Recent studies suggested that interruption of the interaction of advanced glycation end products (AGEs), with the signal-transducing receptor receptor for AGE (RAGE), by administration of the soluble, extracellular ligand-binding domain of RAGE, reversed vascular hyperpermeability and suppressed accelerated atherosclerosis in diabetic rodents. Since the precise molecular target of soluble RAGE in those settings was not elucidated, we tested the hypothesis that predominant specific AGEs within the tissues in disorders such as diabetes and renal failure, N ⑀ -(carboxymethyl)lysine (CML) adducts, are ligands of RAGE. We demonstrate here that physiologically relevant CML modifications of proteins engage cellular RAGE, thereby activating key cell signaling pathways such as NF-B and modulating gene expression. Thus, CML-RAGE interaction triggers processes intimately linked to accelerated vascular and inflammatory complications that typify disorders in which inflammation is an established component.Receptor for AGE 1 (RAGE), a member of the immunoglobulin superfamily, was first described as a cell surface interaction site for advanced glycation end products (AGEs), products of glycation and oxidation of proteins and lipids (1-2). AGEs are a heterogeneous class of compounds, whose accumulation in disorders such as diabetes, renal failure, Alzheimer's disease, and, indeed, natural aging, albeit to a lesser degree, has suggested their potential contribution to the pathogenesis of complications that typify these conditions (3-7). Our previous studies demonstrated that both in vitro and in vivo derived heterogeneous AGEs ligate cell surface RAGE on endothelium (ECs), mononuclear phagocytes (MPs), vascular smooth muscle (VSMC), and neurons to activate cell signaling pathways such as ERK1/ERK2 kinases and NF-B (8 -9), thereby redirecting cellular function in a manner linked to expression of inflammatory and prothrombotic genes important in the pathogenesis of chronic disorders as apparently diverse as diabetic macrovascular disease and amyloidosis (10 -20).Our recent studies suggested that interruption of the interaction of AGEs with RAGE in vivo, by administration of soluble RAGE (sRAGE), the extracellular ligand-binding domain of RAGE, reversed vascular hyperpermeability and suppressed accelerated atherosclerotic lesion development and complexity in diabetic rodents (19 -20). In the latter studies, analysis of plasma demonstrated evidence of an sRAGE⅐AGE complex; immunoprecipitation of plasma obtained from diabetic sRAGEtreated mice with anti-RAGE IgG yielded species immunoreactive with both anti-RAGE IgG or affinity purified anti-AGE IgG, suggesting that sRAGE might bind up AGEs and limit their interaction with and activation of cell surface RAGE. The beneficial effects of sRAGE were independent of alterations in other risk factors, such as hyperglycemia and hyperlipidemia, implicating a role for AGE-RAGE interaction in the development of vascular dysfunction in diabetes (20).These past studies, however, did not elucidate ...

S100/calgranulin polypeptides are present at sites of inflammation, likely released by inflammatory cells targeted to such loci by a range of environmental cues. We report here that receptor for AGE (RAGE) is a central cell surface receptor for EN-RAGE (extracellular newly identified RAGE-binding protein) and related members of the S100/calgranulin superfamily. Interaction of EN-RAGEs with cellular RAGE on endothelium, mononuclear phagocytes, and lymphocytes triggers cellular activation, with generation of key proinflammatory mediators. Blockade of EN-RAGE/RAGE quenches delayed-type hypersensitivity and inflammatory colitis in murine models by arresting activation of central signaling pathways and expression of inflammatory gene mediators. These data highlight a novel paradigm in inflammation and identify roles for EN-RAGEs and RAGE in chronic cellular activation and tissue injury.

Diabetic nephropathy ensues from events involving earliest changes in the glomeruli and podocytes, followed by accumulation of extracellular matrix in the mesangium. Postulated mechanisms include roles for vascular endothelial growth factor (VEGF), produced by podocytes and contributing to enhanced excretion of urinary albumin and recruitment/activation of inflammatory cells, and transforming growth factor-beta (TGF-beta), elicited largely from mesangial cells and driving production of extracellular matrix. RAGE, a receptor for advanced glycation endproducts (AGEs) and S100/calgranulins, displays enhanced expression in podocytes of genetically diabetic db/db mice by age 13 weeks. RAGE-bearing podocytes express high levels of VEGF by this time, in parallel with enhanced recruitment of mononuclear phagocytes to the glomeruli; events prevented by blockade of RAGE. By age 27 weeks, soluble RAGE-treated db/db mice displayed diminished albuminuria and glomerulosclerosis, and improved renal function. Diabetic homozygous RAGE null mice failed to develop significantly increased mesangial matrix expansion or thickening of the glomerular basement membrane. We propose that activation of RAGE contributes to expression of VEGF and enhanced attraction/activation of inflammatory cells in the diabetic glomerulus, thereby setting the stage for mesangial activation and TGF-beta production; processes which converge to cause albuminuria and glomerulosclerosis.

Background-Previous studies suggested that blockade of RAGE in diabetic apolipoprotein (apo) E-null mice suppressed early acceleration of atherosclerosis. A critical test of the potential applicability of RAGE blockade to clinical settings was its ability to impact established vascular disease. In this study, we tested the hypothesis that RAGE contributed to lesion progression in established atherosclerosis in diabetic apoE-null mice. Methods and Results-Male apoE-null mice, age 6 weeks, were rendered diabetic with streptozotocin or treated with citrate buffer. At age 14 weeks, certain mice were killed or treated with once-daily murine soluble RAGE or albumin; all mice were killed at age 20 weeks. Compared with diabetic mice at age 14 weeks, albumin-treated animals displayed increased atherosclerotic lesion area and complexity. In diabetic mice treated with sRAGE from age 14 to 20 weeks, lesion area and complexity were significantly reduced and not statistically different from those observed in diabetic mice at age 14 weeks. In parallel, decreased parameters of inflammation and mononuclear phagocyte and smooth muscle cell activation were observed. Conclusions-RAGE contributes not only to accelerated lesion formation in diabetic apoE-null mice but also to lesion progression. Blockade of RAGE may be a novel strategy to stabilize atherosclerosis and vascular inflammation in established diabetes.

Receptor for advanced glycation end-products (RAGE), and two of its ligands, AGE and EN-RAGEs (members of the S100/calgranulin family of pro-inflammatory cytokines), display enhanced expression in slowly resolving full-thickness excisional wounds developed in genetically diabetic db+/db+ mice. We tested the concept that blockade of RAGE, using soluble(s) RAGE, the extracellular ligand-binding domain of the receptor, would enhance wound closure in these animals. Administration of sRAGE accelerated the development of appropriately limited inflammatory cell infiltration and activation in wound foci. In parallel with accelerated wound closure at later times, blockade of RAGE suppressed levels of cytokines; tumor necrosis factor-alpha; interleukin-6; and matrix metalloproteinases-2, -3, and -9. In addition, generation of thick, well-vascularized granulation tissue was enhanced, in parallel with increased levels of platelet-derived growth factor-B and vascular endothelial growth factor. These findings identify a central role for RAGE in disordered wound healing associated with diabetes, and suggest that blockade of this receptor might represent a targeted strategy to restore effective wound repair in this disorder.