PAI-1 gain-of-function genotype, factors increasing PAI-1 levels, and airway obstruction: The GALA II Cohort

BACKGROUND

PAI-1 gain-of-function variants promote airway fibrosis and are associated with asthma and with worse lung function in subjects with asthma.

OBJECTIVE

We sought to determine whether the association of a gain-of-function polymorphism in plasminogen activator inhibitor-1 (PAI-1) with airway obstruction is modified by asthma status, and whether any genotype effect persists after accounting for common exposures that increase PAI-1 level.

METHODS

We studied 2070 Latino children (8-21y) with genotypic and pulmonary function data from the GALA II cohort. We estimated the relationship of the PAI-1 risk allele with FEV1/FVC by multivariate linear regression, stratified by asthma status. We examined the association of the polymorphism with asthma and airway obstruction within asthmatics via multivariate logistic regression. We replicated associations in the SAPPHIRE cohort of African Americans (n=1056). Secondary analysis included the effect of the at-risk polymorphism on postbronchodilator lung function.

RESULTS

There was an interaction between asthma status and the PAI-1 polymorphism on FEV₁ /FVC (P=.03). The gain-of-function variants, genotypes (AA/AG), were associated with lower FEV₁ /FVC in subjects with asthma (β=-1.25, CI: -2.14,-0.35, P=.006), but not in controls. Subjects with asthma and the AA/AG genotypes had a 5% decrease in FEV₁ /FVC (P<.001). In asthmatics, the risk genotype (AA/AG) was associated with a 39% increase in risk of clinically relevant airway obstruction (OR=1.39, CI: 1.01, 1.92, P=.04). These associations persisted after exclusion of factors that increase PAI-1 including tobacco exposure and obesity.

CONCLUSIONS AND CLINICAL RELEVANCE

The decrease in the FEV₁ /FVC ratio associated with the risk genotype was modified by asthma status. The genotype increased the odds of airway obstruction by 75% within asthmatics only. As exposures known to increase PAI-1 levels did not mitigate this association, PAI-1 may contribute to airway obstruction in the context of chronic asthmatic airway inflammation.

Maternal age and asthma in Latino populations

BACKGROUND

Younger maternal age at birth is associated with increased risk of asthma in offspring in European descent populations, but has not been studied in Latino populations.

OBJECTIVES

We sought to examine the relationship between maternal age at birth and prevalence of asthma in a nationwide study of Latino children.

METHODS

We included 3473 Latino children aged 8-21 years (1696 subjects with physician-diagnosed asthma and 1777 healthy controls) from five US centres and Puerto Rico recruited from July 2008 through November 2011. We used multiple logistic regression models to examine the effect of maternal age at birth on asthma in offspring overall and in analyses stratified by ethnic subgroup (Mexican American, Puerto Rican and other Latino). Secondary analyses evaluated the effects of siblings, acculturation and income on this relationship.

RESULTS

Maternal age < 20 years was significantly associated with decreased odds of asthma in offspring, independent of other risk factors (OR = 0.73, 95% CI: 0.57-0.93). In subgroup analyses, the protective effect of younger maternal age was observed only in Mexican Americans (OR = 0.53, 95% CI: 0.36, 0.79). In Puerto Ricans, older maternal age was associated with decreased odds of asthma (OR = 0.65, 95% CI: 0.44-0.97). In further stratified models, the protective effect of younger maternal age in Mexican Americans was seen only in children without older siblings (OR = 0.44, 95% CI: 0.23-0.81).

CONCLUSION AND CLINICAL RELEVANCE

In contrast to European descent populations, younger maternal age was associated with decreased odds of asthma in offspring in Mexican American women. Asthma is common in urban minority populations but the factors underlying the varying prevalence among different Latino ethnicities in the United States is not well understood. Maternal age represents one factor that may help to explain this variability.

Predicting worsening asthma control following the common cold

The asthmatic response to the common cold is highly variable, and early characteristics that predict worsening of asthma control following a cold have not been identified. In this prospective multicentric cohort study of 413 adult subjects with asthma, the mini-Asthma Control Questionnaire (mini-ACQ) was used to quantify changes in asthma control and the Wisconsin Upper Respiratory Symptom Survey-21 (WURSS-21) to measure cold severity. Univariate and multivariable models were used to examine demographic, physiological, serological and cold-related characteristics for their relationship to changes in asthma control following a cold. Clinically significant worsening of asthma control was observed following a cold (mean+/-SD increase in mini-ACQ score of 0.69+/-0.93). Univariate analysis demonstrated that season, centre location, cold duration and cold severity measurements were all associated with a change in asthma control. Multivariable analysis of the covariates available within the first 2 days of cold onset revealed that the day 2 and cumulative sum of day 1 and 2 WURSS-21 scores were significant predictors of the subsequent changes in asthma control. In asthmatic subjects, cold severity within the first 2 days can be used to predict subsequent changes in asthma control. This information may help clinicians prevent deterioration in asthma control following a cold.

Real-time monitoring of nasal mucosal pH during carbon dioxide stimulation: implications for stimulus dynamics

Carbon dioxide is a commonly employed irritant test compound in nasal chemesthetic studies because it is essentially free of olfactory stimulus properties. CO(2) is thought to act via hydration to H(2)CO(3) and dissociation to H(+) in nasal mucus, with resulting activation of acid sensors. However, transient changes in nasal mucosal pH have not been documented during CO(2) stimulation in humans. We placed a small pH probe on the floor of the right anterior nasal cavity during CO(2) stimulation in eight human subjects with historically high (>30%) and low (< or =20%) CO(2) detection thresholds. Three second pulses of CO(2) (15-45% v/v) paired with air in random order (12-15 s inter-stimulus interval; 60 s inter-trial interval) were administered by nasal cannula at 5 l/min. in an ascending series. For each subject, both a CO(2) detection threshold and suprathreshold psychophysical ratings [psi; labeled magnitude scale] were generated. All subjects showed phasic drops in pH associated with CO(2) stimulation (DeltapH). For all subjects combined, a positive correlation was apparent between applied [CO(2)] and both DeltapH and psi, as well as between DeltapH and psi themselves (P < 0.0001 for each comparison). Subjects with historically low CO(2) thresholds showed steeper dose-response curves for psi as a function of both applied [CO(2)] and DeltapH, but not for DeltapH as a function of applied [CO(2)]. For the six of eight subjects with measurable pH changes at threshold, DeltapH was positively related to log [CO(2) threshold] (P < 0.01). These data imply that variability in CO(2) detection thresholds and suprathreshold rating may derive from intrinsic differences in neural sensitivity, rather than differences in stimulus activation to hydrogen ion.

Effect of a single dose of the selectin inhibitor TBC1269 on early and late asthmatic responses

BACKGROUND

Selectins participate in the initial phase of leucocyte migration from circulation to inflamed tissues and may play a role in inflammatory cellular influx into airways in asthma. In the sheep asthma model, TBC1269, a pan-selectin antagonist, reduced late allergen response by 74%.

OBJECTIVE

To determine whether a single dose of TBC1269 inhibits early (EAR) and late (LAR) asthmatic responses, and whether it inhibits sputum leucocyte influx after inhalation allergen challenge in atopic asthmatic subjects treated with bronchodilators only.

METHODS

Twenty-one asthmatic subjects (mean+/-SD, age=32.5+/-6.7 years, 8 males, FEV1 percent predicted=84+/-15%) with known late asthmatic response based on a screening inhalation allergen challenge were randomly assigned to receive intravenous treatment with either placebo (n=11) or TBC1269 (n=10, 30 mg/kg) infused over 15 min immediately prior to a second (post-treatment) allergen challenge at least 4 weeks after the screening challenge. After each challenge, EAR and LAR were monitored for 7 h. In addition, sputum was induced 1 day before and 1 day after each allergen challenge.

RESULTS

TBC1269 did not attenuate the EAR compared with placebo (largest fall in FEV1 within 1 h of 34.1+/-13.9% vs. 31.8+/-12.2% for TBC1269 and placebo groups respectively, P=0.61) or the LAR (largest fall in FEV1 between 3 and 7 h of 39.3+/-15.3% vs. 32.6+/-13.8%, P=0.24). TBC1269 had only minor effects on allergen-induced sputum eosinophilia.

CONCLUSION

We conclude that TBC1269 administered before allergen challenge as a single intravenous dose does not attenuate early or late asthmatic responses to allergen in asthmatic subjects.

Chlorine inhalation produces nasal congestion in allergic rhinitics without mast cell degranulation

Seasonal allergic rhinitic (SAR) subjects are more sensitive to nasal irritants than nonrhinitic (NR) subjects; however, the mechanism underlying this difference is unclear. This study sought to determine whether irritant-induced nasal congestion involves mast cell degranulation. Eight SAR and eight NR subjects were exposed to both 1.0 parts per million chlorine and filtered air in separate visits; exposures were via nasal mask and lasted 15 min. Rhinomanometry was performed before, immediately after and 15 min after exposure. Following > or = 2 weeks, exposures and symptom reporting were repeated with nasal lavage, rather than rhinomanometry, pre- and postexposure. A separate substudy using rye grass antigen provided a positive control. Mast cell tryptase was measured in nasal lavage fluid from both substudies using an automated fluoroenzyme immunoassay. Chlorine provocation significantly increased nasal airway resistance in SAR but not NR subjects. Conversely, tryptase levels in nasal lavage fluid were unaffected. Nasal allergen challenge significantly increased both nasal obstruction and nasal lavage tryptase in SAR subjects. Irritant-induced nasal congestion is more pronounced among seasonal allergic rhinitic than nonrhinitic subjects. However, unlike nasal allergen challenge, the mechanism of response to chlorine does not appear to involve mast cell degranulation.

Predictors of late asthmatic response. Logistic regression and classification tree analyses

To identify predictors of the late asthmatic response (LAR), we reviewed data from 60 asthmatic subjects who had undergone allergen challenge over the past 5 yr (33 females, age 31.4 +/- 6.7 yr [mean +/- SD], FEV(1) 90% +/- 14% predicted). Variables considered likely predictors of LAR included baseline FEV(1), PC(20) methacholine (PC(20)), sputum eosinophil percent, and the decrease in FEV(1) within 20 min of allergen challenge. A LAR (FEV(1) >/= 15% fall between 3 and 7 h after challenge) was documented in 57% of subjects. A variety of logistic regression methods revealed a significant inverse association between LAR and PC(20) (odds ratio [OR] = 0.14 [95% CI = 0.03-0.66]) and a positive association between LAR and the decrease in FEV(1) at 20 min (OR = 1.18 [1.04 -1.33]). Classification tree analysis revealed that a threshold of 0.25 mg/ml for PC(20) was most predictive of LAR; LAR developed in 87% of those with PC(20) </= 0.25 mg/ml (n = 23) and in 38% of those with PC(20) > 0.25 mg/ml (n = 37). Notably, in subjects with PC(20) > 0.25 mg/ml, the incidence of LAR increased from 38% to 57% if the allergen-induced decline in FEV(1) at 20 min was >/= 27%. Surprisingly, baseline FEV(1) and percent eosinophils in induced sputum were not significantly associated with LAR. We conclude that a threshold value of 0.25 mg/ml for PC(20) methacholine is a good predictor of LAR. Measuring the PC(20) methacholine may be useful as a screening method to improve the efficiency of identifying asthmatic subjects with a LAR.

Effects of allergic inflammation of the nasal mucosa on the severity of rhinovirus 16 cold

BACKGROUND

Despite the strong association of asthma exacerbations with rhinovirus (RV) infection, inoculation of asthmatic subjects with RV only causes small changes in lower airway function, suggesting that RV infection is not itself sufficient to provoke asthma exacerbations.

OBJECTIVE

Our purpose was to test whether allergic inflammation increases the airway response to RV infection.

METHODS

We compared the severity of RV type 16-induced colds in 2 groups of 10 subjects with allergic rhinitis. One group received 3 nasal challenges with allergen and the other received challenges with placebo over the week before nasal inoculation with RV type 16 (4000 tissue culture infective dose 50% per subject). Subjects kept symptom diaries and were assessed with spirometry, methacholine challenge, nasal lavage, and sputum induction on days 2, 4, 7, 10, 15, and 30 after inoculation.

RESULTS

The 2 groups developed equal rates of infection (90%), similar cold symptoms (Jackson score median [interquartile range], 11 [6-33] vs 20.5 [6-42] for allergen and placebo groups respectively, P =.54), and similar changes in cellular profile and in IL-6 and IL-8 concentrations in nasal lavage fluid and induced sputum after RV inoculation. The incubation period was significantly longer in the allergen group (2.5 [1-5.5] vs 1 [1-1] day, P =.03) and the duration of cold symptoms was shorter (5 [4-7] vs 8.5 [6-10] days, P =.008). We also found an inverse correlation between the percent of eosinophils in nasal lavage fluid before inoculation and the severity of cold symptoms (r = -0.58, P =. 008).

CONCLUSION

In subjects with allergic rhinitis, augmented nasal allergic inflammation before inoculation with RV type 16 does not worsen the severity of cold symptoms but delays their onset and shortens their duration.

Effect of clarithromycin on experimental rhinovirus-16 colds: a randomized, double-blind, controlled trial

PURPOSE

Macrolide antibiotics are frequently prescribed to patients with symptoms of a common cold. Despite their lack of proven antiviral activity, macrolide antibiotics may have anti-inflammatory actions, such as inhibition of mucus secretion and production of interleukins 6 and 8 by epithelial cells. Because the symptoms of rhinovirus colds are attributed to the inflammatory response to infection, we studied the effects of treatment with clarithromycin on the symptomatic and inflammatory response to nasal inoculation with rhinovirus.

SUBJECTS AND METHODS

We performed a prospective, double-blind, controlled trial in 24 healthy subjects who were seronegative for antibodies to rhinovirus-16. Subjects were randomly assigned to receive either clarithromycin (500 mg) or trimethoprim-sulfamethoxazole (800/160 mg, as a control antibiotic) twice a day for 8 days, beginning 24 hours before inoculation with rhinovirus-16.

RESULTS

All 12 subjects in each group were infected and developed symptomatic colds. The groups did not differ in the intensity of cold symptoms (median [25th to 75th percentile] score in the clarithromycin group of 25 [5 to 33] versus 21 [11 to 26] in the trimethoprim-sulfamethoxazole group, P = 0.86), weight of nasal secretions (25 g [8 to 56 g] versus 12 g [5 to 28 g], P = 0.27), or decline in nasal peak flow during the 8 days following viral inoculation. In both groups, similar and significant increases from baseline were observed in the numbers of total cells and neutrophils, and in the concentrations of interleukins 6 and 8, in nasal lavage fluid during the cold. The changes that we observed did not differ from those in an untreated historical control group.

CONCLUSIONS

We conclude that clarithromycin treatment has little or no effect on the severity of cold symptoms or the intensity of neutrophilic nasal inflammation in experimental rhinovirus-16 colds.

Rhinovirus-16 colds in healthy and in asthmatic subjects: similar changes in upper and lower airways

Rhinovirus (RV) infections appear to precipitate most asthma exacerbations. To investigate whether RV-16 induces different inflammatory changes in upper and lower airways of asthmatic and healthy subjects, we inoculated 10 nonatopic healthy and 11 atopic asthmatic adults with 2,000 TCID50 RV-16. Subjects recorded symptoms and peak flow daily; and they underwent spirometry, methacholine challenge (PC20), nasal lavage, and sputum induction at baseline and on Days 2, 4, 15, and 29 d after inoculation. One asthmatic subject developed an exacerbation requiring prednisone treatment 5 d after inoculation. The cold symptom severity (Jackson score) did not differ between groups. During the cold, asthma symptoms increased slightly from baseline in the asthmatic group; and PC20 decreased in the healthy group. However, peak flow, bronchodilator use, and spirometry did not change in either group. At baseline, asthmatics had higher neutrophils, eosinophils, and interleukin (IL)-6 in nasal lavage. After inoculation, both groups developed significant increases in nasal neutrophils, IL-6 and IL-8, and modest increases in sputum neutrophils and IL-6, but not IL-8. However, these changes did not differ between groups. IL-5, interferon-gamma, and RANTES were detected only in nasal lavages from two asthmatic subjects, who had the most severe colds. IL-11 was not detected in any sample. We conclude that inflammatory responses of upper and lower airways during RV-16 colds are similar in asthmatic and healthy subjects, and that RV-16 infection is not by itself sufficient to provoke clinical worsening of asthma.

Work-related asthma and latex allergy. Sorting out the types, causes, and consequences

Work-related asthma now has clear definitions based on criteria agreed upon by the American College of Chest Physicians. The clinician should suspect occupational asthma, irritant-induced asthma, or work-aggravated asthma in adults with new-onset asthma or asthma symptoms that worsen during work, after work (late allergic response), or over the course of workdays. The possible cause should be sought, and a skin test or immunoassay should be performed, if possible,to he;lp detect sensation. Workup als o includes objective documentation of worsening of symptoms and airway obstruction during occupational exposure. If this information is inconclusive, an inhalation challenge may be considered. Medical management is the same as for nonoccupational asthma, but cessation of exposure to the specific agent is necessary to improve long-term diagnosis. Latex allergy and latex-induced asthma are becoming more common in the workplace, particularly in the healthcare field. No commercially available standard serum or skin test are available for diagnosis. The principal treatment is avoidance of latex, which can be achieved in most cases without extensive changes to the workplace.