Absorption of aluminium-26 in Alzheimer's disease, measured using accelerator mass spectrometry

Aluminum induced intestinal dysfunction via mechanical, immune, chemical and biological barriers

Aluminum is the most abundant metal element in the Earth's crust, which exists naturally in the form of aluminum compounds. Aluminum is mainly absorbed through the gastrointestinal tract, which varies with different aluminum compounds. During this process, aluminum could induce the disruption of intestinal mucosa barrier. However, its underlying mechanism has not been elucidated yet. Previous studies have reported that aluminum can firstly promote the apoptosis of intestinal epithelial cells, destroy the structure of tight-junction proteins, and increase the intestinal permeability, injuring the mechanical barrier of gut. Also, it can induce the activation of immune cells to secrete inflammatory factors, and trigger immune responses, interfering with immune barrier. Moreover, aluminum treatment can regulate intestinal composition and bio-enzyme activity, impairing the function of chemical barrier. In addition, aluminum accumulation can induce an imbalance of the intestinal flora, inhibit the growth of beneficial bacteria, and promote the proliferation of harmful bacteria, which ultimately disrupting biological barrier. Collectively, aluminum may do extensive damage to intestinal barrier function covering mechanical barrier, immune barrier, chemical barrier and biological barrier.

Physiology-based toxicokinetic modelling of aluminium in rat and man

A sufficient quantitative understanding of aluminium (Al) toxicokinetics (TK) in man is still lacking, although highly desirable for risk assessment of Al exposure. Baseline exposure and the risk of contamination severely limit the feasibility of TK studies administering the naturally occurring isotope 27Al, both in animals and man. These limitations are absent in studies with 26Al as a tracer, but tissue data are limited to animal studies. A TK model capable of inter-species translation to make valid predictions of Al levels in humans-especially in toxicological relevant tissues like bone and brain-is urgently needed. Here, we present: (i) a curated dataset which comprises all eligible studies with single doses of 26Al tracer administered as citrate or chloride salts orally and/or intravenously to rats and humans, including ultra-long-term kinetic profiles for plasma, blood, liver, spleen, muscle, bone, brain, kidney, and urine up to 150 weeks; and (ii) the development of a physiology-based (PB) model for Al TK after intravenous and oral administration of aqueous Al citrate and Al chloride solutions in rats and humans. Based on the comprehensive curated 26Al dataset, we estimated substance-dependent parameters within a non-linear mixed-effect modelling context. The model fitted the heterogeneous 26Al data very well and was successfully validated against datasets in rats and humans. The presented PBTK model for Al, based on the most extensive and diverse dataset of Al exposure to date, constitutes a major advancement in the field, thereby paving the way towards a more quantitative risk assessment in humans.

Derivation of Biomonitoring Equivalents for aluminium for the interpretation of population-level biomonitoring data

Aluminium is widely used in many consumer products, however the primary source of aluminium exposure to the Canadian general population is through food. Aluminium can cause neurotoxicity and reproductive toxicity at elevated exposure levels. Health-based exposure guidance values have been established for oral exposure to aluminium, including a Minimal Risk Level (MRL) by the Agency for Toxic Substances and Disease Registry (ATSDR), a Provincial Tolerable Weekly Intake (PTWI) by the Joint FAO/WHO Expert Committee on Food Additives (JECFA) and a Tolerable Weekly Intake (TWI) by the European Food Safety Authority (EFSA). Aluminium concentration in blood and urine can be used as a tool for exposure characterization in a population. A pharmacokinetic (PK) model was developed based on human dosing data to derive blood Biomonitoring Equivalents (BEs), whereas a mass balance approach was used to derive urine BEs for the above guidance values. The BEs for blood for daily intake consistent with the MRL, PTWI and TWI were 18, 16 and 8 μg/L, respectively. BEs for urine for the same guidance values were 137, 123 and 57 μg/L, respectively. The derived BEs may be useful in interpreting population-level biomonitoring data in a health risk context and thereby screening and prioritizing substances for human health risk assessment and risk management.

Aluminum-Induced Toxicity in Salivary Glands of Mice After Long-term Exposure: Insights into the Redox State and Morphological Analyses

Several studies indicate aluminum (Al) as a potent toxicant, mainly related to central nervous system disorders. However, investigations about the Al effects over salivary glands are still scarce. In this way, the present study aimed to investigate whether the Al chloride (AlCl₃) is able of triggering oxidative stress in parotid and submandibular glands of mice and also, if any morphological impairment is observed. For this, twenty mice were divided into two groups: Exposed group (EG), which received 18.5 mg/kg of AlCl₃ by intragastric gavage for 60 days and control group (CG), which received distilled water by intragastric gavage during the same period of time. After that, levels of reduced glutathione (GSH) and malonaldehyde (MDA) were analyzed and we performed morphological analyses by evaluating the area of parenchyma, stroma, acini, and ducts in both glands. Statistical analyses were performed by Student's t test and two-way ANOVA, adopting p < 0.05. No abnormal body weight was observed and data indicates that although both major salivary glands are susceptible to Al-induced oxidative stress, by increasing MDA and reducing GSH, only submandibular glands decreased the parenchyma and increased stroma area. Moreover, the submandibular glands showed smaller total area of acini and higher total area of ducts, in comparison with the control group. Notably, AlCl₃ induces oxidative stress in both glands, however, submandibular glands showed to be more susceptible to Al effects than parotid glands. Our study gives evidences about Al toxicity in parotid and submandibular glands and claims for new investigations to understand more mechanisms of Al-induced toxicity.

Is aluminum exposure a risk factor for neurological disorders?

Aluminum (Al) is widely found in the nature. Although the relation between Al and neurodegenerative diseases is still controversial, Al is related with many brain diseases including Alzheimer's disease, Parkinson's disease, and multiple sclerosis. Al exposure occurs mainly through environment, occupational, and dietary factors for humans. Al exposure with diet can be through foods, food additives, water, and contamination of Al equipment/utensils. The aim of this review is to summarize various hypotheses, which link Al and neurodegeneration, and to determine the roles of Al exposure through different sources including diet, environment, and occupation. Future studies should be done in vulnerable subgroups of population including children, patients receiving antacid or Al-containing pharmeteucials on a daily basis, patients with reduced renal function, and patients on parenteral nutrition regimens that are likely to be affected by possible adverse health effects of Al. In addition, gender, age, and Al interactions need to be determined. One of the most important challanges in future epidemiological studies is to determine which variables should be controlled. In addition, experimental studies should be more focused and translational. In this context, exposure dose, dose-response effects, and time lapse between exposures and cognitive assessments are very important.

Risk assessment of dietary exposure to aluminium in the Chinese population

In order to address the issue of excessive intake of aluminium (Al) from Al-containing food additives in the Chinese diet, this study conducted a dietary exposure assessment of Al in the general population based on the national surveillance data of Al content in foods and national food consumption data. It was found that the mean dietary exposure of the whole Chinese population to Al from Al-containing food additives was 1.795 mg kg^‒1 bw week^‒1, not exceeding the PTWI, while high dietary exposures (e.g., 97.5^th percentile) to Al were 7.660 and 2.103-2.903 mg kg^‒1 bw week^‒1 for children, respectively, both exceeding the PTWI. It was found that the dietary exposure to Al for 32.5% of the total Chinese population and 42.6% of children aged 4-6 years exceeded the PTWI. Wheat flour and wheat-based products are the main source of dietary A l exposure (85% of the total intake); and puffed foods are the major source of Al intake for children. These findings suggested that consumption of Al-containing food additives could be a health concern for consumers with high food consumption (97.5^th percentile) and children under the age of 14 years.

Aluminum Levels in Brain, Serum, and Cerebrospinal Fluid are Higher in Alzheimer's Disease Cases than in Controls: A Series of Meta-Analyses

BACKGROUND

Aluminum is the most studied environmental agent linked with Alzheimer's disease (AD). However, it remains unclear whether levels are significantly elevated in AD sufferers.

OBJECTIVE

To systematically assess levels of aluminum in brain, serum, and cerebrospinal fluid (CSF) of AD cases and controls.

METHODS

Electronic searches of Medline, Embase, PubMed, and Cochrane Library were conducted up to June 2015. Studies reporting brain, serum, or CSF aluminum levels in individuals with AD and non-demented controls were included. Meta-analyses were performed using random-effects models and the pooled standardized mean difference (SMD) reported with 95% confidence intervals (CI).

RESULTS

Overall, 34 studies involving 1,208 participants and 613 AD cases met the criteria for inclusion. Aluminum was measured in brain tissue in 20 studies (n = 386), serum in 12 studies (n = 698), and CSF in 4 studies (n = 124). Compared to control subjects, AD sufferers had significantly higher levels of brain (SMD 0.88; 95% CI, 0.25-1.51), serum (SMD 0.28; 95% CI, 0.03-0.54), and CSF (SMD 0.48; 95% CI, 0.03-0.93) aluminum. Sensitivity analyses excluding studies without age-matched controls did not impact upon these results.

CONCLUSIONS

The findings of the present meta-analyses demonstrate that aluminum levels are significantly elevated in brain, serum, and CSF of patients with AD. These findings suggest that elevated aluminum levels, particularly in serum, may serve as an early marker of AD and/or play a role in the development of the disease. These results substantially clarify the existing evidence examining the link between chronic aluminum exposure and the development of AD.

Brain biometals and Alzheimer's disease - boon or bane?

Alzheimer's disease (AD) is the most common form of dementia. Several hypotheses have been put forward to explain the basis of disease onset and progression. A complicated array of molecular events has been implicated in the pathogenesis of AD. It is attributed to a variety of pathological conditions that share similar critical processes, such as oxidative stress, proteinaceous aggregations, mitochondrial dysfunctions and energy failure. There is increasing evidence suggesting that metal homeostasis is dysregulated in the pathology of AD. Biometals play an important role in the normal body functioning but AD may be mediated or triggered by disproportion of metal ions leading to changes in critical biological systems and initiating a cascade of events finally leading to neurodegeneration and cell death. The link is multifactorial, and although the source of the shift in oxidative homeostasis is still unclear, current evidence points to changes in the balance of redox transition metals, especially iron, copper (Cu) and other trace metals. Their levels in the brain are found to be elevated in AD. In other neurodegenerative disorders, Cu, zinc, aluminum and manganese are involved. This paper is a review of recent advances of the role of metals in the pathogenesis and pathophysiology of AD and related neurodegenerative diseases.

Variation in the Levels of Aluminum and Manganese in Scalp Hair Samples of the Patients Having Different Psychiatric Disorders with Related to Healthy Subjects

There is very limited information available on the role of trace elements in psychiatric disorders (PSD). Immense pieces of evidence support the idea that exposure to trace and toxic metals, such as aluminum (Al) and manganese (Mn), may be factors or cofactors in the etiopathogenesis of a variety of psychiatric disorders. The aim of our study was to assess the Al and Mn in scalp hair samples of 102 patients having different types of psychiatric disorder PSD diseases together with 120 referent subjects of male patients in the age group of 45-60 years. The understudy elements in scalp hair samples were assessed by the flame atomic absorption spectrophotometry after microwave-assisted acid digestion method .The validity of methodology was checked by the certified human hair reference material (NCS ZC81002). The recovery of studied elements was found in the range of 98.1-99.2 % of certified reference material. The results of this study showed that the mean values of Al and Mn were significantly higher in scalp hair samples of all types of PSD as compared to referents subjects. The resulted data indicated a significant increase in the contents of Mn and Al in scalp hair samples of psychiatric patients than that of its control counterpart, which may provide prognostic tool for the diagnosis of the mental disorders. However, further work is suggested to examine the exact correlation between trace elements level and the degree of disorder.

Correlation of aluminum and manganese concentration in scalp hair samples of patients having neurological disorders

Neurodegenerative diseases are thought to be multifactorial, while metals (aluminum and manganese) can be involved as cofactors in abnormalities or suspected of being risk factors for this disorder. The aim of our study was to assess the aluminum (Al) and manganese (Mn) concentrations in scalp hair samples of 397 patients having different types of neurological disorder diseases. For comparative purpose, scalp hair samples of 201 control subjects does not have any neuro-disorders of same age group (30-60 years) and were selected as referents. The Al and Mn in scalp hair samples were assessed by the electrothermal atomic absorption spectrophotometry after microwave-assisted acid digestion. The validity of methodology was checked by the certified human hair reference material (NCS ZC81002). The results of this study showed that the mean values of Al and Mn were significantly higher in scalp hair samples of all types of neurological disorder patients as compared to controls (p = 0.01-0.001). The high levels of Al and Mn may play a role in the development of neurological disorders. However, further work is suggested to examine the precise correlation between trace elemental level and the degree of disorders in neurological patients.

Physical, chemical, and immunohistochemical investigation of the damage to salivary glands in a model of intoxication with aluminium citrate

Aluminum absorption leads to deposits in several tissues. In this study, we have investigated, to our knowledge for the first time, aluminum deposition in the salivary glands in addition to the resultant cellular changes in the parotid and submandibular salivary glands in a model of chronic intoxication with aluminum citrate in rats. Aluminum deposits were observed in the parotid and submandibular glands. Immunohistochemical evaluation of cytokeratin-18 revealed a decreased expression in the parotid gland with no changes in the submandibular gland. A decreased expression of α-smooth muscle actin was observed in the myoepithelial cells of both glands. The expression of metallothionein I and II (MT-I/II), a group of metal-binding proteins, which are useful indicators for detecting physiological responses to metal exposure, was higher in both glands. In conclusion, we have shown that at a certain time and quantity of dosage, aluminum citrate promotes aluminum deposition in the parotid and submandibular glands, leads to an increased expression of MT-I/II in both the glands, damages the cytoskeleton of the myoepithelial cells in both glands, and damages the cytoskeleton of the acinar/ductal cells of the parotid glands, with the submandibular glands showing resistance to the toxicity of the latter.

Systematic review of potential health risks posed by pharmaceutical, occupational and consumer exposures to metallic and nanoscale aluminum, aluminum oxides, aluminum hydroxide and its soluble salts

Abstract Aluminum (Al) is a ubiquitous substance encountered both naturally (as the third most abundant element) and intentionally (used in water, foods, pharmaceuticals, and vaccines); it is also present in ambient and occupational airborne particulates. Existing data underscore the importance of Al physical and chemical forms in relation to its uptake, accumulation, and systemic bioavailability. The present review represents a systematic examination of the peer-reviewed literature on the adverse health effects of Al materials published since a previous critical evaluation compiled by Krewski et al. (2007) . Challenges encountered in carrying out the present review reflected the experimental use of different physical and chemical Al forms, different routes of administration, and different target organs in relation to the magnitude, frequency, and duration of exposure. Wide variations in diet can result in Al intakes that are often higher than the World Health Organization provisional tolerable weekly intake (PTWI), which is based on studies with Al citrate. Comparing daily dietary Al exposures on the basis of "total Al"assumes that gastrointestinal bioavailability for all dietary Al forms is equivalent to that for Al citrate, an approach that requires validation. Current occupational exposure limits (OELs) for identical Al substances vary as much as 15-fold. The toxicity of different Al forms depends in large measure on their physical behavior and relative solubility in water. The toxicity of soluble Al forms depends upon the delivered dose of Al(+3) to target tissues. Trivalent Al reacts with water to produce bidentate superoxide coordination spheres [Al(O2)(H2O4)(+2) and Al(H2O)6 (+3)] that after complexation with O2(•-), generate Al superoxides [Al(O2(•))](H2O5)](+2). Semireduced AlO2(•) radicals deplete mitochondrial Fe and promote generation of H2O2, O2 (•-) and OH(•). Thus, it is the Al(+3)-induced formation of oxygen radicals that accounts for the oxidative damage that leads to intrinsic apoptosis. In contrast, the toxicity of the insoluble Al oxides depends primarily on their behavior as particulates. Aluminum has been held responsible for human morbidity and mortality, but there is no consistent and convincing evidence to associate the Al found in food and drinking water at the doses and chemical forms presently consumed by people living in North America and Western Europe with increased risk for Alzheimer's disease (AD). Neither is there clear evidence to show use of Al-containing underarm antiperspirants or cosmetics increases the risk of AD or breast cancer. Metallic Al, its oxides, and common Al salts have not been shown to be either genotoxic or carcinogenic. Aluminum exposures during neonatal and pediatric parenteral nutrition (PN) can impair bone mineralization and delay neurological development. Adverse effects to vaccines with Al adjuvants have occurred; however, recent controlled trials found that the immunologic response to certain vaccines with Al adjuvants was no greater, and in some cases less than, that after identical vaccination without Al adjuvants. The scientific literature on the adverse health effects of Al is extensive. Health risk assessments for Al must take into account individual co-factors (e.g., age, renal function, diet, gastric pH). Conclusions from the current review point to the need for refinement of the PTWI, reduction of Al contamination in PN solutions, justification for routine addition of Al to vaccines, and harmonization of OELs for Al substances.

Effects of fertilizing with N, p, se, and zn on regulating the element and functional component contents and antioxidant activity of tea leaves planted in red soil

New fertilizing strategies (with exogenetic N, P, Se, and Zn) were explored to regulate the element (Se, Zn, Mn, and Al) and functional component (polyphenol, catechins, free amino acid, polysaccharide, and caffeine) contents of new (a bud and two leaves, grown for about 10 days) and old tea leaves (grown for >3 months) cultivated in a hilly red soil region. Using four different fertilizing strategies (A, Se + Zn; B, Se + Zn + N; C, Se + Zn + P; D, Se + Zn + N + P), the Al and Mn contents of tea leaves in both new and old leaves were significantly decreased. Meanwhile, the contents of Se and Zn were increased, and the contents of some functional components as well as the antioxidant activities in tea leaves were improved. In particular, fertilizing strategy C showed the highest Se (0.444 μg/kg), total polyphenol (28.294%), and catechins (131.852 mg/g) contents and antioxidant activities (DPPH, 95.06%; FRAP, 3.81 mmol FeSO4/g; reducing power, 1.26) as well as the lowest Al (222.005 mg/kg) content among these four strategies, whereas fertilizing strategy B showed the highest Zn (34.235 mg/kg), total free amino acid (5.60%), tea polysaccharide (5.79%), and caffeine (56.684 mg/g) contents as well as the lowest Mn content (747.658 mg/kg). It has been proven that exogenetic elements (N, P, Se, and Zn) as fertilizers could be an effective way to produce tea leaves with higher Se, Zn, and functional component contents and antioxidant activity as well as lower Al and Mn contents in a red soil region.

Human exposure to aluminium

Human activities have circumvented the efficient geochemical cycling of aluminium within the lithosphere and therewith opened a door, which was previously only ajar, onto the biotic cycle to instigate and promote the accumulation of aluminium in biota and especially humans. Neither these relatively recent activities nor the entry of aluminium into the living cycle are showing any signs of abating and it is thus now imperative that we understand as fully as possible how humans are exposed to aluminium and the future consequences of a burgeoning exposure and body burden. The aluminium age is upon us and there is now an urgent need to understand how to live safely and effectively with aluminium.

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.

Towards the prevention of potential aluminum toxic effects and an effective treatment for Alzheimer's disease

In 1991, treatment with low dose intramuscular desferrioxamine (DFO), a trivalent chelator that can remove excessive iron and/or aluminum from the body, was reported to slow the progression of Alzheimer's disease (AD) by a factor of two. Twenty years later this promising trial has not been followed up and why this treatment worked still is not clear. In this critical interdisciplinary review, we provide an overview of the complexities of AD and involvement of metal ions, and revisit the neglected DFO trial. We discuss research done by us and others that is helping to explain involvement of metal ion catalyzed production of reactive oxygen species in the pathogenesis of AD, and emerging strategies for inhibition of metal-ion toxicity. Highlighted are insights to be considered in the quests to prevent potentially toxic effects of aluminum toxicity and prevention and intervention in AD.

Gene-environment interaction research and transgenic mouse models of Alzheimer's disease

The etiology of the sporadic form of Alzheimer's disease (AD) remains largely unknown. Recent evidence has suggested that gene-environment interactions (GxE) may play a crucial role in its development and progression. Whereas various susceptibility loci have been identified, like the apolipoprotein E4 allele, these cannot fully explain the increasing prevalence of AD observed with aging. In addition to such genetic risk factors, various environmental factors have been proposed to alter the risk of developing AD as well as to affect the rate of cognitive decline in AD patients. Nevertheless, aside from the independent effects of genetic and environmental risk factors, their synergistic participation in increasing the risk of developing AD has been sparsely investigated, even though evidence points towards such a direction. Advances in the genetic manipulation of mice, modeling various aspects of the AD pathology, have provided an excellent tool to dissect the effects of genes, environment, and their interactions. In this paper we present several environmental factors implicated in the etiology of AD that have been tested in transgenic animal models of the disease. The focus lies on the concept of GxE and its importance in a multifactorial disease like AD. Additionally, possible mediating mechanisms and future challenges are discussed.

Targeting the progression of Parkinson's disease

By the time a patient first presents with symptoms of Parkinson's disease at the clinic, a significant proportion (50-70%) of the cells in the substantia nigra (SN) has already been destroyed. This degeneration progresses until, within a few years, most of the cells have died. Except for rare cases of familial PD, the initial trigger for cell loss is unknown. However, we do have some clues as to why the damage, once initiated, progresses unabated. It would represent a major advance in therapy to arrest cell loss at the stage when the patient first presents at the clinic. Current therapies for Parkinson's disease focus on relieving the motor symptoms of the disease, these unfortunately lose their effectiveness as the neurodegeneration and symptoms progress. Many experimental approaches are currently being investigated attempting to alter the progression of the disease. These range from replacement of the lost neurons to neuroprotective therapies; each of these will be briefly discussed in this review. The main thrust of this review is to explore the interactions between dopamine, alpha synuclein and redox-active metals. There is abundant evidence suggesting that destruction of SN cells occurs as a result of a self-propagating series of reactions involving dopamine, alpha synuclein and redox-active metals. A potent reducing agent, the neurotransmitter dopamine has a central role in this scheme, acting through redox metallo-chemistry to catalyze the formation of toxic oligomers of alpha-synuclein and neurotoxic metabolites including 6-hydroxydopamine. It has been hypothesized that these feed the cycle of neurodegeneration by generating further oxidative stress. The goal of dissecting and understanding the observed pathological changes is to identify therapeutic targets to mitigate the progression of this debilitating disease.

APP expression, distribution and accumulation are altered by aluminum in a rodent model for Alzheimer's disease

Up-regulated expression of amyloid precursor protein (APP) occurs early in the cascade of events that leads to amyloid plaque formation in the human brain. APP gene up-regulation, mediated by activated NF-kappaB, is a response to stress from nM concentrations of aluminum ions, aluminum-disregulated iron ions, reactive-oxygen species, cytokines, and physical trauma. We examined in vivo effects of aluminum on APP in aged rats, obtained from previously-reported longitudinal studies, that chronically ingested aluminum in amounts equivalent to total dietary aluminum levels that Americans routinely ingest. These rats exhibited two outcomes: one group remained cognitively-intact, scoring as well on a memory-discrimination task in old age as in middle age. The other developed cognitive deterioration, obtaining significantly lower mean performance scores in old age than in middle age and exhibiting abnormal behaviors associated with dementia. We compared the expression, distribution and accumulation of APP in hippocampal and cortical tissue of these two rat groups. Compared to results from cognitively-intact rats, hippocampal and cortical tissue from the cognitively-deteriorated rats showed elevated APP gene expression, significantly more dense APP deposits in cytoplasm of neural cells, and APP-immunoreactive neurites that were swollen and varicose. This study shows aluminum routinely derived from chronic oral ingestion, that gradually accumulates in brain regions important for memory-processing, is sufficient to increase APP levels in neural cells of those regions. Aluminum may thus launch the cascade that results in the formation of amyloid plaques in human brain.

Aluminum Toxicity Following IV Use of Oral Methadone Solution

BACKGROUND

Aluminum toxicity has been reported in renal failure patients exposed to aluminum-contaminated dialysate and oral phosphate binders. We report a case of significant aluminum toxicity in a non-hemodialysis patient.

CASE REPORT

A 43-year-old male IV drug user presented to the hospital with a seizure disorder of recent onset, progressive cognitive decline, ataxia, and dysarthria. The serum aluminum concentration was 180 micrograms/L (6.65 micromol/L). For 3 to 4 years prior, the patient had injected 'cooked' oral methadone. The methadone solution was heated in an aluminum pot to reduce the volume and then injected intravenously (IV). He was treated with IV deferoxamine over 9 months until he failed to return. Serum aluminum level after 9 months of treatment was 64.5 microgram/L (2.39 micromol/L). Neurological symptoms were partially improved.

CONCLUSION

Chronic IV injection of oral methadone solution heated in an aluminum-based cooking utensil may result in significant aluminum toxicity.

A longitudinal study of rats chronically exposed to aluminum at human dietary levels

According to the World Health Organization, oral ingestion of aluminum additives is the main form of aluminum exposure for the general public. Aluminum salts are added to a range of commercially-prepared foods and beverages: to clarify drinking water, make salt free-pouring, color snack/dessert foods, and make baked goods rise. In the present study, six Wistar rats chronically consumed aluminum from 16 months of age to the conclusion of their lifespan (averaging 29.8 months) in an amount (1.5mg/kg bodyweight) equivalent to the high end of the total aluminum range ingested daily by humans living in contemporary urban society. The rats were memory-trained in a continuous rewarded alternation T-maze task and tested weekly from 5 months of age onwards. This longitudinal study compared their mean memory performances over 15 consecutive weeks during middle age (12-23 months) and old age (> or =24 months). Four out of six rats continued to perform the memory task in old age without significant deficit. The remaining two obtained significantly lower mean memory scores in old age than in middle age and exhibited soft signs associated with dementia. Their hippocampal neurons stained for aluminum, showing some but not all features of aluminum accumulation that occur in human hippocampal neurons. In view of evidenced linkages of aluminum with beta-amyloid plaque and neurofibrillary tangle formation in humans with Alzheimer's disease, the findings suggest this protocol is worth testing in larger groups of animals.

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.

Transport and toxic mechanism for aluminum citrate in human neuroblastoma SH-SY5Y cells

Aluminum (Al) is thought to be a risk factor for neurodegenerative disorders, but the molecular mechanism has been not clarified yet. In this study, we examined how a transport system handled transport of Al citrate, the major Al species in brain, and effect of Al citrate treatment on expression of the transporter and on susceptibility to oxidative stress in human neuroblastoma SH-SY5Y cells. Uptake of Al citrate by the cells was temperature- and concentration-dependent, and inwardly-directed Na(+)-gradient-independent. Simultaneous application and preloading of L-cystine or L-glutamate inhibited and stimulated, respectively, the Al citrate uptake by SH-SY5Y cells, demonstrating kinetically that Na(+)-independent L-cystine/L-glutamate exchanger, system Xc(-), is involved in its uptake. When the cells were treated with Al citrate, but not citrate, for 2 weeks, but not a day, the expression of the transporter was decreased. Although the cell viability and glutathione content of the cells were not altered by the treatment with Al citrate alone, the number of dead cells among the Al citrate-treated cells increased on exposure to oxidative stress caused by a glucose deprivation/reperfusion treatment. These findings demonstrate that Al citrate is a substrate for system Xc(-), and that chronic treatment with Al citrate causes downregulation of the transporter and increases the vulnerability of the cells to oxidative stress without a direct effect on the viability or GSH content.

The aluminum content of bone increases with age, but is not higher in hip fracture cases with and without dementia compared to controls

Aluminum is considered a potentially toxic metal, and aluminum poisoning may lead to three types of disorders: aluminum-induced bone disease, microcytic anemia and encephalopathy. This is well known in patients with chronic renal failure, but since healthy subjects with normal renal function retain 4% of the aluminum consumed, they are also at risk of long-term low-grade aluminum intoxication. Included in this study were a total of 172 patients (age range 16-98 years) with the aim of examining whether aluminum accumulates in bone with increasing age. Additionally, we aimed to investigate whether the aluminum content of bone differs between controls and hip fracture cases with and without dementia, in particular in those with Alzheimer's disease. During operations for all cases, bone biopsies were taken with an aluminum-free instrument from the trabecular bone. The samples were measured for their content of aluminum using an inductively coupled mass spectrometer. We found an exponential increase in aluminum content of bone with age. The average aluminum values, adjusted for age, were similar in men and women (P=0.46). No significant differences in sex- and age-adjusted mean aluminum values between the controls and the hip fracture cases with (P=0.72) and without (P=0.33) dementia could be detected. The average aluminum concentration among cases with Alzheimer's disease was also similar to the values of hip fracture patients with other types of dementia (P=0.47). Odds ratios of hip fracture for each quartile of aluminum content in bone were also estimated to detect non-linear effects, but we did not find any statistically significant association remaining after age and sex adjustment. Thus, our results indicate that we accumulate aluminum in bone over our life span, but this does not seem to be of major pathogenetic significance for the occurrence of hip fracture or dementia.

Transport mechanism for aluminum citrate at the blood–brain barrier: kinetic evidence implies involvement of system Xc− in immortalized rat brain endothelial cells

Although accumulation of aluminum (Al) in the brain is known to cause neurodegenerative disorders and to be regulated mainly by the blood-brain barrier (BBB), the mechanism responsible for Al transport at the BBB has not been clarified yet. In this study, we investigated what kind of transporter is involved in the transport of Al citrate, which is the major species of Al in the brain, at the BBB using a rat immortalized brain endothelial cell line (RBEC1), focusing on the glutamate transporter family. The uptake of Al citrate showed temperature- and concentration-dependency, and did not require an inwardly directed Na+-gradient as a driving force, ruling out the involvement of Na+-dependent glutamate transporters in its transport. By RT-PCR, in RBEC1, there were mRNAs for the components of a Na+-independent glutamate transporter, system Xc-. L-Glutamate and L-cystine, representative ligands for system Xc-, significantly inhibited the uptake of Al citrate, and loading of them into the cells resulted in stimulation of its uptake in RBEC1. These results demonstrated that Al citrate is taken up into RBEC1 via system Xc-, and that this system might play an important role in Al citrate transport at the BBB.

Accelerator Mass Spectrometry for Biomedical Research

Accelerator mass spectrometry (AMS) is the most sensitive method for detecting and quantifying rare long-lived isotopes with high precision. In this chapter, we review the principles underlying AMS-based biomedical studies, focusing on important practical considerations and experimental procedures needed for the detection and quantitation of (14)C- and (3)H-labeled compounds in various experiment types.

The aluminium-amyloid cascade hypothesis and Alzheimer's disease

Aluminium (Al) is found associated with beta-amyloid (Abeta) in the brain in Alzheimer's disease. Al precipitates Abeta in vitro as distinct fibrillar structures composed of beta-pleated sheets of peptide. The aetiology of their association in vivo is not known. Al is known to increase the brain Abeta burden in experimental animals and this might be due to a direct influence upon Abeta anabolism or direct or indirect affects upon Abeta catabolism. It is difficult to rationalise from an evolutionary perspective the precipitation and persistence of Abeta in vivo. However, Al has not been subject to the same evolutionary pressures as Abeta, it is a recent addition to the biotic environment, and its precipitation of Abeta may have only been subjected to natural selection in the recent past. Whether AD is also part of this ongoing selection process remains to be elucidated

Aluminium cycling in the soil-plant-animal-human continuum

A critical review of the literature on Al toxicity in plants, animals and humans reveals a similar mode of Al action in all living organisms, namely interference with the secondary messenger system (phosphoinositide and cytosolic Ca2+ signalling pathways) and enhanced production of reactive oxygen species resulting in oxidative stress. Aluminium uptake by plants is relatively quick (across the intact plasma membrane in < 30 min and across the tonoplast in < 1 h), despite huge proportion of Al being bound in the cell wall. Aluminium absorption in the animal/human digestive system is low (only about 0.1% of daily Al intake stays in the human body), except when Al is complexed with organic ligands (eg. citrate, tartarate, glutamate). Aluminium accumulates in bones and brain, with Al-citrate and Al-transferrin complexes crossing the blood-brain barrier and accumulating in brain cells. Tea plant and other Al-accumulator plant species contain large amounts of Al in the form of non-toxic organic complexes.

ALS-like skin changes in mice on a chronic low-Ca/Mg high-Al diet

Epidemiologic studies of endemic foci of amyotrophic lateral sclerosis (ALS) have shown low concentrations of Ca/Mg and high concentrations of Al/Mn in the drinking water and garden soil, which may play a causative role in the pathogenesis of endemic ALS. We studied the effects of chronic exposure to a low-Ca/Mg high-Al maltol diet on the skin of experimental animals. In ALS patients, atrophy of the epidermis, edematous changes with separated collagen fibrils and an accumulation of amorphous materials between collagen bundles were regarded as pathognomonic skin changes of ALS. Mice chronically fed a low-Ca/Mg high-Al maltol diet showed neuronal degeneration and loss in the spinal cords and cerebral cortices, as well as skin changes including atrophy, separation of collagen fibrils and accumulation of amorphous materials, similar to the skin changes characteristic of ALS. This is the first report of skin changes in animal models similar to those of ALS. We speculate that environmental factors such as chronic low-Ca/Mg high-Al condition play some causative role in the pathogenesis of Kii-ALS.

The role of metals in neurodegenerative processes: aluminum, manganese, and zinc

Until the last decade, little attention was given by the neuroscience community to the neurometabolism of metals. However, the neurobiology of heavy metals is now receiving growing interest, since it has been linked to major neurodegenerative diseases. In the present review some metals that could possibly be involved in neurodegeneration are discussed. Two of them, manganese and zinc, are essential metals while aluminum is non-essential. Aluminum has long been known as a neurotoxic agent. It is an etiopathogenic factor in diseases related to long-term dialysis treatment, and it has been controversially invoked as an aggravating factor or cofactor in Alzheimer's disease as well as in other neurodegenerative diseases. Manganese exposure can play an important role in causing Parkinsonian disturbances, possibly enhancing physiological aging of the brain in conjunction with genetic predisposition. An increased environmental burden of manganese may have deleterious effects on more sensitive subgroups of the population, with sub-threshold neurodegeneration in the basal ganglia, generating a pre-Parkinsonian condition. In the case of zinc, there has as yet been no evidence that it is involved in the etiology of neurodegenerative diseases in humans. Zinc is redox-inactive and, as a result of efficient homeostatic control, does not accumulate in excess. However, adverse symptoms in humans are observed on inhalation of zinc fumes, or accidental ingestion of unusually large amounts of zinc. Also, high concentrations of zinc have been found to kill bacteria, viruses, and cultured cells. Some of the possible mechanisms for cell death are reviewed.

The biological behaviour and bioavailability of aluminium in man, with special reference to studies employing aluminium-26 as a tracer: review and study update

Until 1990 biokinetic studies of aluminium metabolism and biokinetics in man and other animals had been substantially inhibited by analytical and practical difficulties. Of these, the most important are the difficulties in differentiating between administered aluminium and endogenous aluminium-especially in body fluids and excreta and the problems associated with the contamination of samples with environmental aluminium. As a consequence of these it was not possible to detect small, residual body burdens of the metal following experimental administrations. Consequently, many believed aluminium to be quantitatively excreted within a short time of uptake in all, but renal-failure patients. Nevertheless, residual aluminium deposits in a number of different organs and tissues had been detected in normal subjects using a variety of techniques, including histochemical staining methods. In order to understand the origins and kinetics of such residual aluminium deposits new approaches were required. One approach taken was to employ the radioisotope (67)Ga as a surrogate, but this approach has been shown to be flawed-a consequence of the different biological behaviours of aluminium and gallium. A second arose from the availability, in about 1990, of both (26)Al-a rare and expensive isotope of aluminium-and accelerator mass spectrometry for the ultra-trace detection of this isotope. Using these techniques the basic features of aluminium biokinetics and bioavailability have been unravelled. It is now clear that some aluminium is retained in the body-most probably within the skeleton, and that some deposits in the brain. However, most aluminium that enters the blood is excreted in urine within a few days or weeks and the gastrointestinal tract provides an effective barrier to aluminium uptake. Aspects of the biokinetics and bioavailability of aluminium are described below.

Aluminum levels in convenience and fast foods: in vitro study of the absorbable fraction

We evaluated the levels of aluminum in a total of 120 samples of 35 different convenience and fast foods that are widely consumed in Spain. Aluminum was determined in the samples mineralized with HNO3, HClO4 and V2O5, using electrothermal atomic absorption spectrometry as the analytical technique. Reliability of the procedure was checked by statistically comparing the results with those obtained with a previous microwave oven mineralization stage and by analysis of several certified reference materials. No matrix effect was observed and aqueous standard solutions were used for calibration. The detection limit was 4.0 pg and the characteristic mass of 10.0 pg. Aluminum concentrations ranged from 0.85 to 38.10 microg/g, refereed to fresh weight of the edible portion. The presence of this metal was detected in all the samples we analyzed, but the most elevated levels were encountered in pork- and chicken- based foods (mean 8.45 and 13.94 microg/g, respectively). The more elevated Al concentrations were detected in foods with a greater content of spices and aromatic herbs, pasta, certain vegetables and additives, and foods packaged in Al vessels. The absorbable fraction of Al estimated with in vitro assays was between 0.85 and 2.15%. The growing popularity of these products in recent years requires additional data and a periodical control. In addition, the present findings are of potential use to efforts aimed at determining tolerable levels of Al intake from the diet.

Chronic low-Ca/Mg high-Al diet induces neuronal loss

To evaluate the causative role of environmental aluminum (Al) in the development of neurodegeneration in Kiiamyotrophic lateral sclerosis (ALS), we examined how chronic exposure to a low-Ca/Mg and high-Al diet induced neuronal loss and tau-related neuronal degeneration in experimental animals. Optical microscopic examination showed tau-positive cells, atrophic neurons with darkly stained cytoplasms or swollen perikarya in the cerebrum, hippocampus and the brainstem of mice fed a low-Ca/Mg high-Al diet (Group 3). The neuronal loss was found in the frontal and parietal cortices of the mice and was not due to a classical apoptosis as detected by the terminal de ynucl otidyl transferase-mediated dUTP-digoxigenin nick end-labeling (TUNEL) method. Neuronal degeneration and spheroid formation was also seen in the spinal cord of the Group 3 mice. The Morin fluorescence technique showed Al and Ca deposition in the cortical neurons and vessels in the basal ganglia of these mice. An electron microscopic examination showed intranuclear filamentous structures, intracytoplasmic vacuoles and/or darkly stained cytoplasm in the cortical neurons of Group 3 mice. These findings were seen in mice of the 11-month-experimental period and increased until the 25-month-experimental period. The present findings suggested that chronic exposure to a low-Ca/Mg high Al condition induced an accumulation of hyperphosphorylated tau in the cortical neurons, swelling of the neuronal cytoplasm and loss in the cerebrum and spinal cord of mice. Environmental factors such as a low-Ca/Mg high Al exposure might be one of the risk factors for the development of neuronal degeneration of ALS in the Kii Peninsula.

Why the preeminent risk factor in sporadic Alzheimer's disease cannot be genetic

If genetic risk factors are preeminent in the etiology of sporadic Alzheimer's disease, three corollaries follow: age-adjusted death rates from it should be fairly spatially uniform, should not vary significantly over time and should not alter markedly with migration. Globally, none of these corollaries hold true. The APO E(4) allele and other genetic aberrations that promote sporadic Alzheimer's disease do so most effectively in low alkalinity-high aluminum environments, especially if these are experiencing acid rain.

Aluminum: impacts and disease

Aluminum is the most widely distributed metal in the environment and is extensively used in modern daily life. Aluminum enters into the body from the environment and from diet and medication. However, there is no known physiological role for aluminum within the body and hence this metal may produce adverse physiological effects. The impact of aluminum on neural tissues is well reported but studies on extraneural tissues are not well summarized. In this review, the impacts of aluminum on humans and its impact on major physiological systems are summarized and discussed. The neuropathologies associated with high brain aluminum levels, including structural, biochemical, and neurobehavioral changes, have been summarized. In addition, the impact of aluminum on the musculoskeletal system, respiratory system, cardiovascular system, hepatobiliary system, endocrine system, urinary system, and reproductive system are discussed.