Pretranslational and posttranslational regulation of rat hepatic CYPs 3A2 and 2E1 by disulfiram.
The aldehyde dehydrogenase inhibitor disulfiram (DS) has been used to deter drinking in alcoholics, but it also precipitates pharmacokinetic interactions with coadministered drugs. From previous experiments conducted in vitro, it has been proposed that the ethanol-inducible cytochrome P450 2E1 (CYP2E1) is the major target for inhibition by DS, but the inference from reported drug interactions is that the drug inhibits multiple CYPs. The aim of the present study was to evaluate the inhibition of major constitutive CYPs in rat liver by DS. Thus, the effects of DS on activities mediated by CYPs 2A1/2, 2C11, 2E1, and 3A, which constitute approximately 80% of total CYPs in male rat liver, were evaluated. It was found that CYP2E1-mediated aniline 4-hydroxylase activity was weakly inhibited by DS in vitro, but that preincubation of the drug with NADPH-supplemented microsomes to generate metabolites of DS enhanced the extent of inhibition somewhat. In contrast, constitutive testosterone hydroxylases were inhibited effectively at low concentrations of DS (20 microM decreased the activities of all hydroxylation pathways to 40-60% of control), and a preincubation step between DS and NADPH-fortified microsomes enhanced the inhibition of CYP2C11 and 3A2 activities. In vivo studies were undertaken in which a single dose of DS (100 mg/kg, i.p.) was administered to rats; 24 hr later, CYP2E1-mediated aniline 4-hydroxylase activity was decreased to about 50% of the activity in untreated control rats. CYP2E1 apoprotein and mRNA were also decreased to 38% of the respective control, and CYP3A apoprotein and CYP3A2 mRNA responded similarly. In contrast, CYP2C11 apoprotein was decreased to 66% of control after DS administration, and CYP2A1 expression was unchanged. These findings establish that multiple CYPs are targets for inhibition by DS and provide a basis for clinically significant drug interactions involving CYPs other than 2E1. In addition, the in vivo modulation of CYP function by DS administration is not restricted to enzyme inactivation and may also include down-regulatory effects mediated at a pretranslational level.
Martini
R
R
Department of Medicine, University of Sydney, Westmead Hospital, NSW, Australia.
Ingelman-Sundberg
M
M
Murray
M
M
D000427:Alcohol Deterrents / Q000494:pharmacology*; D000818:Animals; D065691:Cytochrome P-450 CYP2E1 Inhibitors; D065607:Cytochrome P-450 Enzyme Inhibitors; D004221:Disulfiram / Q000494:pharmacology*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology*; D010084:Oxidation-Reduction; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D013250:Steroid Hydroxylases / Q000037:antagonists & inhibitors*
D000427:Alcohol Deterrents; D065691:Cytochrome P-450 CYP2E1 Inhibitors; D065607:Cytochrome P-450 Enzyme Inhibitors; D012333:RNA, Messenger; D013250:Steroid Hydroxylases; C022657:steroid hormone 6-beta-hydroxylase; D004221:Disulfiram