Econazole-Induced Ca2+ Fluxes and Apoptosis in Human Oral Cancer Cells

The effect of econazole on cytosolic free Ca2+ concentrations ([Ca2+](i)) and viability was explored in human oral cancer cells (OC2), using the fluorescent dyes fura-2 and WST-1, respectively. Econazole at concentrations of >1 mu M increased [Ca2+]; in a concentration-dependent manner. The Ca2+ signal was reduced partly by removing extracellular Ca2+. The econazole-induced Ca2+ influx was sensitive to blockade of aristolochic acid (phospholipase A(2) inhibitor) and GF109203X (PKC inhibitor). In Ca2+-free medium, after treatment with 1 mu M thapsigargin (an endoplasmic reticulum Ca2+ pump inhibitor), 30 mu M econazole failed to induce a [Ca2+]; rise. Inhibition of phospholipase C with 2 mu M U73122 substantially suppressed econazole-inducecl [Ca2(+)](i) rise. At concentrations of 5-70 mu M econazole killed cells in a concentration-dependent manner. The cytotoxic effect of 50 mu M econazole was enhanced by prechelating cytosolic Ca2+ with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA). The ERK MAPK inhibitor, PD98059 (10 mu M), also enhanced 20 mu M econazole-induced cell death. Propidium iodide staining data suggest that econazole induced apoptosis between concentrations of 10-70 mu M. Collectively, in OC2 cells, econazole induced [Ca2+](i); rises by causing Ca2+ release from the endoplasmic reticulum and Ca2+ influx from phospholipase A(2)/PKC-regulated Ca2+ channels. Furthermore, econazole caused cell death appeared to be regulated by ERK MAPK. Drug Dev Res 71:240-248, 2010. (C) 2010 Wiley-Liss, Inc.