Hexarelin对缺血再灌注心肌的保护作用及机制研究

发布时间：2019-06-01 21:29

【摘要】：心肌缺血再灌注损伤是指缺血心肌组织在供血供氧恢复后心肌损伤反而加重的现象,主要表现为:1)氧化应激损伤;2)钙超载;3)炎症反应加重;4)心肌细胞凋亡;5)血管内皮功能障碍;6)无复流现象;7)心电活动不稳定等。Hexarelin是一种合成的生长激素释放肽,在心肌细胞缺血再灌注、心肌梗死、心肌纤维化和动脉粥样硬化等实验研究中被证实具有明确的心脏保护作用。Hexarelin的心血管效应是通过结合生长激素促分泌素受体1a(growth hormone secretagogue receptor 1a,GHSR 1a)及心脏特异性CD36受体实现的。目前hexarelin对动物在体的心肌缺血再灌注损伤的影响尚不十分明确,并且其作用机制也未阐明。本论文的研究目的是:1)通过建立大鼠心肌缺血再灌注模型,研究hexarelin对缺血再灌注心肌的保护作用;2)研究hexarelin对心肌缺血再灌注损伤的影响与IL-1信号通路之间的联系;3)明确hexarelin对IL-1信号通路的影响是否与心脏特异性GHSR 1a受体激活有关。我们选用6周龄雄性SD大鼠,通过结扎冠状动脉左前降支造成心肌缺血,30分钟后解除结扎形成再灌注,以此建立大鼠心肌缺血再灌注模型。建模后根据实验分组分别给予hexarelin、ghrelin或生理盐水共7天,然后通过超声心动图检查评估心脏收缩功能,丙二醛(malondialdehyde,MDA)检测评估氧化应激损伤,组织切片分析评估存活心肌数量,以此综合评价hexarelin对心肌缺血再灌注损伤的影响,并与ghrelin作对比。接着我们通过免疫组化染色、RT-PCR和Western blot检测各实验组大鼠心肌组织中IL-1信号通路的表达变化,以评估hexarelin对缺血再灌注心肌组织IL-1信号通路的影响;并进一步利用GHSR 1a受体拮抗剂阻断GHSR 1a受体的激活后,通过Western blot观察对IL-1信号通路的影响,以探索心脏特异性GHSR 1a受体在此过程中的作用。我们的研究发现,hexarelin能够改善心肌缺血再灌注损伤后心脏收缩功能障碍,降低氧自由基的生成并增加存活心肌数量,并且其作用优于同剂量的ghrelin,尤其是在抑制氧自由基产生和改善射血分数方面。我们同时发现,hexarelin能引起缺血再灌注心肌组织中IL-1信号通路的表达变化,并且hexarelin对IL-1信号通路的影响能被GHSR 1a受体拮抗剂部分中和。基于上述实验结果,我们得出以下结论:1)hexarelin能够有效改善心肌缺血再灌注损伤,表现为抑制氧自由基的产生、增加存活心肌数量以及改善心脏收缩功能;2)hexarelin对缺血再灌注心肌的保护作用是通过抑制IL-1信号通路的激活来实现的;3)hexarelin对IL-1信号通路的影响是hexarelin激活心脏特异性GHSR1a受体的结果。本论文阐述了 hexarelin对缺血再灌注心肌的保护作用并对其作用机制进行了初步探讨,这为心肌缺血再灌注损伤的治疗提供了新的方向和思路。
[Abstract]:Myocardial ischemia-reperfusion injury refers to the aggravation of myocardial injury after the recovery of blood supply and oxygen supply in ischemic myocardial tissue, which is mainly manifested as follows: 1) oxidative stress injury, 2) calcium overload, 3) aggravation of inflammatory reaction, 4) apoptosis of cardiomyocytes, 2) calcium overload, 3) aggravation of inflammatory reaction, 4) apoptosis of cardiomyocytes, and 4) apoptosis of cardiomyocytes. 5) Vascular endothelial dysfunction, 6) no reflow, 6) no reflow. Hexarelin is a synthetic growth hormone releasing peptide, which is involved in myocardial ischemia-reperfusion and myocardial infarction. Experimental studies such as myocardial fibrosis and atherosclerosis have been confirmed to have definite cardioprotective effects. Hexarelin has cardiovascular effects by binding to growth hormone secretin receptor 1a (growth hormone secretagogue receptor 1a. GHSR 1a) and cardiac specific CD36 receptor. At present, the effect of hexarelin on myocardial ischemia-reperfusion injury in vivo is not very clear, and its mechanism has not been clarified. The purpose of this study was as follows: 1) to study the protective effect of hexarelin on ischemia-reperfusion myocardium by establishing a rat model of myocardial ischemia-reperfusion, 2) to study the relationship between the effect of hexarelin on myocardial ischemia-reperfusion injury and IL-1 signaling pathway. 3) to determine whether the effect of hexarelin on IL-1 signaling pathway is related to the activation of cardiac specific GHSR 1a receptor. We selected 6-week-old male SD rats to establish myocardial ischemia-reperfusion model by ligating the left anterior descending branch of coronary artery to induce myocardial ischemia and reperfusion. After modeling, hexarelin,ghrelin or saline were given to each group for 7 days, then cardiac systolic function was evaluated by echocardiography, and oxidative stress injury was evaluated by malondialdehyde (malondialdehyde,MDA). The number of viable myocardium was evaluated by tissue section analysis, and the effect of hexarelin on myocardial ischemia-reperfusion injury was evaluated and compared with that of ghrelin. Then we detected the expression of IL-1 signaling pathway in myocardial tissue of rats in each experimental group by RT-PCR and Western blot, in order to evaluate the effect of hexarelin on IL-1 signaling pathway in ischemia-reperfusion myocardium. Furthermore, the activation of GHSR 1a receptor was blocked by GHSR 1a receptor antagonist, and the effect of IL-1 signaling pathway was observed by Western blot in order to explore the role of cardiac specific GHSR 1a receptor in this process. Our study found that hexarelin can improve cardiac systolic dysfunction, reduce the production of oxygen free radicals and increase the number of viable myocardium after myocardial ischemia-reperfusion injury, and its effect is better than that of ghrelin, at the same dose. Especially in inhibiting the production of oxygen free radicals and improving ejection fraction. At the same time, we found that hexarelin could induce the expression of IL-1 signaling pathway in ischemia-reperfusion myocardium, and the effect of hexarelin on IL-1 signaling pathway could be partially neutralized by GHSR 1a receptor antagonist. Based on the above experimental results, we draw the following conclusions: 1) hexarelin can effectively improve myocardial ischemia-reperfusion injury, such as inhibiting the production of oxygen free radicals, increasing the number of viable myocardium and improving cardiac contractile function; 2) the protective effect of hexarelin on ischemia-reperfusion myocardium is realized by inhibiting the activation of IL-1 signaling pathway, and 3) the effect of hexarelin on IL-1 signaling pathway is the result of hexarelin activating cardiac specific GHSR1a receptor. In this paper, the protective effect of hexarelin on ischemia-reperfusion myocardium and its mechanism were discussed, which provided a new direction and train of thought for the treatment of myocardial ischemia-reperfusion injury.
【学位授予单位】：山东大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：R54

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