OBJECTIVE-Activation of the receptor for advanced glycation end products (RAGE) in diabetic vasculature is considered to be a key mediator of atherogenesis. This study examines the effects of deletion of RAGE on the development of atherosclerosis in the diabetic apoE Ϫ/Ϫ model of accelerated atherosclerosis. RESEARCH DESIGN AND METHODS-ApoEϪ/Ϫ and RAGE Ϫ/Ϫ / apoE Ϫ/Ϫ double knockout mice were rendered diabetic with streptozotocin and followed for 20 weeks, at which time plaque accumulation was assessed by en face analysis. RESULTS-Although diabetic apoEϪ/Ϫ mice showed increased plaque accumulation (14.9 Ϯ 1.7%), diabetic RAGE Ϫ/Ϫ /apoE Ϫ/Ϫ mice had significantly reduced atherosclerotic plaque area (4.9 Ϯ 0.4%) to levels not significantly different from control apoE Ϫ/Ϫ mice (4.3 Ϯ 0.4%). These beneficial effects on the vasculature were associated with attenuation of leukocyte recruitment; decreased expression of proinflammatory mediators, including the nuclear factor-B subunit p65, VCAM-1, and MCP-1; and reduced oxidative stress, as reflected by staining for nitrotyrosine and reduced expression of various NADPH oxidase subunits, gp91phox, p47phox, and rac-1. Both RAGE and RAGE ligands, including S100A8/A9, high mobility group box 1 (HMGB1), and the advanced glycation end product (AGE) carboxymethyllysine were increased in plaques from diabetic apoE Ϫ/Ϫ mice. Furthermore, the accumulation of AGEs and other ligands to RAGE was reduced in diabetic RAGECONCLUSIONS-This study provides evidence for RAGE playing a central role in the development of accelerated atherosclerosis associated with diabetes. These findings emphasize the potential utility of strategies targeting RAGE activation in the prevention and treatment of diabetic macrovascular complications. Diabetes 57:2461-2469, 2008 T he receptor for advanced glycation end products (RAGE) is a multiligand cell surface molecule belonging to the immunoglobulin superfamily (1). It is expressed as full-length, N-truncated, and C-truncated isoforms, generated in humans by alternative splicing (2). Activation of the full-length RAGE receptor has been implicated in a range of chronic diseases, including various diabetic complications and atherosclerosis (1). In particular, studies in RAGE Ϫ/Ϫ mice that carry the dominant-negative form of the receptor (2-6) and in RAGE-overexpressing mice (7) have confirmed an important role of RAGE activation in the development of diabetic nephropathy, neuropathy, and impaired angiogenesis. RAGE activation has also been implicated in the acceleration of atherosclerotic lesion formation as well as in the maintenance of proinflammatory and prothrombotic mechanisms, characteristic of diabetes-accelerated atherosclerosis (8,9). RAGE also represents an important mediator of oxidative stress in diabetes. Activation of RAGE in vitro leads to increased NADPH oxidase expression, mitochondrial oxidase activity, and downregulation of endogenous antioxidant activity (10,11). RAGE Ϫ/Ϫ mice have a suppression of neointimal proliferation after externally...

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OBJECTIVEProgressive fibrosis in the diabetic kidney is driven and sustained by a diverse range of profibrotic factors. This study examines the critical role of microRNAs (miRNAs) in the regulation of the key fibrotic mediators, TGF-β1 and TGF-β2.RESEARCH DESIGN AND METHODSRat proximal-tubular epithelial cells (NRK52E) were treated with TGF-β1 and TGF-β2 for 3 days, and expression of markers of epithelial-to-mesenchymal transition (EMT) and fibrogenesis were assessed by RT-PCR and Western blotting. The expression of miR-141 and miR-200a was also assessed, as was their role as translational repressors of TGF-β signaling. Finally, these pathways were explored in two different mouse models, representing early and advanced diabetic nephropathy.RESULTSBoth TGF-β1 and TGF-β2 induced EMT and fibrogenesis in NRK52E cells. TGF-β1 and TGF-β2 also downregulated expression of miR-200a. The importance of these changes was demonstrated by the finding that ectopic expression miR-200a downregulated smad-3 activity and the expression of matrix proteins and prevented TGF-β–dependent EMT. miR-200a also downregulated the expression of TGF-β2, via direct interaction with the 3′ untranslated region of TGF-β2. The renal expression of miR-141 and miR-200a was also reduced in mouse models representing early and advanced kidney disease.CONCLUSIONSmiR-200a and miR-141 significantly impact on the development and progression of TGF-β–dependent EMT and fibrosis in vitro and in vivo. These miRNAs appear to be intricately involved in fibrogenesis, both as downstream mediators of TGF-β signaling and as components of feedback regulation, and as such represent important new targets for the prevention of progressive kidney disease in the context of diabetes.

OBJECTIVEIncreased deposition of extracellular matrix (ECM) within the kidney is driven by profibrotic mediators including transforming growth factor-β (TGF-β) and connective tissue growth factor (CTGF). We investigated whether some of their effects may be mediated through changes in expression of certain microRNAs (miRNAs).RESEARCH DESIGN AND METHODSProximal tubular cells, primary rat mesangial cells, and human podocytes were analyzed for changes in the expression of key genes, ECM proteins, and miRNA after exposure to TGF-β (1–10 ng/μl). Tubular cells were also infected with CTGF-adenovirus. Kidneys from diabetic apoE mice were also analyzed for changes in gene expression and miRNA levels.RESULTSTGF-β treatment was associated with morphologic and phenotypic changes typical of epithelial-mesenchymal transition (EMT) including increased fibrogenesis in all renal cell types and decreased E-cadherin expression in tubular cells. TGF-β treatment also modulated the expression of certain miRNAs, including decreased expression of miR-192/215 in tubular cells, mesangial cells, which are also decreased in diabetic kidney. Ectopic expression of miR-192/215 increased E-cadherin levels via repressed translation of ZEB2 mRNA, in the presence and absence of TGF-β, as demonstrated by a ZEB2 3′-untranslated region luciferase reporter assay. However, ectopic expression of miR-192/215 did not affect the expression of matrix proteins or their induction by TGF-β. In contrast, CTGF increased miR-192/215 levels, causing a decrease in ZEB2, and consequently increased E-cadherin mRNA.CONCLUSIONSThese data demonstrate the linking role of miRNA-192/215 and ZEB2 in TGF-β/CTGF–mediated changes in E-cadherin expression. These changes appear to occur independently of augmentation of matrix protein synthesis, suggesting that a multistep EMT program is not necessary for fibrogenesis to occur.