Bezafibrate enhances proliferation and differentiation of osteoblastic MC3T3-E1 cells via AMPK and eNOS activation

Aim： To investigate the effects of bezafibrate on the proliferation and differentiation of osteoblastic MC3T3-E1 cells, and to determine the signaling pathway underlying the effects. Methods： MC3T3-E1 cells, a mouse osteoblastic cell line, were used. Cell viability and proliferation were examined using MTT assay and colorimetric BrdU incorporation assay, respectively. NO production was evaluated using the Griess reagent. The mRNA expression of ALP, collagen I, osteocalcin, BMP-2, and Runx-2 was measured using real-time PCR. Western blot analysis was used to detect the expression of AMPK and eNOS proteins. Results： Bezafibrate increased the viability and proliferation of MC3T3-E1 cells in a dose- and time-dependent manner. Bezafibrate （100 pmol/L） significantly enhanced osteoblastic mineralization and expression of the differentiation markers ALP, collagen I and osteocalcin. Bezafibrate （100 pmoVL） increased phosphorylation of AMPK and eNOS, which led to an increase of NO production by 4.08-fold, and upregulating BMP-2 and Runx-2 mRNA expression. These effects could be blocked by AMPK inhibitor compound C （5 pmol/L）, or the PPARI5 inhibitor GSK0660 （0.5 pmoVL）, but not by the PPARa inhibitor MK886 （10 pmoVL）. Furthermore, GSK0660, compound C, or NG-nitro-L-arginine methyl ester hydrochloride （L-NAME, 1 mmol/L） could reverse the stimulatory effects of bezafibrate （100 pmoVL） on osteoblast proliferation and differentiation, whereas MK886 only inhibited bezafibrate-induced osteoblast proliferation. Conclusion： Bezafibrate stimulates proliferation and differentiation of MC3T3-E1 cells, mainly via a PPARI3-dependent mechanism. The drug might be beneficial for osteoporosis by promoting bone formation.