Protective Effect Of Shenzhiyu Oral Liquid On Early Myelin And Synaptic Damage In AD

ObjectiveAlzheimer's disease(AD)is a chronic progressive disease of central nervous system caused by unknown etiology.It is characterized by progressive cognitive decline,memory impairment,and even personality and behavior changes.AD has many pathological changes.In addition to typical pathological changes,such as A? deposits and NFTs,myelin damage and synaptic loss are also closely related to AD,especially in the early stage of AD.In recent years,it has been found that there are myelin structure destruction,oligodendrocyte loss and axonal damage at every stage.Myelin sheath destruction is a significant pathological change.PI3K/Akt-mTOR signaling pathway is one of the important signaling pathways regulating myelin formation.It not only regulates myelin formation from promoting oligodendrocyte differentiation,but also myelin synthesis through regulating protein synthesis and lipid synthesis.Theaimof this study is to observe the effects of Shen Zhi Ling oral liquid in the early stage of AD by its effects on hippocampal synapses,myelin and oligodendrocytes,and the influence on the expression of PI3K/Akt-mTOR signaling pathway related protein and myelin associated protein,and to provide experimental basis forShen Zhi Ling oral liquid play a therapeutic role in the early stage of AD.Materials and Methods1 75 SPF grade 3-month-old male APP/PS1 mice were randomly divided into three groups:model group,donepezil group,Shen Zhi Ling high-dose group,medium-dose group and low-dose group,15mice in each group.15 male C57/BL6J 3-month-old mice as normal control group.The drugs were treated for 3 months.2 Through Morris water maze test,we observed the behavior of APP/PS1 mice,and evaluated the effect of Shen Zhi Ling oral liquid on learning and memory ability of APP/PS1 mice after 3 months administration.3 The effects of Shen Zhi Ling oral liquid on hippocampal synapse,myelin and oligodendrocyte of APP/PS1 mice were observed by transmission electron microscope.4 The effect of Shen Zhi Ling oral liquid on the cerebral myelin sheath of APP/PS1 mice was observed by Luxol Fast Blue myelin staining.5 Immunohistochemical method,western-blot and RT-PCR were used to observe the expression of PI3K-Akt/mTORsignal pathway related protein and myelin associated protein and synaptic associated protein,and to evaluate the effect of Shen Zhi Ling oral liquid on the signal pathway and myelin associated protein and synapse associated protein in the hippocampus of APP/PS1 mice.Results1 Effect of Shen Zhi Ling oral liquid on the behavior of APP/PS1 double transgenic miceIn the Morris water maze test,from day one,compared with normal group,model group and mice escape latency was significantly prolonged(P<0.01);In the third day,the escape latency of Shen Zhi Ling medium-dose group was shorter than that in the model group(P<0.05).From the fourth day,the latency of Shen Zhi Ling groups were shorter(P<0.05).From second to fifth days,the swimming distance of the model group was significantly longer than that of the normal group(P<0.01).On the third day,the swimming distance of the model group was significantly increased(P<0.05)compared with the medium dose group and the small dose group.From the fourth day,the swimming distance of Shen Zhi Ling medium-dose and low-dose groups was significant decrease(P<0.01).2 Effects of Shen Zhi Ling oral liquid on oligodendrocyte,myelin and synapse structure in CA1 region of hippocampal in APP/PS1 miceTransmission electron microscope(TEM)showed that the myelin sheath structure of the normal group was relatively complete,and the myelin sheath structure of the hippocampus in the model group was obviously damaged.The myelin sheath structure in the hippocampus of each drug group was better than that in the model group,especially in the donepezil group and the Shen Zhi Ling medium-dose and low-dose groups.Oligodendrocytes of the normal group was normal,nuclear membrane,structural integrity,continuous nuclear chromatin distribution;oligodendrocytes of model group showed pyknosis to apoptosis,nuclear chromatin condensation;oligodendrocytes of Shen Zhi Ling groups were improved.The number of synapses was observed by TEM.Compared with the normal group,the number of synapses in hippocampal CA1 area of mice in the model group significantly decreased(P<0.01);and the number of synapses in the drug treatment group are more than the model group(P<0.01).3 Effect of Shen Zhi Ling oral liquid on PI3K/Akt-mTOR pathway and myelin and synaptic associated protein in APP/PS1 miceWestern-blot showed that,compared with the normal group,the expression of PI3K protein in the model group decreased;compared with the model group,PI3K protein expression of donepezil group and Shen Zhi Ling groups was increased.Western-blot showed that,compared with the normal group,the expression of Akt protein in the model group decreased(P<0.05);compared with the model group,Akt protein expression of donepezil group and Shen Zhi Ling groups was increased.The Shen Zhi Ling medium-dose and low-dose groups increased significantly(P<0.05).Western-blot showed that,compared with the normal group,the expression of mTOR protein in the model group decreased significantly(P<0.01);compared with the model group,mTOR protein expression of donepezil group and Shen Zhi Ling groups was increased(P<0.01).Western-blot showed that,compared with the normal group,the expression of p-Akt protein in the model group decreased significantly(P<0.01);compared with the model group,p-Akt protein expression of donepezil group and Shen Zhi Ling groups was increased(P<0.01)Western-blot showed that,compared with the normal group,the expression of p-mTOR protein in the model group decreased significantly(P<0.01);compared with the model group,p-mTOR protein expression of donepezil group and Shen Zhi Ling groups(medium and low dose)was increased significantly(P<0.01)Western-blot showed that,compared with the normal group,the expression of MBP protein in the model group decreased significantly(P<0.01);compared with the model group,MBP protein expression of donepezil group and Shen Zhi Ling group(medium and low dose)was increased significantly(P<0.01)Western-blot showed that,compared with the normal group,the expression of PSD95 protein in the model group decreased significantly(P<0.05);compared with the model group,PSD95 protein expression of donepezil group and Shen Zhi Ling group(medium and low dose)was increased(P<0.05)RT-PCR results showed that compared with the normal group,PI3KmRNA and AktmRNA expression in the model group were decreased,but no significant difference(P>0.05);compared with the model group,PI3KmRNA and AktmRNA expression in the donepezil group and Shen Zhi Ling groups were increased,but the difference was not statistically significant(P>0.05).Compared with the normal group,the expression of mTOR mRNA in model group decreased significantly(P<0.01);compared with the model group,mTOR mRNA expression of the donepezil group and Shen Zhi Ling groups was increased(P<0.01).ConclusionsShen Zhi Ling oral liquid can improve learning and memory in APP/PS1 mice,increase the number of synapses in CA1 area,improve myelin and oligodendrocyte and neuron ultrastructure.It can also regulate the expression of PI3K/Akt-mTOR signaling pathway related proteins and increasethe expression of myelin associated protein and synaptic associated protein.Myelin and synapse were protected by Shen Zhi Ling oral liquid in the early stage of AD.