title: Rat PXR reporter-gene activity correlates with the induction of CYP3A in rat precision-cut liver slices.
abstract: Recent studies have suggested that both constitutive androstane receptor (CAR) and pregnane X-receptor (PXR) are involved in the induction of rat liver microsomal cytochrome P-450 (CYP) 2B and 3A through a mechanism called cross-talk. In this study we intend to determine if a PXR-reporter gene assay could be used for the prediction of CYP3A and/or CYP2B induction in rats. The induction of rat CYP2B and CYP3A by nineteen structurally diverse compounds was evaluated by using rat precision-cut liver slices and a rat PXR reporter-gene system. Induction of CYP2B and CYP3A mRNAs in rat liver slices was quantified by real-time polymerase chain reaction. Rat PXR activation was measured by induction of luciferase activity in rat PXR reporter-gene system. Linear regression analysis of the fold of induction of mRNA in liver slices and the fold of luciferase activity in rat PXR reporter-gene system shows that a reasonable correlation (r2 = 0.6) exists between the CYP3A induction and the rat PXR activation. A much lower correlation was observed between CYP2B induction and the rat PXR activation (r2 = 0.1). The results from this study suggest that the PXR may play a major role in the induction of rat CYP3A, but not CYP2B. Therefore, the PXR-reporter gene assay may be useful in a high-throughput screening to predict CYP3A induction in rats.
authors.affiliation: Department of Drug Metabolism and Pharmacokinetics, Schering-Plough Research Institute, Kenilworth, NJ 07033, USA.
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Cui
authors.forename: Ann
authors.initials: A
authors.lastname: Thomas
authors.forename: Diana
authors.initials: D
authors.lastname: Montgomery
authors.forename: Chunyan
authors.initials: C
authors.lastname: Gu
authors.forename: Richard A
authors.initials: RA
authors.lastname: Morrison
authors.forename: Ronald E
authors.initials: RE
authors.lastname: White
authors.forename: K-C
authors.initials: KC
authors.lastname: Cheng
mesh_terms: D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D001681:Biological Assay; D019362:Cytochrome P-450 CYP2B1 / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D051544:Cytochrome P-450 CYP3A; D004353:Drug Evaluation, Preclinical / Q000379:methods; D004789:Enzyme Activation / Q000187:drug effects; D017930:Genes, Reporter; D066298:In Vitro Techniques; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008156:Luciferases / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D008297:Male; D010089:Oxidoreductases, N-Demethylating / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D000077297:Pregnane X Receptor; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D018160:Receptors, Cytoplasmic and Nuclear / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D011987:Receptors, Steroid / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism
chemical_list: D000077297:Pregnane X Receptor; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D011987:Receptors, Steroid; D008156:Luciferases; D001189:Aryl Hydrocarbon Hydroxylases; D019362:Cytochrome P-450 CYP2B1; D051544:Cytochrome P-450 CYP3A; D010089:Oxidoreductases, N-Demethylating