孕哺期至成年前铝暴露对子鼠空间学习记忆能力和海马miR-132转录的影响
Effect of continuous aluminum exposure from maternal pregnancy and lactation period to offspring adulthood on spatial learning and memory, and miR-132 expression in hippocampus of offspring rats
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摘要:
目的 探讨孕哺期至成年前持续铝暴露对子鼠空间学习记忆和海马miR-132转录的影响。
方法 将12只清洁级健康SD孕鼠随机分为3组，每组4只。各组饮水中氯化铝浓度分别为0、600、1 000 mg/L，即对照组、低铝组、高铝组。母鼠从妊娠第0天至子鼠出生第21天染毒。从每组中随机选择8只子鼠（4雌4雄，同一窝别雌雄比为1:1）延续同组剂量继续染毒至成年（出生第90天），每2周称一次体重，子鼠处死前收集24 h尿液，Morris水迷宫实验检测空间学习记忆能力。处死后光镜观察海马组织的病理变化，采用石墨炉原子吸收法测定尿铝和脑铝含量，用实时荧光定量PCR方法检测海马组织中miR-132转录水平。
结果 与对照组比较，高铝组子鼠出生后0~12周体重均降低（均P < 0.01）。水迷宫结果显示：与对照组相比，染毒组在第3天和第4天逃避潜伏期延长（均P < 0.01），高铝组子鼠首次达台时间延长及穿越平台次数减少（P < 0.05，P < 0.01）。低铝组、高铝组子鼠尿铝和脑铝水平分别为（11.84±1.03）、（16.32±1.32）μg/L，（12.69±0.43）、（16.61±0.93）μg/g，均高于对照组（均P < 0.01）。与对照组比较，染毒组海马神经细胞出现核固缩，染色加深，数量减少和排列紊乱变形等病理改变；miR-132在低铝组、高铝组中的相对转录水平分别为1.48±0.35、1.62±0.38，与对照组（1.00±0.12）比较，miR-132在染毒组中转录水平均升高（P < 0.05，P < 0.01）。
结论 持续铝暴露损害子鼠的空间学习记忆能力，可能与海马组织中的miR-132转录水平升高有关。
Abstract:Objective To explore the potential effects of continuous aluminum exposure from maternal pregnancy and lactation period to offspring adulthood on spatial learning and memory, and miR-132 expression in hippocampus of offspring rats.
Methods Twelve pregnant SD rats were randomly divided into three groups receiving AlCl3 exposure via drinking water at 0, 600, and 1 000 mg/L (control group, low aluminum group, and high aluminum group), respectively. The pregnant rats were treated from pregnant day 0 to postnatal day (PND) 21 of the offspring rats. From PND22 to PND90 (adulthood), eight offspring rats (four males and four females) from each group were treated with the same protocol as the mother rats. The offspring rats were weighed every two weeks, tested in Morris Water Maze, and caged to collect 24-hour urine samples before euthanasia. Then hippocampus samples were collected from the euthanized rats to observe the pathological changes by HE staining. The levels of aluminum in urine and brain were detected by graphite furnance atomic absorption spectrometry. MiR-132 expression levels in hippocampus were measured by real-time PCR.
Results Compared with the control group, the body weights of offspring 0-12 weeks after birth in the high aluminum group were decreased (Ps < 0.01). In the Morris Water Maze test, on the third day and fourth day the escape latency in the exposure groups were increased (Ps < 0.01), the time of first arriving platform increased and the number of passing platform decreased in the high aluminum group compared with the control group (P < 0.05, P < 0.01). The levels of aluminum in urine in the two exposure groups were (11.84±1.03) μg/L and (16.32±1.32) μg/L, and the levels in brain were (12.69±0.43) μg/g and (16.61±0.93) μg/g, all higher than those in the control group (Ps < 0.01). Compared with the control group, the exposure groups showed decreased hippocampus neurons with nuclear pyknosis, hyperchromatic nucleus, and deformation of cells. MiR-132 expression levels in the two exposure groups were 1.48±0.35 and 1.62±0.38, respectively, much higher than that in the control group (1.00±0.12) (P < 0.05, P < 0.01).
Conclusion Continuous exposure to aluminum could impair spatial learning and memory ability of offspring rats, and increased expression of miR-132 in hippocampus may be associated with this phenomenon.
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