Comparison of gel contraction mediated by asthmatic and non-asthmatic airway smooth muscle cells

Abstract

Backgrounds: Exaggerated bronchial constriction is the most significant and life-threatening response of asthmatic patients to inhaled stimuli. However, few studies have investigated the contractility of airway smooth muscle (ASM) from asthmatic 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 compare the contraction between non-asthmatics and asthmatics.

Methods: Gel-contraction to histamine was examined in floating gels containing cultured ASM cells from non-asthmatics and asthmatics 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 15.7 (SEM,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 asthmatic ASM cells was 19 (2)% (n = 8) using method 1 and 22 (3)% (n = 6) using method 2, both of which were greater than that of non-asthmatic cells, 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.