Econazole induces increases in free intracellular Ca2+ concentrations in human osteosarcoma cells

Econazole is an antifungal drug with different in vitro effects. However, econazole's effect on osteoblastlike cells is unknown. In human MG63 osteosarcoma cells, the effect of econazole on intracellular Ca2+ concentrations ([Ca2+](i)) was explored by using fura-2. At a concentration of 0.1 mu M, econazole started to cause a rise in [Ca2+](i) in a concentration-dependent manner. Econazole-induced [Ca2+](i) rise was reduced by 74% by removal of extracellular Ca2+. The econazole-induced Ca2+ influx was mediated via a nimodipine-sensitive pathway. In Ca2+-free medium, thapsigargin, an inhibitor of the endoplasmic reticulum Ca2+-ATPase, caused a [Ca2+](i) rise, after which the increasing effect of econazole on [Ca2+](i) was abolished. Pretreatment of cells with econazole to deplete Ca2+ stores totally prevented thapsigargin from relea-sing Ca2+. U73122, an inhibitor of phospholipase Q abolished histamine (an inositol 1,4,5-trisphosphatedependent Ca2+ mobilizer)-induced, but not econazoleinduced, [Ca2+](i) rise. Econazole inhibited 76% of thapsigargin-induced store-operated Ca2+ entry. These findings suggest that in MG63 osteosarcoma cells, econazole increases [Ca2+](j) by stimulating Ca2+ influx and Ca2+ release from the endoplasmic reticulum via a phospholipase C-independent manner. In contrast, econazole acts as a potent blocker of store-operated Ca2+ entry.