Effect of metal ions on Alzheimer's disease

Aggregation Behavior of Amyloid Beta Peptide Depends Upon the Membrane Lipid Composition

Protein aggregation plays a crucial role in the development of several neurodegenerative diseases. It is important to understand the aggregation process for the detection of the onset of these diseases. Alzheimer's Disease (AD) is one of the most prevalent neurodegenerative diseases caused by the aggregation of Aβ-40 and Aβ-42 peptides. The smaller oligomers lead to the formation of protein plaque at the neural membranes leading to memory loss and other disorders. Interestingly, aggregation takes place at the neural membranes, therefore the membrane composition seems to play an important role in the aggregation process. Despite a large number of literatures on the effect of lipid composition on protein aggregation, there are very few concise reviews that highlight the role of membrane composition in protein aggregation. In this review, we have discussed the implication of membrane composition on the aggregation of amyloid beta peptide with a special emphasis on cholesterol. We have further discussed the role of the degree of unsaturation of fatty acids and the participation of apolipoprotein E4 (ApoE4) in the onset of AD.

Ability of Selected Monoterpenes to Reduce Fe(III) Ions Being Pro-Neurodegenerative Factors: Tests Based on a FRAP Reaction Extended to 48 Hours

Monoterpenes are secondary plant metabolites, and such volatile compounds have antioxidant, antibacterial, antiviral, and enzyme inhibitory properties. These compounds are also able to reduce the potentially pro-neurodegenerative trace metal ions that can be sources of free radicals. One basic method used to evaluate the ability of chemical compounds to reduce Fe(III) is FRAP. To date, most studies based on a FRAP assay were performed within several dozen minutes. However, taking into account the diversity of compounds, it is justified to observe their activity over a much longer period of time. The present study aimed to observe the activity of isopulegol, γ-terpinene, α-terpinene, linalool, carvone, citral, and α-phellandrene over a 48 h period. Our study indicates that the lengthened reaction period enhanced activity from several dozen to several hundred percent. The obtained results also revealed an explicit high correlation of the increase in the activity of compounds with the increase in monoterpene concentration. Due to the hydrophobic character of monoterpenes, the FRAP method was modified by the addition of Tween 20. The highest activity was obtained for α-terpinene and γ-terpinene.

In Vitro and In Silico Antioxidant Activity and Molecular Characterization of Bauhinia ungulata L. Essential Oil

Bauhinia ungulata is an antioxidant medicinal plant that has been manipuled in Brazil to lower glycemic index as well is for alternative treatment for diabetes. Therefore, the present hearch has aimed to investigates the antioxidant effects of the essential oil of Bauhinia ungulata L. (EOBU) collected in Amazon region better specified in Boa Vista, Roraima, Brazil, located in the Amazon region. Gas chromatography had been used to characterize the components, and antioxidant assays such as DPPH, TAC, reducing power, Fe2+ chelation, and total phenols had also been performed. The major constituents had molecularly anchored with the human catalase (CAT) enzyme, and maltol has showed as a positive control. Among the 25 revealed components, the main ones have been α-bisabolol (27.2 %), β-Caryophyllene (12.5 %) and Epi-γ-eudesmol (13.6 %). The EOBU has comproved a TAC value of 618.79 mg of ascorbic acid equivalent, free radical scavenging capacity (DPPH) around 53.7 % and 65.27 %, Fe2+ chelation capacity of 161±6 and 126.7±39.6, for 0.1 mg.mL-1 and 0.5 mg.mL-1 , respectively. The power around the EOBU has appeared percentages equals to 28.66 %, 44.6 %, and 77.03 % in the concentrations tested. As well as, 96.5 % of total phenols. The compounds α-bisabolol (-5.7±0.4 Kcal.mol-1 ) and β-caryophyllene (-6.1±0.5 Kcal.mol-1 ) have showed good interaction with CAT compared to Maltol (-4.4±0.4 Kcal.mol-1 ). The present work has demonstrated that EOBU functions as a potent antioxidant, capable of scavenging free radicals and reducing oxidative stress damage.

Design, synthesis, and biological evaluation of novel tryptanthrin derivatives as selective acetylcholinesterase inhibitors for the treatment of Alzheimer's disease

Two novel series of tryptanthrin (TRYP) derivatives were designed and synthesized as multifunctional agents for the treatment of Alzheimer's disease (AD). Inhibition assay against cholinesterase (ChE) indicated that these derivatives can act as acetylcholinesterase (AChE) inhibitors with selectivity over butyrylcholinesterase (BuChE). Among them, n1 exhibited the most excellent ChE inhibitory potency (AChE, IC50 = 12.17 ± 1.50 nM; BuChE, IC50 = 6.29 ± 0.48 μΜ; selectivity index = 517). Molecular docking studies indicated that compound n1 can interact with amino acid residues in the catalytic active site and peripheral anionic site of AChE and the molecular dynamics (MD) simulation studies demonstrated that the AChE-n1 complex had good stability. N1 also exhibited anti-amyloid-β (Aβ) aggregation (63.48 % ± 1.02 %, 100 μΜ) and anti-neuroinflammation activity (NO, IL-1β, TNF-α; IC50 = 2.13 ± 0.54 μΜ, 2.21 ± 0.37 μΜ, 2.47 ± 0.07 μΜ, respectively), and n1 had neuroprotective and metal-chelating properties. Further studies indicated n1 had proper blood-brain barrier permeability in the Parallel artificial membrane permeation assay. In vivo studies found that n1 effectively improved learning and memory impairment in scopolamine-induced AD mouse models. Nissl staining ofmice hippocampaltissue sections revealed that n1 restored neuronal cells in the hippocampus CA3 and CA1 regions. These findings suggested that n1 can be a promising compound for further development of multifunctional agents for AD treatment.

Polyamine Dysregulation and Nucleolar Disruption in Alzheimer's Disease

A hypothesis of Alzheimer's disease etiology is proposed describing how cellular stress induces excessive polyamine synthesis and recycling which can disrupt nucleoli. Polyamines are essential in nucleolar functions, such as RNA folding and ribonucleoprotein assembly. Changes in the nucleolar pool of anionic RNA and cationic polyamines acting as counterions can cause significant nucleolar dynamics. Polyamine synthesis reduces S-adenosylmethionine which, at low levels, triggers tau phosphorylation. Also, polyamine recycling reduces acetyl-CoA needed for acetylcholine, which is low in Alzheimer's disease. Extraordinary nucleolar expansion and/or contraction can disrupt epigenetic control in peri-nucleolar chromatin, such as chromosome 14 with the presenilin-1 gene; chromosome 21 with the amyloid precursor protein gene; chromosome 17 with the tau gene; chromosome 19 with the APOE4 gene; and the inactive X chromosome (Xi; aka "nucleolar satellite") with normally silent spermine synthase (polyamine synthesis) and spermidine/spermine-N1-acetyltransferase (polyamine recycling) alleles. Chromosomes 17, 19 and the Xi have high concentrations of Alu elements which can be transcribed by RNA polymerase III if positioned nucleosomes are displaced from the Alu elements. A sudden flood of Alu RNA transcripts can competitively bind nucleolin which is usually bound to Alu sequences in structural RNAs that stabilize the nucleolar heterochromatic shell. This Alu competition leads to loss of nucleolar integrity with leaking of nucleolar polyamines that cause aggregation of phosphorylated tau. The hypothesis was developed with key word searches (e.g., PubMed) using relevant terms (e.g., Alzheimer's, lupus, nucleolin) based on a systems biology approach and exploring autoimmune disease tautology, gaining synergistic insights from other diseases.

Pentoxifylline as Add-On Treatment to Donepezil in Copper Sulphate-Induced Alzheimer's Disease-Like Neurodegeneration in Rats

Alzheimer's disease (AD), the most common neurodegenerative disorder, is characterized by behavioral, cognitive, and progressive memory impairments. Extensive neuronal loss, extracellular accumulation of insoluble senile amyloid-β (Aβ) plaques, and intracellular neurofibrillary tangles (NFTs) are the major pathological features. The present study aimed to investigate the therapeutic effect of donepezil (DON) and pentoxifylline (PTX) in combination to combat the neurodegenerative disorders (experimental AD) induced by CuSO4 intake in experimental rats. Thirty adult male Wistar rats (140-160 g) were used in this study. AD was first induced in rats by CuSO4 supplement to drinking water (10 mg/L) for 14 weeks. The AD group received no further treatment. Oral treatment with DON (10 mg/kg/day), PTX (100 mg/kg/day), or DON + PTX for the other three groups was started from the 10th week of CuSO4 intake for 4 weeks. Cortex markers like acetylcholine (ACh), acetylcholinesterase (AChE), total antioxidant capacity (TAC), and malondialdehyde (MDA) and hippocampus markers like β-amyloid precursor protein cleaving enzyme 1 (BACE1), phosphorylated Tau (p-tau), Clusterin (CLU), tumor necrosis factor-α (TNF-α), caspase-9 (CAS-9), Bax, and Bcl-2 were measured. The histopathology studies were done by using hematoxylin and eosin and Congo red stains as well as immunohistochemistry for neurofilament. CuSO4 induced adverse histological and biochemical changes. The histological injury in the hippocampus was inhibited following the administration of the DON and PTX. The brain tissue levels of AChE, MDA, BACE1, p-tau, CLU, CAS-9, Bax, and TNF-α were significantly increased, while brain tissue levels of ACh, TAC, and Bcl-2 were significantly decreased in CuSO4-treated rats as compared with the untreated control group. The effects induced by either DON or PTX on most studied parameters were comparable. Combined treatment of DON and PTX induced remarkable results compared with their individual use. However, more clinical and preclinical studies are still required to further confirm and prove the long-term efficacy of such combination.

A Nanostructured Protein Filtration Device for Possible Use in the Treatment of Alzheimer's Disease-Concept and Feasibility after In Vivo Tests

BACKGROUND

Alzheimer's disease (AD), along with other neurodegenerative disorders, remains a challenge for clinicians, mainly because of the incomplete knowledge surrounding its etiology and inefficient therapeutic options. Considering the central role of amyloid beta (Aβ) in the onset and evolution of AD, Aβ-targeted therapies are among the most promising research directions. In the context of decreased Aβ elimination from the central nervous system in the AD patient, the authors propose a novel therapeutic approach based on the "Cerebrospinal Fluid Sink Therapeutic Strategy" presented in previous works. This article aims to demonstrate the laborious process of the development and testing of an effective nanoporous ceramic filter, which is the main component of an experimental device capable of filtrating Aβ from the cerebrospinal fluid in an AD mouse model.

METHODS

First, the authors present the main steps needed to create a functional filtrating nanoporous ceramic filter, which represents the central part of the experimental filtration device. This process included synthesis, functionalization, and quality control of the functionalization, which were performed via various spectroscopy methods and thermal analysis, selectivity measurements, and a biocompatibility assessment. Subsequently, the prototype was implanted in APP/PS1 mice for four weeks, then removed, and the nanoporous ceramic filter was tested for its filtration capacity and potential structural damages.

RESULTS

In applying the multi-step protocol, the authors developed a functional Aβ-selective filtration nanoporous ceramic filter that was used within the prototype. All animal models survived the implantation procedure and had no significant adverse effects during the 4-week trial period. Post-treatment analysis of the nanoporous ceramic filter showed significant protein loading, but no complete clogging of the pores.

CONCLUSIONS

We demonstrated that a nanoporous ceramic filter-based system that filtrates Aβ from the cerebrospinal fluid is a feasible and safe treatment modality in the AD mouse model. The presented prototype has a functional lifespan of around four weeks, highlighting the need to develop advanced nanoporous ceramic filters with anti-biofouling properties to ensure the long-term action of this therapy.

Electrochemical and Colorimetric Nanosensors for Detection of Heavy Metal Ions: A Review

Human exposure to acute and chronic levels of heavy metal ions are linked with various health issues, including reduced children's intelligence quotients, developmental challenges, cancers, hypertension, immune system compromises, cytotoxicity, oxidative cellular damage, and neurological disorders, among other health challenges. The potential environmental HMI contaminations, the biomagnification of heavy metal ions along food chains, and the associated risk factors of heavy metal ions on public health safety are a global concern of top priority. Hence, developing low-cost analytical protocols capable of rapid, selective, sensitive, and accurate detection of heavy metal ions in environmental samples and consumable products is of global public health interest. Conventional flame atomic absorption spectroscopy, graphite furnace atomic absorption spectroscopy, atomic emission spectroscopy, inductively coupled plasma-optical emission spectroscopy, inductively coupled plasma-mass spectroscopy, X-ray diffractometry, and X-ray fluorescence have been well-developed for HMIs and trace element analysis with excellent but varying degrees of sensitivity, selectivity, and accuracy. In addition to high instrumental running and maintenance costs and specialized personnel training, these instruments are not portable, limiting their practicality for on-demand, in situ, field study, or point-of-need HMI detection. Increases in the use of electrochemical and colorimetric techniques for heavy metal ion detections arise because of portable instrumentation, high sensitivity and selectivity, cost-effectiveness, small size requirements, rapidity, and visual detection of colorimetric nanosensors that facilitate on-demand, in situ, and field heavy metal ion detections. This review highlights the new approach to low-cost, rapid, selective, sensitive, and accurate detection of heavy metal ions in ecosystems (soil, water, air) and consumable products. Specifically, the review highlights low-cost, portable, and recent advances in smartphone-operated screen-printed electrodes (SPEs), plastic chip SPES, and carbon fiber paper-based nanosensors for environmental heavy metal ion detection. In addition, the review highlights recent advances in colorimetric nanosensors for heavy metal ion detection requirements. The review provides the advantages of electrochemical and optical nanosensors over the conventional methods of HMI analyses. The review further provides in-depth coverage of the detection of arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), manganese (Mn), nickel (Ni), lead (Pb), and zinc (Zn) ions in the ecosystem, with emphasis on environmental and biological samples. In addition, the review discusses the advantages and challenges of the current electrochemical and colorimetric nanosensors protocol for heavy metal ion detection. It provides insight into the future directions in the use of the electrochemical and colorimetric nanosensors protocol for heavy metal ion detection.

Genetically encoded protein sensors for metal ion detection in biological systems: a review and bibliometric analysis

Metal ions are indispensable elements in living organisms and are associated with regulating various biological processes. An imbalance in metal ion content can lead to disorders in normal physiological functions of the human body and cause various diseases. Genetically encoded fluorescent protein sensors have the advantages of low biotoxicity, high specificity, and a long imaging time in vivo and have become a powerful tool to visualize or quantify the concentration level of biomolecules in vivo and in vitro, temporal and spatial distribution, and life activity process. This review analyzes the development status and current research hotspots in the field of genetically encoded fluorescent protein sensors by bibliometric analysis. Based on the results of bibliometric analysis, the research progress of genetically encoded fluorescent protein sensors for metal ion detection is reviewed, and the construction strategies, physicochemical properties, and applications of such sensors in biological imaging are summarized.

New Hybrid Compounds Incorporating Natural Products as Multifunctional Agents against Alzheimer's Disease

A series of new hybrid derivatives 1a-c, 2a-c, 3a-c, 4a-c, 5a-c, inspired by nature, were synthesized and studied as multifunctional agents for the treatment of Alzheimer's disease (AD). These compounds were designed to merge together the trifluoromethyl benzyloxyaminic bioactive moiety, previously identified, with different acids available in nature. The ability of the synthesized compounds to chelate biometals, such as Cu2+, Zn2+ and Fe2+, was studied by UV-Vis spectrometer, and through a preliminary screening their antioxidant activity was evaluated by DPPH. Then, selected compounds were tested by in vitro ABTS free radical method and ex vivo rat brain TBARS assay. Compounds 2a-c, combining the strongest antioxidant and biometal chelators activities, were studied for their ability to contrast Aβ1-40 fibrillization process. Finally, starting from the promising profile obtained for compound 2a, we evaluated if it could be able to induce a positive cross-interaction between transthyretin (TTR) and Aβ in presence and in absence of Cu2+.

Influence of cadmium ion on denaturation kinetics of hen egg white-lysozyme under thermal and acidic conditions

To study the influence of Cd(II) ions on denaturation kinetics of hen egg white lysozyme (HEWL) under thermal and acidic conditions, spontaneous Raman spectroscopy in conjunction with Thioflavin-T fluorescence, AFM imaging, far-UV circular dichroism spectroscopy, and transmittance assays was conducted. Four distinctive Raman spectral markers for protein tertiary and secondary structures were recorded to follow the kinetics of conformational transformation. Through comparing variations of these markers in the presence or absence of Cd(II) ions, Cd(II) ions show an ability to efficiently accelerate the disruption of tertiary structure, and meanwhile, to promote the direct formation of organized β-sheets from the uncoiling of α-helices by skipping intermediate random coils. More significantly, with the action of Cd(II) ions, the initially resulting oligomers with disordered structures tend to assemble into aggregates with random structures like gels more than amyloid fibrils, along with a so-called "off-pathway" denaturation pathway. Our results advance the in-depth understanding of corresponding ion-specific effects.

Advances in Portable Heavy Metal Ion Sensors

Heavy metal ions, one of the major pollutants in the environment, exhibit non-degradable and bio-chain accumulation characteristics, seriously damage the environment, and threaten human health. Traditional heavy metal ion detection methods often require complex and expensive instruments, professional operation, tedious sample preparation, high requirements for laboratory conditions, and operator professionalism, and they cannot be widely used in the field for real-time and rapid detection. Therefore, developing portable, highly sensitive, selective, and economical sensors is necessary for the detection of toxic metal ions in the field. This paper presents portable sensing based on optical and electrochemical methods for the in situ detection of trace heavy metal ions. Progress in research on portable sensor devices based on fluorescence, colorimetric, portable surface Raman enhancement, plasmon resonance, and various electrical parameter analysis principles is highlighted, and the characteristics of the detection limits, linear detection ranges, and stability of the various sensing methods are analyzed. Accordingly, this review provides a reference for the design of portable heavy metal ion sensing.

Trace elements and Alzheimer dementia in population-based studies: A bibliometric and meta-analysis

Alterations in the concentrations of trace elements may play a vital role in Alzheimer dementia progression. However, previous research results are inconsistent, and there is still a lack of review on the relationship between all the studied-trace elements and AD from various perspectives of population-based studies. In this study, we systematically reviewed previous population-based studies and identified the altered trace elements in AD patients. We searched the Web of Science Core Collection, PubMed, and Scopus database, and ultimately included 73 articles. A bibliometric analysis was conducted to explore the evolution of the field from an epidemiological perspective. Bibliometric data such as trace elements, biological materials, detection methods, cognitive tests, co-occurrence and co-citation statistics are all analyzed and presented in a quantitative manner. The 73 included studies analyzed 39 trace elements in total. In a further meta-analysis, standardized mean differences (SMDs) of 13 elements were calculated to evaluate their altered in AD patients, including copper, iron, zinc, selenium, manganese, lead, aluminum, cadmium, chromium, arsenic, mercury, cobalt, and manganese. We identified four trace elements-copper (serum), iron (plasma), zinc (hair), and selenium (plasma)-altered in AD patients, with SMDs of 0.37 (95% confidence interval [CI]: 0.10, 0.65), -0.68 (95% CI: -1.34, -0.02), -0.35 (95% CI: -0.62, -0.08), and -0.61 (95% CI: -0.97, -0.25), respectively. Finally, we formed a database of various trace element levels in AD patients and healthy controls. Our study can help future researchers gain a comprehensive understanding of the advancements in the field, and our results provide comprehensive population-based data for future research.

Interlink between the gut microbiota and inflammation in the context of oxidative stress in Alzheimer's disease progression

The microbiota-gut-brain axis is an important pathway of communication and may dynamically contribute to Alzheimer's disease (AD) pathogenesis. Pathological commensal gut microbiota alterations, termed as dysbiosis, can influence intestinal permeability and break the blood-brain barrier which may trigger AD pathogenesis via redox signaling, neuronal, immune, and metabolic pathways. Dysbiosis increases the oxidative stress. Oxidants affect the innate immune system through recognizing microbial-derived pathogens by Toll-like receptors and initiating the inflammatory process. Most of the gut microbiome research work highlights the relationship between the gut microbiota and AD, but the contributory connection between precise bacteria and brain dysfunction in AD pathology cannot be fully demonstrated. Here, we summarize the current information of the fundamental connections between oxidative stress, inflammation, and gut dysbiosis in AD. This review emphasizes on the involvement of gut microbiota in the regulation of oxidative stress, inflammation, immune responses including central and peripheral cross-talk. It provides insights for novel preventative and therapeutic approaches in AD.

Chelation Combination-A Strategy to Mitigate the Neurotoxicity of Manganese, Iron, and Copper?

The chelating thiol dimercaptosuccinate (DMSA) and the traditional agent D-penicillamine (PSH) are effective in enhancing the urinary excretion of copper (Cu) and lead (Pb) in poisoned individuals. However, DMSA, PSH, EDTA (ethylenediamine tetraacetate), and deferoxamine (DFOA) are water-soluble agents with limited access to the central nervous system (CNS). Strategies for mobilization of metals such as manganese (Mn), iron (Fe), and Cu from brain deposits may require the combined use of two agents: one water-soluble agent to remove circulating metal into urine, in addition to an adjuvant shuttler to facilitate the brain-to-blood mobilization. The present review discusses the chemical basis of metal chelation and the ligand exchange of metal ions. To obtain increased excretion of Mn, Cu, and Fe, early experiences showed promising results for CaEDTA, PSH, and DFOA, respectively. Recent experiments have indicated that p-amino salicylate (PAS) plus CaEDTA may be a useful combination to remove Mn from binding sites in CNS, while the deferasirox-DFOA and the tetrathiomolybdate-DMSA combinations may be preferable to promote mobilization of Fe and Cu, respectively, from the CNS. Further research is requested to explore benefits of chelator combinations.