Picroside Ⅱ improves Aβ-induced learning and memory deficits in mice by enhancing autophagy

Abstract:

Objective To investigate the effect of picroside Ⅱ（PicrⅡ） on learning and memory functions in Alzheimer’s disease（AD） model in vivo and in vitro and autophagy-related mechanisms.Methods Western blot was used to observe the effect of PicrⅡ（12.5-400 μmol/L） on the expression of β-amyloid precursor protein（APP），β-site amyloid precursor protein cleaving enzyme 1（BACE1），presenilin 1（PS1），and carboxyl-terminal fragment of β-amyloid precursor protein（CTF） in the cell model of AD；after co-treatment with PicrⅡ and chloroquine（CQ）（50 μmol/L） or bafilomycin（BafA1）（10 μmol/L），its effect on the expression of APP，BACE1，PS1，C99，sequestosome 1（P62），microtubule-associated protein light chain 3（LC3），and ubiquitinated proteins in cells was observed；immunofluorescence assay was used to analyze autophagic flux. Then a mouse model of Aβ was established，and the mice were divided into WT+PBS group，WT+PicrⅡ group，Aβ+PBS group，and Aβ+PicrⅡ group（20 mg/kg）. The Morris water maze test was used to verify the learning and memory functions of Aβ model mice，and the protein expression levels of P62 and LC3 in the hippocampus of mice were measured.Results Western blot showed that compared with the control group，PicrⅡ（50 μmol/L） significantly reduced the protein expression levels of APP[（60.46±7.97）%，P=0.049] and related metabolites，and it also reduced the expression level of P62[（65.31±3.51）%，P=0.041] and increased the expression level of LC3Ⅱ[（162.01±12.24）%，P<0.001]；with the action of CQ，PicrⅡ could reduce the expression levels of P62[（147.24±10.69）%，P<0.001] and LC3Ⅱ[（826.23±39.18）%，P<0.001]. The analysis of autophagic flux showed that compared with the control group，PicrⅡ increased the total number of fluorescent dots（23.24±1.50，P<0.001） and the number of red dots（3.52±0.33，P<0.001）. The behavioral analysis showed that compared with the WT+Aβ group，the Aβ+PicrⅡ group had significant increases in learning ability（F=17.25，P<0.001） and memory ability（F=6.627，P<0.001），as well as a significant reduction in P62[（176.66±11.47）%，P=0.023] and a significant increase in LC3 Ⅱ[（81.20±3.69）%，P<0.001].Conclusion PicrⅡ can enhance autophagy by promoting autophagosome-lysosome fusion，thereby promoting the clearance of Aβ and improving Aβ-induced learning and memory deficits.