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

In ostcoblast-like MC3T3-E1 cells, we recently reported that transforming growth factor-beta (TGF-beta) stimulates the induction of heat shock protein 27 (HSP27). In the present study, we investigated the effects of triiodothyronine (T-3) on the TGF-beta-stimulated induction of HSP27 and synthesis of vascular endothelial growth factor (VEGF) in these cells. T3 by itself had little effect on the level of HSP27, however, it significantly reduced the TGF-beta-stimulated HSP27 accumulation in a dose-dependent manner in the range between 1 pM and 100 nM. The TGF-beta-stimulated increase in the level of mRNA for HSP27 was also attenuated by T3. On the other hand, T-3, which alone stimulated the release of VEGF, more than additively stimulated the TGF-beta-induced VEGF release. T3 enhanced the TGF-beta-induced increase in the levels of mRNA for VEGF. These results strongly suggest that T3 has contrasting effects on HSP27 induction and VEGF synthesis induced by TGF-beta in osteoblasts. (C) 2003 Published by Elsevier Science Ireland Ltd.