The Regulatory Mechanism Of Th22 Cells In The Airway Inflammation Of Asthmatic Mice And The Effects Of Astragaloside IV

Bronchial asthma(asthma)is a heterogeneity disease characterized by chronic airway inflammation and airway hyperreactivity(AHR),a variety of cells and cell components play important roles in the progress of asthma.Asthma is one of the most common chronic disease of childhood.At present,the pathogenesis of asthma is still unclear,the existing research support that T lymphocytes in the airway inflammation of asthma play a key role.Th22 cells is a newly discovered independent CD4 + T cell subgroup,studies have shown that Th22 cells play an important role in the onset of asthma.Interleukin 22(IL-22)is the major effect factor of Th22 cells.The role of Th22 cells and IL-22 in asthma mechanism is unclear.Inhaled corticosteroids(ICS)is the preferred way to control asthma,it is widely used in clinical,but there are still many patients with asthma symptoms after the application of ICS,so looking for new therapeutic targets and new drugs is still one of the most important tasks for asthma prevention and treatment.The anti-inflammatory,immunomodulatory,anti-fibrotic action of Astragaloside IV has been confirmed,some reported results have shown that Astragaloside IV can inhibit airway inflammation in asthmatic mice.But whether Astragaloside IV will affect the process of asthma by affecting the differentiation of Th22 cells and the expression of IL-22 or not,is rarely studied at home and abroad.The intention of this study is to study the effect of Th22 cell and its main effect factor IL-22 on murine asthmatic airway inflammation,observe the effect of Astragaloside IV on Th22 cells and IL-22 of asthmatic mouse model,explore the mechanism of Astragaloside IV in the treatment of asthma.32 female specific-free(SPF)BALB/c mice aged four weeks wererandomly divided into 4 groups with 8 mice per group : control group,asthma group,budesonide treatment group(BUD group)and Astragaloside IV treatment group(AS-IV group).To establish a mouse model of asthma,the following procedure was used: On days 0,7 and 14,0.2 mL of a solution containing 100μg of ovalbumin(OVA)with 1 mg of aluminum potassium sulfate dodecahydrate was injected intraperitoneally to mice in asthma group,BUD group and AS-IV group.Beginning on day 21,ultrasonic nebulization was performed with 6mL of 5% OVA solution,30 min daily for 12 consecutive days.In the control group,PBS was substituted for OVA to perform.1h before the nebulization challenge,inhalation budesonide suspension liquid was administered via nebulization challenge for mice of BUD group.For AS-IV group,Astragaloside IV-Carboxymethylcellulose suspension liquid was administered via the gastrointestinal tract.Control group with intraperitoneal injection of phosphate buffered saline(PBS)for sensitization and nebulization challenge,CMC solution was used for gastrointestinal tract.Within 24 h after the final nebulization challenge,mice were sacrificed and the right lung was ligated immediately.For histopathological examination,HE staining was used to measure the inflammation scores,AB-PAS was used to measure the hyperplasia of goblet cells and mucin,Masson staining was used to measure collagen deposition.The left lung was washed with 0.3 mL PBS for 3 times.The bronchoalveolar lavage fluid(BALF)was centrifuged at 2000 g for 4min at 4°C,recycling supernatant and saved at-80℃.The precipitate of BALF was suspended and smears of BALF cells were stained with Wright’s stain for differential cell counting.IL-22 levels in BALF supernatant were analyzed by enzyme-linked immunosorbent assay(ELISA).The spleen was used to prepare a single-cell suspension for flow cytometry(FCM).The proportion of Th22 cells in spleen single cell suspension were detected by FCM.After OVA sensitization and challenge,the asthma mouse appearedsome behavior changes.For asthma group,the inflammation scores were elevated compared with the control group(P<0.05),and airway remodeling can be observed in asthma mice,including collagen deposition around the airway and the increase of airway smooth muscle mass.Compared with the control group,the percentage of eosinophils and neutrophils were significant increased(P<0.05),IL-22 levels in BALF and the proportion of Th22 cells in spleen single cell suspension were significant increased,too(P<0.05).An overall change towards less severe asthmatic airway inflammation and airway remodeling by the end of the trial was observed in the AS-IV group and BUD group.The percentage of eosinophils and neutrophils,the levels of IL-22 and the proportion of Th22 cells in the AS-IV group and BUD group were significantly lower than those in asthma group(P<0.05),there was no significant difference among AS-IV group and BUD group.We can get the following conclusions: The increasing Th22 cell differentiation and IL-22 secretion can lead to the occurrence of airway inflammation in the pathogenesis of asthma.Astragaloside IV can inhibit Th22 cell differentiation and the expression of IL-22,thereby inhibiting the development of airway inflammation and airway remodeling of asthma.