Characterization and functional analysis of goldfish (Carassius auratus L.) interleukin-10

This is the first report of comprehensive functional analysis of an interleukin-10 in bony fish. Quantitative expression analysis of goldfish IL-10 revealed the greatest mRNA levels in the spleen tissues, peripheral blood leukocytes and granulocytes. The stimulation of cells with recombinant goldfish (rg) TNFα2 significantly reduced IL-10 mRNA levels in granulocytes and monocytes of the goldfish. To functionally assess the goldfish IL-10, we generated a recombinant form of the molecule (rgIL-10). The rgIL-10 substantially reduced the expression of TNFα1, TNFα2, IL-1β1, IL-10, CXCL-8, and NADPH oxidase component, p47phox in monocytes activated with heat-killed Aeromonas salmonicida and reduced the expression of IFNγ in A. salmonicida-activated splenocytes. Pre-treatment of monocytes with rgIL-10 resulted in substantial reduction of the ROI response of the A. salmonicida or rgIFNγ-primed monocytes. The rgIL-10 bound to goldfish monocytes and induced phosphorylation and nuclear translocation of Stat3. The rgIL-10 also induced rapid and robust increase in the mRNA levels of the goldfish monocyte SOCS-3. Our results indicate that the function of IL-10 is highly conserved through evolution.