An altered sputum macrophage transcriptome contributes to the neutrophilic asthma endotype

• Published in: Allergy (Copenhagen) 2022-04, Vol.77 (4), p.1204-1215
• Main Authors: Fricker, Michael, Qin, Ling, Sánchez‐Ovando, Stephany, Simpson, Jodie L., Baines, Katherine J., Riveros, Carlos, Scott, Hayley A., Wood, Lisa G., Wark, Peter AB, Kermani, Nazanin Z., Chung, Kian Fan, Gibson, Peter G.
• Format: Article
• Language: English
• Subjects: Asthma; Asthma - diagnosis; Asthma - genetics; CCR7 protein; DNA microarrays; endotype; Flow cytometry; Humans; Inflammation; Leukocytes (neutrophilic); macrophage; Macrophages; neutrophil; Neutrophils; Phagocytosis; Phenotypes; Respiratory tract; Sputum; Transcription activation; Transcriptome; Transcriptomes; Transcriptomics
• ISSN: 0105-4538; 1398-9995
• DOI: 10.1111/all.15087

Background Neutrophilic asthma (NA) is a clinically important asthma phenotype, the cellular and molecular basis of which is not completely understood. Airway macrophages are long‐lived immune cells that exert important homeostatic and inflammatory functions which are dysregulated in asthma. Unique transcriptomic programmes reflect varied macrophage phenotypes in vitro. We aimed to determine whether airway macrophages are transcriptomically altered in NA. Methods We performed RNASeq analysis on flow cytometry‐isolated sputum macrophages comparing NA (n = 7) and non‐neutrophilic asthma (NNA, n = 13). qPCR validation of RNASeq results was performed (NA n = 13, NNA n = 23). Pathway analysis (PANTHER, STRING) of differentially expressed genes (DEGs) was performed. Gene set variation analysis (GSVA) was used to test for enrichment of NA macrophage transcriptomic signatures in whole sputum microarray (cohort 1 ‐ controls n = 16, NA n = 29, NNA n = 37; cohort 2 U‐BIOPRED ‐ controls n = 16, NA n = 47, NNA n = 57). Results Flow cytometry‐sorting significantly enriched sputum macrophages (99.4% post‐sort, 44.9% pre‐sort, p