Coagulation Abnormalities and Post-Traumatic Ventilator-Associated Pneumonia

描述(申请人提供)：呼吸机相关性肺炎是ICU患者最常见的医院感染。创伤患者比其他ICU患者更容易发生VAP。在创伤患者中，严重组织低灌注者的VAP发生率显著较高，尽管其机制尚不清楚。我们最近的临床研究和我们的小鼠创伤-出血模型的初步数据表明，这种急性低凝主要是由抗凝蛋白C途径的激活引起的。几个小时后，出现促凝血活性，与(A)低水平的血浆APC和(B)高水平的PAI-1引起的纤溶抑制有关。这些凝血功能异常以前与宿主对院内细菌引起的肺部感染的异常反应有关，例如与VAP相关的最常见的革兰氏阴性细菌铜绿假单胞菌，尽管这些异常与VAP的发生之间的机制联系尚不清楚。因此，我们将在这项拨款提案中测试中心假设，即严重组织低灌流后铜绿假单胞菌肺炎的易感性增加部分是通过这些创伤后肺内空隙内的凝血异常来调节的。具体地说，我们将首先研究PAI-1通过激活RhoA并将1v23整合素与其细胞外配体Vitronectin解链来增加铜绿假单胞菌诱导的肺内皮细胞通透性的体外机制(目标1)。其次，我们将研究活化蛋白C抑制铜绿假单胞菌诱导的肺内皮细胞RhoA信号通路激活的机制(目标2)。第三，我们将确定PAI-1和活化蛋白C调节铜绿假单胞菌引起的小鼠严重创伤/出血后肺血管通透性增加的体内相关性。(目标3)。从体外实验和我们的创伤-出血和随后的铜绿假单胞菌肺炎的临床相关小鼠模型中获得的信息将对人类具有重要的治疗意义。事实上，了解医院内细菌操纵凝血蛋白的分子机制可能为创伤患者VAP的因果治疗提供新的途径，例如使用已被证明对人类安全的药物PAI-1或非抗凝剂APC。公共卫生相关性：项目叙述：我们之前已经确定了一种新的机制，可以解释为什么有大出血的创伤患者早期会出现凝血系统异常，其特征是无法正常凝血。我们发现，蛋白C通路的激活对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剂的活性，如蛋白C，并通过抑制纤溶来激活凝血系统。由于已经证明，这些抗凝途径的下调不仅促进血栓形成，还会放大炎症过程，我们将在这项拨款提案中检验这样一种假设，即这些创伤后凝血异常增加了由一种毒力细菌铜绿假单胞菌引起的肺损伤，这种细菌经常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.