Characterization of Uranyl (UO22+) Ion Binding to Amyloid Beta (Aβ) Peptides: Effects on Aβ Structure and Aggregation

Mitigation of depleted uranium-induced mitochondrial damage by ethylmalonic encephalopathy 1 protein via modulation of hydrogen sulfide and glutathione pathways

Depleted uranium (DU) is a byproduct of uranium enrichment, which can cause heavy-metal toxicity and radiation toxicity as well as serious damage to the kidneys. However, the mechanism of renal injury induced by DU is still unclear. This study aimed to explore the role of ethylmalonic encephalopathy 1 (ETHE1) in DU-induced mitochondrial dysfunction and elucidate the underlying mechanisms. Using ETHE1 gene knockout C57BL/6 mice (10 mg/kg DU) and renal cell models (500 µM DU) exposed to DU, we observed significantly reduced levels of hydrogen sulfide (H2S) and glutathione (GSH), alongside decreased adenosine triphosphate (ATP) content and increased oxidative stress. Our results demonstrated that knocking out or silencing ETHE1 led to a significant reduction in H2S and GSH levels, whereas the opposite occurred when was ETHE1 overexpressed. When the H2S donor sodium hydrosulfide and GSH precursor N-acetylcysteine were used to treat animals or cells, cellular ATP levels were increased, oxidative stress markers were reduced, and kidney damage was mitigated. In addition, H2S and GSH interacted with each other after DU poisoning. These findings suggest that the ETHE1/H2S/GSH pathway plays a critical role in mediating DU-induced mitochondrial dysfunction in renal cells, highlighting potential therapeutic targets for mitigating the harmful effects of DU. Thus, this study expands our understanding of DU-induced renal damage pathways, providing avenues for further research and intervention strategies.

Molecular interactions, structural effects, and binding affinities between silver ions (Ag+) and amyloid beta (Aβ) peptides

Because silver is toxic to microbes, but not considered toxic to humans, the metal has been used as an antimicrobial agent since ancient times. Today, silver nanoparticles and colloidal silver are used for antibacterial purposes, and silver-peptide and similar complexes are being developed as therapeutic agents. Yet, the health effects of silver exposure are not fully understood, nor are the molecular details of silver-protein interactions. In Alzheimer's disease, the most common form of dementia worldwide, amyloid-β (Aβ) peptides aggregate to form soluble oligomers that are neurotoxic. Here, we report that monovalent silver ions (Ag+) bind wildtype Aβ40 peptides with a binding affinity of 25 ± 12 µM in MES buffer at 20 °C. Similar binding affinities are observed for wt Aβ40 peptides bound to SDS micelles, for an Aβ40(H6A) mutant, and for a truncated Aβ(4-40) variant containing an ATCUN (Amino Terminal Cu and Ni) motif. Weaker Ag+ binding is observed for the wt Aβ40 peptide at acidic pH, and for an Aβ40 mutant without histidines. These results are compatible with Ag+ ions binding to the N-terminal segment of Aβ peptides with linear bis-his coordination. Because the Ag+ ions do not induce any changes in the size or structure of Aβ42 oligomers, we suggest that Ag+ ions have a minor influence on Aβ toxicity.

Hereditary Transthyretin Amyloidosis (hATTR) with Polyneuropathy Clusters Are Located in Ancient Mining Districts: A Possible Geochemical Origin of the Disease

Hereditary transthyretin amyloidosis (hATTR) with polyneuropathy (formerly known as Familial Amyloid Polyneuropathy (FAP)) is an endemic amyloidosis involving the harmful aggregation of proteins, most commonly transthyretin (TTR) but sometimes also apolipoprotein A-1 or gelsolin. hATTR appears to be transmitted as an autosomal dominant trait. Over 100 point mutations have been identified, with the Val30Met substitution being the most common. Yet, the mechanism of pathogenesis and the overall origin of hATTR remain unclear. Here, we argue that hATTR could be related to harmful metal exposure. hATTR incidence is unevenly distributed globally, and the three largest defined clusters exist in Japan, Portugal, and Sweden. All three disease regions are also ancient mining districts with associated metal contamination of the local environment. There are two main mechanisms for how harmful metals, after uptake into tissues and body fluids, could induce hATTR. First, the metals could directly influence the expression, function, and/or aggregation of the proteins involved in hATTR pathology. Such metal-protein interactions might constitute molecular targets for anti-hATTR drug design. Second, metal exposure could induce hATTR -associated genetic mutations, which may have happened several generations ago. These two mechanisms can occur in parallel. In conclusion, the possibility that hATTR could be related to metal exposure in geochemically defined regions deserves further attention.

Aggregation Dynamics Characteristics of Seven Different Aβ Oligomeric Isoforms-Dependence on the Interfacial Interaction

The aggregation of β-amyloid (Aβ) peptides has been confirmed to be associated with the onset of Alzheimer's disease (AD). Among the three phases of Aβ aggregation, the lag phase has been considered to be the best time for early Aβ pathological deposition clinical intervention and prevention for potential patients with normal cognition. Aβ peptide exists in various lengths in vivo, and Aβ oligomer in the early lag phase is neurotoxic but polymorphous and metastable, depending on Aβ length (isoform), molecular weight, and specific phase, and therefore hardly characterized experimentally. To cope with the problem, molecular dynamics simulation was used to investigate the aggregation process of five monomers for each of the seven common Aβ isoforms during the lag phase. Results showed that Aβ(1-40) and Aβ(1-38) monomers aggregated faster than their truncated analogues Aβ(4-40) and Aβ(4-38), respectively. However, the aggregation rate of Aβ(1-42) was slower than that of its truncated analogues Aβ(4-42) rather than that of Aβpe(3-42). More importantly, Aβ(1-38) is first predicted as more likely to form stable hexamer than the remaining five Aβ isoforms, as Aβ(1-42) does. It is hydrophobic interaction mainly (>50%) from the interfacial β1 and β2 regions of two reactants, pentamer and monomer, aggregated by Aβ(1-38)/Aβ(1-42) rather than by other Aβ isoforms, that drives the hexamer stably as a result of the formation of the effective hydrophobic collapse. This paper provides new insights into the aggregation characteristics of Aβ with different lengths and the conditions necessary for Aβ to form oligomers with a high molecular weight in the early lag phase, revealing the dependence of Aβ hexamer formation on the specific interfacial interaction.