Copper-Mediated β-Amyloid Toxicity and its Chelation Therapy in Alzheimer's Disease

Study on multi-target effects of the novel HDAC6 inhibitor W5 on Aβ/Cu2+-induced Alzheimer's disease model of rats

Histone deacetylase 6 (HDAC6) is a key therapeutic target in neurodegenerative diseases such as Alzheimer's disease (AD), which has been demonstrated to play an essential role in memory function and microtubule-associated tau physiology. In this study, W5 was used to treat AD model rats induced by Aβ/Cu2+ to study the improving effect of W5 on learning and memory impairment in AD rats and its related mechanism, to provide the basis for the subsequent development of W5 as an anti-AD drug. Results showed that W5 could decrease the expression of Aβ, Tau, and p-Tau proteins in the hippocampus of AD rats to inhibit the formation of senile plaques and neurofibrillary tangles, down-regulate the expression of Bax mRNA and Caspase-3 mRNA, and up-regulate the expression of Bcl-2 mRNA to reduce the apoptosis of neuron cells, reverse the expression of TNF-α, IL-1β and IL-6 mRNA to regulate neuroinflammatory response in AD rat brain. W5 also could regulate the oxidative stress state of AD rats, and balance the neurotransmitter disorder in AD rats' brain tissue. Overall, W5 could recover the morphology of hippocampal neurons and improve the learning and memory dysfunction in AD rats by regulating multiple targets in AD rats, providing a promising therapeutic avenue for the treatment of AD.

Investigating the combined effect of copper, zinc, and iron ions on truncated and full-length Aβ peptides: insights from molecular dynamics simulation

The truncated Aβ1 - 16 peptide containing the metal-binding domain is frequently used in in silico and experimental investigations because it is more soluble and thus more suitable for studies in solution and does not form amyloids. Several spectroscopic studies have shown that the metal binding of Aβ1 - 16 is very similar to that of the full-length Aβ1 - 42. However, since small changes can have a significant impact on aggregation, further experimental and theoretical are needed to elucidate the detailed structures of truncated and full-length Aβ. In this research, the binding of copper ion to the Aβ1 - 16 and Aβ1 - 42 has been studied by molecular dynamics simulation method. To investigate the effect of copper ion on beta-amyloid peptide structure, the simulations were repeated in the copper and zinc ions, copper and iron binary system, and the copper, zinc and iron ions ternary system. The conformation factor was calculated to calculate the binding affinity of copper ion to beta-amyloid peptide residues. The results showed that the initial 16 residues of the beta-amyloid peptide have high binding affinity for copper ions, and histidine 13 and histidine 14 have significantly higher binding affinity for copper ions in all studied systems. Zinc and iron ions were found to reduce the conformational factor of peptide residues in binding to copper ions, and the aggregation tendency was lower in the truncated structure. The SASA results suggest that the side chains of peptide residues are more affected by shortening and the presence of ions.Communicated by Ramaswamy H. Sarma.

Amyloid-Like Assembly to Form Film at Interfaces: Structural Transformation and Application

Protein-based biomaterials are attracting broad interest for their remarkable structural and functional properties. Disturbing the native protein's three-dimensional structural stability in vitro and controlling subsequent aggregation is an effective strategy to design and construct protein-based biomaterials. One of the recent developments in regulating protein structural transformation to ordered aggregation is amyloid assembly, which generates fibril-based 1D to 3D nanostructures as functional materials. Especially, the amyloid-like assembly to form films at interfaces has been reported, which is induced by the effective reduction of the intramolecular disulfide bond. The main contribution of this amyloid-like assembly is the large-scale formation of protein films at interfaces and excellent adhesion to target substrates. This review presents the research progress of the amyloid-like assembly to form films and related applications and thereby provides a guide to exploiting protein-based biomaterials.

Exploring the Antioxidant Potential of Talisia esculenta Using In Vitro and In Vivo Approaches

Medicinal plants, such as Talisia esculenta, are rich in antioxidant biomolecules, which are used in the treatment and prevention of many diseases. The antioxidant potential of T. esculenta extracts obtained from leaves and fruit peels was investigated using biochemical and 3T3 cell line assays as well as in vivo assays using an organism model Tenebrio molitor. Four extracts were tested: hydroethanolic extracts from leaves (HF) and from fruit peels (HC), and infusion extracts from leaves (IF) and from fruit peels (IC). The biochemical assays demonstrated an antioxidant capacity verified by TAC, reducing power, DPPH, and copper chelating assays. None of the extracts exhibited cytotoxicity against 3T3 cells, instead offering a protection against CuSO4-induced oxidative stress. The antioxidant activity observed in the extracts, including their role as free radical scavengers, copper chelators, and stress protectors, was further confirmed by T. molitor assays. The CLAE-DAD analysis detected phenolic compounds, including gallic acid, rutin, and quercitrin, as the main constituents of the samples. This study highlights that leaf and fruit peels extracts of T. esculenta could be effective protectors against ROS and copper-induced stress in cellular and invertebrate models, and they should be considered as coadjutants in the treatment and prevention of diseases related to oxidative stress and for the development of natural nutraceutical products.

Lead exposure disturbs ATP7B-mediated copper export from brain barrier cells by inhibiting XIAP-regulated COMMD1 protein degradation

The brain barrier is an important structure for metal ion homeostasis. According to studies, lead (Pb) exposure disrupts the transportation of copper (Cu) through the brain barrier, which may cause impairment of the nervous system; however, the specific mechanism is unknown. The previous studies suggested the X-linked inhibitor of apoptosis (XIAP) is a sensor for cellular Cu level which mediate the degradation of the MURR1 domain-containing 1 (COMMD1) protein. XIAP/COMMD1 axis was thought to be an important regulator in Cu metabolism maintenance. In this study, the role of XIAP-regulated COMMD1 protein degradation in Pb-induced Cu disorders in brain barrier cells was investigated. Pb exposure significantly increased Cu levels in both cell types, according to atomic absorption technology testing. Western blotting and reverse transcription PCR (RT-PCR) showed that COMMD1 protein levels were significantly increased, whereas XIAP, ATP7A, and ATP7B protein levels were significantly decreased. However, there were no significant effects at the messenger RNA (mRNA) level (XIAP, ATP7A, and ATP7B). Pb-induced Cu accumulation and ATP7B expression were reduced when COMMD1 was knocked down by transient small interfering RNA (siRNA) transfection. In addition, transient plasmid transfection of XIAP before Pb exposure reduced Pb-induced Cu accumulation, increased COMMD1 protein levels, and decreased ATP7B levels. In conclusion, Pb exposure can reduce XIAP protein expression, increase COMMD1 protein levels, and specifically decrease ATP7B protein levels, resulting in Cu accumulation in brain barrier cells.

New Pathways Identify Novel Drug Targets for the Prevention and Treatment of Alzheimer’s Disease

Alzheimer’s disease (AD) is an incurable, progressive neurodegenerative disorder. AD is a complex and multifactorial disease that is responsible for 60–80% of dementia cases. Aging, genetic factors, and epigenetic changes are the main risk factors for AD. Two aggregation-prone proteins play a decisive role in AD pathogenesis: β-amyloid (Aβ) and hyperphosphorylated tau (pTau). Both of them form deposits and diffusible toxic aggregates in the brain. These proteins are the biomarkers of AD. Different hypotheses have tried to explain AD pathogenesis and served as platforms for AD drug research. Experiments demonstrated that both Aβ and pTau might start neurodegenerative processes and are necessary for cognitive decline. The two pathologies act in synergy. Inhibition of the formation of toxic Aβ and pTau aggregates has been an old drug target. Recently, successful Aβ clearance by monoclonal antibodies has raised new hopes for AD treatments if the disease is detected at early stages. More recently, novel targets, e.g., improvements in amyloid clearance from the brain, application of small heat shock proteins (Hsps), modulation of chronic neuroinflammation by different receptor ligands, modulation of microglial phagocytosis, and increase in myelination have been revealed in AD research.

Non-Enzymatic Antioxidants against Alzheimer's Disease: Prevention, Diagnosis and Therapy

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by progressive memory loss and cognitive decline. Although substantial research has been conducted to elucidate the complex pathophysiology of AD, the therapeutic approach still has limited efficacy in clinical practice. Oxidative stress (OS) has been established as an early driver of several age-related diseases, including neurodegeneration. In AD, increased levels of reactive oxygen species mediate neuronal lipid, protein, and nucleic acid peroxidation, mitochondrial dysfunction, synaptic damage, and inflammation. Thus, the identification of novel antioxidant molecules capable of detecting, preventing, and counteracting AD onset and progression is of the utmost importance. However, although several studies have been published, comprehensive and up-to-date overviews of the principal anti-AD agents harboring antioxidant properties remain scarce. In this narrative review, we summarize the role of vitamins, minerals, flavonoids, non-flavonoids, mitochondria-targeting molecules, organosulfur compounds, and carotenoids as non-enzymatic antioxidants with AD diagnostic, preventative, and therapeutic potential, thereby offering insights into the relationship between OS and neurodegeneration.

Involvement of the inhibition of mitochondrial apoptotic, p53, NF-κB pathways and the activation of Nrf2/HO-1 pathway in the protective effects of curcumin against copper sulfate-induced nephrotoxicity in mice

Chronic copper exposure could cause potential nephrotoxicity and effective therapy strategies are limited. This study investigated the protective effects of curcumin on copper sulfate (CuSO4)-induced renal damage in a mouse model and the underlying molecular mechanisms. Mice were administrated orally with CuSO4 (100 mg/kg per day) in combination with or without curcumin (50, 100 or 200 mg/kg per day, orally) for 28 days. Results showed that curcumin supplementation significantly reduce the Cu accumulation in the kidney tissues of mice and improved CuSO4-induced renal dysfunction. Furthermore, curcumin supplantation also significantly ameliorated Cu exposure-induced oxidative stress and tubular necrosis in the kidneys of mice. Moreover, compared to the CuSO4 alone group, curcumin supplementation at 200 mg/kg per day significantly decreased CuSO4-induced the expression of p53, Bax, IL-1β, IL-6, and TNF-α proteins, levels of NF-κB mRNA, levels of caspases-9 and - 3 activities, and cell apoptosis, and significantly increased the levels of Nrf2 and HO-1 mRNAs in the kidney tissues. In conclusion, for the first time, our results reveal that curcumin could trigger the inhibition of oxidative stress, mitochondrial apoptotic, p53, and NF-κB pathways and the activation of Nrf2/HO-1 pathway to ameliorate Cu overload-induced nephrotoxicity in a mouse model. Our study highlights that curcumin supplementation may be a promising treatment strategy for treating copper overload-caused nephrotoxicity.

Identification of Copper Metabolism Related Biomarkers, Polygenic Prediction Model, and Potential Therapeutic Agents in Alzheimer's Disease

BACKGROUND

The underlying pathogenic genes and effective therapeutic agents of Alzheimer's disease (AD) are still elusive. Meanwhile, abnormal copper metabolism is observed in AD brains of both human and mouse models.

OBJECTIVE

To investigate copper metabolism-related gene biomarkers for AD diagnosis and therapy.

METHODS

The AD datasets and copper metabolism-related genes (CMGs) were downloaded from GEO and GeneCards database, respectively. Differentially expressed CMGs (DE-CMGs) performed through Limma, functional enrichment analysis and the protein-protein interaction were used to identify candidate key genes by using CytoHubba. And these candidate key genes were utilized to construct a prediction model by logistic regression analysis for AD early diagnosis. Furthermore, ROC analysis was conducted to identify a single gene with AUC values greater than 0.7 by GSE5281. Finally, the single gene biomarker was validated by quantitative real-time polymerase chain reaction (qRT-PCR) in AD clinical samples. Additionally, immune cell infiltration in AD samples and potential therapeutic drugs targeting the identified biomarkers were further explored.

RESULTS

A polygenic prediction model for AD based on copper metabolism was established by the top 10 genes, which demonstrated good diagnostic performance (AUC values). COX11, LDHA, ATOX1, SCO1, and SOD1 were identified as blood biomarkers for AD early diagnosis. 20 agents targeting biomarkers were retrieved from DrugBank database, some of which have been proven effective for the treatment of AD.

CONCLUSIONS

The five blood biomarkers and copper metabolism-associated model can differentiate AD patients from non-demented individuals and aid in the development of new therapeutic strategies.

The co-effect of copper and lipid vesicles on Aβ aggregation

Both metal ions and lipid membranes have a wide distribution in amyloid plaques and play significant roles in AD pathogenesis. Although influences of different metal ions or lipid vesicles on the aggregation of Aβ peptides have been extensively studied, their combined effects are less understood. In this study, we reported a unique effect of copper ion on Aβ aggregation in the presence of lipid vesicles, different from other divalent metal ions. Cu²⁺ in a super stoichiometric amount leads to the rapid formation of β-sheet rich structure, containing abundant low molecular weight (LMW) oligomers. We demonstrated that oligomerization of Aβ40 induced by Cu²⁺ binding was an essential prerequisite for the rapid conformation transition. Overall, the finding provided a new view on the complex triple system of Aβ, copper ion and lipid vesicles, which might help understanding of Aβ pathologies.

Sequence-Activity Relationship of ATCUN Peptides in the Context of Alzheimer's Disease

Amino-terminal Cu^II and Ni^II (ATCUN) binding sequences are widespread in the biological world. Here, we report on the study of eight ATCUN peptides aimed at targeting copper ions and stopping the associated formation of reactive oxygen species (ROS). This study was actually more focused on Cu(Aβ)-induced ROS production in which the Aβ peptide is the "villain" linked to Alzheimer's disease. The full characterization of Cu^II binding to the ATCUN peptides, the Cu^II extraction from Cu^II(Aβ), and the ability of the peptides to prevent and/or stop ROS formation are described in the relevant biological conditions. We highlighted in this research that all the ATCUN motifs studied formed the same thermodynamic complex but that the addition of a second histidine in position 1 or 2 allowed for an improvement in the Cu^II uptake kinetics. This kinetic rate was directly related to the ability of the peptide to stop the Cu^II(Aβ)-induced production of ROS, with the most efficient motifs being HWHG and HGHW.

Why the Ala-His-His Peptide Is an Appropriate Scaffold to Remove and Redox Silence Copper Ions from the Alzheimer’s-Related Aβ Peptide

The progressive, neurodegenerative Alzheimer’s disease (AD) is the most widespread dementia. Due to the ageing of the population and the current lack of molecules able to prevent or stop the disease, AD will be even more impactful for society in the future. AD is a multifactorial disease, and, among other factors, metal ions have been regarded as potential therapeutic targets. This is the case for the redox-competent Cu ions involved in the production of reactive oxygen species (ROS) when bound to the Alzheimer-related Aβ peptide, a process that contributes to the overall oxidative stress and inflammation observed in AD. Here, we made use of peptide ligands to stop the Cu(Aβ)-induced ROS production and we showed why the AHH sequence is fully appropriate, while the two parents, AH and AAH, are not. The AHH peptide keeps its beneficial ability against Cu(Aβ)-induced ROS, even in the presence of Zn^II-competing ions and other biologically relevant ions. The detailed kinetic mechanism by which AHH could exert its action against Cu(Aβ)-induced ROS is also proposed.

Oral Administration of Copper Chloride Damages DNA, Lowers Antioxidant Defense, Alters Metabolic Status, and Inhibits Membrane Bound Enzymes in Rat Kidney

Copper (Cu) is a heavy metal that is widely used in industries and is also an essential micronutrient for living beings. However, excess Cu is toxic and human exposure to high levels of this metal results in numerous adverse health effects. We have investigated the effect of oral administration of copper chloride (CuCl₂), a Cu(II) compound, on various parameters of oxidative stress, cellular metabolism, and DNA integrity in the rat kidney. This was done to delineate the molecular mechanism of Cu(II) toxicity. Adult male rats were randomly divided into five groups. Animals in four CuCl₂-treated groups were separately administered single acute oral dose of CuCl₂ at 5, 15, 30, and 40 mg/kg body weight. Animals in the fifth group were not given CuCl₂ and served as the control. All rats were sacrificed 24 h after the dose of CuCl₂ and their kidneys removed. CuCl₂ administration led to significant alterations in enzymatic and non-enzymatic parameters of oxidative stress. It changed the activities of metabolic and membrane bound enzymes and also decreased the activities of brush border membrane enzymes. CuCl₂ treatment dose-dependently enhanced DNA damage and DNA-protein crosslinking in renal cells, when compared to the control group. The administration of CuCl₂ also resulted in marked morphological changes in the kidney, with more prominent alterations at higher doses of CuCl₂. These results clearly show that CuCl₂ impairs the antioxidant defense system resulting in oxidative damage to the kidney.