Xianglian Pill attenuates ulcerative colitis through TLR4/MyD88/NF-κB signaling pathway

Xianglian Pill (XLP) is a classical Chinese medicine prescription applied for controlling ulcerative colitis (UC). Whereas, the underlying mechanism remains unclear. The present work was aimed to investigate the mechanism of XLP in dextran sulfate sodium (DSS)-induced UC via the Toll Like Receptor 4 (TLR4)/Myeloid Differentiation factor 88 (MyD88)/Nuclear Factor kappa-B (NF-κB) signaling in mice. The major components of XLP were detected by high-performance liquid chromatography-diode array detection (HPLC-DAD). The ulcerative colitis model was induced by DSS in mice. 5-Amino Salicylic Acid (5-ASA) group and XLP group were intragastrically treated. Disease activity index (DAI) and colon length were monitored and hematoxylin-eosin (HE) staining was conducted. Gasdermin D (GSDMD)-N and TLR4 expressions in colon tissues were visualized by immunofluorescence. TLR4 mRNA was measured by Real Time Quantitative PCR (RT-qPCR). The expressions of NOD-like receptor thermal protein domain associated protein 3 (NLRP3), active-caspase-1, GSDMD-N, TLR4, MYD88, NF-κB, p–NF–κB, and the ubiquitination of TLR4 in colon tissues were detected by Western blot. Myeloperoxidase (MPO) enzyme activity was examined and serum inflammatory factors Interleukin (IL)-1β, IL-6, Tumor Necrosis Factor-α (TNF-α), and IL-18 were determined by Enzyme-linked Immunosorbent Assay (ELISA). TLR4⁻/⁻ mice were applied for verifying the mechanism of XLP attenuated DSS symptoms. The XLP treatment extended colon length, reduced DAI, and attenuated histopathological alteration in DSS-induced mice. XLP administration suppressed MPO activity and reduced the content of IL-1β, IL-6, TNF-α and IL-18 in serum. XLP also inhibited the expression levels of GSDMD-N, TLR4, NLRP3, active-caspase-1, MyD88, p–NF–κB/NF-κB in colon tissues of DSS-induced mice. TLR4⁻/⁻ mice proved that TLR4 was involved in XLP-mediated beneficial effect on DSS-induced ulcerative colitis. XLP might treat ulcerative colitis by regulating the TLR4/MyD88/NF-κB signaling pathway.