The Relationship And Mechanism Between IL-6 And Mucus Hypersecretion In Obese Asthma

Objective: Establishment of obese asthma model to observe the expression of IL-6 in obese asthmatic mice and explore the mechanism of airway mucus hypersecretion in obese asthmatic mice.Methods: Sixty three-week-old SPF mice purchased from Beijing were pre-fed for one week and then divided into four groups: normal control group(group A),obesity group(group B),asthma group(group C),obesity asthma group(group D).The obesity model group(group B and D)was fed with HD001(fat ratio 45%)high fat diet,the control group(group A and C)was fed with normal diet(fat ratio 10%)and the four groups were fed with water freely.The body length and weight of the mice were measured daily.According to the classical asthma model establishment method,the asthma model group(group C,D)was given intraperitoneal and aerosol inhalation of ovalbumin,while the control group(group A,B)was given saline accordingly.After the last stimulation,the experimental specimens were collected.The expression levels of IL-6 in serum and bronchoalveolar lavage fluid(BALF)of each group were measured by ELISE.The total number and classification of leukocytes in BALF of mice in each group were counted.The infiltration of airway inflammatory cells was observed.After HE and PAS staining of lung tissue,the airway inflammation and mucus secretion of mice in each group were observed.Immunohistochemical staining was used to observe airway mucus secretion and mucin Muc5 ac expression.The levels of IL-6,Munc18 b and Muc5 ac in lung tissues were measured by RT-PCR.The expression levels of STAT3,Mun18 b and Muc5 ac in each group were quantitatively and qualitatively detected by Western-blot.Results: At the end of 8 weeks,the weight of mice in obesity model group was 20% higher than that in normal group.In asthma model group,shortness of breath,irritability of scratching nose,frequent urination and defecation occurred during stimulation.There was no abnormal behavior change in the control group.At the end of the experiment,no dead mice appeared.BALF cell count showed that the total number of white blood cells,eosinophils and neutrophils in obese asthma group and asthma group were significantly higher than those in normal group and obese group(P < 0.05),while those in obese asthma group were higher than those in asthma group(P < 0.05).The total number of white blood cells and eosinophils in obese group were slightly higher than those in normal group,with no significant difference,but the number of neutrophils was significantly higher than that in normal group.(P<0.05).HE,PAS and immunohistochemical staining of lung tissue,airway integrity deficiency,bronchial epithelial cell exfoliation,mucosal edema,wall thickening,inflammatory cell infiltration and mucus secretion increased in asthma model group(group C,D).Obesity asthma group showed more obvious,obesity group showed a slight change,the normal group basically no change.The levels of IL-6 in serum and BALF measured by ELISA and the expression of IL-6 in lung tissue were similar in all groups.The levels of IL-6 in obesity group and normal group were slightly higher than those in asthma group(P < 0.05),while those in obesity asthma group were significantly higher than those in asthma group(P < 0.05).The expression levels of STAT3,Munc18 b andMuc5ac in lung tissue of each group were measured by Western-blot.Obesity asthma group was higher than the other three groups,and the expression levels of STAT3,Munc18 b and Muc5 ac decreased in asthma group,obesity group and normal group(P < 0.05).Conclusion: Obesity asthma model was successfully established;airway mucus secretion was higher in obese asthma mice;IL-6 up-regulated the expression of Muc5 ac through STAT3-Munc18 b signaling pathway.