Abstract
Harmful algal blooms pose an increasing risk for aquaculture, primarily affecting fish gill physiology, a key organ involved in gas exchange, osmoregulation, and immune barrier function. In this study, the epithelial cell line RTgill-W1, derived from trout gills, was used as an in vitro model to evaluate gene expression changes induced by extracellular compounds produced by Karenia selliformis (strain CREAN-KS02). The extract used was obtained exclusively from cell-free K. selliformis culture medium by adsorption onto HP-20 resin, concentrating potentially bioactive low-polarity extracellular metabolites. Cells were exposed to 2 µg*mL-1 of the extract for 2, 4, 6, 12, and 24 hours. The relative expression of genes associated with oxidative stress (SOD, HSP70), epithelial integrity (E-cadherin, ZO-1, Claudin 12), ion transport (NKA), and apoptosis (caspase-8, caspase-3b) was evaluated by RT-qPCR using extracts from L1 culture medium without microalgae as a control. Results revealed dynamic transcriptional responses, including both upregulation and downregulation of gene expression. The overexpression of antioxidant genes suggests the activation of cellular defense mechanisms against oxidative stress, progressive downregulation of epithelial markers indicates functional impairment of the epithelial barrier. Furthermore, activation of apoptotic pathways confirms cytotoxic effects. These findings support the applicability of the RTgill-W1 cell line as a sensitive and informative model to study the molecular mechanisms underlying the toxicity of harmful algal metabolites.
Keywords
RTgill-W1; Relative gene expression; Harmful algal blooms; Karenia selliformis; Aquatic toxicology.