PAI-1 and Arterial Thrombosis: Models and Mechanisms

描述（由申请人提供）：纤溶酶原激活剂系统的异常与动脉粥样硬化血栓性疾病的发病机制有关。特别是，血浆中纤溶酶原激活剂抑制剂-1 （PAI-1）、组织型纤溶酶原激活剂（t-PA）和tPA/PAI-1复合物水平的升高与心肌梗死（Ml）和/或中风的风险增加有关。血管纤溶平衡在很大程度上是由t-PA和PAI-1的竞争作用决定的，反映了遗传和环境因素之间复杂的相互作用。在过去的几年中，该实验室参与了一系列基础和临床研究，以确定参与PAI-1分子调控及其在动脉血栓形成和动脉硬化中的作用的激素和代谢因素。根据对转基因小鼠的观察，假设内源性纤溶酶原激活剂t-PA和u-PA与血栓调节蛋白一起，作为冠状动脉循环中抵抗血栓形成的关键内源性防御者。因此，PAI-1的过量可能会增加冠状动脉血栓形成的风险，因为PAI-1抑制了这一防御性三要素的所有三个组成部分，即t-PA、u-PA和APC。事实上，有大量的实验和流行病学证据表明PAI-1实际上可能有助于缺血性心血管疾病的发展。在该R01支持的研究中，我们设计了新的转基因小鼠系，这些小鼠过度表达一种稳定形式的人类PAI-1，并报道这些动物发生年龄依赖性自发大血管冠状动脉血栓形成和心内膜下心肌梗死。该建议的中心假设是血管PAI-1过量促进血管内血栓形成和动脉粥样硬化的发展。该申请由四个特定目的组成，旨在推进这些研究，并通过表征在PAI-1蛋白关键功能域表达特定结构突变的新转基因系来明确PAI-1的血栓形成机制。此外，我们打算研究高脂血症对PAI-1诱导的冠状动脉血栓形成的影响，并研究最近开发的PAI-1拮抗剂在动脉和静脉血栓形成的实验模型中的作用。PAI-1是血浆中t-PA的主要生理性抑制剂，在各种临床情况下升高，与缺血性心血管事件的风险增加有关。最近对PAI-1生物学的深入研究表明，它在缺血性心脏病的发病机制中不仅仅是一个无辜的旁观者。PAI-1水平升高似乎会增加动脉粥样硬化血栓事件的风险，也可能促进血管疾病的进展。预计这些研究将为PAI-1促进血管内血栓形成和血管病理发展的机制提供新的见解，并确定治疗PAI-1相关血管疾病的新方法。

DESCRIPTION (provided by applicant): Abnormalities in the plasminogen activator system have been implicated in the pathogenesis of atherothrombotic disorders. In particular, elevated plasma levels of plasminogen activator inhibitor-1 (PAI-1), tissue-type plasminogen activator (t-PA), and tPA/PAI-1 complexes have been found to correlate with increased risk of myocardial infarction (Ml) and/or stroke. Vascular fibrinolytic balance is, to a large part, determined by the competing effects of t-PA and PAI-1, and reflects a complex interplay between genetic and environmental factors. For the last several years, this laboratory has been involved in a series of basic and clinical investigations that have served to define hormonal and metabolic factors that contribute to the molecular regulation of PAI-1 and its role in the arterial thrombosis and arteriosclerosis. Based on observations made in genetically modified mice, it was hypothesized that the endogenous plasminogen activators, t-PA and u-PA, in conjunction with thrombomodulin, serve as the critical endogenous defenders against thrombosis in the coronary circulation. Accordingly, an excess of PAI-1 would be expected to increase the risk of coronary thrombosis, since PAI-1 inhibits all three components of this defensive triad, i.e. t-PA, u-PA, and APC. Indeed, there is substantial experimental and epidemiological evidence that PAI-1 may in fact contribute to the development of ischemic cardiovascular disease. In studies supported by this R01, we have engineered novel lines of transgenic mice that overexpress a stable form of human PAI-1 and reported that these animals develop age-dependent spontaneous macrovascular coronary thrombosis and subendocardial myocardial infarction. The central hypothesis of this proposal is that vascular PAI-1 excess promotes the development of intravascular thrombosis and atherosclerosis. This application is composed of four specific aims designed to advance these investigations and specifically to clarify the prothrombotic mechanism of PAI-1 by characterizing new transgenic lines that express specific structural mutations in critical functional domains of the PAI-1 protein. Additionally, we intend to investigate the impact of hyperlipidemia on PAI-1-induced coronary thrombosis and to investigate the role of recently developed PAI-1 antagonists in experimental models of arterial and venous thrombosis. PAI-1 is the major physiologic inhibitor of t-PA in plasma, and is elevated in a variety of clinical situations that are associated with increased risk of ischemic cardiovascular events. Recent insights into the biology of PAI-1 suggest that it is more than just an innocent bystander in the pathogenesis of ischemic heart disease. Elevated PAI-1 levels appear to increase the risk of atherothrombotic events and may also promote the progression of vascular disease. It is anticipated that these studies will provide new insights into the mechanisms through which PAI-1 contributes to the development of intravascular thrombosis and vascular pathology and identify new approaches for the treatment of PAI-1-associated vascular disease.