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: Shilpa Vyas-Read, Wenyi Wang, Satomi Kato, Jennifer Colvocoresses-Dodds, Nimita H Fifadara, Theresa W Gauthier, My N Helms, David P Carlton, Lou Ann S Brown
• Journal: American journal of physiology. Lung cellular and molecular physiology (Am J Physiol Lung Cell Mol Physiol) Vol. 306 Issue 4 Pg. L326-40 (Feb 15 2014) ISSN: 1522-1504 [Electronic] United States
• PMID: 24375795 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Tgfb1 protein, rat
• Transforming Growth Factor beta1
• Hydrogen Peroxide

Topics

• Alveolar Epithelial Cells (physiology)
• Animals
• Cells, Cultured
• Epithelial-Mesenchymal Transition
• Hydrogen Peroxide (metabolism)
• Hyperoxia (metabolism, pathology)
• Male
• Myofibroblasts (metabolism)
• Phenotype
• Pulmonary Alveoli (metabolism, pathology)
• Rats
• Rats, Sprague-Dawley
• Signal Transduction
• Tissue Culture Techniques
• Transforming Growth Factor beta1 (metabolism)