Abstract:

Objective To investigate the change and the role of interleukin-33 (IL-33) in mice with allergic asthma induced by Dermatophagoides farinae group 1 allergen (Der f 1). Methods Forty female BALB/c mice were randomized into four groups using a random number table method: asthma group (sensitized by Der f 1 allergen), SIT group (specific immunotherapy with Der f 1), inhibitor administration group and negative control group (PBS group) (n = 10 for each). All mice except the PBS group were intraperitoneally injected with Dermatophagoides farinae allergen extract containing 100 μg/ml Der f 1 on days 0, 7 and 14, and those in the inhibition group also received an intraperitoneal injection of inhibitor (soluble ST2) at the same time. From day 21, mice in the three groups were sensitized through aerosol inhalation of the extract (0.5 μg/ml for 30 min , once per day for consecutive days). Mice in the immunotherapy group began to receive an immunotherapy through intraperitoneal injection of 200 μl of Der f 1 protein solution (100 μg/ml) 0.5 h prior to aerosol inhalation, from day 25 on, while in the PBS group, PBS was used instead of Der f 1. Twenty-four hours after the final aerosol inhalation on day 27, all the mice were sacrificed to collect the bronchoalveolar lavage fluid (BALF) and eyeball blood. The total eosinophils in BALF were counted and pulmonary histopathological sections were prepared. ELISA was performed to measure the levels of cytokines IL-5, IL-13, IFN-γ and IL-33 in the BALF, as well as serum levels of IgE and IgG2a. Results All groups except for the PBS group displayed different degrees of asthma symptoms since day 21. From day 25, the asthma symptoms in the immunotherapy group began to show remission. The total numbers of BALF eosinophils in the immunotherapy group and the inhibitor group were (1.43 ± 0.14） × 10⁵/ml and (2.73 ± 0.33） × 10⁵/ml, respectively(t = 24.50, P < 0.01 between the two groups). The numbers of eosinophils in SIT group（1.43 ± 0.14） × 10⁵/ml and the inhibitor administration group (2.73 ± 0.33）× 10⁵/ml were both significantly lower than that in the asthma group（F = 129.72,P < 0.01）. ELISA results showed that the levels of IFN-γ in BALF in the asthma group, the SIT group, the inhibitor administration group and the negative control group were （83.06 ± 11.38）,（277.97 ± 22.46）,（175.13 ± 13.41）and（224.77 ± 19.97）pg/ml, respectively. The BALF IFN-γ levels in the SIT group and the inhibitor administration group were both significantly higher than that in the asthma group (t = 17.31, t = 11.71, P < 0.01). The levels of IL-5 in BALF in the asthma group, the SIT group, the inhibitor administration group and the negative control group were （208.64 ± 11.55）,（106.87 ± 11.39）,（140.71 ± 14.58）and（90.15 ± 9.49）pg/ml, respectively. The BALF IL-5 level in the asthma group was significantly higher than that in the other groups (F = 97.19, P < 0.01). There was a significant difference in the BALF IL-13 level between the asthma group [(308.37 ± 13.67) pg/ml] and the SIT group [(175.66 ± 11.79) pg/ml] (P < 0.01), and that in the inhibition group was significantly lower than that in the asthma group (t = 16.44, P < 0.01). The BALF IL-13 level in the PBS group was (97.57 ± 18.38) pg/ml. Compared with the asthma group, mice in the SIT group showed improved inflammation in the lungs. Although the inhibition group also showed eosinophilia, epithelial cell shedding and bronchial epithelial cells around the bronchus, the symptoms were much attenuated compared with the asthma group. Serum IgE levels in the asthma group, the SIT group, the inhibitor administration group and the PBS group were （31.97 ± 3.48）,（1 2.86 ± 2.22）,（1 8.43 ± 2.30）and（9.68 ± 1.27）IU/ml, respectively. The serum IgE levels in the SIT group and the inhibitor administration group were both significantly lower than that in the asthma group (t = -7.77, P < 0.01). In contrast, the IgG2a level in the SIT group [(35.06 ± 2.57) μg/ml] was significantly higher than that in the asthma group [(26.94 ± 2.96) μg/ml] (t = 6.55, P < 0.01). The IgG2a level in the PBS group was(10.31 ± 1.48) μg/ml. Conclusion The IL-33/ST2 signaling pathway may play a critical role in allergic asthma by ELISA.

Key words: Dermatophagoides farinae, Der f 1 protein, Allergic asthma, IL-33