ABSTRACT
PURPOSE: The aim of the present study was to examine the effect of the root cortex of Paeonia suffruticosa, an anti-inflammatory folk medicine, on nitric oxide (NO) synthesis and the induction of inducible NO synthase (iNOS) gene expression in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages. MATERIALS AND METHODS: We studied the effects of the RAW264.7 macrophage cell line of the extract from the root cortex of P. suffruticosa and NO with western blot and northern blot assays. RESULTS: We found that treatment of RAW264.7 macrophages with the ethylacetate fraction of the ethanolic extract of the root cortex of P. suffruticosa inhibits LPS-induced synthesis of NO in vitro. This effect is dose-dependent and appears to involve the suppression of iNOS gene expression, thereby reducing excessive NO synthesis in LPS-stimulated RAW264.7 macrophages. CONCLUSIONS: As NO is a pro-inflammatory molecule and iNOS inhibitors may have therapeutic potential, our findings may explain the anti-inflammatory property of the root cortex of P. suffruticosa. This root has been used in oriental folk medicine for the treatment of various inflammatory diseases with relatively little knowledge regarding its mechanism of anti-inflammatory action.