ACE2与TGF-β1-Smad3信号对高盐介导高血压血管纤维化的调控作用

High salt-intake causes hypertensive vascular fibrosis. Our previous studies have demonstrated that high dietary salt could lead to hypertension and the fibrosis of aorta, carotid artery and mesenteric artery in Wistar rats. Angiotensin II (Ang II) is critically involved in the pathogenesis of vascular fibrosis through influencing TGF-β1/Smad3 signaling pathway. Angiotensin converting enzyme 2 (ACE2) is a endogenous enzyme of specifically degrading AngII，but its underlying mechanisms involved in hypertensive vascular fibrosis are unclear. The recent studies have showed that activation of miRNA-21 and/or inactivation of miRNA-29b participates in myocardial fibrosis and kidney fibrosis mediated by TGF-β1-Smad3 signaling pathway. Therefore, we propose to apply normal and DOCA salt-sensitive hypertensive rats and gene overexpression or knockout technology, and deeply investigate the activation of TGF-β1/Smad3 is associated with downregulation of ACE2, and Smad3 regulates the expressions of miR-21 and(or) miR-29b to cause vascular fibrosis in vitro and in vivo. We want to clarify the mechanism of ACE2 regulating TGF-β1-Smad3 signaling and miR-21/miR-29b in hypertensive vascular fibrosis caused by high salt. The study will provide theoretical basis and new targets for the prevention and treatment of hypertensive vascular fibrosis induced by high-salt diet.

高盐饮食诱导高血压血管纤维化。我们前期研究表明，长期高盐饮食介导Wistar 大鼠血压升高、主动脉和颈动脉及肠系膜动脉纤维化，血管紧张素II（Ang II）可通过影响TGF-β1-Smad3信号在高盐致高血压血管纤维化中起关键作用。血管紧张素转化酶2（ACE2）是内源性降解Ang II的特异性催化酶，但它对高血压血管纤维化作用及机制不清楚。新近发现，miRNA-21激活和/或miRNA-29b失活参与TGF-β1-Smad3通路介导的心肾纤维化。本项目拟采用正常和DOCA盐敏感型高血压大鼠模型及基因敲除或过表达技术，从整体和细胞水平进行研究，证实高盐通过下调ACE2基因使TGF-β1-Smad3激活、Smad3信号调控miRNA-21和/或miRNA-29b介导高血压血管纤维化。为确立ACE2及miRNA-21/miRNA-29b作为高盐诱导高血压血管纤维化防治的新靶点提供科学依据。

高盐饮食诱导高血压心血管和肾脏纤维化，但其机制和干预靶点未完全阐明。AngII可通过影响TGF-β1-Smad3通路在高盐致高血压血管纤维化中起关键作用。血管紧张素转化酶2（ACE2）是内源性降解AngII的特异性催化酶，主要降解 Ang II 生成 Ang1-7。miRNA-21、miRNA-29b作为新型的基因表达调节剂影响肾脏、心脏和肺脏纤维化的发生发展。本项目采用正常大鼠、盐敏感高血压大鼠和ACE2基因敲出小鼠、ACE2和Smad3基因敲出细胞株、ACE2激动剂、TGF-β1和Smad3特异性阻断剂、RAS阻断剂及TRPV1激动剂、钠氢交换体抑制剂等，从整体和细胞水平进行研究，观察长期高盐饮食对3种鼠模型血压、心血管和肾脏纤维化的影响、高盐培养对大鼠动脉平滑肌细胞（VSMCs）、心脏成纤维细胞（CFs）及人肾小管上皮细胞（HK-2）增殖和胶原产生的影响，探讨高盐是否通过下调ACE2基因使TGF-β1-Smad3激活、Smad3信号调控miRNA-21和/或miRNA-29b等介导高血压靶器官纤维化。结果表明，(1)高盐饮食导致正常大鼠、盐敏感高血压大鼠和ACE2基因敲出小鼠血管、心脏和肾脏纤维化；(2)ACE2激动剂（DIZE）使盐敏感高血压大鼠血压降低，主动脉、肠系膜动脉、心脏和肾脏纤维化改善；(3)体外高盐培养能直接导致大鼠VSMCs、CFs、HK-2细胞的胶原合成及分泌增加；(4)整体和细胞模型检测显示，ACE2-Ang-(1-7)-Mas轴下调、ACE-AngII- AT1R 轴上调、TGF-β1/Smad3通路蛋白表达增高、miRNA-21/29b失常及细胞表型转化等；(5)ACE2基因敲除加重、而ACE2激动剂减弱纤维化并改变TGF-β1/Smad3通路蛋白表达、miRNA-21/29b；(6)Smad3基因敲除减弱VSMCs胶原生成并改变TGF-β1/Smad3通路和miRNA-21/29b；(7)细胞钙、氢离子浓度改变及其相关分子调控失常参与心血管纤维化。提示高盐饮食时心血管和肾脏局部ACE2 基因下调，TGF-β1激活并通过下游Smad3信号调控miR-21和/或miR-29b，介导细胞表型转化，促进细胞增殖、胶原合成，导致心血管和肾脏纤维化。为高盐导致高血压器官纤维化的防治提供理论基础和研发靶点，具有潜在临床应用价值。