Acute Lung Injury: Link Between Apoptosis and Fibrosis

描述（由申请人提供）：急性肺损伤（Acute lung injury, ALl）在美国每年影响超过20万患者，是住院患者发病和死亡的重要原因。呼吸机管理的改变改善了结果，但进一步的进展将取决于对控制ALI发病机制和解决的因素的更好理解。我们的工作表明，ALI患者肺部的fas依赖通路被激活，刺激fas依赖通路导致兔和小鼠肺部上皮细胞凋亡和炎症。我们正在进行的研究使用小鼠肺部重复Fas激活的模型表明，Fas刺激在肺中产生显著纤维化的蛋白水解表型，基质金属蛋白酶在其中起重要作用。主要目标：本提案的主要目标是确定实验性肺损伤中fas依赖性细胞凋亡和纤维化之间的联系机制，并测试减少ALI纤维化反应的重要新疗法。我们假设Fas依赖通路的激活是ALI中肺损伤和纤维化的重要原因，其机制涉及中性粒细胞衍生的氧化剂在肺中聚集sFasL，从而导致巨噬细胞和上皮细胞上的Fas激活。这导致上皮细胞凋亡和巨噬细胞特异性MMP-12的产生，其降解基质并导致晚期纤维化。第二个假设是，这一过程被先天免疫的触发因素放大，包括内源性基质碎片和空气空间中的外源性细菌产物。实验方法：我们将使用fas激活抗体（JO-2）在实验小鼠的肺部触发fas依赖通路，并使用光镜、生化方法和基因表达阵列评估纤维化反应。我们将测试中性粒细胞衍生的氧化剂在激活sFasL中的作用（目的1）。我们将研究MMP-12和相关MMPs的作用（目的2）。我们将确定共存的先天免疫途径激活是否会放大Fas激活的作用（目的3）。最后，我们将比较fas通路抑制剂和MMP抑制剂在fas活化后保护小鼠免受纤维化的作用（目的4）。结果的重要性：这些研究的结果将填补我们对肺上皮细胞凋亡与肺纤维化之间联系的理解的重要空白，并可能导致新的治疗方法来减少肺功能障碍，改善急性肺损伤危重患者的预后。

DESCRIPTION (provided by applicant): Acute lung injury (ALl) affects more than 200,000 patients in the U.S. each year and is an important cause of morbidity and mortality in hospitalized patients. Changes in ventilator management have improved outcome, but further progress will depend on a better understanding of the factors that control the pathogenesis and resolution of ALI Our work has shown that Fas-dependent pathways are activated in the lungs of patients with ALI, and that stimulation of Fas-dependent pathways causes epithelial apoptosis and inflammation in the lungs of rabbits and mice. Our work in progress using a model of repeated Fas activation in the lungs of mice shows that Fas stimulation produces a proteolytic phenotype in the lungs with significant fibrosis and that matrix metalloproteinases play an important role. Major Goals: The major goals of this proposal are to determine the mechanisms that link Fas-dependent apoptosis and fibrosis in experimental lung injury, and to test important new therapies to reduce the fibrotic response in ALI. We hypothesize that activation of Fas-dependent pathways is an important cause of lung injury and fibrosis in ALI, and that the mechanisms involve aggregation of sFasL in the lungs by neutrophil-derived oxidants, which cause Fas activation on macrophages and epithelial cells. This leads to epithelial apoptosis and the production of macrophage-specific MMP-12, which degrades matrix and leads to late fibrosis. A second hypothesis is that this process is amplified by triggers of innate immunity, including endogenous matrix fragments, and exogenous bacterial products in the airspaces. Experimental Approach: We will trigger Fas-dependent pathways in the lungs of experimental mice using a Fas-activating antibody (JO-2) and evaluate the fibrotic response using light microscopy, biochemical methods, and gene expression arrays. We will test the effects of neutrophil-derived oxidants in activating sFasL (Aim 1). We will study the roles of MMP-12 and related MMPs (Aim 2). We will determine whether co-existing activation of innate immunity pathways amplify the effect of Fas activation (Aim 3). Lastly, we will compare the effects of Fas-pathway inhibitors and MMP inhibitors in protecting mice from fibrosis following Fas-activation (Aim 4). Importance of the Results: The results of these studies will fill important gaps in our understanding of the links between epithelial apoptosis and fibrosis in the lungs, and could lead to novel new treatments to reduce pulmonary dysfunction and improve outcome for critically ill patients with acute lung injury.