The Effect Of Xiaoyao San On Poly I:C-induced Liver Depression Syndrome In Mice

Objective:To establish the Poly I:C induced depression model in mice.To investigate the effect of xiaoyao san on Poly I:C-induced depressive-like behaviors in mice,and to discuss the mechanisms.Methods:1.Establishment of the Poly I:C induced depression model in mice.The first set of 40 C57 mice were used to built an Poly I:C induced depression model,which were divided into 4 groups:the vehicle,3mg/kg Poly I:C,6 mg/kg Poly I:C,12mg/kg Poly I:C.The mice received either an intraperitoneal(i.p.)injection of different doses poly I:C or Saline.The second set of 20 C57 mice were used to built a more stable Poly I:C induced depression model,which were divided into 2 groups:the vehicle,12 mg/kg Poly I:C.Saline was injected in the vehicle and 12mg/kg Poly?:C was injected in another.The third set of 60 C57 mice were used to examine the Poly?:C induced liver depression syndrome model,which were divided into 6 groups:the vehicle,the model,the low dose of Xiaoyao San,the medial dose of Xiaoyao San,the high dose of Xiaoyao San and the escitalpram.Saline was gave by intragastric administration before 30 minutes of saline subcutaneously treated in the vehicle,while others drugs gave according to the corresponding dose by intragastric administration before 30 minutes of Poly I:C subcutaneously treated in other groups.2.Evaluation of the ModelThese mice all examined by the open field test,the sucrose preference test,the forced swimming test and the suspension tail test.3.Animal tissue sample collection and detectionThe mice were sacrificed,and the serum was collected from heart after anethetized.The brains were removed of the mice,and levels of inflammation related cytokines were determined using enzyme linked immunosorbent assay.Microglia and astrocyte activation in the mPFC,VTA and NAc were measured using immunohistochemistry.Western blot was carried to detect the related.proteins in these regions.Results:1.The mice were subcutaneously injected with Poly I:C 12mg/kg for 3 weeks to mimic depression model.In the central time of the open field test,there was a decreased significantly in 12mg/kg(P<0.05).In the sucrose preferce test,the preference of sucrose decresed significantly in 12mg/kg(P<0.05).In TST,the immobility time increased in 12mg/kg group significantly(P<0.05).In FST,the immobility time increased in 12mg/kg group significantly(P<0.05).2.Xiaoyao San attenuated the depressive like behavior in the Poly I:C induced depression in mice.In sucrose preferce test,the preference of sucrose decreased significantly in the model group versus vehicle(P<0.05).In the high dose group,there was no significance(P>0.05).In TST and FST,the immobility time increased in the model group significantly(P<0.05)but no significance in the high dose Xiaoyao San group(P>0.05).3.Xiaoyao San regulated the changes of cytokines in mPFC,VTA and NAc.The levels of IL-1?,IL-6 and TNF-a increased in mPFC when mice were treated with Poly I:C(P<0.05).Xiaoyao San and escitalopram decreased these cytokines(P<0.05).The levels of IL-1?,IL-6 and TNF-a increased in VTA when mice were treated with Poly I:C(P<0.05).Escitalopram decreased the levels of IL-1?,IL-6 and TNF-a(P<0.05).Xiaoyao San reversed the elevated IL-6 level but had no effect on the elevated IL-1?and TNF-?(P<0.05).The levels of IL-6 and TNF-a increased in NAc when mice were treated with Poly I:C(P<0.05).Xiaoyao San and escitalopram reversed the elevated IL-6 and TNF-a levels(P<0.05).4.Xiaoyao San decreased the number of microglia on mPFC,VTA and NAc in Poly I:C-treated mice.The number of microglia increased on mPFC when mice were treated with Poly I:C(P<0.05).There was pronouncedly reversed in the number of microglia by high dose Xiaoyao San and escitalopram(P<0.05).Microglia and astrocytes were activated on VTA when mice were treated with Poly I:C(P<0.05).There was pronouncedly reversed in the number of microglia by high dose Xiaoyao San(P<0.05).Escitalopram could reverse the changes of microglia and astrocytes.5.Xiaoyao San reversed the depressive-like behavior maybe through the IDO signaling,p38 signaling or GCH1 signaling.The expression of IDO and p38 increased in the mPFC after Poly I:C stimulated and reversed by Xiaoyao San and escitalopram.The expression of GCH1 increased in the VTA after Poly I:C stimulated and reversed by Xiaoyao San and escitalopram.The expression of GCH1 and p38 increased in the NAc after Poly I:C stimulated and reversed by Xiaoyao San and escitalopram.Conclusions:Long-term,high-dose Poly I:C treatment can lead to distinct neuroinflammation in the mPFC,VTA and NAc.Xiaoyao San attenuated Poly I:C induced neuroinflammation in these regions and ameliorated depressive-like behaviors in mice.