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

Abstract

Econazole is an antifungal drug with different in vitro effects. However, econazole's effect on osteoblast like 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 μM, 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 releasing Ca²⁺. U73122, an inhibitor of phospholipase C, abolished histamine (an inositol 1,4,5-trisphosphate dependent 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⁺]_i 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.