ADMISSION ANGIOPOIETIN LEVELS IN CHILDREN WITH SEPTIC SHOCK

How we use angiopoietin-2 in the diagnosis and management of vascular anomalies

The diagnosis of vascular anomalies remains challenging due to significant clinical heterogeneity and uncertain etiology. Evaluation using biopsy and/or genetic testing for somatic variants is invasive, expensive, and prone to sampling error. There is great need for noninvasive and easily measured blood laboratory biomarkers that can aid not only in diagnosis, but also management of treatments for vascular anomalies. Angiopoietin-2, a circulating blood angiogenic factor, is highly elevated in patients with kaposiform hemangioendothelioma with Kasabach-Merritt phenomenon and kaposiform lymphangiomatosis. Here, we describe our clinical experience using serum angiopoietin-2 as a biomarker for diagnosis and monitoring response to treatment.

Prognostic significance of the angiopoietin-2 for early prediction of septic shock in severe sepsis patients

Aim

The current study investigated the plasma levels of angiopoietin-1/-2 and their association with clinical outcomes of sepsis.

Methods

Angiopoietin-1 and -2 levels were quantified in plasma from 105 patients with severe sepsis by ELISA.

Results

Angiopoietin-2 levels elevated according to the severity of sepsis progression. Angiopoietin-2 levels were correlated with mean arterial pressure and platelets counts, total bilirubin, creatinine, procalcitonin, lactate levels and SOFA score. Angiopoietin-2 levels accurately discriminated for sepsis with an AUC = 0.97 and septic shock from severe sepsis patients (AUC = 0.778).

Conclusion

Plasma angiopoietin-2 levels may serve as an additional biomarker for severe sepsis and septic shock.

New Insights into Clinical and Mechanistic Heterogeneity of the Acute Respiratory Distress Syndrome: Summary of the Aspen Lung Conference 2021

Clinical and molecular heterogeneity are common features of human disease. Understanding the basis for heterogeneity has led to major advances in therapy for many cancers and pulmonary diseases such as cystic fibrosis and asthma. Although heterogeneity of risk factors, disease severity, and outcomes in survivors are common features of the acute respiratory distress syndrome (ARDS), many challenges exist in understanding the clinical and molecular basis for disease heterogeneity and using heterogeneity to tailor therapy for individual patients. This report summarizes the proceedings of the 2021 Aspen Lung Conference, which was organized to review key issues related to understanding clinical and molecular heterogeneity in ARDS. The goals were to review new information about ARDS phenotypes, to explore multicellular and multisystem mechanisms responsible for heterogeneity, and to review how best to account for clinical and molecular heterogeneity in clinical trial design and assessment of outcomes. The report concludes with recommendations for future research to understand the clinical and basic mechanisms underlying heterogeneity in ARDS to advance the development of new treatments for this life-threatening critical illness.

Multi-Omics Techniques Make it Possible to Analyze Sepsis-Associated Acute Kidney Injury Comprehensively

Sepsis-associated acute kidney injury (SA-AKI) is a common complication in critically ill patients with high morbidity and mortality. SA-AKI varies considerably in disease presentation, progression, and response to treatment, highlighting the heterogeneity of the underlying biological mechanisms. In this review, we briefly describe the pathophysiology of SA-AKI, biomarkers, reference databases, and available omics techniques. Advances in omics technology allow for comprehensive analysis of SA-AKI, and the integration of multiple omics provides an opportunity to understand the information flow behind the disease. These approaches will drive a shift in current paradigms for the prevention, diagnosis, and staging and provide the renal community with significant advances in precision medicine in SA-AKI analysis.

Regulation and Dysregulation of Endothelial Permeability during Systemic Inflammation

Systemic inflammation can be triggered by infection, surgery, trauma or burns. During systemic inflammation, an overshooting immune response induces tissue damage resulting in organ dysfunction and mortality. Endothelial cells make up the inner lining of all blood vessels and are critically involved in maintaining organ integrity by regulating tissue perfusion. Permeability of the endothelial monolayer is strictly controlled and highly organ-specific, forming continuous, fenestrated and discontinuous capillaries that orchestrate the extravasation of fluids, proteins and solutes to maintain organ homeostasis. In the physiological state, the endothelial barrier is maintained by the glycocalyx, extracellular matrix and intercellular junctions including adherens and tight junctions. As endothelial cells are constantly sensing and responding to the extracellular environment, their activation by inflammatory stimuli promotes a loss of endothelial barrier function, which has been identified as a hallmark of systemic inflammation, leading to tissue edema formation and hypotension and thus, is a key contributor to lethal outcomes. In this review, we provide a comprehensive summary of the major players, such as the angiopoietin-Tie2 signaling axis, adrenomedullin and vascular endothelial (VE-) cadherin, that substantially contribute to the regulation and dysregulation of endothelial permeability during systemic inflammation and elucidate treatment strategies targeting the preservation of vascular integrity.

Colivelin, a synthetic derivative of humanin, ameliorates endothelial injury and glycocalyx shedding after sepsis in mice

Endothelial dysfunction plays a central role in the pathogenesis of sepsis-mediated multiple organ failure. Several clinical and experimental studies have suggested that the glycocalyx is an early target of endothelial injury during an infection. Colivelin, a synthetic derivative of the mitochondrial peptide humanin, has displayed cytoprotective effects in oxidative conditions. In the current study, we aimed to determine the potential therapeutic effects of colivelin in endothelial dysfunction and outcomes of sepsis in vivo. Male C57BL/6 mice were subjected to a clinically relevant model of polymicrobial sepsis by cecal ligation and puncture (CLP) and were treated with vehicle or colivelin (100-200 µg/kg) intraperitoneally at 1 h after CLP. We observed that vehicle-treated mice had early elevation of plasma levels of the adhesion molecules ICAM-1 and P-selectin, the angiogenetic factor endoglin and the glycocalyx syndecan-1 at 6 h after CLP when compared to control mice, while levels of angiopoietin-2, a mediator of microvascular disintegration, and the proprotein convertase subtilisin/kexin type 9, an enzyme implicated in clearance of endotoxins, raised at 18 h after CLP. The early elevation of these endothelial and glycocalyx damage biomarkers coincided with lung histological injury and neutrophil inflammation in lung, liver, and kidneys. At transmission electron microscopy analysis, thoracic aortas of septic mice showed increased glycocalyx breakdown and shedding, and damaged mitochondria in endothelial and smooth muscle cells. Treatment with colivelin ameliorated lung architecture, reduced organ neutrophil infiltration, and attenuated plasma levels of syndecan-1, tumor necrosis factor-α, macrophage inflammatory protein-1α and interleukin-10. These therapeutic effects of colivelin were associated with amelioration of glycocalyx density and mitochondrial structure in the aorta. At molecular analysis, colivelin treatment was associated with inhibition of the signal transducer and activator of transcription 3 and activation of the AMP-activated protein kinase in the aorta and lung. In long-term outcomes studies up to 7 days, co-treatment of colivelin with antimicrobial agents significantly reduced the disease severity score when compared to treatment with antibiotics alone. In conclusion, our data support that damage of the glycocalyx is an early pathogenetic event during sepsis and that colivelin may have therapeutic potential for the treatment of sepsis-associated endothelial dysfunction.

Diagnosing capillary leak in critically ill patients: development of an innovative scoring instrument for non-invasive detection

BACKGROUND

The concomitant occurrence of the symptoms intravascular hypovolemia, peripheral edema and hemodynamic instability is typically named Capillary Leak Syndrome (CLS) and often occurs in surgical critical ill patients. However, neither a unitary definition nor standardized diagnostic criteria exist so far. We aimed to investigate common characteristics of this phenomenon with a subsequent scoring system, determining whether CLS contributes to mortality.

METHODS

We conducted this single-center, observational, multidisciplinary, prospective trial in two separately run surgical ICUs of a tertiary academic medical center. 200 surgical patients admitted to the ICU and 30 healthy volunteers were included. Patients were clinically diagnosed as CLS or No-CLS group (each N = 100) according to the grade of edema, intravascular hypovolemia, hemodynamic instability, and positive fluid balance by two independent attending physicians with > 10 years of experience in ICU. We performed daily measurements with non-invasive body impedance electrical analysis, ultrasound and analysis of serum biomarkers to generate objective diagnostic criteria. Receiver operating characteristics were used, while we developed machine learning models to increase diagnostic specifications for our scoring model.

RESULTS

The 30-day mortility was increased among CLS patients (12 vs. 1%, P = 0.002), while showing higher SOFA-scores. Extracellular water was increased in patients with CLS with higher echogenicity of subcutaneous tissue [29(24-31) vs. 19(16-21), P < 0.001]. Biomarkers showed characteristic alterations, especially with an increased angiopoietin-2 concentration in CLS [9.9(6.2-17.3) vs. 3.7(2.6-5.6)ng/mL, P < 0.001]. We developed a score using seven parameters (echogenicity, SOFA-score, angiopoietin-2, syndecan-1, ICAM-1, lactate and interleukin-6). A Random Forest prediction model boosted its diagnostic characteristics (AUC 0.963, P < 0.001), while a two-parameter decision tree model showed good specifications (AUC 0.865).

CONCLUSIONS

Diagnosis of CLS in critically ill patients is feasible by objective, non-invasive parameters using the CLS-Score. A simplified two-parameter diagnostic approach can enhance clinical utility. CLS contributes to mortality and should, therefore, classified as an independent entity.

TRIAL REGISTRATION

German Clinical Trials Registry (DRKS No. 00012713), Date of registration 10/05/2017, www.drks.de.

Requirement of respiratory support in acute bronchiolitis in infants is linked to endothelial and neutrophil activation

BACKGROUND

Evidence shows that activation of pulmonary vascular endothelium and neutrophils are involved in the pathophysiology of acute bronchiolitis. We hypothesized that levels of markers of endothelial activation and leukocyte counts are associated with requirement and duration of respiratory support.

METHODS

Thirty-four infants with bronchiolitis and eight controls were included. Nasopharyngeal swabs and blood samples were taken at admission. Serum levels of Angiopoietin (Ang)-1, Ang-2, sP-selectin, sE-selectin, vascular cell adhesion molecule-1 (sVCAM-1), intercellular adhesion molecule-1 (sICAM-1), and leukocyte counts were measured. For univariate analysis, bronchiolitis cases were grouped into two groups, namely those not requiring and those requiring any form of respiratory support. To control for known risk factors for poor outcome (i.e., age, prematurity, and congenital heart disease), and for days post symptom onset, linear regression analysis was performed with duration of any type of respiratory support in days.

RESULTS

Ang-2 levels, Ang-2/Ang-1 ratios, sE-selectin levels, immature neutrophil count, and neutrophil/lymphocyte ratio (NLR) were higher in acute bronchiolitis versus controls. Ang-2, and NLR levels were significantly higher, and lymphocyte counts significantly lower, in infants that required respiratory support versus those that did not. Ang-2 levels (β: .32, 95% confidence interval [CI]: 0.19-1.19) and NLR (β: .68, 95% CI: 0.17-1.19) were positive predictors for the duration of respiratory support.

CONCLUSIONS

Markers of endothelial and neutrophil activation are associated with respiratory support for acute bronchiolitis. Admission Ang-2 levels and NLR may be promising markers to determine requirement of respiratory support and deserve further study.

Serum Levels of Markers of Endothelial Activation Are Not Associated with a Positive Blood Culture in Surinamese Children with Suspected Severe Infection

BACKGROUND

Systemic serum levels of markers of endothelial activation are associated with infection. We hypothesize that levels of markers of endothelial activation are associated with the presence of a positive blood culture as a manifestation of a systemic infection in children with a suspected severe infection in Suriname.

METHODS

In this prospective observational cohort study, children between 1 month and 18 years of age suspected of severe infection as assessed by the threating physician, and in whom laboratory testing and blood culturing was performed before start of intravenous antibiotic treatment, were recruited at the emergency department of the Academic Hospital Paramaribo, Suriname. Serum was collected at blood culturing and after 48-72 h of admission. Serum was stored for measurement of levels of Angiopoietin (Ang)-1, Ang-2, soluble (s)P-selectin, sE-selectin, vascular cell adhesion molecule-1, intercellular adhesion molecule-1 and platelet and endothelial cell adhesion molecule-1.

RESULTS

Fifty-one children were included of whom 10 had a positive blood culture. Baseline characteristics were similar between children with and without a positive blood culture. No significant differences in serum levels of the Angiopoietins or soluble cellular adhesion molecules between groups were observed at start of antibiotic treatment nor after 48-72 h.

CONCLUSIONS

The data from this study indicate that in children with severe infection, serum levels of markers of endothelial cell activation are not associated with a positive blood culture. Thus, having a positive bacterial blood culture may not be the only factor driving endothelial activation in this patient population.

Two to Tango: Kidney-Lung Interaction in Acute Kidney Injury and Acute Respiratory Distress Syndrome

Acute Kidney Injury (AKI) is an independent risk factor for mortality in hospitalized patients. AKI syndrome leads to fluid overload, electrolyte and acid-base disturbances, immunoparalysis, and propagates multiple organ dysfunction through organ "crosstalk". Preclinical models suggest AKI causes acute lung injury (ALI), and conversely, mechanical ventilation and ALI cause AKI. In the clinical setting, respiratory complications are a key driver of increased mortality in patients with AKI, highlighting the bidirectional relationship. This article highlights the challenging and complex interactions between the lung and kidney in critically ill patients with AKI and acute respiratory distress syndrome (ARDS) and global implications of AKI. We discuss disease-specific molecular mediators and inflammatory pathways involved in organ crosstalk in the AKI-ARDS construct, and highlight the reciprocal hemodynamic effects of elevated pulmonary vascular resistance and central venous pressure (CVP) leading to renal hypoperfusion and pulmonary edema associated with fluid overload and increased right ventricular afterload. Finally, we discuss the notion of different ARDS "phenotypes" and the response to fluid overload, suggesting differential organ crosstalk in specific pathological states. While the directionality of effect remains challenging to distinguish at the bedside due to lag in diagnosis with conventional renal function markers and lack of tangible damage markers, this review provides a paradigm for understanding kidney-lung interactions in the critically ill patient.

Systemic Endothelial Activation Is Associated With Early Acute Respiratory Distress Syndrome in Children With Extrapulmonary Sepsis

OBJECTIVES

Systemic endothelial activation may contribute to sepsis-associated organ injury, including acute respiratory distress syndrome. We hypothesized that children with extrapulmonary sepsis with versus without acute respiratory distress syndrome would have plasma biomarkers indicative of increased endothelial activation and that persistent biomarker changes would be associated with poor outcome.

DESIGN

Observational cohort.

SETTING

Academic PICU.

PATIENTS

Patients less than 18 years old with sepsis from extrapulmonary infection with (n = 46) or without (n = 54) acute respiratory distress syndrome and noninfected controls (n = 19).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Endothelial (angiopoietin-1, angiopoietin-2, tyrosine kinase with immunoglobulin-like loop epidermal growth factor homology domain 2, vascular endothelial growth factor, soluble fms-like tyrosine kinase, von Willebrand factor, E-selectin, intercellular adhesion molecule, vascular cell adhesion molecule, thrombomodulin) and inflammatory biomarkers (C-reactive protein, interleukin-6, and interleukin-8) were measured from peripheral plasma collected within 3 days (time 1) of sepsis recognition and at 3-6 days (time 2) and 7-14 days (time 3). Time 1 biomarkers and longitudinal measurements were compared for sepsis patients with versus without acute respiratory distress syndrome and in relation to complicated course, defined as greater than or equal to two organ dysfunctions at day 7 or death by day 28. Angiopoietin-2, angiopoietin-2/angiopoietin-1 ratio, tyrosine kinase with immunoglobulin-like loop epidermal growth factor homology domain 2, vascular endothelial growth factor, von Willebrand factor, E-selectin, intercellular adhesion molecule, vascular cell adhesion molecule, thrombomodulin, endocan, C-reactive protein, interleukin-6, and interleukin-8 were different between sepsis and noninfected control patients at time 1. Among patients with sepsis, those with acute respiratory distress syndrome had higher angiopoietin-2/angiopoietin-1 ratio, vascular endothelial growth factor, vascular cell adhesion molecule, thrombomodulin, endocan, interleukin-6, and interleukin-8 than those without acute respiratory distress syndrome (all p < 0.003). Angiopoietin-2 and angiopoietin-2/angiopoietin-1 ratio remained higher in sepsis with versus without acute respiratory distress syndrome after multivariable analyses. Time 1 measures of angiopoietin-2, angiopoietin-2/-1 ratio, von Willebrand factor, and endocan were indicative of complicated course in all sepsis patients (all area under the receiver operating curve ≥ 0.80). In sepsis without acute respiratory distress syndrome, soluble fms-like tyrosine kinase decreased more quickly and von Willebrand factor and thrombomodulin decreased more slowly in those with complicated course.

CONCLUSIONS

Children with extrapulmonary sepsis with acute respiratory distress syndrome had plasma biomarkers indicative of greater systemic endothelial activation than those without acute respiratory distress syndrome. Several endothelial biomarkers measured near sepsis recognition were associated with complicated course, whereas longitudinal biomarker changes yielded prognostic information only in those without sepsis-associated acute respiratory distress syndrome.

New soluble angiopoietin analog of Hepta-ANG1 prevents pathological vascular leakage

Vascular leak is a key driver of organ injury in diseases, and strategies that reduce enhanced permeability and vascular inflammation are promising therapeutic targets. Activation of the angiopoietin-1 (ANG1)-Tie2 tyrosine kinase signaling pathway is an important regulator of vascular quiescence. Here we describe the design and construction of a new soluble ANG1 mimetic that is a potent activator of endothelial Tie2 in vitro and in vivo. Using a chimeric fusion strategy, we replaced the extracellular matrix (ECM) binding and oligomerization domain of ANG1 with a heptameric scaffold derived from the C-terminus of serum complement protein C4-binding protein α. We refer to this new fusion protein biologic as Hepta-ANG1, which forms a stable heptamer and induces Tie2 phosphorylation in cultured cells, and in the lung following intravenous injection of mice. Injection of Hepta-ANG1 ameliorates vascular endothelial growth factor- and lipopolysaccharide-induced vascular leakage, in keeping with the known functions of Angpt1-Tie2 in maintaining quiescent vascular stability. The new Hepta-ANG1 fusion is easy to produce and displays remarkable stability with high multimericity that can potently activate Tie2. It could be a new candidate ANG1 mimetic therapy for treatments of inflammatory vascular leak, such as acute respiratory distress syndrome and sepsis.

Associations of Plasma Angiopoietins-1 and -2 and Angiopoietin-2/-1 Ratios With Measures of Organ Injury and Clinical Outcomes in Children With Sepsis: A Preliminary Report

OBJECTIVES

Results from preclinical and adult sepsis studies suggest that the balance of circulating angiopoietin-1 and -2 levels, represented as angiopoietin-2/-1 ratios, plays a pivotal role in mediating vascular dysfunction and organ injury during sepsis. However, the relationship of plasma angiopoietins with organ injury and clinical outcomes in children with sepsis remains unknown. We sought to determine whether plasma angiopoietin-1 and -2 levels and angiopoietin-2/-1 ratios in the acute phase of sepsis correlated with measures of organ injury and clinical outcomes in children with sepsis.

DESIGN

Prospective observational cohort study.

SETTING

PICU within a tertiary freestanding children's hospital.

PATIENTS

Children 18 years old or less and greater than 3 kg admitted to the PICU for sepsis.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Plasma angiopoietin-1 and -2 levels were measured in 38 children with sepsis 0-6, 24, 48, and 72 hours following PICU admission. Children with elevated pediatric Sequential Organ Failure Assessment scores on the third day after PICU admission demonstrated significantly higher 24-72-hour angiopoietin-2/-1 ratios predominantly as a function of higher angiopoietin-2 levels. In children with sepsis-induced organ dysfunction, angiopoietin-2/-1 ratios correlated with oxygenation indices and serum levels of creatinine and bilirubin. Forty-eight- and 72-hour angiopoietin-2/-1 ratios correlated with PICU length of stay (Spearman rho = 0.485, p = 0.004 and rho = 0.440, p = 0.015, respectively).

CONCLUSIONS

In the acute phase of sepsis in children, plasma angiopoietin-2/-1 ratios rise significantly above control levels and correlate with measures of organ injury and worse clinical outcomes after 24 hours. Our findings suggest that angiopoietin dysregulation begins early in sepsis and, if sustained, may promote greater organ injury that can lead to worse clinical outcomes.

Angiopoietin Level Trajectories in Toddlers With Severe Sepsis and Septic Shock and Their Effect on Capillary Endothelium

OBJECTIVE

Angiopoietins are postulated diagnostic biomarkers in children and adults with severe sepsis and septic shock. The diagnostic value of angiopoietins in children less than 5 years old has not been established, nor has their effect on permeability in the capillary microvasculature. We aim to determine if levels of angiopoietin-1 or -2 (angpt-1, -2) are diagnostic for severe sepsis/shock in young children and whether they affect the permeability of cultured human dermal microvascular endothelial cells (HDMEC).

DESIGN

Prospective observational study of children < 5 years old. Patients were classified as non-systemic inflammatory response syndrome (SIRS), SIRS/sepsis and severe sepsis/septic shock.

SETTING

Tertiary care pediatric hospitals.

PATIENTS

Critically ill children.

INTERVENTIONS

None.

MEASUREMENTS

Plasma angpt-1 and -2 levels were measured with enzyme-linked immunoassays. Expression of angpt-2 in endothelial cells was assessed with quantitative polymerase chain reaction. Permeability changes in cultured HDMECs were assessed with transendothelial electrical resistance measurements.

RESULTS

Angpt-1 levels were significantly higher in younger children compared with levels found in previous study of older children across disease severity (all P < 0.001). Angpt-2 was significantly higher in this cohort with severe sepsis/septic shock compared with children without SIRS and SIRS/sepsis (all P < 0.003). Angpt-2/1 ratio was also elevated in children with severe sepsis/septic shock but an order of magnitude less than older children (P < 0.02, P = 0.002). Angpt-1 and -2 did not affect basal HDMEC permeability or modulate leak in isolation or in the presence of tumor necrosis factor (TNF).

CONCLUSIONS

Angpt-2 levels and the angpt-2/1 ratio are appropriate diagnostic biomarkers of severe sepsis/septic shock in children less than 5 years old. Neither angpt-1 nor -2 affects basal HDMEC permeability alone or modulates TNF induced capillary leak.

Plasma Levels, Temporal Trends and Clinical Associations between Biomarkers of Inflammation and Vascular Homeostasis after Pediatric Traumatic Brain Injury

Expression of inflammatory (interleukin-6 [IL-6]) and vascular homeostatic (angiopoietin-2 [AP-2], endothelin-1 [ET-1], endocan-2 [EC-2]) biomarkers in pediatric traumatic brain injury (TBI) was examined in this prospective, observational cohort study of 28 children hospitalized with mild, moderate, and severe TBI by clinical measures (age, sex, Glasgow Coma Scale score [GCS], Injury Severity Score [ISS], and cerebral autoregulation status). Biomarker patterns suggest an inverse relationship between GCS and AP-2, GCS and IL-6, ISS and ET-1, but a direct relationship between GCS and ET-1 and ISS and AP-2. Biomarker patterns suggest an inverse relationship between AP-2 and ET-1, AP-2 and EC-2, but a direct relationship between AP-2 and IL-6, IL-6 and EC-2, and IL-6 and ET-1. Plasma concentrations of inflammatory and vascular homeostatic biomarkers suggest a role for inflammation and disruption of vascular homeostasis during the first 10 days across the severity spectrum of pediatric TBI. Although not statistically significant, without impact on cerebral autoregulation, biomarker patterns suggest a relationship between inflammation and alterations in vascular homeostasis. The large variation in biomarker levels within TBI severity and age groups, and by sex suggests other contributory factors to biomarker expression.

Angiopoietin 1 influences ischemic reperfusion renal injury via modulating endothelium survival and regeneration

Background

Damage to the endothelium due to ischemia reperfusion injury (IRI) leads to a disruption of the microvasculature, which could be influenced by angiopoietin 1 via its effects on endothelium. We investigated the physiological and therapeutic roles of angiopoietin 1 in renal IRI using angiopoietin 1 knockout and over-expression mice.

Methods

Renal IRI was induced by clamping the right renal artery seven days after left uninephrectomy for 25 min followed by reperfusion. A whole body angiopoietin 1 knockout was achieved by induction with tamoxifen. The renal tubule over-expression of angiopoietin 1 was induced by doxycycline.

Results

In the normal mice, the renal expression of angiopoietin 1 increased 7 days to 14 days after IRI. The angiopoietin 1 knockout caused a delay in the recovery of renal function, less tubular regeneration and more residual tubular necrosis. The endothelial density was lower and the VE-cadherin protein loss was greater in the knockout mice. The over-expression of angiopoietin 1 attenuated the tubular necrosis and renal function impairment 1 and 3 days after IRI. The loss of the endothelium was ameliorated in the over-expression mice. This protective effect was associated with the up-regulation of the gene expression of epidermal growth factor, hepatocyte growth factor, and insulin like growth factor-1 and less tubular apoptosis. The over-expression of angiopoietin 1 stimulated tumor necrosis factor-α, C-C chemokine receptor type 2 and CX3C chemokine receptor 1 inflammatory gene expression, but did not influence macrophage infiltration.

Conclusions

Altogether, the augmentation and downregulation of angiopoietin 1 attenuated renal damage and impaired renal recovery, respectively, by influencing the survival/regeneration of the endothelium. The manipulation of angiopoietin 1 represents a novel therapeutic approach for the treatment of ischemic kidney injury.

Electronic supplementary material

The online version of this article (10.1186/s10020-019-0072-7) contains supplementary material, which is available to authorized users.

Evaluation of plasma angiopoietin-2 and vascular endothelial growth factor in healthy dogs and dogs with systemic inflammatory response syndrome or sepsis

Background

Angiopoietin‐2 (Ang‐2) and vascular endothelial growth factor (VEGF) are regulators of endothelial permeability.

Objective

Plasma concentrations of Ang‐2 and VEGF are increased in dogs with systemic inflammatory response syndrome (SIRS) and sepsis and are correlated with disease severity and outcome.

Animals

Healthy dogs (n = 18) and client‐owned dogs with SIRS (n = 34) or sepsis (n = 25).

Methods

Prospective observational study. Ang‐2 and VEGF concentrations in admission plasma samples were compared between healthy dogs and dogs with SIRS or sepsis, and between survivors and non‐survivors. Correlations with the acute patient physiologic and laboratory evaluation (APPLE_fast) disease severity score were examined.

Results

Median Ang‐2 was significantly higher in dogs with SIRS (19.3; interquartile range [IQR]: 8.6‐25.7 ng/mL) and sepsis (21.2; IQR: 10.3‐30.1 ng/mL) compared to healthy dogs (7.6; IQR: 6.7‐9.8 ng/mL). Ang‐2 was significantly higher in non‐survivors (24.1; IQR: 11.9‐50.0 ng/mL) than survivors (10.2; IQR: 7.2‐21.5 ng/mL) but did not correlate with the APPLE_fast score. Admission Ang‐2 predicted negative outcome in dogs with SIRS and sepsis with reasonable accuracy (area under the curve [AUC]: 0.75, confidence interval [CI]: 0.59‐0.85; sensitivity: 0.5, CI: 0.29‐0.71; specificity: 0.87, CI: 0.75‐0.95); differentiation between sepsis and SIRS was poor (AUC: 0.58). Plasma VEGF was significantly higher in dogs with sepsis (45; IQR: 14‐107.5 pg/mL) than in dogs with SIRS (3.3; IQR: 0‐35.6 pg/mL) or healthy dogs (0; IQR: 0 pg/mL; P = 0.008). VEGF was significantly (P = .0004) higher in non‐survivors (34.5; IQR: 0‐105.7 pg/mL) than in survivors (0; IQR: 0‐55.2 pg/mL). The ability of VEGF to predict a negative outcome was poor.

Conclusions and Clinical Importance

Ang‐2 may represent a useful additional prognostic marker in dogs with SIRS.

Angiopoietin 2 Levels in the Risk Stratification and Mortality Outcome Prediction of Sepsis-Associated Coagulopathy

It has been well established that angiopoietin 2 (Ang-2), a glycoprotein involved in activation of the endothelium, plays an integral role in the pathophysiology of sepsis and many other inflammatory conditions. However, the role of Ang-2 in sepsis-associated coagulopathy (SAC) specifically has not been defined. The aim of this study was to measure Ang-2 plasma levels in patients with sepsis and suspected disseminated intravascular coagulation (DIC) in order to demonstrate its predictive value in SAC severity determination and 28-day mortality outcome. Plasma samples were collected from 102 patients with sepsis and suspected DIC at intensive care unit (ICU) admission. The Ang-2 plasma levels were quantified using a sandwich enzyme-linked immunosorbent assay method. The International Society on Thrombosis and Haemostasis DIC scoring system was used to compare the accuracy of Ang-2 levels versus clinical illness severity scores in predicting SAC severity. Mean Ang-2 levels in patients with sepsis and DIC were significantly higher in comparison to healthy controls (P < 0.0001), and median Ang-2 levels showed a downward trend over time (P = 0.0008). Baseline Ang-2 levels and clinical illness severity scores were higher with increasing severity of disease, and Ang-2 was a better predictor of DIC severity than clinical illness scores. This study demonstrates that Ang-2 levels are significantly upregulated in SAC, and this biomarker can be used to risk stratify patients with sepsis into non-overt DIC and overt DIC. Furthermore, the Ang-2 level at ICU admission in a patient with sepsis and suspected DIC may provide a predictive biomarker for mortality outcome.

Low Serum Angiopoietin-1, High Serum Angiopoietin-2, and High Ang-2/Ang-1 Protein Ratio are Associated with Early Onset Sepsis in Surinamese Newborns

PURPOSE

Vascular inflammation and leakage in sepsis is mediated by Angiopoietin-1 (Ang-1) and Angiopoietin-2 (Ang-2) and their phosphorylation of the endothelial Tie-2 receptor. This study investigates levels of Ang-1 and Ang-2 in newborns to gain insight in the vascular pathophysiology of early onset sepsis (EOS) within 72 h after birth.

METHODS

A prospective cohort study was performed among 71 Surinamese newborns treated with antibiotics for suspected EOS and 20 control newborns. Newborns with suspected EOS were divided in two groups: blood culture negative and positive EOS. Ang-1 and Ang-2 levels were measured in serum obtained at the start of antibiotic treatment and at re-evaluation after 48 to 72 h.

RESULTS

In this cohort 8.5% of newborns had a positive blood culture. At the start of antibiotic treatment Ang-1 serum levels were lower (P < 0.01), and Ang-2 and Ang-2/Ang-1 serum protein ratios were higher (P < 0.01 and P < 0.01, respectively) in newborns with blood culture positive EOS than in controls. These levels were not dependent on timing of first blood draw after birth. After 48 to 72 h levels of Ang-1 further decreased in blood culture positive EOS, while in the other groups no change was observed.

CONCLUSIONS

Our findings support the hypothesis that a disbalance in the Angiopoietins plays a role in the vascular pathophysiology of EOS.

Endothelial Activation: The Ang/Tie Axis in Sepsis

Sepsis, a dysregulated host response to infection that causes life-threatening organ dysfunction, is a highly heterogeneous syndrome with no specific treatment. Although sepsis can be caused by a wide variety of pathogenic organisms, endothelial dysfunction leading to vascular leak is a common mechanism of injury that contributes to the morbidity and mortality associated with the syndrome. Perturbations to the angiopoietin (Ang)/Tie2 axis cause endothelial cell activation and contribute to the pathogenesis of sepsis. In this review, we summarize how the Ang/Tie2 pathway is implicated in sepsis and describe its prognostic as well as therapeutic utility in life-threatening infections.

Biomarkers of endothelial dysfunction predict sepsis mortality in young infants: a matched case-control study

Background

Reducing death due to neonatal sepsis is a global health priority, however there are limited tools to facilitate early recognition and treatment. We hypothesized that measuring circulating biomarkers of endothelial function and integrity (i.e. Angiopoietin-Tie2 axis) would identify young infants with sepsis and predict their clinical outcome.

Methods

We conducted a matched case-control (1:3) study of 98 young infants aged 0–59 days of life presenting to a referral hospital in Bangladesh with suspected sepsis. Plasma levels of Ang-1, Ang-2, sICAM-1, and sVCAM-1 concentrations were measured at admission. The primary outcome was mortality (n = 18); the secondary outcome was bacteremia (n = 10).

Results

Ang-2 concentrations at presentation were higher among infants who subsequently died of sepsis compared to survivors (aOR 2.50, p = 0.024). Compared to surviving control infants, the Ang-2:Ang-1 ratio was higher among infants who died (aOR 2.29, p = 0.016) and in infants with bacteremia (aOR 5.72, p = 0.041), and there was an increased odds of death across Ang-2:Ang-1 ratio tertiles (aOR 4.82, p = 0.013).

Conclusions

This study provides new evidence linking the Angiopoietin-Tie2 pathway with mortality and bacteremia in young infants with suspected sepsis. If validated in additional studies, markers of the angiopoietin-Tie2 axis may have clinical utility in risk stratification of infants with suspected sepsis.

Electronic supplementary material

The online version of this article (10.1186/s12887-018-1087-x) contains supplementary material, which is available to authorized users.

Angiopoietins bind thrombomodulin and inhibit its function as a thrombin cofactor

Angiopoietin-1 (Ang1) and Angiopoietin-2 (Ang2) are ligands for Tie2, an endothelial-specific receptor tyrosine kinase that is an essential regulator of angiogenesis. Here we report the identification, via expression cloning, of thrombomodulin (TM) as another receptor for Ang1 and Ang2. Thrombomodulin is an endothelial cell surface molecule that plays an essential role as a coagulation inhibitor via its function as a cofactor in the thrombin-mediated activation of protein C, an anticoagulant protein, as well as thrombin-activatable fibrinolysis inhibitor (TAFI). Ang1 and Ang2 inhibited the thrombin/TM-mediated generation of activated protein C and TAFI in cultured endothelial cells, and inhibited the binding of thrombin to TM in vitro. Ang2 appears to bind TM with higher affinity than Ang1 and is a more potent inhibitor of TM function. Consistent with a potential role for angiopoietins in coagulation, administration of thrombin to mice rapidly increased plasma Ang1 levels, presumably reflecting release from activated platelets (previously shown to contain high levels of Ang1). In addition, Ang1 levels were significantly elevated in plasma prepared from wound blood, suggesting that Ang1 is released from activated platelets at sites of vessel injury. Our results imply a previously undescribed role for angiopoietins in the regulation of hemostasis.

Angiopoietins and Tie2 in vascular inflammation

PURPOSE OF REVIEW

As a subset of the organism-wide reaction to severe infection, the host vascular response has received increasing attention in recent years. The transformation that small blood vessels undergo to facilitate the clearance of pathogens may become harmful to the host if it occurs too broadly or if it is sustained too long. Adverse clinical manifestations of leaky and inflamed blood vessels include edema impairing the function of critical organs and circulatory shock.

RECENT FINDINGS

The study suggests that this host vascular response may be both measurable and potentially targetable. Tie2 is a receptor tyrosine kinase (RTK) heavily enriched in the vascular endothelium whose tonic signaling actively maintains vascular quiescence. When Tie2 becomes inactivated, important molecular brakes are released in the endothelium, which in turn potentiate inflammation and vascular leakage. The ligands of Tie2, Angiopoietin-1 and Angiopoietin-2, regulate its activation status. Genetic and molecular studies spanning thousands of humans link Tie2 and imbalance of the Angiopoietins to major adverse clinical events arising from bacterial sepsis, other severe infections, and even acute sterile inflammation.

SUMMARY

The Tie2 signaling axis may constitute a molecular switch in systemic inflammation that can be measured and manipulated to target the host vascular response therapeutically.

Angiopoietin-1 deficiency increases renal capillary rarefaction and tubulointerstitial fibrosis in mice

Presence of tubulointerstitial fibrosis is predictive of progressive decline in kidney function, independent of its underlying cause. Injury to the renal microvasculature is a major factor in the progression of fibrosis and identification of factors that regulate endothelium in fibrosis is desirable as they might be candidate targets for treatment of kidney diseases. The current study investigates how loss of Angipoietin-1 (Angpt1), a ligand for endothelial tyrosine-kinase receptor Tek (also called Tie2), affects tubulointerstitial fibrosis and renal microvasculature. Inducible Angpt1 knockout mice were subjected to unilateral ureteral obstruction (UUO) to induce fibrosis, and kidneys were collected at different time points up to 10 days after obstruction. Staining for aSMA showed that Angpt1 deficient kidneys had significantly more fibrosis compared to wildtype mice 3, 6, and 10 days after UUO. Further investigation 3 days after UUO showed a significant increase of Col1a1 and vimentin in Angpt1 deficient mice, as well as increased gene expression of Tgfb1, Col1a1, Fn1, and CD44. Kidney injury molecule 1 (Kim1/Havcr1) was significantly more increased in Angpt1 deficient mice 1 and 3 days after UUO, suggesting a more severe injury early in the fibrotic process in Angpt1 deficient mice. Staining for endomucin showed that capillary rarefaction was evident 3 days after UUO and Angpt1 deficient mice had significantly less capillaries 6 and 10 days after UUO compared to UUO kidneys in wildtype mice. RNA sequencing revealed downregulation of several markers for endothelial cells 3 days after UUO, and that Angpt1 deficient mice had a further downregulation of Emcn, Plvap, Pecam1, Erg, and Tek. Our results suggest that loss of Angpt1 is central in capillary rarefaction and fibrogenesis and propose that manipulations to maintain Angpt1 levels may slow down fibrosis progression.

Endothelial Cell Function and Dysfunction in Critically Ill Children

Endothelial cells (ECs) line the lumen of the entire vascular system and actively regulate blood flow; maintain blood fluidity; control water, solute, and macromolecular transfer between blood and tissue; and modulate circulating immune cell recruitment and activation. These vital functions, combined with the broad anatomic distribution of ECs, implicate them in all forms of critical illness. The present article discusses how ECs adapt and break down during the course of critical illness. We first review the biology of ECs, highlighting the vascular segmental differences and their specific roles in the maintenance of homeostasis. We then discuss how ECs acquire new functions to restore local and systemic homeostasis (activation) as well as how breakdowns in EC functions (dysfunction) contribute to local and systemic pathologic responses, with clinical correlations. Lastly, how these processes have been studied in critically ill children is discussed.

The Angiopoietin-Tie2 Signaling Axis in Systemic Inflammation

Systemic inflammation is a hallmark of commonly encountered diseases ranging from bacterial sepsis to sterile syndromes such as major trauma. Derangements in the host vasculature contribute to the cardinal manifestations of sepsis in profound ways. Recent studies of control pathways regulating the vascular endothelium have illuminated how this single cell layer toggles between quiescence and activation to affect the development of shock and multiorgan dysfunction. This article focuses on one such control pathway, the Tie2 receptor and its ligands the angiopoietins, to describe a growing body of genetic, biochemical, mechanistic, and human studies that implicate Tie2 as a critical switch. In health, activated Tie2 maintains the endothelium in a quiescent state characterized by dynamic barrier function and antiadhesion against circulating leukocytes. In sepsis and related diseases, expression of the angiopoietins becomes markedly imbalanced and Tie2 signaling is greatly attenuated. These rapid molecular changes potentiate pathophysiologic responses throughout the body, resulting in injurious vascular leakage and organ inflammation. The Tie2 axis, therefore, may be a promising avenue for future translational studies.

Pathophysiology of Pediatric Multiple Organ Dysfunction Syndrome

OBJECTIVE

To describe the pathophysiology associated with multiple organ dysfunction syndrome in children.

DATA SOURCES

Literature review, research data, and expert opinion.

STUDY SELECTION

Not applicable.

DATA EXTRACTION

Moderated by an experienced expert from the field, pathophysiologic processes associated with multiple organ dysfunction syndrome in children were described, discussed, and debated with a focus on identifying knowledge gaps and research priorities.

DATA SYNTHESIS

Summary of presentations and discussion supported and supplemented by relevant literature.

CONCLUSIONS

Experiment modeling suggests that persistent macrophage activation may be a pathophysiologic basis for multiple organ dysfunction syndrome. Children with multiple organ dysfunction syndrome have 1) reduced cytochrome P450 metabolism inversely proportional to inflammation; 2) increased circulating damage-associated molecular pattern molecules from injured tissues; 3) increased circulating pathogen-associated molecular pattern molecules from infection or endogenous microbiome; and 4) cytokine-driven epithelial, endothelial, mitochondrial, and immune cell dysfunction. Cytochrome P450s metabolize endogenous compounds and xenobiotics, many of which ameliorate inflammation, whereas damage-associated molecular pattern molecules and pathogen-associated molecular pattern molecules alone and together amplify the cytokine production leading to the inflammatory multiple organ dysfunction syndrome response. Genetic and environmental factors can impede inflammation resolution in children with a spectrum of multiple organ dysfunction syndrome pathobiology phenotypes. Thrombocytopenia-associated multiple organ dysfunction syndrome patients have extensive endothelial activation and thrombotic microangiopathy with associated oligogenic deficiencies in inhibitory complement and a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13. Sequential multiple organ dysfunction syndrome patients have soluble Fas ligand-Fas-mediated hepatic failure with associated oligogenic deficiencies in perforin and granzyme signaling. Immunoparalysis-associated multiple organ dysfunction syndrome patients have impaired ability to resolve infection and have associated environmental causes of lymphocyte apoptosis. These inflammation phenotypes can lead to macrophage activation syndrome. Resolution of multiple organ dysfunction syndrome requires elimination of the source of inflammation. Full recovery of organ functions is noted 6-18 weeks later when epithelial, endothelial, mitochondrial, and immune cell regeneration and reprogramming is completed.

Regulation of angiopoietin-2 secretion from human pulmonary microvascular endothelial cells

INTRODUCTION

Sepsis is characterized by dysregulated systemic inflammation and cytokine storm. Angiopoietin-2 (Ang-2) is known to closely correlate with severity of sepsis-related acute lung injury and mortality. The aim of this study was to clarify the mechanisms involved in Ang-2 secretion to better understand the pathophysiology of sepsis.

MATERIALS AND METHODS

The concentration of Ang-2 was assessed in culture medium of pulmonary microvascular endothelial cells in the presence or absence of Gram-positive bacteria cell wall components [lipoteichoic acid (LTA) and peptidoglycan (PGN)] stimulation at different time points ranging from 15 minutes to 24 hours. Constitutive and LTA-PGN-stimulated Ang-2 level changes were also assessed after cells were pretreated with different pathway inhibitors for 1 hour.

RESULTS

Two distinctive mechanisms of Ang-2 secretion, constitutive and stimulated secretion, were identified. Constitutive secretion resulted in slow but continuous increase in Ang-2 in culture medium over time. It was regulated by 3'5'-cyclic adenosine monophosphate (cAMP)-protein kinase A (PKA)-Ca²⁺ and nitric oxide (NO)-3'5'-cyclic guanosine monophosphate (cGMP)-protein kinase G (PKG)-Ca²⁺ pathways and partially regulated by N-ethyl-maleimide-sensitive factor-Ca²⁺ pathways. LTA-PGN stimulation caused rapid and potent increase followed by gradual decrease of Ang-2. It was partially regulated by both Ral A-phospholipase D and NSF-Ca²⁺ pathways.

CONCLUSIONS

We demonstrated characteristics and involved pathways for two distinctive secretory mechanisms, constitutive and stimulated, of Ang-2 in pulmonary microvascular endothelial cells. Considering the close correlation of Ang-2 with sepsis outcomes, our findings provide a better understanding of an important mechanism associated with sepsis pathophysiology and identify possible therapeutic targets to improve outcomes in the potentially lethal disease.

Circulating markers of endothelial and alveolar epithelial dysfunction are associated with mortality in pediatric acute respiratory distress syndrome

PURPOSE

Angiopoietin 2 (Ang2) and soluble receptor for advanced glycation end products (sRAGE) are markers of endothelial and pulmonary epithelial damage with prognostic implications in adult acute respiratory distress syndrome (ARDS), but unclear significance in pediatric ARDS (PARDS).

METHODS

This was a prospective, observational study in children with PARDS (2012 Berlin and 2015 PALICC definitions) at the Children's Hospital of Philadelphia. Plasma was collected within 48 h of PARDS onset and biomarkers quantified by enzyme-linked immunosorbent assay.

RESULTS

In 82 children with PARDS (12 deaths, 15 %), Ang2 and sRAGE were higher in non-survivors than survivors (p < 0.01 for both). Mortality was highest in patients with Ang2 and sRAGE levels both above median values. Ang2 and sRAGE correlated with the number of non-pulmonary organ failures (both p < 0.001). Ang2 was higher in indirect lung injury and in immunocompromised children. In stratified analysis, both Ang2 and sRAGE were associated with mortality only in direct lung injury and in immunocompetent children, with no association evident in indirect lung injury or in immunocompromised children.

CONCLUSIONS

Ang2 and sRAGE in early PARDS were higher in non-survivors than survivors and strongly correlated with number of non-pulmonary organ failures. When stratified by type of lung injury, Ang2 and sRAGE were associated with mortality only in direct lung injury. Similarly, when stratified by immunocompromised status, Ang2 and sRAGE were associated with mortality only in immunocompetent children. The utility of these biomarkers for prognostication and risk stratification requires investigation.

Regulators of endothelial integrity as severity predictors in dengue

INTRODUCTION

Dengue is currently among the mosquito-borne diseases of greatest global impact. The clinical course of the disease can be unpredictable, so proper handling in its early stages is critical to ensure optimal outcomes. 

OBJECTIVE

To evaluate serum regulators of endothelial integrity (VEGF, sICAM-1, sEndoglina, Ang-1, and Ang-2) as predictive markers of dengue severity. 

MATERIALS AND METHODS

We conducted a case-control study nested in an appropriate cohort. Endothelial regulator levels were first measured by ELISA, after which analysis was performed using logistic regression of clinical and regulatory variables, with severity as an output variable. A possible severity prediction model, based on the variables of interest and output, was defined using the best area under the ROC curve. 

RESULTS

The median subject age was 24 years. Severe cases were associated with Ang-2 serum levels of ≥1,490 ng/ml (OR=3.1; p=0.015). Serum levels of Ang-2 (≥1,490 ng/ml) contributed to the severity prediction model, as did a 0.73 area under the ROC curve, together with the variables rash, impaired consciousness and abdominal pain, with an OR of 3.2 (CI 95%: 1.16 to 8.9; p=0.024). 

CONCLUSION

The endothelial regulator Ang-2 could be a predictor of severity in dengue.

Gene expression profile of angiogenic factors in pulmonary arteries in COPD: relationship with vascular remodeling

Pulmonary vessel remodeling in chronic obstructive pulmonary disease (COPD) involves changes in smooth muscle cell proliferation, which are highly dependent on the coordinated interaction of angiogenic-related growth factors. The purpose of the study was to investigate, in isolated pulmonary arteries (PA) from patients with COPD, the gene expression of 46 genes known to be modulators of the angiogenic process and/or involved in smooth muscle cell proliferation and to relate it to vascular remodeling. PA segments were isolated from 29 patients and classified into tertiles, according to intimal thickness. After RNA extraction, the gene expression was assessed by RT-PCR using TaqMan low-density arrays. The univariate analysis only showed upregulation of angiopoietin-2 (ANGPT-2) in remodeled PA (P < 0.05). The immunohistochemical expression of ANGPT-2 correlated with intimal enlargement (r = 0.42, P < 0.05). However, a combination of 10 factors in a multivariate discriminant analysis model explained up to 96% of the classification of the arteries. A network analysis of 46 genes showed major decentralization. In this network, the metalloproteinase-2 (MMP-2) was shown to be the bridge between intimal enlargement and fibrogenic factors. In COPD patients, plasma levels of ANGPT-2 were higher in current smokers or those with pulmonary hypertension. We conclude that an imbalance in ANGPT-2, combined with related factors such as VEGF, β-catenin, and MMP-2, may partially explain the structural derangements of the arterial wall. MMP-2 may act as a bridge channeling actions from the main fibrogenic factors.

Plasma Biomarker Analysis in Pediatric ARDS: Generating Future Framework from a Pilot Randomized Control Trial of Methylprednisolone: A Framework for Identifying Plasma Biomarkers Related to Clinical Outcomes in Pediatric ARDS

OBJECTIVE

Lung injury activates multiple pro-inflammatory pathways, including neutrophils, epithelial, and endothelial injury, and coagulation factors leading to acute respiratory distress syndrome (ARDS). Low-dose methylprednisolone therapy (MPT) improved oxygenation and ventilation in early pediatric ARDS without altering duration of mechanical ventilation or mortality. We evaluated the effects of MPT on biomarkers of endothelial [Ang-2 and soluble intercellular adhesion molecule-1 (sICAM-1)] or epithelial [soluble receptor for activated glycation end products (sRAGE)] injury, neutrophil activation [matrix metalloproteinase-8 (MMP-8)], and coagulation (plasminogen activator inhibitor-1).

DESIGN

Double-blind, placebo-controlled randomized trial.

SETTING

Tertiary-care pediatric intensive care unit (ICU).

PATIENTS

Mechanically ventilated children (0-18 years) with early ARDS.

INTERVENTIONS

Blood samples were collected on days 0 (before MPT), 7, and 14 during low-dose MPT (n = 17) vs. placebo (n = 18) therapy. The MPT group received a 2-mg/kg loading dose followed by 1 mg/kg/day continuous infusions from days 1 to 7, tapered off over 7 days; placebo group received equivalent amounts of 0.9% saline. We analyzed plasma samples using a multiplex assay for five biomarkers of ARDS. Multiple regression models were constructed to predict associations between changes in biomarkers and the clinical outcomes reported earlier, including P/F ratio on days 8 and 9, plateau pressure on days 1 and 2, PaCO2 on days 2 and 3, racemic epinephrine following extubation, and supplemental oxygen at ICU discharge.

RESULTS

No differences occurred in biomarker concentrations between the groups on day 0. On day 7, reduction in MMP-8 levels (p = 0.0016) occurred in the MPT group, whereas increases in sICAM-1 levels (p = 0.0005) occurred in the placebo group (no increases in sICAM-1 in the MPT group). sRAGE levels decreased in both MPT and placebo groups (p < 0.0001) from day 0 to day 7. On day 7, sRAGE levels were positively correlated with MPT group PaO2/FiO2 ratios on day 8 (r = 0.93, p = 0.024). O2 requirements at ICU transfer positively correlated with day 7 MMP-8 (r = 0.85, p = 0.016) and Ang-2 levels (r = 0.79, p = 0.036) in the placebo group and inversely correlated with day 7 sICAM-1 levels (r = -0.91, p = 0.005) in the MPT group.

CONCLUSION

Biomarkers selected from endothelial, epithelial, or intravascular factors can be correlated with clinical endpoints in pediatric ARDS. For example, MPT could reduce neutrophil activation (⇓MMP-8), decrease endothelial injury (⇔sICAM-1), and allow epithelial recovery (⇓sRAGE). Large ARDS clinical trials should develop similar frameworks.

TRIAL REGISTRATION

https://clinicaltrials.gov, NCT01274260.

Plasma angiopoietin-2 outperforms other markers of endothelial injury in prognosticating pediatric ARDS mortality

Angiopoietin-2 (Ang-2) is a key mediator of pulmonary vascular permeability. This study tested the association between plasma Ang-2 and mortality in pediatric acute respiratory distress syndrome (ARDS), with stratification for prior hematopoietic cellular transplantation (HCT), given the severe, yet poorly understood, ARDS phenotype of this subgroup. We enrolled 259 children <18 years of age with ARDS; 25 had prior HCT. Plasma Ang-2, von Willebrand Factor antigen (vWF), and vascular endothelial growth factor (VEGF) were measured on ARDS days 1 and 3 and correlated with patient outcomes. Day 1 and day 3 Ang-2 levels were associated with mortality independent of age, sex, race, and P/F ratio [odds ratio (OR) 3.7, 95% CI 1.1-11.5, P = 0.027; and OR 10.2, 95% confidence interval (CI) 2.2-46.5, P = 0.003, for each log10 increase in Ang-2]. vWF was associated with mortality (P = 0.027), but VEGF was not. The association between day 1 Ang-2 and mortality was independent of levels of both vWF and VEGF (OR 3.6, 95% CI 1.1-12.1, P = 0.039, for each log10 increase in Ang-2). 45% of the cohort had a rising Ang-2 between ARDS day 1 and 3 (adjusted mortality OR 3.3, 95% CI 1.2-9.2, P = 0.026). HCT patients with a rising Ang-2 had 70% mortality compared with 13% mortality for those without (OR 16.3, 95% CI 1.3-197.8, P = 0.028). Elevated plasma levels of Ang-2 were associated with mortality independent of vWF and VEGF. A rising Ang-2 between days 1 and 3 was strongly associated with mortality, particularly in pediatric HCT patients, suggesting vulnerability to ongoing endothelial damage.

Prognostic significance of the angiopoietin-2/angiopoietin-1 and angiopoietin-1/Tie-2 ratios for early sepsis in an emergency department

Introduction

This study was performed to assess the early diagnostic, risk stratification, and prognostic value of the angiopoietin-2/angiopoietin-1 ratio (Ang-2/Ang-1) and angiopoietin-1/tyrosine kinase with immunoglobulin-like loop epidermal growth factor homology domain 2 ratio (Ang-1/Tie-2) and to compare these factors with procalcitonin (PCT) and the Mortality in Emergency Department Sepsis (MEDS) score in patients with early sepsis in the emergency department (ED).

Methods

Consecutive patients with sepsis (n = 440) were enrolled in this study. They fulfilled the systemic inflammatory response syndrome (SIRS) criteria and were admitted to the ED of Beijing Chao-yang Hospital between August 2014 and February 2015. The control group consisted of 55 healthy blood donors. The patients were categorized into four groups: SIRS, sepsis, severe sepsis, and septic shock. Serum Ang-1, Ang-2, Tie-2, and PCT were measured, and the MEDS score was calculated upon ED arrival. The prognostic values of Ang-2/Ang-1, Ang-1/Tie-2, Ang-1, Ang-2, and Tie-2 were compared with the PCT and MEDS scores. All patients were followed for 28 days.

Results

Upon admission, the median levels of the serum Ang-2 level and Ang-2/Ang-1 ratio increased and the serum Ang-1 levels and Ang-1/Tie-2 ratios decreased with the severity of sepsis. The areas under the receiver operating characteristic curves of the Ang-2/Ang-1 and Ang-1/Tie-2 ratios were greater than those of the Ang-1, Ang-2, and PCT levels and MEDS scores in the diagnosis and prediction of 28-day mortality due to sepsis. Ang-2/Ang-1 was significantly higher and Ang-1/Tie-2 was significantly lower in nonsurvivors than in survivors at the 28-day follow-up examination. Ang-2/Ang-1, Ang-1/Tie-2, and MEDS score were found to be independent predictors of 28-day mortality in patients with sepsis. The levels of serum Ang-1, Ang-2, and Tie-2 were positively correlated with each other. The ratios of Ang-2/Ang-1 and Ang-1/Tie-2 were positively and negatively correlated, respectively, with the MEDS score in every septic group.

Conclusions

The Ang-2/Ang-1 and Ang-1/Tie-2 ratios are valuable for risk stratification in patients with sepsis and are associated with the poor clinical outcome of early sepsis in the ED.

Drug Repurposing Screen Identifies Foxo1-Dependent Angiopoietin-2 Regulation in Sepsis

OBJECTIVE

The recent withdrawal of a targeted sepsis therapy has diminished pharmaceutical enthusiasm for developing novel drugs for the treatment of sepsis. Angiopoietin-2 is an endothelial-derived protein that potentiates vascular inflammation and leakage and may be involved in sepsis pathogenesis. We screened approved compounds for putative inhibitors of angiopoietin-2 production and investigated underlying molecular mechanisms.

DESIGN

Laboratory and animal research plus prospective placebo-controlled randomized controlled trial (NCT00529139) and retrospective analysis (NCT00676897).

SETTING

Research laboratories of Hannover Medical School and Harvard Medical School.

PATIENTS

Septic patients/C57Bl/6 mice and human endothelial cells.

INTERVENTIONS

Food and Drug Administration-approved library screening.

MEASUREMENTS AND MAIN RESULTS

In a cell-based screen of more than 650 Food and Drug Administration-approved compounds, we identified multiple members of the 3-hydroxy-3-methyl-glutaryl-CoA reductase inhibitor drug class (referred to as statins) that suppressed angiopoietin-2. Simvastatin inhibited 3-hydroxy-3-methyl-glutaryl-CoA reductase, which in turn activated PI3K-kinase. Downstream of this signaling, PI3K-dependent phosphorylation of the transcription factor Foxo1 at key amino acids inhibited its ability to shuttle to the nucleus and bind cis-elements in the angiopoietin-2 promoter. In septic mice, transient inhibition of angiopoietin-2 expression by liposomal siRNA in vivo improved absolute survival by 50%. Simvastatin had a similar effect, but the combination of angiopoietin-2 siRNA and simvastatin showed no additive benefit. To verify the link between statins and angiopoietin-2 in humans, we performed a pilot matched case-control study and a small randomized placebo-controlled trial demonstrating beneficial effects on angiopoietin-2.

CONCLUSIONS

3-hydroxy-3-methyl-glutaryl-CoA reductase inhibitors may operate through a novel Foxo1-angiopoietin-2 mechanism to suppress de novo production of angiopoietin-2 and thereby ameliorate manifestations of sepsis. Given angiopoietin-2's dual role as a biomarker and candidate disease mediator, early serum angiopoietin-2 measurement may serve as a stratification tool for future trials of drugs targeting vascular leakage.

Host response biomarkers in the diagnosis of sepsis: a general overview

Critically ill patients who display a systemic inflammatory response syndrome (SIRS) are prone to develop nosocomial infections. The challenge remains to distinguish as early as possible among SIRS patients those who are developing sepsis. Following a sterile insult, damage-associated molecular patterns (DAMPs) released by damaged tissues and necrotic cells initiate an inflammatory response close to that observed during sepsis. During sepsis, pathogen-associated molecular patterns (PAMPs) trigger the release of host mediators involved in innate immunity and inflammation through identical receptors as DAMPs. In both clinical settings, a compensatory anti-inflammatory response syndrome (CARS) is concomitantly initiated. The exacerbated production of pro- or anti-inflammatory mediators allows their detection in biological fluids and particularly within the bloodstream. Some of these mediators can be used as biomarkers to decipher among the patients those who developed sepsis, and eventually they can be used as prognosis markers. In addition to plasma biomarkers, the analysis of some surface markers on circulating leukocytes or the study of mRNA and miRNA can be helpful. While there is no magic marker, a combination of few biomarkers might offer a high accuracy for diagnosis.

Angiopoietin-2 associations with the underlying infection and sepsis severity

Angiopoietin-2 (Ang-2) is an important mediator in sepsis. We have previously shown that endotoxemia levels are related to the underlying infection and affect septic patients' outcome. Based on this background we now investigated if circulating Ang-2 (cAng-2) and monocyte Ang-2 expression in septic patients are associated with the underlying infection and organ failure. We measured cAng-2 in 288 septic patients (121 with sepsis, 167 with severe sepsis/septic shock) at less than 24h post study inclusion (day 1) and on days 3 and 7. Peripheral blood mononuclear cells (PBMCs) were additionally isolated; Ang-2 gene expression was estimated by means of real-time PCR. Levels of cAng-2 were higher under severe sepsis and septic shock, as compared to uncomplicated sepsis; PBMC Ang-2 copies were higher in severe sepsis. On day 1, cAng-2 and Ang-2 gene copies were greater under severe sepsis/septic shock in sufferers from all types of infections with the exception of community-acquired pneumonia and ventilator-associated pneumonia. cAng-2 increased proportionally to the number of failing organs, and was higher under metabolic acidosis and acute coagulopathy as compared to no failing organ. On day 1, copies of Ang-2 were higher in survivors, whereas cAng-2 was higher in non-survivors. In a large cohort of septic patients, cAng-2 kinetics appears associated with the underlying infection and organ failure type.

Plasma angiopoietin 2 concentrations are related to impaired lung function and organ failure in a clinical cohort receiving high-dose interleukin 2 therapy

INTRODUCTION

The pathophysiology and therapeutic options in sepsis-induced lung injury remain elusive. High-dose interleukin 2 therapy (HDIL-2) is an important protocol for advanced malignancies but is limited by systemic inflammation and pulmonary edema that is indistinguishable from sepsis. In preclinical models, IL-2 stimulates angiopoietin 2 (AngP-2) secretion, which increases endothelial permeability and causes pulmonary edema. However, these relationships have not been fully elucidated in humans. Furthermore, the relevance of plasma AngP-2 to organ function is not clear. We hypothesized that plasma AngP-2 concentrations increase during HDIL-2 and are relevant to clinical pathophysiology.

METHODS

We enrolled 13 subjects with metastatic melanoma or renal cell carcinoma admitted to receive HDIL-2 and collected blood and spirometry data daily. The plasma concentrations of AngP-2 and IL-6 were measured with enzyme-linked immunosorbent assay.

RESULTS

At baseline, the mean AngP-2 concentration was 2.5 (SD, 1.0) ng/mL. Angiopoietin 2 concentrations increased during treatment: the mean concentration on the penultimate day was 16.0 (SD, 4.5) ng/mL and increased further to 18.6 (SD, 4.9) ng/mL (P < 0.05 vs. penultimate) during the last day of therapy. The forced expiratory volume in 1 s decreased during treatment. Interestingly, plasma AngP-2 concentrations correlated negatively with forced expiratory volume in 1 s (Spearman r = -0.78, P < 0.0001). Plasma AngP-2 concentrations also correlated with plasma IL-6 concentrations (r = 0.61, P < 0.0001) and Sequential Organ Failure Assessment scores (r = 0.68, P < 0.0001).

CONCLUSIONS

Plasma AngP-2 concentrations increase during HDIL-2 administration and correlate with pulmonary dysfunction. High-dose IL-2 may serve as a clinical model of sepsis and acute lung injury. Further investigation is warranted.

Impaired systemic tetrahydrobiopterin bioavailability and increased oxidized biopterins in pediatric falciparum malaria: association with disease severity

Decreased bioavailability of nitric oxide (NO) is a major contributor to the pathophysiology of severe falciparum malaria. Tetrahydrobiopterin (BH4) is an enzyme cofactor required for NO synthesis from L-arginine. We hypothesized that systemic levels of BH₄ would be decreased in children with cerebral malaria, contributing to low NO bioavailability. In an observational study in Tanzania, we measured urine levels of biopterin in its various redox states (fully reduced [BH₄] and the oxidized metabolites, dihydrobiopterin [BH₂] and biopterin [B₀]) in children with uncomplicated malaria (UM, n = 55), cerebral malaria (CM, n = 45), non-malaria central nervous system conditions (NMC, n = 48), and in 111 healthy controls (HC). Median urine BH4 concentration in CM (1.10 [IQR:0.55-2.18] μmol/mmol creatinine) was significantly lower compared to each of the other three groups - UM (2.10 [IQR:1.32-3.14];p<0.001), NMC (1.52 [IQR:1.01-2.71];p = 0.002), and HC (1.60 [IQR:1.15-2.23];p = 0.005). Oxidized biopterins were increased, and the BH4:BH2 ratio markedly decreased in CM. In a multivariate logistic regression model, each Log10-unit decrease in urine BH4 was independently associated with a 3.85-fold (95% CI:1.89-7.61) increase in odds of CM (p<0.001). Low systemic BH4 levels and increased oxidized biopterins contribute to the low NO bioavailability observed in CM. Adjunctive therapy to regenerate BH4 may have a role in improving NO bioavailability and microvascular perfusion in severe falciparum malaria.

Angiopoietin-1, angiopoietin-2 and bicarbonate as diagnostic biomarkers in children with severe sepsis

Severe pediatric sepsis continues to be associated with high mortality rates in children. Thus, an important area of biomedical research is to identify biomarkers that can classify sepsis severity and outcomes. The complex and heterogeneous nature of sepsis makes the prospect of the classification of sepsis severity using a single biomarker less likely. Instead, we employ machine learning techniques to validate the use of a multiple biomarkers scoring system to determine the severity of sepsis in critically ill children. The study was based on clinical data and plasma samples provided by a tertiary care center's Pediatric Intensive Care Unit (PICU) from a group of 45 patients with varying sepsis severity at the time of admission. Canonical Correlation Analysis with the Forward Selection and Random Forests methods identified a particular set of biomarkers that included Angiopoietin-1 (Ang-1), Angiopoietin-2 (Ang-2), and Bicarbonate (HCO) as having the strongest correlations with sepsis severity. The robustness and effectiveness of these biomarkers for classifying sepsis severity were validated by constructing a linear Support Vector Machine diagnostic classifier. We also show that the concentrations of Ang-1, Ang-2, and HCO enable predictions of the time dependence of sepsis severity in children.

Elevated levels of angiopoietin-2 as a biomarker for respiratory failure after cardiac surgery

OBJECTIVES

Angiopoietin-1 and angiopoietin-2 are important factors in regulating endothelial vascular permeability. This study evaluated perioperative changes in serum levels of angiopoietin-1 and -2 in patients undergoing cardiac surgery.

DESIGN

Measurement of serum levels of angiopoietin-1 and angiopoietin-2 in samples collected during a previously conducted prospective, multicenter, observational study.

SETTING

Three university hospitals.

PARTICIPANTS

Eighty-four adult patients undergoing cardiac surgery.

INTERVENTION

Serum levels of angiopoietins were measured at baseline, immediately after surgery, and the day after surgery (POD-1).

MEASUREMENTS AND MAIN RESULTS

Serum levels of angiopoietin-2 were elevated by POD-1 (median 3.3 ng/mL, interquartile range [IQR] 2.5-4.6 ng/mL) compared with baseline (median 1.6 ng/mL, IQR 1.3-2.1 ng/mL, p < 0.0001), and angiopoietin-1 levels were decreased immediately after surgery (baseline median 23.2 ng/mL, IQR 10.2-32.8 ng/mL; postoperative median 8.0 ng/mL, IQR 1.5-13.2 ng/mL, p<0.0001). Angiopoietin-2 levels on POD-1 in patients undergoing off-pump coronary artery bypass grafting were significantly lower than those in patients undergoing aortic surgery (p = 0.0009) and valve surgery (p = 0.008). Angiopoietin-2 levels on POD-1 had a predictive performance of the area under the curve (AUC) of the receiver operating characteristic curve 0.74 for mechanical ventilation>3 days. Angiopoietin-1 levels and the angiopoietin-2/angiopoietin-1 ratio showed lower predictive performance (AUC values 0.58 and 0.68, respectively).

CONCLUSIONS

Angiopoietin-2 serum levels were elevated after cardiac surgery. Elevated angiopoietin-2 had a good predictive performance for respiratory failure after cardiac surgery, perhaps reflecting the severity of lung dysfunction related to postoperative increases in vascular permeability.

The temporal kinetics of circulating angiopoietin levels in children with sepsis

OBJECTIVE

Capillary integrity continues to challenge critical care physicians worldwide when treating children with sepsis. Vascular growth factors, specifically angiopoietin-1 and angiopoietin-2, play opposing roles in capillary stabilization in patients with sepsis. We aim to determine whether pediatric patients with severe sepsis/shock have persistently high angiopoietin-2/1 ratios when compared with nonseptic PICU patients over a 7-day period.

DESIGN

Prospective observational study. Patients were classified within 24 hours of admission into non-systemic inflammatory response syndrome, systemic inflammatory response syndrome/sepsis, or severe sepsis/shock. Plasma levels of angiopoietin-1 and angiopoietin-2 were measured via enzyme-linked immunosorbent assay. The angiopoietin-2/1 ratio was graphically plotted and determined whether patients fell into "constant" or "variable" patterns.

SETTING

Tertiary care center PICU.

PATIENTS

Critically ill pediatric patients with varying sepsis severity.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Forty-five patients were enrolled (nine non-systemic inflammatory response syndrome, 19 systemic inflammatory response syndrome/sepsis, and 17 severe sepsis/shock). Gender, age, weight, comorbidities, and PICU length of stay were not significantly different between the groups. Admission pediatric risk stratification scores and net fluid ins/outs were significantly elevated in the severe sepsis/shock group when compared (all p < 0.05). Admission angiopoietin-2 levels and angiopoietin-2/1 ratios were significantly different in the severe sepsis/shock group when all groups were compared (both p < 0.05). Additionally, the latter were significantly elevated in the severe sepsis/shock group at multiple time points (all p ≤ 0.05) with the peak occurring on day 2 of illness. In a separate analysis, 32% of systemic inflammatory response syndrome/sepsis and 82% of severe sepsis/shock had variable angiopoietin-2/1 ratio patterns compared with none in the control group (p < 0.001).

CONCLUSIONS

Pediatric patients with severe sepsis and septic shock possess significantly elevated angiopoietin-2/1 ratios during their first 3 days of illness, which peak at day 2 of illness. A subset of these patients demonstrated variable angiopoietin-2/1 ratio patterns.

The angiopoietin:Tie 2 interaction: a potential target for future therapies in human vascular disease

Angiopoietin-1 and -2 are endogenous ligands for the vascular endothelial receptor tyrosine kinase Tie2. Signalling by angiopoietin-1 promotes vascular endothelial cell survival and the sprouting and reorganisation of blood vessels, as well as inhibiting activation of the vascular endothelial barrier to reduce leakage and leucocyte migration into tissues. Angiopoietin-2 generally has an opposing action, and is released naturally at times of vascular growth and inflammation. There is a significant body of emerging evidence that promoting the actions of angiopoietin-1 through Tie2 is of benefit in pathologies of vascular activation, such as sepsis, stroke, diabetic retinopathy and asthma. Similarly, methods to inhibit the actions of angiopoietin-2 are emerging and have been demonstrated to be of preclinical and clinical benefit in reducing tumour angiogenesis. Here the author reviews the evidence for potential benefits of modulation of the interaction of angiopoietins with Tie2, and the potential applications. Additionally, methods for delivery of the complex protein angiopoietin-1 are discussed, as well as potentially deleterious consequences of administering angiopoietin-1.

The dynamics of angiogenic factors and their soluble receptors in relation to organ dysfunction in disseminated intravascular coagulation associated with sepsis

We prospectively studied (1) the relationships between angiogenic factors, their soluble receptors and organ dysfunction and (2) the effects of disseminated intravascular coagulation (DIC)-induced platelet consumption, thrombin generation, and tissue hypoxia on the expression of the factors and receptors. Fifty patients with sepsis were classified into two subgroups: 37 patients with DIC and 13 patients without DIC. DIC patients showed higher Sequential Organ Failure Assessment (SOFA) scores, the prevalence of multiple organ dysfunction syndrome (MODS) and more increased soluble fibrin and lactate levels. We observed lower levels of vascular endothelial growth factor (VEGF), soluble VEGF receptor 2 (sVEGFR2), angiopoietin 1 (Ang1) and Ang1/Ang2, and higher sVEGFR1 and Ang2 levels in DIC patients, but not significant differences in soluble Tie2 expression during the study period. The levels of VEGF, sVEGFR1, and Ang2 in DIC patients correlated with the SOFA scores. Clear differences were observed in the levels of Ang2 in the DIC patients between survivors and nonsurvivors and between those with and without MODS. The area under receiver operating characteristic curves for predicting death and MODS by Ang2 were 0.710 and 0.784, respectively. The VEGF levels showed a marked correlation with the platelet counts. Soluble fibrin and lactate levels independently predicted increases in the levels of VEGF, sVEGFR1, and Ang2 in DIC patients. In conclusion, VEGF, sVEGFR1, Ang2, and Ang1/Ang2, especially Ang2, may have roles in the development of MODS in sepsis associated with DIC, and VEGF, sVEGFR1, and Ang2 serum levels correlated with the extent of DIC-induced platelet consumption, thrombin generation, and blood lactate levels.

Modulation of the release of Ang-2 in experimental endotoxic shock by a species-specific circulating factor

OBJECTIVES

To study the modulation of the release of angiopoietin-2 (Ang-2) in experimental endotoxic shock.

METHODS

Twelve pigs were studied; eight became septic after the intravenous infusion of lipopolysaccharide (LPS) of Escherichia coli O55:B5. The concentrations of LPS, angiopoietin-2 (Ang-2), tumour necrosis factor-alpha (TNFα) and malondialdehyde (MDA) were measured soon after the LPS infusion in the serum samples from the pulmonary and systemic circulation. Peripheral blood mononuclear cells (PBMCs) were isolated from two healthy swine, from two healthy human donors and from four patients with septic shock. The PBMCs were cultured with the serum of the septic animals in the presence or absence of polymyxin B. Concentrations of Ang-2 and TNFα were measured in supernatants.

RESULTS

Serum Ang-2 was higher in the systemic circulation than in the pulmonary circulation. Increased Ang-2 release was noted in swine PBMCs in the presence of polymyxin B. A reciprocal decrease in TNFα release was observed, typically after incubation with serum sampled from the pulmonary circulation.

CONCLUSION

There is evidence for a circulating factor that primes Ang-2 release from blood monocytes in the event of septic shock. The finding indicates a possible site of interference within the septic shock cascade.