Coagulation Abnormalities and Post-Traumatic Ventilator-Associated Pneumonia

描述（申请人提供）：VAP是ICU患者最常见的院内感染。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性出血小鼠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。几小时后，促凝剂活性的发展与(a)血浆aPC水平低和(b)血浆PAI-1水平升高引起的纤维蛋白溶解抑制有关。这些凝血异常与宿主对医院细菌（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反应有关，尽管这些异常与VAP发生之间的机制联系尚不清楚。因此，我们将在本拨款申请中验证这一中心假设，即严重组织灌注不足后铜绿假单胞菌肺炎易感性的增加部分是由肺空间内创伤后凝血异常介导的。具体来说，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玻璃体连接蛋白分离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（目的2）。第三，我们将确定PAI-1和活化蛋白C调节小鼠严重创伤/出血后空气空间铜绿假单胞菌诱导的肺血管通透性增加机制的体内相关性。(3)为目标。从体外实验和我们临床相关的创伤出血及继发铜绿假单胞菌肺炎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，例如使用药理学PAI-1或非抗凝aPC，这些已被证明对人类是安全的。

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.