Ephedrine Alkaloid-Independent High-Affinity Immunoglobulin-E Receptor (FceRI) Internalization Results in CCL2 Production without Inducing Mast Cell Degranulation

Mast cells (MCs) play an important role in allergies, leading to the development of MC-targeted thera-pies. Ephedra herb (Mao) has potent anti-allergic activity, but contains ephedrine alkaloids (EAs); therefore, its hazardous effects are taken into consideration during its clinical use. We previously reported that Mao attenuates robust MC degranulation by an allergen through high-affinity immunoglobulin E (IgE) recep-tor (FccRI) internalization, in which an EA-independent mechanism was suggested to be at play. This study aimed to deepen our understanding of the potential of Mao against FccRI internalization using two strains with different EA contents. Mao extracts were administered to bone marrow-derived MCs (BMMCs), and their cellular responses, including FccRI internalization, were analyzed. In addition, physiological events were evaluated using a passive cutaneous anaphylactic (PCA) reaction mouse model. BMMCs mediate the production of diverse inflammatory mediators. Among these, the potent chemokine CCL2 is thought to be differentially regulated from other pro-inflammatory mediators. We found that Mao significantly induces CCL2 expression in BMMCs despite suppressing robust degranulation through FccRI internaliza-tion. Importantly, this was a distinctly EAs-independent response. In the PCA reaction, local MC activa-tion following allergen challenge was suppressed by Mao treatment, which strengthened the view that Mao sufficiently decreased the rapid activation of MCs and promoted CCL2 secretion. Collectively, these observa-tions provide additional insights into the mechanism of Mao-induced silent FccRI internalization in MCs and the complex and heterogeneous secretory responses operating in MCs.