Multifaceted effects of aluminium in neurodegenerative diseases: A review

Evaluation of neuroprotective effects of wedelolactone and gallic acid on aluminium-induced neurodegeneration: Relevance to sporadic amyotrophic lateral sclerosis

Al exposure causes an alteration in the several ions in the body and causes toxicity. Such as apoptosis, oxidative stress, disruption in neuronal transport, mitochondrial damage, excitotoxicity, generation of inflammatory mediators, and microglial activation. These multiple mechanisms lead to the several neurodegenerative diseases, including sporadic amyotrophic lateral sclerosis (sALS). The study aims to unravel the mechanisms behind the neuroprotective effects of wedelolactone (WL) and gallic acid (GA) against aluminium-induced neurodegeneration and thereby to unlock a platform to find a cure for sALS. We studied the neuroprotective effects of WL (100 & 200 mg/kg) and GA (100 & 200 mg/kg) using aluminium chloride (AlCl₃)-induced neurodegeneration model. The study was conducted using male Wistar rats. We assessed the effects of WL and GA on motor learning ability, motor coordination, locomotor activity, cytokine production, BDNF, glutathione peroxidase (GPx), m-calpain, caspase-3 inhibition and L-glutamate level. The study suggests that the treatment with WL and GA could protect the motor neurons from the toxicity that caused by Al via improving the antioxidant status, BDNF, and by preventing glutamate excitotoxicity. Also, WL and GA are found to be effective in inhibiting caspase-3 activation and downregulating inflammatory cytokines. WL and GA also found effective in improving the motor learning abilities and motor coordination in rats. The protective effects of the WL and GA were further confirmed from histopathological results. WL and GA prevent the neurofibrillary tangle formation and neuronal damage. The study concluded that the WL and GA were dose-dependently effective in managing the AlCl₃-induced neurodegeneration.

Can nonalcoholic beer, silicon and hops reduce the brain damage and behavioral changes induced by aluminum nitrate in young male Wistar rats?

Aluminum consumption has been associated with various neurodegenerative diseases. Previous studies suggest that regular beer intake reverses the pro-oxidant and inflammatory statuses induced by aluminum nitrate intoxication. This paper aims to evaluate the in vitro antioxidant capacity and acetylcholinesterase inhibitory activity of non-alcoholic beer (NABeer), silicon or hops, as well as their effect on animal behavior (e.g. curiosity, immobilization, rearing, grooming, swimming) and brain antioxidant enzyme (activity and gene expression) and anti-inflammatory status in aluminum nitrate intoxicated rats. Male Wistar rats were divided into five groups: 1) Control, 2) Aluminum nitrate (450 μg/kg/day), 3) Aluminum nitrate plus NABeer, 4) Aluminum nitrate plus hops, and 5) Aluminum nitrate plus silicon. Hops showed the highest in vitro antioxidant capacity and silicon the highest anticholinesterase activity. In the Aluminum group the brain aluminum/silicon ratio increased with impairment of brain antioxidant and inflammatory statuses. NABeer, silicon and hops block the negative effect on the in vivo antioxidant and inflammatory statuses induced by Aluminum nitrate and improve swimming and rearing behavioral tests. The various positive results suggest that NABeer is useful as a functional multi-target drink in the prevention of some neurodegenerative events caused by aluminum intoxication. More studies are required to conclude present results.

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.

Spatial Assessment of the Association between Long-Term Exposure to Environmental Factors and the Occurrence of Amyotrophic Lateral Sclerosis in Catalonia, Spain: A Population-Based Nested Case-Control Study

BACKGROUND

It is believed that an interaction between genetic and non-genetic factors may be involved in the development of amyotrophic lateral sclerosis (ALS). With the exception of exposure to agricultural chemicals like pesticides, evidence of an association between environmental risk factors and ALS is inconsistent. Our objective here was to investigate the association between long-term exposure to environmental factors and the occurrence of ALS in Catalonia, Spain, and to provide evidence that spatial clusters of ALS related to these environmental factors exist.

METHODS

We carried out a nested case-control study constructed from a retrospective population-based cohort, covering the entire region. Environmental variables were the explanatory variables of interest. We controlled for both observed and unobserved confounders.

RESULTS

We have found some spatial clusters of ALS. The results from the multivariate model suggest that these clusters could be related to some of the environmental variables, in particular agricultural chemicals. In addition, in high-risk clusters, besides corresponding to agricultural areas, key road infrastructures with a high density of traffic are also located.

CONCLUSION

Our results indicate that some environmental factors, in particular those associated with exposure to pesticides and air pollutants as a result of urban traffic, could be associated with the occurrence of ALS.

Trace elements in ALS patients and their relationships with clinical severity

An exploratory study of trace elements in ALS and their relationships with clinical severity was detected. Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder that causes irreversible damage in humans, with the consequent loss of function of motoneurons (MNs), with a prognosis up to 5 years after diagnosis. Except to genetic rare cases it is not known the etiology of the disorder. Aim of our research is to investigate the possible role of heavy metals in the severity of the disease. In this study, by the use of plasma mass (ICP-MS), we have analyzed the content of essential and heavy metals such: Pb, Cd, Al, Hg, Mn, Fe, Cu, Zn, Se, Mg, and Ca, in blood, urine and hair of ALS patients and controls; moreover we divided the patients in two groups for disease severity and analyzed the difference among the groups, in order to study a possible involvement of metals in the severity of the damage. Our results suggest a protective role of Selenium, involved in protective antioxidant mechanisms, and a risk factor in the case of presence of Lead in blood. The levels of the other metals are not easy to interpret, because these may be due to life style and for essential metals a consequence of the disease condition, not a cause.

Cytoprotective effect of deferiprone against aluminum chloride-induced oxidative stress and apoptosis in lymphocytes

Aluminum (Al) is a toxic metal, and excessive Al accumulation causes immunosuppression. Deferiprone (DFP) is a well-known chelator and used in dialysis patients for removing Al from tissues. The present study aimed to investigate whether DFP treatment can attenuate immunotoxicity induced by aluminum chloride (AlCl3) in cultured lymphocytes. Lymphocytes were treated with 0 and 0.6 mmol/L AlCl3∙6H2O (pH 7.2) and/or 1.8 mmol/L DFP, respectively. Immune function of lymphocytes was assessed by T and B lymphocytes proliferation rates, T lymphocyte subpopulations and IL-2, IL-6 and TNF-α contents. In addition, lymphocyte damage was assessed by LDH activity, NO and MDA contents, NOS, SOD and GSH-Px activities, lymphocyte apoptosis index. These results showed that AlCl3 exposure reduced T and B lymphocyte proliferation rates, CD3+ and CD4+ T lymphocyte subpopulations, CD4+/CD8+ ratio, IL-2, IL-6 and TNF-α contents, SOD and GSH-Px activities, early and later lymphocyte apoptosis indexes while enhanced CD8+ T lymphocyte subpopulation, NO and MDA contents, LDH activity. DFP treatment attenuated the immunotoxicity of lymphocytes and reduced oxidative stress and lymphocyte apoptosis induced by AlCl3, indicating that DFP could protect lymphocytes against immunosuppression induced by AlCl3 through attenuating oxidative stress and apoptosis.

Transcriptome-Wide Identification of Differentially Expressed Genes and Long Non-coding RNAs in Aluminum-Treated Rat Hippocampus

Aluminum (Al) is an environmental neurotoxicant with a wide exposure, but the molecular mechanism underlying its toxicity remains unclear. We used RNA sequencing (RNA-seq) in the hippocampus of Al-treated rats to identify 96 upregulated and 652 downregulated mRNAs, and 37 dysregulated long non-coding (lnc)RNAs. Gene ontology analysis showed that dysregulated genes were involved in glial cell differentiation, neural transmission, and vesicle trafficking. Kyoto Encyclopedia of Genes and Genomes pathway analysis revealed clustering of differentially expressed mRNAs and lncRNA target genes in several pathways, including the "adenosine monophosphate-activated protein kinase signaling pathway," "extracellular matrix receptor interaction," "the phosphatidylinositol 3 kinase-protein kinase B signaling pathway," and "focal adhesion" signaling pathway. RNA-seq results were validated by reverse transcription (RT)-PCR. Additionally, Al induced changes to the number and morphology of glial cells in the hippocampus of rats, as shown by glial fibrillary acidic protein (GFAP) and ionized calcium binding adaptor molecule 1 (Iba1) immunochemistry. RT-PCR and western blotting validated the significant increase in expression of glial cell-related genes GFAP and SOX10 following Al exposure compared with control rats, consistent with RNA-seq results. Collectively, these results suggest that aberrant mRNAs and lncRNAs respond to Al neurotoxicity, and that glial cell-related genes play important roles in the Al neurotoxicity mechanism. These findings provide the basis for designing targeted approaches for the treatment or prevention of Al-induced neurotoxicity.

Exposure to Aluminum in Daily Life and Alzheimer's Disease

Aluminum is the third most abundant element on the earth's crust and has been considered a constituent of rather inert minerals. Therefore, it has often been regarded as not having a significant health hazard. Consequently, aluminum-containing agents have been used in processing, packaging, and storage of food products and also in the treatment of drinking water as flocculants. Recently, acid rain due to environmental pollution has transported more aluminum-containing minerals into residential drinking water resources. It is therefore not surprising that aluminum burden in the human body has increased. Research data showed that aluminum is not as safe as was previously thought and that aluminum may contribute to the initial advancement of Alzheimer's disease. Aluminum-mediated neurodegeneration resulting in cognitive dysfunction has been associated with amyloidβ (Aβ) deposition, formation of intraneuronal neurofibrillary tangles (NFTs), and apoptotic neuronal death characterized histopathologically in AD. The origin of Alzheimer's disease is generally not known; its development is likely triggered by unknown environmental factors. Although it is inconsistent with the link between human exposure to aluminum in everyday life and its contribution to Alzheimer's disease, a growing body of evidence points to aluminum as being one such significant influence.

Volumetric modeling of two sludge piles from water treatment plants in a Brazilian reservoir

Water treatment plants are designed to continuously produce drinkable water, meeting defined criteria of potability. However, besides potable water, these plants produce sludges that are disposed of in the environment. The present work aimed to evaluate the sludges generated in two water treatment plants and disposed of in the margin of the Juturnaíba dam. Since alum has been used as a flocculating agent in these two plants, the concentrations of aluminum were measured in the sludges and in surface sediments. The generated piles are extremely soft to walk on and difficult to measure, so indirect modeling procedures had to be applied. The calculated mass of the sludge piles at each plant are similar and respectively 60,370 and 61,479 tons. The aluminum content of the residues, calculated according to its dosage, was 33.2 and 32.6 g kg^-1 in the piles from the two plants. The amount of alum dosed to the water corresponds almost to the excess of aluminum in the sludge, compared to the sediments. It was concluded that regardless of the fact that residues are disposed of in very restricted areas, they are directly in contact with the water and may constitute a threat for the environment and humans' health.

The Metal Neurotoxins: An Important Role in Current Human Neural Epidemics?

Many published studies have illustrated that several of the present day neurological epidemics (autism, attention deficit disorder, Alzheimer's) cannot be correlated to any single neurotoxicant. However, the present scientific examination of the numerous global blood monitoring databases for adults that include the concentrations of the neurotoxic elements, aluminum (Al), arsenic (As), lead (Pb), manganese (Mn), mercury (Hg), and selenium (Se) clearly indicate that, when considered in combination, for some, the human body may become easily over-burdened. This can be explained by changes in modern lifestyles. Similar data, solely for pregnant women, have been examined confirming this. All these elements are seen to be present in the human body and at not insignificant magnitudes. Currently suggested minimum risk levels (MRL) for humans are discussed and listed together with averages of the reported distributions, together with their spread and maximum values. One observation is that many distributions for pregnant women are not too dissimilar from those of general populations. Women obviously have their individual baseline of neurotoxin values before pregnancy and any efforts to modify this to any significant degree is not yet clearly apparent. For any element, distribution shapes are reasonably similar showing broad distributions with extended tails with numerous outlier values. There are a certain fraction of people that lie well above the MRL values and may be at risk, especially if genetically susceptible. Additionally, synergistic effects between neurotoxins and with other trace metals are now also being reported. It appears prudent for women of child-bearing age to establish their baseline values well before pregnancy. Those at risk then can be better identified. Adequate instrumental testing now is commercially available for this. In addition, directives are necessary for vaccination programs to use only non-neurotoxic adjuvants, especially for young children and all women of child-bearing ages. Additionally, clearer directives concerning fish consumption must now be reappraised.

Hyperforin attenuates aluminum-induced Aβ production and Tau phosphorylation via regulating Akt/GSK-3β signaling pathway in PC12 cells

Aluminum (Al) is a neurotoxicant and cause β-amyloid (Aβ) peptides aggregation and tau hyperphosphorylation. Hyperforin (HF) is one of the major active constituents of the extracts of St. John's Wort (Hypericum perforatum), can treat Alzheimer's disease (AD) and other diseases involving peptide accumulation and cognition impairment. To determine the effects of HF on Al-induced Aβ formation and tau hyperphosphorylation, PC12 cells were cultured and treated with Al-malt (500μM) and/or HF (1μM). The results showed that HF treatment significantly attenuated Al-malt-induced Aβ_1-42 production by reducing the expressions of APP, BACE1 and PS1, while increasing the expressions of sAPPα, ADAM9/10/17, and tau phosphorylation in PC12 cells. In addition, HF treatment also increased phosphorylation of AKT (Ser473) and inhibited GSK-3β activity by increasing phosphorylation of GSK-3β (Ser9). These results indicated that HF may exert the protection via regulating the AKT/GSK-3β signaling to reduce Aβ production and tau phosphorylation in PC12 cells. Furthermore, these results could lead a possible therapeutics for the management of Al neurotoxicity.

A 2-year Double-Blind RCT Follow-up Study with Fermented Papaya Preparation (FPP) Modulating Key Markers in Middle-Age Subjects with Clustered Neurodegenerative Disease-Risk Factors

In recent years a number of studies have reported the significant relationship between metabolic syndrome and neurodegenerative disease. There is accumulating evidence that the interplay of combined genetic and environmental risk factors (from diet to life style to pollutants) to intrinsic age-related oxi-inflammatory changes may be advocated for to explain the pandemic of neurodegenerative diseases. In recent years a specific Fermented Papaya Preparation (FPP) has been shown to significantly affect a number of redox signalling abnormalities in a variety of chronic diseases and as well in aging mechanisms either on experimental and on clinical ground. The aim of the present study was to evaluate FPP use in impending metabolic disease patients with potentially neurodegenerative disease clustered risk factors. The study population consisted of 90 patients aged 45-65 years old, with impending metabolic syndrome and previously selected as to be ApoE4 genotype negative. By applying a RCT, double-blind method, one group received FPP 4.5 g twice a day (the most common dosage utilized in prior clinical studies) while the other received an oral antioxidant cocktail (trans-resveratrol, selenium, vitamin E, vitamin C). Then, after 21 month treatment period, a selected heavy metal chelator was added at the dosage of 3 g/nocte for the final 3 months study treatment. The parameters tested were: routine tests oxidized LDL-cholesterol, anti-oxidised LDL, Cyclophilin-A (CyPA), plasminogen activator inhibitor-1 and CyPA gene expression. From this study it would appear that FPP, unlike the control antioxidant, significantly decreased oxidized-LDL and near normalizing the anti-Ox-LDL/Ox-LDL ratio (p<0.001) although unaffecting the lipid profile per sè. Moreover, only FPP decreased cyclophilin-A plasma level and plasminogen activator-inhibitor (p<0.01) together with downregulating cyclophilin-A gene expression (p<0.01). Insulin resistance was only mildly improved. Heavy metals gut clearance proved to be effectively enhanced by the chelator (p<0.01) and this was not affected by any of the nutraceuticals, nor it added any further benefit to the biological action of FPP.

SEM-EDS-Based Elemental Identification on the Enamel Surface after the Completion of Orthodontic Treatment: In Vitro Studies

Braces as foreign bodies in the mouth carry a risk of side effects and toxicity to the human body. This article presents the results indicating the possible toxic effects of tools used for cleaning the enamel after the completion of orthodontic treatment. The studies were carried out in vitro. The procedure of enamel etching, bonding orthodontic metal brackets, and enamel cleaning after their removal was performed under laboratory conditions. The enamel microstructure and elements present on its surface were evaluated using the scanning electron microscope (SEM). Silicon and aluminium were found in addition to the tooth building elements.