Study On The Effect Mechanism Of Electroacupuncture On Cognitive Function In SAMP8 Mice Of AD Model Based On The Aβ Glymphatic System Clearance Pathway

Objective To discuss the effect of electroacupuncture on cognitive function of SAMP8 mice model of Alzheimer’s disease(AD)and explore its mechanism based on researches on correlation between injury of glymphatic system and deposition of amyloid-β(Aβ)and in perspective of glymphatic system in Aβ clearance,so as to provide more scientific basis for electroacupuncture treatment applied in AD.Methods Accelerated senescence accelerated mouse prone 8(SAMP8)mice aged seven months were selected as AD model rats,and randomized into SAMP8 control group(Pc)and SAMP8 electroacupuncture group(Pe),while age-matched senescence accelerated mouse resistant 1(SAMR1)mice were selected as SAMR1 normal control group(Rc).Mice in the Pe group were stimulated on Baihui(GV20)and Yintang(GV29)for 10 min,at a continuous wave frequency of 2 Hz,and an electric current of 1 m A,and then pricked at Shuigou(GV26).The mice in the Rc and Pc group were caught and fixed.The above treatments were performed once a day,one course of treatment lasted for 5 days,and the treatment continued for 8 courses in total.In each week,electroacupuncture would be applied for first five consecutive days,and ceased at the rest two days.After electroacupuncture treatment,Morris water maze(MWM)test was used to evaluate the cognitive abilities;HE and Nissl staining were performed to observe the brain histomorphology;ELISA,contrast-enhanced MRI,and immunofluorescence were applied to detect the expression of Aβ,glymphatic system function,reactivity of astrocytes and aquaporin-4(AQP4)polarization,respectively.Results1.MWM test results showed that mice in the Pc group had significantly longer escape latency time,the time spent in the platform quadrant and the number of times that crossed the platform were found to be significantly less when compared to those in the Rc group(P<0.001).Compared with the Pc group,the escape latency time in the Pe group deceased significantly,and increased crossing platform and prolonged residence time in the platform quadrant(P<0.05).2.HE and Nissl staining results revealed that the mice in the Pc group had manifestations of loosened arrangement of neurons,partial neuronal degeneration,nuclear pyknosis as well as condensation,and remarkably decrease of Nissl bodies compared with the Rc group(P<0.01).Compared with the mice in the Pc group,those in the Pe group presented relatively aligned arrangement of neurons,a few neuronal degeneration,and evidently increase of Nissl bodies(P<0.05).3.ELISA results revealed that the mice in the Pc group showed dramatically increased expression levels of Aβ1-40 and Aβ1-42 protein compared to those in the Rc group(P<0.001 or P<0.01).Compared with the Pc group,the contents of both Aβ1-40 and Aβ1-42 were reduced significantly in the Pe group(P<0.01 or P<0.05).4.Contrast-enhanced MRI findings demonstrated that the detected regions in mice of the Pc group had enhanced signals compared with the Rc group,showing that they had higher residual concentration of contrast agent,and clearance rate was significantly lower than the controls in brain parenchyma(P<0.01 or P<0.001).Compared with the Pc group,the its clearance rate in the Pe group was significantly increased(P<0.05 or P<0.01).5.Immunofluorescence results showed an increased activation of glial fibrillary acidic protein(GFAP)in the mice of the Pc group compared with the Rc group(P<0.001);AQP4was densely expressed in cell body area of astrocyte,and its polarization was significantly decreased(P<0.001).Activation of GFAP in the mice of the Pe group was decreased compared to those in the Pc group(P<0.05 or P<0.01);AQP4 was densely expressed in astrocyte end-feet,its polarization was significantly increased(P<0.05).Conclusions1.Electroacupuncture regime could alleviate cognitive disorder and neuropathological damage to brain tissue,and has the function of neuroprotection in SAMP8 mice model of AD.2.Electroacupuncture treatment might reduce Aβ accumulation in brain of SAMP8 mice model of AD.3.Electroacupuncture therapy enables to inhibit over-reactivity of astrocytes in the brain of SAMP8 mice model of AD,and maintains AQP4 polarity,thereby improving the function of glymphatic system.4.Electroacupuncture treatment could enhance cognitive function,its mechanism may involving in regulating clearance performance of the glymphatic system,thereby reducing Aβaccumulation from the brain of these mice.