Effect And Mechanism Of Xiaoyao San On Lipopolysaccharide-induced Inflammatory Depression

Objective:To further reveal the antidepressant effect of Xiaoyao San,the study is based on the relationship between inflammation,nerve injury and depression,and investigate the effect and mechanism of Xiaoyaosan by lipopolysaccharide（LPS）-induced inflammatory depression.Methods:⑴Anti-inflammatory effect:Mice were administrated with Xiaoyao San(30 g·kg^-1)for 12 days by gavage,and the inflammatory mice were induced by xylene and acetic acid,and the ear swelling degree and the permeability of abdominal capillary were observed.⑵Effects on LPS-induced depression-like mice:Model mice were administrated with Xiaoyao San(30,15 g·kg^-1)for 12 days by gavage.The depressive mice were induced by LPS injection.The immobility time of forced swim test（FST）and tail suspension test（TST）were investigated.The levels of IL-6 and TNF-αin serum,hippocampus and cortex and the IDO and 5-HT in hippocampus and cortex were measured,and the morphology of hippocampal neurons in depressive mice were calculated by Nissl staining.⑶Effects on LPS-induced Neuroinflammatory depression-like rat:Model rats were administrated with Xiaoyao San(30,15 g·kg^-1)for14 days by gavage.The depressive rats were induced by LPS was infused intracerebroventricularly（i.c.v.）.Open field test（OFT）,splash test（ST）,sucrose preference test（SPT）,novelty suppressed feeding test（NSFT）were investigated.The levels of IL-6,TNF-α,BDNF and NGF in serum,and the expression of IL-6,TNF-α,5-HT1A,IDO1,BDNF,NGF,TrkB,TrkA,CREB,p-CREB,PSD95,SYP in hippocampus and cortex were measured.⑷The inflammatory model of hippocampal neuron cells were induced by LPS.The effect of Xiaoyao San serum（final concentration of 4%,8%）on the levels of IL-6,TNF-αin the supernatant and the levels of 5-HT,IDO in the cell lysate were measured by ELISA.The expression of IL-6,TNF-α,5-HT1A,IDO1,BDNF,NGF,TrkB,TrkA,CREB mRNA in the cell lysate were measured by PCR.The expression of TrkB,CREB,p-CREB,SYP in the cell lysate were measured by Western blot.what’s more,the effect of Xiaoyao San serum（final concentration of 4%,8%）on hippocampal neuron cells proliferation were observed as well.Results:⑴Compared with the control group,Xiaoyao San(30 g·kg^-1)could inhibit xylene-induced ear swelling in mice（P<0.05）and decrease acetic acid-induced the increase of the abdominal capillary permeability in mice.⑵Compared with the model group,Xiaoyao San(30,15 g·kg^-1)could short the immobility time of FST（P<0.01）,decrease the level of IL-6 in the serum and the expressions of TNF-α,IL-6and IDO in the cortex（P<0.05 or P<0.01）,improve the level of 5-HT in the hippocampus（P<0.01）;Xiaoyao San(30 g·kg^-1)could short the immobility time of TST（P<0.01）,up-regulate the level of 5-HT in the cortex（P<0.01）,increase the Mean IOD of Niss bodies（P<0.05）.Xiaoyao San(15 g·kg^-1)could decrease the level of IL-6in the hippocampus（P<0.05）.⑶Compared with the model group,Xiaoyao San(30,15 g·kg^-1)could increase vertical movement times,extend the comb time of splash test and increase the sucrose preference（P<0.05 or P<0.01）,decrease the level of IL-6 and TNF-αand increase the levels of BDNF andβ-NGF in serum（P<0.05 or P<0.01）,and down-regulate the expression of IL-6,TNF-α,IDO1 in hippocampus and cortex（P<0.05 or P<0.01）,and up-regulate the expressions of 5-HT1A,BDNF,NGF,TrkB,TrkA,CREB,PSD95,SYP in hippocampus and cortex（P<0.05 or P<0.01）.⑷Compared with the model group in vitro,4%,8%concentration of Xiaoyao San serum could significantly decrease the levels of IL-6,TNF-αin the supernatant and IDO in the cell lysate（P<0.01）,increase the level of BDNF,β-NGF in the supernatant and 5-HT in the cell lysate（P<0.05 or P<0.01）,and down-regulate the expression of IL-6,TNF-αand IDO1 mRNA（P<0.05 or P<0.01）,up-regulate the expression of 5-HT1A,BNDF,NGF,TrkB,TrkA,CREB mRNA（P<0.05 or P<0.01）and up-regulate the expression of TrkB,CREB,p-CREB,SYP（P<0.05 or P<0.01）,and 8%concentration of Xiaoyao San serum could significantly increase in Brdu/NeuN ratio（P<0.01）.Conclusion:Xiaoyao San has a certain antagonistic effect on LPS-induced inflammatory depression and nerve damage,which suggests that the effect is related to the reduction of inflammatory factors,the inactivation of IDO,the up-regulation of 5-HT,PSD95 and SYP,the activation of the BDNF/NGF-TrkB/TrkA-CREB pathway and the promotion of hippocampal neurons proliferation.