Unravelling the effects of benzo[k]fluoranthene and temperature on the expression of detoxification genes in the rainbow trout liver RTL-W1 cell line

Fish are either acutely or chronically exposed to numerous aquatic contaminants, including polycyclic aromatic hydrocarbons (PAHs), and increased water temperatures due to global warming. Both stressors may impact many of their biochemical and physiological processes, including hepatic metabolism. Combined effects of temperature and xenobiotics can exist, and little is known about these interactions. Fish liver-derived models, including well-established cell lines, can be employed to better understand these connections . The rainbow trout (Oncorhynchus mykiss) liver RTL-W1 cell line has been used to study the effects of PAHs. To test if this cell line, cultured in monolayer (2D), can be utilised as a model to study mixed effects of PAHs and temperature, we exposed RTL-W1 cells (72 h) at 18 °C and 21 °C (simulating warming) to benzo[k]fluoranthene (B[k]F), at 10 nM and 100 nM. After PAH exposures, cell density and viability were assessed (through trypan blue exclusion and LDH assays). The gene expression of detoxification targets (cytochrome P450 (CYP)1A, CYP3A27, glutathione S-transferase omega 1 (GST), uridine diphosphate (UDP)-glucuronosyltransferase (UGT), catalase (CAT), and multidrug resistance-associated protein 2 (MRP2)), was analysed using RT-qPCR. B[k]F at 10 and 100 nM reduced cell density but did not affect cell viability. Temperature did not seem to influence cell density and viability. LDH leakage was higher at 21 °C than at 18 °C. CYP1A, CYP3A27, and UGT expression was increased, compared with the control, by both concentrations of B[k]F. GST and MRP2 gene expression was increased by B[k]F100. CAT mRNA levels were higher at 21 °C than at 18 °C. There were no statistically significant interactions between PAHs and temperature over the assessed targets. Overall, the RTL-W1 in 2D culture can potentially unravel the liver effects of toxicants in a global warming scenario.

Funding: FCT strategic funding UIDB/04423/2020 and UIDP/04423/2020 to CIIMAR/CIMAR.