Pharmacological characterization of guinea pig chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2).

Chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2), a G protein-coupled receptor activated by prostaglandin D2 (PGD2), has been identified as a receptor expressed on cell types critical to the pathogenesis of asthma. The cDNA encoding guinea pig CRTH2 was cloned and mRNA expression examined in selected tissues. Transcript profiling of guinea pig CRTH2 indicated relatively high levels of expression in bone marrow, intermediate levels in brain and relatively low levels in lung, spleen, thymus, lymph node, etc. Characterization of the molecular pharmacology of guinea pig CRTH2 revealed that guinea pig CRTH2 exhibited a greater affinity for Δ12-PGJ2, a stable PGD2 metabolite relative to human CRTH2. The CRTH2 selective agonists 13,14-dihydro-15-keto PGD2 and Δ12-PGJ2 induced the recruitment of eosinophils following intradermal administration of these ligands in guinea pigs. Chemotaxis of guinea pig eosinophils was elicited by either PGD2 or Δ12-PGJ2, and was abolished by a CRTH2-specific antagonist. These results indicate that PGD2 and the stable metabolite, Δ12-PGJ2, play important roles in CRTH2 activation in the guinea pig.