VAP-1, a novel molecule linked to endothelial damage and kidney function in kidney allograft recipients

Serum Vascular Adhesion Protein-1 and Endothelial Dysfunction in Hepatic Cirrhosis: Searching for New Prognostic Markers

Endothelial dysfunction plays a key role in the development of liver cirrhosis. Among the biomarkers of endothelial dysfunction, the soluble form of Vascular Adhesion Protein-1 (sVAP-1) is an unconventional and less known adhesion molecule endowed also with amine oxidase activity. The aim of this study was to explore and correlate the behavior of sVAP-1 with that of the soluble vascular cell adhesion molecule-1 (sVCAM-1) and intercellular adhesion molecule-1 (sICAM-1) and with the severity of liver cirrhosis. A cross-sectional study was carried out by enrolling 28 controls, 59 cirrhotic patients without hepatocellular carcinoma, and 56 patients with hepatocellular carcinoma (HCC), mainly caused by alcohol abuse. The levels of adhesion molecules and of the pro-inflammatory cytokines (IL-6 and TNF-αα) were determined by immunoassay and the enzymatic activity of sVAP-1 by a fluorometric assay. In non-diabetic patients without HCC, a specific behavior of sVAP-1 was highlighted. Differently from sVCAM-1, sICAM-1, and cytokines, the sVAP-1 level was significantly increased only in the early stage of disease, and then, it decreased in the last stage (866 ± 390 ng/mL vs. 545 ± 316 ng/mL, in Child-Pugh class A vs. C, respectively, p < 0.05). Bivariate analysis correlates sVAP-1 to sVCAM-1, in the absence of HCC (Spearman's rho = 0.403, p < 0.01). Multiple linear regression analysis revealed that sVCAM-1 appears to be a predictor of sVAP-1 (β coefficient = 0.374, p = 0.021). In conclusion, in non-diabetic and non-HCC cirrhotic patients, sVAP-1 may be a potential prognostic biomarker that, together with sVCAM-1 and pro-inflammatory cytokines, may provide information on the progression of sinusoidal liver endothelium damage.

Circulating renalase predicts all-cause mortality and renal outcomes in patients with advanced chronic kidney disease

BACKGROUND/AIMS

Patients with chronic kidney disease (CKD) have been found to show markedly increased rates of end-stage renal disease, major adverse cardiovascular and cerebrovascular events (MACCEs), and mortality. Therefore, new biomarkers are required for the early detection of such clinical outcomes in patients with CKD. We aimed to determine whether the level of circulating renalase was associated with CKD progression, MACCEs, and all-cause mortality, using data from a prospective randomized controlled study, Kremezin STudy Against Renal disease progression in Korea (K-STAR; NCT00860431).

METHODS

A retrospective analysis of the K-STAR data was performed including 383 patients with CKD (mean age, 56.4 years; male/female, 252/131). We measured circulating renalase levels and examined the effects of these levels on clinical outcomes.

RESULTS

The mean level of serum renalase was 75.8 ± 34.8 μg/mL. In the multivariable analysis, lower hemoglobin levels, higher serum creatinine levels, and diabetes mellitus were significantly associated with a higher renalase levels. Over the course of a mean follow-up period of 56 months, 25 deaths and 61 MACCEs occurred. Among 322 patients in whom these outcomes were assessed, 137 adverse renal outcomes occurred after a mean follow-up period of 27.8 months. Each 10- μg/mL increase in serum renalase was associated with significantly greater hazards of all-cause mortality and adverse renal outcomes (hazard ratio [HR] = 1.112, p = 0.049; HR = 1.052, p = 0.045). However, serum renalase level was not associated with the rate of MACCEs in patients with CKD.

CONCLUSION

Our results indicated that circulating renalase might be a predictor of mortality and adverse renal outcomes in patients with CKD.

Oxidative Stress and Renal Fibrosis: Recent Insights for the Development of Novel Therapeutic Strategies

Chronic kidney disease (CKD) is a significant worldwide healthcare problem. Regardless of the initial injury, renal fibrosis is the common final pathway leading to end stage renal disease. Although the underlying mechanisms are not fully defined, evidence indicates that besides inflammation, oxidative stress plays a crucial role in the etiology of renal fibrosis. Oxidative stress results from an imbalance between the production of free radicals that are often increased by inflammation and mitochondrial dysfunction, and reduced anti-oxidant defenses. Several studies have demonstrated that oxidative stress may occur secondary to activation of transforming growth factor β1 (TGF-β1) activity, consistent with its role to increase nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (Nox) activity. A number of other oxidative stress-related signal pathways have also been identified, such as nuclear factor erythroid-2 related factor 2 (Nrf2), the nitric oxide (NO)-cyclic guanosine monophosphate (cGMP)-cGMP-dependent protein kinase 1-phosphodiesterase (cGMP-cGK1-PDE) signaling pathway, and the peroxisome proliferator-activated receptor gamma (PPARγ) pathway. Several antioxidant and renoprotective agents, including cysteamine bitartrate, epoxyeicosatrienoic acids (EETs), and cytoglobin (Cygb) have demonstrated ameliorative effects on renal fibrosis in preclinical or clinical studies. The mechanism of action of many traditional Chinese medicines used to treat renal disorders is based on their antioxidant properties, which could form the basis for new therapeutic approaches. This review focuses on the signaling pathways triggered by oxidative stress that lead to renal fibrosis and provides an update on the development of novel anti-oxidant therapies for CKD.

Endocan Concentration in Patients With Primary Hypertension

Inflammation and endothelial dysfunction may play an important role in the multifactorial pathogenesis of hypertension. Endocan is also thought to play a role in cell adhesion and inflammatory disorders. The aim of the study was to compare endocan concentrations in patients with primary hypertension and healthy volunteers. There were 104 patients with hypertension (study group) and 21 healthy volunteers (control group). The correlation between endocan, catecholamines, and blood pressure control in patients with primary hypertension and the control group was analyzed. The median endocan concentration in the study group (2.03 ng/mL) was significantly higher than in the control group (1.09 ng/mL, P = .0001). Endocan concentration was correlated positively with renalase ( r = .2, P = .047) and norepinephrine ( r = .25, P = .02). Negative correlation was observed between endocan and body mass index ( r = −.25, P = .016) and leukocyte count ( r = −.36, P = .0004). The present study reports higher plasma endocan concentration in patients with treated, well-controlled primary hypertension compared with healthy volunteers. The higher endocan concentration in the study group may reflect endothelial dysfunction in this population.

Vascular adhesion protein-1 in hemodialysis and hemodiafiltration patients: effect of single hemodialysis session on its level in regard to type of anticoagulant

PURPOSE

Traditional anticoagulants used in intermittent hemodialysis (HD) are unfractionated heparin (UFH) and increasingly low molecular weight heparins (LMWHs). Repeated and prolonged exposure to UFH and/or LMWHs may further disturb hemostasis in uremic patients. Vascular adhesion protein-1 (VAP-1) is secreted by vascular smooth muscle cells, adipocytes and endothelial cells with functional monoamine oxidase activity and is elevated in atherosclerosis, diabetes mellitus and obesity. The aim of this study was to assess the effects of UFH and LMWHs on VAP-1 concentration in HD patients. The effects on single HD session on VAP-1 were also evaluated as well as VAP-1 levels in regard to type of renal replacement therapy.

METHODS

We studied 82 hemodialyzed patients (mean age 63 years, dialysis vintage 59 months) and 17 patients treated by means of hemodiafiltration (HDF) (mean age 59 years, HD vintage 84 months, HDF 7 months). Patients were anticoagulated with enoxaparin (n = 46), dalteparin (n = 10), nadroparin (n = 6) or UFH (n = 20) during their HD sessions. VAP-1 was assessed using kits from BioVendor, Modrice, Czech Republic.

RESULTS

Patients on HDF had significantly lower VAP-1 when compared with HD patients. We found that VAP-1 concentration in patients dialyzed by using LMWH or UFH was similar. There was no effect on HD session on VAP-1 concentration. Diabetic patients had higher serum VAP-1 than non-diabetic.

CONCLUSIONS

HDF is associated with lower VAP-1 levels indicating less pronounced endothelial cell injury than hemodialysis. Type of heparin seems to have no effect on VAP-1 levels in hemodialyzed patients. However, the cross-sectional but not prospective design is a limitation of this study.

Vascular adhesion protein-1: Role in human pathology and application as a biomarker

Vascular adhesion protein-1 (VAP-1) is a member of the copper-containing amine oxidase/semicarbazide-sensitive amine oxidase (AOC/SSAO) enzyme family. SSAO enzymes catalyze oxidative deamination of primary amines, which results in the production of the corresponding aldehyde, hydrogen peroxide and ammonium. VAP-1 is continuously expressed as a transmembrane glycoprotein in the vascular wall during development and facilitates the accumulation of inflammatory cells into the inflamed environment in concert with other leukocyte adhesion molecules. The soluble form of VAP-1 is released into the circulation mainly from vascular endothelial cells. Over- and under-expression of sVAP-1 result in alterations of the reported reaction product levels, which are involved in the pathogenesis of multiple human diseases. The combination of enzymatic and adhesion capacities as well as its strong association with inflammatory pathologies makes VAP-1 an interesting therapeutic target for drug discovery. In this article, we will review the general characteristics and biological functions of VAP-1, focusing on its important role as a prognostic biomarker in human pathologies. In addition, the potential therapeutic application of VAP-1 inhibitors will be discussed.

Renalase gene polymorphism in patients with hypertension and concomitant coronary heart disease

BACKGROUND/AIMS

This study aimed to investigate renalase gene polymorphism in patients with hypertension and concomitant coronary heart disease (CHD) and to evaluate the risk for CHD in hypertensive patients from the view of genetics.

METHODS

NCBI and HapMap genome database were employed to screen the Single nucleotide polymorphisms (SNP). These SNPs were detected in hypertensive and CHD patients (n=791), hypertensive patients (n=802) and healthy controls (n=812), and the genotypes were recorded. Haploview 4.2 software was used to determine the genotypes, allele frequency, haplotypes, linkage disequilibrium and Hardy-Weinberg (HWE) equilibrium, and odds ratio (OR) was calculated with non-conditioned logistic regression analysis.

RESULTS

The frequency of allele A of rs2576178 in patients with hypertensive and CHD was markedly higher than that in hypertensive patients (p=0.001, OR=1.625,95% CI 1.221-2.160). The frequency of allele C of rs2296545 in hypertensive patients was significantly higher than that in healthy controls (P=0.009, OR=1.436, 95% CI 1.095-1.883).

CONCLUSION

The allele A of rs2576178 may be a predisposing factor of CHD in hypertensive patients, and hypertensive patients with AA genotype are susceptible to develop CHD. The allele C of rs2296545 may be a predisposing factor of hypertension and patients with CC genotype are susceptible to develop hypertension.

Renalase, a new secretory enzyme: Its role in hypertensive-ischemic cardiovascular diseases

Abstract Renalase, a novel amine oxidase, is mainly expressed in the kidney, heart, and skeletal muscle. It has been known to degrade circulating catecholamines and plays a crucial role in human diseases. Recent studies have demonstrated its structure, unique bioactivities, function, and the gene polymorphisms in human diseases. In this review, we summarize the effects of renalase on hypertension, myocardial ischemia, acute kidney injury (AKI), ischemic stroke, cardiac dysfunction, organ transplantation, and diabetes mellitus reported in numerous studies.

Vascular adhesion protein-1, a novel molecule, in kidney and heart allograft recipients

BACKGROUND

VAP-1 (vascular adhesion protein-1) is a copper-containing SSAO (semicarbazide-sensitive amine oxidase) secreted by vascular smooth muscle cells, adipocytes, and endothelial cells. Elevation of SSAO activity is observed in atherosclerosis, diabetes mellitus, and obesity. The aim of the study was to assess VAP-1 in prevalent heart and kidney allograft recipients.

METHODS

Complete blood count, urea, serum lipids, fasting glucose, and creatinine were studied by standard laboratory methods. VAP-1, N-terminal pro brain natriuretic peptide (NT-proBNP) and high-sensitivity C-reactive protein (hsCRP) were estimated using commercially available assays.

RESULTS

Healthy volunteers showed higher hemoglobin and estimated glomerular filtration rate (eGFR) but lower creatinine, NT-proBNP, hsCRP and VAP-1 relative to heart and kidney transplantation (OHT) (KTx). Among heart transplant recipients, VAP-1 correlated with age, presence of diabetes, insulin therapy, ejection fraction, estimated glomerular filtration rate by MDRD (Modification of Diet in Renal Disease), eGFR by CKD-EPI (Chronic Kidney Disease-Epidemiological Collaboration), use of tacrolimus, LVIDd (left ventricular internal end-diastolic dimension), New York Heart Association class and NT-proBNP. VAP-1 was significantly lower among patients treated with tacrolimus than cyclosporine. Diabetic patients versus nondiabetic subjects as well as patients with eGFR below 60 versus ≥ 60 mL/min showed higher serum VAP-1 in OHT and KTx populations. Multiple regression analysis revealed VAP-1 to be predicted in 25% by LVIDd, and use of tacrolimus in OHT. In kidney transplant recipients, VAP-1 correlated only with time after transplantation and serum glucose. CONCLUDING: VAP-1 elevations in heart transplant recipients were predominantly dependent on left ventricular diameter and use of tacrolimus; however, the precise associations with the immunosuppressive regimen warrant further studies. VAP-1 elevations in kidney transplant recipients may relate to glucose control.

Semicarbazide-sensitive amine oxidase and kidney disease

With better understanding of the molecular mechanisms underpinning chronic kidney disease, the roles of inflammation and fibrosis are becoming increasingly inseparable. The progression of renal disease is characterized by pathomorphological changes that consist of early inflammatory responses followed by tubulointerstitial fibrosis, tubular atrophy, and glomerular and vascular sclerosis. Currently available therapies that reduce hypertension, proteinuria, hyperglycemia, and interruption of the renin-angiotensin-aldosterone system are at best only partially effective. Hence, there remains a need to explore agents targeting nonrenin-angiotensin-aldosterone system pathways. In this review, we discuss mechanistic aspects in the physiological and pathological role of semicarbazide-sensitive amine oxidase, a protein enzyme involved in cellular trafficking and inflammation, with respect to the kidney. We explore the evidence for the use of semicarbazide-sensitive amine oxidase inhibitors as potential agents in renal fibrosis to delay the onset and progression of chronic kidney disease.

Increased circulating inflammatory endothelial cells in blacks with essential hypertension

Morbidity and mortality attributable to hypertension are higher in black essential hypertensive (EH) compared with white EH patients, possibly related to differential effects on vascular injury and repair. Although circulating endothelial progenitor cells (EPCs) preserve endothelial integrity, inflammatory endothelial cells (IECs) detach from sites of injury and represent markers of vascular damage. We hypothesized that blood levels of IECs and inflammatory markers would be higher in black EH compared with white EH patients. Inferior vena cava and renal vein levels of CD34+/KDR+ (EPC) and VAP-1+ (IEC) cells were measured by fluorescence-activated cell sorting in white EH and black EH patients under fixed sodium intake and blockade of the renin-angiotensin system, and compared with systemic levels in normotensive control subjects (n=19 each). Renal vein and inferior vena cava levels of inflammatory cytokines and EPC homing factors were measured by Luminex. Blood pressure, serum creatinine, lipids, and antihypertensive medications did not differ between white and black EH patients, and EPC levels were decreased in both. Circulating IEC levels were elevated in black EH patients, and inversely correlated with EPC levels (R(2)=0.58; P=0.0001). Systemic levels of inflammatory cytokines and EPC homing factors were higher in black EH compared with white EH patients, and correlated directly with IECs. Renal vein inflammatory cytokines, EPCs, and IECs did not differ from their circulating levels. Most IECs expressed endothelial markers, fewer expressed progenitor cell markers, but none showed lymphocyte or phagocytic cell markers. Thus, increased release of cytokines and IECs in black EH patients may impair EPC reparative capacity and aggravate vascular damage, and accelerate hypertension-related complications.

Vascular adhesion protein-1 and renalase in regard to diabetes in hemodialysis patients

INTRODUCTION

Vascular adhesion protein-1 (VAP-1) is a copper-containing semicarbazide-sensitive amine oxidase (SSAO) secreted by vascular smooth muscle cells, adipocytes, and endothelial cells with functional monoamine oxidase activity. Renalase, with possible monoamine oxidase activity, which breaks down catecholamines like SSAO, is also expressed in the endothelium as well as in the kidney. The aim of the study was to assess VAP-1 level and its correlation with renalase level in 60 hemodialyzed (HD) patients.

MATERIAL AND METHODS

Complete blood count, urea, serum lipids, fasting glucose and creatinine were studied by the standard laboratory method in the hospital central laboratory. We assessed VAP-1 and renalase with commercially available assays.

RESULTS

The mean level of VAP-1 as well as renalase was significantly higher in HD patients when compared to the control group (291.01 ±94.91 ng/ml vs. 158.34 ±56.89 ng/ml, p < 0.01; 27.53 ±9.394.91 µg/ml vs. 4.00 ±1.37 µg/ml, p < 0.001, respectively). In hemodialysis patients VAP-1 correlated with presence of diabetes (r = 0.27, p < 0.05), presence of hypertension (r = 0.32, p < 0.05), use of calcium channel blockers (r = 0.30, p < 0.05), use of β-blockers (r = 0.25, p < 0.05), ejection fraction (r = -0.38, p < 0.01), systolic blood pressure before (r = 0.52, p < 0.001) and after hemodialysis (r = 0.30, p < 0.01), and weight gain (r = 0.41, p < 0.01). Renalase was not significantly different in diabetic and non-diabetic patients or between hypertensive and normotensive patients. In multiple regression analysis VAP-1 was predicted 77% by serum ejection fraction and fibrinogen.

CONCLUSIONS

Vascular adhesion protein-1, elevated in patients on hemodialysis, was predominantly dependent on blood pressure and diabetes, both factors associated with endothelial damage and promoting cardiovascular complications. Renalase appeared to be unrelated to VAP, at least in the HD population.