Human Ciliary Muscle Cell Responses to FP-Class Prostaglandin Analogs: Phosphoinositide Hydrolysis,Intracellular Ca 2+ Mobilization and MAP Kinase Activation

Abstract

Phospholipase C induced phosphoinositide (PI) turnover, intracellular Ca²⁺ ([Ca²⁺]_i) mobilization and mitogen-activated protein (MAP) kinase activation by FP-class prostaglandin analogs was studied in normal human ciliary muscle (h-CM) cells. Agonist potencies obtained in the PI turnover assays were: travoprost acid ((+)-fluprostenol; EC₅₀ = 2.6 ± 0.8 nM) > bimatoprost acid (EC₅₀ = 3.6 ± 1.2 nM) > (±)-fluprostenol (EC₅₀ = 4.3 ± 1.3 nM) >> prostaglandin F_2α (PGF_2α) (EC₅₀ = 134 ± 17 nM) > latanoprost acid (EC₅₀ = 198 ± 83 nM) > S-1033 (EC₅₀ = 2930 ± 1420 nM) > unoprostone (EC₅₀ = 5590 ± 1490 nM) > bimatoprost (EC₅₀ = 9600 ± 1100 nM). Agonist potencies in h-CM cells correlated well with those previously obtained for the cloned human ciliary body-derived FP receptor (r = 0.96, p< 0.001) and that present on h-TM cells (r = 0.94, p< 0.0001). Travoprost acid, PGF_2α and unoprostone also stimulated [Ca²⁺]_i mobilization in h-CM cells with travoprost acid being the most potent agonist. MAP kinase activity was stimulated in the h-CM cells with the following rank order of activity (at 100 nM): travoprost acid > PGF_2α > latanoprost acid > PGD₂ > bimatoprost > latanoprost = bimatoprost acid = fluprostenol > PGE₂ = S-1033 > unoprostone > PGI₂. The PI turnover, [Ca²⁺]_i mobilization and MAP kinase activation induced by several of these agonists was blocked by the FP receptor antagonist, AL-8810 (11β-fluoro-15-epiindanyl PGF_2α) (e.g. K_i = 5.7 μM versus PI turnover). These studies have characterized the biochemical and pharmacological properties of the native FP prostaglandin receptor present on h-CM cells using three signal transduction mechanism assays and a broad panel of FP-class agonist analogs (including free acids of bimatoprost, travoprost and latanoprost) and the FP receptor antagonist, AL-8810.