Gegen Qinlian decoction alleviates experimental colitis via suppressing TLR4/NF-κB signaling and enhancing antioxidant effect

Abstract Background Gegen Qinlian decoction (GQ), a Chinese medicinal herb decoction, has been widely used as efficient medicine for the treatment of acute colitis in clinics, but underlying molecular mechanisms have not been fully clarified. Hypothesis/purpose Inflammation and oxidative stress have been reported to constitute a crucial part in the pathogenesis of ulcerative colitis (UC). Hence, this study was designed to investigate the antiinflammatory activity and antioxidative effect of GQ. Study design Mice induced by 5% dextran sulfate sodium (DSS) and macrophage RAW264.7 cells stimulated by lipopolysaccharide (LPS) were used in this study. Methods Ethanol extracts of GQ were orally administered for 1 week on the dosage of 0.3, 1.5, or 7.5 g/kg/day and berberine (BBR, 100 mg/kg/d) was selected as a positive group in the animal experiments. In vitro, GQ (25, 50, 100 µg/ml) or BBR (20 µM) co-cultured with RAW264.7 for 2 h prior to LPS stimulation. Results The results showed that GQ oral administration alleviated the severity of colitis notably. It reduced toll-like receptor 4 (TLR4) expression and NF-κB activation in mucosa, which was accompanied with down regulation of several inflammatory cytokines in the colon, including tumor necrosis factor (TNF-α), interleukin (IL)-6, IL-1β and IL-4. Furthermore, GQ oral administration attenuated the oxidative stress in the colon of UC mice, evidenced by the decrease of myeloperoxidase (MPO) activity and malondialdehyde (MDA) level, and the elevation of glutathione (GSH) content. In parallel with the vivo experiment results, cell research indicated GQ dramatically reduced the production of TNF-α, IL-6, IL-1β and nitric oxide (NO), as well as that of reactive oxygen species (ROS) upon stimulation of LPS. Conclusion Together, our present study indicates that inhibition of TLR4/NF-κB signaling and enhancement of antioxidant effect might be the potential mechanisms for the therapeutic effect of GQ against UC.