The mechanism of carvacrol-evoked [Ca2+]i rises and non-Ca2+-triggered cell death in OC2 human Oral cancer cells

Carvacrol is one of the main substances of essential oil which triggers intracellular Ca2+ mobilization and causes cytotoxicity in diverse cell models. However, the mechanism of carvacrol-induced Ca2+ movement and cytotoxicity is not fully understood. This study examined the effect of carvacrol on cytosolic free Ca2+ concentrations ([Ca2+](i)), cell viability and apoptosis in OC2 human oral cancer cells. Carvacrol induced a [Ca2+](i) rise and the signal was reduced by removal of extracellular Ca2+. Carvacrol-induced Ca2+ entry was not altered by store-operated Ca2+ channel inhibitors and protein kinase C (PKC) activator, but was inhibited by a PKC inhibitor. In Ca2+ -free medium, treatment with the endoplasmic reticulum Ca2+ pump inhibitor thapsigargin (TG) or 2,5-di-tert-butylhydroquinone (BHQ) inhibited carvacrol-induced [Ca2+](i) rise. Conversely, incubation with carvacrol inhibited TG or BHQ-induced [Ca2+](i) rise. Inhibition of phospholipase C (PLC) with U73122 abolished carvacrol-induced [Ca2+](i) rise. Carvacrol decreased cell viability, which was not reversed when cytosolic Ca2+ was chelated with BAPTA-AM (1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester). Carvacrol-induced apoptosis and activation of reactive oxygen species (ROS) and caspase-3. Together, carvacrol induced a [Ca2+](i); rise by inducing PLC-dependent Ca2+ release from the endoplasmic reticulum and Ca2+ entry via PKC-sensitive, non store-operated Ca2+ channels. Carvacrol-induced ROS- and caspase-3-associated apoptosis. (C) 2012 Elsevier Ireland Ltd. All rights reserved.