Ji Jin-Zi, Huang Bei-Bei, Gu Tong-Tong, Tai Ting, Zhou Huan, Jia Yu-Meng, Mi Qiong-Yu, Zhang Meng-Ran, Xie Hong-Guang
General Clinical Research Center, Nanjing First Hospital, Nanjing Medical University, Nanjing, 210006, China.
Department of Clinical Pharmacy, School of Basic Medicine and Clinical Pharmacy, China Pharmaceutical University, Nanjing, 211198, China.
Biopharm Drug Dispos. 2018 Feb;39(2):88-98. doi: 10.1002/bdd.2117. Epub 2018 Jan 9.
Clopidogrel is predominantly hydrolyzed to clopidogrel carboxylic acid (CCA) by carboxylesterase 1, and subsequently CCA is glucuronidated to clopidogrel acyl glucuronide (CAG) by uridine diphosphate-glucuronosyltransferases (UGTs); however, the UGT isoenzymes glucuronidating CCA remain unidentified to date. In this study, the glucuronidation of CCA was screened with pooled human liver microsomes (HLMs) and 7 human recombinant UGT (rUGT) isoforms. Results indicated that rUGT2B7 exhibited the highest catalytical activity for the CCA glucuronidation as measured with a mean V value of 120.9 pmol/min/mg protein, 3- to 12-fold higher than that of the other rUGT isoforms tested. According to relative activity factor approach, the relative contribution of rUGT2B7 to CCA glucuronidation was estimated to be 58.6%, with the minor contributions (3%) from rUGT1A9. Moreover, the glucuronidation of CCA followed Michaelis-Menten kinetics with a mean K value of 372.9 μM and 296.4 μM for pooled HLMs and rUGT2B7, respectively, showing similar affinity for both. The formation of CAG was significantly inhibited by azidothymidine and gemfibrozil (well-characterized UGT2B7 substrates) in a concentration-dependent manner, or by fluconazole (a typical UGT2B7-selective inhibitor) in a time-dependent manner, for both HLMs and rUGT2B7, respectively. In addition, CCA inhibited azidothymidine glucuronidation (catalyzed almost exclusively by UGT2B7) by HLMs and rUGT2B7 in a concentration-dependent manner, indicating that CCA is a substrate of UGT2B7. These results reveal that UGT2B7 is the major enzyme catalyzing clopidogrel glucuronidation in the human liver, and that there is the potential for drug-drug interactions between clopidogrel and the other substrate drugs of UGT2B7.
氯吡格雷主要通过羧酸酯酶1水解为氯吡格雷羧酸（CCA），随后CCA由尿苷二磷酸 - 葡萄糖醛酸转移酶（UGTs）葡萄糖醛酸化生成氯吡格雷酰基葡萄糖醛酸（CAG）；然而，至今尚未确定使CCA葡萄糖醛酸化的UGT同工酶。在本研究中，使用人肝微粒体（HLMs）池和7种人重组UGT（rUGT）同工型对CCA的葡萄糖醛酸化进行了筛选。结果表明，rUGT2B7对CCA葡萄糖醛酸化表现出最高的催化活性，平均V值为120.9 pmol/分钟/毫克蛋白，比其他测试的rUGT同工型高3至12倍。根据相对活性因子法，rUGT2B7对CCA葡萄糖醛酸化的相对贡献估计为58.6%，rUGT1A9的贡献较小（3%）。此外，CCA的葡萄糖醛酸化遵循米氏动力学，HLMs和rUGT2B7的平均K值分别为372.9 μM和296.4 μM，表明两者对底物具有相似的亲和力。对于HLMs和rUGT2B7，齐多夫定和吉非贝齐（特征明确的UGT2B7底物）以浓度依赖性方式显著抑制CAG的形成，或氟康唑（一种典型的UGT2B7选择性抑制剂）以时间依赖性方式分别抑制CAG的形成。此外，CCA以浓度依赖性方式抑制HLMs和rUGT2B7对齐多夫定的葡萄糖醛酸化（几乎完全由UGT2B7催化），表明CCA是UGT2B7的底物。这些结果表明，UGT2B7是人体肝脏中催化氯吡格雷葡萄糖醛酸化的主要酶，并且氯吡格雷与UGT2B7的其他底物药物之间存在药物相互作用的可能性。
