Antiasthmatic Effect of Eugenol (4-Allyl-2-Methoxyophenol) Mediated by Both Bronchodilator and Immunomodulatory Properties

Eugenol, an aromatic product, exhibits anti-inflammatory properties, however, little is known about its effect in allergic inflammation mediated by Th2-type cells and cytokines. We examined the pharmacological potential of this compound in a murine model of respiratory allergy to Bt (Blomia tropicalis). For this, AJ mice were sensitized (100 µg/animal s.c.) and challenged (10 μg/animal i.n.) with Bt mite extract. Sensitized animals were treated or not with eugenol (20, 40 or 80 mg/kg) and the following parameters were analyzed: number of total cells in BAL (bronchoalveolar lavage); EPO (eosinophil peroxidase activity) and histopathological changes in the lungs; serum level of specific IgE, IgG1 and IgG2a and; concentration of Th2 cytokines on BAL and spleen cultures. In addition, the capability of eugenol in relaxing tracheal smooth muscle was also evaluated. Our results showed that treatment with eugenol significantly reduced the airway inflammation, decreasing the cellular infiltrate, EPO and mucus in the lungs, as well as the production of Th2 cytokines. It was also demonstrated a dilator effect of eugenol observed by the relaxation of normal and hyper-reactivity isolated trachea upon carbachol stimulation. These results suggest that eugenol has potential as an anti-asthmatic drug by both bronchodilator and immunomodulatory properties.