远隔缺血预处理对老年小鼠神经认知功能及小胶质细胞和突触后致密蛋白95的影响

Effects of remote ischemic preconditioning on neurocognitive function, microglia, and expression of PSD95 in aged mice

目的探讨远隔缺血预处理(RIPre)对老年小鼠神经认知功能及小胶质细胞和突触后致密蛋白95(PSD95)的影响。方法采用异氟醚麻醉+腹腔探查术建立围术期神经认知障碍(PND)模型。15月龄老年雄性C57BL/6小鼠,随机分为四组:对照组(C组)、缺血预处理组(RIPre组)、手术麻醉组(S组)和手术麻醉+缺血预处理组(S+RIPre组)。RIPre组和S+RIPre组于PND模型建立前行远隔缺血-再灌注,小鼠后肢血流阻断5 min后血液复流5 min,共重复缺血-复灌3次。术后第3天行旷场实验,第4、5天分别行条件性恐惧实验训练和测试。每组另外取6只小鼠于术后取海马组织,采用Western blot法检测术后第3天海马离子钙结合适配器分子1(Iba1)和PSD95蛋白含量,ELISA法检测术后第3天海马IL-6浓度。结果与C组比较,S组中央区域停留时间明显减少,僵直反应百分比明显降低,术后第3天海马IL-6浓度明显升高,PSD95蛋白含量明显降低,Iba1蛋白含量明显升高(P<0.05)。与S组比较,S+RIPre组中央区域停留时间明显延长,僵直反应百分比明显增加,术后第3天海马IL-6浓度明显降低,PSD95蛋白含量明显升高,Iba1蛋白含量明显降低(P<0.05)。结论RIPre可减轻异氟醚麻醉手术诱发的老龄小鼠神经认知功能障碍,其作用机制可能是RIPre抑制小胶质细胞过度激活,从而减轻对突触可塑性的损伤,并减弱海马神经炎症反应。

Objective To investigate the effects of remote ischemic preconditioning(RIPre) on neurocognitive function,microglia, and postsynaptic density protein 95(PSD95) in aged mice. MethodsIsoflurane anesthesia and laparotomy were applied to establish the PND model. RIPre was induced by three cycles of 5 min of limb ischemia, followed by 5 min of reperfusion. Fifteen months old male C57 BL/6 mice were randomly divided into four groups: control group(group C), RIPre group(group IPre), isoflurane anesthesia + laparotomy surgery group(group S), and isoflurane anesthesia + laparotomy surgery + RIPre group(group S+RIPre). The group RIPre and S+RIPre were subjected to RIPre before the establishment of the PND model. Open field test was performed on the third day after operation. Contextual and cued fear conditioning training and testing were exhibited on the 4 th and 5 th day after operation respectively. The hippocampus was harvested 1, 3, and 7 d after the surgery. Western blot was used to detect the expressions of ionized calcium binding adapter molecule 1(Iba1) and PSD95 on day 3. The levels of IL-6 in hippocampus on day 3 were measured by ELISA. Results Compared with group C, the retention time in the central area and the freezing time in the contextual fear conditioning test were significantly shortened, the concentration of IL-6 and Iba1 in the hippocampus was increased significantly, and the content of the PSD95 was decreased significantly in group S(P < 0.05). Compared with group S, the retention time in the central area and the freezing time in the contextual fear conditioning test were increased significantly, the concentration of IL-6 and Iba1 were decreased significantly, and the content of the PSD95 was increased significantly in group S+RIPre(P < 0.05). Conclusion RIPre can alleviate neurocognitive dysfunction in aged mice. Its mechanism may be related to the inhibition of microglia overactivation by RIPre, the reduction of damage to synaptic plasticity, and the attenuation of hippocampal neuroinflammatory.