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 radic als metabolism and cell death by apoptosis. In the present study, we examin ed the role of Zn2+. in the regulation of apoptosis in cultured rat hepatoc ytes. The chelation of Zn2+ by a membrane permeable metal ion chelator, N, N, N', N'-tetrakis(2-pyridylmethyl) ethylenediamine (TPEN), induced apoptos is. Addition of ZnSO4 prevented TPEN-induced apoptosis. Unlike the effect o f TPEN, a membrane impermeable metal ion chelator, diethylenetriamine penta acetic acid (DTPA), did not induce apoptosis, indicating that chelation of intracellular Zn2+ was required to trigger apoptosis, Caspase-3-like proteo lytic activity, a general biochemical mediator of apoptosis in a variety of cells and tissues, was also activated with the treatment of TPEN but not D TPA. TPEN treatment, but not DTPA, also resulted in the depletion of intrac ellular reduced glutathione (GSH) but addition of Zn2+ recovered the GSH le vel. N-acetyl-L-cysteine (NAC), a thiol antioxidant, prevented TPEN-induced apoptosis. These results taken together suggest that intracellular Zn2+ in terfere with the apoptosis process, possibly through the regulation of cell ular redox potential involving GSH. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.