肾素原受体在中枢通过RAS-ERK-ROS途径调控心室重构的机制研究

(Pro)rennin receptor (PRR) is the beginning factor of rennin-angiotensin-system(RAS). PRR binds prorennin/renin to activate RAS. In our past project, we found that few brain PRR over-expression mice had the sudden death due to heart failure in the hypertension model which induced by Ang II. To our surprise, brain PRR over-expressing mice were observed more seriously ventricular remodeling than control. We guess that brain PRR is important to regulate ventricular remodeling. To clarify the mechanism of brain PRR aggravated ventricular remodeling， we build the mouse heart failure(HF) model by ascending aortic constriction. Moreover, we found that PRR expression was much higher in cardio-vascular central nervous area including PVN, NTS and RVLM of HF group than control. In our neuronal cell experiment, the data implicated that ERK can induce reactive oxygen sepsis (ROS) activation. ROS activation is important to sympathetic tone. We hypothesize that brain PRR regulate the sympathetic tone and spontaneous baroreflex sensitivity to induce ventricular remodeling, through RAS-ERK-ROS signaling pathway to excite neuron of heart area such as PVN, NTS ,RVLM , and AVP releasing in brain. In this project, we will focus on the brain PRR and the downstream ERK signaling pathway ,reactive oxygen sepsis(ROS) regulate the neuronal excitation and AVP releasing .Furthermore ,we will administrate the PRR peptide PRO20 to brain(PVN, NTS, RVLM ) by mini-pump. PRO20 is a new blocker which can block the binding of PRR to (pro)rennin, inhibit the downstream of RAS-ERK-ROS pathway. Furthermore, PRR-shRNA and ERK or ROS inhibitor will be treated to silent the RNA expression of PRR in Neuro-2A cells, to explore the involvement of RAS-ERK-ROS pathway. This presence will explain the mechanism of brain PRR inducing ventricular remodeling. The blocking of PRR in cardio-vascular central nervous area might be a new strategy to resist ventricular remodeling, prevent heart failure.

交感神经兴奋性增高和水钠潴留是心室重构的主要原因。我们既往观察到中枢PRR过表达的转基因鼠在血管紧张素Ⅱ（AngⅡ）诱导高血压模型时存在着较对照组更为严重的心室重构，少量模型鼠还因心力衰竭死亡。体外细胞研究证实PRR通过肾素血管紧张素系统（RAS）激活ERK信号通路，活化活性氧（ROS），兴奋神经细胞。我们推测中枢PRR参与心室重构的调控,但机制不详。本课题拟通过构建小鼠主动脉狭窄致心衰模型，研究中枢PRR通过调节心血管中枢神经元兴奋性和精氨酸加压素（AVP）释放，从而调控外周交感神经的兴奋和水钠潴留，导致心室重构的机制。并应用PRR多肽或基因沉默技术在动物或细胞模型上，给予ERK信号通路或ROS的抑制剂后，探索PRR 通过RAS-ERK-ROS途径调控心室重构的机制。本课题将阐明中枢PRR对病理性心室重构的调控机制。并为中枢干预PRR拮抗心室重构，预防心力衰竭提供新的思路。

过去研究中意外发现中枢肾素受体（PRR）过表达的转基因鼠在制造体外AngⅡ诱导高血压模型时有发生猝死的现象，心功能衰竭是死亡的直接原因。进一步的研究发现中枢PRR过表达基因背景的高血压模型鼠有明显的心室重构，但其形成的机制不明确。本课题通过构建结扎左冠状动脉制造心衰小鼠模型，采用大脑外微泵持续给予心血管中枢包括室旁核(PVN)，孤束核(NTS)，延髓腹外侧区(RVLM）等部位PRR肽PRO20阻遏PRR与肾素原结合，抑制了其下游的肾素血管紧张素系统（RAS）。并进一步研究了中枢RAS通过调控心血管中枢神经元兴奋性和AVP释放，调节交感神经的兴奋和全身水钠平衡，最终调控心室重构。最后应用PRR-shRNA沉默技术在神经元细胞系neuro2A上继续介导其中的ERK信号通路及其下游的活性氧（ROS)的分子学机制。研究结果发现中枢PRR 与肾素原/肾素结合，裂解血管紧张素原为血管紧张素Ⅰ，血管紧张素Ⅰ在血管紧张素转化酶作用下裂解为有活性的血管紧张素Ⅱ，调控颅内心血管中枢，传递给神经，调节全身的水钠平衡，最终达到调控心室重构。而且细胞研究还进一步提示PRR结合肾素原启动RAS后通过激活ERK- ROS途径兴奋心血管中枢神经元，并刺激AVP的合成分泌。继而引起外周交感神经兴奋，水钠储留，最终导致心室重构。本课题了阐明中枢PRR对心肌病理性肥大和凋亡，心室重构、以及心力衰竭的调控机制。并为中枢给药干预RAS拮抗心室重构、预防心力衰竭提供新的思路。