Ephedra Herb, Mao, Inhibits Antigen-Induced Mast Cell Degranulation by Induction of the Affinity Receptor for IgE Internalization

Ephedra herb (Mao) exerts potent anti-allergic effects. This study aimed to examine the underlying mechanisms of Mao on allergic inflammation using in vitro cultured mast cells (MCs) and an in vivo model of MC-dependent anaphylaxis. Bone marrow-derived MCs (BMMCs) were presensitized with anti-2,4-dinitrophenol (DNP) immunoglobulin E (IgE) and challenged with antigens (Ag; DNP-human serum albumin). Degranulation responses and cell surface high-affinity receptor for IgE (FceRI) expression were assessed with/without Mao treatment. Passive systemic anaphylaxis (PSA)-treated mice were administered Mao and the pathophysiological responses were evaluated. Mao inhibited Ag-induced BMMC degranulation, but not polyclonal activation with phorbol 12-myristate 13-acetate (PMA) and ionomycin, indicating that Mao inhibits IgE-dependent activation of BMMCs. Mao-treated BMMCs exhibited significant reductions in expression of surface IgE and its receptor FceRI. Analysis of subcellular localization revealed that Mao induces FceRI internalization in BMMCs without degranulation. In the PSA mouse model, Mao administration prevented antigen-induced hypothermia. Mao administration significantly reduced cell surface expression of IgE-bound FceRI on peritoneal MCs. Mao induced FceRI internalization in MCs, thereby inhibiting Ag-induced IgE-dependent degranulation. The inhibitory effects of Mao on MC degranulation may offer a novel therapeutic approach for allergic diseases.