SAHA Regulates HDAC2/ER Stress To Alleviate Bleomycin-induced Pulmonary Fibrosis In Mice

Objective: To investigate the role of histone deacetylases(HDACs)and endoplasmic reticulum(ER)stress in idiopathic pulmonary fibrosis(IPF)in C57BL/6 mice.Methods: The mice were divided into the following six groups(n = 8 each): normal saline(NS);suberoylanilide hydroxamic acid(SAHA);bleomycin(BLM,2 mg/kg);BLM + SAHA(20 mg/kg for 14 days);BLM + SAHA(20 mg/kg for 28 days);and BLM + SAHA(40 mg/kg for 28 days)groups.Chest CT scan,Hematoxylin-Eosin and Masson staining of lung tissue sections,real-time quantitative reverse transcription PCR,and western blotting were performed to quantitatively measure HDAC,ER stress,and pulmonary fibrosis markers.Results: 1.Bleomycin successfully constructed mice pulmonary fibrosis: Compared with NS group,after bleomycin treatment of mice,chest CT scan showed that the density of lung tissue was significantly increased,and the gross morphology showed that the volume of lung tissue was reduced,the elasticity was poor,see the gray-white scar-like change,HE staining showed that the alveolar structure was obviously damaged,the alveolar space was thickened and filled with fibrous tissue,and Masson staining showed diffuse blue collagen fiber deposition in the alveolar septum and interstitial lung.2.Bleomycin-induced HDAC activation and ER Stress in mice: Compared with NS group,the expression of GRP78 and CHOP m RNA and protein in lung tissue of BLM group was significantly increased,and the expression of HDAC2 protein was also significantly increased.3.SAHA alleviates bleomycin-induced pulmonary fibrosis in mice: treatment of bleomycin-treated mice with different doses(20 mg/kg,14d;20mg/kg,28d;40mg/kg,28d)of SAHA,compared with the BLM group,chest CT scan showed a decrease in lung tissue density,gross morphology observation showed an increase in lung tissue volume,and gray-white scar-like changes were alleviated;HE staining showed alveolar structure destruction,alveolar septal thickening and fibrous tissue Filling was alleviated;Masson staining showed a decrease in blue collagen fibers in the alveolar septum and interstitial lung distribution.4.SAHA regulates HDAC2/ER Stress to attenuate pulmonary fibrosis in mice: Treatment with bleomycin-treated mice with different doses of SAHA found that SAHA treatment down-regulated bleomycin-induced elevation of HDAC2.SAHA treatment also down-regulated bleomycin-induced elevation of GRP78,CHOP m RNA and protein.5.SAHA downregulates the expression of pulmonary fibrosis-related markers: bleomycin-treated mice were treated with different doses of SAHA,and it was found that SAHA downregulated bleomycin-induced elevation in Collagen I,Fn1 m RNA,and in TGF-β1,Collagen I,α-SMA protein.Conclusion: SAHA can alleviate bleomycin-induced pulmonary fibrosis in mice,and its possible mechanism is that SAHA inhibits the HDAC2/ER Stress pathway.