Cattaruzza M, Dimigen C, Ehrenreich H, Hecker M
Department of Cardiovascular Physiology, University of Goettingen. Max-Planck-Institute for Experimental Medicine and Departments of Neurology and Psychiatry, University of Goettingen, Germany.
FASEB J. 2000 May;14(7):991-8. doi: 10.1096/fasebj.14.7.991.
Growing evidence suggests that a pressure-induced increase in the synthesis of endothelin (ET-1) is involved in arterial remodeling and, as a consequence, in the manifestation of chronic hypertension. To study potential stretch-induced changes in gene expression and their functional consequences, we have cultured rat aortic smooth muscle cells (raSMC) and porcine aortic endothelial cells (PAEC) on flexible elastomer membranes. The cells were periodically stretched (up to 20% elongation, 0.5 Hz, 6 h) and the expression of prepro-ET-1 and that of the endothelin A and B receptors (ET(A)-R and ET(B)-R) were analyzed by semi-quantitative RT-PCR analysis and ELISA (ET-1). In contrast to PAEC where ET-1 synthesis was up-regulated up to eightfold on exposure to cyclic stretch, ET-1 synthesis in raSMC was decreased by more than 80% under these conditions. ET(A) R -mRNA expression in stretched raSMC declined to 50% whereas ET(B) R -mRNA levels were increased up to 10-fold. One functional consequence of this apparent shift in receptor abundance was an apoptosis-promoting action of exogenous ET-1 (10 nM), as judged by the appearance of subdiploid peaks during FACS analysis, caspase-3 activation and chromatin condensation. This ET-1-induced apoptosis appeared to be ET(B)-R mediated, as it was completely suppressed by the ET(B)-R antagonist BQ 788 but not by the ET(A)-R antagonist BQ 123. Moreover, raSMC derived from homozygous spotting lethal rats, which lack a functional ET(B)-R, showed no signs of apoptosis after exposure to cyclic strain and exogenous ET-1. These findings suggest a central role for the endothelin system in the onset of hypertension-induced remodeling in conduit arteries, which may proceed via an initial stretch-induced apoptosis of the smooth muscle cells.
越来越多的证据表明，压力诱导的内皮素（ET-1）合成增加与动脉重塑有关，进而与慢性高血压的表现有关。为了研究潜在的拉伸诱导的基因表达变化及其功能后果，我们在柔性弹性体膜上培养了大鼠主动脉平滑肌细胞（raSMC）和猪主动脉内皮细胞（PAEC）。细胞被周期性拉伸（伸长至20%，0.5Hz，6小时），并通过半定量RT-PCR分析和ELISA（ET-1）分析前体ET-1以及内皮素A和B受体（ET(A)-R和ET(B)-R）的表达。与PAEC不同，PAEC在暴露于周期性拉伸时ET-1合成上调高达8倍，而在这些条件下raSMC中的ET-1合成减少了80%以上。拉伸的raSMC中ET(A)R-mRNA表达下降至50%，而ET(B)R-mRNA水平增加至10倍。受体丰度的这种明显变化的一个功能后果是外源性ET-1（10nM）的促凋亡作用，这通过FACS分析期间亚二倍体峰的出现、caspase-3激活和染色质浓缩来判断。这种ET-1诱导的凋亡似乎是由ET(B)-R介导的，因为它被ET(B)-R拮抗剂BQ 788完全抑制，而不被ET(A)-R拮抗剂BQ 123抑制。此外，来自缺乏功能性ET(B)-R的纯合斑点致死大鼠的raSMC在暴露于周期性应变和外源性ET-1后没有显示出凋亡迹象。这些发现表明内皮素系统在传导动脉高血压诱导的重塑起始中起核心作用，这可能通过平滑肌细胞的初始拉伸诱导凋亡来进行。
