Poster Presentation 26th Annual Lorne Proteomics Symposium 2021

Understanding how azithromycin reduces asthma exacerbations and the underlying mechanisms of macrolides (#60)

Lisa M Jurak 1 , John W Upham 1 2 , Michelle M Hill 1 3 , Ian A Yang 4 5 , Jodie L Simpson 6
  1. The University of Queensland Diamantina Institute, Woolloongabba, QLD, Australia
  2. Princess Alexandra Hospital, Woolloongabba, QLD, Australia
  3. 4QIMR Berghofer Medical Research Institute, Brisbane, QLD, Australia
  4. 5UQ Thoracic Research Centre, The University of Queensland, Brisbane, QLD, Australia
  5. The Prince Charles Hospital, Brisbane, QLD, Australia
  6. University of Newcastle, Hunter Medical Research Institute, Newcastle, NSW, Australia

Abstract:

Introduction/Aim:

New interventions are needed for non-eosinophilic or non-T2 asthma phenotypes. Although the AMAZES study (Lancet 2017) showed that azithromycin (AZM) reduces asthma exacerbations, there is limited understanding of involved mechanisms.

 

This study’s aim was to identify differentially expressed proteins in sputum from AMAZES participants, comparing sputum obtained before and after 48 weeks of AZM or placebo treatment in order to generate an AZM-sensitive protein signature.

 

Methods:

Using a robust high throughput method (mass spectroscopy) for the global analysis of the sputum proteome, 52 samples were selected with clinical characteristics balanced to ensure these were representative of the entire AMAZES cohort. Protein intensities were extracted for external statistical analyses using R studio. Differentially enriched proteins were identified by a log-fold change of 1.5 and a p-value of 0.05.

 

Results:

1446 identified proteins were common across all samples. A further 240 proteins were uniquely expressed at week 48 in AZM-treated patients and 214 in placebo-treated patients. Using a univariate model, 32 proteins were differentially expressed in AZM-treated patients, comparing week 48 to baseline. In addition, 90 proteins were differentially expressed at week 48 between AZM and placebo-treated samples. Finally, placebo-treated patients showed no significant changes in protein expression between baseline and week 48.

 

Multivariate modelling identified a unique signature of 60 proteins that distinguish AZM from placebo in comparison to the baseline proteome. Finally, protein interactions and pathway analysis identified overrepresented pathways including apoptosis, phagocytosis, IL-5 pathway, endogenous TLR/chemokine signalling and bacterial invasion, independent of asthma phenotype.

Conclusion:

We have identified known and unique proteins that change with add-on AZM therapy. Analysis of the sputum proteome provides a unique insight into AZM’s mechanisms of action. This will facilitate development of novel treatment options for severe persistent asthma.