The Role Of Astrocyte PRDX6 And Its Underlying Mechanisms In The Occurrence Of Depression-like Behaviors

Objective: Genetic factors and stress together contribute to the occurrence of major depression,with the key drivers remain poorly defined.Peroxiredoxin 6(PRDX6)is a multifunctional enzyme mainly located in astrocytes.Although previous studies have indicated the involvements of PRDX6 in several neuropsychiatric disorders,its alteration and roles in major depression remain inconclusive.The present study,using animal models with genetic or stress susceptibility to depression-like behaviors,investigates the role of astrocyte PRDX6 and its underlying mechanisms in the occurrence of depression-like behaviors,aiming to further elucidate the disease pathogenesis and provide new ideas for the development of targeted drugs in major depression.Methods:The inbred male Wistar Kyoto(WKY)rats were used as an animal model with endogenous depression-like behaviors,and male C57BL/6J mice were used to establish the stress-induced depression-like mouse models by chronic social defeat stress(CSDS),chronic restraint stress(CRS),or sub-threshold social defeat stress(SSDS).Male C57BL/6J mice and Prdx6-flox mice were employed for the adeno-associated virus-mediated conditional overexpression(c OE)or knockdown(c KD)of PRDX6 expression in astrocytes.Intraperitoneal administration of MJ33,an inhibitor targeting the PRDX6-ai PLA2 activity,was conducted in the CSDS mouse model(125mg/kg/12 h,five consecutive times).The animal depression-like and anxiety-like behaviors were comprehensively evaluated via the social interaction test(SI),sucrose preference test(SPT),forced swimming test(FST),tail suspension test(TST),open field test(OFT),and elevated plus maze(EPM).Golgi staining and quantitative proteomics analyses were respectively performed to examine the neuron dendrite morphology and protein expression profiles in the medial prefrontal cortex(m PFC),nucleus accumbens,and hippocampus of the WKY rats.RNA-sequencing was used to determine the downstream targets by which PRDX6 mediated the occurrence of depression-like behaviors.Real-time PCR and Western blotting were used to quantify the relative tissue m RNA and protein levels,respectively.Both the distributions and alterations of PRDX6 in the brain were detected by immunohistochemistry or immunofluorescence staining analysis.The brain enzyme activities were tested by enzyme-linked immunosorbent measurement or colorimetry.The proteomics and RNA-sequencing data were further analyzed by differential expression analysis,enrichment analysis,and weighted gene co-expression network analysis.Results:1.The WKY strain,when compared with the Wistar one,displayed significantly increased immobility time in the FST but reduced sucrose preference ratio in the SPT.Based on their differences in the behavioral performances,the WKY rats can be further divided into the depression-like WKY(d-WKY)subgroup and the none-depression-like WKY(nd-WKY)one.Both the neuronal dendritic spine density and the number and length of dendritic branches were reduced to varying degrees in the m PFC,nucleus accumbens,and hippocampus of the d-WKY rats when compared with the Wistar or nd-WKY rats.Moreover,compared with the Wistar rats,the WKY ones showed significant differences in the differentially-expressed protein profiles across the three brain regions,with common and specific signaling pathways enriched among different brain regions;while less significance was found between the d-and nd-WKY subgroups.We preliminarily identified PRDX6 as a potential driver for genetic vulnerability to depression-like behaviors.2.PRDX6 was widely distributed in the mouse brain,with specific location in astrocytes,and gradually increased with the brain development.In the WKY rats and the two chronic stress-induced mouse models,the expression levels of PRDX6 were consistently increased in the m PFC,and showed strong negative correlations with both social interaction ratio in the SI and sucrose preference ratio in the SPT but positive correlations with immobility time in the FST.Hence,the expression levels of PRDX6 were highly related with the occurrence of depression-like behaviors.3.Compared with the control(Ctrl)group,C57BL/6J mice in the c OE group displayed significantly reduced both social interaction ratio in the SI and sucrose preference ratio in the SPT;after two days of SSDS procedures,the c OE+SSDS group,when compared with the c OE+None-SSDS group,displayed significant reductions in both social interaction ratio in the SI and total distance in the OFT,with no significant differences found between the Ctrl+SSDS group and the Ctrl+None-SSDS one.On the other hand,compared with the Ctrl group,C57BL/6J mice in the c KD group showed significant increases in sucrose preference ratio in the SPT,total and central distance in the OFT,and open arm duration in the EPM,but decreased immobility time in the FST;after 5 consecutive days of CSDS procedures,the Ctrl+CSDS group displayed significantly reduced social interaction ratio in the SI when compared with the Ctrl+None-CSDS group,with no significant differences found between the c KD+CSDS group and the c KD+None-CSDS one.Additionally,compared with the Ctrl group,Prdx6-flox mice in the c KD group showed striking increases in sucrose preference ratio in the SPT,social interaction ratio in the SI,and open arm duration in the EPM,but decreased immobility time in both the FST and TST.Taken together,the expressions of PRDX6 in astrocyte mediate the occurrence of depression-like behavior in mice.4.Compared with their respective Ctrls,both the m RNA and protein expression levels of fatty acid binding protein 7(Fabp7)in the m PFC were significantly decreased in the c OE group but increased in the both two c KD groups.WGCNA revealed that three out of the seven modules related with the phenotypes were mainly enriched in fatty acid metabolism-related signaling pathways.These results suggested that PRDX6 may modulate the mouse depression-like behaviors through regulating the FABP7-mediated fatty acid metabolism.5.Compared with mice administrated with saline,those with MJ33 injection showed significantly reduced body weight but increased central distance in the OFT;and systemic injection of MJ33 exacerbated the reduced social interaction ratio in the SI of the susceptible mice.Conclusions:1.The WKY strain is an animal model with endogenous susceptibility to depression-like behaviors,with significant differences in not only the behavioral performances but the structural synaptic plasticity and protein expression profiles in the key depression-related brain regions.2.The astrocyte PRDX6 in the m PFC may mediate the occurrence of depression-like behaviors by regulating the FABP7-mediated fatty acid metabolism,while systemic inhibition of PRDX6-ai PLA2 enzyme activity deteriorates the social avoidance of the stress-susceptible mice.