SuPAR, an emerging biomarker in kidney and inflammatory diseases

Soluble urokinase plasminogen activator receptor (suPAR) in children with obesity or type 1 diabetes as a marker of endothelial dysfunction: a cross-sectional study

Pediatric obesity and type 1 diabetes mellitus (T1DM) represent two common chronic diseases associated with chronic inflammation, endothelial dysfunction and long-term complications. The aim of the present study was to assess the possible diagnostic and prognostic value of soluble urokinase plasminogen activator receptor (suPAR), a marker of inflammation and impaired endothelial function, in children with the diseases. In this cross-sectional study, children and adolescents with T1DM (N = 41) or obesity (N = 37), aged < 18 years old, and without proteinuria were included, together with children of similar age and without evident morbidity that served as controls (N = 42). Serum samples were obtained during standard outpatient follow up and the urokinase-type plasminogen activator receptor (suPAR) concentrations were measured using a commercially available sandwich ELISA kit (DUP00, R&D systems). Clinical and biochemical indices that were also assessed include body mass index (BMI) z-score, Tanner stages, glycosylated haemoglobin (HbA1c), fasting lipid profile and serum creatinine. Mean serum suPAR levels were significantly higher in patients with obesity compared to patients with T1DM and controls, while children with T1DM had similar suPAR levels to controls. Also, serum suPAR levels showed a negative correlation with age (Spearman rho -0.359, p < 0.001) and serum creatinine levels (Spearman rho -0.334, p = 0.005), and a positive correlation with BMI z-score (Spearman rho 0.354, p = 0.009) in the whole cohort.  Conclusion: Serum suPAR may be a useful predictive marker of inflammation or endothelial dysfunction for children with obesity and T1DM, as well as a promising therapeutic target. Further studies are needed in order to clarify whether the reported differences in suPAR levels could reflect a greater impairment of the inflammation status and endothelial function in children with obesity compared to children with T1DM. What is Known: • Paediatric obesity and type 1 diabetes are characterised by chronic inflammation and metabolic dysregulation. • Urokinase plasminogen activator receptor (uPAR) has been proposed as a useful biomarker for chronic inflammation and cardiovascular risk in adults. What is New: • Serum suPAR levels were increased in children and adolescents with obesity compared to those with T1DM and healthy controls; thus, obesity may affect the inflammatory status and endothelial function to a higher degree than T1DM during childhood. • Serum suPAR may serve as a diagnostic and predictive marker of inflammation and endothelial dysfunction for children and adolescents with obesity and T1DM.

The Soluble Urokinase Plasminogen Activator Receptor as a Severity Biomarker in Children With Acute COVID-19 or Multisystem Inflammatory Syndrome

BACKGROUND

Elevated soluble urokinase plasminogen activator receptor (suPAR) has been associated with a poor prognosis in serious infections. The aim of this study was to evaluate the clinical value of suPAR in children with acute coronavirus disease 2019 (COVID-19) or multisystem inflammatory syndrome (MIS-C).

METHODS

Serum suPAR was measured using the suPARnostic AUTO Flex enzyme-linked immunosorbent assay in hospitalized children with COVID-19, MIS-C, bacterial pneumonia, and healthy controls.

RESULTS

A total of 211 children with a mean (±SD) age of 6.9 ± 4.96 years were tested; with COVID-19: 59 (28%), MIS-C: 36 (17%), pneumonia: 78 (37%) and healthy controls: 38 (18%). In the acute phase, the levels of suPAR (mean ± SD) were: MIS-C: 8.11 ± 2.80 ng/mL, COVID-19: 4.91 ± 1.90 ng/mL, pneumonia: 4.25 ± 1.44 ng/mL and controls: 2.09 ± 0.47 ng/mL ( P < 0.001). Children with acute COVID-19 and a severe or moderate clinical presentation had higher values than those with mild symptoms: 5.79 ± 1.58 versus 5.40 ± 1.94 versus 3.19 ± 0.73 ng/mL, respectively ( P < 0.001). In the MIS-C group, children hospitalized in the intensive care unit and in need of mechanical ventilation had higher suPAR than those who were not admitted to an intensive care unit: 9.32 ± 3.06 versus 7.13 ± 2.19 ng/mL, respectively ( P = 0.023). In children with COVID-19 or MIS-C, a correlation was detected between suPAR values and length of hospitalization ( rs = 0.418, P < 0.001).

CONCLUSIONS

The findings suggest that suPAR may be a valuable biomarker of disease severity in children with COVID-19 or MIS-C. This could facilitate the identification of children in need of intensive anti-inflammatory treatment, as it has been shown in adults with severe COVID-19.

Post-transplant recurrence of focal segmental glomerular sclerosis: consensus statements

Focal segmental glomerular sclerosis (FSGS) is 1 of the primary causes of nephrotic syndrome in both pediatric and adult patients, which can lead to end-stage kidney disease. Recurrence of FSGS after kidney transplantation significantly increases allograft loss, leading to morbidity and mortality. Currently, there are no consensus guidelines for identifying those patients who are at risk for recurrence or for the management of recurrent FSGS. Our work group performed a literature search on PubMed/Medline, Embase, and Cochrane, and recommendations were proposed and graded for strength of evidence. Of the 614 initially identified studies, 221 were found suitable to formulate consensus guidelines for recurrent FSGS. These guidelines focus on the definition, epidemiology, risk factors, pathogenesis, and management of recurrent FSGS. We conclude that additional studies are required to strengthen the recommendations proposed in this review.

New biomarkers in acute kidney injury

Acute kidney injury (AKI) is a commonly encountered clinical syndrome. Although it often complicates community acquired illness, it is more common in hospitalized patients, particularly those who are critically ill or who have undergone major surgery. Approximately 20% of hospitalized adult patients develop an AKI during their hospital care, and this rises to nearly 60% in the critically ill, depending on the population being considered. In general, AKI is more common in older adults, in those with preexisting chronic kidney disease and in those with known risk factors for AKI (including diabetes and hypertension). The development of AKI is associated with an increase in both mortality and morbidity, including the development of post-AKI chronic kidney disease. Currently, AKI is defined by a rise in serum creatinine from either a known or derived baseline value and/or oliguria or anuria. However, clinicians may fail to recognize the initial development of AKI because of a delay in the rise of serum creatinine or because of inaccurate urine output monitoring. This, in turn, delays any putative measures to treat AKI or to limit its degree. Consequently, efforts have focused on new biomarkers associated with AKI that may allow early recognition of this syndrome with the intent that this will translate into improved patient outcomes. Here we outline current biomarkers associated with AKI and explore their potential in aiding diagnosis, understanding the pathophysiology and directing therapy.

Current Trends in Vascular Biomarkers for Systemic Sclerosis: A Narrative Review

Systemic sclerosis (SSc, scleroderma) is a multifaceted rare connective tissue disease whose pathogenesis is dominated by immune dysregulation, small vessel vasculopathy, impaired angiogenesis, and both cutaneous and visceral fibrosis. Microvascular impairment represents the initial event of the disease, preceding fibrosis by months or years and accounting for the main disabling and/or life-threatening clinical manifestations, including telangiectasias, pitting scars, periungual microvascular abnormalities (e.g., giant capillaries, hemorrhages, avascular areas, ramified/bushy capillaries) clinically detectable by nailfold videocapillaroscopy, ischemic digital ulcers, pulmonary arterial hypertension, and scleroderma renal crisis. Despite a variety of available treatment options, treatment of SSc-related vascular disease remains problematic, even considering SSc etherogenity and the quite narrow therapeutic window. In this context, plenty of studies have highlighted the great usefulness in clinical practice of vascular biomarkers allowing clinicians to assess the evolution of the pathological process affecting the vessels, as well as to predict the prognosis and the response to therapy. The current narrative review provides an up-to-date overview of the main candidate vascular biomarkers that have been proposed for SSc, focusing on their main reported associations with characteristic clinical vascular features of the disease.

Novel inflammatory biomarkers in the prognosis of COVID-19

BACKGROUND

The central role of inflammatory progression in the development of Coronavirus disease 2019 (COVID-19), especially in severe cases, is indisputable. However, the role of some novel inflammatory biomarkers in the prognosis of COVID-19 remains controversial.

OBJECTIVE

To assess the effect of some novel inflammatory biomarkers in the occurrence and prognosis of COVID-19.

METHODS

We systematically retrieved the studies related to COVID-19 and the inflammatory biomarkers of interest. The data of each biomarker in different groups were extracted, then were categorized and pooled. The standardized mean difference was chosen as an effect size measure to compare the difference between groups.

RESULTS

A total of 90 studies with 12,059 participants were included in this study. We found higher levels of endocan, PTX3, suPAR, sRAGE, galectin-3, and monocyte distribution width (MDW) in the COVID-19 positive groups compared to the COVID-19 negative groups. No significant differences for suPAR and galectin-3 were detected between the severe group and mild/moderate group of COVID-19. In addition, the deaths usually had higher levels of PTX3, sCD14-ST, suPAR, and MDW at admission compared to the survivors. Furthermore, patients with higher levels of endocan, galectin-3, sCD14-ST, suPAR, and MDW usually developed poorer comprehensive clinical prognoses.

CONCLUSIONS

In summary, this meta-analysis provides the most up-to-date and comprehensive evidence for the role of the mentioned novel inflammatory biomarkers in the prognosis of COVID-19, especially in evaluating death and other poor prognoses, with most biomarkers showing a better discriminatory ability.

Kinetics of SuPAR hemoadsorption in critical COVID-19 patients on renal replacement therapy

Background

SARS-CoV-2 viral infection is associated with a rapid and vigorous systemic inflammatory response syndrome. Soluble urokinase-type plasminogen activator receptor (suPAR) is a novel biomarker, both indicative of inflammation and propagating it. Hemoadsorption has been proposed as a potential therapy in COVID-19 patients, therefore the aim of this study is to determine suPAR kinetics during hemoadsoprtion.

Methods

This was a prospective observational study of critical COVID-19 patients, enrolled when hemoperfusion therapy was initiated. Hemoadsorber was integrated into the continuous renal replacement therapy circuit. The first series of suPAR measurements was performed 10 minutes after the start of the session, sampling both incoming and outgoing lines of the adsorber. A second series of the measurements was performed beforefinishing the session with the same adsorber. Statistical significance level was set < 0.05.

Results

This study included 18 patients. In the beginning of the session the fraction of suPAR cleared across the adsorber was 29.5% [16-41], and in the end of the session it decreased to 7.2% [4-22], 4 times lower, p = 0.003. The median length of session was 21 hours, with minimal duration of 16 hours and maximal duration of 24 hours. The median suPAR before the procedure was 8.71 [7.18-10.78] and after the session was 7.35 [6.53-11.28] ng/ml. There was no statistically significant difference in suPAR concentrations before and after the session (p = 0.831).

Conclusions

This study concluded that in the beginning of the hemoadsorption procedure significant amount of suPAR is removed from the circulation. However, in the end of the procedure there is a substantial drop in adsorbed capacity. Furthermore, despite a substantial amount of suPAR cleared there is no significant difference in systemic suPAR concentrations before and after the hemoadsorption procedure.

The Perspective of Vitamin D on suPAR-Related AKI in COVID-19

The coronavirus disease 2019 (COVID-19) pandemic has claimed the lives of millions of people around the world. Severe vitamin D deficiency can increase the risk of death in people with COVID-19. There is growing evidence that acute kidney injury (AKI) is common in COVID-19 patients and is associated with poorer clinical outcomes. The kidney effects of SARS-CoV-2 are directly mediated by angiotensin 2-converting enzyme (ACE2) receptors. AKI is also caused by indirect causes such as the hypercoagulable state and microvascular thrombosis. The increased release of soluble urokinase-type plasminogen activator receptor (suPAR) from immature myeloid cells reduces plasminogen activation by the competitive inhibition of urokinase-type plasminogen activator, which results in low plasmin levels and a fibrinolytic state in COVID-19. Frequent hypercoagulability in critically ill patients with COVID-19 may exacerbate the severity of thrombosis. Versican expression in proximal tubular cells leads to the proliferation of interstitial fibroblasts through the C3a and suPAR pathways. Vitamin D attenuates the local expression of podocyte uPAR and decreases elevated circulating suPAR levels caused by systemic inflammation. This decrease preserves the function and structure of the glomerular barrier, thereby maintaining renal function. The attenuated hyperinflammatory state reduces complement activation, resulting in lower serum C3a levels. Vitamin D can also protect against COVID-19 by modulating innate and adaptive immunity, increasing ACE2 expression, and inhibiting the renin–angiotensin–aldosterone system. We hypothesized that by reducing suPAR levels, appropriate vitamin D supplementation could prevent the progression and reduce the severity of AKI in COVID-19 patients, although the data available require further elucidation.

Air pollution and biomarkers of cardiovascular disease and inflammation in the Malmö Diet and Cancer cohort

INTRODUCTION

Air pollution is associated with increased risk of cardiovascular disease, possibly through chronic systemic inflammation that promotes the progression of atherosclerosis and the risk of cardiovascular events. This study aimed to investigate the associations between air pollution and established biomarkers of inflammation and cardiovascular disease.

METHODS

The Cardiovascular Subcohort of the Malmö Diet and Cancer cohort includes 6103 participants from the general population of Malmö, Sweden. The participants were recruited 1991-1994. Annual mean residential exposure to particulate matter < 2.5 and < 10 μm (PM_2.5 and PM₁₀), and nitrogen oxides (NO_x) at year of recruitment were assigned from dispersion models. Blood samples collected at recruitment, including blood cell counts, and biomarkers (lymphocyte- and neutrophil counts, C-reactive protein (CRP), soluble urokinase-type plasminogen activator receptor (suPAR), lipoprotein-associated phospholipase A₂ (Lp-PLA₂), ceruloplasmin, orosomucoid, haptoglobin, complement-C3, and alpha-1-antitrypsin) were analyzed. Multiple linear regression models were used to investigate the cross-sectional associations between air pollutants and biomarkers.

RESULTS

The mean annual exposure levels in the cohort were only slightly or moderately above the new WHO guidelines of 5 μg/m³ PM_2.5 (10.5 μg/m³ PM_2.5). Residential PM_2.5 exposure was associated with increased levels of ceruloplasmin, orosomucoid, C3, alpha-1-antitrypsin, haptoglobin, Lp-PLA₂ and the neutrophil-lymphocyte ratio. Ceruloplasmin, orosomucoid, C3 and alpha-1-antitrypsin were also positively associated with PM₁₀. There were no associations between air pollutants and suPAR, leukocyte counts or CRP. The associations between particles and biomarkers were still significant after removing outliers and adjustment for CRP levels. The associations were more prominent in smokers.

CONCLUSION

Long-term residential exposure to moderate levels of particulate air pollution was associated with several biomarkers of inflammation and cardiovascular disease. This supports inflammation as a mechanism behind the association between air pollution and cardiovascular disease.

Crystal structure and cellular functions of uPAR dimer

Receptor dimerization of urokinase-type plasminogen activator receptor (uPAR) was previously identified at protein level and on cell surface. Recently, a dimeric form of mouse uPAR isoform 2 was proposed to induce kidney disease. Here, we report the crystal structure of human uPAR dimer at 2.96 Å. The structure reveals enormous conformational changes of the dimer compared to the monomeric structure: D1 of uPAR opens up into a large expanded ring that captures a β-hairpin loop of a neighboring uPAR to form an expanded β-sheet, leading to an elongated, highly intertwined dimeric uPAR. Based on the structure, we identify E49P as a mutation promoting dimer formation. The mutation increases receptor binding to the amino terminal fragment of its primary ligand uPA, induces the receptor to distribute to the basal membrane, promotes cell proliferation, and alters cell morphology via β1 integrin signaling. These results reveal the structural basis for uPAR dimerization, its effect on cellular functions, and provide a basis to further study this multifunctional receptor.

Soluble urokinase plasminogen activator receptor levels are predictive of COVID-19 severity in Afro-Caribbean patients

Aim: To investigate association between soluble urokinase plasminogen activator receptor (suPAR) plasma levels at admission and incidence of complications in COVID-19 patients. Patients & methods: We considered Afro-Caribbean patients (n = 64) admitted to the hospital between 1 February 2020 and 28 February 2021. Primary outcome was time from the hospital admission until intensive care unit care or death. Results: Primary outcome (hazard ratio, HR [95%CI]) was associated with higher CT scan severity score (3.18 [1.15-8.78], p = 0.025), National Early Warning Score (NEWS2; 1.43 [1.02-2.02], p = 0.041) and suPAR (1.28 [1.06-2.06], p = 0.041). Kaplan-Meier analysis indicated patients with suPAR level above 8.95 ng/ml had a worse outcome (7.95 [3.33-18.97], p < 0.001). Conclusion: Our study suggests that COVID-19 patients with increased baseline suPAR levels are at a high risk of complications.

Urinary levels of pro-fibrotic transglutaminase 2 (TG2) may help predict progression of chronic kidney disease

Renal clinical chemistry only detects kidney dysfunction after considerable damage has occurred and is imperfect in predicting long term outcomes. Consequently, more sensitive markers of early damage and better predictors of progression are being urgently sought, to better support clinical decisions and support shorter clinical trials. Transglutaminase 2 (TG2) is strongly implicated in the fibrotic remodeling that drives chronic kidney disease (CKD). We hypothesized that urinary TG2 and its ε-(γ-glutamyl)-lysine crosslink product could be useful biomarkers of kidney fibrosis and progression. Animal models: a rat 4-month 5/6th subtotal nephrectomy model of CKD and a rat 8-month streptozotocin model of diabetic kidney disease had 24-hour collection of urine, made using a metabolic cage, at regular periods throughout disease development. Patients: Urine samples from patients with CKD (n = 290) and healthy volunteers (n = 33) were collected prospectively, and progression tracked for 3 years. An estimated glomerular filtration rate (eGFR) loss of 2–5 mL/min/year was considered progressive, with rapid progression defined as > 5 mL/min/year. Assays: TG2 was measured in human and rat urine samples by enzyme-linked immunosorbent assay (ELISA) and ε-(γ-glutamyl)-lysine by exhaustive proteolytic digestion and amino acid analysis. Urinary TG2 and ε-(γ-glutamyl)-lysine increased with the development of fibrosis in both animal model systems. Urinary TG2 was 41-fold higher in patients with CKD than HVs, with levels elevated 17-fold by CKD stage 2. The urinary TG2:creatinine ratio (UTCR) was 9 ng/mmol in HV compared with 114 ng/mmol in non-progressive CKD, 1244 ng/mmol in progressive CKD and 1898 ng/mmol in rapidly progressive CKD. Both urinary TG2 and ε-(γ-glutamyl)-lysine were significantly associated with speed of progression in univariate logistic regression models. In a multivariate model adjusted for urinary TG2, ε-(γ-glutamyl)-lysine, age, sex, urinary albumin:creatinine ratio (UACR), urinary protein:creatinine ratio (UPCR), and CKD stage, only TG2 remained statistically significant. Receiver operating characteristic (ROC) curve analysis determined an 86.4% accuracy of prediction of progression for UTCR compared with 73.5% for UACR. Urinary TG2 and ε-(γ-glutamyl)-lysine are increased in CKD. In this pilot investigation, UTCR was a better predictor of progression in patients with CKD than UACR. Larger studies are now warranted to fully evaluate UTCR value in predicting patient outcomes.

The Soluble Urokinase-Type Plasminogen Activator Receptor as a Biomarker for Survival and Early Treatment Effect in Metastatic Colorectal Cancer

The soluble urokinase-type plasminogen activator receptor (suPAR) is prognostic for overall survival (OS) in colorectal cancer (CRC). Our study explored the association between baseline suPAR and OS and progression-free survival (PFS) in metastatic CRC (mCRC). It is also the first study to explore the association between the initial change in suPAR level and OS, PFS and the first CT response evaluation. The study included 132 patients with mCRC treated with chemotherapy (FOLFIRI) with or without an EGFR-inhibitor. Blood samples were drawn before the first treatment cycle and in between the first and second treatment cycle. suPAR levels were determined using an ELISA assay. Using the Kaplan-Meyer method, we demonstrated a significantly shorter OS for patients with suPAR levels above the median (HR = 1.79, 95%CI = 1.10-2.92, p = 0.01). We also showed association between plasma suPAR level, gender and performance status (PS). However, we could not show any association with PFS, and analysis on the change in suPAR level provided no significant results. The results showing association between baseline suPAR and OS are in line with previous findings.

Improved diagnostics of infectious diseases in emergency departments: a protocol of a multifaceted multicentre diagnostic study

BACKGROUND

The major obstacle in prescribing an appropriate and targeted antibiotic treatment is insufficient knowledge concerning whether the patient has a bacterial infection, where the focus of infection is and which bacteria are the agents of the infection. A prerequisite for the appropriate use of antibiotics is timely access to accurate diagnostics such as point-of-care (POC) testing.The study aims to evaluate diagnostic tools and working methods that support a prompt and accurate diagnosis of hospitalised patients suspected of an acute infection. We will focus on the most common acute infections: community-acquired pneumonia (CAP) and acute pyelonephritis (APN). The objectives are to investigate (1) patient characteristics and treatment trajectory of the different acute infections, (2) diagnostic and prognostic accuracy of infection markers, (3) diagnostic accuracy of POC urine flow cytometry on diagnosing and excluding bacteriuria, (4) how effective the addition of POC analysis of sputum to the diagnostic set-up for CAP is on antibiotic prescriptions, (5) diagnostic accuracy of POC ultrasound and ultralow dose (ULD) computerized tomography (CT) on diagnosing CAP, (6) diagnostic accuracy of specialist ultrasound on diagnosing APN, (7) diagnostic accuracy of POC ultrasound in diagnosing hydronephrosis in patients suspected of APN.

METHODS AND ANALYSIS

It is a multifaceted multicentre diagnostic study, including 1000 adults admitted with suspicion of an acute infection. Participants will, within the first 24 hours of admission, undergo additional diagnostic tests including infection markers, POC urine flow cytometry, POC analysis of sputum, POC and specialist ultrasound, and ULDCT. The primary reference standard is an assigned diagnosis determined by a panel of experts.

ETHICS, DISSEMINATION AND REGISTRATION

Approved by Regional Committees on Health Research Ethics for Southern Denmark, Danish Data Protection Agency and clinicaltrials.gov. Results will be presented in peer-reviewed journals, and positive, negative and inconclusive results will be published.

TRIAL REGISTRATION NUMBERS

NCT04661085, NCT04681963, NCT04667195, NCT04652167, NCT04686318, NCT04686292, NCT04651712, NCT04645030, NCT04651244.

Experimental and Clinical Evidence Supports the Use of Urokinase Plasminogen Activation System Components as Clinically Relevant Biomarkers in Gastroesophageal Adenocarcinoma

Simple Summary

Patients with gastric and oesophageal adenocarcinomas (GOCs) have short life expectancies as their tumours spread to other sites early. This is facilitated by the increased expression of the urokinase plasminogen activation system (uPAS); a feature of the majority of GOCs. There is increasing appreciation of the importance of uPAS expression in a range of cell types within the tumour microenvironment. Abundant clinical evidence indicates that altered expression of uPAS proteins is associated with worse outcomes, including time to tumour recurrence and patient survival. Emerging technologies, including liquid biopsy, suggest a role of uPAS for the detection of circulating tumour cells, which are responsible for the dissemination of cancers. We review and summarise pre-clinical and clinical data that supports the use of uPAS as a biomarker in GOC.

Abstract

Gastric and oesophageal cancers (GOCs) are lethal cancers which metastasise early and recur frequently, even after definitive surgery. The urokinase plasminogen activator system (uPAS) is strongly implicated in the invasion and metastasis of many aggressive tumours including GOCs. Urokinase plasminogen activator (uPA) interaction with its receptor, urokinase plasminogen activator receptor (uPAR), leads to proteolytic activation of plasminogen to plasmin, a broad-spectrum protease which enables tumour cell invasion and dissemination to distant sites. uPA, uPAR and the plasminogen activator inhibitor type 1 (PAI-1) are overexpressed in some GOCs. Accumulating evidence points to a causal role of activated receptor tyrosine kinase pathways enhancing uPAS expression in GOCs. Expression of these components are associated with poorer clinicopathological features and patient survival. Stromal cells, including tumour-associated macrophages and myofibroblasts, also express the key uPAS proteins, supporting the argument of stromal involvement in GOC progression and adverse effect on patient survival. uPAS proteins can be detected on circulating leucocytes, circulating tumour cells and within the serum; all have the potential to be developed into circulating biomarkers of GOC. Herein, we review the experimental and clinical evidence supporting uPAS expression as clinical biomarker in GOC, with the goal of developing targeted therapeutics against the uPAS.

Evaluation of the relationship between KIM-1 and suPAR levels and clinical severity in COVID-19 patients: A different perspective on suPAR

Coronavirus disease 2019 (COVID-19) is one of the most pressing health problems of this century, but our knowledge of the disease is still limited. In this study, we aimed to examine serum-soluble urokinase plasminogen activator receptor (suPAR) and kidney injury molecule 1 (KIM-1) levels based on the clinical course of COVID-19. Our study included 102 patients over the age of 18 who were diagnosed as having COVID-19 between September 2020 and December 2020 and a control group of 50 health workers over the age of 18 whose severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) PCR results were negative. KIM-1 was measured by ELISA and suPAR by suPARnostic™ assay. Analysis of previously identified variables of prognostic significance in COVID-19 revealed high neutrophil to lymphocyte ratio, lactose dehydrogenase, prothrombin time, C-reactive protein, PaO₂ /FiO₂ , D-dimer, ferritin, and fibrinogen levels in patients with severe disease (p < 0.05 for all). KIM-1 and suPAR levels were significantly higher in COVID-19 patients compared to the control group (p = 0.001 for all). KIM-1 level was higher in severe patients compared to moderate patients (p = 0.001), while suPAR level was lower (p = 0.001). KIM-1, which is believed to play an important role in the endocytosis of SARS-CoV-2, was elevated in patients with severe COVID-19 and may be a therapeutic target in the future. SuPAR may have a role in defense mechanism and fibrinolysis, and low levels in severe patients may be associated with poor prognosis in the early period.

Admission levels of Soluble Urokinase Plasminogen Activator Receptor (suPAR) are Associated with the Development of Severe Complications in Hospitalised COVID-19 Patients: A Prospective Cohort Study

Objective

To examine the association between plasma levels of the soluble urokinase plasminogen activator receptor (suPAR) and the incidence of severe complications of COVID-19.

Methods

403 RT-PCR-confirmed COVID-19 patients were recruited and prospectively followed-up at a major hospital in the United Arab Emirates. The primary endpoint was time from admission until the development of a composite outcome, including acute respiratory distress syndrome (ARDS), intensive care unit (ICU) admission, or death from any cause. Patients discharged alive were considered as competing events to the primary outcome. Competing risk regression was used to quantify the association between suPAR and the incidence of the primary outcome.

Results

6.2% of patients experienced ARDS or ICU admission, but none died. Taking into account competing risk, the incidence of the primary outcome was 11.5% (95% confidence interval [CI], 6.7–16.3) in patients with suPAR levels >3.91 ng/mL compared to 2.9% (95% CI, 0.4–5.5) in those with suPAR ≤3.91 ng/mL. Also, an increase by 1 ng/mL in baseline suPAR resulted in a 58% rise in the hazard of developing the primary outcome (hazard ratio 1.6, 95% CI, 1.2–2.1, p = 0.003).

Conclusion

suPAR has an excellent prognostic utility in predicting severe complications in hospitalised COVID-19 patients.

Urine soluble urokinase plasminogen activator receptor as a potential biomarker of lupus nephritis activity

There is a lack of non-invasive biomarkers to identify lupus nephritis (LN). Soluble urokinase plasminogen activator receptor (suPAR) is a sensitive biomarker of ongoing inflammation and a potential marker of podocyte dysfunction. The aim of this study was to assess urine and plasma suPAR in LN. 14 systemic lupus erythematosus (SLE) patients with newly diagnosed LN, 8 active SLE patients (SLEDAI >8) without LN and 31 healthy individuals were enrolled. Urine and plasma samples were taken before the initiation of LN induction therapy, and monthly thereafter. Global and renal disease activity were defined using the SLEDAI-2K and the SLEDAI-2K renal domain score, respectively. suPAR concentrations were measured with the suPARnostic Flex ELISA assay. Urine and plasma suPAR levels were elevated in SLE patients with active LN compared with resolved LN and healthy controls. Urine suPAR levels were comparable to healthy controls in active SLE without LN. Urine and plasma suPAR levels were higher before than after the initiation of LN induction therapy. Prospective follow-up measurements also suggested that urine suPAR levels raised again in patients with a relapse of LN according to SLEDAI-2K renal domain score, whereas plasma suPAR levels did not correlate with renal disease activity. Urine suPAR is a promising LN activity biomarker, given its isolated elevation in urine in active LN and pronounced decrease with LN improvement.

Soluble urokinase-type plasminogen activator receptor strongly predicts global mortality in acute heart failure patients: insight from the STADE-HF registry

Background

Whether soluble urokinase-type plasminogen activator receptor (suPAR) could be a valuable prognostic indicator remains uncertain.

Materials & methods

Patients from STADE-HF (Soluble Suppression of Tumorigenesis-2 as a Help for Management of Diagnosis, Evaluation and Management of Heart Failure) were included for analysis.

Results

95 patients were included. The suPAR level of expression was significantly higher in the group of patients who died at one month (7.90 ± 4.35 ng/ml vs 11.94 ± 6.86 ng/ml; p < 0.05) or 1 year (7.28 ± 4.27 ng/ml vs 11.81 ± 4.88 ng/ml; p < 0.01), but there was no significant difference according to the readmission.

Conclusion

High suPAR levels during hospitalization for acute heart failure were highly predictive for the risk of mortality, but not the risk of readmission.

Association of soluble urokinase plasminogen activator receptor levels with fibrotic and vascular manifestations in systemic sclerosis

OBJECTIVE

We assessed the association of suPAR (soluble urokinase plasminogen activator receptor) plasma levels with fibrotic and vascular manifestations in patients with systemic sclerosis (SSc).

METHODS

suPAR plasma levels were measured in 121 consecutive patients with SSc and correlated to pulmonary and vascular features of SSc, including interstitial lung disease as characterized by percentage of predicted CO diffusing capacity (DLco) and forced vital capacity (FVC), pulmonary fibrosis by computed tomography, and pulmonary arterial hypertension, telangiectasias, and digital ulcers.

RESULTS

Overall, 121 SSc patients (84% females; mean age, 57 ± 12 [range: 22-79] years) were enrolled; 35% had diffuse cutaneous SSc. suPAR plasma levels ranged from 1.3-10.2 [median: 2.9 (p25-p75: 2.3-3.9)] ng/mL. Log(suPAR) levels correlated with DLco (r = -0.41, p <0.0001) and FVC (r = -0.26, p = 0.004), also when adjusted for age, sex, and pulmonary hypertension. A suPAR cut-off level of >2.5 ng/mL showed a sensitivity of 91% for identifying patients with either DLco <50% or FVC < 60% of the predicted values. Similarly, 19 (90%) had a suPAR >2.5 ng/mL among those diagnosed with pulmonary fibrosis vs. 59 (60%) among those who did not (p = 0.008). suPAR values were not associated with vascular manifestations.

CONCLUSION

suPAR levels strongly correlated with pulmonary involvement in SSc. Future studies should test if suPAR estimation can be used for surveillance of severe pulmonary involvement in SSc.

PEGylated Serp-1 Markedly Reduces Pristane-Induced Experimental Diffuse Alveolar Hemorrhage, Altering uPAR Distribution, and Macrophage Invasion

Diffuse alveolar hemorrhage (DAH) is one of the most serious clinical complications of systemic lupus erythematosus (SLE). The prevalence of DAH is reported to range from 1 to 5%, but while DAH is considered a rare complication there is a reported 50-80% mortality. There is at present no proven effective treatment for DAH and the therapeutics that have been tested have significant side effects. There is a clear necessity to discover new drugs to improve outcomes in DAH. Serine protease inhibitors, serpins, regulate thrombotic and thrombolytic protease cascades. We are investigating a Myxomavirus derived immune modulating serpin, Serp-1, as a new class of immune modulating therapeutics for vasculopathy and lung hemorrhage. Serp-1 has proven efficacy in models of herpes virus-induced arterial inflammation (vasculitis) and lung hemorrhage and has also proved safe in a clinical trial in patients with unstable coronary syndromes and stent implant. Here, we examine Serp-1, both as a native secreted protein expressed by CHO cells and as a polyethylene glycol modified (PEGylated) variant (Serp-1m5), for potential therapy in DAH. DAH was induced by intraperitoneal (IP) injection of pristane in C57BL/6J (B6) mice. Mice were treated with 100 ng/g bodyweight of either Serp-1 as native 55 kDa secreted glycoprotein, or as Serp-1m5, or saline controls after inducing DAH. Treatments were repeated daily for 14 days (6 mice/group). Serp-1 partially and Serp-1m5 significantly reduced pristane-induced DAH when compared with saline as assessed by gross pathology and H&E staining (Serp-1, p = 0.2172; Serp-1m5, p = 0.0252). Both Serp-1m5 and Serp-1 treatment reduced perivascular inflammation and reduced M1 macrophage (Serp-1, p = 0.0350; Serp-1m5, p = 0.0053), hemosiderin-laden macrophage (Serp-1, p = 0.0370; Serp-1m5, p = 0.0424) invasion, and complement C5b/9 staining. Extracellular urokinase-type plasminogen activator receptor positive (uPAR+) clusters were significantly reduced (Serp-1, p = 0.0172; Serp-1m5, p = 0.0025). Serp-1m5 also increased intact uPAR+ alveoli in the lung (p = 0.0091). In conclusion, Serp-1m5 significantly reduces lung damage and hemorrhage in a pristane model of SLE DAH, providing a new potential therapeutic approach.

Long term pronostic value of suPAR in chronic heart failure: reclassification of patients with low MAGGIC score

OBJECTIVES

Inflammation is a hallmark of heart failure (HF) and among inflammatory biomarkers, the most studied remains the C-reactive protein (CRP). In recent years several biomarkers have emerged, such as sST2 and soluble urokinase-type plasminogen activator receptor (suPAR). This study set out to examine the relative importance of long-time prognostic strength of suPAR and the potential additive information on patient risk with chronic HF in comparison with pronostic value of CRP and sST2.

METHODS

Demographics, clinical and biological variables were assessed in a total of 182 patients with chronic HF over median follow-up period of 80 months. Inflammatory biomarkers (i.e., CRP, sST2, and suPAR) were performed.

RESULTS

In univariate Cox regression analysis age, NYHA class, MAGGIC score and the five biomarkers (N-terminal pro brain natriuretic peptide [NT-proBNP], high-sensitive cardiac troponin T [hs-cTnT], CRP, sST2, and suPAR) were associated with both all-cause and cardiovascular mortality. In the multivariate model, only NT-proBNP, suPAR, and MAGGIC score remained independent predictors of all-cause mortality as well as of cardiovascular mortality. Risk classification analysis was significantly improved with the addition of suPAR particularly for all-cause short- and long-term mortality. Using a classification tree approach, the same three variables could be considered as significant classifier variables to predict all-cause or cardiovascular mortality and an algorithm were reported. We demonstrated the favorable outcome associated with patients with a low MAGGIC score and a low suPAR level by comparison to patients with low MAGGIC score but high suPAR values.

CONCLUSIONS

The main findings of our study are (1) that among the three inflammatory biomarkers, only suPAR levels were independently associated with 96-month mortality for patients with chronic HF and (2) that an algorithm based on clinical score, a cardiomyocyte stress biomarker and an inflammatory biomarker could help to a more reliable long term risk stratification in heart failure.

Serum soluble urokinase plasminogen activator receptor in adolescents: interaction of chronic pain and obesity

Pediatric chronic pain is exacerbated by obesity. Serum soluble urokinase plasminogen activator receptor, a novel inflammation biomarker, was increased in obese adolescents with chronic pain indicating interactive inflammatory conditions.

Introduction:

Obesity in adolescents is increasing in frequency and is associated with short-term and long-term negative consequences that include the exacerbation of co-occurring chronic pain.

Objective:

To determine whether the interaction between chronic pain and obesity would be reflected in changes in serum soluble urokinase plasminogen activator receptor (suPAR) concentrations, a novel marker of systemic inflammation associated with obesity, insulin resistance, and cardiovascular disease.

Methods:

We measured serum suPAR levels in 146 adolescent males and females with no pain or obesity (healthy controls; n = 40), chronic pain with healthy weight (n = 37), obesity alone (n = 41), and the combination of chronic pain and obesity (n = 28).

Results:

Serum suPAR (median [interquartile range]) was not increased by chronic pain alone (2.2 [1.8–2.4] ng/mL) or obesity alone (2.2 [2.0–2.4] ng/mL) but was increased significantly with the combination of chronic pain and obesity (2.4 [2.1–2.7] ng/mL; P < 0.019). This finding confirms the proposition that pain and obesity are inflammatory states that display a classic augmenting interaction.

Conclusion:

We propose that measurement of serum suPAR can be added to the armamentarium of serum biomarkers useful in the evaluation of mechanisms of inflammation in adolescent obesity and chronic pain.

SuPAR, a potential inflammatory mediator in psoriasis pathogenesis

Psoriasis is an inflammatory skin disorder that is strongly associated with the metabolic syndrome. The sole reliance on clinical examination to guide prognostication and treatment is insufficient at best; accurate diagnostic and prognostic psoriatic molecular biomarkers are needed. Soluble urokinase plasminogen activator receptor (suPAR) has been implicated in inflammation. The aim of this study is to determine whether suPAR plays a role in the pathogenesis of psoriasis and whether an association exists between suPAR levels, disease severity, and other variables like insulin, erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP). This study also compares the pattern of uPAR staining in healthy vs psoriatic skin: 39 psoriatic and 30 control subjects were included. Two biopsies (affected and unaffected skin) and one biopsy were taken from psoriasis patients and healthy controls, respectively, with uPAR staining of all skin biopsies. Blood samples from all subjects were obtained to determine suPAR, ESR, CRP, and fasting insulin levels. uPAR staining was prominent in unaffected skin from psoriasis patients and healthy individuals vs weak/absent uPAR staining in psoriatic skin. CRP, ESR and suPAR levels were not significantly elevated in the mild psoriasis group compared to healthy controls. The loss of epidermal uPAR is suggestive of its tentative role in the pathogenesis of psoriasis. Patients with mild-moderate psoriasis possibly lack the powerful association attributed to metabolic syndrome in psoriatic patients. Further studies on larger cohorts are needed to ascertain the validity of the mentioned conclusions.

Expression of the Novel Cardiac Biomarkers sST2, GDF-15, suPAR, and H-FABP in HFpEF Patients Compared to ICM, DCM, and Controls

Background: Heart failure with preserved ejection fraction (HFpEF) remains an ongoing therapeutic and diagnostic challenge to date. In this study we aimed for an analysis of the diagnostic potential of four novel cardiovascular biomarkers, GDF-15, H-FABP, sST2, and suPAR in HFpEF patients compared to controls as well as ICM, and DCM. Methods: In total, we included 252 stable outpatients and controls (77 DCM, 62 ICM, 18 HFpEF, and 95 controls) in the present study. All patients were in a non-decompensated state and on a stable treatment regimen. Serum samples were obtained and analyzed for GDF-15 (inflammation, remodeling), H-FABP (ischemia and subclinical ischemia), sST2 (inflammation, remodeling) and suPAR (inflammation, remodeling) by means of ELISA. Results: A significant elevation of GDF-15 was found for all heart failure entities compared to controls (p < 0.005). Similarly, H-FABP evidenced a significant elevation in all heart failure entities compared to the control group (p < 0.0001). Levels of sST2 were significantly elevated in ICM and DCM patients compared to the control group and HFpEF patients (p < 0.0001). Regarding suPAR, a significant elevation in ICM and DCM patients compared to the control group (p < 0.0001) and HFpEF patients (p < 0.01) was observed. An AUC analysis identified H-FABP (0.792, 95% CI 0.713–0.870) and GDF-15 (0.787, 95% CI 0.696–0.878) as paramount diagnostic biomarkers for HFpEF patients. Conclusion: Based on their differences in secretion patterns, novel cardiovascular biomarkers might represent a promising diagnostic tool for HFpEF in the future.

Sex Differences in Circulating Soluble Urokinase-Type Plasminogen Activator Receptor (suPAR) Levels and Adverse Outcomes in Coronary Artery Disease

Background

Women have higher circulating levels of soluble urokinase‐type plasminogen activator receptor (suPAR), and elevated suPAR is associated with cardiovascular risk. The independent association of sex with suPAR and the impact of sex on its association with cardiovascular risk are unknown.

Methods and Results

Plasma suPAR was measured using ELISA in 2 cohorts of 666 asymptomatic individuals (49 years, 65% women) and 4184 patients with coronary artery disease (63 years, 37% women). Independent association of sex with suPAR was studied using linear regression models adjusted for demographics, risk factors, and visceral adiposity in asymptomatic participants. Impact of sex on association of suPAR with all‐cause mortality was studied in patients with coronary artery disease using multivariable‐adjusted Cox models. Sex‐specific suPAR cutoffs for predicting all‐cause mortality were calculated. Asymptomatic women had 10% higher suPAR compared with men after adjusting for confounders, and visceral adiposity partly accounted for this association. Over a median follow‐up of 5.2 years, 795 deaths were recorded in patients with coronary artery disease. Log₂‐transformed suPAR was independently associated with mortality (hazard ratio per 1‐SD 1.72, 95% CI 1.60–1.85) and an interaction with sex was noted (P=0.005). Association of suPAR with mortality was slightly weaker in women (hazard ratio 1.61, 95% CI 1.41–1.83) compared with men (hazard ratio 1.83, 95% CI 1.67–2.00). However, using sex‐specific suPAR cut‐offs (4392 pg/mL for women and 3187 pg/mL for men), a similar mortality incidence was observed for both sexes (38.5% and 35.5%, respectively, P=0.3).

Conclusions

Women have 10% higher plasma suPAR levels compared with men. Elevated sex‐specific plasma suPAR levels are equally predictive of risk of adverse events in both sexes.

Soluble urokinase plasminogen activator receptor associates with higher risk, advanced disease severity as well as inflammation, and might serve as a prognostic biomarker of severe acute pancreatitis

Background

This study aimed to explore the potential of soluble urokinase plasminogen activator receptor (suPAR) as a biomarker for severe acute pancreatitis (SAP) risk prediction and disease management in SAP patients.

Methods

Totally 225 acute pancreatitis (AP) patients (including 75 SAP, 75 moderate‐severe acute pancreatitis [MSAP], and 75 mild acute pancreatitis [MAP] patients) were recruited based on the Atlanta classification, and their serum samples were obtained within 24 hours after admission. Meanwhile, 75 health controls (HCs) were recruited with their serum samples collected at the enrollment. The serum suPAR was then detected using enzyme‐linked immunosorbent assay.

Results

The suPAR level was increased in SAP patients compared with MSAP patients (P = .023), MAP patients (P < .001), and HCs (P < .001). Receiver operating characteristic (ROC) curve presented that suPAR could not only differentiate SAP patients from HCs (AUC: 0.920, 95%CI: 0.875‐0.965) but also differentiate SAP patients from MSAP (AUC: 0.684, 95%CI: 0.600‐0.769) and MAP patients (AUC: 0.855, 95%CI: 0.797‐0.912). In SAP patients, suPAR was positively correlated with Ranson score (P < .001), acute physiology and chronic healthcare evaluation II score (P = .001), sequential organ failure assessment score (P < .001), and C‐reaction protein (P = .002). Further ROC curve exhibited that suPAR (AUC: 0.806, 95%CI: 0.663‐0.949) was of good value in predicting increased inhospital mortality of SAP patients.

Conclusion

Soluble urokinase plasminogen activator receptor is of good predictive value for SAP risk and may serve as a potential biomarker for disease severity, inflammation, and inhospital mortality in SAP patients.

The diagnostic roles of neutrophil in bloodstream infections

Bloodstream infections remain a leading cause of death worldwide, despite advances in critical care and understanding of the pathophysiology and treatment strategies. No specific biomarkers or therapy are available for these conditions. Neutrophils play a critical role in controlling infection and it is suggested that their migration and antimicrobial activity are impaired during sepsis which contribute to the dysregulation of immune responses. Recent studies further demonstrated that interruption or reversal of the impaired migration and antimicrobial function of neutrophils improves the outcome of sepsis in animal models. In this review, we provide an overview of the associated diagnostic biomarkers involved neutrophils in sepsis, and discuss the potential of neutrophils as a target to specifically predict the outcome of sepsis.

Serum soluble urokinase type plasminogen activated receptor and focal segmental glomerulosclerosis: a systematic review and meta-analysis

OBJECTIVES

Soluble urokinase plasminogen activated receptor (suPAR) is a biomarker that may predict the occurrence of focal segmental glomerulosclerosis (FSGS); however, there is still controversy about whether suPAR can predict FSGS. In this study, we performed a systematic evaluation and meta-analysis to prove whether suPAR can predict FSGS, and to detect a threshold concentration of suPAR that can be used to diagnose FSGS. In addition, a threshold concentration of suPAR for the diagnosis of FSGS was proposed.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

We systematically searched PubMed, Embase, Cochrane Library, Web of Science and China Biology Medicine databases for studies published from the inception dates to 1 December 2018. ELIGIBILITY CRITERIA: (1) Data involving the suPAR level were from blood samples; (2) FSGS was diagnosed by biopsy; and (3) randomised controlled trials, cohort studies, case-control studies and cross-sectional studies.

DATA EXTRACTION AND SYNTHESIS

Initially, a total of 364 studies were searched, among which 29 studies were finally included. In addition, seven studies described the cut-off value of suPAR, which ranged from 2992.6 to 5500 pg/mL.

RESULTS

The results showed that the suPAR levels in the primary FSGS group were significantly higher when compared with that in the normal control group (p<0.001; standard mean difference (SMD): 2.56; 95% CI 1.85 to 3.28), and significant differences were observed in the secondary FSGS and in the normal control group (p<0.001; SMD: 1.68; 95% CI 1.37 to 1.98). A suPAR concentration of 3000 pg/mL may be the best threshold for the diagnosis of primary FSGS (sensitivity=0.72; specificity=0.88; area under the curve=0.85).

CONCLUSION

Our results suggested that suPAR might be a potential biomarker for predicting primary and secondary FSGS. In addition, our data showed that a suPAR concentration of 3000 pg/mL might be used as a threshold for the diagnosis of FSGS.

TRIAL REGISTRATION NUMBER

CRD42019120948.

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.

Novel Pure αVβ3 Integrin Antagonists That Do Not Induce Receptor Extension, Prime the Receptor, or Enhance Angiogenesis at Low Concentrations

The integrin αVβ3 receptor has been implicated in several important diseases, but no antagonists are approved for human therapy. One possible limitation of current small-molecule antagonists is their ability to induce a major conformational change in the receptor that induces it to adopt a high-affinity ligand-binding state. In response, we used structural inferences from a pure peptide antagonist to design the small-molecule pure antagonists TDI-4161 and TDI-3761. Both compounds inhibit αVβ3-mediated cell adhesion to αVβ3 ligands, but do not induce the conformational change as judged by antibody binding, electron microscopy, X-ray crystallography, and receptor priming studies. Both compounds demonstrated the favorable property of inhibiting bone resorption in vitro, supporting potential value in treating osteoporosis. Neither, however, had the unfavorable property of the αVβ3 antagonist cilengitide of paradoxically enhancing aortic sprout angiogenesis at concentrations below its IC₅₀, which correlates with cilengitide's enhancement of tumor growth in vivo.

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.