Isolation and characterization of two binding proteins for advanced glycosylation end products from bovine lung which are present on the endothelial cell surface

Identification of T1D susceptibility genes within the MHC region by combining protein interaction networks and SNP genotyping data

AIM

To develop novel methods for identifying new genes that contribute to the risk of developing type 1 diabetes within the Major Histocompatibility Complex (MHC) region on chromosome 6, independently of the known linkage disequilibrium (LD) between human leucocyte antigen (HLA)-DRB1, -DQA1, -DQB1 genes.

METHODS

We have developed a novel method that combines single nucleotide polymorphism (SNP) genotyping data with protein-protein interaction (ppi) networks to identify disease-associated network modules enriched for proteins encoded from the MHC region. Approximately 2500 SNPs located in the 4 Mb MHC region were analysed in 1000 affected offspring trios generated by the Type 1 Diabetes Genetics Consortium (T1DGC). The most associated SNP in each gene was chosen and genes were mapped to ppi networks for identification of interaction partners. The association testing and resulting interacting protein modules were statistically evaluated using permutation.

RESULTS

A total of 151 genes could be mapped to nodes within the protein interaction network and their interaction partners were identified. Five protein interaction modules reached statistical significance using this approach. The identified proteins are well known in the pathogenesis of T1D, but the modules also contain additional candidates that have been implicated in beta-cell development and diabetic complications.

CONCLUSIONS

The extensive LD within the MHC region makes it important to develop new methods for analysing genotyping data for identification of additional risk genes for T1D. Combining genetic data with knowledge about functional pathways provides new insight into mechanisms underlying T1D.

RAGE mediates oxidized LDL-induced pro-inflammatory effects and atherosclerosis in non-diabetic LDL receptor-deficient mice

AIMS

Receptor for advanced glycation end products (RAGE) plays a pivotal role in the genesis of diabetic vascular diseases. To further explore the mechanisms underlying atherosclerosis under non-diabetic conditions, we examined the effect of RAGE deficiency on atherosclerosis in hyperlipidaemic mice.

METHODS AND RESULTS

RAGE-/- mice were crossed with low-density lipoprotein receptor-deficient (LDLr-/-) mice to generate the double knockout (DKO) mice. After feeding with high-fat diet for 12 weeks, aortic atherosclerotic lesions were analysed histologically in these mice. Although there were no differences in serum levels of glucose and known RAGE ligands between DKO and LDLr-/- mice, DKO mice exhibited a significant decrease in the size and macrophage content in atherosclerotic lesions compared with LDLr-/- mice. Expression of intracellular adhesion molecule-1 and vascular cell adhesion molecule-1 in the aorta was lower in DKO mice than in LDLr-/- mice. Fluorescence-based assays revealed that oxidative stress in the vessel wall was attenuated in DKO mice than in LDLr-/- mice. Cell culture experiments revealed that RAGE mediated oxidative LDL-induced activation of p42/44 mitogen-activated protein kinases and oxidative stress in macrophages.

CONCLUSION

Oxidative LDL may be a ligand of RAGE in the hyperlipidaemic state. RAGE inactivation inhibits the atherosclerosis through reducing oxLDL-induced pro-inflammatory responses and oxidative stress in hyperlipidaemia.

Soluble receptor for advanced glycation end products (sRAGE) and endogenous secretory RAGE (esRAGE) in amniotic fluid: modulation by infection and inflammation

OBJECTIVE

The receptor for advanced glycation end products (RAGE) has been proposed to participate in the innate and adaptive immune responses. RAGE can induce production of pro-inflammatory cytokines and chemokines, as well as neutrophil chemotaxis in a manner that may be suppressed or stimulated by soluble, truncated forms of RAGE including the soluble form of RAGE (sRAGE) and endogenous secretory RAGE (esRAGE). The objective of this study was to determine whether intra-amniotic infection/inflammation (IAI) is associated with changes in the amniotic fluid concentration of sRAGE and esRAGE.

STUDY DESIGN

Amniotic fluid (AF) was retrieved from patients in the following groups: 1) mid-trimester (14-18 weeks of gestation; n=68); 2) term not in labor (n=24); 3) term in labor (n=51); 4) preterm labor and intact membranes (n=124); and 5) preterm PROM (n=80). Intra-amniotic infection and inflammation were defined as the presence of a positive amniotic fluid culture for microorganisms and an AF interleukin-6 concentration >or=2.6 ng/mL, respectively. The AF concentration of sRAGE and esRAGE were determined using specific and sensitive ELISAs which measured total immunoreactive sRAGE and esRAGE, respectively. Patients were matched for gestational age at amniocentesis to compare the AF concentration of sRAGE and esRAGE in patients with and without IAI. Non-parametric statistics were used for analysis and a P<0.05 was considered significant.

RESULTS

1) Patients at term not in labor had higher median AF concentrations of sRAGE and esRAGE than those in the mid-trimester (P<0.001 for both comparisons) and those at term in labor (P=0.03 and P=0.04, respectively); 2) patients with preterm labor and intact membranes with intra-amniotic infection/inflammation (IAI) had higher median AF concentrations of sRAGE and esRAGE than those without IAI (P=0.02 and P=0.005, respectively); 3) similarly, patients with preterm PROM with IAI had higher median AF concentrations of sRAGE and esRAGE than those without IAI (P=0.03 and P=0.02, respectively).

CONCLUSION

Intra-amniotic infection/inflammation is associated with increased amniotic fluid concentrations of sRAGE and esRAGE. Changes in the amniotic fluid concentration of sRAGE and esRAGE may represent part of the immune response to intra-amniotic infection/inflammation.

Receptor for advanced glycation end-products (RAGE) and soluble RAGE (sRAGE): cardiovascular implications

Disorders of glucose metabolism are associated with increased risk for cardiovascular disease (CVD) complications, including coronary, peripheral and cerebral arterial disease, that account for the majority of morbidity and mortality among patients with diabetes mellitus (DM). These associations between glucose and CVD risk extend continuously well below the glycaemic thresholds established for the diagnosis of diabetes, including significantly increased risk associated with impaired fasting glucose, impaired glucose tolerance, and even high normal glucose concentrations. While these epidemiological observations have established a clear association between cardiovascular disease and dysglycaemia and suggest a direct causal link, the mechanisms by which hyperglycaemia may contribute to the development, progression and instability of atherosclerosis remain unclear. A number of recent advances in the realm of vascular biology have identified several novel, plausible pathways that might link hyperglycaemia with atherosclerosis, individually or in aggregate. Key among them are the interaction between advanced glycation end-products (AGEs) and the receptor for AGEs (RAGE), which exists as a trans-membrane signalling receptor and as a circulating form, soluble RAGE (sRAGE). The purpose of this review is to provide an overview of the present understanding of RAGE and sRAGE, their plausible role linking perturbed glucose metabolism with the development, progression and instability of atherosclerosis, and the potential therapeutic implications of modulation of this biological system.

Tempering the wrath of RAGE: an emerging therapeutic strategy against diabetic complications, neurodegeneration, and inflammation

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.

Binding of S100 proteins to RAGE: an update

The Receptor for Advanced Glycation Endproducts (RAGE) is a multi-ligand receptor of the immunoglobulin family. RAGE interacts with structurally different ligands probably through the oligomerization of the receptor on the cell surface. However, the exact mechanism is unknown. Among RAGE ligands are members of the S100 protein family. S100 proteins are small calcium binding proteins with high structural homology. Several members of the family have been shown to interact with RAGE in vitro or in cell-based assays. Interestingly, many RAGE ligands appear to interact with distinct domains of the extracellular portion of RAGE and to trigger various cellular effects. In this review, we summarize the modes of S100 protein-RAGE interaction with regard to their cellular functions.

Advanced glycation end-products in senile diabetic and non-diabetic patients with cardiovascular complications

Advanced glycation end products (AGEs) have been reported to contribute to aging and cardiovascular complications. In the present study, the immunoreactivity of AGEs in human serum samples of healthy older subjects (n = 31), senile diabetic patients without cardiovascular complications (n = 33), senile diabetic patients with cardiovascular complications (n = 32), senile non-diabetic patients with cardiovascular complications (n = 30) ,and healthy young subjects (n = 31) were investigated. The patients were selected on clinical grounds from the National Institute of Cardiovascular Disease, Karachi and the Jinnah Postgraduate Medical Centre, Karachi, Pakistan. Fasting blood glucose, HbA(1C) and serum fructosamine levels were significantly (P < 0.001) increased in senile diabetic patients with and without cardiovascular complications as compared to non-diabetic senile patients with cardiovascular complications and healthy older subjects. Additionally, serum AGEs were found to be significantly (P < 0.001) increased in senile diabetic patients with cardiovascular complications and senile non-diabetic patients with cardiovascular complications, followed by diabetic patients without cardiovascular complications as compared to healthy older subjects and young control subjects. However, no significant difference was found in the senile diabetic patients without cardiovascular complications and senile non-diabetic patients with cardiovascular complications. In contrast to all four senile groups, serum AGEs were significantly (P < 0.001) lower in young control subjects. The AGEs distribution in the senile groups corroborates the hypothesis that the advanced glycation process might play a role in the development of cardiovascular complications, which are more severe in diabetic patients compared with non-diabetic patients with cardiovascular complications.

Development of Receptor for Advanced Glycation End Products–Directed Imaging of Atherosclerotic Plaque in a Murine Model of Spontaneous Atherosclerosis

Background— The receptor for advanced glycation end products (RAGE) is implicated in the development and progression of atherosclerosis. We tested the hypothesis that 99m Tc-labeled anti-RAGE F(ab′) 2 can be used as a noninvasive tool to image atherosclerotic lesions in apolipoprotein E–deficient (apoE −/− ) mice.

Methods and Results— A sequence in the V-type Ig extracellular domain of RAGE was used to develop a peptide injected into rabbits; serum was retrieved, IgG prepared and affinity-purified, and pepsin-digested into F(ab′) 2 . Thirteen 6-week apoE −/− mice were fed a Western diet. At 20 weeks, 6 were injected with 15.2�1.9 MBq (350 to 411 μCi) 99m Tc-labeled anti-RAGE F(ab′) 2 , 6 were injected with 99m Tc-labeled control nonspecific IgG F(ab′) 2 , and 1 was injected with dual-labeled 99m Tc and rhodamine anti-RAGE F(ab′) 2 . Four 20-week C57BL/6 mice were injected with 99m Tc-labeled anti-RAGE F(ab′) 2 . All mice were imaged on a high resolution mini-γ camera 4 hours after injection and euthanized. The aortic tree was dissected and photographed, and the proximal aorta was sectioned for staining after γ scintillation counting. All 6 apoE −/− mice injected with 99m Tc-labeled anti-RAGE F(ab′) 2 fragments showed focal tracer uptake in the proximal aorta (mean %ID/g, 1.98%). Disease and antibody controls showed no focal tracer uptake in the thorax (%ID/g, <1.0%). Histological sections of the proximal aorta showed American Heart Association class III lesions with lipid laden macrophages, smooth muscle cells, and positive staining for RAGE. On immunofluorescence, RAGE colocalized with macrophages.

Conclusion— These data show the feasibility of noninvasively imaging RAGE in atherosclerotic lesions in a murine model and confirm levels of RAGE expression sufficient to allow detection on in vivo imaging.

Advanced oxidation protein products activate vascular endothelial cells via a RAGE-mediated signaling pathway

The accumulation of advanced oxidation protein products (AOPPs) has been linked to vascular lesions in diabetes, chronic renal insufficiency, and atherosclerosis. However, the signaling pathway involved in AOPPs-induced endothelial cells (ECs) perturbation is unknown and was investigated. AOPPs modified human serum albumin (AOPPs-HSA) bound to the receptor for advanced glycation end products (RAGE) in a dose-dependent and saturable manner. AOPPs-HSA competitively inhibited the binding of soluble RAGE (sRAGE) with its preferential ligands advanced glycation end products (AGEs). Incubation of AOPPs, either prepared in vitro or isolated from uremic serum, with human umbilical vein ECs induced superoxide generation, activation of NAD(P)H oxidase, ERK 1/2 and p38, and nuclear translocation of NF-kappaB. Activation of signaling pathway by AOPPs-ECs interaction resulted in overexpression of VCAM-1 and ICAM-1 at both gene and protein levels. This AOPPs-triggered biochemical cascade in ECs was prevented by blocking RAGE with either anti-RAGE IgG or excess sRAGE, but was not affected by the neutralizing anti-AGEs IgG. These data suggested that AOPPs might be new ligands of endothelial RAGE. AOPPs-HSA activates vascular ECs via RAGE-mediated signals.

Reduced expression of endogenous secretory receptor for advanced glycation endproducts in hippocampal neurons of Alzheimer's disease brains

The receptor for advanced glycation endproducts (RAGE) is a cell-surface multiligand receptor, which interacts with amyloid beta (Abeta), a key protein in Alzheimer's disease (AD). RAGE-Abeta interaction is thought to be associated with pathological progression in AD. A splice variant of RAGE, endogenous secretory RAGE (esRAGE) can act as a decoy receptor for RAGE ligands that would prevent the progression of some pathologic conditions. In this study, the expression of esRAGE in the hippocampal tissues from AD brains compared with control (non-AD) was examined by immunohistochemistry and Western blot analysis. Semiquantitative immunohistochemical analysis of hippocampal tissues using esRAGE-specific antibody revealed significantly decreased immunoreactivities in pyramidal cells in CA1 and CA3 regions of AD compared with non-AD. On the other hand, immunoreactivities of astrocytes for esRAGE significantly increased in those regions. Dentate granule cells and astrocytes showed essentially invariant immunoreactivities between AD and non-AD. Changes in esRAGE immunoreactivity in CA3 neurons and astrocytes were observed from the early pathological stages. Moreover, the esRAGE-immunoreactive bands of AD samples were weaker than those of non-AD samples in Western blot analysis. The results indicate that low expression of esRAGE in the hippocampus would be associated with the development of AD.

Advanced glycation end products and their circulating receptors and level of kidney function in older community-dwelling women

BACKGROUND

Advanced glycation end products (AGEs) and the receptor for AGE (RAGE) are implicated in the pathogenesis of kidney disease; however, their relation with level of kidney function has not been well characterized.

STUDY DESIGN

Cross-sectional and prospective.

SETTING & PARTICIPANTS

548 moderately to severely disabled community-dwelling women in the Women's Health and Aging Study I in Baltimore, MD.

PREDICTOR

Serum carboxymethyl-lysine (CML), a dominant AGE; total soluble RAGE (sRAGE); and endogenous secretory RAGE (esRAGE).

OUTCOMES & MEASUREMENTS

Glomerular filtration rate (GFR), prevalent and incident decreased GFR (GFR < 60 mL/min/1.73 m(2)). Serum CML, sRAGE, and esRAGE.

RESULTS

Of 548 women, 283 (51.6%) had decreased GFR at baseline. Serum CML level was associated with decreased GFR (OR [all expressed per 1 SD], 1.98; 95% CI, 1.41 to 2.76; P < 0.001) in a multivariate logistic regression model adjusting for age, race, hemoglobin A(1c) level, and chronic diseases. Serum sRAGE and esRAGE levels (both in nanograms per milliliter) were associated with decreased GFR (OR, 1.42; 95% CI, 1.12 to 1.79; P = 0.003; OR, 1.42; 95% CI, 1.14 to 1.77; P = 0.001, respectively) in separate multivariate logistic regression models adjusting for potential confounders. Of 230 women without decreased GFR at baseline, 32 (13.9%) developed decreased GFR by the follow-up visit 12 months later. Serum CML (in micrograms per milliliter), sRAGE, and esRAGE levels at baseline were associated with the prevalence of decreased GFR 12 months later (OR, 1.80; 95% CI, 1.19 to 2.71; P = 0.005; OR, 1.32; 95% CI, 1.01 to 1.74; P = 0.05; and OR, 1.33; 95% CI, 1.01 to 1.77; P = 0.05, respectively) in separate multivariate logistic regression models adjusting for potential confounders.

LIMITATIONS

Small number of incident cases, limited follow-up, creatinine values not standardized.

CONCLUSIONS

AGE and circulating RAGE levels are independently associated with decreased GFR and seem to predict decreased GFR. AGEs are amenable to interventions because serum AGE levels can be decreased by change in dietary pattern and pharmacological treatment.

Endothelial dysfunction: from molecular mechanisms to measurement, clinical implications, and therapeutic opportunities

Endothelial dysfunction has been implicated as a key factor in the development of a wide range of cardiovascular diseases, but its definition and mechanisms vary greatly between different disease processes. This review combines evidence from cell-culture experiments, in vitro and in vivo animal models, and clinical studies to identify the variety of mechanisms involved in endothelial dysfunction in its broadest sense. Several prominent disease states, including hypertension, heart failure, and atherosclerosis, are used to illustrate the different manifestations of endothelial dysfunction and to establish its clinical implications in the context of the range of mechanisms involved in its development. The size of the literature relating to this subject precludes a comprehensive survey; this review aims to cover the key elements of endothelial dysfunction in cardiovascular disease and to highlight the importance of the process across many different conditions.

Diabetic threesome (hyperglycaemia, renal function and nutrition) and advanced glycation end products: evidence for the multiple-hit agent?

Complex chemical processes termed non-enzymic glycation that operate in vivo and similar chemical interactions between sugars and proteins that occur during thermal processing of food (known as the Maillard reaction) are one of the interesting examples of a potentially-harmful interaction between nutrition and disease. Non-enzymic glycation comprises a series of reactions between sugars, alpha-oxoaldehydes and other sugar derivatives and amino groups of amino acids, peptides and proteins leading to the formation of heterogeneous moieties collectively termed advanced glycation end products (AGE). AGE possess a wide range of chemical and biological properties and play a role in diabetes-related pathology as well as in several other diseases. Diabetes is, nevertheless, of particular interest for several reasons: (1) chronic hyperglycaemia provides the substrates for extracellular glycation as well as intracellular glycation; (2) hyperglycaemia-induced oxidative stress accelerates AGE formation in the process of glycoxidation; (3) AGE-modified proteins are subject to rapid intracellular proteolytic degradation releasing free AGE adducts into the circulation where they can bind to several pro-inflammatory receptors, especially receptor of AGE; (4) kidneys, which are principally involved in the excretion of free AGE adducts, might be damaged by diabetic nephropathy, which further enhances AGE toxicity because of diminished AGE clearance. Increased dietary intake of AGE in highly-processed foods may represent an additional exogenous metabolic burden in addition to AGE already present endogenously in subjects with diabetes. Finally, inter-individual genetic and functional variability in genes encoding enzymes and receptors involved in either the formation or the degradation of AGE could have important pathogenic, nutrigenomic and nutrigenetic consequences.

Receptor for advanced glycation end products: fundamental roles in the inflammatory response: winding the way to the pathogenesis of endothelial dysfunction and atherosclerosis

The multiligand receptor for advanced glycation end products (RAGE) of the immunoglobulin superfamily is expressed on multiple cell types implicated in the immune-inflammatory response and in atherosclerosis. Multiple studies have elucidated that ligand-RAGE interaction on cells, such as monocytes, macrophages, and endothelial cells, mediates cellular migration and upregulation of proinflammatory and prothrombotic molecules. In addition, recent studies reveal definitive rules for RAGE in effective T lymphocyte priming in vivo. RAGE ligand AGEs may be formed in diverse settings; although AGEs are especially generated in hyperglycemia, their production in settings characterized by oxidative stress and inflammation suggests that these species, in part via RAGE, may contribute to the pathogenesis of atherosclerosis. In murine models of atherosclerosis, vascular inflammation is a key factor and one which is augmented, in parallel with even further increases in RAGE ligands, in diabetic macrovessels. The findings that antagonism and genetic disruption of RAGE in atherosclerosis-susceptible mice strikingly reduces vascular inflammation and atherosclerotic lesion area and complexity link RAGE intimately to these processes and suggest that RAGE is a logical target for therapeutic intervention in aberrant inflammatory mechanisms and in atherosclerosis.

Calcitriol blunts pro-atherosclerotic parameters through NFkappaB and p38 in vitro

BACKGROUND

Disturbances in vitamin D(3) metabolism are associated with an increased cardiovascular morbidity and mortality. The aim of this study was to assess the effects of calcitriol, the active metabolite of vitamin D3, on pro-atherosclerotic parameters in human umbilical vein cord endothelial cells (HUVEC).

MATERIALS AND METHODS

Calcitriol at 10(-10) and/or 10(-9) mol L(-1) was given to cultured HUVEC which were either non-stimulated or lipopolysaccharide (LPS) stimulated. Inter cellular adhesion molecule-1 and platelet-endothelial cell adhesion molecule-1, were determined by flow cytometry analysis. The receptor of advanced glycation end product (RAGE) and interleukin-6 (IL-6) mRNA expressions by RT-PCR and IL-6 secretion by enzyme-linked immunosorbent assay (ELISA). Nuclear p65 DNA-binding activity was measured by transcription factor assay kit and the inhibitor-kappaBalpha (IkappaBalpha), phosphorylated-IkappaBalpha (P-IkappaBalpha) and phosphorylated-p38 mitogen-activated protein kinase (MAPK) protein levels were determined by Western blot. Results Calcitriol decreased the adhesion molecules expression, as well as the LPS-induced mRNA expressions of RAGE and IL-6 and LPS induced IL-6 secretion. Furthermore, the LPS induced nuclear factor kappaB (NFkappaB)-p65 DNA-binding activity was also decreased by calcitriol. IkappaBalpha levels were increased and p-IkappaBalpha levels decreased after calcitriol treatment. The increased levels of activated p38 MAPK after LPS treatment were also decreased due to pre-incubation with calcitriol.

CONCLUSIONS

The decreased NFkappaB and p38 activities followed by calcitriol treatment may explain the anti-inflammatory/atherosclerotic properties of calcitriol that were observed previously and were emphasized in this study, demonstrating the inhibitory effect of calcitriol on the pro-inflammatory parameters: adhesion molecules, RAGE and IL-6.

Receptor for advanced glycation end products (RAGE) mediates neuronal differentiation and neurite outgrowth

The receptor for advanced glycation end products (RAGE) plays a crucial role in several disease processes, such as diabetes, inflammation, and neurodegeneration. In this article we report multiple roles of RAGE in neuronal differentiation and neurite outgrowth. In retinoic-induced P19 embryonic carcinoma stem cells, silencing the expression of RAGE by RNA interference (RNAi) blocked differentiation of the P19 cells into neuronal cells and enhanced the formation of vimentin-positive fibroblast-like cells. RAGE knockdown inhibited retinoic acid-induced activation and blocked nuclear translocation of NF-kappaB, suggesting RAGE regulates activation of NF-kappaB. RAGE was also shown to be involved in survival of P19 cells during retinoic acid differentiation. Additionally, knockdown of RAGE strongly inhibited neurite outgrowth in retinoic acid-differentiated P19 cells, indicating that RAGE is required for neurite outgrowth of differentiated P19 cells. Retinoic acid-treated P19 cells activated GTPases, Rac1, and Cdc42. This activation of the GTPases was inhibited in RAGE-knockdown cells. In primary cerebellar granule neurons, the knockdown of RAGE also inhibited neurite outgrowth. In these cells, overexpression of dominant-negative forms of Rac1 and Cdc42 inhibited neurite outgrowth, whereas overexpression of constitutively active forms of Rac1 and Cdc42 in RAGE-deficient neurons restored neurite outgrowth, indicating that RAGE mediated neurite outgrowth through the Rac1/Cdc42 pathway. This is the first report on the role of RAGE in cell lines and primary neurons, as determined by RNAi knockdown.

RAGE and modulation of ischemic injury in the diabetic myocardium

OBJECTIVE

Subjects with diabetes experience an increased risk of myocardial infarction and cardiac failure compared with nondiabetic age-matched individuals. The receptor for advanced glycation end products (RAGE) is upregulated in diabetic tissues. In this study, we tested the hypothesis that RAGE affected ischemia/reperfusion (I/R) injury in the diabetic myocardium. In diabetic rat hearts, expression of RAGE and its ligands was enhanced and localized particularly to both endothelial cells and mononuclear phagocytes.

RESEARCH DESIGN AND METHODS

To specifically dissect the impact of RAGE, homozygous RAGE-null mice and transgenic (Tg) mice expressing cytoplasmic domain-deleted RAGE (DN RAGE), in which RAGE-dependent signal transduction was deficient in endothelial cells or mononuclear phagocytes, were rendered diabetic with streptozotocin. Isolated perfused hearts were subjected to I/R.

RESULTS

Diabetic RAGE-null mice were significantly protected from the adverse impact of I/R injury in the heart, as indicated by decreased release of LDH and lower glycoxidation products carboxymethyl-lysine (CML) and pentosidine, improved functional recovery, and increased ATP. In diabetic Tg mice expressing DN RAGE in endothelial cells or mononuclear phagocytes, markers of ischemic injury and CML were significantly reduced, and levels of ATP were increased in heart tissue compared with littermate diabetic controls. Furthermore, key markers of apoptosis, caspase-3 activity and cytochrome c release, were reduced in the hearts of diabetic RAGE-modified mice compared with wild-type diabetic littermates in I/R.

CONCLUSIONS

These findings demonstrate novel and key roles for RAGE in I/R injury in the diabetic heart.

Large scale isolation and purification of soluble RAGE from lung tissue

The receptor for advanced glycation end-products (RAGE) has been implicated in numerous disease processes including: atherosclerosis, diabetic nephropathy, impaired wound healing and neuropathy to name a few. Treatment of animals with a soluble isoform of the receptor (sRAGE) has been shown to prevent and even reverse many disease processes. Isolating large quantities of pure sRAGE for in vitro and in vivo studies has hindered its development as a therapeutic strategy in other RAGE mediated diseases that require long-term therapy. This article provides an improvement in both yield and detail of a previously published method to obtain 10mg of pure, endotoxin free sRAGE from 65 g of lung tissue.

Priming of neutrophil oxidative burst in diabetes requires preassembly of the NADPH oxidase

Hyperglycemia associated with diabetes mellitus results in the priming of neutrophils leading to oxidative stress that is, in part, responsible for diabetic complications. p47phox, a NADPH oxidase cytosolic subunit, is a key protein in the assembly of the NADPH oxidase leading to superoxide generation. Little is known about the priming mechanism of oxidative pathways in neutrophils of people with diabetes. In this study, the kinetics of p47phox activation was investigated by comparing neutrophils from diabetic and healthy subjects, and the mechanism of hyperglycemia-induced changes was studied by using neutrophil-like HL-60 cells as a model. In resting neutrophils from diabetic subjects, p47phox prematurely translocates to the cell membrane and preassembles with p22phox, a NADPH oxidase membrane subunit. This premature p47phox translocation and preassembly with p22phox were also observed in HL-60 cells cultured with high glucose (HG; 25 mM) and with the specific ligand for the receptor for advanced glycation end products (RAGE), S100B. Phosphorylation of ERK1/2, but not p38 MAPK, was the primary signaling pathway, as evidenced by PD98059 suppressing the translocation of p47phox in HL-60 cells incubated with HG and S100B. HL-60 cells cultured in HG and S100B exhibited a 1.8-fold increase in fMLP-induced superoxide generation compared with those cultured in normal glucose (5.5 mM). These data suggest that HG and increased AGE prime neutrophils and increase oxidative stress inducing the translocation of p47phox to the cell membrane and preassembly with p22phox by stimulating a RAGE-ERK1/2 pathway.

Mechanisms of disease: advanced glycation end-products and their receptor in inflammation and diabetes complications

Many important biochemical mechanisms are activated in the presence of high levels of glucose, which occur in diabetes. Elevated levels of glucose accelerate the formation of advanced glycation end-products (AGEs). Via their chief signaling receptor-the AGE-specific receptor (commonly abbreviated as RAGE)-AGEs generate reactive oxygen species and activate inflammatory signaling cascades. Consequently, AGEs have key roles in the pathogenesis of diabetic complications. Two discoveries have advanced our knowledge of the roles of RAGE in inflammation. First, this receptor has multiple ligands and binds not only AGEs but also proinflammatory, calcium-binding S100 proteins (also known as calgranulins) and nuclear high mobility group protein box-1. Second, RAGE is expressed on T lymphocytes, monocytes and macrophages; RAGE expression on T lymphocytes is essential for effective priming of immune responses in vivo. In this Review, we chronicle roles for RAGE in the pathogenesis of diabetic complications and develop the hypothesis that, in addition to RAGE's central role in the inflammatory response, it is critically linked to the pathogenesis of types 1 and 2 diabetes.

Involvement of advanced glycation end products in the pathogenesis of diabetic complications: the protective role of regular physical activity

Advanced glycation end products (AGEs) may play an important role in the pathogenesis of chronic diabetic complications and in the natural process of biological aging. In fact, maintained hyperglycaemia favours the formation of AGEs at the tissue level in diabetic patients, which may influence the triggering of different chronic pathologies of diabetes such as retinopathy, nephropathy, neuropathy and macro- and micro-vascular diseases. Moreover, the literature has also demonstrated the involvement of AGEs in biological aging, which may explain the accelerated process of aging in diabetic patients. The practice of regular physical activity appears to positively influence glycaemic control, particularly in type 2 diabetes mellitus patients. This occurs through the diminution of fasting glycaemia, with a consequent reduction of glycation of plasmatic components suggested by the normalisation of HbA1c plasmatic levels. This exercise-induced positive effect is evident in the blood of diabetic patients and may also reach the endothelium and connective tissues of different organs, such as the kidneys and eyes, and systems, such as the cardiovascular and nervous systems, with a local reduction of AGEs production and further deceleration of organ dysfunction. The aim of this paper was to review the literature concerning this topic to coherently describe the harmful effects of AGEs in organ dysfunction induced by diabetes in advanced age as well as the mechanisms behind the apparent protection given by the practice of regular physical activity.

Targeting of stabilized plasmid lipid particles to hepatocytes in vivo by means of coupled lactoferrin

For non-viral gene delivery we prepared stabilized plasmid lipid particles (SPLPs), to which lactoferrin (LF) was coupled as a hepatocyte specific targeting ligand. LF-SPLPs and untargeted SPLPs labeled with [3H]cholesteryloleyl-ether were injected into rats. About 87% of the LF-SPLPs were eliminated from the blood within 5 min, while 80% of untargeted SPLPs were still circulating after 2 h. Fifty-two percent of the LF-SPLPs were taken up by hepatocytes, while non-parenchymal liver cells accounted for 16% of the uptake. Despite the efficient targeting of LF-SPLPs to hepatocytes and their capacity to transfect HepG2 and COS-7 cells in vitro, expression of a reporter gene was not detected in vivo. Overall, covalent coupling of LF to SPLPs leads to massive delivery in hepatocytes after systemic administration. However, these LF-SPLPs are not able to transfect these cells in vivo.

AGEs-RAGE system mediates atrial structural remodeling in the diabetic rat

BACKGROUND

Diabetes mellitus (DM) is one of the independent risk factors for atrial fibrillation (AF). Our previous study has indicated that DM causes atrial structural remodeling with intraatrial conduction disturbances. We tested the hypothesis that the advanced glycation end products (AGEs) and the receptor for AGE (RAGE), which have been implicated in diabetic complications, are responsible for the atrial structural remodeling.

METHODS AND RESULTS

Diabetes was induced by streptozotocin (65 mg/kg i.p.) in 8-week-old female Sprague-Dawley rats. When 24 weeks old, their atria were subjected to histology, Western blotting, and immunohistochemistry. The HbA(1c) value of induced-DM rats was significantly higher than that of control rats. Histological and immunohistochemical examinations revealed that the atria of diabetic rats showed remarkable structural changes characterized by diffuse interstitial fibrosis with abundant expressions of RAGE and connective tissue growth factor (CTGF), which findings were also confirmed by Western blotting analysis. This diabetes-induced atrial fibrosis was remarkably prevented by administration of an inhibitor of AGEs formation, OPB-9195, along with reduction of CTGF expression.

CONCLUSIONS

DM promoted atrial structural remodeling via the activation of the AGEs-RAGE system with upregulating CTGF. The inhibition of AGEs formation could be a novel upstream therapeutic approach for diabetes-related atrial fibrosis.

A role for the receptor for advanced glycation end products in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a severely debilitating disease associated with a dismal prognosis. There are currently no effective therapies for IPF, thus the identification of novel therapeutic targets is greatly needed. The receptor for advanced glycation end products (RAGE) is a member of the immunoglobulin superfamily of cell surface receptors whose activation has been linked to various pathologies. In healthy adult animals, RAGE is expressed at the highest levels in the lung compared to other tissues. To investigate the hypothesis that RAGE is involved in IPF pathogenesis, we have examined its expression in two mouse models of pulmonary fibrosis and in human tissue from IPF patients. In each instance we observed a depletion of membrane RAGE and its soluble (decoy) isoform, sRAGE, in fibrotic lungs. In contrast to other diseases in which RAGE signaling promotes pathology, immunohistochemical and hydroxyproline quantification studies on aged RAGE-null mice indicate that these mice spontaneously develop pulmonary fibrosis-like alterations. Furthermore, when subjected to a model of pulmonary fibrosis, RAGE-null mice developed more severe fibrosis, as measured by hydroxyproline assay and histological scoring, than wild-type controls. Combined with data from other studies on mouse models of pulmonary fibrosis and human IPF tissues indicate that loss of RAGE contributes to IPF pathogenesis.

Nepsilon-(carboxymethyl)lysine, a major advanced glycation end product in exhaled breath condensate as a biomarker of small airway involvement in asthma

N(epsilon) -(carboxymethyl)lysine (CML) expression is selectively present in the lower respiratory tract. We compared CML levels in exhaled breath condensate (EBC) between 19 asthmatics and 10 normal control subjects and its levels before and after tiotropium therapy in 11 non-smoking asthmatics and 10 smoking asthmatics. CML levels were significantly lower in asthmatics than in normal control subjects. Moreover, low CML level was associated with small airway dysfunction. After tiotropium therapy, CML level in non-smoking asthmatics was unchanged, while that in smoking asthmatics was significantly increased. Therefore, CML level in EBC is a non-invasive biomarker for evaluating small airway involvements in asthma.

Radon-induced proteomic profile of lung tissue in rats

The aim of this study was to investigate the differential expression of proteins in lung of rats following long-term exposure to radon. The total proteins of lung tissue from Wistar rats exposed to radon for cumulative doses up to 100, 200, or 400 WLM (working level months) were isolated by two-dimensional electrophoresis (2-DE) and analyzed with ImageMaster 2D Platinum software. Comparison of the 2-DE images between the control and radon-exposed groups resulted in 14 upregulated and 9 downregulated protein spots, of which 15 were identified by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) or matrix-assisted laser desorption/ionization time-of-flight/time-of-flight mass spectrometry (MALDI-TOF/TOF-MS). The simultaneous up-expressions of RAGE and S100A6 indicated that both proteins might be applied as biomarkers for lung injury induced by long-term radon exposure.

Arguing for the motion: yes, RAGE is a receptor for advanced glycation endproducts

Advanced glycation endproducts (AGEs) are an heterogenous class of compounds formed by diverse stimuli, including hyperglycemia, oxidative stress, inflammation, renal failure, and innate aging. Recent evidence suggests that dietary sources of AGE may contribute to pathology. AGEs impart diverse effects in cells; evidence strongly suggests that crosslinking of proteins by AGEs may irrevocably alter basement membrane integrity and function. In addition, the ability of AGEs to bind to cells and activate signal transduction, thereby affecting broad properties in the cellular milieu, indicates that AGEs are not innocent bystanders in the diseases of AGEing. Here, we present evidence that receptor for AGE (RAGE) is a receptor for AGEs.

Comparison of pharmacokinetics between highly and mildly modified AGE proteins in mice

We previously demonstrated that RAW 264.7 cells (murine macrophage cell line) recognize highly modified advanced glycation end products (AGE)-bovine serum albumin (BSA) (high-AGE-BSA), which was prepared by incubating BSA with 1600 mmol/L glucose for 40 weeks. In the present study, we prepared mildly modified AGE-BSA (mild-AGE-BSA) and conducted an endocytic uptake study using human monocyte-derived macrophages and Chinese hamster ovary cells which overexpressed such scavenger receptors as CD36, SR-BI (scavenger receptor class B type-I), and LOX-1 (lectin-like oxidized low-density lipoprotein receptor-1). Although high-AGE-BSA was significantly recognized by these cells, mild-AGE-BSA did not show any ligand activity to these cells. Furthermore, when 111 In-labeled mild- or high-AGE-BSA was injected into the tail vein of male ddY mice, 111 In-high-AGE-BSA was rapidly cleared from the circulation, with about 80% of the injected 111 In-high-AGE-BSA being eliminated within 5 min. In contrast, the clearance rate of 111 In-mild-AGE-BSA was very slow, similar to the 111 In-native BSA. Taken together, our results indicate that the ligand activity of AGE-BSA to scavenger receptors and those pharmacokinetic properties depend on their rate of modification by AGEs.

Vieillissement: rôle et contrôle de la glycation

PURPOSE

Advanced glycation end-products (AGEs) accumulate in aging tissues and organs during rheumatoid arthritis and Alzheimer disease. These aging toxins are especially involved in cell alteration during diabetes mellitus (glycotoxin) and renal failure (uremic toxin). AGEs participate to the endothelial dysfunction leading to diabetic macro but also micro-angiopathy. AGEs binding to cell receptors are critical steps in the deleterious consequences of AGE excess. AGE-receptor activation altered cell and organ functions by a pro-inflammatory, pro-coagulant and pro-fibrosis factors cell response.

CURRENT KNOWLEDGE AND KEY POINTS

Non-enzymatic glycation and glycoxidation with glucose auto-oxidation represent the two main pathways resulting in AGE formation. No exclusive AGE classification is actually available. Pathophysiological mechanisms are described to explain AGE toxicity. AGEs bind to cell receptors inducing deleterious consequences such as endothelial dysfunction after endothelial RAGE activation. AGEs can also have deleterious effects through glycated protein accumulation or in situ protein glycation.

FUTURE PROSPECTS AND PROJECTS

Many in vitro or animal studies demonstrated that AGE deleterious effects can be prevented by glycation inhibitors, AGE cross-link breakers or AGE-RAGE interaction inhibition. New molecules are actually studied as new strategy to prevent or treat the deleterious effects of these aging toxins.

Expression and characterization of recombinant C-terminal biotinylated extracellular domain of human receptor for advanced glycation end products (hsRAGE) in Escherichia coli

The receptor for advanced glycation end products (RAGE) is a multi-ligand receptor involved in the development of diabetic complications. Using an Escherichia coli expression system, we have successfully expressed and purified the C-terminal biotinylated extracellular domain of human RAGE (hsRAGE), which consists of three immunoglobulin-like domains carrying three putative disulfide bonds. Over 90% of hsRAGE was expressed in soluble form in trxB and gor mutant E. coli strain Origami (DE3). Most hsRAGE was biotinylated with a C-terminal AviTag, and stably immobilized onto matrix via streptavidin without any treatment. Immobilized hsRAGE without glycosylation recognized its ligands, such as AGEs. Biotinylated hsRAGE was also able to apply in the detection of AGEs on microtitre wells like antibodies used in enzyme-linked immunoassay. SPR analysis demonstrated that the dissociation constant (K(d)) of RAGE for AGE-BSA was 23.1 nM with the two-state reaction model, and 13.5 nM with the 1:1 binding model, comparable to those of RAGEs on cell surface. These results indicate that biotinylated hsRAGE must be useful not only in analysing RAGE-ligand interactions but also detect AGEs.

Advanced glycation end products inhibit production and activity of matrix metalloproteinase-2 in human umbilical vein endothelial cells

The aim of this study was to investigate the effects of advanced glycation end products (AGEs) on the expression and activity of matrix metalloproteinases-2 (MMP-2) in human umbilical vein endothelial cells (HUVECs). Cultured HUVECs were incubated with various concentrations of AGEs-modified albumin or unmodified albumin for different time periods. Protein and gene expression of MMP-2 and the receptor for AGEs (RAGE) were measured by Western blot and reverse transcription-polymerase chain reaction, respectively. The activity of MMP-2 in the conditioned medium was measured by gelatin zymography. The AGE-modified albumin inhibited MMP-2 but increased RAGE protein and gene expression in HUVECs in a concentration- and time-dependent manner. An inhibition of MMP-2 activity was also detected in the conditioned medium of HUVECs incubated with AGEs-modified albumin. In conclusion, AGEs inhibited the expression and activity of MMP-2 in HUVECs; this may be mediated through upregulation of RAGE.

RAGE and soluble RAGE: potential therapeutic targets for cardiovascular diseases

Receptor for advanced glycation end-products (RAGE) is known to be involved in microvascular complications in diabetes. RAGE is also profoundly associated with macrovascular complications in diabetes through regulation of atherogenesis, angiogenic response, vascular injury, and inflammatory response. The potential significance of RAGE in the pathogenesis of cardiovascular disease appears not to be confined solely to nondiabetic rather than diabetic conditions. Numerous truncated forms of RAGE have recently been described, and the C-terminally truncated soluble form of RAGE has received much attention. Soluble RAGE consists of several forms, including endogenous secretory RAGE (esRAGE), which is a spliced variant of RAGE, and a shedded form derived from cell-surface RAGE. These heterogeneous forms of soluble RAGE, which carry all of the extracellular domains but are devoid of the transmembrane and intracytoplasmic domains, bind ligands including AGEs and can antagonize RAGE signaling in vitro and in vivo. ELISA systems have been developed to measure plasma esRAGE and total soluble RAGE, and the pathophysiological roles of soluble RAGE have begun to be unveiled clinically. In this review, we summarize recent findings regarding pathophysiological roles in cardiovascular disease of RAGE and soluble RAGE and discuss their potential usefulness as therapeutic targets and biomarkers for the disease.

S100A11, an dual mediator for growth regulation of human keratinocytes

We previously revealed a novel signal pathway involving S100A11 for inhibition of the growth of normal human keratinocytes (NHK) caused by high Ca(++) or transforming growth factor beta. Exposure to either agent resulted in transfer of S100A11 to nuclei, where it induced p21(WAF1). In contrast, S100A11 has been shown to be overexpressed in many human cancers. To address this apparent discrepancy, we analyzed possible new functions of S100A11, and we provide herein evidence that 1) S100A11 is actively secreted by NHK; 2) extracellular S100A11 acts on NHK to enhance the production of epidermal growth factor family proteins, resulting in growth stimulation; 3) receptor for advanced glycation end products, nuclear factor-kappaB, Akt, and cAMP response element-binding protein are involved in the S100A11-triggered signal transduction; and 4) production and secretion of S100A11 are markedly enhanced in human squamous cancer cells. These findings indicate that S100A11 plays a dual role in growth regulation of epithelial cells.

Oxidative stress, AGE, and atherosclerosis

Numerous reports on the molecular mechanism of atherogenesis indicate an increase in oxidative stress, formation of advanced glycoxidation end products (AGEs), chronic inflammation, and activated cellular response particularly in diabetic patients. To elucidate the initiating and early accelerating events this review will focus on the molecular causes of the induction of these stress factors, their interactions, and their contribution to atherogenesis. Metabolic factors such as elevated free fatty acids, high glucose levels or AGEs induce reactive oxygen species (ROS) in vascular cells leading to ongoing AGE formation and to gene induction of proinflammatory cytokines. Vice versa, numerous cytokines found elevated in obesity and diabetes may also induce oxidative stress thus a circulus vitious may be initiated and accelerated. Increased production of ROS, mainly from mitochondria and NAD(P)H oxidase, stimulates signaling cascades including protein kinase C and mitogen-activated protein kinase pathway leading to nuclear translocation of transcription factors such as nuclear factor-kappaB (NF-kappaB), activator protein 1, and specificity protein 1. Subsequently, the expression of numerous genes including cytokines is rapidly induced, which, in turn, may act on vascular cells promoting the deleterious effects. From animal models of accelerated atherosclerosis a causal role of NAD(P)H oxidase and the AGE/RAGE/NF-kappaB axis to atherogenesis is suggested. Because all factors involved form a highly interwoven network of interactions, the blockade of ROS or AGE formation at different sites may interrupt the vicious cycle. Promising candidate agents are, currently on trial. Most important to clinical practice, a number of drugs commonly used in the treatment of diabetes, hypertension, or cardiovascular disease, such as angiotensin-converting enzyme inhibitors, AT(1) receptor blockers, 3-hydroxy-3-methyl-glutaryl-CoA reductase inhibitors (statins), and thiazolidindiones have shown promising 'preventive' intracellular antioxidant activity in addition to their primary pharmacological actions.

Receptor for advanced glycation endproducts and atherosclerosis: From basic mechanisms to clinical implications

The receptor for advanced glycation endproducts (RAGE) is a member of the immunoglobulin superfamily of cell-surface molecules with a diverse repertoire of ligands. In the atherosclerotic milieu, three classes of RAGE ligands, i.e., products of non-enzymatic glycoxidation, S100 proteins and amphoterin, appear to drive receptor-mediated cellular activation and potentially, acceleration of vascular disease. The interaction of RAGE-ligands effectively modulates several steps of atherogenesis, triggering an inflammatory-proliferative process and furthermore, critically contributing to propagation of vascular perturbation, mainly in diabetes. RAGE has a circulating truncated variant isoform, soluble RAGE (sRAGE), corresponding to its extracellular domain only. By competing with cell-surface RAGE for ligand binding, sRAGE may contribute to the removal/neutralization of circulating ligands thus functioning as a decoy. The critical role of RAGE in the chronic vascular inflammation processes highlights this receptor-ligand axis as a possible and attractive candidate for therapeutic intervention to limit vascular damage and its associated clinical disorders.

Short-chain aldehyde-derived ligands for RAGE and their actions on endothelial cells

The formation and accumulation of advanced glycation endproducts (AGE) have been implicated in the development of diabetic vascular complications. Their biological responses are known to be mediated by the receptor for AGE (RAGE). Recently, AGE have been proposed to be derived not only from the classical Maillard reaction but also from other pathways of sugar autoxidation and metabolism. Here, we report the identification of glyceraldehydes (Gcer)- and glycolaldehyde (Gcol)-derived AGE as RAGE ligands and their presence in vivo. The apparent dissociation constants assessed by surface-plasmon resonance (SPR) analysis with purified human RAGE proteins were 360 nM for Gcer-AGE and 1.35 microM for Gcol-AGE. The radiolabeled-ligand binding assay with RAGE-expressing COS-7 cells revealed similar association kinetics. Competitive SPR assay with antibodies specific to the respective AGE fractions demonstrated abundant existence of both Gcer- and Gcol-AGE in RAGE affinity-purified proteins from human sera. The serum contents of Gcer- and Gcol-AGE in a diabetic patient were about twice as high as those in a healthy control. Functionally, Gcer- and Gcol-AGE upregulated the endothelial cell levels of mRNA for vascular endothelial growth factor (VEGF) and the secretion of its protein product into the culture media and DNA synthesis in a dose-dependent manner. Further, these endothelial responses were augmented by RAGE overexpression. The results suggest that RAGE engagement of Gcer- and Gcol-AGE may elicit angiogenesis through the induction of autocrine VEGF, thereby contributing to the development and progression of diabetic angiopathies.

Advanced glycation endproducts induce podocyte apoptosis by activation of the FOXO4 transcription factor

Advanced glycation endproducts (AGEs) and a receptor for AGEs (RAGE) have been linked in the pathogenesis of diabetic nephropathy. RAGE is usually localized to podocytes and is increased in diabetes. RAGE activation increases reactive oxygen species production, which mediates hyperglycemia-induced podocyte apoptosis in early diabetic nephropathy. Here, we examined the interaction of AGE and RAGE on podocyte apoptosis. When we exposed murine cultured podocytes to bovine serum albumin (BSA) that was modified by AGEs or to carboxymethyl-lysine BSA, more apoptosis was found when compared with unmodified BSA. Similarly, more podocytes underwent detachment and apoptosis when cultured on AGE-modified collagen IV than on native collagen IV. AGEs isolated from sera of patients with chronic kidney disease also caused apoptosis of podocytes. Apoptosis was diminished by small interference RNA (siRNA) for RAGE in podocytes exposed to AGE-BSA, but not to AGE-modified collagen IV. Both AGE- and carboxymethyl-lysine modified-BSA activated p38MAP kinase and inhibition of this kinase reduced the apoptotic effect of AGE-BSA. Exposure to AGE-BSA was associated with Akt dephosphorylation and FOXO4 transcriptional activation leading to an increase in the expression of an effector protein of apoptosis, Bim. siRNA for FOXO4 abolished AGE-BSA-induced apoptosis of podocytes. Our study suggests that an AGE-RAGE interaction contributes to podocyte apoptosis by activation of the FOXO4 transcription factor.

The innate immune system in allograft rejection and tolerance

As T cells alone are both necessary and sufficient for the rejection of virtually all allogeneic tissues, much of transplantation immunology has focused on cells of the adaptive immune system. During the past decade, advances in our understanding of innate responses to pathogen-associated molecules have spurred a "rediscovery" of innate immunity. Fueled by this, an increasing body of literature has emerged in which the role of the innate immune system in allograft rejection and tolerance has been examined more closely. This review will give an overview of recent studies and emerging concepts of how the cellular components of the innate immune system participate in the immune response to solid organ transplantation. These important studies highlight the complex interplay between diverse cells of the immune response and provide the basis for optimal strategies of tolerance induction.

Proteolysis of milk proteins lactosylated in model systems

Five different milk proteins (alpha-casein, beta-casein, kappa-casein, beta-lactoglobulin, and lactoferrin) and a peptide substrate were applied as substrates for the investigation of how lactosylation affected proteolysis by different proteases. After a lactosylation period of 4 days in aqueous solution, at 65 degrees C and pH 6.8 in a protein: lactose ratio of 1000 the proteins were enzymatically hydrolyzed by the three milk relevant proteases plasmin, cathepsin D, and chymosin. Lactosylation of all substrates affected hydrolysis by plasmin negatively, with the largest effect on the globular proteins. This could be explained by modification of lysine residues, being the preferred cleavage site for plasmin, but also the residue generally preferred for lactosylation. Lactosylation of the caseins and of beta-lactoglobulin did not affect subsequent cleavage by cathepsin D and chymosin significantly, but for beta-lactoglobulin, both the secondary as well as the tertiary structure were affected by lactosylation. In contrast, decreased hydrolysis by cathepsin D and chymosin was observed for lactoferrin after lactosylation. Decreased hydrolysis may be caused by a more compact tertiary structure induced by lactosylation of lactoferrin, as indicated by fluorescence spectroscopy measurements.

De-N-glycosylation or G82S mutation of RAGE sensitizes its interaction with advanced glycation endproducts

Interactions between advanced glycation endproducts (AGE) and the receptor for AGE (RAGE) have been implicated in the development of diabetic vascular complications. RAGE has two N-glycosylation sites in and near the AGE-binding domain, and G82S mutation in the second N-glycosylation motif was recently reported in human. In this study, we examined whether de-N-glycosylation or G82S of RAGE affect its ability to bind AGE and cellular response to AGE. Recombinant wild-type, de-N-glycosylation and G82S RAGE proteins were produced in COS-7 cells, purified and assayed for ligand-binding abilities. De-N-glycosylation at N81 and G82S mutation decreased Kd for glycolaldehyde-derived AGE to three orders of magnitude lower levels compared with wild-type. AGE-induced upregulation of VEGF mRNA was significantly augmented in endothelial cell-derived ECV304 cells expressing de-N-glycosylated and G82S RAGE when compared with wild-type expressor. Exposure to low glucose resulted in the appearance of RAGE proteins of deglycosylated size in wild-type RAGE-expressing cells and significantly enhanced glycolaldehyde-derived AGE-induced VEGF mRNA expression. De-N-glycosylation or G82S mutation of RAGE increases affinity for AGE ligands, and may sensitize cells or conditions with it to AGE.

Increased serum levels of advanced glycation endproducts predict total, cardiovascular and coronary mortality in women with type 2 diabetes: a population-based 18 year follow-up study

AIMS/HYPOTHESIS

AGEs, modification products formed by glycation or glycoxidation of proteins and lipids, have been linked to premature atherosclerosis in patients with diabetes. We investigated whether increased serum levels of AGEs predict total, cardiovascular (CVD) or CHD mortality in a population-based study.

SUBJECTS AND METHODS

Serum levels of AGEs were determined by immunoassay in a random sample of 874 Finnish diabetic study participants (488 men, 386 women), aged 45-64 years. These participants were followed for 18 years for total, CVD and CHD mortality.

RESULTS

Multivariate Cox regression models revealed that serum levels of AGEs were significantly associated with total (p = 0.002) and CVD mortality (p = 0.021) in women, but not in men. Serum levels of AGEs in the highest sex-specific quartile predicted all-cause (hazards ratio [HR] 1.51; 95% confidence intervals [CI], 1.14-1.99; p = 0.004), CVD (HR 1.56; 95% CI 1.12-2.19; p = 0.009), and CHD (HR 1.68; 95% CI 1.11-2.52; p = 0.013) mortality in women, even after adjustment for confounding factors, including high-sensitivity C-reactive protein.

CONCLUSIONS/INTERPRETATION

Increased serum levels of AGEs predict total and CVD mortality in women with type 2 diabetes.

Atherosclerosis in diabetes and insulin resistance

Atherosclerosis and cardiovascular disease are the major causes of morbidity and mortality in patients with diabetes and those with insulin resistance and the metabolic syndrome. Both conditions profoundly accelerate the development of atherosclerosis and increase the morbidity and mortality of cardiovascular events. The question, therefore, is what are the molecular/biochemical mechanisms that underlie the potentiating influence of diabetes, the metabolic syndrome and/or insulin resistance on the development and progression of atherosclerosis? The following review will focus on the molecular mechanism whereby hyperglycaemia and/or hyperinsulinemia either directly or indirectly promote atherosclerosis.

Antibodies against RAGE in sepsis and inflammation: implications for therapy

Many agents have been tried in the hope of providing clinical benefit in sepsis and inflammatory processes. The receptor for advanced glycation end products (RAGE) is involved in inflammation and sepsis, and anti-RAGE antibodies have been studied in models of diabetic complications, chronic inflammation and sepsis. Several characteristics of RAGE make anti-RAGE antibody an attractive treatment possibility. The pathophysiology of sepsis and inflammation is incompletely understood. The complicated nature of these processes may make new techniques, such as computer simulation and genomics, vital in understanding how to target therapies.

Advanced-glycation end products (AGEs) derived from glycated albumin suppress early beta1-adrenergic preconditioning

Ischemic heart disease in diabetic patients might be linked to the accumulation of advanced-glycation end products (AGEs). In ischemic rat hearts, expression of receptor for AGEs and its ligands is significantly enhanced and involved in cardiac ischemia/reperfusion (I/R) injury even in the absence of diabetes. It has recently been reported that diabetic human myocardium cannot be protected by preconditioning. In this context, our hypothesis was that beta1-adrenergic preconditioning might be altered in the presence of AGEs. Using an isolated non-working rat heart model, this study investigated the effect of AGEs on cardioprotection induced by transient beta1-adrenoceptor (beta1-AR) stimulation with xamoterol (Xa). After 6-hydroxydopamine (6-OHDA) pre-treatment and a 20-min stabilization period, hearts were perfused at constant pressure for 20 min, then subjected to 40 min of global ischemia and 30 min of reperfusion (I/R, Ctrl); and exposed to 0.01 microm Xa for 5 min framed with or without 15.2 microm albumin (Alb) or glycated albumin (Gly Alb). The main endpoints were the mean coronary flow (MCF), the left ventricular end-diastolic pressure (LVEDP), rate-pressure product (RPP) and creatine kinase (CK) release and necrosis area. XA induced an increase in the MCF after I/R (t = 85 min), a protective effect on the LVEDP, an improvement in RPP, a decrease of CK release during reperfusion and a reduction of necrotic area. The beneficial effects induced by Xa during reperfusion were suppressed by the administration of Gly Alb during Xa infusion, whereas Alb did not hamper Xa-induced protection. These results suggest that AGEs suppress the cardioprotection resulting from the activation of beta1-ARs and thus might contribute to cardiovascular damages seen in diabetic patients.