Ziziphus jujuba “Huizao” Polysaccharides Exert Immunomodulatory Activity In Vitro and In Vivo by Modulating the TLR4/MAPK/NF-κB Signalling Pathway

Ziziphus jujuba is an important source of polysaccharides in food supply, and studies have demonstrated that polysaccharides serve as the principal active constituents responsible for immunomodulatory effects. The results indicated that “Huizao” polysaccharides (HP2-1) increased the viability and phagocytic activity of RAW264.7 cells and triggered immune responses by promoting cytokines TNF-α, IL-6, and IL-1β secretion, as well as NO and ROS production. In addition, HP2-1 also stimulated cytokine production, elevated immunoglobulin levels, and alleviated oxidative stress via increasing antioxidant enzyme activities and reducing MDA production in immunosuppressed mice. Furthermore, HP2-1 potentiated immune responses both in vitro and in vivo by modulating the TLR4/MAPK/NF-κB pathway due to upregulating TLR4 expression, leading to phosphorylation of ERK, JNK, and p38 MAPKs, thereby activating NF-κB and subsequent cytokine secretion.