Safeguarding Female Reproductive Health against Endocrine Disrupting Chemicals : The FREIA Project

Funding: This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement no. 825100.Peer reviewedPublisher PD

Mechanistic considerations for reduced endometrial cancer risk by smoking

This review provides mechanistic explanations on why smoking reduces endometrial cancer risk with the primary focus on polyaromatic hydrocarbons (PAHs). PAHs from cigarette smoke can activate aryl hydrocarbon receptor–mediated pathways. This leads to (i) increased levels of anticarcinogenic metabolites of estradiol, (ii) suppression of estrogen receptor (ER)–mediated actions, and (iii) induction of endometrial apoptosis. In addition, hydroxylated metabolites of PAHs may also evoke antitumor effects via the ER, specifically ERβ. The nuclear receptor expression profile in the human endometrium continuously changes throughout the menstrual cycle. In addition, endometrial apoptosis plays a fundamental role in the regulation of the menstrual cycle. The dynamic ER, progesterone receptor, and aryl hydrocarbon receptor expression together with the importance of apoptosis in the human endometrium likely explains the anticarcinogenic effect of PAHs from smoking on the endometrium as opposed to that on the mammary gland

Mechanistic considerations for reduced endometrial cancer risk by smoking

This review provides mechanistic explanations on why smoking reduces endometrial cancer risk with the primary focus on polyaromatic hydrocarbons (PAHs). PAHs from cigarette smoke can activate aryl hydrocarbon receptor–mediated pathways. This leads to (i) increased levels of anticarcinogenic metabolites of estradiol, (ii) suppression of estrogen receptor (ER)–mediated actions, and (iii) induction of endometrial apoptosis. In addition, hydroxylated metabolites of PAHs may also evoke antitumor effects via the ER, specifically ERβ. The nuclear receptor expression profile in the human endometrium continuously changes throughout the menstrual cycle. In addition, endometrial apoptosis plays a fundamental role in the regulation of the menstrual cycle. The dynamic ER, progesterone receptor, and aryl hydrocarbon receptor expression together with the importance of apoptosis in the human endometrium likely explains the anticarcinogenic effect of PAHs from smoking on the endometrium as opposed to that on the mammary gland

One TEF concept does not fit all: The case for human risk assessment of polychlorinated biphenyls

Human risk assessment of dioxins and dioxin-like compounds relies heavily on toxic equivalency factors (TEFs) that are mainly based on in vivo rodent studies. However, especially for the PCBs there are many uncertainties with respect to the actual dioxin-like activities and subsequent health effects in humans. For example, the relative effect potencies (REPs) for PCB126 are consistently up to two orders of magnitude lower in human cell models than in rodents and rodent cell cultures. For other dioxin-like (DL) PCBs, REPs can often not be obtained in human models due to a lack of AHR-mediated responses. In addition, DL-PCB-related effects such as thyroid disruption are largely attributed to mechanisms that are not (directly) AHR-mediated. Consequently, the AHR-mediated risk in humans for DL-PCBs is likely overestimated in the current TEF concept. The increasing availability of in vitro models using human cells will provide great opportunities to determine human-specific REP/TEFs based on toxicologically relevant endpoints. A better understanding of human-specific responses should lead to more reliable potency estimates of human effects and ultimately improved human risk assessment for DL-PCBs

Mechanistic considerations for reduced endometrial cancer risk by smoking

This review provides mechanistic explanations on why smoking reduces endometrial cancer risk with the primary focus on polyaromatic hydrocarbons (PAHs). PAHs from cigarette smoke can activate aryl hydrocarbon receptor–mediated pathways. This leads to (i) increased levels of anticarcinogenic metabolites of estradiol, (ii) suppression of estrogen receptor (ER)–mediated actions, and (iii) induction of endometrial apoptosis. In addition, hydroxylated metabolites of PAHs may also evoke antitumor effects via the ER, specifically ERβ. The nuclear receptor expression profile in the human endometrium continuously changes throughout the menstrual cycle. In addition, endometrial apoptosis plays a fundamental role in the regulation of the menstrual cycle. The dynamic ER, progesterone receptor, and aryl hydrocarbon receptor expression together with the importance of apoptosis in the human endometrium likely explains the anticarcinogenic effect of PAHs from smoking on the endometrium as opposed to that on the mammary gland

Conazole fungicides inhibit Leydig cell testosterone secretion and androgen receptor activation in vitro

Abstract Conazole fungicides are widely used in agriculture despite their suspected endocrine disrupting properties. In this study, the potential (anti-)androgenic effects of ten conazoles were assessed and mutually compared with existing data. Effects of cyproconazole (CYPRO), fluconazole (FLUC), flusilazole (FLUS), hexaconazole (HEXA), myconazole (MYC), penconazole (PEN), prochloraz (PRO), tebuconazole (TEBU), triadimefon (TRIA), and triticonazole (TRIT) were examined using murine Leydig (MA-10) cells and human T47D-ARE cells stably transfected with an androgen responsive element and a firefly luciferase reporter gene. Six conazoles caused a decrease in basal testosterone (T) secretion by MA-10 cells varying from 61% up to 12% compared to vehicle-treated control. T secretion was concentration-dependently inhibited after exposure of MA-10 cells to several concentrations of FLUS (IC50 = 12.4 μM) or TEBU (IC50 = 2.4 μM) in combination with LH. The expression of steroidogenic and cholesterol biosynthesis genes was not changed by conazole exposure. Also, there were no changes in reactive oxygen species (ROS) formation that could explain the altered T secretion after exposure to conazoles. Nine conazoles decreased T-induced AR activation (IC50s ranging from 10.7 to 71.5 μM) and effect potencies (REPs) were calculated relative to the known AR antagonist flutamide (FLUT). FLUC had no effect on AR activation by T. FLUS was the most potent (REP = 3.61) and MYC the least potent (REP = 0.03) AR antagonist. All other conazoles had a comparable REP from 0.12 to 0.38. Our results show distinct in vitro anti-androgenic effects of several conazole fungicides arising from two mechanisms: inhibition of T secretion and AR antagonism, suggesting potential testicular toxic effects. These effects warrant further mechanistic investigation and clearly show the need for accurate exposure data in order to perform proper (human) risk assessment of this class of compounds

Anti-tumor properties of methoxylated analogues of resveratrol in malignant MCF-7 but not in non-tumorigenic MCF-10A mammary epithelial cell lines

Resveratrol is a plant-derived polyphenol that is known for its anti-inflammatory and anti-tumorigenic properties in in vitro and in vivo models. Recent studies show that some resveratrol analogues might be more potent anti-tumor agents, which may partly be attributed to their ability to activate the aryl hydrocarbon receptor (AHR). Here, the anti-tumorigenic properties of resveratrol and structural analogues oxyresveratrol, pinostilbene, pterostilbene and tetramethoxystilbene (TMS) were studied in vitro, using in the malignant human MCF-7 breast cancer cell line and non-tumorigenic breast epithelial cell line MCF-10A. Cell viability and migration assays showed that methoxylated analogues of resveratrol are more potent anti-tumorigenic compounds than resveratrol and its hydroxylated analogue oxyresveratrol, with 2,3’,4,5’-tetramethoxy-trans-stilbene (TMS) being the most potent compound. TMS decreased MCF-7 tumor cell viability with 50% at 3.6 μM and inhibited migration with 37.5 ± 14.8% at 3 μM. In addition, TMS activated the AHR more potently (EC50 in a reporter gene assay 2.0 μM) and induced AHR-mediated induction of cytochrome P450 1A1 (CYP1A1) activity (EC50 value of 0.7 μM) more than resveratrol and the other analogues tested. Cell cycle analysis showed that TMS induced a shift in cell cycle status from the G1 to the G2/M phase causing a cell cycle arrest in the MCF-7 cells, while no effect of TMS was observed in the non-tumorigenic MCF-10A mammary epithelial cell line. Gene expression analysis showed that 3 μM TMS increased gene expression of CYP1A1 (289-fold), CYP1B1 (5-fold) and Nqo1 (2-fold), and decreased gene expression of IL-8 (3-fold) in MCF-7 cells. In MCF-10A cells, 10 μM TMS also increased gene expression of CYP1A1 (5-fold) and CYP1B1 (2-fold), but decreased gene expression of Nqo1 (1.4-fold) in contrast to MCF-7 cells. TMS displays more potent anti-tumorigenic properties and activates the AHR more effectively than resveratrol. In addition, this is the first study to show that TMS, but not resveratrol, selectively inhibits the cell cycle of breast tumor cells and not the non-tumorigenic cells. Our study provides more insight in the anti-tumor properties of the methoxylated analogues of resveratrol in breast cells in vitro

Experimental human placental models for studying uptake, transport and toxicity of micro- and nanoplastics

Micro- and nanoplastics (MNPs) are ubiquitous in the environment and have recently been found in human lungs, blood and placenta. However, data on the possible effects of MNPs on human health is extremely scarce. The potential toxicity of MNPs during pregnancy, a period of increased susceptibility to environmental insults, is of particular concern. The placenta provides a unique interface between maternal and fetal circulation which is essential for in utero survival and healthy pregnancy. Placental toxicokinetics and toxicity of MNPs are still largely unexplored and the limited studies performed up to now focus mainly on polystyrene particles. Practical and ethical considerations limit research options in humans, and extrapolation from animal studies is challenging due to marked differences between species. Nevertheless, diverse in vitro and ex vivo human placental models exist e.g., plasma membrane vesicles, mono-culture and co-culture of placental cells, placenta-on-a-chip, villous tissue explants, and placental perfusion that can be used to advance this research area. The objective of this concise review is to recapitulate different human placental models, summarize the current understanding of placental uptake, transport and toxicity of MNPs and define knowledge gaps. Moreover, we provide perspectives for future research urgently needed to assess the potential hazards and risks of MNP exposure to maternal and fetal health

Excessive levels of diverse phytoestrogens can modulate steroidogenesis and cell migration of KGN human granulosa-derived tumor cells

Abstract Phytoestrogens are plant-derived estrogen-like compounds that are increasingly used for their suggested health promoting properties, even by healthy, young women. However, scientific concerns exist regarding potential adverse effects on female reproduction. In this study, naringenin (NAR), 8-prenylnaringenin (8-PN), genistein (GEN), coumestrol (COU), quercetin (QUE) and resveratrol (RSV) up-regulated steroidogenic acute regulatory protein (StaR) mRNA levels in KGN human granulosa-like tumor cells. Most of the phytoestrogens tested also increased CYP19A1 (aromatase) mRNA levels via activation of ovary-specific I.3 and II promoters. Yet, only NAR (3 and 10 μM), COU (10 and 30 μM) and QUE (10 μM) also statistically significantly induced aromatase activity in KGN cells after 24 h. 8-PN, aromatase inhibitor letrozole and estrogen receptor antagonist ICI 182,780 concentration-dependently inhibited aromatase activity with IC50 values of 8 nM, 10 nM and 72 nM, respectively. Co-exposure with ICI 182,780 (0.1 μM) statistically significantly attenuated the induction of aromatase activity by QUE and COU, but not NAR. Cell cycle status and proliferation of KGN cells were not affected by any of the phytoestrogens tested. Nonetheless, the migration of KGN cells was significantly reduced with approximately 30% by COU, RSV and QUE and 46% by GEN at 10 μM, but not NAR and 8-PN. Our results indicate that phytoestrogens can affect various pathways in granulosa-like cells in vitro at concentrations that can be found in plasma upon supplement intake. This implies that phytoestrogens may interfere with ovarian function and caution is in place regarding the use of supplements with high contents of phytoestrogens