Celecoxib-induced increase in cytosolic Ca²⁺ levels and apoptosis in HA59T human hepatoma cells

Celecoxib has been shown to have antitumor effect in previous studies but the mechanisms are unclear. The effect of celecoxib on cytosolic Ca²⁺ concentrations ([Ca²⁺]i) and viability in HA59T human hepatoma cells was explored. The Ca²⁺-sensitive fluorescent dye fura-2 was applied to measure [Ca²⁺]_i. Celecoxib at concentrations of 10-50 μM induced a [Ca²⁺]_i rise in a concentration-dependent manner. The response was reduced by 80% by removing Ca²⁺. Celecoxib induced Mn2+ influx, leading to quenching of fura-2 fluorescence. Celecoxib-evoked Ca²⁺ entry was suppressed by nifedipine, econazole, SK&F96365, and protein kinase C modulators. In the absence of extracellular Ca²⁺, incubation with the endoplasmic reticulum Ca²⁺ pump inhibitor thapsigargin nearly abolished celecoxib-induced [Ca²⁺]_i rise. Incubation with celecoxib abolished thapsigargin-induced [Ca²⁺]i rise. Inhibition of phospholipase C with U73122 abolished celecoxib-induced [Ca²⁺]i rise. At 1-50 μM, celecoxib inhibited cell viability by less than 20%, 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). Celecoxib (10-50 μM) also induced apoptosis. In sum, in HA59T hepatoma cells, celecoxib induced a [Ca²⁺]_i rise by evoking phospholipase C-dependent Ca²⁺ release from the endoplasmic reticulum and Ca²⁺ entry via protein kinase C-sensitive store-operated Ca²⁺ channels. Celecoxib also caused cell death via apoptosis.