Tiam1-Rac1调控突触结构和功能参与氯胺酮抗抑郁效应的机制研究

Depression is a serious mental disorder that afflicts approximately 17 percent of the world’s population, resulting in enormous personal suffering. However, the current available antidepressant medications have weeks of lag for onset and low remission rates. Recent studies have found that sub-anesthetic dose of ketamine has a rapid and lasting antidepressant effect, but the underlying mechanism is still unclear. A large amount of evidence suggests that glutamatergic synaptic structure and dysfunction are closely related to the pathogenesis and treatment of depression. Small G protein Rac1 plays an important role in modulating the structure and function of synapse and is regulated by Tiam1 (GDP/GTP exchanging factor). Our previous study showed that ketamine could improve the depressive behavior of rats and increase the expression levels of Rac1 and Tiam1 in hippocampus. Therefore, we hypothesized that the antidepressant efficacy of ketamine maybe associated with regulating the expression and activity of Tiam1 and Rac1 in the depressive-related brain regions, which in turn affects the synaptic structure and enhances synaptic function. With small G protein Rac1 and its regulatory proteins Tiam1 as the breakthrough point, the behavioral tests, molecular assay, shRNA interference, and patch clamp will be applied in this study to explore the specific molecular mechanism of ketamine antidepressant effect. This study will provide a new theoretical basis and molecular target for the treatment of depression in clinic.

抑郁症是一种严重的精神障碍性疾病，传统药物治疗起效慢、缓解率低。近期研究发现，亚麻醉剂量氯胺酮具有起效快速、作用持久的抗抑郁效应，但其分子机制尚不完全清楚。大量证据表明，谷氨酸能神经突触结构及功能异常与抑郁症的发病和治疗密切相关。小G蛋白Rac1是参与突触结构和功能调控的重要分子，其活性受GDP/GTP转换因子Tiam1的调控。本课题组前期研究发现，氯胺酮能够改善大鼠抑郁行为，并上调海马内Rac1和Tiam1的表达。因此，我们推测氯胺酮可能通过调控抑郁相关脑区Tiam1和Rac1表达及活性，继而影响突触结构并增强突触功能，从而发挥抗抑郁效应。本项目拟从调控神经突触结构和功能的角度出发，以小G蛋白Rac1及其调节蛋白Tiam1为切入点，采用行为学、分子生物学、shRNA干扰、膜片钳电生理学等实验技术，研究并揭示氯胺酮抗抑郁效应的具体分子机制，以期为抑郁症的药物治疗提供新的理论依据和分子靶点。

临床研究发现，氯胺酮具有快速而持久的抗抑郁作用，尤其是在患有重度抑郁症（MDD）的患者中。然而，氯胺酮抗抑郁的分子机制仍不清楚。在本研究中，我们观察了氯胺酮对应激大鼠海马Rac1表达、神经元形态和突触传递功能的影响。慢性不可预见性轻度应激（CUMS）用于构建应激大鼠模型。大鼠接受不同的药物处理，如氯胺酮（20mg/kg，腹腔注射）和Rac1抑制剂NSC23766（50μg，ICV）治疗。通过糖水偏好试验和旷场试验评价大鼠的抑郁样行为。Western blot检测海马区Rac1、GluA1、synapsin1和PSD95的蛋白表达。Pull-down分析用于检查Rac1的活性。高尔基染色和电生理学研究观察神经元形态和长时程增强（LTP）。我们的结果表明，氯胺酮可以上调Rac1的表达和活性；增加应激大鼠海马中的树突棘密度和突触相关蛋白如GluA1、Synapsin1和PSD95的表达；减少CUMS引起的LTP损伤；从而改善抑郁样行为。然而，Rac1抑制剂NSC23766可以有效地逆转氯胺酮介导的大鼠海马相关结构和分子变化并抵消其抗抑郁作用。另外，通过构建构建Rac1N17过表达腺病毒/Tiam1干扰腺病毒，其下游突触相关蛋白GluA1、Synapsin1和PSD95的表达也明显下调，进一步明确了Rac1在氯胺酮抗抑郁效应中发挥关键作用；氯胺酮抗抑郁作用的具体机制可能与上调应激大鼠海马Rac1的表达和活性，从而增强突触可塑性有关。