Person:

Israel, Elliot

Background: Severe asthma occurs more often in older adult patients. We hypothesized that the greater risk for severe asthma in older individuals is due to aging, and is independent of asthma duration. Methods: This is a cross-sectional study of prospectively collected data from adult participants (N=1130; 454 with severe asthma) enrolled from 2002 – 2011 in the Severe Asthma Research Program. Results: The association between age and the probability of severe asthma, which was performed by applying a Locally Weighted Scatterplot Smoother, revealed an inflection point at age 45 for risk of severe asthma. The probability of severe asthma increased with each year of life until 45 years and thereafter increased at a much slower rate. Asthma duration also increased the probability of severe asthma but had less effect than aging. After adjustment for most comorbidities of aging and for asthma duration using logistic regression, asthmatics older than 45 maintained the greater probability of severe asthma [OR: 2.73 (95 CI: 1.96; 3.81)]. After 45, the age-related risk of severe asthma continued to increase in men, but not in women. Conclusions: Overall, the impact of age and asthma duration on risk for asthma severity in men and women is greatest over times of 18-45 years of age; age has a greater effect than asthma duration on risk of severe asthma.

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.

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. Electronic supplementary material The online version of this article (10.1186/s12890-018-0612-x) contains supplementary material, which is available to authorized users.

BACKGROUND: Mast cells are present in the airways of patients who have severe asthma despite glucocorticoid treatment; these cells are associated with disease characteristics including poor quality of life and inadequate asthma control. Stem cell factor and its receptor, KIT, are central to mast-cell homeostasis. We conducted a proof-of- principle trial to evaluate the effect of imatinib, a KIT inhibitor, on airway hyper- responsiveness, a physiological marker of severe asthma, as well as on airway mast-cell numbers and activation in patients with severe asthma. METHODS: We conducted a randomized, double-blind, placebo-controlled, 24-week trial of ima- tinib in patients with poorly controlled severe asthma who had airway hyperrespon- siveness despite receiving maximal medical therapy. The primary end point was the change in airway hyperresponsiveness, measured as the concentration of metha- choline required to decrease the forced expiratory volume in 1 second by 20% (PC20 ). Patients also underwent bronchoscopy. RESULTS: Among the 62 patients who underwent randomization, imatinib treatment reduced airway hyperresponsiveness to a greater extent than did placebo. At 6 months, the methacholine PC20 increased by a mean (±SD) of 1.73±0.60 doubling doses in the imatinib group, as compared with 1.07±0.60 doubling doses in the placebo group (P=0.048). Imatinib also reduced levels of serum tryptase, a marker of mast-cell activa- tion, to a greater extent than did placebo (decrease of 2.02±2.32 vs. 0.56±1.39 ng per milliliter, P=0.02). Airway mast-cell counts declined in both groups. Muscle cramps and hypophosphatemia were more common in the imatinib group than in the placebo group. CONCLUSIONS: In patients with severe asthma, imatinib decreased airway hyperresponsiveness, mast- cell counts, and tryptase release. These results suggest that KIT-dependent processes and mast cells contribute to the pathobiologic basis of severe asthma. (Funded by the National Institutes of Health and others; ClinicalTrials.gov number, NCT01097694.)

Rationale: Airway inflammation is common in severe asthma despite antiinflammatory therapy with corticosteroids. Lipoxin A4 (LXA4) is an arachidonic acid–derived mediator that serves as an agonist for resolution of inflammation.

Objectives: Airway levels of LXA4, as well as the expression of lipoxin biosynthetic genes and receptors, in severe asthma.

Methods: Samples of bronchoalveolar lavage fluid were obtained from subjects with asthma and levels of LXA4 and related eicosanoids were measured. Expression of lipoxin biosynthetic genes was determined in whole blood, bronchoalveolar lavage cells, and endobronchial biopsies by quantitative polymerase chain reaction, and leukocyte LXA4 receptors were monitored by flow cytometry.

Measurements and Main Results: Individuals with severe asthma had significantly less LXA4 in bronchoalveolar lavage fluids (11.2 ± 2.1 pg/ml) than did subjects with nonsevere asthma (150.1 ± 38.5 pg/ml; P < 0.05). In contrast, levels of cysteinyl leukotrienes were increased in both asthma cohorts compared with healthy individuals. In severe asthma, 15-lipoxygenase-1 mean expression was decreased fivefold in bronchoalveolar lavage cells. In contrast, 15-lipoxgenase-1 was increased threefold in endobronchial biopsies, but expression of both 5-lipoxygenase and 15-lipoxygenase-2 in these samples was decreased. Cyclooxygenase-2 expression was decreased in all anatomic compartments sampled in severe asthma. Moreover, LXA4 receptor gene and protein expression were significantly decreased in severe asthma peripheral blood granulocytes.

Conclusions: Mechanisms underlying pathological airway responses in severe asthma include lipoxin underproduction with decreased expression of lipoxin biosynthetic enzymes and receptors. Together, these results indicate that severe asthma is characterized, in part, by defective lipoxin counterregulatory signaling circuits.

Background

Previous studies have identified asthma phenotypes based on small numbers of clinical, physiologic or inflammatory characteristics. However, no studies have utilized a wide range of variables using machine learning approaches.

Objectives

To identify subphenotypes of asthma utilizing blood, bronchoscopic, exhaled nitric oxide and clinical data from the Severe Asthma Research Program using unsupervised clustering, and then characterize them using supervised learning approaches.

Methods

Unsupervised clustering approaches were applied to 112 clinical, physiologic and inflammatory variables from 378 subjects. Variable selection and supervised learning techniques were employed to select relevant and nonredundant variables, address their predictive values, as well as the predictive value of the full variable set.

Results

Ten variable clusters and six subject clusters were identified, which differed and overlapped with previous clusters. Traditionally defined severe asthmatics distributed through subject Clusters 3–6. Cluster 4 identified early onset allergic asthmatics with low lung function and eosinophilic inflammation. Later onset, mostly severe asthmatics with nasal polyps and eosinophilia characterized Cluster 5. Cluster 6 asthmatics manifested persistent inflammation in blood and bronchoalveolar lavage and exacerbations despite high systemic corticosteroid use and side effects. Age of asthma onset, quality of life, symptoms, medications and health care utilization were some of the 51 nonredundant variables distinguishing subject clusters. These 51 variables classified test cases with 88% accuracy, compared to 93% accuracy with all 112 variables.

Conclusion

The unsupervised machine learning approaches used here provide unique insights into disease, confirming other approaches while revealing novel additional phenotypes.

Background Exhaled nitric oxide (FeNO) associates with asthma and eosinophilic inflammation. However, relationships between nitric oxide synthases, arginase, FeNO, asthma severity and inflammation remain poorly understood.

Objectives To determine the relationships of iNOS expression/activation and arginase 2 expression with asthma severity, FeNO, nitrotyrosine (NT) and eosinophilic inflammation.

Methods Bronchial brushings and sputum were obtained from 25 Normal Controls, 8 Mild/no inhaled corticosteroids (ICS), 16 Mild-Moderate/with ICS and 35 Severe Asthmatics. FeNO was measured the same day by ATS/ERS standards. iNOS, Arginase2 mRNA/protein and NT protein were measured in lysates from bronchial brushings by quantitative real time PCR and Western Blot. Induced sputum differentials were obtained.

Results Severe asthma was associated with the highest levels of iNOS protein and mRNA, although the index of iNOS mRNA to arginase2 mRNA most strongly differentiated severe from milder asthma. When evaluating NO-related enzyme functionality, iNOS mRNA/protein expression both strongly predicted FeNO (r=0.61, p<0.0001 for both). Only iNOS protein predicted NT levels (r=0.48, p=0.003) with the strongest relationship in severe asthma (r=0.61, p=0.009). iNOS protein, FeNO and NT all correlated with sputum eosinophils, but the relationships were again strongest in severe asthma. Controlling for arginase 2 mRNA/protein did not impact any functional outcome.

Conclusions and Clinical Relevance These data suggest that while iNOS expression from epithelial brushings is highest in severe asthma, factors controlling arginase2 mRNA expression significantly improve differentiation of severity. In contrast, functionality of the NO pathway as measured by FeNO, NT and eosinophilic inflammation, is strongly associated with iNOS expression alone, particularly in severe asthma.

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 better understanding of non-type 2 mechanisms of severe asthma. We considered the possibility that systemic inflammation - which occurs in subgroups of obese and older patients - modifies asthma to make it worse. Interleukin 6 (IL6) is a biomarker of systemic inflammation and metabolic dysfunction, and we aimed to explore the relationship between IL6, metabolic dysfunction, and asthma severity.

Methods We generated a reference range in health for plasma IL6 in a cohort of healthy controls (n=93). We compared the clinical characteristics of asthmatics with plasma IL6 levels below and above the upper limit of normal (“IL6 low” and “IL-high” asthma) in two asthma cohorts - predominantly non-severe asthmatics recruited at the University of California San Francisco (UCSF)(n=249) and predominantly severe asthmatics recruited by the Severe Asthma Research Program (SARP)(n=387).

Findings The upper 95th centile value for plasma IL6 in the healthy cohort was 3·1pg/mL, and 14% of UCSF cohort and 26% of the SARP cohort had plasma IL6 levels above this upper limit. The “IL6-high” patients in both asthma cohorts had a significantly higher body mass index and a higher prevalence of metabolic disease than the IL6-low patients (all p values < 0.01). IL6-high patients also had significantly lower lung function and more frequent asthma exacerbations than IL6-low patients (all p values < 0·01). Although 75% of IL6-high asthmatics were obese, 63% of obese patients were IL6-low. Among obese patients, the forced expired volume in one second (FEV1) was significantly lower in IL6-high than in IL6-low patients (mean FEV1 70·8 [S.D. 19·5] vs. 78·1 [19·7] % predicted, p = 0·002), and the percentage of patients reporting an asthma exacerbation in the past 1-2 years was higher in IL6-high than in IL6-low patients (66 vs. 48%, p = 0·003). Among non-obese asthmatics, FEV1% and asthma exacerbation outcomes were also significantly worse in IL6-high than in IL6-low patients (mean FEV1 66·4 [SD 23·1] vs. 83·2 [20·4] % predicted, p< 0·01; 59 vs. 34 %, p=0·008).

Interpretation Systemic IL6 inflammation and clinical features of metabolic dysfunction - occurring most commonly among a subset of obese asthmatics but also in a small subset of non-obese patients - is associated with more severe asthma. IL6 inhibitors or treatments that improve metabolic dysfunction represent rational clinical trials to pursue for a subset of patients with severe asthma, and plasma IL6 is a biomarker that could guide patient stratification.

Background Severe adverse life-threatening events associated with long-acting beta agonists (LABA) use have caused the FDA to review LABA safety which has resulted in a boxed warning and a mandatory LABA safety study in 46,800 asthmatics. Identification of an at-risk, susceptible subpopulation using predictive biomarkers is critical in understanding LABA safety. The β2-adrenergic receptor gene (ADRB2) contains a common, nonsynonymous single nucleotide polymorphism, Gly16Arg, that is unlikely to account for rare, life-threatening events. We hypothesize that rare ADRB2 variants with strong effects modulate therapeutic responses to long-acting beta agonist (LABA) therapy and contribute to rare, severe adverse events.

Methods ADRB2 was sequenced in 197 African Americans, 191 non-Hispanic Whites, and 73 Puerto Ricans. Sequencing identified six rare variants which were genotyped in 1,165 asthmatics (total=1,626). The primary hypothesis was that severe asthma exacerbations requiring hospitalization were associated with rare ADRB2 variants. Replication was performed in 659 non-Hispanic White asthma subjects.

Findings Asthmatics receiving LABA with a rare variant had increased asthma-related hospitalizations (meta-analysis for all ethnic groups: p=2·83 × 10−4), specifically LABA-treated non-Hispanic Whites with the rare Ile164 allele (only rare variant in Whites, OR4·48, 95% CI 1·40–14·0, p=0·01) and African Americans with a 25 base-pair promoter polynucleotide insertion (OR 13·43, 95% CI 2·02–265·4, p=0·006). The subset of non-Hispanic Whites and African Americans receiving LABAs with these rare variants had increased exacerbations requiring urgent outpatient healthcare visits (non-Hispanic Whites with or without the rare Ile164 allele: 2·6 visits versus 1·1 visits, p=8·4 × 10−7 and African Americans with or without the rare insertion: 3·7 visits versus 2·4 visits, 0·01), and more frequently were treated with chronic systemic corticosteroids (OR4·2, 95% CI1·4–14, p=0·01 and OR12·83, 95% CI 1·96–251·9, 0·006). Non-Hispanic Whites from the primary and replication cohorts with the rare Ile164 allele were more than twice as likely to experience uncontrolled, persistent symptoms during LABA treatment (p=0·008–0·04).

Interpretation Rare ADRB2 variants are associated with adverse events during LABA therapy and should be evaluated in large clinical trials including the current FDA-mandated LABA safety study.