Phenotypic and functional translation of IL1RL1 locus polymorphisms in lung tissue and asthmatic airway epithelium
Michael A. Portelli, … , Gerard H. Koppelman, Ian Sayers
Michael A. Portelli, … , Gerard H. Koppelman, Ian Sayers
Published April 23, 2020
Citation Information: JCI Insight. 2020;5(8):e132446. https://doi.org/10.1172/jci.insight.132446.
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Research Article Cell biology Genetics

Phenotypic and functional translation of IL1RL1 locus polymorphisms in lung tissue and asthmatic airway epithelium

Abstract

The IL1RL1 (ST2) gene locus is robustly associated with asthma; however, the contribution of single nucleotide polymorphisms (SNPs) in this locus to specific asthma subtypes and the functional mechanisms underlying these associations remain to be defined. We tested for association between IL1RL1 region SNPs and characteristics of asthma as defined by clinical and immunological measures and addressed functional effects of these genetic variants in lung tissue and airway epithelium. Utilizing 4 independent cohorts (Lifelines, Dutch Asthma GWAS [DAG], Genetics of Asthma Severity and Phenotypes [GASP], and Manchester Asthma and Allergy Study [MAAS]) and resequencing data, we identified 3 key signals associated with asthma features. Investigations in lung tissue and primary bronchial epithelial cells identified context-dependent relationships between the signals and IL1RL1 mRNA and soluble protein expression. This was also observed for asthma-associated IL1RL1 nonsynonymous coding TIR domain SNPs. Bronchial epithelial cell cultures from asthma patients, exposed to exacerbation-relevant stimulations, revealed modulatory effects for all 4 signals on IL1RL1 mRNA and/or protein expression, suggesting SNP-environment interactions. The IL1RL1 TIR signaling domain haplotype affected IL-33–driven NF-κB signaling, while not interfering with TLR signaling. In summary, we identify that IL1RL1 genetic signals potentially contribute to severe and eosinophilic phenotypes in asthma, as well as provide initial mechanistic insight, including genetic regulation of IL1RL1 isoform expression and receptor signaling.

Authors

Michael A. Portelli, F. Nicole Dijk, Maria E. Ketelaar, Nick Shrine, Jenny Hankinson, Sangita Bhaker, Néomi S. Grotenboer, Ma’en Obeidat, Amanda P. Henry, Charlotte K. Billington, Dominick Shaw, Simon R. Johnson, Zara E.K. Pogson, Andrew Fogarty, Tricia M. McKeever, David C. Nickle, Yohan Bossé, Maarten van den Berge, Alen Faiz, Sharon Brouwer, Judith M. Vonk, Paul de Vos, Corry-Anke Brandsma, Cornelis J. Vermeulen, Amisha Singapuri, Liam G. Heaney, Adel H. Mansur, Rekha Chaudhuri, Neil C. Thomson, John W. Holloway, Gabrielle A. Lockett, Peter H. Howarth, Robert Niven, Angela Simpson, John D. Blakey, Martin D. Tobin, Dirkje S. Postma, Ian P. Hall, Louise V. Wain, Martijn C. Nawijn, Christopher E. Brightling, Gerard H. Koppelman, Ian Sayers

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Figure 6

Functional analyses of the IL1RL1 TIR risk haplotype in an in vitro reductionist model identifies an exaggerated response to IL-33 that is more amenable to anti–IL-33/IL1RL1 treatment.

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Functional analyses of the IL1RL1 TIR risk haplotype in an in vitro redu...
Transient transfection of HEK–NF-κB–SEAP reporter cells with IL1RL1 containing the 2 TIR domain polymorphism haplotypes provides a platform to identify differential NF-κB signaling. (A) Cells transfected with empty vector, IL1RL1 containing the asthma risk haplotype (Ala433/Gln501/Thr549/Leu551), or IL1RL1 containing the protective haplotype (Thr433/Arg501/Ile549/Ser551) have the same capacity to signal via the NF-κB pathways in response to 10 ng/mL TNF-α. (B) The presence of the IL1RL1 receptor carrying the asthma risk haplotype identified a 2-fold and 3-fold increase in signaling on stimulation with 10 ng/mL and 50 ng/mL of human recombinant IL-33, respectively, whereas an attenuated response was observed in the protective haplotype. (C) The response induced by 50 ng/mL IL-33 in the risk haplotype was amenable to blocking using either 10 μg/mL anti–IL-33 or anti-IL1RL1 leading to an antiinflammatory effect. (D) The effect of blocking IL-33 induced inflammation by anti–IL-33 or anti-IL1RL1 was minimal in carriers of the protective TIR domain haplotype. *P < 0.05, **P < 0.01, ****P < 0.0001. n = 3 for all experiments. Statistics were run using a Kruskal-Wallis test. Data are represented by Tukey box and whisker plots, where the box covers data from the 25th to the 75th percentiles, with the center line denoting the median of the data. Whisker plots identify the interquartile range as determined by the Tukey method, with resulting outlier data displayed as distinct points outside the whiskers.