Molecular characterization and comparative expression analysis of two teleostean pro-inflammatory cytokines, IL-1β and IL-8, from Sebastes schlegeli

Interleukin 1 beta (IL-1 beta) and interleukin 8 (IL-8) are two major pro-inflammatory cytokines which play a central role in initiation of inflammatory responses against bacterial- and viral-infections. IL-1 beta is a member of the interleukin 1 family proteins and IL-8 is classified as a CXC-chemokine. In the current study, putative IL-1 beta and IL-8 counterparts were identified from a black rockfish transcriptomic database and designated as RfIL-1 beta and RfIL-8. The RfIL-1 beta cDNA sequence consists of 1140 nucleotides with a 759 bp open reading frame (ORF) which encodes a 252 amino acid (aa) protein, whereas the RfIL-8 cDNA sequence (898 bp) harbors a 300 bp ORF encoding a 99 aa protein. Furthermore, the RflL-1 beta aa sequence contains an IL-1 super family-like domain and an N-terminal IL-1 super family propeptide, while the amino acid sequence of RflL-8 consists of a typical chemokine-CXC domain. Analysis of sequenced BAC clones containing RfIL-1 beta and RfIL-8 showed each gene to contain 4 exons interrupted by 3 introns. Pairwise comparison and phylogeny analysis of these cytokine sequences clearly revealed their closer relationship with other corresponding members of teleosts compared to birds and mammals. Constitutive differences in RfIL-1 beta and RflL-8 mRNA expression were detected in a tissue-specific manner with the highest expression of each mRNA in spleen tissue. Two immune challenge experiments were conducted with Streptococcus iniae and polyinosinic:polycytidylic acid (poly I:C; a viral double stranded RNA mimic), and transcripts were quantified in spleen and peripheral blood cells. Significantly increased RfIL-1 beta and RflL8 transcript levels were detected with almost similar profile patterns, further suggesting a putative involvement of these pro-inflammatory cytokines in the rockfish immunity. (C) 2015 Elsevier B.V. All rights reserved.