Bcrp1;Mdr1a/b;Mrp2 combination knockout mice: altered disposition of the dietary carcinogen PhIP (2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine) and its genotoxic metabolites.

Abstract

The multidrug transporters breast cancer resistance protein (BCRP), multidrug-resistance protein 1 (MDR1), and multidrug-resistance-associated protein (MRP) 2 and 3 eliminate toxic compounds from tissues and the body and affect the pharmacokinetics of many drugs and other potentially toxic compounds. The food-derived carcinogen PhIP (2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine) is transported by BCRP, MDR1, and MRP2. To investigate the overlapping functions of Bcrp1, Mdr1a/b, and Mrp2 in vivo, we generated Bcrp1;Mdr1a/b;Mrp2(-/-) mice, which are viable and fertile. These mice, together with Bcrp1;Mrp2;Mrp3(-/-) mice, were used to study the effects of the multidrug transporters on the pharmacokinetics of PhIP and its metabolites. Thirty minutes after oral or intravenous administration of PhIP (1 mg/kg), the PhIP levels in the small intestine were reduced 4- to 6-fold in Bcrp1;Mdr1a/b;Mrp2(-/) (-) and Bcrp1;Mrp2;Mrp3(-/-) mice compared with wild-type mice. Fecal excretion of PhIP was reduced 8- to 20-fold in knockouts. Biliary PhIP excretion was reduced 41-fold in Bcrp1;Mdr1a/b;Mrp2(-/-) mice. Biliary and small intestine levels of PhIP metabolites were reduced in Bcrp1;Mrp2-deficient mice. Furthermore, in both knockout strains, kidney levels and urinary excretion of genotoxic PhIP-metabolites were significantly increased, suggesting that reduced biliary excretion of PhIP and PhIP metabolites leads to increased urinary excretion of these metabolites and increased systemic exposure. Bcrp1 and Mdr1a limited PhIP brain accumulation. In Bcrp1;Mrp2;Mrp3(-/-), but not Bcrp1;Mdr1a/b;Mrp(-/-) mice, the carcinogenic metabolites N2-OH-PhIP (2-hydroxyamino-1-methyl-6-phenylimidazo[4,5-b]pyridine) and PhIP-5-sulfate (a genotoxicity marker) accumulated in liver tissue, indicating that Mrp3 is involved in the sinusoidal secretion of these compounds. We conclude that Bcrp1, Mdr1a/b, Mrp2, and Mrp3 significantly affect tissue disposition and biliary and fecal elimination of PhIP and its carcinogenic metabolites and may affect PhIP-induced carcinogenesis as a result.