Regular albuterol or nedocromil sodium — effects on airway subepithelial tenascin in asthma

Abstract

Both albuterol and nedocromil sodium have been recognized to possess certain anti-inflammatory properties. However, there are no data on the impact of these drugs on the pathophysiology of the bronchial extracellular matrix in asthma characterized by enhanced tenascin (Tn) expression, known to occur proportional to the severity of asthma. This paper reports data from a morphometric study on the effects of regular treatment with inhaled albuterol or nedocromil sodium on the extent of bronchial subepithelial deposition of Tn, collagen types III, IV, and VII and mucosal infiltration with macrophages. Thirty-two patients (14 women) with chronic asthma, aged 38·7 years (median) with a median forced expiratory volume in 1 sec (FEV 1) of 74·4% predicted, were selected to undergo fibre-optic bronchoscopy with bronchial biopsies before and after 12 weeks of treatment with either inhaled albuterol 0·2 mg or nedocromil sodium 4 mg four times daily according to a double-blind protocol. Cryostat sections of the biopsy specimens were studied by indirect immunostaining techniques using monoclonal antibodies and computer-assisted quantitative image analysis. Albuterol treatment significantly reduced the median thickness of subepithelial Tn expression from 9·7 to 6·3 μm ( P=0·023) and macrophage numbers in the epithelium ( P=0·034), lamina propria ( P=0·039) and entire mucosa ( P=0·033), whereas nedocromil sodium had no effect. Expression of the collagen types was not affected by either treatment. There was no identifiable statistical difference between the two treatments for any of the outcome variables measured. Nevertheless, the results demonstrate that even a short-acting β 2-agonist may exert anti-inflammatory potential sufficient to interfere with the basic mechanisms of asthma as shown by reduction of subepithelial Tn content and mucosal macrophage count.