P865 The protective effect of Saccharomyces boulardii on intestinal mucosal barrier of inflammatory bowel disease

Abstract

Background: The role of Saccharomyces boulardii (Sb) in Inflammatory bowel disease (IBD) is controversial,1,2 and the mechanism of Sb in IBD is unclear. The objectives of this study were to evaluate the effects of Sb on colits and intestinal flora, and to explore its possible mechanism in IBD. Methods: Forty C57BL/6J male mice were randomly divided into five groups: normal control group (Group A), pathologic control group (Group B), Sb treating group (Group C), mesalazine treating group (Group D), and Sb combined mesalazine treating group (Group E). Colitis was induced by the addition of 2.5% DSS (wt/vol) in the drinking water ad libitum for 7 days. Disease activity index (DAI) and histological damage scoring were evaluated. The expression of ZO-1 and Occludin in intestinal tissue was measured by immunohistochemistry. The level of TNF-α and IL-8 was measured by ELISA. Intercellular tight junctions were observed by transmission electron microscopy. Faces and intestinal content were collected sterilely, intestinal flora were analysed by 16S rRNA sequencing. Results: (1) DAI of group B was higher than group A, C and D, with statistical differences; but the DAI of group E was higher than group B. (2) Histological damage score and the level of TNF-α and IL-8 of group B were higher than the other groups, and the level of ZO-1 and Occludin in group B was lower than the other groups, with statistical differences, but there was no statistical difference between group C, D and E (Figures 1-4). (3) Transmission electron microscopy revealed normal ultrastructural appearance in group A, with normal tight junctions and microvilli on the surface of epithelial cells. In group B, tight junctions and microvilli were destroyed severely. Areas with histological lesions in C, D, E group were ameliorated on different extent, and the improvement of group C is the most evident (Figure 5). (4) Firmicutes and Bacteroidetes took the priority to the intestinal flora of group A, while Firmicutes decreased and Proteobacteria increased in the other groups, with statistical differences. Besides, Bacteroidetes increased in group C compared with group A, with statistical differences. The proportion of family S24-7 increased in group C, with significant difference in abundance, compared with group B, D and E (Figure 6). (Figure presented) Conclusions: Sb shows an anti-inflammatory effect on experimental colitis and has a protective effect of intestinal mucosal mechanical barrier, which is as effective as mesalazine. Combined Sb with mesalazine does not show a better effect. Dysbacteriosis exist in DSS induced colitis, which are expressed in decreased Firmicutes and increased Proteobacteria. Sb can upregulate the abundance of family S24-7 specifically, which may be a mechanism of its functioning.