|
|
Blanc, M., Alfonso, S., Begout, M. - L., Barrachina, C., Hyotylainen, T., Keiter, S. H., et al. (2021). An environmentally relevant mixture of polychlorinated biphenyls (PCBs) and polybrominated diphenylethers (PBDEs) disrupts mitochondrial function, lipid metabolism and neurotransmission in the brain of exposed zebrafish and their unexposed F2 offspring. Sci. Total Environ., 754, 142097.
Résumé: Polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) are persistent organic pollutants still present in aquatic environments despite their total or partial ban. Previously, we observed that an environmentally realistic mixture of these compounds affects energy balance, growth, and reproduction in exposed zebrafish (F0), and behavior in their unexposed offspring (F1-F4). In the present work, we performed lipidomic and transcriptomic analyses on brains of zebrafish (F0-F2) from exposed and control lineages to identify molecular changes that could explain the observed phenotypes. The use of both technologies highlighted that F0 zebrafish displayed impaired mitochondrial function and lipid metabolism regulation (depletion in triacylglycerols and phospholipids) which can explain disruption of energy homeostasis. A subset of the regulated biological pathways related to energetic metabolism and neurotransmission were inherited in 12. In addition, there were increasing effects on epigenetic pathways from the F0 to the F2 generation. Altogether, we show that the effects of an environmental exposure to PCBs and PBDEs on energetic metabolism as well as neurotransmission extend over 2 generations of zebrafish, possibly due to transgenerational epigenetic inheritance. (C) 2020 The Authors. Published by Elsevier B.V.
|
|
|
|
Cormier, B., Batel, A., Cachot, J., Begout, M. - L., Braunbeck, T., Cousin, X., et al. (2019). Multi-Laboratory Hazard Assessment of Contaminated Microplastic Particles by Means of Enhanced Fish Embryo Test With the Zebrafish (Danio rerio). Front. Environ. Sci., 7, 135.
Résumé: As wide-spread pollutants in the marine environment, microplastics (MPs) have raised public concern about potential toxic effects in aquatic organisms, and, among others, MPs were suspected to act as a vector for organic pollutants to biota. The purpose of the present study was to investigate effects by three model pollutants, oxybenzone (BP3), benzo[a] pyrene (BaP), and perfluorooctane sulfonate (PFOS) adsorbed to polyethylene MPs on the basis of a standard assay, the acute fish embryo toxicity test (FET; OECD TG 236) with zebrafish (Danio rerio) supplemented by additional endpoints such as induction of ethoxyresorufin-O-deethylase (EROD) activity, modification of cyp1a gene transcription and changes in larval swimming behavior. FET assays were performed in three laboratories using slightly different husbandry and exposure conditions, which, however, were all fully compatible with the limits defined by OECD TG 236. This allowed for testing of potential changes in the FET assay due to protocol variations. The standard endpoints of the FET (acute embryotoxicity) did not reveal any acute toxicity for both virgin MPs and MPs spiked with BP3, BaP, and PFOS. With respect to sublethal endpoints, EROD activity was increased after exposure to MPs spiked with BP3 (3 h pulse) and MPs spiked with BaP (96 h continuous exposure). Cyp1a transcription was increased upon exposure to MPs spiked with BP3 or BaP. For the selected combination of MPs particles and contaminants, the basic FET proved not sensitive enough to reveal effects of (virgin and spiked) MPs. However, given that the FET can easily be supplemented by a broad variety of more subtle and sensitive endpoints, an enhanced FET protocol may provide a relevant approach with developmental stages of a vertebrate animal model, which is not protected by current EU animal welfare legislation (Directive EU 2010/63).
|
|
|
|
Fleury, E., Moal, J., Boulo, V., Daniel, J. Y., Mazurais, D., Henaut, A., et al. (2010). Microarray-Based Identification of Gonad Transcripts Differentially Expressed Between Lines of Pacific Oyster Selected to Be Resistant or Susceptible to Summer Mortality. Mar. Biotechnol., 12(3), 326–339.
Résumé: Summer mortality of the Pacific oyster Crassostrea gigas is the result of a complex interaction between oysters, their environment, and pathogens. Heredity appears to be a major factor determining the sensitivity of oysters to summer mortality, allowing resistant (R) and susceptible (S) lines to be produced. We conducted genome-wide expression profiling of R and S gonads during the 3-month period preceding a summer mortality event, using a cDNA microarray that we designed. ANOVA analysis revealed that 34 genes were differentially expressed between R and S lines on four dates preceding the mortality event. Annotation of some of these genes highlights reproduction and its allocation and antioxidant defenses as the main pathways that operate differentially between R and S lines. This transcriptional analysis provides new indications to define markers for quantitative trait loci searches and functional studies and evaluate the potential role of each gene in the resistance to summer mortality.
|
|
|
|
L'Honore, T., Farcy, E., Blondeau-Bidet, E., & Lorin-Nebel, C. (2020). Inter-individual variability in freshwater tolerance is related to transcript level differences in gill and posterior kidney of European sea bass. Gene, 741, 144547.
Résumé: Acclimation to low salinities is a vital physiological challenge for euryhaline fish as the European sea bass Dicentrarchus labrax. This species undertakes seasonal migrations towards lagoons and estuaries where a wide range of salinity variations occur along the year. We have previously reported intraspecific differences in freshwater tolerance, with an average 30% mortality rate. In this study, we bring new evidence of mechanisms underlying freshwater tolerance in sea bass at gill and kidney levels. In fresh water (FW), intraspecific differences in mRNA expression levels of several ion transporters and prolactin receptors were measured. We showed that the branchial Cl-/HCO3- anion transporter (slc26a6c) was over-expressed in freshwater intolerant fish, probably as a compensatory response to low blood chloride levels and potential metabolic alkalosis. Moreover, prolactin receptor a (prlra) and Na+/Cl- cotransporter (ncc1) but not ncc-2a expression seemed to be slightly increased and highly variable between individuals in freshwater intolerant fish. In the posterior kidney, freshwater intolerant fish exhibited differential expression levels of slc26 anion transporters and Na+/K+/2Cl(-) co-transporter 1b (nkcc1b). Lower expression levels of prolactin receptors (prlra, prlrb) were measured in posterior kidney which probably contributes to the failure in ion reuptake at the kidney level. Freshwater intolerance seems to be a consequence of renal failure of ion reabsorption, which is not sufficiently compensated at the branchial level.
|
|
|
|
L'Honore, T., Farcy, E., Chatain, B., Gros, R., Ruelle, F., Hermet, S., et al. (2019). Are European sea bass as euryhaline as expected? Intraspecific variation in freshwater tolerance. Mar. Biol., 166(8), 102.
Résumé: In teleosts, the regulation of hydromineral balance has a direct impact on several physiological functions, biochemical processes, and can influence behaviour, distribution and survival. As European sea bass Dicentrarchus labrax undertake seasonal migrations from seawater (SW) to brackish, estuarine and fresh water (FW) in their habitat, this study investigates their capacity to tolerate fresh water and explores intraspecific variations in physiological responses. Juvenile D. labrax were transferred from SW to FW at various ages. Freshwater-tolerant and non-tolerant phenotypes were discriminated according to behavioural and morphological characteristics. About 30% of the fish exposed to FW were identified as freshwater intolerant following FW challenges performed at different ages. Interestingly, intolerant fish exhibited the same phenotypic traits: erratic swimming, lower speed, isolation from the shoal and darker colour. Freshwater-intolerant fish were also characterised by a significant lower blood osmolality compared to tolerant fish, and significantly lower Na+/K+-ATPase alpha 1a expression in the posterior kidney. An imbalance in ion regulatory mechanisms was further confirmed by a blood Na+/Cl- ratio imbalance observed in some freshwater-intolerant fish. The analysis of glucocorticoid and mineralocorticoid receptor expression levels in gills and kidney revealed significant differences between freshwater-intolerant and -tolerant fish in both organs, suggesting differential stress-related responses. This study clearly shows an intraspecific difference in the responses following FW transfer with a decreased renal ion uptake capacity as a major cause for freshwater intolerance.
|
|
