Inhibition by Rikko-san and its Major Ingredients of LPS-stimulated Nitric Oxide Production by Mouse Macrophage-like Cells

Abstract

Rikko-san and its ingredients were investigated for their activity to modify nitric oxide (NO) production by unstimulated and lipopolysaccharide (LPS)-stimulated mouse macrophage-like Raw 264.7 cells. LPS significantly stimulated the NO production by Raw 264.7 cells, and Rikko-san effectively inhibited the stimulation effect of LPS even at non-cytotoxic concentrations. Among 5 Rikko-san ingredients, Kanzo showed a similar magnitude of inhibition of NO production. Shoma was also slightly inhibitory. On the other hand, Ryutan, Saishin and Bofu did not show such a clear-cut stimulation effect, due to the co-existence of both inhibitory and stimulatory substance(s) for NO production. Thus NO stimulators were present in Rikko-san and its four ingredients except for Kanzo. Western blot analysis demonstrated that LPS induced the production of inducible NO synthase (iNOS), and that non-cytotoxic concentrations of Rikko-san and Kanzo significantly inhibited the LPS-stimulated iNOS expression. ESR spectroscopy showed that Rikko-san, Kanzo, Shoma and Saishin, but not Ryutan and Bofu, produced radical(s) under alkaline condition. All samples scavenged superoxide (produced by hypoxanthine-xanthine oxidase reaction) and NO (produced by 1-hydroxy-2-oxo-3-(N-3-methyl-3-aminopropyl)-3-methyl-1-triazene (NOC-7)), possibly by their general reducing activity. These data suggest that the inhibition of NO production by Chinese medicines investigated here may be the result of both the inhibition of iNOS expression and their radical scavenging activity.