KLF4/FOXF1 axis alleviates silicosis fibrosis by modulating fibroblast behavior and extracellular matrix remodeling.

Silicosis has consistently remained a pivotal and challenging focus area in occupational diseases, characterized by progressive pulmonary interstitial fibrosis caused by inhalation of crystalline SiO2 dust. Fibroblast activation constitutes a key cellular basis for silicotic fibrosis. Transcription factors are important switches that drive fibroblast activation. In this study, by analyzing the lung tissues of silicosis animal models, we observed a significant downregulation of KLF4 and FOXF1 in silicosis fibroblasts. Transcriptome sequencing and TGF-β1-induced NIH-3T3 activation model revealed a potential negative correlation between KLF4/FOXF1 and cell invasive, migratory, and proliferative phenotypes. Using the JASPAR database, we further found that KLF4 has a high affinity for the promoter region of Foxf1, and CHIP-qPCR confirmed this. Furthermore, Co-immunoprecipitation confirmed the interaction between KLF4 and FOXF1 protiens. Restoration experiments revealed that Foxf1 knockdown inhibited the regulatory effect of KLF4 on fibroblast activation, while inhibiting SMAD pathway greatly impedes the dynamic changes of fibroblasts. Moreover, using adeno-associated virus (AAV) to overexpress Foxf1 in lung, we validated that FOXF1 alleviated silicosis fibrosis. Taken together, KLF4 directly targeted FOXF1, inhibiting fibroblast activation and alleviating silicosis fibrosis through TGF-β1/SMAD2/3 signaling pathway, which is expected to be a potential therapeutic target for silicosis fibrosis.