Effects of transforming growth factor-betas on endothelial anticoagulant activity

为探讨转化生长因子-β1(TGF-β1)对内皮细胞抗凝血活性的影响，本实验采用体外培养的人脐静脉内皮细胞(HUVECs)，通过检测血栓调节蛋白(TM)活性和抗原水平的变化来探讨转化生长因子-β1对血管内皮细胞抗凝活性的影响。转化生长因子-β1对细胞表面TM活性和表面TM抗原水平的抑制作用在孵育12h后最大，呈剂量依赖关系。在抑制它们方面，转化生长因子-β2与转化生长因子-β1几乎等同。两者均抑制HUVECs总TM抗原水平，且抑制作用的时程与细胞表面TM抗原水平相似。经转化生长因子-β1诱导的人脐静脉内皮细胞TM基因表达水平的最大下降出现在比表面和总TM抗原表达水平提前数小时的时间，提示转化生长因子-β基因介导的抑制血管内皮细胞TM抗原的作用主要在TM基因水平上进行。我们的工作表明，在体内，转化生长因子-β1诱导的内皮细胞TM水平的下调有助于促进血管壁损伤部位的血栓形成，如动脉粥样硬化性病变中，转化生长因子-β1从血小板、平滑肌细胞和单核细胞中释放出来，或在分泌转化生长因子-β2的肿瘤中在新生血管壁形成。

To investigate the effects of transforming growth factor-betas (TGF-betas) on endothelial anticoagulant activity, we assayd thrombomodulin (TM) activity and antigen levels of human umbilical vein endothelial cells (HUVECs) incubated with TGF-betas in vitro. TGF-beta1 suppressed surface TM activity and surface TM antigen levels maximally 12 h after incubation by dose-dependent manners. TGF-beta2 was almost equipotent with TGF-beta1 for the suppression of them. Both TGF-betas suppressed total TM antigen level in HUVECs, and the time course of the suppression was similar to that of the cell surface TM antigen level. The maximal reductions of TM mRNA levels by TGF-betas were observed at several hours ahead of those observed in both surface and total TM antigen levels, suggesting that the TGF-beta-mediated suppression of TM antigen of HUVECs is primarily regulated at the TM mRNA level. Our present work suggests that the down-modulation of TM level induced by TGF-betas in HUVECs contributes in vivo to promoting the thrombogenesis either at the sites of injury of vessel walls, such as atherosclerotic lesions where TGF-beta1 is released from platelets, smooth muscle cells and monocytes, or at neovascular walls in tumors secreting TGF-beta2.