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  • Title: Inhibitory effect of naringin on lipopolysaccharide (LPS)-induced endotoxin shock in mice and nitric oxide production in RAW 264.7 macrophages.
    Author: Kanno S, Shouji A, Tomizawa A, Hiura T, Osanai Y, Ujibe M, Obara Y, Nakahata N, Ishikawa M.
    Journal: Life Sci; 2006 Jan 11; 78(7):673-81. PubMed ID: 16137700.
    Abstract:
    Lipopolysaccharide (LPS) has been known to induce endotoxin shock via production of inflammatory modulators such as tumor necrosis factor alpha (TNF-alpha), or nitric oxide (NO). In this study, we have examined the effect of naringin (NG), one of the flavonoids, on LPS-induced endotoxin shock in mice and NO production in RAW 264.7 macrophages. For intraperitoneal (i.p., 20 mg/kg) injection of LPS at 48 h, the survival rate of mice administered with LPS alone (n=10) or pretreated with NG at 10, 30 and 60 mg/kg (i.p.) group (n=10) was 0% or 10%, 50% and 70%, respectively. NG dose-dependently suppressed LPS-induced production of TNF-alpha. LPS-induced production of NO at 6 h (125.89+/-16.35 microM), as measured by nitrite formation, was significantly reduced by NG at 30 or 60 mg/kg for 49.49+/-4.81 or 27.91+/-1.81 microM (P<0.01 vs. LPS alone), respectively. To further examine the mechanism by which NG suppresses LPS-induced endotoxin shock, we used an in vitro model, RAW 264.7 mouse macrophage cells. NG (1 mM) suppressed LPS (0.01, 0.1 or 1 microg/ml)-induced production of NO and the expression of inflammatory gene products such as inducible NO synthase (iNOS), TNF-alpha, inducible cyclooxygenase (COX-2) and interleukin-6 (IL-6) as determined by RT-PCR assay. NG was found to have blocked the LPS-induced transcriptional activity of NF-kappaB in electrophoretic mobility shift assay and reporter assay. These findings suggest that suppression of the LPS-induced mortality and production of NO by NG is due to inhibition of the activation of NF-kappaB.
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