Inhibitory effects of enzyme-treated dried sardine extract on IgE-mediated degranulation of RBL-2H3 cells and a murine model of Japanese cedar pollinosis

The effects of small dried sardine on IgE-mediated allergic responses are herein reported. Small dried sardine extract digested with an acidic protease from Aspergillus niger suppressed degranulation of rat basophilic leukemia RBL-2H3 cells in a dose-dependent manner without cytotoxicity. Size-exclusion chromatography analysis and a dialysis experiment indicated that the molecular weight of bioactive components contained in enzyme-treated dried sardine extract (EDS extract) ranges from 4800 to 14 000. Immunoblot analysis revealed that EDS extract does not affect the signaling pathway via the spleen tyrosine kinase Syk. Although degranulation of RBL-2H3 cells induced by either antigen or a calcium ionophore A23187 was suppressed by EDS extract, the elevation in intracellular Ca 2+ concentration was not affected. Immunofluorescence staining revealed that EDS extract significantly suppresses microtubule formation in RBL-2H3 cells during degranulation induced by antigen. In addition, oral administration of EDS extract significantly suppressed passive cutaneous anaphylaxis reaction in mice and an allergic symptom in Cry j1- and Cry j2-induced pollinosis model mice. In conclusion, small dried sardine treated with a protease has potential as a health-promoting foodstuff with an anti-allergic effect. Protease-digested small dried sardine extract relieved allergic symptoms in mice through inhibiting microtubule dynamics.