脑脊液miR-16对中缝核5-羟色胺转运体基因表达的调节及其在抑郁症发病机制中的作用研究

Depression is predicted to be the second-leading cause of disease burden worldwide just after coronary heart disease in the year of 2020. Its prevalence rate in China tends to be increasing year by year. However, the mechanism of depression remains unclear. The current studies demonstrated that miR-16 may regulate the expression of serotonin transporter (SERT) gene post-transcriptionally. In our preliminary study, miR-16 levels in cerebrospinal fluid (CSF) and raphe nuclei of depression subjects were obviously lower than those in healthy controls, while no significant difference was observed in prefrontal cortex or hippocampus. Therefore, we hypothesize that miR-16 level in CSF is associated with that in raphe nuclei. CSF miR-16 may involve in the mechanism of depression via influencing the level of miR-16 in raphe nulei and regulating the expression of SERT gene in this tissue. However, relevant studies are still lacking. To test our hypothesis, in this study, we intend to establish rat depression model induced by chronic unpredictable mild stress, then analyze the association between CSF miR-16 and depression-like behaviors, as well as the regulation effects of CSF miR-16 on miR-16, SERT mRNA, SERT protein levels in raphe nuclei by increasing or decreasing the amount of CSF miR-16. We aim to explore the role of CSF miR-16 in the physiopathology and its mechanism involved in the depression. Thus, our study is of great significance on clarification the 5-HT theory of depression. And the study findings will help to predict the potential usage of CSF miR-16 as the biomarker and new pharmacological target of depression.

预计到2020年，抑郁症将成为全球仅次于冠心病的第2大疾病，我国患病率亦逐年升高，但其发病机制未明。现有文献显示，miR-16可能在转录后调节5-羟色胺转运体（SERT）基因表达。我们前期预实验表明，抑郁症脑脊液和中缝核miR-16水平比健康对照低；而前额叶和海马则无显著差异。据此，我们提出假设：脑脊液miR-16与中缝核miR-16相关，脑脊液miR-16可影响中缝核miR-16水平，调节该区SERT基因表达，参与抑郁症发病。但至今尚无相关报道。本项目拟建立慢性不可预知温和应激大鼠抑郁模型，研究脑脊液miR-16与抑郁样行为的关联性，并通过升高或降低脑脊液miR-16水平，分析其对中缝核miR-16、SERT mRNA及蛋白表达水平的影响，旨在探索脑脊液miR-16在抑郁症病理生理学中的作用及其机制，对阐明抑郁症5-HT假说有重要意义，同时，为寻找抑郁症生物标志以及新的药物靶点提供参考。

抑郁症已成为全球关注的公共卫生问题，但其发病机制未明。现有文献显示，miR-16在转录后水平调节中缝核5-羟色胺转运体（serotonin transporter, SERT）基因表达，从而可能参与抑郁症的发病过程。我们前期实验表明，抑郁症患者脑脊液miR-16水平显著降低。据此，本研究提出了假设：脑脊液miR-16水平的降低，可能通过影响中缝核SERT的表达，参与抑郁症发病机制。本研究在慢性不可预知温和应激抑郁模型上，分析脑脊液miR-16对抑郁样行为的影响；另外，通过侧脑室注射miR-16 agomir 或 antagomir，改变脑脊液miR-16水平后，比较大鼠抑郁样行为以及中缝核miR-16和该区SERT基因表达变化。结果显示，抑郁模型大鼠脑脊液和中缝核miR-16明显低于对照大鼠（P=0.007和0.031），中缝核SERT显著高于对照组(P=0.005)；脑脊液miR-16与中缝核miR-16存在显著正相关关系(r=0.95, P=0.000)，而与中缝核SERT存在明显负相关关系(r=−0.86, P=0.002)。miR-16 antagomir注入脑脊液后，与对照大鼠比较，糖水偏好指数下降、不动时间延长；同时，中缝核miR-16水平下降，与注射剂量呈负相关关系(r=-0.57，P=0.000)；而中缝核SERT水平升高，与注射剂量呈正相关关系(r=0.49，P=0.000)。注射agomir后，糖水偏好指数升高、不动时间缩短；中缝核miR-16水平升高，与注射剂量呈正相关关系；中缝核SERT水平降低(r=0.41，P=0.000)，与注射剂量呈负相关关系(r=-0.32，P=0.000)。因此，脑脊液miR-16低水平可能是抑郁症的一个特征，脑脊液miR-16可能通过影响中缝核miR-16与SERT的表达，参与抑郁症的发病机制。本次研究对抑郁症机制的探明具有重要意义，研究结果对抑郁症生物标志以及新型药物靶点的寻找提供了证据。