Sword Bean (Canavalia gladiata) Pod Exerts Anti-Allergic and Anti-Inflammatory Effects through Modulation of Th1/Th2 Cell Differentiation

Allergy is an immunoglobulin E (IgE)-mediated process, and its incidence and prevalence have increased worldwide in recent years. Therapeutic agents for allergic diseases are continuously being developed, but side effects follow when used for a long-term use. Therefore, treatments based on natural products that are safe for the body are urgently required. Sword bean (Canavalia gladiata) pod (SBP) has been traditionally used to treat inflammatory diseases, but there is still no scientific basis for its anti-allergic effect. Accordingly, this study investigates the anti-allergic effect and its mechanism of SBP in vitro and in vivo. SBP reduced the nitric oxide production and decreased mRNA and protein expression of inflammatory mediates (inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2)), and inhibited the phosphorylation of nuclear factor kappa B (NF-κB), a major signaling molecule in the inflammatory response. Additionally, SBP extract treatment inhibited phosphatidylinositol-3-kinase/mammalian target of rapamycin (PI3K/mTOR) signaling activity to further inhibit degranulation and allergy mediator generation and control the balance of Th1/Th2 cells, which can induce an allergic reaction when disrupted. Furthermore, the SBP extract exhibited anti-allergic effects in anti-dinitrophenyl IgE-induced RBL-2H3 cells and ovalbumin-treated mice. These findings have potential clinical implications for the treatment as well as prevention of allergic diseases.