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

Abstract

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.