The Effect Of α-synuclein On Tau Phosphorylation And Its Role In Methamphetamine Induced Neurodegeneration

BACKGROUNDThe mechanism of neurodegenerative changes induced by methamphetamine(METH)mainly includes neuro-excitatory toxicity,mitochondrial dysfunction and autophagy dysfunction.Alpha-synuclein,a pathogenic protein of Parkinson’s disease(PD),could mediate the METH neurotoxicity,and is accompanied by the increase of tau phosphorylation level.Our previous experiments found that inhibition of a-syn could alleviate the phosphorylation of tau induced by METH.Based on this,this study used a-syn knockout mice to establish a chronic METH model.By detecting the level of related proteins,observing the pathological changes of related brain areas of mice,and explore the effect of a-syn on tau phosphorylation and the mechanism of it in METH induced neurodegeneration.Due to the similarities of the neuron and podocyte,the role of p-Tau in METH induced nephrotoxicology.OBJECTIVETo explore the roles of α-synuclein induced tau phosphorylation and p-Tau in methamphetamine induced neurodegeneration and nephrotoxicology.METHODSIn chapter 1,Immunohistochemistry staining and ultrastructure analysis were used to observe the pathology in hippocampus and substantial nigra.And evaluate the effect of α-syn knockout on those pathological changes.In chapter 2,Immunoblotting and immunohistochemistry staining were used to assess the α-syn,different phosphorylation sites of Tau in hippocampus and substantial nigra.Evaluating the effect of knockout of α-syn on Tau phosphorylation level,microtubule number and the formation of autolysosome;In chapter 3 To determined the mechanism of α-syn on Tau phosphorylation,Tau kinase(GSK3β and CDK5)level were assessed by immunohistochemistry staining;In chapter 4 Neuphropathology and the expression levels of GSK3β,p-tau,synaptopodin and podocalyxin like 1 immunohistochemistry were conducted to figure out the role of GSK3 β-p-tau pathway in METH induced nephropathological changes and podocyte damage.RESULTSChapter 1(1)The increased the α-syn protein was mainly located in the stratum oriens,pyramidal layer,stratum radiatum and stratum moleculare of CA1,CA2 and CA3,and polymorph layer of DG;The increased α-syn induced by METH mainly aggregated in the mitochondria and myelin sheath;(2)METH induced mitochondrial vacuolization,sphere like myelin sheath destruction and synaptic vesicles;the decreasing of DA neurons and hippocampal neurons;glial cells number increasing;the above neuropathological changes were alleviated by α-syn knockout;Chapter 2(1)METH increased the levels of α-syn monomers and polymers in hippocampus and substantia nigra;(2)The up-regulated α-syn had a positive correlation to p-Tau in SN and hippocampus after chronic METH exposure.(3)METH could lead to p-Tau upregulation,microtubule number decreasing,autophagsome and lysosome fusion deficit;knockout of α-syn could alleviate the increasing of p-Tau,microtubule number decreasing and autolysosome formation deficit induced by METH;Chapter 3METH lead to GSK3β transformed into activated form,and CDK5 level increasing,activated form of GSK3β and CDK5 levels were down-regulated by a-syn knockout;Chapter 4METH treatment may induce glomerular pathological changes and fibrosis,increase the level of activated form of GSK3 β and p-Tau level and decrease podocyte protein including synaptopodin and podocalyxin like 1;LiCl can alleviate glomerular pathological changes,decrease activated form of GSK3β and p-Tau level,and increase synaptopodin and podocalyxin like 1.Luteolin,a flavonoid,also can alleviate glomerular pathological changes,decrease activated form of GSK3β and p-Tau level,and increase synaptopodin and podocalyxin like 1 in chronic METH mice model.CONCLUSION(1)METH increased the level of α-syn,and α-syn might damage mitochondria,myelin sheath and synaptic vesicles directly,the indirect effect is that α-syn can promote tau phosphorylation through GSK3β and CDK5,microtubule depolymerization,autophagysome and lysosome fusion deficit,leading to autophagy blocking,the direct and indirect effect of α-syn jointly participates in the process of neurodegeneration;(2)METH activate GSK3β-p-Tau pathway leading to podocyte damage,LiCl and luteolin can alleviate METH induced nephropathology and podocyte damage by inhibiting GSK3β.