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Abstract #11976 Published in IGR 7-1
Molecular pharmacology of the DP/EP2 class prostaglandin AL-6598 and quantitative autoradiographic visualization of DP and EP2 receptor sites in human eyes
Sharif NA; Williams GW; Crider JY; Xu SX; Davis TLJournal of Ocular Pharmacology and Therapeutics 2004; 20: 489-508
DP-class prostaglandins and prostaglandin analogs (collectively, prostaglandins or PGs) such as PGD2 , BW245C, ZK110841, and ZK118182, lower intraocular pressure (IOP) in animal models of ocular hypertension. A new analog of ZK118182 (AL-6556; 13,14-dihydro-ZK118182) was synthesized, and the isopropyl ester of AL-6556 (AL-6598) was shown recently to lower IOP in the ocular hypertensive cynomolgus monkey model of glaucoma and in human subjects. AL-6556 and AL-6598 had an affinity (Ki ) of 2.66-4.43 μM for DP receptors but a much lower affinity (Ki s = 38-103 μM) for EP3 , FP, IP, and TP receptors (n = 3-5). In addition, AL-6556 and AL-6598 exhibited Ki s > 100 μM for 19 nonprostanoid receptors. Both PGs stimulated cAMP production (EC50 = 1.07 ± 0.1 μM and EC50 = 2.64 ± 0.84 μM; n = 3) by way of DP receptors in embryonic bovine tracheal fibroblasts. While AL-6556 and AL-6598 were partial agonists (EC50 s = 0.47-0.69 μM; Emax = 35%-46%) at EP2 receptors in human nonpigmented epithelial cells, neither had any agonist activity at EP4 , IP, or FP receptors. The DP antagonist, BWA868C, effectively antagonized the effects of AL-6556 with a high potency (IC50 = 22.8 ± 3.9 nM; n = 3). DP receptors radiolabeled with [3 H]BWA868C on human eye sections by quantitative autoradiography were highly concentrated in the ciliary process (CP), longitudinal (LCM) and circular (CCM) ciliary muscles, and iris with much lower specific binding in the cornea (CN), lens (LNS), and retina (RET). EP2 receptors labeled with [3 H]PGE2 were concentrated in the LCM, CM, RET, and iris. In conclusion, AL-6598 and AL-6556 are relatively DP-receptor-selective PGs with full agonist activity at the DP and partial agonist activity at the EP2 receptor. The IOP-lowering activities of these compounds may involve both the inflow and outflow mechanisms, as DP and EP2 receptors were visualized in human ocular tissues involved in such aqueous humor dynamics.
Dr. N.A. Sharif, Molecular Pharmacology Unit (R2-19), Alcon Research, Ltd., 6201 South Freeway, Fort Worth, TX 76134-2099, USA
Classification:
11.14 Investigational drugs; pharmacological experiments (Part of: 11 Medical treatment)
