The Role of Apoptotic Cell Clearance in Acute Lung Injury

描述（由申请人提供）：本提案概述了一个为期五年的培训计划，为Dr. Kadl建立在肺和重症医学的学术生涯。在候选人的导师Kodi Ravichandran博士的指导下，她的监督委员会和医学部提供的机构支持下，Kadl博士将获得研究方法方面的新知识和专业知识，并培养成为独立临床科学家所需的技能。急性肺损伤和急性呼吸窘迫综合征是重症监护病房的常见问题，死亡率为30-40%。尽管在过去的45年里进行了广泛的研究，但药物治疗并没有显著改善这种疾病的死亡率。肺上皮细胞的凋亡被描述为急性肺损伤进展的早期事件，随后是肺泡内炎症细胞的积累。尽管募集的中性粒细胞在急性肺损伤中表现出延长的寿命，但它们最终会发生凋亡。对凋亡细胞的识别和随后的清除导致吞噬细胞产生抗炎细胞因子。然而，ALI期间清除的机制尚不清楚。本研究的总体目标是阐明急性肺损伤过程中凋亡细胞是如何被清除的，并进一步研究促进这一过程是否可以为急性肺损伤提供新的治疗选择。具体而言，本研究将(1)验证凋亡细胞激活吞噬细胞可改善肺损伤和解决组织炎症的假说；(2)验证非专业吞噬细胞（如支气管上皮细胞）可积极参与组织稳态和预防ALI/ARDS的假说。先前的研究表明，外源性凋亡细胞可以改善肺损伤，可能是通过创造一个支持组织修复和炎症消退的抗炎环境。我们将更进一步，仔细评估外源性灌注凋亡细胞如何有助于肺损伤的衰减和炎症的解决。利用博来霉素诱导的实验性肺损伤模型，并使用缺乏识别凋亡细胞受体（如BAI1和TIM4）或下游信号分子（如Elmo1、Dock180和Rac1）的转基因小鼠，我们将验证吞噬级联的激活是凋亡细胞有益作用所必需的假设。我们将进一步测试非专业吞噬细胞（如支气管上皮细胞）是否通过旁分泌释放抗炎细胞因子来促进这种治疗效果，挑战目前ALI的概念。意义：本研究将有助于更好地理解细胞凋亡和凋亡细胞吞噬在急性肺损伤进展中的作用。使用遗传小鼠模型将阐明凋亡细胞识别的下游途径。本研究结果可能提供新的分子靶点，并可能为ALI/ARDS患者提供新的基于细胞的治疗策略。

DESCRIPTION (provided by applicant): This proposal outlines a five-year training program for Dr. Kadl to establish an academic career in Pulmonary and Critical Care Medicine. With the guidance of the candidate's mentor Dr. Kodi Ravichandran, her supervising committee and the institutional support provided by the Department of Medicine, Dr. Kadl will acquire new knowledge and expertise in research methods and develop the skills needed to evolve into an independent clinician scientist. Acute lung injury and acute respiratory distress syndrome are a common problem in the intensive care unit with a mortality rate of 30-40%. Despite extensive research in the past 45 years, pharmacotherapy has not resulted in significant improvement in mortality of this disease condition. Apoptosis of lung epithelial cells has been described as an early event in the progression of acute lung injury, followed by accumulation of inflammatory cells within the alveolus. Although recruited neutrophils show an extended life span in acute lung injury they eventually undergo apoptosis. Recognition and subsequent clearance of apoptotic cells results in the production of anti-inflammatory cytokines from the engulfing phagocytes. However, mechanisms involved in clearance during ALI are yet not clearly understood. The overall goal of this study is to elucidate how apoptotic cells are removed during acute lung injury and furthermore, investigate whether boosting this process could lead to new treatment option for acute lung injury. In detail, this study will (1) test the hypothesis that activation of phagocytes by apoptotic cells will improve lung injury and resolve tissue inflammation, and (2) test the hypothesis that non-professional phagocytes (such as bronchial epithelial cells) can actively contribute to tissue homeostasis and prevention of ALI/ARDS. Previous studies have suggested that exogenous apoptotic cells can ameliorate lung injury, potentially by creation of an anti-inflammatory environment supporting tissue repair and resolution of inflammation. We will take this a step further and evaluate carefully how exogenously instilled apoptotic cells can contribute to attenuation of lung injury and resolution o inflammation. Using an experimental lung injury model induced by bleomycin, and using genetically modified mice that lack receptors that recognize apoptotic cells, such as BAI1 and TIM4 or downstream signaling molecules, such as Elmo1, Dock180, and Rac1 we will test the hypothesis that activation of the engulfment cascade is required for the beneficial effects seen with apoptotic cells. We will further test whether non-professional phagocytes such as bronchial epithelial cells contribute to this therapeutic effect by paracrine release of anti-inflammatory cytokines, challenging the current concept of ALI. SIGNIFICANCE: This study will lead to a better understanding of the role of apoptosis and engulfment of apoptotic cells in the progression of acute lung injury. The use of genetic mouse models will elucidate pathways involved downstream of the recognition of the apoptotic cell. The results of this study may provide new molecular targets and may result in a new cell based treatment strategy for patients with ALI/ARDS.