Possible involvement of Ca2+ signaling in rotenone-induced apoptosis in human neuroblastoma SH-SY5Y cells

Rotenone, an inhibitor of mitochondrial respiratory chain complex I, is a useful tool to elicit animal model of Parkinson's disease. Rotenone-induced neuronal apoptosis may contribute to the etiology of Parkinson's disease. However, the mechanism of rotenone-induced apoptosis is not fully understood. In the present study, we show that Ca2+ signaling is essential for rotenone-induced apoptosis in human neuroblastoma SH-SY5Y cells. By using Fluo-3/AM and Fura-2/AM, the fluorescent calcium indicator, rotenone was found to cause a rise in intracellular free Ca2+ ([Ca2+]i). The intracellular Ca2+ chelator BAPTA attenuated rotenone-induced apoptosis. Notably, Ca2+ suppression also prevented rotenone-induced apoptotic related events including reactive oxygen species production, G2/M cell cycle arrest and caspase activation, suggesting that Ca2+ signaling is upstream to these events. In the absence of extracellular Ca2+, the rotenone-induced [Ca2+]i elevation was inhibited. Further, the voltage-dependent Ca2+ channel blocker nifedipine suppressed most of the elevation of [Ca2+]i induced by rotenone. These results demonstrate that rotenone leads to an elevation in [Ca2+]i through Ca2+ influx by the opening of voltage-gated Ca2+ channel. This study of rotenone may help to elucidate the neurodegenerative mechanims in Parkinson's disease.