Longitudinal changes in CSF alpha-synuclein species reflect Parkinson's disease progression

Background: Parkinson's disease (PD) diagnosis is mainly based on clinical criteria, with a high risk of misdiagnosis. The identification of reliable biomarkers for disease diagnosis and progression has a key role for developing disease-modifying therapies. In this article, we investigated the longitudinal changes of CSF α-synuclein species in early PD patients and explored the potential use of these species as surrogate biomarkers for PD progression. Methods: We used our newly developed enzyme-linked immunosorbent assay systems for measuring different forms of α-synuclein, such as oligomeric-α-synuclein, phosphorylated-α-synuclein at serine 129, or total-α-synuclein in CSF from the longitudinal Deprenyl and Tocopherol Antioxidative Therapy for Parkinsonism study cohort (n = 121). CSF Alzheimer's disease biomarkers (total-tau, phosphorylated-tau, Aβ₄₀, and Aβ₄₂) were also measured for this cohort. Results: Interestingly, total-α-synuclein and oligomeric-α-synuclein levels significantly increased during the 2-year Deprenyl and Tocopherol Antioxidative Therapy for Parkinsonism study follow-up period, whereas phosphorylated-α-synuclein at serine 129 levels showed a longitudinal decrease. We have also noted an association between a change of the oligomeric-α-synuclein/total-α-synuclein ratio and a worsening of motor signs, in particular in the postural-instability and gait-difficulty dominant PD group. A strong positive correlation between the changes in CSF total-α-synuclein and oligomeric-α-synuclein during the 2-year Deprenyl and Tocopherol Antioxidative Therapy for Parkinsonism study was also noted (r = 0.84, P <.001). Conclusion: Our data show that CSF α-synuclein species have a dynamic pattern along the course of the disease, supporting their possible role as progression biomarkers for PD and their link with PD clinical phenotypes.