2.2. Experimental Mouse Model of Allergic Asthma

Sixty BALB/c male mice weighing 18-20 g were stochastically distributed into 6 groups (equal distribution): normal group (control), ovalbumin- (OVA-) induced asthma model group (OVA), SCH (Sigma-Aldrich, China) low-dose group (15 mg/kg, OVA+SCH-L), SCH middle-dose group (30 mg/kg, OVA+SCH-M), SCH megadose group (60 mg/kg, OVA+SCH-H), and positive control group (0.5 mg/kg, dexamethasone, OVA+DXM). Mice were sensitized several times by injecting a 2 mg/mL ovalbumin (OVA, Grade V) solution with 4% aluminum hydroxide gel (Sigma-Aldrich, China) to establish an asthma model. On the first day, 0.5 mL of the OVA solution was injected into the hind feet, groin, subcutaneous, cervical subcutaneous area, and abdominal cavity of each mouse [12]. Then, on the 14^th day, 0.2 mL of the OVA solution was injected into the abdominal cavity to strengthen the allergic response. Finally, on the 23^rd day, an aerosolized physiological saline solution with 10 mg/mL ovalbumin was inhaled by mice for 30 min, at a frequency of 3 times a week for 2 months. Along with OVA physiological saline, all mice were administrated SCH or normal saline by oral gavage 1 h before OVA challenge once a day for 2 months. Dexamethasone (Sigma-Aldrich, China) was administered to mice in the positive control group 3 times a week for 2 months.