Abstract
BACKGROUND/AIM: Although stimulation of erythropoietin receptor (EPOR) signaling demonstrates cytoprotective effects-including anti-apoptosis, pro-proliferation, and promotion of inflammation resolution-in various disease models, its alterations and specific role in the process of pulmonary fibrosis are still not well understood. The study aimed at investigating the changes of lung EPOR signal in pulmonary fibrosis and the effect of different cell EPOR signal on pulmonary fibrosis. MATERIALS AND METHODS: In a bleomycin-induced C57BL/6J mice model, fibrosis was assessed via Hematoxylin and eosin (H&E) staining, Masson's trichrome staining, and hydroxyproline content. EPOR expression was measured in lung tissue and specific cells. Conditioned media (CM) from BLM/EPO-treated MLE-12, PMs, and C166 cells were applied to 3T3 fibroblasts, which were also treated with TGF-β1/EPO. Fibroblast activation was evaluated by α-SMA and Col-1 expression using RT-qPCR. Macrophage-specific (MΦ-EPOR(cko)) and type II alveolar epithelial cell-specific (Sftpc-EPOR(cko)) knockout mice were used to assess fibrosis severity. RESULTS: Lung overall EPOR expression decreased after fibrosis. Type II alveolar epithelial cells and macrophages showed the highest baseline EPOR expression, which declined post-fibrosis. CM from BLM+EPO-treated MLE-12 cells inhibited fibroblast activation, while media from PMs and C166 cells promoted it. Direct EPOR activation in fibroblasts enhanced their activation. MΦ-EPOR(cko) mice exhibited attenuated fibrosis, whereas Sftpc-EPOR(cko) mice displayed exacerbated fibrosis. CONCLUSION: EPOR signaling in macrophages and type II alveolar epithelial cells exerts opposing effects on pulmonary fibrosis, with targeted activation EPOR signaling in alveolar epithelial cells representing a potential therapeutic strategy.