Cinobufotalin Ameliorates the Development of Pulmonary Fibrosis by Suppressing the TGF-β/Smad Pathway via Regulating PI15

Pulmonary fibrosis (PF) is a common hallmark of several types of interstitial lung diseases (ILDs), for which effective therapeutic drugs are lacking. The small-molecule chemical compound cinobufotalin (CB) has demonstrated significant anti-cancer effects in lung cancer. In this study, we first found that CB attenuated bleomycin (BLM)-induced PF and inhibited transforming growth factor-beta 1 (TGF-β1)-induced myofibroblast activation and epithelial-mesenchymal transition (EMT). Subsequently, comparative RNA sequencing (RNA-Seq) was conducted to analyse the lung gene expression profiles in mice. Interestingly, peptidase inhibitor 15 (PI15) was identified as a significantly differentially expressed gene (DEG) and may be a potential target in PF progression. Mechanistic studies showed that CB exerts anti-PF effects by inhibiting PI15 and thereby regulating the TGF-β/Smad signalling pathway. Our data demonstrated that CB represents a promising anti-PF drug and may be a candidate therapeutic for PF patients.