六价铬对发育期大鼠海马神经细胞凋亡和学习记忆的影响

Effect of hexavalent chromium on apoptosis of hippocampal neurons and learning-memory function injury in developing rats

目的探讨六价铬(Cr^(6+))暴露对发育期大鼠海马CA1区神经细胞凋亡和学习记忆能力的影响及其作用机制。方法选择SPF级健康孕期SD大鼠12只,待仔鼠出生后将孕鼠随机分为对照(双蒸水)组、重铬酸钾溶液染毒组(染毒剂量分别为0.8、4和20 mg/kg·bw)。仔鼠出生后第1天起通过母乳染毒,进食阶段(21 d后)采用经口灌胃染毒,1次/d,连续染毒6个月。选取各组雄性子代大鼠进行实验。采用原子吸收分光光度计检测血液中Cr^(6+)的含量;Morris水迷宫试验评价学习记忆能力;苏木素-伊红(HE)染色观察海马CA1区神经元形态学变化;免疫组织化学检测Caspase-3以观察海马神经元凋亡数量;酶联免疫吸附试验(ELISA法)检测脑组织中炎症因子TNF-α、IL-1β的含量。结果重铬酸钾各染毒组大鼠的学习记忆能力均低于对照组(P<0.05);重铬酸钾各染毒组血液中Cr^(6+)的含量均高于对照组(P<0.05)差异有统计学意义;HE染色显示各染毒组海马CA1区神经元随染毒剂量增加呈现出不同程度的细胞间隙增宽,细胞排列稀疏紊乱,部分细胞体积减小等病理改变;免疫组化染色显示随着重铬酸钾浓度的增加,活化的Caspase-3阳性细胞数量明显增多;重铬酸钾各染毒组大鼠脑组织中TNF-α、IL-1β的含量均高于对照组(P<0.05),差异有统计学意义。结论 Cr^(6+)暴露损害大鼠学习记忆能力的作用机制可能与Cr^(6+)导致炎症因子增多,造成海马CA1区神经元凋亡有关。

Objective To explore the effect of hexavalent chromium on apoptosis of hippocampal CA1 neurons and learning-memory function injury in developing rats and its mechanisms. Methods Twelve healthy pregnant SD rats were selected at grade SPF. After offspring rats were born,pregnant rats were randomly divided into 4 groups： the control group（ distilled water）,the potassium dichromate solution exposure groups with different doses of 0. 8,4 and 20 mg/kg·bw. The offspring rats were exposed to breast milk at lactation stage,the feeding stage（ after 21 d） was treated by oral gavage,once a day. The treatments were conducted for six mouths. Male offspring rats were selected for experiment. The content of hexavalent chromium in blood was detected by atomic absorption spectrophotometer. Morris water maze test was used to evaluate the learning-memory ability. HE staining was used to observe the morphologic changes of hippocampal CA1 neurons,and the apoptosis quantity of hippocampal neurons in Caspase-3 was observed by Immunohistochemical detection. The contents of TNF-α and IL-1β in brain tissue were detected by ELISA. Result The learning-memory abilities of the potassium dichromate rats were lower than those of the control group（ P 0. 05）; the content of hexavalent chromium in blood of the potassium dichromate groups were higher than that of the control group（ P 0. 05）; HE staining showed the hippocampal CA1 region neurons present different degree of intercellular broadening with the increase of exposure dose,cell arrangement was sparse and disordered,partial cell volume decreased.Immunohistochemical staining showed that the number of activated Caspase-3 positive cells increased significantly with the increase of the potassium dichromate concentration; the expression levels of TNF-α and IL-1β in brain tissue of the potassium dichromate rats were higher than those in control group（ P 0. 05）. Conclusion The mechanism of hexavalent chromium exposure impairs learning and memory ability in rats,which may be associated with an increase in inflammatory factors by hexavalent chromium and cause the apoptosis in hippocampal CA1 neurons.