Advanced glycation end products (AGEs) on the surface of diabetic erythrocytes bind to the vessel wall via a specific receptor inducing oxidant stress in the vasculature: a link between surface-associated AGEs and diabetic complications.

Abstract

Vascular complications are an important cause of morbidity and mortality in patients with diabetes. The extent of vascular complications has been linked statistically to enhanced adherence ofdiabetic erythrocytes to endothelial cells (ECs) and to the accumulation of a class of glycated proteins termed advanced glycation end products (AGEs). We Nonenzymatic glycation ofproteins, such as hemoglobin, has been shown to provide a useful index for management of patients with diabetes (1). The ultimate result of the nonenzymatic glycation and oxidation of proteins is formation of advanced glycation end products (AGEs), whose presence in plasma and tissues has been linked to the development of complications in diabetics (2-5). The cellular interactions of AGEs are mediated by receptors/cell surface binding proteins identified on endothelial cells (ECs) and mononuclear phagocytes (MPs), engagement of which leads to perturbation of cellular functions (3,(6)(7)(8). Our studies have characterized an integral membrane protein, receptor for AGE (RAGE), a newly discovered member of the immunoglobulin superfamily, which has a central role in mediating the interactions of AGEs with cellular surfaces (7-9).We previously showed that erythrocytes from diabetic patients exhibited enhanced binding to cultured endothelium (10). We hypothesized that, dependent on the duration of exposure of erythrocytes to plasma hyperglycemia, AGE modification oferythrocyte surface membrane proteins could occur, allowing them to bind and thereby to modulate properties of RAGE-expressing vessel wall cells. Our studies demonstrate that the molecular basis of the increased adherence of diabetic erythrocytes results largely from AGEs on the erythrocyte surface interacting with EC RAGE. This results in the induction of oxidant stress in the endothelium, potentially modulating expression of a spectrum ofgenes that could contribute to the pathogenesis of vascular complications.MATERIALS AND METHODS Subjects. The group of patients (n = 18 each for the normal and diabetic subjects) was comparable in age, duration of diabetes, fasting blood glucose, and hemoglobin Alc levels.Erythrocytes from two patients homozygous for sickle cell disease were also studied.Erythrocyte Adhesion Assay. Cultured human umbilical vein ECs were prepared and assayed as described (10-12).The specific activity of 51Cr-labeled erythrocytes for normal and diabetic erythrocytes was 3750 ± 260 and 3820 ± 253 cpm per mg of hemoglobin, respectively. The adhesion ratio (AR) was calculated as follows: AR = (cpm of diabetic erythrocytes)/(cpm of normal erythrocytes). An AR value of 1 represents the adhesion observed with normal erythrocytes. Where indicated, either erythrocytes or ECs were preincubated with soluble RAGE (sRAGE) or antibodies and EC nuclear extracts were prepared (13).Preparation of AGE-Modified Proteins, AGE Binding Proteins, and Antisera. AGE albumin was prepared and characterized as described (3,7,8). AGE binding proteins were purified from bovine lung (7) and cons...

Advanced glycation end products and their receptors co-localise in rat organs susceptible to diabetic microvascular injury

“…Both these proteins can bind to AGEs. It has been suggested that RAGE functions as a cell surface receptor for AGEs and mediates their cellular effects [30]. For example, AGE-induced increases in expression of vascular cell adhesion molecule-1 can be inhibited by either antibodies to RAGE or soluble RAGE [31].…”

Advanced glycation endproducts inhibit prostacyclin production and induce plasminogen activator inhibitor-1 in human microvascular endothelial cells

“…The AGE-RAGE interaction is reported to induce oxidant stress and then to activate nuclear factor kappa B (NF-k B) [42]. Since NF-k B binding sites are identified in the PAI-1 promotor region [43], AGE probably enhanced the transcription of PAI-1 gene through the NF-k B-mediated pathway.…”

Skin Autofluorescence and the Association with Renal and Cardiovascular Risk Factors in Chronic Kidney Disease Stage 3

“…The larger number of participants in our study likely afforded greater power to detect this association. The mechanisms whereby low hemoglobin may contribute to AGE formation and increased SAF remain to be elucidated (39,40). Hemoglobin binds reactive oxygen species, and anemia is therefore associated with increased oxidative stress, due to reduced tissue oxygen delivery (41) as well as reduced antioxidant effects.…”