Anti-allergic activity of emodin on IgE-mediated activation in RBL-2H3 cells

Background: emodin (1,3,8-trihydroxy-6-methylanthraquinone) is a chinese herbal anthraquinone derivative from the rhizome of rhubarb (rheum palmatum l.) that exhibits numerous biological activities,such as antitumor,antibacterial,antiinflammatory,and immunosuppressive. in the present studies,the anti-allergic activities of emodin were investigated to elucidate the underlying active mechanisms. methods: the inhibitory effects of emodin on the ige-mediated allergic response in rat basophilic leukemia (rbl-2h3) cells were evaluated by measuring the release of granules and cytokines. the ca 2+ mobilization in rbl-2h3 cells loaded with the ca 2+-reactive fluorescent probe fluo-4 am was also measured by laser scanning confocal microscope. results: emodin inhibited the release of β-hexosaminidase (β-hex; ic50 = 5.5 μm) and tumor necrosis factor (tnf)-α (ic50 = 11.5 μm) from rbl-2h3 cells induced by 2,4-dinitrophenylated bovine serum albumin (dnp-bsa) and displayed stronger inhibition of β-hex release than ketotifen fumarate salt (ic 50 = 63.8 μm). emodin at a concentration of 12.5 μm also inhibited the dnp-bsa-induced influx of extracellular ca2+ in rbl-2h3 cells. conclusions: these results suggested that emodin likely exhibits anti-allergic activities via increasing the stability of the cell membrane and inhibiting extracellular ca2+ influx. copyright © 2012 by institute of pharmacology.