Involvement of ADAM17 in LPS-induced lung inflammation

描述（由申请人提供）：气道粘膜表面的过度炎症破坏正常生理，并可导致急性肺损伤（ALI）及其最严重的急性呼吸窘迫综合征（ARDS）。在这些临床综合征期间，肺部炎症反应的特点是大量中性粒细胞浸润，产生促炎细胞因子和组织破坏因子。最终，肺泡-毛细血管完整性和气体交换受损。已知诱发ALI/ARDS的主要病因是气道粘膜表面暴露于革兰氏阴性菌的细胞壁成分，特别是脂多糖（LPS）。新出现的证据表明，胞外结构域脱落，即细胞表面蛋白水解转化为可溶胞外结构域片段，是调节炎症的重要翻译后机制。ADAM17是介导胞外结构域脱落的关键蛋白酶；然而，在小鼠的所有细胞中使其基因失活是致命的，因此目前对其在体内调节炎症中的作用知之甚少。为了解决我们理解中的这一关键空白，我们培养了只有白细胞缺乏功能性ADAM17的小鼠。我们的研究表明，ADAM17是成熟中性粒细胞和巨噬细胞释放功能广泛的粘附蛋白l -选择素、多效性细胞因子TNFa及其两种受体TNFRI和TNFRII的主要机制，这两种受体在lps诱导的肺部炎症中都具有重要功能。因此，我们假设ADAM17在调节lps诱导的急性肺部炎症中起核心作用。我们的研究目的是识别和分析lps暴露小鼠呼吸道中的炎症事件，当白细胞阻止ADAM17底物脱落时，这些炎症事件发生改变，并研究这些改变的机制。我们的目标包括在条件ADAM17敲除小鼠和对照小鼠中进行比较研究，使用气道暴露于LPS模型，模拟ALI/ARDS的典型临床症状。多路复用阵列将用于广泛调查炎症肺中细胞因子和趋化因子的产生，以确定白细胞表达的ADAM17在时间上促进的细胞因子/趋化因子网络。此外，我们将通过测量中性粒细胞在肺血管、支气管肺泡灌洗液和肺间质中的积累，来测试ADAM17是否以及如何参与中性粒细胞向炎症肺的募集。总的来说，我们预计我们的研究将为ADAM17调节肺部炎症的机制提供新的见解，并将允许设计新的治疗ALI和ARDS的策略。免疫系统对感染的最初反应是白细胞的募集和炎症的开始，虽然这通常是有益的，但当过度活跃时可能是有害的。已知诱发急性呼吸窘迫综合征（ARDS）的一种病因是气道粘膜表面暴露于革兰氏阴性菌的细胞壁成分，特别是脂多糖（LPS）。我们假设白细胞表达的ADAM17在调节lps诱导的急性肺部炎症中起关键作用，并可能作为防止其过度激活的治疗靶点。本提案的总体目标是了解白细胞表达的ADAM17对直接暴露于LPS的肺部早期炎症反应的影响。

DESCRIPTION (provided by applicant): Excessive inflammation at mucosal surfaces in the airway disrupts normal physiology and can lead to acute lung injury (ALI) and its most severe form the acute respiratory distress syndrome (ARDS). The pulmonary inflammatory response during these clinical syndromes is characterized by a considerable neutrophil infiltrate that produces pro-inflammatory cytokines and tissue destructive factors. Ultimately, alveolar-capillary integrity and gas exchange become impaired. A major etiology known to induce ALI/ARDS is the exposure of the airway mucosal surface to components of the cell wall of Gram-negative bacteria, in particular, lipopolysaccharide (LPS). Emerging evidence suggests that ectodomain shedding, which is defined as the proteolytic conversion of a cell surface protein into a soluble extracellular domain fragment, is an important post-translational mechanism involved in regulating inflammation. ADAM17 is a key protease that mediates ectodomain shedding; however, inactivating its gene in all cells of mice is lethal, and therefore little is currently known about its role in regulating inflammation in vivo. To address this critical gap in our understanding, we have generated mice in which only the leukocytes lack functional ADAM17. These animals are viable and our studies have demonstrated that ADAM17 is the principle mechanism of shedding by mature neutrophils and macrophages of the broad functioning adhesion protein L-selectin, the pleiotropic cytokine TNFa, and its two receptors TNFRI and TNFRII, all of which have important functions in LPS-induced lung inflammation. Hence, we hypothesize that ADAM17 plays a central role in regulating LPS-induced, acute pulmonary inflammation. The aim of our study is to identify and analyze inflammatory events in the LPS-exposed respiratory tract of mice that are altered when the shedding of ADAM17 substrates by leukocytes is prevented, and investigate the mechanisms of these alterations. Our objectives include comparative studies in conditional ADAM17 knock-out mice and control mice using a model of airway exposure to LPS, which mimics features typical of the clinical condition ALI/ARDS. Multiplexed arrays will be used to broadly survey cytokine and chemokine production in the inflamed lungs to determine the cytokine/chemokine network promoted by leukocyte- expressed ADAM17 in a temporal manner. In addition, we will test whether and how ADAM17 is involved in neutrophil recruitment into the inflamed lungs by measuring their accumulation in the lung blood vessels, brochoalveolar lavage fluid, and in the interstitial spaces of the lung. Overall, we anticipate that our study will provide novel insights into the mechanisms by which ADAM17 regulates lung inflammation, and will allow for the design of new treatment strategies for ALI and ARDS. . The immune system's initial response to infection is the recruitment of leukocytes and initiation of inflammation, which, though generally beneficial, can be harmful when overly exuberant. One etiology known to induce the acute respiratory distress syndrome (ARDS) is the exposure of the airway mucosal surface to components of the cell wall of Gram-negative bacteria and in particular lipopolysaccharide (LPS). We hypothesize that leukocyte-expressed ADAM17 plays a critical role in regulating LPS-induced acute pulmonary inflammation and may serve as a therapeutic target to prevent its over-activation. The overall goal of this proposal is to understand the influences of ADAM17 expressed by leukocytes on the early inflammatory response in the lungs directly exposed to LPS.