Quercetin-driven M2 polarization of macrophages via ALOX5 inhibition in kupffer cells: A strategy for mouse liver fibrosis treatment.

Abstract

BACKGROUND: Liver fibrosis, a key feature of chronic liver diseases, involves dysregulated extracellular matrix accumulation, and whether quercetin alleviates fibrosis by targeting 5-lipoxygenase (ALOX5) in Kupffer cells to modulate macrophage polarization remains unclear. METHODS: Using a dimethylnitrosamine (DMN)-induced liver fibrosis mouse model, mice were treated with quercetin (20, 50, 80&#xa0;mg/kg/day) or controls. Hepatic fibrosis was evaluated via histopathology (HE/Masson staining), serum liver function markers (ALT, AST, TBIL), and Suzuki scoring. Kupffer cells and macrophages were isolated for flow cytometry, co-culture assays, and molecular analyses (RT-qPCR, Western blot). ALOX5 expression was manipulated using shRNA lentivirus or overexpression vectors to validate its role in quercetin's mechanism. RESULTS: Quercetin dose-dependently reduced hepatic inflammatory cell infiltration, collagen deposition, and liver function injury (p&#xa0;<&#xa0;0.01 or p&#xa0;<&#xa0;0.001). Mechanistically, quercetin suppressed ALOX5 expression predominantly in Kupffer cells, promoting macrophage polarization from pro-inflammatory M1 (iNOS) to anti-inflammatory M2 (CD206) phenotypes (p&#xa0;<&#xa0;0.01 or p&#xa0;<&#xa0;0.001). Co-culture experiments showed ALOX5 knockdown in Kupffer cells mimicked the polarization effects of quercetin (p&#xa0;<&#xa0;0.001), while ALOX5 overexpression promoted M1 polarization (p&#xa0;<&#xa0;0.001). In vivo, quercetin did not show further antifibrotic benefit when ALOX5 was silenced (p&#xa0;>&#xa0;0.05), suggesting that ALOX5 is involved in its antifibrotic mechanism. CONCLUSIONS: Quercetin alleviates liver fibrosis by targeting ALOX5 in Kupffer cells to promote M2 macrophage polarization. These findings suggest that ALOX5 may represent a potential therapeutic target and supports the clinical application of quercetin.