Tougu, V. | bioRxiv Science

bioRxiv2023

Characterization of uranyl ion binding to amyloid beta (Aβ) peptides: effects on Aβ structure and aggregation

AbstractUranium (U) is naturally present in ambient air, water, and soil, and depleted uranium (DU) is released into the environment via industrial and military activities. While the radiological damage from U is rather well understood, less is known about the chemical damage mechanisms, which dominate in DU. Heavy metal exposure is associated with numerous health conditions including Alzheimers disease (AD), the most prevalent age-related cause of dementia. The pathological hallmark of AD is deposition of amyloid plaques, consisting mainly of amyloid-{beta} (A{beta}) peptides aggregated into amyloid fibrils in the brain. However, the toxic species in AD are likely oligomeric A{beta} aggregates. Exposure to heavy metals such as Cd, Hg, Mn, and Pb is known to increase A{beta} production, and these metals bind to A{beta} peptides and modulate their aggregation. Possible effects of U in AD pathology have been sparsely studied. Here, we use biophysical techniques to study in vitro interactions between A{beta} peptides and uranyl ions, UO22+, of DU. We show for the first time that uranyl ions bind to A{beta} peptides with affinities in the micromolar range, induce structural changes in A{beta} monomers and oligomers, and inhibit A{beta} fibrillization. General toxic mechanisms of uranyl ions could be modulation of protein folding, misfolding, and aggregation.

biophysics↗

bioRxiv2021

α-lipoic acid has the potential to normalize copper metabolism, which is dysregulated in Alzheimer's disease

Alzheimers disease (AD) is an age-dependent progressive neurodegenerative disorder and the most common cause of dementia. The treatment and prevention of AD present immense yet unmet needs. One of the hallmarks of AD is the formation of extracellular amyloid plaques in the brain, composed of amyloid-beta (A{beta}) peptides. Multiple amyloid-targeting drug candidates have recently failed in clinical trials, which creates the necessity to focus also on alternative therapeutic strategies. One factor contributing to the development of AD is dysregulated copper metabolism, reflected in the intracellular copper deficit and excess extracellular copper levels. In the current study, we follow the widely accepted hypothesis that the normalization of copper metabolism leads to the prevention or slowing of the disease and searched for new copper-regulating ligands. We demonstrate that the natural intracellular copper chelator, -lipoic acid (LA) translocates copper from extracellular to intracellular space in a SH-SY5Y-based neuronal cell model, and is thus suitable to alleviate the intracellular copper deficit characteristic of AD neurons. Furthermore, we show that supplementation with LA protects the Drosophila melanogaster model of AD from developing AD phenotype, reflecting in decreased locomotor activity. Collectively, these results provide evidence that LA has the potential to normalize copper metabolism in AD and supports the hypothesis that LA supplementation may serve as a promising cost-effective method for the prevention and/or treatment of AD. Significance statementAlzheimers disease (AD) is a major biomedical concern that requires novel effective prevention and treatment approaches. An early determinant of AD pathology is dysregulated copper metabolism, which initiates the amyloid cascade, induces oxidative stress and impairs the functioning of cellular copper proteins, all contributing to the development of neurodegeneration. We suggest that the natural copper chelator -lipoic acid (LA) can normalize impaired copper metabolism in AD. We demonstrate that LA promotes the influx of copper into SH-SY5Y cells in a dose-dependent manner. Moreover, we show that LA alleviates the disease phenotype in a Drosophila melanogaster model of AD. Together with previously published data, these results support the hypothesis that LA has the potential for the prevention and treatment of AD.

neuroscience↗