RAT KUPFFER CELL-DERIVED NITRIC-OXIDE SUPPRESSES PROLIFERATION AND INDUCES APOPTOSIS OF SYNGENEIC HEPATOMA-CELLS

Background & Aims: Evidence increasingly indicates that nitric oxide p lays an important role in antitumor mechanisms. The aim of this study was to investigate the role of NO in the mechanisms regulating the pro liferation and death of hepatoma cells cocultured with Kupffer cells. Methods: Kupffer cells were isolated from male Wistar rats and cocultu red with rat hepatoma AH70 cells, Proliferation was determined by calc ulating the number of total and 5-bromodeoxyuridine-positive AH70 cell s, Apoptosis was assessed by electron-microscopic and fluorescence-mic roscopic observations and in situ nick end labeling method. Immunofluo rescence and in situ hybridization studies were performed to investiga te the induction of inducible NO synthase (iNOS), Results: Kupffer cel ls reduced proliferation and induced apoptosis of AH70 cells, which we re attenuated by the NO synthesis inhibitors N-G-monomethyl-L-arginine and aminoguanidine. Increased inductions of iNOS messenger RNA and iN OS were observed in Kupffer cells cocultured with AH70 cells, Addition of monoclonal antibody directed against either rat CD18 or intercellu lar adhesion molecule 1 also attenuated the increased NO production of Kupffer cells and the alterations of AH70 cells, Conclusions: Kupffer cell-derived NO suppresses proliferation and induces apoptosis of hep atoma cells, The CD18 intercellular adhesion molecule 1-dependent adhe sive interaction with hepatoma cells triggers NO production by Kupffer cells.