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Hydrogen peroxide produced by oral Streptococci induces macrophage cell death.

Okahashi N, Nakata M, Sumitomo T, Terao Y, Kawabata S - PLoS ONE (2013)

Bottom Line: Although the cytotoxicity of H2O2 has been widely recognized, the effects of H2O2 produced by oral streptococci on host defense systems remain unknown.Catalase, an enzyme that catalyzes the decomposition of H2O2, inhibited the cytotoxic effect of S. oralis.Furthermore, H2O2 alone was capable of inducing cell death.

View Article: PubMed Central - PubMed

Affiliation: Department of Oral Frontier Biology, Osaka University Graduate School of Dentistry, Suita-Osaka, Japan. okahashi@dent.osaka-u.ac.jp

ABSTRACT
Hydrogen peroxide (H2O2) produced by members of the mitis group of oral streptococci plays important roles in microbial communities such as oral biofilms. Although the cytotoxicity of H2O2 has been widely recognized, the effects of H2O2 produced by oral streptococci on host defense systems remain unknown. In the present study, we investigated the effect of H2O2 produced by Streptococcus oralis on human macrophage cell death. Infection by S. oralis was found to stimulate cell death of a THP-1 human macrophage cell line at multiplicities of infection greater than 100. Catalase, an enzyme that catalyzes the decomposition of H2O2, inhibited the cytotoxic effect of S. oralis. S. oralis deletion mutants lacking the spxB gene, which encodes pyruvate oxidase, and are therefore deficient in H2O2 production, showed reduced cytotoxicity toward THP-1 macrophages. Furthermore, H2O2 alone was capable of inducing cell death. The cytotoxic effect seemed to be independent of inflammatory responses, because H2O2 was not a potent stimulator of tumor necrosis factor-α production in macrophages. These results indicate that streptococcal H2O2 plays a role as a cytotoxin, and is implicated in the cell death of infected human macrophages.

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Deletion of spxB gene reduces S. oralis cytotoxicity.THP-1 macrophages were infected with S. oralis wild-type strain (WT), mutant strain defective in H2O2 production (spxB KO), or reverse mutant (spxB Rev) for 2 h, washed with PBS, and cultured in fresh medium containing antibiotics for 18 h. Macrophage viability was determined by a trypan blue dye exclusion method. Data are shown as the mean ± SD of triplicate samples. *p<0.05 as compared with untreated control (None). **p<0.05 as compared with the cells infected with WT at the same MOI.
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pone-0062563-g005: Deletion of spxB gene reduces S. oralis cytotoxicity.THP-1 macrophages were infected with S. oralis wild-type strain (WT), mutant strain defective in H2O2 production (spxB KO), or reverse mutant (spxB Rev) for 2 h, washed with PBS, and cultured in fresh medium containing antibiotics for 18 h. Macrophage viability was determined by a trypan blue dye exclusion method. Data are shown as the mean ± SD of triplicate samples. *p<0.05 as compared with untreated control (None). **p<0.05 as compared with the cells infected with WT at the same MOI.

Mentions: S. oralis WT and spxB Rev strains induced THP-1 macrophage cell death in a dose-dependent manner (Figure 5). On the other hand, spxB KO mutants had a reduced cytotoxic effect, even at an MOI of 200, indicating that H2O2 produced by S. oralis contributes to the induction of macrophage cell death.


Hydrogen peroxide produced by oral Streptococci induces macrophage cell death.

Okahashi N, Nakata M, Sumitomo T, Terao Y, Kawabata S - PLoS ONE (2013)

Deletion of spxB gene reduces S. oralis cytotoxicity.THP-1 macrophages were infected with S. oralis wild-type strain (WT), mutant strain defective in H2O2 production (spxB KO), or reverse mutant (spxB Rev) for 2 h, washed with PBS, and cultured in fresh medium containing antibiotics for 18 h. Macrophage viability was determined by a trypan blue dye exclusion method. Data are shown as the mean ± SD of triplicate samples. *p<0.05 as compared with untreated control (None). **p<0.05 as compared with the cells infected with WT at the same MOI.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3643943&req=5

pone-0062563-g005: Deletion of spxB gene reduces S. oralis cytotoxicity.THP-1 macrophages were infected with S. oralis wild-type strain (WT), mutant strain defective in H2O2 production (spxB KO), or reverse mutant (spxB Rev) for 2 h, washed with PBS, and cultured in fresh medium containing antibiotics for 18 h. Macrophage viability was determined by a trypan blue dye exclusion method. Data are shown as the mean ± SD of triplicate samples. *p<0.05 as compared with untreated control (None). **p<0.05 as compared with the cells infected with WT at the same MOI.
Mentions: S. oralis WT and spxB Rev strains induced THP-1 macrophage cell death in a dose-dependent manner (Figure 5). On the other hand, spxB KO mutants had a reduced cytotoxic effect, even at an MOI of 200, indicating that H2O2 produced by S. oralis contributes to the induction of macrophage cell death.

Bottom Line: Although the cytotoxicity of H2O2 has been widely recognized, the effects of H2O2 produced by oral streptococci on host defense systems remain unknown.Catalase, an enzyme that catalyzes the decomposition of H2O2, inhibited the cytotoxic effect of S. oralis.Furthermore, H2O2 alone was capable of inducing cell death.

View Article: PubMed Central - PubMed

Affiliation: Department of Oral Frontier Biology, Osaka University Graduate School of Dentistry, Suita-Osaka, Japan. okahashi@dent.osaka-u.ac.jp

ABSTRACT
Hydrogen peroxide (H2O2) produced by members of the mitis group of oral streptococci plays important roles in microbial communities such as oral biofilms. Although the cytotoxicity of H2O2 has been widely recognized, the effects of H2O2 produced by oral streptococci on host defense systems remain unknown. In the present study, we investigated the effect of H2O2 produced by Streptococcus oralis on human macrophage cell death. Infection by S. oralis was found to stimulate cell death of a THP-1 human macrophage cell line at multiplicities of infection greater than 100. Catalase, an enzyme that catalyzes the decomposition of H2O2, inhibited the cytotoxic effect of S. oralis. S. oralis deletion mutants lacking the spxB gene, which encodes pyruvate oxidase, and are therefore deficient in H2O2 production, showed reduced cytotoxicity toward THP-1 macrophages. Furthermore, H2O2 alone was capable of inducing cell death. The cytotoxic effect seemed to be independent of inflammatory responses, because H2O2 was not a potent stimulator of tumor necrosis factor-α production in macrophages. These results indicate that streptococcal H2O2 plays a role as a cytotoxin, and is implicated in the cell death of infected human macrophages.

Show MeSH
Related in: MedlinePlus