| Alzheimer’s disease (AD) is a kind of neurodegeneration disease. Its incidence raise year by year. The characteristics of AD patients are progressive impairments of memory, cognitive, language and behavior. In the end, AD patients lose self-care ability absolutely and totally rely on the caregivers.The pathogenesis of AD remains unknown. The amyloid hypothesis shows that the overexpression of amyloid β in brain will deposit and form senile plaques, and the neurotoxicity of senile plaques is the main cause of AD. At present, intracerebral ventricle injection of Aβ is still the common method to build the non-transgenic AD model. We injected neurotoxic segment Aβ25-35in the bilateral parococeles of littermate mice. We used group of sham and group of CSF injection in parococeles as control, and used Morris water maze to evaluate whether PS2had an impact on the mice’s ability of spatial learning and memory under the stimulation of AP25-35. The results showed that, compared with control, injection of Aβ25-35can impair the mice’s ability of spatial learning and memory, which was more serious in the PS2KO mice. The Nissl Dye results of murine brain section showed that, AP25-35can result in more serious neuron damage in PS2KO mice. The immunohistochemical results of murine brain section showed that, Aβ25-35can result in the proliferation of microglia and astrocytes. We measured the proinflammatory factor release in the cerebral homogenate and serum by ELISA, and we found that Aβ25-35can result in obvious higher level of IL-la and IL-1β releases, compared with control, and the IL-la release of PS2KO mice was a little higher than wild-type. Then we injected LPS in the bilateral parococeles of littermate wild-type and PS2KO mice. The results showed that LPS can also damage the ability of spatial learning and memory of mice, but the impact of PS2was not apparent.The results of immunohistochemical and immunofluorescent staining showed that there existed a higher level of P2X7receptors in cortex and hippocampus of PS2 KO mice, and the P2X7receptors had clear colocations with neurons and microglia. We also found that the injection of Aβ25-35in parococeles of mice can enhance the expression of P2X7in the brain of wild-type mice.We isolated and purified primary microglia from littermate wild-type and PS2KO mice to build in vitro cell model. Under the stimulation of Aβ25-35, the ATP release of primary microglia from PS2KO mice was increased, and the expression and secretion level of IL-la in PS2KO mice were both higher; By culturing microglia with100ng/mL LPS for2h to enable microglia activated before the experiment, we found that the ATP release of primary microglia from PS2KO mice under the stimulation of Aβ25-35was more apparent, and the transcription and protein level of cytokines (IL-1α, IL-1β and TNF-a) were also obviously higher than wild-type, and the expression and secretion of cytokines can be inhibited by the selective inhibitor of P2X7receptor, oATP. The results of Western blot showed that Aβ25-35can enhance the phosphorylation levels of transcription factor Erk, JNK and p38, which suggests that on the transcription level, AP25-35regulated the expression of cytokines through MAPK signal pathway.Above all, under the stimulation of exogenous Aβ25-35, microglia released signal molecule ATP and activated P2X7receptor through MAPK signal pathway to induce inflammation, and the deletion of PS2can result in a higher level of P2X7expression, which was involved in more serious inflammation and neuron damage in PS2KO mice, and in the end result in the more serious impairment of ability of spatial learning and memory. Thus, the dysfunction resulted from the deletion or mutation of PS2may regulate the immune response of microglia to AP through P2X7, and then had an impact on the pathogenesis of AD. |
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