Morus bombycis extract suppresses mast cell activation and IgE-mediated allergic reaction in mice

Ethnopharmacological relevance: Morus bombycis Koidzumi (MB) is widely distributed throughout Korea, where it is used as a traditional folk remedy for the treatment of allergic diseases including asthma. However, the pharmacological effect and the mechanistic study of MB have not been investigated. We aimed to investigate the anti-allergic activity of MB in vitro and in vivo and the mechanism of its action on mast cells. Materials and methods: The anti-allergic activity of MB extract (MBE) was assessed using passive cutaneous anaphylaxis (PCA) in mice and mouse bone marrow-derived mast cells (BMMCs) in vitro. The effects of MBE on mast cell activation were evaluated by using the β-hexosaminidase release assay, reverse transcriptase-polymerase chain reaction, enzyme-linked immunosorbent assay, and western blotting analysis. Results: MBE reversibly inhibited degranulation and generation of cytokines (TNF-α and IL-4) in antigen-stimulated mast cells. With regard to its mechanism of action, MBE inhibited the activation of Lyn and Syk, which have essential roles in degranulation and the production of various inflammatory cytokines. MBE also inhibited the activating phosphorylation of mitogen-activated protein (MAP) kinases, Erk1/2, p38, JNK, and Akt. In agreement with its in vitro effect, MBE significantly inhibited mast cell-mediated PCA reactions in IgE-sensitized mice. Conclusions: The present results strongly suggest that MBE exerts an anti-allergic effect, both in vitro and in vivo by inhibiting the Lyn and Syk pathways in mast cells. Therefore, MBE may be useful for the treatment of allergic diseases, including atopic dermatitis and allergic asthma.