Prostaglandin F-2 alpha stimulates interleukin-6 synthesis via activation of PKC in osteoblast-like cells

In previous studies, we reported that prostaglandin F-2 alpha (PGF(2 alpha)) stimulates phosphoinositide hydrolysis by phospholipase C and phosphatidylcholine hydrolysis by phospholipase D in osteoblast-like MC3T3-E1 cells. in the present study, we examined the effect of PGF(2 alpha), on synthesis of interleukin-6 (IL-6) and the involvement of protein kinase C (PKC) activation in the IL-6 synthesis in these cells. PGF(2 alpha) significantly stimulated IL-6 synthesis in a dose-dependent manner in the range between 10 nM and 10 mu M. A PKC-activating phorbol ester, 12-O-tetradecanoylphorbol-13-acetate (TPA), induced IL-6 synthesis. On the contrary, 4 alpha-phorbol 12,13-didecanoate, a PKC-nonactivating phorbol ester, had no effect. The synthesis of IL-6 stimulated by a combination of PGF(2 alpha), and TPA was not additive. Staurosporine, an inhibitor for protein kinases that suppressed the TPA-induced IL-6 synthesis, significantly inhibited the PGF(2 alpha)-induced IL-6 synthesis. Calphostin C, a highly specific PKC inhibitor, also suppressed the PGF(2 alpha)-stimulated synthesis of IL-6. The effect of PGF(2 alpha) on IL-6 synthesis in PKC-downregulated cells was much weaker than that in intact cells. These results strongly suggest that PGF(2 alpha) induces IL-6 synthesis via PKC activation in osteoblast-like cells.