TY - JOUR T1 - UGT1A9-overexpressing HeLa Cells Is a Appropriate Tool to Delineate the Kinetic Interplay between BCRP and UGT and to Rapidly Identify the Glucuronide Substrates of BCRP JF - Drug Metabolism and Disposition JO - Drug Metab Dispos DO - 10.1124/dmd.111.041467 SP - dmd.111.041467 AU - Wen Jiang AU - Beibei Xu AU - Baojian Wu AU - Rong Yu AU - Ming Hu Y1 - 2011/11/09 UR - http://dmd.aspetjournals.org/content/early/2011/11/09/dmd.111.041467.abstract N2 - The interplay between phase II enzymes and efflux transporters leads to extensive metabolism and low bioavailability for flavonoids. To investigate the simplest interplay between one UGT isoform and one efflux transporter in flavonoid disposition, engineered HeLa cells stably overexpressing UGT1A9 were developed, characterized and further applied to investigate the metabolism of two model flavonoids (genistein and apigenin) and excretion of their glucuronides. The results indicated that the engineered HeLa cells overexpressing UGT1A9 rapidly excreted the glucuronides of genistein and apigenin. The kinetic characteristics of genistein or apigenin glucuronidation were similar when using UGT1A9 overexpressed in HeLa cells or the commercially available UGT1A9. siRNA-mediated UGT1A9 silencing resulted in the substantial decrease in glucuronide excretion (>75%, p<0.01). Furthermore, a potent inhibitor of BCRP Ko143 caused, in a dose-dependent manner, a substantial and marked reduction of the clearance (74%-94%, p<0.01), and a substantial increase in the intracellular glucuronide levels (4 to 8 folds, p<0.01), resulting in a moderate decrease in glucuronide excretion (19%-59%, p<0.01). In addition, a significant albeit moderate reduction in the fraction of genistein metabolized (or fmet) in the presence of Ko143 was observed. In contrast, LTC4 and siRNA against MRP2 and MRP3 did not affect excretion of flavonoid glucuronides. In conclusion, the engineered HeLa cells overexpressing UGT1A9 is an appropriate model to study the kinetic interplay between UGT1A9 and BCRP in the phase II disposition of flavonoids. This simple cell model should also be very useful to rapidly identify if a phase II metabolite is the substrate of BCRP. ER -