ABSTRACT
Bronchopulmonary dysplasia (BPD) is characterized by alveolar dysplasia, and evidence indicates that interferon regulatory factor 4 (IRF4) is involved in the pathogenesis of various inflammatory lung diseases. Nonetheless, the significance and mechanism of IRF4 in BPD remain unelucidated. Consequently, we established a mouse model of BPD through hyperoxia exposure, and ELISA was employed to measure interleukin-17 A (IL-17 A) and interleukin-6 (IL-6) expression levels in lung tissues. Western blotting was adopted to determine the expression of IRF4, surfactant protein C (SP-C), and podoplanin (T1α) in lung tissues. Flow cytometry was utilized for analyzing the percentages of FOXP3+ regulatory T cells (Tregs) and FOXP3+RORγt+ Tregs in CD4+ T cells in lung tissues to clarify the underlying mechanism. Our findings revealed that BPD mice exhibited disordered lung tissue structure, elevated IRF4 expression, decreased SP-C and T1α expression, increased IL-17 A and IL-6 levels, reduced proportion of FOXP3+ Tregs, and increased proportion of FOXP3+RORγt+ Tregs. For the purpose of further elucidating the effect of IRF4 on Treg phenotype switching induced by hyperoxia in lung tissues, we exposed neonatal mice with IRF4 knockout to hyperoxia. These mice exhibited regular lung tissue structure, increased proportion of FOXP3+ Tregs, reduced proportion of FOXP3+RORγt+ Tregs, elevated SP-C and T1α expression, and decreased IL-17 A and IL-6 levels. In conclusion, our findings demonstrate that IRF4-mediated Treg phenotype switching in lung tissues exacerbates alveolar epithelial cell injury under hyperoxia exposure.
Subject(s)
Bronchopulmonary Dysplasia , Hyperoxia , Animals , Mice , Alveolar Epithelial Cells/pathology , T-Lymphocytes, Regulatory/metabolism , Interleukin-17/metabolism , Interleukin-6/metabolism , Nuclear Receptor Subfamily 1, Group F, Member 3/genetics , Nuclear Receptor Subfamily 1, Group F, Member 3/metabolism , Hyperoxia/complications , Bronchopulmonary Dysplasia/metabolism , Interferon Regulatory Factors/genetics , Interferon Regulatory Factors/metabolism , Phenotype , Forkhead Transcription Factors/genetics , Forkhead Transcription Factors/metabolismABSTRACT
Objective To explore the phenotypic conversion of regulatory T cells (Tregs) in the lungs of mice with bronchopulmonary dysplasia (BPD)-affected mice. Methods A total of 20 newborn C57BL/6 mice were divided into air group and hyperoxia group, with 10 mice in each group. The BPD model was established by exposing the newborn mice to hyperoxia. Lung tissues from five mice in each group were collected on postnatal days 7 and 14, respectively. Histopathological changes of the lung tissues was detected by HE staining. The expression level of surfactant protein C (SP-C) in the lung tissues was examined by Western blot analysis. Flow cytometry was performed to assess the proportion of FOXP3+ Tregs and RORγt+FOXP3+ Tregs in CD4+ lymphocytes. The concentrations of interleukin-17A (IL-17A) and IL-6 in lung homogenate were measured by using ELISA. Spearman correlation analysis was used to analyze the correlation between FOXP3+Treg and the expression of SP-C and the correlation between RORγt+FOXP3+ Tregs and the content of IL-17A and IL-6. Results The hyperoxia group exhibited significantly decreased levels of SP-C and radical alveolar counts in comparison to the control group. The proportion of FOXP3+Tregs was reduced and that of RORγt+FOXP3+Tregs was increased. IL-17A and IL-6 concentrations were significantly increased. SP-C was positively correlated with the expression level of RORγt+FOXP3+ Tregs. RORγt+FOXP3+ Tregs and IL-17A and IL-6 concentrations were also positively correlated. Conclusion The number of FOXP3+ Tregs in lung tissue of BPD mice is decreased and converted to RORγt+ FOXP3+ Tregs, which may be involved in hyperoxy-induced lung injury.
