Suppression of leukotriene B4 production is involved in the anti-pruritic action of Grifola frondosa in pollen allergy-induced ocular itching in mice

Grifola frondosa (G. frondosa) is an edible mushroom consumed as a health food in Asia that has recently been reported to have anti-allergic effects. In this study, we investigated the effects of G. frondosa on pollen allergy-induced ocular itching in mice. G. frondosa was boiled and freeze-dried (heat-treated G. frondosa). Oral administration of heat-treated G. frondosa (0.1 and 1 g/kg) suppressed pollen allergy-induced ocular itching and plasma extravasation but not histamine-induced plasma extravasation. Oral administration of ergosterol, an active ingredient in G. frondosa (5 and 50 mg/kg), or zileuton (100 mg/kg), which is an inhibitor of 5-lipoxygenase (the main enzyme required for leukotriene B4 production), inhibited pollen allergy-induced ocular itching. In addition, ergosterol inhibited antigen-induced leukotriene B4 production in mast cells. These findings suggest that G. frondosa and its active ingredient ergosterol prevent pollen allergy-induced itching through the inhibition of leukotriene B4 production in mast cells