Dichotomous Roles of Men1 in Macrophages and Fibroblasts in Bleomycin-Induced Pulmonary Fibrosis

Pulmonary fibrosis therapy is limited by the unclear mechanism of its pathogenesis. C57BL/6 mice were used to construct the pulmonary fibrosis model in this study. The results showed that Men1, which encodes menin protein, was significantly downregulated in bleomycin (BLM)-induced pulmonary fibrosis. Mice were made to overexpress or had Men1 knockdown with adeno-associated virus (AAV) infection and then induced with pulmonary fibrosis. BLM-induced pulmonary fibrosis was attenuated by Men1 overexpression and exacerbated by Men1 knockdown. Further analysis revealed the distinct roles of Men1 in fibroblasts and macrophages. Men1 inhibited fibroblast activation and extracellular matrix (ECM) protein expression while promoting macrophages to be profibrotic (M2) phenotype and enhancing their migration. Accordingly, pyroptosis was potentiated by Men1 in mouse peritoneal macrophages (PMCs) and lung tissues upon BLM stimulation. Furthermore, the expression of profibrotic factor OPN was positively regulated by menin in Raw264.7 cells and lung tissues by binding to the OPN promoter region. Taken together, although Men1 showed antifibrotic properties in BLM-induced pulmonary fibrosis mice, conflictive roles of Men1 were displayed in fibroblasts and macrophages. The profibrotic role of Men1 in macrophages may occur via the regulation of macrophage pyroptosis and OPN expression. This study extends the current pathogenic understanding of pulmonary fibrosis.