The Molecular Mechanism Of Thioredoxin-1 Regulating Brain Damage Induced By Environmental Toxicant Morphine And Methamphetamine

Drug addiction is a chronic recurrent encephalopathy characterized by reckless compulsive use of drugs.It is a state of dependence caused by abuse of addictive drugs.Drug withdrawal leads to withdrawal symptoms,which is also known as drug dependence and drug abuse.Drug addiction not only seriously harms people's health,erodes people's will and destroys family happiness,but also seriously consumes social wealth,poisons social atmosphere and pollutes the social environment.Moreover,the discharge and storage of wastewater from illegal drug-making activities cause serious pollution of groundwater and surrounding soil,leading to serious environmental pollution problems.Abuse of addictive drugs results in abnormal compensatory adaptation in neurons,drug tolerance,sensitization,dependence,relapse and other symptoms,and ultimately leads to neuronal damage.The neuroanatomical basis of drug addiction is mesolimbic system.Various addictive drugs act on the reward system and results in abnormal release of neurotransmitters and reward effect.Pathological memory of drug addiction is enhanced by both positive reward and negative punishment of drug addiction,it is difficult to subside and persists for a long time.Opioid and amphetamine(METH)are the most dangerous drugs.The mechanism of nervous system injury caused by drug addiction is complex,and various pathophysiological processes are involved in.So far,the mechanism is not completely clear.Apoptosis,inflammation,free radicals production,endoplasmic reticulum stress,mitochondrial dysfunction and so on are involved in drug addiction-induced nervous system injury.Endoplasmic reticulum stress(ER stress)is a very important stress protection mechanism.It mainly activates unfolded protein response to reduce abnormal accumulation of intracellular proteins.When ER stress is serious,apoptosis will be induced.Endoplasmic reticulum stress is associated with many diseases,such as sepsis,Parkinson's disease and drug addiction.Under normal conditions,three transmembrane proteins,protein kinase RNA-like ER kinase(PERK),activating transcription factor 6(ATF6)and inositol requiring enzyme 1(IRE1)bind to the chaperone glucose regulated protein 78(GRP78).When a large number of unfolded or misfolded proteins are aggregated in the endoplasmic reticulum,GRP78 is separated from the transmembrane proteins and activated.If the ER stress persists,the C/EBP homologous protein(CHOP)/ Cysteinyl aspartate specific proteinase 12(Caspase 12)pathway will be activated.In many cases,endoplasmic reticulum(ER)induced apoptosis pathway,mitochondrial apoptosis pathway and NF-kappa B inflammatory signaling pathways cross-link each other.Thioredoxin-1(Trx-1)is a multifunctional protein,molecular weight of 12 kDa with a conserved sequence of active sites: Cys-Gly-Pro-Cys-.Trx-1 has antioxidant,anti-inflammatory and anti-apoptotic effects,as well as cell protection function.Trx-1 also regulates endoplasmic reticulum stress.In present study,the addiction model was constructed by morphine and METH.We used C57BL/6 strain mice and Trx-1 transgenic mice to study the protective role of Trx-1 in morphine and METH addiction injury.Then we detected the levels of neurotransmitter in ventral tegmental area(VTA),nucleus accumbens(NAc)and serum by HPLC,and proinflammatory cytokines and ER stress pathway by PCR,western blot.The main findings of this study are as following:1.The levels of dopamine(DA),norepinephrine(NE)and glutamate(Glu)in VTA and NAc regions were significantly elevated by morphine and METH,while Trx-1 overexpression resisted the further elevation of DA,NE and Glu levels induced by morphine and METH addiction.It is indicated that the overexpression of Trx-1 resists the changes of DA and Glu levels.The levels of D1 receptor(D1R)and N-methyl-D-aspartic acid receptor 2B(NR2B)in VTA,NAc were significantly elevated by morphine and METH,while the overexpression of Trx-1 inhibited the further elevation of D1 R and NR2 B expressons.These results suggest that the overexpression of Trx-1 inhibits the elevation of D1 and NR2 B levels.2.Overexpression of Trx-1 in mice inhibited the demyelination induced by morphine and METH.Myelin basic protein(MBP)and myelin associated glycoprotein(MAG)in VTA and NAc were detected by western blot.The results showed that the expressions of MBP and MAG were decreased significantly in VTA and NAc of wild type mice when compared with the control group,while the expressions of MBP and MAG in Trx-1 transgenic mice by morphine and METH were not significant changed compared with the control group.These results suggest that morphine and METH lead to demyelination damage in VTA and NAc.Trx-1 suppresses and protects the demyelination damage in VTA and NAc caused by morphine and METH.3.Overexpression of Trx-1 inhibited the inflammation signaling pathway induced by ER stress of morphine and METH in mice.The levels of pro-inflammatory cytokines the IL-1 beta(IL-1?)mRNA,TNF-alpha(TNF-?)mRNA,NF-kappa B(NF-?B)were significantly increased and inhibitory protein of NF-?B-?(I?B-?)were significantly decreased.Overexpression of Trx-1 resisted the increases of of IL-1?,TNF-? mRNA,NF-?B expression and decrease of I?B-? expression in VTA and NAc induced by morphine and METH,then inhibited inflammatory response.4.Overexpression of Trx-1 inhibited ER stress and mitochondrial apoptosis signaling pathways induced by morphine and METH.The expressions of extracellular signal-regulated kinase(ERK),C/EBP homologous protein(CHOP),glucose regulated protein 78(GRP78),Bcl-2-associated X protein(Bax),Caspase 12,Caspase 3 and Caspase 9 were significantly increased in VTA and NAc of wild mice by morphine and METH,while the overexpression of Trx-1 inhibited the increases of above molecules.The expression of anti-apoptotic protein B cell lymphoma-2(Bcl-2)was decreased significantly in wild mice,while the expression of Bcl-2 was restored in Trx-1 transgenic mice.It indicates that overexpression of Trx-1 resists ER stress and mitochondrial pathways induced apoptosis.In conclusion: Trx-1 protects mice against injury induced by morphine and METH.Trx-1 inhibits the demyelination in VTA and NAc induced by morphine and METH by inhibiting the inflammatory signaling pathway and cell apoptosis signaling pathways of ER stress and mitochondria.This study further charifies the injury molecualr mechanism of morphine and METH,and provides a target for the development of treatment of brain injury induced by morphine and METH.