Prostaglandin E2 receptors in asthma and in chronic rhinosinusitis/nasal polyps with and without aspirin hypersensitivity

Chronic rhinosinusitis with nasal polyps (CRSwNP) and asthma frequently coexist and are always present in patients with aspirin exacerbated respiratory disease (AERD). Although the pathogenic mechanisms of this condition are still unknown, AERD may be due, at least in part, to an imbalance in eicosanoid metabolism (increased production of cysteinyl leukotrienes (CysLTs) and reduced biosynthesis of prostaglandin (PG) E2), possibly increasing and perpetuating the process of inflammation. PGE2 results from the metabolism of arachidonic acid (AA) by cyclooxygenase (COX) enzymes, and seems to play a central role in homeostasis maintenance and inflammatory response modulation in airways. Therefore, the abnormal regulation of PGE2 could contribute to the exacerbated processes observed in AERD. PGE2 exerts its actions through four G-protein-coupled receptors designated E-prostanoid (EP) receptors EP1, EP2, EP3, and EP4. Altered PGE2 production as well as differential EP receptor expression has been reported in both upper and lower airways of patients with AERD. Since the heterogeneity of these receptors is the key for the multiple biological effects of PGE2 this review focuses on the studies available to elucidate the importance of these receptors in inflammatory airway diseases.