Heme-mediated STAT1 Dysfunction in Macrophages During Klebsiella pneumoniae Lung Infection

项目摘要/摘要 巨噬细胞是宿主抵御病原体入侵的关键效应免疫细胞， 了解在严重感染期间导致巨噬细胞功能障碍的因素仍然是 生物医学研究。巨噬细胞吞噬红细胞的急剧增加，称为应激 红细胞吞噬症，发生在病理条件下，如输血血红素-铁超载，贫血 炎症、某些溶血性贫血或严重败血症，并涉及对过量衰老红的摄取。 细胞(SRBC)。利用红细胞输注和急性肺部感染的两次打击模型，我们最近发现 应激性吞噬红细胞导致克雷伯氏菌免疫抑制的机制 小鼠肺炎(KP)感染。这种免疫抑制状态是由干扰素的干扰引起的。 感染期间肝脏中的信号，是由巨噬细胞过度处理血红素引起的，并导致 干扰素反应的主要调节者STAT1缺乏。我们之前建立了一个试验性的 巨噬细胞暴露于KP感染和伴随的SRBC传递或过量的氯化血红素中的系统 体外培养。此外，我们已经使用KP开发了一个成熟的细菌性肺炎模型系统，该系统将 结合SRBC或血红素直接输送到肺，以检查巨噬细胞的变化 体内的表型和免疫细胞库。这一提议将检验这样一种假设，即地球上过量的血红素 肺部，例如在严重感染期间局部组织受损的情况下，可导致STAT1缺乏的状态 在巨噬细胞中，部分是通过损害STAT1蛋白的稳定性，从而对宿主防御造成有害后果。 利用体外和体内模型系统，我建议通过以下方式来研究这一假说 目的：目的1.确定过量的血红素是否会导致巨噬细胞在KP期间处于STAT1缺乏的状态 在体外通过损害STAT1蛋白稳定性而感染。目的2.检查过量的血红素是否会改变巨噬细胞 在活体感染KP期间，肺脏的表型和损害有效的宿主防御。成功完成 该项目将提供有关病原菌与宿主相互作用的新信息。 过量的血红素，并将解决在重症期间肺内宿主反应失调的理解上的差距。 呼吸道感染。

PROJECT SUMMARY/ABSTRACT Macrophages are key effector immune cells in host defense against pathogen invasion, and understanding factors that cause macrophage dysfunction during severe infection remains a high priority in biomedical research. An acute rise in red blood cell engulfment by macrophages, called stressed erythrophagocytosis, occurs in pathologic conditions such as transfusion heme-iron overload, anemia of inflammation, certain hemolytic anemias, or severe sepsis, and involves the uptake of excess senescent red cells (sRBCs). Using a two-hit model of red cell transfusion and acute pulmonary infection, we recently uncovered a mechanism whereby stressed erythrophagocytosis led to a state of immunosuppression following Klebsiella pneumoniae (KP) infection in mice. This state of immunosuppression arose from a disruption in interferon signaling in the liver during infection, was caused by excess heme handling by macrophages, and led to a deficiency of STAT1, a master regulator of interferon responses. We previously established an experimental system in which macrophages are exposed to KP infection and concomitant sRBC delivery or excess hemin in vitro. In addition, we have developed a well-established bacterial pneumonia model system using KP that will be combined with direct delivery of sRBC or heme to the lung in order to examine alterations in macrophage phenotype and the immune cell repertoire in vivo. This proposal will test the hypothesis that excess heme in the lung, such as in conditions of local tissue damage during severe infection, can induce a state of STAT1-deficiency in macrophages, in part, by impairing STAT1 protein stability with deleterious consequences on host defense. Utilizing in vitro and in vivo model systems, I propose to investigate this hypothesis by pursuing the following aims: Aim 1. Determine whether excess heme induces a state of STAT1 deficiency in macrophages during KP infection by impairing STAT1 protein stability in vitro. Aim 2. Examine whether excess heme alters macrophage phenotype in the lung and impairs effective host defense during KP infection in vivo. Successful completion of this project will provide novel information regarding host-pathogen interactions during pathologic conditions of excess heme, and will address a gap in understanding of dysregulated host response in the lung during severe respiratory infection.