Prenatal Pb Exposure Research Articles

Cross-sectional and prospective associations of early childhood circulating metals with early and mid-childhood cognition in the Project Viva cohort

BackgroundRelatively little is known about the immediate and prospective neurodevelopmental impacts of joint exposure to multiple metals (i.e., metal mixtures) in early childhood. ObjectivesTo estimate associations of early childhood (∼3 years of age) blood metal concentrations with cognitive test scores at early and mid-childhood (∼8 years of age). MethodsWe studied children from the Project Viva cohort. We measured erythrocyte concentrations of seven essential (Co, Cu, Mg, Mn, Mo, Se, and Zn) and eight non-essential metals (As, Ba, Cd, Cs, Hg, Pb, Sn, and Sr) in early childhood blood samples. Trained research assistants administered cognitive tests assessing vocabulary, visual-motor ability, memory, and general intelligence (standard deviations: ∼10 points), in early and mid-childhood. We employed multivariable linear regression to examine associations of individual metals with test scores adjusting for confounders, other concurrently measured metals, and first-trimester maternal blood metals. We also estimated joint associations and explored interaction between metals in mixture analyses. ResultsWe analyzed 349 children (median whole blood Pb ∼1 μg/dL). In cross-sectional analyses, each doubling of Pb was associated with lower visual-motor function (mean difference: −2.43 points, 95% confidence interval (CI): −4.01, −0.86) and receptive vocabulary, i.e., words understood (−1.45 points, 95% CI: −3.26, 0.36). Associations of Pb with mid-childhood cognition were weaker and less precise by comparison. Mg was positively associated with cognition in cross-sectional but not prospective analyses, and cross-sectional associations were attenuated in a sensitivity analysis removing adjustment for concurrent metals. We did not observe joint associations nor interactions. DiscussionIn this cohort with low blood Pb levels, increased blood Pb was robustly associated with lower cognitive ability in cross-sectional analyses, even after adjustment for prenatal Pb exposure, and regardless of adjustment for metal co-exposures. However, associations with mid-childhood cognition were attenuated and imprecise, suggesting some buffering of Pb neurotoxicity in early life. What this study addsRelatively few studies have comprehensively separated the effects of neurotoxic metals such as lead (Pb) from pre- and postnatal co-occurring metals, nor examined persistence of associations across childhood. In a cohort of middle-class children, we found higher early childhood (∼3 y) blood Pb was associated with lower scores on cognitive tests, independent of other metals and prenatal blood Pb. However, early childhood Pb was only weakly associated with cognition in mid-childhood (∼8 y). Our results suggest the effects of low-level Pb exposure may attenuate over time in some populations, implying the presence of factors that may buffer Pb neurotoxicity in early life.

Prenatal Lead Exposure Is Associated with Reduced Abundance of Beneficial Gut Microbial Cliques in Late Childhood: An Investigation Using Microbial Co-Occurrence Analysis (MiCA).

Many analytical methods used in gut microbiome research focus on either single bacterial taxa or the whole microbiome, ignoring multibacteria relationships (microbial cliques). We present a novel analytical approach to identify microbial cliques within the gut microbiome of children at 9-11 years associated with prenatal lead (Pb) exposure. Data came from a subset of participants (n = 123) in the Programming Research in Obesity, Growth, Environment and Social Stressors cohort. Pb concentrations were measured in maternal whole blood from the second and third trimesters of pregnancy. Stool samples collected at 9-11 years old underwent metagenomic sequencing to assess the gut microbiome. Using a novel analytical approach, Microbial Co-occurrence Analysis (MiCA), we paired a machine learning algorithm with randomization-based inference to first identify microbial cliques that were predictive of prenatal Pb exposure and then estimate the association between prenatal Pb exposure and microbial clique abundance. With second-trimester Pb exposure, we identified a two-taxa microbial clique that included Bifidobacterium adolescentis and Ruminococcus callidus and a three-taxa clique that also included Prevotella clara. Increasing second-trimester Pb exposure was associated with significantly increased odds of having the two-taxa microbial clique below the median relative abundance (odds ratio (OR) = 1.03, 95% confidence interval (CI) [1.01-1.05]). Using a novel combination of machine learning and causal inference, MiCA identified a significant association between second-trimester Pb exposure and the reduced abundance of a probiotic microbial clique within the gut microbiome in late childhood.

Prenatal Lead Exposure, Genetic Factors, and Cognitive Developmental Delay

Although the effects of lead (Pb) exposure on neurocognition in children have been confirmed, the individual associations of prenatal Pb exposure and its interaction with genetic factors on cognitive developmental delay (CDD) in children remain unclear. To investigate the association of prenatal Pb exposure and its interaction with genetic factors with CDD risk. Women in Wuhan, China, who had an expected delivery date between March 2014 and December 2017, were recruited for this prospective cohort study. Children were assessed for cognitive development at approximately 2 years of age (March 2016 to December 2019). Maternal venous blood, cord blood, and venous blood from children were collected in a longitudinal follow-up. Data analysis was performed from March 2022 to February 2023. Prenatal Pb exposure, and genetic risk for cognitive ability evaluated by polygenic risk score constructed with 58 genetic variations. Cognitive developmental delay of children aged approximately 2 years was assessed using the Chinese revision of the Bayley Scale of Infant Development. A series of multivariable logistic regressions was estimated to determine associations between prenatal Pb exposure and CDD among children with various genetic backgrounds, adjusting for confounding variables. This analysis included 2361 eligible mother-child pairs (1240 boys [52.5%] and 1121 girls [47.5%]; mean [SD] ages of mothers and children, 28.9 [3.6] years and 24.8 [1.0] months, respectively), with 292 children (12.4%) having CDD. Higher maternal Pb levels were significantly associated with increased risk of CDD (highest vs lowest tertile: odds ratio, 1.55; 95% CI, 1.13-2.13), adjusting for demographic confounders. The association of CDD with maternal Pb levels was more evident among children with higher genetic risk (highest vs lowest tertile: odds ratio, 2.59; 95% CI, 1.48-4.55), adjusting for demographic confounders. In this cohort study, prenatal Pb exposure was associated with an increased risk of CDD in children, especially in those with a high genetic risk. These findings suggest that prenatal Pb exposure and genetic background may jointly contribute to an increased risk of CDD for children and indicate the possibility for an integrated strategy to assess CDD risk and improve children's cognitive ability.

Prenatal lead exposure is negatively associated with the gut microbiome in childhood.

Metal exposures are associated with gut microbiome (GM) composition and function, and exposures early in development may be particularly important. Considering the role of the GM in association with many adverse health outcomes, understanding the relationship between prenatal metal exposures and the GM is critically important. However, there is sparse knowledge of the association between prenatal metal exposure and GM later in childhood. This analysis aims to identify associations between prenatal lead (Pb) exposure and GM composition and function in children 9-11 years old. Data come from the Programming Research in Obesity, Growth, Environment and Social Stressors (PROGRESS) cohort based in Mexico City, Mexico. Prenatal metal concentrations were measured in maternal whole blood drawn during the second and third trimesters of pregnancy. Stool samples collected at 9-11 years old underwent metagenomic sequencing to assess the GM. This analysis uses multiple statistical modeling approaches, including linear regression, permutational analysis of variance, weighted quantile sum regression (WQS), and individual taxa regressions, to estimate the association between maternal blood Pb during pregnancy and multiple aspects of the child GM at 9-11 years old, adjusting for relevant confounders. Of the 123 child participants in this pilot data analysis, 74 were male and 49 were female. Mean prenatal maternal blood Pb was 33.6 (SE = 2.1) ug/L and 34.9 (SE = 2.1) ug/L at second and third trimesters, respectively. Analysis suggests a consistent negative relationship between prenatal maternal blood Pb and the GM at age 9-11, including measures of alpha and beta diversity, microbiome mixture analysis, and individual taxa. The WQS analysis showed a negative association between prenatal Pb exposure and the gut microbiome, for both second and third trimester exposures (2Tβ = -0.17, 95%CI = [-0.46,0.11]; 3Tβ = -0.17, 95%CI = [-0.44,0.10]). Ruminococcus gnavus, Bifidobacterium longum, Alistipes indistinctus, Bacteroides caccae, and Bifidobacterium bifidum all had weights above the importance threshold from 80% or more of the WQS repeated holdouts in association with both second and third trimester Pb exposure. Pilot data analysis suggests a negative association between prenatal Pb exposure and the gut microbiome later in childhood; however, additional investigation is needed.

Abstract P168: Early Life Metal Profiles and Kidney Function in Mid-Adolescence: A Preliminary Study in Project Viva

Introduction: The developing kidney is vulnerable to pre- and postnatal environmental stressors. Suboptimal environmental conditions during early life, such as exposure to toxic metals and deficiency in essential metals, can alter the risk of kidney dysfunction later in life. In this pilot study, we aimed to examine the relationship between prenatal exposure to metals and adolescent kidney function using data from Project Viva, a Boston-area prospective pre-birth cohort. Hypothesis: Prenatal exposure to higher metal concentrations, both individually and as mixtures, will be associated with altered kidney function in mid-adolescence. Methods: We assessed the following metals in erythrocyte samples collected during pregnancy: 1 st -trimester [arsenic (As), barium (Ba), cadmium (Cd), cesium (Cs), mercury (Hg), lead (Pb), copper (Cu), magnesium (Mg), manganese (Mn), selenium (Se), and Zinc (Zn)]; 2 nd -trimester (Pb, Mn, Hg, and Se). We measured plasma cystatin C and creatinine from blood samples collected in mid-adolescence (mean age 18 years) in a sub-sample of Project Viva participants. We calculated the estimated glomerular filtrate rate (eGFR) using a cystatin C-based equation for children. We examined associations of prenatal metal exposure and mid-adolescent eGFR using linear regression for single metal analyses, and Bayesian kernel machine regression and quantile-based g-computation for mixture analyses. In all models, we adjusted for maternal education level, annual household income, race/ethnicity, child sex, and age at eGFR assessment. Results: A total of 146 participants had complete data for 1 st -trimester erythrocyte metals and mid-adolescent eGFR, and 105 participants had complete data for 2 nd -trimester blood metals and mid-adolescent eGFR. All children had eGFR values in the normal range (i.e., >60 mL/min/1.73m 2 ); the mean (SD) eGFR was 92.0 (13.7) mL/min/1.73m 2 . Most pairwise metal-eGFR relationships were statistically null; however, a 2-fold increase in 1 st -trimester Zn was associated with higher eGFR (β 7.25 mL/min/1.73m 2 ; 95% CI 0.33, 14.16), while a 2-fold increase in 2 nd -trimester Pb was associated with lower eGFR (β -4.90 mL/min/1.73m 2 ; 95% CI -8.32, -1.48). Mixture analyses did not identify statistically significant findings but suggested some non-linear associations and interactions between metals. Conclusions: Preliminary evidence suggests that prenatal Zn exposure is associated with higher kidney function while prenatal Pb exposure is associated with lower kidney function in mid-adolescence. We plan to assess eGFR in additional participants to increase the power of the analyses.

Periconceptional maternal diet quality influences blood heavy metal concentrations and their effect on low birth weight: the Japan Environment and Children’s Study

BackgroundBoth poor maternal nutrition and toxic heavy metal exposure influence foetal growth and development. However, whether consumption of a variety of healthy foods modifies the association between prenatal heavy metal exposure and foetal growth is unknown. ObjectiveWe examined whether long-term maternal diet quality in periconception modifies the associations between maternal circulating concentrations of heavy metals and foetal growth. DesignData of 72,317 Japanese women who delivered singleton infants was extracted from the Japan Environment and Children’s Study. Maternal diet over a 1-year before the first trimester of pregnancy was assessed using a validated food frequency questionnaire, and overall diet quality was determined using the balanced diet score based on the Japanese Food Guide Spinning Top. Maternal whole-blood concentrations of mercury (Hg), lead (Pb) and cadmium (Cd) were measured during the second/third trimester of pregnancy. Bayesian inference of multiple linear regression analysis was performed to evaluate the relationships between maternal diet quality and the blood concentrations of heavy metals; Bayesian logistic regression was used to analyse the risk of low birth weight (LBW; <2,500 g). ResultsAfter controlling for confounders, a high maternal balanced diet score was associated with low concentrations of blood Pb and Cd and high Hg. While all heavy metals assessed were positively associated with LBW risk, a higher maternal balanced diet score was negatively associated with LBW risk. A high-quality maternal diet attenuated the effect of Pb on LBW, an effect that was more marked at high blood Pb concentrations. ConclusionA high-quality, ‘well-balanced’ diet prior to conception may reduce exposure to some heavy metals and mitigate the elevated risk of LBW associated with prenatal Pb exposure in Japanese mother–child pairs.

Perinatal Lead Exposure Promotes Sex-Specific Epigenetic Programming of Disease-Relevant Pathways in Mouse Heart.

Environmental contaminants such as the metal lead (Pb) are associated with cardiovascular disease, but the underlying molecular mechanisms are poorly understood. In particular, little is known about how exposure to Pb during early development impacts the cardiac epigenome at any point across the life course and potential differences between sexes. In a mouse model of human-relevant perinatal exposures, we utilized RNA-seq and Enhanced Reduced Representation Bisulfite Sequencing (ERRBS) to investigate the effects of Pb exposure during gestation and lactation on gene expression and DNA methylation, respectively, in the hearts of male and female mice at weaning. For ERRBS, we identified differentially methylated CpGs (DMCs) or differentially methylated 1000 bp regions (DMRs) based on a minimum absolute change in methylation of 10% and an FDR < 0.05. For gene expression data, an FDR < 0.05 was considered significant. No individual genes met the FDR cutoff for gene expression; however, we found that Pb exposure leads to significant changes in the expression of gene pathways relevant to cardiovascular development and disease. We further found that Pb promotes sex-specific changes in DNA methylation at hundreds of gene loci (280 DMCs and 99 DMRs in males, 189 DMCs and 121 DMRs in females), and pathway analysis revealed that these CpGs and regions collectively function in embryonic development. In males, differential methylation also occurred at genes related to immune function and metabolism. We then investigated whether genes exhibiting differential methylation at weaning were also differentially methylated in hearts from a cohort of Pb-exposed mice at adulthood. We found that a single gene, Galnt2, showed differential methylation in both sexes and time points. In a human cohort investigating the influence of prenatal Pb exposure on the epigenome, we also observed an inverse association between first trimester Pb concentrations and adolescent blood leukocyte DNA methylation at a locus in GALNT2, suggesting that this gene may represent a biomarker of Pb exposure across species. Together, these data, across two time points in mice and in a human birth cohort study, collectively demonstrate that Pb exposure promotes sex-specific programming of the cardiac epigenome, and provide potential mechanistic insight into how Pb causes cardiovascular disease.

Early life exposure to lead and its association with parent-reported aggression and conduct problems during childhood and adolescence

Background and AimAn association between lead (Pb) exposure and antisocial behaviors has been documented, but findings have been inconclusive. We aimed to estimate the association between prenatal, early childhood, and preadolescent/adolescent (periadolescent) Pb exposure and aggression and conduct problems in periadolescent residents of Mexico City. MethodsUsing information from the ELEMENT cohort study, we assessed prenatal Pb exposure through maternal patella Pb (MPPb) measurement during the puerperium, early childhood (birth to 5 years of age) exposure through a cumulative blood lead index (CBLI), and periadolescent exposure through a blood Pb (BPb) measurement concurrent with the evaluation of the outcomes. Outcomes were assessed during periadolescence using the parent-reported scales of aggression and conduct problems of the Behavioral Assessment System for Children-2nd version (BASC-2). We modeled the association between Pb exposure at each stage and each outcome (defined as a T-score ≥60 in the corresponding behavioral scale) using logistic regression, adjusting for sex, maternal age at delivery, maternal education, and household socioeconomic status (SES). The differential effect by sex was assessed with an interaction term in the models. Results743, 704, and 595 participants were respectively eligible for inclusion in final models of prenatal, early childhood, and periadolescent Pb exposure. Median Pb exposure at each stage was 9.9 µg/g for MPPb (prenatal), 5.19 µg/dl for CBLI (early childhood), and 2.62 µg/dl for concurrent BPb (periadolescence). 12 % of participants met the criterion for aggression, and 15 % for conduct problems. In adjusted models, a one interquartile range increase in MPPb increased the odds of conduct problems (OR:1.31; 95 % CI: 1.01, 1.70) and aggression (OR=1.24; 95 % CI: 0.93, 1.65) during periadolescence. Pb exposure during early childhood or periadolescence was not associated with either outcome. We found no evidence of interactions by sex. ConclusionsExposure to Pb during the prenatal stage was associated with aggression and conduct problems during periadolescence.

Prenatal lead (Pb) exposure is associated with differential placental DNA methylation and hydroxymethylation in a human population

ABSTRACT Prenatal lead (Pb) exposure is associated with adverse developmental outcomes and to epigenetic alterations such as DNA methylation and hydroxymethylation in animal models and in newborn blood. Given the importance of the placenta in foetal development, we sought to examine how prenatal Pb exposure was associated with differential placental DNA methylation and hydroxymethylation and to identify affected biological pathways linked to developmental outcomes. Maternal (n = 167) and infant (n = 172) toenail and placenta (n = 115) samples for prenatal Pb exposure were obtained from participants in a US birth cohort, and methylation and hydroxymethylation data were quantified using the Illumina Infinium MethylationEPIC BeadChip. An epigenome-wide association study was applied to identify differential methylation and hydroxymethylation associated with Pb exposure. Biological functions of the Pb-associated genes were determined by overrepresentation analysis through ConsensusPathDB. Prenatal Pb quantified from maternal toenail, infant toenail, and placenta was associated with 480, 27, and 2 differentially methylated sites (q < 0.05), respectively, with both increases and decreases associated with exposure. Alternatively, we identified 2, 1, and 14 differentially hydroxymethylated site(s) associated with maternal toenail, infant toenail, and placental Pb, respectively, with most showing increases in hydroxymethylation with exposure. Significantly overrepresented pathways amongst genes associated with differential methylation and hydroxymethylation (q < 0.10) included mechanisms pertaining to nervous system and organ development, calcium transport and regulation, and signalling activities. Our results suggest that both methylation and hydroxymethylation in the placenta can be variable based on Pb exposure and that the pathways impacted could affect placental function.

Prenatal lead exposure and childhood lung function: Influence of maternal cortisol and child sex

IntroductionMaternal hypothalamic-pituitary-adrenal (HPA) axis disruption in pregnancy may contribute to the programming of childhood respiratory disease and may modify the effect of chemical toxins, like lead (Pb), on lung development. Child sex may further modify these effects. We sought to prospectively examine associations between maternal HPA axis disruption, prenatal Pb and childhood lung function and explore potential effect modification by maternal cortisol and child sex on the association between prenatal Pb and lung function outcomes. Materials and methodsAnalyses included 222 mothers and children enrolled in a longitudinal birth cohort study in Mexico City. Maternal diurnal salivary cortisol was assessed in pregnancy; cortisol awakening response (CAR) and diurnal slope were calculated. Blood Pb was measured during the second trimester of pregnancy. Post-bronchodilator lung function was tested at ages 8–11 years. Associations were modeled using generalized linear models with interaction terms, adjusting for covariates. ResultsA higher (flatter) diurnal slope was associated with lower FEV1/FVC ratio (β: 0.433, 95%CI [-0.766, −0.101]). We did not find any main effect associations between prenatal Pb and lung function outcomes. We report an interaction between Pb and cortisol in relation to FEV1/FVC and FEF25–75% (pinteraction<0.05 for all). Higher prenatal Pb was associated with reduced FEV1/FVC only in children whose mothers had a high CAR. Higher prenatal Pb was also associated with reduced FEV1/FVC and FEF25–75% in mothers with a flatter diurnal slope. A 3-way interaction between prenatal Pb, CAR and sex on FEV1/FVC, indicated that boys born to women with high CAR and higher prenatal Pb levels had lower FEV1/FVC ratios (pinteraction = 0.067). ConclusionsAssociations between prenatal Pb and childhood lung function were modified by disrupted maternal cortisol in pregnancy and child sex. These findings underscore the need to consider complex interactions to fully elucidate effects of prenatal Pb exposure on childhood lung function.

Early-life exposure to lead and antisocial behaviors during childhood and adolescence

BACKGROUND AND AIM: An association between lead (Pb) exposure and antisocial behaviors has been documented over the last decades, but the findings have been inconsistent. We aimed to estimate the association between prenatal, early-childhood, and preadolescent/adolescent (periadolescent) Pb exposure, and aggression and conduct problems in periadolescents of Mexico City. METHODS: We studied participants from the Early Life Exposures in Mexico to Environmental Toxicants (ELEMENT) cohorts. We used 1) maternal patella Pb at puerperium as a proxy for prenatal Pb exposure, 2) cumulative blood lead index (a summary of repeated blood Pb (BPb) measurements) between birth and 60 months of age as a measure of early-childhood Pb exposure, and 3) a single BPb measurement concurrent with behavioral evaluation as a measure of periadolescent Pb exposure. The parent-reported scales of aggression and conduct problems of the Behavioral Assessment System for Children-2nd version (BASC-2) were evaluated during periadolescence (at a mean age of 10.38 years). We estimated the association between Pb exposure at each stage and having obtained an elevated T-score (≥60) in each scale, while adjusting for household socioeconomic status, maternal education and age at delivery, child sex, and Pb exposure at previous stages. RESULTS:743, 704, and 595 participants were included in the models for prenatal, early-childhood, and periadolescent Pb exposure, respectively. On average, mothers had 10.6 years of education, and were 26.3 years old at delivery. 49% of children were female. A one-unit increase in Pb exposure during the prenatal period (1 µg/g of maternal patella Pb), but not during childhood or periadolescence, was associated with increased odds of aggression (Odds Ratio (OR)=1.021; 95% Confidence Interval (CI): 1, 1.041) and conduct problems (OR=1.019; 95% CI: 1.002, 1.037) CONCLUSIONS:Exposure to Pb during the prenatal stage, but not during childhood or adolescence, was associated with aggression and conduct problems during periadolescence in this longitudinal cohort study. KEYWORDS: Heavy metals, Neurodevelopmental outcomes, Children's environmental health

Prenatal Lead (Pb) Exposure and Peripheral Blood DNA Methylation (5mC) and Hydroxymethylation (5hmC) in Mexican Adolescents from the ELEMENT Birth Cohort.

Background:Gestational lead (Pb) exposure can adversely affect offspring health through multiple mechanisms, including epigenomic alterations via DNA methylation (5mC) and hydroxymethylation (5hmC), an intermediate in oxidative demethylation. Most current methods do not distinguish between 5mC and 5hmC, limiting insights into their individual roles.Objective:Our study sought to identify the association of trimester-specific (T1, T2, T3) prenatal Pb exposure with 5mC and 5hmC levels at multiple cytosine-phosphate-guanine sites within gene regions previously associated with prenatal Pb (HCN2, NINJ2, RAB5A, TPPP) in whole blood leukocytes of children ages 11–18 years of age.Methods:Participants from the Early Life Exposure in Mexico to Environmental Toxicants (ELEMENT) birth cohorts were selected () for pyrosequencing analysis following oxidative or standard sodium bisulfite treatment. This workflow directly quantifies total methylation () and 5mC only; 5hmC is estimated by subtraction.Results:Participants were 51% male, and mean maternal blood lead levels (BLL) were in Trimester 1 (T1), in Trimester 2 (T2), and in Trimester 3 (T3). In addition, 5hmC levels were calculated for HCN2 (, ), NINJ2 (G/C: ; GG: ), RAB5A (), and TPPP (). Furthermore, 5mC levels were measured in HCN2 (), NINJ2 (heterozygotes: ; GG homozygotes: ), RAB5A (), and TPPP (). Several significant associations between BLLs and 5mC/5hmC were identified: T1 BLLs with 5mC in HCN2 (, ) and 5hmC in NINJ2 (, ); T2 BLLs with 5mC in HCN2 (, ) and 5hmC in NINJ2 (, ); and T3 BLLs with 5mC in HCN2 (, ) and NINJ2 (, ) and 5hmC in NINJ2 (, ). NINJ2 5mC was negatively correlated with gene expression (Pearson , ), whereas 5hmC was positively correlated (, ).Discussion:These findings suggest there is variable 5hmC in human whole blood and that prenatal Pb exposure is associated with gene-specific 5mC and 5hmC levels at adolescence, providing evidence to consider 5hmC as a regulatory mechanism that is responsive to environmental exposures. https://doi.org/10.1289/EHP8507

Ferulic acid exerts Nrf2-dependent protection against prenatal lead exposure-induced cognitive impairment in offspring mice

Prenatal and/or early postnatal exposure to lead (Pb) may be associated with deficits in cognitive function in the toddler offspring, and oxidative stress likely play a central role in mediating these adverse effects. Here, we tested the hypothesis that ameliorative effect of ferulic acid (FA) on lead-induced cognitive deficits attributed to its antioxidant properties in a nuclear factor (erythroid-derived 2)-like 2 (Nrf2)-dependent manner in the context of prenatal Pb exposure. To test this hypothesis, Nrf2 knockout and C57BL/6 wild type mouse dams were exposed/unexposed to PbAc (250 ppm) during gestation day 5 to postnatal day 14 via drinking water, and FA (50 mg/kg)/vehicle was administered orally to dams for 31 d. Spatial learning and memory in pups was assessed by Morris water maze. Biochemical assays, real-time PCR, western blot techniques were employed to evaluate oxidative stress and signaling pathways in the brain of pups. We report that lead acetate (PbAc) leads to deficits in cognitive functions in offspring, which were partially attenuated by FA (P<.05). In parallel, pretreatment with FA also significantly inhibited the PbAc-induced oxidative stress, as indicated by a change in NAD+/NADH ratio, glutathione (GSH) and malondialdehyde contents (all P<.05). Interestingly, FA significantly elevated the glutamate cysteine ligase and heme oxygenase 1 at levels of transcription and translation in both mice exposed and unexposed to Pb, increasing de novo synthesis of GSH (all P<.05). Furthermore, maternal FA administration activates extracellular signal-regulated kinases 1 and 2 and promotes more Nrf2 nuclear accumulation by increasing the Nrf2 total protein in brain of offspring mice (all P<.05). Conversely, FA failed to influence Pb-induced both memory deficits and oxidative stress in offspring of Nrf2 knockout mice (all P≥.05), suggesting that Nrf2 is essential in mediating the cognition-enhancing and antioxidant effects of FA. Overall, our results demonstrate that FA protects against Pb-induced offspring's cognitive deficits, suggesting that it is a promising candidate for the treatment of Pb toxicity.

Prenatal Lead (Pb) Exposure’s Effect on DNA Methylation (5mC) and Hydroxymethylation (5hmC) in Adolescent Whole Blood

Gestational lead (Pb) exposure may adversely impact offspring health through epigenetic alterations via DNA methylation (5mC), addition of a methyl group to the 5th carbon of cytosine, and hydroxymethylation (5hmC), an intermediate in oxidative demethylation associated with increased gene expression. Most current methods collectively measure 5mC and 5hmC without distinguishing between the two. This study aims to identify the association of prenatal Pb exposure at each trimester (T1, T2, T3) with 5mC and 5hmC levels at multiple cytosine-phosphate-guanine (CpG) sites within candidate regions of genes previously associated with prenatal Pb exposure (HCN2, NINJ2, RAB5A, and TPPP) in blood leukocytes of children ages 11-18 years. Participants from the Early Life Exposure in Mexico to Environmental Toxicants (ELEMENT) birth cohorts were selected (n=144) for pyrosequencing analysis following oxidative or standard sodium bisulfite treatment. Participants are 51% male with concurrent blood lead levels (BLL) averaging 3.29±4.44µg/dL and historical maternal BLL averaging 6.43±5.16µg/dL (T1), 5.66±5.21µg/dL (T2), and 5.86±4.34µg/dL (T3). 5mC levels were quantified in HCN2 (mean±SD, 81.3±9.63%), NINJ2 (36.7±22.5%), RAB5A (1.40±1.20%), and TPPP (92.5±8.03%). 5hmC levels were estimated in HCN2 (2.04±4.30%), NINJ2 (2.15±5.43%), RAB5A (0.64±0.80%), and TPPP (0.45±8.01%), providing evidence for 5hmC presence in blood leukocytes. Controlling for sex, current BLL, child’s age, and pyrosequencing batch, T1 maternal BLL was associated with 5mC in HCN2 (β=-1.256, p=0.019) and NINJ2 (β=0.426, p=0.004); T2 BLL with 5mC in HCN2 (β=0.368, p=0.028) and 5hmC in NINJ2 (β=0.232, p=0.011); and T3 BLL with 5mC in HCN2 (β=0.502, p=0.016) and 5hmC in NINJ2 (β=0.372, p=0.001). No associations were identified between Pb and RAB5A and TPPP. Together, these data suggest that perinatal Pb exposure results may alter 5mC and 5hmC in blood in a gene-specific manner that persists into adolescence.

Association between blood lead level during pregnancy and birth weight: A meta-analysis.

We aimed to provide a quantitative summary of evidence for a relationship between prenatal lead (Pb) exposure and birth weight. PubMed and Web of Science databases were searched for eligible epidemiological studies. We transformed findings in eligible studies with different effect-size metrics to standardized regression coefficients, and used fixed-effects or random-effects models to assess the pooled effects of prenatal Pb exposure on birth weight. There was a significant negative association between prenatal Pb exposure and birth weight. Birth weight reduction was associated with elevated lead levels in maternal blood (β = -0.094; 95% confidence interval [CI]: -0.157 to -0.030) and cord blood (β = -0.120; 95% CI: -0.239 to -0.001). This meta-analysis is the first to provide a quantitative assessment of Pb exposure during pregnancy and an increased risk of lower birth weight.

Trimester-Specific Associations of Prenatal Lead Exposure With Infant Cord Blood DNA Methylation at Birth.

Gestational exposure to lead (Pb) adversely impacts offspring health through multiple mechanisms, one of which is the alteration of the epigenome including DNA methylation. This study aims to identify differentially methylated CpG sites associated with trimester-specific maternal Pb exposure in umbilical cord blood (UCB) leukocytes. Eighty-nine mother-child dyads from the Early Life Exposure in Mexico to Environmental Toxicants (ELEMENT) longitudinal birth cohorts with available UCB samples were selected for DNA methylation analysis via the Infinium Methylation EPIC BeadChip, which quantifies methylation at >850 000 CpG sites. Maternal blood lead levels (BLLs) during each trimester (T1: 6.56 ± 5.35 µg/dL; T2: 5.93 ± 5.00 µg/dL; T3: 6.09 ± 4.51 µg/dL), bone Pb (patella: 11.8 ± 9.25 µg/g; tibia: 11.8 ± 6.73 µg/g), a measure of cumulative Pb exposure, and UCB Pb (4.86 ± 3.74 µg/dL) were measured. After quality control screening, data from 786 024 CpG sites were used to identify differentially methylated positions (DMPs) and differentially methylated regions (DMRs) by Pb biomarkers using separate linear regression models, controlling for sex and estimated UCB cell-type proportions. We identified 3 DMPs associated with maternal T1 BLL, 2 with T3 BLL, and 2 with tibia bone Pb. We identified one DMR within PDGFRL associated with T1 BLL, one located at chr6:30095136-30095295 with T3 BLL, and one within TRHR with tibia bone Pb (adjusted P-value < .05). Pathway analysis identified 15 overrepresented gene pathways for differential methylation that overlapped among all 3 trimesters with the largest overlap between T1 and T2 (adjusted P-value < .05). Pathways of interest include nodal signaling pathway and neurological system processes. These data provide evidence for differential methylation by prenatal Pb exposure that may be trimester-specific.

Genome-wide gene by lead exposure interaction analysis identifies UNC5D as a candidate gene for neurodevelopment

BackgroundNeurodevelopment is a complex process involving both genetic and environmental factors. Prenatal exposure to lead (Pb) has been associated with lower performance on neurodevelopmental tests. Adverse neurodevelopmental outcomes are more frequent and/or more severe when toxic exposures interact with genetic susceptibility.MethodsTo explore possible loci associated with increased susceptibility to prenatal Pb exposure, we performed a genome-wide gene-environment interaction study (GWIS) in young children from Mexico (n = 390) and Bangladesh (n = 497). Prenatal Pb exposure was estimated by cord blood Pb concentration. Neurodevelopment was assessed using the Bayley Scales of Infant Development.ResultsWe identified a locus on chromosome 8, containing UNC5D, and demonstrated evidence of its genome-wide significance with mental composite scores (rs9642758, pmeta = 4.35 × 10−6). Within this locus, the joint effects of two independent single nucleotide polymorphisms (SNPs, rs9642758 and rs10503970) had a p-value of 4.38 × 10−9 for mental composite scores. Correlating GWIS results with in vitro transcriptomic profiles identified one common gene, SLC1A5, which is involved in synaptic function, neuronal development, and excitotoxicity. Further analysis revealed interconnected interactions that formed a large network of 52 genes enriched with oxidative stress genes and neurodevelopmental genes.ConclusionsOur findings suggest that certain genetic polymorphisms within/near genes relevant to neurodevelopment might modify the toxic effects of Pb exposure via oxidative stress.

Effects of low-level prenatal lead exposure on child IQ at 4 and 8 years in a UK birth cohort study

BackgroundThe association between childhood exposure to lead (Pb) and deficits in cognitive function is well established. The association with prenatal exposure, however, is not well understood, even though the potential adverse effects are equally important. ObjectivesTo evaluate the association between low prenatal exposure to lead and IQ in children, to determine whether there were sex differences in the associations, and to evaluate the moderation effect of prenatal Pb exposure on child IQ. MethodsWhole blood samples from pregnant women enrolled in ALSPAC (n=4285) and from offspring at age 30 months (n=235) were analysed for Pb. Associations between prenatal blood lead concentrations (B-Pb) and child IQ at age 4 and 8 years (WPPSI and WISC-III, respectively) were examined in adjusted regression models. ResultsThere was no association of prenatal lead exposure with child IQ at 4 or 8 years old in adjusted regression models, and no moderation of the association between child B-Pb and IQ. However, there was a positive association for IQ at age 8 years in girls with a predicted increase in IQ (points) per 1μg/dl of: verbal 0.71, performance 0.57, total 0.73. In boys, the coefficients tended to be negative (−0.15, −0.42 and −0.29 points, respectively). ConclusionPrenatal lead exposure was not associated with adverse effects on child IQ at age 4 or 8 years in this study. There was, however, some evidence to suggest that boys are more susceptible than girls to prenatal exposure to lead. Further investigation in other cohorts is required.

Maternal blood lead concentrations, DNA methylation of MEG3 DMR regulating the DLK1/MEG3 imprinted domain and early growth in a multiethnic cohort.

Prenatal exposure to lead (Pb) is known to decrease fetal growth; but its effects on postnatal growth and mechanistic insights linking Pb to growth are not clearly defined. Genomically imprinted genes are powerful regulators of growth and energy utilization, and may be particularly vulnerable to environmental Pb exposure. Because imprinting is established early and maintained via DNA methylation, we hypothesized that prenatal Pb exposure alters DNA methylation of imprinted genes resulting in lower birth weight and rapid growth. Pb was measured by inductively coupled plasma mass spectrometry (ICP-MS) in peripheral blood of 321 women of the Newborn Epigenetic STudy (NEST) obtained at gestation ∼12 weeks. Linear and logistic regression models were used to evaluate associations between maternal Pb levels, methylation of differentially methylated regions (DMRs) regulating H19, MEG3 , PEG3 , and PLAGL1 , measured by pyrosequencing, birth weight, and weight-for-height z score gains between birth and age 1 year, ages 1–2 years, and 2–3 years. Children born to women with Pb levels in the upper tertile had higher methylation of the regulatory region of the MEG3 DMR imprinted domain (β = 1.57, SE = 0.82, P = 0.06). Pb levels were also associated with lower birth weight (β = −0.41, SE = 0.15, P = 0.01) and rapid gains in adiposity (OR = 12.32, 95% CI = 1.25–121.30, P = 0.03) by age 2–3 years. These data provide early human evidence for Pb associations with hypermethylation at the MEG3 DMR regulatory region and rapid adiposity gain – a risk factor for childhood obesity and cardiometabolic diseases in adulthood.

Lead exposure induces changes in 5-hydroxymethylcytosine clusters in CpG islands in human embryonic stem cells and umbilical cord blood

Prenatal exposure to neurotoxicants such as lead (Pb) may cause stable changes in the DNA methylation (5mC) profile of the fetal genome. However, few studies have examined its effect on the DNA de-methylation pathway, specifically the dynamic changes of the 5-hydroxymethylcytosine (5hmC) profile. Therefore, in this study, we investigate the relationship between Pb exposure and 5mC and 5hmC modifications during early development. To study the changes in the 5hmC profile, we use a novel modification of the Infinium™ HumanMethylation450 assay (Illumina, Inc.), which we named HMeDIP-450K assay, in an in vitro human embryonic stem cell model of Pb exposure. We model Pb exposure-associated 5hmC changes as clusters of correlated, adjacent CpG sites, which are co-responding to Pb. We further extend our study to look at Pb-dependent changes in high density 5hmC regions in umbilical cord blood DNA from 48 mother-infant pairs from the Early Life Exposure in Mexico to Environmental Toxicants (ELEMENT) cohort. For our study, we randomly selected umbilical cord blood from 24 male and 24 female children from the 1st and 4th quartiles of Pb levels. Our data show that Pb-associated changes in the 5hmC and 5mC profiles can be divided into sex-dependent and sex-independent categories. Interestingly, differential 5mC sites are better markers of Pb-associated sex-dependent changes compared to differential 5hmC sites. In this study we identified several 5hmC and 5mC genomic loci, which we believe might have some potential as early biomarkers of prenatal Pb exposure.