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Calprotectin Increases the Activity of the SaeRS Two Component System and Murine Mortality during Staphylococcus aureus Infections.

Cho H, Jeong DW, Liu Q, Yeo WS, Vogl T, Skaar EP, Chazin WJ, Bae T - PLoS Pathog. (2015)

Bottom Line: The activity of the SaeRS TCS is repressed by certain divalent ions found in blood or neutrophil granules; however, the Zn bound-form of calprotectin relieves this repression.During staphylococcal encounter with murine neutrophils or staphylococcal infection of the murine peritoneal cavity, calprotectin increases the activity of the SaeRS TCS as well as the production of proinflammatory cytokines such as IL-1β and TNF-α, resulting in higher murine mortality.These results suggest that, under certain conditions, calprotectin can be exploited by S. aureus to increase bacterial virulence and host mortality.

View Article: PubMed Central - PubMed

Affiliation: Indiana University School of Medicine-Northwest, Gary, Indiana, United States of America.

ABSTRACT
Calprotectin, the most abundant cytoplasmic protein in neutrophils, suppresses the growth of Staphylococcus aureus by sequestering the nutrient metal ions Zn and Mn. Here we show that calprotectin can also enhance the activity of the SaeRS two component system (TCS), a signaling system essential for production of over 20 virulence factors in S. aureus. The activity of the SaeRS TCS is repressed by certain divalent ions found in blood or neutrophil granules; however, the Zn bound-form of calprotectin relieves this repression. During staphylococcal encounter with murine neutrophils or staphylococcal infection of the murine peritoneal cavity, calprotectin increases the activity of the SaeRS TCS as well as the production of proinflammatory cytokines such as IL-1β and TNF-α, resulting in higher murine mortality. These results suggest that, under certain conditions, calprotectin can be exploited by S. aureus to increase bacterial virulence and host mortality.

No MeSH data available.


Related in: MedlinePlus

CP enhances the activity of the SaeRS TCS and cytokine production in mice.(A) The activity of the SaeRS TCS in C57BL/6 (WT) and C57BL/6 S100A9-/- (A9-/-) mice. Mice were infected with S. aureus (2 × 108 cfu) by peritoneal injection, and peritoneal fluid was acquired at the indicated time points. After being separated by centrifugation (200 ×g), the GFP expression of S. aureus in supernatant (host cell-free) or in pellet (host cell-associated) was measured by flow cytometry (top panel), where the gray color represents GFP expression from pCL-gfp. The quantification results are shown in S5 Fig. (B) The effect of CP on the expression of select genes. (C) The production of proinflammatory cytokines in wild type (WT) and S100A9-/- (A9-/-) mice upon infection with S. aureus USA300 (USA) or the sae deletion mutant (Δsae). At the time points indicated, mice were sacrificed and the concentrations of proinflammatory cytokines in peritoneal fluids were determined by ELISA. The data are from three pooled mice per genotype and represent three independent experiments. Error bars indicate standard error of the mean. -, no bacteria. Statistical significance was assessed by t-test. * p < 0.05; ** p < 0.01; *** p < 0.001
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ppat.1005026.g006: CP enhances the activity of the SaeRS TCS and cytokine production in mice.(A) The activity of the SaeRS TCS in C57BL/6 (WT) and C57BL/6 S100A9-/- (A9-/-) mice. Mice were infected with S. aureus (2 × 108 cfu) by peritoneal injection, and peritoneal fluid was acquired at the indicated time points. After being separated by centrifugation (200 ×g), the GFP expression of S. aureus in supernatant (host cell-free) or in pellet (host cell-associated) was measured by flow cytometry (top panel), where the gray color represents GFP expression from pCL-gfp. The quantification results are shown in S5 Fig. (B) The effect of CP on the expression of select genes. (C) The production of proinflammatory cytokines in wild type (WT) and S100A9-/- (A9-/-) mice upon infection with S. aureus USA300 (USA) or the sae deletion mutant (Δsae). At the time points indicated, mice were sacrificed and the concentrations of proinflammatory cytokines in peritoneal fluids were determined by ELISA. The data are from three pooled mice per genotype and represent three independent experiments. Error bars indicate standard error of the mean. -, no bacteria. Statistical significance was assessed by t-test. * p < 0.05; ** p < 0.01; *** p < 0.001

Mentions: To further investigate the role of CP in the activation of the SaeRS TCS in vivo, we infected wild type and the CP-deficient mice with the P1-gfp reporter strain via intraperitoneal injection; then the GFP signal was measured in the host cell-free or host cell-associated fraction of peritoneal fluid by flow cytometry. Wild type mice showed a higher GFP signal than did CP-deficient mice in both host cell-free and host cell-associated fractions at both 2 h and 12 h post infection (Fig 6A and S5 Fig), confirming that CP contributes to the activation of the SaeRS TCS during staphylococcal infection. Host cell-associated fraction showed 6–20 times higher GFP signal than host cell-free fraction, indicating that the SaeRS TCS is activated mainly upon contact with host cells. In addition, the GFP signal at 2 h was 2–4 times higher than that at 12 h, suggesting decreased SaeRS activity or bleaching of GFP-signals [39,40]. To confirm the higher activity of the SaeRS TCS in the wild type mice, we collected S. aureus from peritoneal fluid at 12 h post infection; then the transcription of the known sae target genes (saeP, coa, hla, fnbA, sak, and lukS-PV) and two non-sae target genes (psmα and spa) were analyzed. Indeed, all sae target genes showed lower transcription in CP-deficient mice (Fig 6B). Of the two non-sae targets, the transcription of psmα was not affected by CP; however, the transcription of spa was significantly decreased in the CP-deficient mice, indicating that the effect of CP is not limited to the SaeRS TCS.


Calprotectin Increases the Activity of the SaeRS Two Component System and Murine Mortality during Staphylococcus aureus Infections.

Cho H, Jeong DW, Liu Q, Yeo WS, Vogl T, Skaar EP, Chazin WJ, Bae T - PLoS Pathog. (2015)

CP enhances the activity of the SaeRS TCS and cytokine production in mice.(A) The activity of the SaeRS TCS in C57BL/6 (WT) and C57BL/6 S100A9-/- (A9-/-) mice. Mice were infected with S. aureus (2 × 108 cfu) by peritoneal injection, and peritoneal fluid was acquired at the indicated time points. After being separated by centrifugation (200 ×g), the GFP expression of S. aureus in supernatant (host cell-free) or in pellet (host cell-associated) was measured by flow cytometry (top panel), where the gray color represents GFP expression from pCL-gfp. The quantification results are shown in S5 Fig. (B) The effect of CP on the expression of select genes. (C) The production of proinflammatory cytokines in wild type (WT) and S100A9-/- (A9-/-) mice upon infection with S. aureus USA300 (USA) or the sae deletion mutant (Δsae). At the time points indicated, mice were sacrificed and the concentrations of proinflammatory cytokines in peritoneal fluids were determined by ELISA. The data are from three pooled mice per genotype and represent three independent experiments. Error bars indicate standard error of the mean. -, no bacteria. Statistical significance was assessed by t-test. * p < 0.05; ** p < 0.01; *** p < 0.001
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4492782&req=5

ppat.1005026.g006: CP enhances the activity of the SaeRS TCS and cytokine production in mice.(A) The activity of the SaeRS TCS in C57BL/6 (WT) and C57BL/6 S100A9-/- (A9-/-) mice. Mice were infected with S. aureus (2 × 108 cfu) by peritoneal injection, and peritoneal fluid was acquired at the indicated time points. After being separated by centrifugation (200 ×g), the GFP expression of S. aureus in supernatant (host cell-free) or in pellet (host cell-associated) was measured by flow cytometry (top panel), where the gray color represents GFP expression from pCL-gfp. The quantification results are shown in S5 Fig. (B) The effect of CP on the expression of select genes. (C) The production of proinflammatory cytokines in wild type (WT) and S100A9-/- (A9-/-) mice upon infection with S. aureus USA300 (USA) or the sae deletion mutant (Δsae). At the time points indicated, mice were sacrificed and the concentrations of proinflammatory cytokines in peritoneal fluids were determined by ELISA. The data are from three pooled mice per genotype and represent three independent experiments. Error bars indicate standard error of the mean. -, no bacteria. Statistical significance was assessed by t-test. * p < 0.05; ** p < 0.01; *** p < 0.001
Mentions: To further investigate the role of CP in the activation of the SaeRS TCS in vivo, we infected wild type and the CP-deficient mice with the P1-gfp reporter strain via intraperitoneal injection; then the GFP signal was measured in the host cell-free or host cell-associated fraction of peritoneal fluid by flow cytometry. Wild type mice showed a higher GFP signal than did CP-deficient mice in both host cell-free and host cell-associated fractions at both 2 h and 12 h post infection (Fig 6A and S5 Fig), confirming that CP contributes to the activation of the SaeRS TCS during staphylococcal infection. Host cell-associated fraction showed 6–20 times higher GFP signal than host cell-free fraction, indicating that the SaeRS TCS is activated mainly upon contact with host cells. In addition, the GFP signal at 2 h was 2–4 times higher than that at 12 h, suggesting decreased SaeRS activity or bleaching of GFP-signals [39,40]. To confirm the higher activity of the SaeRS TCS in the wild type mice, we collected S. aureus from peritoneal fluid at 12 h post infection; then the transcription of the known sae target genes (saeP, coa, hla, fnbA, sak, and lukS-PV) and two non-sae target genes (psmα and spa) were analyzed. Indeed, all sae target genes showed lower transcription in CP-deficient mice (Fig 6B). Of the two non-sae targets, the transcription of psmα was not affected by CP; however, the transcription of spa was significantly decreased in the CP-deficient mice, indicating that the effect of CP is not limited to the SaeRS TCS.

Bottom Line: The activity of the SaeRS TCS is repressed by certain divalent ions found in blood or neutrophil granules; however, the Zn bound-form of calprotectin relieves this repression.During staphylococcal encounter with murine neutrophils or staphylococcal infection of the murine peritoneal cavity, calprotectin increases the activity of the SaeRS TCS as well as the production of proinflammatory cytokines such as IL-1β and TNF-α, resulting in higher murine mortality.These results suggest that, under certain conditions, calprotectin can be exploited by S. aureus to increase bacterial virulence and host mortality.

View Article: PubMed Central - PubMed

Affiliation: Indiana University School of Medicine-Northwest, Gary, Indiana, United States of America.

ABSTRACT
Calprotectin, the most abundant cytoplasmic protein in neutrophils, suppresses the growth of Staphylococcus aureus by sequestering the nutrient metal ions Zn and Mn. Here we show that calprotectin can also enhance the activity of the SaeRS two component system (TCS), a signaling system essential for production of over 20 virulence factors in S. aureus. The activity of the SaeRS TCS is repressed by certain divalent ions found in blood or neutrophil granules; however, the Zn bound-form of calprotectin relieves this repression. During staphylococcal encounter with murine neutrophils or staphylococcal infection of the murine peritoneal cavity, calprotectin increases the activity of the SaeRS TCS as well as the production of proinflammatory cytokines such as IL-1β and TNF-α, resulting in higher murine mortality. These results suggest that, under certain conditions, calprotectin can be exploited by S. aureus to increase bacterial virulence and host mortality.

No MeSH data available.


Related in: MedlinePlus