Mechanisms Of Impaired Macrophage Function in Lung Injury - Project 4

项目概要/摘要：本项目的广泛、长期目标是更好地了解 通过检查不同的宿主， 病原体相互作用严重的急性下呼吸道感染或肺炎仍然是导致 脓毒症是全球急性呼吸窘迫综合征（ARDS）的危险因素。然而，细菌 肺炎也是ARDS和延长机械通气的常见并发症， 患者发病率、住院时间和卫生保健费用。然而，宿主-病原体相互作用的许多方面 仍然知之甚少，在关键时期发生的宿主控制机制的潜在缺陷 疾病仍然是ARDS中突出问题。我们已经开发了一种针对 单核吞噬细胞系统的肝脏，以研究严重的肺部感染引起的后果 肺炎克雷伯氏菌是一种胞外革兰氏阴性病原体，是医院感染的常见原因。 肺炎，以及与全身免疫抑制的潜在联系。我们发现干扰素的表达受损- 调节因子1（IRF-1），一种对增强抗微生物和抗病毒先天免疫至关重要的转录因子， 在这个2-hit模型中，我们提出IRF-1缺陷介导免疫抑制表型， 削弱对宿主防御重要的关键先天免疫基因的反式激活。此外，初步 研究结果表明，一部分重症患者表现出免疫抑制表型， 其特征在于不能控制相对无毒的产碳青霉烯酶肺炎克雷伯氏菌（KP） 体外生长和KP的血清杀伤受损与替代性而非经典性的缺陷有关。 补体活性大多数补体蛋白在肝脏中合成，但巨噬细胞/单核细胞也 合成这些因子，其中许多因子受干扰素调节。总体而言， 2-命中模型和患者血清使我们提出了一个主要假设，即巨噬细胞功能障碍 特征在于IRF-1的缺陷标志着宿主在感染期间的免疫抑制命运， 受损的细胞因子应答、微生物杀伤和补体活性。目标1将决定是否 IRF-1信号传导的损伤是免疫缺陷性疾病中趋化因子和细胞因子应答缺陷的机制， 2-hit模型。目的2将评估线粒体乌头酸脱羧酶1（ACOD 1）缺陷是否 在KP感染期间和在2次打击模型中，IRF-1下游的蛋白质会损害宿主的抗微生物程序。目标3将 评价IRF-1激活，旁路途径补体因子合成的动力学， 单核吞噬细胞，以及与重症患者队列中AP活性的关系。成功 这些目标的完成将阐明宿主控制的新机制，并有助于实现长期目标， 了解重症肺炎并发免疫抑制信号。

Project Summary/Abstract: The broad, long-term objective of this Project is to better understand the underlying mechanisms of immunosuppression following infection in the lungs by examining distinct host- pathogen interplay. Severe acute lower respiratory tract infection or pneumonia remains a major cause of sepsis and risk factor for the acute respiratory distress syndrome (ARDS) worldwide. However, bacterial pneumonia is also a frequent complication of ARDS and prolonged mechanical ventilation that increases patient morbidity, length of stay, and health-care costs. Yet, many aspects of host-pathogen interactions remain poorly understood and the underlying defects in host control mechanisms that occur during critical illness remain outstanding questions in ARDS. We have developed a 2-hit murine model targeting the mononuclear phagocyte system of the liver to study the consequences of severe lung infection induced by Klebsiella pneumoniae, an extracellular Gram-negative pathogen that is a common cause of nosocomial pneumonia, and potential link to systemic immunosuppression. We identified impaired expression of interferon- regulatory factor 1 (IRF-1), a transcription factor critical for boosting antimicrobial and antiviral innate immunity, in this 2-hit model leading us to propose that defects in IRF-1 mediates the immunosuppressive phenotype by impairing transactivation of key innate immunity genes important for host defense. Moreover, preliminary findings suggest that a proportion of critically ill patients exhibit an immunosuppressive phenotype characterized by failure to control relatively avirulent carbapenamase-producing Klebsiella pneumoniae (KP) growth in vitro, and impaired serum killing of KP is associated with defects in alternative but not classical complement activity. Most complement proteins are synthesized in the liver, but macrophages/monocytes also synthesize these factors, many of which are regulated by interferons. Collectively, preliminary findings from the 2-hit model and patient serum have led us to propose a major hypothesis that macrophage dysfunction characterized by defects in IRF-1 marks the host for an immunosuppressive fate during infection due to impaired cytokine response, microbial killing, and complement activity. Aim 1 will determine whether impairment in IRF-1 signaling is a mechanism for defective chemokine and cytokine response in the 2-hit model. Aim 2 will evaluate whether defects in mitochondrial aconitate decarboxylase 1 (ACOD1) downstream of IRF-1 impairs host anti-microbial program during KP infection and in the 2-hit model. Aim 3 will evaluate IRF-1 activation, the dynamics of alternative pathway complement factors synthesized by mononuclear phagocytes, and relationship to AP activity in a cohort of critically ill patients. Successful completion of the aims will elucidate novel mechanisms of host control and aid in the long-term objective of understanding immunosuppressive signals complicating severe pneumonia.