Resveratrol suppresses prostaglandin F2α-induced osteoprotegerin synthesis in osteoblasts: Inhibition of the MAP kinase signaling

Resveratrol, a natural polyphenol abundantly found in grape skins and red wine, possesses various beneficial properties for human health. In the present study, we investigated the mechanism underlying the effects of prostaglandin F2α (PGF2α) on osteoprotegerin (OPG) synthesis and of resveratrol on the OPG synthesis in osteoblast-like MC3T3-E1 cells. PGF2α stimulated both the release of the OPG protein and the expression of OPG mRNA. Treatment with PD98059, SB203580 and SP600125, specific inhibitors of MEK1/2, p38 mitogen-activated protein (MAP) kinase and stress-activated protein kinase/c-jun N-terminal kinase (SAPK/JNK) all suppressed the OPG release induced by PGF2α. Resveratrol also significantly reduced the PGF2α-stimulated OPG release and the mRNA levels of OPG. Similarly, treatment with SRT1720, an activator of SIRT1, also suppressed the PGF2α-stimulated OPG release. Resveratrol and SRT1720 both attenuated the phosphorylation of p44/p42 MAP kinase, MEK1/2, Raf-1, p38 MAP kinase and SAPK/JNK induced by PGF2α. These findings strongly suggest that resveratrol suppresses PGF2α-stimulated OPG synthesis by inhibiting the MAP kinase pathways in osteoblasts, and that the effect is mediated via SIRT1 activation.