Effect of diallyl disulfide on Ca2+ movement and viability in PC3 human prostate cancer cells

The effect of diallyl disulfide (DADS) on cytosolic Ca2+ concentrations ([Ca2+]i) and viability in PC3 human prostate cancer cells is unclear. This study explored whether DADS changed [Ca2+]i in PC3 cells by using fura-2. DADS at 50-1000 μM increased [Ca2+]i in a concentration-dependent manner. The signal was reduced by removing Ca2+. DADS-induced Ca2+ influx was not inhibited by nifedipine, econazole, SK&F96365, and protein kinase C modulators; but was inhibited by aristolochic acid. In Ca2+-free medium, pretreatment with the endoplasmic reticulum Ca2+ pump inhibitors thapsigargin or 2,5-di-tert-butylhydroquinone (BHQ) nearly abolished DADS-induced [Ca2+]i rise. Incubation with DADS inhibited thapsigargin or BHQ-induced [Ca2+]i rise. Inhibition of phospholipase C with U73122 did not alter DADS-induced [Ca2+]i rise. At 500-1000 μM, DADS killed cells in a concentration-dependent manner. The cytotoxic effect of DADS was partly reversed by prechelating cytosolic Ca2+ with 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid (BAPTA). Propidium iodide staining suggests that DADS (500 μM) induced apoptosis in a Ca2+-independent manner. Annexin V/PI staining further shows that 10 μM and 500 μM DADS both evoked apoptosis. DADS also increased reactive oxygen species (ROS) production. Collectively, in PC3 cells, DADS induced [Ca2+]i rise probably by causing phospholipase C-independent Ca2+ release from the endoplasmic reticulum and Ca2+ influx via phospholipase A2-sensitive channels. DADS induced Ca2+-dependent cell death, ROS production, and Ca2+-independent apoptosis.