The loss of IL-31 signaling attenuates bleomycin-induced pulmonary fibrosis

Idiopathic Pulmonary Fibrosis (IPF) is a severe fibrotic lung disease characterized by excessive collagen deposition and progressive decline in lung function. Multiple Th2 T cell-derived cytokines including IL-4 and IL-13 have been shown to contribute to inflammation and fibrotic remodeling in multiple tissues. Interleukin-31 (IL-31) is a newly identified cytokine that is predominantly produced by CD4 TH2 T cells, but its signaling receptor called IL-31RA has been shown predominately expressed by non-hematopoietic cells. However, the potential role of the IL-31-IL31RA axis in pulmonary inflammation and fibrosis has remained largely unknown. To determine the role of IL-31 signaling in pulmonary fibrosis, wildtype, and IL-31RA knockout mice were treated with bleomycin and measured changes in collagen deposition and lung function. Notably, the loss of IL-31 signaling attenuated collagen deposition and lung function decline during bleomycin-induced pulmonary fibrosis. However, the loss of IL-31RA signaling did not affect inflammation in the lungs. The total lung transcriptome analysis showed a significant reduction in fibrosis-associated gene transcripts including ECM- and epithelial cell-associated gene networks. Furthermore, the lungs of IPF showed an elevated expression of IL-31 when compared to control subjects. In support, the percentage of IL-31 producing CD4+ T cells was greater in the lungs and PBMCs from IPF patients compared to healthy controls. Our findings suggest a pathogenic role for IL-31/IL-31RA signaling during bleomycin-induced pulmonary fibrosis. In summary, therapeutic targeting of the IL-31-IL-31RA axis could be beneficial in pulmonary fibrosis and has translational benefits specifically by preventing collagen deposition and improving lung function.