title: P-glycoprotein: a major determinant of rifampicin-inducible expression of cytochrome P4503A in mice and humans.
abstract: The P-glycoprotein (Pgp) efflux pump can influence the hepatocellular concentration of xenobiotics that are modulators and substrates of cytochrome P4503A (CYP3A). We tested the hypothesis that Pgp is a determinant of drug-inducible expression of CYP3A. The magnitude of CYP3A induction by rifampicin was compared in the human parental colon carcinoma cell line LS 180/WT (wild type) and in two derivative clones overexpressing the human multidrug resistance gene MDR1 (also designated PGY1) because of either drug selection (LS 180/ADR) or transfection with MDRI cDNA (LS 180/MDR). In both MDR1 cDNA-overexpressing clones, rifampicin induction of CYP3A mRNA and protein was decreased and required greater rifampicin concentrations compared with parental cells. The role of Pgp in regulation of CYP3A expression in vivo was analyzed in mice carrying a targeted disruption of the mdr1a mouse gene. Oral treatment with increasing doses of rifampicin resulted in elevated drug levels in the livers of mdr1a (-/-) mice compared with mdr1a (+/+) mice at all doses. Consistent with the enhanced accumulation of rifampicin in mdr1a (-/-) mice, lower doses of rifampicin were required for induction of CYP3A proteins, and the magnitude of CYP3A induction was greater at all doses of rifampicin in mdr1a (-/-) mice compared with mdr1a (+/+) mice. We conclude that Pgp-mediated transport is a critical element influencing the CYP3A inductive response.
authors.affiliation: Department of Pharmaceutical Sciences, St. Jude Children's Research Hospital, Memphis, TN 38105-2794, USA.
authors.forename: E G
authors.initials: EG
authors.lastname: Schuetz
authors.forename: A H
authors.initials: AH
authors.lastname: Schinkel
authors.forename: M V
authors.initials: MV
authors.lastname: Relling
authors.forename: J D
authors.initials: JD
authors.lastname: Schuetz
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport; D015152:Blotting, Northern; D002460:Cell Line; D003110:Colonic Neoplasms; D019392:Cytochrome P-450 CYP2E1; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis*; D018432:Drug Resistance, Multiple / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D005838:Genotype; D006801:Humans; D007700:Kinetics; D051379:Mice; D008815:Mice, Inbred Strains; D018345:Mice, Knockout; D008862:Microsomes, Liver / Q000201:enzymology*; D006899:Mixed Function Oxygenases / Q000096:biosynthesis*; D012293:Rifampin / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D014747:Vinblastine / Q000378:metabolism*
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D014747:Vinblastine; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D019392:Cytochrome P-450 CYP2E1; D012293:Rifampin