Biomarkers of oxidative stress in Calanus finmarchicus exposed to a water accommodated fraction of a naphthenic North Atlantic crude oil

Calanus finmarchicus is an ecologically important species in the North, Norwegian and Barents Seas, periodically constituting up to 90% of the standing stock of zooplankton. Due to continued development of areas for oil and gas production, there are environmental discharges of contaminants occurring both continuously and accidentally in these areas. Existence of reliable biomarkers for oil exposure are fundamental for monitoring programs and decision-making processes in case of environmental discharges and oil spills. To assess the potential negative effects of oil exposure on keystone component of marine ecosystems, adult females of Calanus finmarchicus were exposed to the water-accommodated fraction (WAF) of a naphthenic North Atlantic crude oil. Adult non-ovulating females from the continuous lab culture at SINTEF/NTNU Sealab, were exposed without feeding to sub-lethal concentration of WAF in seawater and collected at 5 different time points 0, 24, 48, 72 and 96 hours. Several oxidative stress biomarkers were tested with gene expression (qPCR), enzymatic activity analyses and lipid peroxidation assay for malondialdehyde (MDA) concentrations. Enzymatic assays demonstrated induction of glutathione S-transferases (GST) and increase of glutathione (GSH) and MDA concentrations at each time point sampled. Gene expression results showed inconsistent responses with both up- and downregulation of GST at 48 and 72 hours and downregulation of superoxide dismutase (SOD) at 72 hours. Our study indicates that GST enzymatic activity, and GSH and MDA concentrations can be applied as a biomarkers of crude oil exposure in C. finmarchicus, while SOD gene expression is less suitable

Étude des effets d'un xénoestrogènes sur le développement larvaire chez le bar Européen

Les milieux estuariens et côtiers sont des lieux de grande importance écologique accueillant une grande biodiversité et qui sont en même temps influencés par les activités humaines et la présence de polluants. Certains de ces polluants sont des perturbateurs endocriniens, ils sont capables d'interagir avec le système endocrinien et de provoquer des effets délétères chez les organismes. Parmi eux, les xénoestrogènes (XEs), principalement étudiés pour leurs effets sur la reproduction notamment sur les gonades, peuvent aussi influencer d’autres organes et fonctions. L'objectif de ce travail était d'évaluer les effets d’une exposition aux XEs sur les premiers stades de vie d'un téléostéen marin, le bar européen. Nos résultats montrent que l'exposition au 17α-éthinylestradiol influence la croissance larvaire, l'ontogenèse de l'axe neuroendocrine gonadotrope et perturbe les comportements larvaires, des effets qui pour la plupart dépendent de la période larvaire d’exposition.Au cours du développement larvaire, le bar est donc sensible à l'exposition aux XEs avec des effets induits qui pourraient à long terme affecter la fitness des individus.Estuarine and coastal environments are areas of high ecological importance, housing a large biodiversity and at the same time influenced by human activities and the presence of pollutants.Some of these pollutants are endocrine disrupting chemicals (EDCs) able to interact with the endocrine system and to cause deleterious effects on organisms. Among EDCs, xenoestrogens mostly studied for their effects on reproduction particularly on the gonads, might also exert their actions on the brain and the pituitary. The objective of this work was to evaluate the effects of xenoestrogen exposure on early life stages of a marine teleost, the European sea bass (Dicentrarchus labrax). We demonstrated that 17α-ethinylestradiol (EE2) exposure influences the larval growth, the ontogenesis of the neuroendocrine gonadotropic axis and disrupts larval behaviours. Most of the effects were shown to be age-dependent.Our results demonstrated that early life stages of sea bass are rather sensitive to xenoestrogens exposure with observed effects that could in the long term affect individual fitness

Oil-mediated oxidative-stress responses in a keystone zooplanktonic species, Calanus finmarchicus

The copepod Calanus finmarchicus is an ecologically important species in the North Atlantic, Norwegian and Barents seas. Accidental or continuous petroleum pollution from oil and gas production in these seas may pose a significant threat to this low trophic level keystone species. Responses related to oxidative stress, protein damage and lipid peroxidation were investigated in C. finmarchicus exposed to a water-accommodated fraction (WAF) of a naphthenic North Atlantic crude oil. The exposure concentration corresponded to 50% of the 96 h LC50, and samples were obtained at 0, 24, 48, 72 and 96 h after exposure initiation. Gene expressions (superoxide dismutase, catalase, glutathione S-transferase, glutathione synthetase, heat shock protein 70 and 90, ubiquitin and cytochrome P-450 330A1), enzyme activities (superoxide dismutase, catalase, glutathione S-transferase) and concentrations of total glutathione and malondialdehyde were analyzed. Gene expression analyses showed no differences between controls and the exposed animals, however significantly higher glutathione S-transferase activity and malondialdehyde concentrations were found in the exposed group, suggests lipid peroxidation as main toxic effect.publishedVersio

Development of an exposure protocol for toxicity test (FEET) for a marine species: the European sea bass (Dicentrarchus labrax)

International audienceRegulatory assessment of the effects of chemicals requires the availability of validated tests representing different environments and organisms. In this context, developing new tests is particularly needed for marine species from temperate environments. It is also important to evaluate effects that are generally poorly characterized and seldom included in regulatory tests. In this study, we designed an exposure protocol using European sea bass (Dicentrarchus labrax) larvae. We examined classical toxicological values (LCx) as well as behavioral responses. By comparing different hatching and breeding strategies, we defined the optimal conditions of exposure as non-agitated conditions in 24- or 48-well microplates. Our exposure protocol was then tested with 3,4-dichloroaniline (3,4-DCA), a recommended reference molecule. Based on our results, the 96 h LC50 for 3,4-DCA corresponded to 2.04 mg/L while the 168 h LC50 to 0.79 mg/L. Behavioral analyses showed no effect of 3,4-DCA at low concentration (0.25 mg/L). In conclusion, the present work established the basis for a new test which includes behavioral analysis and shows that the use of sea bass is suitable to early-life stage toxicity tests

17α-Ethinylestradiol exposure disrupts anxiety-like behaviours but not social preference in sea bass larvae (Dicentrarchus labrax)

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Effects of 17α-ethinylestradiol on the neuroendocrine gonadotropic system and behavior of European sea bass larvae (Dicentrarchus labrax)

International audienceThe widespread use of 17α-ethinylestradiol (EE2), and other estrogenic endocrine disruptors, results in a continuous release of estrogenic compounds into aquatic environments. Xenoestrogens may interfere with the neuroendocrine system of aquatic organisms and may produce various adverse effects. The aim of the present study was to expose European sea bass larvae (Dicentrarchus labrax) to EE2 (0.5 and 50 nM) for 8 d and determine the expression levels of brain aromatase (cyp19a1b), gonadotropin-releasing hormones (gnrh1, gnrh2, gnrh3), kisspeptins (kiss1, kiss2) and estrogen receptors (esr1, esr2a, esr2b, gpera, gperb). Growth and behavior of larvae as evidenced by locomotor activity and anxiety-like behaviors were measured 8 d after EE2 treatment and a depuration period of 20 d. Exposure to 0.5 nM EE2 induced a significant increase in cyp19a1b expression levels, while upregulation of gnrh2, kiss1, and cyp19a1b expression was noted after 8 d at 50 nM EE2. Standard length at the end of the exposure phase was significantly lower in larvae exposed to 50 nM EE2 than in control; however, this effect was no longer observed after the depuration phase. The upregulation of gnrh2, kiss1, and cyp19a1b expression levels was found in conjunction with elevation in locomotor activity and anxiety-like behaviors in larvae. Behavioral alterations were still detected at the end of the depuration phase. Evidence indicates that the long-lasting effects of EE2 on behavior might impact normal development and subsequent fitness of exposed fish

Oil-mediated oxidative-stress responses in a keystone zooplanktonic species, Calanus finmarchicus

The copepod Calanus finmarchicus is an ecologically important species in the North Atlantic, Norwegian and Barents seas. Accidental or continuous petroleum pollution from oil and gas production in these seas may pose a significant threat to this low trophic level keystone species. Responses related to oxidative stress, protein damage and lipid peroxidation were investigated in C. finmarchicus exposed to a water-accommodated fraction (WAF) of a naphthenic North Atlantic crude oil. The exposure concentration corresponded to 50% of the 96 h LC50, and samples were obtained at 0, 24, 48, 72 and 96 h after exposure initiation. Gene expressions (superoxide dismutase, catalase, glutathione S-transferase, glutathione synthetase, heat shock protein 70 and 90, ubiquitin and cytochrome P-450 330A1), enzyme activities (superoxide dismutase, catalase, glutathione S-transferase) and concentrations of total glutathione and malondialdehyde were analyzed. Gene expression analyses showed no differences between controls and the exposed animals, however significantly higher glutathione S-transferase activity and malondialdehyde concentrations were found in the exposed group, suggests lipid peroxidation as main toxic effect

Effects of 17α-Ethinylestradiol (EE2) exposure during early life development on the gonadotropic axis ontogenesis of the European sea bass, Dicentrarchus labrax

Exposure of young organisms to oestrogenic endocrine disrupting chemicals (EDCs) can elicit adverse effects, particularly on the reproductive function. In fish, as in other vertebrates, reproduction is controlled by the neuroendocrine gonadotropic axis, whose components are mainly regulated by sex steroids and may then be targets for EDCs. In the present study, we investigated the effects of a xenoestrogen exposure on the ontogenesis of the gonadotropic axis in European sea bass. After exposure of hatching larvae for 8 days to 17α-ethinylestradiol (EE2) (0.5 nM and 50 nM), gene expression for kisspeptins (kiss1, kiss2), gonadotropin-releasing hormones (gnrh1, gnrh2, gnrh3), gonadotropin beta subunits (lhβ and fshβ) and brain type aromatase (cyp19a1b) were measured using quantitative real-time PCR. Our results demonstrate that EE2 strongly stimulated the expression of brain type aromatase (cyp19a1b) in sea bass larvae. In addition, EE2 exposure also affected the mRNA levels of kiss1, gnrh1 and gnrh3 by inducing a downregulation of these genes during the early developmental stages, while no effect was seen in gnrh2, lhβ and fshβ. These results reinforce the idea that the larval development is a sensitive critical period in regard to endocrine disruption and that the gonadotropic axis in the developing sea bass is sensitive to xenoestrogen exposure

Neuroendocrine effects of 17α-ethynilestradiol during the early developmental stages of sea bass (Dicentrarchus labrax).

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