Person:

Israel, Elliot

In 1979 and 1980, the chemical structures of the material previously known as slow-reacting substance of anaphylaxis were elucidated as 5(S)- hydroxy- 6(R)-glutathionyl- 7,9-trans-11,14- cis - eico- satetraenoic acid1 and its cysteinyl-glycyl and cysteinyl congener (also known as leukotrienes C4, D4, and E4, respectively). These molecules were so named because the parent molecule was originally isolated from leukocytes, and its carbon backbone contained three double bonds in series, which constitutes a triene. This structural information provided the key to the oxidative pathway of lipid metabolism known as the 5-lipoxygenase pathway.

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.

Rationale: Several studies suggest that patients with asthma who are homozygous for arginine at the 16th position of the β2-adrenergic receptor may not benefit from short-acting β-agonists.

Objectives: We investigated whether such genotype-specific effects occur when patients are treated with long-acting β-agonists and whether such effects are modified by concurrent inhaled corticosteroid (ICS) use.

Methods: We compared salmeterol response in patients with asthma homozygous for arginine at B16 (B16Arg/Arg) with those homozygous for glycine at B16 (B16Gly/Gly) in two separate cohorts. In the first, subjects were randomized to regular therapy with salmeterol while simultaneously discontinuing ICS therapy. In the second, subjects were randomized to regular therapy with salmeterol while continuing concomitant ICS.

Results: In both trials, B16Arg/Arg subjects did not benefit compared with B16Gly/Gly subjects after salmeterol was initiated. In the first cohort, compared with placebo, the addition of salmeterol was associated with a 51.4 L/min lower A.M. peak expiratory flow (PEF; p = 0.005) in B16Arg/Arg subjects(salmeterol, n = 12; placebo, n = 5) as compared with B16Gly/Gly subjects (salmeterol, n = 13; placebo, n = 13). In the second cohort, B16Arg/Arg subjects treated with salmeterol and ICS concurrently (n = 8) had a lower A.M. PEF (36.8 L/min difference, p = 0.048) than B16Gly/Gly subjects (n = 22) treated with the same regimen. In addition, B16 Arg/Arg subjects in the second cohort had lower FEV1 (0.42 L, p = 0.003), increased symptom scores (0.2 units, p = 0.034), and increased albuterol rescue use (0.95 puffs/d, p = 0.004) compared with B16Gly/Gly subjects.

Conclusions: Relative to B16Gly/Gly patients with asthma, B16Arg/Arg patients with asthma may have an impaired therapeutic response to salmeterol in either the absence or presence of concurrent ICS use. Investigation of alternate treatment strategies may benefit this group.

Compared with normal individuals, subjects with asthma have elevated levels of expired nitric oxide (NO). These levels are hypothesized to reflect the degree of airway inflammation. Expired NO levels rise during the late phase of allergen challenge and decrease in asthmatics after steroid treatment. Isocapnic cold air hyperventilation (ISH) is believed to cause airway narrowing through noninflammatory mechanisms. We measured mixed expired NO in 10 individuals with atopic asthma who underwent both ISH challenge and allergen challenge, and compared these measurements with the change in expired NO that occurred after serial spirometry alone. We found that ambient NO levels affected mixed expired NO. Controlling for inspired NO, we found that repeated spirometry alone produced a significant fall in mixed expired NO (p < 0.01) that was maximal after 30 min (36.6 ± 8.5% fall). After allergen and ISH challenges, expired NO was elevated relative to levels after repeated spirometry (p < 0.01 and p = 0.065, respectively). In addition, we found that prechallenge expired NO levels were significantly correlated with the magnitude of the late fall in FEV1 following allergen challenge (r = 0.80, p < 0.01). These data demonstrate that repeated spirometry results in reduced mixed expired NO and suggest that both ISH and allergen-induced bronchoconstriction share pathobiologic mechanisms that produce increases in mixed expired NO.

Expression of pulmonary eotaxin protein and mRNA was determined in six subjects with atopic asthma and five nonatopic normal subjects. Levels of eotaxin expression and eosinophil mobilization were compared before and after segmental allergen challenge in subjects with atopic asthma. In the absence of allergen challenge, we found significantly higher levels of eotaxin in the bronchoalveolar lavage (BAL) fluid of subjects with asthma than in that of normal subjects (25 +/- 3 versus 15 +/- 2 pg/ml, p < 0.05). BAL eotaxin levels increased after segmental allergen challenge in all six subjects with atopic asthma tested, with a mean increase from 22 +/- 4 to 53 +/- 10 pg/ml (p = 0.013). Segmental allergen challenge was associated with a significant increase in the percentage of BAL macrophages and eosinophils that were immunopositive for eotaxin. Eotaxin mRNA was detectable by northern analysis in BAL cells exclusively from allergen-challenged segments. Allergen- induced increases in eotaxin levels were strongly associated with increases in BAL eosinophil recovery (r(2) = 0.88, p = 0.0036). Segmental allergen challenge also increased eotaxin expression in airway epithelial and endothelial cells obtained by endobronchial biopsy. These findings demonstrate, for the first time, that the airways of subjects with allergic asthma respond to allergen by increasing eotaxin expression. The tissue loci of eotaxin expression, the levels of eotaxin recovered in BAL fluid, and the association of eotaxin levels with eosinophil mobilization suggest either that eotaxin plays a mechanistic role in allergen-induced airway eosinophilia or that it serves as a biomarker for the causal mechanisms.

Measurement of the fraction of exhaled nitric oxide (FeNO) has been proposed as a noninvasive assessment of asthmatic airway inflammation. The influence of the expiratory flow rate during the collection maneuver on the ability of FeNO to discriminate healthy subjects from those with asthma is unknown. We compared online and offline measurement of FeNO at different flow rates. FeNO was collected with expiratory flows of 50–500 ml/second in 34 patients with asthma (PC20 of less than 8 mg/ml) and 28 healthy subjects (PC20 of more than 10 mg/ml) using offline collection techniques. In a subgroup of 18 individuals with asthma and 17 healthy subjects, we additionally measured FeNO at multiple expiratory flow rates (47–250 ml/second) using online methods. FeNO fell with an increasing expiratory flow rate; FeNO was higher in subjects with asthma as compared with healthy subjects at each flow rate studied with both techniques (p < 0.001). Receiver operating characteristic (ROC) curves for the diagnosis of asthma indicated that FeNO is a robust discriminator between individuals with asthma and healthy subjects (area under the ROC curves 0.79 ± 0.06 to 0.86 ± 0.06, p for significant discrimination < 0.0001). Neither expiratory flow rate nor collection technique (online versus offline) significantly altered this discriminatory capacity (area under the ROC curves = 0.84 ± 0.07 with the slowest online method versus 0.80 ± 0.07 with the fastest offline method, p = 0.46). These data indicate that the choice of expiratory flow rate and collection method can be based on practicality and patient comfort without compromising the utility of this test for asthma.

Five lipoxygenase (5-LO) is the first committed enzyme in the metabolic pathway leading to the synthesis of the leukotrienes. We examined genomic DNA isolated from 25 normal subjects and 31 patients with asthma (6 of whom had aspirin-sensitive asthma) for mutations in the known transcription factor binding regions and the protein encoding region of the 5-LO gene. A family of mutations in the G + C-rich transcription factor binding region was identified consisting of the deletion of one, deletion of two, or addition of one zinc finger (Sp1/Egr-1) binding sites in the region 176 to 147 bp upstream from the ATG translation start site where there are normally 5 Sp1 binding motifs in tandem. Reporter gene activity directed by any of the mutant forms of the transcription factor binding region was significantly (P < 0.05) less effective than the activity driven by the wild type transcription factor binding region. Electrophoretic mobility shift assays (EMSAs) demonstrated the capacity of wild type and mutant transcription factor binding regions to bind nuclear extracts from human umbilical vein endothelial cells (HUVECs). These data are consistent with a family of mutations in the 5-LO gene that can modify reporter gene transcription possibly through differences in Sp1 and Egr-1 transactivation.

Background Combined long-acting β2-agonist and inhaled corticosteroid (LABA/ICS) therapy improves outcomes in many asthmatics. Some studies suggest that patients homozygous for arginine at the 16th amino-acid position of the β2 adrenergic receptor (B16 Arg/Arg) benefit less than those with B16 Gly/Gly.

Methods In an NIH-funded, B16 genotype-stratified, prospective, randomized, double-blind, placebo-controlled, cross-over trial (www.ClinicalTrials.gov registration ID NCT00200967), we compared adding salmeterol or placebo to ICS in patients with moderate asthma, using AM PEF as the primary outcome.

Findings After 18 weeks, Arg/Arg (n=42) and Gly/Gly (n=45) subjects had greater AM PEF with salmeterol than placebo, with no difference in improvement by genotype (Arg/Arg 21.4 (p<0.0001) vs. Gly/Gly 21.5 L/min (p<0.0001); 0.1 L/min difference between genotypes, 95% CI (−14.2, 14.4), p=0.99). In Gly/Gly subjects, methacholine PC20 (a secondary outcome) doubled when salmeterol was added to ICS (p<0.0001), but remained unchanged in Arg/Arg subjects (p=0.87) (1.32 doubling dose difference between genotypes (95%CI 0.43,2.21), p=0.0038). An exploratory posthoc subset analysis of African Americans showed that salmeterol improved the AM and PM PEF for the 8 Gly/Gly subjects (29 L/min, p=0.013 and 45 L/min, p= 0.0005, respectively) but not for the 9 Arg/Arg subjects (−12 L/min, p=0.57 and−2.2 L/min, p=0.92, respectively).

Interpretation B16 Arg/Arg and Gly/Gly patients experience improved airway function with salmeterol added to moderate-dose ICS. While these data provide reassurance that in the general population these polymorphisms should not alter the use of LABA with moderate-dose ICS, the significance of the genotype-differentiated response in airway reactivity favoring Gly/Gly subjects and the post-hoc analysis in African Americans require further investigation.

Protectins are newly identified natural chemical mediators that counter leukocyte activation to promote resolution of inflammation. In this study, we provide the first evidence for protectin D1 (PD1, 10R,17S-dihydroxy-docosa-4Z,7Z,11E,13E,15Z,19Z-hexaenoic acid) formation from docosahexaenoic acid in human asthma in vivo and PD1 counterregulatory actions in allergic airway inflammation. PD1 and 17S-hydroxy-docosahexaenoic acid were present in exhaled breath condensates from healthy subjects. Of interest, levels of PD1 were significantly lower in exhaled breath condensates from subjects with asthma exacerbations. PD1 was also present in extracts of murine lungs from both control animals and those sensitized and aerosol challenged with allergen. When PD1 was administered before aeroallergen challenge, airway eosinophil and T lymphocyte recruitment were decreased, as were airway mucus, levels of specific proinflammatory mediators, including IL-13, cysteinyl leukotrienes, and PGD2, and airway hyperresponsiveness to inhaled methacholine. Of interest, PD1 treatment after aeroallergen challenge markedly accelerated the resolution of airway inflammation. Together, these findings provide evidence for endogenous PD1 as a pivotal counterregulatory signal in allergic airway inflammation and point to new therapeutic strategies for modulating inflammation in asthmatic lung.

Inhaled glucocorticoids are the most commonly used medications for the long-term treatment of patients with asthma. Whether long-term therapy with inhaled glucocorticoids reduces bone mass, as oral glucocorticoid therapy does, is controversial. In a three-year prospective study, we examined the relation between the dose of inhaled glucocorticoids and the rate of bone loss in premenopausal women with asthma. METHODS: We studied 109 premenopausal women, 18 to 45 years of age, who had asthma and no known conditions that cause bone loss and who were treated with inhaled triamcinolone acetonide (100 μg per puff). We measured bone density by dual-photon absorptiometry at base line, at six months, and at one, two, and three years. Serum osteocalcin and parathyroid hormone and urinary N-telopeptide, cortisol, and calcium excretion were measured serially. We measured inhaled glucocorticoid use by means of monthly diaries, supported by the use of an automated actuator-monitoring device. RESULTS: Inhaled glucocorticoid therapy was associated with a dose-related decline in bone density at both the total hip and the trochanter of 0.00044 g per square centimeter per puff per year of treatment (P=0.01 and P=0.005, respectively). No dose-related effect was noted at the femoral neck or the spine. Even after the exclusion of all women who received oral or parenteral glucocorticoids at any time during the study, there was still an association between the decline in bone density and the number of puffs per year of use. Serum and urinary markers of bone turnover or adrenal function did not predict the degree of bone loss.