. Here we discuss mechanisms by which changes in
cilia can contribute to the formation and growth of tumors. We emphasize the
cancer-relevance of cilia-dependent signaling pathways and proteins including
mTOR, VHL, TSC, WNT, Aurora-A, NEDD9, and Hedgehog, and highlight the emerging
role of ciliary dysfunction in renal cell carcinoma, medulloblastoma, and breast
cancer. Epidermal growth factor (EGF) signaling regulates cell growth, proliferation,
and differentiation. Upon receptor binding, EGF triggers cascades of downstream
signaling, including the MAPK and phosphoinositide-3-kinase (PI3K)/Akt signaling
pathways. Aberrant expression/activation of EGFR is found in multiple human
cancers, including medulloblastoma, the most prevalent pediatric brain cancer,
and often has been associated with metastasis, poor prognosis, and resistance to
chemotherapy. Na,K-ATPase is an ion pump well known for its role in
intracellular ion homeostasis. Recent studies showed that Na,K-ATPase also
functions as a signaling platform and revealed a role in EGFR, MAPK, and PI3K
signaling. While both EGFR and Na,K-ATPase seem to modulate similar signaling
pathways, cardiac glycosides that are steroid-like inhibitors of Na,K-ATPase,
exhibit antiproliferative and proapoptotic properties in cancer cells. Thus, we
sought to better understand the relationship between EGF and cardiac glycoside
signaling. Here, we show that in medulloblastoma cells, both EGF and ouabain
activate Erk1/2 and PI3K/Akt signaling. Nevertheless, in medulloblastoma cells
ouabain did not transactivate EGFR as has been reported in various other cell
lines. Indeed, ouabain inhibited EGF-induced Erk1/2 and Akt activation and,
moreover, prevented EGF-induced formation of actin stress fibers and cell
motility, probably by activating a stress signaling response. Na,K-ATPase has
been proposed to act as a signaling scaffold and our studies suggest that in
medulloblastoma cells Na,K-ATPase might act as a check point to integrate
EGF-associated signaling pathways. Thus, Na,K-ATPase might serve as a valid
target to develop novel therapeutic approaches in tumors with aberrant
activation of the EGFR signaling cascades. |
What is the role of invadopodia in EMT? | In a process of epithelial-mesenchymal transition (EMT), besides changing their adhesive repertoire, cancer cells employ developmental processes to gain migratory and invasive properties that involve a dramatic reorganization of the actin cytoskeleton and the concomitant formation of membrane protrusions required for invasive growth. An important type of such membrane protrusions are the invadopodia, which have been increasingly recognized as important drivers of local invasion in metastasis. They are basally-localized, actin-rich structures that concentrate protease activity to areas of the cell in contact with the extracellular matrix. | The metastatic process, i.e. the dissemination of cancer cells throughout the
body to seed secondary tumors at distant sites, requires cancer cells to leave
the primary tumor and to acquire migratory and invasive capabilities. In a
process of epithelial-mesenchymal transition (EMT), besides changing their
adhesive repertoire, cancer cells employ developmental processes to gain
migratory and invasive properties that involve a dramatic reorganization of the
actin cytoskeleton and the concomitant formation of membrane protrusions
required for invasive growth. The molecular processes underlying such cellular
changes are still only poorly understood, and the various migratory organelles,
including lamellipodia, filopodia, invadopodia and podosomes, still require a
better functional and molecular characterization. Notably, direct experimental
evidence linking the formation of migratory membrane protrusions and the process
of EMT and tumor metastasis is still lacking. In this review, we have summarized
recent novel insights into the molecular processes and players underlying EMT on
one side and the formation of invasive membrane protrusions on the other side. The Twist1 transcription factor is known to promote tumor metastasis and induce
Epithelial-Mesenchymal Transition (EMT). Here, we report that Twist1 is capable
of promoting the formation of invadopodia, specialized membrane protrusions for
extracellular matrix degradation. Twist1 induces PDGFRα expression, which in
turn activates Src, to promote invadopodia formation. We show that Twist1 and
PDGFRα are central mediators of invadopodia formation in response to various
EMT-inducing signals. Induction of PDGFRα and invadopodia is essential for
Twist1 to promote tumor metastasis. Consistent with PDGFRα being a direct
transcriptional target of Twist1, coexpression of Twist1 and PDGFRα predicts
poor survival in breast tumor patients. Therefore, invadopodia-mediated matrix
degradation is a key function of Twist1 in promoting tumor metastasis. Twist, the basic helix-loop-helix transcription factor, is involved in the
process of epithelial to mesenchymal transitions (EMTs), which play an essential
role in cancer metastasis. Overexpression of Twist or its promoter methylation
is a common scenario in metastatic carcinomas. Twist is activated by a variety
of signal transduction pathways, including Akt, signal transducer and activator
of transcription 3, mitogen-activated protein kinase, Ras, and Wnt signaling.
Activated Twist upregulates N-cadherin and downregulates E-cadherin, which are
the hallmarks of EMT. Moreover, Twist plays an important role in some
physiological processes involved in metastasis, like angiogenesis, invadopodia,
extravasation, and chromosomal instability. Twist also protects cancer cells
from apoptotic cell death. In addition, Twist is responsible for the stemness of
cancer cells and the generation of drug resistance. Recently, targeting Twist
has gained significant interests in cancer therapeutics. The inactivation of
Twist by small RNA technology or chemotherapeutic approach has been proved
successful. Moreover, several inhibitors which are antagonistic to the upstream
or downstream molecules of Twist signaling pathways have also been identified.
Development of potential treatment strategies by targeting Twist has a great
promise in cancer therapeutics. Metastasis is a major cause of mortality in cancer patients. Invadopodia are
considered to be crucial structures that allow cancer cells to penetrate across
the extracellular matrix (ECM) by using matrix metalloproteinases (MMPs).
Previously, we isolated a highly invasive A431-III subline from parental A431
cells by Boyden chamber assay. The A431-III cells possess higher invasive and
migratory abilities, elevated levels of MMP-9 and an enhanced
epithelial-mesenchymal transition (EMT) phenotype. In this study, we discovered
that A431-III cells had an increased potential to form invadopodia and an
improved capacity to degrade ECM compared with the original A431 cells. We also
observed enhanced phosphorylation levels of cortactin and Src in A431-III cells;
these phosphorylated proteins have been reported to be the main regulators of
invadopodia formation. Flavonoids, almost ubiquitously distributed in food
plants and plant food products, have been documented to exhibit anti-tumor
properties. Therefore, it was of much interest to explore the effects of
flavonoid antioxidants on the metastatic activity of A431-III cells. Exposure of
A431-III cells to two potent dietary flavonoids, namely luteolin (Lu) and
quercetin (Qu), caused inhibition of invadopodia formation and decrement in ECM
degradation. We conclude that Lu and Qu attenuate the phosphorylation of
cortactin and Src in A431-III cells. As a consequence, there ensues a disruption
of invadopodia generation and the suppression of MMP secretion. These changes,
in concert, bring about a reduction in metastasis. |
What are cancer driver genes? | Recent sequencing and resequencing (i.e., polymorphism identification) efforts have catalyzed the quest for 'driver' mutations (i.e., those genetic alterations which contribute to the transformation of a normal cell to a proliferating cancerous cell) in distinction to 'passenger' mutations which reflect mutations that merely build up in course of normal and unchecked (i.e., cancerous) somatic cell replication and proliferation. Analysis of the frequency of specific mutations across different tumors has been able to identify some, but not all of the mutated genes that contribute to tumor initiation and progression. A subset of these mutations contribute to tumor progression (known as "driver" mutations) whereas the majority of these mutations are effectively neutral (known as "passenger" mutations). | Recent studies investigating the genetic determits of cancer suggest that
some of the genetic alterations contributing to tumorigenesis may be inherited,
but the vast majority is somatically acquired during the transition of a normal
cell to a cancer cell. A systematic understanding of the genetic and molecular
determits of cancers has already begun to have a transformative effect on the
study and treatment of cancer, particularly through the identification of a
range of genetic alterations in protein kinase genes, which are highly
associated with the disease. Since kinases are prominent therapeutic targets for
intervention within the cancer cell, studying the impact that genomic
alterations within them have on cancer initiation, progression, and treatment is
both logical and timely. In fact, recent sequencing and resequencing (i.e.,
polymorphism identification) efforts have catalyzed the quest for protein kinase
'driver' mutations (i.e., those genetic alterations which contribute to the
transformation of a normal cell to a proliferating cancerous cell) in
distinction to kinase 'passenger' mutations which reflect mutations that merely
build up in course of normal and unchecked (i.e., cancerous) somatic cell
replication and proliferation. In this review, we discuss the recent progress in
the discovery and functional characterization of protein kinase cancer driver
mutations and the implications of this progress for understanding tumorigenesis
as well as the design of 'personalized' cancer therapeutics that target an
individual's unique mutational profile. Recent large-scale tumor resequencing studies have identified a number of
mutations that might be involved in tumorigenesis. Analysis of the frequency of
specific mutations across different tumors has been able to identify some, but
not all of the mutated genes that contribute to tumor initiation and
progression. One reason for this is that other functionally important genes are
likely to be mutated more rarely and only in specific contexts. Thus, for
example, mutation in one member of a collection of functionally related genes
may result in the same net effect, and/or mutations in certain genes may be
observed less frequently if they play functional roles in later stages of tumor
development, such as metastasis. We modified and applied a network
reconstruction and coexpression module identification-based approach to identify
functionally related gene modules targeted by somatic mutations in cancer. This
method was applied to available breast cancer, colorectal cancer, and
glioblastoma sequence data, and identified Wnt/TGF-beta cross-talk, Wnt/VEGF
signaling, and MAPK/focal adhesion kinase pathways as targets of rare driver
mutations in breast, colorectal cancer, and glioblastoma, respectively. These
mutations do not appear to alter genes that play a central role in these
pathways, but rather contribute to a more refined shaping or "tuning" of the
functioning of these pathways in such a way as to result in the inhibition of
their tumor-suppressive signaling arms, and thereby conserve or enhance
tumor-promoting processes. MOTIVATION: Major tumor sequencing projects have been conducted in the past few
years to identify genes that contain 'driver' somatic mutations in tumor
samples. These genes have been defined as those for which the non-silent
mutation rate is significantly greater than a background mutation rate estimated
from silent mutations. Several methods have been used for estimating the
background mutation rate.
RESULTS: We propose a new method for identifying cancer driver genes, which we
believe provides improved accuracy. The new method accounts for the functional
impact of mutations on proteins, variation in background mutation rate among
tumors and the redundancy of the genetic code. We reanalyzed sequence data for
623 candidate genes in 188 non-small cell lung tumors using the new method. We
found several important genes like PTEN, which were not deemed significant by
the previous method. At the same time, we determined that some genes previously
reported as drivers were not significant by the new analysis because mutations
in these genes occurred mainly in tumors with large background mutation rates.
AVAILABILITY: The software is available at:
http://linus.nci.nih.gov/Data/YounA/software.zip. Identifying genomic alterations driving breast cancer is complicated by tumor
diversity and genetic heterogeneity. Relevant mouse models are powerful for
untangling this problem because such heterogeneity can be controlled. Inbred
Chaos3 mice exhibit high levels of genomic instability leading to mammary tumors
that have tumor gene expression profiles closely resembling mature human mammary
luminal cell signatures. We genomically characterized mammary adenocarcinomas
from these mice to identify cancer-causing genomic events that overlap common
alterations in human breast cancer. Chaos3 tumors underwent recurrent copy
number alterations (CNAs), particularly deletion of the RAS inhibitor
Neurofibromin 1 (Nf1) in nearly all cases. These overlap with human CNAs
including NF1, which is deleted or mutated in 27.7% of all breast carcinomas.
Chaos3 mammary tumor cells exhibit RAS hyperactivation and increased sensitivity
to RAS pathway inhibitors. These results indicate that spontaneous NF1 loss can
drive breast cancer. This should be informative for treatment of the significant
fraction of patients whose tumors bear NF1 mutations. Herein we report a proof-of-principle study illustrating a novel dog-human
comparison strategy that addresses a central aim of cancer research, namely
cancer driver-passenger distinction. We previously demonstrated that sporadic
canine colorectal cancers (CRCs) share similar molecular pathogenesis mechanisms
as their human counterparts. In this study, we compared the genome-wide copy
number abnormalities between 29 human and 10 canine sporadic CRCs. This led to
the identification of 73 driver candidate genes (DCGs), altered in both species,
and with 27 from the whole genome and 46 from dog-human genomic rearrangement
breakpoint (GRB) regions, as well as 38 passenger candidate genes (PCGs),
altered in humans only and located in GRB regions. We noted that DCGs
significantly differ from PCGs in every analysis conducted to assess their
cancer relevance and biological functions. Importantly, although PCGs are not
enriched in any specific functions, DCGs possess significantly enhanced
functionality closely associated with cell proliferation and death regulation,
as well as with epithelial cell apicobasal polarity establishment/maintece.
These observations support the notion that, in sporadic CRCs of both species,
cell polarity genes not only contribute in preventing cancer cell invasion and
spreading, but also likely serve as tumor suppressors by modulating cell growth.
This pilot study validates our novel strategy and has uncovered four new
potential cell polarity and colorectal tumor suppressor genes (RASA3, NUPL1,
DENND5A and AVL9). Expansion of this study would make more driver-passenger
distinctions for cancers with large genomic amplifications or deletions, and
address key questions regarding the relationship between cancer pathogenesis and
epithelial cell polarity control in mammals. The identification of cancer drivers is a major goal of current cancer research.
Finding driver genes within large chromosomal events is especially challenging
because such alterations encompass many genes. Previously, we demonstrated that
zebrafish maligt peripheral nerve sheath tumors (MPNSTs) are highly
aneuploid, much like human tumors. In this study, we examined 147 zebrafish
MPNSTs by massively parallel sequencing and identified both large and focal copy
number alterations (CNAs). Given the low degree of conserved synteny between
fish and mammals, we reasoned that comparative analyses of CNAs from fish versus
human MPNSTs would enable elimination of a large proportion of passenger
mutations, especially on large CNAs. We established a list of orthologous genes
between human and zebrafish, which includes approximately two-thirds of human
protein-coding genes. For the subset of these genes found in human MPNST CNAs,
only one quarter of their orthologues were co-gained or co-lost in zebrafish,
dramatically narrowing the list of candidate cancer drivers for both focal and
large CNAs. We conclude that zebrafish-human comparative analysis represents a
powerful, and broadly applicable, tool to enrich for evolutionarily conserved
cancer drivers. |
What is a mitochondrial nucleoid? | A naked mtDNA molecule is longer than a typical mitochondrion and is therefore compacted in vivo to form a nucleoprotein complex, denoted the mitochondrial nucleoid. | Nuclear DNA is tightly packed into nucleosomal structure. In contrast, human
mitochondrial DNA (mtDNA) had long been believed to be rather naked because
mitochondria lack histone. Mitochondrial transcription factor A (TFAM), a member
of a high mobility group (HMG) protein family and a first-identified
mitochondrial transcription factor, is essential for maintece of
mitochondrial DNA. Abf2, a yeast counterpart of human TFAM, is abundant enough
to cover the whole region of mtDNA and to play a histone-like role in
mitochondria. Human TFAM is indeed as abundant as Abf2, suggesting that TFAM
also has a histone-like architectural role for maintece of mtDNA. When human
mitochondria are solubilized with non-ionic detergent Nonidet-P40 and then
separated into soluble and particulate fractions, most TFAM is recovered from
the particulate fraction together with mtDNA, suggesting that human mtDNA forms
a nucleoid structure. TFAM is tightly associated with mtDNA as a main component
of the nucleoid. Mitochondrial DNA plays a crucial role in cellular homeostasis; however, the
molecular mechanisms underlying mitochondrial DNA inheritance and propagation
are only beginning to be understood. To ensure the distribution and propagation
of the mitochondrial genome, mitochondrial DNA is packaged into macromolecular
assemblies called nucleoids, composed of one or more copies of mitochondrial DNA
and associated proteins. We review current research on the mitochondrial
nucleoid, including nucleoid-associated proteins, nucleoid dynamics within the
cell, potential mechanisms to ensure proper distribution of nucleoids, and the
impact of nucleoid organization on mitochondrial dysfunction. The nucleoid is
the molecular organizing unit of mitochondrial genetics, and is the site of
interactions that ultimately determine the bioenergetic state of the cell as a
whole. Current and future research will provide essential insights into the
molecular and cellular interactions that cause bioenergetic crisis, and yield
clues for therapeutic rescue of mitochondrial dysfunction. Emerging research shows that the packaging of mitochondrial DNA (mtDNA) into
protein-DNA assemblies called nucleoids confers higher-order organization to the
mitochondrial genome. Studies of nucleoid composition, structure and dynamics
reveal the mitochondrial nucleoid to be tightly regulated in its genetic
autonomy, macromolecular organization and distribution throughout the cell. Our
recent research shows that mitochondrial nucleoids are self-contained genetic
entities that do not exchange mtDNAs with each other frequently. This suggests
that the genetic composition of a cell's nucleoids will be the key determit
of the cell's mtDNA dynamics, and provides a mechanistic basis for therapeutic
methods to rescue dysfunction due to mutations in mtDNA. Mitochondrial DNA (mtDNA) is organized in nucleoids in complex with accessory
proteins, proteins of mtDNA replication and gene expression machinery. A robust
mtDNA genome is represented by hundreds to thousands of nucleoids in cell
mitochondrion. Detailed information is lacking about the dynamics of nucleoid
distribution within the mitochondrial network upon physiological and
pathological events. Therefore, we used confocal microscopy to study
mitochondrial nucleoid redistribution upon mitochondrial fission and following
reintegration of the mitochondrial network. Fission was induced by oxidative
stress at respiration inhibition by rotenone or upon elimination of the
protonmotive force by uncoupling or upon canceling its electrical component,
ΔΨ(m), by valinomycin; and by silencing of mitofusin MFN2. Agent withdrawal
resulted in concomitant mitochondrial network reintegration. We found two major
principal morphological states: (i) a tubular state of the mitochondrial network
with equidistant nucleoid spacing, 1.10±0.2 nucleoids per μm, and (ii) a
fragmented state of solitary spheroid objects in which several nucleoids were
clustered. We rarely observed singular mitochondrial fragments with a single
nucleoid inside and very seldom we observed empty fragments. Reintegration of
fragments into the mitochondrial network re-established the tubular state with
equidistant nucleoid spacing. The two major morphological states coexisted at
intermediate stages. These observations suggest that both mitochondrial network
fission and reconnection of the disintegrated network are nucleoid-centric,
i.e., fission and new mitochondrial tubule formation are initiated around
nucleoids. Analyses of combinations of these morphological icons thus provide a
basis for a future mitochondrial morphology diagnostics. The packaging of mitochondrial DNA (mtDNA) into DNA-protein assemblies called
nucleoids provides an efficient segregating unit of mtDNA, coordinating mtDNA's
involvement in cellular metabolism. From the early discovery of mtDNA as
"extranuclear" genetic material, its organization into nucleoids and integration
into both the mitochondrial organellar network and the cell at large via a
variety of signal transduction pathways, mtDNA is a crucial component of the
cell's homeostatic network. The mitochondrial nucleoid is composed of a set of
DNA-binding core proteins involved in mtDNA maintece and transcription, and a
range of peripheral factors, which are components of signaling pathways
controlling mitochondrial biogenesis, metabolism, apoptosis, and retrograde
mitochondria-to-nucleus signaling. The molecular interactions of nucleoid
components with the organellar network and cellular signaling pathways provide
exciting clues to the dynamic integration of mtDNA into cellular metabolic
homeostasis. |
What is the treatment of amiodarone-induced thyrotoxicosis? | Treatment of amiodarone-induced thyrotoxicosis is complex and may include drugs such as antithyroid drugs, beta-blockers, corticosteroids lithium as well as iopanoic acid in preparation of thyroidectomy. Total thyroidectomy and radioiodine represent alternative treatment options | OBJECTIVE: To investigate how North American thyroidologists assess and treat
amiodarone-induced thyrotoxicosis (AIT) and to compare the results with those of
the same questionnaire-based survey previously carried out among European
thyroidologists.
DESIGN: Members of the American Thyroid Association (ATA) with clinical
interests were sent by e-mail a questionnaire on the diagnosis and management of
AIT, 115 responses were received from the United States and Canada, representing
about one-third of ATA members with clinical interests.
RESULTS: The majority of respondents (91%vs. 68% in Europe, P < 0.05) see < 10
new cases of AIT per year, and AIT seems less frequent than amiodarone-induced
hypothyroidism (AIH) in North America (34% and 66% of amiodarone-induced thyroid
dysfunction, respectively, vs. 75% and 25%, respectively, in Europe, P < 0.001).
When AIT is suspected, in North America hormonal assessment is mostly based on
serum free T4 (FT4) and TSH measurements, while serum free T3 (FT3)
determination is requested less frequently than in Europe; thyroid autoimmunity
is included in the initial assessment less than in Europe. Most commonly used
additional diagnostic procedures include, as in Europe, thyroid colour-flow
Doppler sonography, and to a lesser extent, thyroid radioactive iodine uptake
and scan, but Europeans tend to request multiple tests more than North
Americans. Withdrawal of amiodarone is more often considered unnecessary by
North American thyroidologists (21%vs. 10% in Europe in type 1 AIT, P < 0.05,
34%vs. 20% in type 2 AIT, P < 0.05). In type 1 AIT thionamides represent the
treatment of choice for North Americans as well as for Europeans, but the former
use them as monotherapy in 65%vs. 51% of Europeans (P < 0.05) who more often
consider potassium perchlorate as an useful addition (31%vs. 15% of North
Americans, P < 0.01). Glucocorticoids are the selected treatment for type 2 AIT,
alone (62%vs. 46% in Europe, P < 0.05) or in association with thionamides
(16%vs. 25% in Europe, P = NS). After restoration of euthyroidism, thyroid
ablation in the absence of recurrent thyrotoxicosis is recommended in type 1 AIT
less frequently by North Americans. If amiodarone therapy needs to be
reinstituted, prophylactic thyroid ablation is advised by 76% in type 1 AIT,
while a 'wait-and-see' strategy is adopted by 61% in type 2 AIT, similar to
behaviour of European thyroidologists.
CONCLUSION: Similarities and differences exist between expert North American and
European thyroidologists concerning the diagnosis and management of AIT. While
differences reflect the frequent uncertainty of the underlying mechanism leading
to AIT, similarities may represent the basis to refine the diagnostic criteria
and to improve the therapeutic outcomes of this challenging clinical situation. We report the treatment of four thyrotoxic patients. Two were cases of type I
amiodarone-induced thyrotoxicosis (AIT) treated with methimazole. The third
Graves' disease patient, who became hypothyroid 25 years after subtotal
thyroidectomy, developed type II AIT. Furthermore, one case with heart failure
and ventricular tachycardia, who developed an adverse reaction to antithyroid
agents and was prescribed amiodarone, underwent total thyroidectomy. The
clinical course was uneventful, and the patient is doing well. Since amiodarone
contains a large amount of iodine, it is frequently difficult to make a
differential diagnosis. Surgical treatment of Graves' disease patients is
recommended when immediate control of hyperthyroidism and heart failure is
required. INTRODUCTION: Amiodarone (AM) is frequently used in the therapy of patients with
cardiac disorders. However, due to high iodine content, it has side effects on
thyroid function. The use of radioiodine therapy (RIT) in amiodarone-induced
thyrotoxicosis (AIT) with low radioactive iodine uptake (RAIU) is still
controversial. In these patients therapeutic choices for refractory disease
include surgery, antithyroid drugs, or glu ocorticosteriods.
AIM: The aim of the study was to evaluate the efficacy of RIT in patients
presenting AIT and low RAIU in two-year follow-up.
PATIENTS AND METHODS: 40 patients (25 men and 15 women) aged from 63 to 83 years
(x +/- SD: 66.2 +/- 5.0 years; median: 65 years) treated with RIT were included
into the study. In these patients AM therapy was essential for the underlying
heart disorder, while surgery, antithyroid drugs or glucocorticosteroids, were
contraindicated. Forty seven patients with toxic multinodular goiter (TMNG) (39
women and 8 men), matched for age (67 +/- 12 yr; range 54-89 yr), were enrolled
into the study as a comparative group. The diagnostic procedures included
baseline thyroid function tests (thyrothropin - TSH, free triiodothyronine - fT3
and free thyroxine - fT4 levels), thyroid autoantibodies measurement
(antithyroglobulin autoantibodies - TgAb, antithyroid peroxidase autoantibodies
- TPOAb, anti-TSH receptor autoantibodies - TRAb), thyroid ultrasonography,
thyroid scintiscan and RAIU assessment.
RESULTS: Serum values of TSH, TgAb, TPOAb and TRAb were undetectable in both
groups. In patients with AIT fT4 level was 18.7 to 38.7 pmol/l (mean: 27.1 +/-
5.8) and fT3 concentration was 3.9 to 5.6 pmo/l (mean: 5.7 +/- 1.4), while in
TMNG patients level of fT4 was 31.5 to 22.2 pmol/l (mean: 25,3 +/- 5,8) and fT3
concentration was 3.8 to 4,2 pmo/l (mean: 4,2 +/- 0,2). Mean RAIU values after
5h and 24h in AIT patients were 2.3 +/- 0.5 and 3.1 +/- 0.9%, while in TMNG
patients were 18,0 +/- 3,8 and 35,7 +/- 9,1%, respectively. A significant
difference (p<0.001) between 5h and 24h RAIU in AIT compared to TMNG was noted.
In all patients with AIT, a dose of 800 MBq of 131I was administered. During
two-year-observation recurrence of hyperthyroidism was observed in two patients
(5%) with TMNG. These patients received a second radioiodine dose 16.2 +/- 15
months later (the mean re-treatment dose was 735.93 +/- 196.1 MBq). In
comparison, none of the patients with AIT required a second 131I dose and only
one patient (2.5%) 6 months after ablative 131I dose needed anti-thyroid
medication. Transient hypothyroidism was observed in only two patients (5%) with
AIH, though was not observed in TMNG. During follow-up time, no sudden deaths in
AIT patients were observed; one patient was diagnosed with prostate cancer, and
in one patient acute toxic hepatitis after AM occurred.
CONCLUSION: RIT may be a safe and useful method of AIT therapy in patients with
low RAIU, in whom other treatment methods are contraindicated. BACKGROUND/OBJECTIVE: The identification of the different subtypes of
amiodarone-induced thyrotoxicosis (AIT) may provide a rational basis for the
choice of the appropriate medical treatment. The aim of this study was to
evaluate differential diagnosis and treatment regimens of AIT in children and
adolescent.
PATIENTS: We reported 3 patients: A 6.7 years old boy with type I AIT; a 17.9
years old girl with type II AIT and a 14.6 years old girl with mixed type AIT.
CONCLUSIONS: AIT is not an uncommon complication in countries with low iodine
intake. AIT can be asymptomatic and can occur at any time in patients receiving
amiodarone therapy. It is also very important to distinguish the type of AIT
when planning therapy. Steroid therapy should be started when findings indicate
type II or mixed-type AIT. Beta blockers may prevent heart thyrotoxicosis and
recurrence of primary arrhythmia if amiodarone is discontinued. CONTEXT: Patients with amiodarone-induced thyrotoxicosis (AIT) and left
ventricular (LV) systolic dysfunction have a high mortality rate. Usually,
medical therapy is the first choice for AIT patients, whereas the role of the
thyroidectomy is unsettled.
OBJECTIVE: The objective of the study was to evaluate the effect of a total
thyroidectomy on cardiac function and survival of AIT patients with severe LV
systolic dysfunction.
DESIGN: This was a retrospective cohort study.
SETTINGS: The study was conducted at a tertiary university center.
PATIENTS: All AIT patients (n=24; nine patients with type 1 AIT, 15 patients
with type 2 AIT) referred to the Department of Endocrinology and submitted to a
total thyroidectomy at the Department of Surgery, both at the University of
Pisa, during the years 1997-2010.
INTERVENTION: The intervention was a total thyroidectomy.
MAIN OUTCOME MEASURE: LV ejection fraction (EF) after the thyroidectomy and
survival in December 2011 were measured.
RESULTS: All enrolled patients had previously undergone to medical treatment for
AIT, as appropriate, without achieving euthyroidism. Patients with moderate to
severe LV systolic dysfunction (EF<40%, group 1, n=9) or with mild systolic
dysfunction (40%≤EF≤50%, group 2, n=5) were compared with patients with normal
systolic function (EF>50%, group 3, n=10). Two months after thyroidectomy, under
levothyroxine replacement therapy, LVEF improved in patients with LV systolic
dysfunction, particularly in those of group 1, in whom it increased from
28.2±7.2 to 38.3±6% (P=0.007). On the contrary, LVEF did not significantly
change in group 3 (from 57.1±3.0 to 59.8±6.6%, P=0.242). The mean follow-up was
67±42 months. No death occurred during and 2 months after surgery. One death
occurred in one patient of group 1, 30 months after the thyroidectomy, due to
acute myocardial infarction. No patient had relevant complications of
thyroidectomy.
CONCLUSIONS: Total thyroidectomy, by rapidly restoring euthyroidism, may improve
cardiac function and reduce the risk of mortality in AIT patients with severe LV
dysfunction. |
How does exercise affect thyroid hormone receptors expression in the heart? | Exercise has been shown to increase TRβ1 receptor expression in young rats. Exercise has been shown to increase both TRα1 and TRβ1 receptor expression in aged rats. | Physiological and pathological cardiac hypertrophy have directionally opposite
changes in transcription of thyroid hormone (TH)-responsive genes, including
alpha- and beta-myosin heavy chain (MyHC) and sarcoplasmic reticulum
Ca(2+)-ATPase (SERCA), and TH treatment can reverse molecular and functional
abnormalities in pathological hypertrophy, such as pressure overload. These
findings suggest relative hypothyroidism in pathological hypertrophy, but serum
levels of TH are usually normal. We studied the regulation of TH receptors (TRs)
beta1, alpha1, and alpha2 in pathological and physiological rat cardiac
hypertrophy models with hypothyroid- and hyperthyroid-like changes in the TH
target genes, alpha- and beta-MyHC and SERCA. All 3 TR subtypes in myocytes were
downregulated in 2 hypertrophy models with a hypothyroid-like mRNA phenotype,
phenylephrine in culture and pressure overload in vivo. Myocyte TRbeta1 was
upregulated in models with a hyperthyroid-like phenotype, TH (triiodothyronine,
T3), in culture and exercise in vivo. In myocyte culture, TR overexpression, or
excess T3, reversed the effects of phenylephrine on TH-responsive mRNAs and
promoters. In addition, TR cotransfection and treatment with the
TRbeta1-selective agonist GC-1 suggested different functional coupling of the TR
isoforms, TRbeta1 to transcription of beta-MyHC, SERCA, and TRbeta1, and
TRalpha1 to alpha-MyHC transcription and increased myocyte size. We conclude
that TR isoforms have distinct regulation and function in rat cardiac myocytes.
Changes in myocyte TR levels can explain in part the characteristic molecular
phenotypes in physiological and pathological cardiac hypertrophy. Exercise training improves the aging-induced downregulation of myosin heavy
chain (MHC) and sarcoplasmic reticulum (SR) Ca(2+)-ATPase, which participate in
the regulation of cardiac contraction and relaxation. Thyroid hormone receptor
(TR), a transcriptional activator, affected the regulation of gene expression of
MHC and SR Ca(2+)-ATPase. We hypothesized that myocardial TR signaling
contributes to a molecular mechanism of exercise training-induced improvement of
MHC and SR Ca(2+)-ATPase genes with cardiac function in old age. We investigated
whether TR signaling and gene expression of MHC and SR Ca(2+)-ATPase in the aged
heart are affected by exercise training, using the hearts of sedentary young
rats (4 mo old), sedentary aged rats (23 mo old), and trained aged rats (23 mo
old, swimming training for 8 wk). Trained aged rats showed improvement in
cardiac function. Expression of TR-alpha1 and TR-beta1 proteins in the heart
were significantly lower in sedentary aged rats than in sedentary young rats and
were significantly higher in trained aged rats than in sedentary aged rats. The
activity of TR DNA binding to the transcriptional regulatory region in the
alpha-MHC and SR Ca(2+)-ATPase genes and the mRNA and protein expression of
alpha-MHC and SR Ca(2+)-ATPase in the heart and plasma 3,3'-triiodothyronine and
thyroxine levels were altered in association with changes in the myocardial TR
protein levels. These findings suggest that exercise training improves the
aging-induced downregulation of myocardial TR signaling-mediated transcription
of MHC and SR Ca(2+)-ATPase genes, thereby contributing to the improvement of
cardiac function in trained aged hearts. |
Is the Drosophila Translational Control Element (TCE) involved in spermatogenesis? | Yes. The Drosophila Translational Control Element (TCE), a 12 nucleotide long sequence element, was demonstrated to be necessary for translational control of expression in the male germ line of Drosophila melanogaster. | To investigate the importance of core promoter elements for tissue-specific
transcription of RNA polymerase II genes, we examined testis-specific
transcription in Drosophila melanogaster. Bioinformatic analyses of core
promoter sequences from 190 genes that are specifically expressed in testes
identified a 10 bp A/T-rich motif that is identical to the translational control
element (TCE). The TCE functions in the 5' untranslated region of Mst(3)CGP
mRNAs to repress translation, and it also functions in a heterologous gene to
regulate transcription. We found that among genes with focused initiation
patterns, the TCE is significantly enriched in core promoters of genes that are
specifically expressed in testes but not in core promoters of genes that are
specifically expressed in other tissues. The TCE is variably located in core
promoters and is conserved in melanogaster subgroup species, but conservation
dramatically drops in more distant species. In transgenic flies, short (300-400
bp) genomic regions containing a TCE directed testis-specific transcription of a
reporter gene. Mutation of the TCE significantly reduced but did not abolish
reporter gene transcription indicating that the TCE is important but not
essential for transcription activation. Finally, mutation of testis-specific
TFIID (tTFIID) subunits significantly reduced the transcription of a subset of
endogenous TCE-containing but not TCE-lacking genes, suggesting that tTFIID
activity is limited to TCE-containing genes but that tTFIID is not an obligatory
regulator of TCE-containing genes. Thus, the TCE is a core promoter element in a
subset of genes that are specifically expressed in testes. Furthermore, the TCE
regulates transcription in the context of short genomic regions, from variable
locations in the core promoter, and both dependently and independently of
tTFIID. These findings set the stage for determining the mechanism by which the
TCE regulates testis-specific transcription and understanding the dual role of
the TCE in translational and transcriptional regulation. |
What are the symptoms of abacavir hypersensitivity? | Patients receiving abacavir develop an idiosyncratic hypersensitivity reaction that can include a wide range of symptoms. The most common are: fever, enathema, skin rash, nausea, vomiting, diarrhoea, cough, gastrointestinal disorders, anaphylactic shock, respiratory symptoms. | Abacavir is a nucleoside analogue reverse transcriptase inhibitor used in
combination with other antiretroviral drugs for the treatment of HIV
1-infection. Approximately 3% of patients who receive abacavir develop an
idiosyncratic hypersensitivity reaction. The most common symptoms are fever,
skin rash and gastrointestinal disorders. Respiratory symptoms occurred in
approximately 20% of patients who have hypersensitivity reaction. We describe
the first case, to our knowledge, of hypesensitivity reaction characterized by
ethema and fever without skin rash promptly resolved after discontinuation of
abacavir Differentiation between abacavir hypersensitivity and viral respiratory
infections is problematic. Fifteen cases of abacavir hypersensitivity were
matched to 30 controls with culture proven influenza A with no abacavir
exposure. Rash was associated with hypersensitivity (odds ratio [OR] = 13.1, P =
0.02) as was the presence of nausea (OR = 30, P < 0.001), vomiting (OR = 17.1, P
= 0.001) or diarrhoea (OR = 22, P < 0.001). The number of gastrointestinal
symptoms was also predictive of hypersensitivity reaction (P < 0.001).
Respiratory symptoms (cough, sore throat, or dyspnoea) were not associated with
abacavir hypersensitivity (OR = 0.08, P = 0.001). Multivariate analysis
confirmed the following associations for abacavir hypersensitivity: the number
of gastrointestinal symptoms (OR = 8.6, P = 0.0032), cough (OR = 0.039, P =
0.02) and rash (OR = 16.9, P = 0.07). Abacavir hypersensitivity is strongly
associated with gastrointestinal (GI) symptoms. Cough without GI symptoms is
associated with influenza. PURPOSE: Abacavir is associated with an infrequent but potentially serious
hypersensitivity reaction (HSR) that can include a wide range of signs and
symptoms. Identification of this reaction through medical insurance claims could
provide a simple and efficient means of monitoring the incidence of abacavir
hypersensitivity in large populations of patients.
METHODS: Using data from a safety study of 948 abacavir users with 22
hypersensitivity events identified from claims and validated through medical
record review, we used a recursive partitioning analysis to construct an
algorithm to differentiate between patients with and without validated adverse
events. Bootstrap resampling techniques provided validation for the analysis.
RESULTS: The analysis produced a classification tree with three decision nodes
that comprised the best indicators of HSRs. The predictors included any one of
several specific symptoms commonly found with this reaction, a claims diagnosis
of adverse effect of drug, anaphylactic shock or unspecified allergy, and a
discontinuation in abacavir prior to completing a 90-day course of therapy. The
algorithm demonstrated 95% sensitivity and 90% specificity when tested using a
bootstrap resampling approach with the current data.
CONCLUSIONS: A sensitive and specific algorithm for identifying abacavir
hypersensitivity from claims was created. This algorithm would permit efficient
identification of charts for medical review. Further testing of the algorithm
with additional medical claims data for abacavir users will be required to
ascertain its validity across databases. |
What is the effect of ivabradine in heart failure with preserved ejection fraction? | I(f)-channel inhibition potentially exhibits beneficial effects in diastolic heart failure. In patients with heart failure with preserved ejection fraction (HFpEF), short-term treatment with ivabradine increased exercise capacity, with a contribution from improved left ventricular filling pressure response to exercise as reflected by the ratio of peak early diastolic mitral flow velocity to peak early diastolic mitral annular velocity. Ivabradine has demonstrated benefits in HFpEF without improving mortality. In db/db, a model of HFpEF, ivabradine improved vascular stiffness, left ventricular contractility, and diastolic function. Furthermore, ivabradine reduces cardiac fibrosis in hypercholesterolemic rabbits. | Selective heart rate (HR) reduction by I(f)-channel inhibition is a recently
developed pharmacological principle in cardiovascular therapy. Among these newly
identified HR-lowering drugs, only ivabradine has now become approved for
clinical use. I(f)-channel inhibition mainly reduces HR, thereby improving
myocardial oxygen supply, energy balance, and cardiac function. Ivabradine was
well tolerated and revealed a good safety profile in the investigated study
populations. The guiding experimental and clinical results of I(f)-channel
inhibition were compared to those of beta-blockade as a HR reducing principle as
well as cornerstone of heart failure standard therapy. Beside its use in therapy
of coronary artery disease, I(f)-channel inhibition potentially exhibits
beneficial effects in systolic and diastolic heart failure as well. Therefore,
hemodynamic effects of ivabradine and its limitations in heart failure together
with the biological impact of HR reduction will be considered in this context.
Because no clinical data with specific heart-rate-reducing agents are available
in heart failure patients until now, the prospective significance of
I(f)-channel inhibition can only be speculated on. However, the presented
results and considerations are encouraging: ivabradine may play a therapeutic
role in the future protecting left ventricular function and structure from early
deterioration in heart failure with reduced and preserved ventricular ejection
fraction. AIMS: In diabetes mellitus, heart failure with preserved ejection fraction
(HFPEF) is a significant comorbidity. No therapy is available that improves
cardiovascular outcomes. The aim of this study was to characterize myocardial
function and ventricular-arterial coupling in a mouse model of diabetes and to
analyse the effect of selective heart rate (HR) reduction by If-inhibition in
this HFPEF-model.
METHODS AND RESULTS: Control mice, diabetic mice (db/db), and db/db mice treated
for 4 weeks with the If-inhibitor ivabradine (db/db-Iva) were compared. Aortic
distensibility was measured by magnetic resoce imaging. Left ventricular (LV)
pressure-volume analysis was performed in isolated working hearts, with
biochemical and histological characterization of the cardiac and aortic
phenotype. In db/db aortic stiffness and fibrosis were significantly enhanced
compared with controls and were prevented by HR reduction in db/db-Iva. Left
ventricular end-systolic elastance (Ees) was increased in db/db compared with
controls (6.0 ± 1.3 vs. 3.4 ± 1.2 mmHg/µL, P < 0.01), whereas other
contractility markers were reduced. Heart rate reduction in db/db-Iva lowered
Ees (4.0 ± 1.1 mmHg/µL, P < 0.01), and improved the other contractility
parameters. In db/db active relaxation was prolonged and end-diastolic
capacitance was lower compared with controls (28 ± 3 vs. 48 ± 8 μL, P < 0.01).
These parameters were ameliorated by HR reduction. Neither myocardial fibrosis
nor hypertrophy were detected in db/db, whereas titin N2B expression was
increased and phosphorylation of phospholamban was reduced both being prevented
by HR reduction in db/db-Iva.
CONCLUSION: In db/db, a model of HFPEF, selective HR reduction by If-inhibition
improved vascular stiffness, LV contractility, and diastolic function.
Therefore, If-inhibition might be a therapeutic concept for HFPEF, if confirmed
in humans. PURPOSE OF REVIEW: Heart failure is a major health problem with significant
morbidity and mortality. Although impressive advances in treatment and reduction
in mortality have marked heart failure with reduced ejection fraction (HFrEF),
the mortality in patients with heart failure with preserved ejection fraction
(HFpEF), which accounts for nearly half of heart failure cases, has remained
unchanged. This may be because of the lack of consistent diagnostic criteria and
limited understanding of the pathophysiology of HFpEF, and thus appropriate
treatment options.
RECENT FINDINGS: Recent data suggest that HFpEF consists of multiple
abnormalities rather than a distinct entity. Advances in testing have improved
diagnosis, but further validation is required. The discoveries of new
pathological abnormalities have identified potential new drug therapy targets.
Traditional agents with strong evidence in HFrEF have proved unsuccessful in
HFpEF. Newer agents such as angiotensin receptor neprilysin inhibitor,
sildenafil, and ivabradine have demonstrated benefits without improving
mortality. Lastly, as HFpEF patients are older with more comorbidities,
alternate endpoints to survival benefit should be considered.
SUMMARY: Although enormous strides have been made in understanding the
pathophysiology and refining the diagnostic criteria of HFpEF, there is
currently no pharmacological therapy with mortality benefits. Further
characterization and the recruitment of more homogeneous patient populations
will be essential to identify effective treatments. OBJECTIVES: The aim of this study was to test the effects of treatment with
ivabradine on exercise capacity and left ventricular filling in patients with
heart failure with preserved ejection fraction (HFpEF).
BACKGROUND: Because symptoms of HFpEF are typically exertional, optimization of
diastolic filling time by controlling heart rate may delay the onset of
symptoms.
METHODS: Sixty-one patients with HFpEF were randomly assigned to ivabradine 5 mg
twice daily (n = 30) or placebo (n = 31) for 7 days in this double-blind trial.
Cardiopulmonary exercise testing with echocardiographic assessment of myocardial
function and left ventricular filling were undertaken at rest and after
exercise.
RESULTS: The ivabradine group demonstrated significant improvement between
baseline and follow-up exercise capacity (4.2 ± 1.8 METs vs. 5.7 ± 1.9 METs, p =
0.001) and peak oxygen uptake (14.0 ± 6.1 ml/min/kg vs. 17.0 ± 3.3 ml/min/kg, p
= 0.001), with simultaneous reduction in exercise-induced increase in the ratio
of peak early diastolic mitral flow velocity to peak early diastolic mitral
annular velocity (3.1 ± 2.7 vs. 1.3 ± 2.0, p = 0.004). Work load-corrected
chronotropic response (the difference in heart rate at the same exercise time at
the baseline and follow-up tests) showed a slower increase in heart rate during
exercise than in the placebo-treated group. Therapy with ivabradine (β = 0.34, p
= 0.04) and change with treatment in exertional increase in the ratio of peak
early diastolic mitral flow velocity to peak early diastolic mitral annular
velocity (β = -0.30, p = 0.02) were independent correlates of increase in
exercise capacity, and therapy with ivabradine (β = 0.32, p = 0.007) was
independently correlated with increase in peak oxygen uptake.
CONCLUSIONS: In patients with HFpEF, short-term treatment with ivabradine
increased exercise capacity, with a contribution from improved left ventricular
filling pressure response to exercise as reflected by the ratio of peak early
diastolic mitral flow velocity to peak early diastolic mitral annular velocity.
Because this patient population is symptomatic on exertion, therapeutic
treatments targeting abnormal exercise hemodynamic status may prove useful. (Use
of Exercise and Medical Therapies to Improve Cardiac Function Among Patients
With Exertional Shortness of Breath Due to Lung Congestion;
ACTRN12610001087044). |
Is low T3 syndrome a prognostic marker in patients with renal insufficiency? | Low fT3 is an independent predictor of death in chronic kidney disease, in particular in dialised patients at end-stage renal diseases. | In 22 patients with hepatic or renal insufficiency the serum concentrations of
trijodothyronin, thyroxine and thyrotropin and also the T4-binding capacity of
TBG were determined. The mean serum T3 concentration was found to be
significantly lower in patients with hepatic coma when compared with euthyroid
subjects. In the cases of renal insufficiency the serum T3 concentrations were
in the normal range. Due to hormone loss through dialysis however, the mean
value of the T3 concentrations was slightly lower than the average concentration
of normal subjects. The obtained results agree with those of our earlier studies
which showed that there are significant differences between liver artery and
vein T3 concentrations in serum, whereas no such differences could be
ascertained between serum concentrations in renal artery and vein. On the basis
of these findings it is assumed that conversion of T4 into T3 occurs
predomitly in the liver. Thirty-eight patients with chronic renal insufficiency who were in a dialysis
program underwent studies of thyroid function and metabolic status. Mean values
for serum total and free thyroxine (T4) concentrations and thyroxine-binding
globulin capacity were within normal limits. Although mean serum total
triiodothyronine (T3) concentration was normal, 43% of the group had low serum
T3 and 54% had low serum free T3 concentrations. Serum thyrotrophin (TSH)
concentrations were normal in all but four subjects who had very slight
elevations. Metabolic status was assessed by various metabolic tests; mean
values for each of these tests were normal, and the clinical index scores
indicated that all patients were euthyroid. Results of metabolic testing were
similar in patients with low and those with normal serum T3 concentrations. Low
serum T3 measurements did not accurately reflect metabolic state in patients
with chronic renal failure, whereas serum free T4 and TSH concentrations were
reliable indicators of thyroid state. The authors studied the serum level of T3, T4 and TTH in 30 euthyroid patients
with chronic renal insufficiency (CRI), distributed in three groups of 10
patients. I group includes patients with CRI II and III stage without dialysis
treatment, patients with CRI are included in the II group, being under
hemodialysis treatment from 5 to 12 months, and in III group--patients dialized
three and more years. Low average values of T3--0.65 mg/ml were established only
in the first group; in 8 patients, out of 10 examined, the values were under the
lower limit of the norm. Though the T4 values in the first group were within the
limits of the norm (5.87 mkg/100 ml), they were under the average normal values
(8.5 mkg/100 ml) and lower, with a statistical significance (pt less than 0.025)
as compared with those of the other two groups. The values of T3 and T4 in both
groups dialyzed patients were within the limits of the norm regardless of the
duration of dialysis. In none of the patients from the three groups examined,
deviations in TTH level were found. The authors drew the conclusion that
biochemical hypothyroidism, manifested with low T3 values, normal TTH level and
a tendency of T4 decrease was observed in nondialyzed patients even with CRI II
stage (creatine 6.8 mg%). Biochemical hypothyroidism abates with the adequate
and effective hemodialysis treatment, suggesting that uremic toxins play and
essential role in its development. It was stressed that abatement could be used
as a criterion of adequate and effective dialysis programme and a reliable
rehabilitation of the patients, under chronodialysis treatment. BACKGROUND: Low T3 is a frequent alteration in patients with ESRD. This
derangement has been recently linked to inflammation in haemodialysis patients.
Whether this association holds true in peritoneal dialysis patients has not been
studied.
METHODS: We investigated the relationship between low-grade inflammation [IL-6,
C-reactive protein (CRP) and serum albumin levels] and free tri-iodothyronine
(fT3) in a cohort of 41 CAPD patients (mean age, 66 years; M, 26; F, 15) without
heart failure and inter-current illnesses.
RESULTS: CAPD patients had lower fT3 levels (2.7 +/- 0.8 pg/ml) than healthy
subjects (3.7 +/- 1.0 pg/ml, P < 0.001) of similar age. Free T3 levels were
directly related to those of serum albumin (r = 0.52, P = 0.001) and inversely
to IL-6 (r = -0.30, P = 0.05) and CRP (r = -0.54, P < 0.001). Age (r = -0.61, P
< 0.001), haemoglobin levels (r = 0.32, P = 0.05) and diastolic blood pressure
(r = 0.50, P = 0.001) were also related to fT3. In multiple regression models
adjusting for all variables related to fT3, CRP and albumin were retained as
independent correlates of fT3. During the follow-up (2.8 +/- 1.7 years) 27
patients died. Plasma fT3 levels were lower in patients who died (2.5 +/- 0.8
pg/ml) compared with survivors (3.3 +/- 0.5 pg/ml P = 0.001). In Cox analyses,
fT3 was a significant predictor of mortality independent of the main traditional
as well as non-traditional risk factors.
CONCLUSIONS: The relationship between fT3, CRP and serum albumin suggests that
inflammation-malnutrition might be involved in the low T3 syndrome in CAPD
patients. Thyroid dysfunction might be implicated in the pathogenic pathway
which links micro-inflammation to survival in PD patients. OBJECTIVES: In this study, we explore the associations of decreased thyroid
hormone levels with inflammation, wasting and survival in biochemically
euthyroid patients with end-stage renal disease (ESRD).
DESIGN: After exclusion of 23 patients with thyroid-stimulating hormone (TSH)
values outside the normal range (0.1-4.5 mIU L(-1)), 187 clinically and
biochemically euthyroid incident ESRD stage 5 patients starting dialysis were
followed for a median of 20 (range 1-60) months. Measurements of total and free
forms of thyroid hormones, s-albumin, hs-CRP, interleukin (IL)-6, vascular
adhesion molecule (VCAM)-1 and insulin-like growth factor 1 (IGF-1) were
performed at baseline.
RESULTS: In this population, 17 out of 210 patients (8%) were defined as
subclinically hypothyroid. Multivariate analysis, according to receiver
operating characteristic (ROC) curves, showed that mortality was best predicted
by total triiodothyronine (T3). When using the cut-off levels derived from ROC,
low T3 levels were associated with increased inflammation (higher hs-CRP, IL-6
and VCAM-1) and lower concentration of both s-albumin and IGF-1. Finally, low T3
but not low free triiodothyronine was associated with worse all-cause
(Likelihood ratio = 45.4; P < 0.0001) and cardiovascular mortality (Likelihood
ratio = 47.8; P < 0.0001) after adjustment for confounding factors.
CONCLUSION: This study showed that low T3 levels are independent predictors of
all-cause and also cardiovascular disease mortality in biochemically euthyroid
patients, perhaps due to an intimate association with inflammation. Based on
these results, the use of T3 levels in studies assessing the relationship
between thyroid dysfunction and mortality risk is recommended. INTRODUCTION. It has been shown that inflammation affects thyroid function. In
patients with end-stage renal disease, low plasma triiodothyronine (T3) may be
an unsuspected expression of the inflammatory state of these patients. This
study evaluated the correlation between T3 and high-sensitivity C-reactive
protein (HSCRP) levels in patients on peritoneal dialysis (PD) and hemodialysis.
MATERIALS AND METHODS. This is a cross-sectional study aiming at the correlation
between T3 and HSCRP levels among 30 patients on PD, 30 patients on
hemodialysis, and 20 healthy individuals. Serum levels of HSCRP, T3, thyroxine
(T4), thyroid stimulating hormone, T3 resin uptake, and free T3 index (FT3I) and
free T4 index (FT4I) were compared between the three groups. RESULTS. There were
no significant differences between hemodialysis and PD patients in respect to
T3, T4, FT3I, and FT4I. In PD and hemodialysis patients, T3 and FT3I were lower
than in controls (P < .001), but there was no significant difference between PD
and hemodialysis patients. T3 resin uptake and thyroid stimulating hormone
differed significantly between PD and hemodialysis patients. There was a
significant inverse correlation between HSCRP and T3 and FT3I among hemodialysis
patients (P = .04); however, there was no such correlations in PD patients.
CONCLUSIONS. The relationship between T3 and HSCRP suggests that inflammation
might be involved in the low T3 syndrome in hemodialysis patients, but we did
not find a significant correlation between T3 and HSCRP levels in patients on
peritoneal dialysis. BACKGROUND: Serum free triiodothyronine (fT3) level is suggested to be a risk
factor for mortality in unselected dialysis patients. We investigated the
prognostic value of serum fT3 levels and also low-T3 syndrome on overall
survival in a large cohort of hemodialysis (HD) patients with normal
thyroid-stimulating hormone levels.
METHODS: A total of 669 prevalent HD patients were enrolled in the study. Serum
fT3 level was measured by enzyme immune assay in frozen sera samples at the time
of enrollment. Overall mortality was assessed during 48 months of follow-up.
RESULTS: Baseline fT3 was 1.47 ± 0.43 (0.01-2.98) pg/ml, and low-T3 syndrome was
present in 71.7% of the cases. During a mean follow-up of 34 ± 16 months, 165
(24.7%) patients died. fT3 level was a strong predictor for mortality in crude
and adjusted Cox models including albumin or high-sensitivity C-reactive protein
(hs-CRP). Further adjustment for both albumin and hs-CRP made the impact of fT3
on mortality disappear. The presence of low-T3 syndrome was associated with
mortality in only the unadjusted model.
CONCLUSIONS: Low-T3 syndrome is a frequent finding among HD patients, but it
does not predict outcome. However, serum fT3 level is a strong and inverse
mortality predictor, in part explained by its underlying association with
nutritional state and inflammation. OBJECTIVE: The aim of this study was to analyze the prevalence, clinical
significance and prognostic implications of alterations in thyroid function
tests (TFTs) in patients with acute kidney injury (AKI).
METHODS: A prospective study was carried out in patients hospitalized for AKI
for 2 consecutive years. TFTs (serum thyrotropin [TSH], free thyroxine [FT4] and
total triiodothyronine [T3] concentrations) were completed for each patient on 3
occasions: at admission, at hospital discharge and at their first outpatient
visit. TFTs were related to clinical and analytical data. Thirty-five patients
(16 women [45.7%], mean age ± SD, 65.2 ± 18.0 years) with AKI (creatinine 5.6 ±
2.2 mg/dL) were studied. There were 10 (28.6%), 10 (28.6%), 11 (31.4%) and 4
(11.4%) patients with prerenal, renal, mixed (prerenal and renal), and postrenal
AKI, respectively.
RESULTS: Total prevalence of alterations in TFTs was 82.9% (n=29). Of those,
euthyroid sick syndrome (ESS) with low T3 only was the most common (n=13, 37.1%)
derangement. In the whole group of patients, median TSH (0.93 µU/mL,
interquartile range 0.35-2.27 µU/mL)and mean FT4 (1.2 ± 0.3 ng/dL) were normal,
whereas mean T3 was low (0.7 ± 0.1 ng/mL). TSH, FT4 and T3 were similar in
different types of AKI. On simple regression analysis, we found a negative
correlation only between TSH and serum urea concentrations (ro=-0.382; p=0.024).
At hospital discharge (median hospital stay 6 days; range 2-10 days), TFT showed
significant changes only in T3 concentrations (0.8 ± 0.3 ng/mL, p=0.013). At
this point, the percentage of patients with normal TFT increased from 17.1% at
baseline to 40% at discharge and then to 66.7% at their first outpatient visit.
We found no association between the presence and type of alterations in TFT and
clinical factors (sex, age, personal history of diabetes and/or hypertension,
number and type of drugs used, number of signs and symptoms at AKI diagnosis,
and degree, type and cause of AKI) or prognostic factors (hospital stay,
recovery of renal function, need for renal replacement therapy by hemodialysis,
development and degree of residual chronic renal failure and mortality)
associated with AKI.
CONCLUSION: Over 80% of AKI patients exhibit alterations in TFT. The commonest
derangement is ESS (~70%), mainly low T3 syndrome, which is present in about one
third of the patients with altered TFT. ESS recovers spontaneously as renal
function improves. The presence of TFT alterations seems to not be associated
with clinical and prognostic implications in AKI patients. Numerous abnormalities of thyroid hormones in end-stage renal disease (ESRD)
have been described. Our aim was to analyze the impact of these abnormalities on
survival. In 167 hemodialyzed ESRD patients, TSH and thyroid hormone levels (T4,
fT4, T3, fT3, rT3) were determined. The patients were then prospectively
followed up for up to 5 years and the possible impact of any observed
abnormalities on their mortality was studied. Only 16.8 % patients had all six
tests within the reference range. The pattern of nonthyroidal illness syndrome
was found in 56.3 %. Low T3 was particularly common (44.3 %), and clearly
associated with increased 6- and 12-month mortality and decreased overall
survival (log rank test, P=0.007). Independent of T3 levels (Spearman
correlation, NS), increased rT3 was more frequently observed (9.9 %) than
expected from the literature, and was also related to increased mortality and
decreased survival (log rank test, P=0.021). Increased rT3 may be more common in
ESRD patients than previously described, and together with decreased T3 it may
serve as an indicator of poor prognosis in subsequent months. OBJECTIVE: Little is known about the impact of low triiodothyronine (T3) levels
on mortality in end-stage renal disease (ESRD) patients starting hemodialysis
(HD) and whether this impact is mediated by malnutrition, inflammation, or
cardiac dysfunction.
DESIGN AND METHODS: A prospective cohort of 471 incident HD patients from 36
dialysis centers within the Clinical Research Center for ESRD in Korea was
selected for this study. Based on the median value of T3, patients were divided
into 'higher' and 'lower' groups, and all-cause and cardiovascular (CV)
mortality rates were compared. In addition, associations between T3 levels and
various nutritional, inflammatory, and echocardiographic parameters were
determined.
RESULTS: Compared with those in the 'higher' T3 group, albumin, cholesterol, and
triglyceride levels, lean body mass estimated by creatinine kinetics (LBM-Cr),
and normalized protein catabolic rate (nPCR) were significantly lower in
patients with 'lower' T3 levels. The 'lower' T3 group also had a higher left
ventricular mass index (LVMI) and a lower ejection fraction (EF). Furthermore,
correlation analysis revealed significant associations between T3 levels and
nutritional and echocardiographic parameters. All-cause and CV mortality rates
were significantly higher in patients with 'lower' T3 levels than in the
'higher' T3 group (113.4 vs 18.2 events per 1000 patient-years, P<0.001, and
49.8 vs 9.1 events per 1000 patient-years, P=0.001, respectively). The
Kaplan-Meier analysis also showed significantly worse cumulative survival rates
in the 'lower' T3 group (P<0.001). In the Cox regression analysis, low T3 was an
independent predictor of all-cause mortality even after adjusting for
traditional risk factors (hazard ratio=3.76, P=0.021). However, the significant
impact of low T3 on all-cause mortality disappeared when LBM-Cr, nPCR, LVMI, or
EF were incorporated into the models.
CONCLUSION: Low T3 has an impact on all-cause mortality in incident HD patients,
partly via malnutrition and cardiac dysfunction. |
Does burning mouth syndrome preferentially affect post-mepopausal women? | BMS is observed principally in middle-aged patients and postmenopausal women
BMS mostly affects elderly citizens, especially postmenopausal women with prevalence up to 12-18%. | The analysis of etiopathogenetic and clinical aspects of burning mouth syndrome,
allow to suppose the participation of more factors in the determinism of
disease. Consequently, also the therapy, might to require the presence of many
specialist. Twenty-five patients with a diagnosis of nonorganic burning mouth syndrome were
matched for age and sex with twenty-five patients with organically based painful
disorders of the mouth. All patients were interviewed by a psychiatrist and
completed the General Health Questionnaire to screen for psychiatric disorders.
A diagnosis of psychiatric disorder based on clinical examination findings was
made in 44% (11/25) of the patients with burning mouth syndrome and in 16%
(4/25) of the controls. The burning mouth complaint of each of fifty-seven patients was thoroughly
studied. Psychogenesis was found to be the most frequent cause, followed by
geographic tongue and moniliasis. Multiple causative factors, such as
psychogenesis and moniliasis and psychogenesis and geographic tongue, were found
in some patients. The purely psychogenic group was composed mostly of
postmenopausal women. The tongue and palate were the most frequently affected
sites. There were some similarities among patients in the geographic tongue and
psychogenesis groups. A diagnostic protocol for patients with burning mouth is
described. Though it has been the subject of much research, burning mouth syndrome--a
chronic oral-facial pain condition that affects many U.S. adults--remains poorly
understood. It has been associated with numerous oral and systemic conditions.
Treatment options frequently include various medications. While patients with
symptoms of BMS are more likely to seek care from physicians, dentists should be
involved in the evaluation and management of these patients. Burning mouth syndrome (BMS) is a distinct clinical entity characterized by a
chief complaint of unremitting oral burning concomitant with no oral mucosal
clinically observable lesions. Numerous causes of this condition have been
suggested, including local factors, systemic factors, and psychogenic disorders.
A total of 36 consecutive subjects, 32 women and 4 men, complaining of BMS, who
had attended the Dental Clinic of the University of Ferrara during a period of 2
years, was studied. The method of assessment followed closely a strictly
co-ordinated management protocol based on conventional guidelines, namely
history, clinical examination and special investigations. A detailed history was
taken of duration of the condition, site affected, and pattern of burning. The
severity and the response to treatment were assessed with a Visual Linear
Analogue Scale (VLAS). A full medical history was taken, with regard to
xerostomia-inducing drug assumption. The presence and the severity of menopausal
symptoms were explored. Inquiries were made on use of mouthwashes. For the
denture-wearers, specific questioning was directed to the length of
denture-wearing experience, temporal association of the symptom with the wearing
of dentures, relationship to burning sensation of any relines or repairs,
denture cleaning technique, and use of fixatives. A complete routine intraoral
and extraoral examination was performed. The presence of parafunctional habits,
such as tongue thrusting, clenching, grinding, lip and cheek biting, was
investigated. If dentures were worn, their design and condition were examined.
In particular, the relation between the vertical and horizontal components of
the jaw and the denture base extension was assessed and the freeway space
measured.(ABSTRACT TRUNCATED AT 250 WORDS) The relationship between burning mouth syndrome and 48 variables was
investigated in 241 patients, 45 years old and older, who had attended the Oral
Medicine Clinic of the Faculty of Dentistry, University of Stellenbosch during a
period of 4 years. A total of 85 cases of burning mouth syndrome were diagnosed
in 65 women and 20 men. Statistically significant relationships (p < 0.05) were
found with self-medication, xerostomia, and other salivary disturbances in both
men and women with burning mouth syndrome when compared with their respective
controls. Among the women with BMS, significant relationships were also found
with anemia, inadequate diet, chronic infection, hormone therapy,
ulcerative/erosive lesions, and atrophy. In contrast men with BMS showed
statistically significant relationships between taking prescribed medication,
central nervous system disturbances, gingivitis, and denture-related problems.
In addition, significant associations were related to variables such as
psychogenic factors, regurgitation, flatulence, and periodontitis. Burning mouth syndrome is a common condition particularly affecting elderly
women. Numerous precipitating factors are recognized that lead to a burning
sensation in clinically normal mucosa. By taking each precipitating factor into
account, a favorable treatment outcome usually can be achieved. This article
highlights the significance of precipitating factors in burning mouth syndrome
and suggests a treatment protocol based on current scientific evidence. STATEMENT OF PROBLEM: Dental practitioners occasionally have patients present
clinically with a history of chief complaint of burning and painful sensations
in the oral cavity. Often the patient demonstrates clinically normal mucosa,
which can make formulating a diagnosis challenging. This scenario, has been
referred to as burning mouth syndrome, a multifactorial syndrome.
PURPOSE: The purpose of this article is to present a review of etiologic factors
and clinical implications related to the condition of burning mouth syndrome. Complaint of a burning mouth is an increasingly common problem in the aging
population. This has remained an enigma for the treating clinician, because
visible pathologic lesions or processes are usually not evident. Local, systemic
and environmental causes must be assessed to elicit the predisposing factors.
Some suggestions for managing burning mouth syndrome are offered. Burning mouth syndrome is a complicated, poorly understood, predomitly oral
condition that affects more than 1 million people in the United States. Women
are particularly affected by the condition; they are diagnosed with symptoms
seven times more frequently than males. Burning mouth syndrome is characterized
by a burning, painful sensation of the oral mucosa that most commonly involves
the anterior tongue. Many precipitating factors to burning mouth syndrome have
been proposed, and treatment addressing these factors has had limited success.
Patients with burning mouth syndrome are more likely to be evaluated by
physicians, and therefore it is advantageous for the physician to be familiar
with this oral condition. This paper reviews burning mouth syndrome, associated
causative factors, and treatment strategies for the physician. Symptoms of a burning sensation of the oral mucosa mainly occur in the elderly,
more often in women than in men. Often accompanying symptoms are complaints of a
dry mouth and taste disturbances, all together referred to as the burning mouth
syndrome. In the majority of cases there is no detectable cause. Although a
psychogenic aetiology has often been put forward, no scientific evidence has
ever been provided on this matter. In the majority of patients the burning mouth
syndrome will disappear spontaneously, although this may take many years. A critical component of the dental hygiene process of care is assessment of the
oral and general health conditions of clients. Some clients present with burning
and painful sensations in the oral cavity in the absence of any noticeable
disease. This condition has been referred to as burning mouth syndrome (BMS), an
often complicated condition. Various local, systemic, and psychological factors
have been linked with BMS, but its etiology is not fully understood. Yet as many
as one million people are affected by it in the United States, and it is an
increasingly-common problem in the aging population. Middle-aged women, mostly
postmenopausal, are diagnosed with symptoms seven times more frequently than
men. Careful diagnosis and treatment are necessary to alleviate the symptoms of
this condition. Referral to a physician is warranted in some cases. The purposes
of this course are to review the etiologic factors and clinical implications
related to this condition and to discuss appropriate dental hygiene
interventions. Collaboration among the client, dental hygienist, dentist, and
physician provides for interdisciplinary actions that can lead to palliation of
symptoms and evaluation of the possible underlying factors contributing to the
condition. Burning mouth syndrome is characterized by a burning sensation in the tongue or
other oral sites, usually in the absence of clinical and laboratory findings.
Affected patients often present with multiple oral complaints, including
burning, dryness and taste alterations. Burning mouth complaints are reported
more often in women, especially after menopause. Typically, patients awaken
without pain but note increasing symptoms through the day and into the evening.
Conditions that have been reported in association with burning mouth syndrome
include chronic anxiety or depression, various nutritional deficiencies, type 2
diabetes (formerly known as non-insulin-dependent diabetes) and changes in
salivary function. However, these conditions have not been consistently linked
with the syndrome, and their treatment has had little impact on burning mouth
symptoms. Recent studies have pointed to dysfunction of several cranial nerves
associated with taste sensation as a possible cause of burning mouth syndrome.
Given in low dosages, benzodiazepines, tricyclic antidepressants or
anticonvulsants may be effective in patients with burning mouth syndrome.
Topical capsaicin has been used in some patients. Burning sensation of the tongue is a common complaint. In some patients this is
diagnosed as Burning Mouth Syndrome (BMS). The prevalence of BMS is 0.8-19% of
the general population. The typical complaint is localized to the anterior part
of the tongue and may be accompanied by dry mouth sensation or taste disorder.
The differential diagnosis of BMS is based on the specific details of the
complaint, the clinical findings and laboratory results. The patients population
consists of mainly post-menopausal women, even though it can appear in younger
patients of both genders. The pathogenesis is only partially identified. There
are different treatment approaches. OBJECTIVES: To know the most important clinical features of Burning Mouth
Syndrome (BMS) in our environment.
MATERIAL AND METHODS: A prospective study of 30 BMS patients, 29 female and 1
male, with a mean age of 60.2 years (range 37-89), was made. A previously
designed clinical protocol, including blood counts, levadure culture, oral pH
measurement and non-stimulated salivary flow rate, was completed by all
patients. Comparative and descriptive statistical analysis was performed. The
Chi-square test was applied (p< 0.05).
RESULTS: Moreover of a burning sensation, 60 % of patients presented oral
dryness and 60 % dysgeusia. The tongue was the most frequent site affected of
burning sensation (66.7 %). Type II of BMS was the most common (53.3%). In
women, 82.9 % were postmenopausal. A 13.3 % of patients suffered type II
Diabetes, 6.7 % vitamin deficiency and 56.6 % used xerostomy-inducer medication.
The 56.6 % of patients showed chronic anxiety and/or depression. The 46.7 % had
a deficient oral hygiene level and 44.4 % wore inadequate dentures. Salivary
flow rate was decreased in 50 % of patients. Significant levadure growth was not
detected in any case.
CONCLUSIONS: BMS patients in our environment are principally postmenopausal
women, with tongue burning, xerostomy, dysgeusia and chronic anxiety and/or
depression. Burning mouth syndrome is a condition characterized by burning sensations of the
oral cavity in the absence of physical abnormalities of the mucosa or a
detectable underlying medical disorder. It is a multifactorial disorder with
unclear etiology, affecting predominatly middle-aged women. Multiple approaches
to treatment have been described in the literature, with few controlled clinical
trials regarding their efficacy. The objectives of this retrospective study were
to: 1. determine the epidemiologic characteristics of BMS patients referred to
an oral medicine practice; 2. determine if BMS classification correlates with
response to treatment; 3. determine the efficacy of a variety of known therapies
for BMS. A database was constructed from the charts of 150 consecutive patients
diagnosed with BMS; and these charts were reviewed. Patients were classified
according to previously published criteria for BMS. Presumed etiologies were
grouped into depression/anxiety-associated; hematinic deficiencies, including
iron, folate and vitamin B complex; oral habits: and idiopathic BMS. Treatment
approaches were divided into seven categories: soft desensitizing appliance;
tricyclic antidepressants (TCA); benzodiazepines (BZD); topical analgesics;
hematinic supplements; habit awareness counseling; and multi-modal therapy
(combining two or more of the above). Improvement was recorded using a zero to
100% VAS scale and classified as no relief (0%); mild (0-40%);
meaningful/moderate (41-80%); and profound relief (81-100%). Burning mouth
syndrome without any identifiable cause (idiopathic) was diagnosed in 33
patients (46.6%). Patients were followed up at one month (4 weeks) after the
initial visit. Nine patients (12.7%) reported profound relief; 17 patients
(23.9%) reported meaningful relief; 39 patients (54.9%) reported mild relief.
This retrospective review showed no significant correlation between
classification of BMS and response to therapy. The most effective treatment
modalities were habit awareness, followed by TCAs. Burning Mouth Syndrome (BMS) is a chronic pain syndrome that mainly affects
middle-aged/old women with hormonal changes or psychological disorders. This
condition is probably of multifactorial origin, often idiopathic, and its
etiopathogenesis remains largely enigmatic. The present paper discusses several
aspects of BMS, updates current knowledge, and provides guidelines for patient
management. There is no consensus on the diagnosis and classification of BMS.
The etiopathogenesis seems to be complex and in a large number of patients
probably involves interactions among local, systemic, and/or psychogenic
factors. In the remaining cases, new interesting associations have recently
emerged between BMS and either peripheral nerve damage or dopaminergic system
disorders, emphasizing the neuropathic background in BMS. Based on these recent
data, we have introduced the concepts of "primary" (idiopathic) and "secondary"
(resulting from identified precipitating factors) BMS, since this allows for a
more systematic approach to patient management. The latter starts with a
differential diagnosis based on the exclusion of both other orofacial chronic
pain conditions and painful oral diseases exhibiting muco-sal lesions. However,
the occurrence of overlapping/overwhelming oral mucosal pathologies, such as
infections, may cause difficulties in the diagnosis ("complicated BMS"). BMS
treatment is still unsatisfactory, and there is no definitive cure. As a result,
a multidisciplinary approach is required to bring the condition under better
control. Importantly, BMS patients should be offered regular follow-up during
the symptomatic periods and psychological support for alleviating the
psychogenic component of the pain. More research is necessary to confirm the
association between BMS and systemic disorders, as well as to investigate
possible pathogenic mechanisms involving potential nerve damage. If this goal is
to be achieved, a uniform definition of BMS and strict criteria for its
classification are mandatory. Thirty-two patients with burning mouth syndrome and 32 matched control subjects
were evaluated for their personality profile using a comprehensive, reliable,
and validated inventory. All subjects were requested to complete the Neo PI-R
questionnaire that measures the 5 dimensions of personality and their facets. A
t-test and univariate correlations (Pearson's correlation coefficient) were used
to compare the 2 groups. Results show high significant differences in some
personality factors. Neuroticism and all its facets, which include anxiety,
angry hostility, depression, self-consciousness, impulsiveness and
vulnerability, were significant at P<.001. Other domains like extraversion,
openness, and conscientiousness showed significant differences also (P<.05).
Many personality characteristics differentiate burning mouth syndrome patients
from controllers according to the Neo PI-R and this should affect the treatment
plan according to the identified characteristics. Burning mouth syndrome is a common disorder that frequently affects women in the
5th-7th decade. It is characterized by persisting painful symptoms mainly
involving the anterior two-thirds of the tongue. For several years it has been
attributed to psychological causes. We investigated the innervation of the
epithelium of the tongue to assess whether damage of peripheral nerve fibers
underlies the pathogenesis of the disease. We examined 12 patients with
clinically definite burning mouth syndrome for at least 6 months. We obtained
superficial biopsies of the lateral aspect of the anterior two-thirds of the
tongue from all patients and nine healthy controls. Immunohistochemical and
confocal microscope co-localization studies were performed with cytoplasmatic,
cytoskeletric, Schwann cell, and myelin markers for pathological changes. The
density of epithelial nerve fibers was quantified. Patients showed a
significantly lower density of epithelial nerve fibers than controls, with a
trend toward correlation with the duration of symptoms. Epithelial and
sub-papillary nerve fibers showed diffuse morphological changes reflecting
axonal degeneration. Our study demonstrates that burning mouth syndrome is
caused by a trigeminal small-fiber sensory neuropathy and that superficial
biopsy of the tongue can be helpful in assessing the diagnosis. These findings
shed light into the pathogenesis of this common disorder and could contribute to
evaluate targeted therapies in patients. OBJECTIVE: The aim of this study is to present a new approach of burning mouth
syndrome treatment by cognitive and behavioral therapy.
METHODS: Cognitive and behavioral therapy in a patient with severe and resistant
burning mouth syndrome.
RESULTS: Disappearing of the oral pain of the burning mouth syndrome.
CONCLUSION: After a review of the literature, we propose the treatment of
burning mouth syndrome by cognitive and behavioral therapy. Burning mouth syndrome (BMS) is characterized by burning sensations of the oral
cavity in the absence of abnormalities of the oral mucosa. BMS predomitly
affects middle-aged women. This condition has a multifactorial etiology.
Multiple approaches to treatment have been described. This article examines BMS,
its related factors, and treatment options. AIM: The burning mouth syndrome (BMS) is an oral disorder that consists of a
burning pain in the mouth without any visible clinical manifestations: its
etiology is still unclear and the etiological factors have been classified as
local, systemic and psychogenic. In this study, we reported the evaluation of
the psychological profile of BMS and non-BMS subjects in order to identify any
psychological disease affecting these patients and to evaluate a possible
psychological factor in the ethiopathogenesis of BMS.
METHODS: Twenty-eight patients affected by BMS, evaluated at the Section of
Dentistry of the University of Parma, and 24 matched control subjects were
evaluated for their personality profile using the Minnesota Multiphasic
Personality Inventory-2 (MMPI-2), a questionnaire which analyses various aspects
of personality through 10 scales: hypochondriasis, depression, hysteria,
psychopathic deviation, masculinity-femininity, paranoia, psychasthenia,
schizophrenia, hypomania, social introversion. From this study, 7 BMS patients
and 12 control subjects were excluded due to high scores reported in one or more
of the 3 control scales. The t-test and the Mann-Whitney test were used to
compare the 2 groups and the results were considered statistically significant
with P<0.01.
RESULTS: The results show no significant differences in personality profiles
between the BMS and the control subjects suggesting an etiology for BMS
different from the psychogenic hypothesis.
CONCLUSIONS: Further researches and the evaluation of larger BMS subjects groups
are necessary in order to validate the hypothesis of the neurological etiology
of BMS. Burning in the mouth in and of itself is not all that uncommon. It may result
from a variety of local or generalized oral mucosal disorders, or may be
secondary to referred phenomena from other locations. Primary burning mouth
syndrome, on the other hand, is relatively uncommon. Burning mouth syndrome is
an idiopathic pain disorder, which appears to be neuropathic in origin. Thoughts
on management of secondary and particularly primary burning mouth syndrome are
discussed. OBJECTIVE: Burning mouth syndrome (BMS) has been attributed secondarily to
diabetes, poor glycemic control, and diabetic neuropathy. The prevalence and
predictor factors of BMS were compared in type 1 diabetes mellitus (T1DM) and
nondiabetic subjects.
STUDY DESIGN: An assessment of 371 adult T1DM subjects and 261 control subjects
participating in a cross-sectional epidemiological study of oral health
complications of diabetes was performed. Subjects were participants of the
Pittsburgh Epidemiology of Diabetes Complications study. Prevalence of BMS was
determined by response to the following questions: "Do you now or in the last
month had any persistent uncomfortable sensations in your mouth or tongue? If
yes, would you describe the feeling as tingling, burning, sore, numb, or other?"
RESULTS: Burning mouth syndrome symptoms were reported by 28 T1DM and control
subjects (4.6%). Eleven had oral pathologies that might explain the BMS,
including atrophy of the tongue papillae, fissured tongue, denture stomatitis,
and candidiasis. The prevalence of BMS within the two groups with no pathologies
was similar; 12/371 (3.2%) vs. 5/233 (2.1%). Multivariate analyses of the 12
T1DM subjects with BMS found significant associations for female gender (P=.042)
and a diagnosis of diabetic peripheral neuropathy (P=.024).
CONCLUSIONS: In this T1DM population, BMS or related discomforts occurred
slightly more frequently than in the control group. Symptomatic T1DM subjects
were more likely to be female who had also developed peripheral neuropathy.
These findings and other similarities between BMS and diabetic peripheral
neuropathy suggest that a neuropathic process may be an underlying source of BMS
in some patients who have no apparent oral abnormality. Burning mouth syndrome (BMS) is a complex disease of unknown cause. It is
characterized by a burning sensation in the oral mucosa, notwithstanding its
clinical normal aspect. BMS is particularly seen in postmenopausal women. The
purpose of this study was to investigate this syndrome on a clinical basis and,
in addition, to analyze its possible relation to the frequency of Candida
species. Thirty-one patients (28 women and 3 men; 13 Caucasians and 18
non-Caucasians; mean age = 61.3, range 30-85 years) were evaluated. Most
patients (80.6%) were under long-term medication, antihypertensive, ansiolitic
and antidepressant drugs being the most used. Burning mouth complaint was
associated with other secondary oral complaints in 83.8% of the cases. Tongue
was the most commonly affected site (70.9%), followed by the vermillion border
of the lower lip (38.7%) and hard palate (32.2%). The association of the burning
sensation with oral cancer (cancer phobia) was reported by 67.7% of the
patients. Haematologic examination (hematocrit, haemoglobin and fasting blood
glucose level) revealed 2 cases each of anemia and type 2 diabetes. Local
factors, tooth extractions and dentures wearing, were associated with the onset
of symptoms in 35.5% of the cases. Daily activities were changed as a
consequence of BMS in 29% of the patients. Among the species of the genus
Candida, C. albicans was the most frequent in BMS patients (9 - 29.03%) and
controls (12 - 38.70%), followed respectively by C. parapsilosis (2 - 6.45% and
0 - 0%); C. tropicalis (1 - 3.22% and 2 - 6.45%); C. krusei and C. kefyr (1 -
3.22% and 0 - 0%). Therefore, such difference did not reach valuable results. In
conclusion, these data were similar to those reported in other studies. The
highlights of the present findings were the possible relation of BMS with
chronic drug use, depression, menopause and cancer phobia. No association was
found between BMS and the prevalence of Candida species. Burning mouth syndrome (BMS) is defined as a burning sensation of the oral
mucosa, in the absence of specific oral lesions. The underlying etiology remains
unclear. Peripheral alterations may be related to the density or reactive
capacity of the oral mucosal membrane receptors - these being largely influenced
by BMS-related risk factors such as stress, anxiety, the female gender,
climacterium and advanced age. The present study compiles the cases of BMS
induced by drugs reported in the literature, and attempts to draw a series of
conclusions. A search was conducted in the PubMed database using the following
key words: burning mouth syndrome, drug-induced, antihypertensive and
chemically-induced. The search was carried out in April 2007. The literature
yielded clinical cases in which oral burning sensation is described after the
administration of drugs belonging to different therapeutic groups:
antiretrovirals, antiseizure drugs, hormones and particularly antihypertensive
medication. Curiously, among the different types of antihypertensive drugs, BMS
was only associated with those compounds that act upon the angiotensin-renin
system. Burning mouth syndrome is characterized by a painful burning or stinging
sensation affecting the tongue or other areas of the mouth without obvious signs
of an organic cause on physical examination. A burning mouth sensation can occur
in several cutaneous or systemic diseases that must be ruled out prior to making
a diagnosis of burning mouth syndrome, since this term is used exclusively to
refer to idiopathic forms and is included within the cutaneous sensory
disorders. In most cases, patients with burning mouth syndrome have accompanying
psychologic or psychiatric conditions. Consequently, the syndrome has
traditionally been included among the psychogenic dermatoses. However, it is
currently unclear whether psychologic factors are a cause or a consequence of
the syndrome, or whether each exacerbates the other. Recent studies propose the
etiology to be neurologic, either neuropathic or related to taste. Burning mouth syndrome (BMS) is a chronic disease characterized by burning of
the oral mucosa associated with a sensation of dry mouth and/or taste
alterations. BMS occurs more frequently among postmenopausal women. The
pathophysiology of the disease is still unknown, and evidence is conflicting;
although some studies suggest a central origin, others point to a peripheral
neuropathic origin. The efficacy of some medications in the treatment of BMS
suggests that the dopaminergic system may be involved. INTRODUCTION: Burning mouth syndrome mainly affects women, particularly after
the menopause, when its prevalence may be 18-33%.
METHODS AND OUTCOMES: We conducted a systematic review and aimed to answer the
following clinical question: What are the effects of treatments for burning
mouth syndrome? We searched: Medline, Embase, The Cochrane Library, and other
important databases up to February 2007 (Clinical Evidence reviews are updated
periodically, please check our website for the most up-to-date version of this
review). We included harms alerts from relevant organisations such as the US
Food and Drug Administration (FDA) and the UK Medicines and Healthcare products
Regulatory Agency (MHRA).
RESULTS: We found 12 systematic reviews, RCTs, or observational studies that met
our inclusion criteria. We performed a GRADE evaluation of the quality of
evidence for interventions.
CONCLUSIONS: In this systematic review we present information relating to the
effectiveness and safety of the following interventions: anaesthetics (local),
antidepressants, benzodiazepines (topical clonazepam), benzydamine
hydrochloride, cognitive behavioural therapy (CBT), dietary supplements, and
hormone replacement therapy (HRT) in postmenopausal women. PURPOSE: To provide an overview of burning mouth syndrome (BMS), describe the
role of the clinician when a patient presents with the burning mouth complaint,
offer guidance in differentiating the cause of the complaint, and identify
potential treatment options for the patient suffering from BMS.
DATA SOURCES: A search of MD Consult, Medline, and EBSCO Host Research Databases
with the terms "burning mouth" and "BMS."
CONCLUSIONS: BMS is a common, chronic disorder of unknown etiology with no
underlying or systemic causes or oral signs identified. It affects more than 1
million people in the United States, predomitly postmenopausal women. Despite
the common nature of the disorder, it is often misunderstood. Palliative
treatment, education, and support should be offered to the patient with
idiopathic BMS. A variety of treatment options exist, including benzodiazepines,
tricyclic antidepressants, anticonvulsants, alpha-lipoic acid, topical
capsaicin, and cognitive therapy can be added to the medication regimen for
greater benefit.
IMPLICATIONS FOR PRACTICE: The role of the clinician is to obtain a meticulous
history and physical examination of the patient, order relevant diagnostic
tests, and rule out treatable conditions that may be causing the burning mouth
symptom. If secondary causes of BMS are ruled out, the clinician should present
treatment options to the patient and consider referral to specialists as
necessary. A combination of medications may be more effective than a single
medication. BACKGROUND: Burning mouth syndrome (BMS) is characterized by an oral burning
sensation (OBS) in the tongue or other oral mucous membrane in the absence of
any clinical abnormal findings. It frequently affects middle-aged and aged
women. Although there are many oral disorders with OBS besides BMS, the
prevalence of OBS is unclear.
AIM: To investigate the prevalence of OBS and analyze the gender differences in
a Japanese population.
METHODS: The study subjects were 2599 dental patients in two dental offices in
Tokyo, Japan. The prevalence of OBS was investigated using a questionnaire.
RESULTS: The mean ages of the subjects were 42.7 +/- 13.8 (mean +/- SD) years of
age in male and 40.1 +/- 15.4 (mean +/- SD) years of age in female. The
prevalence of OBS "at present" was 2.8% of 1310 male subjects and 3.2% of 1289
female subjects. There was no statistically significant difference between them
for each decade. The prevalence including "at present" and "in the past" were
9.3% in male subjects and 10.8% in female subjects; this difference was not
statistically significant.
CONCLUSION: These findings fail to demonstrate a female predilection for OBS. Burning mouth syndrome (BMS) is a chronic condition characterized by burning of
the oral mucosa, with or without dysgeusia and xerostomia, in the setting of no
underlying systemic disease or identifiable abnormalities on physical
examination or laboratory testing. BMS disproportionately affects postmenopausal
women. The pathophysiology of the disease is unknown; no single treatment has
proven universally successful. In light of these shortcomings, having a
practical approach to the evaluation and management of patients with BMS can
improve both patient quality of life and physician satisfaction. INTRODUCTION: Burning mouth syndrome mainly affects women, particularly after
the menopause, when its prevalence may be 18% to 33%.
METHODS AND OUTCOMES: We conducted a systematic review and aimed to answer the
following clinical question: What are the effects of treatments for burning
mouth syndrome? We searched: Medline, Embase, The Cochrane Library, and other
important databases up to November 2009 (Clinical Evidence reviews are updated
periodically, please check our website for the most up-to-date version of this
review). We included harms alerts from relevant organisations such as the US
Food and Drug Administration (FDA) and the UK Medicines and Healthcare products
Regulatory Agency (MHRA).
RESULTS: We found 15 systematic reviews, RCTs, or observational studies that met
our inclusion criteria. We performed a GRADE evaluation of the quality of
evidence for interventions.
CONCLUSIONS: In this systematic review we present information relating to the
effectiveness and safety of the following interventions: anaesthetics (local),
antidepressants, benzodiazepines (topical clonazepam), benzydamine
hydrochloride, cognitive behavioural therapy (CBT), dietary supplements, and
hormone replacement therapy (HRT) in postmenopausal women. AIMS: To evaluate the prevalence of unexplained extraoral symptoms in a group of
patients with burning mouth syndrome (BMS) and compare the prevalence with that
in patients with oral lichen planus (OLP) and age- and gender-matched controls.
METHODS: The occurrence of extraoral symptoms was analyzed in a group of 124 BMS
patients, a group of 112 oral lichen planus (OLP) patients, and a group of 102
healthy patients. Oral symptoms were collected by a specialist in oral medicine
and a general dentist, while data concerning unexplained extraoral symptoms were
gathered by each specialist ward, ie, ophthalmology, gynecology, otolaryngology,
gastroenterology, neurology, cardiology, internal medicine, and dermatology. A
Fisher exact test (α = .05) and Kruskal-Wallis test (α = .05) were performed for
statistical analysis.
RESULTS: In the BMS group, 98 (96.1%) patients reported unexplained extraoral
symptoms, while 4 (3.9%) patients reported only oral symptoms. A painful
symptomatology in different bodily regions was reported more frequently by BMS
patients (83.3%) than by OLP patients (1.8%) and healthy patients (11.7%) (P <
.0001). The differences in the overall unexplained extraoral symptoms between
BMS (96.1%) and OLP patients (9.3%) (P < .0001) and between BMS (96.1%) and
healthy patients (15.7%) (P < .0001) were statistically significant. The
unexplained extraoral symptoms in BMS patients consisted of pain perceived in
different bodily areas (odds ratio [OR]: 255; 95% confidence interval [CI]:
58.4-1112), ear-nose-throat symptoms (OR: 399.7; 95%CI: 89.2-1790), neurological
symptoms (OR: 393; 95% CI: 23.8-6481), ophthalmological symptoms (OR: 232.3; 95%
CI: 14.1-3823), gastrointestinal complaints (OR: 111.2; 95% CI: 42.2-293),
skin/gland complaints (OR: 63.5; 95% CI: 3.8-1055), urogenital complaints (OR:
35; 95% CI: 12-101), and cardiopulmonary symptoms (OR: 19; 95% CI: 4.5-82).
CONCLUSION: The great majority of BMS patients presented with several additional
unexplained extraoral comorbidities, indicating that various medical disciplines
should be involved in the BMS diagnostic process. Furthermore, the results
suggest that BMS may be classified as a complex somatoform disorder rather than
a neuropathic pain entity. It should be emphasized that at the present stage there is no consensus achieved
regarding the etiopathogenesis of BMS. Almost all researchers point to lots of
factors, simultaneously participating in genesis and development of BMS and at
the same time most of them agreed on one - psychological factors play a crucial
role in formation and maintece of painful sensations. The aim of the study
was the identification of psychological or psychiatric deviations (changes)
among the patients with BMS to perform an adequate differentiated therapy.
Clinico-psychological examination (dentist, neurologist, psychiatrist) was
carried out in 39 patients from 46 to 70 years of age. Among them women - 36 and
men - 3. To identify clinical types of BMS a classification of P.J. Lamey (1996)
was used and as a result, depression, insomnia, cancerophobia, severe neurologic
disorders, phobic syndrome were revealed. Three main categories - a chronic
somatoform dysfunction (23 cases), chronic vegetative disorders (8), and chronic
pain phenomenon (12) were identified. Only in one case was revealed a paranoid
syndrome. Alongside with the well-known scheme of treatment (antidepressants,
anticonvulsants, or neuroleptics) Psychotherapy was conducted, while EEG-feed
back (Biofeed back, Neurofeed back) method was used for the first time. A number
of important decisions were made the most important of which are the following:
BMS - must be regarded as a psychosomatic problem rather than a psychiatric
disorder. In addition to psychotherapy, using of EEG - feedback method greatly
improved patients' condition and in 4 cases BMS clinical manifestations were
evened-out completely. A retrospective study was conducted on patients with burning mouth syndrome
(BMS) to assess demographics, onset characteristics, temporal behavior
(frequency), duration, and progression of oral burning symptoms. Additionally,
treatments provided by health practitioners prior to a definitive diagnosis of
BMS were analyzed with an overview of current management strategies. The records
of 49 adult patients diagnosed with BMS were reviewed. Descriptive statistics
and a Pearson correlation with a statistical significance at p < 0.05 were
utilized to analyze the data. The majority of patients were mid-life white women
who reported a sudden onset of constant oral burning symptoms that increased in
intensity. On average, patients reported oral burning symptoms for 41 months
(standard deviation = 73.5, range = 2-360 months, median = 20 months), and 38 of
the patients received/trialed 71 various interventions (mean = 1.9) prior to
receiving a definitive diagnosis for their oral burning symptoms. This study
sample shared many characteristics with those reported previously in the
literature. The authors found that patients frequently reported delays in
receiving a definitive diagnosis with an array of various trialed interventions.
For this reason, the authors provide this overview of current management
strategies in order to assist dental practitioners in providing appropriate
interventions for patients with BMS. Primary burning mouth syndrome (BMS) is severe, disabling and chronic intraoral
pain condition for which no local or systemic cause can be found and clinical
examination is normal. It mostly affects elderly citizens, especially
postmenopausal women with prevalence up to 12-18%. In addition to spontaneous
burning pain, patients may complain of taste alterations. Recent
neurophysiologic, psychophysical, neuropathological, and functional imaging
studies have elucidated that several neuropathic mechanisms, mostly subclinical,
act at different levels of the neuraxis and contribute to the pathophysiology of
primary BMS. Demonstration of loss of small diameter nerve fibres in the tongue
epithelium explains thermal hypoesthesia and increase in taste detection
thresholds found in quantitative sensory testing. As in neuropathic pain,
decreased brain activation to heat stimuli has been demonstrated with fMRI in
BMS patients. However, it seems that the clinical diagnosis of primary BMS
encompasses at least three distinct, subclinical neuropathic pain states that
may overlap in individual patients. The first subgroup (50-65%) is characterized
by peripheral small diameter fibre neuropathy of intraoral mucosa. The second
subgroup (20-25%) consists of patients with subclinical lingual, mandibular, or
trigeminal system pathology that can be dissected with careful neurophysiologic
examination but is clinically indistinguishable from the other two subgroups.
The third subgroup (20-40%) fits the concept of central pain that may be related
to hypofunction of dopaminergic neurons in the basal ganglia. The neurogenic
factors acting in these subgroups differ, and will require different treatment
strategies. In the future, with proper use of diagnostic tests, BMS patients may
benefit from interventions specifically targeted at the underlying
pathophysiological mechanisms. OBJECTIVE: To provide a review on the aetiology and therapeutic options for the
management of patients with burning mouth syndrome (BMS).
BACKGROUND: BMS is a chronic disorder that frequently affects women and is
characterised by burning symptoms of the oral mucosa without clinical signs.
This syndrome has a complex and multifactorial characteristics, but its
aetiology remains unknown and this makes it difficult with regard to the
treatment and management of such patients. Despite not being accompanied by
evident organic changes and not presenting risks to health, BMS can
significantly reduce the quality of life for patients.
METHODS AND MATERIALS: The article reviews the literature regarding aetiologic
factors, clinical implications and treatment of BMS.
CONCLUSION: involvement of neurological, emotional and hormonal alterations is
proposed in BMS aetiology. However the mechanisms of its development are complex
and not completely understood. Tricyclic antidepressants, benzodiazepines and
antipsychotic drugs are the most accepted options in treatment and show variable
results. The correct diagnosis of BMS and the exclusion of possible local or
systemic factors that can be associated with the symptoms are fundamental. It is
also important to evaluate the quality of life for these patients to recognise
the potential impact of this condition on their lives. Pain in the tongue or oral tissues described as "burning" has been referred to
by many terms including burning mouth syndrome. When a burning sensation in the
mouth is caused by local or systemic factors, it is called secondary burning
mouth syndrome and when these factors are treated the pain will resolve. When
burning mouth syndrome occurs in the absence of identified risk indicators, the
term primary burning mouth syndrome is utilized. This article focuses on
descriptions, etiologic theories, and management of primary burning mouth
syndrome, a condition for which underlying causative agents have been ruled out. Burning mouth syndrome (BMS) is characterized by the presence of burning
sensation of the oral mucosa in the absence of clinically apparent mucosal
alterations. It occurs more commonly in middle-aged and elderly women and often
affects the tongue tip and lateral borders, lips, and hard and soft palate. In
addition to a burning sensation, the patients with BMS may also complain
unremitting oral mucosal pain, dysgeusia, and xerostomia. BMS can be classified
into two clinical forms: primary and secondary BMS. The primary BMS is essential
or idiopathic, in which the organic local/systemic causes cannot be identified
and a neuropathological cause is likely. The diagnosis of primary BMS depends
mainly on exclusion of etiological factors. The secondary BMS is caused by
local, systemic, and/or psychological factors; thus, its diagnosis depends on
identification of the exact causative factor. When local, systemic or
psychological factors are present, treatment or elimination of these factors
usually results in a significant clinical improvement of BMS symptoms. Vitamin,
zinc, or hormone replacement therapy has been found to be effective for reducing
the oral burning or pain symptom in some BMS patients with deficiency of the
corresponding factor. If patients still have the symptoms after the removal of
potential causes, drug therapy should be instituted. Previous randomized
controlled clinical trials found that drug therapy with capsaicin, alpha-lipoic
acid, clonazepam, and antidepressants may provide relief of oral burning or pain
symptom. In addition, psychotherapy and behavioral feedback may also help
eliminate the BMS symptoms. The aim of the research was to detect the stomatologic, endocrine and
psycho-neurologic status in patients with burning mouth syndrome, elaborate
different diagnostic criteria and effective therapy for the patients with
burning mouth syndrome. 92 patients with burning mouth syndrome were studied.
Patients ranged in age from 28 to 72 years. The conducted studies gave the
possibility to make conclusions, the most important of which are: burning mouth
syndrome (BMS) is not only stomatologic problem; this psychosomatic syndrome
belongs to gerontologic disease and tendency of its "rejuvenation" was revealed
as well (in the current study --2 women (28 and 32 year old, and 38 year old
man); degree of revelation of the symptoms of depression, anxiety, obsession and
somatization is closely related with duration of the diseases. These symptoms
are progressing together with aging and reach the peak at 60-70 years old.
Individual scheme of therapy was developed on the background of
clinico-paraclinical study. |
Which biomarker is widely used in the diagnosis of Ewing sarcoma? | CD99 is a hallmark marker for Ewing sarcoma and primitive neuroectodermal tumors. | Precursor B-cell lymphoblastic lymphomas (B-LBLs) are rare and most often
involve the skin in the head and neck region. Histologically, cutaneous B-LBLs
may be confused with other small round-cell neoplasms. Moreover, half of B-LBL
patients are negative for CD45 (leucocyte common antigen, LCA), a widely used
marker for the diagnosis of lymphoma, and a significant portion express CD99, a
marker for Ewing's sarcoma (ES) or primitive neuroectodermal tumor (PNET).
Therefore, an extranodal B-LBL may be misinterpreted as PNET or ES. Here, we
report on 2 boys, aged 10 and 5 years, with primary cutaneous B-LBL of the
scalp. PNET was initially misdiagnosed because the tumor cells were negative for
CD45 but strongly positive for CD99. Advanced stage of acute lymphoblastic
leukemia (ALL) developed later and both patients died during the course of
treatment for ALL. In retrospective analyses, tumor cells in the initial biopsy
specimens of both patients were found to be reactive to terminal
deoxynucleotidyl transferase (TdT), CD43 and CD10. Thus, the diagnosis of B-LBL
was confirmed. These cases illustrate the possibility that primary cutaneous
B-LBL may mimic ES or PNET immunophenotypically, and that correct diagnosis in
doubtful cases may be facilitated by analysis using a complete panel of
antibodies, particularly including TdT and CD43. |
Proteomic analyses have revealed proteins associated with the triple-negative breast cancers. List some proposed proteins. | Selected proteins of interest proposed from triple-negative cancer proteomic studies are CD44, PARP1, Mage-A4, LSR, RAB25, S100A14, MUC1, Hsp90, Actin, 14-3-3, vimentin, HSP70, CK18, moesin, IDH2, CRABP2, SEC14L2, beta-catenin, MUC18, Stat1 and CD74. | Triple-negative breast cancers (TNBCs) are defined by a lack of expression of
estrogen, progesterone, and HER2 receptors. Because of the absence of identified
targets and targeted therapies, and due to a heterogeneous molecular
presentation, treatment guidelines for patients with TNBC include only
conventional chemotherapy. Such treatment, while effective for some, leaves
others with high rates of early relapse and is not curative for any patient with
metastatic disease. Here, we demonstrate that these tumors are sensitive to the
heat shock protein 90 (Hsp90) inhibitor PU-H71. Potent and durable anti-tumor
effects in TNBC xenografts, including complete response and tumor regression,
without toxicity to the host are achieved with this agent. Notably, TNBC tumors
respond to retreatment with PU-H71 for several cycles extending for over 5
months without evidence of resistance or toxicity. Through a proteomics
approach, we show that multiple oncoproteins involved in tumor proliferation,
survival, and invasive potential are in complex with PU-H71-bound Hsp90 in TNBC.
PU-H71 induces efficient and sustained downregulation and inactivation, both in
vitro and in vivo, of these proteins. Among them, we identify downregulation of
components of the Ras/Raf/MAPK pathway and G(2)-M phase to contribute to its
anti-proliferative effect, degradation of activated Akt and Bcl-xL to induce
apoptosis, and inhibition of activated NF-kappaB, Akt, ERK2, Tyk2, and PKC to
reduce TNBC invasive potential. The results identify Hsp90 as a critical and
multimodal target in this most difficult to treat breast cancer subtype and
support the use of the Hsp90 inhibitor PU-H71 for clinical trials involving
patients with TNBC. We compared the protein expression pattern of triple-negative breast carcinomas
(HER2-, ER-, PR-) versus those being positive for HER2 and negative for the
hormone receptors (HER2+, ER-, PR-) by 2-D DIGE and mass spectrometry. We
obtained differential expression patterns for several glycolytic enzymes (as for
example MDH2, PGK1, TKT, Aldolase1), cytokeratins (CK7, 8, 9, 14, 17, 19),
further structure proteins (vimentin, fibronectin, L-plastin), for NME1-NME2,
lactoferrin, and members of the Annexin family. Western blot analysis and
immunohistochemistry were conducted to verify the results. The identified marker
proteins may advance a more detailed characterization of triple-negative breast
cancers and may contribute to the development of better treatment strategies. Breast cancer is by far the most common diagnosed form of cancer and the leading
cause of cancer death in women today. Clinically useful biomarkers for early
detection of breast cancer could lead to a significant reduction in mortality.
Here we describe a detailed analysis using gel-based proteomics in combination
with mass spectrometry and immunohistochemistry (IHC) of the tumour interstitial
fluids (TIF) and normal interstitial fluids (NIF) collected from 69 prospective
breast cancer patients. The goal of this study was to identify abundant cancer
up-regulated proteins that are externalised by cells in the tumour
microenvironment of most if not all these lesions. To this end, we applied a
phased biomarker discovery research strategy to the analysis of these samples
rather than comparing all samples among each other, with inherent inter and
intra-sample variability problems. To this end, we chose to use samples derived
from a single tumour/benign tissue pair (patient 46, triple negative tumour),
for which we had well-matched samples in terms of epithelial cell numbers, to
generate the initial dataset. In this first phase we found 110 proteins that
were up-regulated by a factor of 2 or more in the TIF, some of which were
confirmed by IHC. In the second phase, we carried out a systematic computer
assisted analysis of the 2D gels of the remaining 68 TIF samples in order to
identify TIF 46 up-regulated proteins that were deregulated in 90% or more of
all the available TIFs, thus representing common breast cancer markers. This
second phase singled out a set of 26 breast cancer markers, most of which were
also identified by a complementary analysis using LC-MS/MS. The expression of
calreticulin, cellular retinoic acid-binding protein II, chloride intracellular
channel protein 1, EF-1-beta, galectin 1, peroxiredoxin-2, platelet-derived
endothelial cell growth factor, protein disulfide isomerase and ubiquitin
carboxyl-terminal hydrolase 5 were further validated using a tissue microarray
containing 70 maligt breast carcinomas of various grades of atypia. A
significant number of these proteins have already been detected in the
blood/plasma/secretome by others. The next steps, which include biomarker
prioritization based on the hierarchal evaluation of these markers, antibody and
antigen development, assay development, analytical validation, and preliminary
testing in the blood of healthy and breast cancer patients, are discussed. PURPOSE: To identify molecular markers of pathologic response to neoadjuvant
paclitaxel/radiation treatment, protein and gene expression profiling were done
on pretreatment biopsies.
EXPERIMENTAL DESIGN: Patients with high-risk, operable breast cancer were
treated with three cycles of paclitaxel followed by concurrent
paclitaxel/radiation. Tumor tissue from pretreatment biopsies was obtained from
19 of the 38 patients enrolled in the study. Protein and gene expression
profiling were done on serial sections of the biopsies from patients that
achieved a pathologic complete response (pCR) and compared to those with
residual disease, non-pCR (NR).
RESULTS: Proteomic and validation immunohistochemical analyses revealed that
alpha-defensins (DEFA) were overexpressed in tumors from patients with a pCR.
Gene expression analysis revealed that MAP2, a microtubule-associated protein,
had significantly higher levels of expression in patients achieving a pCR.
Elevation of MAP2 in breast cancer cell lines led to increased paclitaxel
sensitivity. Furthermore, expression of genes that are associated with the
basal-like, triple-negative phenotype were enriched in tumors from patients with
a pCR. Analysis of a larger panel of tumors from patients receiving presurgical
taxane-based treatment showed that DEFA and MAP2 expression as well as
histologic features of inflammation were all statistically associated with
response to therapy at the time of surgery.
CONCLUSION: We show the utility of molecular profiling of pretreatment biopsies
to discover markers of response. Our results suggest the potential use of immune
signaling molecules such as DEFA as well as MAP2, a microtubule-associated
protein, as tumor markers that associate with response to neoadjuvant
taxane-based therapy. Basal-like breast cancers are commonly negative for expression of estrogen and
progesterone receptors and HER-2 (triple-negative breast cancer), which makes
this subtype of breast cancers more aggressive and less responsive to standard
treatment. We have applied a small-scale chemical proteomics method using
bisindolylmaleimide (Bis) class of protein kinase C inhibitors to study the
Bis-binding proteome in a cell culture model of basal breast carcinoma
(MDA-MB-231). Using MS, we identified 174 proteins captured by the Bis-probe in
phorbol ester (PMA) stimulated cells. Gene ontology analysis broadly categorised
these proteins as ATP binding (42%), GTP binding (6%) and having
nucleoside-triphosphatase activity (21%). Of the 64 enzymes captured by the
Bis-probe, the majority had either ATP and/or nucleotide binding functions. Two
previously unreported Bis binding protein kinases, serine/arginine-rich
protein-specific kinase 1 (SRPK1) and interferon-induced RNA-dependent protein
kinase (PKR) were observed. We then incorporated SILAC for quantitation to
examine the proteins that were differentially captured by the Bis-probe
following 30 and 60 min PMA stimulation. This provided novel evidence for PMA
regulation of the enzymes glyceraldehyde-3-phosphate dehydrogenase, nucleolar
RNA helicase 2 and Heterogeneous nuclear ribonucleoprotein M. Triple-negative breast cancer is difficult to treat because of the lack of
rationale-based therapies. There are no established markers and targets that can
be used for stratification of patients and targeted therapy. Here we report the
identification of novel molecular features, which appear to augment metastasis
of triple negative breast tumors. We found that triple-negative breast tumors
can be segregated into 2 phenotypes based on their genome-wide protein abundance
profiles. The first is characterized by high expression of Stat1, Mx1, and CD74.
Seven out of 9 tumors from this group had invaded at least 2 lymph nodes while
only 1 out of 10 tumors in group 2 was lymph node positive. In vitro experiments
showed that the interferon-induced increase in Stat1 abundance correlates with
increased migration and invasion in cultured cells. When CD74 was overexpressed,
it increased cell adhesion on matrigel. This effect was accompanied with a
marked increase in the membrane expression of beta-catenin, MUC18, plexins,
integrins, and other proteins involved in cell adhesion and cancer metastasis.
Taken together, our results show that Stat1/CD74 positive triple-negative tumors
are more aggressive and suggest an approach for development of better
diagnostics and more targeted therapies for triple negative breast cancer. This
article is part of a Special Issue entitled: Proteomics: The clinical link. Breast cancer is the second leading cause of cancer death for women in the
United States. Of the different subtypes, estrogen receptor-negative (ER(-))
tumors, which are ErbB2+ or triple-negative, carry a relatively poor prognosis.
In this study, we used system-wide analysis of breast cancer proteomes to
identify proteins that are associated with the progression of ER(-) tumors. Our
two-step approach included an initial deep analysis of cultured cells that were
obtained from tumors of defined breast cancer stages, followed by a validation
set using human breast tumors. Using high-resolution mass spectrometry and
quantification by Stable Isotope Labeling with Amino Acids in Cell Culture
(SILAC), we identified 8,750 proteins and quantified 7,800 of them. A
stage-specific signature was extracted and validated by mass spectrometry and
immunohistochemistry on tissue microarrays. Overall, the proteomics signature
reflected both a global loss of tissue architecture and a number of metabolic
changes in the transformed cells. Proteomic analysis also identified high levels
of IDH2 and CRABP2 and low levels of SEC14L2 to be prognostic markers for
overall breast cancer survival. Together, our findings suggest that global
proteomic analysis provides information about the protein changes specific to
ER(-) breast tumor progression as well as important prognostic information. The CD44(hi) compartment in human breast cancer is enriched in tumor-initiating
cells; however, the functional heterogeneity within this subpopulation remains
poorly defined. We used a triple-negative breast cancer cell line with a known
bilineage phenotype to isolate and clone CD44(hi) single cells that exhibited
mesenchymal/basal B and luminal/basal A features, respectively. Herein, we
demonstrate in this and other triple-negative breast cancer cell lines that,
rather than CD44(hi)/CD24(-) mesenchymal-like basal B cells, the
CD44(hi)/CD24(lo) epithelioid basal A cells retained classic cancer stem cell
features, such as tumor-initiating capacity in vivo, mammosphere formation and
resistance to standard chemotherapy. These results complement previous findings
using oncogene-transformed normal mammary cells showing that only cell clones
with a mesenchymal phenotype exhibit cancer stem cell features. Further, we
performed comparative quantitative proteomic and gene array analyses of these
cells and identified potential novel markers of breast cancer cells with
tumor-initiating features, such as lipolysis-stimulated lipoprotein receptor
(LSR), RAB25, S100A14 and mucin 1 (MUC1), as well as a novel 31-gene signature
capable of predicting distant metastasis in cohorts of estrogen
receptor-negative human breast cancers. These findings strongly favor functional
heterogeneity in the breast cancer cell compartment and hold promise for further
refinements of prognostic marker profiling. Our work confirms that, in addition
to cancer stem cells with mesenchymal-like morphology, those tumor-initiating
cells with epithelial-like morphology should also be the focus of drug
development. |
Which signalling pathway is involved in Tuberous Sclerosis? | Tuberous Sclerosis is a multisystem genetic disorder caused by mutation in TSC1 or TSC2 gene, that leads to hyperactivation of the mTOR signalling pathway, and subsequent dysregulation of cell growth control. | Understanding the mechanisms through which multicellular organisms regulate
cell, organ and body growth is of relevance to developmental biology and to
research on growth-related diseases such as cancer. Here we describe a new
effector in growth control, the small GTPase Rheb (Ras homologue enriched in
brain). Mutations in the Drosophila melanogaster Rheb gene were isolated as
growth-inhibitors, whereas overexpression of Rheb promoted cell growth. Our
genetic and biochemical analyses suggest that Rheb functions downstream of the
tumour suppressors Tsc1 (tuberous sclerosis 1)-Tsc2 in the TOR (target of
rapamycin) signalling pathway to control growth, and that a major effector of
Rheb function is ribosomal S6 kinase (S6K). Insulin signalling is a potent stimulator of cell growth and has been proposed
to function, at least in part, through the conserved protein kinase TOR (target
of rapamycin) [corrected]. Recent studies suggest that the tuberous sclerosis
complex Tsc1-Tsc2 may couple insulin signalling to Tor activity [corrected].
However, the regulatory mechanism involved remains unclear, and additional
components are most probably involved. In a screen for novel regulators of
growth, we identified Rheb (Ras homologue enriched in brain), a member of the
Ras superfamily of GTP-binding proteins. Increased levels of Rheb in Drosophila
melanogaster promote cell growth and alter cell cycle kinetics in multiple
tissues. In mitotic tissues, overexpression of Rheb accelerates passage through
G1-S phase without affecting rates of cell division, whereas in endoreplicating
tissues, Rheb increases DNA ploidy. Mutation of Rheb suspends larval growth and
prevents progression from first to second instar. Genetic and biochemical tests
indicate that Rheb functions in the insulin signalling pathway downstream of
Tsc1-Tsc2 and upstream of TOR. Levels of rheb mRNA are rapidly induced in
response to protein starvation, and overexpressed Rheb can drive cell growth in
starved animals, suggesting a role for Rheb in the nutritional control of cell
growth. Ras homologue enriched in brain (Rheb) represents a unique group of small
GTPases and shares moderate sequence identity with the Ras/Rap subfamily. It
acts downstream of nutrient signalling as the direct target of the tuberous
sclerosis complex (TSC) and upstream of mTOR/S6K1/4EBP in the insulin-signalling
pathway. The GTPase domain of human Rheb (hRheb) has been recombitly
expressed in Escherichia coli, purified and cocrystallized in complexes with
GDP, GTP and GppNHp using the hanging-drop vapour-diffusion method. Crystals of
the hRheb-GDP complex belong to space group P2(1)2(1)2(1), with unit-cell
parameters a = 44.5, b = 52.3, c = 70.6 A. The hRheb-GppNHp complex crystallized
in two crystal forms: one has the same space group and unit-cell parameters as
the hRheb-GDP complex and the other belongs to space group C222(1), with
unit-cell parameters a = 102.9, b = 99.2, c = 48.0 A. The hRheb-GTP complex also
crystallized in two crystal forms: one belongs to space group C222(1), with
unit-cell parameters a = 102.4, b = 98.3, c = 47.9 A, and the other belongs to
space group P2(1), with unit-cell parameters a = 77.3, b = 47.9, c = 71.9 A,
beta = 89.0 degrees. All these crystals diffract X-rays to better than 2.8 A
resolution and at least one diffraction data set has been collected for each
crystal form using an in-house R-AXIS IV++ diffractometer. Structural studies of
hRheb in complexes with various substrates may provide insights into the
recognition and specificity of substrate and the catalytic mechanism of
mammalian Rhebs and shed light on the biological functions of Rhebs in the mTOR
signalling pathway. Focal cortical dysplasia (FCD) type IIB is a malformation of cortical
development characterized by presence of balloon cells. These cells share
phenotypic features of giant cells found in tuberous sclerosis complex (TSC),
but the relationship between FCD type IIB and TSC is not well established. TSC
is an autosomal domit disorder caused by mutation in either of two genes:
TSC1, encoding hamartin, and TSC2, encoding tuberin. Both proteins form a
complex inhibiting mTOR signalling pathway and thus regulate cell size and
proliferation. In this study, tuberin and hamartin expression was evaluated
under a confocal microscope in six cases of Taylor's balloon cell type FCD.
Three patients met the clinical criteria for TSC. In three other patients, TSC
was excluded based on a panel of clinical and radiological examinations.
Additionally, two cases of FCD type I and 3 samples of normal brain tissue were
used as a reference group. We found loss of tuberin and hamartin expression in
FCD type IIB lesions from patients with TSC. In sporadic FCD type IIB cases,
only a few tuberin and hamartin positive cells were detected in the white-grey
matter junction and in deeper parts of the white matter. Cortical balloon cells
showed loss of both tuberin and hamartin. In contrast, the expression of tuberin
and hamartin in FCD type I samples was strong, similarly to normal brain tissue.
In conclusion, loss of TSC1 and TSC2 products expression in balloon cells of
both cortical dysplasia type IIB in TSC-related and sporadic patients suggests
that FCD type IIB may represent the focal form of TSC. Tuberous sclerosis, caused by germline mutations in the TSC1 or TSC2 genes, is
associated with aberrant upregulation of the mammalian target of rapamycin
(mTOR) signalling pathway, resulting in growth of tumours, including renal
angiomyolipomas (AMLs). AMLs may cause hypertension, renal failure and
spontaneous life-threatening haemorrhage. Previously, invasive interventions
were required to treat AMLs. More recently, mTOR inhibitors have been used as
molecularly targeted treatment to treat AMLs. We present here the case of a
paediatric patient with TSC in whom sirolimus has been used successfully to halt
growth of renal AMLs. Tuberous Sclerosis Complex (TSC) is a multisystem genetic disorder caused by
mutation in either Tsc1 or Tsc2 genes that leads to the hyper activation of the
mTOR pathway, a key signalling pathway for synaptic plasticity. TSC is
characterized by benign tumors arising in different organs and severe
neuropsychiatric symptoms, such as epilepsy, intellectual disability, autism,
anxiety and depressive behaviour. Rapamycin is a potent inhibitor of mTOR and
its efficacy in treating epilepsy and neurological symptoms remains elusive. In
a mouse model in which Tsc1 has been deleted in embryonic telencephalic neural
stem cells, we analyzed anxiety- and depression-like behaviour by elevated-plus
maze (EPM), open-field test (OFT), forced-swim test (FST) and tail-suspension
test (TST), after chronic administration of rapamycin. In addition, spectral
analysis of background EEG was performed. Rapamycin-treated mutant mice
displayed a reduction in anxiety- and depression-like phenotype, as shown by the
EPM/OFT and FST, respectively. These results were inline with EEG power spectra
outcomes. The same effects of rapamycin were observed in wild-type mice.
Notably, in heterozygous animals we did not observe any EEG and/or behavioural
variation after rapamycin treatment. Together these results suggest that both
TSC1 deletion and chronic rapamycin treatment might have a role in modulating
behaviour and brain activity, and point out to the potential usefulness of
background EEG analysis in tracking brain dysfunction in parallel with
behavioural testing. |
Can life style changes reduce oxidative stress | Our results suggested that life style changes which related to migration might reduce DNA damage in Hasake nationalities. | OBJECTIVE: To explore the relationship of migration and oxidative DNA damage by
comparative study of oxidative DNA damage effects on people with different years
of migration among Xinjiang Hasake ethnicity in Shenzhen.
METHODS: Sixty Hasake residents in Shenzhen were selected, and were divided into
three groups (n=20) according to the years of migration. Major changes of their
life style were investigated. 8-hydroxy-2'-deoxyguanosine (8-OH-dG) levels in
urine were analyzed, and comet assay of peripheral blood lymphocytes conducted.
RESULTS: When comparing with the group having a shorter than 1 year of stay,a
significant decrease of oliveira tail moment and tail/head length in comet assay
in the >3 years group (P < 0.05) was observed 8-OH-dG level decreased
significantly in 1-3 years group (P < 0.05) and >3 years group (P < 0.01).
CONCLUSION: Our results suggested that life style changes which related to
migration might reduce DNA damage in Hasake nationalities. The pericyte's role has been extensively studied in retinal tissues of diabetic
retinopathy; however, little is known regarding its role in such tissues as the
pancreas and skeletal muscle. This supportive microvascular mural cell, plays an
important and novel role in cellular and extracellular matrix remodeling in the
pancreas and skeletal muscle of young rodent models representing the metabolic
syndrome and type 2 diabetes mellitus (T2DM). Transmission electron microscopy
can be used to evaluate these tissues from young rodent models of insulin
resistance and T2DM, including the transgenic Ren2 rat, db/db obese insulin
resistant - T2DM mouse, and human islet amyloid polypeptide (HIP) rat model of
T2DM. With this method, the earliest pancreatic remodeling change was widening
of the islet exocrine interface and pericyte hypercellularity, followed by
pericyte differentiation into islet and pancreatic stellate cells with early
fibrosis involving the islet exocrine interface and interlobular interstitium.
In skeletal muscle there was a unique endothelial capillary connectivity via
elongated longitudinal pericyte processes in addition to pericyte to pericyte
and pericyte to myocyte cell-cell connections allowing for paracrine
communication. Initial pericyte activation due to moderate oxidative stress
signaling may be followed by hyperplasia, migration, and differentiation into
adult mesenchymal cells. Continued robust oxidative stress may induce pericyte
apoptosis and impaired cellular longevity. Circulating antipericyte
autoantibodies have recently been characterized, and may provide a screening
method to detect those patients who are developing pericyte loss and are at
greater risk for the development of complications of T2DM due to pericytopathy
and rarefaction. Once detected, these patients may be offered more aggressive
treatment strategies such as early pharmacotherapy in addition to life style
changes targeted to maintaining pericyte integrity. In conclusion, we have
provided a review of current knowledge regarding the pericyte and novel
ultrastructural findings regarding its role in metabolic syndrome and T2DM. As antioxidants play a protective role in the pathophysiology of diabetes and
cardiovascular diseases, understanding the physiological status of antioxidant
concentration among people at high risk for developing these conditions, such as
Metabolic Syndrome, is of interest. In present study out of 187 first degree
non-diabetic relatives and 192 non-diabetic spouses, 33.1% and 19.7% were found
to have metabolic syndrome respectively. Subjects with metabolic syndrome (≥3
risk factors) had poor antioxidants status as reflected by significantly low
levels of vitamin A, C & E and significantly increased (p<0.01) oxidative stress
as compared to those without metabolic syndrome. At the same time serum insulin
levels and insulin resistance were found to be significantly high (p<0.001) in
metabolic syndrome. A strong positive correlation (r=0.946; p<0.001) between
oxidative stress and insulin resistance was observed in metabolic syndrome. Low
levels of antioxidants and increased oxidative stress with insulin resistance in
metabolic syndrome suggests that besides therapeutic life style changes (TLC) as
suggested in ATP III guidelines inclusion of antioxidant vitamins, fruits and
vegetable could be beneficial to ward off the consequences of metabolic
syndrome. |
Which is the relation between sweating and anaerobic threshold? | There is no clear evidence of the relationship between sweating and anaerobic threshold | The influence of 10 min warming-up at 40% VO2 max on thermal, circulatory, and
metabolic responses to an incremental exercise to exhaustion as well as on the
anaerobic threshold at the blood lactate level of 4 mmol.l-1 (AT) and the
individual anaerobic threshold (IAT) was investigated in eight cross-country
skiers. During exercise preceded by warming-up, the mean skin temperature (T sk)
and external auditory canal temperature (Tac) did not change significantly in
contrast to exercise without warming-up, producing a rise in both T sk and Tac
(by approx. 1.2 degrees C and 1.1 degrees C, respectively). Warming-up did not
alter the course of the rectal temperature changes during exercise. With
warming-up skin humidity rose immediately after the beginning of exercise,
whereas the onset of sweating without warming-up appeared much later at higher
work intensities. Warming-up did not change the circulatory and ventilatory
responses to incremental exercise and the oxygen uptake (VO2) either at
submaximal or maximal work loads. With warming-up a significant increase was
found in the threshold work load both at the AT and the IAT. The data
demonstrated that warming-up has an advantageous effect on the efficiency of
thermoregulation in endurance-trained athletes producing an early sweating
response to the incremental exercise that results in attenuation of
hyperthermia. An increase in the anaerobic threshold during incremental exercise
preceded by warming-up may indicate an enhancement of the endurance capacity
subsequent to warming-up. |
Name monoclonal antibody against SLAMF7. | Elotuzumab is a humanized monoclonal antibody specific for signaling lymphocytic activation molecule-F7 (SLAMF7, also known as CS1, CD319, or CRACC) that enhances natural killer cell-mediated antibody-dependent cellular cytotoxicity of SLAMF7-expressing myeloma cells. | New agents are awaited for the treatment of multiple myeloma and research is
ongoing for the development of monoclonal antibodies (MoAbs) targeting the tumor
cells. One of the most promising MoAb is elotuzumab, the only humanized IgG1
MoAb specifically targeting CS1 (SLAMF7), a cell surface glycoprotein that is
highly expressed in plasma cells. Preclinical and clinical data on elotuzumab
will be presented in this article. Signaling lymphocytic activation molecule F7 (SLAMF7) is a receptor present on
immune cells, including natural killer (NK) cells. It is also expressed on
multiple myeloma (MM) cells. This led to development of an anti-SLAMF7 antibody,
elotuzumab, showing efficacy against MM. SLAMF7 mediates activating or
inhibitory effects in NK cells, depending on whether cells express or do not
express the adaptor EAT-2. Since MM cells lack EAT-2, we elucidated the
inhibitory effectors of SLAMF7 in EAT-2-negative NK cells and tested whether
these effectors were triggered in MM cells. SLAMF7-mediated inhibition in NK
cells lacking EAT-2 was mediated by SH2 domain-containing inositol phosphatase 1
(SHIP-1), which was recruited via tyrosine 261 of SLAMF7. Coupling of SLAMF7 to
SHIP-1 required Src kinases, which phosphorylated SLAMF7. Although MM cells lack
EAT-2, elotuzumab did not induce inhibitory signals in these cells. This was at
least partly due to a lack of CD45, a phosphatase required for Src kinase
activation. A defect in SLAMF7 function was also observed in CD45-deficient NK
cells. Hence, SLAMF7-triggered inhibition is mediated by a mechanism involving
Src kinases, CD45, and SHIP-1 that is defective in MM cells. This defect might
explain why elotuzumab eliminates MM cells by an indirect mechanism involving
the activation of NK cells. BACKGROUND: Elotuzumab, an immunostimulatory monoclonal antibody targeting
signaling lymphocytic activation molecule F7 (SLAMF7), showed activity in
combination with lenalidomide and dexamethasone in a phase 1b-2 study in
patients with relapsed or refractory multiple myeloma.
METHODS: In this phase 3 study, we randomly assigned patients to receive either
elotuzumab plus lenalidomide and dexamethasone (elotuzumab group) or
lenalidomide and dexamethasone alone (control group). Coprimary end points were
progression-free survival and the overall response rate. Final results for the
coprimary end points are reported on the basis of a planned interim analysis of
progression-free survival.
RESULTS: Overall, 321 patients were assigned to the elotuzumab group and 325 to
the control group. After a median follow-up of 24.5 months, the rate of
progression-free survival at 1 year in the elotuzumab group was 68%, as compared
with 57% in the control group; at 2 years, the rates were 41% and 27%,
respectively. Median progression-free survival in the elotuzumab group was 19.4
months, versus 14.9 months in the control group (hazard ratio for progression or
death in the elotuzumab group, 0.70; 95% confidence interval, 0.57 to 0.85;
P<0.001). The overall response rate in the elotuzumab group was 79%, versus 66%
in the control group (P<0.001). Common grade 3 or 4 adverse events in the two
groups were lymphocytopenia, neutropenia, fatigue, and pneumonia. Infusion
reactions occurred in 33 patients (10%) in the elotuzumab group and were grade 1
or 2 in 29 patients.
CONCLUSIONS: Patients with relapsed or refractory multiple myeloma who received
a combination of elotuzumab, lenalidomide, and dexamethasone had a significant
relative reduction of 30% in the risk of disease progression or death. (Funded
by Bristol-Myers Squibb and AbbVie Biotherapeutics; ELOQUENT-2
ClinicalTrials.gov number, NCT01239797.). |
What is the mode of action of bedaquiline? | Bedaquiline works by inhibiting bacterial adenosine triphosphate (ATP) synthase and represents the first novel class of antituberculosis agents that is used for treatment of multi drug resistant tuberculosis. | PURPOSE: The history and prevalence of tuberculosis and the role of bedaquiline
in multidrug-resistant (MDR) tuberculosis are reviewed.
SUMMARY: Tuberculosis continues to cause significant morbidity and mortality
worldwide. Increasing rates of drug-resistant tuberculosis are a significant
concern and pose serious implications for current and future treatment of the
disease. In December 2012, the Food and Drug Administration approved bedaquiline
as part of the treatment regimen for pulmonary MDR tuberculosis. Bedaquiline's
unique mechanism of action presents an alternative approach to current
antimycobacterial killing. By directly inhibiting adenosine triphosphate (ATP)
synthase, bedaquiline is effective against both replicating and dormant
mycobacteria. Pulmonary cavitary lesions can contain heterogeneous populations.
This potential mix of semireplicating and hypometabolic mycobacteria is more
difficult to eliminate with conventional antitubercular drugs, thus increasing
the risk of resistance. No in vitro cross-resistance between bedaquiline and
currently available antitubercular agents has been observed thus far. Because
bedaquiline targets a completely different enzyme, cross-resistance with other
conventional agents remains unlikely. Enhanced sterilizing capacity via
synergistic depletion of ATP further exhibits the promising potential of
bedaquiline with pyrazinamide. A course of bedaquiline requires 24 weeks of
therapy in combination with other antitubercular drugs.
CONCLUSION: The approval of bedaquiline represents a major milestone in MDR
tuberculosis therapy. Bedaquiline should be considered in patients who have not
responded to a regimen containing four second-line drugs and pyrazinamide and
patients with documented evidence of MDR tuberculosis resistant to
fluoroquinolones. The exact role of bedaquiline cannot be determined until
further efficacy and safety data are obtained through ongoing Phase III trials. OBJECTIVE: To review the chemistry, pharmacology, microbiology,
pharmacokinetics, pharmacodynamics, clinical efficacy, safety, dosage, and
administration of bedaquiline, a novel oral diarylquinoline antimycobacterial
agent approved by the Food and Drug Administration for the treatment of adults
with pulmonary multidrug-resistant tuberculosis (MDR-TB).
DATA SOURCES: A search of PubMed (January 2004-May 2013) and International
Pharmaceutical Abstracts (January 2004-May 2013) using the search terms
bedaquiline, diarylquinoline, R207910, and TMC207 was performed. Supplementary
sources included proceedings of the Union World Conference on Lung Health.
STUDY SELECTION AND DATA EXTRACTION: Preclinical data as well as Phase 1 and 2
studies published in English were evaluated.
DATA SYNTHESIS: Bedaquiline possesses a unique mechanism of action that disrupts
the activity of the mycobacterial adenosine triphosphate synthase. Clinical
trials have been conducted evaluating the use of bedaquiline in combination with
a background regimen for the treatment of adults with pulmonary MDR-TB.
Bedaquiline has an excellent in vitro activity against Mycobacterium
tuberculosis, including multidrug resistant M tuberculosis; however, its side
effect profile limits its use against MDR-TB when no other effective regimen can
be provided. Bedaquiline carries Black Box warnings for increased risk of
unexplained mortality and QT prolongation. Bedaquiline is metabolized via the
CYP3A4 isoenzyme and thus interacts with rifamycins and several antiretrovirals.
CONCLUSIONS: In an era of emerging resistance and given the suboptimal efficacy
and toxicity of currently available regimens for MDR-TB, bedaquiline represents
a great addition to the existing armamentarium of anti-TB agents particularly in
areas of the world where the disease is endemic. Increasing incidence of MDR-TB, long duration of treatment and co-infection with
HIV are the significant problems in achieving the eradication of tuberculosis.
Bedaquiline is an anti-tuberculosis drug with unique mechanism of action. It
selectively inhibits the mycobacterial energy metabolism i.e. ATP synthesis and
found to be effective against all states of Mycobacterium tuberculosis like
active, dormant, replicating, non-replicating, intracellular and extracellular.
Preclinical studies have shown the efficacy of bedaquiline in terms of reduction
in bacterial load and treatment duration. Phase II clinical studies have
established the safety, tolerability and earlier sputum conversion time in
patients with MDR-TB. In 2012 FDA approved bedaquiline for treatment of MDR-TB
and XDR-TB. Mycobacterium tuberculosis develops spontaneous resistance mutants to virtually
every drug in use. Courses of therapy select for these mutants and
drug-resistant organisms emerge. The development of drug-resistant organisms has
reached the point that drug resistance now threatens to undermine global success
against tuberculosis (TB). New drugs are needed. The last new class of drugs
specifically developed for treatment of TB was the rifamycins over 40 years ago.
New funding sources and the development of product development partnerships have
energized the TB drug development effort. There are now more TB drugs in
development than at any time in the past. The first of these drugs to be
developed and marketed was bedaquiline. Bedaquiline has an entirely novel
mechanism of action and so should be active against otherwise highly resistant
organisms. It acts on the transmembrane component of adenosine triphosphate
synthase and acts by preventing electron transport. This raises the exciting
possibility that bedaquiline may be active against less metabolically active
organisms. Drug-drug interactions between rifamycins and the cytochrome P450-3A
system will limit bedaquiline's utility and create complexity in treatment
regimens. In clinical trials, treatment with bedaquiline added to a background
multidrug-resistant TB regimen was associated with earlier culture conversion
and higher cure rates, but there were unexplained excess deaths in the
bedaquiline arms of these trials. Food and Drug Administration approved
bedaquiline for the treatment of multidrug-resistant TB when an effective
treatment regimen cannot otherwise be provided. They required a black box
warning about excess deaths and require that a phase III trial be completed. A
planned Phase III trial is being reorganized. While bedaquiline is an exciting
drug and marks a dramatic moment in the history of TB treatment, its ultimate
place in the anti-TB drug armamentarium is unclear pending the Phase III trial
and the development of other new drugs that are in the pipeline. Bedaquiline is a diarylquinoline antitubercular drug with a novel mechanism of
action against Mycobacterium tuberculosis. Bedaquiline works by inhibiting
bacterial adenosine triphosphate (ATP) synthase and represents the first novel
class of antituberculosis agents in more than 40 years. Bedaquiline is indicated
for the treatment of multidrug-resistant tuberculosis (MDR TB) in combination
with at least three other antitubercular drugs when no other effective regimen
is available. The recommended bedaquiline dosage is 400 mg orally once/day for 2
weeks followed by 200 mg orally 3 times/week for 22 weeks. Bedaquiline should be
administered with food, which increases the bioavailability 2-fold. Bedaquiline
is metabolized by cytochrome P450 isoenzyme 3A4 and is impacted by both inducers
and inhibitors of this isoenzyme. Concentration-dependent bactericidal activity
was observed in laboratory and murine studies. Accelerated approval was granted
in the United States and European Union based on the results of two phase IIb
clinical studies that used sputum culture clearance as a surrogate end point for
clinical efficacy. These studies showed greater sputum culture clearance up to
week 24 for the bedaquiline group compared with placebo. Common adverse events
in clinical trials included nausea, arthralgia, and headache. Serious adverse
events included elevated serum transaminase levels and rate-corrected
QT-interval prolongation. Unexplained higher mortality was seen in patients
receiving bedaquiline versus those receiving placebo. Bedaquiline is a novel
agent with a unique mechanism of action and has the potential to meet a great
need in patients with MDR TB who have no other treatment options. Due to safety
concerns and limited clinical information, phase III trials are needed to fully
determine its place in therapy. |
Does helicobacter pylori infection increase risk for ischemic stroke? | Findings regarding association between helicobacter pylori infection and ischemic stroke risk are conflicting. There is evidence to suggest that helicobacter pylori infection is associated with increased risk for ischemic stroke and should be considered stroke risk factors. However, some studies reported no association between helicobacter pylori infection and stroke. | Cardiac and cerebrovascular diseases are an important cause of mortality in
industrialized countries. "Classical" risk factors cannot fully explain
epidemiological variations of these diseases. From several years infections have
been linked to ischemic vascular events and recent publications pointed to the
role of Helicobacter pylori, a Gram negative bacterium, involved in the
pathogenesis of gastritis and peptic ulcer. Results on the association between
this bacterium and acute myocardial infarction or stroke are controversial, due
to the degree of studies heterogeneity. There is the need for extensive
prospectic studies to evaluate the incidence of these diseases in relation to
the presence of Helicobacter pylori infection. Interventional randomized studies
employing an antibiotic treatment for patients affected by ischemic vascular
diseases will rapidly answer the question of wheather Helicobacter pylori has a
causal role in the pathogenesis of acute myocardial infarction and ischemic
stroke. BACKGROUND AND PURPOSE: Several lines of evidence point toward a relationship
between infection and atherosclerotic vascular disease. Thus, infection and
inflammation often precede ischemic neurological events. Transient alterations
in coagulation and direct arterial invasion by certain microorganisms have been
reported. Helicobacter pylori infection is the major cause of peptic ulcer
disease and appears to be a risk factor for ischemic cerebrovascular disease.
However, in contrast to other chronic infectious agents, H pylori has not been
consistently isolated from atherosclerotic lesions.
METHODS: We investigated the presence of H pylori in 38 atherosclerotic plaques
obtained at carotid endarterectomy by using morphological and
immunohistochemical techniques and a highly sensitive polymerase chain reaction
method. We performed immunohistochemical detection of intercellular adhesion
molecule-1, a marker related to inflammatory cell response. We also examined 7
carotid arteries obtained at autopsy from subjects without carotid
atherosclerosis.
RESULTS: H pylori DNA was found in 20 of 38 atherosclerotic plaques. Ten of the
H pylori DNA-positive plaques also showed morphological and immunohistochemical
evidence of H pylori infection. None of 7 normal carotid arteries was positive
for H pylori. Intercellular adhesion molecule-1 was expressed in 75% of H
pylori-positive plaques and in 22% of H pylori-negative plaques. The presence of
the microorganism was associated with male sex but was independent of age,
vascular risk factor profile, and prior neurological symptoms.
CONCLUSIONS: H pylori is present in a substantial number of carotid
atherosclerotic lesions and is associated with features of inflammatory cell
response. This study provides additional evidence of the relationship between H
pylori infection and atherosclerotic disease. Chronic infection may increase the risk for ischemic stroke. Presently, it is
insufficiently established whether Helicobacter pylori infection represents a
risk factor for ischemic stroke. We analyzed IgG antibodies against H. pylori in
109 patients with acute cerebral ischemia and 82 age- and sex-matched control
patients with non-vascular and non-inflammatory neurological diseases. Antibody
titers were significantly higher in patients than in control subjects (p=0.007).
H. pylori seropositivity tended to be more common in patients (odds ratio (OR)
1.55, 95% confidence interval (ci) 0.87-2.76), but this trend was further
attenuated in multivariate analysis (OR 1.42; 95% 0.75-2.67) with hypertension,
diabetes mellitus, current or previous smoking, previous cerebral ischemia and
low socioeconomic status. H. pylori seropositivity increased the odds for
cerebral ischemia of atherothrombotic origin in univariate (OR 3.63; 95% ci
1.37-9.65) and multivariate analysis (OR 3.53; 95% ci 1.09-11.4). H. pylori
seropositivity may be an independent risk factor for stroke of atherothrombotic
origin. BACKGROUND AND PURPOSE: Helicobacter pylori and Chlamydia pneumoniae have been
associated epidemiologically and pathogenetically with coronary atherosclerosis.
However, population-based data on chronic infection and stroke are lacking.
Therefore, we investigated the association of both bacterial pathogens and
ischemic stroke subtypes in a population-based case-control study.
METHODS: Patients with first ischemic stroke in the population-based Erlangen
Stroke Project were collected as cases. Neighborhood controls were drawn from
the study population, matched for age, sex, and place of residence. IgG
antibodies to H pylori were measured by enzyme immunoassay, and IgG antibodies
to C pneumoniae were measured by microimmunofluorescence technique. Conditional
logistic regression was used. Analyses were stratified for etiologic stroke
subtypes according to Trial of Org 10172 in Acute Stroke Treatment (TOAST)
criteria.
RESULTS: A total of 145 case and 260 control subjects were included. Chronic H
pylori infection was associated with a higher risk of stroke caused by
small-artery occlusion (adjusted odds ratio, 3.31; 95% CI, 1.15 to 9.56) and a
lower risk of cardioembolic stroke (adjusted odds ratio, 0.21; 95% CI, 0.06 to
0.71). Overall, elevated H pylori as well as elevated C pneumoniae antibodies
were not associated with ischemic stroke.
CONCLUSIONS: Our population-based study does not provide evidence of any strong
association between the immune response to C pneumoniae as a marker of prior
infection and ischemic stroke. Further studies are required to reveal the role
of chronic H pylori infection as an independent risk factor for the subgroup
small-artery occlusion. BACKGROUND/AIMS: Helicobacter pylori (H. pylori) infection has been associated
with several vascular obstructive disorders. The infection induces the
production of proinflammatory cytokines that could increase platelet aggregates
in circulation. The aim of this case-controlled study was to evaluate the
prevalence of H. pylori infection in patients with acute ischemic stroke not
related to cardiac causes.
METHODOLOGY: A group of 80 consecutive patients (58 males, age range: 49-65
years) with acute ischemic stroke was studied. All patients received a cranial
CT and/or brain magnetic resoce imaging scan, extracranial vessel duplex
ultrasonography, and transthoracic echocardiography. H. pylori infection was
diagnosed by means of both 13C urea breath test and IgG antibodies to H. pylori.
A group of 320 blood donors (232 males and 88 females, age range: 49-65 years)
matched for sex and age served as controls. Among the patients, we investigated
the presence of hypertension, cholesterol and glucose levels in serum,
fibrinogen in plasma and the smoking habit.
RESULTS: The presence of H. pylori infection was higher in patients than in
controls: 64/80 (80%) versus 190/320 (59.4%) (P < 0.001); when analyzed for sex
in 45/58 (77.5%) among male patients and in 139/232 (59.9%) among controls (P <
0.05); of the females 19 out of 22 (86.3%) patients were infected at variance
with only 51/88 (57.9%) of the controls (P < 0.05). Classical risk factors for
stroke did not differ among patients with and without H. pylori infection. H.
pylori infection was not differently associated with current smoking, serum
total cholesterol and glucose levels, fibrinogen value in plasma and
hypertension when compared to the H. pylori-negative status.
CONCLUSIONS: H. pylori infection appears to be significantly more frequent in
middle-aged patients with acute ischemic stroke than in controls. BACKGROUND: It is uncertain whether Helicobacter pylori is associated with
ischemic syndromes and whether this association is mediated by the induction of
atherosclerosis. In this study, we tested the hypothesis that atherosclerotic
stroke shows a selective association with virulent H pylori strains.
METHODS AND RESULTS: The seroprevalence of infection by H pylori and by strains
bearing the cytotoxin-associated gene-A (CagA), a strong virulence factor, was
assessed by ELISA in 138 patients with large-vessel stroke (group A), in 61
patients with cardioembolic stroke (group B), and in 151 healthy control
subjects. The 3 groups had a similar socioeconomic status. Serum levels of
C-reactive protein were also measured by ELISA. The prevalence of infection was
71% in group A, 63.9% in group B, and 70.2% in the control group (P=NS), whereas
the prevalence of CagA-positive strains was higher in group A than in group B
(42.8% versus 19.7%, respectively; odds ratio 3.04, 95% CI 1.43 to 6.49;
P<0.001) and higher in group A than in the control group (42.8% versus 17.9%,
respectively; odds ratio 4.3, 95% CI 2.12 to 8.64; P<0.001), after adjusting for
main cardiovascular risk factors and social class. A trend toward a difference
in C-reactive protein was observed between CagA-positive (2.00+/-3.43
[mean+/-SD] mg/dL) and CagA-negative (1.31+/-1.72 [mean+/-SD] mg/dL) patients
(P=0.072, Mann-Whitney U test).
CONCLUSIONS: The association between H pylori and acute cerebrovascular disease
seems to be due to a higher prevalence of more virulent H pylori strains in
patients with atherosclerotic stroke. BACKGROUND: Infection by Helicobacter pylori (Hp) has been linked to
extradigestive pathologies including ischemic cerebral disease. The aim of our
study was to assess the relationship between chronic Hp infection and ischemic
stroke risk factors.
MATERIAL/METHODS: 80 patients (pts) aged 60-75 years with ischemic stroke
confirmed by CT scans (group I) and 80 age- and gender-matched healthy controls
(group II) were included into trial. Atherosclerotic plaques from 20 Hp positive
pts were obtained at carotid endarterectomy for Hp DNA assessment by PCR. In all
groups following parameters were determined; 1) the prevalence of Hp infection
using (13)C-Urea Breath Test (UBT), 2) plasma anti-Hp and anti-CagA IgG and
interleukin-8 (IL-8), and 3) plasma lipids and fibrinogen. Hp positive pts and
controls received one-week anti-Hp therapy and after six months total
cholesterol, low-density lipoprotein (LDL)-cholesterol, fibrinogen and IL-8
levels were re-examined.
RESULTS: Hp infection was detected by UBT in 83.75% of stroke pts but only in
65% of controls. CagA seropositivity was also significantly higher in stroke pts
(57.5%) than in controls (33.75%). Plasma levels of cholesterol, LDL-cholesterol
and fibrinogen as well as IL-8 were significantly higher in Hp positive
subjects, especially in pts with ischemic stroke. Six months following
successful anti-Hp therapy, the plasma levels of total cholesterol,
LDL-cholesterol, fibrinogen and IL-8 were significantly lower than those in Hp
positive stroke pts and controls.
CONCLUSIONS: Hp infection represents risk factor of ischemic stoke via an
interaction of Hp cytotoxins or cytokines with atherosclerotic plaques in
carotic arteries. AIMS: To determine whether infection with Helicobacter pylori is a significant
risk factor for stroke.
SUBJECTS: A total 467 in-patients with clinical evidence of acute ischaemic
stroke and 388 healthy controls with no evidence of cerebrovascular disease.
METHODS: This was a case control study. The prevalence of Helicobacter pylori
was measured by enzyme-linked immunosorbent assay in stroke patients and
controls. A positive titre was defined as >15 U/ml and relationship with
circulating plasma fibrinogen and social depravation was expressed using the
Townsend Index.
RESULTS: There were significantly more Helicobacter pylori positive individuals
(274/398 (69%)) in the cases compared to the controls (206/352 (58.5%)).
Fibrinogen levels were also significantly higher in Helicobacter pylori positive
(mean 4.14, standard deviation 1.33) than negative individuals (mean 3.78,
standard deviation 1.28). The association between Helicobacter pylori and stroke
was lost in a logistic model controlling for socio-economic status. Furthermore,
fibrinogen levels were not associated with Helicobacter pylori status in a
linear regression model controlling for socio-economic status.
CONCLUSIONS: Infection with Helicobacter pylori is associated with an increased
risk of stroke and increased fibrinogen levels but these findings can be
attributed to a confounding effect of socio-economic status. BACKGROUND: Inflammatory processes have fundamental roles in stroke in both the
etiology of ischemic cerebrovascular disease and the pathophysiology of cerebral
ischemia. We summarize clinical data on infection and inflammation as risk or
trigger factors for human stroke and investigate current evidence for the
hypothesis of a functional interrelation between traditional risk factors,
genetic predisposition, and infection/inflammation in stroke pathogenesis.
SUMMARY OF REVIEW: Several traditional vascular risk factors are associated with
proinflammatory alterations, including leukocyte activation, and predispose
cerebral vasculature to thrombogenesis on inflammatory stimulation. Furthermore,
accumulation of inflammatory cells, mainly monocytes/macrophages, within the
vascular wall starts early during atherogenesis. During later disease stages,
their activation can lead to plaque rupture and thrombus formation, increasing
stroke risk. Inflammatory markers (eg, leukocytes, fibrinogen, C-reactive
protein) are independent predictors of ischemic stroke. Chronic infections (eg,
infection with Chlamydia pneumoniae or Helicobacter pylori) were found to
increase the risk of stroke; however, study results are at variance, residual
confounding is not excluded, and causality is not established at present. In
case-control studies, acute infection within the preceding week was a trigger
factor for ischemic stroke. Acute and exacerbating chronic infection may act by
activating coagulation and chronic infections and may contribute to
atherogenesis. Genetic predisposition of the inflammatory host response may be
an important codetermit for atherogenesis and stroke risk.
CONCLUSIONS: Inflammation contributes to stroke risk via various interrelated
mechanisms. Infectious diseases, traditional risk factors, and genetic
susceptibility may cooperate in stimulating inflammatory pathways. Final proof
of a causal role of infectious/inflammatory mechanisms in stroke pathogenesis is
still lacking and will require interventional studies. Case-control studies and a few prospective studies have indicated that chronic
infections may add to the risk of stroke and that acute infections may act as
trigger factors for stroke. Such chronic infections include periodontal disease,
infection with Chlamydia pneumoniae or Helicobacter pylori, and chronic
bronchitis. A causal role of these infectious diseases has not been proved,
given conflicting study results, possible residual confounding in observational
studies, and the lack of evidence from interventional trials. Therefore, special
treatment regimens for stroke prevention based on serologic or genomic evidence
of infection are not indicated outside of randomized studies at present.
However, the preliminary available evidence suggests that in patients with
previous cerebral ischemia, clinically diagnosed chronic infections should be
taken seriously and should receive the treatment that is indicated according to
current guidelines. This may include appropriate treatment of moderate or severe
periodontitis and of chronic bronchitis. Inflammatory parameters (eg, C-reactive
protein, leukocyte count, fibrinogen) are independently associated with the risk
of first or recurrent stroke. The question of whether these indexes are causally
related to stroke or merely represent risk markers is not sufficiently
clarified. Their use in monitoring individual risk in daily clinical practice is
limited at present by the lack of clearly defined therapeutic strategies to
modify these parameters, although statins and other drugs can influence
inflammatory markers. Observational studies have shown that influenza
vaccination is significantly and independently associated with a reduced risk of
stroke and myocardial infarction. Although interventional studies in stroke are
lacking, it is recommendable that in accordance with current guidelines patients
with previous vascular disease, including stroke, patients with high risk of
stroke, and all subjects above age 60, receive an influenza vaccination
annually. INTRODUCTION: There is increasing evidence that infective pathogens such as
Helicobacter pylori is linked to atherosclerosis of cerebral vessels. As an
independent contributing factor, the CD14 receptor-lipopolysaccharide complex
plays an important role in activating inflammatory reactions. In particular, the
C(-260)T polymorphism in the CD14 receptor may be implicated in atherosclerotic
disease. In this study, we investigated a possible association between H. pylori
infection and the polymorphism of CD14, and ischemic stroke.
MATERIALS AND METHODS: A total of 125 patients with ischemic stroke and 125 age-
and sex-matched controls were included in the study. The stroke subtype of each
of the patients was characterized based on the underlying etiology. H. pylori
serologic status and the CD14 genotype were determined in both patients and
controls.
RESULTS: H. pylori seropositivity was more common in the stroke patients than in
the controls (80.0% vs. 60.0%, P=0.001). Moreover, H. pylori seropositivity was
more common in the stroke subtype of large artery disease (87.7%, P<0.001). The
distribution of CD14 genotypes was as follows: patients, T/T 21.6%, C/T 63.2%,
C/C 15.2%; controls, T/T 19.2%, C/T 57.6%, C/C 23.2%. There was no significant
difference between these two CD14 genotype distributions.
CONCLUSIONS: These results suggest that H. pylori infection is a risk factor for
ischemic stroke and that CD14 polymorphism is not. There is increasing evidence that, in addition to conventional risk factors,
acute and chronic infectious diseases increase the risk of stroke. Acute
infection, mainly respiratory, and both bacterial and viral infection, represent
temporarily active trigger factors for cerebral ischemia. Chronic infectious
diseases that may increase the risk of stroke include periodontitis, chronic
bronchitis and infections with microbial antigens, such as Helicobacter pylori
and Chlamydia pneumoniae. From observational studies, there is evidence that
vaccination against influenza is associated with a reduced risk of stroke,
myocardial infarction and all-cause mortality. This report provides an overview
on the influence of infection on stroke risk and potential anti-infective
strategies that may play a future role in stroke prevention. Since the discovery of Helicobacter pylori (H. pylori), numerous studies have
considered the possibility that it plays a role in different extragastric
diseases. Most of these studies may be classified as epidemiological studies or
investigations of H. pylori eradication, but there are also case reports and in
vitro studies. This review reveals the limitations common to most of them.
Idiopathic thrombocytopenic purpura is the disease for which the strongest
association with H. pylori infection has been shown. Data are also accumulating
about the role of H. pylori infection in idiopathic iron deficiency anemia and
chronic idiopathic urticaria. Interesting results show that H. pylori infection
affects atherosclerosis and is weakly associated with ischemic heart disease and
stroke. Moreover, CagA-positive H. pylori strains may play a role in the natural
history of atherosclerotic stroke. Recent studies suggest a link between H.
pylori and Parkinson's disease. Preliminary data indicate that H. pylori
infection impairs gastric ghrelin production and may influence nutritional
status. The association between H. pylori infection and other extragastric
diseases remains controversial. H. pylori infection may cause extragastric
manifestations directly or indirectly, by various mechanisms including atrophic
gastritis, the release of inflammatory mediators, molecular mimicry, and
systemic immune response. Evidence suggests that anti-H. pylori therapy improves
idiopathic thrombocytopenic purpura (significant increase of platelet count in
half of the cases), iron-deficiency anemia, and chronic urticaria (30% remission
rate), but the data from randomized controlled trials are insufficient to
confirm these positive effects. BACKGROUND: Previous studies suggested an association between CagA-positive H.
pylori strains and ischemic stroke. The aim of the present study was to assess
the prevalence of Helicobacter pylori infection and CagA status in patients with
atherosclerotic stroke in the primary care setting.
MATERIALS AND METHODS: A total of 106 consecutive patients (age 76.6 +/- 8
years; males 52%) with well-documented history of atherosclerotic stroke and 106
sex-age- (age 76.5 +/- 9 years; males 52%) and social background-matched
controls without relevant vascular diseases. Risk factors for ischemic stroke
were recorded in all subjects. H. pylori infection was assessed by[13]C-urea
breath test. A serologic assay for specific IgG against CagA was performed in
infected subjects.
RESULTS: A trend toward a higher prevalence of H. pylori was observed in cases
(63%) with respect to controls (54%) without reaching a statistical
significance. CagA positivity was associated to a higher risk of atherosclerotic
stroke (adjusted odds ratio 2.69, 95% confidence interval 1.37-5.30).
CONCLUSIONS: Our findings suggest that CagA-positive strains of H. pylori are
significantly associated to atherosclerotic stroke. This is not a merely
confirmative study since it has been performed for the first time in the primary
care setting and included only subjects with an active infection. Stroke is among the most common causes of death and persisting disability and
therefore represents a great social and economic burden worldwide. In order to
lower this burden it is essential to identify risk factors and respective
preventive strategies. Besides the established stroke risk factors (e.g.
hypertension, diabetes, hypercholesterolemia, atrial fibrillation) both acute
and chronic infectious diseases have emerged as risk factors for stroke. Mainly
acute respiratory tract infection but also urinary tract infections
independently increase the risk of ischemic stroke. Such additional risk was
shown to be highest for infection within 3 days before ischemia and the risk
steadily declines with increasing time intervals between infection and stroke.
Associations between stroke incidence and mortality and influenza epidemics have
been demonstrated. Observational studies showed an inverse association between
influenza vaccination and stroke risk; however, interventional studies in this
field have not been performed so far. Chronic infections, presently discussed as
stroke risk factors mainly include periodontitis and infections with
Helicobacter pylori (Hp) and Chlamydia pneumoniae (Cp). Although most respective
studies identified these infectious diseases as independent stroke risk factors
interventional trials have not been performed so far and causality is not
proven, yet. There is preliminary evidence that the number of pathogens to which
a subject had been exposed to rather than single pathogens are associated with
the risk of stroke or other cardiovascular diseases. Chronic infectious diseases
are treatable conditions and their identification as causal contributors to
stroke risk could offer new avenues in stroke prevention. The occurrence of stroke in populations is incompletely explained by traditional
vascular risk factors. Data from several case-control studies and one large
study using case series methodology indicate that recent infection is a
temporarily acting, independent trigger factor for ischemic stroke. Both
bacterial and viral infections, particularly respiratory tract infections,
contribute to this association. A causal role for infection in stroke is
supported by a graded temporal relationship between these conditions, and by
multiple pathophysiological pathways linking infection and inflammation,
thrombosis, and stroke. Furthermore, observational studies suggest that
influenza vaccination confers a preventive effect against stroke. Case-control
and prospective studies indicate that chronic infections, such as periodontitis,
chronic bronchitis and infection with Helicobacter pylori, Chlamydia pneumoniae
or Cytomegalovirus, might increase stroke risk, although considerable variation
exists in the results of these studies, and methodological issues regarding
serological results remain unresolved. Increasing evidence indicates that the
aggregate burden of chronic and/or past infections rather than any one single
infectious disease is associated with the risk of stroke. Furthermore, genetic
predispositions relating to infection susceptibility and the strength of the
inflammatory response seem to co-determine this risk. Here, we summarize and
analyze the evidence for common acute and chronic infectious diseases as stroke
risk factors. OBJECTIVE: Chronic infection by Helicobacter pylori is regarded as an
etiological factor for vascular diseases. However, there are conflicting results
on the relevance of chronic infection by Helicobacter pylori as a risk factor
for ischemic stroke. The aim of our study was to investigate the association
between Helicobacter pylori infection and ischemic stroke subtypes in Chinese.
METHOD: A total of 150 patients with ischemic stroke were enrolled in the
patient group. Analyses were stratified for etiologic stroke subtypes according
to 2007 modified Trial of Org 10172 in Acute Stroke Treatment criteria: 119
patients with atherothrombosis, 15 patients with cardioembolism, and 12 patients
with small artery disease. One hundred and thirty-one control subjects without
clinical and instrumental evidence of atherosclerotic diseases were randomly
selected from health check-up center. The potential risk factors for
Helicobacter pylori infection and traditional risk factors for ischemic stroke
of all subjects were analyzed. The serum specific antibody IgG of Helicobacter
pylori was detected by enzyme-linked immunosorbent assay. Conditional logistic
regression was used to analyze the data.
RESULTS: The Helicobacter pylori/IgG-positive rate in the patient group was
higher than that in the healthy control group, but the difference was not
statistically significant [67.3% versus 61.8%; odds ratio (OR) = 1.272; P =
0.336]. This result remained non-significant after adjustment for other
established risk factors [OR = 1.222; 95% confidence interval (CI): 0.688-2.171;
P = 0.494]. Subgroup analysis using univariate and multivariate analyses yielded
similar results in all etiologic stroke subtypes (univariate analysis,
atherothrombosis: OR = 1.368, 95%CI: 0.810-2.311, P = 0.241; cardioembolism: OR
= 0.926, 95%CI:0.311-2.758, P = 0.890; small artery disease: OR = 1.852, 95%CI:
0.478-7.167, P = 0.366; multivariate analysis, atherothrombosis: OR = 1.385,
95%CI: 0.726-2.639, P = 0.323; cardioembolism: OR = 0.832, 95%CI: 0.236-2.932, P
= 0.775; small artery disease: OR = 1.836, 95%CI: 0.396-8.503, P = 0.437).
CONCLUSIONS: This case-control study does not reveal any strong association
between chronic Helicobacter pylori infection and ischemic stroke. Large
case-control prospective studies are required for further investigation of the
potential association between Helicobacter pylori infection and ischemic stroke
risk, particularly in certain subgroups. In the last years, a considerable number of studies have been performed on the
relationship between infection from Helicobacter Pylori and atherosclerotic
diseases, like stroke and ischemic heart disease. In particular, some infections
could have a role on the genesis and development of damage to the vascular wall
and of atheromatous plaque. It has been suggested that HP could influence the
development of IHD through different pathways, such as endothelial cells
colonization, changes in the lipid profiles, increased coagulation and platelet
aggregation levels, induction of molecular mimicry mechanisms and the promotion
of a low-grade systemic inflammation. Based on this hypothesis, it has been
performed a considerable number of studies in order to investigate the role of
HP in the development and pathogenesis of CAD. Most of this trials gave
conflicting results, some denying the presence of a possible relationship
between HP infection and increased risk of CAD. Despite of that, results from
these studies have raised new interesting perspectives on coronary heart
disease, especially regarding the possibility of modifying the clinical history
of the disease through eradication of these microorganisms. The results are
contradictory and require further investigation. Chronic infection of Helicobacter pylori (H. pylori) in ischemic stroke (IS)
incidence has been previously studied in several publications; however,
conflicting results have been reported. A meta-analysis was used to assess
whether chronic infection of H. pylori was associated with risk of IS, and which
of the following was more effective for predication of IS risk, antibody IgG of
H. pylori (anti-H. pylori IgG), antibody IgG of cytotoxin-associated gene-A
(anti-Cag A IgG) or the (13)C-urea breath test. We searched the databases of
Medline and Embase, and latest update was January 1, 2012. Case-control studies
were considered to be eligible. The odds ratio (OR) and 95 % confidence interval
(95 % CI) were calculated using the random-effect model. A total of 13 studies
including 4,041 participants were included in this meta-analysis. Of these
studies, ten, four and four studies were for anti-H. pylori IgG, anti-Cag A IgG
and the (13)C-urea breath test, respectively. Combined analysis indicated that
positive anti-H. pylori IgG, anti-Cag A IgG and (13)C-urea breath test were
significantly associated with increased risk of IS, respectively, and positive
anti-Cag A IgG was more effective for predication of IS risk [OR (95 % CI) =
1.60 (1.21-2.11), P (heterogeneity) = 0.001 for positive versus negative anti-H.
pylori IgG; 2.33 (1.76-3.09), P (heterogeneity) = 0.71 for positive versus
negative anti-Cag A IgG and 1.65 (1.11-2.47), P (heterogeneity) = 0.17 for
positive versus negative (13)C-urea breath test]. In addition, we found that
positive anti-H. pylori IgG was closely associated with risk of IS caused by
atherosclerosis and small artery disease, but not for cardioembolic IS. This
meta-analysis indicated that chronic H. pylori infection was significantly
associated with an increased risk of IS, especially for non-cardioembolic IS.
Compared with anti-H. pylori IgG and the (13)C-urea breath test, anti-Cag A IgG
seemed more effective for prediction of risk of IS. Helicobacter pylori (H. pylori) infection is reported to be associated with many
extragastrointestinal manifestations, such as hematological diseases [idiopathic
thrombocytopenic purpura (ITP) and unexplained iron deficiency anemia (IDA)],
cardiovascular diseases (ischemic heart diseases), neurological disorders
(stroke, Parkinson's disease, Alzheimer's disease), obesity and skin disorders.
Among these, the best evidence so far is in ITP and unexplained IDA, with
high-quality studies showing the improvement of IDA and ITP after H. pylori
eradication. The evidence of its association with coronary artery disease is
weak and many of the results may be erroneous. The role of H. pylori infection
in affecting serum leptin and ghrelin levels has attracted a lot of attention
recently and available data to date have been conflicting. There have also been
many uncontrolled, small sample studies suggesting an association between H.
pylori infection and neurological disorders or chronic urticaria. However, more
studies are required to clarify such proposed causal links. |
Which are the major types of the motor speech disorder dysarthria? | Dysarthria is a motor speech disorder which can be classified according to the underlying neuropathology and is associated with disturbances of respiration, laryngeal function, airflow direction, and articulation resulting in difficulties of speech quality and intelligibility. There are six major types of dysarthria: "flaccid dysarthria" associated with lower motor neuron impairment, "spastic dysarthria" associated with damaged upper motor neurons linked to the motor areas of the cerebral cortex, "ataxic dysarthria" primarily caused by cerebellar dysfunction, and "hyperkinetic dysarthria" and "hypokinetic dysarthria", which are related to a disorder of the extrapyramidal system. The sixth is generally termed a "mixed dysarthria" and is associated with damage in more than one area, resulting in speech characteristics of at least two groups. | Cerebellar disease affects a number of skilled movements, including those in
speech. Ataxic dysarthria, the speech disorder that typically accompanies
cerebellar disease, was studied by acoustic methods. Control subjects and
subjects with ataxic dysarthria were recorded while performing a number of
speaking tasks, including sustained vowel phonation, syllable repetition,
monosyllabic word production (intelligibility test), sentence recitation, and
conversation. Acoustic data derived from the speech samples confirmed the
hypothesis that temporal dysregulation is a primary component of the speech
disorder. The data also show that the nature of the disorder varies with the
speaking task. This result agrees with observations on other motor systems in
subjects with cerebellar disease and may be evidence of a dissociation of
impairments. Suggestions are offered on the selection of measures for a given
task and on the role of the cerebellum in the regulation of speaking. Perceptual analysis is not sufficient enough to identify specific dysarthria
types. In order to improve the discrimination between dysarthria types, we
developed a standardized evaluation of different functions controlling speech
motor performances. This was applied to 90 patients suffering from hypokinetic,
spastic or ataxic dysarthria and 15 control subjects. A discriminate analysis
showed that 71.4 p. 100 of the cases were correctly classified. This model was
validated within a new group of 21 patients and showed that the less severe
dysarthric parkinsonian patients were difficult to distinguish from control
subjects. The discriminate analysis was then used for 20 patients with atypical
parkinsonism. Seven patients with progressive supranuclear palsy were considered
to have hypokinetic dysarthria. The 6 patients with multisystem atrophy and 7
with corticobasal degeneration were classified among the 3 dysarthric types. We
suggest that motor speech evaluation may contribute to differential diagnosis
within groups of patients suffering from atypical parkinsonism. BACKGROUND AND AIMS: Dysarthria affects linguistic domains such as respiration,
phonation, articulation, resoce and prosody due to upper motor neuron, lower
motor neuron, cerebellar or extrapyramidal tract lesions. Although Bengali is
one of the major languages globally, dysarthric Bengali speech has not been
subjected to neurolinguistic analysis. We attempted such an analysis with the
goal of identifying the speech defects in native Bengali speakers in various
types of dysarthria encountered in neurological disorders.
SETTINGS AND DESIGN: A cross-sectional observational study was conducted with 66
dysarthric subjects, predomitly middle-aged males, attending the
Neuromedicine OPD of a tertiary care teaching hospital in Kolkata.
MATERIALS AND METHODS: After neurological examination, an instrument comprising
commonly used Bengali words and a text block covering all Bengali vowels and
consots were used to carry out perceptual analysis of dysarthric speech. From
recorded speech, 24 parameters pertaining to five linguistic domains were
assessed. The Kruskal-Wallis analysis of variance, Chi-square test and Fisher's
exact test were used for analysis.
RESULTS: The dysarthria types were spastic (15 subjects), flaccid (10), mixed
(12), hypokinetic (12), hyperkinetic (9) and ataxic (8). Of the 24 parameters
assessed, 15 were found to occur in one or more types with a prevalence of at
least 25%. Imprecise consot was the most frequently occurring defect in most
dysarthrias. The spectrum of defects in each type was identified. Some
parameters were capable of distinguishing between types.
CONCLUSIONS: This perceptual analysis has defined linguistic defects likely to
be encountered in dysarthric Bengali speech in neurological disorders. The
speech distortion can be described and distinguished by a limited number of
parameters. This may be of importance to the speech therapist and neurologist in
planning rehabilitation and further management. BACKGROUND: Classification of dysarthria types comprises flaccid, spastic,
ataxic, hypo- and hyperkinetic and mixed dysarthria. This study focussed on the
ability of neurologists to clinically identify the correct type of dysarthria in
neurological patients.
METHODS: Eighteen patients with dysarthria and 4 healthy controls were enrolled
in the study. The gold standard for dysarthria type was the underlying
neurological disease. Recordings of a standard reading passage and free speech
were made. Raters were neurologists, residents in neurology and speech
therapists, whose scores were compared.
RESULTS: Neurologists correctly identified 40% of the recordings, residents 41%,
and speech therapists 37%. Interrater agreement was fair among all 3 groups;
intrarater agreement was fair to moderate.
CONCLUSION: This study suggests that neurologists should be aware of the
unreliability of identifying the dysarthria type without the use of additional
validated instruments or rating scales in a clinical setting. BACKGROUND: Dysprosody is a common feature in speakers with hypokinetic
dysarthria. However, speech prosody varies across different types of speech
materials. This raises the question of what is the most appropriate speech
material for the evaluation of dysprosody.
AIMS: To characterize the prosodic impairment in Cantonese speakers with
hypokinetic dysarthria associated with Parkinson's disease, and to determine the
effect of different types of speech stimuli on the perceptual rating of prosody.
METHODS & PROCEDURES: Speech data in the form of sentence reading, passage
reading, and monologue were collected from ten Cantonese speakers with
Parkinson's disease. Perceptual analysis was conducted on ten prosodic
parameters to evaluate five dimensions of prosody, based on a theoretical
framework: pitch, loudness, duration, voice quality, and degree of reduction.
OUTCOMES & RESULTS: The results showed that the most severely affected prosodic
parameters were monopitch, harsh voice, and monoloudness, followed by breathy
voice and prolonged interval. Differences were noted between speakers with mild
and moderate dysprosody. No statistically significant differences were found
between the three types of stimuli. However, qualitative analysis revealed
noticeable differences between the three stimuli in two speakers.
CONCLUSIONS & IMPLICATIONS: The prosodic profile of Cantonese speakers with
hypokinetic dysarthria is similar to those of other languages (for example,
English). The involvement of two new dimensions in the definition of prosody
(voice quality and degree of reduction) provides additional insight in
differentiating patients with mild and moderate dysarthria. Further
investigation on the use of speech materials in the clinical evaluation of
speech prosody in speakers with dysarthria is needed, as no single task was
found to represent a patient's performance under all circumstances. Children with classic galactosemia are at risk for motor speech disorders
resulting from disruptions in motor planning and programming (childhood apraxia
of speech or CAS) or motor execution (dysarthria). In the present study of 33
children with classic galactosemia, 21% were diagnosed with CAS, 3% with ataxic
dysarthria, and 3% with mixed CAS-dysarthria. Voice disorders due to laryngeal
insufficiency were common in children with dysarthria and co-occurred with CAS.
Most (58%) of the children with classic galactosemia had decreased
respiratory-phonatory support for speech, and 33% had disturbed vocal quality
that was indicative of cerebellar dysfunction. Three children, two diagnosed
with CAS and one not diagnosed with a motor speech disorder, had vocal tremors.
Treatment of voice dysfunction in neurogenic speech disorders is discussed. |
Is oxidative stress affected by FOXO expression? | Yes. In different cell types, induction of forkhead transcription factor FOXO1 was found to increase expression of the mitochondrial antioxidant manganese superoxide dismutase, and lead to suppression of oxidative stress. | The integrity of the feto-maternal interface is critical for survival of the
conceptus. This interface, consisting of the maternal decidua and the invading
placental trophoblast, is exposed to profound changes in oxygen tension during
pregcy. We demonstrate that human endometrial stromal cells become
extraordinarily resistant to oxidative stress-induced apoptosis upon
decidualization in response to cAMP and progesterone signaling. This
differentiation process is associated with the induction of the forkhead
transcription factor FOXO1, which in turn increases the expression of the
mitochondrial antioxidant manganese superoxide dismutase. However, silencing of
FOXO1 did not increase the susceptibility of decidualized cells to oxidative
cell death. Comparative analysis demonstrated that hydrogen peroxide, a source
of free radicals, strongly induces FOXO3a mRNA and protein expression in
undifferentiated human endometrial stromal cells but not in decidualized cells.
Expression of a constitutively active FOXO3a mutant elicited apoptosis in
decidualized cells. Furthermore, silencing of endogenous FOXO3a in
undifferentiated cells abrogated apoptosis induced by hydrogen peroxide. These
results suggest that the induction of FOXO1 may enhance the ability of
decidualized cells to prevent oxidative damage while the simultaneous repression
of FOXO3a expression disables the signaling pathway responsible for oxidative
cell death. The differential regulation of FOXO expression provides the decidua
with a robust system capable of coping with prolonged episodes of oxidative
stress during pregcy. Repression of excessive increase and enlargement of adipocytes that is closely
associated with obesity is effective in the prevention and treatment of
metabolic syndrome. Generally, apoptosis is induced in cells via a wide variety
of intracellular or extracellular substances, and recently, it has been
suggested that the FoxO subfamily is involved in the induction of apoptosis. We
aimed to elucidate the mechanism of FoxO-mediated apoptosis-induction in the
adipocytes under the reactive oxygen species (ROS) stimulus. The treatment of
differentiated and undifferentiated 3T3-L1 cells with glucose oxidase (GOD), an
enzyme that generates H(2)O(2), induced apoptosis and led to the accumulation of
8-OHdG. Apoptosis analysis revealed that GOD treatment induced apoptosis in
differentiated 3T3-L1 cells less efficiently than in undifferentiated
preadipocytes. GOD remarkably increased the levels of Bad, Bax, and Bim-the
genes that are actively involved in cell apoptosis. GOD treatment also increased
the expression of FoxO3a mRNA and protein. The introduction of FoxO3a-siRNA into
3T3-L1 cells suppressed the oxidative stress-induced expression of Bim mRNA, as
well as the GOD-induced apoptosis. Furthermore, the expression of MnSOD,
Cu/ZnSOD, and catalase, as well as of FoxO, increased significantly along with
the progression of adipocyte differentiation. These results indicated that
ROS-induced apoptosis in undifferentiated 3T3-L1 cells via the expression of
FoxO3a, whereas FoxO expression suppressed the ROS-induced apoptosis in
differentiated 3T3-L1 cells via the expression of ROS-scavenging enzymes. BACKGROUND: We recently reported that long-term cyclosporine (CsA)-induced
oxidative stress is associated with decreased expression of klotho, an
anti-aging gene. This study evaluated whether the antioxidant effect of statin
might upregulate klotho expression in CsA-induced renal injury.
METHODS: Two separate experiments were performed. First, the dose-dependent
effect of statin on klotho expression was evaluated in normal mouse kidneys.
Second, the effect of statin on klotho expression was evaluated in experimental
chronic CsA nephropathy in mice. We performed immunohistochemistry and
immunoblotting for klotho, Forkhead box O transcription factors [FoxOs;
phosphorylated FoxO1 (p-FoxO1) and FoxO3a (p-FoxO3a)] and their target
molecules, manganese superoxide dismutase (MnSOD), Bim and hemeoxygenase-1.
RESULTS: Statin treatment upregulated klotho expression in a dose-dependent
manner in the normal mouse kidney and alleviated the decrease in klotho
expression in kidneys exhibiting CsA nephropathy. CsA administration increased
p-FoxO1 expression and decreased p-FoxO3a expression, whereas concurrent statin
treatment reversed these changes, increased the expression of the antioxidant
enzymes MnSOD and hemeoxygenase-1 and decreased the expression of the
pro-apoptotic protein Bim.
CONCLUSION: Statin-mediated upregulation of klotho expression and differential
regulation of FoxO expression promote resistance to CsA-induced oxidative
stress. OBJECTIVE: Aging is a major risk factor for osteoarthritis (OA). Forkhead-box
class O (FoxO) transcription factors regulate mechanisms of cellular aging,
including protein quality control, autophagy and defenses against oxidative
stress. The objective of this study was to analyze FoxO transcription factors in
normal, aging and OA cartilage.
DESIGN: Knee joints from humans ages 23-90 and from mice at the age of 4-24
months and following surgically induced OA were analyzed for expression of FoxO
proteins. Regulation of FoxO protein expression and activation was analyzed in
cultured chondrocytes.
RESULTS: Human cartilage expressed FOXO1 and FOXO3 but not FOXO4 proteins. FOXO1
and FOXO3 were more strongly expressed the superficial and mid zone as compared
to the deep zone and were mainly localized in nuclei. During human joint aging,
expression of FOXO1 and FOXO3 was markedly reduced in the superficial zone of
cartilage regions exposed to maximal weight bearing. In OA cartilage,
chondrocyte clusters showed strong FOXO phosphorylation and cytoplasmic
localization. Similar patterns of FOXO expression in normal joints and changes
in aging and OA were observed in mouse models. In cultured chondrocytes, IL-1β
and TNF-α suppressed FOXO1, while TGF-β and PDGF increased FOXO1 and FOXO3
expression. FOXO1 and FOXO3 phosphorylation was increased by IL-1β, PDGF, bFGF,
IGF-1, and the oxidant t-BHP.
CONCLUSIONS: Normal articular cartilage has a tissue specific signature of FoxO
expression and activation and this is profoundly altered in aging and OA in
humans and mice. Changes in FoxO expression and activation may be involved in
cartilage aging and OA. |
Describe the mechanism of action of the LINX system for treatment of gastroesophageal reflux disease. | LINX Reflux Management System is a sphincter augmentation device designed to prevent gastroesophageal reflux due to abnormal opening of the lower esophageal sphincter (LES) by augmenting the sphincter barrier. It is implanted via laparoscopic procedure that does not alter gastric anatomy and is easily reversible. | This article covers some new areas of development in esophageal surgery.
Specific topics include reviews of long-term outcomes after laparoscopic
antireflux surgery, the use of surgically placed implantable device for LES
augmentation (Linx), the use of mesh for hiatal hernioplasty, and prone and
nonthoracic approaches to minimally invasive esophagectomy. OBJECTIVES: One- and 2-year evaluation of a feasibility trial
(clinicaltrials.gov registration numbers NCT01057992, NCT01058070, and 01058564)
to assess the safety and efficacy of a laparoscopically implanted sphincter
augmentation device for the treatment of gastroesophageal reflux disease (GERD).
METHODS: A sphincter augmentation device (LINX Reflux Management System; Torax
Medical, Shoreview, MN), designed to prevent reflux due to abnormal opening of
the lower esophageal sphincter (LES), was laparoscopically implanted at the
gastroesophageal junction in 44 patients. At baseline, all patients had abnormal
esophageal acid exposure on 24-hour pH monitoring and improved, but persistent,
typical GERD symptoms while on acid suppression therapy with proton pump
inhibitors (PPIs). The device comprises a miniature string of interlinked
titanium beads, with magnetic cores, placed around the gastroesophageal
junction. The magnetic bond between adjacent beads augments sphincter
competence. The beads temporarily separate to accommodate a swallowed bolus,
allow belching or vomiting, and reapproximate to augment the LES in the closed
position. Patients were evaluated after surgery by GERD Health-Related Quality
of Life symptom score, PPI usage, endoscopy, esophageal manometry, and 24-hour
esophageal pH monitoring.
RESULTS: The total mean GERD Health-Related Quality of Life symptom scores
improved from a mean baseline value of 25.7 to 3.8 and 2.4 at 1- and 2-year
follow-up, representing an 85% and 90% reduction, respectively (P < 0.0001).
Complete cessation of PPI use was reported by 90% of patients at 1 year and by
86% of patients at 2 years. Early dysphagia occurred in 43% of the patients and
self-resolved by 90 days. One device was laparoscopically explanted for
persistent dysphagia without disruption of the anatomy or function of the
cardia. There were no device migrations, erosions, or induced mucosal injuries.
At 1 and 2 years, 77% and 90% of patients had a normal esophageal acid exposure.
The mean percentage time pH was less than 4 decreased from a baseline of 11.9%
to 3.1% (P < 0.0001) at 1 year and to 2.4% (P < 0.0001) at 2 years. Patient
satisfaction was 87% at 1 year and 86% at 2 years.
CONCLUSIONS: The new laparoscopically implanted sphincter augmentation device
eliminates GERD symptoms without creating undue side effects and is effective at
1 and 2 years of follow-up. Gastroesophageal reflux disease (GERD) is the most common gastrointestinal
diagnosis recorded during visits to outpatient clinics in west countries. The
prevalence of symptom-defined GERD in China is as high as 3% to 5%. Asa
dysfunction, GERD is characterized by reflux and heartburn. The pathophysiologic
process of GERD is very complicated and subtle. The spectrum of injury from
long-term reflux of acid or bile includes damage mucosa, Barrett's esophagus,
dysplasia, and esophageal cancer. Therefore, the therapies of GERD should focus
on controlling symptom,treating complications, and surveillance the possibility
of oncologic transform. As with therapy with proton-pump inhibitors (PPI),
modifying lifestyle is another most important modality for most GERD. The window
of surgical treatment for GERD is narrow. Surgical therapy is alternative
management approach to the patients with PPI failure, complications, or huge
hernia. The laparoscopic minimally invasive procedure improves the acceptance of
patients to surgical therapy, but the long-term complication and drawbacks of
anti-reflux surgery cannot be ignored, and which is even more common than open
procedures. The limitations of current therapy for GERD have encouraged a search
for more effective treatment.The Linx sphincter augmentation device has been
developed to address this gap with improvement of the barrier function of LES
and reversible design if necessary. Gastroesophageal reflux disease (GERD), commonly manifested by heartburn or
regurgitation, is a chronic, progressive condition in which failed sphincter
function allows the contents of the stomach to reflux into the esophagus, the
airways and the mouth. Chronic GERD affects 10% of Western society. The majority
of patients receive adequate relief from proton pump inhibitors, but up to 40%
have incomplete relief of symptoms that cannot be addressed by increasing the
dose of medications. The laparoscopic Nissen fundoplication is the surgical gold
standard; however, the level of technical difficulty and its side effects have
limited its use to less than 1% of the GERD population. These factors have
contributed to the propensity of patients to persist with medical therapy, even
when inadequate to control symptoms and complications of the disease.
Consequently, a significant gap in the treatment continuum for GERD remains
evident in current clinical practice. The LINX(™) Reflux Management System
(Torax Medical) is designed to provide a permanent solution to GERD by
augmenting the physiologic function of the sphincter barrier with a simple and
reproducible laparoscopic procedure that does not alter gastric anatomy and can
be easily reversed if necessary. Gastroesophageal reflux disease (GERD) results from incompetency of the lower
esophageal sphincter that allows the contents of the stomach to reflux into the
esophagus, the airways, and the mouth. The disease affects about 10% of the
western population and has a profound negative impact on quality of life. The
majority of patients are successfully treated with proton-pump inhibitors, but
up to 40% have incomplete relief of symptoms even after dose adjustment. The
laparoscopic Nissen fundoplication represents the surgical gold standard, but is
largely underused because of the level of technical difficulty and the
prevalence of side effects. These factors have contributed to the propensity of
patients to continue with medical therapy despite inadequate symptom control and
complications of the disease. As a consequence, a significant 'therapy gap' in
the treatment of GERD remains evident in current clinical practice. The LINX(®)
Reflux Management System (Torax Medical, St. Paul, MN, USA) is designed to
provide a permanent solution to GERD by augmenting the sphincter barrier with a
standardized, reproducible laparoscopic procedure that does not alter gastric
anatomy and is easily reversible. Two single-group trials confirmed that a
magnetic device designed to augment the lower esophageal sphincter can be safely
and effectively implanted using a standard laparoscopic approach. The device
decreased esophageal acid exposure, improved reflux symptoms and quality of
life, and allowed cessation of proton-pump inhibitors in the majority of
patients. This paper includes commentaries on outcomes of esophageal surgery, including
the mechanisms by which fundoduplication improves lower esophageal sphincter
(LES) pressure; the efficacy of the Linx™ management system in improving LES
function; the utility of radiologic characterization of antireflux valves
following surgery; the correlation between endoscopic findings and reported
symptoms following antireflux surgery; the links between laparoscopic sleeve
gastrectomy and decreased LES pressure, endoscopic esophagitis, and
gastroesophageal reflux disease (GERD); the less favorable outcomes following
fundoduplication among obese patients; the application of bioprosthetic meshes
to reinforce hiatal repair and decrease the incidence of paraesophageal hernia;
the efficacy of endoluminal antireflux procedures, and the limited efficacy of
revisional antireflux operations, underscoring the importance of good primary
surgery and diligent work-up to prevent the necessity of revisional procedures. BACKGROUND: Gastroesophageal reflux disease (GERD) is a common chronic disease
requiring adequate treatment since it represents one major cause of development
of Barrett's esophagus and eventually carcinoma. Novel laparoscopic magnetic
sphincter augmentation for GERD was evaluated prospectively.
PATIENTS AND METHODS: A total of 23 patients with GERD underwent minimally
invasive implantation of LINX™ Reflux Management System. Primary outcome
measures were overall feasibility, short-term procedure safety and efficacy.
Secondary GERD-related quality of life was assessed.
RESULTS: All implantations were performed without serious adverse events. A
significant decrease in all major GERD complaints were found: heartburn: 96%-22%
(p<0.001); bloating: 70%-30% (p=0.006); respiratory complaints: 57%-17%
(p=0.039); sleep disturbance: 65%-4% (p<0.001). A four-week follow-up reduction
of ≥50% of proton pump inhibitor (PPI) dose was achieved in over 80% of
patients. Self-limiting difficulty in swallowing was found in 70% within four
weeks. One patient required for endoscopic dilation. GERD-related quality of
life improved significantly.
CONCLUSION: LINX™ implantation is a standardized, technically simple, safe and
well-tolerated expeditious procedure. A best evidence topic in surgery was written according to a structured protocol.
The question addressed whether LINX™ Reflux management system is an efficacious
treatment for patients with symptoms of gastro-oesophageal reflux disease (GORD)
not controlled by proton pump inhibitors (PPI). Forty-eight LINX-related papers
were identified using the reported search, of which three represented the best
evidence to answer the clinical question. The authors, journal, date and country
of publication, patient group, study type, relevant outcomes and results of
these papers are tabulated. All three studies were prospective case studies.
They demonstrated that LINX is an efficacious treatment for GORD patients with
good short and medium term outcomes and an acceptable safety profile. Further
studies are required to determine its long term outcomes and its relative
efficacy as compared to other established treatments. |
Which enzyme deficiency can cause GM1 gangliosidoses? | GM1 gangliosidoses are associated with deficiency of β-galactosidase. | A sister and brother, now aged 7 and 9 years, presented with developmental
arrest, gait disturbance, dementia, and a progressive myoclonic epilepsy
syndrome with hyperacusis in the second year of life. Then, spastic
quadriparesis led to a decerebrate state. In the absence of macular or retinal
degeneration, organomegaly, and somatic-facial features suggesting
mucopolysaccharidosis, the presence of hyperacusis together with sea-blue
histiocytes in bone marrow biopsies and deficient beta-galactosidase activity
but normal glucosidase, hexosaminidase, and neuraminidase activity on lysosomal
enzyme assays constitutes the clinical-pathologic-biochemical profile of GM1
gangliosidosis type 2. This is a rare, late infantile onset, progressive
gray-matter disease in which beta-galactosidase deficiency is largely localized
to the brain, though it can be demonstrated in leukocytes and cultured skin
fibroblasts. It must be distinguished from the Jansky-Bielschowsky presentation
of neuronal ceroid lipofuscinosis, mitochondrial encephalopathy, lactic
acidosis, strokelike episodes (MELAS) and myoclonic epilepsy with ragged-red
fibers (MERRF) syndromes, atypical presentations of GM2 gangliosidoses
(Tay-Sachs and Sandhoff's diseases), primary sialidosis (neuraminidase
deficiency), galactosialidosis, and Alpers' disease. GM1-gangliosidosis is a genetic neurological disorder caused by mutations in the
lysosomal acid beta-galactosidase gene. While its phenotypic expression is
complex, it is usually classified as being of infantile, juvenile, or adult
form, on the basis of age at onset, the rate of symptomatic progression, and
severity of central nervous system involvement. We have analyzed the acid
beta-galactosidase gene in 12 Japanese patients from nine families. The aim was
to identify mutations in individual patients and then to examine possible
correlation between the mutations and the clinical phenotypes. Northern blotting
studies with a full-length human beta-galactosidase cDNA showed that the mRNA
ranged from undetectable to substantially decreased in the infantile patients
but was normal in quantity and size in all juvenile and adult patients. Four
distinct missense mutations have been identified, each limited to the respective
clinical forms within our small-size samples. In the infantile patient with
decreased but detectable mRNA, a point mutation was found resulting in
Arg49----Cys. In the infantile patient with nearly undetectable mRNA, mutation
Arg457----Ter was identified. The mutation Arg201----Cys was found in all four
of the juvenile patients, while all six adult patients were homozygous for the
point mutation Ile51----Thr. The mutations found in the juvenile and adult
patients alter restriction sites in the normal gene and thus are amendable to
quick screening. The prediction that these mutations are responsible for the
clinical disease was confirmed by no expression of the catalytic activity of the
mutant proteins in the COS-I cell expression system.(ABSTRACT TRUNCATED AT 250
WORDS) A female infant with early-onset GM1-gangliosidosis type I was investigated. The
lymphocytes, transformed lymphocytes and cultured skin fibroblasts of the
patient were demonstrated to have severe beta-D-galactosidase deficiency. The
beta-D-galactosidase activities of these cells from the patient's father and
mother were at the lower limit of the normal range. The oligosaccharide
accumulation in urine of the patient showed the typical type I
GM1-gangliosidosis pattern, but no GM1 ganglioside was detected in the patient's
urine or transformed lymphocytes. The clinical features were compatible with
infantile GM1-gangliosidosis. The mixture of homogenates from the cultured
fibroblasts or transformed lymphocytes of the patient and controls showed no
complementation of beta-D-galactosidase activity against the controls. GM1-gangliosidosis is a rare neurovisceral storage disease caused by an
inherited deficiency of acid beta-galactosidase. The characteristic neurological
feature of type 3 (adult or chronic) GM1-gangliosidosis is usually a slowly
progressive dystonia with dysarthria due to predomit involvement of basal
ganglia. About 20 adult patients with this disorder have been reported in the
literature. However, there are no reports of 3 brothers with type 3
GM1-gangliosidosis, and MRI findings. Case 1 (proband): A 28-year-old man was
hospitalized because of facial grimace, dysarthria, and generalized dystonia. He
was born after normal pregcy and delivery. His development was normal until 3
years of age when the difficulties of speaking and walking were noticed by his
parents. These neurological abnormalities progressed slowly and facial grimace
and dystonic movements occurred 7 years later. He could not walk at 22 years of
age. On admission, he was bedridden with marked scoliosis and subluxation of the
mandibule. The communication was possible only by pointing the words written on
the board. Case 2: A 33-year-old man, elder brother of case 1, showed the
similar neurological features and clinical course. Slit-lamp examination
revealed corneal opacities which were located in the deep stroma. Case 3: A
33-year-old man, elder brother of case 1 or case 2. At age 10-11, he noted
similar symptoms as case 1 or case 2. The severity of dystonia was milder than
his brothers. A diagnosis of GM1-gangliosidosis in three patients was made on
the basis of the following data.(ABSTRACT TRUNCATED AT 250 WORDS) alpha-Galactosidase and beta-galactosidase activities have been determined in
leukocyte preparations from 100 randomly selected Chinese adults. For
alpha-galactosidase, two groups with low activities were identified: group I
consisted of 3 females having activities below 40% of normal, and group II
consisted of 5 males and 1 female with activities about 60% of normal. Family
studies suggested that these low alpha-galactosidase activities are genetically
determined. Only 1 individual was found to have about 50% of normal
beta-galactosidase activity; presumably he is a carrier for beta-galactosidase
deficiency (GM1 gangliosidosis). Immunoelectron microscopy was performed to study the biosynthesis of lysosomal
beta-galactosidase (beta-gal) in normal and mutant human fibroblasts. Using
polyclonal and monoclonal antibodies we show in normal cells precursor forms of
beta-gal in the rough endoplasmic reticulum (RER) and in the Golgi apparatus
throughout the stack of cisternae. In the lysosomes virtually all beta-gal
exists as a high molecular weight multimer of mature enzyme. In the autosomal
recessive disease GM1-gangliosidosis caused by a beta-gal deficiency and in
galactosialidosis, associated with a combined deficiency of lysosomal
neuraminidase and beta-gal, precursor forms of the latter enzyme are found in
RER, Golgi and some labeling is present at the cell surface. The lysosomes
remain unlabeled, indicative for the absence of enzyme molecules in this
organelle. In galactosialidosis fibroblasts also no mature beta-gal is found in
the lysosomes but in these cells the presence of the monomeric form can be
increased by leupeptin (inhibition of proteolysis) whereas addition of a partly
purified 32 kDa "protective protein" results in the restoration of high
molecular weight beta-gal multimers in the lysosomes. Cerebral lipids of patients with GM1-gangliosidoses, infantile, juvenile, and
chronic type which are caused by deficiency of beta-galactosidase, were examined
and compared to each other. The infantile type demonstrated abnormal
accumulation of GM1 and asialo-GM1 in contrast with marked decrease in such
major cerebral lipids as cholesterol, phospholipids, cerebroside, and sulfatide.
It was also noted that significant amounts of such unusual lipids as free fatty
acids, GlcCer, LacCer, GbOse3Cer, and GbOse-4Cer plus nLcOse4Cer were found in
the brain. These findings pointed out that this infantile type might accompany a
severe cerebral dysgenesis with poor myelination. The juvenile type also showed
marked increase in GM1 and asialo-GM1, but the decrease in cholesterol,
phospholipids, cerebroside, and sulfatide was not so much as the infantile type.
These findings along with the occurrence of cholesterol ester suggested that the
brain caused progressive demyelination after the immature myelin appeared. An
autopsized brain tissue of a male patient who was eventually diagnosed as a case
of GM1-gangliosidosis chronic type after his death, showed some accumulation of
GM1 and asialo-GM1 particularly in the caudate nucleus and putamen, whereas it
showed moderate amounts of GM1 in apparently normal gray and white matters. It
seemed that there are no abnormal cerebral lipids except for gangliosides and
some neutral glycosphingolipids in the chronic type. GM1 gangliosidosis is a genetic disease with lysosomal beta-galactosidase
deficiency caused by mutations of the gene coding for this enzyme. However,
apparently normal enzyme activity was found in plasma or serum from juvenile GM1
gangliosidosis patients homozygous for a mutation, R201C (201Arg-->Cys), after
clotting for 30 min. This extracellular fluid finding is unusual in patients
with primary and genetic deficiency of beta-galactosidase. The serum enzyme
activity became relatively low only after 3 1/2-hour clotting because its
increase in normal controls was not observed in these patients.
beta-Galactosidase assay is not always reliable, particularly with serum or
plasma as an enzyme source, for the diagnosis of hereditary beta-galactosidase
deficiency, unless it is conducted under well-controlled conditions. GM1 gangliosidosis and Morquio B disease are distinct disorders both clinically
and biochemically yet they arise from the same beta-galactosidase enzyme
deficiency. On the other hand, galactosialidosis and sialidosis share common
clinical and biochemical features, yet they arise from two separate enzyme
deficiencies, namely, protective protein/cathepsin A and neuraminidase,
respectively. However distinct, in practice these disorders overlap both
clinically and biochemically so that easy discrimination between them is
sometimes difficult. The principle reason for this may be found in the fact that
these three enzymes form a unique complex in lysosomes that is required for
their stability and posttranslational processing. In this review, I focus mainly
on the primary and secondary beta-galactosidase deficiency states and offer some
hypotheses to account for differences between GM1 gangliosidosis and Morquio B
disease. Mutations in the lysosomal acid beta-galactosidase (EC 3.2.1.23) underlie two
different disorders: GM1 gangliosidosis, which involves the nervous system and
visceral organs to varying extents, and Morquio's syndrome type B (Morquio B
disease), which is a skeletal-connective tissue disease without any CNS
symptoms. This article shows that transduction of human GM1 gangliosidosis
fibroblasts with retrovirus vectors encoding the human acid beta-galactosidase
cDNA leads to complete correction of the enzymatic deficiency. The newly
synthesized enzyme is correctly processed and targeted to the lysosomes in
transduced cells. Cross-correction experiments using retrovirus-modified cells
as enzyme donors showed, however, that the human enzyme is transferred at low
efficiencies. Experiments using a different retrovirus vector carrying the human
cDNA confirmed this observation. Transduction of human GM1 fibroblasts and mouse
NIH 3T3 cells with a retrovirus vector encoding the mouse beta-galactosidase
cDNA resulted in high levels of enzymatic activity. Furthermore, the mouse
enzyme was found to be transferred to human cells at high efficiency. Enzyme
activity measurements in medium conditioned by genetically modified cells
suggest that the human beta-galactosidase enzyme is less efficiently released to
the extracellular space than its mouse counterpart. This study suggests that
lysosomal enzymes, contrary to the generalized perception in the field of gene
therapy, may differ significantly in their properties and provides insights for
design of future gene therapy interventions in acid beta-galactosidase
deficiency. GM1 gangliosidosis is a glycosphingolipid (GSL) lysosomal storage disease caused
by a genetic deficiency of acid beta-galactosidase (beta-gal), the enzyme that
catabolyzes GM1 within lysosomes. Accumulation of GM1 and its asialo form (GA1)
occurs primarily in the brain, leading to progressive neurodegeneration and
brain dysfunction. Substrate reduction therapy aims to decrease the rate of GSL
biosynthesis to counterbalance the impaired rate of catabolism. The imino sugar
N-butyldeoxygalactonojirimycin (NB-DGJ) is a competitive inhibitor of the
ceramide-specific glucosyltransferase that catalyzes the first step in GSL
biosynthesis. Neonatal C57BL/6J (B6) and beta-gal knockout (-/-) mice were
injected daily from post-natal day 2 (p-2) to p-5 with either vehicle or NB-DGJ
at 600 mg or 1200 mg/kg body weight. These drug concentrations significantly
reduced total brain ganglioside and GM1 content in the B6 and the beta-gal (-/-)
mice. Drug treatment had no significant effect on viability, body weight, brain
weight, or brain water content in the B6 and beta-gal (-/-) mice. Significant
elevations in neutral lipids (GA1, ceramide, and sphingomyelin) were observed in
the NB-DGJ-treated beta-gal (-/-) mice, but were not associated with adverse
effects. Also, NB-DGJ treatment of B6 and beta-gal (-/-) mice from p-2 to p-5
had no subsequent effect on brain ganglioside content at p-21. Our results show
that NB-DGJ is effective in reducing total brain ganglioside and GM1 content at
early neonatal ages. These findings suggest that substrate reduction therapy
using NB-DGJ may be an effective early intervention for GM1 gangliosidosis and
possibly other GSL lysosomal storage diseases. Retinal abnormalities are well documented in patients with ganglioside storage
diseases. The total content and distribution of retinal glycosphingolipids was
studied for the first time in control mice and in Sandhoff disease (SD) and GM1
gangliosidosis mice. Light and electron microscopy of the SD and the GM1 retinas
revealed storage in ganglion cells. Similar to previous findings in rat retina,
GD3 was the major ganglioside in mouse retina, while GM2 and GM1 were minor
species. Total ganglioside content was 44% and 40% higher in the SD and the GM1
retinas, respectively, than in the control retinas. Furthermore, GM2 and GM1
content were 11-fold and 51-fold higher in the SD and the GM1 retinas than in
the control retinas, respectively. High concentrations of asialo-GM2 and
asialo-GM1 were found in the SD and the GM1 retinas, respectively, but were
undetectable in the control retinas. The GSL abnormalities in the SD and the GM1
retinas reflect significant reductions in beta-hexosaminidase and
beta-galactosidase enzyme activities, respectively. Although electroretinograms
appeared normal in the SD and the GM1 mice, visual evoked potentials were
subnormal in both mutants, indicating visual impairments. Our findings present a
model system for assessing retinal pathobiology and therapies for the
gangliosidoses. The gangliosidoses comprise a family of lysosomal storage diseases characterized
by the accumulation of complex glycosphingolipids in the nervous system and
other tissues, secondary to the deficient activity of lysosomal hydrolases or
their associated activator proteins. GM1 and GM2 gangliosidosis are associated
with deficiency of β-galactosidase and β-hexosaminidase respectively. All
gangliosidoses are characterized by progressive neurodegeneration, the severity
of which is proportional to the residual enzyme activity. The GM1 gangliosidoses
are characterized by dysostosis, organomegaly and coarsening in their most
severe forms, whereas children with classic infantile GM2 gangliosidosis
(Tay-Sachs disease) are usually spared systemic involvement, except in the case
of the Sandhoff variant, in which organomegaly may occur. Cherry-red macular
spots occur in the early onset forms of the gangliosidoses, but are less
frequently seen in the less severe, later onset phenotypes. Macrocephaly, an
exaggerated startle response, cognitive decline, seizures, ataxia, and
progressive muscular atrophy may occur in different forms of gangliosidosis. The
diagnosis is made by assay of enzyme activity, and can be confirmed by mutation
analysis. Carrier screening for Tay-Sachs disease has been remarkably successful
in reducing the incidence of this disease in the at-risk Ashkenazi population.
There are no proven disease-modifying therapies for the gangliosidoses. |
What is the characteristic feature of the Dyke-Davidoff-Masson syndrome. | Cerebral hemiatrophy (atrophy of one cerebral hemisphere) is the characteristic feature of the Dyke-Davidoff-Masson syndrome. It develops due to an insult to the brain in fetal or early childhood period. Calvarial thickening, skull and facial asymmetry, contralateral hemiparesis, cognitive impairment and seizures are also characteristic to the Dyke-Davidoff-Masson syndrome.
. | A patient with Dyke-Davidoff-Masson Syndrome had a lifelong history of spatial
disorientation and visual-spatial cognitive defects demonstrated by
psychological tests. We suggest that the abnormalities of behavior and test
performance may be related atrophic lesions demonstrated by
pneumoencephalography and computerized axial tomography. We consider several
explanations to account for the lack of compensation for these cognitive
defects. A growing skull fracture or leptomeningeal cyst most commonly occurs in children
under the age of 3 years, and is extremely rare in adults. The reason for a
growing skull fracture is usually a dural tear in association with the fracture.
This paper presents an 18-year-old mentally retarded patient with cerebral
hemiatrophy (Dyke-Davidoff-Masson syndrome) associated with a growing skull
fracture in the ipsilateral hemicranium, in whom not only a dural tear but also
the ipsilaterally displaced and dilated lateral ventricle due to the original
disease apparently contributed to the development of growing skull fracture. We reported a 39-year-old man with Dyke-Davidoff-Masson syndrome presenting with
total hemiatrophy. The patient had a muscle defect in the left occipital lesion
at birth and left hemiatrophy including the face in his infancy. The present
illness consists of atrophy of the left face, trunk and extremities, a muscle
defect accompanied with scleroderma of the left dorsal cervical lesion,
bilateral pes cavus, cleft palate, left hemiparesis, including facial palsy and
diminished superficial sensation of the left side of the body. Decrease in right
cranial volume and slight elevation of the right temporal pyramid and the
superior border of the orbit were seen on the X-ray study of the head. Atrophy
of the right cerebrum and cerebral peduncle was seen on magnetic resoce
imaging. These findings suggest that hemiatrophy of the brain was responsible
for total hemiatrophy of the body in this patient. The etiology of cerebral
hemiatrophy is not known. There is only a report of Dyke-Davidoff-Masson
syndrome accompanied with total hemiatrophy. Cerebral hemiatrophy or Dyke-Davidoff-Masson syndrome is a condition
characterized by seizures, facial asymmetry, contralateral hemiplegia or
hemiparesis, and mental retardation. These findings are due to cerebral injury
that may occur early in life or in utero. The radiological features are
unilateral loss of cerebral volume and associated compensatory bone alterations
in the calvarium, like thickening, hyperpneumatization of the paranasal sinuses
and mastoid cells and elevation of the petrous ridge. The authors describe three
cases. Classical findings of the syndrome are present in variable degrees
according to the extent of the brain injury. Pathogenesis is commented. We reported five cases of Dyke-Davidoff-Masson syndrome (DDMS) with different
clinical and radiological findings. The evaluated parameters were the location
of the lesions, midline structural shift effect, pathological and morphological
changes on the ipsilateral calvarium, paranasal sinuses and mesencephalon,
presence of compensatory contralateral hypertrophy. With the help of both
magnetic resoce (MR) and computerized tomography (CT) images, changing
degrees of all the evaluated parameters were observed in all five of our
patients. In conclusion, no relationship was found between parenchymal and
calvarial changes and between the time after onset of the disease and amount of
the morphologic and pathological changes. The patient was a 19-year-old woman who presented with hemiatrophy and
diminished superficial sensation on the left side of her body including her
face. She had a past history of tonic-clonic seizures accompanied by left
hemiparesis in late childhood. Brain CT demonstrated dilatation of the frontal
sinus, calvarial thickening, cerebral hemiatrophy and dilatation of the lateral
ventricle on the right side. Brain MRI showed atrophy of the right cerebrum and
midbrain and dilatation of the lateral ventricle on T1-weighted images, as well
as a high signal intensity area from the parietal to the occipital lobe on
T2-weighted images. These findings are suggestive of an episode that may have
caused a transient ischemia through the right cerebral hemisphere after the
intrauterine period. Although radiological findings of cerebral hemiatrophy (Dyke-Davidoff-Masson
Syndrome) are well known, there is no systematic study about the gender and the
affected side in this syndrome. Brain images in 26 patients (mean aged 11) with
cerebral hemiatrophy were retrospectively reviewed. Nineteen patients (73.5%)
were male and seven patients (26.5%) were female. Left hemisphere involvement
was seen in 18 patients (69.2%) and right hemisphere involvement was seen in
eight patients (30.8%). We conclude that male gender and left side involvement
are frequent in cerebral hemiatrophy disease. Dyke-Davidoff-Masson syndrome is a condition characterized by seizures, facial
asymmetry, contralateral hemiplegia or hemiparesis and mental retardation. We
report the clinical and imaging features in two patients with epilepsy revealing
a Dyke-Davidoff-Masson syndrome. Brain MRI showed unilateral loss of cerebral
volume with hypertrophy and hyperpneumatization of the paranasal sinuses and
mastoid cells. Ipsilateral fronto-parietal polymicrogyria was present in one
patient. The so-called Dyke-Davidoff-Masson syndrome (DDMS) is a rare disorder of
cerebral hemiatrophy. The clinical presentation may consist of facial asymmetry,
contralateral atrophy (including the trunk, and the extremities) and
hemiparesis, speech difficulties, mental retardation, and epilepsy. Because it
involves multiple systems, especially problem of the airway, occult myopathy,
and seizure disorder, anesthesia for such a patient is a challenge to any
anesthesiologist. However, there are no clinical reports which concern the
anesthetic management of such patients in the literature. We herein report a
5-year-old girl, a sufferer of DDMS, scheduled for burr trephination. The
successful anesthetic management is brought forward with highlights of inference
from the experience. BACKGROUND: The purpose of this study was to emphasize the clinical and imaging
findings of 19 child cases of cerebral hemiatrophy.
METHODS: A total of 11 male and eight female patients underwent assessment with
computed tomography and magnetic resoce imaging. The patients ranged from 1
to 17 years in age. The evaluated parameters were: location of the lesions,
midline structural shift effect, ipsilateral calvarial and parenchymal changes.
RESULTS: Left cerebral hemiatrophy was seen in 14 of the cases while right
cerebral hemiatrophy was observed in five cases. Unilateral calvarial thickening
was seen in 11 cases, hyperpneumatization of paranasal sinuses in five, and
hypoplasia of the middle frontal cranial fossa in three patients. Cerebral
peduncle atrophy was noted in seven cases. In total, 11 patients had thalamic
atrophy and lentiform nucleus hypoplasia. In one case, cerebral hemiatrophy was
associated with ipsilateral large schizencephalic cleft and absence of the
septum pellucidum, whereas in another case, there was diffuse cerebellar atrophy
associated with cerebral hemiatrophy.
CONCLUSION: Computed tomography and, in particular, magnetic resoce imaging
are the procedures of choice with respect to assessment of the etiology and
extent of cerebral parenchymal involvement in cerebral hemiatrophy. Dyke Davidoff Masson syndrome (DDMS) is characterized by seizures, facial
asymmetry, contralateral hemiplegia and mental retardation. The characteristic
radiologic features are cerebral hemiatrophy with homolateral hypertrophy of the
skull and sinuses. We report a case of DDMS in an 18-month-old girl who
presented with right sided focal seizures, hemiparesis of the same side, and
delayed milestones. Dyke-Davidoff-Masson syndrome, or cerebral hemiatrophy, is a pre- or perinatally
acquired entity characterized by predomitly neurologic symptoms, such as
seizures, facial asymmetry, contralateral hemiplegia, and mental retardation.
Psychiatric symptoms are rarely reported. We report the first case of left
cerebral hemiatrophy and a late onset of treatment-resistant schizoaffective
disorder after a stressful life event. The patient finally responded well to
clozapine. The clinical history and results from structural neuroimaging are
highlighted to discuss the possible developmental bias for psychotic disorders. Dyke-Davidoff-Masson syndrome is a disorder involving hemiatrophy or hypoplasia
of 1 cerebral hemisphere secondary to an insult in the developing brain. Often
this will manifest with seizures, hemiparesis, mental retardation, and facial
changes. Associated with this pathology are the radiologically evident changes,
such as thickening of the calvarium, hyperpneumatization of the sinuses, and
dilation of the ipsilateral lateral ventricle among others. The following is a
case presentation of an 18-year-old female emigrating from Ghana who presented
to the emergency department with complaints of seizures diagnosed as being
caused by cerebral malaria at 13 years of age. We hypothesize that the cerebral
malaria and related vascular occlusion are the causes of her acquired cerebral
changes. Included are computed tomography images. BACKGROUND: cerebral hemiatrophy (CHA) can present in childhood or adulthood, if
it presents before or after two years of age. This two entities differ in
etiology, clinical presentation and imaging characteristics. The CHA of
childhood or Dyke-Davidoff-Masson syndrome, is originated by intrauterine or
perinatal insults that affect the perfusion of a single cerebral hemisphere,
manifesting clinically by variable mental retardation, refractory epilepsy,
facial asymmetry, hemiplegia/hemiparesis or abnormal movements of the
contralateral extremities and by imaging studies, loss of volume in one cerebral
hemisphere and ipsilateral compensatory cranial changes such as skull vault
thickening, elevation of the orbital roof and petreous ridge, also
hyperpneumatization of the frontal sinus and mastoid cells. Instead, the CHA of
the adult is multifactorial and by imaging it only manifests as loss of volume
in one cerebral hemisphere, without compensatory changes in the skull.
CASES REPORT: we present a classic clinical case of CHA secondary to perinatal
insult and another case of CHA of adulthood secondary to multiple embolic
strokes in a patient with inactive rheumatic heart disease, commenting the
imaging differences of these rare clinical entities. The purpose of this study was to retrospectively evaluate the cognitive and
electroclinical characteristics of right cerebral hemiatrophy
(Dyke-Davidoff-Masson syndrome [DDMS]). Cognitive assessments with a particular
emphasis on visuospatial functions, electroclinical features, and neuroimaging
characteristics were analyzed for five patients with a clinically and
neuroradiologically confirmed diagnosis of right-sided DDMS. Intelligence tests
revealed mental retardation in all but one. Neuropsychological assessments
demonstrated consistent impairments in tasks that have a spatial component
(spatial processing and orientation discrimination), whereas attention,
executive functions and verbal memory domains were variably impaired.
Electroclinically, the main seizure types were simple partial motor, complex
partial, and secondarily generalized seizures. Interictal EEG delineated lower
amplitudes and slow background activity in the affected hemisphere. Overall, the
cognitive performance of patients with DDMS encompasses a broad spectrum of
impairments affecting multiple domains. Our findings support the concept that
dorsal visual pathways responsible for spatial processing may be lateralized to
the right hemisphere. A 15-year-old female presented with seizures, right-sided hemiparesis,
hemiatrophy of the right side of the body and mental retardation. MRI brain
revealed characteristic features diagnostic of congenital type of cerebral
hemiatrophy or Dyke-Davidoff-Masson syndrome. Dyke-Davidoff-Masson syndrome (DDMS) is a rare epilepsy syndrome that is
characterized by cerebral hemiatrophy, homolateral skull hyperplasia,
hyperpneumatization of the paranasal sinuses, seizures with or without mental
retardation, and contralateral hemiparesis. We describe a case of DDMS in a
40-year-old female who had complex partial seizures with occasional secondary
generalization since the age of 4 years. Her seizure frequency was 10-20
seizures/month even though she took four antiepileptic drugs. We applied
magnetic resoce imaging (MRI), positron emission tomography (PET), functional
MRI, and invasive electroencephalography (EEG) to define her epileptogenic and
functional zones. Brain MRI showed prominent atrophy in the left frontal dorsal
and lateral regions and mild atrophy of the left superior temporal gyrus and
left parietal gyri. Interictal PET revealed decreased glucose metabolism in the
atrophic regions. Functional MRI demonstrated that the inferior frontal and
inferior parieto-occipital regions of the right hemisphere were activated by
language testing. Invasive EEG revealed that the left lateral temporal lobe was
the sole source of her seizures. Our results imply that the "metabolic border
zone" rather than the atrophic region plays an important role in seizure
activity, and that reorganization of functional zones occur after cerebral
damage early in life. Invasive craniocerebral aspergillosis, often encountered in an immunocompromised
setting, is almost uniformly fatal despite radical surgical and medical
management, and is frequently a necropsy finding. The authors report a unique,
self-resolving clinical course of this aggressive infection in a 10-month-old
infant. The infant was brought to the emergency services in altered sensorium
with a 1-week history of left-sided hemiparesis, excessive irritability, and
vomiting. An MRI study of the brain revealed multiple, heterogeneously enhancing
lesions in the right cerebral hemisphere with mass effect. The largest lesion in
the frontotemporal cortical and subcortical regions was decompressed on an
emergent basis. Histopathological findings were suggestive of invasive
aspergillosis, although there was no evidence of the infection in the lungs or
paranasal sinuses. Computed tomography-guided aspiration of the remaining
lesions and follow-up antifungal therapy were recommended. The parents, however,
requested discharge without further treatment. The child was seen at a follow-up
visit 3 years later without having received any antifungal treatment. Imaging
showed resolution of the infection and features of Dyke-Davidoff-Masson syndrome
(cerebral hemiatrophy). This report of invasive cerebral aspergillosis resolving
without medical therapy is the first of its kind. Its clinicoradiological
aspects are discussed in light of previously reported cases. Authors describe the case of a 16-year-old girl who presented with fever,
tonic-clonic seizures, unequal arm blood pressures and pulselessness in the left
upper limb. On examination, there was a systolic bruit over umbilical region, a
pansystolic murmur of mitral regurgitation was found. Neurological examination
was normal except for an asymmetry in brain hemicircumference one side compared
with the other. She has borderline intelligence (IQ 70) according to Wechsler
Adult Performance Intelligence Scale. Magnetic resoce imaging (MRI) of brain
revealed atrophic of left cerebral hemisphere with mildly ventricular
dilatation, prominent paranasal and mastoid air cells, suggestive of
Dyke-Davidoff-Masson syndrome (DDMS). Conventional angiography showed narrowed
left internal carotid artery. There was also stenosed brachial artery, absent
left renal artery with narrowed infrarenal abdominal aorta. The patient was put
on antihypertensive drugs. We hypothesise that Takayasu arteritis and related
vascular occlusion is the cause of her acquired cerebral changes. A rare syndrome, Dyke-Davidoff-Masson Syndrome (DDMS), with a diagnostic
conundrum, and the way it was solved is presented. A 13-year-old boy presented
with recurrent seizures for the past 10 years. He had been treated with
anticonvulsant medication which was satisfactory at first but later the seizures
recurred. Recently, the frequency of the seizures increased with preictal
dizziness and postictal drowsiness. Physical examination revealed mild left
hemiparesis and left deviated gait irregularity. He was mentally alert but had
not achieved all the developmental milestones as compared to normal child of his
age. CT and MRI scan of the head showed hemiatrophic cerebral parenchyma with
prominent sulci and encephalomalacia. 24-hour intensive video EEG monitoring
revealed suppression of alpha rhythm and local slow wave activity on the side of
the atrophic hemisphere. PET-CT showed highly functional left cerebral
hemisphere and less functional right cerebral hemisphere. The patient underwent
functional hemispherectomy under neurophysiological monitoring and the
nonfunctional brain tissues were resected while selectively preserving the
functional areas detected by fMRI and PET-CT scan. During follow up, the patient
was seizure free as well as without difficulties in performing his daily
activities and communications. Functional hemispherectomy for DDMS patient has a
good prognosis. Prenatal ultrasonographic detection of unilateral cerebral ventriculomegaly
arises suspicion of pathological condition related to cerebrospinal fluid flow
obstruction or cerebral parenchimal pathology. Dyke-Davidoff-Masson syndrome is
a rare condition characterized by cerebral hemiatrophy, calvarial thickening,
skull and facial asymmetry, contralateral hemiparesis, cognitive impairment and
seizures. Congenital and acquired types are recognized and have been described,
mainly in late childhood, adolescence and adult ages. We describe a female
infant with prenatal diagnosis of unilateral left ventriculomegaly in which
early brain MRI and contrast enhanced-MRI angiography, showed cerebral left
hemiatrophy associated with reduced caliber of the left middle cerebral artery
revealing the characteristic findings of the Dyke-Davidoff-Masson syndrome.
Prenatal imaging, cerebral vascular anomaly responsible for the cerebral
hemiatrophy and the early clinical evolution have never been described before in
such a young child and complete the acquired clinical descriptions in older
children. Differential diagnosis, genetic investigations, neurophysiologic
assessments, short term clinical and developmental follow up are described.
Dyke-Davidoff-Masson syndrome must be ruled out in differential diagnosis of
fetal unilateral ventriculomegaly. Early clinical assessment, differential
diagnosis and cerebral imaging including cerebral MRI angiography allow the
clinicians to diagnose also in early infancy this rare condition. We describe a case of hemitrophy in a 12-year-old child presenting with
seizures, hemiplegia and mental retardation. Hemiatrophy of one cerebral
hemisphere is not frequently encountered in clinical practice. When this
develops early in life (during the first two years), certain cranial changes
like ipsilateral hypertrophy of the skull and sinuses occur. Asymmetry of
cerebral hemispheric growth with atrophy on one side, ipsilateral osseous
hypertrophy and hyper-pneumatization of sinuses with contralateral paresis are
features of Dyke Davidoff Masson Syndrome (DDMS). Probably vascular occlusion
was most important cause of hemiatrophy in our case. Dyke Davidoff Masson syndrome (DDMS) refers to atrophy or hypoplasia of one
cerebral hemisphere following a prior fetal or childhood insult. It has
characteristics of clinical and radiological changes. These changes include
hemiparesis, seizures, facial-asymmetry, and mental retardation. We present a
25-year-old man with crossed cerebrocerebellar atrophy and DDMS. His seizures
were well controlled using a combination of antiepileptic drugs. Dyke-Davidoff-Masson syndrome (DDMS) has cerebral hemiatrophy and compensatory
ipsilateral skull thickening, and is manifested by recurrent seizures and
hemiparesis. We present one case with typical DDMS, who had a brother suffering
from epilepsy with mild imaging abnormality relevant to DDMS and similar seizure
semiology. A 26-year-old man had a history of developmental delay, mental
retardation, hemiparesis and recurrent seizures. His brother, 23-year-old man
had also experienced recurrent seizures, but he had no neurological deficits.
Older brother experienced focal motor seizures with/without secondary
generalization. Sometimes, he noted an auditory aura. MRI demonstrated the
hemispheric atrophy with the adjacent bony hypertrophy. The seizures of younger
brother were mainly of the auditory type and the MRI showed mild hemispheric
atrophy with hippocampal sclerosis without any bony change. Our sibling cases
might have a familial predisposition and support the idea that clinical courses
and radiological findings of DDMS are varied even within one family. BACKGROUND: Dyke-Davidoff-Masson Syndrome (DDMS) is a rarely seen clinical
entity which is characterised by cerebral hemiatrophy, contralateral hemiparesis
and epilepsy. Radiological features are typical, such as unilateral atrophy of
the cerebral hemisphere and associated compensatory bone changes in the skull,
like thickening, enlargement of the paranasal sinuses and mastoid air cells.
CASE REPORT: In this article, we report the first case of DDMS associated with
epidermoid tumour and arachnoid cyst, who underwent operation for an epidermoid
tumour in the inter-hemispheric region. To our knowledge, this is the first
report of DDMS associated with multiple intracranial pathologies and this
association has not been previously described in the literature.
CONCLUSION: Any patient who receives DDMS in the light of clinical and
radiological findings should be investigated for concomitant pathologies.
Different sequences of MRI may be useful in the diagnosis of other intracranial
lesions. |
Which gene is involved in the development of Barth syndrome? | Tafazzin is a mitochondrial phospholipid transacylase, and its mutations cause Barth syndrome (BTHS) | Many advances have occurred in the field of Barth Syndrome biology in the 26
years since it was first described as an X-linked cardiomyopathy. Barth Syndrome
is the first human disease recognized in which the primary causative factor is
an alteration in cardiolipin remodeling. Cardiolipin is required for the optimal
function of many proteins within the mitochondria, particularly in the
respiratory chain and is involved in the mitochondrial-mediated apoptotic
process. The appropriate content of cardiolipin appears to be critical for these
functions. Cardiolipin is synthesized de novo in mitochondria and is rapidly
remodeled to produce CL enriched in linoleic acid. The Barth Syndrome gene TAZ
has been identified and expression of the gene yields proteins known as
tafazzins. Mutations in TAZ result in a decrease in tetra-linoleoyl species of
cardiolipin and an accumulation of monolysocardiolipin within cells from Barth
Syndrome patients. Although the protein product of the TAZ gene shows sequence
homology to the glycerolipid acyltransferase family of enzymes, its precise
biochemical function remains to be elucidated. In this review we highlight some
of the recent literature on cardiolipin metabolism and Barth Syndrome. Barth syndrome is an X-linked disorder characterized by cardiomyopathy, skeletal
myopathy, neutropenia, organic aciduria, and growth retardation caused by
mutations in tafazzin. The sequence similarity of tafazzin to acyltransferases
suggests a role in mitochondrial phospholipid metabolism. To study the role of
tafazzin in heart function and development, we created a knockdown zebrafish
model. Zebrafish tafazzin mRNA is first evident at 7 hours post-fertilization
(hpf). At 10 and 24 hpf, tafazzin mRNA is ubiquitous, with highest levels in the
head. By 51 hpf, expression becomes cardiac restricted. The tafazzin knockdown
created by antisense morpholino yolk injection resulted in dose-dependent
lethality, severe developmental and growth retardation, marked bradycardia and
pericardial effusions, and generalized edema, signs that resemble human Barth
syndrome heart failure. This knockdown phenotype was rescued by concomitant
injection of normal tafazzin mRNA. Abnormal cardiac development, with a linear,
nonlooped heart, and hypomorphic tail and eye development proves that tafazzin
is essential for overall zebrafish development, especially of the heart. The
tafazzin knockdown zebrafish provides an animal model similar to Barth syndrome
to analyze the severity of human mutants and to test potential treatments. Mutations in the human TAZ gene are associated with Barth Syndrome, an often
fatal X-linked disorder that presents with cardiomyopathy and neutropenia. The
TAZ gene encodes Tafazzin, a putative phospholipid acyltranferase that is
involved in the remodeling of cardiolipin, a phospholipid unique to the inner
mitochondrial membrane. It has been shown that the disruption of the Tafazzin
gene in yeast (Taz1) affects the assembly and stability of respiratory chain
Complex IV and its supercomplex forms. However, the implications of these
results for Barth Syndrome are restricted due to the additional presence of
Complex I in humans that forms a supercomplex with Complexes III and IV. Here,
we investigated the effects of Tafazzin, and hence cardiolipin deficiency in
lymphoblasts from patients with Barth Syndrome, using blue-native polyacrylamide
gel electrophoresis. Digitonin extraction revealed a more labile Complex
I/III(2)/IV supercomplex in mitochondria from Barth Syndrome cells, with Complex
IV dissociating more readily from the supercomplex. The interaction between
Complexes I and III was also less stable, with decreased levels of the Complex
I/III(2) supercomplex. Reduction of Complex I holoenzyme levels was observed
also in the Barth Syndrome patients, with a corresponding decrease in
steady-state subunit levels. We propose that the loss of mature cardiolipin
species in Barth Syndrome results in unstable respiratory chain supercomplexes,
thereby affecting Complex I biogenesis, respiratory activities and subsequent
pathology. The authors report a 6 yr old boy with Barth syndrome who presented with
cardiomyopathy, neutropenia and hypotonia. Urine gas chromatography showed high
level of 3-methylglutaconic acid. The DNA of both the patient and the mother
showed a heterozygous 3 bp deletion in exon 8 of the tafazzin gene. This
abnormality involves the deletion of the bases TGA starting at cDNA nucleotide
891 (c891_893delTGA), resulting in the absence of glutamic acid at codon 202
from a highly conserved area of the tafazzin protein, consistent with the
diagnosis of Barth syndrome. This is the first case report of Barth syndrome in
Arab population emphasizing the importance of detailed investigations in cases
of hereditary cardiomyopathy. Barth syndrome (BTHS), a rare, X-linked, recessive disease, is characterized by
neutropenia and cardiomyopathy. BTHS is caused by loss-of-function mutations of
the tafazzin (TAZ) gene. We developed a model of BTHS by transfecting human HL60
myeloid progenitor cells with TAZ-specific shRNAs. Results demonstrate a
significant downregulation in TAZ expression, mimicking the effects of naturally
occurring truncation mutations in TAZ. Flow cytometry analyses of cells with
TAZ-specific, but not scrambled, shRNAs demonstrate nearly twofold increase in
the proportion of annexin V-positive cells and significantly increased
dissipation of mitochondrial membrane potential as determined by DIOC6 staining.
Transfection of TAZ-specific shRNA had similar effects in U937 myeloid cells but
not in lymphoid cell lines. Further studies in HL60 myeloid progenitor cells
revealed aberrant release of cytochrome c from mitochondria and significantly
elevated levels of activated caspase-3 in response to TAZ knockdown. Treatment
with caspase-specific inhibitor zVAD-fmk resulted in substantially reduced
apoptosis to near-normal levels. These data suggest that neutropenia in BTHS is
attributable to increased dissipation of mitochondrial membrane potential,
aberrant release of cytochrome c, activation of caspase-3, and accelerated
apoptosis of myeloid progenitor cells, and that this defect can be partially
restored in vitro by treatment with caspase-specific inhibitors. Cardiolipin is a mitochondrion-specific phospholipid that stabilizes the
assembly of respiratory chain complexes, favoring full-yield operation. It also
mediates key steps in apoptosis. In Barth syndrome, an X chromosome-linked
cardiomyopathy caused by tafazzin mutations, cardiolipins display acyl chain
modifications and are present at abnormally low concentrations, whereas
monolysocardiolipin accumulates. Using immortalized lymphoblasts from Barth
syndrome patients, we showed that the production of abnormal cardiolipin led to
mitochondrial alterations. Indeed, the lack of normal cardiolipin led to changes
in electron transport chain stability, resulting in cellular defects. We found a
destabilization of the supercomplex (respirasome) I+III2+IVn but also decreased
amounts of individual complexes I and IV and supercomplexes I+III and III+IV. No
changes were observed in the amounts of individual complex III and complex II.
We also found decreased levels of complex V. This complex is not part of the
supercomplex suggesting that cardiolipin is required not only for the
association/stabilization of the complexes into supercomplexes but also for the
modulation of the amount of individual respiratory chain complexes. However,
these alterations were compensated by an increase in mitochondrial mass, as
demonstrated by electron microscopy and measurements of citrate synthase
activity. We suggest that this compensatory increase in mitochondrial content
prevents a decrease in mitochondrial respiration and ATP synthesis in the cells.
We also show, by extensive flow cytometry analysis, that the type II apoptosis
pathway was blocked at the mitochondrial level and that the mitochondria of
patients with Barth syndrome cannot bind active caspase-8. Signal transduction
is thus blocked before any mitochondrial event can occur. Remarkably, basal
levels of superoxide anion production were slightly higher in patients' cells
than in control cells as previously evidenced via an increased protein
carbonylation in the taz1Δ mutant in the yeast. This may be deleterious to cells
in the long term. The consequences of mitochondrial dysfunction and alterations
to apoptosis signal transduction are considered in light of the potential for
the development of future treatments. Cardiolipin is a major membrane phospholipid in the mitochondria and is
essential for cellular energy metabolism mediated through mitochondrial
oxidative phosphorylation. Recent studies indicate that it plays a diverse role
in cellular metabolism. Eukaryotic cardiolipin is synthesized de novo from
phosphatidic acid via the cytidine-5'-diphosphate-1,2-diacyl-sn-glycerol pathway
and is deacylated to monolysocardiolipin in order for it to be remodelled into
the form that is observed in mitochondrial membranes. This resynthesis of
deacylated cardiolipin from monolysocardiolipin occurs via the Barth Syndrome
gene product tafazzin and acyllysocardiolipin acyltransferase-1,
monolysocardiolipin acyltransferase-1 and the alpha subunit of trifunctional
protein. Heart failure is a disease condition in which the amount and type of
cardiolipin is altered. Several animal models have been generated to study the
role of altered cardiolipin in heart failure. In many of these models loss of
the tetralinoleoyl-cardiolipin species is observed during the development of the
heart failure. In the doxycycline inducible short hairpin RNA tafazzin knock
down mouse, loss of tetralinoleoyl-cardiolipin is associated with a
mitochondrial bioenergetic disruption. Reduction in mitochondrial supercomplex
formation and NADH dehydrogenase activity within these supercomplexes is
observed. Modulation of CL fatty acyl composition may serve as a therapeutic
strategy for the treatment of several pathologies including cardiac
dysfunction.We propose that increasing cardiolipin may improve mitochondrial
function and potentially serve as a therapy for diseases which exhibit
mitochondrial dysfunction involving reduced cardiolipin. Author information:
(1)1] Department of Cardiology, Boston Children's Hospital, Boston,
Massachusetts, USA. [2].
(2)1] Wyss Institute for Biologically Inspired Engineering, School of
Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts,
USA. [2].
(3)1] Wyss Institute for Biologically Inspired Engineering, School of
Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts,
USA. [2] Department of Genetics, Harvard Medical School, Boston, Massachusetts,
USA.
(4)Department of Cardiology, Boston Children's Hospital, Boston, Massachusetts,
USA.
(5)Wyss Institute for Biologically Inspired Engineering, School of Engineering
and Applied Sciences, Harvard University, Cambridge, Massachusetts, USA.
(6)1] Department of Cardiology, Boston Children's Hospital, Boston,
Massachusetts, USA. [2] Department of Medicine, Division of Genetics, Boston
Children's Hospital, Boston, Massachusetts, USA.
(7)1] Allele Biotechnology & Pharmaceuticals, Inc., San Diego, California, USA.
[2] Department of Photobiology and Bioengineering, The Scintillon Institute, San
Diego, California, USA.
(8)Department of Clinical Chemistry and Pediatrics, Laboratory of Genetic
Metabolic Diseases, Academic Medical Center, Amsterdam, The Netherlands.
(9)Department of Pathology, Center for Cardiovascular Biology and Institute for
Stem Cell and Regenerative Medicine, University of Washington, Seattle,
Washington, USA.
(10)1] Department of Pathology, Center for Cardiovascular Biology and Institute
for Stem Cell and Regenerative Medicine, University of Washington, Seattle,
Washington, USA. [2] Department of Bioengineering, Center for Cardiovascular
Biology, Institute for Stem Cell and Regenerative Medicine, University of
Washington, Seattle, Washington, USA. [3] Department of Medicine and Cardiology,
Center for Cardiovascular Biology, Institute for Stem Cell and Regenerative
Medicine, University of Washington, Seattle, Washington, USA.
(11)Department of Cell and Molecular Biology and Medicine, Karolinska
Institutet, Stockholm, Sweden.
(12)Division of Metabolism, Kennedy Krieger Institute, Baltimore, Maryland, USA.
(13)1] Wyss Institute for Biologically Inspired Engineering, School of
Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts,
USA. [2] Harvard Stem Cell Institute, Harvard University, Cambridge,
Massachusetts, USA.
(14)1] Department of Cardiology, Boston Children's Hospital, Boston,
Massachusetts, USA. [2] Harvard Stem Cell Institute, Harvard University,
Cambridge, Massachusetts, USA. Tafazzin, a mitochondrial acyltransferase, plays an important role in
cardiolipin side chain remodeling. Previous studies have shown that dysfunction
of tafazzin reduces cardiolipin content, impairs mitochondrial function, and
causes dilated cardiomyopathy in Barth syndrome. Reactive oxygen species (ROS)
have been implicated in the development of cardiomyopathy and are also the
obligated byproducts of mitochondria. We hypothesized that tafazzin knockdown
increases ROS production from mitochondria, and a mitochondria-targeted
antioxidant prevents tafazzin knockdown induced mitochondrial and cardiac
dysfunction. We employed cardiac myocytes transduced with an adenovirus
containing tafazzin shRNA as a model to investigate the effects of the
mitochondrial antioxidant, mito-Tempo. Knocking down tafazzin decreased steady
state levels of cardiolipin and increased mitochondrial ROS. Treatment of
cardiac myocytes with mito-Tempo normalized tafazzin knockdown enhanced
mitochondrial ROS production and cellular ATP decline. Mito-Tempo also
significantly abrogated tafazzin knockdown induced cardiac hypertrophy,
contractile dysfunction, and cell death. We conclude that mitochondria-targeted
antioxidant prevents cardiac dysfunction induced by tafazzin gene knockdown in
cardiac myocytes and suggest mito-Tempo as a potential therapeutic for Barth
syndrome and other dilated cardiomyopathies resulting from mitochondrial
oxidative stress. Barth syndrome (BTHS) is an X-linked recessive disease primarily affecting
males. Clinically, the disease is characterized by hypertrophic or dilated
cardiomyopathy, skeletal myopathy, chronic/cyclic neutropenia,
3-methylglutaconic aciduria, growth retardation and respiratory chain
dysfunction. It is caused by mutations in the TAZ gene coding for the tafazzin
protein which is responsible for cardiolipin remodeling. In this work, we
present a novel pathogenic TAZ mutation c.83T>A, p.Val28Glu, found in mosaic
form in almost all female members of a Polish family. Sanger sequencing of DNA
from peripheral blood and from epithelial cells showed female mosaicism in three
generations. This appears to be a new mechanism of inheritance and further
research is required in order to understand the mechanism of this mosaicism. We
conclude that BTHS genetic testing should include two or more tissues for women
that appear to be noncarriers when blood DNA is initially tested. The results of
our study should not only be applicable to BTHS families, but also to families
with other X-linked diseases. |
What is the treatment of subacute thyroiditis? | Common treatment of subacute thyroiditis is with anti-inflammatory drug agents, namely corticosteroids | BACKGROUND: Propylthiouracil (PTU) therapy is associated with a variety of
adverse reactions, among the most rare being interstitial pneumonia. To date,
this has been reported in four Asian patients with autoimmune hyperthyroidism.
Here we describe a Caucasian woman who developed a bronchiolitis obliterans
organizing pneumonia (BOOP)-like interstitial pneumonia after PTU administration
for amiodarone-induced thyrotoxicosis.
PATIENT FINDINGS: The patient was a 68-year-old woman who had been treated with
amiodarone for chronic atrial fibrillation starting in May 2004. She had been a
heavy smoker with a history of hypertension but no dust exposures. In October
2006, amiodarone was stopped after she developed thyrotoxicosis. In January 2007
serum thyroid-stimulating hormone (TSH) was 0.01 mIU/L (0.35-4.94) and free T4
was 17.5 pg/mL (7 to 15). She was initially started on methimazole and then
changed to PTU after she developed pruritus. She developed severe dyspnea 9
months after starting PTU. At the time she was also taking warfarin, enalapril,
and sotalol. Chest X-ray showed diffuse interstitial peripheral opacities and
transbronchial lung biopsy revealed subacute lung injury with organizing
pneumonia with hyperplasia of the alveolar type 2 pneumocytes, and
characteristics of BOOP-like interstitial pneumonia. Signs and symptoms
progressively improved after PTU discontinuation as confirmed at X-ray and
computed tomography (CT) scan of the chest and by respiratory function tests.
She has been recurrence free for 4 years after stopping PTU.
SUMMARY: This woman of Caucasian ancestral origin developed BOOP-like
interstitial pneumonia after PTU treatment for apparent amiodarone-induced
thyrotoxicosis, with resolution of her lung disease after stopping PTU. Tests
for TSH receptor antibodies, thyroid peroxidase antibodies, and antinuclear
cytoplasmic autoantibody were negative. Thyroid ultrasound was consistent with
thyroiditis without nodules.
CONCLUSIONS: PTU-associated interstitial pneumonia is not limited to patients of
Asian origin or those with autoimmune thyroid disease. PTU must be withdrawn in
the presence of respiratory symptoms and documented interstitial pneumonia.
X-ray films, CT-scan, respiratory function tests, and lung biopsy are needed to
diagnose PTU-induced interstitial pneumonia with certainty and to monitor the
evolution of the disease after PTU discontinuation. BACKGROUND: Oral glucocorticoids are administered in moderate and severe cases
of subacute thyroiditis (SAT), providing dramatic relief from pain and fever.
However, there have been no reports regarding the optimal dose of prednisolone
(PSL) for treatment of SAT. In this study, we used 15 mg/day of PSL as the
initial dosage and tapered it by 5 mg every 2 weeks. We assessed the
effectiveness of this treatment protocol.
METHODS: We examined 384 consecutive and untreated patients with SAT who visited
our thyroid clinic between February 2005 and December 2008. We excluded patients
who did not fit our protocol, and the final number of subjects was 219. When
patients complained of pain in their neck or C-reactive protein (CRP) was still
high, physicians were able to extend the tapering of the dose of PSL or increase
it at 2-week intervals. The endpoint of the study was the duration of the PSL
medication. We also compared the severity of thyrotoxicosis and rate of
hypothyroidism after SAT between the short medication group (patients who
recovered within 6 weeks) and long medication group (patients who recovered in
12 weeks or more).
RESULTS: The number of patients whose thyroiditis improved within 6 weeks and
did not recur was 113 (51.6%), and 61 (27.9%) improved within 7 to 8 weeks and
did not have a recurrence. The longest duration was 40 weeks. Seven patients
(3.2%) needed increases in the dosage of PSL. Thyroid hormone (free thyroxine
and free triiodothyronine) levels measured at the initial visit in the short
medication group were significantly higher than those in the long medication
group (p<0.05). Serum CRP, male-to-female ratio, body weight, and age showed no
differences between the two groups. There were no differences in the rate of
hypothyroidism after SAT between the two groups (p=0.0632).
CONCLUSIONS: The treatment protocol that we employed had 15 mg/day of PSL as the
initial dosage for the treatment of SAT, with tapering by 5 mg every 2 weeks,
and was effective and safe for Japanese patients. However, 20% of patients with
SAT needed longer than 8 weeks to recover from the inflammation. |
What are the effects of BMAL1 deficiency? | BMAL1 deficiency is associated with premature aging and reduced lifespan and BMAL1 deficiency leads to development of stress induced senescence in vivo. Down-regulation of Bmal1 also accelerates the development of tumours, adipogenesis. | Deficiency of the transcription factor BMAL1, a core component of the circadian
clock, results in an accelerated aging phenotype in mice. The circadian clock
regulates many physiological processes and was recently implicated in control of
brain-based activities, such as memory formation and the regulation of emotions.
Aging is accompanied by the decline in brain physiology, particularly decline in
the response and adaptation to novelty. We investigated the role of the
circadian clock in exploratory behavior and habituation to novelty using the
open field paradigm. We found that mice with a deficiency of the circadian
transcription factor BMAL1 display hyperactivity in novel environments and
impaired intra- and intersession habituation, indicative of defects in short-
and long-term memory formation. In contrast, mice double-deficient for the
circadian proteins CRY1 and CRY2 (repressors of the BMAL1-mediated
transcription) demonstrate reduced activity and accelerated habituation when
compared to wild type mice. Mice with mutation in theClock gene (encoding the
BMAL1 transcription partner) show normal locomotion, but increased rearing
activity and impaired intersession habituation. BMAL1 is highly expressed in the
neurons of the hippocampus - a brain region associated with spatial memory
formation; BMAL1 deficiency disrupts circadian oscillation in gene expression
and reactive oxygen species homeostasis in the brain, which may be among the
possible mechanisms involved. Thus, we suggest that the BMAL1:CLOCK activity is
critical for the proper exploratory and habituation behavior, and that the
circadian clock prepares organism for a new round of everyday activities through
optimization of behavioral learning. Circadian clock is implicated in the regulation of aging. The transcription
factor CLOCK, a core component of the circadian system, operates in complex with
another circadian clock protein BMAL1. Recently it was demonstrated that BMAL1
deficiency results in premature aging in mice. Here we investigate the aging of
mice deficient for CLOCK protein. Deficiency of the CLOCK protein significantly
affects longevity: the average lifespan of Clock-/- mice is reduced by 15%
compared with wild type mice, while maximum lifespan is reduced by more than
20%. CLOCK deficiency also results in the development of two age-specific
pathologies in these mice, cataracts and dermatitis, at a much higher rate than
in wild type mice. In contrast to BMAL1 deficient animals, Clock-/- mice do not
develop a premature aging phenotype and do not develop the multiple
age-associated pathologies characteristic of BMAL1 deficiency. Thus, although
CLOCK and BMAL1 form a transcriptional complex, the physiological result of
their deficiency is different. Our results suggest that CLOCK plays an important
role in aging, specifically; CLOCK activity is critical for the regulation of
normal physiology and aging of the lens and skin. Deficiency of the circadian clock transcriptional factor BMAL1 results in the
development of premature aging in mice. In agreement with the accelerated aging
phenotype, we observed an increase in the number of senescent cells in different
tissues (lungs, liver and spleen) of Bmal1(-/-) mice, which suggests the
important role of BMAL1 in the control of senescence in vivo. However, no
difference in the rate of proliferation and senescence between primary
fibroblasts isolated from wild-type and Bmal1(-/-) mice has been detected,
suggesting that BMAL1 does not play a significant role in replicative senescence
in vitro. BMAL1 deficient fibroblasts had an increased sensitivity to hydrogen
peroxide treatment, and reduced sensitivity to DNA damaging anticancer drugs
etoposide and daunorubicin. Increased sensitivity of Bmal1(-/-) cells to
oxidative stress was p53 independent and correlated with the disrupted
regulation of reactive oxygen species (ROS) homeostasis in BMAL1 deficient
cells: indeed, circadian oscillations of ROS level can be induced in wild-type
but not in Bmal1(-/-) cells. We propose that BMAL1 is important for the
regulation of oxidative stress and DNA damage responses, while deregulation of
these processes upon BMAL1 deficiency leads to development of stress induced
senescence in vivo. Circadian clocks in adipose tissue are known to regulate adipocyte biology.
Although circadian dysregulation is associated with development of obesity, the
underlying mechanism has not been established. Here we report that disruption of
the clock gene, brain and muscle Arnt-like 1 (Bmal1), in mice led to increased
adipogenesis, adipocyte hypertrophy, and obesity, compared to wild-type (WT)
mice. This is due to its cell-autonomous effect, as Bmal1 deficiency in
embryonic fibroblasts, as well as stable shRNA knockdown (KD) in 3T3-L1
preadipocyte and C3H10T1/2 mesenchymal stem cells, promoted adipogenic
differentiation. We demonstrate that attenuation of Bmal1 function resulted in
down-regulation of genes in the canonical Wnt pathway, known to suppress
adipogenesis. Promoters of these genes (Wnt10a, β-catenin, Dishevelled2, TCF3)
displayed Bmal1 occupancy, indicating direct circadian regulation by Bmal1. As a
result, Wnt signaling activity was attenuated by Bmal1 KD and augmented by its
overexpression. Furthermore, stabilizing β-catenin through Wnt ligand or GSK-3β
inhibition achieved partial restoration of blunted Wnt activity and suppression
of increased adipogenesis induced by Bmal1 KD. Taken together, our study
demonstrates that Bmal1 is a critical negative regulator of adipocyte
development through transcriptional control of components of the canonical Wnt
signaling cascade, and provides a mechanistic link between circadian disruption
and obesity. |
Which histone modifications are associated with Polycomb group (PcG) proteins? | A member of the polycomb repressive complex 2 (PRC2) directly mediates the addition of K27me3 to histone H3, a modification associated with heterochromatin, and it is believed that this activity mediates transcriptional repression. At the same time PRC2 activity results in a global increase in H3K27 acetylation. Some members of the PcG display affinity towards both histone H3 trimethylated at K9 and H3K27me3, and one CD prefers K9me3. | The chromodomain (CD) of the Drosophila Polycomb protein exhibits preferential
binding affinity for histone H3 when trimethylated at lysine 27. Here we have
investigated the five mouse Polycomb homologs known as Cbx2, Cbx4, Cbx6, Cbx7,
and Cbx8. Despite a high degree of conservation, the Cbx chromodomains display
significant differences in binding preferences. Not all CDs bind preferentially
to K27me3; rather, some display affinity towards both histone H3 trimethylated
at K9 and H3K27me3, and one CD prefers K9me3. Cbx7, in particular, displays
strong affinity for both H3K9me3 and H3K27me3 and is developmentally regulated
in its association with chromatin. Cbx7 associates with facultative
heterochromatin and, more specifically, is enriched on the inactive X
chromosome. Finally, we find that, in vitro, the chromodomain of Cbx7 can bind
RNA and that, in vivo, the interaction of Cbx7 with chromatin, and the inactive
X chromosome in particular, depends partly on its association with RNA. We
propose that the capacity of this mouse Polycomb homolog to associate with the
inactive X chromosome, or any other region of chromatin, depends not only on its
chromodomain but also on the combination of histone modifications and RNA
molecules present at its target sites. DNA methylation patterns are established and maintained by three DNA
methyltransferases (DNMT): DNMT1, DNMT3A, and DNMT3B. Although essential for
development, methylation patterns are frequently disrupted in cancer and
contribute directly to carcinogenesis. Recent studies linking polycomb group
repression complexes (PRC1 and PRC2) to the DNMTs have begun to shed light on
how methylation is targeted. We identified previously a panel of genes regulated
by DNMT3B. Here, we compare these with known polycomb group targets to show that
approximately 47% of DNMT3B regulated genes are also bound by PRC1 or PRC2. We
chose 44 genes coregulated by DNMT3B and PRC1/PRC2 to test whether these
criteria would accurately identify novel targets of epigenetic silencing in
colon cancer. Using reverse transcription-PCR, bisulfite genomic sequencing, and
pyrosequencing, we show that the majority of these genes are frequently silenced
in colorectal cancer cell lines and primary tumors. Some of these, including
HAND1, HMX2, and SIX3, repressed cell growth. Finally, we analyzed the histone
code, DNMT1, DNMT3B, and PRC2 binding by chromatin immunoprecipitation at
epigenetically silenced genes to reveal a novel link between DNMT3B and the mark
mediated by PRC1. Taken together, these studies suggest that patterns of
epigenetic modifiers and the histone code influence the propensity of a gene to
become hypermethylated in cancer and that DNMT3B plays an important role in
regulating PRC1 function. Polycomb group (PcG) proteins are transcriptional repressors, which regulate
proliferation and cell fate decisions during development, and their deregulated
expression is a frequent event in human tumours. The Polycomb repressive complex
2 (PRC2) catalyzes trimethylation (me3) of histone H3 lysine 27 (K27), and it is
believed that this activity mediates transcriptional repression. Despite the
recent progress in understanding PcG function, the molecular mechanisms by which
the PcG proteins repress transcription, as well as the mechanisms that lead to
the activation of PcG target genes are poorly understood. To gain insight into
these mechanisms, we have determined the global changes in histone modifications
in embryonic stem (ES) cells lacking the PcG protein Suz12 that is essential for
PRC2 activity. We show that loss of PRC2 activity results in a global increase
in H3K27 acetylation. The methylation to acetylation switch correlates with the
transcriptional activation of PcG target genes, both during ES cell
differentiation and in MLL-AF9-transduced hematopoietic stem cells. Moreover, we
provide evidence that the acetylation of H3K27 is catalyzed by the
acetyltransferases p300 and CBP. Based on these data, we propose that the PcG
proteins in part repress transcription by preventing the binding of
acetyltransferases to PcG target genes. Polycomb-group proteins are transcriptional repressors with essential roles in
embryonic development. Polycomb repressive complex 2 (PRC2) contains the
methyltransferase activity for Lys27. However, the role of other histone
modifications in regulating PRC2 activity is just beginning to be understood.
Here we show that direct recognition of methylated histone H3 Lys36 (H3K36me), a
mark associated with activation, by the PRC2 subunit Phf19 is required for the
full enzymatic activity of the PRC2 complex. Using NMR spectroscopy, we provide
structural evidence for this interaction. Furthermore, we show that Phf19 binds
to a subset of PRC2 targets in mouse embryonic stem cells and that this is
required for their repression and for H3K27me3 deposition. These findings show
that the interaction of Phf19 with H3K36me2 and H3K36me3 is essential for PRC2
complex activity and for proper regulation of gene repression in embryonic stem
cells. |
Where is the protein CLIC1 localized? | CLIC1 is an intracellular chloride ion channel that is localized both to the nucleus and to the cytolasm. | ERK7, a member of the mitogen-activated protein kinase family, has a
carboxyl-terminal tail that is required for ERK7 activation, cellular
localization, and its ability to inhibit DNA synthesis. To identify proteins
that interact with ERK7, we utilized a yeast two-hybrid screen with the
COOH-terminal tail of ERK7 as bait and isolated the cDNA for a novel protein
termed CLIC3. The interaction between CLIC3 and ERK7 in mammalian cells was
confirmed by co-immunoprecipitation. CLIC3 has significant homology to human
intracellular chloride channels 1 (NCC27/CLIC1) and 2 and bovine kidney chloride
channel p64. Like NCC27/CLIC1, CLIC3 is predomitly localized in the nucleus
and stimulates chloride conductance when expressed in cells. Taken together,
these results suggest that CLIC3 is a new member of the human CLIC family. The
observed interaction between CLIC3 and ERK7 is the first demonstration of a
stable complex between a protein that activates chloride ion transport and a
member of the mitogen-activated protein kinase family of signal transducers. The
specific association of CLIC3 with the COOH-terminal tail of ERK7 suggests that
CLIC3 may play a role in the regulation of cell growth. OBJECTIVE: To study the localization and expression of CLIC1 in mouse
hepatocarcinoma ascites cell lines with different metastatic potentials.
METHODS: Mouse hepatocarcinoma ascites models (a high potential of lymphatic
metastasis cell line-Hca-F, and a low potential of lymphatic metastasis cell
line-Hca-P) were investigated using fluorescent two-dimensional difference-gel
electrophoresis (2-D DIGE) and mass spectrometry for detecting the localization
and expression of CLIC1. Immunofluorescence, immunocytochemistry and Western
blot were used to assess CLIC1 protein status in the two cell lines.
RESULTS: CLIC1 expression was obtained in the cytoplasm and plasma membrane of
cells in both cell lines. 2-D DIGE showed that CLIC1 was overexpressed in Hca-F
cells, 1.6 folds higher than that of the Hca-P cells. Hca-F cells also had a
higher integral membrane CLIC1 in the Hca-P cells.
CONCLUSIONS: Although CLIC1 expression is detected in both Hca-F and Hca-P cell
lines, a higher protein expression level is present in Hca-F cells. CLIC1 may
play an important role in tumor metastasis. |
List phosphorylation consensus motifs for Casein Kinase 1 (CK1)? | The most common consensus motifs for CK1 are: pSer-Xaa-Xaa-Ser, K/R-X-K/R-X-X-S/T, SLS and acidic cluster motifs and SerP/ThrP-Xaa-Xaa-Ser/Thr. | The major phosphorylation site for both casein kinase-2 (CK2) and casein
kinase-1 (CK1) in protein phosphatase-1 (PP-1) inhibitor-2 (I-2) is Ser86. Minor
phosphorylation sites affected by either CK2 or CK1 are Ser120/Ser121 and
Ser174, respectively. A synthetic peptide of 25 amino acids encompassing
residues 67-93 of I-2 is phosphorylated by either CK2 or CK1 at its seryl
residue corresponding to Ser86 with higher Vmax and Km values similar to those
of the intact protein (9 vs 7.2 microM and 14.2 vs 5.3 microM with CK2 and CK1,
respectively). No detectable phosphorylation of this peptide which also includes
the glycogen synthase kinase-3 (GSK-3) site (Thr72), could be observed with
either GSK-3 or p34cdc2 kinase whether or not its seryl residue equivalent to
Ser86 had been previously phosphorylated by CK2. Shorter derivatives of
I-2(67-93), encompassing residues 72-93 and 78-93, are also readily
phosphorylated by both CK1 and CK2, with phosphorylation efficiencies similar to
those of the parent peptide. A synthetic heptadecapeptide reproducing the
phosphoacceptor site around Ser120/Ser121 is phosphorylated by CK2, but not to
any detectable extent by CK1, with a Km value fivefold higher than that of the
corresponding pentadecapeptide including Ser86 (78-93). A synthetic
pentadecapeptide (166-180) reproducing the phosphoacceptor site around Ser174 is
phosphorylated by CK1 less efficiently than the pentadecapeptide including its
main phosphorylation site (78-93) (Km 280 microM vs 33 microM). This peptide is
readily phosphorylated by CK2 as well, although it lacks the canonical consensus
sequence for CK2 and its Ser174 is almost unaffected by CK2 in intact I-2. These
data provide the clear-cut demonstration that the consensus sequence with
N-terminal prephosphorylated residue(s), SerP/ThrP-Xaa-Xaa-Ser/Thr, [Flotow, H.,
Graves, P. R., Wang, A., Fiol, C. J., Roeske, R. W. & Roach, P. J. (1990) J.
Biol. Chem. 265, 14264-14269; Meggio, F., Perich, J. W., Reynolds, E. C. &
Pinna, L. A. (1991) FEBS Lett. 283, 303-306] is not always required to achieve
efficient and high-affinity phosphorylation by CK1. They also show that the
specificity determits for I-2 phosphorylation by either CK2 or CK1, but not
by GSK3, are entirely grounded on local structural features of the
phosphoacceptor site, being only marginally affected by the overall structure of
I-2. Protein kinase casein kinase 1 (CK1) phosphorylates Ser-45 of beta-catenin,
"priming" the subsequent phosphorylation by glycogen synthase-3 of residues 41,
37, and 33. This concerted phosphorylation of beta-catenin signals its
degradation and prevents its function in triggering cell division. The sequence
around Ser-45 does not conform to the canonical consensus for CK1 substrates,
which prescribes either phosphoamino acids or acidic residues in position n-3
from the target serine. However, the beta-catenin sequence downstream from
Ser-45 is very similar to a sequence recognized by CK1 in nuclear factor for
activated T cells 4. The common features include an SLS motif followed two to
five residues downstream by a cluster of acidic residues. Synthetic peptides
reproducing residues 38-65 of beta-catenin were assayed with purified rat liver
CK1 or recombit CK1 alpha and CK1 alpha L from zebrafish. The results
demonstrate that SLS and acidic cluster motifs are crucial for CK1 recognition.
Pro-44 and Pro-52 are also important for efficient phosphorylation. Similar
results were obtained with the different isoforms of CK1. Phosphorylation of
mutants of full-length recombit beta-catenin from zebrafish confirmed the
importance of the SLS and acidic cluster motifs. A search for proteins with
similar motifs yielded, among other proteins, adenomatous polyposis coli,
previously found to be phosphorylated by CK1. There is a strong correlation of
beta-catenin mutations found in thyroid tumors with the motifs recognized by CK1
in this protein. The protein kinase CK1 phosphorylates serine residues that are located close to
another phosphoserine in the consensus pSer-Xaa-Xaa-Ser. This specificity
generates regions in its target proteins containing two or more neighbouring
phosphoserine residues, termed here multisite phosphorylation domains (MPDs). In
this paper, we demonstrate that D4476 is a potent and rather selective inhibitor
of CK1 in vitro and in cells. In H4IIE hepatoma cells, D4476 specifically
inhibits the phosphorylation of endogenous forkhead box transcription factor O1a
(FOXO1a) on Ser322 and Ser325 within its MPD, without affecting the
phosphorylation of other sites. Our results indicate that these residues are
targeted by CK1 in vivo and that the CK1-mediated phosphorylation of the MPD is
required for accelerated nuclear exclusion of FOXO1a in response to IGF-1 and
insulin. D4476 is much more potent and specific than IC261 or CKI-7, and is
therefore the most useful CK1 inhibitor currently available for identifying
physiological substrates of CK1. A novel phosphorylation motif for casein kinase 1 (CK1) in response to two
sulfated lipids [sulfatide and cholesterol-3-sulfate (SCS)] was determined,
using three functional proteins [myelin basic protein (MBP), tau protein (TP)
and RhoA (a small GTPase)] and five synthetic MBP peptides as phosphate
acceptors for the kinase in vitro. It was found that (i) MBP, p8 (positions
38-118) cleaved from MBP, and a synthetic peptide M103 were effectively
phosphorylated by CK1delta in the presence of SCS; (ii) sulfatide in comparison
with CH-3S highly enhanced autophosphorylation of CK1delta; (iii) SCS had a high
binding affinity with MBP and peptide M103, but not other MBP peptides lacking
K-G-R; and (iv) a novel consensus phosphorylation motif (K/R-X-K/R-X-X-S/T) for
CK1 was identified among several SCS-binding proteins (SCS-BPs) and three CK1
isoforms (delta, epsilon and gamma). The binding of SCS to two basic brain
proteins (MBP and TP) resulted in the high stimulation of their phosphorylation
by three CK1 isoforms (alpha, delta and epsilon), but not CK1gamma. In contrast,
an acidic protein (RhoA) was effectively phosphorylated by CK1delta in the
presence of SCS, and also highly phosphorylated by CK1gamma in the presence of
sulfatide. Our results presented here suggest that (i) sulfatide may function as
an effective stimulator for autophosphorylation of CK1; and (ii) cellular
SCS-binding proteins, containing novel phosphorylation motifs for CK1, may be
preferentially phosphorylated by CK1 with isoform specificity at the highly
accumulated level of SCS in the brain. In eukaryotes, protein phosphorylation of serine, threonine or tyrosine residues
by protein kinases plays an important role in many cellular processes. Members
of the protein kinase CK1 family usually phosphorylate residues of serine that
are close to other phosphoserine in a consensus motif of pS-X-X-S, and they are
implicated in the regulation of a variety of physiological processes as well as
in pathologies like cancer and Alzheimer's disease. Using a structure-based
virtual screening (SBVS) approach we have identified two anthraquinones as novel
CK1delta inhibitors. These amino-anthraquinone analogs (derivatives 1 and 2) are
among the most potent and selective CK1delta inhibitors known today (IC(50)=0.3
and 0.6 microM, respectively). |
What medication were compared in the ROCKET AF Trial? | ROCKET-AF trial compared rivaroxaban and warfarin for for prevention of stroke and embolism. | BACKGROUND: The overall analysis of the rivaroxaban versus warfarin in Japanese
patients with atrial fibrillation (J-ROCKET AF) trial revealed that rivaroxaban
was not inferior to warfarin with respect to the primary safety outcome. In
addition, there was a strong trend for a reduction in the rate of
stroke/systemic embolism with rivaroxaban compared with warfarin.
METHODS: In this subanalysis of the J-ROCKET AF trial, we investigated the
consistency of safety and efficacy profile of rivaroxaban versus warfarin among
the subgroups of patients with previous stroke, transient ischemic attack, or
non-central nervous system systemic embolism (secondary prevention group) and
those without (primary prevention group).
RESULTS: Patients in the secondary prevention group were 63.6% of the overall
population of J-ROCKET AF. In the secondary prevention group, the rate of the
principal safety outcome (% per year) was 17.02 in rivaroxaban-treated patients
and 18.26 in warfarin-treated patients (hazard ratio [HR] 0.95; 95% confidence
interval [CI] 0.70-1.29), while the rate of the primary efficacy endpoint was
1.66 in rivaroxaban-treated patients and 3.25 in warfarin-treated patients (HR
0.51; 95% CI 0.23-1.14). There were no significant interactions in the principal
safety and the primary efficacy endpoints of rivaroxaban compared to warfarin
between the primary and secondary prevention groups (P=.090 and .776 for both
interactions, respectively).
CONCLUSIONS: The safety and efficacy profile of rivaroxaban compared with
warfarin was consistent among patients in the primary prevention group and those
in the secondary prevention group. OBJECTIVES: The purpose of this study was to understand the possible risk of
discontinuation in the context of clinical care.
BACKGROUND: Rivaroxaban is noninferior to warfarin for preventing stroke in
atrial fibrillation patients. Concerns exist regarding possible increased risk
of stroke and non-central nervous system (CNS) thromboembolic events early after
discontinuation of rivaroxaban.
METHODS: We undertook a post-hoc analysis of data from the ROCKET AF
(Rivaroxaban Once-Daily, Oral, Direct Factor Xa Inhibition Compared With Vitamin
K Antagonism for Prevention of Stroke and Embolism Trial in Atrial Fibrillation,
n = 14,624) for stroke or non-CNS embolism within 30 days after temporary
interruptions of 3 days or more, early permanent study drug discontinuation, and
end-of-study transition to open-label therapy.
RESULTS: Stroke and non-CNS embolism occurred at similar rates after temporary
interruptions (rivaroxaban: n = 9, warfarin: n = 8, 6.20 vs. 5.05/100
patient-years, hazard ratio [HR]: 1.28, 95% confidence interval [CI]: 0.49 to
3.31, p = 0.62) and after early permanent discontinuation (rivaroxaban: n = 42,
warfarin: n = 36, 25.60 vs. 23.28/100 patient-years, HR: 1.10, 95% CI: 0.71 to
1.72, p = 0.66). Patients transitioning to open-label therapy at the end of the
study had more strokes with rivaroxaban (n = 22) versus warfarin (n = 6, 6.42
vs. 1.73/100 patient-years, HR: 3.72, 95% CI: 1.51 to 9.16, p = 0.0044) and took
longer to reach a therapeutic international normalized ratio with rivaroxaban
versus warfarin. All thrombotic events within 30 days of any study drug
cessation (including stroke, non-CNS embolism, myocardial infarction, and
vascular death) were similar between groups (HR: 1.02, 95% CI: 0.83 to 1.26, p =
0.85).
CONCLUSIONS: In atrial fibrillation patients who temporarily or permanently
discontinued anticoagulation, the risk of stroke or non-CNS embolism was similar
with rivaroxaban or warfarin. An increased risk of stroke and non-CNS embolism
was observed in rivaroxaban-treated patients compared with warfarin-treated
patients after the end of the study, underscoring the importance of therapeutic
anticoagulation coverage during such a transition. The majority of patients with nonvalvular atrial fibrillation (AF) will require
anticoagulation therapy for reducing the risk of stroke, the most devastating
complication of AF. Although traditionally vitamin K antagonists have been used
for this purpose, they have important limitations that interfere with their use
in clinical practice. Different clinical trials have shown the benefits of new
oral anticoagulants over warfarin, but patients included in the ROCKET-AF trial
were found to be at a higher risk of AF-related complications. Moreover,
rivaroxaban has been proven to be effective and safe in patients with AF and
moderate renal dysfunction as well as in those with ischemic heart disease.
Rivaroxaban is taken only once daily; this may improve medication adherence and,
secondarily, it provides a higher protection and reduction in the risk of
stroke. This article provides an extensive review of the available evidence
about rivaroxaban, with a special focus on nonvalvular AF. OBJECTIVES: This study sought to investigate the outcomes following
cardioversion or catheter ablation in patients with atrial fibrillation (AF)
treated with warfarin or rivaroxaban.
BACKGROUND: There are limited data on outcomes following cardioversion or
catheter ablation in AF patients treated with factor Xa inhibitors.
METHODS: We compared the incidence of electrical cardioversion (ECV),
pharmacologic cardioversion (PCV), or AF ablation and subsequent outcomes in
patients in a post hoc analysis of the ROCKET AF (Efficacy and Safety Study of
Rivaroxaban With Warfarin for the Prevention of Stroke and Non-Central Nervous
System Systemic Embolism in Patients With Non-Valvular Atrial Fibrillation)
trial.
RESULTS: Over a median follow-up of 2.1 years, 143 patients underwent ECV, 142
underwent PCV, and 79 underwent catheter ablation. The overall incidence of ECV,
PCV, or AF ablation was 1.45 per 100 patient-years (n = 321; 1.44 [n = 161] in
the warfarin arm, 1.46 [n = 160] in the rivaroxaban arm). The crude rates of
stroke and death increased in the first 30 days after cardioversion or ablation.
After adjustment for baseline differences, the long-term incidence of stroke or
systemic embolism (hazard ratio [HR]: 1.38; 95% confidence interval [CI]: 0.61
to 3.11), cardiovascular death (HR: 1.57; 95% CI: 0.69 to 3.55), and death from
all causes (HR: 1.75; 95% CI: 0.90 to 3.42) were not different before and after
cardioversion or AF ablation. Hospitalization increased after cardioversion or
AF ablation (HR: 2.01; 95% CI: 1.51 to 2.68), but there was no evidence of a
differential effect by randomized treatment (p value for interaction = 0.58).
The incidence of stroke or systemic embolism (1.88% vs. 1.86%) and death (1.88%
vs. 3.73%) were similar in the rivaroxaban-treated and warfarin-treated groups.
CONCLUSIONS: Despite an increase in hospitalization, there were no differences
in long-term stroke rates or survival following cardioversion or AF ablation.
Outcomes were similar in patients treated with rivaroxaban or warfarin. (An
Efficacy and Safety Study of Rivaroxaban With Warfarin for the Prevention of
Stroke and Non-Central Nervous System Systemic Embolism in Patients With
Non-Valvular Atrial Fibrillation [ROCKET AF]; NCT00403767). OBJECTIVES: Based on clinical trials the oral anticoagulants (OACs) apixaban,
dabigatran, and rivaroxaban are efficacious for reducing stroke risk for
non-valvular atrial fibrillation (NVAF) patients. Based on the clinical trials,
this study evaluated the medical costs for clinical events among NVAF patients
≥75 and <75 years of age treated with individual OACs vs warfarin.
METHODS: Rates for primary and secondary efficacy and safety outcomes (i.e.,
clinical events) among NVAF patients receiving warfarin or each of the OACs were
determined for NVAF populations aged ≥75 years and <75 years of age from the OAC
vs warfarin trials. One-year incremental costs among patients with clinical
events were obtained from published literature and inflation adjusted to 2010
costs. Medical costs, excluding medication costs, for clinical events associated
with each OAC and warfarin were then estimated and compared.
RESULTS: Among NVAF patients aged ≥75, compared to warfarin, use of either
apixaban or rivaroxaban was associated with a reduction in medical costs per
patient year (apixaban = -$825, rivaroxaban =-$23), while dabigatran use was
associated with increased medical costs of $180 per patient year. Among NVAF
patients <75 years of age medical costs per patient year were estimated to be
reduced -$254, -$367, and -$88, for apixaban, dabigatran, and rivaroxaban,
respectively, in comparison to warfarin.
LIMITATIONS: This economic analysis was based on clinical trial data and,
therefore, the direct application of the results to routine clinical practice
will require further assessment.
CONCLUSIONS: Difference in medical costs between OAC and warfarin treated NVAF
patients vary by age group and individual OACs. Although reductions in medical
costs for NVAF patients aged ≥75 and <75 were observed for those using either
apixaban or rivaroxaban vs warfarin, the reductions were greater per patient
year for both the older and younger NVAF populations using apixaban. OBJECTIVES: This study sought to report additional safety results from the
ROCKET AF (Rivaroxaban Once-daily oral Direct Factor Xa Inhibition Compared with
Vitamin K Antagonism for Prevention of Stroke and Embolism Trial in Atrial
Fibrillation).
BACKGROUND: The ROCKET AF trial demonstrated similar risks of stroke/systemic
embolism and major/nonmajor clinically relevant bleeding (principal safety
endpoint) with rivaroxaban and warfarin.
METHODS: The risk of the principal safety and component bleeding endpoints with
rivaroxaban versus warfarin were compared, and factors associated with major
bleeding were examined in a multivariable model.
RESULTS: The principal safety endpoint was similar in the rivaroxaban and
warfarin groups (14.9 vs. 14.5 events/100 patient-years; hazard ratio: 1.03; 95%
confidence interval: 0.96 to 1.11). Major bleeding risk increased with age, but
there were no differences between treatments in each age category (<65, 65 to
74, ≥75 years; pinteraction = 0.59). Compared with those without (n = 13,455),
patients with a major bleed (n = 781) were more likely to be older,
current/prior smokers, have prior gastrointestinal (GI) bleeding, mild anemia,
and a lower calculated creatinine clearance and less likely to be female or have
a prior stroke/transient ischemic attack. Increasing age, baseline diastolic
blood pressure (DBP) ≥90 mm Hg, history of chronic obstructive pulmonary disease
or GI bleeding, prior acetylsalicylic acid use, and anemia were independently
associated with major bleeding risk; female sex and DBP <90 mm Hg were
associated with a decreased risk.
CONCLUSIONS: Rivaroxaban and warfarin had similar risk for major/nonmajor
clinically relevant bleeding. Age, sex, DBP, prior GI bleeding, prior
acetylsalicylic acid use, and anemia were associated with the risk of major
bleeding. (An Efficacy and Safety Study of Rivaroxaban With Warfarin for the
Prevention of Stroke and Non-Central Nervous System Systemic Embolism in
Patients With Non-Valvular Atrial Fibrillation: NCT00403767). BACKGROUND: During long-term anticoagulation in atrial fibrillation, temporary
interruptions (TIs) of therapy are common, but the relationship between patient
outcomes and TIs has not been well studied. We sought to determine reasons for
TI, the characteristics of patients undergoing TI, and the relationship between
anticoagulant and outcomes among patients with TI.
METHODS AND RESULTS: In the Rivaroxaban Once Daily, Oral, Direct Factor Xa
Inhibition Compared With Vitamin K Antagonism for Prevention of Stroke and
Embolism Trial in Atrial Fibrillation (ROCKET AF), a randomized, double-blind,
double-dummy study of rivaroxaban and warfarin in nonvalvular atrial
fibrillation, baseline characteristics, management, and outcomes, including
stroke, non-central nervous system systemic embolism, death, myocardial
infarction, and bleeding, were reported in participants who experienced TI (3-30
days) for any reason. The at-risk period for outcomes associated with TI was
from TI start to 30 days after resumption of study drug. In 14 236 participants
who received at least 1 dose of study drug, 4692 (33%) experienced TI.
Participants with TI were similar to the overall ROCKET AF population in regard
to baseline clinical characteristics. Only 6% (n=483) of TI incidences involved
bridging therapy. Stroke/systemic embolism rates during the at-risk period were
similar in rivaroxaban-treated and warfarin-treated participants (0.30% versus
0.41% per 30 days; hazard ratio [confidence interval]=0.74 [0.36-1.50]; P=0.40).
Risk of major bleeding during the at-risk period was also similar in
rivaroxaban-treated and warfarin-treated participants (0.99% versus 0.79% per 30
days; hazard ratio [confidence interval]=1.26 [0.80-2.00]; P=0.32).
CONCLUSIONS: TI of oral anticoagulation is common and is associated with
substantial stroke risks and bleeding risks that were similar among patients
treated with rivaroxaban or warfarin. Further investigation is needed to
determine the optimal management strategy in patients with atrial fibrillation
requiring TI of anticoagulation.
CLINICAL TRIAL REGISTRATION URL: http://www.clinicaltrials.gov. Unique
identifier: NCT00403767. Rivaroxaban, a direct factor Xa inhibitor, is a novel oral anticoagulant
approved for stroke prevention in patients with nonvalvular atrial fibrillation
and also approved in Europe (but not in the United States) to prevent recurrent
ischemic events in patients with recent acute coronary syndromes. Advantages of
rivaroxaban over oral anticoagulants such as warfarin are the lack of need for
ongoing monitoring, a fixed-dose regimen, and fewer drug and food interactions.
Drawbacks include a lack of an antidote and the absence of a widely available
method to reliably monitor the anticoagulant effect. In patients at risk of
stroke due to atrial fibrillation, rivaroxaban was noninferior compared to
warfarin in preventing stroke/systemic embolism in the Rivaroxaban Once Daily
Oral Direct Factor Xa Inhibition Compared with Vitamin K Antagonism for
Prevention of Stroke and Embolism Trial in Atrial Fibrillation (ROCKET-AF) trial
and was associated with a similar risk of major bleeding; the incidence of
intracranial hemorrhage was 33% lower with rivaroxaban. Concerns raised about
the trial were the adequacy of warfarin management and the increase in event
rate at the end of the trial. The drug acquisition cost of rivaroxaban is higher
than that of warfarin although decision-analytic models suggest that it is cost
effective in atrial fibrillation. In patients with recent acute coronary
syndrome, low-dose rivaroxaban reduced mortality and the composite end point of
death from cardiovascular causes, myocardial infarction and stroke, but this was
accompanied by an increased risk of intracranial hemorrhage and major bleeding
in the Rivaroxaban in Combination With Aspirin Alone or With Aspirin and a
Thienopyridine in Patients With Acute Coronary Syndromes-Thrombolysis in
Myocardial Infarction (ATLAS ACS 2-TIMI) 51 trial. Thus, rivaroxaban appears to
be a valuable addition to the therapeutic armamentarium in atrial fibrillation
although caution should be exercised, given the limited experience in
combination with novel oral antiplatelet agents. The role of rivaroxaban as part
of a modern regimen in acute coronary syndrome continues to be evaluated. Atrial fibrillation (AF) is the most common cardiac arrhythmia in the developed
world and is associated with a fivefold increase in the risk of stroke,
accounting for up to 15% of strokes in the general population. The European
Society of Cardiology now recommends direct oral anticoagulants, such as
rivaroxaban, apixaban, and dabigatran, in preference to vitamin K antagonist
therapy for the prevention of stroke in patients with A F. This review focuses
on the direct Factor Xa inhibitor rivaroxaban, summarizing the properties that
make rivaroxaban appropriate for anticoagulant therapy in this indication
(including its predictable pharmacokinetic and pharmacodynamic profile and
once-daily dosing regimen) and describing data from the Phase III ROCKET AF
trial, which showed once-daily rivaroxaban to be noninferior to warfarin for the
prevention of stroke in patients with nonvalvular AF. In this trial, similar
rates of major and nonmajor clinically relevant bleeding were observed; however,
when compared with warfarin, rivaroxaban was associated with clinically
significant reductions in intracranial and fatal bleeding. On the basis of these
results, rivaroxaban was approved in both the United States and the European
Union for the prevention of stroke and systemic embolism in patients with
nonvalvular AF. Subanalyses of ROCKET AF data showed rivaroxaban to have
consistent efficacy and safety across a wide range of patients, and studies to
confirm these results in real-world settings are underway. This review also
describes practical considerations for treatment with rivaroxaban in clinical
practice (including dose reductions in specific high-risk patients, eg, those
with renal impairment), recommendations for the transition from vitamin K
antagonists to rivaroxaban, the management of bleeding events, and the
measurement of rivaroxaban exposure. OBJECTIVES AND BACKGROUND: Rivaroxaban, an oral direct factor Xa-inhibitor was
non-inferior to adjusted dose warfarin in the prevention of stroke and embolism
among patients with atrial fibrillation (AF) in the ROCKET-AF trial and has been
approved for stroke prevention in AF.
CASE REPORT: A 88-years-old female (body-mass-index = 19.95) with AF,
hypertension and diabetes mellitus, hospitalized because of heart failure and a
non-convulsive epileptic state, was treated by valproate, mirtazepin, nebivolol,
digitoxin, lisinopril, gliclazide and amlodipine. Irrespective of renal
insufficiency, rivaroxaban 15 mg/d was started. After 3 days rivaroxaban was
stopped because of concerns about the bleeding risk. Coagulation tests 28 h
after rivaroxaban-intake showed INR 2.26, PT 35%, aPTT 38.3 s and anti-Factor
Xa-activity 2.00 U/ml. Explanations for the prolonged anticoagulant activity of
rivaroxaban comprise renal failure, the low body-mass-index, the advanced age
and drug-drug interactions of rivaroxaban with mirtazepin, valproate and
amlodipine.
CONCLUSION: Health care providers should consider renal function, concomitant
medication, polymorbidity and age prior to prescribing rivaroxaban. Care has to
be taken when prescribing rivaroxaban to patients who are different from those
included in the ROCKET AF trial. Atrial fibrillation (AF) is associated with a fivefold increase in the risk of
stroke. The Phase III ROCKET AF (Rivaroxaban Once-Daily Oral Direct Factor Xa
Inhibition Compared with Vitamin K Antagonism for Prevention of Stroke and
Embolism Trial in Atrial Fibrillation) trial showed that rivaroxaban, an oral,
direct Factor Xa inhibitor, was noninferior to warfarin for the reduction of
stroke or systemic embolism in patients with AF. Compared with warfarin,
rivaroxaban significantly reduced rates of intracranial and fatal hemorrhages,
although not rates of bleeding overall. XANTUS (Xarelto(®) for Prevention of
Stroke in Patients with Atrial Fibrillation) is a prospective, international,
observational, postauthorization, noninterventional study designed to collect
safety and efficacy data on the use of rivaroxaban for stroke prevention in AF
in routine clinical practice. The key goal is to determine whether the safety
profile of rivaroxaban established in ROCKET AF is also observed in routine
clinical practice. XANTUS is designed as a single-arm cohort study to minimize
selection bias, and will enroll approximately 6,000 patients (mostly from
Europe) with nonvalvular AF prescribed rivaroxaban, irrespective of their level
of stroke risk. Overall duration of follow-up will be 1 year; the first patient
was enrolled in June 2012. Similar studies (XANTUS-EL [Xarelto(®) for Prevention
of Stroke in Patients with Nonvalvular Atrial Fibrillation, Eastern Europe,
Middle East, Africa and Latin America] and XANAP [Xarelto(®) for Prevention of
Stroke in Patients with Atrial Fibrillation in Asia-Pacific]) are ongoing in
Latin America and Asia-Pacific. Data from these studies will supplement those
from ROCKET AF and provide practical information concerning the use of
rivaroxaban for stroke prevention in AF. AIM: Anticoagulation prophylaxis for stroke is recommended for at-risk patients
with either persistent or paroxysmal atrial fibrillation (AF). We compared
outcomes in patients with persistent vs. paroxysmal AF receiving oral
anticoagulation.
METHODS AND RESULTS: Patients randomized in the Rivaroxaban Once Daily Oral
Direct Factor Xa Inhibition Compared With Vitamin K Antagonism for Prevention of
Stroke and Embolism Trial in Atrial Fibrillation (ROCKET-AF) trial (n = 14 264)
were grouped by baseline AF category: paroxysmal or persistent. Multivariable
adjustment was performed to compare thrombo-embolic events, bleeding, and death
between groups, in high-risk subgroups, and across treatment assignment
(rivaroxaban or warfarin). Of 14 062 patients, 11 548 (82%) had persistent AF
and 2514 (18%) had paroxysmal AF. Patients with persistent AF were marginally
older (73 vs. 72, P = 0.03), less likely female (39 vs. 45%, P < 0.0001), and
more likely to have previously used vitamin K antagonists (64 vs. 56%, P <
0.0001) compared with patients with paroxysmal AF. In patients randomized to
warfarin, time in therapeutic range was similar (58 vs. 57%, P = 0.94). Patients
with persistent AF had higher adjusted rates of stroke or systemic embolism
(2.18 vs. 1.73 events per 100-patient-years, P = 0.048) and all-cause mortality
(4.78 vs. 3.52, P = 0.006). Rates of major bleeding were similar (3.55 vs. 3.31,
P = 0.77). Rates of stroke or systemic embolism in both types of AF did not
differ by treatment assignment (rivaroxaban vs. warfarin, Pinteraction = 0.6).
CONCLUSION: In patients with AF at moderate-to-high risk of stroke receiving
anticoagulation, those with persistent AF have a higher risk of thrombo-embolic
events and worse survival compared with paroxysmal AF. BACKGROUND: Digoxin is a widely used drug for ventricular rate control in
patients with atrial fibrillation (AF), despite a scarcity of randomised trial
data. We studied the use and outcomes of digoxin in patients in the Rivaroxaban
Once Daily Oral Direct Factor Xa Inhibition Compared with Vitamin K Antagonism
for Prevention of Stroke and Embolism Trial in Atrial Fibrillation (ROCKET AF).
METHODS: For this retrospective analysis, we included and classified patients
from ROCKET AF on the basis of digoxin use at baseline and during the study.
Patients in ROCKET AF were recruited from 45 countries and had AF and risk
factors putting them at moderate-to-high risk of stroke, with or without heart
failure. We used Cox proportional hazards regression models adjusted for
baseline characteristics and drugs to investigate the association of digoxin
with all-cause mortality, vascular death, and sudden death. ROCKET AF was
registered with ClinicalTrials.gov, number NCT00403767.
FINDINGS: In 14,171 randomly assigned patients, digoxin was used at baseline in
5239 (37%). Patients given digoxin were more likely to be female (42% vs 38%)
and have a history of heart failure (73% vs 56%), diabetes (43% vs 38%), and
persistent AF (88% vs 77%; p<0·0001 for each comparison). After adjustment,
digoxin was associated with increased all-cause mortality (5·41 vs 4·30 events
per 100 patients-years; hazard ratio 1·17; 95% CI 1·04-1·32; p=0·0093), vascular
death (3·55 vs 2·69 per 100 patient-years; 1·19; 1·03-1·39, p=0·0201), and
sudden death (1·68 vs 1·12 events per 100 patient-years; 1·36; 1·08-1·70,
p=0·0076).
INTERPRETATION: Digoxin treatment was associated with a significant increase in
all-cause mortality, vascular death, and sudden death in patients with AF. This
association was independent of other measured prognostic factors, and although
residual confounding could account for these results, these data show the
possibility of digoxin having these effects. A randomised trial of digoxin in
treatment of AF patients with and without heart failure is needed.
FUNDING: Janssen Research & Development and Bayer HealthCare AG. |
Describe the usefulness of the SPIKE database in human signaling pathways | The rapid accumulation of knowledge on biological signaling pathways and their regulatory mechanisms has highlighted the need for specific repositories that can store, organize and allow retrieval of pathway information in a way that will be useful for the research community. SPIKE (Signaling Pathways Integrated Knowledge Engine; http://www.cs.tau.ac.il/&~spike/) is a database for achieving this goal, containing highly curated interactions for particular human pathways, along with literature-referenced information on the nature of each interaction. To make database population and pathway comprehension straightforward, a simple yet informative data model is used, and pathways are laid out as maps that reflect the curator’s understanding and make the utilization of the pathways easy. The database currently focuses primarily on pathways describing DNA damage response, cell cycle, programmed cell death and hearing related pathways. Pathways are regularly updated, and additional pathways are gradually added. The complete database and the individual maps are freely exportable in several formats. The database is accompanied by a stand-alone software tool for analysis and dynamic visualization of pathways. | BACKGROUND: Biological signaling pathways that govern cellular physiology form
an intricate web of tightly regulated interlocking processes. Data on these
regulatory networks are accumulating at an unprecedented pace. The assimilation,
visualization and interpretation of these data have become a major challenge in
biological research, and once met, will greatly boost our ability to understand
cell functioning on a systems level.
RESULTS: To cope with this challenge, we are developing the SPIKE knowledge-base
of signaling pathways. SPIKE contains three main software components: 1) A
database (DB) of biological signaling pathways. Carefully curated information
from the literature and data from large public sources constitute distinct tiers
of the DB. 2) A visualization package that allows interactive graphic
representations of regulatory interactions stored in the DB and superposition of
functional genomic and proteomic data on the maps. 3) An algorithmic inference
engine that analyzes the networks for novel functional interplays between
network components.SPIKE is designed and implemented as a community tool and
therefore provides a user-friendly interface that allows registered users to
upload data to SPIKE DB. Our vision is that the DB will be populated by a
distributed and highly collaborative effort undertaken by multiple groups in the
research community, where each group contributes data in its field of expertise.
CONCLUSION: The integrated capabilities of SPIKE make it a powerful platform for
the analysis of signaling networks and the integration of knowledge on such
networks with omics data. |
Is the Dictyostelium discoideum proteome known? | Yes, The Dictyostelium discoideum genome has been sequenced, assembled and annotated to a high degree of reliability. The parts-list of proteins and RNA encoded by the six chromosomes can now be accessed and analyzed. Consequently, this genomic sequence information can now be exploited to realize D. discoideum proteomics projects. | Secretion of spore coat proteins from the prespore secretory vesicles (PSVs) in
Dictyostelium discoideum is a signal mediated event that underlies terminal cell
differentiation, and represents an important case of developmentally regulated
secretion. In order to study the biochemical mechanisms that govern the
regulated fusion of the PSVs with the plasma membrane and the subsequent
secretion of their cargo, we purified this organelle from prespore cells.
Analysis of protein extracts of highly purified PSVs indicated that, in addition
to the cargo of structural spore coat proteins, many more proteins are
associated with the PSVs. Their identification is paramount to the understanding
of the mechanism of regulated secretion in this system. In this study we have
taken the first comprehensive proteomic approach to the analysis of an entire,
previously uncharacterized, organelle, with the goal of identifying the major
proteins associated with the PSVs. We show that in addition to the structural
spore coat proteins, the PSVs contain the enzymes needed for proper spore coat
assembly (thioredoxin 2 and 3), regulatory proteins which we predict receive and
transduce the developmental signal for secretion (rab7 GTPase, PI-3 kinase, NDP
kinase and the calcium binding proteins calfumirin-1 and calreticulin) as well
as proteins that interact with the cytoskeleton to mediate movement of the PSVs
to the plasma membrane (actin binding proteins coactosin and profilin 1). In
addition, the results suggest that proteins can play multiple roles in the cell,
and that protein function can be dictated in part by subcellular localization.
The identification of the PSV proteins is allowing us to develop testable
hypotheses about the roles of these proteins within the functional context of
developmentally regulated secretion. The Dictyostelium discoideum genome has been sequenced, assembled and annotated
to a high degree of reliability. The parts-list of proteins and RNA encoded by
the six chromosomes can now be accessed and analyzed. One of the initial
surprises was the remarkably large number of genes that are shared with plants,
animals, and fungi that must have been present in their common progenitor over a
billion years ago. The genome encodes a total of about 10,300 proteins including
protein families involved in cytoskeletal control, posttranslational protein
modification, detoxification, secondary metabolism, cell adhesion, and signal
transduction. The genome has a higher proportion of homopolymeric tracts and
simple sequence repeats, such as [CAA]n, than most other genomes. Triplet
repeats in translated regions produce the highest known proportion of
polyglutamine tracts in any known proteome. Phylogenetic analyses based on
complete proteomes confirm that the amoebozoa are a sister group to the animals
and fungi, distinct from plants and early diverging species such as Leishmania,
Plasmodium, or Giardia. The completed Dictyostelium sequence opens the door to
large-scale functional exploration of its genome. The social amoeba Dictyostelium discoideum is already known as a model organism
for a variety of cellular and molecular studies. Now that the genome sequencing
project has been completed and different tools with which to overexpress or
knock out genes are available, this species has also moved into the spotlight of
functional genomics studies. Consequently, this genomic sequence information can
now be exploited to realize D. discoideum proteomics projects. Here, we present
validated protocols adapted for analysis of the D. discoideum proteome. The
workflow described in this chapter comprises two-dimensional polyacrylamide gel
electrophoresis for protein separation and peptide mass fingerprint
(matrix-assisted laser desorption/ionization time-of-flight mass spectrometry)
for protein identification. The availability of complete genome sequence information for diverse organisms
including model genetic organisms has ushered in a new era of protein sequence
comparisons making it possible to search for commonalities among entire
proteomes using the Basic Local Alignment Search Tool (BLAST). Although the
identification and analysis of proteins shared by humans and model organisms has
proven an invaluable tool to understanding gene function, the sets of proteins
unique to a given model organism's proteome have remained largely unexplored. We
have constructed a searchable database that allows biologists to identify
proteins unique to a given proteome. The Negative Proteome Database (NPD) is
populated with pair-wise protein sequence comparisons between each of the
following proteomes: Homo sapiens, Mus musculus, Drosophila melanogaster,
Caenorhabditis elegans, Saccharomyces cerevisiae, Dictyostelium discoideum,
Chlamydomonus reinhardti, Escherichia coli K12, Arabidopsis thaliana and
Methanoscarcina acetivorans. Our analysis of negative proteome datasets using
the NPD has thus far revealed 107 proteins in humans that may be involved in
motile cilia function, 1628 potential pesticide target proteins in flies, 659
proteins shared by flies and humans that are not represented in the less
neurologically complex worm proteome, and 180 nuclear encoded human disease
associated proteins that are absent from the fly proteome. The NPD is the only
online resource where users can quickly perform complex negative and positive
comparisons of model organism proteomes. We anticipate that the NPD and the
adaptable algorithm which can readily be used to duplicate this analysis on
custom sets of proteomes will be an invaluable tool in the investigation of
organism specific protein sets. In this study, a quantitative comparative proteomics approach has been used to
analyze the Dictyostelium discoideum mitochondrial proteome variations during
vegetative growth, starvation and the early stages of development. Application
of 2-D DIGE technology allowed the detection of around 2000 protein spots on
each 2-D gel with 180 proteins exhibiting significant changes in their
expression level. In total, 96 proteins (51 unique and 45 redundant) were
unambiguously identified. We show that the D. discoideum mitochondrial proteome
adaptations mainly affect energy metabolism enzymes (the Krebs cycle,
anaplerotic pathways, the oxidative phosphorylation system and energy
dissipation), proteins involved in developmental and signaling processes as well
as in protein biosynthesis and fate. The most striking observations were the
opposite regulation of expression of citrate synthase and aconitase and the very
large variation in the expression of the alternative oxidase that highlighted
the importance of citrate and alternative oxidase in the physiology of the
development of D. discoideum. Mitochondrial energy states measured in vivo with
MitoTracker Orange CM Ros showed an increase in mitochondrial membrane
polarization during D. discoideum starvation and starvation-induced development. |
List proteins of lipids droplets | perilipins
adipose differentiation-related protein
lipid storage droplet protein 5
tail-interacting protein of 47 kilodaltons
S3-12 | Animals have evolved mechanisms to maintain circulating nutrient levels when
energy demands exceed feeding opportunities. Mammals store most of their energy
as triacylglycerol in the perilipin-coated lipid droplets of adipocytes. How
newly synthesized triacylglycerol is delivered to perilipin-coated lipid
droplets is poorly understood. Perilipin is a member of the evolutionarily
related family of PAT proteins (Perilipin, Adipophilin, TIP47), which is defined
by sequence similarity and association with lipid droplets. We previously showed
that S3-12, which is also a member of this family, associates with a separate
pool of lipid droplets that emerge when triacylglycerol storage is driven by
adding oleate to the culture medium of adipocytes. Our current data extend these
findings to demonstrate that nascent lipid droplets emerge with a coat composed
of S3-12, TIP47, and adipophilin. After 100 min of oleate treatment, the nascent
lipid droplets are more heterogeneous: S3-12 and TIP47 coat smaller, peripheral
droplets and adipophilin coats a more medial population of droplets.
Fractionation of untreated and oleate-treated adipocytes shows oleate-dependent
redistribution of TIP47 and adipophilin from cytosolic fractions to the lipid
droplet fraction. Inhibition of protein synthesis with cycloheximide does not
block the oleate-induced formation of the nascent lipid droplets, nor does it
prevent TAG accumulation. We suggest that the non-lipid droplet pools of S3-12,
adipophilin, and TIP47 constitute a ready reservoir of coat proteins to permit
rapid packaging of newly synthesized triacylglycerol and to maximize energy
storage during nutrient excess. Lipolysis is an important metabolic pathway controlling energy homeostasis
through degradation of triglycerides stored in lipid droplets and release of
fatty acids. Lipid droplets of mammalian cells are coated with one or more
members of the PAT protein family, which serve important functions in regulating
lipolysis. In this study, we investigate the mechanisms by which PAT family
members, perilipin A, adipose differentiation-related protein (ADFP), and LSDP5,
control lipolysis catalyzed by hormone-sensitive lipase (HSL), a major lipase in
adipocytes and several non-adipose cells. We applied fluorescence microscopic
tools to analyze proteins in situ in cultured Chinese hamster ovary cells using
fluorescence recovery after photobleaching and anisotropy Forster resoce
energy transfer. Fluorescence recovery after photobleaching data show that ADFP
and LSDP5 exchange between lipid droplet and cytoplasmic pools, whereas
perilipin A does not. Differences in protein mobility do not correlate with PAT
protein-mediated control of lipolysis catalyzed by HSL or endogenous lipases.
Forster resoce energy transfer and co-immunoprecipitation experiments reveal
that each of the three PAT proteins bind HSL through interaction of the lipase
with amino acids within the highly conserved amino-terminal PAT-1 domain. ADFP
and LSDP5 bind HSL under basal conditions, whereas phosphorylation of serine
residues within three amino-terminal protein kinase A consensus sequences of
perilipin A is required for HSL binding and maximal lipolysis. Finally, protein
kinase A-mediated phosphorylation of HSL increases lipolysis in cells expressing
ADFP or LSDP5; in contrast, phosphorylation of perilipin A exerts the major
control over HSL-mediated lipolysis when perilipin is the main lipid droplet
protein. Fatty acid-induced triacylglycerol synthesis produces triacylglycerol droplets
with a protein coat that includes perilipin 3/TIP47 and perilipin 4/S3-12. This
study addresses the following two questions. Where do lipid droplets emerge, and
how are their coat proteins recruited? We show that perilipin 3- and perilipin
4-coated lipid droplets emerge along the endoplasmic reticulum (ER). Blocking
membrane trafficking with AlF(4)(-) during fatty acid-induced triacylglycerol
synthesis drove perilipin 3 to the tubular ER. Forskolin, which like AlF(4)(-)
activates adenylate cyclase, did not redistribute perilipin 3, but when added
together with AlF(4)(-) perilipin 3 was recruited to lipid droplets rather than
the ER. Thus inhibiting trafficking with AlF(4)(-) redistributed perilipin 3
differently under conditions of triacylglycerol synthesis (fatty acid addition)
versus hydrolysis (forskolin) suggesting a shared acylglycerol-mediated
mechanism. We tested whether diacylglycerol (DG), the immediate precursor of
triacylglycerol and its first hydrolytic product, affects the distribution of
perilipin 3. Stabilizing DG with the DG lipase inhibitor RHC80267 enhanced the
perilipin 3 recruited to lipid droplets and raised DG levels in this fraction.
Treating cells with a membrane-permeable DG recruited perilipin 3 to the ER.
Stabilizing DG, by blocking its hydrolysis with RHC80267 or its acylation with
triacsin C, enhanced recruitment of perilipin 3 to the ER. Expressing the ER
enzyme DGAT1, which removes DG by converting it to triacylglycerol, attenuated
perilipin 3 DG-induced ER recruitment. Membrane-permeable DG also drove
perilipin 4 and 5 onto the ER. Together the data suggest that these lipid
droplet proteins are recruited to DG-enriched membranes thereby linking lipid
coat proteins to the metabolic state of the cell. We previously reported that a single exercise session protects against fatty
acid (FA)-induced insulin resistance, perhaps in part through augmented
intramyocellular triacylglycerol (IMTG) synthesis. The aim of this study was to
examine the effect of elevated FA availability after exercise on factors
regulating IMTG metabolism. After exercise (90 minutes, 65% peak oxygen uptake),
7 healthy women (body mass index, 23 ± 1 kg/m(2)) were infused overnight (16
hours) with either a lipid and heparin solution (LIPID, 0.11 g fat per kilogram
per hour) or saline (SALINE). We measured resting FA oxidation (indirect
calorimetry) and obtained a skeletal muscle biopsy sample the next morning. The
4-fold increase in overnight plasma FA concentration during LIPID increased IMTG
by approximately 30% during LIPID vs SALINE. This was accompanied by an
approximately 25% greater membrane-associated abundance of the FA transporter
FAT/CD36 (P < .01) and an approximately 8% increase in the activity of the IMTG
synthesis enzyme glycerol-3-phosphate acyltransferase (GPAT, P < .01). In
contrast, resting FA oxidation was not affected. We also found no difference in
the protein abundance of GPAT1 and diacylglycerol acyltransferase-1,
diacylglycerol acyltransferase activity, or the abundance of the lipid droplet
coat proteins (perilipins 2, 3, 4, and 5) between treatments. Our findings
suggest that augmented capacity for FA flux into muscle (ie, via
membrane-associated FAT/CD36), perhaps together with a slight yet significant
increase in activity of a key IMTG synthesis enzyme (GPAT), may enhance IMTG
storage when FA availability is high after exercise. The importance of the
absence of a change in perilipin protein abundance despite increased muscle
lipid storage remains to be determined. This study investigated the lipid droplet coat proteins perilipin 1 (PLIN1) and
perilipin 2 (PLIN2) localization in pig skeletal muscle and their relationship
with intramuscular fat (IMF) content. PLIN1 and PLIN2 proteins were
immunostained in semimembranosus muscle cross-sections from two groups of
samples divergent for IMF and the gene expression was quantified. PLIN1
localized in the periphery of intramuscular adipocytes, whereas PLIN2 localized
within myofibers with high lipid content. The high IMF group showed higher total
cross-sectional area of PLIN1-stained adipocytes compared with the low IMF group
(P<0.05), while the cross-sectional area and percentage of PLIN2-positive
myofibers did not differ between IMF-divergent groups. This suggested that IMF
content is mainly determined by extra-myocellular lipids. At mRNA level, PLIN2
expression was higher in high IMF muscles (P<0.05). The results indicate for the
first time that in pig muscle PLIN1 and PLIN2 proteins are localized in
correspondence with extra and intra-myocellular lipids, respectively. Adipose triglyceride lipase (ATGL) is the key triacylglycerol hydrolase in
adipocytes. The precise mechanisms by which ATGL action is regulated by lipid
droplet (LD) coat proteins and responds to hormonal stimulation are incompletely
defined. By combining usage of loss- and gain-of-function approaches, we sought
to determine the respective roles of perilipin 1 and fat-specific protein 27
(FSP27) in the control of ATGL-mediated lipolysis in adipocytes. Knockdown of
endogenous perilipin 1 expression resulted in elevated basal lipolysis that was
less responsive to β-adrenergic agonist isoproterenol. In comparison, depletion
of FSP27 protein increased both basal and stimulated lipolysis with no
significant impact on the overall response of cells to isoproterenol. In vitro
assays showed that perilipin but not FSP27 was able to inhibit the
triacylglycerol hydrolase activity of ATGL. Perilipin 1 also attenuated
dose-dependent activation of ATGL by its Coactivator Comparative Gene
identification-58. Accordingly, depletion of perilipin 1 and CGI-58 in
adipocytes inversely affected basal lipolysis specifically mediated by
overexpressed ATGL. Moreover, although depletion of perilipin 1 abolished the LD
translocation of ATGL stimulated by isoproterenol, absence of FSP27 resulted in
multilocularization of LDs along with increased LD presence of ATGL under both
basal and stimulated conditions. Interestingly, knockdown of ATGL expression
increased LD size and decreased LD number in FSP27-depeleted cells. Together,
our results demonstrate that although FSP27 acts to constitutively limit the LD
presence of ATGL, perilipin 1 plays an essential role in mediating the response
of ATGL action to β-adrenergic hormones. Cytosolic lipid storage droplets are primary functional organelles that regulate
cellular lipid metabolism and homeostasis. Paradoxically, excess lipid stores
are linked to both adaptive (fasting and chronic exercise) and mal-adaptive
(obesity and related health complications) conditions. Thus, collective
metabolic and physiological processes must balance lipid storage and utilization
with prevention of lipocytotoxicity and compounding tissue dysfunctions, urging
the need to further define the connection of mammalian lipid droplet function
and lipid homeostasis. The perilipins are a multi-protein family that targets
lipid droplet surfaces and regulates lipid storage and hydrolysis. Study of
perilipin functions has provided insight into the physiological roles of
cytosolic lipid droplets and their relationship with obesity-related
pathologies. Here, we review the current knowledge of the multiple perilipin
proteins in regulating tissue-specific lipid droplets and associations with
tissue and systemic energetics. |
What is the Barr body? | The Barr body is the inactive X chromosome in a female somatic cell. It is readily identified as plano-convex structure of 2-3 micron in diameter on the periphery of the nuclear membrane. One of the X-chromosomes by a random inactivation process condenses to form X-chromatin (Barr body) in early embryonic life. Once this occurs, it is final and fixed for that cell and all its descendants (1,2). Barr body is an inactivated X chromosome in the normal female somatic cell. Inactivation of these chromosomes is known as Lyonization. Lyonization has both genetic and clinical significance. Barr body can be easily identified with ordinary stains. It also helps in identifying the sex of an individual when used judiciously. The Barr body has long been recognized as the cytological manifestation of the inactive X chromosome (Xi) in interphase nuclei. Despite being known for over 50 years, relatively few components of the Barr body have been identified. | This study provides a three-dimensional (3D) analysis of differences between the
3D morphology of active and inactive human X interphase chromosomes (Xa and Xi
territories). Chromosome territories were painted in formaldehyde-fixed,
three-dimensionally intact human diploid female amniotic fluid cell nuclei (46,
XX) with X-specific whole chromosome compositive probes. The colocalization of a
4,6-diamidino-2-phenylindole dihydrochloride-stained Barr body with one of the
two painted X territories allowed the unequivocal discrimination of the inactive
X from its active counterpart. Light optical serial sections were obtained with
a confocal laser scanning microscope. 3D-reconstructed Xa territories revealed a
flatter shape and exhibited a larger and more irregular surface when compared to
the apparently smoother surface and rounder shape of Xi territories. The
relationship between territory surface and volume was quantified by the
determination of a dimensionless roundness factor (RF). RF and surface area
measurements showed a highly significant difference between Xa and Xi
territories (P < 0.001) in contrast to volume differences (P > 0.1). For
comparison with an autosome of similar DNA content, chromosome 7 territories
were additionally painted. The 3D morphology of the chromosome 7 territories was
similar to the Xa territory but differed strongly from the Xi territory with
respect to RF and surface area (P < 0.001). DNA undermethylation is a characteristic feature of ICF syndrome and has been
implicated in the formation of the juxtacentromeric chromosomal abnormalities of
this rare syndrome. We have previously shown that in female ICF patients the
inactive X chromosome (Xi) is also undermethylated. This result was unexpected
since female ICF patients are not more severely affected than male patients.
Here we show that CpG island methylation is abnormal in some ICF patients but in
other ICF patients, the difference in methylation pattern between Xi and Xa
(active X) is maintained. The consequences of Xi undermethylation on gene
expression were investigated by enzyme assays. They showed that significant gene
expression did not correlate with CpG island methylation status. The widespread
Xi undermethylation does not affect overall Xi replication timing and does not
prevent Barr body formation suggesting that a normal methylation pattern is not
required for normal chromatin organization of Xi. Molecular investigation of
some X-chromosome intron regions showed that the methylation changes in ICF
female patients extend to non CpG islands sequences. Our results suggest that
the genetic alteration of DNA methylation in ICF syndrome has little consequence
on X chromosome gene expression and chromatin organization. The Barr body has long been recognized as the cytological manifestation of the
inactive X chromosome (Xi) in interphase nuclei. Despite being known for over 50
years, relatively few components of the Barr body have been identified. In this
study, we have screened over 30 histone variants, modified histones and
non-histone proteins for their association with or exclusion from the Barr body.
We demonstrate that, similar to the histone variant macroH2A, heterochromatin
protein-1 (HP1), histone H1 and the high mobility group protein HMG-I/Y are
elevated at the territory of the Xi in interphase in human cell lines, but only
when the Xi chromatin is heteropycnotic, implicating each as a component of the
Barr body. Surprisingly, however, virtually all other candidate proteins
involved in establishing heterochromatin and gene silencing are notably absent
from the Barr body despite being localized generally elsewhere throughout the
nucleus, indicating that the Barr body represents a discrete subnuclear
compartment that is not freely accessible to most chromatin proteins. A similar
dichotomous pattern of association or exclusion describes the spatial
relationship of a number of specific histone methylation patterns in relation to
the Barr body. Notably, though, several methylated forms of histone H3 that are
deficient in Xi chromatin generally are present at a region near the
macrosatellite repeat DXZ4, as are the chromatin proteins CTCF and SAP30,
indicating a distinctive chromatin state in this region of the Xi. Taken
together, our data imply that the Xi adopts a distinct chromatin configuration
in interphase nuclei and are consistent with a mechanism by which HP1, through
histone H3 lysine-9 methylation, recognizes and assists in maintaining
heterochromatin and gene silencing at the human Xi. Barr body is an inactivated X chromosome in the normal female somatic cell.
Inactivation of these chromosomes is known as Lyonization. Lyonization has both
genetic and clinical significance. Barr body can be easily identified with
ordinary stains. It also helps in identifying the sex of an individual when used
judiciously. A review is made on the lyonization of Barr body and its utility in
sex determination. In the late 1940s, a microanatomist from London Ontario, Murray Barr, discovered
a mark of sex chromosome status in bodily tissues, what came to be known as the
'Barr body'. This discovery offered an important diagnostic technology to the
burgeoning clinical science community engaged with the medical interpretation
and management of sexual anomalies. It seemed to offer a way to identify the
true, underlying sex in those whose bodies or lives were sexually anomalous
(intersexuals, homosexuals and transsexuals). The hypothesis that allowed the
Barr body to stand in for 'chromosomal' or 'genetic' sex was provisional, but it
supported the expectation that genetic information established one's primary
identity, and the conviction that the animal world could be neatly divided into
two, and only two, sexes. Ultimately, this provisional hypothesis, and its
status as an unambiguous arbiter of true sex, was overturned. But during much of
the 1950s, Barr's thesis about the identity of the Barr body was consistent with
a coherent set of theories and evidence explaining sexual development and sexual
pathology. Though provisional, the scientific status of the sex chromatin within
this system of knowledge was good enough to support a flourishing research
enterprise in the clinical sciences. Interest has recently reawakened in whether loss of the heterochromatic X
chromosome (Barr body) is prevalent in certain breast and ovarian cancers, and
new insights into the mechanisms involved have emerged. Mitotic segregation
errors commonly explain the loss of the inactive X chromosome (Xi), but
compromise of Xi heterochromatin in some cancers may signal broader deficits of
nuclear heterochromatin. The debated link between BRCA1 and Xi might reflect a
general relationship between BRCA1 and heterochromatin, which could connect
BRCA1 to both epigenetic and genetic instability. We suggest that
heterochromatic instability is a common but largely unexplored mechanism,
leading to widespread genomic misregulation and the evolution of some cancers. The Barr body is the inactive X chromosome in a female somatic cell. It is
readily identified as plano-convex structure of 2-3 micron in diameter on the
periphery of the nuclear membrane. The aim of this study is to evaluate the
significance of Barr body count in maligt ovarian tumors on fine needle
aspiration cytology (FNAC) smears. In this retrospective study, Barr body was
counted in FNAC smears of 20 successive maligt ovarian lesions and expressed
as percentage. Mean (±SD) Barr body score was 2.4 ± 2.58. Minimum Barr body
count was 1 and maximum was 9. The gross reduction of Barr body in ovarian
neoplasms is an interesting cytomorphologic finding. In humans, sexual dimorphism is associated with the presence of two X
chromosomes in the female, whereas males possess only one X and a small and
largely degenerate Y chromosome. How do men cope with having only a single X
chromosome given that virtually all other chromosomal monosomies are lethal?
Ironically, or even typically many might say, women and more generally female
mammals contribute most to the job by shutting down one of their two X
chromosomes at random. This phenomenon, called X-inactivation, was originally
described some 50 years ago by Mary Lyon and has captivated an increasing number
of scientists ever since. The fascination arose in part from the realisation
that the inactive X corresponded to a dense heterochromatin mass called the
"Barr body" whose number varied with the number of Xs within the nucleus and
from the many intellectual questions that this raised: How does the cell count
the X chromosomes in the nucleus and inactivate all Xs except one? What kind of
molecular mechanisms are able to trigger such a profound, chromosome-wide
metamorphosis? When is X-inactivation initiated? How is it transmitted to
daughter cells and how is it reset during gametogenesis? This review retraces
some of the crucial findings, which have led to our current understanding of a
biological process that was initially considered as an exception completely
distinct from conventional regulatory systems but is now viewed as a paradigm
"par excellence" for epigenetic regulation. Human inactive X chromosome (Xi) forms a compact structure called the Barr body,
which is enriched in repressive histone modifications such as trimethylation of
histone H3 Lys9 (H3K9me3) and Lys27 (H3K27me3). These two histone marks are
distributed in distinct domains, and X-inactive specific transcript (XIST)
preferentially colocalizes with H3K27me3 domains. Here we show that Xi
compaction requires HBiX1, a heterochromatin protein 1 (HP1)-binding protein,
and structural maintece of chromosomes hinge domain-containing protein 1
(SMCHD1), both of which are enriched throughout the Xi chromosome. HBiX1
localization to H3K9me3 and XIST-associated H3K27me3 (XIST-H3K27me3) domains was
mediated through interactions with HP1 and SMCHD1, respectively. Furthermore,
HBiX1 was required for SMCHD1 localization to H3K9me3 domains. Depletion of
HBiX1 or SMCHD1, but not Polycomb repressive complex 2 (PRC2), resulted in Xi
decompaction, similarly to XIST depletion. Thus, the molecular network involving
HBiX1 and SMCHD1 links the H3K9me3 and XIST-H3K27me3 domains to organize the
compact Xi structure. |
Is single-cell analysis (SCA) possible in proteomics? | No, it is not yet feasible, although smaller pilot studies has been performed where a limited number of proteins has been analysed. | Protein phosphorylation is crucial in the regulation of signaling pathways that
control various biological responses. Recent progress in diverse methodologies
to investigate protein phosphorylation in complex biological samples has
resulted in more rapid, detailed and quantitative analyses of signaling
networks. In particular, advances in mass spectrometry (MS) have enabled the
identification and quantification of thousands of both known and novel
phosphorylation sites. Initial MS-based information can be complemented with a
variety of recently developed and improved phosphoproteomic techniques. These
include multiplexed microbead or kinase activity assays, flow cytometry based
single-cell analysis, protein microarrays and interaction studies. The
combination of multiple approaches, coupled with phenotypic response
measurements, computational modeling and biochemical manipulations, will
ultimately reveal the mechanistic regulation of signaling networks. Cancer is a highly complex and heterogeneous disease involving a succession of
genetic changes (frequently caused or accompanied by exogenous trauma), and
resulting in a molecular phenotype that in turn results in a maligt
specification. The development of maligcy has been described as a multistep
process involving self-sufficiency in growth signals, insensitivity to
antigrowth signals, evasion of apoptosis, limitless replicative potential,
sustained angiogenesis, and finally tissue invasion and metastasis. The
quantitative analysis of networking molecules within the cells might be applied
to understand native-state tissue signalling biology, complex drug actions and
dysfunctional signalling in transformed cells, that is, in cancer cells.
High-content and high-throughput single-cell analysis can lead to systems
biology and cytomics. The application of cytomics in cancer research and
diagnostics is very broad, ranging from the better understanding of the tumour
cell biology to the identification of residual tumour cells after treatment, to
drug discovery. The ultimate goal is to pinpoint in detail these processes on
the molecular, cellular and tissue level. A comprehensive knowledge of these
will require tissue analysis, which is multiplex and functional; thus, vast
amounts of data are being collected from current genomic and proteomic platforms
for integration and interpretation as well as for new varieties of updated
cytomics technology. This overview will briefly highlight the most important
aspects of this continuously developing field. Neuropeptides are widespread signal molecules that display a great chemical and
functional diversity. Predictions of neuropeptide cleavage from precursor
proteins are not always correct, and thus, biochemical identification is
essential. Single-cell analysis is valuable to identify peptides processed from
a single precursor, but also to determine coexpression of further neuropeptides
from other precursors. We have developed an approach to isolate single
identified neurons from the fruit fly Drosophila melanogaster for mass
spectrometric analysis. By using Gal4 promoter lines to drive green fluorescent
protein under UAS control, we identified specific peptidergic neurons. These
neurons were isolated singly under a fluorescence microscope and subjected to
MALDI-TOF mass spectrometry. Two Gal4 lines were used here to identify
pigment-dispersing factor (PDF) and hugin-expressing neurons. We found that the
large PDF expressing clock neurons only give rise to a single peptide, PDF. The
three different classes of hugin expressing neurons all display the same mass
signal, identical to pyrokinin-2. The other peptide predicted from the hugin
precursor, hugin gamma, was not detected in any of the cells. Single-cell
peptidomics is a powerful tool in Drosophila neuroscience since Gal4 drivers can
be produced for all known neuropeptide genes and thus provide detailed
information about neuropeptide complements in neurons of interest. Comprehensive two-dimensional liquid chromatography-capillary electrophoresis
systems are summarized in this chapter. A variety of combinations of capillary
electrophoresis and liquid chromatography modes as well as interfaces and
detection technologies are discussed. A typical, comprehensive two-dimensional
system coupled with reverse-phase liquid chromatography with fast capillary
electrophoresis and hyphenated to mass spectrometry was demonstrated for
proteomic analysis. A two-dimensional capillary electrophoresis system of
coupling capillary sieving electrophoresis with micellar electrokinetic
chromatography and its application in single cell analysis for protein
expression profiling are presented. In order to investigate the individual and inhomogenous cellular response, e.g.
to external stimuli, single cell analysis is mandatory and may provide new
cognitions in proteomics as well as in other fields of systems biology in the
future. Here, we report on novel chip architectures for single cell analysis
based on full body quartz glass microfluidic chips (QG chips) that extend our
previous studies in polydimethylsiloxane (PDMS) chips, and enhance the detection
sensitivity of native UV laser-induced fluorescence (UV-LIF) detection.
Detection of a 10nM tryptophan solution with an S/N ratio of 11.9, which gives a
theoretical limit of detection of 2.5 nM (with S/N=3), was possible. With these
optimizations the three proteins alpha-chymotrypsinogen A, ovalbumin and
catalase each at a concentration of 100 microg/mL (equal to 4 microM, 0.4 microM
and 2.2 microM) were injected electrokinetically and could be separated with
nearly baseline resolution. Furthermore, fluorescence spectra (excitation
wavelength, lambda(ex) = 266 nm) clearly demonstrate the favourable properties
like the very high UV transparency and the nearly vanishing background
fluorescence of the QG chips as compared to PDMS chips and to PDMS quartz window
(PQW) chips. Finally we exploit the improved sensitivity for single cell
electropherograms of Spodoptera frugiperda (Sf9) insect cells. For this special issue of J. R. Soc. Interface we present an overview of the
driving forces behind technological advances in the field of single-cell
analysis. These range from increasing our understanding of cellular
heterogeneity through to the study of rare cells, areas of research that cannot
be tackled effectively using current high-throughput population-based averaging
techniques. Biological analyses traditionally probe cell ensembles in the range of 103-106
cells, thereby completely averaging over relevant individual cell responses,
such as differences in cell proliferation, responses to external stimuli or
disease onset. In past years, this fact has been realized and increasing
interest has evolved for single-cell analytical methods, which could give
exciting new insights into genomics, proteomics, transcriptomics and systems
biology. Microfluidic or lab-on-a-chip devices are the method of choice for
single-cell analytical tools as they allow the integration of a variety of
necessary process steps involved in single-cell analysis, such as selection,
navigation, positioning or lysis of single cells as well as separation and
detection of cellular analytes. Along with this advantageous integration,
microfluidic devices confine single cells in compartments near their intrinsic
volume, thus minimizing dilution effects and increasing detection sensitivity.
This review overviews the developments and achievements of microfluidic
single-cell analysis of intracellular compounds in the past few years, from
proof-of-principle devices to applications demonstrating a high biological
relevance. Single-cell analysis is essential for understanding the processes of cell
differentiation and metabolic specialisation in rare cell types. The amount of
single proteins in single cells can be as low as one copy per cell and is for
most proteins in the attomole range or below; usually considered as insufficient
for proteomic analysis. The development of modern mass spectrometers possessing
increased sensitivity and mass accuracy in combination with o-LC-MS/MS now
enables the analysis of single-cell contents. In Arabidopsis thaliana, we have
successfully identified nine unique proteins in a single-cell sample and 56
proteins from a pool of 15 single-cell samples from glucosinolate-rich S-cells
by oLC-MS/MS proteomic analysis, thus establishing the proof-of-concept for
true single-cell proteomic analysis. Dehydrin (ERD14_ARATH), two myrosinases
(BGL37_ARATH and BGL38_ARATH), annexin (ANXD1_ARATH), vegetative storage
proteins (VSP1_ARATH and VSP2_ARATH) and four proteins belonging to the
S-adenosyl-l-methionine cycle (METE_ARATH, SAHH1_ARATH, METK4_ARATH and
METK1/3_ARATH) with associated adenosine kinase (ADK1_ARATH), were amongst the
proteins identified in these single-S-cell samples. Comparison of the functional
groups of proteins identified in S-cells with epidermal/cortical cells and whole
tissue provided a unique insight into the metabolism of S-cells. We conclude
that S-cells are metabolically active and contain the machinery for de novo
biosynthesis of methionine, a precursor for the most abundant glucosinolate
glucoraphanine in these cells. Moreover, since abundant TGG2 and TGG1 peptides
were consistently found in single-S-cell samples, previously shown to have high
amounts of glucosinolates, we suggest that both myrosinases and glucosinolates
can be localised in the same cells, but in separate subcellular compartments.
The complex membrane structure of S-cells was reflected by the presence of a
number of proteins involved in membrane maintece and cellular organisation. We describe a microchip designed to quantify the levels of a dozen cytoplasmic
and membrane proteins from single cells. We use the platform to assess
protein-protein interactions associated with the EGF-receptor-mediated PI3K
signaling pathway. Single-cell sensitivity is achieved by isolating a defined
number of cells (n = 0-5) in 2 nL volume chambers, each of which is patterned
with two copies of a miniature antibody array. The cells are lysed on-chip, and
the levels of released proteins are assayed using the antibody arrays. We
investigate three isogenic cell lines representing the cancer glioblastoma
multiforme, at the basal level, under EGF stimulation, and under erlotinib
inhibition plus EGF stimulation. The measured protein abundances are consistent
with previous work, and single-cell analysis uniquely reveals single-cell
heterogeneity, and different types and strengths of protein-protein
interactions. This platform helps provide a comprehensive picture of altered
signal transduction networks in tumor cells and provides insight into the effect
of targeted therapies on protein signaling networks. Single-cell analysis (SCA) has been increasingly recognized as the key
technology for the elucidation of cellular functions, which are not accessible
from bulk measurements on the population level. Thus far, SCA has been achieved
by miniaturization of established engineering concepts to match the dimensions
of a single cell. However, SCA requires procedures beyond the classical approach
of upstream processing, fermentation, and downstream processing because the
biological system itself defines the technical demands. This review
characterizes currently available microfluidics and microreactors for invasive
(i.e., chemical) and noninvasive (i.e., biological) SCA. We describe the recent
SCA omics approaches as tools for systems biology and discuss the role of SCA in
genomics, transcriptomics, proteomics, metabolomics, and fluxomics. Furthermore,
we discuss applications of SCA for biocatalysis and metabolic engineering as
well as its potential for bioprocess optimization. Finally, we define present
and future challenges for SCA and propose strategies to overcome current
limitations. Mass spectrometry imaging and profiling of individual cells and subcellular
structures provide unique analytical capabilities for biological and biomedical
research, including determination of the biochemical heterogeneity of cellular
populations and intracellular localization of pharmaceuticals. Two mass
spectrometry technologies-secondary ion mass spectrometry (SIMS) and matrix
assisted laser desorption/ionization mass spectrometry (MALDI MS)-are most often
used in micro-bioanalytical investigations. Recent advances in ion probe
technologies have increased the dynamic range and sensitivity of analyte
detection by SIMS, allowing two- and three-dimensional localization of analytes
in a variety of cells. SIMS operating in the mass spectrometry imaging (MSI)
mode can routinely reach spatial resolutions at the submicron level; therefore,
it is frequently used in studies of the chemical composition of subcellular
structures. MALDI MS offers a large mass range and high sensitivity of analyte
detection. It has been successfully applied in a variety of single-cell and
organelle profiling studies. Innovative instrumentation such as scanning
microprobe MALDI and mass microscope spectrometers enables new subcellular MSI
measurements. Other approaches for MS-based chemical imaging and profiling
include those based on near-field laser ablation and inductively-coupled plasma
MS analysis, which offer complementary capabilities for subcellular chemical
imaging and profiling. Traditional technologies to investigate system biology are limited by the
detection of parameters resulting from the averages of large populations of
cells, missing cells produced in small numbers, and attempting to uniform the
heterogeneity. The advent of proteomics and genomics at a single-cell level has
set the basis for an outstanding improvement in analytical technology and data
acquisition. It has been well demonstrated that cellular heterogeneity is
closely related to numerous stochastic transcriptional events leading to
variations in patterns of expression among single genetically identical cells.
The new-generation technology of single-cell analysis is able to better
characterize a cell's population, identifying and differentiating outlier cells,
in order to provide both a single-cell experiment and a corresponding bulk
measurement, through the identification, quantification and characterization of
all system biology aspects (genomics, transcriptomics, proteomics, metabolomics,
degradomics and fluxomics). The movement of omics into single-cell analysis
represents a significant and outstanding shift. |
Is shotgun lipidomics the direct infusion of a lipid sample into a mass spectrometer? | Yes, shotgun lipidomics relies on direct infusion of total lipid extracts into a high-resolution tandem mass spectrometer. | This article presents the strategies underlying the automated identification and
quantification of individual lipid molecular species through array analysis of
multidimensional mass spectrometry-based shotgun lipidomics (MDMS-SL) data,
which are acquired directly from lipid extracts after direct infusion and
intrasource separation. The automated analyses of individual lipid molecular
species in the program employ a strategy in which MDMS-SL data from building
block analyses using precursor ion scans, neutral loss scans, or both are used
to identify individual molecular species, followed by quantitation. Through this
strategy, the program screens and identifies species in a high-throughput
fashion from a built-in database of over 36,000 potential lipid molecular
species constructed employing known building blocks. The program then uses a
two-step procedure for quantitation of the identified species possessing a
linear dynamic range over 3 orders of magnitude and reverifies the results when
necessary through redundant quantification of multidimensional mass spectra.
This program is designed to be easily adaptable for other shotgun lipidomics
approaches that are currently used for mass spectrometric analysis of lipids.
Accordingly, the development of this program should greatly accelerate
high-throughput analysis of lipids using MDMS-based shotgun lipidomics. Holistic analysis of lipids is becoming increasingly popular in the life
sciences. Recently, several interesting, mass spectrometry-based studies have
been conducted, especially in plant biology. However, while great advancements
have been made we are still far from detecting all the lipids species in an
organism. In this study we developed an ultra performance liquid
chromatography-based method using a high resolution, accurate mass, mass
spectrometer for the comprehensive profiling of more than 260 polar and
non-polar Arabidopsis thaliana leaf lipids. The method is fully compatible to
the commonly used lipid extraction protocols and provides a viable alternative
to the commonly used direct infusion-based shotgun lipidomics approaches. The
whole process is described in detail and compared to alternative lipidomic
approaches. Next to the developed method we also introduce an in-house developed
database search software (GoBioSpace), which allows one to perform targeted or
un-targeted lipidomic and metabolomic analysis on mass spectrometric data of
every kind. An efficient shotgun lipidomics strategy was established and optimized for fast
phospholipid profiling of viscera from three fish species: Lateolabrax
japonicas, Ctenopharyngodon idellus, and Carassius auratus. This strategy relies
on direct infusion of total lipid extracts into a tandem mass spectrometer
without additional separation of the individual molecular species. Four classes
of phospholipids, including phosphatidylcholine (PC), phosphatidylethanolamine
(PE), phosphatidylinositol (PI), and phosphatidylserine (PS), were analyzed, and
at least 81 molecular species of phospholipids were identified, including 34
species of PC, 24 species of PE, 12 species of PS, and 11 species of PI, in both
positive- and negative-ion electrospray ionization mode. The results show that
fish viscera, which are traditionally discarded as fisheries wastes, are
nutritional in phospholipids with total contents of the four detected
phospholipid classes ranging from 1.52 to 3.29 mg/g in the three tested fish
species. Regardless of the tested fish species, PC and PE are the domit
phospholipid classes, followed by PI and PS. Furthermore, principal component
analysis (PCA) was applied to normalize the relative amounts of the identified
phospholipid species. The results demonstrate that PS 18:0/22:6, PI 18:0/20:4,
and PI 18:0/20:5 were the main contributors of cumulative value and could be
used as an indicator for fish species differentiation. This shotgun lipidomics
method was >10 times faster than traditional methods, because no chromatographic
separation was needed. The successful application of this strategy paves the way
for full utilization of traditionally discarded fisheries wastes and provides an
alternative means for fish species differentiation. |
How many genes are in the gene signature screened by MammaPrint? | Mammaprint has a 70 gene signature. | PURPOSE: Most node-negative breast cancer patients are older and postmenopausal
and are increasingly being offered adjuvant chemotherapy despite their low
overall risk of distant relapse. A molecular diagnostic test with high negative
predictive value (NPV) for distant metastasis in this subgroup would spare many
older breast cancer patients adjuvant treatment.
EXPERIMENTAL DESIGN: We determined the NPV and positive predictive value of the
MammaPrint assay in breast cancer patients who were consecutively diagnosed and
treated at the Massachusetts General Hospital between 1985 and 1997. Primary
tumors from 100 patients with node-negative, invasive breast cancer (median age,
62.5 years; median follow-up, 11.3 years) were subjected to MammaPrint analysis
and classified as being at either low or high risk for distant metastasis.
RESULTS: The MammaPrint 70-gene signature displayed excellent NPV as in previous
studies, correctly identifying 100% of women at low risk for distant metastases
at 5 years. However, this assay had a lower positive predictive value (12% at 5
years) than previously observed.
CONCLUSIONS: The MammaPrint assay was originally designed to identify younger
breast cancer patients at low risk for distant metastasis, who might
consequently be spared systemic treatment. We show here that the same signature
has a very high NPV for distant recurrence after adjuvant treatment in older
breast cancer patients. BACKGROUND: Numerous studies have used microarrays to identify gene signatures
for predicting cancer patient clinical outcome and responses to chemotherapy.
However, the potential impact of gene expression profiling in cancer diagnosis,
prognosis and development of personalized treatment may not be fully exploited
due to the lack of consensus gene signatures and poor understanding of the
underlying molecular mechanisms.
METHODS: We developed a novel approach to derive gene signatures for breast
cancer prognosis in the context of known biological pathways. Using unsupervised
methods, cancer patients were separated into distinct groups based on gene
expression patterns in one of the following pathways: apoptosis, cell cycle,
angiogenesis, metastasis, p53, DNA repair, and several receptor-mediated
signaling pathways including chemokines, EGF, FGF, HIF, MAP kinase, JAK and
NF-kappaB. The survival probabilities were then compared between the patient
groups to determine if differential gene expression in a specific pathway is
correlated with differential survival.
RESULTS: Our results revealed expression of cell cycle genes is strongly
predictive of breast cancer outcomes. We further confirmed this observation by
building a cell cycle gene signature model using supervised methods. Validated
in multiple independent datasets, the cell cycle gene signature is a more
accurate predictor for breast cancer clinical outcome than the previously
identified Amsterdam 70-gene signature that has been developed into a FDA
approved clinical test MammaPrint.
CONCLUSION: Taken together, the gene expression signature model we developed
from well defined pathways is not only a consistently powerful prognosticator
but also mechanistically linked to cancer biology. Our approach provides an
alternative to the current methodology of identifying gene expression markers
for cancer prognosis and drug responses using the whole genome gene expression
data. The 70-gene signature (MammaPrint) is a prognostic tool used to guide adjuvant
treatment decisions. The aim of this study was to assess its value to predict
chemosensitivity in the neoadjuvant setting. We obtained the 70-gene profile of
stage II-III patients prior to neoadjuvant chemotherapy and classified the
prognosis-signatures. Pathological complete remission (pCR) was used to measure
chemosensitivity. Among 167 patients, 144 (86%) were having a poor and 23 (14%)
a good prognosis-signature. None of the good prognosis-signature patients
achieved a pCR (0/23), whereas 29/144 patients (20%) in the poor
prognosis-signature group did (P = 0.015). All triple-negative tumors (n = 38)
had a poor prognosis-signature. Within the non triple-negative subgroup, the
response of the primary tumor remained associated with the classification of the
prognosis-signature (P = 0.023). A pCR is unlikely to be achieved in tumors that
have a good prognosis-signature. Tumors with a poor prognosis-signature are more
sensitive to chemotherapy. BACKGROUND: Mammographic screening and increased awareness has led to an
increase in the detection of T1 breast tumors that are generally estimated as
having low risk of recurrence after locoregional treatment. However, even small
tumors can metastasize, which leaves us with the question for the necessity of
adjuvant treatment. Therefore, additional prognostic markers are needed to
tailor adjuvant systemic treatment for these relatively low-risk patients. The
aim of our study was to evaluate the accuracy of the 70-gene MammaPrint
signature in T1 breast cancer.
MATERIALS AND METHODS: We selected 964 patients from previously reported studies
with pT1 tumors (<or=2 cm). Frozen tumor samples were hybridized on the 70-gene
signature array at the time of the initial study and classified as having good
prognosis or poor prognosis.
RESULTS: The median follow-up was 7.1 years (range 0.2-25.2). The 10-year
distant metastasis-free (DMFS) and breast cancer specific survival (BCSS)
probabilities were 87% (SE 2%) and 91% (SE 2%), respectively, for the good
prognosis-signature group (n = 525), and 72% (SE 3%) and 72% (SE 3%),
respectively, for the poor prognosis-signature group (n = 439). The signature
was an independent prognostic factor for BCSS at 10 years (multivariate hazard
ratio [HR] 3.25 [95% confidence interval, CI, 1.92-5.51; P < .001]). Moreover,
the 70-gene MammaPrint signature predicted DMFS at 10 years for 139 patients
with pT1ab cancers (HR 3.45 [95% CI 1.04-11.50, P = .04]).
CONCLUSIONS: The 70-gene MammaPrint signature is an independent prognostic
factor in patients with pT1 tumors and can help to individualize adjuvant
treatment recommendation in this increasing breast cancer population. Multigene assays have been developed and validated to determine the prognosis of
breast cancer. In this study, we assessed the additional predictive value of the
70-gene MammaPrint signature for chemotherapy (CT) benefit in addition to
endocrine therapy (ET) from pooled study series. For 541 patients who received
either ET (n = 315) or ET + CT (n = 226), breast cancer-specific survival (BCSS)
and distant disease-free survival (DDFS) at 5 years were assessed separately for
the 70-gene high and low risk groups. The 70-gene signature classified 252
patients (47%) as low risk and 289 (53%) as high risk. Within the 70-gene low
risk group, BCSS was 97% for the ET group and 99% for the ET + CT group at 5
years with a non-significant univariate hazard ratio (HR) of 0.58 (95% CI
0.07-4.98; P = 0.62). In the 70-gene high risk group, BCSS was 81% (ET group)
and 94% (ET + CT group) at 5 years with a significant HR of 0.21 (95% CI
0.07-0.59; P < 0.01). DDFS was 93% (ET) versus 99% (ET + CT), respectively, in
the 70-gene low risk group, HR 0.26 (95% CI 0.03-2.02; P = 0.20). In the high
risk group DDFS was 76 versus 88%, HR of 0.35 (95% CI 0.17-0.71; P < 0.01).
Results were similar in multivariate analysis, showing significant survival
benefit by adding CT in the 70-gene high risk group. A significant and
clinically meaningful benefit was observed by adding chemotherapy to endocrine
treatment in 70-gene high risk patients. This benefit was not significant in low
risk patients, who were at such low risk for recurrence and cancer-related
death, that adding CT does not appear to be clinically meaningful. BACKGROUND: The 70-gene signature (MammaPrint) is a prognostic test used to
guide adjuvant treatment decisions in patients with node-negative breast cancer.
In order to decide upon its use, a systematic comparative analysis of the
effects of the 70-gene signature, the Sankt Gallen guidelines and the Adjuvant
Online Software for these patients on survival, quality of life and costs is
warranted.
METHODS: A Markov decision model was used to simulate the 20-year costs and
outcomes (survival and quality-of-life adjusted survival (QALYs)) in a
hypothetical cohort of node-negative, estrogen receptor positive breast cancer
patients. Sensitivity and specificity of the three prognostic tools were based
on 5 and 10 years breast cancer specific survival and distant metastasis as
first event, derived from a pooled analysis consisting of 305 tumour samples
from 3 previously reported validation studies concerning the 70-gene signature.
RESULTS: Small differences in survival, but substantial differences in
quality-adjusted survival between the prognostic tools were observed.
Quality-adjusted survival was highest when using the 70-gene signature. Based on
costs per QALY, the 70-gene has the highest probability of being cost-effective
for a willingness to pay for a QALY higher than euro12.000. Sankt Gallen showed
the highest survival rates compared to the 70-gene signature, but leads to a
substantial larger amount of adjuvant chemotherapy and lower cost-effectiveness,
thus demanding a high willingness to pay to save a life year.
CONCLUSIONS: When deciding upon the cost-effectiveness of the prognostic tests,
the 70-gene signature improves quality-adjusted survival and has the highest
probability of being cost-effective. BACKGROUND: MammaPrint was developed as a diagnostic tool to predict risk of
breast cancer metastasis using the expression of 70 genes. To better understand
the tumor biology assessed by MammaPrint, we interpreted the biological
functions of the 70-genes and showed how the genes reflect the six hallmarks of
cancer as defined by Hanahan and Weinberg.
RESULTS: We used a bottom-up system biology approach to elucidate how the
cellular processes reflected by the 70-genes work together to regulate tumor
activities and progression. The biological functions of the genes were analyzed
using literature research and several bioinformatics tools. Protein-protein
interaction network analyses indicated that the 70-genes form highly
interconnected networks and that their expression levels are regulated by key
tumorigenesis related genes such as TP53, RB1, MYC, JUN and CDKN2A. The
biological functions of the genes could be associated with the essential steps
necessary for tumor progression and metastasis, and cover the six well-defined
hallmarks of cancer, reflecting the acquired maligt characteristics of a
cancer cell along with tumor progression and metastasis-related biological
activities.
CONCLUSION: Genes in the MammaPrint gene signature comprehensively measure the
six hallmarks of cancer-related biology. This finding establishes a link between
a molecular signature and the underlying molecular mechanisms of tumor cell
progression and metastasis. OBJECTIVE: To evaluate the cost-effectiveness of 70-gene MammaPrint signature
(Agendia Inc, Huntington Beach, CA) vs Adjuvant! Online software (AS)
(http://www.adjuvantonline.com) in patients 60 years or younger with early-stage
breast cancer.
STUDY DESIGN: Cost-effectiveness and cost-utility analyses from a US payer
perspective.
METHODS: A Markov model with 3 health states was constructed. In the base case
model, risk classification and patient outcomes were based on a 70-gene
signature validation study. Efficacy of chemotherapy was derived from a
published meta-analysis of clinical trials. An alternative model using data from
AS and from the Surveillance, Epidemiology and End Results registry was built to
examine the external validity of the base case model. The incremental benefits,
costs, and cost-effectiveness of treatment guided by 70-gene signature were
calculated.
RESULTS: In the base case model, 70-gene signature reclassified 29% of patients
and spared 10% of patients from chemotherapy. Compared with the AS strategy, the
70-gene signature strategy was associated with $1440 higher total cost per
patient and with 0.14 additional life-year or 0.15 additional quality-adjusted
life-year. Overall, the incremental cost-effectiveness ratios were approximately
$10,000 per life-year or quality-adjusted life-year in the base case model and
$700 in the alternative model. The model results were sensitive to estrogen
receptor status, the proportion of patients classified as high risk vs low risk,
and the overall survival in each risk group.
CONCLUSION: A 70-gene signature is likely to be a cost-effective strategy to
guide adjuvant chemotherapy treatment in younger patients with early-stage
breast cancer. HINTERGRUND: Ziel dieser Arbeit war die Evaluierung der 70-Gen-Prognose-Signatur
MammaprintTM bei Patientinnen ≥ 60 Jahre mit einem invasiven Mammakarzinom.
PATIENTEN UND METHODEN: 60 Patientinnen wurden für diese prospektive Studie
rekrutiert. Einschlusskriterien waren: pT1c-3, pN0–1a, Grading 2/3,
Hormonrezeptor-Positivität und HER2-negativer Tumor. Das klinische Risikoprofil
wurde mit dem Programm Adjuvant! Online (AOL) eingeschätzt.
ERGEBNISSE: 38 Frauen (63%) wurden durch die 70-Gen-Signatur als
Niedrigrisiko-Patienten eingestuft; demgegenüber stehen 22 (37%) in der
Hochrisiko-Gruppe. Beim Vergleich zwischen den Niedrigund Hochrisiko-Gruppen
wurde kein statistisch signifikanter Unterschied für die konventionellen
Prognoseparameter gefunden, insbesondere nicht für Ki-67. In der AOL-Analyse
wurden 33 Patientinnen (55%) als Hochrisiko-Patienten eingestuft, von denen 20
ein diskordantes 70-Gen-Signaturergebnis hatten. Eine Diskordanz zwischen der
70-Gen-Signatur und dem AOL-Ergebnis wurde bei 48% der Patientinnen ermittelt.
Diese Rate liegt höher als in früheren Publikationen. Die Kombination von
klinisch-pathologischer Risikoeinstufung und Gensignatur führte bei 11
Patientinnen (18%) zu einer Änderung der adjuvanten systemischen
Therapieempfehlung.
SCHLUSSFOLGERUNGEN: Die 70-Gen-Signatur könnte bei älteren Frauen mit einem
mittleren Risiko ein Zusatzkriterium für bzw. gegen eine adjuvante
Chemotherapieempfehlung sein. Die konventionellen klinischpathologischen
Parameter korrelierten nicht mit der 70-Gen-Signatur für diese Patientinnen. BACKGROUND: Breast cancer patients with node positive disease can have an
excellent outcome with tamoxifen only. It is unclear whether analysing both the
70-gene signature and hormone receptors provides superior prediction of outcome
in tamoxifen-treated patients than either alone.
METHODS: Three series were evaluated: 121 patients (81% node positive) received
adjuvant tamoxifen, 151 patients did not receive tamoxifen (10% node positive)
and 92 patients received tamoxifen for metastatic disease. The 70-gene signature
was analysed using MammaPrint. Oestrogen receptor (ER) and progesterone receptor
(PR) immunohistochemistry was evaluated following St. Gallen Consensus (Highly
Endocrine Responsive: ER and PR ≥ 50%, Incompletely Endocrine Responsive: ER
and/or PR low or either one absent).
RESULTS: In patients treated with adjuvant tamoxifen, both the 70-gene signature
(adjusted for Endocrine Response Categories HR 2.17, 95%CI 1.01-4.66) as well as
the Endocrine Response Categories (adjusted for 70-gene signature HR 6.35, 95%CI
1.90-21.3) were associated with breast-cancer-specific-survival (BCSS). Also in
patients treated with tamoxifen for metastatic disease, combined analysis of the
70-gene signature and ER/PR revealed additional value (multivariate Cox
regression, p = 0.013). In patients who did not receive tamoxifen, only the
70-gene signature was associated with outcome.
CONCLUSION: In the series analysed, the 70-gene signature was mainly a
prognostic factor, while ER and PR levels were mainly associated with outcome
after tamoxifen. Combination of these three factors may improve outcome
prediction in tamoxifen-treated patients. BACKGROUND: The 70 gene-signature (MammaPrint(®)) is a prognostic profile of
distant recurrence and survival of primary breast cancer (BC). BC patients with
4-9 positive nodes (LN 4-9) are considered clinically at high-risk. Herein we
examined MammaPrint(®) added prognostic value in this group.
PATIENTS AND METHODS: MammaPrint(®) profiles were generated from frozen tumours
of patients operated from primary BC. Samples were classified as genomic Low
Risk (GLR) or genomic High Risk (GHR).
RESULTS: Among the 173 samples, 70 (40%) were classified as GLR and 103 (60%) as
GHR. Tumours in the GHR group were significantly more often ductal carcinomas
(93%), grade 3 (60%), oestrogen and progesterone-negative, Her2 positive (25%).
In the GLR category, the 5-year overall survival was 97% vs. 76% for in the GHR
group (p < 0.01); Distant Metastasis Free Survival (DMFS) at 5 years was 87% for
GLR patients and 63% for GHR patients (p < 0.01). In the Luminal A subgroup, the
genomic profile was the only independent risk factor for DM and BC specific
death.
CONCLUSION: In the Luminal A subgroup, MammaPrint(®) is an independent
prognostic marker in BC patients with LN 4-9 and may be integrated in a
selection strategy of patients candidate for more aggressive therapeutic
approaches. The 70-gene signature (MammaPrint™) has been developed on retrospective series
of breast cancer patients to predict the risk of breast cancer distant
metastases. The microarRAy-prognoSTics-in-breast-cancER (RASTER) study was the
first study designed to prospectively evaluate the performance of the 70-gene
signature, which result was available for 427 patients (cT1-3N0M0). Adjuvant
systemic treatment decisions were based on the Dutch CBO 2004 guidelines, the
70-gene signature and doctors' and patients' preferences. Five-year
distant-recurrence-free-interval (DRFI) probabilities were compared between
subgroups based on the 70-gene signature and Adjuvant! Online (AOL) (10-year
survival probability <90% was defined as high-risk). Median follow-up was 61.6
months. Fifteen percent (33/219) of the 70-gene signature low-risk patients
received adjuvant chemotherapy (ACT) versus 81% (169/208) of the 70-gene
signature high-risk patients. The 5-year DRFI probabilities for 70-gene
signature low-risk (n = 219) and high-risk (n = 208) patients were 97.0% and
91.7%. The 5-year DRFI probabilities for AOL low-risk (n = 132) and high-risk
(n = 295) patients were 96.7% and 93.4%. For 70-gene signature low-risk-AOL
high-risk patients (n = 124), of whom 76% (n = 94) had not received ACT, 5-year
DRFI was 98.4%. In the AOL high-risk group, 32% (94/295) less patients would be
eligible to receive ACT if the 70-gene signature was used. In this prospective
community-based observational study, the 5-year DRFI probabilities confirmed the
additional prognostic value of the 70-gene signature to clinicopathological risk
estimations such as AOL. Omission of adjuvant chemotherapy as judged appropriate
by doctors and patients and instigated by a low-risk 70-gene signature result,
appeared not to compromise outcome. |
Is apixaban effective for treatment of acute venous thromboembolism? | Apixaban is a direct inhibitor of factor Xa, and is a potential alternative for the treatment of acute venous thromboembolism. These results suggest a lack of clear superiority of apixaban relative to enoxaparin. Apixaban is an oral alternative with similar efficacy and safety to existing anticoagulant therapies. | Indirect systemic and direct oral factor Xa and direct oral factor IIa
inhibitors with improved pharmacologic profiles compared with heparins and
vitamin K antagonists are currently in clinical development. This overview
focuses on the indirect antithrombin dependent pentasaccharide derivatives of
idraparinux and on the most advanced oral direct inhibitors to factor Xa
(rivaroxaban and apixaban) and IIa (dabigatran). Specifically, the results of
dose-finding studies for the prevention of venous thromboembolism after elective
orthopedic surgery, the results of dose-finding studies for treatment of acute
venous thromboembolism including prolonged prophylaxis of recurrent events, and
the designs of ongoing clinical trials are reviewed. Patients with antiphospholipid syndrome are at increased risk for recurrent
arterial and venous thrombosis and therefore benefit from long term warfarin
therapy. The optimal duration of warfarin therapy after a first venous
thromboembolic event is however a matter of some controversy and many questions
remain uswered. After reviewing and analysing the available evidence, we
discuss some common scenarios in everyday clinical practice where treatment
decisions are difficult. The treatment of choice for acute venous thromboembolism is anticoagulant
therapy with fast-acting drugs (unfractionated or low-molecular-weight heparin
or fondaparinux) aimed at preventing thrombus extension, followed by extended
prophylaxis with vitamin K antagonists aimed at preventing recurrence.
Experience accumulated over the years has demonstrated that strict laboratory
monitoring is required for unfractionated heparin and vitamin K antagonists,
making use of these drugs problematic for patients and physicians and prompting
researchers to develop new anticoagulants equally effective but without the
requirement for laboratory monitoring. The results of clinical trials to date,
albeit limited, suggest that these new drugs will probably keep their promise.
However, the definitive answer will come subsequent to these clinical trials,
when clinicians will start to use these drugs to treat patients in the real
world. It is likely that some sort of laboratory monitoring will be required at
least for selected categories of patients. Accordingly, clinical laboratories
should still be prepared to monitor patients, although the numbers may hopefully
decrease sharply in the next decade or so. Anticoagulant drugs reduce the risk of venous thromboembolic events after total
hip and knee arthroplasty. However, the use of current drugs, such as low
molecular weight heparins, is hampered by their subcutaneous route of
administration. The use of vitamin K antagonists is hampered by the requirement
for routine coagulation monitoring and dose titration to provide effective
anticoagulation without an increased risk of bleeding and numerous food and drug
interactions. Clearly, there is a need for new oral, fixed-dose anticoagulant
drugs that do not require coagulation monitoring, while demonstrating similar or
better efficacy and safety profiles when compared with current agents. Vitamin-K antagonists have played a domit role in the long-term management of
patients with venous thromboembolism, and large trials from the past decade
reinforced warfarin's effectiveness as an intermediate-duration and
extended-duration anticoagulant. However, promising new oral direct thrombin
inhibitors are proving to be at least as effective and as safe as the vitamin-K
antagonists, without the associated hepatic toxicity that was seen with earlier
orally administered direct thrombin inhibitors. This article reviews the
recently published Dabigatran versus Warfarin in the Treatment of Acute Venous
Thromboembolism clinical trial, and discusses the limitations and clinical
applicability of the trial, especially in comparison with vitamin-K antagonists
and the recently studied oral direct factor Xa inhibitors, rivaroxaban and
apixaban. For the last 60 years, heparin and vitamin K antagonists have been the
cornerstone of anticoagulation. Nowadays, the new anticoagulants, such as
dabigatran, rivaroxaban and apixaban, show potential advantages over classical
treatments. These agents inhibit specific coagulation factors and are
administered orally at fixed doses. Furthermore, heparin and vitamin K
antagonists have a fast onset of action, short-duration and predictable
therapeutic effects. No interactions with foods have been described, although
some drug-drug interactions have been reported. At the moment, no antidotes are
available. However, due to the short half-life of these agents, antidotes are
less essential. The new anticoagulants are at least as effective and safe as
traditional treatments in the prevention of venous thromboembolism after
orthopedic surgery, as well as in the prevention of stroke and systemic embolism
in non-valvular atrial fibrillation. Dabigatran and rivaroxaban have also been
shown to be effective in the treatment of acute venous thromboembolism. Due to
their properties, these drugs could gradually replace heparin and especially
vitamin K antagonists. Hopefully, many of our patients will be able to
discontinue classical anticoagulant treatment and others will never begin it. OBJECTIVE: To critically review the effectiveness of the novel oral
anticoagulants (rivaroxaban, dabigatran, ximelagatran, and apixaban) in the
treatment of acute venous thromboembolism.
DESIGN: Systematic review and random effects meta-analysis. Data were extracted
independently by two investigators. An adjusted indirect comparison was
performed to compare between novel oral anticoagulants.
DATA SOURCES: Medline, Embase, and Cochrane Library (from inception to April
2012). Hand searching of relevant scientific works and contact with experts.
STUDY SELECTION: Randomised controlled trials of novel oral anticoagulants
compared with vitamin K antagonists for acute venous thromboembolism. Selected
outcomes were recurrent events, major bleeding, and all cause mortality.
RESULTS: Nine studies met our inclusion criteria, involving 16,701 patients
evaluated for efficacy and 16,611 for safety. Data were stratified according to
different novel oral anticoagulants. For recurrent acute venous thromboembolism,
there were no significant differences in events rates between any of the
anticoagulants and conventional treatment (rivaroxaban (four studies): relative
risk 0.85, 95% confidence interval 0.55 to 1.31; dabigatran (two studies): 1.09,
0.76 to 1.57; ximelagatran (two studies): 1.06, 0.62 to 1.80; and apixaban (one
study): 0.98, 0.20 to 4.79). Rivaroxaban reduced the risk of major bleeding
compared with conventional treatment (0.57, 0.39 to 0.84), whereas other novel
oral anticoagulants did not (0.76 (0.49 to 1.18) for dabigatran; 0.54 (0.28 to
1.03) for ximelagatran; 2.95 (0.12 to 71.82) for apixaban). For all cause
mortality there were no significant differences between the novel oral
anticoagulants and conventional treatment (0.96 (0.72 to 1.27) for rivaroxaban;
1.00 (0.67 to 1.50) for dabigatran; 0.67 (0.42 to 1.08) for ximelagatran; 6.89
(0.36 to 132.06) for apixaban). The adjusted indirect comparison between
rivaroxaban and dabigatran did not show superiority of either drug over the
others for major bleeding (0.75, 0.41 to 1.34) or the other endpoints.
CONCLUSIONS: Compared with vitamin K antagonists, the novel oral anticoagulants
had a similar risk of recurrence of acute venous thromboembolism and all cause
mortality, though rivaroxaban was associated with a reduced risk of bleeding. Acute venous thromboembolism poses significant problems in pregcy, a time
when objective diagnosis and prompt treatment are essential. Events can occur at
any stage in pregcy, but the period of greatest risk is in the weeks after
delivery. Ultrasound venography remains the diagnostic technique of choice for
deep venous thrombosis. For pulmonary thromboembolism, ventilation perfusion
lung scan is usually preferred more than computerized tomography pulmonary
angiography because of the lower maternal radiation dose and the lower
prevalence of coexisting pulmonary problems. Low-molecular-weight heparin is the
agent of choice for treatment of venous thromboembolism in pregcy, and
treatment should be provided for a minimum of 3 months and for at least 6 weeks
after delivery. New anticoagulant agents such as dabigatran, rivaroxaban, or
apixaban are not recommended for use in pregcy. Collaborators: Agnelli G, Buller H, Cohen A, Gallus A, Raskob G, Weitz J, Prins
M, Brandjes D, Kolbach D, Limburg M, Mac Gillavry M, Otten JM, Peters R, Roos Y,
Segers A, Slagboom T, Bounameaux H, Hirsh J, Samama MM, Wedel H, Curto M,
Johnson M, Masiukiewicz U, Pak R, Porcari A, Sanders P, Sisson M, Sullivan B,
Thompson J, Auerbach J, Cesario L, Crawford J, Gordon M, Noble M, Pennington A,
Reinhold P, Simmons M, Urwin K, Ceresetto J, McRae S, Pabinger I, Pereira AH,
Spencer F, Wang C, Zhang J, Gorican K, Husted SE, Mottier D, Harenberg J, Vértes
A, Pinjala R, Zeltser D, Prandoni P, Sandset M, Torbicki A, Fijalkowska A,
Alvares JP, Kirienko A, Shvarts Y, Sala LA, Jacobson B, Gudz I, Ortel T,
Spyropoulos A, Beyer-Westendorf J, Sipos G, Bredikhin R, Della Siega A, Klinke
W, Lawall H, Zwettler U, Prasol V, Cannon K, Vasylyuk S, Jin B, Prandoni P,
Desai S, Zaichuk A, Katelnitskiy I, De Pellegrin A, Santonastaso M, Skupyy O,
Pesant Y, Shvalb P, Spacek R, Visonà A, Alvarez Sala L, Borja V, Gudz I, Noori
E, Sereg M, Ortel T, Braester A, Falvo N, Mottier D, Jacobson B, Vöhringer H,
Laperna L, Oliven A, Skalicka L, Bolster D, Haidar A, Schellong S, Vértes A,
Smith S, Sergeev O, Pullman J, Torp-Pedersen C, Zimlichman R, Elias M, Fourie N,
Pernod G, Panchenko E, Pendleton R, van Nieuwenhuizen E, Vinereanu D, Agnelli G,
Becattini C, Manina G, Leduc J, Dunaj M, Frost L, Gavish D, Jakobsen T, Lishner
M, Morales L, Chochola J, Gubka O, Holaj R, Hussein O, Katona A, Sergeeva E,
Bova C, Cepeda J, Cohen K, Sobkowicz B, Grzelakowski P, Husted S, Lupkovics G,
Spencer F, Dedek V, Liu C, Puskas A, Ritchie B, Ambrosio G, Parisi R, Heuer H,
Livneh A, Podpera I, Stanbro M, Caraco Y, Fulmer J, Ghirarduzzi A, Schmidt-Lucke
J, Bergmann J, Cizek V, Leyden M, Stein R, Abramov I, Chong B, Colan D, Jindal
R, Liu S, Pereira A, Porreca E, Salem H, Welker J, Yusen R, Dhar A, Gallus A,
Podczeck-Schweighofer A, Shtutin O, Vital Durand D, Zeltser D, Zhang J, Balaji
V, Correa J, Harenberg J, Kline J, Runyon M, Laszlo Z, Martelet M, Parakh R,
Sandset PM, Schmidt J, Yeo E, Bhagavan N, Bura-Riviere A, Cepeda J, Ferrer J,
Lacroix P, Lewczuk J, Pilger E, Sokurenko G, Yu H, Nikulnikov P,
Pabinger-Fasching I, Sanchez-Diaz C, Schuller D, Shvarts Y, Suresh K, Wang C,
Lobo S, Lyons R, Marschang P, Palla A, Schulman S, Spyropoulous A, Fraiz J,
Gerasymov V, Lerner R, Llamas Esperón G, Manenti E, Masson J, Moreira R, Poy C,
Rodoman G, Bruckner I, Gurghean A, Carrier M, Freire A, Gan E, Gibson K, Herold
M, Hudcovic M, Kamath G, Koslow A, Meneveau N, Roos J, Zahn R, Balanda J,
Bratsch H, Dolan S, Gould T, Hirschl M, Hoffmann U, Kaatz S, Shah V, Kadapatti
K, Kræmmer Nielsen H, Lahav M, Natarajan S, Tuxen C, Tveit A, Alves C, Formiga
A, Brudevold R, Cardozo M, Gorican K, Lorch D, Marais H, Mismetti P, Panico M,
Pop C, Quist-Paulsen P, Stevens D, Tarleton G, Yoshida W, Cox M, Crispin P,
Czekalski P, Ebrahim I, Game M, Ghanima W, Harrington D, Jackson D, Lawall H,
Lee A, Matoska P, Meade A, Camargo AC, Nishinari K, Sanchez Llamas F, Tosetto A,
Vejby-Christensen H, Basson M, Blombery P, Fu G, Jha V, Keltai K, Le Jeunne C,
Lodigiani C, Ma Y, Nagy A, Neumeister A, Pinjala R, Shotan A, Wong T, Ying K,
Anderson S, Brenner B, Carnovali M, Cerana S, Cunha C, Diaz-Castañon J, Graham
M, Kirenko A, Palareti G, Rodriguez-Cintron W, Nathanson A, Rosenthal S, Sanders
D, Scheinberg P, Schjesvold F, Torp R, van Zyl L, Venher I, Xia G, Brockmyre A,
Chen Z, Hakki S, Hanefield C, Mügge A, Janczak D, Karpovych D, Lancaster G,
Lavigne C, Lugassy G, Melaniuk M, Moran J, Oliver M, Schattner A, Staroverov I,
Timi J, Vöhringer F, von Bilderling P, Warr T, White R, Wronski J, Wu C, Almeida
C, Blum A, Bono J, Durán M, Erzinger F, Fu W, Jagadesan R, Jurecka W, Korban E,
Nguyen D, Raval M, Willms D, Zevin S, Zhu H, Abdullah I, Achkar A, Albuquerque
L, Ali M, Bai C, Bloomfield D, Chen J, Fajardo Campos P, Garcia Bragado F, Kobza
I, Lindhoff-Last E, Lourenço A, Marchena Yglesias P, Marshall P, Siegel M,
Mikhailova O, Oliva M, Pottier P, Pruszczyk P, Sauer M, Baloira A, Cromer M,
D'Angelo A, Faucher J, Gutowski P, Hong S, Lissauer M, Lopes A, Lopes R, Maholtz
M, Mesquita E, Miekus P, Mohan B, Ng H, Peterson M, Piovella F, Siragusa S,
Srinivas R, Tiberio G, Van Bellen B, Arutyunov G, Assi N, Baker R, Blanc F,
Curnow J, Fu C, Gonzalez-Porras J, Guijarro Merino R, Gunasingam S, Gupta P,
Laule M, Liu Z, Luber J, Masson J, Serifilippi G, Paulson R, Shevela A,
Simonneau G, Siu D, Sosa Liprandi M, Takács J, Tay J, Vora K, Witkiewicz W, Zhao
L, Aquilanti S, Dabbagh O, Dellas C, Denaro C, Doshi A, Fijalkowska A, Flippo G,
Giumelli C, Gomez Cerezo J, Han D, Harris L, Hofmann L Jr, Kamerkar D, Kaminski
L, Kazimir M, Kloczko J, Ko Y, Koura F, Lavender R, Maly J, Margolis B, McRae S,
Mos L, Sanchez-Escalante L, Solvang A, Soroka V, Szopinski P, Thawani H, Vickars
L, Welker J, Yip G, Zangroniz P. Apixaban is a direct inhibitor of factor Xa, and is a potential alternative for
the treatment of acute venous thromboembolism. This study sought to evaluate the
efficacy and safety of apixaban versus enoxaparin. A systematic search of the
literature for randomized controlled trials of apixaban thromboprophylaxis
versus enoxaparin was conducted using three databases: PubMed, EMBASE, and the
Cochrane library. Five studies that included a total of 12,938 patients were
analyzed using Bayesian random-effects meta-analysis. To evaluate efficacy, a
composite of venous thromboembolism and death during follow-up was measured. To
evaluate safety, major and total bleeding events were considered. The odds ratio
(OR) for the composite outcome of efficacy was 0.66 (95 % CI 0.33-1.29) for
apixaban compared to enoxaparin, while there was a similar risk of major
bleeding (OR 1.03, 95 % CI 0.36-3.73) and total bleeding (OR 0.92, 95 % CI
0.64-1.20). These results suggest a lack of clear superiority of apixaban
relative to enoxaparin. Apixaban is an oral alternative with similar efficacy
and safety to existing anticoagulant therapies. Patients with pulmonary embolism (PE) can be stratified into two different
prognostic categories, based on the presence or absence of shock or sustained
arterial hypotension. Some patients with normotensive PE have a low risk of
early mortality, defined as <1% at 30 days or during hospital stay. In this
paper, we will discuss the new prospective for the optimal management of
low-risk PE: prognostic assessment, early discharge, and single-drug therapy
with new oral anticoagulants. Several parameters have been proposed and
investigated to identify low-risk PE: clinical prediction rules, imaging tests,
and laboratory markers of right ventricular dysfunction or injury. Moreover,
outpatient management has been suggested for low-risk PE: it may lead to a
decrease in unnecessary hospitalizations, acquired infections, death, and costs
and to an improvement in health-related quality of life. Finally, the main
characteristics of new oral anticoagulant drugs and the most recent published
data on phase III trials on PE suggest that the single-drug therapy is a
possible suitable option. Oral administration, predictable anticoagulant
responses, and few drug-drug interactions of direct thrombin and factor Xa
inhibitors may further simplify PE home therapy avoiding administration of
low-molecular-weight heparin. Cardiovascular diseases are still the most important cause of morbidity and
mortality worldwide and anti-thrombotic treatment is widely used as a result.
The currently used drugs include heparin and its derivatives, vitamin K
antagonists, though efficacious, have their own set of limitations like
unpredictable pharmacokinetic profile, parenteral route (with heparin and its
derivatives only), narrow therapeutic window, and constant laboratory monitoring
for their efficacy and safety. This lead to the development of novel factor Xa
inhibitors which could be given orally, have predictable dose response
relationship and are associated with lesser hemorrhagic complications. They
include rivaroxaban, apixaban, and edoxaban among others. Apixaban has currently
been approved for use in patients undergoing total knee or hip replacement
surgery and to prevent stroke in patients with atrial fibrillation. Many trials
are ongoing for apixaban to firmly establish its place in future, among the
anti-thrombotic drugs. |
Is the tricarboxylic acid (TCA) cycle affected in inflammation? | Metabolic reprogramming is implicated in macrophage activation. In many cases, intermediates of the TCA cycle are involved in the response to hypoxic conditions brought about by inflammation. | Astrocytes play an important role in nervous system homeostasis. In particular,
they contribute to the regulation of local energy metabolism and to oxidative
stress defence. In previous experiments, we showed that long-term treatment with
interleukin 1alpha (IL-1alpha) or tumor necrosis factor-alpha (TNFalpha) alone
increases glucose utilization in primary culture of mouse astrocytes. In our
study, we report that a combination of IL-1beta and TNFalpha exerts a
synergistic effect on glucose utilization and markedly modifies the metabolic
phenotype of astrocytes. Thus, IL-1beta+TNFalpha treated astrocytes show a
marked decrease in glycogen levels, a slight but not significant decrease in
lactate release as well as a massive increase in both the pentose phosphate
pathway and TCA cycle activities. Glutamate-stimulated glucose utilization and
lactate release, a typical feature of astrocyte energy metabolism, are altered
after pretreatment with IL-1beta+TNFalpha. As far as mechanisms for oxidative
stress defence are concerned, we observed that treatment with IL-1beta+TNFalpha
decreases cellular glutathione content and increases glutathione release into
the extracellular space while stimulating superoxide anion and nitric oxide
production as well as H(2)O(2) release. Interestingly, stimulation of glucose
utilization by IL-1beta+TNFalpha is not affected by the antioxidant
N-acetyl-L-cysteine, suggesting that cellular stress does not account for this
effect. Finally, the effects of cytokines on glucose utilization appear to
involve multiple signaling cascades including the phosphoinositide 3-kinase and
mitogen-activated protein kinases. Taken together these results establish that a
proinflammatory environment such as observed in several neuropathological
conditions including Alzheimer's disease, markedly modifies the metabolic
phenotype of astrocytes. BACKGROUND: Metabolomics provides data about all the metabolic processes of a
cell or organism. So far, the changes that occur in the levels of metabolites
during the development of colitis have not been fully elucidated. Here we
examined the changes of metabolite levels in the serum and colon tissue of
colitis mice using gas chromatography mass spectrometry (GC/MS) with the aim of
achieving a detailed understanding of the pathogenesis of inflammatory bowel
disease (IBD).
METHODS: To induce colitis, C57BL/6J mice were administered 3.0% dextran sulfate
sodium (DSS) in their drinking water for 5 days and were subsequently given
drinking water alone.
RESULTS: A total of 77 and 92 metabolites were detected in serum and colon
tissue, respectively, and among the metabolites the compositions of TCA cycle
intermediates and amino acids changed depending on the degree of colitis. Then,
partial least square discrimit analysis (PLS-DA), a multiple classification
analysis, showed distinct clustering and clear separation of the groups
according to the degree of colitis. Furthermore, PLS-DA loadings plots revealed
that succinic acid, indole-3-acetic acid, glutamic acid, and glutamine were the
main contributors to the separation of each stage of colitis. In addition, it
was revealed that supplementation with glutamine, the level of which was
significantly decreased in the acute phase of colonic inflammation, attenuated
colitis induced by DSS.
CONCLUSIONS: Our results suggest that metabolomics is capable of representing
the various degrees of colitis, and our findings will aid in the discovery of
therapeutic agents for IBD and other inflammatory disorders by metabolomic
approaches. OBJECTIVE: The roles that amino acids play in immunity and inflammation are well
defined, and the relationship between inflammatory bowel disease (IBD) and
certain amino acids has recently attracted attention. In this study, the levels
of amino acids and trichloroacetic acid (TCA) cycle-related molecules in the
colonic tissues and sera of patients with ulcerative colitis (UC) were profiled
by gas chromatography/mass spectrometry (GC/MS), with the aim of evaluating
whether the clinical state induced by UC leads to variations in the amino acid
profile.
MATERIALS AND METHODS: Colonic biopsy samples from 22 UC patients were used, as
well as serum samples from UC patients (n = 13), Crohn's disease (CD) patients
(n = 21), and healthy volunteers (n = 17).
RESULTS: In the GC/MS-based profiling of amino acids and TCA cycle-related
molecules, lower levels of 16 amino acids and 5 TCA cycle-related molecules were
observed in the colonic lesion tissues of the UC patients, and the serum
profiles of amino acids and TCA cycle-related molecules of the UC patients were
different from those of the CD patients and healthy volunteers.
CONCLUSIONS: Our study raises the possibility that GC/MS-based profiling of
amino acids and TCA cycle-related molecules is a useful early diagnostic tool
for UC. Inflammation is a fundamental defensive response to harmful stimuli. However, it
can cause damage if it does not subside. To avoid such damage, organisms have
developed a mechanism called resolution of inflammation. Here we applied an
untargeted metabolomics approach to a sterile and self-resolving animal model of
acute inflammation, namely zymosan-induced peritonitis in mice, to examine the
effect of inflammation and resolution on the metabolomic profiles. Significant
and time-dependent changes in metabolite profiles after zymosan administration
were observed in both peritoneal wash fluid (PWF) and plasma. These metabolomic
changes correlated well with inflammatory chemokine or cytokine production. In
PWF, most of metabolites that could detected increased in zymosan-treated mice,
which is suggestive of inflammation, oxidative stress and increased energy
demands. In plasma, most metabolites in the central metabolic pathway
(glycolysis and TCA cycle) were significantly downregulated after zymosan
administration. The concentration of the ketone body 3-hydroxybutyric acid
(3-HB) in plasma and PWF increased in zymosan-injected animals indicating
upregulation of fatty acid β-oxidation. Increased 3-HB level was observed in the
cells that infiltrated into the peritoneal cavity and these infiltrated cells
might contribute, at least in part, to the production of 3-HB in the peritoneal
cavity. Acute intermittent porphyria (AIP), an inherited hepatic disorder, is due to a
defect of hydroxymethylbilane synthase (HMBS), an enzyme involved in heme
biosynthesis. AIP is characterized by recurrent, life-threatening attacks at
least partly due to the increased hepatic production of 5-aminolaevulinic acid
(ALA). Both the mitochondrial enzyme, ALA synthase (ALAS) 1, involved in the
first step of heme biosynthesis, which is closely linked to mitochondrial
bioenergetic pathways, and the promise of an ALAS1 siRNA hepatic therapy in
humans, led us to investigate hepatic energetic metabolism in Hmbs KO mice
treated with phenobarbital. The mitochondrial respiratory chain (RC) and the
tricarboxylic acid (TCA) cycle were explored in the Hmbs(-/-) mouse model. RC
and TCA cycle were significantly affected in comparison to controls in mice
treated with phenobarbital with decreased activities of RC complexes I (-52%,
(**)p<0.01), II (-50%, (**)p<0.01) and III (-55%, (*)p<0.05), and decreased
activity of α-ketoglutarate dehydrogenase (-64%, (*)p<0.05), citrate synthase
(-48%, (**)p<0.01) and succinate dehydrogenase (-53%, (*)p<0.05). Complex
II-driven succinate respiration was also significantly affected. Most of these
metabolic alterations were at least partially restored after the phenobarbital
arrest and heme arginate administration. These results suggest a cataplerosis of
the TCA cycle induced by phenobarbital, caused by the massive withdrawal of
succinyl-CoA by ALAS induction, such that the TCA cycle is unable to supply the
reduced cofactors to the RC. This profound and reversible impact of AIP on
mitochondrial energetic metabolism offers new insights into the beneficial
effect of heme, glucose and ALAS1 siRNA treatments by limiting the cataplerosis
of TCA cycle. BACKGROUND AND OBJECTIVES: While animal studies have implicated derangements of
global energy homeostasis in the pathogenesis of acute alcoholic hepatitis
(AAH), the relevance of these findings to the development of human AAH remains
unclear. Using global, unbiased serum metabolomics analysis, we sought to
characterize alterations in metabolic pathways associated with severe AAH and
identify potential biomarkers for disease prognosis.
METHODS: This prospective, case-control study design included 25 patients with
severe AAH and 25 ambulatory patients with alcoholic cirrhosis. Serum samples
were collected within 24 hours of the index clinical encounter. Global, unbiased
metabolomics profiling was performed. Patients were followed for 180 days after
enrollment to determine survival.
RESULTS: Levels of 234 biochemicals were altered in subjects with severe AAH.
Random-forest analysis, principal component analysis, and integrated
hierarchical clustering methods demonstrated that metabolomics profiles
separated the two cohorts with 100% accuracy. Severe AAH was associated with
enhanced triglyceride lipolysis, impaired mitochondrial fatty acid beta
oxidation, and upregulated omega oxidation. Low levels of multiple lysolipids
and related metabolites suggested decreased plasma membrane remodeling in severe
AAH. While most measured bile acids were increased in severe AAH, low
deoxycholate and glycodeoxycholate levels indicated intestinal dysbiosis.
Several changes in substrate utilization for energy homeostasis were identified
in severe AAH, including increased glucose consumption by the pentose phosphate
pathway, altered tricarboxylic acid (TCA) cycle activity, and enhanced peptide
catabolism. Finally, altered levels of small molecules related to glutathione
metabolism and antioxidant vitamin depletion were observed in patients with
severe AAH. Univariable logistic regression revealed 15 metabolites associated
with 180-day survival in severe AAH.
CONCLUSION: Severe AAH is characterized by a distinct metabolic phenotype
spanning multiple pathways. Metabolomics profiling revealed a panel of
biomarkers for disease prognosis, and future studies are planned to validate
these findings in larger cohorts of patients with severe AAH. |
What are the indications for treatment with anti-hepcidin? | improving anemia control
anemia management in hemodialysis
iron-restricted anemias | In this issue of Blood, Cooke et al demonstrate the potential of a fully human
anti-hepcidin antibody as a novel therapeutic for iron-restricted anemias such
as anemia of inflammation, cancer, or chronic kidney disease (formerly known as
“anemia of chronic diseases”). The anemia of chronic kidney disease and hemodialysis is characterized by
chronic inflammation and release of cytokines, resulting in the upregulation of
the iron hormone hepcidin, also increased by iron therapy and reduced glomerular
filtration, with consequent reduction in iron absorption, recycling, and
availability to the erythron. This response proves advantageous in the
short-term to restrain iron availability to pathogens, but ultimately leads to
severe anemia, and impairs the response to erythropoietin (Epo) and iron.
Homozygosity for the common C282Y and H63D HFE polymorphisms influence iron
metabolism by hampering hepcidin release by hepatocytes in response to increased
iron stores, thereby resulting in inadequate inhibition of the activity of
Ferroportin-1, inappropriately high iron absorption and recycling, and iron
overload. However, in hemodialysis patients, carriage of HFE mutations may
confer an adaptive benefit by decreasing hepcidin release in response to iron
infusion and inflammation, thereby improving iron availability to
erythropoiesis, anemia control, the response to Epo, and possibly survival.
Therefore, anti-hepcidin therapies may improve anemia management in
hemodialysis. However, HFE mutations directly favor hemoglobinization
independently of hepcidin, and reduce macrophages activation in response to
inflammation, whereas hepcidin might also play a beneficial anti-inflammatory
and anti-microbic action during sepsis, so that direct inhibition of
HFE-mediated regulation of iron metabolism may represent a valuable alternative
therapeutic target. Genetic studies may offer a valuable tool to test these
hypotheses and guide the research of new therapies. |
How many genera comprise the Flaviviridae family? | The family Flaviviridae is comprised of three genera: Flavivirus, Pestivirus and Hepacivirus. | Sequence motifs within the nonstructural protein NS3 of members of the
Flaviviridae family suggest that this protein possesses nucleoside
triphosphatase (NTPase) and RNA helicase activity. The RNA-stimulated NTPase
activity of this protein from prototypic members of the Pestivirus and
Flavivirus genera has recently been established and enzymologically
characterized. Here, we experimentally demonstrate that the NS3 protein from a
member of the third genus of Flaviviridae, human hepatitis C virus (HCV), also
possesses a polynucleotide-stimulated NTPase activity. Characterization of the
purified HCV NTPase activity showed that it exhibited reaction condition optima
with respect to pH, MgCl2, and salt identical to those of the representative
pestivirus and flavivirus enzymes. However, each NTPase also possessed several
unique properties when compared with one another. Notably, the profile of
polynucleotide stimulation of the NTPase activity was distinct for the three
enzymes. The HCV NTPase was the only one whose activity was significantly
enhanced by a deoxyribopolynucleotide. Additional distinguishing features among
the three enzymes relating to the kinetic properties of their NTPase activities
are discussed. These studies provide a foundation for investigation of the
putative RNA helicase activity of these proteins and for further study of the
role of the NS3 proteins of members of the Flaviviridae in the replication cycle
of these viruses. Forty-three 2-[(benzotriazol-1/2-yl)methyl]benzimidazoles, bearing either linear
(dialkylamino)alkyl- or bulkier (quinolizidin-1-yl)alkyl moieties at position 1,
were evaluated in cell-based assays for cytotoxicity and antiviral activity
against viruses representative of two of the three genera of the Flaviviridae
family, i.e. Flaviviruses (Yellow Fever Virus (YFV)) and Pestiviruses (Bovine
Viral Diarrhoea Virus (BVDV)), as Hepaciviruses can hardly be used in routine
cell-based assays. Compounds were also tested against representatives of other
virus families. Among ssRNA+ viruses were a retrovirus (Human Immunodeficiency
Virus type 1 (HIV-1)), two picornaviruses (Coxsackie Virus type B2 (CVB2), and
Poliovirus type-1, Sabin strain (Sb-1)); among ssRNA- viruses were a
Paramyxoviridae (Respiratory Syncytial Virus (RSV)) and a Rhabdoviridae
(Vesicular Stomatitis Virus (VSV)) representative. Among double-stranded RNA
(dsRNA) viruses was a Reoviridae representative (Reo-1). Two representatives of
DNA virus families were also included: Herpes Simplex type 1, (HSV-1;
Herpesviridae) and Vaccinia Virus (VV; Poxviridae). Most compounds exhibited
potent activity against RSV, with EC(50) values as low as 20 nM. Moreover, some
compounds, in particular when bearing a (quinolizidin-1-yl)alkyl residue, were
also moderately active against BVDV, YFV, and CVB2. In prosecution of an anti-Flaviviridae project a new series of variously
substituted 2-diphenyl-benzimidazoles were synthesized and tested in vitro for
antiviral and antiproliferative activities. Compounds were tested in cell-based
assays against viruses representative of: i) two of the three genera of the
Flaviviridae family, i.e. Flaviviruses and Pestiviruses; ii) other RNA virus
families, such as Retroviridae, Picornaviridae, Paramyxoviridae, Rhabdoviridae
and Reoviridae; iii) two DNA virus families (Herpesviridae and Poxviridae). The
5-Acetyl-2-(4'-nitrobiphenyl-4-yl)-1H-benzimidazole (24) emerged as potent
active lead compound against Yellow Fever Virus (a Flavivirus) (EC(50) = 0.5
microM) and CVB-2 at 1 microM and was not cytotoxic, whereas the other title
benzimidazoles showed no antiviral activity at concentrations not cytotoxic for
the resting cell monolayers. Among the examined series, the most cytotoxic
derivatives (11,12,14,16,18,19,20,21,23,25-30) against mock-infected MT-4 cells
(CC50 < 8.0 microM) were evaluated against a panel of human cell lines derived
from haematological and solid tumours,using 6-mercaptopurine (6-MP) and
etoposide as reference drugs. In particular, compounds 26 and 28 showed a
similar potency of 6-MP and etoposide. BACKGROUND: Usutu virus belongs to the Flaviviridae viral family and constitutes
an important pathogen. The viral helicase is an ideal target for inhibitor
design, since this enzyme is essential for the survival, proliferation and
transmission of the virus.
RESULTS: Towards a drug-design approach, the 3D model of the Usutu virus
helicase structure has been designed, using conventional homology modelling
techniques and the known 3D-structure of the Murray Valley Encephalitis virus
helicase, of the same viral family, as template. The model was then subjected to
extended molecular dynamics simulations in a periodic box, filled with explicit
water molecules for 10 oseconds. The reliability of the model was confirmed
by obtaining acceptable scores from a variety of in silico scoring tools,
including Procheck and Verify3D.
CONCLUSION: [corrected] The 3D model of the Usutu virus helicase exhibits in
silico all known structural characteristics of the Flaviviridae viral family
helicase enzymes and could provide the platform for further de novo
structure-based design of novel anti-Usutu agents. As a follow up of an anti-Flaviviridae project, a new series of variously
substituted 2-styryl-benzimidazoles were synthesized and tested in vitro for
biological activity. Compounds were tested in cell-based assays against viruses
representative of: i) two of the three genera of the Flaviviridae family, i.e.
Pestiviruses and Flaviviruses; ii) other RNA virus families, such as
Retroviridae, Picornaviridae, Paramyxoviridae, Rhabdoviridae and Reoviridae;
iii) two DNA virus families (Herpesviridae and Poxviridae) as well as for
cytotoxicity tests, run in parallel with antiviral assays,against MDBK, BHK and
Vero 76 cells. In the series examined, new leads emerged against BVDV, CVB-2 and
RSV. Compounds 11, 12, 17, 18, 24, 31 exhibited anti-BVDV activity in the
concentration range 1.7-16 microM; among them, compound 17 was the most active,
with an EC(50) = 1.7 microM. Compounds 18 and 21 were equally active against
CVB-2, with EC(50) values of 7 - 8 microM, while the derivative 30 was active
against RSV with EC(50)= 1 microM and represents a new lead compound. Viruses in the Flavivirus genus of the Flaviviridae family are
arthropod-transmitted and contribute to staggering numbers of human infections
and significant deaths annually across the globe. To identify cellular factors
with antiviral activity against flaviviruses, we screened a cDNA library using
an iterative approach. We identified a mammalian Hsp40 chaperone protein
(DNAJC14) that when overexpressed was able to mediate protection from yellow
fever virus (YFV)-induced cell death. Further studies revealed that DNAJC14
inhibits YFV at the step of viral RNA replication. Since replication of bovine
viral diarrhea virus (BVDV), a member of the related Pestivirus genus, is also
known to be modulated by DNAJC14, we tested the effect of this host factor on
diverse Flaviviridae family members. Flaviviruses, including the pathogenic
Asibi strain of YFV, Kunjin, and tick-borne Langat virus, as well as a
Hepacivirus, hepatitis C virus (HCV), all were inhibited by overexpression of
DNAJC14. Mutagenesis showed that both the J-domain and the C-terminal domain,
which mediates self-interaction, are required for anti-YFV activity. We found
that DNAJC14 does not block YFV nor HCV NS2-3 cleavage, and using non-inhibitory
mutants demonstrate that DNAJC14 is recruited to YFV replication complexes.
Immunofluorescence analysis demonstrated that endogenous DNAJC14 rearranges
during infection and is found in replication complexes identified by dsRNA
staining. Interestingly, silencing of endogenous DNAJC14 results in impaired YFV
replication suggesting a requirement for DNAJC14 in YFV replication complex
assembly. Finally, the antiviral activity of overexpressed DNAJC14 occurs in a
time- and dose-dependent manner. DNAJC14 overexpression may disrupt the proper
stoichiometry resulting in inhibition, which can be overcome upon restoration of
the optimal ratios due to the accumulation of viral nonstructural proteins. Our
findings, together with previously published work, suggest that the members of
the Flaviviridae family have evolved in unique and important ways to interact
with this host Hsp40 chaperone molecule. The family Flaviviridae contains three genera of positive-strand RNA viruses,
namely, Flavivirus, Hepacivirus (e.g., hepatitis C virus [HCV]), and Pestivirus.
Pestiviruses, like bovine viral diarrhea virus (BVDV), bear a striking degree of
similarity to HCV concerning polyprotein organization, processing, and function.
Along this line, in both systems, release of nonstructural protein 3 (NS3) is
essential for viral RNA replication. However, both viruses differ significantly
with respect to processing efficiency at the NS2/3 cleavage site and abundance
as well as functional relevance of uncleaved NS2-3. In BVDV-infected cells,
significant amounts of NS2-3 accumulate at late time points postinfection and
play an essential but ill-defined role in the production of infectious virions.
In contrast, complete cleavage of the HCV NS2-3 counterpart has been reported,
and unprocessed NS2-3 is not required throughout the life cycle of HCV, at least
in cell culture. Here we describe the selection and characterization of the
first pestiviral genome with the capability to complete productive infection in
the absence of uncleaved NS2-3. Despite the insertion of a ubiquitin gene or an
internal ribosomal entry site between the NS2 and NS3 coding sequences, the
selected chimeric BVDV-1 genomes gave rise to infectious virus progeny. In this
context, a mutation in the N-terminal third of NS2 was identified as a critical
determit for efficient production of infectious virions in the absence of
uncleaved NS2-3. These findings challenge a previously accepted dogma for
pestivirus replication and provide new implications for virion morphogenesis of
pestiviruses and HCV. Many viruses within the Flavivirus genus cause significant disease in humans;
however, effective antivirals against these viruses are not currently available.
We have previously shown that a thiopurine drug, 6-methylmercaptopurine riboside
(6MMPr), inhibits replication of distantly related viruses within the
Flaviviridae family in cell culture, including bovine viral diarrhea virus and
hepatitis C virus replicon. Here we further examined the potential antiviral
effect of 6MMPr on several diverse flaviviruses. In cell culture, 6MMPr
inhibited virus production of yellow fever virus, dengue virus-2 (DENV-2) and
West Nile virus (WNV) in a dose-dependent manner, and DENV-2 was significantly
more sensitive to 6MMPr treatment than WNV. We then explored the use of 6MMPr as
an antiviral against WNV in an immunocompetent mouse model. Once a day treatment
of mice with 0.5 mg 6MMPr was just below the toxic dose in our mouse model, and
this dose was used in subsequent studies. Mice were treated with 6MMPr
immediately after subcutaneous inoculation with WNV for eight consecutive days.
Treatment with 6MMPr exacerbated weight loss in WNV-inoculated mice and did not
significantly affect mortality. We hypothesized that 6MMPr has low
bioavailability in the central nervous system (CNS) and examined the effect of
pre-treatment with 6MMPr on viral loads in the periphery and CNS. Pre-treatment
with 6MMPr had no significant effect on viremia or viral titers in the
periphery, but resulted in significantly higher viral loads in the brain,
suggesting that the effect of 6MMPr is tissue-dependent. In conclusion, despite
being a potent inhibitor of flaviviruses in cell culture, 6MMPr was not
effective against West Nile disease in mice; however, further studies are
warranted to reduce the toxicity and/or improve the bioavailability of this
potential antiviral drug. |
Are reduced-nicotine cigarettes effective for smoking cessation? | Yes, reduced-nicotine cigarettes are effective for smoking cessation. | Preliminary studies suggest an extinction-based smoking cessation treatment
using reduced nicotine content (RNC) cigarettes decreases self-report craving
for cigarettes prior to quitting and may be an effective smoking cessation
treatment. The aims of this study was to evaluate the effect of an
extinction-based smoking cessation treatment on brain responses to smoking cues
using blood-oxygen level-dependent (BOLD) functional magnetic resoce imaging
(fMRI). Sixteen (n = 16) dependent smokers were scanned using BOLD fMRI at
baseline, following 2-4 weeks of smoking RNC cigarettes while wearing a 21-mg
nicotine patch, and 2-4 weeks following quitting smoking. During scanning,
participants viewed smoking-related pictures (e.g. lit cigarette) and pictures
of people engaged in everyday activities (e.g. using a stapler). Event-related
BOLD responses to smoking and control cues were analyzed in regions of interest
(ROIs) known to subserve reward, attention, motivation and emotion. The
extinction-based treatment simultaneously attenuated responses to smoking cues
in amygdala while potentiating responses to control cues. Exploratory analysis
indicated that this pattern was also observed in the thalamus of future
abstinent but not relapsing smokers. The results of this preliminary study
suggest that an extinction-based treatment for smoking cessation alters brain
responses to smoking and control cues in amygdala--a region previously
associated with drug cue reactivity and extinction. A randomized double-blind, active controlled, parallel group, multi-center phase
II clinical trial was conducted to evaluate the efficacy of reduced-nicotine
cigarettes as a novel smoking cessation treatment (under Investigational Device
Exemption 69,185). The concept for a reduced-nicotine cigarette designed to
progressively wean smokers from the smoking habit is based on research
demonstrating that successful smoking cessation is not only dependent on
withdrawal of nicotine, but also on weaning from the habitual sensory and
behavioral reinforcement of smoking. Treatment consisted of Quest brand of
cigarettes (Quest 1, 2, and 3), which respectively deliver 0.59+/-0.06,
0.3+/-0.05, and less than 0.05 mg nicotine, either alone or in combination with
nicotine replacement therapy (NRT). The primary endpoint was 4 weeks of
continuous abstinence (Weeks 7-10), with additional follow-up at 3 and 6 months.
Adult men and women smokers (N = 346), motivated to quit, were randomized to one
of three treatment groups: Quest plus NRT (NRT pretreatment 2 weeks before, and
NRT after the quit date), Quest plus placebo patch, or active control plus NRT
(conventional cigarette, followed by NRT after quit date). Results showed that
Quest plus NRT was more effective than active control plus NRT in achieving 4
weeks of continuous abstinence (32.8% vs. 21.9%). Quest plus placebo patch
yielded an abstinence rate similar to that of the active control plus NRT (16.4%
vs. 21.9%). No serious adverse events were attributable to the investigational
product. Quest plus NRT offers promise as a new smoking cessation treatment. INTRODUCTION: Current smoking cessation treatments largely address
pharmacological dependence on nicotine. New approaches are needed that address
both nicotine dependence and psychological dependence on cigarettes as the
source of nicotine. One such approach is the use of cigarettes with reduced
nicotine content.
METHODS: We reviewed the available literature on the use of reduced-nicotine
content cigarettes as a cessation aid.
RESULTS: One case series study and trial data indicate that reduction in the
level of nicotine in cigarette tobacco can reduce the level of nicotine
dependence in smokers and do so without adverse effects on cardiovascular
biomarkers or significant compensatory smoking. We identified three clinical
trials (total n = 489) that suggest that smokers can dissociate nicotine
delivery from the act of smoking if they use reduced-nicotine content cigarettes
in combination with nicotine replacement therapy.
DISCUSSION: The identified studies point to a benefit but involved only a small
number of participants and provide only limited data on long-term abstinence.
More definitive evidence from larger trials with longer follow-up is needed to
clarify the role of reduced nicotine cigarettes as an aid to smoking cessation. AIMS: To examine the effects of reduced nicotine cigarettes on smoking behavior,
toxicant exposure, dependence and abstinence.
DESIGN: Randomized, parallel arm, semi-blinded study. Setting University of
Minnesota Tobacco Use Research Center.
INTERVENTIONS: Six weeks of: (i) 0.05 mg nicotine yield cigarettes; (ii) 0.3 mg
nicotine yield cigarettes; or (iii) 4 mg nicotine lozenge; 6 weeks of follow-up.
Measurements Compensatory smoking behavior, biomarkers of exposure, tobacco
dependence, tobacco withdrawal and abstinence rate.
FINDINGS: Unlike the 0.3 mg cigarettes, 0.05 mg cigarettes were not associated
with compensatory smoking behaviors. Furthermore, the 0.05 mg cigarettes and
nicotine lozenge were associated with reduced carcinogen exposure, nicotine
dependence and product withdrawal scores. The 0.05 mg cigarette was associated
with greater relief of withdrawal from usual brand cigarettes than the nicotine
lozenge. The 0.05 mg cigarette led to a significantly higher rate of cessation
than the 0.3 mg cigarette and a similar rate as nicotine lozenge.
CONCLUSION: The 0.05 mg nicotine yield cigarettes may be a tobacco product that
can facilitate cessation; however, future research is clearly needed to support
these preliminary findings. BACKGROUND: Reduced nicotine content (RNC) cigarettes have led to smoking fewer
cigarettes, withdrawal relief, and facilitation of cessation. The aim of this
study is to examine the effects RNC cigarettes with and without nicotine patch
and patch alone on smoking behavior, toxicant exposure, withdrawal discomfort,
and as an exploratory analysis, on long-term abstinence.
METHODS: This study involved a randomized, parallel arm design and six weeks of:
(i) 0.05-0.09 mg nicotine yield cigarettes (N = 79); (ii) 21 mg nicotine patch
(N = 80), or (iii) 0.05-0.09 nicotine yield cigarettes with 21 mg nicotine patch
(N = 76); all groups received six weeks of additional behavioral treatment with
follow-ups up to six months.
RESULTS: Combination approach led to lower rates of smoking assigned cigarettes
and hence lower carbon monoxide levels than RNC cigarettes alone. In addition,
the combination approach was associated with less withdrawal severity when
switching from usual brand to assigned product, and less smoking of usual brand
cigarettes during treatment, but not after treatment compared with the other
approaches.
CONCLUSION: Combining very low nicotine content cigarettes with nicotine patch
may improve the acute effects resulting from switching to either of these
products alone.
IMPACT: These findings may have implications for smoking cessation treatment or
a policy measure to reduce nicotine content in cigarettes. BACKGROUND: The Food and Drug Administration can set standards that reduce the
nicotine content of cigarettes.
METHODS: We conducted a double-blind, parallel, randomized clinical trial
between June 2013 and July 2014 at 10 sites. Eligibility criteria included an
age of 18 years or older, smoking of five or more cigarettes per day, and no
current interest in quitting smoking. Participants were randomly assigned to
smoke for 6 weeks either their usual brand of cigarettes or one of six types of
investigational cigarettes, provided free. The investigational cigarettes had
nicotine content ranging from 15.8 mg per gram of tobacco (typical of commercial
brands) to 0.4 mg per gram. The primary outcome was the number of cigarettes
smoked per day during week 6.
RESULTS: A total of 840 participants underwent randomization, and 780 completed
the 6-week study. During week 6, the average number of cigarettes smoked per day
was lower for participants randomly assigned to cigarettes containing 2.4, 1.3,
or 0.4 mg of nicotine per gram of tobacco (16.5, 16.3, and 14.9 cigarettes,
respectively) than for participants randomly assigned to their usual brand or to
cigarettes containing 15.8 mg per gram (22.2 and 21.3 cigarettes, respectively;
P<0.001). Participants assigned to cigarettes with 5.2 mg per gram smoked an
average of 20.8 cigarettes per day, which did not differ significantly from the
average number among those who smoked control cigarettes. Cigarettes with lower
nicotine content, as compared with control cigarettes, reduced exposure to and
dependence on nicotine, as well as craving during abstinence from smoking,
without significantly increasing the expired carbon monoxide level or total puff
volume, suggesting minimal compensation. Adverse events were generally mild and
similar among groups.
CONCLUSIONS: In this 6-week study, reduced-nicotine cigarettes versus
standard-nicotine cigarettes reduced nicotine exposure and dependence and the
number of cigarettes smoked. (Funded by the National Institute on Drug Abuse and
the Food and Drug Administration Center for Tobacco Products; ClinicalTrials.gov
number, NCT01681875.). |
Is the Wnt protein modified by notum? | Yes, Notum deacylates Wnt proteins to suppress signalling activity. | Wnt and Decapentaplegic cell signaling pathways act synergistically in their
contribution to macrochaete (sense organ) patterning on the notum of Drosophila
melanogaster. The Wingless-signaling pathway was ectopically activated by
removing Shaggy activity (the homologue of vertebrate glycogen synthase kinase
3) in mosaics. Proneural activity is asymmetric within the Shaggy-deficient
clone of cells and shows a fixed "polarity" with respect to body axis,
independent of the precise location of the clone. This asymmetric response
indicates the existence in the epithelium of a second signal, which we suggest
is Decapentaplegic. Ectopic expression of Decapentaplegic induces extra
macrochaetes only in cells which also receive the Wingless signal. Activation of
Hedgehog signaling generates a long-range signal which can promote macrochaete
formation in the Wingless activity domain. This signal depends upon
decapentaplegic function. Autonomous activation of the Wingless signal response
in cells causes them to attenuate or sequester this signal. Our results suggest
a novel patterning mechanism which determines sense organ positioning in
Drosophila. Drosophila Wingless (Wg) is the founding member of the Wnt family of secreted
proteins. During the wing development, Wg acts as a morphogen whose
concentration gradient provides positional cues for wing patterning. The
molecular mechanism(s) of Wg gradient formation is not fully understood. Here,
we systematically analyzed the roles of glypicans Dally and Dally-like protein
(Dlp), the Wg receptors Frizzled (Fz) and Fz2, and the Wg co-receptor Arrow
(Arr) in Wg gradient formation in the wing disc. We demonstrate that both Dally
and Dlp are essential and have different roles in Wg gradient formation. The
specificities of Dally and Dlp in Wg gradient formation are at least partially
achieved by their distinct expression patterns. To our surprise, although Fz2
was suggested to play an essential role in Wg gradient formation by ectopic
expression studies, removal of Fz2 activity does not alter the extracellular Wg
gradient. Interestingly, removal of both Fz and Fz2, or Arr causes enhanced
extracellular Wg levels, which is mainly resulted from upregulated Dlp levels.
We further show that Notum, a negative regulator of Wg signaling, downregulates
Wg signaling mainly by modifying Dally. Last, we demonstrate that Wg movement is
impeded by cells mutant for both dally and dlp. Together, these new findings
suggest that the Wg morphogen gradient in the wing disc is mainly controlled by
combined actions of Dally and Dlp. We propose that Wg establishes its
concentration gradient by a restricted diffusion mechanism involving Dally and
Dlp in the wing disc. The Drosophila Notum gene, which is regulated by the Wingless pathway, encodes a
secreted hydrolase that modifies heparan sulfate proteoglycans. In comparative
analysis of the gene expression profiles in primary human hepatocellular
carcinomas (HCC) and normal organs, we observed that the human ortholog of
Drosophila Notum was overexpressed markedly in a subset of HCC, but expressed
rarely in adult normal tissues. Immunoblotting confirmed the overexpression of
NOTUM protein in 12 of 40 primary HCC cases (30%). High levels of NOTUM protein
were significantly associated with intracellular (nuclear or cytoplasmic)
accumulation of beta-catenin protein: all 10 HCC with high intracellular
beta-catenin also had high NOTUM expression, whereas only 2 of 30 cases (6.7%)
without intracellular beta-catenin had high NOTUM expression (P < 0.00001).
NOTUM expression in HepG2 cells was downregulated significantly by induction of
a domit-negative mutant of TCF4, a beta-catenin partner. In vivo binding of
the beta-catenin/TCF complex to the NOTUM promoter was demonstrated by chromatin
immunoprecipitation in HepG2 and SW480 cells, where canonical Wnt signaling is
activated constitutively. These findings provide evidence that NOTUM is a novel
target of beta-catenin/TCF4 and is upregulated in Wnt/beta-catenin
signaling-activated HCC. Glypicans are heparan sulfate proteoglycans that are bound to the outer surface
of the plasma membrane by a glycosyl-phosphatidylinositol anchor. Homologs of
glypicans are found throughout the Eumetazoa. There are six family members in
mammals (GPC1 to GPC6). Glypicans can be released from the cell surface by a
lipase called Notum, and most of them are subjected to endoproteolytic cleavage
by furin-like convertases. In vivo evidence published so far indicates that the
main function of membrane-attached glypicans is to regulate the signaling of
Wnts, Hedgehogs, fibroblast growth factors and bone morphogenetic proteins
(BMPs). Depending on the context, glypicans may have a stimulatory or inhibitory
activity on signaling. In the case of Wnt, it has been proposed that the
stimulatory mechanism is based on the ability of glypicans to facilitate and/or
stabilize the interaction of Wnts with their signaling receptors, the Frizzled
proteins. On the other hand, GPC3 has recently been reported to inhibit Hedgehog
protein signaling during development by competing with Patched, the Hedgehog
receptor, for Hedgehog binding. Surprisingly, the regulatory activity of
glypicans in the Wnt, Hedgehog and BMP signaling pathways is only partially
dependent on the heparan sulfate chains. Evolution of novel structures is often made possible by changes in the timing or
spatial expression of genes regulating development. Macrochaetes, large sensory
bristles arranged into species-specific stereotypical patterns, are an
evolutionary novelty of cyclorraphous flies and are associated with changes in
both the temporal and spatial expression of the proneural genes achaete (ac) and
scute (sc). Changes in spatial expression are associated with the evolution of
cis-regulatory sequences, but it is not known how temporal regulation is
achieved. One factor required for ac-sc expression, the expression of which
coincides temporally with that of ac-sc in the notum, is Wingless (Wg; also
known as Wnt). Wingless downregulates the activity of the serine/threonine
kinase Shaggy (Sgg; also known as GSK-3). We demonstrate that Scute is
phosphorylated by Sgg on a serine residue and that mutation of this residue
results in a form of Sc with heightened proneural activity that can rescue the
loss of bristles characteristic of wg mutants. We suggest that the
phosphorylated form of Sc has reduced transcriptional activity such that sc is
unable to autoregulate, an essential function for the segregation of bristle
precursors. Sgg also phosphorylates Pannier, a transcriptional activator of
ac-sc, the activity of which is similarly dampened when in the phosphorylated
state. Furthermore, we show that Wg signalling does not act directly via a
cis-regulatory element of the ac-sc genes. We suggest that temporal control of
ac-sc activity in cyclorraphous flies is likely to be regulated by permissive
factors and might therefore not be encoded at the level of ac-sc gene sequences. During adult homeostasis and regeneration, the freshwater planarian must
accomplish a constant balance between cell proliferation and cell death, while
also maintaining proper tissue and organ size and patterning. How these ordered
processes are precisely modulated remains relatively unknown. Here we show that
planarians use the downstream effector of the Hippo signaling cascade, yorkie
(yki; YAP in vertebrates) to control a diverse set of pleiotropic processes in
organ homeostasis, stem cell regulation, regeneration and axial patterning. We
show that yki functions to maintain the homeostasis of the planarian excretory
(protonephridial) system and to limit stem cell proliferation, but does not
affect the differentiation process or cell death. Finally, we show that Yki acts
synergistically with WNT/β-catenin signaling to repress head determination by
limiting the expression domains of posterior WNT genes and that of the
WNT-inhibitor notum. Together, our data show that yki is a key gene in
planarians that integrates stem cell proliferation control, organ homeostasis,
and the spatial patterning of tissues. Mechanisms that enable injury responses to prompt regenerative outgrowth are not
well understood. Planarians can regenerate essentially any tissue removed by
wounding, even after decapitation, due to robust regulation of adult pluripotent
stem cells of the neoblast population. Formation of pole signaling centers
involving Wnt inhibitors or Wnt ligands promotes head or tail regeneration,
respectively, and this process requires the use of neoblasts early after injury.
We used expression profiling of purified neoblasts to identify factors needed
for anterior pole formation. Using this approach, we identified zic-1, a
Zic-family transcription factor, as transcriptionally activated in a
subpopulation of neoblasts near wound sites early in head regeneration. As head
regeneration proceeds, the Wnt inhibitor notum becomes expressed in the newly
forming anterior pole in zic-1-expressing cells descended from neoblasts.
Inhibition of zic-1 by RNAi resulted in a failure to express notum at the
anterior pole and to regenerate a head, but did not affect tail regeneration.
Both injury and canonical Wnt signaling inhibition are required for zic-1
expression, and double-RNAi experiments suggest zic-1 inhibits Wnt signaling to
allow head regeneration. Analysis of neoblast fate determits revealed that
zic-1 controls specification of notum-expressing cells from foxD-expressing
neoblasts to form the anterior pole, which organizes subsequent outgrowth.
Specialized differentiation programs may in general underlie injury-dependent
formation of tissue organizing centers used for regenerative outgrowth. Signalling by Wnt proteins is finely balanced to ensure normal development and
tissue homeostasis while avoiding diseases such as cancer. This is achieved in
part by Notum, a highly conserved secreted feedback antagonist. Notum has been
thought to act as a phospholipase, shedding glypicans and associated Wnt
proteins from the cell surface. However, this view fails to explain specificity,
as glypicans bind many extracellular ligands. Here we provide genetic evidence
in Drosophila that Notum requires glypicans to suppress Wnt signalling, but does
not cleave their glycophosphatidylinositol anchor. Structural analyses reveal
glycosaminoglycan binding sites on Notum, which probably help Notum to
co-localize with Wnt proteins. They also identify, at the active site of human
and Drosophila Notum, a large hydrophobic pocket that accommodates palmitoleate.
Kinetic and mass spectrometric analyses of human proteins show that Notum is a
carboxylesterase that removes an essential palmitoleate moiety from Wnt proteins
and thus constitutes the first known extracellular protein deacylase. |
List functions that are evaluated with the Full Outline of Unresponsiveness score? | The FOUR (Full Outline of UnResponsiveness) score, a new coma scale, evaluates 4 components: eye and motor responses, brainstem reflexes and respiration. | BACKGROUND: The Glasgow coma scale (GCS) was introduced as a scoring system for
patients with impaired consciousness after traumatic brain injury (TBI). Since,
it has become the worldwide standard in TBI assessment. The GCS has repeatedly
been criticized for its several failures to reflect verbal reaction in intubated
patients, and to test brain stem reflexes. Recently, the full outline of
unresponsiveness (FOUR) score was introduced, which is composed of four
clinically distinct categories of evaluation: eye reaction, motor function,
brainstem reflexes and respiratory pattern. This study aims to validate the FOUR
score in neurosurgical patients.
METHODS: FOUR score and GCS were assessed in a consecutive series of
neurosurgical patients with severely impaired consciousness (GCS < 9). Their
correlation with the 30-day Glasgow outcome score (GOS) was compared. Patients
admitted for TBI, spontaneous intracranial hemorrhage (intracerebral hemorrhage,
aneurysmal subarachnoid hemorrhage, cerebellar hemorrhage), or maligt middle
cerebral artery infarction were included.
RESULTS: We assessed a total of 101 patients (mean age = 64y, SD = 36.1y). The
area under the curve (AUC) for mortality was 0.768 (P = 0.0001) for the FOUR
Score, and 0.699 (P = 0.001) for the GCS. For poor outcome (GOS = 2-3) the FOUR
score AUC was 0.683 (P = 0.018), the GCS AUC was 0.682 (P = 0.019). The FOUR
score value for favorable outcome (GOS = 4-5) was 0.748 (P = 0.001), the
corresponding GCS value was 0.704 (P = 0.002).
CONCLUSIONS: The FOUR score was more robust than the GCS in predicting mortality
after 30 days in neurosurgical patients with severely impaired consciousness.
There was no relevant difference in predicting poor and good outcome. The Full Outline of UnResponsiveness (FOUR) Score is a coma scale that consists
of four components (eye and motor response, brainstem reflexes, and
respiration). It was originally validated among the adult population and
recently in a pediatric population. To enhance clinical assessment of pediatric
intensive care unit patients, including those intubated and/or sedated, at our
children's hospital, we modified the FOUR Score Scale for this population. This
modified scale would provide many of the same advantages as the original, such
as interrater reliability, simplicity, and elimination of the verbal component
that is not compatible with the Glasgow Coma Scale (GCS), creating a more
valuable neurological assessment tool for the nursing community. Our goal was to
potentially provide greater information than the formally used GCS when
assessing critically ill, neurologically impaired patients, including those
sedated and/or intubated. Experienced pediatric intensive care unit nurses were
trained as "expert raters." Two different nurses assessed each subject using the
Pediatric FOUR Score Scale (PFSS), GCS, and Richmond Agitation Sedation Scale at
three different time points. Data were compared with the Pediatric Cerebral
Performance Category (PCPC) assessed by another nurse. Our hypothesis was that
the PFSS and PCPC should highly correlate and the GCS and PCPC should correlate
lower. Study results show that the PFSS is excellent for interrater reliability
for trained nurse-rater pairs and prediction of poor outcome and in-hospital
mortality, under various situations, but there were no statistically significant
differences between the PFSS and the GCS. However, the PFSS does have the
potential to provide greater neurological assessment in the intubated and/or
sedated patient based on the outcomes of our study. |
For the constructions of which organs has 3D printing been tested? | Nose, ear and meniscus prototypes/constructs have been produced with 3D (3-dimesional) printing. | We recently developed a cell printer (Wilson and Boland, 2003) that enables us
to place cells in positions that mimic their respective positions in organs.
However, this technology was limited to the printing of two-dimensional (2D)
tissue constructs. Here we describe the use of thermosensitive gels to generate
sequential layers for cell printing. The ability to drop cells on previously
printed successive layers provides a real opportunity for the realization of
three-dimensional (3D) organ printing. Organ printing will allow us to print
complex 3D organs with computer-controlled, exact placing of different cell
types, by a process that can be completed in several minutes. To demonstrate the
feasibility of this novel technology, we showed that cell aggregates can be
placed in the sequential layers of 3D gels close enough for fusion to occur. We
estimated the optimum minimal thickness of the gel that can be reproducibly
generated by dropping the liquid at room temperature onto a heated substrate.
Then we generated cell aggregates with the corresponding (to the minimal
thickness of the gel) size to ensure a direct contact between printed cell
aggregates during sequential printing cycles. Finally, we demonstrated that
these closely-placed cell aggregates could fuse in two types of thermosensitive
3D gels. Taken together, these data strongly support the feasibility of the
proposed novel organ-printing technology. Organ printing or biomedical application of rapid prototyping, also defined as
additive layer-by-layer biomanufacturing, is an emerging transforming technology
that has potential for surpassing traditional solid scaffold-based tissue
engineering. Organ printing has certain advantages: it is an automated approach
that offers a pathway for scalable reproducible mass production of tissue
engineered products; it allows a precised simultaneous 3D positioning of several
cell types; it enables creation tissue with a high level of cell density; it can
solve the problem of vascularization in thick tissue constructs; finally, organ
printing can be done in situ. The ultimate goal of organ-printing technology is
to fabricate 3D vascularized functional living human organs suitable for
clinical implantation. The main practical outcomes of organ-printing technology
are industrial scalable robotic biofabrication of complex human tissues and
organs, automated tissue-based in vitro assays for clinical diagnostics, drug
discovery and drug toxicity, and complex in vitro models of human diseases. This
article describes conceptual framework and recent developments in organ-printing
technology, outlines main technological barriers and challenges, and presents
potential future practical applications. With the advantages of high throughput, digital control, and highly accurate
placement of cells and biomaterial scaffold to the desired 2D and 3D locations,
bioprinting has great potential to develop promising approaches in translational
medicine and organ replacement. The most recent advances in organ and tissue
bioprinting based on the thermal inkjet printing technology are described in
this review. Bioprinting has no or little side effect to the printed mammalian
cells and it can conveniently combine with gene transfection or drug delivery to
the ejected living systems during the precise placement for tissue construction.
With layer-by-layer assembly, 3D tissues with complex structures can be printed
using scanned CT or MRI images. Vascular or nerve systems can be enabled
simultaneously during the organ construction with digital control. Therefore,
bioprinting is the only solution to solve this critical issue in thick and
complex tissues fabrication with vascular system. Collectively, bioprinting
based on thermal inkjet has great potential and broad applications in tissue
engineering and regenerative medicine. This review article introduces some
important patents related to bioprinting of living systems and the applications
of bioprinting in tissue engineering field. The ability to three-dimensionally interweave biological tissue with functional
electronics could enable the creation of bionic organs possessing enhanced
functionalities over their human counterparts. Conventional electronic devices
are inherently two-dimensional, preventing seamless multidimensional integration
with synthetic biology, as the processes and materials are very different. Here,
we present a novel strategy for overcoming these difficulties via additive
manufacturing of biological cells with structural and oparticle derived
electronic elements. As a proof of concept, we generated a bionic ear via 3D
printing of a cell-seeded hydrogel matrix in the anatomic geometry of a human
ear, along with an intertwined conducting polymer consisting of infused silver
oparticles. This allowed for in vitro culturing of cartilage tissue around an
inductive coil antenna in the ear, which subsequently enables readout of
inductively-coupled signals from cochlea-shaped electrodes. The printed ear
exhibits enhanced auditory sensing for radio frequency reception, and
complementary left and right ears can listen to stereo audio music. Overall, our
approach suggests a means to intricately merge biologic and oelectronic
functionalities via 3D printing. 3D printing is a method of manufacturing in which materials, such as plastic or
metal, are deposited onto one another in layers to produce a three dimensional
object, such as a pair of eye glasses or other 3D objects. This process
contrasts with traditional ink-based printers which produce a two dimensional
object (ink on paper). To date, 3D printing has primarily been used in
engineering to create engineering prototypes. However, recent advances in
printing materials have now enabled 3D printers to make objects that are
comparable with traditionally manufactured items. In contrast with conventional
printers, 3D printing has the potential to enable mass customisation of goods on
a large scale and has relevance in medicine including ophthalmology. 3D printing
has already been proved viable in several medical applications including the
manufacture of eyeglasses, custom prosthetic devices and dental implants. In
this review, we discuss the potential for 3D printing to revolutionise
manufacturing in the same way as the printing press revolutionised conventional
printing. The applications and limitations of 3D printing are discussed; the
production process is demonstrated by producing a set of eyeglass frames from 3D
blueprints. Author information:
(1)1] State Key Laboratory of Biotherapy and Cancer Center, West China Hospital,
West China Medical School, Sichuan University, Chengdu 610041, P.R. China [2]
Shiley Eye Center and Institute for Genomic Medicine, University of California,
San Diego, La Jolla, California 92093, USA [3].
(2)1] Department of NanoEngineering, University of California, San Diego, La
Jolla, California 92093, USA [2].
(3)Department of NanoEngineering, University of California, San Diego, La Jolla,
California 92093, USA.
(4)State Key Laboratory of Biotherapy and Cancer Center, West China Hospital,
West China Medical School, Sichuan University, Chengdu 610041, P.R. China.
(5)School of Chemistry and Chemical Engineering, Shaanxi Normal University,
Xi'an 710062, P.R. China.
(6)1] Shiley Eye Center and Institute for Genomic Medicine, University of
California, San Diego, La Jolla, California 92093, USA [2] Biomaterials and
Tissue Engineering Center, University of California, San Diego, La Jolla,
California 92093, USA [3] Veterans Administration Healthcare System, San Diego,
California 92093, USA.
(7)1] Department of NanoEngineering, University of California, San Diego, La
Jolla, California 92093, USA [2] Biomaterials and Tissue Engineering Center,
University of California, San Diego, La Jolla, California 92093, USA. A new epoxy-based ink is reported, which enables 3D printing of lightweight
cellular composites with controlled alignment of multiscale, high-aspectratio
fiber reinforcement to create hierarchical structures inspired by balsa wood.
Young's modulus values up to 10 times higher than existing commercially
available 3D-printed polymers are attainable, while comparable strength values
are maintained. Additive manufacturing, otherwise known as three-dimensional (3D) printing, is
driving major innovations in many areas, such as engineering, manufacturing,
art, education and medicine. Recent advances have enabled 3D printing of
biocompatible materials, cells and supporting components into complex 3D
functional living tissues. 3D bioprinting is being applied to regenerative
medicine to address the need for tissues and organs suitable for
transplantation. Compared with non-biological printing, 3D bioprinting involves
additional complexities, such as the choice of materials, cell types, growth and
differentiation factors, and technical challenges related to the sensitivities
of living cells and the construction of tissues. Addressing these complexities
requires the integration of technologies from the fields of engineering,
biomaterials science, cell biology, physics and medicine. 3D bioprinting has
already been used for the generation and transplantation of several tissues,
including multilayered skin, bone, vascular grafts, tracheal splints, heart
tissue and cartilaginous structures. Other applications include developing
high-throughput 3D-bioprinted tissue models for research, drug discovery and
toxicology. An additive manufacturing process that combines digital modeling and 3D printing
was used to prepare fiber reinforced hydrogels in a single-step process. The
composite materials were fabricated by selectively pattering a combination of
alginate/acrylamide gel precursor solution and an epoxy based UV-curable
adhesive (Emax 904 Gel-SC) with an extrusion printer. UV irradiation was used to
cure the two inks into a single composite material. Spatial control of fiber
distribution within the digital models allowed for the fabrication of a series
of materials with a spectrum of swelling behavior and mechanical properties with
physical characteristics ranging from soft and wet to hard and dry. A comparison
with the "rule of mixtures" was used to show that the swollen composite
materials adhere to standard composite theory. A prototype meniscus cartilage
was prepared to illustrate the potential application in bioengineering. There is an unmet need for a consistent set of tools for the evaluation of
3D-printed constructs. A toolbox developed to design, characterize, and evaluate
3D-printed poly(propylene fumarate) scaffolds is proposed for vascularized
engineered tissues. This toolbox combines modular design and non-destructive
fabricated design evaluation, evaluates biocompatibility and mechanical
properties, and models angiogenesis. A systematic characterisation of bone tissue scaffolds fabricated via 3D
printing from hydroxyapatite (HA) and poly(vinyl)alcohol (PVOH) composite
powders is presented. Flowability of HA:PVOH precursor materials was observed to
affect mechanical stability, microstructure and porosity of 3D printed
scaffolds. Anisotropic behaviour of constructs and part failure at the
boundaries of interlayer bonds was highlighted by compressive strength testing.
A trade-off between the ability to facilitate removal of PVOH thermal
degradation products during sintering and the compressive strength of green
parts was revealed. The ultimate compressive strength of 55% porous green
scaffolds printed along the Y-axis and dried in a vacuum oven for 6h was 0.88 ±
0.02 MPa. Critically, the pores of 3D printed constructs could be user designed,
ensuring bulk interconnectivity, and the imperfect packing of powder particles
created an inherent surface roughness and non-designed porosity within the
scaffold. These features are considered promising since they are known to
facilitate osteoconduction and osteointegration in-vivo. Characterisation
techniques utilised in this study include two funnel flow tests, scanning
electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR),
compressive strength testing and computed tomography (CT). A multimaterial bio-ink method using polyethylene glycol crosslinking is
presented for expanding the biomaterial palette required for 3D bioprinting of
more mimetic and customizable tissue and organ constructs. Lightly crosslinked,
soft hydrogels are produced from precursor solutions of various materials and 3D
printed. Rheological and biological characterizations are presented, and the
promise of this new bio-ink synthesis strategy is discussed. 3D printing has evolved into a versatile technology for fabricating
tissue-engineered constructs with spatially controlled cells and biomaterial
distribution to allow biomimicking of in vivo tissues. In this paper, we
reported a novel study of 3D printing of cell lines derived from human embryonic
kidney tissue into a macroporous tissue-like construct. Nozzle temperature,
chamber temperature and the composition of the matrix material were studied to
achieve high cell viability (>90%) after 3D printing and construct formation.
Long-term construct stability with a clear grid structure up to 30 days was
observed. Cells continued to grow as cellular spheroids with strong cell-cell
interactions. Two transfected cell lines of HEK 293FT were also 3D printed and
showed normal biological functions, i.e. protein synthesis and gene activation
in responding to small molecule stimulus. With further refinement, this 3D cell
printing technology may lead to a practical fabrication of functional embryonic
tissues in vitro. OBJECTIVE: Temporal bone dissection is a fundamental element of otologic
training. Cadaveric temporal bones (CTB) are the gold standard surgical training
model; however, many institutions do not have ready access to them and their
cost can be significant: $300 to $500. Furthermore, pediatric cadaveric temporal
bones are not readily available. Our objective is to develop a pediatric
temporal bone model.
STUDY DESIGN: Temporal bone model.
SETTING: Tertiary Children's Hospital.
SUBJECTS: Pediatric patient model.
METHODS: We describe the novel use of a 3D printer for the generation of a
plaster training model from a pediatric high- resolution CT temporal bone scan
of a normal pediatric temporal bone.
RESULTS: Three models were produced and were evaluated. The models utilized
multiple colors (white for bone, yellow for the facial nerve) and were of high
quality. Two models were drilled as a proof of concept and found to be an
acceptable facsimile of the patient's anatomy, rendering all necessary surgical
landmarks accurately. The only negative comments pertaining to the 3D printed
temporal bone as a training model were the lack of variation in hardness between
cortical and cancellous bone, noting a tactile variation from cadaveric temporal
bones.
CONCLUSION: Our novel pediatric 3D temporal bone training model is a viable,
low-cost training option for previously inaccessible pediatric temporal bone
training. Our hope is that, as 3D printers become commonplace, these models
could be rapidly reproduced, allowing for trainees to print models of patients
before performing surgery on the living patient. 3D Printing promises to produce complex biomedical devices according to computer
design using patient-specific anatomical data. Since its initial use as
pre-surgical visualization models and tooling molds, 3D Printing has slowly
evolved to create one-of-a-kind devices, implants, scaffolds for tissue
engineering, diagnostic platforms, and drug delivery systems. Fueled by the
recent explosion in public interest and access to affordable printers, there is
renewed interest to combine stem cells with custom 3D scaffolds for personalized
regenerative medicine. Before 3D Printing can be used routinely for the
regeneration of complex tissues (e.g. bone, cartilage, muscles, vessels, nerves
in the craniomaxillofacial complex), and complex organs with intricate 3D
microarchitecture (e.g. liver, lymphoid organs), several technological
limitations must be addressed. In this review, the major materials and
technology advances within the last five years for each of the common 3D
Printing technologies (Three Dimensional Printing, Fused Deposition Modeling,
Selective Laser Sintering, Stereolithography, and 3D
Plotting/Direct-Write/Bioprinting) are described. Examples are highlighted to
illustrate progress of each technology in tissue engineering, and key
limitations are identified to motivate future research and advance this
fascinating field of advanced manufacturing. |
Is ospemifene effective for treatment of dyspareunia? | Yes, ospamifene is effective for treatment of dyspareunia. Ospemifene is a selective estrogen receptor modulator, or estrogen receptor agonist/antagonist, that was recently approved by the US Food and Drug Administration for the treatment of dyspareunia associated with vulvar and vaginal atrophy, a chronic condition that affects up to 60% of postmenopausal women. Ospemifene is the first non-estrogen treatment approved for moderate to severe dyspareunia in women with menopause-related vulvar and vaginal atrophy. | OBJECTIVE: The aim of this work was to study the role of ospemifene, a novel
selective estrogen receptor modulator, in the treatment of vulvar and vaginal
atrophy in postmenopausal women with moderate to severe dyspareunia and
physiological vaginal changes.
METHODS: This multicenter phase 3 study used a randomized, double-blind,
parallel-group design to compare the efficacy, safety, and tolerability of oral
ospemifene 60 mg/day versus placebo. A total of 605 women aged 40 to 80 years
who self-reported a most bothersome symptom of dyspareunia and had a diagnosis
of vulvar and vaginal atrophy were randomized to take a once-daily dose of
ospemifene (n = 303) or placebo (n = 302) for 12 weeks.
RESULTS: Analysis of the intent-to-treat (n = 605) population found the efficacy
of ospemifene to be significantly greater than that of placebo for each of the
following coprimary endpoints: percentages of parabasal and superficial cells,
vaginal pH, and severity of dyspareunia. With ospemifene, the percentage of
parabasal cells and vaginal pH significantly decreased; the percentage of
superficial cells significantly increased; and dyspareunia was significantly
reduced versus placebo (all P < 0.0001, except for dyspareunia: P = 0.0001).
Among the randomized women, 186 (61.4%) in the ospemifene group and 154 (51.0%)
in the placebo group reported at least one treatment-emergent adverse event. Hot
flushes were the most frequently reported treatment-related adverse event
(ospemifene 6.6% vs placebo 3.6%); only one participant discontinued in each
group. As determined by the investigators, no serious adverse events related to
the study drug were reported.
CONCLUSIONS: In this study, once-daily oral ospemifene 60 mg was effective for
the treatment of vulvar and vaginal atrophy in postmenopausal women with
dyspareunia. Ospemifene (Osphena™) is an oral selective estrogen receptor modulator (SERM),
with tissue-specific estrogenic agonist/antagonist effects. QuatRx
Pharmaceuticals conducted the global development of the agent before licensing
it to Shionogi for regulatory filing and commercialization worldwide. Ospemifene
is the first non-estrogen treatment approved for moderate to severe dyspareunia
in women with menopause-related vulvar and vaginal atrophy. The drug is approved
in the USA, and application for EU regulatory approval is underway. This article
summarizes the milestones in the development of ospemifene leading to this first
approval for moderate to severe dyspareunia, a symptom of postmenopausal vulvar
and vaginal atrophy. OBJECTIVE: Vaginal estrogen therapy at the lowest effective dose is generally
recommended for the treatment of vulvar and vaginal atrophy (VVA), but not all
women are candidates. Selective estrogen receptor modulators (SERMs) aim to
elicit specific positive effects on targeted tissues with neutral or minimal
negative effects on other tissues. This review compares the vaginal effects of
currently available and investigational SERMs.
METHODS: Relevant English-language articles published between 1980 and 2012 were
identified through the PubMed database (search string "[Selective Estrogen
Receptor Modulator OR SERM] AND [Vulvar OR Vaginal] AND Atrophy"), article
reference lists, and EMBASE searches for individual SERMs. Both authors reviewed
all articles, which formed the basis of this narrative literature review.
RESULTS: Activity profiles of SERMs in various tissues are distinct. Tamoxifen
and arzoxifene have no specific positive vaginal effects but have reported
variable or adverse gynecologic effects. Raloxifene does not improve VVA but can
be used safely in combination with vaginal estrogen. Bazedoxifene has no
demonstrated efficacy for VVA but, in combination with oral conjugated equine
estrogens, improves the signs and symptoms of VVA. SERMs with positive vaginal
effects (such as improvement in the vaginal maturation index, reduced vaginal
pH, and improvement in the signs and symptoms of VVA) on postmenopausal
symptomatic women include lasofoxifene (clinical development on hold) and
ospemifene, which was recently approved for the treatment of VVA-related
dyspareunia, with a class effect warning of potential venous thrombosis risk.
CONCLUSIONS: SERMs that specifically target the pathophysiology underlying VVA
may provide an alternative to vaginal or systemic estrogen therapy. Vulvar and vaginal atrophy (VVA) is a chronic, progressive medical condition
prevalent among postmenopausal women, which produces symptoms such as
dyspareunia, vaginal dryness, and vaginal irritation. Currently, the only
prescription options are systemic and vaginal estrogen therapies that may be
limited by concerns about long-term safety and breast cancer risk. Ospemifene is
a tissue-selective estrogen agonist/antagonist (a selective estrogen receptor
modulator) recently approved by the US Food and Drug Administration for
treatment of dyspareunia, a symptom of VVA, due to menopause. Ospemifene, the
first nonestrogen oral treatment for this indication, may provide an alternative
to treatment with estrogen. Animal models with ospemifene suggest an inhibitory
effect on growth of maligt breast tissue, but animal data cannot necessarily
be extrapolated to humans. Clinical trials, including 3 long-term studies
assessing the overall safety of ospemifene, support that ospemifene is generally
well tolerated, with beneficial effects on the vagina, neutral effects on the
breast, and minimal effects on the endometrium. The multifactorial consequences of menopausal estrogen deficiency affect
numerous tissues throughout the body. Supplemental hormonal therapies carry the
burden of a risk/benefit ratio that must be highly individualized. Selective
estrogen receptor modulators (SERMs) are estrogen receptor (ER)
agonist/antagonists designed to induce benefits comparable with estrogen while
minimizing adverse effects. Here, we review the estrogen agonist/antagonist
profile of ospemifene, a novel triphenylethylene derivative recently approved to
treat dyspareunia, a symptom of vulvar and vaginal atrophy (VVA) due to
menopause, both preclinically and clinically. Ospemifene binds ERα and ERβ with
approximately equal affinities. In preclinical models, ospemifene increased
vaginal and uterine epithelial thickness and mucification to the same extent as
estrogen. Ospemifene did not induce endometrial hyperplasia in animal models;
there also was no stimulatory effect on endometrial cells. In rat and human
mammary cells in vitro, ospemifene evokes a dose-dependent inhibition on
estrogen-induced cell responses and cell proliferation, supporting an
antiestrogenic effect in breast. In contrast, ospemifene has an estrogenic
effect on bone, as seen by improved bone mineral density, strength, mass, and
histomorphometry in preclinical models, consistent with improvements in markers
of bone resorption and formation in postmenopausal women. Based on the
preclinical evidence, ospemifene has beneficial estrogen-like effects on the
vaginal epithelium, preliminary evidence to support a neutral endometrial
profile, antiproliferative effects in breast, and estrogenic effects in bone.
Taken together, especially regarding estrogen-like effects on the vaginal
epithelium, ospemifene presents a profile of tissue-specific effects that appear
novel among available SERMs and well-suited for the treatment of VVA. OBJECTIVE: To characterize the pharmacokinetics of the oral, non-estrogen agent
ospemifene, an estrogen agonist/antagonist with tissue-selective effects (also
called a selective estrogen receptor modulator) that was recently approved for
the treatment of dyspareunia associated with vulvar and vaginal atrophy in
postmenopausal women.
METHODS: Two open-label, Phase 1 studies were conducted to determine the
pharmacokinetics of ospemifene in healthy postmenopausal women. In the
single-dose study, 60 mg of [3H]-ospemifene was orally administered to 6
subjects. Blood, urine, and fecal samples were collected predose and serially up
to 240 hours postdose. In the multiple-dose study, 12 subjects received 60 mg of
ospemifene once daily for 9 days. Blood samples were collected predose and
serially postdose on Day 1, predose on Days 7 and 8, and predose and serially
postdose on Day 9.
RESULTS: Ospemifene exhibited high plasma protein binding and was extensively
metabolized, predomitly to 4-hydroxyospemifene and 4'-hydroxyospemifene. In
the single-dose study, ospemifene was rapidly absorbed, with a median tmax of
1.50 hours and geometric mean Cmax of 612 ng/ml. The geometric mean (CV%) t1/2
was 24.5 (21.3) hours and 29.0 (18.0) hours for ospemifene and
4-hydroxyospemifene, respectively. Fecal elimination accounted for 75% of the
administered [3H]-ospemifene dose in 240 hours. In the multiple dosing study,
steady state was reached by Day 7. The mean t1/2 at steady state for ospemifene
was 29.1 hours. High values for volume of distribution and total clearance
suggested extensive tissue distribution and efficient elimination of ospemifene.
CONCLUSIONS: In healthy postmenopausal women, ospemifene 60 mg/day reached
steady state concentrations by Day 7 and showed minimal accumulation of parent
drug or its two main metabolites, indicating that once daily dosing is
appropriate. INTRODUCTION: Ospemifene, a novel selective estrogen receptor modulator, has
been developed for the treatment of vulvovaginal atrophy and dyspareunia in
postmenopausal women.
AIM: We carried out a systematic review and meta-analysis to assess the efficacy
and safety of the drug for treating dyspareunia associated with postmenopausal
vulvar and vaginal atrophy.
METHODS: A literature review was performed to identify all published randomized
double-blind, placebo-controlled trials of ospemifene for the treatment of
vulvovaginal atrophy and dyspareunia. The search included the following
databases: MEDLINE, EMBASE, and the Cochrane Controlled Trials Register. The
reference lists of the retrieved studies were also investigated. A systematic
review and meta-analysis was conducted.
MAIN OUTCOME MEASURES: Six publications involving a total of 1,772 patients were
used in the analysis, including three randomized controlled trials (RCTs) that
were short-term (12 weeks) comparisons of ospemifene with placebo and three RCTs
that were long-term (1 year) comparisons of ospemifene with placebo.
RESULTS: For the comparison of short-term ospemifene with placebo, parabasal
cells (the standardized mean difference [SMD] = -37.5, 95% confidence interval
[CI] = -41.83 to -33.17, P < 0.00001), superficial cells (SMD = 9.24, 95% CI =
7.70 to 10.79, P < 0.00001), vaginal PH (SMD = -0.89, 95% CI = -0.98 to -0.80, P
= 0.00001), and dyspareunia (SMD = -0.37, 95% CI = -0.43 to -0.30, P = 0.00001)
indicated that ospemifene was more effective than the placebo. For the
comparison of long-term ospemifene with placebo, endometrial thickness (SMD =
0.90, 95% CI = 0.58 to 1.23, P = 0.00001), treatment emergent adverse event,
discontinuations due to adverse event, and serious adverse event indicated that
ospemifene was generally safe.
CONCLUSIONS: This meta-analysis indicates that ospemifene to be an effective and
safe treatment for dyspareunia associated with postmenopausal vulvar and vaginal
atrophy. |
Is pregabalin effective for treatment of patients with restless leg syndrome? | Yes, numerous evidence from clinical trials indicate that pregabalic is effective for treatment of patients diagnosed with restless leg syndrome. | BACKGROUND: Restless legs syndrome (RLS) is a common neurological disorder
complicated in many patients by augmentation to dopaminergic therapy or
comorbidities such as neuropathic pain.
AIMS: To explore the effectiveness of pregabalin in RLS in a pragmatic clinical
setting.
METHODS: After observing improvement of restless legs symptoms in seven patients
treated with pregabalin for neuropathic pain, we extended the clinical
observation to a total of 16 patients with secondary RLS, in most of them due to
neuropathy, and to three patients with idiopathic RLS.
RESULTS: Three patients discontinued pregabalin because of side effects (rash,
fatigue, loss of efficacy). The other 16 patients self-rated a satisfactory or
good alleviation of RLS symptoms and maintained pregabalin, five with add-on
medication, on a mean daily dose of 305 mg (standard deviation, 185 mg), and
with a mean duration of 217 (standard deviation, 183) days.
CONCLUSION: These data propose pregabalin as a new option in the treatment of
secondary RLS for patients with neuropathic pain, which should be further
investigated with randomized, placebo-controlled trials. Restless-legs syndrome (RLS) is a sensorimotor disorder, characterized by an
irresistible urge to move the legs usually accompanied or caused by
uncomfortable and unpleasant sensations. It begins or worsens during periods of
rest or inactivity, is partially or totally relieved by movements and is
exacerbated or occurs at night and in the evening. RLS sufferers represent 2 to
3% of the general population in Western countries. Supportive criteria include a
family history, the presence of periodic-leg movements (PLM) when awake or
asleep and a positive response to dopaminergic treatment. The RLS phenotypes
include an early onset form, usually idiopathic with a familial history and a
late onset form, usually secondary to peripheral neuropathy. Recently, an
atypical RLS phenotype without PLM and l-DOPA resistant has been characterized.
RLS can occur in childhood and should be distinguished from attention
deficit/hyperactivity disorder, growing pains and sleep complaints in childhood.
RLS should be included in the diagnosis of all patients consulting for sleep
complaints or discomfort in the lower limbs. It should be differentiated from
akathisia, that is, an urge to move the whole body without uncomfortable
sensations. Polysomnographic studies and the suggested immobilization test can
detect PLM. Furthermore, an l-DOPA challenge has recently been validated to
support the diagnosis of RLS. RLS may cause severe-sleep disturbances, poor
quality of life, depressive and anxious symptoms and may be a risk factor for
cardiovascular disease. In most cases, RLS is idiopathic. It may also be
secondary to iron deficiency, end-stage renal disease, pregcy, peripheral
neuropathy and drugs, such as antipsychotics and antidepressants. The
small-fiber neuropathy can mimic RLS or even trigger it. RLS is associated with
many neurological and sleep disorders including Parkinson's disease, but does
not predispose to these diseases. The pathophysiology of RLS includes an altered
brain-iron metabolism, a dopaminergic dysfunction, a probable role of pain
control systems and a genetic susceptibility with nine loci and three
polymorphisms in genes serving developmental functions. RLS treatment begins
with the elimination of triggering factors and iron supplementation when
deficient. Mild or intermittent RLS is usually treated with low doses of l-DOPA
or codeine; the first-line treatment for moderate to severe RLS is dopaminergic
agonists (pramipexole, ropinirole, rotigotine). In severe, refractory or
neuropathy-associated RLS, antiepileptic (gabapentin, pregabalin) or opioid
(oxycodone, tramadol) drugs can be used. OBJECTIVE: This study evaluated the dose-related efficacy and safety of
pregabalin in patients with idiopathic restless legs syndrome (RLS).
METHODS: This six-arm, double-blind, placebo-controlled, dose-response study
randomized patients (N=137) with moderate-to-severe idiopathic RLS in an equal
ratio to placebo or pregabalin 50, 100, 150, 300, or 450 mg/day. The
dose-response was characterized using an exponential decay model, which
estimates the maximal effect (E(max)) for the primary endpoint, the change in
the International Restless Legs Study Group Rating Scale (IRLS) total score from
baseline to week 6 of treatment. Secondary outcomes included Clinical Global
Impressions-Improvement Scale (CGI-I) responders, sleep assessments, and safety.
RESULTS: The separation of treatment effect between placebo and pregabalin began
to emerge starting at week 1 which continued and increased through week 6 for
all dose groups. The IRLS total score for pregabalin was dose dependent and well
characterized for change from baseline at week 6. The model estimated 50%
(ED(50)) and 90% (ED(90)) of the maximal effect in reducing RLS symptoms that
occurred at pregabalin doses of 37.3 and 123.9 mg/day, respectively. A higher
proportion of CGI-I responders was observed at the two highest doses of
pregabalin (300 and 450 mg/day) versus placebo. Dizziness and somnolence were
the most common adverse events and appeared to be dose-related.
CONCLUSIONS: In this 6-week phase 2b study, pregabalin reduced RLS symptoms in
patients with moderate-to-severe idiopathic RLS. The symptom reduction at week 6
was dose-dependent with 123.9 mg/day providing 90% efficacy. Pregabalin was safe
and well tolerated across the entire dosing range. Gabapentin enacarbil XR is a new extended-release formulation which attempts to
overcome the reduced efficacy of shorter-acting gabapentin, with sustained
delivery over a 24-hour period. It is a gabapentin prodrug which is efficiently
and rapidly converted to gabapentin during active transport throughout the
length of the intestine via high-capacity monocarboxylate type 1 nutrient
transporters unlike its predecessor, which is absorbed via low-capacity
transporters largely confined to the upper intestinal region. Its lack of
saturable absorption allows for dose-proportional absorption and hence increased
bioavailability. Several clinical trials addressing its efficacy in moderate to
severe restless legs syndrome (RLS) demonstrate improvements in the
International RLS Rating Scale after a 2-week to 3-month period. Open-label
studies of 52 weeks' duration showed maintece of symptom reduction with
once-daily administration of the extended-release formulation. The most commonly
reported treatment-emergent adverse effects were somnolence and dizziness.
Although the incidence of emergent adverse effects is high, it is comparable
with that of gabapentin. No studies thus far have documented augmentation as an
issue, unlike that observed with most dopaminergic agents. In addition, both
dopamine precursors and agonists have not been shown to increase slow wave sleep
or improve overall sleep architecture consistently despite improvement in the
periodic leg movement index, in contrast with gabapentin enacarbil. Presently,
gabapentin enacarbil has not been approved by the Therapeutic Goods
Administration or Medsafe for use in RLS. The cost of this medication may also
be a potential barrier for many patients. Future comparative efficacy studies
with gabapentin, first-line dopaminergic agents, rotigotine, being the other
once daily RLS medication, and pregabalin, the structural analog of gabapentin,
will be necessary. A systematic literature review and meta-analyses (where appropriate) were
performed to update the previous AASM practice parameters on the treatments,
both dopaminergic and other, of RLS and PLMD. A considerable amount of
literature has been published since these previous reviews were performed,
necessitating an update of the corresponding practice parameters. Therapies with
a STANDARD level of recommendation include pramipexole and ropinirole. Therapies
with a GUIDELINE level of recommendation include levodopa with dopa
decarboxylase inhibitor, opioids, gabapentin enacarbil, and cabergoline (which
has additional caveats for use). Therapies with an OPTION level of
recommendation include carbamazepine, gabapentin, pregabalin, clonidine, and for
patients with low ferritin levels, iron supplementation. The committee
recommends a STANDARD AGAINST the use of pergolide because of the risks of heart
valve damage. Therapies for RLS secondary to ESRD, neuropathy, and superficial
venous insufficiency are discussed. Lastly, therapies for PLMD are reviewed.
However, it should be mentioned that because PLMD therapy typically mimics RLS
therapy, the primary focus of this review is therapy for idiopathic RLS. BACKGROUND: Since the publication of the first European Federation of
Neurological Societies (EFNS) guidelines in 2005 on the management of restless
legs syndrome (RLS; also known as Willis-Ekbom disease), there have been major
therapeutic advances in the field. Furthermore, the management of RLS is now a
part of routine neurological practice in Europe. New drugs have also become
available, and further randomized controlled trials have been undertaken. These
guidelines were undertaken by the EFNS in collaboration with the European
Neurological Society and the European Sleep Research Society.
OBJECTIVES: To provide an evidence-based update of new treatments published
since 2005 for the management of RLS.
METHODS: First, we determined what the objectives of management of primary and
secondary RLS should be. We developed the search strategy and conducted a review
of the scientific literature up to 31 December 2011 (print and electronic
publications) for the drug classes and interventions employed in RLS treatment.
Previous guidelines were consulted. All trials were analysed according to class
of evidence, and recommendations made according to the 2004 EFNS criteria for
rating.
RECOMMENDATIONS: Level A recommendations can be made for rotigotine, ropinirole,
pramipexole, gabapentin enacarbil, gabapentin and pregabalin, which are all
considered effective for the short-term treatment for RLS. However, for the
long-term treatment for RLS, rotigotine is considered effective, gabapentin
enacarbil is probably effective, and ropinirole, pramipexole and gabapentin are
considered possibly effective. Cabergoline has according to our criteria a level
A recommendation, but the taskforce cannot recommend this drug because of its
serious adverse events. PURPOSE OF REVIEW: This article reviews the sleep-related movement disorders,
including restless legs syndrome (RLS; Willis-Ekbom disease), periodic limb
movement disorder, rhythmic movement disorders, sleep-related bruxism, and
sleep-related leg cramps.
RECENT FINDINGS: The prevalence of clinically significant RLS is 1.5% to 3.0%.
The pathophysiology of RLS may involve abnormal iron transport across the
blood-brain barrier and down-regulation of putaminal D2 receptors. The
availability of the rotigotine patch provides an additional form of dopaminergic
therapy for RLS. Calcium channel alpha-2-delta ligands (gabapentin, gabapentin
enacarbil, and pregabalin) provide alternative therapies for RLS especially in
patients with augmentation, impulse control disorders, or hypersomnia induced by
dopamine agonists. Long-term use of opioid medication is safe and effective for
refractory cases of RLS.
SUMMARY: RLS is a common disorder causing considerable morbidity. Accurate
diagnosis and appropriate investigations are essential. Many effective therapies
are available, but the side effects of each class of medication should be
considered in determining optimal treatment. Periodic limb movements of sleep,
bruxism, and rhythmic movement disorders are sleep-related phenomena often
accompanying other sleep disorders and only sometimes requiring primary therapy.
Sleep-related leg cramps are generally idiopathic. Management is challenging
with few effective therapies. Restless legs syndrome (RLS) is a common sensory motor neurological disorder
that is characterised by an irresistible urge to move the legs that
significantly affects the quality of life of the patient. Prevalence in the
general population is 5-25% and it is twice as prevalent in women as in men. RLS
is the most common movement disorder in pregcy with a fourfold increased risk
of developing this disorder later in life. The pathophysiology of RLS is centred
on dopaminergic dysfunction, reduced central nervous system iron, genetic
linkages, or alteration in neurotransmitters such as hypocretins, endorphins
levels and immune dysfunction and inflammatory mechanisms. With the emergence of
new evidence, there are changes to the previous treatment recommendations for
RLS. There is sufficient evidence to conclude that dopamine agonists such as
rotigotine transdermal patch, pramipexole, ropinirole, gabapentin enacarbil,
pregabalin and gabapentin are effective in the short-term treatment of RLS and
rotigotine, followed by gabapentin enacarbil, ropinirole, pramipexole and
gabapentin for long-term treatment. Based on expert consensus, the
recommendation for daily RLS is dopamine agonists or gabapentin or low-potency
opioids. Levodopa is less preferred for treating daily RLS due to its high risk
of augmentation. For intermittent RLS, it is levodopa or dopamine agonists or
low-potency opioids or benzodiazepines. For refractory RLS, the choice is to
change to gabapentin or a different dopamine agonist, addition of a second agent
like gabapentin or benzodiazepine to the existing drug or changing to a
high-potency opioid or tramadol. Medications with safety record in pregcy
include opioids and antiepileptics such as carbamazepine and gabapentin. There
are concerns that patients with RLS are at risk for metabolic deregulation,
autonomic dysfunction and cardiovascular morbidity. However, a recent study
concluded that RLS is not associated with increased risk of cardiovascular
complications. BACKGROUND: At the time of writing only dopamine agonists are licensed for the
treatment of restless legs syndrome (RLS) in various countries, but randomized
controlled trials (RCTs) have been performed with other treatments. We performed
comprehensive meta-analyses and indirect comparisons of RCTs for all currently
recommended treatments of RLS.
METHODS: We searched the Central, Medline, Embase, PsycINFO and CINAHL
databases. Outcome measures were the international RLS study group severity
scale (IRLS), clinical global impression-improvement, (CGI-I), periodic limb
movement index (PLMI), and psychosocial parameters such as quality of life
(QoL). We also conducted indirect comparisons by testing for heterogeneity
between the substance groups.
RESULTS: Placebo (58 trials) and actively (4 trials) controlled RCTs with
dopamine agonists (38 trials), levodopa (4 trials), anticonvulsants (13 trials),
most of them with α₂δ ligands (11 trials), opioids (1 trial), and iron
treatments (6 trials) were included (9596 patients). Although treatment effects
showed large variations, changes in the IRLS in the substance groups were
comparable (P = 0.78), with a mean reduction in the IRLS of -5.47 points for
dopamine agonists, -5.12 points for anticonvulsants (α₂δ ligands and
levetiracetam), and -4.59 points for iron treatments. The CGI-I indicated
slightly different treatment effects between the substance groups, while PLMI
changes during treatment differed (P = 0.002), showing a marked decrease with
dopamine agonists (-22.50/h), levodopa (-26.01/h), and oxycodone (-34.46/h)
compared with a slight decrease for anticonvulsants (α₂δ ligands and
levetiracetam; -8.48/h) and iron treatments (-13.10/h). Quality of sleep and QoL
improved moderately in most of the RCTs investigating these parameters
(standardized mean difference, SMD) 0.40 and 0.33, respectively). In the few
studies evaluating the change of depressive (n = 4) or anxiety symptoms (n = 3),
these symptoms improved slightly (SMD -0.24, and -0.21). Adverse effects and
dropouts were comparable in number across all substance groups. In
meta-regressions, the treatment effect was predicted by the design of the trial
(the more sites involved in a trial the lower the effect) and by the duration of
action of a medication (the longer the duration of action, expressed as the
half-life time of a substance, the greater the improvement), the latter
indicating potential superiority of treatments with stable blood concentration.
CONCLUSION: This first meta-analysis of all RCTs for the pharmacological
treatment of RLS provides evidence that, besides the well-defined efficacy of
dopaminergic treatment, other treatments with different pharmacological
principles show efficacy in small samples and may be well-tolerated alternatives
for the treatment of RLS. In the group of anticonvulsants, only the trials
performed with α₂δ ligands such as gabapentin, gabapentin enacarbil, and
pregabalin showed good efficacy. This indicates a specific mechanism of action
of these substances in RLS. The group of iron treatments consisted of a few
trials with different compounds in oral and intravenous application form,
respectively. For a more differentiated evaluation of the efficacy of iron
treatments further studies are necessary. The large efficacy of one opioid RCT
in RLS has to be confirmed in further studies. We report a case with refractory insomnia. We diagnosed her case as depression
with high levels of anxiety, weakness, with diminished ability to think or
concentrate and with a sensory-motor disorder. Although this last symptom was
very distressing, it did not satisfy the criteria for RLS (Restless Legs
Syndrome). After treatment with paroxetine (20 mg) and zolpidem (10 mg), anxiety
and mood deflection were attenuated. Nevertheless, a mild depression, an
intermittent awakening (fragmentation of the sleep-wake rhythm) and subsyndromal
RLS persisted. Her resistant insomnia was treated with benzodiazepine sleeping
drugs (triazolam 0.25 mg, lorazepam 2.5 mg, fluorazepam 30 mg) with only partial
insomnia remission, antidepressants (trazodone 150 mg RP, mirtazapine 15-30 mg,
agomelatine 50 mg) and antipsychotics (levomepromazine 25 mg, zuclopentixol 25
mg) without results. Her intractable insomnia was markedly responsive to
pregabalin without side effects. Our hypothesis is that the therapy with
pregabalin may be indicated for resistant insomnia associated with subsyndromal
RLS, even when the latter does not satisfy fully all the criteria for diagnosis. A Task Force was established by the International Restless Legs Syndrome Study
Group (IRLSSG) to develop evidence-based and consensus-based recommendations for
the long-term pharmacologic treatment of restless legs syndrome/Willis-Ekbom
disease (RLS/WED). The Task Force reviewed the results of all studies of RLS/WED
treatments with durations of 6 months or longer presented at meetings over the
past 2 years, posted on Web sites of pharmaceutical companies, or published in
peer-reviewed journals, asking the questions, "What is the efficacy of this
treatment in patients with RLS/WED?" and "What is the safety of this treatment
in patients with RLS/WED?" The Task Force developed guidelines based on their
review of 61 papers meeting inclusion criteria, and using a modified
evidence-grading scheme. Pregabalin has been established as effective for up to
1 year in treating RLS/WED (Level A evidence). Pramipexole, ropinirole, and
rotigotine have been established as effective for up to 6 months in treating
RLS/WED (Level A). The following drugs have been established as probably
effective (Level B) in treating RLS/WED for durations ranging from 1 to 5 years:
gabapentin enacarbil, pramipexole, and ropinirole (1 year); levodopa (2 years);
and rotigotine (5 years). Because of associated safety concerns, pergolide and
cabergoline should not be used in the treatment of RLS/WED unless the benefits
clearly outweigh the risks. Other pharmacologic therapies have insufficient
evidence to support their long-term use in treating RLS/WED. The IRLSSG Task
Force also developed consensus-based strategies for the prevention and treatment
of complications (such as augmentation, loss of efficacy, excessive daytime
sleepiness, and impulse control disorders) that may develop with the long-term
pharmacologic treatment of RLS/WED. The use of either a dopamine-receptor
agonist or α2δ calcium-channel ligand is recommended as the first-line treatment
of RLS/WED for most patients, with the choice of agent dependent on the
patient's severity of RLS/WED symptoms, cognitive status, history, and comorbid
conditions. Pregabalin is approved for the treatment of a variety of clinical conditions and
its analgesic, anxiolytic and anticonvulsant properties are well documented.
Pregabalin's effects on sleep, however, are less well known. This review
summarizes the published data on the effects of pregabalin on sleep disturbance
associated with neuropathic pain, fibromyalgia, restless legs syndrome, partial
onset seizures and general anxiety disorder. The data demonstrate that
pregabalin has a positive benefit on sleep disturbance associated with several
different clinical conditions. Polysomnographic data reveal that pregabalin
primarily affects sleep maintece. The evidence indicates that pregabalin has
a direct effect on sleep that is distinct from its analgesic, anxiolytic and
anticonvulsant effects. BACKGROUND: Dopaminergic medications relieve symptoms of the restless legs
syndrome (RLS) but have the potential to cause iatrogenic worsening
(augmentation) of RLS with long-term treatment. Pregabalin may be an effective
alternative.
METHODS: In this 52-week, randomized, double-blind trial, we assessed efficacy
and augmentation in patients with RLS who were treated with pregabalin as
compared with placebo and pramipexole. Patients were randomly assigned to
receive 52 weeks of treatment with pregabalin at a dose of 300 mg per day or
pramipexole at a dose of 0.25 mg or 0.5 mg per day or 12 weeks of placebo
followed by 40 weeks of randomly assigned active treatment. The primary analyses
involved a comparison of pregabalin and placebo over a period of 12 weeks with
use of the International RLS (IRLS) Study Group Rating Scale (on which the score
ranges from 0 to 40, with a higher score indicating more severe symptoms), the
Clinical Global Impression of Improvement scale (which was used to assess the
proportion of patients with symptoms that were "very much improved" or "much
improved"), and a comparison of rates of augmentation with pregabalin and
pramipexole over a period of 40 or 52 weeks of treatment.
RESULTS: A total of 719 participants received daily treatment, 182 with 300 mg
of pregabalin, 178 with 0.25 mg of pramipexole, 180 with 0.5 mg of pramipexole,
and 179 with placebo. Over a period of 12 weeks, the improvement (reduction) in
mean scores on the IRLS scale was greater, by 4.5 points, among participants
receiving pregabalin than among those receiving placebo (P<0.001), and the
proportion of patients with symptoms that were very much improved or much
improved was also greater with pregabalin than with placebo (71.4% vs. 46.8%,
P<0.001). The rate of augmentation over a period of 40 or 52 weeks was
significantly lower with pregabalin than with pramipexole at a dose of 0.5 mg
(2.1% vs. 7.7%, P=0.001) but not at a dose of 0.25 mg (2.1% vs. 5.3%, P=0.08).
There were six cases of suicidal ideation in the group receiving pregabalin,
three in the group receiving 0.25 mg of pramipexole, and two in the group
receiving 0.5 mg of pramipexole.
CONCLUSIONS: Pregabalin provided significantly improved treatment outcomes as
compared with placebo, and augmentation rates were significantly lower with
pregabalin than with 0.5 mg of pramipexole. (Funded by Pfizer;
ClinicalTrials.gov number, NCT00806026.). |
What is the biological role of expansins in fungi? | Expansins are extracellular proteins that increase plant cell-wall extensibility. These wall-loosening proteins are involved in cell wall extension and polysaccharide degradation. In fungi expansins and expansin-like proteins have been found to localize in the conidial cell wall and are probably involved in cell wall remodeling during germination. | alpha-Expansins are extracellular proteins that increase plant cell-wall
extensibility. We analysed their pattern of expression in cucumber roots in the
presence and in the absence of the mycorrhizal fungus, Glomus versiforme. The
distribution of alpha-expansins was investigated by use of two polyclonal
antibodies (anti-EXPA1 and anti-EXPA2, prepared against two different cucumber
alpha-expansins) in immunoblotting, immunofluorescence, and immunogold
experiments. Immunoblot results indicate the presence of a 30-kDa band specific
for mycorrhizal roots. The two antibodies identify antigens with a different
distribution in mycorrhizal roots: anti-EXPA1 labels the interface zone, but the
plant cell walls only weakly. By contrast, the anti-EXPA2 labels only the plant
cell walls. In order to understand the potential role of alpha-expansins during
the accommodation of the fungus inside root cells, we prepared semi-thin
sections to measure the size of cortical cells and the thickness of cortical
cell walls in mycorrhizal and non-mycorrhizal root. Mycorrhizal cortical cells
were significantly larger than non-mycorrhizal cells and had thicker cell walls.
In double-labelling experiments with cellobiohydrolase-gold complex, we observed
that cellulose was co-localized with alpha-expansins. Taken together, the
results demonstrate that alpha-expansins are more abundant in the cucumber cell
walls upon mycorrhizal infection; we propose that these wall-loosening proteins
are directly involved in the accommodation of the fungus by infected cortical
cells. Swollenin, a protein first characterized in the saprophytic fungus Trichoderma
reesei, contains an N-terminal carbohydrate-binding module family 1 domain (CBD)
with cellulose-binding function and a C-terminal expansin-like domain. This
protein was identified by liquid chromatography-mass spectrometry among many
other cellulolytic proteins secreted in the coculture hydroponics medium of
cucumber (Cucumis sativus) seedlings and Trichoderma asperellum, a well-known
biocontrol agent and inducer of plant defense responses. The swollenin gene was
isolated and its coding region was overexpressed in the same strain under the
control of the constitutive pki1 promoter. Trichoderma transformants showed a
remarkably increased ability to colonize cucumber roots within 6 h after
inoculation. On the other hand, overexpressors of a truncated swollenin sequence
bearing a 36-amino acid deletion of the CBD did not differ from the wild type,
showing in vivo that this domain is necessary for full protein activity. Root
colonization rates were reduced in transformants silenced in swollenin gene
expression. A synthetic 36-mer swollenin CBD peptide was shown to be capable of
stimulating local defense responses in cucumber roots and leaves and to afford
local protection toward Botrytis cinerea and Pseudomonas syringae pv lachrymans
infection. This indicates that the CBD domain might be recognized by the plant
as a microbe-associated molecular pattern in the Trichoderma-plant interaction. Although the process of conidial germination in filamentous fungi has been
extensively studied, many aspects remain to be elucidated since the asexual
spore or conidium is vital in their life cycle. Breakage and reformation of cell
wall polymer bonds along with the maintece of cell wall plasticity during
conidia germination depend upon a range of hydrolytic enzymes whose activity is
analogous to that of expansins, a highly conserved group of plant cell wall
proteins with characteristic wall loosening activity. In the current study, we
identified and characterized the eglD gene in Aspergillus nidulans, an
expansin-like gene the product of which shows strong similarities with bacterial
and fungal endo-beta1,4-glucanases. However, we failed to show such activity in
vitro. The eglD gene is constitutively expressed in all developmental stages and
compartments of A. nidulans asexual life cycle. However, the EglD protein is
exclusively present in conidial cell walls. The role of the EglD protein in
morphogenesis, growth and germination rate of conidia was investigated. Our
results show that EglD is a conidial cell wall localized expansin-like protein,
which could be involved in cell wall remodeling during germination. Expression kinetics of six cellulase and four expansin-related genes were
studied in the hypercellulolytic Trichoderma reesei CL847 mutant in response to
Solka Floc cellulose and soluble inducers. Real-time PCR showed a parallel
increase of transcript levels for the cellulase genes cbh1/cel7a, egl1/cel7b,
egl4/cel61a, the beta-glucosidase genes bgl1/cel3a, bgl2/cel1a, and the swo1
gene, encoding the cell-wall loosening protein swollenin. To evaluate a putative
implication of three newly identified expansin/family 45 endoglucanase-like
(EEL) proteins in lignocellulose degradation, their expression was also
analysed. Only eel2 was found to be transcribed under the present conditions,
and showed constitutive expression similar to the endoglucanase encoding cel5b
gene. Several recombit fungal enzymes (endoglucanase and pectinase) were studied
for their interactions with alpha-expansin in cell wall extension and
polysaccharide degradation. Both Cel12A and Cel5A were able to hydrolyze
cellulose CMC-Na and mixed-linkage beta-glucan. In contrast to Cel5A, Cel12A
could also hydrolyze xyloglucan and induce wall extension of cucumber hypocotyls
in an in vitro assay. Combining alpha-expansin, even at high concentrations,
with Cel12A did not enhance the maximum/final wall extension rate induced by
Cel12A alone. These results strongly suggest that modification/degradation of
the xyloglucan molecule/network is the key for cell wall extension, and
alpha-expansin and Cel12A may share the same acting site in the substrate.
Pectinase (Pel1, a pectin lyase) enhanced alpha-expansin-induced wall extension
in a concentration-dependent manner, suggesting that the pectin network may
normally regulate accessibility of expansin to the xyloglucan-cellulose complex.
alpha-Expansin enhanced Cel12A's hydrolytic activity on cellulose CMC-Na but not
on xyloglucan and beta-glucan. Expansin did not affect Cel5A's hydrolytic
activity. Interestingly, expansin also enhanced Pel1's activity on degrading
high esterified pectin. A potential explanation for why expansin could
synergistically interact with only certain enzymes on specific polysaccharides
is discussed. Additional results also suggested that cell wall swelling may not
be a significant event during the action of expansin and hydrolases. |
Can zinc finger nucleases be used to combat disease? | Yes, zinc finger nucleases are a useful tool for treating disease. | Permanent modification of the human genome in vivo is impractical owing to the
low frequency of homologous recombination in human cells, a fact that hampers
biomedical research and progress towards safe and effective gene therapy. Here
we report a general solution using two fundamental biological processes: DNA
recognition by C2H2 zinc-finger proteins and homology-directed repair of DNA
double-strand breaks. Zinc-finger proteins engineered to recognize a unique
chromosomal site can be fused to a nuclease domain, and a double-strand break
induced by the resulting zinc-finger nuclease can create specific sequence
alterations by stimulating homologous recombination between the chromosome and
an extrachromosomal DNA donor. We show that zinc-finger nucleases designed
against an X-linked severe combined immune deficiency (SCID) mutation in the
IL2Rgamma gene yielded more than 18% gene-modified human cells without
selection. Remarkably, about 7% of the cells acquired the desired genetic
modification on both X chromosomes, with cell genotype accurately reflected at
the messenger RNA and protein levels. We observe comparably high frequencies in
human T cells, raising the possibility of strategies based on zinc-finger
nucleases for the treatment of disease. The ability to achieve site-specific manipulation of the mammalian genome has
widespread implications for basic and applied research. Gene targeting is a
process in which a DNA molecule introduced into a cell replaces the
corresponding chromosomal segment by homologous recombination, and thus presents
a precise way to manipulate the genome. In the past, the application of gene
targeting to mammalian cells has been limited by its low efficiency. Zinc finger
nucleases (ZFNs) show promise in improving the efficiency of gene targeting by
introducing DNA double-strand breaks in target genes, which then stimulate the
cell's endogenous homologous recombination machinery. Recent results have shown
that ZFNs can be used to create targeting frequencies of up to 20% in a human
disease-causing gene. Future work will be needed to translate these in vitro
findings to in vivo applications and to determine whether zinc finger nucleases
create undesired genomic instability. The selective degradation of mutated mitochondrial DNA (mtDNA) molecules is a
potential strategy to re-populate cells with wild-type (wt) mtDNA molecules and
thereby alleviate the defective mitochondrial function that underlies mtDNA
diseases. Zinc finger nucleases (ZFNs), which are nucleases conjugated to a
zinc-finger peptide (ZFP) engineered to bind a specific DNA sequence, could be
useful for the selective degradation of particular mtDNA sequences. Typically,
pairs of complementary ZFNs are used that heterodimerize on the target DNA
sequence; however, conventional ZFNs were ineffective in our system. To overcome
this, we created single-chain ZFNs by conjugating two FokI nuclease domains,
connected by a flexible linker, to a ZFP with an N-terminal mitochondrial
targeting sequence. Here we show that these ZFNs are efficiently transported
into mitochondria in cells and bind mtDNA in a sequence-specific manner
discriminating between two 12-bp long sequences that differ by a single base
pair. Due to their selective binding they cleave dsDNA at predicted sites
adjacent to the mutation. When expressed in heteroplasmic cells containing a
mixture of mutated and wt mtDNA these ZFNs selectively degrade mutated mtDNA,
thereby increasing the proportion of wt mtDNA molecules in the cell. Therefore,
mitochondria-targeted single-chain ZFNs are a promising candidate approach for
the treatment of mtDNA diseases. Zinc Finger nucleases (ZFNs) have been used to create precise genome
modifications at frequencies that might be therapeutically useful in gene
therapy. We created a mouse model of a generic recessive genetic disease to
establish a preclinical system to develop the use of ZFN-mediated gene
correction for gene therapy. We knocked a mutated GFP gene into the ROSA26 locus
in murine embryonic stem (ES) cells and used these cells to create a transgenic
mouse. We used ZFNs to determine the frequency of gene correction by gene
targeting in different primary cells from this model. We achieved targeting
frequencies from 0.17 to 6% in different cell types, including primary
fibroblasts and astrocytes. We demonstrate that ex vivo gene-corrected
fibroblasts can be transplanted back into a mouse where they retained the
corrected phenotype. In addition, we achieved targeting frequencies of over 1%
in ES cells, and the targeted ES cells retained the ability to differentiate
into cell types from all three germline lineages. In summary, potentially
therapeutically relevant frequencies of ZFN-mediated gene targeting can be
achieved in a variety of primary cells and these cells can then be transplanted
back into a recipient. Recent work has shown that it is possible to target regulatory elements to DNA
sequences of an investigator's choosing, increasing the armamentarium for
probing gene function. In this review, we discuss the development and use of
designer zinc finger proteins (ZFPs) as sequence specific tools. While the main
focus of this review is to discuss the attachment of the FokI nuclease to ZFPs
and the ability of the resulting fusion protein (termed zinc finger nucleases
(ZFNs)) to genomically manipulate a gene of interest, we will also cover the
utility of other functional domains, such as transcriptional activators and
repressors, and highlight how these are being used as discovery and therapeutic
tools. BACKGROUND: Multidrug-resistant Plasmodium is of major concern today. Effective
vaccines or successful applications of RNAi-based strategies for the treatment
of malaria are currently unavailable. An unexplored area in the field of malaria
research is the development of DNA-targeting drugs that can specifically
interact with parasitic DNA and introduce deleterious changes, leading to loss
of vital genome function and parasite death.
PRESENTATION OF THE HYPOTHESIS: Advances in the development of zinc finger
nuclease (ZFN) with engineered DNA recognition domains allow us to design and
develop nuclease of high target sequence specificity with a mega recognition
site that typically occurs only once in the genome. Moreover, cell-penetrating
peptides (CPP) can cross the cell plasma membrane and deliver conjugated
protein, nucleic acid, or any other cargo to the cytoplasm, nucleus, or
mitochondria. This article proposes that a drug from the combination of the CPP
and ZFN systems can effectively enter the intracellular parasite, introduce
deleterious changes in its genome, and eliminate the parasite from the infected
cells.
TESTING THE HYPOTHESIS: Availability of a DNA-binding motif for more than 45
triplets and its modular nature, with freedom to change number of fingers in a
ZFN, makes development of customized ZFN against diverse target DNA sequence of
any gene feasible. Since the Plasmodium genome is highly AT rich, there is
considerable sequence site diversity even for the structurally and functionally
conserved enzymes between Plasmodium and humans. CPP can be used to deliver ZFN
to the intracellular nucleus of the parasite. Signal-peptide-based heterologous
protein translocation to Plasmodium-infected RBCs (iRBCs) and different
Plasmodium organelles have been achieved. With successful fusion of CPP with
mitochondrial- and nuclear-targeting peptides, fusion of CPP with 1 more
Plasmodium cell membrane translocation peptide seems achievable.
IMPLICATIONS OF THE HYPOTHESIS: Targeting of the Plasmodium genome using ZFN has
great potential for the development of anti-malarial drugs. It allows the
development of a single drug against all malarial infections, including
multidrug-resistant strains. Availability of multiple ZFN target sites in a
single gene will provide alternative drug target sites to combat the development
of resistance in the future. We have developed induced pluripotent stem cells (iPSCs) from a patient with
X-linked chronic granulomatous disease (X-CGD), a defect of neutrophil
microbicidal reactive oxygen species (ROS) generation resulting from gp91(phox)
deficiency. We demonstrated that mature neutrophils differentiated from X-CGD
iPSCs lack ROS production, reproducing the pathognomonic CGD cellular phenotype.
Targeted gene transfer into iPSCs, with subsequent selection and full
characterization to ensure no off-target changes, holds promise for correction
of monogenic diseases without the insertional mutagenesis caused by multisite
integration of viral or plasmid vectors. Zinc finger nuclease-mediated gene
targeting of a single-copy gp91(phox) therapeutic minigene into one allele of
the "safe harbor" AAVS1 locus in X-CGD iPSCs without off-target inserts resulted
in sustained expression of gp91(phox) and substantially restored neutrophil ROS
production. Our findings demonstrate how precise gene targeting may be applied
to correction of X-CGD using zinc finger nuclease and patient iPSCs. Zinc-finger nucleases (ZFNs) are a powerful tool that can be used to edit the
human genome ad libitum. The technology has experienced remarkable development
in the last few years with regard to both the target site specificity and the
engineering platforms used to generate zinc-finger proteins. As a result, two
phase I clinical trials aimed at knocking out the CCR5 receptor in T cells
isolated from HIV patients to protect these lymphocytes from infection with the
virus have been initiated. Moreover, ZFNs have been successfully employed to
knockout or correct disease-related genes in human stem cells, including
hematopoietic precursor cells and induced pluripotent stem cells. Targeted
genome engineering approaches in multipotent and pluripotent stem cells hold
great promise for future strategies geared toward correcting inborn mutations
for personalized cell replacement therapies. This review describes how ZFNs have
been applied to models of gene therapy, discusses the opportunities and the
risks associated with this novel technology, and suggests future directions for
their safe application in therapeutic genome engineering. Genetic engineering has emerged as a powerful mechanism for understanding
biological systems and a potential approach for redressing congenital disease.
Alongside, the emergence of these technologies in recent decades has risen the
complementary analysis of the ethical implications of genetic engineering
techniques and applications. Although viral-mediated approaches have dominated
initial efforts in gene transfer (GT) methods, an emerging technology involving
engineered restriction enzymes known as zinc finger nucleases (ZFNs) has become
a powerful new methodology for gene editing. Given the advantages provided by
ZFNs for more specific and diverse approaches in gene editing for basic science
and clinical applications, we discuss how ZFN research can address some of the
ethical and scientific questions that have been posed for other GT techniques.
This is of particular importance, given the momentum currently behind ZFNs in
moving into phase I clinical trials. This study provides a historical account of
the origins of ZFN technology, an analysis of current techniques and
applications, and an examination of the ethical issues applicable to
translational ZFN genetic engineering in early phase clinical trials. Using engineered nucleases, such as Zinc Finger Nucleases (ZFNs) or
Transcription Activator-Like Effector Nucleases (TALENs), to make targeted
genomic modifications has become a common technique to create new model
organisms and custom cell lines, and has shown great promise for disease
treatment. However, these nucleases have the potential for off-target cleavage
that could confound interpretation of experimental results and be detrimental
for therapeutic use. Here, we describe a method to test for nuclease cleavage at
potential off-target sites predicted by bioinformatics models. Zinc finger nucleases (ZFNs) are associated with cell death and apoptosis by
binding at countless undesired locations. This cytotoxicity is associated with
the binding ability of engineered zinc finger domains to bind dissimilar DNA
sequences with high affinity. In general, binding preferences of transcription
factors are associated with significant degenerated diversity and complexity
which convolutes the design and engineering of precise DNA binding domains.
Evolutionary success of natural zinc finger proteins, however, evinces that
nature created specific evolutionary traits and strategies, such as modularity
and rank-specific recognition to cope with binding complexity that are critical
for creating clinical viable tools to precisely modify the human genome. Our
findings indicate preservation of general modularity and significant alteration
of the rank-specific binding preferences of the three-finger binding domain of
transcription factor SP1 when exchanging amino acids in the 2nd finger. |
What is known about depression in acoustic neuroma patients? | From 10.2% to 38% acoustic neuroma patients report depression. Depression is predicted by the number of symptoms, prolonged postoperative headache, deterioration of hearing and female gender. | Individuals who undergo removal of an acoustic neuroma are usually apprehensive
in spite of the intrinsically benign nature of the disease. Fears surrounding
the experience are related to the real risks involved in surgery near the brain
and the complications which can ensue. The intensity of the patients' feelings
of anxiety and uncertainty might be decreased if nurses were aware of and
attended to the informational needs of these patients. In order to describe the
informational needs of acoustic neuroma patients, a retrospective survey of 21
subjects who had had removal of such a tumor six to eighteen months previously
was carried out. The survey determined: (1) the type of information patients
received preoperatively and postoperatively (2) the type of information patients
wanted (3) the type of problems experienced postoperatively and (4) the length
and severity of the problems if they occurred. Content analysis indicated that
the majority of subjects experienced tiredness, depression, headache, and
dryness of eyes and mouth in the postoperative and convalescent phases. The
actual illness experience persisted much longer than the subjects had expected.
Subjects expressed explicit informational needs related to self-management after
the surgery. The implications for nursing care will be discussed and the
recommendations for an interdisciplinary patient education programme will be
outlined. The purpose of this study was to establish the frequency and pattern of
depressive disorders after surgery for acoustic neuroma, and to look for
associations. Twenty seven patients with acoustic neuroma underwent thorough
psychiatric assessment before surgery and at three and 12 months after surgery.
Three patients had a depressive disorder in the preoperative assessment. Of the
remaining 24 patients, nine (38%) had a depressive disorder at the three month
check up. Deterioration of hearing was the only postoperative detriment
associated with a depressive disorder (P = 0·024). All nine patients with a
depressive disorder were women (P = 0·001), giving them a 69% incidence. None of
the patients without preoperative depression required inpatient treatment for
depressive disorder, but three patients out of nine still had a depressive
disorder 12 months after surgery. Headache and depression were studied in patients who had undergone operation for
acoustic neuroma. A questionnaire with headache and Beck Depression Inventory
scale were sent to 228 patients, of whom 192 (84%) responded. Preoperative
headache was reported by 61 (32%) of the respondents (47 migraine and nine
tension-type headache) and 122 (64%) respondents had postoperative headache (15
new migraine and four new tension-type headache). The new postoperative headache
was chronic (>/=3 months) in 86% and continued at the time of the survey in 55%
and presented typically as severe short-lasting attacks provoked by physical
stress, bending or coughing. Non-steroidal anti-inflammatory drugs were
effective in most cases. Depression (usually mild) occurred in 24% of the
respondents, being significantly more common in prolonged postoperative headache
patients. The operation doubled the prevalence of headache (from 32% to 64%).
Headache after acoustic neuroma operation appears to be a specific subgroup of
postcraniotomy headache. The objectives of this study were to describe anxiety and depression levels
among acoustic neuroma patients; examine differences in anxiety and depression
across the acoustic neuroma management options of microsurgery, radiation and
observation; and to investigate management, medical and demographic factors that
might predict anxiety and depression in this patient group. A cross-sectional
questionnaire was completed by 205 adults diagnosed with, or treated for, a
unilateral acoustic neuroma within five years of questionnaire distribution.
Median age of participants was 57.0 years, and 120 (58.5%) were female. Anxiety
and depression were measured using the Hospital Anxiety and Depression Scale
(HADS). Clinically significant anxiety was reported by 29.8% of participants and
10.2% were depressed. Mean anxiety and depression scores did not differ from
general population norms. No significant differences in anxiety and depression
were found across management options. Time since management, number of symptoms
and comorbid medical conditions predicted anxiety, while depression was
predicted by number of symptoms. This appears to be the first study among
acoustic neuroma patients in which anxiety and depression were compared across
management options. Treating physicians should be aware that as the number of
acoustic neuroma symptoms increases, so may the likelihood of clinically
significant anxiety and depression. |
Mutation of which gene is associated with Achondroplasia? | Achondroplasia is due to mutations in the fibroblast growth factor receptor 3 (FGFR3) gene. | Achondroplasia (ACH) is the most frequent form of short-limb dwarfism. Recently,
the gene mutation responsible for ACH has been identified in the transmembrane
domain of the fibroblast growth factor receptor 3 gene. The cause of ACH is a
point mutation at nucleotide 1138 of the cDNA, resulting in the substitution of
an arginine residue for a glycine. For the purpose of prenatal diagnosis of ACH,
we have used the nested polymerase chain reaction to ensure the gene
amplification. Although the normal allele has no restriction site around the
causative sequence, we have devised an unique method to incorporate a
restriction site of SplI into the normal allele only using modified primer sets.
We report here the use of this polymerase chain reaction methodology which can
ensure the gene amplification and omit the complicated steps of sequencing for
prenatal diagnosis. We report the case of a boy with achondroplasia and i(21q) Down syndrome.
Besides craniofacial features typical in Down syndrome, the skeletal findings of
achondroplasia dominate the clinical picture. The diagnosis of Down syndrome was
based on clinical features and the cytogenetic finding of i(21q) trisomy 21. The
diagnosis of achondroplasia was based on the presence of clinical and
radiographic findings and confirmed by the presence of a common FGFR3 gene
mutation (Gly380Arg) detected by restriction enzyme analysis and sequencing of
the polymerase chain reaction products. This is the first report of
achondroplasia associated with i(21q) Down syndrome. OBJECTIVE: To study the gene mutation of Chinese patients with
achondroplasia(ACH) and to set up a simple and rapid molecular diagnostic method
to differentiate ACH from other similar genetic dwarfism.
METHODS: The specific fragment of fibroblast growth factor receptor 3(FGFR3)
transmembrane domain was amplified from dried blood spots of 21 patients with
ACH and 6 suspicious patients with ACH by polymerase chain reaction, then
mutation was screened and detected by restrictive enzyme analysis, single strand
conformation polymorphism(SSCP) and denaturing gradient gel
electrophoresis(DGGE).
RESULTS: One out of 6 suspicious cases was ACH and 5 were
pseudoachondroplasia(PSACH). Twenty-one out of 22 patients with ACH bore a G to
A transition at nucleotide 1138 and 1 bore a G to C transversion at this same
position.
CONCLUSION: The nucleotide 1138 of FGFR3 gene is also the hotspot of mutation in
Chinese patients with ACH. A simple and rapid molecular diagnostic method has
been set up to differentiate ACH from other similar genetic dwarfism. Achondroplasia is a common form of human dwarfism with characteristically
rhizomelic shortening of extremities and relative macrocephaly. It is
transmitted as an autosomally domit inheritance, and about 80% of affected
individuals result from sporadic mutations without positive family histories.
Achondroplasia comes from the genetic point mutations in the fibroblastic growth
factor receptor 3 gene (FGFR3), which enables abnormal cartilage growth-plate
differentiation and insufficient bony development. The most common genetic
mutations in this receptor are G to A at position 1138 (G1138A), which result in
the substitution of glycine to arginine at codon 380. Based on genetic
information, molecular genetic testing can provide an exact diagnosis comparing
to radiological and prenatal ultrasound evaluations. Here we introduce
denaturing high-performance liquid chromatography (DHPLC) for the detection of
17 cases of achondroplasia and 120 unaffected cases. After coupling heteroduplex
and fluorescence-enhanced primer-extension analysis, all affected patients with
G1138A were identified successfully. In conclusion, we demonstrated that DHPLC
is an efficient, accurate, and sensitive technique to detect the single gene
mutation of achondroplasia in clinical applications. |
What is the mode of action of Hsp90 inhibitors? | Pharmacologic inhibition of Hsp90 involves interaction with the ATP-binding site of the chaperone. This exerts antiproliferative effects resulting in a marked suppression of tumor growth. Following treatment with a Hsp90 inhibitor, expression of a number of proteins is affected, and most notably the Hsp90 clients, leading to dysregulation of intracellular signal transduction, immune response, cell growth and maintenance, transport, and metabolism, finally resulting in cancer cell death through activation of both intrinsic and extrinsic apoptotic pathways. | A number of molecular therapeutic agents, derived from exploiting our knowledge
of the oncogenic pathways that are frequently deregulated in cancer, are now
entering clinical trials. One of these is the novel agent
17-allylamino-17-demethoxygeldanamycin that acts to inhibit the hsp90 molecular
chaperone. Treatment of four human colon cancer cell lines with iso-effective
concentrations of this agent resulted in depletion of c-raf-1 and akt and
inhibition of signal transduction. We have used gene expression array analysis
to identify genes responsive to treatment with this drug. The expression of
hsp90 client protein genes was not affected, but hsc hsp70, hsp90beta, keratin
8, keratin 18 and caveolin-1 were deregulated following treatment. These
observations were consistent with inhibition of signal transduction and
suggested a possible mechanism of resistance or recovery from
17-allylamino-17-demethoxygeldanamycin treatment. The results shed light on the
molecular mode of action of the hsp90 inhibitors, and suggest possible molecular
markers of drug action for use in hypothesis testing clinical trials. Oncogene
(2000) 19, 4125 - 4133 |
Is RET the major gene involved in Hirschsprung disease? | The RET proto-oncogene is the major gene associated to Hirschsprung disease (HSCR) with differential contributions of its rare and common, coding and noncoding mutations to the multifactorial nature of this pathology. | Distinct point mutations in the RET proto-oncogene are the cause of the
inherited multiple endocrine neoplasia type 2 syndromes (MEN 2), and the
congenital gut disorder Hirschsprung disease. The site and type of these
mutations suggests that they have differing effects on the activity of the
receptor tyrosine kinase encoded by RET. The normal function of the RET receptor
tyrosine kinase has yet to be determined. However, this has been investigated by
the inactivation of the RET gene in transgenic mice. The developmental
abnormalities apparent in these mice, together with the observation that the
major tissues affected in MEN 2 and Hirschsprung disease have a common origin in
the embryonal neural crest, suggest that RET encodes a receptor for a
developmental regulator involved in the genesis of a variety of neural crest
derivatives, and in the organogenesis of the kidney. Hirschsprung disease is a congenital malformation, where absence of intramural
ganglia in the hindgut results in a defect in the coordination of peristaltic
movement. This leads to ileus in the newborn or, more often, constipation in
children and adults. The disease affects one in 5000 live births. Siblings of
affected cases are at an increased risk (4%) of developing the disease. Among
cases. males are affected more often than females. The first major
susceptibility gene for Hirschsprung disease is the RET proto-oncogene on
10q11.2. Germline RET mutations in Hirschsprung disease are mainly inactivating,
and have been reported to account for up to 20 and 50% of sporadic and familial
cases, respectively. We have screened Swedish population-based samples from 62
sporadic cases and seven familial cases of Hirschsprung disease with single
strand conformation polymorphism (SSCP), and found five mutations. We report on mutation analysis of five genes involved in the receptor tyrosine
kinase (RET) or the endothelin-signalling pathways in 28 sporadic Japanese
patients with Hirschsprung disease. Analysis of DNA obtained from peripheral
blood cells revealed six mutations in the RET proto-oncogene, four of which were
disease-causing mutations in exon 9 (D584G), the splice donor site of intron 10
(+2T to A), exon 11 (A654T), and exon 12 (T706A). A heterozygous A to G
transition was found in 47 bases upstream from the 5' end of exon 2 in two HD
patients but was also seen in one control subject (2/28; 1/24). A silent 2307T
to G transversion was observed in exon 13. Two disease-causing mutations were
detected in the endothelin receptor (EDNRB) gene, in the non-coding region of
exon 1 (-26 G to A) and in exon 4 (A301T); the latter mutation was a novel one.
One silent mutation was observed in exon 4 (codon 277). One heterozygous T to C
mutation was found in the glial cell line-derived neurotrophic factor gene in 25
bases upstream of the coding region in exon 1. No nucleotide changes were
detected in either the endothelin-3 or neurturin genes. Disease-causing mutation
rates in the RET proto-oncogene and the EDNRB gene were estimated at 14.3%
(4/28) and 10.7% (3/28), respectively. In addition to mutations in the RET and
EDNRB genes, embryonic environmental factors and/or other genetic factors appear
to be involved in the development of Hirschsprung disease. Further systematic
studies of genetic variation in a large series of patients and controls are
necessary for elucidating the pathogenesis of this disorder.
CONCLUSION: This study provides further gene alterations as disease-causing
mutations in Japanese cases of sporadic Hirschsprung disease. However, the low
mutation rate of the susceptibility genes may indicate that Hirschsprung disease
arises from a combination of genetic and environmental factors. Hirschsprung disease (HSCR) is a congenital disorder characterised by intestinal
obstruction due to an absence of intramural ganglia along variable lengths of
the intestine. RET is the major gene involved in HSCR. Mutations in the GDNF
gene, and encoding one of the RET ligands, either alone or in combination with
RET mutations, can also cause HSCR, as can mutations in four other genes (EDN3,
EDNRB, ECE1, and SOX10). The rare mutations in the latter four genes, however,
are more or less restricted to HSCR associated with specific phenotypes. We have
developed a novel comprehensive mutation detection system to analyse all but
three amplicons of the RET and GDNF genes, based on denaturing gradient gel
electrophoresis. We make use of two urea-formamide gradients on top of each
other, allowing mutation detection over a broad range of melting temperatures.
For the three remaining (GC-rich) PCR fragments we use a combination of DGGE and
constant denaturing gel electrophoresis (CDGE). These two dual gel systems
substantially facilitate mutation scanning of RET and GDNF, and may also serve
as a model to develop mutation detection systems for other disease genes. In a
screening of 95 HSCR patients, RET mutations were found in nine out of 17
familial cases (53%), all containing long segment HSCR. In 11 of 78 sporadic
cases (14%), none had long segment HSCR. Only one GDNF mutation was found, in a
sporadic case. BACKGROUND: The RET gene encodes a tyrosine kinase receptor involved in
different human neurocristopathies, such as specific neuroendocrine tumours and
Hirschsprung disease (HSCR). Gene expression is developmentally regulated and
the RET transcript is undetectable in most adult cells, including lymphocytes.
The impossibility of performing functional studies on RET mRNA has to date
limited the detection and characterisation of an indefinite proportion of gene
anomalies that cannot be identified by conventional DNA genomic screening in
HSCR cases.
AIMS: Development of a protocol suitable to activate RET expression in RET
negative cell lines and therefore to investigate directly RET mRNA, extending
the conventional gene mutation analysis to detection of splicing anomalies and
impaired expression of the RET gene.
METHODS: The effect of sodium butyrate (NaB), a histone deacetylase inhibitor,
on rescuing RET expression was tested by one round of reverse transcription-
polymerase chain reaction from total RNA of treated lymphoblasts from both HSCR
patients and control individuals.
RESULTS: Analysis of RET expression was possible by NaB treatment of RET
negative cells, such as lymphoblasts. This treatment allowed us to detect
impaired RET expression as well as a splicing defect in two HSCR patients
previously believed to be devoid of any gene abnormality.
CONCLUSIONS: The full application of the proposed protocol in most of the
unexplained HSCR cases will allow us to establish the precise role of RET not
only in causing but also in predisposing to HSCR pathogenesis. The RET proto-oncogene is the major gene involved in the complex genetics of
Hirschsprung disease (HSCR), or aganglionic megacolon, showing causative
loss-of-function mutations in 15-30% of the sporadic cases. Several RET
polymorphisms and haplotypes have been described in association with the
disease, suggesting a role for this gene in HSCR predisposition, also in the
absence of mutations in the coding region. Finally, the presence of a functional
variant in intron 1 has repeatedly been proposed to explain such findings. Here
we report a case-control study conducted on 97 Italian HSCR sporadic patients
and 85 population matched controls, using 13 RET polymorphisms distributed
throughout the gene, from the basal promoter to the 3'UTR. Linkage
disequilibrium and haplotype analyses have shown increased recombination between
the 5' and 3' portions of the gene and an over-representation, in the cases
studied, of two haplotypes sharing a common allelic combination that extends
from the promoter up to intron 5. We propose that these two disease-associated
haplotypes derive from a single founding locus, extending up to intron 19 and
successively rearranged in correspondence with a high recombination rate region
located between the proximal and distal portions of the gene. Our results
suggests the possibility that a common HSCR predisposing variant, in linkage
disequilibrium with such haplotypes, is located further downstream than the
previously suggested interval encompassing intron 1. The RET proto-oncogene is the major gene involved in the pathogenesis of
Hirschsprung (HSCR), a complex genetic disease characterized by lack of ganglia
along variable lengths of the gut. Here we present a survey of the different
molecular mechanisms through which RET mutations lead to the disease
development. Among these, loss of function, gain of function, apoptosis,
aberrant splicing and decreased gene expression are exemplified and considered
with respect to their pathogenetic impact. In particular, RET transcription
regulation represents a new insight into the outline of HSCR susceptibility, and
having reached important progress in the last few years, deserves to be
reviewed. Notably, gene expression impairment seems to be at the basis of the
association of HSCR disease with several RET polymorphisms, allowing us to
define a predisposing haplotype spanning from the promoter to exon 2. Putative
functional variants, in the promoter and in intron 1, and proposed as low
penetrant predisposing alleles, are presented and discussed. Finally, based on
the RET mutation effects thus summarized, we attempt to derive conclusions which
may be useful for HSCR risk prediction and genetic counselling. We report on a multigenerational family with isolated Hirschsprung's disease
(HSCR). Five patients were affected by either short segment or long segment
HSCR. The family consists of two main branches: one with four patients (three
siblings and one maternal uncle) and one with one patient. Analysis of the RET
gene, the major gene involved in HSCR susceptibility, revealed neither linkage
nor mutations. A genome wide linkage analysis was performed, revealing
suggestive linkage to a region on 4q31-q32 with a maximum parametric multipoint
LOD score of 2.7. Furthermore, non-parametric linkage (NPL) analysis of the
genome wide scan data revealed a NPL score of 2.54 (p = 0.003) for the same
region on chromosome 4q (D4S413-D4S3351). The minimum linkage interval spans a
region of 11.7 cM (12.2 Mb). No genes within this chromosomal interval have
previously been implicated in HSCR. Considering the low penetrance of disease in
this family, the 4q locus may be necessary but not sufficient to cause HSCR in
the absence of modifying loci elsewhere in the genome. Our results suggest the
existence of a new susceptibility locus for HSCR at 4q31.3-q32.3. Complex diseases are common genetic disorders showing familial aggregation but
no typical Mendelian inheritance. Hirschsprung disease (HSCR), a developmental
disorder characterized by the absence of enteric neurons in distal segments of
the gut, shows a complex pattern of inheritance, with the RET protooncogene
acting as a major gene and additional susceptibility loci playing minor roles.
In the last years, we have identified a "protective" RET haplotype, which is
underrepresented in HSCR patients with respect to controls. Here, we demonstrate
that the protective effect of this haplotype is due to a variant located in the
3' untranslated region (UTR) of the RET gene, which slows down the physiological
mRNA decay of the gene transcripts. Such a functional effect of this common RET
variant explains the under-representation of the whole haplotype and its role as
a modifying factor in HSCR pathogenesis. PURPOSE: The RET proto-oncogene is considered to be the major susceptibility
gene involved in Hirschsprung disease. Traditional RET germline mutations
account for a small subset of Hirschsprung disease patients, but several studies
have shown that there is a specific haplotype of RET associated with the
sporadic forms of Hirschsprung disease. We have investigated for RET germline
mutations and analyzed the RET haplotypic distribution in carriers versus
noncarriers of RET germline mutations.
METHODS: We have screened the coding region of RET in 106 Spanish Hirschsprung
disease patients using dHPLC technology. Statistical comparisons of the
distribution of RET haplotypes between sporadic patients with and without a RET
germline mutation were performed.
RESULTS: Nine novel germline mutations and one previously described were
identified. A significant over-transmission of the "Hirschsprung disease
haplotype" was detected when comparing transmitted versus nontransmitted alleles
in the group of Hirschsprung disease triads without mutation. However, no
distortion of the transmission of alleles was found in the group of mutated
families.
CONCLUSIONS: These results would be concordant with a complex additive model of
inheritance. The whole findings seem to suggest that low-penetrance mutations
would be necessary but not sufficient and the additional presence of the
"Hirschsprung disease haplotype" could contribute to the manifestation of the
disease. Hirschsprung disease (HSCR, aganglionic megacolon) represents the main genetic
cause of functional intestinal obstruction with an incidence of 1/5000 live
births. This developmental disorder is a neurocristopathy and is characterised
by the absence of the enteric ganglia along a variable length of the intestine.
In the last decades, the development of surgical approaches has importantly
decreased mortality and morbidity which allowed the emergence of familial cases.
Isolated HSCR appears to be a non-Mendelian malformation with low, sex-dependent
penetrance, and variable expression according to the length of the aganglionic
segment. While all Mendelian modes of inheritance have been described in
syndromic HSCR, isolated HSCR stands as a model for genetic disorders with
complex patterns of inheritance. The tyrosine kinase receptor RET is the major
gene with both rare coding sequence mutations and/or a frequent variant located
in an enhancer element predisposing to the disease. Hitherto, 10 genes and five
loci have been found to be involved in HSCR development. Hirschsprung's disease (HSCR) is a congenital disorder in which ganglion cells
are absent in variable portions of the lower digestive tract according to which
patients are classified. The RET gene is the major HSCR gene, although reduced
penetrance of RET mutations and variable expression of HSCR phenotype indicates
that more than one gene is required. An unidentified RET-dependent modifier on
3p21 appears to be necessary for transmission of the short HSCR (S-HSCR)
phenotype. We investigated 6 Mb of the 3p21 region on a quest for the
HSCR-susceptibility locus. Fifty-eight S-HSCR case-parent trios were genotyped
using Sequenom technology for 214 tag single nucleotide polymorphisms (SNPs)
distributed along 6 Mb of the 3p21 region. A five-marker haplotype, spanning a
118 kb gene-rich region, was found to be overtransmitted to affected offspring.
The associated haplotype encompasses three genes involved in neurological
phenotypes. Importantly, this association was replicated in an independent
sample of 172 S-HSCR cases and 153 unrelated controls. Ranking markers by
proximity to candidate genes or by expected functional consequences could be
used in follow-up studies to finally pinpoint this HSCR locus. The major gene for Hirschsprung disease (HSCR) encodes the receptor tyrosine
kinase RET. In a study of 690 European- and 192 Chinese-descent probands and
their parents or controls, we demonstrate the ubiquity of a >4-fold
susceptibility from a C-->T allele (rs2435357: p = 3.9 x 10(-43) in European
ancestry; p = 1.1 x 10(-21) in Chinese samples) that probably arose once within
the intronic RET enhancer MCS+9.7. With in vitro assays, we now show that the T
variant disrupts a SOX10 binding site within MCS+9.7 that compromises RET
transactivation. The T allele, with a control frequency of 20%-30%/47% and case
frequency of 54%-62%/88% in European/Chinese-ancestry individuals, is involved
in all forms of HSCR. It is marginally associated with proband gender (p = 0.13)
and significantly so with length of aganglionosis (p = 7.6 x 10(-5)) and
familiality (p = 6.2 x 10(-4)). The enhancer variant is more frequent in the
common forms of male, short-segment, and simplex families whereas multiple,
rare, coding mutations are the norm in the less common and more severe forms of
female, long-segment, and multiplex families. The T variant also increases
penetrance in patients with rare RET coding mutations. Thus, both rare and
common mutations, individually and together, make contributions to the risk of
HSCR. The distribution of RET variants in diverse HSCR patients suggests a
"cellular-recessive" genetic model where both RET alleles' function is
compromised. The RET allelic series, and its genotype-phenotype correlations,
shows that success in variant identification in complex disorders may strongly
depend on which patients are studied. X-linked hydrocephalus (XLH) has an incidence of 1/30,000 male births and is
characterized by intellectual disability, spastic paraplegia, adducted thumbs,
and agenesis of corpus callosum, and/or corticospinal tract. The great
proportion of cases is ascribed to loss of function mutations of L1CAM gene.
Hirschsprung disease (HSCR) is characterized by the absence of ganglion cells in
the submucosal and myenteric plexuses along a variable portion of the intestinal
tract and has incidence of about 1/5,000. Although with several genes involved
in its pathogenesis, the major HSCR gene is the RET proto-oncogene. To date only
a few patients have been reported with both phenotypes and mutations in the
L1CAM gene. In this report, we describe a new patient with concurrent XLH and
HSCR. L1CAM mutational screening showed the presence of the G698R hemizygous
mutation, which is a deleterious substitution affecting a key residue necessary
for the correct folding of the protein. Moreover, the patient also carried the
transcriptional enhancer RET mutation (c.73 + 9277T > C) in heterozygosis. We
speculate that both the RET enhancer variant, and the L1CAM mutation may act in
combination to produce the enteric phenotype, probably with the participation of
other still unidentified molecular events. While it is obvious that additional
studies are necessary to further delineate the association between XLH and HSCR
in the presence of L1CAM mutations, the documentation of this new patient
reinforces the role of this gene acting either in a direct or indirect way in
the pathogenesis of Hirschsprung disease. Hirschsprung disease (HSCR, OMIM 142623) is a developmental disorder
characterized by the absence of ganglion cells along variable lengths of the
distal gastrointestinal tract, which results in tonic contraction of the
aganglionic gut segment and functional intestinal obstruction. The RET
proto-oncogene is the major gene for HSCR with differential contributions of its
rare and common, coding and noncoding mutations to the multifactorial nature of
this pathology. Many other genes have been described to be associated with the
pathology, as NRG1 gene (8p12), encoding neuregulin 1, which is implicated in
the development of the enteric nervous system (ENS), and seems to contribute by
both common and rare variants. Here we present the results of a comprehensive
analysis of the NRG1 gene in the context of the disease in a series of 207
Spanish HSCR patients, by both mutational screening of its coding sequence and
evaluation of 3 common tag SNPs as low penetrance susceptibility factors,
finding some potentially damaging variants which we have functionally
characterized. All of them were found to be associated with a significant
reduction of the normal NRG1 protein levels. The fact that those mutations
analyzed alter NRG1 protein would suggest that they would be related with HSCR
disease not only in Chinese but also in a Caucasian population, which reinforces
the implication of NRG1 gene in this pathology. Hirschsprung disease is a congenital form of aganglionic megacolon that results
from cristopathy. Hirschsprung disease usually occurs as a sporadic disease,
although it may be associated with several inherited conditions, such as
multiple endocrine neoplasia type 2. The rearranged during transfection (RET)
proto-oncogene is the major susceptibility gene for Hirschsprung disease, and
germline mutations in RET have been reported in up to 50% of the inherited forms
of Hirschsprung disease and in 15-20% of sporadic cases of Hirschsprung disease.
The prevalence of Hirschsprung disease in multiple endocrine neoplasia type 2
cases was recently determined to be 7.5% and the cooccurrence of Hirschsprung
disease and multiple endocrine neoplasia type 2 has been reported in at least 22
families so far. It was initially thought that Hirschsprung disease could be due
to disturbances in apoptosis or due to a tendency of the mutated RET receptor to
be retained in the Golgi apparatus. Presently, there is strong evidence favoring
the hypothesis that specific inactivating haplotypes play a key role in the
fetal development of congenital megacolon/Hirschsprung disease. In the present
study, we report the genetic findings in a novel family with multiple endocrine
neoplasia type 2: a specific RET haplotype was documented in patients with
Hirschsprung disease associated with medullary thyroid carcinoma, but it was
absent in patients with only medullary thyroid carcinoma. Despite the limited
number of cases, the present data favor the hypothesis that specific haplotypes
not linked to RET germline mutations are the genetic causes of Hirschsprung
disease. Hirschsprung disease (HSCR, OMIM 142623) is a developmental disorder
characterized by the absence of ganglion cells along variable lengths of the
distal gastrointestinal tract, which results in tonic contraction of the
aganglionic colon segment and functional intestinal obstruction. The RET
proto-oncogene is the major gene associated to HSCR with differential
contributions of its rare and common, coding and noncoding mutations to the
multifactorial nature of this pathology. In addition, many other genes have been
described to be associated with this pathology, including the semaphorins class
III genes SEMA3A (7p12.1) and SEMA3D (7q21.11) through SNP array analyses and by
next-generation sequencing technologies. Semaphorins are guidance cues for
developing neurons implicated in the axonal projections and in the determination
of the migratory pathway for neural-crest derived neural precursors during
enteric nervous system development. In addition, it has been described that
increased SEMA3A expression may be a risk factor for HSCR through the
upregulation of the gene in the aganglionic smooth muscle layer of the colon in
HSCR patients. Here we present the results of a comprehensive analysis of SEMA3A
and SEMA3D in a series of 200 Spanish HSCR patients by the mutational screening
of its coding sequence, which has led to find a number of potentially
deleterious variants. RET mutations have been also detected in some of those
patients carrying SEMAs variants. We have evaluated the A131T-SEMA3A,
S598G-SEMA3A and E198K-SEMA3D mutations using colon tissue sections of these
patients by immunohistochemistry. All mutants presented increased protein
expression in smooth muscle layer of ganglionic segments. Moreover, A131T-SEMA3A
also maintained higher protein levels in the aganglionic muscle layers. These
findings strongly suggest that these mutants have a pathogenic effect on the
disease. Furthermore, because of their coexistence with RET mutations, our data
substantiate the additive genetic model proposed for this rare disorder and
further support the association of SEMAs genes with HSCR. Hirschsprung disease (HSCR, aganglionic megacolon) is a complex genetic disorder
of the enteric nervous system (ENS) characterized by the absence of enteric
neurons along a variable length of the intestine. While rare variants (RVs) in
the coding sequence (CDS) of several genes involved in ENS development lead to
disease, the association of common variants (CVs) with HSCR has only been
reported for RET (the major HSCR gene) and NRG1. Importantly, RVs in the CDS of
these two genes are also associated with the disorder. To assess independent and
joint effects between the different types of RET and NRG1 variants identified in
HSCR patients, we used 254 Chinese sporadic HSCR patients and 143 ethnically
matched controls for whom the RET and/or NRG1 variants genotypes (rare and
common) were available. Four genetic risk factors were defined and interaction
effects were modeled using conditional logistic regression analyses and
pair-wise Kendall correlations. Our analysis revealed a joint effect of RET CVs
with RET RVs, NRG1 CVs or NRG1 RVs. To assess whether the genetic interaction
translated into functional interaction, mouse neural crest cells (NCCs; enteric
neuron precursors) isolated from embryonic guts were treated with NRG1 (ErbB2
ligand) or/and GDNF (Ret ligand) and monitored during the subsequent neural
differentiation process. Nrg1 inhibited the Gdnf-induced neuronal
differentiation and Gdnf negatively regulated Nrg1-signaling by down-regulating
the expression of its receptor, ErbB2. This preliminary data suggest that the
balance neurogenesis/gliogenesis is critical for ENS development. |
Which type of lung cancer is the most strongly associated with Lambert-Eaton syndrome? | Small-cell lung cancer is most commonly associated with Lambert-Eaton syndrome. Case reports suggest that other non-small-cell lung cancer types, such as large-cell neuroendocrine carcinoma and squamous cell carcinoma, can be also very rarely associated this syndrome. | Utilizing the whole-cell patch-clamp method we assessed the Ca2+ current (ICa)
in well-established cell lines from human small-cell carcinoma (SCC) of the
lung, NCI-H209 and NCI-H187. The Ca2+ current was readily observed in H209
tumour cells (90% of the cells tested), whereas H187 tumour cells only
occasionally expressed Ca2+ channels (26% of the cells tested). H209 Ca2+
current was evoked by potentials greater than -30 mV and exhibited partial
inactivation over the duration of a 40 ms command potential. This inward current
was unchanged by alteration of the holding potential from -80 to -40 mV and the
activation phase of the Ca2+ current was best fitted by Hodgkin-Huxley m(t)2
kinetics. H209 Ca2+ current was reduced over 80% by verapamil (100 microM),
whereas w-conotoxin (5 microM) appeared to be without effect. In contrast, H209
Ca2+ current was rapidly abolished by nifedipine (10 microM), strongly
suggesting the presence of L-type Ca2+ channels. Voltage-gated Ca2+ channels may
be important to the secretion of ectopic hormones and the etiology and
pathogenesis of Lambert-Eaton syndrome, an autoimmune disorder of the motor
nerve terminal in which autoantibodies directed against voltage-gated Ca2+
channels are produced. Lambert-Eaton syndrome is a myasthenia-like syndrome of paraneoplastic origin
which is often associated with anaplastic small-cell lung cancer. It seems to be
an autoimmune disease responsible for a deficit of acetylcholine ejection in the
motor end plate. On the occasion of two recent cases, we review the clinical,
physiopathological and diagnostic aspects of this paraneoplastic syndrome. The clinical and electrophysiological data of 18 consecutive adult patients with
paraneoplastic Lambert-Eaton myasthenic syndrome (LMES) have been reviewed. The
cancer associated with LEMS was small-cell lung carcinoma (SCLC) in 15 cases and
epidermoid lung carcinoma in 3 cases. The main clinical neurological features
were proximal lower limb weakness (100%), depressed tendon reflexes (94%) and
dryness of the mouth (66%). The results of repetitive nerve stimulation (RNS)
were not statistically different in the paraneoplastic LEMS group and in a group
of 6 LMS patients in whom no carcinoma had been detected. Low-amplitude compound
muscle action potential (CMAP) was present in all cases; decremental response at
low stimulation rates was present in 13/15 cases. An abnormal incremental
response at high stimulation rates was observed in all cases. A close
correlation between CMAP amplitude and clinical condition was found in 4 cases
during the long-term follow-up. In one patient the RNS electrical pattern could
be misinterpreted as myasthenia gravis in only one muscle tested. We underline
the usefulness of a 50 Hz stimulation during 4 seconds to establish the
diagnosis unequivocally, and that of post-exercise facilitation in routine
detection among an SCLC population. Our results suggest that CAMP amplitude and
RNS test could be used to evaluate the short-term improvement of LMS under
treatment and, in some cases, for the long-term follow-up. The infraclinical
axonal neuropathy detected in 8 patients probably was another associated
autoimmune paraneoplastic complication. Plasma and IgG obtained from 10 Lambert-Eaton myasthenic syndrome (LES) patients
(5 with carcinoma, 5 without associated cancer), 6 healthy subjects, and 1
patient with small-cell lung cancer (SCLC) were examined in their ability to
recognize chromaffin cell antigens on Western blots. The pattern of antigen
recognition was compared with the magnitude of inhibition of voltage-dependent
calcium and sodium currents recorded with the patch-clamp technique from
chromaffin cells. Eight of the 11 patients with LES and/or SCLC recognized
plasma membrane proteins and 9 of the patients' IgG interacted with cytoplasmic
antigens with no apparent pattern of antigen recognition between patients. Also,
there was no obvious band pattern distinguishing patients with LES from those
with LES and concurrent SCLC. Eighty percent of the LES patients' antibodies
were capable of reducing the calcium current (ICa) in chromaffin cells. One of
the novel findings of this study is that 30% of the patients had produced
antibodies which were able to inhibit both calcium and sodium currents (INa).
The heterogeneous response of the IgG on the Western blots does not appear to
correlate with the efficacy of reducing the inward currents. Lambert-Eaton myasthenic syndrome (LEMS) is a paraneoplastic autoimmune disorder
caused by an IgG-mediated reduction in number of presynaptic voltage-gated
calcium channels (VGCC) at the neuromuscular junction. In at least 50% of cases,
the stimulus for antibody production may be VGCC on small cell lung cancer
(SCLC). In this study membranes isolated from a human small cell lung cancer
xenograft (Mar), that bound [3H]PN200-110, a VGCC antagonist, were subjected to
Western blotting using plasma from 12 LEMS patients and eight controls. Although
one band recognised by 3/12 LEMS IgGs might be associated with the VGCC, a
number of other proteins were recognised both by LEMS plasma, and by plasma from
patients with other disorders. The results illustrate the difficulties found
using Western blotting with autoimmune plasma to identify specific polypeptides
in a crude antigen preparation. A patient with the Lambert-Eaton syndrome (LES) and small cell lung cancer
developed respiratory failure several hours after verapamil was given.
Improvement in respiratory function did not occur when guanidine was given, but
was delayed until verapamil was discontinued 3 days later. Although other
factors may have contributed to the clinical deterioration of our patient, the
temporal relationship to verapamil and the theoretical danger of calcium channel
blockade lead us to believe that the drug should be used cautiously in LES. We report a case of neuromuscular disease overlap between myasthenia gravis and
Lambert-Eaton syndrome (LES). Clinical features were those of LES and occurred
insidiously in this 68-year old man: proximal weakness predomit in the lower
limbs, generalized areflexia, dryness of the mouth and partial right eye palsy.
Investigations disclosed a small cell lung cancer. On the other hand, an
electrophysiological study showed low amplitude of all motor evoked potentials,
and significant decrement in the median nerve at repeated 3 Hz stimulation, but
failed to disclose any increment of the motor evoked potential in abductor
digiti minimi pedis muscle after both maximal voluntary contraction and repeated
20 Hz stimulation. In addition, the patient improved under anticholinesterase
drugs, but failed to respond to guanidine. Titres for both
anti-acetylcholine-receptor antibodies and calcium channel antibodies were
negative. The relationship between our case and recently reported cases of
co-existence of the Lambert-Eaton myasthenic syndrome and myasthenia gravis is
discussed. Plasma from patients with Lambert-Eaton myasthenic syndrome (LEMS), an
autoimmune disease of neuromuscular transmission, contains antibodies that bind
to the synaptic vesicle protein synaptotagmin. Synaptotagmin associates with
calcium channels and appears to regulate synaptic vesicle docking at the plasma
membrane prior to rapid neurotransmitter release. Autoantibodies directed
against a synaptotagmin-calcium channel complex may be involved in the etiology
of LEMS. In the majority of patients LEMS is associated with small cell lung
cancer (SCLC). We have detected the expression of proteins of the secretory
pathway, including synaptotagmin, syntaxin and N-type calcium channels, in a
panel of SCLC tumor lines. These observations are compatible with the hypothesis
that the initial autoimmune response in LEMS is triggered by the tumor. 1. Human small-cell lung cancer (SCLC) cells are believed to express the
antigens responsible for the production of pathological antibodies in the
Lambert-Eaton syndrome (LES), a Ca2+ channel disorder in which quantal
transmitter release from the motor nerve terminal is impaired. Whole-cell
patch-clamp techniques were used to study the voltage-dependent Ca2+ channels
expressed by H146 SCLC cells and the effects of LES antibodies on these
channels. The types of Ca2+ channels were determined using biophysical
properties and pharmacological sensitivity to several antagonists. 2. Whole-cell
Ca2+ currents (ICa) in SCLC cells are sensitive to the dihydropyridine (DHP)
nicardipine, omega-conotoxin GVIA (omega-CgTX GVIA) and omega-agatoxin IVA
(omega-AgTX IVA). Nicardipine at 100 nM and 10 microM reduced ICa by 35 and 45%
(n = 38 cells), respectively, while omega-CgTX GVIA (1 microM) inhibited ICa by
32% (n = 31). Application of omega-AgTX IVA at 50 and 100 nM to the cancer cells
decreased ICa by 41 and 42%, respectively (n = 22). 3. Measurement of cell
membrane capacitance (Cm) revealed that Ca(2+)-dependent exocytosis underlies
the secretory activity of SCLC cells. Exocytosis, when induced by step
depolarizing pulses and measured by increases in Cm, was markedly inhibited by
nicardipine (10 microM) and omega-AgTX IVA (100 nM). In contrast, omega-CgTX
GVIA (1 microM) was not as effective in altering increases in Cm. 4. From
negative (-80 mV) and depolarized (-40 mV) holding potentials, both peak and
plateau ICa were inhibited by the presence of LES antibodies (1 mg ml-1 IgG).
LES serum also reduced depolarization-induced increases in Cm by 48% (n = 15).
5. To determine whether the LES antibodies are downregulating a specific type(s)
of Ca2+ channel, nicardipine (10 microM), omega-CgTX GVIA (1 microM) or
omega-AgTX IVA (100 nM) was applied to tumour cells that had been previously
exposed to LES serum for 24 h. The most pronounced change was that omega-AgTX
IVA was 38-84% less effective at reducing ICa after the IgG treatment. The
effectiveness of nicardipine was diminished by 18% after incubation with the LES
antibodies, whereas the omega-CgTX GVIA was seen to be more effective. These
results suggest that LES IgG downregulates P-type Ca2+ channels and, possibly,
to a lesser extent L-type channels. 6. In view of recent evidence that P-type
Ca2+ channels mediate cholinergic transmitter release at the mammalian
neuromuscular junction (NMJ), the expression of P-type Ca2+ channels in the SCLC
cells and the reactivity of LES IgG with these channels support the hypothesis
that P-type Ca2+ channels in these cancer cells may trigger the autoantibody
production in this disorder. The antibodies so produced are implicated in the
functional impairment of the Ca2+ channels characteristic of LES. The Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune disease in which
autoantibodies are directed against voltage-gated calcium channels (VGCCs) at
presynaptic nerve terminals. We first demonstrated the presence of P/Q-type and
N-type VGCCs in digitonin extracts prepared from human and rabbit cerebellum
using the specific ligands 125I-omega-conotoxin MVIIC (125I-omega-CmTx) and
125I-omega-conotoxin GVIA (125I-omega-CgTx), respectively. We then tested sera
from 72 LEMS patients' 25 with proven small cell lung cancer (SCLC) and 66
healthy or other neurological, SCLC or autoimmune disease controls in an
immunoprecipitation assay using 125I-omega-CmTx-labelled (P/Q-type) VGCCs in
human cerebellar extract. Sixty-six of 72 LEMS serum samples (91.7%) were
positive for the presence of VGCC antibodies, as defined as a titre greater than
3 standard deviations above the mean for the healthy controls (n = 22). Rabbit
cerebellar extract as antigen gave similar results (r = 0.94, P < 0.001, n =
30). By contrast, only 24/72 (33%) LEMS sera were positive in the assay for
anti-N-type VGCC antibodies using 125I-omega-CgTx. All these 24 were also
positive in the 125I-omega-CmTx assay. All healthy and disease control sera were
negative in both assays. The anti-P/Q-type VGCC antibody titres did not
correlate with an electrophysiological index of disease severity across
individuals; however, longitudinal studies in a LEMS patient with SCLC receiving
chemotherapy, and in a non-SCLC LEMS patient receiving immunosuppressive therapy
showed an inverse relation between antibody titre and disease severity. These
results support the view that anti-P/Q-type VGCC antibodies are implicated in
the motor disorder in LEMS, and show that the omega-CmTx radioimmunoassay is a
highly specific and sensitive means of detecting them. We have used human beta 2 and beta 4 cDNA probes to map the genes encoding two
isoforms of the regulatory beta subunit of voltage-activated Ca2+ channels, viz.
CACNB2 (beta 2) and CACNB4 (beta 4), to human chromosomes 10p12 and 2q22-q23,
respectively, by fluorescence in situ hybridization. The gene encoding the beta
2 protein, first described as a Lambert-Eaton myasthenic syndrome (LEMS) antigen
in humans, is found close to a region that undergoes chromosome rearrangements
in small cell lung cancer, which occurs in association with LEMS. CACNB2 (beta
2) and CACNB4 (beta 4) genes are members of the ion-channel gene superfamily and
it should now be possible to examine their loci by linkage analysis of
ion-channel-related disorders. To date, no such disease-related gene has been
assigned to 10p12 and 2q22-q23. The sera of patients with Lambert-Eaton myasthenic syndrome (LEMS) contain
autoantibodies against several extracellular and intracellular components of the
voltage-gated calcium channel (VGCC)/synaptic vesicle release complex. An
example of the latter are anti-beta-subunit antibodies (anti-MysB antibodies).
We constructed a full-length cDNA clone of a human VGCC beta-subunit to produce
purified beta-subunit fusion protein (MysB protein). Using this protein, we
demonstrated that anti-beta-subunit antibodies are present in the sera of 23% of
LEMS patients and only, in low titer, in 2% of small cell lung cancer patients
without LEMS. The presence of anti-beta-subunit antibodies was closely
associated with high titers of P/Q- and N-type VGCC antibodies. Immunization of
rats with the purified MysB protein induced high antibody titers, but no signs
of neurologic dysfunction were found. We conclude that anti-beta-subunit
antibodies are not likely to interfere with ion channel function, but their
presence could explain the cross-reactivity of LEMS sera with several subtypes
of VGCCs and the lack of correlation between anti-VGCC antibody titer and
clinical severity of disease. We report a case of paraneoplastic myasthenic syndrome with clinical features
suggesting Lambert Eaton syndrome but without the electromyographic elements
required for diagnosis. Anti-calcium channel antibodies were also lacking. The
electromyogram evidenced a block and the Tensilon test was positive. The
efficacy of anticholinesterases argued in favor of myasthenia but
anti-acetylcholine receptor antibodies were negative. The block was more of a
mixed nature, involving both presynaptic transmission as in Lambert Eaton
syndrome and post-synaptic transmission as in paraneoplastic myasthenia. The
primary tumor was identified as a small-cell neuroendocrine lung carcinoma on
mediastinal biopsies obtained directly on CT-scan guided puncture of a
mediastinal node. Thoracotomy was thus avoided. The Lambert Eaton syndrome is a
paraneoplastic manifestation of small-cell lung cancer in 50% of the cases
unlike generalized myasthenia which apparently is never associated with
small-cell lung cancer. A mixed paraneoplastic neuro-muscle junction disorder
with aspects of each can be exceptionally observed. Lambert-Eaton myasthenic syndrome (LEMS) is a neuromuscular disorder
characterized by defective neurotransmitter release at presynaptic terminals. It
is caused by an IgG autoantibody reacting against voltage-gated calcium
channels. Severe LEMS complicated by ventilatory failure is rare. We report a
case of small-cell lung cancer (SCLC) presenting with LEMS and ventilatory
failure in a 67-year-old man who initially presented with progressive limb
weakness for 6 months and tachypnea with shallow breathing for 1 week. LEMS was
diagnosed through electrophysiologic studies. Chest radiography and computerized
tomography showed a huge mass lesion over the left anterior and middle
mediastinum with an encasement of the left pulmonary artery. Cytologic
examination of ultrasound-guided fine needle aspiration disclosed SCLC.
Successful treatment in combination with plasma exchange and chemotherapy
resulted in dramatic tumor regression and LEMS remission, which were confirmed
by chest radiography and electrophysiologic studies. This case suggests that
plasma exchange and chemotherapy can be effective in treating SCLC with severe
LEMS that produces ventilatory failure. In the nervous system, voltage-gated Ca2+ channels regulate numerous processes
critical to neuronal function including secretion of neurotransmitters,
initiation of action potentials in dendritic regions of some neurons, growth
cone elongation, and gene expression. Because of the critical role which Ca2+
channels play in signaling processes within the nervous system, disruption of
their function will lead to profound disturbances in neuronal function.
Voltage-gated Ca2+ channels are the targets of several relatively rare
neurological or neuromuscular diseases resulting from spontaneously-occurring
mutations in genes encoding for parts of the channel proteins, or from
autoimmune attack on the channel protein responses. Mutations in CACNAIA, which
encodes for the alpha1A subunit of P/Q-type Ca2+ channels, lead to symptoms seen
in familial hemiplegic migraine, episodic ataxia type 2, and spinocerebellar
ataxia type 6. Conversely, autoimmune attack on Ca2+ channels at motor axon
terminals causes peripheral cholinergic nerve dysfunction observed in
Lambert-Eaton Myasthenic Syndrome (LEMS), the best studied of the disorders
targeting voltage-gated Ca2+ channels. LEMS is characterized by decreased evoked
quantal release of acetylcholine (ACh) and disruption of the presynaptic active
zones, the sites at which ACh is thought to be released. LEMS is generally
believed to be due to circulating antibodies directed specifically at the Ca2+
channels located at or near the active zone of motor nerve terminals (P/Q-type)
and hence involved in the release of ACh. However, other presynaptic proteins
have also been postulated to be targets of the autoantibodies. LEMS has a high
degree of coincidence (approximately 60%) with small cell lung cancer; the
remaining 40% of patients with LEMS have no detectable tumor. Diagnosis of LEMS
relies on characteristic patterns of electromyographic changes; these changes
are observable at neuromuscular junctions of muscle biopsies from patients with
LEMS. In the majority of LEMS patients, those having detectable tumor, the
disease is thought to occur as a result of immune response directed initially
against voltage-gated Ca2+ channels found on the lung tumor cells. In these
patients, effective treatment of the underlying tumor generally causes marked
improvement of the symptoms of LEMS as well. Animal models of LEMS can be
generated by chronic administration of plasma, serum or immunoglobulin G to
mice. These models have helped dramatically in our understanding of the
pathogenesis of LEMS. This "passive transfer" model mimics the
electrophysiological and ultrastructural findings seen in muscle biopsies of
patients with LEMS. In this model, we have shown that the reduction in amplitude
of Ca2+ currents through P/Q-type channels is followed by "unmasking" of an
L-type Ca2+ current not normally found at the motor nerve terminal which
participates in release of ACh from terminals of mice treated with plasma from
patients with LEMS. It is unclear what mechanisms underlie the development of
this novel L-type Ca2+ current involved in release of ACh at motor nerve
terminals during passive transfer of LEMS. INTRODUCTION: The diagnosis and treatment of the neurological paraneoplastic
syndromes associated with lung cancer can pose a challenge both to general
physicians and neurologists as well as pulmonologists.
CASE REPORT: A 53 year-old heavy smoker presented with a Lambert-Eaton
myasthenic syndrome (LEMS). Bronchoscopy was normal but radiological
examinations revealed a lymph node in site 4R. The pathological diagnosis after
mediastinoscopy was negative. Twenty-five months later, an opacity on chest
X-ray led to a biopsy which revealed a squamous cell carcinoma. A lobectomy was
performed for a pT2N0M0 lesion. A significant improvement of neurological
symptoms was seen. The myasthenic syndrome reappeared 21 months later. A local
and general relapse was diagnosed. The patient died 10 months later despite
chemotherapy.
CONCLUSION: LEMS occurs because of an immunological reaction against
voltage-dependent calcium channels. LEMS is generally associated with small cell
lung cancer occurring in three percent of cases. However, the case that we
report shows the unusual association of LEMS with non small-cell lung cancer and
highlights the difficulties associated in the management of this condition. We studied whether a difference exists in the development of symptoms of the
Lambert-Eaton myasthenic syndrome (LEMS) between patients with or without small
cell lung cancer (SCLC). We assessed symptoms in 38 LEMS patients, 13 with SCLC,
by interviewing them using a structured checklist, backed up by a review of
their clinical records, and compared the frequency and time scale of symptoms
during the course of LEMS. Bulbar (87%) and autonomic (95%) symptoms for the
whole group were more common than reported in the literature. Frequencies of
symptoms did not differ significantly between patients with and without SCLC,
but symptoms in patients with SCLC appeared within a shorter time-frame,
indicating a more rapid clinical course. The presence of a particular symptom
associated with LEMS did not predict the presence of SCLC, but in patients with
rapidly progressive LEMS the possibility of underlying lung cancer should be of
particular concern. BACKGROUND/OBJECTIVE: We reported that 43% of patients with Lambert-Eaton
myasthenic syndrome (LEMS) and small cell lung cancer (SCLC) had an antibody
called anti-glial nuclear antibody (AGNA), defined by the immunoreaction with
the nuclei of the Bergmann glia of the cerebellum. This study was undertaken to
identify the antigen recognized by AGNA and to confirm the association with
paraneoplastic LEMS in a larger series.
METHODS: We probed a fetal brain cDNA library with AGNA-positive sera. The
presence of antibodies against the isolated antigen was detected by immunoblot
of phage plaques from two positive clones. We studied 105 patients with LEMS (55
with SCLC), 50 with paraneoplastic neurologic syndromes, SCLC, and Hu
antibodies, and 50 with only SCLC.
RESULTS: Probing of the fetal brain expression library with AGNA sera resulted
in the isolation of SOX1, a highly immunogenic tumor antigen in SCLC. IgG eluted
from SOX1 clones produced the same cerebellar immunoreactivity as of AGNA sera.
SOX1 antibodies were present in 64% of patients with LEMS and SCLC but in none
of the 50 with idiopathic LEMS (p < 0.0001). Compared with paraneoplastic LEMS,
the frequency of SOX1 antibodies was significantly lower in patients with Hu
antibodies (32%, p = 0.002) and in those with only SCLC (22%).
CONCLUSIONS: SOX1 is the antigen recognized by anti-glial nuclear
antibody-positive sera. The detection of SOX1 antibodies in patients with
Lambert-Eaton myasthenic syndrome (LEMS) predicts the presence of small cell
lung cancer and may be used to follow more closely those LEMS patients with no
evidence of cancer at the initial workup. Lambert-Eaton syndrome (LES) is an immune-mediated disorder of the presynaptic
neuromuscular junction due to the blocking effect of the voltage-gated calcium
channel (VGCC) antibodies. Small-cell lung cancer (SCLC) is the most common
cause of LES. We report an unusual case of LES associated with large-cell
neuroendocrine carcinoma (LCNEC) of the lung. In this case, clinical symptoms of
LES predated the diagnosis of LCNEC by 6 years. After tumor resection, the
patient experienced clinical and electrophysiological improvement. In addition,
he had a decrease in VGCC antibody titer from 130 to 80 pmol/L. The onset of LES
can be prolonged, and tumor surveillance should continue in these cases. BACKGROUND: Neuromuscular symptoms in patients with Lambert-Eaton myasthenic
syndrome (LEMS) and a small cell lung cancer (SCLC) develop more rapidly than in
LEMS patients without a SCLC. We studied how this clinical information, which is
readily available at the first consultation, can be used to predict the presence
of SCLC.
PATIENTS AND METHODS: In our study we included 52 LEMS patients with SCLC and 45
non-tumor patients (NT-LEMS). We interviewed patients using a structured
checklist and reviewed their clinical records. We compared frequency and onset
of symptoms during the course of LEMS.
RESULTS: In the first six months, over half the SCLC-LEMS patients had developed
seven separate symptoms, while NT-LEMS patients developed only two symptoms.
Proximal leg weakness and dry mouth were early symptoms in both groups. Rapid
involvement of proximal arm muscles (p=0.0001), distal arm muscles (p=0.0037),
distal leg muscles (p=0.0002), dysartria (p=0.0091) and the presence of erectile
dysfunction (p=0.007) were found significantly more often in SCLC-LEMS patients
in both cohorts. Cerebellar symptoms, although present in 9% of LEMS patients,
were almost exclusively related to SCLC-LEMS.
CONCLUSION: A rapidly progressive course of disease from onset in LEMS patients
should raise a high suspicion of SCLC. Special attention should be paid to
involvement of upper extremities, involvement of distal arm and distal leg
muscles, to erectile dysfunction and probably ataxia in order to discriminate
between SCLC-LEMS and NT-LEMS. We report the case of a 50-year-old man with paraneoplastic cerebellar
degeneration (PCD) and Lambert-Eaton myasthenic syndrome (LEMS) associated with
primary double lung cancer. He developed acute progressive double vision,
slurred speech, and gait disturbance. Neurological examination revealed
diplopia, mild ptosis, bilateral horizontal gaze-evoked nystagmus, and
cerebellar limb and truncal ataxia. The diffusion image of brain magnetic
resoce imaging (MRI) revealed no abnormal findings in the cerebellum. On the
basis of the diagnosis of acute cerebelitis, he was given methylprednisolone
pulse therapy followed by oral prednisolone, which gradually improved his
neurological signs and symptoms. The analysis of the possible etiology suggested
that the PCD was induced by lung cancer, which led to ataxia. A chest computed
tomography scan revealed mass lesions of irregular shape and unclear margins in
the upper lobe of the right lung and a small nodule tumor in the upper lobe of
the left lung. We performed transbronchial needle aspiration and detected the
bronchioloalveolar carcinoma of the right lung. An electromyogram showed waxing
phenomenon in the ulnar nerve at high-frequency (50Hz) stimulation. The serum
levels of anti-P/Q-type voltage-gated calcium channel (VGCC) antibody were
elavated in the patient. These findings confirmed that the pathogenesis of the
condition of this patient to be associated with LEMS. His cerebellar symptoms
were considered to be caused by the PCD, and the diplopia, ptosis, and
hyporeflexia were attributed to LEMS. We performed upper left lobectomy with
mediastinal lymphnode dissection via video-assisted thoracoscopic surgery. A
histological study detected small cell carcinoma. A diagnosis of double primary
lung cancer was made. Physicians need to be aware that patients may develop PCD
and LEMS associated with anti-VGCC antibody caused by small cell lung cancer,
and a mass survey should be conducted and careful examinations performed. Paraneoplastic cerebellar degeneration may occur in association with
Lambert-Eaton myasthenic syndrome (LEMS), but to our knowledge, the
co-occurrence of paraneoplastic opsoclonus-myoclonus syndrome and LEMS has not
been previously reported. A 67-year-old woman presented with a complex partial
seizure and evolving ocular flutter, opsoclonus, myoclonus and 'cerebellar'
signs, all of which improved spontaneously within 6 weeks. Approximately 8 weeks
after symptom onset, the patient became encephalopathic, she had a further
complex partial seizure, and she became areflexic with potentiation of deep
tendon reflexes. Radiological, bronchoscopic and histological investigations
revealed small-cell lung cancer, and neurophysiological investigations confirmed
a diagnosis of LEMS. High-titre anti-P/Q-type voltage-gated calcium-channel
antibodies were identified in the serum, which increased as the signs of
opsoclonus and myoclonus resolved. The encephalopathy and clinical features of
LEMS responded dramatically to chemotherapy and radiotherapy. Spontaneous
improvement of paraneoplastic opsoclonus-myoclonus syndrome may occur, and this
syndrome may occur in association with LEMS. Antivoltage-gated calcium-channel
antibodies are not implicated in the pathogenesis of paraneoplastic
opsoclonus-myoclonus syndrome. Brain FDG-PET after radiation therapy is classically used to differentiate
between tumor recurrence and radiation-related tumor necrosis. Little is known
about FDG-PET in patients with radiation-induced leukoencephalopathy without
radiological aspect of necrosis. We present a 69-year-old woman who had
preventive whole brain radiation after a diagnosis of paraneoplastic
Lambert-Eaton syndrome related to small cell lung cancer Five months after
radiation therapy, she developed radiation-induced leukoencephalopathy
manifested by ataxia. Profound cerebellar hypometabolism on FDG-PET was in
contrast with the presence of only discrete cerebellar white matter changes on
MRI. FDG-PET abnormalities seem to correlate better with clinical signs related
to radiation-associated brain toxicity than MRI. BACKGROUND: To enhance the acknowledgement of Lambert-Eaton syndrome in patients
with small cell lung cancer.
METHODS: Retrospective case analysis of Lambert-Eaton syndrome in patients with
small cell lung cancer in our hospital.
RESULTS: The characteristics of electromyography for Lambert-Eaton syndrome was
reduction in action potential amplitude after repetitive peripheral nerve
stimulation at low frequency and increased amplitude at high frequency.There
were 10 cases of Lambert-Eaton syndrome in 332 pathologically diagnosed small
cell lung cancer,9 male and 1 female with an average age of 57.6±4.9.Nine of 10
cases were among 50 to 69.All patients except one experienced myasthenia,mainly
in lower extremities,2 to 36 months (median:6 months) before the diagnosis of
small cell lung cancer.Treatment of small cell lung cancer may improve the
symptoms of Lambert-Eaton syndrome.
CONCLUSIONS: Improving the recognition of Lambert-Eaton syndrome may be helpful
to identify early small cell lung cancer and improve the prognosis,as the
symptom of muscular weakness usually appears early before the diagnosis of small
cell lung cancer. |
What distinguishes lantibiotics from antibiotics? | Lantibiotic compounds are ribosomally synthesized antimicrobial peptides against which bacteria are not able to produce resistance, hence making them a good alternative to antibiotics. It is interesting that low levels of resistance have been reported for lantibiotics compared with commercial antibiotics. Given that there are very few examples of naturally occurring lantibiotic resistance, attempts have been made to deliberately induce resistance phenotypes in order to investigate this phenomenon. Other general forms of resistance include the formation of spores or biofilms, which are a common mechanistic response to many classes of antimicrobials. | Nisin produced by Lactococcus lactis 6F3 is used as a food preservative and is
the most important member of a group of peptide-antibiotics containing
lanthionine bridges (lantibiotics) (N. Schnell, K.-D. Entian, U. Schneider, F.
Götz, H. Zähner, R. Kellner, and G. Jung, Nature [London] 333:276-278, 1988).
Nisin is ribosomally synthesized, and its structural gene, nisA, encodes a
prepeptide that is posttranslationally modified, revealing the active
lantibiotic (C. Kaletta and K.-D. Entian, J. Bacteriol. 171:1597-1601, 1989).
Adjacent to nisA, the additional genes nisB, nisT, and nisC were identified.
Over their entire sequences, these genes were homologous to genes recently
identified as important for the biosynthesis of lantibiotics, that is, subtilin
from Bacillus subtilis ATCC 6633 and epidermin from Staphylococcus epidermidis
Tü 3298. Genes nisB, nisT, and nisC corresponded to open reading frames of 993,
600, and 418 amino acid residues, respectively. The nisT open reading frame is
homologous to proteins of the HlyB (hemolysin B protein of Escherichia coli)
subfamily. Proteins of this subfamily are responsible for the secretion of a
variety of compounds, including large polypeptides, polysaccharides, and
anti-drug tumors, indicating that NisT may be involved in nisin transport.
Northern (RNA) blot analysis revealed a 0.3-kb transcript for the nisA
structural gene, and the transcriptional start point of the nisA gene was
determined by primer extension. Additionally, a mRNA of at least 3 kb was
identified by using a hybridization probe specific to nisB. Antibodies were
raised against the NisB protein, and Western blot (immunoblot) analysis revealed
a molecular weight of about 115 kDa, which is in accordance with the theoretical
protein size of 117.5 kDa as calculated from the nisB open reading frame.
Several amphipathic transmembrane alpha-helices indicated that NisB is
associated with the membrane. This was confirmed by preparing L. lactis
vesicles. The NisB protein was tightly associated with the vesicle fraction and
was released by sodium dodecyl sulfate treatment only. These results suggest
that NisB is membrane associated and that nisin biosynthesis occurs at the cell
membrane. Lantibiotics are defined as peptide antibiotics containing the unusual amino
acids mesolanthionine, 3-methyllanthionine, dehydroalanine, and dehydrobutyrine.
They are synthesized by some gram-positive bacteria. Their inhibitory effect on
certain other gram-positive bacteria is explained by detergent-like damage of
cytoplasmic membranes. Prominent members of the lantibiotics are nisin of
Lactococcus lactis, which can be used as a food preservative, subtilin of
Bacillus subtilis, which is similar to nisin, and epidermin of Staphylococcus
epidermidis, which is considered in the treatment of acne. Lantibiotics are
ribosomally synthesized as prepeptides, which are posttranslationally modified.
Genes probably encoding these biosynthetic enzymes and regulatory factors have
been identified adjacent to the structural genes of the lantibiotics subtilin,
nisin, and epidermin. Lantibiotics are antibiotic peptides distinguished by the presence of the rare
thioether amino acids lanthionine and/or methyllanthionine. They are produced by
Gram-positive bacteria as gene-encoded precursor peptides and undergo
post-translational modification to generate the mature peptide. The structural
gene for the prepeptide and the genes involved in biosynthesis, processing,
export as well as regulation and producer strain self-protection are organized
in clusters. Based on their structural and functional features lantibiotics are
currently divided into two major groups. The flexible amphiphilic type-A
lantibiotics act primarily by pore formation in the bacterial membrane, a
mechanism which was recently shown, e.g. for nisin and epidermin, to involve the
interaction with specific docking molecules such as the membrane precursor lipid
II. The rather rigid and globular type-B lantibiotics inhibit enzyme functions
through interaction with the respective substrates: mersacidin and actagardine
inhibit the cell wall biosynthesis by complexing lipid II, whereas the
cinnamycin-like peptides inhibit phospholipases by binding phosphoethanolamine.
Lantibiotics have attracted much attention in recent years and undergone
extensive characterization. New insights into the mode of action and
structure-function relationships as well as the biochemistry and the genetics
will be outlined in this review. Recent studies on the mode of action have revealed exciting features of multiple
activities of nisin and related lantibiotics making these peptides interesting
model systems for the design of new antibiotics (Molec. Microbiol. 30 (1998)
317; Science 286 (1999) 2361; J. Biol. Chem. 276 (2001) 1772.). In contrast to
other groups of antibiotic peptides, the lantibiotics display a substantial
degree of specificity for particular components of bacterial membranes.
Mersacidin and actagardine were shown to bind with high affinity to the lipid
coupled peptidoglycan precursor, the so-called lipid II, which prevents the
polymerisation of the cell wall monomers into a functional murein sacculus. The
lantibiotics nisin and epidermin also bind tightly to this cell wall precursor;
however, for these lantibiotics the binding of lipid II has two consequences.
Like with mersacidin blocking of lipid II inhibits peptidoglycan biosynthesis;
in addition, lipid II is used as a specific docking molecule for the formation
of pores. This combination of lethal effects explains the potency of these
peptides, which are active in omolar concentration. Other type-A lantibiotics
are believed to also use docking molecules for pore formation, although
identification of such membrane components has not yet been achieved. Lantibiotics, a group of lanthionine-containing peptides, display their
antibiotic activity by combining different killing mechanisms within one
molecule. The prototype lantibiotic nisin was shown to possess both inhibition
of peptidoglycan synthesis and pore formation in bacterial membranes by
interacting with lipid II. Gallidermin, which shares the lipid II binding motif
with nisin but has a shorter molecular length, differed from nisin in pore
formation in several strains of bacteria. To simulate the mode of action, we
applied cyclic voltammetry and quartz crystal microbalance to correlate pore
formation with lipid II binding kinetics of gallidermin in model membranes. The
inability of gallidermin to form pores in DOPC
(1,2-dioleoyl-sn-glycero-3-phosphocholine) (C18/1) and DPoPC
(1,2-dipalmitoleoyl-sn-glycero-3-phosphocholine) (C16/1) membranes was related
to the membrane thickness. For a better simulation of bacterial membrane
characteristics, two different phospholipids with branched fatty acids were
incorporated into the DPoPC matrix. Phospholipids with methyl branches in the
middle of the fatty acid chains favored a lipid II-independent DPoPC
permeabilization by gallidermin, while long-branched phospholipids in which the
branch is placed near the hydrophilic region induced an identical lipid
II-dependent pore formation of gallidermin and nisin. Obviously, the branched
lipids altered lipid packing and reduced the membrane thickness. Therefore, the
duality of gallidermin activity (pore formation and inhibition of the cell wall
synthesis) seems to be balanced by the bacterial membrane composition. Lantibiotics are peptide antibiotics, realizing their unique secondary structure
by posttranslational modifications, the most important one being the formation
of the characteristic amino acid lanthionine. Like other ribosomal peptide
antibiotics, they are synthesized with an N-terminal leader peptide important
for posttranslational processing by modifying enzymes; after peptide maturation,
the leader peptide is proteolytically cleaved off. Numerous studies of the
leader peptides of class I and II lantibiotics already showed their crucial role
in recognition, self-immunity, and extracellular transport. The recently
described labyrinthopeptins, members of the family of class III lantibiotics,
exhibit the characteristic novel amino acid labionin, which was revealed by
elucidation of the structure of labyrinthopeptin A2. The assembly of the
labionin motif in the linear peptide chain is mediated by the
lyase-kinase-cyclase-type enzyme LabKC through a serine side chain
phosphorylation with GTP, elimination of the phosphate group, and a subsequent
2-fold Michael-type addition cyclization. In this work, we systematically
investigated for the first time the importance of the leader peptide in the
processing of class III lantibiotics using the example of the labyrinthopeptin
A2 precursor peptide. In vitro studies with synthetic leader peptide analogues
revealed that a conserved N-terminal hydrophobic patch on a putative helical
structure is required for the proper peptide processing by the modifying enzyme
LabKC. On the other hand, studies showed that the C-terminal part of the leader
peptide serves as a spacer between the binding site and active sites for
phosphorylation and elimination, thus restricting the number of hydroxy amino
acid side chains that could undergo dehydration. Finally, a model for the
peptide recognition and processing by the LabKC has been postulated. The increasing prevalence of antibiotic resistance in bacterial pathogens has
renewed focus on natural products with antimicrobial properties. Lantibiotics
are ribosomally synthesized peptide antibiotics that are posttranslationally
modified to introduce (methyl)lanthionine bridges. Actinomycetes are renowned
for their ability to produce a large variety of antibiotics, many with clinical
applications, but are known to make only a few lantibiotics. One such compound
is planosporicin produced by Planomonospora alba, which inhibits cell wall
biosynthesis in Gram-positive pathogens. Planosporicin is a type AI lantibiotic
structurally similar to those which bind lipid II, the immediate precursor for
cell wall biosynthesis. The gene cluster responsible for planosporicin
biosynthesis was identified by genome mining and subsequently isolated from a P.
alba cosmid library. A minimal cluster of 15 genes sufficient for planosporicin
production was defined by heterologous expression in Nonomuraea sp. strain ATCC
39727, while deletion of the gene encoding the precursor peptide from P. alba,
which abolished planosporicin production, was also used to confirm the identity
of the gene cluster. Deletion of genes encoding likely biosynthetic enzymes
identified through bioinformatic analysis revealed that they, too, are essential
for planosporicin production in the native host. Reverse transcription-PCR
(RT-PCR) analysis indicated that the planosporicin gene cluster is transcribed
in three operons. Expression of one of these, pspEF, which encodes an ABC
transporter, in Streptomyces coelicolor A3(2) conferred some degree of
planosporicin resistance on the heterologous host. The inability to delete these
genes from P. alba suggests that they play an essential role in immunity in the
natural producer. BACKGROUND: The emergence of bacterial drug resistance encourages the
re-evaluation of the potential of existing antimicrobials. Lantibiotics are
post-translationally modified, ribosomally synthesised antimicrobial peptides
with a broad spectrum antimicrobial activity. Here, we focussed on expanding the
potential of lacticin 3147, one of the most studied lantibiotics and one which
possesses potent activity against a wide range of Gram positive species
including many nosocomial pathogens. More specifically, our aim was to
investigate if lacticin 3147 activity could be enhanced when combined with a
range of different clinical antibiotics.
RESULTS: Initial screening revealed that polymyxin B and polymyxin E (colistin)
exhibited synergistic activity with lacticin 3147. Checkerboard assays were
performed against a number of strains, including both Gram positive and Gram
negative species. The resultant fractional inhibitory concentration (FIC) index
values established that, while partial synergy was detected against Gram
positive targets, synergy was obvious against Gram negative species, including
Cronobacter and E. coli.
CONCLUSIONS: Combining lacticin 3147 with low levels of a polymyxin could
provide a means of broadening target specificity of the lantibiotic, while also
reducing polymyxin use due to the lower concentrations required as a result of
synergy. |
List three major features of the CCFDN syndrome. | Congenital cataracts, facial dysmorphism and peripheral neuropathy are three major features of the CCFDN syndrome. Other described signs and symptoms of the CCFDN syndrome include microcornea, microphthalmos, micropupil, floppy eyelid syndrome, pseudoptosis, nystagmus, congenital esotropia, impairment of distant visual acuity, ataxia, pyramidal signs, mild chorea, short stature, muscular atrophy, delayed early motor and intellectual development, hypogonadotrop hypogonadism, hypomyelination of the peripheral nervous system, serious complications related to general anaesthesia and parainfectious rhabdomyolysis. | During a study of hereditary motor and sensory neuropathy-Lom in Bulgaria, a
previously unrecognized neurological disorder was encountered, mainly in
Wallachian Gypsies, who represent a relatively recent genetic isolate. The
disorder has been termed the congenital cataracts facial dysmorphism neuropathy
(CCFDN) syndrome to emphasize its salient features. Fifty individuals from 19
extended pedigrees were identified and examined clinically and
electrophysiologically. At least 1 patient from each family was admitted to the
hospital in Sofia for full investigation. Pedigree analysis indicates autosomal
recessive inheritance. The disorder is recognized in infancy by the presence of
congenital cataracts and microcorneas. A predomitly motor neuropathy
beginning in the lower limbs and later affecting the upper limbs develops during
childhood and leads to severe disability by the third decade. Associated
neurological features are a moderate nonprogressive cognitive deficit in most
affected individuals together with pyramidal signs and mild chorea in some.
Accompanying nonneurological features include short stature, characteristic
facial dysmorphism, and hypogonadotrophic hypogonadism. Nerve conduction studies
suggest a hypomyelinating/demyelinating neuropathy, confirmed by nerve biopsy.
The CCFDN syndrome is thus a pleomorphic autosomal recessive disorder displaying
a combination of neurological and nonneurological features. We have identified a novel developmental disorder with complex phenotypic
characteristics involving primarily the nervous system, which appears to be
common in a specific Gypsy group in Bulgaria. We propose to refer to the
syndrome as congenital cataracts facial dysmorphism neuropathy (CCFDN). We have
assigned the disease locus to the telomeric region of chromosome 18q. Linkage
disequilibrium and highly conserved haplotypes suggest genetic homogeneity and
founder effect. CCFDN co-localises with an EST which shows high homology to a
conserved Drosophila gene involved in the regulation of nervous system
development in vertebrates. Observations have been made on the peripheral nerve changes in four patients,
ranging in age from 4 to 32 years, with the congenital cataracts facial
dysmorphism neuropathy syndrome. Myelinated fibre density was within normal
limits. The salient abnormality was diffuse hypomyelination which, in the older
patients, was associated with demyelination and then axonal degeneration. These
findings could be correlated with the relative preservation of sensory action
potential amplitude despite markedly reduced nerve conduction velocity.
Unmyelinated axon density was preserved. The morphological observations suggest
the operation of a developmental process affecting myelination with a later
superimposed degenerative disorder. OBJECTIVE AND BACKGROUND: To describe three Gypsy families with
Marinesco-Sjögren syndrome (MSS), demyelinating neuropathy, and recurrent
episodes of myoglobinuria in five of the six affected subjects. Because these
families originated from the same genetically isolated founder population as did
patients with congenital cataracts facial dysmorphism neuropathy (CCFDN)
syndrome, and because the two syndromes have clinical manifestations in common,
we hypothesized that the two related, albeit distinct, syndromes may represent
clinical variants of a single genetic disorder.
METHODS: Clinical studies were conducted and linkage and haplotype analyses were
performed for the three families. A total of 16 individuals, including the 6
with MSS and 10 unaffected relatives, were genotyped for six polymorphic
microsatellite markers from the CCFDN region on 18qter.
RESULTS: Linkage analysis of markers in the 18qter region, where we previously
had located the CCFDN gene, produced a lod score of 3.55, demonstrating
colocalization of the gene responsible for MSS with demyelinating neuropathy and
myoglobinuria with the CCFDN gene. Moreover, the patients with MSS shared the
conserved marker haplotype found in CCFDN chromosomes.
CONCLUSIONS: These data suggest that Marinesco-Sjögren syndrome with peripheral
neuropathy and myoglobinuria, and congenital cataracts facial dysmorphism
neuropathy syndrome are genetically identical and are caused by a single founder
mutation. OBJECTIVE: To determine the nature and course of ophthalmologic abnormalities in
congenital cataracts facial dysmorphism neuropathy (CCFDN) syndrome in a
genetically verified group of 9 patients.
STUDY DESIGN: Observational case series.
PARTICIPANTS: Nine affected male individuals of 5 pedigrees aged 1.3 to 16.8
years were examined. Four individuals were recruited during an ongoing
prospective study of congenital cataracts; 5 individuals could be assigned to
the CCFDN group on the basis of our retrospective data.
MAIN OUTCOME MEASURES: Linkage and haplotype analysis, neurologic examinations,
bilateral cataracts, axial length, corneal diameter, pupil diameter and
pupillary reactions, intraoperative and postoperative complications, lid
changes, aphakic correction problems, refractive results, and visual function.
RESULTS: All families originated from the eastern part of Serbia, close to the
border with Romania. The 8 tested individuals were homozygous for the conserved
ancestral CCFDN haplotype in the telomeric region of chromosome 18q. All
patients showed a peripheral, demyelinating neuropathy and varying degrees of
ataxia. In the older patients, muscular atrophy in distal muscles and facial
dysmorphism was evident. Early-onset bilateral congenital cataracts associated
with microcornea, microphthalmos, and micropupil could be found in all patients.
All children had floppy eyelid syndrome and pseudoptosis. An increased
inflammatory reaction to contact lenses and intraocular lenses could be
documented in all. All patients had syndrome-associated nystagmus and congenital
esotropia. Distant visual acuity could be classified as severe to moderate
impairment, whereas near visual acuity was much better (mild to moderate
impairment).
CONCLUSIONS: Early-onset congenital cataracts associated with microcornea,
microphthalmos, and micropupil are essential ocular features of the CCFDN
syndrome and are the first recognizable signs during early infancy. Awareness of
this syndrome by pediatric ophthalmologists is important, because these typical
findings, combined with information on ethnic origin, may lead to very early
diagnosis at an age when the nature and severity of nonophthalmologic features
are not apparent. Affected individuals may benefit from careful ophthalmologic
treatment and follow-up, as well as from early management of the neurologic
problems and developmental delay. Affected families will benefit from genetic
counseling and predictive testing. Congenital Cataracts Facial Dysmorphism Neuropathy (CCFDN) syndrome is a complex
developmental disorder of autosomal recessive inheritance. To date, CCFDN has
been found to occur exclusively in patients of Roma (Gypsy) ethnicity; over 100
patients have been diagnosed. Developmental abnormalities include congenital
cataracts and microcorneae, primary hypomyelination of the peripheral nervous
system, impaired physical growth, delayed early motor and intellectual
development, mild facial dysmorphism and hypogonadism. Para-infectious
rhabdomyolysis is a serious complication reported in an increasing number of
patients. During general anaesthesia, patients with CCFDN require careful
monitoring as they have an elevated risk of complications. CCFDN is a
genetically homogeneous condition in which all patients are homozygous for the
same ancestral mutation in the CTDP1 gene. Diagnosis is clinical and is
supported by electrophysiological and brain imaging studies. The major
differential diagnosis is Marinesco-Sjögren syndrome. The definitive diagnosis
is molecular, based on homozygosity for the CTDP1 mutation. CTDP1 maps to 18qter
and encodes a protein phosphatase whose only known substrate is the
phosphorylated serine residues of the carboxy-terminal domain of the largest
subunit of RNA polymerase II, indicating that CCFDN affects basic cellular
processes of gene expression and developmental regulation. Families benefit from
genetic counselling and predictive testing. Management includes surgical
treatment of the cataracts, and rehabilitation and corrective orthopaedic
surgery for the peripheral neuropathy. Thus, the most disabling manifestations,
though not curable, are manageable, and allow an acceptable quality of life and
everyday living. Current data indicate that patients survive well into
adulthood. Congenital cataracts-facial dysmorphism-neuropathy syndrome (CCFDN, MIM:
604168), is a recently delineated neurogenetic disease causing recurrent
episodes of rhabdomyolysis; prevention and early diagnosis of rhabdomyolysis
should be part of the clinical management of the disease. The congenital cataracts facial dysmorphism neuropathy (CCFDN) syndrome (OMIM
604168) is a recently described autosomal recessive developmental disorder. It
is almost completely restricted to an endogamous group of the European Vlax Roma
population, called the Rudari. The CCFDN syndrome is a complex phenotype
involving multiple systems, characterized by facial dysmorphism, congenital
cataracts, microcorneae, delayed early motor and intellectual development,
hypogonadotrop hypogonadism, hypomyelination of the peripheral nervous system,
and serious complications related to general anaesthesia. This disorder is
caused by a homozygous mutation of the carboxy-terminal domain phosphatase 1
(CTDP1) gene, localized to the 18q23 region. Authors present one genetically
identified case in a large Roma family. The case documents that the CCFDN
mutation is present also in the Hungarian Roma population. Underlie of
antropomorphological data the authors presume that the CCFDN mutation reached
Hungary as a result of emigration of Vlax Gypsies in the 18th century. The paper
calls attention to the fact that molecular genetic diagnostics can replace
invasive methods and makes possible the identification of heterozygotes without
clinical symptoms. The introduction of the genetic screening enables us to
perform genetic counselling and prevention in this high-risk population. Recent medical genetic research has identified a number of novel, or previously
known, but rare conditions, caused by private founder mutations. The Finnish and
Ashkenazi Jew populations provide the best examples for identifying genes in
unique genetic disorders. In these populations, research efforts and high-level
medical services resulted in intense improvements of medical care and in
organization of population-based screening programs. Hereditary disorders of the
Roma populations are known for a long time. The genetic background of these
diseases has been established by extensive molecular genetic studies. The Romas
represent 6% of the Hungarian population and live under extremely bad health
conditions. Therefore, our aim was to map the incidence of the hereditary
neuromuscular disorders among the Hungarian Roma population. Moreover, we
intended to provide proper information, genetic counseling and possible
prevention strategies for the families at risk, which should represent a primer
task in public health. Because of our experience in neuromuscular disorders, we
choose six, frequent, autosomal recessive disorders for these clinical and
genetic studies: hereditary motor and sensory neuropathy type Lom (HMSNL),
hereditary motor and sensory neuropathy type Russe (HMSNR), congenital cataracts
facial dysmorphism syndrome (CCFDN), limb-girdle muscular dystrophy 2C (LGMD2C),
congenital myasthenic syndrome (CMS) and spinal muscular atrophy (SMA).
Following identification of the founder mutations, the possibility of prenatal
diagnosis and carrier screening for family members will contribute to the
decrease of the recurrence risk for these severe, mostly untreatable disorders. OBJECTIVE: We describe the 10-year follow-up in a cohort of 16 patients with
genetically confirmed congenital cataracts, facial dysmorphism, and neuropathy
(CCFDN) syndrome, providing new insights in the clinical course of the disease.
METHODS: We performed a detailed clinical and paraclinical characterization and
10-year follow-up study in 16 patients with molecularly defined CCFDN syndrome,
illustrating that CCFDN is a severe disabling disorder.
RESULTS: All patients initially presented with congenital cataracts along with
strabismus, facial dysmorphism, short stature, and demyelinating neuropathy. In
all patients, paresis of small hand muscles and foot extensors worsened with
disease progression, while ataxia scores remained stable or improved. Nerve
conduction velocity was normal in early infancy up to 18 months, decreased to
approximately 20 m/s around age 10 years, and then remained stable; distal motor
latency was prolonged. Sensory nerve conduction velocities were slowed, and
initially of normal amplitude. With disease progression, both sensory and motor
nerves showed reduction of amplitudes indicating axonal loss. In 6 patients,
acute severe proximal weakness and myalgia after febrile infections, along with
rhabdomyolysis, myoglobinuria, and hyperCKemia, led to a less favorable outcome
and permanent loss of ambulation in 3 patients.
CONCLUSIONS: CCFDN should be classified as a recessive demyelinating
sensory-motor neuropathy, and axonal loss is a major determit of long-term
outcomes and disability. Patients benefit from early and ongoing physiotherapy,
and should be thoroughly counseled regarding virus-triggered rhabdomyolysis and
the risk of maligt hyperthermia. Whether supplementation with liposoluble
vitamins results in a therapeutic benefit should be evaluated in further
studies. |
is intense physical activity associated with longevity ? | Several survival studies showed that professional athletes has higher longevity than general population. These epidemiological data matches the evidences that long-term endurance training induces in elderly subjects an increased HRV and a higher exercise working capacity, which are well-established predictors of cardiovascular and overall mortality, and also telomere length. | OBJECTIVE: To compare the long term survival of a group of athletes taking
prolonged vigorous physical exercise to that of the general population.
DESIGN: Follow up of a cohort of participants in the Dutch eleven cities ice
skating tour (a race and recreational tour) over a distance of 200 kilometers.
SETTING: Data on participation from the organising committee and data on
mortality from all municipalities in The Netherlands.
SUBJECTS: 2259 Male athletes.
MAIN OUTCOME MEASURES: Comparison of all cause mortality in male participants in
the tour with that in the general population of The Netherlands.
RESULTS: The standardised mortality ratio for all participants during 32 years
of follow up was 0.76 (95% confidence interval 0.68 to 0.85), and 0.90 (0.48 to
1.44) for participants in the race, and 0.72 (0.60 to 0.86) for participants in
the recreational tour who finished within the time limit.
CONCLUSIONS: The capacity for prolonged and vigorous physical exercise,
particularly if the exercise is recreational, is a strong indicator of
longevity. BACKGROUND: Electrocardiographic abnormalities and premature ventricular
contractions are common in athletes and are generally benign. However, the
specific outcome of high-level endurance athletes with frequent and complex
ventricular arrhythmias is unclear. Also, information on the predictive accuracy
of different investigations in this subgroup is unknown.
RESULTS: We report on 46 high-level endurance athletes with ventricular
arrhythmias (45 male; median age 31 years) followed-up for a median of 4.7
years. Eighty percent were cyclists. Hypertrophic cardiomyopathy or coronary
abnormalities were present in < or =5%. Eighty percent of the arrhythmias had a
left bundle branch morphology. Right ventricular (RV) arrhythmogenic involvement
(based on a combination of multiple criteria) was manifest in 59% of the
athletes, and suggestive in another 30%. Eighteen athletes developed a major
arrhythmic event (sudden death in nine, all cyclists). They were significantly
younger than those without event (median 23 years vs 38 years; P=0.01). Outcome
could not be predicted by presenting symptoms, non-invasive arrhythmia
evaluation or morphological findings at baseline. Only the induction of
sustained ventricular tachycardia (VT) or ventricular fibrillation (VF) during
invasive electrophysiological testing was significantly related to outcome (RR
3.4; P=0.02). Focal arrhythmias were associated with a better prognosis than
those due to reentry (P=0.02) but the mechanism could be determined in only 22
(48%).
CONCLUSIONS: Complex ventricular arrhythmias do not necessarily represent a
benign finding in endurance athletes. An electrophysiological study is indicated
for risk evaluation, both by defining inducibility and identifying the
arrhythmogenic mechanism. Endurance athletes with arrhythmias have a high
prevalence of right ventricular structural and/or arrhythmic involvement.
Endurance sports seems to be related to the development and/or progression of
the underlying arrhythmogenic substrate. Moderate exercise and intense physical training are associated with increased
life expectancy (LE). Boxing is characterized by intentional and repetitive head
blows, sometimes causing brain injury, possibly reducing LE. We examined a
sample of male athletes born between 1860 and 1930 selected from the
international "hall of fame" inductees in baseball (n = 154), ice hockey (n =
130), tennis (n = 83), football (n = 81), boxing (n = 81), track and field (n =
59), basketball (n = 58), swimming (n = 37) and wrestling (n = 32). In boxing,
we analyzed the number of disputed bouts/rounds and career records. Sports were
also analyzed according to physiological demand and occurrence and kind of
contact (intentional, unintentional). The Kaplan-Meier product limit method was
used to compare survival curves (significance: p <or= 0.05). Median LE of the
samples was 76.0 yrs and no differences were observed in different sports,
although it was lower in boxers (73.0 yrs) and higher in tennis players (79.0
yrs). Sports of different physiological demand were similar in respect to LE. No
differences in LE were found related to occurrence and kind of impact. Similar
LE was found in boxers of different weight or career records. In conclusion,
this study indicates that LE in top-level athletes is unaffected by the type of
discipline, and not related to physiological demand and intentional contact. In 1982, a nationwide program of preparticipation screening of all individuals
embarking in competitive sports activity was launched in Italy. The screening
protocol includes athlete's personal and family history, physical examination,
and twelve-lead electrocardiogram (ECG) as first-line examination; additional
tests such as echocardiography or exercise testing are requested only for
subjects who have positive findings at the initial evaluation. This screening
algorithm, which has been used for preparticipation evaluation of millions of
Italian athletes over a period of > 25 years has provided adequate sensitivity
and specificity for detection of athletes affected by potentially dangerous
cardiomyopathy or arrhythmia at risk of athletic-field death and has led to
substantial reduction of mortality of young competitive athletes (by
approximately 90%), mostly by preventing sudden death from cardiomyopathy. Leisure-time physical activity is associated with better health and a reduced
risk of all-cause mortality. It is unclear if this association is also present
with a high level of physical activity as it is found in professional athletes.
In a population-based retrospective cohort study, we compared the survival
experience of all soccer players participating for Germany in international
matches between 1908 and 2006 to that of the general population. To summarize
survival experience, we calculated cumulative relative survival ratios (RSRs)
from a life table. We included data of 812 international players, of which 428
(=52.7%) died during follow-up. In all 13 intervals, cumulative observed
survival was smaller than cumulative expected survival, resulting in cumulative
RSRs being <1. The cumulative RSRs are statistically significantly different
from 1 in all but the last interval. This impaired survival experience of the
internationals translates into a loss of median residual lifetime of 1.9 years
[95% confidence interval: 0.6, 3.2] years at the entry time into the cohort.
This loss is mainly driven by the mortality of internationals from the earlier
half of the observation period. Reasons for this might be poorer medical care in
former times, internationals being killed in action during World War II, and a
changing distribution of causes of death during the 20th century. BACKGROUND: While the promotion of health-related fitness is thereby widespread,
less focus is currently being given on the biological influence that physical
activity might exert on results of laboratory testing. As such, this study was
undertaken to assess the kinetics of liver injury markers following physical
exercise.
DESIGN AND METHODS: Total and direct bilirubin as well as the activity of
biochemical markers of liver injury including aspartate aminotransferase (AST),
alanine aminotransferase (ALT), alkaline phosphatase (ALP), lactate
dehydrogenase (LDH), gamma-glutamyl transpeptidase (GGT) and creatine kinase
(CK), were measured before and after a half-marathon.
RESULTS: Significant increases occurred for GGT, AST, LDH, CK, total and direct
bilirubin immediately after the run. AST, LDH, CK, total and direct bilirubin
were still increased 24h thereafter, whereas GGT decreased after 6h. None of the
athletes exceed the upper reference limit for ALT, ALP and GGT, whereas
significant variations were instead observed for LDH, AST, CK, total and direct
bilirubin.
CONCLUSIONS: Taken together, the results of our prospective investigation
clearly attest that an acute bulk of aerobic physical exercise, such as a
half-marathon, might produce significant changes in the activity of traditional
biomarkers of liver injury, which should be carefully considered when
investigating physically active individuals undergoing laboratory testing. BACKGROUND: Sudden death in athletes can occur during sport activities and is
presumably related to ventricular arrhythmias. There are no guidelines
concerning athletes who develop ventricular arrhythmias during an exercise test.
It is unclear whether they should be allowed to continue with their competitive
activity or not.
OBJECTIVES: To investigate the long-term follow-up of athletes with ventricular
arrhythmias during an exercise test.
METHODS: From a database of 56,462 athletes we identified 192 athletes, less
than 35 years old, who had ventricular arrhythmias during an exercise test.
Ninety athletes had > or = 3 ventricular premature beats (group A) and 102
athletes had ventricular couplets or non-sustained ventricular tachycardia
during an exercise test (group B). A control group of 92 athletes without
ventricular arrhythmias was randomly selected from the database (group C).
RESULTS: All athletes, except one who died from a dilated cardiomyopathy, were
alive during a follow-up period of 70 +/- 25 months. An abnormal echocardiogram
was obtained in seven athletes from group A (10%), four from group B (5%), and
one from group C (3%) (not significant). An abnormal echocardiogram was more
likely to be present in competitive athletes (P = 0.001) and in female athletes
(P = 0.01).
CONCLUSIONS: Our results showed that ventricular arrhythmias during exercise are
more commonly associated with cardiovascular abnormalities in young competitive
athletes and in female athletes. When present, they necessitate a thorough
investigation and follow-up. In this paper, we report survival estimates for male and female Olympic medal
winners and for male and female finalists at the British and U S national tennis
championships. We find a consistent longevity advantage of Olympic medal-winning
female athletes over Olympic medal-winning male athletes competing separately in
the same events since 1900 and for female finalists over male finalists
competing separately in the finals of the national tennis championships of
Britain and of the United States since the 1880s. This is the case for sample
mean comparisons, for Kaplan-Meier survival function estimates, including life
expectancy, and for Cox proportional hazard estimates, which show statistically
significant lower hazard rates for women with birth year and other variables
constant. The female longevity advantage over males is similar in the early
period samples (birth years before 1920) and in the full period samples, and is
5-7 years. OBJECTIVE: To assess the mortality risk in subsequent years (adjusted for year
of birth, nationality, and sex) of former Olympic athletes from disciplines with
different levels of exercise intensity.
DESIGN: Retrospective cohort study.
SETTING: Former Olympic athletes.
PARTICIPANTS: 9889 athletes (with a known age at death) who participated in the
Olympic Games between 1896 and 1936, representing 43 types of disciplines with
different levels of cardiovascular, static, and dynamic intensity exercise; high
or low risk of bodily collision; and different levels of physical contact.
MAIN OUTCOME MEASURE: All cause mortality.
RESULTS: Hazard ratios for mortality among athletes from disciplines with
moderate cardiovascular intensity (1.01, 95% confidence interval 0.96 to 1.07)
or high cardiovascular intensity (0.98, 0.92 to 1.04) were similar to those in
athletes from disciplines with low cardiovascular intensity. The underlying
static and dynamic components in exercise intensity showed similar
non-significant results. Increased mortality was seen among athletes from
disciplines with a high risk of bodily collision (hazard ratio 1.11, 1.06 to
1.15) and with high levels of physical contact (1.16, 1.11 to 1.22). In a
multivariate analysis, the effect of high cardiovascular intensity remained
similar (hazard ratio 1.05, 0.89 to 1.25); the increased mortality associated
with high physical contact persisted (hazard ratio 1.13, 1.06 to 1.21), but that
for bodily collision became non-significant (1.03, 0.98 to 1.09) as a
consequence of its close relation with physical contact.
CONCLUSIONS: Among former Olympic athletes, engagement in disciplines with high
intensity exercise did not bring a survival benefit compared with disciplines
with low intensity exercise. Those who engaged in disciplines with high levels
of physical contact had higher mortality than other Olympians later in life. OBJECTIVE: To determine whether Olympic medallists live longer than the general
population.
DESIGN: Retrospective cohort study, with passive follow-up and conditional
survival analysis to account for unidentified loss to follow-up.
SETTING AND PARTICIPANTS: 15,174 Olympic athletes from nine country groups
(United States, Germany, Nordic countries, Russia, United Kingdom, France,
Italy, Canada, and Australia and New Zealand) who won medals in the Olympic
Games held in 1896-2010. Medallists were compared with matched cohorts in the
general population (by country, age, sex, and year of birth).
MAIN OUTCOME MEASURES: Relative conditional survival.
RESULTS: More medallists than matched controls in the general population were
alive 30 years after winning (relative conditional survival 1.08, 95% confidence
interval 1.07 to 1.10). Medallists lived an average of 2.8 years longer than
controls. Medallists in eight of the nine country groups had a significant
survival advantage compared with controls. Gold, silver, and bronze medallists
each enjoyed similar sized survival advantages. Medallists in endurance sports
and mixed sports had a larger survival advantage over controls at 30 years
(1.13, 1.09 to 1.17; 1.11, 1.09 to 1.13) than that of medallists in power sports
(1.05, 1.01 to 1.08).
CONCLUSIONS: Olympic medallists live longer than the general population,
irrespective of country, medal, or sport. This study was not designed to explain
this effect, but possible explanations include genetic factors, physical
activity, healthy lifestyle, and the wealth and status that come with
international sporting glory. |
Are cyclophilins proteins that bind to prolines? | Cyclophilins are ubiquitously expressed proteins that bind to prolines. | The immunosuppressor cyclosporin A inhibits the
peptidyl-prolyl-cis/trans-isomerase activity of cyclophilins and the resulting
complex inhibits the phosphatase activity of calcineurin. Both enzymes were
detected in peripheral nerve endings isolated from the electric organ of Torpedo
and shown to be affected by 10 micro m cyclosporin A. Among the cholinergic
properties studied, choline uptake was specifically inhibited by cyclosporin A
to a maximum of 40%. Cyclosporin A decreased the rate of choline transport but
not the binding of the non-transportable choline analogue hemicholinium-3,
indicating that the number of membrane transporters was not affected. Through
the use of two other immunosuppressors, FK506, which also inhibits calcineurin,
and rapamycin, which does not, two different mechanisms of choline uptake
inhibition were uncovered. FK506 inhibited the rate of choline transport,
whereas rapamycin diminished the affinity for choline. The Torpedo homologue of
the high affinity choline transporter CHT1 was cloned and its activity was
reconstituted in Xenopus oocytes. Choline uptake by oocytes expressing tCHT1 was
inhibited by all three immunosuppressors and also by microinjection of the
specific calcineurin autoinhibitory domain A457-481, indicating that the
phosphatase calcineurin regulates CHT1 activity and could be the common target
of cyclosporin and FK506. Rapamycin, which changed the affinity of the
transporter, may have acted through an immunophilin on the isomerization of
critical prolines that are found in the tCHT1 sequence. The sensor histidine kinase A (KinA) from Bacillus subtilis triggers a
phosphorelay that activates sporulation. The antikinase KipI prevents
sporulation by binding KinA and inhibiting the autophosphorylation reaction.
Using neutron contrast variation, mutagenesis, and fluorescence data, we show
that two KipI monomers bind via their C-domains at a conserved proline in the
KinA dimerization and histidine-phosphotransfer (DHp) domain. Our crystal
structure of the KipI C-domain reveals the binding motif has a distinctive
hydrophobic groove formed by a five-stranded antiparallel beta-sheet; a
characteristic of the cyclophilin family of proteins that bind prolines and
often act as cis-trans peptidyl-prolyl isomerases. We propose that the DHp
domain of KinA transmits conformational signals to regulate kinase activity via
this proline-mediated interaction. Given that both KinA and KipI homologues are
widespread in the bacterial kingdom, this mechanism has broad significance in
bacterial signal transduction. The cyclophilins are widely expressed enzymes that catalyze the interconversion
of the cis and trans peptide bonds of prolines. The immunosuppressive natural
products cyclosporine A and sanglifehrin A inhibit the enzymatic activity of the
cyclophilins. Chemical modification of both the cyclosporine and sanglifehrin
scaffolds has produced many analogues that inhibit cyclophilins in vitro but
have reduced immunosuppressive properties. Three nonimmunosuppressive
cyclophilin inhibitors (alisporivir, SCY-635, and NIM811) have demonstrated
clinical efficacy for the treatment of hepatitis C infection. Additional
candidates are in various stages of preclinical development for the treatment of
hepatitis C or myocardial reperfusion injury. Recent publications suggest that
cyclophilin inhibitors may have utility for the treatment of diverse viral
infections, inflammatory indications, and cancer. In this review, we document
the structure-activity relationships of the nonimmunosuppressive cyclosporins
and sanglifehrins in clinical and preclinical development. Aspects of the
pharmacokinetic behavior and chemical biology of these drug candidates are also
described. Cyclophilins are ubiquitously expressed proteins that bind to prolines and can
catalyse cis/trans isomerization of proline residues. There are 17 annotated
members of the cyclophilin family in humans, ubiquitously expressed and
localized variously to the cytoplasm, nucleus or mitochondria. Surprisingly, all
eight of the nuclear localized cyclophilins are found associated with
spliceosomal complexes. However, their particular functions within this context
are unknown. We have therefore adapted three established assays for in vitro
pre-mRNA splicing to probe the functional roles of nuclear cyclophilins in the
context of the human spliceosome. We find that four of the eight
spliceosom-associated cyclophilins exert strong effects on splicing in vitro.
These effects are dose-dependent and, remarkably, uniquely characteristic of
each cyclophilin. Using both qualitative and quantitative means, we show that at
least half of the nuclear cyclophilins can act as regulatory factors of
spliceosome function in vitro. The present work provides the first quantifiable
evidence that nuclear cyclophilins are splicing factors and provides a novel
approach for future work into small molecule-based modulation of pre-mRNA
splicing. |
Can a given genotype exhibit opposite fitness effects (beneficial and detrimental) within the same environment? | A given genotype can be either beneficial or detrimental, even deleterious, depending on the environment in which an organism lives. This is known as antagonistic pleiotropy. Antagonistic pleiotropy can operate even within the same environment. For example, in Escherichia coli, certain mutations can exhibit beneficial, deleterious or neutral fitness effects at different growth rates. Also, antagonistic pleiotropy is involved in the evolution of ageing, since a certain genotype may affect late- and early-life fitness in opposite directions. | Two genetic models exist to explain the evolution of ageing - mutation
accumulation (MA) and antagonistic pleiotropy (AP). Under MA, a reduced
intensity of selection with age results in accumulation of late-acting
deleterious mutations. Under AP, late-acting deleterious mutations accumulate
because they confer beneficial effects early in life. Recent studies suggest
that the mitochondrial genome is a major player in ageing. It therefore seems
plausible that the MA and AP models will be relevant to genomes within the
cytoplasm. This possibility has not been considered previously. We explore
whether patterns of covariation between fitness and ageing across 25 cytoplasmic
lines, sampled from a population of Drosophila melanogaster, are consistent with
the genetic associations predicted under MA or AP. We find negative covariation
for fitness and the rate of ageing, and positive covariation for fitness and
lifespan. Notably, the direction of these associations is opposite to that
typically predicted under AP. |
Has the protein SETMAR (Metnase) a transposase domain? | Yes, the protein SETMAR (Metnase) has a transposase domain. | The molecular mechanism by which foreign DNA integrates into the human genome is
poorly understood yet critical to many disease processes, including retroviral
infection and carcinogenesis, and to gene therapy. We hypothesized that the
mechanism of genomic integration may be similar to transposition in lower
organisms. We identified a protein, termed Metnase, that has a SET domain and a
transposase/nuclease domain. Metnase methylates histone H3 lysines 4 and 36,
which are associated with open chromatin. Metnase increases resistance to
ionizing radiation and increases nonhomologous end-joining repair of DNA
doublestrand breaks. Most significantly, Metnase promotes integration of
exogenous DNA into the genomes of host cells. Therefore, Metnase is a
nonhomologous end-joining repair protein that regulates genomic integration of
exogenous DNA and establishes a relationship among histone modification, DNA
repair, and integration. The data suggest a model wherein Metnase promotes
integration of exogenous DNA by opening chromatin and facilitating joining of
DNA ends. This study demonstrates that eukaryotic transposase domains can have
important cell functions beyond transposition of genetic elements. The emergence of new genes and functions is of central importance to the
evolution of species. The contribution of various types of duplications to
genetic innovation has been extensively investigated. Less understood is the
creation of new genes by recycling of coding material from selfish mobile
genetic elements. To investigate this process, we reconstructed the evolutionary
history of SETMAR, a new primate chimeric gene resulting from fusion of a SET
histone methyltransferase gene to the transposase gene of a mobile element. We
show that the transposase gene was recruited as part of SETMAR 40-58 million
years ago, after the insertion of an Hsmar1 transposon downstream of a
preexisting SET gene, followed by the de novo exonization of previously
noncoding sequence and the creation of a new intron. The original structure of
the fusion gene is conserved in all anthropoid lineages, but only the N-terminal
half of the transposase is evolving under strong purifying selection. In vitro
assays show that this region contains a DNA-binding domain that has preserved
its ancestral binding specificity for a 19-bp motif located within the
terminal-inverted repeats of Hsmar1 transposons and their derivatives. The
presence of these transposons in the human genome constitutes a potential
reservoir of approximately 1,500 perfect or nearly perfect SETMAR-binding sites.
Our results not only provide insight into the conditions required for a
successful gene fusion, but they also suggest a mechanism by which the circuitry
underlying complex regulatory networks may be rapidly established. Transposons have contributed protein coding sequences to a unexpectedly large
number of human genes. Except for the V(D)J recombinase and telomerase, all
remain of unknown function. Here we investigate the activity of the human SETMAR
protein, a highly expressed fusion between a histone H3 methylase and a mariner
family transposase. Although SETMAR has demonstrated methylase activity and a
DNA repair phenotype, its mode of action and the role of the transposase domain
remain obscure. As a starting point to address this problem, we have dissected
the activity of the transposase domain in the context of the full-length protein
and the isolated transposase domain. Complete transposition of an engineered
Hsmar1 transposon by the transposase domain was detected, although the extent of
the reaction was limited by a severe defect for cleavage at the 3' ends of the
element. Despite this problem, SETMAR retains robust activity for the other
stages of the Hsmar1 transposition reaction, namely, site-specific DNA binding
to the transposon ends, assembly of a paired-ends complex, cleavage of the 5'
end of the element in Mn(2+), and integration at a TA dinucleotide target site.
SETMAR is unlikely to catalyze transposition in the human genome, although the
nicking activity may have a role in the DNA repair phenotype. The key activity
for the mariner domain is therefore the robust DNA-binding and looping activity
which has a high potential for targeting the histone methylase domain to the
many thousands of specific binding sites in the human genome provided by copies
of the Hsmar1 transposon. Metnase (SETMAR) is a SET and transposase fusion protein that promotes in vivo
end joining activity and mediates genomic integration of foreign DNA. Recent
studies showed that Metnase retained most of the transposase activities,
including 5'-terminal inverted repeat (TIR)-specific binding and assembly of a
paired end complex, and cleavage of the 5'-end of the TIR element. Here we show
that R432 within the helix-turn-helix motif is critical for sequence-specific
recognition, as the R432A mutation abolishes its TIR-specific DNA binding
activity. Metnase possesses a unique DNA nicking and/or endonuclease activity
that mediates cleavage of duplex DNA in the absence of the TIR sequence. While
the HTH motif is essential for the Metnase-TIR interaction, it is not required
for its DNA cleavage activity. The DDE-like motif is crucial for its DNA
cleavage action as a point mutation at this motif (D483A) abolished its DNA
cleavage activity. Together, our results suggest that Metnase's DNA cleavage
activity, unlike those of other eukaryotic transposases, is not coupled to its
sequence-specific DNA binding. Metnase, also known as SETMAR, is a SET and transposase fusion protein with an
undefined role in mammalian DNA repair. The SET domain is responsible for
histone lysine methyltransferase activity at histone 3 K4 and K36, whereas the
transposase domain possesses 5'-terminal inverted repeat (TIR)-specific DNA
binding, DNA looping, and DNA cleavage activities. Although the transposase
domain is essential for Metnase function in DNA repair, it is not clear how a
protein with sequence-specific DNA binding activity plays a role in DNA repair.
Here, we show that human homolog of the ScPSO4/PRP19 (hPso4) forms a stable
complex with Metnase on both TIR and non-TIR DNA. The transposase domain
essential for Metnase-TIR interaction is not sufficient for its interaction with
non-TIR DNA in the presence of hPso4. In vivo, hPso4 is induced and co-localized
with Metnase following ionizing radiation treatment. Cells treated with
hPso4-siRNA failed to show Metnase localization at DSB sites and
Metnase-mediated stimulation of DNA end joining coupled to genomic integration,
suggesting that hPso4 is necessary to bring Metnase to the DSB sites for its
function(s) in DNA repair. Transposase domain proteins mediate DNA movement from one location in the genome
to another in lower organisms. However, in human cells such DNA mobility would
be deleterious, and therefore the vast majority of transposase-related sequences
in humans are pseudogenes. We recently isolated and characterized a SET and
transposase domain protein termed Metnase that promotes DNA double-strand break
(DSB) repair by non-homologous end-joining (NHEJ). Both the SET and transposase
domain were required for its NHEJ activity. In this study we found that Metnase
interacts with DNA Ligase IV, an important component of the classical NHEJ
pathway. We investigated whether Metnase had structural requirements of the free
DNA ends for NHEJ repair, and found that Metnase assists in joining all types of
free DNA ends equally well. Metnase also prevents long deletions from processing
of the free DNA ends, and improves the accuracy of NHEJ. Metnase levels
correlate with the speed of disappearance of gamma-H2Ax sites after ionizing
radiation. However, Metnase has little effect on homologous recombination repair
of a single DSB. Altogether, these results fit a model where Metnase plays a
role in the fate of free DNA ends during NHEJ repair of DSBs. Metnase is a human SET and transposase domain protein that methylates histone H3
and promotes DNA double-strand break repair. We now show that Metnase physically
interacts and co-localizes with Topoisomerase IIalpha (Topo IIalpha), the key
chromosome decatenating enzyme. Metnase promotes progression through
decatenation and increases resistance to the Topo IIalpha inhibitors ICRF-193
and VP-16. Purified Metnase greatly enhanced Topo IIalpha decatenation of
kinetoplast DNA to relaxed circular forms. Nuclear extracts containing Metnase
decatenated kDNA more rapidly than those without Metnase, and neutralizing
anti-sera against Metnase reversed that enhancement of decatenation. Metnase
automethylates at K485, and the presence of a methyl donor blocked the
enhancement of Topo IIalpha decatenation by Metnase, implying an internal
regulatory inhibition. Thus, Metnase enhances Topo IIalpha decatenation, and
this activity is repressed by automethylation. These results suggest that cancer
cells could subvert Metnase to mediate clinically relevant resistance to Topo
IIalpha inhibitors. After DNA replication, sister chromatids must be untangled, or decatenated,
before mitosis so that chromatids do not tear during anaphase. Topoisomerase
IIalpha (Topo IIalpha) is the major decatenating enzyme. Topo IIalpha inhibitors
prevent decatenation, causing cells to arrest during mitosis. Here we report
that acute myeloid leukemia cells fail to arrest at the mitotic decatenation
checkpoint, and their progression through this checkpoint is regulated by the
DNA repair component Metnase (also termed SETMAR). Metnase contains a SET
histone methylase and transposase nuclease domain, and is a component of the
nonhomologous end-joining DNA double-strand break repair pathway. Metnase
interacts with Topo IIalpha and enhances its decatenation activity. Here we show
that multiple types of acute leukemia cells have an attenuated mitotic arrest
when decatenation is inhibited and that in an acute myeloid leukemia (AML) cell
line this is mediated by Metnase. Of further importance, Metnase permits
continued proliferation of these AML cells even in the presence of the clinical
Topo IIalpha inhibitor VP-16. In vitro, purified Metnase prevents VP-16
inhibition of Topo IIalpha decatenation of tangled DNA. Thus, Metnase expression
levels may predict AML resistance to Topo IIalpha inhibitors, and Metnase is a
potential therapeutic target for small molecule interference. Although the human genome is littered with sequences derived from the Hsmar1
transposon, the only intact Hsmar1 transposase gene exists within a chimeric
SET-transposase fusion protein referred to as Metnase or SETMAR. Metnase retains
many of the transposase activities including terminal inverted repeat (TIR)
specific DNA-binding activity, DNA cleavage activity, albeit uncoupled from
TIR-specific binding, and the ability to form a synaptic complex. However,
Metnase has evolved as a DNA repair protein that is specifically involved in
nonhomologous end joining. Here, we present two crystal structures of the
transposase catalytic domain of Metnase revealing a dimeric enzyme with unusual
active site plasticity that may be involved in modulating metal binding. We show
through characterization of a dimerization mutant, F460K, that the dimeric form
of the enzyme is required for its DNA cleavage, DNA-binding, and nonhomologous
end joining activities. Of significance is the conservation of F460 along with
residues that we propose may be involved in the modulation of metal binding in
both the predicted ancestral Hsmar1 transposase sequence as well as in the
modern enzyme. The Metnase transposase has been remarkably conserved through
evolution; however, there is a clustering of substitutions located in alpha
helices 4 and 5 within the putative DNA-binding site, consistent with loss of
transposition specific DNA cleavage activity and acquisition of DNA repair
specific cleavage activity. Chromosomal translocations are common in leukemia, but little is known about
their mechanism. Metnase (also termed SETMAR) is a fusion of a histone methylase
and transposase protein that arose specifically in primates. Transposases were
thought to be extinct in primates because they would mediate deleterious DNA
movement. In primates, Metnase interacts with DNA Ligase IV (Lig IV) and
promotes nonhomologous end-joining (NHEJ) DNA repair. We show here that the
primate-specific protein Metnase can also enhance NHEJ in murine cells and can
also interact with murine Lig IV, indicating that it integrated into the
preexisting NHEJ pathway after its development in primates. Significantly,
expressing Metnase in murine cells significantly reduces chromosomal
translocations. We propose that the fusion of the histone methylase SET domain
and the transposase domain in the anthropoid lineage to form primate Metnase
promotes accurate intrachromosomal NHEJ and thereby suppresses interchromosomal
translocations. Metnase may have been selected for because it has a function
opposing transposases and may thus play a key role in suppressing translocations
that underlie oncogenicity. Chk1 both arrests replication forks and enhances repair of DNA damage by
phosphorylating downstream effectors. Although there has been a concerted effort
to identify effectors of Chk1 activity, underlying mechanisms of effector action
are still being identified. Metnase (also called SETMAR) is a SET and
transposase domain protein that promotes both DNA double-strand break (DSB)
repair and restart of stalled replication forks. In this study, we show that
Metnase is phosphorylated only on Ser495 (S495) in vivo in response to DNA
damage by ionizing radiation. Chk1 is the major mediator of this phosphorylation
event. We had previously shown that wild-type (wt) Metnase associates with
chromatin near DSBs and methylates histone H3 Lys36. Here we show that a
Ser495Ala (S495A) Metnase mutant, which is not phosphorylated by Chk1, is
defective in DSB-induced chromatin association. The S495A mutant also fails to
enhance repair of an induced DSB when compared with wt Metnase. Interestingly,
the S495A mutant demonstrated increased restart of stalled replication forks
compared with wt Metnase. Thus, phosphorylation of Metnase S495 differentiates
between these two functions, enhancing DSB repair and repressing replication
fork restart. In summary, these data lend insight into the mechanism by which
Chk1 enhances repair of DNA damage while at the same time repressing stalled
replication fork restart. Previous studies have shown that the DNA repair component Metnase (SETMAR)
mediates resistance to DNA damaging cancer chemotherapy. Metnase has a nuclease
domain that shares homology with the Transposase family. We therefore virtually
screened the tertiary Metnase structure against the 550,000 compound ChemDiv
library to identify small molecules that might dock in the active site of the
transposase nuclease domain of Metnase. We identified eight compounds as
possible Metnase inhibitors. Interestingly, among these candidate inhibitors
were quinolone antibiotics and HIV integrase inhibitors, which share common
structural features. Previous reports have described possible activity of
quinolones as antineoplastic agents. Therefore, we chose the quinolone
ciprofloxacin for further study, based on its wide clinical availability and low
toxicity. We found that ciprofloxacin inhibits the ability of Metnase to cleave
DNA and inhibits Metnase-dependent DNA repair. Ciprofloxacin on its own did not
induce DNA damage, but it did reduce repair of chemotherapy-induced DNA damage.
Ciprofloxacin increased the sensitivity of cancer cell lines and a xenograft
tumor model to clinically relevant chemotherapy. These studies provide a
mechanism for the previously postulated antineoplastic activity of quinolones,
and suggest that ciprofloxacin might be a simple yet effective adjunct to cancer
chemotherapy. |