Induction of apoptosis in lymphoid cells by thiol-mediated oxidative stress

Abstract

In previous studies, oxidants such as hydrogen peroxide (H2O2) or hydroperoxy fatty acids were shown to induce apoptosis in the CEM human T cell line as demonstrated by the cleavage of cellular DNA into a ∼ 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 of low doses (0.1–3 mM) of N-acetyl-L-cysteine (NAC), reduced glutathione (GSH) or cysteine. By contrast, higher concentrations (≥10 mM) of the same thiols displayed a paradoxical lack of toxicity. Thiol-induced apoptosis was completely prevented by the addition of BAPTA-AM, an intracellular calcium chelator, or by simultaneous treatment with 5 mM pyruvate which forms a thiazolidine complex with sulfhydryl compounds. Catalase or glutathione peroxidase, but not Superoxide dismutase, protected the cells from thiol-induced apoptosis demonstrating a role for H2O2. The ability of thiol compounds to either evoke or prevent oxidative stress implies a unique role for these agents in the control of apoptosis in lymphoid cells.