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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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Effect of catalase on macrophage cell death.Prior to infection, either 10 or 100 U/ml of catalase was added to cultures of differentiated THP-1 macrophages, and cells were then infected with viable S. oralis ATCC35037 (MOI: 50, 100, or 200) for 2 h. Cells were washed with PBS and cultured in fresh medium containing catalase and antibiotics for 18 h. 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 at the same MOI without catalase.
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pone-0062563-g002: Effect of catalase on macrophage cell death.Prior to infection, either 10 or 100 U/ml of catalase was added to cultures of differentiated THP-1 macrophages, and cells were then infected with viable S. oralis ATCC35037 (MOI: 50, 100, or 200) for 2 h. Cells were washed with PBS and cultured in fresh medium containing catalase and antibiotics for 18 h. 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 at the same MOI without catalase.

Mentions: It is well known that S. oralis and S. sanguinis produce H2O2, whereas S. mutans and S. salivarius do not [1], [2]. Because reactive oxygen species were previously shown to contribute to cell death of macrophages [17], we investigated the effect of catalase, an H2O2-decomposing enzyme, on S. oralis-induced cell death. Exogenously added catalase was shown to reduce cell death in macrophages infected with S. oralis ATCC35037 (Figure 2), suggesting that H2O2 is involved in this process.


Hydrogen peroxide produced by oral Streptococci induces macrophage cell death.

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

Effect of catalase on macrophage cell death.Prior to infection, either 10 or 100 U/ml of catalase was added to cultures of differentiated THP-1 macrophages, and cells were then infected with viable S. oralis ATCC35037 (MOI: 50, 100, or 200) for 2 h. Cells were washed with PBS and cultured in fresh medium containing catalase and antibiotics for 18 h. 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 at the same MOI without catalase.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3643943&req=5

pone-0062563-g002: Effect of catalase on macrophage cell death.Prior to infection, either 10 or 100 U/ml of catalase was added to cultures of differentiated THP-1 macrophages, and cells were then infected with viable S. oralis ATCC35037 (MOI: 50, 100, or 200) for 2 h. Cells were washed with PBS and cultured in fresh medium containing catalase and antibiotics for 18 h. 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 at the same MOI without catalase.
Mentions: It is well known that S. oralis and S. sanguinis produce H2O2, whereas S. mutans and S. salivarius do not [1], [2]. Because reactive oxygen species were previously shown to contribute to cell death of macrophages [17], we investigated the effect of catalase, an H2O2-decomposing enzyme, on S. oralis-induced cell death. Exogenously added catalase was shown to reduce cell death in macrophages infected with S. oralis ATCC35037 (Figure 2), suggesting that H2O2 is involved in this process.

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