To observe the effect of electroacupuncture (EA) on learning-memory ability, hippocampal myelin and RAS-associated C3 botulinum toxin substrate 1 (Rac1)/P21-activated kinase 1 (PAK1)/LIM kinase 1 (LIMK1)/cofilin signaling pathway in senescence-accelerated mouse prone 8 (SAMP8) mice, so as to explore its mechanisms underlying improvement of Alzheimer′s disease (AD) from the perspective of the cytoskeleton.

Male SAMP8 (AD) mice were randomly divided into model group and EA group, with 9 mice in each group, and 9 male SAMR1 mice of the same age were used as the control group. The mice in the EA group received EA at “Dazhui” (GV14) and “Shenshu” (BL23) and punctured at “Baihui” (GV20) for 20 min, once per day, for 24 d, rest for 2 d after every 8 d of treatment. The Morris water maze test was used to observe the learning-memory ability. The Luxol fast blue (LFB) staining was used to observe the myelin sheath, and the phalloidin staining was used to observe the cytoskeleton in the hippocampus tissue. The mRNA expression levels of Rac1, PAK1, LIMK1, and cofilin were detected using real-time fluorescence quantitative PCR, and the protein expression levels of myelin basic protein (MBP), Rac1, PAK1, phosphorylated (p)-PAK1, LIMK1, p-LIMK1, cofilin, and p-cofilin in the hippocampal tissue were detected using Western blot.

Compared with the control group, the model group showed an obvious increase in the escape latency (P<0.01), and a significant decrease in the number of the original platform-crossing, the swimming time in the original platform quadrant, cytoskeleton fluorescence intensity, mRNA expression levels of Rac1, PAK1, LIMK1, and cofilin, and protein expression levels of MBP and Rac1, and the ratios of p-PAK1/PAK1, p-LIMK1/LIMK1, and p-cofilin/cofilin in the hippocampus tissue (P<0.01). Following EA intervention, the increased level of escape latency and the decreased levels of the number of the original platform-crossing, the swimming time in the original platform quadrant, cytoskeleton fluorescence intensity, and the expression levels of Rac1, PAK1, LIMK1, and cofilin mRNAs, and the expression levels of MBP and Rac1 proteins, and the ratios of p-PAK1/PAK1, p-LIMK1/LIMK1, and p-cofilin/cofilin were reversed (P<0.01, P<0.05). LFB staining showed disordered and loose arrangement of the fibers with vacuoles in the model group. Compared with the model group, the number of myelin fibers was increased with the fibers arranged in relatively regular order in the EA group, suggesting a reduction of the degree of demyelination.

EA can improve the learning-memory ability of SAMP8 mice, which may be related to its functions in up-regulating the activity of Rac1/PAK1/LIMK1/cofilin signaling, and promoting the cytoskeletal reorganization to improve myelin function.

To observe the effects of electroacupuncture (EA) on anxiety-like behavior, learning and memory ability and expressions of myelin-related proteins in the hippocampus of senescence accelerated mice prone 8 (SAMP8), so as to explore the mechanism of EA in improving Alzheimer’s disease (AD) from the perspective of myelin sheath injury and regeneration.

Twenty-four male SAMP8 mice were randomly and equally divided into model group and EA group. Twelve male SAMR1 mice of the same age as SAMP8 mice were used as the control group. The rats in the EA group received acupuncture at “Baihui” (GV20), “Dazhui” (GV14) and “Shenshu” (BL23), among which GV14 and BL23 received EA intervention (1.5—2 mA, 2 Hz), the intervention lasted for 20 min once daily for a total of 3 courses, with every 8 d as a course and an interval of 2 d between each 2 courses. The anxiety-like behavior of mice was observed by open field test. The learning and memory ability of mice was observed by Morris water maze test. The neuronal demyelination in the hippocampus of mice was observed after luxol fast blue (LFB) staining. The positive expressions of myelin basic protein (MBP) and myelin protein lipid protein (PLP) in hippocampal CA1 region were detected by immunofluorescence. The mRNA expression levels of MBP, chondroitin sulfate proteoglycan (NG2) and PLP, and the protein expression levels of myelin-associated proteins MBP, NG2, PLP, myelin-associated glycoprotein (MAG) and myelin oligodendrocyte glycoprotein (MOG) in the hippocampus were detected by qPCR and Western blot, respevtively.

Compared with the control group, the activity distance and activity time in the central region in open field test of the model group were significantly shortened (P<0.01), the escape latency of the Morris water maze test was prolonged (P<0.01), the number of crossing the original platform and the residence time in the original platform quadrant were decreased (P<0.01). The LFB staining in the hippocampus was shallow, the myelin fibers were sparse, the positive expressions of MBP and PLP in the hippocampal CA1 region, and the mRNA expression levels of MBP, NG2 and PLP, as well as the protein expression levels of MBP, NG2, PLP, MAG and MOG in the hippocampus were significantly decreased (P<0.01) in the model group than those of the control group. After the acupuncture or EA interventions, the activity distance and activity time in the central region in open field test of the mice in the EA group were significantly prolonged (P<0.01), the escape latency of the Morris water maze test was shortened (P<0.01), the number of crossing the original platform and the residence time in the original platform quadrant were increased (P<0.01), the LFB staining in the hippocampus was deepened, the myelin fibers were arranged more densely, the positive expression levels of MBP and PLP in the hippocampal CA1 region, and the mRNA expression levels of MBP, NG2 and PLP in the hippocampus, and the protein expression levels of MBP, NG2, PLP, MAG and MOG in the hippocampus were all increased (P<0.01, P<0.05) in the EA group relative to the model group.

EA can improve the anxiety-like behavior and learning and memory ability of SAMP8 mice, which may be related to its effects in improving myelin regeneration via up-regulating myelin-related proteins expressions in the hippocampus.