Mitophagy pathways in cellular cross-talk in the myocardium

心肌梗死(MI)合并缺血性心肌病和心力衰竭位居前列 美国退伍军人发病和死亡的原因。在缺血性心肌病中，持续 而不受调控的炎症信号被认为是心力衰竭发病的驱动因素。因此， 了解免疫细胞和心肌细胞之间的串扰可能有助于 治疗策略。心肌中的免疫细胞通过细胞影响心肌细胞的结构和功能 自主和非自主机制。心脏巨噬细胞日益被认为是 在应激状态下驱动促炎信号的优势免疫细胞类型。另一方面，研究也 指出驻留的心脏巨噬细胞在维持心脏结构和 功能。事实上，在心肌梗死后时期，浸润性外周单核细胞分化为巨噬细胞，并 推测与驻留的心脏巨噬细胞协同起双重作用，其特征是促- 炎症信号和吞噬清除死亡细胞的早期阶段和转向抗- 炎症信号促进修复期。在已发表的退伍军人事务部功绩支持研究中，我们有 发现巨噬细胞中溶酶体功能受损是促炎信号的驱动因素的证据。 我们的研究进一步证明了通过以下方式刺激巨噬细胞溶酶体生物发生程序的有效性 自噬-溶酶体途径的主要调节者TFEB的激活在产生表型转换中的作用 巨噬细胞和促进心肌梗死后愈合。在平行的研究中，我们发现了一个重要的作用 TRAF2在心肌细胞执行生理性有丝分裂中的作用--一种选择性的溶酶体降解途径 去除受损的线粒体以防止线粒体DNA泄漏和抑制无菌炎症 心肌。在这项提案中，我们将研究TRAF2和有丝分裂在巨噬细胞中的作用。 塑造心肌内稳态；了解靶向有丝分裂如何影响细胞串扰 心肌处于动态平衡和应激状态。我们的初步数据表明，TRAF2在 巨噬细胞通过促进有丝分裂吞噬和产生25- 羟基胆固醇抑制炎性小体激活，维持心肌内稳态。的确，我们的 初步研究表明，使用遗传方法可诱导巨噬细胞TRAF2消融诱导 心肌细胞肥大、左室肥厚和收缩功能障碍以及炎症性增加 心肌内有细胞浸润。我们已经获得了试剂，并发展了合作来测试 假设。具体地说，我们将评估TRAF2在巨噬细胞中丢失的后果 炎症信号。在特定目标2中，我们将评估TRAF2在巨噬细胞中丢失的后果 关于心肌细胞有丝分裂的研究，并进行机制研究，以了解心肌细胞的作用 在观察到的表型中有丝分裂。在目标3中，我们将定义25-羟基胆固醇的生成在 心肌中的巨噬细胞-肌细胞串扰。成功完成这些研究将确定 心肌巨噬细胞-肌细胞串扰的亚细胞机制。利用巨噬细胞 丝裂原吞噬和氧固醇信号转导具有减轻炎症和治疗缺血的潜力 心肌病占所有心力衰竭病例负担的2/3。

Myocardial infarction (MI) with resultant ischemic cardiomyopathy and heart failure rank among the leading causes of morbidity and mortality among Veterans in the United States. In ischemic cardiomyopathy, sustained and unregulated inflammatory signaling is recognized as a driver of heart failure pathogenesis. Therefore, understanding the crosstalk between immune cells and cardiac myocytes has the potential to inform therapeutic strategies. Immune cells in the myocardium affect cardiac myocyte structure and function via cell autonomous and non-autonomous mechanisms. Cardiac macrophages are increasingly recognized as the dominant immune cell type driving pro-inflammatory signaling under stress. On the other hand, studies also point to critical homeostatic roles for resident cardiac macrophages in maintenance of cardiac structure and function. Indeed, in the post-MI period, infiltrated peripheral monocytes differentiate into macrophages and are postulated to play a dual role in concert with the resident cardiac macrophages, characterized by pro- inflammatory signaling and phagocytic removal of dead cells in the early phase and a shift towards anti- inflammatory signaling to promote reparative phase. In published VA MERIT-supported studies, we have uncovered evidence for impaired lysosome function in macrophages as a driver of pro-inflammatory signaling. Our studies further demonstrated the efficacy of stimulating the macrophage lysosome biogenesis program by activation of TFEB, a master regulator of autophagy-lysosome pathway, in engendering a phenotypic switch in macrophages and promoting post-MI healing. In parallel studies, we have uncovered an essential role for TRAF2 in cardiac myocytes in executing physiologic mitophagy, a selective lysosomal degradative pathway that removes damaged mitochondria to prevent mitochondrial DNA leak and suppress sterile inflammation in the myocardium. In this proposal, we will examine the role of TRAF2 and mitophagy in macrophages in shaping myocardial homeostasis; to understand how targeting mitophagy affects cellular crosstalk in the myocardium in homeostasis and under stress. Our preliminary data suggest the hypothesis that TRAF2 plays an essential role in macrophages by facilitating macrophage mitophagy and generation of 25- hydroxycholesterol to restrain inflammasome activation, to maintain myocardial homeostasis. Indeed, our preliminary studies demonstrate that inducible macrophage TRAF2 ablation using genetic approaches induces cardiac myocyte hypertrophy, left ventricular hypertrophy and systolic dysfunction, and increased inflammatory cell infiltration in the myocardium. We have acquired reagents and developed collaborations to test the hypothesis. In specific aim, we will evaluate the consequences of loss of TRAF2 in macrophages on inflammatory signaling. In specific aim 2, we will evaluate the consequences of loss of TRAF2 in macrophages on cardiac myocyte mitophagy, and perform mechanistic studies to understand the role of cardiac myocyte mitophagy in the observed phenotype. In aim 3, we will define the role of 25-hydroxycholesterol generation in macrophage-myocyte crosstalk in the myocardium. Successful completion of these studies will define subcellular mechanisms of macrophage-myocyte crosstalk in the myocardium. Harnessing macrophage mitophagy and oxysterol signaling has the potential to mitigate inflammation and treat ischemic cardiomyopathy that contributes to 2/3rds of all heart failure case burden.