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Pseudomonas aeruginosa pyocyanin induces neutrophil death via mitochondrial reactive oxygen species and mitochondrial acid sphingomyelinase.

Managò A, Becker KA, Carpinteiro A, Wilker B, Soddemann M, Seitz AP, Edwards MJ, Grassmé H, Szabò I, Gulbins E - Antioxid. Redox Signal. (2015)

Bottom Line: Because many strains of P. aeruginosa are resistant to antibiotics, therapeutic options are limited.This reduced death, on the other hand, is associated with an increase in the release of interleukin-8 from pyocyanin-activated acid sphingomyelinase-deficient neutrophils but not from wild-type cells.These findings demonstrate a novel mechanism of pyocyanin-induced death of neutrophils and show how this apoptosis balances innate immune reactions.

View Article: PubMed Central - PubMed

Affiliation: 1 Department of Biology, University of Padova , Padova, Italy .

ABSTRACT

Aims: Pulmonary infections with Pseudomonas aeruginosa are a serious clinical problem and are often lethal. Because many strains of P. aeruginosa are resistant to antibiotics, therapeutic options are limited. Neutrophils play an important role in the host's early acute defense against pulmonary P. aeruginosa. Therefore, it is important to define the mechanisms by which P. aeruginosa interacts with host cells, particularly neutrophils.

Results: Here, we report that pyocyanin, a membrane-permeable pigment and toxin released by P. aeruginosa, induces the death of wild-type neutrophils; its interaction with the mitochondrial respiratory chain results in the release of reactive oxygen species (ROS), the activation of mitochondrial acid sphingomyelinase, the formation of mitochondrial ceramide, and the release of cytochrome c from mitochondria. A genetic deficiency in acid sphingomyelinase prevents both the activation of this pathway and pyocyanin-induced neutrophil death. This reduced death, on the other hand, is associated with an increase in the release of interleukin-8 from pyocyanin-activated acid sphingomyelinase-deficient neutrophils but not from wild-type cells.

Innovation: These studies identified the mechanisms by which pyocyanin induces the release of mitochondrial ROS and by which ROS induce neutrophil death via mitochondrial acid sphingomyelinase.

Conclusion: These findings demonstrate a novel mechanism of pyocyanin-induced death of neutrophils and show how this apoptosis balances innate immune reactions.

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Related in: MedlinePlus

Pyocyanin-induced interleukin-8 is negatively regulated by acid sphingomyelinase. Peritoneal neutrophils were obtained from wt or Asm-deficient mice and stimulated with 50 μM Pyo for 8 h. Interleukin-8 levels were determined by ELISA. Shown are the means±SD of four independent experiments; *p<0.05 compared with untreated, Δp<0.05 compared with treated wild-type cells, by ANOVA. ELISA, enzyme-linked immunosorbent assay; Pyo, pyocyanin.
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f6: Pyocyanin-induced interleukin-8 is negatively regulated by acid sphingomyelinase. Peritoneal neutrophils were obtained from wt or Asm-deficient mice and stimulated with 50 μM Pyo for 8 h. Interleukin-8 levels were determined by ELISA. Shown are the means±SD of four independent experiments; *p<0.05 compared with untreated, Δp<0.05 compared with treated wild-type cells, by ANOVA. ELISA, enzyme-linked immunosorbent assay; Pyo, pyocyanin.

Mentions: Mitochondria have been shown to be crucial in the activation of inflammasomes by recruiting and activating proinflammatory caspases; they are also crucial in the induction of cell death by the release of cytochrome c (6, 38). Therefore, we tested the effect of pyocyanin on the release of IL-8 and on the induction of death in freshly isolated neutrophils from wild-type and Asm-deficient neutrophils. The results demonstrate that pyocyanin induces the release of a higher amount of IL-8 from Asm-deficient neutrophils than from wild-type cells (Fig. 6). Basal levels of IL-8 were also higher in Asm-deficient neutrophils than in wild-type neutrophils. These findings indicate a negative regulation of IL-8 release from neutrophils by Asm and ceramide.


Pseudomonas aeruginosa pyocyanin induces neutrophil death via mitochondrial reactive oxygen species and mitochondrial acid sphingomyelinase.

Managò A, Becker KA, Carpinteiro A, Wilker B, Soddemann M, Seitz AP, Edwards MJ, Grassmé H, Szabò I, Gulbins E - Antioxid. Redox Signal. (2015)

Pyocyanin-induced interleukin-8 is negatively regulated by acid sphingomyelinase. Peritoneal neutrophils were obtained from wt or Asm-deficient mice and stimulated with 50 μM Pyo for 8 h. Interleukin-8 levels were determined by ELISA. Shown are the means±SD of four independent experiments; *p<0.05 compared with untreated, Δp<0.05 compared with treated wild-type cells, by ANOVA. ELISA, enzyme-linked immunosorbent assay; Pyo, pyocyanin.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4403017&req=5

f6: Pyocyanin-induced interleukin-8 is negatively regulated by acid sphingomyelinase. Peritoneal neutrophils were obtained from wt or Asm-deficient mice and stimulated with 50 μM Pyo for 8 h. Interleukin-8 levels were determined by ELISA. Shown are the means±SD of four independent experiments; *p<0.05 compared with untreated, Δp<0.05 compared with treated wild-type cells, by ANOVA. ELISA, enzyme-linked immunosorbent assay; Pyo, pyocyanin.
Mentions: Mitochondria have been shown to be crucial in the activation of inflammasomes by recruiting and activating proinflammatory caspases; they are also crucial in the induction of cell death by the release of cytochrome c (6, 38). Therefore, we tested the effect of pyocyanin on the release of IL-8 and on the induction of death in freshly isolated neutrophils from wild-type and Asm-deficient neutrophils. The results demonstrate that pyocyanin induces the release of a higher amount of IL-8 from Asm-deficient neutrophils than from wild-type cells (Fig. 6). Basal levels of IL-8 were also higher in Asm-deficient neutrophils than in wild-type neutrophils. These findings indicate a negative regulation of IL-8 release from neutrophils by Asm and ceramide.

Bottom Line: Because many strains of P. aeruginosa are resistant to antibiotics, therapeutic options are limited.This reduced death, on the other hand, is associated with an increase in the release of interleukin-8 from pyocyanin-activated acid sphingomyelinase-deficient neutrophils but not from wild-type cells.These findings demonstrate a novel mechanism of pyocyanin-induced death of neutrophils and show how this apoptosis balances innate immune reactions.

View Article: PubMed Central - PubMed

Affiliation: 1 Department of Biology, University of Padova , Padova, Italy .

ABSTRACT

Aims: Pulmonary infections with Pseudomonas aeruginosa are a serious clinical problem and are often lethal. Because many strains of P. aeruginosa are resistant to antibiotics, therapeutic options are limited. Neutrophils play an important role in the host's early acute defense against pulmonary P. aeruginosa. Therefore, it is important to define the mechanisms by which P. aeruginosa interacts with host cells, particularly neutrophils.

Results: Here, we report that pyocyanin, a membrane-permeable pigment and toxin released by P. aeruginosa, induces the death of wild-type neutrophils; its interaction with the mitochondrial respiratory chain results in the release of reactive oxygen species (ROS), the activation of mitochondrial acid sphingomyelinase, the formation of mitochondrial ceramide, and the release of cytochrome c from mitochondria. A genetic deficiency in acid sphingomyelinase prevents both the activation of this pathway and pyocyanin-induced neutrophil death. This reduced death, on the other hand, is associated with an increase in the release of interleukin-8 from pyocyanin-activated acid sphingomyelinase-deficient neutrophils but not from wild-type cells.

Innovation: These studies identified the mechanisms by which pyocyanin induces the release of mitochondrial ROS and by which ROS induce neutrophil death via mitochondrial acid sphingomyelinase.

Conclusion: These findings demonstrate a novel mechanism of pyocyanin-induced death of neutrophils and show how this apoptosis balances innate immune reactions.

Show MeSH
Related in: MedlinePlus