Abstract
BACKGROUND: Exaggerated bronchial constriction is the most significant and life threatening response of patients with asthma to inhaled stimuli. However, few studies have investigated the contractility of airway smooth muscle (ASM) from these patients. The purpose of this study was to establish a method to measure contraction of ASM cells by embedding them into a collagen gel, and to compare the contraction between subjects with and without asthma. METHODS: Gel contraction to histamine was examined in floating gels containing cultured ASM cells from subjects with and without asthma following overnight incubation while unattached (method 1) or attached (method 2) to casting plates. Smooth muscle myosin light chain kinase protein levels were also examined. RESULTS: Collagen gels containing ASM cells reduced in size when stimulated with histamine in a concentration-dependent manner and reached a maximum at a mean (SE) of 15.7 (1.2) min. This gel contraction was decreased by inhibitors for phospholipase C (U73122), myosin light chain kinase (ML-7) and Rho kinase (Y27632). When comparing the two patient groups, the maximal decreased area of gels containing ASM cells from patients with asthma was 19 (2)% (n = 8) using method 1 and 22 (3)% (n = 6) using method 2, both of which were greater than that of cells from patients without asthma: 13 (2)% (n = 9, p = 0.05) and 10 (4)% (n = 5, p = 0.024), respectively. Smooth muscle myosin light chain kinase levels were not different between the two groups. CONCLUSION: The increased contraction of asthmatic ASM cells may be responsible for exaggerated bronchial constriction in asthma.