Biochemical, Functional, and Pharmacological Characterization of AT-56, an Orally Active and Selective Inhibitor of Lipocalin-type Prostaglandin D Synthase

• Published in: The Journal of biological chemistry 2009-03, Vol.284 (12), p.7623-7630
• Main Authors: Irikura, Daisuke, Aritake, Kosuke, Nagata, Nanae, Maruyama, Toshihiko, Shimamoto, Shigeru, Urade, Yoshihiro
• Format: Article
• Language: English
• Subjects: Administration, Oral; Animals; Calcimycin - pharmacology; Cyclooxygenase 1 - genetics; Cyclooxygenase 1 - metabolism; Cyclooxygenase 2 - genetics; Cyclooxygenase 2 - metabolism; Dinoprost - biosynthesis; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Evaluation, Preclinical; Enzyme Catalysis and Regulation; Enzyme Inhibitors - pharmacology; Eosinophils - enzymology; Humans; Intramolecular Oxidoreductases - antagonists & inhibitors; Intramolecular Oxidoreductases - genetics; Intramolecular Oxidoreductases - metabolism; Ionophores - pharmacology; Lipocalins - antagonists & inhibitors; Lipocalins - genetics; Lipocalins - metabolism; Male; Megakaryocytes - enzymology; Membrane Proteins - genetics; Membrane Proteins - metabolism; Mice; Mice, Knockout; Monocytes - enzymology; Pneumonia - drug therapy; Pneumonia - enzymology; Pneumonia - metabolism; Prostaglandin D2 - biosynthesis; Wound Healing - drug effects; Wounds, Stab - drug therapy; Wounds, Stab - enzymology; Wounds, Stab - genetics
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M808593200

We report here that 4-dibenzo[a,d]cyclohepten-5-ylidene-1-[4-(2H-tetrazol-5-yl)-butyl]-piperidine (AT-56) is an orally active and selective inhibitor of lipocalin-type prostaglandin (PG) D synthase (L-PGDS). AT-56 inhibited human and mouse L-PGDSs in a concentration (3–250 μm)-dependent manner but did not affect the activities of hematopoietic PGD synthase (H-PGDS), cyclooxygenase-1 and -2, and microsomal PGE synthase-1. AT-56 inhibited the L-PGDS activity in a competitive manner against the substrate PGH2 (Km = 14 μm) with a Ki value of 75 μm but did not inhibit the binding of 13-cis-retinoic acid, a nonsubstrate lipophilic ligand, to L-PGDS. NMR titration analysis revealed that AT-56 occupied the catalytic pocket, but not the retinoid-binding pocket, of L-PGDS. AT-56 inhibited the production of PGD2 by L-PGDS-expressing human TE-671 cells after stimulation with Ca2+ ionophore (5 μm A23187) with an IC50 value of about 3 μm without affecting their production of PGE2 and PGF2α but had no effect on the PGD2 production by H-PGDS-expressing human megakaryocytes. Orally administered AT-56 (