AMPA-BDNF-mTOR/miR132信号通路介导川陈皮素快速抗抑郁作用的机制研究

Currently available antidepressant medications have significant limitation with time lag for treatment response, further highlighting a major clinical need for rapid-acting antidepressant agents. Our preliminary study showed that nobiletin stimulated the hippocampal brain-derived neurotrophic factor (BDNF) protein synthesis and exerted rapid antidepressant-like effect, which was mediated by AMPA receptor. Previous reports indicated that expression of the rapid response gene miR132 in hippocampal neurons induced neuronal cell proliferation, and rapidly increased gene and protein expressions involved in neuronal cell proliferation were stimulated by mammalian target of rapamycin (mTOR) signaling pathway. Therefore, we speculate that miR132 and mTOR signaling pathway is involved in the rapid antidepressant-like effect of nobiletin. To evaluate the hypothesis, this proposal is designed to reveal the role of miR132 in the depression pathology using the index sucrose preference and hippocampal neuronal cell proliferation in the rat chronic mild stress (CMS). In addition, we also explore the mechanism related to involvement of AMPA receptor in the hippocampal rapid synthesis of BDNF, involvement BDNF-TrkB-ERK/Akt-mTOR/miR132 signaling pathway in the rapid antidepressant-like effect of nobiletin. This reseach will provide a new thought and a new target in the rapid-acting antidepressant agents development based on the rapid AMPA receptor, rapid mTOR signaling pathway and rapid response gene miR132.

目前抗抑郁治疗由于存在起效时间延迟的不足，因此临床迫切需要起效迅速的药物。前期预实验发现川陈皮素单次给药后可基于AMPA受体增加海马脑源性神经营养因子（BDNF）含量，产生快速抗抑郁作用。根据文献报道，上调快速调节基因miR132表达可解除对海马神经细胞增殖的抑制；激活依赖mTOR调控的下游信号通路可迅速促进与神经细胞增殖相关基因表达。因此，我们推测川陈皮素快速抗抑郁作用与miR132、mTOR相关。为证实该假说，本课题采用大鼠慢性温和应激（CMS）模型，以糖水偏爱百分比和海马神经细胞增殖为指标，在动物水平探讨miR132在抑郁症病理机制中的重要作用；系统评价川陈皮素如何基于AMPA受体参与海马BDNF快速释放，介导BDNF-TrkB-ERK/Akt-mTOR/miR132信号通路产生快速抗抑郁作用的分子机制。本课题将从快速受体、信号通路、调节基因角度为开发快速抗抑郁药提供新思路和新靶点。

本研究基于慢性温和不可预知应激（CUMS）模型，分别对BDNF、mTOR和miR-132分子及其调控机制进行了相关研究，首次发现：（1）CUMS导致海马BDNF和海马神经细胞增殖的昼夜节律性调节机制受到破坏，表现为BDNF表达和神经细胞增殖持续低下，夜间未能出现峰值；（2）CUMS抑制大脑mTOR信号通路，但是这种抑制性的调节依赖于脑区（海马、扁桃体mTOR信号通路受到抑制，皮层和下丘脑mTOR信号通路不受影响）；（3）筛选出可能与快速抗抑郁药作用相关的15个miRNAs；（4）川陈皮素具有快速抗抑郁作用，这种快速抗抑郁作用与激活海马BDNF-TrkB-ERK/Akt-mTOR信号通路及增加海马星形胶质细胞ATP释放量有关；（5）CUMS抑郁模型miR-132表达显著降低，齐墩果酸长期给药可以激活依赖于BDNF-TrkB-ERK-CREB-miR-132的信号通路，促进海马神经细胞增殖，产生抗抑郁作用。上述结果证实了我们提出的miR-132参与抑郁症发生的假说；验证了川陈皮素基于BDNF-TrkB-ERK/Akt-mTOR信号通路发挥快速抗抑郁作用的预测；以及齐墩果酸基于BDNF-TrkB-ERK-CREB-miR-132信号通路发挥抗抑郁作用的机制，这些研究结果为抑郁症的防治提供一个新靶点，以及进一步揭示了川陈皮素和齐墩果酸的抗抑郁作用机制。