Epigenetics and environmental chemicals

Epigenetic control of atherosclerosis via DNA methylation: A new therapeutic target?

Atherosclerosis is a disease in which lipid-laden plaques are developed inside the vessel walls of arteries. The immune system is activated, resulting in inflammation and oxidative stress. Endothelial cells (ECs) are activated, arterial smooth muscle cells (SMCs) proliferate, macrophages are activated, and foam cells are developed, leading to dysfunctional ECs. Epigenetic regulatory mechanisms, including DNA methylation, histone modifications, and microRNAs are involved in the modulation of genes that play distinct roles in several aspects of cell biology and physiology, hence linking environmental stimuli to gene regulation. Recent research has investigated the involvement of DNA methylation in the etiopathogenesis of atherosclerosis, and several studies have documented the role of this mechanism in various aspects of the disease. Regulation of DNA methylation plays a critical role in the integrity of ECs, SMC proliferation and formation of atherosclerotic lesions. In this review, we seek to clarify the role of DNA methylation in the development of atherosclerosis through different mechanisms.

Agnathia otocephaly: A case from the Katanga Copperbelt

BACKGROUND

Agnathia otocephaly is a rare craniofacial malformation complex characterised by absent/hypoplastic mandible, abnormally positioned ears meeting at level of neck. Besides mutations in two genes, PRRX1 and OTX2, a teratogenic cause has been suggested. A higher risk of congenital malformations has been associated with paternal work in mining in the Democratic Republic of the Congo's part of the Copperbelt.

CASE

We studied a female neonate with a clinical diagnosis of agnathia otocephaly, stillborn in Lubumbashi in 2019. The child's father had been working as an artisanal mineworker at the time of conception.

RESULTS

Genetic analysis did not reveal a causal mutation. The concentrations of cobalt, arsenic cadmium, and uranium in cord blood of the infant were much higher than those of normal neonates from a previous study.

CONCLUSION

In the absence of identified genetic causes, we hypothesize this case of agnathia otocephaly was related to an exogenous cause, possibly the father's mining-related job.

Mobility of trace metals in serpentinite-derived soils of the Pollino Massif (Southern Italy): insights on bioavailability and toxicity

This paper deals with the evaluation of geo- and bioavailability of trace elements, including heavy metals, present in a typical serpentinite-derived soil of the Pollino Massif (Southern Italy). Precisely, the research was aimed to (1) assess processes and factors controlling the mobility of metals in the soil in order to identify the elements "potentially harmful" for the human health, (2) estimate possible metals accumulation in horticultural crops, and (3) evaluate phyto- and genotoxicity of Cr naturally present in soils and water. The studied profile has a homogeneous mineralogical composition consisting of metal-rich phases as prevailing minerals. The three-step sequential extraction was performed on soil samples from which four fractions (exchangeable, reducible, oxidizable, and residual) were obtained and analysed by ICP-MS. The lowest contents of metals are in the exchangeable and oxidizable fractions suggesting a metal contamination is unlikely for the studied soil. Conversely, the residual and reducible fractions are the more metal enriched fractions. Among heavy metals, mainly Pb and Cd and subordinately Ni, Cr, Cu, and Zn are associated with Fe- and Mn-oxi/hydroxides that, under acidic conditions, may release the adsorbed metals in circulating water. The high contents of heavy metals, including Cr and Ni, of analysed vegetables suggest a metal transfer from soil to plant. However, no significant effects on Vicia faba seeds were observed by in vivo phyto- and genotoxicity tests. Conversely in vitro genotoxicity tests, performed on HepG2 human cell line, showed that DNA damage and cytotoxic effect depending on Cr concentration may occur.

Genome-wide analysis of DNA methylation in testis of male rat exposed to chlorpyrifos

In our previous study, we found that subchronic exposure of chlorpyrifos (CPF) can cause reproductive damage in male rats. However, the mechanisms underlying the reproductive effects of CPF are not well understood. DNA methylation is essential for epigenetic gene regulation in development and disease. Therefore, we aim to compare DNA methylation profiles between controls and CPF-treated rats in order to identify the epigenetic mechanism of male reproductive toxicity induced by CPF. Methylated DNA immunoprecipitation with high-throughput sequencing (MeDIP-seq) was used to investigate the genome-wide DNA methylation pattern in testes of control and CPF-treated rats for 90 days. We identified 27 019 differentially methylated regions (DMRs) (14 150 upmethylated and 12 869 downmethylated) between CPF-exposed and control groups. The DMR-related genes are mainly involved in 113 pathways predicted by Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. The result showed that high methylation gene PIK3CD may play a key role in epigenetic regulation of multiple pathways, such as Ras signaling pathway, AGE-RAGE signaling pathway in diabetic complications, HIF-1 signaling pathway, VEGF signaling pathway, and glioma and Fc epsilon RI signaling pathway in rats exposed to CPF. Our study provides significant explanations for the epigenetic mechanism of male reproductive toxicology induced by CPF.

Fetal Programming by Methyl Donors Modulates Central Inflammation and Prevents Food Addiction-Like Behavior in Rats

Fetal programming by hypercaloric intake leads to food addiction-like behavior and brain pro-inflammatory gene expression in offspring. The role of methylome modulation during programming on central immune activation and addiction-like behavior has not been characterized. We employed a nutritional programming model exposing female Wistar rats to chow diet, cafeteria (CAF), or CAF-methyl donor’s diet from pre-pregnancy to weaning. Addiction-like behavior in offspring was characterized by the operant training response using Skinner boxes. Food intake in offspring was determined after fasting–refeeding schedule and subcutaneous injection of ghrelin. Genome-wide DNA methylation in the nucleus accumbens (NAc) shell was performed by fluorescence polarization, and brain immune activation was evaluated using real-time PCR for pro-inflammatory cytokines (IL-1β, TNF-1α, and IL-6). Molecular effects of methyl modulators [S-adenosylmethionine (SAM) or 5-azatidine (5-AZA)] on pro-inflammatory cytokine expression and phagocytosis were identified in the cultures of immortalized SIM-A9 microglia cells following palmitic acid (100 μM) or LPS (100 nM) stimulation for 6 or 24 h. Our results show that fetal programming by CAF exposure increases the number of offspring subjects and reinforcers under the operant training response schedule, which correlates with an increase in the NAc shell global methylation. Notably, methyl donor’s diet selectively decreases lever-pressing responses for reinforcers and unexpectedly decreases the NAc shell global methylation. Also, programmed offspring by CAF diet shows a selective IL-6 gene expression in the NAc shell, which is reverted to control values by methyl diet exposure. In vitro analysis identified that LPS and palmitic acid activate IL-1β, TNF-1α, and IL-6 gene expression, which is repressed by the methyl donor SAM. Finally, methylation actively represses phagocytosis activity of SIM-A9 microglia cells induced by LPS and palmitic acid stimulation. Our in vivo and in vitro data suggest that fetal programming by methyl donors actively decreases addiction-like behavior to palatable food in the offspring, which correlates with a decrease in NAc shell methylome, expression of pro-inflammatory cytokine genes, and activity of phagocytic microglia. These results support the role of fetal programming in brain methylome on immune activation and food addiction-like behavior in the offspring.

Endocrine disruption and obesity: A current review on environmental obesogens

Obesity represents an important public health concern because it substantially increases the risk of multiple chronic diseases and thereby contributing to a decline in both quality of life and life expectancy. Besides unhealthy diet, physical inactivity and genetic susceptibility, environmental pollutants also contribute to the rising prevalence of obesity epidemic. An environmental obesogen is defined as a chemical that can alter lipid homeostasis to promote adipogenesis and lipid accumulation whereas an endocrine disrupting chemical (EDC) is defined as a synthetic chemical that can interfere with the endocrine function and cause adverse health effects. Many obesogens are EDCs that interfere with normal endocrine regulation of metabolism, adipose tissue development and maintenance, appetite, weight and energy balance. An expanding body of scientific evidence from animal and epidemiological studies has begun to provide links between exposure to EDCs and obesity. Despite the significance of environmental obesogens in the pathogenesis of metabolic diseases, the contribution of synthetic chemical exposure to obesity epidemic remains largely unrecognised. Hence, the purpose of this review is to provide a current update on the evidences from animal and human studies on the role of fourteen environmental obesogens in obesity, a comprehensive view of the mechanisms of action of these obesogens and current green and sustainable chemistry strategies to overcome chemical exposure to prevent obesity. Designing of safer version of obesogens through green chemistry approaches requires a collaborative undertaking to evaluate the toxicity of endocrine disruptors using appropriate experimental methods, which will help in developing a new generation of inherently safer chemicals.

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Many environmental obesogens are endocrine disrupting chemicals that interfere with normal endocrine regulation of metabolism.

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Understanding the role of environmental obesogens in the epidemics of obesity is in an infant stage.

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Green chemistry approach aims to design a safer version of these chemicals by understanding their hazardous effects.

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Further studies are necessary to fully establish the hazardous effects of obesogens and their association to human obesity.

The Impact of Environmental Factors on 5-Hydroxymethylcytosine in the Brain

PURPOSE OF REVIEW

The aims of this review are to evaluate the methods used to measure 5-hydroxymethylcytosine (5-hmC), and then summarize the available data investigating the impact of environmental factors on 5-hydroxymethylcytosine (5-hmC) in the brain.

RECENT FINDINGS

Recent research has shown that some environmental factors, including exposure to exogenous chemicals, stress, altered diet, and exercise, are all associated with 5-hmC variation in the brain. However, due to a lack of specificity in the methods used to generate a majority of the available data, it cannot be determined whether environment-induced changes in 5-hmC occur in specific biological pathways. Environment appears to shape 5-hmC levels in the brain, but the available literature is hampered by limitations in measurement methods. The field of neuroepigenetics needs to adopt new tools to increase the specificity of its data and enhance biological interpretation of exposure-related changes in 5-hmC. This will help improve understanding of the potential roles for environmental factors and 5-hmC in neurological disease.

Gene-Environment Interaction of FOXO and Residential Greenness on Mortality Among Older Adults

Residential greenness is an important environmental factor that is strongly associated with mortality. To our knowledge, there was no previous study on the gene-environment interaction analysis between residential greenness and forkhead box O (FOXO) gene, a candidate longevity gene. Our sample consisted of 3179 participants aged 65 and older from the Chinese Longitudinal Healthy Longevity Survey. Residential greenness was measured by satellite-derived normalized difference vegetation index (NDVI) using a 500-m radius around each residential location. Contemporaneous NDVI, cumulative NDVI, and changes in NDVI over time were calculated. We used Cox-proportional hazard regression models to assess the main effect and gene-environment interaction effect of FOXO single nucleotide polymorphism (SNP) and residential greenness on mortality. We found that participants carrying two minor alleles of the three studied FOXO3A SNPs had lower mortality risk than those without minor allele (hazard ratio [HR]: 0.803 95% confidence interval [CI]: 0.654-0.987 for rs4946936, HR: 0.807 95% CI: 0.669-0.974 for rs2802292, HR: 0.803 95% CI: 0.666-0.968 for rs2253310). We found no difference in mortality among the genotypes of the other three FOXO1A SNPs (rs17630266, rs2755213, or rs2755209). Higher contemporaneous NDVI was associated with lower mortality risk (HR: 0.887 95% CI: 0.863-0.911 for 0.1-U of NDVI). The protective effect of both contemporaneous NDVI and cumulative NDVI was stronger for two minor allele carriers compared with zero minor allele carriers of the three FOXO3A SNPs. Compared with the zero minor allele genotype of the three FOXO3A SNPs, the protective effect on the mortality risk of minor allele homozygotes also increased with the increasing NDVI level at percentile 25, 50, and 75 (interaction term coefficient p < 0.05). We found gene-environment interaction between FOXO and residential greenness on mortality in this population study. A higher level of greenness may interact with FOXO pathways.

The Effects of Cadmium Toxicity

Cadmium (Cd) is a toxic non-essential transition metal that poses a health risk for both humans and animals. It is naturally occurring in the environment as a pollutant that is derived from agricultural and industrial sources. Exposure to cadmium primarily occurs through the ingestion of contaminated food and water and, to a significant extent, through inhalation and cigarette smoking. Cadmium accumulates in plants and animals with a long half-life of about 25-30 years. Epidemiological data suggest that occupational and environmental cadmium exposure may be related to various types of cancer, including breast, lung, prostate, nasopharynx, pancreas, and kidney cancers. It has been also demonstrated that environmental cadmium may be a risk factor for osteoporosis. The liver and kidneys are extremely sensitive to cadmium's toxic effects. This may be due to the ability of these tissues to synthesize metallothioneins (MT), which are Cd-inducible proteins that protect the cell by tightly binding the toxic cadmium ions. The oxidative stress induced by this xenobiotic may be one of the mechanisms responsible for several liver and kidney diseases. Mitochondria damage is highly plausible given that these organelles play a crucial role in the formation of ROS (reactive oxygen species) and are known to be among the key intracellular targets for cadmium. When mitochondria become dysfunctional after exposure to Cd, they produce less energy (ATP) and more ROS. Recent studies show that cadmium induces various epigenetic changes in mammalian cells, both in vivo and in vitro, causing pathogenic risks and the development of various types of cancers. The epigenetics present themselves as chemical modifications of DNA and histones that alter the chromatin without changing the sequence of the DNA nucleotide. DNA methyltransferase, histone acetyltransferase, histone deacetylase and histone methyltransferase, and micro RNA are involved in the epigenetic changes. Recently, investigations of the capability of sunflower (Helianthus annuus L.), Indian mustard (Brassica juncea), and river red gum (Eucalyptus camaldulensis) to remove cadmium from polluted soil and water have been carried out. Moreover, nanoparticles of TiO2 and Al2O3 have been used to efficiently remove cadmium from wastewater and soil. Finally, microbial fermentation has been studied as a promising method for removing cadmium from food. This review provides an update on the effects of Cd exposure on human health, focusing on the cellular and molecular alterations involved.

Environmental Epigenetics and Genome Flexibility: Focus on 5-Hydroxymethylcytosine

Convincing evidence accumulated over the last decades demonstrates the crucial role of epigenetic modifications for mammalian genome regulation and its flexibility. DNA methylation and demethylation is a key mechanism of genome programming and reprogramming. During ontogenesis, the DNA methylome undergoes both programmed changes and those induced by environmental and endogenous factors. The former enable accurate activation of developmental programs; the latter drive epigenetic responses to factors that directly or indirectly affect epigenetic biochemistry leading to alterations in genome regulation and mediating organism response to environmental transformations. Adverse environmental exposure can induce aberrant DNA methylation changes conducive to genetic dysfunction and, eventually, various pathologies. In recent years, evidence was derived that apart from 5-methylcytosine, the DNA methylation/demethylation cycle includes three other oxidative derivatives of cytosine-5-hydroxymethylcytosine (5hmC), 5-formylcytosine, and 5-carboxylcytosine. 5hmC is a predominantly stable form and serves as both an intermediate product of active DNA demethylation and an essential hallmark of epigenetic gene regulation. This makes 5hmC a potential contributor to epigenetically mediated responses to environmental factors. In this state-of-the-art review, we consolidate the latest findings on environmentally induced adverse effects on 5hmC patterns in mammalian genomes. Types of environmental exposure under consideration include hypnotic drugs and medicines (i.e., phenobarbital, diethylstilbestrol, cocaine, methamphetamine, ethanol, dimethyl sulfoxide), as well as anthropogenic pollutants (i.e., heavy metals, particulate air pollution, bisphenol A, hydroquinone, and pentachlorophenol metabolites). We put a special focus on the discussion of molecular mechanisms underlying environmentally induced alterations in DNA hydroxymethylation patterns and their impact on genetic dysfunction. We conclude that DNA hydroxymethylation is a sensitive biosensor for many harmful environmental factors each of which specifically targets 5hmC in different organs, cell types, and DNA sequences and induces its changes through a specific metabolic pathway. The associated transcriptional changes suggest that environmentally induced 5hmC alterations play a role in epigenetically mediated genome flexibility. We believe that knowledge accumulated in this review together with further studies will provide a solid basis for new approaches to epigenetic therapy and chemoprevention of environmentally induced epigenetic toxicity involving 5hmC patterns.

Effect of titanium dioxide nanoparticles on DNA methylation in multiple human cell lines

Nanoscale titanium dioxide (TiO2) is manufactured in wide scale, with a range of applications in consumer products. Significant toxicity of TiO2 nanoparticles has, however, been recognized, suggesting considerable risk to human health. To evaluate fully their toxicity, assessment of the epigenetic action of these nanoparticles is critical. However, only few studies are available examining capability of nanoparticles to alter epigenetic integrity. In the present study, the effect of TiO2 nanoparticles exposure on DNA methylation, a major epigenetic mechanism, was investigated in in vitro cellular model systems. A panel of cells relevant to portals of human exposure (Caco-2 (colorectal), HepG2 (liver), NL20 (lung), and A-431 (skin)) was exposed to TiO2 nanoparticles to assess effects on global methylation, gene-specific methylation, and expression levels of DNA methyltransferases, MBD2, and UHRF1. Global methylation was determined by enzyme-linked immunosorbent assay-based immunochemical analysis. Degree of promoter methylation across a defined panel of genes was evaluated using EpiTect Methyl II Signature PCR System Array technology. Expression of DNMT1, DNMT3a, DNMT3b, MBD2, and URHF1 was quantified by qRT-PCR. Decrease in global DNA methylation in cell lines Caco-2, HepG2, and A-431 exposed to TiO2 nanoparticles was shown. Across four cell lines, eight genes (CDKN1A, DNAJC15, GADD45A, GDF15, INSIG1, SCARA3, TP53, and BNIP3) were identified in which promotors were methylated after exposure. Altered expression of these genes is associated with disease etiology. The results also revealed aberrant expression of epigenetic regulatory genes involved in DNA methylation (DNMT1, DNMT3a, DNMT3b, MBD2, and UHRF1) in TiO2 exposed cells, which was cell type dependent. Findings from this study clearly demonstrate the impact of TiO2 nanoparticles exposure on DNA methylation in multiple cell types, supporting potential involvement of this epigenetic mechanism in the toxicity of TiO2 nanoparticles. Hence for complete assessment of potential risk from nanoparticle exposure, epigenetic studies are critical.

Particulate Air Pollution, Clock Gene Methylation, and Stroke: Effects on Stroke Severity and Disability

Circadian rhythm disturbances have been consistently associated with the development of several diseases, particularly cardiovascular diseases (CVDs). A central clock in the brain maintains the daily rhythm in accordance with the external environment. At the molecular level, the clock is maintained by “clock genes”, the regulation of which is mainly due to DNA methylation, a molecular mechanism of gene expression regulation, able to react to and be reprogrammed by environmental exposure such as exposure to particulate matter (PM). In 55 patients with a diagnosis of acute ischemic stroke, we showed that PM_2.5 exposure experienced before the event influenced clock genes methylation (i.e., circadian locomotor output cycles protein kaput CLOCK, period 2 PER2, cryprochrome 1 CRY1, Neuronal PAS Domain Protein 2 NPAS2), possibly modulating the patient prognosis after the event, as cryptochrome 1 CRY1 and period 1 PER1 methylation levels were associated with the Rankin score. Moreover, if PM_2.5 annual average was low, CRY1/CRY2 methylation levels were positively associated with the National Institutes of Health Stroke Scale (NIHSS) score, whereas they were negatively associated if PM_2.5 exposure was high. Whether epigenetic changes in clock genes need to be considered as a prognostic marker of stroke or rather a causal agent in stroke development remains to be determined. Further studies are needed to determine the role of clock gene methylation in regulating the response to and recovery after a stroke event.

Tissue-specific epigenetic inheritance after paternal heat exposure in male wild guinea pigs

External temperature change has been shown to modify epigenetic patterns, such as DNA methylation, which regulates gene expression. DNA methylation is heritable, and as such provides a mechanism to convey environmental information to subsequent generations. Studies on epigenetic response to temperature increase are still scarce in wild mammals, even more so studies that compare tissue-specific epigenetic responses. Here, we aim to address differential epigenetic responses on a gene and gene pathway level in two organs, liver and testis. We chose these organs, because the liver is the main metabolic and thermoregulation organ, and epigenetic modifications in testis are potentially transmitted to the F2 generation. We focused on the transmission of DNA methylation changes to naive male offspring after paternal exposure to an ambient temperature increase of 10 °C, and investigated differential methylated regions of sons sired before and after the paternal exposure using Reduced Representation Bisulfite Sequencing. We detected both a highly tissue-specific epigenetic response, reflected in genes involved in organ-specific metabolic pathways, and a more general regulation of single genes epigenetically modified in both organs. We conclude that genomes are context-specifically differentially epigenetically regulated in response to temperature increase. These findings emphasize the epigenetic relevance in cell differentiation, which is essential for the specific function(s) of complex organs, and is represented in a diverse molecular regulation of genes and gene pathways. The results also emphasize the paternal contribution to adaptive processes.

Metal mining and birth defects: a case-control study in Lubumbashi, Democratic Republic of the Congo

BACKGROUND

Widespread environmental contamination caused by mining of copper and cobalt has led to concerns about the possible association between birth defects and exposure to several toxic metals in southern Katanga, Democratic Republic of the Congo (DRC). We therefore aimed to assess the possible contribution of parental and antenatal exposure to trace metals to the occurrence of visible birth defects among neonates.

METHODS

We did a case-control study between March 1, 2013, and Feb 28, 2015, in Lubumbashi, DRC. We included newborns with visible birth defects (cases) and healthy neonates born in the same maternity ward (controls). Mothers were interviewed about potentially relevant exposures, including their partners' jobs. Various trace metals were measured by inductively coupled plasma mass spectrometry in maternal urine, maternal blood, umbilical cord blood, placental tissue, and surface dust at home. Multivariable logistic regression analyses were done to calculate adjusted odds ratios and their 95% CIs (CI).

FINDINGS

Our study included 138 neonates with visible birth defects (about 0·1% of the 133 662 births in Lubumbashi during the study period) and 108 control neonates. Potential confounders were similarly distributed between cases and controls. Vitamin consumption during pregnancy was associated with a lower risk of birth defects (adjusted odds ratio 0·2, 95% CI 0·1-0·5). Mothers having paid jobs outside the home (2·8, 1·2-6·9) and fathers having mining-related jobs (5·5, 1·2-25·0) were associated with a higher risk of birth defects. We found no associations for trace metal concentrations in biological samples, except for a doubling of manganese (Mn; 1·7, 1·1-2·7) and zinc (Zn; 1·6, 0·9-2·8) in cord blood. In a separate model including placentas, a doubling of Mn at the fetal side of the placenta was associated with an increased risk of birth defects (3·3, 1·2-8·0), as was a doubling of cord blood Zn (5·3, 1·6-16·6).

INTERPRETATION

To our knowledge, this is the first study of the effects of mining-related pollution on newborns in sub-Saharan Africa. Paternal occupational mining exposure was the factor most strongly associated with birth defects. Because neither Mn nor Zn are mined in Lubumbashi, the mechanism of the association between their increased prenatal concentrations and birth defects is unclear.

FUNDING

Flemish Interuniversity Council-University Development Cooperation, The Coalition of the North-South movement in Flanders 11.11.11.

Dioxin and endometriosis: a new possible relation based on epigenetic theory

Endometriosis is a chronic disease characterized by the growth of endometrial-like glands and stroma outside the uterine cavity. Nowadays, the exact etiology of endometriosis is unclear and the interaction between a variety of environmental physical and chemical compounds may potentially promote the disease in women with an individual susceptibility. The first demonstration of a relation between an environmental factor and endometriosis was obtained with the chronic dietary exposure of a primate colony to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Besides the well-known dioxin's pathway of action, several papers are focusing on the role of epigenetic mechanisms, a way through which the genome responds to the environment and can lead to permanent changes in gene expression until affecting the phenotypes or cause disease. In this review, we focus on the possible role of dioxin epigenetics modification in endometriosis.

AhR ligands reactivate LINE-1 retrotransposon in triple-negative breast cancer cells MDA-MB-231 and non-tumorigenic mammary epithelial cells NMuMG

Breast cancer is the most common cancer type in females worldwide. Environmental exposure to pesticides affecting hormonal homeostasis does not necessarily induce DNA mutations but may influence gene expression by disturbances in epigenetic regulation. Expression of long interspersed nuclear element-1 (LINE-1) has been associated with tumorigenesis in several cancers. In nearly all somatic cells, LINE-1 is silenced by DNA methylation in the 5́'UTR and reactivated during disease initiation and/or progression. Strong ligands of aryl hydrocarbon receptor (AhR) activate LINE-1 through the transforming growth factor-β1 (TGF-β1)/Smad pathway. Hexachlorobenzene (HCB) and chlorpyrifos (CPF), both weak AhR ligands, promote cell proliferation and migration in breast cancer cells, as well as tumor growth in rat models. In this context, our aim was to examine the effect of these pesticides on LINE-1 expression and ORF1p localization in the triple-negative breast cancer cell line MDA-MB-231 and the non-tumorigenic epithelial breast cell line NMuMG, and to evaluate the role of TGF-β1 and AhR pathways. Results show that 0.5 μM CPF and 0.005 μM HCB increased LINE-1 mRNA expression through Smad and AhR signaling in MDA-MB-231. In addition, the methylation of the first sites in 5́'UTR of LINE-1 was reduced by pesticide exposure, although the farther sites remained unaffected. Pesticides modulated ORF1p localization in MDA-MB-231: 0.005 μM HCB and 50 μM CPF increased nuclear translocation, while both induced cytoplasmic retention at 0.5 and 5 μM. Moreover, both stimulated double-strand breaks, enhancing H2AX phosphorylation, coincidentally with ORF1p nuclear localization. In NMuMG similar results were observed, since they heighten LINE-1 mRNA levels. CPF effect was through AhR and TGF-β1 signaling, whereas HCB action depends only of AhR. In addition, both pesticides increase ORF1p expression and nuclear localization. Our results provide experimental evidence that HCB and CPF exposure modify LINE-1 methylation levels and induce LINE-1 reactivation, suggesting that epigenetic mechanisms could contribute to pesticide-induced breast cancer progression.

Epigenetic effects of (nano)materials in environmental species - Cu case study in Enchytraeus crypticus

Chemical stressors can induce epigenomic changes, i.e., changes that are transferred to the next generation, even when the stressor is removed. Literature on chemical induced epigenetic effects in environmental species is scarce. We here provide the first results on epigenetic effects caused by nanomaterials with an environmental OECD standard soil model species Enchytraeus crypticus species. We assessed the epigenetic potential in terms of global DNA methylation, gene-specific methylation via bisulfite sequencing and MS-HRM (Methylation Sensitive - High Resolution Melting), and gene expression qPCR for genes involved in DNA methylation, histone modifications, non-coding RNA and stress response mechanisms). We have exposed E. crypticus in a multigenerational (MG) test design to Cu (copper oxide nanomaterials (CuO NMs) and copper salt (CuCl₂)). To link possible epigenetic effects to population changes, we used exposure concentrations (ECx) that caused a 10% and 50% reduction in the reproductive output (10% and 50% are the standards for regulatory Risk Assessment), the organisms were exposed for five consecutive generations (F1-F5) plus two generations after transferring to clean media (F5-F7), 7 generations in a total of 224 days. Results showed that MG exposure to Cu increased global DNA methylation and corresponded with phenotypic effects (reproduction). Gene expression analyses showed changes in the epigenetic, stress and detoxification gene targets, depending on the generation and Cu form, also occurring in post-exposure generations, hence indicative of transgenerational effects. There were in general clear differences between organisms exposed to different Cu-forms, hence indicate nanoparticulate-specific effects.

Environmental epigenetics and epigenetic inheritance in domestic farm animals

Epigenetics refers to molecular factors and processes around DNA that can affect genome activity and gene expression independent of DNA sequence. Epigenetic mechanisms drive developmental processes and have also been shown to be tied to disease development. Many epigenetic studies have been done using plants, rodent, and human models, but fewer have focused on domestic livestock species. The goal of this review is to present current epigenetic findings in livestock species (cattle, pigs, sheep and poultry). Much of this research examined epigenetic effects following exposure to toxicants, nutritional changes or infectious disease in those animals directly exposed, or in the offspring they produced. A limited number of studies in domestic animals have examined epigenetic transgenerational inheritance in the absence of continued exposures. One example used a porcine model to investigate the effect that feeding males a diet supplemented with micronutrients had on liver DNA methylation and muscle mass in grand-offspring (the transgenerational F2 generation). Further research into how epigenetic mechanisms affect the health and production traits of domestic livestock and their offspring is important to elucidate.

Prospects for incorporation of epigenetic biomarkers in human health and environmental risk assessment of chemicals

Epigenetic mechanisms have gained relevance in human health and environmental studies, due to their pivotal role in disease, gene × environment interactions and adaptation to environmental change and/or contamination. Epigenetic mechanisms are highly responsive to external stimuli and a wide range of chemicals has been shown to determine specific epigenetic patterns in several organisms. Furthermore, the mitotic/meiotic inheritance of such epigenetic marks as well as the resulting changes in gene expression and cell/organismal phenotypes has now been demonstrated. Therefore, epigenetic signatures are interesting candidates for linking environmental exposures to disease as well as informing on past exposures to stressors. Accordingly, epigenetic biomarkers could be useful tools in both prospective and retrospective risk assessment but epigenetic endpoints are currently not yet incorporated into risk assessments. Achieving a better understanding on this apparent impasse, as well as identifying routes to promote the application of epigenetic biomarkers within environmental risk assessment frameworks are the objectives of this review. We first compile evidence from human health studies supporting the use of epigenetic exposure-associated changes as reliable biomarkers of exposure. Then, specifically focusing on environmental science, we examine the potential and challenges of developing epigenetic biomarkers for environmental fields, and discuss useful organisms and appropriate sequencing techniques to foster their development in this context. Finally, we discuss the practical incorporation of epigenetic biomarkers in the environmental risk assessment of chemicals, highlighting critical data gaps and making key recommendations for future research within a regulatory context.

Dietary phytochemicals as the potential protectors against carcinogenesis and their role in cancer chemoprevention

Health-threatening consequences of carcinogen exposure are mediated via occurrence of electrophiles or reactive oxygen species. As a result, the accumulation of biomolecular damage leads to the cancer initiation, promotion or progression. Accordingly, there is an association between lifestyle factors including inappropriate diet or carcinogen formation during food processing, mainstream, second or third-hand tobacco smoke and other environmental or occupational carcinogens and malignant transformation. Nevertheless, increasing evidence supports the protective effects of naturally occurring phytochemicals against carcinogen exposure as well as carcinogenesis in general. Isolated phytochemicals or their mixtures present in the whole plant food demonstrate efficacy against malignancy induced by carcinogens widely spread in our environment. Phytochemicals also minimize the generation of carcinogenic substances during the processing of meat and meat products. Based on numerous data, selected phytochemicals or plant foods should be highly recommended to become a stable and regular part of the diet as the protectors against carcinogenesis.

Oxidative Stress and DNA methylation in male rat pups provoked by the transplacental and translactational exposure to bisphenol A

The epigenetic changes induced by environmental contaminants play important roles in the inheritance of male reproductive dysfunction. The present study investigated DNA methylation changes and some oxidative stress biomarkers induced by bisphenol A (BPA) in male offspring. A total number of 48 female albino rats were administered orally with 50 μg/kg of BPA/day during gestation and/or lactation periods. At postnatal day 60, the samples were collected from the male pups to assess the serum testosterone, malondialdehyde (MDA) level, superoxide dismutase (SOD), glutathione S-transferase, and glutathione peroxidase (GSH-Px) activities in testicular tissue. DNA methylation in both DNA (cytosine-5)-methyltransferase 3A and estrogen receptor alpha genes was detected by methylation-specific PCR. BPA exposure resulted in significant decrease in the anogenital distance, testis and epididymis weights, serum testosterone level, SOD, GST, and GSH-Px levels with significant increase in weaning body weight and the MDA level. Additionally, BPA caused marked hypermethylation within Dnmt3A and ER- ∝ genes promoter regions in the testis of rat male pups. Graphical abstract.

Elemental bioimaging shows mercury and other toxic metals in normal breast tissue and in breast cancers

OBJECTIVE

Exposure to toxic metals such as mercury has been proposed to be a risk factor for the development of breast cancer since some metals can promote genetic mutations and epigenetic changes. We sought to find what toxic metals are present in normal breast tissue and in the tumours of women who had mastectomies for invasive ductal breast carcinoma.

MATERIALS AND METHODS

Formalin-fixed paraffin-embedded blocks from mastectomies for breast carcinoma were examined from 50 women aged 34-69 years. Paraffin blocks selected for elemental analysis were from breast tissue not involved by carcinoma and from the carcinoma itself. Seven micrometer-thick sections were stained with autometallography to demonstrate the presence of mercury, and subjected to laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) to confirm the presence of mercury and to detect other toxic metals.

RESULTS

Autometallography-detected mercury was seen in intraductal secretions and some luminal epithelial cells of normal breast lobules in 26 (55%) of the 47 samples where lobules were present, and in 10 (23%) of carcinomas from the 44 samples where carcinoma was present. In eight samples ductal carcinoma in situ was present and one of these contained mercury. LA-ICP-MS confirmed the presence of mercury in samples that stained with autometallography, and detected lead, iron, nickel, aluminium, chromium and cadmium in some samples.

CONCLUSIONS

Mercury was present in normal breast lobules in more than half of mastectomy samples that contained an invasive carcinoma, and in a smaller proportion of carcinomas and ductal carcinomas in situ. Other toxic metals that may interact synergistically with mercury could be detected in some samples. These findings do not provide direct evidence that toxic metals such as mercury play a role in the pathogenesis of breast cancer, but suggest that future molecular biological investigations on the role of toxic metals in breast cancer are warranted.

Biomarkers of exposure, effect, and susceptibility in occupational exposure to traffic-related air pollution: A review

There is a well-recognized association between environmental air pollution exposure and several human diseases. However, the relationship between diseases related to occupational air pollution exposure on roads and high levels of traffic-related air pollutants (TRAPs) is less substantiated. Biomarkers are essential tools in environmental and occupational toxicology, and studies on new biomarkers are increasingly relevant due to the need to determine early biomarkers to be assessed in exposure conditions. This review aimed to investigate the main advances in the biomonitoring of subjects occupationally exposed to air pollution, as well as to summarize the biomarkers of exposure, effect, and susceptibility. Furthermore, we discuss how biomarkers could be used to complement the current application of methods used to assess occupational exposures to xenobiotics present in air pollution. The databases used in the preparation of this review were PubMed, Scopus, and Science Direct. Considering the significant deleterious effects on health associated with chronic occupational exposure to xenobiotics, this topic deserves attention. As it is difficult to avoid occupational exposure to TRAPs, biomonitoring should be applied as a strategy to reduce the toxic effects of workplace exposure.

Nickel: Human Health and Environmental Toxicology

Nickel is a transition element extensively distributed in the environment, air, water, and soil. It may derive from natural sources and anthropogenic activity. Although nickel is ubiquitous in the environment, its functional role as a trace element for animals and human beings has not been yet recognized. Environmental pollution from nickel may be due to industry, the use of liquid and solid fuels, as well as municipal and industrial waste. Nickel contact can cause a variety of side effects on human health, such as allergy, cardiovascular and kidney diseases, lung fibrosis, lung and nasal cancer. Although the molecular mechanisms of nickel-induced toxicity are not yet clear, mitochondrial dysfunctions and oxidative stress are thought to have a primary and crucial role in the toxicity of this metal. Recently, researchers, trying to characterize the capability of nickel to induce cancer, have found out that epigenetic alterations induced by nickel exposure can perturb the genome. The purpose of this review is to describe the chemical features of nickel in human beings and the mechanisms of its toxicity. Furthermore, the attention is focused on strategies to remove nickel from the environment, such as phytoremediation and phytomining.

Benzene Exposure Induces Insulin Resistance in Mice

Benzene is a ubiquitous pollutant associated with hematotoxicity but its metabolic effects are unknown. We sought to determine if and how exposure to volatile benzene impacted glucose handling. We exposed wild type C57BL/6 mice to volatile benzene (50 ppm × 6 h/day) or HEPA-filtered air for 2 or 6 weeks and measured indices of oxidative stress, inflammation, and insulin signaling. Compared with air controls, we found that mice inhaling benzene demonstrated increased plasma glucose (p = .05), insulin (p = .03), and HOMA-IR (p = .05), establishing a state of insulin and glucose intolerance. Moreover, insulin-stimulated Akt phosphorylation was diminished in the liver (p = .001) and skeletal muscle (p = .001) of benzene-exposed mice, accompanied by increases in oxidative stress and Nf-κb phosphorylation (p = .025). Benzene-exposed mice also demonstrated elevated levels of Mip1-α transcripts and Socs1 (p = .001), but lower levels of Irs-2 tyrosine phosphorylation (p = .0001). Treatment with the superoxide dismutase mimetic, TEMPOL, reversed benzene-induced effects on oxidative stress, Nf-κb phosphorylation, Socs1 expression, Irs-2 tyrosine phosphorylation, and systemic glucose intolerance. These findings suggest that exposure to benzene induces insulin resistance and that this may be a sensitive indicator of inhaled benzene toxicity. Persistent ambient benzene exposure may be a heretofore unrecognized contributor to the global human epidemics of diabetes and cardiovascular disease.

Epigenetics recording varied environment and complex cell events represents the origin of cellular aging

Although a relationship between epigenetics and aging phenotypic changes has been established, a theoretical explanation of the intrinsic connection between the epigenetics and aging is lacking. In this essay, we propose that epigenetic recording of varied cell environment and complex history could be an origin of cellular aging. Through epigenetic modifications, the environment and historical events can induce the chromatin template into an activated or repressive accessible structure, thereby shaping the DNA template into a spectrum of chromatin states. The inner nature of diversity and conflicts born by the cell environment and its historical events are hence recorded into the chromatin template. This could result in a dissipated spectrum of the chromatin state and chaos in overall gene expression. An unavoidable degradation of epigenome entropy, similar to Shannon entropy, would be consequently induced. The resultant disorder in epigenome, characterized by corrosion of epigenome entropy as reflected in chromatin template, can be stably memorized and propagated through cell division. Furthermore, the hysteretic nature of epigenetics responding to the emerging environment could exacerbate the degradation of epigenome entropy. As well as stochastic errors, we propose that outside entropy (or chaos) derived from the varied environment and complex cell history, gradually input and imprinted into the chromatin via epigenetic modifications, would lead inevitably to cellular aging, the extent of which could be aggravated by hysteresis of epigenetics without error erasing and correction.

Bisphenol a Exposure, DNA Methylation, and Asthma in Children

Epidemiological studies have reported the relationship between bisphenol A (BPA) exposure and increased prevalence of asthma, but the mechanisms remain unclear. Here, we investigated whether BPA exposure and DNA methylation related to asthma in children. We collected urinary and blood samples from 228 children (Childhood Environment and Allergic Diseases Study cohort) aged 3 years. Thirty-three candidate genes potentially interacting with BPA exposure were selected from a toxicogenomics database. DNA methylation was measured in 22 blood samples with top-high and bottom-low exposures of BPA. Candidate genes with differential methylation levels were validated by qPCR and promoter associated CpG islands have been investigated. Correlations between the methylation percentage and BPA exposure and asthma were analyzed. According to our findings, MAPK1 showed differential methylation and was further investigated in 228 children. Adjusting for confounders, urinary BPA glucuronide (BPAG) level inversely correlated with MAPK1 promoter methylation (β = -0.539, p = 0.010). For the logistic regression analysis, MAPK1 methylation status was dichotomized into higher methylated and lower methylated groups with cut off continuous variable of median of promoter methylation percentage (50%) while performing the analysis. MAPK1 methylation was lower in children with asthma than in children without asthma (mean ± SD; 69.82 ± 5.88% vs. 79.82 ± 5.56%) (p = 0.001). Mediation analysis suggested that MAPK1 methylation acts as a mediation variable between BPA exposure and asthma. The mechanism of BPA exposure on childhood asthma might, therefore, be through the alteration of MAPK1 methylation. The mechanism of BPA exposure on childhood asthma might, therefore, be through the alteration of MAPK1 methylation.

Next-Generation Genotoxicology: Using Modern Sequencing Technologies to Assess Somatic Mutagenesis and Cancer Risk

Mutations have a profound effect on human health, particularly through an increased risk of carcinogenesis and genetic disease. The strong correlation between mutagenesis and carcinogenesis has been a driving force behind genotoxicity research for more than 50 years. The stochastic and infrequent nature of mutagenesis makes it challenging to observe and to study. Indeed, decades have been spent developing increasingly sophisticated assays and methods to study these low-frequency genetic errors, in hopes of better predicting which chemicals may be carcinogens, understanding their mode of action, and informing guidelines to prevent undue human exposure. While effective, widely used genetic selection-based technologies have a number of limitations that have hampered major advancements in the field of genotoxicity. Emerging new tools, in the form of enhanced next-generation sequencing platforms and methods, are changing this paradigm. In this review, we discuss rapidly evolving sequencing tools and technologies, such as error-corrected sequencing and single cell analysis, which we anticipate will fundamentally reshape the field. In addition, we consider a variety emerging applications for these new technologies, including the detection of DNA adducts, inference of mutational processes based on genomic site and local sequence contexts, and evaluation of genome engineering fidelity, as well as other cutting-edge challenges for the next 50 years of environmental and molecular mutagenesis research. Environ. Mol. Mutagen. 61:135-151, 2020. © 2019 The Authors. Environmental and Molecular Mutagenesis published by Wiley Periodicals, Inc. on behalf of Environmental Mutagen Society.

DNA Methylation in Nasal Epithelium: Strengths and Limitations of an Emergent Biomarker for Childhood Asthma

Asthma is one of the most widespread chronic respiratory conditions. This disease primarily develops in childhood and is influenced by different factors, mainly genetics and environmental factors. DNA methylation is an epigenetic mechanism which may represent a bridge between these two factors, providing a tool to comprehend the interaction between genetics and environment. Most epidemiological studies in this field have been conducted using blood samples, although DNA methylation marks in blood may not be reliable for drawing exhaustive conclusions about DNA methylation in the airways. Because of the role of nasal epithelium in asthma and the tissue specificity of DNA methylation, studying the relationship between DNA methylation and childhood asthma might reveal crucial information about this widespread respiratory disease. The purpose of this review is to describe current findings in this field of research. We will present a viewpoint of selected studies, consider strengths and limitations, and propose future research in this area.

Neuropsychopathology of Autism Spectrum Disorder: Complex Interplay of Genetic, Epigenetic, and Environmental Factors

Autism spectrum disorder (ASD) is a complex heterogeneous consortium of pervasive development disorders (PDD) which ranges from atypical autism, autism, and Asperger syndrome affecting brain in the developmental stage. This debilitating neurodevelopmental disorder results in both core as well as associated symptoms. Core symptoms observed in autistic patients are lack of social interaction, pervasive, stereotyped, and restricted behavior while the associated symptoms include irritability, anxiety, aggression, and several comorbid disorders.ASD is a polygenic disorder and is multifactorial in origin. Copy number variations (CNVs) of several genes that regulate the synaptogenesis and signaling pathways are one of the major factors responsible for the pathogenesis of autism. The complex integration of various CNVs cause mutations in the genes which code for molecules involved in cell adhesion, voltage-gated ion-channels, scaffolding proteins as well as signaling pathways (PTEN and mTOR pathways). These mutated genes are responsible for affecting synaptic transmission by causing plasticity dysfunction responsible, in turn, for the expression of ASD.Epigenetic modifications affecting DNA transcription and various pre-natal and post-natal exposure to a variety of environmental factors are also precipitating factors for the occurrence of ASD. All of these together cause dysregulation of glutamatergic signaling as well as imbalance in excitatory: inhibitory pathways resulting in glial cell activation and release of inflammatory mediators responsible for the aberrant social behavior which is observed in autistic patients.In this chapter we review and provide insight into the intricate integration of various genetic, epigenetic, and environmental factors which play a major role in the pathogenesis of this disorder and the mechanistic approach behind this integration.

Long-term residential exposure to PM2.5 constituents and mortality in a Danish cohort

Studies on health effects of long-term exposure to specific PM_2.5 constituents are few. Previous studies have reported an association between black carbon (BC) exposure and cardiovascular diseases (CVD) and a few studies have found an association between sulfate exposure and mortality. These studies, however, relied mainly on exposure data from centrally located air-monitoring stations, which is a crude approximation of personal exposure. We focused on specific chemical constituents of PM_2.5, i.e. elemental and primary organic carbonaceous particles (BC/OC), sea salt, secondary inorganic aerosols (SIA, i.e. NO₃^-, NH₄⁺, and SO₄^2-), and secondary organic aerosols (SOA), in relation to all-cause, CVD and respiratory disease mortality. We followed a Danish cohort of 49,564 individuals from enrollment in 1993-1997 through 2015. We combined residential address history from 1979 onwards with mean annual air pollution concentrations obtained by the AirGIS air pollution modelling system, lifestyle information from baseline questionnaires and socio-demography obtained by register linkage. During 895,897 person-years of follow-up, 10,193 deaths from all causes occurred - of which 2319 were CVD-related and 870 were related to respiratory disease. The 15-year time-weighted average concentrations of PM_2.5, BC/OC, sea salt, SIA and SOA were 13.8, 2.8, 3.4, 4.9, and 0.3 µg/m³, respectively. For all-cause mortality, a higher risk was observed with higher exposure to PM_2.5, BC/OC and SOA with adjusted hazard ratios of 1.03 (95% confidence intervals: 1.01, 1.05), 1.06 (1.03, 1.09), and 1.08 (1.03, 1.13) per interquartile range, respectively. The associations for BC/OC and SOA remained after adjustment for PM_2.5 in two-pollutant models. For CVD mortality, we observed elevated risks with higher exposure to PM_2.5, BC/OC and SIA. The results showed no clear relationship between sea salt and mortality. In this study, we observed a relationship between long-term exposure to PM_2.5, BC/OC, and SOA and all-cause mortality and between PM_2.5, BC/OC, and SIA and CVD mortality.

Embryonic development, locomotor behavior, biochemical, and epigenetic effects of the pharmaceutical drugs paracetamol and ciprofloxacin in larvae and embryos of Danio rerio when exposed to environmental realistic levels of both drugs

For several years, the scientific community has been concerned about the presence of pharmaceuticals in the wild, since these compounds may have unpredictable deleterious effects on living organisms. Two examples of widely used pharmaceuticals that are present in the environment are paracetamol and ciprofloxacin. Despite their common presence in the aquatic environment due to their poor removal by sewage treatment plants, knowledge concerning their putative toxic effects is still scarce. This work aimed to characterize the effects of paracetamol (0.005, 0.025, 0.125, 0.625, and 3.125 mg/L) and ciprofloxacin (0.005, 0.013, 0.031, 0.078, 0.195, and 0.488 μg/L) in zebrafish embryos and larvae, exposed to environmentally relevant levels, close to the real concentrations of these pharmaceuticals in surface waters and effluents. The adopted toxic end points were developmental, a behavioral parameter (total swimming time), and a biomarker-based approach (quantification of the activities of catalase, glutathione-S-transferase, cholinesterases, glutathione peroxidase, and lipid peroxidation levels) combined with epigenetic analysis (immunohistochemical detection of 5-methylcytidine). Exposure to paracetamol had effects on all of the adopted toxic end points; however, ciprofloxacin only caused effects on behavioral tests and alterations in biomarkers. It is possible to ascertain the occurrence of oxidative stress following exposure to both drugs, which was more evident regarding paracetamol, an effect that may be related to the observed epigenetic modifications.

Association of Sperm Methylation at LINE-1, Four Candidate Genes, and Nicotine/Alcohol Exposure With the Risk of Infertility

In this study, we examined whether smoking and drinking affect sperm quality and the DNA methylation of the repetitive element LINE-1, MEST, P16, H19, and GNAS in sperm. Semen samples were obtained from 143 male residents in a minority-inhabited district of Guizhou province in southwest China. Quantitative DNA methylation analysis of the samples was performed using MassARRAY EpiTYPER assays. Sperm motility was significantly lower in both the nicotine-exposed (P = 0.0064) and the nicotine- and alcohol-exposed (P = 0.0008) groups. Follicle-stimulating hormone (FSH) levels were higher in the nicotine-exposed group (P = 0.0026). The repetitive element LINE-1 was hypermethylated in the three exposed groups, while P16 was hypomethylated in the alcohol and both the alcohol and nicotine exposure groups. Our results also show that alcohol and nicotine exposure altered sperm cell quality, which may be related to the methylation levels of MEST and GNAS. In addition, MEST, GNAS, and the repetitive element LINE1 methylation was significantly associated with the concentration of sperm as well as FSH and luteinizing hormone levels.

Microtia epigenetics: An overview of review and new viewpoint

INTRODUCTION

Microtia is a congenital malformation of the external and middle ear caused by the abnormal development of the first and second zygomatic arch and the first sulcus. There is currently no consensus concerning the pathogenesis and etiology of microtia; genetic and environmental factors may play a role. Gene-based studies have focused on finding the genes that cause microtia and on gene function defects. However, no clear pathogenic genes have so far been identified. Microtia is multifactorial; gene function defects cannot completely explain its pathogenesis. In recent years, the epigenetic aspects of microtia have begun to receive attention.

CONCLUSIONS

Analysis of the existing data suggests that certain key genes and pathways may be the underlying cause of congenital microtia. However, further exploration is needed.

Effect of particulate matter-bound metals exposure on prothrombotic biomarkers: A systematic review

Environmental pollution is an important modifiable determinant for preventing cardiovascular diseases. Acute exposure to air pollution is linked to severe adverse cardiovascular events, including venous thromboembolism risk. The adverse health effects seem to arise from blood-borne metals and transition metal components from exposure to particulate matter that, when breathed, passes through the lungs into the heart and the blood stream. Pollution affects health via mechanisms including oxidative stress and inflammation, and metals may have a detrimental effect on both the blood cells, particularly platelets, and circulation. Some evidences demonstrates atherotrombotic consequences of acute and chronic exposure to air pollution, but few studies have examined exposure effects on the prothrombotic biomarkers leading to venous thromboembolism. Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) methodology, we performed a systematic review (14 papers) of the past twelve years, focusing on the relationship between inhalable airborne metal exposures and coagulative biomarker disorders leading to lower limb venous thromboembolisms, e.g., deep vein thrombosis. Results support the hypothesis that exposure to inhalable metals, as elemental compounds in particulate matter, cause changes or activation of a number of human prothrombotic hemostatic biomarkers.

Air pollution exposure and risk of spontaneous abortion in the Nurses' Health Study II

STUDY QUESTION

Is there an association between air pollution exposures and the risk of spontaneous abortion (SAB)?

SUMMARY ANSWER

Higher exposure to particulate matter (PM) air pollution above and beyond a woman's average exposure may be associated with greater risk of SAB, particularly among women experiencing at least one SAB during follow-up.

WHAT IS KNOWN ALREADY

There is sufficient biologic plausibility to suggest that air pollution adversely affects early pregnancy outcomes, particularly pregnancy loss; however, the evidence is limited.

STUDY DESIGN, SIZE, DURATION

Our prospective cohort study included 19 309 women in the Nurses' Health Study II who contributed a total of 35 025 pregnancies between 1990 and 2008. We also conducted a case-crossover analysis among 3585 women (11 212 pregnancies) with at least one SAB and one live birth during follow-up.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Proximity to major roadways and exposure to PM <10 microns (PM10), 2.5-10 microns (PM2.5-10) and <2.5 microns (PM2.5) were determined for residential addresses between 1989 and 2007. Pregnancy outcomes were self-reported biannually throughout follow-up and comprehensively in 2009. Multivariable log-binomial regression models with generalized estimating equations were used to estimate the risk ratios and 95% CIs of SAB. Conditional logistic regression was used for the case-crossover analysis.

MAIN RESULTS AND THE ROLE OF CHANCE

During the 19 years of follow-up, 6599 SABs (18.8% of pregnancies) were reported. In the main analysis, living closer to a major roadway and average exposure to PM10, PM10-2.5 or PM2.5 in the 1 or 2 years prior to pregnancy were not associated with an increased risk of SAB. However, small positive associations between PM exposures and SAB were observed when restricting the analysis to women experiencing at least one SAB during follow-up. In the case-crossover analysis, an increase in PM10 (per 3.9 μg/m3), PM2.5-10 (per 2.3 μg/m3) and PM2.5 (per 2.0 μg/m3) in the year prior to pregnancy was associated with 1.12 (95% CI 1.06, 1.19), 1.09 (95% CI 1.03, 1.14) and 1.10 (95% CI 1.04, 1.17) higher odds of SAB, respectively.

LIMITATIONS, REASONS FOR CAUTION

We did not have information on the month or day of SAB, which precluded our ability to examine specific windows of susceptibility or acute exposures. We also used ambient air pollution exposures as a proxy for personal exposure, potentially leading to exposure misclassification.

WIDER IMPLICATIONS OF THE FINDINGS

In our case-crossover analysis (but not in the entire cohort) we observed positive associations between exposure to all size fractions of PM exposure and risk of SAB. This may suggest that changes in PM exposure confer greater risk of SAB or that women with a history of SAB are a particularly vulnerable subgroup.

STUDY FUNDING/COMPETING INTEREST(S)

The authors are supported by the following NIH grants UM1CA176726, R00ES026648 and P30ES000002. The authors have no actual or potential competing financial interests to disclose.

Genomic DNA methylation signatures in different tissues after ambient air particulate matter exposure

DNA methylation (5-mc) is one of the several epigenetic markers, and is generally associated with the inhibition of gene expression. Both hyper and hypo DNA methylation are associated with the diseases. Exposure to fine particles with a diameter of 2.5 μm or less (PM_2.5) is a pervasive risk factor for cardiopulmonary mortality, metabolic disorders, cognition damage, and etc.. Recent reports pointed toward that these diseases were associated with the altered DNA methylation level of some specific-gene, potentially suggesting that the DNA methylation alteration was involved in the health hazard derived from the PM_2.5 exposure. In this study, we systematically investigated the global DNA methylation level of most tissues, including lung, heart, testis, thymus, spleen, epididymal fat, hippocampus, kidney, live, after short and long term PM_2.5 exposure. After acute PM_2.5 exposure, the global hypo-methylation in DNA was observed in lung and heart. Notably, after chronic PM_2.5 exposure, level of global DNA methylation decreased in most organs which included lung, testis, thymus, spleen, epididymal fat, hippocampus and blood. The present study systematically demonstrated the global DNA methylation changes by PM_2.5 exposure, and put forward a possible orientation for further exploring the effects of ambient air particles exposure on the specific organs.

Updates on the Effect of Mycotoxins on Male Reproductive Efficiency in Mammals

Mycotoxins are ubiquitous and unavoidable harmful fungal products with the ability to cause disease in both animals and humans, and are found in almost all types of foods, with a greater prevalence in hot humid environments. These mycotoxins vary greatly in structure and biochemical effects; therefore, by better understanding the toxicological and pathological aspects of mycotoxins, we can be better equipped to fight the diseases, as well as the biological and economic devastations, they induce. Multiple studies point to the association between a recent increase in male infertility and the increased occurrence of these mycotoxins in the environment. Furthermore, understanding how mycotoxins may induce an accumulation of epimutations during parental lifetimes can shed light on their implications with respect to fertility and reproductive efficiency. By acknowledging the diversity of mycotoxin molecular function and mode of action, this review aims to address the current limited knowledge on the effects of these chemicals on spermatogenesis and the various endocrine and epigenetics patterns associated with their disruptions.

Global DNA methylation changes in rock pigeon (Columba livia) as a sentinel species due to polycyclic aromatic hydrocarbons exposure in Tehran (Iran) as a megacity

Global DNA methylation, as an epigenetic modifications, can be a promising genomic marker for monitoring the contaminants and predicting their adverse health effects. The study aims to assess the effects of 16 PAH concentration on the altered DNA methylation levels in the kidney and liver of rock pigeon (Columba livia), as a sentinel species, from Tehran megacity as well as 40 days benzo(a)pyrene in vitro exposure: (0.1, 2.5, 5, 7.5, and 10 mg kg^-1 bw). Data indicated that the total LMW-PAH (low molecular weight PAHs) group (120.22, 121.34, 103.69, and 128.79 ng g^-1 dw in liver, kidney, skin, and muscle, respectively) in the Tehran samples have higher levels than the other PAHs groups. In addition, the DNA methylation level had negative relation with the total amount of PAHs in liver and kidney. A comparatively higher global DNA hypomethylation (by 8.65% in liver and 3.76% in kidney) was observed in birds exposed to B(a)P. Our results lead us to suggest that DNA hypomethylation in liver and kidney associated with the B(a)P may be useful biomarker discovery (more than the amount of PAH concentration in different tissues of C. livia) in urban areas. In conclusion, based on the overall results assessed, DNA methylation changes in pigeon may show a new target pathway for evaluation of environmental health.

Unravelling the molecular mechanisms of nickel in woodlice

During the last few years, there has been an alarming increase in the amount of nickel (Ni) being released into the environment, primarily due to its use in the production of stainless steel but also from other sources such as batteries manufacturing and consequent disposal. The established biotic ligand models provide precise estimates for Ni bioavailability, in contrast, studies describing the mechanisms underpinning toxicological effect of Ni are scarce. This study exploits RNA-seq to determine the transcriptomic responses of isopods using Porcellionides pruinosus as an example of a terrestrial metal-resistant woodlouse. Furthermore, the recently proposed model for Ni adverse outcome pathways (Ni-AOP) presents an unprecedented opportunity to fit isopod responses to Ni toxicity and define Porcellionides pruinosus as a metalomic model. Prior to this study, P. pruinosus represented an important environmental sentinel, though lacking genetic/omic data. The reference transcriptome generated here thus represents a major advance and a novel resource. A detailed annotation of the transcripts obtained is presented together with the homology to genes/gene products from Metazoan and Arthropoda phylum, Gene Ontology (GO) classification, clusters of orthologous groups (COG) and assignment to KEGG metabolic pathways. The differential gene expression comparison was determined in response to nickel (Ni) exposure and used to derive the enriched pathways and processes. It revealed a significant impact on ion trafficking and storage, oxidative stress, neurotoxicity, reproduction impairment, genetics and epigenetics. Many of the processes observed support the current Ni-AOP although the data highlights that the current model can be improved by including epigenetic endpoints, which represents key chronic risks under a scenario of Ni toxicity.

Functions and mechanisms of epigenetic inheritance in animals

The idea that epigenetic determinants such as DNA methylation, histone modifications or RNA can be passed to the next generation through meiotic products (gametes) is long standing. Such meiotic epigenetic inheritance (MEI) is fairly common in yeast, plants and nematodes, but its extent in mammals has been much debated. Advances in genomics techniques are now driving the profiling of germline and zygotic epigenomes, thereby improving our understanding of MEI in diverse species. Whereas the role of DNA methylation in MEI remains unclear, insights from genome-wide studies suggest that a previously underappreciated fraction of mammalian genomes bypass epigenetic reprogramming during development. Notably, intergenerational inheritance of histone modifications, tRNA fragments and microRNAs can affect gene regulation in the offspring. It is important to note that MEI in mammals rarely constitutes transgenerational epigenetic inheritance (TEI), which spans multiple generations. In this Review, we discuss the examples of MEI in mammals, including mammalian epigenome reprogramming, and the molecular mechanisms of MEI in vertebrates in general. We also discuss the implications of the inheritance of histone modifications and small RNA for embryogenesis in metazoans, with a particular focus on insights gained from genome-wide studies.

Multigenerational epigenetic inheritance: One step forward, two generations back

Modifications to DNA and histone proteins serve a critical regulatory role in the developing and adult brain, and over a decade of research has established the importance of these "epigenetic" modifications in a wide variety of brain functions across the lifespan. Epigenetic patterns orchestrate gene expression programs that establish the phenotypic diversity of various cellular classes in the central nervous system, play a key role in experience-dependent gene regulation in the adult brain, and are commonly implicated in neurodevelopmental, psychiatric, and neurodegenerative disease states. In addition to these established roles, emerging evidence indicates that epigenetic information can potentially be transmitted to offspring, giving rise to inter- and trans-generational epigenetic inheritance phenotypes. However, our understanding of the cellular events that participate in this information transfer is incomplete, and the ability of this transfer to overcome complete epigenetic reprogramming during embryonic development is highly controversial. This review explores the existing literature on multigenerational epigenetic mechanisms in the central nervous system. First, we focus on the cellular mechanisms that may perpetuate or counteract this type of information transfer, and consider how epigenetic modification in germline and somatic cells regulate important aspects of cellular and organismal development. Next, we review the potential phenotypes resulting from ancestral experiences that impact gene regulatory modifications, including how these changes may give rise to unique metabolic phenotypes. Finally, we discuss several caveats and technical limitations that influence multigenerational epigenetic effects. We argue that studies reporting multigenerational epigenetic changes impacting the central nervous system must be interpreted with caution, and provide suggestions for how epigenetic information transfer can be mechanistically disentangled from genetic and environmental influences on brain function.

Holoprosencephaly: A case series from an area with high mining-related pollution

BACKGROUND

The extraction and processing of copper and cobalt in the African Copperbelt in the Democratic Republic of Congo have led to substantial environmental pollution, causing concerns about possible adverse effects on human health, including birth defects.

CASES

We report three neonates with clinically diagnosed holoprosencephaly who were part of a case-control study performed in Lubumbashi between February 2013 and February 2015. One mother had a high concentration of uranium in urine, and high manganese concentrations were found in blood of another mother and in cord blood of one infant. Two of the three fathers had a mining-related job.

DISCUSSION

We hypothesize that these cases of holoprosencephaly were connected to mining-related pollution, possibly via epigenetic alterations induced by paternal occupational exposure to toxic metals.

Establishing a role for environmental toxicant exposure induced epigenetic remodeling in malignant transformation

Humans are exposed to a wide variety of environmental exposures throughout their lifespan. These include both naturally occurring toxins and chemical toxicants like pesticides, herbicides, and industrial chemicals, many of which have been implicated as possible contributors to human disease susceptibility [1-3]. We, and others, have hypothesized that environmental exposures may cause adaptive epigenetic changes in regenerative cell populations and developing organisms, leading to abnormal gene expression and increased disease susceptibility later in life [3]. Common epigenetic changes include changes in miRNA expression, covalent histone modifications, and methylation of DNA. Importantly, due to their heritable nature, abnormal epigenetic modifications which occur within stem cells may be particularly deleterious. Abnormal epigenetic changes in regenerative cell linages can be passed onto a large population of daughter cells and can persist for long periods of time. It is well established that an accumulation of epigenetic changes can lead to many human diseases including cancer [4-6]. Subsequently, it is imperative that we increase our understanding of how common environmental toxins and toxicants can induce epigenetic changes, particularly in stem cell populations. In this review, we will discuss how common environmental exposures in the United States and around the world may lead to epigenetic changes and discuss potential links to human disease, including cancer.

Reproductive toxicity of acute Cd exposure in mouse: Resulting in oocyte defects and decreased female fertility

Cadmium (Cd), a known metal contaminant, is widespreadly used in industry, thereby human health is severely affected through the way of occupational and environmental exposure. The adverse effects of the exposure to Cd on the female reproductive system, especially oocyte maturation and fertility have not been clearly defined. In this study, we found the arrested development of ovaries and uteri after Cd exposure and determined oocyte quality via assessing the key regulators during meiotic maturation and fertilization. We found that Cd exposure impeded the mouse oocyte meiotic progression by disrupting the normal spindle assembly, chromosome alignment and actin cap formation. Besides, exposure to Cd induced oxidative stress with the increased reactive oxygen species and apoptosis levels, leading to abnormal mitochondrial distribution, insufficient energy supply, and DNA damage, which ultimately led to oocyte quality deterioration. We also analyzed the effects of cadmium on epigenetic modifications, and the levels of 5mC, H3K9me3 and H3K9ac decreased after acute exposure to cadmium. Further experiments showed that the litter size in Cd-exposed female mice reduced, thereby indicating increased reproductive Cd toxicity. In conclusion, Cd exposure impairs oocyte maturation and fertilization ability induced by oxidative stress, early apoptosis and epigenetic modifications, which lead to the decrease of female fertility.

Pesticide Exposure Modifies DNA Methylation of Coding Region of WRAP53α, an Antisense Sequence of p53, in a Mexican Population

The influence of pesticide exposure in alteration of DNA methylation patterns of specific genes is still limited, specifically in natural antisense transcripts (NAT), such as the WRAP53α gene. The aim of this study was to determine the methylation of the WRAP53α gene in mestizo and indigenous populations as well as its relationship with internal (age, sex, and body mass index) and external factors (pesticide exposure and micronutrient intake). A cross-sectional study was conducted including 91 mestizo individuals without occupational exposure to pesticides, 164 mestizo urban sprayers and 189 indigenous persons without occupational exposure to pesticides. Acute pesticide exposure was evaluated by measurement of urinary dialkylphosphate (DAP) concentration by gas chromatograph coupled to a mass spectrometer. Anthropometric characteristics, unhealthy habits, and chronic pesticide exposure were assessed using a structured questionnaire. The frequency of macro- and micronutrient intake was determined using SNUT software. DNA methylation of the WRAP53α gene was determined by pyrosequencing of bisulfite-modified DNA. The mestizo sprayers group had the higher values of %5mC. In addition, this group had the most DAP urinary concentration with respect to the indigenous and reference groups. Bivariate analysis showed an association between %5mC of the WRAP53α gene with micronutrient intake and pesticide exposure in mestizo sprayers, whereas changes in %5mC of the WRAP53α gene was associated with body mass index in the indigenous group. These data suggest that the %5mC of the WRAP53α gene can be influenced by pesticide exposure and ethnicity in the study population, and changes in the WRAP53α gene might cause an important cell process disturbance.