HCN2在血管性痴呆大鼠神经元焦亡中的作用及调控机制

The neuronal damage caused by chronic cerebral hypoperfusion is an important factor of cognitive impairments, which is closely related to vascular dementia (VaD). Our previous study has reported that the up-regulation of HCN2 surface expression in hippocampal CA1 caused by chronic cerebral hypoperfusion is associated with cognitive impairments in VaD rats, but the underlying mechanisms remain largely unknown. Recent preliminary study indicated that the neuronal pyroptosis was occurred in hippocampal CA1 after chronic cerebral hypoperfusion. Additionally, a blocker of HCN channel rescued the neuronal damage and reversed the up-regulation of NLRP3 and caspase-1 induced by oxygen and glucose deprivation in cultured neurons. Based on the referrences and above results, we hypothesize that the up-regulation of HCN2 surface expression caused by chronic cerebral hypoperfusion may active NLRP3/caspase-1-dependent neuronal pyroptosis, which may further lead to cognitive impairments and accelerate the progression of VaD. In this project, targeted interference of HCN2 will be used to investigate the role of HCN2 on neuronal pyroptosis in primary hippocampal neurons. Furthermore, the VaD rat model will be employed to demonstrate the effects and underlying mechanisms of HCN2 on neuronal pyroptosis and cognitive impairments. This study will aim at understanding the mechanism and providing promising pharmacological targets of VaD.

慢性脑缺血引起的神经元损伤是导致认知障碍的重要因素，与血管性痴呆(VaD)的发病密切相关。我们近期报道：慢性脑缺血大鼠海马CA1区超极化激活的环核苷酸门控阳离子通道(HCN)亚型HCN2膜表达上调与认知障碍有关，但机制不详。预实验发现：慢性脑缺血引起CA1区神经元焦亡(Pyroptosis)，而HCN通道阻断剂可逆转神经元离体缺血损伤后NLRP3和caspase-1的表达上调。综合文献与前期工作，我们推测：慢性脑缺血所致的HCN2膜表达上调可能通过激活NLRP3/caspase-1介导的焦亡引起神经元损伤并导致认知障碍，从而加速VaD的发展。本项目拟靶向干预HCN2，首先在细胞水平明确HCN2在神经元焦亡中的作用；再以VaD模型大鼠为研究对象，进一步阐明靶向干预HCN2对神经元焦亡的调控机制及对认知障碍的影响，旨在深入了解慢性脑缺血致VaD的病理机制，为疾病的防治提供潜在药物靶点及依据。

慢性脑缺血引起的神经元损伤是导致认知障碍的重要因素，与血管性痴呆(VaD)的发病密切相关。我们前期发现慢性脑缺血大鼠海马CA1区超极化激活的环核苷酸门控阳离子通道(HCN)亚型HCN2膜表达上调与认知障碍有关，但机制不详。预实验发现：慢性脑缺血引起CA1区神经元焦亡(Pyroptosis)，而HCN通道阻断剂可逆转神经元离体缺血损伤（OGD）后NLRP3和caspase-1的表达上调。我们推测：慢性脑缺血所致的HCN2膜表达上调可能通过激活NLRP3/caspase-1介导的焦亡引起神经元损伤并导致认知障碍，从而加速VaD的发展。本研究首先在细胞水平研究HCN2对NLRP3/caspase-1介导神经元焦亡的调控，然后在动物水平研究靶向干预研究HCN2对VaD大鼠神经元焦亡的调控机制及对认知障碍的影响。结果发现OGD模型能引起神经元焦亡并伴有HCN2表达升高，沉默HCN2可逆转OGD模型导致的神经元损伤，减少神经元K+外流，并逆转焦亡相关蛋白表达增加（NLRP3、caspase-1、ASC、GSDMD、IL-1β等）；我们进一步采用过表达HCN2，发现NLRP3、caspase-1抑制剂能部分逆转过表达HCN2联合OGD处理导致的神经元焦亡，以上结果在离体水平明确了HCN2对神经元焦亡的作用；最后，以VaD模型大鼠为研究对象，发现沉默海马CA1区HCN2，能减轻脑缺血所致的认知功能损伤并逆转焦亡相关蛋白表达升高。本研究较系统的从离体到整体水平，证实了HCN2通过NLRP3/caspase-1途径调节神经元焦亡，作为脑缺血致认知障碍的新机制，为疾病的防治及今后开发潜在药物靶点提供了一定的依据。