Role of intracellular calcium on hydrogen peroxide-induced apoptosis in rat pancreatic acinar AR42J cells

Abstract

The authors investigated whether cytosolic free calcium concentration ([Ca2+]c) plays a role in hydrogen peroxide-induced pancreatic acinar AR42J cells apoptosis. We analysed mitochondrial depolarization, [Ca2+]c determination and caspase-3 activity by fluorimetric methods, and cytochrome c release by subcellular fractionation and western blotting. The data shown that hydrogen peroxide, which causes a sustained [Ca2+]c increase, induces mitochondrial depolarization and cytochrome c release, and activation of caspase-3. Dimethyl-BAPTA loading did not affect hydrogen peroxide-evoked mitochondrial apoptosis, suggesting that these responses are independent of increases in [Ca2+]c. Treatment with thapsigargin, to induce extensive calcium store depletion and subsequent increases in [Ca2+]c, also stimulates mitochondrial depolarization cytochrome c release, and caspase-3 activation. Similar results were observed in AR42J cells loaded with dimethyl-BAPTA, suggesting that activation of apoptosis by thapsigargin does not require rises in [Ca2+]c. However, the blockade of mitochondrial calcium entry by pretreating with Ru360 showed protection against hydrogen peroxide- and thapsigargin-induced mitochondrial apoptosis. These results indicate that the apoptosis evoked by hydrogen peroxide and thapsigargin is mediated by mitochondrial calcium uptake.