Effect of electroacupuncture on hippocampal myelin and Rac1/PAK1/LIMK1/cofilin signaling pathway in Alzheimer′s disease mice

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.