ACE2基因对高血压Fractalkine/CX3CR1信号及其心肌损害的作用机制

Hypertension is the first death cause of cardiovascular diseases, which seriously endanger human life and health. It was well confirmed that the abnormalities of inflammatory chemokine Fractalkine (FKN)/CX3CR1 signaling has been implicated in hypertensive myocardial injury and was closely related to the activation of angiotensin II (Ang II). The newly-discovered angiotensin-converting enzyme 2 (ACE2) catalyzes the conversion of Ang II to Ang-(1-7). Our previous studies have shown abnormal ACE2 activity involving the occurrence of cardiovascular fibrosis and dysfunction in hypertension (Circulation, 2010; Hypertension, 2011), but its relevant mechanism is still unclear. Based on this, ACE2 gene knockout mice and their genetic normal wildtype controls are used to induce hypertensive animal models by an osmotic minipump with Ang II and by pressure overload using aortic banding operation. In addition, recombinant human ACE2 gene and recombinant FKN gene are used for in vivo & in vitro intervention experiments on the animal model and cells in order to investigate the regulatory roles and relevant mechanisms of the ACE2 in the myocardial FKN/CX3CR1 signaling, inflammation, the expression and activities of matrix metalloproteinases (MMPs) and a disintegrin and metalloprotease (ADAM) as well as myocardial injury in hypertension. Therefore, it has a prospective future and far-reaching significance on the aspects of basic study and clinical practice to establish ACE2 gene as a new target for early prevention and treatment of hypertension and to reduce the occurrence of cardiovascular events in patients with hypertension.

高血压病为心血管疾病的第一致死原因，严重危害人类健康。业已证实炎症趋化因子Fractalkine(FKN)/CX3CR1信号异常参与高血压心肌损害发病，与血管紧张素II(Ang II)作用密切相关。血管紧张素转换酶2（ACE2）可催化Ang II转化为Ang-(1-7)。前期研究我们发现ACE2活性异常涉及心血管纤维化及功能紊乱的发生(Circulation 2010; Hypertension 2011)，但其机制不明。本课题在此基础上，利用ACE2基因敲除小鼠和正常野生型小鼠经Ang II微泵与主动脉缩窄术诱导高血压动物模型，通过重组ACE2基因、重组FKN基因对高血压模型动物及细胞进行体内外干预实验，旨在探讨ACE2 对心肌FKN/CX3CR1信号、炎症、MMPs/ADAMs活性及高血压心肌损害的作用和机制，将为确立ACE2作为高血压早期防治新靶点及减少该病心血管事件发生，意义深远。

高血压和心力衰竭与全球高发病率和高死亡率密切相关。血管紧张素转换酶2(ACE2)/ Apelin与和Ang II-AT1信号为血压和心功能重要的调控因子。本项目我们评估了ACE2基因对高血压介导的心肌损伤的调控作用。研究发现，高血压小鼠和ApoEKO小鼠心肌组织中ACE2和AMPKa的水平明显下调。与正常WT对照组相比，ACE2KO小鼠和ApoE/ACE2 DKO双敲除小鼠血压和Ang II水平均增加。ACE2基因缺失导致收缩压升高、心肌AMPKa磷酸化下调，而促炎症因子表达上升，包括FKN、IL-1b、IL-6、MCP-1、TNFa等。Pyr1-apelin-13治疗可促进高血压合并动脉粥样硬化小鼠心肌ACE2表达上调，氧自由基生成降低，伴有促肥厚和促纤维化因子表达下调，包括骨桥蛋白、ANF、BNP、b-MHC、TGFb1及I型和III型胶原，最终导致高血压小鼠心肌肥厚、纤维化程度及心功能改善。另外，重组ACE2干预后可通过增加AMPKa磷酸化减轻高血压大鼠介导的心肌炎症、凋亡及超微结构损伤。在原代培养大鼠心肌成纤维细胞中，Ang II刺激减少细胞中ACE2蛋白、Akt和eNOS磷酸化水平降低，增加超氧阴离子的产生，同时可激活TGFb-CTGF-ERK1/2信号促进细胞增殖与迁移。重组ACE2干预治疗可逆转CFs细胞中Ang II介导的促氧化、促凋亡和促纤维化作用，伴有FKN、CX3CR1、MMP2、MMP9、MT1-MMP活性与表达下调。ACE2的细胞保护效应可被A779所逆转，故ACE2基因的细胞保护功效是经由Ang-(1-7)/ Mas受体信号而实现的。我们研究结果提示，ACE2通过改善FKN-CTGF-ERK, Akt-eNOS及MMPs信号减轻高血压介导心肌炎症、凋亡、纤维化及超微结构损伤，从而实现其心肌保护效应 (Circulation Journal; Hypertension 2014, 2017; J Transl Med 2015; Circulation Research 2016; Biochim Biophys Acta-Mol Bas Dis 2017)。本项目为确立ACE2和FKN作为高血压心肌重构损伤防治的新靶点提供了实验依据，具有重要的临床意义和潜在的研发价值。