Brain manganese and the balance between essential roles and neurotoxicity

Manganese-Induced Toxicity in C. elegans: What Can We Learn from the Transcriptome?

Manganese (Mn) is an essential ubiquitous transition metal and, when occupationally or environmentally overexposed, a well-known risk factor for several neurological pathologies. However, the molecular mechanisms underlying Mn-induced neurotoxicity are largely unknown. In this study, addressing RNA-Seq analysis, bioavailability and survival assays, key pathways of transcriptional responses to Mn overexposure were investigated in the model organism Caenorhabditis elegans (C. elegans), providing insights into the Mn-induced cellular stress and damage response. Comparative transcriptome analyses identified a large number of differentially expressed genes (DEGs) in nematodes exposed to MnCl₂, and functional annotation suggested oxidative nucleotide damage, unfolded protein response and innate immunity as major damage response pathways. Additionally, a time-dependent increase in the transcriptional response after MnCl₂ exposure was identified by means of increased numbers of DEGs, indicating a time-dependent response and activation of the stress responses in Mn neurotoxicity. The data provided here represent a powerful transcriptomic resource in the field of Mn toxicity, and therefore, this study provides a useful basis for further planning of targeted mechanistic studies of Mn-induced neurotoxicity that are urgently needed in the face of increasing industrially caused environmental pollution with Mn.

Potential Health Effects of Heavy Metals and Carcinogenic Health Risk Estimation of Pb and Cd Contaminated Eggs from a Closed Gold Mine Area in Northern Thailand

Gold-mining activities have been demonstrated to result in significant environmental pollution by Hg, Pb, and Mn, causing serious concerns regarding the potential threat to the public health of neighboring populations around the world. The present study focused on heavy-metal contamination in the eggs, blood, feed, soil, and drinking water on chicken farms, duck farms, and free-grazing duck farms located in areas < 25 km and > 25 km away from a gold mine in northern Thailand. In an area < 25 km away, Hg, Pb, and Mn concentrations in the eggs of free-grazing ducks were significantly higher than > 25 km away (p < 0.05). In blood, Hg concentration in free-grazing ducks was also significantly higher than those in an area > 25 km away (p < 0.05). Furthermore, the Pb concentration in the blood of farm ducks was significantly higher than in an area > 25 km away (p < 0.05). The concentration of Cd in drinking water on chicken farms was significantly higher for farms located within 25 km of the gold mine (p < 0.05). Furthermore, a high correlation was shown between the Pb (r2 = 0.84) and Cd (r2 = 0.42) found between drinking water and blood in free-grazing ducks in the area < 25 km away. Therefore, health risk from heavy-metal contamination was inevitably avoided in free-grazing activity near the gold mine. The incremental lifetime cancer risk (ILCR) in the population of both Pb and Cd exceeded the cancer limit (10−4) for all age groups in both areas, which was particularly high in the area < 25 km for chicken-egg consumption, especially among people aged 13−18 and 18−35 years old. Based on these findings, long-term surveillance regarding human and animal health risk must be strictly operated through food chains and an appropriate control plan for poultry businesses roaming around the gold mine.

Relationships between urinary metals concentrations and cognitive performance among U.S. older people in NHANES 2011-2014

Background

Epidemiological evidence on Urine metals and cognitive impairment in older individuals is sparse and limited. The goal of this study was to analyze if there was a link between urinary metal levels and cognitive performance in U.S. people aged 60 and up.

Methods

The National Health and Nutrition Examination Survey (NHANES) data from 2011 to 2014 were utilized in this cross-sectional analysis. Memory function was quantified using the following methods: Established Consortium for Word Learning in Alzheimer's Disease (CERAD-WL) (immediate learning and recall and delayed recall), Animal Fluency Test (AFT), and Digit Symbol Substitution Test (DSST). An inductively coupled plasma mass spectrometry (ICP-MS) was used to estimate urine metal concentrations. The connection of Urine metals level with cognitive function was investigated employing binary logistic regression and restricted cubic spline models.

Results

A total of 840 participants aged 60 years and over were enrolled in this study. After controlling for confounders, the association between cadmium, barium, cobalt, cesium, manganese, and thallium and poor cognitive performance showed significance in multiple logistic regression compared to the lowest quartile of metals. In the DSST test, the weighted multivariate adjusted ORs (95% CI) for cadmium in the highest quartile, barium and cesium in the third quartile were 2.444 (1.310-4.560), 0.412 (0.180-0.942) and 0.440 (0.198-0.979), respectively. There were L-shaped associations between urine cesium, barium, or manganese and low cognitive performance in DSST. Urine lead, molybdenum and uranium did not show any significant relationships with cognitive impairment, respectively, compared to the respective lowest quartile concentrations.

Conclusion

The levels of barium (Ba), cobalt (Co), cesium (Cs), manganese (Mn), and thallium (Tl) in urine were found to be negatively related to the prevalence of impaired cognitive performance in our cross-sectional investigation. Higher cadmium (Cd) levels were associated with cognitive impairment.

Manganese induces S-nitrosylation of PINK1 leading to nerve cell damage by repressing PINK1/Parkin-mediated mitophagy

Chronic exposure to excess manganese (Mn) causes neurotoxicity, which is characterized by Parkinson-like symptoms and referred to as manganism. In the last few decades, mitochondrial damage and subsequent energy failure have been reported to be important mechanisms of Mn toxicity, yet how Mn causes mitochondrial damage remains largely unknown. Here, we demonstrated that Mn induced S-nitrosation of phosphatase and tensin homolog (PTEN)-induced putative kinase 1 (PINK1), a master regulator in the mitophagy pathway, results in dysregulation of mitophagy and nerve cell injury in the rat striatum. We cultured primary neurons and used 1400 W, a potent and selective inducible nitric oxide synthase (iNOS) inhibitor, as an intervention to verify the precise mechanism of Mn-induced dysregulation of mitophagy. We demonstrated that Mn-induced S-nitrosylation of PINK1 decreased the phosphorylated level of parkin RBR E3 ubiquitin-protein ligase (Parkin), as well as the translocation of Parkin to damaged mitochondria, which led to the accumulation of damaged mitochondria and mitochondrial-mediated apoptosis. Our findings indicated the unusual connection between nitrative stress and mitochondrial dysfunction in Mn-induced neurotoxicity. These data highlight the role of S-nitrosation of PINK1 in Mn-induced dysregulation of mitophagy and provide a reliable target for the development of specific drugs and the early treatment of manganism, which has important theoretical and practical significance.

Associations of Heavy Metals with Activities of Daily Living Disability: An Epigenome-Wide View of DNA Methylation and Mediation Analysis

BACKGROUND

Exposure to heavy metals has been reported to be associated with multiple diseases. However, direct associations and potential mechanisms of heavy metals with physical disability remain unclear.

OBJECTIVES

We aimed to quantify associations of heavy metals with physical disability and further explore the potential mechanisms of DNA methylation on the genome scale.

METHODS

A cross-sectional study of 4,391 older adults was conducted and activities of daily living (ADL) disability were identified using a 14-item scale questionnaire including basic and instrumental activities to assess the presence of disability (yes or no) rated on a scale of dependence. Odds ratios (ORs) and 95% confidence intervals (CI) were estimated to quantify associations between heavy metals and ADL disability prevalence using multivariate logistic regression and Bayesian kernel machine regression (BKMR) models. Whole blood-derived DNA methylation was measured using the HumanMethylationEPIC BeadChip array. An ADL disability-related epigenome-wide DNA methylation association study (EWAS) was performed among 212 sex-matched ADL disability cases and controls, and mediation analysis was further applied to explore potential mediators of DNA methylation.

RESULTS

Each 1-standard deviation (SD) higher difference in log10-transformed manganese, copper, arsenic, and cadmium level was significantly associated with a 14% (95% CI: 1.05, 1.24), 16% (95% CI:1.07, 1.26), 22% (95% CI:1.13, 1.33), and 15% (95% CI:1.06, 1.26) higher odds of ADL disability, which remained significant in the multiple-metal and BKMR models. A total of 85 differential DNA methylation sites were identified to be associated with ADL disability prevalence, among which methylation level at cg220000984 and cg23012519 (annotated to IRGM and PKP3) mediated 31.0% and 31.2% of manganese-associated ADL disability prevalence, cg06723863 (annotated to ESRP2) mediated 32.4% of copper-associated ADL disability prevalence, cg24433124 (nearest to IER3) mediated 15.8% of arsenic-associated ADL disability prevalence, and cg07905190 and cg17485717 (annotated to FREM1 and TCP11L1) mediated 21.5% and 30.5% of cadmium-associated ADL disability prevalence (all p<0.05).

DISCUSSION

Our findings suggested that heavy metals contributed to higher prevalence of ADL disability and that locus-specific DNA methylation are partial mediators, providing potential biomarkers for further cellular mechanism studies. https://doi.org/10.1289/EHP10602.

MnCO3@BSA-ICG nanoparticles as a magnetic resonance/photoacoustic dual-modal contrast agent for functional imaging of acute ischemic stroke

Timely and accurate diagnosis of acute ischemic stroke (AIS) and simultaneous functional imaging of cerebral oxygen saturation (sO₂) are essential to improve the survival rate of stroke patients but remains challenging. Herein, we developed a pH-responsive manganese (Mn)-based nanoplatform as a magnetic resonance/photoacoustic (MR/PA) dual-modal contrast agent for AIS diagnosis. The Mn-based nanoplatform was prepared via a simple and green biomimetic method using bovine serum albumin (BSA) as a scaffold for fabrication of MnCO₃ NPs as the T₁ MR contrast agent and accommodation of indocyanine green (ICG) as the PA probe. The obtained MnCO₃@BSA-ICG NPs were biocompatible and exhibited a pH-responsive longitudinal relaxation rate and a concentration-dependent PA signal. In vivo MR/PA dual-modal imaging demonstrated that MnCO₃@BSA-ICG NPs quickly and efficiently led to the MR/PA contrast enhancements in the infarcted area while not in the normal region, allowing a timely and accurate diagnosis of AIS. Moreover, PA imaging could directly monitor the sO₂ level, enabling a functional imaging of AIS. Therefore, MnCO₃@BSA-ICG NPs could be applied as a potential MR/PA contrast agent for timely and functional imaging of AIS.

Associations Between Plasma Metals and Cognitive Function in People Aged 60 and Above

The objective of the study was to explore the relationship between the plasma levels of 22 metals and cognition status in older adults aged 60 years and above. A cross-sectional survey was conducted between 2018 and 2019. Inductively coupled plasma mass spectrometry (ICP-MS) was used to detect the concentrations of metals, and a mini-mental state examination (MMSE) questionnaire was used to estimate the cognition status of the elderly. Based on the years of education and MMSE scores, the participants were separated into the normal and impaired cognition groups. Lasso regression, logistic regression, and restricted cubic spline models were used to explore the relationship between the metals and cognitive status. A total of 1667 subjects were included in the study, and 333 (19.97%) of the participants had impaired cognition. Then, 12 metals, including Al, Fe, Ni, Cu, As, Se, Rb, Sr, Mo, Cd, Sn, and Sb were selected by lasso regression. Before the multivariate adjustment, Al and Cu were associated with the risk of increasing cognitive impairment (OR = 1.756, 95% CI: 1.166-2.646, P = 0.007; OR = 1.519, 95% CI: 1.050-2.197, P = 0.026, respectively). By contrast, Rb was associated with a decrease in the risk of cognitive impairment (OR = 0.626, 95% CI: 0.427-0.918, P = 0.017), but Cd was significantly associated with an increase in this risk (OR = 1.456, 95% CI: 1.003-2.114, P = 0.048). After multivariate adjustment, only Al (OR = 1.533, 95% CI: 1.000-2.350, P = 0.050) maintained a borderline difference with the risk of cognitive impairment. A significant positive correlation was found between the risk of cognitive impairment and Al, Cu, and Cd, contrary to the negative correlation found with Rb.

Executive functions in school-aged children exposed to airborne manganese: A multilevel analysis

Neuropsychological alterations have been identified in populations heavily exposed to metals with neurotoxic potential, such as manganese (Mn). This study examined the associations between Mn environmental exposure in school-aged children and executive functions, using structural equation modeling. Children, aged between 7 and 12 years (N = 181), were recruited from four elementary schools located in a region that is under the influence of atmospheric emissions from a ferro-manganese alloy plant in the municipality of Simões Filho, Bahia, Brazil. The following cognitive functions were evaluated: Intelligence, Inhibitory Control, Cognitive Flexibility, Verbal and Design Fluency, Verbal and Visual Working Memory and Attention. We performed structural equation modeling to identify the following executive functions latent variables: working memory, inhibitory control and cognitive flexibility. We further analyzed the relations between executive functions and Mn measured in hair (MnH) and toenails (MnTn) with linear mixed models, after controlling for co-variables. A positive effect at the individual level on working memory, inhibition control and cognitive flexibility was observed with MnTn after controlling for co-variables, but no association was found with MnH levels. However, children attending school most environmentally exposed to Mn emissions, which had the highest rate of Mn dust deposition, had the poorest scores on working memory. These findings suggest both benefits and risk of Mn on children's cognitive development.

Environmentally relevant manganese concentrations evoke anxiety phenotypes in adult zebrafish

Manganese (Mn) is an essential metal for living organisms. However, the excess of Mn can be toxic, especially for the central nervous system. Herein, we used adult zebrafish as model organism to investigate the relationship of an environmentally relevant Mn exposure with the onset of neurobehavioral disturbances and brain biochemical alterations. Fish were exposed to MnCl₂ at 0.5, 2.0, 7.5 and 15.0 mg/L for 96 h, and after submitted to trials for examining exploratory, locomotor and anxiety-related behaviors. The neurobehavioral parameters were followed by the analyses of cell viability, Mn accumulation and acetylcholinesterase activity in the brain, and whole-body cortisol levels. By Novel tank, Light dark and Social preference test, we found that the exposure to Mn, along with locomotor deficits induced anxiety-like phenotypes in zebrafish. Most of these behavioral changes were evoked by the highest concentrations, which also caused cell viability loss, higher accumulation of Mn and increased AChE activity in the brain, and an increase in the whole-body cortisol content. Our findings demonstrated that zebrafish are quite sensitive to levels of Mn found in the environment, and that the magnitude of the neurotoxic effects may be associated with the levels of manganese accumulated in the brain. Interestingly, we showed that Mn exposure in addition to motor deficits may also cause psychiatric abnormalities, namely anxiety.

Exposing the role of metals in neurological disorders: a focus on manganese

Metals are ubiquitous chemical entities involved in a myriad of biological processes. Despite their integral role in sustaining life, overexposure can lead to deleterious neurological outcomes posing a public health concern. Excess exposure to metals has been associated with aberrant neurodevelopmental and neurodegenerative diseases and prominently contributes to environmental risk for neurological disorders. Here, we use manganese (Mn) to exemplify the gap in our understanding of the mechanisms behind acute metal toxicity and their relationship to chronic toxicity and disease. This challenge frustrates understanding of how individual exposure histories translate into preventing and treating brain diseases from childhood through old age. We discuss ways to enhance the predictive value of preclinical models and define mechanisms of chronic, persistent, and latent neurotoxicity.

Evaluating the neuroprotective activities of vinpocetine, punicalagin, niacin and vitamin E against behavioural and motor disabilities of manganese-induced Parkinson's disease in Sprague Dawley rats

The current study investigated the neuroprotective activity of some drugs and nutriceuticals with antioxidant and anti-inflammatory potential on the pathogenesis of Parkinson's disease (PD). Rats were categorized into seven groups: Rats received tween80 daily for 5 weeks as a control group, MnCl₂ (10 mg/kg, i.p) either alone (group II) or in combination with vinpocetine (VIN) (20 mg/kg) (group III), punicalagin (PUN) (30 mg/kg) (group IV), niacin (85 mg/kg) (group V), vitamin E (Vit E) (100 mg/kg) (group VI) or their combination (group VII). Motor activities was examined using open-field and catalepsy. Striatal monamines, acetylcholinesterase, excitatory/inhibitory neurotransmitters, redox status, pro-oxidant content, brain inflammatory, apoptotic and antioxidant biomarkers levels were assessed. Besides, histopathological investigations of different brain regions were determined. Groups (IV -GVII) showed improved motor functions of PD rats. Applied drugs significantly increased the brain levels of monoamines with the strongest effect to PUN. Meanwhile, they significantly decreased levels of acetylcholinesterase with a strongest effect to PUN. Moreover, they exhibited significant neuronal protection and anti-inflammatory abilities through significant reduction of the brain levels of COX2, TNF-α and Il-1β with a strongest effect to the PUN. Interestingly; groups (IV - GVII) showed restored glutamate/GABA balance and exhibited a pronounced decrease in caspase-3 content and GSK-3β protein expression levels. In addition, they significantly increased Bcl2 mRNA expression levels with a strongest effect for PUN. All these findings were further confirmed by the histopathological examinations. As a conclusion, we propose VIN and PUN to mitigate the progression of PD via their antioxidant, anti-inflammatory, anti-apoptotic, neurotrophic and neurogenic activities.

Neurotoxicity and gene expression alterations in zebrafish larvae in response to manganese exposure

Manganese (Mn) is an essential trace element, but excessive exposure can damage mental, cognitive, and motor functions. Although many studies have reported the toxicity of Mn, the underlying mechanism remains unclear. Here, wild-type and/or Tg(NBT:DsRed) zebrafish embryos/larvae were exposed to different dosages of Mn to determine the effects on mortality, malformation, and hatching rates. A video tracking system was used to analyze the locomotor activities of zebrafish larvae. The terminal deoxynucleotidyl transferase dUTP nick end labeling assay and acridine orange staining were performed to monitor cell apoptosis, while dopamine transporter and tyrosine hydroxylase (TH) expression were detected by immunohistochemical staining. Meanwhile, transcriptome sequencing of the head tissues of zebrafish larvae was performed to search for molecular targets of Mn neurotoxicity. The results showed that Mn exposure increased the mortality and malformation rates of zebrafish larvae, and significantly reduced swim distance and velocity. In addition, the proportion of apoptotic dopaminergic neurons increased, while TH expression significantly decreased. The results of transcriptome sequencing showed that a large number of differentially expressed genes associated with apoptosis and DNA damage repair were upregulated, consistent with the above results. Meanwhile, Western blot analysis showed that higher exposure level of Mn could induce activation of MAPK pathway. These data demonstrate that Mn exposure can damage dopaminergic neurons and cause apoptosis, which has detrimental effects on the motor abilities of zebrafish larvae.

Higher Lead and Lower Calcium Levels Are Associated with Increased Risk of Mortality in Malaysian Older Population: Findings from the LRGS-TUA Longitudinal Study

The main objective of this study is to determine the association of various trace elements’ status with the 5-year mortality rate among community-dwelling older adults in Malaysia. This study was part of the Long-term Research Grant Scheme—Towards Useful Ageing (LRGS-TUA). The participants were followed up for five years, and their mortality status was identified through the Mortality Data Matching Service provided by the National Registration Department, Malaysia. Of the 303 participants included in this study, 34 (11.2%) participants had died within five years after baseline data collection. As compared to the survivors, participants who died earlier were more likely (p < 0.05) to be men, smokers, have a lower intake of total dietary fiber and molybdenum, higher intake of manganese, lower zinc levels in toenail samples, lower calcium and higher lead levels in hair samples during baseline. Following the multivariate Cox proportional hazard analysis, lower total dietary fiber intake (HR: 0.681; 0.532−0.871), lower calcium (HR: 0.999; 95% CI: 0.999−1.000) and higher lead (HR: 1.309; 95% CI: 1.061−1.616) levels in hair samples appeared as the predictors of mortality. In conclusion, higher lead and lower calcium levels are associated with higher risk of mortality among community-dwelling older adults in Malaysia. Our current findings provide a better understanding of how the trace elements’ status may affect older populations’ well-being and mortality rate.

Electrochemical Determination of Manganese in Whole Blood with Indium Tin Oxide Electrode

In this work, we demonstrate accurate and precise measurement of manganese (Mn) concentration in human whole blood with indium tin oxide (ITO) electrode using square wave stripping voltammetry. While an essential trace metal for human health, elevated levels of Mn due to environmental or occupational exposure have been associated with severe neuromotor dysfunction characterized by parkinsonism and cognitive dysfunction making the monitoring of Mn in whole blood necessary. Pediatric populations are particularly susceptible to Mn given their developing brain and potential long-term impacts on neurodevelopment. The current gold standard for whole blood Mn measurements is by ICP-MS, which is costly and time consuming. The electrochemical detection with ITO working electrode in this work showed a limit of detection of 0.5 μg l^-1 and a linear range of 5 to 500 μg l^-1, which encompasses the physiological Mn levels in human whole blood (5-18 μg l^-1). Our results of Mn measurement in whole blood show an average precision of 96.5% and an average accuracy of 90.3% compared to ICP-MS for both the normal range (5-18 μg l^-1) and the elevated levels (>36 μg l^-1) that require medical intervention. These results demonstrate the feasibility of Mn measurements in human blood with electrochemical sensors.

Multiple metals in children's deciduous teeth: results from a community-initiated pilot study

BACKGROUND

Characterizing retrospective exposure to toxicants during multiple early-life developmental periods is challenging, yet critical for understanding developmental effects.

OBJECTIVE

To characterize early-life metal exposure using deciduous teeth in a community concerned about past exposures.

METHODS

Naturally shed teeth were collected from 30 children ages 5-13 years who resided in Holliston, Massachusetts since conception. We estimated weekly prenatal and postnatal (up to 1 year of age) exposure to 12 metals by measuring dentine concentrations using laser ablation-inductively coupled plasma-mass spectrometry. Multivariable linear mixed models were used to explore sociodemographic, dietary, and behavioral correlates of dentine metal concentrations.

RESULTS

Temporal trends in dentine levels differed by metal. Source of milk during the first year of life was associated with dentine barium (Ba) levels, where being fed predominantly breastmilk was associated with 39% (95% CI: -57%, -13%) lower dentine Ba compared to predominantly formula use. Females had higher prenatal and postnatal dentine Mn and Pb, compared to males (e.g., % difference, postnatal Mn: 122% (17%, 321%); postnatal Pb: 60% (95% CI: -8%, 178%)).

SIGNIFICANCE

Deciduous teeth provide retrospective information on dose and timing of early-life metals exposure at high resolution. We demonstrate their utility in a community-based study with known past contamination of drinking water.

IMPACT STATEMENT

We conducted a community-initiated pilot study in a community concerned with historical exposure to multiple metals. Using deciduous teeth, a novel noninvasive biomarker, we characterized early-life exposure to 12 metals in approximately weekly increments during sensitive developmental periods, thus demonstrating the utility of this biomarker in communities concerned with past exposures.

Relationship of Blood and Urinary Manganese Levels with Cognitive Function in Elderly Individuals in the United States by Race/Ethnicity, NHANES 2011-2014

Manganese (Mn) is an essential metal with a biphasic relationship with health outcomes. High-level exposure to Mn is associated with manganism, but few data explore the effects of chronic, lower-level Mn on cognitive function in adults. We sought to determine the relationship between blood/urinary manganese levels and cognitive function in elderly individuals using 2011-2014 data from the National Health and Nutrition Examination Survey (NHANES). Weighted multivariate regression models were used to determine correlations, adjusting for several covariates. Blood Mn was inversely associated with the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) immediate learning of new verbal information (p-value = 0.04), but lost significance after adjusting for medical history (p-value = 0.09). In addition, blood Mn was inversely associated with Animal Fluency scores after adjusting for all covariates. Urinary Mn was inversely associated with CERAD immediate learning after adjusting for all covariates (p-value = 0.01) and inversely associated with the Digit Symbol Substitution Test scores (p-value = 0.0002), but lost significance after adjusting for medical history (p-value = 0.13). Upon stratifying by race/ethnicity, other Races and Non-Hispanic (NH)-Blacks had significantly higher blood Mn levels when compared to NH-Whites. Collectively, these findings suggest that increased blood and urinary Mn levels are associated with poorer cognitive function in an elderly US population.

Protective effect of calpain inhibitors against manganese-induced toxicity in rats

Development of manganism is a major complication of manganese exposure in which neurological dysfunction is linked to accumulation of metal in the brain. Current therapies do not prevent progression of the disease. Therefore, development of effective therapeutic strategies for treatment of manganism is of utmost importance. Since the hyperactivation of calpain family proteases in CNS during manganism in an animal model is observed, we assumed that inhibition of calpains can suppress the development of Mn-induced neurological disturbances. The goal of this study is to delineate protective effect and the mechanism of neuroprotection of calpain inhibitor in rat model of Mn-induced neurological symptoms. Using the Gait analysis test, we found that chronic intranasal administration of the calpain inhibitor Cast (184-210) (peptide, which is corresponding to the 184-210 amino acid of the endogenous inhibitor of calpains-human calpastatin) to Mn-treated rats contributed to a significant decrease in the severity of gait disorders, although it did not lead to a decrease in the Mn deposition in the striatum and hippocampus. Accordingly to the results of PCR-RT, this effect was accompanied by a partial reduction in the content of neuro-inflammatory markers (IL-1β, TNF-α, NFκB mRNA in the hippocampus and, additionally, IBA-1 mRNA in the striatum), as well as normalization of the content of dopamine and its metabolites in the hippocampus and striatum, which was assessed by HPLC. In striatum cells, the application of Cast (184-210) also led to a significant increase in the production of tyrosine hydroxylase, which was analyzed by immunoblotting method. These findings suggest that calpain inhibitors may be a valid therapeutic agent in manganism.

Environmentally Relevant Hexavalent Chromium Disrupts Elemental Homeostasis and Induces Apoptosis in Zebrafish Liver

Although hexavalent chromium Cr [VI] is known as a toxicant in the aquatic environment, its effect in low, environmentally relevant concentration (ERC; 2 mg L^-1) is less characterized. Against this backdrop, the effects of Cr [VI] in ERC on zebrafish liver has been investigated in this study. Fluorescence microscopy and gel electrophoresis detected excess DNA damage and cell death via apoptosis in 2 mg L^-1 Cr [VI]-treated fish when compared with that of control. Besides, there were transcriptional activations of p53, Bax, Caspase 9 and Caspase 3 genes but downregulation of Bcl2 gene in the treated group, confirming the apoptotic pathway. Energy dispersive X-ray fluorescence (EDXRF) data showed significant (p < 0.05) increase in hepatic content of Cr, selenium, iron, manganese, calcium, sulfur and magnesium but depletion of zinc, copper and cobalt in the treated group. Collectively, the study shows that even a low, ERC of Cr [VI] is toxic to the zebrafish as it elicited marked apoptosis in the hepatocytes and altered the liver elemental profile.

Differences and Interactions in Placental Manganese and Iron Transfer across an In Vitro Model of Human Villous Trophoblasts

Manganese (Mn) as well as iron (Fe) are essential trace elements (TE) important for the maintenance of physiological functions including fetal development. However, in the case of Mn, evidence suggests that excess levels of intrauterine Mn are associated with adverse pregnancy outcomes. Although Mn is known to cross the placenta, the fundamentals of Mn transfer kinetics and mechanisms are largely unknown. Moreover, exposure to combinations of TEs should be considered in mechanistic transfer studies, in particular for TEs expected to share similar transfer pathways. Here, we performed a mechanistic in vitro study on the placental transfer of Mn across a BeWo b30 trophoblast layer. Our data revealed distinct differences in the placental transfer of Mn and Fe. While placental permeability to Fe showed a clear inverse dose-dependency, Mn transfer was largely independent of the applied doses. Concurrent exposure of Mn and Fe revealed transfer interactions of Fe and Mn, indicating that they share common transfer mechanisms. In general, mRNA and protein expression of discussed transporters like DMT1, TfR, or FPN were only marginally altered in BeWo cells despite the different exposure scenarios highlighting that Mn transfer across the trophoblast layer likely involves a combination of active and passive transport processes.

Prenatal trace elements mixture is associated with learning deficits on a behavioral acquisition task among young children

Children are exposed to many trace elements throughout their development. Given their ubiquity and potential to have effects on children's neurodevelopment, these exposures are a public health concern. This study sought to identify trace element mixture-associated deficits in learning behavior using operant testing in a prospective cohort. We included 322 participants aged 6-7 years recruited in Mexico City with complete data on prenatal trace elements measurements (third trimester blood lead and manganese levels, and & urine cadmium and arsenic levels), demographic covariates, and the Incremental Repeated Acquisition (IRA), an associative learning task. Weighted quantile sum (WQS) regression models were used to estimate the joint association of the mixture of all four trace elements and IRA performance. Performance was adversely impacted by the mixture, with different elements relating to different aspects of task performance suggesting that prenatal exposure to trace element mixtures yields a broad dysregulation of learning behavior.

Drinking Water Quality and Public Health in the Kathmandu Valley, Nepal: Coliform Bacteria, Chemical Contaminants, and Health Status of Consumers

Residents of Nepal’s Kathmandu Valley draw drinking water from tube wells, dug wells, and stone spouts, all of which have been reported to have serious water quality issues. In this study, we analyzed drinking water samples from 35 tube wells, dug wells, stone spouts, and municipal tap water for bacterial and chemical contaminants, including total and fecal coliform, aluminum, arsenic, barium, beryllium, boron, cadmium, cobalt, chromium, copper, fluoride, iron, mercury, manganese, molybdenum, nickel, lead, antimony, selenium, thallium, uranium, vanadium, and zinc. We also asked a sampling of households who used these specific water sources to rate the taste of their water, list any waterborne diseases they were aware of, and share basic health information about household members. This survey provided us with information from 146 households and 603 individuals. We found widespread bacterial contamination of water sources, with 94% of sources having detectable total or fecal coliform. Nepal Drinking Water Quality Standards and World Health Organization (WHO) Drinking-Water Guidelines or health-based values were exceeded for aluminum (max = 0.53 mg/L), arsenic (max = 0.071 mg/L), iron (max = 7.22 mg/L), and manganese (max = 3.229 mg/L). The distribution of water sources with high arsenic, iron, and manganese appeared to be associated with floodplain deposits. Mixed effects logistic regression models were used to examine the interactions between social factors and water contaminants and their effects on household members’ health. Consumers of water sources with both high and low concentrations of manganese were less likely to have a positive attitude towards school than those whose water sources had moderate concentrations of manganese. Social factors, especially education, played a large role in predicting individual health outcomes. Household taste ratings of drinking water were not correlated with iron or manganese concentrations, suggesting that WHO’s reliance on aesthetic criteria for these contaminants instead of formal drinking-water guidelines may not be sufficient to protect public health.

Manganese-induced hyperactivity and dopaminergic dysfunction depend on age, sex and YAC128 genotype

Manganese (Mn) is an essential micronutrient but is neurotoxic in excess. Environmental and genetic factors influence vulnerability to Mn toxicity, including sex, age, and the autosomal dominant mutation that causes Huntington disease (HD). To better understand the differential effects of Mn in wild-type (WT) versus YAC128 mice, we examined impacts of Mn exposure across different ages and sexes on disease-relevant behavioral tasks and dopamine dynamics. Young (3-week) and aged (12-month) WT and YAC128 mice received control (70 ppm) or high (2400 ppm) Mn diet for 8 weeks followed by a battery of behavioral tasks. In young female WT mice, high Mn diet induced hyperactivity across two independent behavioral tasks. Changes in the expression of tyrosine hydroxylase (TH) were consistent with the behavioral data in young females such that elevated TH in YAC128 on control diet was decreased by high Mn diet. Aged YAC128 mice showed the expected disease-relevant behavioral impairments in females and decreased TH expression, but we observed no significant effects of Mn diet in either genotype of the aged group. Fast-scan cyclic voltammetry recorded dopamine release and clearance in the nucleus accumbens of eight-month-old WT and YAC128 mice following acute Mn exposure (3×/1 week subcutaneous injections of 50 mg/kg MnCl[2]-tetrahydrate or saline). In WT mice, Mn exposure led to faster dopamine clearance that resembled saline treated YAC128 mice. Mn treatment increased dopamine release only in YAC128 mice, possibly indirectly correcting the faster dopamine clearance observed in saline treated YAC128 mice. The same exposure paradigm led to decreased dopamine and serotonin and metabolites (3-MT, HVA and 5-HIAA) in striatum and increased glutamate in YAC128 mice but not WT mice. These studies confirm an adverse effect of Mn in young, female WT animals and support a role for Mn exposure in stabilizing dopaminergic dysfunction and motivated behavior in early HD.

Serum Trace Elements Concentrations in Patients with Restless Legs Syndrome

Increased brain and serum zinc levels in patients with idiopathic restless legs syndrome (idiopathic RLS or iRLS) were described when compared with controls, suggesting a possible role of zinc in the pathogenesis of this disease. However, serum magnesium, calcium, manganese, iron, and copper levels of RLS patients were similar to controls, suggesting a specific impairment of zinc-dependent metabolism in RLS. The aim of this study is to assess the serum concentrations of trace elements involved in oxidative stress or causing peripheral nerve toxicity in a large series of patients with iRLS and controls. We determined serum levels of iron, copper, manganese, zinc, magnesium, selenium, calcium, aluminium, lead, cadmium, arsenic and mercury in 100 patients diagnosed with iRLS and in 110 age- and sex-matched controls using Inductively Coupled Plasma Mass Spectrometry. Serum copper, magnesium, selenium, and calcium concentrations were significantly higher in RLS patients than in controls. These differences were observed both in men and women. There were no major correlations between serum trace metal concentrations and age at onset of RLS or RLS severity, nor was there any association with a family history of RLS or drug response. This study shows an association between increased serum concentrations of copper, magnesium, selenium, and calcium with RLS in a Spanish Caucasian population and does not confirm the previously reported increase in serum zinc concentrations in patients suffering from this disease, suggesting that the different accuracy of the analytical methods used could have influenced the inconsistent results found in the literature.

Role of excretion in manganese homeostasis and neurotoxicity: a historical perspective

The essential metal manganese (Mn) induces incurable neurotoxicity at elevated levels that manifests as parkinsonism in adults and fine motor and executive function deficits in children. Studies on Mn neurotoxicity have largely focused on the role and mechanisms of disease induced by elevated Mn exposure from occupational or environmental sources. In contrast, the critical role of excretion in regulating Mn homeostasis and neurotoxicity has received less attention although 1) studies on Mn excretion date back to the 1920s; 2) elegant radiotracer Mn excretion assays in the 1940s to 1960s established the routes of Mn excretion; and 3) studies on patients with liver cirrhosis in the 1990s to 2000s identified an association between decreased Mn excretion and the risk of developing Mn-induced parkinsonism in the absence of elevated Mn exposure. Notably, the last few years have seen renewed interest in Mn excretion largely driven by the discovery that hereditary Mn neurotoxicity due to mutations in SLC30A10 or SLC39A14 is caused, at least in part, by deficits in Mn excretion. Quite remarkably, some of the recent results on SLC30A10 and SLC39A14 provide explanations for observations made ∼40-50 years ago. The goal of the current review is to integrate the historic studies on Mn excretion with more contemporary recent work and provide a comprehensive state-of-the-art overview of Mn excretion and its role in regulating Mn homeostasis and neurotoxicity. A related goal is to discuss the significance of some of the foundational studies on Mn excretion so that these highly consequential earlier studies remain influential in the field.

Cross-sectional study: Relationship between serum trace elements and hypertension

BACKGROUND

A balanced intake of trace elements is beneficial for chronic diseases such as hypertension. However, the available information regarding trace elements that may be independently associated with hypertension is limited, and the relationship between this disorder and element ratios also remains unclear.

METHODS

A total of 6,754 subjects from rural China were selected, after exclusion of patients who were under 18, had incomplete data or had additional related disorders, by multi-stage simple random and cluster sampling (participation rate: 95.22 %). Subjects were divided into a hypertensive (H) and a control (C) group. Data were collected on blood pressure and 12 serum trace elements were measured by flame atomic absorption spectrometry and inductively coupled plasma-mass spectrometry. Other basic information was collated from questionnaires and biochemical indicators were measured via kits.

RESULTS

Differences in serum levels of magnesium (Mg(mg/l): H: 27.43 ± 12.72; C: 26.33 ± 12.16), iron (Fe(mg/l): H: 1.99 ± 1.24; C: 1.84 ± 1.16), copper (Cu(mg/l): H: 1.19 ± 0.37; C: 1.10 ± 0.36), boron (B(μg/l): H: 50.00 ± 25.21; C: 47.57 ± 26.25), selenium (Se(μg/l): H: 125.12 ± 32.81; C: 118.80 ± 29.72) and chromium (Cr(μg/l): H: 8.77 ± 10.12; C: 10.12 ± 10.72) between the hypertensive and control groups were found. There were no differences in serum contents of calcium (Ca(mg/l): H: 112.43 ± 58.25; C: 111.00 ± 59.49), zinc (Zn(mg/l): H: 1.50 ± 1.97; C: 1.44 ± 1.88), arsenic (As(μg/l): H: 4.17 ± 3.94; C: 4.10 ± 4.00), manganese (Mn(μg/l): H: 4.15 ± 4.03; C: 4.07 ± 4.05), cadmium (Cd(μg/l): H: 1.14 ± 1.11; C: 1.18 ± 1.12) or lead (Pb(μg/l): H: 4.22 ± 8.90; C: 4.26 ± 10.25). The serum Cr and Cd concentrations of hypertensive men were lower than that of male controls while Mg, Cu, Ca and Se concentrations in male controls were lower. Further differences were apparent and Fe, B, Se, Mg and Cu all showed higher levels in hypertensive females whereas Cr concentrations were higher in female controls. Serum Zn and B levels showed age-related variations among hypertensive patients and concentrations of serum Cu, Zn, Se and B showed age-related variations among control subjects. For hypertensive patients, the odds ratio (OR) and 95 % confidence interval (CI) for the association of serum Cu, Se and Cr levels with hypertension were Cu: 1.36 (1.12-1.66); Se: 1.03 (1.01-1.05); Cr: 0.89 (0.83-0.96). Moreover, when the participants in the grouping with the highest copper/zinc (Cu/Zn) and magnesium/manganese (Mg/Mn) ratios were compared with the reference group, the OR and 95 % CI for hypertension were 1.22 (1.04-1.44) and 1.20 (1.01-1.42), respectively.

CONCLUSIONS

Levels of serum trace elements showed age- and sex-related differences in a group of rural Chinese adults with hypertension and healthy participants. Serum concentrations of Cu, Se and Cr may be independently associated with hypertension. Higher serum ratios of Cu:Zn and Mg:Mn may also be associated with hypertension. Further randomized trials are necessary to elucidate the true relationship between levels of Cu, Se, Cr, Cu:Zn, Mg:Mn and hypertension.

Vitamin D: A Critical Regulator of Intestinal Physiology

Calcium is required for the functioning of numerous biological processes and is essential for skeletal health. The major source of new calcium is from the diet. The central role of vitamin D in the maintenance of calcium homeostasis is to increase the absorption of ingested calcium from the intestine. The critical importance of vitamin D in this process is noted in the causal link between vitamin D deficiency and rickets, as well as in studies using genetically modified mice including mice deficient in the vitamin D receptor (Vdr null mice) or in the cytochrome P‐450 enzyme, 25‐hydroxyvitamin D₃‐1α‐ hydroxylase (CYP27B1) that converts 25‐hydroxyvitamin D₃ to the hormonally active form of vitamin D, 1,25‐dihydroxyvitamin D₃ [1,25(OH)₂D₃] (Cyp27b1 null mice). When these mice are fed diets with high calcium and lactose, rickets is prevented. The studies using mouse models provide supporting evidence indicating that the major physiological function of 1,25(OH)₂D₃/VDR is intestinal calcium absorption. This review summarizes what is known about mechanisms involved in vitamin D‐regulated intestinal calcium absorption. Recent studies suggest that vitamin D does not affect a single entity, but that a complex network of calcium‐regulating components is involved in the process of 1,25(OH)₂D₃‐mediated active intestinal calcium absorption. In addition, numerous 1,25(OH)₂D₃ actions in the intestine have been described independent of calcium absorption. Although the translatability to humans requires further definition, an overview is presented that provides compelling evidence from the laboratory of 1,25(OH)₂D₃ intestinal effects, which include the regulation of adhesion molecules to enhance barrier function, the regulation of intestinal stem cell function, cellular homeostasis of other divalent cations, the regulation of drug metabolizing enzymes, and anti‐inflammatory effects. © 2021 The Author. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Manganese transport in mammals by zinc transporter family proteins, ZNT and ZIP

Manganese (Mn) is an essential trace element required for various biological processes. However, excess Mn causes serious side effects in humans, including parkinsonism. Thus, elucidation of Mn homeostasis at the systemic, cellular, and molecular levels is important. Many metal transporters and channels can be involved in the transport and homeostasis of Mn, and an increasing body of evidence shows that several zinc (Zn) transporters belonging to the ZIP and ZNT families, specifically, ZNT10, ZIP8, and ZIP14, play pivotal roles in Mn metabolism. Mutations in the genes encoding these transporter proteins are associated with congenital disorders related to dysregulated Mn homeostasis in humans. Moreover, single nucleotide polymorphisms of ZIP8 are associated with multiple clinical phenotypes. In this review, we discuss the recent literature on the structural and biochemical features of ZNT10, ZIP8, and ZIP14, including transport mechanisms, regulation of expression, and pathophysiological functions. Because a disturbance in Mn homeostasis is closely associated with a variety of phenotypes and risk of human diseases, these transporters constitute a significant target for drug development. An understanding of the roles of these key transporters in Mn metabolism should provide new insights into pharmacological applications of their inhibitors and enhancers in human diseases.

Cu(II), Mn(II) and Zn(II) complexes of hydrazones with a quaternary ammonium moiety: synthesis, experimental and theoretical characterization and cytotoxic activity

In this paper, Cu(II), Mn(II) and Zn(II) complexes with N,N,N-trimethyl-2-oxo-2-(2-(1-(thiazol-2-yl)ethylidene)hydrazinyl)ethan-1-aminium chloride (HL1Cl) were synthesized and characterized by single-crystal X-ray diffraction, IR spectroscopy, elemental analysis and DFT calculations. In all three complexes, a ligand (L1) is coordinated in a deprotonated formally neutral zwitterionic form via NNO donor set atoms. Cu(II) and Zn(II) form mononuclear penta-coordinated complexes [CuL1(N₃)(CH₃OH)]BF₄ and [ZnL1(N₃)₂], respectively, while Mn(II) forms a binuclear [Mn₂L1₂(μ-_1,1-N₃)₂(N₃)₂]·2CH₃OH complex, with unusual distorted trigonal-prismatic geometry around the metal centers. The antimicrobial activity of these complexes was tested against a panel of Gram-negative and Gram-positive bacteria, two yeasts and one fungal strain. The binuclear Mn(II) complex showed antifungal activity of similar intensity to amphotericin B. Based on the results of the brine shrimp test and DPPH radical scavenging activity, the most active Cu(II) and Mn(II) complexes were selected for evaluation of cytotoxic activity against five malignant cancer cell lines (HeLa, A375, MCF7, PC-3 and A549) and one normal cell line HaCaT. Both complexes showed significant activity. It should be pointed out that the activity of the Mn(II) complex against the MCF7 breast cancer cell line is only slightly weaker than that of cisplatin, but with selectivity to the tumor cell line in comparison to normal HaCaT cells, which is non-existent in the case of cisplatin.

YAC128 mouse model of Huntington disease is protected against subtle chronic manganese (Mn)-induced behavioral and neuropathological changes

Manganese (Mn) is an essential micronutrient but excessive levels induce neurotoxic effects. Increasing evidence suggests a deficit of bioavailable Mn in Huntington disease (HD), an inherited neurodegenerative disease characterized by motor and cognitive disturbances. Previous studies have shown rescue of some molecular HD phenotypes by acute Mn exposure. This study simultaneously examined the potential for chronic Mn exposure to attenuate HD behavioral phenotypes, and for the HD genotype to offer protection against detrimental effects of chronic Mn exposure. In two independent studies a chronic Mn exposure paradigm was implemented in the YAC128 mouse model of HD and behavior was assessed at several timepoints. Study 1 exposed WT and YAC128 mice to twice weekly subcutaneous injections of 0, 5, 15, or 50 mg/kg MnCl[2] tetrahydrate from 12 to 32 weeks of age. A promising protective effect against motor coordination decline in 5 mg/kg MnCl[2] tetrahydrate-treated YAC128 mice was detected. Study 2 thus exposed WT and YAC128 mice to either 0 or 5 mg/kg MnCl[2] tetrahydrate from 12 to 52 weeks of age (with a partial randomized treatment crossover at 31 weeks). The same protective effect was not observed under these conditions at higher statistical power. We report subtle toxicological changes in exploratory behavior and total activity induced by chronic Mn exposure in WT mice only, despite similar total increases in brain Mn in WT and YAC128 mice. Further, chronic Mn treatment resulted in a 10-12 % decrease in striatal NeuN positive cell density in WT mice but not YAC128 mice, despite vehicle cell counts already being reduced compared to WT mice as expected for the HD genotype. The subtle changes observed in specific outcome measures, but not others, following long-term low-level Mn exposure in WT mice delineate the neurobehavioral and neuropathological effects at the threshold of chronic Mn toxicity. We conclude that these chronic low-dose Mn exposures do not significantly rescue behavioral HD phenotypes, but YAC2128 mice are protected against the subtle Mn-induced behavioral changes and decreased striatal neuron density observed in Mn-exposed WT mice.

Critical windows of susceptibility in the association between manganese and neurocognition in Italian adolescents living near ferro-manganese industry

INTRODUCTION

Understanding the neurodevelopmental effects of manganese (Mn) is complicated due to its essentiality for growth and development. While evidence exists for the harmful effects of excess Mn, pediatric epidemiologic studies have observed inconsistent associations between Mn and child cognition.

OBJECTIVE

We sought to estimate prospective associations between Mn measured in three different early-life time windows with adolescent cognition using deciduous teeth biomarkers.

METHODS

Deciduous teeth were collected from 195 participants (ages 10-14 years) of the Public Health Impact of Manganese Exposure (PHIME) study in Brescia, Italy. Measurements of tooth Mn represented prenatal (∼14 weeks gestation - birth), early postnatal (birth - 1.5 years) and childhood (∼1.5 - 6 years) time windows. Neuropsychologists administered the Wechsler Intelligence Scale for Children, 3rd edition (WISC-III), to obtain composite IQ and subtest scores. Associations between tooth Mn at each time window and adolescent WISC-III scores were estimated using multivariable linear regression. We tested differences in associations between Mn and outcomes across time windows using multiple informant models. Sex-specific associations were explored in stratified models.

RESULTS

Adjusted associations between tooth Mn and composite IQ scores were positive in the prenatal period and negative in the childhood period. Associations were strongest for subtest scores that reflect working memory, problem solving, visuospatial ability and attention: prenatal Mn was positively associated with Digits backward [SD change in score per interquartile range increase in Mn: β = 0.20 (95 % CI: 0.02, 0.38)] and Block design [β = 0.21 (0.01, 0.41)] and early postnatal Mn was positively associated with Digits forward [β = 0.24 (0.09, 0.40)], while childhood Mn was negatively associated with Coding [β = -0.14 (-0.28, -0.001)]. Sex-stratified analyses suggested different Mn-cognition associations for boys and girls and was also dependent on the time window of exposure.

CONCLUSION

Our results suggest that exposure timing is critical when evaluating Mn associations between Mn and cognition. Higher prenatal Mn was beneficial for adolescent cognition; however, these beneficial associations shifted towards harmful effects in later time windows. Cognitive domains most sensitive to Mn across time windows included visuospatial ability, working memory, attention and problem-solving.

Genome-wide CRISPR-Cas9 screens identify mechanisms of BET bromodomain inhibitor sensitivity

BET bromodomain inhibitors hold promise as therapeutic agents in diverse indications, but their clinical progression has been challenging and none have received regulatory approval. Early clinical trials in cancer have shown heterogeneous clinical responses, development of resistance, and adverse events. Increased understanding of their mechanism(s) of action and identification of biomarkers are needed to identify appropriate indication(s) and achieve efficacious dosing. Using genome-wide CRISPR-Cas9 screens at different concentrations, we report molecular mechanisms defining cellular responses to BET inhibitors, some of which appear specific to a single compound concentration. We identify multiple transcriptional regulators and mTOR pathway members as key determinants of JQ1 sensitivity and two Ca²⁺/Mn²⁺ transporters, ATP2C1 and TMEM165, as key determinants of JQ1 resistance. Our study reveals new molecular mediators of BET bromodomain inhibitor effects, suggests the involvement of manganese, and provides a rich resource for discovery of biomarkers and targets for combination therapies.

•

CRISPR screens identify genes regulating sensitivity to BET bromodomain inhibitors

•

Sensitivity and resistance hit lists are concentration-dependent

•

mTOR pathway mediates sensitivity to BET bromodomain inhibitors

•

Manganese regulates sensitivity to BET bromodomain inhibitors

Prenatal metal exposure, cord blood DNA methylation and persistence in childhood: an epigenome-wide association study of 12 metals

BACKGROUND

Prenatal exposure to essential and non-essential metals impacts birth and child health, including fetal growth and neurodevelopment. DNA methylation (DNAm) may be involved in pathways linking prenatal metal exposure and health. In the Project Viva cohort, we analyzed the extent to which metals (As, Ba, Cd, Cr, Cs, Cu, Hg, Mg, Mn, Pb, Se, and Zn) measured in maternal erythrocytes were associated with differentially methylated positions (DMPs) and regions (DMRs) in cord blood and tested if associations persisted in blood collected in mid-childhood. We measured metal concentrations in first-trimester maternal erythrocytes, and DNAm in cord blood (N = 361) and mid-childhood blood (N = 333, 6-10 years) with the Illumina HumanMethylation450 BeadChip. For each metal individually, we tested for DMPs using linear models (considered significant at FDR < 0.05), and for DMRs using comb-p (Sidak p < 0.05). Covariates included biologically relevant variables and estimated cell-type composition. We also performed sex-stratified analyses.

RESULTS

Pb was associated with decreased methylation of cg20608990 (CASP8) (FDR = 0.04), and Mn was associated with increased methylation of cg02042823 (A2BP1) in cord blood (FDR = 9.73 × 10-6). Both associations remained significant but attenuated in blood DNAm collected at mid-childhood (p < 0.01). Two and nine Mn-associated DMPs were identified in male and female infants, respectively (FDR < 0.05), with two and six persisting in mid-childhood (p < 0.05). All metals except Ba and Pb were associated with ≥ 1 DMR among all infants (Sidak p < 0.05). Overlapping DMRs annotated to genes in the human leukocyte antigen (HLA) region were identified for Cr, Cs, Cu, Hg, Mg, and Mn.

CONCLUSIONS

Prenatal metal exposure is associated with DNAm, including DMRs annotated to genes involved in neurodevelopment. Future research is needed to determine if DNAm partially explains the relationship between prenatal metal exposures and health outcomes.

Manganese exposure causes movement deficit and changes in the protein profile of the external globus pallidus in Sprague Dawley rats

Manganese (Mn) is required for normal brain development and function. Excess Mn may trigger a parkinsonian movement disorder but the underlying mechanisms are incompletely understood. We explored changes in the brain proteomic profile and movement behavior of adult Sprague Dawley (SD) rats systemically treated with or without 1.0 mg/mL MnCl₂ for 3 months. Mn treatment significantly increased the concentration of protein-bound Mn in the external globus pallidus (GP), as demonstrated by inductively coupled plasma mass spectrometry. Behavioral study showed that Mn treatment induced movement deficits, especially of skilled movement. Proteome analysis by two-dimensional fluorescence difference gel electrophoresis coupled with mass spectrometry revealed 13 differentially expressed proteins in the GP of Mn-treated versus Mn-untreated SD rats. The differentially expressed proteins were mostly involved in glycolysis, metabolic pathways, and response to hypoxia. Selected pathway class analysis of differentially expressed GP proteins, which included phosphoglycerate mutase 1 (PGAM1), primarily identified enrichment in glycolytic process and innate immune response. In conclusion, perturbation of brain energy production and innate immune response, in which PGAM1 has key roles, may contribute to the movement disorder associated with Mn neurotoxicity.

The role of manganese dysregulation in neurological disease: emerging evidence

Manganese is an essential trace metal. The dysregulation of manganese seen in a broad spectrum of neurological disorders reflects its importance in brain development and key neurophysiological processes. Historically, the observation of acquired manganism in miners and people who misuse drugs provided early evidence of brain toxicity related to manganese exposure. The identification of inherited manganese transportopathies, which cause neurodevelopmental and neurodegenerative syndromes, further corroborates the neurotoxic potential of this element. Moreover, manganese dyshomoeostasis is also implicated in Parkinson's disease and other neurodegenerative conditions, such as Alzheimer's disease and Huntington's disease. Ongoing and future research will facilitate the development of better targeted therapeutical strategies than are currently available for manganese-associated neurological disorders.

Critical Involvement of Glial Cells in Manganese Neurotoxicity

Over the years, most of the research concerning manganese exposure was restricted to the toxicity of neuronal cells. Manganese is an essential trace element that in high doses exerts neurotoxic effects. However, in the last two decades, efforts have shifted toward a more comprehensive approach that takes into account the involvement of glial cells in the development of neurotoxicity as a brain insult. Glial cells provide structural, trophic, and metabolic support to neurons. Nevertheless, these cells play an active role in adult neurogenesis, regulation of synaptogenesis, and synaptic plasticity. Disturbances in glial cell function can lead to neurological disorders, including neurodegenerative diseases. This review highlights the pivotal role that glial cells have in manganese-induced neurotoxicity as well as the most sounding mechanisms involved in the development of this phenomenon.

Combined exposure to multiple metals and cognitive function in older adults

Single toxic metal exposure has been reported to be associated with impaired cognitive function, but less is known about the effects of combined exposure to multiple metals. The aim of the study was to investigate the potential associations and interactions of multiple metals with cognitive function in older adults using multi-pollutants approach. A cross-sectional study was conducted in a total of 2879 participants aged ≥ 60 years old. We systematically measured levels of 22 blood metals and used the Mini-Mental State Examination (MMSE) to assess the cognitive function. The least absolute shrinkage and selection operator (LASSO) penalized regression was applied to identify independently main metals. Adjusted estimates of cognitive function with selected metals were investigated by generalized linear regression in the multi-metal model. We found that calcium, titanium, vanadium, copper, zinc, arsenic, selenium, rubidium, molybdenum, cadmium, barium, and lead were independently identified based on LASSO penalized regression. The multi-metal model showed a higher MMSE of 0.384 (95% CI: 0.122-0.646) for a 1-SD increment in log-transformed rubidium and a lower MMSE of 0.460 (95% CI: - 0.706 to - 0.214) for a 1-SD increment in log-transformed cadmium (P < 0.05). The significantly negative associations between cadmium and cognitive function were attenuated to null accompanying with increasing concentrations of rubidium (P _interaction = 0.256). Our findings suggested that blood rubidium and cadmium were mainly associated with cognitive function when accounting for co-exposure to other metals and higher level of rubidium appeared to attenuate the toxic effects of cadmium on cognitive function in older adults.

Association of Manganese Biomarker Concentrations with Blood Pressure and Kidney Parameters among Healthy Adolescents: NHANES 2013-2018

Deficiency or excess exposure to manganese (Mn), an essential mineral, may have potentially adverse health effects. The kidneys are a major organ of Mn site-specific toxicity because of their unique role in filtration, metabolism, and excretion of xenobiotics. We hypothesized that Mn concentrations were associated with poorer blood pressure (BP) and kidney parameters such as estimated glomerular filtration rate (eGFR), blood urea nitrogen (BUN), and albumin creatinine ratio (ACR). We conducted a cross-sectional analysis of 1931 healthy U.S. adolescents aged 12-19 years participating in National Health and Nutrition Examination Survey cycles 2013-2014, 2015-2016, and 2017-2018. Blood and urine Mn concentrations were measured using inductively coupled plasma mass spectrometry. Systolic and diastolic BP were calculated as the average of available readings. eGFR was calculated from serum creatinine using the Bedside Schwartz equation. We performed multiple linear regression, adjusting for age, sex, body mass index, race/ethnicity, and poverty income ratio. We observed null relationships between blood Mn concentrations with eGFR, ACR, BUN, and BP. In a subset of 691 participants, we observed that a 10-fold increase in urine Mn was associated with a 16.4 mL/min higher eGFR (95% Confidence Interval: 11.1, 21.7). These exploratory findings should be interpreted cautiously and warrant investigation in longitudinal studies.

Manganese concentration in patients with encephalopathy following ephedrone use: a narrative review and analysis of case reports

BACKGROUND

Numerous case reports describe manganese encephalopathy in patients using ephedrone (methcathinone). The aim of this narrative review of case reports was to relate manganese ion concentrations in peripheral blood to the reported neurological deficits.

METHODS

International databases, including Thomson (Web of Knowledge), PubMed/Medline, Science Direct, Scopus and Google Scholar were searched for literature items published between 2007 and 2020, in which the authors measured the manganese concentration in patients taking ephedrone.

RESULTS

We identified 39 patients in two case series comprising of twenty-three and twelve patients, respectively, and four case reports meeting inclusion criteria. The study showed that 93% of them had elevated blood manganese concentration in relation to the accepted norm (>219 nmol/L), and the median was 364 nmol/L. The median duration of ephedrone use in individual groups of patients was approximately 48 months, and it did not show a relationship with the manganese concentration in the blood. A greater percentage of the people with manganese concentration higher than 250 nmol/L exhibited more severe gait, speech and handwriting disorders. The median duration of ephedrone withdrawal was a month in the group of people with the highest level of manganese ions (>500 nmol/L).

CONCLUSION

Manganese concentrations did not vary with the duration of ephedrone use.

Dysregulated APP expression and α-secretase processing of APP is involved in manganese-induced cognitive impairment

Excessive exposure to manganese (Mn) can cause cognitive impairment, a common feature of Alzheimer's disease (AD), but the mechanisms remain unclear. Amyloid precursor protein (APP) is key to AD pathogenesis, and whether APP and its secretase processing are involved in Mn-induced cognitive impairment remains unknown. In the present study, we established a model of Mn-induced neurotoxicity in vivo (male C57BL/6, 0-100 mg/kg Mn, 90 days, gastric gavage) and in vitro (Neuro-2a (N2a) cells, 0-800 μM Mn for 24 h; APP overexpression and APP shRNA N2a cells, 0 and 800 μM Mn for 24 h). We found impaired cognition of Mn-treated mice. Both in vivo and in vitro results consistently showed that Mn exposure inhibited the expression of APP, α-secretase, soluble APP alpha protein (sAPPα), and synapse proteins as well as the activity of α-secretase. However, Mn exposure showed no effect on the protein levels of β-secretase, Aβ40, and Aβ42 or the activity of β-secretase. Collectively, these findings demonstrate key roles of APP and its α-secretase processing in the regulation of Mn-induced cognitive impairment, which may act as a target for ameliorating Mn-induced neurotoxicity.

Up-regulation of the manganese transporter SLC30A10 by hypoxia-inducible factors defines a homeostatic response to manganese toxicity

Manganese (Mn) is an essential metal that induces incurable parkinsonism at elevated levels. However, unlike other essential metals, mechanisms that regulate mammalian Mn homeostasis are poorly understood, which has limited therapeutic development. Here, we discovered that the exposure of mice to a translationally relevant oral Mn regimen up-regulated expression of SLC30A10, a critical Mn efflux transporter, in the liver and intestines. Mechanistic studies in cell culture, including primary human hepatocytes, revealed that 1) elevated Mn transcriptionally up-regulated SLC30A10, 2) a hypoxia response element in the SLC30A10 promoter was necessary, 3) the transcriptional activities of hypoxia-inducible factor (HIF) 1 or HIF2 were required and sufficient for the SLC30A10 response, 4) elevated Mn activated HIF1/HIF2 by blocking the prolyl hydroxylation of HIF proteins necessary for their degradation, and 5) blocking the Mn-induced up-regulation of SLC30A10 increased intracellular Mn levels and enhanced Mn toxicity. Finally, prolyl hydroxylase inhibitors that stabilize HIF proteins and are in advanced clinical trials for other diseases reduced intracellular Mn levels and afforded cellular protection against Mn toxicity and also ameliorated the in vivo Mn-induced neuromotor deficits in mice. These findings define a fundamental homeostatic protective response to Mn toxicity-elevated Mn levels activate HIF1 and HIF2 to up-regulate SLC30A10, which in turn reduces cellular and organismal Mn levels, and further indicate that it may be possible to repurpose prolyl hydroxylase inhibitors for the management of Mn neurotoxicity.

Simultaneous Quantification and Speciation of Trace Metals in Paired Serum and CSF Samples by Size Exclusion Chromatography-Inductively Coupled Plasma-Dynamic Reaction Cell-Mass Spectrometry (SEC-DRC-ICP-MS)

BACKGROUND

Transition metals play a crucial role in brain metabolism: since they exist in different oxidation states they are involved in ROS generation, but they are also co-factors of enzymes in cellular energy metabolism or oxidative defense.

METHODS

Paired serum and cerebrospinal fluid (CSF) samples were analyzed for iron, zinc, copper and manganese as well as for speciation using SEC-ICP-DRC-MS. Brain extracts from Mn-exposed rats were additionally analyzed with SEC-ICP-DRC-MS.

RESULTS

The concentration patterns of transition metal size fractions were correlated between serum and CSF: Total element concentrations were significantly lower in CSF. Fe-ferritin was decreased in CSF whereas a LMW Fe fraction was relatively increased. The 400-600 kDa Zn fraction and the Cu-ceruloplasmin fraction were decreased in CSF, by contrast the 40-80 kDa fraction, containing Cu- and Zn-albumin, relatively increased. For manganese, the α-2-macroglobulin fraction showed significantly lower concentration in CSF, whereas the citrate Mn fraction was enriched. Results from the rat brain extracts supported the findings from human paired serum and CSF samples.

CONCLUSIONS

Transition metals are strictly controlled at neural barriers (NB) of neurologic healthy patients. High molecular weight species are down-concentrated along NB, however, the Mn-citrate fraction seems to be less controlled, which may be problematic under environmental load.

Manganese nanoparticles induce blood-brain barrier disruption, cerebral blood flow reduction, edema formation and brain pathology associated with cognitive and motor dysfunctions

Nanoparticles affect blood-brain barrier (BBB) and brain edema formation resulting in sensory-motor dysfunction. Exposure of Mn nanoparticles from industrial sources in humans could target basal ganglia resulting in Parkinson's disease. In present investigation, Mn exposure on brain pathology in a rat model was examined. Rats received Mn nanoparticles (30-40nm size) in a dose of 10 or 20mg/kg, i.p. once daily for 7 days and behavioral dysfunctions on Rota Rod performance, inclined plane angle and grid-walking tests as well as gait performances were examined. In addition, BBB breakdown to Evans blue and radioiodine, brain edema formation and neural injuries were also evaluated. Mn nanoparticles treated rats exhibited cognitive and motor dysfunction on the 8th day. At this time, BBB disruption, reduction in cerebral blood flow (CBF), brain edema formation and brain pathology were most marked in the sensory-motor cortex, hippocampus, caudate putamen, cerebellum and thalamus followed by hypothalamus, pons, medulla and spinal cord. In these brain areas, neuronal injuries using Nissl staining was clearly seen. These effects of Mn nanoparticle are dose dependent. These results are the first to demonstrate that Mn nanoparticles induce selective brain pathology resulting in cognitive and motor dysfunction, not reported earlier.