Rhopilema esculentum polysaccharides enhance epithelial cell barrier in vitro and alleviate chronic colitis in mice

The purposes of this study were to characterize polysaccharides from Rhopilema esculentum and to explore their impacts on gut barrier function and inflammation in vitro and in mice with chronic colitis triggered by long-term administration of dextran sulfate sodium (DSS). Two polysaccharides were isolated and purified from Rhopilema esculentum, named REP-1 and REP-2. REP-1 with a molecular weight of 8.21 kDa was composed of mannose, glucosamine, galactosamine, glucose, galactose, and arabinose with a molar ratio of 0.04:0.03:0.38:1:1.36:0.06, and REP-2 with a molecular weight of 10.11 kDa mainly consisted of mannose, glucuronic acid, galactosamine, glucose, galactose, and arabinose with a molar ratio of 0.04:0.12:0.41:1:1.2:0.06. Compared to REP-1, REP-2 displayed better ability to up-regulate the expression of genes related to tight junctions and mucus in LPS-stimulated Caco-2 cells and better immunomodulatory activities in RAW264.7 macrophages. Then animal experiments showed that REP-2 efficiently attenuated the symptoms of colitis, decreased the secretion of pro-inflammatory cytokines, and restored intestinal barrier function in mice with chronic colitis. These results demonstrate that REP-2 might be a promising agent for protecting intestinal and mucus barrier and mitigating inflammation-associated intestinal diseases such as ulcerative colitis.