Multiple Environmental Stressors: Biological Interactions Between Parameters of Climate Change and Perfluorinated Alkyl Substances in Fish
Doctoral thesis
Permanent lenke
http://hdl.handle.net/11250/2386492Utgivelsesdato
2016Metadata
Vis full innførselSamlinger
- Institutt for biologi [2596]
Sammendrag
Aquatic organisms continuously acclimatize to fluctuations in environment parameters and
contaminant insult. The aim of this thesis was to investigate effects of combined exposure to
quantifiable measures of climate change (hypercapnia and hypoxia) and perfluorinated alkyl
substances (PFASs) on oxidative stress, lipid homeostasis and endocrine disruption in fish. The thesis
consists of four papers (Paper I-IV). In Paper I and II, Atlantic cod (Gadus morhua) juveniles was
exposed to perfluorooctane sulfonic acid (PFOS) (0, 100 or 200 μg/L) 1 H/day for 5 days, followed by
exposure to different concentrations of carbon dioxide (CO2) (848, 2735 or 7963 ppm). Sampling was
performed 3, 6 and 9 days after initiated CO2 exposure. We observed interactions between PFOS and
CO2 exposure on transcription of gill glutathione peroxidase 1 (GPx1), gill manganese superoxide
dismutase (MnSOD) and liver phosphatidylethanolamine N-methyltransferase (PEMT) (Paper I).
Peroxisome proliferator-activated receptor β (PPAR-β) was increased in cod liver by CO2, and the
response was higher in the presence of PFOS (Paper I). In Paper II, PCA-biplots showed clustering of
samples based on CO2 concentration, and the distribution of response parameters indicated that
hypercapnia was the main driver of hormone responses. Changes in estradiol-17β (E2), testosterone
(T) and 11-ketotestosterone (11-KT) levels and E2-responsive genes were increased by hypercapnia
alone at day 3 and 9, and by combined exposure scenarios (Paper II). Hypercapnia increased
cytochrome P450 1A (CYP1A) mRNA alone and in combination with PFOS (Paper II). In Paper III and
IV, primary Atlantic salmon (Salmo salar) hepatocytes were exposed to perfluorooctane sulfonamide
(PFOSA) (0, 25 and 50 μM) singly, and in combination with hypoxia-inducible compounds (cobalt
chloride: CoCl2 and deferoxamine: DFO) for 24 and 48 h. We observed that combined exposure
generally altered the transcription of antioxidant responses and lipid regulation, showing higher
effect of hypoxia, compared to PFOSA (PCA-plots Paper III-IV). Hypoxic condition alone, and in
combination with PFOSA, increased transcription of E2-responsive genes, CYP1A and CYP3A
responses (Paper III). Transcription of PPAR-α, -β and –γ, and the ω6:ω3 ratio was increased by DFO
and these responses were modulated in the presence of PFOSA (Paper IV). In addition, we observed
a parallel increase of hypoxia-inducible factor 1α (HIF-1α), acyl coenzyme A oxidase (ACOX) and
PPAR-γ, indicating a link between lipid metabolism and hypoxic responses (Paper IV). Changes in
PPAR system and FA β-oxidation (ACOD and ACOX) suggests complex changes in the regulation of
lipid homeostasis and FA metabolism, where PFASs modulated the responses produced by
hypercapnia or hypoxia alone (Paper I and IV). Changes in the composition of ω6 and ω3 FAs in
salmon hepatocytes and reduced PEMT transcription in cod liver were observed (Paper I and IV),
indicating that climate change variables alone and in combination with PFASs may potentially alter
membrane lipid composition and possibly produce overt physiological consequences. These studies
indicate that parameters of climate change and PFASs affect sex steroids, E2-responsive genes and
the CYP system, and that combined exposure generally produced higher response than single
exposure (Paper II and III). These findings show that processes involved in endocrine signaling and
biotransformation are very complex and hard to predict due to biphasic responses and possibly
interaction between stressors. This thesis provides new and valuable insight on the combined effects
of quantifiable parameters of climate change and environmental pollutants. Potential interaction
between environmental stressors and the relevance of considering exposure duration were
revealed, emphasizing the importance of investigating combined and chronic exposure scenarios
Består av
Paper 1: Oxidative stress and lipid regulation in cod liver and gills after exposure to carbon dioxide (CO2) and perfluorooctane sulfonic acid (PFOS), given singly or in combination. - Is not included due to copyrightPaper 2: Preus-Olsen, Gunnhild; Olufsen, Marianne Opsahl; Pedersen, Sindre Andre; Letcher, RJ; Arukwe, Augustine. Effects of elevated dissolved carbon dioxide and perfluorooctane sulfonic acid, given singly and in combination, on steroidogenic and biotransformation pathways of atlantic cod. Aquatic Toxicology 2014 ;Volum 155. s. 222-235 http://dx.doi.org/10.1016/j.aquatox.2014.06.017 This article is reprinted with kind permission from Elsevier, sciencedirect.com
Paper 3: Olufsen, Marianne Opsahl; Arukwe, Augustine. Endocrine, biotransformation, and oxidative stress responses in salmon hepatocytes exposed to chemically induced hypoxia and perfluorooctane sulfonamide (PFOSA), given singly or in combination. Environmental science and pollution research international 2015 ;Volum 22.(22) s. 17350-17366. Is not included due to copyright avialable at http://dx.doi.org/10.1007/s11356-014-3847-y
Paper 4: Olufsen, Marianne Opsahl; Cangialosi, Maria Vittoria; Arukwe, Augustine. Modulation of membrane lipid composition and homeostasis in salmon hepatocytes exposed to hypoxia and perfluorooctane sulfonamide, given singly or in combination. PLoS ONE 2014 ;Volum 9.(7) http://dx.doi.org/10.1371/journal.pone.0102485 This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.