PGE2 receptor (EP4) agonists: Potent dilators of human bronchi and future asthma therapy?

BackgroundAsthma and chronic obstructive pulmonary disease are characterized by inappropriate constriction of the airway smooth muscle. In this context, the physiological response of the human airways to selective relaxant agonists like PGE2 is highly relevant. The aim of this study was thus to characterize the PGE2 receptor subtypes (EP2 or EP4) involved in the relaxation of human bronchial preparations.MethodsHuman bronchial preparations cut as rings were mounted in organ baths for isometric recording of tension and a pharmacological study was performed using selective EP2 or EP4 ligands.ResultsIn the presence of a thromboxane TP receptor antagonist and indomethacin, PGE2 induced the relaxation of human bronchi (Emax = 86 ± 04% of papaverine response; pEC50 value = 7.06 ± 0.13; n = 6). This bronchodilation was significantly blocked by a selective EP4 receptor antagonist (GW627368X, 1 and 10 μmol/L) with a pKB value of 6.38 ± 0.19 (n = 5). In addition, the selective EP4 receptor agonists (ONO-AE1-329; L-902688), but not the selective EP2 receptor agonist (ONO-AE1-259), induced potent relaxation of bronchial preparations pre-contracted with histamine or anti-IgE.ConclusionPGE2 and EP4 agonists induced potent relaxations of human bronchial preparations via EP4 receptor. These observations suggest that EP4 receptor agonists could constitute therapeutic agents to treat the increased airway resistance in asthma.