The Role And Mechanisms Of IL-1β Mediated Synaptic Plasticity Regulation In Depression

Objective:Depression is a nervous and mental disease which is mainly characterized by low mood and pessimism,amd is serious endangers the health of human.Recent studies have shown that the development of depression is the result of a variety of factors such as genetic,neuroendocrine and neuroinflammation.More and more studies paied attention to the hypothesis of neuroinflammation in depression.The latest clinical studies have found that the proportion of brain inflammation in patients with depression increased significantly,and the incidence of inflammation was positively correlated with the severity of depression.However,the role of neuroinflammation in the pathogenesis of depression,especially its pathological mechanism,has not yet been elucidated.Therefore,The aim of this study was to investigate the role and mechanism of Il-1β(interleukin-1β,IL-1β)mediated neural plasticity regulation in the depression model of rats induced by chronic unpredictability mild stress(CUMS),The experiments were studied by molecular biology and behavioral methods.It is expected to provides new targets and scientific theoretical for the research and development of antidepressant drugs.Methods:(1)120g-140g Wister male rats were randomly divided into four groups:non-stressed control group,CUMS group,drug pretreatment group and solvent control group.Except for the blank control group,the other three groups were given chronic unpredictability mild stimulus for 6 weeks.30 minutes before each stimulation,the drug pretreatment group was given G-Rg1(40mg/kg)by intraperitoneal injection,and intraperitoneal injection of 0.9%Nacl(1ml/kg)in the solvent control group at 30 minutes before each stress.After six weeks of chronic stress,the rats were tested by forced swimming test and sucrose preference test.(2)After behavioral tests,the tissue of medial prefrontal cortex(mPFC)was used to observe the activation of microglial cells by Immunofluorescence.The expression of inflammatory factors such as IL-1β and IL-6 were detected by using ELISA and qPCR technique,and the changes of dendritic spines and synaptic structures by using the technique of Golgi staining and transmission electron microscope.Western blot were used to detect the expression of synapse related protein such as SSH1,Cofilin,p-cofilin,F-actin.(3)The male Wister rats were randomly divided into non-stressed control group,CUMS group,IL-1β receptor antagonist(IL-IRa)pretreatment group(IL-1Ra+CUMS)and solvent control group(dH2O+CUMS).IL-1Ra(1.25 mg/kg)or dH20(100ul/kg)was injected into the lateral ventricle of the rat 30 minutes before each stress stimulus,and tested by forced swimming test and sucrose preference test after six weeks.Golgi staining and transmission electron microscopy(TEM)were used to observe the changes of dendritic spines and synaptic structures in the brain region of the prefrontal cortex,and the expression of synapse related proteins were detected by western blot.(4)The male Wister rats were randomly divided into non-stressed control group,CUMS group,NF-κB inhibitor pretreatment group(PDTC+CUMS)and solvent control group(0.9%NacI+CUMS).The PDTC pretreatment group and the solvent control group were treated with PDTC and 0.9%Nacl by intraperitoneal injection 30 minutes before each stress stimulus.After six weeks,the behavioral tests were performed and the changes of structural in the neurons were observed by using Golgi staining and transmission electron microscopy(TEM)technology,the expression of synapses related proteins was detected by western blot technology.Results:(1)Compared to the non-stressed control group,the immobility time of CUMS group rats increased significantly,while the swimming time decreased significantly(P<0.05)in the forced swimming test.In the experiment of sucrose preference test,the consumption of sucrose was significantly reduced(P<0.05).(2)The results of immunofluorescence showed that the m protuberance of icroglial cells in mPFC of CUMS group rat retraction and reduction while the volume of the cell body increased,which indicated that the cell was activated.ELISA and qPCR results showed that the expression of inflammatory factors such as 11-1β and IL-6 in CUMS group increased.(3)Golgi staining results showed that after giving chronic stress,the number of dendritic spine in the mPFC area of rats was significantly reduced,the volume narrowed,and the neck was slender,whichi indicated the structural plasticity was changed.TEM showed that after chronic stress,the number of synapses of mPFC neurons decreased,as well as the synaptic activity zone decreases and the postsynaptic dense becomes thinner.(4)Western Blot results showed that,compared with the non-stressed control group,the levels of phosphorylation of NF-κB P65 significantlly increased,the protein expression levels of SSH1 were significantlly increased,as well as the levels of phosphorylation of cofilin decreased and the protein expression levels of F-actin decreased in CUMS group.(5)Preadministration of IL-1Ra(i.c.v)for six weeks can obviously improve the depression-like behavior of rats.The morphological and structural abnormalities of dendritic spines and synapses and the changes of related proteins eapression or activity were significantly improved.(6)Compared with CUMS group,the protein expression levels of SSH1 in PDTC pretreatment group decreased,as well as the levels of phosphorylation of cofilin and the protein expression levels of F-actin increased.Meanwhile,the density of neuronal dendritic spines and the number of synapse increased,the depression-like behaviors were improved significantly.Conclusion:(1)CUMS can effectively induce depression-like behavior in rats,accompanied by activation of microglia in the medial prefrontal cortex and the increasesd expression of inflammatory factors such as IL-1β.(2)CUMS caused the changes of the structural plasticity of the dendritic spines and synapses in the medial prefrontal cortex of the rat,accompanied with the increased SSH1 expression,the decreased cofilin phosphorylation levels and the decreased expression levels of F-actin,(3)IL-1β may regulate synaptic plasticity and improve depression-like behavior via NF-κB/SSH1/Cofilin/F-actin signaling pathways.