Oxidative stress induces amyloid-like aggregate formation of NACP/α-synuclein in vitro

TLDR

NACP/α‑synuclein is a presynaptic protein linked to familial Parkinson’s disease and found in Lewy bodies, yet the mechanisms driving its aggregation remain unclear. The study examined whether iron and peroxide promote NACP/α‑synuclein aggregation, implicating oxidative stress in Parkinson’s disease. Immunoblotting revealed that ferric ions trigger NACP/α‑synuclein aggregation, which is blocked by deferoxamine, while ferrous ions require hydrogen peroxide to induce aggregation. The resulting aggregates displayed amyloid‑like thioflavine‑S and Congo‑red staining, indicating that oxidative reactions may drive neurodegeneration in Lewy body disorders.

Abstract

The precursor of non-amyloid β protein component of Alzheimer's disease amyloid (NACP/α-synuclein), found in Lewy bodies of Parkinson's disease (PD), is a presynaptic protein genetically linked to some familial types PD. Mechanisms of abnormal NACP/α-synuclein aggregation in neurodegenerative diseases are unclear. Since oxidative stress might play a role in PD pathogenesis, we investigated the role of iron and peroxide in NACP/α-synuclein aggregation. Immunoblot analysis showed that human NACP/α-synuclein (but not β-synuclein) aggregated in the presence of ferric ion and was inhibited by the iron chelator deferoxamine. Ferrous ion was not effective by itself, but it potentially aggregated NACP/α-synuclein in the presence of hydrogen peroxide. NACP/α-synuclein aggregates displayed strong thioflavine-S and congo-red reactivity, reminiscent of amyloid. This study suggests that NACP/α-synuclein aggregation might be closely related to oxidative reactions which may play a critical role in neurodegeneration in disorders with Lewy bodies.