Inhibition of UDP-glucuronosyltransferase 2B7-catalyzed morphine glucuronidation by ketoconazole: Dual mechanisms involving a novel noncompetitive mode
Inhibition of UDP-glucuronosyltransferase 2B7-catalyzed morphine glucuronidation by ketoconazole: Dual mechanisms involving a novel noncompetitive mode
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DOI：
10.1124/dmd.106.009738
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发表时间：
2006-08-01
影响因子：
3.9
通讯作者：
Yamada, Hideyuki
中科院分区：
文献类型：
--
作者：
Takeda, Shuso;Kitajima, Yurie;Yamada, Hideyuki
人体中吗啡的葡萄糖醛酸化主要由UDP-葡萄糖醛酸转移酶2B 7（UGT 2B 7）催化。由于我们最近的研究表明细胞色素P450（P450）与UGT 2B 7相互作用以影响其功能[Takeda S et al.（2005）Mol Pharmacol 67：665 - 672]，因此预期P450抑制剂可调节UGT 2B 7催化的活性。为了解决这一问题，我们研究了P450抑制剂（西咪替丁、磺胺苯吡唑、红霉素、硝苯地平和酮康唑）对UGT 2B 7催化的吗啡-3-葡糖苷酸（M-3-G）和吗啡-6-葡糖苷酸（M-6-G）形成的影响。在检测的抑制剂中，酮康唑是人肝微粒体形成M-3-G和M-6-G的最强效抑制剂。除硝苯地平对M-6-G形成的抑制作用与酮康唑相当外，其他药物的作用均较弱。添加NADPH或溶解肝微粒体均不影响酮康唑抑制吗啡葡萄糖醛酸化的能力。此外，酮康唑具有抑制从P450游离的重组UGT 2B 7的吗啡UGT活性的能力。动力学分析表明，酮康唑产生的抑制吗啡葡萄糖醛酸化涉及混合型机制。可待因增强酮康唑对吗啡葡萄糖醛酸化的抑制作用。相反，另一种底物，睾酮，除了酮康唑产生的抑制吗啡UGT显示没有或轻微的影响。这些结果表明：1）抑制UGT 2B 7催化的吗啡葡萄糖醛酸化不需要P450代谢酮康唑; 2）该药物通过竞争性和非竞争性抑制的新机制对吗啡UGT发挥抑制作用。
Glucuronidation of morphine in humans is predominantly catalyzed by UDP-glucuronosyltransferase 2B7 (UGT2B7). Since our recent research suggested that cytochrome P450s (P450s) interact with UGT2B7 to affect its function [Takeda S et al. (2005) Mol Pharmacol 67: 665 - 672], P450 inhibitors are expected to modulate UGT2B7catalyzed activity. To address this issue, we investigated the effects of P450 inhibitors (cimetidine, sulfaphenazole, erythromycin, nifedipine, and ketoconazole) on the UGT2B7-catalyzed formation of morphine-3-glucuronide (M-3-G) and morphine-6-glucuronide (M-6-G). Among the inhibitors tested, ketoconazole was the most potent inhibitor of both M-3-G and M-6-G formation by human liver microsomes. The others were less effective except that nifedipine exhibited an inhibitory effect on M-6-G formation comparable to that by ketoconazole. Neither addition of NADPH nor solubilization of liver microsomes affected the ability of ketoconazole to inhibit morphine glucuronidation. In addition, ketoconazole had an ability to inhibit morphine UGT activity of recombinant UGT2B7 freed from P450. Kinetic analysis suggested that the ketoconazole-produced inhibition of morphine glucuronidation involves a mixed-type mechanism. Codeine potentiated inhibition of morphine glucuronidation by ketoconazole. In contrast, addition of another substrate, testosterone, showed no or a minor effect on ketoconazole-produced inhibition of morphine UGT. These results suggest that 1) metabolism of ketoconazole by P450 is not required for inhibition of UGT2B7-catalyzed morphine glucuronidation; and 2) this drug exerts its inhibitory effect on morphine UGT by novel mechanisms involving competitive and noncompetitive inhibition.