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。气道上皮细胞为吸入颗粒、过敏原和环境毒素提供了复杂的物理和生化屏障，因此在宿主防御中起着至关重要的作用。上皮完整性的破坏是增加渗透性和肺泡充满富含蛋白质的水肿液的主要原因，这是ALI的标志。然而，对肺上皮细胞对损伤的反应的理解仍然不完全。E-钙粘蛋白调节的粘附连接起着关键作用，因为粘附连接的形成随后导致其他细胞连接的形成。脂多糖（LPS）诱导的肺损伤是研究ALI免疫病理变化和机制的一个非常有用的实验模型。我们和其他人发现，在LPS诱导的ALI小鼠模型和原代培养的肺上皮细胞中，肺上皮细胞中E-钙粘蛋白的细胞质错误定位诱导上皮脱落并增加肺上皮细胞的通透性。此外，我们和其他人的一些研究表明，E-钙粘蛋白和酪氨酸激酶受体，如c-Met酪氨酸激酶之间的关联，表明调节上皮细胞中E-钙粘蛋白定位的复杂分子机制。我们最近报道，溶血磷脂酸（LPA），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，PGE 2和IL-13 R 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定义不清，并且在该提议中，假设"LPA后处理通过LPA-Rs和c-Met之间的相互作用保护免受LPS引起的肺上皮屏障功能障碍，从而导致细胞-细胞连接处的E-钙粘蛋白积累增强"。以下特定目的将使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ALI小鼠模型，阐述LPA介导的屏障功能在呼吸道上皮中的作用和调节。具体目标#1将通过恢复细胞-细胞连接处的E-钙粘蛋白积累来定义LPA在LPS诱导的上皮屏障功能障碍中的保护作用。具体目标#2将表征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-钙粘蛋白重新分布至细胞-细胞连接和LPA减弱LPS介导的肺上皮屏障功能障碍中的作用。具体目标#3将表征LPA后处理在保护小鼠免受LPS诱导的肺损伤中的作用。这些研究将确定将涉及LPA受体的LPA信号通路与肺上皮屏障功能联系起来的分子机制，这对于开发旨在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，因此在宿主防御中起着至关重要的作用。这些研究将确定连接溶血磷脂酸（LPA）和LPA受体与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.