Vascular endothelial growth factor and uPA/suPAR system in early and advanced chronic kidney disease patients: a new link between angiogenesis and hyperfibrinolysis?

Association of vascular endothelial growth factor (VEGF) protein levels and gene polymorphism with the risk of chronic kidney disease

Vascular endothelial growth factor (VEGF) is a heparin-specific growth factor specific for vascular endothelial cells and induces angiogenesis via binding to vascular endothelial growth factor receptor (VEGFR). Chronic kidney disease (CKD), accompanied by microvascular disease, is recognized as an irreversible reduction of renal function. The effects of VEGF on CKD risk were evaluated in this study. 121 CKD patients and 50 healthy volunteers were evaluated in the current study. Data mining using the China Biological Medicine (CBM) and NCBI/PubMed databases, was performed and applicable investigations were pursued. Pooled mean differences (MD) and pooled odds ratios (OR), with corresponding confidence intervals (CIs), were calculated by meta-analysis. The levels of Scr, BUN and VEGF in the CKD group were significantly higher, when compared with the control group (P < 0.01). For the meta-analysis, thirteen articles and our current study were evaluated. VEGF levels was found to be associated with CKD risk (P < 0.00001). In the sub-group meta-analysis, we found that the pooled MD of VEGF levels was related to the early CKD group, although the difference was not notable. However, the meta-analysis itself indicated that the pooled MD of VEGF levels were in accordance with severe CKD group (P < 0.00001). Furthermore, VEGF +936C/T T allele was not associated with CKD risk (P = 0.69). VEGF levels are apparently associated with CKD risk, especially in more severe CKD. Gene polymorphism analysis indicates that the VEGF +936C/T T allele is not associated with CKD risk.

Targeted biomarkers of progression in chronic kidney disease

BACKGROUND

Chronic kidney disease (CKD) is an increasingly significant health issue worldwide. Early stages of CKD can be asymptomatic and disease trajectory difficult to predict. Not everyone with CKD progresses to kidney failure, where kidney replacement therapy is the only life-sustaining therapy. Predicting which patients will progress to kidney failure would allow better use of targeted treatments and more effective allocation of health resources. Current diagnostic tests to identify patients with progressive disease perform poorly but there is a suite of new and emerging predictive biomarkers with great clinical promise.

METHODS

This narrative review describes new and emerging biomarkers of pathophysiologic processes of CKD development and progression, accessible in blood or urine liquid biopsies. Biomarkers were selected based on their reported pathobiological functions in kidney injury, inflammation, oxidative stress, repair and fibrosis. Biomarker function and evidence of involvement in CKD development and progression are reported.

CONCLUSION

Many biomarkers reviewed here have received little attention to date, perhaps because of conflicting conclusions of their utility in CKD. The functional roles of the selected biomarkers in the underlying pathobiology of progression of CKD are a powerful rationale for advancing and validating these molecules as prognosticators and predictors of CKD trajectory.

The Plasma Soluble Urokinase Plasminogen Activator Receptor Is Related to Disease Activity of Patients with ANCA-Associated Vasculitis

Objective

The soluble urokinase plasminogen activator receptor (suPAR) is associated with kidney diseases and is used as a prognostic factor of renal function progression. The aim of this study was to explore whether circulating suPAR was associated with antineutrophil cytoplasmic autoantibody- (ANCA-) associated vasculitis (AAV) disease activity.

Methods

We evaluated 90 AAV patients with follow-up data and 35 normal controls; their plasma suPAR and C-reactive protein (CRP) levels were measured by ELISA. Associations between these levels, clinical parameters, and prognosis were analyzed.

Results

Plasma suPAR levels in AAV patients were significantly higher than in healthy controls (5,920.08 ± 3,447.17 vs. 1,441.97 ± 835.04 pg/mL, P < 0.001). Furthermore, suPAR was significantly elevated in AAV patients in active stage compared to those in partial remissions (6,492.19 ± 3,689.48 vs. 5,031.86 ± 2,489.01 pg/mL, P = 0.039). Correlation analyses demonstrated that suPAR levels positively correlated with initial serum creatinine, BVAS, CRP, and procalcitonin concentration, and negatively correlated with eGFR and C3 circulating levels. In a Kaplan-Meier survival analysis, patients with plasma suPAR levels >5683.3 pg/mL showed poorer survival than patients with lower levels (log-rank, P = 0.001). Besides, multivariate analyses confirmed that plasma suPAR levels were an independent adverse prognostic factor for a composite outcome of end-stage renal disease (ESRD) or death, after adjusting for age and gender (HR 1.05, 95% CI = 1.01 − 1.11, P = 0.043). Receiver operating characteristic curves showed a suPAR cutoff value >6662.2 pg/mL for composite outcome with 68% sensitivity and 88% specificity, with an AUC = 0.82, (95% CI = 0.68 − 0.96, P < 0.001).

Conclusion

Circulating suPAR levels might be a marker of activity correlated with disease activity in AAV patients, and, to some extent, could be a factor of poor prognosis.

Association between Soluble Urokinase-Type Plasminogen Activator Receptor Levels and Chronic Kidney Disease: A Systematic Review and Meta-Analysis

Background

Chronic kidney disease (CKD) has become a global public health problem with a high prevalence and mortality. There is no sensitive and effective markers for chronic kidney disease. Previous studies proposed suPAR as an early predict biomarker for chronic kidney disease, but the results are controversial. Therefore, the purpose of the current meta-analysis is to evaluate the association between suPAR and CKD.

Methods

We searched the PubMed, Embase, Cochrane Library databases, and Web of Science before May 1, 2019. The search was based on the key words including suPAR and CKD. Data are extracted independently according to standard format, and quality analysis is performed. We extracted the concentration of suPAR and hazard rate (HR) values of mortality, cardiovascular disease, and end-stage renal disease.

Results

There were 14 studies fulfilling the criteria. The concentration of suPAR was higher in patients with CKD than that in the control group (P < 0.001; SMD: −2.17; 95% CI: −2.71, −1.63; I² = 67.4%). SuPAR had a higher risk of mortality (P=0.001; HR: 1.72; 95% CI: 1.24, 2.39; I² = 68.0%). The higher suPAR level increased the risk of cardiovascular disease (P < 0.001; HR: 3.06; 95% CI: 2.21, 4.22; I² = 0.0%) and the risk of end-stage renal disease (P < 0.001; HR: 1.40; 95% CI: 1.22, 1.60; I² = 0.0%).

Conclusions

Monitoring suPAR concentrations may be used for early diagnosis and prognosis for patients with CKD, and the higher suPAR increased the risk of mortality, cardiovascular events, and end-stage renal disease.

Evaluation of the effects of different treatment modalities on angiogenesis in heart failure patients with reduced/mid-range ejection fraction via VEGF and sVEGFR-1

OBJECTIVES

To investigate the clinical significance of VEGF, sVEGFR-1 in heart failure reduced ejection fraction (HFrEF) and heart failure mid-range ejection fraction (HFmrEF) patients. Methods: A total of 104 people consisting of HFrEF and HFmrEF patients (n=54) and healthy (n=50) subjects were included in this comparative cross-sectional study. The study took place in Gulhane Training and Research Hospital, Ankara, Turkey, between  2011 and 2013. Serum VEGF, sVEGFR-1, plasma pro-BNP analysis and transthoracic echocardiography were performed.  Results: The average sVEGFR-1 level of the HFrEF and HFmrEF patients was significantly higher than the control group (0.185±0.122; 0.141±0.120; p=0.013). The average sVEGFR-1 level of the HFrEF and HFmrEF patients using beta-blocker was significantly higher than the HFrEF and HFmrEF patients not using it (p=0.015). There was a significant and positive correlation between sVEGFR-1 and N-terminal pro-brain natriuretic peptide (pro-BNP)  levels in the group with HF (r=0.211, p=0.044). Conclusion: It increases awareness about the role of sVEGFR-1 in HFrEF anf HFmrEF patients and the need for further studies. Beta-blocker may have a negative effect on angiogenesis in HFrEF and HFmrEF via increasing sVEGFR-1 levels. Additionally, Pro-BNP may contribute to inhibiting angiogenesis by increasing sVEGFR-1 levels and sVEGFR-1 may be an important biomarker in HFrEF and HFmrEF.

Benefit of Apabetalone on Plasma Proteins in Renal Disease

INTRODUCTION

Apabetalone, a small molecule inhibitor, targets epigenetic readers termed BET proteins that contribute to gene dysregulation in human disorders. Apabetalone has in vitro and in vivo anti-inflammatory and antiatherosclerotic properties. In phase 2 clinical trials, this drug reduced the incidence of major adverse cardiac events in patients with cardiovascular disease. Chronic kidney disease is associated with a progressive loss of renal function and a high risk of cardiovascular disease. We studied the impact of apabetalone on the plasma proteome in patients with impaired kidney function.

METHODS

Subjects with stage 4 or 5 chronic kidney disease and matched controls received a single dose of apabetalone. Plasma was collected for pharmacokinetic analysis and for proteomics profiling using the SOMAscan 1.3k platform. Proteomics data were analyzed with Ingenuity Pathway Analysis to identify dysregulated pathways in diseased patients, which were targeted by apabetalone.

RESULTS

At baseline, 169 plasma proteins (adjusted P value <0.05) were differentially enriched in renally impaired patients versus control subjects, including cystatin C and β2 microglobulin, which correlate with renal function. Bioinformatics analysis of the plasma proteome revealed a significant activation of 42 pathways that control immunity and inflammation, oxidative stress, endothelial dysfunction, vascular calcification, and coagulation. At 12 hours postdose, apabetalone countered the activation of pathways associated with renal disease and reduced the abundance of disease markers, including interleukin-6, plasminogen activator inhibitor-1, and osteopontin.

CONCLUSION

These data demonstrated plasma proteome dysregulation in renally impaired patients and the beneficial impact of apabetalone on pathways linked to chronic kidney disease and its cardiovascular complications.

Association between uremic toxin-anthranilic acid and fibrinolytic system activity in predialysis patients at different stages of chronic kidney disease

PURPOSE

Chronic kidney disease (CKD) is an estimated risk factor for increased mortality and morbidity due to fibrinolytic system disturbances. Progressive loss of renal function leads to retention of uremic toxins. Anthranilic acid (AA) is a tryptophan-derived uremic toxin with multidirectional properties that can affect the hemostatic system. The goal of this study was to examine the association between AA and the parameters of fibrinolysis at different stages of CKD.

METHODS

Patients with CKD were divided into two groups: mild-to-moderate (n = 20) and severe-to-end-stage CKD (n = 28). Seventeen healthy volunteers served as an additional control group. Parameters of fibrinolysis, inflammation, and monocytes activation were determined by ELISA immune-enzymatic kits. AA levels were evaluated using high-performance liquid chromatography.

RESULTS

AA concentration and parameters of fibrinolysis: urokinase-type plasminogen activator (uPA), its soluble receptor (suPAR), tissue plasminogen activator (tPA), tissue plasminogen activator inhibitor-1 (PAI-1) and plasmin-antiplasmin complex (PAP) were significantly elevated in the CKD groups compared with the controls. The markers of inflammation, monocyte activation, and impaired kidney function were also increased in those with CKD. AA was positively correlated with the uPA/suPAR system in the early stages of CKD, whereas during severe-to-end-stage CKD, inverse relationships were observed between AA, tPA and PAI-1. Additionally, AA was an independent variable associated with tPA in patients with CKD overall and with uPA levels in the mild-to-moderate CKD group.

CONCLUSIONS

Obtained results suggest for the first time the association between AA and the fibrinolytic system in CKD patients. The distinct relationship between AA and individual parameters of fibrinolysis appears to be dependent on CKD stage.

MMP-2 and 9 in Chronic Kidney Disease

Gelatinases are members of the matrix metalloproteinase (MMPs) family; they play an important role in the degradation of the extracellular matrix (ECM). This effect is also crucial in the development and progression of chronic kidney disease (CKD). Its expression, as well as its activity regulation are closely related to the cell signaling pathways, hypoxia and cell membrane structural change. Gelatinases also can affect the development and progression of CKD through the various interactions with tumor necrosis factors (TNFs), monocyte chemoattractant proteins (MCPs), growth factors (GFs), oxidative stress (OS), and so on. Currently, their non-proteolytic function is a hot topic of research, which may also be associated with the progression of CKD. Therefore, with the in-depth understanding about the function of gelatinases, we can have a more specific and accurate understanding of their role in the human body.

Low-grade risk of hypercoagulable state in patients suffering from diabetes mellitus type 2

OBJECTIVE

Diabetes, including type 1 and type 2, is associated with the hypercoagulable state. The aim of this study is to evaluate the concentration of selected hemostatic parameters and vascular endothelial growth factor-A (VEGF-A) in diabetic subjects.

METHODS

The study was conducted in 62 patients with diabetes. Group I consisted of 27 patients having uncontrolled diabetes with microalbuminuria and Group II included 35 well-controlled diabetic patients. The control group was made up of 25 healthy volunteers. In the citrate plasma, the concentrations of tissue factor (TF), tissue factor pathway inhibitor (TFPI), thrombin-antithrombin (TAT) complexes, and D-dimer were assayed. Serum concentrations of VEGF-A, lipid profile, creatinine, and plasma fasting glucose were measured and in the versene plasma the concentration of HbA1c was determined.

RESULTS

In the patients with uncontrolled diabetes, higher concentrations of TF, TFPI, and VEGF-A were observed, as compared with the well-controlled diabetics group and the control group. A significantly lower activity of antiplasmin was reported in patients from Group I as compared with the control group. In Group I, using the multivariate regression analysis, the glomerular filtration rate was independently associated with VEGF-A and dependently associated with total cholesterol.

CONCLUSIONS

The study showed higher concentrations of TF and TFPI in the patients with uncontrolled diabetes with microalbuminuria, which is associated with rapid neutralization of the thrombin formation, since TFPI inhibits the complex of TF/VIIa/Ca(2+). The manifestation of the above suggestions is the correct TAT complexes and D-dimer, which indicates a low grade of prothrombotic risk in this group of patients, but a higher risk of vascular complications.

The emerging role of coagulation proteases in kidney disease

A role of coagulation proteases in kidney disease beyond their function in normal haemostasis and thrombosis has long been suspected, and studies performed in the past 15 years have provided novel insights into the mechanisms involved. The expression of protease-activated receptors (PARs) in renal cells provides a molecular link between coagulation proteases and renal cell function and revitalizes research evaluating the role of haemostasis regulators in renal disease. Renal cell-specific expression and activity of coagulation proteases, their regulators and their receptors are dynamically altered during disease processes. Furthermore, renal inflammation and tissue remodelling are not only associated, but are causally linked with altered coagulation activation and protease-dependent signalling. Intriguingly, coagulation proteases signal through more than one receptor or induce formation of receptor complexes in a cell-specific manner, emphasizing context specificity. Understanding these cell-specific signalosomes and their regulation in kidney disease is crucial to unravelling the pathophysiological relevance of coagulation regulators in renal disease. In addition, the clinical availability of small molecule targeted anticoagulants as well as the development of PAR antagonists increases the need for in-depth knowledge of the mechanisms through which coagulation proteases might regulate renal physiology.

Serum suPAR levels are modulated by immunosuppressive therapy of minimal change nephrotic syndrome

BACKGROUND

Soluble urokinase-type plasminogen activator receptor (suPAR) could be a causative factor in idiopathic focal segmental glomerulosclerosis (FSGS). It is currently unknown to what extent suPAR levels could be affected by treatment with immunosuppressive drugs such as cyclosporin A (CsA) and mycophenolate mofetil (MMF). Treatment with CsA, but not MMF, is accompanied by nephrotoxicity, and since suPAR levels correlate with glomerular filtration rate (GFR), treatment with these drugs could indirectly modulate suPAR levels by their effect on renal function.

METHODS

We measured suPAR levels in a recent prospective multicenter crossover trial comparing the efficacy of MMF and CsA in pediatric patients with minimal change disease (MCD) and frequently relapsing steroid-sensitive nephrotic syndrome (FR-SSNS). All patients had biopsy-proven MCD and normal renal function; they were treated with each drug for 1 year in a crossover study design. Serum suPAR levels were measured before and after 1 year of therapy with MMF (n = 40) and CsA (n = 35).

RESULTS

The suPAR levels decreased after 1 year of treatment with MMF (p < 0.05). Conversely, suPAR levels increased after 1 year of treatment with CsA in the same patients (p = 0.01). These changes in suPAR levels were not correlated to the estimated glomerular filtration rate (eGFR) or changes in the GFR.

CONCLUSIONS

Data from this prospective randomized trial suggest that treatment with MMF and CsA is associated with different effects on suPAR levels in children with MCD and that these are independent of their effects on GFR.

Decreased glomerular filtration as the primary factor of elevated circulating suPAR levels in focal segmental glomerulosclerosis

BACKGROUND

Circulating factor(s) has been thought to be the underlying cause of focal segmental glomerulosclerosis (FSGS), and recent studies foster this idea by demonstrating increased soluble urokinase receptor (suPAR) levels in the serum of FSGS patients.

METHODS

To explore the possible contribution of suPAR in FSGS pathogenesis, we analyzed serum suPAR levels in 17 patients with FSGS and compared them with those in patients with steroid-sensitive nephrotic syndrome, chronic glomerulonephritis, or non-glomerular kidney diseases.

RESULTS

Serum suPAR levels in patients with FSGS were higher than those in patients with steroid-sensitive nephrotic syndrome or chronic glomerulonephritis, but not higher than those in patients with non-glomerular kidney diseases. suPAR levels negatively correlate with estimated glomerular filtration rate and were decreased after renal transplantation in patients with FSGS as well as in those with non-glomerular kidney diseases. Furthermore, 6 FSGS patients with post-transplant recurrence demonstrated that suPAR levels were not high during the recurrence.

CONCLUSIONS

Based on our results, elevated suPAR levels in FSGS patients were attributed mainly to decreased glomerular filtration. These data warrant further analysis for involvement of possible circulating factor(s) in FSGS pathogenesis.

Correlation of biomarkers for parasite burden and immune activation with acute kidney injury in severe falciparum malaria

Background

Acute kidney injury (AKI) complicating severe Plasmodium falciparum malaria occurs in up to 40% of adult patients. The case fatality rate reaches 75% in the absence of renal replacement therapy (RRT). The precise pathophysiology of AKI in falciparum malaria remains unclear. Histopathology shows acute tubular necrosis with localization of host monocytes and parasitized red blood cells in the microvasculature. This study explored the relationship of plasma soluble urokinase-type plasminogen activator receptor (suPAR), as a proxy-measure of mononuclear cell activation, and plasma P. falciparum histidine rich protein 2 (PfHRP2), as a measure of sequestered parasite burden, with AKI in severe malaria.

Methods

Admission plasma suPAR and PfHRP2 concentrations were assessed in Bangladeshi adults with severe falciparum malaria (n = 137). Patients were stratified according to AKI severity based on admission creatinine clearance.

Results

A total of 106 (77%) patients had AKI; 32 (23%), 42 (31%) and 32 (23%) were classified into ‘mild, ‘moderate’ and ‘severe’ AKI groups, respectively. Plasma suPAR and PfHRP2 concentrations increased with AKI severity (test-for-trend P <0.0001) and correlated with other markers of renal dysfunction. Admission plasma suPAR and PfHRP2 concentrations were higher in patients who later required RRT (P <0.0001 and P = 0.0004, respectively). In a multivariate analysis, both increasing suPAR and PfHRP2 were independently associated with increasing urine neutrophil gelatinase-associated lipocalin concentration, a marker of acute tubular necrosis (β = 16.54 (95% CI 6.36-26.71) and β = 0.07 (0.02-0.11), respectively).

Conclusions

Both sequestered parasite burden and immune activation contribute to the pathogenesis of AKI in severe falciparum malaria.

A multicenter cross-sectional study of circulating soluble urokinase receptor in Japanese patients with glomerular disease

Elevated serum-soluble urokinase receptor (suPAR) levels have been described in patients with focal segmental glomerulosclerosis (FSGS) in several different cohorts. However, it remains unclear whether this is the case for Japanese patients and whether circulating suPAR can be clinically useful as a diagnostic marker. To determine this, we measured serum suPAR levels in 69 Japanese patients with biopsy-proven glomerular diseases in a cross-sectional manner. The serum suPAR levels showed a significant inverse correlation with renal function by univariate (R(2) of 0.242) and multivariate (β=0.226) analyses. Even after excluding patients with renal dysfunction, no significant difference in the suPAR levels was detected among the groups. Receiver operating characteristic analysis and measures of the diagnostic test performance showed that suPAR was not a useful parameter for differentiating FSGS from the other glomerular diseases (AUC-ROC: 0.621), although a small subgroup analysis showed that patients with FSGS, treated with steroids and/or immunosuppressants, had significantly lower suPAR levels. Patients with ANCA-associated glomerulonephritis had significantly higher levels of suPAR compared with the other disease groups, which may be owing to their lower renal function and systemic inflammation. Thus, suPAR levels are significantly affected by renal function and have little diagnostic value even in patients with normal renal function.

Diagnostic tests and treatment options in glomerular disease: 2014 update

Glomerular diseases historically have been challenging disorders to comprehend and treat for patients and physicians alike. Kidney biopsy is the gold standard of diagnosis, but the link between pathophysiology and the histologic representation of kidney injury has remained elusive in many of these diseases. As a result, treatment of glomerular disease usually involves therapies that are not specific to disease pathogenesis, such as blockade of the renin-angiotensin-aldosterone system and various immunosuppression regimens. Recent research has resulted in greater insight into some glomerular diseases, leading to the hope that new diagnostic tests and treatments targeting disease-specific mechanisms are on the horizon. We review recent progress on the understanding, diagnosis, and treatment of 4 glomerular diseases: immunoglobulin A nephropathy, focal segmental glomerulosclerosis, the C3 glomerulopathies, and idiopathic membranous nephropathy.

Serum suPAR in patients with FSGS: trash or treasure?

The urokinase-type plasminogen activator receptor (uPAR) has important functions in cell migration. uPAR can be shed from the cell membrane resulting in soluble uPAR (suPAR). Further cleavage gives rise to shorter fragments with largely unknown functions. Recent studies have demonstrated that both overexpression of uPAR on podocytes and the administration of suPAR cause proteinuria in mice. The common pathogenic mechanism involves the activation of podocyte β3-integrin. Increased activation of β3-integrin is also observed in patients with focal and segmental glomerulosclerosis (FSGS). These observations form the basis for the hypothesis that suPAR may be the circulating factor causing FSGS. A recent study fosters this idea by demonstrating increased suPAR levels in the serum of patients with FSGS and reporting an association with recurrence after transplantation and response to plasmapheresis. However, this study was heavily biased, and subsequent studies have given conflicting results. Although the experimental work is very suggestive, at present there is no proof that any known human suPAR fragment causes FSGS in humans. We therefore suggest that the measurement of suPAR using currently available assays has absolutely no value at the present time in decision-making in routine clinical practice.

Permeability factors in nephrotic syndrome and focal segmental glomerulosclerosis

Circulating permeability factors have been identified in the plasma of patients with focal segmental glomerulosclerosis (FSGS). Post-transplant recurrence of proteinuria, improvement of proteinuria after treatment with plasmapheresis, and induction of proteinuria in experimental animals by plasma fractions each provide evidence for such plasma factors. Advanced proteomic methods have identified candidate molecules in recurrent FSGS. We have proposed cardiotrophin-like cytokine-1 as an active factor in FSGS. Another potential permeability factor in FSGS is soluble urokinase receptor. In our studies, in vitro plasma permeability activity is blocked by substances that may decrease active molecules or block their effects. We have shown that the simple sugar galactose blocks the effect of FSGS serum in vitro and decreases permeability activity when administered to patients. Since the identities of permeability factors and their mechanisms of action are not well defined, treatment of FSGS is empiric. Corticosteroids are the most common agents for initial treatment. Calcineurin inhibitors, such as cyclosporine A, and tacrolimus and immunosuppressive medications, including mycophenylate, induce remission is some patients with steroid-resistant or -dependent nephrotic syndrome. Therapies that diminish proteinuria and slow progression in FSGS as well as other conditions include renin-angiotensin blockade, blood pressure lowering and plasma lipid control. Use of findings from in vitro studies, coupled with definitive identification of pathogenic molecules, may lead to new treatments to arrest FSGS progression and prevent recurrence after transplantation.