The effect of the phenol compound ellagic acid on Ca2+homeostasis and cytotoxicity in liver cells

Abstract Ellagic acid, a natural phenol compound found in numerous fruits and vegetables, causes various physiological effects in different cell models. However, the effect of this compound on Ca 2+ homeostasis in liver cells is unknown. This study examined the effect of ellagic acid on intracellular Ca 2+ concentration ([Ca 2+ ] i ) and established the relationship between Ca 2+ signaling and cytotoxicity in liver cells. The data show that ellagic acid induced concentration-dependent [Ca 2+ ] i rises in HepG2 human hepatoma cells, but not in HA22T, HA59T human hepatoma cells or AML12 mouse hepatocytes. In HepG2 cells, this Ca 2+ signal response was reduced by removing extracellular Ca 2+ and was inhibited by store-operated Ca 2+ channel blockers (2-APB, econazole or SKF96365) and the protein kinase C (PKC) inhibitor GF109203X. In Ca 2+ -free medium, pretreatment with the endoplasmic reticulum Ca 2+ pump inhibitor thapsigargin abolished ellagic acid-induced [Ca 2+ ] i rises. Conversely, incubation with ellagic acid abolished thapsigargin-induced [Ca 2+ ] i rises. Inhibition of phospholipase C (PLC) with U73122 also abolished ellagic acid-induced [Ca 2+ ] i rises. Ellagic acid (25–100 μM) concentration-dependently caused cytotoxicity in HepG2, HA22T or HA59T cells, but not in AML12 cells. Furthermore, this cytotoxic effect was partially prevented by prechelating cytosolic Ca 2+ with BAPTA-AM only in HepG2 cells. Together, in HepG2 cells, ellagic acid induced [Ca 2+ ] i rises by inducing PLC-dependent Ca 2+ release from the endoplasmic reticulum and Ca 2+ entry via PKC-sensitive store-operated Ca 2+ channels. Moreover, ellagic acid induced Ca 2+ -associated cytotoxicity.