Inhibitory effect of sea horse Hippocampus kelloggi ethanol extract on antigen-stimulated degranulation in rat basophilic leukemia RBL-2H3 cells

Abstract

Sea horse Hippocampus kelloggi is used as a traditional medicine in Asia for a tonic. In this study, we prepared a 35% ethanol extract of sea horse (SHEtEx.35), and then demonstrated the effects of SHEtEx.35 on antigen (Ag)-stimulated degranulation in rat basophilic leukemia RBL-2H3 cells. The inhibition level of Ag-stimulated degranulation by SHEtEx.35 gradually increased to 25,μg/mL, but the inhibition levels of Ag-stimulated degranulation by SHEtEx.35 did not change at concentrations above 25,μg/mL. In order to elucidate the underlying mechanisms, we examined the ešects of SHEtEx.35 on early intracellular signaling events (intracellular free Ca2+ ([Ca2]i) concentration, and intracellular reactive oxygen species (ROS) production) by antigen stimulation. Treatment with SHEtEx.35 markedly suppressed antigen-stimulated activation of PLCγ1 and elevation of [Ca2+]i. However, SHEtEx.35 did not suppress antigen-stimulated ROS production. These results indicate that inhibition of antigen-stimulated degranulation by SHEtEx.35 is mainly due to direct inhibition of PLCγ1 activation. Our findings suggest that SHEtEx.35 would be beneficial for alleviating symptoms of type I allergies.