The Role Of Indoleamine 2,3-dioxygenase 1 And The Regulation Of Chaihushugan Decoction In Epilepsy

Background:Epilepsy is one of the most common chronic neurological disorders,characterized by spontaneous and recurrent brain seizures.Indoleamine 2,3-dioxygenase 1(IDO1)is the first and rate-limiting enzyme that catalyzes the conversion of tryptophan(TRP)to kynurenine(KYN).Excessive activation of IDO1 gradually accumulates toxic metabolites such as Quinaldinic acid(QUIN)and 3-hydroxy-kynurenine(3-HK)which have essential role in the regulation of NMD A receptor function.IDO1 activation also leads to inflammation and oxidative stress.Increasing evidence indicates that IDO1 is involved in the development of neurological disorders.However,the role of IDO1 in epilepsy is still unclear.Traditional Chinese medicine(TCM)has a long history in the treatment of epilepsy.Especially,TCM is effective in treating refractory epilepsy.The toxic and side effects of TCM are very small.Chaihushugan decoction(CHSGD)has significant clinical curative effect in the treatment of epilepsy.Therefore,we explored the effect of CHSGD on epilepsy by inhibiting activation of IDO1,affecting the pathway of TRP metabolism in order to find new molecular targets for the effective prevention and regulation of epilepsy.Methods:Blood and cerebrospinal fluid(CSF)samples from patients with epilepsy and controls were collected.The level and activity of IDO 1 in the serum and CSF were measured by ELISA and LC-MS.For animals,lithium chloride and pilocarpine were used to establish epilepsy model in wild-type(WT)and IDO1 knockout mice.Additionally,CHSGD and valproate acid(VPA)were administered to WT epileptic mice.After modeling,behavioral tests were used to evaluate SRS,anxiety-like and depression-like behaviors.Changes in the level and activity of IDO1,KYN metabolites,neuronal damage,glial cells activation,the levels of proinflammatory cytokines and oxidative stress were observed by ELISA,LC-MS,HE staining,Nissl staining and immunochemical staining.Results:First,the level and activity of IDO1 were markedly increased in serum and CSF of patients with epilepsy compared with controls.Furthermore,the activity of IDO1 was significantly elevated in the serum of patients with primary epilepsy and patients with seizure secondary to autoimmune encephalitis.The level and activity of IDO1 were significantly increased in serum and hippocampus of epileptic mice.In addition,proinflammatory cytokines were also elevated in the serum and hippocampus of epileptic mice.IDO1 deficiency prolonged the latency to SE and ameliorated the severity of SRS and depressive-like behaviors.IDO1 deficiency partly prevented the lithium-pilocarpine-induced hippocampal neuronal damage in mice with seizures,reduced the level of QUIN,glial cells activation and proinflammatory cytokines,enhanced the activity of antioxidant enzyme and reduced MDA level.Medium and high dose CHSGD can significantly attenuated the severity of spontaneous recurrent seizures,reduced the level and activity of IDO1,inhibited the production of QUIN,glial cells activation and proinflammatory cytokines,increased the activity of antioxidant enzyme and reduced MDA level.Conclusion:In this study,IDO1 deficiency ameliorated the severity of spontaneous recurrent seizures in the chronic phase of epilepsy by reducing the IDO 1-dependent neurotoxic metabolites,inhibiting the production of proinflammatory cytokines and glial cell activation,and improving the activity of antioxidant enzymes.CHSGD can protect mice from pilocarpine-induced epilepsy mediated by IDO1 regulation.This study provides the feasibility of IDO1 as an important target for clinical treatment of epilepsy.