Interleukin-17A Promotes Airway Remodeling in Chronic Obstructive Pulmonary Disease by Activating C-X-C Motif Chemokine Ligand 12 Secreted by Lung Fibroblasts.

Abstract

The interactions between fibroblasts and bronchial epithelial cells play important roles in the development of chronic obstructive pulmonary disease (COPD). Interleukin (IL)-17A triggers the activation of fibroblasts and secretion of inflammatory mediators, which promotes epithelial mesenchymal transition (EMT) in bronchial epithelial cells. Fibroblasts secrete C-X-C motif chemokine ligand 12 (CXCL12), which specifically binds to its receptor, C-X-C motif chemokine receptor 4 (CXCR4) to mediate inflammatory responses. This study aims to investigate IL-17A- and CXCL12-induced airway remodeling. Primary lung fibroblasts were isolated from human and murine lung tissue for the in vitro experiments, and a mouse model of cigarette smoke (CS)-induced COPD was established for the in vivo experiments. The results were analyzed using one-way ANOVA and Tukey's test or Bonferroni's test for post-hoc test. A p-value < 0.05 was considered statistically significant. Through in vitro experiments, we found that IL-17A-activated primary lung fibroblasts secreted CXCL12 and stimulated EMT in bronchial epithelial cells. However, these effects could be blocked by neutralizing IL-17A or CXCL12. In vivo, an anti-IL-17A antibody or a CXCR4 antagonist (AMD3100) could reverse the degree of EMT in lungs of the COPD mouse model. The IL-17A-induced EMT and increased CXCL12 expression occurred via extracellular signal-regulated kinase (ERK)/phosphorylated (p-)ERK pathways. This study showed that exposure of mice to CS and IL-17A stimulation upregulated CXCL12 expression and induced EMT by activating the ERK signaling pathway. These data offer a novel perspective regarding the molecular mechanism of CXCL12/CXCR4 signaling in IL-17A-induced EMT related to airway remodeling.