Activating proteostasis in aging resident macrophages to prevent muscle and cognitive dysfunction after pneumonia

项目摘要 老年肺炎幸存者发生骨骼肌萎缩的风险增加， 痴呆症和认知功能障碍，这可能是最衰弱的限制，以健康的跨度， 老人我们发现小鼠肺炎后多器官功能障碍的关键特征， 使我们能够使用小鼠模型来阐明可以作为治疗靶点的机制。第一周期 在这个奖项中，我们发现，在甲型流感诱导的肺炎期间，IL-6的全身性增加是必要的， E3-泛素连接酶atrogin-1的上调和年轻和老年动物的肌肉萎缩。而 肌肉功能在年轻的动物中迅速恢复，我们从未观察到它在老年动物中恢复， 肺炎后的几个月我们观察到肌肉修复所必需的肌肉卫星细胞未能增殖 老年动物肺炎后，而不是在年轻的动物，这与表达减少有关， 清道夫受体Mertk幼年小鼠吞噬作用所需基因（Mertk、C3、Cx 3cr 1）的遗传破坏 动物表型模仿老年动物中甲型流感肺炎后受损的卫星细胞增殖。在 在大脑中的平行研究中，我们发现，虽然年轻的小鼠在感染甲型流感后恢复了认知功能， 老年动物会出现持续的神经认知障碍。高灵敏度的流式细胞仪转录组学分析 分选的小胶质细胞显示老化的小胶质细胞表现出清道夫受体（包括Mertk）的表达降低。 这与轴突发生、学习和记忆相关基因的表达减少有关。 在甲型流感诱导的肺炎后，将老年动物与年轻动物的脑转录组进行比较。组织 来自年轻小鼠的常驻肌肉巨噬细胞和小胶质细胞强烈激活了整合的应激反应 (ISR)A型流感病毒感染后，通过激活转录因子-4（Atf 4）的表达增加证明， 和分子伴侣，但老年小鼠缺乏这种反应。 这些初步数据支持我们的假设，即年龄相关的清道夫受体功能丧失损害 组织驻留巨噬细胞的吞噬作用是骨骼肌分子和生理恢复所必需的， 肺炎后的肌肉和认知功能我们将确定这些与年龄有关的变化是否可以 通过ISR和/或ATF 4抑制线粒体复合物I逆转，有两个相互关联的具体目的： 目标1.为了确定骨骼肌巨噬细胞中清道夫受体的活性， 小胶质细胞，是必要的认知和骨骼肌功能的恢复后，甲型流感- 诱发肺炎。 目标2.为了确定线粒体代谢的调节，整合的应激反应 和/或ATF 4可以恢复小胶质细胞和骨骼肌巨噬细胞的清除功能， 改善老年小鼠肺炎后认知和运动功能。

PROJECT SUMMARY Elderly pneumonia survivors are at increased risk of developing skeletal muscle atrophy that impairs mobility, dementia, and cognitive dysfunction, which are perhaps the most debilitating limitations to health-span in the elderly. We found critical features of this multiple organ dysfunction after pneumonia are recapitulated in mice, allowing us to use mouse models to elucidate mechanisms that can be targeted for therapy. In the first cycle of this award, we found that a systemic increase in IL-6 during influenza A-induced pneumonia was necessary for upregulation of the E3-ubiquitin ligase atrogin-1 and muscle wasting in both young and aged animals. While muscle function was rapidly restored in young animals, we never observed it to recover in older animals even months after pneumonia. We observed that muscle satellite cells necessary for muscle repair failed to proliferate after pneumonia in aged, but not in young animals, which was associated with decreased expression of the scavenger receptor Mertk. Genetic disruption of genes required for phagocytosis (Mertk, C3, Cx3cr1) in young animals phenocopied the impaired satellite cell proliferation after influenza A pneumonia in aged animals. In parallel studies in the brain, we found that while young mice recover cognitive function after influenza A infection, older animals develop persistent neurocognitive impairment. Highly sensitive transcriptomic profiling of flow sorted microglia showed aged microglia exhibited decreased expression of scavenger receptors, including Mertk. This was associated with reduced expression of genes related to axonogenesis, learning and memory in whole brain transcriptomes from aged compared with young animals after influenza A-induced pneumonia. Tissue resident muscle macrophages and microglia from young mice robustly activated the integrated stress response (ISR) after influenza A infection as evidenced by increased expression of Activating Transcription Factor-4 (Atf4) and molecular chaperones, but aged mice lacked this response. These preliminary data support our hypothesis that age-related loss of scavenger receptor function impairs phagocytosis in tissue resident macrophages necessary for the molecular and physiologic recovery of skeletal muscle and cognitive function after pneumonia. We will determine whether these age-related changes can be reversed by inhibition of mitochondrial complex I via the ISR and/or ATF4 in two interrelated specific aims: Aim1. To determine whether scavenger receptor activity in resident skeletal muscle macrophages and microglia and is necessary for the recovery of cognitive and skeletal muscle function after influenza A- induced pneumonia. Aim 2. To determine whether modulation of mitochondrial metabolism, the integrated stress response and/or ATF4 can restore scavenger function of the microglia and skeletal muscle macrophages to improve cognitive and motor function in aged mice after pneumonia.