Immune-Enhancing Effects of Red Platycodon grandiflorus Root Extract via p38 MAPK-Mediated NF-κB Activation

Platycodongrandiflorus (PG) root extract has been widely used as an oriental herbal medicine. Red PG root extract (RPGE), which is made by steaming and drying PG several times, contains more saponin than raw (white) PG. Although RPGE has been known to have anti-inflammatory activity, the effects of RPGE on the immune-enhancing response remain unclear. In this study, we aimed to investigate the immune-enhancing effects of RPGE and its mechanism in macrophage cells and splenocytes. Our results revealed that cell proliferation of both macrophages and splenocytes correlate positively with the concentration of RPGE. Moreover, RPGE treatment increased the phagocytic activity of macrophage cells, as well as nitric oxide and cytokines production. Furthermore, RPGE induced phosphorylation of the p38 mitogen-activated protein kinase, which contributed to nuclear factor-kappa B activation. Thus, our findings suggest that RPGE may be a potential functional food for improving immune function.