Am. J. Respir. Crit. Care Med., Volume 162, Number 4, October 2000, 1302-1307

Exercise-induced Bronchoconstriction Does Not Cause Eosinophilic Airway Inflammation or Airway Hyperresponsiveness in Subjects with Asthma

GAIL M. GAUVREAU, GISELLE M. RONNEN, RICK M. WATSON, and PAUL M. O'BYRNE

Asthma Research Group, St. Joseph's Hospital and the Department of Medicine, McMaster University, Hamilton, Ontario, Canada

The cysteinyl leukotrienes (LT) C₄, D₄, and E₄ may partially mediate eosinophilic airway inflammation in patients with asthma. High- intensity exercise by patients with asthma can result in exercise- induced bronchoconstriction, partly due to leukotriene production, but it is still debated whether this causes airway inflammation. Ten subjects completed a randomized, controlled study to examine the effects of exercise-induced bronchoconstriction on airway inflammatory cells. Subjects completed exercise challenge and methacholine challenge in random order separated by 1 wk. Spirometry was measured for 2 h after challenges, and airway responsiveness was measured the day before and 24 h after each challenge. Blood and sputum samples were obtained before, and 2, 4, 7, and 24 h after each challenge for measurement of inflammatory cells. Nine of the subjects inhaled allergen at least 3 wk before or 1 wk after the study. Sputum samples were collected before, 7 h, and 24 h after challenge. The maximum percentage fall in FEV₁ was 21.3 ± 1.5% after exercise, 29.9 ± 1.5% after methacholine, and 28.9±2.7% after allergen. Exercise had no effect on airway responsiveness or inflammatory cells measured in blood or sputum, unlike allergen inhalation, which resulted in significant airway hyperresponsiveness and increases in sputum eosinophils (p < 0.05). This study demonstrates that exercise-induced bronchoconstriction does not cause eosinophilic airway inflammation in subjects with asthma who develop airway inflammation with the same degree of allergen-induced bronchoconstriction. We conclude that exercise-induced bronchoconstriction does not cause airway inflammation or airway hyperresponsiveness.

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