The Mechanism of Safrole-Induced [Ca2+]i Rises and Non-Ca2+-Triggered Cell Death in SCM1 Human Gastric Cancer Cells

Safrole is a carcinogen found in plants. The effect of safrole on cytosolic free Ca2+ concentrations ([Ca2+];) and viability in SCM1 human gastric cancer cells was explored. The Ca2+-sensitive fluorescent dye fura-2 was applied to measure [Ca2+](i). Safrole at concentrations of 150-450 iuM induced a [Ca2+]; rise in a concentration-dependent manner. The response was reduced by 60% by removing extracellular Ca2+. Safrole-evoked Ca2+ entry was not altered by nifedipine, econazole, SKF96365, and protein kinase C activator or inhibitor. In Ca2+-free medium, treatment with the endoplasmic reticulum Ca2+ pump inhibitor thapsigargin or 2,5-di-tert-butylhydroquinone (BHQ) abolished safrole-evoked [Ca2+](i); rises. Conversely, treatment with safrole abolished thapsigargin or BHQ-evoked [Ca2+]; rises. Inhibition of phospholipase C (PLC) with U73122 abolished safrole-induced [Ca2+]; rises. At 250-550 RM, safrole decreased cell viability concentration-dependently, 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). Annexin V/propidium iodide staining data suggest that safrole (350-550 ilM) induced apoptosis concentration-dependently. These studies suggest that in SCM1 human gastric cancer cells, safrole induced [Ca2+]; rises by inducing PLC-dependent Ca2+ release from the endoplasmic reticulum and Ca2+ influx via non-store-operated Ca2+ entry pathways. Safrole-induced cell death may involve apoptosis.