吡格列酮对淀粉样β蛋白片段1-42引起的大鼠海马c-Jun氨基端激酶信号传导通路改变的作用

目的探讨吡格列酮(Pio)对淀粉样β蛋白片段1-42(Aβ1-42)所致大鼠海马神经细胞损伤保护作用的信号传导机制。方法 SD大鼠左侧脑单次icv给予5μlAβ1-422.0mmol.L-1制备大鼠痴呆模型。65只大鼠随机分为正常对照组、Aβ1-42模型组及Pio20,40和80mg.kg-1组;Pio组大鼠在icv单次给予Aβ1-42前24h先ig给予Pio20,40及80mg.kg-1,每天一次,连续给药7d。Western印迹法检测海马CA1区磷酸化丝裂原激活蛋白激酶激酶4(MKK4)、磷酸化c-Jun氨基端激酶1(JNK1)和磷酸化c-Jun的蛋白表达水平;应用激光共聚焦显微镜观察磷酸化JNK在小胶质细胞表达部位。结果与正常对照组比较,Aβ1-42模型组大鼠icv给予Aβ1-42后,可引起海马CA1区磷酸化的MKK4,JNK1和c-Jun的表达明显增加(P<0.01);与Aβ1-42模型组比较,Pio20,40和80mg.kg-1可剂量依赖性地对抗Aβ1-42引起的磷酸化MKK4,JNK1和c-Jun表达的增加(P<0.01),Pio40mg.kg-1使磷酸化MKK4蛋白与总量MKK4蛋白之比从Aβ1-42模型组的1.02±0.35降低到0.44±0.06,磷酸化JNK1从0.94±0.17降低到0.55±0.05,磷酸化c-Jun从4.64±0.41降低到2.48±0.12(P<0.01)。荧光免疫组织化学双染,激光共聚焦显微镜观察结果显示,磷酸化的JNK主要在小胶质细胞表达。结论 Pio通过抑制小胶质细胞内JNK激酶信号传导通路的活化,对抗Aβ1-42引起的海马神经细胞损伤。

Effects of pioglitazone on amyloid beta-protein fragment 1-42-induced c-Jun N-terminal kinase signal pathway in hippocampus of rats

OBJECTIVE To observe neuroprotective effects and protective mechanisms of pioglitazone (Pio) on amyloid beta-protein fragment 1-42 (Aβ_1-42)-induced neurotoxicity in rat hippocampus. METHODS Sixty-five SD rats were randomly divided into 5 groups: normal control group, Aβ_1-42 model group and Pio 20, 40 and 80 mg·kg^-1 groups. Before rats in Pio groups were icv given 5 μl Aβ_1-42 2.0 mmol·L^-1 24 h, they were ig given Pio 20, 40 and 80 mg·kg^-1, once a day, for 7 d. Rats in normal control group were maintained with DMSO for 6 d. After 7 d, Western blotting was used to determine the expression of phospho-mitogen-activated protein kinase kinase 4 (p-MKK4), p-c-Jun and phospho-c-Jun N-terminal kinase 1 (p-JNK1). Immunohistochemistry and double labeling immunofluorescence combined with laser scanning confocal microscope were used to investigate the expression of p-JNK and OX-42 protein in hippocampal CA1 areas. RESULTSCompared with normal control group, p-MKK4, p-JNK1 and p-c-Jun in Aβ_1-42 model group were significantly increased(P<0.01). Compared with Aβ_1-42 model group, Pio 20, 40 and 80 mg·kg^-1 could dose-dependently reverse these activated changes induced by Aβ_1-42. Pio 40 mg·kg^-1 could significantly decrease Aβ_1-42-induced changes in the density ratio of p-MKK4 to total MKK4 from 1.02±0.35 to 0.44±0.06, that of p-JNK1 to total JNK1 from 0.94±0.17 to 0.59±0.03，and that of p-c-Jun to total c-Jun from 4.64±0.41 to 2.48±0.12 (P<0.01). The result of p-JNK and OX-42 expressions examined by double labeling immunofluorescence combined with laser scanning confocal microscope showed that most of p-JNK immunoreactivity co-localized with microglia-speccific protein OX-42. CONCLUSION Pio prevents Aβ_1-42-induced neurotoxicity through suppressing the expression of phosphorylated JNK signal pathway in rat microglial cells.