Involvement of Rho-kinase in prostaglandin E1-stimulated VEGF synthesis through stress-activated protein kinase/c-Jun N-terminal kinase in osteoblast-like MC3T3-E1 cells

We have previously shown that prostaglandin E1 (PGE1) stimulates the synthesis of vascular endothelial growth factor (VEGF) through p38 mitogen-activated protein (MAP) kinase and stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) but not p44/p42 MAP kinase in osteoblast-like MC3T3-E1 cells. In the present study, we investigated the involvement of Rho-kinase in the PGE1-stimulated VEGF synthesis in these cells. PGE1 induced within 3 min the phosphorylation of myosin phosphatase targeting subunit (MYPT-1), a substrate of Rho-kinase. Y27632 and fasudil, specific inhibitors of Rho-kinase, which attenuated the MYPT-1 phosphorylation, significantly suppressed the PGE1-stimulated VEGF synthesis. Y27632 and fasudil markedly reduced the PGE1-induced phosphorylation of SAPK/JNK without affecting the phosphorylation levels of p38 MAP kinase or p44/p42 MAP kinase. These results strongly suggest that Rho-kinase functions at a point upstream of SAPK/JNK and regulates PGE1-stimulated VEGF synthesis in osteoblasts.