The Protective Effect Of Rhodiola On High-altitude Environment-induced Pulmonary Hypertension In Rats--Pathomorphology Research

Objective:To observe the pathomorphology changes of pulmonary arterioles in rats of high-altitude environment-induced pulmonary hypertension (HAEPH), to detect the expression of ET-1, VEGF and TGF-β1 in the wall of pulmonary arterioles, the purpose of this study is to clarify the possible mechanism of HAEPH and investigate the protective effect of rhodiola on HAEPH.Methods:Male wistar rats were randomly divided into three groups:control group, hypoxia group and rhodiola group. Each group included 32 rats. The rats in control group were kept in Chengdu(500 meters above sea level), while those in hypoxia group and rhodiola group were kept in Lhasa(3700 meters above sea level). The rats in rhodiola group were treated intragastrically with 10ml/kg rhodiola every day, while those in control group and hypoxia group were treated with the same volume normal saline. The experimental parameters of 8 rats in each group were detected at day 10, 20,30 and 40. The main procedures were as following:(1)Mean pulmonary arterial pressure (mPAP) was measured with floating right heart catheter. (2)Right ventricle (RV), left ventricle (LV) and septum (S) were obtained to calculate right ventricular hypertrophy index [RV/(LV+S)] in order to reflect the degree of right ventricular hypertrophy.(3)Observed the morphological changes of pulmonary arterioles under light microscopy, and the ratio of wall thickness of pulmonary arterioles to blood vessel diameter (WT%) was obtained and calculated by using image analysis software.(4)Observed the ultrastructure of pulmonary arteries under transmission electron microscope.(5)Detected the expression of ET-1,VEGF, TGF-β1 in the wall of pulmonary arterioles with horseradish peroxidase (HRP)-immunohistochemical method, and test the OD value by image analysis software.Results:1.mPAP in hypoxia group were higher than those in control group at all checkpoints respectively (P<0.05,respectively). There was no significant difference in mPAP between rhodiola group and hypoxia group (P>0.05) at lOd. mPAP in rhodiola group were lower than those in hypoxia group at 20d,30d and 40d(P<0.05, respectively).2.RV/(LV+S) in hypoxia group were higher than those in control group at all checkpoints respectively (P<0.05, respectively). There was no significant difference in RV/(LV+S) between rhodiola group and hypoxia group (P>0.05) at 10d. RV/(LV+S) in rhodiola group were lower than those in hypoxia group at 20d,30d and 40d(P<0.05, respectively).3.WT% in hypoxia group were higher than those in control group at all checkpoints respectively (P<0.05, respectively). There was no significant difference in WT% between rhodiola group and hypoxia group (P>0.05) at lOd. WT% in rhodiola group were lower than those in hypoxia group at 20d,30d and 40d(P<0.05, respectively).4.Ultrastructrural observation:The structure of pulmonary arterioles was normal and regular in control group. However, in hypoxia group, the internal elastic laminar was irregular; the proliferation of medial smooth muscle cells of arteries was shown; the muscularized arteries were observed;The collagenous fibril increased. The proliferation degree of smooth muscle cells and endothelial cells decreased in rhodiola group.5.(1)The expressions levels of ET-1 in hypoxia group were higher than those in control group at all checkpoints respectively (P<0.05, respectively). There was no significant difference in the expression of ET-1 between rhodiola group and hypoxia group (P> 0.05) at 10d. The expression levels of ET-1 in rhodiola group were lower than those in hypoxia group at 20d,30d and 40d(P<0.05, respectively).(2)The expression levels of VEGF in hypoxia group were higher than those in control group at all checkpoints respectively (P< 0.05, respectively). There was no significant difference in the expression of VEGF between rhodiola group and hypoxia group (P> 0.05) at 10d, the expression levels of VEGF in rhodiola group were lower than those in hypoxia group at 20d,30d and 40d(P< 0.05, respectively).(3) The expression levels of TGF-β1 in hypoxia group were higher than those in control group at all checkpoints respectively (P<0.05, respectively). There was no significant difference in the expression of TGF-β1 between rhodiola group and hypoxia group (P> 0.05) at 10d, the expression levels of TGF-β1 in rhodiola group were lower than those in hypoxia group at 20d,30d, and 40d(P< 0.05, respectively).Conclusions:1.It is the pathological basis of HAEPH that hypobaric hypoxia heightens mPAP and increases thickening of the pulmonary artery in rats.2. Hypobaric hypoxia increases the expression of ET-1,VEGF and TGF-β1 in the wall of pulmonary arterioles, which results in the hypoxic vasoconstriction and remodeling of pulmonary vessels.3. Rhodiola reduces the mPAP, (RV/(LV+S) in the HAEPH in rats and reverses the remodeling of pulmonary vessels, which proves that rhodiola has a protective effect on HAEPH.4. Rhodiola is capable of protection for HAEPH.It may be one of the possible mechanism to suppress the expression of ET-1,VEGF and TGF-β1 in the wall of pulmonary arterioles.