P4-283: Dopamine modulates the formation of soluble SDS-stable α-synuclein oligomers via methionine oxidation

Abstract

of Parkinson’s disease (PD) and other synucleinopathies by its presence in Lewy bodies, and by the effects of mutations or increases in gene copy number. In the latter condition, families with duplication or triplication of the gene have concentrations of -synuclein in postmortem brain that is proportional to copy number. In these families increased levels of -synuclein also correlate with severity of disease and earlier age of onset. Knowledge of changes in concentration of -synuclein in brain in diseased compared to normal tissue is thus of considerable interest. Only a few studies measuring -synuclein expression have been carried out, mostly by measuring mRNA rather than protein levels, and results have been contradictory. We have measured -synuclein protein in several regions of post-mortem brain from 5 controls, 6 individuals with PD and 8 with dementia with Lewy bodies (DLB). Methods: Tissue samples from medial temporal, superior parietal, superior occipital, and superior frontal gyri and from cerebellum were obtained via the rapid autopsy programme of the Netherlands Brain Bank from clinically well documented and pathologically confirmed cases. Tissue was dissected, frozen and stored at -80C. Samples of human brain ( 200 mg) were homogenized in 8 mass of 5 M guanidine HCl/50 mM Tris HCl pH 8.0 and centrifuged (16,000 g, 20 min). Prior to assay, the supernatant was diluted 100-fold. Total protein was determined using the BCA protein assay (Pierce). -Synuclein concentrations were quantified with a sandwich ELISA (BioSource) according to the manufacturer’s instructions and results expressed as ng -synuclein/ g total protein. Results: Mean values for the concentrations of -synuclein were calculated for each tissue type within each subject group (control, PD, or DLB). For both diseases, levels of -synuclein were significantly lower compared to controls in all the brain regions tested, with the single exception of superior frontal gyrus in the PD group. Conclusions: Our findings of decreased brain -synuclein in PD are consistent with similar findings previously reported in CSF. This work was supported by the Research and Development Office, Health and Personal Social Services, Northern Ireland.