OBJECTIVES: To observe the effect of electroacupuncture (EA) on behavior and hippocampal protein phosphorylation in rats with chronic fatigue syndrome (CFS), so as to explore its mechanisms underlying improvement of CFS.
METHODS: Male SD rats were randomly divided into control, model and EA groups (n=12 rats in each group). The CFS model was established by chronic multifactor combined with stress stimulation (treadmill training + restraint stress + sleep disturbance + crowded environment). For rats of the EA group, EA (1 mA, frequency of 10 Hz) was applied to "Shenting" (GV24) (with an acupuncture needle penetrated from GV24 to "Baihui" [GV20]) and "Dazhui" (GV14) for 15 min, once daily for 28 days. After treatment, the body weight, food intake and water intake of rats in each group were observed. The fatigue degree of rats was evaluated by Semi-quantitative score observation table of the general condition of experimental rats.The open field test (OFT) was used to assess the rats'anxiety severity by detecting the total number of grid-crossing and the times of the central area entered in 5 min, and Morris water maze test was employed to assess the rats' learning-memory ability by detecting the escape latency in 1 min, and the times of the original platform quadrant crossing in 1 min. The hippocampaus was taken for phosphorylated Label-free quantitative proteomics analysis by using Maxquant technology based on full scan mode to calculate the integral of each peptide signal of liquid chromatography-mass spectrometry(LC-MS). The differentially-expressed proteins (>1.5 folds for up-regulation or <0.67 folds for down-regulation) were evaluated by gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis.
RESULTS: Compared with the control group, the body weight, food intake, and the times of original-platform quadrant crossing of spatial exploring of Morris water maze test were significantly decreased (P<0.01, P<0.05) , and the score of general conditions, times of grid-crossing and center area-entering of OFT, and the escape latency of navigation task were apparently increased (P<0.01) in rats of the model group. After EA intervention, the decreased original-platform quadrant crossing, and the increased score of general conditions, times of grid-crossing and the escape latency of navigation task were all reversed (P<0.01, P<0.05). Outcomes of proteomics analysis indicated that compared with the model group, there were 297 differentially expressed peptide (48 up-regulated and 249 down-regulated) segments in the control group, and there were 245 differentially expressed peptide (185 up-regulated and 60 down-regulated) segments in the EA group, in which, 25 overlapping peptide segments were reversed after EA treatment, corresponding to 24 proteins, mainly involving cytoskeletal structure. GO function annotation analysis showed that the top three differentially expressed phosphorylated proteins involved in the effect of EA intervention were the actin filament polymerization, protein depolymerization and cytoskeletal tissue in the biological process, the actin binding, structural molecular activity and cytoskeletal protein binding in the molecular function, and the cytoskeleton, dendrites and dendritic trees in the cellular component, respectively. The KEGG pathway annotation analysis for differentially expressed phosphorylated proteins showed that theinsulin secretion, axon guidance, phosphatidylinositol signaling system and lysine biosynthesis, etc. were involved in the effect of EA intervention.
CONCLUSIONS: EA of GV24-GV20 and GV14 can improve the general state, anxiety and learning-memory ability of CFS model rats, which may be related to its functions in regulating the hippocampal protein phosphorylation level, and repairing the structure and function of synapses in hippocampus.