Chronic alcohol ingestion alters claudin expression in the alveolar epithelium of rats

• Type of Material: Article
• Authors: Alberto L. Fernandez, Emory University; Michael H Koval, Emory University; Xian Fan, Emory University; David M Guidot, Emory University
• Language: English
• Date: 2007-08
• Publisher: Elsevier Masson
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2007 Elsevier Inc. All rights reserved.
• License: Creative Commons Attribution-NonCommerical-NoDerivs 3.0 Unported
• Final Published Version (URL): http://dx.doi.org/10.1016/j.alcohol.2007.04.010
• Title of Journal or Parent Work: Alcohol
• ISSN: 0741-8329
• Volume: 41
• Issue: 5
• Start Page: 371
• End Page: 379
• Grant/Funding Information: This work was funded by a Merit Review from the Department of Veterans Affairs, the National Institute on Alcohol Abuse and Alcoholism (P50 AA013757, T32 AA013528) and the National Heart Lung and Blood Institute (R01 HL083120).
• Keywords: ARDS; tight junction; type I pneumocyte; claudin; ethanol; type II pneumocyte
• Research Categories: Health Sciences, General

Abstract

Previously we determined that chronic alcohol ingestion (6 wks) in rats increases lung epithelial permeability in vivo ~5-6-fold and promotes flooding of the alveolar airspaces with proteinaceous fluid in response to stresses such as sepsis. In parallel, alveolar epithelial cells isolated from alcohol-fed rats fail to form tight monolayers in vitro, even when cultured for up to 8 days in the absence of alcohol. However, the molecular mechanisms underlying alcohol-induced permeability are unknown. Claudins are key components of tight junctions that restrict the paracellular movement of water, proteins, and solutes across cellular barriers including the alveolar epithelium. In this study, we examined the expression of multiple members of the claudin protein family in the lungs of alcohol-fed vs. control-fed rats (Lieber-DeCarli liquid diet with 36% of calories as alcohol vs. maltin-dextrin for 6 wks). We determined that chronic alcohol ingestion affected the expression of multiple claudins; most striking were decreases in claudin-1 and claudin-7, and an increase in claudin-5, in the whole lung and in alveolar epithelial monolayers derived from alcohol-fed rats. In parallel, immunocytochemistry of alveolar epithelial monolayers from alcohol-fed rats revealed abnormal intracellular accumulation of claudin-7 protein and relatively decreased localization to cell membranes. Claudin-1 and claudin-7 are relatively specific to alveolar epithelial type I pneumocytes that form the vast majority of the alveolar epithelial barrier in vivo, and increases in claudin-5 have been associated with increased epithelial permeability in other systems. Therefore, these findings suggest that changes in claudin expression in the alveolar epithelium produce a “leakier” phenotype that renders the alcoholic lung susceptible to alveolar flooding during acute inflammatory stresses.