Isoflavones suppress the expression of the FcεRI high-affinity immunoglobulin e receptor independent of the estrogen receptor

Isoflavones found in soybeans and soy products possess clinically relevant properties. However, the anti-allergic effect of isoflavones has been poorly studied. We examined the effects of isoflavones, genistein, daidzein, and equol, on the expression of the high-affinity immunoglobulin E (IgE) receptor, FcεRI, which plays a central role in IgE-mediated allergic response. Flow cytometric analysis showed that all of these isoflavones reduced the cell surface expression of FcεRI on mouse bone-marrow-derived mast cells and human basophilic KU812 cells. All isoflavones decreased the levels of the FcεRIα mRNA in the cells. Genistein reduced the mRNA expression of the β chain, and daidzein and equol downregulated that of the γ chain. The suppressive effects of isoflavones on FcεRI expression were unaffected by ICI 182,780, an estrogen receptor antagonist, suggesting that these effects were independent of estrogen receptors.