Pulmonary fibrosis is modulated by MCU-mediated macrophage apoptosis resistance

!在肺的纤维化病症（包括特发性肺纤维化（IPF））中，肺巨噬细胞具有与肺纤维化相关的细胞毒性。 在损伤肺的纤维化修复中起决定性作用。宏观经济在正常的解决方案中发挥着不可或缺的作用， 器官损伤，而且还通过启动免疫应答而促成肺纤维化的发病机制， 通过产生活性氧（ROS），特别是线粒体ROS（mtROS）。肺重塑 在肺纤维化过程中的作用知之甚少;然而，单核细胞中线粒体生物能量学的变化， 衍生的巨噬细胞正在成为纤维化修复的关键决定因素。mtROS的产生是 与钙（Ca 2+）流入线粒体有关，这部分受线粒体Ca 2+的调节 单向传输器（MCU）。慢性疾病中的巨噬细胞通常表现出细胞凋亡抗性，并且它们的延长 存活率与疾病进展相关。代谢重编程脂肪酸氧化（FAO）是一个关键 巨噬细胞活化的特征。FAO的相对效率非常适合于满足代谢 这是修复受损组织所必需的。我们的初步数据显示， IPF受试者的过氧化物酶体增殖物激活受体共激活因子-1（PGC-1a）表达增加， 一种导致FAO酶促能力增加的转录因子，肉毒碱棕榈酰转移酶IA （CPT 1A），限速线粒体脂质转运蛋白，和线粒体Bcl-2相比，正常受试者。 MCU缺陷减弱PGC-1a表达，显性阴性（DN）-MCU表达废除 粮农组织。这些发现是相关的，因为通过使用WT和 MCU+/-小鼠，我们发现接受MCU+/-骨髓的小鼠免受博来霉素诱导的免疫损伤。 肺纤维化 我们假设MCU通过肺巨噬细胞的代谢重编程介导肺纤维化 以诱导凋亡抗性。我们将以三个目标来检验这一假设。 目标1将测试MCU是否调节巨噬细胞对FAO的代谢重编程，以及是否需要MCU 利用在单核细胞衍生的细胞中表达显性阴性（DN）-MCU的小鼠的肺纤维化 巨噬细胞 在目标2中，我们将测试MCU是否通过诱导代谢重编程为FAO来介导凋亡抗性 以及使用遗传方法增强与CPT 1a结合的抗凋亡Bcl-2蛋白的表达， 在单核细胞衍生的巨噬细胞中具有DN-MCU表达或Bcl-2缺失的小鼠。 目的3将通过以下方法提供MCU在纤维化发展中的重要性的人类生物学证据： 确定来自IPF受试者的肺巨噬细胞中MCU的调节是否调节FAO和对 凋亡了解MCU在肺巨噬细胞中的作用可能为预防肺巨噬细胞的死亡提供重要靶点。 或阻止纤维化的进展。

! In fibrotic disorders of the lung, including idiopathic pulmonary fibrosis (IPF), lung macrophages have a decisive role in fibrotic repair of injured lung. Macrophages play an integral role in the normal resolution of organ injury but also contribute to the pathogenesis of pulmonary fibrosis by initiating an immune response and by generating reactive oxygen species (ROS), particularly mitochondrial ROS (mtROS). Lung remodeling during pulmonary fibrosis is poorly understood; however, changes in mitochondrial bioenergetics in monocyte- derived macrophages are emerging as a critical determinant of fibrotic repair. The generation of mtROS is linked to calcium (Ca2+) influx into the mitochondria, which is regulated, in part, by the mitochondrial Ca2+ uniporter (MCU). Macrophages in chronic disease typically exhibit apoptosis resistance, and their prolonged survival is associated with disease progression. Metabolic reprogramming to fatty acid oxidation (FAO) is a key feature in macrophage activation. The relative efficiency of FAO is well suited to meet the metabolic requirements necessary for the repair of injured tissue. Our preliminary data show that lung macrophages from IPF subjects have increased expression of peroxisome proliferator-activated receptor coactivator-1 (PGC-1a), a transcription factor that leads to increased enzymatic capacity for FAO, carnitine palmitoyltransferase IA (CPT1A), the rate limiting mitochondrial lipid transporter, and mitochondrial Bcl-2 compared to normal subjects. MCU deficiency attenuates PGC-1a expression, and dominant-negative (DN)-MCU expression abrogates FAO. These findings are relevant because by generating reciprocal bone marrow chimeras using WT and MCU+/- mice, we found mice that received MCU+/- bone marrow were protected from bleomycin-induced pulmonary fibrosis. We hypothesize that MCU mediates pulmonary fibrosis by metabolic reprogramming of lung macrophages to induce apoptosis resistance. We will test this hypothesis with three aims. Aim 1 will test if MCU modulates macrophage metabolic reprogramming to FAO and if MCU is required for pulmonary fibrosis utilizing mice harboring expression of a dominant-negative (DN)-MCU in monocyte-derived macrophages. In Aim 2, we will test if MCU mediates apoptosis resistance by inducing metabolic reprogramming to FAO and enhancing expression of anti-apoptotic Bcl-2 proteins that bind to CPT1a using genetic approaches and in mice harboring expression of DN-MCU or a deletion of Bcl-2 in monocyte-derived macrophages. Aim 3 will provide human biological evidence of the importance of MCU in fibrosis development by determining if modulation of MCU in lung macrophages from IPF subjects regulates FAO and resistance to apoptosis. Understanding the role of MCU in lung macrophages may provide an important target for preventing or halting progression of fibrosis.