Diagnosis of Parkinson's disease and the level of oxidized DJ-1 protein

Parkinson's disease (PD) is difficult to distinguish from progressive supranuclear palsy (PSP) and multiple system atrophy (MSA); in addition, biomarker studies in PD mostly focused on those found in the cerebrospinal fluid, and there are few reports of simple biomarkers identified by blood analysis. Previously, the DJ-1 gene was identified as a causative gene of familial PD. Oxidized DJ-1 protein (oxDJ-1) levels were reported to increase in the blood of patients with unmedicated PD. Therefore, we determined the levels of oxDJ-1 in the erythrocytes of patients with PD, PSP, and MSA using ELISA. The oxDJ-1 levels were 165 ± 117, 96 ± 78, and 69 ± 40 ng/mg protein in the PD, PSP, and MSA groups, respectively. The mean level in disease control group was 66 ± 31, revealing significant differences between the PD and PSP groups, the PD and MSA groups, and the PD and disease control groups. Our results indicated that oxDJ-1 levels in erythrocytes can be used as a marker for the differential diagnosis of PD.