Effects of protein kinase C inhibition and activation on proliferation and apoptosis of bovine retinal pericytes.
OBJECTIVE
Drop-out of capillary pericytes occurs early and selectively in diabetic retinopathy. High glucose concentrations decrease replication and increase apoptosis of cultured pericytes. Since glucose activates protein kinase C, we investigated the effects of modulating this intracellular mediator on replication, cell cycle and apoptosis of cultured bovine retinal pericytes.


METHODS
Pericytes cultured in 5.6 or 28 mmol/l glucose were exposed to a protein kinase C activator (phorbol 12-myristate 13-acetate) and/or a selective inhibitor of its beta2 isoform (LY379196). Cells were counted after 7 days. Proliferation by the tetrazolium to formazan assay and DNA synthesis by 5-bromo-2'-deoxyuridine incorporation were measured at day 4. Cell cycle by flow cytometry and apoptosis by ELISA were assessed at day 2.


RESULTS
High glucose reduced pericyte replication and increased apoptosis. Protein kinase C activation increased proliferation, while inhibition of its beta2 isoform decreased it. Cell cycle was accelerated by protein kinase C activation and delayed by inhibition. Apoptosis was enhanced by protein kinase C inhibition and reduced by activation.


CONCLUSIONS
Protein kinase C inhibition amplifies the anti-proliferative and pro-apoptotic effects of high glucose on cultured pericytes, whereas stimulation reduces apoptosis and promotes proliferation both in physiological glucose and high glucose. Protein kinase C inhibition, proposed for the treatment of diabetic macular edema and proliferative retinopathy, might accelerate pericyte dropout in earlier stages when these cells are still present in retinal capillaries.
Pomero
F
F
Department of Internal Medicine, University of Turin, Torino, Italy.
Allione
A
A
Beltramo
E
E
Buttiglieri
S
S
D'Alù
F
F
Ponte
E
E
Lacaria
A
A
Porta
M
M
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002417:Cattle; D002452:Cell Count; D002455:Cell Division / Q000187:drug effects; D004247:DNA / Q000096:biosynthesis; D004305:Dose-Response Relationship, Drug; D020536:Enzyme Activators / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005434:Flow Cytometry; D005947:Glucose / Q000494:pharmacology; D007527:Isoenzymes / Q000037:antagonists & inhibitors; D008698:Mesylates / Q000494:pharmacology; D020286:Pericytes / Q000187:drug effects*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D011758:Pyrroles / Q000494:pharmacology; D012160:Retina / Q000166:cytology* / Q000187:drug effects; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013778:Tetrazolium Salts; D013844:Thiazoles
C434605:5,21 - 12,17-dimetheneo-18H-dibenzo(i,o)pyrrolo(3,4-1)(1,8)diazacyclohexandecine-18,10(19H)dione,8((dimethylamino)methyl)-6,7,8,9,10,11-hexahydro,monomethanesulfonate; D020536:Enzyme Activators; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D008698:Mesylates; D011758:Pyrroles; D013778:Tetrazolium Salts; D013844:Thiazoles; D004247:DNA; D011493:Protein Kinase C; C022616:thiazolyl blue; D005947:Glucose; D013755:Tetradecanoylphorbol Acetate