Inflammatory and bronchospastic factors in asthma exacerbations caused by upper respiratory tract infections

It is still uncertain how viral respiratory infections cause acute exacerbations of bronchial asthma, although several mechanisms have been proposed. We studied the relationship between the airway narrowing and the inflammatory and bronchospastic factors in peripheral venous blood and urine, in 30 patients with asthma at the exacerbations caused by upper respiratory tract infections (URTIs). Acute exacerbations caused decreases in peak expiratory flow rate (PEFR) in all 30 patients with asthma. Asthma exacerbations caused the rises in serum levels of interleukin-6, soluble intercellular adhesion molecule-1 and eosinophil cationic protein, concentrations of urinary leukotriene E4 and plasma histamine, compared with those in patients with asthma at a stable condition and those in 30 control subjects (p < 0.05). The values of PEFR at the exacerbations correlated with the levels of these factors. Treatment with oral glucocorticoids reversed the decreases in PEFR and the increases in these factors. At the onset of URTIs, rhinovirus and influenza type A virus were identified in 13 and 7 patients, respectively. Each of parainfluenza virus, adenovirus, and enterovirus was identified in one patient. These findings suggest that respiratory viral infections may cause acute asthma exacerbations via the production of mediators that induce inflammation and bronchospasm.