Unphosphorylated heat shock protein 27 suppresses fibroblast growth factor-2-stimulated vascular endothelial growth factor release in osteoblasts

Heat shock protein 27 (HSP27) also known as heat shock protein beta 1 (HSPB1) is a member of the family of small heat shock proteins ubiquitously expressed in all tissues. It has previously been demonstrated that HSP27 regulated the synthesis of osteocalcin and interleukin-6 in osteoblast-like MC3T3-E1 cells. In the present study, the effect of HSP27 on basic fibroblast growth factor (FGF-2) -stimulated vascular endothelial growth factor (VEGF) synthesis in MC3T3-E1 cells, was observed. The levels of VEGF release stimulated by FGF-2 in the HSP27-overexpressing MC3T3-E1 cells were significantly lower compared with those in the control cells. In addition, the levels of VEGF release stimulated by FGF-2 in the phosphomimic HSP27-overexpressing cells were significantly higher compared with those in the non-phosphorylatable HSP27-overexpressing cells. Furthermore, no significant differences were observed in the FGF-2-induced phosphorylation levels of p44/p42 mitogen-activated protein (MAP) kinase, p38 MAP kinase, stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) or p70 S6 kinase among the four types of transfected cells. These results suggested that unphosphorylated HSP27 attenuated the FGF-2-stimulated VEGF synthesis in osteoblasts.