孕哺期氯化镧暴露对子代大鼠学习记忆及细胞外信号调节激酶通路的影响

Effects of lanthanum chloride exposure during pregnancy and lactation on learning and memory and extracellular-signal-regulated kinases pathway in cerebral cortex of offspring rats

目的研究孕哺期氯化镧暴露对子代大鼠大脑皮质细胞外信号调节激酶(extracellular-signal-regulated kinases,ERK)、MAPK/ERK(MEK)及磷酸化水平和Raf-1表达的影响。方法将32只健康成年雌性Wistar大鼠随机分成对照和低、中、高剂量氯化镧组,与雄性成年Wistar大鼠按1∶1比例同笼交配。自受孕起对照组饮用蒸馏水,低、中、高剂量染镧组分别饮用含1.25、2.5、5.0 g/L LaCl3的蒸馏水溶液,并哺育其子代大鼠,至子代大鼠断乳后结束染毒。采用Morris水迷宫测试子代大鼠空间辨别性学习记忆能力,采用透射电镜法研究子代大鼠大脑皮质神经突触超微结构的改变,采用Western blot法测定子代大鼠大脑皮质Raf-1、MEK、ERK蛋白水平和MEK、ERK磷酸化水平。结果各染镧组仔鼠学习记忆能力与对照组相比明显下降,且随着染镧剂量的增加下降越来越明显。与对照组相比,各染镧组仔鼠大脑皮质神经突触超微结构出现异常改变,如突触活性带变短、突触后致密物变薄,其中5.0 g/L LaCl3组神经突触超微结构异常改变最为明显。各染镧组Raf-1蛋白水平低于对照组(P<0.05),且随着染镧剂量的增加而下降。各染镧组p-MEK和p-ERK蛋白水平低于对照组(P<0.05),且随着染镧剂量的增加而降低,其中5.0 g/L LaCl3组p-MEK和p-ERK蛋白水平与对照组、1.25和2.5 g/L LaCl3组比较均下降(P<0.05)。而各染镧组MEK和ERK蛋白水平与对照组比较无明显变化(P>0.05)。结论孕哺期氯化镧暴露导致子代大鼠大脑皮质中Raf-1表达、MEK和ERK磷酸化水平降低,这可能是氯化镧对神经系统毒性损伤的机制之一。

Objective To understand the effects of lanthanum chloride on the expression of Raf-1 and the phosphorylation of MEK and ERK in cerebral cortex of offspring rats.Methods Thirty-two healthy adult female Wistar rats were randomly divided into control and low,medium and high doses of lanthanum chloride group,and were mated with male adult Wistar rats in a ratio of 1∶1.The pregnant rats in control group drank distilled water,and the pregnant rats in low-dose,moderate-dose and high-dose groups drank distilled water containing 1.25,2.5,and 5.0 g/L LaCl3.These pregnant rats nurtured their offspring rats until the delactation of offspring rats.Morris water maze test was used to detect the spatial learning and memory abilities of offspring rats.Transmission electron microscopy was used to study the ultrastrcture changes of the synapses in cerebral cortex of offspring rats.Western blot was used to detect Raf-1,MEK,ERK protein levels and phosphorylation levels of MEK and ERK in the cerebral cortex of offspring rats.Results Compared with the control group,the spatial learning and memory abilities of the pups of each lanthanum group was significantly decreased with a dose dependent manner.Compared with the control group,there were abnormal changes in synaptic ultrastructure of cerebral cortex in the pups of each lanthanum group,for example,the synaptic active band became shorter and the postsynaptic density became thinner.The abnormal changes of synaptic ultrastructure in the high-dose lanthanum group were most obvious.The protein level of Raf-1 in each lanthanum group was lower than that in the control group with a dose dependent manner(P<0.05).The levels of p-MEK and p-ERK protein in each lanthanum group were lower than those in the control group(P<0.05)with a dose dependent manner.The levels of p-MEK and p-ERK in the high-dose lanthanum group were significantly lower than those in the control group,low-dose group and moderate-dose group(P<0.05).However,the levels of MEK and ERK protein in each lanthanum group had no significant changes compared with the control group(P>0.05).Conclusion The decrease of expression of Raf-1,phosphorylation of MEK and ERK in the cerebral cortex of offspring of rats exposed to lanthanum chloride may be one of the mechanisms through which lanthanum chloride may induce neurotoxicity.