7,8-Dihydroxyflavone alleviates ulcerative colitis by binding keap1 to activate an slc7a11-dependent inhibition of NF-κB p65 signaling in macrophages.

INTRODUCTION

Ulcerative colitis (UC) is characterized by episodic occurrences of bloody diarrhea and can lead to potentially fatal complications, highlighting the urgent need for effective and safe therapeutic options.

OBJECTIVES

This study aims to conduct a mechanistic investigation into the repurposing of 7,8-Dihydroxyflavone (7,8-DHF), a bioactive flavonoid, for ameliorating the clinical symptoms of dextran sulfate sodium (DSS)-induced ulcerative colitis in mice of both sexes.

METHOD: To explore the structural-activity relationship of 7,8-DHF, a series of flavone derivatives with different substitution patterns on the A-ring were synthesized. The active 7,8-DHF were evaluated in both LPS-induced RAW 264.7 macrophage and DSS-induced mice UC models. Then we used RNA-sequencing and 16s rRNA sequencing to identify the mechanism underlying of 7,8-DHF and then identified the critical role of slc7a11-mediated macrophage polarization combining with gene silencing and pharmacological intervention. The interaction between slc7a11 and NF-κB p65 in macrophage was verified through immunoprecipitation-mass spectrometry (IP-MS) and Co-Immunoprecipitation (CO-IP). Furthermore, Nrf2/keap1complex dissociation-induced slc7a11 activation was demonstrated using a biotinylated DHF probe in pull-down and molecular dynamic stimulation assays.

RESULTS

Anti-colitis capacity of 7,8-DHF was superior to both 7-hydroxyflavone (7-HF) and 5-aminosalicylic acid (5-ASA) across all measured clinical and histological parameters. The protective effects of 7,8-DHF against DSS-induced colitis are attributed to the binding of its A-ring ortho-dihydroxy moiety to keap1, which leads to the activation of Nrf2 and subsequent upregulation of slc7a11 expression. The increased slc7a11 protein binds to NF-κB p65, sequestering it from the nucleus and thereby reducing NF-κB signaling. This modulation of the NF-κB pathway affects macrophage polarization and gut inflammation. Additionally, treatment with 7,8-DHF specifically increased the abundance of beneficial Akkermansia spp. and decreased pathobionts such as Escherichia-Shigella spp. in the DSS-induced colitis model.

CONCLUSION

Our study underscores the potential therapeutic application of 7,8-DHF in managing inflammatory conditions, particularly ulcerative colitis.