Epi‐Berberine Alleviates Ulcerative Colitis, Protects the Intestinal Mucosal Barrier, and Inhibits Colonic Inflammation via Glutaminyl‐Peptide Cyclotransferase in a Mouse Model of <scp>DSS</scp> ‐Induced Colitis

The global incidence of ulcerative colitis (UC), a chronic inflammatory bowel disease, is rising. Epi-berberine (EPI), an alkaloid from Coptidis Rhizoma, shows potential for UC treatment. This study aimed to assess EPI's effect on UC and explore the mechanism underlying its UC-alleviating effect. The therapeutic effects of EPI on UC were validated in dextran sulfate sodium (DSS)-induced colitis mice and lipopolysaccharide (LPS)-induced Caco-2 inflammatory models and further investigated the underlying mechanism. In vivo, high-dose EPI (200 mg/kg) attenuated weight loss, reduced disease activity index, increased colon length, lowered colon macroscopic/histological scores, restored intestinal mucosal barrier and inhibited colonic inflammation. EPI (25/50 μM) had similar in vitro effects. mRNA-seq identified EPI-regulated genes in UC mice, revealing six gene clusters with analogous expression patterns. The largest cluster contained genes upregulated by DSS but downregulated by EPI, potentially involved in the MAPK pathway. Key DEGs were enriched in PI3K-Akt and MAPK pathways, verified in vivo and in vitro. Literature retrieval and molecular docking predicted glutaminyl-peptide cyclotransferase (QPCT) as EPI's potential UC therapeutic target. EPI inhibited DSS/LPS-induced QPCT upregulation in vivo and in vitro; QPCT knockdown suppressed inflammation and preserved Caco-2 monolayer barrier function, while QPCT overexpression reversed EPI's therapeutic effects. QPCT mediates PI3K-Akt/MAPK activation, and its overexpression abrogated EPI's inhibitory effects. EPI alleviates murine UC by protecting the intestinal mucosal barrier and inhibiting inflammation, likely via regulating the QPCT-PI3K-Akt/MAPK pathway. It provides a preclinical basis for developing prophylactic strategies for inflammatory bowel disease.