The study aimed to investigate the effects of galangin on learning and memory impairments and Akt/MEF2 D/Beclin-1 signaling pathway in APP/PS1 double-transgenic mice. The mice in this experiment were divided into the normal group, model group, low-(25 mg·kg~(-1)), medium-(50 mg·kg~(-1)), and high-dose(100 mg·kg~(-1)) galangin groups, donepezil(3 mg·kg~(-1)) group, Akt inhibitor(25 mg·kg~(-1)) group, and autophagy inhibitor(30 mg·kg~(-1)) group, with ten in each group, and administered with the corresponding drugs for 30 successive days. On the 24 th day of medication, the water maze and dark avoidance tests were performed. The levels of p-tau, β-amyloid peptide 1-42(Aβ_(42)), acetylcholinesterase(AChE), β-site amyloid precursor protein cleaving enzyme 1(BACE1), and amyloid precursor protein(APP) in hippocampus were detected by ELISA, the Beclin-1 mRNA expression by RT-PCR, the expression of Aβ_(42) and glial fibrillary acidic protein(GFAP) by immunohistochemistry, and the expression of myocyte enhancer factor 2 D(MEF2 D) by immunofluorescence assay. The pathological changes in hippocampus were observed after HE staining, and the expression of Akt, MEF2 D, and Beclin-1 in hippocampus were assayed by Western blot. These results showed that compared with the normal group, the model group exhibited prolonged swimming time, increased number of errors and electric shocks, up-regulated p-tau, Aβ_(42), APP, AChE, BACE1, GFAP, and Beclin-1, shortened incubation period, decreased p-Akt and MEF2 D, and obvious hippocampal injury. Compared with the model group, donepezil and galangin shortened the swimming time, reduced the number of errors and electric shocks, down-regulated the expression of p-tau, Aβ_(42), APP, AChE, BACE1, GFAP, and Beclin-1, prolonged the incubation period, up-regulated p-Akt and MEF2 D, and improved the pathological changes in hippocampus. Compared with the autophagy inhibitor group, galangin prolonged the swimming time, elevated the number of errors and electric shocks, enhanced the expression of p-tau, Aβ_(42), APP, AChE, BACE1, GFAP, and Beclin-1, shortened the incubation period, and diminished the expression of p-Akt and MEF2 D. In conclusion, galangin improves the learning and memory impairments and hippocampal neuron injury of APP/PS1 mice, which may be related to its regulation of Akt/MEF2 D/Beclin-1 signaling pathway.
Keywords: APP/PS1 double-transgenic mice; Akt/MEF2D/Beclin-1 signaling pathway; galangin; hippocampal neurons.