Acacetin ameliorates MASLD by inhibiting the Notch1 pathway in hepatocytes and reprogramming macrophage polarization via Keap1-Nrf2-mediated restraint of ferroptosis.

Metabolic dysfunction-associated steatotic liver disease (MASLD) is the most prevalent chronic liver disease worldwide, with macrophage polarization and ferroptosis playing pivotal roles in its progression. Acacetin has been reported to exert protective effects against MASLD, but its underlying mechanisms remain unclear. Here, male C57BL/6 J mice fed a high-fat diet (HFD) received acacetin by intraperitoneal injection, and RAW264.7, BMDM, and AML12 cells were used for in vitro assays. In our study, acacetin reduced hepatic lipid accumulation, blunted necroptosis, and suppressed the Notch1 pathway in hepatocytes. It also reprogrammed macrophages from an M1-like to an M2-like phenotype while restraining ferroptosis via the Keap1-Nrf2 pathway. Mechanistically, in hepatocytes, N1ICD overexpression attenuated the lipid-lowering effect of acacetin. USP7 was identified as the deubiquitinase for N1ICD, and N1ICD in turn upregulated USP7 transcription, establishing a positive feedback loop. Acacetin disrupted this loop, promoting N1ICD ubiquitination and proteasomal degradation. In macrophages, the ferroptosis activator erastin partially reversed acacetin-induced anti-inflammatory reprogramming, an effect mediated by mitochondrial injury-driven mtDNA release and consequent activation of the cGAS-STING pathway. The Nrf2 inhibitor ML385 also attenuated acacetin-induced protection against macrophage ferroptosis and its promotion of M2-like polarization. Moreover, acacetin enabled Nrf2 nuclear translocation by competitively binding to Keap1 at Arg483. Collectively, this study clarifies a dual-cell mechanism by which acacetin ameliorates MASLD and yields promising insights into MASLD treatment.