Copper, differently from zinc, affects the conformation, oligomerization state and activity of bradykinin

Challenges and Recommendations in Assessing Potential Endocrine-Disrupting Properties of Metals in Aquatic Organisms

New tools and refined frameworks for identifying and regulating endocrine-disrupting chemicals (EDCs) are being developed as our scientific understanding of how they work advances. Although focus has largely been on organic chemicals, the potential for metals to act as EDCs in aquatic systems is receiving increasing attention. Metal interactions with the endocrine system are complicated because some metals are essential to physiological systems, including the endocrine system, and nonessential metals can have similar physiochemical attributes that allow substitution into or interference with these systems. Consequently, elevated metal exposure could potentially cause endocrine disruption (ED) but can also cause indirect effects on the endocrine system via multiple pathways or elicit physiologically appropriate compensatory endocrine-mediated responses (endocrine modulation). These latter two effects can be confused with, but are clearly not, ED. In the present study, we provide several case studies that exemplify the challenges encountered in evaluating the endocrine-disrupting (ED) potential of metals, followed by recommendations on how to meet them. Given that metals have multiple modes of action (MOAs), we recommend that assessments use metal-specific adverse outcome pathway networks to ensure that accurate causal links are made between MOAs and effects on the endocrine system. We recommend more focus on establishing molecular initiating events for chronic metal toxicity because these are poorly understood and would reduce uncertainty regarding the potential for metals to be EDCs. Finally, more generalized MOAs such as oxidative stress could be involved in metal interactions with the endocrine system, and we suggest it may be experimentally efficient to evaluate these MOAs when ED is inferred. These experiments, however, must provide explicit linkage to the ED endpoints of interest. Environ Toxicol Chem 2023;42:2564-2579. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Semax, a Synthetic Regulatory Peptide, Affects Copper-Induced Abeta Aggregation and Amyloid Formation in Artificial Membrane Models

Alzheimer’s disease, the most common form of dementia, is characterized by the aggregation of amyloid beta protein (Aβ). The aggregation and toxicity of Aβ are strongly modulated by metal ions and phospholipidic membranes. In particular, Cu²⁺ ions play a pivotal role in modulating Aβ aggregation. Although in the last decades several natural or synthetic compounds were evaluated as candidate drugs, to date, no treatments are available for the pathology. Multifunctional compounds able to both inhibit fibrillogenesis, and in particular the formation of oligomeric species, and prevent the formation of the Aβ:Cu²⁺ complex are of particular interest. Here we tested the anti-aggregating properties of a heptapeptide, Semax, an ACTH-like peptide, which is known to form a stable complex with Cu²⁺ ions and has been proven to have neuroprotective and nootropic effects. We demonstrated through a combination of spectrofluorometric, calorimetric, and MTT assays that Semax not only is able to prevent the formation of Aβ:Cu²⁺ complexes but also has anti-aggregating and protective properties especially in the presence of Cu²⁺. The results suggest that Semax inhibits fiber formation by interfering with the fibrillogenesis of Aβ:Cu²⁺ complexes.

Ionophore Ability of Carnosine and Its Trehalose Conjugate Assists Copper Signal in Triggering Brain-Derived Neurotrophic Factor and Vascular Endothelial Growth Factor Activation In Vitro

l-carnosine (β-alanyl-l-histidine) (Car hereafter) is a natural dipeptide widely distributed in mammalian tissues and reaching high concentrations (0.7-2.0 mM) in the brain. The molecular features of the dipeptide underlie the antioxidant, anti-aggregating and metal chelating ability showed in a large number of physiological effects, while the biological mechanisms involved in the protective role found against several diseases cannot be explained on the basis of the above-mentioned properties alone, requiring further research efforts. It has been reported that l-carnosine increases the secretion and expression of various neurotrophic factors and affects copper homeostasis in nervous cells inducing Cu cellular uptake in keeping with the key metal-sensing system. Having in mind this l-carnosine ability, here we report the copper-binding and ionophore ability of l-carnosine to activate tyrosine kinase cascade pathways in PC12 cells and stimulate the expression of BDNF. Furthermore, the study was extended to verify the ability of the dipeptide to favor copper signaling inducing the expression of VEGF. Being aware that the potential protective action of l-carnosine is drastically hampered by its hydrolysis, we also report on the behavior of a conjugate of l-carnosine with trehalose that blocks the carnosinase degradative activity. Overall, our findings describe a copper tuning effect on the ability of l-carnosine and, particularly its conjugate, to activate tyrosine kinase cascade pathways.

The interplay between lipid and Aβ amyloid homeostasis in Alzheimer's Disease: risk factors and therapeutic opportunities

Alzheimer's Diseases (AD) is characterized by the accumulation of amyloid deposits of Aβ peptide in the brain. Besides genetic background, the presence of other diseases and an unhealthy lifestyle are known risk factors for AD development. Albeit accumulating clinical evidence suggests that an impaired lipid metabolism is related to Aβ deposition, mechanistic insights on the link between amyloid fibril formation/clearance and aberrant lipid interactions are still unavailable. Recently, many studies have described the key role played by membrane bound Aβ assemblies in neurotoxicity. Moreover, it has been suggested that a derangement of the ubiquitin proteasome pathway and autophagy is significantly correlated with toxic Aβ aggregation and dysregulation of lipid levels. Thus, studies focusing on the role played by lipids in Aβ aggregation and proteostasis could represent a promising area of investigation for the design of valuable treatments. In this review we examine current knowledge concerning the effects of lipids in Aβ aggregation and degradation processes, focusing on the therapeutic opportunities that a comprehensive understanding of all biophysical, biochemical, and biological processes involved may disclose.

THE USE OF MASS SPECTROMETRY TO STUDY ZN-METALLOPROTEASE-SUBSTRATE INTERACTIONS

Zinc metalloproteases (ZnMPs) participate in diverse biological reactions, encompassing the synthesis and degradation of all the major metabolites in living organisms. In particular, ZnMPs have been recognized to play a very important role in controlling the concentration level of several peptides and/or proteins whose homeostasis has to be finely regulated for the correct physiology of cells. Dyshomeostasis of aggregation-prone proteins causes pathological conditions and the development of several different diseases. For this reason, in recent years, many analytical approaches have been applied for studying the interaction between ZnMPs and their substrates and how environmental factors can affect enzyme activities. In this scenario, mass spectrometric methods occupy a very important role in elucidating different aspects of ZnMPs-substrates interaction. These range from identification of cleavage sites to quantitation of kinetic parameters. In this work, an overview of all the main achievements regarding the application of mass spectrometric methods to investigating ZnMPs-substrates interactions is presented. A general experimental protocol is also described which may prove useful to the study of similar interactions. © 2020 John Wiley & Sons Ltd. Mass Spec Rev.

The Dual Role of Kinin/Kinin Receptors System in Alzheimer's Disease

Alzheimer’s disease (AD) is the most common neurodegenerative disease characterized by progressive spatial disorientation, learning and memory deficits, responsible for 60%–80% of all dementias. However, the pathological mechanism of AD remains unknown. Numerous studies revealed that kinin/kinin receptors system (KKS) may be involved in the pathophysiology of AD. In this review article, we summarized the roles of KKS in neuroinflammation, cerebrovascular impairment, tau phosphorylation, and amyloid β (Aβ) generation in AD. Moreover, we provide new insights into the mechanistic link between KKS and AD, and highlight the KKS as a potential therapeutic target for AD treatment.

Metal-dependent hormone function: the emerging interdisciplinary field of metalloendocrinology

For over 100 years, there has been an incredible amount of knowledge amassed concerning hormones in the endocrine system and their central role in human health. Hormones represent a diverse group of biomolecules that are released by glands, communicate signals to their target tissue, and are regulated by feedback loops to maintain organism health. Many disease states, such as diabetes and reproductive disorders, stem from misregulation or dysfunction of hormones. Increasing research is illuminating the intricate roles of metal ions in the endocrine system where they may act advantageously in concert with hormones or deleteriously catalyze hormone-associated disease states. As the critical role of metal ions in the endocrine system becomes more apparent, it is increasingly important to untangle the complex mechanisms underlying the connections between inorganic biochemistry and hormone function to understand and control endocrinological phenomena. This tutorial review harmonizes the interdisciplinary fields of endocrinology and inorganic chemistry in the newly-termed field of "metalloendocrinology". We describe examples linking metals to both normal and aberrant hormone function with a focus on highlighting insight to molecular mechanisms. Hormone activities related to both essential metal micronutrients, such as copper, iron, zinc, and calcium, and disruptive nonessential metals, such as lead and cadmium are discussed.

In Vivo Biosynthesized Zinc and Iron Oxide Nanoclusters for High Spatiotemporal Dual-Modality Bioimaging of Alzheimer's Disease

Alzheimer's disease is still incurable and neurodegenerative, and there is a lack of detection methods with high sensitivity and specificity. In this study, by taking different month old Alzheimer's mice as models, we have explored the possibility of the target bioimaging of diseased sites through the initial injection of zinc gluconate solution into Alzheimer's model mice post-tail vein and then the combination of another injection of ferrous chloride (FeCl₂) solution into the same Alzheimer's model mice post-stomach. Our observations indicate that both zinc gluconate solution and FeCl₂ solution could cross the blood-brain barrier (BBB) to biosynthesize the fluorescent zinc oxide nanoclusters and magnetic iron oxide nanoclusters, respectively, in the lesion areas of the AD model mice, thus enabling high spatiotemporal dual-modality bioimaging (i.e., including fluorescence bioimaging (FL) and magnetic resonance imaging (MRI)) of Alzheimer's disease for the first time. The result presents a novel promising strategy for the rapid and early diagnosis of Alzheimer's disease.

Inhibition of Aβ Amyloid Growth and Toxicity by Silybins: The Crucial Role of Stereochemistry

The self-assembling of the amyloid β (Aβ) peptide into neurotoxic aggregates is considered a central event in the pathogenesis of Alzheimer's disease (AD). Based on the "amyloid hypothesis", many efforts have been devoted to designing molecules able to halt disease progression by inhibiting Aβ self-assembly. Here, we combine biophysical (ThT assays, TEM and AFM imaging), biochemical (WB and ESI-MS), and computational (all-atom molecular dynamics) techniques to investigate the capacity of four optically pure components of the natural product silymarin (silybin A, silybin B, 2,3-dehydrosilybin A, 2,3-dehydrosilybin B) to inhibit Aβ aggregation. Despite TEM analysis demonstrated that all the four investigated flavonoids prevent the formation of mature fibrils, ThT assays, WB and AFM investigations showed that only silybin B was able to halt the growth of small-sized protofibrils thus promoting the formation of large, amorphous aggregates. Molecular dynamics (MD) simulations indicated that silybin B interacts mainly with the C-terminal hydrophobic segment ³⁵MVGGVV⁴⁰ of Aβ40. Consequently to silybin B binding, the peptide conformation remains predominantly unstructured along all the simulations. By contrast, silybin A interacts preferentially with the segments ¹⁷LVFF²⁰ and ²⁷NKGAII³² of Aβ40 which shows a high tendency to form bend, turn, and β-sheet conformation in and around these two domains. Both 2,3-dehydrosilybin enantiomers bind preferentially the segment ¹⁷LVFF²⁰ but lead to the formation of different small-sized, ThT-positive Aβ aggregates. Finally, in vivo studies in a transgenic Caenorhabditis elegans strain expressing human Aβ indicated that silybin B is the most effective of the four compounds in counteracting Aβ proteotoxicity. This study underscores the pivotal role of stereochemistry in determining the neuroprotective potential of silybins and points to silybin B as a promising lead compound for further development in anti-AD therapeutics.

Multiple functions of insulin-degrading enzyme: a metabolic crosslight?

Insulin-degrading enzyme (IDE) is a ubiquitous zinc peptidase of the inverzincin family, which has been initially discovered as the enzyme responsible for insulin catabolism; therefore, its involvement in the onset of diabetes has been largely investigated. However, further studies on IDE unraveled its ability to degrade several other polypeptides, such as β-amyloid, amylin, and glucagon, envisaging the possible implication of IDE dys-regulation in the "aggregopathies" and, in particular, in neurodegenerative diseases. Over the last decade, a novel scenario on IDE biology has emerged, pointing out a multi-functional role of this enzyme in several basic cellular processes. In particular, latest advances indicate that IDE behaves as a heat shock protein and modulates the ubiquitin-proteasome system, suggesting a major implication in proteins turnover and cell homeostasis. In addition, recent observations have highlighted that the regulation of glucose metabolism by IDE is not merely based on its largely proposed role in the degradation of insulin in vivo. There is increasing evidence that improper IDE function, regulation, or trafficking might contribute to the etiology of metabolic diseases. In addition, the enzymatic activity of IDE is affected by metals levels, thus suggesting a role also in the metal homeostasis (metallostasis), which is thought to be tightly linked to the malfunction of the "quality control" machinery of the cell. Focusing on the physiological role of IDE, we will address a comprehensive vision of the very complex scenario in which IDE takes part, outlining its crucial role in interconnecting several relevant cellular processes.