M cell Peyer’s patches lymphatic absorption of CDD-2103 polysaccharide triggers immune responses for colitis prevention

Polysaccharides are believed to be unable to cross the gut epithelial barrier due to their complex structure. Recent studies have reported that the absorption of certain polysaccharides via the lymphatic route triggers immune responses in Peyer’s patches (PPs). However, the therapeutic effects of CDD-2103 (N1) polysaccharide through M cell-mediated PPs lymphatic absorption and its role in triggering immune responses for the prevention of inflammatory colitis remain unknown. In our current study, we first investigated and confirmed the therapeutic effect of N1 polysaccharide in DSS-induced colitis mice. Moreover, we found that pro-inflammatory cytokines and immune cells (macrophages, dendritic cells, and double-positive CD4⁺CD8⁺ T cells) were significantly suppressed in the PPs of the N1 polysaccharide treatment group compared to the DSS group. Furthermore, oral administration of FITC-N1 polysaccharide in normal mice confirmed that M cells transported the polysaccharide into the PPs, where it was taken up by dendritic cells (DCs), while T and B cells did not uptake. In our in vitro study, we found that N1 polysaccharide exhibited pronounced anti-inflammatory effects in LPS stimulated RAW 264.7 cells and bone marrow-derived macrophages (BMDM) by suppressing pro-inflammatory cytokines and inhibiting M1 polarization. RAW 264.7 cells and BMDM mRNA sequencing results revealed significant downregulation of the MAPK and PI3K/AKT signaling pathways in the N1 polysaccharide treatment group compared to the LPS group. These findings provide convincing evidence that N1 polysaccharide has potential therapeutic effects through the lymphatic route for the prevention of inflammatory colitis.