The physiological role of estrogen receptor functional domains

Estrogen receptor (ER) is a member of the nuclear receptor superfamily whose members share conserved domain structures, including a DNA-binding domain (DBD) and ligand-binding domain (LBD). Estrogenic chemicals work as ligands for activation or repression of ER-mediated transcriptional activity derived from two transactivation domains: AF-1 and AF-2. AF-2 is localized in the LBD, and helix 12 of the LBD is essential for controlling AF-2 functionality. The positioning of helix 12 defines the ER alpha (ERα) ligand properties as agonists or antagonists. In contrast, it is still less well defined as to the ligand-dependent regulation of N-terminal AF-1 activity. It has been thought that the action of selective estrogen receptor modulators (SERMs) is mediated by the regulation of a tissue specific AF-1 activity rather than AF-2 activity. However, it is still unclear how SERMs regulate AF-1 activity in a tissue-selective manner. This review presents some recent observations toward information of ERα mediated SERM actions related to the ERα domain functionality, focusing on the following topics. (1) The F-domain, which is connected to helix 12, controls 4-hydroxytamoxifen (4OHT) mediated AF-1 activation associated with the receptor dimerization activity. (2) The zinc-finger property of the DBD for genomic sequence recognition. (3) The novel estrogen responsive genomic DNA element, which contains multiple long-spaced direct-repeats without a palindromic ERE sequence, is differentially recognized by 4OHT and E2 ligand bound ERα transactivation complexes.

The male mammary gland: a novel target of endocrine disrupting chemicals

In the past several decades, the incidence of two male breast diseases, gynecomastia and male breast cancer, have increased in human populations. Whereas male breast cancer remains a rare disease, gynecomastia, a condition that arises due to abnormal development and growth of the male breast epithelium, is fairly common. In this review, we present the male mouse mammary gland as a potential model to understand human male breast diseases. Even though the male mouse typically lacks nipples, the male retains a small mammary rudiment with epithelium that is highly sensitive to estrogenic chemicals during the perinatal and peripubertal periods. In just the last few years, our understanding of the biology of the male mouse mammary gland has expanded. Researchers have characterized the complexity and size of the male mammary epithelium across the life course. Studies have documented that the male mouse mammary gland has left-right asymmetric morphologies, as well as asymmetries in the responsiveness of the left and right glands to estrogens. Recent studies have also revealed that the effect of xenoestrogens on the male mammary gland can differ based on the timing of evaluation (prior to puberty, in puberty, and in adulthood) and the administered dose. Based on the available evidence, we argue that there is a strong case that estrogenic chemicals promote the growth of the male mouse epithelium, consistent with human gynecomastia. We also argue that these outcomes should be characterized as adverse effects and should be considered in regulatory decision-making.

Endocrine-Disrupting Chemicals: Brain–Behavior Effects on Thyroid and Sexual Differentiation

The human population is exposed to literally hundreds of industrial chemicals. Studies show that, on average, there are well over 100 industrial chemicals in cord blood samples taken from babies born in the United States. This observation may be disregarded if it were not for solid—and growing—evidence that many of these chemicals interfere with hormone systems that play important roles in human brain development. For example, thyroid hormone is known to be essential for normal brain development and the human brain is much more sensitive to thyroid hormone insufficiency than believed 50 years ago. Chemicals such as perchlorate, polychlorinated biphenyls, and polybrominated flame retardants are associated with cognitive deficits in humans, and the experimental literature reveals a complex interaction with the thyroid system that can account for these effects. Likewise, estrogenic chemicals like bisphenol A (BPA) can affect the development of many organ systems, including sexually dimorphic regions of the brain. There is now convincing evidence that even slight perturbations in hormonal systems caused by endocrine-disrupting chemicals can impact brain development, reducing cognitive function and gender-specific behaviors throughout the remainder of life. The consequences of such chronic exposures at low doses typical of human exposures had, until relatively recently, not been appreciated due to safety testing strategies that are designed to identify overt toxicities, not endocrine disruption and its consequences.

Determination of the Estrogenic Activity of Coffee Extract Solutions Prepared from Capsule Coffee Using the BG1Luc4E2 Assay

Objectives Estrogenic chemicals (ECs) possess estrogenic activity (EA) which can have harmful effects on the reproductive system. Coffee is known to have estrogenic potency due to its natural phytoestrogens, but coffee prepared from plastic capsules (capsule coffee) may increase exposure to ECs and consequently increase EA, potentially increasing risk to reproductive health. The objective of this study was to determine the EA of capsule coffee extract solutions in vitro. Methods Six varieties of capsule coffee and two varieties of coffee prepared from whole beans using a stainless-steel French press were first brewed then concentrated and extracted. The BG1Luc4E2 assay was then conducted to determine the EA of the coffee extracts. The normalized EA (% RME2) of the coffee extracts was determined as the relative estrogenic potency compared to the maximum normalized EA of the positive control 17β-estradiol (set to 100 % RME2). EA was determined if at least one data point on the concentration-response curve was above 15% RME2 and confirmed via inhibition with the estrogen receptor antagonist ICI 182,780. The correlation between the EA estimated by the BG1Luc4E2 assay and the estrogenic potential (EEQ) was determined with Spearman's rank correlation coefficient. Results All eight coffee extract solutions tested positive for EA and results were confirmed by their complete inhibition with ICI. The level of EA for the six capsule coffee extracts ranged from 48 to 56 % RME2, while the level of EA for the two coffee varieties prepared from whole beans were 40 and 42 % RME2. There was a significant correlation between EA and EEQ was (ρ = 0.8857, P = 0.0333). Conclusions These results indicate that the EAs of capsule coffees were higher than that of coffee prepared from a plastic-free method and that the EA measured in an in vitro model was correlated with the calculated estrogenic potential of the coffee extract's EC contents. Future studies are warranted in in vivo models as well as in humans as tests of estrogenic potency in vitro do not necessarily predict the effects in living organisms. Funding Sources This study was supported by the National Institutes of Health.

Identification and Quantification of Estrogenic Chemicals in Coffee Prepared from Capsules Using Ultra-Performance Liquid Chromatography with Tandem Mass Spectrometry

Objectives Estrogenic chemicals (ECs) are harmful compounds that can leach from plastic, particularly when under high temperature or pressure. Capsule coffee, coffee brewed from a single-serve coffee machine using a pre-packed plastic capsule, is becoming popular but there are concerns that it may increase exposure to ECs. Therefore, the objective of this study was to identify and quantify the ECs in capsule coffee extracts and compare them to the ECs present in coffee extracts prepared using a method devoid of plastic. Methods Twenty-two top-selling varieties of plastic capsule coffee from 4 popular brands were brewed and 15 equivalent varieties of whole bean and ground coffee were brewed using a stainless-steel French press and used as controls. ECs were then extracted from the capsule samples and controls with liquid-liquid extraction. The ultra-performance liquid chromatography with tandem mass spectrometry analytical method was used to identify and quantify ECs in coffee extracts after testing its validity. Results Benzophenone was the most frequently detected EC among the 22 capsule coffee samples, evident in six samples, followed by bisphenol A (four), dibutyl phthalate (three), 4-nonylphenol (three) and bisphenol F (two). Di(2-ethylhexyl) phthalate, caprolactam, bisphenol S and dimethyl terephthalate were either not detected or detected in quantities below the method detection limit. In seven instances the concentration of ECs in capsule coffees was greater than that of coffee prepared from the French press while in five instances the opposite trend was observed. The total exposure to ECs from either capsule coffee or coffee prepared from the French press was well below that of safety guidelines. Conclusions These results indicate that consuming plastic capsule coffee likely increases exposure to ECs compared to coffee brewed without plastic. Future studies are needed to evaluate the estrogenic activities of capsule coffee in vitro and determine whether EC content is a valid predictor of estrogenic activity. Funding Sources This study was supported by the National Institutes of Health.

SAT-732 Historical Occurrence of Intersex in Largemouth Bass (Micropterus Salmoides) and Smallmouth Bass (Micropterus Dolomieu)

The widespread occurrence of gonadal intersex (presence of testicular oocytes) has been recently reported in populations of Largemouth Bass (Micropterus salmoides) and Smallmouth Bass Micropterus dolomieu) from populations across North America. To evaluate the historical occurrence of intersex in bass species, gonads were examined visually and histologically from Largemouth Bass and Smallmouth Bass from museum specimens collected from 16 States. These fishes were collected between 1823-1965, before the widespread discharge of estrogenic chemicals to surface waters via wastewater effluents. All females examined had normal ovaries. Intersex gonads were identified in 17.8 % of male Largemouth Bass, and in 14.2% of male Smallmouth Bass. The intensity of testicular oocytes in some males was as great as observed since 2000. These results indicate that the occurrence of this form of intersex in these bass species is not a recent phenomenon.