Investigating PXR activation by rhamnocitrin as a mechanism for maintaining intestinal barrier function and regulating tryptophan metabolism in DSS-induced colitis

Rhamnocitrin (Rha) is a natural flavonoid from Nervilia fordii (Hance) Schltr. with demonstrated anti-inflammatory, antimicrobial and antioxidant properties. Here, we found that Rha (20 and 50 mg/kg) effectively ameliorated disease manifestations such as body weight loss and colon shortening; improved disease activity index scores; and attenuated histopathological damage in dextran sodium sulfate (DSS)-induced colitis. Rha significantly decreased the serum levels of proinflammatory cytokines and inhibited Nod-like receptor protein 3 (NLRP3) inflammasome activation. Mechanistic studies also indicated that Rha activated pregnane X receptor (PXR) and its drug-metabolizing enzymes ( Cyp3a4 , Ugt1a1 , Mdr1 ) to maintain intestinal mucus barrier function (such as stimulating Mucin 2 and Mucin5AC production) and increase the levels of tight junction proteins (ZO-1, Claudin-1, Claudin-7 and Occludin). Furthermore, metabolomic analysis demonstrated that Rha was able to modulate tryptophan biosynthesis and indole metabolic pathways along with riboflavin metabolism. These findings collectively establish that Rha exerts its therapeutic effects through PXR-mediated mechanisms involving intestinal barrier protection, metabolic regulation and anti-inflammatory activity, highlighting its potential as a multitarget natural therapeutic for inflammatory bowel disease (IBD). Mechanistically, Rha orchestrates NLRP3 inflammasome suppression with PXR pathway activation to reprogram tryptophan-indole metabolism, ultimately resolving intestinal inflammation and reinforcing mucosal barrier protection. • Rhamnocitrin (Rha) activates PXR restoring gut barrier in colitis. • Rha suppresses NLRP3 inflammasome and upregulates tight junction proteins. • Rha reprograms tryptophan-indole metabolism via PXR-dependent mechanisms. • Multitarget natural Rha demonstrates potential as a colitis therapeutic.