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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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Cell death induced by H2O2.(A) Differentiated THP-1 macrophages were cultured in the presence of 1, 5, or 10 mM H2O2 for 18 h, and their viability was determined by the trypan blue staining. Data are shown as the mean ± SD of triplicate samples. *p<0.05. (B) Macrophages treated with 10 mM H2O2 were stained with Live/Dead cell staining kit. EthD-III (red fluorescence) stained the nuclear DNA of dead cells, while calcein AM (green fluorescence) stained live cells. Bar, 50 µm.
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pone-0062563-g006: Cell death induced by H2O2.(A) Differentiated THP-1 macrophages were cultured in the presence of 1, 5, or 10 mM H2O2 for 18 h, and their viability was determined by the trypan blue staining. Data are shown as the mean ± SD of triplicate samples. *p<0.05. (B) Macrophages treated with 10 mM H2O2 were stained with Live/Dead cell staining kit. EthD-III (red fluorescence) stained the nuclear DNA of dead cells, while calcein AM (green fluorescence) stained live cells. Bar, 50 µm.

Mentions: To confirm that H2O2 is, in itself, sufficient to induce cell death, THP-1 macrophages were incubated with H2O2 alone. As shown in Figure 6, the addition of H2O2 to THP-1 cell cultures induced cell death in a dose-dependent manner.


Hydrogen peroxide produced by oral Streptococci induces macrophage cell death.

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

Cell death induced by H2O2.(A) Differentiated THP-1 macrophages were cultured in the presence of 1, 5, or 10 mM H2O2 for 18 h, and their viability was determined by the trypan blue staining. Data are shown as the mean ± SD of triplicate samples. *p<0.05. (B) Macrophages treated with 10 mM H2O2 were stained with Live/Dead cell staining kit. EthD-III (red fluorescence) stained the nuclear DNA of dead cells, while calcein AM (green fluorescence) stained live cells. Bar, 50 µm.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0062563-g006: Cell death induced by H2O2.(A) Differentiated THP-1 macrophages were cultured in the presence of 1, 5, or 10 mM H2O2 for 18 h, and their viability was determined by the trypan blue staining. Data are shown as the mean ± SD of triplicate samples. *p<0.05. (B) Macrophages treated with 10 mM H2O2 were stained with Live/Dead cell staining kit. EthD-III (red fluorescence) stained the nuclear DNA of dead cells, while calcein AM (green fluorescence) stained live cells. Bar, 50 µm.
Mentions: To confirm that H2O2 is, in itself, sufficient to induce cell death, THP-1 macrophages were incubated with H2O2 alone. As shown in Figure 6, the addition of H2O2 to THP-1 cell cultures induced cell death in a dose-dependent manner.

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