CYTOKINE REGULATION OF ADULT HUMAN OSTEOBLAST-LIKE CELL PROSTAGLANDINBIOSYNTHESIS

Prostaglandin (PG) biosynthesis by cytokine stimulated normal adult hu man osteoblast-like (hOB) cells was evaluated by thin layer chromatogr aphy, high performance liquid chromatography, and specific immunoassay s. PGE(2) was the predominant PG formed under all incubation condition s tested. Control samples produced measurable amounts of PGE(2), and t he measured level of this metabolite increased by 22-fold (from 7 to 1 52 ng/ml) following a 20 h treatment with the combination of TGF beta and tumor necrosis factor-alpha(TNF). The production of 6-keto-PGF(1 a lpha) (the stable metabolite of prostacyclin) and of PGF(2 alpha) were each increased by about five-fold (from about 0.5 to 2.5 ng/ml) in sa mples treated with the cytokines. Thus, TGF beta and TNF exerted a reg ulation of hOB cell PG biosynthesis that was principally directed towa rds an increased PGE(2) biosynthesis, with lesser effects on the produ ction 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 TGF beta and TNF could independently increase COX-2 mRNA levels and PG biosynthesis . However, the increased production of PGE(2) resulting fron TNF stimu lation was blocked by the addition of an interleukin-1 beta (IL-1 beta ) neutralizing antibody, suggesting that TNF regulation of hOB cell PG synthesis was secondary to its capacity to increase hOB cell IL-1 bet a production. TGF beta 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. (C) 1997 Wiley-Liss, Inc.