Protective effects of copper against aluminum toxicity on acetylcholinesterase and catecholamine contents of different regions of rat's brain

Protective role of functional food in cognitive deficit in young and senile rats

Cognitive decline and neurodegenerative diseases pose a significant burden on healthcare resources both in developed and developing countries which is a major socio-economic and healthcare concern. Alzheimer's disease is the most common form of progressive neurodegenerative dementia of the aged brain. Aluminum is a constituent of antacids, deodorants, kitchenware and food additives which allows easy access into the body posing risk to development of senile dementia of Alzheimer's type. Virgin coconut oil was declared as a potential cognitive strengthener. Assessment of cognitive and memory-enhancing effects of virgin coconut oil in senile and young rats to gain vital insights into its effective use in the prevention of neurodegeneration in dementia/Alzheimer's disease-like manifestations and alleviate cognitive dysfunction and learning impairment with neuronal damage imparted by daily oral intake of aluminum. Alzheimer's disease-like symptoms and memory impairment were experimentally induced using oral anhydrous aluminum chloride given daily for five successive weeks in young and old age albino rats. Treatment groups received virgin coconut oil to assess protection during the experimental period. Behavioral test, Morris water maze was conducted before/after induction/treatment. At the end of the experimental period, cholinergic, dopaminergic, noradrenergic and serotonergic neurotransmission as well as brain-derived neurotrophic factor were being investigated, in addition to immunochemical and histopathological examination of targeted brain regions. Virgin coconut oil significantly improved cholinergic activity and monoaminergic neurotransmission. Moreover, immunochemical and histopathological examination revealed marked protection with virgin coconut oil against aluminum-induced Alzheimer's disease-like pathology and cognitive deficit.

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

The potential neurotoxic role of Al(iii) and its proposed link with the insurgence of Alzheimer's Disease (AD) have attracted increasing interest towards the determination of the nature of bioligands that are propitious to interact with aluminum. Among them, catecholamine-based neurotransmitters have been proposed to be sensitive to the presence of this non-essential metal ion in the brain. In the present work, we characterize several aluminum-catecholamine complexes in various stoichiometries, determining their structure and thermodynamics of formation. For this purpose, we apply a recently validated computational protocol with results that show a remarkably good agreement with the available experimental data. In particular, we employ Density Functional Theory (DFT) in conjunction with continuum solvation models to calculate complexation energies of aluminum for a set of four important catecholamines: l-DOPA, dopamine, noradrenaline and adrenaline. In addition, by means of the Quantum Theory of Atoms in Molecules (QTAIM) and Energy Decomposition Analysis (EDA) we assessed the nature of the Al-ligand interactions, finding mainly ionic bonds with an important degree of covalent character. Our results point at the possibility of the formation of aluminum-catecholamine complexes with favorable formation energies, even when proton/aluminum competition is taken into account. Indeed, we found that these catecholamines are better aluminum binders than catechol at physiological pH, because of the electron withdrawing effect of the positively-charged amine that decreases their deprotonation penalty with respect to catechol. However, overall, our results show that, in an open biological environment, the formation of Al-catecholamine complexes is not thermodynamically competitive when compared with the formation of other aluminum species in solution such as Al-hydroxide, or when considering other endogenous/exogenous Al(iii) ligands such as citrate, deferiprone and EDTA. In summary, we rule out the possibility, suggested by some authors, that the formation of Al-catecholamine complexes in solution might be behind some of the toxic roles attributed to aluminum in the brain. An up-to-date view of the catecholamine biosynthesis pathway with sites of aluminum interference (according to the current literature) is presented. Alternative mechanisms that might explain the deleterious effects of this metal on the catecholamine route are thoroughly discussed, and new hypotheses that should be investigated in future are proposed.

Copper and the brain noradrenergic system

Copper (Cu) plays an essential role in the development and function of the brain. In humans, genetic disorders of Cu metabolism may cause either severe Cu deficiency (Menkes disease) or excessive Cu accumulation (Wilson disease) in the brain tissue. In either case, the loss of Cu homeostasis results in catecholamine misbalance, abnormal myelination of neurons, loss of normal brain architecture, and a spectrum of neurologic and/or psychiatric manifestations. Several metabolic processes have been identified as particularly sensitive to Cu dis-homeostasis. This review focuses on the role of Cu in noradrenergic neurons and summarizes the current knowledge of mechanisms that maintain Cu homeostasis in these cells. The impact of Cu misbalance on catecholamine metabolism and functioning of noradrenergic system is discussed.

Chenodeoxycholic Acid Ameliorates AlCl3-Induced Alzheimer's Disease Neurotoxicity and Cognitive Deterioration via Enhanced Insulin Signaling in Rats

Insulin resistance is a major risk factor for Alzheimer’s disease (AD). Chenodeoxycholic acid (CDCA) and synthetic Farnesoid X receptor (FXR) ligands have shown promising outcomes in ameliorating insulin resistance associated with various medical conditions. This study aimed to investigate whether CDCA treatment has any potential in AD management through improving insulin signaling. Adult male Wistar rats were randomly allocated into three groups and treated for six consecutive weeks; control (vehicle), AD-model (AlCl₃ 50 mg/kg/day i.p) and CDCA-treated group (AlCl₃ + CDCA 90 mg/kg/day p.o from day 15). CDCA improved cognition as assessed by Morris Water Maze and Y-maze tests and preserved normal histological features. Moreover, CDCA lowered hippocampal beta-site amyloid precursor protein cleaving enzyme 1 (BACE1) and amyloid-beta 42 (Aβ₄₂). Although no significant difference was observed in hippocampal insulin level, CDCA reduced insulin receptor substrate-1 phosphorylation at serine-307 (pSer307-IRS1), while increased protein kinase B (Akt) activation, glucose transporter type 4 (GLUT4), peroxisome proliferator-activated receptor gamma (PPARγ) and glucagon-like peptide-1 (GLP-1). Additionally, CDCA activated cAMP response element-binding protein (CREB) and enhanced brain-derived neurotrophic factor (BDNF). Ultimately, CDCA was able to improve insulin sensitivity in the hippocampi of AlCl₃-treated rats, which highlights its potential in AD management.

Therapeutic Effects of Nano-HAp in a Rat Model of AlCl3 Induced Neurotoxicity

With the advance in nanomedicine, the present study was conducted to explore the possible therapeutic role of intravenous nano- hydroxyapatite (nano-HAp) in male rats after chronic exposure to aluminum chloride (AlCl3). This exposure interposed DNA fragmentation, apoptosis, alters oxidant/antioxidant status as well as change in content of neurotransmitters. The rats were injected with 100 mg/kg. body weight (b.w.) of AlCl3 intraperitoneally for 90 days, after then nano-HAp was injected intravenously (i.v.) three times per week at a dose level 100 mg/kg b.w. Based on the results obtained, it can be concluded that the treatment with the prepared nano-HAp restrains the damage inflicted on brain modulation by lipid oxidation products and decreased the susceptibility of apoptotic cells death with subsequent repaired the fragmented DNA as well as improved the synthesis of neurotransmitters. The most salient finding of nano-HAp treatment is the disappearance of most pathological changes due to AlCl3 administration.

Neurotransmitters and neuronal apoptotic cell death of chronically aluminum intoxicated Nile catfish (Clarias gariepinus) in response to ascorbic acid supplementation

Few studies have been carried out to assess the neurotoxic effect of aluminum (Al) on the aquatic creatures. This study aims to evaluate the neurotoxic effects of long term Al exposure on the Nile catfish (Clarias gariepinus) and the potential ameliorative influence of ascorbic acid (ASA) over a 180 days exposure period. Forty eight Nile catfish were divided into four groups: control group, placed in clean water, ASA exposed group (5mg/l), AlCl3 received group (28.96 μg/l; 1/20 LC50), and group received AlCl3 concomitantly with ASA. Brain tissue was examined by using flow cytometry to monitor the apoptotic cell population, HPLC analysis for the quantitative estimation of brain monoamine neurotransmitters [serotonin (5-HT), dopamine (DA), norepinephrine (NE)]. The amino acid neurotransmitters [serum taurine, glycine, aspartate and glutamine and brain gamma aminobutyric acid (GABA)] levels were assessed, plus changes in brain tissue structure using light microscopy. The concentration of Al in both brain tissue and serum was determined by using atomic absorption spectrophotometery. The Al content in serum and brain tissue were both elevated and Al exposure induced an increase in the number of apoptotic cells, a marked reduction of the monoamine and amino acids neurotransmitters levels and changes in tissue morphology. ASA supplementation partially abolished the effects of AL on the reduced neurotransmitter, the degree of apoptosis and restored the morphological changes to the brain. Overall, our results indicate that, ASA is a promising neuroprotective agent against for Al-induced neurotoxicity in the Nile catfish.

Copper, aluminum, iron and calcium inhibit human acetylcholinesterase in vitro

Acetylcholinesterase (AChE) is an important part of cholinergic nerves where it participates in termination of neurotransmission. AChE can be inhibited by e.g. some Alzheimer disease drugs, nerve agents, and secondary metabolites. In this work, metal salts aluminum chloride, calcium chloride, cupric chloride, ferric chloride, potassium chloride, magnesium chloride and sodium chloride were tested for their ability to inhibit AChE. Standard Ellman assay based on human recombinant AChE was done and inhibition was measured using Dixon plot. No inhibition was proved for sodium, potassium and magnesium ions. However, aluminum, cupric, ferric and calcium ions were able to inhibit AChE via noncompetitive mechanism of inhibition. Though the inhibition is much weaker when compared to e.g. drugs with noncompetitive mechanism of action, biological relevance of the findings can be anticipated.