The gills are an important site of iNOS expression in rainbow trout Oncorhynchus mykiss after challenge with the Gram‐positive pathogen Renibacterium salmoninarum

Abstract

SUMMARYFollowing injection challenge of rainbow trout with the Gram-positive pathogen Renibacterium salmoninarum, serum nitrate levels increased indicative of NO production. The timing and amount of nitrate produced varied with the virulence of the bacterial strain used, with the highest levels seen in ®sh challenged with the most virulent (autoaggregating) strain. Immunization with a killed R. salmoninarum preparation in Freund's incomplete adjuvant signi®cantly increased nitrate levels after challenge. Inducible nitric oxide synthase (iNOS) transcript expression was detectable in rainbow trout tissues after injection challenge with R. salmoninarum, and its induction in the gills was both quick (between 3 and 6 hr) and relatively prolonged (lasting several days). iNOS expression in the kidney was also seen at a later stage (24 hr) but appeared to switch off relatively rapidly. Bath challenge with R. salmoninarum also induced iNOS expression in gill, and a variable expression in the gut and kidney also occurred. These results highlight the importance of the gills, not only as a point of entry of pathogens but also as a tissue capable of mounting an immune response.

Pathological and immunological responses associated with differential survival of Chinook salmon following Renibacterium salmoninarum challenge

“…Expression of the rainbow trout iNOS gene is rapidly up-regulated in the gills and posterior kidney after Renibacterium salmoninarum infection (CamposPerez et al 2000). Avirulent and virulent strains of R. salmoninarum increased serum nitrate (functional measure of iNOS) in trout, with the highest nitrate response observed in fish that received the virulent strain (MT1729) and suffered the highest mortality (Campos-Perez et al 2000). The R. salmoninarum genome possesses at least 2 candidate genes that may be involved in sensing and resisting nitrogen radicals (Wiens et al 2008).…”

“…Several studies have examined immune gene expression changes early after R. salmoninarum infection and demonstrated differential regulation of key immune genes (e.g. interferon pathway genes, in-terleukins and lymphocyte-associated gene markers), as compared with controls (Campos-Perez et al 2000, Grayson et al 2002, Rhodes et al 2009). …”

Molecular cloning, gene organization and expression of rainbow trout (Oncorhynchus mykiss) inducible nitric oxide synthase (iNOS) gene

“…A bacterially stimulated rainbow trout gill cDNA library [12] was used as template, since it has been shown previously that the gill is a site of high iNOS expression in rainbow trout [11]. iNOS-specific primers F6 and R6 were used for the first round of PCR, followed by primers F7 and R7 (see Table 1).…”

“…Thus in the superorder Ostariophysi, including goldfish [4,5], carp [3] and catfish [6,7], and in the superorder Acanthopterygii, including turbot [8,9] and seabream [10], leucocytes can be readily stimulated to produce nitric oxide. This is not the case with trout (superorder Protacanthopterygii), where detection of the iNOS transcript has required nested PCR following stimulation with equivalent stimuli such as lipopolysaccharide or live bacteria [1,11]. As an alternative approach to obtaining the full-length rainbow trout iNOS gene, we have undertaken genomic library screening, and have obtained sequence from two clones that have allowed the full rainbow trout iNOS gene to be sequenced, the first outside mammals.…”

The Immune System Drugs in Fish: Immune Function, Immunoassay, Drugs

“…This equipment is completed with immunocompetent cells such as leucocytes and intraepithelial plasmatic cells (Dorin et al, 1994;Moore et al, 1998;Tort et al, 2003). Recently, several additional defences have been discovered in fish mucous membranes (Bols et al, 2001), such as the production of nitric oxide by the gill as well as antibacterial peptides and proteins by skin (Campos-Perez et al, 2000;Galindo-Villegas & Hosokowa, 2004;Ebran et al, 1999;Tort et al, 2003). Not only the mucous membranes of these tissues are an important physical barrier in fish, but also contain several components with a role in the host-parasite interaction, and release antimicrobial agents or proteins.…”