Ginsenoside Re Ameliorates Inflammation by Inhibiting the Binding of Lipopolysaccharide to TLR4 on Macrophages

Ginseng (the root of Panax ginseng CA. Meyer, family Araliaceae), which contains protopanaxadiol ginsenoside Rb1 and protopanaxatriol ginsenoside Re as main constituents, is frequently used to treat cancer, inflammation, and stress. In the preliminary study, protopanaxatriol ginsenoside Re inhibited NF-kappa B activation in lipopolysaccharide (LPS)-stimulated murine peritoneal macrophages. Therefore, we investigated its anti-inflammatory effect in peptidoglycan (PGN)-, LPS-, or tumor necrosis factor-alpha (TNF-alpha)-stimulated peritoneal macrophages and, in addition, in LPS-induced systemic inflammation and 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis in mice. Ginsenoside Re inhibited IKK-beta phosphorylation and NF-kappa B activation, as well as the expression of proinflammatory cytokines, TNF-alpha and IL-1 beta, in LPS-stimulated peritoneal macrophages, but it did not inhibit them in TNF-alpha- or PG-stimulated peritoneal macrophages. Ginsenoside Re also inhibited IRAK-1 phosphorylation induced by LPS, as well as IRAK-1 and IRAK-4 degradations in LPS-stimulated peritoneal macrophages. Ginsenoside Re inhibited the binding of Alexa Fluor 488-conjugated LPS to TLR4 on peritoneal macrophages. Furthermore, ginsenoside Re inhibited the binding of LPS to TLR4 on peritoneal macrophages transiently transfected with MyD88 siRNAs. Orally administered ginsenoside Re significantly inhibited the expression of IL-1 beta and TNF-alpha on LPS-induced systemic inflammation and TNBS-induced colitis in mice. Ginsenoside Re inhibited colon shortening and myeloperoxidase activity in TNBS-treated mice. Ginsenoside Re reversed the reduced expression of tight-junction-associated proteins ZO-1, claudin-1, and occludin. Ginsenoside Re (20 mg/kg) inhibited the activation of NF-kappa B in TNBS-treated mice. On the basis of these findings, ginsenoside Re may ameliorate inflammation by inhibiting the binding of LPS to TLR4 on macrophages.