Jurjan Aman

Plasma biomarkers for acute respiratory distress syndrome: A systematic review and Meta-Analysis*

Objective:Numerous studies have focused on biomarkers for acute lung injury and acute respiratory distress syndrome. Although several biomarkers have been identified, their relative performance is unclear. We aim to provide a quantitative overview of plasma-derived biomarkers associated with acute respiratory distress syndrome diagnosis or mortality. Data Sources:MEDLINE (inception to January 2012) and personal databases. Study Selection:English-language studies on plasma biomarkers associated with acute respiratory distress syndrome diagnosis or mortality. Data Extraction:Demographic variables, plasma levels of biomarker, statistical data, acute respiratory distress syndrome occurrence, and mortality rates were retrieved. The methodological quality was assessed with the Quality Assessment of Diagnostic Accuracy Studies score. Clinical outcomes included 1) diagnosis of acute respiratory distress syndrome in the at-risk population and 2) mortality in acute respiratory distress syndrome patients. For each biomarker, pooled odds ratios for clinical outcome were calculated by meta-analysis, and biomarkers were ranked according to pooled odds ratio. Data Synthesis:Fifty-four studies appeared eligible for meta-analysis, together including 3,753 patients. We identified 20 biomarkers for diagnosis of acute respiratory distress syndrome in the at-risk population and 19 biomarkers for mortality of acute respiratory distress syndrome patients. The biomarkers most strongly associated with acute respiratory distress syndrome diagnosis in the at-risk population, when increased, were Krebs von den Lungen-6 (odds ratio [95% CI], 6.1 [3.0–12.1]), lactate dehydrogenase (5.7 [1.7–19.1]), soluble receptor for advanced glycation end products (3.5 [1.7–7.2]), and von Willebrand Factor (3.1 [2.0–5.2]). The biomarkers most strongly associated with acute respiratory distress syndrome mortality, when increased, were interleukin-4 (18.0 [6.0–54.2]), interleukin-2 (11.8 [4.3–32.2]), angiopoietin-2 (6.4 [1.3–30.4]), and Krebs von den Lungen-6 (5.1 [3.0–12.2]). Decreased levels of Protein C were associated with increased odds for acute respiratory distress syndrome diagnosis and mortality. Conclusions:This meta-analysis provides a unique ranking of plasma biomarkers according to their strength of association with acute respiratory distress syndrome diagnosis or acute respiratory distress syndrome mortality. The relative performance of biomarkers among studies shown in this ranking may help to improve acute respiratory distress syndrome diagnosis and outcome prediction.

Effective Treatment of Edema and Endothelial Barrier Dysfunction With Imatinib

Background— Tissue edema and endothelial barrier dysfunction as observed in sepsis and acute lung injury carry high morbidity and mortality, but currently lack specific therapy. In a recent case report, we described fast resolution of pulmonary edema on treatment with the tyrosine kinase inhibitor imatinib through an unknown mechanism. Here, we explored the effect of imatinib on endothelial barrier dysfunction and edema formation. Methods and Results— We evaluated the effect of imatinib on endothelial barrier function in vitro and in vivo. In human macro- and microvascular endothelial monolayers, imatinib attenuated endothelial barrier dysfunction induced by thrombin and histamine. Small interfering RNA knock-downs of the imatinib-sensitive kinases revealed that imatinib attenuates endothelial barrier dysfunction via inhibition of Abl-related gene kinase (Arg/Abl2), a previously unknown mediator of endothelial barrier dysfunction. Indeed, Arg was activated by endothelial stimulation with thrombin, histamine, and vascular endothelial growth factor. Imatinib limited Arg-mediated endothelial barrier dysfunction by enhancing Rac1 activity and enforcing adhesion of endothelial cells to the extracellular matrix. Using mouse models of vascular leakage as proof-of-concept, we found that pretreatment with imatinib protected against vascular endothelial growth factor–induced vascular leakage in the skin, and effectively prevented edema formation in the lungs. In a murine model of sepsis, imatinib treatment (6 hours and 18 hours after induction of sepsis) attenuated vascular leakage in the kidneys and the lungs (24 hours after induction of sepsis). Conclusions— Thus, imatinib prevents endothelial barrier dysfunction and edema formation via inhibition of Arg. These findings identify imatinib as a promising approach to permeability edema and indicate Arg as novel target for edema treatment.

Plasma protein levels are markers of pulmonary vascular permeability and degree of lung injury in critically ill patients with or at risk for acute lung injury/acute respiratory distress syndrome*

Objectives:To evaluate the diagnostic value of plasma protein levels for pulmonary vascular permeability and acute respiratory distress syndrome. During acute lung injury and acute respiratory distress syndrome, increased vascular permeability induces protein-rich fluid extravasation. We hypothesized that plasma protein levels predict increased vascular permeability and acute respiratory distress syndrome. Design:A prospective, observational study. Patients:Eighty-three consecutive, mechanically ventilated patients with or at risk for acute lung injury/acute respiratory distress syndrome, of whom 18 had sepsis. Patients with increased pulmonary capillary wedge pressures or central venous pressures were excluded. Interventions:Patients were subjected to pulmonary capillary wedge pressure/central venous pressure-guided fluid loading with saline or colloid fluids. Measurements and Main Results:We measured plasma albumin and transferrin levels and determined the 67Gallium-transferrin pulmonary leak index, the American European Consensus Conference criteria, and the lung injury score. Measurements were performed before and after fluid loading to evaluate effects of fluid loading. Plasma albumin and transferrin levels were approximately 30% lower in acute respiratory distress syndrome than patients with acute lung injury (p < .01) and patients without lung injury (p < .05). Protein levels inversely related to the pulmonary leak index (standardized regression coefficient −0.28, p < .001 for albumin; standardized regression coefficient −0.30, p = .003 for transferrin) and the lung injury score (standardized regression coefficient −0.19, p = .01 for albumin), independently of presence of sepsis, severity of disease, and fluid loading. Albumin and transferrin levels had a high sensitivity (77–93%) and negative predictive value (80–98%) for elevated pulmonary vascular permeability and acute respiratory distress syndrome (American European Consensus Conference criteria and lung injury score). The addition of hypoalbuminemia (<17.5 g/L) and hypotransferrinemia (<0.98 g/L) as criteria to the American European Consensus Conference criteria or the lung injury score increased their predictive values for elevated pulmonary vascular permeability. Conclusions:In critically ill patients, decreased plasma albumin and transferrin levels parallel increased pulmonary vascular permeability irrespective of underlying disease and fluid status. While normal levels help to exclude acute respiratory distress syndrome, hypoalbuminemia and hypotransferrinemia increase the diagnostic accuracy of the American European Consensus Conference criteria and lung injury score for elevated pulmonary vascular permeability.

Predictors of pulmonary edema formation during fluid loading in the critically ill with presumed hypovolemia

Objectives:It is largely unknown why extravascular lung water may increase during fluid loading in the critically ill with presumed hypovolemia. In this study we evaluated the hemodynamic predictors of such an increase. Design:A prospective observational study. Patients:Sixty-three presumed hypovolemic mechanically ventilated patients (22 septic and 41 nonseptic patients). Intervention:Fluid loading with saline or colloid fluids guided by (changes in) cardiac filling pressures. Measurements and Main Results:Before and after fluid-loading, hemodynamic and respiratory variables were recorded, including variables obtained by transpulmonary dilution such as cardiac index, pulmonary blood volume index, and extravascular lung water. Baseline parameters and change in parameters were compared between patients with a change in extravascular lung water <10% and patients with a change in extravascular lung water ≥10%. Predictive values for change in extravascular lung water ≥10% were evaluated. Baseline cardiac index and pulmonary blood volume index were higher, whereas change in cardiac index, change in pulmonary blood volume index, and change in PaO2/FIO2 ratio were lower in patients with a change in extravascular lung water ≥10% than in patients with a change in extravascular lung water <10%. The change in extravascular lung water correlated to baseline cardiac index (r2 = 0.17; p = .001), baseline pulmonary blood volume index (r2 = 0.15; p = .001), change in pulmonary blood volume index (r2 = 0.16; p < .001), and change in PaO2/FIO2 ratio (r2 = 0.13; p = .004). In multiple logistic regression analysis baseline cardiac index, baseline pulmonary blood volume index, the change in cardiac index, change in pulmonary blood volume index, and change in PaO2/FIO2 ratio individually contributed to prediction of a change in extravascular lung water ≥10%, independent of the presence of sepsis, pulmonary vascular permeability, and cardiac filling pressures. A change in extravascular lung water ≥10% was predicted by baseline cardiac index (77% sensitivity, 98% specificity) and pulmonary blood volume index (92% sensitivity, 68% specificity), and by change in cardiac index (69% sensitivity, 59% specificity), change in pulmonary blood volume index (77% sensitivity, 82% specificity), and change in PaO2/FIO2 ratio (77% sensitivity, 66% specificity). Conclusion:Extravascular lung water increase during fluid loading in the critically ill is predicted by a plateau of cardiac function and pulmonary vascular filling at baseline, rather than by pulmonary vascular permeability and filling pressures. Increasing extravascular lung water is further reflected by a decrease of PaO2/FIO2 ratio. These observations may help preventing pulmonary fluid overloading.

ROCK2 primes the endothelium for vascular hyperpermeability responses by raising baseline junctional tension.

Rho kinase mediates the effects of inflammatory permeability factors by increasing actomyosin-generated traction forces on endothelial adherens junctions, resulting in disassembly of intercellular junctions and increased vascular leakage. In vitro, this is accompanied by the Rho kinase-driven formation of prominent radial F-actin fibers, but the in vivo relevance of those F-actin fibers has been debated, suggesting other Rho kinase-mediated events to occur in vascular leak. Here, we delineated the contributions of the highly homologous isoforms of Rho kinase (ROCK1 and ROCK2) to vascular hyperpermeability responses. We show that ROCK2, rather than ROCK1 is the critical Rho kinase for regulation of thrombin receptor-mediated vascular permeability. Novel traction force mapping in endothelial monolayers, however, shows that ROCK2 is not required for the thrombin-induced force enhancements. Rather, ROCK2 is pivotal to baseline junctional tension as a novel mechanism by which Rho kinase primes the endothelium for hyperpermeability responses, independent from subsequent ROCK1-mediated contractile stress-fiber formation during the late phase of the permeability response.

Using cultured endothelial cells to study endothelial barrier dysfunction: Challenges and opportunities

Despite considerable progress in the understanding of endothelial barrier regulation and the identification of approaches that have the potential to improve endothelial barrier function, no drug- or stem cell-based therapy is presently available to reverse the widespread vascular leak that is observed in acute respiratory distress syndrome (ARDS) and sepsis. The translational gap suggests a need to develop experimental approaches and tools that better mimic the complex environment of the microcirculation in which the vascular leak develops. Recent studies have identified several elements of this microenvironment. Among these are composition and stiffness of the extracellular matrix, fluid shear stress, interaction of endothelial cells (ECs) with pericytes, oxygen tension, and the combination of toxic and mechanic injurious stimuli. Development of novel cell culture techniques that integrate these elements would allow in-depth analysis of EC biology that closely approaches the (patho)physiological conditions in situ. In parallel, techniques to isolate organ-specific ECs, to define EC heterogeneity in its full complexity, and to culture patient-derived ECs from inducible pluripotent stem cells or endothelial progenitor cells are likely to advance the understanding of ARDS and lead to development of therapeutics. This review 1) summarizes the advantages and pitfalls of EC cultures to study vascular leak in ARDS, 2) provides an overview of elements of the microvascular environment that can directly affect endothelial barrier function, and 3) discusses alternative methods to bridge the gap between basic research and clinical application with the intent of improving the translational value of present EC culture approaches.

Globular adiponectin controls insulin-mediated vasoreactivity in muscle through AMPKα2

Decreased tissue perfusion increases the risk of developing insulin resistance and cardiovascular disease in obesity, and decreased levels of globular adiponectin (gAdn) have been proposed to contribute to this risk. We hypothesized that gAdn controls insulins vasoactive effects through AMP-activated protein kinase (AMPK), specifically its α2 subunit, and studied the mechanisms involved. In healthy volunteers, we found that decreased plasma gAdn levels in obese subjects associate with insulin resistance and reduced capillary perfusion during hyperinsulinemia. In cultured human microvascular endothelial cells (HMEC), gAdn increased AMPK activity. In isolated muscle resistance arteries gAdn uncovered insulin-induced vasodilation by selectively inhibiting insulin-induced activation of ERK1/2, and the AMPK inhibitor compound C as well as genetic deletion of AMPKα2 blunted insulin-induced vasodilation. In HMEC deletion of AMPKα2 abolished insulin-induced Ser(1177) phosphorylation of eNOS. In mice we confirmed that AMPKα2 deficiency decreases insulin sensitivity, and this was accompanied by decreased muscle microvascular blood volume during hyperinsulinemia in vivo. This impairment was accompanied by a decrease in arterial Ser(1177) phosphorylation of eNOS, which closely related to AMPK activity. In conclusion, globular adiponectin controls muscle perfusion during hyperinsulinemia through AMPKα2, which determines the balance between NO and ET-1 activity in muscle resistance arteries. Our findings provide a novel mechanism linking reduced gAdn-AMPK signaling to insulin resistance and impaired organ perfusion.

Why vessels do matter in pulmonary disease

In addition to structural abnormalities of the diaphragm, congenital diaphragmatic hernia (CDH) presents with severe hypoplasia of lung tissue involving both the pulmonary vasculature and the airways. These developmental defects often yield a severe phenotype of pulmonary hypertension (PH) and lung function impairment. Despite adequate surgical repair of the diaphragm, neonatal mortality of CDH remains high, due to ineffectiveness of inhaled nitric oxide (NO) and absence of alternative therapy for PH in the newborn. Russo et al 1 demonstrate that maternally administered sildenafil reaches therapeutic levels in the rabbit fetus, without toxicity for mother or the fetus. CDH fetuses treated with sildenafil demonstrated increased pulmonary vascular branching compared with placebo-treated fetuses. The improved vascularisation was paralleled by reduced pulmonary artery pressure and by morphological changes in the lung parenchyma and functional improvement. In line with previous rodent studies, Russo et al 1 found that the decreased lung weight due to CDH is not rescued in sildenafil-treated fetuses with CDH, suggesting that the sildenafil-induced improvement of vascular and alveolar development contributes to the lung maturation more than the volume growth. These well-performed studies obtained in an animal model that closely resembles both the pharmacokinetics of human pregnancy and alveolar development in humans provide a next step towards a clinically useful therapy for CDH and its postnatal consequences. In addition to providing relevant steps towards clinical development of sildenafil as a potential therapy for CDH, Russo et al give valuable insights into the mechanisms of lung development. Stressing the key role of cyclic guanosine monophosphate (cGMP)/NO signalling in …

The BCR-ABL1 Inhibitors Imatinib and Ponatinib Decrease Plasma Cholesterol and Atherosclerosis, and Nilotinib and Ponatinib Activate Coagulation in a Translational Mouse Model

Treatment with the second and third generation BCR-ABL1 tyrosine kinase inhibitors (TKIs) increases cardiovascular risk in chronic myeloid leukemia (CML) patients. We investigated the vascular adverse effects of three generations of TKIs in a translational model for atherosclerosis, the APOE*3Leiden.CETP mouse. Mice were treated for sixteen weeks with imatinib (150 mg/kg BID), nilotinib (10 and 30 mg/kg QD) or ponatinib (3 and 10 mg/kg QD), giving similar drug exposures as in CML-patients. Cardiovascular risk factors were analyzed longitudinally, and histopathological analysis of atherosclerosis and transcriptome analysis of the liver was performed. Imatinib and ponatinib decreased plasma cholesterol (imatinib, −69%, p < 0.001; ponatinib 3 mg/kg, −37%, p < 0.001; ponatinib 10 mg/kg−44%, p < 0.001) and atherosclerotic lesion area (imatinib, −78%, p < 0.001; ponatinib 3 mg/kg, −52%, p = 0.002; ponatinib 10 mg/kg, −48%, p = 0.006), which were not affected by nilotinib. In addition, imatinib increased plaque stability. Gene expression and pathway analysis demonstrated that ponatinib enhanced the mRNA expression of coagulation factors of both the contact activation (intrinsic) and tissue factor (extrinsic) pathways. In line with this, ponatinib enhanced plasma levels of FVII, whereas nilotinib increased plasma FVIIa activity. While imatinib showed a beneficial cardiovascular risk profile, nilotinib and ponatinib increased the cardiovascular risk through induction of a pro-thrombotic state.

Recent advances in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a rare disorder with a high mortality rate. Treatment options have improved in the last 20 years, but patients still die prematurely of right heart failure. Though rare, it is heterogeneous at the genetic and molecular level, and understanding and exploiting this is key to the development of more effective treatments. BMPR2, encoding bone morphogenetic receptor type 2, is the most commonly affected gene in both familial and non-familial PAH, but rare mutations have been identified in other genes. Transcriptomic, proteomic, and metabolomic studies looking for endophenotypes are under way. There is no shortage of candidate new drug targets for PAH, but the selection and prioritisation of these are challenges for the research community.