CAPON介导的下丘脑nNOS-NO系统在抑郁症发病机制中的作用

The dysfunction of hypothalamo–pituitary–adrenal (HPA) axis that initiated by the hyperactivity of corticotropin-releasing hormone (CRH) neurons in the hypothalamic paraventricular nucleus (PVN) plays an important role in the pathogenesis of stress and depression. Nitric oxide (NO) is crucial for the regulation of HPA axis activity. CAPON is an adapter protein for neuronal NO synthase (nNOS) and exerts negative regulation on the nNOS activity. We found an up-regulation of CAPON and a down-regulation of nNOS in the prefrontal cortex (PFC) of depressed patients and a significant reduction of nNOS in the hypothalamic PVN of Chronic Unpredicted Stress (CUS) rats. However, it is largely unknown about the exact mechanism that CAPON-mediated nNOS activity regulation participates in stress and depression. This project plan to study the changes of CAPON and nNOS as well as the association between them in the PFC and the hypothalamic PVN of both depressed patients and CUS rats; to observe the effects of specially down-regulating CAPON expression on the nNOS-NO system, HPA axis activity and anxiety/depression behaviors in CUS rats; to elucidated the molecular mechanism by which the CAPON-medicated hypothalamic nNOS-NO system down-regulation promotes stress and depression. We expect to provide scientific evidence for the research and application of those antidepressants targeting nNOS adapter proteins.

下丘脑室旁核（PVN）促肾上腺皮质激素释放激素（CRH）神经元过度激活引起的下丘脑-垂体-肾上腺（HPA）轴功能异常在应激和抑郁症中扮演重要角色。一氧化氮（NO）对HPA轴活性具有调控作用。CAPON是神经系统NO合酶（nNOS）的接头蛋白，能够负性调控其活性，我们发现抑郁症患者前额叶皮层（PFC）中CAPON表达增加而nNOS表达下调，慢性应激（CUS）大鼠PVN中nNOS表达明显降低，但CAPON介导的nNOS活性调控参与应激抑郁的具体机制并不清楚。本项目拟研究CAPON和nNOS在抑郁症患者和CUS大鼠PFC、PVN中的表达变化以及二者之间的关联，观察靶向下调CUS大鼠PVN中CAPON的表达对nNOS-NO系统、HPA轴活性和抑郁焦虑行为的影响，阐明CAPON介导的下丘脑nNOS-NO系统活性下调促进抑郁应激的分子机制，旨在为以nNOS接头蛋白作为靶点的抗抑郁药物研发提供科学依据。

CAPON是神经系统NO合酶（nNOS）的接头蛋白，能够负性调控其活性，前期研究表明抑郁症患者前额叶皮层（PFC）中nNOS表达下调，慢性不可预知性应激（CUS）大鼠室旁核（PVN）中nNOS表达明显降低，但应激抑郁条件下nNOS-NO系统活性改变的具体机制尚不清楚。本研究以抑郁症患者死亡后人脑标本和CUS小鼠为研究对象，应用免疫细胞化学结合图像分析研究CAPON在抑郁症患者和CUS小鼠PFC、下丘脑PVN中的表达变化以及nNOS与CAPON的共定位情况，采用腺相关病毒立体定位注射方法观察过表达或下调小鼠PFC中CAPON对nNOS-NO系统活性和抑郁焦虑行为的影响。结果发现：1）CAPON免疫反应性在重型抑郁患者PFC和下丘脑PVN中上调，CAPON与nNOS在PFC和PVN中存在部分共定位。2）CAPON在CUS小鼠PFC中表达增加，而nNOS表达却下调，二者呈反向变化。3）在地塞米松诱导的细胞应激模型中，CAPON和nNOS蛋白水平呈浓度和时间依赖性表达上调，且在二者表达水平的高峰NO释放减少。4）在PFC中注射CAPON过表达腺相关病毒后第2周和第4周，小鼠表现出抑郁样行为。5) 在PFC中注射CAPON下调腺相关病毒显著改善了CUS引起的抑郁样行为。本研究为解释抑郁症患者PFC和下丘脑nNOS-NO系统活性改变的病理现象提供了有益思路，为以nNOS接头蛋白作为靶点的抗抑郁药物的研发工作奠定了基础。