Zn2+ Interaction with Amyloid-Β: Affinity and Speciation

Recent Advancements in Biosensors for the Detection and Characterization of Amyloids: A Review

Modern medicine has increased the human lifespan. However, with an increase in average lifespan risk of amyloidosis increases. Amyloidosis is a condition characterized by protein misfolding and aggregation. Early detection of amyloidosis is crucial, yet conventional diagnostic methods are costly and lack precision, necessitating innovative tools. This review explores recent advancements in diverse amyloid detection methodologies, highlighting the need for interdisciplinary research to develop a miniaturized electrochemical biosensor leveraging nanotechnology. However, the diagnostics industry faces obstacles such as skilled labor shortages, standardized selection processes, and concurrent multi-analyte identification challenges. Research efforts are focused on integrating electrochemical techniques into clinical applications and diagnostics, with the successful transition of miniaturized technologies from development to testing posing a significant hurdle. Label-free transduction techniques like voltammetry and electrochemical impedance spectroscopy (EIS) have gained traction due to their rapid, cost-effective, and user-friendly nature.

Rationally Designed Cu(I) Ligand to Prevent CuAβ-Generated ROS Production in the Alzheimer's Disease Context

In the context of Alzheimer's disease, copper (Cu) can be loosely bound to the amyloid-β (Aβ) peptide, leading to the formation of CuAβ, which can catalytically generate reactive oxygen species that contribute to oxidative stress. To fight against this phenomenon, the chelation therapy approach has been developed and consists of using a ligand able to remove Cu from Aβ and to redox-silence it, thus stopping the reactive oxygen species (ROS) production. A large number of Cu(II) chelators has been studied, allowing us to define and refine the properties required to design a "good" ligand, but without strong therapeutic outcomes to date. Those chelators targeted the Cu(II) redox state. Herein, we explore a parallel and relevant alternative pathway by designing a chelator able to target the Cu(I) redox state. To that end, we designed LH2 ([1N3S] binding set) and demonstrated that (i) it is perfectly able to extract Cu(I) from Cu(I)Aβ even in the presence of an excess of Zn(II) and (ii) it redox-silences the Cu, preventing the formation of ROS. We showed that LH2 that is sensitive to oxidation can efficiently replace the [Zn(II)L] complex without losing its excellent ability to stop the ROS production while increasing its resistance to oxidation.

Bioinorganic Chemistry of Micronutrients Related to Alzheimer's and Parkinson's Diseases

Metal ions are fundamental to guarantee the regular physiological activity of the human organism. Similarly, vitamins play a key role in many biological functions of the metabolism, among which are coenzymes, redox mediators, and antioxidants. Due to their importance in the human organism, both metals and vitamins have been extensively studied for their involvement in neurodegenerative diseases (NDs). However, the full potential of the interaction between vitamins and metal ions has not been fully explored by researchers yet, and further investigation on this topic is needed. The aim of this review is to provide an overview of the scientific literature on the implications of vitamins and selected metal ions in two of the most common neurodegenerative diseases, Alzheimer's and Parkinson's disease. Furthermore, vitamin-metal ion interactions are discussed in detail focusing on their bioinorganic chemistry, with the perspective of arousing more interest in this fascinating bioinorganic field.

Speciation analysis of manganese against the background of its different content in the blood serum of dairy cows

Studies in the field of microelement speciation in the body of farm animals, in particular dairy cattle, are almost completely absent. The average concentration of Mn in the blood serum of all the studied animals (n = 80) was 2.5 μg/L, which corresponds to normal values. Of the total number of animals, 21% were the cows with the low normal values (serum Mn concentration ≤ 2 µg/L, i.e. less than Q25 of the total sample) and 25% were the animals with the high normal values (serum Mn concentration ≥ 2.72 µg/L, i.e. more than Q75 of the total sample). The data obtained in the course of the study indicate that the change in the Mn level, even in the range of normal values, is accompanied by the redistribution of this element over various protein fractions. The six found Mn blood serum forms are presumably represented by α2-macroglobulin (tetramer, dimer, and monomer), transferrin/albumine, manganese citrates, and "free" metal ions. The analyzed fractions of Mn found in the blood serum of cows had the following hierarchy of concentrations: in the group with low-normal values of Mn ("free" Mn >> tetrameric form of α2-macroglobulin >> transferrin/albumine >> dimeric form of α2-macroglobulin >> monomeric form of α2-macroglobulin >> citrate), in the group with high normal manganese values ("free" Mn >> monomeric form of α2-macroglobulin >> transferring/albumine >> citrate >> tetrameric form of α2-macroglobulin >> dimeric form of α2-macroglobulin). In the group with high normal Mn values relative to the group with low normal values, there was a percentage decrease in the tetrameric fraction of a2-macroglobulin from 17.2 to 4.4%, dimeric fraction of a2-macroglobulin from 6.9 to 2.2%, "free" Mn from 54.3 to 44.4% and an increase in monomeric fraction of a2-macroglobulin from 6.7 to 23.1%, transferrin/albumine from 10.1 to 17.7%, citrate from 4.8 to 8.2%. Our data demonstrate the features of Mn redistribution of dairy cows, which can be used for an extended assessment of the microelement status of animals.

Unveiling the Metal-Dependent Aggregation Properties of the C-terminal Region of Amyloidogenic Intrinsically Disordered Protein Isoforms DPF3b and DPF3a

Double-PHD fingers 3 (DPF3) is a BAF-associated human epigenetic regulator, which is increasingly recognised as a major contributor to various pathological contexts, such as cardiac defects, cancer, and neurodegenerative diseases. Recently, we unveiled that its two isoforms (DPF3b and DPF3a) are amyloidogenic intrinsically disordered proteins. DPF3 isoforms differ from their C-terminal region (C-TERb and C-TERa), containing zinc fingers and disordered domains. Herein, we investigated the disorder aggregation properties of C-TER isoforms. In agreement with the predictions, spectroscopy highlighted a lack of a highly ordered structure, especially for C-TERa. Over a few days, both C-TERs were shown to spontaneously assemble into similar antiparallel and parallel β-sheet-rich fibrils. Altered metal homeostasis being a neurodegeneration hallmark, we also assessed the influence of divalent metal cations, namely Cu²⁺, Mg²⁺, Ni²⁺, and Zn²⁺, on the C-TER aggregation pathway. Circular dichroism revealed that metal binding does not impair the formation of β-sheets, though metal-specific tertiary structure modifications were observed. Through intrinsic and extrinsic fluorescence, we found that metal cations differently affect C-TERb and C-TERa. Cu²⁺ and Ni²⁺ have a strong inhibitory effect on the aggregation of both isoforms, whereas Mg²⁺ impedes C-TERb fibrillation and, on the contrary, enhances that of C-TERa. Upon Zn²⁺ binding, C-TERb aggregation is also hindered, and the amyloid autofluorescence of C-TERa is remarkably red-shifted. Using electron microscopy, we confirmed that the metal-induced spectral changes are related to the morphological diversity of the aggregates. While metal-treated C-TERb formed breakable and fragmented filaments, C-TERa fibrils retained their flexibility and packing properties in the presence of Mg²⁺ and Zn²⁺ cations.

Zinc

Since the discovery of manifest Zn deficiency in 1961, the increasing number of studies demonstrated the association between altered Zn status and multiple diseases. In this chapter, we provide a review of the most recent advances on the role of Zn in health and disease (2010-20), with a special focus on the role of Zn in neurodegenerative and neurodevelopmental disorders, diabetes and obesity, male and female reproduction, as well as COVID-19. In parallel with the revealed tight association between ASD risk and severity and Zn status, the particular mechanisms linking Zn2+ and ASD pathogenesis like modulation of synaptic plasticity through ProSAP/Shank scaffold, neurotransmitter metabolism, and gut microbiota, have been elucidated. The increasing body of data indicate the potential involvement of Zn2+ metabolism in neurodegeneration. Systemic Zn levels in Alzheimer's and Parkinson's disease were found to be reduced, whereas its sequestration in brain may result in modulation of amyloid β and α-synuclein processing with subsequent toxic effects. Zn2+ was shown to possess adipotropic effects through the role of zinc transporters, zinc finger proteins, and Zn-α2-glycoprotein in adipose tissue physiology, underlying its particular role in pathogenesis of obesity and diabetes mellitus type 2. Recent findings also contribute to further understanding of the role of Zn2+ in spermatogenesis and sperm functioning, as well as oocyte development and fertilization. Finally, Zn2+ was shown to be the potential adjuvant therapy in management of novel coronavirus infection (COVID-19), underlining the perspectives of zinc in management of old and new threats.

Potential molecular and graphene oxide chelators to dissolve amyloid-β plaques in Alzheimer's disease: a density functional theory study

The onset of Alzheimer's disease (AD) is caused by amyloid-β (Aβ) aggregation. Elevated levels of metals, specifically copper, zinc, iron, and aluminum, accumulate in senile Aβ; plaque deposits, disrupting normal brain homeostasis and cognitive functions. In this investigation, we studied the potential of several molecular and graphene oxide chelators to be used for future AD research and chelation therapy. To understand the interactions between selected metals (Cu, Zn, Fe, and Al), the Aβ peptide, and various potential metal chelating compounds, we implemented the density functional theory (DFT) method to calculate the binding energies of each metal-molecule complex. The binding energy of each metal-chelator complex was compared with that of the metal-Aβ compound to determine the chelation potential of the selected chelator. The potential chelating agents studied were 8-hydroxyquinoline-2-carboxaldehyde isonicotinoyl hydrazone (INNHQ), 8-hydroxyquinoline-2-carboxaldehyde 2-furoyl hydrazone (HQFUH), quercetin, and graphene oxide (GO). Our calculated binding energies revealed that the HQFUH molecule holds direct ability to chelate copper, zinc, iron, and aluminum. In addition, the GO complex with a 12.5% oxygen concentration demonstrates aluminum chelation ability. Our results demonstrate that HQFUH and GO can be used in future AD drug development research and therapy to target toxic metal-Aβ interactions and reduce Aβ aggregation.

Recent Advances in AIEgens for Metal Ion Biosensing and Bioimaging

Metal ions play important roles in biological system. Approaches capable of selective and sensitive detection of metal ions in living biosystems provide in situ information and have attracted remarkable research attentions. Among these, fluorescence probes with aggregation-induced emission (AIE) behavior offer unique properties. A variety of AIE fluorogens (AIEgens) have been developed in the past decades for tracing metal ions. This review highlights recent advances (since 2015) in AIE-based sensors for detecting metal ions in biological systems. Major concerns will be devoted to the design principles, sensing performance, and bioimaging applications.