title: Experimental diabetes causes breakdown of the blood-retina barrier by a mechanism involving tyrosine nitration and increases in expression of vascular endothelial growth factor and urokinase plasminogen activator receptor.
abstract: The purpose of these experiments was to determine the specific role of reactive oxygen species (ROS) in the blood-retinal barrier (BRB) breakdown that characterizes the early stages of vascular dysfunction in diabetes. Based on our data showing that high glucose increases nitric oxide, superoxide, and nitrotyrosine formation in retinal endothelial cells, we hypothesized that excess formation of ROS causes BRB breakdown in diabetes. Because ROS are known to induce increases in expression of the well-known endothelial mitogen and permeability factor vascular endothelial growth factor (VEGF) we also examined their influence on the expression of VEGF and its downstream target urokinase plasminogen activator receptor (uPAR). After 2 weeks of streptozotocin-induced diabetes, analysis of albumin leakage confirmed a prominent breakdown of the BRB. This permeability defect was correlated with significant increases in the formation of nitric oxide, lipid peroxides, and the peroxynitrite biomarker nitrotyrosine as well as with increases in the expression of VEGF and uPAR. Treatment with a nitric oxide synthase inhibitor (N-omega-nitro-L-arginine methyl ester, 50 mg/kg/day) or peroxynitrite scavenger (uric acid, 160 mg/kg/day) blocked the breakdown in the BRB and prevented the increases in formation of lipid peroxides and tyrosine nitration as well as the increases in expression of VEGF and uPAR. Taken together, these data indicate that early diabetes causes breakdown of the BRB by a mechanism involving the action of reactive nitrogen species in promoting expression of VEGF and uPAR.
authors.affiliation: Vascular Biology Center, Medical College of Georgia, Augusta, Georgia 30909, USA.
authors.forename: Azza B
authors.initials: AB
authors.lastname: El-Remessy
authors.forename: M Ali
authors.initials: MA
authors.lastname: Behzadian
authors.forename: Gamal
authors.initials: G
authors.lastname: Abou-Mohamed
authors.forename: Telina
authors.initials: T
authors.lastname: Franklin
authors.forename: Robert W
authors.initials: RW
authors.lastname: Caldwell
authors.forename: Ruth B
authors.initials: RB
authors.lastname: Caldwell
mesh_terms: D000818:Animals; D001813:Blood-Retinal Barrier / Q000187:drug effects / Q000502:physiology*; D001835:Body Weight / Q000187:drug effects; D003921:Diabetes Mellitus, Experimental / Q000503:physiopathology*; D016228:Endothelial Growth Factors / Q000235:genetics*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015870:Gene Expression; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics*; D015227:Lipid Peroxidation; D008222:Lymphokines / Q000235:genetics*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009566:Nitrates / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism; D018384:Oxidative Stress / Q000502:physiology; D030421:Peroxynitrous Acid / Q000037:antagonists & inhibitors / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D026361:Reactive Nitrogen Species / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000235:genetics*; D055293:Receptors, Urokinase Plasminogen Activator; D012160:Retina / Q000378:metabolism; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000378:metabolism*; D014527:Uric Acid / Q000494:pharmacology; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
chemical_list: D016228:Endothelial Growth Factors; D004791:Enzyme Inhibitors; D036341:Intercellular Signaling Peptides and Proteins; D008222:Lymphokines; D009566:Nitrates; D009573:Nitrites; C524900:Plaur protein, rat; D012333:RNA, Messenger; D026361:Reactive Nitrogen Species; D011956:Receptors, Cell Surface; D055293:Receptors, Urokinase Plasminogen Activator; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D030421:Peroxynitrous Acid; D014527:Uric Acid; C002744:3-nitrotyrosine; D014443:Tyrosine; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester