Effects of administration of the chemoprotective agent oltipraz on CYP1A and CYP2B in rat liver and rat hepatocytes in culture
Effects of administration of the chemoprotective agent oltipraz on CYP1A and CYP2B in rat liver and rat hepatocytes in culture
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DOI：
10.1093/carcin/18.7.1343
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发表时间：
1997-07-01
期刊：
影响因子：
4.7
通讯作者：
Guillouzo, A
中科院分区：
文献类型：
--
作者：
Langouet, S;Maheo, K;Guillouzo, A
奥替拉兹[5-(2-pyrazinyl)-4-methyl-1，2-dithiole-3-thione]作为一种化学保护剂对黄曲霉毒素B-1诱导的大鼠肝癌的成功被认为主要依赖于它通过诱导II相酶，特别是谷胱甘肽转移酶来增强解毒的能力。然而，在原代培养的人肝细胞中，我们最近证实OPZ对人肝AFB(1)代谢的主要细胞色素P450(Cyps)也有重要的抑制作用。这促使了对OPZ对参与AFB(1)在大鼠体内代谢的一些细胞色素P450的影响的详细研究。原代培养的大鼠肝细胞的行为与人肝细胞相似，对OPZ的反应分别是抑制主要与细胞色素P450 1 A和细胞色素P450 2 B有关的乙氧基间苯二酚-O-脱乙基酶(EROD)和戊氧基间苯二酚-O-脱乙基酶(PROD)的活性。时间过程表明，这种抑制作用基本上是可逆的，EROD和PROD活性在12h达到最低值，并在24h内趋于对照组。正如预期的那样，分离的微粒体与OPZ孵育也抑制了CYP1A和2B。OPZ对细胞色素P1a的影响并不局限于培养中的细胞，体内也存在这种现象。使用整个动物，我们能够证明OPZ也可以通过测量血清中发现的甲基黄嘌呤的量来瞬时抑制给予咖啡因的大鼠的CYP1A活性。然而，在体内用OPZ处理过的大鼠体内分离的微粒体没有表现出这种抑制，可能是因为OPZ是一种可逆的抑制剂，它在常规的微粒体制备过程中解离并丢失。这解释了早期在对分离的微生物体的研究中未能观察到OPZ对细胞色素P450的抑制。除了抑制它们的酶活性外，OPZ也是CYP1A和2B的诱导剂，24小时或更长时间后，它们的mRNAs水平和体内咖啡因代谢的水平都有所增加。结论：OPZ对大鼠体内有毒化学代谢的化学保护机制是复杂的，它通过诱导激活酶和解毒酶来竞争性抑制激活。
The success of oltipraz (OPZ) [5-(2-pyrazinyl)-4-methyl-1,2-dithiole-3-thione] as a chemoprotective agent against aflatoxin B-1 (AFB(1))-induced hepatocarcinogenesis in the rat is thought to depend principally on its ability to enhance detoxication by inducing phase II enzymes, especially glutathione transferases. However, in primary cultures of human hepatocytes, we recently demonstrated that OPZ also has an important inhibitory effect on the major cytochromes P450 (CYPs) of human hepatic AFB(1) metabolism. This has prompted a detailed study of the effect of OPZ on some CYPs involved in metabolism of AFB(1) in the rat. Primary cultures of rat hepatocytes behaved similarly to human hepatocytes and responded to OPZ by inhibition of ethoxyresorufin-O-deethylase (EROD) and pentoxyresorufin-O-depentylase (PROD) activities mainly associated, respectively, with CYP1A and CYP2B. A time-course shows that this inhibition is largely reversible, with EROD and PROD activities reaching a minimum at 12 h and tending towards control values within 24 h. As is to be expected, the incubation of isolated microsomes with OPZ also inhibits CYP1A and 2B. The effect of OPZ on CYP1A is not a phenomenon limited to cells in culture, but also occurs in vivo. Using the whole animal, we were able to demonstrate that OPZ also transiently inhibited CYP1A activity in a rat given caffeine, by measuring the amounts of methylxanthines found in the serum. However, microsomes isolated from rats, that had been treated with OPZ in vivo, show no such inhibition, presumably because, since OPZ is a reversible inhibitor, it dissociates and is lost during the course of conventional procedures of microsomal preparation. This explains some earlier failures in studies of isolated microsomes to observe the inhibition of CYPs by OPZ. In addition to inhibiting their enzymatic activity, OPZ is also an inducer of CYP1A and 2B as shown by the increased levels of their mRNAs and of caffeine metabolism in vivo after 24 h or more. It is concluded that the mechanism of chemoprotection by OPZ, of toxic chemical metabolism in the rat, is complex and involves competitive inhibition of activation succeeded by induction of the enzymes of both activation and detoxication.