HCN通道对血管性痴呆大鼠海马自噬稳态的调节及机制研究

Vascular dementia (VD) has become one of the major diseases threatening the elderly health. However, there is currently no effective treatment for VD. Our previous study has shown that changes of HCN1 and HCN2 expression may be associated with the cognition function. We speculate that HCN channel may be involved in the pathophysiology of VD. However, in the occurrence and development of VD, the abnormal of cytobiology caused by HCN channels expression changes and the molecular mechanism are not clear. In our preliminary experiment, enhancement and redistribution of autophagy was observed in hippocampal CA1 in rats with vascular dementia. Furthermore, ZD7288, a blocker of HCN channel, could correct ischemia-induced excessive autophagy. It means that HCN may participate in the regulation of autophagy. What's the internal connection between enhancement and redistribution of autophagy and disorganization of HCN expression, and whether intervention of HCN channel and its targets of autophagy regulation can improve cognitive function? In this project, we plan to investigate the effect and mechanism of HCN1 and HCN2 channel on hippocampal autophagy regulation in rats with vascular dementia, and identify the differences and similarities of autophagy regulation between HCN1 and HCN2. This study will provide strong theoretical basis for seeking specific drug targets and developing more safe and effective drug. The project has clinical significance and social value.

血管性痴呆(VD)是当今威胁老年人健康的重大疾病。然而，对VD的治疗至今仍缺乏疗效确切的药物。我们前期研究发现，VD模型大鼠海马CA1区HCN通道膜表达变化与认知功能密切相关，提示HCN通道可能是VD病理生理变化的主要位点之一。然而，HCN通道表达变化所致的细胞生物学异常及其机制尚不清楚。我们预实验发现：VD模型大鼠海马CA1区自噬增强并发生再分布，表明自噬可能参与VD的发生发展；而HCN通道阻断剂ZD7288可显著抑制急性缺血缺氧诱导的自噬增强。那么，VD模型大鼠海马自噬变化与 HCN通道表达改变存在怎样的内在联系，干预HCN通道调节自噬的靶点能否改善认知功能？本课题拟以VD模型大鼠为研究对象，探究HCN1及HCN2对海马自噬稳态的调节作用、分子机制及其异同点，为寻求更具针对性的药物靶点，开发更安全高效的抗血管性痴呆药物提供科学理论依据，具有重要临床及社会意义。

在中枢神经系统，HCN通道对维持神经元正常功能具有重要作用，近来研究表明，HCN通道参与脑缺血的病理生理进程，但是其机制尚不清楚。在脑缺血情况下，自噬系统被激活。然而，自噬的激活是具有神经保护作用还是具有神经损伤作用仍不清楚。本研究我们探究了在氧糖剥夺/复灌模型（OGD/R）及短暂性全脑缺血（TGCI）HCN通道对自噬的调控及其影响。我们研究结果显示，HCN通道阻断剂ZD7288（10μM）能显著减少OGD/R诱导的海马HT22神经元细胞的凋亡、纠正OGD/R诱导的自噬的过度激活。然而，在OGD/R模型，溶酶体酸化抑制剂氯喹（CQ）可以取消ZD7288对HT22细胞的神经保护作用及其对自噬的调控。我们进一步研究发现，在OGD/R及TGCI模型，HCN2-shRNA可以显著增加神经元的存活率，CQ同样可以逆转HCN2-shRNA的神经保护作用。此外，HCN2-shRNA可以显著减轻自噬蛋白LC3-II在神经元细胞的积累。然而，CQ可以取消HCN2-shRNA对自噬的调控作用。在HCN2-shRNA HT22细胞，ZD7288并不能进一步减少LC3-II在神经元细胞的积累。我们的研究表明，药物阻断及基因干扰HCN2通道可能通过促进自噬的降解而起到神经保护作用。