摘要
目的 探讨蛋白酶体抑制剂MG132对慢性缺氧所致小鼠记忆功能损伤的作用及其机制.方法 (1)利用低氧工作站构建小鼠中脑多巴胺能神经元MN9D细胞缺氧损伤模型.将MN9D细胞分为常氧组及缺氧12 h、24 h和48 h组,观察缺氧对MN9D细胞中酪氨酸羟化酶(TH)、泛素的K48链(Ub-K48)和Ub-K63表达的影响;将MN9D细胞分为常氧组、缺氧组、缺氧+MG132(25、50、100、200)μmol/L组,观察MG132对缺氧细胞中上述蛋白表达的影响.(2)利用低压舱建立低压缺氧小鼠记忆功能损伤模型.将C57小鼠随机分为常氧组、缺氧3 d组、缺氧21 d组,每组10只,观察低压低氧对小鼠中脑黑质致密部(SNc)TH、Ub-K48和Ub-K63表达的影响;将小鼠随机分为常氧组、缺氧21 d组、缺氧21 d+MG132组,每组8只,观察MG132对缺氧所致小鼠空间记忆损伤的影响.(3)采用Western blotting检测不同缺氧时长及MG132预处理再低氧处理的MN9D细胞中TH、Ub-K48和Ub-K63的蛋白表达水平;采用新物体识别测试检测各组小鼠记忆功能,免疫荧光染色检测SNc区TH阳性免疫反应面积百分比,Western blotting检测小鼠SNc区TH、Ub-K48和Ub-K63表达水平.结果 (1)与常氧组比较,缺氧24 h组MN9D细胞中Ub-K48和Ub-K63表达水平增高(P<0.05),TH表达水平降低(P<0.05);各缺氧组Ub-K48/TH和Ub-K63/TH表达水平均增高(P<0.05).与缺氧组比较,缺氧+MG132 100 μmol/L组和缺氧+MG132 200 μmol/L组MN9D细胞中Ub-K48/TH和Ub-K63/TH表达水平降低(P<0.05).(2)与常氧组比较,缺氧3 d组和缺氧21 d组小鼠中脑SNc区TH表达水平降低(P<0.001),Ub-K48/TH和Ub-K63/TH表达水平升高(P<0.05);缺氧21 d组小鼠新物体识别指数降低(P<0.01),SNc区多巴胺能神经元TH阳性免疫反应面积百分比降低(P<0.05).与缺氧21 d组比较,缺氧21 d+ MG132组小鼠新物体识别指数升高(P<0.01).结论 蛋白酶体抑制剂MG132可改善慢性缺氧所致小鼠记忆损伤,其机制可能与抑制Ub-K48和Ub-K63,上调多巴胺能神经元TH表达有关.
Abstract
Objective To investigate the effect and mechanism of proteasome inhibitor MG132 on memory impairment induced by chronic hypoxia in mice.Methods(1)A hypoxic model of the mouse midbrain dopaminergic neuron cell line MN9D was established using a hypoxia workstation.To observe the effects of hypoxia on the expression of TH,Ub-K48 and Ub-K63,MN9D cells were divided into normoxia group and hypoxia(12 h,24 h and 48 h)groups.To observe the effects of MG132 on the expression of the above-mentioned proteins,MN9D cells were divided into normoxia group,hypoxia group and hypoxia + MG132(25,50,100,200 μmol/L)group.(2)A mouse model of memory impairment was established using a hypobaric chamber.To observe the effects of hypobaric hypoxia on the expression of TH,Ub-K48 and Ub-K63 in the substantia nigra compacta(SNc)of mice,thirty C57BL/6 mice were randomly and equally divided into normoxia group and hypobaric hypoxia(3 d and 21 d)groups,10 in each group.To observe the effects of MG132 on spatial memory impairment induced by hypobaric hypoxia,twenty-four C57BL/6 mice were randomly and equally divided into normoxia group,hypobaric hypoxia 21 d group and hypobaric hypoxia 21 d+MG132 group,8 in each group.(3)The protein expression levels of TH,Ub-K48,and Ub-K63 in MN9D cells which were either subjected to different durations of hypoxia treatment or pre-treated with MG132 prior to hypoxia treatment were detected using Western blotting(WB).The novel object recognition test was used to detect the memory function of mice.Immunofluorescence was used to detect the proportion of positive immunoreactive area of TH response in the SNc region.The expression levels of TH,Ub-K48,and Ub-K63 in the SNc region were detected by WB.Results(1)Compared with normoxia group,MN9D cells in hypoxia 24 h group showed increasing expression of Ub-K48 and Ub-K63(P<0.05),and decreasing expression of TH(P<0.05),and MN9D cells in all hypoxia groups showed increasing expression of Ub-K48/TH and Ub-K63/TH(P<0.05).Compared with hypoxia group,MN9D cells showed decreasing expression of Ub-K48/TH and Ub-K63/TH in hypoxia + MG132 100 umol/L group and hypoxia + MG132 200 umol/L group(P<0.05).(2)Compared with the mice in normoxia group,mice in 3 d and 21 d hypobaric hypoxia groups showed decreasing expression of TH(P<0.001),and increasing expression of Ub-K48/TH and Ub-K63/TH(P<0.05)in the SNc region.Compared with normoxia group,the mice in 21 d hypobaric hypoxia group showed a lower new object recognition index(P<0.01),and the proportion of positive immunoreactive area of TH response in the SNc region(P<0.05).Compared with 21 d hypobaric hypoxia group,the mice in hypobaric hypoxia 21 d+MG132 group showed a higher new object recognition index(P<0.01).Conclusion The proteasome inhibitor MG132 could alleviate the memory impairment induced by chronic hypoxia in mice,and its mechanism may be related to the inhibition of Ub-K63 and Ub-K48,which in turn upregulates expression of TH in dopaminergic neurons.
国家科技期刊平台
NSTL
万方数据