Cytokine regulation of adult human osteoblast-like cell prostaglandin biosynthesis

Prostaglandin (PG) biosynthesis by cytokine stimulated normal adult human osteoblast-like (hOB) cells was evaluated by thin layer chromatography, high performance liquid chromatography, and specific immunoassays. PGE₂ was the predominant PG formed under all incubation conditions tested. Control samples produced measurable amounts of PGE₂, and the measured level of this metabolite increased by 22-fold (from 7 to 152 ng/ml) following a 20 h treatment with the combination of TGFβ and tumor necrosis factor-α(TNF). The production of 6-keto-PGF_1α (the stable metabolite of prostacyclin) and of PGF_2α were each increased by about five-fold (from about 0.5 to 2.5 ng/ml) in samples treated with the cytokines. Thus, TGFβ and TNF exerted a regulation of hOB cell PG biosynthesis that was principally directed towards an increased PGE₂ biosynthesis, with lesser effects on the production of other PG metabolites. COX-2 mRNA levels were increased within 2 h of cytokine stimulation, reached a maximum at 6–12 h, and levels had appreciably diminished by 24 h after treatment. Both TGFβ and TNF could independently increase COX-2 mRNA levels and PG biosynthesis. However, the increased production of PGE₂ resulting from TNF stimulation was blocked by the addition of an interleukin-1β (IL-1β) neutralizing antibody, suggesting that TNF regulation of hOB cell PG synthesis was secondary to its capacity to increase hOB cell IL-1β production. TGFβ regulation of PG production was not affected by the addition of the neutralizing antibody. These studies support the proposition that PGs can be important autocrine/paracrine mediators of bone biology, whose production by hOB cells is responsively regulated by osteotropic cytokines. J. Cell. Biochem. 64:618–631. © 1997 Wiley-Liss, Inc.