Expression of Prostaglandin-Endoperoxide Synthase 1 and Prostaglandin-Endoperoxide Synthase 2 in Human Osteoblasts

A Prostaglandin endoperoxide synthase isoenzyme was recently identified in several cell lines. Osteoblasts possess Prostaglandin endoperoxide synthase activity, but it is not known which isoenzymes are present in these cells. Our objective was to identify these isoenzymes in human osteoblasts. Resting cells in culture did not produce measurable amounts of PGE 2 and did not express Prostaglandin endoperoxide synthase-1 or Prostaglandin endoperoxide synthase-2 mRNAs detectable by Northern blot. Treatment with rhIL1α or rhTNFα induced both the expression of Prostaglandin endoperoxide synthase-2 mRNA and the synthesis of PGE 2, rhIL-1α being more potent on an equimolar basis than rhTNFα. Dexamethasone inhibited the increase in Prostaglandin endoperoxide synthase-2 mRNA and the production of PGE 2 induced by both cytokines. These results suggest that Prostaglandin endoperoxide synthase-2 may be the relevant isoenzyme for prostanoid production in human osteoblasts in culture.