Metabolism of 1′- and 4-Hydroxymidazolam by Glucuronide Conjugation Is Largely Mediated by UDP-Glucuronosyltransferases 1A4, 2B4, and 2B7
作者:Kyung-Ah Seo、Soo Kyung Bae、Young-Kil Choi、Chang Soo Choi、Kwang-Hyeon Liu、Jae-Gook Shin
DOI:10.1124/dmd.110.035295
日期:2010.11
Midazolam undergoes oxidative hydroxylation by CYP3A to its metabolites, which are excreted mainly as glucuronidated conjugates into the urine. In this study, we examined the glucuronidation of hydroxymidazolam in human liver microsomes (HLMs) and characterized the UDP-glucuronosyltransferases (UGTs) involved in 1′- and 4-hydroxymidazolam glucuronidation. Among the 12 UGT isoforms tested, the O - and N -glucuronidation of 1′-hydroxymidazolam was mediated by UGT2B4/2B7 and 1A4, respectively. In contrast, the glucuronidation of 4-hydroxymidazolam was mediated by UGT1A4. Consistent with these observations, the UGT1A4 inhibitor hecogenin and the UGT2B7 substrate diclofenac potently inhibited the N - and O -glucuronidation of 1′-hydroxymidazolam in HLMs, respectively. A correlation analysis of UGT enzymatic activity and the formation rate of glucuronide metabolites from 1′- and 4-hydroxymidazolam in 25 HLMs showed that hydroxymidazolam glucuronidation is correlated with UGT1A4-mediated lamotrigine glucuronidation and UGT2B7-mediated diclofenac glucuronidation activity. Taken together, these findings indicate that UGT1A4, 2B4, and 2B7 are major isoforms responsible for glucuronide conjugate formation from 1′- and 4-hydroxymidazolam, which are the two major oxidative metabolites of midazolam.
咪达唑仑通过 CYP3A 氧化羟基化为其代谢物,主要以葡萄糖醛酸化结合物形式排泄到尿液中。在这项研究中,我们检测了羟基咪达唑仑在人肝微粒体 (HLM) 中的葡萄糖醛酸化,并表征了参与 1'- 和 4-羟基咪达唑仑葡萄糖醛酸化的 UDP-葡萄糖醛酸基转移酶 (UGT)。在测试的 12 种 UGT 亚型中,1'-羟基咪达唑仑的 O - 和 N - 葡萄糖醛酸化分别由 UGT2B4/2B7 和 1A4 介导。相反,4-羟基咪达唑仑的葡萄糖醛酸化是由 UGT1A4 介导的。与这些观察结果一致,UGT1A4 抑制剂 hecogenin 和 UGT2B7 底物双氯芬酸分别有效抑制 HLM 中 1'-羟基咪达唑仑的 N - 和 O - 葡萄糖醛酸化。对 25 个 HLM 中 UGT 酶活性与 1′- 和 4-羟基咪达唑仑葡萄糖醛酸代谢物形成率的相关性分析表明,羟基咪达唑仑葡萄糖醛酸化与 UGT1A4 介导的拉莫三嗪葡萄糖醛酸化和 UGT2B7 介导的双氯芬酸葡萄糖醛酸化活性相关。总而言之,这些发现表明 UGT1A4、2B4 和 2B7 是负责从 1'- 和 4-羟基咪达唑仑(咪达唑仑的两种主要氧化代谢物)形成葡萄糖醛酸结合物的主要亚型。