| Background: Alzheimer’s disease(AD)is one of the most common neurodegenerative diseases.Studies have confirmed that mitochondrial toxicity caused by Aβ is an early symptom of AD,which would enhance oxidative stress in the brain and weaken antioxidant capacity,ultimately leading to mitochondrial dysfunction and cell death.Increased oxidative stress and decreased antioxidant capacity in the brain,as well as mitochondrial dysfunction,would further deposit Aβ,thus forming a vicious cycle.A large number of studies have found that exercise has both preventive and therapeutic effects on AD,while the specific molecular mechanism of exercise to prevent the occurrence and development of AD has not been fully understood.Studies have shown that exercise can reduce the level of oxidative stress and improve mitochondrial biogenesis in the hippocampus of AD mice.However,studies about the effect of exercise on mitochondrial toxicity caused by Aβ and the correlation between mitochondrial toxicity caused by Aβ and mitochondrial biogenesis are rarely reported.Therefore,further studies are needed to detect the effects of exercise on mitochondrial toxicity induced by Aβ and mitochondrial biogenesis in the hippocampus of AD mice.Purpose: This study made 3-month old APP/PS1 male mice subject to 12-week treadmill exercise intervention,to observe whether exercise can reduce mitochondrial toxicity caused by Aβ and the effects of exercise on mitochondrial biogenesis in the hippocampus of APP/PS1 mice,and to explore whether the effects of exercise on mitochondrial toxicity caused by Aβ is involved in mitochondrial biogenesis changes in the hippocampus of APP/PS1 mice,which provides a new insight for the development and happening of AD.Methods: Eighteen 3-month-old male APP/PS1(TG)mice and eighteen wild type(WT)male mice were randomly divided into 2 groups,namely,APP/PS1 mice were divided into AD sedentary group(TG-SED group,n=9)and AD exercise group (TG-EXE group,n=9);WT mice were divided into sedentary group(WT-SED group,n=9)and exercise group(WT-EXE group,n=9).Mice in WT-EXE group and TG-EXE group were given a 12-week treadmill exercise.At the end of the 12-week treadmill training,3 mice of each group were selected for clear cardiac perfusion after general anesthesia,followed by cardiac perfusion fixation.The hippocampal tissues were removed,and the tissues were cut off from the CA1 area of the hippocampus to make electron microscope specimens,then the mitochondrial morphology and healthy mitochondria quantity in the hippocampal tissues of the mice in each group were observed.After general anesthesia,blood was extracted from the eyeballs of the remaining 6 mice in each group and their heads were severed.Bilateral hippocampal tissues were quickly removed and stored at low temperature.Later,Aβ40,Aβ42 and ROS content in hippocampus of mice in each group was detected by Elisa assay.Mt DNA content in hippocampus of mice in each group was detected by real-time PCR assay.Mitochondrial biogenesis related proteins such as AMPK,SIRT1,PGC-1α,NRF1,NRF2 and TFAM,antioxidant protein Mn SOD and mitochondrial quantitative protein TOM20 were detected by Western Blot assay.Results:(1)Exercise reduced Aβ40 and Aβ42 in the hippocampus of APP/PS1 transgenic mice : Aβ40 and Aβ42 level in the hippocampus of mice was observed by Elisa,and it was found that compared with WT-SED group,Aβ40(P<0.001)and Aβ42(P<0.01)level in the hippocampus of TG-SED group was significantly increased.Compared with TG-SED group,the hippocampal Aβ40(P<0.01)and Aβ42(P<0.05)level in TG-EXE group was significantly lower.(2)Exercise could improve the morphology and number of healthy mitochondria in the hippocampus of APP/PS1 transgenic mice: mitochondria in the hippocampus CA1 region of mice in each group were observed by transmission electron microscopy,and it was found that compared with WT-SED mice,the morphology of mitochondria in the hippocampus of TG-SED mice was abnormal.Compared with TG-SED group,the mitochondrial morphology in the hippocampal CA1 region of mice in TG-EXE group was improved.(3)Exercise reduced the oxidative stress in the hippocampus of APP/PS1 transgenic mice and improved the antioxidant capacity: the oxidative stress level in the hippocampus of mice was observed by Elisa,and it was found that compared with WT-SED group,the ROS level in the hippocampus of TG-SED group was significantly increased(P<0.001).Compared with TG-SED group,the hippocampal ROS level in TG-EXE group was significantly lower(P<0.01).Western Blot was used to observe the expression level of antioxidant enzyme Mn SOD protein in the hippocampus of mice to detect the antioxidant capacity in the hippocampus of mice.It was found that compared with WT-SED group,the antioxidant capacity of TG-SED group was decreased(P<0.05).Compared with TG-SED group,the hippocampal antioxidant capacity of TG-EXE group was enhanced(P<0.05).(4)Exercise enhanced mitochondrial biogenesis in hippocampus of APP/PS1 mice: Western Blot was used to observe the expression levels of mitochondrial biogenesis related proteins in the hippocampus of mice,such as AMPK,SIRT1,PGC-1α,NRF1,NRF2 and TFAM.In TG-SED group,the levels of mitochondrial biogenesis related proteins AMPK(P<0.05),SIRT1(P<0.05),PGC-1α(P<0.05),NRF1(P<0.05),NRF2(P<0.05)and TFAM(P<0.05)were all decreased.Compared with WT-SED group,the protein expression levels of AMPK(P<0.05),SIRT1(P<0.05),PGC-1α(P=0.01),NRF1(P<0.05),NRF2(P<0.05)and TFAM(P<0.05)in the hippocampus of WT-EXE group were increased.Compared with TG-SED group,the protein expression levels of AMPK(P<0.001),SIRT1(P<0.01),PGC-1α levels(P=0.001),NRF1(P<0.001),NRF2(P<0.01),and TFAM(P=0.05)were all increased in the hippocampus of TG-EXE group.(5)Exercise increased the content of mt DNA and mitochondria number in the hippocampus of APP/PS1 mice: real-time PCR was used to observe the content of mt DNA in the hippocampus of mice,and it was found that compared with WT-SED group,the content of mt DNA in the hippocampus of TG-SED group decreased(P<0.05).Compared with WT-SED group,mt DNA content in hippocampus of WT-EXE group was significantly increased(P<0.001).Compared with TG-SED group,mt DNA content in hippocampus of TG-EXE group was significantly increased(P<0.001).Western blot was used to observe the expression level of TOM20 protein in the hippocampus of mice to detect the number of mitochondria in the hippocampus of mice.It was found that compared with WT-SED group,the number of mitochondria in the hippocampus of TG-SED group decreased(P<0.05).Compared with TG-SED group,the number of mitochondria in the hippocampus of TG-EXE group increased(P<0.05).Conclusion: Exercise can resist Aβ-induced mitochondrial toxicity through reducing the level of oxidative stress in the hippocampus of AD mice,improving mitochondrial morphology and improving the antioxidant capacity in the hippocampus.The specific mechanism may be related to exercise improving the level of mitochondrial biogenesis,increasing the content of mt DNA and the number of healthy mitochondria,and ultimately improving the "quality" and "quantity" of mitochondria in the hippocampus of AD mice,so as to resist the mitochondrial toxicity caused by Aβ,which provides a new insight in exercise preventing the occurrence and development of AD. |
