Differential inhibition and inactivation of human CYP1 enzymes by trans-resveratrol: Evidence for mechanism-based inactivation of CYP1A2

trans-Resveratrol (3,5,4'-trihydroxy-trans-stilbene) has been reported to c onfer chemoprotection against 7,12-dimethylbenz[a]anthracene (DMBA)-induced carcinogenicity in a murine model. A potential mechanism for this effect b y trans-resveratrol is inhibition of DMBA-bioactivating cytochrome P450 (CY P) enzymes such as CYP1B1, CYP1A1, and CYP1A2. In the present study, we exa mined in detail the in vitro inhibitory effects of trans-resveratrol on the se three human CYP enzymes. trans-Resveratrol decreased 7-ethoxyresorufin O -dealkylation activity catalyzed by human recombinant CYP1B1, CYP1A1, and C YP1A2 in a concentration-dependent manner and by a mixed type of inhibition . This direct inhibition was enzyme-selective, as judged by the differences in the apparent K-i values (0.8 +/-0.1 muM, 1.2 +/-0.1 muM, and 15.5 +/-1. 1 muM for CYP1B1, CYP1A1, and CYP1A2, respectively). Preincubating recombin ant CYP1A2 or human liver microsomes with trans-resveratrol and NADPH prior to the initiation of substrate oxidation resulted in a time- and concentra tion-dependent decrease in catalytic activity. The inactivation of liver mi crosomal CYP1A2 by trans-resveratrol required NADPH, was not reversible by dialysis, and was not affected by the trapping agents glutathione, N-acetyl cysteine, catalase, or superoxide dismutase, but was attenuated by a CYP1A2 substrate, imipramine. Analysis of a panel of individual human liver micro somes showed intersample differences in the response to the in vitro inacti vation by trans-resveratrol. In contrast to CYP1A2, CYP1B1 was not subject to inactivation by this compound and the reduction in CYP1A1 activity was t ime- but not concentration-dependent. In summary, trans-resveratrol differe ntially inhibited human CYP1 enzymes and this occurred by two distinct mech anisms: direct inhibition (mainly CYP1B1 and CYP1A1) and mechanism-based in activation (CYP1A2).