The utility of in vitro Precision-Cut Liver Slices to investigate toxicity pathways of contaminants in polar cod (Boreogadus saida)

Abstract

The development of in vitro methodologies has contributed significantly in elucidating mechanisms of xenobiotic toxicity in aquatic organisms. The present study aimed to develop the in vitro methodology Precision-Cut Liver Slices (PCLS) and to investigate the effects of model compounds (WY-14,643 [WY] and benzo(a)pyrene [BaP]) and two mixtures of 2- and 3-4-ring polycyclic aromatic hydrocarbons (PAHs), respectively, in the Arctic key species polar cod (Boreogadus saida). For each model compound and PAHs mixtures, PCLS (4 or 5 replicate slices per concentration) of 2 or 3 fish replicate were exposed to series of increasing concentrations (4 or 5 concentrations) during 48hr. Transcriptional responses of genes involved in biotransformation (cyp1a1), lipid metabolism (pparα, aox) and reproduction (vtg) were investigated. Viability of the slices was tested through the measurement of lactate dehydrogenase (LDH) activity in culture medium and reproducibility of the slice thickness (250μm) was assessed through histological analysis. Analysis of transcription levels only showed significant and dosedependent up-regulation of cyp1a1 in PCLS exposed to BaP and 3-4-ring PAHs mixture. On the other hand, transcription levels of aox, pparα and vtg did not significantly change for any of the model compounds and PAHs mixtures tested. In general, transcriptional levels responses of all target genes were very different between fish replicate and experiments, especially between PAHs mixtures experiments. Slice thickness, sex, PAHs physicochemical properties and species sensitivity were considered potential sources of variability on target genes transcriptional level responses. PCLS was successfully developed and the target genes responses observed show potential deleterious effects of PAHs on important metabolic pathways in polar cod. PCLS are deemed a valuable tool for studying toxicity mechanisms of different model compounds and PAHs mixtures in polar cod. However, an improvement of PCLS methodology should be considered for further studies.