Autophagy-related protein EI24 delays the development of pulmonary fibrosis by promoting autophagy.

Etoposide-induced protein 2.4 (EI24) is an autophagy-associated protein and acts as a tumor suppressor. However, its role in tissue fibrosis remains unknown. Herein, a downregulation of EI24 levels in the lungs from mouse pulmonary fibrosis (PF) model and lung epithelial cells was observed in response to bleomycin (BLM) or transforming growth factor-β1 (TGF-β1). Then, the role of EI24 in PF was investigated through the upregulation of EI24 in vitro and in vivo. EI24 inhibited epithelial-mesenchymal transition (EMT) process and extracellular matrix (ECM) production in EI24-overexpressing cells after stimulation with BLM or TGF-β1. The overexpression of EI24 at 14 days after the establishment of the PF model through tail vein injection delayed the progression of PF. Moreover, the administration of EI24-overexpressing plasmid promoted the autophagy level in the lungs of the PF mouse model. In addition, the inhibition of autophagy by 3-methyladenine limited the role of EI24 in these processes. Thus, the current data indicated that EI24 attenuates PF through inhibition of EMT process and ECM production by promoting autophagy.