Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.24.3 (collagenase)
 18,340 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The involvement of cytochrome P450 in the liver toxicity of the potent carcinogen, N-nitrosodimethylamine (NDMA) was investigated in hepatocytes isolated from the periportal or perivenous region by digitonin-collagenase perfusion. Exposure of hepatocytes in culture to NDMA (0.5 or 5 mM) for up to 18 hrs caused little damage, but after 42 hr loss of cell viability became evident, and the extent of cell death was higher in perivenous cells than in periportal cells. Pretreatment of rats with ethanol caused a dramatically enhanced cell damage in perivenous cells (80%) compared to periportal cells (45%). This ethanol pretreatment caused a several-fold induction of cytochrome P450 2E1, as determined both with Western blot and as NDMA demethylase activity, and the effect was observed almost exclusively in perivenous cells. Isoniazid, an inhibitor of cytochrome P450 2E1, completely protected against NDMA toxicity. Glutathione dependent cytoprotective mechanisms and lipid peroxidation did not appear to be critical in NDMA toxicity, as evidence by lack of potentiation of toxicity by buthionine sulfoximine, an inhibitor of glutathione synthesis, and by the absence of increased lipid peroxidation. Instead, the higher expression of cytochrome P450 2E1 in the perivenous cells seems to be the main determinant for the regiospecific toxicity of NDMA, and, consequently, probably also for the associated genotoxicity.
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PMID:Evidence for cytochrome P450 2E1-mediated toxicity of N-nitrosodimethylamine in cultured perivenous hepatocytes from ethanol treated rats. 143 24

The ethanol-inducible form of cytochrome P-450 (IIE1) is expressed and induced by ethanol, predominantly in the centrilobular region. Because this isoenzyme has a particularly high capacity to convert carbon tetrachloride and several other hepatotoxins into reactive intermediates, its role in producing damage was studied by comparing the effect of carbon tetrachloride exposure on hepatocytes isolated from either the periportal or the perivenous region by digitonin-collagenase perfusion. After exposure for 18 hr of primary culture to 600 mumol/L of carbon tetrachloride, periportal cells were only slightly damaged, as estimated from dye exclusion and lactate dehydrogenase leakage. In marked contrast, perivenous cells, which contained a several-fold higher amount of immunoreactive P-450 IIE1 apoprotein, were partly damaged after exposure to 60 to 150 mumol/L of carbon tetrachloride and severely damaged after 600 mumol/L. Similarly, lipid peroxidation after carbon tetrachloride was much more prominent in perivenous cells. The differences between perivenous and periportal cells in carbon tetrachloride-induced injury were larger when cells were isolated from chronically ethanol-treated rats. Isoniazid, an efficient inhibitor of P-450 IIE1, protected against damage by carbon tetrachloride more efficiently than the general P-450 inhibitor cimetidine. Our results suggest that the greater susceptibility of the perivenous hepatocytes to carbon tetrachloride-induced damage is associated with the high expression of P-450 IIE1 in these cells. This enzyme may also be involved in damage elicited by several other typical centrilobular hepatotoxins.
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PMID:Role of ethanol-inducible cytochrome P-450 IIE1 in carbon tetrachloride-induced damage to centrilobular hepatocytes from ethanol-treated rats. 222 5

To study the mechanism of centrilobular damage developing in the centrilobular region after high doses of acetaminophen (APAP), its metabolism and toxicity were compared in periportal and perivenous hepatocytes isolated by digitonin/collagenase perfusion. Contrary to earlier reports, based on perfusions, no evidence for a periportal dominance of APAP sulfation could be observed. Glucuronidation, the dominant pathway of conjugation at high (5 mM) APAP concentration, was faster in perivenous cells. During primary culture, prolonged exposure (> or = 24 hr) to 5 mM APAP damaged perivenous cells, with a higher P450 2E1 level than periportal cells. When cells were isolated from ethanol-pretreated rats, to induce P450 2E1 levels specifically in the perivenous region, perivenous hepatocytes exhibited enhanced APAP vulnerability and extensive glutathione depletion. In contrast, corresponding periportal cells retained good viability. Isoniazid, an inhibitor of cytochrome P450 2E1, protected cells against APAP toxicity and prevented glutathione depletion. Induction of P450 2E1 also caused a 3-fold increase in the covalent binding of reactive intermediates from [14C]APAP, and this increase was mainly confined to perivenous cells. These results indicate that in rat liver there is only slight perivenous zonation of APAP conjugation and suggest that zone-specific APAP activation, mediated by the regional expression of ethanol-inducible cytochrome P450 2E1, is responsible for the characteristic centrilobular liver damage elicited by APAP.
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PMID:Zonation of acetaminophen metabolism and cytochrome P450 2E1-mediated toxicity studied in isolated periportal and perivenous hepatocytes. 846 46

Tuberculosis is characterized by extensive destruction and remodelling of the pulmonary extracellular matrix. Stromal cell-derived matrix metalloproteinases (MMPs) are implicated in this process and may be a target for adjunctive immunotherapy. We hypothesized that MMPs are elevated in bronchoalveolar lavage fluid of tuberculosis patients and that antimycobacterial agents may have a modulatory effect on MMP secretion. Concentrations of MMP-1, -2, -3, -7, -8, and -9 were elevated in the bronchoalveolar lavage fluid from tuberculosis patients compared to those in bronchoalveolar lavage fluid from patients with other pulmonary conditions. There was a positive correlation between MMP-3, MMP-7, and MMP-8 and a chest radiological score of cavitation and parenchymal damage. Respiratory epithelial cell-derived MMP-3 was suppressed by moxifloxacin, rifampicin, and azithromycin in a dose-dependent manner. Respiratory epithelial cell-derived MMP-1 was suppressed by moxifloxacin and azithromycin, whereas MMP-9 secretion was only decreased by moxifloxacin. In contrast, moxifloxacin and azithromycin both increased MMP-1 and -3 secretion from MRC-5 fibroblasts, demonstrating that the effects of these drugs are cell specific. Isoniazid did not affect MMP secretion. In conclusion, MMPs are elevated in bronchoalveolar lavage fluid from tuberculosis patients and correlate with parameters of tissue destruction. Antimycobacterial agents have a hitherto-undescribed immunomodulatory effect on MMP release by stromal cells.
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PMID:Antimycobacterial drugs modulate immunopathogenic matrix metalloproteinases in a cellular model of pulmonary tuberculosis. 2489 May 93