title: Hyperoxia induces alveolar epithelial-to-mesenchymal cell transition.
abstract: Myofibroblast accumulation is a pathological feature of lung diseases requiring oxygen therapy. One possible source for myofibroblasts is through the epithelial-to-mesenchymal transition (EMT) of alveolar epithelial cells (AEC). To study the effects of oxygen on alveolar EMT, we used RLE-6TN and ex vivo lung slices and found that hyperoxia (85% O2, H85) decreased epithelial proteins, presurfactant protein B (pre-SpB), pro-SpC, and lamellar protein by 50% and increased myofibroblast proteins, α-smooth muscle actin (α-SMA), and vimentin by over 200% (P < 0.05). In AEC freshly isolated from H85-treated rats, mRNA for pre-SpB and pro-SpC was diminished by ∼50% and α-SMA was increased by 100% (P < 0.05). Additionally, H85 increased H2O2 content, and H2O2 (25-50 μM) activated endogenous transforming growth factor-β1 (TGF-β1), as evident by H2DCFDA immunofluorescence and ELISA (P < 0.05). Both hyperoxia and H2O2 increased SMAD3 phosphorylation (260% of control, P < 0.05). Treating cultured cells with TGF-β1 inhibitors did not prevent H85-induced H2O2 production but did prevent H85-mediated α-SMA increases and E-cadherin downregulation. Finally, to determine the role of TGF-β1 in hyperoxia-induced EMT in vivo, we evaluated AEC from H85-treated rats and found that vimentin increased ∼10-fold (P < 0.05) and that this effect was prevented by intraperitoneal TGF-β1 inhibitor SB-431542. Additionally, SB-431542 treatment attenuated changes in alveolar histology caused by hyperoxia. Our studies indicate that hyperoxia promotes alveolar EMT through a mechanism that is dependent on activation of TGF-β1 signaling.
authors.affiliation: 2015 Uppergate Dr. NE, Atlanta, GA 30322. svyasre@emory.edu.
authors.forename: Shilpa
authors.initials: S
authors.lastname: Vyas-Read
authors.forename: Wenyi
authors.initials: W
authors.lastname: Wang
authors.forename: Satomi
authors.initials: S
authors.lastname: Kato
authors.forename: Jennifer
authors.initials: J
authors.lastname: Colvocoresses-Dodds
authors.forename: Nimita H
authors.initials: NH
authors.lastname: Fifadara
authors.forename: Theresa W
authors.initials: TW
authors.lastname: Gauthier
authors.forename: My N
authors.initials: MN
authors.lastname: Helms
authors.forename: David P
authors.initials: DP
authors.lastname: Carlton
authors.forename: Lou Ann S
authors.initials: LA
authors.lastname: Brown
mesh_terms: D056809:Alveolar Epithelial Cells / Q000502:physiology; D000818:Animals; D002478:Cells, Cultured; D058750:Epithelial-Mesenchymal Transition; D006861:Hydrogen Peroxide / Q000378:metabolism; D018496:Hyperoxia / Q000378:metabolism / Q000473:pathology*; D008297:Male; D058628:Myofibroblasts / Q000378:metabolism; D010641:Phenotype; D011650:Pulmonary Alveoli / Q000378:metabolism / Q000473:pathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D046509:Tissue Culture Techniques; D053773:Transforming Growth Factor beta1 / Q000378:metabolism
chemical_list: C508962:Tgfb1 protein, rat; D053773:Transforming Growth Factor beta1; D006861:Hydrogen Peroxide
keywords: hyperoxia; lung fibrosis; oxidative stress; oxygen therapy; transforming growth factor-β1 signaling