Effects of endocrine disruptors in the development of the female reproductive tract

Effects of Endocrine-Disrupting Chemicals and Epigenetic Modifications in Ovarian Cancer: A Review

Ovarian cancer (OC) is a relatively fatal female reproductive malignancy. Since the underlying causes are uncertain, it brings us to believe that both genetic and external factors contribute toward development of this lethal disorder. Exposure to endocrine-disrupting chemicals (EDCs) in the form of occupational usage of pesticides, fungicides, herbicides, plasticizers, cosmetics, and so on is potentially carcinogenic and their ability to cause epigenetic modifications has led us to hypothesize that they may play a catalytic role in OC progression. In response to synthetic chemicals, animal models have demonstrated disturbances in the development of ovaries and steroid hormonal levels but in humans, more research is required. The present review is an attempt to address the impact of EDCs on the hormonal system and gene methylation levels that may lead to malfunctioning of the ovaries which may consequently develop in the form of cancer. It can be concluded that endocrine disruptors do have a potential carcinogenicity and their high proportions in human body may cause epigenetic modifications, prompting ovarian surface epithelium to grow in an abnormal manner.

The Association of Air Pollution With Pubertal Development: Evidence From Hong Kong's "Children of 1997" Birth Cohort

Many pollutants are endocrine disruptors with impacts on reproduction and health in animals, but evidence in humans, of which sex-specific effects on pubertal development may be an indicator, is less clear. We examined the association of air pollution in utero and during early life with pubertal development in Hong Kong, China, an area with a high level of air pollution compared with other similarly developed cities. We assessed sex-specific associations of particulate matter less than or equal to 10 μm in diameter (PM10), nitric oxide, sulfur dioxide, and nitrogen dioxide in different growth phases with clinically assessed pubertal stage at approximately age 11 years (as indicated by Tanner stage) in a large population-representative birth cohort, the "Children of 1997." We used partial least squares regression to account for colinearity between air pollutants. Among 1,938 girls, PM10 exposure in utero and during infancy was negatively associated with pubertal stage and breast development, whereas among 2,136 boys, sulfur dioxide and nitrogen dioxide exposure in utero, during infancy, and in childhood were negatively associated with pubertal stage. These sex-specific associations with pubertal development are consistent with endocrine-disrupting effects. Given the health impact of altered pubertal timing, further investigation across the life course may help quantify the full effects and the corresponding need for preventive measures.

Phthalate exposure and reproductive hormones and sex-hormone binding globulin before puberty - Phthalate contaminated-foodstuff episode in Taiwan

Background

In May 2011, a major incident involving phthalates-contaminated foodstuffs occurred in Taiwan. Di-(2-ethylhexyl) phthalate (DEHP) was added to foodstuffs, mainly juice, jelly, tea, sports drink, and dietary supplements. Concerns arose that normal pubertal development, especially reproductive hormone regulation in children, could be disrupted by DEHP exposure.

Objective

To investigate the association between phthalate exposure and reproductive hormone levels among children following potential exposure to phthalate-tainted foodstuffs.

Methods

A total of 239 children aged <12 years old were recruited from 3 hospitals in north, central, and south Taiwan after the episode. Structured questionnaires were used to collect the frequency and quantity of exposures to 5 categories of phthalate-contaminated foodstuffs to assess phthalate exposure in children. Urine samples were collected for the measurement of phthalate metabolites. The estimated daily intake of DEHP exposure at the time of the contamination incident occurred was calculated using both questionnaire data and urinary DEHP metabolite concentrations. Multiple regression analyses were applied to assess associations between phthalate exposure and reproductive hormone levels in children.

Results

After excluding children with missing data regarding exposure levels and hormone concentrations and girls with menstruation, 222 children were included in the statistical analyses. After adjustment for age and birth weight, girls with above median levels of urinary mono-(2-ethyl-5-hydroxyhexyl) phthalate, mono-(2-ethyl-5-oxohexyl) phthalate, and sum of mono-(2-ethylhexyl) phthalate concentrations had higher odds of above median follicle-stimulating hormone concentrations. Girls with above median estimated average daily DEHP exposures following the contamination episode also had higher odds of sex hormone-binding globulin above median levels.

Conclusions

Phthalate exposure was associated with alterations of reproductive hormone levels in girls.

Predicting the gas-phase concentration of semi-volatile organic compounds from airborne particles: Application to a French nationwide survey

Semi-volatile organic compounds (SVOCs) partition indoors between the gas phase, airborne particles, settled dust, and other surfaces. Unknown concentrations of SVOCs in the gas phase (C_g) can be predicted from their measured concentrations in airborne particles. In previous studies, the prediction of C_g depended largely on choosing a specific equation for the calculation of the particle/gas partition coefficient. Moreover, the prediction of C_g is frequently performed at a reference temperature rather than the real indoor temperature. In this paper, a probabilistic approach based on Monte Carlo simulation was developed to predict the distribution of SVOCs' C_g from their concentrations in airborne particles at the target indoor temperature. Moreover, the distribution of the particle/gas partition coefficient of each SVOC at the target temperature was used. The approach was validated using two measured datasets in the literature: the predicted C_g from concentrations measured in airborne particles and the measured C_g were generally of the same order of magnitude. The distributions of the C_g of 66 SVOCs in the French housing stock were then predicted. The SVOCs with the highest median C_g, ranging from 1ng/m³ to >100ng/m³, included 8 phthalates (DEP, DiBP, DBP, DEHP, BBP, DMP, DiNP, and DMEP), 4 polycyclic aromatic hydrocarbons (fluorene, phenanthrene, fluoranthene, and anthracene), 2 alkylphenols (4-tert-butylphenol and 4-tert-octylphenol), 2 synthetic musks (galaxolide and tonalide), tributyl phosphate, and heptachlor. The nationwide, representative, predicted C_g values of SVOCs are frequently of the same order of magnitude in Europe and North America, whereas these C_g values in Chinese and Indian dwellings and the C_g of polybrominated diphenyl ethers in U.S. dwellings are generally higher.

Increased Urinary Phthalate Levels in Women with Uterine Leiomyoma: A Case-Control Study

We assessed the urinary concentration of 16 phthalate metabolites in 57 women with and without uterine leiomyoma (n = 30 and 27; respectively) to determine the association between phthalate exposure and uterine leiomyoma. To evaluate exposure to di-(2-ethylhexyl) phthalate (DEHP); we calculated the molar sum of DEHP metabolites; ∑3-DEHP (combining mono-(2-ethylhexyl) phthalate (MEHP); mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP); and mono-(2-ethyl-5-oxohexyl) phthalate); ∑4-DEHP (∑3-DEHP plus mono-(2-ethyl-5-carboxypentyl) phthalate); and ∑5-DEHP (∑4-DEHP plus mono (2-(carboxylmethyl)hexyl) phthalate (2cx-MMHP)). The log transformed urinary levels of MEHP; MEHHP; 2cx-MMHP; ∑3-DEHP; ∑4-DEHP; and ∑5-DEHP in the leiomyoma group were significantly higher than those of controls. When we adjusted for age; waist circumference; and parity using multiple logistic regression analyses; we found log ∑3-DEHP (OR = 10.82; 95% CI = 1.25; 93.46) and ∑4-DEHP (OR = 8.78; 95% CI = 1.03; 75.29) were significantly associated with uterine leiomyoma. Our findings suggest an association between phthalate exposure and uterine leiomyoma. However; larger studies are needed to investigate potential interactions between phthalate exposure and uterine leiomyoma.

Human exposure to endocrine disrupting compounds: Their role in reproductive systems, metabolic syndrome and breast cancer. A review

Endocrine disrupting chemicals (EDCs) are released into the environment from different sources. They are mainly used in packaging industries, pesticides and food constituents. Clinical evidence, experimental models, and epidemiological studies suggest that EDCs have major risks for humans by targeting different organs and systems in the body (e.g. reproductive system, breast tissue, adipose tissue, pancreas, etc.). Due to the ubiquity of human exposure to these compounds the aim of this review is to describe the most recent data on the effects induced by phthalates, bisphenol A and parabens in a critical window of exposure: in utero, during pregnancy, infants, and children. The interactions and mechanisms of toxicity of EDCs in relation to human general health problems, especially those broadening the term of endocrine disruption to 'metabolic disruption', should be deeply investigated. These include endocrine disturbances, with particular reference to reproductive problems and breast, testicular and ovarian cancers, and metabolic diseases such as obesity or diabetes.

Impact of endocrine disrupting chemicals on onset and development of female reproductive disorders and hormone-related cancer

A growing body of evidence suggests that exposure to chemical substances designated as endocrine disrupting chemicals (EDCs) due to their ability to disturb endocrine (hormonal) activity in humans and animals, may contribute to problems with fertility, pregnancy, and other aspects of reproduction. The presence of EDCs has already been associated with reproductive malfunction in wildlife species, but it remains difficult to prove causal relationships between the presence of EDCs and specific reproductive problems in vivo, especially in females. On the other hand, the increasing number of experiments with laboratory animals and in vitro research indicate the ability of different EDCs to influence the normal function of female reproductive system, and even their association with cancer development or progression. Research shows that EDCs may pose the greatest risk during prenatal and early postnatal development when organ and neural systems are forming. In this review article, we aim to point out a possible contribution of EDCs to the onset and development of female reproductive disorders and endocrine-related cancers with regard to the period of exposure to EDCs and affected endpoints (organs or processes).

Organochlorine pesticides and female puberty in South Kazakhstan

The purpose of the study was to assess the puberty of females living in cotton-growing regions of South Kazakhstan, where organochlorine pesticides are widely used. The physical growth and sexual development were assessed; organochlorine pesticides, gonadotropic and steroid hormones, as well as insulin-like growth factor 1 in the peripheral blood were determined. 524 females (adolescents aged 10-17) were examined. They were divided into 2 groups, depending on their place of residence. The clinical research included the assessment of physical and sexual development. All examined females lived in rural areas, i.e. they were comparable in terms of social, welfare, and climatographic factors. A high concentration of organochlorine pesticides (lindane-18.51±0.16mg/l, dieldrin-169.16±3.13mg/l, DDT-177.78±2.71mg/l, endrin-37.57±0.9mg/l) in the blood of females living in regions exposed to pesticides compared to their peers (4.05±0.41mg/l, 30.8±3.7mg/l, 109.7±2.58mg/l, 4.85±0.69mg/l respectively) was found (p<0.001). The physical and sexual development of such females was delayed. The research established a correlation between the concentration of pesticides and the endocrine status, as well as with the insulin-like growth factor 1. This shows the adverse effect of organochlorine pesticides on the development of the female reproductive system during puberty.

Etiologies of uterine malformations

Ranging from aplastic uterus (including Mayer-Rokitansky-Kuster-Hauser syndrome) to incomplete septate uterus, uterine malformations as a group are relatively frequent in the general population. Specific causes remain largely unknown. Although most occurrences ostensibly seem sporadic, familial recurrences have been observed, which strongly implicate genetic factors. Through the study of animal models, human syndromes, and structural chromosomal variation, several candidate genes have been proposed and subsequently tested with targeted methods in series of individuals with isolated, non-isolated, or syndromic uterine malformations. To date, a few genes have garnered strong evidence of causality, mainly in syndromic presentations (HNF1B, WNT4, WNT7A, HOXA13). Sequencing of candidate genes in series of individuals with isolated uterine abnormalities has been able to suggest an association for several genes, but confirmation of a strong causative effect is still lacking for the majority of them. We review the current state of knowledge about the developmental origins of uterine malformations, with a focus on the genetic variants that have been implicated or associated with these conditions in humans, and we discuss potential reasons for the high rate of negative results. The evidence for various environmental and epigenetic factors is also reviewed. © 2016 Wiley Periodicals, Inc.

Polycystic ovary syndrome (PCOS) and endocrine disrupting chemicals (EDCs)

Polycystic ovary syndrome (PCOS) is a heterogeneous disorder of unclear etiopathogenesis that is likely to involve genetic and environmental components synergistically contributing to its phenotypic expression. Endocrine disrupting chemicals (EDCs) and in particular Bisphenol A (BPA) represent a group of widespread pollutants intensively investigated as possible environmental contributors to PCOS pathogenesis. Substantial evidence from in vitro and animal studies incriminates endocrine disruptors in the induction of reproductive and metabolic aberrations resembling PCOS characteristics. In humans, elevated BPA concentrations are observed in adolescents and adult PCOS women compared to reproductively healthy ones and are positively correlated with hyperandrogenemia, implying a potential role of the chemical in PCOS pathophysiology, although a causal interference cannot yet be established. It is plausible that developmental exposure to specific EDCs could permanently alter neuroendocrine, reproductive and metabolic regulation favoring PCOS development in genetically predisposed individuals or it could accelerate and/or exacerbate the natural course of the syndrome throughout life cycle exposure.

Bisphenol-A and Female Infertility: A Possible Role of Gene-Environment Interactions

Background: Bisphenol-A (BPA) is widely used and ubiquitous in the environment. Animal studies indicate that BPA affects reproduction, however, the gene-environment interaction mechanism(s) involved in this association remains unclear. We performed a literature review to summarize the evidence on this topic. Methods: A comprehensive search was conducted in PubMed using as keywords BPA, gene, infertility and female reproduction. Full-text articles in both human and animals published in English prior to December 2014 were selected. Results: Evidence shows that BPA can interfere with endocrine function of hypothalamic-pituitary axis, such as by changing gonadotropin-releasing hormones (GnRH) secretion in hypothalamus and promoting pituitary proliferation. Such actions affect puberty, ovulation and may even result in infertility. Ovary, uterus and other reproductive organs are also targets of BPA. BPA exposure impairs the structure and functions of female reproductive system in different times of life cycle and may contribute to infertility. Both epidemiological and experimental evidences demonstrate that BPA affects reproduction-related gene expression and epigenetic modification that are closely associated with infertility. The detrimental effects on reproduction may be lifelong and transgenerational. Conclusions: Evidence on gene-environment interactions, especially from human studies, is still limited. Further research on this topic is warranted.

A review on endocrine disruptors and their possible impacts on human health

Endocrine disruption is a named field of research which has been very active for over 10 years, although the effects of endocrine disruptors in wildlife have been studied mainly in vast since the 1940s. A large number of chemicals have been identified as endocrine disruptors and humans can be exposed to them either due to their occupations or through dietary and environmental exposure (water, soil and air). Endocrine disrupting chemicals are compounds that alter the normal functioning of the endocrine system of both humans and wildlife. In order to understand the vulnerability and risk factors of people due to endocrine disruptors as well as the remedies for these, methods need to be developed in order to predict effects on populations and communities from the knowledge of effects on individuals. For several years there have been a growing interest on the mechanism and effect of endocrine disruptors and their relation with environment and human health effect. This paper, based on extensive literature survey, briefly studies the progress mainly in human to provide information concerning causative substances, mechanism of action, ubiquity of effects and important issues related to endocrine disruptors. It also reviews the current knowledge of the potential impacts of endocrine disruptors on human health so that the effects can be known and remedies applied for the problem as soon as possible.

Triazophos-induced oxidative stress and histomorphological changes in ovary of female Wistar rats

Triazophos (TZ), a non-systemic broad spectrum organophosphate (OP), is being extensively used against a wide range of pests in agricultural practices. The present study was carried out to investigate the toxic effects of triazophos (TZ) in female Wistar rats. Three sub-chronic dose levels of TZ corresponding to 1/10th, 1/20th and 1/40th of LD50 were given for 30 days to adult female Wistar rats through oral intubation. During the treatment period estrous cycle was significantly altered. Activity levels of different oxidative stress (OS) parameters viz. catalase (CAT), superoxide dismutase (SOD), glutathione-S-transferase (GST), glutathione reductase (GR), glutathione peroxidase (GPx) and lipid peroxidation (LPO) were differentially altered in the ovary of treated rats. Estradiol levels were significantly high while progesterone levels were significantly reduced in plasma of 1/10th and 1/20th of LD50 TZ-treated rats. Histomorphological studies of ovary revealed increased follicular atresia and increased ovarian surface epithelial height in 1/10th and 1/20th of LD50 TZ-treated rats. Enhanced apoptosis and necrosis were also observed in ovarian granulosa cells at dose-dependent manner. Results infer that TZ exposure may lead to the number of pathophysiological conditions in female rats and severity increases at high doses.

Influence of α-tocopherol and α-lipoic acid on bisphenol-A-induced oxidative damage in liver and ovarian tissue of rats

Bisphenol A (BPA) is a commonly used material in daily life, and it is argued to cause oxidative stress in liver and ovarian tissue. α-Lipoic acid (ALA) and α-tocopherol (ATF), two of the most effective antioxidants, may play a role in preventing the toxic effect. Therefore, the purpose of this study was to examine the beneficial effects of ALA, ATF, and that of ALA + ATF combination on oxidative damage induced by BPA. Female Wistar rats were divided into five groups (control, BPA, BPA + ALA, BPA + ATF, and BPA + ALA + ATF). BPA (25 mg/kg/day), ALA (100 mg/kg/day), and ATF (20 mg/kg/day) were administered for 30 days.  The levels of serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT), liver malondialdehyde (L-MDA) and glutathione peroxidase (L-GPx), and ovarian malondialdehyde (Ov-MDA) and nitric oxide (Ov-NO) were significantly higher in the BPA-treated groups compared with the control group. The levels of AST and ALT decreased in the BPA + ALA, BPA + ATF, and BPA + ALA + ATF groups compared with the BPA group. Similarly, BPA + ALA or BPA + ATF led to decreases in L-MDA and Ov-MDA levels compared with the BPA group. However, the BPA + ALA + ATF group showed a significant decrease in L-MDA levels compared with the BPA + ALA group and the BPA + ATF group. The levels of L-GPx decreased in the BPA + ATF and the BPA + ALA + ATF groups compared with the BPA group. The administration of ATF and ALA + ATF significantly decreased the Ov-NO levels.  This study demonstrates that BPA causes oxidative damage in liver and ovarian tissues. ALA, ATF, or their combination were found to be beneficial in preventing BPA-induced oxidative stress.