Molecular regulation of pulmonary tight junctions

描述（由申请人提供）：急性呼吸窘迫综合征（ARDS）的特征是终末肺泡上皮功能受损，导致空域充血、呼吸衰竭和死亡率增加。虽然在过去的40年里，人们对ARDS的病理生理学已经有了很多了解，但其死亡率仍然高达50%，令人无法接受。ARDS的存活与维持肺液体清除的能力相关，这反过来又需要肺内健康的气液屏障。这种屏障在很大程度上是通过肺泡上皮紧密连接来维持的，细胞-细胞接触部位的结构选择性地形成一种屏障

DESCRIPTION (provided by applicant): Acute Respiratory Distress Syndrome (ARDS) is characterized by compromised epithelial function in the terminal alveolus leading to airspace flooding, respiratory failure, and increased mortality. While much has been learned about the pathophysiology of ARDS in the past four decades, the mortality rate remains unacceptably high at ~50%. Surviving ARDS correlates with the ability to maintain lung fluid clearance which, in turn, requires a healthy air-liquid barrier in the lung. This barrier is maintained in large part b alveolar epithelial tight junctions, structures at cell-cell contact sites which form a selectively permeable seal to regulate paracellular diffusion of water, ions and solutes. My laboratory has identified specific roles for proteins known as claudins in regulating alveolar epithelial tight junction permeability. However, the downstream effects of claudin dysregulation in response to acute lung injury (ALI) and ARDS have not been fully elucidated. In addition, chronic alcohol abuse worsens the incidence and severity of ARDS. We have found that chronic dietary alcohol ingestion alters alveolar epithelial claudin expression which correlates with impaired barrier function. Here, molecular tools developed by my laboratory combined with cultured cell and model injury systems will be used to understand how claudin dysregulation affects the progression of ARDS in response to ALI. The project will define mechanistic roles for alveolar epithelial claudins, including claudin-4 and claudin-18 which correlate with improved lung fluid clearance and claudin-5 which is upregulated in the alcoholic lung and associates with impaired alveolar barrier function. A series of adenovectors were developed which allows manipulation of claudin expression by cultured primary alveolar epithelial cells and lung epithelia in vivo. This approach will be used to measure the effects of increasing claudin-4, claudin-5 or claudin-18 expression on alveolar epithelial barrier function. The effects of increasing claudin-4, claudin-5 or claudin-18 on lung fluid clearance in vivo will be assessed and correlated changes to tight junction composition during ALI due to two distinct model systems: 1) intratracheal administration of bleomycin and 2) cecal ligation and puncture to induce sepsis. We will also assess the ability of claudin-4 and claudin-18 to reverse the deleterious effects of alcoholic lung syndrome which exacerbate the pathologic consequences of ALI. Measuring the effects of altered alveolar claudin composition on tight junction permeability and turnover in diverse ALI model systems will be used to evaluate therapeutic strategies with the potential to strengthen alveolar barrier function and lessen susceptibility to ARDS.