ACTIVATION OF NUCLEAR RECEPTORS REGULATES ANITI THROMBOTIC ENVIRONMENT ON THE VASCULAR WALL

组织因子（TF）是一种跨膜糖蛋白，似乎是动脉粥样硬化斑块血栓形成的关键决定因素，这对于引发急性冠状动脉综合征很重要。我们发现，用过氧化物酶体增殖物激活受体a （PPARα）配体（如贝扎布酸酯和Wy14643）预处理人脐静脉内皮细胞，可以大大降低肿瘤坏死因子-α (TNFα)诱导的细胞中TF活性的增强。在用PPARγ配体预处理的细胞中没有观察到这种效应。使用含有TF AP-1一致序列的报告质粒进行启动子试验表明，bezafibrate或Wy14643减少TF表达与序列依赖性转录激活的减少有关。电泳迁移率转移实验表明，贝唑菲特和Wy14643降低了Jun/Fos异源二聚体与AP-1基本序列的相互作用，这一现象不仅归因于Jun/Fos相关核蛋白水平的降低，还归因于细胞中RAR/RXR异源二聚体形成的减少导致RAR/JunB异源二聚体形成的增加。瞬时表达研究表明，细胞中RXRα和PPARα的共表达降低了TF的ap -1依赖性启动子活性。这些结果表明，PPARa的配体可能通过改变核受体蛋白的异二聚体伴侣，在各种炎症条件下作为tnf依赖性人内皮细胞血栓形成的抑制因子。另一方面，在本研究中，我们还发现他汀类药物通过抑制Rho家族的小G蛋白来调节血栓调节素（TM）的表达；Rac / Cdc42。他汀类药物介导的内皮细胞TM表达的增加可能有助于他汀类药物对内皮功能的有益作用。

Tissue factor (TF), a transmembrane glycoprotein, appeared to be a critical determinant of atherosclerotic plaque thrombogenicity that is important for triggering acute coronary syndromes. We demonstrated that pretreatment of human umbilical vein endothelial cells with ligands for peroxisome-proliferator activating receptor-a (PPARα), such as bezafibrate and Wy14643, greatly diminished the tumor necrosis factor-α (TNFα)-induced enhancement of TF activity in the cells. Such an effect was not observed in cells pretreated with ligands for PPARγ. Promoter assay using a reporter plasmid containing the AP-1 consensus sequence of TF showed that the reduction of TF expression by bezafibrate or Wy14643 is associated with a decrease in the sequence-dependent transcriptional activation. On electrophoretic mobility shift assay, bezafibrate and Wy14643 decreased the interaction between Jun/Fos heterodimer and the AP-1 elementary sequence, and this phenomenon was ascribed not only to a decrease in the levels of Jun/Fos-related nuclear proteins, but also to an increase in formation of RAR/JunB heterodimer that results from the decrease in RAR/RXR heterodimer formation in the cells. A transient expression study showed that coexpression of RXRα and PPARα in the cells decreased the AP-1-dependent promoter activity of TF. These results suggest that ligands for PPARa may serve as repressors of TF-dependent thrombosis of human endothelial cells under various inflammatory conditions through alteration of the heterodimeric partners of nuclear receptor proteins. In the present study, on the other hand, we also found that statins regulate thrombomodulin (TM) expression via inhibition of small G proteins of Rho family; Rac/Cdc42. A statinmediated increase in TM expression by endothelial cells may contribute the beneficial effects of statins on endothelial function.