Asymmetric Dimethylarginine and NT-proBNP Levels Provide Synergistic Information in Pulmonary Arterial Hypertension.

BACKGROUND: Plasma asymmetric dimethylarginine (ADMA) is elevated in pulmonary arterial hypertension (PAH) and is associated with unfavorable outcomes. OBJECTIVES: The aim of this study was to assess changes in ADMA plasma levels for monitoring disease progression and outcomes during PAH-specific therapy. METHODS: ADMA was measured at baseline and after at least 6 months of follow-up using enzyme-linked immunosorbent assay and high-performance liquid chromatography. Changes in ADMA were analyzed in relation to changes in established PAH markers, including hemodynamic status, N-terminal pro-brain natriuretic peptide (NT-proBNP) and risk assessment scores. Impact on survival was assessed using Kaplan-Meier curves and Cox proportional hazards models. RESULTS: Between 2008 and 2019, ADMA samples were collected prospectively from 215 patients with PAH. Change in ADMA plasma level was a predictor of disease progression and survival. ΔADMA (median -0.03 µmol/L; 95% CI: -0.145 to 0.0135) was correlated with change in mean pulmonary arterial pressure (P < 0.005; rS = 0.287) but was not significantly correlated with ΔNT-proBNP (P = 0.056; rS = 0.135). Patients with decreased ADMA plasma levels at follow-up had better 3-year and 5-year survival rates (88% and 80%, respectively, vs 72% and 53% in those without decreases in ADMA) (P < 0.005; pulmonary hypertension-related mortality or lung transplantation). Patients with decreases in both ADMA and NT-proBNP had better survival rates compared with patients in whom only 1 parameter improved (P < 0.005). ΔADMA was a significant predictor of survival in Cox regression analysis and also when corrected for ΔNT-proBNP (HRs: 1.27 and 1.35, respectively; P < 0.005). CONCLUSIONS: ADMA and NT-proBNP provide synergistic prognostic information for patients with PAH. ADMA could be used as an objective and distinct biomarker for monitoring treatment response in PAH.

Deoxyribonuclease 1 Q222R single nucleotide polymorphism and long-term mortality after acute myocardial infarction.

Upon activation, neutrophils release neutrophil extracellular traps (NETs), which contribute to circulating DNA burden and thrombosis, including ST-segment elevation myocardial infarction (STEMI). Deoxyribonuclease (DNase) 1 degrades circulating DNA and NETs. Lower DNase activity correlates with NET burden and infarct size. The DNase 1 Q222R single nucleotide polymorphism (SNP), impairing DNase 1 function, is linked with myocardial infarction. We assessed whether the Q222R SNP is connected to increased NET burden in STEMI and influences long-term outcomes. We enrolled 711 STEMI patients undergoing primary percutaneous coronary intervention (pPCI), and 1422 controls. Genotyping was performed for DNase 1 Q222R SNP. DNase activity, double-stranded (ds)DNA and citrullinated histone H3 were determined in culprit site and peripheral plasma during pPCI. The association of the Q222R variant on cardiovascular and all-cause mortality was assessed by multivariable Cox regression adjusted for cardiovascular risk factors. Homozygous Q222R DNase 1 variant was present in 64 (9.0%) STEMI patients, at the same frequency as in controls. Patients homozygous for Q222R displayed less DNase activity and increased circulating DNA burden. In overall patients, median survival was 60 months. Homozygous Q222R variant was independently associated with cardiovascular and all-cause mortality after STEMI. dsDNA/DNase ratio independently predicted cardiovascular and all-cause mortality. These findings highlight that the Q222R DNase 1 SNP is associated with increased NET burden and decreased compensatory DNase activity, and may serve as an independent risk factor for poor outcome after STEMI.

Histone citrullination as a novel biomarker and target to inhibit progression of abdominal aortic aneurysms.

Neutrophil extracellular traps (NETs) have been implicated in the pathogenesis of abdominal aortic aneurysms (AAAs). This study has addressed the notion that NET components might serve as AAA biomarkers or novel targets of AAA therapy. Thus, parameters of neutrophil activation and NET formation were measured in plasma. Their diagnostic marker value was explored in 41 AAA patients and 38 healthy controls. The NET parameter citrullinated histone H3 (citH3) was then validated in 63 AAA patients and 63 controls matched for cardiovascular disease. The prognostic marker potential was investigated in 54 observation periods of AAA growth over 6 months. NETs were further assessed in conditioned medium and sections of aortic tissue. CitH3 was found to be increased in blood (median 362 vs 304 ng/mL, P = 0.004) and aortic tissue (50 vs 1.5 ng/mg, P < 0.001) of AAA patients compared to healthy controls and accumulated in the intraluminal thrombus (629 ng/mg). The diagnostic potential of citH3 ranged at 0.705 area under the ROC curve (AUROC) and was validated with the independent sample set. Furthermore, plasma citH3 predicted AAA growth over the next 6 months (AUROC: 0.707, P = 0.015) and dropped significantly after surgical aneurysm repair. In an angiotensin II - based mouse model of experimental AAA, an inhibitor of histone citrullination was applied to block NET formation and AAA progression. Of note, further growth of an established aneurysm was prevented in mice treated with the NET inhibitor (P = 0.040). In conclusion, histone citrullination represents a promising AAA biomarker and potential therapeutic target to control disease progression.

Interruption of vascular endothelial growth factor receptor 2 signaling induces a proliferative pulmonary vasculopathy and pulmonary hypertension.

Pulmonary arterial hypertension is a severe and progressive disease characterized by a pulmonary vascular remodeling process with expansion of collateral endothelial cells and total vessel occlusion. Endothelial cells are believed to be at the forefront of the disease process. Vascular endothelial growth factor (VEGF) and its tyrosine kinase receptor, VEGF receptor-2 (VEGFR-2), play a central role in angiogenesis, endothelial cell protection, but also in the destabilization of endothelial barrier function. Therefore, we investigated the consequences of altered VEGF signaling in an experimental model, and looked for translational correlates of this observation in patients. We performed an endothelial cell-specific conditional deletion of the kinase insert domain protein receptor (kdr) gene, coding for VEGFR-2, in C57/BL6 mice (Kdr∆end) and held them in an environmental chamber with 10% FiO2 or under normoxia for 6 weeks. Kdr knockout led to a mild PH phenotype under normoxia that worsened under hypoxia. Kdr∆end mice exhibited a significant increase in pulmonary arterial wall thickness, muscularization, and VEGFR-3+ endothelial cells obliterating the pulmonary artery vessel lumen. We observed the same proliferative vasculopathy in our rodent model as seen in patients receiving anti-angiogenic therapy. Serum VEGF-a levels were elevated both in the experimental model and in humans receiving bevacizumab. Interrupted VEGF signaling leads to a pulmonary proliferative arteriopathy in rodents after direct ablative gene manipulation of Kdr. Histologically, similar vascular lesions can be observed in patients receiving anti-VEGF treatment. Our findings illustrate the importance of VEGF signaling for maintenance of pulmonary vascular patency.

Neutrophil extracellular traps and fibrocytes in ST-segment elevation myocardial infarction.

Leukocyte-mediated inflammation is central in atherothrombosis and ST-segment elevation myocardial infarction (STEMI). Neutrophil extracellular traps (NETs) have been shown to enhance atherothrombosis and stimulate fibroblast function. We analyzed the effects of NETs on cardiac remodeling after STEMI. We measured double-stranded (ds)DNA and citrullinated histone H3 (citH3) as NET surrogate markers in human culprit site and femoral blood collected during primary percutaneous coronary intervention (n = 50). Fibrocytes were characterized in whole blood by flow cytometry, and in culprit site thrombi and myocardium by immunofluorescence. To investigate mechanisms of fibrocyte activation, isolated NETs were used to induce fibrocyte responses in vitro. Enzymatic infarct size was assessed using creatine-phosphokinase isoform MB area under the curve. Left ventricular function was measured by transthoracic echocardiography. NET surrogate markers were increased at the culprit site compared to the femoral site and were positively correlated with infarct size and left ventricular dysfunction at follow-up. In vitro, NETs promoted fibrocyte differentiation from monocytes and induced fibrocyte activation. Highly activated fibrocytes accumulated at the culprit site and in the infarct transition zone. Our data suggest that NETs might be important mediators of fibrotic remodeling after STEMI, possibly by stimulating fibrocytes.

Differential expression of Plg-RKT and its effects on migration of proinflammatory monocyte and macrophage subsets.

Membrane-bound plasmin is used by immune cells to degrade extracellular matrices, which facilitates migration. The plasminogen receptor Plg-RKT is expressed by immune cells, including monocytes and macrophages. Among monocytes and macrophages, distinct subsets can be distinguished based on cell surface markers and pathophysiological function. We investigated expression of Plg-RKT by monocyte and macrophage subsets and whether potential differential expression might have functional consequences for cell migration. Proinflammatory CD14++CD16+ human monocytes and Ly6Chigh mouse monocytes expressed the highest levels of Plg-RKT and bound significantly more plasminogen compared with the other respective subsets. Proinflammatory human macrophages, generated by polarization with lipopolysaccharide and interferon-γ, showed significantly higher expression of Plg-RKT compared with alternatively activated macrophages, polarized with interleukin-4 and interleukin-13. Directional migration of proinflammatory monocytes was plasmin dependent and was abolished by anti-Plg-RKT monoclonal antibody, ε-amino-caproic acid, aprotinin, and the aminoterminal fragment of urokinase-type plasminogen activator. In an in vivo peritonitis model, significantly less Ly6Chigh monocyte recruitment was observed in Plg-RKT -/- compared with Plg-RKT +/+ mice. Immunohistochemical analysis of human carotid plaques and adipose tissue showed that proinflammatory macrophages also exhibited high levels of Plg-RKT in vivo. Our data demonstrate higher expression of Plg-RKT on proinflammatory monocyte and macrophage subsets that impacts their migratory capacity.

Usefulness of thrombosis and inflammation biomarkers in chronic thromboembolic pulmonary hypertension-sampling plasma and surgical specimens.

BACKGROUND: Chronic thromboembolic pulmonary hypertension (CTEPH) results from persistent pulmonary vascular obstructions, presumably due to inflammatory thrombosis. Because estimates of thrombus volume at diagnosis have no predictive value, we investigated the role of the thrombosis marker, D-dimer, and the inflammation marker, C-reactive protein (CRP), for predicting outcomes in CTEPH. METHODS: A total 289 consecutive patients with CTEPH were followed for 57 (median 45 to 69) months. One hundred fifty-seven of these patients underwent surgical pulmonary endarterectomy (PEA). D-dimer and CRP were collected at the time of CTEPH diagnosis and their impact on outcome was analyzed using Cox and logistic regression models. Their association with thrombus composition was analyzed utilizing HistoQuest. RESULTS: D-dimer and CRP levels were separately and independently predictive of death or need for lung transplantation (p = 0.012 and p = 0.025, respectively). For example, 5-year survival was 90% (confidence limits 84% to 96%) in patients with D-dimer levels <0.5 µg/ml and CRP <1 mg/dl at diagnosis, as compared with 50% (36% to 64%) for patients with D-dimer ≥0.5 µg/ml and CRP ≥1 mg/dl (p < 0.001). D-dimer and CRP both decreased significantly after PEA (p < 0.01). The amount of fresh red thrombus in thrombendarterectomy specimens correlated positively with D-dimer levels at diagnosis (r = 0.37, p = 0.003). CONCLUSIONS: D-dimer and CRP at the time of diagnosis are independent and significant predictors of outcome in CTEPH, available at the time of diagnosis. This observation suggests an important role for fibrin turnover and inflammation in the pathogenesis of CTEPH and the associated complications.

Cardiac extracellular matrix is associated with adverse outcome in patients with chronic heart failure.

AIMS: Accumulation of extracellular matrix (ECM) is known to play a crucial role in the pathophysiology of heart failure (HF). However, its prognostic relevance is poorly investigated. METHODS AND RESULTS: A total of 73 HF patients who underwent LV endomyocardial biopsy were enrolled in our study. ECM area was quantified by TissueFAXS and ImageJ software. Patients were followed-up at 6-month intervals. The study endpoint was defined as hospitalization for a cardiac reason and/or cardiac death. Furthermore, the influence of the ECM on invasively measured haemodynamic parameters was tested. During a median follow-up period of 9.0 months, 34 patients (46.6%) reached the combined endpoint. Median ECM area was 30.5%. Patients with ECM area ≥30.5% experienced significantly more events (67.6% vs. 25.0%, P < 0.001) in comparison with patients with an ECM area <30.5%. ECM area was independently associated with outcome in the total HF cohort [hazard ratio (HR) 1.041, 95% confidence interval (CI) 1.017-1.066, P = 0.001] as well as in HF patients with preserved (HR 1.079, 95% CI 1.001-1.163, P =0 .046) or reduced ejection fraction (HR 1.149, 95% CI 1.036-1.275, P = 0.009). Positive correlations were found between ECM area and LV end-diastolic pressure (P = 0.021, R = 0.303), pulmonary artery wedge pressure (P = 0.042, R = 0.249), mean pulmonary arterial pressure (P = 0.035, R = 0.258), as well as right atrial pressure (P = 0.003, R = 0.353). CONCLUSION: ECM area within the LV myocardium correlates with left and right heart haemodynamics and is associated with clinical course in various non-ischaemic HF types.

Coronary neutrophil extracellular trap burden and deoxyribonuclease activity in ST-elevation acute coronary syndrome are predictors of ST-segment resolution and infarct size.

RATIONALE: Mechanisms of coronary occlusion in ST-elevation acute coronary syndrome are poorly understood. We have previously reported that neutrophil (polymorphonuclear cells [PMNs]) accumulation in culprit lesion site (CLS) thrombus is a predictor of cardiovascular outcomes. OBJECTIVE: The goal of this study was to characterize PMN activation at the CLS. We examined the relationships between CLS neutrophil extracellular traps (NETs), bacterial components as triggers of NETosis, activity of endogenous deoxyribonuclease, ST-segment resolution, and infarct size. METHODS AND RESULTS: We analyzed coronary thrombectomies from 111 patients with ST-elevation acute coronary syndrome undergoing primary percutaneous coronary intervention. Thrombi were characterized by immunostaining, flow cytometry, bacterial profiling, and immunometric and enzymatic assays. Compared with femoral PMNs, CLS PMNs were highly activated and formed aggregates with platelets. Nucleosomes, double-stranded DNA, neutrophil elastase, myeloperoxidase, and myeloid-related protein 8/14 were increased in CLS plasma, and NETs contributed to the scaffolds of particulate coronary thrombi. Copy numbers of Streptococcus species correlated positively with dsDNA. Thrombus NET burden correlated positively with infarct size and negatively with ST-segment resolution, whereas CLS deoxyribonuclease activity correlated negatively with infarct size and positively with ST-segment resolution. Recombinant deoxyribonuclease accelerated the lysis of coronary thrombi ex vivo. CONCLUSIONS: PMNs are highly activated in ST-elevation acute coronary syndrome and undergo NETosis at the CLS. Coronary NET burden and deoxyribonuclease activity are predictors of ST-segment resolution and myocardial infarct size.

Cardiac magnetic resonance postcontrast T1 time is associated with outcome in patients with heart failure and preserved ejection fraction.

BACKGROUND: The underlying pathophysiology of heart failure with preserved ejection fraction (HFPEF) is incompletely understood, but myocardial extracellular matrix accumulation is thought to play a major role. Our aims were to estimate myocardial extracellular matrix using cardiac magnetic resonance T1 mapping and to assess the relationship between pathobiology/pathophysiology and prognosis. METHODS AND RESULTS: Patients with suspected HFPEF (n=100) were enrolled in this prospective, observational study. Confirmatory diagnostic tests, cardiac magnetic resonance imaging including T1 mapping, and invasive hemodynamic assessments were performed at baseline. Sixty-one patients with confirmed HFPEF entered a longitudinal outcome-monitoring phase (mean, 22.9±5.0 months), during which 16 had a cardiac event. Cardiac magnetic resonance T1 time (hazard ratio, 0.99; 95% confidence interval, 0.98-0.99; P=0.046), left atrial area (hazard ratio, 1.08; 95% confidence interval, 1.03-1.13; P<0.01), and pulmonary vascular resistance (hazard ratio, 1.01; 95% confidence interval, 1.00-1.01; P=0.03) were significantly associated with cardiac events. Patients with T1 times below the median (<388.3 ms) were at greater risk of cardiac events than the rest of the group (P<0.01). Extracellular matrix of left ventricular biopsies (n=9), quantified by TissueFAXS technology correlated with T1 time (R=0.98; P<0.01). T1 time also correlated with right ventricular-pulmonary arterial coupling (pulmonary vascular resistance: R=-0.36; P<0.01; right ventricular ejection fraction: R=0.28; P=0.01). CONCLUSIONS: In the present preliminary study, cardiac magnetic resonance postcontrast T1 time is associated with prognosis in HFPEF, suggesting postcontrast T1 as possible biomarker for HFPEF.

Exhaled nitric oxide measurement to monitor pulmonary hypertension in a pneumonectomy-monocrotaline rat model.

The use of fractional exhaled nitric oxide (FeNO) has been suggested as a quantitative marker for pulmonary arterial hypertension (PAH) in humans. To further characterize FeNO in PAH we investigated this marker in a rodent model. Since there is no standardized technique for FeNO measurement in animals, we intended to reduce measuring errors and confounders of an existing published method by mathematical modification and tested its applicability in an NO-regulating therapy concept of PAH. Thirty-three male Sprague-Dawley rats underwent unilateral pneumonectomy and monocrotaline (MCT) injection and were observed for 49 days. A telemetric catheter was introduced into the left pulmonary artery to continuously record mean pulmonary arterial pressure (mPAP), and FeNO was assessed. After 35 days, animals were randomized to receive either oral l-arginine (300 mg/kg) in combination with tetrahydrobiopterin (20 mg/kg) therapy (n = 12) or vehicle (n = 11) daily over a period of 14 days. mPAP at baseline was 17.19 ± 9.62 mmHg, which increased to 53.1 ± 10.63 mmHg 28 days after monocrotaline exposure (P < 0.001). Using the modified technique, we found an inverse correlation between exhaled NO and pulmonary pressures before (r = -0.366, P = 0.043) and after MCT (r = -0.363, P = 0.038) as well as after therapy administration (r = -0.657, P = 0.02). Our modified technique proved robust in a rodent model, since valid and reproducible data were gained and showed an inverse correlation between exhaled NO and mPAP, whereas the existing method did not.