title: Influence of P-glycoprotein on the transport and metabolism of indinavir in Caco-2 cells expressing cytochrome P-450 3A4.
abstract: Caco-2 cells grown in the presence of 1alpha,25-di-OH vitamin D(3) (di-OH vit D(3)) were used as a model to evaluate the effects of P-glycoprotein (Pgp) efflux on CYP3A4-mediated metabolism of indinavir during intestinal absorption. Caco-2 cells grown under these conditions demonstrated significant CYP3A4 activity and maintained Pgp-mediated directional transport of indinavir. Metabolism of indinavir in the di-OH vit D(3)-treated cells correlated with the level of CYP3A activity and generated metabolites consistent with CYP3A4-mediated metabolism. During transport experiments, indinavir metabolites are selectively secreted into the apical compartment, consistent with Pgp-mediated efflux. Using formation of the most abundant metabolite, M6, as a marker for indinavir metabolism, we observed that the extent of indinavir metabolism is not significantly affected by the direction of indinavir transport or by inhibition of Pgp with cyclosporin A. However, because Pgp efflux results in higher indinavir transport in the basolateral-to-apical direction than in the apical-to-basolateral direction, the ratio of M6 produced normalized to the amount of drug transported across the monolayer was higher for apical-to-basolateral transport. Thus, Pgp efflux in a direction opposite to absorptive transport results in more metabolite produced per mole of drug that is absorbed. In summary, the results support a role of Pgp in increasing intestinal presystemic metabolism and in removal of CYP3A4-generated metabolites from the intracellular compartment.
authors.affiliation: Department of Drug Metabolism, Merck Research Laboratories, West Point, PA 19486, USA. jerome_hochman@merck.com
authors.forename: J H
authors.initials: JH
authors.lastname: Hochman
authors.forename: M
authors.initials: M
authors.lastname: Chiba
authors.forename: J
authors.initials: J
authors.lastname: Nishime
authors.forename: M
authors.initials: M
authors.lastname: Yamazaki
authors.forename: J H
authors.initials: JH
authors.lastname: Lin
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000502:physiology*; D001693:Biological Transport, Active; D018938:Caco-2 Cells; D002762:Cholecalciferol; D016572:Cyclosporine / Q000494:pharmacology*; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism*; D004347:Drug Interactions; D017320:HIV Protease Inhibitors / Q000493:pharmacokinetics*; D006801:Humans; D019469:Indinavir / Q000493:pharmacokinetics*; D007408:Intestinal Absorption / Q000187:drug effects*; D006899:Mixed Function Oxygenases / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors; D014407:Tumor Cells, Cultured
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D017320:HIV Protease Inhibitors; D002762:Cholecalciferol; D019469:Indinavir; D016572:Cyclosporine; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; C104464:CYP3A protein, human; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human