Sputum macrophage diversity and activation in asthma: Role of severity and inflammatory phenotype.

Angelica Tiotiu,Yi‐Ke Guo,Yusef Badi,Kian Fan Chung,Stelios Pavlidis,Nazanin Zounemat Kermani,Philip M Hansbro,Ian M Adcock

doi:10.1111/all.14535

Abstract

Macrophages control innate and acquired immunity, but their role in severe asthma remains ill-defined. We investigated gene signatures of macrophage subtypes in the sputum of 104 asthmatics and 16 healthy volunteers from the U-BIOPRED cohort. Forty-nine gene signatures (modules) for differentially stimulated macrophages, one to assess lung tissue-resident cells (TR-Mφ) and two for their polarization (classically and alternatively activated macrophages: M1 and M2, respectively) were studied using gene set variation analysis. We calculated enrichment scores (ES) across severity and previously identified asthma transcriptome-associated clusters (TACs). Macrophage numbers were significantly decreased in severe asthma compared to mild-moderate asthma and healthy volunteers. The ES for most modules were also significantly reduced in severe asthma except for 3 associated with inflammatory responses driven by TNF and Toll-like receptors via NF-κB, eicosanoid biosynthesis via the lipoxygenase pathway and IL-2 biosynthesis (all P<.01). Sputum macrophage number and the ES for most macrophage signatures were higher in the TAC3 group compared to TAC1 and TAC2 asthmatics. However, a high enrichment was found in TAC1 for 3 modules showing inflammatory pathways linked to Toll-like and TNF receptor activation and arachidonic acid metabolism (P<.001) and in TAC2 for the inflammasome and interferon signalling pathways (P<.001). Data were validated in the ADEPT cohort. Module analysis provides additional information compared to conventional M1 and M2 classification. TR-Mφ were enriched in TAC3 and associated with mitochondrial function. Macrophage activation is attenuated in severe granulocytic asthma highlighting defective innate immunity except for specific subsets characterized by distinct inflammatory pathways.

Highlights

Asthma is a heterogeneous disease driven by diverse inflammatory mechanisms, which presents in various clinical forms
Sputum macrophage numbers are reduced in severe asthma compared to mild-moderate asthma and healthy volunteers
Gene set variation analysis (GSVA) analysis of macrophage signatures demonstrated decreased enrichment scores (ES) in severe asthma compared to mild-moderate asthma and healthy volunteers except for CI-Mφ activated by fatty acid (FA) and an alternatively polarized macrophage (M2)-like module

Summary

| INTRODUCTION

Asthma is a heterogeneous disease driven by diverse inflammatory mechanisms, which presents in various clinical forms. Toll-like receptor signalling pathway, TNF-α signalling pathway, IL-1β signalling pathway Fatty acids, triacylglycerol and ketone metabolism, regulation of neutrophil-mediated immunity and degranulation, regulation of IL-1β production and NK cell mediated cytotoxicity IL-2 signalling pathway, T-cell antigen receptor (TCR) pathway, intrinsic apoptosis in response to oxidative stress Oxidative phosphorylation (OXPHOS) in mitochondria, modulation of TGFβ signalling pathway, positive regulation of adaptive immune response OXPHOS system in mitochondria (electron transport) Staphylococcus aureus infection, phagosome Proteasome degradation, inositol phosphate metabolic process Positive regulation of microtubule activity, snRNA metabolic process Glycolysis/gluconeogenesis, amino acid metabolism, steroid catabolic process Ribosome biogenesis, DNA replication Sphingolipid metabolic pathway, apoptotic cell clearance, insulin-like growth factor (IGF1)-Akt signalling pathway Lysosome, Toll-like receptor pathway, carbohydrate digestion and absorption Complement and coagulation cascades, superoxide metabolic process, regulation of lymphocyte activation TGFβ-signalling pathway, regulation of IL-10 secretion, mitochondrial DNA metabolic process NF-κB signalling pathway, TNF signalling pathway, fatty acids biosynthesis Antigen processing and presentation via MHC class II, Th-17 differentiation, allograft rejection DNA damage induced protein phosphorylation, positive regulation of extracellular matrix assembly, TP53 network Ions homeostasis, Toll-like receptor signalling pathway, angiogenesis Negative regulation of acute inflammatory response, negative regulation by host of viral process, intrinsic apoptotic signalling pathway in response to oxidative stress.

| METHODS

Findings

| DISCUSSION