Lysophosphatidic Acid in Airway Barrier Function and Remodeling

描述（由申请人提供）：急性肺损伤（ALI）是由急性肺部炎症引起的急性呼吸衰竭。气道上皮对吸入颗粒、过敏原和环境毒素提供了复杂的物理和生化屏障，在宿主防御中起着至关重要的作用。上皮完整性的破坏是通透性增加和肺泡充血（富含蛋白质的水肿液）的主要原因，这是急性脑损伤的一个标志。然而，对肺上皮对损伤的反应的了解仍然不完整。e -钙粘蛋白调节的粘附结起着至关重要的作用，因为粘附结的形成随后导致其他细胞连接的形成。脂多糖（LPS）诱导的肺损伤是一种非常有用的实验模型，用于研究和表征ALI的免疫致病变化和机制。我们和其他人在lps诱导的小鼠ALI模型和原代培养的肺上皮细胞中发现，肺上皮中E-cadherin的细胞质错定位可诱导上皮脱落并增加肺上皮通透性。此外，我们和其他人的一些研究表明，E-cadherin与酪氨酸激酶受体（如c-Met酪氨酸激酶）之间存在关联，这表明E-cadherin在上皮细胞中定位的调节存在复杂的分子机制。我们最近报道了溶血磷脂酸（LPA），一种从活化血小板释放的生物活性磷脂生长因子，通过增加人支气管上皮细胞（HBEpCs）中IL-8、PGE2和IL-13R α 2的分泌来增强先天免疫和减弱适应性免疫。然而，肺上皮屏障功能的分子机制尚不明确，本提案假设“LPA处理后通过LPA- rs和c-Met之间的串扰导致细胞-细胞连接处E-cadherin积累增强，从而保护肺上皮屏障功能免受LPS引起的肺上皮屏障功能障碍”。本文将利用原代人支气管上皮细胞、肺泡II型上皮细胞、肺泡II型细胞系和小鼠ALI模型，探讨lpa介导的呼吸上皮屏障功能的作用和调控。具体目标#1将通过恢复细胞-细胞连接处的e -钙粘蛋白积累来确定LPA在lps诱导的上皮屏障功能障碍中的保护作用。特异性目的#2将描述g蛋白偶联LPA受体和c-Met受体酪氨酸激酶之间的串扰在LPA介导的c-Met和e -钙粘蛋白再分布到细胞-细胞连接和LPA衰减LPS介导的肺上皮屏障功能障碍中的作用。特异性目的#3将描述LPA后处理对lps诱导的小鼠肺损伤的保护作用。这些研究将确定LPA受体参与的LPA信号通路与肺上皮屏障功能之间的分子机制，这对于开发针对改善肺部炎症性疾病的新疗法至关重要。公共卫生相关性：急性肺损伤（ALI）是由急性肺部炎症引起的急性呼吸衰竭的原因。肺上皮对吸入颗粒、过敏原和环境毒素提供了复杂的物理和生化屏障，在宿主防御中起着至关重要的作用。这些研究将确定溶血磷脂酸（LPA）和LPA受体维持正常肺上皮屏障功能的分子机制，这对于开发针对改善肺部炎症性疾病的新疗法至关重要。

DESCRIPTION (provided by applicant): Acute lung injury (ALI) is a condition of acute respiratory failure resulting from acute pulmonary inflammation. The airway epithelium provides a complex physical and biochemical barrier to inhaled particles, allergens, and environmental toxins and thus plays a vital role in host defense. Disruption of epithelial integrity is a major contributor to increased permeability and alveolar flooding with protein-rich edema fluid, a hallmark of ALI. However, understanding of the responses of the pulmonary epithelium to injury remains incomplete. E-cadherin-modulated adhesion junction plays a critical role since the formation of adhesion junction subsequently leads to the formation of other cell junctions. Lipopolysaccharide (LPS)-induced lung injury is a very useful experimental model for the investigation and characterization of immunopathogenic changes and mechanisms in ALI. We and others have found that cytoplasmic mislocalization of E-cadherin in pulmonary epithelium induces epithelial shedding and increases pulmonary epithelial permeability in a LPS-induced murine model of ALI and in primary cultured pulmonary epithelial cells. Also, several studies from ours and others have indicated an association between E-cadherin and tyrosine kinase receptor, such as c-Met tyrosine kinase, suggesting a complex molecular mechanisms of regulation of E-cadherin localization in epithelial cells. We recently reported that lysophosphatidic acid (LPA), a bioactive phospholipid growth factor released from activated platelets, enhances innate immunity and attenuates adaptive immunity via increasing IL-8, PGE2, and IL-13R alpha2 secretion in human bronchial epithelial cells (HBEpCs). However, molecular mechanisms of pulmonary epithelial barrier function are poorly defined and in this proposal it is hypothesized that "LPA post-treatment protects against pulmonary epithelial barrier dysfunction caused by LPS through cross-talk between LPA-Rs and c-Met resulting in enhanced E-cadherin accumulation at cell-cell junctions". The following Specific Aims will address the role and regulation of LPA-mediated barrier function in respiratory epithelium using primary human bronchial epithelial cells, alveolar type II epithelial cells, alveolar type II cell line and a murine model of ALI. Specific aim #1 will define the protective role of LPA in LPS-induced epithelial barrier dysfunction via restoring E-cadherin accumulation at cell-cell junctions. Specific aim #2 will characterize role of the cross-talk between G-protein-coupled LPA receptors and c-Met receptor tyrosine kinase in LPA-mediated c-Met and E-cadherin redistribution to cell-cell junctions and LPA attenuation of LPS mediated pulmonary epithelial barrier dysfunction. Specific aim #3 will characterize the role of LPA posttreatment in protecting against LPS-induced lung injury in mice. These studies will identify the molecular mechanisms linking the LPA signaling pathways involving LPA receptors to the pulmonary epithelium barrier function, which is critical to the development of new therapies directed at ameliorating lung inflammatory diseases. PUBLIC HEALTH RELEVANCE: Acute lung injury (ALI) is a cause of acute respiratory failure resulting from acute pulmonary inflammation. The pulmonary epithelium provides a complex physical and biochemical barrier to inhaled particles, allergens, and environmental toxins and thus plays a vital role in host defense. These studies will identify the molecular mechanisms linking the lysophophatidic acid (LPA) and LPA receptors to maintenance of normal pulmonary epithelium barrier function, which is critical in developing novel therapies directed at ameliorating lung inflammatory diseases.