Regulation of Pulmonary Host Defenses by the Endoplasmic Reticulum Stress Sensor IRE1α

耐甲氧西林金黄色葡萄球菌(MRSA)感染是全球医院获得性感染的主要原因。仅在美国，它每年就造成大约1400万人感染。这种病原体对抗生素的耐药性日益增加，突显出迫切需要确定新的治疗靶点来治疗MRSA感染。我们最近发现，内质网(ER)应激感受器IRE1α是巨噬细胞、中性粒细胞和小鼠感染脓肿模型中针对MRSA的天然免疫防御的关键组件。我们发现，IRE1α通过促进炎症分子的产生来控制巨噬细胞和中性粒细胞的抗微生物功能，其中包括线粒体活性氧簇(MitoROS)、中性粒细胞胞外陷阱(NETs)和IL-1β，这些分子在体内对解决MRSA感染是必不可少的。在肺部，内质网应激发生在感染、吸入空气污染物以及许多肺部疾病的发展过程中，如特发性肺纤维化和哮喘。然而，IRE1α如何参与肺部疾病的进展和解决还不是很清楚。由于肺是一个重要的器官，巨噬细胞和中性粒细胞必须充分调整它们的反应，以确保有效的抗菌功能，而不会造成可能抑制气体交换的过度组织损伤。因此，研究肺感染时IRE1α介导的应激反应将为肺宿主防御的调节提供有价值的机制。这项建议的首要目标是阐明IRE1α在耐甲氧西林金黄色葡萄球菌感染期间肺宿主防御中的作用。我们的中心假设是感染触发了IRE1α信号，从而增强了肺固有免疫效应功能，包括杀菌活性和炎性介质的产生。我们将完成以下目的来验证我们的假说：(1)表征IRE1MERO的激活和产生对肺巨噬细胞炎症反应的要求；(2)阐明IRE1MRS通路是帮助还是阻碍对肺部α感染的天然免疫防御。本研究的完成将使内质网应激反应成为肺宿主防御的重要调控网络，并为进一步研究细胞应激反应与肺部疾病的交叉点奠定基础。

Methicillin-resistant Staphylococcus aureus (MRSA) infection is the leading cause of hospital-acquired infection worldwide. It causes approximately 14 million infections annually in the United States alone. Increasing antibiotic resistance in this pathogen highlights a compelling need to identify new therapeutic targets to treat MRSA infections. We recently showed that the endoplasmic reticulum (ER) stress sensor, IRE1α, is a key component in innate immune defense against MRSA in macrophages, neutrophils, and in a murine abscess model of infection. We found that IRE1α controls macrophage and neutrophil antimicrobial functions by enhancing production of inflammatory molecules including mitochondrial reactive oxygen species (MitoROS), neutrophil extracellular traps (NETs), and IL-1β, which are essential for resolving MRSA infection in vivo. In the lung, ER stress occurs during infection, air pollutant inhalation and during the development of many pulmonary diseases like Idiopathic Pulmonary Fibrosis and Asthma. However, how IRE1α is involved in progression and resolution of lung diseases is not well understood. Because the lung is a vital organ, macrophages and neutrophils must adequately tune their responses to ensure effective antimicrobial function without excessive tissue damage that could inhibit gas exchange. Therefore, investigation of IRE1α-mediated stress responses during lung infection will lend valuable mechanistic insight into the regulation of pulmonary host defenses. The overarching goal of this proposal is to elucidate the role of IRE1α in pulmonary host defenses during MRSA infection. Our central hypothesis is that infection triggers IRE1α signaling, which enhances lung innate immune effector functions includes bactericidal activity and production of inflammatory mediators. We will accomplish the following Aims to test our hypothesis: (1) Characterize the requirement of IRE1α activation and MitoROS generation to lung macrophage inflammatory responses, and (2) Elucidate whether the IRE1α circuit aids or impedes innate immune defense against pulmonary MRSA infection. Completing this study will establish the ER stress response as an important regulatory network in lung host defense and will lay the groundwork for further studies in the intersection between cellular stress response and lung diseases.