In utero effects of chemicals on reproductive tissues in females

Brominated flame retardants and legacy organochlorines in archived human placenta samples: Sex differences, temporal analysis and associations with infant birth weight

Perinatal exposure to persistent organic pollutants (POPs) has been suggested to play a role in the etiology of adverse pregnancy outcomes. This study evaluated temporal changes in the accumulation of several classes of POPs, including polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs) and several organochlorine pesticides in human placenta and examined their associations with birth outcomes at delivery. Placental tissues (n = 99) previously collected and archived at the Duke University Medical Center from 2009 to 2015 were analyzed for 22 POPs using gas chromatography mass spectrometry. The mean age of mothers was 30.6 years; 8% of newborns were characterized as low birthweight (<2500 g). Of the 22 POPs targeted in the analysis, only p,p'-DDE, BDE-47 and BDE-100 were detected in more than 50% of the samples, with median concentrations of 0.110, 0.310, and 0.033 ng/g wet weight, respectively. Placental PBDE concentrations generally decreased over time, particularly BDE-47. Placental tissues associated with female infants had significantly higher levels of BDE-100 than placental tissues associated with male infants (p = 0.02) and a similar, but not statistically significant trend was observed for BDE-47 (p = 0.07). Multivariate regression models revealed that placental BDE-47 concentrations were associated with a significantly lower birthweight among male, but not female infants. A similar, although non-statistically significant, trend was observed for other POPs, further suggesting sex-specific associations between gestational exposure to POPs and birthweight.

Effects of polycyclic aromatic hydrocarbons on the proliferation and differentiation of placental cells

BACKGROUND

The purpose of this study was to investigate the effects of polycyclic aromatic hydrocarbons (PAHs) other than bisphenol A (BPA) and BPA substitutes on placental cells.

METHODS

HTR-8/SVneo cells were treated with anthracene, benzo[k]fluoranthene, benzo[a]pyrene, and 4,4-(9-fluorenylidene)diphenol, which is used as a substitute for BPA-free products. After confirming the dose response for each reagent using the prepared cells, the cells were incubated for 24, 48, and 72 h. Cell viability was confirmed using the XTT assay. Each experiment was performed with the minimum number of samples (n = 3) required for statistical analysis. The results were analyzed using t-tests; p < 0.05 was considered statistically significant.

RESULTS

After treatment with anthracene, benzo[k]fluoranthene, benzo[a]pyrene, and 4,4-(9-fluorenylidene)diphenol, the absorbance measured using the XTT assay decreased significantly with increasing concentration. The absorbance decreased significantly over time following treatment with each endocrine disruptor at the concentration confirmed by the dose-response analysis.

CONCLUSIONS

This study showed that anthracene, benzo[k]fluoranthene, benzo[a]pyrene, and 4,4-(9-fluorenylidene)diphenol-a BPA substitute-affect cell viability and necrosis in the placental cell line. The study indicates the serious effects of PAHs that negatively affect pregnancy but were previously unknown. Further, this study would serve as a reference for the identification of harmful PAHs during pregnancy prognosis in women who are more susceptible to PAH exposure.

Amitraz induced cytotoxic effect on bovine cumulus cells and impaired oocyte maturation

The aim of this study was to evaluate the genotoxic and cytotoxic effects of amitraz (AMZ) on the primary culture of bovine cumulus cells (CC) and oocyte nuclear maturation. Cytotoxicity was evaluated by assessing mitochondrial activity with the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. Genotoxicity was estimated using the alkaline single cell gel electrophoresis (SCGE) assay. Apoptosis was detected with the Annexin V-affinity assay. The in vitro maturation test was performed in bovine oocytes. To understand AMZ action, glutathione content, superoxide dismutase enzyme activity, and lipid peroxidation were evaluated in CC. Results showed that AMZ lethal concentration (LC 50_24h) for bovine CC was 32.55 μg/mL (MTT assay). A 25 μg/mL induced late apoptosis and necrotic cells (p < 0.05); however, DNA damage was decreased at the same concentration (SCGE assay; p < 0.05). A decrease in metaphase II was observed at 25 μg/mL, and degenerate oocytes were observed at 15 and 25 μg/mL (p < 0.05). None of the oxidative stress parameters evaluated showed significant differences. This study contributes to a better understanding of AMZ in this model, suggesting its potential cytotoxicity and impact on bovine reproduction.

Developmental programming of the female reproductive system-a review

Exposures to adverse conditions in utero can lead to permanent changes in the structure and function of key physiological systems in the developing fetus, increasing the risk of disease and premature aging in later postnatal life. When considering the systems that could be affected by an adverse gestational environment, the reproductive system of developing female offspring may be particularly important, as changes have the potential to alter both reproductive capacity of the first generation, as well as health of the second generation through changes in the oocyte. The aim of this review is to examine the impact of different adverse intrauterine conditions on the reproductive system of the female offspring. It focuses on the effects of exposure to maternal undernutrition, overnutrition/obesity, hypoxia, smoking, steroid excess, endocrine-disrupting chemicals, and pollutants during gestation and draws on data from human and animal studies to illuminate underlying mechanisms. The available data indeed indicate that adverse gestational environments alter the reproductive physiology of female offspring with consequences for future reproductive capacity. These alterations are mediated via programmed changes in the hypothalamic-pituitary-gonadal axis and the structure and function of reproductive tissues, particularly the ovaries. Reproductive programming may be observed as a change in the timing of puberty onset and menopause/reproductive decline, altered menstrual/estrous cycles, polycystic ovaries, and elevated risk of reproductive tissue cancers. These reproductive outcomes can affect the fertility and fecundity of the female offspring; however, further work is needed to better define the possible impact of these programmed changes on subsequent generations.

The impacts of intrauterine Bisphenol A exposure on pregnancy and expression of miRNAs related to heart development and diseases in animal model

This study aimed to examine the impact of BPA exposure on pregnancy and foetuses on cardiac tissues and the expression of cardiac microRNAs (miRNAs) related to heart development and diseases. Pregnancy is known to be the "critical windows" in determining the offspring physical and cells development in their life after birth. The increment of the risk of cardiovascular disease (CVD) in a later stage of life has been reported by few studies demonstrated from prenatal exposure of BPA. BPA has been shown to alter miRNAs expression profiles for organ development, regeneration and metabolic functions. These alterations have been associated with the risk of CVDs. However, the associations between pregnancy outcomes and miRNAs expression in cardiac of mother- and foetuses-exposed to BPA are still not entirely explored. In BPA-exposed pregnant rat groups, a significant weight gained was observed in comparison to control (p < 0.05). Interestingly, significant changes in systolic and diastolic blood pressure between the first and third trimester of BPA-exposed pregnant rats were also observed (p < 0.05). In BPA-exposed pregnant rats, miR-499-5p was significantly altered in the heart (p < 0.01). Meanwhile, altered miR-17-5p, -208-3p, and -210-3p expressions were observed in all heart of the foetuses from BPA-exposed pregnant rats (p < 0.05). In H&E staining, BPA-exposed foetal hearts showed a sign of fibrosis while BPA-exposed pregnant rats showed muscle remnant. Masson trichrome staining further confirmed the presence of fibrosis observed in BPA-exposed foetal heart and reduced expression of cardiac troponin I (cTnI) was also observed in BPA-exposed foetal heart. In summary, altered cardiac miRNAs with histological changes were observed in both mother- and foetus-exposed BPA These findings put forward the importance of future work to further understand how prenatal BPA exposure affect foetuses in their later stage of life.

Environmental polycyclic aromatic hydrocarbons mixture, in human blood levels, decreased oestradiol secretion by granulosa cells via ESR1 and GPER1 but not ESR2 receptor

Tissue-dependent oestrogenic and anti-oestrogenic activity of polycyclic aromatic hydrocarbons (PAHs) has been suggested. In this study, the effect of two PAH mixtures, M1 composed of all 16 priority pollutants and M2 composed of five (noted in the highest levels) compounds, on follicle-stimulating hormone receptor (FSHR) expression, basal or FSH-induced oestradiol (E2) secretion and aromatase cytochrome P450 (P450arom) protein expression, by non-luteinised human granulosa cell line (HGrC1) was determined. In addition, the consequences of gene silencing of oestrogen receptor alfa (siESR1), oestrogen receptor beta (siESR2) and a G protein-coupled receptor (siGPER1) on the above parameters were described. Neither PAH mixture had an effect on basal FSHR protein expression; however, both mixtures increased FSH-induced FSHR expression. Decreased E2 secretion and P450arom expression was also demonstrated. In both basal and FSH treated cells, siESR1 and siGPER1 reversed the inhibitory effect of the mixtures on E2 secretion; however, in siESR2 cells, the inhibitory effect was still observed. This study showed that both classic ESR1 and GPER1 were involved in the inhibitory effect of both PAH mixtures on E2 secretion and confirmed that expression of P450arom could be downregulated through the aryl hydrocarbon receptor and additionally through the ESR2.

The sex-specific association between maternal paraben exposure and size at birth

Parabens are a group of esters of parahydroxybenzoic acid and are utilized as antimicrobial preservatives in the majority of personal care products (PCPs). Epidemiological studies regarding the adverse effects of parabens on fetuses are still limited. The aim of this study was to determine the association between maternal paraben exposure and birth outcomes. One hundred and ninety-nine pregnant women were enrolled, and maternal urine was collected in the third trimester. The urine concentrations of four parabens (methyl (MP), ethyl (EP), propyl (PP), and butyl (BP)) were determined by ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry. Generalized additive model-penalized regression splines and a multivariable regression model were employed to determine the association between paraben exposure levels and birth outcomes. A causal mediation analysis was conducted to determine the mediation effect of oxidative stress on birth outcomes. The geometric means of urinary MP, EP, PP, and BP were 51.79, 1.26, 4.21, and 1.25 μg/g cre., respectively. In the penalized regression splines, sex-specific associations between maternal MP levels and birth outcomes were observed; a downward curvature was observed between the MP level and birth weight, length, head circumference, and thoracic circumference among female newborns. Pregnant women in the group with MP levels above the third quartile had neonates with significantly lower body weight (β = -215.98 g, p value = 0.02) compared to those in the group with MP levels lower than the third quartile. No significant mediation of oxidative stress was observed between maternal MP exposure and female birth weight. The estimated proportion mediated ranged from -6% to 15%. The negative association between maternal paraben exposure and female birth outcomes in relation to child development should be carefully considered.

Occupational exposure to organic particles and combustion products during pregnancy and birth outcome in a nationwide cohort study in Sweden

Objective

To study if children of women exposed to organic particles and combustion products at work during pregnancy, have an increased risk of low birth weight, preterm birth or small for gestational age.

Methods

A nationwide cohort of all occupationally active mothers and their children from single births during 1994 to the end of 2012 (1 182 138 observations) was formed. Information on birth outcome was obtained from the medical birth register. Information on absence from work, education, occupation, age, nationality and smoking habits was obtained from national registers. A job exposure matrix (FINJEM) was used to assess the exposure.

Results

Pregnant women with low absence from work and high (>50th percentile) exposure to organic particles had an increased risk of giving birth to children with low birth weight (OR=1.19; 95% CI: 1.07 to 1.32), small for gestational age (OR=1.22; 95% CI: 1.07 to 1.38) or preterm birth (OR=1.17; 95% CI: 1.08 to 1.27). Subgroup analyses showed an increased risk of small for gestational age in association with exposure to oil mist. Exposure to oil mist and cooking fumes was associated with low birth weight. Paper and other organic dust was associated with preterm birth. Exposure to combustion products showed an increased risk of small for gestational age (OR=1.40; 95% CI: 1.15 to 1.71).

Conclusions

The results indicate that occupational exposure to organic particles or combustion products during pregnancy is associated with restriction of fetal growth and preterm birth. More studies are needed to confirm a casual association.

Review: Polycyclic aromatic hydrocarbons (PAHs)-Action on placental function and health risks in future life of newborns

Polycyclic aromatic hydrocarbons (PAHs) are common environmental pollutants, which are released as products of incomplete combustion processes. Harmful effects of PAHs exposure on human health are observed in increased morbidity of respiratory, cardiovascular and immunological diseases. A particularly sensitive group to PAHs exposure are pregnant women and their developing offspring. PAHs can cross the placental barrier and a lot of published data indicated that prenatal or early postnatal exposure to PAHs can lead to developmental toxicity. Epidemiological data shows increased incidence and prevalence of conditions associated with PAHs exposure, like intrauterine growth retardation. Even more, negative effect of PAHs are observed later in development, low IQ, problems with behavior, allergies or asthma. This review will briefly summarize currently available data on the effects of PAHs on placental function with a specific emphasis on placental differentiation, angiogenesis, hormone signaling and consequences of exposure to PAHs in childhood and adulthood.

Bisphenol A disrupts the temporal pattern of histofunctional changes in the female reproductive tract of Caiman latirostris

Recently, we have described the ontogeny of histofunctional differentiation changes in the oviduct of Caiman latirostris. The expression of estrogen receptor alpha and progesterone receptor shows that the caiman oviduct could be a target of the action of xenoestrogens such as the widely environmentally present Bisphenol A (BPA), early in life. The aims of this study were: to complement oviduct characterization by establishing the ontogenetic changes in androgen receptor (AR) expression and assessing the effects of early postnatal exposure to 17-β-estradiol (E2) or BPA on the histofunctional features of the oviduct. AR was expressed in all the stages studied. The spatial pattern of AR immunostaining changed from neonatal to juvenile caimans. In the luminal epithelium, changes were at the subcellular level, from cytoplasmic to nuclear. In the subepithelium, although both cytoplasmic and nuclear AR expression was observed, changes were mainly at tissue level, from the subepithelial compartment to the outer muscular layer. The oviduct was highly sensitive to E2 and BPA at the early postnatal developmental stage. E2- and BPA-exposed caimans showed increased luminal epithelial height and higher proliferative activity. Changes in histomorphological features (measured by a scoring system), steroid hormone receptors, collagen remodeling and muscle-associated proteins suggest a precocious oviduct histofunctional differentiation in E2- and BPA-exposed caimans. The modification of the temporal pattern of oviductal biomarkers suggests that organizational changes could impair C. latirostris reproductive health later in life. The alterations in the caiman female reproductive tract exposed to BPA highlight the importance of preserving aquatic environments from plastic pollution.

Impact of prenatal exposure to polycyclic aromatic hydrocarbons from maternal diet on birth outcomes: a birth cohort study in Korea

Objective

Polycyclic aromatic hydrocarbons (PAH) are common dietary exposures that cross the human placenta and are classified as a probable human carcinogen. The aim of the present study was to investigate the potential impact of exposure to PAH-containing meat consumed during pregnancy on birth outcomes.

Design

Prospective birth cohort study. Only non-smoking women with singleton pregnancies, who were free from chronic disease such as diabetes and hypertension, were included in the study. Maternal consumption of PAH-rich meat was estimated through FFQ. Multiple linear regression was used to assess factors related to higher intake and the association between dietary PAH and birth outcomes.

Setting

Republic of Korea, 2006–2011.

Subjects

Pregnant women (n 778) at 12–28 weeks of gestation enrolled in the Mothers and Children’s Environmental Health (MOCEH) study.

Results

The multivariable regression model showed a significant reduction in birth weight associated with higher consumption level of foods rich in PAH, such as grilled or roasted meat, during pregnancy (β=−17·48 g, P<0·05 for every 1 point higher in meat score). Further adjusting for biomarkers of airborne PAH did not alter this association. There was no evidence that higher consumption level of PAH-rich meat shortens the duration of gestation (P=0·561). Regression models performed for birth length and head circumference produced negative effects that were not statistically significant.

Conclusions

Consumption of higher levels of barbecued, fried, roasted and smoked meats during pregnancy was associated with reduced birth weight. Dietary risk of PAH exposure in Korean women is of concern.

Transferability and inter-laboratory variability assessment of the in vitro bovine oocyte fertilization test

The dramatic increase in the number of animals required for reproductive toxicity testing imposes the validation of alternative methods to reduce the use of laboratory animals. As we previously demonstrated for in vitro maturation test of bovine oocytes, the present study describes the transferability assessment and the inter-laboratory variability of an in vitro test able to identify chemical effects during the process of bovine oocyte fertilization. Eight chemicals with well-known toxic properties (benzo[a]pyrene, busulfan, cadmium chloride, cycloheximide, diethylstilbestrol, ketoconazole, methylacetoacetate, mifepristone/RU-486) were tested in two well-trained laboratories. The statistical analysis demonstrated no differences in the EC50 values for each chemical in within (inter-runs) and in between-laboratory variability of the proposed test. We therefore conclude that the bovine in vitro fertilization test could advance toward the validation process as alternative in vitro method and become part of an integrated testing strategy in order to predict chemical hazards on mammalian fertility.

Epigenetic regulation of uterine biology by transcription factor KLF11 via posttranslational histone deacetylation of cytochrome p450 metabolic enzymes

Endocrine regulation of uterine biology is critical for embryo receptivity and human reproduction. Uterine endometrium depends on extrinsic sex steroid input and hence likely has mechanisms that enable adaptation to hormonal variation. Emerging evidence suggests that sex steroid bioavailability in the endometrium is determined by adjusting their metabolic rate and fate via regulation of cytochrome (CYP) p450 enzymes. The CYP enzymes are targeted by ubiquitously expressed Sp/Krüppel-like (Sp/KLF) transcription factors. Specifically, KLF11 is highly expressed in reproductive tissues, regulates an array of endocrine/metabolic pathways via epigenetic histone-based mechanisms and, when aberrantly expressed, is associated with diabetes and reproductive tract diseases, such as leiomyoma and endometriosis. Using KLF11 as a model to investigate epigenetic regulation of endometrial first-pass metabolism, we evaluated the expression of a comprehensive array of metabolic enzymes in Ishikawa cells. KLF11 repressed most endometrial CYP enzymes. To characterize KLF11-recruited epigenetic regulatory mechanisms, we focused on the estrogen-metabolizing enzyme CYP3A4. KLF11 expression declined in secretory phase endometrial epithelium associated with increased CYP3A4 expression. Additionally, KLF11 bound to CYP3A4 promoter GC elements and thereby repressed promoter, message, protein as well as enzymatic function. This repression was epigenetically mediated, because KLF11 colocalized with and recruited the corepressor SIN3A/histone deacetylase resulting in selective deacetylation of the CYP3A4 promoter. Repression was reversed by a mutation in KLF11 that abrogated cofactor recruitment and binding. This repression was also pharmacologically reversible with an histone deacetylase inhibitor. Pharmacological alteration of endometrial metabolism could have long-term translational implications on human reproduction and uterine disease.

Endocrine disruption of oestrogen action and female reproductive tract cancers

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.

Environmental pollutants and lifestyle factors induce oxidative stress and poor prenatal development

Developmental toxicity caused by exposure to a mixture of environmental pollutants has become a major health concern. Human-made chemicals, including xenoestrogens, pesticides and heavy metals, as well as unhealthy lifestyle behaviours, mainly tobacco smoking, alcohol consumption and medical drug abuse, are major factors that adversely influence prenatal development and increase susceptibility of offspring to diseases. There is evidence to suggest that the developmental toxicological mechanisms of chemicals and lifestyle factors involve the generation of reactive oxygen species (ROS) and cellular oxidative damage. Overproduction of ROS induces oxidative stress, a state where increased ROS generation overwhelms antioxidant protection and subsequently leads to oxidative damage of cellular macromolecules. Data on the involvement of oxidative stress in the mechanism of developmental toxicity following exposure to environmental pollutants are reviewed in an attempt to provide an updated basis for future studies on the toxic effect of such pollutants, particularly the notion of increased risk for developmental toxicity due to combined and cumulative exposure to various environmental pollutants. The aims of such studies are to better understand the mechanisms by which environmental pollutants adversely affect conceptus development and to elucidate the impact of cumulative exposures to multiple pollutants on post-natal development and health outcomes. Developmental toxicity caused by exposure to mixture of environmental pollutants has become a major health concern. Human-made chemicals, including xenoestrogens, pesticides and heavy metals, as well as unhealthy lifestyle behaviors, mainly tobacco smoking, alcohol consumption and medical drug abuse, are major factors that adversely influence prenatal development and increase the susceptibility of offspring to development complications and diseases. There is evidence to suggest that the developmental toxicological mechanisms of human-made chemicals and unhealthy lifestyle factors involve the generation of reactive oxygen species (ROS) and cellular oxidative damage. Overproduction of ROS induces oxidative stress, a state where increased generation of ROS overwhelms antioxidant protection and subsequently leads to oxidative damage of cellular macromolecules. Exposure to various environmental pollutants induces synergic and cumulative dose-additive adverse effects on prenatal development, pregnancy outcomes and neonate health. Data from the literature on the involvement of oxidative stress in the mechanism of developmental toxicity following in vivo exposure to environmental pollutants will be reviewed in an attempt to provide an updated basis for future studies on the toxic effect of such pollutants, particularly the notion of increased risk for developmental toxicity due to combined and cumulative exposure to various environmental pollutants. The aims of such studies are to better understand the mechanisms by which environmental pollutants adversely affect conceptus development and to elucidate the impact of cumulative exposures to multiple pollutants on postnatal development and health outcomes.

Exposure levels of environmental endocrine disruptors in mother-newborn pairs in China and their placental transfer characteristics

There is a growing concern about the potential health effects of exposure to various environmental chemicals during pregnancy and infancy. The placenta is expected to be an effective barrier protecting the developing embryo against some endocrine disruptors (EDs) circulating in maternal blood. The current study was designed to assess in utero exposure levels of non-persistent organic pollutants (non-POPs) and persistent organic pollutants (POPs) in Chinese newborns and potential role of placenta barrier against fetal exposure to these commonly-used environmental endocrine disruptors. A total of 230 newborn-mother pairs were enrolled during 2010–2011, 201 pairs of which were recruited from Shanghai, and the other 29 pairs came from Wenzhou. Maternal blood, cord blood, and meconium specimens were collected in the subject population from Shanghai and analyzed for non-POPs, including mono-2-ethylhexyl phthalate (MEHP), octylphenol (OP) and 4-nonylphenol (4-NP). A total of 19 polybrominated diphenyl ethers (PBDEs) congeners, which belong to POPs, were detected in maternal and cord blood specimens from the other 29 pairs. Fetal-maternal ratios (F-M ratios) and regression coefficients were presented to assess potential function of placenta on barricading the mother/fetal transfer of these EDs. Concentrations of the detected non-POPs in cord blood samples were approximately 20% lower than those in maternal blood, and regression coefficients of which were all over 0.80. In contrast, PBDEs levels in cord blood samples were significantly higher than those in maternal blood. MEHP levels in meconium were much higher than those in cord blood samples, and highly correlated. Therefore, observations demonstrated that the placental barrier slightly decreased the fetal exposure to most non-POPs, while PBDEs seemed to be totally transferred across the placenta and finally reached the fetus. For in utero exposure assessment of Di-2-ethylhexyl phthalate (DEHP), MEHP level in meconium may be a useful biomarker.

Genetic association of aromatic hydrocarbon receptor (AHR) and cytochrome P450, family 1, subfamily A, polypeptide 1 (CYP1A1) polymorphisms with dioxin blood concentrations among pregnant Japanese women

Dioxins are metabolized by cytochrome P450, family 1 (CYP1) via the aromatic hydrocarbon receptor (AHR). We determined whether different blood dioxin concentrations are associated with polymorphisms in AHR (dbSNP ID: rs2066853), AHR repressor (AHRR; rs2292596), CYP1 subfamily A polypeptide 1 (CYP1A1; rs4646903 and rs1048963), CYP1 subfamily A polypeptide 2 (CYP1A2; rs762551), and CYP1 subfamily B polypeptide 1 (CYP1B1; rs1056836) in pregnant Japanese women. These six polymorphisms were detected in 421 healthy pregnant Japanese women. Differences in dioxin exposure concentrations in maternal blood among the genotypes were investigated. Comparisons among the GG, GA, and AA genotypes of AHR showed a significant difference (genotype model: P=0.016 for the mono-ortho polychlorinated biphenyl concentrations and toxicity equivalence quantities [TEQs]). Second, we found a significant association with the dominant genotype model ([TT+TC] vs. CC: P=0.048 for the polychlorinated dibenzo-p-dioxin TEQs; P=0.035 for polychlorinated dibenzofuran TEQs) of CYP1A1 (rs4646903). No significant differences were found among blood dioxin concentrations and polymorphisms in AHRR, CYP1A1 (rs1048963), CYP1A2, and CYP1B1. Thus, polymorphisms in AHR and CYP1A1 (rs4646903) were associated with maternal dioxin concentrations. However, differences in blood dioxin concentrations were relatively low.

Polycyclic aromatic hydrocarbons (PAHs) as determinants of various anthropometric measures of birth outcome

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental contaminants that are known to induce oxidative stress. There have been several reports about the link between PAH exposure and complications in pregnancy. This cross-sectional study was conducted to: (1) measure the levels of benzo(a)anthracene (BaA), chrysene (Ch), benzo(b)fluoranthene (BbF), benzo(a)pyrene (BaP), and dibenzo(a,h)anthracene (DBahA) in placentas and maternal and -umbilical cord blood obtained at delivery from 1578 women between June 2005 and 2006 in the area of Al-Kharj, Saudi Arabia; (2) assess their influence on various anthropometric measures of birth outcome taking into consideration the carcinogenic properties of these PAHs; and (3) determine the degree of PAH-related oxidative DNA damage and birth outcome. Among the five tested PAHs, only BaP was carcinogenic; therefore, the levels of the other four probable or possible carcinogenic PAHs (BaA, Ch, BaF, and DBahA) were summed as ∑4-PAHs. Levels of 1-hydroxypyrene (1-HP) were determined in maternal urine samples as a biomarker of PAH internal dose. Urinary cotinine (COT) was measured as an index of smoking. The following markers of oxidative stress were selected: malondialdehyde (MDA) in cord (C-MDA) and maternal (M-MDA) serum and 8-hydroxy-2-deoxyguanosine (8-OHdG) in maternal urine. None of the tested PAHs was found in maternal or cord blood. However, all five PAH compounds were detected in placentas; Ch was the highest (6.582 μg/kg dry wt.), and BaA was the lowest (0.236 μg/kg dry wt.). The mean concentration of urinary 1-HP found in this study was 0.216 ± 0.856 μg/g Cr. After adjusting for gestational age and other confounding variables, regression models revealed an inverse relationship between placental weight, cord length and placental BaP. A similar trend was observed between cord length and ∑4-PAHs in placental tissues. Urinary 1-HP, though, cannot be used as an unequivocal biomarker of PAH exposure, but it can be an appropriate indicator of exposure to environmental tobacco smoke (ETS). The data demonstrate that ETS exposure (as measured by urinary COT) may adversely affect birth outcome as shown by reduced head circumference, birth weight, and birth length, as well as increased cephalization index. The positive relationship between 8-OHdG levels and 1-HP in urine provides evidence of an oxidative stress mechanism. Although this study provides no direct evidence of an association between PAH exposure and DNA damage, increased oxidative stress in the form of lipid peroxidation significantly affected various birth measures. Therefore, there is a need for studies regarding PAH exposure and its associated biological effects to determine the extent of potential fetal damage as well as possible long-term effects, such as cancer.

Microbial transformation and sorption of anthracene in liquid culture

Armillaria sp. F022, a white-rot fungus isolated from decayed wood in tropical rain forest was used to biodegrade anthracene in cultured medium. The percentage of anthracene removal by Armillaria sp. F022 reached 13 % after 7 days and at the end of the experiment, anthracene removal level was at 87 %. The anthracene removal through sorption and transformation was investigated. 69 % of eliminated anthracene was transformed by Armillaria sp. F022 to form other organic structure, while only 18 % was absorbed in the mycelia. In the kinetic experiment, anthracene dissipation will not stop even though the biomass had stopped growing. Anthracene removal by Armillaria sp. F022 was correlated with protein concentration (whole biomass) in the culture. The production of enzyme was affected by biomass production. Anthracene was transformed to two stable metabolic products. The metabolites were extracted in ethyl-acetate, isolated by column chromatography, and then identified using gas chromatography-mass spectrometry (GC-MS).

Aryl-hydrocarbon receptor activity modulates prolactin expression in the pituitary

Pituitary tumors account for 15% of intracranial neoplasms, however the extent to which environmental toxicants contribute to the proliferation and hormone expression of pituitary cells is unknown. Aryl-hydrocarbon receptor (AhR) interacting protein (AIP) loss of function mutations cause somatotrope and lactotrope adenomas in humans. AIP sequesters AhR and inhibits its transcriptional function. Because of the link between AIP and pituitary tumors, we hypothesize that exposure to dioxins, potent exogenous ligands for AhR that are persistent in the environment, may predispose to pituitary dysfunction through activation of AhR. In the present study, we examined the effect of AhR activation on proliferation and endogenous pituitary hormone expression in the GH3 rat somatolactotrope tumor cell line and the effect of loss of AhR action in knockout mice. GH3 cells respond to nM doses of the reversible AhR agonist β-naphthoflavone with a robust induction of Cyp1a1. Although mRNA levels of the anti-proliferative signaling cytokine TGFbeta1 are suppressed upon β-naphthoflavone treatment, we did not observe an alteration in cell proliferation. AhR activation with β-naphthoflavone suppresses Ahr expression and impairs expression of prolactin (PRL), but not growth hormone (GH) mRNA in GH3 cells. In mice, loss of Ahr similarly leads to a reduction in Prl mRNA at P3, while Gh is unaffected. Additionally, there is a significant reduction in pituitary hormones Lhb and Fshb in the absence of Ahr. Overall, these results demonstrate that AhR is important for pituitary hormone expression and suggest that environmental dioxins can exert endocrine disrupting effects at the pituitary.

A short exposure to polychlorinated biphenyls deregulates cellular autophagy in mammalian blastocyst in vitro

BACKGROUND

Polychlorinated biphenyls (PCBs) are common environmental contaminants that represent an important risk factor of reproductive disorders in chronically exposed human populations. However, it is not known whether a short accidental exposure of embryos to PCBs before implantation might influence their further development and whether the effect might be reversible.

METHODS AND RESULTS

To this aim, in vitro-matured sheep blastocysts were incubated with 2 or 4 µg/ml Aroclor 1254 (A1254), a mixture of 60 PCB congeners for 48 h after which blastocyst proliferation and ability for outgrowth in vitro were assessed. Blastocysts exposed to A1254 showed: (i) reduced proliferation and cell number (particularly in the inner cell mass compartment); (ii) accumulation of vacuoles and lipid droplets, diffused mitochondrial damage and up-regulation of autophagy markers (ATG6 and LC3), all signs indicative of deregulated autophagy, and (iii) massive cell death. Although exposed embryos resumed growth following A1254 removal, their subsequent development remained severely perturbed.

CONCLUSIONS

These findings indicate that short exposure of blastocysts to PCBs leads to its damage characterized by deregulated autophagy and subsequent cell death.

Endocrine-disrupting chemicals in ovarian function: effects on steroidogenesis, metabolism and nuclear receptor signaling

Endocrine-disrupting chemicals (EDCs) are exogenous agents with the ability to interfere with processes regulated by endogenous hormones. One such process is female reproductive function. The major reproductive organ in the female is the ovary. Disruptions in ovarian processes by EDCs can lead to adverse outcomes such as anovulation, infertility, estrogen deficiency, and premature ovarian failure among others. This review summarizes the effects of EDCs on ovarian function by describing how they interfere with hormone signaling via two mechanisms: altering the availability of ovarian hormones, and altering binding and activity of the hormone at the receptor level. Among the chemicals covered are pesticides (e.g. dichlorodiphenyltrichloroethane and methoxychlor), plasticizers (e.g. bisphenol A and phthalates), dioxins, polychlorinated biphenyls, and polycyclic aromatic hydrocarbons (e.g. benzo[a]pyrene).

Neonatal diethylstilbestrol exposure disrupts female reproductive tract structure/function via both direct and indirect mechanisms in the hamster

We assessed neonatal diethylstilbestrol (DES)-induced disruption at various endocrine levels in the hamster. In particular, we used organ transplantation into the hamster cheek pouch to determine whether abnormalities observed in the post-pubertal ovary are due to: (a) a direct (early) mechanism or (b) an indirect (late) mechanism that involves altered development and function of the hypothalamus and/or pituitary. Of the various disruption endpoints and attributes assessed: (1) some were consistent with the direct mechanism (altered uterine and cervical dimensions/organization, ovarian polyovular follicles, vaginal hypospadius, endometrial hyperplasia/dysplasia); (2) some were consistent with the indirect mechanism (ovarian/oviductal salpingitis, cystic ovarian follicles); (3) some were consistent with a combination of the direct and indirect mechanisms (altered endocrine status); and (4) the mechanism(s) for one (lack of corpora lutea) was uncertain. This study also generated some surprising observations regarding vaginal estrous assessments as a means to monitor periodicity of ovarian function in the hamster.

Preconception omega-3 fatty acid supplementation of adult male mice with a history of developmental 2,3,7,8-tetrachlorodibenzo-p-dioxin exposure prevents preterm birth in unexposed female partners

We have recently reported that adult male C57BL/6 mice exposed in utero to the environmental toxicant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) confer an increased risk of preterm birth (PTB) to unexposed females. Risk of PTB was coincident with decreased placental progesterone receptor (Pgr) mRNA expression and increased toll-like receptor 4 (Tlr4) mRNA expression, suggesting that toxicant exposure induced a heightened inflammatory response at the maternal-fetal interface. Since omega-3 fatty acids exhibit anti-inflammatory activity, in this study, we provided TCDD-exposed males a fish oil-enriched diet prior to mating. Although PTB was common in control females mated to TCDD-exposed males on the standard diet, fish oil supplementation of TCDD-exposed males eliminated PTB in unexposed partners. We also determined the influence of preconception, paternal fish oil supplementation on the placental inflammatory response in late pregnancy (E18.5) by examining the expression of Pgr and Tlr4 mRNA as well as the expression of 15-hydroxyprostaglandin dehydrogenase (PGDH). PGDH catabolizes the inflammatory PGE2 to an inactive form; thus, reduced expression of this enzyme would promote tissue inflammation. Compared with control pregnancies, examination of E18.5 placentas arising from TCDD-exposed males on the standard diet revealed a significant increase in Tlr4 mRNA expression corresponding to a reduction in Pgr mRNA and PGDH protein expression. In contrast, fish oil supplementation of toxicant-exposed males led to normalization of placental expression of both Pgr and Tlr4 mRNA and a marked increase in PGDH expression. These studies suggest that a paternal preconception diet that includes omega-3 fatty acids prevents the toxicant-associated increase in the placental inflammatory response at late gestation, preventing PTB.

Circadian clock disruption in the mouse ovary in response to 2,3,7,8-tetrachlorodibenzo-p-dioxin

Activation of the aryl hydrocarbon receptor (AhR) by the highly toxic, prototypical ligand, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) or other dioxin-like compounds compromises ovarian function by altering follicle maturation and steroid synthesis. Although alteration of transcription after nuclear translocation and heterodimerization of AhR with its binding partner, aryl hydrocarbon nuclear transporter (ARNT), is often cited as a primary mechanism for mediating the toxic effects of dioxins, recent evidence indicates that crosstalk between AhR and several other signaling pathways also occurs. Like the circadian clock genes, AhR is a member of the basic helix-loop-helix, Per-ARNT-SIM (bHLH-PAS) domain family of proteins. Thus, these studies tested the hypothesis that TCDD can act to alter circadian clock regulation in the ovary. Adult female c57bl6/J mice entrained to a typical 12h light/12h dark cycle were exposed to a single 1 μg/kg dose of TCDD by gavage. Six days after exposure, animals were released into constant darkness and ovaries were collected every 4h over a 24h period. Quantitative real-time PCR and immunoblot analysis demonstrated that TCDD exposure alters expression of the canonical clock genes, Bmal1 and Per2 in the ovary. AhR transcript and protein, which displayed a circadian pattern of expression in the ovaries of control mice, were also altered after TCDD treatment. Immunohistochemistry studies revealed co-localization of AhR with BMAL1 in various ovarian cell types. Furthermore, co-immunoprecipitation demonstrated time-of-day dependent interactions of AhR with BMAL1 that were enhanced after TCDD treatment. Collectively these studies suggest that crosstalk between classical AhR signaling and the molecular circadian clockworks may be responsible for altered ovarian function after TCDD exposure.

Activation of the aryl hydrocarbon receptor during pregnancy in the mouse alters mammary development through direct effects on stromal and epithelial tissues

Activation of the aryl hydrocarbon receptor (AHR), an environment-sensing transcription factor, causes profound impairment of mammary gland differentiation during pregnancy. Defects include decreased ductal branching, poorly formed alveolar structures, suppressed expression of milk proteins, and failure to nutritionally support offspring. AHR is activated by numerous environmental toxins, such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), and plays an as yet poorly understood role in development and reproduction. To better understand how AHR activation affects pregnancy-associated mammary gland differentiation, we used a combination of ex vivo differentiation, mammary epithelial transplantation, and AHR-deficient mice to determine whether AHR modulates mammary development through a direct effect on mammary epithelial cells (MECs) or by altering paracrine or systemic factors that drive pregnancy-associated differentiation. Studies using mutant mice that express an AHR protein lacking the DNA-binding domain show that defects in pregnancy-associated differentiation require AHR:DNA interactions. We then used fluorescence-based cell sorting to compare changes in gene expression in MECs and whole mammary tissue to gain insight into affected signaling pathways. Our data indicate that activation of the AHR during pregnancy directly affects mammary tissue development via both a direct effect on MECs and through changes in cells of the fat pad, and point to gene targets in MECs and stromal tissues as putative AHR targets.

The ovarian dysgenesis syndrome

New thinking has arisen about the origin of adult onset diseases stemming from a collective body of evidence commonly referred to as the developmental origins of health and disease. This conceptual paradigm posits that certain adult onset diseases arise during critical or sensitive windows of human development or even transgenerationally. The testicular dysgenesis hypothesis (TDS) postulates an in utero origin for adverse male reproductive outcomes, and is an excellent example of the early origins of the paradigm. Despite similarities in the development of the male and female reproductive tracks, noticeably absent is a collective body of evidence focusing on the plausibility of an early origin for gynecologic outcomes and later onset of adult diseases. Using the TDS paradigm, we synthesized the available literature relative to the ovarian dysgenesis syndrome (ODS), which we define as alterations in ovarian structure or function that may manifest as fecundity impairments, gynecologic disorders, gravid diseases or later onset adult diseases. We evaluated environmental exposures, particularly the role of endocrine disrupting chemicals, in relation to these outcomes, and found evidence (although fragmented) consistent with an in utero origin of gynecologic outcomes, which in turn is associated with later onset of adult diseases. The findings are interpreted within the ODS paradigm while delineating methodological challenges and future research opportunities designed to answer critical data gaps regarding the origin of fecundity, gravid health and chronic diseases affecting the female population.

In utero exposure to tobacco smoke and subsequent reduced fertility in females

BACKGROUND

Animal studies have shown that in utero exposure to chemicals in tobacco smoke reduces female fertility, but epidemiological findings have been inconsistent.

METHODS

We examined the association between in utero exposure to tobacco smoke and female fertility among women in the Norwegian Mother and Child Cohort Study, enrolled from 1999 to 2007. Around the 17th week of pregnancy, participants reported how long they took to conceive (time to pregnancy), and whether their mother smoked while pregnant with the participant. This analysis included 48 319 planned pregnancies among women aged 15-44 years. We estimated fecundability odds ratios (FORs) using a discrete-time survival analysis, adjusting for age, education and adult tobacco smoking.

RESULTS

The adjusted FOR for in utero exposure to tobacco smoke among all subjects was 0.96 [95% confidence interval (CI): 0.93, 0.98], among subjects reporting no adult tobacco smoking or passive exposure it was 0.96 (95% CI: 0.93, 0.99) and among subjects reporting adult tobacco smoking or passive exposure it was 0.95 (95% CI: 0.91, 0.99). We performed a probabilistic sensitivity analysis to estimate the effect of exposure and outcome misclassification on the results, and, as expected, the association became more pronounced after taking misclassification into account.

CONCLUSIONS

This large cohort study supports a small-to-modest association between in utero exposure to tobacco smoke and reduced fertility.

Biomarkers of exposure to combustion by-products in a human population in Shanxi, China

Emissions of complex mixtures of polycyclic aromatic hydrocarbons (PAHs) and other compounds into the environment represent a potential threat to the health of humans. Information regarding the dose and duration of exposure is essential to determine the degree of risk and to identify sensitive receptors within a population. Although measurements of chemical concentrations in air may be used to estimate exposures, internal biomarkers provide more accurate information regarding the dose of exposure and retention of toxic chemicals. This study was conducted in a population in rural China exposed to PAHs from a variety of sources. The study population was located in an area known to have an elevated incidence of birth defects. Parents of children born with a neural tube defect (NTD) were recruited as case participants and parents of children born with no visible birth defect were recruited as controls. The study was designed to test the hypothesis that parents of children born with a NTD would exhibit a biomarker of exposure at higher levels than the parents of a child with no visible birth defect. A total of 35 mothers and 32 fathers were recruited as case participants, and 18 mothers and 19 fathers were recruited as control participants. Venous blood was collected from the study participants by hospital staff as soon as possible following the birth of the child. PAHs were isolated from the whole blood by solvent extraction and DNA was isolated from a separate aliquot of blood for (32)P-postlabeling to measure bulky adducts. Single Nucleotide Polymorphisms (SNPs) in phase II enzymes were also monitored in an attempt to identify sensitive receptors. Both total and carcinogenic PAH (cPAH) concentrations were elevated in the parents of case children. Both values were elevated significantly in mothers, whereas only cPAH concentrations were elevated significantly in fathers. Levels of DNA adducts were highly variable and displayed a reverse pattern to that of PAH levels in blood. None of the polymorphisms evaluated were correlated with PAH levels or DNA adducts. For mothers, whose total PAH concentration was above the median concentration, the age-adjusted odds ratio (OR) for having a child with a NTD was 8.7. Although this suggests that PAHs may be a contributing factor to the risk of NTDs, the lack of a correlation with DNA adducts would suggest a possible non-genotoxic mechanism. Alternatively, the PAHs may be a surrogate for a different exposure that is more directly related to the birth defects. The results have shown that blood levels of PAHs may be used to identify populations exposed to elevated concentrations of combustion by-products.

Dioxin and endometrial progesterone resistance

Development of endometriosis likely requires multiple, interactive mechanisms involving both the endocrine and immune systems. Environmental toxicants, such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), are of particular interest as potential contributory agents in the development of this disease because they can disrupt both systems. Nevertheless, defining the potential role that environmental exposure to TCDD plays in the development of endometriosis requires a better understanding of how this toxicant affects the biological processes that promote the disease. Although the disease mechanism(s) responsible for progesterone resistance in the endometrium of endometriosis patients remains speculative, our studies indicate that developmental exposure of mice to TCDD leads to a progesterone-resistant phenotype in adult animals that can persist for several generations. These studies and others underscore the importance of developing a greater understanding of the mechanisms of TCDD action that relate to reproductive disorders such as endometriosis.

Chronic exposure to fine particulate matter emitted by traffic affects reproductive and fetal outcomes in mice

Air pollution is an important environmental health risk factor that can result in many different gestational and reproductive negative outcomes. In this study, we have investigated the effects of two different times of exposure (before conception and during pregnancy) to urban ambient particulate matter on reproductive and pregnancy outcomes in mice. Using exposure chambers receiving filtered (F) and non-filtered (NF) air, we observed that exposed females exhibited changes in the length of estrus cycle and extended estrus and, therefore, a reduction in the number of cycles during the studied period (F 2.6 +/- 0.22 and NF 1.2 +/- 0.29, p = 0.03). The mean number of antral follicles declined by 36% (p = 0.04) in NF mice (75 +/- 35.2) compared to F mice (118.6 +/- 18.4). Our results further indicate a significant increase in time necessary for mating and decreased fertility and pregnancy indices (p = 0.003) in NF couples. Mean post-implantation loss rates were increased by 70% (p < or = 0.005) in the NF2 group (exposed before and during pregnancy to NF air) compared to the F1 group (exposed before and during pregnancy to F air) and were influenced by both pre-gestational (p < 0.004) and gestational (p < 0.01) period exposure. Fetal weight was significantly higher in the F1 group when compared with the other groups (p < 0.001), at a 20% higher weight in the F1 group (0.86 +/- 0.18 g) than in the NF2 group (0.68 +/- 0.10 g). Furthermore, fetal weight was influenced by both pre-gestational and gestational period exposure, and a significant interaction between these two factors was found (p < 0.001). This study demonstrated that exposure to ambient levels of urban traffic-generated particulate matter negatively affects different functions and stages of the reproductive process. Our results also reinforce the idea that maternal exposure to air pollution is linked to negative pregnancy outcomes, even if the exposure occurs only before conception.

TCDD exposure disrupts mammary epithelial cell differentiation and function

Mammary gland growth and differentiation during pregnancy is a developmental process that is sensitive to the toxic effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). TCDD is a widespread environmental contaminant and a potent ligand for the aryl hydrocarbon receptor (AhR). We demonstrate reduced beta-casein protein induction in mouse mammary glands and in cultured SCp2 mammary epithelial cells following exposure to TCDD. SCp2 cells exposed to TCDD also show reduced cell clustering and less alveolar-like structure formation. SCp2 cells express transcriptionally active AhR, and exposure to TCDD induces expression of the AhR target gene CYP1B1. Exposure to TCDD during pregnancy reduced expression of the cell adhesion molecule E-cadherin in the mammary gland and decreased phosphorylation of STAT5, a known regulator of beta-casein gene expression. These data provide morphological and molecular evidence that TCDD-mediated AhR activation disrupts structural and functional differentiation of the mammary gland, and present an in vitro model for studying the effects of TCDD on mammary epithelial cell function.

Identification of uterine leiomyoma genes developmentally reprogrammed by neonatal exposure to diethylstilbestrol

Environmental exposures during development can alter susceptibility later in life to adult diseases including uterine leiomyoma, a phenomenon termed developmental reprogramming. The goal of this study was to identify genes developmentally reprogrammed by diethylstilbestrol (DES) and aberrantly expressed in leiomyomas. Transcriptional profiling identified 171 genes differentially expressed in leiomyomas relative to normal myometrium, of which 6/18 genes with putative estrogen responsive elements and confirmed to be estrogen-responsive in neonatal uteri were reprogrammed by neonatal DES exposure. Calbindin D9k and Dio2, normally induced by estrogen, exhibited elevated expression in DES-exposed animals during both phases of the estrus cycle. Gdf10, Car8, Gria2, and Mmp3, genes normally repressed by estrogen, exhibited elevated expression in DES-exposed animals during the proliferative phase, when estrogen is highest. These data demonstrate that neonatal DES exposure causes reprogramming of estrogen-responsive genes expressed in uterine leiomyomas, leading to over-expression of these genes in the myometrium of exposed animals prior to the onset of tumorigenesis.

Lymphoma and lung cancer in offspring born to pregnant mice dosed with dibenzo[a,l]pyrene: the importance of in utero vs. lactational exposure

The fetus and neonate cannot be viewed as "little adults"; they are highly sensitive to toxicity from environmental chemicals. This phenomenon contributes to the fetal basis of adult disease. One example is transplacental carcinogenesis. Animal models demonstrate that environmental chemicals, to which pregnant women are daily exposed, can increase susceptibility of the offspring to cancer. It is uncertain to what degree in utero vs. lactational exposure contributes to cancer, especially for hydrophobic chemicals such as polyhalogenated biphenyls, ethers, dioxins, furans, etc., which can partition into breast milk. We developed a pregnant mouse model in which exposure to the polycyclic aromatic hydrocarbon (PAH), dibenzo[a,l]pyrene (DBP), during late gestation, produces an aggressive T-cell lymphoma in offspring between 3 and 6 months of age. Survivors exhibit multiple lung and liver (males) tumors. Here, we adopt a cross-foster design with litters born to dams treated with DBP exchanged with those born to dams treated with vehicle. Exposure to DBP in utero (about 2 days) produced significantly greater mortality than residual DBP exposure only through breast milk (3 weeks of lactation). As previously observed pups in all groups with an ahr(b-1/d) ("responsive") genotype were more susceptible to lymphoma mortality than ahr(d/d) ("non-responsive") siblings. At termination of the study at 10 months, mice exposed in utero also had greater lung tumor multiplicity than mice exposed only during lactation. Our results demonstrate that short exposure to DBP during late gestation presents a greater risk to offspring than exposure to this very hydrophobic PAH following 3 weeks of nursing.

Effects of a low oral dose of diethylstilbestrol (DES) on reproductive tract development in F1 female CD-1 mice

The synthetic estrogen diethylstilbestrol (DES) is a model to study the effects on female reproductive tract of endocrine disrupting chemicals interacting with estrogen receptors. Pregnant CD-1 mice were given daily by gavage 10microg/kg bw of DES (the lower range of therapeutic exposure) during gestational days 9-16, critical period for reproductive tract development. Parameters of sexual development were recorded after weaning and at sexual maturation. No signs of general toxicity were observed in dams. In DES-treated group, reduced litter weight during lactation and earlier vaginal patency was observed. Uterus weight was increased in F1 treated females at weaning. Histological analysis showed reduced endometrium thickness and increased polyovular follicles, irregular and oocytes with condensed chromatin in the ovary at sexual maturity. Prenatal DES oral administration induces subtle but significant effects on puberty onset, uterine and ovary morphology.

In utero exposure to low doses of environmental pollutants disrupts fetal ovarian development in sheep

Epidemiological studies of the impact of environmental chemicals on reproductive health demonstrate consequences of exposure but establishing causative links requires animal models using ‘real life’ in utero exposures. We aimed to determine whether prolonged, low-dose, exposure of pregnant sheep to a mixture of environmental chemicals affects fetal ovarian development. Exposure of treated ewes (n = 7) to pollutants was maximized by surface application of processed sewage sludge to pasture. Control ewes (n = 10) were reared on pasture treated with inorganic fertilizer. Ovaries and blood were collected from fetuses (n = 15 control and n = 8 treated) on Day 110 of gestation for investigation of fetal endocrinology, ovarian follicle/oocyte numbers and ovarian proteome. Treated fetuses were 14% lighter than controls but fetal ovary weights were unchanged. Prolactin (48% lower) was the only measured hormone significantly affected by treatment. Treatment reduced numbers of growth differentiation factor (GDF9) and induced myeloid leukaemia cell differentiation protein (MCL1) positive oocytes by 25–26% and increased pro-apoptotic BAX by 65% and 42% of protein spots in the treated ovarian proteome were differently expressed compared with controls. Nineteen spots were identified and included proteins involved in gene expression/transcription, protein synthesis, phosphorylation and receptor activity. Fetal exposure to environmental chemicals, via the mother, significantly perturbs fetal ovarian development. If such effects are replicated in humans, premature menopause could be an outcome.

Proceedings of the Summit on Environmental Challenges to Reproductive Health and Fertility: executive summary

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 commercial use in the United States, 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 postnatal 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.

Proceedings of the Summit on Environmental Challenges to Reproductive Health and Fertility: executive summary

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 commercial use in the United States, 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 postnatal 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.

The development of an aquatic bivalve model: evaluating the toxic effects on gametogenesis following 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) exposure in the eastern oyster (Crassostrea virginica)

The objective of this study is to develop a gametogenesis protocol to serve as a model for evaluating the toxic effects of chemicals on oogenesis and spermatogenesis in the eastern oyster (Crassostrea virginica). The compound 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) was selected as a "proof of principle" toxicant to examine developmental toxicity in this invertebrate system. The studies were designed to: (1) test the model using 2,3,7,8-TCDD and (2) to use histopathological evaluations to characterize the effects on oocyte and sperm development during stages of gametogenesis. 2,3,7,8-TCDD at 10 pg/g resulted in significant histopathological gonadal lesions by day 14 of gametogenesis in both female and male oysters. These lesions resulted in complete inhibition of gonadogenesis. Studies also showed that a total body dose of 2 and 10 pg/g 2,3,7,8-TCDD caused adverse responses resulting in abnormal gametogenesis in female and male oysters, respectively, such as: (1) incomplete oocyte division, (2) inhibition of oocyte growth and maturation, (3) unsynchronized sperm development, and (4) inhibition of spermatogenesis. The eastern oyster is one of the most responsive invertebrate models tested to date for reproductive effects of chemicals. Therefore, the eastern oyster can be used as a sensitive toxicological model for examining the effects of dioxin-like compounds and other xenobiotics on gametogenesis. The reported studies show that environmentally relevant concentrations of 2,3,7,8-TCDD (2-10 pg/g) have a significant adverse effect on oyster gametogenesis.

Prenatal TCDD exposure predisposes for mammary cancer in rats

Epidemiological data are conflicting in the link between 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure and breast cancer causation. We have hypothesized that timing of exposure to endocrine disruptors, such as TCDD, will alter breast cancer susceptibility. Using a carcinogen induced rat mammary cancer model, we have shown that prenatal exposure to TCDD alters mammary gland differentiation and increases susceptibility for mammary cancer. Investigations into imprinting via DNA methylation mechanisms showed that there were no changes in protein expression in DNA methyltransferases, ER-alpha, ER-beta, GST-pi, or MDGI. Using 2D gels and mass spectrometry, we have found seven proteins to be differentially regulated, including a decrease in superoxide dismutase 1 (SOD1). Down-regulation of SOD1 could provide an environment ill equipped to deal with subsequent free radical exposure. We conclude that prenatal TCDD can predispose for mammary cancer susceptibility in the adult offspring by altering the mammary proteome.