Aluminum and Alzheimer's disease

Assessment of Histopathological Alterations and Oxidative Stress in the Liver and Kidney of Male Rats following Exposure to Aluminum Chloride

The study aims to investigate the residual and histopathological effects of chronic aluminum chloride (AlCl3) toxicity in the kidney and liver of male rats. After 30-, 60-, and 90-day exposure period, analyses were conducted to assess the toxicity in the kidney and liver. The results showed that the concentration of AlCl3 in the kidney and liver increased significantly in 30-, 60-, and 90-day periods. The effects of oxidative stress on the kidneys and liver were dose- and time-dependent. Levels of malondialdehyde (MDA) significantly increased when exposed to AlCl3 groups. Conversely, the activity of antioxidant parameters, including reduced glutathione (GSH), catalase (CAT), and superoxide dismutase (SOD), significantly decreased in the AlCl3 exposed groups, indicating compromised oxidant mechanisms. Both the kidney and liver exhibited severe tissue damage, including necrosis, fibrosis, and inflammatory cell infiltration, in rats exposed to AlCl3. Kidney sections showed hyperplasia of the epithelial cells lining the renal tubules, resembling finger-like structures. Liver sections displayed severe lobular hyperplasia and an increase in mitotic figures. Our study suggests that AlCl3 has a detrimental impact on these vital organs and emphasizes the importance of monitoring and mitigating aluminum exposure, particularly where it is present in high concentration.

Aluminium oxide nanoparticles compromise spatial memory performance and proBDNF-mediated neuronal function in the hippocampus of rats

Background

Alumina nanoparticles (aluminaNPs), which are widely used in a range of daily and medical fields, have been shown to penetrate blood-brain barrier, and distribute and accumulate in different brain areas. Although oral treatment of aluminaNPs induces hippocampus-dependent learning and memory impairments, characteristic effects and exact mechanisms have not been fully elucidated. Here, male adult rats received a single bilateral infusion of aluminaNPs (10 or 20 µg/kg of body weight) into the hippocampal region, and their behavioral performance and neural function were assessed.

Results

The results indicated that the intra-hippocampus infusions at both doses of aluminaNPs did not cause spatial learning inability but memory deficit in the water maze task. This impairment was attributed to the effects of aluminaNP on memory consolidation phase through activation of proBDNF/RhoA pathway. Inhibition of the increased proBDNF by hippocampal infusions of p75^NTR antagonist could effectively rescue the memory impairment. Incubation of aluminaNPs exaggerated GluN2B-dependent LTD induction with no effects on LTD expression in hippocampal slices. AluminaNP could also depress the amplitude of NMDA-GluN2B EPSCs. Meanwhile, increased reactive oxygen specie production was reduced by blocking proBDNF-p75^NTR pathway in the hippocampal homogenates. Furthermore, the neuronal correlate of memory behavior was drastically weakened in the aluminaNP-infused groups. The dysfunction of synaptic and neuronal could be obviously mitigated by blocking proBDNF receptor p75^NTR, implying the involvement of proBDNF signaling in aluminaNP-impaired memory process.

Conclusions

Taken together, our findings provide the first evidence that the accumulation of aluminaNPs in the hippocampus exaggeratedly activates proBDNF signaling, which leads to neural and memory impairments.

Zebrafish as a Promising Tool for Modeling Neurotoxin-Induced Alzheimer's Disease

Drug discovery and development for Alzheimer's disease (AD) are complex and challenging due to the higher failure rate in the drug development process. The overproduction and deposition of Aβ senile plaque and intracellular neurofibrillary tangle (NFT) formation are well-recognized diagnostic hallmarks of AD. Numerous transgenic models of Alzheimer's disease have restrictions on cost-effectiveness and time in the preclinical setup. Zebrafish has emerged as an excellent complementary model for neurodegenerative research due to simpler organisms with robust, clearly visible behavior forms. Glutaminergic and cholinergic pathways responsible for learning and memory are present in zebrafish and actively participate in the transmission process. Therefore, it is imperative to study neurotoxic agents' mechanisms that induce dysfunction of memory, learning, and neurons in the zebrafish. This review illustrates the in-depth molecular mechanism of several neurotoxic agents such as okadaic acid, cigarette smoke extract, and metals to produce cognitive deficits or neurodegeneration similar to mammals. These updates would determine an ideal and effective neurotoxic agent for producing AD pathophysiology in the zebrafish brain for preclinical screening.

Quercetin-Conjugated Superparamagnetic Iron Oxide Nanoparticles Protect AlCl3-Induced Neurotoxicity in a Rat Model of Alzheimer's Disease via Antioxidant Genes, APP Gene, and miRNA-101

Alzheimer's disease (AD) is a neurodegenerative disease with cognitive impairment. Oxidative stress in neurons is considered as a reason for development of AD. Antioxidant agents such as quercetin slow down AD progression, but the usage of this flavonoid has limitations because of its low bioavailability. We hypothesized that quercetin-conjugated superparamagnetic iron oxide nanoparticles (QT-SPIONs) have a better neuroprotective effect on AD than free quercetin and regulates the antioxidant, apoptotic, and APP gene, and miRNA-101. In this study, male Wistar rats were subjected to AlCl3, AlCl3 + QT, AlCl3 + SPION, and AlCl3 + QT-SPION for 42 consecutive days. Behavioral tests and qPCR were used to evaluate the efficiency of treatments. Results of behavioral tests revealed that the intensity of cognitive impairment was decelerated at both the middle and end of the treatment period. The effect of QT-SPIONs on learning and memory deficits were closely similar to the control group. The increase in expression levels of APP gene and the decrease in mir101 led to the development of AD symptoms in rats treated with AlCl3 while these results were reversed in the AlCl3 + QT-SPIONs group. This group showed similar results with the control group. QT-SPION also decreased the expression levels of antioxidant enzymes along with increases in expression levels of anti-apoptotic genes. Accordingly, the antioxidant effect of QT-SPION inhibited progression of cognitive impairment via sustaining the balance of antioxidant enzymes in the hippocampus of AD model rats.

Characterization of the binding mechanism and conformational changes of bovine serum albumin upon interaction with aluminum-maltol: a spectroscopic and molecular docking study

The widespread use of aluminum in the treatment of drinking water, food, agriculture and pharmaceuticals has greatly increased the risk of human exposure to excess aluminum, which is a serious health hazard to human beings.

Elevated heavy metals levels in cognitively impaired patients from Pakistan

The deficit in the visuospatial skills, thinking, learning and memory is termed as cognitive impairment. Human exposure to heavy metals is a potential risk factor for developing cognitive impairment. This study aimed to investigate the possible association between the concentration of heavy metals and the extent of cognitive impairment. Blood samples were subjected to microwave assisted acid digestion and evaluated for metals levels using atomic absorption spectrophotometry. We measured the levels of Cu, Pb, Al, Zn, Cd and Mn in 183 patients diagnosed with cognitive impairment; mild (n = 72), moderate (n = 86) and severe (n = 25) and compared them to age-matched healthy controls (n = 90). Results showed that all the aforementioned elements were significantly higher in cognitively impaired patients and increasing concentration was strongly correlated with increase in severity of the disease. The correlation study has shown that among the studied metals, Al and Cu are strongly associated with the cognitive impairment. This suggests the need for decrease in metal exposure to humans from environment, food and industries.

Development of biodegradable Zn-1X binary alloys with nutrient alloying elements Mg, Ca and Sr

Biodegradable metals have attracted considerable attentions in recent years. Besides the early launched biodegradable Mg and Fe metals, Zn, an essential element with osteogenic potential of human body, is regarded and studied as a new kind of potential biodegradable metal quite recently. Unfortunately, pure Zn is soft, brittle and has low mechanical strength in the practice, which needs further improvement in order to meet the clinical requirements. On the other hand, the widely used industrial Zn-based alloys usually contain biotoxic elements (for instance, ZA series contain toxic Al elements up to 40 wt.%), which subsequently bring up biosafety concerns. In the present work, novel Zn-1X binary alloys, with the addition of nutrition elements Mg, Ca and Sr were designed (cast, rolled and extruded Zn-1Mg, Zn-1Ca and Zn-1Sr). Their microstructure and mechanical property, degradation and in vitro and in vivo biocompatibility were studied systematically. The results demonstrated that the Zn-1X (Mg, Ca and Sr) alloys have profoundly modified the mechanical properties and biocompatibility of pure Zn. Zn-1X (Mg, Ca and Sr) alloys showed great potential for use in a new generation of biodegradable implants, opening up a new avenue in the area of biodegradable metals.

Effects of the aluminium speciation on the morphology of rabbit erythrocytes: a toxicological model

The great majority of papers dealing with aluminium (Al) experimental toxicology in vivo and/or in vitro, do not consider the relevance of the metal chemical speciation as a conditio sine qua non to a correct interpretation of aluminium toxicological data. In fact, different aluminium compounds such as salts, stable, metastable, lipophilic or hydrophilic complexes with different thermodynamics and kinetics properties are indifferently utilized by most laboratories. In this connection, the molecular bases that explain Al toxicity are largely uninterpretable. The aim of this study, therefore, is to demonstrate how relevant is the issue of aluminium speciation to the understanding of the toxic properties of the metal ion. In our experimentation we used, as a heuristic model, rabbit erythrocytes (RBC) (Sheetz and Singer, 1974), because these animals are well known for their sensitivity to Al intoxication (Wisniewski and Sturman, 1989). Results reported herein show how the metal chemical speciation can paradigmatically modify the RBC morphology in a metal speciation-dependent manner. Finally, a new toxicological protocol that, by simplifying the methodology of aluminium solution preparation, could standardize the study of aluminium toxicity is also proposed.

A series of transition and non-transition metal complexes from a N₄O₂ hexadentate Schiff base ligand: Synthesis, spectroscopic characterization and efficient antimicrobial activities

Some transition and non-transition metal complexes of the hexadentate N₄O₂ donor Schiff base ligand 1,8-N-bis(3-carboxy)disalicylidene-3,6-diazaoctane-1,8-diamine, abbreviated to H₄fsatrien, have been synthesized. All the 14 metal complexes have been fully characterized with the help of elemental analyses, molecular weights, molar conductance values, magnetic moments and spectroscopic (UV-Vis, IR, NMR, ESR) data. The analytical data helped to elucidate the structures of the metal complexes. The Schiff base, H₄fsatrien, is found to act as a dibasic hexadentate ligand using N₂N₂O₂ donor set of atoms (leaving the COOH group uncoordinated) leading to an octahedral geometry for the complexes around all the metal ions except VO²(+) and UO₂²(+). However, surprisingly the same ligand functions as a neutral hexadentate and neutral tetradentate one towards UO₂²(+) and VO²(+), respectively. In case of divalent metal complexes they have the general formula [M(H₂fsatrien)] (where M stands for Cu, Co, Hg and Zn); for trivalent metal complexes it is [M(H₂fsatrien)]X·nH₂O (where M stands for Cr, Mn, Fe, Co and X stands for CH₃COO, Cl, NO₃, ClO₄) and for the complexes of VO²(+) and UO₂²(+), [M(H₄fsatrien)]Y (where M=VO and Y=SO₄); M=UO₂ and Y=2 NO₃). The Schiff base ligand and most of the complexes have been screened in vitro to judge their antibacterial (Escherichia coli and Staphylococcus aureus) and antifungal (Aspergillus niger and Pencillium chrysogenum) activities.

Neurotoxic effects of dietary aluminium

Neurochemical responses to chronic oral aluminium administration have been studied in rats. Aluminium (0.3%) was added to drinking water of adult rats for four weeks or longer and weanling rats were given aluminium for eight weeks. Selective cognitive impairment was demonstrated in the adult rats. Aluminium inhibited calcium flux and phosphoinositide metabolism, one product of which (inositol 1,4,5-trisphosphate) modulates intracellular calcium levels. In weanling rats aluminium decreased the in vivo concentration of inositol 1,4,5-trisphosphate in the hippocampus. An increase in cyclic AMP concentrations by 30-70% in various brain regions in adult and weanling rats was found. Aluminium enhanced agonist-stimulated but not basal cyclic AMP production in vitro. It was postulated that aluminium inhibits the GTPase activity of the stimulatory G protein, Gs, leading to prolonged activation of Gs after receptor stimulation and increased cyclic AMP production. Aluminium treatment also increased the phosphorylation of microtubule-associated protein 2 (MAP-2) and the 200 kDa neurofilament protein (NF-H) but several other phosphoproteins were unaffected. Concentrations of seven structural proteins--MAP-2, tau, NF-H, NF-M (150 kDa), NF-L (68 kDa), tubulin and spectrin--were measured in rat brain regions by immunoblot methods. MAP-2 was most consistently decreased. These studies show that chronic oral aluminium administration to rats has significant neurochemical consequences. Three sites of action are implicated: altered calcium homeostasis, enhanced cyclic AMP production, and changes in cytoskeletal protein phosphorylation states and concentrations.

Aluminium and the pathogenesis of Alzheimer's disease: a summary of evidence

Known risk factors for Alzheimer's disease (AD) are few and insufficient knowledge is available to recommend steps to reduce AD in our ageing populations. Although not 'the cause', considerable evidence implicates human ingestion of aluminium as a possible risk factor for the expression of dementia of the Alzheimer type. A recent epidemiological study in Ontario relating the incidence of AD to aluminium in drinking water strongly supports this conclusion. To test further the hypothesis that aluminium may play a role in the pathogenesis of AD we conducted a clinical trial employing the trivalent metal ion binding compound, desferrioxamine. The design was a two-year randomized trial with behavioural assessments blinded to study assignment. Sixty-three patients with probable AD were selected who were living at home and were under 74 years. Forty-eight signed an informed consent and completed all initial testing. The main outcome measure was a video-recorded home-behavioural assessment of measures of skills of daily living. The principal outcome was that the mean slope for performance of the skills of daily living for the group without treatment was -1.72% maximum score/month, compared to -0.87% maximum score/month for the group treated with desferrioxamine (P = 0.038). Considerable evidence supports the hypothesis that aluminium has an active role in the pathogenesis of AD.

Prooxidant Action of Maltol: Role of Transition Metals in the Generation of Reactive Oxygen Species and Enhanced Formation of 8-hydroxy-2′-deoxyguanosine Formation in DNA

Maltol (3-hydroxy-2-methyl-4-pyrone) produced reactive oxygen species as a complex with transition metals. Maltol/iron complex inactivated aconitase the most sensitive enzyme to oxidative stress. The inactivation of aconitase was iron-dependent, and prevented by TEMPOL, a scavenger of reactive oxygen species, suggesting that the maltol/iron-mediated generation of superoxide anion is responsible for the inactivation of aconitase. Addition of maltol effectively enhanced the ascorbate/copper-mediated formation of 8-hydroxy-2'-deoxyguanosine in DNA. Oxidation of ascorbic acid by CuSO(4) was effectively stimulated by addition of maltol, and the enhanced oxidation rate was markedly inhibited by the addition of catalase and superoxide dismutase. These results suggest that maltol can stimulate the copper reduction coupled with the oxidation of ascorbate, resulting in the production of superoxide radical which in turn converts to hydrogen peroxide and hydroxyl radical. Cytotoxic effect of maltol can be explained by its prooxidant properties: maltol/transition metal complex generates reactive oxygen species causing the inactivation of aconitase and the production of hydroxyl radical causing the formation of DNA base adduct.

Microdermabrasion

BACKGROUND

Microdermabrasion has become one of the most popular forms of superficial resurfacing. The benefits and efficacy of microdermabrasion remain an intensely debated topic among dermatologic surgeons.

OBJECTIVE

This article reviews the efficacy, safety, epidermal barrier function, histopathologic effects, complications, advantages, and disadvantages of microdermabrasion.

CONCLUSION

In general, microdermabrasion studies have been conducted in small groups of patients. Protocols, units, and settings have differed. There remains a major disparity between the popularity of microdermabrasion in the public sector and cohesive and comprehensive scientific data documenting the efficacy of the procedure.

Microdermabrasion

Microdermabrasion is a simple, safe, office cosmetic procedure in which aluminum oxide crystals or other abrasive substances are blown onto the face, then vacuumed off, using a single handpiece. This procedure has rapidly become widely utilized for a variety of cosmetic objectives, including the improvement of photoaging, hyperpigmentation, acne, scars and stretch marks. Despite its widespread use, little is known about its actual mechanism of action. The few published studies suggest that patients and physicians alike report a mild benefit when microdermabrasion is utilized for photoaging. Histologic evaluation reveals little actual abrasion of the skin with the procedure, yet changes are seen in the dermis. Given the safety, simplicity and patient satisfaction associated with microdermabrasion, it is likely to remain a popular treatment.

Quantitative proteomic analysis of mitochondria from primary neuron cultures treated with amyloid beta peptide

Increasing evidence supports a role for altered mitochondrial function in the pathogenesis of neuron degeneration in Alzheimer's disease (AD). Although several studies have examined the effect of amyloid beta peptide (Abeta), on activities of individual proteins in primary neuron cultures, there have been no studies of the effects of Abeta on the mitochondrial proteome. Here, we quantitatively measured changes in mitochondrial proteins of primary rat cortical neuron cultures exposed to 25 microM Abeta(25-35) for 16 h using isotope coded affinity tag (ICAT) labeling and 2-dimensional liquid chromatography/tandem mass spectrometry (2D-LC/MS/MS) which allows simultaneous identification and quantification of cysteine-containing proteins. The analysis of enriched mitochondrial fractions identified 10 proteins including sodium/potassium-transporting ATPase, cofilin, dihydropyrimidinase, pyruvate kinase and voltage dependent anion channel 1 that were statistically significantly (P < 0.05) altered in Abeta-treated cultures. Elevations of proteins associated with energy production suggest that cells undergoing Abeta-mediated apoptosis increase synthesis of proteins essential for ATP production and efflux in an attempt to maintain metabolic function.

Aluminum maltolate-induced toxicity in NT2 cells occurs through apoptosis and includes cytochrome c release

Aluminum (Al) compounds are neurotoxic and have been shown to induce experimental neurodegeneration although the mechanism of this effect is unclear. In order to study this neurotoxic effect of Al, we have developed an in vitro model system using Al maltolate and human NT2 cells. Al maltolate at 500 microM caused significant cell death with a 24-h incubation and this toxicity was even more evident after 48 h. Lower doses of Al maltolate were also effective, but required a longer incubation for cell death. Nuclear fragmentation suggestive of apoptosis was observed as early as three hours and increased substantially through 24 h. Chromatin condensation and nuclear fragmentation were confirmed by electron microscopy. In addition, TUNEL positive nuclei were also observed. The release of cytochrome c was demonstrated with Western blot analysis. This in vitro model using human cells adds to our understanding of Al neurotoxicity and could provide insight into the neurodegenerative processes in human disease.

Radio frequency chaff: the effects of its use in training on the environment

Chaff is a radiofrequency countermeasure released by military aircraft, ships, and vehicles to confuse enemy radar. Chaff consists of aluminum-coated glass fibers ranging in lengths from 0.8 to 0.75 cm and is released in packets of 0.5 to 100 million fibers. The Department of Defense has determined that use of chaff in training is required for maintaining proficiency in the use of this countermeasure. At least 500 tons of chaff is released annually during training within selected military operating areas in the United States. Concerns have been raised about impact on the environment and its potential toxicity to humans, livestock, and wildlife. Many of these concerns have been addressed or are being researched by the Department of Defense and other agencies, but much of the data are unpublished. Herein, the authors summarize the issues and review scientific data for the impact of chaff use on humans, animals, and the environment.

Effect of Navy chaff release on aluminum levels in an area of the Chesapeake Bay

The U.S. Navy uses aluminized glass chaff as a passive countermeasure for radar-guided threats to aircraft and surface ships. Over the last 25 years, several hundred thousand pounds of aluminized chaff have been released during flight operations over a training area on the Chesapeake Bay. There is concern that these releases have resulted in the accumulation of significant amounts of aluminum in the soil and sediment of this training area. This study compares the exchangeable and monomeric aluminum content of sediment within the affected area with that of samples taken from outside the training area. We found a less than twofold increase in the content of organic monomeric aluminum in samples taken from the affected area versus background samples, whereas inorganic monomeric aluminum concentrations within the affected area were significantly lower than background. These results suggest that chaff releases have not resulted in a significant accumulation of aluminum in this training area.

Aluminum exposure: a study of an effect on cellular growth rate

Aluminum effects on cultured human brain cells were examined. Human brain cells (neuroblastoma IMR-32) were cultured to examine possible effects of soluble aluminum at a cellular level. The cellular growth rate was measured by counting the number of cells with a hemocytometer under an optical microscope over a period of time. No significant change in cell growth was found during a three-week exposure period to aluminum at concentrations from 0.1 to 10 mg/l. However, after 3 weeks Al started to reduce the growth rate relative to the control, and the decrease became more pronounced as the exposure period to aluminum increased. The effect was greatest at the higher Al-concentration.

Microdermabrasion: a clinical and histopathologic study

BACKGROUND

Microdermabrasion is a widely performed skin rejuvenation procedure. Few studies have examined its efficacy.

OBJECTIVE

To evaluate the clinical and histopathologic effects of microdermabrasion.

METHODS

Fourteen patients underwent microdermabrasion treatments over 12-14 weeks. Self-rated questionnaires were given before and after the treatment series and were evaluated by a paired t-test. Three of the 14 patients were treated for moderate to severe acne scarring. Acute histologic effects were assessed ex vivo on human abdominal skin. Chronic histopathologic effects were examined in three volunteers who underwent skin biopsies before and after a treatment series on the dorsal forearms.

RESULTS

By patient assessment, there was statistically significant improvement in roughness, mottled pigmentation, and overall improvement of skin appearance, but not in rhytides. Acne scarring sometimes improved, but required deeper ablation. Acutely the stratum corneum was homogenized and focally compacted. Chronically there was epidermal hyperplasia, decreased melanization, and some increase in elastin.

CONCLUSION

Microdermabrasion improves some aspects of photoaging and select cases of acne scarring.

Alzheimer disease: current therapy and future therapeutic strategies

Antidementia drugs can be defined as drugs that significantly improve the decreased cognitive functions and/or inhibit the progression of dementia, compared with placebo. The main target of antidementia drugs is Alzheimer disease (AD), and the advent of such drugs is ardently desired. Antidementia drugs that are currently in use or undergoing trial are briefly reviewed. To date, only a few acetylcholine esterase inhibitors have been licensed as antidementia drugs for AD, but more beneficial drugs are being actively sought by many different approaches. The development of additional drugs requires greater basic research on the pathogenesis of AD. Future therapeutic strategies for AD on the basis of recent findings concerning the pathogenesis of AD are also reviewed.

Microbes and sequestered substances as mechanisms for disease: Bartonella and L-forms as common global etiological agents

The pathogenicity of microbes may be determined by substances sequestered from blood and bound to their constituent lipid. The brain may not perceive substances sequestered by microbes, to interfere with control to maintain normal levels. Pathological conditions can be induced as organisms exposed to antimicrobial substances/conditions and/or deprived of nutrients essential to cell wall synthesis, disintegrate to free lipid-bound compounds and produce L-forms that can deplete nutrients as they revert to bacteria. Microbes may act as active carriers for the continuing interaction of sequestered substances. Changes in the molecular structure of substances effected during sequesteration could cause them to be seen as substances 'synthesized' by an organism. In media that contain substances to inhibit 'contaminants', L-forms can be seen as mycoplasma. Elementary bodies of L-forms with a specific substance or tissue affinity may be seen as 'receptors'. Bartonella are global agents for disease--pleomorphic organisms (description suits Proteus)--and they can be seen as 'contaminants'.

Phosphorylation sensitizes microtubule-associated protein tau to Al(3+)-induced aggregation

In Alzheimer's disease the microtubule-associated protein tau becomes hyperphosphorylated and aggregates into paired helical filaments (PHFs). Although the biochemical basis of the aggregation of tau into PHFs is not very clear, Al3+ has been suggested to play some role. Previous studies have shown that Al3+ alters the phosphorylation state and causes aggregation of tau in experimental animals and cultured neurons. In this study Al3+ inhibited phosphorylation of tau by neuronal cdc2-like kinase and dephosphorylation of phosphorylated tau by phosphatase 2B. These inhibitions are very likely due to Al(3+)-induced aggregations of various proteins present in phosphorylation/dephosphorylation assay mixtures since Al3+ caused aggregations of all proteins examined. Furthermore, compared to other proteins, tau displayed only an average sensitivity towards Al(3+)-induced aggregation. However upon phosphorylation, tau's sensitivity towards Al3+ increased 3.5 fold. In the presence of the metal chelator EDTA, Al(3+)-induced aggregates of tau became soluble, whereas Al(3+)-induced phosphorylated tau aggregates were insoluble in the buffer containing EDTA and remained insensitive to proteolysis. Our data suggest that phosphorylation sensitizes tau to Al3+ and phosphorylated tau transforms irreversibly into a phosphatase and protease resistant aggregate in presence of this metal ion.

Pulse exposure of cultured rat neurons to aluminum-maltol affected the axonal transport system

Although chronic aluminum neurotoxicity has been well established, the mechanism of the toxicity has not been elucidated yet. In order to simplify the study of the aluminum neurotoxicity, we employed the pulse exposure of cultured rat cortical neurons to 250 microM aluminum-maltol for 1 h at the early stage (6 h after plating), which resulted in abnormal distribution of neurofilament L (NFL) and fast axonal transported proteins, whereas the axonal transport of tubulin, actin, and clathrin were not impaired. Otherwise, the pulse exposure of neurons at the late stage (4 days after plating) to the same concentration of aluminum-maltol did not affect the cell morphology and the distribution of NFL. The pulse exposure of cultured neurons to aluminum-maltol at the early stage might affect the axonal transport system of NFL and fast axonal transported proteins.

Effect of aluminum on iron-induced lipid peroxidation and protein oxidative modification of mouse brain homogenate

In the present study the authors report on the enhancing effect of aluminum(III) (Al[III]) on iron(II)(Fe[II])-induced lipid peroxidation (LPO) of mice brain homogenate, which occurs in a concentration- and time-dependent manner. No evidence of LPO caused by Al alone was found. Both Al(III) and Fe(II) ions induced protein oxidative modifications in mice brain homogenate, in a time- and concentration-dependent manner. Aluminum enhances Fe(II)-induced protein oxidative modification at a concentration of 2:1 and 1:1 Al:Fe molar ratios. However, Al suppress Fe(II)-induced protein oxidative modification at a concentration of 0.5:1 Al:Fe molar ratio. Addition of ethylenediaminetetraacetic acid (EDTA) inhibits both LPO and protein oxidative modifications induced by Al(III) and Fe(II) ions. Addition of mannitol and of superoxide dismutase (SOD) did not show such effects. It is concluded that in mice brain homogenate, Al accelerates Fe(II)-induced LPO. Protein oxidative modifications caused by Fe(II) and/or Al ions are enhanced at high, but suppressed at low concentrations of Al ions. The latter observation suggests a possible biological role of Al as an antioxidant.

Alzheimer's disease and the aluminium connection: A literature review

This review explores the different areas of research that, over the past 35 years, have provided grounds for linking Alzheimer's disease and aluminium. However, in spite of the growing evidence, exposure to aluminium as a risk factor is yet to be confirmed. The evidence is discussed under four headings: evidence from brain aluminium studies; evidence from aluminium uptake studies; evidence from aluminium-related neurodegenerative conditions; and evidence from chronic aluminium exposure studies: aluminium in drinking water, and by occupational exposure.

27Al-NMR studies of aluminum transport across yeast cell membranes

Aluminum (Al) transport across yeast cells was studied using Dy(NO3)3 as a shift reagent by 27Al-NMR spectroscopy. The results showed that (a) Al enters the yeast cells at 15 min and over a period of time, within 4 h, an equilibrium sets in between outside and inside Al; (b) citrate does not favor Al going into the yeast cells at pH 5.0; and (c) EDTA brings out all the Al that has entered the yeast cells.

Aluminum inhibits neurofilament assembly, cytoskeletal incorporation, and axonal transport. Dynamic nature of aluminum-induced perikaryal neurofilament accumulations as revealed by subunit turnover

The mechanism by which aluminum induces formation of perikaryal neurofilament (NF) inclusions remains unclear. Aluminum treatment inhibits: 1. The incorporation of newly synthesized NF subunits into Triton-insoluble cytoskeleton of axonal neurites; 2. Their degradation and dephosphorylation; 3. Their translocation into axonal neurites. It also fosters the accumulation of phosphorylated NFs within perikarya. In the present study, we addressed the relationship among these effects. Aluminum reduced the assembly of newly synthesized NF subunits into NFs. During examination of those subunits that did assemble in the presence of aluminum, it was revealed that aluminum also interfered with transport of newly assembled NFs into axonal neurites. Similarly, a delay in axonal transport of microinjected biotinylated NF-H was observed in aluminum-treated cells. Aluminum also inhibited the incorporation of newly synthesized and microinjected subunits into the Triton-insoluble cytoskeleton within both perikarya and neurites. Once incorporated into Triton-insoluble cytoskeletons, however, biotinylated subunits were retained within perikarya of aluminum-treated cells to a greater extent than within untreated cells. Notably, these subunits were depleted in the presence and absence of aluminum within 48 h, despite the persistence of the aluminum-induced perikaryal accumulation itself, suggesting that individual NF subunits undergo turnover even within aluminum-induced perikaryal accumulations. These findings demonstrate that aluminum interferes with multiple aspects of neurofilament dynamics and furthermore leaves open the possibility that aluminum-induced perikaryal NF whorls may not represent permanent structures, but rather may require continued recruitment of cytoskeletal constituents.

Are aluminium potroom workers at increased risk of neurological disorders?

OBJECTIVE

To determine whether long term potroom workers in an aluminium smelter are at increased risk of neurological disorders.

METHODS

Cross sectional study of 63 current and former aluminium potroom workers first employed before 1970 and with at least 10 years of service. A group of 37 cast house and carbon plant workers with similar durations of employment and starting dates in the same smelter were used as controls. The prevalence of neurological symptoms was ascertained by questionnaire. Objective tests of tremor in both upper and lower limbs, postural stability, reaction time, and vocabulary were conducted. All subjects were examined by a neurologist.

RESULTS

No significant differences in age, race, or education were found between the two groups. Although the potroom group had higher prevalences for all but one of the neurological symptoms, only three odds ratios (ORs) were significantly increased; for incoordination (OR 10.6), difficulty buttoning (OR 6.2), and depression (OR 6.2). Tests of arm or hand and leg tremor in both the visible and non-visible frequencies did not show any significant differences between the two groups. Testing of postural stability showed no definitive pattern of neurologically meaningful differences between the groups. There were no significant differences between the two groups in reaction time, vocabulary score, or clinical neurological assessment.

CONCLUSIONS

The objective measures of neurological function provided little support for the finding of increased neurological symptom prevalences in the potroom workers, although increased symptoms may be an indicator of early, subtle neurological changes. The results provide no firm basis for concluding that neurological effects among long term potroom workers are related to the working environment, in particular aluminium exposure, in potrooms. These findings should be treated with caution due to the low participation of former workers and the possibility of information bias in the potroom group.

Aluminum (III) induces alterations on the physical state of the erythrocytic membrane: an ESR evaluation

The action of aluminum [Al(III)] as Al(acac)3 on erythrocytes causes biophysical effects such as osmotic fragility and echino-acanthocytes formation. In this paper, we present these effects in terms of variation of membrane fluidity, together with findings regarding conformational modifications of membrane proteins consequent to Al(III) exposure, as well as the effects on the mobility of the membrane protein bound sialic acid. To this end, we utilized ESR measurements of rabbits and humans erythrocytic ghosts after probing or labeling with suitable stable radicals used as spin probes or labels. Our results show that the lipophilic, hydrolytically stable toxicant Al(acac)3 causes a remarkable reduction of membrane fluidity in rabbit erythrocytes, an appreciable structural compacting effect on cytoskeletal and transmembrane proteins, as well as a reduction of rotational mobility of cell-surface sialic acid of human erythrocytes.

Purification of human brain metallothionein by organic and reversed-phase high-performance liquid chromatography under acidic conditions

A simplified high-performance liquid chromatographic method for the detection of metallothioneins, notably metallothionein-III, has been developed. In order to purify metallothionein, differential acetone precipitation at 50% (v/v) and at 80% (v/v) was employed on a 20% normal human brain homogenate. The reconstituted pellet was injected into a C18 microbore reversed-phase HPLC column, equilibrated with 0.1% trifluoroacetic acid, and developed at a flow-rate of 800 microliter/min with a linear gradient from 0% to 60% acetonitrile in 0.094% trifluoroacetic acid for 60 min. Western blots indicated that metallothioneins-I and II eluted at 16% acetonitrile and metallothionein-III eluted at 37% acetonitrile.