CELLULAR REDOX STATUS INFLUENCES BOTH CYTOTOXIC AND NF-KAPPA-B ACTIVATION IN NATURAL-KILLER-CELLS

The role of cellular redox status in both cytotoxic activity and NF-ka ppa B activation in natural killer (NK) cells was investigated. The re sults indicate that stimulation of NK cells, either freshly isolated f rom peripheral blood lymphocytes (PBL) or long-term cultured NK clones , with specific cell targets results in an increased binding activity of NF-kappa B and AP-1 transcription factors measured by gel retardati on. Pretreatment of NK cells with the antioxidant pyrrolidine dithioca rbarmate (PDTC) leads to the inhibition of NF-kappa B activation but t he AP-1 binding to DNA was superinduced. The inhibition of NF-kappa B by PDTC paralleled with an inhibition of spontaneous cytotoxicity medi ated by NK cells. Moreover, the inhibitors of serine proteases, N-alph a-tosyl-L-lysine chloromethyl ketone and N-alpha-tosyl-L-phenylalanine chloromethylketone, also blocked the cytolytic activity of NK cells a gainst the sensitive target K562. In contrast, NK activity was not aff ected by pretreatment of the effector cells with the proteasome inhibi tor N-acetyl-leu-leu-norleucinal which selectively inhibits NF-kappa B activation. Altogether, these results support the hypothesis that the activation of NK cells involved transcriptional and post-transcriptio nal events, and that reactive intermediates may play an important role in the molecular processes related with the generation of a cytotoxic response by NK cells.