eCB系统对ASD认知及社交功能的影响及作用机制研究

Autism spectrum disorders (ASD) are a heterogeneous group of neurodevelopmental disorders with unclear causes. It has been identified that the synaptic neurotransmission dysfunction was correlated to ASD. Our previous work has reported that the association between abnormal polyunsaturated fatty acid (PUFA) metabolism and the occurrence of ASD, however, the underlying mechanism was still unknown. Endocannabinoids are produced “on demand” from PUFAs present in phospholipids in the neuronal cell membranes, binding with their type-1 and type-2 cannabinoid receptors in the presynaptic neuron, and then inhibit the release of several neurotransmitters and affect synaptic plasticity. We hypothesized that there is potential relationship between endocannabinoid system and cognitive and social impairments in autistic children. In the current study, the autistic children and valproic acid (VPA)–induced rat autism model are used as the research objects to analyze the levels of endocannabinoids, cannabinoid receptors and related key enzymes by case control method, and to observe the change of cognitive and social function and the change of endocannabinoid system’s expressions after cannabidiol intervention, in order to explore the connection between endocannabinoid system and cognitive and social impairments. Furthermore, we also use path clamp technique to detect the effect of endocannabinoid system on neuronal synaptic plasticity based on PI3K-Akt/Ras-ERK-mTOR signal transduction pathways, to explore the potential mechanism that endocannabinoid system play an important role in regulating cognitive and social function.

孤独症谱系障碍（ASD）是一种病因不明的神经发育障碍性疾病。已证实ASD与神经突触传导异常有关。本课题组发现PUFAs代谢异常与ASD发病有一定关联，但机制不明。内源性大麻素（eCB）样物质由神经元细胞膜中的PUFAs分解而来，作用于突触前膜相关受体，进而抑制突触前神经元神经递质释放，影响突触可塑性形成，推测eCB系统可能与ASD的认知及社交功能密切相关。本项目以ASD儿童和VPA大鼠为研究对象，进行体内eCB样物质水平及eCB系统相关受体、代谢酶表达的病例-对照研究；观察大麻二酚干预后VPA大鼠eCB系统表达的变化及认知和社交功能改变，探讨eCB系统与ASD认知及社交功能的关联。采用膜片钳技术，以与突触可塑性密切相关PI3K-Akt/Ras-ERK-mTOR双信号转导通路为靶点，观察eCB系统对神经元突触可塑性的影响和调控作用，揭示eCB系统对ASD认知及社交功能的影响及可能的作用机制。

孤独症谱系障碍（ASD）是一种常见的神经发育障碍性疾病，病因不明。研究证实ASD的核心症状与突触传导功能失调密切相关。内源性大麻素（eCB）系统是中枢神经系统的重要调节系统，能够调节突触可塑性和神经递质传递。本课题组前期发现，ASD儿童多不饱和脂肪酸（PUFAs）代谢异常，而eCBs由神经元细胞膜PUFAs分解而来，由此推测eCB系统可能与ASD的发病存在关联。本研究以ASD人群及两种公认的ASD模型鼠为研究对象，开展eCBs水平及其相关受体、代谢酶表达的病例-对照研究；观察eCBs降解酶抑制剂JZL184和URB597干预后ASD模型鼠eCB系统表达的变化及认知和社交功能改变，探讨eCB系统与ASD认知及社交功能的关联。采用分子生物学和膜片钳技术，观察eCB系统对神经元形态和功能的影响和调控作用，揭示eCB系统对ASD认知及社交功能的影响及可能的作用机制。结果发现，ASD儿童血浆eCBs水平明显降低，且与ASD儿童的临床表型特征显著关联；VPA诱导的ASD模型鼠海马组织中2-AG及AEA的水平降低，其降解酶FAAH和MAGL表达显著升高，CB1R及CB2R表达出现代偿性升高。经eCBs降解酶抑制剂JZL184和URB597对VPA模型鼠进行干预可显著升高VPA模型鼠海马组织中eCBs水平，其中，JZL184干预可明显减少海马CA1区神经元的损伤，提高抗氧化能力，缓解海马神经元凋亡，进而改善VPA模型鼠的刻板行为、活动过度、认知及社交功能。提示eCB系统与ASD的认知及社交功能损伤存在明确关联，升高eCBs水平可显著改善ASD模型鼠认知及社交功能。除环境型ASD模型鼠之外，本项目又开展了遗传型ASD模型鼠（BTBR鼠）的研究，同样发现BTBR鼠也存在eCB系统代谢异常，且JZL184干预能发挥相同效应。应用BTBR鼠断头取脑，进行BTBR鼠急性分离海马神经元的提取，采用全细胞膜片钳技术，检测BTBR鼠和正常对照鼠神经元细胞膜基本电生理特性、兴奋性，探讨eCB系统对神经元形态及功能的作用和调控机制。本项目从人群研究到动物模型的机制验证，从行为学、分子生物学及神经电生理等多角度，综合阐明了eCB系统与ASD发病的复杂关联，为临床靶向干预提供了新的思路。