Treg细胞通过脑室脉络丛调节海马区血源性单核细胞浸润在大鼠体外循环诱发术后认知功能障碍中的作用研究

The incidence of post-operative cognitive dysfunction (POCD) is especially high after cardiopulmonary bypass (CPB). Its mechanism is still unclear. Our previous research and others’ work have shown that peripheral regulatory T lymphocytes (Treg) increased after CPB, which lead to decreased number of effector T cells and Th1/Th2 shift (toward Th2), and therefore cause systemic immunosuppression. However the relationship between the immunosuppressive state and POCD has been rarely studied. The choroid plexus (CP) is a perfect platform for the interaction between central nervous system (CNS) and peripheral immune system. Depending on the IFN-γ produced by Th1 lymphocytes, it serves as a gate regulating peripheral immune cells into cerebrospinal fluid affecting CNS function. Blood-borne monocytes infiltrate into CNS through CP, and are the main source of protective M2 macrophages in CNS injury site. They are important in resolving the neuro-inflammation induced by activated microglia. Therefore, we intend to use our established rat CPB model, differentiate the peripheral immune cells from resident microglia by preparing bone marrow chimeric rats, intervene the peripheral Treg cells, Th1/Th2 balance in CP, or Blood-borne monocytes, and observe their effects on hippocampus inflammatory injury and cognitive function, in order to explore the relationship between peripheral immunosuppression and the occurrence of POCD after CPB, so as to provide new ideas and directions for clinical prevention and treatment of POCD.

术后认知功能障碍（POCD）在体外循环（CPB）后发生率非常高，机制不清。课题组前期实验及文献报道发现：CPB后外周调节性T细胞（Treg）增加，Th1/Th2失衡，机体处于免疫抑制状态。而这种状态是否同POCD相关，迄今鲜有研究。脑室脉络丛（CP）是中枢神经系统（CNS）同外周免疫系统相互交流的平台，依赖Th1细胞产生的IFN-γ调节外周免疫细胞进入CNS；血源性单核细胞通过CP进入CNS损伤区，是M2型巨噬细胞的主要来源，具有炎症消解和神经保护作用，能抑制并终止局部小胶质细胞的活化，减轻炎性损伤。故本课题拟利用已建立的大鼠CPB模型，通过制备骨髓嵌合体大鼠以区分小胶质细胞和外周单核细胞，干预Treg，观察其对CP内免疫状态，海马区单核细胞浸润及活化，以及对海马组织炎性损伤和动物认知功能的影响及机制，探讨CPB后外周免疫抑制同认知障碍之间的关系，为临床防治POCD提供新的思路和理论依据。

术后认知功能障碍（POCD）在体外循环（CPB）后发生率高，持续时间长，且机制不清。课题组前期实验和文献报道均发现CPB后外周血中调节性T细胞（Treg）增加，机体处于免疫抑制状态，而这种状态是否同POCD相关，迄今鲜有研究。脑室脉络丛（CP）是中枢神经系统（CNS）同外周免疫系统相互交流的平台，依赖Th1细胞产生的IFN-γ调节外周免疫细胞进入CNS。血源性单核巨噬细胞（Mo-Mφ）在多种中枢神经系统损伤和疾病模型中均被发现具有神经保护作用。Mo-Mφ通过脑室脉络丛进入CNS，是M2型巨噬细胞的主要来源，具有炎症消解和神经保护作用，能抑制并终止局部小胶质细胞的活化，减轻炎性损伤。本课题利用氯磷酸二钠脂质体清除外周Mo-Mφ细胞，观察其对CPB后脑损伤和认知障碍的影响，发现清除Mo-Mφ加重了大鼠CPB后脑损伤和认知功能障碍，这同海马局部促炎因子表达增加，巨噬细胞向M1方向极化相关；而通过组蛋白乙酰转移酶抑制剂p300i抑制Treg细胞的数目和活性能增加CPB后外周血中IFN-γ的水平，增加脑室脉络丛黏附分子VCAM-1的表达，减少大鼠海马组织炎性反应，减少Aβ蛋白的沉积，对认知功能具有促进作用；且抑制Treg细胞所产生的认知保护作用同Mo-Mφ细胞相关，清除Mo-Mφ后这种保护作用消失。这些结果阐明了CPB后外周适应性免疫抑制状态在POCD发生中的作用，为POCD的机制探索提供了新方向，并为随后通过免疫调节预防和治疗POCD提供了新的思路和理论依据。