Angiopoietin-2 Levels as Predictors of Outcome in Mechanically Ventilated Patients with Acute Respiratory Distress Syndrome

Mesenchymal stromal cells reduce evidence of lung injury in patients with ARDS

BACKGROUND

Whether airspace biomarkers add value to plasma biomarkers in studying acute respiratory distress syndrome (ARDS) is not well understood. Mesenchymal stromal cells (MSCs) are an investigational therapy for ARDS, and airspace biomarkers may provide mechanistic evidence for MSCs’ impact in patients with ARDS.

METHODS

We carried out a nested cohort study within a phase 2a safety trial of treatment with allogeneic MSCs for moderate-to-severe ARDS. Nonbronchoscopic bronchoalveolar lavage and plasma samples were collected 48 hours after study drug infusion. Airspace and plasma biomarker concentrations were compared between the MSC (n = 17) and placebo (n = 10) treatment arms, and correlation between the two compartments was tested. Airspace biomarkers were also tested for associations with clinical and radiographic outcomes.

RESULTS

Compared with placebo, MSC treatment significantly reduced airspace total protein, angiopoietin-2 (Ang-2), IL-6, and soluble TNF receptor-1 concentrations. Plasma biomarkers did not differ between groups. Each 10-fold increase in airspace Ang-2 was independently associated with 6.7 fewer days alive and free of mechanical ventilation (95% CI, –12.3 to –1.0, P = 0.023), and each 10-fold increase in airspace receptor for advanced glycation end-products (RAGE) was independently associated with a 6.6-point increase in day 3 radiographic assessment of lung edema score (95% CI, 2.4 to 10.8, P = 0.004).

CONCLUSION

MSCs reduced biological evidence of lung injury in patients with ARDS. Biomarkers from the airspaces provide additional value for studying pathogenesis, treatment effects, and outcomes in ARDS.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02097641.

FUNDING

National Heart, Lung, and Blood Institute.

Circulating angiopoietin-2 and the risk of mortality in patients with acute respiratory distress syndrome: a systematic review and meta-analysis of 10 prospective cohort studies

BACKGROUND

Angiopoietin-2 (Ang-2), as one of the ligands of endothelial receptor Tie2, is known to be significant for vessel maturation and stabilization after birth. Previous studies showed the relationship between Ang-2 level and the risk of mortality in patients with acute respiratory distress syndrome (ARDS). However, the link between circulating Ang-2 and the risk of mortality in patients with ARDS varied in different investigations.

RESULTS

We performed a systematic review and meta-analysis of all available cohort studies regarding the association between baseline circulating Ang-2 and mortality in patients with ARDS. Among the 10 eligible studies, pooled odds ratio (OR) showed that high Ang-2 level contributed to ARDS mortality [OR = 1.56, 95% confidence interval (CI): 1.30-1.89, I² = 76.2%]. Stratified analysis revealed that higher circulating Ang-2 was related to a 30% higher risk in the high-quality scores group (OR = 1.68, 95% CI: 1.33-2.68, I² = 62.4%). The I² of the bad compliance group decreased from 76.2% to 8.5%, which suggested that compliance is a significant source of heterogeneity. This association may be blunted by potential bias, although the results was not meaningfully changed by omitting only one study at a time. Further subgroup analysis and meta-regression support that compliance of patients also affects the results significantly, compared with the publication year, follow-up duration, the samples, or population characteristics.

CONCLUSION

Participants with higher baseline Ang-2 were at a higher risk for future risk of mortality in patients with ARDS. Higher circulating Ang-2 levels could independently predict the risk of mortality in patients with ARDS. However, further large scale prospective cohorts or even interventional studies are warranted to evaluate the diagnostic power of Ang-2 and its causative role on ARDS outcome. The reviews of this paper are available via the supplemental material section.

Novel Perspectives Regarding the Pathology, Inflammation, and Biomarkers of Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) is an acute inflammation of the lung resulting from damage to the alveolar-capillary membrane, and it is diagnosed using a combination of clinical and physiological variables. ARDS develops in approximately 10% of hospitalised patients with pneumonia and has a mortality rate of approximately 40%. Recent research has identified several biomarkers associated with ARDS pathophysiology, and these may be useful for diagnosing and monitoring ARDS. They may also highlight potential therapeutic targets. This review summarises our current understanding of those clinical biomarkers: (1) biomarkers of alveolar and bronchiolar injury, (2) biomarkers of endothelial damage and coagulation, and (3) biomarkers for treatment responses.

Predictive value of perfusion index for mortality in mechanically ventilated patients

AIM

This study aimed to examine the prognostic significance of the perfusion index (PI) in mechanically ventilated patients.

METHODS

Study included sixty patients who had the risk factors for the development of acute respiratory distress syndrome and received mechanical ventilator (MV) support in intensive care unit (ICU) unit between January 2017/January 2018. The demographic characteristics, vital signs, blood gas parameters, lactate levels, prognostic scores, and use of inotropic drugs were recorded. Arterial blood gas and PI measurements at the frontal region were performed at the time of and 12th and 24th hours of admission to the ICU. The patients were followed up for 60 days, and the outcome was recorded.

RESULTS

Twelve patients (20%) died during the first 7 days, and 27 patients (45%) died within 60 days of the admission. Multivariate analyses to determine potential predictors of 7 and 30-day mortality showed that only 24th-hour lactate level was independent predictor of 60-day mortality, and the PI at 24th was the sole independent predictor of 7-day mortality.

CONCLUSION

The PI did not predict 60-day mortality in MV patients who had risk factors for the development of Acute Respiratory Distress Syndrome (ARDS). However, the PI at 24th may be a significant predictor of 7-day mortality.

Endothelial Damage in Acute Respiratory Distress Syndrome

The pulmonary endothelium is a metabolically active continuous monolayer of squamous endothelial cells that internally lines blood vessels and mediates key processes involved in lung homoeostasis. Many of these processes are disrupted in acute respiratory distress syndrome (ARDS), which is marked among others by diffuse endothelial injury, intense activation of the coagulation system and increased capillary permeability. Most commonly occurring in the setting of sepsis, ARDS is a devastating illness, associated with increased morbidity and mortality and no effective pharmacological treatment. Endothelial cell damage has an important role in the pathogenesis of ARDS and several biomarkers of endothelial damage have been tested in determining prognosis. By further understanding the endothelial pathobiology, development of endothelial-specific therapeutics might arise. In this review, we will discuss the underlying pathology of endothelial dysfunction leading to ARDS and emerging therapies. Furthermore, we will present a brief overview demonstrating that endotheliopathy is an important feature of hospitalised patients with coronavirus disease-19 (COVID-19).

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.

Immunomodulatory Therapeutic Proteins in COVID-19: Current Clinical Development and Clinical Pharmacology Considerations

The coronavirus disease 2019 (COVID‐19) pandemic caused by infection with SARS‐CoV‐2 has led to more than 600 000 deaths worldwide. Patients with severe disease often experience acute respiratory distress characterized by upregulation of multiple cytokines. Immunomodulatory biological therapies are being evaluated in clinical trials for the management of the systemic inflammatory response and pulmonary complications in patients with advanced stages of COVID‐19. In this review, we summarize the clinical pharmacology considerations in the development of immunomodulatory therapeutic proteins for mitigating the heightened inflammatory response identified in COVID‐19.

A systematic review of biomarkers multivariately associated with acute respiratory distress syndrome development and mortality

Background

Heterogeneity of acute respiratory distress syndrome (ARDS) could be reduced by identification of biomarker-based phenotypes. The set of ARDS biomarkers to prospectively define these phenotypes remains to be established.

Objective

To provide an overview of the biomarkers that were multivariately associated with ARDS development or mortality.

Data sources

We performed a systematic search in Embase, MEDLINE, Web of Science, Cochrane CENTRAL, and Google Scholar from inception until 6 March 2020.

Study selection

Studies assessing biomarkers for ARDS development in critically ill patients at risk for ARDS and mortality due to ARDS adjusted in multivariate analyses were included.

Data extraction and synthesis

We included 35 studies for ARDS development (10,667 patients at risk for ARDS) and 53 for ARDS mortality (15,344 patients with ARDS). These studies were too heterogeneous to be used in a meta-analysis, as time until outcome and the variables used in the multivariate analyses varied widely between studies. After qualitative inspection, high plasma levels of angiopoeitin-2 and receptor for advanced glycation end products (RAGE) were associated with an increased risk of ARDS development. None of the biomarkers (plasma angiopoeitin-2, C-reactive protein, interleukin-8, RAGE, surfactant protein D, and Von Willebrand factor) was clearly associated with mortality.

Conclusions

Biomarker data reporting and variables used in multivariate analyses differed greatly between studies. Angiopoeitin-2 and RAGE in plasma were positively associated with increased risk of ARDS development. None of the biomarkers independently predicted mortality. Therefore, we suggested to structurally investigate a combination of biomarkers and clinical parameters in order to find more homogeneous ARDS phenotypes.

PROSPERO identifier

PROSPERO, CRD42017078957

Increased mobilization of mesenchymal stem cells in patients with acute respiratory distress syndrome undergoing extracorporeal membrane oxygenation

Background

The acute respiratory distress syndrome (ARDS) is characterized by pulmonary epithelial and endothelial barrier dysfunction and injury. In severe forms of ARDS, extracorporeal membrane oxygenation (ECMO) is often the last option for life support. Endothelial progenitor (EPC) and mesenchymal stem cells (MSC) can regenerate damaged endothelium and thereby improve pulmonary endothelial dysfunction. However, we still lack sufficient knowledge about how ECMO might affect EPC- and MSC-mediated regenerative pathways in ARDS. Therefore, we investigated if ECMO impacts EPC and MSC numbers in ARDS patients.

Methods

Peripheral blood mononuclear cells from ARDS patients undergoing ECMO (n = 16) and without ECMO support (n = 12) and from healthy volunteers (n = 16) were isolated. The number and presence of circulating EPC and MSC was detected by flow cytometry. Serum concentrations of vascular endothelial growth factor (VEGF) and angiopoietin 2 (Ang2) were determined.

Results

In the ECMO group, MSC subpopulations were higher by 71% compared to the non-ECMO group. Numbers of circulating EPC were not significantly altered. During ECMO, VEGF and Ang2 serum levels remained unchanged compared to the non-ECMO group (p = 0.16), but Ang2 serum levels in non-survivors of ARDS were significantly increased by 100% (p = 0.02) compared to survivors.

Conclusions

ECMO support in ARDS is specifically associated with an increased number of circulating MSC, most likely due to enhanced mobilization, but not with a higher numbers of EPC or serum concentrations of VEGF and Ang2.

BMX Represses Thrombin-PAR1-Mediated Endothelial Permeability and Vascular Leakage During Early Sepsis

RATIONALE

BMX (bone marrow kinase on the X chromosome) is highly expressed in the arterial endothelium from the embryonic stage to the adult stage in mice. It is also expressed in microvessels and the lymphatics in response to pathological stimuli. However, its role in endothelial permeability and sepsis remains unknown.

OBJECTIVE

We aimed to delineate the function of BMX in thrombin-mediated endothelial permeability and the vascular leakage that occurs with sepsis in cecal ligation and puncture models.

METHODS AND RESULTS

The cecal ligation and puncture model was applied to WT (wild type) and BMX-KO (BMX global knockout) mice to induce sepsis. Meanwhile, the electric cell-substrate impedance sensing assay was used to detect transendothelial electrical resistance in vitro and, the modified Miles assay was used to evaluate vascular leakage in vivo. We showed that BMX loss caused lung injury and inflammation in early cecal ligation and puncture-induced sepsis. Disruption of BMX increased thrombin-mediated permeability in mice and cultured endothelial cells by 2- to 3-fold. The expression of BMX in macrophages, neutrophils, platelets, and lung epithelial cells was undetectable compared with that in endothelial cells, indicating that endothelium dysfunction, rather than leukocyte and platelet dysfunction, was involved in vascular permeability and sepsis. Mechanistically, biochemical and cellular analyses demonstrated that BMX specifically repressed thrombin-PAR1 (protease-activated receptor-1) signaling in endothelial cells by directly phosphorylating PAR1 and promoting its internalization and deactivation. Importantly, pretreatment with the selective PAR1 antagonist SCH79797 rescued BMX loss-mediated endothelial permeability and pulmonary leakage in early cecal ligation and puncture-induced sepsis.

CONCLUSIONS

Acting as a negative regulator of PAR1, BMX promotes PAR1 internalization and signal inactivation through PAR1 phosphorylation. Moreover, BMX-mediated PAR1 internalization attenuates endothelial permeability to protect vascular leakage during early sepsis.

Association of Ang-2, vWF, and EVLWI with risk of mortality in sepsis patients with concomitant ARDS: A retrospective study

BACKGROUND/PURPOSE

This study aimed to determine the potential effects of angiopoietin-2 (Ang-2), von Willebrand factor (vWF), and extravascular lung water index (EVLWI) on the risk of mortality in sepsis patients with concomitant acute respiratory distress syndrome (ARDS).

METHODS

This retrospective study recruited 41 sepsis patients with concomitant ARDS from January 2015 to June 2018. Data of Ang-2 and vWF levels, EVLWI, and sequential organ failure assessment scores were collected at 0, 24, and 48 h after admission to the hospital.

RESULTS

The length of intensive care unit stay (P = 0.041) and Acute Physiology and Chronic Health Evaluation-2 (APACHE II) score (P = 0.003) were associated with the risk of mortality. Furthermore, increased Ang-2 levels and EVLWI at 24 h and 48 h were associated with an increased risk of mortality. Moreover, the APACHE II score at hospital admission significantly predicted the risk of mortality (area under the curve [AUC], 0.834; 95% confidence interval [CI], 0.665-0.983). Finally, the models containing a combination of Ang-2 level and EVLWI at 24 h (AUC, 0.908; 95% CI, 0.774-0.996) and Ang-2 level and EVLWI at 48 h (AUC, 0.981; 95% CI, 0.817-1.000) had high diagnostic values for predicting risk of mortality.

CONCLUSION

The study findings indicate that Ang-2 levels and EVLWI at 24 h and 48 h after admission are significantly associated with the risk of mortality.

Endocan, sepsis, pneumonia, and acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) and hospital-acquired pneumonia (HAP) are major problems of public health in intensive care units (ICUs), occurring in 15% of critically ill patients. Among the factors explaining ARDS development, sepsis is known as a frequent cause. Sepsis, ARDS, and HAP increase morbidity, mortality, length of stay in the ICU, and the overall costs of healthcare. The major challenge remains to identify accurately among critically ill patients those at risk of poor outcomes who could benefit from novel therapies. Endocan is released by the pulmonary endothelium in response to local or systemic injury. It inhibits mainly leukocyte diapedesis rather than leukocyte rolling or adhesion to the endothelial cells both in vitro and in vivo. Endocan was evaluated in 25 clinical reports, including 2454 critically ill patients and 452 healthy controls. The diagnostic value of endocan for sepsis or sepsis severity was equal to procalcitonin but its prognostic value was better. A predictive value for postoperative pneumonia was evidenced in two studies, and a predictive value for ARDS in four studies from three independent centers. This review presents an overview of the structure, expression, and functions of endocan. We also hereby summarize the potential applications of endocan in the prediction and prognosis of ARDS and HAP, as well as in the prognosis of sepsis.