title: The Consequence of Drug-Drug Interactions Influencing the Interplay between P-Glycoprotein and Cytochrome P450 3a: An Ex Vivo Study with Rat Precision-Cut Intestinal Slices.
abstract: P-glycoprotein (P-gp) and cytochrome P450 3A (CYP3A) are differentially expressed along the intestine and work coordinately to reduce the intracellular concentration of xenobiotics and the absorption of orally taken drugs. Drug-drug interactions (DDIs) based on P-gp/CYP3A interplay are of clinical importance and require preclinical investigation. We investigated the P-gp/Cyp3a interplay and related DDIs with different P-gp inhibitors in the various regions of the rat intestine ex vivo using precision-cut intestinal slices (PCIS) with quinidine (Qi), a dual substrate of P-gp and Cyp3a, as the probe. The results showed that P-gp efflux was the main factor limiting the intracellular Qi content at concentrations below 5µM, whereas both efflux and metabolism were saturated at [Qi] > 50µM. The selective P-gp inhibitors CP100356 [N-(3,4-dimethoxyphenethyl)-4-(6,7-dimethoxy-3,4-dihydroisoquinolin-2[1H]-yl)-6,7-dimethoxyquinazolin-2-amine] and PSC833 [valspodar, 6-[(2S,4R,6E)-4-methyl-2-(methylamino)-3-oxo-6-octenoic acid]-7-l-valine-cyclosporin A] enhanced the Qi accumulation in slices in line with the different P-gp expression in the intestinal regions and, as a result, also enhanced metabolism in the jejunum and ileum. Dual inhibitors of both P-gp and Cyp3a (verapamil and ketoconazole) increased the concentration of Qi in the jejunum and ileum, but less 3-hydroxy-quinidine was produced due to inhibition of Cyp3a. The results indicate that the P-gp/Cyp3a interplay depends on the concentration of the drug and on the intestinal region under study. Furthermore, due to the P-gp/Cyp3a interplay, DDIs can lead to remarkable changes in the intracellular concentration of both the parent drug and the metabolite, which varies among the intestinal regions and depends on the selectivity of the inhibitors, with potentially important implications for disposition and toxicity of drugs and their metabolites.
authors.affiliation: Groningen Research Institute of Pharmacy (M.L., I.A.M.G., S.S., M.H.J. G.M.M.G.), and Interfaculty Mass Spectrometry Center (A.D.), University of Groningen, Groningen, the Netherlands.
authors.forename: Ming
authors.initials: M
authors.lastname: Li
authors.affiliation: Groningen Research Institute of Pharmacy (M.L., I.A.M.G., S.S., M.H.J. G.M.M.G.), and Interfaculty Mass Spectrometry Center (A.D.), University of Groningen, Groningen, the Netherlands i.a.m.de.graaf@rug.nl.
authors.forename: Inge A M
authors.initials: IA
authors.lastname: de Graaf
authors.affiliation: Groningen Research Institute of Pharmacy (M.L., I.A.M.G., S.S., M.H.J. G.M.M.G.), and Interfaculty Mass Spectrometry Center (A.D.), University of Groningen, Groningen, the Netherlands.
authors.forename: Sanna
authors.initials: S
authors.lastname: Siissalo
authors.affiliation: Groningen Research Institute of Pharmacy (M.L., I.A.M.G., S.S., M.H.J. G.M.M.G.), and Interfaculty Mass Spectrometry Center (A.D.), University of Groningen, Groningen, the Netherlands.
authors.forename: Marina H
authors.initials: MH
authors.lastname: de Jager
authors.affiliation: Groningen Research Institute of Pharmacy (M.L., I.A.M.G., S.S., M.H.J. G.M.M.G.), and Interfaculty Mass Spectrometry Center (A.D.), University of Groningen, Groningen, the Netherlands.
authors.forename: Annie
authors.initials: A
authors.lastname: van Dam
authors.affiliation: Groningen Research Institute of Pharmacy (M.L., I.A.M.G., S.S., M.H.J. G.M.M.G.), and Interfaculty Mass Spectrometry Center (A.D.), University of Groningen, Groningen, the Netherlands.
authors.forename: Geny M M
authors.initials: GM
authors.lastname: Groothuis
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism*; D000818:Animals; D003524:Cyclosporins / Q000378:metabolism; D051544:Cytochrome P-450 CYP3A / Q000378:metabolism*; D004347:Drug Interactions / Q000502:physiology*; D007082:Ileum / Q000378:metabolism*; D007408:Intestinal Absorption; D007583:Jejunum / Q000378:metabolism*; D007654:Ketoconazole / Q000378:metabolism; D008297:Male; D004364:Pharmaceutical Preparations / Q000378:metabolism*; D011802:Quinidine / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D014633:Valine / Q000378:metabolism; D014700:Verapamil / Q000378:metabolism
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D003524:Cyclosporins; D004364:Pharmaceutical Preparations; D014700:Verapamil; D051544:Cytochrome P-450 CYP3A; D014633:Valine; D011802:Quinidine; C070272:valspodar; D007654:Ketoconazole