Coptisine alleviates intestinal barrier dysfunction and inflammation in TNBS-induced colitis rats and LPS-stimulated...

Coptidis Rhizoma, documented in the Chinese Pharmacopoeia, is utilized for treating dysentery, abdominal pain, and inflammatory intestinal conditions owing to its heat-clearing and detoxifying properties. Coptisine (COP), a characteristic isoquinoline alkaloid and marker constituent of Coptidis Rhizoma, has demonstrated anti-inflammatory and antioxidant benefits. However, its effects on intestinal barrier function and the latent mechanisms remain unclear. This study aimed to investigate the potential protective effects of COP on intestinal barrier dysfunction and inflammation in both a 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced IBD rat model and lipopolysaccharide (LPS)-stimulated human Caco-2 cells, and to explore the underlying molecular mechanisms. Colitis severity in rats was assessed by monitoring body weight changes, disease activity index (DAI), and colon weight-to-length ratio. Histopathological changes were analyzed by H&E and AB-PAS staining. Cell viability and cytotoxicity were evaluated using CCK-8 and LDH release assays, respectively. Intestinal barrier integrity was assessed by measuring transepithelial electrical resistance (TEER), paracellular permeability, and the expression or distribution of tight junction (ZO-1, occludin) and adherens junction (E-cadherin) proteins. Levels of pro-inflammatory mediators, apoptosis, reactive oxygen species (ROS), and the SIRT1/NLRP3 pathway were analyzed using ELISA, flow cytometry, qRT-PCR, immunofluorescence, and Western blotting. Results suggested that in TNBS-exposed rats, COP administration markedly attenuated disease severity, as evidenced by normalized body weight, decreased DAI score and colon weight-to-length ratio, and preserved colon morphology, with efficacy superior to sulfasalazine (SASP). COP also dose-dependently reduced pro-inflammatory mediators (NO, TNF-α, IL-6, IL-1β and IL-18) in colonic mucosa and improved intestinal barrier function. In vitro, COP dramatically enhanced TEER, decreased the permeability of FITC-dextran, and restored the expression and distribution of tight and adherens junction proteins including ZO-1, occludin, and E-cadherin in LPS-stimulated Caco-2 cells. It also inhibited LPS-induced apoptosis and pro-inflammatory mediator expression. Mechanistically, COP exerted its effects by activating SIRT1 and restraining the ROS/TXNIP/NLRP3 inflammasome pathway through down-regulating the levels of ROS, TXNIP, NLRP3, ASC, caspase-1, IL-1β, and IL-18. These protective effects were significantly reversed by H₂O₂ (a ROS agonist) and EX-527 (a SIRT1 inhibitor). In conclusion, this study demonstrates that COP alleviates intestinal barrier dysfunction and inflammation by activating SIRT1 and inhibiting the ROS/TXNIP/NLRP3 signaling. These findings suggest that COP is a promising therapeutic candidate for IBD and related intestinal inflammation.