Role of capacitative Ca entry in bronchial contraction and remodeling

Sweeney, Michele, Sharon S. McDaniel, Oleksandr Platoshyn, Shen Zhang, Ying Yu, Bethany R. Lapp, Ying Zhao, Patricia A. Thistlethwaite, and Jason X.-J. Yuan. Role of capacitative Ca2 entry in bronchial contraction and remodeling. J Appl Physiol 92: 1594–1602, 2002; 10.1152/japplphysiol.00722.2001.—Asthma is characterized by airway inflammation, bronchial hyperresponsiveness, and airway obstruction by bronchospasm and bronchial wall thickening due to smooth muscle hypertrophy. A rise in cytosolic free Ca2 concentration ([Ca2 ]cyt) may serve as a shared signal transduction element that causes bronchial constriction and bronchial wall thickening in asthma. In this study, we examined whether capacitative Ca2 entry (CCE) induced by depletion of intracellular Ca2 stores was involved in agonist-mediated bronchial constriction and bronchial smooth muscle cell (BSMC) proliferation. In isolated bronchial rings, acetylcholine (ACh) induced a transient contraction in the absence of extracellular Ca2 because of Ca2 release from intracellular Ca2 stores. Restoration of extracellular Ca2 in the presence of atropine, an M-receptor blocker, induced a further contraction that was apparently caused by a rise in [Ca2 ]cyt due to CCE. In single BSMC, amplitudes of the store depletion-activated currents (ISOC) and CCE were both enhanced when the cells proliferate, whereas chelation of extracellular Ca2 with EGTA significantly inhibited the cell growth in the presence of serum. Furthermore, the mRNA expression of TRPC1, a transient receptor potential channel gene, was much greater in proliferating BSMC than in growth-arrested cells. Blockade of the store-operated Ca2 channels by Ni2 decreased ISOC and CCE and markedly attenuated BSMC proliferation. These results suggest that upregulated TRPC1 expression, increased ISOC, enhanced CCE, and elevated [Ca2 ]cyt may play important roles in mediating bronchial constriction and BSMC proliferation.