Multi-omics links IL-6 trans-signalling with neutrophil extracellular trap formation andHaemophilusinfection in COPD

Abstract

BackgroundIL-6 trans-signalling (IL-6TS) is emerging as a pathogenic mechanism in chronic respiratory diseases, however the drivers of IL-6TS in the airways and the phenotypic characteristic of patients with increased IL-6TS pathway activation remain poorly understood.ObjectiveOur aim was to identify and characterize COPD patients with increased airway IL-6TS and to elucidate the biological drivers of IL-6TS pathway activation.MethodsWe used an IL-6TS-specific sputum biomarker profile (sIL-6R, IL-6, IL-1β, IL-8, MIP-1β) to stratify sputum data from patients with COPD (n=74; BEAT-COPD) by hierarchical clustering. The IL-6TS signature was related to clinical characteristics and sputum microbiome profiles. The induction of neutrophil extracellular trap formation (NETosis) and IL-6TS by Haemophilus influenzae were studied in human neutrophils.ResultsHierarchical clustering revealed an IL-6TS-high subset (n=24) of COPD patients, which shared phenotypic traits with an IL-6TS-high subset previously identified in asthma. The subset was characterized by increased sputum cell counts (p=0.0001), persistent sputum neutrophilia (p=0.0004), reduced quality of life (CRQ total score; p=0.008), and increased levels of pro-inflammatory mediators and MMPs in sputum. IL-6TS-high COPD patients showed an increase in Proteobacteria, with Haemophilus as the dominating genus. NETosis induced by H. influenzae was identified as a potential mechanism for increased soluble IL-6 receptor (sIL-6R) levels. This was supported by a significant positive correlation between sIL-6R and NETosis markers in bronchoalveolar lavage fluid from COPD patients.ConclusionIL-6TS pathway activation due to chronic colonization with Haemophilus may be an important disease driver in a subset of COPD patients.

Neutrophils in chronic inflammatory diseases

“…NETosis is induced by the infection of neutrophils with H. influenzae and is thought to be a mechanism for IL6 receptor shedding from neutrophils in COPD. Furthermore, in bronchoalveolar lavage fluid (BALF) from patients with COPD, the levels of shed IL6 receptor positively correlate with markers of NETs [ 180 ].…”

Airway Bacteria Quantification Using Polymerase Chain Reaction Combined with Neutrophil and Eosinophil Counts Identifies Distinct COPD Endotypes

“…H. influenzae colonisation has been associated with elevated sputum pro-inflammatory markers in COPD such as CXCL8, IL-1β, TNF-α and MPO [2,20]. Furthermore, activation of the IL-6 trans-signalling pathway has been associated with the haemophilus genera [33]. Overall, these results indicate that H. influenzae may elicit the production of a distinct inflammatory milieu within the lung, which promotes excessive neutrophilic inflammation.…”

Validation of Sputum Biomarker Immunoassays and Cytokine Expression Profiles in COPD

“…Wang et al also reported that sputum IL-6 level were not associated with H. influenzae colonisation, supported by our findings [ 43 ]. Winslow et al [ 47 ] described an IL-6 trans-signalling (IL-6TS) high COPD subset, defined by elevated levels of sputum IL-1β, IL-6, soluble IL-6 receptor, MIP-1β and IL-8, with increased sputum neutrophilia and HI colonisation. We also report associations between sputum IL-1β, IL-8 and MIP-1β with sputum neutrophils, and IL-1β and IL-8 with H. influenzae colonisation.…”