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.

HIF‐1α regulates EMT via the Snail and β‐catenin pathways in paraquat poisoning‐induced early pulmonary fibrosis

“…Transforming growth factor-b1 is a classical EMT-promoting cytokine, and many studies have shown the relationship between HIF-1a and TGF-b1 in the process of EMT [13,35,36]. We also found that TGF-b1 has a positive correlation with HIF-1a as well as Snail and b-catenin in PQ poisoning-induced pulmonary fibrosis, the latter of which are the two other EMT-promoting cytokines in addition to TGF-b1 [26]. To further investigate the interaction among HIF-1a, Snail and b-catenin, we measured the expression changes of Snail and b-catenin by Western blotting after silencing HIF-1a expression in vitro.…”

“…The regulation of HIF-1a in EMT is partly modulated by Snail and b-catenin in cancer [24,25]. In our previous research, we found a positive correlation among HIF-1a, Snail and b-catenin after PQ poisoning [26]. However, the relationship among HIF-1a, Snail and b-catenin has not been extensively researched in pulmonary fibrosis.…”

Paraquat poisoning induced pulmonary epithelial mesenchymal transition through Notch1 pathway

“…It is reported that PQ induces EMT during pulmonary fibrosis in vitro and in vivo 13, 28 . In our study, we also observed EMT-like phenotypic changes in A549 cells.…”

Hypoxia-inducible factor-1alpha in hepatic fibrosis: A promising therapeutic target

“…It seems that HIF-1a and epigenetics likely to form a network signaling pathway. addition, Xie et al suggested that HIF-1a may cooperate with TGFb1/b-Catenin signaling pathway and play a role as cross linking agency in pulmonary fibrosis [76]. Furthermore, it has been well demonstrated that NF-kB signaling pathway plays an important role in the regulation of HIF-1a [77].…”