水通道蛋白4调节星形胶质细胞功能及其与抑郁症的相关性

Major depressive disorder (MDD) has been associated with astroglial dysfunction, but the underlying mechanisms have remained elusive. Aquaporin-4 (AQP4) is the main aquaporin in the brain and is expressed in highest density in the perivascular and subpial astrocyte end-feet. Our previous studies showed that AQP4 was an essential mediator for regulating glutamate uptake, and AQP4 knockout abolished fluoxetine-induced enhancement of hippocampal neurogenesis and antidepressant effects. Thus, we suppose that AQP4 may be involved in the MDD via regulating the functions of astrocytes. This study is designed to investigate the role of AQP4 in the pathogenesis of MDD, and related possible biological mechanism. Here, using AQP4 knockout and astroglia-conditional knockout mice, we will establish chronic mild stress (CMS)-induced anhedonia model of depression. After evaluating depression-like behaviors in different genotype mice with or without treatment of fluoxetine, we will focus the effects of AQP4 on the glutamate recycle and the balance of brain-derived neurotrophic factor (BDNF) and proBDNF during the MDD. These findings will demonstrate that AQP4 is involved in astrocytic pathology during the development of MDD throught glutamate recycle and BDNF balance, and indicate that AQP4 may be a therapeutic target for novel and more effective anti-depressant treatments.

已经阐明星形胶质细胞谷氨酸循环障碍和营养支持功能下降在抑郁症的病理进程中发挥着重要作用。申请者前期研究发现水通道蛋白4（Aquaporin-4，AQP4）调节星形胶质细胞谷氨酸重摄取和神经营养功能，可能与抑郁症相关。本项目拟应用AQP4敲除和星形胶质细胞AQP4条件敲除小鼠，在整体、细胞和分子水平系统研究AQP4对星形胶质细胞介导的谷氨酸循环和脑源性神经生长因子（BDNF）平衡的调节作用及其在抑郁症病理进程中的作用。预期研究结果将揭示AQP4与抑郁症发生发展的相关性，为基于星形胶质细胞功能调节发展抗抑郁治疗新策略和研发新型抗抑郁药提供重要靶标。

星形胶质细胞功能障碍，尤其是营养支持功能下降，从而引起的神经元功能改变、神经再生减弱在抑郁症的病理生理过程中发挥着重要作用。本课题组前期研究已表明主要表达在星形胶质细胞上的水通道蛋白4（Aquaporin-4，AQP4）与抑郁症相关。本项目应用AQP4敲除小鼠，建立慢性温和应激抑郁症动物模型，研究AQP4对不同抗抑郁药物治疗作用的影响，发现AQP4敲除取消氟西汀、西酞普兰等SSRI类药物的抗抑郁效应。进一步在整体、细胞和分子水平研究AQP4不同亚型和表达丰度对星形胶质细胞介导的脑源性神经生长因子（BDNF）平衡的影响及其机制，发现基础状态下AQP4-/-小鼠海马脑区miR-16表达显著高于AQP4+/+小鼠，氟西汀治疗可以逆转CMS模型所致AQP4+/+小鼠海马脑区miR-16表达水平的增高，AQP4敲除取消氟西汀下调CMS模型小鼠脑内miR-16水平的作用；应用荧光素酶报告基因发现miR-16靶向负调节BDNF表达水平，阐明AQP4敲除通过上调miR-16水平，抑制BDNF表达，取消氟西汀的抗抑郁作用，揭示了其在抑郁发生发展和抗抑郁治疗中的作用和意义。在此基础上，拓展研究了α-突触核蛋白（α-synuclein）、β-淀粉样蛋白（Aβ）对胶质细胞功能的影响和AQP4对Aβ, α-synuclein清除的调节，以及调节代谢性炎症的药物对神经精神疾病的实验治疗学研究。发现AQP4基因缺失后加剧了APP/PS1小鼠认知功能障碍、脑内Aβ斑块聚集、星形胶质细胞萎缩和BDNF表达下调。本项目研究成果不仅在学术上进一步拓展AQP4的神经生物学研究领域，而且为发展靶向胶质细胞功能的抗抑郁药物提供新的策略。