胰淀素对阿尔茨海默病小鼠学习和记忆能力以及Akt信号通路的影响

Effect of amylin on learning and memory abilities and Akt signaling pathway in mice with Alzheimer’s disease

目的探讨胰淀素[也称为胰岛淀粉样多肽(islet amyloid polypeptide,IAPP)]对APP/PS1小鼠的学习和记忆能力,以及磷脂酰肌醇3-激酶/蛋白激酶B(PI3K/Akt)信号通路的影响。方法依据随机数字表法将APP/PS1小鼠分为阿尔茨海默病(Alzheimer’s disease,AD)组、IAPP组,每组10只。IAPP组小鼠腹腔内注射0.5μmol/L的IAPP,每日1次,AD组小鼠腹腔注射相同剂量的PBS。2组小鼠干预时间均为10周。采用Morris水迷宫检测小鼠学习记忆能力,HE染色观察小鼠脑海马组织病理形态变化,透射电镜观察小鼠海马神经元超微结构;生化方法检测小鼠海马组织谷胱甘肽过氧化物酶(GSH-Px)、丙二醛(MDA)水平、超氧化物歧化酶(SOD),酶联免疫吸附实验(ELISA)试剂盒检测炎症因子白细胞介素6(IL-6)、肿瘤坏死因子α(TNF-α)和白细胞介素1β(IL-1β)水平以及Aβ42的含量;Western blot检测PI3K/Akt蛋白表达水平。结果与AD组相比,IAPP组小鼠平台潜伏期减少(P<0.01),穿越平台次数和探索隐藏平台时间均增加(P<0.01),小鼠游泳速度无明显差异。HE染色结果显示与AD组相比,IAPP组小鼠海马组织神经细胞数目较多,排列整齐(P<0.05)。免疫组化结果显示与AD组相比,IAPP组小鼠海马组织Aβ蛋白降低(P<0.01)。与AD组相比,IAPP组小鼠海马组织氧化应激水平和炎症因子水平降低(P<0.01)。与AD组相比,IAPP组小鼠超微结构观察到神经元线粒体结构较为清晰、空泡化减少,微管、微丝排列较为整齐。与AD组相比,IAPP组小鼠p-PI3K/PI3K、p-Akt/Akt蛋白相对表达量均升高(P<0.01)。结论胰淀素能够减少海马组织氧化应激和炎症反应,改善AD小鼠学习记忆能力,并且促进PI3K/Akt信号通路的激活。

Objective To investigate the effects of amylin,also known as islet amyloid polypeptide(IAPP),on learning and memory abilities and the phosphatidylinositol 3-kinase/protein kinase B(PI3K/Akt)signaling pathway in APP/PS1 mice.Methods A total of 20 APP/PS1 mice were randomly divided into Alzheimer’s disease(AD)group and IAPP group,with 10 mice in each group.The mice in the latter group were given an intraperitoneal injection of 0.5μmol/L IAPP,and those of the former group received same dose of PBS.Both interventions were given once per day,for 10 weeks.Morris water maze test was used to measure the learning and memory abilities;HE staining was employed to observe the pathological changes in the hippocampus;Transmission electron microscopy was utilized to observe the ultrastructure of hippocampal neurons;Biochemical assay were conducted to detect the contents of glutathione peroxidase(GSH-Px),malondialdehyde(MDA)and superoxide dismutase(SOD)in hippocampal tissues;ELISA was applied to measure the levels of inflammatory factors such as IL-1β,IL-6,and TNF-αas well as content of Aβ42 in hippocampal tissues;And Western blotting was conducted to detect the expression of PI3K/Akt proteins.Results Compared with the AD group,significantly shorter platform latency(P<0.01),increased number of traversing the platform and longer time to explore the hidden platform(P<0.01)were observed in the IAPP group,but no such difference was seen in the swimming speed of the mice.HE staining displayed that the IAPP group had more and well-arranged nerve cells in the hippocampal tissue when compared with the AD group(P<0.05).Lower Aβprotein expression(P<0.01),reduced oxidative stress and decreased contents of inflammatory factors(P<0.01)in hippocampal tissue were observed in the IAPP group than the AD group.The IAPP group showed clearer structure of neuronal mitochondria,reduced vacuolization,and better arranged microtubules and microfilaments,and elevated expression of p-PI3K/PI3K and p-Akt/Akt proteins when compared with the AD group(P<0.01).Conclusion Amylin can reduce oxidative stress and inflammatory responses,improve learning and memory abilities in AD mice,and promote the activity of PI3K/Akt signaling pathway.