Generation of ferric iron links oxidative stress to α-synuclein oligomer formation.
BACKGROUND
Synucleinopathies such as Parkinson's disease are characterized by the deposition of aggregated α-synuclein in affected brain areas. As genes involved in mitochondrial function, mitochondrial toxins, and age-related mitochondrial impairment have been implicated in Parkinson's disease pathogenesis, an increase in reactive oxygen species resulting from mitochondrial dysfunction has been speculated to induce α-synuclein aggregation. In vitro, pore-forming, SDS-resistant α-synuclein oligomers are formed in presence of ferric iron and may represent an important toxic particle species.


RESULTS
We investigated the interplay of reactive oxygen species, antioxidants and iron oxidation state in regard to α-synuclein aggregation using confocal single particle fluorescence spectroscopy, Phenanthroline spectrometry and thiobarbituric acid reactive substances assay. We found that the formation of α-synuclein oligomers in presence of Fe³⁺ is due to a direct interaction. In contrast, oxidizing agents and hydroxyl radicals generated in the Fenton reaction did not directly affect α-synuclein oligomerization. However, reactive oxygen species could enhance aggregation via oxidation of ferrous to ferric iron when iron ions were present.


CONCLUSIONS
Our data thus indicate that oxidative stress affects α-synuclein aggregation via oxidation of iron to the ferric state. This provides a new perspective on the role of mitochondrial toxins and mitochondrial dysfunction in the pathogenesis of Parkinson's disease.
Neurology Department, Ludwig-Maximilians-University Munich, Munich, Germany.
Johannes
J
Levin
Tobias
T
Högen
Andreas S
AS
Hillmer
Benedikt
B
Bader
Felix
F
Schmidt
Frits
F
Kamp
Hans A
HA
Kretzschmar
Kai
K
Bötzel
Armin
A
Giese
D001205:Ascorbic Acid / Q000494:pharmacology; D003676:Deferoxamine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005290:Ferric Compounds / Q000378:metabolism*; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D018613:Microscopy, Confocal; D008954:Models, Biological; D010084:Oxidation-Reduction / Q000187:drug effects*; D017262:Siderophores / Q000494:pharmacology; D051844:alpha-Synuclein / Q000737:chemistry* / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*
D005290:Ferric Compounds; D017262:Siderophores; D051844:alpha-Synuclein; D006861:Hydrogen Peroxide; D003676:Deferoxamine; D001205:Ascorbic Acid