Estrogenic Environmental Compounds Research Articles

Facile screening of potential xenoestrogens by an estrogen receptor-based reusable optical biosensor

The apparent increase in hormone-induced cancers and disorders of the reproductive tract has led to a growing demand for new technologies capable of screening xenoestrogens. We reported an estrogen receptor (ER)-based reusable fiber biosensor for facile screening estrogenic compounds in environment. The bioassay is based on the competition of xenoestrogens with 17β-estradiol (E2) for binding to the recombinant receptor of human estrogen receptor α (hERα) protein, leaving E2 free to bind to fluorophore-labeled anti–E2 monoclonal antibody. Unbound anti–E2 antibody then binds to the immobilized E2–protein conjugate on the fiber surface, and is detected by fluorescence emission induced by evanescent field. As expected, the stronger estrogenic activity of xenoestrogen would result in the weaker fluorescent signal. Three estrogen-agonist compounds, diethylstilbestrol (DES), 4-n-nonylphenol (NP) and 4-n-octylphenol (OP), were chosen as a paradigm for validation of this assay. The rank order of estrogenic potency determined by this biosensor was DES>OP>NP, which were consistent with the published results in numerous studies. Moreover, the E2–protein conjugate modified optical fiber was robust enough for over 300 sensing cycles with the signal recoveries ranging from 90% to 100%. In conclusion, the biosensor is reusable, reliable, portable and amenable to on-line operation, providing a facile, efficient and economical alternative to screen potential xenoestrogens in environment.

Characteristics and Risk Assessment of Estrogenic Compounds in Rivers of Southern Jiangsu Province, China

Significant attentions are rising for estrogenic compounds in environment, because their potential impacts on water ecosystem and human health. Estrogenic compounds (Estrone[E1], 17b-Estradiol[E2], Estriol[E3], 17a-Ethinylestradiol[EE2] and Bisphenol A [BPA]) in rivers of southern Jiangsu, China were investigated to realize their distributions and risks. The results showed E1, E2, E3 and BPA ranged from 1.96 to 143.29ng/L in rivers, with the detection rates from 12.5% to 100%. These estrogenic compounds in waters showed higher contents in winter than in spring and autumn. Levels of E1, E2 and E3 were higher in rivers nearby livestock breeding areas, while the concentrations of BPA were higher in the rivers nearby industrial areas. The risk assessment of estrogenic compounds were performed by the calculation of risk quotient (RQ) based on the predicted no effect concentration (PNEC), which was deduced through a species sensitivity distribution (SSD) model. The RQ values of E1, E2, E3 and BPA were 0.02∼1.87, 1.28∼23.22, 0.01∼0.80 and 0.03∼0.44 respectively. These results imply that harmful ecological effects might happen in some rivers. It indicates that different anthropogenic activities will lead to diverse inputs of estrogen compounds into rivers and pose different risks.

Effects of perinatal ethinyl estradiol exposure in male and female Wistar rats

Perinatal exposure to endocrine disrupting chemicals with estrogenic activity can adversely affect reproductive development, but few studies evaluating estrogen-sensitive endpoints have been performed in Wistar rats. Therefore, time-mated Wistar rats (n=10) were gavaged during gestation and lactation with 0, 5, 15 or 50μg/kg bw/day of ethinyl estradiol.This potent estrogen was found to induce an increased number of nipples and reduced ovary weight in female offspring. Malformations of female genitalia were found in young as well as adult offspring, as an increased AGD was seen at birth and a deeper urethral slit length was seen in adulthood. In prepubertal male offspring, estrogen-regulated gene expression in ventral prostate was increased dose-dependently and a decreased ventral prostate weight was seen at 15μg/kg.Female external sexual characteristics and prostate development were found to be targets for exposure to estrogenic compounds and may be of interest in studies on estrogenic environmental compounds.

Redox sensitive Pyk2 as a target for therapeutics in breast cancer

Breast cancer progression is dependent on the formation of new blood vessels that not only help the tumor by supplying additional nutrients, but also allow cancer cells to spread from the breast to distant sites in the body. Several studies suggest a positive correlation between new vessel formation and estrogens. Estrogenic environmental chemicals such as PCBs have been shown to increase the expression of factors known to promote vessel formation in breast tumors. These studies highlight a growing concern that women exposed to estrogenic environmental compounds may be more susceptible to either aggressive metastatic tumors or a high recurrence of breast cancer. Our concept offers a fundamental new understanding of the way the environment contributes to breast cancer progression. This review will be focused on a highly novel Pyk2 signaling complex as a target for therapy of estrogen dependent breast tumor angiogenesis. A better understanding of the role of Pyk2 signaling in estrogen dependent tumor vascularization may lead to the development of a new therapy against aggressive breast cancer using small molecule inhibitors of Pyk2.

Gene expression profile of endothelial cells exposed to estrogenic environmental compounds: Implications to pulmonary vascular lesions

Aims The cardiovascular system is an important target of estrogenic compounds. Considering the recent studies that question previously reported cardio-protective effects of estrogen, there is a growing concern that estrogenic environmental compounds may contribute to the pathology of vascular lesion formation. Main methods Real-time quantitative PCR was used to monitor the expression of genes involved in vascularization. Using Bayesian network modeling, we determined a gene network that estrogenic chemicals modulate in human vascular endothelial cells. Key findings We showed that planar and coplanar polychlorinated biphenyls (PCBs) induce the expression of different genes compared to estradiol. Non-planar PCB congener 153 induced NOTCH3 which is a new finding as well as CCL2 and IL8 similar to what has been reported by other non-planar PCBs in endothelial cells. Our gene network indicated that experimental treatments signal a network containing TGF-β receptor and NOTCH3; molecules biologically relevant to signaling pulmonary vascular lesions. Significance We report in the present study that exposure of vascular endothelial cells to environmentally relevant concentrations of estrogenic PCBs induce gene networks implicated in the process of inflammation and adhesion. Our data suggest that PCBs can promote vascular lesion formation by activating gene networks involved in endothelial cell adhesion, cell growth, and pro-inflammatory molecules which were different from natural estrogen. Since inflammation and adhesion are a hallmark in the pathology of endothelial cell dysfunction, reconstructing gene networks provide insight into the potential mechanisms that may contribute to the vascular risks associated with estrogenic environmental chemicals.

Estrogen and xenoestrogens in breast cancer.

There is growing concern that estrogenic environmental compounds that act as endocrine-disrupting chemicals might potentially have adverse effects on hormone-sensitive organs such as the breast. This concern is further fueled by evidence indicating that natural estrogens, specifically 17beta-estradiol, are important factors in the initiation and progression of breast cancer. We have developed an in vitro-in vivo model in which we have demonstrated the carcinogenicity of E2 in human breast epithelial cells MCF-10F. Hypermethylation of NRG1, STXBP6, BMP6, CSS3, SPRY1, and SNIP were found at different progression stages in this model. The use of this powerful and unique model has provided a tool for exploring whether bisphenol A and butyl benzyl phthalate have relevance in the initiation of breast cancer. These studies provide firsthand evidence that the natural estrogen 17beta-estradiol and xenoestrogenic substances like bisphenol A are able to induce neoplastic transformation in human breast epithelial cells.

Possible enhancing effects of atrazine and nonylphenol on 7,12‐dimethylbenz[a]anthracene‐induced mammary tumor development in human c‐Ha‐ras proto‐oncogene transgenic rats

Our transgenic (Tg) strain carrying copies of the human c-Ha-ras proto-oncogene is highly susceptible to 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary carcinogenesis, possibly due to activation of the transgene, and can be used in medium-term bioassay models to test for modifying effects of estrogenic environmental compounds on tumor development. The present study was conducted to assess the influence of dietary feeding of the endocrine disruptors atrazine and nonylphenol on DMBA-induced carcinogenesis in c-Ha-ras Tg rats. Animals of both sexes were given a single oral dose of DMBA (25 mg/kg body weight) at 50 days of age and thereafter received soybean-free diet containing 5, 50 or 500 ppm atrazine, or 10, 25, 100 or 250 ppm nonylphenol. In female Tg rats, atrazine at a dose of 5 ppm increased the incidences of mammary adenomas and adenocarcinomas (P < 0.01 and P < 0.05), while 50 ppm increased the adenocarcinoma incidence (P < 0.05). In males, skin tumor development, in contrast, was significantly decreased at the highest dose. Nonylphenol at 10 ppm increased adenocarcinoma and total mammary tumor multiplicity in female Tg rats (P < 0.05), but there was no dose dependence, a significant quadratic dose-response trend rather being observed (P < 0.05). In vitro, atrazine did not cause proliferation of MCF-7 cells at any of a range of doses tested. These results suggest that endocrine disruptors may enhance mammary carcinogenesis, but only in a certain limited dose range under the present experimental conditions. The doses applied, moreover, were all extremely high compared to the possible environmental human exposure levels.

Identification of Estrogen-Responsive Genes by Complementary Deoxyribonucleic Acid Microarray and Characterization of a Novel Early Estrogen-Induced Gene:EEIG1

Estrogen receptors (ERs) are nuclear transcription factors that regulate gene expression in response to estrogen and estrogen-like compounds. Identification of estrogen-regulated genes in target cells is an essential step toward understanding the molecular mechanisms of estrogen action. Using cDNA microarray examinations, 19 genes were identified as induced by 17 beta-estradiol in MCF-7 cells, 10 of which have been reported previously to be estrogen responsive or to be linked with ER status. Five known estrogen-regulated genes, E2IG4, IGFBP4, SLC2A1, XBP1 and B4GALT1, and AFG3L1, responded quickly to estrogen treatment. A novel estrogen-responsive gene was identified and named EEIG1for early estrogen-induced gene 1. EEIG1 was clearly induced by 17 beta-estradiol within 2 h of treatment, and was widely responsive to a group of estrogenic compounds including natural and synthetic estrogens and estrogenic environmental compounds. EEIG1 was expressed in ER-positive but not in ER-negative breast cancer cell lines. EEIG1 expression was repressed by antiestrogens 4-OH-tamoxifen and ICI 182,780 but not by protein synthesis inhibitors cycloheximide and puromycin. These results provide evidence that some estrogenic compounds differentially enhance the transcription of estrogen-regulated genes and suggest a role for EEIG1 in estrogen action.

Inhibitory effects of 17beta-estradiol and 4-n-octylphenol on 7,12-dimethylbenz[a]anthracene-induced mammary tumor development in human c-Ha-ras proto-oncogene transgenic rats.

Experiments were conducted to determine whether the natural estrogen and an environmental compound with estrogenic action, 4-n-octylphenol (4nOP), could modify tumor development in human c-Ha-ras proto-oncogene transgenic (Tg) rats which are highly susceptible to mammary and skin carcinogens. Female and male Tg and non-transgenic (non-Tg) rats were given a single oral dose of 7,12-dimethylbenz[a]anthracene (DMBA) (25 mg/kg body weight) at 50 days of age and thereafter subcutaneously implanted with cholesterol pellets containing 0.01, 0.1 or 1.0 mg beta-estradiol 3-benzoate (E2) per rat or received diets containing 1000 or 100 p.p.m. 4nOP for 12 weeks in females or for 20 weeks in males. E2 reduced the mammary tumor incidence and multiplicity in a dose dependent manner, especially in female Tg rats. In contrast, E2 increased mammary tumor incidence and multiplicity at the lowest dose (0.01 mg), however it reduced skin tumor induction in male Tg rats. 4nOP at a dose of 100 p.p.m. decreased mammary tumor multiplicity in female Tg rats (P < 0.001). No effects were observed in males. In separate in vitro studies, E2 at low doses (10(-11)-10(-8) M) enhanced the growth of both MCF-7 and T47D cells and this was similarly the case for 4nOP at high doses (10(-7)-10(-5) M) in T47D cells. The finding that E2 and 4nOP at high doses caused reduction in mammary tumor development in female Tg and possibly non-Tg rats, may indicate that excess estrogen can exert a paradoxical inhibitory influence. E2 also appears to have bipotential effects in males, promoting mammary, but inhibiting skin carcinogenesis. These contrasting observations may be caused by differences in background physiological estrogen levels. In addition, the results suggest that Tg rats can be used in medium-term bioassay models to test for the modifying effects of estrogenic environmental compounds on mammary tumor development.