The nitric oxide-producing properties of Solanum lyratum

We examined the effect of Solanum lyratum Thunb. (Solanaceae) (SL) on the p roduction of nitric oxide (NO). Stimulation of mouse peritoneal macrophages with SL after the treatment of recombinant interferon-gamma (rIFN-gamma) r esulted in increased NO synthesis. SL had no effect on NO synthesis by itse lf. When SL was used in combination with rIFN-gamma, there was a marked coo perative induction of NO synthesis in a dose-dependent manner. The optimal effect of SL on NO synthesis was shown 6 h after treatment with rIFN-gamma. The increased production of NO from rIFN-gamma plus SL-stimulated cells wa s decreased by the treatment with staurosporin. In addition, synergy betwee n rIFN-gamma and SL was mainly dependent on SL-induced tumor necrosis facto r-alpha (TNF-alpha) secretion. All the preparations of SL were endotoxin fr ee. The present results indicate that the capacity of SL to increase NO pro duction from rIFN-gamma-primed mouse peritoneal macrophages is the result o f SL-induced TNF-alpha secretion via the signal transduction pathway of PKC activation. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.