Meifang Wang1,2, Guangyi Yang1,2,3, Yu He2, Beibei Xu2, Min Zeng1,2, Shufan Ge2, Taijun Yin2, Song Gao1,2, Ming Hu4,5. 1. Hubei University of Medicine and University-Affiliated Taihe Hospital, Shiyan, China. 2. Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, Houston, TX, USA. 3. Hubei Provincial Technology and Research Center for Comprehensive Development of Medicinal Herbs, Hubei University of Medicine, Shiyan, Hubei, China. 4. Hubei University of Medicine and University-Affiliated Taihe Hospital, Shiyan, China. mhu@uh.edu. 5. Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, Houston, TX, USA. mhu@uh.edu.
Abstract
SCOPE: The purpose of this study is to characterize how overexpression of an efflux transporter and an UDP-glucuronosyltransferase (UGT) affects the cellular kinetics of glucuronidation processes. METHODS AND RESULTS: A new MDCK II cell line overexpressing both MRP2 and UGT1A1 (MDCKII-UGT1A1/MRP2 cells) was developed and used to determine how overexpression of an efflux transporter affects the kinetics of cellular flavonoid glucuronide production. The results showed that most model flavonoids (from a total of 13) were mainly metabolized into glucuronides in the MDCKII-UGT1A1/MRP2 cells and the glucuronides were rapidly excreted. Flavonoids with three or fewer hydroxyl group at 7, 3' or 6 hydroxyl group were also metabolized into sulfates. Mechanistic studies using 7-hydroxylflavone showed that its glucuronide was mainly (90%) effluxed by BCRP with a small (10%) but significant contribution from MRP2. Maximal velocity of glucuronide production MDCK-MRP2/UGT1A1 cells showed a fairly good correlation (R(2) >0.8) with those derived using UGT1A1 microsomes, but other kinetic parameters (e.g., Km ) did not correlate. CONCLUSION: Overexpression of a second efficient efflux transporter did not significantly change the fact that BCRP is the dominant transporter for flavonoid glucuronide nor did it diminish the influence of the efflux transporter as the "gate keeper" of glucuronidation process.
SCOPE: The purpose of this study is to characterize how overexpression of an efflux transporter and an UDP-glucuronosyltransferase (UGT) affects the cellular kinetics of glucuronidation processes. METHODS AND RESULTS: A new MDCK II cell line overexpressing both MRP2 and UGT1A1 (MDCKII-UGT1A1/MRP2 cells) was developed and used to determine how overexpression of an efflux transporter affects the kinetics of cellular flavonoid glucuronide production. The results showed that most model flavonoids (from a total of 13) were mainly metabolized into glucuronides in the MDCKII-UGT1A1/MRP2 cells and the glucuronides were rapidly excreted. Flavonoids with three or fewer hydroxyl group at 7, 3' or 6 hydroxyl group were also metabolized into sulfates. Mechanistic studies using 7-hydroxylflavone showed that its glucuronide was mainly (90%) effluxed by BCRP with a small (10%) but significant contribution from MRP2. Maximal velocity of glucuronide production MDCK-MRP2/UGT1A1 cells showed a fairly good correlation (R(2) >0.8) with those derived using UGT1A1 microsomes, but other kinetic parameters (e.g., Km ) did not correlate. CONCLUSION: Overexpression of a second efficient efflux transporter did not significantly change the fact that BCRP is the dominant transporter for flavonoid glucuronide nor did it diminish the influence of the efflux transporter as the "gate keeper" of glucuronidation process.
Authors: Jun Chen; Stephen Wang; Xiaobin Jia; Susan Bajimaya; Huimin Lin; Vincent H Tam; Ming Hu Journal: Drug Metab Dispos Date: 2005-08-24 Impact factor: 3.922
Authors: Philip A Gregory; Rikke H Lewinsky; Dione A Gardner-Stephen; Peter I Mackenzie Journal: Toxicol Appl Pharmacol Date: 2004-09-15 Impact factor: 4.219