6-Shogaol suppressed lipopolysaccharide-induced up-expression of iNOS and COX-2 in murine macrophages

Ginger, the rhizome of Zingiber officinale, is a traditional medicine with carminative effect, antinausea, anti-inflammatory, and anticarcinogenic properties. In this study, we investigated the inhibitory effects of 6-shogaol and a related compound, 6-gingerol, on the induction of nitric oxide synthase (NOS) and cyclooxygenase-2 (COX-2) in murine RAW 264.7 cells activated with LPS. Western blotting and reverse transcription-PCR. analyses demonstrated that 6-shogaol significantly blocked protein and mRNA expression of inducible NOS (iNOS) and COX-2 in LPS-induced macrophages. The in vivo anti-inflammatory activity was evaluated by a topical 12-O-tetradecanoylphorbol 13-acetate (TPA) application to mouse skin. When applied topically onto the shaven backs of mice prior to TPA, 6-shogaol markedly inhibited the expression of NOS and COX-2 proteins. Treatment with 6-shogaol resulted in the reduction of LPS-induced nuclear translocation of nuclear factor-kappa B (NF kappa B) subunit and the dependent transcriptional activity of NF kappa B by blocking phosphorylation of inhibitor kappa B (I kappa B)alpha and p65 and Subsequent degradation of I kappa B alpha. Transient transfection experiments using NF kappa B reporter Constructs indicated that 6-shogaol inhibits the transcriptional activity of NF kappa B in LPS-stimulated Mouse macrophages. We found that 6-shogaol also inhibited LPS-induced activation of PI3K/Akt and extracellular signal-regulated kinase 1/2, but not p38 mitogen-activated protein kinase (MAPK). Taken together, these results show that 6-shogaol downregulates inflammatory NOS and COX-2 gene expression in macrophages by inhibiting the activation of NF kappa B by interfering with the activation PI3K/Akt/I kappa B kinases IKK and MAPK.