Loss of IL-33 enhances elastase-induced and cigarette smoke extract-induced emphysema in mice

BACKGROUND: IL-33, which is known to induce type 2 immune responses via group 2 innate lymphoid cells, has been reported to contribute to neutrophilic airway inflammation in chronic obstructive pulmonary disease. However, its role in the pathogenesis of emphysema remains unclear. METHODS: We determined the role of interleukin (IL)-33 in the development of emphysema using porcine pancreas elastase (PPE) and cigarette smoke extract (CSE) in mice. First, IL-33(−/−) mice and wild-type (WT) mice were given PPE intratracheally. The numbers of inflammatory cells, and the levels of cytokines and chemokines in the bronchoalveolar lavage (BAL) fluid and lung homogenates, were analyzed; quantitative morphometry of lung sections was also performed. Second, mice received CSE by intratracheal instillation. Quantitative morphometry of lung sections was then performed again. RESULTS: Intratracheal instillation of PPE induced emphysematous changes and increased IL-33 levels in the lungs. Compared to WT mice, IL-33(−/−) mice showed significantly greater PPE-induced emphysematous changes. No differences were observed between IL-33(−/−) and WT mice in the numbers of macrophages or neutrophils in BAL fluid. The levels of hepatocyte growth factor were lower in the BAL fluid of PPE-treated IL-33(−/−) mice than WT mice. IL-33(−/−) mice also showed significantly greater emphysematous changes in the lungs, compared to WT mice, following intratracheal instillation of CSE. CONCLUSION: These observations suggest that loss of IL-33 promotes the development of emphysema and may be potentially harmful to patients with COPD. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12931-021-01705-z.