Orexin-A通过下丘脑室旁核内OX1R/MAPK/PICs通路调节盐敏感大鼠交感神经活动的机制研究

Salt-sensitive hypertension (SSH) and associated complications are serious threat to human health. The enhanced sympathetic nerve activity is implicated to be closely related to the SSH, and currently this is a hot research topic. It has been reported that the paraventricular nucleus of hypothalamus (PVN) and the orexin type 1 receptor (OX1R) played an important role in the regulation of sympathetic nerve activity and blood pressure. Our preliminary results suggest that high-salt diet significantly up-regulated the expression of OX1R in the paraventricular nucleus of salt-sensitive rats, but the underlying mechanism is unclear. The latest studies suggest that activation of OX1R regulates central nervous system through MAPK signal pathway, and the activation of MAPK pathway is implicated in promoting the expression of intracellular proinflammatory cytokines (PICs). Therefore, we hypothesize that high-salt diet can activate the OX1R/MAPK/PICs pathway in the paraventricular nucleus, enhance the sympathetic nerve activity, and further induce the development of SSH. In this study, we will construct a recombinant adeno-associated virus containing OX1R or OX1R-shRNA to increase or decrease the expression of OX1R in vivo and in vitro, and investigate the effects of OX1R upregulation and downregulation on the sympathetic nerve activity, blood pressure, and the changes of related gene and protein expression in Dahl salt-sensitive rats. The purpose of the study is to explore the underlying new mechanism involved in the enhanced sympathetic nerve activity and elevated blood pressure induced by OX1R activation. This study will provide a novel strategy for clinical prevention and treatment of SSH in the paraventricular nucleus.

盐敏感性高血压(SSH)及其引发的并发症严重危害人类健康。研究提示交感神经活动增强与SSH发病密切相关，亦是目前的研究热点。下丘脑室旁核和食欲素1型受体(OX1R)在交感神经活动及血压的调控中起重要作用。申请者前期研究显示，高盐饮食可显著上调盐敏感大鼠室旁核内OX1R表达，而其作用及机制尚不清楚。最新研究显示，OX1R激活可通过MAPK通路参与中枢神经系统调控，MAPK通路激活可促进胞内促炎细胞因子(PICs)表达。由此推测：高盐饮食可激活室旁核内OX1R/MAPK/PICs通路，增强交感神经活动，继而诱发SSH发生。本项目拟构建含OX1R和OX1R-shRNA重组腺相关病毒，采用体内外实验系统研究上调/下调室旁核内OX1R表达，观察对盐敏感大鼠交感神经活动和血压影响，以及相关基因和蛋白的表达变化。旨在深入探讨OX1R激活诱发交感神经活动增强及血压升高的新机制，为SSH临床防治提供新策略。

高血压及其引发的并发症严重危害人类健康，预防和治疗高血压是生物医学的重要任务。交感神经系统激活与高血压的发生发展密切相关，当前通过交感神经切除、射频消融和药物阻滞等方法降低血压已应用临床，但疗效欠佳，有关高血压交感神经兴奋机制是国内外众多学者的研究热点。脑内促食欲素系统不仅参与人体觉醒、应激、奖赏、摄食和能量代谢等，并且在交感神经活动及其心血管功能的调节中发挥重要作用，然而其作用机制依然不清。因此，本项目从中枢促食欲素系统激活可引起交感神经活动过度激活这一关键问题入手，应用多种研究方法，从整体、细胞和分子水平综合研究了下丘脑室旁核内促食欲素系统激活介导交感神经过度激活的潜在分子机制。本项目的研究结果揭示了下丘脑内orexin-A、OX1R、Ca2+、CaMKII、CaMKIIα、CaMKIIβ、MAPK基因蛋白表达相关规律的变化，发现orexin-A与增食欲素1型受体（OX1R）结合可增加细胞钙内流，激活胞内MAPK、TNF-α、IL-6和IL-1β表达水平的改变，其中细胞内钙浓度增加也可激活CaMKII的表达，而抑制下丘脑内CaMKII可降低高血压小鼠升高的血压和交感神经放电，提示CaMKII在心脑血管相关区域如PVN的过度激活与高血压有关，进而发现PVN中OX1R/CaMKII通路在交感神经过度激活中发挥重要作用，推测PVN内的OX1R是干预交感神经过度激活的重要靶点。本项目阐明了交感神经激活的分子机制，为临床高血压的防治提供新思路。