MicroRNA-204-5p In Hippocampus Involved In Stress-induced Depression Via Targeting Neuroinflammation And Oxidative Stress

Background:Depression is a major pervasive mental disorder mainly manifested as a persistent despondent mood,and its specific pathogenesis has not been clarified.Previous studies have reported that oxidative stress played a pivotal role in the pathogenesis of most nervous system diseases,including depression.However,the underlying molecular mechanisms of oxidative stress associated with neuronal injury in depression remain largely uncharacterized.Therefore,based on chronic stress-induced depression model rats,we used transcriptome sequencing,AAV virus injection,electrophysiology and other techniques to identifying potential molecular mechanisms of miR-204-5p in regulating neuroinflammation and oxidative stress response in the hippocampal dentate gyrus(DG)region of depression rats.The results would to clarify the pathological mechanisms of depression and provide potential therapeutic targets for the treatment of depression.Methods:(1)Chronic unpredictable mild stress(CUMS)was used to induce depression-like behaviors in rats.After 6 weeks stimulation,each group conducted behavioral tests simultaneously,and the changes of oxidative marker and inflammation related factors in hippocampal DG region and other relevant regions were detected in each group.(2)RNA-sequencing was used to detect the differentially expressed microRNAs between the CUMS group and the control group.The relationship between miR-204-5p and RGS12 was verified by Target Scan prediction and Dual-luciferase reporter assay.(3)Adreno-Associated virus was constructed to overexpress or knock down miR-204-5p in the DG region of the hippocampus.Stereotactic injection of AAV virus was performed.Behavioral tests were conducted two weeks after the virus infection.Then we detected the expression of miR-204-5p in hippocampal DG region and factors related to oxidative stress and inflammation by immunoblotting or immunofluorescence assay.(4)The number of synapse and morphological changes were observed by transmission electron microscopy.The excitatory postsynaptic currents were recorded by whole-cell patch clamp to analyze the synaptic transmission.Results:(1)Behavioral tests showed that 6 weeks CUMS procedure can effectively induced depression-like behaviors in rats.(2)Compared with the control group,we found that the substantial amounts of ROS are present in the vmPFC,hippocampal CA1 and DG regions in this rat model of depression,Moreover,the antioxidant enzyme activity was decreased in these CUMS rats.(3)Transcriptome sequencing and Q-PCR results showed that the expression of miR-204-5p within the hippocampal DG region of rats was significantly down-regulated after CUMS.Dual-luciferase reporter assay showed that RGS12 was the downstream target gene of miR-204-5p.(4)Within control rats,the expressions of RGS12 was significantly increased and the expressions of Nrf2 and HO-1 were significantly decreased within DG areas following AAV-miR-204-5p-sponge injections,accompanied by the increased expression of pro-inflammatory cytokines and the exhibited depression-like behaviors in rats.(5)In contrast,overexpression of miR-204-5p within the DG region of CUMS rats,the expression of RGS12 was significantly decreased and oxidative stress injury,neuroinflammation response and the depression-like behaviors all showed reductions in these CUMS rats.(6)Electron microscopy results showed that the number and morphological structure of synapses in the hippocampal DG region of CUMS rats were significantly improved after overexpression of miR-204-5p.Electrophysiological recording results showed that the synaptic transmission efficiency was significantly restored.Conclusions:Chronic stress induces oxidative stress injury and neuroinflammation by down-regulating miR-204-5p in the hippocampal DG region,resulting in increased expression of its downstream target gene RGS12,and possibly via regulating the Nrf2 signaling pathway.Conversely,an up-regulation of miR-204-5p attenuates depression-like behaviors,reduces oxidative damage and neuroinflammation within the DG region,as well as augmenting synaptic plasticity in this rat model of depression.Taken together,these results suggest that chronic stress affected neuroinflammation and oxidative stress injury possibly via the miR-204-5p/RGS12/Nrf2 pathway and involved in pathological processes of depression.