Gene transcript changes in individual rainbow trout livers following an inflammatory stimulus.

Inflammatory stimuli elicit liver synthesis and subsequent release into the plasma of several proteins (positive acute phase proteins, APP) with functions in innate immunity, tissue repair and restoration of homeostasis. To expand the basis for evaluating the degree of conservation of the APR in vertebrates and to assess the extent to which genes encoding both cellular and plasma proteins are affected, we profiled transcriptional changes in livers of individual rainbow trout (Oncorhynchus mykiss) after intraperitoneal injection of Listonella (Vibrio) anguillarum bacterin in Freund's Incomplete Adjuvant. Twenty genes were down-regulated, some unexpectedly such as complement component 3 and alpha2-macroglobulin. Sixteen up-regulated genes included three encoding proteins involved in iron metabolism (hepcidin, haptoglobin, and intelectin), from which we infer that sequestration of iron is likely to be a major component of the trout APR. Activated genes encoding proteins of unknown functions included precerebellin-like plasma protein, and differentially regulated trout protein which is predicted to be cell surface associated. The only complement component that increased was C7. Genes encoding proteins that are probably not released into plasma included two fatty acid binding proteins, two transport proteins (SEC61 and a Na - Ca exchanger), GAPDH, an amino transferase, and a hydrolase. When microarray data and quantitative RT-PCR analyses were used to evaluate specific transcripts, variations were notable between individual fish, possibly a basis for natural variation in susceptibility to infectious diseases. This study suggests novel hypotheses relating to NFkappaB, albumin-related protein, pentraxin, hypoferremia and the complement cascade. While the capacity to mount an APR is conserved throughout vertebrate evolution, the responding genes vary from species to species, and considerable variation is observed from individual to individual within a species.