INHIBITION OF NITRIC-OXIDE SYNTHESIS BY BUTANOL FRACTION OF THE METHANOL EXTRACT OF ULMUS-DAVIDIANA IN MURINE MACROPHAGES

Since there is increasing evidence that nitric oxide (NO) plays a cruc ial role in the pathogenesis of inflammatory diseases, this study was undertaken to address whether the methanol (MeOH) extract and its frac tions of the bark of Ulmus davidiana Planch (Ulmaceae) could modulate the expression of inducible NO synthase (iNOS) in thioglycollate-elici ted murine peritoneal macrophages and murine macrophage cell line, RAW 264.7 cells. Stimulation of the peritoneal macrophages and RAW264.7 ce lls with interferon-gamma (IFN-gamma) and lipopolysaccharide (LPS) res ulted in increased production of NO in the medium. However, the butano l (BuOH) fraction of the MeOH extract of U. davidiana barks showed mar ked inhibition of NO synthesis in a dose-dependent manner. The inhibit ion of NO synthesis was reflected in the decreased amount of iNOS prot ein, as determined by Western blotting. The BuOH fraction did not affe ct the viability of RAW264.7 cells, as assessed by methylthiazol-2-yl- 2, 5-diphenyl tetrazolium bromide (MTT) assay; rather, it reduced endo genous NO-induced apoptotic cell death via inhibition of NO synthesis in RAW264.7 cells. On the other hand, the BuOH fraction showed no inhi bitory effect on the synthesis of NO by RAW264.7 cells, when iNOS was already expressed by the stimulation with IFN-gamma and LPS. Collectiv ely these results demonstrate that the BuOH fraction inhibits NO synth esis by inhibition of the induction of iNOS in murine macrophages. (C) 1998 Published by Elsevier Science Ireland Ltd. All rights reserved.