Prenatal polycyclic aromatic hydrocarbons, altered ERα pathway-related methylation and expression, and mammary epithelial cell proliferation in offspring and grandoffspring adult mice

Exposure to oxygenated polycyclic aromatic hydrocarbons and endocrine dysfunction: Multi-level study based on hormone receptor responses

Oxygenated polycyclic aromatic hydrocarbons (OPAHs) are a class of emerging environmental contaminants that exhibit high toxicity compared to parent PAHs. In addition to carcinogenic, teratogenic and mutagenic effects, recent studies show their potential to cause endocrine disruption, but the reports are controversial. In this study, we employed hormone receptors (ERα/AR/GRα/TRβ)-mediated dual luciferase reporter gene assay and molecular docking, and found that five typical OPAHs exhibited agonistic activity towards hormone receptors, and hydrogen bonding and hydrophobic interactions were the primary binding forces involved in OPAHs-receptor interactions. Then, we developed a weighted scoring system coupled with computerized screening and clarified that 1,2-benzanthraquinone (BAQ) had the strongest hormonal effects, while anthraquinone (AQ) exhibited the weakest effects. Using the in vivo exposure model, we clarified that BAQ induced hormone receptor-coupled developmental toxicity in zebrafish larvae, evidenced by increased expression of androgen receptors and key genes involved in hormone synthesis, pericardial edema and reduced body length. Importantly, we successfully constructed androgen response element-enhanced green fluorescent protein (ARE-EGFP) transient transfection zebrafish embryos, and confirmed the androgenic potency of BAQ, but not AQ. These findings highlight the endocrine-disrupting effects in the risk management of OPAHs.

Machine learning-enhanced surface-enhanced spectroscopic detection of polycyclic aromatic hydrocarbons in the human placenta

The detection and identification of polycyclic aromatic hydrocarbons (PAHs) and their derivatives, polycyclic aromatic compounds (PACs), are essential for environmental and health monitoring, for assessing toxicological exposure and their associated health risks. PAHs/PACs are the most dangerous chemicals found in tobacco smoke, and cigarette use during pregnancy can convey these molecules to the developing fetus through the placenta. This exposure is associated with many negative health outcomes, from premature birth to sudden infant death syndrome and adverse neurodevelopmental disorders. This study demonstrates the use of surface-enhanced Raman and surface-enhanced infrared absorption spectroscopies for direct detection of PAHs/PACs in human placental tissue. We applied two spectroscopy-informed machine learning algorithms, Characteristic Peak Extraction (CaPE) and Characteristic Peak Similarity (CaPSim), to identify the specific PAHs and PACs present in the placenta of women who smoked tobacco cigarettes in pregnancy compared to spectra of the placenta from self-reported nonsmokers. CaPE and CaPSim analysis enabled a clear distinction between these two groups. Independent verification was accomplished by detecting PAH-DNA and PAC-DNA adducts in the smoking group by means of a 32P-postlabeling assay. These findings highlight the effectiveness of combining surface-enhanced spectroscopies with informed ML analysis for the streamlined detection of hazardous environmental compounds in human tissues, suggesting broader applications in clinical diagnostics and public health surveillance.

Screening for Endocrine Bioactivity Potential of Tobacco Product Chemicals Including Flavor Chemicals

Adolescence and pregnancy involve elevated levels of hormones (e.g., estrogen, androgen) during which exposure to endocrine disruptors could have long-term developmental and reproductive toxicity (DART) effects. Therefore, the use prevalence and abuse liability of electronic nicotine delivery systems (ENDS) among adolescents and youth, and during pregnancy, raises concerns about possible exposure to endocrine disruptors. In addition, endocrine disruptors have adverse effects on wildlife and environmental health. While many studies focus on carcinogenicity and mutagenicity of tobacco products, research efforts screening chemicals in tobacco products for endocrine disruption potential are few. In this study, we curated 5179 chemicals in tobacco and tobacco smoke, 2803 flavor chemicals, and 156 e-liquid chemicals from literature or openly available databases. We screened the chemicals for endocrine bioactivity using new approach methodologies (NAMs) developed through US Environmental Protection Agency's Endocrine Disruptor Screening Program. The specific NAMs, estrogenic and androgenic pathway models, identified 137 tobacco chemicals, 34 flavor chemicals, and three e-liquid chemicals (Veratraldehyde, (2E)-3-Phenylprop-2-enal, and 2'-Acetonaphthone) as "active," indicating potential endocrine bioactivity. Further, among the tobacco chemicals with endocrine bioactivity potential, 48 were environmentally persistent, 29 bioaccumulative, and 19 both persistent and bioaccumulative. Our findings document many chemicals in tobacco products with potential endocrine bioactivity, which raises concerns for both human and environmental health. These results also underscore the importance of DART potential of tobacco products and flavors. Overall, our study characterizes the endocrine bioactivity potential of tobacco and flavor chemicals and provides a list of chemicals to consider in future ecological and health risk assessments.

Benzo[a]pyrene exposure affects colorectal cancer susceptibility by regulating ERβ-mediated LINC02977 transcription

Environmental pollutants known as polycyclic aromatic hydrocarbons (PAHs) are produced through the incomplete combustion of organic material. While PAHs have been investigated as genotoxicants, they can also operate through nongenotoxic pathways in estrogen-dependent malignancies, such as breast, cervical and ovarian cancer. However, whether PAHs induce colorectal cancer (CRC) risk through estrogenic effects is still illusive. Here, we systematically investigated the abnormal expression and activation of estrogen receptor beta (ERβ) regulated by PAHs in CRC as well as the underlying mechanisms of ERβ-mediated CRC risk. Based on the 300 plasma samples from CRC patients and healthy controls detected by GC-MS/MS, we found that the plasma concentrations of benzo[a]pyrene (BaP) were significantly higher in CRC cases than in healthy controls, with significant estrogenic effects. Moreover, histone deacetylase 2 (HDAC2)-induced deacetylation of the promoter decreases ERβ expression, which is associated with poor overall survival and advanced tumor stage. The study also revealed that BaP and estradiol (E2) had different carcinogenic effects, with BaP promoting cell proliferation and inhibiting apoptosis, while E2 had the opposite effects. Additionally, this study mapped ERβ genomic binding regions by performing ChIP-seq and ATAC-seq and identified genetic variants of rs1411680 and its high linkage disequilibrium SNP rs6477937, which were significantly associated with CRC risk through meta-analysis of two independent Chinese population genome-wide association studies comprising 2,248 cases and 3,173 controls and then validation in a large-scale European population. By integrating data from functional genomics, we validated the regulatory effect of rs6477937 as an ERβ binding-disrupting SNP that mediated allele-specific expression of LINC02977 in a long-range chromosomal interaction manner, which was found to be highly expressed in CRC tissues. Overall, this study suggests that the different active effects on ERβ by PAHs and endogenous E2 may play a crucial role in the development and progression of CRC and highlights the potential of targeting ERβ and its downstream targets for CRC prevention and treatment.

Prenatal airborne polycyclic aromatic hydrocarbon exposure, altered regulation of peroxisome proliferator-activated receptor gamma (Ppar)γ, and links with mammary cancer

Environmental exposure to polycyclic aromatic hydrocarbons (PAH) has been shown to be associated with chronic disease outcomes through multiple mechanisms including altered regulation of the transcription factor peroxisome proliferator-activated receptor gamma (Ppar) γ. Because PAH exposure and Pparγ each have been associated with mammary cancer, we asked whether PAH would induce altered regulation of Pparγ in mammary tissue, and whether this association may underlie the association between PAH and mammary cancer. Pregnant mice were exposed to aerosolized PAH at proportions that mimic equivalent human exposures in New York City air. We hypothesized that prenatal PAH exposure would alter Pparγ DNA methylation and gene expression and induce the epithelial to mesenchymal transition (EMT) in mammary tissue of offspring (F1) and grandoffspring (F2) mice. We also hypothesized that altered regulation of Pparγ in mammary tissue would associate with biomarkers of EMT, and examined associations with whole body weight. We found that prenatal PAH exposure lowered Pparγ mammary tissue methylation among grandoffspring mice at postnatal day (PND) 28. However, PAH exposure did not associate with altered Pparγ gene expression or consistently with biomarkers of EMT. Finally, lower Pparγ methylation, but not gene expression, was associated with higher body weight among offspring and grandoffspring mice at PND28 and PND60. Findings suggest additional evidence of multi-generational adverse epigenetic effects of prenatal PAH exposure among grandoffspring mice.

Dynamic changes of DNA methylation induced by benzo(a)pyrene in cancer

Benzo(a)pyrene (BaP), the earliest and most significant carcinogen among polycyclic aromatic hydrocarbons (PAHs), has been found in foods, tobacco smoke, and automobiles exhaust, etc. Exposure to BaP induced DNA damage directly, or oxidative stress-related damage, resulting in cell apoptosis and carcinogenesis in human respiratory system, digestive system, reproductive system, etc. Moreover, BaP triggered genome-wide epigenetic alterations by methylation, which might cause disturbances in regulation of gene expression, and thereby induced cancer. It has been proved that BaP reduced genome-wide DNA methylation, and activated proto-oncogene by hypomethylation in the promoter region, but silenced tumor suppressor genes by promoter hypermethylation, resulting in cancer initiation and progression. Here we summarized the changes in DNA methylation in BaP exposure, and revealed the methylation of DNA plays a role in cancer development.

Parental occupational exposure to chemicals and risk of breast cancer in female offspring

OBJECTIVES

Parental exposure to chemicals at work has been hypothesized to be a potential predisposing factor for breast cancer in next generations. The objective of the present nationwide nested case-control study was to contribute with evidence to this area.

METHODS

Women with primary breast cancer were identified using the Danish Cancer Registry and they were required to have information on either maternal or paternal employment history, which resulted in the inclusion of 5587 cases. For each case, 20 female cancer free controls were matched on year of birth using the Danish Civil Registration System. Employment history was linked to job exposure matrices to assess specific occupational chemical exposures.

RESULTS

For maternal exposures, we observed an association between ever exposure to diesel exhaust (OR = 1.13, 95% CI: 1.01-1.27) and exposure to bitumen fumes in the perinatal period (OR = 1.51, 95% CI: 1.00-2.26) and breast cancer in female offspring. Highest cumulative exposure to benzo(a)pyrene, diesel exhaust, gasoline and bitumen fumes was further indicated to increase the risk. Results further indicated a stronger association between diesel exhaust (OR = 1.23, 95% CI: 1.01-1.50) and benzo(a)pyrene exposure (OR = 1.23, 95% CI: 0.96-1.57) and estrogen receptor negative tumors than tumors with ER expression, while bitumen fumes seemed to elevate the risk of both hormonal subtypes. For paternal exposures, the main results did not indicate any associations with breast cancer in female offspring.

CONCLUSIONS

Our study suggests an elevated breast cancer risk in daughters of women occupational exposed to some occupational pollutants, including diesel exhaust, benzo(a)pyrene and bitumen fumes. These findings need to be confirmed in future large-scale studies before any firm conclusions can be reached.

Association of the urinary polycyclic aromatic hydrocarbons with sex hormones stratified by menopausal status older than 20 years: a mixture analysis

We examined the relationships between exposure to polycyclic aromatic hydrocarbons (PAH) metabolites and sex hormones in pre- and postmenopausal women from the 2013-2016 National Health and Nutrition Examination Survey. The study comprised 648 premenopausal and 370 postmenopausal women (aged 20 years or older) with comprehensive data on PAH metabolites and sex steroid hormones. To evaluate the correlations between individual or mixture of the PAH metabolites and sex hormones stratified by menopausal status, we used linear regression and Bayesian kernel machine regression (BKMR). After controlling for confounders, 1-Hydroxynaphthalene (1-NAP) was inversely associated with total testosterone (TT), and 1-NAP, 3-Hydroxyfluorene (3-FLU), and 2-Hydroxyfluorene (2-FLU) were inversely associated with estradiol (E2). 3-FLU was positively associated with sex hormone-binding globulin (SHBG) and TT/E2, whereas 1-NAP and 2-FLU were inversely associated with free androgen index (FAI). In the BKMR analyses, chemical combination concentrations at or above the 55th percentile were inversely connected to E2, TT, and FAI values but positively correlated with SHBG when compared with the matching 50th percentile. In addition, we only found that mixed exposure to PAHs was positively associated with TT and SHBG in premenopausal women. Exposure to PAH metabolites, either alone or as a mixture, was negatively associated with E2, TT, FAI, and TT/E2 but positively associated with SHBG. These associations were stronger among postmenopausal women.

The Physiological Effects of Air Pollution: Particulate Matter, Physiology and Disease

Nine out of 10 people breathe air that does not meet World Health Organization pollution limits. Air pollutants include gasses and particulate matter and collectively are responsible for ~8 million annual deaths. Particulate matter is the most dangerous form of air pollution, causing inflammatory and oxidative tissue damage. A deeper understanding of the physiological effects of particulate matter is needed for effective disease prevention and treatment. This review will summarize the impact of particulate matter on physiological systems, and where possible will refer to apposite epidemiological and toxicological studies. By discussing a broad cross-section of available data, we hope this review appeals to a wide readership and provides some insight on the impacts of particulate matter on human health.

Impact of Endocrine Disruptors upon Non-Genetic Inheritance

Similar to environmental factors, EDCs (endocrine-disrupting chemicals) can influence gene expression without modifying the DNA sequence. It is commonly accepted that the transgenerational inheritance of parentally acquired traits is conveyed by epigenetic alterations also known as "epimutations". DNA methylation, acetylation, histone modification, RNA-mediated effects and extracellular vesicle effects are the mechanisms that have been described so far to be responsible for these epimutations. They may lead to the transgenerational inheritance of diverse phenotypes in the progeny when they occur in the germ cells of an affected individual. While EDC-induced health effects have dramatically increased over the past decade, limited effects on sperm epigenetics have been described. However, there has been a gain of interest in this issue in recent years. The gametes (sperm and oocyte) represent targets for EDCs and thus a route for environmentally induced changes over several generations. This review aims at providing an overview of the epigenetic mechanisms that might be implicated in this transgenerational inheritance.

Maternal and early life exposures and their potential to influence development of the microbiome

At the dawn of the twentieth century, the medical care of mothers and children was largely relegated to family members and informally trained birth attendants. As the industrial era progressed, early and key public health observations among women and children linked the persistence of adverse health outcomes to poverty and poor nutrition. In the time hence, numerous studies connecting genetics ("nature") to public health and epidemiologic data on the role of the environment ("nurture") have yielded insights into the importance of early life exposures in relation to the occurrence of common diseases, such as diabetes, allergic and atopic disease, cardiovascular disease, and obesity. As a result of these parallel efforts in science, medicine, and public health, the developing brain, immune system, and metabolic physiology are now recognized as being particularly vulnerable to poor nutrition and stressful environments from the start of pregnancy to 3 years of age. In particular, compelling evidence arising from a diverse array of studies across mammalian lineages suggest that modifications to our metagenome and/or microbiome occur following certain environmental exposures during pregnancy and lactation, which in turn render risk of childhood and adult diseases. In this review, we will consider the evidence suggesting that development of the offspring microbiome may be vulnerable to maternal exposures, including an analysis of the data regarding the presence or absence of a low-biomass intrauterine microbiome.

Exposure to polycyclic aromatic hydrocarbons during pregnancy and breast tissue composition in adolescent daughters and their mothers: a prospective cohort study

BACKGROUND

Polycyclic aromatic hydrocarbons (PAH), which are found in air pollution, have carcinogenic and endocrine disrupting properties that might increase breast cancer risk. PAH exposure might be particularly detrimental during pregnancy, as this is a time when the breast tissue of both the mother and daughter is undergoing structural and functional changes. In this study, we tested the hypothesis that ambient PAH exposure during pregnancy is associated with breast tissue composition, measured one to two decades later, in adolescent daughters and their mothers.

METHODS

We conducted a prospective analysis using data from a New York City cohort of non-Hispanic Black and Hispanic mother-daughter dyads (recruited 1998-2006). During the third trimester of pregnancy, women wore backpacks containing a continuously operating air sampling pump for two consecutive days that measured ambient exposure to eight carcinogenic higher molecular weight nonvolatile PAH compounds (Σ8 PAH) and pyrene. When daughters (n = 186) and mothers (n = 175) reached ages 11-20 and 29-55 years, respectively, optical spectroscopy (OS) was used to evaluate measures of breast tissue composition (BTC) that positively (water content, collagen content, optical index) and negatively (lipid content) correlate with mammographic breast density, a recognized risk factor for breast cancer. Multivariable linear regression was used to evaluate associations between ambient PAH exposure and BTC, overall and by exposure to household tobacco smoke during pregnancy (yes/no). Models were adjusted for race/ethnicity, age, and percent body fat at OS.

RESULTS

No overall associations were found between ambient PAH exposure (Σ8 PAH or pyrene) and BTC, but statistically significant additive interactions between Σ8 PAH and household tobacco smoke exposure were identified for water content and optical index in both daughters and mothers (interaction p values < 0.05). Σ8 PAH exposure was associated with higher water content (β_daughters = 0.42, 95% CI = 0.15-0.68; β_mothers = 0.32, 95% CI = 0.05-0.61) and higher optical index (β_daughters = 0.38, 95% CI = 0.12-0.64; β_mothers = 0.38, 95% CI = 0.12-0.65) in those exposed to household tobacco smoke during pregnancy; no associations were found in non-smoking households (interaction p values < 0.05).

CONCLUSIONS

Exposure to ambient Σ8 PAH and tobacco smoke during pregnancy might interact synergistically to impact BTC in mothers and daughters. If replicated in other cohorts, these findings might have important implications for breast cancer risk across generations.

Prenatal polycyclic aromatic hydrocarbon (PAH) exposure in relation to placental corticotropin releasing hormone (pCRH) in the CANDLE pregnancy cohort

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous endocrine-disrupting combustion by-products that have been linked to preterm birth. One possible mechanism is through disruption of placental corticotropin releasing hormone (pCRH), a key hormone implicated in parturition. As an extension of recent research identifying pCRH as a potential target of endocrine disruption, we examined maternal PAH exposure in relation to pCRH in a large, diverse sample. Participants, drawn from the CANDLE cohort, part of the ECHO-PATHWAYS Consortium, completed study visits at 16-29 weeks (V1) and 22-39 weeks (V2) gestation (n=812). Seven urinary mono-hydroxylated PAH metabolites (OH-PAHs) were measured at V1 and serum pCRH at V1 and V2. Associations between individual log-transformed OH-PAHs (as well as two summed PAH measures) and log(pCRH) concentrations across visits were estimated using mixed effects models. Minimally-adjusted models included gestational age and urinary specific gravity, while fully-adjusted models also included sociodemographic characteristics. We additionally evaluated effect modification by pregnancy complications, fetal sex, and maternal childhood trauma history. We observed associations between 2-OH-Phenanthrene (2-OH-PHEN) and rate of pCRH change that persisted in fully adjusted models (β=0.0009, 0.00006, 0.0017), however, positive associations with other metabolites (most notably 3-OH-Phenanthrene and 1-Hydroxypyrene) were attenuated after adjustment for sociodemographic characteristics. Associations tended to be stronger at V1 compared to V2 and we observed no evidence of effect modification by pregnancy complications, fetal sex, or maternal childhood trauma history. In conclusion, we observed modest evidence of association between OH-PAHs, most notably 2-OH-PHEN, and pCRH in this sample. Additional research using serial measures of PAH exposure is warranted, as is investigation of alternative mechanisms that may link PAHs and timing of birth, such as inflammatory, epigenetic, or oxidative stress pathways.

Polycyclic Aromatic Hydrocarbons and Mammary Cancer Risk: Does Obesity Matter too?

Breast cancer risk remains incompletely explained, and higher incidence rates of breast cancer over recent times and in urban and industrialized areas suggest environmental causes. Polycyclic aromatic hydrocarbons (PAH) are ubiquitous in the environment and epidemiological and rodent studies have shown associations between exposure to PAH and breast cancer incidence as well as mammary tumorigenesis. In addition, in vitro and rodent studies have implicated alterations in estrogen receptor alpha (Erα) signaling pathways following PAH exposure in limited experimental studies. However, our understanding of these mechanisms is incomplete. Sahay et al. addressed this gap by examining the effect of PAH exposure on epigenetic and transcriptional regulation of genes in the Erα pathway in a mouse cohort exposed to aerosolized PAH at proportions measured in urban air. In addition to alterations in the Erα signaling pathway in the pregnant mice and in their offspring and grandoffspring, the investigators observed higher body weights in mice exposed to PAH compared to the control. Given that associations between mammary tissue adiposity, systemic adiposity, and breast cancer risk have been observed previously, the finding of higher body weight in the PAH exposure group raises the possibility that body weight might influence the association between PAH exposure and breast cancer risk. Along with new analyses, we discuss the possibility that body weight may modify the association between PAH exposure, mammary cellular proliferation, and mammary gland ductal hyperplasia in offspring and grandoffspring mice and future research that may be needed to delineate these associations.