von Willebrand Factor in Traumatic Brain Injury and Associated Coagulopathy

项目摘要 创伤性脑损伤通常与血液不能凝结(凝血障碍)有关，导致 继发性或延迟性全身和颅内出血。大量失血，液体稀释 复苏和体温过低是与创伤相关的凝血障碍的最常见原因 身体和四肢以及失血性休克。我们最近证明，受伤的大脑会释放出 细胞外小泡(EVS)进入循环。这些脑源性EV诱导一种高凝状态 很快演变成消耗性凝血障碍。细胞外线粒体(ExMTs)也被释放到 通过暴露在表面的线粒体磷脂促进血液循环和促进凝血。 ExMts还维持呼吸活动，以产生激活血小板和 内皮细胞。这些发现表明，脑外伤导致了消耗性凝血障碍，即 在机制上有别于与颅外创伤相关的缺乏和稀释性凝血障碍 失血性休克。我们最近的研究进一步表明，粘附性配体von Willebrand因子(VWF)对 介导EV致小鼠血管损伤及激活血小板传播性凝血障碍 创伤性脑损伤。这些最近的发现让我们假设：1)大脑衍生的电动汽车 损伤的大脑刺激内皮细胞释放超黏附的VWF多聚体 并被ADAMTS13酶充分切割，2)这些超粘附性VWF多聚体促进EV- 诱导血管渗漏和传播EV引起的凝血障碍；3)VWF的高黏附活性 在不降低VWF止血活性的情况下，可选择性阻断急性脑损伤。在这里，我们 建议在两个具体目标上检验这些假设。第一个是研究ADAMTS-13的变种，VWF A2 结构域和细胞凋亡清除分子Del-1阻断脑损伤后的高黏附作用 VWF保护小鼠创伤性脑损伤所致凝血障碍的活性，并确定 它们在小鼠模型中的潜在作用机制。二是对120名受试者进行队列研究 从小鼠研究中确定脑外伤患者和创伤对照组的临床相关性。 我们将分析患者样本以量化VWF活性和ADAMTS-13裂解作为主要变量和 确定血小板活化、血浆EVS水平和临床凝血障碍为结果变量。我们会 通过多变量分析将主要变量与结果变量相关联，以确定 高黏附性VWF在创伤性脑损伤所致凝血障碍中的作用及开发新的标志物 预测凝血障碍，重点关注VWF高反应性和EV清除。这项研究是一个完整的 我们长期目标的一部分是确定创伤性脑损伤的全身性影响，并研究 创伤性脑损伤导致继发性脑损伤传播性全身改变。

Project Summary Traumatic brain injury is commonly associated with the inability of blood to clot (coagulopathy), resulting in secondary or delayed systemic and intracranial bleeding. Substantial blood loss, hemodilution due to fluid resuscitation, and hypothermia are the most common causes of coagulopathy associated with trauma to the body and limbs and hemorrhagic shock. We have recently demonstrated that an injured brain releases extracellular vesicles (EVs) into circulation. These brain‐derived EVs induce a hypercoagulable state that quickly evolves into consumptive coagulopathy. Extracellular mitochondria (exMTs) are also released into circulation and promote coagulation through the surface‐exposed mitochondrial phospholipid cardiolipin. ExMts also maintain the respiratory activity to generate reactive oxygen species that activate platelets and endothelial cells. These findings demonstrate that TBI induces consumptive coagulopathy that is mechanistically distinct from deficient and dilutional coagulopathy associated with extracranial trauma and hemorrhagic shock. Our recent study further implicates the adhesive ligand von Willebrand factor (VWF) for mediating EV‐induced vascular injury and for activating platelets to propagate coagulopathy in mouse models of traumatic brain injury. These recently findings led us to hypothesize that: 1) brain‐derived EVs released from injured brains stimulate endothelial cells to release hyper‐adhesive VWF multimers that are not timely and sufficiently cleaved by the enzyme ADAMTS13, 2) these hyper‐adhesive VWF multimers facilitate EV‐ induced vascular leakage and propagate EV‐induced coagulopathy, and 3) the hyper‐adhesive activity of VWF can be selectively blocked in acute brain injury without reducing the hemostatic activity of VWF. Here, we propose testing these hypotheses in two specific aims. The first is to study ADAMTS‐13 variants, the VWF A2 domain, and the apoptotic cell‐scavenging molecule Del‐1 for blocking the TBI‐induced hyper‐adhesive activity of VWF to protect mice from developing traumatic brain injury‐induced coagulopathy, and to define the underlying mechanisms of their actions in mouse models. The second is to conduct a cohort study of 120 patients with TBI and trauma controls to determine the clinical relevance of findings from the mouse study. We will analyze patient samples to quantify VWF activity and ADAMTS‐13 cleavage as primary variables and to define platelet activation, plasma levels of EVs and clinical coagulopathy as outcome variables. We will associate primary variables to outcome variables through multivariate analyses to define a causal role of hyper‐adhesive VWF in traumatic brain injury‐induced coagulopathy and to develop new markers for predicting the coagulopathy with focus on VWF hyper‐reactivity and EV clearance. This study is an integral part of our long‐term goal to define the systemic impact of traumatic brain injury and to study a role of the traumatic brain injury‐induced systemic changes in propagating secondary cerebral injury.