Polyamine-dependent migration of retinal pigment epithelial cells.
OBJECTIVE
Migration of retinal pigment epithelial (RPE) cells can be triggered by disruption of the RPE monolayer or injury to the neural retina. Migrating cells may re-establish a confluent monolayer, or they may invade the neural retina and disrupt visual function. The purpose of this study was to examine the role of endogenous polyamines in mechanisms of RPE migration.


METHODS
Endogenous polyamine levels were determined in an immortalized RPE cell line, D407, using HPLC. Activities of the two rate-limiting enzymes for polyamine synthesis, ornithine decarboxylase (ODC), and S-adenosylmethionine decarboxylase (SAMdc), were measured by liberation of ((14)CO(2))(.) Migration was assessed in confluent cultures by determining the number of cells migrating into a mechanically denuded area. All measurements were obtained both in control cultures and in cultures treated with synthesis inhibitors that deplete endogenous polyamines. Subcellular localization of endogenous polyamines was determined using a polyamine antibody.


RESULTS
The polyamines, spermidine and spermine, as well as their precursor, putrescine, were normal constituents of RPE cells. The two rate-limiting synthetic enzymes were also present, and their activities were stimulated dramatically by addition of serum to the culture medium. Cell migration was similarly stimulated by serum exposure. When endogenous polyamines were depleted, migration was blocked. When polyamines were replenished through uptake, migration was restored. Polyamine immunoreactivity was limited to membrane patches in quiescent cells. In actively migrating and dividing cells, immunoreactivity was enhanced throughout the cytoplasm.


CONCLUSIONS
Polyamines are essential for RPE migration. Pharmacologic manipulation of the polyamine pathway could provide a therapeutic strategy for regulating anomalous migration.
Johnson
Dianna A
DA
Department of Ophthalmology, University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA. djohnson@mail.eye.utmem.edu
Fields
Carolyn
C
Fallon
Amy
A
Fitzgerald
Malinda E C
ME
Viar
Mary Jane
MJ
Johnson
Leonard R
LR
D012437:Adenosylmethionine Decarboxylase / Q000037:antagonists & inhibitors / Q000378:metabolism; D002460:Cell Line; D002465:Cell Movement / Q000502:physiology*; D002851:Chromatography, High Pressure Liquid; D000518:Eflornithine / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D008935:Mitoguazone / Q000031:analogs & derivatives* / Q000494:pharmacology; D009955:Ornithine Decarboxylase / Q000378:metabolism; D065108:Ornithine Decarboxylase Inhibitors; D010857:Pigment Epithelium of Eye / Q000166:cytology* / Q000201:enzymology; D011700:Putrescine / Q000502:physiology*; D013095:Spermidine / Q000502:physiology*; D013096:Spermine / Q000502:physiology*
D004791:Enzyme Inhibitors; D065108:Ornithine Decarboxylase Inhibitors; C056522:diethylglyoxal bis(guanylhydrazone); D013096:Spermine; D009955:Ornithine Decarboxylase; D012437:Adenosylmethionine Decarboxylase; D008935:Mitoguazone; D013095:Spermidine; D011700:Putrescine; D000518:Eflornithine