Cellular basis for bimatoprost effects on human conventional outflow.
OBJECTIVE
Bimatoprost is a widely used ocular hypotensive agent to treat glaucoma. It lowers intraocular pressure in humans by increasing both pressure-independent (uveoscleral) and pressure-dependent (conventional) aqueous humor outflow. The present study specifically examines bimatoprost effects on the cells that populate human outflow tissues.


METHODS
The authors tested for prostamide receptor activation in primary cultures of human trabecular meshwork (TM), Schlemm's canal (SC), and ciliary smooth muscle (CSM) cells using cellular dielectric spectroscopy (CDS).


RESULTS
The authors observed that bimatoprost produced an immediate and concentration-dependent increase in cell monolayer impedance for TM, SC, and CSM cells with EC(50) values of 4.3, 1.2, and 1.7 nM, respectively; corresponding to decreased cell contractility. Notably, in TM, SC, and CSM cells, bimatoprost was approximately equipotent to the selective FP receptor agonists fluprostenol and 17-phenyl PGF(2α). Bimatoprost effects were insensitive to cholera toxin and pertussis toxin but were abolished by phorbol 12-myristate 13-acetate pretreatment, suggesting Gq-involvement in cell signaling. The effects of bimatoprost on TM and SC cells were inhibited by the prostamide receptor antagonist AGN211334, with IC(50) values of 1.2 and 3.3 μM, respectively. Interestingly, AGN211334 behaved as an apparent inverse agonist in CDS assays involving TM cells but as a neutral prostamide antagonist with SC cells.


CONCLUSIONS
Taken together, results suggest that bimatoprost specifically activates receptors in both cell types of the human conventional outflow pathway to modify intraocular pressure. However, only TM cell monolayers appear to have autocrine, or agonist-independent, receptor signaling that is sensitive to a prostamide receptor antagonist.
Stamer
W Daniel
WD
Department of Ophthalmology and Vision Science, The University of Arizona, Tucson, Arizona 85711, USA. dstamer@eyes.arizona.edu
Piwnica
David
D
Jolas
Thierry
T
Carling
Robert W
RW
Cornell
Clive L
CL
Fliri
Hans
H
Martos
Jose
J
Pettit
Simon N
SN
Wang
Jenny W
JW
Woodward
David F
DF
D000199:Actins / Q000378:metabolism; D000328:Adult; D000368:Aged; D000577:Amides / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D000959:Antihypertensive Agents / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D001082:Aqueous Humor / Q000378:metabolism*; D000069580:Bimatoprost; D002478:Cells, Cultured; D002924:Ciliary Body / Q000187:drug effects* / Q000378:metabolism; D003008:Cloprostenol / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors / Q000494:pharmacology; D003315:Cornea / Q000187:drug effects* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D017097:Electric Impedance; D006801:Humans; D007223:Infant; D007429:Intraocular Pressure / Q000187:drug effects; D008875:Middle Aged; D009130:Muscle, Smooth / Q000187:drug effects* / Q000378:metabolism; D011982:Receptors, Prostaglandin / Q000378:metabolism; D014019:Tissue Donors; D014129:Trabecular Meshwork / Q000187:drug effects* / Q000378:metabolism
D000199:Actins; D000577:Amides; D000959:Antihypertensive Agents; D011982:Receptors, Prostaglandin; C034671:prostaglandin F2alpha receptor; D003008:Cloprostenol; D000069580:Bimatoprost