Watercress Extract Reduces Experimental Colitis by Modulating Inflammation and Regulating the Gut Microbiota

Background/Objectives: Watercress (Nasturtium officinale), a cruciferous vegetable rich in phenethyl isothiocyanate (PEITC) and bioactive phytochemicals, has demonstrated anti-inflammatory and cytoprotective activities in multiple disease models; however, its effects on colitis remain insufficiently characterized. In the present study, we investigated the effects of watercress extract supplementation in dextran sulfate sodium (DSS)-induced experimental colitis. Methods: Male C57BL/6 mice were fed either a standard AIN-93G diet or a diet supplemented with 0.5% (w/w) watercress extract for 4 weeks, followed by DSS administration to induce acute colitis. Colonic histopathological injury, immune responses, barrier integrity, and gut microbiota composition were evaluated. In addition, the activity of PEITC, a major bioactive constituent of watercress, was examined in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages in vitro. Results: Watercress extract attenuated DSS-induced colon shortening and reduced histopathological injury. The supplementation of watercress extract also decreased colonic immune cell accumulation, suppressed the expression of pro-inflammatory mediators, and preserved intestinal barrier integrity. The 16S rRNA gene amplicon sequencing further revealed that watercress extract reshaped gut microbial composition, including increased abundance of Monoglobus and Adlercreutzia, and reduced abundance of microbial taxa such as Enterococcus and Enterorhabdus. Moreover, PEITC suppressed LPS-induced inflammatory activation in RAW264.7 macrophages by reducing nitric oxide production, inhibiting p38 MAPK phosphorylation, and downregulating multiple inflammatory cytokines and chemokines. Conclusions: These findings demonstrate that watercress extract alleviates experimental colitis through attenuating mucosal inflammation, preserving intestinal barrier function, and modulating the gut microbiota, highlighting watercress as a promising dietary strategy for improving gut health and mitigating intestinal inflammation.