Chronic Alcohol Ingestion in Rats Decreases Krüppel-like Factor 4 Expression and Intracellular Zinc in the Lung

• Type of Material: Article
• Authors: Tiana V. Curry-McCoy, Emory University; David M Guidot, Emory University; Pratibha C. Joshi, Emory University
• Language: English
• Date: 2013-03
• Publisher: Wiley: 12 months
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2012 by the Research Society on Alcoholism
• Final Published Version (URL): http://onlinelibrary.wiley.com/doi/10.1111/j.1530-0277.2012.01946.x/abstract?systemMessage=Wiley+Online+Library+will+be+disrupted+Saturday%2C+15+March+from+10%3A00-12%3A00+GMT+%2806%3A00-08%3A00+EDT%29+for+essential+maintenance
• Title of Journal or Parent Work: Alcoholism: Clinical and Experimental Research
• ISSN: 0145-6008
• Volume: 37
• Issue: 3
• Start Page: 361
• End Page: 371
• Grant/Funding Information: Supported by NIAAA (T32AA013528) and RO1AA017627
• Keywords: zinc; macrophage; lung; alcohol; type II epithelia; Krüppel-like Factor 4
• Research Categories: Health Sciences, Medicine and Surgery

Abstract

Background Chronic alcohol ingestion alters the dynamic balance between granulocyte-macrophage colony stimulating factor (GM-CSF) and transforming growth factor beta1 (TGFβ1) signaling within the alveolar space and, in parallel, impairs alveolar macrophage and epithelial cell function by inhibiting expression of the zinc importer ZIP4 and decreasing zinc bioavailability in the alveolar compartment. Since the transcription factor Krüppel-like factor 4 (KLF4) binds to ZIP4, we hypothesized that alcohol exposure and consequent perturbations in GM-CSF and TGFβ1 signaling could decrease cellular KLF4 expression and/or binding as a mechanism by which it inhibits ZIP4 expression and decreases cellular zinc levels. Methods and Results Alcohol exposure in vitro or chronic ingestion in vivo decreased KLF4 expression in alveolar macrophages and epithelial cells. Treatment with GM-CSF or TGFβ1 showed an enhancing or dampening effect on KLF4 expression and binding, respectively. Further, treatment of a rat alveolar macrophage cell line with alcohol in vitro for 4 weeks decreased the expression of the zinc transporters ZIP4 and ZNT1, and of the zinc storage protein metallothionein 1. In parallel, treating these macrophages with KLF4 siRNA decreased ZIP4 expression, and decreased cellular zinc and phagocytic capacity to levels equivalent to those following alcohol exposure. In epithelial monolayers, TER was significantly decreased by alcohol ingestion as compared to control diets and it was restored by in vitro GM-CSF treatment. In contrast, in vitro TGFβ1 treatment of the epithelial monolayers from control-fed rats significantly decreased TER as compared to untreated control monolayers. Conclusions Taken together, these results suggest that within the alveolar space, chronic alcohol exposure decreases KLF4 and ZIP4 expression and consequently decreases zinc transport into cells, which, in turn, impairs their function. Furthermore, the dynamic decrease in the relative influence of GM-CSF vs. TGFβ1 could mediate the zinc deficiency and consequent cellular dysfunction that characterize the ‘alcoholic lung’ phenotype.