Polysaccharide ofAtractylodes macrocephalaKoidz Enhances Cytokine Secretion by Stimulating theTLR4–MyD88–NF-κBSignaling Pathway in the Mouse Spleen

Polysaccharide of Atractylodes macrocephala Koidz (PAMK) has been reported to have beneficial effects on regulation of immune responses in mammals and poultry. Nonetheless, the immunoregulatory mechanism of action of PAMK remains unclear. The Toll-like receptor 4 (TLR4) signaling cascade has been proved as a classic polysaccharide-regulated pathway. The aim of this study was to explore the effects of PAMK on the TLR4 signaling pathway in the regulation of spleen function in mice. Ninety-six 5-week-old BALB/c female mice were randomly allocated into four groups with three replicates per group and eight mice per replicate in a single-factor completely randomized experimental design. The control group was fed a basic diet (PAMK free); the other three groups were fed 100, 200, or 400 mg/kg PAMK for 28 days. The spleen index, concentrations of cytokines, and mRNA and protein expression levels of genes related to TLR4 signaling were determined in spleen tissue. Compared with the control group, the spleen index significantly increased in all treatment groups. Concentrations of interleukin 2 (IL-2), IL-4, interferon γ (IFN-γ), and tumor necrosis factor α (TNF-α) in the medium-PAMK group also increased significantly. PAMK in the medium-PAMK group significantly increased both mRNA and protein expression of TLR4, myeloid differentiation factor 88 (MyD88), TNFR-associated factor 6 (TRAF6), TRAF3, and nuclear factor kappa B (NF-κB) in the spleen. In conclusion, PAMK may increase immune-response capacity of the spleen in mice via TLR4-MyD88-NF-κB signaling.