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Background The pathophysiology of acute respiratory distress syndrome (ARDS) may eventually result in heterogeneous lung collapse and edema-flooded airways, predisposing the lung to progressive tissue damage known as ventilator-induced lung injury (VILI). Autotaxin (ATX; ENPP2), the enzyme largely responsible for extracellular lysophosphatidic acid (LPA) production, has been suggested to play a pathogenic role in, among others, pulmonary inflammation and fibrosis. Methods C57BL/6 mice were subjected to low and high tidal volume mechanical ventilation using a small animal ventilator: respiratory mechanics were evaluated, and plasma and bronchoalveolar lavage fluid (BALF) samples were obtained. Total protein concentration was determined, and lung histopathology was further performed Results Injurious ventilation resulted in increased BALF levels of ATX. Genetic deletion of ATX from bronchial epithelial cells attenuated VILI-induced pulmonary edema. Conclusion ATX participates in VILI pathogenesis.

Background: Pulmonary fibrosis is a chronic disease, which progressively leads to respiratory failure and ultimately death. Endothelin-1 (ET-1), a vasoconstrictor secreted by endothelial cells, promotes vasoconstriction by activation of its receptors A and B. Objectives: We addressed the role of highly selective ET-1 receptor A (ETA) inhibition in the pathogenesis of experimental pulmonary fibrosis by bleomycin (BLM). Methods: BLM sulfate (2 U/mL) or saline was intratracheally administered to C57/Bl6 mice (4 groups; n = 5-11/group). Pretreatment with the highly selective ETA receptor inhibitor sitaxentan (15 mg/kg/day) was started 1 day prior to BLM injection and continued for the duration of the experiment. Lung mechanics were assessed prior to sacrifice at days 7, 14, and 21 after BLM, followed by procurement of bronchoalveolar lavage fluid (BALF), blood, and lung tissue samples. Results: Time-dependent effects of BLM exposure included decreased static compliance and increased lung elastance, airspace inflammation and microvascular permeability, histological acute lung injury and fibrosis, and lung collagen deposition. Pretreatment with highly selective ETA receptor inhibitor had no adverse effect on control mice but improved lung mechanics and lung injury score in addition to decreasing BALF pleocytosis, protein content, and collagen deposition in BLM-treated mice. Mortality from BLM reached 40% and occurred primarily during the inflammatory stage of the model but was abrogated by sitaxentan pretreatment. Conclusions: We conclude that in our BLM-induced pulmonary fibrosis model, prophylactic highly selective ETA inhibition improves survival, preserves lung function, attenuates lung injury, and reduces collagen deposition. (c) 2017 S. Karger AG, Basel

Increased pulmonary vascular resistance in pulmonary hypertension (PH) is caused by vasoconstriction and obstruction of small pulmonary arteries by proliferating vascular cells. In analogy to cancer, subsets of proliferating cells may be derived from endothelial cells transitioning into a mesenchymal phenotype. To understand phenotypic shifts transpiring within endothelial cells in PH, we injected rats with alkaloid monocrotaline to induce PH and measured lung tissue levels of endothelial-specific protein and critical differentiation marker vascular endothelial (VE)-cadherin. VE-cadherin expression by immonoblotting declined significantly 24 h and 15 days postinjection to rebound to baseline at 30 days. There was a concomitant increase in transcriptional repressors Snail and Slug, along with a reduction in VE-cadherin mRNA. Mesenchymal markers alpha-smooth muscle actin and vimentin were upregulated by immunohistochemistry and immunoblotting, and alpha-smooth muscle actin was colocalized with endothelial marker platelet endothelial cell adhesion molecule-1 by confocal microscopy. Apoptosis was limited in this model, especially in the 24-h time point. In addition, monocrotaline resulted in activation of protein kinase B/Akt, endothelial nitric oxide synthase (eNOS), nuclear factor (NF)-kappa B, and increased lung tissue nitrotyrosine staining. To understand the etiological relationship between nitrosative stress and VE-cadherin suppression, we incubated cultured rat lung endothelial cells with endothelin-1, a vasoconstrictor and pro-proliferative agent in pulmonary arterial hypertension. This resulted in activation of eNOS, NF-kappa B, and Akt, in addition to induction of Snail, downregulation of VE-cadherin, and synthesis of vimentin. These effects were blocked by eNOS inhibitor N-omega-nitro-Larginine methyl ester. We propose that transcriptional repression of VE-cadherin by nitrosative stress is involved in endothelial-mesenchymal transdifferentiation in experimental PH.

Background: Mortality from severe acute respiratory distress syndrome exceeds 40% and there is no available pharmacologic treatment. Mechanical ventilation contributes to lung dysfunction and mortality by causing ventilator-induced lung injury. We explored the utility of simvastatin in a mouse model of severe ventilator-induced lung injury. Methods: Male C57BL6 mice (n = 7/group) were pretreated with simvastatin or saline and received protective (8 mL/kg) or injurious (25 mL/kg) ventilation for four hours. Three doses of simvastatin (20 mg/kg) or saline were injected intraperitoneally on days -2, -1 and 0 of the experiment. Lung mechanics, (respiratory system elastance, tissue damping and airway resistance), were evaluated by forced oscillation technique, while respiratory system compliance was measured with quasi-static pressure-volume curves. A pathologist blinded to treatment allocation scored hematoxylin-eosin-stained lung sections for the presence of lung injury. Pulmonary endothelial dysfunction was ascertained by bronchoalveolar lavage protein content and lung tissue expression of endothelial junctional protein Vascular Endothelial cadherin by immunoblotting. To assess the inflammatory response in the lung, we determined bronchoalveolar lavage fluid total cell content and neutrophil fraction by microscopy and staining in addition to Matrix-Metalloprotease-9 by ELISA. For the systemic response, we obtained plasma levels of Tumor Necrosis Factor-a, Interleukin-6 and Matrix-Metalloprotease-9 by ELISA. Statistical hypothesis testing was undertaken using one-way analysis of variance and Tukey’s post hoc tests. Results: Ventilation with high tidal volume (HVt) resulted in significantly increased lung elastance by 3-fold and decreased lung compliance by 45% compared to low tidal volume (LVt) but simvastatin abrogated lung mechanical alterations of HVt. Histologic lung injury score increased four-fold by HVt but not in simvastatin-pretreated mice. Lavage pleocytosis and neutrophilia were induced by HVt but were significantly attenuated by simvastatin. Microvascular protein permeability increase 20-fold by injurious ventilation but only 4-fold with simvastatin. There was a 3-fold increase in plasma Tumor Necrosis Factor-a, a 7-fold increase in plasma Interleukin-6 and a 20-fold increase in lavage fluid Matrix-Metalloprotease-9 by HVt but simvastatin reduced these levels to control. Lung tissue vascular endothelial cadherin expression was significantly reduced by injurious ventilation but remained preserved by simvastatin. Conclusion: High-dose simvastatin prevents experimental hyperinflation lung injury by angioprotective and anti-inflammatory effects.