Mechanisms underlying the effect of an oral antihyperglycaemic agent glyburide on calcium ion (Ca 2+ ) movement and its related cytotoxicity in prostate cancer cells

Summary Glyburide is an agent commonly used to treat type 2 diabetes and also affects various physiological responses in different models. However, the effect of glyburide on Ca 2+ movement and its related cytotoxicity in prostate cancer cells is unclear. This study examined whether glyburide altered Ca 2+ signalling and viability in PC 3 human prostate cancer cells and investigated those underlying mechanisms. Intracellular Ca 2+ concentrations ([Ca 2+ ] i ) in suspended cells were measured by using the fluorescent Ca 2+ ‐sensitive dye fura‐2. Cell viability was examined by WST ‐1 assay. Glyburide at concentrations of 100–1000 μM induced [Ca 2+ ] i rises. Ca 2+ removal reduced the signal by approximately 60%. In Ca 2+ ‐containing medium, glyburide‐induced Ca 2+ entry was inhibited by 60% by protein kinase C ( PKC ) activator (phorbol 12‐myristate 13 acetate, PMA ) and inhibitor ( GF 109203X), and modulators of store‐operated Ca 2+ channels (nifedipine, econazole and SKF 96365). Furthermore, glyburide induced Mn 2+ influx suggesting of Ca 2+ entry. In Ca 2+ ‐free medium, inhibition of phospholipase C ( PLC ) with U73122 significantly inhibited glyburide‐induced [Ca 2+ ] i rises. Treatment with the endoplasmic reticulum ( ER ) Ca 2+ pump inhibitor 2,5‐di‐tert‐butylhydroquinone ( BHQ ) abolished glyburide‐evoked [Ca 2+ ] i rises. Conversely, treatment with glyburide abolished BHQ ‐evoked [Ca 2+ ] i rises. Glyburide at 100–500 μM decreased cell viability, which was not reversed by pretreatment with the Ca 2+ chelator 1,2‐bis(2‐aminophenoxy)ethane‐N,N,N’,N’‐tetraacetic acid‐acetoxymethyl ester ( BAPTA / AM ). Together, in PC 3 cells, glyburide induced [Ca 2+ ] i rises by Ca 2+ entry via PKC ‐sensitive store‐operated Ca 2+ channels and Ca 2+ release from the ER in a PLC ‐dependent manner. Glyburide also caused Ca 2+ ‐independent cell death. This study suggests that glyburide could serve as a potential agent for treatment of prostate cancer.