PAH biomarker responses in polar cod ( Boreogadus saida) exposed to benzo(a)pyrene

Abstract

With expanding oil and gas activities into the Arctic region, there is a need to evaluate the induction capacity of polycyclic aromatic hydrocarbon (PAH) biomarkers on Arctic marine organisms and to test analytical methods that have been optimized for their temperate counterparts. Polar cod Boreogadus saida were injected intraperitoneally with cod liver oil (solvent control), 6.6 ± 3.7, 85 ± 48 or 378 ± 190 μg kg −1 wet weight of benzo(a)pyrene (B(a)P), or not injected (control), and liver and bile were sampled at 0 and 16 h and 1, 2, 4 and 7 d. The mRNA expression of cytochrome P4501A1 ( cyp1a1) and glutathione S-transferase ( gst) genes showed a dose-dependent induction in the first 16 h following the injection and a return to basal levels after 4 d. The aryl hydrocarbon receptor 2, however, showed no change in mRNA expression. The protein quantification of cytochrome P4501A (CYP1A), through Western blot analysis and the enzyme-linked immunosorbent assay (ELISA), presented similar but weaker and time-delayed responses (4–7 d) compared to the gene (16 h to 2 d). Ethoxyresorufin O-deethylase (EROD) and glutathione S-transferase (GST) activities increased significantly at day 7 following the gene induction and increase in protein levels. Overall, these biomarkers showed dose-dependent but weak responses to B(a)P and low levels of bile metabolites. The mRNA expressions of oxidative stress genes, superoxide dismutases ( sod( Cu/ Zn) and sod( Mn)), catalase ( cat) and glutathione peroxidase ( gpx), were all up-regulated between 16 h and 2 d of B(a)P exposure with cat (72-fold) and s od( Cu/ Zn) (20-fold) giving the strongest responses in the highest dose. Finally, CAT protein level and enzyme activities showed less clear responses than the genes. The mRNA expression showed the earliest responses, followed by the protein levels. The enzymatic activities were the least sensitive and responded to the exposure after 7 d. The study shows the induction capability of biomarkers in polar cod at very low bioavailable doses of B(a)P and provides new information on the selected biomarkers for use in oil monitoring in the Arctic.