Related Articles

Diabetes is associated with increased prevalence, severity, and progression of periodontal disease. To test the hypothesis that activation of RAGE (Receptor for Advanced Glycation End products) contributes to the pathogenesis of diabetes-associated periodontitis, we treated diabetic mice, infected with the human periodontal pathogen Porphyromonas gingivalis, with soluble RAGE (sRAGE). sRAGE is the extracellular domain of the receptor, which binds ligand and blocks interaction with, and activation of, cell-surface RAGE. Blockade of RAGE diminished alveolar bone loss in a dose-dependent manner. Moreover, we noted decreased generation of the proinflammatory cytokines TNF-α and IL-6 in gingival tissue, as well as decreased levels of matrix metalloproteinases. Gingival AGEs were also reduced in mice treated with sRAGE, paralleling the observed suppression in alveolar bone loss. These findings link RAGE and exaggerated inflammatory responses to the pathogenesis of destructive periodontal disease in diabetes.

The receptor for advanced glycation end products (RAGE) is a member of the immunoglobulin superfamily of cell surface proteins that has been implicated as a progression factor in a number of pathologic conditions from chronic inflammation to cancer to Alzheimer’s disease. In such conditions, RAGE acts to facilitate pathogenic processes. Its secreted isoform, soluble RAGE or sRAGE, has the ability to prevent RAGE signaling by acting as a decoy. sRAGE has been used successfully in animal models of a range of diseases to antagonize RAGE-mediated pathologic processes. In humans, sRAGE results from alternative splicing of RAGE mRNA. This study was aimed to determine whether the same holds true for mouse sRAGE and, in addition, to biochemically characterize mouse sRAGE. The biochemical characteristics examined include glycosylation and disulfide patterns. In addition, sRAGE was found to bind heparin, which may mediate its distribution in the extracellular matrix and cell surfaces of tissues. Finally, our data indicated that sRAGE in the mouse is likely produced by carboxyl-terminal truncation, in contrast to the alternative splicing mechanism reported in humans.

Background

The receptor for advanced glycation end products (RAGE) is a multiligand signal transduction receptor that can initiate and perpetuate inflammation. Its soluble isoform (sRAGE) acts as a decoy receptor for RAGE ligands, and is thought to afford protection against inflammation. With the present study, we aimed at determining whether circulating sRAGE is correlated with emphysema and chronic cor pulmonale in chronic obstructive pulmonary disease (COPD).

Methods

In 200 COPD patients and 201 age- and sex-matched controls, we measured lung function by spirometry, and sRAGE by ELISA method. We also measured the plasma levels of two RAGE ligands, N-epsilon-carboxymethyl lysine and S100A12, by ELISA method. In the COPD patients, we assessed the prevalence and severity of emphysema by computed tomography (CT), and the prevalence of chronic cor pulmonale by echocardiography. Multiple quantile regression was used to assess the effects of emphysema, chronic cor pulmonale, smoking history, and comorbid conditions on the three quartiles of sRAGE.

Results

sRAGE was significantly lower (p = 0.007) in COPD patients (median 652 pg/mL, interquartile range 484 to 1076 pg/mL) than in controls (median 869 pg/mL, interquartile range 601 to 1240 pg/mL), and was correlated with the severity of emphysema (p < 0.001), the lower the level of sRAGE the greater the degree of emphysema on CT. The relationship remained statistically significant after adjusting for smoking history and comorbid conditions. In addition, sRAGE was significantly lower in COPD patients with chronic cor pulmonale than in those without (p = 0.002). Such difference remained statistically significant after adjusting for smoking history, comorbidities, and emphysema severity. There was no significant difference in the plasma levels of the two RAGE ligands between cases and controls.

Conclusions

sRAGE is significantly lower in patients with COPD than in age- and sex-matched individuals without airflow obstruction. Emphysema and chronic cor pulmonale are independent predictors of reduced sRAGE in COPD.

Objective: Advanced glycation end-products (AGEs) exert inflammatory and oxidative stress insults to produce diabetic nephropathy mainly through the receptor for AGEs (RAGE). This study aimed to assess the effect of atorvastatin on diabetic nephropathy via soluble RAGE (sRAGE) and RAGE expressions in the rat kidney. Methods: Thirty-two male Sprague-Dawley rats were divided into four groups based on the presence or absence of streptozotocin-induced diabetes with or without atorvastatin treatment (10 mg/kg for 24 weeks). Serum sRAGE and glycated albumin (GA) levels were measured with enzyme-linked immunosorbent assay (ELISA) and improved bromocresol purple methods. Renal AGEs, RAGE, endogenous secretory RAGE (esRAGE), and sRAGE were determined with reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting. Results: Mesangial expansion and microalbuminuria were aggravated in diabetic rats, and improved with atorvastatin treatment. Serum sRAGE levels were lower in diabetic than in normal rats. After atorvastatin treatment, serum and renal sRAGE levels were up-regulated, while renal RAGE expression was decreased in diabetic rats, associated with a reduction in accumulation of AGEs, though renal esRAGE mRNA expression was not significantly increased. Conclusions: Atorvastatin exerted a beneficial effect on diabetic nephropathy with reduced AGE accumulation, down-regulating RAGE expression and up-regulating sRAGE in the kidney.

BACKGROUND:

Interaction of the receptors for advanced glycation end products (RAGEs) with advanced glycation end products (AGEs) results in expression of inflammatory mediators (tumor necrosis factor-alpha [TNF-α] and soluble vascular cell adhesion molecule-1 [sVCAM-1]), activation of nuclear factor-kappa B and induction of oxidative stress – all of which have been implicated in atherosclerosis. Soluble RAGE (sRAGE) acts as a decoy for the RAGE ligand and is protective against atherosclerosis.

OBJECTIVES:

To determine whether levels of serum sRAGE are lower, and whether levels of serum AGEs, TNF-α and sVCAM-1 are higher in non-ST elevation myocardial infarction (NSTEMI) patients than in healthy control subjects; and whether sRAGE or the ratio of AGEs to sRAGE (AGEs/sRAGE) is a predictor/biomarker of NSTEMI.

METHODS:

Serum levels of sRAGE, AGEs, TNF-α and sVCAM-1 were measured in 46 men with NSTEMI and 28 age- and sex-matched control subjects. Angiography was performed in the NSTEMI patients.

RESULTS:

sRAGE levels were lower, and levels of AGEs, TNF-α, sVCAM-1 and AGEs/sRAGE were higher in NSTEMI patients than in control subjects. sRAGE levels were negatively correlated with the number of diseased coronary vessels, serum AGEs, AGEs/sRAGE, TNF-α and sVCAM-1. The sensitivity of the AGEs/sRAGE test is greater than that of the sRAGE test, while the specificity and predictive values of the sRAGE test are greater than those of the AGEs/sRAGE test for identifying NSTEMI patients.

CONCLUSIONS:

Serum levels of sRAGE were low in NSTEMI patients, and were negatively correlated with extent of lesion, inflammatory mediators, AGEs and AGEs/sRAGE. Both sRAGE and AGEs/sRAGE may serve as biomarkers/predictors for identifying NSTEMI patients.

Introduction

The receptor for advanced glycation end products (RAGE) is a member of the immunoglobulin superfamily of cell surface receptor molecules. High concentrations of three of its putative proinflammatory ligands, S100A8/A9 complex (calprotectin), S100A8, and S100A12, are found in rheumatoid arthritis (RA) serum and synovial fluid. In contrast, soluble RAGE (sRAGE) may prevent proinflammatory effects by acting as a decoy. This study evaluated the serum levels of S100A9, S100A8, S100A12 and sRAGE in RA patients, to determine their relationship to inflammation and joint and vascular damage.

Methods

Serum sRAGE, S100A9, S100A8 and S100A12 levels from 138 patients with established RA and 44 healthy controls were measured by ELISA and compared by unpaired t test. In RA patients, associations with disease activity and severity variables were analyzed by simple and multiple linear regressions.

Results

Serum S100A9, S100A8 and S100A12 levels were correlated in RA patients. S100A9 levels were associated with body mass index (BMI), and with serum levels of S100A8 and S100A12. S100A8 levels were associated with serum levels of S100A9, presence of anti-citrullinated peptide antibodies (ACPA), and rheumatoid factor (RF). S100A12 levels were associated with presence of ACPA, history of diabetes, and serum S100A9 levels. sRAGE levels were negatively associated with serum levels of C-reactive protein (CRP) and high-density lipoprotein (HDL), history of vasculitis, and the presence of the RAGE 82Ser polymorphism.

Conclusions

sRAGE and S100 proteins were associated not just with RA inflammation and autoantibody production, but also with classical vascular risk factors for end-organ damage. Consistent with its role as a RAGE decoy molecule, sRAGE had the opposite effects to S100 proteins in that S100 proteins were associated with autoantibodies and vascular risk, whereas sRAGE was associated with protection against joint and vascular damage. These data suggest that RAGE activity influences co-development of joint and vascular disease in rheumatoid arthritis patients.

The receptor for advanced glycation end products (RAGE) is a member of the immunoglobulin superfamily being expressed as a cell surface molecule and binding a variety of ligands. One of these ligands is high-mobility group box chromosomal protein 1, a potent proinflammatory cytokine, expression of which is increased in synovial tissue and in synovial fluid of rheumatoid arthritis (RA) patients. The interaction of high-mobility group box chromosomal protein 1 with cell-surface RAGE leads to an inflammatory response. In contrast, the presence of soluble RAGE (sRAGE) may abrogate cellular activation since the ligand is bound prior to interaction with the surface receptor.

Our aim was to analyse to what extent sRAGE is present in patients with chronic joint inflammation (RA) as compared with patients with non-inflammatory joint disease and with healthy subjects, and to assess whether there is an association between sRAGE levels and disease characteristics.

Matching samples of blood and synovial fluid were collected from 62 patients with RA with acute joint effusion. Blood from 45 healthy individuals, synovial fluid samples from 33 patients with non-inflammatory joint diseases and blood from six patients with non-inflammatory joint diseases were used for comparison. sRAGE levels were analysed using an ELISA.

RA patients displayed significantly decreased blood levels of sRAGE (871 ± 66 pg/ml, P < 0.0001) as compared with healthy controls (1290 ± 78 pg/ml) and with patients with non-inflammatory joint disease (1569 ± 168 pg/ml). Importantly, sRAGE levels in the synovial fluid of RA patients (379 ± 36 pg/ml) were lower than in corresponding blood samples and correlated significantly with blood sRAGE. Interestingly, a significantly higher sRAGE level was found in synovial fluid of RA patients treated with methotrexate as compared with patients without disease-modifying anti-rheumatic treatment.

We conclude that a decreased level of sRAGE in patients with RA might increase the propensity towards inflammation, whereas treatment with methotrexate counteracts this feature.

Background

Inflammation, often accompanied by oxidation, caused by advanced glycation end products (AGEs) may be quenched by the soluble receptor for AGEs (sRAGE). The present study aimed to investigate the influence of physical activity on circulating sRAGE, and the association between changes of circulating sRAGE and paraoxonase1 (PON1) activity (as an antioxidative enzyme) in a physical activity intervention study on an elderly subject cohort.

Methods

Serum sRAGE, PON1 activity and cardiometabolic variables were measured in 30 community-dwelling asymptomatic Japanese volunteers (15 men/15 women, mean age 65 years) in the pre- and post-phase of a 6-month interventional program designed to increase physical activity.

Results

The body mass index and sRAGE levels (1103 ± 496 to 1030 ± 437 ng/L, P < 0.05) were significantly reduced during the intervention period. In addition, the change of sRAGE was significantly and inversely correlated with that of PON1 activity, independent of the other cardiometabolic variables (β = - 0.511, P < 0.01).

Conclusions

This study showed a reduction of sRAGE levels, and an inverse correlation between sRAGE and PON1 activity, after the intervention study increasing physical activity on an elderly population. These findings represent a modest but significant modulation of sRAGE by this type of exercise intervention, which warranted future studies on the clinical relevance of sRAGE changes in physical activity.

Keywords

AGEs; RAGE; Paraoxonase1; Exercise; Atherosclerosis

Cigarette smoking, obesity, type 2 diabetes, and to a less extent, meat cooked at high temperatures are associated with pancreatic cancer. Cigarette smoke and foods cooked at higher temperatures are major environmental sources of advanced glycation end-products (AGEs). AGEs accumulate during hyperglycemia and elicit oxidative stress and inflammation through interaction with the receptor for AGEs (RAGE). Soluble RAGE (sRAGE) acts as an anti-inflammatory factor to neutralize AGEs and block the effects mediated by RAGE. In this study, we investigated the associations of prediagnostic measures of Nε-(carboxymethyl)-lysine (CML)-AGE and sRAGE with pancreatic cancer in a case-cohort study within a cohort of 29,133 Finnish male smokers. Serum samples and exposure information were collected at baseline (1985-1988). We measured CML-AGE, sRAGE, glucose and insulin concentrations in fasting serum from 255 incident pancreatic cancer cases that arose through April 2005 and from 485 randomly sampled subcohort participants. Weighted Cox proportional hazard regression models were used to calculate relative risks (RR) and 95% confidence intervals (CI), adjusted for age, years of smoking and body mass index. CML-AGE and sRAGE were mutually adjusted. CML-AGE levels were not associated with pancreatic cancer (fifth compared with first quintile, RR (95% CI): 0.68 (0.38-1.22), Ptrend = 0.27). In contrast, sRAGE levels were inversely associated with pancreatic cancer (fifth compared with first quintile, RR (95% CI): 0.46 (0.23-0.73), Ptrend = 0.002). Further adjustment for glucose or insulin levels did not change the observed associations. Our findings suggest that sRAGE is inversely associated with pancreatic cancer risk among Finnish male smokers.

Background

Advanced glycation end-products (AGEs) accumulate in human tissue proteins during aging, particularly under hyperglycemia conditions. AGEs induce oxidative stress and inflammation via the receptor for AGEs (RAGE) and soluble RAGE (sRAGE) can neutralize the effects mediated by RAGE/ligand engagement.

Methods

We examined the association between Nε-(carboxymethyl)lysine (CML), a prominent AGEs, and sRAGE and colorectal cancer risk in a prospective case-cohort study nested within a cancer prevention trial among 29,133 Finnish male smokers. Among study subjects who were alive without cancer five years after baseline (1985–1988), we identified 483 incident colorectal cancer cases and randomly sampled 485 subcohort participants as the comparison group with the follow-up to April 2006. Baseline serum levels of CML-AGE, sRAGE, glucose and insulin were determined. Weighted Cox proportional hazard regression models were used to calculate relative risks (RR) and 95% confidence intervals (CI).

Results

Comparing highest with lowest quintile of sRAGE, the RR for incident colorectal cancer was 0.65 (95% CI: 0.39, 1.07; P value for trend = 0.03), adjusting for age, years of smoking, body mass index, and CML-AGE. Further adjustment for serum glucose strengthened the association (RR: 0.52; 95% CI: 0.30, 0.89; P value for trend = 0.009). Highest quintile of CML-AGE was not associated with an increased risk of colorectal cancer (multivariate RR: 1.20; 95% CI: 0.64, 2.26).

Conclusion

Higher prediagnostic levels of serum sRAGE were associated with lower risk of colorectal cancer in male smokers.

Impact

This is the first epidemiologic study to implicate the receptor for advanced glycation end-products in colorectal cancer development.

Background

Advanced glycation end-products (AGEs) have been implicated in diverse pathological settings including diabetes, inflammation and acute ischemia/reperfusion injury in the heart. AGEs interact with the receptor for AGEs (RAGE) and transduce signals through activation of MAPKs and proapoptotic pathways. In the current study, adult cardiomyocytes were studied in an in vitro ischemia/reperfusion (I/R) injury model to delineate the molecular mechanisms underlying RAGE-mediated injury due to hypoxia/reoxygenation (H/R).

Methodology/Principal Findings

Cardiomyocytes isolated from adult wild-type (WT), homozygous RAGE-null (RKO), and WT mice treated with soluble RAGE (sRAGE) were subjected to hypoxia for 30 minutes alone or followed by reoxygenation for 1 hour. In specific experiments, RAGE ligand carboxymethyllysine (CML)-AGE (termed “CML” in this manuscript) was evaluated in vitro. LDH, a marker of cellular injury, was assayed in the supernatant in the presence or absence of signaling inhibitor-treated cardiomyocytes. Cardiomyocyte levels of heterogeneous AGEs were measured using ELISA. A pronounced increase in RAGE expression along with AGEs was observed in H/R vs. normoxia in WT cardiomyocytes. WT cardiomyocytes after H/R displayed increased LDH release compared to RKO or sRAGE-treated cardiomyocytes. Our results revealed significant increases in phospho-JNK in WT cardiomyocytes after H/R. In contrast, neither RKO nor sRAGE-treated cardiomyocytes exhibited increased phosphorylation of JNK after H/R stress. The impact of RAGE deletion on GSK-3β phosphorylation in the cardiomyocytes subjected to H/R revealed significantly higher levels of phospho-GSK-3β/total GSK-3β in RKO, as well as in sRAGE-treated cardiomyocytes versus WT cardiomyocytes after H/R. Further investigation established a key role for Akt, which functions upstream of GSK-3β, in modulating H/R injury in adult cardiomyocytes.

Conclusions/Significance

These data illustrate key roles for RAGE-ligand interaction in the pathogenesis of cardiomyocyte injury induced by hypoxia/reoxygenation and indicate that the effects of RAGE are mediated by JNK activation and dephosphorylation of GSK-3β. The outcome in this study lends further support to the potential use of RAGE blockade as an adjunctive therapy for protection of the ischemic heart.

Interaction of advanced glycation end products (AGEs) with the receptor for advanced AGEs (RAGE) results in activation of nuclear factor kappa-B, release of cytokines, expression of adhesion molecules, and induction of oxidative stress. Oxygen radicals are involved in plaque rupture contributing to thromboembolism, resulting in acute coronary syndrome (ACS). Thromboembolism and the direct effect of oxygen radicals on myocardial cells cause cardiac damage that results in the release of cardiac troponin-I (cTnI) and other biochemical markers. The soluble RAGE (sRAGE) compete with RAGE for binding with AGE, thus functioning as a decoy and exerting a cytoprotective effect. Low levels of serum sRAGE would allow unopposed serum AGE availability for binding with RAGE, resulting in the generation of oxygen radicals and proinflammatory molecules that have deleterious consequences and promote myocardial damage. sRAGE may stabilize atherosclerotic plaques. It is hypothesized that low levels of sRAGE are associated with high levels of serum cTnI in patients with ACS. The main objective of the study was to determine whether low levels of serum sRAGE are associated with high levels of serum cTnI in ACS patients. The serum levels of sRAGE and cTnI were measured in 36 patients with non-ST-segment elevation myocardial infarction (NSTEMI) and 30 control subjects. Serum levels of sRAGE were lower in NSTEMI patients (802.56 ± 39.32 pg/mL) as compared with control subjects (1311.43 ± 66.92 pg/mL). The levels of cTnI were higher in NSTEMI patients (2.18 ± 0.33 μg/mL) as compared with control subjects (0.012 ± 0.001 μg/mL). Serum sRAGE levels were negatively correlated with the levels of cTnI. In conclusion, the data suggest that low levels of serum sRAGE are associated with high serum levels of cTnI and that there is a negative correlation between sRAGE and cTnI.

The receptor for advanced-glycation-end-products (RAGE) has been implicated as a pro-inflammatory factor in chronic inflammatory conditions such as diabetes mellitus and rheumatoid arthritis. The aim of this study was to investigate the inhibitory effect of the soluble-RAGE (sRAGE), the extracellular domain of RAGE, on RAGE expression and NF-κB translocation in human-salivary gland-cell-lines (HSG). Cells were stimulated with agonist S100A4, fusion protein of RAGE encompassing the extracellular domain of RAGE (ex-RAGE), ex-RAGE followed by S100A4, or S100A4 followed by ex-RAGE. Our study indicates that RAGE expression was highest at 150 μg/μl of S100A4 and efficiently down-regulated by 1.8-fold (P < 0.05) when ex-RAGE was incubated prior to agonist S100A4. RAGE protein was also consistently down-regulated by 20–40% with pre-incubation of ex-RAGE. More importantly, nuclear translocation of p65 and p52 of NF-κB by S100A4 was inhibited in the presence of ex-RAGE, confirming anti-inflammatory function of ex-RAGE. In conclusion, ex-RAGE down-regulates RAGE expression and inhibits p65 and p52 activation in HSG, providing evidence that ex-RAGE functions as a “decoy” to RAGE–ligand interaction and thus potentially dampening inflammatory conditions.

OBJECTIVE

To determine the association between circulating soluble receptor for advanced glycation end products (sRAGE) and coronary atherosclerosis.

RESEARCH DESIGN AND METHODS

Using data from the Dallas Heart Study, a probability-based population sample, the association between plasma levels of sRAGE and coronary artery calcium (CAC) was assessed among 2,571 subjects with complete imaging and sRAGE data.

RESULTS

An inverse graded association was observed between sRAGE quartiles and CAC, with CAC prevalence of 28.5% in quartile 1 compared with 15.7% in quartile 4 (P < 0.0001). After multivariable adjustment, the associations between sRAGE levels in the first and second quartiles (versus fourth quartile) and CAC remained statistically significant (adjusted odds ratio 1.71 [95% CI 1.2–2.4] and 1.5 [1.0–2.1], respectively).

CONCLUSIONS

sRAGE is a novel biomarker that is inversely associated with coronary atherosclerosis. The role of sRAGE in the pathobiology of atherosclerosis and its potential prognostic and therapeutic implications warrant further investigation.

Objective

Serum levels of the soluble Receptor for Advanced Glycation End-products (sRAGE) have been associated with risk of cardiovascular disease. We hypothesized that sRAGE levels are associated with subclinical cerebrovascular disease in an ethnically diverse population.

Methods

Clinically stroke-free participants in the multi-ethnic Northern Manhattan Study (NOMAS) underwent brain MRI to quantify subclinical brain infarcts (SBI) and white matter hyperintensity volume (WMHV) (n=1102). Serum levels of sRAGE were measured by ELISA. Logistic and multiple linear regression were employed to estimate associations of sRAGE with SBI and WMHV, after adjusting for demographics and vascular risk factors.

Results

Median sRAGE levels were significantly lower in Hispanics (891.9 pg/ml; n=708) and non-Hispanic blacks (757.4 pg/ml; n=197) than in non-Hispanic whites (1120.5 pg/ml; n=170), and these differences remained after adjusting for other risk factors. Interactions were observed by race-ethnicity between sRAGE levels and MRI measurements, including for SBI in Hispanics (p=0.04) and WMHV among blacks (p=0.03). In Hispanics, increasing sRAGE levels were associated with a lower odds of SBI, with those in the upper sRAGE quartile displaying a 50% lower odds of SBI after adjusting for sociodemographic and vascular risk factors (p=0.05). Among blacks, those in the upper quartile of sRAGE had a similarly reduced increased risk of SBI (p=0.06) and greater WMHV (p=0.04).

Conclusion

Compared to whites, Hispanics and blacks have significantly lower sRAGE levels, and these levels were associated with more subclinical brain disease. Taken together, these findings suggest sRAGE levels may be significantly influence by ethnicity. Further studies of sRAGE and stroke risk, particularly in minorities, are warranted.

OBJECTIVE

Circulating levels of soluble receptor for advanced glycation end products (sRAGE) likely comprise both a secreted isoform (esRAGE) and wild-type RAGE cleaved from the cell membrane. Both sRAGE and esRAGE have been proposed as biomarkers of cardiovascular disease (CVD), but prospective data are limited. We examined the relationship of sRAGE and esRAGE to incident coronary heart disease (CHD) and stroke in type 2 diabetic patients followed for 3.9 years in a trial of atorvastatin: the Collaborative Atorvastatin Diabetes Study (CARDS).

RESEARCH DESIGN AND METHODS

We used a nested case-control design sampling all incident cases of CVD with available plasma and randomly selecting three control subjects, who were free of CVD throughout follow-up, per case. Analysis was by Cox regression with adjustment for treatment allocation and relevant covariates.

RESULTS

sRAGE and esRAGE were strongly correlated (ρ = 0.88) and were both higher in those with lower BMI (P < 0.001), higher adiponectin (P < 0.001), lower estimated glomerular filtration rate (P = 0.009), and white ethnicity (P < 0.001). Both sRAGE and esRAGE were associated with incident CHD events, independently of treatment allocation and the above factors; hazard ratio (HR) = 1.74 (95% CI 1.25–2.41; P = 0.002) for a doubling of the sRAGE level; HR = 1.45 (1.11–1.89; P = 0.006) for a doubling of the esRAGE level. There was no significant association with stroke; HR for sRAGE = 0.66 (0.38–1.14). Atorvastatin, 10 mg daily, did not alter sRAGE.

CONCLUSIONS

Higher levels of sRAGE and esRAGE are associated with incident CHD but not stroke in type 2 diabetes.

Receptor for advanced glycation end products (RAGE) plays an important role in promoting chronic inflammation with activation of NF-κB. Soluble form of RAGE (sRAGE) represents a naturally occurring competitive inhibitor of RAGE-mediated events. In a colonoscopy-based case-control study, we examined the associations of plasma levels of sRAGE, sTNF-αRI, sTNF-αRII, sIL-6R, EGF, IFNα2, G-CSF, MCP1, TNFβ, and VEGF with risk of colorectal adenoma. We prospectively identified 158 cases with colorectal adenoma and 203 polyp-free controls who were frequency-matched according to age, sex, race, and time of blood draw. Exposure information was collected using a questionnaire and fasting plasma samples were obtained before the colonoscopy. We used Luminex bead-based multiplex assays to determine level of biomarkers. Multivariate logistic regression model was used to estimate odds ratio (OR) and its 95% confidence interval (CI). Cases had insignificant lower levels of sRAGE, and higher levels of EGF and VEGF than controls. When the highest compared with the lowest category, the OR (95% CI) of colorectal adenoma was 0.55 (0.31-0.96) (P trend = 0.03) for sRAGE and 1.75 (1.05-2.93) (P trend =0.04) for VEGF, adjusting for age, smoking status, hypertension and type 2 diabetes. The inverse association between sRAGE and colorectal adenoma was seen only among those without hypertension (P interaction = 0.02). An inverse association between sRAGE and colorectal adenoma was in line with an inverse association between sRAGE and colorectal cancer previously reported. This study supported the involvement of RAGE-NF-kB related inflammatory mechanism in the formation of colorectal adenoma.

Some antihypertensive drugs have also renoprotective and anti-inflammatory properties that go beyond their effect on blood pressure. It has been suggested that microalbuminuria and glomerular filtration rate (GFR) are associated with circulating levels of the soluble form of the receptor, sRAGE (soluble receptor for advanced glycation ends-products). In the present analysis, we used data from the TALENT study to evaluate soluble receptor for advanced glycation end-products (sRAGE) plasma levels in patients with hypertension and high-cardiovascular risk-treated nifedipine and telmisartan in combination. Treatment with nifedipine-telmisartan significantly decreased mean systolic and diastolic ambulatory blood pressure and resulted in a significant increase in sRAGE plasma concentrations after 24 weeks of therapy. We concluded that in hypertensive patients with early-stage renal disease, sRAGE concentrations are not influenced by either microalbuminuria or GFR. Long-term treatment with a combination of nifedipine-telmisartan may have a beneficial effect increasing sRAGE plasma levels, thus exerting an atheroprotective and anti-inflammatory activity.

The receptor for advanced glycation endproducts (RAGE) interacts with distinct ligand families linked to the inflammatory response. Studies in animal models suggest that RAGE is upregulated in the inflamed joint and that blockade of the receptor, using a ligand decoy soluble form of RAGE (sRAGE), attenuates joint inflammation and expression of inflammatory and tissue-destructive mediators. In this issue of Arthritis Research & Therapy, Rille Pullerits and colleagues reported that plasma levels of sRAGE were reduced in subjects with rheumatoid arthritis compared with healthy controls or subjects with non-inflammatory joint disease. These findings suggest the possibility that levels of sRAGE might be a biomarker of inflammation. Not resolved by these studies, however, is the intriguing possibility that endogenously higher levels of sRAGE might be linked to a lower incidence of arthritis or to the extent of inflammation. Nevertheless, although 'cause or effect' relationships may not be established in this report, fascinating insights into RAGE, inflammation and human arthritis emerge from these studies.

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 10 mg of pure, endotoxin free sRAGE from 65 g of lung tissue.

Advanced glycation end products (AGEs) and their receptor (RAGE) play an important role in accelerated atherosclerosis in diabetes. We have recently found that the soluble form of RAGE (sRAGE) levels are significantly higher in type 2 diabetic patients than in nondiabetic subjects and positively associated with the presence of coronary artery disease in diabetes. In this study, we examined whether serum levels of sRAGE correlated with inflammatory biomarkers in patients with type 2 diabetes. Eighty-six Japanese type 2 diabetic patients (36 men and 50 women, mean age 68.4 ± 9.6 years) underwent a complete history and physical examination, determination of blood chemistries, sRAGE, monocyte chemotactic protein-1 (MCP-1), adiponectin, tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6). Univariate regression analysis showed that serum levels of sRAGE positively correlated with alanine aminotransferase (ALT) (r = 0.437, P = 0.0001), MCP-1 (r = 0.359, P = 0.001), TNF-α (r = 0.291, P = 0.006), and hyperlipidemia medication (r = 0.218, P = 0.044). After multiple regression analyses, ALT (P < 0.0001), MCP-1 (P = 0.007), and TNF-α (P = 0.023) remained significant. The present study demonstrates for the first time that serum levels of sRAGE are positively associated with MCP-1 and TNF-α levels in type 2 diabetic patients. These observations suggest the possibility that sRAGE level may become a novel biomarker of vascular inflammation in type 2 diabetic patients.

Background and Purpose

Low levels of soluble receptor for advanced glycation end products (sRAGE) are associated with three conventional vascular risk factors (3Fs: diabetes, hypertension, and hypercholesterolemia), nondiabetic coronary artery disease, and Alzheimer's disease. However, the association between sRAGE and acute ischemic stroke (AS), especially AS without a source of cardioembolism, has not yet been established.

Methods

Patients with AS without a source of cardioembolism (n=259) and age-matched controls (n=300) were grouped according to the presence of 3Fs: AS patients with and without 3Fs (3Fs+ AS and 3Fs- AS, respectively) and controls with and without 3Fs (3Fs+ control and 3Fs- control, respectively). Levels of sRAGE were analyzed among the four groups.

Results

sRAGE was significantly higher in the controls than in the AS patients (855 pg/mL vs. 690 pg/mL, p<0.01). sRAGE was significantly higher in 3Fs- controls (996 pg/mL, p<0.05) than in 3Fs+ controls (721 pg/mL), and in AS group regardless of the 3Fs (629 pg/mL in 3Fs- and 705 pg/mL in 3Fs+). The lowest tertile of sRAGE was associated with an increased risk of AS in the 3Fs- group [adjusted odds ratio (OR) 4.0, 95% confidence interval (CI) 1.6-10.3, p<0.01] but not in the 3Fs+ group. The level of sRAGE was also correlated with neurological severity in the 3Fs- AS group (r=-0.32, p<0.05) but not in the 3Fs+ AS group.

Conclusions

Low plasma levels of sRAGE is a potential biomarker for the risk of AS and may reflect the neurological severity of the condition, especially in subjects without identifiable conventional risk factors.

Background

Total circulating soluble receptor for advanced glycation endproducts (sRAGE) and a more defined endogenous secretory splice variant of the receptor (esRAGE) were shown to be associated with different markers of cardiovascular risk in patients with diabetes. Since previous data were partly divergent, the aim of this study was to compare sRAGE and esRAGE in a head-to-head analysis in patients with type 2 diabetes (T2DM) with albuminuria.

Methods

sRAGE and esRAGE were studied in plasma of 110 T2DM patients using enzyme-linked immunosorbant assays (ELISA) detecting either sRAGE or esRAGE only. Both sRAGE and esRAGE were compared with regard to applicability as markers for vascular disease and glucose control in T2DM.

Results

In bivariate analysis, sRAGE correlated with age (R = 0.22, p = 0.02) and the 24 hour albumin excretion rate (R = 0.18, p = 0.05), while esRAGE correlated positively with age only (R = 0.23, p = 0.02). In contrast to previous reports, neither sRAGE nor esRAGE correlated with glucose control or intima-media-thickness (IMT) as a predictor of macrovascular disease. In multivariate regression models, the associations between sRAGE and albuminuria as well as esRAGE and age were shown to be independent of glucose control, diabetes duration, body-mass index, glomerular filtration rate, blood pressure and gender.

Conclusion

This is the first study comparing sRAGE and esRAGE as markers of vascular complications in patients with T2DM. sRAGE but not esRAGE is independently associated with albuminuria in these patients while neither sRAGE nor esRAGE are associated with markers of glucose control or macrovascular disease.

Idiopathic pulmonary fibrosis (IPF) is a progressive disease with poor survival. The identification of therapeutic targets is essential to improving outcomes. Previous studies found that expression of the receptor for advanced glycation end products (RAGE) in the lung is significantly decreased in human IPF lungs and in two animal models of pulmonary fibrosis. In addition, RAGE-null mice spontaneously develop pulmonary fibrosis with age and more severe fibrosis when challenged with asbestos. In contrast to the findings that the lack of RAGE enhanced pulmonary fibrosis, He et al. found that RAGE null mice were protected from bleomycin-induced fibrosis and suggested the effect was due to a lack of HMGB1 induced RAGE signaling. The current study further tests this hypothesis by blocking RAGE signaling via administration of soluble RAGE, a decoy receptor, to determine if this will also protect against pulmonary fibrosis. Wild-type, RAGE+/-, and RAGE-/- mice were treated with bleomycin and assessed for fibrosis. Wild-type mice were also treated with exogenous soluble RAGE or vehicle control. In addition, in vitro studies with primary alveolar epithelial cells from wild-type and RAGE null mice were used to investigate the effect of RAGE on cell viability and migration in response to injury. A lack of RAGE was found to be protective against bleomycin injury in both in vivo and in vitro studies. However, soluble RAGE administration was unable to ameliorate fibrosis. This study confirms paradoxical responses to two different models of pulmonary fibrosis and suggests a further role for RAGE in cellular migration.

In the kidney, the receptor for advanced glycation end products (RAGE) is principally expressed in the podocyte at low levels, but is upregulated in both human and mouse glomerular diseases. Because podocyte injury is central to proteinuric states, such as the nephrotic syndrome, the murine adriamycin nephrosis model was used to explore the role of RAGE in podocyte damage. In this model, administration of the anthracycline antibiotic adriamycin provokes severe podocyte stress and glomerulosclerosis. In contrast to wild-type animals, adriamycin-treated RAGE-null mice were significantly protected from effacement of the podocyte foot processes, albuminuria, and glomerulosclerosis. Administration of adriamycin induced rapid generation of RAGE ligands, and treatment with soluble RAGE protected against podocyte injury and glomerulosclerosis. In vitro, incubation of RAGE-expressing murine podocytes with adriamycin stimulated AGE formation, and treatment with RAGE ligands rapidly activated nicotinamide adenine dinucleotide phosphate (NADPH)-oxidase, via p44/p42 MAP kinase signaling, and upregulated pro-fibrotic growth factors. These data suggest that RAGE may contribute to the pathogenesis of podocyte injury in sclerosing glomerulopathies such as focal segmental glomerulosclerosis.