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.