Apoptosis induced by chelation of intracellular zinc is associated with depletion of cellular reduced glutathione level in rat hepatocytes

Zn2+ has multiple implications in cellular metabolism, including free radicals metabolism and cell death by apoptosis. In the present study, we examined the role of Zn2+. in the regulation of apoptosis in cultured rat hepatocytes. The chelation of Zn2+ by a membrane permeable metal ion chelator, N, N, N', N'-tetrakis(2-pyridylmethyl) ethylenediamine (TPEN), induced apoptosis. Addition of ZnSO4 prevented TPEN-induced apoptosis. Unlike the effect of TPEN, a membrane impermeable metal ion chelator, diethylenetriamine pentaacetic acid (DTPA), did not induce apoptosis, indicating that chelation of intracellular Zn2+ was required to trigger apoptosis, Caspase-3-like proteolytic activity, a general biochemical mediator of apoptosis in a variety of cells and tissues, was also activated with the treatment of TPEN but not DTPA. TPEN treatment, but not DTPA, also resulted in the depletion of intracellular reduced glutathione (GSH) but addition of Zn2+ recovered the GSH level. N-acetyl-L-cysteine (NAC), a thiol antioxidant, prevented TPEN-induced apoptosis. These results taken together suggest that intracellular Zn2+ interfere with the apoptosis process, possibly through the regulation of cellular redox potential involving GSH. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.