Acute Lung Injury: Link Between Apoptosis and Fibrosis

描述(申请人提供)：急性肺损伤(ALL)在美国每年影响20多万名患者，是住院患者发病率和死亡率的重要原因。呼吸机管理的改变改善了预后，但进一步的进展将取决于对控制ALI发病机制和解决因素的更好理解。我们的工作表明，ALI患者的肺组织中激活了Fas依赖的通路，刺激Fas依赖的通路导致兔和小鼠肺上皮细胞的凋亡和炎症。我们正在进行的工作是使用小鼠肺中重复激活Fas的模型，结果表明，Fas的刺激在肺中产生了一种蛋白水解型，并伴有明显的纤维化，基质金属蛋白酶发挥了重要作用。主要目的：本提案的主要目的是确定实验性肺损伤中Fas依赖的细胞凋亡和纤维化之间的联系机制，并测试重要的新疗法以减少ALI的纤维化反应。我们推测Fas依赖的途径的激活是ALI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内聚集sFasL，从而导致巨噬细胞和上皮细胞上Fas的激活。这会导致上皮细胞凋亡和巨噬细胞特异性基质金属蛋白酶-12的产生，从而降解基质，导致晚期纤维化。第二个假设是，这一过程是由先天免疫的触发因素放大的，包括内源性基质碎片和空气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)在实验小鼠的肺中触发Fas依赖的通路，并使用光学显微镜、生化方法和基因表达阵列来评估纤维化反应。我们将测试中性粒细胞衍生的氧化剂在激活sFasL方面的作用(目标1)。我们将研究基质金属蛋白酶-12及其相关基质金属蛋白酶的作用(目标2)。我们将确定先天免疫途径的共存激活是否会放大Fas激活的效果(目标3)。最后，我们将比较Fas途径抑制剂和基质金属蛋白酶抑制剂在保护Fas激活后的小鼠纤维化中的作用(目标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和肺纤维化之间联系的理解的重要空白，并可能导致减少肺功能障碍和改善急性肺损伤危重患者预后的新的治疗方法。

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.