基于脉络丛免疫调控的Th17/Treg失衡在肥胖对铅神经毒性易感性的机制研究

Obesity can promote pathogenesis of neurodegenerative diseases, and environmental Pb exposure also causes nerve damage. The interesting issue is that obesity following lead exposure will lead to neurotoxicity escalation. Previous studies have shown that obesity rats following Pb exposure cause aggravated inflammatory injury of the central nervous system (CNS). Meanwhile, inflammatory levels released by Th17 cells in the cerebrospinal fluid of Pb exposed rat significantly increase and IL-10 released by immunosuppressive Treg cells decreased, suggesting that Th17/Treg imbalance in CNS may be involved in process of nerve injury of obesity rats following Pb exposure. Under physiological condition, there are less Th17 and Treg cells in CNS. However, CNS inflammatory signaling can recruited Th17 and Treg cells of blood to traffick through the choroid plexus. In addition, the choroid plexus is the first barrier blocking blood Pb into the CNS, however, Pb exposure led to dysfunciton of choroid plexus. Accordingly, the current hypothesis is that Th17/Treg imbalance based on choroid plexus immune regulation involved in aggravated neurotoxicity of obesity following Pb exposure. Therefore, the present project intends to elucidate Th17 / Treg imbalance in CNS of obesity mice following Pb exposure, screening the key proteins of choroid plexus involved in regulating Th17/Treg balance by applying in vitro blood cerebrospinal fluid barrier model, high throughput technologies and so on. Meanwhile, obese people with Pb exposure are selected as our subjects to investigate the biological markers of nerve injury. The current research will uncover the united effect of health damage, and to provide a new target for the prevention and treatment of obesity following Pb exposure.

环境铅暴露能够导致神经损伤，而肥胖可促进神经退行性病变的发生。那么，肥胖群体对铅神经毒性是否更敏感？前期研究显示肥胖大鼠铅暴露后中枢神经系统（CNS）炎症损伤加剧；铅暴露大鼠脑脊液中Th17细胞释放的炎性因子增加，免疫抑制细胞Treg分泌的IL-10下降，提示Th17/Treg失衡可能参与了肥胖铅暴露导致的神经损伤。正常CNS中的Th17和Treg细胞非常少，CNS中的炎症信号招募血液中Th17、Treg细胞透过脉络丛进入脑组织；铅暴露可损伤脉络丛的结构和功能。据此我们提出：脉络丛免疫调控Th17/Treg失衡参与了肥胖群体铅神经损伤加剧的过程。本项目拟采用血脑脊液屏障模型、高通量检测等技术阐明肥胖群体铅暴露后Th17/Treg失衡现状，筛选脉络丛中的关键调控蛋白/因子，探讨其神经损伤的生物标志物。初步揭示肥胖和铅暴露对健康损伤的联合效应，为肥胖群体铅神经毒性的防治提供新靶点。

脉络丛调控脑组织免疫平衡在神经退行性疾病起着重要作用，而有关其调控Th17/Treg细胞失衡在肥胖群体铅神经毒性中作用未见报道。本研究结果显示肥胖小鼠在铅暴露后神经行为功能下降和神经炎症损伤加剧；NLRP3炎症通路和Nrf2氧化损伤通路参与了神经炎症损伤加剧的过程；肥胖小鼠脑组织Th17细胞及其分泌的IL-17A和IL-22随铅染毒时间增加而上升；Treg细胞及分泌的IL-10则下降。血液和脾脏中Th17/Treg 变化与脑组织相似。ATRA上调脑中Treg细胞可使高脂饮食小鼠铅暴露后星型胶质细胞活化降低，学习记忆功能增强。脉络丛转录组测序显示铅和棕榈酸（高脂）暴露后紧密连接蛋白claudin 家族变化较大，上调claudin11表达可降低血脑脊液屏障通透性，从而减少对Th17细胞透过；JNK通路在铅和高脂饮食暴露致血脑脊液屏障通透性增加中起着重要作用。此外，脉络丛上皮细胞趋化因子CCL22表达下降，CCL21表达增加，参与了血脑脊液屏障对Treg/Th17细胞转运的调控。Th17细胞和IL-17水平与铅暴露引起的肥胖小鼠侧脑室神经生发相关。肥胖群体铅作业工人情感状态和神经行为损伤严重，这与血清Th17/Treg 细胞比例及其释放的细胞因子相关。Th17%在肥胖群体铅神经毒性起到了中介作用，可作为候选生物标志和防治靶点。此外，铅作业人群血清外泌体miR-124和血清IGF-1和EGF水平与神经行为损伤相关，也可作为铅神经毒性的候选标志物。本研究结果进一步丰富了肥胖群体铅暴露后的神经损伤和神经炎症的机制研究，同时也为其神经毒性的防治提供了新的靶点。