Human Trabecular Meshwork Cell Responses Induced by Bimatoprost, Travoprost, Unoprostone, and other FP Prostaglandin Receptor Agonist Analogues

Abstract

Purpose. To determine the functional agonist potencies of the intraocular pressure (IOP)-lowering prostaglandin F (FP)-class prostaglandin (PG) analogues (e.g., travoprost, latanoprost, bimatoprost, and unoprostone isopropyl ester) in human trabecular meshwork (h-TM) cells, by using phosphoinositide (PI) turnover and intracellular Ca²⁺ ([Ca²⁺]_i) mobilization, and to confirm the FP nature of these receptors by using an FP receptor antagonist, 11β-fluoro-15-epi-15-indanyl-PGF_2α (AL-8810). methods. FP-receptor-mediated PI turnover and [Ca²⁺]_i mobilization were measured in h-TM cells by determining the accumulation of [³H]-inositol phosphates ([³H]-IPs) by anion-exchange chromatography and real-time fluorescence imaging, respectively. results. Various PG analogues concentration-dependently stimulated production of [³H]-IPs in h-TM cells with the following agonist potencies (median effective concentration; EC₅₀): travoprost acid (EC₅₀ = 2.4 nM) > cloprostenol (EC₅₀ = 4.5 nM) > (±)-fluprostenol (EC₅₀ = 10.8 nM) > latanoprost acid (EC₅₀ = 34.7 nM) > bimatoprost acid (EC₅₀ = 112 nM) > PGF_2α (EC₅₀ = 120 nM) ≫ unoprostone (UF-021; EC₅₀ = 3280 nM) > S-1033 (EC₅₀ = 4570 nM; all n = 3–9). Prodrug derivatives of these compounds exhibited the following potencies: travoprost (isopropyl ester; EC₅₀ = 89.1 nM) > latanoprost (isopropyl ester; EC₅₀ = 778 nM) > bimatoprost (amide; EC₅₀ = 1410–6940 nM). Travoprost acid, PGF_2α, unoprostone, and S-1033 were tested in addition for [Ca²⁺]_i mobilization and found to have rapid and dose-dependent effects. The FP receptor-selective antagonist AL-8810 antagonized the (±)-fluprostenol-induced PI turnover in these cells (K _i = 2.56 ± 0.62 μM) as well as that induced by bimatoprost and acids of latanoprost and travoprost. The agonist and antagonist potencies of the PG analogues from the PI turnover assays in h-TM cells correlated well with PI turnover data obtained from the cloned human ciliary body FP receptor (r = 0.92; P < 0.0001). conclusions. The pharmacology of the h-TM cell FP-receptor-mediated PI turnover and [Ca²⁺]_i mobilization was defined using numerous synthetic (FP-selective) PG agonist analogues and an FP receptor antagonist, AL-8810. Bimatoprost, travoprost, latanoprost, unoprostone isopropyl ester, and their respective free acids were shown to be FP agonists in the h-TM cells.