Analysis Of The Changes Of Tau In Scrapie-infected Hamsters And In CSF Of Creutzfeldt-Jakob Disease

Transmissible spongiform encephalopathies(TSEs),prion diseases,are rare degenerative neurological disorders that afflict human beings,including Creutzfeldt-Jakob disease(CJD),Gerstmann-Str(a|¨)ussler-Scheinker syndrome(GSS),Kuru,and fatal familial insomnia(FFI),sheep and goat(scrapie),cattle(bovine spongiform encephalopathy,BSE), and other animals.They may have a sporadic,inherited or acquired origin.This study contains two individual parts,including analysis of the relation of changes of tau profiles in brains of the hamsters infected with scrapie strains 263K or 139A with the alteration of phosphate kinases,and the study of the tau level in CSF of Chinese patients with probable diagnostic Creutzfeldt-Jakob disease.PartⅠ:Changes of tau profiles in brains of the hamsters infected with scrapie strains 263K or 139A possibly associated with the alteration of phosphate kinasesTo investigate the possible changes of tau in scrapie experimental animals,the profiles of tau and phosphorylated tau(p-tau,at Ser396,Ser404,and Ser202/Thr205) in the brain tissues of agents 263K- or 139A-infected hamsters were evaluated by Western blots.The result showed that the contents of total tau and p-tau at Ser202/Thr205 increased,but p-tau at Ser396 and Ser404 decreased at the terminal stages.To assess the transcription of tau mRNA in brains,real time-PCR reactions were performed.The assays revealed that the level of Tau-4 transcript was remarkably increased and that of Tau-2 transcript was slightly increased in the brain tissues of scrapie-infected hamsters.These results highlight that the transcriptional and expressive changes of tau profiles are a common phenomenon of scrapie experimental animals,neither related with scrapie strains nor incubation periods.Both GSK3βand CDK5 played an important role in mediating tau phosphorylation,the expressive and transcriptional levels of these two kinases in the brains of normal and scrapie-infected hamsters were evaluated by Western blot and real-time PCR.It showed higher CDK5,but lower GSK3βtranscriptional and expressive levels in the brains of scrapie-infected animals.In order to investigate the dynamic changes of tau,p-tau(Ser396),p-tau(Ser404), p-tau(Ser202/Thr205),GSK3βand CDK5 in the brains of scrapie-infected hamsters during incubation period,the expressive and transcriptional levels of these biomarkers were evaluated by Western blots and real-time PCR,respectively.Brain samples of the agent 263K-infected hamsters at the 20^th,40^th,50^th,60^th and 70^th days after inoculation were collected.The results showed that the signals of tau,p-tau (Ser202/Thr205),and CDK5 became stronger and that of p-tau(Ser396),p-tau (Ser404) and GSK3βbecame weaker in the infected specimens compared with the normal controls.These results indicate that changes of tau profiles and phosphate kinases happen much earlier than the onset of the clinical manifestations,showing a time-relative pattern.Moreover,gradually declined GSK3βand raised CDK5 levels correspond well with the decrease of p-tau(Ser396 and Ser404) and increase of p-tau (Ser202/Thr205),respectively.These phenomena may highlight the possibility that the increase of p-tau(Ser202/Thr205) is due to the higher level of CDK5 and depression of p-tau(Ser396 and Ser404) owes to the lower level of GSK3β.Alterations of PrP^Sc,tau,p-tau and kinases in the brains of TSE animals during pathogenicity may consist of a complicate network.It is still unclear when and how these components function and impact each other.Except for the deposits of PrP^Sc as the initiative agent,alterations of these bioactive proteins are either intermediate or consequent events in TSE pathogenesiscity and proposed the potential linkage of these bioactive proteins with the pathogenesis of prion diseases.PartⅡ:Raised levels of tau protein in CSF of Chinese patients with probable diagnostic Creutzfeldt-Jakob diseaseIn order to investigate the diagnostic sensitivity and specificity of tau protein in cerebrospinal fluid(CSF) for Chinese patients with sporadic Creutzfeldt-Jakob disease (sCJD) and whether increased concentration of tau protein in CSF is the common feature for all racial CJD,especially Asian patients,total 202 CSF samples from clinically suspected sCJD patients were analyzed for the levels of tau protein with ELISA and the presences of 14-3-3 protein by immunoblot.Among them,40 were classified as probable CJD,27 as possible CJD and 135 as others.Results showed that remarkably higher values of tau protein and positive rates of 14-3-3 were observed in probable CJD,compared with possible CJD and others(p＜0.001).Using a threshold of 1400 pg/ml,tau determination showed a sensitivity of 90%and a specificity of 94%for diagnosis of probable CJD. Combining use of raised tau and positive 14-3-3 increased the specificity,but slightly reduced sensitivity.It indicated that measurement of CSF tau will be helpful for CJD diagnosis antemortem.The relationship between the raised CSF tau and the main clinical data in the patients were analyzed.The patients were grounped according to the onset age,gender,sampling time,appearance of typical EEG,appearance of typical MRI,presentence of 14-3-3,codon 129 genotype of PRNP and appearance of the major neurological symptoms.Statistic analyses indicated that the raised tau did not correlate with main clinical characteristics,e.g. age,gender,clinical manifestations,sampling time,typical EEG and typical MRI but positive correlate with the presence of 14-3-3 in CSF.