Fermented Spirulina platensis alleviated DSS-induced ulcerative colitis by regulating gut microbiota and MyD88/TLR4 signaling pathway

Spirulina platensis (S. platensis) produces a variety of biologically active compounds that exhibit antioxidative, anti-inflammatory, antibacterial, and immunoregulatory properties. Here, dextran sulfate sodium (DSS) was used to develop an animal model of ulcerative colitis (UC) to evaluate the potential protective benefits of fermented S. platensis against DSS-induced colitis in mice. Gut microbiota alterations were investigated using 16S ribosomal RNA (rRNA) gene sequencing. Real-Time Quantitative PCR (RT-qPCR) was used to detect the expression of mRNA of inflammatory factors and pathway-related molecules in the inflammatory process. The results showed that fermented S. platensis could reverse the DSS-induced weight loss and colon length shortening in mice. The study of the 16S rRNA sequence showed that treatment with fermented S. platensis changed the gut microbiota of mice, with an increase in the relative abundance of beneficial bacteria such as Lachnospira. According to RT-qPCR and histopathological analyses, fermented S. platensis also improved the loss of goblet cells and neutrophil infiltration induced by DSS, while improving anti-inflammatory capacity. In addition, compared with the model group, the fermentation group significantly downregulated the relative expression of MyD88/TLR4 signaling pathway genes compared with the nonfermentation group. Overall, this investigation demonstrated that fermentative S. platensis can reduce DSS-induced UC by regulating gut microbiota composition, and the MyD88/TLR4 signaling pathway.