Amygdala Systems Biology Study Of Depression Model And Construction Of A Rat Model Of Depression With Suicidal Behavior

Background : Depression is a common mental disorder,which causes huge harm to human and is a major contributor to the overall global burden of disease.The pathophysiology of depression remains unclear.Amygdala,a key brain region of appetitive and aversive circuit,is involved in the pathophysiology of depression.There is increasing evidence showing that alteration of volume,functional connectivity and metabolism were found in amygdala;however,the underlying mechanism remains poorly understood.Method: We established a rat model of chronic social defeat stress(CSDS)and conducted a series of behavior tests to observe behavioral changes.Then liquid chromatography mass spectrometry(LC-MS)-based metabolomics and isobaric tags for relative and absolute quantitation(i TRAQ)-based proteomics were employed to detect metabolomes and proteomes in the amygdala,respectively.Annotation,hierarchical clustering and enrichment analysis were conducted by Metabo Analyst 4.0and R to uncover the crucial metabolic disorder related to depressive-like behaviours.Meanwhile,volcano plot,hierarchical clustering,GO and KEGG analysis were performed by R,DAVID and Omics Bean to detect protein changes.In addition,Ingenuity pathway analysis(IPA)was used to perform canonical pathway and network analysis by integrating differentially expressed metabolites and proteins.Furthermore,comparative analysis with previous untargeted metabolomics results in the prefrontal cortex(PFC)and hippocampus of CSDS rats was conducted to reveal the common and unique molecular changes among the three brain regions.Results : The significantly lower sucrose preference index in the sucrose preference test and longer immobile time in the forced swimming test were observed in the CSDS rats compared with control rats.In the metabolomics,thirty-seven significantly differentially expressed metabolites were identified including 15 regulated and 22 downregulated.These metabolites were mainly associated with amino acid metabolism and lipid metabolism.Meanwhile,we identified 123 significant proteins including 44 proteins upregulated and 79 downregulated.GO and KEGG analyses revealed that the altered proteins were mainly involved in dopamine receptor binding and the synaptic vesicle cycle.Integrated analysis of differentially expressed metabolites and proteins by IPA revealed molecular changes mainly associated with synaptic long term potentiation,phospholipase c signaling,and glutamine degradation I.We compared the metabolites in the amygdala with those in the hippocampus and prefrontal cortex from our previous studies and found two common metabolites,arachidonic acid and N-acetyl-L-aspartic acid among these three brain regions.In addition,alanine,glutamic acid and aspartic acid metabolism was the top pathway among the three brain regions.Conclusion : Our study revealed the presence of depressive-like behaviors and molecular changes of amygdala in the CSDS rat model,which are potentially related to dysregulation of alanine,glutamic acid and aspartic acid metabolism.Moreover,CSDS resulted in PLC-dependent long term potentiation mediated by glutamate in the amygdala.This study may provide further insights into the pathogenesis of depression,and help to identify potential targets for antidepressants.Background : Suicide is one of the leading causes of death and represents a significant public health problem worldwide;however,the underlying mechanism of suicide remains unclear and there is no existed suicide trait-related animal model for investigating the etiology,the course and the potential treatment targets of suicide.Method: In this study,we performed a stress-diathesis rat model to simulate suicide trait-related behaviors in human including hopelessness,irritability,impulsivity and aggression Two hundred rats were screened by two rounds of learned helplessness(LH)test and selected as congenitally learned helpless(cLH,n=37)group and congenitally non-learned helpless(c NLH,n=39)group.Then,all rats in the cLH group(cLH+SDS,n=37)and one half of rats(selected randomly)in c NLH group(c NLH + SDS,n=20)were exposed to four-week chronic social defeat stress.The other half of rats in c NLH group were handled as controls(c NLH+CON,n=19).We also performed the sucrose perference test(SPT),irritability test(IT),forced swimming test(FST)and resident-intruder paradigm(RIT),as well as the proteomic detection of prefrontal cortex by isobaric tags for relative or absolute quantitation(i TRAQ).Then annotation and pathway analysis were conducted by DAVID,R and IPA software.Results: The stress–diathesis rat model,cLH+SDS,induced rats show more traits associated with suicidal behavior,including significantly longer immobile time in FST(hopelessness,P=0.017),higher scores in IT(irritability,P=0.002),shorter latency to attack(impulsivity,P=0.008)and longer total attack time in RIT(aggression,P=0.009),and lower sucrose preference index(anhedonia,P < 0.001),compared with c NLH + CON group.i TRAQ-based proteomic analyses found 327 differentially expressed proteins including 188 proteins upregulated and 139 proteins downregulated.And bioinformatics revealed that the most related canonical pathways between cLH+SDS group and c NLH+CON group were PKA and GABA receptor pathways.Conclusion: A stress–diathesis paradigm would be a useful way to establish a rat model with suicide trait-related behaviors.The pathological changes in cLH + SDS rats were consistent with the findings of postmortem brain tissue from suicide victim.So,the stress–diathesis model may play a vital role in investigating the mechanism of suicide.