Sodium cromoglycate exerts anti-pulmonary fibrosis effects by targeting the Keap1 protein to activate Nrf2 signaling

Oxidative stress has been confirmed to be closely related to the occurrence and development of pulmonary fibrosis (PF). The Kelch-like ECH-associated protein 1 (Keap1)-nuclear factor erythroid-2 related factor 2 (Nrf2) pathway plays a key role in maintaining cellular redox homeostasis. Targeting the Keap1 protein to activate Nrf2 could be a promising strategy for treating PF. Virtual screening via a pharmacophore model was used to screen candidate compounds with potential Keap1 binding ability from the U.S. Food and Drug Administration (FDA) database. The results revealed that sodium cromoglycate (Cro) has the highest fit value and absolute docking score and could improve the thermal stability of the Keap1 protein in a CETSA, confirming that Cro could bind to the Keap1 protein directly. Further studies revealed that Cro promoted Nrf2 translocation into the nucleus, relieved oxidative stress, prevented the epithelial-mesenchymal transition (EMT) process and upregulated fibrosis markers in TGF-β1-induced A549 cells, indicating that Cro has anti-pulmonary fibrosis activity in an in vitro lung fibrosis model. Moreover, in a mouse model of bleomycin (BLM)-induced pulmonary fibrosis, Cro administration improved pulmonary fibrosis, activated Nrf2 signaling, and blocked the EMT process. In summary, these results demonstrated that Cro could activate Nrf2 signaling to clear reactive oxygen species (ROS) by directly binding to Keap1 and alleviate pulmonary fibrosis by blocking the progression of EMT both in vitro and in vivo.