title: Aquaporin 5 regulates cigarette smoke induced emphysema by modulating barrier and immune properties of the epithelium.
abstract: Chronic obstructive pulmonary disease (COPD) causes significant morbidity and mortality. Cigarette smoke, the most common risk factor for COPD, induces airway and alveolar epithelial barrier permeability and initiates an innate immune response. Changes in abundance of aquaporin 5 (AQP5), a water channel, can affect epithelial permeability and immune response after cigarette smoke exposure. To determine how AQP5-derived epithelial barrier modulation affects epithelial immune response to cigarette smoke and development of emphysema, WT and AQP5(-/-) mice were exposed to cigarette smoke (CS). We measured alveolar cell counts and differentials, and assessed histology, mean-linear intercept (MLI), and surface-to-volume ratio (S/V) to determine severity of emphysema. We quantified epithelial-derived signaling proteins for neutrophil trafficking, and manipulated AQP5 levels in an alveolar epithelial cell line to determine specific effects on neutrophil transmigration after CS exposure. We assessed paracellular permeability and epithelial turnover in response to CS. In contrast to WT mice, AQP5(-/-) mice exposed to 6 months of CS did not demonstrate a significant increase in MLI or a significant decrease in S/V compared with air-exposed mice, conferring protection against emphysema. After sub-acute (4 weeks) and chronic (6 mo) CS exposure, AQP5(-/-) mice had fewer alveolar neutrophil but similar lung neutrophil numbers as WT mice. The presence of AQP5 in A549 cells, an alveolar epithelial cell line, was associated with increase neutrophil migration after CS exposure. Compared with CS-exposed WT mice, neutrophil ligand (CD11b) and epithelial receptor (ICAM-1) expression were reduced in CS-exposed AQP5(-/-) mice, as was secreted LPS-induced chemokine (LIX), an epithelial-derived neutrophil chemoattractant. CS-exposed AQP5(-/-) mice demonstrated decreased type I pneumocytes and increased type II pneumocytes compared with CS-exposed WT mice suggestive of enhanced epithelial repair. Absence of AQP5 protected against CS-induced emphysema with reduced epithelial permeability, neutrophil migration, and altered epithelial cell turnover which may enhance repair.
authors.affiliation: Division of Pulmonary and Critical Care Medicine; Johns Hopkins Asthma and Allergy Center; Baltimore, MD USA.
authors.forename: Neil R
authors.initials: NR
authors.lastname: Aggarwal
authors.affiliation: Division of Pulmonary and Critical Care Medicine; Johns Hopkins Asthma and Allergy Center; Baltimore, MD USA.
authors.forename: Eric
authors.initials: E
authors.lastname: Chau
authors.affiliation: Division of Pulmonary and Critical Care Medicine; Johns Hopkins Asthma and Allergy Center; Baltimore, MD USA.
authors.forename: Brian T
authors.initials: BT
authors.lastname: Garibaldi
authors.affiliation: Division of Pulmonary and Critical Care Medicine; Johns Hopkins Asthma and Allergy Center; Baltimore, MD USA.
authors.forename: Jason R
authors.initials: JR
authors.lastname: Mock
authors.affiliation: School of Public Health; Johns Hopkins University; Baltimore, MD USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Sussan
authors.affiliation: Division of Pulmonary and Critical Care Medicine; Johns Hopkins Asthma and Allergy Center; Baltimore, MD USA.
authors.forename: Keshav
authors.initials: K
authors.lastname: Rao
authors.affiliation: Division of Pulmonary and Critical Care Medicine; Johns Hopkins Asthma and Allergy Center; Baltimore, MD USA.
authors.forename: Kaavya
authors.initials: K
authors.lastname: Rao
authors.affiliation: Department of Molecular Genetics; Biochemistry and Microbiology; University of Cincinnati; Cincinnati OH, USA.
authors.forename: Anil G
authors.initials: AG
authors.lastname: Menon
authors.affiliation: Division of Pulmonary and Critical Care Medicine; Johns Hopkins Asthma and Allergy Center; Baltimore, MD USA.
authors.forename: Franco R
authors.initials: FR
authors.lastname: D'Alessio
authors.affiliation: Division of Pulmonary and Critical Care Medicine; Johns Hopkins Asthma and Allergy Center; Baltimore, MD USA.
authors.forename: Mahendra
authors.initials: M
authors.lastname: Damarla
authors.affiliation: School of Public Health; Johns Hopkins University; Baltimore, MD USA.
authors.forename: Shyam
authors.initials: S
authors.lastname: Biswal
authors.affiliation: Division of Pulmonary and Critical Care Medicine; Johns Hopkins Asthma and Allergy Center; Baltimore, MD USA.
authors.forename: Landon S
authors.initials: LS
authors.lastname: King
authors.affiliation: Division of Pulmonary and Critical Care Medicine; Johns Hopkins Asthma and Allergy Center; Baltimore, MD USA.
authors.forename: Venkataramana K
authors.initials: VK
authors.lastname: Sidhaye
keywords: Aquaporin 5; barrier function; epithelial immune response; epithelial permeability