金属蛋白酶ADAMTS7在高血压肾损害中的作用及其机制

Hypertension is a major cause of chronic kidney disease, leading to chronic renal failure. The current therapeutic options in the clinical setting for hypertensive kidney disease are limited. Therefore, a better understanding of the cellular and molecular mechanisms underlying the initiation and progression of hypertensive renal damage is essential for developing effective strategies to treat this devastating disorder and prevent its progression. A growing body of evidence indicates that inflammation plays a critical role in the pathogenesis of hypertensive nephropathy. The recently described metalloprotease ADAMTS7 is an inflammatory mediator. Accumulating studies showed that ADAMTS7 played an important role in cardiovascular disease, including neointimal formation, vascular calcification and atherosclerosis. However, the role of ADAMTS7 in hypertensive renal damage is poorly understood. Our recent studies showed that a mouse model of angiotensin II-dependent hypertension had evidence of albuminuria, inflammatory cell infiltration and increased ADAMTS7 expression in kidney. Therefore, we hypothesized that ADAMTS7 promoted the development of hypertensive renal damage by mediating inflammation. To investigate the effects of ADAMTS7 in hypertensive kidney injury, firstly we will screen the circulating levels of ADAMTS7 in blood samples from healthy control volunteers and patients with hypertension or hypertensive kidney disease. Furthermore, we will identify the features of ADAMTS7 expression and inflammation levels in kidney of the angiotensin II-dependent hypertensive mice. Thirdly, we will detect the impacts of ADAMTS7 on the pathogenesis of hypertensive renal damage by using ADAMTS7-knockout animals. Finally, we will elucidate the mechanism of ADAMTS7 on hypertensive renal damage at the cellular level. In detail, we will observe the features of ADAMTS7 expression after stimulation of proinflammatory cytokines, the changes of angiotensin II-induced inflammatory cytokines expression levels after overexpression or knockdown ADAMTS7 by using ADAMTS7 expression plasmid or ADAMTS7 siRNA, and the activation of signal transduction pathways. These studies would clarify the role of ADAMTS7 in hypertensive renal damage and provide a new target for preventing from hypertensive kidney disease.

高血压肾损害是指原发性高血压导致的肾小动脉和肾实质损害，炎症在其发生发展过程中发挥了重要作用。ADAMTS7是一种新型金属蛋白酶，亦是一种炎症介质，它促进血管新生内膜形成、血管钙化和动脉粥样硬化发展。前期工作发现：在AngII依赖的高血压小鼠模型中，尿白蛋白、肾脏炎症细胞浸润和ADAMTS7表达增加。据此我们提出假说：ADAMTS7通过介导炎症反应促进高血压肾损害的进程。本项目拟临床观察高血压肾损害与血浆ADAMTS7水平的相关性；利用小鼠模型研究高血压肾损害中肾脏炎症水平和ADAMTS7表达规律；利用ADAMTS7敲除动物明确ADAMTS7在高血压肾损害中的作用；用炎症因子刺激细胞观察ADAMTS7表达变化，敲低或过表达ADAMTS7观察AngII刺激细胞表达炎症因子的变化，并探讨其信号转导机制。从多个层面阐明ADAMTS7在高血压肾损害中的作用和机制，为高血压肾损害的防治提供新的靶点。

高血压肾损害是指原发性高血压导致的肾脏结构和功能的改变，主要表现为肾小动脉和肾实质的损害，如不积极干预，最终可导致慢性肾衰竭。目前认为，血流动力学改变、肾素-血管紧张素系统（RAS）激活、交感神经系统活性升高和遗传等因素影响高血压肾损害的发生发展。临床研究显示，使用ACEI 或ARB类药物对缓解高血压肾损害有一定作用，但部分患者因RAS系统的反馈调节机制或不能耐受其咳嗽和血管性水肿等副作用，不能获得充分治疗。高血压肾损害的确切机制尚未明确，揭示高血压肾损害的机制并尽早干预对改善高血压患者的预后和生存质量有重要意义。我们使用大鼠两肾一夹（2K1C）术后饲养10周或给与大鼠一氧化氮合酶抑制剂L-NAME灌胃8周建立了两种高血压肾损害动物模型，发现模型大鼠血压升高、尿白蛋白增加。HE、Masson和PAS染色结果发现2K1C大鼠模型未夹闭肾脏出现小动脉壁增厚、间质纤维化和肾小球硬化等病理变化，ELISA结果示模型大鼠外周血血管紧张素II和MCP1水平升高、ADAMTS7水平无明显变化，免疫组化、Western blot和PCR结果显示2K1C大鼠非夹闭肾脏ACE/ACE2和AT1R/AT2R表达比升高、ADAMTS7表达无明显变化。黄酮类化合物柚皮素灌胃能明显抑制该模型大鼠肾损害的发生，同时翻转肾脏升高表达的ACE/ACE2和AT1R/AT2R比，提示柚皮素可能通过调节RAS系统抑制高血压肾损害的发生。同时，我们还观察到柚皮素可以抑制L-NAME诱导的高血压大鼠心肌肥大，抑制心肌组织ACE表达，提示柚皮素可能通过调控ACE的表达抑制高血压心肌重塑。综上，本项目研究结果揭示柚皮素可以调控RAS系统的表达、减轻高血压肾脏和心脏损害，为高血压靶器官损伤的防治提供了新的策略。