Role of HSP27 in tumor necrosis factor-α-stimulated interleukin-6 synthesis in osteoblasts

Heat shock protein 27 (HSP27) is known to act as a molecular chaperone. We have recently reported that HSP27 regulates osteocalcin synthesis in osteoblast-like MC3T3-E1 cells. in the present study, we investigated the role of HSP27 in tumor necrosis factor-alpha (TNF-alpha)-stimulated interleukin-6 (IL-6) synthesis in MC3T3-E1 cells. The levels of IL-6 release and IL-6 mRNA stimulated by TNF-alpha in MC3T3-E1 cells transfected with HSP27 was significantly higher than those in the control cells. In addition, the levels of secreted IL-6 and IL-6 mRNA in the phospho-mimic HSP27-overexpressing cells were significantly higher than those in the non-phosphorylatable HSP27-overexpressing cells. Furthermore, we observed no significant differences in the phosphorylation levels of I kappa B/NF kappa B, Akt, and p44/p42 mitogen-activated protein kinase among the 4 types of transfected cells. Therefore, these results strongly suggest that HSP27 enhances TNF-alpha-stimulated synthesis, and that the phosphorylation status of HSP27 is related to IL-6 synthesis in osteoblasts.