Tissue disrepair following injury leads to organ dysfunction and increases morbidity and mortality of those who survive the initial insult. In the lung, the disrepair process is associated with excessive collagen deposition along with failure of both re-epithelialization and epithelial cell tight junction formation. Tissue disrepair is associated with dysregulation of TGF? signaling in a variety of pulmonary diseases including the acute respiratory distress syndrome (ARDS), chronic obstructive pulmonary disease (COPD), and interstitial lung disease (ILD). Our laboratory utilizes experimental models of chronic alcohol ingestion and bleomycin- induced lung injury to assess the molecular mechanisms of lung repair and identify novel preventative and therapeutic interventions. We have previously shown that alcohol induces excessive and persistent TGF? expression in the lung. Additionally, we demonstrated that in the lung of chronic alcohol-exposed animals, TGF? is a critical molecule driving many cellular anomalies by increasing airway oxidative stress, decreasing alveolar macrophages phagocytosis, and priming the lung for fibroproliferative disrepair following acute injury. Our preliminary data show that alcohol-exposed lung fibroblasts interfere with epithelial cell barrier formation likely through induction of epithelial-mesenchymal transition (EMT). Additionally, inhibition of TGF? signaling attenuates the effect of alcohol-exposed fibroblasts on epithelial cells. Interestingly, we also showed that fibroblasts influence epithelial cells indirectly via fibroblast-derived exosomes rather than direct secretion of cytokines or growth factors. Furthermore, we showed that alcohol disturbs the balance of pro- and anti-fibrotic microRNA (miR) expression. Specifically, alcohol increases pro-fibrotic miR-21 and attenuates anti-fibrotic miRNA-1946a in lung fibroblasts. These data lead us to hypothesize that alcohol exposure disrupts alveolar epithelial cell tight junction formation and barrier function following injury through an imbalance of miR-21 and miR-1946a in exosomes secreted by lung fibroblasts. The experimental approaches are designed to test this hypothesis, and these studies are expected to provide a firm scientific basis for the underlying mechanism(s) by which alcohol interferes with normal repair following lung injury. The results from this proposal will set the basis for future studies to investigate potential therapeutic strategies to prevent or mitigate tissue injury and disrepair in the at-risk population (i.e., alcoholic individuals).
Project Narative/Lay Summary: A disrepair of the lung following acute injury leads to a significant reduction in quality of life among individuals with chronic lung diseases including survivors of acute respiratory distress syndrome (ARDS). Chronic alcohol ingestion greatly increases the risk of severe lung injury and disrepair due to abnormal lung fibroblasts and epithelial cells function. Understanding how different cell types interfere with epithelial cells repair could lead to an identification of preventative or therapeutic interventions that can promote healthy lung repair following injury.
