APStracts 3:0202C, 1996.

Pharmacologic activation changes stiffness of cultured human airway smooth muscle cells. Hubmayr, Rolf D., Stephanie A. Shore, Jeffrey J. Fredberg, Emanuelle Planus, Reynold A. Panettieri, Winfried Moller, Joachim Heyder, and Ning Wang. Physiology Program, Department of Environmental Health, Harvard School of Public Health, 665 Huntington Avenue, Boston, MA 02115, Division of Pulmonary & Critical Care Medicine, Mayo Clinic, 200 First Street SW, Rochester, MN, 55905, Pulmonary and Critical Care Division, Department of Medicine, University of Pennsylvania, Philadelphia, PA, 19102, GSF National Research Center for Environment and Health Institute for Inhalation Biology D/85764, Oberschleissheim, Germany

APStracts 3:0202C, 1996.

Using magnetic twisting cytometry (MTC), we measured the cytoskeletal stiffness of adherent human airway smooth muscle (HASM) cells. We hypothesized that modulation of actin-myosin interactions by application of contractile agonists would induce changes in cytoskeletal stiffness. Accordingly, we measured changes of stiffness in response to agonists previously reported to increase intracellular calcium in these cells. We also measured changes in stiffness in response to bronchodilator agonists known to increase cAMP or cGMP. Because the density of the extracellular matrix on which cells are plated has previously been shown to influence stiffness of other cell types, we also examined the effects of varying the density of the collagen matrix on which we plated cells on stiffness changes induced by contractile and dilator agonists. In cells plated on high density collagen, bradykinin (10-6 M) and histamine (10-4 M) increased stiffness by 85 +/- 15% and 68 +/- 16%, respectively. Increases in cell stiffness, though slightly less pronounced, were also consistently observed following acetylcholine, substance P, and KCl. The bronchodilator agonists isoproterenol, prostaglandin E2, forskolin, dibutryl cAMP, and 8-bromo-cGMP each caused a dose -dependent decrease in cell stiffness in unstimulated as well as bradykinin treated cells. HASM cells plated on high density collagen were stiffer than cells plated on low density collagen (126 +/- 16 vs 43 +/- 3 dyne/cm2) and developed more pronounced increases in stiffness in response to bradykinin as well as more pronounced decreases in stiffness in response to isoproterenol. These results are consistent with the hypothesis that modulation of actin-myosin interactions by application of contractile agonists causes changes in cytoskeletal stiffness of HASM cells. As such, MTC may be a valuable tool for evaluating the mechanisms of pharmaco-mechanical coupling in airway smooth muscle cells in culture.

Received 20 October 1995; accepted in final form 7 March 1996.
APS Manuscript Number C638-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 4 July 96