| Medically,plateau refers to an area that is more than 3,000 meters above sea level and produces significant biological effects on the body.The main difference between plateau and plain is that the altitude is higher.The gradual decrease in atmospheric pressure leads to the decrease in oxygen partial pressure（PO2）.Reduced PO2 is the main cause of the medical problems in plateau.Currently,it is found that chronic hypoxia in plateau can cause a series of cardiopulmonary structural and functional lesions.For example,chronic hypoxia in plateau causes hypoxic pulmonary vascular remodeling（HPVR）and hypoxic pulmonary arterial hypertension（HPAH）.Chronic hypoxia in plateau causes a significant increase in the numbers of blood red blood cell（RBC）,which can lead to high altitude polycythemia.And chronic hypoxia in plateau causes a significant increase in the right cardiac posterior load and the right cardiac hypoxic myocardial remodeling,which can lead to myocardial hypertrophy and myocardial fibrosis.In molecular biology,changes of the expression of mRNA and protein in Hyp,HIF-1 alpha,ACE,ACE2,AngⅡand ET-1 are closely related to the chronic hypoxia stimulation in plateau.Under plateau chronic hypoxia condition,abnormal changes in expression of the above molecules and pathological changes in cardiopulmonary structure and function are the basis of high altitude heart disease（HAHD）,which seriously threaten the health of the people who have migrated to plateau from plain.At present,the prevention and treatment of HAHD mainly depend on drug intervention.However,oxygen-enriched technology which is the mean of physical intervention has not been widely applied to prevent the lesions of cardiopulmonary structure and function which are caused by chronic hypoxia in plateau.Therefore,we conducted animal experiments with rats to study the preventive effects and molecular biology effects of the local oxygen-enriched environment which is constructed by the membrane oxygen machine designed independently on the lesions of cardiopulmonary structure and function caused by chronic hypoxia in plateau and we aimed to provide a new method and scientific basis for prevention research of HAHD and maintenance of the health of the people who have migrated to plateau from plain.Part 1:Effects of local oxygen-enriched environment on cardiac structure and function in rats under simulated plateau chronic hypoxia conditionObjective:To study the preventive effects and molecular biology effects of the local oxygen-enriched environment on the lesions of cardiac structure and function in rats caused by chronic hypoxia in plateau and to lay the foundation for further in-depth research and human experimental research.Methods:A small animal hypobaric chamber designed independently was used to simulate chronic hypoxia environment at altitude of 5000 meters.The portable membrane oxygen machine designed independently and the IVC cage were used to construct the local oxygen-enriched environment innovatively in the hypobaric chamber.36 male adult Sprague-Dawley（SD）rats were randomly divided into three groups:normal control group（NC group）,high altitude hypoxia group（HH group）,and high altitude oxygen-enriched group（HO group）,the number of rats in each group is 12.Rats of NC group were fed in plain（Xi’an 400m）for 30 days.Rats of HH and HO groups were fed in simulated chronic hypoxia environment at altitude of 5000 meters for 30 days,22 hours per day.At the same time,rats of HO group were exposed to the local oxygen-enriched environment for 8hours per day.The bodyweight of rats in each group were monitored weekly.After intervention,blood flux of skin,cardiac hemodynamics,blood cytology and ventricular weight index were measured.The morphological structures of myocardial tissue were observed under light microscope.The mRNA expression of Col1α1,Col3α1,HIF-1α,ACE and ACE2 in left and right ventricle were detected by RT-PCR.The protein expression of HIF-1α,ACE and ACE2 in left and right ventricle were detected by Western Blot.The content of Hyp in left and right ventricle were detected by alkaline hydrolysis.The content of AngⅡin left and right ventricle were detected by ELISA.Results:When the simulated altitude was 5000 meters,the oxygen concentration in the hypobaric chamber was 20.9%,while the oxygen concentration in the local oxygen-enriched environment was 28.2%.The bodyweight of rats in HH and HO groups were significantly lower than that in NC group（P<0.01）,and there was no significant difference between HH group and HO group（P>0.05）.The mean values of skin blood flux of rats in HH group were significantly higher than that in NC group（P<0.01）.While the mean values of skin blood flux of rats in HO group were significantly lower than that in HH group（P<0.01）,and there was no significant difference between HO group and NC group（P>0.05）.The RBC count,hematocrit（Hct）and hemoglobin（Hb）of rats in HH group were significantly higher than that in NC group（P<0.01）.While the RBC count,Hct and Hb of rats in HO group were significantly lower than that in HH group（P<0.05,P<0.01,P<0.01）,and there was no significant difference between HO group and NC group（P>0.05）.The mean right ventricular systolic pressure（mRVSP）and mean pulmonary arterial pressure（mPAP）of rats in HH group were significantly higher than that in NC group（P<0.01）.The mRVSP and mPAP of rats in HO group were significantly lower than that in HH group（P<0.05）and even though significantly higher than that in NC group（P<0.05）.There was no significant difference in left ventricular weight index of rats in different groups（P>0.05）.All heart weight index,right ventricular weight index and Hermann-Willson index of rats in HH group were significantly higher than that in NC group（P<0.01）.All heart weight index and right ventricular weight index of rats in HO group were significantly lower than that in HH group（P<0.01）,and there was no significant difference between HO group and NC group（P>0.05）.Hermann-Willson index of rats in HO group was significantly lower than that in HH group（P<0.01）,and even though significantly higher than that in NC group（P<0.05）.There was no significant difference in left ventricular myocardial fiber structure of rats in different groups.The right ventricular wall and myocardial fibers of rats in HH group were significantly thicker than that in NC group.While the degree of thickening of the right ventricular wall and myocardial fibers of rats in HO group were significantly lower than that in HH group.In molecular biology,there was no significant difference in the mRNA expression of Col1α1and Col3α1 in left ventricle of rats in different groups（P>0.05）.The mRNA expression of ACE,ACE2 and HIF-1αin left ventricle of rats in HH group were significantly higher than that in NC group（P<0.01）.The expression of ACE mRNA in the left ventricle of rats in HO group was significantly lower than that in HH group（P<0.01）,and there was no significant difference between HO group and NC group（P>0.05）.The expression of ACE2 mRNA in the left ventricle of rats in HO group was significantly higher than that in NC group and HH group（P<0.01）.The expression of HIF-1αmRNA in the left ventricle of rats in HO group was significantly lower than that in HH group（P<0.01）and even though significantly higher than that in NC group（P<0.01）.There was no significant difference in the expression of ACE2 mRNA in the right ventricle of rats in different groups（P>0.05）.The mRNA expression of ACE,Col1α1,Col3α1 and HIF-1αin the right ventricle of rats in HH group were significantly higher than that in NC group（P<0.01）.The mRNA expression of ACE,Col1α1,Col3α1,and HIF-1αin the right ventricle of rats in HO group were significantly lower than that in HH group（P<0.01）,and even though significantly higher than that in NC group（P<0.01）.The protein expression of HIF-1α,ACE and ACE2 in the left ventricle of rats in HH group were significantly higher than that in NC group（P<0.01,P<0.05,P<0.01）.The protein expression of HIF-1αand ACE in the left ventricle of rats in HO group were significantly lower than that in HH group（P<0.05）,and there was no significant difference between HO group and NC group（P>0.05）.The expression of ACE2 protein in the left ventricle of rats in HO group was significantly higher than that in NC group and HH group（P<0.01）.There was no significant difference in the expression of ACE2 protein in the right ventricle of rats in different groups（P>0.05）.The protein expression of ACE and HIF-1αin the right ventricle of rats in HH group were significantly higher than that in NC group（P<0.01）.The expression of ACE protein in the right ventricle of rats in HO group was significantly lower than that in HH group（P<0.05）,and even though significantly higher than that in NC group（P<0.05）.The expression of HIF-1αprotein in the right ventricle of rats in HO group was significantly higher than that in NC group（P<0.01）,and there was no significant difference between HO group and HH group（P>0.05）.There was no significant difference in the content of Hyp in the left ventricle of rats in different groups（P>0.05）.The content of Hyp in the right ventricle of rats in HH group was significantly higher than that in NC group（P<0.01）.The content of Hyp in the right ventricle of rats in HO group was significantly lower than that in HH group（P<0.01）,and even though significantly higher than that in NC group（P<0.05）.The content of AngⅡin the left ventricle of rats in HO group was significantly lower than that in NC group and HH group（P<0.01）,and there was no significant difference between NC group and HH group（P>0.05）.The content of AngⅡin the right ventricle of rats in HH group was significantly higher than that in NC group（P<0.01）.The content of AngⅡin the right ventricle of rats in HO group was significantly lower than that in HH group（P<0.01）,and even though significantly higher than that in NC group（P<0.01）.Conclusion:1.There was no significant increase in bodyweight of rats in HH group and HO group at the first week under simulated plateau chronic hypoxia condition.It shows that the body of rats is in a state of stress,and it is necessary to adapt to the chronic hypoxia environment gradually through the physiological compensatory adjustment,such as neurohumoral fluid,and then the bodyweight of rats show a slowly increasing trend.Local oxygen-enriched environment under simulated plateau chronic hypoxia condition do not significantly affect the digestive and metabolic activities of rats.2.Local oxygen-enriched environment under simulated plateau chronic hypoxia condition can significantly reduce the mean values of skin blood flux and the numbers of RBC to prevent the high altitude polycythemia.And it can improve the ability of rats to adapt to the more complex,harsher and higher altitude environment significantly by the functional reserve of blood system compensation.3.Local oxygen-enriched environment under simulated plateau chronic hypoxia condition can significantly reduce mPAP,mRVSP,and Hermann-Willson index of rats,and effectively prevent the excessive increase in the right cardiac posterior load and the thickness of right ventricular wall.In addition,the correlation analysis showed that there was a significant positive correlation between mPAP and Hermann-Willson index（n=18,r=0.792,P<0.01）,which further verified that right ventricular hypertrophy of rats under chronic hypoxia conditions is closely related to the significant increase of PAP.4.Local oxygen-enriched environment under simulated plateau chronic hypoxia condition can significantly reduce the expression of HIF-1αand ACE,increase the expression of ACE2,and reduce the content of AngII in the left ventricle of rats.It can effectively relieve myocardial hypoxia and improve the adaptability of the left ventricular myocardium of rats.5.Local oxygen-enriched environment under simulated plateau chronic hypoxia condition can significantly reduce the expression of ACE in the right ventricle of rats,prevent excessive increase of the content of AngⅡin the right ventricular myocardial tissue,and effectively relieve the degree of the right ventricular myocardial fibrosis.Part 2:Effects of local oxygen-enriched environment on pulmonary structure and function in rats under simulated plateau chronic hypoxia conditionObjective:To study the preventive effects and molecular biology effects of the local oxygen-enriched environment on the lesions of pulmonary structure and function in rats caused by chronic hypoxia in plateau and to lay the foundation for further in-depth research and human experimental research.Methods:A small animal hypobaric chamber designed independently was used to simulate chronic hypoxia environment at altitude of 5000 meters.The portable membrane oxygen machine designed independently and the IVC cage were used to construct the local oxygen-enriched environment innovatively in the hypobaric chamber.36 male adult Sprague-Dawley（SD）rats were randomly divided into three groups:normal control group（NC group）,high altitude hypoxia group（HH group）,and high altitude oxygen-enriched group（HO group）,the number of rats in each group is 12.Rats of NC group were fed in plain（Xi’an 400m）for 30 days.Rats of HH and HO groups were fed in simulated chronic hypoxia environment at altitude of 5000 meters for 30 days,22 hours per day.At the same time,rats of HO group were exposed to the local oxygen-enriched environment for 8hours per day.After intervention,mPAP was measured.The morphological structures of the tissue of right lung upper lobe were observed under light microscope.The mRNA expression of Col1α1,Col3α1 and ET-1 in lung tissue were detected by RT-PCR.The content of Hyp in lung tissue was detected by alkaline hydrolysis.The content of ET-1 in lung tissue was detected by ELISA.Results:When the simulated altitude was 5000 meters,the oxygen concentration in the hypobaric chamber was 20.9%,while the oxygen concentration in the local oxygen-enriched environment was 28.2%.The mPAP of rats in HH group was significantly higher than that in NC group（P<0.01）.The mPAP of rats in HO group was significantly lower than that in HH group（P<0.05）and even though significantly higher than that in NC group（P<0.05）.There was significant difference in the structures of lung tissue between HH group and NC group.The lung tissue of rats in HH group showed the typical HPVR morphological changes.At the terminal bronchiolar level and respiratory bronchiole level,the middle membrane of pulmonary arteries were significantly thickened,the smooth muscle cells of pulmonary arteries were significantly proliferated,the lumen of pulmonary arteries were narrow,and the collagen fibers of the adventitia of pulmonary arteries were significantly increased.The degree of thickening of the middle membrane of pulmonary arteries of rats in HO group,the degree of proliferation of the smooth muscle cells of pulmonary arteries of rats in HO group,the degree of narrowing of the lumen of pulmonary arteries of rats in HO group,and the degree of increase of the collagen fibers of the adventitia of pulmonary arteries of rats in HO group were significantly lower than that in HH group.The mRNA expression of Col1α1,Col3α1 and ET-1 in lung tissue of rats in HH group were significantly higher than that in NC group（P<0.01）.The mRNA expression of Col1α1,Col3α1,and ET-1 in lung tissue of rats in HO group was significantly lower than that in HH group（P<0.01）,and even though higher than that in NC group（P<0.01）.The content of Hyp in lung tissue of rats in HH group was significantly higher than that in NC group（P<0.01）.The content of Hyp in lung tissue of rats in HO group was significantly lower than that in HH group（P<0.05）,and even though significantly higher than that in NC group（P<0.01）.The content of ET-1 in lung tissue of rats in HH group was significantly higher than that in NC group（P<0.01）.The content of ET-1 in lung tissue of rats in HO group was significantly lower than that in HH group（P<0.01）,and even though significantly higher than that in NC group（P<0.01）.Conclusion:Local oxygen-enriched environment under simulated plateau chronic hypoxia condition can significantly reduce the expression of ET-1 in lung tissue of rats,significantly reduce the content of Hyp in lung tissue of rats,effectively relieve the extent of HPVR of rats,limit the excessive increase in PAP of rats,and effectively prevent the excessive increase in right cardiac posterior load of rats.It has a positive promotion and protective effect on the functional effectiveness and structural integrity of heart and lung of rats under chronic hypoxia condition.SummaryBased on the two-part experimental conclusions,we can conclude that the local oxygen-enriched environment which is constructed by the membrane oxygen machine designed independently has a preventive and protective effect on the lesions of cardiopulmonary structure and function caused by chronic hypoxia in plateau.Based on the current research results,we can further improve the application efficiency of the membrane oxygen machines in the plateau chronic hypoxia condition by optimizing experimental conditions and exploring the combination of optimal oxygen enrichment concentration and time.What’s more important is that we can lay the foundation for further in-depth research and human experimental research,and provide a new method and scientific basis for prevention research of HAHD and maintenance of the health of the people who have migrated to plateau from plain. |
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