Activation of inducible nitric oxide synthase by Yongdam-Sagan-Tang in mouse peritoneal macrophages

The objective of the current study was to determine the effect of Yongdam-Sagan-Tang (YS-Tang) on the production of nitric oxide (NO). Stimulation of mouse peritoneal macrophages with YS-Tang after the treatment of recombinant interferon-γ (rIFN-γ) resulted in increased NO synthesis. YS-Tang had no effect on NO synthesis by itself. When YS-Tang was used in combination with rIFN-γ, there was a marked co-operative induction of NO synthesis in a dose-dependent manner. The optimal effect of YS-Tang on NO synthesis was shown 6 h after treatment with rIFN-γ. This increase in NO synthesis was reflected as an increased amount of inducible NO synthase (iNOS) protein. NO production was inhibited by N(G)-monomethyl-L-arginine. The increased production of NO from rIFN-γ plus YS-Tang-stimulated cells was decreased by the treatment with staurosporin. In addition, synergy between rIFN-γ and YS-Tang was mainly dependent on YS-Tang-induced tumor necrosis factor-α (TNF-α) secretion. All the preparations of YS-Tang were endotoxin free. These results suggest that the capacity of YS-Tang to increase NO production from rIFN-γ-primed mouse peritoneal macrophages is the result of YS-Tang-induced TNF-α secretion.