Macrophage Apoptosis in Resolution of Acute Lung Injury

项目总结/摘要 急性肺损伤（ALI）及其更严重的形式，急性呼吸窘迫综合征（ARDS）， 其特征在于非心源性的双侧肺浸润和严重的动脉低氧血症。这些 在美国，每年有近200，000人住院治疗，75，000人死亡。 尽管最近取得了进展，但死亡率仍然很高，大多数幸存者患有持续性肺部疾病， 功能障碍和肺纤维化。动物模型已经对启动的机制产生了重要的见解， 肺损伤，然而很少有研究集中在推动其解决的过程。在这方面我们 认为巨噬细胞起着关键作用。肺内有大量巨噬细胞积聚 早期的ALI。在未消退的ALI患者中，巨噬细胞持续存在，并作为促炎剂的丰富来源。 纤维化分子，包括转化生长因子-β（TGF-β）。在自限性ALI的小鼠模型中， 巨噬细胞经历由Fas驱动的凋亡。相反，在以持续性肺损伤为特征的ALI模型中， 在炎症和纤维化中，巨噬细胞凋亡难以检测。这些观察结果构成了 我们的中心假设是，巨噬细胞凋亡是解决ALI所必需的， 对细胞凋亡的抗性导致纤维化。目的1将在自限性和 a）全身给予胱天蛋白酶抑制剂以抑制巨噬细胞凋亡，B） 使用巨噬细胞上Fas死亡受体有条件消除的小鼠，c）选择性诱导 转基因小鼠巨噬细胞凋亡。目的2将检验抗凋亡分子c- FLIP在使用非消退性ALI的小鼠模型对细胞凋亡具有抗性的巨噬细胞中上调。 目的2中的实验还将测试噻唑烷二酮吡格列酮使巨噬细胞对以下物质敏感的能力： Fas通过下调c-FLIP诱导细胞凋亡，并将探讨吡格列酮治疗对 炎症和纤维化。目的3将检验来自非肺结核受试者的肺泡巨噬细胞 正在消退的ALI对细胞凋亡有抵抗作用。一项正在进行的NIH赞助的试验将作为 巨噬细胞和BAL液用于此目的。将分析巨噬细胞凋亡的存在， 将在BAL液中定量测定前胶原肽III的水平。巨噬细胞凋亡与 和前胶原肽III水平将使用单变量和多变量分析来评估。为重点 巨噬细胞在解决肺损伤中的作用是一个新的和未开发的领域，以前尚未得到解决。 我们的研究结果将为调节炎症消退的过程提供重要的见解 并将为针对非解决性急性肺损伤的新治疗策略铺平道路。

PROJECT SUMMARY / ABSTRACT Acute lung injury (ALI) and its more severe form, the acute respiratory distress syndrome (ARDS), are characterized by bilateral pulmonary infiltrates of non-cardiac origin and severe arterial hypoxemia. These diseases account for nearly 200,000 hospitalizations and 75,000 deaths in the United States each year. Despite recent advances, mortality remains high and the majority of survivors suffer from persistent pulmonary dysfunction and lung fibrosis. Animal models have yielded important insights into the mechanisms that initiate lung injury, however few studies have focused on the processes that drive its resolution. In this regard, we believe that macrophages play a pivotal role. There is abundant accumulation of macrophages in the lungs during early ALI. In patients with non-resolving ALI, macrophages persist and serve as a rich source of pro- fibrotic molecules including transforming growth factor-¿ (TGF-¿). In mouse models of self-limited ALI, macrophages undergo apoptosis that is driven by Fas. Conversely in ALI models characterized by persistent inflammation and fibrosis, macrophage apoptosis is difficult to detect. These observations form the basis for our central hypothesis that macrophage apoptosis is required for the resolution of ALI and that macrophage resistance to apoptosis results in fibrosis. Aim 1 will test this hypothesis in mouse models of self-limited and non-resolving ALI by: a) systemically administering caspase inhibitors to inhibit macrophage apoptosis, b) using mice with conditional ablation of the Fas death receptor on macrophages, c) selectively inducing macrophage apoptosis in transgenic mice. Aim 2 will test the hypothesis that the anti-apoptotic molecule, c- FLIP, is upregulated in macrophages that are resistant to apoptosis using mouse models of non-resolving ALI. Experiments in Aim 2 will also test the ability of the thiazolidinedione, pioglitazone, to sensitize macrophages to Fas-induced apoptosis by downregulating c-FLIP and will explore the effects of pioglitazone treatment on inflammation and fibrosis. Aim 3 will test the hypothesis that alveolar macrophages from subjects with non- resolving ALI are resistant to apoptosis. An ongoing NIH-sponsored trial will serve as the source of macrophages and BAL fluid for this aim. Macrophages will be analyzed for the presence of apoptosis and levels of procollagen peptide III will be quantified in BAL fluid. The correlation between macrophage apoptosis and procollagen peptide III levels will be assessed using univariate and multivariate analysis. The focus on the macrophage in resolving lung injury is a new and untapped area that has not been previously addressed. Results of our study will provide essential insight into the processes that regulate the resolution of inflammation in the lungs and will pave the way for novel therapeutic strategies to target non-resolving acute lung injury.