Role of alveolar macrophages in particulate matter-induced cardiopulmonary disease

颗粒物（PM）空气污染是一个全球性的环境健康问题，导致370万人过早死亡。 占全球死亡总数的6.7%。这些死亡主要是由于急性 心肺疾病，包括肺炎。虽然机制还不完全清楚，但肺泡 巨噬细胞（AM）驱动的肺部炎症在PM诱导的健康效应中起重要作用。进一步 为了以公正的方式探索潜在的机制，我们在暴露于PM的AM中进行了RNAseq。在 除了NF-κB靶基因（例如，il 6），我们发现免疫反应基因1（Irg 1）是前10个基因之一 由PM引起。Irg 1编码乌头酸脱羧酶1（Acod 1），一种催化 衣康酸酯合成我们发现PM诱导的Irg 1表达发生较晚，在il 6表达之后， 其他细胞因子。随着Irg 1蛋白的表达，il 6的表达下降。用衣康酸盐治疗AM 减少PM诱导的IL 6，而Irg 1的缺失具有相反的效果，并进一步增加PM诱导的IL 6 表情PM诱导AM中独特的代谢重编程，其特征在于增加糖酵解， 线粒体呼吸，其不同于LPS的作用（其降低呼吸）。PM也引起 线粒体ROS（mROS）通过反向电子传递（RET）从复合物I（Cl）中释放。重要的是，我们发现， 增加的呼吸和RET驱动的mROS都是PM诱导的il 6表达所必需的。衣康酸抑制 通过抑制琥珀酸，PM诱导线粒体呼吸、RET和所得mROS增加 脱氢酶（SDH）（CII）。用PM或衣康酸盐处理降低了炎症反应（IL 6和IL 8）。 抗病毒应答基因）对细菌或流感病毒的作用，表明PM通过Irg 1/衣康酸/SDH抑制 可能削弱对病原体的炎症反应。基于这些初步数据，我们假设PM首先 增加线粒体呼吸，RET和mROS，这是炎症反应所需的， 随后是Irg 1/衣康酸的晚期表达，其通过抑制SDH， 呼吸，RET，mROS，并抑制炎症反应，导致对 病原体我们将在三个具体目标中检验我们的假设。在目标1中，我们将确定如何增加 线粒体呼吸和Irg 1/衣康酸调节PM诱导的代谢变化和转录 在AM中回答。在目标2中，我们将确定Irg 1/衣康酸是否抑制PM诱导的转录， 反应通过抑制反向电子传递和mROS。在目标3中，我们将确定是否PM诱导 irg 1/衣康酸削弱对后续感染的炎症反应。在第一项研究中， PM对AM代谢的影响，同时分析代谢的变化与转录水平的关系， 数据将为我们提供关于新陈代谢如何产生PM诱导的生物效应的重要知识。 我们对PM诱导的Irg 1/衣康酸如何抑制对病原体的炎症反应的研究， 有可能提供新的治疗靶点来预防PM暴露诱发的肺炎。

Particulate matter (PM) air pollution is a global environmental health problem that causes 3.7 million premature deaths annually, representing 6.7% of all deaths worldwide. These deaths are largely due to increased acute cardiopulmonary disease including pneumonia. While the mechanisms are not completely understood, alveolar macrophage (AM)-driven lung inflammation plays an important role in PM-induced health effects. To further explore the potential mechanisms in an unbiased fashion, we performed RNAseq in AMs exposed to PM. In addition to NF-κB target genes (e.g., il6), we found immune response gene 1 (Irg1) as one of the top 10 genes induced by PM. Irg1 encodes aconitate decarboxylase 1 (Acod1), a mitochondrial enzyme that catalyzes the synthesis of itaconate. We found that PM-induced Irg1 expression occurred late, after the expression of il6 and other cytokines. As Irg1 protein was expressed, il6 expression declined. Treatment of AMs with itaconate decreased PM-induced il6, while deletion of Irg1 had an opposite effect and further increased PM-induced il6 expression. PM induced a unique metabolic reprogramming in AMs characterized by increased glycolysis and mitochondrial respiration, which is distinct from the effect of LPS (which reduces respiration). PM also induced mitochondrial ROS (mROS) from complex I (CI) via reverse electron transport (RET). Importantly, we found that both increased respiration and RET-driven mROS are required for PM-induced il6 expression. Itaconate inhibited the PM-induced increase in mitochondrial respiration, RET and resultant mROS via inhibition of succinate dehydrogenase (SDH) (CII) in AMs. Treatment with PM or itaconate reduced the inflammatory response (il6 and antiviral response genes) to bacteria, or influenza virus, suggesting that PM, via Irg1/itaconate/SDH inhibition may impair inflammatory response to pathogens. Based on these preliminary data, we hypothesize that PM first increases mitochondrial respiration, RET and mROS, which are required for the inflammatory response, followed by the late expression of Irg1/itaconate, which by inhibiting SDH, reduces mitochondrial respiration, RET, mROS, and suppresses inflammatory response leading to impaired response to pathogens. We will test our hypothesis in three specific aims. In aim 1, we will determine how increased mitochondrial respiration and Irg1/itaconate regulate PM-induced metabolic changes and transcriptional responses in AMs. In Aim 2, we will determine whether Irg1/itaconate suppresses the PM-induced transcriptional response by inhibiting reverse electron transport and mROS. In Aim 3, we will determine whether PM-induced Irg1/itaconate impairs the inflammatory response to subsequent infection. In this first study that explores the effects of PM on metabolism in AMs, concurrent analysis of the changes in metabolism with the transcriptional data will provide us with important knowledge about how metabolism derives the biologic effects induced by PM. Our investigation of how PM-induced Irg1/itaconate suppresses inflammatory response to pathogens has the potential to offer new therapeutic targets to prevent pneumonia induced by PM exposure.