Down-regulation of early ionotrophic glutamate receptor subunit developmental expression as a mechanism for observed plasticity deficits following gestational exposure to benzo(a)pyrene

Activity-Based Protein Profiling to Probe Relationships between Cytochrome P450 Enzymes and Early-Age Metabolism of Two Polycyclic Aromatic Hydrocarbons (PAHs): Phenanthrene and Retene

A growing body of literature has linked early-life exposures to polycyclic aromatic hydrocarbons (PAH) with adverse neurodevelopmental effects. Once in the body, metabolism serves as a powerful mediator of PAH toxicity by bioactivating and detoxifying PAH metabolites. Since enzyme expression and activity vary considerably throughout human development, we evaluated infant metabolism of PAHs as a potential contributing factor to PAH susceptibility. We measured and compared rates of phenanthrene and retene (two primary PAH constituents of woodsmoke) metabolism in human hepatic microsomes from individuals ≤21 months of age to a pooled sample (n = 200) consisting primarily of adults. We used activity-based protein profiling (ABPP) to characterize cytochrome P450 enzymes (CYPs) in the same hepatic microsome samples. Once incubated in microsomes, phenanthrene demonstrated rapid depletion. Best-fit models for phenanthrene metabolism demonstrated either 1 or 2 phases, depending on the sample, indicating that multiple enzymes could metabolize phenanthrene. We observed no statistically significant differences in phenanthrene metabolism as a function of age, although samples from the youngest individuals had the slowest phenanthrene metabolism rates. We observed slower rates of retene metabolism compared with phenanthrene also in multiple phases. Rates of retene metabolism increased in an age-dependent manner until adult (pooled) metabolism rates were achieved at ∼12 months. ABPP identified 28 unique CYPs among all samples, and we observed lower amounts of active CYPs in individuals ≤21 months of age compared to the pooled sample. Phenanthrene metabolism correlated to CYPs 1A1, 1A2, 2C8, 4A22, 3A4, and 3A43 and retene metabolism correlated to CYPs 1A1, 1A2, and 2C8 measured by ABPP and vendor-supplied substrate marker activities. These results will aid efforts to determine human health risk and susceptibility to PAHs exposure during early life.

Dyslexia is associated with urinary polycyclic aromatic hydrocarbon metabolite concentrations of children from China: Data from the READ program

It has been found that exposure to polycyclic aromatic hydrocarbons (PAHs) is associated with the risk of certain childhood neurodevelopmental disorders. However, no research has investigated the relationship between exposure to PAHs and children's dyslexia odds. The objective of this research was to investigate whether urinary mono-hydroxylated polycyclic aromatic hydrocarbons (OH-PAHs) are associated with increased dyslexia odds in Chinese children. We recruited 1,089 children (542 dyslexic children and 547 non-dyslexic children) for this case-control study. Ten OH-PAHs were measured in the participants' urine samples, which were collected between November 2017 and March 2023. Odds ratios (ORs) of the associations between the OH-PAHs and dyslexia were calculated using logistic regression models, after adjustment for the potential confounding factors. A significant association was found between urinary concentrations of 2-hydroxynaphthalene (2-OHNap) and the elevated odds of dyslexia. The children in the highest quartile of 2-OHNap had a higher OR of dyslexia (1.87, 95% CI: 1.07-3.27) than those in the lowest quartile (P-trend = 0.02) after adjustment for the covariates. After excluding children with maternal disorders during pregnancy, logistic regression analyses showed similar results. Our results suggested a possible association between PAH exposure and the elevated odds of dyslexia.

Exposure to different PM2.5 extracts induces gliosis and changes behavior in male rats similar to autism spectrum disorders features

Epidemiological studies have documented that exposure to fine particulate matter (PM2.5) could affect neurodevelopment, thereby leading to autism spectrum disorders (ASD). Nevertheless, there is little laboratory data to support this epidemiological evidence. In the current study, we carried out a series of experiments to assess whether developmental exposures to different extracts of PM2.5 can result in ASD-like behavioral, biochemical, and immunohistochemical characteristics in male rat offspring. PM2.5 samples were collected daily for a year, and monthly composites were extracted with an acetone-hexane mixture. The extracts were analyzed for their chemical constituents. Three groups of rats were exposed to the different PM2.5 extracts during pre- and postnatal periods. All exposed groups of rats exhibited typical behavioral features of ASD, including increased repetitive and depression-related behaviors. We also found microglia and astrocytes activation and decreased concentrations of oxytocin (OXT) in the brain regions of exposed rats compared with control rats. Comparing the current results with a prior study, the induced biological effects followed a sequence of whole particles of PM2.5 > organic extract > inorganic extract. These findings indicated that exposure to PM2.5 can elicit ASD-like features in rats and raise concerns about particulate matter as a possible trigger for the induction of ASD in humans; therefore, mitigating the contents of the PAHs and metals could reduce the PM2.5 neurotoxicity.

Developmental exposure to polycyclic aromatic hydrocarbons (PAHs): Focus on benzo[a]pyrene neurotoxicity

Polycyclic Aromatic Hydrocarbons (PAHs) are a class of ubiquitous organic compounds produced during the incomplete combustion or pyrolysis of organic material. Dietary source is the main route for PAH human exposure by environmental contamination, food industrial processing or domestic cooking methods. The most studied PAH is benzo[a]pyrene (B[a]P), due to its harmful and multiple effects on human health: in addition to its well-known carcinogenic effects, emerging evidence indicates that B[a]P also induces neurotoxicity earlier and at lower doses than B[a]P-induced carcinogenicity making B[a]P neurotoxicity relevant to human health risk assessment. Developmental neurotoxicity of B[a]P has indeed received increasing attention: both human and experimental studies provide evidence of detrimental effects of prenatal or early postnatal B[a]P exposure, even at low doses. Indeed, in some of the multi-dose animal studies, maximal adverse effects were observed at lower B[a]P doses, according to a non-monotonic dose-response curve typical of endocrine-disrupting compounds. In substantial agreement with epidemiological studies, both rodents and zebrafish developmentally exposed to B[a]P exhibit long-term changes in multiple behavioural domains, in the absence of overt toxicological effects at birth (e.g. body weight and morphologic abnormalities). Notably, most targeted behavioural responses converge on locomotor activity and emotional profile, often, but not always, leading to a disinhibitory/hyperactive profile.

Association of polycyclic aromatic hydrocarbons exposure with child neurodevelopment and adult emotional disorders: A meta-analysis study

BACKGROUND

Polycyclic aromatic hydrocarbons (PAHs) have been demonstrated to be neurotoxic.

OBJECTIVES

To summarize the existing epidemiological studies to quantify the effects of PAHs exposure on child neurodevelopment and adult emotional disorders.

DATA SOURCES AND STUDY ELIGIBILITY CRITERIA

We conducted a systematic literature search for studies of child neurodevelopment and adult emotional disorders published in English up to April 2022 in the databases of PubMed, Web of Science and Embase using combinations of MeSH terms and Entry terms, and the articles were filtered out according to data availability. A variety of common PAHs were included in the meta-analysis: 1-hydroxynaphthalene, 2-hydroxynaphthalene, 2-hydroxyfluorene, 3-hydroxyfluorene, 9-hydroxyfluorene, 1-hydroxyphenanthrene, 2-hydroxyphenanthrene, 3-hydroxyphenanthrene, 4-hydroxyphenanthrene, 9-hydroxyphenanthrene, 1-hydroxypyrene and benzoapyrene (BaP).

STUDY EVALUATION AND SYNTHESIS METHODS

We extracted the content of each article, summarized its design characteristics and performed quality evaluation. We combined the odds ratio (OR) available in various studies to obtain the risk of PAHs exposure and adaptive, language, social, attention, motor skills and child depression/anxiety in children ≤ 15 years old. In addition, we also conducted a meta-analysis on the relationship between PAHs exposure and the risk of depression in adults.

RESULTS

We included a total of 16 epidemiological studies (4 cross-sectional studies and 12 cohort studies). The sample size of all included studies ranged from 110 to 9625. Prenatal exposure to PAHs was found to be associated with increased risk of social behavior (OR = 1.60, 95% CI: 1.00-2.54), attention (OR = 2.99, 95% CI: 1.48-6.02), motor skill problems (OR = 1.91, 95% CI: 1.27-2.86) and any adverse neurodevelopmental outcome in children (OR = 2.10, 95% CI: 1.69-2.62). In addition, we found that PAHs exposure could increase the risk of adult depression, with 2-hydroxyfluorene exposure showing the highest combined OR (OR = 1.48, 95% CI: 1.10-2.00).

CONCLUSIONS

The results suggested that PAHs exposure are associated with increased risk of child neurodevelopment and adult depression. The neurotoxic effects of PAHs exposure in human being should be paid more attention. The results suggested that PAHs exposure are associated with increased risk of child neurodevelopment and adult depression. The neurotoxic effects of PAHs exposure in human being should be paid more attention. Steps should be taken to enhance the biomonitoring of PAHs and to reduce the exposure in general population.

Prenatal exposure to polycyclic aromatic hydrocarbons is not associated with behavior problems in preschool and early school-aged children: A prospective multi-cohort study

BACKGROUND

Epidemiological study findings are inconsistent regarding associations between prenatal polycyclic aromatic hydrocarbon (PAH) exposures and childhood behavior. This study examined associations of prenatal PAH exposure with behavior at age 4-6 years in a large, diverse, multi-region prospective cohort. Secondary aims included examination of PAH mixtures and effect modification by child sex, breastfeeding, and child neighborhood opportunity.

METHODS

The ECHO PATHWAYS Consortium pooled 1118 mother-child dyads from three prospective pregnancy cohorts in six U.S. cities. Seven PAH metabolites were measured in prenatal urine. Child behavior was assessed at age 4-6 using the Total Problems score from the Child Behavior Checklist (CBCL). Neighborhood opportunity was assessed using the socioeconomic and educational scales of the Child Opportunity Index. Multivariable linear regression was used to estimate associations per 2-fold increase in each PAH metabolite, adjusted for demographic, prenatal, and maternal factors and using interaction terms for effect modifiers. Associations with PAH mixtures were estimated using Weighted Quantile Sum Regression (WQSR).

RESULTS

The sample was racially and sociodemographically diverse (38% Black, 49% White, 7% Other; household-adjusted income range $2651-$221,102). In fully adjusted models, each 2-fold increase in 2-hydroxynaphthalene was associated with a lower Total Problems score, contrary to hypotheses (b = -0.80, 95% CI = -1.51, -0.08). Associations were notable in boys (b = -1.10, 95% CI = -2.11, -0.08) and among children breastfed 6+ months (b = -1.31, 95% CI = -2.25, -0.37), although there was no statistically significant evidence for interaction by child sex, breastfeeding, or neighborhood child opportunity. Associations were null for other PAH metabolites; there was no evidence of associations with PAH mixtures from WQSR.

CONCLUSION

In this large, well-characterized, prospective study of mother-child pairs, prenatal PAH exposure was not associated with child behavior problems. Future studies characterizing the magnitude of prenatal PAH exposure and studies in older childhood are needed.

Embryonic exposure to benzo[a]pyrene causes age-dependent behavioral alterations and long-term metabolic dysfunction in zebrafish

Polycyclic aromatic hydrocarbons (PAH) are products of incomplete combustion which are ubiquitous pollutants and constituents of harmful mixtures such as tobacco smoke, petroleum and creosote. Animal studies have shown that these compounds exert developmental toxicity in multiple organ systems, including the nervous system. The relative persistence of or recovery from these effects across the lifespan remain poorly characterized. These studies tested for persistence of neurobehavioral effects in AB* zebrafish exposed 5-120 h post-fertilization to a typical PAH, benzo[a]pyrene (BAP). Study 1 evaluated the neurobehavioral effects of a wide concentration range of BAP (0.02-10 μM) exposures from 5 to 120 hpf during larval (6 days) and adult (6 months) stages of development, while study 2 evaluated neurobehavioral effects of BAP (0.3-3 μM) from 5 to 120 hpf across four stages of development: larval (6 days), adolescence (2.5 months), adulthood (8 months) and late adulthood (14 months). Embryonic BAP exposure caused minimal effects on larval motility, but did cause neurobehavioral changes at later points in life. Embryonic BAP exposure led to nonmonotonic effects on adolescent activity (0.3 μM hyperactive, Study 2), which attenuated with age, as well as startle responses (0.2 μM enhanced, Study 1) at 6 months of age. Similar startle changes were also detected in Study 2 (1.0 μM), though it was observed that the phenotype shifted from reduced pretap activity to enhanced posttap activity from 8 to 14 months of age. Changes in the avoidance (0.02-10 μM, Study 1) and approach (reduced, 0.3 μM, Study 2) of aversive/social cues were also detected, with the latter attenuating from 8 to 14 months of age. Fish from study 2 were maintained into aging (18 months) and evaluated for overall and tissue-specific oxygen consumption to determine whether metabolic processes in the brain and other target organs show altered function in late life based on embryonic PAH toxicity. BAP reduced whole animal oxygen consumption, and overall reductions in total basal, mitochondrial basal, and mitochondrial maximum respiration in target organs, including the brain, liver and heart. The present data show that embryonic BAP exposure can lead to neurobehavioral impairment across the life-span, but that these long-term risks differentially emerge or attenuate as development progresses.

Prenatal urinary metabolites of polycyclic aromatic hydrocarbons and toddler cognition, language, and behavior

BACKGROUND

Animal and epidemiological studies suggest that prenatal exposure to polycyclic aromatic hydrocarbons (PAHs) may negatively impact toddler neurodevelopment.

METHODS

We investigated this association in 835 mother-child pairs from CANDLE, a diverse pregnancy cohort in the mid-South region of the U.S. PAH metabolite concentrations were measured in mid-pregnancy maternal urine. Cognitive and Language composite scores at ages 2 and 3 years were derived from the Bayley Scales of Infant and Toddler Development, 3rd edition (Bayley-3). Behavior Problem and Competence scores at age 2 were derived from the Brief Infant and Toddler Social Emotional Assessment (BITSEA). We used multivariate linear or Poisson regression to estimate associations with continuous scores and relative risks (RR) of neurodevelopment delay or behavior problems per 2-fold increase in PAH, adjusted for maternal health, nutrition, and socioeconomic status. Secondary analyses investigated associations with PAH mixture using Weighted Quantile Sum Regression (WQS) with a permutation test extension.

RESULTS

1- hydroxypyrene was associated with elevated relative risk for Neurodevelopmental Delay at age 2 (RR = 1.20, 95% CI: 1.03,1.39). Contrary to hypotheses, 1-hydroxynaphthalene was associated with lower risk for Behavior Problems at age 2 (RR = 0.90, 95% CI: 0.83,0.98), and combined 1- and 9-hydroxyphenanthrene was associated with 0.52-point higher (95% CI: 0.11,0.93) Cognitive score at age 3. For PAH mixtures, a quintile increase in hydroxy-PAH mixture was associated with lower Language score at age 2 (βwqs = -1.59; 95% CI: -2.84, -0.34; p_permutation = 0.07) and higher Cognitive score at age 3 (βwqs = 0.96; 95% CI: 0.11, 1.82; p_permutation = 0.05). All other estimates were consistent with null associations.

CONCLUSION

In this large southern U.S. population we observed some support for adverse associations between PAHs and neurodevelopment.

Paternal Cannabis Exposure Prior to Mating, but Not Δ9-Tetrahydrocannabinol, Elicits Deficits in Dopaminergic Synaptic Activity in the Offspring

The legalization and increasing availability of cannabis products raises concerns about the impact on offspring of users, and little has appeared on the potential contribution of paternal use. We administered cannabis extract to male rats prior to mating, with two different 28-day exposures, one where there was a 56-day interval between the end of exposure and mating ("Early Cannabis"), and one just prior to mating ("Late Cannabis"); the extract delivered 4 mg/kg/day of the main psychoactive component, Δ9-tetrahydrocannabinol. We then assessed the impact on dopamine (DA) systems in the offspring from the onset of adolescence (postnatal day 30) through middle age (postnatal day 150), measuring the levels of DA and its primary metabolite, 3,4-dihydroxyphenylacetic acid (DOPAC) in various brain regions. Paternal cannabis with either regimen elicited a profound and persistent deficit in DA utilization (DOPAC/DA ratio) in the offspring, indicative of subnormal presynaptic activity. However, the two regimens differed in the underlying mechanism, with Early Cannabis reducing DOPAC whereas Late Cannabis increased DA and elicited a smaller reduction in DOPAC. Effects were restricted to male offspring. The effects of cannabis were not reproduced by equivalent exposure to its Δ9-tetrahydrocannabinol, nor did we see the effects with perinatal exposure to tobacco smoke or some of its fetotoxic contributors (benzo[a]pyrene without or with nicotine). Our studies provide some of the first evidence for adverse effects of paternal cannabis administration on neurodevelopment in the offspring, and reinforce the important consequences of paternal drug use in the preconception period.

Persistent organic pollutants at the synapse: Shared phenotypes and converging mechanisms of developmental neurotoxicity

The developing nervous system is sensitive to environmental and physiological perturbations in part due to its protracted period of prenatal and postnatal development. Epidemiological and experimental studies link developmental exposures to persistent organic pollutants (POPs) including polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins, polybrominated diphenyl ethers, and benzo(a)pyrene to increased risk for neurodevelopmental disorders in children. Mechanistic studies reveal that many of the complex cellular processes that occur during sensitive periods of rapid brain development are cellular targets for developmental neurotoxicants. One area of research interest has focused on synapse formation and plasticity, processes that involve the growth and retraction of dendrites and dendritic spines. For each chemical discussed in this review, we summarize the morphological and electrophysiological data that provide evidence that developmental POP exposure produces long-lasting effects on dendritic morphology, spine formation, glutamatergic and GABAergic signaling systems, and synaptic transmission. We also discuss shared intracellular mechanisms, with a focus on calcium and thyroid hormone homeostasis, by which these chemicals act to modify synapses. We conclude our review highlighting research gaps that merit consideration when characterizing synaptic pathology elicited by chemical exposure. These gaps include low-dose and nonmonotonic dose-response effects, the temporal relationship between dendritic growth, spine formation, and synaptic activity, excitation-inhibition balance, hormonal effects, and the need for more studies in females to identify sex differences. By identifying converging pathological mechanisms elicited by POP exposure at the synapse, we can define future research directions that will advance our understanding of these chemicals on synapse structure and function.

Preliminary evidence for an influence of exposure to polycyclic aromatic hydrocarbons on the composition of the gut microbiota and neurodevelopment in three-year-old healthy children

Background

During the second and third year after birth the gut microbiota (GM) is subjected to important development. The polycyclic aromatic hydrocarbon (PAH) exposure could influence the GM in animal and early postnatal exposure is associated with neurodevelopment disorder in children. This study was designed to explore the possible influence of the polycyclic aromatic hydrocarbons (PAHs) on the composition of the gut microbiota (GM) and neurodevelopment in a sample of 38 healthy children at the age of 3 years.

Methods

A brief development (Gesell Development Inventory, GDI) and behavior test (Child Behavior Checklist, CBCL) were completed on 3-yr-olds and stool samples were collected for 16S rRNA V4-V5 sequencing. The PAH-DNA adduct in the umbilical cord blood and the urinary hydroxyl PAHs (OH-PAHs) at the age of 12 months were measured as pre- and postnatal PAH exposure, respectively.

Results

The most abundant two phyla were Bacteroidetes (68.6%) and Firmicutes (24.2%). The phyla Firmicutes, Actinobacteria, Proteobacteria, Tenericutes, and Lentisphaerae were positively correlated with most domain behaviors of the GDI, whereas the Bacteroidetes, Cyanobacteria, and Fusobacteria were negatively correlated. Correspondingly, the phyla Bacteroidetes, Actinobacteria, and Fusobacteria showed positive correlations with most CBCL core and broadband syndromes, whereas the Firmicutes, Verrucomicrobia, Synergistetes, Proteobacteria and Tenericules were negatively correlated. The OH-PAH levels were not significantly associated with the Firmicutes phylum whereas the Bacteroidetes, Bacteroidia, and Bacteroidales all showed significant negative association with the OH-PAH levels.

Conclusion

The current findings suggest that composition of the GM is associated with neurodevelopment of the child. PAHs seem to change the relative abundance of some taxa (some deleted and some recruited) to counteract the negative effects of the PAHs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12887-021-02539-w.

Prenatal exposure to polycyclic aromatic hydrocarbons modifies the effects of early life stress on attention and Thought Problems in late childhood

BACKGROUND

Risk for childhood psychopathology is complex and multifactorial, implicating direct and interacting effects of familial and environmental factors. The role of environmental neurotoxicants in psychiatric risk is of growing concern, including polycyclic aromatic hydrocarbons (PAH), common in air pollution. Prenatal PAH exposure is linked to adverse physical, behavioral, and cognitive outcomes as well as increasing psychiatric risk. It is unclear whether environmental exposures, like PAH, magnify the effects of exposure to early life stress (ELS), a critical risk factor for psychopathology. The current work aimed to test potential interactions between prenatal PAH exposure and psychosocial/socioeconomic stress on psychiatric symptoms in school-age children.

METHODS

Data were from the Columbia Center for Children's Environmental Health Mothers and Newborns longitudinal birth cohort study. Prenatal PAH exposure was ascertained though air monitoring during pregnancy and maternal PAH-DNA adducts at delivery. Mothers reported on ELS (child age 5) and on child psychiatric symptoms across childhood (child age 5, 7, 9, and 11) using the Child Behavior Checklist (CBCL).

RESULTS

Significant prenatal airborne PAH × ELS interactions (FDR-corrected) predicted CBCL Attention (β = 0.22, t(307) = 3.47, p < .001, p_fdr  = .003) and Thought Problems T-scores (β = 0.21, t(307) = 3.29, p = .001, p_fdr  = .004) at age 11 (n = 319). Relative to those with lower exposure, children with higher prenatal PAH exposure exhibited stronger positive associations between ELS and CBCL Attention and Thought Problem T-scores. This interaction was also significant examining convergent ADHD measures (Conners, DuPaul) and examining maternal PAH-DNA adducts (β = 0.29, t(261) = 2.48, p = .01; n = 273). A three-way interaction with assessment wave indicated that the PAH × ELS interaction on Attention Problems was stronger later in development (β = 0.03, t(1,601) = 2.19, p = .03; n = 477).

CONCLUSIONS

Prenatal exposure to PAH, a common neurotoxicant in air pollution, may magnify or sustain the effects of early life psychosocial/socioeconomic stress on psychiatric outcomes later in child development. This work highlights the critical role of air pollution exposure on child mental health.

Sub-chronic administration of benzo[a]pyrene disrupts hippocampal long-term potentiation via inhibiting CaMK II/PKC/PKA-ERK-CREB signaling in rats

Benzo[a]pyrene (B[a]P) is recognized as a neurotoxic pollutant to mammals, which could impair learning and memory function. Although there is some evidence to suggest that N-methyl-d-aspartate receptor (NMDAR), a glutamate receptor and ion channel protein in nerve cells, is involved into the B[a]P induced neurotoxicity, the exact molecular mechanisms remain to be elucidated, particularly the effects of B[a]P on the NMDAR downstream signaling transduction pathways. In the present study, we examined the neurotoxicity of sub-chronic administrated B[a]P on male Sprague-Dawley rats. Our data suggested that B[a]P exposure caused significant deficits in learning and memory function and the impairment of hippocampal LTP in rats. Further mechanistic studies indicate that B[a]P-induced learning and memory deficits are associated with the inhibition of NMDAR NR1 subunit transcription and protein phosphorylation. More importantly, the inactivation of CaMK II/PKC/PKA-ERK-CREB signaling pathways in hippocampus was detected at both the 2.5 and 6.25 mg/kg B[a]P-treated groups, indicating that multiple targets in NMDAR and downstream signaling pathways are involved in the B[a]P-induced neurotoxicity.

Association between exposure to polycyclic aromatic hydrocarbons and attention deficit hyperactivity disorder in children: a systematic review and meta-analysis

Some studies have shown that exposure to polycyclic aromatic hydrocarbons (PAHs) is a dangerous factor for attention deficit hyperactivity disorder (ADHD). This systematic review and meta-analysis aimed to clarify this relationship, and to collect and analyze all the relevant evidences in published reports of epidemiologic studies. PubMed, Science Direct, Web of Science, Scopus, and Google Scholar databases were searched through September 31, 2018. The study quality was evaluated using the Newcastle-Ottawa Scale. Moreover, fixed- and random-effect models were used. The data in this meta-analysis were presented as adjusted odds ratio (AOR). From 959 articles, six articles were included in the systematic review, and for meta-analysis, one study (that was not AOR) was excluded. The participants included in the studies were 2799 with the age range of 5-15 years old, and 93.6% were living in America. Four of the studies were placed in one group, due to having a common author (Perera). Moreover, a significant association was found between PAH exposure and ADHD in these studies (odds ratio = 2.57, 95% CI = 1.75-3.78); however, in all studies, there was no significant association between PAH exposure and ADHD for children (overall odds ratio = 1.99, 95% CI = 0.96-4.11) with low heterogeneity (I² = 28.73%; P value < 0.001). This study provided a systematic review and meta-analytic evidence for the association between PAH exposure and ADHD by a small number of studies. Further research study can be conducted in various countries. Graphical Abstract.

The association of prenatal exposure to intensive traffic with early preterm infant neurobehavioral development as reflected by the NICU Network Neurobehavioral Scale (NNNS)

INTRODUCTION

Traffic-related air pollution has been shown to be neurotoxic to the developing fetus and in term-born infants during early childhood. It is unknown whether there is an increased risk of adverse neurobehavioral outcome in preterm infants exposed to higher levels of air pollution during the fetal period.

OBJECTIVE

To assess the association between prenatal exposure to traffic-related air pollution on early preterm infant neurobehavior.

METHODS

Air pollution exposure was estimated by two methods: density of major roads and density of vehicle-miles traveled (VMT), each at multiple buffering areas around residential addresses. We examined the association between prenatal exposure to traffic-related air pollution and performance on the Neonate Intensive Care Unit (NICU) Network Behavioral Scale (NNNS), a measure of neurobehavioral outcome in infancy for 240 preterm neonates enrolled in the NICU-Hospital Exposures and Long-Term Health cohort. Linear regression analysis was conducted for exposure and individual NNNS subscales. Latent profile analysis (LPA) was applied to classify infants into distinct NNNS phenotypes. Multinomial logistic regression analysis was conducted between exposure and LPA groups. Covariates included gestational age, birth weight z-score, post-menstrual age at NNNS assessment, socioeconomic status, race, delivery type, maternal smoking status, and medical morbidities during the NICU stay.

RESULTS

Among all 13 NNNS subscales, hypotonia was significantly associated with VMT (10⁴ vehicle-mile/km²) in 150 m (β = 0.01, P-value<0.001), 300 m (β = 0.01, P-value = 0.003), and 500 m (β = 0.01, P-value = 0.002) buffering areas, as well as with road density in a 500 m buffering area (β = 0.03, P-value = 0.03). We identified three NNNS phenotypes by LPA. Among them, high density of major roads within 150 m, 300 m, and 500 m buffers of the residential address was significantly associated with the same phenotype (P < 0.05).

CONCLUSION

Prenatal exposure to intensive air pollution emitted from major roads may impact early neurodevelopment of preterm infants. Motor development may be particularly sensitive to air pollution-related toxicity.

The Role of Cyclooxygenases-2 in Benzo(a)pyrene-Induced Neurotoxicity of Cortical Neurons

With the help of particulate matter, benzo(a)pyrene (BaP) has become a widely distributed environmental contaminant. In addition to the well-known carcinogenicity, a growing number of studies have focused on the neurotoxicity of BaP, especially on adverse neurobehavioral effects. However, the molecular modulating mechanisms remain unclear. In this paper, we confirmed that BaP exposure produced a neuronal insult via its metabolite benzo(a)pyrene diol epoxide (BPDE) on the primary cultured cortical neuron in vitro and mice in vivo models, and the effects were largely achieved by activating cyclooxygenases-2 (COX-2) enhancement. Also, the action of BaP on elevating COX-2 was initiated by BPDE firmly binding to the active pockets of COX-2, then followed by the production of prostaglandin E₂ (PGE₂) and upregulation of its EP2 and EP4 receptors, finally stimulating the cyclic adenosine monophosphate/protein kinase A (cAMP/PKA) signaling pathway. Our results reveal a mechanistic association underlying BaP exposure and increased risk for neurological dysfunction and clarify the ways to prevent and treat brain injuries in polluted environments.

Toxicity of urban air pollution particulate matter in developing and adult mouse brain: Comparison of total and filter-eluted nanoparticles

Air pollution (AirP) is associated with many neurodevelopmental and neurological disorders in human populations. Rodent models show similar neurotoxic effects of AirP particulate matter (PM) collected by different methods or from various sources. However, controversies continue on the identity of the specific neurotoxic components and mechanisms of neurotoxicity. We collected urban PM by two modes at the same site and time: direct collection as an aqueous slurry (sPM) versus a nano-sized sub-fraction of PM0.2 that was eluted from filters (nPM). The nPM lacks water-insoluble PAHs (polycyclic aromatic hydrocarbons) and is depleted by >50% in bioactive metals (e.g., copper, iron, nickel), inorganic ions, black carbon, and other organic compounds. Three biological models were used: in vivo exposure of adult male mice to re-aerosolized nPM and sPM for 3 weeks, gestational exposure, and glial cell cultures. In contrast to larger inflammatory responses of sPM in vitro, cerebral cortex responses of mice to sPM and nPM largely overlapped for adult and gestational exposures. Adult brain responses included induction of IFNγ and NF-κB. Gestational exposure to nPM and sPM caused equivalent depressive behaviors. Responses to nPM and sPM diverged for cerebral cortex glutamate receptor mRNA, systemic fat gain and insulin resistance. The shared toxic responses of sPM with nPM may arise from shared transition metals and organics. In contrast, gestational exposure to sPM but not nPM, decreased glutamatergic mRNAs, which may be attributed to PAHs. We discuss potential mechanisms in the overlap between nPM and sPM despite major differences in bulk chemical composition.

The Developmental Neurotoxicity of Tobacco Smoke Can Be Mimicked by a Combination of Nicotine and Benzo[a]Pyrene: Effects on Cholinergic and Serotonergic Systems

Tobacco smoke contains polycyclic aromatic hydrocarbons (PAHs) in addition to nicotine. We compared the developmental neurotoxicity of nicotine to that of the PAH archetype, benzo[a]pyrene (BaP), and also evaluated the effects of combined exposure to assess whether PAHs might exacerbate the adverse effects of nicotine. Pregnant rats were treated preconception through the first postnatal week, modeling nicotine concentrations in smokers and a low BaP dose devoid of systemic effects. We conducted evaluations of acetylcholine (ACh) and serotonin (5-hydroxytryptamine, 5HT) systems in brain regions from adolescence through full adulthood. Nicotine or BaP alone impaired indices of ACh presynaptic activity, accompanied by upregulation of nicotinic ACh receptors and 5HT receptors. Combined treatment elicited a greater deficit in ACh presynaptic activity than that seen with either agent alone, and upregulation of nAChRs and 5HT receptors was impaired or absent. The individual effects of nicotine and BaP accounted for only 60% of the combination effects, which thus displayed unique properties. Importantly, the combined nicotine + BaP exposure recapitulated the effects of tobacco smoke, distinct from nicotine. Our results show that the effects of nicotine on development of ACh and 5HT systems are worsened by BaP coexposure, and that combination of the two agents contributes to the greater impact of tobacco smoke on the developing brain. These results have important implications for the relative safety in pregnancy of nicotine-containing products compared with combusted tobacco, both for active maternal smoking and secondhand exposure, and for the effects of such agents in "dirty" environments with high PAH coexposure.

Association between prenatal exposure to household inhalants exposure and ADHD-like behaviors at around 3 years of age: Findings from Shenzhen Longhua Child Cohort Study

BACKGROUND

Prenatal exposure to air pollutants has been suggested as a possible etiologic factor for the occurrence of ADHD or ADHD-like behaviors. But we still lack a comprehensive assessment of household air pollutants exposure on the development of ADHD-like behaviors during childhood.

OBJECT

We aimed to assess whether prenatal household inhalants exposure is associated with preschoolers' ADHD-like behaviors in a nonclinical population.

METHODS

This study used the baseline data of the Longhua Child Cohort Study. During 2015-2017, we recruited 42,983 mothers and their kindergarten-aged children who enrolled at kindergarten in the Longhua district of Shenzhen, to obtain the demographic data and relevant exposure information through self-administrated questionnaire survey. The source of prenatal household inhalants exposure include cooking fumes, environmental tobacco smoke, mosqutio coils, home renovated and indoor burning incense. Logistic and censored least absolute deviations (CLAD) models were used to reveal the association between prenatal exposure to household air pollutants and hyperactive behaviors in child.

RESULTS

We found that exposure to five types of household inhalants during pregnancy were independently associated with an increased risk of child hyperactive behaviors. Moreover, we observed a significant interaction between exposure to environmental tobacco smoke and cooking fumes during gestation on child hyperactive behaviors in CLAD models. We also found a significant joint effect between burning mosquito coils and incense during gestation for child hyperactive behaviors risk both in CLAD and Logistic models. Furthermore, a household inhalants exposure index was used to demonstrate a dose-response relationship between the cumulative effect of exposure to the five household air pollutants and child hyperactivity.

CONCLUSIONS

Our results suggest that prenatal exposure to different household inhalants might increase the risk of children's hyperactive behaviors at around 3 years of age with the presence of interaction effects between some inhalants.

Inihibition of mullet (M. liza) brain acetylcholinesterase activity by in vitro polycyclic aromatic hydrocarbon exposure

Polycyclic aromatic hydrocarbons (PAH) have been reported as acetylcholinesterase (AChE) inibitors, although in vitro studies on PAH effects on AChE activity are scarce and have only been performed using electric eel brain extracts. Thus, this study investigated PAH effects on brain AChE activity in a tropical fish species in Southeastern Brazil, mullet (Mugil liza). Mullet specimens were obtained from Guanabara Bay (N = 20), Rio de Janeiro, Brazil. Brain AChE was extracted and exposed to an environmentally relevant concentration of Pyrene, Chrysene, Phenanthrene, and Naphthalene, and PAH metabolites, 2-Naphthol and 1-OH-Pyrene. AChE activity inhibition was observed, although no difference was observed between high- and low- molecular weight PAH. 2-Naphthol was a less potent AChE inhibitor than Naphthalene, albeit non-significantly. Further studies are required, since only one PAH concentration was used herein. Mullet brain extracts seem to be adequate to assess possible neurotoxic PAH effects on fish AChE.

Epigenetic and Neurological Impairments Associated with Early Life Exposure to Persistent Organic Pollutants

The incidence of neurodevelopmental and neurodegenerative diseases worldwide has dramatically increased over the last decades. Although the aetiology remains uncertain, evidence is now growing that exposure to persistent organic pollutants during sensitive neurodevelopmental periods such as early life may be a strong risk factor, predisposing the individual to disease development later in life. Epidemiological studies have associated environmentally persistent organic pollutant exposure to brain disorders including neuropathies, cognitive, motor, and sensory impairments; neurodevelopmental disorders such as autism spectrum disorder (ASD) and attention-deficit hyperactivity disorder (ADHD); and neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis (ALS). In many ways, this expands the classical “Developmental Origins of Health and Disease” paradigm to include exposure to pollutants. This model has been refined over the years to give the current “three-hit” model that considers the individual's genetic factors as a first “hit.” It has an immediate interaction with the early-life exposome (including persistent organic pollutants) that can be considered to be a second “hit.” Together, these first two “hits” produce a quiescent or latent phenotype, most probably encoded in the epigenome, which has become susceptible to a third environmental “hit” in later life. It is only after the third “hit” that the increased risk of disease symptoms is crystallised. However, if the individual is exposed to a different environment in later life, they would be expected to remain healthy. In this review, we examine the effect of exposure to persistent organic pollutants and particulate matters in early life and the relationship to subsequent neurodevelopmental and neurodegenerative disorders. The roles of those environmental factors which may affect epigenetic DNA methylation and therefore influence normal neurodevelopment are then evaluated.

Effect of Benzo[a]pyrene-DNA Adduct in Cord Blood on the Neurodevelopment of 12-Month-Old Infants in Qingdao City

INTRODUCTION

The study was designed to explore the possible adverse effects of prenatal polycyclic aromatic hydrocarbons (PAHs) on the neurodevelopment of the infants at the age of 12 months in a birth cohort in Qingdao of China. Benzo[a]pyrene (BaP)-DNA adduct level in umbilical cord blood was measured by enzyme immunoassay.

METHODS

Child neurodevelopment was assessed at both 6 months and 12 months of age using the Gesell Development Inventory (GDI).

RESULTS

This study results reveal that multivariate linear analysis, cord BaP-DNA adduct level was inversely associated with developmental quotient score in the adaptive domain [β = -0.08; 95% CI: (-0.16, -0.003); p = 0.04], gross motor domain [β = -0.10; 95% CI: (-0.20, -0.01); p = 0.02], fine motor domain [β = -0.15; 95% CI: (-0.25, -0.05); p = 0.01], language domain [β = -0.12; 95% CI: (-0.21, -0.03); p = 0.02], and personal-social domain [β = -0.13; 95% CI: (-0.22, -0.04); p<0.01]. Further, multivariate logistic regression analysis showed increased cord BaP-DNA adduct levels associated with increased odds of delayed in language domain.

CONCLUSION

In conclusion, the study suggested that prenatal PAH exposure monitored by umbilical cord blood BaP-DNA adducts may adversely affect the neurodevelopment of the infants at 12 months of age.

Household incense burning and infant gross motor development: Results from the Taiwan Birth Cohort Study

BACKGROUND

Air pollution from biomass burning were associated with neurodevelopmental deceleration, but limited studies concerned about the effect of indoor biomass burning. Incense burning is a common household ritual practice in Taiwan, while past studies mainly focused on birth weight and allergic disease.

OBJECTIVES

We aimed to find the association between incense burning exposure and children's neurodevelopment.

METHODS

In Taiwan Birth Cohort Study (TBCS), a nationwide representative birth cohort study, children were assessed upon home interview with structured questionnaires upon six and eighteen months old. Multivariate logistic and Cox proportional hazard regression adjusting confounding factors were applied to explore the odds ratio (OR) and hazard ratio (HR) between household incense burning exposure and caregiver-reported neurodevelopment milestones.

RESULTS

In this study, 15,310 term singletons were included, and household incense burning was associated with delay in gross motor neurodevelopment milestone, such as walking with support (Occasional incense burning: OR = 1.26, 95% confidence interval (CI): 1.08 to 1.47, HR = 1.07, 95% CI: 1.03 to 1.11; persistent incense burning: OR = 1.44, 95% CI: 1.22 to 1.69, HR = 1.11, 95% CI: 1.07 to 1.16) and walking steadily (Occasional incense burning: OR = 1.14, 95% CI: 0.98 to 1.32, HR = 1.07, 95% CI: 1.03 to 1.11, persistent incense burning: OR = 1.24, 95% CI: 1.06 to 1.45, HR = 1.09, 95% CI: 1.04 to 1.13).

CONCLUSIONS

Our study suggested household incense burning exposure was associated with delay in gross motor neurodevelopmental milestones. Further research is warranted to elucidate the possible mechanism and causal relationship.

A novel method for source-specific hemoglobin adducts of nitro-polycyclic aromatic hydrocarbons

Polycyclic aromatic hydrocarbons (PAH) are ubiquitous air pollutants associated with negative impacts on growth, development and behavior in children. Source-specific biological markers of PAH exposure are needed for targeting interventions to protect children. Nitro-derivatives of PAH can act as markers of exposure to diesel exhaust, gasoline exhaust, or general combustion sources. Using a novel HPLC-APCI-MS/MS detection method, we examined four hemoglobin (Hb) adducts of nitro-PAH metabolites and the Hb adduct of a benzo[a]pyrene (BaP) metabolite in 22 umbilical cord blood samples. The samples were collected from a birth cohort with comprehensive data on prenatal PAH exposure, including prenatal personal air monitoring and DNA adducts in maternal and umbilical cord blood. Using non-parametric analyses, heat maps, and principal component analysis (PCA), we analyzed the relationship between the five Hb adducts and previous PAH measurements, with each measurement representing a different duration of exposure. We found that Hb adducts derived from several diesel-related nitro-PAHs (2-nitrofluorene and 1-nitropyrene) were significantly correlated (r = 0.77, p ≤ 0.0001) and grouped together in PCA. Nitro-PAH derived Hb adducts were largely unrelated to previously collected measures of exposure to a number of PAH parent compounds. These measures need to be validated in a larger sample.

Combined effects of prenatal exposure to polycyclic aromatic hydrocarbons and material hardship on child ADHD behavior problems

IMPORTANCE

Polycyclic aromatic hydrocarbons (PAH) are carcinogenic and neurotoxic combustion by-products commonly found in urban air. Exposure to PAH is disproportionately high in low income communities of color who also experience chronic economic stress.

OBJECTIVE

In a prospective cohort study in New York City (NYC) we previously found a significant association between prenatal PAH exposure and Attention Deficit Hyperactivity Disorder (ADHD) behavior problems at age 9. Here, we have evaluated the joint effects of prenatal exposure to PAH and prenatal/childhood material hardship on ADHD behavior problems.

MATERIALS AND METHODS

We enrolled nonsmoking African-American and Dominican pregnant women in New York City between 1998 and 2006 and followed their children through 9 years of age. As a biomarker of prenatal PAH exposure, PAH-DNA adducts were measured in maternal blood at delivery and were dichotomized at the limit of detection (to indicate high vs. low exposure). Maternal material hardship (lack of adequate food, housing, utilities, and clothing) was self-reported prenatally and at multiple time points through child age 9. Latent variable analysis identified four distinct patterns of hardship. ADHD behavior problems were assessed using the Conners Parent Rating Scale- Revised. Analyses adjusted for relevant covariates.

RESULTS

Among 351 children in our sample, across all hardship groups, children with high prenatal PAH exposure (high adducts) generally had more symptoms of ADHD (higher scores) compared to those with low PAH exposure. The greatest difference was seen among the children with hardship persisting from pregnancy through childhood. Although the interactions between high PAH exposure and hardship experienced at either period ("persistent" hardship or "any" hardship) were not significant, we observed significant differences in the number of ADHD symptoms between children with high prenatal PAH exposure and either persistent hardship or any hardship compared to the others. These differences were most significant for combined high PAH and persistent hardship: ADHD Index (p < 0.008), DSM-IV Inattentive (p = 0.006), DSM-IV Hyperactive Impulsive problems (p = 0.033), and DSM-IV Index Total (p = 0.009).

CONCLUSION

The present findings add to existing evidence that co-exposure to socioeconomic disadvantage and air pollution in early life significantly increases the risk of adverse neurodevelopmental outcomes. They suggest the need for multifaceted interventions to protect pregnant mothers and their children.

Health, wealth and behavioural change: an exploration of role responsibilities in the wake of epigenetics

The field of epigenetics is leading to new conceptualizations of the role of environmental factors in health and genetic disease. Although more evidence is required, epigenetic mechanisms are being implicated in the link between low socioeconomic status and poor health status. Epigenetic phenomena work in a number of ways: they can be established early in development, transmitted from previous generations and/or responsive to environmental factors. Knowledge about these types of epigenetic traits might therefore allow us to move away from a genetic deterministic perspective, and provide individuals with the opportunity to change their health status. Although this could be equated with patient empowerment, it could also lead to stigmatization and discrimination where individuals are deemed responsible for their health, even if they are not in social situations where they are able to enact change that would alter their health status. In this paper, we will explore the responsibilities of different actors in the healthcare sphere in relation to epigenetics across four different contexts: (1) genetic research, (2) clinical practice, (3) prenatal care and (4) the workplace. Within this exploration of role responsibilities, we will also discuss the potential constraints that might prevent the patient, mother-to-be, research participant or employee, from enacting any necessary steps in order to increase their health status in response to epigenetic information.

Newborn sex-specific transcriptome signatures and gestational exposure to fine particles: findings from the ENVIRONAGE birth cohort

BACKGROUND

Air pollution exposure during pregnancy has been associated with adverse birth outcomes and health problems later in life. We investigated sex-specific transcriptomic responses to gestational long- and short-term exposure to particulate matter with a diameter < 2.5 μm (PM_2.5) in order to elucidate potential underlying mechanisms of action.

METHODS

Whole genome gene expression was investigated in cord blood of 142 mother-newborn pairs that were enrolled in the ENVIRONAGE birth cohort. Daily PM_2.5 exposure levels were calculated for each mother's home address using a spatial-temporal interpolation model in combination with a dispersion model to estimate both long- (annual average before delivery) and short- (last month of pregnancy) term exposure. We explored the association between gene expression levels and PM_2.5 exposure, and identified modulated pathways by overrepresentation analysis and gene set enrichment analysis.

RESULTS

Some processes were altered in both sexes for long- (e.g. DNA damage) or short-term exposure (e.g. olfactory signaling). For long-term exposure in boys neurodevelopment and RhoA pathways were modulated, while in girls defensin expression was down-regulated. For short-term exposure we identified pathways related to synaptic transmission and mitochondrial function (boys) and immune response (girls).

CONCLUSIONS

This is the first whole genome gene expression study in cord blood to identify sex-specific pathways altered by PM_2.5. The identified transcriptome pathways could provide new molecular insights as to the interaction pattern of early life PM_2.5 exposure with the biological development of the fetus.

E3 Ubiquitin Ligases Neurobiological Mechanisms: Development to Degeneration

Cells regularly synthesize new proteins to replace old or damaged proteins. Deposition of various aberrant proteins in specific brain regions leads to neurodegeneration and aging. The cellular protein quality control system develop various defense mechanisms against the accumulation of misfolded and aggregated proteins. The mechanisms underlying the selective recognition of specific crucial protein or misfolded proteins are majorly governed by quality control E3 ubiquitin ligases mediated through ubiquitin-proteasome system. Few known E3 ubiquitin ligases have shown prominent neurodevelopmental functions, but their interactions with different developmental proteins play critical roles in neurodevelopmental disorders. Several questions are yet to be understood properly. How E3 ubiquitin ligases determine the specificity and regulate degradation of a particular substrate involved in neuronal proliferation and differentiation is certainly the one, which needs detailed investigations. Another important question is how neurodevelopmental E3 ubiquitin ligases specifically differentiate between their versatile range of substrates and timing of their functional modulations during different phases of development. The premise of this article is to understand how few E3 ubiquitin ligases sense major molecular events, which are crucial for human brain development from its early embryonic stages to throughout adolescence period. A better understanding of these few E3 ubiquitin ligases and their interactions with other potential proteins will provide invaluable insight into disease mechanisms to approach toward therapeutic interventions.

Environmental PAH exposure and male idiopathic infertility: a review on early life exposures and adult diagnosis

The male reproductive system is acutely and uniquely sensitive to a variety of toxicities, including those induced by environmental pollutants throughout the lifespan. Early life hormonal and morphological development results in several especially sensitive critical windows of toxicity risk associated with lifelong decreased reproductive health and fitness. Male factor infertility can account for over 40% of infertility in couples seeking treatment, and 44% of infertile men are diagnosed with idiopathic male infertility. Human environmental exposures are poorly understood due to limited available data. The latency between maternal and in utero exposure and a diagnosis in adulthood complicates the correlation between environmental exposures and infertility. The results from this review include recommendations for more and region specific monitoring of polycyclic aromatic hydrocarbon (PAH) exposure, longitudinal and clinical cohort considerations of exposure normalization, gene-environment interactions, in utero exposure studies, and controlled mechanistic animal experiments. Additionally, it is recommended that detailed semen analysis and male fertility data be included as endpoints in environmental exposure cohort studies due to the sensitivity of the male reproductive system to environmental pollutants, including PAHs.

Longitudinal effects of prenatal exposure to air pollutants on self-regulatory capacities and social competence

BACKGROUND

We evaluated the influence of prenatal exposure to widespread urban air pollutants on the development of self-regulation and social competence in a longitudinal prospective cohort of children born to nonsmoking minority women in New York City.

METHODS

Air pollutant exposure was estimated categorically by level of polycyclic aromatic hydrocarbon (PAH)-DNA adducts in maternal blood collected at delivery, providing a biomarker of maternal exposure to PAH over a 2- to 3-month period. Deficient emotional self-regulation (DESR) was defined as moderate elevations on three specific scales of the child behavior checklist (anxious/depressed, aggressive behavior, and attention problems). We used generalized estimating equations to assess the influence of prenatal exposure to PAH on DESR in children at 3-5, 7, 9, and 11 years of age, adjusted for gender and race/ethnicity. Next, we assessed the association of prenatal exposure to PAH with social competence, as measured by the social responsiveness scale (SRS), the association of impaired self-regulation with social competence, and whether impairment in self-regulation mediated the association of prenatal exposure to PAH with social competence.

RESULTS

We detected a significant interaction (at p = .05) of exposure with time, in which the developmental trajectory of self-regulatory capacity was delayed in the exposed children. Multiple linear regression revealed a positive association between presence of PAH-DNA adducts and problems with social competence (p < .04), level of dysregulation and problems with social competence (p < .0001), and evidence that self-regulation mediates the association of prenatal exposure to PAH with social competence (p < .0007).

CONCLUSIONS

These data suggest that prenatal exposure to PAH produces long-lasting effects on self-regulatory capacities across early and middle childhood, and that these deficits point to emerging social problems with real-world consequences for high-risk adolescent behaviors in this minority urban cohort.

Transcriptional profiling of the mouse hippocampus supports an NMDAR-mediated neurotoxic mode of action for benzo[a]pyrene

Benzo[a]pyrene (BaP) is a genotoxic carcinogen and a neurotoxicant. The neurotoxicity of BaP is proposed to arise from either genotoxicity leading to neuronal cell death, or perturbed expression of N-methyl-d-aspartate receptor (NMDAR) subunits. To explore these hypotheses, we profiled hippocampal gene expression of adult male Muta(™) Mouse administered 0, 1, 35, or 70 mg BaP/kg bw per day by oral gavage for 3 days. Transcriptional profiles were examined by RNA-sequencing (RNA-seq), DNA microarrays, and real-time quantitative reverse transcription polymerase chain reaction (RT-PCR). BaP-DNA adducts in the cerebellum were quantified by (32) P-post-labeling to measure genotoxicity. RNA-seq revealed altered expression of 0, 260, and 219 genes (P-value < 0.05, fold-change ≥ ± 1.5) following exposure to the low, medium, and high doses, respectively; 54 genes were confirmed by microarrays. Microarray and RT-PCR analysis showed increased expression of NMDAR subunits Grina and Grin2a. In contrast, no effects on DNA-damage response genes were observed despite comparable BaP-DNA adduct levels in the cerebellum and in the lungs and livers of mice at similar BaP doses in previous studies. The results suggest that DNA-damage response does not play a major role in BaP-induced adult neurotoxicity. Meta-analysis revealed that BaP-induced transcriptional profiles are highly correlated with those from the hippocampus of transgenic mice exhibiting similar neurotoxicity outcomes to BaP-exposed mice and rats (i.e., defects in learning and memory). Overall, we suggest that BaP-induced neurotoxicity is more likely to be a consequence of NMDAR perturbation than genotoxicity, and identify other important genes potentially mediating this adverse outcome. Environ. Mol. Mutagen. 57:350-363, 2016. © 2016 Her Majesty the Queen in Right of Canada. Environmental and Molecular Mutagenesis © 2016 Environmental Mutagen Society.

Impact of prenatal polycyclic aromatic hydrocarbon exposure on behavior, cortical gene expression and DNA methylation of the Bdnf gene

Prenatal exposure to polycyclic aromatic hydrocarbons (PAH) has been associated with sustained effects on the brain and behavior in offspring. However, the mechanisms have yet to be determined. We hypothesized that prenatal exposure to ambient PAH in mice would be associated with impaired neurocognition, increased anxiety, altered cortical expression of Bdnf and Grin2b, and greater DNA methylation of Bdnf. Our results indicated that during open-field testing, prenatal PAH exposed offspring spent more time immobile and less time exploring. Females produced more fecal boli. Offspring prenatally exposed to PAH displayed modest reductions in overall exploration of objects. Further, prenatal PAH exposure was associated with lower cortical expression of Grin2b and Bdnf in males, and greater Bdnf IV promoter methylation. Epigenetic differences within the Bdnf IV promoter correlated with Bdnf gene expression, but not with the observed behavioral outcomes, suggesting that additional targets may account for these PAH-associated effects.

Chronic Administration of Benzo(a)pyrene Induces Memory Impairment and Anxiety-Like Behavior and Increases of NR2B DNA Methylation

Background

Recently, an increasing number of human and animal studies have reported that exposure to benzo(a)pyrene (BaP) induces neurological abnormalities and is also associated with adverse effects, such as tumor formation, immunosuppression, teratogenicity, and hormonal disorders. However, the exact mechanisms underlying BaP-induced impairment of neurological function remain unclear. The aim of this study was to examine the regulating mechanisms underlying the impact of chronic BaP exposure on neurobehavioral performance.

Methods

C57BL mice received either BaP in different doses (1.0, 2.5, 6.25 mg/kg) or olive oil twice a week for 90 days. Memory and emotional behaviors were evaluated using Y-maze and open-field tests, respectively. Furthermore, levels of mRNA expression were measured by using qPCR, and DNA methylation of NMDA receptor 2B subunit (NR2B) was examined using bisulfate pyrosequencing in the prefrontal cortex and hippocampus.

Results

Compared to controls, mice that received BaP (2.5, 6.25 mg/kg) showed deficits in short-term memory and an anxiety-like behavior. These behavioral alterations were associated with a down-regulation of the NR2B gene and a concomitant increase in the level of DNA methylation in the NR2B promoter in the two brain regions.

Conclusions

Chronic BaP exposure induces an increase in DNA methylation in the NR2B gene promoter and down-regulates NR2B expression, which may contribute to its neurotoxic effects on behavioral performance. The results suggest that NR2B vulnerability represents a target for environmental toxicants in the brain.

Application of Citizen Science Risk Communication Tools in a Vulnerable Urban Community

A public participatory geographical information systems (PPGIS) demographic, environmental, socioeconomic, health status portal was developed for the Stambaugh-Elwood (SE) community in Columbus, OH. We hypothesized that soil at SE residences would have metal concentrations above natural background levels. Three aims were developed that allowed testing of this hypothesis. Aim 1 focused on establishing partnerships between academia, state agencies and communities to assist in the development of a community voice. Aim 2 was to design and conduct soil sampling for residents of the SE community. Aim 3 was to utilize our interactive, customized portal as a risk communication tool by allowing residents to educate themselves as to the potential risks from industrial sources in close proximity to their community. Multiple comparisons of means were used to determine differences in soil element concentration by sampling location at p < 0.05. The results demonstrated that eight metals (As, Cd, Cu, Pb, Mo, Se, Tl, Zn) occurred at statistically-significantly greater levels than natural background levels, but most were below risk-based residential soil screening levels. Results were conveyed to residents via an educational, risk-communication informational card. This study demonstrates that community-led coalitions in collaboration with academic teams and state agencies can effectively address environmental concerns.

Prenatal exposure to polycyclic aromatic hydrocarbons/aromatics, BDNF and child development

OBJECTIVES

Within a New York City (NYC) birth cohort, we assessed the associations between polycyclic aromatic hydrocarbon (PAH) and other aromatic DNA adducts and brain derived neurotrophic factor (BDNF) concentrations in umbilical cord blood, and neurodevelopment at age 2 years and whether BDNF is a mediator of the associations between PAH/aromatic-DNA adducts and neurodevelopment.

METHODS

PAH/aromatic-DNA adduct concentrations in cord blood were measured in 505 children born to nonsmoking African-American and Dominican women residing in NYC, and a subset was assessed for neurodevelopment at 2 years using the Bayley Scales of Infant Development Mental Development Index (MDI). A spectrum of PAH/aromatic-DNA adducts was measured using the (32)P-postlabeling assay; DNA adducts formed by benzo[a]pyrene (B[a]P), a representative PAH, were measured by High Performance Liquid Chromatography (HPLC)/fluorescence. BDNF mature protein in cord blood plasma was quantified by an ELISA. Multivariate regression analysis, adjusting for potential confounders, was conducted.

RESULTS

PAH/aromatic-DNA adduct concentration measured by postlabeling was inversely associated with BDNF concentration (p=0.02) and with MDI scores at 2 years (p=0.04). BDNF level was positively associated with MDI scores (p=0.003). Restricting to subjects having all three measures (PAH/aromatic-DNA adducts by postlabeling, MDI, and BDNF), results were similar but attenuated (p=0.13, p=0.05, p=0.01, respectively). Associations between B[a]P-DNA adducts and BDNF and B[a]P-DNA adducts and MDI at age 2 years were not significant. At age 3 years, the positive association of BDNF with MDI was not observed.

CONCLUSIONS

The results at age 2 suggest that prenatal exposure to a spectrum of PAH/aromatic pollutants may adversely affect early neurodevelopment, in part by reducing BDNF levels during the fetal period. However, the same relationship was not seen at age 3.

Revealing Behavioral Learning Deficit Phenotypes Subsequent to In Utero Exposure to Benzo(a)pyrene

To characterize behavioral deficits in pre-adolescent offspring exposed in utero to Benzo(a)pyrene [B(a)P], timed-pregnant Long Evans Hooded rats were treated with B(a)P (150, 300, 600, and 1200 µg/kg BW) or peanut oil (vehicle) on E14, 15, 16, and 17. Following birth, during the pre-weaning period, B(a)P metabolites were examined in plasma and whole brain or cerebral cortex from exposed and control offspring. Tissue concentrations of B(a)P metabolites were (1) dose-dependent and (2) followed a time-dependence for elimination with ∼60% reduction by PND5 in the 1200 µg/kg BW experimental group. Spatial discrimination-reversal learning was utilized to evaluate potential behavioral neurotoxicity in P40-P60 offspring. Late-adolescent offspring exposed in utero to 600 and 1200 µg/kg BW were indistinguishable from their control counterparts for ability to acquire an original discrimination (OD) and reach criterion. However, a dose-dependent effect of in utero B(a)P-exposure was evident upon a discrimination reversal as exposed offspring perseverated on the previously correct response. This newly characterized behavioral deficit phenotype for the first reversal was not apparent in either the (1) OD or (2) subsequent reversal sessions relative to the respective control offspring. Furthermore, the expression of activity related-cytoskeletal-associated protein (Arc), an experience-dependent cortical protein marker known to be up-regulated in response to acquisition of a novel behavior, was greater in B(a)P-exposed offspring included in the spatial discrimination cohort versus home cage controls. Collectively, these findings support the hypothesis that in utero exposure to B(a)P during critical windows of development representing peak periods of neurogenesis results in behavioral deficits in later life.

Altered expression of histone deacetylases, inflammatory cytokines and contractile-associated factors in uterine myometrium of Long Evans rats gestationally exposed to benzo[a]pyrene

Etiology of preterm birth (PTB) is multifactorial; therefore, decreasing the incidence of PTB is a major challenge in the field of obstetrics. Epidemiological studies have reported an association between toxicants and PTB. However, there are no studies on the role of benzo[a]pyrene (BaP), an environmental toxicant, in the incidence of PTB. We first assessed the effects of BaP (150 and 300 µg kg(-1) body weight) dosed via gavage from day 14 to 17 of pregnancy on gestation length in Long Evans rats. We further assessed the histopathology of the uterus, expression of inflammatory cytokines, contractile-associated factors, histone deacetylases (HDACs) and NFқB-p65 in myometrium collected on day 22 postpartum versus vehicle-treated controls. In our study, rats exposed to BaP delivered prematurely (P < 0.05) compared to control. Hematoxylin and eosin staining of uterus showed squamous metaplasia, glandular and stromal hyperplasia in BaP-exposed rats versus control. The concentrations of BaP metabolites measured by high-pressure liquid chromatography were higher in uterine myometrium of BaP-exposed rats while they were undetectable in controls. Quantitative real-time polymerase chain reaction showed significant increases in mRNA expression of interleukin-1β and -8, tumor necrosis factor-α, connexin 43, cyclo-oxygenase-2 and prostaglandin F2α receptor as compared to controls (P < 0.05). Western blot analysis revealed that BaP exposure caused decreases in class I HDACs 1 and 3 and increases in class II HDAC 5, cyclo-oxygenase-2 and nuclear translocation of NFκB-p65 relative to controls. Our results suggest that gestational exposure to BaP increases incidence of PTB through epigenetic changes that causes increases in the expression of contractile-associated factors through the NFκB pathway. Copyright © 2015 John Wiley & Sons, Ltd.

Effects of prenatal exposure to air pollutants (polycyclic aromatic hydrocarbons) on the development of brain white matter, cognition, and behavior in later childhood

IMPORTANCE

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous and neurotoxic environmental contaminants. Prenatal PAH exposure is associated with subsequent cognitive and behavioral disturbances in childhood.

OBJECTIVES

To identify the effects of prenatal PAH exposure on brain structure and to assess the cognitive and behavioral correlates of those abnormalities in school-age children.

DESIGN, SETTING, AND PARTICIPANTS

Cross-sectional imaging study in a representative community-based cohort followed up prospectively from the fetal period to ages 7 to 9 years. The setting was urban community residences and an academic imaging center. Participants included a sample of 40 minority urban youth born to Latina (Dominican) or African American women. They were recruited between February 2, 1998, and March 17, 2006.

MAIN OUTCOMES AND MEASURES

Morphological measures that index local volumes of the surface of the brain and of the white matter surface after cortical gray matter was removed.

RESULTS

We detected a dose-response relationship between increased prenatal PAH exposure (measured in the third trimester but thought to index exposure for all of gestation) and reductions of the white matter surface in later childhood that were confined almost exclusively to the left hemisphere of the brain and that involved almost its entire surface. Reduced left hemisphere white matter was associated with slower information processing speed during intelligence testing and with more severe externalizing behavioral problems, including attention-deficit/hyperactivity disorder symptoms and conduct disorder problems. The magnitude of left hemisphere white matter disturbances mediated the significant association of PAH exposure with slower processing speed. In addition, measures of postnatal PAH exposure correlated with white matter surface measures in dorsal prefrontal regions bilaterally when controlling for prenatal PAH.

CONCLUSIONS AND RELEVANCE

Our findings suggest that prenatal exposure to PAH air pollutants contributes to slower processing speed, attention-deficit/hyperactivity disorder symptoms, and externalizing problems in urban youth by disrupting the development of left hemisphere white matter, whereas postnatal PAH exposure contributes to additional disturbances in the development of white matter in dorsal prefrontal regions.

Combined effects of prenatal polycyclic aromatic hydrocarbons and material hardship on child IQ

IMPORTANCE

Polycyclic aromatic hydrocarbons are common carcinogenic and neurotoxic urban air pollutants. Toxic exposures, including air pollution, are disproportionately high in communities of color and frequently co-occur with chronic economic deprivation.

OBJECTIVES

We examined whether the association between child IQ and prenatal exposure to polycyclic aromatic hydrocarbons differed between groups of children whose mothers reported high vs. low material hardship during their pregnancy and through child age 5. We tested statistical interactions between hardships and polycyclic aromatic hydrocarbons, as measured by DNA adducts in cord blood, to determine whether material hardship exacerbated the association between adducts and IQ scores.

DESIGN

Prospective cohort. Participants were recruited from 1998 to 2006 and followed from gestation through age 7 years.

SETTING

Urban community (New York City)

PARTICIPANTS

A community-based sample of 276 minority urban youth EXPOSURE MEASURE: Polycyclic aromatic hydrocarbon-DNA adducts in cord blood as an individual biomarker of prenatal polycyclic aromatic hydrocarbon exposure. Maternal material hardship self-reported prenatally and at multiple timepoints through early childhood.

MAIN OUTCOME MEASURE

Child IQ at 7 years assessed using the Wechsler Intelligence Scale for Children.

RESULTS

Significant inverse effects of high cord PAH-DNA adducts on full scale IQ, perceptual reasoning and working memory scores were observed in the groups whose mothers reported a high level of material hardship during pregnancy or recurring high hardship into the child's early years, and not in those without reported high hardship. Significant interactions were observed between high cord adducts and prenatal hardship on working memory scores (β = -8.07, 95% CI (-14.48, -1.66)) and between high cord adducts and recurrent material hardship (β = -9.82, 95% CI (-16.22, -3.42)).

CONCLUSION

The findings add to other evidence that socioeconomic disadvantage can increase the adverse effects of toxic physical "stressors" like air pollutants. Observed associations between high cord adducts and reduced IQ were significant only among the group of children whose mothers reported high material hardship. These results indicate the need for a multifaceted approach to prevention.

Polycyclic aromatic hydrocarbons and childhood asthma

Asthma is the most common chronic illness in children living in developed countries and the leading cause of childhood hospitalization and school absenteeism. Prevalence rates of asthma are increasing and show disparities across gender, geographic regions, and ethnic/racial groups. Common risk factors for developing childhood asthma include exposure to tobacco smoke, previous allergic reactions, a family history of asthma, allergic rhinitis or eczema, living in an urban environment, obesity and lack of physical exercise, severe lower respiratory tract infections, and male gender. Asthma exacerbation in children can be triggered by a variety of factors, including allergens (e.g., pollen, dust mites, and animal dander), viral and bacterial infections, exercise, and exposure to airway irritants. Recent studies have shown that exposure to polycyclic aromatic hydrocarbons (PAHs), a major component of fine particulate matter from combustion sources, is also associated with onset of asthma, and increasing asthmatic symptoms. In this paper, we review sources of childhood PAH exposure and the association between airborne PAH exposure and childhood asthma prevalence and exacerbation.

Early-life exposure to polycyclic aromatic hydrocarbons and ADHD behavior problems

Importance

Polycyclic aromatic hydrocarbons are widespread urban air pollutants from combustion of fossil fuel and other organic material shown previously to be neurotoxic.

Objective

In a prospective cohort study, we evaluated the relationship between Attention Deficit Hyperactivity Disorder behavior problems and prenatal polycyclic aromatic hydrocarbon exposure, adjusting for postnatal exposure.

Materials and Methods

Children of nonsmoking African-American and Dominican women in New York City were followed from in utero to 9 years. Prenatal polycyclic aromatic hydrocarbon exposure was estimated by levels of polycyclic aromatic hydrocarbon- DNA adducts in maternal and cord blood collected at delivery. Postnatal exposure was estimated by the concentration of urinary polycyclic aromatic hydrocarbon metabolites at ages 3 or 5. Attention Deficit Hyperactivity Disorder behavior problems were assessed using the Child Behavior Checklist and the Conners Parent Rating Scale- Revised.

Results

High prenatal adduct exposure, measured by elevated maternal adducts was significantly associated with all Conners Parent Rating Scale-Revised subscales when the raw scores were analyzed continuously (N = 233). After dichotomizing at the threshold for moderately to markedly atypical symptoms, high maternal adducts were significantly associated with the Conners Parent Rating Scale-Revised DSM-IV Inattentive (OR = 5.06, 95% CI [1.43, 17.93]) and DSM-IV Total (OR = 3.37, 95% CI [1.10, 10.34]) subscales. High maternal adducts were positivity associated with the DSM-oriented Attention Deficit/Hyperactivity Problems scale on the Child Behavior Checklist, albeit not significant. In the smaller sample with cord adducts, the associations between outcomes and high cord adduct exposure were not statistically significant (N = 162).

Conclusion

The results suggest that exposure to polycyclic aromatic hydrocarbons encountered in New York City air may play a role in childhood Attention Deficit Hyperactivity Disorder behavior problems.

The melatonin analog 5-MCA-NAT increases endogenous dopamine levels by binding NRH:quinone reductase enzyme in the developing chick retina

NRH:quinone reductase (QR2) is present in the retinas of embryonic and post-hatched (PH) chicks. 5-Methoxycarbonylamino-N-acetyltryptamine (5-MCA-NAT) is a QR2 ligand that increases cAMP levels in developing retinas, but it does not affect cAMP levels in CHO-QR2 cells. The dopamine quinone reductase activity of QR2 retrieves dopamine, which increases cAMP levels in developing retinas. The objective of the present study was to investigate whether 5-MCA-NAT increases endogenous dopamine levels in retinas from chick embryos and post-hatched chicks. Endogenous dopamine was measured by enzyme-linked immunosorbent assay (ELISA). 5-MCA-NAT increased retinal endogenous dopamine levels at all developmental stages studied and in PH chicks (-logEC50=11.62±0.34 M). This effect was inhibited by non-selective antagonists of receptors and melatonin binding sites N-acetyl-2-benzyltryptamine (luzindole, 5 μM), but it was not inhibited by the Mel1b melatonin receptor antagonist 4-phenyl-2-propionamidotetralin (4-P-PDOT, 10 nM). The QR2 cosubstrate, N-methyl-dihydronicotinamide (NMH) (-logEC50=6.74±0.26 M), increased endogenous dopamine levels in controls and in retinas stimulated with 5-MCA-NAT (3 nM). The QR2 inhibitor benzo[e]pyrene inhibited endogenous dopamine levels in both control (-logIC50=7.4±0.28 M) and NMH-stimulated (at 100 nM and 1 μM benzo[e]pyrene concentrations) retinas. Theoretical studies using Molegro Virtual Docking software corroborated these experimental results. We conclude that 5-MCA-NAT increases the level of endogenous dopamine via QR2. We suggest that this enzyme triggers double reduction of the dopamine quinone, recovering dopamine in retinal development.

Short-term effects of a perinatal exposure to a 16 polycyclic aromatic hydrocarbon mixture in rats: assessment of early motor and sensorial development and cerebral cytochrome oxidase activity in pups

Humans are exposed to polycyclic aromatic hydrocarbons (PAHs), a family of ubiquitous neurotoxic pollutants, mainly through ingestion of contaminated food. Developing organisms can be exposed also to PAHs due to the ability of these compounds to pass through the placental barrier as well as through the breast milk. Previous animal studies have reported that the exposure of rats to a 16 PAH mixture at environmental doses strictly limited to gestation did not induce any long-lasting consequences, whereas gestational and lactational PAH exposure induced long-term behavioral and cerebral metabolic effects. In the present study, short-term effects of exposures to the same PAH mixture during gestation, or during gestation and lactation, were assessed by evaluating motor and sensory development of rat pups, and by measuring cerebral cytochrome oxidase activity (a marker of energetic metabolism) in different brain areas. Brain levels of PAHs and some monohydroxylated metabolites were also evaluated in pups at birth and at 21 days of postnatal life. No significant short-term modifications of behavioral development and of cerebral metabolism were observed following an early PAH exposure whatever the dose and the period of exposure. Surprisingly, the same brain levels of concentration of PAHs and metabolites were observed in control and exposed pups in both studies. These analytical results raise the difficulty in overcoming environmental contamination of control animals and the choice of such controls in experimental studies which focus on neurotoxicity of exposure to low levels of pollutants.

Effects of tobacco smoke on PC12 cell neurodifferentiation are distinct from those of nicotine or benzo[a]pyrene

Although nicotine accounts for a great deal of the neurodevelopmental damage associated with maternal smoking or second-hand exposure, tobacco smoke contains thousands of potentially neurotoxic compounds. We used PC12 cells, a standard in vitro model of neurodifferentiation, to compare tobacco smoke extract (TSE) to nicotine, matching TSE exposure (with its inherent nicotine content) to parallel concentrations of nicotine, or to benzo[a]pyrene, a tobacco combustion product. TSE promoted the transition from cell replication to differentiation, resulting in fewer, but larger cells with greater neurite extension. TSE also biased differentiation into the dopaminergic versus the cholinergic phenotype, evidenced by an increase in tyrosine hydroxylase activity but not choline acetyltransferase. Nicotine likewise promoted differentiation at the expense of cell numbers, but its effect on growth and neurite extension was smaller than that of TSE; furthermore, nicotine did not promote the dopaminergic phenotype. Benzo[a]pyrene had effects opposite to those of TSE, retarding neurodifferentiation, which resulted in higher cell numbers, smaller cells, reduced neurite information, and impaired emergence of both dopaminergic and cholinergic phenotypes. Our studies show that the complex mixture of compounds in tobacco smoke exerts direct effects on neural cell replication and differentiation that resemble those of nicotine in some ways but not others, and most importantly, that are greater in magnitude than can be accounted for from just the nicotine content of TSE. Thus, fetal tobacco smoke exposure, including lower levels associated with second-hand smoke, could be more injurious than would be anticipated from measured levels of nicotine or its metabolites.

Maternal lifestyle and environmental risk factors for autism spectrum disorders

BACKGROUND

Over the past 10 years, research into environmental risk factors for autism has grown dramatically, bringing evidence that an array of non-genetic factors acting during the prenatal period may influence neurodevelopment.

METHODS

This paper reviews the evidence on modifiable preconception and/or prenatal factors that have been associated, in some studies, with autism spectrum disorder (ASD), including nutrition, substance use and exposure to environmental agents. This review is restricted to human studies with at least 50 cases of ASD, having a valid comparison group, conducted within the past decade and focusing on maternal lifestyle or environmental chemicals.

RESULTS

Higher maternal intake of certain nutrients and supplements has been associated with reduction in ASD risk, with the strongest evidence for periconceptional folic acid supplements. Although many investigations have suggested no impact of maternal smoking and alcohol use on ASD, more rigorous exposure assessment is needed. A number of studies have demonstrated significant increases in ASD risk with estimated exposure to air pollution during the prenatal period, particularly for heavy metals and particulate matter. Little research has assessed other persistent and non-persistent organic pollutants in association with ASD specifically.

CONCLUSIONS

More work is needed to examine fats, vitamins and other maternal nutrients, as well as endocrine-disrupting chemicals and pesticides, in association with ASD, given sound biological plausibility and evidence regarding other neurodevelopmental deficits. The field can be advanced by large-scale epidemiological studies, attention to critical aetiological windows and how these vary by exposure, and use of biomarkers and other means to understand underlying mechanisms.