Diabetes-induced superoxide anion and breakdown of the blood-retinal barrier: role of the VEGF/uPAR pathway.
Diabetes-induced breakdown of the blood-retinal barrier (BRB) has been linked to hyperglycemia-induced expression of vascular endothelial growth factor (VEGF) and is likely mediated by an increase in oxidative stress. We have shown that VEGF increases permeability of retinal endothelial cells (REC) by inducing expression of urokinase plasminogen activator receptor (uPAR). The purpose of this study was to define the role of superoxide anion in VEGF/uPAR expression and BRB breakdown in diabetes. Studies were performed in streptozotocin diabetic rats and mice and high glucose (HG) treated REC. The superoxide dismutase (SOD) mimetic tempol blocked diabetes-induced permeability and uPAR expression in rats and the cell permeable SOD inhibited HG-induced expression of uPAR and VEGF in REC. Inhibiting VEGFR blocked HG-induced expression of VEGF and uPAR and GSK-3β phosphorylation in REC. HG caused β-catenin translocation from the plasma membrane into the cytosol and nucleus. Treatment with HG-conditioned media increased REC paracellular permeability that was blocked by anti-uPA or anti-uPAR antibodies. Moreover, deletion of uPAR blocked diabetes-induced BRB breakdown and activation of MMP-9 in mice. Together, these data indicate that diabetes-induced oxidative stress triggers BRB breakdown by a mechanism involving uPAR expression through VEGF-induced activation of the GSK3β/β-catenin signaling pathway.
Vascular Biology Center, Medical College of Georgia, Georgia Regents University, Augusta, Georgia, United States of America.
Azza B
AB
El-Remessy
Telina
T
Franklin
Nagla
N
Ghaley
Jinling
J
Yang
Michael W
MW
Brands
Ruth B
RB
Caldwell
Mohamed Ali
MA
Behzadian
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D001813:Blood-Retinal Barrier / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology*; D015153:Blotting, Western; D002199:Capillary Permeability / Q000187:drug effects; D002417:Cattle; D002463:Cell Membrane Permeability / Q000187:drug effects; D002478:Cells, Cultured; D003497:Cyclic N-Oxides / Q000494:pharmacology; D003921:Diabetes Mellitus, Experimental / Q000503:physiopathology*; D042783:Endothelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D005947:Glucose / Q000494:pharmacology; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D051381:Rats; D055293:Receptors, Urokinase Plasminogen Activator / Q000235:genetics / Q000378:metabolism*; D012171:Retinal Vessels / Q000166:cytology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects; D013113:Spin Labels; D013482:Superoxide Dismutase / Q000494:pharmacology; D013481:Superoxides / Q000378:metabolism*; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D051176:beta Catenin / Q000378:metabolism
D000975:Antioxidants; D003497:Cyclic N-Oxides; D055293:Receptors, Urokinase Plasminogen Activator; D013113:Spin Labels; D042461:Vascular Endothelial Growth Factor A; D051176:beta Catenin; D013481:Superoxides; D013482:Superoxide Dismutase; D038362:Glycogen Synthase Kinase 3; D005947:Glucose; C001803:tempol