Inhibition and activation of the human liver microsomal and human cytochrome P450 3A4 metabolism of testosterone by deployment-related chemicals
Inhibition and activation of the human liver microsomal and human cytochrome P450 3A4 metabolism of testosterone by deployment-related chemicals
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DOI：
10.1124/dmd.31.4.384
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发表时间：
2003-04-01
影响因子：
3.9
通讯作者：
Hodgson, E
中科院分区：
文献类型：
--
作者：
Usmani, KA;Rose, RL;Hodgson, E
细胞色素P450（P450）酶是参与外源性物质和内源性底物如睾酮（TST）代谢的主要催化剂。由人肝微粒体形成的主要TST代谢物包括6 β-羟基睾酮（6 β-OHTST）、2 β-羟基睾酮（2 β-OHTST）和15 β-羟基睾酮（15 β-OHTST）。对16种cDNA表达的人P450亚型的筛选表明，94%的TST代谢产物由CYP3A亚家族成员产生，其中6 β-OHTST占所有TST代谢产物的86%。观察到人肝微粒体（HLM）和CYP 3A4产生6 β-、2 β-和15 β-OHTST的K-m值相似。然而，6 β-OHTST的Vmax和CLint显著高于2 β-OHTST（相似于18倍）和15 β-OHTST（相似于40倍）。HLM与各种配体（包括军事部署中使用的化学品）预孵育，导致TST代谢不同程度的抑制或激活。HLM中TST代谢的最大抑制作用是在与有机磷化合物（包括毒死蜱、甲拌磷和fonofos）预孵育后，对包括6 β-OHTST在内的几种代谢物的抑制作用高达80%。用毒死蜱预孵育CYP3A4，而不是毒死蜱-氧磷，导致98%的TST代谢抑制。甲拌磷和fonofos也抑制CYP3A4的大多数初级代谢产物的产生。动力学分析表明，毒死蜱是TST主要代谢产物的最有效的抑制剂之一，其次是福诺磷和甲拌磷。毒死蜱，fonofos，甲拌磷抑制主要TST代谢物非竞争性和不可逆的。相反，CYP3A4与溴化吡啶斯的明预孵育增加了6 β-OHTST和2 β-OHTST的代谢物水平。人芳香酶（CYP 19）与供试化学品预孵育对内源性雌激素17 β-雌二醇的产生无影响。
Cytochrome P450 (P450) enzymes are major catalysts involved in the metabolism of xenobiotics and endogenous substrates such as testosterone (TST). Major TST metabolites formed by human liver microsomes include 6beta-hydroxytestosterone (6beta-OHTST), 2beta-hydroxytestosterone (2beta-OHTST), and 15beta-hydroxytestosterone (15beta-OHTST). A screen of 16 cDNA-expressed human P450 isoforms demonstrated that 94% of all TST metabolites are produced by members of the CYP3A subfamily with 6beta-OHTST accounting for 86% of all TST metabolites. Similar K-m values were observed for production of 6beta-, 2beta-, and 15beta-OHTST with human liver microsomes (HLM) and CYP3A4. However, V-max and CLint were significantly higher for 6beta-OHTST than 2beta-OHTST (similar to18-fold) and 15beta-OHTST (similar to40-fold). Preincubation of HLM with a variety of ligands, including chemicals used in military deployments, resulted in varying levels of inhibition or activation of TST metabolism. The greatest inhibition of TST metabolism in HLM was following preincubation with organophosphorus compounds, including chlorpyrifos, phorate, and fonofos, with up to 80% inhibition noticed for several metabolites including 6beta-OHTST. Preincubation of CYP3A4 with chlorpyrifos, but not chlorpyrifos-oxon, resulted in 98% inhibition of TST metabolism. Phorate and fonofos also inhibited the production of most primary metabolites of CYP3A4. Kinetic analysis indicated that chlorpyrifos was one of the most potent inhibitors of major TST metabolites followed by fonofos and phorate. Chlorpyrifos, fonofos, and phorate inhibited major TST metabolites noncompetitively and irreversibly. Conversely, preincubation of CYP3A4 with pyridostigmine bromide increased metabolite levels of 6beta-OHTST and 2beta-OHTST. Preincubation of human aromatase (CYP19) with the test chemicals had no effect on the production of the endogenous estrogen, 17beta-estradiol.