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

Paraquat (PQ) poisoning-induced pulmonary fibrosis is one of the primary causes of death in patients with PQ poisoning. Hypoxia-inducible factor-1 (HIF-1) and epithelial-mesenchymal transition (EMT) are involved in the progression of pulmonary fibrosis. Snail and -catenin are two other factors involved in promoting EMT. However, the relationship among HIF-1, Snail and -catenin in PQ poisoning-induced pulmonary fibrosis is not clear. Our research aimed to determine whether the regulation of HIF-1 in EMT occurs via the Snail and -catenin pathways in PQ poisoning-induced pulmonary fibrosis. Sixty-six Sprague-Dawley rats were randomly and evenly divided into a control group and a PQ group. The PQ group was treated with an intragastric infusion of a 20% PQ solution (50 mg/kg) for 2, 6, 12, 24, 48 and 72 hrs. A549 and RLE-6TN cell lines were transfected with HIF-1 siRNA for 48 hrs before being exposed to PQ. Western blotting, real-time quantitative PCR, immunofluorescence, immunohistochemistry and other assays were used in our research. In vivo, the protein levels of HIF-1 and -SMA were increased at 2 hrs and the level of ZO-1 (Zonula Occluden-1) was reduced at 12 hrs. In vitro, the transient transfection of HIF-1 siRNA resulted in a decrease in the degree of EMT. The expression levels of Snail and -catenin were significantly reduced when HIF- was silenced. These data demonstrate that EMT may be involved in PQ poisoning-induced pulmonary fibrosis and regulated by HIF-1 via the Snail and -catenin pathways. Hypoxia-inducible factor-1 may be a therapeutic target for the treatment of PQ poisoning-induced pulmonary fibrosis.