| Objective: This study aimed to construct a mice model of allergic asthma induced by ovalbumin(OVA),and to study the effect of metformin intraperitoneal injection on IL33/ST2 signaling pathway and airway inflammation in mice.Methods: Twenty-four 8-week-old female BALB/c mice were randomly divided into 3 groups,including normal control group(NC group),asthma group(OVA group),and metformin intervention group(MET+OVA group),with 8 mice in each group.On the First,eight and fifteen days of modeling,mice in the OVA group and MET+OVA group were sensitized by intraperitoneal injection of OVA sensitization solution,and normal saline was injected intraperitoneally in the NC group.Starting from the twenty-second day of modeling,mice in the OVA group and MET+OVA group were used for 1% OVA atomization excitation,and the NC group was atomized with normal saline.Mice in the MET+OVA group were given intraperitoneal metformin injection 30 min before nebulization,and normal saline was injected intraperitoneally in NC group and OVA group.Mice were sacrificed after fasting for 12 hours after the last excitation.We observed the morphological changes of lung tissue and airway mucus secretion by HE and PAS staining.The expression of IL33 and ST2 in lung tissues of mouse was detected by immunohistochemical staining and western blotting.The contents of IL4,IL5,IL13 in BALF and Immunoglobulin E in serum were detected by ELISA.Results:1.General state and behavioral changes: sensitization stage: the 3 groups of mice did not have obvious shortness of breath,restlessness,runny nose and scratching nose,and the hair was smooth and shiny.Atomization excitation stage: Mice in the NC group appeared restless and active within 3 minutes of the start of atomization,and quickly returned to normal.After starting atomization,mice in the OVA group experienced shortness of breath,restlessness,scratching of the nose,runny nose,nodded breathing,and the above manifestations gradually eased after stopping atomization for 1h,and the hair was rough after multiple excitations.After starting atomization,mice in the MET+OVA group had shortness of breath,restlessness and nasal runny nose less times,no nod breathing,and the above manifestations were gradually relieved within 30 minutes of stopping atomization,and the hair was rough after multiple excitations which was lighter than that in the OVA group.2.Morphological changes of lung tissue: HE staining of lung tissue showed that there was no bronchial smooth muscle hyperplasia in mice in the NC group,and no obvious infiltration of inflammatory cells around the bronchi.In the OVA group,the thickening of the bronchial wall,luminal stenosis,bronchial smooth muscle hyperplasia,and eosinophil-dominated inflammatory cell infiltrated around the bronchi and vascular.However,compared with the OVA group,the degree of bronchial smooth muscle hyperplasia and eosinophil infiltration in mice in the MET+OVA group was reduced.3.IL33 and ST2 expression in lung tissue: IL33(1.09±0.04)and ST2(0.98±0.07)were significantly higher in lung tissue of mice in the OVA group than that in the NC group by western blotting(0.65±0.10,0.42±0.09).The expression of IL-33(1.09±0.04)and ST2(0.98±0.07)in the MET+OVA group was lower than that in the OVA group.Immunohistochemical staining showed that IL33 was mainly expressed in epithelial cells in bronchus and inflammatory cells infiltrated around the bronchi,and ST2 was mainly expressed in epithelium layer in the airway.The positive expression of IL33(0.37±0.01)and ST2(0.35±0.02)in the OVA group was higher than that in the NC group(0.26±0.01,0.22±0.02).The positive expression of IL33(0.30±0.05)and ST2(0.28±0.02)in the MET+OVA group was lower than that in the OVA group.4.Changes of inflammatory indexes in serum and BALF: The contents of IL4(267.56±40.79),IL5(27.54±4.09),IL13(95.57±13.82)in BALF and Immunoglobulin E(518.49±109.22)in serum in OVA group were significantly higher than those in the NC group(125.43±40.46,170.25±20.0,15.04±0.86,41.46±6.20),and after metformin intervention,the contents of IL4(205.79±24.79),IL5(21.42±1.97),IL13(59.39±8.40)in BALF and Immunoglobulin E(194.14±187.83)in serum decreased).5.Correlation analysis: Pearson correlation analysis showed that IL33 was positively correlated with ST2 expression in lung tissue(r=0.9310,P<0.001).The expression levels of IL33 in lung tissue were positively correlated with IL4,IL5 and IL13 in serum Immunoglobulin E and BALF.The expression levels of ST2 in lung tissues were positively correlated with the contents of IL4,IL5,IL13 in BALF and Immunoglobulin E in serum.Conclusions:1.Metformin can reduce the expression of IL33 and ST2 in the lung tissue of OVA-induced asthmatic mice,improve OVA-induced asthma symptoms,and relieve airway inflammation.2.The correlation analysis showed that the expression level of IL33/ST2 in lung tissue was significantly positively correlated with the expression level of airway inflammatory indexes(IL4,IL5,IL13 in BALF and Immunoglobulin E in serum),and metformin may alleviate OVA-induced allergic airway inflammation through IL33/ST2 signaling. |
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