Inhibition of endogenous TRP1 decreases capacitative Ca entry and attenuates pulmonary artery smooth muscle cell proliferation

Sweeney, Michele, Ying Yu, Oleksandr Platoshyn, Shen Zhang, Sharon S. McDaniel, and Jason X.-J. Yuan. Inhibition of endogenous TRP1 decreases capacitative Ca2 entry and attenuates pulmonary artery smooth muscle cell proliferation. Am J Physiol Lung Cell Mol Physiol 283: L144–L155, 2002. First published February 8, 2002; 10.1152/ ajplung.00412.2001.—Pulmonary vascular medial hypertrophy due to proliferation of pulmonary artery smooth muscle cells (PASMC) greatly contributes to the increased pulmonary vascular resistance in pulmonary hypertension patients. A rise in cytosolic free Ca2 concentration ([Ca2 ]cyt) is an important stimulus for cell growth in PASMC. Resting [Ca2 ]cyt, intracellularly stored [Ca2 ], capacitative Ca2 entry (CCE), and store-operated Ca2 currents (ISOC) are greater in proliferating human PASMC than in growth-arrested cells. Expression of TRP1, a transient receptor potential gene proposed to encode the channels responsible for CCE and ISOC, was also upregulated in proliferating PASMC. Our aim was to determine if inhibition of endogenous TRP1 gene expression affects ISOC and CCE and regulates cell proliferation in human PASMC. Cells were treated with an antisense oligonucleotide (AS, for 24 h) specifically designed to cleave TRP1 mRNA and then returned to normal growth medium for 40 h before the experiments. Then, mRNA and protein expression of TRP1 was downregulated, and amplitudes of ISOC and CCE elicited by passive depletion of Ca2 from the sarcoplasmic reticulum using cyclopiazonic acid were significantly reduced in the AS-treated PASMC compared with control. Furthermore, the rate of cell growth was decreased by 50% in AS-treated PASMC. These results indicate that TRP1 may encode a store-operated Ca2 channel that plays a critical role in PASMC proliferation by regulating CCE and intracellular [Ca2 ]cyt.