Calpastatin overexpression reduces oxidative stress-induced mitochondrial impairment and cell death in human neuroblastoma SH-SY5Y cells by decreasing calpain and calcineurin activation, induction of mitochondrial fission and destruction of mitochondrial fusion.

ABSTRACT

Calpain is an intracellular Ca(2+)-dependent protease, and the activation of calpain has been implicated in neurodegenerative diseases. Calpain activity can be regulated by calpastatin, an endogenous specific calpain inhibitor. Several lines of evidence have demonstrated a potential role of calpastatin in preventing calpain-mediated pathogenesis. Additionally, several studies have revealed that calpain activation and mitochondrial damage are involved in the cell death process; however, recent evidence has not clearly indicated a neuroprotective mechanism of calpastatin against calpain-dependent mitochondrial impairment in the process of neuronal cell death. Therefore, the purpose of this study was to investigate the potential ability of calpastatin to inhibit calpain activation and mitochondrial impairment in oxidative stress-induced neuron degeneration. Calpastatin was stably overexpressed in human neuroblastoma SH-SY5Y cells. In non-calpastatin overexpressing SH-SY5Y cells, hydrogen peroxide significantly decreased cell viability, superoxide dismutase activity, mitochondrial membrane potential, ATP production and mitochondrial fusion protein (Opa1) levels in the mitochondrial fraction but increased reactive oxygen species formation, calpain and calcineurin activation, mitochondrial fission protein (Fis1 and Drp1) levels in the mitochondrial fraction and apoptotic cells. Nevertheless, these toxic effects were abolished in hydrogen peroxide-treated calpastatin-overexpressing SH-SY5Y cells. The results of the present study demonstrate the potential ability of calpastatin to diminish calpain and calcineurin activation and mitochondrial impairment in neurons that are affected by oxidative damage.