Dynamic modeling of α-synuclein aggregation in dopaminergic neuronal system indicates points of neuroprotective intervention: experimental validation with implications for Parkinson's therapy.

Protein aggregation is the major pathological hallmark seen in neurodegenerative disorders such as Parkinson's disease (PD). Alpha-synuclein (αS) is the main component of protein aggregates that form Lewy bodies (LBs) in PD and dementia with LBs. There have been several attempts to intervene in the process of expression, modification, clearance, and aggregation of αS as a therapeutic strategy toward neuroprotection. In this study, we have employed a novel, predictive, system level approach in silico to study four different strategies of anti-aggregation therapies: (a) reduction in αS modifications such as phosphorylation, nitration, or truncation in an approach called "seed clearance;" (b) "anti-oligomerization" approach through blocking the early oligomers formation; (c) "oligomers clearance" process by increasing its lysosomal degradation; and (d) "anti-aggregation" that involves prevention of aggregate formation at a later stage. These strategies were tested in a virtual dopaminergic neuronal system triggered by overexpression (OE) of mutant αS-A53T with or without rotenone (Rot)-induced oxidative stress. The results were compared by analyzing markers related to various end points such as oxidative stress, dopamine (DA) metabolism, proteasome function, survival and apoptosis. The experimental system and anti-oligomerization strategies were recapitulated in vitro in M17 dopaminergic cells overexpressing mutant αS-A53T triggered with Cu(II)-mediated oxidative stress, and the experimental data prospectively corroborated with the predictive results. Through this analysis, we found that intervention in the early part of the aggregation pathway by prevention of oligomer formation and increased clearance is indeed a good neuroprotective strategy, whereas anti-aggregation efforts to break up the aggregate at later stages has negative effects on the system.

Detection of elevated levels of α-synuclein oligomers in CSF from patients with Parkinson disease.

BACKGROUND: To date, there is no accepted clinical diagnostic test for Parkinson disease (PD) that is based on biochemical analysis of blood or CSF. The discovery of mutations in the SNCA gene encoding α-synuclein in familial parkinsonism and the accumulation of α-synuclein in the PD brain suggested a critical role for this protein in PD etiology. METHODS: We investigated total and α-synuclein oligomers levels in CSF from patients clinically diagnosed with PD, progressive supranuclear palsy (PSP), or Alzheimer disease (AD), and age-matched controls, using ELISA developed in our laboratory. RESULTS: The levels of α-synuclein oligomers and oligomers/total-α-synuclein ratio in CSF were higher in the PD group (n = 32; p < 0.0001, Mann-Whitney U test) compared to the control group (n = 28). The area under the receiver operating characteristic curve (AUC) indicated a sensitivity of 75.0% and a specificity of 87.5%, with an AUC of 0.859 for increased CSF α-synuclein oligomers in clinically diagnosed PD cases. However, when the CSF oligomers/total-α-synuclein ratio was analyzed, it provided an even greater sensitivity of 89.3% and specificity of 90.6%, with an AUC of 0.948. In another cross-sectional pilot study, we confirmed that the levels of CSF α-synuclein oligomers were higher in patients with PD (n = 25) compared to patients with PSP (n = 18; p < 0.05) or AD (n = 35; p < 0.001) or control subjects (n = 43; p < 0.05). CONCLUSION: Our results demonstrate that levels of α-synuclein oligomers in CSF and the oligomers/total-α-synuclein ratio can be useful biomarkers for diagnosis and early detection of PD.