Azithromycin increases in vitro fibronectin production through interactions between macrophages and fibroblasts stimulated with Pseudomonas aeruginosa

Theodore J. Cory, Susan E. Birket, Brian S. Murphy, Cynthia Mattingly, Jessica M. Breslow-Deckman, David J. Feola

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


Objectives: Chronic azithromycin therapy has been associated with improved clinical outcomes in patients with cystic fibrosis (CF) who are chronically infected with Pseudomonas aeruginosa. We have previously demonstrated that azithromycin polarizes macrophages towards an alternatively activated phenotype, thereby blunting inflammation associated with infection. Because this phenotype is pro-fibrotic, it is important to evaluate azithromycin's consequential effects upon fibroblast function and extracellular matrix (ECM) protein production. Methods: We co-cultured macrophages and fibroblasts together and stimulated them by adding P. aeruginosa or lipopolysaccharide to assess the ability of azithromycin to alter the macrophage phenotype, along with the impact exerted upon the production of fibronectin and other effectors that govern tissue remodelling, including transforming growth factor β (TGFβ), matrix metalloproteinase-9 (MMP-9) and arginase. We supported these studies by evaluating the impact of azithromycin treatment on these proteins in a mouse model of P. aeruginosa infection. Results: Azithromycin increased arginase expression in vitro, as well as the activation of latent TGFβ, consistent with polarization to the alternative macrophage phenotype. While the drug increased fibronectin concentrations after stimulation in vitro, secretion of the ECM-degrading enzyme MMP-9 was also increased. Neutralization of active TGFβ resulted in the ablation of azithromycin's ability to increase fibronectin concentrations, but did not alter its ability to increase MMP-9 expression. In P. aeruginosa-infected mice, azithromycin significantly decreased MMP-9 and fibronectin concentrations in the alveolar space compared with non-treated, infected controls. Conclusions: Our results suggest that azithromycin's effect on MMP-9 is regulated independently of TGFβ activity. Additionally, the beneficial effects of azithromycin may be partially due to effects on homeostasis in which ECM-degrading mediators like MMP-9 are up-regulated early after infection. This may impact the damaging effects of inflammation that lead to fibrosis in this patient population.

Original languageEnglish
Article numberdks476
Pages (from-to)840-851
Number of pages12
JournalJournal of Antimicrobial Chemotherapy
Issue number4
StatePublished - Apr 2013

Bibliographical note

Funding Information:
This work was supported by the National Center for Research Resources (NCRR; TL1 RR033172), funded by the Office of the Director, National Institutes of Health (NIH) and supported by the NIH Roadmap for Medical Research.


  • Bacterial infections
  • Lung inflammation
  • P. Aeruginosa

ASJC Scopus subject areas

  • Microbiology (medical)
  • Pharmacology (medical)
  • Infectious Diseases
  • Pharmacology


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