觉醒肽orexin兴奋内嗅皮层神经元促进Aβ生成的效应及机制研究

The accumulation of Aβ in the brain initiates the Alzheimer's disease (AD). Recently, the tight relationship between the abnormal sleep/wake cycle and the cause of AD has been reported. Interestingly, orexin, a hypothalamic awakening peptide, increases the level of Aβ in the hippocampus. However, the underlying mechanisms are largely unknown. Based on the preliminary result of this project that orexin excites entorhinal cortex (EC) neurons, we first plan to determine whether the excitation of orexin on EC neurons promote the generation of Aβ, and then the EC neuron-generated Aβ is released and accumulated in the hippocampus via axons of the perforant pathway. Second, whether the calcium signal-elicited Arc expression pathway is involved in the generation of Aβ induced by the excitation of orexin on EC neurons will be determined. Third, based on the knowledge of the involved molecular pathway, we will investigate the specific targets for the intervention of Aβ generation in EC neurons in a sleep deprivation animal model. This project will provide new insights for the improvement of abnormal sleep/wake-induced cognitive deficits and the targeted prevention and treatment of AD.

Aβ在脑内的集聚是阿尔茨海默氏病（Alzheimer's Disease, AD）发病的始动环节。新近文献报道，睡眠-觉醒异常与AD发生密切相关。觉醒肽orexin可升高海马Aβ水平，但具体机制尚不清楚。基于我们前期研究发现的orexin强烈兴奋内嗅皮层神经元的效应，本课题拟首先证明orexin促进EC神经元Aβ的生成，并经穿通纤维通路突触前末梢在海马分泌，升高海马Aβ水平；其次，探索orexin对内嗅皮层神经元的兴奋效应是否经Ca2+信号上调Arc分子的表达以促进Aβ生成；在阐明orexin兴奋内嗅皮层升高海马区Aβ水平的完整分子信号途径基础上，通过睡眠剥夺的动物模型寻找特异性抑制内嗅皮层神经元Aβ生成的靶点。本项目将为改善睡眠-觉醒异常造成的认知功能障碍以及针对性防治AD提供新线索。

睡眠异常将导致Aβ在脑内存积，影响大脑功能活动，甚至诱发AD发生发展。基于觉醒肽orexin在脑室内注射可致海马Aβ水平升高，其具体机制并未明确。课题组首先通过免疫组化证实orexin纤维投射至内嗅皮层（EC），EC浅层神经元表达orexin受体；其次电生理学进一步确认orexin通过EC神经元上的orexin受体兴奋EC神经元，并初步证实orexin刺激其生成分泌Aβ的效应。此外探索了睡眠剥夺影响EC神经元Arc分子表达以及膜上谷氨酸受体的分布，为下一步深入研究orexin兴奋EC神经元促进Aβ分泌的通路和机制提供实验线索。详细分析了orexin兴奋神经元促进Aβ生成的可能途径和机制，发表SCI论文1篇(Neurobiology of Aging，影响因子6.166)，也为后续课题研究orexin兴奋EC神经元促进Aβ生成提高海马Aβ水平的效应和机制研究提供了可行的理论依据。