Leptin Increases Expression Of 5-HT_2B Receptors In Astrocytes Thus Enhancing Action Of Fluoxetine On The Depressive Behavior Induced By Sleep Deprivation

Objective:Long-term sleep disorder seriously affects people's health and quality of life and it is a high risk factor for depression.However the underlying mechanisms connecting sleep deprivation and depression remain unclear.Studies have found that sleep deprivation?SD?can induce neuroinflammation,and the pathogenesis of depression is closely related to neuroinflammation.Our previous studies have found that long-term sleep deprivation can induce neuroinflammation of astrocytes in the brain of mice,while fluoxetine,the clinical first-line antidepressant can alleviate neuroinflammation and protect neurons.However,the specific mechanism between sleep deprivation and depression still needs further study.In addition,the pathogenesis of depression is not only closely related to neuroinflammation but also related to the decrease of brain-derived neurotrophic factor?BDNF?levels in the brain..Our previous studies have reported that the antidepressant effects of fluoxetine depend on astroglial 5-hydroxytryptamine receptor 2B(5-HT_2BR).Recently,the therapeutic potential of leptin in the context of depression has been discovered although the sole treatment with leptin on the pathological changes of depression has not been determined.In our previous studies,we found that leptin can increase the expression of 5-HT_2BB receptor in astrocytes.This interesting phenomenon prompted us to further study the effect of leptin combined with fluoxetine,a classical antidepressant,on depressive-like behavior induced by sleep disorders and its underlying mechanism.It is hoped that through this study,we can reveal the pathological mechanism of long-term sleep disorder as a high-risk factor for depression,clarify the pharmacological mechanism of fluoxetine to improve depressive-like behavioral changes induced by sleep disorder,and explore whether leptin can amplify the antidepressant effect of fluoxetine and related mechanisms.In turn,it can further reduce the incidence of depression in patients with long-term sleep disorders,provide new strategies for the clinical treatment of depression,and provide new targets for the development of new antidepressants.Methods:The research will be carried out from two aspects of animal experiment and cell experiment.The effects of long-term sleep deprivation on specific astrocytes in brain were studied by primary culture of astrocytes and fluorescence labeling of GFAP-GFP transgenic mice.The research contents are as follows:1)To detect the effect of the activation of NLRP3 inflammasome on BDNF level and depressive behavior in astrocytes induced by sleep disorders;2)To detect the role of 5-HT_2BB receptor in fluoxetine regulating the level of BDNF and depressive behavior and its signal transduction pathways;3)To detect the mechanism of leptin increasing the expression of 5-HT_2BB receptor in astrocytes;4)To detect the effect of leptin combined with fluoxetine on the level of BDNF and depressive behavior in SD model.Results:1.SD-induced depressive-like behaviors depends on the activation of NLRP3inflammasome and the decrease level of BDNF.2.Fluoxetine increases BDNF level and alleviates depressive-like behavior via 5-HT_2BR-ERK-c-fos pathway 3.Leptin increases the expression of 5-HT_2BB receptor via lepR-JAK2-STAT3 pathway in astrocytes 4.Leptin enhances the effects of fluoxetine on increasing the level of BDNF and the antidepressant-like behaviorConclusions:SD-induced depressive-like behaviors depends on the activation of NLRP3 inflammasome and SD decreases astrocytic level of BDNF via activating NLRP3 inflammasomes.The antidepressant fluoxetine upregulates BDNF levels by activating the 5-HT_2BB receptor and its downstream ERK-cfos pathway,thereby improving SD-induced depressive-like behavioral performance.Leptin activates JAK2-STAT3 pathway through its receptor LepR on astrocyte,and then up-regulates the expression of 5-HT_2BB receptor at the action site of fluoxetine in astrocyte,thereby enlarging the level of BDNF in the original signal pathway of fluoxetine and enhancing the anti-depressive behavior of fluoxetine.In this study,we found that the activation of NLRP3 inflammasomes in astrocytes is the key link of the depressive-like behaviors induced by SD and decrease in BDNF following SD also required the activation of NLRP3 inflammasomes.This result reveals that the pathological basis of sleep disorder as a high risk factor for depression is the activation of NLRP3 inflammasomes in astrocytes induced by long-term sleep deprivation.The decrease in BDNF by the activated NLRP3 inflammasomes in astrocytes is the key pathological event of the depressive-like behaviors induced by SD.Fluoxetine can up-regulate the level of BDNF by activating the5-HT_2BR-ERK-cfos pathway,which is the mechanism of the drug to improve SD-induced depressive-like behavior,whereas leptin increases expression of 5-HT_2BB receptors in astrocytes thus enhancing action of fluoxetine on the depressive behavior induced by sleep deprivation These results suggest that 5-HT_2BB receptor is a key target for antidepressants to play a pharmacological role,which can provide new ideas and theoretical basis for clinical research and development of new drugs.