Immunomodulatory effect of two hydrolysates of chitin on cyclophosphamide-induced mice via immune response enhancement and gut microbiota modulation

In this study, the hydrolysis products of chitin, COS1 and COS2, had degrees of deacetylation of 5.9% and 85.7%, respectively. Notably, 50 mg/(kg·d) COS1 and COS2 significantly increased the levels of immunoglobulins (IgG and IgM), cytokines (IL-6 and IFN-γ), and the antioxidant activities (SOD and CAT) in cyclophosphamide-induced mice, and upregulated the mRNA expression of cytokines in the spleen. COS1 activated the MAPK signaling pathways of related proteins (ERK, p-ERK, JNK, and p-JNK). After COS1 and COS2 intervention, the gut microbial structure of immunosuppressed mice changed, increasing the abundance of key bacteria such as, Dubosiella, Romboutsia, and Turicibacter, and decreasing the abundance of key bacteria such as, Escherichia-Shigella and Helicobacter. Notably, COS1 exhibited a higher immunoregulatory activity than COS2, which may be associated with the acetyl groups in COS1. COS1 can be developed as an immunomodulatory agent in functional foods and medicine to improve immunity.