Danthron prevents pulmonary fibrosis through improving mitochondrial function by upregulating carboxylesterase 3

BACKGROUND: Idiopathic pulmonary fibrosis (IPF) is marked by excessive deposition of extracellular matrix (ECM) and persistent fibroblast activation in the lungs, posing challenges for advancing effective treatment strategies. Danthron, a natural anthraquinone derivative extracted from traditional Chinese medicine rhubarb, exhibits antitumor and antioxidant efficacy. METHODS: A bleomycin (BLM)-induced pulmonary fibrosis (PF) mouse model and human precision-cut lung slices (hPCLSs) stimulated with a pro-fibrotic solution were employed. The therapeutic effects of danthron on PF were measured by histological manifestations, immunostaining and expression levels of fibrotic markers. Human fibroblasts (HFs) were utilized to explore the underlying mechanism of danthron on fibroblast function. RESULTS: Our data showed that danthron significantly mitigated BLM-induced PF by reducing collagen deposition and Ashcroft scores in mice. Danthron also suppressed the abundance of fibrotic markers in mouse lungs and hPCLSs. Additionally, danthron impeded the transition of lung fibroblasts to myofibroblasts while promoting their dedifferentiation. Mechanistically, the anti-fibrotic effect of danthron was associated with the upregulation of carboxylesterase 3 (CES3), which consequently enhanced mitochondrial function and mitophagy in fibroblasts. Pharmacological CES3 inhibition (WWL229) reversed these effects, whereas genetic CES3 overexpression potentiated its mitochondrial benefits. Moreover, WWL229 nullified the beneficial effects of danthron in BLM-induced PF. The downregulation of CES3 was identified in IPF patients, which exhibited a negative correlation with fibrotic genes. CONCLUSIONS: This study demonstrated danthron as a valuable experimental tool for identifying relevant targets in preclinical models while underscoring CES3 as a potential therapeutic target for PF.