The interaction of aluminum with catecholamine-based neurotransmitters: can the formation of these species be considered a potential risk factor for neurodegenerative diseases?

Zinc Oxide Nanoparticles Attenuated Neurochemical and Histopathological Alterations Associated with Aluminium Chloride Intoxication in Rats

The present investigation explored the potential neuroprotective role of zinc oxide nanoparticles (ZnONPs) on aluminum chloride (AlCl3)-mediated Alzheimer's disease (AD)-like symptoms. Rats were distributed into four treatment groups equally: control, ZnONPs (4 mg/kg b.wt.), AlCl3 (100 mg/kg b.wt.), and ZnONPs + AlCl3 groups. Rats were treated for 42 consecutive days. ZnONPs injection into AlCl3-treated rats suppressed the development of oxidative challenge in the cortical and hippocampal tissues, as demonstrated by the decreased neuronal pro-oxidants (malondialdehyde and nitric oxide), and the increased glutathione and catalase levels. Additionally, ZnONPs injection showed anti-inflammatory potency in response to AlCl3 by decreasing levels of tumor necrosis factor-α and interleukin-1β. Moreover, pretreatment with ZnONPs prevented neuronal cell loss by decreasing the level of pro-apoptotic caspase-3 and enhancing the anti-apoptotic B cell lymphoma 2. Furthermore, ZnONPs ameliorated the disturbed acetylcholinesterase activity, monoamines (norepinephrine, dopamine, and serotonin), excitatory (glutamic and aspartic acids), and inhibitory amino acids (GABA and glycine) in response to AlCl3 exposure. These findings indicate that ZnONPs may have the potential as an alternative therapy to minimize or prevent the neurological deficits in AD model by exhibiting antioxidative, anti-inflammation, anti-apoptosis, and neuromodulatory effects.

Isoimperatorin therapeutic effect against aluminum induced neurotoxicity in albino mice

Background: Although aluminum (Al) is not biologically crucial to the human body, classical studies have demonstrated that excessive human exposure to Al can induce oxidative damage, neuroinflammatory conditions and neurotoxic manifestations implicated in Alzheimer's disease (AD). Exposure to Al was reported to be associated with oxidative damage, neuroinflammation, and to enhance progressive multiregional neurodegeneration in animal models. Several plant-derived natural biomolecules have been recently used to reduce the toxic effects of Al through decreasing the oxidative stress and the associated diseases. A good candidate still to be tested is an active natural furanocoumarin, the isoimperatorin (IMP) that can be extracted from Lemon and lime oils and other plants. Here, we examined the neuroprotective effects of IMP on aluminum chloride (AlCl3)-induced neurotoxicity in albino mice. Methods: Twenty-four male albino mice were used in this study. Mice were randomly devided into 5 groups. The first group was given distilled water as a control, the second group was given AlCl3 orally (10 mg/wt/day) starting from the 2nd week to the end of the 6th week, the third group received AlCl3 orally and IMP interperitoneally, i. p. (30 mg/wt/day) starting from week 2 till week 6 where IMP was supplement 1st and then 4 h later AlCl3 was given to mice. The fourth group received the control (IMP 30 mg/wt, i. p.) from the 2nd week till the end of the experiment. Rodent models of central nervous system (CNS) disorders were assessed using object location memory and Y-maze tests in 6th week began. Essential anti-inflammatory and oxidative stress indicators were evaluated, including interleukin-1 β (IL-1β), tumor necrosis factor α (TNF-α), malondialdehyde (MDA), total antioxidant capacity (TAC), and catalase activity (CAT). In addition, serum levels of brain neurotransmitters such as corticosterone, acetylcholine (ACh), dopamine and serotonin in brain homogenates were measured calorimetrically. Results: The study results revealed that the daily treatment of AlCl3 upregulated the TNF-α and IL-1β levels, increased MDA accumulation, and decreased TAC and CAT activity. In addition, aluminum induced a reduction in concentrations of ACh, serotonin and dopamine in the brain. However, IMP significantly ameliorates the effect of AlCl3 through modulating the antioxidant and regulating the inflammatory response through targeting Nrf2 (NF-E2-related factor 2) and mitogen-activated protein kinase (MAPK). Conclusion: Thus, IMP might be a promising treatment option for neurotoxicity and neurodegenerative diseases, such as Alzheimer's disease and Parkinson's disease, which are associated with neuro-inflammation and oxidative stress.

Study of the DNA binding mechanism and in vitro activity against cancer cells of iron(III) and aluminium(III) kojic acid derivative complexes

Metal ions have unique electrochemical and spectroscopical properties that cannot be attained by purely organic compounds. Most of the metal ions are toxic to humans, but paradoxically, metallodrugs are used in medicine as therapeutics and theranostics. Metallodrugs are eliminated in urine and faeces, and therefore release toxic metals and ligands into aquatic ecosystems, thereby raising concerns regarding environmental risks. The use of metallodrugs based on essential metal ions (i.e., iron, copper and zinc), instead of toxic ions, is a new alternative with minor hazards. Kojic acid is an Asperigillus oryzae metabolite of low toxicity used in the food and cosmetics industries. Its derivatives form stable complexes with iron(III) ions, which bind effectively to DNA and inhibit DNA polymerization. The iron(III)/S2 ligand complexes reduce in vitro colon carcinoma (Caco₂) cell viability and significantly decrease the cell number. The kojic acid derivative complexes with iron(III) presented here are an alternative to the currently used platinum complexes in cancer therapy.

The dopamine system: insights between kidney and brain

BACKGROUND

Chronic kidney disease (CKD) is one of the most common diseases in adult age and it is typical of older adults. Recent data suggest that almost half of the elders have CKD. It is now clear that CKD is accompanied, in the early stages, by cognitive impairment, together with depression and subtle abnormalities in motor control (such as gait and balance alterations).

SUMMARY

Several data suggest a link between brain dopamine and kidney diseases. Metabolic syndrome and diabetes can affect dopamine neuron survival (leading to Parkinson's Disease). Several uremic toxins in CKD (uric acid, indoxyl sulphate) and trace elements accumulating in CKD (aluminium, manganese) can also modify the dopaminergic system. Hormones produced by the kidney such as vitamin D are neuroprotective for dopamine neurons. Dopaminergic drugs are useful for the treatment of a common sleep disorder in CKD, the restless legs syndrome. However, experiments on animal models of CKD show conflicting results regarding a modification of dopamine neurons.

KEY MESSAGES

Several observations suggest a limited relevance of the dopaminergic system in CKD-related cognitive impairment. However, a common sleep disturbance in CKD, the restless leg syndrome, improves with dopaminergic drugs. Therefore, it remains to be established the role of the dopamine system in subtle motor dysfunction observed in CKD, such as tremors, gait alterations, and central sleep apnea.

Can aluminum, a non-redox metal, alter the thermodynamics of key biological redox processes? The DPPH-QH2 radical scavenging reaction as a test case

The increased bioavailability of aluminum has led to a concern about its toxicity on living systems. Among the most important toxic effects, it has been proven that aluminum increases oxidative stress in biological systems, a controversial fact, however, due to its non-redox nature. In the present work, we characterize in detail how aluminum can alter redox equilibriums by analyzing its effects on the thermodynamics of the redox scavenging reaction between DPPH^., a radical compound often used as a reactive oxygen species model, and hydroquinones, a potent natural antioxidant. For the first time, theoretical and experimental redox potentials within aluminum biochemistry are directly compared. Our results fully agree with experimental reduction and oxidation potentials, unequivocally revealing how aluminum alters the spontaneity of the reaction by stabilizing the reduction of DPPH⋅ to DPPH^- and promoting a proton transfer to the diazine moiety, leading to the production of a DPPH-H species. The capability of aluminum to modify redox potentials shown here confirms previous experimental findings on the role of aluminum to interfere with free radical scavenging reactions, affecting the natural redox processes of living organisms.

A new “turn-on” molecular switch for idiosyncratic detection of Al3+ ion along with its application in live cell imaging

A new highly sensitive, reversible, reusable and fluorogenic “turn-on” switch (HBTC) has been fabricated for the sole detection of Al3+.

Effect of Resveratrol, L-Carnitine, and Aromatic Amino Acid Supplements on the Trace Element Content in the Organs of Mice with Dietary-Induced Obesity

Given environmental contamination with toxic metals, diets that promote the elimination of these metals from the body of individuals, including those suffering from obesity, are urgently needed. The aim of this study was to determine the effects of supplementation with resveratrol (Res), L-carnitine (L-Car), tyrosine (Tyr), and tryptophan (Trp) on the content of trace elements in the organs of mice. DBA/2J mice and DBCB tetrahybrid mice received diets high in carbohydrate and fat supplemented with Res, L-Car, Tyr, or Trp for 65 days. In the liver, kidneys, and brain, the contents of 18 elements, including Al, As, Cu, Fe, Mn, Pb, Se, and Zn, were determined by inductively coupled plasma mass spectrometry. Res, L-Car, Tyr, and Trp had minimal or no effect on the essential elements (Fe, Mg, Cu, Zn, Se) in all organs studied. The Mn content notably increased in the organs of mice consuming L-Car and Trp. Mn accumulation was stimulated by Res in organs exclusively in DBCB mice and by Tyr exclusively in livers and brains of DBA/2J mice. Al levels were significantly reduced by L-Car and Trp in all organs of the mice, by Res in only DBCB mice, and by Tyr in only kidneys and livers of DBA/2J mice. In addition, L-Car and Trp decreased Pb accumulation in most organs of mice. Res and Tyr also inhibited Pb accumulation in some cases. Thus, the studied supplements affected the metabolism of trace elements, which may contribute to dietary treatments for obese individuals.

Kojic acid derivatives as double face ligands for metal and phosphate ions

A family of combined Kojic acid and polyamine derivatives has been synthesized as phosphate anion and metal ion ligands. The stoichiometry, stability and structure of the ion/ligand adducts were determined by ¹H NMR spectroscopy, potentiometry, EXAFS and DFT calculations. The presented dual ligands bind effectively both phosphate anions and metal ions and could be used as effective ion receptors in challenging water conditions in the broad pH range. A careful analysis of the heatmaps of the stability constants allows to choose the most appropriate ligand for the ion for qualitative and/or quantitative analysis in water, without analyte pre-treatment. Extremely high-water solubility (>0.6 M) and ion(s)/ligand stability of the adducts in the pH 3-11 are the greatest advantages of the presented here molecules over other known ion sensors. The presented here molecules represent an innovative class of dual metal/anion ligands, with perspective of medical and environmental use.

Premna odorata extract as a protective agent on neurotoxic effect of aluminum: neurochemical, molecular, and histopathological alterations

Premna odorata Blanco (Lamiaceae) is an ethnomedicinal plant, where some reports claimed their anti-inflammatory, cytotoxic, and antituberculosis effects, without investigating its role on the brain. Therefore, forty mature male rats were equally divided into 4 groups; the 1st was kept as control. Rats in groups 2 and 4 were orally given P. odorata extract daily at a dose of 500 mg/kg B.W., while those in groups 3 and 4 were daily administrated aluminum chloride "AlCl₃" (70 mg/kg B.W.). The treatments extended for 30 successive days. At the end of the experimental period, brain samples were collected for biochemical assay of glutathione reductase (GSH), catalase, malondialdehyde (MDA), and acetylcholinesterase activity (AChE). Besides, monoamines (norepinephrine, dopamine, serotonin), amino acids (glutamine, serine, arginine, taurine and gamma-aminobutyric acid (GABA)), neurotransmitters, DNA damage, cyclooxygenase-2 (COX-2), and tumor necrosis factor (TNF)-α genes were estimated. Moreover, brain samples were obtained for histopathological investigation. Aluminum toxicity resulted in a decline of GSH concentration, elevation of MDA, and AChE activity. Except for GABA which exhibited a significant decrease, there was a marked increase in the measured amino acid and monoamine neurotransmitters. Also, an increase in mRNA expressions of TNF-α and COX-2 was detected. It was noticed that Premna odorata extract reduced the oxidative stress and counteracted the augmentations in AChE caused by AlCl₃. Marked improvements in most measured neurotransmitters with downregulation of pro-inflammatory gene expression were recorded in P. odorata + AlCl₃ group. Premna odorata restores the altered histopathological feature induced by AlCl₃. In conclusion, the present findings clarify that P. odorata extract could be important in improving and treatment of neurodegenerative disorders as it was able to reduce oxidative stress, DNA damage, biochemical alterations, and histopathological changes in rats exposed to AlCl₃ toxicity.

Quantum chemical molecular dynamics and metadynamics simulation of aluminium binding to amyloid-β and related peptides

We report semi-empirical tight-binding simulations of the interaction between Al(III) and biologically relevant peptides. The GFN2-XTB method is shown to accurately reproduce previously reported and density functional theory (DFT)-calculated geometries of model systems. Molecular dynamics simulations based on this method are able to sample peptide flexibility over timescales of up to nanoseconds, but these timescales are insufficient to explore potential changes in metal-peptide binding modes. To achieve this, metadynamics simulations using root mean square deviation as a collective variable were employed. With suitably chosen biasing potentials, these are able to efficiently explore diverse coordination modes, for instance, through Glu and/or Asp residues in a model peptide. Using these methods, we find that Al(III) binding to the N-terminal sequence of amyloid-β is highly fluxional, with all acidic sidechains and several backbone oxygens participating in coordination. We also show that such simulations could provide a means to predict a priori possible binding modes as a precursor to longer, atomistic simulations.

The bio-relevant metals of the periodic table of the elements

The bio-relevant metals (and derived compounds) of the Periodic Table of the Elements (PTE) are in the focus. The bulk elements sodium (Na), potassium (K), magnesium (Mg), and calcium (Ca) from the s-block, which are essential for all kingdoms of life, and some of their bio-activities are discussed. The trace elements of the d-block of the PTE as far as they are essential for humans (Mn, Fe, Co, Cu, Zn, Mo) are emphasized, but V, Ni, Cd, and W, which are essential only for some forms of life, are also considered. Chromium is no longer classified as being essential. From the p-block metals only the metalloid (half-metal) selenium (Se) is essential for all forms of life. Two other metalloids, silicon and arsenic, are briefly mentioned, but they have not been proven as being essential for humans. All metals of the PTE and a plethora of their compounds are used in industry and many of them are highly toxic, like lead (Pb), which is discussed as a prime example. Several metals of the PTE, that is, their ions and complexes, are employed in medicine and we discuss the role of lithium, gallium, strontium, technetium, silver, gadolinium (the only f-block element), platinum, and gold.