Histones and chymotrypsin-like elastases play significant roles in the antimicrobial activity of tongue sole neutrophil extracellular traps

• Published in: Fish & shellfish immunology Vol. 72; pp. 470 - 476
• Main Authors: Wen, Li-lian, Zhao, Ming-li, Chi, Heng, Sun, Li
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.01.2018
• Subjects: Antimicrobial; Cynoglossus semilaevis; Elastase; Histone; Neutrophil extracellular traps; Antimicrobial; Elastase; Cynoglossus semilaevis; Histone; Neutrophil extracellular traps
• ISSN: 1050-4648; 1095-9947
• DOI: 10.1016/j.fsi.2017.11.004

Neutrophil extracellular traps (NETs) are a form of extracellular antimicrobial structure of neutrophils observed in higher and lower vertebrates, the latter including the teleost fish tongue sole Cynoglossus semilaevis. However, the antimicrobial mechanism of fish NETs is unknown. In the present study, we examined the potential contribution of histones and elastases to the antibacterial effect of tongue sole NETs. For this purpose, two histones (CsH2B and CsH4) and two elastases (CsEla1 and CsEla2) of tongue sole were investigated. The histones and elastases possess the conserved domain structures characteristic of that of histones H2B/H4 and trypsin-like serine protease, respectively. Recombinant CsH2B, CsH4, CsEla1, and CsEla2 bound a wide range of Gram-negative and Gram-positive bacteria, and some of the bound bacteria were inhibited in growth by the bound histones/elastases. CsH2B, CsH4, CsEla1, and CsEla2 were all localized in NETs induced by various stimuli including bacterial pathogen. Treatment of NETs with antibodies targeting CsH2B, CsH4, CsEla1, and CsEla2 significantly reduced the antimicrobial effect of NETs. These results indicate that histones and chymotrypsin-like elastases are fundamental components of teleost NETs that play important roles in the antimicrobial activity of NETs. •Two histones and two elastases from tongue sole were analyzed for immune effect.•Recombinant proteins of the histones and elastases bound a wide range of bacteria.•Some of the histone/elastase-bound bacteria were inhibited in growth.•The histones and elastases were localized in neutrophil extracellular traps (NETs).•Antibody blocking of histones/elastases reduced the antimicrobial effect of NETs.