H2O2 and antioxidants have opposite effects on activation of NF-kappa B and AP-1 in intact cells: AP-1 as secondary antioxidant-responsive factor.

Abstract

We show that AP‐1 is an antioxidant‐responsive transcription factor. DNA binding and transactivation by AP‐1 were induced in HeLa cells upon treatment with the antioxidants pyrrolidine dithiocarbamate (PDTC) and N‐acetyl‐L‐cysteine (NAC), and upon transient expression of the antioxidative enzyme thioredoxin. While PDTC and NAC enhanced DNA binding and transactivation of AP‐1 in response to phorbol ester, the oxidant H2O2 suppressed phorbol ester activation of the factor. H2O2 on its own was only a weak inducer of AP‐1. Activation of AP‐1 by PDTC was dependent on protein synthesis and involved transcriptional induction of c‐jun and c‐fos genes. Transcriptional activation of c‐fos by PDTC was conferred by the serum response element, suggesting that serum response factor and associated proteins function as primary antioxidant‐responsive transcription factors. In the same cell line, the oxidative stress‐responsive transcription factor NF‐kappa B behaved in a manner strikingly opposite to AP‐1. DNA binding and transactivation by NF‐kappa B were strongly activated by H2O2, while the antioxidants alone were ineffective. H2O2 potentiated the activation of NF‐kappa B by phorbol ester, while PDTC and NAC suppressed PMA activation of the factor. PDTC did not influence protein kinase C (PKC) activity and PKC activation by PMA, indicating that the antioxidant acted downstream of and independently from PKC.