Molecular Characterization and Pathogen-Responsive Expression of Galectin-8 in Starry Flounder (Platichthys stellatus): Preliminary Assessment of Leukocyte ROS Responses

Galectin-8 is a tandem-repeat member of the galectin family involved in cellular and immune-related processes in vertebrates, but its role in teleost fish remains poorly understood. In this study, galectin-8 (PsGal8) was identified and characterized in starry flounder, and its tissue distribution and expression following viral and bacterial challenges were investigated. The predicted PsGal8 protein contained two carbohydrate recognition domains connected by a linker peptide and possessed conserved carbohydrate-binding motifs characteristic of galectin-8. PsGal8 transcripts were detected in all examined tissues, with the highest expression in the trunk kidney. Following the viral hemorrhagic septicemia virus challenge, significant changes in PsGal8 expression were observed in the liver, intestine, and heart. The Streptococcus parauberis PH0710 challenge also modulated PsGal8 expression, with significant upregulation in the spleen, liver, brain, and intestine at 7 days post-infection. In an exploratory in vitro assay, peripheral blood leukocytes exposed to a recombinant PsGal8-containing preparation showed increased reactive oxygen species fluorescence at concentrations of 5 μg/mL and above. However, the preparation was not fully homogeneous, and its endotoxin content was not quantified. This observation should be considered preliminary. Overall, these findings provide molecular and transcriptional evidence that PsGal8 is responsive to viral and bacterial challenges in starry flounder.