Hu Y, Mishin V, Johansson I, von Bahr C, Cross A, Ronis M J, Badger T M, Ingelman-Sundberg M
Department of Medical Biochemistry and Biophysics, Karolinska Institute, Stockholm, Sweden.
J Pharmacol Exp Ther. 1994 Jun;269(3):1286-91.
Ethanol-inducible cytochrome P450 (CYP) 2E1 (CYP2E1) is responsible for the metabolism of many xenobiotics which exert toxic effects in humans. Specific inhibitors might constitute valuable tools in the elucidation of the pharmacological and toxicological roles of this isozyme in vivo. In the present investigation we have evaluated the effects of a drug used for treatment of ethanol withdrawal states, chloromethiazole (CMZ), on CYP2E1 expression in rat liver. A 4-fold induction of CYP2E1 was observed after 3 days of starvation, accompanied by a similar increase in the level of the corresponding mRNA. CMZ specifically inhibited the elevation of CYP2E1 mRNA and protein, but did not prevent CYP2B1 and CYP3A1 or CYP1A1 induction caused by treatment with phenobarbital or beta-naphthoflavone, respectively. From nuclear run-off experiments it was apparent that the rate of the CYP2E1 gene transcription was inhibited greatly by CMZ treatment. Rats treated with ethanol in a total enteral nutrition model had higher CYP2E1-dependent hepatic microsomal activities of p-nitrophenol hydroxylase and carbon tetrachloride-induced lipid peroxidation than controls, and simultaneous CMZ treatment abolished the ethanol-dependent induction. In vitro experiments with rat liver microsomes showed that CMZ did not act as an inhibitor of CYP2E1-dependent catalytic activities or as an inhibitor of microsomal NADPH and CYP2E1-dependent lipid peroxidation. In conclusion, we suggest that CMZ might constitute an efficient and specific inhibitor of CYP2E1 expression suitable for in vivo experiments.
乙醇诱导型细胞色素P450（CYP）2E1（CYP2E1）负责许多外源性物质的代谢，这些物质在人体内具有毒性作用。特异性抑制剂可能是阐明该同工酶在体内药理和毒理作用的有价值工具。在本研究中，我们评估了一种用于治疗乙醇戒断状态的药物氯美噻唑（CMZ）对大鼠肝脏中CYP2E1表达的影响。饥饿3天后观察到CYP2E1诱导了4倍，相应mRNA水平也有类似增加。CMZ特异性抑制CYP2E1 mRNA和蛋白质的升高，但不阻止分别由苯巴比妥或β-萘黄酮处理引起的CYP2B1、CYP3A1或CYP1A1的诱导。从核转录实验明显看出，CMZ处理极大地抑制了CYP2E1基因的转录速率。在全肠内营养模型中用乙醇处理的大鼠，其对硝基苯酚羟化酶的CYP2E1依赖性肝微粒体活性和四氯化碳诱导的脂质过氧化作用高于对照组，同时给予CMZ处理消除了乙醇依赖性诱导。用大鼠肝脏微粒体进行的体外实验表明，CMZ既不充当CYP2E1依赖性催化活性的抑制剂，也不充当微粒体NADPH和CYP2E1依赖性脂质过氧化的抑制剂。总之，我们认为CMZ可能是一种适用于体内实验的CYP2E1表达的有效且特异性抑制剂。
