Per- and polyfluoroalkyl substances (PFASs) - New endocrine disruptors in polar bears (Ursus maritimus)?
Per- and polyfluoroalkyl substances (PFASs) are emerging in the Arctic and accumulate in brain tissues of East Greenland (EG) polar bears. In vitro studies have shown that PFASs might possess endocrine disrupting abilities and therefore the present study was conducted to investigate potential PFAS induced alterations in brain steroid concentrations. The concentrations of eleven steroid hormones were determined in eight brain regions from ten EG polar bears. Pregnenolone (PRE), the dominant progestagen, was found in mean concentrations of 5-47ng/g (ww) depending on brain region. PRE showed significantly (p<0.01) higher concentrations in female compared to male bears. Dehydroepiandrosterone (DHEA) found in mean concentrations 0.67-4.58ng/g (ww) was the androgen found in highest concentrations. Among the estrogens estrone (E1) showed mean concentrations of 0.90-2.21ng/g (ww) and was the most abundant. Remaining steroid hormones were generally present in concentrations below 2ng/g (ww). Steroid levels in brain tissue could not be explained by steroid levels in plasma. There was however a trend towards increasing estrogen levels in plasma resulting in increasing levels of androgens in brain tissue. Correlative analyses showed positive associations between PFASs and 17α-hydroxypregnenolone (OH-PRE) (e.g. perflouroalkyl sulfonates (∑PFSA): p<0.01, r=0.39; perfluoroalkyl carboxylates (∑PFCA): p<0.01, r=0.61) and PFCA and testosterone (TS) (∑PFCA: p=0.03, r=0.30) across brain regions. Further when investigating correlative associations in specific brain regions significant positive correlations were found between ∑PFCA and several steroid hormones in the occipital lobe. Correlative positive associations between PFCAs and steroids were especially observed for PRE, progesterone (PRO), OH-PRE, DHEA, androstenedione (AN) and testosterone (TS) (all p≤0.01, r≥0.7). The results from the present study generally indicate that an increase in PFASs concentration seems to concur with an increase in steroid hormones of EG polar bears. It is, however, not possible to determine whether alterations in brain steroid concentrations arise from interference with de novo steroid synthesis or via disruption of peripheral steroidogenic tissues mainly in gonads and feedback mechanisms. Steroids are important for brain plasticity and gender specific behavior as well as postnatal development and sexually dimorph brain function. The present work indicates an urgent need for a better mechanistic understanding of how PFASs may affect the endocrine system of polar bears and potentially other mammal species.
Toxicology Laboratory, Section of Advanced Drug Analysis, Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark. Electronic address: kep@plen.ku.dk.
Kathrine Eggers
KE
Pedersen
Wildlife and Landscape Science Directorate, Science and Technology Branch, Environment and Climate Change Canada, National Wildlife Research Centre, Carleton University, Ottawa, ON K1A 0H3, Canada.
Robert J
RJ
Letcher
Aarhus University, Faculty of Science and Technology, Department of Bioscience, Arctic Research Centre, P.O. Box 358, Roskilde DK-4000, Denmark.
Christian
C
Sonne
Aarhus University, Faculty of Science and Technology, Department of Bioscience, Arctic Research Centre, P.O. Box 358, Roskilde DK-4000, Denmark.
Rune
R
Dietz
Toxicology Laboratory, Section of Advanced Drug Analysis, Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark.
Bjarne
B
Styrishave
D000476:Alkanesulfonates; D000818:Animals; D001110:Arctic Regions; D001921:Brain / Q000187:drug effects* / Q000378:metabolism; D001923:Brain Chemistry / Q000187:drug effects; D002264:Carboxylic Acids; D052244:Endocrine Disruptors / Q000032:analysis / Q000378:metabolism / Q000633:toxicity*; D004784:Environmental Monitoring; D004785:Environmental Pollutants / Q000009:adverse effects / Q000032:analysis / Q000378:metabolism; D005260:Female; D006116:Greenland; D006728:Hormones / Q000378:metabolism*; D006845:Hydrocarbons, Fluorinated / Q000032:analysis / Q000378:metabolism / Q000633:toxicity*; D008297:Male; D013256:Steroids / Q000378:metabolism*; D001503:Ursidae / Q000378:metabolism*
D000476:Alkanesulfonates; D002264:Carboxylic Acids; D052244:Endocrine Disruptors; D004785:Environmental Pollutants; D006728:Hormones; D006845:Hydrocarbons, Fluorinated; D013256:Steroids
Arctic pollution; Brain; Endocrine disruption; PFAS; Perfluorinated substances; Steroid hormones