Role of MUC5AC in the pathogenesis of exercise-induced bronchoconstriction

BACKGROUND

The pathogenesis of exercise-induced bronchoconstriction (EIB) involves the release of mediators from several airway cells in response to exercise challenge, but the mechanism leading to airflow obstruction during EIB is incompletely understood.

OBJECTIVE

To evaluate the role of secreted mucin in the pathogenesis of EIB.

METHODS

Induced sputum was collected at baseline and 30 minutes after exercise challenge in patients with asthma with EIB. The expression of gel-forming mucins and epidermal growth factor receptor ligands were assessed by quantitative polymerase chain reaction. Secreted mucin 5AC (MUC5AC), the eicosanoids cysteinyl leukotrienes (cysLTs) and 15S-hydroxyeicosatetraenoic acid (15S-HETE), and tachykinins neurokinin A (NKA) and substance P (SP) were measured in induced sputum supernatant.

RESULTS

Among the gel-forming mucins, MUC5AC was expressed at the highest level. The gene expression of MUC5AC increased after exercise challenge compared with baseline and was associated with EIB severity by regression analysis. The relative levels of MUC5AC in induced sputum increased from a geometric mean of 9.5 at baseline to 18.4 postexercise challenge. Associations between the levels of MUC5AC and cysLTs and between the levels of cysLTs and NKA postexercise challenge were identified by regression analysis.

CONCLUSIONS

These data indicate that (1) the predominant gel-forming mucin expressed in induced sputum of patients with asthma with EIB is MUC5AC; (2) an increase in MUC5AC gene expression and release of MUC5AC protein occurs after exercise challenge; and (3) MUC5AC release may occur through the cysLT-associated activation of sensory airway nerves.

Chronic productive cough in school children: prevalence and associations with asthma and environmental tobacco smoke exposure

Background

The relationships between chronic productive cough (CPC), environmental tobacco smoke (ETS) exposure, and asthma are not clearly established in children. Therefore, we wished to determine the prevalence of CPC and examine the relationships between CPC, ETS exposure, and asthma in young teenagers.

Methods

We performed a cross sectional survey of 2397 Seattle middle school students, 11–15 years old, using written and video respiratory-symptom questionnaires. We defined CPC as – daily cough productive of phlegm for at least 3 months out of the year; current asthma as – yes to "Have you had wheezing or whistling in your chest in the past 12 months?" and yes in the past year to any of the four video wheezing/asthma video scenarios; and ETS exposure as exposed to tobacco smoke at least several hours each day. We used multilogistic regression to examine relationships between CPC, asthma, and ETS exposure and included in the model the potentially confounding variables race, gender, and allergic rhinitis.

Results

The prevalence of CPC was 7.2%. Forty-seven percent (82/173) of children with CPC met criteria for current asthma, while only 10% (214/2224) of those without CPC had current asthma. Current asthma had the strongest associated with CPC, odds ratio (OR) 6.4 [95% CI 4.5–9.0], and ETS was independently associated with both CPC, OR 2.7 [1.8–4.1] and asthma, OR 2.7 [1.5–4.7].

Conclusion

In a population of young teenagers, CPC was strongly associated with report of current asthma symptoms and also with ETS exposure. This suggests that asthma and ETS exposure may contribute to CPC in children. However, this study was not designed to determine whether asthma was the actual cause of CPC in this population of children.

Prevalence and impact of gastroesophageal reflux in adolescents with asthma: a population-based study

We determined the prevalence of gastroesophageal reflux disease (GERD) symptoms and the associations between GERD symptoms and asthma morbidity in a population of adolescents with asthma. Two thousand, three hundred and ninety-seven students attending six middle schools in Seattle completed the International Study of Asthma and Allergy in Children (ISAAC) written and video survey that included additional questions pertaining to GERD symptoms and asthma morbidity. Based on their responses, children were categorized as having undiagnosed current asthma, physician-diagnosed current asthma, or no asthma symptoms. The prevalence of GERD symptoms occurring at least weekly or daily was determined for each group. The asthma morbidity outcomes were emergency department visits, physician visits, missed school days, and use of inhaled medications for respiratory symptoms within the past year. Associations between GERD symptoms and asthma morbidity outcomes were determined using logistic regression. The prevalence of GERD symptoms was significantly higher among students with current asthma (19.3%; 95% confidence interval (CI), 14.9-24.2) than students with no asthma symptoms (2.5%; 95% CI, 1.8-3.4). In children with current asthma (n = 296), symptoms of GERD that occurred at least weekly were strongly associated with emergency department visits (odds ratio (OR), 5.0; 95% CI, 2.6-9.6), physician visits (OR, 2.5; 95% CI, 1.3-4.6), missed school (OR, 2.0; 95% CI, 1.1-3.7), and inhaled medication use (OR, 2.5; 95% CI, 1.3-4.7). The associations between GERD symptoms and emergency department visits, physician visits, and inhaled medication use were stronger among children with asthma who reported daily GERD symptoms (n = 14) than among children reporting weekly GERD symptoms (n = 57). The prevalence of GERD symptoms was greater in adolescents with current asthma than in those without asthma. In addition, the presence of at least weekly GERD symptoms was strongly associated with greater asthma morbidity and the use of asthma medications.

Changes in asthma prevalence and impact on health and function in Seattle middle-school children: 1995 vs 2003

BACKGROUND

The prevalence of asthma has increased during the past several decades but may have stabilized during the last 5 years. It is not known whether the functional and health impact of asthma has decreased during the past decade.

OBJECTIVE

To evaluate changes during a recent 8-year period in the prevalence and health and functional impact of current asthma symptoms in young teenagers.

METHODS

In 1995 and 2003, 2,330 and 2,397 middle-school students from Seattle, WA, respectively (median age, 13 years), completed written surveys and answered questions pertaining to 4 wheezing or asthma video scenarios. Children were categorized as having physician-diagnosed current asthma (wheeze in the past year and a physician diagnosis of asthma), undiagnosed current asthma symptoms (wheeze in the past year without a physician diagnosis), or no asthma. Outcome measures were the prevalence of asthma and undiagnosed asthma symptoms and the differences between years in respiratory-associated functional impairment (exercise limitation, missed school, disrupted sleep) and health impact (physician visits, wheeze-limited speech).

RESULTS

The prevalence of physician-diagnosed current asthma increased from 1995 to 2003 (3.0% to 6.2%), whereas that for undiagnosed current asthma symptoms decreased (12.0% to 6.2%). The degree of functional and health impairment was similar between the 2 study periods for each subgroup and was highest in the children with physician-diagnosed current asthma.

CONCLUSIONS

The prevalence of current asthma symptoms in middle-school children from Seattle decreased slightly between 1995 and 2003, whereas the diagnosis of asthma increased. However, the health and functional impact of asthma did not diminish. Asthma is being diagnosed more often, but many children with asthma are still not achieving good asthma control.

The prevalence of ibuprofen-sensitive asthma in children: a randomized controlled bronchoprovocation challenge study

OBJECTIVE

To determine the prevalence of ibuprofen-sensitive asthma in school-aged children with mild or moderate persistent asthma.

STUDY DESIGN

A randomized, double-blind, placebo-controlled, crossover bronchoprovocation challenge study in children 6 to 18 years of age with mild or moderate persistent asthma. Patients received a single dose of ibuprofen or placebo, per randomization, and then returned 2 to 7 days later to repeat the procedures after taking that study drug not received at the first visit. At each visit, patients performed spirometry before and (1/2), 1, 2, and 4 hours after administration of study drug. We defined bronchospasm as a > or =20% decrease from baseline in the forced expired volume in the first second (FEV1) and ibuprofen sensitivity as bronchospasm following administration of ibuprofen but not placebo.

RESULTS

Of the 127 patients screened, 100 (mean age, 11 years) completed the study. Two patients met criteria for ibuprofen-sensitive asthma, resulting in a prevalence of 2% (95% CI: 0.2%-7%). Neither patient was known to have had any exposure to ibuprofen before the study.

CONCLUSION

The prevalence of ibuprofen-sensitive asthma was low but non-zero in this group of children with mild or moderate asthma. The possibility of ibuprofen-induced bronchospasm should be considered before administering ibuprofen to children with asthma.

Childhood asthma hospitalization risk after cesarean delivery in former term and premature infants

BACKGROUND

Cesarean delivery modifies infant gut bacterial flora composition, which may result in hindered tolerance to allergenic substances, thereby increasing the risk of asthma in accordance with the hygiene hypothesis. Results of previous studies regarding an association between birth route and asthma are conflicting, and these studies have not evaluated some potential confounding effects, including prematurity and maternal asthma.

OBJECTIVE

To determine whether cesarean delivery in full-term and premature infants increases the risk of subsequent childhood asthma hospitalization.

METHODS

We conducted a case-control study using the Washington State Birth Events Record Database linked to statewide hospitalization data. The study included 2,028 children hospitalized for asthma (cases) and 8,292 age-matched controls.

RESULTS

Cesarean delivery was modestly associated with an increased risk of asthma hospitalization (odds ratio [OR], 1.20; 95% confidence interval [CI], 1.04-1.39). However, when analyzed separately, there was an association between cesarean delivery and asthma hospitalization in premature infants (OR, 1.90; 95% CI, 1.09-3.02) but not in full-term infants (OR, 1.15; 95% CI, 0.97-1.34).

CONCLUSIONS

Cesarean delivery was associated with subsequent asthma hospitalization only in premature infants. Because mothers with asthma are reported to have increased rates of cesarean delivery and premature delivery, other factors in addition to the hygiene hypothesis, including genetic and in utero influences associated with maternal asthma, may contribute to the increased risk of asthma in premature infants.

Impact of adolescence and gender on asthma hospitalization: a population-based birth cohort study

Our objective was to determine the impact of gender and age on asthma hospitalization rates among children. We used a population-based retrospective birth cohort study to determine yearly age- and gender-specific asthma hospitalization rates between ages 2-18 years in a cohort of all children born in Washington State between 1980-1985. In addition, we assessed factors associated with the hospitalization of a given child for asthma both before and during adolescence, and factors associated with an initial asthma hospitalization during adolescence. Outcome measures included age- and gender-specific rates of hospitalization for asthma, diabetes, seizures/epilepsy, and nonasthma respiratory diagnoses. Asthma hospitalization rates for boys were significantly higher than for girls between ages 2-12 years, the gender gap in asthma hospitalizations reversed between ages 13-14 years, and rates for girls were significantly higher than boys between 16-18 years of age. The male peak asthma hospitalization rate per 100,000 cohort members occurred at age 4 years (12.7; 95% confidence interval (CI), 11.1-14.3), and the male trough rate occurred at age 18 years (4.1; 95% CI, 2.8-5.4), whereas the female peak asthma hospitalization rate occurred at age 17 years (9.4; 95% CI, 7.8-11) and the female trough rate at age 2 years (5.2; 95% CI, 4.2-6.2). Age-specific hospitalization rates for diabetes mellitus and epilepsy were similar for boys and girls throughout childhood. Female gender was strongly associated with asthma hospitalization occurring in an individual child both prior to and during adolescence (rate ratio (RR), 2.0; 95% CI, 1.4-2.9), and was modestly associated with initial hospitalization in adolescence (RR, 1.15; 95% CI, 1.0-1.3). In conclusion, asthma hospitalization rates for boys and girls exhibit strikingly different patterns during adolescence. Potential explanations for these gender differences include hormonal changes during puberty, or gender-specific differences in environmental exposures such as diet, obesity, allergen exposure, or cigarette smoking.