Coagulation Abnormalities and Post-Traumatic Ventilator-Associated Pneumonia

描述（由申请人提供）：VAP是ICU患者中最常见的医院感染。创伤患者比其他ICU患者更容易发生VAP。在创伤患者中，严重组织灌注不足的患者VAP的发生率明显较高，尽管其机制尚不清楚。我们最近的临床研究结果和创伤出血小鼠模型的初步数据表明，这种急性低凝状态主要是由抗凝蛋白C通路的激活引起的。几小时后，出现与（a）aPC的低血浆水平和（B）派-1的血浆水平升高引起的纤维蛋白溶解抑制相关的促凝血活性。这些凝血异常之前曾与院内细菌（例如铜绿假单胞菌，与VAP相关的最常见的革兰氏阴性菌）诱导的肺部感染的异常宿主反应有关，尽管这些异常与VAP发展之间的机制联系尚不清楚。因此，我们将在本资助申请中检验一个中心假设，即严重组织灌注不足后铜绿假单胞菌肺炎的易感性增加部分是由肺气隙内的这些创伤后凝血异常介导的。具体而言，我们将首先研究派-1通过激活RhoA并将1v 23整联蛋白从其细胞外配体玻连蛋白解链来增加铜绿假单胞菌诱导的肺内皮通透性的体外机制（目的1）。其次，我们将研究活化蛋白C抑制肺内皮细胞中铜绿假单胞菌诱导的RhoA信号通路活化的机制（目的2）。第三，我们将确定派-1和活化蛋白C调节小鼠严重创伤/出血后空气隙铜绿假单胞菌诱导的肺血管通透性增加的机制的体内相关性。(aim 3）。从体外实验和我们的临床相关的创伤-出血和随后的铜绿假单胞菌肺炎的小鼠模型中获得的信息将在人类中具有重要的治疗意义。事实上，了解院内细菌操纵凝血蛋白的分子机制可能为创伤患者VAP的病因治疗提供新的途径，例如使用药理学派-1或非抗凝剂aPC，这些药物已被证明在人类中是安全的。公共卫生相关性：项目叙述：我们以前已经确定了一个新的机制，解释了为什么创伤患者大出血发展早期异常的凝血系统，其特点是不能正常凝血。我们发现蛋白C通路的激活对于这些早期凝血异常的发展至关重要。随着创伤后炎症的发展，它通过降低这些天然抗凝血剂（如蛋白C）的活性和抑制纤维蛋白溶解来激活凝血系统。因为它已经表明，下调这些抗凝途径不仅促进血栓形成，而且还放大了炎症过程，我们将测试在这个拨款申请的假设，这些创伤后凝血异常增加肺损伤所造成的有毒细菌，铜绿假单胞菌，往往感染严重创伤患者的肺部。

DESCRIPTION (provided by applicant): VAP is the most common nosocomial infection in ICU patients. Trauma patients are more susceptible to develop VAP than other ICU patients. Among trauma patients, those with severe tissue hypoperfusion have a significantly higher incidence of VAP, although the mechanisms are not well understood. Results from our recent clinical studies and preliminary data from our mouse model of trauma-hemorrhage indicate that this acute hypocoagulation is primarily caused by the activation of the anticoagulant protein C pathway. Several hours later, there is the development of a procoagulant activity associated with (a) low plasma levels of aPC and (b) an inhibition of the fibrinolysis caused by elevated plasma levels of PAI-1. These coagulation abnormalities have previously been associated with an abnormal host response to lung infection induced by nosocomial bacteria, such as P. aeruginosa, the most common gram-negative bacteria associated with VAP, although the mechanistic link between these abnormalities and the development of VAP is unknown. Thus, we will test in this grant proposal the central hypothesis that increased susceptibility to P. aeruginosa pneumonia following severe tissue hypoperfusion is mediated in part by these posttraumatic coagulation abnormalities within the airspaces of the lung. Specifically, we will first examine the in vitro mechanisms by which PAI-1 increases P. aeruginosa-induced lung endothelial permeability by activating RhoA and unligating the 1v23 integrin from its extracellular ligand vitronectin (aim 1). Second, we will examine the mechanisms by which activated protein C inhibits the P. aeruginosa-induced activation of the RhoA signaling pathway in lung endothelial cells (aim 2). Third, we will determine the in vivo relevance of the mechanisms by which PAI-1 and activated protein C modulate the increase in lung vascular permeability induced by airspace P. aeruginosa following severe trauma/hemorrhage in mice. (aim 3). The information obtained from the in vitro experiments and our clinically relevant mouse model of trauma-hemorrhage and subsequent P. aeruginosa pneumonia will have important therapeutic significance in humans. Indeed, understanding the molecular mechanisms by which nosocomial bacteria manipulate coagulation proteins may provide new avenues for causal therapy for VAP in trauma patients, such as using pharmacologic PAI-1 or non-anticoagulant aPC that have been shown to be safe in humans. PUBLIC HEALTH RELEVANCE: Project Narrative: We have previously identified a new mechanism that explains why trauma patients with major bleeding develop early abnormalities in their coagulation system that are characterized by an inability to coagulate normally. We found that the activation of the protein C pathway is critical for the development of these early coagulation abnormalities. As the posttraumatic inflammation develops, it then activates the coagulation system by decreasing the activity of these natural anticoagulants, such as the protein C, and by inhibiting the fibrinolysis. Because it has been shown that the downregulation of these anticoagulant pathways not only promotes thrombosis, but also amplifies the inflammatory process, we will test in this grant proposal the hypothesis that these posttraumatic coagulation abnormalities increase the lung injury caused by a virulent bacterium, Pseudomonas aeruginosa, that often infects the lungs of severely traumatized patients.