title: Expression and significance of HIF-1α in pulmonary fibrosis induced by paraquat.
abstract: It is commonly accepted that epithelial-mesenchymal transition contributes to fibrotic remodeling, but the molecular pathways involved in paraquat (PQ)-induced epithelial-mesenchymal transition remain uncharacterized. The objective of this study was to evaluate the potential involvement of HIF-1α in TGF-β1/β-Catenin and Snail pathway after PQ poisoning. In our study, 86 Spragne-Dawley rats were randomly divided into control group and PQ group, which received intragastric infusion of 20% PQ solution 50 mg/kg. Rats in the PQ group were subsequently divided into eight subgroups (10 for each subgroup) and samples were collected at different predetermined time points (2, 6, 12, 24, 48, 72, 96 h and 7 d). Fibrosis markers, including β-catenin, snail and α-SMA, were measured by western blot. The activity of HIF-1α was determined by western blot and immunofluorescence. We found that in PQ-induced pulmonary fibrosis, the level of PaO2 was significantly reduced in the 6-h subgroup, when compared to the control group (P < 0.01). Interestingly, between 6 and 72 h, there was no significant difference in PaO2. On the other hand, the level of PaCO2 started to increase from 72-h subgroup (P < 0.01). Fibrosis markers including β-catenin, snail and α-SMA, measured by western blot, were significantly increased at 2 h, while the level of p-GSK-3β was increased at 6 h. And the level of GSK-3β showed significant reduction beginning at 24 h. The activity of HIF-1α measured by western blot assays was significantly increased starting from 2 h with sustained expression. The result of Pearson coefficient analysis showed that HIF-1α was positively correlated with Snail (r = 0.935, P < 0.01) and β-catenin (r = 0.761, P < 0.05). Meanwhile, immunofluorescent analysis of HIF-1α revealed partial staining appearing from 2 h. Our data illustrated a positive correlation between Snail, β-catenin signaling and HIF-1α, suggesting a potential synergistic role of HIF-1α in PQ-induced pulmonary fibrosis, which may be independent of GSK-3β. It might also represent a potential therapeutic window for treatment of paraquat poisoning.
authors.affiliation: Intensive Care Unit, Shanghai First People's Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 0086 201620, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Xie
authors.forename: Jiu-Ting
authors.initials: JT
authors.lastname: Tan
authors.forename: Rui-Lan
authors.initials: RL
authors.lastname: Wang
authors.forename: Xiao-Xiao
authors.initials: XX
authors.lastname: Meng
authors.forename: Xue
authors.initials: X
authors.lastname: Tang
authors.forename: Shan
authors.initials: S
authors.lastname: Gao
mesh_terms: D000199:Actins / Q000378:metabolism / Q000502:physiology; D000818:Animals; D002245:Carbon Dioxide / Q000097:blood; D058750:Epithelial-Mesenchymal Transition; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D010100:Oxygen / Q000097:blood; D010269:Paraquat; D011658:Pulmonary Fibrosis / Q000139:chemically induced / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors / Q000378:metabolism / Q000502:physiology; D053773:Transforming Growth Factor beta1 / Q000378:metabolism / Q000502:physiology; D051176:beta Catenin / Q000378:metabolism / Q000502:physiology
chemical_list: D000199:Actins; D002245:Carbon Dioxide; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D010100:Oxygen; D010269:Paraquat; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors; D053773:Transforming Growth Factor beta1; D051176:beta Catenin; C495268:Ctnnb1 protein, rat; C497444:Hif1a protein, rat; C000604450:Snai2 protein, rat; C498862:Acta2 protein, rat
keywords: Paraquat; epithelial–mesenchymal transition; hypoxia-inducible factor 1α; pulmonary fibrosis; transforming growth factor β1