Transcriptional activation and redox regulation of the tumor necrosis factor alpha promoter in human T cells: Role of the CRE/kappa 3 promoter region

Aberrancies in T cell expression of tumor necrosis factor-alpha (TNF-alpha) are frequently observed in inflammatory states characterized by oxidative stress due to excessive generation of hydrogen peroxide (H2O2) and other re active oxygen species (ROS), In this study, we examined the possible effect s of oxidative stress on the expression of TNF-alpha protein and transcript ional activation of the TNF-alpha promoter in human T cells, Results show t hat exposure of resting T cells to micromolar concentrations of H2O2 did no t induce TNF-alpha protein production or transcriptional activation of the TNF-alpha promoter. However, oxidative signals resulted in a dose-dependent suppression of TNF-alpha protein production and transcriptional activation in T cells stimulated with the lectin phytohemagglutinin (PHA) and phorbol myristate acetate (PMA), Optimal suppression of TNF-alpha promoter activit y was observed when cells were exposed to oxidative stress during early T c ell activation, and other experiments demonstrated that the transactivation responses of the TNF-alpha promoter were quite susceptible to inhibition b y both oxidative and reducing changes in cellular redox, Furthermore, repor ter gene assays with 5' deletion mutants of the TNF-alpha promoter showed t hat the CRE/kappa 3 composite site played a major role in activation of the TNF-alpha promoter by dual stimulatory signals and suppression of the TNF- alpha promoter by oxidative signals. Thus, T cell expression of TNF-alpha a t the protein and transcriptional levels is highly regulated by changes in cellular redox, and the CRE/kappa 3 composite site is important for both ac tivation and redox regulation of the TNF-alpha promoter.