title: TGFβ1 mediates alcohol-induced Nrf2 suppression in lung fibroblasts.
abstract: BACKGROUND
  Chronic alcohol ingestion induces the expression of transforming growth factor beta-1(TGFβ1), inhibits nuclear factor (erythroid-derived 2)-like 2 (Nrf2)-mediated activation of the antioxidant response element (ARE), depletes alveolar glutathione pools, and potentiates acute lung injury. In this study, we examined the mechanistic relationship between TGFβ1 and Nrf2-ARE signaling in the experimental alcoholic lung.
  
  
  METHODS
  Wild-type mice were treated ± alcohol in drinking water for 8 weeks and their lungs were assessed for Nrf2 expression. In parallel, mouse lung fibroblasts were cultured ± alcohol and treated ± sulforaphane (SFP; an activator of Nrf2), ±TGFβ1, ±TGFβ1 neutralizing antibody, and/or ±activin receptor-like kinase 5 inhibitors (to block TGβ1 receptor signaling) and then analyzed for the expression of Nrf2, Kelch-like ECH-associated protein 1 (Keap1) and TGFβ1, Nrf2-ARE activity, and the expression of the Nrf2-ARE-dependent antioxidants glutathione s-transferase theta 2 (GSTT2) and glutamate-cysteine ligase catalytic subunit (GCLC). Finally, silencing RNA (siRNA) of Nrf2 was then performed prior to alcohol exposure and subsequent analysis of TGFβ1 expression.
  
  
  RESULTS
  Alcohol treatment in vivo or in vitro decreased Nrf2 expression in murine whole lung and lung fibroblasts, respectively. In parallel, alcohol exposure in vitro decreased Keap1 gene and protein expression in lung fibroblasts. Furthermore, alcohol exposure increased TGFβ1 expression but decreased Nrf2-ARE activity and expression of the ARE-dependent genes for GSTT2 and GCLC. These effects of alcohol were prevented by treatment with SFP; in contrast, Nrf2 SiRNA expression exacerbated alcohol-induced TGFβ1 expression. Finally, TGFβ1 treatment directly suppressed Nrf2-ARE activity whereas blocking TGFβ1 signaling attenuated alcohol-induced suppression of Nrf2-ARE activity.
  
  
  CONCLUSIONS
  Alcohol-induced oxidative stress is mediated by TGFβ1, which suppresses Nrf2-ARE-dependent expression of antioxidant defenses and creates a vicious cycle that feeds back to further increase TGFβ1 expression. These effects of alcohol can be mitigated by activation of Nrf2, suggesting a potential therapy in individuals at risk for lung injury due to alcohol abuse.
authors.affiliation: Division of Pulmonary, Allergy & Critical Care, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia.
authors.forename: Viranuj
authors.initials: V
authors.lastname: Sueblinvong
authors.forename: Victor
authors.initials: V
authors.lastname: Tseng
authors.forename: Tierra
authors.initials: T
authors.lastname: Smith
authors.forename: Ramin
authors.initials: R
authors.lastname: Saghafi
authors.forename: Stephen T
authors.initials: ST
authors.lastname: Mills
authors.forename: David C
authors.initials: DC
authors.lastname: Neujahr
authors.forename: David M
authors.initials: DM
authors.lastname: Guidot
mesh_terms: D000818:Animals; D002461:Cell Line, Transformed; D000431:Ethanol / Q000633:toxicity*; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D008168:Lung / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D051267:NF-E2-Related Factor 2 / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D041681:NIH 3T3 Cells; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology / Q000502:physiology*
chemical_list: D051267:NF-E2-Related Factor 2; C495636:Nfe2l2 protein, mouse; C508961:Tgfb1 protein, mouse; D053773:Transforming Growth Factor beta1; D000431:Ethanol
keywords: Alcohol; Antioxidant Response Element; Glutathione; Lung Fibroblasts; Nrf2; TGFβ1