Phenylbutyric Acid Inhibits Epithelial-Mesenchymal Transition During Bleomycin-Induced Lung Fibrosis

Objective: To Investigate the Effect of PBA on BLM-induced Epithelial-Mesenchymal Transition(EMT) and Lung Fibrosis.Method: Adult male ICR mice(28-32g) were divided randomly in four groups. In BLM group, mice were intratracheally injected with a single dose of BLM(3.0mg/kg body weigh) in 50 ul phosphate buffered saline. In BLM+PBA group, mice were intratracheally injected with BLM in combination with PBA(150mg/kg i.p., daily). Lungs were collected 21 days after BLM. Lung tissues were fixed in 4% formalin and embedded in paraffin. Tissue sections were stained with hematoxylin and eosin and scored for extend of inflammation. Immunochemistry was used to estimate the expression of α-SMA and NF-κb. Sirius red staining was used to estimate extend of pulmonary fibrosis. Western blotting was used to detect the expression of ER stress-associated protein GRP78、CHOP、p-e IF2α、e IF2α、IRE1α、p-IRE1α and EMT-associated protein α-SMA. The level of TNF-α、IL-1β、IFN-γ 、TGF-β1 and Col1α1、Col1α2 in pulmonary of each group were detected using RT-PCR.Result: Pulmonary GRP78、CHOP、p-e IF2α and p-IRE1α were up-regulated in BLM-treated mice and PBA markedly inhibited BLM-induced up-regulation of GRP78、CHOP、p-e IF2α and p-IRE1α. Histological examination showed an infiltration of numerous inflammatory cells in the lung in BLM-treated mice and PBA significantly attenuated BLM-induced infiltration of inflammatory cells in the lung. Immunohistochemistry showed that the number of NF-κb positive cells was significantly elevated in the lungs of BLM-treated mice and PBA markedly inhibited BLM-induced NF-κb activation in the lungs. Result of RT-PCR showed that the level of TNF-α、IL-1β、IFN-γ and TGF-β1 were up-regulated in the lungs of BLM-treated mice. The upregulation of pulmonary TNF-α、IL-1β、IFN-γ and TGF-β1 was repressed by PBA. Immunochemistry showed that the number of α-SMA-positive cells was significantly elevated in BLM-treated mice and the number of α-SMA-positive cells was reduced in BLM +PBA-treated mice as compared with BLM-treated mice. As evidenced by western blotting, PBA markedly inhibited the upregulation of α-SMA in pulmonary of BLM-treated mice. The expression of pulmonary Col1α1 and Col1α2 were significantly upregulated in BLM-treated mice and PBA markedly attenuated BLM-induced upregulation of Col1α1 and Col1α2. Sirius red staining showed an obvious matrix protein deposition in the lungs of BLM-treated mice and PBA significantly alleviated BLM-induced matrix protein deposition in the lungs.Conclusion: PBA may alleviate ER stress-mediated EMT in the pathogenesis of BLM-induced lung fibrosis.