Overexpression of TRPC1 enhances pulmonary vasoconstriction induced by capacitative Ca2+ entry

Division of Pulmonary and Critical Care Medicine, Department of Medicine, School of Medicine, University of California, San Diego, La Jolla, California 92093 Submitted 22 December 2003 ; accepted in final form 23 June 2004 Transient receptor potential (TRP) cation channels are a critical pathway for Ca 2+ entry during pulmonary artery (PA) smooth muscle contraction. However, whether canonical TRP (TRPC) subunits and which TRP channel isoforms are involved in store depletion-induced pulmonary vasoconstriction in vivo remain unclear. This study was designed to test whether overexpression of the human TRPC1 gene ( hTRPC1 ) in rat PA enhances pulmonary vasoconstriction due to store depletion-mediated Ca 2+ influx. The hTRPC1 was infected into rat PA rings with an adenoviral vector. RT-PCR and Western blot analyses confirmed the mRNA and protein expression of hTRPC1 in the arterial rings. The amplitude of active tension induced by 40 mM K + (40K) in PA rings infected with an empty adenoviral vector (647 ± 88 mg/mg) was similar to that in PA rings infected with hTRPC1 (703 ± 123 mg/mg, P = 0.3). However, the active tension due to capacitative Ca 2+ entry (CCE) induced by cyclopiazonic acid was significantly enhanced in PA rings overexpressing hTRPC1 (91 ± 13% of 40K-induced contraction) compared with rings infected with an empty adenoviral vector (61 ± 14%, P < 0.001). Endothelial expression of hTRPC1 was not involved since the CCE-induced vasoconstriction was also enhanced in endothelium-denuded PA rings infected with the adenoviral vector carrying hTRPC1 . These observations demonstrate that hTRPC1 is an important Ca 2+ -permeable channel that mediates pulmonary vasoconstriction when PA smooth muscle cell intracellular Ca 2+ stores are depleted. transient receptor potential cation channels; calcium; capacitative calcium entry Address for reprint requests and other correspondence: J. X.-J. Yuan, Div. of Pulmonary and Critical Care Medicine, Univ. of California, San Diego, 9500 Gilman Dr., MC 0725, La Jolla, CA 92093-0725 (E-mail: xiyuan{at}ucsd.edu )