Effects of Lactobacillus reuteri strain DSM and Lactobacillus taiwanensis strain BCRC on intestinal inflammation

Abstract:

[Objective] This study aims to investigate the effects of Lactobacillus reuteri strain DSM (LR) and Lactobacillus taiwanensis strain BCRC (LT) on intestinal inflammation using a mouse model of dextran sodium sulfate (DSS) induced colitis. [Methods] Twenty-four 8-week-old C57BL/6J male mice with similar body weight were selected and randomly divided into 4 groups (6 replicates in each group):normal group, DSS group, LR bacteria treatment group and LT bacteria treatment group. After 7 days adaptation period and 16 days experiment period, the mice were sacrificed and sampled. [Results] Compared with the normal group, the body weight and colon length of the DSS group were significantly reduced, and the disease activity index (DAI) scores as significantly increased (P<0.05). There was no significant difference in body weight between the LR and LT bacteria treatment groups and the DSS group (P>0.05), whereas the LR and LT bacteria treatment significantly reduced the DAI scores and the LT bacteria treatment treatment increased the colon length. The colonic histopathological scores of the normal group and the LT bacteria treatment group were significantly lower than those of the DSS and LR bacteria treatment groups (P<0.05). Colonic myeloperoxidase (MPO) activity was also significantly lower in the normal group and the LT bacteria treatment group than the DSS group, and there was no significant difference between the LR bacteria treatment group and the DSS group (P>0.05). Compared with the normal group, the levels of pro-inflammatory factors TNF-α, IL-1β, and IL-6 in the colon and plasma of the DSS group were significantly increased, while the levels of the anti-inflammatory factor IL-10 were significantly decreased. Compared with the DSS group, LT bacteria treatment group significantly reduced the levels of TNF-α, IL-1β, and IL-6 in the colon and plasma, and increased the level of IL-10; the LR bacteria treatment group significantly reduced the levels of colonic TNF-α and plasma IL-1β, and increase the level of IL-10 (P<0.05). The results of immunohistochemistry and ELISA showed that compared with the normal group, the DSS group reduced the expression levels of colonic tight junction proteins including Claudin-1, Occludin, ZO-1, and mucin Muc-2, while the treatment of LR and LT bacteria up-regulated the expression of those barrier-related proteins under the influence of DSS. The composition of colonic flora was detected by using 16S rDNA sequencing technology. PCoA analysis showed that the normal group and the DSS group are significantly separated, and the flora composition of the LT treatment group was closer to the normal group. At the phylum level, the abundance of Proteobacteria in the normal group was significantly lower than that of the DSS group (P<0.05). Compared with the DSS group, the LT bacteria treatment group could also reduce the abundance of Proteobacteria, but did not reach a significant level (P>0.05). At the genus level, Muribaculaceae_norank in the normal group was significantly higher than the other three groups, and Bacteroides in the normal control group was significantly lower than the other three groups (P<0.05). Compared with the DSS group, the treatment of LR and LT bacteria increased Muribaculaceae_norank abundance, and reduced Bacteroides abundance, but the difference was not significant (P>0.05). [Conclusion] Lactobacillus reuteri and Lactobacillus taiwanensis can strengthen the intestinal epithelial barrier and relieve the intestinal inflammation caused by DSS to a certain extent. Among them, Lactobacillus taiwanensis has a more significant protective effect on the intestinal epithelial barrier.

Key words:Lactobacillus;intestinal inflammation;DSS;intestinal epithelial barrier