Expression of aryl hydrocarbon receptor–regulated genes and superoxide dismutase in the Antarctic eelpout Pachycara brachycephalum exposed to benzo[a]pyrene

Abstract

The aryl hydrocarbon receptor (AhR) pathway mediates many, if not all, responses of fish to dioxin-like compounds. The Southern Ocean is progressively exposed to increasing concentrations of anthropogenic pollutants. Antarctic fish are known to accumulate those pollutants, yet nothing is known about their capability to induce chemical biotransformation via the AhR pathway. The objective of the present study was to investigate whether Antarctic eelpout, Pachycara brachycephalum, respond to anthropogenic pollutants by activation of the AhR and its target gene cytochrome P4501A (CYP1A), and of superoxide dismutase (SOD), which served as a representative for oxidative stress. We exposed P. brachycephalum to 10 and 100 mg benzo[a]pyrene (BaP)/kg body weight for 10 d and measured the expression of AhR, CYP1A, and SOD in liver tissue via quantitative polymerase chain reaction. We identified two distinct AhR isoforms in the liver of P. brachycephalum. Antarctic eelpout responded to both BaP exposures by an up-regulation of AhR and SOD, and by a particularly strong induction of CYP1A expression, which remained high until day 10 of the exposure time. Our data suggest that P. brachycephalum possesses the potential to up-regulate xenobiotic biotransformation pathways, at least at the gene expression level. The time course of the AhR and CYP1A response points to an efficient but slow xenobiotics metabolism. Moreover, BaP exposure could include adverse effects such as oxidative stress. Environ Toxicol Chem 2018;37:1487-1495. © 2018 SETAC.

A rapid method of preparing complex organohalogen extracts from avian eggs: Applications to in vitro toxicogenomics screening

“…The transcriptomic evaluation of Cyp1a4 was in agreement with the findings from the EROD assay, which measures induction of the Cyp1a4 enzyme and is widely used as a biomarker for exposure of wildlife to substances that bind to the AhR (e.g. Strobel et al 2018). The variability in Cyp1a4 mRNA induction was also in agreement with the relative organohalogen contaminant burdens of key DLC classes measured in double-crested cormorant extracts (i.e., Middle Sister Island had the highest P PCBs and total TEQs [10 300 ng/g and 32.6 pg/g, respectively], and Mandarte Island had the lowest [254 ng/g and 7 pg/g, respectively]).…”

“…Within the Great Lakes cluster, doublecrested cormorant fractions from Mud Island and Hamilton Harbour formed distinct branches and altered 22 and 14/43 target genes on the ToxChip, respectively. Strobel et al 2018). The highest Cyp1a4 induction was observed at Middle Sister Island (87-fold) versus only an 8-fold induction at the non-Great Lakes control, Mandarte Island (Figure 2 and Supplemental Data, Table S10).…”

The Role of the Ecotoxicology Applied to Seafood as a Tool for Human Health Risk Assessments Concerning Polycyclic Aromatic Hydrocarbons

“…However, a common mechanism of action has not yet been well-explored, even though PAH effects on Phase 1 and 2 biotransformation detoxification markers are clear (Figure 6). This process, essential in xenobiotic detoxification, is initiated by the transcription of enzymes by the aryl hydrocarbon receptor (AhR) pathway, which can also be applied as a PAH toxicity biomarker [92]. The enzymes involved in this process, such as the cytochrome P450 enzymes that act in Phase 1, can be classified as a function of the biotransformation stage during which they act, with polarity being responsible for transforming liposoluble compounds into more water-soluble forms, easier to excrete [86], typically generating different metabolites.…”

“…The enzymes involved in this process, such as the cytochrome P450 enzymes that act in Phase 1, can be classified as a function of the biotransformation stage during which they act, with polarity being responsible for transforming liposoluble compounds into more water-soluble forms, easier to excrete [86], typically generating different metabolites. Some enzymes also act in the conjugation of these metabolites (Phase II), resulting in xenobiotic conjugates, which are more readily excreted (Figure 7) [59,92]. The CYP1A subfamily (Figure 7) is the most studied among the cytochrome P450 family of enzymes as it is significantly induced by PAHs.…”

“…The CYP1A subfamily (Figure 7) is the most studied among the cytochrome P450 family of enzymes as it is significantly induced by PAHs. The activity of this marker in fish and shellfish has been applied in many assessments to verify PAH effects, especially BaP, which significantly increases the expression of CYP1A as a function of exposure time and dose [47,59,[85][86][87][88][89]92,93,100].…”