Defective gallium-transferrin binding in Alzheimer disease and Down syndrome: possible mechanism for accumulation of aluminium in brain

Osteogenesis and angiogenesis of a bulk metallic glass for biomedical implants

Implantation is an essential issue in orthopedic surgery. Bulk metallic glasses (BMGs), as a kind of novel materials, attract lots of attentions in biological field owing to their comprehensive excellent properties. Here, we show that a Zr61Ti2Cu25Al12 (at. %) BMG (Zr-based BMG) displays the best cytocompatibility, pronounced positive effects on cellular migration, and tube formation from in-vitro tests as compared to those of commercial-pure titanium and poly-ether-ether-ketone. The in-vivo micro-CT and histological evaluation demonstrate the Zr-based BMG can significantly promote a bone formation. Immunofluorescence tests and digital reconstructed radiographs manifest a stimulated effect on early blood vessel formation from the Zr-based BMG. Accordingly, the intimate connection and coupling effect between angiogenesis and osteogenesis must be effective during bone regeneration after implanting Zr-based BMG. Dynamic gait analysis in rats after implanting Zr-based BMG demonstrates a tendency to decrease the pain level during recovery, simultaneously, without abnormal ionic accumulation and inflammatory reactions. Considering suitable mechanical properties, we provide a realistic candidate of the Zr61Ti2Cu25Al12 BMG for biomedical applications.

Hair Mineral and Trace Element Content in Children with Down's Syndrome

The objective of the present study was to assess the level of minerals and trace elements in 40 children with Down's syndrome and 40 controls aged 1-2 years old. Hair mineral and trace element analysis was performed using inductively coupled plasma mass spectrometry. The obtained data demonstrate that hair levels of Mg, P, I, Cr, Si, Zn, and Pb in Down's syndrome patients exceeded the respective control values by 36, 36, 93, 57, 45, 28, and 54%, whereas hair mercury was more than twofold lower in children with Down's syndrome. The observed difference in the levels of trace elements was age-dependent. In particular, in 1-year-olds, major differences were observed for essential elements (Cr, Si, Zn), whereas in 2-year-olds-for toxic elements (Hg, Pb). At the same time, hair P levels in Down's syndrome patients were 14 and 35% higher at the age of 1 and 2 years in comparison to the respective controls. Multiple regression analysis demonstrated that a model incorporating all elements, being characterized by a significant group difference, accounted for 42.5% of status variability. At the same time, only hair phosphorus was significantly interrelated with Down's syndrome status (β = 0.478; p < 0.001). Principal component analysis (PCA) used As, Ca, Cr, Fe, Hg, I, Mg, P, Pb, Se, Si, Sn, and Zn as predictors, with the resulting R² = 0.559. The OPLS-DA models also separated between Down's and health control groups. Therefore, 1-2-year-old patients with Down's syndrome are characterized by significant alterations of mineral and trace element status.

Entry and Deposit of Aluminum in the Brain

Aluminum, as a known neurotoxicant, contributes to cognitive dysfunction and may contribute to Alzheimer's disease. The important reason is that aluminum can enter and be deposited in the brain. There have been three routes by which aluminum could enter the brain from systemic circulation or the site of absorption. Aluminum fluxes into brain across the blood-brain barrier (BBB), the choroid plexuses and the nasal cavity. Some factors, such as the increasing of the blood-brain barrier permeability, citric acid and parathyroid hormone (PTH), and vitamin D, can promote aluminum to enter the brain. But the redistribution of aluminum out of the brain is slow, so aluminum can be deposited in the brain for a long time.

Metals and neurodegenerative diseases. A systematic review

Neurodegenerative processes encompass a large variety of diseases with different pathological patterns and clinical presentation such as Amyotrophic Lateral Sclerosis (ALS), Alzheimer Disease (AD) and Parkinson's disease (PD). Genetic mutations have a known causative role, but the majority of cases are likely to be probably caused by a complex gene-environment interaction. Exposure to metals has been hypothesized to increase oxidative stress in brain cells leading to cell death and neurodegeneration. Neurotoxicity of metals has been demonstrated by several in vitro and in vivo experimental studies and it is likely that each metal could be toxic through specific pathways. The possible pathogenic role of different metals has been supported by some epidemiological evidences coming from occupational and ecological studies. In order to assess the possible association between metals and neurodegenerative disorders, several case-control studies have also been carried out evaluating the metals concentration in different biological specimens such as blood/serum/plasma, cerebrospinal fluid (CSF), nail and hair, often reporting conflicting results. This review provides an overview of our current knowledge on the possible association between metals and ALS, AD and PD as main neurodegenerative disorders.

Applications of vitamin B6 cofactor pyridoxal 5'-phosphate and pyridoxal 5'-phosphate crowned gold nanoparticles for optical sensing of metal ions

Vitamin B6 cofactor pyridoxal 5'-phosphate (PLP) and PLP crowned gold nanoparticles (PLP-AuNPs) was applied for the optical chemosensing of metal ions in aqueous medium. PLP showed a visually detectable colour change from colourless to yellow and 'turn-off' fluorescence in the presence of Fe³⁺. The fluorescence intensity of PLP at 433nm was also blue-shifted and enhanced at 395nm upon addition of Al³⁺. When the PLP was functionalized over AuNPs surface, the wine red colour of PLP-AuNPs was turned to purplish-blue and the SPR band at ~525nm was red-shifted upon addition of Al³⁺, Cd²⁺ and Pb²⁺ due to the complexation-induced aggregation of nanoparticles. The developed sensing systems exhibited good selectivity and specificity for the detected analytes (Fe³⁺, Al³⁺, Cd²⁺ and Pb²⁺).

Role of metal ions in the cognitive decline of Down syndrome

Down syndrome (DS), caused by trisomy of whole or part of chromosome 21 is the most common mental impairment. All people with DS suffer from cognitive decline and develop Alzheimer’s disease (AD) by the age of 40. The appearance of enlarged early endosomes, followed by Amyloid βpeptide deposition, the appearance of tau-containing neurofibrillary tangles and basal forebrain cholinergic neuron (BFCN) degeneration are the neuropathological characteristics of this disease. In this review we will examine the role of metal ion dyshomeostasis and the genes which may be involved in these processes, and relate these back to the manifestation of age-dependent cognitive decline in DS.

Geochemical Risk Factors for Mental Functioning, Based on the Ontario Longitudinal Study of Aging (LSA) VI. The Effects of Iron on the Associations of Aluminum and Fluoride Water Concentrations and of pH with Mental Functioning, Based on Results Obtained from the LSA and from Death Certificates Mentioning Dementia

Des articles précédents dans la même série ont établi un lien positif entre les concentrations d'aluminium dans l'eau et une mesure de la déficience intellectuelle, ainsi qu'une association négative entre les concentrations de fluorure et la même mesure de la déficience intellectuelle. Les résultats obtenus étaient similaires, qualitativement, aux associations correspondantes établies à partir des données des certificats de décés sur lesquels la maladie d'Alzheimer figurait comme cause antécédente du décés. Les résultats étaient également similaires, du point de vue qualitatif, à ceux obtenus dans le cadre d'un certain nombre d'autres études réalisées à des périodes différentes, des endroits différents et un utilisant différents indicateurs de résultat comme mesure de la déficience intellectuelle. La présente étude examine le rôle de la concentration de fer et, plus précisément, tente de déterminer si les associations mentionnées précédement en regard de l'aluminium persistent lorsqu'on tient compte des concentrations de fer. Les résultats montrent qu'il semble en être ainsi et ils laissent croire également que le fer peut faire concurrence avec l'aluminium et qu'ils peuvent tous deux augmenter ou réduire la vraisemblance de présenter des signes de déficience intellectuelle. Les résultats ne montrent pas, de façon systématique, que léeau traitée sera moins biotoxique si les méthodes de purification étaient modifiées de manière a utiliser du fer plutôt que de l'aluminium; il pourrait toute fois y avoir des cas, en particulier lorsque les concentrations en aluminium sont relativement élevées, où l'utilisation de composés de fer est bénéfique.

Gold nanoparticle-based colorimetric assay for selective detection of aluminium cation on living cellular surfaces

A colorimetric assay based on pentapeptide (CALNN) functionalized gold nanoparticles exhibits high sensitivity and selectivity for detection of aluminium cation (Al(3+)) both in aqueous solution and on living cellular surfaces under physiological condition.

Progressive leukoencephalopathy associated with aluminum deposits in myelin sheath

A 20-year-old woman with progressive leukoencephalopathy developed mental and motor disabilities and fell into a coma after suffering head trauma and febrile episodes from infancy. Brain imaging showed massive abnormal signals in the white matter. The electron spectroscopic imaging of biopsied brain tissue confirmed the electron-dense deposits to be associated with aluminum accumulation in the myelin sheath. Her brain pathology, which showed ferritin- and naphtochrome green-positive deposits, supported the imaging analysis. The clinicopathological features indicate a new form of progressive leukoencephalopathy.

Iron out-of-balance: a risk factor for acute and chronic diseases

The numerous acute and chronic diseases associated with excessive/misplaced iron are categorized in this review in the following sections: 1) iron, by itself, can initiate the disease; 2) iron can be a cofactor in promoting the disease; 3) iron deposits are observed in disease-associated tissue sites; 4) body iron loading is associated with above normal incidence of the disease; and 5) maternal antibodies can impair fetal iron metabolism. Also discussed is the anomalous condition in which persons whose macrophages are low in iron are resistant to microbial pathogens that require iron loaded macrophages for in vivo growth. Thus, hemochromatotic mutations have apparently had survival value during outbreaks of tuberculosis, plague and typhoid fever.

Aluminium accumulation, beta-amyloid deposition and neurofibrillary changes in the central nervous system

Deposition of beta-amyloid and the formation of neurofibrillary tangles (NFTs) are central to the aetiopathogenesis of Alzheimer's disease (AD). The possible effects of aluminium on these processes have been investigated in patients with renal failure who are exposed chronically to high blood levels of aluminium. Focal accumulation of aluminium was observed in neurons with high densities of transferrin receptors, indicating transferrin-mediated uptake, in regions such as cortex and hippocampus which are selectively vulnerable in AD. Increased staining for the beta-amyloid precursor protein (APP) in cortical pyramidal neurons was evident in the majority of renal patients and immature senile plaques were present in 30% of cases, suggesting that aluminium may induce or accelerate beta-amyloid deposition. The absence of neurofibrillary changes in this group of renal patients indicates that aluminium does not directly cause the formation of NFTs. The brain aluminium content was not raised in neuropathologically assessed cases of AD and we have been unable to confirm claims of defective transferrin binding in this disorder. If aluminium contributes to the development of sporadic AD, it must do so indirectly, perhaps via effects on the synthesis or metabolism of APP, or by contributing generally to the age-related attrition of neurons and thus reducing the threshold for deficits produced by more specific disease-related processes.

Analysis of the effect of aluminum in drinking water and transferrin C2 allele on Alzheimer's disease

Although highly controversial, the hypothesis of a link between aluminum (Al) in drinking water and Alzheimer's disease (AD) has been supported by several epidemiological studies. Transferrin (Tf) is a major transport protein for both iron and Al. Moreover, it has been demonstrated that defective binding of iron and Al to the Tf variant C2 could be present in AD. Individuals carrying the Tf C2 allele might therefore be at greater risk of developing AD. We investigated whether the Tf C2 allele might be responsible for susceptibility to AD in a sample of 292 subjects (with 55 AD) aged > or = 75 years from south-west France, some exposed to high levels of Al in tap water (n = 181 subjects) and others to low levels of Al (n = 111 subjects). We also examined the combined genetic effects of Tf C2 and epsilon4 allele of apolipoprotein E gene (ApoE). Logistic regression analysis showed that neither Tf C2 nor its interaction with Al or with the epsilon4 allele of the ApoE were significantly associated with the risk of AD.

Neurotoxic effects of aluminium among foundry workers and Alzheimer's disease

BACKGROUND

In a cross-sectional case-control study conducted in northern Italy, 64 former aluminium dust-exposed workers were compared with 32 unexposed controls from other companies matched for age, professional training, economic status, educational and clinical features. The findings lead the authors to suggest a possible role of the inhalation of aluminium dust in pre-clinical mild cognitive disorder which might prelude Alzheimer's disease (AD) or AD-like neurological deterioration.

METHODS

The investigation involved a standardised occupational and medical history with particular attention to exposure and symptoms, assessments of neurotoxic metals in serum: aluminium (Al-s), copper (Cu-s) and zinc (Zn-s), and in blood: manganese (Mn-b), lead (Pb-b) and iron (Fe-b). Cognitive functions were assessed by the Mini Mental State Examination (MMSE), the Clock Drawing Test (CDT) and auditory evoked Event-Related Potential (ERP-P300). To detect early signs of mild cognitive impairment (MCI), the time required to solve the MMSE (MMSE-time) and CDT (CDT-time) was also measured.

RESULTS

Significantly higher internal doses of Al-s and Fe-b were found in the ex-employees compared to the control group. The neuropsychological tests showed a significant difference in the latency of P300, MMSE score, MMSE-time, CDT score and CDT-time between the exposed and the control population. P300 latency was found to correlate positively with Al-s and MMSE-time. Al-s has significant effects on all tests: a negative relationship was observed between internal Al concentrations, MMSE score and CDT score; a positive relationship was found between internal Al concentrations, MMSE-time and CDT-time. All the potential confounders such as age, height, weight, blood pressure, schooling years, alcohol, coffee consumption and smoking habit were taken into account.

CONCLUSIONS

These findings suggest a role of aluminium in early neurotoxic effects that can be detected at a pre-clinical stage by P300, MMSE, MMSE-time, CDT-time and CDT score, considering a 10 micrograms/l cut-off level of serum aluminium, in aluminium foundry workers with concomitant high blood levels of iron. The authors raise the question whether pre-clinical detection of aluminium neurotoxicity and consequent early treatment might help to prevent or retard the onset of AD or AD-like pathologies.

Biocompatibility and osteogenesis of refractory metal implants, titanium, hafnium, niobium, tantalum and rhenium

To evaluate the biocompatibility of refractory metals, titanium, hafnium, niobium, tantalum and rhenium were implanted in rats, and histological observation and elemental mapping were performed by X-ray scanning analytical microscope (XSAM) and electron probe microanalyzer (EPMA). The titanium, hafnium, niobium, tantalum and rhenium wires were implanted in the subcutaneous tissue of the abdominal region and in femoral bone marrow of rats for either 2 or 4 weeks. No inflammatory response was observed around the implants, and all the implants were encapsulated with thin fibrous connective tissue. No dissolution of these metals was detected by XSAM in the soft tissue. Histological examination of the hard tissue showed that the amount of new bone formation decreased slightly from the second to the fourth week after implantation, and that the percentage of bone in contact with the implant increased markedly over the same period. No dissolution of these metals was detected by EPMA in the hard tissue. The Ca and P intensities in the mapping images of newly formed bone were higher after 4 weeks than those after 2 weeks, which suggests that the newly formed bone continued to mature from 2 to 4 weeks after implantation. These results indicate that titanium, hafnium, niobium, tantalum and rhenium have good biocompatibility and osteoconductivity.

Effects of aluminum on activity of krebs cycle enzymes and glutamate dehydrogenase in rat brain homogenate

Aluminum is a neurotoxic agent for animals and humans that has been implicated as an etiological factor in several neurodegenerative diseases and as a destabilizer of cell membranes. Due to its high reactivity, Al3+ is able to interfere with several biological functions, including enzymatic activities in key metabolic pathways. In this paper we report that, among the enzymes that constitute the Krebs cycle, only two are activated by aluminum: alpha-ketoglutarate dehydrogenase and succinate dehydrogenase. In contrast, aconitase, shows decreased activity in the presence of the metal ion. Al3+ also inhibits glutamate dehydrogenase, an allosteric enzyme that is closely linked to the Krebs cycle. A possible correlation between aluminum, the Krebs cycle and aging processes is discussed.

Disturbance of cerebral function in people exposed to drinking water contaminated with aluminium sulphate: retrospective study of the Camelford water incident

OBJECTIVE

To establish whether people exposed to drinking water contaminated with 20 tonnes of aluminium sulphate in the Camelford area of Cornwall in the south west of England in July 1988 had suffered organic brain damage as opposed to psychological trauma only.

DESIGN

Retrospective study of affected people.

PARTICIPANTS

55 affected people and 15 siblings nearest in age to one of the group but who had not been exposed to the contaminated water were studied.

MAIN OUTCOME MEASURES

Various clinical and psychological tests to determine medical condition and anxiety levels in affected people. Assessment of premorbid IQ (pFSIQ) with the national adult reading test, a computerised battery of psychomotor testing, and measurement of the difference in latencies between the flash and pattern visual evoked potentials in all participants.

RESULTS

The mean (SE) pFSIQ was above average at 114.4 (1.1). The most sensitive of the psychomotor tests for organic brain disease was the symbol digit coding (SDC) test (normal score 100, abnormal <85). PARTICIPANTS performed less well on this test (54.5 (6.0)) than expected from their pFSIQ (P<0.0001) and a little less poorly on the averaged less discriminating tests within the battery (86.1 (2.5), P<0.0001). In a comparison with the 15 sibling pairs (affected people's age 41.0 (3.3) years v sibling age of 42.7 (3.1) years (P=0.36) the exposed people had similar pFSIQ (114.7 (2.1)) to their siblings (116.3 (2.1), (P=0.59) but performed badly on the symbol digit coding test (51.8 (16.6)) v (87.5 (4.9) for siblings, P=0.03). The flash-pattern differences in exposed people were greater than in 42 unrelated control subjects of similar age (27.33 (1.64) ms v 18. 57 (1.47) ms, P=0.0002). The 15 unexposed siblings had significantly better flash-pattern differences than their affected siblings (13.4 (2.4) ms v 29.6 (2.9) ms, P=0.0002). No effect of anxiety could be shown on these measurements from the analysis of the anxiety scores of exposed people.

CONCLUSION

People who were exposed to the contaminated water at Camelford suffered considerable damage to cerebral function, which was not related to anxiety. Follow up studies would be required to determine the longer term prognosis for affected individuals.

Mechanisms of uptake of gallium by human neuroblastoma cells and effects of gallium and aluminum on cell growth, lysosomal protease, and choline acetyl transferase activity

We have studied the uptake and removal of gallium, used as an analogue of aluminum, and the effects of aluminum itself on cultured human neuroblastoma cells treated with soluble metal complexes. The prohibitively high cost of measurement of the only available radioisotope of aluminum (26Al) precluded its usage, and so we considered that gallium, which is chemically extremely similar, would be the most suitable model. Gallium has been used thus in a number of previous biological studies and has been found to behave like aluminum in many respects. We have previously shown that Al-EDTA treatment results in uptake of aluminum and expression of hyperphosphorylated tau, a key component of Alzheimer's disease paired helical filaments. Here we demonstrate that gallium uptake can occur by two separate methods, both leading to physiologically relevant intracellular metal concentrations. Uptake from medium containing bovine transferrin occurred mainly by pinocytosis, but in the presence of human transferrin (hTf), uptake by transferrin-mediated endocytosis occurred also, despite a very low level of hTf saturation, indicating that Tf-mediated uptake is a very effective method of Ga internalization. The intracellular gallium is relatively stable, though partially removable by (1 mM) EDTA, desferrioxamine, or 1,2-dimethyl-3-hydroxypyrid-4-one. Aluminum and gallium treatment were found to increase the overall activity of lysosomal proteases, enzymes implicated in amyloid precursor protein cleavage. No effects were detected on choline acetyl transferase activity, cell growth, or tritiated thymidine incorporation or on the structure of the cells, as judged by light or electron microscopy.

Uptake of aluminum and gallium into tissues of the rat: influence of antibody against the transferrin receptor

Transport of aluminum and gallium from blood into rat tissues following continuous i.v. infusion of metals in different chemical forms has been investigated. Tissue uptake of aluminum and gallium was similar and highly dependent on the chemical species of the metals. Aluminum and gallium accumulated in liver and spleen when infused in the chloride form. Raised citrate markedly enhanced aluminum and gallium uptake into renal cortex and bone; in contrast with gallium-transferrin, citrate increased uptake of 67Ga into renal cortex and bone by 8- and 14-fold respectively. Uptake of 67Ga with citrate into renal cortex was around 3 times smaller than that of aluminum. The antitransferrin receptor antibody OX-26 enhanced 67Ga uptake from gallium citrate into all rat tissues. 67Ga from purified gallium-transferrin was also taken into all tissues in the presence of OX-26, the effect being greatest in renal cortex and bone. No influence of antibody on aluminum transport into rat tissues was, however, observed when aluminum was infused in the citrate form. Therefore, transport of aluminum and gallium into tissues is not similar under all conditions. Transport of each metal occurs into all tissues in the presence of antitransferrin receptor antibody. The potential for such transport is much greater in the case of gallium. Transport of aluminum and gallium citrate complexes appears important especially in the renal cortex and bone.

Increased absorption of aluminium from a normal dietary intake in dementia

Serum aluminium was significantly raised (p < 0.01) up to 2-3-fold, in patients with dementia including Alzheimers Disease (AD) 0.66 +/- 0.2 (mumol/l mean +/- 1 s.d.) and patients on regular aluminium hydroxide therapy 0.54 +/- 0.17, compared with healthy volunteers 0.21 +/- 0.13, although not as high as in patients with end stage renal failure on regular dialysis 0.88 +/- 0.42. The urine outputs (mumol/l mean +/- 1 s.d.) of aluminium and silicon, respectively, were also significantly increased up to 5-fold in dementia 2.89 +/- 1.78 (n = 23) and 1587 +/- 645 (n = 22) and patients on regular aluminium hydroxide therapy 5.03 +/- 2.08 (n = 8) and 998 +/- 364 (n = 21) compared with healthy volunteers 0.95 +/- 0.82 (n = 84) and 471 +/- 332 (n = 114). The increase in urine aluminium was thus associated with a similarly marked increase in the output of silicon. The increased absorption of aluminium in dementia patients is equivalent to the intestinal loading in Aludrox therapy. Also silicon appears to be important in the renal excretion of the absorbed aluminium. Whether this is a phenomenon related to the elderly or the process of dementia warrants further study.

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.

Brain microvascular changes in Alzheimer's disease and other dementias

Vasculopathy in Alzheimer's disease (AD) may represent an important pathogenetic factor of this disorder. In the present study, microvasculature was studied by immunohistochemistry using a monoclonal antibody against a vascular heparan sulfate proteoglycan. Vascular changes were consistently observed in AD and included decrease in vascular density, presence of atrophic and coiling vessels, and glomerular loop formations. The laminar and regional distribution of these vascular alterations was correlated with the presence of neurofibrillary tangles. However, vascular changes may also follow neuronal loss. Vascular density may be related to a decrease in brain metabolism. Furthermore, one of the main features of AD is the presence of amyloid deposits within brain parenchyma and blood vessel walls. It is not yet clear whether amyloid components are derived from the blood or the central nervous system. Because AD is clearly heterogeneous, based on clinical and genetic data, evidence for either a brain or peripheral origin is discussed. Microvasculature was also analyzed in other neurodegenerative disorders devoid of amyloid deposits including amyotrophic lateral sclerosis/parkinsonism-dementia complex of Guam and Pick's disease. In conclusion, if vasculopathy in neurodegenerative disorders is not directly involved in pathogenesis, it may act synergistically with other pathogenetic mechanisms including genetic and environmental factors. This aspect of pathology is particularly interesting in view of its accessibility to therapeutic interventions.

Excessive glutamine sensitivity in Alzheimer's disease and Down syndrome lymphocytes

In addition to clinical and neuropathological similarities between Alzheimer's disease and Down syndrome there are genetic and biochemical data which suggest common disease mechanism. Using an in vitro assay examining variations of the mitotic index in the presence or absence of various inhibitors or metabolites of purine and/or pyrimidine synthesis, we studied 19 Alzheimer disease patients and 16 patients with both Down syndrome and Alzheimer type dementia. A highly significant decrease in mitotic index in the presence of exogenous glutamine was noted in patients presenting an Alzheimer type dementia with or without associated Down syndrome. These findings suggest that glutamine sensitivity or some dysregulation of the glutamine/glutamate pathway may play a role in the pathogenesis of Alzheimer's disease. If these findings are confirmed, they would have important implications in the development of preventive strategies.

Comparison of tissue retention of aluminum and Ga-67: effects of iron status in rats

The purposes of this study were to separate the effect of iron status from the effect of acute iron intake on tissue retention of aluminum and Ga-67 and to evaluate Ga-67 as a marker for aluminum. Anemic and control rats were dosed by gavage with a citrate solution containing 20 microCi Ga-67 with no added aluminum and iron (Gavage Ga-67), with 0.8 mmol aluminum (Gavage Al), with 0.8 mmol iron (Gavage Fe), or with both 0.8 mmol aluminum and 0.8 mmol iron (Gavage Fe and Al). After 24 h, anemic rats in the Gavage Al treatment had lower concentrations of aluminum in their tibias, kidneys, and spleens than control rats in that treatment. In contrast, anemic rats dosed with only Ga-67 (Gavage Ga-67 treatment) had lower concentrations of Ga-67 in their tibias and kidneys, but greater concentrations of Ga-67 in their livers and spleens than control rats in that treatment. The single dose of iron had no effect on tissue aluminum concentrations but depressed tissue Ga-67 concentrations. All rats accumulated aluminum predominantly in bone and control rats accumulated Ga-67 predominantly in bone, but anemic rats accumulated Ga-67 predominantly in liver. A major limitation of Ga-67 as a marker for aluminum is its greater sensitivity than aluminum to iron intake and status.

Involvement of a lysine residue in the N-terminal Ni2+ and Cu2+ binding site of serum albumins. Comparison with Co2+, Cd2+ and Al3+

We report one-dimensional and two-dimensional 1H-NMR studies of the binding of Ni2+, Cu2+, Co2+, Cd2+ and Al3+ to defatted bovine and human serum albumins. The diamagnetic shifts induced by Ni2+, and paramagnetic effects due to Cu2+, were consistent with strong binding to a square-planar site formed by the three N-terminal amino acid residues (Asp-Thr-His for bovine, and Asp-Ala-His for human albumin). In contrast to previous studies on isolated 1-24 N-terminal peptide, a Lys residue also appeared to be involved in the binding site, and is assigned as Lys4. A second His residue is also close to the Cu2+/Ni2+ binding site in bovine serum albumin and is assigned to His59 (not present in human albumin). Co2+ caused specific perturbation of the resonances for the three N-terminal residues as well as those for Lys4. This is the first evidence for Co2+ binding to the N-terminal metal site of serum albumin. Neither Al3+ nor Cd2+ perturbed resonances for the N-terminal amino acids, but bind elsewhere in the protein.

Effect of oral aluminium citrate on short-term tissue distribution of aluminium

Aluminium (Al) concentrations in the plasma, bone, lung, liver, kidney, spleen, duodenum and brain of rats were measured 2, 4 and 24 hr after a single oral dose of 0.46 mmol as Al citrate (1:5 molar ratio). Compared with control animals, very high concentrations were found at 2 hr post-administration in plasma (539 micrograms/litre) and in all tissues except the brain where Al did not change throughout the 24-hr period. The increased levels in the liver (161 ng/g) and lung (89.7 ng/g) at 2 hr were maintained until 4 hr and then decreased. At 24 hr the plasma value decreased to 24.6 micrograms/litre as compared with the peak value of 539 micrograms/litre. In a typical soft tissue such as the kidney the peak at 2 hr of 682 ng/g decreased to 241 ng/g, which was still more than 10-fold greater than the control level. Uniquely, in the case of bone Al increased throughout the period of the experiment. Our results indicate that Al in the citrate form is readily absorbed and that it appears to equilibrate rapidly between plasma and the intracellular compartments of most soft tissues but does not readily permeate the blood-brain barrier. In a group of rats previously given silicic acid in the drinking water and co-administered with the Al dose, the tissue Al distribution pattern at 4 hr post-administration was modified in comparison with the test animals not loaded with silicic acid. Al concentrations in plasma and soft tissues were significantly reduced except for the spleen, in which Al increased, and there was complete inhibition of the very high Al uptake/deposition in bone.

Specific non-enzymatic glycation of the rat histone H1 nucleotide binding site in vitro in the presence of AlF4-. A putative mechanism for impaired chromatin function

We show here that an aluminium derivative, AlF4-, stimulates glycation of histone H1 selectively in the proximity of its nucleotide-binding site. This adduct formation interferes with nucleoside triphosphate hydrolysis by H1 and with nucleotide modulation of H1 DNA binding. The present mode of aluminium action may in part be responsible for its effects on the chromatin structure and expression of tissue-specific genes, and may constitute a mechanism in the pathogenesis of aluminium-induced encephalopathy and in that of Alzheimer's disease, for example.

Membrane fluidity of platelets and erythrocytes in patients with Alzheimer's disease and the effect of small amounts of aluminium on platelet and erythrocyte membranes

The membrane fluidity of platelet and erythrocyte membranes in 10 Alzheimer's disease patients and 9 age-matched controls was studied. The platelet membranes of patients with Alzheimer's disease were found to be significantly more fluid than those of controls (p less than 0.02). However, erythrocyte membranes of Alzheimer patients were less fluid (more viscous) than those of controls (p less than 0.05). On further investigation of platelet and erythrocyte membranes obtained from healthy volunteers, the fluidity was found to change with increasing aluminium concentrations. When aluminium ammonium sulphate (0.01-10 microM) was added to membrane suspensions, the fluidity of platelet membranes was increased, whereas the fluidity of erythrocyte membranes was decreased (i.e. the microviscosity was increased).