Isoliquiritigenin alleviates ulcerative colitis by enhancing the intestinal barrier and improving intestinal microbiota via inhibiting the TLR4/MyD88/NF-κB pathway

Ulcerative colitis (UC) is a chronic disease characterized by intestinal inflammation, mucosal damage, and immune dysregulation. Current treatments are often inadequate, driving the search for alternatives with fewer side effects. Isoliquiritigenin (ISL), a flavonoid from licorice, has demonstrated anti-inflammatory effects, but its efficacy in UC remains uncertain. Male C57BL/6 mice were divided into six groups: Control, DSS model, low-, medium-, and high-dose ISL (25, 50, 100 mg/kg), and 5-aminosalicylic acid (5-ASA, 100 mg/kg). UC was induced by administering 3% DSS, followed by ISL or 5-ASA treatment. Disease activity index (DAI), histopathology, real-time PCR, Western blotting, immunohistochemistry, and 16 S rRNA sequencing were used to assess inflammation, intestinal barrier integrity, and gut microbiota (GM) composition. a Caco-2 cell-based model of UC was developed. After transfection to induce the overexpression of TLR4 and its adaptor protein MyD88, the cells were incubated with ISL. The effects of this intervention were evaluated by measuring the expression of inflammatory cytokines, tight junction-associated proteins, and components of the TLR4/MyD88 signaling pathway. ISL significantly alleviated DSS-induced UC symptoms, such as weight loss and colonic shortening. ISL reduced colonic mucosal damage and inflammatory cell infiltration, downregulated TLR4, MyD88, and phosphorylated NF-κB expression, and lowered TNF-α, IL-1β, and IL-6 levels. It also improved intestinal barrier function by upregulating ZO-1, Claudin-1, and Occludin expression. ISL modulated GM by increasing beneficial bacteria (Muribaculaceae) and reducing pathogenic bacteria (Escherichia-Shigella). Overexpression of TLR4 and MyD88 in the Caco-2 cell line abrogated the protective effects of ISL, as evidenced by increased expression of inflammatory cytokines and downregulated expression of tight junction proteins. Overall, these findings suggest ISL may protects against DSS-induced UC by suppressing the TLR4/MyD88/NF-κB pathway, enhancing intestinal barrier function, and modulating GM, supporting its potential as a therapeutic supplement for UC.