title: Inhibitory effects of sesquiterpene lactones isolated from Eupatorium chinense L. on IgE-mediated degranulation in rat basophilic leukemia RBL-2H3 cells and passive cutaneous anaphylaxis reaction in mice.
abstract: Sesquiterpene lactones (SQTLs) have been shown to suppress the degranulation as inferred by histamine release in rat basophilic leukemia RBL-2H3 cells. In this study, we isolated the 9 kinds of SQTLs from Eupatorium chinense L. and examined the effects of these SQTLs on the degranulation in RBL-2H3 cells. The chemical structures of two novel compounds (SQTL-3 and 8) were determined. All the SQTLs suppressed the degranulation from Ag-stimulated RBL-2H3 cells. To disclose the inhibitory mechanism of degranulation by SQTLs, we examined the activation of intracellular signaling molecules such as Lyn, Syk, and PLCgammas and intracellular free Ca(2+) concentration ([Ca(2+)]i). None of these SQTLs showed the activation of Syk and PLCgammas. The intracellular free Ca(2+) concentration ([Ca(2+)]i) was elevated by Fc epsilonRI activation, but SQTLs treatment reduced the elevation of [Ca(2+)]i by suppressing Ca(2+) influx. Thus, it was suggested that the suppression of Ag-stimulated degranulation by these SQTLs is mainly due to the decreased Ca(2+) influx. Furthermore, in order to clarify the in vivo effect of SQTL-rich extract, we administered SQTL-rich extract to the type I allergic model mice and measured the passive cutaneous anaphylaxis (PCA) reaction induced by IgE-antigen complex. The SQTLs remarkably suppressed PCA reaction in a dose-dependent manner. Thus, it was suggested that SQTLs would be a candidate as an anti-allergic agent.
authors.affiliation: Gifu International Institute of Biotechnology, 1-1 Naka-Fudogaoka, Kakamigahara, Gifu 504-0838, Japan. titoh@giib.or.jp
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Itoh
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Oyama
authors.forename: Norihiko
authors.initials: N
authors.lastname: Takimoto
authors.forename: Chihiro
authors.initials: C
authors.lastname: Kato
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Nozawa
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Akao
authors.forename: Munekazu
authors.initials: M
authors.lastname: Iinuma