The Effect And Mechanism Of CD39 On Depressive-like Behaviors Induced By Chronic Social Defeat Stress Of Mice

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The effect of CD39 on depressive-like behaviors induced by chronic social defeat stress of miceObjective:Emerging evidence implicates deficient astrocytic release of 5'-adenosine triphosphate(ATP)as a component of major depressive disorder(MDD)pathophysiology.ATP,when released into the extracellular space,is hydrolyzed by ectonucleoside triphosphate diphosphohydrolase(ENTPD).However,the role of ENTPD in depression remains poorly understood.In the current study,we therefore aimed to investigate the role of ectonucleoside triphosphate diphosphohydrolase 1(ENTPD 1,also known as CD39)in the context of chronic social defeat stress(CSDS).Methods:Real-time Quantitative PCR(qPCR)and western blot were used to examine ENTPD mRNA and protein expression level in the hippocampus and medial prefrontal cortex(mPFC)of C57BL/6J mice that underwent CSDS.We defined the cell types that express CD39 by immunohistochemistry.Enzymatic activities of extracellular ATP-degrading enzymes activity and extracellular ATP level were examine with malachite green phosphate assay kit and bioluminescent ATP assay kit,respectively.Mice were infused with a CD39 functional analog followed by ATP,or inhibitor and their depression-like behaviors were measured.To assess the direct role of CD39,we used lentiviral-mediated RNAi to silence endogenous CD39 of mice and evaluated their depression-like behaviors,enzymatic activities of extracellular ATP-degrading enzymes and extracellular ATP level.Results:(1)We observed that CSDS enhanced the CD39 mRNA to 1.39 ± 0.050(P<0.001),protein expression level to 1.58 ± 0.063(P<0.001)and enzymatic activities of extracellular ATP-degrading enzymes from 2.23± 0.19nmol of Pi release/min/mg protein to 3.54 ±0.30nmol of Pi release/min/mg protein(P<0.01)in hippocampus,but not in the mPFC.(2)CD39 expression is enriched in neurons and astrocytes but seldom in microglial cells.(3)Furthermore,we found that the administration of a CD39 functional analog apyrase induced depression-like behaviors.The social interaction time was reduced from 54.6 ± 5.2 s tol9.2 ± 5.2 s(P<0.01)and sucrose preference was decreased from 84.83 ± 4.10%to 60.27 ± 5.06%(P<0.01)after intracerebro ventricular infusions of apyrase(80U/ml).The social interaction time was reduced from 46.2 ± 4.0 s to 19.5±3.4 s(P<0.001)and sucrose preference was decreased from 86.5 ± 1.46%to 63.0±4.27%(P<0.001)after hippocampal infusions of apyrase(40U/ml).Social avoidance behavior induced by apyrase could be ameliorated via the hippocampal administration of ATP,which increased social interaction time from 28.9±5.9 s to 54.5±8.6 s(P<0.05).(4)Pharmacological inhibition of CD39 induced antidepressant-like effects in mouse models of depression.Intracerebroventricular infusions of ARL67156,a inhibitor of CD39,in CSDS susceptible mice increased social interaction time from 9.1 ± 3.0 s to 38.6 ± 5.9 s(P<0.01)and sucrose preference from 55.10 ± 6.72%to 80.72 ± 3.21%(P<0.001).Hippacampal infusions of ARL67156 in CSDS susceptible mice increased social interaction time from 24.5 ± 3.6 s to 41.8 ± 5.3 s(P<0.05).(5)Genetic inhibition of CD39 in the hippocampus of CSDS susceptible mice also induced antidepressant-like effects through decreasing hippocampal CD39 enzyme activity and increasing extracellular ATP level.The slience of CD39 gene decreased enzymatic activities of extracellular ATP-degrading enzymes from 5.82±4.49 nmol of Pi release/min/mg protein to 4.09±0.44 nmol of Pi release/min/mg protein(P<0.05),increased extracellular ATP level from 0.82± 0.22 nM mg-1 to 2.50 ± 0.53 nM mg-1(P<0.01)and increased social interaction time from 19.9±4.0 s to 56.8 ±7.3 s(P<0.001).Conclusion:These data suggest that the enhanced hippocampal CD39 contributes to the CSDS-elicited depression-like behaviors via hydrolyzing extracellular ATP.These results highlight aberrant CD39 function as a potential molecular mechanism underlying MDD pathophysiology and suggest that CD39 may be a promising new target for the treatment of depression.Part ? The mechanism of CD39 mediates depressive-like behaviors induced by chronic social defeat stress of miceObjective:It was reported that hippocampal neurogenesis is decreased by stress and and antidepressants increase the net magnitude of hippocampal neurogenesis.This suggests that augmenting hippocampal neurogenesis represents a potential new strategy for treating depression.In addition,chronic stress induces dendrite and dendritic spine pathology.Available evidence suggests that CD39 may be involved in the neuroplasticty through regulation the ATP level.Therefore,we investigated the role of CD39 on hippocampal neurogenesis and dendritic spine pathology in the context of CSDS.Methods:In order to evaluate the hippocampal neurogenesis,the dividing cells and immature neuronsin the adult hippocampus were identified through immunohistochemistry and the number of both cells was respectively quantificated.Mice were infused lateral intracerebroventricular(i.c.v.)with a CD39 inhibitor and their hippocampal neurogenesis were measured.To investigate the effect of chronic stress and CD39 knockdown on dendritic spine,neurons in the dentate gyrus(DG)were infected with lentivirus that carry GFP and their dendritic segments were imaged with confucal microscope and anlysized using automated three-dimensional dendritic spine reconstruction.Results:(1)CSDS reduced the hippocampal neurogenesis.The number of dividing cells and immature neurons was significantly reduced in the hippocampus of CSDS induced mice.CSDS decreased the number of BrdU+cells(dividing cells)from 1120±66 to 740 ± 109(P<0.05)and BrdU+/DCX+ cells(immature neurons)from 568 ±66 to 285± 56(P<0.05)in the hippocampus.The number of these cells was significantly increased in chronic stress induced mice that received CD39 inhibitor ARL67156 treatment.Intracerebroventricular infusions of ARL67156 in susceptible mice increased the number of BrdU+cells from 2700 ± 150 to 3985 ± 268(P<0.01)and BrdU+/DCX+ cells from 1150 ± 25 to 1770 ± 164(P<0.01).(2)Chronic stress resulted in a decrease in the total spine density from 2.9 ± 0.2 ?m-1 to 2.3 ± 0.1?m-1(P<0.05),which could be rescued to 2.8 ± 0.2 ?m-1(P<0.05)by CD39 knockdown.Only the density of stubby spines selectively decreased from 1.2 ± 0.1?m-1 to 0.7±0.1 ?m-1(P<0.01)in the hippocampus of susceptible mice,and knockdown of CD39 could improve the density to 1.4±0.1 ?m-1(P<0.001).However,mushroom or thin spines had no changes.Conclusion:Hippocampal neurogenesis was decreased by chronic stress and inhibition of CD39 increased the magnitude of hippocampal neurogenesis.The density of spines was decreased in the hippocampus by chronic stress and knockdown of CD39 could improve the density.Inhibition of CD39 amelioratedchronic stress-elicited abarrent neuroplasticity,which may be the neurobiological mechanism of CD39 on depressive-like behaviors.