title: The relative balance of GM-CSF and TGF-β1 regulates lung epithelial barrier function.
abstract: Lung barrier dysfunction is a cardinal feature of the acute respiratory distress syndrome (ARDS). Alcohol abuse, which increases the risk of ARDS two- to fourfold, induces transforming growth factor (TGF)-β1, which increases epithelial permeability and impairs granulocyte/macrophage colony-stimulating factor (GM-CSF)-dependent barrier integrity in experimental models. We hypothesized that the relative balance of GM-CSF and TGF-β1 signaling regulates lung epithelial barrier function. GM-CSF and TGF-β1 were tested separately and simultaneously for their effects on lung epithelial cell barrier function in vitro. TGF-β1 alone caused an ∼ 25% decrease in transepithelial resistance (TER), increased paracellular flux, and was associated with projections perpendicular to tight junctions ("spikes") containing claudin-18 that colocalized with F-actin. In contrast, GM-CSF treatment induced an ∼ 20% increase in TER, decreased paracellular flux, and showed decreased colocalization of spike-associated claudin-18 with F-actin. When simultaneously administered to lung epithelial cells, GM-CSF antagonized the effects of TGF-β1 on epithelial barrier function in cultured cells. Given this, GM-CSF and TGF-β1 levels were measured in bronchoalveolar lavage (BAL) fluid from patients with ventilator-associated pneumonia and correlated with markers for pulmonary edema and patient outcome. In patient BAL fluid, protein markers of lung barrier dysfunction, serum α2-macroglobulin, and IgM levels were increased at lower ratios of GM-CSF/TGF-β1. Critically, patients who survived had significantly higher GM-CSF/TGF-β1 ratios than nonsurviving patients. This study provides experimental and clinical evidence that the relative balance between GM-CSF and TGF-β1 signaling is a key regulator of lung epithelial barrier function. The GM-CSF/TGF-β1 ratio in BAL fluid may provide a concentration-independent biomarker that can predict patient outcomes in ARDS.
authors.affiliation: Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Medicine, Emory University, Atlanta, Georgia; Emory Alcohol and Lung Biology Center, Emory University, Atlanta, Georgia;
authors.forename: Christian E
authors.initials: CE
authors.lastname: Overgaard
authors.affiliation: Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Medicine, Emory University, Atlanta, Georgia;
authors.forename: Barbara
authors.initials: B
authors.lastname: Schlingmann
authors.affiliation: Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Medicine, Emory University, Atlanta, Georgia;
authors.forename: StevenClaude
authors.initials: S
authors.lastname: Dorsainvil White
authors.affiliation: Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Medicine, Emory University, Atlanta, Georgia; Emory Alcohol and Lung Biology Center, Emory University, Atlanta, Georgia;
authors.forename: Christina
authors.initials: C
authors.lastname: Ward
authors.affiliation: Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Medicine, Emory University, Atlanta, Georgia; Atlanta Veterans Affairs Medical Center, Decatur, Georgia.
authors.forename: Xian
authors.initials: X
authors.lastname: Fan
authors.affiliation: Drug Development Diagnostics and Biotechnology, CSIR-Indian Institute of Chemical Biology, Kolkata, India;
authors.forename: Snehasikta
authors.initials: S
authors.lastname: Swarnakar
authors.affiliation: Emory Alcohol and Lung Biology Center, Emory University, Atlanta, Georgia; Division of Neonatology, Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia;
authors.forename: Lou Ann S
authors.initials: LA
authors.lastname: Brown
authors.affiliation: Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Medicine, Emory University, Atlanta, Georgia; Emory Alcohol and Lung Biology Center, Emory University, Atlanta, Georgia; Atlanta Veterans Affairs Medical Center, Decatur, Georgia.
authors.forename: David M
authors.initials: DM
authors.lastname: Guidot
authors.affiliation: Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Medicine, Emory University, Atlanta, Georgia; Emory Alcohol and Lung Biology Center, Emory University, Atlanta, Georgia; Department of Cell Biology, Emory University, Atlanta, Georgia; mhkoval@emory.edu.
authors.forename: Michael
authors.identifier: http://orcid.org/0000-0002-5422-5614
authors.initials: M
authors.lastname: Koval
mesh_terms: D000818:Animals; D004847:Epithelial Cells / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000378:metabolism*; D006801:Humans; D015151:Immunoblotting; D008168:Lung / Q000166:cytology / Q000378:metabolism*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D012143:Respiratory Physiological Phenomena; D053773:Transforming Growth Factor beta1 / Q000378:metabolism*
chemical_list: D053773:Transforming Growth Factor beta1; D016178:Granulocyte-Macrophage Colony-Stimulating Factor
keywords: claudin; granulocyte/macrophage colony-stimulating factor; lung epithelium; pulmonary edema; tight junctions