Related Experiment Video
Updated: May 25, 2026
Pseudomonas aeruginosa Induced Lung Injury Model
Published on: October 29, 2014
MudPIT analysis of released proteins in Pseudomonas aeruginosa laboratory and clinical strains in relation to
Gabriella Bergamini1, Dario Di Silvestre, Pierluigi Mauri
1Cystic Fibrosis Center - Azienda Ospedaliera Universitaria Integrata di Verona, piazzale Stefani, 1-37126 Verona, Italy.
Abstract:
Pseudomonas aeruginosa (Pa) is the most common virulent pathogen contributing to the pathogenesis of cystic fibrosis (CF). During bacterial lung colonization, the products of its metabolism are released in the extracellular space contributing to the pathogenic events associated with its presence. To gain insights on the mechanisms involved in the Pa pathogenesis we focused our attention on proteins released by Pa using a MudPIT approach combined with cell biology assays. Conditioned medium (CM) collected under aerobic and microaerobic conditions from Pa clinical strains (in early and late colonization), unlike the laboratory strain, induced expression of IL-8 mRNA in CF airway epithelial cells. We have identified proteins released by clinically relevant Pa strains, focusing on the pro-inflammatory effects as metalloproteases (MMPs). In fact, their expression pattern was associated with the highest pro-inflammatory activity measured in the early clinically isolated strain. The relation was further supported by the result of the analysis of a larger and independent set of Pa isolates derived from sporadically and chronically infected CF patients: 76% of sporadic samples expressed protease activity (n = 44), while only 27% scored positive in the chronically infected individuals (n = 38, p < 0.0001, Fisher's exact test). Finally, looking for a possible mechanism of action of bacterial MMPs, we found that CM from early clinical isolates can cleave CXCR1 on the surface of human neutrophils, suggesting a potential role for the bacterially released MMPs in the protection of the pathogen from the host's response.
Insights
Pseudomonas aeruginosa bacterial metalloproteases (MMPs) are released during cystic fibrosis lung infections. These MMPs contribute to inflammation and may help bacteria evade host defenses by cleaving neutrophil receptors.
Area of Science:
- Microbiology
- Immunology
- Pathogenesis
Background:
- Pseudomonas aeruginosa (Pa) is a primary pathogen in cystic fibrosis (CF) lung infections.
- Bacterial metabolic products released extracellularly contribute to Pa pathogenesis in CF.
- Understanding secreted proteins is crucial for elucidating Pa virulence mechanisms.
Purpose of the Study:
- To identify proteins released by Pa clinical strains.
- To investigate the pro-inflammatory effects of these secreted proteins, particularly metalloproteases (MMPs).
- To explore the mechanism by which Pa MMPs interact with host immune cells.
Main Methods:
- MudPIT (Multi-Dimensional Protein Identification Technology) for protein identification.
- Cell biology assays using conditioned medium (CM) from Pa strains.
- Analysis of IL-8 mRNA expression in CF airway epithelial cells.
- Protease activity assays on clinical Pa isolates.
- Investigation of CXCR1 cleavage on human neutrophils.
Main Results:
- CM from Pa clinical strains (early and late colonization) induced IL-8 mRNA expression in CF cells, unlike a lab strain.
- Bacterial metalloproteases (MMPs) were identified and correlated with high pro-inflammatory activity in early clinical isolates.
- Protease activity was significantly higher in Pa from sporadic CF infections (76%) compared to chronic infections (27%).
- Pa CM cleaved CXCR1 on neutrophils, suggesting a mechanism for immune evasion.
Conclusions:
- Pseudomonas aeruginosa releases metalloproteases that contribute to inflammation in cystic fibrosis lung infections.
- Bacterial MMPs may play a role in protecting the pathogen from host immune responses by targeting neutrophil surface receptors like CXCR1.
- The reduced protease activity in chronic infections suggests a potential adaptation or shift in virulence factors over time.
