Effects of volatile constituents of a rosemary extract on allergic airway inflammation related to house dust mite allergen in mice

Perilla leaf extract is known to have anti-inflammatory properties. Recently, we have demonstrated that rosmarinic acid, a polyphenolic liquid component in perilla, inhibits the allergic airway inflammation induced by house dust mites (HDMs) in vivo. The purpose of this study was to evaluate the effects of intratracheal (i.t.) exposure to volatile constituents of a rosemary extract (VR), gaseous components in perilla, on a murine model of allergic asthma induced by HDM. C3H/HeN mice were treated 7 times weekly with i.t. exposure. The HDM allergen challenge elicited a pulmonary eosinophilic inflammation accompanied by an increase in the lung expression of interleukin (IL)-5, IL-13, and eotaxin. VR inhibited increases in the number of eosinophils, neutrophils, and mononuclear cells around the airways and those in the bronchoalveolar lavage fluid. VR exposure also significantly suppressed the expression of IL-13 enhanced by HDM allergen. These results suggest that i.t. exposure to VR can, at least partially, prevent allergic airway inflammation induced by HDM. The preventive effect is associated with inhibition of the enhanced local expression of IL-13.