In the United States (U.S.), the acute respiratory distress syndrome (ARDS) remains a significant public health problem. Despite substantial efforts to improve the outcome, mortality remains ~45%. More importantly, ~ 80% of ARDS survivors experience reduced health-related quality of life, and these survivors also have changes consistent with early fibrosis on chest imaging for up to 5 years after a diagnosis of ARDS. Although there is no direct evidence that fibroproliferative ARDS is associated with an increase in mortality, indirect evidence suggests an increased risk of death in patients with elevated pro-fibrotic markers, transforming growth factor-beta (TGF?) and procollagen III in the bronchoalveolar lavage. Dysregulation of TGF? drives tissue disrepair following injury. Our laboratory utilizes experimental models of chronic alcohol ingestion and bleomycin-induced acute lung injury (ALI) to assess the molecular mechanisms of lung repair as well as identify novel preventative and therapeutic interventions. We showed that alcohol induced excessive and persistent TGF? expression in the lung. We showed that TGF? is a key molecule that drives many cellular anomalies in the lung of chronic alcohol-exposed animals including increase oxidative stress in the airway, decrease in alveolar macrophages phagocytosis, and primes the lung toward fibroproliferative disrepair following acute injury. Elucidating the mechanisms by which TGF? being induced in the lung would allow the development of novel strategies to promote effective repair following ALI. Our preliminary data show that one of the mechanism by which alcohol induces TGF? is by disturbing 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. Very little is known regarding the function of miR-1946a and how it is regulated. In silico analysis showed that miR-1946a targeted TGF?, in this proposal, we show that inhibition of miR-1946a increases TGF? expression while overexpression of miR-1946a attenuates TGF? expression. This is the first direct evidence suggesting the role of miR-1946a on TGF? expression. These exciting results lead us to hypothesize that alcohol increases TGF? expression by inhibiting anti-fibrotic miR-1946a, thereby priming the lung for fibroproliferative disrepair. The experimental approaches are designed to test this hypothesis, and these studies are expected to provide a firm scientific basis for the underlying mechanisms by which alcohol interferes with normal repair following ALI.
Project Narative/Lay Summary: A disrepair of the lung following acute injury leads to a significant reduction in quality of life among acute respiratory distress syndrome (ARDS) survivors. Chronic alcohol ingestion greatly increases the risk of severe lung injury and disrepair due to a dysregulation of transforming growth factor (TGF)-beta leading to scar formation following an injury. Understanding the mechanisms by which TGF-beta is dysregulated could lead to an identification of preventative or therapeutic interventions that can promote healthy lung repair following injury.
