Prenatal Bisphenol A exposure delays the development of the male rat mammary gland

Branching morphogenesis of the mouse mammary gland after exposure to benzophenone-3

Pubertal mammary branching morphogenesis is a hormone-regulated process susceptible to exposure to chemicals with endocrine disruptive capacity, such as the UV-filter benzophenone-3 (BP3). Our aim was to assess whether intrauterine or in vitro exposure to BP3 modified the branching morphogenesis of the female mouse mammary gland. For this, pregnant mice were dermally exposed to BP3 (0.15 or 50 mg/kg/day) from gestation day (GD) 8.5 to GD18.5. Sesame oil treatment served as control. Changes of the mammary glands of the offspring were studied on postnatal day 45. Further, mammary organoids from untreated mice were cultured under branching induction conditions and exposed for 9 days to BP3 (1 × 10-6 M, 1 × 10-9 M, or 1 × 10-12 M with 0.01% ethanol as control) to evaluate the branching progression. Mice that were exposed to BP3 in utero showed decreased mRNA levels of progesterone receptor (PR) and WNT4. However, estradiol and progesterone serum levels, mammary histomorphology, proliferation, and protein expression of estrogen receptor alpha (ESR1) and PR were not significantly altered. Interestingly, direct exposure to BP3 in vitro also decreased the mRNA levels of PR, RANKL, and amphiregulin without affecting the branching progression. Most effects were found after exposure to 50 mg/kg/day or 1 × 10-6 M of BP3, both related to sunscreen application in humans. In conclusion, exposure to BP3 does not impair mammary branching morphogenesis in our models. However, BP3 affects PR transcriptional expression and its downstream mediators, suggesting that exposure to BP3 might affect other developmental stages of the mammary gland.

Nontargeted Analysis Reveals a Broad Range of Bioactive Pollutants in Drinking Water by Estrogen Receptor Affinity-Mass Spectrometry

Exposure to environmental endocrine-disrupting chemicals (EDCs) can cause extensive health issues. However, specific EDCs remain elusive. This work aimed at performing nontargeted identification of estrogen receptor α (ERα)-active compounds using an ERα protein affinity assay combined with high-resolution mass spectrometry in the source and drinking water sampled from major rivers in China. Fifty-one potential ERα-active compounds across 13 categories were identified. For the first time, diisodecyl phenyl phosphate was found to have antiestrogenic activity, and three chemicals (galaxolidone, bensulfuron methyl, and UV234) were plausible ERα ligands. Among the 51 identified compounds, 12 were detected in the aquatic environment for the first time, and the concentration of N-phenyl-2-naphthylamine, a widely used antioxidant in rubber products, was up to 1469 and 1190 ng/L in source and drinking water, respectively. This study demonstrated the widespread presence of known and unknown ERα estrogenic and antiestrogenic pollutants in the major rivers that serve as key sources of drinking water in China and the low removal efficiency of these chemicals in drinking water treatment plants.

Mammary Gland Development in Male Rats Perinatally Exposed to Propiconazole, Glyphosate, or their Mixture

This study aimed to assess whether perinatal exposure to propiconazole (PRO), glyphosate (GLY) or their mixture (PROGLY) alters key endocrine pathways and the development of the male rat mammary gland. To this end, pregnant rats were orally exposed to vehicle, PRO, GLY, or a mixture of PRO and GLY from gestation day 9 until weaning. Male offspring were euthanized on postnatal day (PND) 21 and PND60. On PND21, GLY-exposed rats showed reduced mammary epithelial cell proliferation, whereas PRO-exposed ones showed increased ductal p-Erk1/2 expression without histomorphological alterations. On PND60, GLY-exposed rats showed reduced mammary gland area and estrogen receptor alpha expression and increased aromatase expression, whereas PRO-exposed ones showed enhanced lobuloalveolar development and increased lobular hyperplasia. However, PROGLY did not modify any of the endpoints evaluated. In summary, PRO and GLY modified the expression of key molecules and the development of the male mammary gland individually but not together.

Re-evaluation of the risks to public health related to the presence of bisphenol A (BPA) in foodstuffs

In 2015, EFSA established a temporary tolerable daily intake (t-TDI) for BPA of 4 μg/kg body weight (bw) per day. In 2016, the European Commission mandated EFSA to re-evaluate the risks to public health from the presence of BPA in foodstuffs and to establish a tolerable daily intake (TDI). For this re-evaluation, a pre-established protocol was used that had undergone public consultation. The CEP Panel concluded that it is Unlikely to Very Unlikely that BPA presents a genotoxic hazard through a direct mechanism. Taking into consideration the evidence from animal data and support from human observational studies, the immune system was identified as most sensitive to BPA exposure. An effect on Th17 cells in mice was identified as the critical effect; these cells are pivotal in cellular immune mechanisms and involved in the development of inflammatory conditions, including autoimmunity and lung inflammation. A reference point (RP) of 8.2 ng/kg bw per day, expressed as human equivalent dose, was identified for the critical effect. Uncertainty analysis assessed a probability of 57-73% that the lowest estimated Benchmark Dose (BMD) for other health effects was below the RP based on Th17 cells. In view of this, the CEP Panel judged that an additional uncertainty factor (UF) of 2 was needed for establishing the TDI. Applying an overall UF of 50 to the RP, a TDI of 0.2 ng BPA/kg bw per day was established. Comparison of this TDI with the dietary exposure estimates from the 2015 EFSA opinion showed that both the mean and the 95th percentile dietary exposures in all age groups exceeded the TDI by two to three orders of magnitude. Even considering the uncertainty in the exposure assessment, the exceedance being so large, the CEP Panel concluded that there is a health concern from dietary BPA exposure.

Histopathologic, apoptotic and autophagic, effects of prenatal bisphenol A and/or di(2-ethylhexyl) phthalate exposure on prepubertal rat testis

Bisphenol A (BPA) and di(2-ethylhexyl) phthalate (DEHP) are endocrine-disrupting chemicals (EDCs) used in a wide variety of industrial products as plasticizers. Exposure to EDCs, particularly in mixtures, in prenatal and early postnatal periods may lead to unwanted effects and can cause both developmental and reproductive problems. In this study, we aimed to determine the individual and combined effects of prenatal and lactational exposure to BPA and/or DEHP on testicular histology, apoptosis, and autophagic proteins. Pregnant Sprague-Dawley rats (n = 3) were divided into four groups (control, BPA (50 mg/kg/day), DEHP (30 mg/kg/day), and BPA (50 mg/kg/day) + DEHP (30 mg/kg/day)) and dosed by oral gavage during pregnancy and lactation. The male offspring (n = 6) from each group were chosen randomly, and their testicular examinations were performed on the twelfth week. The results showed that fetal and neonatal exposure to BPA and DEHP could lead to significant testicular histopathological alterations and cause increases in apoptosis markers (as evidenced by increases in caspase 3 and caspase 8 levels; increased TUNEL-positive spermatogonia and TUNEL-positive testicular apoptotic cells) and autophagic proteins (as evidenced by increased LC3 and Beclin levels and decreased p62 levels) in testicular tissue. We can suggest that EDCs cause more dramatic changes in both testicular structure and cell death when there is combined exposure.

Exposure to a Glyphosate-based Herbicide Alters the Expression of Key Regulators of Mammary Gland Development on Pre-pubertal Male Rats

We previously reported that exposure during gestation and lactation to a low dose of glyphosate-based herbicide (GBH) reduced the area and perimeter of male offspring mammary gland at postnatal day 60 (PND60), whereas a higher dose increased the longitudinal growth of the gland. Here, our aim was to assess whether perinatal exposure to GBH exhibits endocrine disruptive action in male mammary gland at an early time point (pre-puberty), which could be related to the changes observed after puberty. We also wanted to explore whether an early evaluation of the male rat mammary gland is appropriate to assess exposure to potential endocrine disrupting chemicals (EDCs). Pregnant rats were orally exposed, through the diet, to vehicle (saline solution), 3.5 or 350 mg/kg/day of GBH from gestational day 9 until weaning. At PND21, the male offspring were euthanized, and mammary gland samples were collected. The histology and proliferation index of the mammary glands were evaluated, and the mRNA expression of estrogen (ESR1) and androgen (AR) receptors, cyclin D1 (Ccnd1), amphiregulin (Areg), insulin-like growth factor 1 (IGF1), epidermal growth factor receptor (EGFR) and IGF1 receptor (IGF1R) were assessed. Moreover, the phosphorylated-Erk1/2 (p-ERK1/2) protein expression was determined. No differences were observed in mammary epithelial structures and AR expression between experimental groups; however, the proliferation index was reduced in GBH3.5-exposed males. This result was associated with decreased ESR1, Ccnd1, Areg, IGF1, EGFR and IGF1R mRNA expressions, as well as reduced p-Erk1/2 protein expression in these animals. ESR1, Ccnd1, IGF1R and EGFR expressions were also reduced in GBH350-exposed males. In conclusion, the mammary gland development of pre-pubertal male rats is affected by perinatal exposure to GBH. Although further studies are still needed to understand the molecular mechanisms involved in GBH350 exposure, the present results may explain the alterations observed in mammary gland growth of post-pubertal males exposed to low doses of GBH. Our results also suggest that early evaluation of the male rat mammary gland is useful in assessing exposure to potential EDCs. However, analysis of EDCs effects at later time points should not be excluded.

Impact of gestational low protein diet and postnatal bisphenol A exposure on chemically induced mammary carcinogenesis in female offspring rats

This study evaluated the effect of gestational low protein diet (LPD) and/or postnatal bisphenol A (BPA) exposure on mammary gland development and carcinogenesis in female offspring. Pregnant Sprague-Dawley rats were fed a normal protein diet (NPD, 17% protein) or LPD (6% protein). At weaning, female offspring were distributed in four groups (NPD, LPD, NPD + BPA, and LPD + BPA) and received vehicle or BPA in drinking water (0.1%), during postnatal day (PND) 21 to 51. On PND 51, some female offspring were euthanized or received a single dose of 7,12-dimethylbenzoanthracene (DMBA, 30 mg/kg, i.g.) and were euthanized on PND 250. On PND 51, neither gestational LPD nor postnatal BPA exposure, individually or in combination, significantly altered the development of mammary gland tree, mean number of terminal structures or estrogen receptor beta (ER-β), proliferating cell nuclear antigen (PCNA) or caspase-3 protein expression in the mammary tissue. A significant reduction in mammary epithelial area (%) was observed in both LPD groups and a significant increase in ER-α protein expression was detected only in LPD group. In LPD + BPA group was observed a significant increase in both fat pad area (%) and in mean number of mammary epithelial cells positive for progesterone receptor (PR). On PND 250, the groups that received BPA presented lower latency and higher tumor incidence and tumor multiplicity and LPD + BPA group more aggressive tumors. These findings suggest that postnatal BPA exposure associated with gestational LPD is able to induce morphological changes in the mammary gland and increase susceptibility to mammary carcinogenesis.

Male mammary gland development and methylation status of estrogen receptor alpha in Wistar rats are modified by the developmental exposure to a glyphosate-based herbicide

Postnatal treatment with glyphosate-based herbicides (GBHs) induces endocrine-disrupting effects on the male rat mammary gland. In this study, the effects of developmental exposure to GBH on mammary gland growth and development, and the possible molecular mechanisms involved, were evaluated in pre- and post-pubertal male rats. To this end, pregnant rats were orally exposed through the food to 0, 3.5 or 350 mg GBH/kg bw/day from gestational day 9 until weaning. Mammary gland development and estradiol (E2) and testosterone (T) serum levels of male offspring were evaluated on postnatal day (PND)21 and PND60. Besides, prolactin (PRL) serum levels, proliferation index, androgen (AR) and estrogen receptor alpha (ESR1) expression, ESR1 alternative transcript mRNA levels, and DNA methylation status of ESR1 promoters were assessed on PND60. No differences between groups were observed in mammary gland development at PND21 or in E2 and T levels on both PNDs studied. On PND60, GBH3.5-exposed animals presented similar mammary gland histology but higher AR protein expression than controls, whereas GBH350-exposed males presented a less developed mammary gland, accompanied by a lower proliferation index, similar AR levels, and slightly increased PRL serum levels than controls. In both exposed groups, ESR1 expression was lower than in control rats, being lower in GBH350-exposed rats. GBH also altered the abundance of ESR1 transcript variants by hypermethylation of ESR1 promoters. GHB3.5 decreased only ESR1-OS expression, whereas GBH350 affected ESR1-O, OT and E1 expression. Our results show that developmental exposure to GBH induces epigenetic changes in ESR1, which could be responsible for the altered male mammary gland development observed in GBH350-exposed animals.

Postnatal exposure to a glyphosate-based herbicide modifies mammary gland growth and development in Wistar male rats

Our aim was to evaluate whether postnatal exposure to a glyphosate-based herbicide (GBH) modifies mammary gland development in pre- and post-pubertal male rats. From postnatal day 1 (PND1) to PND7, male rats were injected subcutaneously every 48 h with either saline solution (vehicle) or 2 mg GBH/kg·bw. On PND21 and PND60, mammary gland and blood samples were collected. Estradiol (E2) and testosterone (T) serum levels, mammary gland histology, collagen fiber organization, mast cell infiltration, proliferation index, and estrogen (ESR1) and androgen receptor (AR) expression levels were evaluated. At PND21, GBH-exposed male rats exhibited greater development of the mammary gland with increased stromal collagen organization and terminal end buds (TEBs) compared to control rats. At PND60, the number of TEBs remained high and was accompanied by an increase in mast cell infiltration, proliferation and ESR1 expression in GBH-exposed male rats. In contrast, no effects were observed in E2 and T serum levels and AR expression in both days studied. Our results showed that a postnatal subacute treatment with GBH induces endocrine-disrupting effects in the male mammary gland in vivo, altering its normal development.

New insights into bisphenols removal by nitrogen-rich nanocarbons: Synergistic effect between adsorption and oxidative degradation

In this work, nitrogen-rich graphene-like carbon sheets (N-GLCS) with high specific surface area (488.4m²/g), narrow pore distribution and high N-doping (18.4 at%) were prepared and applied as both adsorbent and catalyst for the removal of bisphenols. Adsorption experiments demonstrated the high adsorption capacities of the N-GLCS toward bisphenol F (BPF) (222.9mg/g), bisphenol A (BPA) (317.8mg/g), and bisphenol C (BPC) (540.4mg/g). Results showed that about 98.6% of BPA (70mg/L) was removed at pH 7.0 within 80min after the adsorption-catalytic degradation process. The N-GLCS also showed a superb reusability for the catalytic oxidative degradation of BPA (70mg/L) with the removal percentage maintains over 83% after 5 cycles. With the synergistic combination of the excellent adsorption and catalytic properties of the N-GLCS, trace amount of pollutants can be preconcentrated and immobilized at the surface of N-GLCs, at the same time, active radicals were also produced at the surface of the N-GLCS by the activation of peroxydisulfate (PS), and finally the pollutants can be degraded in-situ by the active radicals. These findings provide a new avenue towards the efficient removal of trace-level EDCs from water solution by using the coupled adsorption-advanced oxidation processes.

Renal and hepatic effects following neonatal exposure to low doses of Bisphenol-A and 137Cs

137-Cesium (¹³⁷Cs) is one of the most important distributed radionuclides after a nuclear accident. Humans are usually co-exposed to various environmental toxicants, being Bisphenol-A (BPA) one of them. Exposure to IR and BPA in early life is of major concern, due to the higher vulnerability of developing organs. We evaluate the renal and hepatic effects of low doses of ionizing radiation (IR) and BPA. Sixty male mice (C57BL/6J) were randomly assigned to six experimental groups (n=10) and received a single subcutaneous dose of 0.9% saline solution, ¹³⁷Cs and/or BPA on postnatal day 10: control, BPA (25 μg/kgbw), Cs4000 (4000 Bq ¹³⁷Cs/kgbw), Cs8000 (8000 Bq ¹³⁷Cs/kgbw), BPA/Cs4000 and BPA/Cs8000. At the age of two months, urines (24h) and blood samples were collected from animals of each group to determine biochemical parameters. Finally, kidneys and liver were removed to quantify DNA damage (8-OHdG), as well as to determine CYP1A2 mRNA expression. Data suggest that both BPA and ¹³⁷Cs induced renal and liver damage evidenced by oxidative stress. However, when there is a co-exposure, it seems that there are compensatory mechanisms that may reverse the damage induced by each toxic itself. Notwithstanding, more studies are necessary to better understand the synergistic mechanisms behind.

Early postnatal exposure to endosulfan interferes with the normal development of the male rat mammary gland

Our aim was to evaluate whether postnatal exposure to endosulfan (ENDO) modifies mammary gland (MG) development in pre- and post-pubertal male rats. From postnatal day 1 (PND1) to PND7, male rats were injected subcutaneously every 48h with either corn oil (vehicle) or 600μg ENDO/kg.bw. On PND21 and PND60, MG and blood samples were collected. Estradiol (E2) and testosterone (T) serum levels, MG histology, collagen fiber organization, proliferation index, and estrogen (ESR1) and androgen receptor (AR) expressions were evaluated. On PND21, E2 and T levels were similar between groups, whereas MG area, perimeter, number of terminal end buds and ESR1 expression were increased in ENDO-exposed rats. These changes were associated with alveolar development and increased organized collagen in the stroma. On PND60, a higher proliferation index in ENDO-exposed rats was correlated with a more developed lobuloalveolar structure. Hyperplastic alveoli and, hyperplastic ducts surrounded by a dense stroma were also observed in this group. T levels and ESR1 expression were similar between groups, whereas E2 levels and AR expression were decreased in ENDO-exposed rats. The exposure to ENDO in the first week of life interferes with the normal development of the MG and induces pre-malignant lesions in post-pubertal male rats.

Differences in the Rate of in Situ Mammary Gland Development and Other Developmental Endpoints in Three Strains of Female Rat Commonly Used in Mammary Carcinogenesis Studies: Implications for Timing of Carcinogen Exposure

The potential of chemicals to alter susceptibility to mammary tumor formation is often assessed using a carcinogen-induced study design in various rat strains. The rate of mammary gland (MG) development must be considered so that the timing of carcinogen administration is impactful. In this study, in situ MG development was assessed in females of the Harlan Sprague-Dawley (Hsd:SD), Charles River Sprague-Dawley (Crl:SD), and Charles River Long-Evans (Crl:LE) rat strains at postnatal days 25, 33, and 45. Development was evaluated by physical assessment of growth parameters, developmental scoring, and quantitative morphometric analysis. Although body weight (BW) was consistently lower and day of vaginal opening (VO) occurred latest in female Hsd:SD rats, they exhibited accelerated pre- and peripubertal MG development compared to other strains. Glands of Crl:SD and Crl:LE rats exhibited significantly more terminal end buds (TEBs) and TEB/mm than Hsd:SD rats around the time of VO. These data suggest a considerable difference in the rate of MG development across commonly used strains, which is independent of BW and timing of VO. In mammary tumor induction studies employing these strains, administration of the carcinogen should be timed appropriately, based on strain, to specifically target the peak of TEB occurrence.

Low-dose effects of bisphenol A on mammary gland development in rats

Bisphenol A (BPA) is widely used in food contact materials, toys, and other products. Several studies have indicated that effects observed at doses near human exposure levels may not be observed at higher doses. Many studies have shown effects on mammary glands at low doses of BPA, however, because of small number of animals or few doses investigated these data have not been used by EFSA as point of departure for the newly assessed tolerable daily intake (TDI). We performed a study with perinatal exposure to BPA (0, 0.025, 0.25, 5, and 50 mg/kg bw/day) in rats (n = 22 mated/group). One of the aims was to perform a study robust enough to contribute to the risk assessment of BPA and to elucidate possible biphasic dose-response relationships. We investigated mammary gland effects in the offspring at 22, 100, and 400 days of age. Male offspring showed increased mammary outgrowth on pup day (PD) 22 at 0.025 mg/kg BPA, indicating an increased mammary development at this low dose only. Increased prevalence of intraductal hyperplasia was observed in BPA females exposed to 0.25 mg/kg at PD 400, but not at PD 100, and not at higher or lower doses. The present findings support data from the published literature showing that perinatal exposure to BPA can induce increased mammary growth and proliferative lesions in rodents. Our results indicate that low-dose exposure to BPA can affect mammary gland development in male and female rats, although higher doses show a different pattern of effects. The observed intraductal hyperplasia in female rats could be associated with an increased risk for developing hyperplastic lesions, which are parallels to early signs of breast neoplasia in women. Collectively, current knowledge on effects of BPA on mammary gland at low doses indicates that highly exposed humans may not be sufficiently protected.

EDC-2: The Endocrine Society's Second Scientific Statement on Endocrine-Disrupting Chemicals

The Endocrine Society's first Scientific Statement in 2009 provided a wake-up call to the scientific community about how environmental endocrine-disrupting chemicals (EDCs) affect health and disease. Five years later, a substantially larger body of literature has solidified our understanding of plausible mechanisms underlying EDC actions and how exposures in animals and humans-especially during development-may lay the foundations for disease later in life. At this point in history, we have much stronger knowledge about how EDCs alter gene-environment interactions via physiological, cellular, molecular, and epigenetic changes, thereby producing effects in exposed individuals as well as their descendants. Causal links between exposure and manifestation of disease are substantiated by experimental animal models and are consistent with correlative epidemiological data in humans. There are several caveats because differences in how experimental animal work is conducted can lead to difficulties in drawing broad conclusions, and we must continue to be cautious about inferring causality in humans. In this second Scientific Statement, we reviewed the literature on a subset of topics for which the translational evidence is strongest: 1) obesity and diabetes; 2) female reproduction; 3) male reproduction; 4) hormone-sensitive cancers in females; 5) prostate; 6) thyroid; and 7) neurodevelopment and neuroendocrine systems. Our inclusion criteria for studies were those conducted predominantly in the past 5 years deemed to be of high quality based on appropriate negative and positive control groups or populations, adequate sample size and experimental design, and mammalian animal studies with exposure levels in a range that was relevant to humans. We also focused on studies using the developmental origins of health and disease model. No report was excluded based on a positive or negative effect of the EDC exposure. The bulk of the results across the board strengthen the evidence for endocrine health-related actions of EDCs. Based on this much more complete understanding of the endocrine principles by which EDCs act, including nonmonotonic dose-responses, low-dose effects, and developmental vulnerability, these findings can be much better translated to human health. Armed with this information, researchers, physicians, and other healthcare providers can guide regulators and policymakers as they make responsible decisions.

Application of Sholl analysis to quantify changes in growth and development in rat mammary gland whole mounts

Studies that utilize the rodent mammary gland (MG) as an endpoint for assessing the developmental toxicity of chemical exposures typically employ either basic dimensional measurements or developmental scoring of morphological characteristics as a means to quantify MG development. There are numerous means by which to report these developmental changes, leading to inconsistent translation across laboratories. The Sholl analysis is a method historically used for quantifying neuronal dendritic patterns. The present study describes the use of the Sholl analysis to quantify MG branching characteristics. Using this method, we were able to detect significant differences in branching density in MG of peripubertal female Sprague Dawley rats that had been exposed to vehicle or a potent estrogen. These data suggest the Sholl analysis can be an effective tool for quantitatively measuring an important characteristic of MG development and for examining associations between MG growth and density and adverse effects in the breast.

Superovulation does not affect the endocrine activity nor increase susceptibility to carcinogenesis of uterine and mammary glands of female offspring in mice

PURPOSE

To evaluate the dual effects of superovulation on the endocrine activity and susceptibility to carcinogenesis of uterine and mammary glands of female offspring in mice

METHOD

The mice were superovaluted. The relative uterine weight, ERα protein expression, and endocrine activity of female offspring (F1 generation and F2 generation) were measured. Furthermore, proliferative lesion of uterine and mammary glands of female offspring (F1 generation and F2 generation) was assessed by histopathologic examinations.

RESULTS

There were no significant differences in relative uterine weight, ERα protein expression, incidence of proliferative lesion in mammary glands, and incidence of atypical hyperplasia, adenocarcinoma, and squamous metaplasia in uterine among the offspring (F1 generation and F2 generation) in each group. Likewise, there were no significant intergroup differences in the serum levels of sex related hormones.

CONCLUSIONS

No significant alterations were found in the endocrine activity and susceptibility to carcinogenesis of uterine and mammary glands of female offspring in mice produced by superovaluted oocytes compared with those of naturally conceived offspring.