Azelastine--a novel in vivo inhibitor of leukotriene biosynthesis: a possible mechanism of action: a mini review.
Leukotrienes have been proposed as important chemical mediators of allergic inflammation, and there is evidence that azelastine (Astelin) can affect leukotriene-mediated allergic responses. One of the enzymes required for the synthesis of leukotrienes from arachidonic acid is 5-lipoxygenase (5-LO). Azelastine, which is preferentially taken up by the lung and alveolar macrophages, inhibits leukotriene generation in the airways. This property of azelastine may contribute to its therapeutic efficacy in the long-term treatment and management of rhinitis and asthma. Azelastine does not directly inhibit 5-LO in disrupted murine peritoneal cells and rat basophilic leukemia cells (IC50 > 100 microM), but does have moderate 5-LO inhibitory activity in intact murine peritoneal cells (IC50 = 10 microM, 5 min) and in chopped guinea pig liver (IC50 = 14 microM, 2 hr). The generation and release of leukotrienes in human neutrophils and eosinophils is also inhibited by azelastine (IC50 = 0.9-1.1 microM). Furthermore, azelastine is a potent and specific inhibitor of allergen-induced generation of leukotrienes in the nose of the guinea pig (ID50 < 100 micrograms/kg, im, 20 min) as well as in patients with rhinitis (2 mg, po, 4 hr; ID50 < 30 micrograms/kg). Azelastine also inhibits allergen-induced, leukotriene-mediated, pyrilamine-resistant bronchoconstriction (oral ID50 = 60 micrograms/kg, 2 hr and 120 micrograms/kg, 24 hr). This profile suggests that azelastine may be a novel inhibitor of Ca(2+)-dependent translocation of 5-lipoxygenase from cytosol to the nuclear envelope or a FLAP inhibitor rather than a direct 5-LO inhibitor.
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Wallace Laboratories, Division of Carter-Wallace, Inc., Cranbury, New Jersey 08512, USA.
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D000818:Animals; D001094:Arachidonate 5-Lipoxygenase / Q000378:metabolism; D001993:Bronchodilator Agents / Q000494:pharmacology*; D002118:Calcium / Q000502:physiology; D002478:Cells, Cultured; D006801:Humans; D066298:In Vitro Techniques; D015289:Leukotrienes / Q000096:biosynthesis*; D016859:Lipoxygenase Inhibitors / Q000494:pharmacology*; D010793:Phthalazines / Q000494:pharmacology*
D001993:Bronchodilator Agents; D015289:Leukotrienes; D016859:Lipoxygenase Inhibitors; D010793:Phthalazines; D001094:Arachidonate 5-Lipoxygenase; D002118:Calcium; C020976:azelastine