Alexander Lukasz

Excess circulating angiopoietin-2 is a strong predictor of mortality in critically ill medical patients

IntroductionThe endothelial specific angiopoietin (Ang)-Tie2 ligand-receptor system has been identified as a non-redundant mediator of endothelial activation in experimental sepsis. Binding of circulating Ang-1 to the Tie2 receptor protects the vasculature from inflammation and leakage, whereas binding of Ang-2 antagonises Tie2 signalling and disrupts endothelial barrier function. Here, we examine whether circulating Ang-1 and/or Ang-2 independently predict mortality in a cohort of critically ill medical patients.MethodsCirculating vascular endothelial growth factor (VEGF), Ang-1 and Ang-2 were prospectively measured in sera from 29 healthy controls and 43 medical ICU patients by immunoradiometric assay (IRMA) and ELISA, respectively. Survival after 30 days was the primary outcome studied.ResultsMedian serum Ang-2 concentrations were increasingly higher across the following groups: healthy controls, patients without sepsis, patients with sepsis and patients with septic shock. In contrast, Ang-1 and VEGF concentrations were significantly lower in all patient groups compared with healthy controls. Ang-2 correlated with partial pressure of oxygen in arterial blood (PaO2)/fraction of inspired oxygen (FiO2), tissue hypoxia, Sequential Organ Failure Assessment (SOFA) and Physiology and Chronic Health Evaluation II (APACHE II) score. Multivariate Cox regression analyses confirmed a strong independent prognostic impact of high Ang-2 as a novel marker of 30-day survival.ConclusionsA marked imbalance of the Ang-Tie system in favour of Ang-2 is present in critically ill medical patients. Our findings highlight the independent prognostic impact of circulating Ang-2 in critical illness. Ang-2 may be used as a readily available powerful predictor of outcome and may open new perspectives to individualise treatment in the ICU.

Serum neutrophil gelatinase-associated lipocalin at inception of renal replacement therapy predicts survival in critically ill patients with acute kidney injury

IntroductionNeutrophil gelatinase-associated lipocalin (NGAL) is a promising novel biomarker that correlates with the severity and outcome of acute kidney injury (AKI). However, its prognostic utility during the late course of AKI, especially in patients that require renal replacement therapy (RRT) remains unknown. The aim of this study was to evaluate the predictive value of serum NGAL in patients with established AKI at inception of RRT in the intensive care unit (ICU).MethodsSerum NGAL (ELISA methodology) was measured in 109 critically ill patients with AKI at inception of RRT in 7 ICUs of a tertiary care university hospital. The primary outcome studied was 28-day mortality. Secondary outcome measures were ICU length of stay, ventilator-free days, and renal recovery at day 28.ResultsThere was a significant difference in serum NGAL between healthy subjects (median [interquartile range] 39.0 [37.5-42.75] ng/mL), critically ill patients with systemic inflammatory response syndrome (SIRS) (297 [184-490] ng/mL), and critically ill patients with sepsis (708 [365-1301] ng/mL; P < 0.0001), respectively. Multiple linear regression showed that NGAL levels were independently related to the severity of AKI and the extent of systemic inflammation. NGAL levels were higher in non-survivors (430 [303-942] ng/mL) compared to survivors (298 [159-506] ng/mL; P = 0.004). Consistently, Cox proportional hazards regression analysis identified NGAL as a strong independent predictor for 28-day survival (hazard ratio 1.6 (95% confidence interval [CI] 1.15 - 2.23), P = 0.005).ConclusionsThis is the first prospective evaluation of serum NGAL as an outcome-specific biomarker in critically ill patients at initiation of RRT. The results from this study indicate that serum NGAL is as an independent predictor of 28-day mortality in ICU patients with dialysis-dependent AKI.

Time course of angiopoietin-2 release during experimental human endotoxemia and sepsis

IntroductionEndothelial activation leading to vascular barrier breakdown denotes a devastating event in sepsis. Angiopoietin (Ang)-2, a circulating antagonistic ligand of the endothelial specific Tie2 receptor, is rapidly released from Weibel-Palade and has been identified as a non-redundant gatekeeper of endothelial activation. We aimed to study: the time course of Ang-2 release during human experimental endotoxemia; the association of Ang-2 with soluble adhesion molecules and inflammatory cytokines; and the early time course of Ang-2 release during sepsis in critically ill patients.MethodsIn 22 healthy volunteers during a 24-hour period after a single intravenous injection of lipopolysaccharide (LPS; 4 ng/kg) the following measurement were taken by immuno luminometric assay (ILMA), ELISA, and bead-based multiplex technology: circulating Ang-1, Ang-2, soluble Tie2 receptor, the inflammatory molecules TNF-alpha, IL-6, IL-8 and C-reactive protein, and the soluble endothelial adhesion molecules inter-cellular adhesion molecule-1 (ICAM-1), E-selectin, and P-selectin. A single oral dose of placebo or the p38 mitogen activated protein (MAP) kinase inhibitor drug, RWJ-67657, was administered 30 minutes before the endotoxin infusion. In addition, the course of circulating Ang-2 was analyzed in 21 septic patients at intensive care unit (ICU) admission and after 24 and 72 hours, respectively.ResultsDuring endotoxemia, circulating Ang-2 levels were significantly elevated, reaching peak levels 4.5 hours after LPS infusion. Ang-2 exhibited a kinetic profile similar to early pro-inflammatory cytokines TNF-alpha, IL-6, and IL-8. Ang-2 levels peaked prior to soluble endothelial-specific adhesion molecules. Finally, Ang-2 correlated with TNF-alpha levels (r = 0.61, P = 0.003), soluble E-selectin levels (r = 0.64, P < 0.002), and the heart rate/mean arterial pressure index (r = 0.75, P < 0.0001). In septic patients, Ang-2 increased in non-survivors only, and was significantly higher compared with survivors at baseline, 24 hours, and 72 hours.ConclusionsLPS is a triggering factor for Ang-2 release in men. Circulating Ang-2 appears in the systemic circulation during experimental human endotoxemia in a distinctive temporal sequence and correlates with TNF-alpha and E-selectin levels. In addition, not only higher baseline Ang-2 concentrations, but also a persistent increase in Ang-2 during the early course identifies septic patients with unfavorable outcome.

Circulating angiopoietins in idiopathic pulmonary arterial hypertension

AIMS To determine the diagnostic utility of circulating angiopoietin-1 (Ang-1) and its antagonist angiopoietin-2 (Ang-2) as potential biomarkers of disease severity or response to treatment in idiopathic pulmonary arterial hypertension (IPAH). Imbalances in angiogenic factors including vascular endothelial cell growth factor (VEGF) and the angiopoetin-Tie2 receptor system have been implicated in the pathogenesis of IPAH. METHODS AND RESULTS Plasma Ang-1, Ang-2, soluble Tie2 (sTie2), and VEGF were determined by in-house immunoassays in two cohorts of IPAH patients: a retrospective cohort (n = 81) and a prospective cohort (n = 25). Ten patients with normal pulmonary artery pressures and 14 apparently healthy subjects served as controls. Plasma levels of all angiogenic factors were elevated in IPAH patients compared with controls (all P < 0.005). Angiopoietin-2, but not Ang-1, sTie2, and VEGF correlated with cardiac index (r = -0.53, P < 0.001), pulmonary vascular resistance (PVR) (r= 0.60, P < 0.001), and mixed venous oxygen saturation (SvO(2)) (r= -0.63, P < 0.001). In multivariate analysis, elevated Ang-2 was an independent risk factor of mortality (P = 0.004). The patients in the prospective cohort were studied longitudinally at baseline and 3 months after initiation of therapy. Changes in Ang-2 after initiation of therapy correlated with changes in mean right atrial pressure (r = 0.6, P = 0.008), PVR (r = 0.51, P = 0.04), and inversely related to changes in SvO(2) (r = -0.75, P < 0.001). Histological studies showed that the expression of Ang-2 mRNA and protein was up-regulated in plexiform lesions from IPAH lung tissue samples. CONCLUSION Ang-2 may be involved in the pathogenesis of IPAH, and plasma Ang-2 might serve as a promising new biomarker of disease severity and response to treatment in patients with IPAH.

Circulating angiopoietin-1 and angiopoietin-2 in critically ill patients: development and clinical application of two new immunoassays.

IntroductionIn critically ill patients, the massive release of angiopoietin-2 (Ang-2) from endothelial Weibel–Palade bodies interferes with constitutive angiopoietin-1 (Ang-1)/Tie2 signaling in endothelial cells, thus leading to vascular barrier breakdown followed by leukocyte transmigration and capillary leakage. The use of circulating Ang-1 and Ang-2 as novel biomarkers of endothelial integrity has therefore gained much attention. The preclinical characteristics and clinical applicability of angiopoietin immunoassays, however, remain elusive.MethodsWe developed sandwich immunoassays for human Ang-1 (immunoradiometric sandwich assay/immunoluminometric sandwich assay) and Ang-2 (ELISA), assessed preanalytic characteristics, and determined circulating Ang-1 and Ang-2 concentrations in 30 healthy control individuals and in 94 critically ill patients. In addition, Ang-1 and Ang-2 concentrations were measured in 10 patients during a 24-hour time course with respect to interference by intravenous antibiotic treatment and by extended daily dialysis.ResultsThe assays had detection limits of 0.12 ng/ml (Ang-1) and 0.2 ng/ml (Ang-2). Inter-assay and intra-assay imprecision was ≤8.8% and 3.7% for Ang-1 and was ≤4.6% and 5.2% for Ang-2, respectively. Angiopoietins were stable for 24 hours and were resistant to four freeze–thaw cycles. Angiopoietin concentrations were not associated with age, body mass index or renal function in healthy individuals. Ang-1 and Ang-2 concentrations correlated with severity of illness in critically ill patients. Angiopoietin concentrations were not influenced by antibiotic treatment or by extended daily dialysis.ConclusionAng-1 and Ang-2 might serve as a novel class of biomarker in critically ill patients. According to preclinical and clinical validation, circulating Ang-1 and Ang-2 can be reliably assessed by novel immunoassays in the intensive care unit setting.

Damage of the endothelial glycocalyx in chronic kidney disease

BACKGROUND AND OBJECTIVES The endothelial glycocalyx (eGC), a mesh of anionic biopolymers covering the luminal surface of endothelial cells, is considered as an intravascular compartment that protects the vessel wall against pathogenic insults in cardiovascular disease. We hypothesized that chronic kidney disease (CKD) is associated with reduced eGC integrity and subsequent endothelial dysfunction. METHODS & RESULTS Shedding of two major components of the eGC, namely syndecan-1 (Syn-1) and hyaluronan (HA), was measured by ELISA in 95 patients with CKD (stages 3-5) and 31 apparently healthy controls. Plasma levels of Syn-1 and HA increased steadily across CKD stages (5- and 5.5-fold, respectively P < 0.001) and were independently associated with impaired renal function after multivariate adjustment. Furthermore, Syn-1 and HA correlated tightly with plasma markers of endothelial dysfunction such as soluble fms-like tyrosine kinase-1 (sFlt-1), soluble vascular adhesion molecule-1 (sVCAM-1), von-Willebrand-Factor (vWF) and angiopoietin-2 (P < 0.001). Experimentally, excessive shedding of the eGC, evidenced by 11-fold increased Syn-1 plasma levels, was also observed in an established rat model of CKD, the 5/6-nephrectomized rats. Consistently, an atomic force microscopy-based approach evidenced a significant decrease in eGC thickness (360 ± 79 vs. 157 ± 29 nm, P = 0.001) and stiffness (0.33 ± 0.02 vs. 0.22 ± 0.01 pN/nm, P < 0.001) of aorta endothelial cell explants isolated from CKD rats. CONCLUSION Our findings provide evidence for damage of the atheroprotective eGC as a consequence of CKD and potentially open a new avenue to pathophysiology and treatment of cardiovascular disease in renal patients.

Circulating angiopoietin-2 in essential hypertension: relation to atherosclerosis, vascular inflammation, and treatment with olmesartan/pravastatin.

Background Endothelial activation has emerged as an early event in the pathogenesis of cardiovascular disease. Angiopoietin-2 (Ang-2) has been identified as a nonredundant endothelial-specific facilitator of vascular responsiveness to inflammatory stimuli. We have earlier shown that angiotensin II receptor blocker (ARB) reduces mediators of vascular inflammation in hypertension and cardiovascular disease. We aimed at studying the effect of ARB and/or 3-hydroxy-3-methyl-glutaryl-CoA blockade on Ang-2 and the association between vascular inflammation markers and Ang-2 levels in hypertensive patients. Methods We assessed a panel of vascular inflammation markers and Ang-2 during 12 weeks of therapy with the ARB olmesartan (n = 94) or placebo (n = 96) in a prospective, double-blind, multicenter study in patients with essential hypertension (re-evaluation of the European Trial on Olmesartan and Pravastatin in Inflammation blood samples). Pravastatin was added to the double-blind therapy at week 6 in both arms. The association of demographic variables and inflammation markers with Ang-2 has been investigated. Results Initial Ang-2 concentrations in the study population were elevated compared with healthy controls (4.23 ± 3.1 versus 0.88 ± 0.43 ng/ml; P < 0.0001). Ang-2 was higher in the elderly (P = 0.01), women (P < 0.001), and in the presence of atherosclerosis (P = 0.02). Ang-2 correlated significantly with soluble TEK tyrosine kinase-2, interleukin-6, vascular cell adhesion molecule-1, and inter-cellular adhesion molecule-1. Surprisingly, neither monotherapy with olmesartan or pravastatin nor the combination therapy affected Ang-2 concentrations. Conclusion Ang-2 concentrations are elevated in hypertensive patients, particularly those with atherosclerosis, possibly reflecting pronounced endothelial activation. ARBs effectively decreased several inflammatory mediators, but did not affect vascular responsiveness in an Ang-2-dependent manner. Elevated Ang-2 levels in hypertensive patients correlate with adhesion molecules.

Circulating angiopoietin-2 levels increase with progress of chronic kidney disease

BACKGROUND Angiopoietin-2 (Ang-2) is an antagonistic ligand of the endothelial-specific Tie2 receptor. Patients on dialysis have markedly elevated Ang-2 levels, and those correlate with their atherosclerotic burden. The aim of the current study was to investigate the relationship between the circulating levels of Ang-2 and renal function throughout all stages of chronic kidney disease (CKD). In addition, we aimed to detect a potential link between the nitric oxide (NO) synthase inhibitor asymmetric dimethylarginine (ADMA) and the Ang-2 levels. METHODS Glomerular filtration rate (GFR) was assessed by the inulin clearance technique ((i)GFR) and compared to serum Ang-2 (immunoluminometric assay) and ADMA levels (liquid chromatography-electrospray tandem mass spectrometry) in 44 untreated non-smokers at the different stages of CKD 1-4. Ang-2 was also measured in 19 patients on dialysis (CKD stage 5). In addition, the Ang-2 and (c)GFR (cystatin C) measurements were taken in 15 healthy individuals before and 72 h after kidney donation. RESULTS The median Ang-2 levels steadily increased across the following groups: healthy controls: 0.77 (0.32-1.08) ng/mL; CKD 1: 0.83 (0.67-1.09) ng/mL; CKD 2: 0.93 (0.74-1.15) ng/mL; CKD 3: 1.13 (0.87-1.49) ng/mL; CKD 4: 1.75 (1.23-2.61) ng/mL; and CKD 5: 4.87 (3.22-7.59) ng/mL, respectively (non-parametric ANOVA P < 0.0001). Ang-2 was associated with the degree of CKD as evidenced by an inverse correlation with the (i)GFR (r = -0.509, P < 0.0001) and positive correlations with homocysteine (r = 0.365, P = 0.015) and phosphate (r = 0.53, P < 0.0001). Additionally, Ang-2 correlated with the ADMA levels (r = 0.35, P = 0.01). We detected a close inverse correlation between the mean changes in GFR and circulating Ang-2 at 72 h after kidney donation (r = -0.54, P = 0.03). CONCLUSIONS Circulating Ang-2, a putative marker and potential mediator of accelerated atherosclerosis, is inversely related to GFR and increases with advanced CKD. The correlation between Ang-2 and ADMA points towards the hypothesis that the ADMA-driven NO deficiency might trigger Ang-2 release and account for the Ang-2 increase in CKD patients.

High permeability dialysis membrane allows effective removal of myoglobin in acute kidney injury resulting from rhabdomyolysis.

Objective:The objective of this study was to test the ability of myoglobin removal of a novel, high-permeability polysulphone dialyzer in acute kidney injury as a result of rhabdomyolysis. Setting:Intensive care unit of a tertiary care hospital. Patients:Six patients (one female; aged 24, 36, 41, 55, 63, and 65 yrs) with oligoanuric acute kidney injury resulting from rhabdomyolysis. Interventions:Extended dialysis was performed using a single-pass batch dialysis system and a novel polysulphone high-flux dialyzer (effective surface area 1.8 m2; inner lumen 220 &mgr;m; wall thickness 35 &mgr;m; allowing elimination of substances with a molecular weight of up to 30 kDa). Measurements and Main Results:Samples were collected at prefilter and postfilter sites as well as from the collected spent dialysate. The dialyzer clearance was calculated from concentrations before and directly after the dialysis membrane, the blood flow, and the ultrafiltration rate. The total amount of the myoglobin removed was measured directly as the whole dialysate was preserved. A median myoglobin clearance of 90.5 mL/min (range, 52.4–126.3 mL/min) was achieved, resulting in a median myoglobin removal per treatment hour of 0.54 g (range, 0.15–2.21 g). Conclusions:Extended dialysis with a high-flux, high-permeability membrane allowed effective elimination of myoglobin with a clearance of myoglobin that surpassed all previously reported dialysis techniques. This membrane may be advantageous in preventing acute kidney injury or avoiding complete loss of kidney function in patients with rhabdomyolysis. Further studies are needed to determine whether improving renal recovery or mortality in patients with acute kidney injury resulting from rhabdomyolysis is possible.

Circulating Biomarkers for Discrimination Between Aseptic Joint Failure, Low-Grade Infection And High-Grade Septic Failure

BACKGROUND Late-onset chronic (low-grade) periprosthetic joint infections are often accompanied by unspecific symptoms, false-negative cultures or nonspecific low values of serum biomarkers. This may lead to the unintended implantation of a revision prosthesis into an infected surgical site with the risk of short-term failure developing again. Conversely, false diagnosis of joint infection may result in multistage revision procedures, which expose the patient to unnecessary surgical procedures and inappropriate antibiotic treatment. Here, we investigated whether circulating biomarkers can preoperatively distinguish between aseptic prosthesis loosening and low-grade joint infection, and which biomarker combinations are most accurate. METHODS Inclusion criteria for the study were indication for revision arthroplasty due to aseptic implant failure, acute high-grade infection, or (suspected) low-grade infection. C-reactive protein (CRP), procalcitonin, tumor necrosis factor α, interleukin 6 (IL-6), interleukin 10, and lipopolysaccharide binding protein were assessed preoperatively in the serum of 98 adult patients. RESULTS The classification tree method revealed IL-6 and CRP as the most suitable biomarker combination for the discrimination of aseptic loosening vs low-grade joint infection. The combination of IL-6 >5.12 pg/mL and CRP >0.3 mg/dL correctly identified 15 of 16 patients as having low-grade infection (94%) whereas just one patient was aseptic (6%). CONCLUSIONS This is the first comprehensive prospective clinical study to our knowledge investigating the significance of a combined biomarker approach in differentiating between aseptic prosthesis loosening and low-grade joint infection. CRP plus IL-6 seems to be the most helpful combination for preoperative discrimination of aseptic loosening vs low-grade joint infection.