Preparation And Therapeutic Effects Of Chitosan Oligosaccharide On 2,4,6-trinitrobenzene Sulfonic Acid-induced Rat Model Of Inflammatory Bowel Disease

Objective Mucosal barrier destruction and oxidative stress response have been identified as important links in the pathogenesis of inflammatory bowel disease（IBD）.Chitosan oligosaccharide（COS）is a natural immunomodulator with unique antioxidant properties.This study aimed to investigate the biosafety and efficacy of COS as an oral therapy for a rat model of IBD in comparsion with the clinical drug 5-ASA,and to explore the underlying mechanisms of action.Methods COS was prepared from chitosan with a deacetylation degree of 87%and molecular weight of 140 k Da by enzymatic hydrolysis.The chemical structure of COS was characterized by Fourier transform infrared spectroscopy（FT-IR）and ~1H nuclear magnetic resonance（NMR）.The elemental analysis method was applied to determine the contents of carbon,hydrogen and nitrogen in the COS.A trinitrobenzene sulfonic acid（TNBS）-induced rat model of IBD was adopted to investigate the pharmacology of COS,and 5-ASA treatment was set as the positive control at an equivalent dosage of clinical recommendation.The rats were randomly divided into four groups（Control,Model,5-ASA,and COS）.H＆E and Masson trichromatic staining were used to evaluate the histological and fibrosis scores of the colon tissues.The indexes of inflammation,tumor necrosis factor（TNF-α）and interleukin-6 were determined by enzyme-linked immunoassay.The Immunohistochemical method was used to detect the expression levels of fibrosis related indicators such as type I collagen andα-SMA.The activities of related antioxidant enzymes in tissue homogenate were detected.Results As compared with 5-aminosalicylic acid（5-ASA）,the levels of IL-1β,TNF-αand IL-6 cytokines in the COS treatment group were decreased（P<0.01）.COS can significantly relieve active inflammation and restored epithelial function.COS treatment decreased the content of MDA,NO and NOS,and increased the activities of antioxidant enzymes GSH-Px and SOD in colon tissues,which had significant differences compared with 5-ASA（P<0.01）.The Investigation demonstrated that COS treatment regulated the redox state of the colon tissue by stimulating the transcription factor Nrf2,increasing the production of endogenous antioxidants and alleviating oxidative stress.Masson staining showed that collagen fibers increased significantly in the model group.The expression of collagen 1 andα-SMA in COS group was significantly different from that in the 5-ASA group（P<0.01）.Conclusions The present results indicate that COS can inhibit TNBS-induced inflammatory signal transduction in rats with colitis,play an anti-inflammatory role,improve intestinal barrier caused by TNBS,restore the mucosal barrier,and improve the antioxidant capacity of colon tissue by stimulating Nrf2,relieve intestinal oxidative stress and play a role in inhibiting fibrosis.