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

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 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 < 0.01 or p < 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 < 0.01 or p < 0.001). Co-culture experiments showed ALOX5 knockdown in Kupffer cells mimicked the polarization effects of quercetin (p < 0.001), while ALOX5 overexpression promoted M1 polarization (p < 0.001). In vivo, quercetin did not show further antifibrotic benefit when ALOX5 was silenced (p > 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.