Anti-inflammatory effects of iridoid glycosides fraction of Folium syringae leaves on TNBS-induced colitis in rats.

To investigate the effects and the protective mechanism of iridoid glycosides (IG) enriched from Folium syringae leaves on ulcerative colitis (UC) model induced by 2,4,6-trinitrobenzenesulfonic acid (TNBS) in rats. UC in rats was induced by colonic administration with TNBS. IG (80, 160 and 240 mg/kg) was administered for 2 weeks to experimental colitis rats. The inflammatory degree was assessed by macroscopic score, histology and myeloperoxidase (MPO) activity. Nitric oxide (NO) and malondialdehyde (MDA) levels were measured with biochemical methods. The protein expressions of nuclear factor-kappaBp65 (NF-κBp65) and mRNA expressions of pro-inflammatory cytokines, such as tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and NF-κBp65, were determined by immunohistochemistry and real-time quantitative PCR, respectively. IG significantly ameliorated macroscopic damage and histological changes, reduced the activity of MPO, depressed MDA and NO levels and effectively inhibited the protein and mRNA expressions of NF-κBp65, TNF-α and IL-6 in the colon tissues of experimental colitis in a dose-dependent manner. Moreover, the effects of IG (160 mg/kg and 240 mg/kg) were superior to salicylazosulfapyridine (150 mg/kg). We demonstrated for the first time that IG possessed marked protective effects on experimental colitis through its antioxidation and inhibiting inflammatory mediators by down-regulation of the expressions of NF-κBp65. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.