Effect of Carvacrol on Ca²⁺ Movement and Viability in PC3 Human Prostate Cancer Cells

Carvacrol, a monoterpenic phenol compound, has been shown to possess various biological effects in different models. However, the effect of carvacrol on intracellular Ca²⁺ and its related physiology in human prostate cancer is unknown. This study explored the effect of carvacrol on cytosolic free Ca²⁺ levels ([Ca²⁺]i) and viability in PC3 human prostate cancer cells. Fura-2, a Ca²⁺- sensitive fluorescent dye, was used to assess [Ca²⁺]i. Cell viability was measured by the detecting reagent WST-1. Carvacrol at concentrations of 200-800 μM caused [Ca²⁺]i rises in a concentration-dependent manner. Removal of extracellular Ca²⁺ reduced carvacrol’s effect by approximately 60%. Carvacrol-induced Ca²⁺ entry was confirmed by Mn²⁺ entry-induced quench of fura-2 fluorescence, and was inhibited by approximately 30% by nifedipine, econazole, SKF96365, and the protein kinase C (PKC) inhibitor GF109203X. In Ca²⁺-free medium, treatment with the endoplasmic reticulum Ca²⁺ pump inhibitor thapsigargin (TG) abolished carvacrol-induced [Ca²⁺]i rises. Treatment with carvacrol also abolished TG-induced [Ca²⁺]i rises. Carvacrol-induced Ca²⁺ release from the endoplasmic reticulum was abolished by inhibition of phospholipase C (PLC). Carvacrol killed cells at concentrations of 200-600 μM in a concentration-dependent fashion. Chelating cytosolic Ca²⁺ with BAPTA/AM did not prevent carvacrol’s cytotoxicity. Together, in PC3 cells, carvacrol induced [Ca²⁺]i rises by inducing PLC-dependent Ca²⁺ release from the endoplasmic reticulum and Ca²⁺ entry via PKC-sensitive store-operated Ca²⁺ channels and other unknown channels. Carvacrol also induced Ca²⁺-dissociated cell death.