Ginkgolide B enhances the differentiation of preosteoblastic MC3T3-E1 cells through VEGF: Involvement of the p38 MAPK signaling pathway

摘要

Ginkgolide B (GB) is one of the ginkgolides isolated from the leaves of the Ginkgo biloba tree. Our previous study indicated that GB promotes the proliferation, migration and adhesion of endothelial progenitor cells, and the induction of angiogenesis through vascular endothelial factor (VEGF). In the present study, the effects of GB on the differentiation of MC3T3-E1 cells and the signaling pathway involved were investigated in vitro. The MC3T3-E1 cell viability activities were assessed using an MTS assay. Measurements of alkaline phosphatase activity and Alizarin Red staining were used to identify osteoblastic differentiation of the MC3T3-E1 cells. The mRNA and secretion levels of VEGF were detected using reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis and enzyme-linked immunosorbent assays, respectively. The protein expression levels of phosphorylation-associated markers were detected using western blot analysis and associated gene expression was determined using RT-qPCR analysis. It was found that GB significantly promoted alkaline phosphatase activity and osteoblastic mineralization in the MC3T3-E1 cells. In addition, the mRNA expression and secretion levels of VEGF in the MC3T3-E1 cells were significantly increased in MC3T3-E1 cells treated with GB. SB203580, a specific inhibitor of p38 mitogen-activated protein (MAP) kinase, markedly suppressed the GB-induced p38 kinase phosphorylation and GB-induced synthesis of VEGF. PD98059, an inhibitor of the upstream kinase, which activates p44/p42 MAP kinase, had minimal effect on the GB-induced phosphorylation of p44/p42 MAP kinase or the GB-induced synthesis of VEGF. Taken together, these results indicated that GB promoted osteoblastic differentiation of the MC3T3-E1 cells through VEGF, and that the p38, but not the p44/p42 MAP kinase signaling pathway, was involved in the GB-induced synthesis of VEGF.