title: Molecular characterization, expression analysis, and biological effects of interleukin-8 in grass carp Ctenopharyngodon idellus.
abstract: Interleukin-8 (IL-8) is a CXC chemokine that plays key regulatory roles in the immune and inflammatory responses implicated in many human diseases. In this study, we identified and characterized an IL-8 homologue from the grass carp, Ctenopharyngodon idellus. A sequence alignment of the full-length cDNA and genomic DNA showed that the exon/intron organization of grass carp IL-8 (gcIL-8) is identical to those of other known CXC chemokine genes. A multiple alignment analysis showed that gcIL-8 is an ELR(-)CXC chemokine, and its deduced amino acid sequence shares 81% and 36% identity with common carp IL-8s L1 (GenBank ID: ABE47600) and L2 (GenBank ID: AB470924), respectively, suggesting that it belongs to the lineage 1 group of fish IL-8 proteins. On a phylogenetic tree, gcIL-8 clustered with other teleost IL-8 proteins to form a fish-specific clade, clearly distinct from those of bird, mammal, and amphibian proteins. Real-time quantitative PCR analysis indicated that gcIL-8 is differentially expressed in various tissues under normal conditions and that the expression of gcIL-8 mRNA in immune-related tissues is clearly upregulated by Aeromonas hydrophila infection. To explore the biological effects of gcIL-8, we produced a recombinant protein, rgcIL-8, in a prokaryotic expression system. Purified rgcIL-8 was confirmed to be chemoattractive for head kidney neutrophils and mononuclear leukocytes in vitro. Our histopathological study also revealed that rgcIL-8 exerts proinflammatory effects by inducing neutrophil infiltration and erythrocyte extravasation. Overall, these results suggest that IL-8 is crucially involved in the inflammatory responses of fish.
authors.affiliation: Department of Hydrobiology, School of Biology and Basic Medical Sciences, Soochow University, 199 Ren'ai Road, Suzhou, Jiangsu 215123, China.
authors.forename: Ting-Ting
authors.initials: TT
authors.lastname: Wang
authors.forename: Xue-Hong
authors.initials: XH
authors.lastname: Song
authors.forename: Guang-Ming
authors.initials: GM
authors.lastname: Bao
authors.forename: Li-Xiang
authors.initials: LX
authors.lastname: Zhao
authors.forename: Xiao
authors.initials: X
authors.lastname: Yu
authors.forename: Jie
authors.initials: J
authors.lastname: Zhao
mesh_terms: D000595:Amino Acid Sequence; D000704:Analysis of Variance; D000818:Animals; D001483:Base Sequence; D002347:Carps / Q000235:genetics* / Q000276:immunology; D003001:Cloning, Molecular; D016000:Cluster Analysis; D019295:Computational Biology; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D020869:Gene Expression Profiling / Q000662:veterinary; D005786:Gene Expression Regulation / Q000235:genetics / Q000276:immunology*; D016209:Interleukin-8 / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010802:Phylogeny; D011487:Protein Conformation; D060888:Real-Time Polymerase Chain Reaction / Q000662:veterinary; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA / Q000662:veterinary
chemical_list: D017931:DNA Primers; D018076:DNA, Complementary; D016209:Interleukin-8
keywords: Gene expression pattern; Grass carp Ctenopharyngodon idellus; Interleukin-8 (IL-8); Phylogenetic analysis; Proinflammatory activity