INDUCTION OF APOPTOSIS IN LYMPHOID-CELLS BY THIOL-MEDIATED OXIDATIVE STRESS

In previous studies, oxidants such as hydrogen peroxide (H2O2) Or hydr operoxy fatty acids were shown to induce apoptosis in the CEM human T cell line as demonstrated by the cleavage of cellular DNA into a simil ar to 180-base pair ''ladder''. Oxidant-induced DNA fragmentation was detectable within 3 h and inhibitable by various antioxidants. In the present study, apoptosis is shown to also be induced by the addition o f low doses (0.1-3 mM) of N-acetyl-L-cysteine (NAG), reduced glutathio ne (GSH) or cysteine. By contrast, higher concentrations (greater than or equal to 10 mM) of the same thiols displayed a paradoxical lack of toxicity. Thiol-induced apoptosis was completely prevented by the add ition of BAPTA-AM, an intracellular calcium chelator, or by simultaneo us treatment with 5 mM pyruvate which forms a thiazolidine complex wit h sulfhydryl compounds. Catalase or glutathione peroxidase, but not su peroxide dismutase, protected the cells from thiol-induced apoptosis d emonstrating a role for H2O2 The ability of thiol compounds to either evoke or prevent oxidative stress implies a unique role for these agen ts in the control of apoptosis in lymphoid cells.