title: Streptococcus sanguinis induces neutrophil cell death by production of hydrogen peroxide.
abstract: Streptococcus is the dominant bacterial genus in the human oral cavity and a leading cause of infective endocarditis. Streptococcus sanguinis belongs to the mitis group of streptococci and produces hydrogen peroxide (H2O2) by the action of SpxB, a pyruvate oxidase. In this study, we investigated the involvement of SpxB in survival of S. sanguinis in human blood and whether bacterial H2O2 exhibits cytotoxicity against human neutrophils. Results of a bactericidal test with human whole blood revealed that the spxB mutation in S. sanguinis is detrimental to its survival in blood. When S. sanguinis strains were exposed to isolated neutrophils, the bacterial survival rate was significantly decreased by spxB deletion. Furthermore, human neutrophils exposed to the S. sanguinis wild-type strain, in contrast to those exposed to an spxB mutant strain, underwent cell death with chromatin de-condensation and release of web-like extracellular DNA, reflecting induction of neutrophil extracellular traps (NETs). Since reactive oxygen species-mediated NET induction requires citrullination of arginine residues in histone proteins and subsequent chromatin de-condensation, we examined citrullination levels of histone in infected neutrophils. It is important to note that the citrullinated histone H3 was readily detected in neutrophils infected with the wild-type strain, as compared to infection with the spxB mutant strain. Moreover, decomposition of streptococcal H2O2 with catalase reduced NET induction. These results suggest that H2O2 produced by S. sanguinis provokes cell death of neutrophils and NET formation, thus potentially affecting bacterial survival in the bloodstream.
authors.affiliation: Department of Oral and Molecular Microbiology, Osaka University Graduate School of Dentistry, Suita-Osaka, Japan.|Department of Restorative Dentistry and Endodontology, Osaka University Graduate School of Dentistry, Suita-Osaka, Japan.
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Sumioka
authors.affiliation: Department of Oral and Molecular Microbiology, Osaka University Graduate School of Dentistry, Suita-Osaka, Japan.
authors.forename: Masanobu
authors.initials: M
authors.lastname: Nakata
authors.affiliation: Center for Frontier Oral Science, Osaka University Graduate School of Dentistry, Suita-Osaka, Japan.
authors.forename: Nobuo
authors.initials: N
authors.lastname: Okahashi
authors.affiliation: Department of Oral and Molecular Microbiology, Osaka University Graduate School of Dentistry, Suita-Osaka, Japan.
authors.forename: Yixuan
authors.initials: Y
authors.lastname: Li
authors.affiliation: Department of Oral and Molecular Microbiology, Osaka University Graduate School of Dentistry, Suita-Osaka, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Wada
authors.affiliation: Department of Oral and Molecular Microbiology, Osaka University Graduate School of Dentistry, Suita-Osaka, Japan.
authors.forename: Masaya
authors.initials: M
authors.lastname: Yamaguchi
authors.affiliation: Department of Oral and Molecular Microbiology, Osaka University Graduate School of Dentistry, Suita-Osaka, Japan.
authors.forename: Tomoko
authors.initials: T
authors.lastname: Sumitomo
authors.affiliation: Department of Restorative Dentistry and Endodontology, Osaka University Graduate School of Dentistry, Suita-Osaka, Japan.
authors.forename: Mikako
authors.initials: M
authors.lastname: Hayashi
authors.affiliation: Department of Oral and Molecular Microbiology, Osaka University Graduate School of Dentistry, Suita-Osaka, Japan.
authors.forename: Shigetada
authors.initials: S
authors.lastname: Kawabata
mesh_terms: D000328:Adult; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D001770:Blood Bactericidal Activity; D016923:Cell Death; D002843:Chromatin / Q000648:ultrastructure; D002956:Citrulline / Q000032:analysis; D065206:Extracellular Traps; D017353:Gene Deletion; D006657:Histones / Q000097:blood; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism*; D009504:Neutrophils / Q000382:microbiology* / Q000502:physiology; D011499:Protein Processing, Post-Translational; D011771:Pyruvate Oxidase / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D017382:Reactive Oxygen Species; D013298:Streptococcus sanguis / Q000235:genetics / Q000472:pathogenicity / Q000502:physiology*; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; D002843:Chromatin; D006657:Histones; D017382:Reactive Oxygen Species; D002956:Citrulline; D006861:Hydrogen Peroxide; D011771:Pyruvate Oxidase