IL ‐25 Improves MAFLD by Suppressing the Notch Signalling in Hepatic Macrophages

ABSTRACT Background and Aims Hepatic steatosis is characterised by hepatic lipid accumulation, inflammation and fibrosis, with macrophage polarisation playing a central role in disease progression. This study investigates the role of interleukin‐25 (IL‐25) in modulating macrophage polarisation and Notch signalling in a methionine‐choline‐deficient (MCD) diet‐induced metabolic dysfunction‐associated fatty liver disease (MAFLD) model. Methods C57BL/6 mice were fed a MCD diet to induce MAFLD. Human hepatocytes and primary hepatic macrophages were treated with palmitic acid and/or IL‐25. Methods included RT‐qPCR, ELISA, Western blot and immunofluorescence for gene/protein expression. ChIP and luciferase assays were used to analyse STAT3/Notch‐1 signalling. Results We found that IL‐25 expression was significantly downregulated in the livers of MCD‐fed mice and in palmitic acid‐treated hepatocytes. IL‐25 treatment promoted M2 macrophage polarisation, evidenced by increased expression of Arg1, Chi3l3 and anti‐inflammatory cytokines (IL‐10, TGF‐β), while suppressing pro‐inflammatory cytokines (TNF‐α, IL‐6). Mechanistically, IL‐25 inhibited the STAT3/Notch‐1 pathway and induced IL‐33, which negatively regulated the NF‐κB/Jagged‐1 axis, preventing M1 macrophage polarisation. Adoptive transfer of IL‐25‐induced M2a macrophages ameliorated hepatic steatosis and reduced ductular reaction in MCD‐fed mice. Conclusions These findings suggest a role for IL‐25 in modulating macrophage polarisation and inflammation in metabolic dysfunction‐associated fatty liver disease, supporting its further exploration as a potential therapeutic strategy for inflammatory liver diseases.