| Alzheimer’s disease(AD)is a typical age-related neurodegenerative disease.AD patients show severe memory loss and cognitive dysfunction,accompanied by emotional abnormalities.The pathogenesis of AD is very complex and affected by many genetic and environmental factors,which has not yet been elucidated.Studies have found that amyloid-β(Aβ)deposition and Tau hyperphosphorylation occur in the hippocampus and entorhinal cortex of AD patients,accompanied by a large loss of neurons.In addition to the two pathological features typical of AD described above(Aβand Tau),impaired autophagic flux is also an important component of the known pathological features of AD.As one of the intracellular protein quality control mechanisms,autophagy degrades proteins and abnormal organelles that accumulate due to misfolding in cells.Autophagy is impaired in the brain before the patient presents with clinical manifestations of AD.Autophagy has a dual role in the progression of AD,and when autophagy functions normally,it plays a role in removing misfolded proteins in the brain.Immature autophagosome accumulation was observed in the brains of AD patients,suggesting impaired autophagosomelysosome degradation processes.Abnormal autophagy is characterized by the accumulation of a large number of autophagic vesicles in neurons,in which misfolded proteins such as Aβ are encapsulated and unable to degrade,and autophagic flux is blocked.Autophagy is tightly regulated by the transcription factor EB,and TFEB regulates gene expression associated with the autophagy-lysosome pathway and promotes lysosome biogenesis,and its activity can be regulated through the mTOR signaling pathway.More and more research evidence shows that exercise has a positive impact on brain function,which can reduce the risk of neurodegenerative diseases,including AD,improve cognitive function and relieve patients’ neuropsychiatric symptoms.Compared with AD drug therapy,exercise intervention has the characteristics of less side effects,no significant economic cost,and good patient compliance.However,the effect of exercise on autophagy in the brain and whether it can improve the cognitive function of AD mice through autophagy is not clear.Lactic acid is one of the metabolites produced after exercise,which has been proved to promote neurogenesis.In addition,recent studies have shown that exogenous administration of lactic acid can simulate the changes of lactic acid during exercise.However,whether exercise can regulate lactic acid to regulate mTOR/TFEB signaling pathway,activate autophagy lysosomal function in AD mice,and resist oxidative stress injury in AD neurons remains to be verified.The purpose of this study is to explore the intervention mechanism of exercise regulating lactate/mTOR/TFEB pathway in the regulation of neurocognitive impairment in Alzheimer’s disease at the animal and cell levels,and to explore the molecular mechanism of exercise mimetic lactic acid activating autophagy lysosome function in neurons.The experimental research contents are as follows:1.Exercise protects neuronal damage in D-gal combined with AlC13-induced cognitive dysfunction miceMethods:At the animal level,AD mouse model was constructed by D-gal combined with AlC13.After modeling,the model mice were divided into lactic acid administration group and exercise training group.After 8 weeks,the learning and memory ability of the control group,AD model group,lactic acid administration group and exercise training group were observed by Morris water maze experiment.HE staining and Nissl staining were performed on brain tissue sections of mice in each group.TUNEL staining was used to detect neuronal apoptosis in mouse brain tissue sections.The changes of lactic acid content in the tissues of mice under normal conditions,after exercise intervention and lactic acid administration were detected by lactic acid detection kit.At the cellular level,the oxidative stress injury model of N2 a neuron cells induced by hydrogen peroxide was used,and the cell viability was detected by MTT method to verify the protective effect of lactic acid on neuron cells.Results:The learning and memory ability of mice in AD model group was significantly impaired,while lactic acid administration and exercise intervention showed significant improvement.The mice in the AD model group showed neuronal loss,while lactic acid administration and exercise intervention changed the neuronal loss of AD model mice.The number of apoptosis in AD model group increased,while the number of apoptosis decreased significantly after lactic acid administration and exercise intervention.Compared with the blank control group,the lactic acid content in serum,skeletal muscle and brain tissue increased significantly after lactic acid administration and exercise intervention.The results showed that the cognitive dysfunction of AD model mice was significantly improved after exercise intervention,and the cognitive function of lactic acid group was significantly improved,which was not significantly different from that of exercise group,suggesting that exogenous lactic acid intervention can simulate the improvement of exercise training on the cognition of AD mice.Lactic acid has the potential to become a drug for the treatment of AD.Sodium lactate increased the survival rate of N2a cells in a dose-dependent manner and could protect N2a cells from hydrogen peroxide.2.Effect of exercise intervention on autophagic lysosome function of neurons in model miceMethods:In this part of the experiment,at the animal level,the expression of autophagy-related proteins(LC3I/II,SQSTM1/P62)and lysosome-related proteins(Cathepsin B)in the brain tissue of each group of mice was detected by immunoblotting.At the cellular level,MDC fluorescence staining was used to detect autophagosome changes in the oxidative stress injury model of N2 a cells induced by hydrogen peroxide.Results:After exercise intervention and lactic acid administration,the ratio of LC3 II/I in brain tissue of mice increased,and the protein expression of cathepsin B increased.The results suggested that exercise intervention and exercise mimetic lactic acid reversed the impaired autophagic lysosome function in AD model mice.Compared with the model group,the green fluorescent particles increased after sodium lactate administration,suggesting that the number of autophagosomes increased;the number of lysosomes was detected by Lysotracker Red staining.The number and fluorescence intensity of lysosomes were increased after sodium lactate administration,indicating that lactate administration enhanced autophagic lysosome function.Exercise regulates lactate/mTOR/TFEB signaling pathway to improve autophagic lysosomal functionMethods:At the animal level,immunofluorescence staining was used to detect TFEB nuclear translocation in brain tissue sections of mice in each group.The expression of pathway-related proteins p-mTOR/mTOR and p-TFEB/TFEB was detected by immunoblotting.Conclusion:Compared with the model group,the cortical area of mice in the exercise intervention and lactic acid administration groups showed obvious TFEB into the nucleus.Compared with the model group,p-mTOR/mTOR and p-TFEB/TFEB decreased in the exercise intervention and lactic acid administration groups,indicating that exercise promotes TFEB nuclear translocation by inhibiting mTOR.In summary,this study used hydrogen peroxide-induced neuronal cell N2a to construct an oxidative stress model,and D-gal combined with AlC13 AD mouse model,which proved that exercise enhanced neuronal autophagy lysosome function through lactic acid and played an important role in improving the pathological symptoms of AD mice.It is clear that exercise can regulate the lactic acid/mTOR/TFEB signaling pathway to enhance the function of autophagic lysosomes and promote the smooth flow of autophagy,thereby reducing cognitive dysfunction in AD mice. |
PDF Full Text Request