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血管损伤时促进止血但也导致血管血栓形成相关疾病的凝血机制的理解。在目标1中，我们将描绘一个以前未被认识到的收敛的外源性和内源性凝血途径的差异调节的生理和药理学抑制剂和相关的凝血酶生成。该目的基于以下新观察结果：在没有凝血酶反馈贡献的情况下，由TF-FVIIa产生的新生FXa可提供功能性内在张力酶（FIXa-FVIIIa）和凝血酶原酶（FXa-FVa）复合物组装分别所需的活化辅因子FVIIIa和FVa。我们将定义这一新认识的协同凝血途径的机制，研究与纯化成分或血浆中的反应;我们将建立这些机制如何促进血液流过TF和胶原蛋白作为模型血栓形成表面的血栓形成，从而评估个体反应的差异性。在目标2中，我们将剖析不同凝血途径对 促止血或血栓形成过程。这些研究源于以下观察结果：生理性凝血抑制剂和针对FXa的抗凝剂与凝血酶原酶功能所需的FXa不同地调节产生FVIIIa和FVa的TF依赖性FXa活性。因此，与TF途径活化直接相关的凝血酶生成可被显著抑制，同时保留内源性张力酶驱动的凝血酶原酶活性所需的TF依赖性FVIIIa和FVa辅因子产生。因此，我们假设，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，从而激活外源性和内源性凝血途径。因此，我们将评估个体血浆样本对临床使用的直接FXa抑制剂（如利伐沙班和阿哌沙班）的抗凝作用的反应的变异性，并研究血管壁的细胞和基质成分引起的血栓形成机制，以确定其对凝血起始的相对贡献。此外，我们将建立不同的凝血途径，包括新发现的外源性和内源性凝血之间的协同联系，有助于血小板血栓形成和纤维蛋白沉积诱导的动脉粥样硬化斑块的成分。认识到不同的凝血途径有助于血栓形成，可能区分正常止血血栓形成将促进我们对血管闭塞以及过度出血导致的严重病理条件的理解。最终，我们的研究将对与动脉和静脉血栓形成或出血相关的社会相关疾病的预防和治疗相关的基础和转化研究产生积极影响。

 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.