Immunomodulatory effects of polysaccharopeptide (PSP) in human PBMC through regulation of TRAF6/TLR immunosignal-transduction pathways

Context: Polysaccharopeptide (PSP) was extracted from Coriolus versicolor, and has been proved to be a valuable adjuvant for the combination with chemotherapy or radiotherapy in the treatment of various cancers. Objective: To understand the mechanism of PSP on immunomodulation, we examined gene expression and cytokine secretion associated with immunosignal-transduction signaling in human peripheral blood mononuclear cells (PBMCs). Methods: cDNA microarray and cytokine antibody array were used to identify differential gene expression profiles and cytokines secretion of PBMCs in the presence or absence of PSP for 24 h. The expression of the key genes and proteins related to Toll-like receptor (TLR) signaling and its downstream pathway was determined by RT-PCR or Western blot. Results: Compared with the control group, PSP up-regulated 22 genes expression (such as IFN-gamma, CXCL10, TLR4, TLR5) in 117 genes associated with TLR signaling. Twenty-three of genes (e.g., TLR9, TLR10, SARM1, TOLLIP) related with TLR signaling pathway were down-regulated in PBMCs under PSP treatments. Five of cytokines (GCSF, GM-CSF, IL-1 alpha, IL-6, IFN-gamma) were up-regulated more than 1.3 times by PSP. The mRNA levels of TRAM, TRIF, and TRAF6, which are the key molecules of TLR signaling pathway, were markedly increased (P < 0.05). Moreover, the protein level of TRAF6 was also markedly increased (P < 0.01). Conclusions: PSP-regulated gene expression and cytokine secretion related to TLR signaling pathway in human PBMCs. Especially, TRAM-TRIF-TRAF6 subsignaling pathway of TLR may be one of the key associated signaling pathways in the immunomodulation of PSP.