Metabolism and possible health effects of aluminum

Electrochemical Assembly Strategies of Polymer and Hybrid Thin Films for (Bio)sensors, Charge Storage, and Triggered Release

In the context of functional and hierarchical materials, electrode reactions coupled with one or more chemical reactions constitute the most powerful bottom-up process for the electrosynthesis of film components and their electrodeposition, enabling the localized functionalization of conductive surfaces using an electrical stimulus. In analogy with developmental biological processes, our group introduced the concept of morphogen-driven film buildup. In this approach, the gradient of a diffusing reactive molecule or ion (called a morphogen) is controlled by an electrical stimulus to locally induce a chemical process (solubility change, hydrolysis, complexation, and covalent reaction) that induces a film assembly. One of the prominent advantages of this technique is the conformal nature of the deposits toward the electrode. This Feature Article presents the contributions made by our group and other researchers to develop strategies for the assembly of different polymer and nanoparticle/polymer hybrid films by using electrochemically generated reagents and/or catalysts. The main electrochemical-chemical approaches for conformal films are described in the case where (i) the products are noncovalent aggregates that spontaneously precipitate on the electrode (film electrodeposition) or (ii) new chemical compounds are generated, which do not necessarily spontaneously precipitate and enable the formation of covalent or noncovalent films (film electrosynthesis). The applications of those electrogenerated films will be described with a focus on charge storage/transport, (bio)sensing, and stimuli-responsive cargo delivery systems.

Aluminum as a Possible Cause Toward Dyslipidemia

Aluminum, the third most abundant metal present in the earth's crust, is present almost in all daily commodities we use, and exposure to it is unavoidable. The interference of aluminum with various biochemical reactions in the body leads to detrimental health effects, out of which aluminum-induced neurodegeneration is widely studied. However, the effect of aluminum in causing dyslipidemia cannot be neglected. Dyslipidemia is a global health problem, which commences to the cosmic of non-communicable diseases. The interference of aluminum with various iron-dependent enzymatic activities in the tri-carboxylic acid cycle and electron transport chain results in decreased production of mitochondrial adenosine tri-phosphate. This ultimately contributes to oxidative stress and iron-mediated lipid peroxidation. This mitochondrial dysfunction along with modulation of α-ketoglutarate and L-carnitine perturbs lipid metabolism, leading to the atypical accumulation of lipids and dyslipidemia. Respiratory chain disruption because of the accumulation of reduced nicotinamide adenine di-nucleotide as a consequence of oxidative stress and the stimulatory effect of aluminum exposure on glycolysis causes many health issues including fat accumulation, obesity, and other hepatic disorders. One major factor contributing to dyslipidemia and enhanced pro-inflammatory responses is estrogen. Aluminum, being a metalloestrogen, modulates estrogen receptors, and in this world of industrialization and urbanization, we could corner down to metals, particularly aluminum, in the development of dyslipidemia. As per PRISMA guidelines, we did a literature search in four medical databases to give a holistic view of the possible link between aluminum exposure and various biochemical events leading to dyslipidemia.

Identifying Geogenic and Anthropogenic Aluminum Pollution on Different Spatial Distributions and Removal of Natural Waters and Soil in Çanakkale, Turkey

The Çanakkale-Kirazlı region (Turkey) is enriched with minerals, especially aluminum (Al), which dangerously get transported into aquatic media due to several mining and geological activities in recent years. In this study, Al and other potentially toxic metals (PTMs) including B, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Si, and Zn, in both water and soil samples, were measured for quality determination. Selected metals were also analyzed by the enrichment factor (EF), the geoaccumulation index (I _geo), the contamination factor (CF), and the pollution load index (PLI) to evaluate both water and soil pollution geogenically or anthropogenically. Also, the metals were clustered to support the pollution source with Pearson's correlation, principal component analysis (PCA), and hierarchical cluster analysis (HCA). Forty-five natural water samples and 12 soil samples were collected spatially. To perform pollution assessment, two fundamental treatment processes to remove Al pollution from the sample including the highest Al concentration (38.38 mg/L) in water were applied: (1) precipitation with pH adjustment and (2) removal with ion exchange. The pH values of water samples were changed in the range of 3-9 to test the dissolution of Al. The results demonstrated that the study area was mostly under the influence of geogenic aluminum pollution.

Immunomodulatory biomaterials for implant-associated infections: from conventional to advanced therapeutic strategies

Implant-associated infection (IAI) is increasingly emerging as a serious threat with the massive application of biomaterials. Bacteria attached to the surface of implants are often difficult to remove and exhibit high resistance to bactericides. In the quest for novel antimicrobial strategies, conventional antimicrobial materials often fail to exert their function because they tend to focus on direct bactericidal activity while neglecting the modulation of immune systems. The inflammatory response induced by host immune cells was thought to be a detrimental force impeding wound healing. However, the immune system has recently received increasing attention as a vital player in the host's defense against infection. Anti-infective strategies based on the modulation of host immune defenses are emerging as a field of interest. This review explains the importance of the immune system in combating infections and describes current advanced immune-enhanced anti-infection strategies. First, the characteristics of traditional/conventional implant biomaterials and the reasons for the difficulty of bacterial clearance in IAI were reviewed. Second, the importance of immune cells in the battle against bacteria is elucidated. Then, we discuss how to design biomaterials that activate the defense function of immune cells to enhance the antimicrobial potential. Based on the key premise of restoring proper host-protective immunity, varying advanced immune-enhanced antimicrobial strategies were discussed. Finally, current issues and perspectives in this field were offered. This review will provide scientific guidance to enhance the development of advanced anti-infective biomaterials.

Global Scientific Research Landscape on Aluminum Toxicology

This study aimed to identify the landscape of current aluminum toxicity based on knowledge mapping of the 100 most-cited articles on toxicological aspects of aluminum in biological organisms. The research was searched in the Web of Science Core Collection (WoS-CC) with publications between 1945 and 2022. Data regarding authorship, title, journal, year of publication, citation count, country, keywords, study design, and research hotspots were extracted and all elected articles were analyzed. Our results showed that among the articles selected, literature review and in vivo studies were the most common study designs. The USA and England were found as the countries with most publications. Alzheimer's disease (AD), aluminum, and neurotoxicity were found as the most frequent keywords. The articles most cited in world literature suggested that aluminum exposure is associated with Alzheimer's disease, Parkinson's disease (PD), dialysis encephalopathy, amyotrophic lateral sclerosis, neurodegeneration changes, cognitive impairment, such as bone damage, oxidative alterations, and cytotoxicity.

Effects of Aluminium Contamination on the Nervous System of Freshwater Aquatic Vertebrates: A Review

Aluminium (Al) is the most common natural metallic element in the Earth’s crust. It is released into the environment through natural processes and human activities and accumulates in aquatic environments. This review compiles scientific data on the neurotoxicity of aluminium contamination on the nervous system of aquatic organisms. More precisely, it helps identify biomarkers of aluminium exposure for aquatic environment biomonitoring in freshwater aquatic vertebrates. Al is neurotoxic and accumulates in the nervous system of aquatic vertebrates, which is why it could be responsible for oxidative stress. In addition, it activates and inhibits antioxidant enzymes and leads to changes in acetylcholinesterase activity, neurotransmitter levels, and in the expression of several neural genes and nerve cell components. It also causes histological changes in nerve tissue, modifications of organism behaviour, and cognitive deficit. However, impacts of aluminium exposure on the early stages of aquatic vertebrate development are poorly described. Lastly, this review also poses the question of how accurate aquatic vertebrates (fishes and amphibians) could be used as model organisms to complement biological data relating to the developmental aspect. This “challenge” is very relevant since freshwater pollution with heavy metals has increased in the last few decades.

Movement Disorders and Dementia in a Woman With Chronic Aluminium Toxicity: Video-MRI Imaging

Background:

Aluminium encephalopathy results from exposure to aluminium from occupational, recreational, and environmental sources. Movement disorders, cerebellar ataxia, pyramidal tract signs, dementia, microcytic anemia and bone disease are typical manifestations.

Case Report:

A 55-year-old woman had clinical manifestations, persistent hyperaluminemia without magnetic resonance imaging (MRI) scan changes of toxic encephalopathy following a prolonged exposure to marine grade paints containing 30% aluminium. Chelation therapy with ethylenediaminetetraacetic acid (EDTA) demonstrated decreased levels of aluminemia and significant neurological improvement over time.

Discussion:

This diagnosis should be entertained in patients with movement disorders, cerebellar ataxia, pyramidal signs, and dementia of unknown etiology.

Highlights:

Aluminium encephalopathy (AE) is a neurological syndrome caused by aluminium neurotoxicity. Manifestations include cognitive impairment, motor dysfunction, microcytic anemia and bone disease. This case illustrates AE with hyperaluminemia associated with chronic exposure to industrial paints and clinical and biochemical reversibility after chelation therapy with ethylenediaminetetraacetic acid. Movement disorders are highlighted.

Antioxidant Property of the Egyptian Propolis Extract Versus Aluminum Silicate Intoxication on a Rat's Lung: Histopathological Studies

In this study, we evaluated the inflammatory responses induced by aluminum silicate (AS) cytotoxicity in rat lungs. The prophylactic effect of propolis extract was evaluated in 60 adult male albino rats. The rats were divided into six groups: (1) a normal, healthy control group; (2) a normal group fed with 200 mL of propolis extract/Kg; (3) a low-dose positive control group injected with 5 mg/kg of AS; (4) a treated group given propolis and a low dose of AS; (5) a high-dose positive control group injected with 20 mg/kg of AS; and (6) a treated group given propolis with a high-dose of AS. At the end of the two-month experiment, the rats’ lungs were removed. For each pair of lungs, one portion was subjected to biochemical analysis and the other underwent hematoxylin and eosin (H&E) staining in order to study its histology. The rats that received AS doses displayed significant disorders in their antioxidant contents as well as in their enzymatic activities and their histopathological structures revealed severe damage to their lung tissues. Upon the rats being treated with propolis, the enzymatic and antioxidant contents improved and partial improvements in the lung structures appeared, including minimized congestion, a reduced hemorrhage of blood vessels and preserved bronchioles, alveolar ducts, and alveoli. The prophylactic effectiveness of propolis extract on the cytotoxicity of AS, owing to the antioxidant properties of propolis, were studied.

Biomonitoring of Aluminum in Urine of Young Lebanese Children Living in Beirut

Background

Aluminum (Al) is a ubiquitous, toxic metal to which infants and young toddlers are highly vulnerable. High Al exposure has been associated with various human pathologies. The aim of the present biomonitoring (BM) study was to provide a background for the levels of urinary aluminum (Al) in children ages 7 months to 4 years living in Beirut.

Material/Methods

We collected and analyzed 120 urine specimens using the Shimadzu Atomic Absorption Spectrophotometer-6300 system equipped with an electrothermal atomization, and using a GFA-EX7i graphite furnace.

Results

The mean and standard deviation of Al level in urine revealed 8.978±12.275 μg/L, which is within the lower range of each of populations in Germany, Taiwan, and Poland. Vitamin intake, powder rice, and the use of Al utensils proved to be major determinants for Al level in urine (significant at 95%).

Conclusions

The Shimadzu Atomic Absorption Spectrophotometer-6300 system proved again to be an optimal and reliable instrument that can be used for the determination of Al level in urine, especially if using a GFA-EX7i pyrolytic graphite furnace. High levels of Al were found in the urine of Lebanese children. However, the frequent consumption of canned food did not prove to be a significant factor in determining the Al level in urine.

Lung Toxicity Analysis of Nano-Sized Kaolin and Bentonite: Missing Indications for a Common Grouping

Kaolin and bentonite (nanoclay NM-600) are nanostructured aluminosilicates that share a similar chemical composition, platelet-like morphology, and high binding capacity for biomolecules. To investigate if these material-based criteria allow for a common grouping, we prepared particle suspensions of kaolin and bentonite with a similar hydrodynamic diameter and administered them to NR8383 alveolar macrophages in vitro and also to a rat lung using quartz DQ12 as a reference material. Bentonite was far more bioactive in vitro, indicated by a lower threshold for the release of enzymes, tumor necrosis factor α, and H₂O₂. In addition, in the lung, the early effects of bentonite exceeded those of kaolin and even those of quartz, due to strongly increased numbers of inflammatory cells, and elevated concentrations of total protein and fibronectin within the bronchoalveolar lavage fluid. The pro-inflammatory effects of bentonite decreased over time, although assemblies of particle-laden alveolar macrophages (CD68 positive), numerous type-2 epithelial cells (immunopositive for pro-surfactant protein C), and hypertrophic lung epithelia persisted until day 21. At this point in time, kaolin-treated lungs were completely recovered, whereas quartz DQ12 had induced a progressive inflammation. We conclude that bentonite is far more bioactive than equally sized kaolin. This argues against a common grouping of aluminosilicates, previously suggested for different kaolin qualities.

Cadmium-Sensitive Measurement Using a Nano-Copper-Enhanced Carbon Fiber Electrode

Enrichment of cadmium ion (Cd2+) from the environment may lead to kidney disease and weakened immunity in the body. Current techniques are not convenient enough to measure Cd2+ concentration in the environment due to low sensitivity and poor linear range. In this paper, a new measurement technique is proposed using a new sensing electrode made of nano-copper-enhanced carbon fiber. Nano-copper was deposited onto the surface of carbon fiber to enhance the current concentration and mass transfer rate of Cd2+ during measurement, which improved the electrochemical detection sensitivity significantly (by up to 3.7 × 108 nA/nM) and broadened the linear range to 10~105 nM. This device provides a low-cost solution for measuring Cd2+ concentration in the environment.

Aluminium toxicosis: a review of toxic actions and effects

Aluminium (Al) is frequently accessible to animal and human populations to the extent that intoxications may occur. Intake of Al is by inhalation of aerosols or particles, ingestion of food, water and medicaments, skin contact, vaccination, dialysis and infusions. Toxic actions of Al induce oxidative stress, immunologic alterations, genotoxicity, pro-inflammatory effect, peptide denaturation or transformation, enzymatic dysfunction, metabolic derangement, amyloidogenesis, membrane perturbation, iron dyshomeostasis, apoptosis, necrosis and dysplasia. The pathological conditions associated with Al toxicosis are desquamative interstitial pneumonia, pulmonary alveolar proteinosis, granulomas, granulomatosis and fibrosis, toxic myocarditis, thrombosis and ischemic stroke, granulomatous enteritis, Crohn's disease, inflammatory bowel diseases, anemia, Alzheimer's disease, dementia, sclerosis, autism, macrophagic myofasciitis, osteomalacia, oligospermia and infertility, hepatorenal disease, breast cancer and cyst, pancreatitis, pancreatic necrosis and diabetes mellitus. The review provides a broad overview of Al toxicosis as a background for sustained investigations of the toxicology of Al compounds of public health importance.

Aluminum in liver cells - the element species matters

Aluminum (Al) can be ingested from food and released from packaging and can reach key organs involved in human metabolism, including the liver via systemic distribution. Recent studies discuss the occurrence of chemically distinct Al-species and their interconversion by contact with biological fluids. These Al species can vary with regard to their intestinal uptake, systemic transport, and therefore could have species-specific effects on different organs and tissues. This work aims to assess the in vitro hepatotoxic hazard potential of three different relevant Al species: soluble AlCl₃ and two nanoparticulate Al species were applied, representing for the first time an investigation of metallic nanoparticles besides to mineral bound γ-Al₂O₃ on hepatic cell lines. To investigate the uptake and toxicological properties of the Al species, we used two different human hepatic cell lines: HepG2 and differentiated HepaRG cells. Cellular uptake was determined by different methods including light microscopy, transmission electron microscopy, side-scatter analysis, and elemental analysis. Oxidative stress, mitochondrial dysfunction, cell death mechanisms, and DNA damage were monitored as cellular parameters. While cellular uptake into hepatic cell lines occurred predominantly in the particle form, only ionic AlCl₃ caused cellular effects. Since it is known, that Al species can convert one into another, and mechanisms including 'trojan-horse'-like uptake can lead to an Al accumulation in the cells. This could result in the slow release of Al ions, for which reason further hazard cannot be excluded. Therefore, individual investigation of the different Al species is necessary to assess the toxicological potential of Al particles.

Association Between Serum Aluminum Level and Uremic Pruritus in Hemodialysis Patients

Uremic pruritus (UP) is a common symptom in patients undergoing hemodialysis (HD). The pathogenesis of UP is complex. Aluminum (Al) is a common metal and is toxic to patients undergoing HD. Al is also a known human allergen which can induce immune reactions. However, the correlation between Al and UP remains unclear in dialysis patients. A total of 866 patients on maintenance HD were enrolled for analysis. The HD patients with higher serum Al levels had higher a prevalence of UP than those with lower serum Al levels. After adjusting for confounding variables, the serum Al level was significantly associated with UP. Overall, each 10-fold increase in serum Al level was associated with a 5.64-fold increase in the risk of developing UP in these subjects. The results of this cross-sectional study suggest that serum Al level may be associated with the development of UP in patients on maintenance HD.

Aluminum in Tobacco Products Available in the United States

A quantitative method for the analysis of aluminum in tobacco products was developed, validated and applied to select samples. Samples were prepared using standard microwave digestion of tobacco from various products. Detection and quantification utilized sector field inductively coupled plasma-mass spectrometry. Method applicability to analyze aluminum in a range of tobacco products was demonstrated with quantitative analyses of smokeless tobacco products, cigarette tobacco, little cigar tobacco and roll-your-own/pipe tobacco. Though these products represent a convenience sampling, we observed that smokeless tobacco products, as a category, had the lowest average aluminum concentrations. Roll-your-own or pipe tobacco and little cigar tobacco had higher median and ranges of aluminum concentrations than cigarette and smokeless tobacco samples.

Human predisposition to cognitive impairment and its relation with environmental exposure to potentially toxic elements

New lines of evidence suggest that less than 10% of neurodegenerative diseases have a strict genetic aetiology and other factors may be prevalent. Environmental exposures to potentially toxic elements appear to be a risk factor for Parkinson's, Alzheimer's and sclerosis diseases. This study proposes a multidisciplinary approach combining neurosciences, psychology and environmental sciences while integrating socio-economic, neuropsychological, environmental and health data. We present the preliminary results of a neuropsychological assessment carried out in elderly residents of the industrial city of Estarreja. A battery of cognitive tests and a personal questionnaire were administered to the participants. Multivariate analysis and multiple linear regression analysis were used to identify potential relationships between the cognitive status of the participants and environmental exposure to potentially toxic elements. The results suggest a relationship between urinary PTEs levels and the incidence of cognitive disorders. They also point towards water consumption habits and profession as relevant factors of exposure. Linear regression models show that aluminium (R ² = 38%), cadmium (R ² = 11%) and zinc (R ² = 6%) are good predictors of the scores of the Mini-Mental State Examination cognitive test. Median contents (µg/l) in groundwater are above admissible levels for drinking water for aluminium (371), iron (860), manganese (250), and zinc (305). While the World Health Organization does not provide health-based reference values for aluminium, results obtained from this study suggest that it may have an important role in the cognitive status of the elderly. Urine proved to be a suitable biomarker of exposure both to elements with low and high excretion rates.

Binding of trivalent metal ions (Al3+, In3+, La3+) with phosphatidylcholine liposomal membranes investigated by microelectrophoresis

Interactions between trivalent metal ions (Al³⁺, In³⁺, La³⁺) and phosphatidylcholine (PC) liposomes are studied by microelectrophoresis. The dependence of the PC membrane surface charge density and zeta potential on [Formula: see text] ([Formula: see text] range from 2 to 10) of the aqueous metal chloride solutions is determined. The obtained results indicate the adsorption of Al³⁺, In³⁺ and La³⁺ ions on phosphatidylcholine model membranes, leading to changes in the electrical properties of the membranes. The theoretical considerations on equilibria occurring between phosphatidylcholine liposomal membrane and trivalent metal ions are presented. A mathematical model describing the interactions in a quantitative way is proposed.

Glutathione alleviated peripheral neuropathy in oxaliplatin-treated mice by removing aluminum from dorsal root ganglia

Oxaliplatin, a platinum-based anti-cancer drug, induces peripheral neuropathy as a side effect and causes cold hyperalgesia in cancer patients receiving anti-cancer chemotherapy. In oxaliplatin-treated mice, aluminum was accumulated in the dorsal root ganglia (DRG), and accumulated aluminum in DRG or other organs aggravated oxaliplatin-induced neuropathic pain. To investigate whether aluminum oxalate, which is the compound of aluminum and oxaliplatin, might be the peripheral neuropathy inducer, the withdrawal responses of mice to coldness, the expression of transient receptor potential ankyrin 1 and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assays in DRG were analyzed in mice administered with aluminum oxalate. In addition, the concentrations of aluminum in aluminum oxalate-treated mice were significantly increased compared to those of mice treated with aluminum chloride. To alleviate neuropathic pain, glutathione (GSH), known as an antioxidant and a metal chelator, was injected into oxaliplatin-treated mice. The concentrations of aluminum in the DRG were decreased by the chelation action of GSH. Taken together, behavioral and molecular analyses also supported that aluminum accumulation on the DRG might be a factor for neuropathic pain. This result also suggested that the aluminum chelation by GSH can provide an alleviatory remedy of neuropathic pain for cancer patients with oxaliplatin-induced neuropathic pain.

Effects of aluminum on the reduction of neural stem cells, proliferating cells, and differentiating neuroblasts in the dentate gyrus of D-galactose-treated mice via increasing oxidative stress

Aluminum (Al) accumulation increases with aging, and long-term exposure to Al is regarded as a risk factor for Alzheimer's disease. In this study, we investigated the effects of Al and/or D-galactose on neural stem cells, proliferating cells, differentiating neuroblasts, and mature neurons in the hippocampal dentate gyrus. AlCl₃ (40 mg/kg/day) was intraperitoneally administered to C57BL/6J mice for 4 weeks. In addition, vehicle (physiological saline) or D-galactose (100 mg/kg) was subcutaneously injected to these mice immediately after AlCl₃ treatment. Neural stem cells, proliferating cells, differentiating neuroblasts, and mature neurons were detected using the relevant marker for each cell type, including nestin, Ki67, doublecortin, and NeuN, respectively, via immunohistochemistry. Subchronic (4 weeks) exposure to Al in mice reduced neural stem cells, proliferating cells, and differentiating neuroblasts without causing any changes to mature neurons. This Al-induced reduction effect was exacerbated in D-galactose-treated mice compared to vehicle-treated adult mice. Moreover, exposure to Al enhanced lipid peroxidation in the hippocampus and expression of antioxidants such as Cu, Zn- and Mn-superoxide dismutase in D-galactose-treated mice. These results suggest that Al accelerates the reduction of neural stem cells, proliferating cells, and differentiating neuroblasts in D-galactose-treated mice via oxidative stress, without inducing loss in mature neurons.

DNA damage in the kidney tissue cells of the fish Rhamdia quelen after trophic contamination with aluminum sulfate

Even though aluminum is the third most common element present in the earth's crust, information regarding its toxicity remains scarce. It is known that in certain cases, aluminum is neurotoxic, but its effect in other tissues is unknown. The aim of this work was to analyze the genotoxic potential of aluminum sulfate in kidney tissue of the fish Rhamdia quelen after trophic contamination for 60 days. Sixty four fish were subdivided into the following groups: negative control, 5 mg, 50 mg and 500 mg of aluminum sulfate per kg of fish. Samples of the posterior kidney were taken and prepared to obtain mitotic metaphase, as well as the comet assay. The three types of chromosomal abnormalities (CA) found were categorized as chromatid breaks, decondensation of telomeric region, and early separation of sister chromatids. The tests for CA showed that the 5 mg/kg and 50 mg/kg doses of aluminum sulfate had genotoxic potential. Under these treatments, early separation of the sister chromatids was observed more frequently and decondensation of the telomeric region tended to increase in frequency. We suggest that structural changes in the proteins involved in DNA compaction may have led to the decondensation of the telomeric region, making the DNA susceptible to breaks. Moreover, early separation of the sister chromatids may have occurred due to changes in the mobility of chromosomes or proteins that keep the sister chromatids together. The comet assay confirmed the genotoxicity of aluminum sulfate in the kidney tissue of Rhamdia quelen at the three doses of exposure.

Aluminum-induced entropy in biological systems: implications for neurological disease

Over the last 200 years, mining, smelting, and refining of aluminum (Al) in various forms have increasingly exposed living species to this naturally abundant metal. Because of its prevalence in the earth's crust, prior to its recent uses it was regarded as inert and therefore harmless. However, Al is invariably toxic to living systems and has no known beneficial role in any biological systems. Humans are increasingly exposed to Al from food, water, medicinals, vaccines, and cosmetics, as well as from industrial occupational exposure. Al disrupts biological self-ordering, energy transduction, and signaling systems, thus increasing biosemiotic entropy. Beginning with the biophysics of water, disruption progresses through the macromolecules that are crucial to living processes (DNAs, RNAs, proteoglycans, and proteins). It injures cells, circuits, and subsystems and can cause catastrophic failures ending in death. Al forms toxic complexes with other elements, such as fluorine, and interacts negatively with mercury, lead, and glyphosate. Al negatively impacts the central nervous system in all species that have been studied, including humans. Because of the global impacts of Al on water dynamics and biosemiotic systems, CNS disorders in humans are sensitive indicators of the Al toxicants to which we are being exposed.

Aluminium in biological environments: a computational approach

The increased availability of aluminium in biological environments, due to human intervention in the last century, raises concerns on the effects that this so far “excluded from biology” metal might have on living organisms. Consequently, the bioinorganic chemistry of aluminium has emerged as a very active field of research. This review will focus on our contributions to this field, based on computational studies that can yield an understanding of the aluminum biochemistry at a molecular level. Aluminium can interact and be stabilized in biological environments by complexing with both low molecular mass chelants and high molecular mass peptides. The speciation of the metal is, nonetheless, dictated by the hydrolytic species dominant in each case and which vary according to the pH condition of the medium. In blood, citrate and serum transferrin are identified as the main low molecular mass and high molecular mass molecules interacting with aluminium. The complexation of aluminium to citrate and the subsequent changes exerted on the deprotonation pathways of its tritable groups will be discussed along with the mechanisms for the intake and release of aluminium in serum transferrin at two pH conditions, physiological neutral and endosomatic acidic. Aluminium can substitute other metals, in particular magnesium, in protein buried sites and trigger conformational disorder and alteration of the protonation states of the protein's sidechains. A detailed account of the interaction of aluminium with proteic sidechains will be given. Finally, it will be described how alumnium can exert oxidative stress by stabilizing superoxide radicals either as mononuclear aluminium or clustered in boehmite. The possibility of promotion of Fenton reaction, and production of hydroxyl radicals will also be discussed.

Aluminum concentrations in central and peripheral areas of malignant breast lesions do not differ from those in normal breast tissues

Background

Aluminum is used in a wide range of applications and is a potential environmental hazard. The known genotoxic effects of aluminum might play a role in the development of breast cancer. However, the data currently available on the subject are not sufficient to establish a causal relationship between aluminum exposure and the augmented risk of developing breast cancer. To achieve maximum sensitivity and specificity in the determination of aluminum levels, we have developed a detection protocol using graphite furnace atomic absorption spectrometry (GFAAS). The objective of the present study was to compare the aluminum levels in the central and peripheral areas of breast carcinomas with those in the adjacent normal breast tissues, and to identify patient and/or tumor characteristics associated with these aluminum levels.

Methods

A total of 176 patients with breast cancer were included in the study. Samples from the central and peripheral areas of their tumors were obtained, as well as from the surrounding normal breast tissue. Aluminum quantification was performed using GFAAS.

Results

The average (mean ± SD) aluminum concentrations were as follows: central area, 1.88 ± 3.60 mg/kg; peripheral area, 2.10 ± 5.67 mg/kg; and normal area, 1.68 ± 11.1 mg/kg. Overall and two-by-two comparisons of the aluminum concentrations in these areas indicated no significant differences. We detected a positive relationship between aluminum levels in the peripheral areas of the tumors, age and menopausal status of the patients (P = .02).

Conclusions

Using a sensitive quantification technique we detected similar aluminum concentrations in the central and peripheral regions of breast tumors, and in normal tissues. In addition, we did not detect significant differences in aluminum concentrations as related to the location of the breast tumor within the breast, or to other relevant tumor features such as stage, size and steroid receptor status. The next logical step is the assessment of whether the aluminum concentration is related to the key genomic abnormalities associated with breast carcinogenesis.

Cognitive deterioration and associated pathology induced by chronic low-level aluminum ingestion in a translational rat model provides an explanation of Alzheimer's disease, tests for susceptibility and avenues for treatment

A translational aging rat model for chronic aluminum (Al) neurotoxicity mimics human Al exposure by ingesting Al, throughout middle age and old age, in equivalent amounts to those ingested by Americans from their food, water, and Al additives. Most rats that consumed Al in an amount equivalent to the high end of the human total dietary Al range developed severe cognitive deterioration in old age. High-stage Al accumulation occurred in the entorhinal cortical cells of origin for the perforant pathway and hippocampal CA1 cells, resulting in microtubule depletion and dendritic dieback. Analogous pathological change in humans leads to destruction of the perforant pathway and Alzheimer's disease dementia. The hippocampus is thereby isolated from neocortical input and output normally mediated by the entorhinal cortex. Additional evidence is presented that Al is involved in the formation of neurofibrillary tangles, amyloid plaques, granulovacuolar degeneration, and other pathological changes of Alzheimer's disease (AD). The shared characteristics indicate that AD is a human form of chronic Al neurotoxicity. This translational animal model provides fresh strategies for the prevention, diagnosis, and treatment of AD.

Effect of calabash chalk on the histomorphology of the gastro-oesophageal tract of growing wistar rats

BACKGROUND

Calabash chalk is a naturally occurring mineral consumed by members of some Nigerian communities for pleasure and by pregnant women as a remedy for morning sickness. The consumption of this geophagic material motivated our interest on the effect of the chalk on the histomorphology of the gastro-oesophageal tract.

METHODS

Twenty-eight young Wistar rats, 4 weeks old, were divided into 4 groups of equal size. Group 1 animals served as controls and received 1 mL of distilled water. Groups 2, 3, and 4 received orally 1 mL of a Calabash chalk suspension containing 40 mg/mL for 14, 21, and 28 days, respectively. Upon completion of the treatments, the animals in groups 2, 3, and 4 were sacrificed on days 15, 22, and 29, respectively, and the control group animals were sacrificed on day 29. All animals were euthanised using chloroform anaesthesia. The oesophagus and the stomach of each animal were dissected out and routinely processed for histological studies.

RESULTS

There was oedema with haemorrhages in the mucosa of the stomach, and acanthosis, hyperkeratosis, and koilocytic changes were observed in the mucosa of the oesophagus of the groups treated with 40 mg/mL of Calabash chalk suspension.

CONCLUSION

Calabash chalk caused histological changes to the stomach and the oesophagus that may lead to other pathophysiological conditions.

Bio-corrosion characterization of Mg-Zn-X (X = Ca, Mn, Si) alloys for biomedical applications

The successful applications of magnesium-based alloys as biodegradable orthopedic implants are mainly inhibited due to their high degradation rates in physiological environment. This study examines the bio-corrosion behaviour of Mg-2Zn-0.2X (X = Ca, Mn, Si) alloys in Ringer's physiological solution that simulates bodily fluids, and compares it with that of AZ91 magnesium alloy. Potentiodynamic polarization and electrochemical impedance spectroscopy results showed a better corrosion behaviour of AZ91 alloy with respect to Mg-2Zn-0.2Ca and Mg-2Zn-0.2Si alloys. On the contrary, enhanced corrosion resistance was observed for Mg-2Zn-0.2Mn alloy compared to the AZ91 one: Mg-2Zn-0.2Mn alloy exhibited a four-fold increase in the polarization resistance than AZ91 alloy after 168 h exposure to the Ringer's physiological solution. The improved corrosion behaviour of the Mg-2Zn-0.2Mn alloy with respect to the AZ91 one can be ascribed to enhanced protective properties of the Mg(OH)(2) surface layer. The present study suggests the Mg-2Zn-0.2Mn alloy as a promising candidate for its applications in degradable orthopedic implants, and is worthwhile to further investigate the in vivo corrosion behaviour as well as assessed the mechanical properties of this alloy.

Potential release of aluminum and other metals by food-grade aluminum foil used for skin allograft cryo preservation

Since 1991, the skin bank of the Queen Astrid Military Hospital uses food-grade aluminum foil as a primary support for storing cryo preserved human donor skin (511 donors). The possible release of heavy metals into the cryo preservation media (30% (v/v) glycerol in physiological water) and the possible impact this release could have on the quality of the cryo preserved donor skin was evaluated. Aluminum was the principal detection target. Possible contaminants of the aluminum foil as such (arsenic, cadmium, chromium and lead) were also investigated. The evaluation was set up after a Belgian Competent Authority inspection remark. Aluminum was detected at a concentration of 1.4 mg/l, arsenic and lead were not detected, while cadmium and chromium were detected in trace element quantities. An histological analysis revealed no differences between cryo preserved and fresh donor skin. No adverse reactions in patients, related to the presence of aluminum or heavy metal traces, were reported since the introduction of the cryo preserved donor skin in our burn wound centre.

Immunotoxicity Following Pre- and Post-natal Aluminum Exposure in Rats

The present study was designed to explore the immunotoxic effects of orally administered aluminum (AI) on pregnant rats (n = 60) and their growing fetuses and consequently on the animal wealth. The animals were randomly allocated into three equal groups of 20 rats each. The first group has no treatment and kept as a control (G1). The second and third groups of pregnant rats were treated orally with aluminum chloride at 345 mg/Kg b.wt. The second group (G2) received the tested compound from the 6^th day of gestation to the end of weaning, whereas the third group (G3) received the tested compound from the 15^th day of gestation to the end of weaning. Control and treated animals (dams and offspring) were immunized ip with (0.5 ml) 20% sheep red blood cell (SRBC) suspension seven days before the end of experiments. At the end of exposure, ten dams and ten offspring from each group were used for assessment of cell-mediated immunity and a similar number of animals were sacrificed for evaluating the humoral immune response and serum protein profile. Aluminum chloride exposure of dams (G₂ & G₃) caused significant suppression of both cell mediated and humoral immune responses in the obtained offsprings compared to the control group (G₁) without any significant effect on the immune responses of these dams. Moreover, the serum total globulins, albumin/ globulin (A/G) ratio and gamma globulin fraction were significantly decreased in the treated dam’s offsprings compared to the corresponding controls while the serum total protein and all serum protein fractions showed non significant difference between the control and treated dams and between the two treated dam groups themselves. There were no histopatho-logical changes observed in thymus, spleen and liver of the control and treated dams. Thymus of treated dam’s offsprings (G2) showed lymphoid depletion in both cortex and medulla. Their spleens showed lymphoid depletion in the white pulps and congestion with hemosiderosis in the red pulps. Liver of treated dam’s offsprings showed dilation and congestion of its central vein with degenerative changes in the hepatocytes. These histopathological changes were more severe in G2 than in G3 offsprings. It can be concluded that gestational and/ or lactation exposure of pregnant dams to AI chloride caused suppression of both cellular and humoral immune responses of their offsprings.

Short-term exposure of female rats to industrial metal salts: Effect on implantation and pregnancy

Aim: The objective of this study was to characterize the adverse effects of industrial metal salts during the early stages of pregnancy. Methods: Successfully mated female rats were exposed to the following metal salts via intragastric intubation; manganese sulfate, lead acetate, aluminum chloride, ferrous chloride and ferric chloride in doses of 50 mg/kg body weight and chromium chloride and potassium dichromate in doses of 25 mg/kg body weight on days l-3 or 4-6 of pregnancy. Female rats were killed on day 20 of gestation and the pregnancy outcome was determined. Results: The administration of manganese sulfate, chromium chloride, potassium dichromate and ferric chloride to female rats on days 1-3 of pregnancy caused pregnancy failure. However, the administration of manganese sulfate and potassium dichromate reduced the number of implantations. The administration of manganese sulfate, potassium dichromate and ferric chloride reduced the number of viable fetuses. The total number of resorptions increased in the lead acetate, aluminum chloride, ferrous chloride and ferric chloride exposed groups. In contrast, the administration of manganese sulfate, aluminum chloride and ferric chloride on days 4-6 of pregnancy caused pregnancy failure. However, the administration of ferric chloride reduced the number of implantations. The administration of manganese sulfate, aluminum chloride, potassium dichromate, ferrous chloride and ferric chloride reduced the number of viable fetuses. The total number of resorptions increased in the manganese sulfate, lead acetate, aluminum chloride, potassium dichromate, ferrous chloride and ferric chloride exposed groups. Conclusion: This work demonstrates that the short-term exposure of female rats to industrial metal salts during the early stages of gestation would cause failure of pregnancy and produce fetotoxic or fetal resorptive potentials. (Reprod Med Biol 2007; 6: 179-183).

No association between the aluminium content of trabecular bone and bone density, mass or size of the proximal femur in elderly men and women

Background

Aluminium is considered a bone toxic metal since poisoning can lead to aluminium-induced bone disease in patients with chronic renal failure. Healthy subjects with normal renal function retain 4% of the aluminium consumed. They might thus also accumulate aluminium and eventually be at risk of long-term low-grade aluminium intoxication that can affect bone health.

Methods

We therefore examined 62 patients with femoral neck fractures or osteoarthritis of the hip (age range 38–93), with the aim of examining whether aluminium in bone is associated with bone-mineral density (BMD), content (BMC) or width of the femoral neck measured by dual-energy X-ray absorptiometry (DXA). During operations bone biopsies were taken from the trabecular bone of the proximal femur. The samples were measured for their content of aluminium using a mass spectrometer.

Results

No significant association between the aluminium content in bone and femoral neck BMD, BMC or width could be found after multivariate adjustment.

Conclusion

Our results indicate that the accumulated aluminium content in bone during life does not substantially influence the extent of osteoporosis.

Response of atmospheric methane consumption by maine forest soils to exogenous aluminum salts

Atmospheric methane consumption by Maine forest soils was inhibited by additions of environmentally relevant levels of aluminum. Aluminum chloride was more inhibitory than nitrate or sulfate salts, but its effect was comparable to that of a chelated form of aluminum. Inhibition could be explained in part by the lower soil pH values which resulted from aluminum addition. However, significantly greater inhibition by aluminum than by mineral acids at equivalent soil pH values indicated that inhibition also resulted from direct effects of aluminum per se. The extent of inhibition by exogenous aluminum increased with increasing methane concentration for soils incubated in vitro. At methane concentrations of >10 ppm, inhibition could be observed when aluminum chloride was added at concentrations as low as 10 nmol g (fresh weight) of soil(-1). These results suggest that widespread acidification of soils and aluminum mobilization due to acid precipitation may exacerbate inhibition of atmospheric methane consumption due to changes in other parameters and increase the contribution of methane to global warming.

Aluminum enhances melanin-induced lipid peroxidation

The present study was conducted to characterize the possible interaction of Al3+ and Fe2+ with synthetic melanin in the potentiation of lipid peroxidation in liposomes and rat caudate-putamen homogenates. Al3+ stimulated melanin-initiated lipid peroxidation as measured by the production of 2-thiobarbituric acid-reactive substances (TBARS) and conjugated dienes. The effect of A13+ was dependent on melanin (10-100 microg/ml) and A13+ (2.5-250 microM) concentrations and no synergism between Fe2+ and Al3+ was observed. The prooxidant effect of Al3+ was partially inhibited by superoxide dismutase indicating the involvement of O2*- . Ga3+ and Be2+ which can increase NADH oxidation in the presence of O2*-, also were shown to stimulate melanin-initiated TBARS production. Based on the effect of Al3+ and other non redox metals, we suggest that Al3+ does not act through either the induction of melanin free radicals, or the induction of changes in membrane physical properties. Results show that Al3+ enhances melanin-initiated lipid peroxidation in part through an interaction with O2*- generated from the autoxidation of melanin. We speculate that Al3+ contributes to neuromelanin-mediated oxidative damage in dopaminergic neurons and subsequent neuronal degeneration and death in Parkinson's disease.

Effects of aluminum sulphate and citric acid ingestion on lipid peroxidation and on activities of superoxide dismutase and catalase in cerebral hemisphere and liver of developing young chicks

Effect of oral administration of aluminum sulphate (200 and 400 mg/kg body wt/day) without or with citric acid (62 mg/kg body wt/day) to day-old White Leghorn male chicks (n = 5 per group) for 30 days was studied on the activities of superoxide dismutase (SOD) and catalase, and level of lipid peroxidation in cerebral hemisphere and liver. A 400 mg dose of Al in the presence of citric acid inhibited cytosolic total and CN -sensitive superoxide dismutase activities of the cerebral hemisphere in 7- and 30-day treated chicks, whereas in 15-day treated chicks the enzyme activities were decreased in response to both doses in the presence of citric acid. In case of liver, activities of these enzymes significantly decreased after 7, 15 and 30 days of treatment with 200 and 400 mg Al together with citric acid, whereas 400 mg Al alone inhibited the enzyme activities after 15 and 30 days of treatment. Cerebral catalase activity decreased in response to 400 mg Al when the chicks were also fed with citric acid for 7 and 30 days, but in 15-day treated chicks the enzyme activity was depleted following treatment with 200 and 400 mg Al combined with citric acid. 400 mg Al treatment for 7 days in combination with citric acid inhibited hepatic catalase activity and extension of the treatment period to 15 and 30 days also produced reduction in its activity even in response to the lower Al dose mixed with citric acid. CN -insensitive SOD activity of cerebral hemisphere and liver was unaffected by Al. Al also failed to induce lipid peroxidation in both the tissues throughout the course of exposure. Activities of SOD and catalase of cerebral hemisphere and liver of 30-day old chicks were observed to be inhibited by in vitro incubation with different concentrations of Al. Our in vivo study demonstrates that only CN -sensitive SOD is susceptible to Al. Further, responses of SOD and catalase to Al is tissue specific. The observed inhibition of antioxidant enzyme activities by Al is suggestive of a prooxidant state. Induction of such an oxidative condition of the tissues may be attributed to a direct effect of the metal on enzyme molecules or in their synthesis.

Membrane composition can influence the rate of Al3+-mediated lipid oxidation: effect of galactolipids

In the first part of the present study we investigated the effects of pre-natal and early postnatal exposure of mice to high levels of dietary Al3+ on myelin lipid composition and lipid oxidation. We found: (1) a significantly higher (104%; P<0.01) content of brain myelin galactolipids in the high-Al3+ group than in controls, and, (2) a significant correlation (r2=0.70; P<0.01) between the concentration of myelin galactolipids and TBARS (2-thiobarbituric acid-reactive substances) content, a parameter of lipid oxidation. Based on these results, we evaluated in an in vitro model (liposomes) whether galactolipids could affect the capacity of Al3+ to stimulate Fe2+-initiated lipid oxidation, and whether this effect could be due to the promotion of changes in membrane physical properties (membrane phase separation and rigidification). The presence of galactolipids (10-40 mol%) in the liposomes caused a concentration-dependent increase in the stimulatory effect of Al3+ on Fe2+-induced TBARS production, and on the ability of Al3+ to induce phase separation and membrane rigidification. The capacity of Al3+ (10-100 microM) to induce lateral phase separation in liposomes composed of phosphatidylcholine/phosphatidylserine/galactolipid (36:24:40, molar ratio) was correlated significantly (r2=0.99; P<0. 001) with the stimulatory action of Al3+ on Fe2+-induced TBARS production. We propose that the high content of galactolipids found in myelin from Al3+-intoxicated mice could favour Al3+-induced changes in membrane physical properties, with the subsequent acceleration of lipid oxidation rates.

Run-on gene transcription in human neocortical nuclei. Inhibition by nanomolar aluminum and implications for neurodegenerative disease

The incorporation of [alpha-32P]-uridine triphosphate into DNA transcription products was examined in short post-mortem interval (PMI) human brain neocortical nuclei (n, 22; PMI, 0.5-24 h) using run-on-gene transcription. Reverse Northern dot-blot hybridization of newly synthesized RNA against either total cDNA or Alu repetitive DNA indicated that human brain neocortical nuclei of up to 4-h PMI were efficient in incorporating radiolabel into new transcription products, after which there was a graded decline in de novo RNA biosynthetic capacity. To test the effects of 0-3000 nM concentrations of ambient aluminum on RNA polymerase I (RNAP I) and RNA polymerase II (RNAP II) transcription, dot blots containing 0.5, 1.0, 2.0, and 5.0 micrograms of DNA for (1) the human-specific Alu repetitive element (2) the neurofilament light (NFL) chain, and (3) glial fibrillary acidic protein (GFAP) were Northern hybridized against newly synthesized radiolabeled total RNA. These DNAs represent heterogeneous nuclear RNA (hnRNA), neuronal-, and glial-specific markers, respectively. We report here a dose-dependent repression in the biosynthetic capabilities of brain RNAP II in the range of 50-100 nM aluminum, deficits similar to those previously described using a rabbit neocortical nuclei transcription system and at concentrations that have been reported in Alzheimer's disease (AD) euchromatin. Transcription from RNAP II and the neuron-specific NFL gene in the presence of aluminum was found to be particularly affected. These findings support the hypothesis that brain gene transcription in the presence of trace amounts of ambient aluminum impairs mammalian brain DNA to adequately read out genetic information.

Metal selectivity of in situ microcolonies in biofilms of the Elbe river

The ultrastructure of natural complex biofilm communities of the Elbe river grown in situ on microscopic glass coverslips was studied by using transmission electron microscopy and energy-dispersive x-ray (EDX) analysis. Characteristic microcolonies which measured between 3.3 and 9.3 microm in diameter were frequently observed. They had an outer envelope and harbored 6 to 30 cells. The cells formed short rods measuring 1.09 +/- 0.28 microm (n = 10) in length and 0.55 + 0.07 microm (n = 21) in width. They were surrounded by a thick layer of electron-transparent, nonosmicated matter, 120 to 300 nm thick. Individual cells exhibited a unique ultrastructural trait, namely, a concentric membrane stack which completely surrounded the cytoplasm. It consisted of three membrane doublets, which showed an overall thickness of 57 to 66 nm. The center-to-center spacing between two membrane doublets was 22.2 +/- 1.0 nm (n = 12). The bacterial cell wall seemed to be of the gram-negative type. The fact that upon shrinkage hexagonal clefts appeared proved the cells to be tightly packed, and septum formation by binary fissions was observed. All of these morphological details indicate that the cells within these microcolonies were actively growing and did not represent spore-like states. EDX analysis showed that only the electron-dense surface deposit of the microcolonies contained Mn and Fe in significant amounts, while these two elements were absent from the intercellular space and the cytoplasm of the microorganisms. In contrast, aluminum ions were able to penetrate the outer envelope of the microcolonies and were detected in the intercellular space. They were, however, completely absent from the microbial cytoplasm, indicating a filter cascade with respect to aluminum. From the ultrastructural data together with the deposition of iron and manganese on the microcolony surface, it appears that these organisms may belong to the genus Siderocapsa or Nitrosomonas. They do not precisely match any of the described species and may therefore represent a new species.

Cytogenetic, developmental, and biochemical effects of aluminum, iron, and their mixture in sea urchins and mussels

The present study was undertaken to evaluate the toxicity of aluminum sulfate, ferric chloride and their 1:1 mixture (Mix) on early development, fertilization and offspring quality in three sea urchins species (Sphaerechinus granularis, Paracentrotus lividus, Psammechinus microtuberculatus) and in mussels (Mytilus galloprovincialis). The endpoints were the following: a) larval malformations; b) developmental arrest; c) embryonic mortality; d) fertilization success; e) cytogenetic effects, and f) luminol-dependent chemiluminescence (LDCL). Overall data point to the induction of developmental defects in both sea urchin and mussel embryos following exposure of embryos to Al(III) or Fe(III) (10(-7) to 10(-6) M), whereas Mix caused varied effects vs. Al(III) or Fe(III) alone, from scarce or no additive effects (M. galloprovincialis and P. lividus) to a dramatic rise in embryolethality even at nominal levels of 10(-8) M (Ps. microtuberculatus).S. granularis sperm underwent a dose-dependent decrease in fertilization success following exposure to Al(III), or Fe(III), or Mix at levels ranging from 10(-8) to 10(-5) M. A significant increase of developmental defects was observed in the offspring of S. granularis sperm exposed to micromolar levels of the agents, suggesting an Al(III)- and Fe(III)-related transmissible damage to sperm. The cytogenetic analysis of Al(III)-, Fe(III)-, or Mix-exposed S. granularis embryos showed a significant increase in mitotic aberrations. A relevant feature of the observed cytogenetic damage included scattered chromosomes, suggesting cytoskeleton damage. The LDCL emission in S. granularis embryos showed a dose-related inhibition by agent levels ranging from 10(-7) to 10(-5) M; this held true for both spontaneous and, to a larger extent, for horseradish peroxidase (HRP)-activated LDCL. LDCL associated with fertilization was affected by Al(III), Fe(III) and Mix, with a time- and dose-related shift from stimulation to inhibition. The changes observed in LDCL emission suggested that the observed damage to embryogenesis, fertilization and mitotic activity may be related, at least partly, to alterations of the embryo prooxidant state. The present data point to developmental, cytogenetic and biochemical changes related to realistic levels of Al(III), Fe(III) and their mixtures, raising concern as to their environmental, occupational and iatrogenic exposures.

Microbial interactions with aluminium

Although aluminium is the most abundant metal in the Earth's crust, it lacks biological functions and shows a low bioavailability. Acid rain, however, solubilizes aluminium to toxic levels. Most research on the biological effects of aluminium has been centred on the analysis of aluminium-tolerant plants as well as its possible relationship with neurological disorders in humans. Also, several studies have been reported concerning aluminium effects on microorganisms, with more interest directed to cyanobacteria, soil bacteria and mycorrhizal fungi. Competition with iron and magnesium, and binding to DNA, membranes or cell walls are considered the main toxic effects of aluminium in microbes.

Aluminum chelation by 3-hydroxypyridin-4-ones in the rat demonstrated by microdialysis

The ability and site of the metal-chelating 3-hydroxypyridin-4-ones (HPs) to mobilize aluminum (Al) was assessed in Al-loaded rats using microdialysis. Four HPs with greatly varying lipophilicity were studied. One week after Al loading, microdialysis probes were implanted in the liver, a jugular vein, and the frontal cortex. An HP was given iv followed by continuous microdialysis for 5 h. Al concentrations in dialysates from the liver increased rapidly and were consistently greater than from blood, suggesting that liver was a primary site of Al chelation. Brain dialysate Al concentrations remained low, suggesting little Al chelation in the brain and little distribution of the Al HP complex into the brain. Al concentrations were determined in the main organs/tissues of a separate group of Al-loaded rats, and the percentage of the total Al body burden in each organ/tissue was calculated. The skeletal system and liver had 57 and 28% of the Al body burden, consistent with the liver as a primary site of Al chelation. The HPs chelate extravascular Al and have been shown by others to be orally active. They warrant further investigation as Al chelators.

Bioaccumulation of water soluble aluminium chloride in the hippocampus after transdermal uptake in mice

Normally, only very small amounts of ingested aluminium are absorbed and accumulated. Despite the percutaneous absorption of many drugs and chemicals, the skin has not been considered as a possible site at which aluminium could enter the body. Application of low aqueous concentrations of aluminium chloride (A1C1(3), 6H20) (0.025-0.1 micrograms/cm2) to healthy shaved Swiss mouse skin for 130 days led to a significant increase in urine, serum and whole brain aluminium, especially in the hippocampus, compared to control animals. This percutaneous uptake and accumulation of aluminium in the brain was greater than that caused by dietary exposure to 2.3 micrograms per day in feed and water. In vitro studies demonstrated the passage of aluminium through viable mouse skin. This study shows for the first time that aluminium is absorbed through the skin of mice in vivo and this contributes to a greater body burden than does oral uptake.

Metals and selenium in wild animals from Norwegian areas close to Russian nickel smelters

This paper reports the concentrations of metals (Al, As, Cd, Cr, Cu, Hg, Ni, Pb, and/or Zn) and selenium (Se) in kidney and/or liver samples from capercaillie (Tetrao urogallus), willow ptarmigan (Lagopus lagopus), hares (Lepus timidus), common shrews (Sorex araneus) and grey-sided voles (Clethrionomus rufocanus) from the Norwegian areas most heavily contaminated by pollutants from the Russian smelters on the Kola peninsula. In addition to comparing areas that differed in expected pollution rate within Sør-Varanger, comparisons are drawn with reference data from other parts of Norway. The relatively highest levels of metals were found for Cu and Ni in the sub-area most heavily exposed to pollution from the smelters. Also the highest Cr concentrations were found in the areas closest to the smelters. In this study, there is evidence for a direct link between increased metal concentrations in wild animals and pollution from the Russian smelters for Cu and Ni and to some extent for Cr. relatively high concentration of Hg and slight increases in Pb are also documented, but regional differences within Sør-Varanger indicate no direct relationship to the Russian smelters. No samples showed concentrations of any of the analysed metals in excess of the limits where negative effects on animals can be measured.

The biological speciation and toxicokinetics of aluminum

This review discusses recent literature on the chemical and physiological factors that influence the absorption, distribution, and excretion of aluminum in mammals, with particular regard to gastrointestinal absorption and speciation in plasma. Humans encounter aluminum, a ubiquitous yet highly insoluble element in most forms, in foods, drinking water, and pharmaceuticals. Exposure also occurs by inhalation of dust and aerosols, particularly in occupational settings. Absorption from the gut depends largely on pH and the presence of complexing ligands, particularly carboxylic acids, with which the metal can form absorbable neutral aluminum species. Uremic animals and humans experience higher than normal body burdens of aluminum despite increased urinary clearance of the metal. In plasma, 80-90% of aluminum binds to transferrin, an iron-transport protein for which receptors exist in many tissue. The remaining fraction of plasma aluminum takes the form of small-molecule hydroxy species and small complexes with carboxylic acids, phosphate, and, to a much lesser degree, amino acids. Most of these species have not been observed in vivo but are predicted from equilibrium models derived from potentiometric methods and NMR investigations. These models predict that the major small-molecule aluminum species under plasma conditions are charged and hence unavailable for uptake into tissues.

Intestinal perfusion of dietary levels of aluminium: association with the mucosa

An aluminium (93 microM) sulphate solution freshly adjusted to pH 7.0 was perfused through the rat small bowel to mimic the reported physiological conditions that follow dietary aluminium ingestion. One third of this aluminium was taken up from the perfusate, but > 90% of this was then recovered from the intestinal mucus/mucosa and most (> 70%) from the distal third of the small bowel. The fresh perfusate was shown by ultrafiltration to contain largely particulate/colloidal aluminium-hydroxide, and this probably adhered to intestinal mucus which may be an important barrier to the gastrointestinal absorption of aluminium.

Stable intrachain and interchain complexes of neurofilament peptides: a putative link between Al3+ and Alzheimer disease

The etiologic role of Al3+ in Alzheimer disease has been controversial. Circular dichroism (CD) spectroscopic studies on two synthetic fragments of human neurofilament protein mid-sized subunit (NF-M), NF-M13 (KSPVPKSPVEEKG) and NF-M17 (EEKGKSPVPKSPVEEKG), and their alanine-substituted and/or serine-phosphorylated derivatives were carried out in an attempt to find a molecular mechanism for the effect of Al3+ to induce aggregation of neuronal proteins or their catabolic fragments. Al3+ and Ca2+ ions were found to induce beta-pleated sheet formation in the phosphorylated fragments. The cation sensitivity depended on the length and charge distribution of the sequence and site of phosphorylation. Al3+-induced conformational changes were irreversible to citric acid chelation, whereas Ca(2+)-induced conformational changes were reversible with citric acid. Studies of the alanine derivatives demonstrated which residues affected Al3+ or Ca2+ binding. Peptides containing at least one free (nonphosphorylated) serine residue were shown to form an intramolecular Al3+ complex, rather than an intermolecular one. In the intramolecular (intrachain) complex, the ligand function of the deprotonated serine hydroxyl was delineated [(Al.pepH-1)-type complex]. Ca2+ ions did not show a tendency for intramolecular complexing. The potential role of Al3+ in Alzheimer disease tangle and plaque formation is strongly suggested.

Aluminum: a pH-dependent inhibitor of NADP-isocitrate dehydrogenase from porcine heart

Aluminum showed a pH-dependent inhibitory effect on NADP-isocitrate dehydrogenase from porcine heart. Aluminum ions (Al3+) acted as a partial competitive inhibitor of the enzyme with respect to the substrate threo-Ds-isocitrate and inhibited the enzyme non-competitively with respect to NADP at pH 6.85. Fractional velocity plot analysis showed the Ki of the enzyme for aluminum ions to be 0.88 microM. When pH was elevated to 8.0, aluminum ions, which occur as a form of the Al(OH)4- anion, acted as partial uncompetitive and non-competitive inhibitors of the enzyme with respect to the substrates isocitrate and NADP, respectively. The Kí of the enzyme was determined to be 5.64 microM at pH 8.0 by fractional velocity plot analysis. The inhibition of NADP-isocitrate dehydrogenase by two forms of aluminum ions may explain aluminum toxicity in various tissues and organs.

Aluminium transport in blood serum. Binding of aluminium by human transferrin in the presence of human albumin and citrate

The binding of Al3+ by human serum transferrin has been investigated by u.v.-visible difference spectroscopy. In the presence of 25 mM-HCO3- at pH 7.4, the apparent association constants were found to be 1.69 x 10(12) M-1 and 5.36 x 10(11) M-1. These association constants are pH-dependent, reducing with both increasing and decreasing pH. The apparent pKa values were found to be 6.7 and 8.2. Competitive assays of binding of Al3+ to transferrin in the presence of citrate and human serum albumin at molar ratios corresponding to those found in normal plasma showed that a considerable amount of Al3+ was not bound to transferrin. Taking a concentration of 5 microM as a typical value observed for the plasma of patients on haemodialysis [Harris & Sheldon (1990) Inorg. Chem. 29, 119-124] the competitive binding assay indicate that approximately 60% of it is bound to transferrin, approximately 34% to albumin and the remainder to citrate. These results therefore suggest that, although transferrin at pH 7.4 is the major Al(3+)-binding component of plasma, an appreciable amount of Al3+ present in patients on haemodialysis may be bound to albumin.

Mortality from dementia among gastroduodenal ulcer patients

STUDY OBJECTIVE

The aim was to examine whether a high intake of aluminium containing antacids is a risk for Alzheimer's disease.

DESIGN

The mortality from dementia (1970-87), coded from death certificates as underlying or contributory cause of death, was compared with national rates in a cohort of patients who had surgery for gastroduodenal ulcer disease between 1911 and 1978.

SETTING

Patient data were obtained from patient records from major hospitals in western Norway.

PARTICIPANTS

4179 patients were identified who met the study criteria, which included having had a documented stomach operation, having a reliably identifiable personal number, and being alive on Jan 1, 1970.

MEASUREMENTS AND MAIN RESULTS

The standardised mortality ratio for dementia was 1.10 (95% CI 0.85-1.40, n = 64) for all patients, while for patients operated on in the period 1967-78 it was 1.25 (95% CI 0.66-2.13, n = 13).

CONCLUSIONS

As the majority of patients operated on after 1963 have probably been heavy consumers of aluminium containing antacids, the study provides meager evidence that a high intake of aluminium is an important risk factor for Alzheimer's disease, the major cause of dementia. However, the possibility of a raised mortality from Alzheimer's disease cannot be ruled out due to probable misclassification both in diagnosis and exposure. In addition, the observation period may have been too short to detect an effect since the latent period for Alzheimer's disease may be very long.