Vascular Dysfunction Induced by AGE is Mediated by VEGF via Mechanisms Involving Reactive Oxygen Species, Guanylate Cyclase, and Protein Kinase C

Objective: These experiments were designed to elucidate mechanisms mediating, vascular dysfunction induced by advanced glycation end product, (AGEs), Methods: Skin chambers were mounted on the backs of Sprague-Dawley rats and 1 week later. granulation tissue that formed in the bottom of dir chamber was exposed twice daily for 7 days to glycated rat serum albumin in the presence and absence of inhibitors of reactive oxygen intermediates, nitric oxide synthase and guanylate cyclase, protein kinase C (PKC). and a neutralizing vascular endothelial growth factor (VEGF) antibody. Vascular I-125-albumin clearance and blood flow were quantified by use Of a double isotope-dilution technique and radiolabeled microspheres. respectively. Results: Albumin permeation and blood flow were increased dose-dependently to a maximum of 2 to 3 times controls by increasing, the extent of glucose modification, the concentration, or the duration of exposure to glycated albumin, These increases were significantly attenuated by probucol and superoxide dismutase, N-G-nitro-L-arginine-methyl ester (L-NAME), a nitric oxide synthase inhibitor. LY83583, a guanylate cyclase inhibitor, and LY333531, a beta -isoform-selective protein kinase C inhibitor. A neutralizing VEGF monoclonal antibody also markedly attenuated the permeability and blood flow increased induced by glycated albumin. Conclusions: These observations indicate potentially important role,, for oxygen free-radicals and nitric oxide in mediating permeability and blood flow changed induced by glycated proteins via mechanisms involving increased protein kinase C activity and VEGF production. Striking similarities in the mechanism by which hyperglycemia and glycated proteins induce vascular dysfunction suggest that a common pathway mediates effects of these different metabolic imbalances on vascular dysfunction.