Effects of molecular weight of chitosan on anti-inflammatory activity and modulation of intestinal microflora in an ulcerative colitis model

This study investigated the therapeutic effects and mechanisms of chitosans (CSs) with different molecular weights on ulcerative colitis (UC). Three size classes of CSs (Mw ≤ 3, 50, and 200 kDa) were used in this study. The effect of large CSs (Mw ≤ 200 kDa) on UC was the best, followed by that of medium CSs (Mw ≤ 50 kDa), and that of small CSs (Mw ≤ 3 kDa) was the least in the LPS-induced Raw 264.7 cell model and DSS-induced UC mice model. The therapeutic mechanisms of three CSs are related to anti-oxidation, anti-inflammation, and regulation of immunoglobulin and intestinal flora by attenuating body weight loss, decreasing the disease activity index (DAI) and MPO activity, suppressing proinflammatory cytokines and IgG levels, down-regulating the level of oxidative stress, increasing anti-inflammatory cytokines, SOD activity and Prevotellaceae_UCG-001 levels, and reducing the abundance of Proteobacteria, Actinobacteria, and Escherichia-Shigella. In general, the molecular weight of CSs influences their efficacy against UC. CSs with an optimal molecular weight demonstrate good development prospects for ameliorating UC.