Fig. 1

a Experimental protocol. In the leptin-treated groups, leptin (25 μg/125 μL phosphate-buffered saline [PBS] for wild-type, 50 μg/250 μL PBS for ob/ob) was injected intraperitoneally on days 1, 3, 5, and 8–11. In the IL-33-treated groups, IL-33 (1 μg/50 μL PBS) was instilled intranasally on days 9–11. On day 12, airway responsiveness, bronchoalveolar lavage fluid (BALF), and lung sections were assessed. b Effect of exogenous leptin on endogenous serum leptin concentrations over time. The mice were given a single intraperitoneal injection of leptin (25 μg for wild-type, 50 μg for ob/ob). Serum leptin levels were measured at 0, 1, 3 and 24 h after injection. Data are expressed as mean ± standard error of the mean (SEM). n = 2–3 for each group. c The cell differentials of BALF and d airway responsiveness to methacholine in leptin-treated wild-type mice. Resistance of the respiratory system (Rrs). n = 4 for each group. e Body weight on day 12. Data are expressed as mean ± standard error of the mean (SEM). n = 7–9 for each group. ^###p < 0.001 vs. mice with an identical treatment