Effect of celecoxib on Ca2+ movement and cell proliferation in human osteoblasts

In human osteoblasts, the effect of the widely prescribed cyclooxygenase-2 inhibitor celecoxib on intracellular Ca2+ concentrations ([Ca2+](i)) and cell proliferation was explored by using fura-2 and the tetrazolium assay, respectively. Celecoxib at concentrations greater than 1 muM caused a rapid rise in [Ca2+](i) in a concentration-dependent manner (EC50 = 10 muM). Celecoxib-induced [Ca2+](i) rise was reduced by 90% by removal of extracellular Ca2+, and by 30% by L-type Ca2+ channel blockers. Celecoxib-induced Mn2+-associated quench of intracellular fura-2 fluorescence also suggests that celecoxib-induced extracellular Ca2+ influx. In Ca2+-free medium, thapsigargin, an inhibitor of the endoplasmic reticulum Ca2+-ATPase,caused a monophasic [Ca2+](i) rise, after which the increasing effect of celecoxib on [Ca2+](i) was greatly inhibited. Conversely, pretreatment with celecoxib to deplete intracellular Ca2+ stores totally prevented thapsigargin from releasing more Ca2+. U73122, an inhibitor of phoispholipase C, abolished histamine (an inositol 1,4,5-trisphosphate-dependent Ca2+ mobilizer)-induced, but not celecoxib-induced, [Ca2+](i) rise. Pretreatment with phorbol 12-myristate 13-acetate and forskolin to activate protein kinase C and adenylate cyclase, respectively, partly inhibited celecoxib-induced [Ca2+](i) rise in Ca2+-containing medium. Separately, overnight treatment with 1-100 muM celecoxib inhibited cell proliferation in a concentration-dependent manner. These findings suggest that in human osteoblasts, celecoxib increases [Ca2+](i) by stimulating extracellular Ca2+ influx and also by causing intracellular Ca2+ release from the endoplasmic reticulum via a phospholiase C-independent manner. Celecoxib may be cytotoxic at higher concentrations. (C) 2003 Published by Elsevier Inc.