Nitric oxide production by high molecular weight water-soluble chitosan via nuclear factor-kappa B activation

High molecular weight water-soluble chitosan (WSC), having an average molec ular weight of 300000 Da and a degree of deacethylation over 90%, can be pr oduced using a simple multi-step membrane separation process. In this study , the effect of WSC on the production of nitric oxide (NO) in RAW 264.7 mac rophages was evaluated. Water-insoluble chitosan alone has been previously shown to exhibit in vitro stimulatory effect on macrophages NO production. However, WSC had no effect on NO production by itself. When WSC was used in combination with recombinant interferon-gamma (rIFN-gamma), there was a ma rked cooperative induction of NO synthesis in a dose-dependent manner. The optimal effect of WSC on NO synthesis was shown 24 h after treatment with r IFN-gamma. The increased production of NO from rIFN-gamma plus WSC-stimulat ed RAW 264.7 macrophages was decreased by the treatment with NG-monomethyl- L-arginine (N(G)MMA). The increase in NO synthesis was reflected, as an inc reased amounts of inducible NO synthase protein. In addition, synergy betwe en rIFN-gamma and WSC was mainly dependent on WSC-induced tumor necrosis fa ctor-alpha (TNF-alpha) and nuclear factor-kappaB (NF-kappaB) activation. Th e present results indicate that the capacity of WSC to increase NO producti on from rIFN-gamma -primed RAW 264.7 macrophages is the result of WSC-induc ed TNF-alpha secretion via the signal transduction pathway of NF-kappaB act ivation. (C) 2000 International Society for Immunopharmacology. Published b y Elsevier Science Ltd. All rights reserved.