Protective Effects Of The Terminalia Bellirica Tannin-induced Nrf2/HO-1 Signaling Pathway On Rats With High-altitude Pulmonary Hypertension

Objective:To investigate the protective effect of Terminalia bellirica Tannin on high altitude pulmonary hypertension（HAPH）rats and pulmonary artery endothelial cells（PAECs）in plateau and its molecular mechanism.Methods:Animal experiment:60 male SD rats were randomly divided into control group（saline solution,1m L/100g/d）,model group（saline solution,1m L/100g/d）,positive control group（sildenafil citrate tablets 30mg/kg/d）,low,medium and high dose TTR groups（TTR100 mg/kg/d,200mg/kg/d and 400mg/kg/d）.The control group was placed in the plain environment（800 meters above sea level）,and the other groups were placed in the low-pressure oxygen chamber（simulating the environment of 6000m meters above sea level）for 30 days to make models,and then intervened for 15days.（1）Measurement of pulmonary artery pressure;（2）Detection of oxidative stress related indexes in serum by ELISA;（3）The pathological changes of lung tissue was observed under microscope,and measure the wall thickness（WT）and percentage（WT%）of pulmonary arterioles to evaluate vascular remodeling;（4）Detect the expression of Nrf2/HO-1 pathway and apoptosis-related proteins in lung tissue by Western Blot.Cell experiment:PAECs was divided into control group（normal culture in complete medium）,model group（incubation with 500μmo L/m LH2O2 for 1h after 24h in complete medium）,experimental group（incubation with 500μmo L/m LH2O2 for 1 h after 24h in TTR（20,40 and80μg/m L））and blank group（only complete medium was added without inoculation）.（1）The effect of TTR on the proliferation of cells was determined by CCK-8;（2）Detect the apoptosis by Annexin V-FITC/PI method;（3）ROS levels were detected by flow cytometry;（4）The expression of Nrf2/HO-1 pathway and apoptosis-related proteins was detected by WB.Results:Animal experiment:（1）The PAP of the model group increased significantly compared with the control group.The PAP in the positive control group and TTR group was decreased.（2）The activities of GSH-Px and SOD in the model group decreased,while the content of MDA increased.TTR increased GSH-Px and SOD activities and decreased MDA content.（3）Microscopically,pathological damage was observed in the model group,while the positive control group and TTR dosage groups improved the pathological damage of lung tissue to varying degrees,and decreased the WT and WT%.（4）Compared with the control group,the expression of Bax/Bcl-2 in the model group increased,while the expression of Nrf2,HO-1decreased;TTR down-regulated Bax/Bcl-2 and up-regulated the expressions of Nrf2,HO-1in lung tissue of HAPH rats.Cell experiment:（1）TTR increased the proliferation activity of PAECs induced by H₂O₂ in vitro;（2）TTR inhibits H₂O₂-induced PAECs apoptosis;（3）TTR inhibits H₂O₂-induced ROS production in PAECs;（4）TTR down-regulated Bax/Bcl-2 in PAECs induced by H₂O₂,and up-regulated the expression levels of Nrf2,HO-1.Conclusion:TTR may reduce oxidative stress and apoptosis damage of lung tissue and pulmonary artery endothelial cells by up-regulating Nrf2/HO-1 signaling pathway,thus reducing pulmonary artery pressure and inhibiting pulmonary vascular remodeling in HAPH rats.