Fullerenol Had Antidepressant-like Properties In An LPS-induced Depressive Mouse Model

Background:Depression is a mental illness characterised by a persistent depressed mood and loss of interest in life.Depression is highly recurrent and in severe cases will lead to suicidal symptoms,which undoubtedly places a great burden on the patient,family and even society.Fullerenol(Ful),a novel nanomaterial,has shown its advantages in terms of antioxidant and antiviral properties and anti-inflammation.However,it is not clear whether fullerenol has antidepressant effects.Therefore,this study investigates the effect of fullerenol on Lipopolysaccharide(LPS)-induced depressive behaviour in mice and reveals the possible molecular mechanisms by which fullerenol improves depressive behaviour in mice.Methods:In this study,a mouse depression model was established by intraperitoneal injection of lipopolysaccharide into mice,and five consecutive days of intraperitoneal injection of LPS(1 mg/kg)resulted in depression-like behavior in mice.The depression-like behavior of mice was examined by the sucrose preference test,tail suspension test and forced swimming test.The anxiety-like behavior of mice was evaluated by the open field test,elevated plus maze test and light-dark box test.The protein expression levels of IL-1β,TNFa and other inflammatory factors in the hippocampus of mice were measured by western blot.The mRNA expression levels of IL-1β and TNF-α in the mouse hippocampus were measured using real-time quantitative PCR.Immunohistochemical staining was used to detect the effects of fullerenol and lipopolysaccharide treatment on the number and morphology of microglia in the mouse hippocampus and to investigate the effects of fullerenol and lipopolysaccharide stimulation on neurogenesis;the potential molecular mechanisms and key genes were analysed in conjunction with the sequencing data of RNAseq in the mouse hippocampus.Results:Compared with the saline group,the LPS-treated mice consumed less sugar water in the sucrose preference test and increased the immobility time in both the tail suspension and forced swimming tests,suggesting that LPS induced depression-like behaviour in the mice;the expression levels of IL-1β and TNF-α protein and mRNA increased in the hippocampal tissue after LPS treatment;LPS treatment increased the number of microglia in the hippocampus and significantly increased the number of activated microglia;in addition,the number of DCX-positive cells and the expression level of DCX protein in the hippocampal tissue decreased significantly after LPS treatment.Compared with mice in the LPS-treated group,fullerenol-pretreated mice increased the proportion of sugar water consumed in the sugar-water preference experiment and significantly decreased the immobility time in both the tail suspension and forced swimming experiments;fullerenol pretreatment significantly decreased the expression levels of IL-1β and TNF-α protein and mRNA in hippocampal tissues.Fullerenol pretreatment significantly reduced the number of activated microglia in the hippocampus,while significantly increasing the number of DCXpositive cells and protein expression in hippocampal tissue.Finally,RNA-seq sequencing of hippocampal tissues revealed that the biological events associated with depression-like behaviour improved by fullerenol pretreatment were mainly related to inflammation and neurogenesis,and the analysis of co-regulated genes suggested that Rtn4 might be the key gene.Conclusions:Fullerenol improves LPS-induced depression-like behaviour in mice by inhibiting inflammatory responses in the hippocampus and increasing neurogenesis,suggesting a preventive effect of fullerenol on inflammation-induced depression-like behaviour.The sequencing results also reveal the mechanism by which fullerenol can modulate inflammation and neurogenesis,providing potential targets and candidate nanomaterials for the clinical treatment of depression.