Mechanisms of resveratrol-induced changes in cytosolic free calcium ion concentrations and cell viability in OC2 human oral cancer cells

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.