Capsazepine elevates intracellular Ca2+ in human osteosarcoma cells, questioning its selectivity as a vanilloid receptor antagonist.
Capsazepine is thought to be a selective antagonist of vanilloid type 1 receptors; however, its other in vitro effect on different cell types is unclear. In human MG63 osteosarcoma cells, the effect of capsazepine on intracellular Ca(2+) concentrations ([Ca(2+)](i)) and cytotoxicity was explored by using fura-2 and tetrazolium, respectively. Capsazepine caused a rapid rise in [Ca(2+)](i) in a concentration-dependent manner with an EC(50) value of 100 microM. Capsazepine-induced [Ca(2+)](i) rise was partly reduced by removal of extracellular Ca(2+), suggesting that the capsazepine-induced [Ca(2+)](i) rise was composed of extracellular Ca(2+) influx and intracellular Ca(2+). In Ca(2+)-free medium, thapsigargin, an inhibitor of the endoplasmic reticulum Ca(2+)-ATPase, caused a monophasic [Ca(2+)](i) rise, after which the increasing effect of capsazepine on [Ca(2+)](i) was inhibited by 75%. Conversely, pretreatment with capsazepine to deplete intracellular Ca(2+) stores totally prevented thapsigargin from releasing more Ca(2+). U73122, an inhibitor of phospholipase C, abolished histamine (an inositol 1,4,5-trisphosphate-dependent Ca(2+) mobilizer)-induced, but not capsazepine-induced, [Ca(2+)](i) rise. Overnight treatment with 1-100 microM capsazepine inhibited cell proliferation in a concentration-dependent manner. These findings suggest that in human MG63 osteosarcoma cells, capsazepine increases [Ca(2+)](i) by stimulating extracellular Ca(2+) influx and also by causing intracellular Ca(2+) release from the endoplasmic reticulum via a phospholiase C-independent manner. Capsazepine may be mildly cytotoxic.
Teng
Hsiu-Peng
HP
Department of Orthopaedic Surgery, Kaohsiung Veterans General Hospital, Kaohsiung 813, Taiwan.
Huang
Chun-Jen
CJ
Yeh
Jeng-Hsien
JH
Hsu
Shu-Shong
SS
Lo
Yuk-Keung
YK
Cheng
Jin-Shiung
JS
Cheng
He-Hsiug
HH
Chen
Jin-Shyr
JS
Jiann
Bang-Ping
BP
Chang
Hong-Tai
HT
Huang
Jong-Khing
JK
Jan
Chung-Ren
CR
D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects*; D002211:Capsaicin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects; D045744:Cell Line, Tumor / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004963:Estrenes / Q000494:pharmacology; D005456:Fluorescent Dyes / Q000378:metabolism; D016257:Fura-2 / Q000378:metabolism; D006801:Humans; D012516:Osteosarcoma / Q000378:metabolism*; D011760:Pyrrolidinones / Q000494:pharmacology; D011955:Receptors, Drug / Q000037:antagonists & inhibitors*; D019284:Thapsigargin / Q000494:pharmacology; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism
D004791:Enzyme Inhibitors; D004963:Estrenes; D005456:Fluorescent Dyes; D011760:Pyrrolidinones; D011955:Receptors, Drug; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D019284:Thapsigargin; D010738:Type C Phospholipases; C071423:capsazepine; D002211:Capsaicin; D002118:Calcium; D016257:Fura-2