Production of nitric oxide in mouse peritoneal macrophages after priming with interferon-gamma by the stem of Sinomenium acutum.

The present study demonstrates that the aqueous extract of Sinomenium acutum stem (SSAE) produces nitric oxide (NO) upon treatment with recombinant interferon gamma (rIFN-gamma) in mouse peritoneal macrophages. Apparently SSAE has no effect on NO production by itself. This production is dependent on L-arginine and can be inhibited by the L-arginine analogue N(G)-monomethyl-L-arginine. The increased production of NO from rIFN-gamma plus SSAE-stimulated cells was decreased by the treatment of protein kinase C inhibitor. Tumor necrosis factor-alpha (TNF-alpha) has been shown to stimulate the oxidative metabolism of L-arginine to produce NO. Mouse peritoneal macrophages secrete high levels of TNF-alpha after incubation with rIFN-gamma plus SSAE. In addition, SSAE-induced NO production is progressively inhibited by anti-murine TNF-alpha neutralizing antibody. These results show that the capacity of SSAE to increase NO production from rIFN-gamma-primed mouse peritoneal macrophages is the result of SSAE-induced TNF-alpha secretion.