The role of leukotrienes in allergic rhinitis

Objective: To review the role of cysteinyl leukotrienes (cysLTs) in allergic rhinitis and the scientific rationale for therapy with leukotriene receptor antagonists (LTRAs). Data Sources: Relevant basic science and clinical articles were identified by a search of the PubMed database for articles published from 1984 to 2004 using the following keywords: allergic rhinitis; nose; immune response; allergen challenge; leukotrienes C, D, and E; cysteinyl leukotriene; cysteinyl leukotriene receptor; cytokine; leukocyte; montelukast; zafirlukast; and pranlukast. Study Selection: The authors' expert opinion was used to select studies for inclusion in this review. Results: CysLTs are synthesized via 5-lipoxygenase metabolism of arachidonic acid by mast cells and basophils during the early-phase response to antigen and by eosinophils and macrophages during the late phase. The cysLT levels in nasal secretions are elevated after short-term allergen instillation and in allergy season in patients with allergic rhinitis. These lipid mediators act locally and systemically by interacting with receptors, particularly the cysLT, receptor, on target cells. Evidence derived from topical application of cysLTs in the nose and from the effects of LTRAs indicates that cysLTs contribute to nasal mucous secretion, congestion, and inflammation. CysLTs promote allergic inflammation by enhancing immune responses and the production, adhesion, migration, and survival of inflammatory cells such as eosinophils. They also increase the generation of an array of other proinflammatory mediators, such as cytokines, which in turn increase the production of and receptors for cysLTs. Clinical trials have demonstrated that LTRAs have significant but modest efficacy as single agents but additive efficacy when used with other classes of agents. Conclusions: CysLTs fulfill the criteria for relevant mediators of allergic rhinitis via their diverse effects on immune, inflammatory, and local structural components of disease. By blocking the cysLT, receptor responsible for most of these effects, LTRAs represent a useful approach to treatment of this important and prevalent disorder.