Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Little is known about treatment of hepatitis C virus (HCV) infection in "other groups" than the general population, namely patients with hematologic or renal disorders and patients with human immune deficiency (HIV) co-infection. The aim was to better define HCV therapies in these groups. We analyzed the medical literature focusing on treatment of HCV infection in other populations to suggest conclusions about indications based on tolerance and efficacy. As in the general population, the decision to treat should be based mainly on liver pathology, and to a lesser extent on virologic profiles (genotype, quantitative viremia). Hemophilia does not modify therapeutic strategies which combine interferon-alpha and ribavirin. Similar combinations should be discussed in patients with inherited hemoglobin disorders but iron overload (secondary hemochromatosis) associated with multiple transfusions may decrease the potential efficacy of interferon-alpha and chronic anemia may limit the use of ribavirin. In hemodialyzed patients, therapy by interferon-alpha is feasible with 3 MU subcutaneously after each hemodialysis three times weekly for 6-12 months. Virologic results are at least similar to those obtained in the general population with frequent pathological improvement. Combinations are not possible because ribavirin is contraindicated for pharmacokinetic reasons. In kidney recipients, interferon-alpha is deleterious and inefficient; ribavirin monotherapy has a potential interest which remains to be evaluated. In HIV co-infected patients, treatment is mandatory given the high rate of cirrhosis and the improved survival related to multiple anti-HIV therapies (which have no clear efficacy for quantitative HCV viremia). Due to the limited efficacy of interferon-alpha monotherapy, the combination of interferon-alpha and ribavirin appears to be the logical treatment. An important point is the in vitro inhibition of phosphorylation by ribavirin of HIV reverse transcriptase inhibitors which has to be analyzed in vivo before the combination can be recommended. On the basis of the results of liver biopsy, antiviral treatments may be proposed for HCV-infected patients with hematologic or renal disorders as well as for HIV co-infected patients. The choice of therapy (monotherapy or combined therapies) should be based on the clinical situation (contraindicated with chronic anemia or renal failure, for example) and its duration on the virologic factors of response as in the general population.
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PMID:Treatment of chronic hepatitis C in special groups. 1062 89

We describe an autopsy case of primary hepatic leiomyosarcoma in a 68-year-old man with hepatitis C virus-related liver cirrhosis. The patient, who had a history of acute hepatitis 20 years previously, died of a ruptured hepatic tumor. At autopsy, a well-circumscribed 14 x 16 x 15 cm tumor replaced the medial site of the right hepatic lobe with multiple intrahepatic and distant metastases. Histologically the tumor, which had extensive central necrosis, consisted predominantly of well or moderately differentiated spindle-shaped cells, which were positive for smooth muscle actin and vimentin on immunohistochemical staining. In addition, clusters of markedly atypical cells and myxoid change of the matrix were discretely found in the focal and small areas of the tumor. These findings indicated that many sections were necessary for the histologically accurate estimation of primary hepatic smooth muscle tumor. The histological examination of a non-tumorous lesion showed liver cirrhosis. Hepatitis C virus was detected in the cytoplasm of cirrhotic hepatocytes by immunohistochemistry and reverse transcriptase-polymerase chain reaction, but not in the tumor cells. This suggested that the virus was not directly involved in the development of primary hepatic leiomyosarcoma.
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PMID:Primary hepatic leiomyosarcoma in a patient with hepatitis C virus-related liver cirrhosis. 1069 76

Thirty-nine patients with chronic liver disease who were being evaluated in a U.S. military treatment facility were tested for antibody to hepatitis C virus (anti-HCV) and for hepatitis G virus (HGV) RNA by reverse transcriptase-polymerase chain reaction. Serum samples from 20 patients (51%) were positive for anti-HCV by immunoblot assay. HGV RNA was found in the sera of only two patients, both of whom were also positive for anti-HCV. HGV appears to have a limited role in causing chronic liver disease in this population of military patients, many of whom had traveled outside the United States. However, HCV infection was commonly associated with chronic hepatitis and cirrhosis, as in civilian patients.
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PMID:Chronic liver disease among U.S. military patients: the role of hepatitis C and G virus infection. 1074 Oct 77

The therapeutic goals in chronic hepatitis B are to prevent or decrease cirrhosis and hepatocellular carcinoma in patients with pre-cirrhotic or early cirrhotic disease and to stabilise patients with end-stage cirrhosis. Lamivudine is an oral nucleoside analogue that suppresses hepatitis B virus (HBV) replication, and so may achieve both these treatment objectives. The active 5'-triphosphate metabolite of lamivudine has two modes of viral suppression. First, it mimics deoxycytidine triphosphate and is incorporated into newly synthesised HBV DNA to cause chain termination. Second, it demonstrates competitive inhibition of viral DNA-dependent and RNA-dependent DNA polymerase activity (i.e., reverse transcriptase activity). Lamivudine may, therefore, act at four possible stages during HBV replication: reverse transcription of pre-genomic mRNA into nascent minus-strand DNA; formation of plus strand DNA from nascent minus-strand DNA; completion of double-stranded DNA; and formation of covalently closed circular DNA. In clinical studies, lamivudine therapy reduced serum HBV DNA and this was associated with significant improvements in liver histology and significant and sustained enhancement of the proliferative CD4-mediated response to HBeAg and hepatitis B core antigen (HBcAg), and an increased frequency of HBeAg-specific T cells. HBV DNA concentrations often returned to pre-treatment values when therapy ended prior to the loss of hepatitis B e antigen (HBeAg). Although the emergence of HBV variants with a mutation in the YMDD (tyrosine-methionine-aspartate-aspartate) motif has been observed, such variants show reduced susceptibility to lamivudine due to limited replication competence, and their emergence is not a signal to cease lamivudine therapy. In conclusion, viral suppression with lamivudine offers a means of disease improvement and immunological control in chronic hepatitis B.
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PMID:Profound suppression of hepatitis B virus replication with lamivudine. 1086 48

Currently seven viruses, A, B, C, D, E, G and transfusion transmitted virus (TTV), are recognised in the hepatitis virus alphabet. Hepatitis G virus and TTV probably do not cause liver disease in humans. Hepatitis A and E usually cause a self-limiting hepatitis followed by complete recovery but occasionally cause fulminant hepatic failure. Hepatitis B and C are major public health problems worldwide due to their sequelae of chronic hepatitis, cirrhosis and primary liver cancer. Chronic hepatitis C is a particular health issue for Western Europe already, accounting for 40% of end-stage cirrhosis and 30% of liver transplants. The contribution of hepatitis C to chronic liver disease is predicted to rise in the future. Vaccines can prevent hepatitis A and B. Interferon alpha is effective treatment in 25-30% of patients with chronic hepatitis B or C. The prospects for treating chronic hepatitis B have been improved by the introduction of reverse transcriptase inhibitors. Lamivudine is the first drug of this class to be licensed. The optimal use of these new drugs is currently being studied. The success rate for treating chronic hepatitis C can be raised to about 40% with combination therapy of interferon alpha and ribavirin. A large research effort to discover new antiviral agents against hepatitis C is already giving the prospect of more effective therapies in the next few years.
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PMID:Virus hepatitis update. 1119 85

Treatment of chronic hepatitis B is directed at interrupting the natural history and clinical outcomes of the disease. It needs to take into account the virology and replication cycle of the hepatitis B virus (HBV), and the host immune response to HBV. Long term follow-up of patients treated with interferon supports the paradigm that a sustained, major suppression of HBV replication, particularly that associated with hepatitis B e antigen (HBeAg) seroconversion, interrupts the natural history of hepatitis B. The availability of potent but well tolerated and orally available HBV antivirals, of which lamivudine is the prototype, has allowed clearer treatment objectives to be formulated. These are: temporary or permanent reduction of hepatitis (necroinflammatory) activity, arrest of fibrotic progression, prevention of cirrhosis and liver failure, and prevention of recurrent HBV infection after liver transplantation. Lamivudine has good medium term efficacy in achieving each of these objectives. The only significant problem for the longer term is emergence of antiviral resistance conferred by mutations in the YMDD (tyrosine-methionine-aspartic acid-aspartic acid) motif of the HBV reverse transcriptase. As a result, contentious issues remain about defining when antiviral therapy is indicated, whether to treat for a defined interval or indefinitely, and when to stop treatment if HBeAg seroconversion is not achieved. Some personal views are expressed in this review. Among newer HBV antivirals in clinical studies, adefovir dipivoxil, entecavir and emtricitabine appear to be at least as potent as lamivudine in suppressing HBV replication. Famciclovir appears less potent. In vitro studies show that YMDD mutations confer cross-resistance between lamivudine, emtricitabine and beta-L-Fd4C (L-2',3'-didehydro-dideoxy-5-fluorocytidine). However, adefovir dipivoxil, lobucavir, entecavir, DAPD (beta-D-2,6-diaminopurine dioxolane) and possibly clevudine (L-FMAU) suppress replication of YMDD mutant HBV, as well as wildtype. Preliminary studies indicate clinical efficacy of adefovir dipivoxil once resistance to lamivudine has developed. Immunomodulatory approaches to treatment of chronic hepatitis B are conceptually attractive, but newer agents used to date (thymalfasin, interleukin-12, therapeutic vaccines) have not demonstrated sufficient efficacy for widespread use. The next challenge for HBV treatment is to use antivirals in combination and/or in cyclical therapy to reduce the emergence of drug resistance and increase efficacy, particularly to achieve sustainable post-treatment suppression of hepatitis B.
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PMID:Clinical potential of emerging new agents in hepatitis B. 1108 96

Hepatic stellate cells (HSCs) are responsible for type I collagen deposition in liver fibrosis that leads to cirrhosis. The purpose of this study was to examine potential molecular signals that lead to increased alpha(2)(I) collagen gene expression by acetaldehyde, the primary metabolite of alcohol and malondialdehyde (MDA), a lipid peroxidation product known to be associated with chronic liver injury. MDA and the combination of MDA and acetaldehyde were employed to determine the effect on alpha(2)(I) collagen gene expression as assessed by transient transfection analysis and reverse transcriptase polymerase chain reaction (RT-PCR). Immunoblot and subsequent immunoprecipitation analysis examined stress-activated protein kinase (SAPK) activity. Cotransfection with a dominant negative mutant for c-jun nuclear kinase (dnJNK1) was also employed with the alpha(2)(I) collagen promoter. MDA increased alpha(2)(I) collagen gene expression nearly 2.5- to 3-fold, however there was no synergistic effect of the combination of acetaldehyde and MDA on alpha(2)(I) collagen gene activation and expression. Acetaldehyde, MDA, or both significantly increased JNK activity when compared to untreated stellate cells. The dnJNK1 expression vector abrogated alpha(2)(I) collagen transgene activity. In conclusion, JNK activation appears to be critical in the signaling cascade of oxidative metabolites of chronic alcohol-related liver injury and collagen gene activation.
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PMID:Aldehydes potentiate alpha(2)(I) collagen gene activity by JNK in hepatic stellate cells. 1129 27

p62 is a RNA-binding protein that was isolated by immunoscreening a cDNA expression library with autoantibodies from patients with hepatocellular carcinoma (HCC). This autoantigen binds to mRNA encoding insulin-like growth factor II, which has been found to be overexpressed in HCC and is tumorigenic in transgenic animals. Immunohistochemical analysis of HCC liver showed that 33% (9 of 27) exhibited readily detectable staining of p62 protein in the cytoplasm of all malignant cells in cancer nodules, whereas it was undetectable in adjacent nonmalignant liver cells. In addition one of two patients with cholangiocarcinoma expressed p62 in malignant bile duct epithelial cells. p62 expression was also detected in scattered cells in cirrhotic nodules in contrast to uniform expression in all cells in HCC nodules. In HCC nodules, p62 mRNA was also detected by reverse transcriptase-polymerase chain reaction analysis. Nine normal adult livers did not contain detectable p62 mRNA or p62 protein whereas five fetal livers were all positive for mRNA and protein. The observations show that p62 is developmentally regulated, expressed in fetal, but not in adult liver, and aberrantly expressed in HCC and could be playing a role in abnormal cell proliferation in HCC and cirrhosis by modulating expression of growth factors such as insulin-like growth factor II.
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PMID:Aberrant expression of fetal RNA-binding protein p62 in liver cancer and liver cirrhosis. 1154 87

Hepatitis C virus (HCV) is a major cause of chronic hepatitis with liver-related death occurring in 20-25% of patients who develop cirrhosis. Detection of the virus RNA in liver is difficult since viral expression is very low. In situ polymerase chain reaction (PCR) in situ hybridisation (ISH) was developed for detection and localisation of viral RNA in formalin-fixed, paraffin-embedded liver tissue. Nested PCR technology was adapted for in situ use employing primers derived from the 5' end of the HCV genome. Seventeen liver blocks from known HCV-infected patients were examined. Viral RNA was detected in liver from eleven patients using solution phase reverse transcriptase-PCR. Of these positive samples, ten were positive by the in situ method. Positive signal was detected in the cytoplasm of hepatocytes and mononuclear cells. No Kupffer cell or bile duct epithelial positivity was observed. No positive signal was evident in any of the negative controls. A reliable method is described to demonstrate the presence and localisation of HCV RNA in liver tissue using an in situ PCR-ISH assay and it is believed that this will be a valuable tool for the understanding of HCV replication and pathogenesis.
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PMID:Development of a novel nested in situ PCR-ISH method for detection of hepatitis C virus RNA in liver tissue. 1168 3

Hepatic resection in cirrhotic patients is associated with impaired liver regeneration and poor clinical outcome. Because experimental cirrhosis is associated with hepatic cell hypoxia, we herein investigated whether hypoxia might alter the mechanisms of liver regeneration in the cirrhotic liver. Cirrhosis was induced by diethylnitrosamine in rats. Immunohistochemistry was performed to assess hepatocellular hypoxia and proliferation 24 hours after a two-thirds partial hepatectomy (PH) in cirrhotic and control rats. Cultured hepatocytes and myofibroblastic hepatic stellate cells were submitted to hypoxia using anaerobic jars. Hepatocyte growth factor (HGF) and c-Met expressions were determined by reverse transcriptase-polymerase chain reaction, Northern blot, and Western blot. In control rats, hypoxia was restricted to perivenular hepatocytes, and PH induced a marked increase in hepatocyte proliferation and in liver HGF expression, whereas c-Met expression remained unchanged. In cirrhotic rats, hypoxia was detected virtually in all of the hepatocytes, and PH induced no significant change in hepatocyte proliferation and in liver HGF expression, whereas c-Met expression was decreased as compared to normal livers. In vitro, the expression of HGF in myofibroblastic hepatic stellate cells and of c-Met in hepatocytes underwent a dramatic decrease under hypoxia. Our results suggest that hepatocellular hypoxia causes inhibition of HGF (and of c-Met)-mediated proliferation and thereby might contribute to liver regeneration failure in cirrhotic liver.
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PMID:Hepatocyte growth factor and c-Met inhibition by hepatic cell hypoxia: a potential mechanism for liver regeneration failure in experimental cirrhosis. 1183 82


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