GSTM1 upregulation contributes to ursolic acid-alleviated hepatic steatosis and liver injury in chronic alcohol-fed mice.

Alcohol-associated liver disease (ALD) is a major cause of liver-related morbidity and mortality worldwide. Ursolic acid (UA), a plant-derived pentacyclic triterpenoid, has been reported to exert protective effects against ALD; however, its molecular targets remain unclear. This study aimed to identify the potential targets and underlying mechanisms of UA in ALD. C57BL/6N mice were fed a Lieber-DeCarli liquid alcohol diet to establish an ALD model and were administered UA by gavage. We found that UA treatment alleviated hepatic steatosis in both ALD mice and ethanol-exposed AML-12 hepatocytes, accompanied by normalization of lipid metabolism-related gene expression. UA also exerted hepatoprotective effects by attenuating alcohol-induced liver injury and inflammation, while rebalancing ethanol metabolism and antioxidant defense, particularly through increasing the activity of glutathione S-transferases. Mechanistically, UA selectively upregulated glutathione S transferase mu 1 (GSTM1) at both the transcriptional and protein levels compared with other GST isoforms. In vitro, UA increased GSTM1 expression, whereas GSTM1 silencing abolished the protective effects of UA against intracellular lipid accumulation, dysregulation of lipid metabolism-related genes, and inflammatory responses in ethanol-exposed hepatocytes, indicating that GSTM1 is a key mediator of UA action. In addition, UA reduced alcohol-induced phosphorylation of apoptosis signal-regulating kinase 1 (ASK1) and its downstream effectors c-Jun N-terminal kinase (JNK) and p38. Pharmacological inhibition of ASK1 reversed the exacerbated intracellular lipid accumulation caused by GSTM1 knockdown during ethanol exposure. Collectively, these findings demonstrate that UA alleviates ALD by upregulating GSTM1 and inhibiting the ASK1-JNK/p38 pathway, thereby identifying GSTM1 as a promising therapeutic target in ALD.