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)

A circulating form of the membrane-bound ICAM-1 (CD54), a ligand for lymphocyte function-associated antigen-1 (LFA-1), has recently been identified in normal human serum. In this study, serum levels of soluble ICAM-1 (sICAM-1) were determined by sandwich ELISA both in normal healthy individuals of both sexes and in subjects with autoimmune liver diseases. Patients with primary biliary cirrhosis (PBC), primary sclerosing cholangitis and chronic active hepatitis (autoimmune) showed significant elevations in sICAM-1 compared with normal healthy subjects. The median level in PBC was approximately seven-fold above normal. Significant elevations in sICAM-1 were also detected, however, in patients with inactive alcoholic cirrhosis, suggesting that impaired liver clearance might at least in part account for the increased serum levels seen in patients with autoimmune liver disease. In patients with PBC, sICAM-1 levels were related to summary assessment of disease severity (Child-Pugh classification) and correlated significantly with serum biochemical indices of liver function, including measures both of cholestasis and liver cell injury. In contrast, serum levels of E-selectin did not differ significantly from healthy controls. Although it has been suggested that peripheral blood mononuclear cells (PBMC) may be a source of sICAM-1, investigation of ICAM-1 gene expression by reverse transcriptase polymerase chain reaction revealed similar basal levels of ICAM-1 message in PBMC of normal individuals and those with active PBC. This suggests that PBMC may not be a significant source of sICAM-1 in this disease. Similar increases in ICAM-1 mRNA expression were found in cultured, concanavalin A (Con A)-stimulated lymphocytes of both PBC patients and controls. Significantly, stimulation of cultured, normal human hepatocytes with proinflammatory cytokines and endotoxin induced cell surface expression of ICAM-1 and the secretion/shedding of sICAM-1 into the hepatocyte culture medium. This new finding suggests that hepatocytes may be an important source of sICAM-1 in autoimmune and other chronic liver diseases. The possible role of sICAM-1 in inflammatory disorders remains to be determined.
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PMID:Circulating intercellular adhesion molecule-1 (ICAM-1) in autoimmune liver disease and evidence for the production of ICAM-1 by cytokine-stimulated human hepatocytes. 790 46

The aim was to explore whether biliary epithelial cells show muscarinic acetylcholine receptors and to investigate their role in ductular bile formation. In both, isolated rat biliary epithelial cells and Mz-Cha-1 cells, a biliary epithelial cell line, binding of [3H]N-methyl-scopolamine occurred with 0.718 +/- 0.08 and 0.482 +/- 0.05 fmol per 10(6) cells, respectively. To characterize the involved second messenger, intracellular Ca2+ levels were monitored by confocal microscopy. Stimulation of biliary epithelial cells with carbachol produced an increase in free cytosolic Ca2+ levels that declined to baseline values describing a sinusoidal oscillation curve. Increasing concentrations of the agonist decreased latency of the response and increased oscillation frequency. Similar results were obtained in Mz-Cha-1 cells. The intracellular Ca2+ originated from IP3 sensitive intracellular stores and from the extracellular medium. The Ca2+ response could partially be blocked by atropine and completely by pirenzepine, a specific muscarinic receptor-type M1 antagonist. The presence of M1 receptor messenger RNA (mRNA) in biliary epithelial cells was confirmed by reverse transcriptase polymerase chain reaction. In the isolated perfused guinea pig liver, a model with high ductular bile flow, carbachol induced a dose dependent decrease of bile flow by 79.6% +/- 9.8% at 50 mumol/L carbachol (P < .001), without affecting perfusion pressure or biliary electrolyte concentrations. It is concluded that biliary epithelial cells express muscarinic acetylcholine receptors. Stimulation of this receptor leads to cholestasis. This could be because of changes in peribiliary permeability and/or inhibition of biliary epithelial cell secretory function.
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PMID:Muscarinic acetylcholine receptor stimulation of biliary epithelial cells and its effect on bile secretion in the isolated perfused liver [corrected]. 909 80

Hepatocytes do not express Bcl-2, a repressor of apoptosis. In contrast, cholangiocytes, which are in direct contact with bile, do express Bcl-2. Because cholestasis results in the retention of bile within hepatocytes, we reasoned cholestasis may induce hepatocellular expression of Bcl-2. Thus our aim was to determine whether hepatocytes express Bcl-2 or alter expression of other Bcl-2 family members in cholestasis using the bile duct-ligated (BDL) rat as a model of cholestasis. De novo Bcl-2 expression was observed in hepatocytes of BDL rats assessed by reverse transcriptase-polymerase chain reaction and immunoblot analysis. Immunohistochemistry demonstrated that Bcl-2 expression in hepatocytes was greater in periportal hepatocytes than pericentral hepatocytes. Expression of Bcl-x (an antiapoptotic Bcl-2 family protein) was not altered by bile duct ligation, whereas expression of Bax (a proapoptotic Bcl-2 family protein) increased slightly as determined by Northern and Western blot analyses. Bcl-2-positive hepatocytes isolated from BDL rats were resistant to induction of apoptosis by 50 microM glycochenodeoxycholate. Our results demonstrate, for the first time, expression of Bcl-2 by hepatocytes during cholestasis. We suggest that hepatocellular expression of Bcl-2 during cholestasis is an adaptive phenomenon to resist apoptosis by toxic bile salts.
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PMID:Hepatocytes in the bile duct-ligated rat express Bcl-2. 922 97

Rab3 isotypes are expressed in regulated secretory cells. Here, we report that rab3D is also expressed in rat hepatocytes, classic models for constitutive secretion. Using reverse transcriptase polymerase chain reaction (RT-PCR) with primers specific for rat rab3D, we amplified a 151 base pair rab3D fragment from total RNA extracted from primary cultures of rat hepatocytes. Immunoblot analysis using polyclonal antibodies to peptides representing the N- and C-terminal hypervariable regions of murine rab3D recognized a protein of approximately 25 kd in hepatocyte lysates, hepatic subcellular fractions, and tissue extracts. The distribution of rab3D was primarily cytosolic; however, only membrane-associated rab3D significantly bound guanosine triphosphate (GTP) in overlay assays. Several lines of investigation indicate that rab3D is associated with the transcytotic pathway. First, rab3D was enriched in a crude vesicle carrier fraction (CVCF), which includes transcytotic carriers. Vesicular compartments immunoisolated from the CVCF on magnetic beads coated with anti-rab3D antibody were enriched in the transcytosed form of the polymeric IgA receptor (pIgA-R), but lacked not only the pIgA-R precursor form associated with the secretory pathway, but also a Golgi marker protein. Second, indirect immunofluorescence on frozen liver sections and in polarized cultured hepatocytes localized rab3D-positive sites at or near the apical plasma membrane and to the pericanalicular cytoplasm. Finally, cholestasis induced by bile duct ligation (BDL), a manipulation known to slow transcytosis, caused rab3D to accumulate in the pericanalicular cytoplasm of cholestatic hepatocytes. Our results indicate that rab3D plays a role in the regulation of apically directed transcytosis in rat hepatocytes.
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PMID:Rab3D, a small GTP-binding protein implicated in regulated secretion, is associated with the transcytotic pathway in rat hepatocytes. 1091 42

Lactic acidosis and hepatic steatosis caused by mitochondrial toxicity of nucleoside reverse transcriptase inhibitors (NRTI) is a rare cause of liver disease with a high mortality rate. This report describes a male, HIV-positive patient with a 4-week history of nausea, vomiting and abdominal pain. His medication consisted of prednisone 5 mg od (because of auto-immune thrombocytopenia), didanosine (for 2 years) and stavudine (for 3 months). Laboratory studies showed cholestasis and elevation of aminotransferases. Lactic level was not measured. Liver biopsy revealed steatosis and cholestatic hepatitis. In the absence of other causes of liver disease a probable diagnosis of stavudine-induced hepatic toxicity was made. After discontinuation of NRTI, he recovered completely. Because lactic acidosis had not been confirmed, stavudine was restarted and within 1 week the lactate level increased significantly. Therefore stavudine was discontinued again. One year later the patient is doing well on a double protease inhibitor regimen. In conclusion, clinicians treating patients with NRTI should be aware of the risk of lactic acidosis and hepatic steatosis. When this is suspected, all NRTI must be stopped. The diagnosis can be made when elevated lactate levels and hepatic steatosis are present in the absence of other causes of liver disease.
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PMID:Hepatic steatosis and lactic acidosis caused by stavudine in an HIV-infected patient. 1106 65

Cholestasis is associated with retention of potentially toxic bile acids and profound cytoskeletal alterations of hepatocytes. Given the well-established cytoprotective role of hepatocyte keratins this study aimed to determine the effects of cholestasis on the cytokeratin (CK) intermediate filament network in mouse liver. Mice were subjected to common bile duct ligation or sham operation. Mice were also fed a cholic acid or ursodeoxycholic acid (UDCA)-supplemented diet (0.1%, 0.5%, and 1%) or control diet for 7 days. CK 8 and CK 18 expression was studied by competitive reverse transcriptase-polymerase chain reaction, in situ hybridization, Western blot analysis, and immunofluorescence microscopy. Common bile duct ligation and cholic acid feeding significantly stimulated CK 8 and CK 18 mRNA and protein levels compared to controls, whereas UDCA had no effect. CK overexpression was accompanied by pronounced phosphorylation. Our results show that potentially toxic bile acids induce hepatocytic CK 8 and CK 18 expression and phosphorylation whereas nontoxic UDCA has no effect on CKs. Thus, increased hepatocellular CK expression and phosphorylation in cholestasis may be caused by retention of toxic bile acids and reflect a hepatocellular stress response with potential beneficial effects.
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PMID:Cytokeratins as targets for bile acid-induced toxicity. 1183 69

The diagnosis of hepatitis C infection in the setting of liver transplantation in based on several variables, including histopathologic changes and the presence of viral RNA in the serum. It may be difficult to differentiate acute rejection from recurrent viral hepatitis in liver biopsies from patients who received liver transplants for end-stage hepatitis C infection. The purpose of this study was to analyzed the histologic features, viral load, and in situ viral detection in 37 biopsies taken from 25 people who underwent liver transplant for end-stage hepatitis C infection. Hepatitis C antigen was detected in 9 of 37 (24%) biopsies using immunohistochemistry; the detection rate increased to 19 of 37 (51%) using reverse transcriptase in situ polymerase chain reaction for viral cDNA. Hepatitis E cDNA was detected in 4 of 37 (11%) cases, hepatitis G cDNA in 3 of 37 (8%) cases and in 1 case cytomegalovirus was noted; with several cases of dual infection, 22 of 37 (59%) of tissues were positive for at least 1 virus. Histologic parameters that significantly correlated with in situ viral detection included single-cell hepatocyte necrosis (P = 0.02), bile duct damage (P = 0.03), lymphoid aggregates (P = 0.02), and cholestasis (P = 0.01). Further, a serum viral load exceeding 1,250,000 viral equivalents/ml was strongly correlated with in situ viral detection in the liver (P = 0.01). We conclude that certain histologic features and an increased viral load are highly correlated with the in situ detection of viral RNA in the liver, which is consistent with recurrent viral infection.
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PMID:Correlation of histology, viral load, and in situ viral detection in hepatic biopsies from patients with liver transplants secondary to hepatitis C infection. 1197 67

Chronic cholestasis is associated with retention of bile acids and profound cytoskeletal alterations in hepatocytes including Mallory body (MB) formation. The mechanisms responsible for MB formation in cholestatic liver diseases are unclear. The aim of our study was to determine the relevance of cholestasis and bile acids for MB formation. For this purpose mice received a 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC)-supplemented diet for 2.5 months to induce MB formation. After recovery from DDC intoxication for 4 weeks followed by disappearance of MBs, these drug-primed mice were subjected to DDC refeeding, common bile duct ligation (CBDL), and feeding of a cholic acid (CA)-supplemented diet for 7 days, respectively. Cytokeratin (CK) 8 and CK 18 expression was studied by competitive reverse transcriptase-polymerase chain reaction and Western blot analysis. Cytoskeletal alterations of hepatocytes and MB formation were monitored by immunofluorescence microscopy and immunohistochemistry using CK-, ubiquitin-, and MB-specific antibodies. Like DDC refeeding, both CBDL and CA feeding of drug-primed mice significantly increased CK 8 and CK 18 mRNA and protein levels (with excess of CK 8) and resulted in ubiquitination and abnormal phosphorylation of CKs. Furthermore, CBDL and CA feeding resulted in rapid neoformation of MBs in drug-primed mice. It is concluded that MB formation in cholestatic liver diseases may be triggered by the action of potentially toxic bile acids.
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PMID:Bile acid-induced Mallory body formation in drug-primed mouse liver. 1246 18

Mrp3(Abcc3) is markedly induced following bile duct ligation (BDL) in the rat and in some human cholestatic liver diseases and is believed to ameliorate liver injury in this setting. Recently, the orphan nuclear receptor fetoprotein transcription factor/cholesterol-7alpha-hydroxylase promoter factor (CPF/FTF/Lrh-1) has been shown to activate Mrp3 expression. However, whether inflammatory cytokines or elevated bile acid levels increased Lrh-1/Mrp3 expression in obstructive cholestasis was not known. We hypothesized that induction of Mrp3 would be associated with Lrh-1 up-regulation and would require intact cytokine signaling. Male tumor necrosis factor (Tnf) receptor I (Tnfr-/-) mice and C57BLJ wild type (WT) controls were subjected to sham surgery or bile duct ligation. HepG2 cells were treated with bile acids or cytokines. Immunoblot assay and real time reverse transcriptase-PCR were used to determine expression of MRP3/Mrp3, CPF/Lrh-1, Mrp2, and Bsep. CPF/Lrh-1 DNA binding to the MRP3/Mrp3 promoter was assessed using electrophoretic mobility shift assay, and promoter activity was determined by luciferase assay. Total bile acids and lactate dehydrogenase were measured using colorimetric assays, and cytokine abundance was determined by enzyme-linked immunosorbent assay. Lrh-1 and Mrp3 were significantly induced after BDL in WT but not Tnfr-/- mice. This was associated with more severe hepatocellular necrosis in Tnfr-/- mice. Lrh-1 binding to the Mrp3 promoter increased after BDL in WT but not in Tnfr-/- mice. Tnfalpha treatment of HepG2 cells also up-regulated CPF and MRP3, increased CPF binding to the MRP3 promoter, and up-regulated MRP3 promoter activity. These results indicate that induction of Mrp3 after BDL is due to Tnfalpha-dependent up-regulation of Lrh-1. They provide strong evidence that induction of Mrp3 plays a significant role in hepatocyte protection during obstructive cholestasis.
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PMID:Tumor necrosis factor alpha-dependent up-regulation of Lrh-1 and Mrp3(Abcc3) reduces liver injury in obstructive cholestasis. 1283 54

The liver plays a major role in biotransformation and elimination of various therapeutic agents and xenobiotics, many of which are organic cations and substrates of the organic cation transporter 1 (Oct1, Slc22a1). Oct1 is expressed at the basolateral membranes of hepatocytes and proximal renal tubules. Although Oct1 is the major uptake mechanism in hepatocytes for many pharmaceutical compounds, little is known about the effects of liver injury on this process. Our aim was to investigate the effects of obstructive cholestasis on Oct1 expression and function in liver and kidney. The effects of bile duct ligation (BDL) on Oct1 protein, messenger RNA (mRNA) expression, and tissue localization were determined in rat liver and kidney with Western analysis, real-time reverse transcriptase-mediated polymerase chain reaction (RT-PCR), and immunofluorescence. To assess Oct1 function, the model substrate tetraethylammonium ([(14)C]TEA) was administered intravenously to BDL and control rats and distribution of radioactivity was determined. Oct1 protein significantly decreased in cholestatic livers to 42.1 +/- 17.7% (P <.001), 15.5 +/- 4.7% (P <.05), and 8.6 +/- 2.7% (P <.05) of controls after 3, 7, and 14 days, respectively, but not in kidneys. Hepatic Oct1 mRNA decreased to 77.2 +/- 12.7%, 40.7 +/- 8.1% (P <.05), and 50.3 +/- 7.5% (P <.05) 3, 7, and 14 days after BDL, respectively. Tissue immunofluorescence corroborated these data. Hepatic accumulation of [(14)C]TEA in 14-day BDL rats was reduced to 29.6 +/- 10.9% of controls (P <.0005). In conclusion, obstructive cholestasis down-regulates Oct1 and impairs Oct1-mediated uptake in rat liver, suggesting that hepatic uptake of small cationic drugs may be impaired in cholestatic liver injury.
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PMID:Down-regulation of the organic cation transporter 1 of rat liver in obstructive cholestasis. 1512 67


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