Conférences Lauréats Prix CIAPE

Vicki Marlatt – Présidente du Comité sur les initiatives et excellence en recherche.

Dr. Jennifer Adibi, Professor, University of Pittsburgh 

Résumé

Introduction: As a fetal endocrine organ, the placenta has a critical role in fetal reproductive tract development. Thus far, it has been proposed that placental human chorionic gonadotropin (hCG) and progesterone are causal determinants of fetal masculinization. Environmental chemicals, maternal stress and infections disrupt the expression of placental hormones and possibly with consequences for fetal development.
Methods: We employed a primary tissue model in which human placental and gonad tissues are minimally manipulated and grown long term in 3D at low oxygen. The placenta is dosed with endocrine disrupting chemicals (EDCs), and the conditioned media is placed on the fetal gonads. Secreted fetal testosterone is measured by RIA. Indirect and direct effects were calculated separately and jointly using mediation analysis. We sampled 15 placentas (6-12 weeks gestation) and 10 fetal testes (10-14 weeks gestation). Placental tissue (male and female) was dosed with mono-n-butyl phthalate (120 nM MnBP) and monobenzyl phthalate (60 nM MBzP). Placental mRNAs (CGA, CGB, PPARG, HSD3B1) and placental secreted hCG (alpha and beta subunits, hyperglycosylated hCG, intact hCG) and progesterone were measured by qPCR, IFMA and ELISA respectively. We assessed and controlled for variability between tissue samples, and variability due to gestational age, maternal age, BMI, and smoking.
Results: MnBP had stronger effects on CGA vs. CGB, the alpha and beta subunits respectively, of the same hCG protein. The effects of MnBP on CGA and CGB were opposite in direction, and they were also opposite in direction by sex of the cells. MnBP had a negative effect on CGA in male cells and a positive effect in female cells. Yet, MnBP had had a negative effect on CGA in male cells, and a positive effect in female cells. This finding was supported in part by effects on secreted proteins. In males only, placental CGA and hCG-alpha were associated with fetal secreted testosterone. In a mediation model, MnBP had a pro-androgenic effect on fetal testosterone when mediated by placental CGA and an anti-androgenic effect when mediated by CGB, or HSD3B1.
Conclusion: These paradoxes may hold important clues regarding placental-fetal steroidogenesis and endocrine disruption, how they occur, and how to measure them. In our data, we are pursuing opportunities to evaluate these insights through translation to epidemiologic studies in which we have measured exposures, placental biomarkers, and clinical endpoints causally related to fetal testosterone. 

Chloe Devoy, M.Sc. student at the University of Lethbridge

Résumé

The novel brominated flame retardant (BFR), 1,2,5,6-tetrabromocyclooctane (TBCO), is a replacement option for major use BFRs that are being phased out of usage due to concerns about toxicity. Little is currently known about the toxic effects of TBCO however, waterborne exposure has been demonstrated to induce toxicity in early life stage zebrafish (Danio rerio) and dietary exposure has been demonstrated to impair reproduction in Japanese Medaka (Oryzias latipes). Maternal transfer is a mechanism by which developing offspring can be exposed to toxicants. Objectives of this research were to investigate effects of maternally deposited TBCO on development and reproductive success in three generations of Japanese medaka (F1, F2, F3). Sexually mature fish (F0 generation) were fed either a control diet or a low (40.6 μg/g) or high (1034.4 μg/g) diet containing TBCO for 21 days and three generations of embryos were reared to determine reproductive performance. Once the F1, F2, and F3 generations reached sexual maturity, reproductive performance was assessed by use of a 21-day short term reproduction assay where fecundity and fertility were measured daily. Additionally, embryotoxicity was assessed during the final week of each reproduction assay. Molecular mechanism(s) of effect were investigated by use of enzyme-linked immunoassay (ELISA) and Quantitative Real-Time PCR. Concentrations of TBCO in eggs (F1 generation) from fish given the low and high diets were 711.3 and 2535.5 ng/g wet weight, respectively, confirming maternal transfer of TBCO. Embryotoxicity was evident in the F1 generation, but not the F2 or F3 generation. Cumulative fecundity of the F1 generation in the low and high treatment were reduced by 33.9% and 33.3%, respectively, compared to the control. In the F2 generation, cumulative fecundity of the low treatment returned to the level of the controls, but the high treatment was decreased by 29.8%. There was no decrease in cumulative fecundity in the F3 generation compared to controls. This research ultimately provides insight into the long-term effects of TBCO as its usage is poised to increase. Maternally deposited TBCO causes embryotoxicity, and also causes multigenerational, but not transgenerational decreases in fecundity of female Japanese medaka. Interestingly, recovery of fecundity was concentration dependent. Mechanistically, decreased fecundity was unlikely to have been caused by developmental reprogramming of steroidogenesis.

Dr. Aleksandra Buha Đorđević, Assistant Professor, University of Belgrade

Résumé

Reproductive disorders and infertility have recently become more common among the general population. Toxic metal(oid)s are known as endocrine disruptors and as they are widespread in nature, they may be linked to reproductive problems general population is facing nowadays. The first part of the study was conducted as a cross-sectional study and its aim was to examine the dose-response relationship between cadmium (Cd), arsenic (As), lead (Pb), mercury (Hg), chromium (Cr), and nickel (Ni) and serum hormone levels of testosterone in both sexes and luteinizing hormone (LH), and follicle-stimulating hormone (FSH) in men using the Benchmark dose approach (BMD). Blood samples were collected from 218 women and 217 men and digested in a microwave, and the levels of the tested metals were determined by atomic absorption spectrophotometry (AAS) or inductively coupled plasma-mass spectrometry (ICP-MS). The study found a dose-response relationship between all metals and hormones, with the narrowest BMD interval found for As-testosterone and Hg-testosterone in women and Cd-testosterone and Hg-LH pairs in men. Levels estimated to produce a 10% extra risk of testosterone serum level disturbances were lower than median levels measured in the general population, suggesting that exposure to toxic metal(oid)s may contribute to reproductive disorders and infertility.

To further investigate the effects of exposure to real-life mixtures of toxic metals on female reproductive function, an experimental study was conducted in rats. The study found changes in some parameters even after exposure to the lowest doses. The strongest dose-response relationship was found between LH and FSH and toxic metals after 28-day exposure and between sulfhydryl groups, ischemia-modified albumin, and Nrf2 and toxic metals levels after 90-day exposure. After 28-day exposure, changes could be observed in both prooxidants and antioxidants. However, after 90-day exposure, redox status imbalance was mainly caused by the disturbance of antioxidants.

Overall, the study suggests that exposure to toxic metals may contribute to reproductive disorders and infertility in both sexes, and prolonged exposure to real-life mixtures of toxic metals may have detrimental effects on female reproductive function. These findings highlight the need for further research to scale up the quality of collected data and possibly improve the existing regulations in the field.
This research was supported by the Science Fund of the Republic of Serbia, PROMIS, Grant No 6066532, DecodExpo.

Julie Robitaille, PhD student at Institut national de la recherche scientifique

Résumé

Endocrine disrupting chemicals (EDCs) are a type of chemicals which can interact with the hormonal system and generate adverse effects. The release of EDCs in aquatic environment can have important impact on wildlife by affecting reproduction, growth, and behaviour. Despite those known impacts, EDCs are still hardly regulated in freshwater around the world. Moreover, there is a need to move from traditional chemical monitoring to effect-based monitoring which uses bioanalytical tools or bioassays. Through this presentation, the use of bioassay for monitoring EDCs will be explored first by focusing on the strategy being developed for wastewater in the province of Quebec, Canada. In this strategy, wastewater sample would be evaluated for EDCs using a two-Tier bioassay-based approach. The first Tier of testing would be completely in vitro and composed of the transactivation assay for the receptor of estrogen (ER) and androgen (AR). The second Tier would be in vivo with the fish short-term reproduction assay in Pimephales promelas, which would only be use if a confirmation of effect is required. Results from current validation study using municipal wastewater will be presented. In the second part of the presentation, the process of developing policy recommendations for EDCs in freshwater for OECD countries will be discussed. Through the evaluation of country case studies, a conceptual framework is currently being created to guide regulators and other stakeholders in the development of a monitoring strategy for EDCs based on their need. The framework aims to inform on available choice for the design of a monitoring strategy, the monitoring methods, the ways to palliate uncertainties and the possible mitigation action. This works also highlights the need for international collaboration on various topics such as the standardization of methods and the development of bioassays for other endpoints.