Effect of miconazole on intracellular Ca²⁺ levels and proliferation in human osteosarcoma cells

The effect of miconazole, an anti-fungal drug, on cytoplasmic free Ca ²⁺ concentrations ([Ca²⁺]_i) in human osteosarcoma cells (MG63) was explored by using the Ca²⁺-sensitive dye fura-2. Miconazole acted in a concentration-dependent manner with an EC ₅₀ of 75 μM. The Ca²⁺ signal comprised a gradual rise and a sustained elevation. Removal of extracellular Ca²⁺ reduced 50% of the signal. In Ca²⁺-free medium, the [Ca²⁺]_i rise induced by 1 μM thapsigargin (an endoplasmic reticulum Ca²⁺ pump inhibitor) was completely inhibited by pretreatment with 20 μM miconazole. Pretreatment with thapsigargin partly inhibited miconazole-induced Ca²⁺ release. The miconazole-induced Ca²⁺ release was not changed by inhibition of phospholipase C with 2 μM U73122. By using tetrazolium as a fluorescent probe, it was shown that 10-100 μM miconazole decreased cell proliferation rate in a concentration-dependent manner. Collectively, this study shows that miconazole induces [Ca²⁺] _i rises in human osteosarcoma cells via releasing Ca²⁺ mainly from the endoplasmic reticulum in a manner independent of phospholipase C activity, and by causing Ca²⁺ influx. Furthermore, miconazole may be cytotoxic to the cells at higher concentrations.