脱落酸通过减轻海马突触损伤改善低氧诱导的小鼠学习记忆障碍

Abscisic acid alleviates hypoxia-induced learning and memory deficits by suppressing hippocampal synaptopathy in mice

目的:探索脱落酸对低氧诱导小鼠学习记忆障碍及海马突触损伤的保护作用。方法:3周龄C57BL/6雄性小鼠分为对照组、低氧组、低氧+脱落酸组,通过高原环境模拟舱低氧暴露2周(氧分压为72~75 mmHg)制备小鼠学习记忆损伤模型,低氧+脱落酸组给予脱落酸饮水干预(210 mg/L)。通过Y迷宫、水迷宫和条件恐惧实验检测小鼠学习记忆能力,使用高尔基染色法观察海马神经元树突棘形态,利用透射电镜技术观察海马突触超微结构,通过Western Blot法检测N-甲基-D-天门冬氨酸受体亚型1(NMDAR1)、N-甲基-D-天门冬氨酸受体亚型2A(NMDAR2A)、突触后致密蛋白-95(PSD-95)和核Dbf2相关激酶1/2(NDR1/2)表达。结果:与对照组相比,低氧组小鼠Y迷宫实验中进入新臂探索次数及停留时间比下降(P<0.05),水迷宫实验中平台周边探索距离、穿越平台次数、目标象限停留时间减少(P<0.05),条件恐惧实验中僵直时间减少(P<0.05),海马神经元树突棘密度降低(P<0.05),突触超微结构被破坏,NMDAR1、NMDAR2A、PSD-95和NDR1/2表达下降(P<0.05)。低氧+脱落酸组小鼠学习记忆能力改善,海马神经元树突棘密度增加(P<0.05),突触结构基本恢复正常,NMDAR1、NMDAR2A、PSD-95和NDR1/2表达升高(P<0.05)。结论:脱落酸可缓解低氧导致的学习记忆障碍、海马神经元树突棘密度减少以及突触结构损伤,并上调NMDAR1、NMDAR2A、PSD-95和NDR1/2蛋白表达。

Objective:To explore the protective effect of abscisic acid(ABA)on learning and memory impairment and hippocampal synaptopathy induced by hypoxia.Methods:Three-week-old C57BL/6 male mice were divided into control group,hypoxia group and hypoxia+ABA group.The animal model of learning and memory impairment was established by hypoxic exposure in a high-altitude simulation cabin(oxygen partial pressure=72~75 mmHg)for two weeks,and animals in hypoxia+ABA group were treated with ABA dissolved in drinking water(210 mg/L).The learning and memory ability of mice was tested by Y maze,Morris water maze and conditioned fear test.The dendritic spines density of hippocampal neurons was detected by Golgi staining.The synapse ultrastructure of hippocampal neurons was observed by transmission electron microscope.The protein expression levels of N-methyl-D-aspartate receptor type 1(NMDAR1),N-methyl-D-aspartate receptor type 2A(NMDAR2A),postsynaptic density-95(PSD-95)and nuclear Dbf2-related kinase 1/2(NDR1/2)were detected by Western Blot.Results:In the Y maze test,the percent age of entries and percent age of time in the novel arm of hypoxia-exposed mice were decreased compared with control group(P<0.05).In the Morris water maze test,the exploration distance around plaform,the plaform crossing times,and the distance in target quadrant were decreased in the hypoxia group(P<0.05).The freezing time of hypoxiaexposed mice was decreased in the conditioned fear test(P<0.05).Compared with control group,the hippocampal dendritic spines density of hypoxia-exposed mice was reduced(P<0.05).The hippocampal synaptic ultrastructure was injured and the hippocampal expressions of NMDAR1,NMDAR2A,PSD-95,and NDR1/2 were suppressed by hypoxic exposure(P<0.05).In the ABA treatment group,the memory ability was restored,and the density of neuronal dendritic spines was increased(P<0.05).The synaptic structure was nearly recovered,and the protein expressions were increased(P<0.05).Conclusion:ABA treatment can alleviate learning and memory deficits,hippocampal dendritic spine density decreasing and synaptopathy induced by hypoxic exposure,which may be related to changed expressions of NMDAR1,NMDAR2A,PSD-95,and NDR1/2.