Total Glucosides of Paeonia lactiflora Pall Suppress Nitric Oxide Production and iNOS Expression in Lipopolysaccharide-Stimulated RAW264.7 Macrophages

Purpose: To investigate the effect of total glucosides of Paeonia lactiflora (TGPL) on nitric oxide (NO) production and its potential mechanism in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophage cells.Methods: RAW264.7 cells were treated with 10 - 300 µg/ml TGPL and 1 µg/ml LPS. Cell survival was determined by MTT assay. NO level was determined by Griess reaction assay. Inducible NO synthase (iNOS) expression and inhibitor-kBα (IkBα) degradation were determined by Western blot assay. DNA binding activity of NF-kB was determined by ELISA assay using Trans AM™ kit for p65.Results: The concentrations of TGPL (10 - 300 ìg/ml) used in this study did not affect cell survival of RAW264.7 cells, which suggest that 10-300 µg/ml TGPL did not show cytotoxic effect on RAW264.7 cells. NO level and iNOS protein expression significantly increased in LPS-stimulated RAW264.7 cellscompared to the unstimulated cells. However, 10 - 300 µg/ml TGPL significantly decreased LPSinduced NO level and iNOS protein expression compared to LPS-stimulated RAW264.7 cells alone. Furthermore, 10 - 300 µg/mL TGPL significantly reduced the content of IkBα protein in LPS-stimulated RAW264.7 cells, which suggests that TGPL inhibited LPS-induced degradation of IkBα protein. TGPL remarkably repressed LPS-induced DNA binding activity of P65 in RAW264.7 cells.Conclusion: These findings suggest that TGP inhibits NO production and iNOS expression through suppression of NF-kB activation in LPS-stimulated RAW264.7 cells.Keywords: Total glucosides, Paeonia lactiflora, Nitric oxide, iNOs, Nuclear factor-kB