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

Objective: 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.

Methods: 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.

Results: 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.

Conclusion: These results support the concept that PCP may exhibit immunomodulatory activity through TLR4/TRAF6/NF-κB signaling both in vitro and in vivo.