Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.3.1.28 (chloramphenicol acetyltransferase)
 5,100 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In the present study, we analysed the expression of monooxygenase activities and mRNAs associated with cytochrome P-450 (CYP), including CYP1A1/2, CYP2B1/2, CYP2C6, CYP2E1, CYP3A1/2, glutathione transferase alpha (GST alpha), aldehyde dehydrogenase and epoxide hydrolase in co-cultures of primary rat hepatocytes and rat liver epithelial cells. We observed that pentoxyresorufin O-deethylation activity was well maintained and ethoxyresorufin O-deethylation activity gradually decreased during co-culture time. In addition, we showed that phenobarbital and 3-methylcholanthrene treatments resulted in a significant increase of these activities. Two general patterns of accumulation of liver-specific mRNAs were observed. CYP1A1/2, CYP2B1/2, CYP3A1/2, GST alpha, aldehyde dehydrogenase and epoxide hydrolase mRNAs were maintained at a stable level, whereas CYP2C6 and CYP2E1 mRNAs showed a continuous decline. In addition, we observed a strong increase of CYP1A1/2 (13.6-fold) and GST alpha (3.9-fold) mRNA expression in 3-methylcholanthrene-treated co-cultures and induction of CYP2B1/2 (19-fold), CYP2C6 (10-fold), CYP3A1/2 (11.2-fold), GST alpha (9-fold), aldehyde dehydrogenase (6-fold) and epoxide hydrolase (5-fold) mRNA expression in phenobarbital-treated co-cultures. Furthermore, we demonstrated that liver-specific gene expression was restricted to hepatocytes, with the notable exception of epoxide hydrolase and CYP2E1 which were expressed in both cell types during the co-culture, as shown by the selective recovery of both hepatocytes and rat liver epithelial cells. Finally, to investigate whether co-cultures could be used to study the molecular mechanisms regulating CYP transcription, we performed transfection of hepatocytes, before the establishment of the co-culture, with large CYP2B1 (3.9 kb) or CYP2B2 (4.5 kb) promoter chloramphenicol acetyltransferase constructs or with a construct containing a 163-bp DNA sequence element reported to confer phenobarbital responsiveness. A 2-3-fold increase over the basal level of chloramphenicol acetyltransferase activity was observed in phenobarbital-treated co-cultures transfected with the phenobarbital-responsive element construct, although phenobarbital had no effect on large CYP2B1 or CYP2B2 promoter fragments. Our results demonstrate that the co-culture system provides a good tool for studying drug metabolism, and shows promise as a new tool for analysing transcriptional regulation under the influence of xenobiotics within primary hepatocytes.
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PMID:Regulation of the major detoxication functions by phenobarbital and 3-methylcholanthrene in co-cultures of rat hepatocytes and liver epithelial cells. 906 51

Pyridine and its metabolites have been shown in previous studies to induce cytochrome P4501A1 (CYP1A1) expression in vivo in the rat and in vitro in cultured human lung explants. In this study, we assessed the role of the metabolites in CYP1A1 induction by the parent compound. This was accomplished by comparing pyridine, 2-hydroxypyridine, 3-hydroxypyridine, pyridine N-oxide, and N-methylpyridinium in terms of the induction of CYP1A1 mRNA, CYP1A1 catalytic activity, and a xenobiotic response element-directed chloramphenicol acetyltransferase reporter gene, using HepG2 cells as the experimental system. We also assessed the effect of expression of the pyridine-metabolizing enzyme cytochrome P4502E1 on CYP1A1 induction by the parent pyridine. Only 2-hydroxypyridine significantly induced the CYP1A1 mRNA expression and CYP1A1-preferential activity ethoxyresorufin O-deethylase in wild-type HepG2 cells. Similarly, only 2-hydroxypyridine induced the expression of a xenobiotic response element-directed reporter gene in transfected HepG2 cells. Pyridine elevated CYP1A1 mRNA abundance 4.6-fold in HepG2 cells transfected with a human CYP2E1 expression vector relative to the abundance of the transcript in empty vector-transfected (control) HepG2 cells; the elevation was inhibited by the CYP2E1 inhibitor dimethyl sulfoxide. The results indicate that CYP1A1 induction by pyridine is mediated largely by metabolites, the formation of which may be catalyzed by CYP2E1.
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PMID:CYP1A1 induction by pyridine and its metabolites in HepG2 cells. 1214 72