Identification of Ellagic Acid as a Natural GPR35 Agonist for Ulcerative Colitis Therapy

The escalating global burden of Ulcerative Colitis (UC) underscores the urgent need for novel therapeutic strategies. Although dietary modulation is known to influence UC progression, the specific molecular mediators remain largely undefined. Recently, the G protein coupled receptor 35 (GPR35) has emerged as a promising target for maintaining gut homeostasis and promoting intestinal epithelium repair. Yet, whether the therapeutic benefits of dietary polyphenols are mediated through the direct activation of GPR35 remains unexplored. Here, the NanoLuc Binary Technology (NanoBiT) assay was first used to identify the potential GPR35 agonist from a library of 30 natural polyphenolic compounds. We discovered Ellagic acid (EA), a natural polyphenol abundant in fruits and nuts, as the potent GPR35 agonist owing to its most potent agonistic effect. The dose-dependent effect was further confirmed by both NanoBiT and Bret assay. Then, the binding site of the ligand-receptor complex was predicted via molecular docking, and key interactions were validated by site-directed mutagenesis. The results indicated the key binding site of the complex was Gln93, Arg100, Arg151, Phe163 and Ser262. And the conformation of the complex was verified stable by the molecular dynamics simulation. The bioactivity of EA was then evaluated in vivo. And the in vivo experiment indicated that EA alleviated the symptoms of UC. In addition, complementary in vitro assays, including a wound healing (scratch) assay and an SRB proliferation assay, were employed to investigate its effect on intestinal epithelial repair. The in vitro experiment demonstrated that EA enhanced the migration and proliferation of human colonic epithelial cells, an effect that was specifically abolished by the GPR35 antagonist CID2745687, indicating the key role GPR35 played in the intestinal repair. Collectively, our study demonstrates that the natural polyphenolic compound EA promotes epithelial healing and ameliorates colitis by acting as a GPR35 agonist.