Limosilactobacillus mucosae and Lactobacillus amylovorus Protect Against Experimental Colitis via Upregulation of Colonic 5-Hydroxytryptamine Receptor 4 and Transforming Growth Factor-beta 2

Background: Limosilactobacillus mucosae (LM) exerts anti-inflammatory and health-promoting effects. However, its role in the modulation of gut serotonin or 5-hydroxytryptamine (5-HT) metabolism and 5-HT receptors (HTRs) in inflammation requires further investigation. Objectives: We compared LM with Lactobacillus amylovorus (LA) for the regulation of 5-HT, HTRs, inflammatory mediators, and their correlations in the colon of mice with experimental colitis. Methods: Male C57BL/6 mice were randomly assigned to 6 groups: control (Con), LM, LA, dextran sodium sulfate (DSS), and DSS with pre-administration of LM (thornLM) or LA (thornLA). After 7 d of DSS treatment, mice were killed to analyze the expression of inflammatory mediators, HTRs, and concentrations of 5-HT and microbial metabolites in the colon. Results: LM was more effective than LA in alleviating DSS-induced colonic inflammation. Compared with mice in the DSS group, mice receiving DSS thorn LM or DSS thorn LA treatment had lower (P < 0.05) colonic mRNA expression of proinflammatory cytokines. DSS thorn LM treatment had lower mRNA expression of Il1b, Tnfa, and Ccl3, an abundance of p-STAT3, and greater expression of Tgfb2 and Htr4 in the colon (P < 0.05). The expression of inflammatory mediators (including Tgfb-1) was positively correlated (P < 0.05) with 5-HT and Htr2a and negatively correlated (P < 0.05) with Htr4. However, the expression of Tgfb-2 showed reversed correlations with the 5-HT and HTRs described above. Patterns for these correlations were different for LM and LA. Mice receiving the DSS thorn LM treatment had greater (P < 0.05) concentrations of acetate and valerate and lower (P < 0.05) concentrations of indole-3-acetic acid in the cecal and colonic contents. Conclusions: LM showed greater efficacy than LA in alleviating DSS-induced colonic inflammation. The coordinated regulation of transforming growth factor-beta subtypes and serotonin receptors in the colon may be one of the most important mechanisms underlying the probiotic effects of lactobacilli in gut inflammation.

Automated summary

LM showed greater efficacy than LA in alleviating DSS-induced colonic inflammation. The coordinated regulation of transforming growth factor-beta subtypes and serotonin receptors in the colon may be one of the most important mechanisms underlying the probiotic effects of lactobacilli in gut inflammation.