Platelet and coagulation activation in response to vascular injury

 描述(由申请人提供)：本项目的目的是促进对凝血机制的理解，凝血机制在应对血管损伤时促进止血，但也会导致涉及血管血栓的疾病。在目标1中，我们将描绘一种以前未知的外源性和内源性凝血途径的汇聚，这些途径受到生理和药物抑制物的不同调节，并与凝血酶生成有关。这一目标是基于一项新的观察，即在没有凝血酶反馈贡献的情况下，由Tf-FVIIa产生的新生FXA可以提供组装功能性固有肌腱酶(FixA-FVIIIa)和凝血酶原酶(FXA-FVA)复合体所需的激活辅因子FVIIIa和FVA。我们将确定这一新发现的协同凝血途径背后的机制，研究与纯化成分或在血浆中的反应；我们将建立这些机制如何促进血液中血栓的形成，通过TF和胶原作为模型血栓形成表面，从而评估个体的反应变异性。在目标2中，我们将剖析不同的凝血途径对 有利于止血或血栓形成的过程。这些研究源于观察到，生理性凝血抑制剂和FXA导向的抗凝血剂不同地调节依赖于TF的FXA活性，产生FVIIIa和FVA，而不是凝血酶原酶功能所需的FXA。因此，与TF途径激活直接相关的凝血酶生成可能被显著抑制，同时保留了内在张力酶驱动的凝血酶原酶活性所需的依赖于TF的FVIIIa和FVA辅因子的产生。因此，我们假设，在止血或血栓形成过程中，凝血酶的产生可能涉及促凝血和抗凝途径的不同平衡，以响应不同的血管病变和/或血液状况，这些不同的血管病变和/或血液状况不同地激活了外在和内在的凝血途径。因此，我们将评估单个血浆样本对临床使用的直接FXA抑制剂(如利伐沙班和阿普沙班)抗凝作用的反应的差异性，并研究血管壁细胞和基质成分引发血栓形成的机制，以确定它们对凝血启动的相对贡献。此外，我们将确定不同的凝血途径，包括新发现的外源性和内源性凝血之间的协同联系，如何促进动脉粥样硬化斑块成分诱导的血小板血栓形成和纤维蛋白沉积。认识到血栓形成的不同凝血途径可以区分正常止血和血栓形成，这将促进我们对血管闭塞和出血过多所导致的严重病理情况的理解。最终，我们的研究将对与预防和治疗与动、静脉血栓形成或出血相关的社会相关疾病相关的基础和转化性研究产生积极影响。

 DESCRIPTION (provided by applicant): Purpose of this project is to advance understanding of coagulation mechanisms that promote hemostasis in response to vascular injury but also cause diseases involving vascular thrombosis. In Aim 1, we will delineate a previously unrecognized convergence of extrinsic and intrinsic coagulation pathways differentially regulated by physiological and pharmacologic inhibitors and relevant to thrombin generation. This aim is predicated on the novel observation that, without thrombin feedback contribution, nascent FXa generated by TF-FVIIa can provide the activated cofactors, FVIIIa and FVa, required for assembly of functional intrinsic tenase (FIXa- FVIIIa) and prothrombinase (FXa-FVa) complexes, respectively. We will define the mechanisms underlying this newly recognized synergistic coagulation pathway studying reactions with purified components or in plasma; and we will establish how these mechanisms contribute to thrombus formation in blood flowing over TF and collagen as model thrombogenic surfaces, thus evaluating individual variability in response. In Aim 2, we will dissect the distinct contributions of different coagulation pathways to pro-hemostatic or thrombogenic processes. These studies stem from the observation that physiological coagulation inhibitors and FXa-directed anticoagulants differentially regulate the TF-dependent FXa activity generating FVIIIa and FVa as opposed to FXa required for prothrombinase function. Consequently, thrombin generation directly linked to TF pathway activation may be markedly inhibited while preserving TF-dependent FVIIIa and FVa cofactor production required for intrinsic tenase-driven prothrombinase activity. We hypothesize, therefore, that thrombin generation during hemostasis or thrombosis may involve a different balance of procoagulant and anticoagulant pathways in response to distinct vascular lesions and/or blood conditions that variably activate extrinsic and intrinsic coagulation pathways. Thus, we will evaluate the variability in the response of individual plasma samples to the anticoagulant effect of direct FXa inhibitors in clinical use - such as rivaroxaban and apixaban - and study mechanisms of thrombus formation elicited by cellular and matrix components of the vessel wall to define their relative contribution to coagulation initiation. Moreover, we will establish how different coagulation pathways, including the newly identified synergistic link between extrinsic and intrinsic coagulation, contribute to platelet thrombus formation and fibrin deposition induced by components of the atherosclerotic plaque. Recognizing the distinct coagulation pathways contributing to thrombus formation that may differentiate normal hemostasis from thrombosis will advance our understanding of serious pathological conditions resulting from vascular occlusion as well as excessive bleeding. Ultimately, our studies will have a positive impact on basic and translational research relevant to the prevention and treatment of socially relevant diseases associated with arterial and venous thrombosis or hemorrhage.