Fluorinated sulfonamide-flavonoid derivatives as novel Keap1-Nrf2 inhibitors: Potent induction of cytoprotective gene HO-1 in vivo

Nuclear factor-erythroid 2 related factor 2 (Nrf2) is a key regulator in cellular defense against oxidative stress. While flavonoids have been identified as Nrf2 activators by inhibiting Keap1-Nrf2 protein-protein interaction (PPI), their limited bioactivity presents significant challenges for therapeutic applications. To compensate for this shortcoming, 28 sulfonamide-flavonoid analogues targeting the Keap1-Nrf2 PPI were synthesized by a fragment-based approach. Among these, SG16, which incorporates a fluorine atom, exhibited potent Nrf2-activated capacity and notable anti-inflammatory properties. In AML12 hepatocytes, SG16 significantly enhanced the expression of antioxidant genes by promoting Nrf2 nuclear translocation. In an acute liver injury (ALI) mouse model, SG16 treatment led to a substantial, hundredfold upregulation of the cytoprotective gene HO-1 mRNA. Meanwhile, a dose-dependent decline in ALT, AST, and inflammatory cytokine levels was observed, reflecting improved liver function. Histopathological evaluations, including hematoxylin and eosin (HE) staining, TUNEL, myeloperoxidase (MPO) activity assessment, and F4/80 macrophage marker analysis, consistently demonstrated substantial attenuation of liver tissue damage following SG16 treatment. Moreover, Co-IP assays combined with experiments in Nrf2 knockout mice suggested that the novel sulfonamide-containing flavonoids are a promising class of Nrf2-targeted therapeutic candidates, warranting further exploration for oxidative stress-related disorders.