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 5

Azithromycin blocks phagosomal degradation and phagosome-lysosome fusion.

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Azithromycin blocks phagosomal degradation and phagosome-lysosome fusion...
(A) OVA-coated beads were incubated with primary human macrophages (1-hour pulse, 23-hour chase). Internalized beads were released, and the amount of OVA coating was quantified by flow cytometry after incubation with fluorescent anti-OVA antibody. Treatment with azithromycin (20 μg/ml) significantly reduced OVA degradation compared with untreated cells, to levels close to those achieved by BafA1 (100 nM) or leupeptin/pepstatin. (B) Human primary macrophages were incubated (1-hour pulse, 4-hour chase) with TMR- and biotin-conjugated dextran to load lysosomes and then fed with IgG-coated streptavidin-conjugated fluorescent latex beads (30-minute pulse, 2-hour chase) with no treatment or in the presence of azithromycin (80 μg/ml) or BafA1 (400 nM). Beads were recovered by cell disruption, and the degree of bound dextran fluorescence was quantified by flow cytometry. Shown are a representative histogram and average geometric mean fluorescence of triplicate samples.