JNK (C-JUN NH2-TERMINAL KINASE) IS A TARGET FOR ANTIOXIDANTS IN T-LYMPHOCYTES

AP-1 has been shown to behave as a redox-sensitive transcription facto r that can be activated by both oxidant and antioxidant stimuli. Howev er, the mechanisms involved in the activation of AP-1 by antioxidants are largely unknown. In this study we show that the structurally unrel ated antioxidant agents pyrrolidine dithiocarbamate (PDTC), butylated hydroxyanisole, and N-acetylcysteine activated JNK (c-Jun NH2-terminal kinase) in Jurkat T cells. This activation differed substantially fro m that mediated by phorbol 12-myristate 13-acetate (PMA) and Ca2+ iono phore or produced by costimulation with antibodies against the T cell receptor-CD3 complex and to CD28. The activation of JNK by classical T cell stimuli was transient, whereas that mediated by PDTC and butylat ed hydroxyanisole (but not N-acetylcysteine) was sustained. The kineti cs of JNK activation correlated with the expression of c-jun which was transient after stimulation with PMA plus ionophore and prolonged in response to PDTC, which also transiently induced c-fos. In addition, J NK activation by PMA plus ionophore was sensitive to inhibitors of sig naling pathways involving Ca2+, protein kinase C, and tyrosine phospho rylation, which failed to inhibit the activation mediated by PDTC. Tra nsfection of transdominant negative expression vectors of ras and raf, together with AP-l-dependent reporter constructs, as web as Western b lot analysis using anti-ERR (extracellular signal-regulated kinase) an tibodies, indicated that the Ras/Raf/ERK pathway did not appear to med iate the effect of the antioxidant. However, the combined treatment wi th PDTC and PMA, two agents that synergize on AP-1 activation, resulte d in the persistent phosphorylation of ERR-2. In conclusion, our resul ts identify JNK as a target of antioxidant agents which can be regulat ed differentially under oxidant and antioxidant conditions.