Immunomodulatory effects exerted by Poria Cocos polysaccharides via TLR4/TRAF6/NF-κB signaling in vitro and in vivo

Poria cocos polysaccharide (PCP) is the major active ingredients of P. cocos and possesses various pharmacological effects, including anti-oxidative and anti-apoptosis effects and activity against cancer. This study investigated the immunomodulatory mechanism by which PCP acts on RAW 264.7 macrophages and LLC tumors in mice. The concentrations of nitric oxide, and Th1, Th2, and Th17 cytokines were examined by Griess reaction and using a bead-based cytokine assessment kit. qRT-PCR and western blotting were used to investigate relevant signaling molecule expression. Levels of nitric oxide, IL-2, IL-6, IL-17 A, TNF, and IFN-γ were increased by PCP while levels of IL-4 and IL-10 were unaffected. The addition of TAK-242 (TLR4 inhibitor) or assessment in C57BL/10ScNJ (TLR4-deficient) mice markedly reduced this effect. In C57BL/10 J (TLR4+/+wild-type) mice, the indices of organ immune activity were all elevated, and oral PCP delivery resulted in a significant reduction in tumor volume over a 25 day period. Relative to controls, TLR4, MyD88, TRAF-6, p-NF-κB and p-c-JUN expression significantly increased, while TRAM expression did not change. Nevertheless, there was no PCP-dependent activation of MyD88, TRAF-6, TRAM, p-NF-κB or p-c-JUN in TLR4-deficient mice. These results support the concept that PCP may exhibit immunomodulatory activity through TLR4/TRAF6/NF-κB signaling both in vitro and in vivo.