Depletion of intracellular glutathione mediates zinc-induced cell death in rat primary astrocytes

Abstract

In the present study, we investigated the possible mechanisms of cellular injury induced by zinc in rat primary astrocytes and C6 glioma cells. Reactive oxygen species (ROS) production, cellular glutathione (GSH) level and mitochondrial transmembrane potential were examined. Exposure to 200–300 μM Zn²⁺ for 24 h resulted in significant lactate dehydrogenase (LDH) release in rat primary astrocytes and C6 glioma cells. An exposure of 200 μM Zn²⁺ resulted in profound morphological changes, for example, shrunken and fragmented nuclei. Pretreatment of a protein synthesis inhibitor, cycloheximide, did not attenuate cellular toxicity induced by Zn²⁺. Zn²⁺ exposure increased intracellular ROS levels by about 250%, and depleted cellular GSH within 2 h, which preceded observable LDH release from the cell. Addition of GSH, N-acetylcysteine (NAC) and ascorbic acid substantially attenuated cellular death induced by Zn²⁺ in a concentration dependent manner. ROS production and morphological changes induced by zinc were also inhibited by co-treatment of GSH or NAC with Zn²⁺. Zn²⁺ significantly depolarized mitochondrial transmembrane potential, which was reversed by co-treatment of GSH or NAC with zinc. In summary, ROS generation, GSH depletion and mitochondrial dysfunction may be key factors in Zn²⁺-induced glial toxicity.