A1/A3腺苷受体增敏调控小胶质细胞炎性及促髓鞘重塑修复慢性缺血性脑白质损伤作用和机制

Chronic ischemic white matter lesion is an important cause of chronic vascular dementia, but the regulatory mechanism has been unclear. Our previous study has revealed that chronic cerebral ischemia induces downregulation of adenosine A1 receptor in white matter lesion, the reduction of adenosine A1 receptors are concomitant with the inhibition of IL-10 expression, reduced PLP expression of oligodendrocytes; in addition, A1AR is able to activate mTOR signaling pathways, induce MBP expression, and inhibit inflammatory responses; suggesting that A1AR plays a leading role in white matter inflammatory lesions caused by chronic hypoperfusion. Microglia is the major inflammatory response cell, Oligodendrocytes function as the direct effector cells in white matter lesion. Many studies have shown that A1AR/A3AR may develop into a dimer structure and play a major role in neural protection, and lies in the upstream in the inflammatory response. Therefore, A1AR/A3AR may function as a synergistic regulator in white matter lesion, followed by adjusting the inflammatory response of microglia and inducing oligodendrocyte regeneration to repair white matter lesions. The aims of this study are: to clarify the synergistic effect by activation/inhibition of A1AR and A3AR, and corresponding responses of inflammatory cytokines and white matter lesion; to explore the synergistic mechanism of adenosine A1/A3 receptor-inducing oligodendrocytes regeneration in chronic ischemic white matter lesions. This study will facilitate in revealing the mechanisms of microglial inflammation and myelin remodeling in chronic ischemic white matter lesion, and provide new theory and drug targets for its effective prevention and treatment.

慢性缺血性脑白质损伤，是造成慢性血管性痴呆的重要根源，其调控机制尚不清楚。本课题组前期发现慢性脑缺血导致小鼠白质内腺苷A1AR表达下调， IL-10表达受抑制、少突胶质细胞PLP蛋白表达减少；此外，A1AR能够激活mTOR信号通路、诱导MBP表达、抑制炎性反应；提示A1AR在慢性低灌注所致白质炎性损害中发挥重要作用。小胶质细胞为主要炎性反应细胞，少突胶质细胞为脑白质损伤的直接效应细胞。研究显示A1AR/A3AR可能存在二聚体结构并参与调节神经保护作用，处于炎症反应上游。因而，A1AR/A3AR可能发挥增敏调节作用，通过调节小胶质细胞炎性反应，诱导少突胶质细胞再生从而修复脑白质损伤。本课题研究目的：明确慢性脑白质缺血中A1AR与A3AR增敏效应、炎症因子、白质损伤变化及相关性；探讨A1AR/A3AR调控小胶质细胞炎症反应及慢性缺血性脑白质损伤中髓鞘重塑机制，为其有效防治提供新理论和药物靶点。

背景：慢性脑缺血模型被广泛用于研究皮质下缺血性血管性痴呆探究白质病变的潜在病理生理机制。与皮质下血管性痴呆严重影响了患者的生活质量。因此，亟待研发针对慢性脑缺血引起的认知功能障碍的有效的治疗方略。.主要研究内容：通过调控A1/A3腺苷受体，明确A3AR在慢性缺血性白质损伤中的作用，明确A3AR/A1AR、炎性因子、少突胶质细胞、小胶质细胞活化、白质损伤的变化相关性及规律，探讨A1AR/A3AR调控少突胶质细胞修复慢性缺血性白质损伤的信号通路。.重要结果：A3腺苷受体刺激可以改善CCI引起的记忆障碍，调节ERK信号通路，保留MAP-2和神经丝的表达，调节GFAP的表达，并上调抗炎细胞因子IFN-β。因此，A3腺苷受体可能是治疗认知障碍和脑部炎症疾病的治疗靶点。A1/A3腺苷受体的刺激可以调节ERK信号，减轻神经炎症反应，促进MOG和PLP的表达，并改善记忆功能障碍。.关键数据：在抑制性回避实验中，与安慰剂组小鼠相比，IB-MECA小鼠的潜伏期显著增加（F=16.18, p<0.05）。通过免疫组化实验以及Western blot实验结果显示，和假手术小鼠相比较发现，安慰剂组小鼠的 p-ERK、GFAP和 IFN-β表达增加，而MAP-2和神经丝减少（均 p<0.01）。与安慰剂组相比，IB-MECA 降低了ERK磷酸化（p<0.01）和 GFAP表达（p<0.05），但上调了MAP-2和 IFN-β（两者均 p<0.01）。MRS1523阻断了IB-MECA对记忆缺陷、ERK磷酸化以及 MAP-2、神经丝、GFAP和IFN-β水平的作用（P<0.05）。.科学意义：本研究探讨和明确了A3AR在慢性缺血性白质炎症损伤中的作用，及其与A1AR的调节效应，慢性缺血性状态下对应的小胶质细胞活化、炎症因子、白质损伤变化规律；A1AR/A3AR对缺血、缺氧状态下少突胶质细胞增殖、分化、及髓鞘形成的影响；以及慢性缺血性白质损伤中A1AR/A3AR介导炎症反应的信号途径。本研究阐明了A1AR/A3AR调节小胶质细胞炎性反应及髓鞘重塑在慢性缺血性脑白质损伤中的作用和机制，为本病有效治疗提供新依据和药物靶点。