Breast Cancer Resistance Protein and Multidrug Resistance Protein 2 Regulate the Disposition of Acacetin Glucuronides

Purpose To determine the mechanism responsible for acacetin glucuronide transport and the bioavailability of acacetin. Methods Area under the curve (AUC), clearance (CL), half-life (T 1/2 ) and other pharmacokinetic parameters were determined by the pharmacokinetic model. The excretion of acacetin glucuronides was evaluated by the mouse intestinal perfusion model and the Caco-2 cell model. Results In pharmacokinetic studies, the bioavailability of acacetin in FVB mice was 1.3%. Acacetin was mostly exposed as acacetin glucuronides in plasma. AUC of acacetin-7-glucuronide (Aca-7-Glu) was 2-fold and 6-fold higher in Bcrp1 (−/−) mice and Mrp2 (−/−) mice, respectively. AUC of acacetin-5-glucuronide (Aca-5-Glu) was 2-fold higher in Bcrp1 (−/−) mice. In mouse intestinal perfusion, the excretion of Aca-7-Glu was decreased by 1-fold and 2-fold in Bcrp1 (−/−) and Mrp2 (−/−) mice, respectively. In Caco-2 cells, the efflux rates of Aca-7-Glu and Aca-5-Glu were significantly decreased by breast cancer resistance protein (BCRP) inhibitor Ko143 and multidrug resistance protein 2 (MRP2) inhibitor LTC4. The use of these inhibitors markedly increased the intracellular acacetin glucuronide content. Conclusions BCRP and MRP2 regulated the in vivo disposition of acacetin glucuronides. The coupling of glucuronidation and efflux transport was probably the primary reason for the low bioavailability of acacetin.