Up-regulation of nitric oxide production by interferon-γ in cultured peritoneal macrophages from patients with cirrhosis

We previously described a long-lasting overproduction of nitric oxide (NO) in cirrhotic patients with spontaneous bacterial peritonitis. The aim of the present study was to investigate the presence of the inducible NO pathway in peritoneal macrophages. Ascitic fluids were collected from 29 patients with cirrhosis, aged between 35 and 82 years. Peritoneal macrophages were isolated and cultured in the presence or absence of 1  μ g/ml lipopolysaccharide and/or 500 units/ml interferon-γ (IFN-γ) for 6 days. NO production was measured as nitrate+nitrite (NO x ), inducible NO synthase (iNOS) protein expression was analysed by immunocytochemistry and Western blot analysis using a specific anti-(human iNOS) antibody, and the catalytic activity of NOS was revealed by cytochemical staining for NADPH-dependent diaphorase. Cultured macrophages spontaneously released small amounts of NO x [median (10–90th percentile) of 18 separate experiments: 3.3 (0–8)  μ mol/l]. Addition of lipopolysaccharide alone or in combination with IFN-γ to the culture medium did not change the levels of NO x , while IFN-γ alone dramatically increased NO production [13.4 (3.5–28.3)  μ mol/l; P n = 13) than in those in a stable clinical condition ( n = 18) [19.8 (10.5–30.1) and 10.0 (3.2–14.5)  μ mol/l respectively; P