Oxidised IL-33 drives COPD epithelial pathogenesis via ST2-independent RAGE/EGFR signalling complex

Epithelial damage, repair and remodelling are critical features of chronic airway diseases including chronic obstructive pulmonary disease (COPD). Interleukin (IL)-33 released from damaged airway epithelia causes inflammation via its receptor, serum stimulation-2 (ST2). Oxidation of IL-33 to a non-ST2-binding form (IL-33^ox) is thought to limit its activity. We investigated whether IL-33^ox has functional activities that are independent of ST2 in the airway epithelium.

In vitro epithelial damage assays and three-dimensional, air-liquid interface (ALI) cell culture models of healthy and COPD epithelia were used to elucidate the functional role of IL-33^ox. Transcriptomic changes occurring in healthy ALI cultures treated with IL-33^ox and COPD ALI cultures treated with an IL-33-neutralising antibody were assessed with bulk and single-cell RNA sequencing analysis.

We demonstrate that IL-33^ox forms a complex with receptor for advanced glycation end products (RAGE) and epidermal growth factor receptor (EGFR) expressed on airway epithelium. Activation of this alternative, ST2-independent pathway impaired epithelial wound closure and induced airway epithelial remodelling in vitro. IL-33^ox increased the proportion of mucus-producing cells and reduced epithelial defence functions, mimicking pathogenic traits of COPD. Neutralisation of the IL-33^ox pathway reversed these deleterious traits in COPD epithelia. Gene signatures defining the pathogenic effects of IL-33^ox were enriched in airway epithelia from patients with severe COPD.

Our study reveals for the first time that IL-33, RAGE and EGFR act together in an ST2-independent pathway in the airway epithelium and govern abnormal epithelial remodelling and muco-obstructive features in COPD.