目的 观察二氢杨梅素（dihydromyricetin,DHM）缓解低压低氧暴露诱导记忆能力损伤的作用,并探讨其作用机制。方法 雄性 Sprague Dawley（SD）大鼠 48 只随机分为常氧组（NOR）、常氧干预组（NOR+DHM）、低氧组(HYP) 、低氧干预组(HYP+DHM),每组 12 只。采用低压氧舱模拟海拔6000 m处低压低氧环境,低氧组与低氧干预组大鼠每天暴露低氧环境23 h,连续7 d,干预组灌胃DHM 100 mg/（kg·d）,常氧组和低氧组给予同等体积蒸馏水灌胃作为对照。所有大鼠通过Morris水迷宫测试检测低氧暴露后的记忆能力。测试结束后取大鼠脑组织,透射电镜观察分析海马神经元突触超微结构,蛋白免疫印迹实验检测分析突触结构相关蛋白及BDNF信号通路蛋白的表达水平。结果 HYP组大鼠在水迷宫目标象限所花费的时间和游动的路径长度显著低于NOR组（P<0.05）,而HYP+DHM组大鼠显著高于HYP组。透射电镜观察显示：与NOR组相比,HYP组大鼠海马CA1区神经元的突触后致密区较薄且少,神经元线粒体较大、肿胀,出现空泡结构且观察到嵴结构部分丢失,而HYP+DHM组相对于HYP组的神经元结构明显改善。蛋白免疫印迹检测分析显示：与NOR组相比,HYP组PSD95和SYP的表达减少（P<0.05）,HYP+DHM组表达显著增加（P<0.05）;与NOR组相比,HYP组BDNF、TrkB蛋白表达水平明显下降（P<0.05）,PI3K、Akt蛋白磷酸化水平显著性下降（P<0.05）;而DHM干预后BDNF、TrkB蛋白和PI3K、Akt蛋白磷酸化水平均显著性升高（P<0.05）。结论 低压低氧急性暴露会损伤记忆能力;DHM可通过调节BDNF信号通路保护海马神经元突触结构形态,有效缓解低压缺氧暴露诱导的记忆损伤。
Abstract
Objective To study the effect of dihydromyricetin (DHM) on memory impairment induced by hypobaric hypoxia and its mechanism. Methods Fourty-eight male Sprague Dawley rats were randomly divided into normoxia group (NOR), normoxia plus dihydromyricetin group (NOR+DHM), hypoxia group (HYP) and hypoxia dihydromyricetin group (HYP+DHM), with 12 rats in each group. A hypobaric oxygen chamber was used to simulate hypobaric hypoxia environment equivalent to altitude 6000 m. The rats in the HYP group and HYP+DHM group were exposed to hypobaric hypoxia environment for 23 hours every day. The NOR+DHM and HYP+DHM groups were given 100mg/(kg·d) DHM by gavage, and the NOR group and HYP group were given the same volume of distilled water as the control group. All rats were tested for their memory ability after hypobaric hypoxia using the Morris water maze probe test. After the second probe test, the brains of the rats were further analyzed. The ultrastructure changes of synapse in the hippocampus were observed by transmission electron microscopy. The expressions of synaptic structure-related proteins and BDNF signaling pathway proteins were detected and analyzed by Western blots. Results The rats in the HYP group spent significantly less time and path length in the target quadrant than those in the NOR group (P<0.05), while the rats in the HYP+DHM group spent significantly more time and path length in the target quadrant than those in the HYP group. The observation by transmission electron microscope showed that the postsynaptic density of neurons in hippocampal CA1 region in the HYP group was thinner and less, and the mitochondria of the neurons were larger and swollen with vacuolar structure and partial loss of ridge structure was observed. The postsynaptic density was thicker in the HYP+DHM group than that in the HYP group, and the mitochondrial ridge structure was clearer than that in in the HYP group. Western blots analysis showed that compared with the NOR group, the expressions of PSD95 and SYP in the HYP group were decreased (P<0.05), while the expressions of PSD95 and SYP in the HYP+DHM group were significantly increased (P<0.05). Compared with the NOR group, the protein expression levels of BDNF and TrkB in the HYP group were significantly decreased (P<0.05), and the phosphorylation levels of PI3K and Akt in the HYP group were significantly decreased (P<0.05). After DHM intervention, the protein expression levels of BDNF and TrkB and the phosphorylation levels of PI3K and Akt in the HYP+DHM group were significantly increased (P<0.05). Conclusion Acute exposure to hypobaric hypoxia can impair memory ability. DHM can protect the synaptic structure and morphology of hippocampal neurons via the BDNF signaling pathway, and effectively alleviate memory impairment induced by hypobaric hypoxia exposure.
关键词
二氢杨梅素 /
低压低氧 /
大鼠 /
记忆损伤 /
脑源性神经营养因子 /
突触可塑性
Key words
dihydromyricetin /
hypobaric hypoxia /
rat /
memory impairment /
brain-derived neurotrophic factor /
synaptic plasticity
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基金
国家自然科学基金青年项目（No.81901911）
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