MOLECULAR REGULATION OF ARTERIAL THROMBOSIS

动脉血栓形成是动脉粥样硬化的主要并发症，在西方世界是主要的死亡原因。体内血栓形成通常发生在血管腔内破裂导致血管内皮下促凝血剂(如组织因子)暴露于流动的血液中，与组织因子VIIa结合导致因子IX和X激活以及随后的纤维蛋白沉积。组织因子途径抑制物(TFPI)是一种库尼茨型丝氨酸蛋白酶抑制物，通过两步反应与凝血因子VIIa催化复合体和Xa因子结合，形成抑制凝血的四元复合体，从而在体内独特地调节凝血级联反应。我们最近已经证明，尽管TFPI在动脉粥样硬化斑块中表达，但TF活性占主导地位。因此，我们的工作假设是，动脉粥样硬化斑块中存在TFPI的相对缺乏，TF和TFPI之间的失衡是血管血栓形成的重要来源，可能有助于斑块的发生和发展。为了进一步定义这种不平衡的重要性，我们提出了两个主要目标。首先，我们将产生一种转基因小鼠，以一种仅限于血管壁的靶向方式过度表达TFPI，以确定改变有利于抑制TF的局部平衡是否会抑制动脉血栓形成和动脉粥样硬化的发展和进展。其次，为了改变血液来源细胞的这种平衡，我们将产生不能从循环血细胞中产生TFPI的小鼠，并在已建立的血栓形成模型中对这些小鼠进行测试。我们的具体目标是：1)有针对性地产生过表达TFPI的转基因小鼠，2)确定血管TFPI过表达在动脉粥样硬化发展中的作用，3)确定血管TFPI表达在小鼠动脉血栓形成模型中的作用，以及4)确定血源性TFPI表达在小鼠动脉血栓形成模型中的作用。我们预计，这些研究将：1)阐明TF和TFP I之间的平衡调节动脉粥样硬化和血栓形成的新机制；2)为血源性和循环形式的TFP I的相对重要性提供见解。最终，这些见解将导致新的治疗方法来预防和治疗动脉粥样硬化及其最重要的并发症-血栓形成。

Arterial thrombosis, a major complication of atherosclerosis, is the leading cause of death in the Western world. Thrombosis in vivo is usually initiated when endoluminal disruption leads to exposure of subendothelial procoagulants such as tissue factor (TF) to flowing blood, with binding of TF to factor VIIa resulting in activation of factors IX and X and subsequent fibrin deposition. Tissue factor pathway inhibitor (TFPI), a Kunitz-type serine-protease inhibitor, uniquely modifies the coagulation cascade in vivo by binding in a two-step process to TF-factor VIIa catalytic complex and factor Xa forming a quaternary inhibitory complex which dampens further coagulation. We have recently demonstrated that in spite of TFPI expression in atherosclerotic plaque, TF activity predominates. Thus our working hypothesis is that there is a relative deficiency of TFPI in atherosclerotic plaque and that the imbalance between TF and TFPI is an important source of vascular thrombogenicity and may contribute to plaque development and progression. To further define the importance of this imbalance, we propose two major goals. First, we will generate genetically modified mice that overexpress TFPI in a targeted manner limited to the vessel wall to determine whether altering the local balance favoring TF inhibition will inhibit arterial thrombosis and the development and progression of atherosclerosis. Second, to alter this balance in blood- derived cells, we will generate mice incapable of producing TFPI from circulating blood cells and test these mice in an established model of thrombosis. Our Specific Aims are: 1) To generate transgenic mice which overexpress TFPI in a targeted manner, 2) To determine the role of vascular TFPI overexpression in the development of atherosclerosis, 3) To determine the role of vascular TFPI expression in a murine model of arterial thrombosis and 4) To determine the role of blood-derived TFPI expression in a murine model of arterial thrombosis. We anticipate that these studies will; 1) elucidate new mechanisms by which the balance between TF and TFPI regulates the development of atherosclerosis and thrombosis and 2) provide insights into the relative importance of blood-derived and circulating forms of TFPI. Ultimately these insights will lead to new therapeutic approaches to prevent and treat atherosclerosis and its most important complication, thrombosis.