Ca2+-independent caspase-3 but not Ca2+-dependent caspase-2 activation induced by oxidative stress leads to SH-SY5Y human neuroblastoma cell apoptosis

Continuous and long-lasting exposure to tert-butylhy-droperoxide (t-BOOH) increased the number of apoptotic SH-SY5Y human neuroblastoma cells both in the presence and in the absence of the intracellular Ca 2 + ion chelator 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetra-acetic acid (BAPTA). In addition, t-BOOH exposure induced activation of CPP32, as demonstrated by poly-(ADP-ribose) polymerase (PARP) cleavage, and of ICH-1L caspases. Exposure to t-BOOH also induced a time-dependent release of cytochrome c. Interestingly, in the presence of BAPTA, CPP32 activation still occurred, whereas ICH-1 L activation was blocked. Ac-DEVD-CHO, an inhibitor of CPP32 activity, prevented the appearance of apoptotic cells, whereas the inhibitor of ICH-1 L activity Z-VDVAD-FMK did not. Collectively, these findings demonstrate that in SH-SY5Y neuroblastoma cells exposure to continuous and long-lasting oxidative stress induced activation of caspase-3 that was independent of intracellular Ca 2 + ion concentration ([Ca 2 + ] i ) elevation but led to cell apoptosis. In contrast, caspase-2 activation was dependent on [Ca 2 + ] i increase but did not result in apoptosis.