AIM OF THE STUDY: A Chinese herbal formula (RCM-101) has shown to be effective in reducing symptoms of seasonal allergic rhinitis (SAR) in a randomised, placebo-controlled clinical trial. The aim of this study is to investigate the effects of RCM-101 on the actions and synthesis of nitric oxide (NO). l-Arginine-induced endothelium-independent relaxations were studied in rat isolated aorta which was pre-treated with lipopolysaccharide (LPS). MATERIALS AND METHODS: NO production and inducible nitric oxide synthase (iNOS) protein expression were studied in LPS and interferon gamma-stimulated murine macrophages (Raw 264.7), measured by NO sensors and Western blotting. RESULTS: In rat aortic preparations, RCM-101 significantly inhibited endothelium-independent relaxations to l-arginine, but not affected those to sodium nitroprusside (SNP). In Raw 264.7 cells, RCM-101 and some of its individual ingredients (e.g., Radix glycyrrhizae, Radix bupleuri, Radix saposhnikoviae and Atractylodis rhizome macrocephalae) significantly inhibited the NO production and iNOS protein expression. CONCLUSIONS: The findings indicate that RCM-101 may inhibit inducible NO production by suppressing iNOS. In addition, its inhibitory action of iNOS is likely to be mediated by several key herbal ingredients.
AIM OF THE STUDY: A Chinese herbal formula (RCM-101) has shown to be effective in reducing symptoms of seasonal allergic rhinitis (SAR) in a randomised, placebo-controlled clinical trial. The aim of this study is to investigate the effects of RCM-101 on the actions and synthesis of nitric oxide (NO). l-Arginine-induced endothelium-independent relaxations were studied in rat isolated aorta which was pre-treated with lipopolysaccharide (LPS). MATERIALS AND METHODS: NO production and inducible nitric oxide synthase (iNOS) protein expression were studied in LPS and interferon gamma-stimulated murine macrophages (Raw 264.7), measured by NO sensors and Western blotting. RESULTS: In rat aortic preparations, RCM-101 significantly inhibited endothelium-independent relaxations to l-arginine, but not affected those to sodium nitroprusside (SNP). In Raw 264.7 cells, RCM-101 and some of its individual ingredients (e.g., Radix glycyrrhizae, Radix bupleuri, Radix saposhnikoviae and Atractylodis rhizome macrocephalae) significantly inhibited the NO production and iNOS protein expression. CONCLUSIONS: The findings indicate that RCM-101 may inhibit inducible NO production by suppressing iNOS. In addition, its inhibitory action of iNOS is likely to be mediated by several key herbal ingredients.