Calcium and Reactive Oxygen Species Mediated Zn2+-Induced Apoptosis in PC12 Cells

The release of excessive Zn2+ from presynaptic boutons into extracellular regions contributes to neuronal apoptotic events, which result in neuronal cell death. However, the mechanisms of Zn2+-induced neuronal cell death are still unclear. Therefore, we investigated the dynamics of intracellular Zn2+, calcium, and reactive oxygen species in PC12 cells. The addition of Zn2+ produced cell death in a concentration- and time-dependent manner. 45Ca2+ influx occurred just after the treatment with Zn2+, although subsequent hydroxyl radical (•OH) production did not begin until 3 h after Zn2+ exposure. •OH production was significantly attenuated in Ca2+-free medium or by L-type Ca2+ channel antagonist treatment, but it was independent of the intracellular Zn2+ content. Dantrolene treatment had no protective effects against Zn2+-induced cell death. Treatment with N-acetyl-L-cysteine blocked •OH generation and subsequent cell death. These data indicate that Ca2+ influx and subsequent •OH production are critical events in Zn2+-induced toxicity in PC12 cells.