SUBLETHAL LEVELS OF OXIDATIVE STRESS STIMULATE TRANSCRIPTIONAL ACTIVATION OF C-JUN AND SUPPRESS IL-2 PROMOTER ACTIVATION IN JURKAT T-CELLS

Sublethal levels of oxidative stress are well known to alter T cell fu nctional responses, but the underlying mechanisms are unknown. The cur rent study examined the effects of oxidative stress on transcriptional activities mediated by c-Fos/c-Jun AP-1 and the nuclear factor of act ivated T cells (NF-AT). The present results show that Jurkat T cells a cutely exposed to micromolar concentrations of H2O2 exhibit substantia l increases in AP-1 binding activity and the expression of c-jun but n ot c-fos mRNA. The preferential induction of c-jun by H2O2 did not rep resent redox stabilization of mRNA transcripts, and oxidative signals closely resembled PHA/PMA stimulation by effectively transactivating t he full length c-jun promoter via the proximal jun1 tumor promoter-res ponsive element (TRE)-like promoter element. Similarly, the complexes binding the consensus AP-1 TRE and jun TRE-like motifs in cells expose d to oxidative signals or PHA/PMA were indistinguishable, being compos ed of c-Fos, c-Jun, and JunD. However, PHA/PMA but not oxidative signa ls induced the coordinate activation of reporter constructs containing the AP-1-TRE, NF-AT, and IL-2 promoter regions along with IL-2 mRNA e xpression. Furthermore, sublethal levels of H2O2 actively suppressed t he transcriptional activation of NF-AT and IL-2 reporters as well as t he expression of IL-2 mRNA in cells stimulated with PHA/PMA. Gel shift analysis revealed that oxidative suppression of NF-AT represented inh ibition in the early generation of NF-AT complexes rather than the bin ding of preformed NF-AT complexes. These results suggest that oxidativ e signals can positively and negatively regulate T cell transcriptiona l events and that changes in cellular redox can uncouple AP-1 regulati on of c-jun from transcriptional up-regulation of IL-2 via NF-AT.