七氟烷多次暴露通过AKT/GSK-3/NOTCH信号通路抑制发育脑海马神经发生的作用及机制研究

Clinically, in order to treat some kinds of diseases, many infants and young children have to accept surgeries and anesthesia for several times. It is still unclear that whether multiple exposures of anesthetics, especially sevoflurane which is the most commonly used inhalation anesthetic for the infant and children, could cause neuroplasticity dysfunction. Neurogenesis, which is the most important feature of the developing brain, has a crucial influence on the neuroplasticity. Our previous work indicated that several times of sevoflurane exposure during this period could decrease the learning and memory ability, neurogenesis as well as the level of GSK-3α/β Ser21/9 phosphorylation in hippocampal neural stem cells. Specific AKT inhibitor reversed GSK-3β Ser9 dephosphorylation and neurogenesis inhibition in cultured hippocampal neural stem cells. Moreover, multiple sevoflurane exposures activated NOTCH pathway. So, we hypothesized that multiple exposures of sevoflurane might lead to developmental brain hippocampal neurogenesis inhibition through AKT/GSK-3/NOTCH pathway. The successful completion of this research project will provide answers to the clinical problem of repeated exposure of sevoflurane on developmental neurotoxicity. It will provide clinical reference with the timing of operation and choice of the number of anesthesia. Improving medication safety and reducing the side effects of anesthetics has significant scientific value and social meaning.

临床上很多婴幼儿疾病需要接受多次麻醉暴露才能进行手术。多次麻醉暴露，特别是中国现今首选的婴幼儿麻醉药——七氟烷的多次暴露，对婴幼儿神经可塑性的影响并未见报道。神经发生作为发育脑最重要的特点，深刻影响着婴幼儿的神经可塑性。我们的研究发现，此阶段多次七氟烷暴露：①降低幼鼠的学习记忆水平；②减少神经发生；③诱发GSK-3α/β Ser21/9磷酸化下降；④AKT抑制剂逆转了GSK-3β Ser9去磷酸化；⑤激活NOTCH通路。据此我们提出本项目假说:多次七氟烷暴露可能通过AKT/GSK-3/NOTCH通路抑制海马神经发生导致认知功能障碍。本项目的完成将为回答多次七氟烷暴露对发育脑神经毒性这一临床问题提供科学依据，为患儿手术时机及接受麻醉药物次数的选择提供临床参考，提高用药安全性、降低药物副作用，具有极其重要的科学价值和社会意义。

神经发生作为发育脑最重要的特点，深刻影响着婴幼儿的神经可塑性。作为临床上婴幼儿麻醉最常用的吸入麻醉药，七氟烷被大量基础研究报道其可诱发发育脑神经毒性并引起认知功能障碍，但机制尚不明确。我们的研究发现，在PND6.7.8这一神经发生高峰期，多次七氟烷暴露可能诱导乳鼠发育脑海马神经干细胞 GSK-3α/β 和 AKT 相互作用增加,导致 Ser21/9 去磷酸化激活,进而激活 Notch 通路,进而介导了发育脑海马神经干细胞发生异常，引起成年后的远期认知功能障碍。体外实验方面，利用七氟烷多次暴露处理体外培养的海马神经干细胞，发现多次七氟烷暴露组 NSCs 向神经元细胞分化的比例降低，向神经胶质细胞分化的比例增高。此外，我们研究发现，早期的低浓度（1.2%）七氟烷暴露6小时可以增强乳鼠的海马神经发生和突触可塑性，并改善成年后的空间学习和认知功能。本项目的完成将为回答多次七氟烷暴露对发育脑神经毒性这一临床问题提供科学依据，提示七氟烷通过作用于GSK-3途径调控神经再生进而影响发育脑认知功能障碍可能是研究七氟烷神经毒性的新思路。