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Updated: Mar 11, 2026
Long Term Chronic Pseudomonas aeruginosa Airway Infection in Mice
Published on: March 17, 2014
Azithromycin Attenuates Pseudomonas-Induced Lung Inflammation by Targeting Bacterial Proteins Secreted in the
Teresinha Leal1, Gabriella Bergamini2, François Huaux1
1Louvain Centre for Toxicology and Applied Pharmacology, Institut de Recherche Expérimentale et Clinique, Université catholique de Louvain , Brussels , Belgium.
Background:
Pseudomonas aeruginosa airway infections are a major cause of morbidity and mortality in patients with cystic fibrosis (CF). Azithromycin improves the related clinical outcomes, but its mechanisms of action remain poorly understood. We tested the hypothesis that azithromycin downregulates P. aeruginosa-induced pro-inflammatory responses by modifying release of bacterial proteins.
Methods:
We monitored inflammatory markers in lungs of CF mutant mice and their littermate controls in response to conditioned media (CM) collected from the reference P. aeruginosa PAO1 strain cultured in the presence or in the absence of azithromycin. A mass spectrometry-based proteomic approach was applied to examine whether the macrolide elicits a differential release of bacterial proteins.
Results:
CM collected from azithromycin-untreated PAO1 cultures induced powerful pro-inflammatory neutrophil-dominated responses. Azithromycin attenuated the responses, mainly of macrophage chemoattractant protein-1, tumor necrosis factor-α, and interferon-γ, in CF but not in wild-type mice. Proteomic analysis showed that azithromycin upregulated an array of bacterial proteins including those associated with regulation of immune functions and with repair and resolution of inflammatory responses like the chaperone DnaK and the S-adenosylmethionine synthase, while it downregulated the extracellular heme acquisition protein HasA and the catalytic enzyme lysylendopeptidase.
Conclusion:
Supernatants collected from cultures of the bacterial strain PAO1 represent a novel experimental model to trigger in vivo lung inflammatory responses that should be closer to those obtained with live bacteria, but without bacterial infection. Combined with a bactericidal effect, complex regulation of bacterial innate immune and metabolic factors released in the cultured medium by the action of the macrolide can contribute to its anti-inflammatory effects.
Insights
Azithromycin reduces Pseudomonas aeruginosa-induced inflammation in cystic fibrosis (CF) mice by altering bacterial protein release. This macrolide modulates immune responses, offering new insights into CF treatment strategies.
Area of Science:
- Microbiology
- Immunology
- Pharmacology
Background:
- Pseudomonas aeruginosa infections are a significant cause of morbidity and mortality in cystic fibrosis (CF) patients.
- Azithromycin treatment improves clinical outcomes in CF, but its anti-inflammatory mechanisms are not fully understood.
- This study investigates how azithromycin affects bacterial protein release to modulate host inflammatory responses.
Purpose of the Study:
- To test the hypothesis that azithromycin downregulates Pseudomonas aeruginosa-induced pro-inflammatory responses by modifying bacterial protein release.
- To explore the potential of bacterial culture supernatants as a model for studying lung inflammation in vivo.
Main Methods:
- Inflammatory markers were monitored in CF mutant mice lungs exposed to Pseudomonas aeruginosa conditioned media (CM) with or without azithromycin.
- A mass spectrometry-based proteomic approach was used to analyze differential protein release from P. aeruginosa cultures treated with azithromycin.
- CF mutant and wild-type mice were used to assess differential inflammatory responses.
Main Results:
- Azithromycin-treated P. aeruginosa CM significantly attenuated pro-inflammatory responses (e.g., macrophage chemoattractant protein-1, tumor necrosis factor-α, interferon-γ) in CF mice.
- Proteomic analysis revealed azithromycin upregulated bacterial proteins involved in immune regulation and inflammatory repair (e.g., DnaK, S-adenosylmethionine synthase).
- Azithromycin downregulated bacterial proteins such as HasA and lysylendopeptidase.
Conclusions:
- Bacterial culture supernatants provide a novel in vivo model for lung inflammation without live bacterial infection.
- Azithromycin's anti-inflammatory effects in CF may stem from complex regulation of bacterial immune and metabolic factors, in addition to its bactericidal activity.
- Understanding azithromycin's impact on bacterial protein release offers new therapeutic insights for Pseudomonas aeruginosa infections in CF.
