ROLE OF OXIDANTS AND ANTIOXIDANTS IN THE INDUCTION OF AP-1, NF-KAPPA-B, AND GLUTATHIONE-S-TRANSFERASE GENE-EXPRESSION

Transcription factors AP-1 and NF-kappa B have been implicated in the inducible expression of a variety of genes in response to oxidative st ress. Recently, based on the observation that butylated hydroxyanisole (BHA) and pyrrolidine dithiocarbamate (PDTC) induce AP-1 binding acti vity and AP-1-dependent gene expression and assuming that these compou nds exert an antioxidant effect, it was claimed that AP-1 is an antiox idant-responsive factor. To determine whether AP-1 can be responsive t o both oxidant and antioxidant, we examined the nature of BHA and PDTC inducing activity. Using EPR spectroscopy to detect semiquinone radic als, we demonstrate the autoxidation of BHA metabolite tert-butylhydro quinone (TBHQ) to tert-butylquinone. The kinetics of TBHQ-mediated gen erations of (OH)-O-. radicals were monitored in intact hepatoma HepG2 cells by EPR spin trapping technique. Exogenous catalase inhibited the rate and amount of (OH)-O-. radical formation and the induction of AP -1-mediated glutathione S-transferase (GST) Ya gene expression by BHA and TBHQ, thus indicating the intermediate formation of H2O2 in the me tabolism of these chemicals. Furthermore, we show that the induction o f AP-1 and NF-kappa B activities and GST Ya gene expression by BHA and TBHQ is due to a pro-oxidant activity, since this induction was inhib ited by thiol compounds N-acetyl cysteine and GSH. The present finding s do not support the notion that the induction of AP-1 by BHA, TBHQ, o r PDTC is an antioxidant response and demonstrate that both AP-1 and N F-kappa B activities are induced by oxygen radicals.