Upregulation of Na+/Ca2+ exchanger contributes to the enhanced Ca2+ entry in pulmonary artery smooth muscle cells from patients with idiopathic pulmonary arterial hypertension

2007 ◽  
Vol 292 (6) ◽  
pp. C2297-C2305 ◽  
Author(s):  
Shen Zhang ◽  
Hui Dong ◽  
Lewis J. Rubin ◽  
Jason X.-J. Yuan
Keyword(s):  
Smooth Muscle ◽  
Pulmonary Arterial Hypertension ◽  
Pulmonary Artery ◽  
Arterial Hypertension ◽  
Smooth Muscle Cells ◽  
Idiopathic Pulmonary Arterial Hypertension ◽  
Reverse Mode ◽  
Pulmonary Vasoconstriction ◽  
Pulmonary Arterial ◽  
Pulmonary Artery Smooth Muscle

A rise in cytosolic Ca2+ concentration ([Ca2+]cyt) in pulmonary artery smooth muscle cells (PASMC) is a trigger for pulmonary vasoconstriction and a stimulus for PASMC proliferation and migration. Multiple mechanisms are involved in regulating [Ca2+]cyt in human PASMC. The resting [Ca2+]cyt and Ca2+ entry are both increased in PASMC from patients with idiopathic pulmonary arterial hypertension (IPAH), which is believed to be a critical mechanism for sustained pulmonary vasoconstriction and excessive pulmonary vascular remodeling in these patients. Here we report that protein expression of NCX1, an NCX family member of Na+/Ca2+ exchanger proteins is upregulated in PASMC from IPAH patients compared with PASMC from normal subjects and patients with other cardiopulmonary diseases. The Na+/Ca2+ exchanger operates in a forward (Ca2+ exit) and reverse (Ca2+ entry) mode. By activating the reverse mode of Na+/Ca2+ exchange, removal of extracellular Na+ caused a rapid increase in [Ca2+]cyt, which was significantly enhanced in IPAH PASMC compared with normal PASMC. Furthermore, passive depletion of intracellular Ca2+ stores using cyclopiazonic acid (10 μM) not only caused a rise in [Ca2+]cyt due to Ca2+ influx through store-operated Ca2+ channels but also mediated a rise in [Ca2+]cyt via the reverse mode of Na+/Ca2+ exchange. The upregulated NCX1 in IPAH PASMC led to an enhanced Ca2+ entry via the reverse mode of Na+/Ca2+ exchange, but did not accelerate Ca2+ extrusion via the forward mode of Na+/Ca2+ exchange. These observations indicate that the upregulated NCX1 and enhanced Ca2+ entry via the reverse mode of Na+/Ca2+ exchange are an additional mechanism responsible for the elevated [Ca2+]cyt in PASMC from IPAH patients.

Abstract 379: Enhancement of TRPC6-mediated Ca 2+ Entry in Pulmonary Artery Smooth Muscle Cells of Idiopathic Pulmonary Arterial Hypertension Patients

Circulation ◽  
2007 ◽  
Vol 116 (suppl_16) ◽  
Author(s):  
Ying Yu ◽  
Olga Safrina ◽  
Oleksandr Platoshyn ◽  
Michael D Cahalan ◽  
Lewis J Rubin ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Pulmonary Arterial Hypertension ◽  
Pulmonary Artery ◽  
Arterial Hypertension ◽  
Smooth Muscle Cells ◽  
Muscle Cells ◽  
Idiopathic Pulmonary Arterial Hypertension ◽  
Pulmonary Arterial ◽  
Pulmonary Artery Smooth Muscle ◽  
Excessive Proliferation

Background & Hypothesis: Excessive proliferation of pulmonary artery smooth muscle cells (PASMCs) and sustained pulmonary vasoconstriction are thought to play critical roles in the development of idiopathic pulmonary arterial hypertension (IPAH). Recently, we demonstrated that upregulation of the canonical transient receptor potential 6 (TRPC6) channel contributes to excessive proliferation of PASMCs isolated from IPAH patients. This study aimed at characterizing whether up-regulated TRPC6 expression affects resting cytosolic [Ca 2+ ] ([Ca 2+ ] cyt ) level and Ca 2+ entry in PASMCs of IPAH patients. Methods & Results: [Ca 2+ ] cyt was measured by fluorescence ratio video imaging with the Ca 2+ indicator fura-2. 1-Oleoyl-2-acetyl-sn-glycerol (OAG), a cell-permeable diacylglycerol analog that activates TRPC6 channels, was used to stimulate channel activities in the presence of extracellular Ca 2+ . The resting [Ca 2+ ] cyt andOAG-mediated increase in [Ca 2+ ]cyt were significantly higher in PASMCs from IPAH patients compared to PASMCs isolated from secondary pulmonary artery hypertension and normotensive patients. In PASMCs from IPAH patients, inhibition of TRPC6 expression by adenovirus-mediated siRNA specifically targeted the human TRPC6 gene led to an approximately 90% reduction of TRPC6 mRNA and protein levels and significantly attenuated OAG-mediated increase in [Ca 2+ ] cyt . Treatment of the IPAH-PASMCs with siRNA also decreased the resting [Ca 2+ ] cyt and significantly inhibited cell proliferation in comparison to cells treated with scrambled control siRNA. Furthermore, exogenous overexpression of human TRPC6 increased the resting [Ca 2+ ] cyt and enhanced OAG-mediated Ca 2+ entry in normal PASMCs. C onclusions: These results suggest that upregulation of TRPC6 channels in PASMC from IPAH patients serves as an important pathway for agonist-mediated Ca 2+ entry, mitogen-mediated PASMC proliferation and, ultimately, pulmonary vascular remodeling. Targeting TRPC6 expression and function in PASMCs would help develop novel therapeutic approaches for IPAH patients.

Abstract 659: Simvastatin Inhibits Proliferation and Migration of Pulmonary Artery Smooth Muscle Cells from Patients with Idiopathic Pulmonary Arterial Hypertension

Circulation ◽  
2007 ◽  
Vol 116 (suppl_16) ◽  
Author(s):  
Kazufumi Nakamura ◽  
Tetsuya Ikeda ◽  
Hideki Fujio ◽  
Aiko Ogawa ◽  
Kaoru Kobayashi ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Pulmonary Arterial Hypertension ◽  
Pulmonary Artery ◽  
Arterial Hypertension ◽  
Smooth Muscle Cells ◽  
Idiopathic Pulmonary Arterial Hypertension ◽  
Pulmonary Arterial ◽  
Pulmonary Artery Smooth Muscle ◽  
And Migration ◽  
Proliferation And Migration

Background: Idiopathic pulmonary arterial hypertension (IPAH) is a progressive disease characterized by inappropriate increase of pulmonary artery smooth muscle cells (PASMCs) leading to occlusion of pulmonary arterioles and causing pulmonary hypertension. In this study, we assessed the inhibitory effects of simvastatin, an HMG-CoA reductase inhibitor, on proliferation and migration of PASMCs obtained from patients with IPAH. Methods and Results: PASMCs were obtained from 6 patients with IPAH who underwent lung transplantation, and PASMCs were obtained as control cells from 6 patients with bronchogenic carcinoma who underwent lung lobectomy. Platelet-derived growth factor (PDGF) (10 ng/mL) stimulation caused a significantly higher growth rate of PASMCs from patients with IPAH than that of control cells assessed by 3 H-thymidine incorporation ( P< 0.05). Simvastatin at 0.1 Â113>mol/L significantly inhibited PDGF-induced cell proliferation of PASMCs from IPAH patients but did not inhibit proliferation of control cells at the same concentration. Simvastatin at 1 Â113>mol/L also inhibited PDGF-induced migration of PASMCs from IPAH patients assessed by a transwell migration assay ( P< 0.05). Immunofluorescence staining revealed that simvastatin at 1 Â113>mol/L inhibited translocation of Rho A from the cytoplasm to membrane and disorganized actin fibers in PASMCs from IPAH patients. Conclusions: Simvastatin had an inhibitory effect on the inappropriate proliferation and migration of PASMCs from IPAH patients. Simvastatin may be useful for treatment of patients with IPAH.

Sign in / Sign up

Export Citation Format

Share Document