Circulatory Levels of Toxic Metals (Aluminum, Cadmium, Mercury, Lead) in Patients with Alzheimer's Disease: A Quantitative Meta-Analysis and Systematic Review

SIRT5-Mediated Desuccinylation of RAB7A Protects Against Cadmium-Induced Alzheimer's Disease-Like Pathology by Restoring Autophagic Flux

Cadmium (Cd) is a neurotoxic contaminant that induces cognitive decline similar to that observed in Alzheimer's disease (AD). Autophagic flux dysfunction is attributed to the pathogenesis of AD, and this study aimed to investigate the effect of autophagy on environmental Cd-induced AD progression and the underlying mechanism. Here, Cd exposure inhibited autophagosome-lysosome fusion and impaired lysosomal function, leading to defects in autophagic clearance and then to APP accumulation and nerve cell death. Proteomic analysis coupled with Ingenuity Pathway Analysis (IPA) identified SIRT5 as an essential molecular target in Cd-impaired autophagic flux. Mechanistically, Cd exposure hampered the expression of SIRT5, thus increasing the succinylation of RAB7A at lysine 31 and inhibiting RAB7A activity, which contributed to autophagic flux blockade. Importantly, SIRT5 overexpression led to the restoration of autophagic flux blockade, the alleviation of Aβ deposition and memory deficits, and the desuccinylation of RAB7A in Cd-exposed FAD4T mice. Additionally, SIRT5 levels decrease mainly in neurons but not in other cell clusters in the brains of AD patients according to single-nucleus RNA sequencing data from the public dataset GSE188545. This study reveals that SIRT5-catalysed RAB7A desuccinylation is an essential adaptive mechanism for the amelioration of Cd-induced autophagic flux blockade and AD-like pathogenesis.

Metal Toxicity and Dementia Including Frontotemporal Dementia: Current State of Knowledge

Frontotemporal dementia (FTD) includes a number of neurodegenerative diseases, often with early onset (before 65 years old), characterized by progressive, irreversible deficits in behavioral, linguistic, and executive functions, which are often difficult to diagnose due to their similar phenotypic characteristics to other dementias and psychiatric disorders. The genetic contribution is of utmost importance, although environmental risk factors also play a role in its pathophysiology. In fact, some metals are known to produce free radicals, which, accumulating in the brain over time, can induce oxidative stress, inflammation, and protein misfolding, all of these being key features of FTD and similar conditions. Therefore, the present review aims to summarize the current evidence about the environmental contribution to FTD-mainly dealing with toxic metal exposure-since the identification of such potential environmental risk factors can lead to its early diagnosis and the promotion of policies and interventions. This would allow us, by reducing exposure to these pollutants, to potentially affect society at large in a positive manner, decreasing the burden of FTD and similar conditions on affected individuals and society overall. Future perspectives, including the application of Artificial Intelligence principles to the field, with related evidence found so far, are also introduced.

Epigenetic Mechanisms of Aluminum-Induced Neurotoxicity and Alzheimer's Disease: A Focus on Non-Coding RNAs

Aluminum (Al) is known to induce neurotoxic effects, potentially contributing to Alzheimer's disease (AD) pathogenesis. Recent studies suggest that epigenetic modification may contribute to Al neurotoxicity, although the mechanisms are still debatable. Therefore, the objective of the present study was to summarize existing data on the involvement of epigenetic mechanisms in Al-induced neurotoxicity, especially AD-type pathology. Existing data demonstrate that Al exposure induces disruption in DNA methylation, histone modifications, and non-coding RNA expression in brains. Alterations in DNA methylation following Al exposure were shown to be mediated by changes in expression and activity of DNA methyltransferases (DNMTs) and ten-eleven translocation proteins (TETs). Al exposure was shown to reduce histone acetylation by up-regulating expression of histone deacetylases (HDACs) and impair histone methylation, ultimately contributing to down-regulation of brain-derived neurotrophic factor (BDNF) expression and activation of nuclear factor κB (NF-κB) signaling. Neurotoxic effects of Al exposure were also associated with aberrant expression of non-coding RNAs, especially microRNAs (miR). Al-induced patterns of miR expression were involved in development of AD-type pathology by increasing amyloid β (Aβ) production through up-regulation of Aβ precursor protein (APP) and β secretase (BACE1) expression (down-regulation of miR-29a/b, miR-101, miR-124, and Let-7c expression), increasing in neuroinflammation through NF-κB signaling (up-regulation of miR-9, miR-125b, miR-128, and 146a), as well as modulating other signaling pathways. Furthermore, reduced global DNA methylation, altered histone modification, and aberrant miRNA expression were associated with cognitive decline in Al-exposed subjects. However, further studies are required to evaluate the contribution of epigenetic mechanisms to Al-induced neurotoxicity and/or AD development.

The Effects of Fisetin and Curcumin on Oxidative Damage Caused by Transition Metals in Neurodegenerative Diseases

Neurodegenerative diseases pose a significant health challenge for the elderly. The escalating presence of toxic metals and chemicals in the environment is a potential contributor to central nervous system dysfunction and the onset of neurodegenerative conditions. Transition metals play a crucial role in various pathophysiological mechanisms associated with prevalent neurodegenerative diseases such as Alzheimer's and Parkinson's. Given the ubiquitous exposure to metals from diverse sources in everyday life, the workplace, and the environment, most of the population faces regular contact with different forms of these metals. Disturbances in the levels and homeostasis of certain transition metals are closely linked to the manifestation of neurodegenerative disorders. Oxidative damage further exacerbates the progression of neurological consequences. Presently, there exists no curative therapy for individuals afflicted by neurodegenerative diseases, with treatment approaches primarily focusing on alleviating pathological symptoms. Within the realm of biologically active compounds derived from plants, flavonoids and curcuminoids stand out for their extensively documented antioxidant, antiplatelet, and neuroprotective properties. The utilization of these compounds holds the potential to formulate highly effective therapeutic strategies for managing neurodegenerative diseases. This review provides a comprehensive overview of the impact of abnormal metal levels, particularly copper, iron, and zinc, on the initiation and progression of neurodegenerative diseases. Additionally, it aims to elucidate the potential of fisetin and curcumin to inhibit or decelerate the neurodegenerative process.

The involvement of SigmaR1K142 degradation mediated by ERAD in neural senescence linked with CdCl2 exposure

Alzheimer's disease (AD) is the most common cause of dementia worldwide. Due to its uncertain pathogenesis, there is currently no treatment available for AD. Increasing evidences have linked cellular senescence to AD, although the mechanism triggering cellular senescence in AD requires further exploration. To investigate the involvement of cellular senescence in AD, we explored the effects of cadmium chloride (CdCl2) exposure, one of the potential environmental risk factors for AD, on neuron senescence in vivo and in vitro. β-amyloid (Aβ) and tubulin-associated protein (tau) pathologies were found to be enhanced by CdCl2 exposure in the in vitro models, while p53/p21/Rb cascade-related neuronal senescence pathways were activated. Conversely, the use of melatonin, a cellular senescence inhibitor, or a cadmium ion chelator suppressed CdCl2-induced neuron senescence, along with the Aβ and tau pathologies. Mechanistically, CdCl2 exposure activated the suppressor enhancer Lin-12/Notch 1-like (SEL1L)/HMG-CoA reductase degradation 1 (HRD1)-regulated endoplasmic reticulum-associated degradation (ERAD), which enhanced the ubiquitin degradation of sigma-1 receptor (SigmaR1) by specifically recognizing its K142 site, resulting in the activation of the p53/p21/Rb pathway via the induction of Ca2+ dyshomeostasis and mitochondrial dysfunction. In the in vivo models, the administration of the SigmaR1 agonist ANAVEX2-73 rescues neurobehavioral inhibition and alleviates cellular senescence and AD-like pathology in the brain tissue of CdCl2-exposed mice. Consequently, the present study revealed a novel senescence-associated regulatory route for the SEL1L/HRD1/SigmaR1 axis that affects the pathological progression of CdCl2 exposure-associated AD. CdCl2 exposure activated SEL1L/HRD1-mediated ERAD and promoted the ubiquitinated degradation of SigmaR1, activating p53/p21/Rb pathway-regulated neuronal senescence. The results of the present study suggest that SigmaR1 may function as a neuroprotective biomarker of neuronal senescence, and pharmacological activation of SigmaR1 could be a promising intervention strategy for AD therapy.

Metals on the Menu-Analyzing the Presence, Importance, and Consequences

Metals are integral components of the natural environment, and their presence in the food supply is inevitable and complex. While essential metals such as sodium, potassium, magnesium, calcium, iron, zinc, and copper are crucial for various physiological functions and must be consumed through the diet, others, like lead, mercury, and cadmium, are toxic even at low concentrations and pose serious health risks. This study comprehensively analyzes the presence, importance, and consequences of metals in the food chain. We explore the pathways through which metals enter the food supply, their distribution across different food types, and the associated health implications. By examining current regulatory standards for maximum allowable levels of various metals, we highlight the importance of ensuring food safety and protecting public health. Furthermore, this research underscores the need for continuous monitoring and management of metal content in food, especially as global agricultural and food production practices evolve. Our findings aim to inform dietary recommendations, food fortification strategies, and regulatory policies, ultimately contributing to safer and more nutritionally balanced diets.

Zeolite and Neurodegenerative Diseases

Neurodegenerative diseases (NDs), characterized by progressive degeneration and death of neurons, are strongly related to aging, and the number of people with NDs will continue to rise. Alzheimer's disease (AD) and Parkinson's disease (PD) are the most common NDs, and the current treatments offer no cure. A growing body of research shows that AD and especially PD are intricately related to intestinal health and the gut microbiome and that both diseases can spread retrogradely from the gut to the brain. Zeolites are a large family of minerals built by [SiO4]4- and [AlO4]5- tetrahedrons joined by shared oxygen atoms and forming a three-dimensional microporous structure holding water molecules and ions. The most widespread and used zeolite is clinoptilolite, and additionally, mechanically activated clinoptilolites offer further improved beneficial effects. The current review describes and discusses the numerous positive effects of clinoptilolite and its forms on gut health and the gut microbiome, as well as their detoxifying, antioxidative, immunostimulatory, and anti-inflammatory effects, relevant to the treatment of NDs and especially AD and PD. The direct effects of clinoptilolite and its activated forms on AD pathology in vitro and in vivo are also reviewed, as well as the use of zeolites as biosensors and delivery systems related to PD.

Sensing lead ions in water: a comprehensive review on strategies and sensor materials

It is well-known fact that elevated lead ions (Pb2+), the third most toxic among heavy metal ions in aqueous systems, pose a threat to human health and aquatic ecosystems when they exceed permissible limits. Pb2+ is commonly found in industrial waste and fertilizers, contaminating water sources and subsequently entering the human body, causing various adverse health conditions. Unlike being expelled, Pb2+ accumulates within the body, posing potential health risks. The harmful impact of presence of Pb2+ in water have prompted researchers to diligently work toward maintaining water quality. Recognizing the importance of Pb2+, this review article makes a sincere and effective effort to address the issues associated with Pb2+. This overview article gives insights into various sensing approaches to detect Pb2+ in water using different sensing materials, including 2-dimensional materials, thiols, quantum dots, and polymers. Herein, different sensing approaches such as electrochemical, optical, field effect transistor-based, micro-electromechanical system-based, and chemi resistive are thoroughly explained. Field effect transistor-based and chemiresistive work on similar principles and are compared on the basis of their fabrication processes and sensing capabilities. In conclusion, future directions for chemiresistive sensors in Pb2+ detection are proposed, emphasizing their simplicity, portability, straightforward functionality, and ease of fabrication. Notably, it sheds light on various thiol and ligand compounds and coupling strategies utilized in Pb2+ detection. This comprehensive study is expected to benefit individuals engaged in Pb2+ detection.

New bithiophene derivative attenuated Alzheimer's disease induced by aluminum in a rat model via antioxidant activity and restoration of neuronal and synaptic transmission

BACKGROUND

One of the hypotheses that leads to an increased incidence of Alzheimer's disease (AD) is the accumulation of aluminum in the brain's frontal cortex. The present study aimed to evaluate the therapeutic role of a novel bithiophene derivative at two doses against AlCl3-induced AD in a rat model.

METHODOLOGY

Adult male rats were divided into six groups, 18 rats each. Group 1: naïve animals, group 2: animals received a daily oral administration of bithiophene dissolved in DMSO (1 mg/kg) for 30 days every other day, groups 3-6: animals received a daily oral administration of AlCl3 (100 mg/kg/day) for 45 consecutive days. Groups 4 and 5 received an oral administration of low or high dose of the bithiophene (0.5 or 1 mg/kg, respectively). Group 6; Animals were treated with a daily oral dose of memantine (20 mg/kg) for 30 consecutive days.

MAIN FINDINGS

Al disturbed the antioxidant milieu, elevated the lipid peroxidation, and depleted the antioxidants. It also disturbed the synaptic neurotransmission by elevating the activities of acetylcholine esterase and monoamine oxidase resulting in the depletion of dopamine and serotonin and accumulation of glutamate and norepinephrine. Al also deteriorated the expression of genes involved in apoptosis and the production of amyloid-β plaques as well as phosphorylation of tau. The new bithiophene at the low dose reversed most of the previous deleterious effects of aluminum in the cerebral cortex and was in many instances superior to the reference drug; memantine.

CONCLUSION

Taking together, the bithiophene modulated the AD etiology through antioxidant activity, prevention of neuronal and synaptic loss, and probably mitigating the formation of amyloid-β plaques and phosphorylation of tau.

Exposure to heavy metal elements may significantly increase serum prostate-specific antigen levels with overdosed dietary zinc

BACKGROUND

Serum prostate-specific antigen (PSA) is a primary metric for diagnosis and prognosis of prostate cancer (PCa). Exposure to heavy metals, such as lead, cadmium, mercury, and zinc can impact PSA levels in PCa patients. However, it is unclear whether this effect also occurs in men without PCa, which may lead to the overdiagnosis of PCa.

METHOD

Data on a total of 5089 American men who had never been diagnosed with PCa were obtained from the National Health and Nutrition Examination Survey performed from 2003-2010. The relationship between serum PSA levels (dependent variable) and concentrations of lead (μmol/L), cadmium (nmol/L), and mercury (μmol/L) were investigated with dietary zinc intake being used as a potential modifier or covariate in a weighted linear regression model and a generalized additive model. A series of bootstrapping analyses were performed to evaluate sensitivity and specificity using these models.

RESULTS

Regression analyses suggested that, in general, lead, cadmium, or mercury did not show an association with PSA levels, which was consistent with the results of the bootstrapping analyses. However, in a subgroup of participants with a high level of dietary zinc intake (≥14.12 mg/day), a significant positive association between cadmium and serum PSA was identified (1.06, 95% CI, P = 0.0268, P for interaction=0.0249).

CONCLUSIONS

With high-level zinc intake, serum PSA levels may rise in PCa-free men as the exposure to cadmium increases, leading to a potential risk of an overdiagnosis of PCa and unnecessary treatment. Therefore, environmental variables should be factored in the current diagnostic model for PCa that is solely based on PSA measurements. Different criteria for PSA screening are necessary based on geographical variables. Further investigations are needed to uncover the biological and biochemical relationship between zinc, cadmium, and serum PSA levels to more precisely diagnose PCa.

Mechanisms of Cadmium Neurotoxicity

Cadmium is a heavy metal that increasingly contaminates food and drink products. Once ingested, cadmium exerts toxic effects that pose a significant threat to human health. The nervous system is particularly vulnerable to prolonged, low-dose cadmium exposure. This review article provides an overview of cadmium's primary mechanisms of neurotoxicity. Cadmium gains entry into the nervous system via zinc and calcium transporters, altering the homeostasis for these metal ions. Once within the nervous system, cadmium disrupts mitochondrial respiration by decreasing ATP synthesis and increasing the production of reactive oxygen species. Cadmium also impairs normal neurotransmission by increasing neurotransmitter release asynchronicity and disrupting neurotransmitter signaling proteins. Cadmium furthermore impairs the blood-brain barrier and alters the regulation of glycogen metabolism. Together, these mechanisms represent multiple sites of biochemical perturbation that result in cumulative nervous system damage which can increase the risk for neurological and neurodegenerative disorders. Understanding the way by which cadmium exerts its effects is critical for developing effective treatment and prevention strategies against cadmium-induced neurotoxic insult.

Chronic cadmium exposure induces Parkinson-like syndrome by eliciting sphingolipid disturbance and neuroinflammation in the midbrain of C57BL/6J mice

Cadmium (Cd) is known as a widespread environmental neurotoxic pollutant. Cd exposure is recently recognized as an etiological factor of Parkinson's disease (PD) in humans. However, the mechanism underlying Cd neurotoxicity in relation to Parkinsonism pathogenesis is unclear. In our present study, C57BL/6 J mice were exposed to 100 mg/L CdCl2 in drinking water for 8 weeks. It was found Cd exposure caused motor deficits, decreased DA neurons and induced neuropathological changes in the midbrain. Non-targeted lipidomic analysis uncovered that Cd exposure altered lipid profile, increased the content of proinflammatory sphingolipid ceramides (Cer), sphingomyelin (SM) and ganglioside (GM3) in the midbrain. In consistency with increased proinflammatory lipids, the mRNA levels of genes encoding sphingolipids biosynthesis in the midbrain were dysregulated by Cd exposure. Neuroinflammation in the midbrain was evinced by the up-regulation of proinflammatory cytokines at mRNA and protein levels. Blood Cd contents and lipid metabolites in Parkinsonism patients by ICP-MS and LC-MS/MS analyses demonstrated that elevated blood Cd concentration and proinflammatory lipid metabolites were positively associated with the score of Unified Parkinson's Disease Rating Scale (UPDRS). 3 ceramide metabolites in the blood showed good specificity as the candidate biomarkers to predict and monitor Parkinsonism and Cd neurotoxicity (AUC>0.7, p < 0.01). In summary, our present study uncovered that perturbed sphingomyelin lipid metabolism is related to the Parkinsonism pathogenesis and Cd neurotoxicity, partially compensated for the deficiency in particular metabolic biomarkers for Parkinsonism in relation to Cd exposure, and emphasized the necessity of reducing Cd exposure at population level.

The Effects of a Mixture of Cadmium, Lead, and Mercury on Metabolic Syndrome and Its Components, as well as Cognitive Impairment: Genes, MicroRNAs, Transcription Factors, and Sponge Relationships : The Effects of a Mixture of Cadmium, Lead, and Mercury on Metabolic Syndrome and Its Components, as well as Cognitive Impairment: Genes, MicroRNAs, Transcription Factors, and Sponge Relationships

Converging evidence indicates heavy metal-induced genes, transcription factors (TFs), and microRNAs (miRNAs) are critical pathological components of metabolic syndrome (MetS) and cognitive impairment. Thus, our goals are to identify the interaction of mixed heavy metals (cadmium + lead + mercury) with genes, TFs, and miRNAs involved in MetS and its components, as well as cognitive impairment development. The most commonly retrieved genes for each disease were different, but essential biological pathways such as oxidative stress, altered lipoprotein metabolism, fluid shear stress and atherosclerosis, apoptosis, the IL-6 signaling pathway, and Alzheimer's disease were highlighted. The genes CASP3, BAX, BCL2, IL6, TNF, APOE, HMOX1, and IGF were found to be mutually affected by the heavy metal mixture studied, suggesting the importance of apoptosis, inflammation, lipid, heme, and glucose metabolism in MetS and cognitive impairment, as well as the potentiality of targeting these genes in prospective therapeutic intervention for these diseases. EGR2, ATF3, and NFE2L2 were noted as the most key TFs implicated in the etiology of MetS and its components, as well as cognitive impairment. We also found six miRNAs induced by studied heavy metals were the mutual miRNAs linked to MetS, its components, and cognitive impairment. In particular, we used miRNAsong to construct and verify a miRNA sponge sequence for these miRNAs. These sponges are promising molecules for the treatment of MetS and its components, as well as cognitive impairment.

Interaction between aluminum exposure and ApoEε4 gene on cognitive function of in-service workers

The occurrence and development of cognitive impairment, the early stage of AD, may be affected both by factors of environmental (aluminum exposure) and genetic (ApoEε4 gene). But whether there is an interaction between the two factors on cognitive function is still unknown. To explore the interaction between the two factors on cognitive function of in-service workers. A total of 1121 in-service workers in a large aluminum factory were investigated in Shanxi Province. Cognitive function was assessed by the Mini-mental State Examination (MMSE), the clock-drawing test (CDT), the Digit Span Test (DST, including DSFT and DSBT), the fuld object memory evaluation (FOM), and the verbal fluency task (VFT). The plasma-Al (p-Al) concentrations were measured by inductively coupled plasma-mass spectrometry (ICP-MS) as an internal exposure indicator, and the participants were divided into four Al exposure groups according to the quartile of p-Al concentrations, namely Q1, Q2, Q3, and Q4. ApoE genotype was determined by Ligase Detection Reaction (LDR). The multiplicative model was fitted using non-conditional logistic regression and additive model was fitted using crossover analysis to analyze the interaction between p-Al concentrations and the ApoEε4 gene. Finally, a dose-response relationship between p-Al concentrations and cognitive impairment was observed, with the p-Al concentrations increased, cognitive function performance gradually becomes worse (P_trend＜0.05), and the risk of cognitive impairment gradually increases (P_trend＜0.05), mainly in executive/visuospatial impairment, auditory memory impairment (particularly the working memory impairment). And ApoEε4 gene may be a risk factor for cognitive impairment, while no association between the ApoEε2 gene and cognitive impairment is observed. Additionally, an additive but no multiplicative interaction between p-Al concentrations and ApoEε4 gene is observed, and when the two factors work together, the risk of cognitive impairment further increased, of which 44.2% can be attributed to the interaction effect.

Metals in Alzheimer's Disease

The role of metals in the pathogenesis of Alzheimer's disease (AD) is still debated. Although previous research has linked changes in essential metal homeostasis and exposure to environmental heavy metals to the pathogenesis of AD, more research is needed to determine the relationship between metals and AD. In this review, we included human studies that (1) compared the metal concentrations between AD patients and healthy controls, (2) correlated concentrations of AD cerebrospinal fluid (CSF) biomarkers with metal concentrations, and (3) used Mendelian randomization (MR) to assess the potential metal contributions to AD risk. Although many studies have examined various metals in dementia patients, understanding the dynamics of metals in these patients remains difficult due to considerable inconsistencies among the results of individual studies. The most consistent findings were for Zn and Cu, with most studies observing a decrease in Zn levels and an increase in Cu levels in AD patients. However, several studies found no such relation. Because few studies have compared metal levels with biomarker levels in the CSF of AD patients, more research of this type is required. Given that MR is revolutionizing epidemiologic research, additional MR studies that include participants from diverse ethnic backgrounds to assess the causal relationship between metals and AD risk are critical.

Phyllodulcin improves hippocampal long-term potentiation in 5XFAD mice

Alzheimer's disease (AD) is a well-known neurodegenerative brain disease, and no curative treatment has yet been developed. The main symptoms include various brain lesions, caused by amyloid β (Aβ) aggregation, and cognitive decline. Therefore, it is believed that substances that control Aβ will inhibit the onset of Alzheimer's disease and slow its progression. In this study, the effect of phyllodulcin, a major component of hydrangea, on Aβ aggregation and brain pathology in an animal model of AD was studied. Phyllodulcin inhibited the aggregation of Aβ and decomposed the pre-aggregated Aβ in a concentration-dependent manner. In addition, it inhibited the cytotoxicity of Aβ aggregates. Oral administration of phyllodulcin improved Aβ-induced memory impairments in normal mice, reduced Aβ deposition in the hippocampus, inhibited the activation of microglia and astrocytes, and improved synaptic plasticity in 5XFAD mice. These results suggest that phyllodulcin may be a candidate for the treatment of AD.

Zebrafish as a Potential Model for Neurodegenerative Diseases: A Focus on Toxic Metals Implications

In the last century, industrial activities increased and caused multiple health problems for humans and animals. At this moment, heavy metals are considered the most harmful substances for their effects on organisms and humans. The impact of these toxic metals, which have no biological role, poses a considerable threat and is associated with several health problems. Heavy metals can interfere with metabolic processes and can sometimes act as pseudo-elements. The zebrafish is an animal model progressively used to expose the toxic effects of diverse compounds and to find treatments for different devastating diseases that human beings are currently facing. This review aims to analyse and discuss the value of zebrafish as animal models used in neurological conditions, such as Alzheimer's disease (AD), and Parkinson's disease (PD), particularly in terms of the benefits of animal models and the limitations that exist.

Neuroprotective efficacy of the bacterial metabolite, prodigiosin, against aluminium chloride-induced neurochemical alternations associated with Alzheimer's disease murine model: Involvement of Nrf2/HO-1/NF-κB signaling

Prodigiosin (PDG) is a bacterial metabolite with numerous biological and pharmaceutical properties. Exposure to aluminium is considered a root etiological factor in the pathological progress of Alzheimer's disease (AD). Here, in this investigation, we explored the neuroprotective potential of PDG against aluminium chloride (AlCl₃ )-mediated AD-like neurological alterations in rats. For this purpose, rats were gavaged either AlCl₃ (100 mg/kg), PDG (300 mg/kg), or both for 42 days. As a result of the analyzes performed on the hippocampal tissue, it was observed that AlCl₃ induced biochemical, molecular, and histopathological changes like those related to AD. PDG pre-treatment significantly decreased acetylcholinesterase activity and restored the levels of brain-derived neurotrophic factor, monoamines (dopamine, norepinephrine, and serotonin), and transmembrane protein (Na⁺ /K⁺ -ATPase). Furthermore, PDG boosted the hippocampal antioxidant capacity, as shown by the increased superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, and glutathione contents. These findings were accompanied by decreases in malondialdehyde and nitric oxide levels. The antioxidant effect may promote the upregulation of the expression of antioxidant genes (Nrf2 and HO-1). Moreover, PDG exerted notable anti-inflammatory effects via the lessening of interleukin-1 beta, tumor necrosis factor-alpha, cyclooxygenase-2, nuclear factor kappa B, and decreases in the gene expression of inducible nitric oxide synthase. In addition, noteworthy decreases in pro-apoptotic (Bax and caspase-3) levels and increases in anti-apoptotic (Bcl-2) biomarkers suggested an anti-apoptotic effect of PDG. In support, the hippocampal histological examination validated the aforementioned changes. To summarize, the promising neuromodulatory, antioxidative, anti-inflammatory, and anti-apoptotic activities of PDG establish it as a potent therapeutic option for AD.

The relationship between cadmium and cognition in the elderly: a systematic review

Context: The relationship between cadmium (Cd) and the cognition of the elderly is indistinct.Objective: To summarise the studies on the relationship between the cognition of the elderly and Cd.Methods: Literatures were searched in PubMed, Web of Science, China National Knowledge Infrastructure (CNKI), and Wan fang database on April 25, 2022. The entries in the STROBE statement were used to evaluate the literature quality; all the quantitative studies that met the requirements were systematically summarised.Results: Blood Cd was negatively correlated with the cognitive ability of the elderly, corresponding to different cognitive ability assessment methods, the regression coefficients were: -0.11 (-0.20, -0.03), -0.46 (-0.71, -0.21), -0.54 (-0.90, -0.17), -0.19 (-0.37, -0.01), and -2.29 (-3.41, -1.16). The regression coefficients between urinary Cd level and cognition score were -1.42 (-2.38, -0.46), and 0.76 (-1.28, -0.23). When dietary Cd increased by 1 μg/kg, the composite z-score decreased by 3.64 (p = 0.001). There was no significant correlation between drinking water Cd, fingernail Cd and cognition (p > 0.05).Conclusion: We concluded that blood Cd (including whole blood and plasma), urine Cd and dietary Cd were negatively correlated with the cognition of the elderly, but the relationship between Cd in drinking water and fingernails and cognition was not statistically significant.

Microglial Activation in Metal Neurotoxicity: Impact in Neurodegenerative Diseases

Neurodegenerative processes encompass a large variety of diseases with different pathological patterns and clinical features, such as Alzheimer's and Parkinson's diseases. 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 most probably, each metal has its specific pathway to trigger cell death. As a result, exposure to essential metals, such as manganese, iron, copper, zinc, and cobalt, and nonessential metals, including lead, aluminum, and cadmium, perturbs metal homeostasis at the cellular and organism levels leading to neurodegeneration. In this contribution, a comprehensive review of the molecular mechanisms by which metals affect microglia physiology and signaling properties is presented. Furthermore, studies that validate the disruption of microglia activation pathways as an essential mechanism of metal toxicity that can contribute to neurodegenerative disease are also presented and discussed.

Is There Correlation Between Aluminum-Based Food Consumption and Plasma Level in Pregnant Women?

To explore the correlation of AL-based food consumption, known to have negative impact on health, and Al plasma levels with pregnancy status. A cross-sectional study was conducted on 75 participants, including 50 pregnant women. Al plasma levels were analyzed by ET-AAS. Exposure to food was positively correlated to Al mean plasma levels (reaching 2.12 ± 1.17 μg/L) by 32%, specifically for potatoes, fruits, soft drinks, and ready meals. Usage of Al cookware was associated to higher Al plasma levels while pregnancy status was protective. Establishment of national recommendation to maintain lower levels of Al in food is required.

Dietary Selenomethionine Reduce Mercury Tissue Levels and Modulate Methylmercury Induced Proteomic and Transcriptomic Alterations in Hippocampi of Adolescent BALB/c Mice

Methylmercury (MeHg) is a well-known environmental contaminant, particularly harmful to the developing brain. The main human dietary exposure to MeHg occurs through seafood consumption. However, seafood also contains several nutrients, including selenium, which has been shown to interact with MeHg and potentially ameliorate its toxicity. The aim of this study was to investigate the combined effects of selenium (as selenomethionine; SeMet) and MeHg on mercury accumulation in tissues and the effects concomitant dietary exposure of these compounds exert on the hippocampal proteome and transcriptome in mice. Adolescent male BALB/c mice were exposed to SeMet and two different doses of MeHg through their diet for 11 weeks. Organs, including the brain, were sampled for mercury analyses. Hippocampi were collected and analyzed using proteomics and transcriptomics followed by multi-omics bioinformatics data analysis. The dietary presence of SeMet reduced the amount of mercury in several organs, including the brain. Proteomic and RNA-seq analyses showed that both protein and RNA expression patterns were inversely regulated in mice receiving SeMet together with MeHg compared to MeHg alone. Several pathways, proteins and RNA transcripts involved in conditions such as immune responses and inflammation, oxidative stress, cell plasticity and Alzheimer’s disease were affected inversely by SeMet and MeHg, indicating that SeMet can ameliorate several toxic effects of MeHg in mice.

Neuron Protection by EDTA May Explain the Successful Outcomes of Toxic Metal Chelation Therapy in Neurodegenerative Diseases

Many mechanisms have been related to the etiopathogenesis of neurodegenerative diseases (NDs) such as multiple sclerosis, amyotrophic lateral sclerosis, Parkinson’s disease, and Alzheimer’s disease. In this context, the detrimental role of environmental agents has also been highlighted. Studies focused on the role of toxic metals in the pathogenesis of ND demonstrate the efficacy of treatment with the chelating agent calcium disodium ethylenediaminetetraacetic acid (EDTA) in eliminating toxic metal burden in all ND patients, improving their symptoms. Lead, cadmium, aluminum, nickel, and mercury were the most important toxic metals detected in these patients. Here, I provide an updated review on the damage to neurons promoted by toxic metals and on the impact of EDTA chelation therapy in ND patients, along with the clinical description of a representative case.

Uma revisão de escopo de revisões sistemáticas sobre exposição humana ao mercúrio

Resumo: Introdução: a promulgação da Convenção de Minamata no Brasil em 2018 incentivou o cumprimento dos seus objetivos em reduzir o uso e a poluição por mercúrio. Objetivo: caracterizar a produção científica sobre exposição humana ao mercúrio e identificar lacunas de conhecimento a fim de subsidiar a tomada de decisão em saúde. Métodos: revisão de escopo de revisões sistemáticas e metanálises, sem restrição de idioma ou data de publicação, utilizando as bases PubMed, BVS e Cochrane Library. Resultados: 71 estudos atenderam aos critérios de elegibilidade, com 40 revisões sistemáticas, 30 metanálises e 1 overview. Amálgama dentário e contaminação alimentar e ambiental por atividades que utilizam mercúrio foram as fontes de exposição mais mencionadas. Os temas mais estudados contaram com transtornos mentais e comportamentais, assim como uso de biomarcadores e testes neurocomportamentais relacionados à exposição ao mercúrio. Discussão: lacunas como a exposição ocupacional ao mercúrio, uso em práticas tradicionais e em cosméticos apontam para a necessidade de mais estudos. As revisões identificadas podem oferecer subsídios para sínteses de evidências e protocolos de atenção à saúde de populações expostas, assim como para a elaboração de políticas públicas que visem o controle do uso e da exposição ao mercúrio.

Lab-on-a-ZnO-Submicron-Particle Sensor Array for Monitoring AD upon Cd2+ Exposure with CSF Tau441% as an Effective Hallmark

In this study, based on the posttreatment strategy, blue-color-emissive ZnO submicron particles (B-ZnO SMPs) and red-color-emissive ZnO submicron particles (R-ZnO SMPs) were obtained from rationally designed Zn-infinite coordination polymer (ICP) precursors. After modification of thiol-containing aptamers, diverse spectral changes in the ultraviolet and visible regions of B- and R-ZnO SMPs toward different tau species were explored to construct a lab-on-a-ZnO-submicron-particle sensor array. Assisted by principal component analysis (PCA), the unique fingerprints of the sensor array enabled the simultaneous differentiation and quantitative detection of different tau species (tau381, tau410, and tau441) for the first time. Furthermore, the dynamic changes of tau441% (the ratio of the two most reported representative 4R isoform (full-length tau441) and 3R isoform (tau381)) in cerebrospinal fluid (CSF) during the Alzheimer's disease (AD) onset of Cd²⁺-exposed rats could also be monitored by the lab-on-a-ZnO-submicron-particle sensor array, which was supposed to be an effective hallmark and highly correlated with the formation of neurofibrillary tangles (NFTs). This study not only provides a further insight into the involvement of subchronic Cd²⁺ exposure in the tau etiology of AD but also offers more comprehensive and effective information about the asymptomatic stage of AD upon environmental risk, which has potential applications in the early diagnosis and therapy.

Environmental Substances Associated with Alzheimer's Disease-A Scoping Review

Alzheimer’s disease (AD) is the most common form of dementia, prevalent in approximately 50–70% of the dementia cases. AD affects memory, and it is a progressive disease interfering with cognitive abilities, behaviour and functioning of the person affected. In 2015, there were 47 million people affected by dementia worldwide, and the figure was estimated to increase to 75 million in 2030 and to 132 million by 2050. In the framework of European Human Biomonitoring Initiative (HBM4EU), 18 substances or substance groups were prioritized for investigation. For each of the priority substances, a scoping document was prepared. Based on these scoping documents and complementary review of the recent literature, a scoping review of HBM4EU-priority substances which might be associated with AD was conducted. A possible association between risk of AD and pesticides was detected. For mercury (Hg), association is possible but inconsistent. Regarding cadmium (Cd) and arsenic (As), the results are inconsistent but inclined towards possible associations between the substances and the risk of disease. The evidence regarding lead (Pb) was weaker than for the other substances; however, possible associations exist. Although there is evidence of adverse neurological effects of environmental substances, more research is needed. Environmental chemical exposure and the related hazards are essential concerns for public health, and they could be preventable.

Disorders of the Reproductive Health of Cattle as a Response to Exposure to Toxic Metals

The aim of this review is to comprehensively present disorders of the reproductive system in cattle exposed to contact with toxic metals. Toxic metals are a common environmental pollutant and can come from mines, smelters, fossil fuel combustion, or volcanic eruptions. Metals have the ability to bioaccumulate in living organisms, thus contaminating the food chain and may pose a threat to humans. They accumulate mainly in the liver and kidneys, but also in muscles and fat tissue. Toxic metals such as lead (Pb), arsenic (As), mercury (Hg), and cadmium (Cd) have a negative impact on the fertility of animals; they can lead to abortions, premature calving, or oocyte dysfunction. Moreover, in the male reproductive system, they disrupt spermatogenesis, and cause apoptosis of sperm and oxidative damage. The main source of exposure of livestock to toxic metals is through the consumption of feed or contaminated water. It is important to monitor the level of heavy metals in animal products to prevent human poisoning. Toxic metal biomonitoring can be performed by testing urine, blood, milk, plasma, or hair. Chromium (Cr), arsenic (As), and cadmium (Cd) are excreted in the urine, while lead can be detected by examining the blood of animals, while in milk, arsenic (As), cadmium (Cd), nickel (Ni), and lead (Pb) can be detected. Moreover, toxic metals do not biodegrade in the environment. To purify soil and waters, remediation methods, e.g., biological or chemical, should be used.

Detection of Mercury Ion with High Sensitivity and Selectivity Using a DNA/Graphene Oxide Hybrid Immobilized on Glass Slides

Excessive mercury ions (Hg²⁺) cause great pollution to soil/water and pose a major threat to human health. The high sensitivity and high selectivity in the Hg²⁺ detection demonstrated herein are significant for the research areas of analytical chemistry, chemical biology, physical chemistry, drug discovery, and clinical diagnosis. In this study, a series of simple, low-cost, and highly sensitive biochips based on a graphene oxide (GO)/DNA hybrid was developed. Hg²⁺ is detected with high sensitivity and selectivity by GO/DNA hybrid biochips immobilized on glass slides. The performance of the biosensors can be improved by introducing more phosphorothioate sites and complementary bases. The best limit of detection of the biochips is 0.38 nM with selectivity of over 10:1. This sensor was also used for Hg²⁺ detection in Dendrobium. The results show this biochip is promising for Hg²⁺ detection.

Molecular Mechanisms of Environmental Metal Neurotoxicity: A Focus on the Interactions of Metals with Synapse Structure and Function

Environmental exposure to neurotoxic metals and metalloids such as arsenic, cadmium, lead, mercury, or manganese is a global health concern affecting millions of people worldwide. Depending on the period of exposure over a lifetime, environmental metals can alter neurodevelopment, neurobehavior, and cognition and cause neurodegeneration. There is increasing evidence linking environmental exposure to metal contaminants to the etiology of neurological diseases in early life (e.g., autism spectrum disorder) or late life (e.g., Alzheimer’s disease). The known main molecular mechanisms of metal-induced toxicity in cells are the generation of reactive oxygen species, the interaction with sulfhydryl chemical groups in proteins (e.g., cysteine), and the competition of toxic metals with binding sites of essential metals (e.g., Fe, Cu, Zn). In neurons, these molecular interactions can alter the functions of neurotransmitter receptors, the cytoskeleton and scaffolding synaptic proteins, thereby disrupting synaptic structure and function. Loss of synaptic connectivity may precede more drastic alterations such as neurodegeneration. In this article, we will review the molecular mechanisms of metal-induced synaptic neurotoxicity.

Association between serum iron concentrations and cognitive impairment in older adults aged 60 years and older: A dose-response analysis of National Health and Nutrition Examination Survey

Epidemiological evidence on peripheral iron and cognitive impairment in older adults is sparse and limited. Results on serum iron and cognitive impairment in older adults from the National Health and Nutrition Examination Survey have not been reported. Data on serum iron and cognitive impairment from individuals ≥ 60 years of age were obtained from the 2011–2014 NHANES (N = 3,131). Serum iron concentrations were determined with DcX800 method. Cognitive impairment was assessed with four cognitive tests: the Digit Symbol Substitution Test (DSST), the Animal Fluency (AF), the Consortium to Establish a Registry for Alzheimer’s Disease Delayed Recall (CERAD-DR) and Word Learning (CERAD-WL) tests. Logistic regression and restricted cubic splines were adopted to explore the dose-response relationship between serum iron concentrations and cognitive impairment. Comparing the highest to lowest tertile of serum iron concentrations, the multivariate-adjusted odds ratios of scoring low on the DSST were 0.70 (0.49–1.00), 0.88 (0.65–1.20) for CERAD-WL, 0.65 (0.48–0.88) for CERAD-DR, and 0.78 (0.53–1.15) for AF. Stratified analyses by sex showed that the above-mentioned associations were mainly found in men; however, the interaction with sex was not significant. Dose-response analysis showed that relationships between serum iron and cognitive impairment evaluated by DSST and CERAD-DR were linear, respectively.

Curcumin Attenuated Neurotoxicity in Sporadic Animal Model of Alzheimer's Disease

Alzheimer's disease (AD) is one of the most common neurodegenerative diseases leading to dementia. Despite research efforts, currently there are no effective pharmacotherapeutic options for the prevention and treatment of AD. Recently, numerous studies highlighted the beneficial effects of curcumin (CUR), a natural polyphenol, in the neuroprotection. Especially, its dual antioxidant and anti-inflammatory properties attracted the interest of researchers. In fact, besides its antioxidant and anti-inflammatory properties, this biomolecule is not degraded in the intestinal tract. Additionally, CUR is able to cross the blood-brain barrier and could therefore to be used to treat neurodegenerative pathologies associated with oxidative stress, inflammation and apoptosis. The present study aimed to assess the ability of CUR to induce neuronal protective and/or recovery effects on a rat model of neurotoxicity induced by aluminum chloride (AlCl3), which mimics the sporadic form of Alzheimer's disease. Our results showed that treatment with CUR enhances pro-oxidant levels, antioxidant enzymes activities and anti-inflammatory cytokine production and decreases apoptotic cells in AlCl3-exposed hippocampus rats. Additionally, histopathological analysis of hippocampus revealed the potential of CUR in decreasing the hallmarks in the AlCl3-induced AD. We also showed that CUR post-treatment significantly improved the behavioral, oxidative stress and inflammation in AlCl3-exposed rats. Taken together, our data presented CUR as a nutraceutical potential through its protective effects that are more interesting than recovery ones in sporadic model of AD.

Cognitive Improvement and Safety Assessment of a Dietary Supplement Containing Propolis Extract in Elderly Japanese: A Placebo-Controlled, Randomized, Parallel-Group, Double-Blind Human Clinical Study

Objectives. This study aimed to evaluate the effect of propolis on cognitive function in elderly Japanese with a placebo-controlled design. Material and Methods. This study was performed on 79 elderly Japanese. Participants orally received either a placebo or dietary supplement containing propolis extract for 24 weeks. Cognitive function assessed by Cognitrax and various blood or urine markers were measured at pre- and postadministration. Results and Conclusion. Eligible data from 68 subjects (placebo: 33, propolis: 35) who completed the study were analyzed. Compared to the placebo group, the propolis group showed significant improvement in verbal memory in Cognitrax (P=0.028). Total cholesterol, LDL cholesterol, urea nitrogen, creatinine, and uric acid were significantly improved in the propolis group compared to the placebo group (P = 0.011, P = 0.004, P = 0.048, P = 0.045, and P = 0.005, respectively). However, urea nitrogen, creatinine, and uric acid fluctuated within the normal level. Furthermore, a subgroup analysis was performed on those with higher than 100 of the standardized score of the neurocognitive index indicated by the overall Cognitrax score. Significant improvements in the propolis group compared to placebo were confirmed in verbal memory (P = 0.007) and processing speed as indications for information processing ability, complex attention, and concentration (P = 0.029). No side effects were observed in any of the groups. This study demonstrates that propolis is effective in improving cognitive functions such as memory, information processing, complex attention, and concentration in elderly Japanese.

Cu2+-Regulated reversible coordination interaction of GQD@Tb/GMP ICP nanoparticles: towards directly monitoring cerebrospinal acetylcholinesterase as a biomarker for cholinic brain dysfunction

This work demonstrates a new strategy for sensing cerebrospinal acetylcholinesterase (AChE) as a cholinergic biomarker for brain dysfunction based on graphene quantum dot (GQD)-functionalized lanthanide infinite coordination polymer (Ln-ICP) nanoparticles. The ICPs used in this work were comprised of two components, i.e. a supramolecular Ln-ICP host formed by the coordination between the GMP ligand and central metal ion Tb3+, and guest GQDs with abundant functional groups, which were utilized as antenna ligands to further sensitize the fluorescence of Tb/GMP. Upon excitation at 300 nm, the obtained GQD@Tb/GMP ICP nanoparticles exhibited enhanced green fluorescence from Tb/GMP. With the addition of Cu2+, the competitive coordination between Cu2+ and GQDs weakened the antenna effect, leading to a decrease in the fluorescence of GQD@Tb/GMP ICPs. However, in the presence of thiocholine (TCh), a thiol-containing compound hydrolyzed from acetylthiocholine (ATCh) by AChE, a stronger coordination interaction between Cu2+ and TCh occurred, resulting in the restoration of the fluorescence of GQD@Tb/GMP ICPs. Using the method established herein, the cerebrospinal AChE fluctuation of rats with acute organophosphorus pesticide (OP) poisoning or chronic Alzheimer's disease (AD) could be monitored. This study essentially provides a novel approach to realize the direct monitoring of a biomarker for brain dysfunction by regulating the competitive coordination interaction reversibly, which is critical in the early diagnosis and therapy of brain diseases.

Emerging risk of environmental factors: insight mechanisms of Alzheimer's diseases

Neurodegenerative disorders are typically sporadic in nature in addition to usually influenced through an extensive range of environmental factors, lifestyle, and genetic elements. Latest observations have hypothesized that exposure of environmental factors may increase the prospective risk of Alzheimer's diseases (AD). However, the role of environmental factors as a possible dangerous issue has extended importance concerned in AD pathology, although actual etiology of the disorder is still not yet clear. Thus, the aim of this review is to highlight the possible correlation between environmental factors and AD, based on the present literature view. Environmental risk factors might play an important role in decelerating or accelerating AD progression. Among well-known environmental risk factors, prolonged exposure to several heavy metals, for example, aluminum, arsenic, cadmium, lead, and mercury; particulate air, and some pesticides as well as metal-containing nanoparticles have been participated to cause AD. These heavy metals have the capacity to enhance amyloid β (Aβ) peptide along with tau phosphorylation, initiating amyloid/senile plaques, as well as neurofibrillary tangle formation; therefore, neuronal cell death has been observed. Furthermore, particulate air, pesticides, and heavy metal exposure have been recommended to lead AD susceptibility and phenotypic diversity though epigenetic mechanisms. Therefore, this review deliberates recent findings detailing the mechanisms for a better understanding the relationship between AD and environmental risk factors along with their mechanisms of action on the brain functions.

Comparison of Plasma Concentrations of Mercury, Cadmium, and Arsenic among Women in 2005 and 2012 in a Historically Contaminated Area in China

Mercury (Hg), cadmium (Cd), and arsenic (As) concentrations in women were measured and compared to evaluate the effects of environmental heavy-metal pollution control on internal exposure levels. In 2005 and 2012, 200 and 182 women, respectively, were enrolled in the study. Demographic and diet information were collected using a questionnaire. Fasting venous blood samples were collected, and plasma concentrations of Hg, Cd, and As were measured using inductive coupled plasma mass spectrometry. The median concentrations (P₂₅-P₇₅) of Hg, Cd, and As decreased from 0.56 (0.46-0.75) ng/mL, 0.14 (0.09-0.21) ng/mL, and 0.83 (0.66-1.09) ng/mL in 2005 to 0.39 (0.19-0.66) ng/mL, 0.09 (0.05-0.13) ng/mL, and 0.48 (0.29-0.72) ng/mL in 2012, respectively. The difference in plasma metal concentrations between measurements in 2005 and 2012 remained statistically significant after we adjusted for confounders. The adjusted ORs were 0.31 (0.16-0.60), 0.24 (0.12-0.48), and 0.25 (0.13-0.50) for Hg, Cd, and As concentrations, respectively, in 2012, relative to those in 2005. The levels of Hg, Cd, and As were 30% to 40% lower in 2012 than in 2005, indicative of lower human internal exposure to these contaminants due to the implementation of environmental pollution control. Engagement with agriculture and high-frequency water product consumption were associated with high Hg levels, and a high frequency of consumption of fresh fruit and eggs was negatively associated with lower levels of Cd in plasma.

Positive regulation of the CREB phosphorylation via JNK-dependent pathway prevents antimony-induced neuronal apoptosis in PC12 cell and mice brain

Antimony (Sb) is a potentially toxic chemical element abundantly found in the environment. We previously reported that Sb promoted neuronal deathvia reactive oxygen species-dependent autophagy. Here, we assessed the role of cyclic adenosine monophosphate response element-binding protein (CREB) in Sb-induced neuronal damage. We found that Sb treatment induced CREB phosphorylation and neuronal apoptosis both in vitro and in vivo. Interestingly, inhibition of CREB's transcriptional activity with 666-15 dramatically enhanced apoptosis in PC12 cells by downregulating B-cell lymphoma 2 (Bcl-2). Additionally, Sb activated ERK, JNK, and p38 signaling ; however, only JNK promoted CREB phosphorylation. In conclusion, our findings suggest that CREB phosphorylation by JNK attenuates Sb-induced neuronal apoptosis via Bcl-2 upregulation. These data suggest that JNK-dependent CREB activation prevents neurons from Sb-induced apoptosis and guides the development of novel strategies to prevent Sb-induced neurotoxicity.

Cadmium-Induced Cytotoxicity: Effects on Mitochondrial Electron Transport Chain

Cadmium (Cd) is a well-known heavy metal and environmental toxicant and pollutant worldwide, being largely present in every kind of item such as plastic (toys), battery, paints, ceramics, contaminated water, air, soil, food, fertilizers, and cigarette smoke. Nowadays, it represents an important research area for the scientific community mainly for its effects on public health. Due to a half-life ranging between 15 and 30 years, Cd owns the ability to accumulate in organs and tissues, exerting deleterious effects. Thus, even at low doses, a Cd prolonged exposure may cause a multiorgan toxicity. Mitochondria are key intracellular targets for Cd-induced cytotoxicity, but the underlying mechanisms are not fully elucidated. The present review is aimed to clarify the effects of Cd on mitochondria and, particularly, on the mitochondrial electron transport chain.

Akt inhibition-dependent downregulation of the Wnt/β-Catenin Signaling pathway contributes to antimony-induced neurotoxicity

Antimony (Sb), as a newly identified nerve poison, can lead to neuronal apoptosis. However, its neurotoxicological mechanisms remain largely unclear. Here, we evaluated the role and regulation of Wnt/β-catenin pathway in Sb-mediated neurotoxicity. Under Sb treatment, β-catenin was dramatically downregulated in vivo and in vitro. Moreover, overexpression of β-catenin effectively attenuated Sb-induced survivin gene expression suppression and subsequent apoptosis in PC12 cells. In addition, Sb stimualted glycogen synthase kinase-3β (GSK-3β) activation, shown as decreased phosphorylation levels at Ser 9 both in PC12 cells and mice brain. Paramacological inhibition of GSK-3β using lithium chloride (LiCl) significantly rescued β-catenin expression. For upstream pathway analysis, we found Sb treatment decreased protein kinase B (Akt) phosphorylation, and Akt activator protected PC12 cells from GSK-3β activation and subsequent β-catenin suppression. In summary, our data provided a novel molecular mechanism of Sb-associated neurotoxicity, namely that Sb induces Wnt/β-catenin pathway suppression through Akt inhibition, thus resulted in neuronal apoptosis.

Genotoxic Effect of Lead and Cadmium on Workers at Wastewater Plant in Iraq

Heavy metal poisoning is a worldwide problem that is caused by different human industrial activities such as battery and painting manufacturing and occupational exposure of those working at petrol stations. Wastewater is known to contain higher amounts of heavy metals such as lead (Pd) and cadmium (Cd) and might be sources of exposure for workers at the wastewater treatment plant. However, to our best knowledge, no studies were done to evaluate the level of cadmium and lead in blood of workers at wastewater treatment plants and evaluate the subsequent effect of lead and cadmium on delta-aminolevulinic acid dehydratase (δ-ALAD), urinary delta-aminolevulinic acid (Uδ-ALA), and 8-hydroxy-2'-deoxyguanosine (8-OHdG) as markers of lead and cadmium toxicity. In this case-control study, 79 workers at the Al-Rustumiya wastewater plant in Baghdad, Iraq, and 40 control subjects were included. The levels of lead and cadmium were measured in blood of the study subjects using the atomic absorption spectroscopy (AAS) method. 8-OHdG was analysed using enzyme-linked immunosorbent assay (ELISA) technique. δ-ALAD and Uδ-ALA were estimated using spectrophotometry-based methods. Our work showed that workers had a significantly higher level of lead and cadmium when compared with the control group (P < 0.05), yet, still within the World Health Organization permissible limit. The level of both metals was positively associated with duration of work at the plant (P < 0.01). The activity of δ-ALAD was inversely associated with the lead level, while both Uδ-ALA and 8-OHdG were positively correlated with the lead level (P < 0.05). These three markers lacked any statistically significant association with the cadmium level (P > 0.05). To sum up, working at the wastewater treatment plant was associated with a higher blood level of lead and cadmium and their possible health hazard. Health and occupational safety authorities are required to set up tighter regulations and protocols to minimize these hazards and ensure a safe working environment.

Camellia oil alleviates the progression of Alzheimer's disease in aluminum chloride-treated rats

Alzheimer's disease (AD), the most common type of dementia, is associated with oxidative stress, inflammation, and gut microbiota (GM) imbalance. Recent studies have demonstrated that camellia oil has antioxidant and anti-inflammatory activity and modulates the immune system and GM. However, the effect of camellia oil in alleviating AD pathogenesis remains unclear. An SD rat model of cognitive decline was established by the daily oral administration of aluminum chloride. The results revealed that the aluminum chloride-treated group exhibited deteriorated memory capacity and increased expression of AD-related proteins, whereas these features were mitigated in camellia oil-treated groups. Treatment with camellia oil increased antioxidant enzyme levels and decreased MDA levels. Additionally, camellia oil modulated the expression of cytokines by inhibiting RAGE/NF-κB signaling and microglial activation. Interestingly, autophagy-related proteins were increased in the camellia oil-treated groups. Moreover, camellia oil increased the abundance of probiotics in the GM. Camellia oil can reverse AD brain pathology by alleviating deficits in memory, increasing learning capacity, increasing antioxidant activity, modulating the expression of immune-related cytokines, enhancing autophagy and improving the composition of GM in aluminum chloride-treated rats, implying that AD pathogenesis may be mitigated by treatment with camellia oil through the microbiome-gut-brain axis.

Evidence-based umbrella review of 162 peripheral biomarkers for major mental disorders

The literature on non-genetic peripheral biomarkers for major mental disorders is broad, with conflicting results. An umbrella review of meta-analyses of non-genetic peripheral biomarkers for Alzheimer's disease, autism spectrum disorder, bipolar disorder (BD), major depressive disorder, and schizophrenia, including first-episode psychosis. We included meta-analyses that compared alterations in peripheral biomarkers between participants with mental disorders to controls (i.e., between-group meta-analyses) and that assessed biomarkers after treatment (i.e., within-group meta-analyses). Evidence for association was hierarchically graded using a priori defined criteria against several biases. The Assessment of Multiple Systematic Reviews (AMSTAR) instrument was used to investigate study quality. 1161 references were screened. 110 met inclusion criteria, relating to 359 meta-analytic estimates and 733,316 measurements, on 162 different biomarkers. Only two estimates met a priori defined criteria for convincing evidence (elevated awakening cortisol levels in euthymic BD participants relative to controls and decreased pyridoxal levels in participants with schizophrenia relative to controls). Of 42 estimates which met criteria for highly suggestive evidence only five biomarker aberrations occurred in more than one disorder. Only 15 meta-analyses had a power >0.8 to detect a small effect size, and most (81.9%) meta-analyses had high heterogeneity. Although some associations met criteria for either convincing or highly suggestive evidence, overall the vast literature of peripheral biomarkers for major mental disorders is affected by bias and is underpowered. No convincing evidence supported the existence of a trans-diagnostic biomarker. Adequately powered and methodologically sound future large collaborative studies are warranted.

Positive association between soil arsenic concentration and mortality from alzheimer's disease in mainland China

OBJECTIVES

The current study was designed to investigate the relationship between the soil arsenic (As) concentration and the mortality from Alzheimer's disease (AD) in mainland China.

STUDY DESIGN

Ecological study.

METHODS

Twenty-two provinces and 3 municipal districts in mainland China were included in this study. The As concentrations in soil in 1990 was obtained from the China State Environmental Protection Bureau; the data on annual mortality of AD from 1991 to 2000 were obtained from the National Death Cause Surveillance Database of China. Using these data, we calculated the spearman correlation coefficient between soil As concentration and AD mortality, and the relative risk (RR) between soil As levels and AD mortality by quartile-dividing study groups.

RESULTS

The spearman correlation coefficient between As concentration and AD mortality was 0.552 (p = 0.004), 0.616 (p = 0.001) and 0.622 (p = 0.001) in the A soil As (eluvial horizon), the C soil As (parent material horizon), and the Total soil As (A soil As + C soil As), respectively. When the A soil As concentration was over 9.05 mg/kg, 10.40 mg/kg and 13.10 mg/kg, the relative risk was 0.835 (95 % CI: 0.832, 0.838), 1.969 (95 %CI: 1.955, 1.982), and 2.939 (95 % CI: 2.920, 2.958), respectively; when the C soil As reached 9.45 mg/kg, 11.10 mg/kg and 13.55 mg/kg, the relative risk was 4.349 (95 % CI: 4.303, 4.396), 6.108 (95 % CI: 6.044, 6.172), and 9.125 (95 %CI: 9.033, 9.219), respectively. No correlation was found between lead, cadmium, and mercury concentration in the soil and AD mortality.

CONCLUSION

There was an apparent soil As concentration dependent increase in AD mortality. Results of this study may provide evidence for a possible causal linkage between arsenic exposure and the death risk from AD.

Sildenafil for the Treatment of Alzheimer's Disease: A Systematic Review

Nitric oxide/cyclic guanosine monophosphate (cGMP) signaling is compromised in Alzheimer’s disease (AD), and phosphodiesterase 5 (PDE5), which degrades cGMP, is upregulated. Sildenafil inhibits PDE5 and increases cGMP levels. Integrating previous findings, we determine that most doses of sildenafil (especially low doses) likely activate peroxisome proliferator-activated receptor-γ coactivator 1α (PGC1α) via protein kinase G-mediated cyclic adenosine monophosphate (cAMP) response element binding protein (CREB) phosphorylation and/or Sirtuin-1 activation and PGC1α deacetylation. Via PGC1α signaling, low-dose sildenafil likely suppresses β-secretase 1 expression and amyloid-β (Aβ) generation, upregulates antioxidant enzymes, and induces mitochondrial biogenesis. Plus, sildenafil should increase brain perfusion, insulin sensitivity, long-term potentiation, and neurogenesis while suppressing neural apoptosis and inflammation. A systematic review of sildenafil in AD was undertaken. In vitro, sildenafil protected neural mitochondria from Aβ and advanced glycation end products. In transgenic AD mice, sildenafil was found to rescue deficits in CREB phosphorylation and memory, upregulate brain-derived neurotrophic factor, reduce reactive astrocytes and microglia, decrease interleukin-1β, interleukin-6, and tumor necrosis factor-α, decrease neural apoptosis, increase neurogenesis, and reduce tau hyperphosphorylation. All studies that tested Aβ levels reported significant improvements except the two that used the highest dosage, consistent with the dose-limiting effect of cGMP-induced phosphodiesterase 2 (PDE2) activation and cAMP depletion on PGC1α signaling. In AD patients, a single dose of sildenafil decreased spontaneous neural activity, increased cerebral blood flow, and increased the cerebral metabolic rate of oxygen. A randomized control trial of sildenafil (ideally with a PDE2 inhibitor) in AD patients is warranted.

Heavy Metals Exposure and Alzheimer's Disease and Related Dementias

Alzheimer's disease and related dementias lack effective treatment or cures and are major public health challenges. Risk for Alzheimer's disease and related dementias is partially attributable to environmental factors. The heavy metals lead, cadmium, and manganese are widespread and persistent in our environments. Once persons are exposed to these metals, they are adept at entering cells and reaching the brain. Lead and cadmium are associated with numerous health outcomes even at low levels of exposure. Although manganese is an essential metal, deficiency or environmental exposure or high levels of the metal can be toxic. In cell and animal model systems, lead, cadmium, and manganese are well documented neurotoxicants that contribute to canonical Alzheimer's disease pathologies. Adult human epidemiologic studies have consistently shown lead, cadmium, and manganese are associated with impaired cognitive function and cognitive decline. No longitudinal human epidemiology study has assessed lead or manganese exposure on Alzheimer's disease specifically though two studies have reported a link between cadmium and Alzheimer's disease mortality. More longitudinal epidemiologic studies with high-quality time course exposure data and incident cases of Alzheimer's disease and related dementias are warranted to confirm and estimate the proportion of risk attributable to these exposures. Given the widespread and global exposure to lead, cadmium, and manganese, even small increases in the risks of Alzheimer's disease and related dementias would have a major population impact on the burden on disease. This article reviews the experimental and epidemiologic literature of the associations between lead, cadmium, and manganese on Alzheimer's disease and related dementias and makes recommendations of critical areas of future investment.