| Objective: This study mainly investigated the effect of exercise-induced Irisin on depression-like performance of chronic unpredictable mild stimulation（CUMS）depressed mice and preliminarily revealed its mechanism,in order to provide more theoretical support for exercise intervention to prevent and treat depression.Methods: 95 male C57BL/6 mice at the age of 5 weeks old were randomly divided into control group（N group,n=8）and model group（CUM group,n=87）.Mice in N group were subjected to normal physiological activities without intervention.Mice in the CUM group were subjected to chronic unpredictable mild stress for seven weeks to establish depression model mice.Sucrose preference test（SPT）and forced swimming test（FST）were conducted before and after the experiment to verify whether the modeling was successful.The modeled mice were randomly divided into irisin administration group（group I,n=8）,exercise group（group E,n=8）,irisin combined exercise group（group EI,n=8）and depression model group（group M,n=8）.Group I,group E and group EI were treated for 4 weeks.In group I,depressed mice were intraperitoneally injected with 500（?）g/kg irisin 5 times a week.Group E: Mice were subjected to treadmill exercise with an intensity of10m/min for 40 min,and the frequency was 5 times per week;EI group: Mice were given 500（?）g/kg irisin intraperitoneally after 40 min of 10m/min treadmill exercise,5times a week.Mice in group M were fed normally without intervention.The weight of experimental mice was recorded once a week,and SPT and FST tests were performed after the intervention to detect the improvement of depression-like behavior in experimental mice.The experimental mice were sacrificed 24 hours after the end of the intervention,and the serum,hippocampus and cortex tissue samples were taken.The contents of irisin and BDNF in serum were detected by ELISA,HE staining was used to observe the morphology of hippocampal neurons,the damage of neurons was observed by Nissner staining,and the apoptosis of hippocampal nerve cells was detected by TUNEL staining.Hippocampal nerve regeneration was evaluated by immunofluorescence.The synaptic plasticity of hippocampus and cortex was observed by electron microscopy,and the expression and changes of apoptosis,neurogenesis and proteins associated with prominent plasticity in hippocampus and cortex were investigated by Western Blot.Resuits:1.General changes:1)Weight: The body weight of mice in group N continued to increase;After receiving CUMS stimulation,the body weight of depressed mice increased slowly from 1 to 4 weeks,and decreased significantly from 4 weeks（P < 0.001）.After 4weeks of intervention,the weight of experimental mice in groups I,E and EI increased significantly before intervention（P < 0.001）.2)SPT: Before CUMS intervention,there was no significant difference in sugar water preference among all groups（P > 0.05）.After CUMS stimulation,the sugar water preference rate of depressed mice was significantly lower than that of normal mice（P< 0.001）.After 4 weeks of intervention,the preference rate of sugar water in groups I,E and EI was significantly higher than that in model group（P < 0.05）.3)FST: Before CUMS intervention,the immobile time of forced swimming was within 40 s in all experimental groups,and there was no statistical difference among all groups（P > 0.05）.After CUMS stimulation,the immobile time of forced swimming in model group was significantly longer than that in N group（P <0.001）.After intervention,the immobility time of forced swimming was significantly shortened in groups I,E and EI（P < 0.001）.2.Cytokine changes: The protein expressions of irisin and BDNF in serum of mice in M group were significantly decreased（P < 0.01）,after intervention,the protein expression levels of irisin and BDNF in serum of group I,group E and group EI were significantly increased compared with that of group M（P < 0.01）.3.Changes in organizational structure:1)HE staining: Compared with mice in N group,the number of hippocampal neurons in mice in M group was significantly reduced,with uneven cell distribution and different sizes,swelling and deformation of neurons,obvious widening of cell space,loose and disorderly arrangement and unclear hierarchy;After 4 weeks of intervention,the number of hippocampal neurons in groups I,E and EI increased,the cell space decreased,the arrangement was more regular,the nucleus was clearer,and the nuclear pyknosis was improved.2)Nissl staining: the morphology of hippocampal CA1 neurons of mice in M group was changed,including disorder of cell arrangement,cell damage,cytoplasm concentration,massive loss of Nissl bodies in cells,nuclear atrophy and deep staining.Compared with M group,the neurons in CA1 region of mice in groups I,E and EI were arranged in a relatively uniform and orderly manner,the nuclei hyperchromatism and pyknosis of neurons’ small cells were improved to a certain extent,and the number of Neurons’ small bodies was slightly increased.3)TUNEL staining: the apoptosis rate of hippocampal nerve cells in M group was significantly higher than that in N group（P < 0.01）.After intervention,the apoptosis rate of hippocampal nerve cells in groups I,E and EI was significantly lower than that in group M（P < 0.01）.4)Immunofluorescence double staining: Compared with N group,the number of GFAP and Nestin positive staining cells in the hippocampus of mice in M group was significantly decreased（P < 0.01,P < 0.01）;Compared with M group,the number of GFAP and Nestin positive staining cells in the hippocampus of mice in groups I,E and EI were significantly increased（P < 0.01,P < 0.01）.5)Transmission electron microscopy（TEM）: Compared with group N,the postsynaptic density of hippocampal and cortical neurons in group M decreased,the synaptic gap widened,and the synaptic vesicles were not clear.Compared with group M,the synaptic structure of hippocampus and cortex of mice in groups I,E and EI was more intact,the density of postsynaptic dense substance was higher,and synaptic vesicles were clearly visible.4.Western blot analysis:1)Effect of intervention on FNDC5 expression in muscle,hippocampus and cortex:Compared with group N,p-AMPK /AMPK ratio,PGC-1α and FNDC5 expression levels in hippocampus,cortex and muscle of mice in group M were significantly decreased（P < 0.01）;The expression levels of p-AMPK/AMPK,PGC-1α and FNDC5 in hippocampus,cortex and muscle of mice in groups I,E and EI were all increased（P < 0.01）.2)Expression levels of apoptosis-related proteins: Compared with N group,the expression levels of apoptosis-related proteins Bax and Cleaved caspase-3 were up-regulated in the hippocampus and cortex of M group（P < 0.01）,and the expression level of anti-apoptotic protein Bcl-2 was significantly decreased（P <0.001）;The expression of Bax and Cleaved caspase-3 in the hippocampus and cortex of mice in group I,group E,and group EI was significantly decreased compared with that in group M（P < 0.05）,while the expression of Bcl-2 was significantly increased（P < 0.01）.3)Hippocampal neurogenesis related protein expression levels: Compared with N group,the protein expression levels of PI3 K,p-Akt /AKT,Nestin,GAP43,Trk B and BDNF in hippocampal and cortex of mice in M group were significantly decreased（P< 0.05）.The expression levels of PI3 K,p-Akt /AKT,Nestin,GAP43,Trk B and BDNF in hippocampus and cortex of mice in group I,group E and group EI were significantly higher than those in group M（P < 0.05）.4)Expression levels of synaptic plasticity related proteins: Compared with N group,the expression levels of PSD95,SYN,p-ERK/ERK and p-mTOR /mTOR in hippocampus and cortex of M group were significantly decreased（P < 0.001）,and the expression level of GSK-3β was significantly increased（P < 0.001）.Compared with M group,the expression levels of PSD95,SYN,p-ERK/ERK and p-mTOR /mTOR in hippocampus and cortex of mice in group I,E and EI were significantly increased（P< 0.001）,and the expression level of GSK-3β was significantly decreased（P <0.001）.Conclusion: Exercise-induced irisin and exogenous irisin injection can reduce nerve cell apoptosis,promote nerve regeneration and synaptic plasticity,and play a role in depression prevention and rehabilitation. |
PDF Full Text Request