ABSTRACT: Ulcerative colitis (UC) remains a therapeutic challenge due to its chronicity, adverse effects of current drugs, and high relapse rates. Smoking inversely correlates with UC risk. Nicotine (NIC) shows UC efficacy but causes non-smoker intolerance. Bioinformatic identification of tobacco-derived quercetin (QUE), an α7 nAChR enhancer, suggests its potential as a NIC synergist for reduced side effects. We thus hypothesized that half-dose NIC-QUE co-therapy would exert superior anti-colitis effects. Using a DSS-induced murine colitis model, we performed a multidimensional assessment spanning: Clinical phenotypes (body weight, disease activity index (DAI), colon length, histopathology), Gut microenvironment (gut microbiota composition, short-chain fatty acids (SCFAs) and barrier integrity) and Inflammatory mechanisms (inflammatory cytokines and signaling pathways). The half-dose NIC-QUE combination almost outperformed monotherapies across all dimensions, such as body weight, DAI, colon length, histopathology. Mechanistically, synergy arose from: the synergistic effect involved: reshaping gut microbiota structure (notably increasing Clostridia and Eubacterium while reducing Erysipelotrichia), restoring key SCFA levels (acetate, butyrate, propionate, valerate), enhancing intestinal barrier integrity (ZO-1, Muc2), and critically, suppressing the activation of the PI3K/AKT and NF-κB signaling pathways. To our knowledge, this is the first study demonstrating that half-dose NIC-QUE co-administration constitutes a novel UC therapeutic strategy. Its core mechanism involves coordinated restoration of the gut microbiome-metabolite barrier and suppression of the PI3K/AKT/NF-κB inflammatory cascade
