海马F-肌动蛋白聚合在老年小鼠围术期神经认知障碍中的作用

Roles of hippocampal F-actin polymerization in aged mice with perioperative neurocognitive disorders

目的研究海马F-肌动蛋白聚合在老年小鼠围术期神经认知障碍(PND)中的作用并探讨其可能的作用机制。方法20月龄雄性C57BL/6小鼠72只,随机均分为四组:对照+溶质组(CV组)、对照+jasplakinolide(F-肌动蛋白聚合诱导剂)组(CJ组)、模型+溶质组(PV组)及模型+jasplakinolide组(PJ组),每组18只。采用异氟醚麻醉+腹腔探查术建立PND模型。手术麻醉开始前2 h和行为学训练后即刻左侧脑室注射jasplakinolide(0.5μg/1.5μl)(CJ组和PJ组)或等容量溶质(97.5%生理盐水+2.5%DMSO)(CV组和PV组)。手术麻醉后第2天行场景性条件恐惧实验训练、第3天行场景性条件恐惧实验测试僵直时间百分比。行为学测试结束后90 min取脑组织。采用Western blot检测海马F-actin、G-actin、突触体和神经元膜上GluR1和GluR2含量;采用高尔基染色检测海马CA1区神经元树突棘数目和分型;采用免疫荧光检测海马CA1区c-fos数目。结果条件性恐惧实验训练阶段,四组僵直时间百分比差异无统计学意义。与CV组比较,PV组在手术麻醉后第3天场景性条件恐惧实验测试中的僵直时间百分比明显下降,海马F-actin/G-actin数值、突触体和神经元膜上GluR1和GluR2含量明显降低,CA1区神经元树突棘总数、丝状伪足和蘑菇型数目以及c-fos数目明显减少(P<0.05)。与PV组比较,PJ组僵直时间百分比明显上升,海马F-actin/G-actin数值、突触体和神经元膜上GluR1和GluR2含量明显升高,CA1区神经元树突棘总数、丝状伪足和蘑菇型数目以及c-fos数目明显增多(P<0.05)。结论F-肌动蛋白聚合诱导剂jasplakinolide可改善老年小鼠术后的场景性恐惧记忆损害,其作用机制可能与促进树突棘重塑和AMPA受体转运上膜,增加神经元活动有关。

Objective To understand the roles of hippocampal F-actin polymerization on perioperative neurocognitive disorders(PND)in aged mice,and then to explore the potential underling mechanisms.Methods The PND model was established by isoflurane anesthesia+laparotomy surgery.Seventy-two male C57BL/6 mice aged 20 months old were randomly divided into four groups:control+vehicle group(group CV),control+jasplakinolide group(a filamentous-actin stabilizer,group CJ),model+vehicle group(group PV),and model+jasplakinolide group(group PJ).Mice were subjected to an administration of Jasplakinolide(0.5μg/1.5μl)or isochoric vehicle(97.5%saline+2.5%DMSO)via left lateral ventricle injection,which was given 2 hours before the anesthesia and immediately after training session of contextual fear conditioning test.The training and the test sessions of contextual fear conditioning test were exhibited 2 days and 3 days after operation,respectively.The brain tissues were harvested 90 minutes after the last behavioral test.Western blot was used to detect the expressions of hippocampal F-actin,G-actin,GluR1 and GluR2 in synaptosome and on membrane.Golgi staining and immunofluorescence staining were applied to observe the changes of dendritic spines or the number of c-fos in hippocampal CA1 region,respectively.Results In the training session of fear conditioning test,no significantly differences were calculated in the percentage of freezing time among the four groups.Compared to group CV,the percentage of freezing time was dramatically decreased,the expressions of F-actin/G-actin ratio,GluR1 and GluR2 in hippocampal synaptosome and membrane were significantly reduced,the total number of dendritic spine as well as the number of filopodia-and mushroom-spine,and the number of c-fos in CA1 region were apparently decreased in group PV(P<0.05).Relative to the group PV,the above changes were reversed by jasplakinolide treatment(P<0.05).Conclusion Jasplakinolide,a filamentous-actin stabilizer,can improve the deficits of contextual fear memory in PND-aged mice via facilitating hippocampal F-actin polymerization,and then increase dendritic spine remodeling and AMPA receptor membrane delivery,which augments the neuronal activities.