Saiboku-to, a Kampo herbal medicine, inhibits LTC4 release from eosinophils

Abstract

Saiboku-to (TJ-96), a traditional Kampo herbal formation, has been used in the treatment of bronchial asthma in Japan as an anti-allergy herbal medicine. We investigated the effect of TJ-96 on leukotriene (LT)C4 release from eosinophils and basophils isolated from healthy volunteers. Pre-incubation of eosinophils with TJ-96 inhibited ionophore- or formyl-methionyl-leucyl-phenylalanine (FMLP)-induced LTC4 generation by eosinophils in a dose-dependent fashion. The TJ-96 was more potent in the release by ionophore (IC50 = 60 mg/mL) than the release induced by FMLP (IC50 = 300 mg/mL). Maximal inhibition was observed when eosinophils were pretreated with TJ-96 for 5 min. Although TJ-96 at high concentrations inhibited IgE-mediated histamine release from human basophils, inhibition of IgE-mediated LTC4 release was not statistically significant. The potent inhibitory activity was found in the extract of Glycyrrhiza root, one of the herbal components of TJ-96, but the inhibitory effects were not due to either glycyrrhizin or liquiritin, the main elements of the Glycyrrhiza root. These results raise the possibility that the clinical efficacy of TJ-96 is derived, at least in part, from its potent inhibitory effect on LTC4 release from eosinophils.

Keywords

• basophil
• bronchial asthma
• eosinophil
• Glycyrrhiza root
• LTC4
• Saiboku-to