Studies On The Protective Effect Of L-theanine On The Toxicity Of Cell Induced By Cadmium Chloride

With the development of scientific research,people have a deeper understanding of the composition and efficacy of tea.L-Theanine is the most abundant free amino acid in tea,which is widely used as food additive,and L-theanine has a neuroprotective effect.Cadmium is the most common heavy metal environmental pollutants.The half-life of Cd in the human body is more than 15 years,and it has been reported that the accumulation of Cd within the human body is likely to increase in the future,which may result in a higher incidence of Cd-related diseases,including carcinogenesis,immune-depression and neurodegeneration.In this paper,we studied the effects of cadmium on the brain tissue toxicity and the mechanism of L-theanine regulated Cd-induced oxidative stress and apoptosis.1 Protective Effect of L-Theanine on Cadmium-Induced Apoptosis in PC12 Cells by Inhibiting the Mitochondria-Mediated PathwayL-Theanine is an amino acid derivative from green tea.The present work was aimed at the effect of L-theanine on neuron-like rat pheochromocytoma(PC12)cells stimulated with cadmium chloride.Treatment with L-theanine before cadmium exposure increased cell viability;the experiments of Annexin V/PI staining indicatedthat L-theanine inhibited cadmium-induced cell apoptosis.Immunoblotting experiments showed that CdCl2 induced caspase-3 activation and poly(ADP-ribose)polymerase(PRAP)cleavage,while L-theanine was significantly inhibited caspase-3 activation and decreased PRAP cleavage.ROS was detected by DCFH-DA fluorescent probe,which showed that L-theanine could inhibit the production of Cd induced ROS.Meanwhile,L-theanine decreased the loss of mitochondrial membrane potential induced by cadmium.Compared with cadmium treated group,the levels of cytochrome C in the cytoplasm of the cells of the pretreatment L-theanine group were significantly reduced,and the mitochondrial cytochrome C increased.Compared with cadmium treated cells,L-theanine could also decrease the ratio of Bax/Bcl-2,as well as the level of cleaved caspase-9.Furthermore,L-theanine depresses cadmium-induced up regulation of phosphorylations of PI3K/Akt,MAPK ERK1/2,and JNKsignaling.These data suggest that L-theanine pretreatment reduces severity of cadmium toxicity probably via mitochondria-mediated pathway.Therefore,it may be concluded that L-theanine could be exploited for prevention of cadmium-induced diseases.2 L-Theanine attenuates cadmium-induced neurotoxicity through the inhibition of oxidative damage and tau hyperphosphorylationL-Theanine is one of the major amino acid components in green tea.Cadmium has long been known to induce neurological degenerative disorders.The present study investigates the possible neuroprotective efficacy of L-theanine on cadmium-induced toxicity.Male ICR mice were divided into five groups:gp.? control,gp.? L-Theanine(200 mg/kg bwt)injection,gp.? CdCl2(30mg/L)orally,gp.? Co-treated with both CdCl2 and L-theanine(100 mg/kg bwt)and gp.? Co-treated with both CdCl2 and L-theanine(200 mg/kg bwt);in all gps the treatment is day after day for 8 weeks.The brains of cadmium-treated mice displayed numerous pathological effects,induced neuronal cell death,increased tissue malondialdehyde(MDA)and ROS levels and also decreased glutathione(GSH)content,superoxide dismutase(SOD)and catalase(CAT)enzyme activities in brain compared with the control.L-theanine reduced cadmium levels in brain tissue and the plasma,and reduced cadmium-induced neuronal cell death in the cortex and hippocampus of the brain.Administration of L-theanine with cadmium significantly decreased the levels of MDA and ROS,and significantly elevated the levels of antioxidant enzymes in tissue.Emerging evidence indicates that hyperphosphorylated tau is associated with neurodegenerative diseases,but whether L-theanine plays a role in cadmium-induced hyperphosphorylation tau remains unclear.To fill this gap,treatment of mice with cadmium increased the phosphorylation of tau at Ser199,Ser202,and Ser396 as detected by Western blot.Treatment of L-theanine markedly reduced the tau Ser396 immunoreactivity of degenerating neurons.Furthermore,cadmium induced the activation of Akt/mTOR.And the activation of Akt was involved in the activation of glycogen synthase kinase-3?(GSK-3?)kinase,which also contributed to the hyperphosphorylation of tau and the cytotoxicity in cells induced by cadmium.L-Theanine inhibited cadmium-induced GSK-3? and Akt/mTOR.These data indicate that theanine protected cells against cadmium-induced neurotoxicity through the inhibition of oxidative damage and tau hyperphosphorylation.In summary,L-theanine can alleviate the oxidative stress induced by cadmium.It inhibited Cd-induced apoptosis and abnormal phosphorylation of tau protein by regulating the PI3K/Akt,GSK-3?,mTOR and MAPK.The results suggested that L-could be used as a potential drug for the treatment of Cd induced neurodegenerative diseases.