Xu Q, Schett G, Li C, Hu Y, Wick G
Institute for Biomedical Aging Research, Austrian Academy of Sciences, Innsbruck, Austria.
Circ Res. 2000 Jun 9;86(11):1122-8. doi: 10.1161/01.res.86.11.1122.
-Previous studies have documented that acute elevation in blood pressure results in heat shock protein (hsp) 70-mRNA expression followed by hsp70-protein production in rat aortas. In this article, we provide evidence that mechanical forces evoke rapid activation of heat shock transcription factor (HSF) and hsp70 accumulation. In our study, Western blot analysis demonstrated that hsp70-protein induction peaked between 6 and 12 hours after treatment with cyclic stain stress (60 cycles/minute, up to 30% elongation). Elevated protein levels were preceded by hsp70-mRNA transcription, which was associated with HSF1 phosphorylation and activation stimulated by mechanical forces, suggesting that the response was regulated at the transcriptional level. Conditioned medium from cyclic strain-stressed vascular smooth muscle cells (VSMCs) did not result in HSF-DNA-binding activation. Furthermore, mitogen-activated protein kinases (MAPKs), including extracellular signal-regulated kinases, c-Jun NH(2)-terminal protein kinases or stress-activated protein kinases, and p38 MAPKs, were also highly activated in response to cyclic strain stress. Inhibition of extracellular signal-regulated kinase and p38-MAPK activation by their specific inhibitors (PD 98059 and SB 202190) did not influence HSF1 activation. Interestingly, VSMC lines stably expressing dominant-negative rac (rac N17) abolished hsp-protein production and HSF1 activation induced by cyclic strain stress, whereas a significant reduction of hsp70 expression was seen in ras N17-transfected VSMC lines. Thus, our findings demonstrate that cyclic strain stress-induced hsp70 expression is mediated by HSF1 activation and regulated by rac and ras GTP-binding proteins. Induction of hsp70 could be important in maintaining VSMC homeostasis during vascular remodeling in response to hemodynamic stimulation.
以往的研究表明，血压急性升高会导致大鼠主动脉中热休克蛋白（hsp）70-mRNA表达，随后产生hsp70蛋白。在本文中，我们提供证据表明机械力可迅速激活热休克转录因子（HSF）并导致hsp70积累。在我们的研究中，蛋白质印迹分析表明，在用循环拉伸应力（60次/分钟，最大伸长30%）处理后6至12小时，hsp70蛋白诱导达到峰值。hsp70蛋白水平升高之前有hsp70-mRNA转录，这与机械力刺激引起的HSF1磷酸化和激活有关，表明该反应在转录水平受到调节。来自循环拉伸应激的血管平滑肌细胞（VSMC）的条件培养基不会导致HSF-DNA结合激活。此外，丝裂原活化蛋白激酶（MAPK），包括细胞外信号调节激酶、c-Jun NH(2)-末端蛋白激酶或应激激活蛋白激酶以及p38 MAPK，也会在循环拉伸应激反应中被高度激活。其特异性抑制剂（PD 98059和SB 202190）对细胞外信号调节激酶和p38-MAPK激活的抑制并不影响HSF1激活。有趣的是，稳定表达显性负性rac（rac N17）的VSMC系消除了循环拉伸应激诱导的hsp蛋白产生和HSF1激活，而在ras N17转染的VSMC系中可见hsp70表达显著降低。因此，我们的研究结果表明，循环拉伸应激诱导的hsp70表达由HSF1激活介导，并受rac和ras GTP结合蛋白调节。在响应血流动力学刺激的血管重塑过程中，hsp70的诱导对于维持VSMC稳态可能很重要。
