Involvement of autophagy in exacerbation of eosinophilic airway inflammation in a murine model of obese asthma

Obesity is a common comorbidity in patients with asthma, and obese asthma patients present the most refractory phenotype among patients with severe asthma. Similar to the observations in non-obese asthma patients, clinical studies have revealed heterogeneity in obese asthma patients, including the occurrences of T helper (Th)2-high and Th2-low phenotypes. However, the mechanisms underlying obesity-related asthma are not completely understood. Though macroautophagy/autophagy is involved in asthma and obesity, its role in obesity-associated asthma is unknown. We hypothesized that autophagy is involved in the pathogenesis of obese asthma. For our investigations, we used high-fat diet-induced Atg5 (autophagy related 5)-deficient mice and epithelial cell-specific atg5(−/−) (Scgb1a1/CCSP-atg5(−/−)) obesity-induced mice. House dust mite (HDM)-sensitized atg5(−/−) obese mice exhibited marked eosinophilic inflammation and airway hyper-reactivity (AHR), compared to wild-type (WT) obese mice. Analyses of atg5(−/−) obese mice showed increased levels of Th2 cells but not ILC2s together with elevated expression of Th2 cytokines in the lung. In response to the HDM challenge, activated epithelial autophagy was observed in lean but not obese WT mice. Epithelium-specific deletion of Atg5 induced eosinophilic inflammation in Scgb1a1/CCSP-atg5(−/−) obese mice, and genetic analyses of epithelial cells from HDM-immunized atg5(−/−) obesity-induced mice showed an elevated expression of thymic stromal lymphopoietin (TSLP) and IL33. Notably, HDM-sensitized atg5(−/−) mice developed TSLP- and IL33-dependent eosinophilic inflammation and AHR. Our results suggest that autophagy contributes to the exacerbation of eosinophilic inflammation in obese asthma. Modulations of autophagy may be a therapeutic target in obesity-associated asthma. Abbreviations: AHR: airway hyper-reactivity; BAL: bronchoalveolar lavage; C(dyn): dynamic compliance; BM: bone marrow; HDM: house dust mite; HFD: high-fat diet; ILC2s: type 2 innate lymphocyte cells; ROS: reactive oxygen species; R(L): lung resistance; TSLP: thymic stromal lymphopoietin; TCC: total cell count; WT: wild type.