Inhibitory effects of flavonoids isolated from Fragaria ananassa Duch on IgE-mediated degranulation in rat basophilic leukemia RBL-2H3

We isolated the 4 kinds of flavonoids from strawberry ‘Nohime’ and examined the effect of these flavonoids on the degranulation in RBL-2H3 cells. The flavonoids were found to suppress the degranulation from Ag-stimulated RBL-2H3 cells to different extents. To disclose the inhibitory mechanism of degranulation by flavonoids, we examined their effects on the intracellular free Ca2+ concentration ([Ca2+]i) and the intracellular signaling pathway such as Lyn, Syk, and PLCγs. The intracellular free Ca2+ concentration ([Ca2+]i) was elevated by FcεRI activation, but these flavonoid treatments reduced the elevation of [Ca2+]i by suppressing Ca2+ influx. Kaempferol strongly suppressed the activation of Syk and PLCγs. It was thus suggested that suppression of Ag-stimulated degranulation by the flavonoids is mainly due to suppression of [Ca2+]i elevation and Syk activation. These results suggested that strawberry would be of some ameliorative benefit for the allergic symptoms.

In this study, we have demonstrated that flavonoids isolated from Fragaria ananassa Duch., significantly suppressed the degranulation in Ag-mediated activation of FcεRI in RBL-2H3 cells. It was thus suggested that inhibition of degranulation by the flavonoids was mainly due to the inhibition of [Ca2+]i elevation and Syk inactivation. Thus, strawberry-flavonoids would be an effective agent for anti-allergy.Figure optionsDownload as PowerPoint slide