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1.  Mitochondrial Haplogroups and Risk of Pulmonary Arterial Hypertension 
PLoS ONE  2016;11(5):e0156042.
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.
PMCID: PMC4880300  PMID: 27224443
2.  Increased mitochondrial arginine metabolism supports bioenergetics in asthma 
The Journal of Clinical Investigation  null;126(7):2465-2481.
High levels of arginine metabolizing enzymes, including inducible nitric oxide synthase (iNOS) and arginase (ARG), are typical in asthmatic airway epithelium; however, little is known about the metabolic effects of enhanced arginine flux in asthma. Here, we demonstrated that increased metabolism sustains arginine availability in asthmatic airway epithelium with consequences for bioenergetics and inflammation. Expression of iNOS, ARG2, arginine synthetic enzymes, and mitochondrial respiratory complexes III and IV was elevated in asthmatic lung samples compared with healthy controls. ARG2 overexpression in a human bronchial epithelial cell line accelerated oxidative bioenergetic pathways and suppressed hypoxia-inducible factors (HIFs) and phosphorylation of the signal transducer for atopic Th2 inflammation STAT6 (pSTAT6), both of which are implicated in asthma etiology. Arg2-deficient mice had lower mitochondrial membrane potential and greater HIF-2α than WT animals. In an allergen-induced asthma model, mice lacking Arg2 had greater Th2 inflammation than WT mice, as indicated by higher levels of pSTAT6, IL-13, IL-17, eotaxin, and eosinophils and more mucus metaplasia. Bone marrow transplants from Arg2-deficient mice did not affect airway inflammation in recipient mice, supporting resident lung cells as the drivers of elevated Th2 inflammation. These data demonstrate that arginine flux preserves cellular respiration and suppresses pathological signaling events that promote inflammation in asthma.
PMCID: PMC4922712  PMID: 27214549
3.  Impact of Age and Sex on Outcomes and Hospital Cost of Acute Asthma in the United States, 2011-2012 
PLoS ONE  2016;11(6):e0157301.
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.
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.
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.
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.
PMCID: PMC4905648  PMID: 27294365
4.  Asthma is Different in Women 
Gender differences in asthma incidence, prevalence and severity have been reported worldwide. After puberty, asthma becomes more prevalent and severe in women, and is highest in women with early menarche or with multiple gestations, suggesting a role for sex hormones in asthma genesis. However, the impact of sex hormones on the pathophysiology of asthma is confounded by and difficult to differentiate from age, obesity, atopy, and other gender associated environmental exposures. There are also gender discrepancies in the perception of asthma symptoms. Understanding gender differences in asthma is important to provide effective education and personalized management plans for asthmatics across the lifecourse.
PMCID: PMC4572514  PMID: 26141573
Asthma; Gender difference; Sex hormones
5.  Alterations of the Arginine Metabolome in Asthma 
Rationale: As the sole nitrogen donor in nitric oxide (NO) synthesis and key intermediate in the urea cycle, arginine and its metabolic pathways are integrally linked to cellular respiration, metabolism, and inflammation.
Objectives: We hypothesized that arginine (Arg) bioavailability would be associated with airflow abnormalities and inflammation in subjects with asthma, and would be informative for asthma severity.
Methods: Arg bioavailability was assessed in subjects with severe and nonsevere asthma and healthy control subjects by determination of plasma Arg relative to its metabolic products, ornithine and citrulline, and relative to methylarginine inhibitors of NO synthases, and by serum arginase activity. Inflammatory parameters, including fraction of exhaled NO (FeNO), IgE, skin test positivity to allergens, bronchoalveolar lavage, and blood eosinophils, were also evaluated.
Measurements and Main Results: Subjects with asthma had greater Arg bioavailability, but also increased Arg catabolism compared with healthy control subjects, as evidenced by higher levels of FeNO and serum arginase activity. However, Arg bioavailability was positively associated with FeNO only in healthy control subjects; Arg bioavailability was unrelated to FeNO or other inflammatory parameters in severe or nonsevere asthma. Inflammatory parameters were related to airflow obstruction and reactivity in nonsevere asthma, but not in severe asthma. Conversely, Arg bioavailability was related to airflow obstruction in severe asthma, but not in nonsevere asthma. Modeling confirmed that measures of Arg bioavailabilty predict airflow obstruction only in severe asthma.
Conclusions: Unlike FeNO, Arg bioavailability is not a surrogate measure of inflammation; however, Arg bioavailability is strongly associated with airflow abnormalities in severe asthma.
PMCID: PMC2556449  PMID: 18635886
asthma; arginine; arginase; nitric oxide; methylarginine
6.  Carboxyhemoglobin and Methemoglobin in Asthma 
Lung  2015;193(2):183-187.
Nitric oxide (NO) and carbon monoxide (CO) are synthesized at high levels in asthmatic airways. NO can oxidize hemoglobin (Hb) to methemoglobin (MetHb). CO binds to heme to produce carboxyhemoglobin (COHb). We hypothesized that MetHb and COHb may be increased in asthma. COHb, MetHb, and Hb were measured in venous blood of healthy controls (n=32) and asthmatics (n=31). Arterial COHb and oxyhemoglobin were measured by pulse CO-oximeter. Hb, oxyhemoglobin, and deoxyhemoglobin were similar among groups, but arterial COHb was higher in asthmatics than controls (p=0.04). Venous COHb was similar among groups, and thus arteriovenous COHb (a-v COHb) concentration difference was greater in asthma compared with controls. Venous MetHb was lower in asthma compared to controls (p=0.01) and correlated to venous NO (p=0.009). The greater a-v COHb in asthma suggests CO offloading to tissues, but lower than normal MetHb suggests countermeasures to avoid adverse effects of high NO on gas transfer.
PMCID: PMC4500073  PMID: 25680415
carboxyhemoglobin; asthma; methemoglobin; nitric oxide; hemoglobin
7.  Future Research Directions in Asthma. An NHLBI Working Group Report 
Asthma is a common chronic disease without cure. Our understanding of asthma onset, pathobiology, classification, and management has evolved substantially over the past decade; however, significant asthma-related morbidity and excess healthcare use and costs persist. To address this important clinical condition, the NHLBI convened a group of extramural investigators for an Asthma Research Strategic Planning workshop on September 18–19, 2014, to accelerate discoveries and their translation to patients. The workshop focused on (1) in utero and early-life origins of asthma, (2) the use of phenotypes and endotypes to classify disease, (3) defining disease modification, (4) disease management, and (5) implementation research. This report summarizes the workshop and produces recommendations to guide future research in asthma.
PMCID: PMC4731702  PMID: 26305520
asthma; prevention; phenotype; disease modification; implementation
8.  Fasting 2-Deoxy-2-[18F]fluoro-d-glucose Positron Emission Tomography to Detect Metabolic Changes in Pulmonary Arterial Hypertension Hearts over 1 Year 
Background: The development of tools to monitor the right ventricle in pulmonary arterial hypertension (PAH) is of clinical importance. PAH is associated with pathologic expression of the transcription factor hypoxia-inducible factor (HIF)-1α, which induces glycolytic metabolism and mobilization of proangiogenic progenitor (CD34+CD133+) cells. We hypothesized that PAH cardiac myocytes have a HIF-related switch to glycolytic metabolism that can be detected with fasting 2-deoxy-2-[18F]fluoro-d-glucose positron emission tomography (FDG-PET) and that glucose uptake is informative for cardiac function.
Methods: Six healthy control subjects and 14 patients with PAH underwent fasting FDG-PET and echocardiogram. Blood CD34+CD133+ cells and erythropoietin were measured as indicators of HIF activation. Twelve subjects in the PAH cohort underwent repeat studies 1 year later to determine if changes in FDG uptake were related to changes in echocardiographic parameters or to measures of HIF activation.
Measurements and Results: FDG uptake in the right ventricle was higher in patients with PAH than in healthy control subjects and correlated with echocardiographic measures of cardiac dysfunction and circulating CD34+CD133+ cells but not erythropoietin. Among patients with PAH, FDG uptake was lower in those receiving β-adrenergic receptor blockers. Changes in FDG uptake over time were related to changes in echocardiographic parameters and CD34+CD133+ cell numbers. Immunohistochemistry of explanted PAH hearts of patients undergoing transplantation revealed that HIF-1α was present in myocyte nuclei but was weakly detectable in control hearts.
Conclusions: PAH hearts have pathologic glycolytic metabolism that is quantitatively related to cardiac dysfunction over time, suggesting that metabolic imaging may be useful in therapeutic monitoring of patients.
PMCID: PMC3960991  PMID: 23509326
hypoxia-inducible factor 1; alpha subunit; positron emission tomography; fluorodeoxyglucose F18; right ventricle; heart failure
9.  Biomarkers in Asthma: A Real Hope to Better Manage Asthma 
Clinics in chest medicine  2012;33(3):459-471.
Diagnosis and treatment of asthma are currently based on assessment of patient symptoms and physiologic tests of airway reactivity. The morbidities and costs associated with the over and/or under treatment of this common disease, as well as the growing numbers of biologically-specific targeted strategies for therapy, provide a rationale for development of biomarkers to evaluate the presence and type of inflammation in individuals with asthma in order to optimize treatment plans. Research over the past decade has identified an array of biochemical and cellular biomarkers, which reflect the heterogeneous and multiple mechanistic pathways that may lead to asthma. These mechanistic biomarkers offer hope for optimal design of therapies targeting the specific pathways that lead to inflammation. This article provides an overview of blood, urine and airway biomarkers, summarizes the pathologic pathways that they signify, and begins to describe the utility of biomarkers in the future care of patients with asthma.
PMCID: PMC3494969  PMID: 22929095
asthma; biomarkers; asthma management
10.  IL6R Variation Asp358Ala Is a Potential Modifier of Lung Function in Asthma 
The IL6R SNP rs4129267 has recently been identified as an asthma susceptibility locus in subjects of European ancestry but has not been characterized with respect to asthma severity. The SNP rs4129267 is in linkage disequilibrium (r2=1) with the IL6R coding SNP rs2228145 (Asp358Ala). This IL6R coding change increases IL6 receptor shedding and promotes IL6 transsignaling.
To evaluate the IL6R SNP rs2228145 with respect to asthma severity phenotypes.
The IL6R SNP rs2228145 was evaluated in subjects of European ancestry with asthma from the Severe Asthma Research Program (SARP). Lung function associations were replicated in the Collaborative Study on the Genetics of Asthma (CSGA) cohort. Serum soluble IL6 receptor (sIL6R) levels were measured in subjects from SARP. Immunohistochemistry was used to qualitatively evaluate IL6R protein expression in BAL cells and endobronchial biopsies.
The minor C allele of IL6R SNP rs2228145 was associated with lower ppFEV1 in the SARP cohort (p=0.005), the CSGA cohort (0.008), and in combined cohort analysis (p=0.003). Additional associations with ppFVC, FEV1/FVC, and PC20 were observed. The rs2228145 C allele (Ala358) was more frequent in severe asthma phenotypic clusters. Elevated serum sIL6R was associated with lower ppFEV1 (p=0.02) and lower ppFVC (p=0.008) (N=146). IL6R protein expression was observed in BAL macrophages, airway epithelium, vascular endothelium, and airway smooth muscle.
The IL6R coding SNP rs2228145 (Asp358Ala) is a potential modifier of lung function in asthma and may identify subjects at risk for more severe asthma. IL6 transsignaling may have a pathogenic role in the lung.
PMCID: PMC3409329  PMID: 22554704
soluble interleukin 6 receptor; sIL6R; interleukin 6; IL6; asthma; pulmonary lung function; severe asthma; IL6 transsignaling; genetic variation; SNP rs2228145
11.  High Levels of Zinc-Protoporphyrin Identify Iron Metabolic Abnormalities in Pulmonary Arterial Hypertension 
Iron homeostasis influences the development of pulmonary arterial hypertension (PAH) associated with hypoxia or hematologic disorders. To investigate whether severity of idiopathic PAH (IPAH) is impacted by alterations in iron metabolism, we assessed iron metabolic markers, including levels of Zinc-protoporphyrin (Zn-pp), transferrin receptor, and red blood cell numbers and morphology in IPAH, associated PAH (APAH) and sleep apnea induced pulmonary hypertension (PH) patients in comparison to healthy controls and asthmatics. Despite similarly normal measures of iron metabolism, Zn-pp levels in IPAH and sleep apnea patients were elevated ~2-fold, indicating deficient iron incorporation to form heme and levels were closely related to measures of disease severity. Consistent with high Zn-PP, PAH patients had increased red cell distribution width (RDW). In an expanded cohort including patients with IPAH and familial disease (FPAH) the RDW was validated and related to clinical parameters of severity, including pulmonary artery pressures and 6 minute walk distances. These results reveal an increased prevalence of subclinical functional iron deficiency in primary forms of PAH that is quantitatively related to disease severity. This suggests that altered iron homeostasis influences disease progression and demonstrates the importance of closely monitoring iron status in PAH patients.
PMCID: PMC3575639  PMID: 21884511
12.  Severe Asthma 
The National Heart, Lung, and Blood Institute Severe Asthma Research Program (SARP) has characterized over the past 10 years 1,644 patients with asthma, including 583 individuals with severe asthma. SARP collaboration has led to a rapid recruitment of subjects and efficient sharing of samples among participating sites to conduct independent mechanistic investigations of severe asthma. Enrolled SARP subjects underwent detailed clinical, physiologic, genomic, and radiological evaluations. In addition, SARP investigators developed safe procedures for bronchoscopy in participants with asthma, including those with severe disease. SARP studies revealed that severe asthma is a heterogeneous disease with varying molecular, biochemical, and cellular inflammatory features and unique structure–function abnormalities. Priorities for future studies include recruitment of a larger number of subjects with severe asthma, including children, to allow further characterization of anatomic, physiologic, biochemical, and genetic factors related to severe disease in a longitudinal assessment to identify factors that modulate the natural history of severe asthma and provide mechanistic rationale for management strategies.
PMCID: PMC3297096  PMID: 22095547
asthma; remodeling; inflammation; bronchoscopy; imaging
13.  eQTL of bronchial epithelial cells and bronchial alveolar lavage deciphers GWAS-identified asthma genes 
Allergy  2015;70(10):1309-1318.
Genome-wide association studies (GWASs) have identified various genes associated with asthma, yet, causal genes or single nucleotide polymorphisms (SNPs) remain elusive. We sought to dissect functional genes/SNPs for asthma by combining expression quantitative trait loci (eQTLs) and GWASs.
Cis-eQTL analyses of 34 asthma genes were performed in cells from human bronchial epithelial biopsy (BEC, n =107) and from bronchial alveolar lavage (BAL, n = 94).
For TSLP-WDR36 region, rs3806932 (G allele protective against eosinophilic esophagitis) and rs2416257 (A allele associated with lower eosinophil counts and protective against asthma) were correlated with decreased expression of TSLP in BAL (P = 7.9x10−11 and 5.4x10−4, respectively) and BEC, but not WDR36. Surprisingly, rs1837253 (consistently associated with asthma) showed no correlation with TSLP expression levels. For ORMDL3-GSDMB region, rs8067378 (G allele protective against asthma) was correlated with decreased expression of GSDMB in BEC and BAL (P = 1.3x10−4 and 0.04) but not ORMDL3. rs992969 in the promoter region of IL33 (A allele associated with higher eosinophil counts and risk for asthma) was correlated with increased expression of IL33 in BEC (P = 1.3x10−6) but not in BAL.
Our study illustrates cell-type-specific regulation of the expression of asthma-related genes documenting SNPs in TSLP, GSDMB, IL33, HLA-DQB1, C11orf30, DEXI, CDHR3, and ZBTB10 affect asthma risk through cis-regulation of its gene expression. Whenever possible, disease-relevant tissues should be used for transcription analysis. SNPs in TSLP may affect asthma risk through up-regulating TSLP mRNA expression or protein secretion. Further functional studies are warranted.
PMCID: PMC4583797  PMID: 26119467
asthma susceptibility genes; bronchial alveolar lavage; bronchial epithelial cells; eQTL; GWAS
14.  Safety of Investigative Bronchoscopy in the Severe Asthma Research Program 
Investigative bronchoscopy was performed in a subset of participants in the Severe Asthma Research Program (SARP) to gain insights into the pathobiology of severe disease. We evaluated the safety aspects of this procedure in this cohort with specific focus on patients with severe asthma.
To prospectively evaluate changes in lung function and the frequency of adverse events related to investigative bronchoscopy.
Bronchoscopy was performed using a common Manual of Procedures. A subset of very severe asthma was defined by severe airflow obstruction, chronic oral corticosteroid use and recent asthma exacerbations. Subjects were monitored for changes in lung function and contacted by telephone for 3 days after the procedure.
436 subjects underwent bronchoscopy (97 normal, 196 not severe, 102 severe and 41 very severe asthma). Nine subjects were evaluated in hospital settings after bronchoscopy; seven of these were respiratory related events. Recent Emergency Department visits, chronic oral corticosteroid use and a history of pneumonia were more frequent in subjects who had asthma exacerbations after bronchoscopy. The fall in FEV1 following bronchoscopy was similar in the severe compared to milder asthma group. Pre-bronchodilator FEV1 was the strongest predictor of change in FEV1 after bronchoscopy with larger decreases observed in subjects with better lung function.
Bronchoscopy in severe asthma subjects was well tolerated. Asthma exacerbations were rare and reduction in pulmonary function after the procedure was similar to subjects with less severe asthma. With proper precautions, investigative bronchoscopy can be performed safely in severe asthma.
PMCID: PMC3149754  PMID: 21496892
investigative bronchoscopy; safety; severe asthma; exacerbation
15.  Use of Exhaled Nitric Oxide Measurement to Identify a Reactive, at-Risk Phenotype among Patients with Asthma 
Rationale: Exhaled nitric oxide (FeNO) is a biomarker of airway inflammation in mild to moderate asthma. However, whether FeNO levels are informative regarding airway inflammation in patients with severe asthma, who are refractory to conventional treatment, is unknown. Here, we hypothesized that classification of severe asthma based on airway inflammation as defined by FeNO levels would identify a more reactive, at-risk asthma phenotype.
Methods: FeNO and major features of asthma, including airway inflammation, airflow limitation, hyperinflation, hyperresponsiveness, and atopy, were determined in 446 individuals with various degrees of asthma severity (175 severe, 271 nonsevere) and 49 healthy subjects enrolled in the Severe Asthma Research Program.
Measurements and Main Results: FeNO levels were similar among patients with severe and nonsevere asthma. The proportion of individuals with high FeNO levels (>35 ppb) was the same (40%) among groups despite greater corticosteroid therapy in severe asthma. All patients with asthma and high FeNO had more airway reactivity (maximal reversal in response to bronchodilator administration and by methacholine challenge), more evidence of allergic airway inflammation (sputum eosinophils), more evidence of atopy (positive skin tests, higher serum IgE and blood eosinophils), and more hyperinflation, but decreased awareness of their symptoms. High FeNO identified those patients with severe asthma characterized by the greatest airflow obstruction and hyperinflation and most frequent use of emergency care.
Conclusions: Grouping of asthma by FeNO provides an independent classification of asthma severity, and among patients with severe asthma identifies the most reactive and worrisome asthma phenotype.
PMCID: PMC2874447  PMID: 20133930
nitric oxide; severe asthma; phenotype; airway reactivity; exhaled breath
16.  Pulmonary Gas Transfer Related to Markers of Angiogenesis during the Menstrual Cycle 
Gas transfer in the female lung varies over the menstrual cycle in parallel with the cyclic angiogenesis that occurs in the uterine endometrium. Given that vessels form and regress in the uterus under the control of hormones, angiogenic factors and pro-angiogenic circulating bone marrow-derived progenitor cells, we tested the possibility that variation in pulmonary gas transfer over the menstrual cycle is related to a systemic cyclic pro-angiogenic state that influences lung vascularity. Women were evaluated over the menstrual cycle with weekly measures of lung diffusing capacity and its components, the pulmonary vascular capillary bed and membrane diffusing capacity, and their relation to circulating CD34+CD133+ progenitor cells, hemoglobin, factors affecting hemoglobin binding affinity, and pro-angiogenic factors. Lung diffusing capacity varied over the menstrual cycle, reaching a nadir during the follicular phase following menses. The decline in lung diffusing capacity was accounted for by ~25% decrease in pulmonary capillary blood volume. In parallel, circulating CD34+CD133+ progenitor cells decreased by ~24%, and were directly related to angiogenic factors, and to lung diffusing capacity and pulmonary capillary blood volume. The finding of greater number of lung microvessels in ovariectomized female mice receiving estrogen as compared to placebo verified that pulmonary vascularity is influenced by hormonal changes. These findings suggest that angiogenesis in the lungs may participate in the cyclic changes in gas transfer that occur over the menstrual cycle.
PMCID: PMC3038173  PMID: 17717117
Gas transfer; endothelial progenitor cell; angiogenesis; menstrual cycle
17.  Features of severe asthma in school-age children: Atopy and increased exhaled nitric oxide 
Children with severe asthma have persistent symptoms despite treatment with inhaled corticosteroids (ICSs). The differentiating features of severe asthma in children are poorly defined.
To identify features of severe versus mild-to-moderate asthma in school-age children using noninvasive assessments of lung function, atopy, and airway inflammation.
A total of 75 children (median age, 10 years) with asthma underwent baseline characterization including spirometry and lung volume testing, methacholine bronchoprovocation, allergy evaluation, and offline measurement of exhaled nitric oxide (FENO). Twenty-eight were followed longitudinally over 6 months. Participants were assigned to the severe asthma subgroup if they required high-dose ICS plus 2 or more minor criteria.
Children with severe versus mild-to-moderate asthma had more symptoms, greater airway obstruction, more gas trapping, and increased bronchial responsiveness to methacholine. Subjects with severe asthma also had higher concentrations of FENO and significantly greater sensitization to aeroallergens. With long-term study, both the reduction in FEV1 and increase in FENO persisted in the severe versus mild-to-moderate group. Furthermore, despite adjustments in ICS doses, the frequency of exacerbations was significantly higher in subjects with severe (83%) versus mild-to-moderate asthma (43%).
Severe asthma in childhood is characterized by poor symptom control despite high-dose ICS treatment and can be differentiated from mild-to-moderate asthma by measurement of lung function and FENO.
Clinical implications
Clinicians should suspect severe asthma in children with poor response to ICS, airway obstruction, and high FENO.
PMCID: PMC2878140  PMID: 17157650
Children; asthma; atopy; nitric oxide; pulmonary function testing
18.  Characterization of the severe asthma phenotype by the National Heart, Lung, and Blood Institute’s Severe Asthma Research Program 
Severe asthma causes the majority of asthma morbidity. Understanding mechanisms that contribute to the development of severe disease is important.
The goal of the Severe Asthma Research Program is to identify and characterize subjects with severe asthma to understand pathophysiologic mechanisms in severe asthma.
We performed a comprehensive phenotypic characterization (questionnaires, atopy and pulmonary function testing, phlebotomy, exhaled nitric oxide) in subjects with severe and not severe asthma.
A total of 438 subjects with asthma were studied (204 severe, 70 moderate, 164 mild). Severe subjects with asthma were older with longer disease duration (P < .0001), more daily symptoms, intense urgent health care utilization, sinusitis, and pneumonia (P ≤ .0001). Lung function was lower in severe asthma with marked bronchodilator reversibility (P < .001). The severe group had less atopy by skin tests (P = .0007), but blood eosinophils, IgE, and exhaled nitric oxide levels did not differentiate disease severity. A reduced FEV1, history of pneumonia, and fewer positive skin tests were risk factors for severe disease. Early disease onset (age < 12 years) in severe asthma was associated with longer disease duration (P < .0001) and more urgent health care, especially intensive care (P = .002). Later disease onset (age ≥ 12 years) was associated with lower lung function and sinopulmonary infections (P ≤ .02).
Severe asthma is characterized by abnormal lung function that is responsive to bronchodilators, a history of sinopulmonary infections, persistent symptoms, and increased health care utilization.
Clinical implications
Lung function abnormalities in severe asthma are reversible in most patients, and pneumonia is a risk factor for the development of severe disease.
PMCID: PMC2837934  PMID: 17291857
Severe asthma; definition; bronchodilator response; pathophysiology; phenotype; pneumonia
19.  Gene Expression Profile of Human Airway Epithelium Induced by Hyperoxia In Vivo 
Hyperoxia leads to oxidative modification and damage of macromolecules in the respiratory tract with loss of biological functions. Given the lack of antioxidant gene induction with acute exposure to 100% oxygen, we hypothesized that clearance pathways for oxidatively modified proteins may be induced and serve in the immediate cellular response to preserve the epithelial layer. To test this, airway epithelial cells were obtained from individuals under ambient oxygen conditions and after breathing 100% oxygen for 12 h. Gene expression profiling identified induction of genes in the chaperone and proteasome-ubiquitin-conjugation pathways that together comprise an integrated cellular response to manage and degrade damaged proteins. Analyses also revealed gene expression changes associated with oxidoreductase function, cell cycle regulation, and ATP synthesis. Increased HSP70, protein ubiquitination, and intracellular ATP were validated in cells exposed to hyperoxia in vitro. Inhibition of proteasomal degradation revealed the importance of accelerated protein catabolism for energy production of cells exposed to hyperoxia. Thus, the human airway early response to hyperoxia relies predominantly upon induction of cytoprotective chaperones and the ubiquitin-proteasome–dependent protein degradation system to maintain airway homeostatic integrity.
PMCID: PMC2643263  PMID: 16690988
airways; gene expression; hyperoxia; proteasome; ubiquitin
20.  Metabolomic Endotype of Asthma 
Metabolomics, the quantification of small biochemicals in plasma and tissues, can provide insight into complex biochemical processes and enable the identification of biomarkers that may serve as therapeutic targets. We hypothesized that the plasma metabolome of asthma would reveal metabolic consequences of the specific immune and inflammatory responses unique to endotypes of asthma.
The plasma metabolomic profiles of 20 asthmatic subjects and 10 healthy controls were examined using an untargeted global and focused metabolomic analysis. Individuals were classified based upon clinical definitions of asthma severity or by levels of fraction of exhaled nitric oxide (FENO), a biomarker of airway inflammation.
Of the 293 biochemicals identified in the plasma, 25 were significantly different among asthma and healthy controls (p<0.05). Plasma levels of taurine, lathosterol, bile acids (taurocholate and glycodeoxycholate), nicotinamide, and adenosine-5-phosphate, were significantly higher in asthmatics compared with healthy controls. Severe asthmatics had biochemical changes related to steroid and amino acid/protein metabolism. Asthmatics with high FENO, compared with those with low FENO, had higher levels of plasma branched chain amino acids and bile acids.
Asthmatics have a unique plasma metabolome that distinguishes them from healthy controls and points to activation of inflammatory and immune pathways. The severe asthmatic and high FENO asthmatic have unique endotypes that suggest changes in NO-associated taurine transport and bile acid metabolism.
PMCID: PMC4490949  PMID: 26048149
21.  Increased Mutagen Sensitivity and DNA Damage in Pulmonary Arterial Hypertension 
Rationale: Pulmonary arterial hypertension (PAH) is a serious lung condition characterized by vascular remodeling in the precapillary pulmonary arterioles. We and others have demonstrated chromosomal abnormalities and increased DNA damage in PAH lung vascular cells, but their timing and role in disease pathogenesis is unknown.
Objectives: We hypothesized that if DNA damage predates PAH, it might be an intrinsic cell property that is present outside the diseased lung.
Methods: We measured DNA damage, mutagen sensitivity, and reactive oxygen species (ROS) in lung and blood cells from patients with Group 1 PAH, their relatives, and unrelated control subjects.
Measurements and Main Results: Baseline DNA damage was significantly elevated in PAH, both in pulmonary artery endothelial cells (P < 0.05) and peripheral blood mononuclear cells (PBMC) (P < 0.001). Remarkably, PBMC from unaffected relatives showed similar increases, indicating this is not related to PAH treatments. ROS levels were also higher (P < 0.01). DNA damage correlated with ROS production and was suppressed by antioxidants (P < 0.001). PBMC from patients and relatives also showed markedly increased sensitivity to two chemotherapeutic drugs, bleomycin and etoposide (P < 0.001). Results were consistent across idiopathic, heritable, and associated PAH groups.
Conclusions: Levels of baseline and mutagen-induced DNA damage are intrinsically higher in PAH cells. Similar results in PBMC from unaffected relatives suggest this may be a genetically determined trait that predates disease onset and may act as a risk factor contributing to lung vascular remodeling following endothelial cell injury. Further studies are required to fully characterize mutagen sensitivity, which could have important implications for clinical management.
PMCID: PMC4532823  PMID: 25918951
DNA damage; reactive oxygen species; genetic susceptibility; BMPR2
22.  Correlation of Systemic Superoxide Dismutase Deficiency to Airflow Obstruction in Asthma 
Rationale: Increased oxidative stress and decreased superoxide dismutase (SOD) activity in the asthmatic airway are correlated to airflow limitation and hyperreactivity. We hypothesized that asthmatic individuals with higher levels of oxidative stress may have greater loss of SOD activity, which would be reflected systemically in loss of circulating SOD activity and clinically by development of severe asthma and/or worsening airflow limitation. Methods: To investigate this, serum SOD activity and proteins, the glutathione peroxidase/glutathione antioxidant system, and oxidatively modified amino acids were measured in subjects with asthma and healthy control subjects. Results: SOD activity, but not Mn-SOD or Cu,Zn-SOD protein, was lower in asthmatic serum as compared with control, and activity loss was significantly related to airflow limitation. Further, serum SOD activity demonstrated an inverse correlation with circulating levels of 3-bromotyrosine, a posttranslational modification of proteins produced by the eosinophil peroxidase system of eosinophils. Exposure of purified Cu,Zn-SOD to physiologically relevant levels of eosinophil peroxidase-generated reactive brominating species, reactive nitrogen species, or tyrosyl radicals in vitro confirmed that eosinophil-derived oxidative pathways promote enzyme inactivation. Conclusion: These findings are consistent with greater oxidant stress in asthma leading to greater inactivation of SOD, which likely amplifies inflammation and progressive airflow obstruction.
PMCID: PMC2718470  PMID: 15883124
asthma; superoxide dismutase; glutathione; pulmonary functions; peroxidase
23.  Detection of Lung Cancer by Sensor Array Analyses of Exhaled Breath 
Rationale: Electronic noses are successfully used in commercial applications, including detection and analysis of volatile organic compounds in the food industry. Objectives: We hypothesized that the electronic nose could identify and discriminate between lung diseases, especially bronchogenic carcinoma. Methods: In a discovery and training phase, exhaled breath of 14 individuals with bronchogenic carcinoma and 45 healthy control subjects or control subjects without cancer was analyzed. Principal components and canonic discriminant analysis of the sensor data was used to determine whether exhaled gases could discriminate between cancer and noncancer. Discrimination between classes was performed using Mahalanobis distance. Support vector machine analysis was used to create and apply a cancer prediction model prospectively in a separate group of 76 individuals, 14 with and 62 without cancer. Main Results: Principal components and canonic discriminant analysis demonstrated discrimination between samples from patients with lung cancer and those from other groups. In the validation study, the electronic nose had 71.4% sensitivity and 91.9% specificity for detecting lung cancer; positive and negative predictive values were 66.6 and 93.4%, respectively. In this population with a lung cancer prevalence of 18%, positive and negative predictive values were 66.6 and 94.5%, respectively. Conclusion: The exhaled breath of patients with lung cancer has distinct characteristics that can be identified with an electronic nose. The results provide feasibility to the concept of using the electronic nose for managing and detecting lung cancer.
PMCID: PMC2718462  PMID: 15750044
breath tests; bronchogenic cancer; electronic nose; volatile organic compounds
24.  Distal vessel stiffening is an early and pivotal mechanobiological regulator of vascular remodeling and pulmonary hypertension 
JCI insight  2016;1(8):e86987.
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.
PMCID: PMC4918638  PMID: 27347562
25.  Distal vessel stiffening is an early and pivotal mechanobiological regulator of vascular remodeling and pulmonary hypertension 
JCI Insight  null;1(8):e86987.
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.
Distal pulmonary arterial stiffening promotes vascular remodeling and pulmonary hypertension development via suppression of cyclooxygenase-2–dependent prostaglandin production.
PMCID: PMC4918638  PMID: 27347562

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