INVOLVEMENT OF PROSTAGLANDIN ENDOPEROXIDE-H SYNTHASE-2 IN OSTEOCLAST-LIKE CELL-FORMATION INDUCED BY INTERLEUKIN-1-BETA

Interleukin-1 beta (IL-1 beta) stimulates osteoclast-like cell formati on via prostaglandin E(2) (PGE(2)) production, However, the regulatory mechanism for the production of PGE(2) in bone cells is still unclear , Recently, it has been shown that two prostaglandin endoperoxide H sy nthase (PGHS) isozymes exist, termed PGSH-1 and PGHS-2, We report here that IL-1 beta induces PGE(2) production in bone marrow culture induc ed by a PGHS-2-dependent mechanism, IL-1 beta stimulated the formation of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells (MNC) and the production of PGE(2) in mouse bone marrow culture s, The dose response curves for the indomethacin inhibition of TRAP-po sitive MNC formation and PGE(2) production were nearly identical, Cycl oheximide (CHX) suppressed IL-1 beta-induced PGE(2) production, sugges ting that the production of PGE(2) induced by IL-1 beta required de no vo protein synthesis, Northern blot analysis determined that IL-1 beta induced PGHS-2 expression by 30 minutes and mRNA levels were maximal by 1-2 h, Cycloheximide potentiated the accumulation of PGHS-2 mRNA li nearly up to 8 h, Dexamethasone, an inhibitor of the induction of PGHS -2, inhibited IL-1 beta-induced PGHS-2 mRNA expression and also suppre ssed IL-1 beta-stimulated formation of TRAP-positive MNC, Furthermore NS-398, as a selective PGHS-2 inhibitor, completely inhibited IL-1 bet a-induced TRAP-positive MNC formation, Moreover, IL-1 beta-induced PGH S-2 mRNA expression and formation of TRAP-positive MNC were inhibited by calphostin C, a selective inhibitor of protein kinase C (PKC), Thes e results indicate that IL-1 beta-induced formation of osteoclastlike cells requires PKC activation, induction of PGHS-2, and subsequent pro staglandin synthesis by this enzyme.