ExoU activates NF-κB and increases IL-8/KC secretion during Pseudomonas aeruginosa infection.

Abstract

ExoU, a Pseudomonas aeruginosa cytotoxin injected into host cytosol by type III secretion system, exhibits a potent proinflammatory activity that leads to a marked recruitment of neutrophils to infected tissues. To evaluate the mechanisms that account for neutrophil infiltration, we investigated the effect of ExoU on IL-8 secretion and NF-κB activation. We demonstrate that ExoU increases IL-8 mRNA and protein levels in P. aeruginosa-infected epithelial and endothelial cell lines. Also, ExoU induces the nuclear translocation of p65/p50 NF-κB transactivator heterodimer as well as NF-κB-dependent transcriptional activity. ChIP assays clearly revealed that ExoU promotes p65 binding to NF-κB site in IL-8 promoter and the treatment of cultures with the NF-κB inhibitor Bay 11-7082 led to a significant reduction in IL-8 mRNA levels and protein secretion induced by ExoU. These results were corroborated in a murine model of pneumonia that revealed a significant reduction in KC secretion and neutrophil infiltration in bronchoalveolar lavage when mice were treated with Bay 11-7082 before infection with an ExoU-producing strain. In conclusion, our data demonstrate that ExoU activates NF-κB, stimulating IL-8 expression and secretion during P. aeruginosa infection, and unveils a new mechanism triggered by this important virulence factor to interfere in host signaling pathways.

• Authors: Carolina Diettrich Mallet de Lima, Teresa Cristina Calegari-Silva, Renata Meirelles Santos Pereira, Sabrina Alves de Oliveira Lima Santos, Ulisses Gazos Lopes, Maria-Cristina Maciel Plotkowski, Alessandra Mattos Saliba
• Journal: PloS one (PLoS One) Vol. 7 Issue 7 Pg. e41772 ( 2012) ISSN: 1932-6203 [Electronic] United States
• PMID: 22848596 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Bacterial Proteins
• Interleukin-8
• NF-kappa B
• RNA, Messenger
• pseudomonas exoprotein A protein, Pseudomonas aeruginosa

Topics

• Animals
• Bacterial Proteins (biosynthesis, metabolism)
• Bronchoalveolar Lavage Fluid (microbiology)
• Capillaries (cytology)
• Cell Line
• Endothelial Cells (metabolism, microbiology)
• Epithelial Cells (metabolism, microbiology)
• Female
• Gene Expression Regulation
• Interleukin-8 (genetics, metabolism)
• Mice
• NF-kappa B (metabolism)
• Neutrophil Infiltration
• Pseudomonas aeruginosa (metabolism, physiology)
• RNA, Messenger (genetics, metabolism)
• Respiratory System (immunology, microbiology)