An epithelial gene signature of trans-IL-6 signaling defines a subgroup of type 2-low asthma.

BACKGROUND: Asthma is stratified into type 2-high and type 2-low inflammatory phenotypes. Limited success has been achieved in developing drugs that target type 2-low inflammation. Previous studies have linked IL-6 signaling to severe asthma. IL-6 cooperates with soluble-IL-6Rα to activate cell signaling in airway epithelium. OBJECTIVE: We sought to study the role of sIL-6Rα amplified IL-6 signaling in airway epithelium and to develop an IL-6+ sIL-6Rα gene signature that may be used to select asthma patients who potentially respond to anti-IL-6 therapy. METHODS: Human airway epithelial cells were stimulated with combinations of IL-6, sIL-6Rα, and inhibitors, sgp130 (Olamkicept), and anti-IL-6R (Tocilizumab), to assess effects on pathway activation, epithelial barrier integrity, and gene expression. A gene signature was generated to identify IL-6 high patients using bronchial biopsies and nasal brushes. RESULTS: Soluble-IL-6Rα amplified the activation of the IL-6 pathway, shown by the increase of STAT3 phosphorylation and stronger gene induction in airway epithelial cells compared to IL-6 alone. Olamkicept and Tocilizumab inhibited the effect of IL-6 + sIL-6Rα on gene expression. We developed an IL-6 + sIL-6Rα gene signature and observed enrichment of this signature in bronchial biopsies but not nasal brushes from asthma patients compared to healthy controls. An IL-6 + sIL-6Rα gene signature score was associated with lower levels of sputum eosinophils in asthma. CONCLUSION: sIL-6Rα amplifies IL-6 signaling in bronchial epithelial cells. Higher local airway IL-6 + sIL-6Rα signaling is observed in asthma patients with low sputum eosinophils.

Association of asthma genetic variants with asthma-associated traits reveals molecular pathways of eosinophilic asthma.

INTRODUCTION: Asthma is a complex, polygenic, heterogenous inflammatory disease. Recently, we generated a list of 128 independent single nucleotide polymorphisms (SNPs) associated with asthma in genome-wide association studies. However, it is unknown if asthma SNPs are associated with specific asthma-associated traits such as high eosinophil counts, atopy, and airway obstruction, revealing molecular endotypes of this disease. Here, we aim to identify the association between asthma SNPs and asthma-associated traits and assess expression quantitative trait locus (e-QTLs) to reveal their downstream functional effects and find drug targets. METHODS: Association analyses between 128 asthma SNPs and associated traits (blood eosinophil numbers, atopy, airway obstruction, airway hyperresponsiveness) were conducted using regression modelling in population-based studies (Lifelines N = 32,817/Vlagtwedde-Vlaardingen N = 1554) and an asthma cohort (Dutch Asthma genome-wide association study N = 917). Functional enrichment and pathway analysis were performed with genes linked to the significant SNPs by e-QTL analysis. Genes were investigated to generate novel drug targets. RESULTS: We identified 69 asthma SNPs that were associated with at least one trait, with 20 SNPs being associated with multiple traits. The SNP annotated to SMAD3 was the most pleiotropic. In total, 42 SNPs were associated with eosinophil counts, 18 SNPs with airway obstruction, and 21 SNPs with atopy. We identified genetically driven pathways regulating eosinophilia. The largest network of eosinophilia contained two genes (IL4R, TSLP) targeted by drugs currently available for eosinophilic asthma. Several novel targets were identified such as IL-18, CCR4, and calcineurin. CONCLUSION: Many asthma SNPs are associated with blood eosinophil counts and genetically driven molecular pathways of asthma-associated traits were identified.

The genetics of asthma and the promise of genomics-guided drug target discovery.

Asthma is an inflammatory airway disease that is estimated to affect 339 million people globally. The symptoms of about 5-10% of patients with asthma are not adequately controlled with current therapy, and little success has been achieved in developing drugs that target the underlying mechanisms of asthma rather than suppressing symptoms. Over the past 3 years, well powered genetic studies of asthma have increased the number of independent asthma-associated genetic loci to 128. In this Series paper, we describe the immense progress in asthma genetics over the past 13 years and link asthma genetic variants to possible drug targets. Further studies are needed to establish the functional significance of gene variants associated with asthma in subgroups of patients and to describe the biological networks within which they function. The genomics-guided discovery of plausible drug targets for asthma could pave the way for the repurposing of existing drugs for asthma and the development of new treatments.