Detection and Localization of IL-8 and CXCR1 in Rainbow Trout Larvae in Response to Pseudomonas aeruginosa Lipopolysaccharide.

Simple Summary: The salmonid industry is susceptible to opportunistic pathogens particularly affecting fish in early developmental stages. Understanding the immunological capacity during these stages is crucial for effective disease control. The receptor for Interleukin 8 (CXCR1), plays a key role in various inflammatory conditions. This study analyzed the expression of IL-8R and IL8 in rainbow trout larvae in response to bacterial lipopolysaccharide (LPS). The larvae 19 day post-hatching (dph) exhibited strong immune responses after 8 h of LPS stimulation, with IL-8 and omCXCR1 protein expression increasing. The use of specific antisera allowed localization of both proteins in mucosal tissue cells. This study highlights the effectiveness of LPS immersion in activating the innate immune system of trout larvae using IL-8/CXCR1 as immunological markers. The salmonid industry faces challenges due to the susceptibility of fish to opportunistic pathogens, particularly in early developmental stages. Understanding the immunological capacity during these stages is crucial for developing effective disease control strategies. IL-8R, a member of the G-protein-coupled receptor family, acts as a receptor for Interleukin 8 (IL-8). The binding of IL-8 to IL-8R plays a major role in the pathophysiology of a wide spectrum of inflammatory conditions. This study focused on the immune response capacity of rainbow trout (Oncorhynchus mykiss) larvae by analyzing IL-8/CXCR1 response to lipopolysaccharide (LPS) from Pseudomonas aeruginosa. Previous research demonstrated that LPS from P. aeruginosa acts as a potent immunostimulant in teleost, enhancing pro-inflammatory cytokines. The methodology included in silico analysis and the synthesis and characterization of an omCXCR1-derived epitope peptide, which was used to produce omCXCR1-specific anti98 serum in mice. The research revealed that rainbow trout larvae 19 days post-hatching (dph) exhibited pronounced immune responses post-stimulation with 1 µg/mL of LPS. This was evidenced by the upregulated protein expression of IL-8 and omCXCR1 in trout larvae 2 and 8 h after LPS challenge, as analyzed by ELISA and immunohistochemistry. Furthermore, fluorescence microscopy successfully revealed the colocalization of IL-8 and its receptor in cells from mucosal tissues after LPS challenge in larvae 19 dph. These findings underscore the efficacy of LPS immersion as a method to activate the innate immune system in trout larvae. Furthermore, we propose IL-8 and its receptor as molecular markers for evaluating immunostimulation in the early developmental stages of salmonids. [ABSTRACT FROM AUTHOR]