The Role Of CD47 In Chronic Social Defeat Stress-induced Depressive-like Behavior In Mice

Objective: CD47 is a widely expressed transmembrane protein.CD47 and signal regulatory protein α(SIRPα,also known as CD172α)constitute a cell-cell communication system,which plays an important role in the brain.SIRPα is mainly expressed in macrophages and myeloid cells,and can recognize the "shut down" signal.The interaction of SIRPα and CD47 can inhibit the phagocytosis of macrophages or microglia.The CD47 in the visual system during development has been shown to act as a "not eat me" signal,inhibiting excessive microglial phagocytosis during synaptic pruning.In addition,CD47-SIRPα signaling plays an important role in the development of neuroinflammation after central nervous system injury,and the expression of CD47 is reduced in multiple sclerosis.However,it is unclear whether CD47 is involved in depression.Therefore,this research explores the role of CD47 in chronic stress-induced depressive-like behavior in mice.Methods: Chronic social defeat stress(CSDS)was used for the built of animal model of depression.Social interaction test(SIT)and sucrose preference test(SPT)were used to evaluate depressive-like behavior.Western blotting(WB)and quantitative polymerase chain reaction(QPCR)were used to detect CD47 and SIRPα protein and m RNA level in the peripheral blood,the hippocampus and other brain regions of control mice and stressed mice.Recombinant CD47 protein,neutralizing antibody and the lentivirus that overexpressed CD47 gene were administered to investigate the role of CD47 in the depressive-like behavior.Results:(1)After CSDS,the susceptible mice showed significant depressive-like behaviors,including the decreased social interaction ratio from 1.42 ± 0.10 to 0.56 ± 0.05(n = 14-21,p < 0.001 vs Control)and the declined sucrose preference ratio from 85.23 ± 2.07 % to65.15 ± 4.74 %(n = 14-21,p < 0.01 vs Control);(2)QPCR results revealed changed expression of CD47 in brain of susceptible mice.The CD47 m RNA level significantly reduced from 1.00 ± 0.03 to 0.87 ± 0.03(n = 6-9,p < 0.05 vs Control)in the medium prefrontal cortex(m PFC)brain region.The CD47 m RNA levels were reduced in the dorsal hippocampus(DH)and the ventral hippocampus(VH)brain area(DH: Control: 1.00 ± 0.03,n = 6;Susceptible: 0.84 ± 0.03,n = 10,p < 0.01 vs Control;VH: Control: 1.00 ± 0.02,n =11;Susceptible: 0.80 ± 0.04,n = 19,p < 0.001 vs Control).Likewise,the CD47 m RNA level was also reduced in the CA1 brain region(Control: 1.00 ± 0.04,n = 6;Susceptible:0.81 ± 0.04,n = 9,p < 0.05 vs Control)in susceptible mice,however,it was increased from1.00 ± 0.04 to 1.14 ± 0.03 in the dentate gyrus(DG)brain area(n = 7-8,p <0.05 vs Control).There was no significant change in the anterior cingulate cortex(ACC)brain area.(3)WB found the CD47 protein level was declined from 1.00 ± 0.04 to 0.84 ± 0.04(n = 12-14,p <0.05 vs Control)in the VH brain region and reduced from 1.00 ± 0.08 to 0.80 ± 0.04(n = 7,p < 0.05 vs Control)in the CA1 brain region,but not changed in the m PFC,DH and DG brain regions in the susceptible mice.(4)QPCR and WB found that there were no changes in the SIRPα m RNA and protein levels in the CA1 and DG brain regions of the susceptible mice.The m RNA level decreased in the m PFC(Control:1.00 ± 0.05,n = 6;Susceptible:0.84 ± 0.03,n = 9,p < 0.05 vs Control)and VH region(Control: 1.00 ± 0.03,n = 11;Susceptible: 0.90 ± 0.02,n =19,p < 0.05 vs Control),but the SIRPα protein levels did not change.(5)QPCR showed that the m RNA level of CD47 significantly reduced from 1.00 ±0.11 to 0.44 ± 0.06(n = 9-11,p < 0.001 vs Control)in blood of susceptible mice,but the m RNA level of SIRPα did not change significantly.(6)Administration of 40 μg/ml CD47 neutralizing antibody in the VH brain region could up-regulate the immobility time in TST and reduce sucrose preference(TST: PBS: 148.70 ± 8.65 s,n = 6;40 μg/ml: 224.30 ± 17.91 s,n = 7,p < 0.05 vs Control;SPT: PBS: 90.22 ± 2.18 %,n = 7;40 μg/ml: 62.40 ± 7.79 %,n= 7,p < 0.01 vs Control).In the CA1 brain area,administration of 40 μg/ml CD47 neutralizing antibody obviously down-regulated the sucrose preference(PBS: 72.60 ±3.90 %,n = 27;CD47 neutralizing antibody: 60.65 ± 3.97 %,n = 29,p < 0.05 vs Control),and increase the immobility time in TST or FST(TST: PBS: 106.70 ± 6.88 s,n = 23;CD47neutralizing antibody: 126.40 ± 6.80 s,n = 25,p < 0.05 vs Control;FST: PBS: 47.00 ± 5.52 s,n = 23;CD47 neutralizing antibody: 70.11 ± 9.44 s,n = 19,p < 0.05 vs Control).The administration of CD47 neutralizing antibody did not affect the motor ability and anxiety-like behavior in mice.(7)Administration of recombinant CD47 protein in the CA1 improved depressive-like behavior of susceptible mice.Specifically,the social interaction ratio of the Susceptible + Recombinant CD47 group was higher than that of Susceptible +PBS group(Susceptible + PBS group: 0.61 ± 0.34,n = 5;Susceptible + Recombinant CD47group: 3.08 ± 0.62,n = 5,p < 0.05 vs Susceptible + PBS),but the immobility time of the mice in TST in the Susceptible + Recombinant CD47 group did not change significantly.(8)Lentivirus-specific overexpression of the CD47 gene in the CA1 brain region of susceptible mice did not reverse depressive-like behaviors.Conclusion: CSDS induces a decline of CD47 expression in the hippocampus(CA1 and VH)brain regions of mice without affecting the SIRPα protein expression.The administration of CD47 neutralizing antibody induces depressive-like behavior in mice.Conversely,the administration of recombinant CD47 protein in the hippocampal brain area improves the depressive-like behavior of susceptible mice.