Association between fetal exposure to phthalate endocrine disruptor and genome-wide DNA methylation at birth

Epigenetic footprints: Investigating placental DNA methylation in the context of prenatal exposure to phenols and phthalates

BACKGROUND

Endocrine disrupting compounds (EDCs) such as phthalates and phenols can affect placental functioning and fetal health, potentially via epigenetic modifications. We investigated the associations between pregnancy exposure to synthetic phenols and phthalates estimated from repeated urine sampling and genome wide placental DNA methylation.

METHODS

The study is based on 387 women with placental DNA methylation assessed with Infinium MethylationEPIC arrays and with 7 phenols, 13 phthalates, and two non-phthalate plasticizer metabolites measured in pools of urine samples collected twice during pregnancy. We conducted an exploratory analysis on individual CpGs (EWAS) and differentially methylated regions (DMRs) as well as a candidate analysis focusing on 20 previously identified CpGs. Sex-stratified analyses were also performed.

RESULTS

In the exploratory analysis, when both sexes were studied together no association was observed in the EWAS. In the sex-stratified analysis, 114 individual CpGs (68 in males, 46 in females) were differentially methylated, encompassing 74 genes (36 for males and 38 for females). We additionally identified 28 DMRs in the entire cohort, 40 for females and 42 for males. Associations were mostly positive (for DMRs: 93% positive associations in the entire cohort, 60% in the sex-stratified analysis), with the exception of several associations for bisphenols and DINCH metabolites that were negative. Biomarkers associated with most DMRs were parabens, DEHP, and DiNP metabolite concentrations. Some DMRs encompassed imprinted genes including APC (associated with parabens and DiNP metabolites), GNAS (bisphenols), ZIM2;PEG3;MIMT1 (parabens, monoethyl phthalate), and SGCE;PEG10 (parabens, DINCH metabolites). Terms related to adiposity, lipid and glucose metabolism, and cardiovascular function were among the enriched phenotypes associated with differentially methylated CpGs. The candidate analysis identified one CpG mapping to imprinted LGALS8 gene, negatively associated with ethylparaben.

CONCLUSIONS

By combining improved exposure assessment and extensive placental epigenome coverage, we identified several novel genes associated with the exposure, possibly in a sex-specific manner.

Association between pre- and postnatal exposure to endocrine-disrupting chemicals and birth and neurodevelopmental outcomes: an extensive review

Endocrine-disrupting chemicals (EDCs) are natural or synthetic chemicals that mimic, block, or interfere with the hormones in the body. The most common and well- studied EDCs are bisphenol A, phthalates, and persistent organic pollutants including polychlorinated biphenyls, polybrominated diphenyl ethers, per- and polyfluoroalkyl substances, other brominated flame retardants, organochlorine pesticides, dioxins, and furans. Starting in embryonic life, humans are constantly exposed to EDCs through air, diet, skin, and water. Fetuses and newborns undergo crucial developmental processes that allow adaptation to the environment throughout life. As developing organisms, they are extremely sensitive to low doses of EDCs. Many EDCs can cross the placental barrier and reach the developing fetal organs. In addition, newborns can be exposed to EDCs through breastfeeding or formula feeding. Pre- and postnatal exposure to EDCs may increase the risk of childhood diseases by disrupting the hormone-mediated processes critical for growth and development during gestation and infancy. This review discusses evidence of the relationship between pre- and postnatal exposure to several EDCs, childbirth, and neurodevelopmental outcomes. Available evidence suggests that pre- and postnatal exposure to certain EDCs causes fetal growth restriction, preterm birth, low birth weight, and neurodevelopmental problems through various mechanisms of action. Given the adverse effects of EDCs on child development, further studies are required to clarify the overall associations.

Prenatal exposure to environmental phenols and phthalates and altered patterns of DNA methylation in childhood

INTRODUCTION

Epigenetic marks are key biomarkers linking the prenatal environment to health and development. However, DNA methylation associations and persistence of marks for prenatal exposure to multiple Endocrine Disrupting Chemicals (EDCs) in human populations have not been examined in great detail.

METHODS

We measured Bisphenol-A (BPA), triclosan, benzophenone-3 (BP3), methyl-paraben, propyl-paraben, and butyl-paraben, as well as 11 phthalate metabolites, in two pregnancy urine samples, at approximately 13 and 26 weeks of gestation in participants of the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS) study (N = 309). DNA methylation of cord blood at birth and child peripheral blood at ages 9 and 14 years was measured with 450K and EPIC arrays. Robust linear regression was used to identify differentially methylated probes (DMPs), and comb-p was used to identify differentially methylated regions (DMRs) in association with pregnancy-averaged EDC concentrations. Quantile g-computation was used to assess associations of the whole phenol/phthalate mixture with DMPs and DMRs.

RESULTS

Prenatal BPA exposure was associated with 1 CpG among males and Parabens were associated with 10 CpGs among females at Bonferroni-level significance in cord blood. Other suggestive DMPs (unadjusted p-value < 1 × 10-6) and several DMRs associated with the individual phenols and whole mixture were also identified. A total of 10 CpG sites at least suggestively associated with BPA, Triclosan, BP3, Parabens, and the whole mixture in cord blood were found to persist into adolescence in peripheral blood.

CONCLUSIONS

We found sex-specific associations between prenatal phenol exposure and DNA methylation, particularly with BPA in males and Parabens in females. Additionally, we found several DMPs that maintained significant associations with prenatal EDC exposures at age 9 and age 14 years.

Effects of Developmental Lead and Phthalate Exposures on DNA Methylation in Adult Mouse Blood, Brain, and Liver: A Focus on Genomic Imprinting by Tissue and Sex

BACKGROUND

Maternal exposure to environmental chemicals can cause adverse health effects in offspring. Mounting evidence supports that these effects are influenced, at least in part, by epigenetic modifications. It is unknown whether epigenetic changes in surrogate tissues such as the blood are reflective of similar changes in target tissues such as cortex or liver.

OBJECTIVE

We examined tissue- and sex-specific changes in DNA methylation (DNAm) associated with human-relevant lead (Pb) and di(2-ethylhexyl) phthalate (DEHP) exposure during perinatal development in cerebral cortex, blood, and liver.

METHODS

Female mice were exposed to human relevant doses of either Pb (32  ppm ) via drinking water or DEHP (5 mg / kg-day ) via chow for 2 weeks prior to mating through offspring weaning. Whole genome bisulfite sequencing (WGBS) was utilized to examine DNAm changes in offspring cortex, blood, and liver at 5 months of age. Metilene and methylSig were used to identify differentially methylated regions (DMRs). Annotatr and ChIP-enrich were used for genomic annotations and gene set enrichment tests of DMRs, respectively.

RESULTS

The cortex contained the majority of DMRs associated with Pb (66%) and DEHP (57%) exposure. The cortex also contained the greatest degree of overlap in DMR signatures between sexes (n = 13 and 8 DMRs with Pb and DEHP exposure, respectively) and exposure types (n = 55 and 39 DMRs in males and females, respectively). In all tissues, detected DMRs were preferentially found at genomic regions associated with gene expression regulation (e.g., CpG islands and shores, 5' UTRs, promoters, and exons). An analysis of GO terms associated with DMR-containing genes identified imprinted genes to be impacted by both Pb and DEHP exposure. Of these, Gnas and Grb10 contained DMRs across tissues, sexes, and exposures, with some signatures replicated between target and surrogate tissues. DMRs were enriched in the imprinting control regions (ICRs) of Gnas and Grb10, and we again observed a replication of DMR signatures between blood and target tissues. Specifically, we observed hypermethylation of the Grb10 ICR in both blood and liver of Pb-exposed male animals.

CONCLUSIONS

These data provide preliminary evidence that imprinted genes may be viable candidates in the search for epigenetic biomarkers of toxicant exposure in target tissues. Additional research is needed on allele- and developmental stage-specific effects, as well as whether other imprinted genes provide additional examples of this relationship. https://doi.org/10.1289/EHP14074.

Translational toxicoepigenetic Meta-Analyses identify homologous gene DNA methylation reprogramming following developmental phthalate and lead exposure in mouse and human offspring

Although toxicology uses animal models to represent real-world human health scenarios, a critical translational gap between laboratory-based studies and epidemiology remains. In this study, we aimed to understand the toxicoepigenetic effects on DNA methylation after developmental exposure to two common toxicants, the phthalate di(2-ethylhexyl) phthalate (DEHP) and the metal lead (Pb), using a translational paradigm that selected candidate genes from a mouse study and assessed them in four human birth cohorts. Data from mouse offspring developmentally exposed to DEHP, Pb, or control were used to identify genes with sex-specific sites with differential DNA methylation at postnatal day 21. Associations of human infant DNA methylation in homologous mouse genes with prenatal DEHP or Pb were examined with a meta-analysis. Differential methylation was observed on 6 cytosines (adjusted-p < 0.05) and 90 regions (adjusted-p < 0.001). This translational approach offers a unique method that can detect conserved epigenetic differences that are developmentally susceptible to environmental toxicants.

Phthalates and uterine disorders

Humans are ubiquitously exposed to environmental endocrine disrupting chemicals such as phthalates. Phthalates can migrate out of products and enter the human body through ingestion, inhalation, or dermal application, can have potential estrogenic/antiestrogenic and/or androgenic/antiandrogenic activity, and are involved in many diseases. As a female reproductive organ that is regulated by hormones such as estrogen, progesterone and androgen, the uterus can develop several disorders such as leiomyoma, endometriosis and abnormal bleeding. In this review, we summarize the hormone-like activities of phthalates, in vitro studies of endometrial cells exposed to phthalates, epigenetic modifications in the uterus induced by phthalate exposure, and associations between phthalate exposure and uterine disorders such as leiomyoma and endometriosis. Moreover, we also discuss the current research gaps in understanding the relationship between phthalate exposure and uterine disorders.

Accurate determination of 11 representative phthalates and di(2-ethylhexyl) terephthalate in polyvinyl chloride using isotope dilution-gas chromatography/mass spectrometry

Phthalates are mainly used as plasticizers in polyvinyl chloride (PVC). However, prolonged exposure to phthalates poses considerable risks to human health. Consequently, the utilization of phthalates in consumer products is subject to regulations, with a defined threshold of 0.1 %. In this study, we developed an accurate and simultaneous method for determination of 11 representative phthalates and a non-phthalate plasticizer (di(2-ethylhexyl) terephthalate, DEHT) in PVC as a higher-order reference method. Homogeneously prepared PVC samples, each containing approximately 0.1 % of the target plasticizer compounds, were analyzed using gas chromatography-mass spectrometry (GC-MS) with deuterium-labeled phthalates and DEHT. The developed method could effectively separate and quantify all target plasticizers without interference with each other and potential overlap between the isomeric forms of phthalates, di-isodecyl phthalate, and di-isononyl phthalate. The developed method has high-order metrological quality, exhibiting exceptional selectivity, accuracy, repeatability (≤ 2.17 %), reproducibility (≤ 2.16 %), and relative expanded uncertainty (≤ 5.6 %). This analytical method is thus suitable for accurately assessing the target plasticizer levels in PVC products for ensuring compliance with the established 0.1 % threshold. This method was successfully applied to quantify twelve distinct plasticizers in PVC products obtained from the Korean market, validating its effectiveness and reliability in real-world scenarios.

Imprinting and Reproductive Health: A Toxicological Perspective

This overview discusses the role of imprinting in the development of an organism, and how exposure to environmental chemicals during fetal development leads to the physiological and biochemical changes that can have adverse lifelong effects on the health of the offspring. There has been a recent upsurge in the use of chemical products in everyday life. These chemicals include industrial byproducts, pesticides, dietary supplements, and pharmaceutical products. They mimic the natural estrogens and bind to estradiol receptors. Consequently, they reduce the number of receptors available for ligand binding. This leads to a faulty signaling in the neuroendocrine system during the critical developmental process of 'imprinting'. Imprinting causes structural and organizational differentiation in male and female reproductive organs, sexual behavior, bone mineral density, and the metabolism of exogenous and endogenous chemical substances. Several studies conducted on animal models and epidemiological studies provide profound evidence that altered imprinting causes various developmental and reproductive abnormalities and other diseases in humans. Altered metabolism can be measured by various endpoints such as the profile of cytochrome P-450 enzymes (CYP450's), xenobiotic metabolite levels, and DNA adducts. The importance of imprinting in the potentiation or attenuation of toxic chemicals is discussed.

Effects of Developmental Lead and Phthalate Exposures on DNA Methylation in Adult Mouse Blood, Brain, and Liver Identifies Tissue- and Sex-Specific Changes with Implications for Genomic Imprinting

Background

Maternal exposure to environmental chemicals can cause adverse health effects in offspring. Mounting evidence supports that these effects are influenced, at least in part, by epigenetic modifications.

Objective

We examined tissue- and sex-specific changes in DNA methylation (DNAm) associated with human-relevant lead (Pb) and di(2-ethylhexyl) phthalate (DEHP) exposure during perinatal development in cerebral cortex, blood, and liver.

Methods

Female mice were exposed to human relevant doses of either Pb (32ppm) via drinking water or DEHP (5 mg/kg-day) via chow for two weeks prior to mating through offspring weaning. Whole genome bisulfite sequencing (WGBS) was utilized to examine DNAm changes in offspring cortex, blood, and liver at 5 months of age. Metilene and methylSig were used to identify differentially methylated regions (DMRs). Annotatr and Chipenrich were used for genomic annotations and geneset enrichment tests of DMRs, respectively.

Results

The cortex contained the majority of DMRs associated with Pb (69%) and DEHP (58%) exposure. The cortex also contained the greatest degree of overlap in DMR signatures between sexes (n = 17 and 14 DMRs with Pb and DEHP exposure, respectively) and exposure types (n = 79 and 47 DMRs in males and females, respectively). In all tissues, detected DMRs were preferentially found at genomic regions associated with gene expression regulation (e.g., CpG islands and shores, 5' UTRs, promoters, and exons). An analysis of GO terms associated with DMR-containing genes identified imprinted genes to be impacted by both Pb and DEHP exposure. Of these, Gnas and Grb10 contained DMRs across tissues, sexes, and exposures. DMRs were enriched in the imprinting control regions (ICRs) of Gnas and Grb10, with 15 and 17 ICR-located DMRs across cortex, blood, and liver in each gene, respectively. The ICRs were also the location of DMRs replicated across target and surrogate tissues, suggesting epigenetic changes these regions may be potentially viable biomarkers.

Conclusions

We observed Pb- and DEHP-specific DNAm changes in cortex, blood, and liver, and the greatest degree of overlap in DMR signatures was seen between exposures followed by sex and tissue type. DNAm at imprinted control regions was altered by both Pb and DEHP, highlighting the susceptibility of genomic imprinting to these exposures during the perinatal window of development.

Associations between prenatal phthalate exposure and childhood epigenetic age acceleration

BACKGROUND

Phthalates, a group of pervasive endocrine-disrupting chemicals found in plastics and personal care products, have been associated with a wide range of developmental and health outcomes. However, their impact on biomarkers of aging has not been characterized. We tested associations between prenatal exposure to 11 phthalate metabolites on epigenetic aging in children at birth, 7, 9, and 14 years of age. We hypothesized that prenatal phthalate exposure will be associated with epigenetic age acceleration measures at birth and in early childhood, with patterns dependent on sex and timing of DNAm measurement.

METHODS

Among 385 mother-child pairs from the CHAMACOS cohort, we measured DNAm at birth, 7, 9, and 14 years of age, and utilized adjusted linear regression to assess the association between prenatal phthalate exposure and Bohlin's Gestational Age Acceleration (GAA) at birth and Intrinsic Epigenetic Age Acceleration (IEAA) throughout childhood. Additionally, quantile g-computation was utilized to assess the effect of the phthalate mixture on GAA at birth and IEAA throughout childhood.

RESULTS

We found a negative association between prenatal di (2-ethylhexyl) phthalate (DEHP) exposure and IEAA among males at age 7 (-0.58 years; 95% CI: 1.02 to -0.13), and a marginal negative association between the whole phthalate mixture and GAA among males at birth (-1.54 days, 95% CI: 2.79 to -0.28), while most other associations were nonsignificant.

CONCLUSIONS

Our results suggest that prenatal exposure to certain phthalates is associated with epigenetic aging in children. Additionally, our findings suggest that the influence of prenatal exposures on epigenetic age may only manifest during specific periods of child development, and studies relying on DNAm measurements solely from cord blood or single time points may overlook potential relationships.

Prenatal phthalate exposure and cord blood DNA methylation

Exposure to phthalates has been shown to impede the human endocrine system, resulting in deleterious effects on pregnant women and their children. Phthalates modify DNA methylation patterns in infant cord blood. We examined the association between prenatal phthalate exposure and DNA methylation patterns in cord blood in a Korean birth cohort. Phthalate levels were measured in 274 maternal urine samples obtained during late pregnancy and 102 neonatal urine samples obtained at birth, and DNA methylation levels were measured in cord blood samples. For each infant in the cohort, associations between CpG methylation and both maternal and neonate phthalate levels were analyzed using linear mixed models. The results were combined with those from a meta-analysis of the levels of phthalates in maternal and neonatal urine samples, which were also analyzed for MEOHP, MEHHP, MnBP, and DEHP. This meta-analysis revealed significant associations between the methylation levels of CpG sites near the CHN2 and CUL3 genes, which were also associated with MEOHP and MnBP in neonatal urine. When the data were stratified by the sex of the infant, MnBP concentration was found to be associated with one CpG site near the OR2A2 and MEGF11 genes in female infants. In contrast, the concentrations of the three maternal phthalates showed no significant association with CpG site methylation. Furthermore, the data identified distinct differentially methylated regions in maternal and neonatal urine samples following exposure to phthalates. The CpGs with methylation levels that were positively associated with phthalate levels (particularly MEOHP and MnBP) were found to be enriched genes and related pathways. These results indicate that prenatal phthalate exposure is significantly associated with DNA methylation at multiple CpG sites. These alterations in DNA methylation may serve as biomarkers of maternal exposure to phthalates in infants and are potential candidates for investigating the mechanisms by which phthalates impact maternal and neonatal health.

Epigenotoxicity: a danger to the future life

Environmental toxicants can regulate gene expression in the absence of DNA mutations via epigenetic mechanisms such as DNA methylation, histone modifications, and non-coding RNAs' (ncRNAs). Here, all three epigenetic modifications for seven important categories of diseases and the impact of eleven main environmental factors on epigenetic modifications were discussed. Epigenetic-related mechanisms are among the factors that could explain the root cause of a wide range of common diseases. Its overall impression on the development of diseases can help us diagnose and treat diseases, and besides, predict transgenerational and intergenerational effects. This comprehensive article attempted to address the relationship between environmental factors and epigenetic modifications that cause diseases in different categories. The studies main gap is that the precise role of environmentally-induced epigenetic alterations in the etiology of the disorders is unknown; thus, still more well-designed researches need to be accomplished to fill this gap. The present review aimed to first summarize the adverse effect of certain chemicals on the epigenome that may involve in the onset of particular disease based on in vitro and in vivo models. Subsequently, the possible adverse epigenetic changes that can lead to many human diseases were discussed.

DNA methylation-mediated inhibition of MGARP is involved in impaired progeny testosterone synthesis in mice exposed to DBP in utero

The dibutyl phthalate (DBP) has been detected in fetuses and infants and can cause damage to the reproductive system in adulthood, but the exact mechanism remains unclear. Here, we aim to investigate the effects of intrauterine DBP exposure on offspring reproductive function and explore possible mechanisms. SPF C57BL/6 pregnant mice were given DBP (0.5, 5, 75 mg/kg/d) or corn oil from day 5 to day 19 by gavage. After weaning, the pups were fed a standard diet for 5 weeks. In addition, TM3 Leydig cell cultures were used to study the relevant mechanisms in vitro. The results showed that intrauterine DBP exposure could reduce sperm density and sperm motility, cause testicular tissue damage, down-regulate serum T and LH levels, and up-regulate serum FSH levels at 75 mg/kg/d. Western blot and methylation detection revealed intrauterine exposure to DBP down-regulated testosterone synthesis-related proteins StAR, P450scc, 3β-HSD, PKA, and PKC expression, while up-regulated the levels of methyltransferase proteins expression and DNA 5-methylcytosine (5mC) in testicular tissue of mouse offspring at 75 mg/kg/d. Further detection found in utero 75 mg/kg/d DBP exposure down-regulated MGARP protein expression, and induced incomplete methylation of the MGARP gene. An in vitro analysis showed that MGARP inhibition is involved in an impaired testosterone synthesis in TM3 cells. Cell culture results suggest that MGARP down-regulation may be involved in impaired testosterone production in monobutyl phthalate-treated cells. The present study revealed that 75 mg/kg/d DBP exposure in utero resulted in testosterone synthesis disorders and reproductive function impairment in mouse offspring, and the mechanism may be related to DNA methylation-mediated down-regulation of MGARP in the testis.

Epigenetics as a Biomarker for Early-Life Environmental Exposure

PURPOSE OF REVIEW

There is interest in evaluating the developmental origins of health and disease (DOHaD) which emphasizes the role of prenatal and early-life environments on non-communicable health outcomes throughout the life course. The ability to rigorously assess and identify early-life risk factors for later health outcomes, including those with childhood onset, in large population samples is often limited due to measurement challenges such as impractical costs associated with prospective studies with a long follow-up duration, short half-lives for some environmental toxicants, and lack of biomarkers that capture inter-individual differences in biologic response to external environments.

RECENT FINDINGS

Epigenomic patterns, and DNA methylation in particular, have emerged as a potential objective biomarker to address some of these study design and exposure measurement challenges. In this article, we summarize the literature to date on epigenetic changes associated with specific prenatal and early-life exposure domains as well as exposure mixtures in human observational studies and their biomarker potential. Additionally, we highlight evidence for other types of epigenetic patterns to serve as exposure biomarkers. Evidence strongly supports epigenomic biomarkers of exposure that are detectable across the lifespan and across a range of exposure domains. Current and future areas of research in this field seek to expand these lines of evidence to other environmental exposures, to determine their specificity, and to develop predictive algorithms and methylation scores that can be used to evaluate early-life risk factors for health outcomes across the life span.

Adverse cardiovascular effects and potential molecular mechanisms of DEHP and its metabolites-A review

Currently, cardiovascular disease (CVD) is a health hazard that is associated with progressive deterioration upon exposure to environmental pollutants. Di(2-ethylhexyl) phthalate (DEHP) has been one of the focuses of emerging concern due to its ubiquitous nature and its toxicity to the cardiovascular (CV) system. DEHP has been noted as a causative risk factor or a risk indicator for the initiation and augment of CVDs. DEHP represents a precursor that contributes to the pathogenesis of CVDs through its active metabolites, which mainly include mono (2-ethylhexyl) phthalate (MEHP). Herein, we systematically presented the association between DEHP and its metabolites and adverse CV outcomes and discussed the corresponding effects, underlying mechanisms and possibly interventions. Epidemiological and experimental evidence has suggested that DEHP and its metabolites have significant impacts on processes and factors involved in CVD, such as cardiac developmental toxicity, cardiac injury and apoptosis, cardiac arrhythmogenesis, cardiac metabolic disorders, vascular structural damage, atherogenesis, coronary heart disease and hypertension. DNA methylation, PPAR-related pathways, oxidative stress and inflammation, Ca²⁺ homeostasis disturbance may pinpoint the relevant mechanisms. The preventive and therapeutic measures are potentially related with P-glycoprotein, heat-shock proteins, some antioxidants, curcumin, apigenin, β-thujaplicin, glucagon-like peptide-1 receptor agonists and Ang-converting enzyme inhibitors and so on. Promisingly, future investigations should aid in thoroughly assessing the causal relationship and molecular interactions between CVD and DEHP and its metabolites and explore feasible prevention and treatment measures accordingly.

Fetal exposure to phthalates and bisphenols and DNA methylation at birth: the Generation R Study

BACKGROUND

Phthalates and bisphenols are non-persistent endocrine disrupting chemicals that are ubiquitously present in our environment and may have long-lasting health effects following fetal exposure. A potential mechanism underlying these exposure-outcome relationships is differential DNA methylation. Our objective was to examine the associations of maternal phthalate and bisphenol concentrations during pregnancy with DNA methylation in cord blood using a chemical mixtures approach.

METHODS

This study was embedded in a prospective birth cohort study in the Netherlands and included 306 participants. We measured urine phthalates and bisphenols concentrations in the first, second and third trimester. Cord blood DNA methylation in their children was processed using the Illumina Infinium HumanMethylation450 BeadChip using an epigenome-wide association approach. Using quantile g-computation, we examined the association of increasing all mixture components by one quartile with cord blood DNA methylation.

RESULTS

We did not find evidence for statistically significant associations of a maternal mixture of phthalates and bisphenols during any of the trimesters of pregnancy with DNA methylation in cord blood (all p values > 4.01 * 10^-8). However, we identified one suggestive association (p value < 1.0 * 10^-6) of the first trimester maternal mixture of phthalates and bisphenols and three suggestive associations of the second trimester maternal mixture of phthalates and bisphenols with DNA methylation in cord blood.

CONCLUSIONS

Although we did not identify genome-wide significant results, we identified some suggestive associations of exposure to a maternal mixture of phthalates and bisphenols in the first and second trimester with DNA methylation in cord blood that need further exploration in larger study samples.

Associations between plasma levels of brominated flame retardants and methylation of DNA from peripheral blood: A cross-sectional study in a cohort of French women

BACKGROUND

Brominated flame retardants (BFRs) are organic compounds that are widespread in the environment. Because of their persistence, they are able to bioaccumulate with major impacts on human health. It has been hypothesized that the effect of BFRs on human health is mediated by alterations of DNA methylation.

OBJECTIVE

The aim of this study was to examine the association between methylation of DNA extracted from peripheral blood and circulating levels of BFRs measured in plasma.

METHODS

We conducted a methylation wide association study on 336 blood samples from a study within the E3N (Etude Epidémiologique auprès de femmes de l'Education Nationale) cohort, a long-term longitudinal cohort of French women. DNA methylation at more than 850 000 cytosine-guanine dinucleotide (CpG) sites was measured with the Illumina Infinium HumanMethylation - EPIC BeadChip. Circulating levels of seven BFRs (BDE-28, BDE-47, BDE-99, BDE-100, BDE-153, BDE-154 and PBB-153) were measured by gas chromatography coupled to high-resolution mass spectrometry in plasma samples. The association between DNA methylation and BFRs plasma levels was assessed through linear mixed-effects models followed by gene-set enrichment analyses (GSEA).

RESULTS

We identified 253 CpG sites whose methylation levels were significantly associated with exposure to BFRs after Bonferroni correction. For 50 of these CpGs the p-values were less than 2.2x10^-9 with the strongest association being between BDE-154 and cg23619365 (4.32x10^-13). GSEA of CpG sites associated with exposure to BFRs identified significant enrichment of genes involved in hypoxia, glycolysis and adipogenesis.

CONCLUSIONS

Exposure to BFRs appears to be related to numerous alterations in DNA methylation. These findings, if replicated in independent studies, provide insights into the biological and health effects of BFRs.

Environmental Exposure to Non-Persistent Endocrine Disrupting Chemicals and Endometriosis: A Systematic Review

Endometriosis is a disease characterized by the presence of the uterine endometrium outside of its normal location. As the etiology of endometriosis is not well known and hormonal imbalance is central to disease pathogenesis, the potential contribution of exposure to endocrine-disrupting chemicals (EDCs) has been hypothesized in endometriosis. A systematic search of the literature was carried out to identify relevant studies using: PubMed, Scopus, Elsevier, Springer; EBSCO, and Web of Science. A total of 22 studies were considered. Most of the studies reviewed in this paper showed an association between exposure to BPA and phthalates and endometriosis. In the case of phthalate exposure, the reviewed studies found an association between the concentration of at least one phthalate metabolite and endometriosis. Only one study was performed to assess the exposure to parabens and a significant relationship with endometriosis was found. Additionally, only one study assessed the relationship of non-persistent pesticide exposure with endometriosis, observing a significant association between endometriosis and the urinary concentration of diazinon, chlorpyrifos, and chlorpyrifos-methyl. Studies struggled to provide a conclusion on the effect of exposure to benzophenones on endometriosis. Despite the numerous limitations of the results, the reviewed studies suggest that exposure to non-persistent endocrine disruptors, especially bisphenol A and phthalates may affect endometriosis. The results of the studies on exposure to parabens, benzophenones, and non-persistent insecticides are inconclusive.

Prenatal exposure to phthalates and peripheral blood and buccal epithelial DNA methylation in infants: An epigenome-wide association study

BACKGROUND

Prenatal exposure to phthalates has been associated with adverse health and neurodevelopmental outcomes. DNA methylation (DNAm) alterations may be a mechanism underlying these effects, but prior investigations of prenatal exposure to phthalates and neonatal DNAm profiles are limited to placental tissue and umbilical cord blood.

OBJECTIVE

Conduct an epigenome-wide association study (EWAS) of the associations between prenatal exposure to phthalates and DNAm in two accessible infant tissues, venous buffy coat blood and buccal epithelial cells (BECs).

METHODS

Participants included 152 maternal-infant pairs from the Alberta Pregnancy Outcomes and Nutrition (APrON) study. Maternal second trimester urine samples were analyzed for nine phthalate metabolites. Blood (n = 74) or BECs (n = 78) were collected from 3-month-old infants and profiled for DNAm using the Infinium HumanMethylation450 (450K) BeadChip. Robust linear regressions were used to investigate the associations between high (HMWPs) and low molecular weight phthalates (LMWPs) and change in methylation levels at variable Cytosine-phosphate-Guanine (CpG) sites in infant tissues, as well as the sensitivity of associations to potential confounders.

RESULTS

One candidate CpG in gene RNF39 reported by a previous study examining prenatal exposure to phthalates and cord blood DNAm was replicated. The EWAS identified 12 high-confidence CpGs in blood and another 12 in BECs associated with HMWPs and/or LMWPs. Prenatal exposure to bisphenol A (BPA) associated with two of the CpGs associated with HMWPs in BECs.

DISCUSSION

Prenatal exposure to phthalates was associated with DNAm variation at CpGs annotated to genes associated with endocrine hormone activity (i.e., SLCO4A1, TPO), immune pathways and DNA damage (i.e., RASGEF1B, KAZN, HLA-A, MYO18A, DIP2C, C1or109), and neurodevelopment (i.e., AMPH, NOTCH3, DNAJC5). Future studies that characterize the stability of these associations in larger samples, multiple cohorts, across tissues, and investigate the potential associations between these biomarkers and relevant health and neurodevelopmental outcomes are needed.

Prenatal Exposures to Common Phthalates and Prevalent Phthalate Alternatives and Infant DNA Methylation at Birth

Phthalates are a diverse group of chemicals used in consumer products. Because they are so widespread, exposure to these compounds is nearly unavoidable. Recently, growing scientific consensus has suggested that phthalates produce health effects in developing infants and children. These effects may be mediated through mechanisms related to the epigenome, the constellation of mitotically heritable chemical marks and small compounds that guide transcription and translation. The present study examined the relationship between prenatal, first-trimester exposure of seven phthalates and epigenetics in two pregnancy cohorts (n = 262) to investigate sex-specific alterations in infant blood DNA methylation at birth (cord blood or neonatal blood spots). Prenatal exposure to several phthalates was suggestive of association with altered DNA methylation at 4 loci in males (all related to ΣDEHP) and 4 loci in females (1 related to ΣDiNP; 2 related to BBzP; and 1 related to MCPP) at a cutoff of q < 0.2. Additionally, a subset of dyads (n = 79) was used to interrogate the relationships between two compounds increasingly used as substitutions for common phthalates (ΣDINCH and ΣDEHTP) and cord blood DNA methylation. ΣDINCH, but not ΣDEHTP, was suggestive of association with DNA methylation (q < 0.2). Together, these results demonstrate that prenatal exposure to both classically used phthalate metabolites and their newer alternatives is associated with sex-specific infant DNA methylation. Research and regulatory actions regarding this chemical class should consider the developmental health effects of these compounds and aim to avoid regrettable substitution scenarios in the present and future.

Effect of prenatal exposure to phthalates on epigenome-wide DNA methylations in cord blood and implications for fetal growth: The Hokkaido Study on Environment and Children's Health

Prenatal exposure to phthalates negatively affects the offspring's health. In particular, epigenetic alterations, such as DNA methylation, may connect phthalate exposure with health outcomes. Here, we evaluated the association of di-2-ethylhexyl phthalate (DEHP) exposure in utero with cord blood epigenome-wide DNA methylation in 203 mother-child pairs enrolled in the Hokkaido Study on Environment and Children's Health, using the Illumina HumanMethylation450 BeadChip. Epigenome-wide association analysis demonstrated the predominant positive associations between the levels of the primary metabolite of DEHP, mono(2-ethylhexyl) phthalate (MEHP), in maternal blood and DNA methylation levels in cord blood. The genes annotated to the CpGs positively associated with MEHP levels were enriched for pathways related to metabolism, the endocrine system, and signal transduction. Among them, methylation levels of CpGs involved in metabolism were inversely associated with the offspring's ponderal index (PI). Further, clustering and mediation analyses suggested that multiple increased methylation changes may jointly mediate the association of DEHP exposure in utero with the offspring's PI at birth. Although further studies are required to assess the impact of these changes, this study suggests that differential DNA methylation may link phthalate exposure in utero to fetal growth and further imply that DNA methylation has predictive value for the offspring's obesity.

Phthalates and Their Impacts on Human Health

Phthalates are a series of widely used chemicals that demonstrate to be endocrine disruptors and are detrimental to human health. Phthalates can be found in most products that have contact with plastics during producing, packaging, or delivering. Despite the short half-lives in tissues, chronic exposure to phthalates will adversely influence the endocrine system and functioning of multiple organs, which has negative long-term impacts on the success of pregnancy, child growth and development, and reproductive systems in both young children and adolescents. Several countries have established restrictions and regulations on some types of phthalates; however, we think that more countries should establish constraints or substitute measures for phthalates to reduce health risks. This article aims to summarize the adverse impacts of phthalates on human health, analyze the toxicity mechanism, assess the risks, and finally provide feasible strategies to reduce exposure of the public to phthalates.

Transgenerational Effects of Di(2-Ethylhexyl) Phthalate on Anogenital Distance, Sperm Functions and DNA Methylation in Rat Offspring

Di(2-ethylhexyl) phthalate (DEHP) is widely used as a plasticizer in the manufacture of polyvinylchloride plastics and has been associated with concerns regarding male reproductive toxicity. In this study, we hypothesized that maternal exposure to DEHP induces transgenerational inheritance of adult-onset adverse reproductive outcomes through the male germline in the F1, F2, and F3 generations of male offspring. Pregnant rats were treated with 5 or 500 mg of DEHP/kg/day through gavage from gestation day 0 to birth. The offspring body weight, anogenital distance (AGD), anogenital index (AGI), sperm count, motility, and DNA fragmentation index (DFI) were measured for all generations. Methyl-CpG binding domain sequencing was performed to analyze sperm DNA methylation status in the F3. DEHP exposure at 500 mg/kg affected AGD, AGI, sperm count, mean DFI, and %DFI in the F1; AGD, sperm count, and mean DFI in the F2; and AGD, AGI, mean DFI, and %DFI in the F3. DEHP exposure at 5 mg/kg affected AGD, AGI, sperm count, and %DFI in the F1; sperm count in the F2; and AGD and AGI in F3. Compared with the control group, 15 and 45 differentially hypermethylated genes were identified in the groups administered 5 mg/kg and 500 mg/kg DEHP, respectively. Moreover, 130 and 6 differentially hypomethylated genes were observed in the groups administered 5 mg/kg and 500 mg/kg DEHP. Overall, these results demonstrated that prenatal exposure to DEHP caused transgenerational epigenetic effects, which may explain the observed phenotypic changes in the male reproductive system.

Perinatal Exposure to Phthalates: From Endocrine to Neurodevelopment Effects

Phthalates, as other endocrine disrupting chemicals (EDCs), may alter the homeostasis and the action of hormones and signaling molecules, causing adverse health outcomes. This is true especially for infants, who are both more exposed and sensitive to their effects. Phthalates are particularly harmful when the exposure occurs during certain critical temporal windows of the development, such as the prenatal and the early postnatal phases. Phthalates may also interfere with the neuroendocrine systems (e.g., thyroid hormone signaling or metabolism), causing disruption of neuronal differentiation and maturation, increasing the risk of behavioral and cognitive disorders (ADHD and autistic behaviors, reduced mental, psychomotor, and IQ development, and emotional problems). Despite more studies being needed to better understand the role of these substances, plenty of evidence suggests the impact of phthalates on the neuroendocrine system development and function. This review aims to update the knowledge on the neuroendocrine consequences of neonatal and perinatal exposure to phthalates.

Associations among phthalate exposure, DNA methylation of TSLP, and childhood allergy

BACKGROUND

Dysregulation of thymic stromal lymphopoietin (TSLP) expressions is linked to asthma and allergic disease. Exposure to phthalate esters, a widely used plasticizer, is associated with respiratory and allergic morbidity. Dibutyl phthalate (DBP) causes TSLP upregulation in the skin. In addition, phthalate exposure is associated with changes in environmentally induced DNA methylation, which might cause phenotypic heterogeneity. This study examined the DNA methylation of the TSLP gene to determine the potential mechanism between phthalate exposure and allergic diseases.

RESULTS

Among all evaluated, only benzyl butyl phthalate (BBzP) in the settled dusts were negatively correlated with the methylation levels of TSLP and positively associated with children's respiratory symptoms. The results revealed that every unit increase in BBzP concentration in the settled dust was associated with a 1.75% decrease in the methylation level on upstream 775 bp from the transcription start site (TSS) of TSLP (β =  - 1.75, p = 0.015) after adjustment for child's sex, age, BMI, parents' smoking status, allergic history, and education levels, PM_2.5, formaldehyde, temperature; and relative humidity. Moreover, every percentage increase in the methylation level was associated with a 20% decrease in the risk of morning respiratory symptoms in the children (OR 0.80, 95% CI 0.65-0.99).

CONCLUSIONS

Exposure to BBzP in settled dust might increase children's respiratory symptoms in the morning through decreasing TSLP methylation. Therefore, the exposure to BBzP should be reduced especially for the children already having allergic diseases.

Mitigation of indoor air pollution: A review of recent advances in adsorption materials and catalytic oxidation

Indoor air pollution with toxic volatile organic compounds (VOCs) and fine particulate matter (PM2.5) is a threat to human health, causing cancer, leukemia, fetal malformation, and abortion. Therefore, the development of technologies to mitigate indoor air pollution is important to avoid adverse effects. Adsorption and photocatalytic oxidation are the current approaches for the removal of VOCs and PM2.5 with high efficiency. In this review we focus on the recent development of indoor air pollution mitigation materials based on adsorption and photocatalytic decomposition. First, we review on the primary indoor air pollutants including formaldehyde, benzene compounds, PM2.5, flame retardants, and plasticizer: Next, the recent advances in the use of adsorption materials including traditional biochar and MOF (metal-organic frameworks) as the new emerging porous materials for VOCs absorption is reviewed. We review the mechanism for mitigation of VOCs using biochar (noncarbonized organic matter partition and adsorption) and MOF together with parameters that affect indoor air pollution removal efficiency based on current mitigation approaches including the mitigation of VOCs using photocatalytic oxidation. Finally, we bring forward perspectives and directions for the development of indoor air mitigation technologies.

The role of epigenetics in the reproductive toxicity of environmental endocrine disruptors

Environmental endocrine disruptors (EEDs) seriously endanger human health by interfering with the normal function of reproductive systems. In males, EEDs can affect sperm formation and semen quality as well spermatogenesis, ultimately reducing fertility. In females, EEDs can affect uterine development and the expression levels of reproduction-related genes, ultimately reducing female fertility and the normal development of the fetus. There are a large number of putative mechanisms by which EEDs can induce reproductive toxicity, and many studies have shown the involvement of epigenetics. In this review, we summarize the role of DNA methylation, noncoding RNAs, genomic imprinting, chromatin remodeling and histone modification in the reproductive toxicity of EEDs.

Clinical expression of endocrine disruptors in children

PURPOSE OF REVIEW

Health status is the result of complex interaction between individual factors, general environmental factors and specific factors as nutrition or the presence of chemicals. Aim of this review is to point out the more recent knowledge covering the role of the endocrine disrupting chemical (EDC) on pediatric population wellbeing.

RECENT FINDINGS

Prenatal, postnatal life and puberty are the three main temporal windows of susceptibility when EDCs may act. The mechanism is independent from dose or duration of exposition, sex, age or combination of chemicals and may also be transgenerational, affecting both growth and pubertal timing. A window of susceptibility for breast cancer has been detected. Thyroid gland is influenced by environmental chemicals, both in utero and during childhood. Alteration in Thyrotropin stimulating hormone (TSH) levels and neurodevelopmental impairment have been demonstrate. It has been detected a pro-obesogenic action of specific chemicals, impairing also glucose homeostasis during childhood.

SUMMARY

With a multidisciplinary approach and the use of big data platforms, an attempt has to be made to verify biological variations related to a disease, and how much the risk is influenced by the presence of the endocrine disruptors. This may help the future generation to better interpret uncommunicable diseases.

The association between prenatal endocrine-disrupting chemical exposure and altered resting-state brain fMRI in teenagers

Many studies have reported that prenatal exposure to endocrine-disrupting chemicals (EDCs) can cause adverse behavioral effects or cognitive dysfunction in children. This study aimed to investigate a relationship of the concentration of prenatal EDCs and brain function in teenagers. We recruited 59 mother-child pairs during the third trimester of pregnancy, and collected and examined the concentration of EDCs, such as heavy metals, phthalates and perfluoroalkyl substances (PFASs), in maternal urine and serum. Resting-state functional magnetic resonance imaging (rs-fMRI) data were collected in teenagers 13-16 years of age, and fractional amplitude of low-frequency fluctuation (fALFF) and regional homogeneity (ReHo) were performed to find the association between maternal EDC concentrations and the functional development of the teenage brain. We found a correlation between MBP concentration and activity in the superior frontal gyrus, middle frontal gyrus, middle temporal gyrus and inferior temporal gyrus in the combined group of boys and girls. We also observed a correlation between MBzP concentration and activity in the anterior cingulum gyrus and insula in girls. We found a correlation between lead concentration and activity in the cuneus in the combined group. We also observed a correlation between MeHg concentration and activity in the superior temporal gyrus, caudate nucleus and putamen in the combined group. The PFOS results revealed a negative relationship between activity in the right putamen in boys, girls and the combined group after phthalate or heavy metals were applied as covariates. The PFNA results showed a negative correlation between activity in the left/right putamen and left caudate nucleus in boys, girls and the combined group after phthalate, heavy metals or PFOS were applied as covariates. We examined the correlations between maternal EDC concentrations and brain development and found that the associations with resting-state teenage brains in some circumstances are sex-related.

Phthalate Exposure and Long-Term Epigenomic Consequences: A Review

Phthalates are esters of phthalic acid which are used in cosmetics and other daily personal care products. They are also used in polyvinyl chloride (PVC) plastics to increase durability and plasticity. Phthalates are not present in plastics by covalent bonds and thus can easily leach into the environment and enter the human body by dermal absorption, ingestion, or inhalation. Several in vitro and in vivo studies suggest that phthalates can act as endocrine disruptors and cause moderate reproductive and developmental toxicities. Furthermore, phthalates can pass through the placental barrier and affect the developing fetus. Thus, phthalates have ubiquitous presence in food and environment with potential adverse health effects in humans. This review focusses on studies conducted in the field of toxicogenomics of phthalates and discusses possible transgenerational and multigenerational effects caused by phthalate exposure during any point of the life-cycle.

Exposure to DEHP or its metabolite MEHP promotes progesterone secretion and inhibits proliferation in mouse placenta or JEG-3 cells

Di (2-ethyl-hexyl)phthalate (DEHP) is an environmental endocrine disruptor and commonly used as plasticizer. Maternal DEHP exposure during pregnancy reduces placental size and destroys placental structure. However, the underlying mechanisms were unclear. In this study, we supposed that DEHP disturbs endocrine function of placenta to inhibit the proliferation of placental cell. Using radioimmunoassay and ELISA, we found that DEHP and its active metabolite mono (2-ethyl-hexyl) phthalate (MEHP) promoted progesterone secretion in pregnant mouse and in JEG-3 cells, respectively. Therefore, placental endocrine function was altered by DEHP. The mRNA and protein level of progesterone synthetase 3β-HSD1 was elevated by DEHP, which is conducive to the synthesis of progesterone. The level of progesterone receptor was down-regulated by DEHP and MEHP in mouse placenta and in JEG-3 cells, respectively. PR deficiency further promoted the level of 3β-HSD1, which leads to a higher progesterone level. In turn, higher concentration of progesterone further inhibited the expression of PGR (PR gene). Therefore, higher progesterone down-regulated the level of its receptor PR. Meanwhile, decreased PR induced more progesterone secretion. There is a feedback loop between progesterone and PR. PR deficiency down-regulated the protein level of Cyclin D1 which plays an important role in cell proliferation. Accordingly, DEHP and its active metabolite MEHP can restrain proliferation of placental cell and disturb the progesterone secretion via decreasing the level of PR.

Gestational Exposures to Phthalates and Folic Acid, and Autistic Traits in Canadian Children

BACKGROUND

The etiology of autism spectrum disorder is poorly understood. Few studies have investigated the link between endocrine-disrupting chemicals and autistic traits. We examined the relationship between gestational phthalates and autistic traits in 3- to 4-y-old Canadian children. We also investigated potential effect modification by sex and folic acid supplementation.

METHODS

We enrolled 2,001 women>18 years of age during the first trimester of pregnancy between 2008 and 2011 from 10 cities in Canada. At 3-4 years of age, 610 children underwent neuropsychological assessments including the Social Responsiveness Scale-II (SRS-2) as a measure of autistic traits and social impairment. We measured 11 phthalate metabolites in maternal first trimester urine samples and assessed folic acid supplementation from reported intakes. We estimated covariate-adjusted differences in SRS-2 T-scores with a doubling in phthalate concentrations in 510 children with complete data.

RESULTS

Mean total SRS T-score was 45.3 (SD=6.1). Children with higher gestational exposure to mono-n-butyl (MBP) and mono-3-carboxypropyl (MCPP) concentrations exhibited significantly higher total SRS T-scores, indicating greater overall social impairment, as well as higher scores on subdomains, indicating deficits in social cognition, social communication, social motivation, and restricted interests/repetitive behaviors. A doubling in MBP or MCPP concentrations was associated with 0.6 (95% CI: 0.1, 1.0) and 0.5 (95% CI: 0.1, 0.8) higher total SRS T-scores. Associations were consistently and significantly stronger in boys (βMBP=1.0; 95% CI: 0.4, 1.6; n=252) compared with girls (βMBP=0.1; 95% CI: -0.6, 0.7; n=258) and among children who had lower prenatal folic acid supplementation (<400μg/d) (βMBP=1.3; 95% CI: 0.4, 2.3; n=59) compared with those who had adequate folic acid supplementation (≥400μg/d) (βMBP=0.4; 95% CI: -0.1, 0.8; n=451).

CONCLUSIONS

Higher gestational concentrations of some phthalate metabolites were associated with higher scores of autistic traits as measured by the SRS-2 in boys, but not girls; these small size effects were mitigated by first trimester-of-pregnancy folic acid supplementation. https://doi.org/10.1289/EHP5621.

The Promises and Challenges of Toxico-Epigenomics: Environmental Chemicals and Their Impacts on the Epigenome

BACKGROUND

It has been estimated that a substantial portion of chronic and noncommunicable diseases can be caused or exacerbated by exposure to environmental chemicals. Multiple lines of evidence indicate that early life exposure to environmental chemicals at relatively low concentrations could have lasting effects on individual and population health. Although the potential adverse effects of environmental chemicals are known to the scientific community, regulatory agencies, and the public, little is known about the mechanistic basis by which these chemicals can induce long-term or transgenerational effects. To address this question, epigenetic mechanisms have emerged as the potential link between genetic and environmental factors of health and disease.

OBJECTIVES

We present an overview of epigenetic regulation and a summary of reported evidence of environmental toxicants as epigenetic disruptors. We also discuss the advantages and challenges of using epigenetic biomarkers as an indicator of toxicant exposure, using measures that can be taken to improve risk assessment, and our perspectives on the future role of epigenetics in toxicology.

DISCUSSION

Until recently, efforts to apply epigenomic data in toxicology and risk assessment were restricted by an incomplete understanding of epigenomic variability across tissue types and populations. This is poised to change with the development of new tools and concerted efforts by researchers across disciplines that have led to a better understanding of epigenetic mechanisms and comprehensive maps of epigenomic variation. With the foundations now in place, we foresee that unprecedented advancements will take place in the field in the coming years. https://doi.org/10.1289/EHP6104.

Prenatal and ancestral exposure to di(2-ethylhexyl) phthalate alters gene expression and DNA methylation in mouse ovaries

Di(2-ethylhexyl) phthalate (DEHP) is a commonly used plasticizer and known endocrine disrupting chemical, which causes transgenerational reproductive toxicity in female rodents. However, the mechanisms of action underlying the transgenerational toxicity of DEHP are not understood. Therefore, this study determined the effects of prenatal and ancestral DEHP exposure on various ovarian pathways in the F1, F2, and F3 generations of mice. Pregnant CD-1 dams were orally exposed to corn oil (vehicle control) or DEHP (20 μg/kg/day-750 mg/kg/day) from gestation day 10.5 until birth. At postnatal day 21 for all generations, ovaries were removed for gene expression analysis of various ovarian pathways and for 5-methyl cytosine (5-mC) quantification. In the F1 generation, prenatal DEHP exposure disrupted the expression of cell cycle regulators, the expression of peroxisome-proliferator activating receptors, and the percentage of 5-mC compared to control. In the F2 generation, exposure to DEHP decreased the expression of steroidogenic enzymes, apoptosis factors, and ten-eleven translocation compared to controls. It also dysregulated the expression of phosphoinositide 3-kinase (PI3K) factors. In the F3 generation, ancestral DEHP exposure decreased the expression of steroidogenic enzymes, PI3K factors, cell cycle regulators, apoptosis factors, Esr2, DNA methylation mediators, and the percentage of 5-mC compared to controls. Overall, the data show that prenatal and ancestral DEHP exposure greatly suppress gene expression of pathways required for folliculogenesis and steroidogenesis in the ovary in a transgenerational manner and that gene expression may be influenced by DNA methylation. These results provide insight into some of the mechanisms of DEHP-mediated toxicity in the ovary across generations.

Di-n-butyl phthalate epigenetically induces reproductive toxicity via the PTEN/AKT pathway

Di-n-butyl phthalate (DBP) is a kind of ubiquitous chemical linked to hormonal disruptions that affects male reproductive system. However, the mechanism of DBP-induced germ cells toxicity remains unclear. Here, we demonstrate that DBP induces reduction of proliferation, increase of apoptosis and DNA damage dependent on the PTEN/AKT pathway. Mechanistically, DBP decreases PTEN promoter methylation and increases its transcriptional activity, leading to increased PTEN expression. Notably, DNMT3b is confirmed as a target of miR-29b and miR-29b-mediated status of PTEN methylation is involved in the effects of DBP treatment. Meanwhile, DBP decreases AKT pathway expression via increasing PTEN expression. In addition, the fact that DBP decreases the sperm number and the percentage of motile and progressive sperm is associated with downregulated AKT pathway and sperm flagellum-related genes. Collectively, these findings indicate that DBP induces aberrant PTEN demethylation, leading to inhibition of the AKT pathway, which contributes to the reproductive toxicity.

Positive association of low-level environmental phthalate exposure with sperm motility was mediated by DNA methylation: A pilot study

Accumulating evidence indicates that phthalate exposures may affect human semen quality. Epigenetic modifications such as DNA methylation might be linked chemical exposure and spermatogenesis epigenetic reprogramming. In the present study, we investigated associations between phthalate exposures, DNA methylation and sperm quality in undergoing fertility assessment male population. Urine was used for phthalate exposures monitoring, six selected metabolites (i.e., monomethyl phthalate (MMP), monoethyl phthalate (MEP), mono-n-butyl phthalate (MBP), monobenzyl phthalate (MBzP), mono-(2-ethylhexyl) phthalate (MEHP) and mono (2-ethyl-5-oxohexyl) phthalate (MEOHP)) were measured by using HPLC-MS/MS. Sperm quality parameters were determined by computer-assisted semen analysis (CASA). Sperm DNA methylation patterns (long interspersed nuclear element-1(LINE-1), H19 and LIT1) were analysed employing high-melting resolution (HRM) PCR. Urinary MMP, MEHP, MEOHP, sum of DEHP metabolites (∑DEHP) and sum of selected phthalates metabolites (∑PAEs) were significantly positively associated with sperm motility. Sperm LINE-1 DNA methylation were found to be negatively associated with ∑DEHP exposure and sperm quality (ejaculate volume, total sperm number and motility). Epigenetic modification LINE-1 DNA methylation demonstrated mediating effects in association between DEHP exposure and sperm motility, and 20.7% of the association was mediated by serum LIEN-1 DNA methylation. These results extend the previous studies in association between phthalate exposures and classical semen parameters, mainly of inverse association, and sperm DNA methylation may be linked phthalate exposures and male reproductive health outcome.

Primers on nutrigenetics and nutri(epi)genomics: Origins and development of precision nutrition

Understanding the relationship between genotype and phenotype is a central goal not just for genetics but also for medicine and biological sciences. Despite outstanding technological progresses, genetics alone is not able to completely explain phenotypes, in particular for complex diseases. Given the existence of a "missing heritability", growing attention has been given to non-mendelian mechanisms of inheritance and to the role of the environment. The study of interaction between gene and environment represents a challenging but also a promising field with high potential for health prevention, and epigenetics has been suggested as one of the best candidate to mediate environmental effects on the genome. Among environmental factors able to interact with both genome and epigenome, nutrition is one of the most impacting. Not just our genome influences the responsiveness to food and nutrients, but vice versa, nutrition can also modify gene expression through epigenetic mechanisms. In this complex picture, nutrigenetics and nutrigenomics represent appealing disciplines aimed to define new prospectives of personalized nutrition. This review introduces to the study of gene-environment interactions and describes how nutrigenetics and nutrigenomics modulate health, promoting or affecting healthiness through life-style, thus playing a pivotal role in modulating the effect of genetic predispositions.

Comparative Overview of the Mechanisms of Action of Hormones and Endocrine Disruptor Compounds

Endocrine Disruptor Compounds (EDCs) are synthetic or natural molecules in the environment that promote adverse modifications of endogenous hormone regulation in humans and/or in wildlife animals. In the present paper, we review the potential mechanisms of EDCs and point out the similarities and differences between EDCs and hormones. There was only one mechanism, out of nine identified, in which EDCs acted like hormones (i.e. binding and stimulated hormone receptor activity). In the other eight identified mechanisms of action, EDCs exerted their effects either by affecting endogenous hormone concentration, or its availability, or by modifying hormone receptor turn over. This overview is intended to classify the various EDC mechanisms of action in order to better appreciate when in vitro tests would be valid to assess their risks towards humans and wildlife.

Comparing dietary and non-dietary source contribution of BPA and DEHP to prenatal exposure: A Catalonia (Spain) case study

Bisphenol A (BPA) and Di-(2-ethylhexyl) phthalate (DEHP) are two wide spread chemicals classified as endocrine disruptors (ED). The present study aims to estimate the non-dietary (dermal, non-dietary ingestion and inhalation) exposure to BPA and DEHP for a pregnant women cohort. In addition, to assess the prenatal exposure for the fetus, a physiologically based pharmacokinetic (PBPK) model was used. It was adapted for pregnancy in order to assess the internal dosimetry levels of EDs (BPA and DEHP) in the fetus. Estimates of exposure to BPA and DEHP from all pathways along with their relative importance were provided in order to establish which proportion of the total exposure came from diet and which came from non-dietary exposures. In this study, the different oral dosing scenarios (dietary and non-dietary) were considered keeping inhalation as a continuous exposure case. Total non-dietary mean values were 0.002 µg/kg_bw/day (0.000; 0.004 µg/kg_bw/day for 5th and 95th percentile, respectively) for BPA and 0.597 µg/kg_bw/day (0.116 µg/kg_bw/day and 1.506 µg/kg_bw/day for 5th and 95th percentile, respectively) for DEHP. Indoor environments and especially dust ingestion were the main non-dietary contributors to the total exposure of BPA and DEHP with 60% and 81%. However, as expected, diet showed the higher contribution to total exposure with > 99.9% for BPA and 63% for DEHP. Although diet was considered the primary source of exposure to BPA and phthalates, it must be taken into account that with non-dietary sources the first-pass metabolism is lacking, so these may be of equal or even higher toxicological relevance than dietary sources. The present study is in the framework of "Health and environmental-wide associations based on large population surveys" (HEALS) project (FP7-603946).

Prenatal phthalate exposure, birth outcomes and DNA methylation of Alu and LINE-1 repetitive elements: A pilot study in China

BACKGROUND

Epigenetic mechanisms, such as altered DNA methylation, may participate in the relationship between prenatal phthalate exposure and adverse birth outcomes.

OBJECTIVE

To explore the mediation effect of DNA methylation in the associations of phthalate exposure before delivery with birth outcomes in a Chinese cohort.

METHODS

Eight phthalate metabolites in maternal urine before delivery and DNA methylation of Alu and long interspersed nucleotide elements (LINE-1) in cord blood were determined among 106 mother-infant pairs. General additive models were used to assess the associations of maternal urinary phthalate metabolites with birth outcomes and DNA methylation; the mediating role of DNA methylation in cord blood was evaluated by mediation analysis.

RESULTS

We found sex-specific associations between prenatal phthalate exposure and birth outcomes and DNA methylation of cord blood. For example, the molar sum of di-2-(ethylhexyl) phthalate (∑DEHPm) metabolites in maternal urine was positively associated with gestational age among male newborns only (P < 0.05); maternal urinary monobenzyl phthalate (MBzP) was negatively associated with Alu methylation among female newborns only (P < 0.05). Mediation analysis did not find that methylation of Alu and LINE-1 to be a direct mediator in the relationships between maternal urinary phthalate metabolites before delivery and birth outcomes.

CONCLUSION

Prenatal exposure to certain phthalates was associated with altered birth outcomes and decreased repetitive element methylation of newborns. However, the altered birth outcomes exerted by prenatal phthalate exposure does not seem to be directly mediated through repetitive element methylation in cord blood.