Stress lowers the threshold dose at which bisphenol A disrupts blastocyst implantation, in conjunction with decreased uterine closure and e-cadherin

Toxicological Impact of Bisphenol A on Females' Reproductive System: Review Based on Experimental and Epidemiological Studies

The study encompassing research papers documented in the last two decades pertaining to the possible influence of bisphenol A (BPA) on the fertility of females are appraised with emphasis on the influence of BPA in reproductive organs (uterus and ovaries) and pregnancy outcomes including discussion on the reproductive process (implantation, estrous cycle, hormone secretion); outcomes reveal a connection amongst BPA and female infertility. Ovary, uterus, and its shape as well as function can alter a person's ability to become pregnant by influencing the hypothalamus-pituitary axis in the ovarian model. Additionally, implantation and the estrous cycle may be affected by BPA. However, more research is warranted to comprehend the underlying action mechanisms and to promptly identify any imminent reproductive harm.

Associations between urinary concentrations of bisphenols and serum concentrations of sex hormones among US. Males

BACKGROUND

Bisphenol A (BPA) exposure and its structural analogs (BPS and BPF) might cause endocrine alterations and adverse physiological effects. Few studies to date have directly explored the association between its structural analogs (BPS, BPF) and sex hormones in adult male participants. Therefore, we aimed to assess the associations between BPA, BPS, BPF, and sex hormones in American adult men.

METHODS

We used data from the U.S. National Health and Nutrition Examination Survey 2011-2016. We excluded participants without data available on sex hormones and urinary bisphenols. Furthermore, participants consuming sex hormone medications were excluded. Multivariable regression models were performed to assess the association between bisphenols and sex hormones.

RESULTS

In this study, 2367 participants were included. Of 2367, in 1575 participants, the data on BPS and BPF were available. We found that a per unit increase in BPF was associated with 0.575 ng/dL higher total testosterone (TT) (Model 2: 95% CI: 0.047, 1.103, P = 0.033). However, there was no significant association between BPA or BPS and TT. Furthermore, increased BPA and BPS levels were associated with higher levels of sex hormone-binding globulin (SHBG) (Model 2: β = 0.364, 95% CI: 0.158, 0.571; β = 0.25, 95% CI: 0.071, 0.429, respectively). Additionally, participants in the highest BPA exposure quartile (quartile 4) had 4.072 nmol/L higher levels of SHBG than those in quartile 1 (Model 2: 95% CI: 0.746, 7.397, P = 0.017; P for trend =0.005). Both BPA and BPS were negatively associated with free testosterone (FT, nmol/L) after full adjustment (Model 2, β = - 0.01%, P = 0.0211, P = 0.0211; Model 2, β = - 0.01%, P = 0.0258, respectively). However, BPF was positively associated with FT (Model 2, β = 0.0029%, P = 0.0028).

CONCLUSION

Our study indicated that exposure to both BPA and its substitutions could alter sex hormone levels. This finding supports the possibility that human exposure to bisphenols at environmental levels might affect the endogenous hormone balance.

Using Live Imaging and Fluorescence Ubiquitinated Cell Cycle Indicator Embryonic Stem Cells to Distinguish G1 Cell Cycle Delays for General Stressors like Perfluoro-Octanoic Acid and Hyperosmotic Sorbitol or G2 Cell Cycle Delay for Mutagenic Stressors like Benzo(a)pyrene

Lowest observable adverse effects level (LOAEL) is a standard point-of-departure dose in toxicology. However, first observable adverse effects level (FOAEL) was recently reported and is used, in this study, as one criterion to detect a mutagenic stimulus in a live imager. Fluorescence ubiquitinated cell cycle indicator (FUCCI) embryonic stem cells (ESC) are green in the S-G2-M phase of the cell cycle and not green in G1-phase. Standard media change here is a mild stress that delays G1-phase and media change increases green 2.5- to 5-fold. Since stress is mild, media change rapidly increases green cell number, but higher stresses of environmental toxicants and positive control hyperosmotic stress suppress increased green after media change. Perfluoro-octanoic acid (PFOA) and diethyl phthalate (DEP) previously suppressed progression of nongreen to green cell cycle progression. Here, bisphenol A (BPA), cortisol, and positive control hyperosmotic sorbitol also suppress green fluorescence, but benzo(a)pyrene (BaP) at high doses (10 μM) increases green fluorescence throughout the 74-h exposure. Since any stress can affect many cell cycle phases, messenger RNA (mRNA) markers are best interpreted in ratios as dose-dependent mutagens increase in G2/G1 and nonmutagens increase G1/G2. After 74-h exposure, RNAseq detects G1 and G2 markers and increasing BaP doses increase G2/G1 ratios but increasing hyperosmotic sorbitol and PFOA doses increase G1/G2 marker ratios. BaP causes rapid green increase in FOAEL at 2 h of stimulus, whereas retinoic acid caused significant green fluorescence increases only late in culture. Using a live imager to establish FOAEL and G2 delay with FUCCI ESC is a new method to allow commercial and basic developmental biologists to detect drugs and environmental stimuli that are mutagenic. Furthermore, it can be used to test compounds that prevent mutations. In longitudinal studies, uniquely provided by this viable reporter and live imager protocol, follow-up can be done to test whether the preventative compound itself causes harm.

Stress Decreases Host Viral Resistance and Increases Covid Susceptibility in Embryonic Stem Cells

Stress-induced changes in viral receptor and susceptibility gene expression were measured in embryonic stem cells (ESC) and differentiated progeny. Rex1 promoter-Red Fluorescence Protein reporter ESC were tested by RNAseq after 72hr exposures to control stress hyperosmotic sorbitol under stemness culture (NS) to quantify stress-forced differentiation (SFD) transcriptomic programs. Control ESC cultured with stemness factor removal produced normal differentiation (ND). Bulk RNAseq transcriptomic analysis showed significant upregulation of two genes involved in Covid-19 cell uptake, Vimentin (VIM) and Transmembrane Serine Protease 2 (TMPRSS2). SFD increased the hepatitis A virus receptor (Havcr1) and the transplacental Herpes simplex 1 (HSV1) virus receptor (Pvrl1) compared with ESC undergoing ND. Several other coronavirus receptors, Glutamyl Aminopeptidase (ENPEP) and Dipeptidyl Peptidase 4 (DPP4) were upregulated significantly in SFD>ND. Although stressed ESC are more susceptible to infection due to increased expression of viral receptors and decreased resistance, the necessary Covid-19 receptor, angiotensin converting enzyme (ACE)2, was not expressed in our experiments. TMPRSS2, ENPEP, and DPP4 mediate Coronavirus uptake, but are also markers of extra-embryonic endoderm (XEN), which arise from ESC undergoing ND or SFD. Mouse and human ESCs differentiated to XEN increase TMPRSS2 and other Covid-19 uptake-mediating gene expression, but only some lines express ACE2. Covid-19 susceptibility appears to be genotype-specific and not ubiquitous. Of the 30 gene ontology (GO) groups for viral susceptibility, 15 underwent significant stress-forced changes. Of these, 4 GO groups mediated negative viral regulation and most genes in these increase in ND and decrease with SFD, thus suggesting that stress increases ESC viral susceptibility. Taken together, the data suggest that a control hyperosmotic stress can increase Covid-19 susceptibility and decrease viral host resistance in mouse ESC. However, this limited pilot study should be followed with studies in human ESC, tests of environmental, hormonal, and pharmaceutical stressors and direct tests for infection of stressed, cultured ESC and embryos by Covid-19.

Effects of Endocrine-Disrupting Chemicals on Endometrial Receptivity and Embryo Implantation: A Systematic Review of 34 Mouse Model Studies

Several available studies have already analyzed the systemic effects of endocrine-disrupting chemicals (EDCs) on fertile woman and neonatal outcomes, but little is still known in humans about the precise mechanisms of interference of these compounds with the endometrial receptivity. There is consistent evidence that continuous and prolonged exposure to EDCs is a risk factor for reduced fertility and fecundity in women. Preliminary studies on mammalian models provide robust evidence about this issue and could help gynecologists worldwide to prevent long term injury caused by EDCs on human fertility. In this systematic review, we aimed to systematically summarize all available data about EDC effects on blastocyst endometrial implantation. We performed a systematic review using PubMed^®/MEDLINE^® to summarize all in vivo studies, carried out on mice models, analyzing the molecular consequences of the prolonged exposure of EDC on the implantation process. 34 studies carried out on mouse models were included. Primary effects of EDC were a reduction of the number of implantation sites and pregnancy rates, particularly after BPA and phthalate exposure. Furthermore, the endometrial expression of estrogen (ER) and progesterone receptors (PR), as well as their activation pathways, is compromised after EDC exposure. Finally, the expression of the primary endometrial markers of receptivity (such as MUC1, HOXA10, Inn and E-cadherin) after EDC contact was analyzed. In conclusion EDC deeply affect blastocyst implantation in mouse model. Several players of the implantation mechanism are strongly influenced by the exposure to different categories of EDC.

Associations among urinary triclosan and bisphenol A concentrations and serum sex steroid hormone measures in the Canadian and U.S. Populations

Exposure to triclosan, an antimicrobial agent, and bisphenol A (BPA), the monomer of polycarbonate plastics, is widespread. Endocrine-disrupting impacts of these chemicals have been demonstrated in in vitro studies, rodent toxicology studies, and some human observational studies. Here we compared urinary concentrations of triclosan and BPA in the Canadian and U.S. populations using nationally-representative data from the 2012-2015 Canadian Health Measures Survey (CHMS) and the 2013-2016 National Health and Nutrition Examination Survey (NHANES). We then examined the cross-sectional associations of urinary triclosan or BPA with serum sex steroid hormones, including estradiol (E2), progesterone (P4), and testosterone (T), using multivariable regression. We observed differences in creatinine-standardized chemical concentrations between countries; urinary triclosan was higher in Canadian females aged 12-19 years, while BPA was higher in U.S. females aged 20-49 years. We also found significant associations among urinary chemicals and serum E2 and T, but not P4. Increasing triclosan was associated with higher levels of E2 in 6-11-year-old girls, but with lower levels of E2 and T in adolescent boys aged 12-19 years. Increasing BPA was associated with lower levels of E2 in 6-11-year-old boys and in adolescents aged 12-19 years of either sex. We observed a U-shaped association between urinary triclosan and E2 in male adults aged 50-79 years; no associations between BPA and hormones were detected in adults. These results, in accordance with the in vitro and animal literature, suggest that triclosan and BPA exposures may be cross-sectionally associated with altered reproductive hormone levels, especially in children and adolescents. Further research and prospective studies are necessary to elucidate country-specific differences in chemical exposures and the potential public health significance of these findings.

Parental perinatal exposure to bisphenol A reduces the threshold to disrupt blastocyst implantation via decreasing talin, occudin and E-cadherin levels

The aim was to evaluate the effect of perinatal BPA exposure of one or both parents on the implantation index and expression of talin, occludin and E-cadherin in the uterine epithelial cells (UEC) of the offspring. Pregnant Wistar dams (F0) received BPA or vehicle from gestational day (GD) 6 to lactation day 21. F1 animals were mated forming four groups: Control dam-Control sire (C♀-C♂), BPA dam -Control sire (B♀-C♂), Control dam -BPA sire (C♀-B♂), BPA dam -BPA sire (B♀-B♂). F1 dams were sacrificed at GD 6. Significantly decreased number of implantation sites was observed in the B♀-B♂ group as compared to the C♀-C♂ group, which correlated with decreased talin apical/basal expression ratio, occludin apical expression, and E-cadherin apical/lateral expression ratio in the UEC. Furthermore, decreased E-cadherin expression in the blastocyst was observed. Our data suggest that reduced protein expressions in F1 BPA offspring could result from decreased progesterone serum levels.

Bisphenol A decreases the spontaneous contractions of rat uterus in vitro through a nitrergic mechanism

BACKGROUND

Bisphenol A (BPA), a chemical used in the manufacture of plastics, has toxic effects on various systems of the human body including the reproductive system. BPA possesses estrogenic activity and is implicated in altering oogenesis, ovulation, and fertility. In addition to ovulatory changes, uterine contractility is an important factor for fertility. However, the effects of BPA on myometrial contractions are not known. Therefore, we examined the effect of BPA on rat uterine contractions.

METHODS

The uterus was isolated from adult rats showing estrous phase, and spontaneous in vitro contractions were recorded (35±1 °C). The effect of cumulative concentrations of BPA was determined. Further, the involvement of nitric oxide (NO) and guanylyl cyclase (GC) for the BPA-induced changes on uterine contractility was evaluated using the NO synthase inhibitor (L-NAME) or GC inhibitor (methylene blue).

RESULTS

BPA decreased the amplitude and frequency of spontaneous uterine contractions in a concentration-dependent manner. A decrease of 50% occurred at 1 and 3 μM for amplitude and frequency, respectively. L-NAME (N-ω-nitro-l-arginine methyl ester) blocked the BPA-induced decrease in amplitude at all concentrations but antagonized the frequency only at the maximum concentration (10 μM). Methylene blue (a GC inhibitor) did not block the BPA-induced responses but for the frequency at 10 μM of BPA.

CONCLUSIONS

The results indicate that BPA decreased the amplitude and frequency of spontaneous uterine contractions by involving the nitrergic mechanism; however, the GC mechanism is not involved in the depression.

The Impact of Bisphenol A on Fertility, Reproductive System, and Development: A Review of the Literature

Bisphenol A (BPA) has been used since the 1950s, in food packaging, industrial materials, dental sealants, and personal hygiene products. Everyone is exposed to BPA through skin, inhalation, and digestive system. BPA disrupts endocrine pathways, because it has weak estrogenic, antiandrogenic, and antithyroid activities. Despite the rapid metabolism, BPA can accumulate in different tissues. Many researchers proved the impact of BPA on human development, metabolism, and finally reproductive system. There is increasing evidence that BPA has impact on human fertility and is responsible for the reproductive pathologies, e.g., testicular dysgenesis syndrome, cryptorchidism, cancers, and decreased fertility in male and follicle loss in female.

The role of toxic stimuli combinations in determining safe exposure limits

This editorial addresses the effects of toxic stimuli combinations on determination of safe Exposure Limits. Examination of thousands of Medline abstracts showed typically that combinations of toxic stimuli can produce damage even when the exposure level of each member of the combination is less than the lowest exposure level of the member that produced damage when tested in isolation. The synergy of the toxic stimuli in combination means less of each component stimulus is required to cause damage compared to exposure levels when tested in isolation. This Editorial concludes there is no reason to believe today that the Exposure Limits on potentially toxic stimuli that have been set by the regulatory agencies are fully protective against serious adverse health effects in all real life exposure scenarios. The conclusion is applicable to essentially all potential contributing factors to disease amenable to Exposure Limits, including not only chemicals but other types of exposures such as radiofrequency radiation (RFR).

Effects of Bisphenol A and 4-tert-Octylphenol on Embryo Implantation Failure in Mouse

Miscarriage due to blastocyst implantation failure occurs in up to two-thirds of all human miscarriage cases. Calcium ion has been shown to be involved in many cellular signal transduction pathways as well as in the regulation of cell adhesion, which is necessary for the embryo implantation process. Exposure to endocrine-disrupting chemicals (EDs) during early gestation results in disruption of intrauterine implantation and uterine reception, leading to implantation failure. In this study, ovarian estrogen (E2), bisphenol A (BPA), or 4-tert-octylphenol (OP), with or without ICI 182,780 (ICI) were injected subcutaneously from gestation day 1 to gestation day 3 post-coitus. The expression levels of the calcium transport genes were assessed in maternal uteri and implantation sites. The number of implantation sites was significantly low in the OP group, and implantation sites were absent in the E2, ICI and EDs + ICI groups. There were different calcium transient transport channel expression levels in uterus and implantation site samples. The levels of TRPV5 and TRPV6 gene expression were significantly increased by EDs with/without ICI treatment in utero. Meanwhile, TRPV5 and TRPV6 gene expression were significantly lower in implantation sites samples. NCX1 and PMCA1 mRNA levels were significantly decreased by OP and BPA in the implantation site samples. Compared to vehicle treatment in the uterus, both the MUC1 mRNA and protein levels were markedly high in all but the BPA group. Taken together, these results suggest that both BPA and OP can impair embryo implantation through alteration of calcium transport gene expressions and by affecting uterine receptivity.

Hypoxic Stress Forces Adaptive and Maladaptive Placental Stress Responses in Early Pregnancy

This review focuses on hypoxic stress and its effects on the placental lineage and the earliest differentiation events in mouse and human placental trophoblast stem cells (TSCs). Although the placenta is a decidual organ at the end of pregnancy, its earliest rapid growth and function at the start of pregnancy precedes and supports growth and function of the embryo. Earliest function requires that TSCs differentiate, however, "hypoxia" supports rapid growth, but not differentiation of TSCs. Most of the literature on earliest placental "hypoxia" studies used 2% oxygen which is normoxic for TSCs. Hypoxic stress happens when oxygen level drops below 2%. It decreases anabolism, proliferation, potency/stemness and increases differentiation, despite culture conditions that would sustain proliferation and potency. Thus, to study the pathogenesis due to TSC dysfunction, it is important to study hypoxic stress below 2%. Many studies have been performed using 0.5 to 1% oxygen in cultured mouse TSCs. From all these studies, a small number has examined human trophoblast lines and primary first trimester placental hypoxic stress responses in culture. Some other stress stimuli, aside from hypoxic stress, are used to elucidate common and unique aspects of hypoxic stress. The key outcomes produced by hypoxic stress are mitochondrial, anabolic, and proliferation arrest, and this is coupled with stemness loss and differentiation. Hypoxic stress can lead to depletion of stem cells and miscarriage, or can lead to later dysfunctions in placentation and fetal development. Birth Defects Research 109:1330-1344, 2017. © 2017 Wiley Periodicals, Inc.

Blastocyst-Derived Stem Cell Populations under Stress: Impact of Nutrition and Metabolism on Stem Cell Potency Loss and Miscarriage

Data from in vitro and in vivo models suggest that malnutrition and stress trigger adaptive responses, leading to small for gestational age (SGA) blastocysts with fewer cell numbers. These stress responses are initially adaptive, but become maladaptive with increasing stress exposures. The common stress responses of the blastocyst-derived stem cells, pluripotent embryonic and multipotent placental trophoblast stem cells (ESCs and TSCs), are decreased growth and potency, and increased, imbalanced and irreversible differentiation. SGA embryos may fail to produce sufficient antiluteolytic placental hormone to maintain corpus luteum progesterone secretion that provides nutrition at the implantation site. Myriad stress inputs for the stem cells in the embryo can occur in vitro during in vitro fertilization/assisted reproductive technology (IVF/ART) or in vivo. Paradoxically, stresses that diminish stem cell growth lead to a higher level of differentiation simultaneously which further decreases ESC or TSC numbers in an attempt to functionally compensate for fewer cells. In addition, prolonged or strong stress can cause irreversible differentiation. Resultant stem cell depletion is proposed as a cause of miscarriage via a "quiet" death of an ostensibly adaptive response of stem cells instead of a reactive, violent loss of stem cells or their differentiated progenies.

Gestational bisphenol S impairs placental endocrine function and the fusogenic trophoblast signaling pathway

Exposure to bisphenolic chemicals during pregnancy occurs in > 90% of pregnancies. Bisphenolic compounds can cross the placental barrier reaching fetal circulation. However, the effects of emerging bisphenolic compounds, such as bisphenol S (BPS), on placental function remain untested. The aim was to determine if bisphenol A (BPA) or BPS, at an environmentally relevant dose, impairs placental function. Pregnant sheep were randomly distributed into three treatment groups (n = 7-8/group): control, BPA, and BPS. All animals received daily injections of corn oil (control), BPA, or BPS (0.5 mg/kg; s.c.; internal fetal doses were ~ 2.6 ng/mL unconjugated BPA and ~ 7.7 ng/mL of BPS) from gestational day 30-100. After a 20-day washout period, placentas were weighed and placentomes collected. Placental endocrine function was assessed on biweekly maternal blood samples. Gestational exposure to BPS, but not BPA, reduced maternal circulating pregnancy-associated glycoproteins without change in placental weight or placental stereology. BPS-exposed placentas had 50% lower e-cadherin protein expression, ~ 20% fewer binucleate cells, and ~ threefold higher glial cell missing-1 protein expression. BPA placentas were not affected highlighting the intrinsic differences among bisphenolic chemicals. This is the first study to demonstrate that gestational BPS can result in placental endocrine dysfunction and points to a dysregulation in the fusogenic trophoblast signaling pathway.

A mixture of five endocrine-disrupting chemicals modulates concentrations of bisphenol A and estradiol in mice

Most people in developed countries are exposed to multiple endocrine-disrupting synthetic chemicals. We previously showed that a single dose of triclosan, tetrabromobisphenol A (TBBPA), butyl paraben, propyl paraben, or di(2-ethylhexyl) phthalate elevated concentrations of bisphenol A (BPA) in mice. Here we investigated whether concurrent exposure to lower doses of these five chemicals could modulate concentrations of bisphenol A (BPA) or the natural estrogen, 17β-estradiol (E2). CF1 mice were injected subcutaneously with 0.1 or 0.5 mg of one chemical, or a 0.5 mg mixture containing 0.1 mg of each of all five chemicals, then given dietary 50 μg kg^-114C-BPA. The mixture elevated ¹⁴C-BPA concentrations in the lungs, muscle, uterus, ovaries, kidney, and blood serum of female mice. When administered alone, triclosan and TBBPA elevated ¹⁴C-BPA concentrations in the uterus, ovaries, and blood serum. In another experiment, CF1 mice were injected subcutaneously with the 0.5 mg mixture containing 0.1 mg of all five chemicals, then E2 was measured in urine 2-12 h later. The mixture elevated E2 at 8 h after injection in female mice. No treatments significantly altered concentrations of ¹⁴C-BPA or E2 in male mice. These data show that these endocrine-disrupting chemicals interact in vivo, magnifying one another's effects, consistent with inhibition of enzymes that are critical for estrogen metabolism. These findings highlight the importance of considering exposure to multiple chemicals when assessing health outcomes and determining regulatory exposure limits.

Influence of Tetrabromobisphenol A, with or without Concurrent Triclosan, upon Bisphenol A and Estradiol Concentrations in Mice

BACKGROUND

Humans are commonly exposed to multiple environmental chemicals, including tetrabromobisphenol A (TBBPA; a flame retardant), triclosan (an antimicrobial agent), and bisphenol A (BPA; polycarbonate plastics). These chemicals are readily absorbed and may interact with each other.

OBJECTIVES

We sought to determine whether TBBPA, given alone or in combination with triclosan, can modulate the concentrations of BPA and 17β-estradiol (E2).

METHODS

Female and male CF-1 mice were each given a subcutaneous injection of 0-27mg TBBPA, with or without concurrent 0.33mg triclosan, followed by dietary administration of 50μg/kg body weight ¹⁴C-BPA. Radioactivity was measured in blood serum and tissues through liquid scintillation counting. In subsequent experiments, female and male CF-1 mice were each given a subcutaneous injection of 0 or 1mg TBBPA and E2 was measured in urine 2-12 h after injection.

RESULTS

Doses as low as 1mg TBBPA significantly elevated ¹⁴C-BPA concentrations in the uterus and ovaries of females; in the testes, epididymides, vesicular-coagulating glands, and preputial glands of males; and in blood serum, heart, lungs, and kidneys of both sexes; urinary E2 concentrations were also elevated. Lower doses of TBBPA or triclosan that had no effects on their own elevated ¹⁴C-BPA concentrations when the two substances were given concurrently.

CONCLUSION

These data indicate that TBBPA, triclosan, and BPA interact in vivo, consistent with evidence that TBBPA and triclosan inhibit enzymes that are critical for BPA and E2 metabolism. https://doi.org/10.1289/EHP1329.

Using stem cell oxygen physiology to optimize blastocyst culture while minimizing hypoxic stress

This review is a response to the Fellows Forum on testing 2% oxygen for best culture of human blastocysts (J Ass Reprod Gen 34:303-8, 1; J Ass Reprod Gen 34:309-14, 2) prior to embryo transfer. It is a general analysis in support of the position that an understanding of stem cell physiology and responses to oxygen are necessary for optimization of blastocyst culture in IVF and to enhance reproductive success in fertile women.

Concurrent administration of diethylhexyl phthalate reduces the threshold dose at which bisphenol A disrupts blastocyst implantation and cadherins in mice

Many people are repeatedly exposed to both bisphenol A (BPA) and diethylhexyl phthalate (DEHP), but there has been little research concerning their effects in combination. Both can disrupt blastocyst implantation in inseminated females, albeit at high doses. We exposed mice on gestation days (GD) 1-4 to combinations of BPA and DEHP in doses below the threshold necessary to disrupt implantation on their own. On GD 6, there were fewer normally-developed implantation sites and more underdeveloped implantation sites in females given the combined subthreshold doses. Uterine epithelial cadherin (e-cadherin), a protein that assists in blastocyst adhesion to the uterine epithelium, was significantly reduced by these combined doses, but not by the individual doses. A similar trend was seen in integrin αvβ3, another uterine adhesion molecule. Cadherin-11 was disrupted by BPA but not DEHP. These data are consistent with competition of BPA and DEHP for conjugating enzymes.

Triclosan elevates estradiol levels in serum and tissues of cycling and peri-implantation female mice

Triclosan, an antimicrobial agent added to personal care products, can modulate estrogenic actions. We investigated whether triclosan affects concentrations of exogenous and endogenous estradiol. Female mice were given injections of triclosan followed by 1μCi tritium-labeled estradiol. Mice given daily 2-mg triclosan doses (57.9mg/kg/dose) showed significantly elevated radioactivity in tissues and serum compared to controls. A single dose of 1 or 2mg triclosan increased radioactivity in the uterus in both cycling and peri-implantation females. We also measured natural urinary estradiol at 2-12h following triclosan injection. Unconjugated estradiol was significantly elevated for several hours following 1 or 2mg of triclosan. These data are consistent with evidence that triclosan inhibits sulfonation of estrogens by interacting with sulfotransferases, preventing metabolism of these steroids into biologically inactive forms. Elevation of estrogen concentrations by triclosan is potentially relevant to anti-reproductive and carcinogenic actions of excessive estrogen activity.

Evidence for bisphenol A-induced female infertility: a review (2007-2016)

We summarized the scientific literature published from 2007 to 2016 on the potential effects of bisphenol A (BPA) on female fertility. We focused on overall fertility outcomes (e.g., ability to become pregnant, number of offspring), organs that are important for female reproduction (i.e., oviduct, uterus, ovary, hypothalamus, and pituitary), and reproductive-related processes (i.e., estrous cyclicity, implantation, and hormonal secretion). The reviewed literature indicates that BPA may be associated with infertility in women. Potential explanations for this association can be generated from experimental studies. Specifically, BPA may alter overall female reproductive capacity by affecting the morphology and function of the oviduct, uterus, ovary, and hypothalamus-pituitary-ovarian axis in animal models. In addition, BPA may disrupt estrous cyclicity and implantation. Nevertheless, further studies are needed to better understand the exact mechanisms of action and to detect potential reproductive toxicity at earlier stages.

Bisphenol A affects early bovine embryo development and metabolism that is negated by an oestrogen receptor inhibitor

Increasing evidence supports an association between exposure to endocrine disruptors, such as the xenoestrogen bisphenol A (BPA), a commonly used plasticiser, and the developmental programming of offspring health. To date however animal studies to investigate a direct causal have mainly focussed on supra-environmental BPA concentrations, without investigating the effect on the early embryo. In this study we investigated the effect of acute BPA exposure (days 3.5 to 7.5 post-fertilisation) at environmentally relevant concentrations (1 and 10 ng/mL) on in vitro bovine embryo development, quality and metabolism. We then examined whether culturing embryos in the presence of the oestrogen receptor inhibitor fulvestrant could negate effects of BPA and 17β-oestradiol (E2). Exposure to BPA or E2 (10 ng/mL) decreased blastocyst rate and the percentage of transferrable quality embryos, without affecting cell number, lineage allocation or metabolic gene expression compared to untreated embryos. Notably, blastocysts exposed to BPA and E2 (10 ng/mL) displayed an increase in glucose consumption. The presence of fulvestrant however negated the adverse developmental and metabolic effects, suggesting BPA elicits its effects via oestrogen-mediated pathways. This study demonstrates that even acute exposure to an environmentally relevant BPA concentration can affect early embryo development and metabolism. These may have long-term health consequences on an individual.