Alveolar Macrophages as Age-Related Drivers of Disordered Tissue Repair

摘要 年龄相关性免疫功能障碍最重要的临床表现之一是 肺炎的易感性和死亡率，肺炎是传染病最常见的死亡原因 全世界。在出院后的一年内，老年肺炎幸存者罹患肺炎的风险增加 与年龄相关的疾病包括持续性肺损伤，骨骼肌功能障碍导致行动不便， 心肌梗死、慢性肾病、痴呆症和认知障碍。因此，肺炎是一种 在生命末期限制健康寿命的复合性发病率的门户。肺泡巨噬细胞是 肺泡腔内最丰富的常驻免疫群体，在那里它们充当哨兵细胞和效应细胞 对周围空气中的吸入颗粒物、毒素和病原体做出反应的设备。我们使用了因果关系的组合 针对巨噬细胞的基因实验和流式分选的无偏转录和蛋白质组学分析 甲型流感感染小鼠肺组织中的细胞群提示肺泡的修复功能 巨噬细胞在衰老过程中减少。这些发现与线粒体兴奋作用的概念相一致 从森本博士和尚德尔博士的工作中脱颖而出(项目2)。他们发现，低水平的抑制作用 线虫线粒体电子传递诱导蛋白稳定保护反应，增强 衰老动物的弹性，而更戏剧性的电子传递抑制是有毒的。在老鼠身上，我们发现 二甲双胍抑制肺泡巨噬细胞线粒体电子传递复合体I诱导 蛋白质平衡保护基因的表达对环境胁迫的响应。线粒体电子 运输通过整合的应激反应和转录的激活与蛋白平衡联系在一起 因子ATF4。始终如一地，我们发现了一种整合应激反应的小分子抑制物，ISRIB， 加速老年小鼠感染甲型流感后的肺修复。这些数据支持我们的假设，即年龄- 短暂低水平可逆转肺泡巨噬细胞修复功能的相关损害 通过ISR和ATF4抑制复合I抑制剂的电子传递，同时阴燃激活 衰老过程中的这些途径阻碍了正常的修复。我们将在三个相互关联的具体实例中检验这一假设 目标： 目的1.确定老年肺泡巨噬细胞是否存在清道夫受体MerTK的缺失 损害甲型流感引起的损伤后的肺修复。 目的2.探讨二甲双胍能否通过以下途径恢复肺泡巨噬细胞修复功能 抑制衰老过程中线粒体电子传递的复合体I。 目的3.确定线粒体是否通过eIF2？介导的蛋白平衡激活 翻译抑制和/或ATF4可改善衰老过程中肺损伤后的修复。

Abstract One of the most important clinical manifestations of age-related immune dysfunction is an enhanced susceptibility to and mortality from pneumonia, the most common cause of death from an infectious disease worldwide. In the year after hospital discharge older pneumonia survivors have an increased risk of developing age-related disorders including persistent lung injury, skeletal muscle dysfunction leading to immobility, myocardial infarction, chronic kidney disease, dementia and cognitive impairment. As such, pneumonia is a gateway for the compounding morbidity that limits healthspan at the end of life. Alveolar macrophages are the most abundant resident immune population in the alveolar space, where they serve as sentinel and effector cells that respond to inhaled particles, toxins and pathogens in the ambient air. We used a combination of causal genetic experiments targeting macrophages and unbiased transcriptomic and proteomic analyses of flow-sorted cell populations from the lungs of influenza A infected mice to suggest that the reparative function of alveolar macrophages is reduced during aging. These findings converge with the concept of mitochondrial hormesis that emerged from Dr. Morimoto and Dr. Chandel's work (Project 2). They found that low level inhibition of mitochondrial electron transport in C. elegans induced a proteostasis-protective response that enhanced the resilience of aging animals, while more dramatic inhibition of electron transport was toxic. In mice, we found that metformin inhibits mitochondrial electron transport at complex I in alveolar macrophages to induce the expression of proteostasis protective genes in response to environmental stress. Mitochondrial electron transport is linked with proteostasis through the integrated stress response and activation of the transcription factor ATF4. Consistently, we found a small molecule inhibitor of the integrated stress response, ISRIB, accelerated lung repair after influenza A infection in aged mice. These data support our hypothesis that age- related impairments in the reparative function of alveolar macrophages can be reversed by transient low level inhibition of electron transport with complex I inhibitors via the ISR and ATF4, while smoldering activation of these pathways during aging precludes normal repair. We will test this hypothesis in three interrelated Specific Aims: Aim 1. To determine whether deficiency of the scavenger receptor Mertk in aged alveolar macrophages impairs lung repair after influenza A-induced injury. Aim 2. To determine whether metformin can restore the reparative function of alveolar macrophages via inhibition of complex I of mitochondrial electron transport during aging. Aim 3. To determine whether mitochondrial activation of proteostasis through eIF2?-mediated translational inhibition and/or ATF4 improves lung repair after injury during aging.