The mechanism of NPC-14686-induced [Ca²⁺]i rises and non-Ca²⁺-triggered cell death in MG63 human osteosarcoma cells.

Abstract

NPC-14686 has been shown to have anti-inflammatory effect in previous studies, but the mechanisms are unclear. The effect of NPC-14686 on cytosolic Ca²⁺ concentrations ([Ca²⁺]i) and viability in MG63 human osteosarcoma cells was explored. The Ca²⁺-sensitive fluorescent dye fura-2 was applied to measure [Ca²⁺]i. NPC-14686 at concentrations of 100-500 μM induced a [Ca²⁺]i rise in a concentration-dependent manner. The response was reduced by 80% by removing Ca²⁺. NPC-14686 induced Mn²⁺ influx leading to quenching of fura-2 fluorescence. NPC-14686-evoked Ca²⁺ entry was suppressed by nifedipine, econazole, SK&F96365, and protein kinase C inhibitor. Inhibition of phospholipase C with U73122 abolished NPC-14686-induced [Ca²⁺]i rise. At 20-50 μM, NPC-14686 decreased cell viability, which was not reversed by chelating cytosolic Ca²⁺ with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid/acetoxy methyl (BAPTA/AM). Annexin V/propidium iodide staining data suggest that NPC-14686 (30-50 μM) induced apoptosis in a concentration-dependent manner. NPC-14686 also increased levels of reactive oxygen species. Together, in human osteosarcoma cells, NPC-14686 induced a [Ca²⁺]i rise by inducing phospholipase C-dependent Ca²⁺ release from the endoplasmic reticulum and Ca²⁺ entry via protein kinase C-sensitive store-operated Ca²⁺ channels. NPC-14686 induced cell death that might involve apoptosis via mitochondrial pathways.