Proteolysis in the Pathogenesis of ARDS

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PROJECT SUMMARY/ABSTRACT The Acute respiratory distress syndrome (ARDS) is the severest form of acute lung injury (ALI), and is characterized by injury to the alveolar-capillary unit and compromised alveolar epithelial integrity, leading to high permeability pulmonary edema and neutrophilic alveolar inflammation. Failure to repair the damaged alveolar membrane leads to significant mortality. Studies from several laboratories, including our own, have found that induction of ALI in animal models is associated with increased expression of matrix metalloproteinase-3 (MMP-3), a protease that has been shown to directly target cell-cell junctions and to degrade basement membranes, although it was unknown at what stages of ALI pathology this process was most critical. Other laboratories and ours have also found that transgenic mice lacking MMP-3 are resistant to lung injury induced by multiple stimuli, indicating that inhibitors of MMP-3 have potential as therapeutic agents for ARDS, although such a therapeutic strategy would need to be highly selective, as other MMPs have been shown to play key roles in repair of lung injury. In this translational application, we propose experiments which will bridge these critical gaps. In Aim 1, we will use physiologically relevant cell culture and animal models of ALI/ARDS including novel transgenic mice to define how MMP-3 affects the resolution of epithelial injury in response to acid aspiration or influenza infection. In Aim 2, we will use our directed molecular evolution platform to create variants of Tissue Inhibitor of Metalloproteinase-1 (TIMP-1) with greatly increased affinity for MMP-3 and decreased binding to beneficial MMPs, and we will define the therapeutic utility of these TIMP variants in mouse models of ALI/ARDS. In Aim 3, we will interrogate clinical samples of ARDS to determine the precise stages of human disease progression at which therapeutic intervention would be most beneficial. Our research proposal will define a newly-discovered mechanism by which MMP-3 drives ARDS pathology through an integrated research plan that links single cell RNA sequencing of cell populations isolated from ARDS patient tissue, cell culture and animal models of ARDS, and analysis of relevant ARDS biomarkers and ex vivo culture of precision cut human lung slices, and will develop a novel selective inhibitor with immediate therapeutic potential. Our multidisciplinary research team is uniquely suited to address these questions. Our work will address critical mechanisms underlying ALI/ARDS, will use this knowledge to develop personalized strategies that will identify patients at highest risk of developing ALI/ARDS, and will create therapeutic approaches based on the pivotal role of MMP-3 in the pathogenesis of epithelial injury leading to ALI/ARDS.