IDDF2022-ABS-0079 Short-chain fatty acid-producing mixed bacteria improve experimental colitis via promoting M2-like macrophages polarization

Background

There is a decrease in probiotic bacteria, especially the depletion of short-chain fatty acids (SCFAs)-producing bacteria in Inflammatory bowel diseases (IBD). Although intestinal probiotic bacteria have been identified to alleviate colitis, however, the efficacy of mixed SCFAs-producing bacteria in inflammatory patients remains unclear.

Methods

We used a reasonable approach to isolate and culture several SCFAs-producing bacteria from the feces of the healthy donors. The objective of this study was to compare the effects of 7-mixed bacteria, mixed supernatant, and human FMT on DSS-induced acute experimental colitis and to explore their mechanisms.

Results

We observed that mice gavage with mix-sup, 7-mix and hu-FMT more effectively improved weight loss, DAI scores, colon lengths and colonic inflammation, and less inflammatory cell infiltration than mice gavage with PBS (IDDF2022-ABS-0079 Figure 1a-f. Mix-sup and 7-mix gavage meliorated the DSS-induced acute colitis and enhanced gut barrier). Immunohistochemistry results of ZO-1 and occludin also observed that mix-sup, 7-mix and hu-FMT had more beneficial to gut barrier reinforcement than PBS (IDDF2022-ABS-0079 Figure 1g-h. Mix-sup and 7-mix gavage meliorated the DSS-induced acute colitis and enhanced gut barrier). We further demonstrated that mix-sup, 7-mix and hu-FMT gavage group diminished M1 associated pro-inflammatory cytokines, i.e., iNOS, IL-1β, IL-12, IL-23, IL-6, TNF-α (IDDF2022-ABS-0079 Figure 2a. Mix-sup and 7-mix triggered beneficial role via facilitating an M2-like macrophage response in vivo and in vitro), while promoted the expression of M2-related anti-inflammatory cytokines, i.e., CD206, TGF-β, and IL-5, compared to PBS group in mice acute colitis (IDDF2022-ABS-0079 Figure 2b. Mix-sup and 7-mix triggered beneficial role via facilitating an M2-like macrophage response in vivo and in vitro). Moreover, flow cytometry data further confirmed that intervention of mix-sup and 7-mix obviously promoted M2-like macrophage polarization, and the ratio of M1/M2 further clarified seven strains mixture, especially supernatant mixture play a beneficial role in intestinal barrier repair (IDDF2022-ABS-0079 Figure 2c. Mix-sup and 7-mix triggered beneficial role via facilitating an M2-like macrophage response in vivo and in vitro). To confirm whether mix-sup and 7-mix induced M2-like macrophage (CD206) polarization in vitro, RAW264.7 cells/mix-sup and RAW264.7 cells/7-mix transwell chamber co-culture system was employed (IDDF2022-ABS-0079 Figure 2d. Mix-sup and 7-mix triggered beneficial role via facilitating an M2-like macrophage response in vivo and in vitro). All data clarified mix-sup and 7-mix via facilitating an M2-like macrophage response to alleviate inflammatory in vivo and in vitro.

Conclusions

We selected seven probiotic microorganisms and metabolites (SCFAs) that are comparable or superior to FMT in repairing leak gut barrier via facilitating an M2-like macrophage response.