Immunomodulatory activity of single chitooligosaccharides in LPS-induced RAW264.7 cells and endotoxemia mice.

Chitooligosaccharides is a green and non-toxic amino sugar, and its immunomodulatory activity has attracted much attention in recent years. However, most of the test samples in the existing chitooligosaccharides activity studies are mixtures, and the immunomodulatory structure-activity relationship is difficult to understand. In the present study, we successfully isolated five single chitooligosaccharides from dimer to hexamer by ion-exchange chromatography, and further investigated the size effects of chitooligosaccharides on its immunomodulatory activity. In vitro experiments showed that chitooligosaccharides with higher degree of polymerization (DP) show stronger inhibitory effect on lipopolysaccharide (LPS)-induced NO release in RAW264.7 macrophages. The high DP chitooligosaccharides were further selected for in vivo experiments. The results suggested that in LPS-induced endotoxemia model mice, chitooligosaccharides tetramer (D4), pentamer (D5) and hexamer (D6) significantly restored serum levels of alanine aminotransferase (ALT) and creatinine (CREA), while concurrently elevating pro-inflammatory cytokines (IL-1β, IFN-γ) and upregulating anti-inflammatory IL-10 expression, revealing bidirectional immunoregulatory capabilities. Moreover, these three high DP chitooligosaccharides were also effective in protecting the intestinal villus structure and attenuating hepatic and renal injuries.