Background Aerobic exercise can improve symptoms,reduce airway inflammation,and even ameliorate airway remodeling in asthmatic animals and patients.However,previous studies have focused mainly on the effect of aerobic exercise on steroid-sensitive asthma （SSA）.The goals of this study were to determine the effect of low-intensity aerobic exercise training on airway hyperresponsiveness,inflammation,and remodeling in a rat model of steroid-resistant asthma （SRA） and to identify the potential mechanisms underlying these effects.Methods Endotoxin-free ovalbumin with or without lipopolysaccharide were applied to establish rat models of SRA and SSA,respectively.Airway hyperresponsiveness,inflammation,remodeling,expression of interleukin （IL）-25,IL-33,thymic stromal lymphopoietin （TSLP）,high mobility group box-1 （HMGB1）,and IL-17 in bronchoalveolar lavage fluid （BALF）,and the role of dexamethasone （DXM） were compared between these two asthmatic rat models.The effect of low-intensity aerobic exercise training and anti-HMGB1 treatment on airway hyperresponsiveness,inflammation,and remodeling in SRA rats also was evaluated.Results SRA rats developed neutrophil-dominated airway inflammation （（29.5±4.1）％ of the total cell numbers in BALF）,whereas SSA rats developed eosinophil-dominated airway inflammation （（24.0±6.1）％ of the total cell numbers in BALF）.Compared with SSA rats,SRA rats had more severe airway hyperresponsiveness,lower levels of IL-25 （（33.6±10.3） vs.（104.8±24.9） pg/ml）,IL-33 （（87.5±25.0） vs.（226.6±40.7） pg/ml）,and TSLP （（1 933.2±899.5） vs.（7 224.0±992.1） pg/ml）,and higher levels of HMGB1 （（21.2±4.5） vs.（5.4±1.6） ng/ml） and IL-17 （（780.5±261.7） vs.（291.4±76.4） pg/ml） in BALF （all P ＜0.05）.However,there was no significant difference in goblet cell hyperplasia,subepithelial collagen thickness,and airway smooth muscle remodeling between the two groups.Compared with control SSA rats,airway hyp
