The Study On The Biomarkers Of Neurodegenerative Diseases

OBJECTIVE:Alzheimer's disease(AD)and Parkinson's'disease(PD)are the most common neurodegenerative diseases.Current diagnoses of both diseases depend mainly on clinical symptoms and lack of objective biomarkers.In recent years,the role of inflammation in the development of AD and PD has been paid more and more attention.In AD,this study attempts to establish a combination of plasma protein biomarkers with the potential to detect and warning early AD.In sporadic PD patients,decreased DJ-1 protein level was found,and our previous results showed that knockout of DJ-1 gene could lead to neuronal inflammation and dopaminergic neuron loss.In this study,we sought to explore the relationship between polymorphisms in DJ-1 gene promoter region and PD,and the mechanism underneath.METHODS:In AD,the levels of 70 plasma immune and inflammatory related proteins were tested in training set consisting of 28 AD patients and27 healthy controls(HC).Mann-Whitney U test,correlation analysis,and factor analysis were used to screen plasma proteins strongly related to AD.Establishment of AD prediction algorithm with AD strongly associated protein was conducted,and the sensitivity and specificity of the algorithm for AD diagnosis were determined in testing set consisting of another 10HC,8 patients with mild cognitive impairment(MCI)and 10 AD patients.In order to evaluate the predictive power of the algorithm for AD,we conducted neuropsychological assessment again after 2 years'follow-up of MCI patients and analyzed the changes of cognitive function with reference to baseline.In PD,we sequenced the DJ-1 promoter region in 319 sporadic PD patients and 381 normal controls to screen the DJ-1 promoter region polymorphism and assess the possible association between DJ-1 promoter polymorphisms,PD risk and clinical phenotypes.Dual-luciferase reporter assay was conducted to examine the function of polymorphisms associated with PD.RESULTS:In the AD study,the algorithm was established with 11 plasma immune and inflammatory proteins.In training set,the diagnosis accuracy was 87.3%,the sensitivity was 75.0%,the specificity was 100%,the area under the ROC curve(AUC)was 0.981,p<0.0001;In testing set,the diagnosis accuracy was 90%,the sensitivity was 90%,the specificity was90%,the AUC was 0.950,p=0.001.In testing set of eight MCIs,two were identified as AD.After 2 years follow-up,among the two patients,one converted to AD,and the other had progressed to a worse state of cognitive function,the other four MCI patients in the cohort and 10 HC still maintained the baseline level of cognitive statuses.In the association study of the promoter polymorphisms of DJ-1 gene with PD,we found that the rs226249 C>T polymorphism locus may be a risk factor for PD(OR:1.79,P=0.021).Subgroup analysis showed that the frequency of rs226249 T allele was significantly higher in Akinetic/Rigid PD patients than in normal controls(42.3%vs.31.5%,P=0.001).Dual-luciferase reporter assay showed that rs226249 T allele could not effectively upregulate the transcriptional activity of DJ-1 promoter under MPP~+stimulation.CONCLUSIONS:1)11 immune and inflammatory proteins(CCL2/MCP-1,CCL8/MCP-2,CCL13/MCP-4,CCL17/TARC,CCL22/MDC,CCL27/CTACK,CXCL1/GRO,EGF,GCP-2,KITLG/SCF,TNFSF10/TRAIL)were selected as potential AD biomarkers with an adequate efficacy in detecting and warning early AD.To further enhance the credibility of the conclusion,verification in a larger sample set would be needed.2)The rs226249 C>T polymorphism might increase PD risk and modulate PD phenotypes.Such an effect might be caused by the ineffective regulation of DJ-1 transcription by T allele under harmful attacks.