Integrative proteomics and phosphoproteomics in pulmonary arterial hypertension

Pulmonary arterial endothelial cells (PAEC) are mechanistically linked to origins of pulmonary arterial hypertension (PAH). Here, global proteomics and phosphoproteomics of PAEC from PAH (n = 4) and healthy lungs (n = 5) were performed using LC-MS/MS to confirm known pathways and identify new areas of investigation in PAH. Among PAH and control cells, 170 proteins and 240 phosphopeptides were differentially expressed; of these, 45 proteins and 18 phosphopeptides were located in the mitochondria. Pathologic pathways were identified with integrative bioinformatics and human protein-protein interactome network analyses, then confirmed with targeted proteomics in PAH PAEC and non-targeted metabolomics and targeted high-performance liquid chromatography of metabolites in plasma from PAH patients (n = 30) and healthy controls (n = 12). Dysregulated pathways in PAH include accelerated one carbon metabolism, abnormal tricarboxylic acid (TCA) cycle flux and glutamate metabolism, dysfunctional arginine and nitric oxide pathways, and increased oxidative stress. Functional studies in cells confirmed abnormalities in glucose metabolism, mitochondrial oxygen consumption, and production of reactive oxygen species in PAH. Altogether, the findings indicate that PAH is typified by changes in metabolic pathways that are primarily found in mitochondria.

A network-based approach to uncover microRNA-mediated disease comorbidities and potential pathobiological implications

Disease-disease relationships (e.g., disease comorbidities) play crucial roles in pathobiological manifestations of diseases and personalized approaches to managing those conditions. In this study, we develop a network-based methodology, termed meta-path-based Disease Network (mpDisNet) capturing algorithm, to infer disease-disease relationships by assembling four biological networks: disease-miRNA, miRNA-gene, disease-gene, and the human protein-protein interactome. mpDisNet is a meta-path-based random walk to reconstruct the heterogeneous neighbors of a given node. mpDisNet uses a heterogeneous skip-gram model to solve the network representation of the nodes. We find that mpDisNet reveals high performance in inferring clinically reported disease-disease relationships, outperforming that of traditional gene/miRNA-overlap approaches. In addition, mpDisNet identifies network-based comorbidities for pulmonary diseases driven by underlying miRNA-mediated pathobiological pathways (i.e., hsa-let-7a- or hsa-let-7b-mediated airway epithelial apoptosis and pro-inflammatory cytokine pathways) as derived from the human interactome network analysis. The mpDisNet offers a powerful tool for network-based identification of disease-disease relationships with miRNA-mediated pathobiological pathways.

Severe asthma during childhood and adolescence: A longitudinal study

BACKGROUND

Morbidity and mortality associated with childhood asthma are driven disproportionately by children with severe asthma. However, it is not known from longitudinal studies whether children outgrow severe asthma.

OBJECTIVE

We sought to study prospectively whether well-characterized children with severe asthma outgrow their asthma during adolescence.

METHODS

Children with asthma were assessed at baseline with detailed questionnaires, allergy tests, and lung function tests and were reassessed annually for 3 years. The population was enriched for children with severe asthma, as assessed by the American Thoracic Society/European Respiratory Society guidelines, and subject classification was reassessed annually.

RESULTS

At baseline, 111 (59%) children had severe asthma. Year to year, there was a decrease in the proportion meeting the criteria for severe asthma. After 3 years, only 30% of subjects met the criteria for severe asthma (P < .001 compared with enrollment). Subjects experienced improvements in most indices of severity, including symptom scores, exacerbations, and controller medication requirements, but not lung function. Surprisingly, boys and girls were equally likely to has resolved asthma (33% vs 29%). The odds ratio in favor of resolution of severe asthma was 2.75 (95% CI, 1.02-7.43) for those with a peripheral eosinophil count of greater than 436 cells/μL.

CONCLUSIONS

In longitudinal analysis of this well-characterized cohort, half of the children with severe asthma no longer had severe asthma after 3 years; there was a stepwise decrease in the proportion meeting severe asthma criteria. Surprisingly, asthma severity decreased equally in male and female subjects. Peripheral eosinophilia predicted resolution. These data will be important for planning clinical trials in this population.

Development and initial validation of the Asthma Severity Scoring System (ASSESS)

BACKGROUND

Tools for quantification of asthma severity are limited.

OBJECTIVE

We sought to develop a continuous measure of asthma severity, the Asthma Severity Scoring System (ASSESS), for adolescents and adults, incorporating domains of asthma control, lung function, medications, and exacerbations.

METHODS

Baseline and 36-month longitudinal data from participants in phase 3 of the Severe Asthma Research Program (NCT01606826) were used. Scale properties, responsiveness, and a minimally important difference were determined. External replication was performed in participants enrolled in the Severe Asthma Research Program phase 1/2. The utility of ASSESS for detecting treatment response was explored in participants undergoing corticosteroid responsiveness testing with intramuscular triamcinolone and participants receiving biologics.

RESULTS

ASSESS scores ranged from 0 to 20 (8.78 ± 3.9; greater scores reflect worse severity) and differed among 5 phenotypic groups. Measurement properties were acceptable. ASSESS was responsive to changes in quality of life with a minimally important difference of 2, with good specificity for outcomes of asthma improvement and worsening but poor sensitivity. Replication analyses yielded similar results, with a 2-point decrease (improvement) associated with improvements in quality of life. Participants with a 2-point or greater decrease (improvement) in ASSESS scores also had greater improvement in lung function and asthma control after triamcinolone, but these differences were limited to phenotypic clusters 3, 4, and 5. Participants treated with biologics also had a 2-point or greater decrease (improvement) in ASSESS scores overall.

CONCLUSIONS

The ASSESS tool is an objective measure that might be useful in epidemiologic and clinical research studies for quantification of treatment response in individual patients and phenotypic groups. However, validation studies are warranted.

BAL Cell Gene Expression in Severe Asthma Reveals Mechanisms of Severe Disease and Influences of Medications

Rationale: Gene expression of BAL cells, which samples the cellular milieu within the lower respiratory tract, has not been well studied in severe asthma.Objectives: To identify new biomolecular mechanisms underlying severe asthma by an unbiased, detailed interrogation of global gene expression.Methods: BAL cell expression was profiled in 154 asthma and control subjects. Of these participants, 100 had accompanying airway epithelial cell gene expression. BAL cell expression profiles were related to participant (age, sex, race, and medication) and sample traits (cell proportions), and then severity-related gene expression determined by correlating transcripts and coexpression networks to lung function, emergency department visits or hospitalizations in the last year, medication use, and quality-of-life scores.Measurements and Main Results: Age, sex, race, cell proportions, and medications strongly influenced BAL cell gene expression, but leading severity-related genes could be determined by carefully identifying and accounting for these influences. A BAL cell expression network enriched for cAMP signaling components most differentiated subjects with severe asthma from other subjects. Subsequently, an in vitro cellular model showed this phenomenon was likely caused by a robust upregulation in cAMP-related expression in nonsevere and β-agonist-naive subjects given a β-agonist before cell collection. Interestingly, ELISAs performed on BAL lysates showed protein levels may partly disagree with expression changes.Conclusions: Gene expression in BAL cells is influenced by factors seldomly considered. Notably, β-agonist exposure likely had a strong and immediate impact on cellular gene expression, which may not translate to important disease mechanisms or necessarily match protein levels. Leading severity-related genes were discovered in an unbiased, system-wide analysis, revealing new targets that map to asthma susceptibility loci.

Interdependence of hypoxia and β-adrenergic receptor signaling in pulmonary arterial hypertension

The β-adrenergic receptor (βAR) exists in an equilibrium of inactive and active conformational states, which shifts in response to different ligands and results in downstream signaling. In addition to cAMP, βAR signals to hypoxia-inducible factor 1 (HIF-1). We hypothesized that a βAR-active conformation (R**) that leads to HIF-1 is separable from the cAMP-activating conformation (R*) and that pulmonary arterial hypertension (PAH) patients with HIF-biased conformations would not respond to a cAMP agonist. We compared two cAMP agonists, isoproterenol and salbutamol, in vitro. Isoproterenol increased cAMP and HIF-1 activity, while salbutamol increased cAMP and reduced HIF-1. Hypoxia blunted agonist-stimulated cAMP, consistent with receptor equilibrium shifting toward HIF-activating conformations. Similarly, isoproterenol increased HIF-1 and erythropoiesis in mice, while salbutamol decreased erythropoiesis. βAR overexpression in cells increased glycolysis, which was blunted by HIF-1 inhibitors, suggesting increased βAR leads to increased hypoxia-metabolic effects. Because PAH is also characterized by HIF-related glycolytic shift, we dichotomized PAH patients in the Pulmonary Arterial Hypertension Treatment with Carvedilol for Heart Failure trial (NCT01586156) based on right ventricular (RV) glucose uptake to evaluate βAR ligands. Patients with high glucose uptake had more severe disease than those with low uptake. cAMP increased in response to isoproterenol in mononuclear cells from low-uptake patients but not in high-uptake patients' cells. When patients were treated with carvedilol for 1 wk, the low-uptake group decreased RV systolic pressures and pulmonary vascular resistance, but high-uptake patients had no physiologic responses. The findings expand the paradigm of βAR activation and uncover a novel PAH subtype that might benefit from β-blockers.

Multiview Cluster Analysis Identifies Variable Corticosteroid Response Phenotypes in Severe Asthma

Rationale: Corticosteroids (CSs) are the most effective asthma therapy, but responses are heterogeneous and systemic CSs lead to long-term side effects. Therefore, an improved understanding of the contributing factors in CS responses could enhance precision management. Although several factors have been associated with CS responsiveness, no integrated/cluster approach has yet been undertaken to identify differential CS responses. Objectives: To identify asthma subphenotypes with differential responses to CS treatment using an unsupervised multiview learning approach. Methods: Multiple-kernel k-means clustering was applied to 100 clinical, physiological, inflammatory, and demographic variables from 346 adult participants with asthma in the Severe Asthma Research Program with paired (before and 2-3 weeks after triamcinolone administration) sputum data. Machine-learning techniques were used to select the top baseline variables that predicted cluster assignment for a new patient. Measurements and Main Results: Multiple-kernel clustering revealed four clusters of individuals with asthma and different CS responses. Clusters 1 and 2 consisted of young, modestly CS-responsive individuals with allergic asthma and relatively normal lung function, separated by contrasting sputum neutrophil and macrophage percentages after CS treatment. The subjects in cluster 3 had late-onset asthma and low lung function, high baseline eosinophilia, and the greatest CS responsiveness. Cluster 4 consisted primarily of young, obese females with severe airflow limitation, little eosinophilic inflammation, and the least CS responsiveness. The top 12 baseline variables were identified, and the clusters were validated using an independent Severe Asthma Research Program test set. Conclusions: Our machine learning-based approaches provide new insights into the mechanisms of CS responsiveness in asthma, with the potential to improve disease treatment.

Racial disparities in asthma-related health care use in the National Heart, Lung, and Blood Institute's Severe Asthma Research Program

BACKGROUND

Despite advances in asthma care, disparities persist. Black patients are disproportionally affected by asthma and also have poorer outcomes compared with white patients.

OBJECTIVE

We sought to determine associations between black and white patients and asthma-related health care use, accounting for complex relationships.

METHODS

This study was completed as part of the National Heart, Lung, and Blood Institute's Severe Asthma Research Program, a prospective observational cohort. Between November 2012 and February 2015, it enrolled 579 participants 6 years and older with 1 year of observation time and complete data. Inverse probability of treatment weighting was used to balance racial groups with respect to community and family socioeconomic variables and environmental exposure variables. The primary outcome was emergency department (ED) use for asthma. Secondary outcomes included inhaled corticosteroid use, outpatient physician's office visits for asthma, and asthma-related hospitalization.

RESULTS

Black patients had greater odds of ED use over 1 year (odds ratio, 2.19; 95% CI, 1.43-3.35) but also differed in the majority (>50%) of baseline variables measured. After statistical balancing of the racial groups, the difference between black and white patients with respect to ED use no longer reached the level of significance. Instead, in secondary analyses black patients were less likely to see an outpatient physician for asthma management (adjusted odds ratio, 0.57; 95% CI, 0.38-0.85).

CONCLUSIONS

The disparity in ED use was eliminated after consideration of multiple variables. Social and environmental policies and interventions tailored to black populations with a high burden of asthma are critical to reduction (or elimination) of these disparities.

Extracellular DNA, Neutrophil Extracellular Traps, and Inflammasome Activation in Severe Asthma

Rationale: Extracellular DNA (eDNA) and neutrophil extracellular traps (NETs) are implicated in multiple inflammatory diseases. NETs mediate inflammasome activation and IL-1β secretion from monocytes and cause airway epithelial cell injury, but the role of eDNA, NETs, and IL-1β in asthma is uncertain. Objectives: To characterize the role of activated neutrophils in severe asthma through measurement of NETs and inflammasome activation. Methods: We measured sputum eDNA in induced sputum from 399 patients with asthma in the Severe Asthma Research Program-3 and in 94 healthy control subjects. We subdivided subjects with asthma into eDNA-low and -high subgroups to compare outcomes of asthma severity and of neutrophil and inflammasome activation. We also examined if NETs cause airway epithelial cell damage that can be prevented by DNase. Measurements and Main Results: We found that 13% of the Severe Asthma Research Program-3 cohort is "eDNA-high," as defined by sputum eDNA concentrations above the upper 95th percentile value in health. Compared with eDNA-low patients with asthma, eDNA-high patients had lower Asthma Control Test scores, frequent history of chronic mucus hypersecretion, and frequent use of oral corticosteroids for maintenance of asthma control (all P values <0.05). Sputum eDNA in asthma was associated with airway neutrophilic inflammation, increases in soluble NET components, and increases in caspase 1 activity and IL-1β (all P values <0.001). In in vitro studies, NETs caused cytotoxicity in airway epithelial cells that was prevented by disruption of NETs with DNase. Conclusions: High extracellular DNA concentrations in sputum mark a subset of patients with more severe asthma who have NETs and markers of inflammasome activation in their airways.

Endothelial Phenotype Evoked by Low Dose Carvedilol in Pulmonary Hypertension

Background: The therapeutic benefits of β-blockers are well established in left heart failure. The Pulmonary Arterial Hypertension Treatment with Carvedilol for Heart Failure [PAHTCH] study showed safety and possible benefit of carvedilol in pulmonary arterial hypertension (PAH) associated right heart failure over 6 months. This study aims at evaluating the short-term cardiovascular effects and early mechanistic biomarkers of carvedilol therapy.

Methods: Thirty patients with pulmonary hypertension (PH) received low dose carvedilol (3.125 mg twice daily) for 1 week prior to randomization to placebo, low-dose, or dose-escalating carvedilol therapy. Echocardiography was performed at baseline and 1 week. Exercise capacity was assessed by 6 min walk distance (6MWD). The L-arginine/nitric oxide pathway and other biological markers of endothelial function were measured.

Results: All participants tolerated 1 week of carvedilol without adverse effects. After 1 week of carvedilol, 6MWD and heart rate at peak exercise did not vary (both p > 0.1). Heart rate at rest and 1 min post walk dropped significantly (both p < 0.05) with a trend for increase in heart rate recovery (p = 0.08). Right ventricular systolic pressure (RVSP) decreased by an average of 13 mmHg (p = 0.002). Patients who had a decrease in RVSP of more than 10 mm Hg were defined as responders (n = 17), and those with a lesser drop as non-responders (n = 13). Responders had a significant drop in pulmonary vascular resistance (PVR) after 1 week of carvedilol (p = 0.004). In addition, responders had a greater decrease in heart rate at rest and 1 min post walk compared to non-responders (both p < 0.05). Responders had higher plasma arginine and global bioavailability of arginine at baseline compared to non-responders (p = 0.03 and p = 0.05, respectively). After 1 week of carvedilol, responders had greater increase in urinary nitrate (p = 0.04). Responders treated with carvedilol had a sustained drop in RVSP and PVR after 6 months of carvedilol with no change in cardiac output.

Conclusions: Low-dose carvedilol for 1 week can potentially identify a PH responder phenotype that may benefit from β-blockers that is associated with less endothelial dysfunction.

Clinical Trial Registration:http://www.clinicaltrials.gov. identifier: NCT01586156.

The utility of biomarkers in diagnosis of aspirin exacerbated respiratory disease

Background

Aspirin-exacerbated respiratory disease (AERD) is a distinct eosinophilic phenotype of severe asthma with accompanying chronic rhinosinusitis, nasal polyposis, and hypersensitivity to aspirin. Urinary 3-bromotyrosine (uBrTyr) is a noninvasive marker of eosinophil-catalyzed protein oxidation. The lack of in vitro diagnostic test makes the diagnosis of AERD difficult. We aimed to determine uBrTyr levels in patients with AERD (n = 240) and aspirin-tolerant asthma (ATA) (n = 226) and to assess whether its addition to urinary leukotriene E₄ (uLTE₄) levels and blood eosinophilia can improve the prediction of AERD diagnosis.

Methods

Clinical data, spirometry and blood eosinophilis were evaluated. UBrTyr and uLTE₄ levels were measured in urine by HPLC and ELISA, respectively.

Results

Both groups of asthmatics (AERD, n = 240; ATA, n = 226) had significantly higher uBrTyr, uLTE₄ levels, and blood eosinophils than healthy controls (HC) (n = 71) (p < 0.05). ULTE₄ levels and blood eosinophils were significantly higher in AERD as compared to ATA (p = 0.004, p < 0.0001, respectively). whereas uBrTyr levels were not significantly different between both asthma phenotypes (p = 0.34). Asthmatics with high levels of uBrTyr (> 0.101 ng/mg Cr), uLTE₄ levels (> 800 pg/mg Cr) and blood eosinophils (> 300 cells/ul) were 7 times more likely to have AERD.. However, uBrTyr did not increase the benefit for predicting AERD when uLTE₄ and blood eosinophils were already taken into account (p = 0.57).

Conclusion

UBrTyr levels are elevated both in AERD and ATA as compared to HC, but they could not differentiate between these asthma phenotypes suggesting a similar eosinophilic activation. The addition of uBrTyr to elevated uLTE4 levels and blood eosinophils did not statistically enhance the prediction of AERD diagnosis.

Neutrophil cytoplasts induce TH17 differentiation and skew inflammation toward neutrophilia in severe asthma

Severe asthma is a debilitating and treatment refractory disease. As many as half of these patients have complex neutrophil-predominant lung inflammation that is distinct from milder asthma with type 2 eosinophilic inflammation. New insights into severe asthma pathogenesis are needed. Concomitant exposure of mice to an aeroallergen and endotoxin during sensitization resulted in complex neutrophilic immune responses to allergen alone during later airway challenge. Unlike allergen alone, sensitization with allergen and endotoxin led to NETosis. In addition to neutrophil extracellular traps (NETs), enucleated neutrophil cytoplasts were evident in the lungs. Surprisingly, allergen-driven airway neutrophilia was decreased in peptidyl arginine deiminase 4-deficient mice with defective NETosis but not by deoxyribonuclease treatment, implicating the cytoplasts for the non-type 2 immune responses to allergen. Neutrophil cytoplasts were also present in mediastinal lymph nodes, and the cytoplasts activated lung dendritic cells in vitro to trigger antigen-specific interleukin-17 (IL-17) production from naïve CD4+ T cells. Bronchoalveolar lavage fluid from patients with severe asthma and high neutrophil counts had detectable NETs and cytoplasts that were positively correlated with IL-17 levels. Together, these translational findings have identified neutrophil cytoplast formation in asthmatic lung inflammation and linked the cytoplasts to T helper 17-mediated neutrophilic inflammation in severe asthma.

Nitric oxide alters hyaluronan deposition by airway smooth muscle cells

Asthma is a chronic inflammatory disease that is known to cause changes in the extracellular matrix, including changes in hyaluronan (HA) deposition. However, little is known about the factors that modulate its deposition or the potential consequences. Asthmatics with high levels of exhaled nitric oxide (NO) are characterized by greater airway reactivity and greater evidence of airway inflammation. Based on these data and our previous work we hypothesized that excessive NO promotes the pathologic production of HA by airway smooth muscle cells (SMCs). Exposure of cultured SMCs to various NO donors results in the accumulation of HA in the form of unique, cable-like structures. HA accumulates rapidly after exposure to NO and can be seen as early as one hour after NO treatment. The cable-like HA in NO-treated SMC cultures supports the binding of leukocytes. In addition, NO produced by murine macrophages (RAW cells) and airway epithelial cells also induces SMCs to produce HA cables when grown in co-culture. The modulation of HA by NO appears to be independent of soluble guanylate cyclase. Taken together, NO-induced production of leukocyte-binding HA by SMCs provides a new potential mechanism for the non-resolving airway inflammation in asthma and suggests a key role of non-immune cells in driving the chronic inflammation of the submucosa. Modulation of NO, HA and the consequent immune cell interactions may serve as potential therapeutic targets in asthma.

Activation of Anoctamin-1 Limits Pulmonary Endothelial Cell Proliferation via p38-Mitogen-activated Protein Kinase-Dependent Apoptosis

Hyperproliferative endothelial cells (ECs) play an important role in the pathogenesis of pulmonary arterial hypertension (PAH). Anoctamin (Ano)-1, a calcium-activated chloride channel, can regulate cell proliferation and cell cycle in multiple cell types. However, the expression and function of Ano1 in the pulmonary endothelium is unknown. We examined whether Ano1 was expressed in pulmonary ECs and if altering Ano1 activity would affect EC survival. Expression and localization of Ano1 in rat lung microvascular ECs (RLMVECs) was assessed using immunoblot, immunofluorescence, and subcellular fractionation. Cell counts, flow cytometry, and caspase-3 activity were used to assess changes in cell number and apoptosis in response to the small molecule Ano1 activator, Eact. Changes in mitochondrial membrane potential and mitochondrial reactive oxygen species (mtROS) were assessed using 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolylcarbocyanine, iodide (mitochondrial membrane potential dye) and mitochondrial ROS dye, respectively. Ano1 is expressed in RLMVECs and is enriched in the mitochondria. Activation of Ano1 with Eact reduced RLMVEC counts through increased apoptosis. Ano1 knockdown blocked the effects of Eact. Ano1 activation increased mtROS, reduced mitochondrial membrane potential, increased p38 phosphorylation, and induced release of apoptosis-inducing factor. mtROS inhibition attenuated Eact-mediated p38 phosphorylation. Pulmonary artery ECs isolated from patients with idiopathic PAH (IPAH) had higher expression of Ano1 and increased cell counts compared with control subjects. Eact treatment reduced cell counts in IPAH cells, which was associated with increased apoptosis. In summary, Ano1 is expressed in lung EC mitochondria. Activation of Ano1 promotes apoptosis of pulmonary ECs and human IPAH-pulmonary artery ECs, likely via increased mtROS and p38 phosphorylation, leading to apoptosis.

Effects of endogenous sex hormones on lung function and symptom control in adolescents with asthma

BACKGROUND

Although pre-puberty asthma is more prevalent in males, after puberty through middle-age, asthma is more prevalent in females. The surge of sex hormones with puberty might explain this gender switch.

METHODS

To examine the effects of sex hormones on lung function and symptoms with puberty, Tanner stage was assessed in 187 children 6-18 years of age (59% severe) enrolled in the NIH/NHLBI Severe Asthma Research Program (SARP). The effects of circulating sex hormones (n = 68; testosterone, dehydroepiandrosterone sulfate (DHEA-S), estrogen, and progesterone) on lung function and 4 week symptom control (ACQ6) in cross-section were tested by linear regression.

RESULTS

From pre-/early to late puberty, lung function did not change significantly but ACQ6 scores improved in males with severe asthma. By contrast females had lower post-BD FEV₁% and FVC% and worse ACQ6 scores with late puberty assessed by breast development. In males log DHEA-S levels, which increased by Tanner stage, associated positively with pre- and post-BD FEV₁%, pre-BD FVC %, and negatively (improved) with ACQ6. Patients treated with high-dose inhaled corticosteroids had similar levels of circulating DHEA-S. In females, estradiol levels increased by Tanner stage, and associated negatively with pre-BD FEV₁% and FVC %.

CONCLUSIONS

These results support beneficial effects of androgens on lung function and symptom control and weak deleterious effects of estradiol on lung function in children with asthma. Longitudinal data are necessary to confirm these cross-sectional findings and to further elucidate hormonal mechanisms informing sex differences in asthma features with puberty.

TRIAL REGISTRATION

ClinicalTrials.gov registration number: NCT01748175 .

Refractory airway type 2 inflammation in a large subgroup of asthmatic patients treated with inhaled corticosteroids

BACKGROUND

Airway type 2 inflammation is usually corticosteroid sensitive, but the role of type 2 inflammation as a mechanism of asthma in patients receiving high-dose inhaled corticosteroids (ICSs) is uncertain.

OBJECTIVE

We sought to determine whether airway type 2 inflammation persists in patients treated with ICSs and to evaluate the clinical features of patients with steroid-resistant airway type 2 inflammation.

METHODS

We used quantitative PCR to generate a composite metric of type 2 cytokine gene expression (type 2 gene mean [T2GM]) in induced sputum cells from healthy control subjects, patients with severe asthma receiving ICSs (n = 174), and patients with nonsevere asthma receiving ICSs (n = 85). We explored relationships between asthma outcomes and T2GM values and the utility of noninvasive biomarkers of airway T2GM.

RESULTS

Sputum cell T2GM values in asthmatic patients were significantly increased and remained high after treatment with intramuscular triamcinolone. We used the median T2GM value as a cutoff to classify steroid-treated type 2-low and steroid-resistant type 2-high (srT2-high) subgroups. Compared with patients with steroid-treated type 2-low asthma, those with srT2-high asthma were older and had more severe asthma. Blood eosinophil cell counts predicted srT2-high asthma when body mass index was less than 40 kg/m² but not when it was 40 kg/m² or greater, whereas blood IgE levels strongly predicted srT2-high asthma when age was less than 34 years but not when it was 34 years or greater.

CONCLUSION

Despite ICS therapy, many asthmatic patients have persistent airway type 2 inflammation (srT2-high asthma), and these patients are older and have more severe disease. Body weight and age modify the performance of blood-based biomarkers of airway type 2 inflammation.

Mucus plugs in patients with asthma linked to eosinophilia and airflow obstruction

BACKGROUND

The link between mucus plugs and airflow obstruction has not been established in chronic severe asthma, and the role of eosinophils and their products in mucus plug formation is unknown.

METHODS

In clinical studies, we developed and applied a bronchopulmonary segment-based scoring system to quantify mucus plugs on multidetector computed tomography (MDCT) lung scans from 146 subjects with asthma and 22 controls, and analyzed relationships among mucus plug scores, forced expiratory volume in 1 second (FEV1), and airway eosinophils. Additionally, we used airway mucus gel models to explore whether oxidants generated by eosinophil peroxidase (EPO) oxidize cysteine thiol groups to promote mucus plug formation.

RESULTS

Mucus plugs occurred in at least 1 of 20 lung segments in 58% of subjects with asthma and in only 4.5% of controls, and the plugs in subjects with asthma persisted in the same segment for years. A high mucus score (plugs in ≥ 4 segments) occurred in 67% of subjects with asthma with FEV1 of less than 60% of predicted volume, 19% with FEV1 of 60%-80%, and 6% with FEV1 greater than 80% (P < 0.001) and was associated with marked increases in sputum eosinophils and EPO. EPO catalyzed oxidation of thiocyanate and bromide by H2O2 to generate oxidants that crosslink cysteine thiol groups and stiffen thiolated hydrogels.

CONCLUSION

Mucus plugs are a plausible mechanism of chronic airflow obstruction in severe asthma, and EPO-generated oxidants may mediate mucus plug formation. We propose an approach for quantifying airway mucus plugging using MDCT lung scans and suggest that treating mucus plugs may improve airflow in chronic severe asthma.

TRIAL REGISTRATION

Clinicaltrials.gov NCT01718197, NCT01606826, NCT01750411, NCT01761058, NCT01761630, NCT01759186, NCT01716494, and NCT01760915.

FUNDING

NIH grants P01 HL107201, R01 HL080414, U10 HL109146, U10 HL109164, U10 HL109172, U10 HL109086, U10 HL109250, U10 HL109168, U10 HL109257, U10 HL109152, and P01 HL107202 and National Center for Advancing Translational Sciences grants UL1TR0000427, UL1TR000448, and KL2TR000428.

Pulmonary arterial hypertension treatment with carvedilol for heart failure: a randomized controlled trial

BACKGROUND

Right-sided heart failure is the leading cause of death in pulmonary arterial hypertension (PAH). Similar to left heart failure, sympathetic overactivation and β-adrenoreceptor (βAR) abnormalities are found in PAH. Based on successful therapy of left heart failure with β-blockade, the safety and benefits of the nonselective β-blocker/vasodilator carvedilol were evaluated in PAH.

METHODS

PAH Treatment with Carvedilol for Heart Failure (PAHTCH) is a single-center, double-blind, randomized, controlled trial. Following 1-week run-in, 30 participants were randomized to 1 of 3 arms for 24 weeks: placebo, low-fixed-dose, or dose-escalating carvedilol. Outcomes included clinical measures and mechanistic biomarkers.

RESULTS

Decreases in heart rate and blood pressure with carvedilol were well tolerated; heart rate correlated with carvedilol dose. Carvedilol-treated groups had no decrease in exercise capacity measured by 6-minute walk, but had lower heart rates at peak and after exercise, and faster heart rate recovery. Dose-escalating carvedilol was associated with reduction in right ventricular (RV) glycolytic rate and increase in βAR levels. There was no evidence of RV functional deterioration; rather, cardiac output was maintained.

CONCLUSIONS

Carvedilol is likely safe in PAH over 6 months of therapy and has clinical and mechanistic benefits associated with improved outcomes. The data provide support for longer and larger studies to establish guidelines for use of β-blockers in PAH.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01586156FUNDING. This project was supported by NIH R01HL115008 and R01HL60917 and in part by the National Center for Advancing Translational Sciences, UL1TR000439.

Arginine metabolic endotypes related to asthma severity

Aims

Arginine metabolism via inducible nitric oxide synthase (iNOS) and arginase 2 (ARG2) is higher in asthmatics than in healthy individuals. We hypothesized that a sub-phenotype of asthma might be defined by the magnitude of arginine metabolism categorized on the basis of high and low fraction of exhaled nitric oxide (F_ENO).

Methods

To test this hypothesis, asthmatics (n = 52) were compared to healthy controls (n = 51) for levels of F_ENO, serum arginase activity, and airway epithelial expression of iNOS and ARG2 proteins, in relation to clinical parameters of asthma inflammation and airway reactivity. In parallel, bronchial epithelial cells were evaluated for metabolic effects of iNOS and ARG2 expression in vitro.

Results

Asthmatics with high F_ENO (≥ 35 ppb; 44% of asthmatics) had higher expression of iNOS (P = 0.04) and ARG2 (P = 0.05) in the airway, indicating F_ENO is a marker of the high arginine metabolic endotype. High F_ENO asthmatics had the lowest FEV₁% (P < 0.001), FEV₁/FVC (P = 0.0002) and PC₂₀ (P < 0.001) as compared to low F_ENO asthmatics or healthy controls. Low F_ENO asthmatics had near normal iNOS and ARG2 expression (both P > 0.05), and significantly higher PC₂₀ (P < 0.001) as compared to high F_ENO asthmatics. In vitro studies to evaluate metabolic effects showed that iNOS overexpression and iNOS+ARG2 co-expression in a human bronchial epithelial cell line led to greater reliance on glycolysis with higher rate of pyruvate going to lactate.

Conclusions

The high F_ENO phenotype represents a large portion of the asthma population, and is typified by greater arginine metabolism and more severe and reactive asthma.

Inflammatory and Comorbid Features of Patients with Severe Asthma and Frequent Exacerbations

RATIONALE

Reducing asthma exacerbation frequency is an important criterion for approval of asthma therapies, but the clinical features of exacerbation-prone asthma (EPA) remain incompletely defined.

OBJECTIVES

To describe the clinical, physiologic, inflammatory, and comorbidity factors associated with EPA.

METHODS

Baseline data from the NHLBI Severe Asthma Research Program (SARP)-3 were analyzed. An exacerbation was defined as a burst of systemic corticosteroids lasting 3 days or more. Patients were classified by their number of exacerbations in the past year: none, few (one to two), or exacerbation prone (≥3). Replication of a multivariable model was performed with data from the SARP-1 + 2 cohort.

MEASUREMENTS AND MAIN RESULTS

Of 709 subjects in the SARP-3 cohort, 294 (41%) had no exacerbations and 173 (24%) were exacerbation prone in the prior year. Several factors normally associated with severity (asthma duration, age, sex, race, and socioeconomic status) did not associate with exacerbation frequency in SARP-3; bronchodilator responsiveness also discriminated exacerbation proneness from asthma severity. In the SARP-3 multivariable model, blood eosinophils, body mass index, and bronchodilator responsiveness were positively associated with exacerbation frequency (rate ratios [95% confidence interval], 1.6 [1.2-2.1] for every log unit of eosinophils, 1.3 [1.1-1.4] for every 10 body mass index units, and 1.2 [1.1-1.4] for every 10% increase in bronchodilatory responsiveness). Chronic sinusitis and gastroesophageal reflux were also associated with exacerbation frequency (1.7 [1.4-2.1] and 1.6 [1.3-2.0]), even after adjustment for multiple factors. These effects were replicated in the SARP-1 + 2 multivariable model.

CONCLUSIONS

EPA may be a distinct susceptibility phenotype with implications for the targeting of exacerbation prevention strategies. Clinical trial registered with www.clinicaltrials.gov (NCT 01760915).

Gene Expression Correlated with Severe Asthma Characteristics Reveals Heterogeneous Mechanisms of Severe Disease

RATIONALE

Severe asthma (SA) is a heterogeneous disease with multiple molecular mechanisms. Gene expression studies of bronchial epithelial cells in individuals with asthma have provided biological insight and underscored possible mechanistic differences between individuals.

OBJECTIVES

Identify networks of genes reflective of underlying biological processes that define SA.

METHODS

Airway epithelial cell gene expression from 155 subjects with asthma and healthy control subjects in the Severe Asthma Research Program was analyzed by weighted gene coexpression network analysis to identify gene networks and profiles associated with SA and its specific characteristics (i.e., pulmonary function tests, quality of life scores, urgent healthcare use, and steroid use), which potentially identified underlying biological processes. A linear model analysis confirmed these findings while adjusting for potential confounders.

MEASUREMENTS AND MAIN RESULTS

Weighted gene coexpression network analysis constructed 64 gene network modules, including modules corresponding to T1 and T2 inflammation, neuronal function, cilia, epithelial growth, and repair mechanisms. Although no network selectively identified SA, genes in modules linked to epithelial growth and repair and neuronal function were markedly decreased in SA. Several hub genes of the epithelial growth and repair module were found located at the 17q12-21 locus, near a well-known asthma susceptibility locus. T2 genes increased with severity in those treated with corticosteroids but were also elevated in untreated, mild-to-moderate disease compared with healthy control subjects. T1 inflammation, especially when associated with increased T2 gene expression, was elevated in a subgroup of younger patients with SA.

CONCLUSIONS

In this hypothesis-generating analysis, gene expression networks in relation to asthma severity provided potentially new insight into biological mechanisms associated with the development of SA and its phenotypes.

Antioxidant defense and oxidative damage vary widely among high-altitude residents

OBJECTIVES

People living at high altitude experience unavoidable low oxygen levels (hypoxia). While acute hypoxia causes an increase in oxidative stress and damage despite higher antioxidant activity, the consequences of chronic hypoxia are poorly understood. The aim of the present study is to assess antioxidant activity and oxidative damage in high-altitude natives and upward migrants.

METHODS

Individuals from two indigenous high-altitude populations (Amhara, n = 39), (Sherpa, n = 34), one multigenerational high-altitude population (Oromo, n = 42), one upward migrant population (Nepali, n = 12), and two low-altitude reference populations (Amhara, n = 29; Oromo, n = 18) provided plasma for measurement of superoxide dismutase (SOD) activity as a marker of antioxidant capacity, and urine for measurement of 8-hydroxy-2'-deoxyguanosine (8-OHdG) as a marker of DNA oxidative damage.

RESULTS

High-altitude Amhara and Sherpa had the highest SOD activity, while highland Oromo and Nepalis had the lowest among high-altitude populations. High-altitude Amhara had the lowest DNA damage, Sherpa intermediate levels, and high-altitude Oromo had the highest.

CONCLUSIONS

High-altitude residence alone does not associate with high antioxidant defenses; residence length appears to be influential. The single-generation upward migrant sample had the lowest defense and nearly the highest DNA damage. The two high-altitude resident samples with millennia of residence had higher defenses than the two with multiple or single generations of residence.

ALX receptor ligands define a biochemical endotype for severe asthma

BACKGROUND

In health, inflammation resolution is an active process governed by specialized proresolving mediators and receptors. ALX/FPR2 receptors (ALX) are targeted by both proresolving and proinflammatory ligands for opposing signaling events, suggesting pivotal roles for ALX in the fate of inflammatory responses. Here, we determined if ALX expression and ligands were linked to severe asthma (SA).

METHODS

ALX expression and levels of proresolving ligands (lipoxin A4 [LXA4], 15-epi-LXA4, and annexin A1 [ANXA1]), and a proinflammatory ligand (serum amyloid A [SAA]) were measured in bronchoscopy samples collected in Severe Asthma Research Program-3 (SA [n = 69], non-SA [NSA, n = 51] or healthy donors [HDs, n = 47]).

RESULTS

Bronchoalveolar lavage (BAL) fluid LXA4 and 15-epi-LXA4 were decreased and SAA was increased in SA relative to NSA. BAL macrophage ALX expression was increased in SA. Subjects with LXA4loSAAhi levels had increased BAL neutrophils, more asthma symptoms, lower lung function, increased relative risk for asthma exacerbation, sinusitis, and gastroesophageal reflux disease, and were assigned more frequently to SA clinical clusters. SAA and aliquots of LXA4loSAAhi BAL fluid induced IL-8 production by lung epithelial cells expressing ALX receptors, which was inhibited by coincubation with 15-epi-LXA4.

CONCLUSIONS

Together, these findings have established an association between select ALX receptor ligands and asthma severity that define a potentially new biochemical endotype for asthma and support a pivotal functional role for ALX signaling in the fate of lung inflammation.

TRIAL REGISTRATION

Severe Asthma Research Program-3 (SARP-3; ClinicalTrials.gov NCT01606826)FUNDING Sources. National Heart, Lung and Blood Institute, the NIH, and the German Society of Pediatric Pneumology.

Enhancing Insights into Pulmonary Vascular Disease through a Precision Medicine Approach. A Joint NHLBI-Cardiovascular Medical Research and Education Fund Workshop Report

The Division of Lung Diseases of the NHLBI and the Cardiovascular Medical Education and Research Fund held a workshop to discuss how to leverage the anticipated scientific output from the recently launched "Redefining Pulmonary Hypertension through Pulmonary Vascular Disease Phenomics" (PVDOMICS) program to develop newer approaches to pulmonary vascular disease. PVDOMICS is a collaborative, protocol-driven network to analyze all patient populations with pulmonary hypertension to define novel pulmonary vascular disease (PVD) phenotypes. Stakeholders, including basic, translational, and clinical investigators; clinicians; patient advocacy organizations; regulatory agencies; and pharmaceutical industry experts, joined to discuss the application of precision medicine to PVD clinical trials. Recommendations were generated for discussion of research priorities in line with NHLBI Strategic Vision Goals that include: (1) A national effort, involving all the stakeholders, should seek to coordinate biosamples and biodata from all funded programs to a web-based repository so that information can be shared and correlated with other research projects. Example programs sponsored by NHLBI include PVDOMICS, Pulmonary Hypertension Breakthrough Initiative, the National Biological Sample and Data Repository for PAH, and the National Precision Medicine Initiative. (2) A task force to develop a master clinical trials protocol for PVD to apply precision medicine principles to future clinical trials. Specific features include: (a) adoption of smaller clinical trials that incorporate biomarker-guided enrichment strategies, using adaptive and innovative statistical designs; and (b) development of newer endpoints that reflect well-defined and clinically meaningful changes. (3) Development of updated and systematic variables in imaging, hemodynamic, cellular, genomic, and metabolic tests that will help precisely identify individual and shared features of PVD and serve as the basis of novel phenotypes for therapeutic interventions.

Gene Expression Correlated with Severe Asthma Characteristics Reveals Heterogeneous Mechanisms of Severe Disease

RATIONALE

Severe asthma (SA) is a heterogeneous disease with multiple molecular mechanisms. Gene expression studies of bronchial epithelial cells in individuals with asthma have provided biological insight and underscored possible mechanistic differences between individuals.

OBJECTIVES

Identify networks of genes reflective of underlying biological processes that define SA.

METHODS

Airway epithelial cell gene expression from 155 subjects with asthma and healthy control subjects in the Severe Asthma Research Program was analyzed by weighted gene coexpression network analysis to identify gene networks and profiles associated with SA and its specific characteristics (i.e., pulmonary function tests, quality of life scores, urgent healthcare use, and steroid use), which potentially identified underlying biological processes. A linear model analysis confirmed these findings while adjusting for potential confounders.

MEASUREMENTS AND MAIN RESULTS

Weighted gene coexpression network analysis constructed 64 gene network modules, including modules corresponding to T1 and T2 inflammation, neuronal function, cilia, epithelial growth, and repair mechanisms. Although no network selectively identified SA, genes in modules linked to epithelial growth and repair and neuronal function were markedly decreased in SA. Several hub genes of the epithelial growth and repair module were found located at the 17q12-21 locus, near a well-known asthma susceptibility locus. T2 genes increased with severity in those treated with corticosteroids but were also elevated in untreated, mild-to-moderate disease compared with healthy control subjects. T1 inflammation, especially when associated with increased T2 gene expression, was elevated in a subgroup of younger patients with SA.

CONCLUSIONS

In this hypothesis-generating analysis, gene expression networks in relation to asthma severity provided potentially new insight into biological mechanisms associated with the development of SA and its phenotypes.

Effects of Age and Disease Severity on Systemic Corticosteroid Responses in Asthma

RATIONALE

Phenotypic distinctions between severe asthma (SA) and nonsevere asthma (NONSA) may be confounded by differential adherence or incorrect use of corticosteroids.

OBJECTIVES

To determine if there are persistent phenotypic distinctions between SA (as defined by 2014 American Thoracic Society/European Respiratory Society guidelines) and NONSA after intramuscular triamcinolone acetonide (TA), and to identify predictors of a corticosteroid response in these populations.

METHODS

A total of 526 adults age 18 years and older (315 SA) and 188 children age 6 to less than 18 years (107 SA) in the NHLBI Severe Asthma Research Program III were characterized before and 3 weeks after TA. The primary outcome for corticosteroid response was defined as greater than or equal to 10-point improvement in percent predicted FEV1.

MEASUREMENTS AND MAIN RESULTS

Adult asthma groups exhibited a small but significant mean FEV1% predicted improvement after TA (SA group mean difference, 3.4%; 95% confidence interval, 2.2-4.7%; P = 0.001), whereas children did not. Adult SA continued to manifest lower FEV1 and worse asthma control as compared with NONSA after TA. In children, after TA only prebronchodilator FEV1 distinguished SA from NONSA. A total of 21% of adults with SA and 20% of children with SA achieved greater than or equal to 10% improvement after TA. Baseline bronchodilator response and fractional exhaled nitric oxide had good sensitivity and specificity for predicting response in all groups except children with NONSA.

CONCLUSIONS

One in five patients with SA exhibit greater than or equal to 10% improvement in FEV1 with parenteral corticosteroid. Those likely to respond had greater bronchodilator responsiveness and fractional exhaled nitric oxide levels. In adults, differences in airflow obstruction and symptoms between SA and NONSA persist after parenteral corticosteroids, suggesting a component of corticosteroid nonresponsive pathobiology in adults with SA that may differ in children. Clinical trial registered with www.clinicaltrials.gov (NCT 01606826).

Genomic stability of pulmonary artery endothelial colony-forming cells in culture

Pulmonary vascular remodeling, including proliferation and migration of pulmonary artery endothelial cells (PAEC), is a pathologic hallmark of pulmonary arterial hypertension (PAH). Multiple studies have shown evidence of increased levels of DNA damage and lineage-specific genetic changes in PAH lung vascular cells, suggesting increased genomic instability. Highly proliferative endothelial colony-forming cell (ECFC) clones can be isolated from PAEC. Here we utilized ECFC to track chromosomal copy number of 20 PAH and eight control clones across serial passages using genome-wide microarrays. All PAH clones were genomically stable for at least 20–22 population doublings. At very late passages, ECFC developed a highly aneuploid karyotype, but this was generally associated with senescence and was common to both PAH and controls. We also utilized ECFC to isolate the chromosomally abnormal cells from a mixed population of PAH PAEC. Analysis of PAEC harboring two different changes affecting chromosomes 1 and X demonstrated that both abnormalities were present in the same clone, indicating they originated in a common ancestral cell. In a second case, with a partial duplication of chromosome 17, clones carrying the duplication were more frequent at later passages than chromosomally normal clones from the same PAEC culture, suggesting the rearrangement may confer a proliferative advantage. Overall, this small study suggests that endothelial cells from PAH lungs are stable in culture, but that when chromosome abnormalities do occur, they may confer a selective advantage that allows expansion of the abnormal cell population and could contribute to lung vascular remodeling in vivo.

Modulation of Endothelial Bone Morphogenetic Protein Receptor Type 2 Activity by Vascular Endothelial Growth Factor Receptor 3 in Pulmonary Arterial Hypertension

BACKGROUND

Bone morphogenetic protein (BMP) signaling has multiple roles in the development and function of the blood vessels. In humans, mutations in BMP receptor type 2 (BMPR2), a key component of BMP signaling, have been identified in the majority of patients with familial pulmonary arterial hypertension (PAH). However, only a small subset of individuals with BMPR2 mutation develops PAH, suggesting that additional modifiers of BMPR2 function play an important role in the onset and progression of PAH.

METHODS

We used a combination of studies in zebrafish embryos and genetically engineered mice lacking endothelial expression of Vegfr3 to determine the interaction between vascular endothelial growth factor receptor 3 (VEGFR3) and BMPR2. Additional in vitro studies were performed by using human endothelial cells, including primary lung endothelial cells from subjects with PAH.

RESULTS

Attenuation of Vegfr3 in zebrafish embryos abrogated Bmp2b-induced ectopic angiogenesis. Endothelial cells with disrupted VEGFR3 expression failed to respond to exogenous BMP stimulation. Mechanistically, VEGFR3 is physically associated with BMPR2 and facilitates ligand-induced endocytosis of BMPR2 to promote phosphorylation of SMADs and transcription of ID genes. Conditional, endothelial-specific deletion of Vegfr3 in mice resulted in impaired BMP signaling responses, and significantly worsened hypoxia-induced pulmonary hypertension. Consistent with these data, we found significant decrease in VEGFR3 expression in pulmonary arterial endothelial cells from human PAH subjects, and reconstitution of VEGFR3 expression in PAH pulmonary arterial endothelial cells restored BMP signaling responses.

CONCLUSIONS

Our findings identify VEGFR3 as a key regulator of endothelial BMPR2 signaling and a potential determinant of PAH penetrance in humans.

Metabolic and Functional Evaluation of the Heart and Lungs in Pulmonary Hypertension by Gated 2-[18F]-Fluoro-2-deoxy-D-glucose Positron Emission Tomography

Pulmonary hypertension (PH) is associated with a metabolic shift towards glycolysis in both the right ventricle and lung. This results in increased glucose uptake to compensate for the lower energy yield of glycolysis, which creates a potential for 2-[18F] fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) to be a useful tool in the evaluation of participants with PH. We investigated the utility of PET for PH by comparing FDG-PET uptake in the right ventricle and lungs in 30 participants with PH and eight healthy controls and correlating these measurements with echocardiographic (ECHO) measurements and other traditional assessments commonly used in PH. All participants underwent gated FDG-PET scanning in the fasting state, ECHO, six-minute walk test (6MWT), and blood draw for NT-proBNP. Participants also completed the CAMPHOR questionnaire. Right ventricular (RV) end-diastolic and end-systolic volumes, RV ejection fraction, and FDG uptake by PET were significantly different between PH and healthy controls and strongly correlated with plasma NT-proBNP levels and RV ECHO parameters including TAPSE, RV systolic pressure, Tei index, and global peak systolic strain. In addition, lung standardized uptake value (SUV) was also found to be significantly higher in participants with PH than healthy controls. However, lung SUV did not show any significant correlations with NT-proBNP levels, 6MWT, or functional and pressure measurements by ECHO. In this study, we demonstrated the ability to evaluate both lung and right heart metabolism and function in PH by using a single gated FDG-PET scan.

Natural killer cell-mediated inflammation resolution is disabled in severe asthma

Severe asthma is typically characterized by chronic airway inflammation that is refractory to corticosteroids and associated with excess morbidity. Patients were recruited into the National Heart, Lung, and Blood Institute-sponsored Severe Asthma Research Program and comprehensively phenotyped by bronchoscopy. Bronchoalveolar lavage (BAL) cells were analyzed by flow cytometry. Compared with healthy individuals (n = 21), patients with asthma (n = 53) had fewer BAL natural killer (NK) cells. Patients with severe asthma (n = 29) had a marked increase in the ratios of CD4⁺ T cells to NK cells and neutrophils to NK cells. BAL NK cells in severe asthma were skewed toward the cytotoxic CD56^dim subset, with significantly increased BAL fluid levels of the cytotoxic mediator granzyme A. The numbers of BAL CD56^dim NK cells and CCR6^-CCR4^- T helper 1-enriched CD4⁺ T cells correlated inversely with lung function [forced expiratory volume in 1 s (FEV₁) % predicted] in asthma. Relative to cells from healthy controls, peripheral blood NK cells from asthmatic patients had impaired killing of K562 myeloid target cells despite releasing more cytotoxic mediators. Ex vivo exposure to dexamethasone markedly decreased blood NK cell lysis of target cells and cytotoxic mediator release. NK cells expressed airway lipoxin A₄/formyl peptide receptor 2 receptors, and in contrast to dexamethasone, lipoxin A₄-exposed NK cells had preserved functional responses. Together, our findings indicate that the immunology of the severe asthma airway is characterized by decreased NK cell cytotoxicity with increased numbers of target leukocytes, which is exacerbated by corticosteroids that further disable NK cell function. These failed resolution mechanisms likely contribute to persistent airway inflammation in severe asthma.

Co-Occurrence of Asthma and Nephrolithiasis in Children

It has been proposed that epithelial dysfunction and inflammation may predispose patients to kidney stone formation. Asthma is another chronic condition related to epithelial dysfunction and inflammation. We hypothesized that pediatric patients with asthma would have an increased prevalence of nephrolithiasis. Furthermore, we investigated if asthma patients with nephrolithiasis have clinical characteristics and urine profiles that point to mechanisms of stone formation. We evaluated 865 pediatric patients who had a diagnosis of nephrolithiasis. Clinical/demographic data and 24 hour urine samples were compared between asthma + stone (n = 142) and stone only patients. Data from asthmatics without stone were also available for evaluation of medication differences among asthma + stone and asthma only patients. The prevalence of nephrolithiasis in the pediatric population at our institution was 0.08% vs. 0.31% in our pediatric asthmatic population. The prevalence of asthma in our pediatric population was 6.8% vs. 26.7% in our pediatric stone patients. Asthma + stone patients were more likely to be on a combination inhaled corticosteroid + long acting beta agonist inhaler as compared to age/gender/BMI matched asthma patients without stone (29.7% vs. 13.7%, p = 0.0012). 259 kidney stone patients had 24 hour urine samples for comparison. There was no difference in 24 hour urine profiles between asthma + stone and stone only patients. Children with asthma have a 4-fold greater prevalence of kidney stones than the general pediatric population. Similarly, children with kidney stones have a 4-fold greater prevalence of asthma. This correlation may suggest a mechanistic link between asthma and nephrolithiasis. Further investigation is needed to elucidate the pathophysiologic origin of this relationship.

Hypoxia sensing through -adrenergic receptors

Life-sustaining responses to low oxygen, or hypoxia, depend on signal transduction by HIFs, but the underlying mechanisms by which cells sense hypoxia are not completely understood. Based on prior studies suggesting a link between the β-adrenergic receptor (β-AR) and hypoxia responses, we hypothesized that the β-AR mediates hypoxia sensing and is necessary for HIF-1α accumulation. Beta blocker treatment of mice suppressed hypoxia induction of renal HIF-1α accumulation, erythropoietin production, and erythropoiesis in vivo. Likewise, beta blocker treatment of primary human endothelial cells in vitro decreased hypoxia-mediated HIF-1α accumulation and binding to target genes and the downstream hypoxia-inducible gene expression. In mechanistic studies, cAMP-activated PKA and/or GPCR kinases (GRK), which both participate in β-AR signal transduction, were investigated. Direct activation of cAMP/PKA pathways did not induce HIF-1α accumulation, and inhibition of PKA did not blunt HIF-1α induction by hypoxia. In contrast, pharmacological inhibition of GRK, or expression of a GRK phosphorylation-deficient β-AR mutant in cells, blocked hypoxia-mediated HIF-1α accumulation. Mass spectrometry-based quantitative analyses revealed a hypoxia-mediated β-AR phosphorylation barcode that was different from the classical agonist phosphorylation barcode. These findings indicate that the β-AR is fundamental to the molecular and physiological responses to hypoxia.

Alternative hematological and vascular adaptive responses to high-altitude hypoxia in East African highlanders

Elevation of hemoglobin concentration, a common adaptive response to high-altitude hypoxia, occurs among Oromo but is dampened among Amhara highlanders of East Africa. We hypothesized that Amhara highlanders offset their smaller hemoglobin response with a vascular response. We tested this by comparing Amhara and Oromo highlanders at 3,700 and 4,000 m to their lowland counterparts at 1,200 and 1,700 m. To evaluate vascular responses, we assessed urinary levels of nitrate (NO₃^-) as a readout of production of the vasodilator nitric oxide and its downstream signal transducer cyclic guanosine monophosphate (cGMP), along with diastolic blood pressure as an indicator of vasomotor tone. To evaluate hematological responses, we measured hemoglobin and percent oxygen saturation of hemoglobin. Amhara highlanders, but not Oromo, had higher NO₃^- and cGMP compared with their lowland counterparts. NO₃^- directly correlated with cGMP (Amhara R² = 0.25, P < 0.0001; Oromo R² = 0.30, P < 0.0001). Consistent with higher levels of NO₃^- and cGMP, diastolic blood pressure was lower in Amhara highlanders. Both highland samples had apparent left shift in oxyhemoglobin saturation characteristics and maintained total oxyhemoglobin content similar to their lowland counterparts. However, deoxyhemoglobin levels were significantly higher, much more so among Oromo than Amhara. In conclusion, the Amhara balance minimally elevated hemoglobin with vasodilatory response to environmental hypoxia, whereas Oromo rely mainly on elevated hemoglobin response. These results point to different combinations of adaptive responses in genetically similar East African highlanders.

Expression of asthma susceptibility genes in bronchial epithelial cells and bronchial alveolar lavage in the Severe Asthma Research Program (SARP) cohort

OBJECTIVE

Genome-wide association studies (GWASs) have identified genes associated with asthma, however expression of these genes in asthma-relevant tissues has not been studied. This study tested expression and correlation between GWAS-identified asthma genes and asthma or asthma severity.

METHODS

Correlation analyses of expression levels of GWAS-identified asthma genes and asthma-related biomarkers were performed in cells from human bronchial epithelial biopsy (BEC, n = 107) and bronchial alveolar lavage (BAL, n = 94).

RESULTS

Expression levels of asthma genes between BEC and BAL and with asthma or asthma severity were weakly correlated. The expression levels of IL18R1 were consistently higher in asthma than controls or in severe asthma than mild/moderate asthma in BEC and BAL (p < 0.05). In RAD50-IL13 region, the expression levels of RAD50, not IL4, IL5, or IL13, were positively correlated between BEC and BAL (ρ = 0.53, P = 4.5 × 10(-6)). The expression levels of IL13 were positively correlated with IL5 in BEC (ρ = 0.35, P = 1.9 × 10(-4)) and IL4 in BAL (ρ = 0.42, P = 2.5 × 10(-5)), respectively. rs3798134 in RAD50, a GWAS-identified SNP, was correlated with IL13 expression and the expression levels of IL13 were correlated with asthma (P = 0.03). rs17772583 in RAD50 was significantly correlated with RAD50 expression in BAL and BEC (P = 7.4 × 10(-7) and 0.04) but was not associated with asthma.

CONCLUSIONS

This is the first report studying the expression of GWAS-identified asthma genes in BEC and BAL. IL13, rather than RAD50, IL4, or IL5, is more likely to be the asthma susceptibility gene. Our study illustrates tissue-specific expression of asthma-related genes. Therefore, whenever possible, disease-relevant tissues should be used for transcription analysis.

Eosinophil Peroxidase Catalyzed Protein Carbamylation Participates in Asthma

The biochemical mechanisms through which eosinophils contribute to asthma pathogenesis are unclear. Here we show eosinophil peroxidase (EPO), an abundant granule protein released by activated eosinophils, contributes to characteristic asthma-related phenotypes through oxidative posttranslational modification (PTM) of proteins in asthmatic airways through a process called carbamylation. Using a combination of studies we now show EPO uses plasma levels of the pseudohalide thiocyanate (SCN^-) as substrate to catalyze protein carbamylation, as monitored by PTM of protein lysine residues into N^ϵ-carbamyllysine (homocitrulline), and contributes to the pathophysiological sequelae of eosinophil activation. Studies using EPO-deficient mice confirm EPO serves as a major enzymatic source for protein carbamylation during eosinophilic inflammatory models, including aeroallergen challenge. Clinical studies similarly revealed significant enrichment in carbamylation of airway proteins recovered from atopic asthmatics versus healthy controls in response to segmental allergen challenge. Protein-bound homocitrulline is shown to be co-localized with EPO within human asthmatic airways. Moreover, pathophysiologically relevant levels of carbamylated protein either incubated with cultured human airway epithelial cells in vitro, or provided as an aerosolized exposure in non-sensitized mice, induced multiple asthma-associated phenotypes including induction of mucin, Th2 cytokines, IFNγ, TGFβ, and epithelial cell apoptosis. Studies with scavenger receptor-A1 null mice reveal reduced IL-13 generation following exposure to aerosolized carbamylated protein, but no changes in other asthma-related phenotypes. In summary, EPO-mediated protein carbamylation is promoted during allergen-induced asthma exacerbation, and can both modulate immune responses and trigger a cascade of many of the inflammatory signals present in asthma.

Plugs of the Air Passages: A Clinicopathologic Review

Although mucus is a normal product of the tracheobronchial tree, some diseases of the respiratory tract are characterized by unusually thick (inspissated) forms of mucus that accumulate within the airways. These are known as mucus plugs. The pathologic composition of these plugs is surprisingly diverse and, in many cases, correlates with distinctive clinical, radiologic, and bronchoscopic findings. The best-known conditions that involve mucus plugs are allergic bronchopulmonary aspergillosis, plastic bronchitis, and asthma. Other lung diseases occasionally associated with plugs within the airways include Aspergillus tracheobronchitis, hyper-IgE syndrome, exogenous lipoid pneumonia, pulmonary alveolar proteinosis, and chronic eosinophilic pneumonia. In this review, we describe and illustrate the bronchoscopic, pathologic, and imaging findings in respiratory disorders characterized by mucus plugs or plugs composed of other similar materials. Recognition of the characteristic appearance and differential diagnosis of mucus plugs will hopefully facilitate diagnosis and management of these diseases.

Impact of Age and Sex on Outcomes and Hospital Cost of Acute Asthma in the United States, 2011-2012

Background

Worldwide, asthma is a leading cause of morbidity, mortality and economic burden, with significant gender and racial disparities. However, little attention has been given to the independent role of age on lifetime asthma severity and hospitalization. We aimed to assess the effect of age, gender, race and ethnicity on indicators of asthma severity including asthma related hospitalization, mortality, hospital cost, and the rate of respiratory failure.

Methods

We analyzed the 2011 and 2012 Healthcare Cost and Utilization Project- National Inpatient Sample (NIS). We validated and extended those results using the National Heart, Lung, and Blood Institute-Severe Asthma Research Program (SARP; 2002–2011) database. Severe asthma was prospectively defined using the stringent American Thoracic Society (ATS) definition.

Results

Hospitalization for asthma was reported in 372,685 encounters in 2012 and 368,528 in 2011. The yearly aggregate cost exceeded $2 billion. There were distinct bimodal distributions for hospitalization age, with an initial peak at 5 years and a second at 50 years. Likewise, this bimodal age distribution of patients with severe asthma was identified using SARP. Males comprised the majority of individuals in the first peak, but women in the second. Aggregate hospital cost mirrored the bimodal peak distribution. The probability of respiratory failure increased with age until the age of 60, after which it continued to increase in men, but not in women.

Conclusions

Severe asthma is primarily a disease of young boys and middle age women. Greater understanding of the biology of lung aging and influence of sex hormones will allow us to plan for targeted interventions during these times in order to reduce the personal and societal burdens of asthma.

Plasma interleukin-6 concentrations, metabolic dysfunction, and asthma severity: a cross-sectional analysis of two cohorts

BACKGROUND

Severe asthma is a complex heterogeneous disease associated with older age and obesity. The presence of eosinophilic (type 2) inflammation in some but not all patients with severe asthma predicts responsiveness to current treatments, but new treatment approaches will require a better understanding of non-type 2 mechanisms of severe asthma. We considered the possibility that systemic inflammation, which arises in subgroups of obese and older patients, increases the severity of asthma. Interleukin-6 (IL-6) is a biomarker of systemic inflammation and metabolic dysfunction, and we aimed to explore the association between IL-6 concentrations, metabolic dysfunction, and asthma severity.

METHODS

In this cross-sectional analysis, patients were recruited from two cohorts: mainly non-severe asthmatics from the University of California San Francisco (UCSF) and mainly severe asthmatics from the Severe Asthma Research Program (SARP). We generated a reference range for plasma IL-6 in a cohort of healthy control patients. We compared the clinical characteristics of asthmatics with plasma IL-6 concentrations above (IL-6 high) and below (IL-6 low) the upper 95% centile value for plasma IL-6 concentration in the healthy cohort. We also compared how pulmonary function, frequency of asthma exacerbations, and frequency of severe asthma differed between IL-6 low and IL-6 high asthma populations in the two asthma cohorts.

FINDINGS

Between Jan 1, 2005, and Dec 31, 2014, we recruited 249 patients from UCSF and between Nov 1, 2012, and Oct 1, 2014, we recruited 387 patients from SARP. The upper 95th centile value for plasma IL-6 concentration in the healthy cohort (n=93) was 3·1 pg/mL, and 14% (36/249) of UCSF cohort and 26% (102/387) of the SARP cohort had plasma IL-6 concentrations above this upper limit. The IL-6 high patients in both asthma cohorts had a significantly higher average BMI (p<0·0001) and a higher prevalence of hypertension (p<0·0001) and diabetes (p=0·04) than the IL-6 low patients. IL-6 high patients also had significantly worse lung function and more frequent asthma exacerbations than IL-6 low patients (all p values <0·0001). Although 80% (111/138) of IL-6 high asthmatic patients were obese, 62% (178/289) of obese asthmatic patients were IL-6 low. Among obese patients, the forced expiratory volume in 1 s (FEV1) was significantly lower in IL-6 high than in IL-6 low patients (mean percent predicted FEV1=70·8% [SD 19·5] vs 78·3% [19·7]; p=0·002), and the percentage of patients reporting an asthma exacerbation in the past 1-2 years was higher in IL-6 high than in IL-6 low patients (66% [73/111] vs 48% [85/178]; p=0·003). Among non-obese asthmatics, FEV1 values and the frequency of asthma exacerbations within the past 1-2 years were also significantly worse in IL-6 high than in IL-6 low patients (mean FEV1 66·4% [SD 23·1] vs 83·2% [20·4] predicted; p<0·0001; 59% [16/27] vs 34% [108/320]; p=0·01).

INTERPRETATION

Systemic IL-6 inflammation and clinical features of metabolic dysfunction, which occur most commonly in a subset of obese asthma patients but also in a small subset of non-obese patients, are associated with more severe asthma. These data provide strong rationale to undertake clinical trials of IL-6 inhibitors or treatments that reduce metabolic dysfunction in a subset of patients with severe asthma. Plasma IL-6 is a biomarker that could guide patient stratification in these trials.

FUNDING

NIH and the Parker B Francis Foundation.

Distal vessel stiffening is an early and pivotal mechanobiological regulator of vascular remodeling and pulmonary hypertension

Pulmonary arterial (PA) stiffness is associated with increased mortality in patients with pulmonary hypertension (PH); however, the role of PA stiffening in the pathogenesis of PH remains elusive. Here, we show that distal vascular matrix stiffening is an early mechanobiological regulator of experimental PH. We identify cyclooxygenase-2 (COX-2) suppression and corresponding reduction in prostaglandin production as pivotal regulators of stiffness-dependent vascular cell activation. Atomic force microscopy microindentation demonstrated early PA stiffening in experimental PH and human lung tissue. Pulmonary artery smooth muscle cells (PASMC) grown on substrates with the stiffness of remodeled PAs showed increased proliferation, decreased apoptosis, exaggerated contraction, enhanced matrix deposition, and reduced COX-2-derived prostanoid production compared with cells grown on substrates approximating normal PA stiffness. Treatment with a prostaglandin I₂ analog abrogated monocrotaline-induced PA stiffening and attenuated stiffness-dependent increases in proliferation, matrix deposition, and contraction in PASMC. Our results suggest a pivotal role for early PA stiffening in PH and demonstrate the therapeutic potential of interrupting mechanobiological feedback amplification of vascular remodeling in experimental PH.

Mitochondrial Haplogroups and Risk of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a serious and often fatal disease. It is a panvasculopathy of the pulmonary microcirculation characterized by vasoconstriction and arterial obstruction due to vascular proliferation and remodeling and ultimately right ventricular failure. Mitochondrial dysfunction is a universal finding in pulmonary vascular cells of patients with PAH, and is mechanistically linked to disease origins in animal models of pulmonary hypertension. Mitochondria have their own circular DNA (mtDNA), which can be subgrouped into polymorphic haplogroup variants, some of which have been identified as at-risk or protective from cardiovascular and/or neurodegenerative diseases. Here, we hypothesized that mitochondrial haplogroups may be associated with PAH. To test this, mitochondrial haplogroups were determined in a cohort of PAH patients and controls [N = 204 Caucasians (125 PAH and 79 controls) and N = 46 African Americans (13 PAH and 33 controls)]. Haplogroup L was associated with a lower rate of PAH as compared to macrohaplogroups N and M. When haplogroups were nested based on ancestral inheritance and controlled for age, gender and race, haplogroups M and HV, JT and UK of the N macro-haplogroup had significantly higher rates of PAH compared to the ancestral L (L0/1/2 and L3) (all p ≤ 0.05). Overall, the findings suggest that mitochondrial haplogroups influence risk of PAH and that a vulnerability to PAH may have emerged under the selective enrichment of specific haplogroups that occurred with the migration of populations out of Africa.