A Teleost CXCL10 Is Both an Immunoregulator and an Antimicrobial

Abstract

Chemokines are a group of cytokines that play important roles in cell migration, inflammation, and immune defense. In this study, we identified a CXC chemokine, CXCL10, from Japanese flounder Paralichthys olivaceus (named PoCXCL10) and investigated its immune function. Structurally, PoCXCL10 possesses an N-terminal coil, three β-strands, and a C-terminal α-helix with cationic and amphipathic properties. PoCXCL10 expression occurred in multiple tissues and was upregulated by bacterial pathogens. Recombinant PoCXCL10 (rPoCXCL10) promoted the migration, cytokine expression, and phagocytosis of flounder peripheral blood leukocytes (PBLs). rPoCXCL10 bound to and inhibited the growth of a variety of common Gram-negative and Gram-positive fish pathogens. rPoCXCL10 killed the pathogens by causing bacterial membrane permeabilization and structure destruction. When introduced in vivo, rPoCXCL10 significantly inhibited bacterial dissemination in fish tissues. A peptide derived from the C-terminal α-helix exhibited bactericidal activity and competed with rPoCXCL10 for bacterial binding. Deletion of the α-helix affected the in vitro bactericidal activity but not the chemotaxis or in vivo antimicrobial activity of PoCXCL10. Together, these results indicate that PoCXCL10 exerts the role of both an immunoregulator and a bactericide/bacteriostatic via different structural domains. These findings provide new insights into the immune function and working mechanism of fish CXC chemokines.

Gene expression profiles of white bass (Morone chrysops) and hybrid striped bass (M. chrysops x M. saxatilis) gill tissue following Flavobacterium covae infection

“…IL-8 mediates the inflammatory response and has been found to function as a neutrophil activator (chemoattractant) in mandarin fish ( Siniperca chuasti ) after F. columnare G 4 infection, among other species [37] . CCL16 is thought to be constitutively expressed and is involved in the maturation of immune cells [38] . CXCL9 is one of the lesser studied chemokines of the CXCL9–11/CXCR3 axis; however, a reduction of CXCL9 transcription following amoebic gill disease was identified in resistant Atlantic salmon ( Salmo salar ) compared to non-resistant fish [39] .…”

A Non-Canonical Teleost NK-Lysin: Antimicrobial Activity via Multiple Mechanisms

“…The cells were then resuspended in L-15 medium. The chemotaxis assay was performed as reported previously [ 50 ]. P35 or NCP was diluted to 0.25~10 µM with L15 medium, and 500 μL of the diluted peptide was added into the lower wells of a 24-well Transwell plate (Corning Costar Co., Cambridge, MA, USA), which were covered with nitrocellulose filter membrane.…”

Japanese Flounder HMGB1: A DAMP Molecule That Promotes Antimicrobial Immunity by Interacting with Immune Cells and Bacterial Pathogen

“…Japanese flounder were purchased from an aquaculture farm in Shandong Province, China. The fish were maintained in the laboratory and treated with tricaine methanesulfonate (Sigma, St. Louis, MO, USA) prior to tissue collection, as previously reported [ 30 ]. The experiments involving live animals were approved by the Ethics Committee of the Institute of Oceanology of the Chinese Academy of Sciences (permit No.…”

“…After incubation for 2 h, ROS production was measured using a fluorescence spectrophotometer (Infinite M1000, Tecan, Switzerland). The phagocytosis of bacteria by PBLs was determined by flow cytometry, as previously reported [ 30 ].…”

“…The binding index was defined as follows: A 450 of HMGB1 or HMG20A/ A 450 of the PBS control. A microscopic examination of HMGB1 and HMG20A binding to bacteria was performed as reported previously [ 30 ]. To examine the competitive effect of HMGB1 on the binding of HMG20A to bacteria, P. fluorescens and S. iniae in coating buffer were added to 96-well microtiter plates.…”