Thomson Paisley, Langlois Valerie S
School of Environmental Studies, Queen's University, Kingston, ON, Canada.
School of Environmental Studies, Queen's University, Kingston, ON, Canada; Institut national de la recherche scientifique - Centre Eau Terre Environnement (INRS-ETE), Quebec City, QC, Canada; Department of Chemistry and Chemical Engineering, Royal Military College of Canada, Kingston, ON, Canada.
Gen Comp Endocrinol. 2018 Sep 1;265:4-14. doi: 10.1016/j.ygcen.2018.05.017. Epub 2018 May 18.
Environmental gestagens are an emerging class of contaminants that have been recently measured in surface water and can interfere with reproduction in aquatic vertebrates. Gestagens include endogenous progestogens, such as progesterone (P4), which bind P4-receptors and have critically important roles in vertebrate physiology and reproduction. Gestagens also include synthetic progestins, which are components of human and veterinary drugs, such as melengestrol acetate (MGA). Endogenous progestogens are essential in the regulation of reproduction in mammalian species, but the role of P4 in amphibian larval development remains unclear. This project aims to understand the roles and the regulatory mechanisms of P4 in amphibians and to assess the consequences of exposures to environmental gestagens on the P4-receptor signaling pathways in frogs. Here, we established the developmental profiles of the P4 receptors: the intracellular progesterone receptor (ipgr), the membrane progesterone receptor β (mpgrβ), and the progesterone receptor membrane component 1 (pgrmc1) in Western clawed frog (Silurana tropicalis) embryos using real-time qPCR. P4-receptor mRNAs were detected throughout embryogenesis. Transcripts for ipgr and pgrmc1 were detected in embryos at Nieuwkoop and Faber (NF) stage 2 and 7, indicative of maternal transfer of mRNA. We also assessed the effects of P4 and MGA exposure in embryonic and early larval development. Endocrine responses were evaluated through transcript analysis of a suite of gene targets of interest, including: ipgr, mpgrβ, pgrmc1, androgen receptor (ar), estrogen receptor α (erα), follicle stimulating hormone β (fshβ), prolactin (prl), and the steroid 5-alpha reductase family (srd5α1, 2, and 3). Acute exposure (NF 12-46) to P4 caused a 2- to 5-fold change increase of ipgr, mpgrβ, pgrmc1, and ar mRNA levels at the environmentally relevant concentration of 195 ng/L P4. Acute exposure to MGA induced a 56% decrease of srd5α3 at 1140 ng/L MGA. We conclude that environmental exposure to P4 induced multiple endocrine-related transcript responses in amphibians; however, the differential responses of MGA suggest that the effects of MGA are not mediated through the classical P4 signaling pathway in S. tropicalis.
环境孕类激素是一类新出现的污染物，最近在地表水中检测到，并且会干扰水生脊椎动物的繁殖。孕类激素包括内源性孕激素，如孕酮（P4），它能与P4受体结合，在脊椎动物生理和繁殖过程中发挥至关重要的作用。孕类激素还包括合成孕激素，它们是人和兽药的成分，如醋酸美仑孕酮（MGA）。内源性孕激素对哺乳动物物种的繁殖调节至关重要，但P4在两栖动物幼体发育中的作用仍不清楚。本项目旨在了解P4在两栖动物中的作用和调节机制，并评估暴露于环境孕类激素对青蛙P4受体信号通路的影响。在此，我们使用实时定量PCR建立了西方爪蟾（热带爪蟾）胚胎中P4受体的发育图谱：细胞内孕酮受体（ipgr）、膜孕酮受体β（mpgrβ）和孕酮受体膜成分1（pgrmc1）。在整个胚胎发育过程中都检测到了P4受体的mRNA。在Nieuwkoop和Faber（NF）2期和7期的胚胎中检测到了ipgr和pgrmc1的转录本，这表明mRNA存在母体传递现象。我们还评估了P4和MGA暴露对胚胎和幼体早期发育的影响。通过对一系列感兴趣的基因靶点进行转录本分析来评估内分泌反应，这些靶点包括：ipgr、mpgrβ、pgrmc1、雄激素受体（ar）、雌激素受体α（erα）、促卵泡激素β（fshβ）、催乳素（prl）以及类固醇5-α还原酶家族（srd5α1、2和3）。在环境相关浓度195 ng/L的P4下急性暴露（NF 12 - 46）会导致ipgr、mpgrβ、pgrmc1和ar mRNA水平增加2至5倍。在1140 ng/L的MGA下急性暴露会导致srd5α3减少56%。我们得出结论，环境暴露于P4会在两栖动物中诱导多种与内分泌相关转录本的反应；然而，MGA的不同反应表明MGA的作用不是通过热带爪蟾中的经典P4信号通路介导的。
