邻苯二甲酸二丁酯围生期暴露对子代大鼠认知功能的影响及机制

Effect of di-n-butyl phthalate on the cognitive function in offspring rats after perinatal exposure and its mechanism

摘要:

目的：研究邻苯二甲酸二丁酯（di-n-butyl phthalate，DBP）暴露对子代大鼠的神经毒性并探索其可能机制。方法：妊娠SD大鼠随机分为DBP低剂量（n=10）和高剂量染毒组（n=10），分别给予DBP 50 mg/（kg·d）和200 mg/（kg·d）从妊娠第6天到产后23 d连续灌胃染毒，并予以同等体积玉米油灌胃为对照组（n=8）。除观察DBP染毒后孕鼠、子鼠的一般情况外，采用水迷宫实验检测子鼠认知功能、皮质脑电图记录脑电活动，观察海马形态变化，并以Western blot测定子代海马脑源性神经营养因子（brain-derived neurotrophic factor，BDNF）、神经肽Y（neuropeptide Y，NPY）、雌激素受体β（estrogen receptor β，ERβ）蛋白的表达情况。结果：与对照组比较，高剂量染毒组子鼠的体质量均低于同性别对照组（P<0.05）。DBP染毒后子鼠的逃避潜伏期延长（P<0.05），在目标象限的停留时间缩短（P<0.05），跨越平台次数减少（P<0.05）；染毒后子鼠δ波比例增加（P<0.05），θ、α波比例减少（P<0.05），δ波+θ波（慢波总和）比例增加（P<0.01）。HE染色显示，高剂量染毒组海马CA3区和DG区细胞层数稍减少，细胞密集度轻度降低。低剂量和高剂量染毒组子鼠海马BDNF、NPY、ERβ蛋白表达下降（P<0.01）。结论：DBP围生期染毒后可引起子代大鼠认知功能障碍，脑电节律慢化，其机制可能与BDNF、NPY、ERβ表达下调有关。

Abstract:

Objective：To study the neurotoxicity of di-n-butyl phthalate（DBP） exposure on offspring rats and explore the underlying mechanism. Methods：Pregnant SD rats were randomly divided into three groups；50 mg/（kg·d） DBP（low-dose treatment group，n=10），200 mg/（kg·d） DBP（high-dose treatment group，n=10） or vehicle only（control group，n=8） was given respectively by gavage once a day from gestation day-6（GD6） to postnatal day-23（PND23） consecutively. The general effects of DBP on pregnant and off－spring rats were observed. The cognitive function of the offspring was evaluated through Morris water maze. The brain activity was recorded with electrocorticography. The morphological changes of the hippocampus were observed via HE staining. The expression levels of brain-derived neurotrophic factor（BDNF），neuropeptide Y（NPY） and estrogen receptor β（ERβ） protein in the hippocampus were measured by Western blot analysis. Results：Compared with those of the same sex in the control group，the pups in the high-dose treatment group showed lower birth weight（P<0.05）. In the water maze test，the escaping latency of both treatment groups was longer than that of the control（P<0.05）. The pups in the treatment groups also spent less time in the target quadrant（P<0.05），and the num－bers of crossing the platform were fewer，too（P<0.05）. During EEG recording，the pups in DBP treatment groups were found to have more delta activity（P<0.05） and delta+theta activity（P<0.01），but less theta and alpha activity（P<0.05）. HE staining showed that in the high-dose treatment group，the cell number in CA3 and DG region of the hippocampus decreased slightly，and so did the cell density. Furthermore，the expressions of BDNF，NPY and ERβ protein in the hippocampus were significantly reduced in both treatment groups（P<0.01）. Conclusion：DBP could cause cognitive dysfunction and slower brain rhythms in offspring rats after perinatal exposure，which may be related to the down-regulated expressions of BDNF，NPY and ERβ.