Activated human neutrophils rapidly release the chemotactically active D2D3 form of the urokinase-type plasminogen activator receptor (uPAR/CD87)

suPAR in cardiovascular disease

Soluble urokinase plasminogen activator receptor (suPAR), the soluble counterpart of urokinase plasminogen activator receptor, is found in the circulation at various levels. suPAR and its parent molecule, cell surface uPAR, exhibit similar structure and extracellular functional roles facilitating fibrinolysis, cellular adhesion, and migration. Studies have assessed the correlation between suPAR in cardiovascular disease (CVD). It is postulated that suPAR may serve as an indicator of inflammatory activation and burden during CVD progression. Increased suPAR independently predicts poorer outcomes in acute coronary syndromes, in heart failure, as well as in coronary artery disease and atherosclerosis. To guide translation into clinical utization, suPAR has been assessed in numerous CVD settings for improved risk discrimination independently or in association with established traditional risk factors. Whilst the involvement of suPAR has been explored in other diseases such as kidney diseases and cancer, there is only emerging evidence of suPAR's mechanistic involvement in cardiovascular disease. In this review, we provide a background into suPAR and its potential role as a biomarker in CVD.

Role of Formyl Peptide Receptors and β-Arrestin-1 in suPAR Signal Transduction in Mouse Podocytes: Interactions with αVβ3-Integrin

The soluble urokinase plasminogen activator receptor (suPAR) has been implicated in a wide range of pathological conditions including primary nephrotic syndromes and acute kidney injuries. suPAR can trigger transduction cascades in podocytes by outside-in activation of αVβ3-integrin, but there is evidence that the functional cell surface response element is actually a complex of different types of receptors, which may also include the receptor for advanced glycation end-products (RAGE) and formyl peptide receptors (FPRs). Here we observed that ROS accumulation and Src activation could be evoked by continuous 24 h exposure to either suPAR or the FPR agonist fMLF. Responses to suPAR and fMLF were completely blocked by either the FPR antagonist WRW4 or by the αV-integrin inhibitor cilengitide. Moreover, endogenous podocyte mouse Fpr1 co-immunoprecipitates with β3-integrin, suggesting that these receptors occur as a complex on the cell surface. suPAR- and fMLF-evoked activation of Src and ROS differed in time course. Thus, robust pertussis toxin (PTX)-sensitive responses were evoked by 60 min exposures to fMLF but not to suPAR. By contrast, responses to 24 h exposures to either suPAR or fMLF were PTX-resistant and were instead abolished by knockdown of β-arrestin-1 (BAR1). FPRs, integrins, and RAGE (along with various Toll-like receptors) can all function as pattern-recognition receptors that respond to "danger signals" associated with infections and tissue injury. The fact that podocytes express such a wide array of pattern-recognition receptors suggests that the glomerular filter is designed to change its function under certain conditions, possibly to facilitate clearance of toxic macromolecules.

suPAR as a risk Prediction Biomarker in Extracorporeal Membrane Oxygenation

suPAR is a promising biomarker of cardiovascular diseases, as it reflects “low-grade inflammation” and is associated with lifestyle factors such as smoking, alcohol, and an inactive lifestyle. suPAR is expressed in various cells involved in the development of atherosclerosis, including macrophages, endothelial cells, and smooth muscle cells, and an accumulation of suPAR in the atheroma has also been found. suPAR plays a role in the coagulation cascade during plasminogen activation and fibrinolysis. This abstract provides description of three case series showing the utility of suPAR as a risk prediction biomarker on VA extracorporeal membrane oxygenation (ECMO). We used SUPAR in 15 patients undergoing cardiac surgery of which three went on VA ECMO. Herein, we describe in detail three such patients and discuss each with good review of the literature.

suPAR to Risk-Stratify Patients With Malaria

Severe malaria (SM) is a leading cause of global morbidity and mortality, particularly in children in sub-Saharan Africa. However, existing malaria diagnostic tests do not reliably identify children at risk of severe and fatal outcomes. Dysregulated host immune and endothelial activation contributes to the pathogenesis of SM. Current research suggests that measuring markers of these pathways at presentation may have clinical utility as prognostic indicators of disease progression and risk of death. In this review, we focus on the available evidence implicating soluble urokinase-type plasminogen activator receptor (suPAR) as a novel and early predictor of severe and fatal malaria and discuss its potential utility for malaria triage and management.

Targeting of neutrophil activation in the early phase of the disease for prevention of Coronavirus disease-19 severity

The prevention of the disease severity seems critical for reducing the mortality of Coronavirus (CoV) disease‐19. The neutrophils play a key role in the induction of severity. It is proposed here that inhibition of neutrophil activation and/or cascade reactions of complement, leading to this cell activation at the early phase of the disease, is a potential tool to inhibit aggravation of the disease. The need for appropriate timing in intervention is emphasized as follows. (1) Intervention at the very early stage of severe acute respiratory syndrome‐CoV‐2 infection may harm the defensive host response to the infection because of the critical function of neutrophils in this response, and (2) intervention at too late a stage will not stop the infiltration of fully activated neutrophils that produce large amounts of toxic substances.

Left Atrial Phasic Function in Older Adults Is Associated with Fibrotic and Low-Grade Inflammatory Pathways

INTRODUCTION

Concomitant risk factors challenge the mechanistic understanding of cardiac aging. We determined the degree to which the left atrial function could be distinguished by advanced cardiac magnetic resonance (CMR) imaging in older adults and assessed associations between the left atrial function and the plasma biomarkers related to biological aging and cardiovascular disease [serum monocyte chemoattractant protein-1 (MCP1), matrix metallopeptidase 9 (MMP-9), B-type natriuretic peptides (BNPs), galectin-3 (Gal-3), high-sensitivity cardiac troponin I (hsTn1), high-sensitivity C-reactive protein (hs-CRP), and soluble urokinase plasminogen activator receptor (sUPAR)].

METHODS

Among a cross-sectional population-based cohort of older adults, longitudinal LA strain including reservoir strain (εs), conduit strain (εe), and booster strain (εa) as well as peak strain rates (SRs, SRe, SRa) were determined using CMR and studied in association with blood biomarkers.

RESULTS

We studied 243 community adults (42.8% female, mean age 70.3 ± 9.5 years). In bivariate analysis, εe and SRe were reduced in gradation with increasing risk factors (all p values <0.0001). Corresponding levels of sUPAR (ng/mL) were quantitatively higher in older adults with <2 risk factors (2.5 ± 1.6 vs. 1.7 ± 1.3, p = 0.0005), in those with ≥2 risk factors (3.3 ± 2.4 vs. 1.7 ± 1.3, p < 0.0001), compared to young adults; including between older adults with ≥2 risk factors and older adults with <2 risk factors (3.3 ± 2.4 vs. 2.5 ± 1.6, p = 0.017). Based on multivariate analysis, sUPAR was significantly associated with both εe (OR 1.52, p = 0.006) and SRe decline (OR 1.5, p = 0.019). The associations between Gal-3 and εe reduction (OR 1.2, p = 0.022) and between BNP and SRe decline were generally weaker (OR 1.03, p = 0.027). The addition of sUPAR to a model consisting of age, risk factors, Gal-3, and BNPs increased the area under the curve of εe from 0.72 to 0.77 (p = 0.015).

CONCLUSION

By advanced CMR imaging, a panel of circulating biomarkers comprising galectin, MMP-9 and sUPAR were associated with left atrial dysfunction in older adults. Higher levels of Gal-3 and MMP-9 may be suggestive of fibrotic mechanisms in left atrial aging while impairments in left atrial strain seen in association with circulating sUPAR may be related to immune activation in the left atrium in response to left atrial remodeling and fibrotic processes.

Soluble Urokinase Plasminogen Activator Receptor (suPAR) as a Biomarker of Systemic Chronic Inflammation

Systemic chronic inflammation (SCI) is persistent, health-damaging, low-grade inflammation that plays a major role in immunosenescence and in development and progression of many diseases. But currently, there are no recognized standard biomarkers to assess SCI levels alone, and SCI is typically measured by combining biomarkers of acute inflammation and infection, e.g., CRP, IL-6, and TNFα. In this review, we highlight 10 properties and characteristics that are shared by the blood protein soluble urokinase plasminogen activator receptor (suPAR) and SCI, supporting the argument that suPAR is a biomarker of SCI: (1) Expression and release of suPAR is upregulated by immune activation; (2) uPAR and suPAR exert pro-inflammatory functions; (3) suPAR is associated with the amount of circulating immune cells; (4) Blood suPAR levels correlate with the levels of established inflammatory biomarkers; (5) suPAR is minimally affected by acute changes and short-term influences, in contrast to many currently used markers of systemic inflammation; (6) Like SCI, suPAR is non-specifically associated with multiple diseases; (7) suPAR and SCI both predict morbidity and mortality; (8) suPAR and SCI share the same risk factors; (9) suPAR is associated with risk factors and outcomes of inflammation above and beyond other inflammatory biomarkers; (10) The suPAR level can be reduced by anti-inflammatory interventions and treatment of disease. Assessing SCI has the potential to inform risk for morbidity and mortality. Blood suPAR is a newer biomarker which may, in fact, be a biomarker of SCI since it is stably associated with inflammation and immune activation; shares the same risk factors as many age-related diseases; is both elevated by and predicts age-related diseases. There is strong evidence that suPAR is a prognostic marker of adverse events, morbidity, and mortality. It is associated with immune activity and prognosis across diverse conditions, including kidney disease, cardiovascular disease, cancer, diabetes, and inflammatory disorders. Thus, we think it likely represents a common underlying disease-process shared by many diseases; that is, SCI. We review the supporting literature and propose a research agenda that can help test the hypothesis that suPAR indexes SCI, with the potential of becoming the new gold standard for measuring SCI.

Association of the Circulating Supar Levels with Inflammation, Fibrinolysis, and Outcome in Severe Burn Patients

BACKGROUND

Hyperfibrinolysis and pro/anti-inflammatory imbalance usually occur in the early stage of severe burns. Soluble urokinase-type plasminogen activator receptor (suPAR) is involved in fibrinolysis and inflammation. To date, the levels of circulating suPAR in non-survivors with severe burns remain unknown. This study aimed to investigate the early association between circulating suPAR levels and biomarkers of fibrinolysis, pro/anti-inflammatory, and prognosis.

METHODS

Sixty-four consecutive Chinese patients with severe burns and 26 healthy volunteers were enrolled in a prospective observational cohort. Clinical characteristics and laboratory data were collected prospectively. Blood samples were collected at 48 h post-burn, and suPAR and biomarkers of pro/anti-inflammatory and fibrinolysis were detected by enzyme-linked immunosorbent assays. Important indicators between non-survivors and survivors were compared. Linear regression analysis was performed to screen variables associated with suPAR. Logistic regression analysis and receiver operating characteristic curve (ROC) analysis were performed to evaluate the prognostic value of suPAR.

RESULT

Compared with the control group, the circulating suPAR levels in the survivors (P < 0.001) and non-survivors (P = 0.017) were higher. Compared with survivors, non-survivors had lower circulating suPAR levels at 48 h post-burn, and they showed a higher degree of fibrinolysis (higher D-dimer) and a lower TNF-α/IL-10 ratio. According to linear regression analysis, the variables independently associated with a lower suPAR level were lower platelet factor 4 (PF-4), urokinase-type plasminogen activator (uPA), and TNF-α/IL-10 levels and a higher D-dimer level. Logistic regression and ROC analyses indicated that a suPAR level ≤ 4.70 μg/L was independently associated with 30-day mortality.

CONCLUSION

Low circulating suPAR levels at 48 h post-burn in severe burn patients may reflect decreased TNF-α/IL-10 ratio and increased hyperfibrinolysis. suPAR can predict 30-day mortality in patients with severe burn.

Impact of cardiopulmonary bypass and surgical complexity on plasma soluble urokinase-type plasminogen activator receptor levels after cardiac surgery

BACKGROUND

Circulating soluble urokinase plasminogen activator receptor (suPAR) is a marker of inflammation with prognostic value for elevated risk of morbidity and mortality. It has not yet been shown how the inflammatory process induced by cardiac surgery affects suPAR concentrations postoperatively.

METHODS

In a prospective observational study, plasma suPAR levels were measured in 30 patients undergoing cardiac surgery with cardiopulmonary bypass (CPB), pre-, peri, post-operatively, and 3-5 days after surgery. Fifteen patients underwent coronary artery bypass grafting (CABG) and 15 underwent complex procedures with longer CPB duration. Concentrations of suPAR at each time point were compared to the preoperative levels and compared between the two groups.

RESULTS

In both groups, plasma suPAR concentrations were significantly higher on the first postoperative day (3.27 (interquartile range (IQR) 2.75-3.86) µg/L compared to baseline (2.62 (1.98-3.86)) µg/L, p < .001. There were no significant differences in suPAR concentrations between the groups at any time point. Preoperatively, the median suPAR concentration was 2.57 (2.01-3.60) µg/L in the CABG group versus 2.67 (1.89-3.97) µg/L in the complex group (p = .567). At ICU arrival 2.48 (2.34-3.23) µg/L versus 2.73 (2.28-3.44) µg/L in CABG and complex patients, respectively (p = .914). There was no difference in suPAR concentrations between the groups on postoperative day 1 (3.34 (2.89-3.89) versus 3.19 (2.57-3.62) p = .967) or 3-5 days after surgery (2.72 (1.98-3.16) versus 2.96 (2.39-4.28) p = .085.

CONCLUSIONS

After a transient rise on the first postoperative day, the suPAR levels returned to the preoperative levels by the third postoperative day. There was no significant difference in suPAR levels between the routine CABG and complex group with longer CPB time.

Clinical and molecular parameters associated to pneumonitis development in non-small-cell lung cancer patients receiving chemoimmunotherapy from NADIM trial

BACKGROUND

Pneumonitis (Pn) is one of the main immune-related adverse effects, having a special importance in lung cancer, since they share affected tissue. Despite its clinical relevance, Pn development remains an unpredictable treatment adverse effect, whose mechanisms are mainly unknown, being even more obscure when it is associated to chemoimmunotherapy.

METHODS

In order to identify parameters associated to treatment related Pn, we analyzed clinical variables and molecular parameters from 46 patients with potentially resectable stage IIIA non-small-cell lung cancer treated with neoadjuvant chemoimmunotherapy included in the NADIM clinical trial (NCT03081689). Pn was defined as clinical or radiographic evidence of lung inflammation without alternative diagnoses, from treatment initiation to 180 days.

RESULTS

Among 46 patients, 12 developed Pn (26.1%). Sex, age, smoking status, packs-year, histological subtype, clinical or pathological response, progression-free survival, overall survival and number of nivolumab cycles, were not associated to Pn development. Regarding molecular parameters at diagnosis, Pn development was not associated to programmed death ligand 1, TPS, T cell receptor repertoire parameters, or tumor mutational burden. However, patients who developed Pn had statistically significant lower blood median levels of platelet to monocyte ratio (p=0.012) and teratocarcinoma-derived growth factor 1 (p=0.013; area under the curve (AUC) 0.801), but higher median percentages of natural killers (NKs) (p=0.019; AUC 0.786), monocytes (p=0.017; AUC 0.791), MSP (p=0.006; AUC 0.838), PARN (p=0.017; AUC 0.790), and E-Cadherin (p=0.022; AUC 0.788). In addition, the immune scenario of Pn after neoadjuvant treatment involves: high levels of neutrophils and NK cells, but low levels of B and T cells in peripheral blood; increased clonality of intratumoral T cells; and elevated plasma levels of several growth factors (EGF, HGF, VEGF, ANG-1, PDGF, NGF, and NT4) and inflammatory cytokines (MIF, CCL16, neutrophil gelatinase-associated lipocalin, BMP-4, and u-PAR).

CONCLUSIONS

Although statistically underpowered, our results shed light on the possible mechanisms behind Pn development, involving innate and adaptative immunity, and open the possibility to predict patients at high risk. If confirmed, this may allow the personalization of both, the surveillance strategy and the therapeutic approaches to manage Pn in patients receiving chemoimmunotherapy.

Cardio-Renal Biomarker Soluble Urokinase-Type Plasminogen Activator Receptor Is Associated With Cardiovascular Death and Myocardial Infarction in Patients With Coronary Artery Disease Independent of Troponin, C-Reactive Protein, and Renal Function

Background Risk stratification among patients with coronary artery disease (CAD) is of considerable interest due to the potential to guide secondary preventive therapies. Thus, we evaluated the predictive value of soluble urokinase-type plasminogen activator receptor (suPAR) levels for cardiovascular mortality and nonfatal myocardial infarction in patients with CAD. Methods and Results Plasma levels of suPAR were measured in a cohort of 1703 patients with documented CAD as evidenced by coronary angiography-including 626 patients with acute coronary syndrome and 1077 patients with stable angina pectoris. Cardiovascular death and/or nonfatal myocardial infarction were defined as main outcome measures. During a median follow-up of 3.5 years, suPAR levels reliably predicted cardiovascular death or myocardial infarction in CAD, evidenced by survival curves stratified for tertiles of suPAR levels. In Cox regression analyses, the hazard ratio for the prediction of cardiovascular death and/or myocardial infarction was 2.19 (P<0.001) in the overall cohort and 2.56 in the acute coronary syndrome cohort (P<0.001). Even after adjustment for common cardiovascular risk factors, renal function and the biomarkers C-reactive protein, N-terminal pro-B-type natriuretic peptide and high-sensitivity troponin I suPAR still enabled a reliable prediction of cardiovascular death or myocardial infarction with a hazard ratio of 1.61 (P=0.022) in the overall cohort and 2.22 (P=0.005) in the acute coronary syndrome cohort. Conclusions SuPAR has a strong and independent prognostic value in secondary prevention settings, and thereby might represent a valuable biomarker for risk estimation in CAD.

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.

High suPAR and Low Blood Eosinophil Count are Risk Factors for Hospital Readmission and Mortality in Patients with COPD

Introduction

The biomarker soluble urokinase plasminogen activator receptor (suPAR) has been associated with increased mortality in chronic obstructive pulmonary disease (COPD), while elevated blood eosinophils have been associated with better survival. We hypothesized that suPAR and blood eosinophil count are independent risk factors for readmission and mortality after an acute admission in patients with COPD.

Methods

This retrospective cohort study comprised 4022 patients with prevalent COPD acutely admitted to Hvidovre Hospital, Denmark. Irrespective of cause of admission, suPAR and blood eosinophils were measured, and patients were followed up to 365 days. Associations with 365-day respiratory readmission, all-cause readmission and all-cause mortality were investigated by Cox regression analyses adjusted for age, sex, Charlson score and C-reactive protein.

Results

suPAR was significantly elevated in patients who later experienced readmission or died. At 365 days, hazard ratios (HRs) for all-cause readmission and mortality reached 1.61 (95% CI 1.40–1.85; p<0.0001) and 3.40 (95% CI 2.64–4.39; p<0.0001), respectively, for COPD patients in the fourth suPAR quartile compared to patients in the first suPAR quartile. High blood eosinophils (>300 cells/μL) were associated with lower risk of mortality (HR 0.49, 95% CI 0.39–0.62; p<0.0001) compared with patients with <150 cells/μL. When stratifying patients by suPAR quartiles and blood eosinophil counts, the highest relative mortality rate was found in patients belonging to both the fourth suPAR quartile and the low blood eosinophil (<150 cells/μL) group.

Conclusion

In this cohort of COPD patients acutely admitted to a hospital, elevated suPAR concentrations were associated with both higher risk of all-cause readmission and mortality, whereas higher blood eosinophil count was associated with lower risk of mortality.

Assessment of saliva and gingival crevicular fluid soluble urokinase plasminogen activator receptor (suPAR), galectin-1, and TNF-α levels in periodontal health and disease

OBJECTIVE

The aim of the study is to evaluate saliva and gingival crevicular fluid (GCF) levels of suPAR and galectin-1 in different periodontal health status and relationship between these molecules and TNF-α to understand the roles of these molecules in periodontal inflammation process.

BACKGROUND

Soluble urokinase plasminogen activator receptor (suPAR) has been described as a biological marker of inflammation and immunological activation. Galectin-1, a member of the galectin family, is an anti-inflammatory cytokine. However, to date, levels of these two molecules in periodontal health and disease have not been well documented.

METHODS

A total of 60 individuals, 20 with chronic periodontitis (group P), 20 with gingivitis (group G), and 20 with healthy periodontium (group H) were recruited for this study. Full-mouth clinical periodontal measurements were recorded in periodontal charts. GCF and whole saliva samples were collected to determine the levels of suPAR, galectin-1, and TNF-α in study groups using enzymelinked immunosorbent assay (ELISA) method.

RESULTS

The GCF total amount of suPAR, galectin-1, and TNF-α in GCF was similar in group P and G (P > .05). The GCF total amounts of these molecules in GCF were higher in the group G and P compared to the group H (P < .05), whereas the GCF concentrations of suPAR and galectin-1 were lower in the group G and P compared to the group H (P < .05).The saliva concentration of suPAR was significantly higher in group P compared to the group G and H (P < .05). It was also higher in the group G compared to the group H but there is no significant difference between the groups (P > .05). Salivary galectin-1 levels were similar in the study groups (P > .05).

CONCLUSION

Increased levels of GCF suPAR, galectin-1, and saliva suPAR in periodontal disease suggest that these molecules may play a role in the periodontal inflammation. suPAR and galectin-1 may be considered as potential biomarkers in periodontal disease.

Soluble urokinase-type plasminogen activator receptor represents exercise tolerance and predicts adverse cardiac events in patients with heart failure

Soluble urokinase-type plasminogen activator receptor (suPAR) is a membrane-binding protein that is released into the blood stream by immune activation. Recent reports suggest that circulating suPAR levels are associated with adverse cardiovascular outcomes. Exercise tolerance is an independent predictor of prognosis in patients with heart failure (HF); however, the relationship between serum suPAR level and exercise tolerance is unclear. We prospectively enrolled 94 patients who were hospitalized for worsening of HF. All patients underwent a symptom-limited cardiopulmonary exercise test to evaluate exercise tolerance. The median value of serum suPAR was 4848 pg/ml. During follow up, 44 patients (47%) were admitted for all-cause mortality and re-hospitalization for HF. Median serum suPAR was significantly higher in the patients with cardiac events than in the patients with non-event group. Patients were divided into two groups according to circulating suPAR levels. Kaplan-Meier analysis demonstrated that adverse cardiac events were significantly higher in the high suPAR group (log-rank p = 0.023). Multivariate analysis revealed that suPAR was independently correlated with the parameters of exercise tolerance such as anaerobic threshold (p = 0.007) and peak oxygen uptake (p = 0.005). suPAR levels predicted adverse cardiac events and independently correlated with the parameters of exercise tolerance. suPAR could be a useful surrogate biomarker of exercise tolerance in patients with HF.

The biomarkers suPAR and blood eosinophils are associated with hospital readmissions and mortality in asthma - a retrospective cohort study

Introduction

Prognostic biomarkers in asthma are needed. The biomarker soluble urokinase plasminogen activator receptor (suPAR) has been associated with asthma control and with prognosis in acutely admitted medical patients. We investigated if suPAR and blood eosinophil counts at the time of admission for asthma are associated with readmission and mortality.

Methods

Our cohort comprised 1341 patients (median age 45.3, IQR 30.1–63.1) acutely admitted with a diagnosis of asthma to Hvidovre Hospital, Denmark (November 2013 to March 2017). Patients had suPAR and blood eosinophils measured at admission. Outcomes were 365-day readmission and all-cause mortality. Logistic regression analysis adjusted for age, sex, C-reactive protein, and Charlson comorbidity score was used to assess the association of the two biomarkers with readmission and all-cause mortality.

Results

Compared to event-free patients, patients who were either readmitted (n = 452, 42.3%) or died (n = 57, 5.3%) had significantly higher suPAR concentrations (p < 0.0001) and lower eosinophil counts (p = 0.0031) at admission. The highest odds of readmission or mortality were observed for patients in either the 4th suPAR quartile (p < 0.0001) or with eosinophil counts < 150 cells/μL at admission. Increasing levels of suPAR were associated with 365-day readmission (OR 1.3 [1.0–1.6]; p = 0.05) and mortality (OR 2.9 [1.7–5.1]; p = 0.0002). Eosinophil count > 300 cells/μL was significantly associated with lower odds of readmission (OR 0.64 [0.5–0.9]; p = 0.005) and lower mortality (OR 0.7 [0.6–0.9]; p = 0.0007).

Conclusions

In patients acutely admitted with asthma, elevated suPAR concentrations together with blood eosinophil count < 150 cells/μL at the time of hospital admission were associated with both 365-day all-cause readmission and mortality.

Kinetics of the soluble urokinase plasminogen activator receptor (suPAR) in cirrhosis

Background

The soluble urokinase plasminogen activator receptor (suPAR) is related to hepatic inflammation and fibrosis and has been suggested to participate in the development of liver cirrhosis. Therefore, the aim of the current study was to measure the concentration of suPAR in the hepatic vein of cirrhotic patients during a liver vein catheterization to identify a possible hepatic suPAR generation. Furthermore, we explored if suPAR levels were associated with the degree of cirrhosis and liver dysfunction.

Methods and patients

We included 105 cirrhotic patients and 19 liver-healthy controls. Blood was sampled from the hepatic vein and the femoral artery and suPAR was measured by enzyme-linked immunosorbent assay.

Results

We identified significantly higher median suPAR concentrations among the cirrhotic patients (7.2 ng/ml in the hepatic vein; 6.8 ng/ml in the femoral artery) compared to the controls (2.6 ng/ml, respectively, p-values <0.001). However, the median hepatic suPAR formation was 0.0 ng/ml in both groups. We observed significantly increasing suPAR levels according to higher Child classes (4.5 ng/ml, 6.9 ng/ml and 9.0 ng/ml, Child A, B, C respectively; p-value<0.001), and significantly higher median suPAR concentrations in patients with ascites versus patients without ascites (8.1 ng/ml versus 5.3 ng/ml, respectively, p-value<0.001). suPAR levels were significantly related to bilirubin (r = 0.48, p<0.001), the hepatic venous pressure gradient (r = 0.39, p<0.001), the cardiac index (r = 0.24, p = 0.02) and the plasma volume (r = 0.33, p = 0.001), whereas suPAR levels were significantly inversely related to albumin (r = -0.59, p<0.001), plasma coagulation factors (r-0.39, p<0.001), the mean arterial pressure (r = -0.28, p = 0.004), the systemic vascular resistance (r = 0.26, p = 0.007), the indocyanine green clearance (r = -0.51, p<0,001) and the galactose elimination capacity (r = -0.39, p<0.001).

Conclusion

We identified elevated suPAR concentration in cirrhotic patients, which correlated significantly with the degree of cirrhosis and liver failure, but we were not able to demonstrate hepatic suPAR generation per se. This suggests that further investigations of the source of suPAR in cirrhotic patients need to be undertaken.

Serum plasminogen activator urokinase receptor predicts elevated risk of acute respiratory distress syndrome in patients with sepsis and is positively associated with disease severity, inflammation and mortality

The present study aimed to evaluate the predictive value of serum soluble urokinase plasminogen activator receptor (suPAR) regarding the risk of acute respiratory distress syndrome (ARDS) in sepsis patients, and investigate its correlation/association with disease severity, inflammation and mortality in sepsis patients with ARDS. A total of 57 sepsis patients with ARDS and 58 sepsis patients without ARDS were recruited for the present case-control study. Laboratory tests, acute physiology and chronic health evaluation (APACHE) II score and sequential organ failure assessment (SOFA) score were evaluated, and mortality during hospitalization was recorded. Blood samples were collected and serum suPAR was detected by ELISA. Furthermore, tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, IL-8, IL-10 and IL-17, as well as C-reactive protein (CRP) were detected. The results indicated that the serum levels of suPAR in sepsis patients with ARDS were higher than those in sepsis patients without ARDS. Receiver operating characteristics (ROC) curve analysis indicated that it was possible to distinguish sepsis patients with ARDS from sepsis patients without ARDS based on their serum suPAR levels, and multivariate logistic regression analysis suggested that serum suPAR levels were an independent predictor of the risk of ARDS in sepsis patients. In sepsis patients with ARDS, serum suPAR levels were positively correlated with the APACHE II score, SOFA score and the levels of CRP, TNF-α, IL-1β and IL-8. In addition, serum suPAR levels were lower in survivors compared with those in non-survivors, and ROC curve analysis suggested that serum suPAR was able to predict the probability of mortality. In conclusion, serum suPAR independently predicted an elevated risk of ARDS in patients with sepsis, and was correlated/associated with greater disease severity, higher inflammation and increased mortality in patients with sepsis and ARDS.

Increased Serum Soluble Urokinase Plasminogen Activator Receptor Predicts Short-Term Outcome in Patients with Hepatitis B-Related Acute-on-Chronic Liver Failure

Aims

Soluble urokinase plasminogen activator receptor (suPAR) reflects the immune activation in circumstances of inflammation and infection. It has been considered as a risk biomarker associated with poor outcome in various low-grade inflammation and infectious diseases. The study is aimed at investigating whether suPAR has a predictive value with short-term survival in patients with hepatitis B-related acute-on-chronic liver failure (HB-ACLF).

Methods

Serum suPAR expression was compared among patients with different states of chronic hepatitis B virus infection. Sixty HB-ACLF patients were recruited as the training cohort and followed up for 90 days. Serum suPAR level and the clinical relevance with short-term outcome were investigated. The temporal dynamics of suPAR were evaluated in 50 HB-ACLF patients with available serum sequentially at baseline, week 2 and week 4. Another 167 HB-ACLF patients were enrolled to validate the predictive value of suPAR with respect to the prognosis.

Results

Serum suPAR level was significantly increased in HB-ACLF patients compared to non-ACLF patients. In the training set of HB-ACLF, we observed higher suPAR level, INR, MELD score, and more complications in nonsurvivors than survivors. Longitudinal analysis revealed an increased trend of suPAR level in nonsurvivors during week 0 to week 4 and the modest decline in survivors. It showed that the synchronous suPAR level was higher in nonsurvivors at all indicated time points. Elevated suPAR level at baseline was identified as a strong predictor of a 90-day mortality of HB-ACLF patients. It was confirmed suPAR > 16.26 ng/ml had a positive predictive value of 72.22% and a negative predictive value of 77.88% for poor outcome in the validation cohort.

Conclusions

Serum suPAR level increases significantly in HB-ACLF patients and associated with a 90-day mortality. It suggests that suPAR might be a potential biomarker to predict the prognosis of HB-ACLF patients.

Neutrophils are a main source of circulating suPAR predicting outcome in critical illness

Background

Circulating levels of soluble urokinase plasminogen activation receptor (suPAR) have been proposed as a prognostic biomarker in patients with critical illness and sepsis. However, the origin of suPAR in sepsis has remained obscure. We investigated the potential cellular sources of suPAR by analyzing membrane-bound urokinase plasminogen activator receptor (uPAR, CD87) and evaluated its clinical relevance in critically ill patients.

Methods

We studied 87 critically ill patients (44 with sepsis, 43 without sepsis) from the medical intensive care unit (ICU) in comparison to 48 standard care patients with infections and 27 healthy controls in a prospective single-center non-interventional cohort study. Cellular uPAR expression of different immune cell subsets (by flow cytometry from peripheral blood) and corresponding serum suPAR concentrations were determined upon ICU admission and at day 3. Furthermore, we analyzed the effects of serum from sepsis patients on the activation and uPAR cleavage of primary human neutrophils and macrophages in vitro.

Results

In healthy controls, uPAR (CD87) expression was detected on nearly all blood neutrophils and monocytes, but only scarcely on lymphocytes. While uPAR expression on monocytes was maintained in ICU patients, only 58% of neutrophils from critically ill patients expressed uPAR, which was significantly lower than in healthy controls or standard care patients. Concomitantly, serum suPAR levels were significantly increased in ICU patients. We noted a clear inverse correlation between low neutrophilic uPAR and high serum suPAR in standard care and ICU patients, indicating that shedding of uPAR from activated neutrophils represents a main source of suPAR in systemic inflammation. Both low uPAR and high suPAR were closely associated with mortality in critically ill patients. Furthermore, serum from sepsis patients induced uPAR protein expression and subsequent receptor shedding on isolated primary neutrophils, but not on macrophages, in vitro.

Conclusions

The inverse correlation between low uPAR surface expression on neutrophils and high serum suPAR in critically ill patients supports that neutrophils are a main source of shed suPAR proteins in systemic inflammation. Furthermore, high suPAR levels and low neutrophilic uPAR expression predict mortality in ICU patients.

Electronic supplementary material

The online version of this article (10.1186/s40560-019-0381-5) contains supplementary material, which is available to authorized users.

Predictive value of soluble urokinase-type plasminogen activator receptor for mortality in patients with suspected myocardial infarction

BACKGROUND

Early risk stratification of patients with suspected acute myocardial infarction (AMI) constitutes an unmet need in current daily clinical practice. We aimed to evaluate the predictive value of soluble urokinase-type plasminogen activator receptor (suPAR) levels for 1-year mortality in patients with suspected AMI.

METHODS AND RESULTS

suPAR levels were determined in 1314 patients presenting to the emergency department with suspected AMI. Patients were followed up for 12 months to assess all-cause mortality. Of 1314 patients included, 308 were diagnosed with AMI. Median suPAR levels did not differ between subjects with AMI compared to non-AMI (3.5 ng/ml vs. 3.2 ng/ml, p = 0.066). suPAR levels reliably predicted all-cause mortality after 1 year. Hazard ratio for 1-year mortality was 12.6 (p < 0.001) in the quartile with the highest suPAR levels compared to the first quartile. The prognostic value for 6-month mortality was comparable to an established risk prediction model, the Global Registry of Acute Coronary Events (GRACE) score, with an AUC of 0.79 (95% CI 0.72-0.86) for the GRACE score and 0.77 (95% CI 0.69-0.84) for suPAR. Addition of suPAR improved the GRACE score, as shown by integrated discrimination improvement statistics of 0.036 (p = 0.03) suggesting a further discrimination of events from non-events by the addition of suPAR.

CONCLUSIONS

suPAR levels reliably predicted mortality in patients with suspected AMI.

STUDY REGISTRATION

http://www.clinicaltrials.gov (NCT02355457).

Diagnostic Value of Soluble Urokinase-Type Plasminogen Activator Receptor in Addition to High-Sensitivity Troponin I in Early Diagnosis of Acute Myocardial Infarction

The soluble urokinase-type plasminogen activator receptor (suPAR) is a new marker for immune activation and inflammation and may provide diagnostic value on top of established biomarkers in patients with suspected acute myocardial infarction (AMI). Here, we evaluate the diagnostic potential of suPAR levels on top of high-sensitivity troponin I (hs-TnI) in a cohort of patients with suspected AMI. A total of 1220 patients presenting to the emergency department with suspected AMI were included, of whom 245 were diagnosed with AMI. Median suPAR levels at admission were elevated in subjects with AMI compared to non-AMI (3.8 ng/mL vs. 3.3 ng/mL, p = 0.001). In C-statistics, the area under the curve (AUC) regarding the diagnosis of AMI was low (0.57 at an optimized cut-off of 3.7 ng/mL). Moreover, baseline suPAR levels on top of troponin values at admission and hour 1 reduced the number of patients who were correctly ruled-out as non-AMI, and who were correctly ruled-in as AMI. Our study shows that circulating levels of suPAR on top of high-sensitivity troponin I do not improve the early diagnosis of AMI.

The Role of Fibrinolytic Regulators in Vascular Dysfunction of Systemic Sclerosis

Systemic sclerosis (SSc) is a connective tissue disease of autoimmune origin characterized by vascular dysfunction and extensive fibrosis of the skin and visceral organs. Vascular dysfunction is caused by endothelial cell (EC) apoptosis, defective angiogenesis, defective vasculogenesis, endothelial-to-mesenchymal transition (EndoMT), and coagulation abnormalities, and exacerbates the disease. Fibrinolytic regulators, such as plasminogen (Plg), plasmin, α2-antiplasmin (α2AP), tissue-type plasminogen activator (tPA), urokinase-type plasminogen activator (uPA) and its receptor (uPAR), plasminogen activator inhibitor 1 (PAI-1), and angiostatin, are considered to play an important role in the maintenance of endothelial homeostasis, and are associated with the endothelial dysfunction of SSc. This review considers the roles of fibrinolytic factors in vascular dysfunction of SSc.

The cell surface phenotype of human dendritic cells

Dendritic cells (DC) are bone marrow derived leucocytes that are part of the mononuclear phagocytic system. These are surveillance cells found in all tissues and, as specialised antigen presenting cells, direct immune responses. Membrane molecules on the DC surface form a landscape that defines them as leucocytes and part of the mononuclear phagocytic system, interacts with their environment and directs interactions with other cells. This review describes the DC surface landscape, reflects on the different molecules confirmed to be on their surface and how they provide the basis for manipulation and translation of the potent functions of these cells into new diagnostics and immune therapies for the clinic.

Soluble Urokinase-type Plasminogen Activator Receptor Predicts All-cause 5-Year Mortality in Ischemic Stroke and TIA

AIM

We evaluated soluble urokinase-type plasminogen activator receptor (suPAR) levels in different stroke subtypes and assessed their prognostic value regarding 5-year outcomes.

MATERIALS AND METHODS

The study included 117 stroke patients (81 males; mean=age 61±11 years) with suspected cardioembolic stroke whose plasma suPAR concentration was assessed. Altogether, 20 (17.1%) patients suffered from stroke as a result of cardioembolism, 12 (10.3%) from large-artery atherosclerosis, 9 (7.7%) from small-vessel disease, 11 (9.4%) from both large-artery and cardioembolic etiology, and 65 (55.6%) had cryptogenic stroke. The mean follow-up period was 5 years.

RESULTS

suPAR concentration was higher in patients who suffered from stroke/transient ischemic attack due to large-artery atherosclerosis (3.2±0.9 ng/ml) compared to small-vessel disease (2.0±0.5 ng/ml, p<0.001). An elevated plasma suPAR concentration was associated with all-cause mortality during the follow-up period (p=0.003).

CONCLUSION

Elevated plasma suPAR concentrations predicted all-cause mortality during the 5-year follow-up after ischemic stroke. suPAR was not able to differentiate patients with cardioembolic stroke from those with other stroke types.

Soluble Urokinase-Type Plasminogen Activator Receptor Improves Risk Prediction in Patients With Chronic Heart Failure

OBJECTIVES

This study investigated the predictive value of soluble urokinase-type plasminogen activator receptor (suPAR) in patients with chronic heart failure (CHF).

BACKGROUND

SuPAR originates from proteolytic cleavage of the membrane-bound receptor from activated immune and endothelial cells and reflects the level of immune activation. As inflammation plays a crucial role in the complex pathophysiology of CHF, we hypothesized that suPAR might be a suitable prognostic biomarker in patients with CHF.

METHODS

SuPAR levels were determined in 319 patients with CHF admitted to our outpatient department for heart failure and in a second cohort consisting of 346 patients with CHF, for validation.

RESULTS

During a median follow-up time of 3.2 years, 119 patients (37.3%) died. SuPAR was a strong predictor of mortality with a crude hazard ratio (HR) per increase of 1 SD (HR per 1 SD) of 1.96 (95% confidence interval [CI]: 1.63 to 2.35; p < 0.001) in univariate analysis and remained significant after comprehensive multivariate adjustment with an adjusted HR per 1 SD of 1.38 (95% CI: 1.04 to 1.83; p = 0.026). SuPAR added prognostic value beyond the multivariate model indicated by improvements in C-statistics (area under the curve: 0.72 vs 0.74, respectively; p = 0.02), the category-free net reclassification index (24.9%; p = 0.032), and the integrated discrimination improvement (0.011; p = 0.05). Validation in the second cohort yielded consistent results.

CONCLUSIONS

SuPAR is a strong and independent predictor of mortality in patients with CHF, potentially suitable to refine risk assessment in this vulnerable group of patients. Our results emphasize the impact of immune activation on survival in patients with CHF.

Value of soluble Urokinase plasminogen activator receptor over age as a biomarker of impaired myocardial relaxation

Background

SuPAR is a biomarker that reflects the level of immune activation. As inflammation plays an important role in the ageing process of the cardiovascular system, we hypothesized that suPAR might be a useful predictive biomarker of the ageing heart.

Methods

We performed conventional and tissue Doppler echocardiography and measured plasma suPAR levels.

Results

We studied community adults (n=120, 37.5% female) (mean age: 70.3±9.3 years) without known cardiovascular disease (CVD). Participants with impaired myocardial relaxation were older (84% vs 59% were aged ≥71 years, p=0.002), with more diabetes mellitus (27% vs 11%, p=0.034). SuPAR levels were higher among participants with impaired myocardial relaxation (3.9 ng/ml vs 3.0 ng/ml, p=0.015). At the univariate level, older age (OR 3.6; 95%CI 1.6, 8.5; p=0.003), diabetes mellitus (OR 3.04; 95%CI 1.1, 8.8; p=0.04), systolic blood pressure (OR 1.03; 95%CI 1.001, 1.1; p=0.041) and suPAR levels ≥3.00ng/ml (OR 3.4; 95%CI 1.16, 7.4; p=0.002) were associated with impaired myocardial relaxation. In multivariable regression analysis, only older age (OR 2.8; 95%CI 1.1, 6.7; p=0.026) and suPAR (OR 2.7; 95%CI 1.2, 6.1; p=0.018) remained independently associated with impaired myocardial relaxation. Receiver operating characteristics (ROC) curve analysis revealed an area under the curve (AUC) value of 0.63 (95% CI 0.54, 0.71) for model that included age alone. Addition of suPAR significantly increased AUC value to 0.70 (95%CI 0.60, 0.79), which was significantly larger than the model with age alone (p=0.016).

Conclusion

We demonstrate additional ability of suPAR, over age, to predict impaired myocardial relaxation.

Trial registration

ClinicalTrials.gov Identifier: NCT02791139 (Registered May 31, 2016).

Plasma Soluble Urokinase-Type Plasminogen Activator Receptor Is Not Associated with Neurological Outcome in Patients with Aneurysmal Subarachnoid Hemorrhage

Object

Aneurysmal subarachnoid hemorrhage (aSAH) is a common cause of death or long-term disability. Despite advances in neurocritical care, there is still only a very limited ability to monitor the development of secondary brain injury or to predict neurological outcome after aSAH. Soluble urokinase-type plasminogen activator receptor (suPAR) has shown potential as a prognostic and as an inflammatory biomarker in a wide range of critical illnesses since it displays an association with overall immune system activation. This is the first time that suPAR has been evaluated as a prognostic biomarker in aSAH.

Methods

In this prospective population-based study, plasma suPAR levels were measured in aSAH patients (n = 47) for up to 5 days. suPAR was measured at 0, 12, and 24 h after patient admission to the intensive care unit (ICU) and daily thereafter until he/she was transferred from the ICU. The patients’ neurological outcome was evaluated with the modified Rankin Scale (mRS) at 6 months after aSAH.

Results

suPAR levels (n = 47) during the first 24 h after aSAH were comparable in groups with a favorable (mRS 0–2) or an unfavorable (mRS 3–6) outcome. suPAR levels during the first 24 h were not associated with the findings in the primary brain CT, with acute hydrocephalus, or with antimicrobial medication use during 5-days’ follow-up. suPAR levels were associated with generally accepted inflammatory biomarkers (C-reactive protein, leukocyte count).

Conclusion

Plasma suPAR level was not associated with either neurological outcome or selected clinical conditions. While suPAR is a promising biomarker for prognostication in several conditions requiring intensive care, it did not reveal any value as a prognostic biomarker after aSAH.

Effects of Acute Exercise on Circulating Soluble Form of the Urokinase Receptor in Patients With Major Depressive Disorder

Inflammation has been proposed to play a role in the generation of depressive symptoms. Previously, we demonstrated that patients with major depressive disorder (MDD) have increased plasma levels of the soluble form of the urokinase receptor (suPAR), a marker for low-grade inflammation. The aim of this study was to test the hypothesis that acute exercise would induce inflammatory response characterized by increased suPAR and elucidate whether patients with MDD display altered levels of suPAR in response to acute exercise. A total of 17 patients with MDD and 17 controls were subjected to an exercise challenge. Plasma suPAR (P-suPAR) was analyzed before, during, and after exercise. There was a significantly higher baseline P-suPAR in the patients with MDD, and the dynamic changes of P-suPAR during the exercise were significantly lower in the patients with MDD, compared with the controls. This study supports the hypothesis that an activation of systemic inflammatory processes, measured as elevated P-suPAR, is involved in the pathophysiology of depression. The study concludes that P-suPAR is influenced by acute exercise, most likely due to release from activated neutrophils.

The plasminogen activation system in neuroinflammation

The plasminogen activation (PA) system consists in a group of proteases and protease inhibitors regulating the activation of the zymogen plasminogen into its proteolytically active form, plasmin. Here, we give an update of the current knowledge about the role of the PA system on different aspects of neuroinflammation. These include modification in blood-brain barrier integrity, leukocyte diapedesis, removal of fibrin deposits in nervous tissues, microglial activation and neutrophil functions. Furthermore, we focus on the molecular mechanisms (some of them independent of plasmin generation and even of proteolysis) and target receptors responsible for these effects. The description of these mechanisms of action may help designing new therapeutic strategies targeting the expression, activity and molecular mediators of the PA system in neurological disorders involving neuroinflammatory processes. This article is part of a Special Issue entitled: Neuro Inflammation edited by Helga E. de Vries and Markus Schwaninger.

Soluble urokinase plasminogen activator receptor and incidence of venous thromboembolism

Raised plasma levels of the soluble urokinase plasminogen activator receptor (suPAR) have been associated with increased incidence of cardiovascular diseases. Whether suPAR is associated with venous thromboembolism (VTE) is largely unknown. The purpose of the present study was to investigate the relationship between suPAR and incidence of VTE in a cohort study. suPAR was measured in 5,203 subjects (aged 46-68 years, 58 % women) from the general population, who participated in the Malmö Diet and Cancer (MDC) study between 1991 and 1994. Incident cases of VTE were identified from the Swedish patient register during a mean follow-up of 15.7 years. Of 5,203 subjects with measurements of suPAR, 239 had VTE during follow-up (127 venous thrombosis, 86 lung embolism, 26 both). Incidence of VTE was significantly higher in subjects with suPAR levels in the top quartile. Adjusted for age and sex, the HR (4th vs 1st quartile) was 1.74 (95 %CI: 1.2-2.6, p for trend=0.003). After adjustments for risk factors, the HR was 1.66 (95 %CI: 1.1-2.5, p for trend=0.016). High level of suPAR was a risk indicator for incidence of VTE in this population-based cohort study. The causal relationships between suPAR and VTE remain to be explored.

Soluble urokinase plasminogen activator receptor levels are associated with severity of fibrosis in nonalcoholic fatty liver disease

The identification of individuals with severe liver fibrosis among patients with chronic liver disease is of major importance when evaluating prognosis, potential risk for complications, and when deciding treatment strategies. Although percutaneous liver biopsy is still considered a "gold standard" for staging of liver fibrosis, attempts to find reliable noninvasive markers of liver fibrosis are frequent. Inflammation is essential for the progression of fibrosis. The urokinase plasminogen activator and its receptor have been associated with hepatic inflammation and fibrosis in mice. High serum concentrations of soluble urokinase plasminogen activator receptor (suPAR) are suggested to be involved in inflammation, tissue remodeling, and cancer metastasis. Here, we evaluated serum suPAR as a noninvasive test to detect liver fibrosis in 82 well-characterized patients with nonalcoholic fatty liver disease (NAFLD), and in 38 untreated patients with chronic hepatitis C virus (HCV) infection at the time of their first liver biopsy. suPAR levels were increased in chronic liver disease compared with blood donors (P < 0.001). Patients with HCV had higher suPAR concentrations than patients with NAFLD (P < 0.002). suPAR levels were associated with the severity of fibrosis, particularly in NAFLD, but did not correlate with inflammation. Regarding the performance in predicting severity of fibrosis, suPAR was essentially as good as other commonly used noninvasive fibrosis scoring systems. The results in HCV confirm previous observations. However, this is the first study to investigate suPAR as a biomarker in NAFLD, and the results indicate that suPAR may constitute a severity marker related to fibrosis and prognosis rather than reflecting inflammation.

Extracellular NAD(+) inhibits human neutrophil apoptosis

Regulation of neutrophil apoptosis plays a critical role in the inflammatory response. Inflammation has previously been shown to increase levels of extracellular β-nicotinamide adenine dinucleotide (NAD(+)). The present study demonstrates that extracellular NAD(+) at concentrations found in the inflamed tissues profoundly delays spontaneous apoptosis of human neutrophils as was evidenced by inhibition of phosphatidylserine (PS) exposure, DNA fragmentation and caspase-3 activation. The effect was abrogated by NF157, an antagonist of P2Y11 receptor, and was pertussis toxin-insensitive. The NAD(+)-mediated delay of neutrophil apoptosis was reversed by 2',5'-dideoxyadenosine, an inhibitor of adenylyl cyclase, and Rp-8-Br-cAMPS, an inhibitor of type I cAMP-dependent protein kinase A (PKA). Blocking of NAD(+)-induced influx of extracellular Ca(2+) with EGTA did not abolish the pro-survival effect of NAD(+). Extracellular NAD(+) inhibited proteasome-dependent degradation of Mcl-1 upstream of caspase activation and, furthermore, suppressed Bax translocation to the mitochondria and attenuated both dissipation of mitochondrial transmembrane potential (ΔΨm) and cytochrome c release from the mitochondria into the cytosol. Finally, we found that extracellular NAD(+) inhibited spontaneous activation of caspase-9, but not caspase-8, and the pro-survival effect of extracellular NAD(+) was abrogated by the inhibitor of caspase-9, but not by the inhibitor of caspase-8. Together, these results demonstrate that extracellular NAD(+) inhibits neutrophil apoptosis via P2Y11 receptor and cAMP/PKA pathway by regulating Mcl-1 level, Bax targeting to the mitochondria and mitochondrial apoptotic pathway. Thus, extracellular NAD(+) acts as a neutrophil survival factor that can contribute to prolonged neutrophil lifespan in inflammatory response.

Soluble urokinase plasminogen activator receptor--a valuable biomarker in systemic lupus erythematosus?

Systemic lupus erythematosus (SLE) is a potentially severe autoimmune condition with an unpredictable disease course, often with fluctuations in disease activity over time. Long term inflammation and drug-related side-effects may subsequently lead to permanent organ damage, a consequence which is intimately connected to decreased quality of life and mortality. New lupus biomarkers that convey information regarding inflammation and/or organ damage are thus warranted. Today, there is no clinical biomarker that indicates the risk of damage accrual. Herein we highlight the urokinase plasminogen activator receptor (uPAR) and especially its soluble form (suPAR) that besides having biological functions in e.g. proteolysis, cell migration and tissue homeostasis, recently has emerged as a promising biomarker of inflammation and prognosis of several disorders. A strong association between suPAR and organ damage in SLE was recently demonstrated, and preliminary data (presented in this review) suggests the possibility of a predictive value of suPAR blood levels. The involvement of suPAR in the pathogenesis of SLE remains obscure, but its effects in leukocyte recruitment, phagocytic uptake of dying cells (efferocytosis) and complement regulation suggests that the central parts of the SLE pathogenesis could be regulated by suPAR, and vice versa.

Soluble urokinase-type plasminogen activator levels are related to plasma cytokine levels but have low predictive value for mortality in trauma patients

INTRODUCTION

Soluble urokinase-type plasminogen activator (suPAR) represents a marker for immune activation and has predictive value in critically ill patients. The kinetics of suPAR and its correlation with the immune response and outcome in trauma patients are unknown.

METHODS

Plasma concentrations of inflammatory cytokines and suPAR were determined in adult trauma patient (n = 69) samples obtained by the Helicopter Emergency Medical Services at arrival at the emergency department (ED) and at days 1, 3, 5, 7, 10, and 14.

RESULTS

Initial suPAR levels were unrelated to injury severity score and higher in nonsurvivors compared with survivors, although no difference was observed between early and late mortality. The area under the receiver operating characteristic curve to predict mortality was 0.6 (95% confidence interval, 0.48-0.72). Soluble urokinase-type plasminogen activator levels increased over time in 94% of patients, although suPAR increase did not precede death. Tumor necrosis factor α at the ED correlated with suPAR at that time point, whereas concentrations of other proinflammatory cytokines at the ED correlated with suPAR levels at days 1 and 5.

CONCLUSIONS

After trauma, initial suPAR plasma concentrations are higher in nonsurvivors compared with survivors, but its predictive value is low. Soluble urokinase-type plasminogen activator levels increase over time after trauma, and concentrations at later time points are related to cytokine levels at the ED.

Plasma-soluble urokinase-type plasminogen activator receptor levels are associated with clinical and pathological activities in lupus nephritis: a large cohort study from China

BACKGROUND

In this study, we detected plasma urokinase plasminogen activator (uPA) and soluble urokinase-type plasminogen activator receptor (uPAR) levels in Chinese lupus nephritis patients from a large cohort. The associations between plasma uPA and soluble uPAR and clinico-pathological characteristics were further analyzed.

METHODS

The levels of plasma uPA and soluble uPAR were detected by ELISA in 202 patients with active lupus nephritis, 17 systemic lupus erythematosus (SLE) patients without renal involvement and 21 normal controls.

RESULTS

There were no significant differences in the levels of the average plasma uPA among the lupus nephritis group, non-renal SLE group and normal control group (p = 0.129). The plasma-soluble uPAR level in the lupus nephritis group was significantly higher than that in the non-renal involvement SLE group (p = 0.004) and that in normal controls (p < 0.001). The plasma uPAR levels were positively associated with SLEDAI scores (r = 0.215, p = 0.007). In renal pathological data, there was significant difference of plasma-soluble uPAR levels among various pathological classes, which was the highest in the class IV group (p = 0.012). The level of plasma-soluble uPAR was found to be a risk factor for long-term renal outcomes in lupus nephritis by univariate survival analysis (p = 0.013, HR = 6.326, 95% CI: 1.466-27.298).

CONCLUSIONS

Our study showed that the significantly increased plasma levels of soluble uPAR could be found in active lupus nephritis, and they were associated with some clinico-pathological features. Its involvement in the pathogenesis of lupus nephritis warrants further study.

Unchanged plasma levels of the soluble urokinase plasminogen activator receptor in elective coronary artery bypass graft surgery patients and cardiopulmonary bypass use

OBJECTIVE AND DESIGN

The soluble urokinase plasminogen activator receptor (suPAR) has been recently recognized as a potential biological marker of various disease states, but the impact of a major surgical intervention on the suPAR level has not yet been established. The aim of our study was to investigate if the induction of a systemic inflammatory reaction in response to cardiopulmonary bypass would be accompanied by an increase in the plasma suPAR level.

METHODS AND SUBJECTS

Patients undergoing coronary artery bypass grafting under cardiopulmonary bypass (CPB) were added. Based on the baseline suPAR level, patients were divided into group 1 (suPAR within normal range) or group 2 (suPAR above range). Blood was collected before the induction of anesthesia and 6 and 24 hours after surgery. Plasma suPAR, IL-6, IL-8, TNF-α, troponin I, NT-proBNP, and NGAL were quantified to assess the impact of surgical trauma on these markers.

RESULTS

The baseline suPAR level was within the normal range in 31 patients (3.3 ng/mL), and elevated in 29 (5.1 ng/mL) (p<0.001). Baseline mediators of systemic inflammatory reaction concentrations (IL-6, TNF-α, and IL-8) and organ injury indices (troponin I, NT-proBNP, and NGAL) were low and increased after surgery in all patients (p<0.05). The surgery did not cause significant changes in the suPAR level either at 6 or 24 hours after, however the difference between groups observed at baseline remained substantial during the postoperative period.

CONCLUSIONS

There was no change in the suPAR level observed in patients subjected to elective cardiac coronary artery bypass surgery and CPB, despite activation of a systemic inflammatory reaction.

Urinary soluble urokinase receptor levels are elevated and pathogenic in patients with primary focal segmental glomerulosclerosis

BACKGROUND

Focal segmental glomerulosclerosis (FSGS) is a major cause of end-stage renal disease. Recent studies have proposed that plasma soluble urokinase receptor (suPAR) might be a causative circulating factor but this proposal has caused controversy. This study aimed to measure urinary suPAR levels in patients with primary FSGS and its significance in the pathogenesis of FSGS.

METHODS

Sixty-two patients with primary FSGS, diagnosed between January 2006 and January 2012, with complete clinical and pathologic data were enrolled, together with disease and normal controls. Urinary suPAR levels were measured using commercial ELISA kits and were corrected by urinary creatinine (Cr). The associations between urinary suPAR levels and clinical data at presentation and during follow up were analyzed. Conditionally immortalized human podocytes were used to study the effect of urinary suPAR on activating β3 integrin detected by AP5 staining.

RESULTS

The urinary suPAR level of patients with primary FSGS (500.56, IQR 262.78 to 1,059.44 pg/μmol Cr) was significantly higher than that of patients with minimal change disease (307.86, IQR 216.54 to 480.18 pg/μmol Cr, P = 0.033), membranous nephropathy (250.23, IQR 170.37 to 357.59 pg/μmol Cr, P <0.001), secondary FSGS (220.45, IQR 149.38 to 335.54 pg/μmol Cr, P <0.001) and normal subjects (183.59, IQR 103.92 to 228.78 pg/μmol Cr, P <0.001). The urinary suPAR level of patients with cellular variant was significantly higher than that of patients with tip variant. The urinary suPAR level in the patients with primary FSGS was positively correlated with 24-hour urine protein (r = 0.287, P = 0.024). During follow up, the urinary suPAR level of patients with complete remission decreased significantly (661.19, IQR 224.32 to 1,115.29 pg/μmol Cr versus 217.68, IQR 121.77 to 415.55 pg/μmol Cr, P = 0.017). The AP5 signal was strongly induced along the cell membrane when human differentiated podocytes were incubated with the urine of patients with FSGS at presentation, and the signal could be reduced by a blocking antibody specific to uPAR.

CONCLUSIONS

Urinary suPAR was specifically elevated in patients with primary FSGS and was associated with disease severity. The elevated urinary suPAR could activate β3 integrin on human podocytes.

Administration of recombinant soluble urokinase receptor per se is not sufficient to induce podocyte alterations and proteinuria in mice

Circulating levels of soluble forms of urokinase-type plasminogen activator receptor (suPAR) are generally elevated in sera from children and adults with FSGS compared with levels in healthy persons or those with other types of kidney disease. In mice lacking the gene encoding uPAR, forced increases in suPAR concentration result in FSGS-like glomerular lesions and proteinuria. However, whether overexpression of suPAR, per se, contributes to the pathogenesis of FSGS in humans remains controversial. We conducted an independent set of animal experiments in which two different and well characterized forms of recombinant suPAR produced by eukaryotic cells were administered over the short or long term to wild-type (WT) mice. In accordance with the previous study, the delivered suPARs are deposited in the glomeruli. However, such deposition of either form of suPAR in the kidney did not result in increased glomerular proteinuria or altered podocyte architecture. Our findings suggest that glomerular deposits of suPAR caused by elevated plasma levels are not sufficient to engender albuminuria.

Performance of galactomannan, beta-d-glucan, Aspergillus lateral-flow device, conventional culture, and PCR tests with bronchoalveolar lavage fluid for diagnosis of invasive pulmonary aspergillosis

Galactomannan detection in bronchoalveolar lavage (BAL) fluid samples (GM test) is currently considered the gold standard test for diagnosing invasive pulmonary aspergillosis (IPA). The limitations, however, are the various turnaround times and availability of testing. We compared the performance of GM testing with that of conventional culture, an Aspergillus lateral-flow-device (LFD) test, a beta-d-glucan (BDG) test, and an Aspergillus PCR assay by using BAL fluid samples from immunocompromised patients. A total of 78 BAL fluid samples from 78 patients at risk for IPA (74 samples from Graz and 4 from Mannheim) collected between December 2012 and May 2013 at two university hospitals in Austria and Germany were included. Three patients had proven IPA, 14 probable IPA, and 17 possible IPA, and 44 patients had no IPA. The diagnostic accuracies of the different methods for probable/proven IPA were evaluated. The diagnostic odds ratios were the highest for the GM, PCR, and LFD tests. The sensitivities for the four methods (except culture) were between 70 and 88%. The combination of the GM (cutoff optical density index [ODI], >1.0) and LFD tests increased the sensitivity to 94%, while the combination of the GM test (>1.0) and PCR resulted in 100% sensitivity (specificity for probable/proven IPA, 95 to 98%). The performance of conventional culture was limited by low sensitivity, while that of the BDG test was limited by low specificity. We evaluated established and novel diagnostic methods for IPA and found that the Aspergillus PCR, LFD, and GM tests were the most useful methods for diagnosing the disease by using BAL fluid samples. In particular, the combination of the GM test and PCR or, if PCR is not available, the LFD test, allows for sensitive and specific diagnosis of IPA.

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.

Differential effects of the autophagy inhibitors 3-methyladenine and chloroquine on spontaneous and TNF-α-induced neutrophil apoptosis

Autophagy and apoptosis cooperate to modulate cell survival. Neutrophils are short-lived cells and apoptosis is considered to be the major mechanism of their death. In the present study, we addressed whether autophagy regulates neutrophil apoptosis and investigated the effects of autophagy inhibition on apoptosis of human neutrophils. We first showed that the established autophagy inhibitors 3-methyladenine (MA) and chloroquine (CQ) markedly accelerated spontaneous neutrophil apoptosis as was evidenced by phosphatidylserine exposure, DNA fragmentation and caspase-3 activation. Apoptosis induced by the autophagy inhibitors was completely abrogated by a pan-caspase inhibitor Q-VD-OPh. Unexpectedly, both MA and CQ significantly delayed neutrophil apoptosis induced by TNF-α, although the inhibitors did attenuate late pro-survival effect of the cytokine. The effect was specific for TNF-α because it was not observed in the presence of other inflammation-associated cytokines (IL-1β or IL-8). The autophagy inhibitors did not modulate surface expression of TNF-α receptors in the absence or presence of TNF-α. Both MA and CQ induced a marked down-regulation of a key anti-apoptotic protein Mcl-1 but did not affect significantly the levels of another anti-apoptotic protein Bcl-X(L). Finally, to confirm the effects of the pharmacological inhibition of autophagy by a genetic approach, we evaluated the consequences of siRNA-mediated autophagy suppression in neutrophil-like differentiated HL60 cells. Knockdown of ATG5 in the cells resulted in accelerated spontaneous apoptosis but attenuated TNF-α-induced apoptosis. Together, these data suggest that autophagy regulates neutrophil apoptosis in an inflammatory context-dependent manner and mediates the early pro-apoptotic effect of TNF-α in neutrophils.

Soluble urokinase plasminogen activator receptor levels reflect organ damage in systemic lupus erythematosus

Assessments of disease activity and organ damage in systemic lupus erythematosus (SLE) remain challenging because of the lack of reliable biomarkers and disease heterogeneity. Ongoing inflammation can be difficult to distinguish from permanent organ damage caused by previous flare-ups or medication side effects. Circulating soluble urokinase plasminogen activator receptor (suPAR) has emerged as a potential marker of inflammation and disease severity, and an outcome predictor in several disparate conditions. This study was done to evaluate suPAR as a marker of disease activity and organ damage in SLE. Sera from 100 healthy donors and 198 patients with SLE fulfilling the 1982 American College of Rheumatology classification criteria and/or the Fries criteria were analyzed for suPAR by enzyme immunoassay. Eighteen patients with varying degree of disease activity were monitored longitudinally. Disease activity was assessed by the SLE disease activity index 2000 and the physician's global assessment. Organ damage was evaluated by the Systemic Lupus International Collaborating Clinics/American College of Rheumatology damage index (SDI). Compared with healthy control subjects, serum suPAR levels were elevated significantly in patients with SLE. No association was recorded regarding suPAR levels and SLE disease activity in cross-sectional or consecutive samples. However, a strong association was observed between suPAR and SDI (P < 0.0005). Considering distinct SDI domains, renal, neuropsychiatric, ocular, skin, and peripheral vascular damage had a significant effect on suPAR levels. This study is the first to demonstrate an association between serum suPAR and irreversible organ damage in SLE. Further studies are warranted to evaluate suPAR and other biomarkers as predictors of evolving organ damage.

Soluble Urokinase Plasminogen Activator Receptor for Risk Prediction in Patients Admitted with Acute Chest Pain

BACKGROUND

Plasma concentrations of soluble urokinase plasminogen activator receptor (suPAR) predict mortality in several clinical settings, but the long-term prognostic importance of suPAR in chest pain patients admitted on suspicion of non–ST-segment elevation acute coronary syndrome (NSTEACS) is uncertain.

METHODS

suPAR concentrations were measured on admission in 449 consecutive chest pain patients in a single center between January 3, 2005, and February 14, 2006. Patients were followed for all-cause mortality from discharge until July 28, 2011.

RESULTS

The diagnoses at discharge comprised high-risk NSTEACS [non–ST elevation myocardial infarction or unstable angina with electrocardiogram (ECG) abnormalities] in 77 patients (17.2%) and low-risk NSTEACS without evidence of myocardial ischemia in 257 (57.2%) of patients. Another 115 (25.6%) of patients received other diagnoses. During a median follow-up of 5.7 years (range, 0.01–6.6 years) there were 162 (36.1%) deaths. suPAR was predictive of mortality independent of age, sex, smoking, final diagnosis for the hospitalization, comorbidities (diabetes, hypertension, previous myocardial infarction, and heart failure), and variables measured on the day of admission (renal function, inflammatory markers, and markers of myocardial ischemia) with a hazard ratio (95% CI) of 1.93 (1.48–2.51) per SD increase in log-transformed suPAR, P &lt; 0.0001. The use of suPAR improved the predictive accuracy of abnormal ECG findings and increased troponin concentrations regarding all-cause mortality (c statistics, 0.751–0.805; P &lt; 0.0001).

CONCLUSIONS

suPAR is a strong predictor of adverse long-term outcomes and improves risk stratification beyond traditional risk variables in chest pain patients admitted with suspected NSTEACS.

Soluble urokinase plasminogen activator receptor is compartmentally regulated in decompensated cirrhosis and indicates immune activation and short-term mortality

OBJECTIVE

Patients with decompensated cirrhosis are susceptible to bacterial infections, which are associated with organ failure and a high mortality rate. Reliable biomarkers are needed to identify patients who require intensified treatment. Our objective was to study the regulation and prognostic relevance of elevated concentrations of soluble urokinase plasminogen activator receptor (suPAR) in patients with advanced cirrhosis.

DESIGN, SETTING AND PARTICIPANTS

We examined the associations between serum and ascitic fluid (AF) suPAR and liver function, bacterial infection, and short-term mortality in 162 consecutive patients with decompensated cirrhosis undergoing diagnostic paracentesis in a tertiary health care centre in Germany.

MAIN OUTCOME MEASURE

Twenty-eight-day mortality.

RESULTS

Circulating suPAR levels were increased in patients with decompensated cirrhosis and correlated with the severity of liver dysfunction and systemic inflammation but were not indicative of bacterial infection. Circulating suPAR levels >14.4 ng mL(-1) predicted 28-day mortality, even after adjustment for liver function and confounders [HR = 3.05 (1.35-6.90); P = 0.0076] equal to the MELD score (AUC = 0.71; 95% CI = 0.61-0.81; P < 0.001). Cut-off levels derived from cohorts without liver disease were not applicable due to the low specificity. AF suPAR levels were elevated during spontaneous bacterial peritonitis (SBP), but not during episodes in which bacteria or bacterial DNA was translocated into the ascites. AF suPAR levels correlated poorly with systemic suPAR but were associated with a more severe course of SBP and a worse outcome. In vitro experiments revealed that monocytes, and to a lesser extent neutrophils, secrete suPAR after Toll-like-receptor ligation, which led to rapid urokinase plasminogen activator receptor cleavage followed by increased synthesis.

CONCLUSION

Blood and ascitic suPAR levels provide distinct, but relevant prognostic information on the severity of complications in patients with end-stage liver disease.

Serum soluble urokinase-type plasminogen activator receptor levels and idiopathic FSGS in children: a single-center report

BACKGROUND AND OBJECTIVES

FSGS is the primary cause of childhood nephrotic syndrome leading to ESRD. Permeability factors, including circulating serum soluble urokinase-type plasminogen activator receptor (suPAR), have been postulated as putative causes in adults with primary FSGS. Similar results have yet to be proven in children.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This cross-sectional single-center study assessed the association of serum suPAR in children with FSGS or other glomerular and nonglomerular kidney diseases.

RESULTS

This study examined 110 samples retrieved from 99 individuals (between January 2011 and April 2012), aged 1-21 years; of these individuals, 20 had primary FSGS, 24 had non-FSGS glomerular disease, 26 had nonglomerular kidney disease, and 29 were healthy controls. suPAR levels were not significantly different in children with FSGS, non-FSGS glomerular disease, and healthy controls (P>0.05). However, suPAR levels (median [25%-75%]) were higher in children with nonglomerular kidney disease (3385 pg/ml [2695-4392]) versus FSGS (2487 pg/ml [2191-3351]; P<0.05). Female patients with nephrotic-range proteinuria (U-Pr/Cr >2) had lower suPAR levels than those without proteinuria (2380 pg/ml [2116-2571] versus 3125 pg/ml [2516-4198], respectively; P<0.001). This trend was not seen among male participants; suPAR levels in all female participants were lower than in male participants (P=0.03). Thirty-four patients studied were kidney transplant recipients; transplant status was not associated with suPAR levels in patients with FSGS or non-FSGS diagnoses, independent of proteinuria, race, or sex (P>0.05).

CONCLUSIONS

On the basis of these results, circulating suPAR is unlikely the leading cause for childhood idiopathic FSGS.