海马背侧注射β-淀粉样蛋白25～35激活胶质细胞和 p38丝裂原活化蛋白激酶诱导神经元凋亡

Ativation of gliacytes and p38 mitogen-activated protein kinase and possible mechanism of neuronal apoptosis induced by Aβ_(25-35) injection into hippocampus in rats

目的：探讨海马背侧注射β-淀粉样蛋白25～35（ Aβ25～35）后胶质细胞与p38丝裂原活化蛋白激酶（p38MAPK）激活的关系，及Aβ25～35诱导神经元凋亡的可能机制。方法采用免疫组织化学及免疫印迹方法观察海马背侧注射Aβ25～35后不同时段小胶质细胞（ MG）、星形胶质细胞（ AS）的激活和磷酸化p38MAPK（ p-p38MAPK）在海马组织中的表达；酶联免疫吸附法检测肿瘤坏死因子-α（ TNF-α）及白细胞介素-1β（ IL-1β）在海马组织中的含量；Nissl染色法观察海马神经元存活；TUNEL染色观察海马神经元凋亡。结果注射Aβ25～35后海马内抗特异性标记小胶质细胞（ox-42）、胶质原纤维酸性蛋白（GFAP）、和p-p38MAPK的表达与TNF-α、IL-1β的含量同步增加，于7d达到高峰，而Nissl阳性神经元数量逐渐减少，TUNEL阳性神经元数量则逐渐增多，亦于7d达到高峰。结论海马背侧注射Aβ25～35可能通过激活胶质细胞和p38MAPK，使TNF-α，IL-1β含量增加导致海马神经元凋亡。

Objective To investigate the relationship between activation of gliacytes , mitogen-activated protein kinase （p38MAPK） and neuronal apoptosis after microinjecting aggregated Aβ25-35 into hippocampus.Methods The model was established by using stereotaxic technique to inject 10μg aggregated Aβ25-35 into dorsal hippocampus in rats .The rats were grouped as the control , vehicle and model groups .Immunohistochemistry and Western blotting were used for detection of activation of microglia（MG）, atrocytes （AS） and expression of p-p38MAPK in the hippocampus.ELISA was used to evaluate the level of TNF-αand IL-1β.The survival neurons were observed by Nissl staining and the apoptotic neurons were identified by tunnel staining .Results Expression of ox-42, GFAP, p-p38MAPK were up-regulated in hippocampus, as well as TNF-α、IL-1β, which reached a highest value on the 7th day after injection of Aβ25-35.However, the number of neuron with Nissl positive decreased gradually , and the tunnel positive neurons increased highly and reached a peak value on the 7th day.There were significant differences between the control and vehicle group （ P 〈0.01）. Conclusion Apoptosis of the neuron caused by Aβ25-35 injection may result from activation of gliacytes , p38 MAPK and increase of TNF-αand IL-1βlevel.