下丘脑SIK1-CRTC1通路在抑郁症病理过程中的作用及机制研究

Hyperfunction of hypothalamic-pituitary-adrenal (HPA) axis is critical for chronic stress-induced depression, and however, the underlying molecular mechanisms remain elusive. We assume that chronic stress induces HPA axis hyperfunction and depression via the following pathway: 1, decreasing the expression of salt-inducible kinase 1 (SIK1) in hypothalamus; 2, leading to dephosphorylation of cytoplasmic CREB regulated transcription coactivator 1 (CRTC1) and its transportation into nucleus; 3, increased CRTC1-CREB binding in nucleus; 4, enhanced CREB activation and more biosynthesis of CRF. Here we are going to use various methods to explore: (1) The molecular effects of chronic stress on hypothalamic SIK1-CRTC1 pathway. (2) Whether dysfunction of hypothalamic SIK1-CRTC1 pathway modulates depression, leading to various depressive-like symptoms? Are these effects mediated by modulating the function of HPA axis ? (3) Whether targeting hypothalamic SIK1 and CRTC1 prevents chronic stress and leads to antidepressant effects ? (4) Do those antidepressants used in clinical (fluoxetine, venlafaxine, etc.) have effects on hypothalamic SIK1-CRTC1 system? Is this system involved in their antidepressant mechanisms ? Collectively, this project will make further progress in the research of depression, developing novel antidepressant targets, and has notable clinical values.

下丘脑-垂体-肾上腺（HPA）轴功能亢奋在慢性应激诱发抑郁症的过程中十分重要，但其分子机理依旧不明。我们推测慢性应激通过减少下丘脑内盐诱导激酶1（SIK1）表达，引发其胞浆CREB转录调节共激活因子1（CRTC1）去磷酸化而入核增加并结合CREB，促进核内CREB活性并使得CRF转录合成增加，最终导致HPA轴亢奋，诱导抑郁症。本项目综合采用多种手段，研究慢性应激对下丘脑SIK1-CRTC1通路功能水平的具体影响；研究下丘脑SIK1-CRTC1通路的改变能否模拟慢性应激，诱发各种抑郁样症状，且该效应是否通过调控HPA轴亢奋所致；研究以下丘脑SIK1与CRTC1为分子干预靶点能否逆转/阻止慢性应激，产生抗抑郁效应；研究氟西汀、文拉法辛等临床抗抑郁药物是否作用于下丘脑SIK1-CRTC1系统，后者是否参与其抗抑郁机理。本研究将拓展对抑郁症发病机理的认识，发现新型抗抑郁靶点，具有显著临床应用价值。

阐明慢性应激诱发下丘脑-垂体-肾上腺（HPA）轴功能亢奋的分子机制对于抑郁症发病机理以及相关治疗都是十分重要的。已发现下丘脑室旁核（PVN）神经元合成分泌促肾上腺皮质激素释放激素（CRH）这一过程受到盐诱导激酶（SIKs）与CREB转录共激活因子（CRTCs）的调控。由此，我们推测PVN区SIK-CRTC系统可能介导参与抑郁症神经生物学。本项目研究综合采用慢性社会挫败应激（CSDS）与慢性不可预测温和应激（CUMS）抑郁模型，各种行为学测试，病毒基因干扰，ELISA，western blotting，免疫共沉淀，实时荧光定量PCR以及组织免疫荧光等技术手段。我们的结果发现CSDS与CUMS皆显著引起PVN区SIK1-CRTC1信号通路水平变化。基因沉默PVN区SIK1与过表达PVN区CRTC1皆能模拟慢性应激，使正常小鼠表现出抑郁样症状。相反，基因过表达PVN区SIK1与沉默PVN区CRTC1皆能对抗CSDS与CUMS，产生抗抑郁样效应。再者，PVN定位给予TAT-SIK1生物重组蛋白也能对抗慢性应激。另外，我们还发现PVN区SIK1-CRTC1系统还介导参与氟西汀，帕罗西汀，文拉法辛以及度洛西汀的抗抑郁效应。因此，可以得出结论，PVN区SIK1和CRTC1皆与抑郁症神经生物学密切相关，二者为潜在的新型抗抑郁靶点。