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A1851 - Loss of Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) Drives Lung Endothelial Barrier Failure in Pneumonia-Induced Acute Respiratory Distress Syndrome (ARDS)
Author Block: L. Erfinanda1, B. Schneider2, B. Gutbier2, L. Zou1, K. Reppe2, J. Lienau2, A. C. Hocke2, W. Liedtke3, M. Witzenrath2, W. M. Kuebler1; 1Institute of Physiology, Charité - Universitätsmedizin, Berlin, Germany, 2Dep. of Infectious Diseases and Respiratory Medicine, Charité - Universitätsmedizin, Berlin, Germany, 3Dep. of Medicine, Neurology, and Neurobiology, Duke University, Durham, NC, United States.
Rationale: Pneumonia is the most common cause of the acute respiratory distress syndrome (ARDS), a potentially fatal lung disease characterized by hyperinflammation and loss of endothelial barrier function. Cystic fibrosis transmembrane conductance regulator (CFTR) is rapidly downregulated from the cell surface in infectious and inflammatory conditions, and inhibition of CFTR was found to increase lung microvascular endothelial permeability in vitro.
Objective: We therefore hypothesized that loss of CFTR may present an important pathomechanism in endothelial barrier failure in pneumonia-induced ARDS, and aimed to elucidate the molecular signaling mechanisms underlying this effect.
Methods: Human lung tissues and C57/BL6J mice lungs were infected ex vivo or in vivo respectively with Streptococcus pneumoniae and CFTR expression was determined. TRPV4-deficient (trpv4-/-) mice and their wild type (C57/BL6J) control were infected with S. pneumoniae transnasally and lung permeability was quantified after 48h by determination of human serum albumin (HSA) leakage in bronchoalveolar lavage fluid (BALF). In isolated perfused rat lungs, lung edema formation, endothelial Cl- ([Cl-]i) and Ca2+ concentration ([Ca2+]i) was quantified by weight gain measurement and real time fluorescence imaging, respectively.
Results: CFTR expression is downregulated in human and murine lung tissue after S. pneumoniae infection. In vivo, trpv4-/- infected with S. pneumoniae developed less lung permeability as compared to their wild type controls. In isolated rat lungs, CFTR inhibition by CFTRinh-172 increased endothelial permeability, [Cl-]i and [Ca2+]i. Inhibition of the Cl- sensitive with no lysine kinase 1 (WNK1) by tyrphostin replicated the effect of CFTR inhibition on endothelial permeability and [Ca2+]i, while WNK1 activation by temozolomide blocked the effects of CFTR inhibition. CFTRinh-172 induced increases in endothelial [Ca2+]i and permeability were similarly prevented by inhibition of transient receptor potential vanilloid 4 (TRPV4), an endothelial Ca2+ channel negatively regulated by WNK1, with HC-067047.
Conclusion: S. pneumoniae infection causes loss of CFTR that promotes endothelial barrier failure through inhibition of Cl--sensitive WNK1 and subsequent disinhibition of TRPV4. With TRPV4 antagonists being presently tested in clinical trials, inhibition of TRPV4 may present a promising strategy to prevent or treat ARDS in pneumonia patients.