Ginsenoside Rp₁, a ginsenoside derivative, blocks promoter activation of iNOS and Cox-2 genes by suppression of an IKKβ-mediated NF-κB pathway in HEK293 cells

Ginsenoside (G) Rp₁ is a ginseng saponin derivative with anti-cancer and anti-inflammatory activities. In this study, we examined the mechanism by which G-Rp₁ inhibits inflammatory responses of cells. We did this using a strategy in which DNA constructs containing cyclooxygenase (COX)-2 and inducible nitric oxide synthase (iNOS) promoters were transfected into HEK293 cells. G-Rp₁ strongly inhibited the promoter activities of COX-2 and iNOS; it also inhibited lipopolysaccharide induced upregulation of COX-2 and iNOS mRNA levels in RAW264.7 cells. In HEK293 cells G-Rp₁ did not suppress TANK binding kinase 1-, Toll-interleukin-1 receptor-domain-containing adapter-inducing interferon-β (TRIF)-, TRIFrelated adaptor molecule (TRAM)-, or activation of interferon regulatory factor (IRF)-3 and nuclear factor (NF)-κB by the myeloid differentiation primary response gene (MyD88)-induced. However, G-Rp₁ strongly suppressed NF-κB activation induced by IκB kinase (IKK)β in HEK293 cells. Consistent with these results, G-Rp₁ substantially inhibited IKKβ-induced phosphorylation of IκBα and p65. These results suggest that G-Rp₁ is a novel anti-inflammatory ginsenoside analog that can be used to treat IKKβ/NF-κB-mediated inflammatory diseases.