| Objective : Alzheimer’s disease(AD)is an age-related irreversible neurodegenerative disease whose incidence is increasing worldwide.Its clinical manifestations are mainly memory loss and cognitive dysfunction.The patient’s independent living ability is lost in the late stage,and the quality of life is seriously degraded.At present,AD is clinically incurable.The treatment is to reduce the production of amyloid β-protein(Aβ)and accelerate the clearance of Aβ,which can slow or delay the occurrence and development of the disease.In recent years,domestic and foreign studies have shown that exercise intervention as a non-pharmacological treatment has a certain effect and efficacy on the treatment of AD,and has no side effects.The pathogenesis of AD is complex,and oxidative stress is one of the important pathogenic factors driving AD.Therefore,research to improve the body’s ability to resist oxidative stress is an important direction to delay the AD process.Nuclear factor E2 related factor 2(Nrf2)is a member of the basic leucine zipper(b ZIP)family.Nrf2 is a major switch regulating human endogenous antioxidant defense systems,and activation of Nrf2 and its related pathways protects against neurodegenerative diseases.There is no systematic study on the molecular mechanism of Nrf2 and related signaling molecules in brain tissue of AD.This study intends to explore the effect of moderate load exercise on the learning and memory ability of AD model rats,as well as the role and molecular mechanism of nrf2-related pathway in the regulation of anti-oxidative stress in AD,which may open up new ideas for the study of the pathogenesis and treatment of AD.Methods:In this study,60 healthy male SD rats were selected as subjects,2.5 months old,and randomly divided into 3 groups according to body weight.There were 20 rats in the normal control group(NC group),20 mice in the Alzheimer’s disease control group(AC group),and 20 mice in the Alzheimer’s disease exercise group(AE group).Normal control group: Rats were intraperitoneally injected with normal saline daily at a dose of 160 mg/Kg,and were routinely bred for 8 weeks.AD model control group: Daily morning rats were intraperitoneally injected with D-galactose and aluminum trichloride at doses of 120 mg/kg and 40 mg/kg,respectively,for 8 weeks.AD model training group: D-galactose(120mg/kg)and aluminum trichloride(40mg/kg)were injected daily in the morning as in the AD model control group,and treadmill exercise was conducted in the afternoon,followed by routine feeding for a total of 8 weeks.Rat treadmill exercise program: training for 5 days in the first week,training for 15 minutes every day,running speed 10m/min,slope 0°,rest for 2 days.Training for 5 days in the second week,30min/d,15m/min,slope 0 °,rest 2 days.Training for 5 days in the 3-5 weeks,40min/d,15m/min,slope 5°,rest 2 days.Training for 5 days in the 6-8 weeks,50min/day,15m/min,slope 5°,rest 2 days.The body weight of each group before and after the treadmill training was recorded and the general condition of the rats was observed.In the 9th week,Morris water maze was used to test the learning and memory ability of each group of rats.HE staining was used to observe the changes of neuronal morphology in hippocampal of each group.The expression of HO-1 and NQO1 in cortex and hippocampus of each group was measured by immunohistochemistry.Chemical colorimetry were used to detect glutathione catalase(GSH)content,superoxide dismutase(SOD)activity and malondialdehyde(MDA)in cortex and hippocampus of each group.The expression levels of HO-1 and NQO1 in cortex and hippocampus of each group were detected by Western Blot.The analysis was performed using SPSS 19.0 software and the results were expressed as mean ± standard deviation(?±SD).The water maze positioning navigation data was analyzed by analysis of variance of two-factor repeated measures.The pairwise comparison between groups was LSD-t test.The other indicators were compared by one-way ANOVA,and the differences between groups were measured by LSD-t test.P<0.05 was considered statistically significant.Results:The Morris water maze place navigation test results showed that the escape latency of each group was shortened with the increase of the number of tests.On the first day,there was no significant difference in escape latency between the groups.;On the second day,compared with the NC group,the escape latency was significantly increased in the AC group only(P<0.01),but significantly decreased in the AE group compared with the AC group(P<0.05);On the third to fifth day,compared with the NC group,the escape latency of both AC group and AE group was significantly increased(P<0.01,P<0.05).Compared with the AC group,the escaping latency of the AE group was significantly shortened before the first three days(P<0.05),and the shortening of the escape latency on the last day was extremely significant(P<0.01).The results of spatial probe test on the 6th day showed that compared with the NC group,the target quadrant dwell time and the number of crossing platforms in the AC group and the AE group significantly less(P<0.01,P<0.01).Compared with the AC group,the target quadrant dwell time and the number of crossing platforms in the AE group were significantly increased(P<0.01,P<0.05).The results of HE staining showed that the neurons in the NC group were arranged neatly,the cell structure was intact,the cell density was high,and the cell morphology was consistent.The neurons in the AC group were disordered,the number of cells was reduced,the gaps were increased and the size was different.The structure of the cells was different,and a large number of cell deaths occurred,and the nuclei coagulated and contracted.In the AE group,the whole cells of the neurons were arranged neatly,and only part of the cell bodies were shrunk,and the nuclei were coagulated.Immunohistochemical results showed that the HO-1 and NQO1 proteins in hippocampus were the highest in the NC group,followed by the AE group and the lowest in the AC group.The results of enzyme activity showed that in the hippocampus and cortex,compared with the AC group,SOD activity and GSH content in AE group were significantly increased(P<0.05,P<0.05),and MDA content was significantly decreased(P<0.05).Western Blot results showed that in the cerebral cortex,the relative expression levels of HO-1 and NQO1 in AC and AE groups were significantly lower than those in NC group(P<0.01),while the relative expression levels of HO-1 and NQO1 in AE group were significantly higher than those in AC group.Increased(P<0.05,P<0.01).In the hippocampus of the brain,the relative expression levels of HO-1 and NQO1 in NC group were higher than those in AC and AE groups,the difference was significant(P<0.01,P<0.05),while the relative expression levels of HO-1 and NQO1 in AC and AE groups were also significant.There was a difference,and the content of the AC group was lower(P<0.01).Conclusions:(1)8-week treadmill exercise can effectively improve the learning and memory ability of AD model rats.(2)The 8-week treadmill exercise can increase the activity of SOD and GSH in the cerebral cortex and hippocampus of AD model rats,and decrease the MDA content,which reduces the oxidative stress in the AD process and slows the progression of AD.(3)By activating the expression of HO-1 and NQO1 downstream molecules of Nrf2 pathway,8-week running exercise can enhance the defense ability of endogenous antioxidant system of AD model rats,so as to improve the learning and memory of AD model rats. |
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