Azithromycin blocks autophagy and may predispose cystic fibrosis patients to mycobacterial infection
Maurizio Renna, … , David C. Rubinsztein, R. Andres Floto
Maurizio Renna, … , David C. Rubinsztein, R. Andres Floto
Published August 1, 2011
Citation Information: J Clin Invest. 2011;121(9):3554-3563. https://doi.org/10.1172/JCI46095.
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Research Article Immunology

Azithromycin blocks autophagy and may predispose cystic fibrosis patients to mycobacterial infection

Abstract

Azithromycin is a potent macrolide antibiotic with poorly understood antiinflammatory properties. Long-term use of azithromycin in patients with chronic inflammatory lung diseases, such as cystic fibrosis (CF), results in improved outcomes. Paradoxically, a recent study reported that azithromycin use in patients with CF is associated with increased infection with nontuberculous mycobacteria (NTM). Here, we confirm that long-term azithromycin use by adults with CF is associated with the development of infection with NTM, particularly the multi-drug-resistant species Mycobacterium abscessus, and identify an underlying mechanism. We found that in primary human macrophages, concentrations of azithromycin achieved during therapeutic dosing blocked autophagosome clearance by preventing lysosomal acidification, thereby impairing autophagic and phagosomal degradation. As a consequence, azithromycin treatment inhibited intracellular killing of mycobacteria within macrophages and resulted in chronic infection with NTM in mice. Our findings emphasize the essential role for autophagy in the host response to infection with NTM, reveal why chronic use of azithromycin may predispose to mycobacterial disease, and highlight the dangers of inadvertent pharmacological blockade of autophagy in patients at risk of infection with drug-resistant pathogens.

Authors

Maurizio Renna, Catherine Schaffner, Karen Brown, Shaobin Shang, Marcela Henao Tamayo, Krisztina Hegyi, Neil J. Grimsey, David Cusens, Sarah Coulter, Jason Cooper, Anne R. Bowden, Sandra M. Newton, Beate Kampmann, Jennifer Helm, Andrew Jones, Charles S. Haworth, Randall J. Basaraba, Mary Ann DeGroote, Diane J. Ordway, David C. Rubinsztein, R. Andres Floto

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Figure 1

Azithromycin blocks autophagy by impairing autophagic flux.

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Azithromycin blocks autophagy by impairing autophagic flux. (A) At Papwo...
(A) At Papworth Hospital, the numbers of adult CF patients on long-term azithromycin (AZM; red) and with new sputum cultures positive for NTM (gray) rose over the last 5 years. (B) Analysis of the 2007–2008 CF patient cohort. In patients currently or previously infected with NTM, long-term azithromycin use (current or within 6 months of first NTM culture) was significantly more common that in uninfected patients (P = 0.0009; 2-tailed uncorrected χ2). (C) In GFP-LC3+ COS7 cells, 24-hour treatment with azithromycin increased the number of cells containing 10 or more GFP-LC3+ vesicles more so than rapamycin (200 nM). (D) In HeLa cells, azithromycin caused a dose-dependent increase in LC3-II levels (EC50, 4.5 μg/ml). exp., exposure. (E) In the presence of 400 nM BafA1, azithromycin treatment of HeLa cells did not increase LC3-II compared with BafA1 alone. (F) Azithromycin treatment (16 μg/ml) of HeLa cells, while increasing LC3-II, did not alter mTOR-dependent signaling (monitored by changes in phosphorylation of S6 and p70S6 kinase); however, it did increase p62 levels. (G) Azithromycin dose-dependently increased LC3-II and p62 levels in primary human macrophages. (H) Similar effect of azithromycin, assessed by LC3-II and p62 levels, in primary macrophages derived from clinically stable CF patients and healthy controls (n = 3 per group). *P < 0.05; **P < 0.005.