Hypospadias in DES grandsons : a cohort study

image of grandsons

Hypospadias: a transgenerational effect of diethylstilbestrol ?

2002 Study Abstract

BACKGROUND
Transgenerational effects of diethylstilbestrol (DES) have been reported in animals, but effects in human beings are unknown. Alerted by two case reports, we aimed to establish the risk of hypospadias in the sons of women who were exposed to DES in utero.

METHODS
We did a cohort study of all sons of a Dutch cohort of 16284 women with a diagnosis of fertility problems. We used a mailed questionnaire assessing late effects of fertility treatment to identify boys with hypospadias. We compared the prevalence rate of hypospadias between boys with and without maternal DES exposure in utero.

FINDINGS
16284 mothers (response rate 67%) reported 8934 sons. The mothers of 205 boys reported DES exposure in utero. Four of these children were reported to have hypospadias. In the remaining 8729 children, only eight cases of hypospadias were reported (prevalence ratio 21.3 [95% CI 6.5-70.1]). All cases of hypospadias were medically confirmed. Maternal age or fertility treatment did not affect the risk of hypospadias. Children conceived after assisted reproductive techniques such as in-vitro fertilisation were not at increased risk of hypospadias compared with children conceived naturally (1.8, 0.6-5.7).

INTERPRETATION
Our findings suggest an increased risk of hypospadias in the sons of women exposed to DES in utero. Although the absolute risk of this anomaly is small, this transgenerational effect of DES warrants additional studies.

Sources

  • Hypospadias in sons of women exposed to diethylstilbestrol in utero: a cohort study, Lancet, NCBI PubMed PMID: 11943257, 2002 Mar 30.
  • Featured image Donna Borzyskowski.
DES DIETHYLSTILBESTROL RESOURCES

Transgenerational Inheritance of DES Exposure

Mechanisms of the Maternal Exposome and Implications for Health Outcomes

2016 Study Abstract

It is well established that the environment contributes to health. However, few studies have evaluated environmental exposures in women that may influence future health of their offspring. Knowledge gained may inform nursing how to better advocate for patients and families; and provide individualized interventions and education. Therefore, a more comprehensive investigation of the maternal exposome to uncover mechanistic insight into complex disease in offspring is warranted. To advance understanding of biological mechanisms that contribute to high-risk birth outcomes and offspring predisposition to disease, it will be necessary to measure a range of exposures and biomarkers before and during pregnancy.

Evidence for Trans-generational Inheritance of Exposures

Exposures of the gametes, including those that occur during the prenatal period and early development, have been found to play a large role in risk of disease over the lifespan. Studies in animal models have documented epigenetic changes that persist from generation to generation. For example, in murine models, the methylation changes associated with DES exposure persist into the third generation suggesting in utero exposures may have a lasting impact on the health of future generations. The same chemical clearly demonstrates a link between environment and germ-line mutations in humans as a trans-generational alteration in DNA methylation patterns of the fetus caused by exposure to DES in utero. DES is a synthetic estrogen that was administered to pregnant women to prevent spontaneous abortions prior to the mid 1970’s. DES causes hypermethylation of the homeobox protein Hox-A10 (HOXA10), a gene that controls uterine organ development, resulting in reproductive tract anomalies that persist into adulthood. Hypermethylation of HOXA10 was specific to the fetus and did not occur in laboratory experiments using cell lines or the somatic cells of pregnant women who received DES, suggesting that this molecular alteration is unique to in utero exposure.

Investigations are ongoing in grandchildren of women given DES. Current clinical evidence suggests DES granddaughters have more menstrual irregularities, infertility, and stillbirths; and both granddaughters and grandsons exhibit more birth defects. This accumulating evidence supports that epimutations occur from exposure during gonadal sex determination, a highly vulnerable period when the germ line DNA is demethylated and remethylated in a sex specific manner. The chemically-induced modifications in epigenetic programming of the germ line results in differentially altered epigenomes and transcriptomes in all tissues propagated from the affected sperm or ovum, which can influence development of disease in later life. Although data is sparse related to trans-generational effects of environmental exposures in human studies, there is a need to better inform clinicians and patients about this critically vulnerable period during, and prior to, pregnancy. Confirmation of animal models of trans-generational effects will require the enrollment at least 3 generations of participants (grandparent, parent, and child).

Sources

  • Full study (free access) : Mechanisms of the Maternal Exposome and Implications for Health Outcomes, ANS Adv Nurs Sci, NCBI PubMed, PMC4860277, 2016 Apr-Jun.
  • Exposome Penetrance featured image PMC4860277/figure/F2.
DES DIETHYLSTILBESTROL RESOURCES

DES transgenerational transmission of defects

image of transgenerational transmission

Adverse health effects in children of women exposed in utero to diethylstilbestrol (DES)

2016 Abstract

OBJECTIVE
Exposure to diethylstilbestrol (DES) in utero is associated with adverse health effects, including genital anomalies in women and men, and cancers in women. Animal studies showed birth defects and tumors in the offspring of DES exposed mice, revealing transgenerational transmission of DES effects. In humans, birth defects, such as hypospadias were observed in children of prenatally exposed women. The aim of this research was to further assess the health effects in children of prenatally exposed women.

METHODS
In a retrospective cohort study, the reports of women exposed to DES in utero on their 4409 children were compared with those of unexposed women on their 6203 children. Comparisons used odd ratios (OR) between children of exposed and unexposed women and standardized incidence rate (SIR) with the general population. These cohorts were recruited on a voluntary basis to answer questionnaires.

RESULTS
There was a global increase of defects in children born to exposed women when compared with those born to unexposed (OR 2.29, 95% CI: 1.80-2.79, P<0.001) and with the general population (SIR 2.39, 95% CI: 2.11-2.68). Increased defects were observed in male genital tract, esophagus, lip or palate, musculoskeletal and circulatory systems. For female genital tract anomalies, there was no significant increase. However, this cohort being relatively young, further follow-up is needed. An increase of cerebral palsy was revealed. The incidence of cancers was not increased, in particular for breast, uterus and ovary.

CONCLUSION
Our results confirmed a transgenerational transmission of defects in male genital tract. With caution due to possible bias associated with this method, our data suggest an increase of defects for esophagus, lip or palate, musculoskeletal and circulatory system in children of exposed women.

Sources

  • Adverse health effects in children of women exposed in utero to diethylstilbestrol (DES), Therapie, NCBI PubMed, PMID: 27203157, 2016 Feb 5.
  • Featured image Thought Catalog.
DES DIETHYLSTILBESTROL RESOURCES

In utero DES exposure effects on reproductive capacity in several generations

The effects of in utero bisphenol A exposure on reproductive capacity in several generations of mice

2015 Study Abstract

In utero bisphenol A (BPA) exposure affects reproductive function in the first generation (F1) of mice; however, not many studies have examined the reproductive effects of BPA exposure on subsequent generations.

In this study, pregnant mice (F0) were orally dosed with vehicle, BPA (0.5, 20, and 50 μg/kg/day) or diethylstilbestrol (DES; 0.05 μg/kg/day) daily from gestation day 11 until birth. Diethylstilbestrol (DES; 0.05 µg/kg/day) was chosen as a positive control to ensure the animals were responsive to estrogenic compounds.

F1 females were used to generate the F2 generation, and F2 females were used to generate the F3 generation. Breeding studies at the ages of 3, 6, and 9 months were conducted to evaluate reproductive capacity over time. Further, studies were conducted to evaluate pubertal onset, litter size, and percentage of dead pups; and to calculate pregnancy rate, and mating, fertility, and gestational indices.

The results indicate that BPA exposure (0.5 and 50 μg/kg/day) significantly delayed the age at vaginal opening in the F3 generation compared to vehicle control. Both DES (0.05 μg/kg/day) and BPA (50 μg/kg/day) significantly delayed the age at first estrus in the F3 generation compared to vehicle control. BPA exposure reduced gestational index in the F1 and F2 generations compared to control. Further, BPA exposure (0.5 μg/kg/day) compromised the fertility index in the F3 generation compared to control. Finally, in utero BPA exposure reduced the ability of female mice to maintain pregnancies as they aged.

Collectively, these data suggest that BPA exposure affects reproductive function in female mice and that some effects may be transgenerational in nature.

Sources

  • Full paper (free access) : The effects of in utero bisphenol A exposure on reproductive capacity in several generations of mice, Toxicology and applied pharmacology, NCBI PubMed, PMC4410077, 2015 May 1.
  • Featured image Lucas Vasques.
DES DIETHYLSTILBESTROL RESOURCES

Transgenerational transmission of environmental effects through epigenetic modifications

The history of Distilbène® (Diethylstilbestrol) told to grandchildren – the transgenerational effect

2015 Study Abstract

The Distilbène® story is a dramatic episode which belongs to the history of medicine. It provided several useful lessons such as the importance of evidence-based medicine and the hazard to develop treatments during pregnancy without careful animal verifications. However, this experience has also provided unexpected progress by suggesting new pathophysiological concepts: fetal programming of adult diseases and/or transgenerational transmission of environmental effects through epigenetic modifications.

Overview

  • Introduction
  • History
  • Diseases reported in second generation after foetal exposure to DES
    • Developmental and reproductive anomalies
    • Non-reproductive anomalies
  • Diseases reported in the third generation after the grandmother was treated with DES during pregnancy
    • Human abnormalities
    • Concordance with rodent model
  • Which molecular mechanisms?
    • Exposure window
    • Chemical nature of estrogens
    • The mechanisms involved in foetal programming of adult diseases – epigenetic modifications
    • Transgenerational transmission mechanisms
  • Conclusion
  • Disclosure of interest

Sources

  • Full paper (free access) : The history of Distilbène® (Diethylstilbestrol) told to grandchildren–the transgenerational effect, ANNALES D’ENDOCRINOLOGIE, EM Consulte, article/990390, 22/07/15.
  • Featured image Isaiah Rustad.
DES DIETHYLSTILBESTROL RESOURCES

The trans-generational effects of DES exposure may pose a risk for future generations

Endocrine disruption of oestrogen action and female reproductive tract cancers

2014 Study Abstract

Endocrine disrupting chemicals (EDC) are ubiquitous and persistent compounds that have the capacity to interfere with normal endocrine homoeostasis. The female reproductive tract is exquisitely sensitive to the action of sex steroids, and oestrogens play a key role in normal reproductive function. Malignancies of the female reproductive tract are the fourth most common cancer in women, with endometrial cancer accounting for most cases. Established risk factors for development of endometrial cancer include high BMI and exposure to oestrogens or synthetic compounds such as tamoxifen. Studies on cell and animal models have provided evidence that many EDC can bind oestrogen receptors and highlighted early life exposure as a window of risk for adverse lifelong effects on the reproductive system. The most robust evidence for a link between early life exposure to EDC and adverse reproductive health has come from studies on women who were exposed in utero to diethylstilbestrol. Demonstration that EDC can alter expression of members of the HOX gene cluster highlights one pathway that might be vulnerable to their actions. In summary, evidence for a direct link between EDC exposure and cancers of the reproductive system is currently incomplete. It will be challenging to attribute causality to any single EDC when exposure and development of malignancy may be separated by many years and influenced by lifestyle factors such as diet (a source of phytoestrogens) and adiposity. This review considers some of the evidence collected to date.

  • ER signalling
  • ER expression and actions of oestrogens in reproductive tract tissues
  • Oestrogen biosynthesis and ER expression in benign and malignant endometrial tract disorders
  • Evidence that oestrogens increase the risk of developing a reproductive cancer
  • Endocrine disruptors implicated in reproductive tract disorders and cancer
Diethylstilbestrol

DES, a synthetic non-steroidal oestrogen, is often regarded as the archetypal endocrine disruptor. From about 1940 to 1970, DES was given to pregnant women in the mistaken belief that it would reduce the risk of pregnancy complications. Herbst et al. reported a probable link between DES and vaginal clear cell adenocarcinoma in girls and young women who had been exposed to this drug. It is estimated that five to ten million people were exposed to DES, including the pregnant mothers who received treatment and their offspring. Of the several million women exposed to DES in utero, a cohort of 4653 DES-exposed women have been followed up to investigate the long-term consequences of exposure (Hoover et al. 2011). Patient data stratified to account for the extent of exposure or dose effects of DES identified an association between treatment of mothers earlier during their pregnancy and adverse vaginal epithelial changes at a younger age in their offspring. While DES exposure is associated with increased risk of breast and cervical/vaginal clear cell adenocarcinoma, several studies have indicated that there is no associated risk of endometrial or ovarian cancer. As endometrial cancer is most likely to present after menopause, many of the DES-exposed women may not yet be old enough to determine whether they are at excess risk, as in the 2011 report only 27% were older than 50 years. Although to date epidemiological data indicate that DES-exposed women may not be at increased risk of developing endometrial cancer, studies in animal models provide evidence to the contrary.

In the early 1990s, Newbold et al. developed a mouse model for investigating hormonal carcinogenesis in mice by investigating the effects of neonatal exposure to oestrogens on cancer development. Treatment of CD1 neonatal mice with DES on postnatal days 1–5, which correspond to late prenatal human development, resulted in 90% of DES-exposed mice developing uterine adenocarcinomas after 18 months while none of the control animals had neoplastic lesions. Crucially, while administration of DES increased the risk of uterine adenocarcinoma, endogenous oestrogen was required for tumour development with prepubertal ovariectomy preventing tumour development. In DES-exposed women, vaginal and cervical carcinomas were only detected post-menarche consistent with a requirement for endogenous oestrogen in tumour development. ERα knockout mice (ERKO) did not develop tumours following neonatal DES exposure (Couse & Korach 2004); transgenic mice overexpressing ERα displayed accelerated tumour development but mice with a dominant negative isoform of ERα (ERΔ3) were not protected, highlighting the complexity of the molecular signalling mechanisms involved.

Interestingly, gene expression analysis indicates that developmental DES exposure results in persistent altered gene expression of oestrogen-responsive genes in the uterus that may explain the increased susceptibility to tumour development. Gene ontology analysis of microarray data revealed altered expression of genes involved in cell growth, differentiation and adhesion. Kabbarah et al. collected uterine cancer tissue RNA from DES-exposed mice by laser capture microdissection to minimise contamination with other cell types and performed targeted transcriptional profiling. Interestingly, the tumour suppressor PTEN was down-regulated in the majority of tumours, analogous to loss of PTEN expression in human tumours. In addition, genes associated with cell adhesion, such as Decorin, were down-regulated in DES-induced tumours while suppressor of cytokine signalling 3 (Socs3) was over-expressed. Other studies have also identified molecular similarities between DES-induced tumours in mice and endometrial cancer in humans, such as microsatellite instability brought about by defects in expression of DNA mismatch repair genes such as MSH2 and MSH6.

It could be argued that the apparent trans-generational effect of endocrine disruption is of greater significance. Following neonatal DES exposure in mice, the F1 generation of DES daughters have an increased incidence of uterine adenocarcinoma. Newbold et al.  found that 31% of F1 females from the maternal germ cell lineage developed tumours after 18 months despite there being no exogenous endocrine exposure in these animals, highlighting the potential for future risk to the daughters of DES-exposed women. DES is reported to induce epigenetic changes. Altered methylation patterns have been reported for several uterine genes that are permanently dysregulated after developmental DES exposure; lactoferrin and c-Fos are permanently up-regulated following neonatal DES exposure to due to hypomethylation of the promoter region.

DES has been reported to promote hypermethylation of the homeobox gene Hoxa10 in mice exposed in utero to DES. DES exposure was also associated with increased expression of DNA methyltransferases 1 and 3b leading to long-term altered expression of Hoxa10. Contrary to the reported action of DES on Hoxa10, exposure to BPA in mice in utero results in hypomethylation of the Hoxa10 promoter, which leads to enhanced binding of ERα to EREs in the promoter region and an increase in an ERE-driven reporter gene in vitro.

Thus, epigenetic changes in uterine genes may indicate a possible mechanism for trans-generational effects of DES because altered expression of genes is reported to persist in DES-lineage females.

  • Evidence that expression of HOX genes can be altered by exposure to EDC
  • Evidence that early life exposure to EDC can alter onset of puberty or timing of menopause
  • Evidence that lifestyle factors can increase the influence of EDC on lifetime risk of developing reproductive tract cancers
  • Summary and future perspectives

Sources

  • Endocrine disruption of oestrogen action and female reproductive tract cancers, Endocrine-Related Cancer, endocrinology-journals, doi: 10.1530/ERC-13-0342, April 1, 2014.
  • Featured image chuttersnap.
DES DIETHYLSTILBESTROL RESOURCES

DES effects on the female reproductive system

image of female on sofa

Epigenetic effects of endocrine-disrupting chemicals on female reproduction: An ovarian perspective

2010 Study Abstract

The link between in utero and neonatal exposure to environmental toxicants, such as endocrine-disrupting chemicals (EDCs) and adult female reproductive disorders is well established in both epidemiological and animal studies. Recent studies examining the epigenetic mechanisms involved in mediating the effects of EDCs on female reproduction are gathering momentum. In this review, we describe the developmental processes that are susceptible to EDC exposures in female reproductive system, with a special emphasis on the ovary. We discuss studies with select EDCs that have been shown to have physiological and correlated epigenetic effects in the ovary, neuroendocrine system, and uterus. Importantly, EDCs that can directly target the ovary can alter epigenetic mechanisms in the oocyte, leading to transgenerational epigenetic effects. The potential mechanisms involved in such effects are also discussed.

DES effects on the female reproductive system

DES is a nonsteroidal synthetic estrogen that was prescribed to pregnant women at doses of 5–150 mg/day to prevent miscarriages from 1940s to 1970s). Even though early on DES was shown to be an ineffective drug, it was continued in use till the 1970s. Numerous abnormalities in the reproductive, cardiovascular, and immune systems have since been reported in both male and female offspring of women treated with DES, and validated in animal models. There are limited reports that these effects are being observed in the granddaughters of DES-treated women as well. While DES caused vaginal clear cell adenocarcinoma in only 0.1% of the female offspring, over 95 % reported reproductive tract dysfunction and poor pregnancy outcomes. Since there is evidence of multi-generational effects, epigenetic mechanisms could play an important role and were therefore investigated.

Mice injected with a single dose of 10 μg/kg DES on E15 and examined at 7 months of age had no CL and numerous atretic follicles. They were also found to have vacuolated interstitial tissue with lipid droplet inclusions. Other studies with varying doses of DES (5 μg/kg to 100 μg/kg) administered either in utero (E9-E16), or neonatally (PND1-PND5) , demonstrated that adult DES ovaries developed similar hypertrophy and vacuolation of interstitial tissue, hemorrhagic cysts and lack of corpora lutea. These animals also had high levels of testosterone. There was a dose-dependent reduction in the number of the litters as well as the number of oocytes ovulated after stimulation with exogenous gonadotropins. The oocytes derived from such treated ovaries and used in IVF showed lower levels of fertilizability, suggesting reduced oocyte quality. However, 5 µg/day DES-treated ovaries transplanted into untreated ovariectomized host mice were able to give rise to normal female offspring that in turn gave birth to normal size litters and had normal uterine morphology, suggesting that the DES treatment effects were not mediated via germ cells. However, the age at which these animals were sacrificed was 8–12 weeks, and other studies have shown that DES-treated animals do develop epithelial cancers of the uterus by 18 months of age.

DES can bind to both ERs with many fold higher affinity than estradiol. Multiple studies from Iguchi and colleagues showed that in utero (E15–18) and neonatally (PND1-5) DES-treated mice had ovaries containing excessive number of MOFs by adulthood. MOFs were also observed in ovaries that were treated in vitro at PND1-5, following their transplantation to untreated mice, suggesting a direct effect of DES in the ovary. Recent studies showed that neonatal exposure to 3 μg/kg DES induced MOFs, a process mediated by ERβ and not ERα. DES exposure was shown to reduce oocyte apoptosis (potentially suppressing oocyte nest breakdown) via ERβ signaling mechanisms. Furthermore, it was hypothesized that such alterations in the germ cell and somatic cell populations may affect the invasion of pregranulosa cells and basement membrane remodeling during primordial follicle formation. Interestingly, the incidence of MOFs has been reported with other EDC exposures as well).

The effects of DES on the sexual dimorphism of the brain have been documented. In utero and postnatal exposures increased the size of SDN-POA in females thereby defeminizing the region. It was also found that PND1-10 treatment led to a significant reduction in the levels of LH secreted although a similar effect was not found when the exposure was prenatal (E16-20), highlighting the importance of DES actions on the neuroendocrine circuits.

It is well known that DES caused T-shaped uteri and clear cell adenocarcinoma of the uterus, cervix, and vagina in women whose mothers were exposed to DES during pregnancy. There are numerous animal studies validating these human reports. For example, progeny of DES-treated mice have shown malformations of the uterus, squamous metaplasia of the luminar and glandular epithelium, endometrial hyperplasia and leiomyomas, and oviductal proliferative lesions. Ovariectomized animals when supplemented with estradiol are able to respond by a transient increase in gene expression and concomitant uterine proliferation and growth. When such a stimulus is removed, the uterus returns to its unstimulated state. However, when DES or estradiol is administered during neonatal development, expression of immediate early genes such as lactoferrin, EGF, and proto-oncogenes such as c-fos, c-jun, and c-myc is upregulated even into adulthood. Inversely, expression of genes that are necessary for uterine development, such as the Abdominal B (AbdB) Hox gene, Hoxa-10, (known to be controlled by estradiol and progesterone,), Wnt7a as well as Msx2 are repressed leading to structural abnormalities of the reproductive tract. Numerous studies have been conducted to assess the methylation patterns of promoters of several of these estrogen-responsive genes associated with uterine development.

Neonatal DES exposure in mice caused nearly 90% incidence of epithelial cancers of the uterus by 18 months of age. In mice similarly treated with DES, the promoter region of the lactoferrin gene was found to be hypomethylated in the adult uterus. However, if the animals were exposed for the same length of time during adulthood, no such methylation or expression defects were observed. Subsequently, it was also found that exon 4 of the c-fos gene was extensively hypomethylated while the promoter region and intron 1 was unaffected, thereby potentially allowing for the upregulation of c-fos expression. QPCR studies performed by Sato and colleagues examining the expression of Dnmts in neonatally DES exposed C57BL/6 mice, revealed that expression of Dnmt1 and Dnmt3b was decreased at PND5 in DES-treated mice, and the pattern continued until PND14. Interestingly, it was found that human leiomyoma samples had alterations in the levels of Dnmts as well, with concomitant global hypomethylation.

As mentioned above, DES down-regulates Hoxa gene expression. These effects are akin to those associated with uterine abnormalities found in Hoxa KO mice. The predominant phenotype is the loss of boundary between the oviduct and uterus. It has been shown that the anterior to posterior specific pattern of Hoxa-9 is essential for the normal development and function of the uterus and that DES causes a posterior shift of Hoxa-9 and Hoxa-10 expression and homeotic anterior transformations. A recent report by Bromer and colleagues has shown that after in utero (E9-16) exposure to 10 μg/kg DES, there is hyper-methylation in the promoter and intron 1 regions of Hoxa-10 gene, in the caudal part of the uterus with a concomitant increase in the Hoxa-10 expression in the same region. While these data are interesting from the point of epigenetic regulation of the regionalization of the uterus, the authors suggest that the apparently conflicting data i.e., increased methylation vs increased gene expression might be due to differential binding to transcriptional repressors. Since previous studies have shown that no epigenetic changes were detected in the promoters of Hoxa-10 and Hoxa-11 genes, continuation of these studies is warranted.

Alworth and colleagues showed that in utero exposure (E12-18) of CD-1 mice to DES doses of 0.1–100 μg/kg followed by estradiol administration at 7–8 months of age caused opposite responses between low and high doses. The lower dose enhanced the response to exogenous estrogens, resulting in an increase in uterine weight, while the high dose dampened the response resulting in lighter uteri. A global methylation assay was conducted employing DMH, which was suitable to detect hypermethylation events. Over 300 CpG island loci were examined and five candidates were identified in 18S rDNA and 45S pre-rDNA methylation, suggesting a role for ribosomal assembly and protein synthesis in the mediation of DES effects.

Couse and colleagues have shown that ERα is essential for the mediation of DES effects in the uterus: αERKO female mice exhibited a complete resistance to the effects of DES while βERKO mice did not. Additionally, as mentioned earlier, ERα induction is necessary for activation of estrogen responsive gene expression including that of the lactoferrin and c-fos genes. Since these genes are all downstream of ERα signaling, it is imperative to thoroughly examine the potential role of epigenetic mechanisms in the regulation of ERα expression after EDC exposure. Interesting new studies by Bredfeldt and colleagues have now provided a link between ER signaling and regulation of histone modifications. It was found that rapid PI3K/Akt signaling downstream of membrane-associated ER, in response to estradiol as well as DES, caused reduction in trimethylation of H3K27. More interestingly, activation of this non-genomic signaling caused reprogramming of the uterine gene expression profile. Whether such altered epigenetic mechanisms are transgenerational would be of great interest to the field.

Tang and colleagues recently investigated whether neonatal DES/genistein exposure could cause epigenetic changes and alter gene expression in adult uteri and whether there are interactions between adult ovarian hormones and such epigenetic reprogramming. CD-1 mice were exposed to DES (1 μg and 1000 μg/kg) or genistein (50 mg/kg) from PND1-5. Subsequently, some animals were sacrificed at PND19 while others were aged to 6 and 18 months with or without ovariectomies. Genome-wide methylation analysis was conducted with MSRF and candidate genes were identified. Of interest was the nucleosomal binding protein 1 (Nsbp1), which was shown to be hypomethylated at PND19 and hyper-methylated by puberty, in the control. Low-dose DES- and genistein- treated vs high-dose DES-treated animals had opposing methylation patterns. Furthermore, it was shown that in the aged animals, both DES and genistein caused hyper-methylation in the ovariectomized animals but remained hypomethylated in non-ovariectomized animals. These data suggest that Nsbp1 is hyper-methylated in intact mice with age and that DES and genistein have opposing effects on the methylation patterns in intact vs ovariectomized aging animals (hypomethylation vs hyper-methylation), respectively. These studies highlighted the age-dependent aspect of epigenetic reprogramming and also its interaction with steroid hormones.

Transgenerational epigenetic effects associated with DES exposures

Documentation of the transgenerational epigenetic effects of EDCs has been accumulating such as the case of transgenerational effects of DES exposure reported in humans. Exposure to DES while in utero was shown to affect the female F2 generation but not males in mice. Later studies with DES exposure showed that it leads to reproductive tract tumors in both F2 generation males and female mice.

Sources

  • Full text (free access) : Epigenetic effects of endocrine-disrupting chemicals on female reproduction: An ovarian perspective, Frontiers in neuroendocrinology, NCBI PubMed, PMC3009556, 2010 Jul 4.
  • Featured image credit Luis Sarabia.
DES DIETHYLSTILBESTROL RESOURCES

DES Developmental Programming and Fetal Origins of Adult Disease

Proceedings of the Summit on Environmental Challenges to Reproductive Health and Fertility: Executive Summary

Introduction

The 2007 Summit on “Environmental Challenges to Reproductive Health and Fertility” convened scientists, health care professionals, community groups, political representatives and the media to hear presentations on the impact of environmental contaminants on reproductive health and fertility and to discuss opportunities to improve health through research, education, communication and policy. Environmental reproductive health focuses on exposures to environmental contaminants, particularly during critical periods of development, and their potential effects on future reproductive health, including conception, fertility, pregnancy, adolescent development and adult health. Approximately 87,000 chemical substances are registered for use in commerce in the US, with ubiquitous human exposures to environmental contaminants in air, water, food and consumer products. Exposures during critical windows of susceptibility may result in adverse effects with lifelong and even intergenerational health impacts. Effects can include impaired development and function of the reproductive tract and permanently altered gene expression, leading to metabolic and hormonal disorders, reduced fertility and fecundity and illnesses such as testicular, prostate, uterine and cervical cancers later in life. This executive summary reviews effects of pre- and post-natal exposures on male and female reproductive health and provides a series of recommendations for advancing the field in the areas of research, policy, health care and community action.

Abstracts

Developmental Programming and Fetal Origins of Adult Disease

The DES Example

Prenatal exposure to diethylstilbestrol (DES), a synthetic estrogen and thus EDC, provides an unfortunate example of developmental programming. DES was given to U.S. pregnant women between 1938 and 1971 under the erroneous assumption that it would prevent pregnancy complications. In fact, in utero exposure to DES alters the normal programming of gene families, such as Hox and Wnt, that play important roles in reproductive tract differentiation. As a result, female offspring exposed to DES in utero are at increased risk of clear cell adenocarcinoma of the vagina and cervix, structural reproductive tract anomalies, infertility and poor pregnancy outcomes, while male offspring have an increased incidence of genital abnormalities and a possibly increased risk of prostate and testicular cancer. These observed human effects have been confirmed in numerous animal models which have also provided information on the toxic mechanisms of DES. Animal experiments have also predicted changes later found in DES-exposed humans, such as oviductal malformations, increased incidence of uterine fibroids and second-generational effects such as increased menstrual irregularities and possibly ovarian cancer in DES-granddaughters and increased hypospadias in DES-grandsons.

DES is but one example of how exposure to EDCs can disrupt developing organ systems and cause abnormalities, many of which only appear much later in life or in the subsequent generation, such as endometriosis, fibroids and breast, cervical and uterine cancer in women; poor sperm quality and increased incidence of cryptorchidism and hypospadias in men; and subfertility and infertility in men and women.

Reproductive Effects of Early Life Exposures in Females

Uterus Development and the Environment

Women exposed to DES in utero during critical periods of reproductive tract development developed several types of reproductive tract abnormalities, as well as an increased incidence of cervical-vaginal cancer later in life. Animal studies that simulate the human DES experience have since shown that exposure of the developing reproductive tract of CD-1 mice to DES imparts a permanent estrogen imprint that alters reproductive tract morphology, induces persistent expression of the lactoferrin and c-fos genes and induces a high incidence of uterine adenocarcinoma. Experiments in rats have shown exposure to DES during the critical window of uterine development leaves a hormonal imprint on the developing uterine myometrium in rats that were genetically predisposed to uterine leiomyoma, increasing the risk for adult uterine leiomyoma from 65% to greater than 90% and increasing tumor multiplicity and size. DES-induced developmental programming appears to require the estrogen receptor α, suggesting that signaling through this receptor is crucial for establishing developmental programming.

Sources

  • Full study (free access) : Proceedings of the Summit on Environmental Challenges to Reproductive Health and Fertility: Executive Summary, Fertility and sterility, NCBI PubMed, PMC2440710, 2009 Feb 1.
  • Featured image credit Kiệt Hí.
DES DIETHYLSTILBESTROL RESOURCES