Single-cell investigation of lead toxicity from neurodevelopment to neurodegeneration: Current review and future opportunities.

Human exposure to the metal lead (Pb) is prevalent and associated with adverse neurodevelopmental and neurodegenerative outcomes. Pb disrupts normal brain function by inducing oxidative stress and neuroinflammation, altering cellular metabolism, and displacing essential metals. Prior studies on the molecular impacts of Pb have examined bulk tissues, which collapse information across all cell types, or in targeted cells, which are limited to cell autonomous effects. These approaches are unable to represent the complete biological implications of Pb exposure because the brain is a cooperative network of highly heterogeneous cells, with cellular diversity and proportions shifting throughout development, by brain region, and with disease. New technologies are necessary to investigate whether Pb and other environmental exposures alter cell composition in the brain and whether they cause molecular changes in a cell-type-specific manner. Cutting-edge, single-cell approaches now enable research resolving cell-type-specific effects from bulk tissues. This article reviews existing Pb neurotoxicology studies with genome-wide molecular signatures and provides a path forward for the field to implement single-cell approaches with practical recommendations.

Enviromental endocrine disruptor risks in the central nervous system: Neurotoxic effects of PFOS and glyphosate.

Endocrine disruptors (EDs) pose significant risks to human and environmental health, with potential implications for neurotoxicity. This study investigates the synergistic neurotoxic effects of perfluorooctane sulfonate (PFOS) and glyphosate (GLY), two ubiquitous EDs, using SHSY5Y neuronal and C6 astrocytic cell lines. While individual exposures to PFOS and glyphosate at non-toxic concentrations did not induce significant changes, their combination resulted in a marked increase in oxidative stress and neuroinflammatory responses. Specifically, the co-exposure led to elevated levels of interleukin-6, tumor necrosis factor alpha, and interferon gamma, along with reduced interleukin-10 expression, indicative of heightened neuroinflammatory processes. These findings underscore the importance of considering the synergistic interactions of EDs in assessing neurotoxic risks and highlight the urgent need for further research to mitigate the adverse effects of these compounds on neurological health.

Neurotoxicity assessment of the herbicide pethoxamid in zebrafish (Danio rerio) embryos/larvae.

Pethoxamid, a member of the chloroacetamide herbicide family, is a recently approved chemical for pre- or post-emergence weed control; however, toxicity data for sublethal effects in aquatic organisms exposed to pethoxamid are non-existent in literature. To address this, we treated zebrafish embryos/larvae to pethoxamid over a 7-day period post-fertilization and evaluated several toxicological endpoints associated with oxidative stress and neurotoxicity. Continuous pethoxamid exposure did not affect survival nor hatch success in embryos/larvae for 7 days up to 1000 µg L-1. Exposure to pethoxamid did not affect embryonic ATP-linked respiration, but it did reduce non-mitochondrial respiration at the highest concentration tested. We also noted a significant increase in both apoptosis and levels of reactive oxygen species (ROS) in larvae zebrafish following exposure to pethoxamid. Increases in apoptosis and ROS, however, were not correlated with any altered gene expression pattern for apoptotic and oxidative damage response transcripts. To assess neurotoxicity potential, we measured behavior and several transcripts implicated in neural processes in the central nervous system. While locomotor activity of larval zebrafish was affected by pethoxamid exposure (hyperactivity was observed at concentrations below 1 µg L-1, and hypoactivity was noted at higher exposures to 10 and 100 µg L-1 pethoxamid), there were no effects on steady state mRNA abundance for neurotoxicity-related transcripts tested. This data contributes to knowledge regarding exposure risks for chloroacetamide-based herbicides and is the first study investigating sublethal toxicity for this newly registered herbicide.

Neurotoxicology: a clinical systems-based review.

Neurological disease caused by toxins is widespread but under-recognised. Despite increasing public interest and a growing number of novel potential neurotoxins, diagnosis of neurotoxic disease is often delayed or missed, resulting in poorer patient outcomes. This article discusses neurotoxic syndromes using a systems-based approach, focusing on environmental and occupational agents. We do not discuss recreational drugs, pharmaceutical agents or developmental neurotoxins in detail. We aim to provide neurologists with a working understanding of the scenarios in which a clinical presentation may be due to a neurotoxin and how to approach confirmation of the diagnosis.

Lambda-Cyhalothrin induced behavioural, neurotoxic and oxidative stress on vertebrate model Danio rerio (Hamilton-Buchanan 1822).

λ-cyhalothrin, a synthetic type II pyrethroid, has become increasingly popular for control of aphids, butterfly larvae, and beetles, replacing other agricultural chemicals. As a result of which, residues of this synthetic pesticide are being reported across the globe in natural water, which poses a serious threat to aquatic life. Therefore, the present study was designed to understand the toxicity effects of λ-cyhalothrin on behaviour, oxidative stress and neurotoxicity in a vertebrate aquatic model, zebrafish (Danio rerio). The fish were exposed to 0.129, 0.194 and 0.388 µg/L corresponding to 5%, 10% and 20% of 96hLC50 (1.94 µg/L) for 28 days. Upon exposure to the highest concentration (0.388 µg/L), the test animal exhibited significant alterations in behavioural patterns like number of entries to the top zone (n), decrease in average speed (m/s) and decrease in time spent in top zone (s). Moreover, the shoaling test demonstrated a significant decrease (p < 0.05) in the relative time spent by the tested fish (%) near the stimulus fish. The change in behavioural alterations might be linked to a significant decrease (p < 0.05) in the brain acetylcholine esterase activity. Furthermore, the present study also illustrates oxidative stress exerted by λ-cyhalothrin through an increase in the production of reactive oxygen species, which is again clearly depicted by a significant increase (p < 0.05) in Superoxide dismutase, Catalase and Glutathione peroxidase activities. Overall, the present study systematically demonstrates the chronic effects of λ-cyhalothrin on adult fish behaviour and physiology, which will contribute to assessing the risks of λ-cyhalothrin to organismal health.

A novel class of insecticidal alkylsulfones are potent inhibitors of vesicular acetylcholine transport.

Pyridine alkylsulfone derivatives typified by oxazosulfyl (Sumitomo Chemical Company Ltd.) and compound A2 (Syngenta) represent a new class of insecticides, with potent activity against several insect orders. Whilst the MOA of this class has been attributed to interaction with the voltage-gated sodium channel (VGSC), here we present strong evidence that their toxicity to insects is mediated primarily through inhibition of the vesicular acetylcholine transporter (VAChT). Alkylsulfone intoxication in insects is characterised by (i) a reduction in cholinergic synaptic transmission efficiency demonstrated by a depression of cercal afferent activity in giant-interneurone preparations of American cockroach (Periplaneta americana), (ii) selective block of cholinergic-transmission dependent post-synaptic potentials in the Drosophila giant-fibre pathway and (iii) abolition of miniature excitatory post-synaptic currents (mEPSCs) in an identified synapse in Drosophila larvae. Ligand-binding studies using a tritiated example compound ([3H]-A1) revealed a single saturable binding-site, with low nanomolar Kd value, in membrane fractions of green bottle fly (Lucilia sericata). Binding is inhibited by vesamicol and by several examples of a previously identified class of insecticidal compounds known to target VAChT, the spiroindolines. Displacement of this binding by analogues of the radioligand reveals a strong correlation with insecticidal potency. No specific binding was detected in untransformed PC12 cells but a PC12 line stably expressing Drosophila VAChT showed similar affinity for [3H]-A1 as that seen in fly head membrane preparations. Previously identified VAChT point mutations confer resistance to the spiroindoline class of insecticides in Drosophila by Gal-4/UAS directed expression in cholinergic neurones and by CRISPR gene-editing of VAChT, but none of these flies show detectable cross-resistance to this new chemical class. Oxazosulfyl was previously shown to stabilise voltage-gated sodium channels in their slow-inactivated conformation with an IC50 value of 12.3µM but inhibits binding of [3H]-A1 with approximately 5000 times greater potency. We believe this chemistry class represents a novel mode-of-action with high potential for invertebrate selectivity.

Prenatal exposure to pyrethroids and chlorpyrifos and IQ in 7-year-old children from the Odense Child Cohort.

BACKGROUND: Organophosphates and pyrethroids are two major groups of insecticides used for crop protection worldwide. They are neurotoxicants and exposure during vulnerable windows of brain development may have long-term impact on human neurodevelopment. Only few longitudinal studies have investigated associations between prenatal exposure to these substances and intelligence quotient (IQ) at school age in populations with low, mainly dietary, exposure. OBJECTIVE: To investigate associations between maternal urinary concentrations of insecticide metabolites at gestational week 28 and IQ in offspring at 7-years of age. MATERIALS AND METHODS: Data was derived from the Odense Child Cohort (OCC). Metabolites of chlorpyrifos (TCPy) and pyrethroids (3-PBA, cis- and trans-DCCA, 4-F-3PBA, cis-DBCA) were measured in maternal urine collected at gestational week (GW) 28. An abbreviated version of the Danish Wechsler Intelligence Scale for Children fifth edition (WISC-V) consisting of four subtests to estimate full scale IQ (FSIQ) was administered by trained psychologists. Data were analyzed by use of multiple linear regression and adjusted for confounders. RESULTS: 812 mother/child-pairs were included. Median concentrations were 0.21 µg/L for 3-PBA, 1.67 µg/L for TCPy and the mean IQ for children were 99.4. Null association between maternal 3-PBA and child IQ at 7 years was seen, but with trends suggesting an inverse association. There was a significant association for maternal TCPy and child IQ at mid-level exposure. Trans-DCCA above the level of detection (LOD) was also associated with slightly lower child IQ, but the association was also not statistically significant. CONCLUSIONS: We found no significant associations between maternal 3-PBA metabolites and child IQ at 7 years, but with trends suggesting an inverse association. A non-significant trend between maternal TCPy exposure and child IQ in 7-year-children was seen even in this low exposed population. Given the widespread exposure and increasing use of insecticides, this should be elaborated in future studies.

Application of Single Cell Gene Expression Technologies to Neurotoxicology.

Neurotoxicological research faces the challenge of linking biological changes resulting from exposures to neuronal function. An additional challenge is understanding cell-type specific differences and selective vulnerabilities of distinct neuronal populations to toxic insults. Single cell RNA-sequencing (scRNA-seq) allows for measurement of the transcriptome of individual cells. This makes it a valuable tool for validating and characterizing cell types present in multicell type samples in complex tissue or cell culture models, but also for understanding how different cell types respond to toxic insults. Pathway analysis of differentially expressed genes can provide in depth insights into underlying cell type-specific mechanisms of neurotoxicity. Toxicological data often has to be translated to outcomes for human health which requires an understanding of inter-species differences. Transcriptomic data aids in understanding these differences, including understanding developmental timelines of different species. We believe that scRNA-seq holds exciting promises for future neurotoxicological research.

What does scientometry tell us about mercury toxicology and its biological impairments?

Mercury is a toxic pollutant that poses risks to both human and environmental health, making it a pressing public health concern. This study aimed to summarize the knowledge on mercury toxicology and the biological impairments caused by exposure to mercury in experimental studies and/or diagnosis in humans. The research was conducted on the main collection of Web of Science, employing as a methodological tool a bibliometric analysis. The selected articles were analyzed, and extracted data such as publication year, journal, author, title, number of citations, corresponding author's country, keywords, and the knowledge mapping was performed about the type of study, chemical form of mercury, exposure period, origin of exposure, tissue/fluid of exposure measurement, mercury concentration, evaluation period (age), mercury effect, model experiments, dose, exposure pathway, and time of exposure. The selected articles were published between 1965 and 2021, with Clarkson TW being the most cited author who has also published the most articles. A total of 38% of the publications were from the USA. These studies assessed the prenatal and postnatal effects of mercury, emphasizing the impact of methylmercury on neurodevelopment, including motor and cognitive evaluations, the association between mercury and autism, and an evaluation of its protective effects against mercury toxicity. In observational studies, the blood, umbilical cord, and hair were the most frequently used for measuring mercury levels. Our data analysis reveals that mercury neurotoxicology has been extensively explored, but the association among the outcomes evaluated in experimental studies has yet to be strengthened. Providing metric evidence on what is unexplored allows for new studies that may help governmental and non-governmental organizations develop guidelines and policies.

Tacrolimus-associated neurotoxicity isolated to the brainstem: two illustrative cases and a systematic review of the literature.

INTRODUCTION: Tacrolimus-associated neurotoxicity (TAN) manifests with wide clinical spectrum, ranging from mild tremors to severe encephalopathy. The isolated involvement of the brainstem is a rarely documented presentation of TAN, and its clinical and diagnostic characteristics are unclear. METHODS: We report two cases of brainstem-isolated TAN (bi-TAN). Moreover, we performed a systematic review of the literature on bi-TAN and extracted data concerning demographics, clinical characteristics, radiological features, and management. The systematic literature search followed PRISMA guidelines and a pre-defined protocol. RESULTS: Eleven patients, including our two, were identified (mean age: 41.3 years, ± 18.8; five males, 45%). Speech disturbance was the most common clinical presentation (45%). The mean latency from Tacrolimus initiation to bi-TAN onset was 26 days (± 30.8). Tacrolimus serum level tested above the reference range in three patients (mean: 26.83 ± 5.48). Brain MRI showed T2-FLAIR hyperintensities; three showed restricted diffusion on ADC maps. Neurological symptoms resolved completely in seven patients (63%) after Tacrolimus withdrawal or dose reduction. CONCLUSIONS: Our findings suggest that bi-TAN could represent a brainstem variant of posterior reversible encephalopathy syndrome. Recognition of bi-TAN as a potential cause of isolated brainstem lesions is crucial to disentangle the diagnostic work-up and ensure prompt withdrawal or reduction of the offending agent.

Antibiomania: clarithromycin-induced neurotoxicity mimicking autoimmune limbic encephalitis.

We describe a 64-year-old woman with relapsing encephalopathy. She initially presented with 5 days of psychomotor agitation, progressing to mania, psychosis and seizures that mimicked autoimmune limbic encephalitis. During her first hospital admission, extensive investigation failed to establish the underlying cause, and she improved with antiseizure medication alone. After a month at home, she relapsed with identical symptoms, and only then did we recognise that both episodes had been provoked by clarithromycin, prescribed for Helicobacter pylori eradication. Clarithromycin-induced neurotoxicity is rarely reported but likely to be under-recognised. It usually manifests within days of starting treatment, with delirium, mania, psychosis or visual hallucinations, sometimes termed 'antibiomania'. Seizures and status epilepticus appear to be less frequent. A full recovery is expected on stopping the medication.

Synchrotron speciation of umbilical cord mercury and selenium after environmental exposure in Niigata.

The insidious and deadly nature of mercury's organometallic compounds is informed by two large scale poisonings due to industrial mercury pollution that occurred decades ago in Minamata and Niigata, Japan. The present study examined chemical speciation for both mercury and selenium in a historic umbilical cord sample from a child born to a mother who lived near the Agano River in Niigata. The mother had experienced mercury exposure leading to more than 50 ppm mercury measured in her hair and was symptomatic 9 years prior to the birth. We sought to determine the mercury and selenium speciation in the child's cord using Hg Lα1 and Se Kα1 high-energy resolution fluorescence detected X-ray absorption spectroscopy, the chemical speciation of mercury was found to be predominantly organometallic and coordinated to a thiolate. The selenium was found to be primarily in an organic form and at levels higher than those of mercury, with no evidence of mercury-selenium chemical species. Our results are consistent with mercury exposure at Niigata being due to exposure to organometallic mercury species.

Uncovering the common factors of chemical exposure and behavior: Evaluating behavioral effects across a testing battery using factor analysis.

Although specific environmental chemical exposures, including flame retardants, are known risk factors for neurodevelopmental disorders (NDDs), direct experimental evidence linking specific chemicals to NDDs is limited. Studies focusing on the mechanisms by which the social processing systems are vulnerable to chemical exposure are underrepresented in the literature, even though social impairments are defining characteristics of many NDDs. We have repeatedly demonstrated that exposure to Firemaster 550 (FM 550), a prevalent flame retardant mixture used in foam-based furniture and infant products, can adversely impact a variety of behavioral endpoints. Our recent work in prairie voles (Microtus ochrogaster), a prosocial animal model, demonstrated that perinatal exposure to FM 550 sex specifically impacts socioemotional behavior. Here, we utilized a factor analysis approach on a battery of behavioral data from our prior study to extract underlying factors that potentially explain patterns within the FM 550 behavior data. This approach identified which aspects of the behavioral battery are most robust and informative, an outcome critical for future study designs. Pearson's correlation identified behavioral endpoints associated with distance and stranger interactions that were highly correlated across 5 behavioral tests. Using these behavioral endpoints, exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) extracted 2 factors that could explain the data: Activity (distance traveled endpoints) and Sociability (time spent with a novel conspecific). Exposure to FM 550 significantly decreased Activity and decreased Sociability. This factor analysis approach to behavioral data offers the advantages of modeling numerous measured variables and simplifying the data set by presenting the data in terms of common, overarching factors in terms of behavioral function.

Developmental organophosphate flame retardant exposure disrupts adult hippocampal neurogenesis in Wistar rats.

Organophosphate flame retardant (OPFR) contamination is ubiquitous and bio-monitoring studies have shown that human exposure is widespread and may be unavoidable. OPFRs bear structural similarities to known neurotoxicants such as organophosphate insecticides and have been shown to have both endocrine disrupting and developmental neurotoxic effects. The perinatal period in rodents represents a critical period in the organization of the developing nervous system and insults during this time can impart profound changes on the trajectory of neural development and function, lasting into adulthood. Adult hippocampal neurogenesis (AHN) facilitates dentate gyrus function and broader hippocampal circuit activity in adults; however, the neurogenic potential of this process in adulthood is vulnerable to disruption by exogenous factors during early life. We sought to assess the impact of OPFRs on AHN in offspring of dams exposed during gestation and lactation. Results indicate that developmental OPFR exposure has significant, sex specific impacts on multiple markers of AHN in the dentate gyrus of rats. In males, OPFR exposure significantly reduced the number of neural progenitors the number of new/immature neurons and reduced dentate gyrus volume. In females, exposure increased the number of neural progenitors, decreased the number of new/immature neurons, but had no significant effect on dentate gyrus volume. These results further elucidate the developmental neurotoxic properties of OPFRs, emphasize the long-term impact of early life OPFR exposure on neural processes, and highlight the importance of including sex as a biological variable in neurotoxicology research.

Childhood exposure to pyrethroids and neurodevelopment in Canadian preschoolers.

BACKGROUND: Pyrethroid insecticides are used both residentially and agriculturally and their toxicity targets the nervous system of insects. They might also interfere with development and function of the human brain. A few epidemiological studies suggest that exposure to pyrethroids may be associated with neurobehavioral problems in children but there is little data on potential associations with cognitive outcomes. Furthermore, many studies showed that the neurotoxic effects of several pesticides are modified by sex, hence, considerations of potential sex-differences are important to investigate. OBJECTIVE: To study the cross-sectional association between urinary levels of pyrethroid metabolites and neurodevelopment, including neurobehavioral and cognitive outcomes, in preschool-age children, and to examine whether sex might modify these associations. METHODS: We used data from a follow-up examination of the Maternal-Infant Research on Environmental Chemicals (MIREC), the MIREC Child Development study (MIREC-CD Plus) on children at age 3-4 years living in 6 Canadian cities. For each participant, we collected a urine sample for measurements of pyrethroids metabolites (cis-DBCA, cis-DCCA, trans-DCCA, 3-PBA, 4-F-3-PBA). We assessed neurodevelopment with the Wechsler Primary and Preschool Scale of Intelligence-III (WPPSI-III) and two scales of the Behavior Rating Inventory of Executive Function-Preschool (BRIEF-P). Parents reported children's behavior using the Behavior Assessment System for Children-2 (BASC-2) and the Social Responsiveness Scale-2 (SRS-2). We examined associations between children's urinary pyrethroid metabolite concentrations and neurodevelopmental scores with multiple linear regression models, adjusting for confounders, in boys and girls separately. RESULTS: The study included 179 children (mean age: 3.2 y, range 2.8-4.0). The detection frequencies were high for most pyrethroid metabolites (83-100%), but lower for 4-F-3-PBA (36%). Higher concentrations of cis-DBCA were significantly associated with lower verbal, performance and full-scale IQ scores in boys (e.g., for a 2-fold increase in cis-DBCA, ß = -2.0; 95% CI: -3.4, -0.6 for full-scale IQ). In girls, the only metabolite associated with cognitive scores was 3-PBA, which was associated with lower verbal IQ scores (ß = -1.3, 95% CI: -2.6, -0.1). For neurobehavioral outcomes in boys, there were associations between poorer BASC-2 Adaptive Skills scores with higher concentrations of cis-DCCA (ß = -1.6, 95% CI: -2.3, -0.9), trans-DCCA (ß = -1.5, 95% CI: -2.2, -0.8), 3-PBA (ß = -1.7, 95% CI: -2.5, -0.9), and sum of pyrethroid metabolites (ß = -1.8, 95% CI: -2.6, -0.9). In girls, we observed a significant association between higher concentration of cis-DCCA and better BASC-2 Adaptive Skills score (ß = 1.0; 95% CI, 0.2, 1.8), but not with other urinary pyrethroids metabolites. Scores on the SRS-2 and BRIEF-P were not associated with pyrethroid metabolites. CONCLUSION: There were associations between some pyrethroid pesticide metabolites and indicators of neurodevelopmental disorder, especially among boys. These associations are in agreement with previous studies and could suggest that exposure to pyrethroid pesticides represents a risk of potential toxicity for the cognitive development of children, and a risk for behavioral development. However, the cross-sectional nature of this study limits causal inferences.

Synchrotron X-ray methods in the study of mercury neurotoxicology.

In situ methods are valuable in all fields of research. In toxicology, the importance of dose is well known, elevating the need for in situ techniques to measure levels of toxicants and their byproducts in precise anatomically identifiable locations. More recently, additional emphasis has been placed on the value of techniques which can detect chemical form or speciation, which is equally important in the toxicology of a chemical compound. Many important but conventional methods risk losing valuable information due to extractions, digestions, or the general reliance on mobile phases. Few analytical tools possess the power and diversity of X-ray methods as in-situ methods. Here we present an overview, intended for toxicologists and pathologists, of a variety of synchrotron X-ray methods for determining in situ chemical form and distribution of heavier elements. The versatility and range of these synchrotron techniques, which are both established and emerging, is demonstrated in the context of the study of neurotoxicology of mercury, a global pollutant with the ability to harm both human health and the environment.

Maternal concentrations of phthalates and Attention-Deficit Hyperactivity Disorder (ADHD-) related symptoms in children aged 2 to 4 years from Odense child cohort.

BACKGROUND: Phthalates are endocrine disrupting chemicals used in everyday consumer products. Several epidemiological studies have examined the association between prenatal phthalate concentration and Attention-Deficit Hyperactivity Disorder (ADHD) in offspring, but the findings have been inconclusive. OBJECTIVES: To investigate the association between maternal urinary concentrations of phthalate metabolites during pregnancy and ADHD related symptoms in children at 2 to 4 years in a large prospective cohort. METHODS: In the Odense Child Cohort from Denmark were women recruited in early pregnancy from 2010 to 2012. Phthalate concentrations were measured in urine samples collected in 3rd trimester and separated into low and high weight phthalates. Parents filled in the Child Behavior Checklist for ages 1.5 to 5 years (CBCL/1½-5), including a 6-item ADHD symptom scale at children aged 2 to 4 years. Data were analysed by use of adjusted negative binomial regression. RESULTS: A total of 658 mother-child pairs were included. Urinary phthalate metabolite concentrations were generally low compared to previous cohorts. A doubling in maternal concentration of the low-weighted phthalate metabolite MCPP was significantly associated with lower ADHD symptoms score in children (IRR: 0.95 (95 % CI 0.91-0.98)), strongest in girls (IRR: 0.92 (0.87-0.98)). Sex differences were observed. High maternal phthalate metabolite concentrations were associated with lower ADHD symptom score in girls, significant trends across tertile of MCPP and MnBP (p = 0.018, p = 0.038, respectively). In boys, maternal concentrations of high-molecular-weight phthalates (MBzP, ∑DiNP and ∑DEHP) were associated with an almost significantly higher ADHD symptom score (IRR for a doubling in concentration: 1.04 (95 % CI: 0.99-1.10), IRR: 1.05 (95 % CI: 0.97-1.13), IRR: 1.04 (95 % CI: 0.99-1.10), respectively). CONCLUSION: Maternal concentration of the low-weighted phthalate metabolite MCPP was significantly associated with a lower ADHD symptom score in children, strongest in girls. Maternal concentrations of high-molecular-weight phthalates were associated with non-significant increase in ADHD symptom score in boys.

Modeling early human cortical development and evaluating neurotoxicity with a forebrain organoid system.

The complexity and subtlety of brain development renders it challenging to examine effects of environmental toxicants on human fetal brain development. Advances in pluripotent cell-derived organoid systems open up novel avenues for human development, disease and toxicity modeling. Here, we have established a forebrain organoid system and recapitulated early human cortical development spatiotemporally including neuroepithelium induction, apical-basal axis formation, neural progenitor proliferation and maintenance, neuronal differentiation and layer/region patterning. To explore whether this forebrain organoid system is suitable for neurotoxicity modeling, we subjected the organoids to bisphenol A (BPA), a common environmental toxicant of global presence and high epidemic significance. BPA exposure caused substantial abnormalities in key cortical developmental events, inhibited progenitor cell proliferation and promoted precocious neuronal differentiation, leading premature progenitor cell depletion and aberrant cortical layer patterning and structural organization. Consistent with an antagonistic mechanism between thyroid hormone and BPA, T3 supplementation attenuated BPA-mediated cortical developmental abnormalities. Altogether, our in vitro recapitulation of cortical development with forebrain organoids provides a paradigm for efficient neural development and toxicity modeling and related remedy testing/screening.

Multi-omics approach reveals dysregulated genes during hESCs neuronal differentiation exposure to paracetamol.

Prenatal paracetamol exposure has been associated with neurodevelopmental outcomes in childhood. Pharmacoepigenetic studies show differences in cord blood DNA methylation between unexposed and paracetamol-exposed neonates, however, causality and impact of long-term prenatal paracetamol exposure on brain development remain unclear. Using a multi-omics approach, we investigated the effects of paracetamol on an in vitro model of early human neurodevelopment. We exposed human embryonic stem cells undergoing neuronal differentiation with paracetamol concentrations corresponding to maternal therapeutic doses. Single-cell RNA-seq and ATAC-seq integration identified paracetamol-induced chromatin opening changes linked to gene expression. Differentially methylated and/or expressed genes were involved in neurotransmission and cell fate determination trajectories. Some genes involved in neuronal injury and development-specific pathways, such as KCNE3, overlapped with differentially methylated genes previously identified in cord blood associated with prenatal paracetamol exposure. Our data suggest that paracetamol may play a causal role in impaired neurodevelopment.