Whether fetal neurodevelopment is disrupted by traffic-related air pollution is uncertain. Animal studies suggest that chemical and non-chemical stressors interact to impact neurodevelopment, and that this association is further modified by sex.

Chronic lithium treatment stimulates adult hippocampal neurogenesis, but whether increased neurogenesis contributes to its therapeutic mechanism remains unclear. We use a genetic model of neural progenitor cell (NPC) ablation to test whether a lithium-sensitive behavior requires hippocampal neurogenesis. NPC-ablated mice were treated with lithium and assessed in the forced swim test (FST). Lithium reduced time immobile in the FST in NPC-ablated and control mice but had no effect on activity in the open field, a control for the locomotion-based FST. These findings show that hippocampal NPCs that proliferate in response to chronic lithium are not necessary for the behavioral response to lithium in the FST. We further show that 4-6 week old immature hippocampal neurons are not required for this response. These data suggest that increased hippocampal neurogenesis does not contribute to the response to lithium in the forced swim test and may not be an essential component of its therapeutic mechanism.

Lithium (Li) is a potent mood stabilizer and displays neuroprotective and neurogenic properties. Despite extensive investigations, the mechanisms of action have not been fully elucidated, especially in the juvenile, developing brain. Here we characterized lithium distribution in the juvenile mouse brain during 28 days of continuous treatment that result in clinically relevant serum concentrations. By using Time-of-Flight Secondary Ion Mass Spectrometry- (ToF-SIMS) based imaging we were able to delineate temporospatial lithium profile throughout the brain and concurrent distribution of endogenous lipids with high chemical specificity and spatial resolution. We found that Li accumulated in neurogenic regions and investigated the effects on hippocampal neurogenesis. Lithium increased proliferation, as judged by Ki67-immunoreactivity, but did not alter the number of doublecortin-positive neuroblasts at the end of the treatment period. Moreover, ToF-SIMS revealed a steady depletion of sphingomyelin in white matter regions during 28d Li-treatment, particularly in the olfactory bulb. In contrast, cortical levels of cholesterol and choline increased over time in Li-treated mice. This is the first study describing ToF-SIMS imaging for probing the brain-wide accumulation of supplemented Li in situ. The findings demonstrate that this technique is a powerful approach for investigating the distribution and effects of neuroprotective agents in the brain.

Genetic and environmental factors contribute to the etiologies of autism spectrum disorder (ASD), but evidence of specific environmental exposures and susceptibility windows is limited. Here we study monozygotic and dizygotic twins discordant for ASD to test whether fetal and postnatal metal dysregulation increases ASD risk. Using validated tooth-matrix biomarkers, we estimate pre- and post-natal exposure profiles of essential and toxic elements. Significant divergences are apparent in metal uptake between ASD cases and their control siblings, but only during discrete developmental periods. Cases have reduced uptake of essential elements manganese and zinc, and higher uptake of the neurotoxin lead. Manganese and lead are also correlated with ASD severity and autistic traits. Our study suggests that metal toxicant uptake and essential element deficiency during specific developmental windows increases ASD risk and severity, supporting the hypothesis of systemic elemental dysregulation in ASD. Independent replication in population-based studies is needed to extend these findings.

Endocrine disruption from environmental contaminants has been linked to a broad spectrum of adverse outcomes. One concern about endocrine-disrupting xenobiotics is the potential for additive or synergistic (i.e., greater-than-additive) effects of mixtures. A short-term dosing model to examine the effects of environmental mixtures on thyroid homeostasis has been developed. Prototypic thyroid-disrupting chemicals (TDCs) such as dioxins, polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers have been shown to alter thyroid hormone homeostasis in this model primarily by up-regulating hepatic catabolism of thyroid hormones via at least two mechanisms. Our present effort tested the hypothesis that a mixture of TDCs will affect serum total thyroxine (T4) concentrations in a dose-additive manner. Young female Long-Evans rats were dosed via gavage with 18 different polyhalogenated aromatic hydrocarbons [2 dioxins, 4 dibenzofurans, and 12 PCBs, including dioxin-like and non-dioxin-like PCBs] for 4 consecutive days. Serum total T4 was measured via radioimmunoassay in samples collected 24 hr after the last dose. Extensive dose-response functions (based on seven to nine doses per chemical) were determined for individual chemicals. A mixture was custom synthesized with the ratio of chemicals based on environmental concentrations. Serial dilutions of this mixture ranged from approximately background levels to 100-fold greater than background human daily intakes. Six serial dilutions of the mixture were tested in the same 4-day assay. Doses of individual chemicals that were associated with a 30% TH decrease from control (ED30), as well as predicted mixture outcomes were calculated using a flexible single-chemical-required method applicable to chemicals with differing dose thresholds and maximum-effect asymptotes. The single-chemical data were modeled without and with the mixture data to determine, respectively, the expected mixture response (the additivity model) and the experimentally observed mixture response (the empirical model). A likelihood-ratio test revealed statistically significant departure from dose additivity. There was no deviation from additivity at the lowest doses of the mixture, but there was a greater-than-additive effect at the three highest mixtures doses. At high doses the additivity model underpredicted the empirical effects by 2- to 3-fold. These are the first results to suggest dose-dependent additivity and synergism in TDCs that may act via different mechanisms in a complex mixture. The results imply that cumulative risk approaches be considered when assessing the risk of exposure to chemical mixtures that contain TDCs.

Deficiencies and excess of essential elements and toxic metals are implicated in amyotrophic lateral sclerosis (ALS), but the age when metal dysregulation appears remains unknown. This study aims to determine whether metal uptake is dysregulated during childhood in individuals eventually diagnosed with ALS.

Early life stress negatively impacts brain development and affects structure and function of parvalbumin immunopositive (PV+) inhibitory neurons. Main regulators of PV+ interneurons activity and plasticity are perineuronal nets (PNNs), an extracellular matrix formation that enwraps PV+ interneurons mainly in the neocortex and hippocampus. To experimentally address the impact of early life stress on the PNNs and PV+ interneurons in the medial prefrontal cortex and dorsal hippocampus in rats, we employed a 24 h maternal deprivation protocol. We show that maternal deprivation in the medial prefrontal cortex of adult rats caused a decrease in density of overall PNNs and PNNs that enwrap PV+ interneurons in the rostral cingulate cortex. Furthermore, a staining intensity decrease of overall PNNs and PNN+/PV+ cells was found in the prelimbic cortex. Finally, a decrease in both intensity and density of overall PNNs and PNNs surrounding PV+ cells was observed in the infralimbic cortex, together with increase in the intensity of VGAT inhibitory puncta. Surprisingly, maternal deprivation did not cause any changes in the density of PV+ interneurons in the mPFC, neither had it affected PNNs and PV+ interneurons in the hippocampus. Taken together, our findings indicate that PNNs, specifically the ones enwrapping PV+ interneurons in the medial prefrontal cortex, are affected by early life stress.

Humans are continuously exposed to chemicals with suspected or proven endocrine disrupting chemicals (EDCs). Risk management of EDCs presents a major unmet challenge because the available data for adverse health effects are generated by examining one compound at a time, whereas real-life exposures are to mixtures of chemicals. In this work, we integrate epidemiological and experimental evidence toward a whole mixture strategy for risk assessment. To illustrate, we conduct the following four steps in a case study: (1) identification of single EDCs ("bad actors")-measured in prenatal blood/urine in the SELMA study-that are associated with a shorter anogenital distance (AGD) in baby boys; (2) definition and construction of a "typical" mixture consisting of the "bad actors" identified in Step 1; (3) experimentally testing this mixture in an in vivo animal model to estimate a dose-response relationship and determine a point of departure (i.e., reference dose [RfD]) associated with an adverse health outcome; and (4) use a statistical measure of "sufficient similarity" to compare the experimental RfD (from Step 3) to the exposure measured in the human population and generate a "similar mixture risk indicator" (SMRI). The objective of this exercise is to generate a proof of concept for the systematic integration of epidemiological and experimental evidence with mixture risk assessment strategies. Using a whole mixture approach, we could find a higher rate of pregnant women under risk (13%) when comparing with the data from more traditional models of additivity (3%), or a compound-by-compound strategy (1.6%).

Aims: The authors sought to examine associations between urinary exosomal miRNAs (exo-miRs), emerging biomarkers of renal health, and cardiorenal outcomes in early childhood. Materials & methods: The authors extracted exo-miRs in urine from 88 healthy Mexican children aged 4-6 years. The authors measured associations between 193 exo-miRs and cardiorenal outcomes: systolic/diastolic blood pressure, estimated glomerular filtration rate and urinary sodium and potassium levels. The authors adjusted for age, sex, BMI, socioeconomic status, indoor tobacco smoke exposure and urine specific gravity. Results: Multiple exo-miRs were identified meeting a false discovery rate threshold of q < 0.1. Specifically, three exo-miRs had increased expression with urinary sodium, 17 with urinary sodium-to-potassium ratio and one with decreased estimated glomerular filtration rate. Conclusions: These results highlight urinary exo-miRs as early-life biomarkers of children's cardiorenal health.

Per- and poly-fluoroalkyl substances (PFAS) are chemicals, detected in 95% of Americans, that induce osteotoxicity and modulate hormones, thereby influencing bone health. Previous studies found associations between individual PFAS and bone mineral density in adults but did not analyze their combined effects.

Prenatal exposure to metals has been associated with a range of adverse neurocognitive outcomes; however, associations with early behavioral development are less well understood. We examined joint exposure to multiple co-occurring metals in relation to infant negative affect, a stable temperamental trait linked to psychopathology among children and adults.

Prenatal exposure to a mixture (MIX N) of eight endocrine-disrupting chemicals has been associated with language delay in children in a Swedish pregnancy cohort. A novel approach was proposed linking this epidemiological association with experimental evidence, where the effect of MIX N on thyroid hormone signaling was assessed using the Xenopus eleuthero-embryonic thyroid assay (XETA OECD TG248). From this experimental data, a point of departure (PoD) was derived based on OECD guidance. Our aim in the current study was to use updated toxicokinetic models to compare exposures of women of reproductive age in the US population to MIX N using a Similar Mixture Approach (SMACH). Based on our findings, 66% of women of reproductive age in the US (roughly 38 million women) had exposures sufficiently similar to MIX N. For this subset, a Similar Mixture Risk Index (SMRIHI) was calculated comparing their exposures to the PoD. Women with SMRIHI > 1 represent 1.1 million women of reproductive age. Older women, Mexican American and other/multi race women were less likely to have high SMRIHI values compared to Non-Hispanic White women. These findings indicate that a reference mixture of chemicals identified in a Swedish cohort-and tested in an experimental model for establishment of (PoDs)-is also of health relevance in a US population.

Emerging research suggests that exposures to metals during pregnancy and gut microbiome (GM) disruptions are associated with depressive disorders in childhood. Akkermansia muciniphila, a GM bacteria, has been studied for its potential antidepressant effects. However, its role in the influence of prenatal metal exposures on depressive symptoms during childhood is unknown. Leveraging a well-characterized pediatric longitudinal birth cohort and its microbiome substudy (n=112) and using a state-of-the-art machine-learning model, we investigated whether the presence of A.muciniphila in GM of 9-11-year-olds modifies the associations between exposure to a specific group of metals (or metal-clique) during pregnancy and concurrent childhood depressive symptoms. Among children with no A.muciniphila, a metal-clique of Zinc-Chromium-Cobalt was strongly associated with increased depression score (P<0.0001), whereas, for children with A.muciniphila, this same metal-clique was weakly associated with decreased depression score(P<0.4). Our analysis provides the first exploratory evidence hypothesizing A. muciniphila as a probiotic intervention attenuating the effect of prenatal metal-exposures-associated depressive disorders in late childhood.

Environmental factors or socioeconomic status variables used in regression models to explain environmental chemical exposures or health outcomes are often in practice modeled at the same buffer distance or spatial scale. In this paper, we present four model selection algorithms that select the best spatial scale for each buffer-based or area-level covariate. Contamination of drinking water by nitrate is a growing problem in agricultural areas of the United States, as ingested nitrate can lead to the endogenous formation of N-nitroso compounds, which are potent carcinogens. We applied our methods to model nitrate levels in private wells in Iowa. We found that environmental variables were selected at different spatial scales and that a model allowing spatial scale to vary across covariates provided the best goodness of fit. Our methods can be applied to investigate the association between environmental risk factors available at multiple spatial scales or buffer distances and measures of disease, including cancers.

Laterality is a basic characteristic of the brain which is detectable early in life. Although early experiences affect laterality of the mature brain, there are no reports on their immediate neurochemical effects during neonatal life, which could provide evidence as to the mechanisms leading to the lateralized brain. In order to address this issue, we determined the differential protein expression profile of the left and right hippocampus of 13-day-old rat control (CTR) pups, as well as following exposure to an early experience involving either receipt (RER) or denial (DER) of the expected reward of maternal contact. Proteomic analysis was performed by 2-dimensional polyacrylamide gel electrophoresis (PAGE) followed by mass spectroscopy. The majority of proteins found to be differentially expressed either between the three experimental groups (DER, RER, CTR) or between the left and right hemisphere were cytoskeletal (34%), enzymes of energy metabolism (32%), and heat shock proteins (17%). In all three groups more proteins were up-regulated in the left compared to the right hippocampus. Tubulins were found to be most often up-regulated, always in the left hippocampus. The differential expression of β-tubulin, β-actin, dihydropyrimidinase like protein 1, glial fibrillary acidic protein (GFAP) and Heat Shock protein 70 revealed by the proteomic analysis was in general confirmed by Western blots. Exposure to the early experience affected brain asymmetry: In the RER pups the ratio of proteins up-regulated in the left hippocampus to those in the right was 1.8, while the respective ratio was 3.6 in the CTR and 3.4 in the DER. Our results could contribute to the elucidation of the cellular mechanisms mediating the effects of early experiences on the vulnerability for psychopathology, since proteins shown in our study to be differentially expressed (e.g. tubulins, dihydropyrimidinase like proteins, 14-3-3 protein, GFAP, ATP synthase, α-internexin) have also been identified in proteomic analyses of post-mortem brains from psychiatric patients.

Residential proximity to ferroalloy production has been associated with increased manganese exposure, which can adversely affect health, particularly among children. Little is known, however, about which environmental samples contribute most to internal levels of manganese and other ferroalloy metals. We aimed to characterize sources of exposure to metals and evaluate the ability of internal biomarkers to reflect exposures from environmental media. In 717 Italian adolescents residing near ferromanganese industry, we examined associations between manganese, lead, chromium, and copper in environmental samples (airborne particles, surface soil, indoor/outdoor house dust) and biological samples (blood, hair, nails, saliva, urine). In multivariable regression analyses adjusted for child age and sex, a 10% increase in soil Mn was associated with increases of 3.0% (95% CI: 1.1%, 4.9%) in nail Mn and 1.6% (95% CI: -0.2%, 3.4%) in saliva Mn. Weighted-quantile-sum (WQS) regression estimated that higher soil and outdoor dust Mn accounted for most of the effect on nail Mn (WQS weights: 0.61 and 0.22, respectively, out of a total of 1.0). Higher air and soil Mn accounted for most of the effect on saliva Mn (WQS weights: 0.65 and 0.29, respectively). These findings can help inform biomarker selection in future epidemiologic studies and guide intervention strategies in exposed populations.

Fluoride from environmental sources accumulates preferentially in the pineal gland which produces melatonin, the hormone that regulates the sleep-wake cycle. However, the effects of fluoride on sleep regulation remain unknown. This population-based study examined whether chronic low-level fluoride exposure is associated with sleep patterns and daytime sleepiness among older adolescents in the United States (US).

Exposure to maternal stress in utero negatively impacts cognitive and behavioral outcomes of children born at term. The neonatal intensive care unit (NICU) can be stressful for preterm infants during a developmental period corresponding to the third trimester of gestation. It is unknown whether stress in the NICU contributes to adverse neurodevelopment among NICU graduates. The aim was to examine the association between salivary cortisol and early neurodevelopment in preterm infants.

Prenatal exposure to arsenic (As), cadmium (Cd), mercury (Hg), and lead (Pb) may be nephrotoxic, yet limited studies have examined subclinical kidney injury biomarkers in children. We assessed whether metal exposure in the second trimester (2T), a crucial time of kidney development, is associated with altered urine kidney injury and function biomarkers in preadolescent children. Analyses included 494 children participating in a birth cohort study in Mexico City. Concentrations of As, Cd, and Pb were measured from pregnant women in 2T blood and urine, and Hg in urine only. Kidney biomarkers were measured from children in urine at age 8-12 years. We assessed the associations between individual metals and (1) kidney biomarkers using linear regression and (2) a multi-protein kidney mixture using weighted quantile sum (WQS) regression. Associations of separate urine and blood metal mixtures with individual kidney biomarkers were assessed via WQS. Within the multi-protein mixture, the association with increased urinary As was predominated by urine alpha-1-microglobulin (A1M), interferon gamma-induced protein 10 (IP10), and fatty acid binding protein 1; the association with increased urinary Cd was predominated by A1M, clusterin, and albumin. The urine metal mixture was associated with increased albumin (0.23 ng/mL; 95% confidence interval (CI): 0.10, 0.37), IP10 (0.15 ng/mL; 95% CI: 0.02, 0.28), and cystatin C (0.17 ng/mL; 95% CI: 0.04, 0.31); these associations were mainly driven by urinary As and Cd. We observed null associations between prenatal blood or urine metal mixtures and estimated glomerular filtration rate. Higher prenatal urinary metals, individually and as a mixture were associated with altered kidney injury biomarkers in children. Further research and longer participant follow-up are required to ascertain the risk of kidney disease later in life.

Dezocine is an opioid that was used in clinical practice for acute pain management in the US (1986 to 2011) and is currently in use in China. It is not listed as a controlled substance in the US due to no reported cases of addiction. Dezocine is a partial agonist at the mu opioid receptor (MOR); however, it is unclear whether dezocine can activate both the G protein pathway and the beta-arrestin pathway. In this study we hypothesized that dezocine does not activate the beta-arrestin pathway, which could be the potential molecular mechanism by which dezocine is not addictive or at least less addictive than other classic opioids. Both morphine, a MOR full agonist and buprenorphine, a partial MOR agonist similar to dezocine, were used for comparison purposes. The major side effects of dezocine in clinical usage are its gastrointestinal side effects and first pass effects; therefore, we explored the possibility of administering dezocine intranasally in rodents to demonstrate the feasibility of intranasal administration for new clinical usage purposes. With proper formulation it is possible to administer dezocine intranasally to achieve a high concentration in the brain in the rodent model. The results indicate that dezocine does not activate the beta-arrestin pathway in MOR. Intranasal delivery of dezocine achieves a much higher medication concentration in the blood and brain as compared to intraperitoneal injection. It also persists a longer time before it falls below detection in the blood. This study provides a possible explanation of why dezocine is not addictive or at least less addictive than other commonly used opioids. This study also demonstrates that intranasal administration offers an alternative strategy for its potential clinical applications.