病原菌血流感染对阿尔茨海默病小鼠记忆力和海马锥体细胞的影响

Effects of bloodstream infection with pathogenic bacteria on the memory and hippocampal pyramidal cells of Alzheimer's disease mice

目的 探讨病原菌血流感染对阿尔茨海默病(AD)小鼠记忆力和海马锥体细胞的影响。方法 50只C57BL/6J雄性小鼠腹壁皮下注射D-半乳糖液[200 mg/(kg·d)]连续8周构建AD模型并于造模期间每周观测小鼠的一般状态及体质量;造模结束后均分为生理盐水(对照)组、大肠埃希菌组、铜绿假单胞菌组、肺炎克雷伯杆菌组、金黄色葡萄球菌组及白念珠菌组,对照组小鼠尾静脉注射生理盐水,其余病原菌感染组小鼠尾静脉注射低(1.5×107CFU/L)、中(1.5×108CFU/L)及高(1.5×109CFU/L)浓度的对应病原菌菌液,观察14 d,分别于注射后第1、2、3天及第1、2周测定各组小鼠的体质量及体温;观察结束后,于第15天采用Morris水迷宫实验检测各组小鼠逃逸潜伏期、游泳速度及穿越平台次数,水迷宫实验共进行6 d;实验结束后处死各组小鼠,取海马组织,采用苏木精-伊红(HE)染色观察海马组织学的改变。结果 小鼠于第8周体质量开始下降,且精神状况较造模初期明显下降;部分病原菌感染组小鼠逃避潜伏期较对照组延长(P<0.05),第5天肺炎克雷伯菌高浓度组小鼠水迷宫实验游泳速度较对照组下降(P<0.05);对照组小鼠海马CA1和CA3区神经细胞及皮层未见明显异常,白念珠菌组小鼠海马组织中发现少量凋亡细胞,肺炎克雷伯菌组、金黄色葡萄球菌组小鼠海马神经细胞轻度排列紊乱。结论 AD患者来源的病原菌经尾静脉血流感染可导致AD小鼠记忆力下降及海马锥体细胞的形态改变。

Objective To investigate the effects of bloodstream infection with pathogenic bacteria on memory and hippocampal pyramidal cells in mice with Alzheimer's disease(AD).Methods Fifty C57BL/6J male mice were injected subcutaneously with D-galactose solution[200 mg/(kg·d)]on the abdominal wall for 8 weeks to construct AD model.During the modeling period,the general state and body mass of mice were observed weekly.After modeling,mice were divided into normal saline(control)group,Escherichia coli group,Pseudomonas aeruginosa group,Klebsiella pneumoniae group,Staphylococcus aureus group and Candida albicans group.Mice in the control group were injected with normal saline through tail vein.Mice in other groups were injected with low(1.5×107 CFU/L),medium(1.5×108 CFU/L)and high(1.5×109 CFU/L)concentrations of corresponding pathogens through tail vein,and observed for 14 days.Body mass and body temperature of mice in each group were measured at the 1 th,2 th,and 3 th day and the 1 th and 2 th week after injection,respectively.After the observation,the escape latency,swimming speed and times of crossing the platform were detected by Morris water maze test on the 15 th day.The water maze experiment lasted for 6 days.After the experiment,mice in each group were sacrificed,and hippocampal tissues were collected and stained with hematoxylin-eosin(HE)to observe the changes of hippocampal histology.Results The body mass of the mice began to decline at the 8 th week,and the mental state of the mice decreased obviously compared with the early stage of modeling.The escape latency of some mice in the pathogenic bacteria infection group was longer than that in the control group(P<0.05),and the swimming speed of mice in the high concentration Klebsiella pneumoniae group in the water maze experiment on the 5th day was significantly decreased compared with that in the control group(P<0.05).No obvious abnormalities were found in the hippocampal CA1 and CA3 nerve cells and cortex of mice in the control group,while a small number of apoptotic cells were found in the hippocampal tissue of mice in the Candida albicans group in the experimental group,and the hippocampal nerve cells were slightly disordered in the Klebsiella pneumoniae group and Staphylococcus aureus group.Conclusion Caudal vein infection from AD patients result in memory loss and morphological changes of hippocampal pyramidal cells in AD mice.