Mechanisms of trauma and hemorrhage-induced impairment of innate immunity

描述（由申请人提供）： 创伤和失血性休克是由VA医疗中心的外科医生和医生每天管理的关键外科疾病。它迅速触发先天免疫系统的抑制，导致对感染的易感性增加。以前，医生和科学家 已经广泛研究了先天免疫细胞的功能是否以及如何被严重创伤和失血性休克破坏。相比之下，我们对严重创伤和失血性休克导致非免疫细胞先天免疫受损的分子机制的了解有限。因此，我们长期研究的目标是研究严重创伤和失血性休克对非免疫细胞抗感染功能的影响及其分子机制。最近的研究表明，自噬机制是非吞噬细胞对抗细胞内微生物的关键先天免疫效应子。特别是，Atg12已被证明在通过上皮细胞消除侵入的细菌中发挥重要作用。在这个项目中，我们将测试我们的中心假设，即创伤和出血诱导肺上皮细胞中Atg12的下调，这反过来又会损害肺上皮细胞中Atg12依赖的先天防御系统对机会病原体的防御。在具体目标1中，我们将使用分子生物学方法表征亚致死出血应激对肺中Atg12表达的影响。将使用经典的鼠出血模型。此外，我们将研究是否与肺中铜绿假单胞菌感染的易感性增加相关的药物诱导的Atg12的改变。此外，我们将研究是否敲低Atg12的结果在体外肺上皮细胞使用慢病毒为基础的基因沉默方法消除细菌的衰减。最后，我们将删除 使用一种新的基因敲除方法，在体内肺上皮细胞中检测Atg12，并检查肺上皮特异性下调Atg12是否有助于损害小鼠对铜绿假单胞菌感染的肺先天免疫。在特定目标2中，我们将研究手术创伤衍生的促炎性炎症介质改变人呼吸道上皮细胞中Atg12基因表达的分子机制。具体而言，我们将表征特定的结合模体在人类Atg12基因的启动子和它们的结合蛋白，并研究它们在改变Atg12的表达在严重的手术环境中的作用。将应用分析基因启动子功能的标准方法。在具体目标3中，我们研究了一种天然分子是否能够保持呼吸道上皮细胞中的Atg12水平，从而在严重的手术条件下维持肺部的先天免疫。这些研究涉及用铜绿假单胞菌感染后老化的小鼠，然后评估临床过程，包括存活率、菌血症、组织损伤以及炎症和细胞因子反应。在这个项目完成后，我们将提供新的机制，严重的手术应激（即创伤和出血）抑制非吞噬细胞的先天免疫功能。这项工作将扩大我们对严重手术情况下患者先天免疫抑制的理解和治疗的知识。

DESCRIPTION (provided by applicant): Trauma and hemorrhagic shock are critical surgical conditions that are managed daily by surgeons and physicians in VA medical centers. It rapidly triggers suppression of innate immune system, leading to an increased susceptibility to infections. Previously, physicians and scientists have extensively studied whether and how the function of innate immune cells is disrupted by severe trauma and hemorrhagic shock. In contrast, our knowledge about molecular mechanisms involved in impairment of innate immunity in non-immune cells by severe trauma and hemorrhagic shock is limited. Thus, the objective of our long-term research is to study effects of severe trauma and hemorrhagic shock on non-immune cell function against infections and molecular mechanisms involved. Recent studies have revealed that autophagic machinery is a critical innate immune effector against intracellular microbes for non-phagocytic cells. Particularly, Atg12 has been shown to play an important role in eliminating invaded bacteria by epithelial cells. In this project, we will test our central hypothesis that trauma and hemorrhage induce down-regulation of Atg12 in lung epithelial cells, which in turn impairs Atg12-dependent innate defense system against opportunistic pathogens in lung epithelial cells. In Specific Aim 1, we will characterize the effect of sublethal hemorrhage stress on Atg12 expression in lungs using a molecular biology approach. A classic murine hemorrhage model will be used. Furthermore, we will study whether hemorrhage-induced alteration of Atg12 is associated with increase in susceptibility to Pseudomonas aeruginosa infection in lungs. In addition, we will investigate whether knockdown of Atg12 results in attenuation of eliminating bacteria by lung epithelial cells in vitro using a lentivirus-based gene silencing approach. Finally, we will delete Atg12 in lung epithelial cells in vivo using a novel gene knockout approach and examine whether lung epithelial-specific down-regulation of Atg12 contributes to impairing pulmonary innate immunity against P. aeruginosa infection in mice. In Specific Aim 2, we will investigate molecular mechanisms by which surgical insult-derived proinflammatory inflammatory mediators alter Atg12 gene expression in human respiratory epithelial cells. Specifically, we will characterize specific binding motifs in the promoter of human Atg12 gene and their binding proteins, and study their role in alteration of expression of Atg12 during severe surgical circumstances. The standard approach for analysis of the gene promoter function will be applied. In Specific Aim 3, we investigate whether a nature molecule is able to preserve Atg12 levels in respiratory epithelial cells, which in turn sustains innate immunity in lungs during severe surgical conditions. The studies involve infection of post-hemorrhaged mice with Pseudonumo aeruginosa followed by assessing the clinical course including survival rate, bacteremia, tissue injury, and inflammatory and cytokine response. At the completion of this project, we will provide novel mechanisms by which severe surgical stresses (i.e. trauma and hemorrhage) suppress innate immune function in non-phagocytes. This work will expand our knowledge on understanding and treatment of suppression of innate immunity in patients under severe surgical circumstances.