Curdione alleviates renal fibrosis through Fblim1-dependent inhibition of the TGF-β1/Smad3 signaling pathway.

Chronic Kidney Disease (CKD) inevitably progresses to End-Stage Renal Disease (ESRD) via tubulointerstitial fibrosis, a process predominantly driven by the transforming growth factor-β (TGF-β)/SMAD family member 3 (Smad3) signaling pathway. Although curdione, a major sesquiterpenoid from Curcumae Rhizoma, exhibits anti-fibrotic activity, its specific mechanism in renal fibrosis remains undefined. Here, we investigated the protective effects of curdione using the Unilateral Ureteral Obstruction (UUO) mouse model and TGF-β1-stimulated renal tubular epithelial cells (TCMK1). We found that curdione (25 and 100 mg/kg) significantly mitigated UUO-induced renal injury and tubular necrosis, suppressed the injury marker kidney injury molecule-1 (KIM-1), and dose-dependently inhibited α-smooth muscle actin (α-SMA), fibronectin (FN), and Collagen I. Consistently, in TGF-β1-stimulated TCMK1 cells, curdione prevented fibrotic morphological changes and suppressed the upregulation of profibrotic markers. Mechanistically, curdione suppressed the expression of Filamin Binding LIM Protein 1 (Fblim1) and the phosphorylation of Smad2/3 in vivo and in vitro. Crucially, Fblim1 overexpression, achieved in vivo via ultrasound microbubble-mediated plasmid delivery and confirmed in vitro, significantly abrogated curdione's anti-fibrotic effects and restored p-Smad3 levels. Furthermore, molecular docking predicted a strong binding affinity (-6.7 kcal/mol), while cellular thermal shift assay (CETSA) and drug affinity responsive target stability (DARTS) assays physically validated that curdione directly binds to Fblim1, enhancing its molecular stability. In conclusion, this study provides convergent evidence at the tissue, cellular, and molecular levels that curdione exerts potent anti-fibrotic and renoprotective effects by directly targeting Fblim1, thereby functionally suppressing the TGF-β1/Smad3 signaling cascade. These findings establish curdione as a promising natural therapeutic candidate for CKD.