The immunomodulatory effect of Poria cocos polysaccharides is mediated by the Ca2+/PKC/p38/NF-κB signaling pathway in macrophages

Poria cocos polysaccharide (PCP), extracted from Poria cocos sclerotium, has many biological activities. The present study explored the immunomodulatory effect and the underlying molecular mechanism of PCP in RAW 264.7 macrophages. Griess reaction, ELISA assays and confocal laser scanning microscopy revealed that the production of nitric oxide (NO), TNF-α, IL-1β, IL-6 and intracellular calcium level were increased by PCP. However, this effect on cytokines was suppressed with a Ca²⁺ channel blocker or a p38 inhibitor, which indicates that Ca²⁺ and p38 are crucial to the immunomodulatory effect of PCP. We further demonstrated that PCP-treated cells also exhibited increased the activity of PKC, mRNA and protein expression levels of p38 and NF-κB, which is also reduced with a Ca²⁺ channel blocker. Taken together, the Ca²⁺/PKC/p38/NF-κB signaling pathway may involve in the immunomodulatory effects of PCP.