Contrasting effects of triiodothyronine on heat shock protein 27 induction and vascular endothelial growth factor synthesis stimulated by TGF-β in osteoblasts

Abstract

In osteoblast-like MC3T3-E1 cells, we recently reported that transforming growth factor-β (TGF-β) stimulates the induction of heat shock protein 27 (HSP27). In the present study, we investigated the effects of triiodothyronine (T 3) on the TGF-β-stimulated induction of HSP27 and synthesis of vascular endothelial growth factor (VEGF) in these cells. T 3 by itself had little effect on the level of HSP27, however, it significantly reduced the TGF-β-stimulated HSP27 accumulation in a dose-dependent manner in the range between 1 pM and 100 nM. The TGF-β-stimulated increase in the level of mRNA for HSP27 was also attenuated by T 3. On the other hand, T 3, which alone stimulated the release of VEGF, more than additively stimulated the TGF-β-induced VEGF release. T 3 enhanced the TGF-β-induced increase in the levels of mRNA for VEGF. These results strongly suggest that T 3 has contrasting effects on HSP27 induction and VEGF synthesis induced by TGF-β in osteoblasts.