Effects Of Treadmill Exercise On Aβ Transportation And Clearance Cross The Blood-brain Barrier In TgAPP/PS1 Mice

Objective:In this study,we explore the effect of 12 weeks of moderate intensity treadmill exercise on memory and clearance of Aβ cross BBB transport of Tg APP/PS1 mouse.Take Aβ cross the BBB transport and clearance as the starting point,we discussed the possible molecular mechanisms of accelerated Aβ clearance by long-term aerobic exercise from the BBB structure and function,peripheral Aβclearance,Wnt/beta-catenin signaling pathway and microvascular function.Methods:3 month old male Tg APP/PS1 mice were randomly divided into transgenic exercise group(Transgenic type exercise,TG-EXE,N=18)and transgenic sedentary group(Transgenic type Sed group,TG-Sed,N=18),wild type littermates were selected as normal control group(Wild type Sed,WT-Sed,N= 18)and exercise control group(Wild type exercise,WT-EXE,N=18).Mice in group WT-EXE and group TG-EXE were subjected to treadmill exercise intervention for 12 weeks.Group WT-Sed and TG-Sed was fed without any exercise intervention.After the treadmill training,the water maze test and the opening field test were carried out to test the learning and memory ability and the activity ability of the mice.12 hours after the behavioral experiment,6 mice of each group were randomly selected to perform 0.9%Nacl perfusion and brain was fixed in 4%paraformaldehyde used for paraffin section immunohistochemical experiments;6 mice of each group were sacrificed to collect blood and isolate bilateral hippocampus for RT-PCR and Elisa test;the remaining 6 mice were sacrificed to collect bilateral hippocampus for Western blot.RT-PCR and Western blot were used to examine the gene and protein expression of LRP-1,APOE,APOE3,a2M,ABCB1,ABCG2,ABCA1,RAGE,AGE,Wnt3a,β-catenin,GSK-3β,VEGF,VEGFR and Angiopoietin.Western blot was used to detect the expression of LRP-1 protein in the liver;Elisa assay was used to detect Aβ40 and Aβ42 content in peripheral blood,sLRP-1 and sRAGE content.Immunohistochemical assay was used to determine the numbers of senile plaques.Results:(1)7 month old Tg APP/PS1 mice showed impaired learning and memory,with learning and memory ability significantly lower than that of wild type littermates,with decreased ability to explore activities.12 weeks of moderate intensity treadmill exercise significantly improved learning and memory ability of Tg APP/PS1 mice and increased its spontaneous inquiry activity ability.(2)The content of Aβ40 and Aβ42 increased significantly in hippocampus of 7 month old Tg APP/PS1 mice,peripheral blood Aβ40 and Aβ42 content in 7 months old Tg APP/PS1 mice increased significantly,Aβ transporter LRP-1,ABCA1,ABCBland ABCG2 protein decreased,while APOE,a2M,RAGE and AGE protein were increased in hippocampus of 7 month old Tg APP/PS1 mice,peripheral blood sLRP-1 content significantly decreased while blood sRAGE content increased significantly,liver LRP-1 protein significantly decreased.12 weeks of moderate intensity treadmill exercise significantly reduced hippocampus Aβ40 and Aβ42 content as well as peripheral blood Aβ40 and Aβ42 content,significantly reduced senile plaque content,significantly increased Aβ transporter LRP-1,ABCA1,ABCB1 and ABCG2 protein,significantly reduced RAGE and AGE protein as well as APOE and a2M,significantly increased peripheral blood sLRP-1 content and liver LRP-1 protein level,significantly reduced peripheral blood content of sRAGE in Tg APP/PS1 mice.(3)Hippocampal BBB structure and function of 7 months old Tg APP/PS1 mice were dysfunctional,Wnt/β-catenin signaling pathway activity decreased.The expression of VEGF,VEGFR and Angiogenin protein in hippocampus of 7 months old Tg APP/PS1 mice was significantly reduced as well as Wnt3a protein level and CLDN3 mRNA level.GSK3β activity significantly increased,β-catenin activity showed a trend of rising.12 weeks of moderate intensity treadmill exercise significantly increased hippocampal Wnt/β-catenin signaling pathway activity of Tg APP/PS1 mice,improve the structure and function of BBB,significantly increased VEGF,VEGFR,Wnt3a,Angiogenin protein expression,β-catenin activity showed a trend of declining.12 weeks of moderate intensity treadmill exercise significantly increased hippocampal Wnt/β-catenin signaling pathway activity of TgAPP/PS1 mice hippocampus and improve the structure and function of BBB.Conclusions:(1)Moderate intensity treadmill exercise can improve learning and memory ability in Tg APP/PS1 mice,increase spontaneous inquiry ability of Tg APP/PS1 mice.(2)Moderate intensity treadmill exercise increased the expression of Aβoutward transporter protein and reduced expression of Aβ intward transporter protein in the surface of BBB,increased Aβ outflow rate,reduces Aβ inward transport rate,increase of the rate of Aβ clearance,reduces Aβ content and numbers of senile plaque in hippocampus of Tg APP/PS1 mice.(3)Moderate intensity treadmill exercise activated Wnt/β-catenin signaling pathway and improvement of brain microvascular function,improve the structure and function of BBB.From the view of prevention,long-term aerobic endurance is a kind of an effective way to prevent and delay the onset of AD.