亚慢性铝暴露致大鼠认知障碍的Sirt1-Keap1/Nrf2信号通路机制

Sirt1-Keap1/Nrf2 signaling pathway mechanism of cognitive dysfunction induced by subchronic aluminum exposure in rats

目的:观察亚慢性铝暴露对大鼠海马沉默信息调节因子1(silent information regulator 1,Sirt1)、Kelch样环氧氯丙烷相关蛋白(Kelch-like ECH-associated protein-1,Keap1)、核因子E2相关因子2(nuclear factor E2-related factor2,Nrf2)和微小RNA-128-3p(miR-128-3p)表达水平的影响,探讨miR-128-3p和Sirt1-Keap1/Nrf2信号通路在铝致大鼠认知障碍中的机制。方法:选取32只6周龄SPF级健康雄性SD大鼠,体重(190±20)g,按体质量随机分为4组:对照组、低剂量(10μmol/kg)组、中剂量(20μmol/kg)组和高剂量(40μmol/kg)组,每组8只。腹腔注射麦芽酚铝建立大鼠染毒模型。染毒结束后,Morris水迷宫实验来检验大鼠的学习记忆能力,Western blot检测大鼠海马组织中Sirt1、Keap1和Nrf2蛋白的表达,RT-qPCR检测海马组织miR-128-3p的表达,冰冻切片荧光染色检测大脑皮层活性氧(reactive oxygen species,ROS)水平。结果:(1)在定位巡航实验中,第3、4和5天铝暴露组大鼠的逃避潜伏期均显著高于对照组(P<0.05)。第6天,高剂量组与对照组和低剂量组相比穿越平台和平台象限的次数均减少(P<0.01)。(2)各组大鼠海马组织中Sirt1和Nrf2的相对表达水平随着麦芽酚铝暴露剂量的增加逐渐降低;Keap1的相对表达水平随着麦芽酚铝暴露剂量的增加逐渐升高,且高剂量组中miR-128-3p相对表达水平显著高于对照组(P<0.05)。(3)随着染毒剂量的增加,大鼠海马中谷胱甘肽过氧化物酶的含量逐渐减少,ROS水平逐渐升高。结论:亚慢性铝暴露可激活大鼠海马中miR-128-3p的表达,抑制Sirt1-Keap1/Nrf2通路,使Sirt1-Keap1/Nrf2通路不能被激活发挥抗氧化能力,大鼠的抗氧化系统失衡,导致大鼠神经细胞氧化损伤,表现为大鼠的认知功能降低。

AIM:To investigate the effects of subchronic aluminum exposure on the expression of silent infor-mation regulator(Sirt1),Kelch-like ECH-associated protein 1(Keap1),nuclear factor E2-related factor 2(Nrf2),and microRNA-128-3p(miR-128-3p)in the hippocampus of rats.Additionally,we aimed to explore the mechanism of miR-128-3p and the Sirt1-Keap1/Nrf2 signaling pathways in aluminum-induced cognitive impairment in rats.METHODS:Thirty-two healthy 6-week-old SPF male SD rats,weighing(190±20)g,were randomly divided into four groups based on body weight:control group,low-dose(10μmol/kg)group,medium-dose(20μmol/kg)group,and high-dose(40μmol/kg)group,with 8 rats in each group.The rat exposure model was established by intraperitoneal injection of maltol alumi-num.The Morris water maze test was used to assess the learning and memory ability of the rats.Western blot analysis was performed to measure the protein expression of Sirt1,Keap1 and Nrf2 in the hippocampus,while RT-qPCR was used to measure the expression of miR-128-3p in the hippocampus.The level of reactive oxygen species(ROS)in the cerebral cor-tex was detected using fluorescence staining in frozen sections.RESULTS:(1)In the positioning cruise experiment,the escape latency of the aluminum exposure group was significantly higher than that of the control group on the 3rd,4th,and 5th days(P<0.05).On day 6,the number of times the rats crossed the platform and the platform quadrant in the high-dose group was reduced compared to the control and low-dose groups(P<0.01).(2)The expression levels of Sirt1 and Nrf2 in the hippocampal tissues of all groups decreased gradually with increasing maltol aluminum exposure dose.The ex-pression level of Keap1 increased gradually with increasing maltol aluminum exposure dose.The expression level of miR-128-3p in the high-dose group was significantly higher than that in the control group(P<0.05).(3)The content of gluta-thione peroxidase in the hippocampus of rats decreased with increasing exposure dose,while ROS levels gradually in-creased.CONCLUSION:Subchronic aluminum exposure can increase the expression of miR-128-3p in the rat hippo-campus and suppress the Sirt1-Keap1/Nrf2 signaling pathway.This inhibition prevents the activation of the Sirt1-Keap1/Nrf2 signaling pathway,leading to a reduced antioxidant capacity.The imbalance in the antioxidant system in rats results in oxidative damage to nerve cells and a subsequent decline in cognitive function.