Molecular characterization, inductive expression and mechanism of interleukin-10 gene induction in the Indian major carp, catla (Catla catla)

Interleukin-10 (IL-10) is a multifunctional cytokine and plays an important role in diseases. In this study, IL-10 gene was cloned and characterized from catla (Catla catla), which is a highly commercially important fish species in the Indian subcontinent. The result indicated that the full-length catla IL-10 (cIL-10) gene had five exons and four introns with an open reading frame of 540 nucleotides encoding a polypeptide of 179 amino acids. A phylogenetic analysis of cIL-10 gene sequence showed that cIL-10 clustered with freshwater carps group as expected. Quantitative real-time polymerase chain reaction analysis showed that cIL-10 was expressed in gill, liver, kidney, intestine, skin and heart and its expression profile was up-regulated in bacterial infection and LPS treatment. A close relationship of high cIL-10 expression and low pro-inflammatory cytokine IL-1 beta expression was observed in the treated group of fish, which might reveal the role of cIL-10 as an anti-inflammatory cytokine. Mechanism of cIL-10 induction was investigated by blocking nuclear factor (NF)-?B -signalling with BAY 11-7082 in catla kidney cell culture. Blocking NF-?B suppressed IL-10 induction by LPS, and thus it revealed that cIL-10 was induced through NF-?B signalling. These data could be helpful to understand the function of IL-10 in fish in response to vaccinations, probiotics and various diseases.