The Influence Of Mk2 And Il-6 Expression After β-amyloid Injection Into Hippocampus Of Rats

Background and objectiveAlzheimer's disease(AD) is an age-dependent neurodegenerative disorder. There's even no effective diagnosis and therapy currently.In the advanced countries,AD,which endangers people's health severely,becomes the fourth killer of mankind following heart disease,cancer and stroke.The main symptoms of AD are progressive dysmnesia,cognitive impairment and personality changes.The appearance of senile plaques,nerve fiber tangles(NFT),apoptosis and loss of neurons as well as inflammatory reaction in hippocampus,amygdala and cerebral cortex are the main pathological characteristics of AD.Most scholars considered that the formation of senile plaques by the accumulation ofβ-amyloid protein(Aβ) was one of the core pathological mechanisms of AD.Recent research suggests the theory that senile plaques which are formed by anomalous sediment of Aβare neural inflammatory plaques.The remarkable neurodegenerative change of plaques surrounding and the activation of microglia suggests that Aβmay be one of the reasons of causing the loss of neuron and inflammatory reaction in AD.Recent research suggests the activation of P38MAPK pathways has an important relationship with phlogistic changes in AD brain,which is confirmed by the pathological examination results both in AD patients and the animal models. However,at present,wether at home or abroad,the correlational study is seldom between AD and MAPK- activated protein kinase2(MAPKAPK2 or MK2) which is considered as one of several downstream kinases directly regulated by P38MAPK. To clear the function of MK2 in the inflammatory mechanism of AD,we microinject signally Aβ_1-42 in the hippocampus of rats in the experiments to build the animal model of AD.We observe the influence of Aβon the expression of MK2 and IL-6 and further study the relationship between them and the function of signal transduction system in the inflammatory mechanism in AD.Methods1.Building the animal model of AD We select the active and sensitive to electric shock ones from the healthy male SD rats aged 9-12 months old for the experiment by means of Y-shape maze test.These rats are randomized into three groups,namely the model group,the sham group and the normal group.The AD models are established by the injection of Aβ_1-42 into the bilateral hippocampus of rats by means of stereotaxic technique.Isometric physiological saline is injected into the sham group,and there's no process to the normal group.2.The test of the ethology Conduct the test in the Y-shape maze.(1)The learning test: It's the correct response that the rats escape from the starting region to the safe region after sufferring the electric shock.The frequency of the electric shock(namely trial frequency) required before reaching the state that all the response of the ten times continuous electric shock is correct is the ability of learning and obtaining.(2)The memory test:After the above-mentioned rats which meet the standard resting 24 hours,we carry on the memory test by the same way,and take the frequency of the correct response of the ten times continuous electric shock as the memory ability of every rat.3.Hematoxylin-Eosin(HE) and immunohistochemistry stain After HE and immunohistochemistry stain of paraffin sections of every group,we observe the morphological change and the expression of MK2 and IL-6 in the CA1 region of hippocampi.The statistical results which are shown by mean±standard deviation((?)±s) are analysed by SPSS13.0 statistical software with variance analysis and LSD.The significant level is a =0.05. 4.Western blot Observe the expression of MK2 of every group in the CA1 region of hippocampi.Ditto for the statistical treatment on the resultsResults1.The animal model of AD and the ethological test Two weeks after establishing the model,we carry on the test in the Y-shape maze.It's shown that the ability of the learning and memory of the model group rats dramaticdeclines with a statistical significance compared with the other two groups(p＜0.05);The ability of the learning and memory of the rats in the sham group decreases slightly with no statistical significance compared with the normal group(p＞0.05).2.The morphological features and the detection of MK2 and IL-6 By HE staining, hippocampal neuronal loss and denaturation with the microglia predominance in the CA1 region of hippocampi are observed in the model group.By immunohistochemistry stain,the number of MK2 and IL-6 imunoreactive neurons within the hippocampal CA1 region in the model group is obviously increased compared with the control groups(p＜0.05),and there is some correlation between IL-6 and MK2.The increasing expression of MK2(0.92±0.02) and the broadening band of MK2 are demonstrated by Western blot in hippocampus in the model group(p＜0.05)compared with the sham group(0.35±0.03) and the normal group (0.32±0.02).There's a statistical significance(p＜0.05).Conclusion1.Establish the animal model of AD successfully by the injection of Aβinto the bilateral hippocampus of rats.2.It's first proved that MK2 and IL-6 participate in pathologic process of AD in-vivo. Further make clear the function of the inflammatory reaction in the pathogenesis of AD,and what's more,we offer the theoretical principle for a new therapeutic target of AD.