MRNA And MicroRNA Expression Profiles Of Amygdala In Mice Are Associated With Stress-induced Depression And Resilience

Objective: Depression is one of the most common mental illnesses characterized by recurrent negative emotions.Long-term chronic stress in the absence of rewards may cause imbalances in brain rewards and penalty circuits,leading to depression.Studies have shown that chronic stress can lead to depression-like behavior,but numerous individuals may not suffer from depressive mood in response to the stress,suggesting that there are endogenous factors in the brain that are resistant to chronic stress.The amygdala is an important structure in the brain that produces,processes and regulates emotions,especially negative emotions.However,the molecular mechanisms by which the amygdala is involved in regulating depression and resilience induced by chronic stress remain unclear.Therefore,this study will use chronic unpredictable mild stress(CUMS)to induce CUMS-susceptible and CUMS-resilience mice as models,using high-throughput sequencing technology and bioinformatics analysis methods to reveal the changes of mRNA and microRNA molecules in the amygdala with CUMS-susceptible and CUMS-resilience mice after stress.Methods: After mice were treated by the chronic unpredictable mild stress for four weeks,they were screened by sucrose preference,Y-maze and forced swimming tests to examine whether their behaviors were depression-like or not.mRNA and microRNA profiles were quantified by high-throughput sequencing in amygdala tissues harvested from control,CUMS-susceptible and CUMS-resilience mice.Using bioinformatics analysis method,combined with sequencing results of mRNA and microRNA expression profiles,to construct mRNA/microRNA regulatory network maps of amygdala in the CUMS-susceptible and CUMS-resilience mice.qRT-PCR and dual-luciferase reporter were used to verify the molecular biology of important mRNA/microRNA regulatory relationships.Results: Behavioral data indicates that depression and resilience mice were produced by chronic unpredictable mild stress;mRNA high-throughput sequencing results in amygdala showed that compared with the control group,161 differentially expressed mRNAs were screened in the CUMS-susceptible mice,in which 67 mRNAs were upregulated and 94 mRNAs were downregulated,the upregulated mRNAs in CUMS-susceptible mice include genes that encode PI3K-Akt signaling pathway,long-term depression,amphetamine addiction and inflammatory mediated regulation of TRP channels,whereas the downregulated mRNAs that encode neural processes about dopaminergic type-II receptor,G-protein coupled dopaminergic/serotonergic/GABAergic synapse,metabolic pathway and calcium signal pathway;Compared with the control,87 differentially expressed mRNAs were screened in CUMS-resilience mice,in which 37 mRNAs were upregulated and 50 mRNAs were downregulated,the upregulated mRNAs in CUMS-resilience mice include genes that encode neural processes about neuroactive ligand-receptor interaction,synaptic vesicle cycle and nicotine addiction,whereas the downregulated mRNAs that encode neural events about metabolic pathway,PI3K-Akt signaling pathway and G-protein coupled dopaminergic/serotonergic/GABAergic synapse;High-throughput sequencing results of microRNA in the amygdala showed that 119 differentially expressed micrornas were screened from the CUMS-susceptible mice compared with the control group,in which 71 microRNAs were upregulated and 48 microRNAs were downregulated,159 differentially expressed microRNAs were screened in CUMS-resilience mice,in which 55 microRNAs were upregulated and 104 microRNAs were downregulated;The prediction results of target genes of differentially expressed microRNA showed that 111 differentially expressed microRNAs and 132 differentially expressed mRNAs may have a targeted regulatory relationship in the CUMS-susceptible group;In CUMS-resilience group,there was a possible targeted regulatory relationship between 120 differentially expressed microRNAs and 68 differentially expressed mRNAs;The results of qRT-PCR showed that miR-34a-5p was negatively correlated with P2ry2 and Npffr1,respectively;The results of dual luciferase reporter showed that P2ry2 and Npffr1 mRNA were the direct targets of miR-34a-5p,P2ry2 and Npffr1 were negatively regulated by miR-34a-5p.Conclusion: Chronic unpredictable mild stress can induce mice to exhibit CUMS-susceptible and CUMS-resilience;Our data suggest that the impairments of dopaminergic receptors and calcium signaling in the amygdala may be involved in CUMS-induced depression,that the upregulations in genes relevant to neuroactive ligand-receptor interaction,synaptic vesicle cycle and nicotine addiction in the amygdala may be involved in mouse resilience to the CUMS,and that the downregulations of genes relevant to G-protein coupled dopaminergic serotonergic and GABAergic synapses as well as metabolic pathways may be involved in CUMS treatment.