Microcystin-LR impacts viability, migration, and proliferation of the Atlantic salmon gill epithelial cell line, ASG-10: implications for tissue repair.

Harmful algal blooms pose significant threats to Atlantic salmon farming and aquaculture sustainability. Microcystin-LR (MC-LR), one of the most common freshwater cyanobacterial toxins, has been reported to be associated with Net Pen Liver Disease in marine environments; however, its effect on gill is less understood. This study used an Atlantic salmon gill epithelial cell line, ASG-10, to investigate the effects of MC-LR on gill health and the potential protective role of supplementary antioxidants. ASG-10 was exposed to different concentrations of MC-LR with or without N-Acetyl-L-cysteine (NAC), a precursor of glutathione. We assessed cell toxicity, proliferation and migration, reactive oxygen species (ROS) and glutathione (GSH) concentrations, mitochondrial membrane potential, and expression of immune- and stress-related genes at different time points up to 5 days post-exposure (dpe). MC-LR induced cytotoxicity at 40 μg/ml and at 20 μg/ml when combined with NAC at 5dpe. Cell proliferation and migration were significantly reduced in 40 μg/ml MC-LR as early as 20 h post-exposure, with this reduction becoming significant in all treatments except 5 μg/ml MC-LR by 60 h post-exposure. MC-LR alone did not impact ROS and GSH levels and mitochondrial membrane potential, suggesting a limited oxidative response. While MC-LR exposure did not alter gene expression, co-exposure to MC-LR and NAC suppressed mucin5 expression at 3 dpe, suggesting that combined treatment may impact mucosal immune responses. Overall, these findings show the adverse effects of MC-LR on gill epithelial cell viability, migration and proliferation, with implications for gill growth, repair/regeneration which depends on these cellular processes.