| [objective] JNK is a member of the MAPK(mitogen-activated protein kinase) super family. The JNK signaling pathway can be activated by a variety of factors, such as cytokines, growth factors, oxidative stress,ect. And JNK is involved in the development and progression of many diseases in vivo. Recent studies indicate that the JNK signaling pathway is closely related to the mainly pathological changes in Alzheimer’s disease. Our previous research showed that activated JNK was significantly increased and coexisted with senile plaques, glial cells, and the phosphorylation of Tau proteins in APPswe/PS1 d E9 mice, suggesting that the activation of JNK may play an important role in the Alzheimer’s disease pathological damage. However, the critical role and molecular mechanism of JNK activation in AD is still unclear currently;Whether JNK specific inhibitor SP600125 would prevent the development of different pathological features in AD is still unknown. On the basis of previous research, this study describes the protective effect and molecular mechanisms of JNK inhibitor SP600125 in AD, whichmay provide a new drug target for prevention and treatment of Alzheimer’s disease.[Methods] In this study, nine-month-old female APPswe/PS1 d E9 mice and their nontransgenic wild-type littermates were randomized into 4 groups(n=8, each group): SP600125-treated APPswe/PS1 d E9 mice, vehicle-treated APPswe/PS1 d E9 mice, SP600125-treated wild-type mice and vehicle-treated wild-type mice. Each mouse with SP600125 treatment received SP600125 dissolved in 2% DMSO in PBS, whereas each mouse with vehicle treatment received an equal volume of 2% DMSO in PBS as control. Using passive avoidance test to assess all experiment animal’s ability of learning and spatial memory. The Application of Western Blots was used to detect the expression of JNK, phospho-JNK, synaptophysin SYP and density protein PSD-95 in all experiment animal brain. The immunohistochemistry method was used to detect the expression of activatived astrocytes and activatived microglia in mouse brain. The levels of interleukin-1beta(IL-1b), interleukin-6(IL-6) and tumor necrosis factor alpha(TNFa) were determined by ELISA method.[Results] 1. The passive avoidance task showed that acquisition latency in the acquisition trail did not differ among the 4 groups of mice. However, we demonstrated that the vehicle-treated APPswe/PS1 d E9 mice exhibited impaired contextual memory in the passive avoidance task, as indicated by decreased retention latency compared with vehicle- and SP600125-treated wild-type mice. In contrast,SP600125 treatment significantly improved the contextual memory impairment seen in the vehicle-treated APPswe/PS1 d E9 mice, as evidenced by longer retention latency. 2. The western blot results revealed that the total JNK expression remained unchanged among the 4 groups of mice. However, compared with the vehicle- and SP600125-treated wild-type mice, levels of phosphorylated JNK(p-JNK) were markedly increased in the cerebral cortex and hippocampus in the vehicle-treated APPswe/PS1 d E9 mice, while the levels of SYP and PSD-95 expression significantly declined in the cerebral cortex and hippocampus of vehicle-treated APPswe/PS1 d E9 mice. Compared with the vehicle-treated APPswe/PS1 d E9 mice, SP600125 treatment resulted in a dramatic decrease of p-JNK in both brain areas, and the levels of SYP and PSD-95 expression significantly increased inboth brain areas comparing with vehicle-treated APPswe/PS1 d E9 mice. 3. The immunohistochemical staining results showed that SP600125 treatment significantly reduced the percentage of brain area occupied by GFAP-positive astrocytes and Iba1-positive microglia relative to the vehicle-treated APPswe/PS1 d E9 mice. The further ELISA assay results showed that the levels of IL-1β,IL-6, and TNFa were dramatically decreased in the SP600125-treated APPswe/PS1 d E9 mice comparing with the vehicle-treated APPswe/PS1 d E9 mice.[Conclusion] SP600125 provides the effective treatment in APPswe/PS1 d E9 Mice through the pathway of inhibition JNK phosphorylation. SP600125 treatment resulted in dramatic reduction of p-JNK in the cerebral cortex and hippocampus areas of APPswe/PS1 d E9 mice. And SP600125-treated APPswe/PS1 d E9 mice markedly increased SYP and PSD-95 expression in both brain areas. Moreover, SP600125-treated APPswe/PS1 d E9 mice significantly reduced the activation of astrocytes and microglia, and decreased the expression of inflammatory cytokines IL-1β, IL-6, TNFα, etc. In conclusion, these results show that JNK inhibitor SP600125 can rescues cognitive deficits and reverses neuropathological changes such as neuroinflammation and synaptic loss in APPswe/PS1 d E9 Mice. SP600125 treatment is effective to prenvent the development and progression of AD, which may provide new drug target for treatment AD in clinical practice. |
