Action of the insecticide cyfluthrin on Ca2+signal transduction and cytotoxicity in human osteosarcoma cells

Cyfluthrin is a pyrethroid insecticide and common household pesticide. The effect of cyfluthrin on Ca2+-related physiology in human osteosarcoma is unclear. This study investigated the effect of cyfluthrin on cytosolic-free Ca2+concentrations ([Ca2+]i) and viability in MG63 human osteosarcoma cells. Cyfluthrin concentration-dependently induced [Ca2+]irises. Cyfluthrin-induced Ca2+entry was confirmed by the Mn2+-induced quench of fura-2 fluorescence. Cyfluthrin at concentrations of 10–100 μM induced [Ca2+]irises. Ca2+removal reduced the signal by approximately 50%. Cyfluthrin (100 μM) induced Mn2+influx suggesting Ca2+entry. Cyfluthrin-induced Ca2+entry was inhibited 50% by protein kinase C (PKC) activator (phorbol 12-myristate 13-acetate) and inhibitor (GF109203X) and also by three inhibitors of store-operated Ca2+channels: nifedipine, econazole, and SKF96365. In Ca2+-free medium, treatment with the endoplasmic reticulum Ca2+pump inhibitor thapsigargin (TG) completely inhibited cyfluthrin-evoked [Ca2+]irises. Conversely, treatment with cyfluthrin abolished TG-evoked [Ca2+]irises. Inhibition of phospholipase C (PLC) with 1-[6-[((17β)-3-methoxyestra-1,3,5[10]-trien-17-yl)amino]hexyl]-1H-pyrrole-2,5-dion abolished cyfluthrin-induced [Ca2+]irises. Cyfluthrin at 25–65 μM decreased cell viability, which was not reversed by pretreatment with the Ca2+chelator 1,2-bis(2-aminophenoxy)ethane- N, N, N′, N′-tetraacetic acid–acetoxymethyl ester. Together, in MG63 cells, cyfluthrin induced [Ca2+]irises by evoking PLC-dependent Ca2+release from the endoplasmic reticulum and Ca2+entry via PKC-sensitive store-operated Ca2+entry. Cyfluthrin also caused Ca2+-independent cell death.