Cigarette smoke with IL-33 delivery leads to an exacerbated phenotype and hallmarks of mixed type 1/type 2 lung inflammation in mice

<bold>Rationale:</bold> Chronic obstructive pulmonary disease (COPD) is a heterogenous disease characterized by type 1/17 (T1/17) neutrophilic airway inflammation in ~60% of patients and mixed T1/T17 and type 2 (T2) inflammation in ~30-40% of patients. However, few mouse models exist that capture these distinct phenotypes. <bold>Aim:</bold> To devise a mouse model of COPD that captures the features of mixed airway inflammation by combining acute smoke exposure with concurrent intranasal (i.n.) delivery of IL-33. <bold>Methods:</bold> Mice were exposed to cigarette smoke, i.n. IL-33, or a combination regimen. Lungs were harvested and processed for protein analysis, flow cytometry, and bulk RNA sequencing. <bold>Results:</bold> Intranasal delivery of IL-33 alone, or smoke exposure alone resulted in neutrophil infiltration and T1/T17 cytokine production in the lung. Of note, IL-33 alone distinctly induced eosinophil infiltration and T2 cytokine production, resulting in mixed airway inflammation. A combination of i.n. IL-33 and smoke showed a gene signature in the lung that contained the signatures found in the single treatment groups. Additionally, the combination treatment revealed 410 unique differentially expressed genes, showed trends of reduced lung alveolar macrophages, and increased lung neutrophils, TNF-a, IL-1a, MIP-1a compared to both single treatment groups. <bold>Conclusion:</bold> We developed a mouse model of mixed airway inflammation and highlighted a distinct transcriptional signature in mice exposed to acute cigarette smoke compared to an IL-33 combined with smokeregimen. This highlights the role of IL-33 in initiating and driving mixed airway inflammation in COPD.