Divergent gene expression in the gills of juvenile turbot (Psetta maxima) exposed to chronic severe hypercapnia indicates dose-dependent increase in intracellular oxidative stress and hypoxia.

Hermann, Bernd T. , Würtz, Sven, Vanselow, Klaus H., Schulz, Carsten and Stiller, Kevin T. (2019) Divergent gene expression in the gills of juvenile turbot (Psetta maxima) exposed to chronic severe hypercapnia indicates dose-dependent increase in intracellular oxidative stress and hypoxia. Aquatic Toxicology, 206 . pp. 72-80. DOI 10.1016/j.aquatox.2018.10.023.

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Abstract

Elevated concentrations of carbon dioxide are a common stressor for fish and other aquatic animals. In particular, intensive aquaculture can impose prolonged periods of severe environmental hypercapnia, manifold exceeding CO2 concentrations of natural habitats. In order to cope with this stressor, gills are essential and constitute the primary organ in the acclimatization process. Yet, despite a general understanding of changes in ion regulation, not much is known with regard to other cellular mechanisms. In this study, we apply RT-qPCR to investigate changes in the expression of several genes associated with metabolism, stress and immunity within gills of juvenile turbot (Psetta maxima) after an eight-week exposure to different concentrations of CO2 (low = ~3000 μatm, medium = ~15000 μatm and high = ~25000 μatm CO2). Histological examination of the gill tissue only found a significant increase of hypertrophied secondary lamella in the highest tested treatment level. gene expression results, on the other hand, implied both, mutual and dose-dependent transcriptional adjustments. Comparable up-regulation of IL-1ß, LMP7 and Grim19 at medium and high hypercapnia indicated an increase of reactive oxygen species (ROS) within gill cells. Simultaneous increase in Akirin and PRDX transcripts at medium CO2 indicated enhanced anti-oxidant activity and regulation of transcription, while reduced mRNA concentrations of COX, EF1α and STAT2 at high CO2 denoted suppressed protein synthesis and reduced metabolic capacity. In addition to upregulated DFAD and ApoE expression, implying compensating repair measures, gills exposed to the highest tested treatment level seemed to operate close to or even beyond their maximum capacity. Thus, fitting the model of capacity limitation, our results provide evidence for accretive intracellular hypoxia and oxidative stress in the gills of turbot, dependent on the level of environmental hypercapnia. Further, genes, such as COX, may be valuable biomarkers when attempting to discriminate between a successful and an overpowered stress response.

Document Type: Article
Research affiliation: Kiel University > Kiel Marine Science
OceanRep > GEOMAR > FB3 Marine Ecology > FB3-EV Marine Evolutionary Ecology
OceanRep > The Future Ocean - Cluster of Excellence
Kiel University
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1016/j.aquatox.2018.10.023
ISSN: 0166-445X
Projects: NEMO, Future Ocean
Date Deposited: 12 Nov 2018 12:59
Last Modified: 30 Jan 2019 12:10
URI: http://oceanrep.geomar.de/id/eprint/44654

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