The Role of Heavy Metal Pollution in Neurobehavioral Disorders: a Focus on Autism

Evaluating the portable X-ray fluorescence reliability for metal(loid)s detection and soil contamination status

Marginalized communities experience barriers that can prevent soil monitoring efforts and knowledge transfer. To address this challenge, this study compared two analytical methods: portable X-ray fluorescence spectroscopy (pXRF, less time, cost) and inductively coupled plasma mass spectrometry (ICP-MS, "gold standard"). Surface soil samples were collected from residential sites in Arizona, USA (N = 124) and public areas in Troy, New York, USA (N = 33). Soil preparation differed between groups to account for community practice. Statistical calculations were conducted, paired t test, Bland-Altman plot, and a two-way ANOVA indicated no significant difference for As, Ba, Ca, Cu, Mn, Pb, and Zn concentrations except for Ba in the t test. Iron, Ni, Cr, and K were statistically different for Arizona soils and V, Ni, Fe, and Al concentrations were statistically different for New York soils. Zinc was the only element with high R2 and low p value. Pollution load index (PLI), enrichment factors (EF), and geo-accumulation index (Igeo) were calculated for both methods using U.S. Geological Survey data. The PLI were > 1, indicating soil pollution in the two states. Between pXRF and ICP-MS, the Igeo and EF in Arizona had similar degree of contamination for most elements except Zn in garden and Pb in yard, respectively. For New York, the Igeo of As, Cu, and Zn differed by only one classification index between the two methods. The pXRF was reliable in determining As, Ba, Ca, Cu, Mn, Pb, and Zn in impacted communities. Therefore, the pXRF can be a cost-effective alternative to using ICP-MS techniques to screen soil samples for several environmentally relevant contaminants to protect environmental public health.

An ecological study shows increased prevalence of autism spectrum disorder in children living in a heavily polluted area

The burden of autism spectrum disorder (ASD) is increasing worldwide with genetic, epigenetic, and environmental factors being possibly responsible for the observed epidemiological figures. In the setting of environmental exposure, the city of Taranto, in Southern Italy, represents an interesting case study as it hosts well inside the city one of the biggest steel plants in Europe. This is a cross-sectional ecological study carried out in the year 2020 in the province of Taranto designed to estimate the burden of ASD in the municipalities of Taranto and Statte, classified as high environmental risk areas (Contaminated Site of National Interest-SIN), compared to the other 27 municipalities of the same province. Differences have been evaluated using the Chi Square Test. Children aged 6-11 years identified in SIN municipalities had a statistically significant higher prevalence of ASD than children of other municipalities (9.58 vs. 6.66/1000 respectively, p = 0.002). No statistically significant difference was observed for the 12-18 years group (3.41 vs. 2.54/1000, p = 0.12). The findings observed in this study are suggestive of the association between urban residential proximity to industrial facilities emitting air pollutants and higher ASD prevalence.

Leek (Allium ampeloprasum var. kurrat) aqueous extract loaded on selenium nanoparticles protects against testis and brain injury induced by mercuric chloride in rats

BACKGROUND

Mercuric chloride (HgCl2) is poisonous to humans and animals and typically damages the nervous system and other organs. Mercuric chloride exposition disclosed to initiation of oxidative stress pathway can result in a defect in male fertility and testis tissue. Synthesized selenium nanoparticles (SeNPs) were characterized with a diameter range minimal than 100 nm, having the effective sets of the biological matter. The present study aimed to evaluate the effect of biosynthesized SeNPs, prepared by leek extract on Wistar rats' testicles and brain.

METHODS

Thirty-five Wistar male rats (120-150 g) were randomly split into five groups (n = 7), orally ingested with leek aqueous extract loaded on SeNPs, and then the animals were administered with mercury II chloride (HgCl2) to induce testis injury and damage the nervous system.

RESULTS

The used dose of mercuric chloride led to oxidative stress damage in the testis of the rats which was evidenced by a decrease in testosterone, luteinizing hormone (LH), follicle-stimulating hormone (FSH) and proliferating cell nuclear antigen (PCNA) levels, and an increase in nuclear factor-kappa B (NF-κB) and caspase-3. Also, HgCl2 decreased the levels of dopamine (DA), serotonin (5-HT), norepinephrine (NE) and brain-derived neurotrophic factor (BDNF) in the brains of rats. In addition, A decrease was observed in the levels of antioxidant markers, B-cell lymphoma-2 (Bcl-2), as well as an increase in malondialdehyde (MDA), nitric oxide (NO), NF-κB, tumor necrosis factor (TNF)-α, interleukin (IL)-1β and Bax in both testes and brains. Pre-treatment with leek extract loaded on SeNPs significantly ameliorated testosterone, LH, FSH, PCNA and caspase-3 levels in the testis and DA, 5-HT, NE and BDNF in brains. Although the contents of MDA, NO, TNF-α, IL-1β, NF-κB and Bax decreased significantly in both. glutathione, glutathione peroxidase, glutathione reductase, catalase, superoxide dismutase and Bcl-2 levels were significantly improved in both organs.

CONCLUSION

Our findings suggest that treatment with aqueous leek extract loaded on SeNPs may offer promising prospects for the advancement of anti-inflammation activity against testis injury and also have a very key role in neurobehavioral alterations as a result of mercury toxicity. © 2024 Society of Chemical Industry.

Melatonin is a Neuroprotective and Antioxidant Agent against Neurotoxicity Induced by an Intrahippocampal Injection of Nickel in Rats

The investigation into the hippocampal function and its response to heavy metal exposure is crucial for understanding the mechanisms underlying neurotoxicity, this can potentially inform strategies for mitigating the adverse effects associated with heavy metal exposure. Melatonin is an essential neuromodulator known for its efficacy as an antioxidant. In this study, we aimed to determine whether melatonin could protect against Nickel (Ni) neurotoxicity. To achieve this, we performed an intracerebral injection of Ni (300 µM NiCl2) into the right hippocampus of male Wistar rats, followed by melatonin treatment. Based on neurobehavioral and neurobiochemical assessments, our results demonstrate that melatonin efficiently enhances Ni-induced behavioral dysfunction and cognitive impairment. Specifically, melatonin treatment positively influences anxious behavior, significantly reduces immobility time in the forced swim test (FST), and improves learning and spatial memory abilities. Moreover, neurobiochemical assays revealed that melatonin treatment modulates the Ni-induced alterations in oxidative stress balance by increasing antioxidant enzyme activities, such as superoxide dismutase (SOD) and catalase (CAT). Additionally, we observed that melatonin significantly attenuated the increased levels of lipid peroxidation (LPO) and nitric oxide (NO). In conclusion, the data from this study suggests that melatonin attenuates oxidative stress, which is the primary mechanism responsible for Ni-induced neurotoxicity. Considering that the hippocampus is the main structure involved in the pathology associated with heavy metal intoxication, such as Ni, these findings underscore the potential therapeutic efficacy of melatonin in mitigating heavy metal-induced brain damage.

Prenatal exposure to metal mixtures and childhood temporal processing in the PROGRESS Birth Cohort Study: Modification by childhood obesity

Children are frequently exposed to various biological trace metals, some essential for their development, while others can be potent neurotoxicants. Furthermore, the inflammatory and metabolic conditions associated with obesity may interact with and amplify the impact of metal exposure on neurodevelopment. However, few studies have assessed the potential modification effect of body mass index (BMI). As a result, we investigated the role of child BMI phenotype on the relationship between prenatal exposure to metal mixtures and temporal processing. Leveraging the PROGRESS birth cohort in Mexico City, children (N = 563) aged 6-9 years completed a Temporal Response Differentiation (TRD) task where they had to hold a lever down for 10-14 s. Blood and urinary metal (As, Pb, Cd, and Mn) measurements were collected from mothers in the 2nd and 3rd trimesters. Child BMI z-scores were dichotomized to normal (between -2 and +0.99) and high (≥1.00). Covariate-adjusted weighted quantile sum (WQS) regression models were used to estimate and examine the combined effect of metal biomarkers (i.e., blood and urine) on TRD measures. Effect modification by the child's BMI was evaluated using 2-way interaction terms. Children with a high BMI and greater exposure to the metal mixture during prenatal development exhibited significant temporal processing deficits compared to children with a normal BMI. Notably, children with increased exposure to the metal mixture and higher BMI had a decrease in the percent of tasks completed (β = -10.13; 95 % CI: -19.84, -0.42), number of average holds (β = -2.15; 95 % CI: -3.88, -0.41), longer latency (β = 0.78; 95 % CI: 0.13, 1.44), and greater variability in the standard deviation of the total hold time (β = 2.08; 95 % CI: 0.34, 3.82) compared to normal BMI children. These findings implicate that high BMI may amplify the effect of metals on children's temporal processing. Understanding the relationship between metal exposures, temporal processing, and childhood obesity can provide valuable insights for developing targeted environmental interventions.

Cadmium exposure exacerbates immunological abnormalities in a BTBR T+ Itpr3tf/J autistic mouse model by upregulating inflammatory mediators in CD45R-expressing cells

Autism spectrum disorder (ASD) is a neurodevelopmental illness characterized by behavior, learning, communication, and social interaction abnormalities in various situations. Individuals with impairments usually exhibit restricted and repetitive actions. The actual cause of ASD is yet unknown. It is believed, however, that a mix of genetic and environmental factors may play a role in its development. Certain metals have been linked to the development of neurological diseases, and the prevalence of ASD has shown a positive association with industrialization. Cadmium chloride (Cd) is a neurotoxic chemical linked to cognitive impairment, tremors, and neurodegenerative diseases. The BTBR T+ Itpr3tf/J (BTBR) inbred mice are generally used as a model for ASD and display a range of autistic phenotypes. We looked at how Cd exposure affected the signaling of inflammatory mediators in CD45R-expressing cells in the BTBR mouse model of ASD. In this study, we looked at how Cd affected the expression of numerous markers in the spleen, including IFN-γ, IL-6, NF-κB p65, GM-CSF, iNOS, MCP-1, and Notch1. Furthermore, we investigated the effect of Cd exposure on the expression levels of numerous mRNA molecules in brain tissue, including IFN-γ, IL-6, NF-κB p65, GM-CSF, iNOS, MCP-1, and Notch1. The RT-PCR technique was used for this analysis. Cd exposure increased the number of CD45R+IFN-γ+, CD45R+IL-6+, CD45R+NF-κB p65+, CD45R+GM-CSF+, CD45R+GM-CSF+, CD45R+iNOS+, and CD45R+Notch1+ cells in the spleen of BTBR mice. Cd treatment also enhanced mRNA expression in brain tissue for IFN-γ, IL-6, NF-κB, GM-CSF, iNOS, MCP-1, and Notch1. In general, Cd increases the signaling of inflammatory mediators in BTBR mice. This study is the first to show that Cd exposure causes immune function dysregulation in the BTBR ASD mouse model. As a result, our study supports the role of Cd exposure in the development of ASD.

Two-photon excited luminescence of sulfur quantum dots for heavy metal ion detection

Spectrally-resolved third-order nonlinear optical properties of water-dispersed sulfur quantum dots (SQDs) were investigated in the wavelength range from 740 nm to 820 nm with the two-photon excited emission technique using a tunable femtosecond laser system. The maximum value of the two-photon absorption (TPA) cross-section (σ2) for ∼5.4 nm size SQDs was found to be 185 GM (Goeppert-Mayer unit), while the two-photon brightness (σ2 × η) was found to be 1.5 GM at 780 nm, the wavelength being in the first biological transmittance window. The TPA properties are presented here as appropriate cross-sections normalized per molecular weight which enables meaningful comparison of the nonlinear factors of the studied quantum dots with those of various nanomaterials. The optimized TPA properties of these hydrophilic colloidal SQDs may be potentially useful for detection of Fe3+ metal ions. The experimentally determined limit of Fe3+ detection for both one- and two-photon regime was 10 μmol L-1 (0.6 μg mL-1). Förster resonance energy transfer between SQDs as donors and Fe3+ metal ions as acceptors was confirmed as one of the possible detection mechanisms using a time-correlated single photon counting technique.

Mercury and Autism Spectrum Disorder: Exploring the Link through Comprehensive Review and Meta-Analysis

Mercury (Hg) is a non-essential trace metal with unique neurochemical properties and harmful effects on the central nervous system. In this study, we present a comprehensive review and meta-analysis of peer-reviewed research encompassing five crucial clinical matrices: hair, whole blood, plasma, red blood cells (RBCs), and urine. We assess the disparities in Hg levels between gender- and age-matched neurotypical children (controls) and children diagnosed with autism spectrum disorder (ASD) (cases). After applying rigorous selection criteria, we incorporated a total of 60 case-control studies into our meta-analysis. These studies comprised 25 investigations of Hg levels in hair (controls/cases: 1134/1361), 15 in whole blood (controls/cases: 1019/1345), 6 in plasma (controls/cases: 224/263), 5 in RBCs (controls/cases: 215/293), and 9 in urine (controls/cases: 399/623). This meta-analysis did not include the data of ASD children who received chelation therapy. Our meta-analysis revealed no statistically significant differences in Hg levels in hair and urine between ASD cases and controls. In whole blood, plasma, and RBCs, Hg levels were significantly higher in ASD cases compared to their neurotypical counterparts. This indicates that ASD children could exhibit reduced detoxification capacity for Hg and impaired mechanisms for Hg excretion from their bodies. This underscores the detrimental role of Hg in ASD and underscores the critical importance of monitoring Hg levels in ASD children, particularly in early childhood. These findings emphasize the pressing need for global initiatives aimed at minimizing Hg exposure, thus highlighting the critical intersection of human-environment interaction and neurodevelopment health.

Exposure to environmental pollutants and attention-deficit/hyperactivity disorder: an overview of systematic reviews and meta-analyses

Although heritability estimates suggest a role for genetic components, environmental risk factors have been described as relevant in the etiology of attention deficit/hyperactivity disorder (ADHD). Several studies have investigated the role of toxicological pollution, i.e., air pollution, heavy metals, POPs, and phthalates. Clear evidence for association of ADHD and environmental factors has not been provided yet. To answer this, we have assessed all available systematic reviews and meta-analyses that focused on the association between pollutant exposure and either ADHD diagnosis or symptoms. More than 1800 studies were screened of which 14 found eligible. We found evidence of a significant role for some pollutants, in particular heavy metals and phthalates, in the increased risk of developing ADHD symptoms. However, at the current stage, data from existing literature also do not allow to weight the role of the different environmental pollutants. We also offer a critical examination of the reviews/meta-analyses and provide indications for future studies in this field. PROSPERO registration: CRD42022341496.

Interaction of heavy metals in Drosophila melanogaster larvae: Fourier transform infrared spectroscopy and single-cell electrophoresis study

The present study evaluates the Murraya Koenigii (CuLE) and Tinospora Crispa (TiSE) antimutagenic effect and the impact of industrial soil and solid waste leachate on Drosophila larvae. Larvae were exposed to leachate prepared at different pH (7, 4.93, 2.88) and treated with TiSE and CuLE at different concentration (4 g/L and 6 g/L) mixed with standard Drosophila medium. Emphasis was given to the binding interaction of heavy metals with proteins in Drosophila. The change in structure and molecular composition in Drosophila by leachate containing heavy metals induced toxicity has been studied by using Fourier transform infrared (FTIR) spectroscopy. Results from the study demonstrated that CuLE/TiSE administration restored the level of oxidative stress as evidenced by an enhanced antioxidant system and a decrease in lipid peroxidation and protein oxidation. The amide I and amide II bands spectral shifting revealed the binding interaction. The shift in the peak of PO2- asymmetric stretching might be due to compositional changes in nucleic acids. Single-cell electrophoresis was performed to detect the DNA damage which also proved to be ameliorated by administration of CuLE/TiSE. The result concludes that CuLE/TiSE may have great potential in the protection of Drosophila larvae from leachate induced oxidative stress through antioxidant and antimutagenic mechanisms this might help to cope with environmental toxicants.Communicated by Ramaswamy H. Sarma.

Association of heavy metal complex exposure and neurobehavioral function of children

Background

Exposure to heavy metals is a public health concern worldwide. Previous studies on the association between heavy metal exposure and neurobehavioral functions in children have focused on single exposures and clinical manifestations. However, the present study evaluated the effects of heavy metal complex exposure on subclinical neurobehavioral function using a Korean Computerized Neurobehavior Test (KCNT).

Methods

Urinary mercury, lead, cadmium analyses as well as symbol digit substitution (SDS) and choice reaction time (CRT) tests of the KCNT were conducted in children aged between 10 and 12 years. Reaction time and urinary heavy metal levels were analyzed using partial correlation, linear regression, Bayesian kernel machine regression (BKMR), the weighted quantile sum (WQS) regression and quantile G-computation analysis.

Results

Participants of 203 SDS tests and 198 CRT tests were analyzed, excluding poor cooperation and inappropriate urine sample. Partial correlation analysis revealed no association between neurobehavioral function and exposure to individual heavy metals. The result of multiple linear regression shows significant positive association between urinary lead, mercury, and CRT. BMKR, WQS regression and quantile G-computation analysis showed a statistically significant positive association between complex urinary heavy metal concentrations, especially lead and mercury, and reaction time.

Conclusions

Assuming complex exposures, urinary heavy metal concentrations showed a statistically significant positive association with CRT. These results suggest that heavy metal complex exposure during childhood should be evaluated and managed strictly.

Estimation of the cumulative risks from dietary exposure to cadmium, arsenic, nickel, lead and chromium Guangzhou, China

Heavy metals, such as cadmium and lead, are ubiquitously present as single substances and compounds in the environment. These substances have various and overlapping health effects. Consumption of contaminated foods is the main pathway of the human exposure, however, estimation of their dietary exposure in combination with health risk analysis, particularly at various endpoints, has rarely been reported. In this study, we integrated relative potency factor (RPF) analysis into the margin of exposure (MOE) model to evaluate the health risk of combined heavy metal (including cadmium, arsenic, lead, chromium, and nickel) exposure in the residents in Guangzhou, China, after quantifying the heavy metals in various food samples and estimating their dietary exposure. The results indicated that rice, rice products and leafy vegetables contributed primarily to the dietary exposure of all metals except arsenic, which exposed the population largely through consumption of sea-foods. With all the five metals contributing to nephro- and neurotoxicity, the 95% confidence limits of MOE for the residents were clearly below 1.0 in the 3∼6-year group, suggesting a recognizable risk to young children. This study provides substantial evidence for the non-negligible health risk in young children due to increased heavy metal exposure,at least on some toxicity targets.

The Effect of Maternal Exposure to Air Pollutants and Heavy Metals during Pregnancy on the Risk of Neurological Disorders Using the National Health Insurance Claims Data of South Korea

The objective of this study was to evaluate the effects of high levels of maternal exposure to ambient air pollution and heavy metals on risks of autism spectrum disorder (ASD) and epilepsy using the National Health Insurance claims data of South Korea. The data of mothers and their newborns from 2016 to 2018 provided by the National Health Insurance Service were used (n = 843,134). Data on exposure to ambient air pollutants (PM2.5, CO, SO₂, NO₂, and O₃) and heavy metals (Pb, Cd, Cr, Cu, Mn, Fe, Ni, and As) during pregnancy were matched based on the mother's National Health Insurance registration area. SO₂ (OR: 2.723, 95% CI: 1.971-3.761) and Pb (OR: 1.063, 95% CI: 1.019-1.11) were more closely associated with the incidence of ASD when infants were exposed to them in the third trimester of pregnancy. Pb (OR: 1.109, 95% CI: 1.043-1.179) in the first trimester of pregnancy and Cd (OR: 2.193, 95% CI: 1.074-4.477) in the third trimester of pregnancy were associated with the incidence of epilepsy. Thus, exposure to SO₂, NO₂, and Pb during pregnancy could affect the development of a neurologic disorder based on the timing of exposure, suggesting a relationship with fetal development. However, further research is needed.

Heavy metals and inflammatory, oxidative/antioxidant and DNA damage biomarkers among people living with HIV/AIDS (PLWHA) in Niger Delta, Nigeria

This study evaluated the association of heavy metals (HMs) and effect biomarkers (inflammation, oxidative stress/antioxidant capacity and DNA damage) among people living with HIV/AIDS (PHWHA) in Niger Delta area, Nigeria. Blood levels of lead (BPb), cadmium (BCd), copper (BCu), zinc (BZn), iron (BFe), C-reactive protein (CRP), Interleukin-6 (IL-6), Tumor necrosis factor-α (TNF-α), Interferon-γ (IFN-γ), Malondialdehyde (MDA), Glutathione (GSH) and 8-hydroxy-2-deoxyguanosine (8-OHdG) were determined in a total of 185 participants, 104 HIV-positive and 81 HIV-negative sampled in both Niger Delta and non-Niger Delta regions. BCd (p < 0.001) and BPb (p = 0.139) were higher in HIV-positive subjects compared to HIV-negative controls; on the contrary, BCu, BZn and BFe levels were lower (p < 0.001) in HIV-positive subjects compared to HIV-negative controls. The Niger Delta population had higher levels of heavy metals (p < 0.01) compared to non-Niger Delta residents. CRP and 8-OHdG were higher (p < 0.001) in HIV-positive than in HIV-negative subjects and in Niger-Delta than in non-Niger Delta residents. BCu had significant positive dose-response relationship with CRP (61.9%, p = 0.063) and GSH (1.64%, p = 0.035) levels in HIV-positive subjects, and negative response with MDA levels (26.6%, p < 0.001). Periodic assessment of HMs levels among PLWHA is recommended.

Multi-matrix biomonitoring approach to assess exposure to metals and trace elements in the Lebanese population and associations with drinking water consumption

This study is the first attempt to assess exposure to metals and trace elements in subgroups of the Lebanese population using a multi-matrix biomonitoring approach. Concentrations of 11 metals and trace elements (aluminum (Al), arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), lead (Pb), manganese (Mn), selenium (Se), uranium (U), zinc (Zn)) were measured in urine, hair and toenails. Biological levels were compared according to age, sex, smoking status, socioeconomic status, geographical area and drinking water source. While most urinary and toenail concentrations of metals and trace elements were not different between males and females, measured concentrations of several elements in hair were higher in females compared to males. Urinary concentrations of some metals (Al, Cu, Se and Zn) were higher in children compared to teenagers and adults. Hair and toenail concentrations of several elements (As, Cd, Pb, Mn, Se in hair and toenails plus Al, Fe in toenails) were also significantly higher in children compared to teenagers and/or adults. Smoking status had no influence on metal and trace element concentrations. Levels of Cd, Pb and Mn were also higher in samples from subgroups with lower economic status (Cd and Pb in the three matrices and Mn in hair and toenails). Very few correlations were identified between sources of drinking water and urine, hair, and toenail concentrations of metals and trace elements. However, a correlation was observed between hair and toenails levels of As, Cd and Pb. Overall, results highlight that a special attention should be given to metal and trace element exposure in this population (including Pb, As, Cd, Mn, and Se). It could be relevant to scale up this kind of investigation with a large human biomonitoring initiative in the Lebanese population in order to generalize results, and assess trends over time.

A critical review on microbes-based treatment strategies for mitigation of toxic pollutants

Contamination of the environment through toxic pollutants poses a key risk to the environment due to irreversible environmental damage(s). Industrialization and urbanization produced harmful elements such as petrochemicals, agrochemicals, pharmaceuticals, nanomaterials, and herbicides that are intentionally or unintentionally released into the water system, threatening biodiversity, the health of animals, and humans. Heavy metals (HMs) in water, for example, can exist in a variety of forms that are inclined by climate features like the presence of various types of organic matter, pH, water system hardness, transformation, and bioavailability. Biological treatment is an important tool for removing toxic contaminants from the ecosystem, and it has piqued the concern of investigators over the centuries. In situ bioremediation such as biosparging, bioventing, biostimulation, bioaugmentation, and phytoremediation and ex-situ bioremediation includes composting, land farming, biopiles, and bioreactors. In the last few years, scientific understanding of microbial relations with particular chemicals has aided in the protection of the environment. Despite intensive studies being carried out on the mitigation of toxic pollutants, there have been limited efforts performed to discuss the solutions to tackle the limitations and approaches for the remediation of heavy metals holistically. This paper summarizes the risk assessment of HMs on aquatic creatures, the environment, humans, and animals. The content of this paper highlights the principles and limitations of microbial remediation to address the technological challenges. The coming prospect and tasks of evaluating the impact of different treatment skills for pollutant remediation have been reviewed in detail. Moreover, genetically engineered microbes have emerged as powerful bioremediation capabilities with significant potential for expelling toxic elements. With appropriate examples, current challenging issues and boundaries related to the deployment of genetically engineered microbes as bioremediation on polluted soils are emphasized.

Silica nanoparticles are novel aqueous additive mitigating heavy metals toxicity and improving the health of African catfish, Clarias gariepinus

Silica nanoparticles (SiNPs) are among the non-toxic nanoparticles (NPs) that have magnetic capabilities. It is hypothesized that SiNPs may be able to reduce toxic effects exerted by a mixture of lead (Pb) and mercury (Hg) in African catfish Clarias gariepinus. The in vitro magnetic potential of SiNPs to absorb Pb and Hg was tested. Fish (N = 240) were divided into four groups in triplicates for 30 days. The first group served as control and the second group (SiNPs) was exposed to 1/10 of 96 h LC50 of SiNPs (14.45 mg/L). The third group (HMM) was exposed to 1/10 of 96-h LC50 of a mixture of mercury chloride (HgCl₂) and lead chloride (PbCl₂) equal to 0.04 mg/ L and 23.1 mg/L. The fourth group (SiNPs+ HMM) was exposed to a suspension composed of SiNPs, HgCl₂, and PbCl₂ at the same concentrations as the third group. Results showed that fish exposed to heavy metals revealed the following consequences; a significant decrease in hematological, immunological (complement-3 and nitric oxide), and antioxidants (total antioxidant capacity, glutathione peroxidase, superoxide dismutase, and catalase) indices, down-regulation of IL-1β, IL-8, TGF-β, NF-κβ, HSP70, and Hepcidin genes, the highest mortality rate (48.33%), higher values of alkaline phosphatase, alanine, and aspartate aminotransferases, urea, creatinine, and branchial malondialdehyde, marked up-regulation of CC chemokine and CXC chemokines, and high HMs residues levels in muscles. Extensive pathology showed degeneration with diffuse vacuolation of hepatopancreatic cells and hemorrhage in the HMM group. Interestingly, the exposed group to SiNPs and HMM demonstrated a decline of HMs concentration in fish muscles and modulated the abovementioned parameters with the regeneration of histological alterations of liver and gills. Based on the study outcomes, we highlight the importance and the safety of SiNPs as a novel aqueous additive to alleviate HMs toxicity and recommend using SiNPs for enhancing fish performance for sustaining aquaculture without adverting safety of human health by their little accumulation in muscular tissue.

Role of microbes in bioaccumulation of heavy metals in municipal solid waste: Impacts on plant and human being

The presence of heavy metals in municipal solid waste (MSW) is considered as prevalent global pollutants that cause serious risks to the environment and living organisms. Due to industrial and anthropogenic activities, the accumulation of heavy metals in the environmental matrices is increasing alarmingly. MSW causes several adverse environmental impacts, including greenhouse gas (GHG) emissions, river plastic accumulation, and other environmental pollution. Indigenous microorganisms (Pseudomonas, Flavobacterium, Bacillus, Nitrosomonas, etc.) with the help of new pathways and metabolic channels can offer the potential approaches for the treatment of pollutants. Microorganisms, that exhibit the ability of bioaccumulation and sequestration of metal ions in their intracellular spaces, can be utilized further for the cellular processes like enzyme signaling, catalysis, stabilizing charges on biomolecules, etc. Microbiological techniques for the treatment and remediation of heavy metals provide a new prospects for MSW management. This review provides the key insights on profiling of heavy metals in MSW, tolerance of microorganisms, and application of indigenous microorganisms in bioremediation. The literatures revealed that indigenous microbes can be exploited as potential agents for bioremediation.

Association between placental toxic metal exposure and NICU Network Neurobehavioral Scales (NNNS) profiles in the Rhode Island Child Health Study (RICHS)

BACKGROUND

Prenatal exposure to heavy metals has been linked to a variety of adverse outcomes in newborn health and later life. Toxic metals such as cadmium (Cd), manganese (Mn) and lead (Pb) have been implicated to negatively affect newborn neurobehavior. Placental levels of these metals may provide additional understandings on the link between prenatal toxic metal exposures and neurobehavioral performances in newborns.

OBJECTIVE

To evaluate associations between placental concentrations of toxic metals and newborn neurobehavioral performance indicated through the NICU Network Neurobehavioral Scales (NNNS) latent profiles.

METHOD

In the Rhode Island Child Health Study cohort (n = 625), newborn neurobehavioral performance was assessed with NNNS, and a latent profile analysis was used to define five discrete neurobehavioral profiles based on summary scales. Using multinomial logistic regression, we determined whether increased levels of placental toxic metals Cd, Mn and Pb associated with newborns assigned to the profile demonstrating atypical neurobehavioral performances.

RESULTS

Every doubling in placenta Cd concentration was associated with increased odds of newborns belonging to the atypical neurobehavior profile (OR: 2.72, 95% CI [1.09, 6.79]). Detectable placental Pb also demonstrated an increased odds of newborns assignment to the atypical profile (OR: 3.71, 95% CI [0.97, 13.96]) compared to being in the typical neurobehavioral profile.

CONCLUSIONS

Toxic metals Cd and Pb measured in placental tissue may adversely impact newborn neurobehavior. Utilizing the placenta as a prenatal toxic metal exposure biomarker is useful in elucidating the associated impacts of toxic metals on newborn health.

Metal mixtures are associated with increased anxiety during pregnancy

BACKGROUND

Exposure to low-dose toxic metals in the environment is ubiquitous. Several murine studies have shown metals induce anxiety-like behaviors, and mechanistic research supports that metals disrupt neurotransmitter signaling systems implicated in the pathophysiology of anxiety. In this study, we extend prior research by examining joint exposure to six metals in relation to maternal anxiety symptoms during pregnancy.

METHODS

The sample includes 380 participants enrolled in the PRogramming of Intergenerational Stress Mechanisms (PRISM) pregnancy cohort. Spot urine was collected during pregnancy (mean ± standard deviation: 31.1 ± 6.1 weeks), and concentrations of six metals (barium [Ba], cadmium [Cd], chromium [Cr], cesium [Cs], lead [Pb], antimony [Sb]) were measured by Inductively Coupled Plasma - Mass Spectrometry. Trait anxiety symptoms were measured during pregnancy using a short version of the Spielberger State Trait Anxiety Inventory (STAI-T) and information on covariates was collected by questionnaire. We used weighted quantile sum (WQS) regression as the primary modeling approach to examine metals, treated as a mixture, in relation to higher (≥20) vs. lower anxiety symptoms while adjusting for urinary creatinine and key sociodemographic variables.

RESULTS

The sample is socioeconomically and racially/ethnically diverse. Urinary metal concentrations were log-normally distributed and 25% of the sample had an STAI-T score ≥20. Joint exposure to metals was associated with elevated anxiety symptoms (OR_WQS = 1.56, 95% CI: 1.24, 1.96); Cd (61.8%), Cr (14.7%), and Cs (12.7%) contributed the greatest weight to the mixture effect.

CONCLUSION

Exposure to metals in the environment may be associated with anxiety symptoms during pregnancy. This is a public health concern, as anxiety disorders are highly prevalent and associated with significant co-morbidities, especially during pregnancy when both the mother and developing fetus are susceptible to adverse health outcomes.

Research into the Association of Cadmium and Manganese Excretion with Thyroid Function and Behavioral Areas in Adolescents with Autism Spectrum Disorders

Thyroid dysfunction and toxic metal exposure have been linked to the increased risk of autism spectrum disorders (ASD); however, the relationship between those factors remains unclear. We aimed to evaluate the relationship between the serum level of hormones, namely thyroid-stimulating hormone (TSH), free triiodothyronine (fT3), free thyroxine (fT4), and urinary cadmium (U-Cd) and urinary manganese (U-Mn), in patients with ASD. The study group consisted of 129 adolescents with ASD, and the control group consisted of 86 healthy persons. Ion chromatography with spectrophotometric detection (IC-UV/ViS) was used to quantitatively determine Cd and Mn in all 24-h urine samples. These results indicate that severity of certain symptoms in autism is associated with thyroid function. Correlation analysis between Childhood Autism Rating Scale (CARS) results and the content of both U-Mn and U-Cd as well as fT3, fT4 and TSH values in ASD patients showed significantly positive correlation of CARS7 (visual reaction) with fT3 and fT4 and a negative correlation with TSH for the whole study group. In the group of adolescents over 14 years of age, it was also observed that CARS10 (anxiety reaction) negatively correlates with serum TSH levels, and among younger individuals, CARS9 (near receptor responsiveness, taste, smell) positively correlates with TSH.

Early-life lead exposure induces long-term toxicity in the central nervous system: From zebrafish larvae to juveniles and adults

Lead induced neurotoxicity has been extensively investigated. However, the potential connections between early-life lead exposure and the frequently observed aberrant neurobehavior in juveniles and adults remain unclear. In this study, zebrafish model was used to explore the immediate and long-term effects of early-life exposure to environmental levels of lead on the central nervous system, and the cellular and molecular mechanisms underlying the consequent abnormal neurobehavior. Lead exposed zebrafish larvae exhibited neurologic damage and defective neurobehavior. Consistent with clinical studies, despite being raised in lead-free conditions, the juvenile and adult fish experienced lead exposure earlier, presented ADHD-like symptoms, and the adult fish exhibited remarkably affected vitality and shoaling behavior. Their anxiety levels were elevated, whereas their social interaction, as well as learning and memory were strongly depressed. The expression profiles of key genes involved in neurodevelopment and neurotransmitter systems were significantly modulated, in similar patterns as in the larval stage. Notably, the density of neurons was decreased and varicosities in neuronal axons were frequently observed in the lead-exposed groups. It's tempting to speculate that the disruption of early neurodevelopment as well as the prolonged modulation of neuromorphic and neurotransmitter systems contribute to the lead-induced neurobehavioral disorders observed in juveniles and adulthood.

Association of autism with toxic metals: A systematic review of case-control studies

Environmental factors have been associated with the etiology of autism spectrum disorder ASD in recent times. The involvement of toxic metals in the generation of reactive oxygen species and their epigenetics effects have been implicated in ASD. This systemic review examines the association of toxic metals with autism in children. A systematic literature search was performed in scientific databases such as PubMed, Google scholar, and Scopus. Case-control studies evaluating toxic metal levels in different tissues of ASD children and comparing them to healthy children (control group) were identified. The Newcastle-Ottawa Scale was used to evaluate the risk of bias of the included studies. Six case-control studies with 425 study subjects met our inclusion criteria. A total of four studies indicated higher levels of As, Pb, Hg, Cd, Al, Sn, Sb, Ba, TI, W, and Zr in whole blood, RBC, in whole blood, RBC, and hair samples of children with autism compared with control suggestive of a greater toxic metal exposure (immediate and long-term). Three studies identified significantly higher concentrations of Cd, Pb and Hg in urine and hair samples of autistic children compared to control suggesting decreased excretion and possible high body burden of these metals. The findings from this review demonstrate that high levels of toxic metals are associated with ASD, therefore, critical care is necessary to reduce body burden of these metals in children with ASD as a major therapeutic strategy.

Lead (Pb)-induced oxidative stress mediates sex-specific autistic-like behaviour in Drosophila melanogaster

Autism spectrum disorder (ASD) is a highly prevalent neurodevelopmental disorder characterised by three main behavioural symptoms: abnormal social interaction, verbal and non-verbal communication impairments, and repetitive and restricted activities or interests. Even though the exact aetiology of ASD remains unknown, studies have shown a link between genetics and environmental pollutants. Heavy metal lead (Pb), the environmental pollutant, is associated with ASD. Pb may also exhibit sex-specific ASD behaviour, as has been demonstrated in the global human populations. Drosophila melanogaster as a model has been used in the present study to understand the involvement of Pb-induced oxidative stress in developing ASD behaviour. The larval feeding technique has been employed to administer different Pb concentrations (0.2-0.8 mM) to Oregon-R (ORR), superoxide dismutase (Sod), or catalase (Cat) antioxidants overexpressed or knockdown flies. Adult Drosophila (5-day old) were used for Pb content, biochemical, and behavioural analysis.Pb accumulated in the Drosophila brain induces oxidative stress and exhibited a human autistic-like behaviour such as reduced climbing, increased grooming, increased social spacing, and decreased learning and memory in a sex-specific manner.Pb-induced autistic-like behaviour was intensified in Sod or Cat-knockdown flies, whereas Sod or Cat-overexpressed flies overcome that behavioural alterations. These results unequivocally proved that Pb-induced oxidative stress causes ASD behaviour of humans in Drosophila. Thus, Drosophila is used as a model organism to analyse ASD-like human behaviour and underlines the importance of using antioxidant therapy in alleviating ASD symptoms in children.

Developmental Exposure to Low Concentrations of Methylmercury Causes Increase in Anxiety-Related Behaviour and Locomotor Impairments in Zebrafish

Methylmercury (MeHg) is a ubiquitous pollutant shown to cause developmental neurotoxicity, even at low levels. However, there is still a large gap in our understanding of the mechanisms linking early-life exposure to life-long behavioural impairments. Our aim was to characterise the short- and long-term effects of developmental exposure to low doses of MeHg on anxiety-related behaviours in zebrafish, and to test the involvement of neurological pathways related to stress-response. Zebrafish embryos were exposed to sub-acute doses of MeHg (0, 5, 10, 15, 30 nM) throughout embryo-development, and tested for anxiety-related behaviours and locomotor activity at larval (light/dark locomotor activity) and adult (novel tank and tap assays) life-stages. Exposure to all doses of MeHg caused increased anxiety-related responses; heightened response to the transition from light to dark in larvae, and a stronger dive response in adults. In addition, impairment in locomotor activity was observed in the higher doses in both larvae and adults. Finally, the expressions of several neural stress-response genes from the HPI-axis and dopaminergic system were found to be disrupted in both life-stages. Our results provide important insights into dose-dependent differences in exposure outcomes, the development of delayed effects over the life-time of exposed individuals and the potential mechanisms underlying these effects.

Lead (Pb) induced Oxidative Stress as a Mechanism to Cause Neurotoxicity in Drosophila melanogaster

The widespread use of lead (Pb) has caused global contamination, inevitable human exposure, and public health problems. Pb neurotoxicity has been linked to various human diseases, but its associated mechanism causing neurotoxicity is unknown. Drosophila melanogaster as a model organism has been used to study the mechanism involved in Pb-caused neurotoxicity and the potential role of antioxidants in ameliorating its harmful effects. The larval feeding technique was adopted to administer different concentrations of Pb (0.2-0.8 mM) to Oregon-R (ORR), superoxide dismutase (Sod), or catalase (Cat) overexpressing, and Sod or Cat knockdown flies to analyse Pb load, oxidative stress components, DNA damage, apoptosis and vacuolation in the brain. The results revealed that Pb accumulation in the Drosophila brain induces oxidative stress by generating reactive oxygen species (ROS) and lipid peroxidation (LPO), depleting antioxidant enzymes. Molecular docking studies have evidenced it. Pb directly binds to antioxidants and major grooves of DNA, leading to DNA damage. Increased DNA damage, apoptosis, vacuolation in brains of Pb-treated ORR, Sod, or Cat knockdown flies; and on the contrary, reduced oxidative DNA damage, apoptosis, and vacuolation in brains of Pb treated Sod or Cat overexpressed flies put forward that oxidative stress is the mechanism in Pb caused neurotoxicity.

Correlation between concentrations of four heavy metals in cord blood and childhood blood of Jamaican children

This study investigated whether the concentrations of four metals [lead (Pb), mercury (Hg), manganese (Mn), and aluminum (Al)] are correlated in cord blood and childhood blood samples from Jamaican children. Cord blood samples were obtained from 21 pregnant women enrolled in the second Jamaican Birth Cohort Study from July 1, 2011 to September 30, 2011, and blood samples were drawn from their children who participated in a follow up study when the children were 4-8 years old. Correlations were assessed by the Pearson or the Spearman's rank correlation coefficient. The mean ages of children at the childhood visit and their mother at the child's birth were 5.5 years and 29.8 years, respectively. About 47.6% of children were male. Statistically significant correlations between cord blood and childhood blood concentrations of Pb (r_Spearman =0.45; P = 0.04) and Mn (r_Pearson=0.48; P = 0.03) were found, and these remained significant when adjusted for the child's sex, age, or both. For Al and Hg, r_Spearman=0.29 and 0.08, respectively, but the correlations were not statistically significant (both P ≥ 0.20). A significant correlation between cord blood and childhood blood Pb concentrations for children 4-8 years old has not been previously reported.

Gestational blood levels of toxic metal and essential element mixtures and associations with global DNA methylation in pregnant women and their infants

BACKGROUND

Pregnant women and their fetuses are exposed to multiple toxic metals that together with variations in essential element levels may alter epigenetic regulation, such as DNA methylation.

OBJECTIVES

The aim of the study was to investigate the associations between gestational levels of toxic metals and essential elements and mixtures thereof, with global DNA methylation levels in pregnant women and their newborn children.

METHODS

Using 631 mother-child pairs from a prospective birth cohort (The Norwegian Mother, Father and Child Cohort Study), we measured maternal blood concentration (gestation week ~18) of five toxic metals and seven essential elements. We investigated associations as individual exposures and two-way interactions, using elastic net regression, and total mixture, using quantile g-computation, with blood levels of 5-methylcytocine (5mC) and 5-hydroxymethylcytosine (5hmC) in mothers during pregnancy and their newborn children (cord blood). Multiple testing was adjusted for using the Benjamini and Hochberg false discovery rate (FDR) approach.

RESULTS

The most sensitive marker of DNA methylation appeared to be 5mC levels. In pregnant mothers, elastic net regression indicated associations between 5mC and selenium and lead (non-linear), while in newborns results indicated relationships between maternal selenium, cobalt (non-linear) and mercury and 5mC, as well as copper (non-linear) and 5hmC levels. Several possible two-way interactions were identified (e.g. arsenic and mercury, and selenium and maternal smoking in newborns). None of these findings met the FDR threshold for multiple testing. No net effect was observed in the joint (mixture) exposure-approach using quantile g-computation.

CONCLUSION

We identified few associations between gestational levels of several toxic metals and essential elements and global DNA methylation in pregnant mothers and their newborn children. As DNA methylation dysregulation might be a key mechanism in disease development and thus of high importance for public health, our results should be considered as important candidates to investigate in future studies.

Intrahippocampal Effects of Nickel Injection on the Affective and Cognitive Response in Wistar Rat: Potential Role of Oxidative Stress

The present study focused on affective and cognitive behaviors in male Wistar rats, following direct and unique exposure to nickel chloride (NiCl₂), as well as the possible involvement of oxidative stress. The rats were exposed to NiCl₂ (300 μM), by intracerebral administration of 2 μL of this metal at the right hippocampus, using the stereotaxic approach. Five days after the surgery, a battery of behavioral tests was performed, including the open-field test (OFT) and elevated plus maze test (EPM) to assess the state of anxiety-like behavior and forced swimming test (FST) for depressive-like behavior. Y-maze and Morris Water Maze (MWM) were used to evaluate working memory and spatial learning. Thereafter, oxidative stress markers of the hippocampus were evaluated. The results confirm that NiCl₂ exerts anxiogenic effects in both anxiety tests and depressogenic effects in the FST. In addition, MWM and Y-maze data show that NiCl₂ causes memory and spatial learning disorders. The biochemical assay results showed that intrahippocampal injection of NiCl₂ increased the levels of nitric oxide and lipid peroxidation (p < 0.001), while the activities of catalase and superoxide dismutase were significantly decreased in the hippocampus (p < 0.01). Overall, these results suggest that NiCl₂ causes affective and cognitive disorders and oxidative stress in rats.

Spectrum of neurological diseases across gangetic belt: a hospital based prospective observational study

OBJECTIVE

Neurological disorders are the most common cause of morbidity and mortality in riverside cities. Earlier studies reported the presence of heavy metals in the riverside of Gangetic belt. Our study objective was to determine the prevalence of neurological diseases in Ganga riverside and further divided into sections as just across riverside within 25 kms and non-riverside as 25 kms away from the Ganga river.

METHODS

This was a prospective observational study conducted in a tertiary care hospital of selected Gangetic belt.

RESULTS

A total of 2016 patients were recorded in this period. Mean age of the participants was 47.89 years, majority were males 59.2%. Most of the patients n = 1154 were from within 25 kms of Ganga riverside and n = 862 patients were from non-riverside (25 kms away from Ganga river). Common neurological diseases were ischemic stroke 22.7%, haemorrhagic stroke 20.7%, seizures 13.7%, septic encephalopathy 9.4%, neuropathy 8.9%, Parkinson's disease 4.3%, myopathy 4.1%, myelitis 2.8%, headache 2.4%, amyotrophic lateral sclerosis 1.9% and functional disorder 1.9%.

CONCLUSION

Present study showed that neurological diseases were more common in Ganga riverside and stroke including ischemic and hemorrhagic are most common neurological diseases noted in our study.

Toxic Mechanisms of Five Heavy Metals: Mercury, Lead, Chromium, Cadmium, and Arsenic

The industrial activities of the last century have caused massive increases in human exposure to heavy metals. Mercury, lead, chromium, cadmium, and arsenic have been the most common heavy metals that induced human poisonings. Here, we reviewed the mechanistic action of these heavy metals according to the available animal and human studies. Acute or chronic poisonings may occur following exposure through water, air, and food. Bioaccumulation of these heavy metals leads to a diversity of toxic effects on a variety of body tissues and organs. Heavy metals disrupt cellular events including growth, proliferation, differentiation, damage-repairing processes, and apoptosis. Comparison of the mechanisms of action reveals similar pathways for these metals to induce toxicity including ROS generation, weakening of the antioxidant defense, enzyme inactivation, and oxidative stress. On the other hand, some of them have selective binding to specific macromolecules. The interaction of lead with aminolevulinic acid dehydratase and ferrochelatase is within this context. Reactions of other heavy metals with certain proteins were discussed as well. Some toxic metals including chromium, cadmium, and arsenic cause genomic instability. Defects in DNA repair following the induction of oxidative stress and DNA damage by the three metals have been considered as the cause of their carcinogenicity. Even with the current knowledge of hazards of heavy metals, the incidence of poisoning remains considerable and requires preventive and effective treatment. The application of chelation therapy for the management of metal poisoning could be another aspect of heavy metals to be reviewed in the future.

Detection, Distribution and Health Risk Assessment of Toxic Heavy Metals/Metalloids, Arsenic, Cadmium, and Lead in Goat Carcasses Processed for Human Consumption in South-Eastern Nigeria

Notwithstanding the increased toxic heavy metals/metalloids (THMs) accumulation in (edible) organs owed to goat′s feeding habit and anthropogenic activities, the chevon remains increasingly relished as a special delicacy in Nigeria. Specific to the South-Eastern region, however, there is paucity of relevant data regarding the prevalence of THMs in goat carcasses processed for human consumption. This work was, therefore, aimed to investigate the detection, distribution and health risk assessment of THMs in goat carcass processed for human consumption in South-Eastern Nigeria. To achieve this, a total of 450 meat samples (kidney, liver and muscle) were evaluated from 150 randomly selected goat carcasses processed in two major slaughterhouses in Enugu State. The detection, distribution, as well as health risk assessment parameters followed standard procedures. Results revealed that at least one THM was detected in 56% of the carcasses. Mean concentrations of arsenic (As) were 0.53 ± 0.10 mg/kg, 0.57 ± 0.09 mg/kg and 0.45 ± 0.08 mg/kg, lead (Pb) were 0.48 ± 0.38 mg/kg, 0.45 ± 0.24 mg/kg and 0.82 ± 0.39 mg/kg, cadmium (Cd) was 0.06 ± 0.32 mg/kg, 0.02 ± 0.00 mg/kg, and 0.02 ± 0.00 mg/kg for kidney, liver and muscle tissues, respectively. The estimated daily intakes (EDI) for all THMs were above the recommended safe limits. The target hazard quotient (THQ) and hazard index (HI) computed for all As, Cd and Pb fell below unity in all the studied organs, which indicated no non-carcinogenic risks. Curtailing the anthropogenic activities that aid the THM-contamination in goat production/processing lines is recommended. Screening for THM-contamination in Nigerian slaughterhouses is imperative, so as to ascertain the toxicological safety of meats intended for human consumption.

Air pollution and neurological development in children

Pregnancy and early childhood are periods with high plasticity in neurological development. Environmental perturbations during these sensitive windows can have lifelong developmental consequences. This review summarizes key findings relevant to the effects of air pollution on neurological development. Mounting evidence suggests that exposure to air pollution, both during pregnancy and childhood, is associated with childhood developmental outcomes ranging from changes in brain structures to subclinical deficits in developmental test scores, and, ultimately, developmental disorders such as attention-deficit/hyperactivity disorders or autism spectrum disorders. Although the biological mechanisms of effects remain to be elucidated, multiple pathways are probably involved and include oxidative stress, inflammation, and/or endocrine disruption. Given the alarming global increase in developmental disorders in recent years, and increased human exposures to pollution, it is critical to reduce personal and community-level exposures through tight collaboration of interdisciplinary and multi-level bodies including community partners, physicians, industry partners, policy makers, public health practitioners, and researchers. WHAT THIS PAPER ADDS: Exposure to air pollution is associated with a range of childhood developmental complications. Biological mechanisms may include oxidative stress, inflammation, and endocrine disruption.

Neural stem cell-based in vitro bioassay for the assessment of neurotoxic potential of water samples

Intensive agriculture activities, industrialization and growing numbers of wastewater treatment plants along river banks collectively contribute to the elevated levels of neurotoxic pollutants in natural water reservoirs across Europe. We established an in vitro bioassay based upon neural stem cells isolated from the subventricular zone of the postnatal mouse to evaluate the neurotoxic potential of raw wastewater, treated sewage effluent, groundwater and drinking water. The toxic potential of water samples was evaluated employing viability, proliferation, differentiation and migration assays. We found that raw wastewater could reduce the viability and proliferation of neural stem cells, and decreased the neuronal and astrocyte differentiation, neuronal neurite growth, astrocyte growth and cell migration. Treated sewage water also showed inhibitory effects on cell proliferation and migration. Our results indicated that relatively high concentrations of nitrogenous substances, pesticides, mercuric compounds, bisphenol-A, and phthalates, along with some other pollutants in raw wastewater and treated sewage water, might be the reason for the neuroinhibitory effects of these water samples. Our model successfully predicted the neurotoxicity of water samples collected from different sources and also revealed that the incomplete removal of contaminants from wastewater can be problematic for the developing nervous system. The presented data also provides strong evidence that more effective treatments should be used to minimize the contamination of water before release into major water bodies which may be considered as water reservoirs for human usage in the future.

Vascular Dysfunction in the Brain; Implications for Heavy Metal Exposures

Normal or diseased conditions that alter the brain's requirement for oxygen and nutrients via alterations to neurovascular coupling have an impact on the level of the neurovascular unit; comprising neuronal, glial and vascular components. The communications between the components of the neurovascular unit are precise and accurate for its functions; hence a minute disturbance can result in neurovascular dysfunction. Heavy metals such as cadmium, mercury, and lead have been identified to increase the vulnerability of the neurovascular unit to damage. This review examines the role of heavy metals in neurovascular dysfunctions and the possible mechanisms by which these metals act. Risk factors ranging from lifestyle, environment, genetics, infections, and physiologic ageing involved in neurological dysfunctions were highlighted, while stroke was discussed as the prevalent consequence of neurovascular dysfunctions. Furthermore, the role of these heavy metals in the pathogenesis of stroke consequently pinpoints the importance of understanding the mechanisms of neurovascular damage in a bid to curb the occurrence of neurovascular dysfunctions.

Neuroprotective Effect of α-Mangostin in the Ameliorating Propionic Acid-Induced Experimental Model of Autism in Wistar Rats

Several studies have documented the role of hyper-activation of extracellular signal-regulated kinases (ERK) in Autism pathogenesis. Alpha-mangostin (AMG) is a phytoconstituents with anti-oxidants, anti-inflammatory, and ERK inhibition properties in many diseases. Our research aims to investigate the neuroprotective effect of AMG in the rat model of intracerebroventricular-propionic acid (ICV-PPA) induced autism with a confirmation of its effect on the ERK signaling. Autism was induced in Wistar rats (total 36 rats; 18 male/18 female) by multiple doses of PPA through ICV injection for 11 days. Actophotometer and beam walking tasks were used to evaluate animals’ motor abilities, and the Morris water maze task was utilized to confirm the cognition and memory in animals. Long term administration of AMG100 mg/kg and AMG200 mg/kg continued from day 12 to day 44 of the experiment. Before that, animals were sacrificed, brains isolated, morphological, gross pathological studies were performed, and neurochemical analysis was performed in the brain homogenates. Cellular and molecular markers, including ERK, myelin basic protein, apoptotic markers including caspase-3, Bax, Bcl-2, neuroinflammatory markers, neurotransmitters, and oxidative stress markers, have been tested throughout the brain. Thus, AMG reduces the overactivation of the ERK signaling and also restored autism-like behavioral and neurochemical alterations.

Environment permissible concentrations of glyphosate in drinking water can influence the fate of neural stem cells from the subventricular zone of the postnatal mouse

The developing nervous system is highly vulnerable to environmental toxicants especially pesticides. Glyphosate pesticide induces neurotoxicity both in humans and rodents, but so far only when exposed to higher concentrations. A few studies, however, have also reported the risk of general toxicity of glyphosate at concentrations comparable to allowable limits set up by environmental protection authorities. In vitro data regarding glyphosate neurotoxicity at concentrations comparable to maximum permissible concentrations in drinking water is lacking. In the present study, we established an in vitro assay based upon neural stem cells (NSCs) from the subventricular zone of the postnatal mouse to decipher the effects of two maximum permissible concentrations of glyphosate in drinking water on the basic neurogenesis processes. Our results demonstrated that maximum permissible concentrations of glyphosate recognized by environmental protection authorities significantly reduced the cell migration and differentiation of NSCs as demonstrated by the downregulation of the expression levels of the neuronal ß-tubulin III and the astrocytic S100B genes. The expression of the cytoprotective gene CYP1A1 was downregulated whilst the expression of oxidative stresses indicator gene SOD1 was upregulated. The concentration comparable to non-toxic human plasma concentration significantly induced cytotoxicity and activated Ca2+ signalling in the differentiated culture. Our findings demonstrated that the permissible concentrations of glyphosate in drinking water recognized by environmental protection authorities are capable of inducing neurotoxicity in the developing nervous system.

Autism Spectrum and Other Neurodevelopmental Disorders in Children of Immigrants: A Brief Review of Current Evidence and Implications for Clinical Practice

Children of immigrants may have higher neurodevelopmental risks than those of non-immigrant populations. Yet, some evidence suggests that this group may receive late diagnosis, and therefore miss beneficial early interventions. Clinicians may misattribute symptoms of disorders to other social, behavioral or language problems. Likewise, there might be cultural differences in parents' likelihood of perceiving or reporting first developmental concerns to clinicians. Population-based standardized screening may play an important role in addressing ethnic inequalities in the age at diagnosis, although further research focusing on cross-cultural use is necessary. Once children are diagnosed, clinicians may rely on culturally sensitive procedures (translation services, cultural mediators) to increase the accessibility of interventions and improve adherence among immigrant families. In this brief review, we provide an overview about what is currently known about the epidemiology and risk factors of neurodevelopmental disorders, paying special attention to autism spectrum disorder (ASD), in children of immigrants and suggest the necessity of population-based screening and culturally sensitive care.

Environmental influence on neurodevelopmental disorders: Potential association of heavy metal exposure and autism

Environmental factors have been severally established to play major roles in the pathogenesis of neurodevelopmental disorders including autism spectrum disorder (ASD). ASD is a neurodevelopmental disorder that is associated with symptoms that reduce the quality of life of affected individuals such as social interaction deficit, cognitive impairment, intellectual disabilities, restricted and repetitive behavioural patterns. ASD pathogenesis has been associated with environmental and genetic factors that alter physiologic processes during development. Here, we review literatures highlighting the environmental impact on neurodevelopmental disorders, and mechanisms by which environmental toxins may influence neurodevelopment. Furthermore, this review discusses reports highlighting neurotoxic metals (specifically, lead, mercury, cadmium, nickel and manganese) as environmental risk factors in the aetiology of ASD. This work, thus suggests that improving the environment could be vital in the management of ASD.

Autism spectrum disorder in the United Arab Emirates: potential environmental links

Autism spectrum disorder (ASD) has been experiencing an increase in global prevalence in recent decades. While many factors could account for this reality, certain environmental links have been shown to contribute to ASD development and etiology. The Middle East has had relatively little published research on ASD etiology although statistics indicate that ASD affects 1 in 146 births in the United Arab Emirates (UAE). This review therefore aims to examine potential causes of ASD within the UAE specifically, focusing on environmental links that may contribute to the rise in ASD cases in this population. Significantly, suboptimal breastfeeding practices, high levels of vitamin D deficiency, increased exposure to pollution, pesticides and heavy metals within the UAE may all be potentially important contributing factors to ASD in this population. Our findings support the notion that there are key links between various environmental factors and ASD prevalence in the UAE. The lack of knowledge and much research on ASD within the UAE deeply necessitates further studies on its etiology as it poses a serious public health challenge in the region and globally.

The status of chemical elements in the blood plasma of children with autism spectrum disorder in Tunisia: a case-control study

Autism spectrum disorders (ASDs) are a group of neurodevelopmental disorders defined by a deficit in social interactions and the presence of restricted and stereotypical behaviors or interests. The etiologies of autism remain mostly unknown. Many genetic and environmental factors have been suspected. Among these environmental factors, exposure to several chemical elements has been previously studied. The purpose of this study was to compare the levels of trace elements in the blood plasma of children with ASD with typically developed children (TDC). The participants in this study consisted of 89 children with ASD (14 girls and 74 boys) and 70 TD children (29 girls and 41 boys). The levels of 33 chemical elements have been analyzed by inductively coupled plasma spectrometry (ICP-MS). We detected significant differences in the levels of eight elements between the two groups, among which there were three rare earth elements (REEs): Eu, Pr, and Sc (p = 0.000, p = 0.023, and p < 0.001 respectively); four heavy metals: Bi, Tl, Ti, and V (p = 0.004, p < 0.001, p = 0.001, and p = 0.001 respectively); and one essential element: Cu (p = 0.043). Children with ASD had higher levels of Er, Pr, Sc, Bi, Tl, Ti, and V, and lower levels of Cu in comparison with the TD group. The children exposed to passive smoking had lower levels of lead (Pb) compared with children without exposure (p = 0.018). Four elements (Cr, Er, Dy, and Pr) were negatively correlated to the severity of ASD. The level of Cu was significantly associated with autistic children's behavior (p = 0.014). These results suggest that children with ASD might have abnormal plasma levels of certain chemical elements (including Er, Pr, Sc, Bi, Tl, Ti, and V, and Cu), and some of these elements might be associated with certain clinical features.

Manganese-induced Mitochondrial Dysfunction Is Not Detectable at Exposures Below the Acute Cytotoxic Threshold in Neuronal Cell Types

Manganese (Mn) is an essential metal, but excessive exposures have been well-documented to culminate in neurotoxicity. Curiously, the precise mechanisms of Mn neurotoxicity are still unknown. One hypothesis suggests that Mn exerts its toxicity by inhibiting mitochondrial function, which then (if exposure levels are high and long enough) leads to cell death. Here, we used a Huntington's disease cell model with known differential sensitivities to manganese-STHdhQ7/Q7 and STHdhQ111/Q111 cells-to examine the effects of acute Mn exposure on mitochondrial function. We determined toxicity thresholds for each cell line using both changes in cell number and caspase-3/7 activation. We used a range of acute Mn exposures (0-300 µM), both above and below the cytotoxic threshold, to evaluate mitochondria-associated metabolic balance, mitochondrial respiration, and substrate dependence. In both cell lines, we observed no effect on markers of mitochondrial function at subtoxic Mn exposures (below detectable levels of cell death), yet at supratoxic exposures (above detectable levels of cell death) mitochondrial function significantly declined. We validated these findings in primary striatal neurons. In cell lines, we further observed that subtoxic Mn concentrations do not affect glycolytic function or major intracellular metabolite quantities. These data suggest that in this system, Mn exposure impairs mitochondrial function only at concentrations coincident with or above the initiation of cell death and is not consistent with the hypothesis that mitochondrial dysfunction precedes or induces Mn cytotoxicity.

Oxidative Stress in Autism Spectrum Disorder

According to the United States Centers for Disease Control and Prevention (CDC), as of July 11, 2016, the reported average incidence of children diagnosed with an autism spectrum disorder (ASD) was 1 in 68 (1.46%) among 8-year-old children born in 2004 and living within the 11 monitoring sites' surveillance areas in the United States of America (USA) in 2012. ASD is a multifaceted neurodevelopmental disorder that is also considered a hidden disability, as, for the most part; there are no apparent morphological differences between children with ASD and typically developing children. ASD is diagnosed based upon a triad of features including impairment in socialization, impairment in language, and repetitive and stereotypic behaviors. The increasing incidence of ASD in the pediatric population and the lack of successful curative therapies make ASD one of the most challenging disorders for medicine. ASD neurobiology is thought to be associated with oxidative stress, as shown by increased levels of reactive oxygen species and increased lipid peroxidation, as well as an increase in other indicators of oxidative stress. Children with ASD diagnosis are considered more vulnerable to oxidative stress because of their imbalance in intracellular and extracellular glutathione levels and decreased glutathione reserve capacity. Several studies have suggested that the redox imbalance and oxidative stress are integral parts of ASD pathophysiology. As such, early assessment and treatment of antioxidant status may result in a better prognosis as it could decrease the oxidative stress in the brain before it can induce more irreversible brain damage. In this review, many aspects of the role of oxidative stress in ASD are discussed, taking into account that the process of oxidative stress may be a target for therapeutic interventions.

Exposure to Inorganic Arsenic and Lead and Autism Spectrum Disorder in Children: A Systematic Review and Meta-Analysis

Inorganic arsenic (iAs) and lead (Pb) rank first and second on the U.S. Environmental Protection Agency's priority list of hazardous substances. Both are known neurotoxic metals that cause detrimental effects on brain development and lead to deficits in cognitive function and behavioral performance in children. Studies have indicated a potential link between iAs and Pb exposure and a higher risk for autism spectrum disorder (ASD). To provide further insight into whether developmental exposure to iAs or Pb is associated with ASD, we conducted a systematic review and combined data into a meta-analysis to evaluate the available human evidence on the relationships. We systematically reviewed relevant studies published through December 30, 2018 and identified 14 studies on iAs and 37 studies on Pb exposure and their respective associations with ASD. Among them, 8 (53.3%) and 19 (51.3%) studies reported a positive association for iAs and Pb, respectively, and none reported a sole inverse association. In the following meta-analysis, we found statistically significant higher iAs concentrations, in hair and in blood, for children diagnosed with ASD compared with controls across studies. However, the findings on Pb exposure were inconsistent, with a significant association for hair Pb, no association for urinary Pb, and an inverse association for blood Pb. After considering strengths and limitations of the body of research, we concluded that there is consistent evidence supporting a positive association between early life iAs exposure and diagnosis of ASD and inconsistent evidence for Pb exposure and ASD risk. We believe it is in the best interest of policy makers and the public to reduce exposures to iAs and Pb among pregnant women and children. Further, our research supports the need for large perspective human studies with accurate measurement and determination of the long-term body burden of iAs and Pb exposures to assess the impact of iAs and Pb exposures on ASD risk.

Understanding intellectual disability and autism spectrum disorders from common mouse models: synapses to behaviour

Normal brain development is highly dependent on the timely coordinated actions of genetic and environmental processes, and an aberration can lead to neurodevelopmental disorders (NDDs). Intellectual disability (ID) and autism spectrum disorders (ASDs) are a group of co-occurring NDDs that affect between 3% and 5% of the world population, thus presenting a great challenge to society. This problem calls for the need to understand the pathobiology of these disorders and to design new therapeutic strategies. One approach towards this has been the development of multiple analogous mouse models. This review discusses studies conducted in the mouse models of five major monogenic causes of ID and ASDs: Fmr1, Syngap1, Mecp2, Shank2/3 and Neuroligins/Neurnexins. These studies reveal that, despite having a diverse molecular origin, the effects of these mutations converge onto similar or related aetiological pathways, consequently giving rise to the typical phenotype of cognitive, social and emotional deficits that are characteristic of ID and ASDs. This convergence, therefore, highlights common pathological nodes that can be targeted for therapy. Other than conventional therapeutic strategies such as non-pharmacological corrective methods and symptomatic alleviation, multiple studies in mouse models have successfully proved the possibility of pharmacological and genetic therapy enabling functional recovery.

Association between hair lead levels and autism spectrum disorder in children: A systematic review and meta-analysis

A number of studies measured lead levels in hair from children with autism spectrum disorder (ASD) to detect the relationship between cumulated lead exposure and the development of ASD, but results are inconsistent. We aimed to conduct a systematic review and meta-analysis using the published studies to explore the actual association of hair lead levels with ASD in children. We searched PubMed, Embase, PsycINFO, and Cochrane Library databases (up to December 11, 2018). The random-effects model was applied to summarize effect sizes. Subgroup and meta-regression analyses were performed simultaneously. Twenty eligible studies involving 1787 participants (941 autistic children and 846 healthy subjects) were included. Our results of primary analysis showed that there were no statistically significant differences in the levels of hair lead between children with ASD and healthy individuals (Hedges's g = 0.251; 95% confidence interval: -0.121, 0.623; P = 0.187). We identified 2 sources of between-study heterogeneity: analytical technology and the sample size of patients. Additionally, no publication bias was observed in this meta-analysis. In conclusion, this study does not support the association of hair lead levels with ASD in children, and the involvement of cumulated lead exposure in the occurrence of ASD.

Disturbance of trace element and gut microbiota profiles as indicators of autism spectrum disorder: A pilot study of Chinese children

Autism spectrum disorder (ASD) is a neuro-developmental disorder that is characterized by impairments of reciprocal social interaction and restricted stereotyped repetitive behavior. The goal of the present study was to investigate the trace element and gut microbiota profiles of Chinese autistic children and screen out potential metallic or microbial indicators of the disease. One hundred and thirty-six children (78 with ASD and 58 healthy controls) aged from 3 to 7 years were enrolled. The levels of lead, cadmium, arsenic, copper, zinc, iron, mercury, calcium and magnesium in hair samples from the children were analyzed. Fecal samples were also collected and the children's gut microbiota profiles were characterized by 16s rRNA sequencing. Concentrations of lead, arsenic, copper, zinc, mercury, calcium and magnesium were significantly higher in the ASD group than in the control group. Linear discriminant analysis effect size analysis indicated that the relative abundance of nine genera was increased in the autistic children. Redundancy analysis showed that arsenic and mercury were significantly associated with Parabacteroides and Oscillospira in the gut. A random forest model was trained with high accuracy (84.00%) and the metallic and microbial biomarkers of ASD were established. Our results indicate significant alterations in the trace element and gut microbiota profiles of Chinese children with ASD and reveal the potential pathogenesis of this disease in terms of metal metabolism and gut microecology.

MicroRNA Cross-Involvement in Autism Spectrum Disorders and Atopic Dermatitis: A Literature Review

Autism Spectrum Disorder (ASD) is a category of neurodevelopmental disturbances seriously affecting social skills, to which the scientific community has paid great attention in last decades. To date, their pathogenesis is still unknown, but several studies highlighted the relevance of gene-environment interactions in the onset of ASD. In addition, an immune involvement was seen in a wide number of ASD subjects, leading several researchers to hypothesize a possible common pathogenesis between ASD and immune disturbances, including Atopic Dermatitis (AD). In general, among potential contributing factors, microRNAs (miRNAs), small molecules capable of controlling gene expression and targeting mRNA transcripts, might represent one of the major circulating link, possibly unraveling the connections between neurodevelopmental and immune conditions. Under such premises, we conducted a systematic literature review, under the PRISMA guidelines, trying to define the panel of common miRNAs involved in both ASD and AD. The review retrieved articles published between January 1, 2005, and December 13, 2018, in PubMed, ScienceDirect, PsycARTICLES, and Google Scholar. We found a handful of works dealing with miRNAs in ASD and AD, with the most overlapping dysregulated miRNAs being miR-146 and miR-155. Two possible compounds are abnormally regulated in both ASD and AD subjects, possibly cross-contributing to the interactions between the two disorders, setting the basis to investigate more precisely the possible link between ASD and AD from another, not just clinical, perspective.

Possible Metabolic Alterations among Autistic Male Children: Clinical and Biochemical Approaches

The present cross-sectional, hospital-based study was carried out on 146 Egyptian male children, 73 males with autism who were comparable with another 73 healthy age- and sex-matched children, recruited from the outpatients' psychiatric clinics of the Neuropsychiatric and Pediatric Departments of South Valley and Assiut University Hospitals, Egypt. Neuropsychological assessments of autistic males were done using CARS, short sensory profile and intelligent quotients. Serum markers of mitochondrial dysfunction (lactate, pyruvate, and lactate to pyruvate ratio, creatine kinase (CK), L-carnitine, ammonia, lactate dehydrogenase, pyruvate kinase, alanine transaminase and aspartate transaminase), oxidative stress and blood levels of heavy metals (mercury, lead and aluminium) were measured. Serum cholesterol, cortisol, free testosterone, estradiol, dehydroepiandrostenedione, adenosine deaminase and Helicobacter pylori antigen in stool were also performed. There was evidence of mitochondrial dysfunction among autistic children. Additionally, there were significantly lower serum total cholesterol, cortisol and estradiol as well as significantly higher dehydroepiandrostenedione (DHEA) and free testosterone (p < 0.05 for all markers). Twenty-eight (38%) cases were positive for H. pylori antigen in their stool with significant higher serum ammonia and lower adenosine deaminase than in H. pylori-negative autistic children. Mitochondrial dysfunction, H. pylori infection and low cholesterol were prevalent among autistic male children, which should be targeted during autism management.