Ursolic acid inhibits FcεRI-mediated mast cell activation and allergic inflammation.

• UA inhibited mast cell degranulation by reducing intracellular calcium level. • UA attenuated secretion of pro-inflammatory cytokines in mast cells. • These effects of UA were dependent on inhibition of FcεRI-mediated signaling. • UA suppressed the local and systemic anaphylactic reactions. • UA might be a potential candidate for the treatment of allergic diseases. Mast cells are the primary cells that play a crucial role in the allergic diseases via secretion of diverse allergic mediators. Ursolic acid (UA) is a naturally occurring anti-inflammatory triterpenoid possessing various biological properties such as immune regulation, antioxidant, and anti-fibrotic. The aim of this study was to evaluate the effects of UA in FcεRI-mediated mast cell activation and allergic inflammation. In this study, mast cells were stimulated with immunoglobulin E (IgE) and the anti-allergic effects of UA were assessed by measuring the levels of allergic mediators. In vivo effects of UA were observed by generating passive cutaneous anaphylaxis (PCA) and active systemic anaphylaxis (ASA) in mouse model. We found that UA inhibited the degranulation of mast cell by suppressing the intracellular calcium level in a concentration-dependent manner. UA inhibited the expression and the release of pro-inflammatory cytokines in mast cells. Anti-allergic effects of UA were demonstrated via suppression of FcεRI-mediated signaling molecules. In addition, UA inhibited the IgE-mediated PCA and ovalbumin-induced ASA reactions in a dose-dependent manner. Based on these findings, we suggest that UA might have potential as a therapeutic candidate for the treatment of allergic inflammatory diseases via inhibition of FcεRI-mediated mast cell activation. [ABSTRACT FROM AUTHOR]