The effect of fendiline on cytosolic free Ca2+ concentrations ([Ca2+]i) and proliferation has not been explored in human oral cancer cells. This study examined whether fendiline altered Ca2+ levels and caused cell death in OC2 human oral cancer cells. [Ca2+]i and cell viability were measured using the fluorescent dyes fura-2 and WST-1, respectively. Fendiline at concentrations above 10 μM increased [Ca2+]i in a concentration-dependent manner. The Ca2+ signal was reduced partly by removing extracellular Ca2+. The fendiline-induced Ca2+ influx was sensitive to blockade of L-type Ca2+ channel blockers. In Ca2+-free medium, after pretreatment with 50 μM fendiline, 1 μM thapsigargin (an endoplasmic reticulum Ca2+ pump inhibitor)-induced [Ca2+]i rises were inhibited; and conversely, thapsigargin pretreatment nearly abolished fendiline-induced [Ca2+]i rises. Inhibition of phospholipase C with 2 μM U73122 did not change fendiline-induced [Ca2+]i rises. At concentrations between 5 and 25 μM, fendiline killed cells in a concentration-dependent manner. The cytotoxic effect of 15 μM fendiline was not reversed by prechelating cytosolic Ca2+ with BAPTA/AM. Collectively, in OC2 cells, fendiline induced [Ca2+]i rises by causing Ca2+ release from the endoplasmic reticulum and Ca2+ influx from L-type Ca2+ channels. Furthermore, fendiline-caused cytotoxicity was not via a preceding [Ca2+]i rise.

Rheumatoid arthritis (RA)

Resveratrol is a natural compound that affects cellular calcium (Ca2+) homeostasis and viability in different cells. This study examined the effect of resveratrol on cytosolic free Ca2+ concentrations ([Ca2+]i) and viability in OC2 human oral cancer cells. The Ca2+-sensitive fluorescent dye fura-2 was used to measure [Ca2+]i, and water-soluble tetrazolium-1 was used to measure viability. Resveratrol evoked concentration-dependent increase in [Ca2+]i. The response was reduced by removing extracellular Ca2+. Resveratrol also caused manganese-induced fura-2 fluorescence quench. Resveratrol-evoked Ca2+ entry was inhibited by nifedipine and the protein kinase C (PKC) inhibitor GF109203X but was not altered by econazole, SKF96365, and the PKC activator phorbol 12-myristate 13 acetate. In Ca2+-free medium, treatment with the endoplasmic reticulum Ca2+ pump inhibitor 2,5-di- tert-butylhydroquinone (BHQ) abolished resveratrol-evoked [Ca2+]i rise. Conversely, treatment with resveratrol inhibited BHQ-evoked [Ca2+]i rise. Inhibition of phospholipase C (PLC) with U73122 abolished resveratrol-evoked [Ca2+]i rise. At 20–100 μM, resveratrol decreased cell viability, which was not affected by chelating cytosolic Ca2+with 1,2-bis(2-aminophenoxy)ethane- N, N, N′, N′-tetraacetic acid-acetoxymethyl ester. Annexin V-fluorescein isothiocyanate staining data suggest that resveratrol at 20–40 μM induced apoptosis in a concentration-dependent manner. Collectively, in OC2 cells, resveratrol induced [Ca2+]i rise by evoking PLC-dependent Ca2+ release from the endoplasmic reticulum and by causing Ca2+ entry via nifedipine-sensitive, PKC-regulated mechanisms. Resveratrol also caused Ca2+-independent apoptosis.

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+]i rises. Cyfluthrin-induced Ca2+ entry was confirmed by the Mn2+-induced quench of fura-2 fluorescence. Cyfluthrin at concentrations of 10–100 μM induced [Ca2+]i rises. 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+]i rises. Conversely, treatment with cyfluthrin abolished TG-evoked [Ca2+]i rises. 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+]i rises. 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+]i rises 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.