补充血管紧张素(1-7)联合运动疗法对肾性高血压大鼠心脏重塑的作用与机制

Effect and mechanism of angiotensin(1-7)supplementation combined with exercise therapy on cardiac remodeling in rats with renal hypertension

背景:肾素-血管紧张素系统在高血压发生发展中起关键作用,其中血管紧张素(1-7)具有降压作用并反向调节血管紧张素Ⅱ的不良效应。运动康复疗法是防治高血压的重要非药物手段,然而血管紧张素(1-7)与运动是否具有协同效应尚未明确。目的:观察补充血管紧张素(1-7)联合运动疗法对肾性高血压大鼠心脏重塑的影响,并探讨血管紧张素(1-7)及其受体信号轴在其中的可能作用机制。方法:60只雄性SD大鼠随机选取12只作为正常血压组,其余48只利用两肾一夹法制作肾性高血压模型并随机分为高血压对照组、高血压运动组、血管紧张素(1-7)组、联合治疗组。造模成功1周后,各组分别给予不同干预(为期6周):高血压运动组在电动跑台上进行跑步训练,血管紧张素(1-7)组通过植入大鼠背部皮下的Alzet微渗透泵灌流血管紧张素(1-7),联合治疗组在跑步训练后灌流血管紧张素(1-7),正常血压组和高血压对照组在鼠笼内安静饲养。末次训练后48 h,通过无创血压仪测定尾动脉血压;超声心动图检测心脏结构与功能;取左心室心肌,利用苏木精-伊红和马松染色进行心肌组织病理学观察,通过图像分析软件获取心肌细胞横截面积和胶原容积分数分别作为心肌肥大和心肌纤维化标志物;高效液相色谱法检测心脏血管紧张素(1-7)含量;qRT-PCR检测心脏胚胎基因心钠素和β-肌球蛋白重链mRNA表达量;免疫印迹法测定心脏Mas受体、血管紧张素2型受体和内皮型一氧化氮合成酶蛋白表达量。结果与结论:①与正常血压组比较,高血压对照组血压升高(P<0.05),心功能差异无显著变化(P>0.05),心肌细胞横截面积和胶原容积分数增加(P<0.05),心钠素和β-肌球蛋白重链mRNA表达量上调,血管紧张素(1-7)含量以及Mas受体、血管紧张素2型受体和内皮型一氧化氮合成酶蛋白表达量下调(P<0.05)。②与高血压对照组比较,运动组血压下降(P<0.05),心功能提高(P<0.05),胶原容积分数下降(P<0.05),心肌细胞横截面积和血管紧张素(1-7)含量无显著变化(P>0.05),心钠素和β-肌球蛋白重链mRNA表达量下调(P<0.05),Mas受体、血管紧张素2型受体和内皮型一氧化氮合成酶蛋白表达量上调(P<0.05);血管紧张素(1-7)组除心肌血管紧张素(1-7)含量升高(P<0.05)外,其他各参数差异均无显著性意义(P>0.05)。③与运动组比较,联合治疗组血压下降(P<0.05),心肌细胞横截面积和心功能无显著变化(P>0.05),胶原容积分数下降(P<0.05),血管紧张素(1-7)含量升高(P<0.05),心钠素和β-肌球蛋白重链mRNA表达量下调(P<0.05),Mas受体、血管紧张素2型受体和内皮型一氧化氮合成酶蛋白表达量上调(P<0.05)。④提示单独补充血管紧张素(1-7)并不能改善肾性高血压大鼠心脏重塑,但却能够增强运动的疗效,其机制与血管紧张素(1-7)受体缺陷改善并恢复其信号通路功能有关。

BACKGROUND:The renin-angiotensin system plays a key role in the occurrence and development of hypertension,in which angiotensin(1-7)has antihypertensive effect and reversely regulates the adverse effects of angiotensin II.Exercise rehabilitation therapy is an important non-pharmaceutical means to prevent and treat hypertension;however,whether angiotensin(1-7)and exercise have a synergistic effect is not yet clear.OBJECTIVE:To explore the effect of angiotensin(1-7)supplementation combined with exercise therapy on cardiac remodeling in rats with renal hypertension and to investigate the possible mechanism of angiotensin(1-7)and its receptor signal axis.METHODS:Sixty male Sprague-Dawley rats were selected,of which 12 rats were randomly selected as normotensive group and the remaining 48 rats were used to make animal models of renal hypertension using two-kidney one-clip method and were then randomly divided into hypertension control group,hypertension exercise group,angiotensin(1-7)group and combined treatment group.One week after successful modeling,different interventions were given(for a period of 6 weeks)as follows:the hypertension exercise group was subjected to a running training on an electric treadmill,the angiotensin(1-7)group was perfused with angiotensin(1-7)by implanting Alzet microosmotic pump subcutaneously on the back of the rats,and the combined treatment group was perfused with angiotensin(1-7)after running training,while the normotensive group and hypertension control group were caged quietly.At 48 hours after the last training session,the tail artery blood pressure was measured with a non-invasive sphygmomanometer;the heart structure and function were detected by echocardiography;the left ventricular myocardium was taken for histopathological observation by hematoxylin-eosin and Masson staining,and the cardiomyocyte cross-sectional area and collagen volume fraction were obtained by image analysis software as markers of myocardial hypertrophy and fibrosis,respectively;the content of angiotensin(1-7)in the heart was detected by high performance liquid chromatography;the mRNA expression of cardiac embryonic genes,atrial natriuretic peptide andβ-myosin heavy chain,was detected by real-time fluorescence quantitative PCR;and the protein expression of cardiac Mas receptor,angiotensin II type 2 receptor and endothelial nitric oxide synthase was measured by western blot assay.RESULTS AND CONCLUSION:Compared with the normotensive group,blood pressure increased(P<0.05),cardiac function had no significant changes(P>0.05),cardiomyocyte cross-sectional area and collagen volume fraction increased(P<0.05),mRNA expression of atrial natriuretic peptide andβ-myosin heavy chain was upregulated(P<0.05),angiotensin(1-7)content and protein expression of Mas receptor,angiotensin II type 2 receptor and endothelial nitric oxide synthase was downregulated(P<0.05)in the hypertension control group.Compared with the hypertension control group,blood pressure decreased(P<0.05),cardiac function improved(P<0.05),collagen volume fraction decreased(P<0.05),cardiomyocyte cross-sectional area and angiotensin(1-7)content showed no significant changes(P>0.05),mRNA expression of atrial natriuretic peptide andβ-myosin heavy chain was downregulated(P<0.05),and the protein expression of Mas receptor,angiotensin II type 2 receptor and endothelial nitric oxide synthase was upregulated(P<0.05)in the hypertension exercise group;except for an increase in myocardial angiotensin(1-7)content(P<0.05),other parameters had no statistical significance(P>0.05)in the hypertension angiotensin(1-7)group.Compared with the hypertension exercise group,blood pressure decreased(P<0.05),cardiomyocyte cross-sectional area and cardiac function had no significant changes(P>0.05),collagen volume fraction decreased(P<0.05),angiotensin(1-7)content increased(P<0.05),mRNA expression of atrial natriuretic peptide andβ-myosin heavy chain was downregulated(P<0.05),and the protein expression of Mas receptor,angiotensin II type 2 receptor and endothelial nitric oxide synthase was upregulated(P<0.05)in the combined treatment group.To conclude,supplementation of angiotensin(1-7)alone cannot improve cardiac remodeling in rats with renal hypertension,but it can enhance the efficacy of exercise.The mechanism is related to the improvement of angiotensin(1-7)receptor deficiency and restoration of its signaling pathway function.