ACE2/Apelin信号对高血压血管外膜炎症、氧化应激及重构的调控作用与机制

Hypertension is the first death cause of cardiovascular diseases with high morbidity and mortality in China, resulting in severe cardiovascular complications and increased risk for heart failure, myocardial infarction and stroke. The rapid increase in hypertension is a major public health problem in our country which requires new prevention and treatment tools. It was well confirmed that the pathological basis of hypertension is vascular remodeling, in which adventitial inflammation and oxidative stress play critical roles and the abnormalities of the renin-angiotensin system (RAS) and Apelin signaling are closely related to its pathogenesis. Activation of the RAS and the subsequent generation of angiotensin II (Ang II) contribute to the development of hypertension and its vascular complications. Recently, a new member of the RAS, angiotensin converting enzyme 2 (ACE2) has been identified as a specific Ang II-degrading enzyme leading to the formation of Ang-(1-7), which functions as a cardioprotective peptide with vasodilator, anti-inflammatory, anti-oxidative and anti-fibrotic actions. Our previous study demonstrated that the ACE2/Apelin overexpression contributes to the improvement of inflammation and vascular function (Hypertension 2011; Cardiovas Res 2007) and attenuation of cardiovascular fibrosis (Circulation, 2010), but the mechanism underlying is still unknown. In this project, we hypothesize that ACE2 is a negative regulator of vascular adventitial inflammation, oxidative stress and remodeling in hypertension. Based on this, the ACE2 or Apelin gene knockout mice, spontaneous hypertensive rats and their normal WKY control rats are used to induce hypertensive animal models by pressure overload using aortic banding operation or by an osmotic minipump with Ang II, respectively. In addition, recombinant human ACE2 gene and Apelin-13 are used for in vivo & in vitro intervention experiments on the animal model and vascular adventitial fibroblasts in order to investigate the regulatory roles and relevant mechanisms of the ACE2 and Apelin on vascular adventitial inflammation, oxidative stress and target signaling (PI3K-Akt-ERK, AMPK-mTOR). Therefore, it has a prospective future and far-reaching significance on the aspects of basic study and clinical practice to reduce the occurrence of cardiovascular events in patients with hypertension and to provide a scientific basis of the establishing ACE2/Apelin as new targets for the early prevention of the vascular remodeling and damage in order to make a new breakthrough in the prevention and treatment of hypertension.

高血压是我国重大的公共卫生问题，其病理学基础为血管重构。外膜炎症与氧化应激参与血管重构的发生，与血管紧张素II（Ang II）和Apelin信号异常密切相关。血管紧张素转换酶2（ACE2）为Ang II特异性催化酶。前期研究中我们证实ACE2/Apelin有助于炎症与血管功能改善（Hypertension 2011; Cardiovasc Res 2007）及心血管纤维化的减轻（Circulation, 2010），但其机制不明。在此基础上，利用基因敲除模型及经主动脉弓缩窄术与Ang II微泵诱导高血压血管损伤模型大鼠，通过重组ACE2、Apelin进行体内外干预实验，旨在探讨ACE2/Apelin对血管外膜炎症、氧化应激及靶信号（PI3K-Akt-ERK、AMPK-mTOR）的影响，为确立ACE2/Apelin作为血管重构与损伤早期防治新靶点提供科学依据，以期在高血压防治上取得新的突破。

血管重构是高血压病靶器官损害的主要病理学基础，与血管紧张素转换酶2(ACE2)/Apelin活性异常密切相关。本项目旨在探讨ACE2/Apelin对高血压血管炎症、氧化应激、纤维化及重构的调控作用。与WT对照组相比，Ang II诱导的高血压小鼠收缩压水平升高，血管组织中ACE2、Apelin水平下调，促炎症因子FKN、TNF-a、IL-1b、IL-6及氧自由基生成增加，导致血管结构损伤。重组ACE2(rACE2)干预后可显著减轻Ang II诱导的高血压小鼠以及自发性高血压大鼠的血压、血管炎症、氧化应激及重构。ACE2基因缺失进一步促使Ang II介导的高血压小鼠（ACE2KO+Ang II）血压水平增加，主动脉氧自由基生成及凋亡增加，血管中膜和外膜肥厚重构及结构损伤加重，伴有MMP2、MMP9及活化型Caspase-3和Caspase-8水平升高。与Sham假手术组相比，主动脉弓缩窄术（TAC）致超压力负荷诱导的高血压大鼠血压水平出现增加、主动脉血管组织Apelin、APJ水平下调，而I型和III型胶原、TGFb1、CTGF、NFAT5、Akt、mTOR及ERK1/2磷酸化增加，导致血管外膜纤维化和重构明显增加，上述可被Apelin-13和AT1受体阻断剂干预后所逆转。各组大鼠之间血管组织ANF和Mas受体水平无明显差异。在原代培养的大鼠血管外膜成纤维细胞中，Ang II (100 nmol•L−1)刺激后细胞迁移程度和氧自由基明显增加，细胞TGFb1、CTGF、NFAT5、Akt、mTOR及ERK1/2磷酸化增加，上述Ang II的作用可被Apelin-13(100 ng•mL−1)、rhACE2 (1 mg•mL−1)或Irbesartan (10 μmol•L−1)所阻断。我们的研究提示ACE2/Apelin可通过改善血管Caspase、TGFb-CTGF及MMP信号，促使高血压血管炎症、氧化应激、外膜纤维化及结构损伤得到改善(Hypertension 2014; J Transl Med 2015; Circulation Research 2016; Peptides 2016; Biochim Biophys Acta 2016)。本项目为确立ACE2/Apelin作为高血压血管重构损伤防治的新靶点提供了实验依据，具有潜在的研发价值和重要的临床意义。