Background: Panax ginseng (i.e., ginseng) root is extensively used in traditional oriental medicine. It is a modern pharmaceutical reagent for preventing various human diseases such as cancer. Ginsenosides-the major active components of ginseng-exhibit immunomodulatory effects. However, the mechanism and function underlying such effects are not fully elucidated, especially in human monocytes and dendritic cells (DCs).
Methods: We investigated the immunomodulatory effect of ginsenosides from Panax ginseng root on CD14(+) monocytes purified from human adult peripheral blood mononuclear cells (PBMCs) and on their differentiation into DCs that affect CD4(+) T cell activity.
Results: After treatment with ginsenoside fractions, monocyte levels of tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-10 increased through phosphorylation of extracellular signal-regulated kinase (ERK)1/2 and c-Jun N-terminal kinase (JNK), but not p38 mitogen-activated protein kinase (MAPK). After treatment with ginsenoside fractions, TNF-α production and phosphorylation of ERK1/2 and JNK decreased in lipopolysaccharide (LPS)-sensitized monocytes. We confirmed that DCs derived from CD14(+) monocytes in the presence of ginsenoside fractions (Gin-DCs) contained decreased levels of the costimulatory molecules CD80 and CD86. The expression of these costimulatory molecules decreased in LPS-treated DCs exposed to ginsenoside fractions, compared to their expression in LPS-treated DCs in the absence of ginsenoside fractions. Furthermore, LPS-treated Gin-DCs could not induce proliferation and interferon gamma (IFN-γ) production by CD4(+) T cells with the coculture of Gin-DCs with CD4+ T cells.
Conclusion: These results suggest that ginsenoside fractions from the ginseng root suppress cytokine production and maturation of LPS-treated DCs and downregulate CD4(+) T cells.
Keywords: CD14+ monocytes; CD4+ T cells; Panax ginseng; dendritic cells; ginsenosides.