Affiliation:
1. Food Science College, Northeast Agricultural University, Harbin 150030, China
2. Department of Pharmaceutical Engineering, School of Chemical and Environmental Engineering, Key Laboratory of Green Chemical Engineering in Heilongjiang Province, Harbin University of Science and Technology, Harbin 150040, China
3. The First Affiliated Hospital of Harbin Medical University, Harbin 150001, China
4. Department of Pharmacology, School of Medicine, Yale University, New Haven, Connecticut 06520, USA
Abstract
Iridoid glycoside (IG) is the major active fraction extracted from the leaves of Syringa oblata Lindl. In view of its antimicrobial and antidiarrheal potential, it could be beneficial for the treatment of ulcerative colitis (UC). In the present study, IG (20, 40, and 80 mg/kg) was administered orally for 14 days to dextran sulfate sodium- (DSS-) induced colitis rats. The anti-inflammatory effects of IG on DSS-induced UC were evaluated by comparing observations in DSS-induced colitis and drug-treated groups using disease activity index (DAI), macroscopic score, histological analysis, and apoptosis assay. To elucidate the antioxidant mechanisms of IG on NOX-dependent ROS production, the activities of 8-OHdG, NOX1, and NOX2 in DSS-induced colitis were determined. The levels of proinflammatory cytokines such as IL-2, IL-4, IL-5, IL-12p40, and IL-13 were detected. The inflammation-associated protein and mRNA expressions of TLR-2, TLR-4, MyD88, and NF-κBp65 were assessed by immunohistochemistry and real-time quantitative PCR, respectively. The results suggested that IG treatment significantly reduced DAI, macroscopic score, and histological damage compared to untreated animals (p<0.01), whereas administration of IG remarkably attenuated the upregulation of 8-OHdG, NOX1, and NOX2 and the expression of proinflammatory cytokines such as IL-2, IL-4, IL-5, IL-12p40, and IL-13 in DSS-treated rats in a concentration-dependent manner. In addition, IG treatment could dose dependently suppress the protein and mRNA levels of TLR-2, TLR-4, MyD88, and NF-κBp65. The dose of IG that produced the most significant protective effect was 80 mg/kg. The above results demonstrate that IG exerts its inhibitory effect on cell apoptosis, oxidative stress, and proinflammatory cytokines in DSS-induced colitis through modulation of the TLR2/4/MyD88/NF-κB signaling pathway.
Funder
China Scholarship Council
Subject
General Immunology and Microbiology,General Biochemistry, Genetics and Molecular Biology,General Medicine