| dc.description.abstract | The marine environment is under constant pollution pressure mainly due to anthropogenic activities in the sea and on land. Polycyclic aromatic hydrocarbons (PAHs) and Perfluoroalkyl substances (PFASs) are among the most common xenobiotics found in the aquatic environment and represent a significant threat to aquatic and terrestrial organisms. Recent studies have shown that PAHs and PFASs produce harmful effects on fish species, but a few studies have been conducted to explore genes and pathways affected with the use of high throughput transcriptomics approach. Like in other vertebrates, the fish brain is actively involved in stress response and is influenced by external factors. In the present study, the molecular changes (transcriptome profiling) in the brain of juvenile Atlantic cod after exposure to two different concentrations of PAHs and PFASs have been investigated. Both the PAHs and PFASs exposure groups contained different congeners. Low and high-dose PAHs exposure produced 131 and 5 deferentially expressed genes (DEGs), respectively. For the PFASs, a similar pattern with a large number of DEGs in the low-dose exposure group (94 DEGs), compared to a high dose with only one (1) DEG, was observed. Functional characterization of DEGs revealed pathways belonging to signal transduction such as neuron signalling, transmembrane signalling, biological adhesions and calcium signalling which were significantly affected in the brain of fish after PAHs and PFASs exposure. The GnRH signalling pathway was also enriched in both low PAH and PFASs exposure groups. Some enriched terms related to oxidative stress such as respiratory chain, sodium and electron transport, and oxidative phosphorylation were only affected in low PFASs exposure. High PAHs exposure increased the expression of genes functionally involved in DNA -binding and DNA packaging. On the other hand, DEG belonging to high PFASs exposure were involved in signal transduction and chemical response. The findings of the study suggest that exposure of fish to an environmentally relevant concentration of PAHs and PFASs modulates brain cellular molecules to trigger the signalling cascades in the brain which activates the stress response that can ultimately have adverse effects on fish at the systems level. However, the high exposure doses may have caused exhaustion in stress response leading to a finite number of the differentially expressed gene when compared to low exposure groups. These effects need to be investigated further. | |
