Melandryoside attenuates steatohepatitis and fibrosis by restoring PPM1A-mediated SMAD signaling termination.

Metabolic dysfunction-associated steatohepatitis (MASH) is characterized by hepatic steatosis, inflammation, and fibrosis, yet effective pharmacological therapies remain limited. Melandrii Herba, a traditional East Asian medicinal herb used to improve blood circulation and relieve inflammatory disorders, has reported anti-inflammatory activity. However, its therapeutic potential and active constituents in MASH remain unclear. This study investigated the hepatoprotective and anti-fibrotic effects of Melandrii Herba ethanol extract (MHE) and its purified constituent melandryoside in MASH and explored the underlying mechanisms. Palmitic acid-challenged HepG2 hepatocytes and TGF-β-stimulated HSC-LX2 cells were used to evaluate metabolic and fibrogenic stress responses. In vivo efficacy was examined in choline-deficient, L-amino acid-defined, high-fat diet (CDAHFD)-fed mice, with MHE administered therapeutically after disease establishment (weeks 8-12) under continued dietary challenge. Interactome analysis, co-immunoprecipitation, and PPM1A loss-of-function approaches were used to investigate the underlying mechanisms. MHE reduced lipid accumulation and oxidative stress in palmitic acid-treated hepatocytes and suppressed TGF-β-induced hepatic stellate cell activation, fibrogenic gene expression, and SMAD2/3 phosphorylation in HSC-LX2 cells. In CDAHFD-fed mice, oral administration of MHE attenuated hepatic steatosis, inflammatory injury, and collagen deposition. Mechanistically, MHE and melandryoside restored PPM1A-SMAD interaction and reduced SMAD2/3 phosphorylation, whereas PPM1A knockdown diminished their anti-fibrotic effects. MHE and melandryoside alleviated pathological features of MASH by reducing metabolic stress and suppressing fibrotic signaling. These findings identify melandryoside as a bioactive constituent of Melandrii Herba and suggest that regulation of PPM1A-SMAD signaling may represent a potential therapeutic strategy for MASH.