Nitrite oxide and inducible nitric oxide synthase were regulated by polysaccharides isolated from Glycyrrhiza uralensis Fisch

Water-soluble polysaccharide(Glycyrrhiza polysaccharide, GP) was isolated from Glycyrrhiza uralensis Fisch, with glycosidic units were composed of α (1–4) linked D-glucana. We demonstrated that GP significantly induces nitric oxides (NO) production and inducible NO synthase (iNOS) transcription in peritoneal macrophages. Moreover, iNOS mRNA expression was strongly induced by GP. NO in the culture supernatant was measured by Griess reaction, the production of iNOS was determined by commercially available iNOS kit. GP (10–400 μg/ml) alone increased significantly NO and iNOS production in macrophages. Macrophages simultaneously treated with GP plus lipopolysaccharide (LPS)/interferon-γ (IFN-γ) increased NO and iNOS production as compared to that of GP treatments alone. The production of NO and iNOS in macrophages pretreated with LPS followed by GP was higher than that of treatment with GP and LPS simultaneously. Using RT-PCR reveals that GP may provide a second triggering signal for the expression of iNOS mRNA. Thus, the iNOS-mediated NO synthesis in response to GP may be one of the mechanisms whereby this herbal medicine elicits its therapeutic effects.