Lufenuron exposure temporarily repress gene expression and the SUMO pathway in liver of Atlantic salmon

Lufenuron is among the insecticides in use to combat salmon lice infestation in marine aquaculture. This benzoylurea drug acts as a chitin synthesis inhibitor, and prevent molting in the developing salmon lice larvae. In this work we aimed to study the molecular response to lufenuron exposure in Atlantic salmon given a standard oral dose. Juvenile salmon weighing about 40 g were treated with the drug for one week, and transcriptional responses were studied in liver tissue one (day 8) and seven days (day 14) after the treatment period. Exposure gave a transient inhibition of transcription in the liver at day 8 (2437 significant DEGs), followed by a weaker compensatory response at day 14 (169 significant DEGs). Many pathways associated with RNA metabolism were impacted at day 8. The sumoylation pathway was most strongly affected at day 8. Potential hepatic biomarkers for lufenuron exposure in fish could be phactr3, mst1r and slc47a1. In conclusion, this study shows that a 7-day standard dose of lufenuron downregulates transcription in liver tissue. The inhibitory effect on transcription was transitory, with a much weaker response one week after the medication period. Overall design: The four treatment groups were control and exposed fish collected at day 8 (one day after the end of the lufenuron treatment period), and control and exposed fish collected at day 14 (seven days after the end of the lufenuron treatment).