Low pH enhances 2-aminoethoxydiphenyl borate-induced cell death of PC12 cells

2-Aminoethoxydiphenyl borate (2-APB) is widely used as a pharmacological tool for analysis of cellular Ca(2+) regulation. In this study, we found that external acid potentiated neural cell death induced by 2-APB in rat pheochromocytoma 12 (PC12) cells. 2-APB induced cell death in half of the PC12 cells within 30min at pH 6.6 but not at pH 7.4. The extent of the 2-APB-induced cell death increased in a dose-, time- and pH-dependent manner. Ca(2+)-imaging revealed that 2-APB increased [Ca(2+)](i) in PC12 cells at pH 6.6. Removal of extracellular Ca(2+) and chelation of intracellular Ca(2+) inhibited the 2-APB-induced cell death. Antagonists of the store-operated Ca(2+) (SOC) channel (SKF96365 and ruthenium red) blocked both 2-APB-induced cell death and Ca(2+) influx, but those for transient receptor potential channels (BCTC, TRIM and BTP2), acid-sensing ion channels (amiloride) and proton-sensing G-protein-coupled receptors (U73122) did not. These results suggest that 2-APB induces neural cell death via Ca(2+) overload through SOC channel activation under acidic pH.