Blocking ATF4 attenuates pulmonary fibrosis by preventing lung fibroblast activation and macrophage M2 program

Idiopathic pulmonary fibrosis (IPF) is a devastating disease characterized by myofibroblasts accumulation and uncontrolled extracellular matrix (ECM) deposition. Here, we reported that activating transcription factor 4 (ATF4), a multifunctional transcription regulatory protein, is overexpressed in IPF lungs and mouse fibrotic lungs, mainly in myofibroblasts and macrophages. Haplodeletion of Atf4 in mice or blockage of Atf4 with Atf4 shRNA-loaded lentiviruses in mice reduced bleomycin (BLM)-induced pulmonary fibrosis (PF) in vivo. Mechanistically, we found that ATF4 directly binds to the promoter of Acta2 (encodes α-SMA), and promotes lung fibroblasts activation and myofibroblasts accumulation. Additionally, ATF4 regulates macrophage M2 program, and promotes TGFβ1 secretion by directly influencing Tgfb1 gene expression in macrophages, subsequently enhances crosstalk between macrophages and lung fibroblasts. These data suggest that strategies for inhibiting ATF4 may represent an effective treatment for PF.