Expression And Significance Of IL-17A In Pulmonary Fibrosis Of Experimental Mice

Objective:To study the effects and significance of IL-17 in the pathogenesis of pulmonary fibrosis, by means of observation the expression and significance of IL-17A which secreted by Th17 cells at various periods and after treatment with prednisone in lung tissues of mice with pulmonary fibrosis induced by bleomycin.Methods:1. Seventy two weight 18～22g of C57BL/6 male mice were randomly divided into three groups:the control group (n=24), the experimental group (n=24) and the treatment group (n=24).2. The mice of control group were treated with normal saline (0.07-0.09ml) one at a time by intratracheal instillation. While the mice of experimental group and treatment group were assigned to receive intratracheal instillation of bleomycin solution diluted with normal saline 0.08ml around (5mg/kg), with the purpose of copying the pulmonary fibrosis model. The mice of treatment group were injected into abdominal cavity with dexamethasone (5mg/kg) every day.3. On the day of 3rd,7th,14th and 28th after administration,6 mice of each group were executed and the lung tissues were harvested. The pulmonary inflammation and the level of pulmonary fibrosis of mice in different groups were observed by pathological methods. Hydroxyproline content of lung tissue was determined. The expressions of IL-17 A in lung tissue of mice were detected by immunohistochemical methods. With RT-PCR detected the expressions of IL-17A mRNA.Results:1. It was observed in the slices by pathological methods that there were no obvious difference between the experimental group and the treatment group in the early inflammation stage, but at the later stage the pulmonary fibrosis degree of the experimental group was more significant than that of the treatment group(P<0.05). There were not obvious inflammation and pulmonary fibrosis in the control group.2. Hydroxyproline content in the experimental group were higher than them in the control group and the treatment group (P<0.05).3. Immunohistochemical detection displayed that in the experimental group the expressions of IL-17A were higher on the 7th and 14th day, but were decreased obviously on the 28th day; while the treatment group expressed lighter but still higher than those in the control group(P<0.05).4. The expressions of IL-17A mRNA detected in lung tissue of the experimental group were higher than that of the control group and the treatment group on the 7th,14th and 28th day(P<0.05), and peaked on the 14th day. In the treatment group, the expression of IL-17A mRNA showed obviously lower than that of the experimental group but also showed significant different from the control group (P＜0.05).Conclusion:1. IL-17A may play a role in the development of pulmonary fibrosis pathological process.2. IL-17A may promote inflammation in the pulmonary alveolitis stage, also may direct participation in later period of pulmonary fibrosis.3. Dexamethasone has a certain degree therapeutic effect in pulmonary fibrosis by means of change IL-17A expression.