Faculty Bibliography

The multi-ligand Receptor for Advanced Glycation Endproducts (RAGE) is expressed in podocytes and endothelial cells in the human and murine glomerulus. Although present at low levels in homeostasis, RAGE expression is increased during disease. Pharmacological antagonism of RAGE or its genetic deletion imparts marked protection from podocyte effacement, albuminuria and glomerular sclerosis in disease models. In human subjects, associations between specific genetic polymorphisms of RAGE and levels of soluble forms of RAGE are linked to disease states in the kidney. In this review, we summarize the evidence from mouse to man, linking RAGE to the pathogenesis of nephropathy

Exaggerated inflammatory responses and the resultant increases in alveolar-capillary permeability underlie the pathogenesis of acute lung injury during sepsis. This study examined the functions of aldose reductase (AR) in mediating acute lung inflammation. Transgenic mice expressing human AR (ARTg) were used to study the functions of AR since mice have low intrinsic AR activity. In a mild cecal ligation and puncture model, ARTg mice demonstrated an enhanced AR activity and a greater inflammatory response as evaluated by circulating cytokine levels, neutrophil accumulation in the lungs, and activation of Rho kinase in lung endothelial cells (ECs). Compared with WT lung cells, ARTg lung cells produced more IL-6 and showed augmented JNK activation in response to LPS stimulation ex vivo. In human neutrophils, AR activity was required for fMLP-included CD11b activation and up-regulation, respiratory burst, and shape changes. In human pulmonary microvascular ECs, AR activity was required for TNF-alpha-induced activation of the Rho kinase/MKK4/JNK pathway and IL-6 production, but not p38 activation or ICAM-1 expression. Importantly, AR activity in both human neutrophils and ECs was required for neutrophil adhesion to TNF-alpha-stimulated ECs. These data demonstrate a novel role for AR in regulating the signaling pathways leading to neutrophil-EC adhesion during acute lung inflammation

OBJECTIVE: The progression of diabetes is associated with profound endothelial dysfunction. We tested the hypothesis that cellular stress would be detectable in ECs retrieved from arterial and venous vessels of diabetic mice. METHOD: We describe a method for direct isolation of well-characterised aortic and venous ECs from mice in which cells are not subjected to propagation in culture. RESULTS: Gene expression profiling, confirmed by real-time PCR, revealed a progressive increase in markers of injury within two main gene families, EC activation and EC apoptosis, in aortic and venous ECs recovered from diabetic versus non-diabetic mice. In short-term diabetes, Il1b mRNA transcripts were higher in aortic and venous ECs of diabetic mice versus controls. In long-term diabetes, casp-1 mRNA transcripts were higher in aortic and venous ECs of diabetic mice versus controls. CONCLUSION: These data suggest that diabetes imparts diffuse endothelial perturbation in the arterial and venous endothelium

The RAGE binds multiple ligand families linked to hyperglycemia, aging, inflammation, neurodegeneration, and cancer. Activation of RAGE by its ligands stimulates diverse signaling cascades. The recent observation that the cytoplasmic domain of RAGE interacts with diaphanous or mDia-1 links RAGE signal transduction to cellular migration and activation of the Rho GTPases, cdc42 and rac-1. Pharmacological blockade of RAGE or genetic deletion of RAGE imparts significant protection in murine models of diabetes, inflammatory conditions, Alzheimer's disease, and tumors. Intriguingly, soluble forms of RAGE, including the splice variant-derived esRAGE, circulate in human plasma. Studies in human subjects suggest that sRAGE levels may be modulated by the diseases impacted by RAGE and its ligands. Thus, in addition to being a potential therapeutic target in chronic disease, monitoring of plasma sRAGE levels may provide a novel biomarker platform for tracking chronic inflammatory diseases, their severity, and response to therapeutic intervention

Recent and compelling investigation has expanded our view of the biological settings in which the products of nonenzymatic glycation and oxidation of proteins and lipids - the advanced glycation endproducts (AGEs) - form and accumulate. Beyond diabetes, natural ageing and renal failure, AGEs form in inflammation, oxidative stress and in ischaemia-reperfusion. The chief signal transduction receptor for AGEs - the receptor for AGEs (RAGE) - is a multiligand-binding member of the immunoglobulin superfamily. In addition to AGEs, RAGE binds certain members of the S100/calgranulin family, high-mobility group box 1 (HMGB1), and beta-amyloid peptide and beta-sheet fibrils. Recent studies demonstrate beneficial effects of RAGE antagonism and genetic deletion in rodent models of atherosclerosis and ischaemia-reperfusion injury in the heart and great vessels. Experimental evidence is accruing that RAGE ligand generation and release during ischaemia-reperfusion may signal through RAGE, thus suggesting that antagonism of this receptor might provide a novel form of therapeutic intervention in heart disease. However, it is plausible that innate, tissue-regenerative roles for these RAGE ligands may also impact the failing heart - perhaps through RAGE and/or distinct receptors. In this review, we focus on RAGE and the consequences of its activation in the cardiovasculature

The actors in the pathogenesis of diabetes and its complications are many and multifaceted. The effects of elevated levels of glucose are myriad; among these is the generation of advanced glycation end products (AGEs), the products of nonenzymatic glycoxidation of proteins and lipids. The finding that AGEs stimulate signal transduction cascades through the multiligand receptor RAGE unveiled novel insights into diabetes and its complications. Inextricably woven into AGE-RAGE interactions in diabetes is the engagement of the innate and adaptive immune responses. Although glucose may be the triggering stimulus to draw RAGE into diabetes pathology, consequent cellular stress results in release of proinflammatory RAGE ligands S100/calgranulins and HMGB1. We predict that once RAGE is engaged in the diabetic tissue, a vicious cycle of ligand-RAGE perturbation ensues, leading to chronic tissue injury and suppression of repair mechanisms. Targeting RAGE may be a beneficial strategy in diabetes, its complications, and untoward inflammatory responses

Aldose reductase (AR), a member of the aldo-keto reductase family, has been demonstrated to play a central role in mediating myocardial ischemia-reperfusion (I/R) injury. Recently, using transgenic mice broadly overexpressing human AR (ARTg), we demonstrated that AR is an important component of myocardial I/R injury and that inhibition of this enzyme protects heart from I/R injury (20-22, 48, 49, 56). To rigorously delineate mechanisms by which AR pathway influences myocardial ischemic injury, we investigated the role played by reactive oxygen species (ROS), antioxidant enzymes, and mitochondrial permeability transition (MPT) pore opening in hearts from ARTg or littermates [wild type (WT)] subjected to I/R. MPT pore opening after I/R was determined using mitochondrial uptake of 2-deoxyglucose ratio, while H2O2 was measured as a key indicator of ROS. Myocardial 2-deoxyglucose uptake ratio and calcium-induced swelling were significantly greater in mitochondria from ARTg mice than in WT mice. Blockade of MPT pore with cyclosphorin A during I/R reduced ischemic injury significantly in ARTg mice hearts. H2O2 measurements indicated mitochondrial ROS generation after I/R was significantly greater in ARTg mitochondria than in WT mice hearts. Furthermore, the levels of antioxidant GSH were significantly reduced in ARTg mitochondria than in WT. Resveratrol treatment or pharmacological blockade of AR significantly reduced ROS generation and MPT pore opening in mitochondria of ARTg mice hearts exposed to I/R stress. This study demonstrates that MPT pore opening is a key event by which AR pathway mediates myocardial I/R injury, and that the MPT pore opening after I/R is triggered, in part, by increases in ROS generation in ARTg mice hearts. Therefore, inhibition of AR pathway protects mitochondria and hence may be a useful adjunct for salvaging ischemic myocardium

The multiligand receptor RAGE (receptor for advanced glycation end-products) is emerging as a central mediator in the immune/inflammatory response. Epidemiological evidence accruing in the human suggests upregulation of RAGE's ligands (AGEs, S100/calgranulins, high mobility group box-1 (HMGB1), and amyloid beta-peptide and beta-sheet fibrils) and the receptor itself at sites of inflammation and in chronic diseases such as diabetes and neurodegeneration. The consequences of ligand-RAGE interaction include upregulation of molecules implicated in inflammatory responses and tissue damage, such as cytokines, adhesion molecules, and matrix metalloproteinases. In this review, we discuss the localization of RAGE and its ligand families and the biological impact of this axis in multiple cell types implicated in chronic diseases. Lastly, we consider findings from animal model studies suggesting that although tissue-damaging effects ensue from recruitment of the ligand-RAGE interaction, in distinct settings, adaptive and repair/regeneration outcomes appear to override detrimental effects of RAGE. As RAGE blockade moves further into clinical development, clarifying the biology of RAGE garners ever-increasing importance

OBJECTIVE: The receptor for advanced glycation end products (RAGE) is expressed at high levels in the lung, particularly in type 1 alveolar cells, and has been shown to amplify injury triggered by acute stress. Previous studies suggest serum concentrations of soluble RAGE increase during pulmonary reperfusion injury after transplantation. RAGE blockade has been shown to suppress hepatic and cardiac ischemia and reperfusion injury in mice. Thus we tested the hypothesis that RAGE mediates tissue-injury mechanisms in ischemia and reperfusion injury in the lung. METHODS: C57BL/6 mice were subjected to 30 minutes of pulmonary ischemia by clamping the left hilum, followed by 60 minutes of reperfusion. Lung function was assessed by means of blood gas analysis, and capillary leak was assessed by injecting fluorescein isothiocyanate-labeled albumin and comparing fluorescence in bronchial lavage fluid with that in serum. Histologic analysis of the lung was performed by a pathologist naive to the experimental conditions. RESULTS: In animals subjected to RAGE blockade, significant increases in Po(2) (108 vs 73 mm Hg, P = .0094) and more than 3-fold decrease in capillary leak Relative Fluorescent Units (RFU, 6.12 vs 1.75; P = .001) were observed. Histologic examination revealed significant injury reduction in soluble RAGE-treated animals versus control animals. RAGE knockout mice exhibited a protected phenotype when exposed to pulmonary ischemia and reperfusion. Additionally, interleukin 8 production and nuclear factor kappaB activation were increased in control mice. CONCLUSION: Abrogation of RAGE signaling attenuates pulmonary ischemia and reperfusion injury. This study suggests that RAGE might play a central role in pulmonary reperfusion injury and in transplantation and that blockade of RAGE might offer a potential target to abrogate pulmonary reperfusion injury in clinical transplantation

We investigated the role of polyol pathway enzymes aldose reductase (AR) and sorbitol dehydrogenase (SDH) in mediating injury due to ischemia-reperfusion (IR) in Type 2 diabetic BBZ rat hearts. Specifically, we investigated, (a) changes in glucose flux via cardiac AR and SDH as a function of diabetes duration, (b) ischemic injury and function after IR, (c) the effect of inhibition of AR or SDH on ischemic injury and function. Hearts isolated from BBZ rats, after 12 weeks or 48 weeks diabetes duration, and their non-diabetic littermates, were subjected to IR protocol. Myocardial function, substrate flux via AR and SDH, and tissue lactate:pyruvate (L/P) ratio (a measure of cytosolic NADH/NAD+), and lactate dehydrogenase (LDH) release (a marker of IR injury) were measured. Zopolrestat, and CP-470,711 were used to inhibit AR and SDH, respectively. Myocardial sorbitol and fructose content, and associated changes in L/P ratios were significantly higher in BBZ rats compared to non-diabetics, and increased with disease duration. Induction of IR resulted in increased ischemic injury, reduced ATP levels, increases in L/P ratio, and poor cardiac function in BBZ rat hearts, while inhibition of AR or SDH attenuated these changes and protected hearts from IR injury. These data indicate that AR and SDH are key modulators of myocardial IR injury in BBZ rat hearts and that inhibition of polyol pathway could in principle be used as a therapeutic adjunct for protection of ischemic myocardium in Type 2 diabetic patients