Effects of platelet-derived growth factor on aqueous humor dynamics.
OBJECTIVE
It is well known that the small GTPase RhoA modulates actin cytoskeleton and cellular contractility in the trabecular meshwork (TM). Several substances known to contract the TM reduce outflow facility, whereas cellular relaxation is commonly associated with the opposite effect. Inhibitors of the RhoA pathway are under development as antiglaucoma drugs. Here the authors investigate the role of platelet-derived growth factor (PDGF), a known activator of the Rac1 pathway, in cell cytoskeleton, outflow facility, and intraocular pressure (IOP).


METHODS
Effects of PDGF on actin cytoskeleton, Rac1, and AKT activation were tested in preconfluent and confluent bovine TM cells in culture. Rac1 and AKT/P-AKT activation were assessed by Western blot analysis. Trabecular outflow facility was measured in bovine perfused anterior segments. Changes in IOP were measured for up to 6 hours after topical application in the cornea of rabbit eyes by means of a contact tonometer.


RESULTS
In TM cells, PDGF (10 ng/mL) activated Rac1 through AKT and induced actin cytoskeleton rearrangement with lamellipodia formation. In this sense, lamellipodia formation in TM cells was prevented by NSC23766, a Rac1 inhibitor, and LY294002, a PI3K inhibitor. In perfused anterior segments, PDGF (100 ng/mL) increased trabecular outflow facility by 26%. In vivo, when topically applied to rabbit corneas, PDGF induced a 20% decrease in IOP (100 ng/mL). This reduction was concentration dependent and presented an EC(50) value of 2.7 nM.


CONCLUSIONS
PDGF, by activating the Rac1 pathway, induces cytoskeletal changes in TM cells that enhance outflow facility. Decreased IOP after PDGF application is likely caused by the facilitation of aqueous humor outflow. Rac1 pathway activation appears to be a positive modulator of outflow facility and an interesting target for decreasing IOP after ocular hypertension.
Syriani
Emilio
E
Department of Physiological Sciences, School of Medicine, University of Barcelona, Barcelona, Spain.
Cuesto
German
G
Abad
Elena
E
Pelaez
Teresa
T
Gual
Arcadi
A
Pintor
Jesus
J
Morales
Miguel
M
Gasull
Xavier
X
D000199:Actins / Q000378:metabolism; D000287:Administration, Topical; D000818:Animals; D000869:Anterior Eye Segment / Q000187:drug effects / Q000378:metabolism; D001082:Aqueous Humor / Q000378:metabolism*; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D002417:Cattle; D002478:Cells, Cultured; D019084:Fluorescent Antibody Technique, Indirect; D007429:Intraocular Pressure / Q000187:drug effects; D010982:Platelet-Derived Growth Factor / Q000008:administration & dosage / Q000494:pharmacology*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011817:Rabbits; D014065:Tonometry, Ocular; D014129:Trabecular Meshwork / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000378:metabolism
D000199:Actins; D010982:Platelet-Derived Growth Factor; D051057:Proto-Oncogene Proteins c-akt; D020830:rac1 GTP-Binding Protein; D002118:Calcium