Induction of cyclooxygenase-2 on activated T lymphocytes: regulation of T cell activation by cyclooxygenase-2 inhibitors.

Cyclooxygenase (COX), known to exist in two isoforms, COX-1 and COX-2, is a key enzyme in prostaglandin synthesis and the target for most nonsteroidal anti-inflammatory drugs. In this study, we show that human T lymphocytes express the COX-2 isoenzyme. COX-2 mRNA and protein were induced in both Jurkat and purified T cells stimulated by TCR/CD3 or PMA activation. COX-2 mRNA was induced very early after activation and superinduced by protein synthesis inhibitors, whereas it was inhibited by the immunosuppressive drug cyclosporin A, identifying it as an early T cell activation gene. Interestingly, treatment with COX-2-specific inhibitors such as NS398 or Celecoxib severely diminished early and late events of T cell activation, including CD25 and CD71 cell surface expression, IL-2, TNF-alpha, and IFN-gamma production and cell proliferation, but not the expression of CD69, an immediate early gene. COX-2 inhibitors also abolished induced transcription of reporter genes driven by IL-2 and TNF-alpha promoters. Moreover, induced transcription from NF-kappaB- and NF-AT-dependent enhancers was also inhibited. These results may have important implications in anti-inflammatory therapy and open a new field on COX-2-selective nonsteroidal anti-inflammatory drugs as modulators of the immune activation.