Inhibition of release of vasoactive and inflammatory mediators in airway and vascular tissues and macrophages by a Chinese herbal medicine formula for allergic rhinitis

Herbal therapies are being used increasingly for the treatment of allergic rhinitis. The aim of this study was to investigate the possible pharmacological actions and cellular targets of a Chinese herbal formula (RCM-101), which was previously shown to be effective in reducing seasonal allergic rhinitis symptoms in a randomized, placebo-controlled clinical trial. Rat and guinea pig isolated tissues (trachea and aorta) were used to study the effects of RCM-101 on responses to various mediators. Production of leukotriene 134 in porcine neutrophils and of prostaglandin E-2 and nitric oxide (NO) in Raw 264.7 cells were also measured. In rat and guinea pig tracheal preparations, RCM-101 inhibited contractile responses to compound 48/80 but not those to histamine (guinea pig preparations) or serotonin (rat preparations). Contractile responses of guinea pig tracheal preparations to carbachol and leukotriene C-4. and relaxant responses to substance P and prostaglandin E2 were not affected by RCM-101. In rat aortic preparations, precontracted with phenylephrine, endothelium-dependent relaxant responses to acetylcholine and endothelium-independent relaxant responses to sodium nitroprusside were not affected by RCM-101. However, RCM-101 inhibited relaxations to L-arginine in endothelium-denuded rat aortic preparations, which had been pre-incubated with lipopolysaccharide. RCM-101 did not affect leukotriene 134 formation in isolated porcine neutrophils, induced by the calcium ionophore A23187; however, it inhibited prostaglandin E-2 and NO production in lipopolysaccharide-stimulated murine macrophages (Raw 264.7 cells). The findings indicate that RCM-101 may have multiple inhibitory actions on the release and/or synthesis of inflammatory mediators involved in allergic rhinitis.