Received for publication December 30, 2008.
Revised May 14, 2009.
Accepted for publication May 14, 2009.

Complex pharmacokinetic behaviour of ezetimibe depends on Abcc2, Abcc3 and Abcg2

Abstract

Abstract Ezetimibe lowers plasma cholesterol levels by inhibiting the uptake of cholesterol in the intestine. Due to extensive enterohepatic circulation of ezetimibe, relative low doses are required to be effective. In blood and bile the majority of ezetimibe is present as a glucuronide-conjugate, which is formed in the enterocyte. Presently, it is not clear which mechanisms are responsible for this efficient enterohepatic circulation. Abcc2, Abcc3 and Abcg2 are ABC transporters, which are expressed in both liver and intestine and are capable of transporting glucuronidated compounds. The aim of this study was to investigate the contribution of these transporters in the enterohepatic cycling of ezetimibe-glucuronide (Ez-gluc). Transport studies were performed in plasma membrane vesicles from ABCC2, ABCC3 and ABCG2 expressing Sf21 insect cells. Furthermore, intestinal explants from wild-type and Abcc3-/- mice were used to study vectorial transport in an Ussing chamber setup. Finally, biliary excretion of Ez-gluc was measured in vivo after duodenal delivery of ezetimibe in wild-type, Abcc3-/-, Abcc2-/-, Abcg2-/- and Abcg2-/-/Abcc2-/- mice. ABCC3-, ABCC2- and ABCG2-mediated transport was dose dependently inhibited by Ez-gluc. In the Ussing chamber Ez-gluc recovered from the basolateral side was significantly reduced in duodenal (2.2%), in jejunal (23%) and in ileal (23%) tissue of Abcc3-/- compared to wild-type mice. Biliary excretion of Ez-gluc was significantly reduced in Abcc3-/- (34%), Abcc2-/- (56%) and Abcg2-/-/Abcc2-/- (2.5%) compared to wild-type mice. These data demonstrate that enterohepatic circulation of Ez-gluc strongly depends on the joint function of Abcc3, Abcc2 and Abcg2.

Key words: ABC transporters, active transport, hepatobiliary transport, intestinal transport