Alarmins and Related Molecules in Elective Surgery

Surgery is associated with alterations of alarmins' and related molecules' levels. The aim of this study was to investigate which biomarkers are most involved in surgery. The studied group consisted of 58 patients with inguinal or umbilical hernia or cholecystolithiasis and 21 healthy controls for compa-rison. We also added seven acute patients with appendicitis, cholecystitis and incarcerated hernia. Serum concentrations of soluble receptor of advanced glycation end-products (sRAGE), extracellular newly identified receptor for advanced glycation end-products binding protein (EN-RAGE), calprotectin, high mobility group box 1 (HMGB1) and interleukin 6 (IL-6) were analysed by ELISA before and after surgery. Preoperative concentrations of calprotectin were significantly decreased while concentrations of sRAGE were significantly increased in patients compared to controls; the concentrations of EN-RAGE and HMGB1 did not differ significantly. IL-6 levels were undetectable in elective patients preoperatively and in controls. Postoperatively, there was a significant increase of EN-RAGE, calprotectin, HMGB1, and IL-6 and a significant decrease of sRAGE compared to preoperative levels. In acute patients, all tested molecules except for sRAGE were significantly increased preoperatively, and sRAGE was significantly decreased. In contrast, after surgery, we could observe a further increase in IL-6; the other biomarkers did not differ significantly. We can conclude that the concentrations of all tested biomarkers are significantly influenced by elective surgery. The postoperative levels of all tested molecules increase except for sRAGE, whose level is significantly decreased after surgery. In acute states, these molecules are already increased, and the influence of surgery is, apart from IL-6, insignificant.

S100A12 in renal and cardiovascular diseases

Expression of S100A12, a small calcium-binding protein, by neutrophils and monocytes/macrophages induces proinflammatory responses via ligation with the receptor for advanced glycation end-products (RAGE) and subsequent activation of intracellular signal transduction pathways such as the nuclear factor (NF)-κB pathway. Although S100A12 has been demonstrated to be a useful biomarker during inflammatory conditions, its precise role in the pathogenesis of renal and cardiovascular diseases has not been fully understood. Recently, several studies have employed S100A12 transgenic mice to investigate its pathological effects. Further studies using these models are required before we can translate these findings to human diseases such as renal and cardiovascular diseases.

Associations between Soluble Receptor for Advanced Glycation End Products (sRAGE) and S100A12 (EN-RAGE) with Mortality in Long-term Hemodialysis Patients

Hemodialysis (HD) patients experience vascular calcification, ultimately leading to high mortality rates. Previously, we reported associations between soluble receptor for advanced glycation end products (sRAGEs) and extracellular newly identified RAGE-binding protein S100A12 (EN-RAGE) and vascular calcification. Here, we extended our observations, investigating whether these biomarkers may be useful for predicting cardiovascular morbidity and mortality in these subjects. Thus, we evaluated the relationship between sRAGE and S100A12 and mortality in long-term HD patients. This was a prospective observational cohort study in 199 HD patients from an extended analysis of our previous study. Plasma sRAGE, S100A12, comorbidities, and other traditional risk factors were investigated. The cumulative incidences for death using Cox proportional hazards regression were evaluated in multivariable analyses. The observation period was 44 months. During the observation period, 27 (13.6%) patients died. Univariate analysis demonstrated that S100A12 was correlated with diabetes (P = 0.040) and high-sensitivity C-reactive protein (hsCRP) (P = 0.006). In multivariable analyses, plasma sRAGE (hazard ratio [HR] = 1.155; 95% confidence interval [CI] = 0.612-2.183; P = 0.656) and S100A12 (HR = 0.960; 95% CI = 0.566-1.630; P = 0.881) were not associated with mortality in HD patients, although traditional predictors of mortality, including age, history of cardiovascular diseases (CVDs), and serum levels of albumin and hsCRP were related to mortality. Powerful predictors of mortality were age, CVD, and albumin levels. Plasma sRAGE and S100A12 may be weak surrogate markers for predicting all-cause mortality in patients undergoing HD, although S100A12 was partly related to diabetes and inflammation.

Elevated Circulating S100A12 Associates with Vascular Disease and Worse Clinical Outcome in Peritoneal Dialysis Patients

♦

BACKGROUND

The pro-inflammatory receptor of advanced glycation end-products (RAGE)-ligand S100A12 is thought to promote, whereas anti-inflammatory soluble RAGE (sRAGE) may protect against, vascular disease. We evaluated circulating S100A12 and sRAGE in relation to vascular disease, inflammation, nutritional status, and mortality risk in peritoneal dialysis (PD) patients. ♦

METHODS

Plasma S100A12 and sRAGE, biomarkers of inflammation, nutritional status, and comorbidities were analyzed in 82 prevalent PD patients (median age 65 years; 70% men; median vintage 12 months) and, for comparative analysis, also in 190 hemodialysis (HD) patients and 50 control subjects. Associations between mortality risk and concentrations of S100A12 and sRAGE were assessed in PD and HD patients after a mean follow-up period of 31 and 29 months respectively using a competing risk Cox regression model. ♦

RESULTS

In PD patients, median S100A12, sRAGE and S100A12/sRAGE were markedly higher than in controls, and S100A12 was 1.9 times higher and median sRAGE 14% lower compared with HD patients. In PD patients, S100A12 associated with C-reactive protein (ρ = 0.46; p < 0.001) and interleukin-6 (ρ = 0.38; p < 0.001), and, negatively, with s-albumin (ρ = -0.27; p < 0.05) whereas sRAGE associated negatively with body mass index (ρ = -0.37; p < 0.001), fat body mass index (ρ = -0.34; p < 0.001), and lean body mass index (ρ = -0.36; p < 0.001). Peripheral vascular disease or cerebrovascular disease (PCVD) was present in 28% of PD patients and, in multivariate analysis, associated mainly with high S100A12 (odds ratio [OR] 3.52, p = 0.04). In both PD and HD patients, the highest versus other tertiles of S100A12 associated with increased mortality. In contrast, sRAGE did not associate with PCVD or mortality in PD and HD patients. ♦

CONCLUSIONS

Plasma S100A12 and sRAGE are markedly elevated in PD patients. Soluble RAGE was inversely related to body mass indices while S100A12 associated with increased inflammation, PCVD, and mortality, suggesting that S100A12 may identify PD patients at high risk for vascular disease and increased mortality.

Do elevated plasma S100A12 levels predict atherosclerosis in peritoneal dialysis patients?

AIM

Atherosclerotic cardiovascular disease is one of the major causes of mortality and morbidity in peritoneal dialysis (PD) patients. S100A12 is an endogenous receptor ligand of advanced glycation end-products. It was shown to contribute to the development of atherosclerosis in animal models. The aim of this study was to evaluate the relationship between S100A12 levels and carotid atherosclerosis in PD patients.

METHODS

A cross-sectional study was performed in 56 PD patients and 20 control subjects. Plasma S100A12 levels were measured from all participants beside routine laboratory evaluation. All subjects underwent high-resolution B-mode ultrasonography to determine carotid intima media thickness (CIMT). S100A12 levels were compared between patient and control groups. Correlation analyses of S100A12 with other laboratory values and CIMT were also performed.

RESULTS

Plasma S100A12 levels were higher in PD patients compared with control subjects (129.5 ± 167.2 ng/mL vs. 48.5 ± 30.3 ng/mL, respectively, p < 0.001). In the patient group, CIMT was found to be positively correlated with age (r = 0.354; p = 0.007), CRP level (r = 0.269; p = 0.045), and S100A12 (r = 0.293; p = 0.028) level while it was found to be negatively correlated with hemoglobin concentration (r = -0.264; p = 0.049). In the linear regression analysis, the model, including CRP, S100A12, age, and Hgb, was found to be significant (F: 4.177, p: 0.005). When the parameters are analyzed age and S100A12 were found to be independent determinants of CIMT (β = 0.308, p = 0.018 and β = 0.248, p = 0.049, respectively).

CONCLUSIONS

This study suggests that an elevated plasma S100A12 level was closely associated with atherosclerosis. With aging elevated plasma S100A12 may show a powerful proatherogenic potential in patients undergoing PD.

Low glucose degradation product peritoneal dialysis regimen is associated with lower plasma EN-RAGE and HMGB-1 proinflammatory ligands of receptor for advanced glycation end products

Intraperitoneal glucose degradation products (GDP) load influences systemic advanced glycation end products (AGEs) but the effects on soluble receptor for AGEs (s-RAGE) and its proinflammatory ligands: extracellular newly identified receptor for advanced glycation end-products binding protein(EN-RAGE) and high mobility group box-1 protein (HMGB-1) are unknown. We aimed to compare plasma and peritoneal s-RAGE, EN-RAGE and HMGB-1 between three peritoneal dialysis (PD) prescription regimens with different intraperitoneal GDP loads. High GDP load (glucose-lactate PD fluid, D; N = 8) was compared with a low (glucose-bicarbonate/lactate with icodextrin for overnight dwell, E; N = 9) and a very low GDP load (glucose-bicarbonate/lactate, P; N = 16). D group demonstrated higher plasma EN-RAGE, 77.8 ng/mL, vs. both E, 11.2, P < 0.001 and P, 27.0, P < 0.001 as well as higher plasma HMGB-1, 2.2 ng/mL vs. both E, 1.1, P < 0.01 and P, 1.5, P < 0.01. Plasma s-RAGE, which did not differ between D, E and P, correlated with its effluent levels. Patients with faster peritoneal transport (D/Pcr > 0.65) tended to have higher plasma s-RAGE compared to slow transporters (2300 vs. 1762 pg/mL, P = 0.056). Peritoneal clearance of s-RAGE and EN-RAGE was higher with E compared to both D and P (P < 0.001 resp. P < 0.01). Subgroup of PD patients with CRP above median demonstrated higher plasma HMGB-1 and EN-RAGE, P < 0.05 for both. A lower intraperitoneal GDP load is associated with decreased plasma levels of EN-RAGE and HMGB-1. Peritoneal transport, microinflammation and the capability of icodextrin to increase peritoneal clearance of middle molecular weight substances might also exert an effect on plasma s-RAGE and its proinflammatory ligands levels.

Circulating levels of soluble receptor for advanced glycation end product are inversely associated with vascular calcification in patients on haemodialysis independent of S100A12 (EN-RAGE) levels

AIM

The receptor for advanced glycation end products (RAGE) has emerged as a central regulator of vascular inflammation and atherosclerosis. Soluble RAGE (sRAGE) has an anti-inflammatory effect by quenching ligands for RAGE. On the other hand, extracellular RAGE-binding protein S100A12 (EN-RAGE) shows a pro-inflammatory effect in a way, but may play pleiotropic roles related to inflammatory process. Therefore, we determined the levels of sRAGE and S100A12 in haemodialysis (HD) patients and evaluated their relationship with vascular calcification.

METHODS

We performed a cross-sectional study with 199 HD patients. Plain X-ray images of the lateral lumbar spine from all subjects were studied to calculate semiquantitative vascular calcification scores (VCS), as described by Kauppila. Commercially available enzyme linked immunosorbent assay (ELISA) kits were used to quantify the serum concentration of sRAGE and S100A12.

RESULTS

The patients were 57.1 ± 13.7 years of age; 54.3% were male, 49.2% were diabetic, and 36.2% had a history of cardiovascular disease. In a univariate analysis, serum sRAGE was negatively associated with VCS (log sRAGE, r=-0.208, P=0.003), whereas S100A12 showed a positive tendency (log S100A12, r=0.235, P=0.085). Even after adjustments for confounding risk factors, sRAGE was independently associated with VCS (β=-1.679, P=0.002).

CONCLUSION

This study demonstrated that the circulating sRAGE level was inversely associated with VCS in HD patients independent of the S100A12 level and the severity of systemic inflammation.

The axis AGE-RAGE-soluble RAGE and oxidative stress in chronic kidney disease

Chronic kidney disease (CKD) has been shown to be associated with high oxidative stress and cardiovascular disease. In this chapter our focus will be on the role of advanced glycation end products (AGE) and their receptor, RAGE in CKD progression and their role on cardiovascular complications. We provide a succinct, yet comprehensive summary of the current knowledge, the challenges and the future therapeutic avenues that are stemming out from novel recent findings. We first briefly review glycation and AGE formation and the role of the kidney in their metabolism. Next, we focus on the RAGE, its signaling and role in oxidative stress. We address the possible role of soluble RAGEs as decoys and the controversy regarding this issue. We then provide the latest information on the specific role of both AGE and RAGE in inflammation and perpetuation of kidney damage in diabetes and in CKD without diabetes, which is the main purpose of the review. Finally, we offer an update on new avenues to target the AGE-RAGE axis in CKD.

The AGE-RAGE pathway and its relation to cardiovascular disease in patients with chronic kidney disease

Chronic kidney disease (CKD) carries an unequivocal high risk for cardiovascular disease (CVD) contributing to high morbimortality; however, the underlying reasons are not fully known. Among mechanisms involved in the pathophysiology of CVD, chronic overstimulation of the advanced glycation end-products (AGE)-receptor for AGE (RAGE) pathway is likely a major contributor in patients with CKD. This review describes briefly some of the components of this pathway, highlighting especially differences between circulating AGE and tissue AGE and how activation of the AGE-RAGE pathway may promote CVD in CKD.

Placental growth factor, pregnancy-associated plasma protein-A, soluble receptor for advanced glycation end products, extracellular newly identified receptor for receptor for advanced glycation end products binding protein and high mobility group box 1 levels in patients with acute kidney injury: a cross sectional study

BACKGROUND

Placental growth factor (PlGF), pregnancy-associated plasma protein-A (PAPP-A), soluble receptor for advanced glycation end products (sRAGE), extracellular newly identified receptor for RAGE binding protein (EN-RAGE) and high mobility group box 1 (HMGB-1) are novel biomarkers in chronic kidney disease (CKD). However, their clinical significance in acute kidney injury (AKI) is unknown. The aim of this cross-sectional study was to determine whether selected biomarkers are changed in AKI patients.

METHODS

Serum PlGF, PAPP-A, sRAGE, EN-RAGE and HMGB-1 levels were assessed in 40 patients with AKI, 42 CKD 5 patients, 31 haemodialysis patients (HD) and 39 age-matched healthy controls.

RESULTS

PAPP-A was elevated in AKI (20.6 ± 16.9 mIU/L) compared with controls (9.1 ± 2.3 mIU/L, p < 0.001). PlGF was not increased in AKI (11.7 ± 7.4 pg/mL) versus controls (8.5 ± 2.4 pg/mL, n.s.), as well as sRAGE was not elevated in AKI (2400 ± 1400 pg/mL) compared with controls (1760 ± 730 pg/mL, n.s), but was lower compared with CKD 5 (3200 ± 1500 pg/mL, p < 0.05); EN-RAGE was elevated in AKI 480 ± 450 ng/mL in comparison with controls (60 ± 62 ng/mL), CKD 5 (190 ± 120 ng/mL), and HD (120 ± 100 ng/mL), all p < 0.001. Similarly, HMGB-1 was increased in AKI (5.8 ± 7.5 ng/mL) versus controls (1.7 ± 1.4 ng/mL), CKD 5 (3.2 ± 3.1 ng/mL) and HD (2.5 ± 2.1 ng/mL), all p < 0.001.In AKI group, in multivariate regression analysis: PAPP-A levels were associated with transferrin (p <0.001), negatively with albumin (p < 0.01) and prealbumin (p < 0.05); PlGF levels were associated with C--reactive protein (p < 0.001). EN-RAGE levels were associated with ferritin (p < 0.01) and orosomucoid (p = 0.02), and HMGB-1 levels with leukocyte count (p < 0.01) and negatively with proteinuria (p = 0.02).

CONCLUSIONS

In AKI patients, PAPP-A, EN-RAGE and HMGB1 are elevated, but sRAGE and PlGF are not increased. Whereas PAPP-A correlates with markers of nutrition; PlGF, EN-RAGE and HMGB-1 are related to inflammatory parameters.

Soluble form of receptor for advanced glycation end-products (sRAGE): do sRAGE ligands or anti-sRAGE auto-antibodies interfere with sRAGE quantification?

Background

The soluble form of the receptor for advanced glycation end-products (sRAGE) has been studied in various diseases. It is not clear why sRAGE levels vary between studies, with controversial results. What also remains to be determined is whether receptor for advanced glycation end-products (RAGE) ligands could affect sRAGE assessment by epitope masking. Recently described anti-sRAGE autoantibodies may play an interfering role. The aim of this study was therefore to investigate the influence of RAGE ligands and anti-sRAGE autoantibodies on sRAGE quantification.

Methods

The RAGE ligands carboxymethyllysine (CML; AGEs with a high affinity for RAGE), S100 proteins, high-mobility group protein B1 (HMGB1) and β-amyloid peptide (aβ) were tested by enzyme-linked immunosorbent assay (ELISA) with recombinant sRAGE (rHu-sRAGE) or serum from healthy controls. Using ELISA, anti-sRAGE autoantibodies (IgGs) were identified in haemodialysis (HD) patients, then purified and incubated with rHu-sRAGE or serum to investigate their effects on sRAGE levels.

Results

RAGE ligands, either alone at three different concentrations (CML was also tested at different glycation levels) or a mixture of all these ligands, did not affect sRAGE levels when incubated with rHu-sRAGE or control serum. Compared with healthy controls, HD patients had higher levels of sRAGE ( P < 0.001) and anti-sRAGE IgGs ( P < 0.05). However, incubation of rHu-sRAGE with purified IgGs from HD patients had no effect on sRAGE quantification.

Conclusions

RAGE ligands or anti-sRAGE autoantibodies did not interfere with sRAGE quantification. Further studies are required to elucidate the variability in sRAGE levels reported in the literature and to define the potential of sRAGE for use as a reliable biomarker.

EN-RAGE (extracellular newly identified receptor for advanced glycation end-products binding protein) and mortality of long-term hemodialysis patients: A prospective observational cohort study

OBJECTIVES

EN-RAGE is extracellular newly identified receptor for advanced glycation end-products binding protein playing a role in inflammation. The aim was to test the relationship of EN-RAGE to prognosis of long-term hemodialysis patients (HD).

DESIGN AND METHODS

This is a prospective observational cohort study in 261 HD patients followed up for five years. Laboratory parameters were measured at the beginning of the study.

RESULTS

EN-RAGE was slightly but unsignificantly increased in HD patients compared with healthy controls and correlated significantly with inflammatory markers. Univariate Cox analysis demonstrated EN-RAGE as a significant predictor for mortality due to infection (HR (95%CI): 1.305 (1.063-1.602), per standard deviation, p=0.01), but this significance disappeared in multivariate Cox analysis when CRP was included into the model.

CONCLUSIONS

Our study demonstrates EN-RAGE as an inflammatory biomarker. It is related to mortality of HD patients due to infection, but in our study, it did not provide additional information to CRP.