Chang HT, Hsu SS, Chou CT, Cheng JS, Wang JL, Lin KL, Fang YC, Chen WC, Chien JM, Lu T, Pan CC, Cheng HH, Huang JK, Kuo CC, Chai KL, Jan CR
The effect of the natural product thymol on cytosolic Ca(2+) concentrations ([Ca(2+)](i)) and viability in MG63 human osteosarcoma cells was examined.
The Ca(2+)-sensitive fluorescent dye fura-2 was applied to measure [Ca(2+)](i).
Thymol at concentrations of 200-1,000 μmol/l induced a [Ca(2+)](i) rise in a concentration-dependent fashion. The response was decreased partially by removal of extracellular Ca(2+). Thymol-induced Ca(2+) entry was inhibited by nifedipine, econazole, SK&F96365 and protein kinase C modulators. When extracellular Ca(2+) was removed, incubation with the endoplasmic reticulum Ca(2+) pump inhibitor thapsigargin or 2,5-di-tert-butylhydroquinone (BHQ) inhibited the thymol-induced [Ca(2+)](i) rise. Incubation with thymol also inhibited the thapsigargin or BHQ-induced [Ca(2+)](i) rise. Inhibition of phospholipase C with U73122 abolished the thymol-induced [Ca(2+)](i) rise. At concentrations of 100-600 μmol/l, thymol killed cells in a concentration-dependent manner. This cytotoxic effect was not changed by chelating cytosolic Ca(2+) with 1,2-bis(2-aminophenoxy)ethane-N,N,N’,N’-tetraacetic acid/AM. Annexin V/propidium iodide staining data suggest that thymol (200 and 400 μmol/l) induced apoptosis in a concentration-dependent manner. Thymol (200 and 400 μmol/l) also increased levels of reactive oxygen species.
In MG63 cells, thymol induced a [Ca(2+)](i) rise by inducing phospholipase C-dependent Ca(2+) release from the endoplasmic reticulum and Ca(2+) entry via protein kinase C-sensitive store-operated Ca(2+) channels. Thymol induced cell death that may involve apoptosis via mitochondrial pathways.
Chang HT, Hsu SS, Chou CT, Et Al. Effect of thymol on Ca2+ homeostasis and viability in MG63 human osteosarcoma cells. Pharmacology. 2011;88(3-4):201-212.