In vitro effects of astaxanthin on bacterial and cell viability, cell migration and mitochondrial activities in four fish cell lines

Astaxanthin (AX) is a pigment commonly used in aquaculture. It is added to salmonid, shrimp, and crayfish feeds to produce the appropriate pink coloration to the flesh of these animals. Different in vitro effects of AX were studied to understand its mode of action in fish. The antioxidant activity and the potential bactericidal effects of AX on three fish pathogenic bacteria (Vibrio harveyi, V anguillarum and Photobacterium damselae) were determined. After 24 h of incubation with AX, no significant effects on the viability of V. harveyi were observed, while the viability of V. anguillarum and P. damselae was increased and decreased, respectively. These results are discussed according to the presence or absence of bacterial carotenoid cleavage oxygenases. Fish cell lines (SAF1, DLB-1, FuB-1 and PLHC-1) were cultured and incubated for 24 h with different concentrations of AX (0, control, 0.1, 1 and 10 & mu;M) and then cell viability was assessed. No significant effects or increased viability were observed in cells incubated with AX. To determine the effects of AX on cell migration, the scratch assay was performed. While no significant differences were detected when using SAF-1 or PLHC-1 cells, the inclusion of AX, at any of the concentrations tested, significantly (p < 0.05) increased the forward velocity in DLB-1 and FuB-1 cells. In addition, several parameters of mitochondrial metabolism were evaluated using the Agilent Seahorse XF mitochondrial stress assay kit. Different results were obtained depending on the cell line used and the mitochondrial parameter assayed but, in general, no significant effects or increases were detected after incubation of cells with AX. In conclusion, the results revealed that the effects of AX depend on the bacterium and cell line used in the assays and these findings improve our understanding of the mode of action of AX in fish and its potential applications in aquaculture.