以Nrf2为靶点预防慢性间歇低氧和睡眠片段化所致认知损害的作用

Obstructive sleep apnea hypopnea syndrome (OSAHS) is a severe disease that causes central nervous system impairment and cognition dysfunction in children. Chronic intermittent hypoxia(CIH) and sleep fragmentation(SF) are considered as the important mechanism in the cognitive impairment. In our previous studies, we have successfully established animal model of chronic intermittent hypoxia (CIH) as tools for study of OSAHS. We have demonstrated that endoplasmic reticulum stress (ERS) mediated cell apoptosis may be one of the underlying mechanisms of cognitive dysfunction in CIH. Previous study also showed that ERS plays an important role in cognition dysfunction associated with SF. It has been indicated that the nuclear factor-erythroid 2-related factor (Nrf2) is a transcription factor that plays a crucial role in the cellular redox homeostasis and anti-ERS damage through up-regulation of several antioxidants and detoxifying enzymes. Based on these findings, we hypothesize that Nrf2 is a potential therapeutic target for the prevention of cognitive dysfunction associated with CIH and SF. Sulforaphane（SFN）, a major inducer of Nrf2 that can activate Nrf2 and protect the neurons from ERS mediated damage. To test our hypothesis, we construct CIH and SF model by using neuron-specific Nrf2 knockout and overexpression transgenic mice to detect the effect of SFN in ERS- induced apoptosis. Three specific aims are proposed as below; ① To determine the effect of PERK/Nrf2 signalinginpreventing CIH and SF-associated cognitive dysfunction; ② To examine whether the PERK/Nrf2 and PERK/eIF2α signal pathway alleviate neuronal damage caused by ERS in a synergistic way; ③ To verify whether SFN can prevent CIH and SF-associated cognitive dysfunction. The results of this project may provide scientific evidences for using Nrf2 as a therapeutic target to prevent cognitive dysfunction in OSAHS children.

儿童阻塞性睡眠呼吸暂停低通气综合征(OSAHS)可造成脑神经功能损害而致认知功能障碍。既往研究表明慢性间歇性低氧（CIH）和睡眠片段化（SF）是引起这种损伤的重要机制。课题组前期通过建立CIH小鼠模型，发现内质网应激(ERS)相关的细胞凋亡是认知损害机制之一，也有研究表明ERS在SF认知损害中起重要作用。而核因子E2相关因子2(Nrf2)在调节机体氧化－还原平衡和抗ERS损伤中起着关键的作用。据此，我们提出假设：Nrf2是预防CIH和SF所致认知损害的有效靶点，采用Nrf2激动剂上调Nrf2的功能，增强其下游抗内质网应激信号，能有效防止神经细胞损伤。本研究使用Nrf2诱导剂萝卜硫素(SFN)激活Nrf2，探讨其在预防神经细胞ERS损伤，改善认知损害的可行性，利用CIH和SF动物与细胞模型，以神经元特异性Nrf2基因敲除和过表达转基因小鼠为研究手段，解析SFN预防神经细胞ERS损伤的机制。

儿童阻塞性睡眠呼吸暂停低通气综合征(OSAHS)可造成脑神经功能损害而致认知功能障碍。既往研究表明慢性间歇性低氧（CIH）和睡眠片段化（SF）是引起这种损伤的重要机制。课题组前期通过建立CIH小鼠模型，发现内质网应激(ERS)相关的细胞凋亡是认知损害机制之一，也有研究表明ERS在SF认知损害中起重要作用。而核因子E2相关因子2(Nrf2)在调节机体氧化－还原平衡和抗ERS损伤中起着关键的作用。在本研究中，我们通过体内实验证实慢性间歇低氧和睡眠片段化可通过内质网应激诱发小鼠海马神经元凋亡，导致小鼠出现认知功能障碍。此外，Nrf2在间歇低氧和睡眠片段化引起的认知损伤中起重要作用。Nrf2的激活可保护海马神经元，通过调控下游抗氧化基因（Prdx1）的表达降低炎症反应，从而对小鼠认知功能损害起到保护作用，而敲除Nrf2可增加海马神经元凋亡，炎症反应增强，认知功能损害加剧。由此，我们推测，提高Nrf2的活性可能对OSAHS有潜在治疗效果。后通过体外实验证实CIH可通过内质网应激诱发细胞凋亡，应用Nrf2激动剂后对CIH造成的凋亡有明显缓解作用，同时Nrf2的激活可通过调控下游抗氧化基因（Gclc、HO-1）的表达减轻凋亡发挥保护作用。因此，深入研究Nrf2与儿童OSAHS认知功能损害的关系，有利于为儿童OSAHS的防治提供新的思路。