Abstract 17752: Altered Expression of Chloride Transporters in Rat Pulmonary Arterial Smooth Muscle Associated with Chronic Hypoxic Pulmonary Hypertension
Chloride channels play an important role in regulating smooth muscle contraction and proliferation, and contribute to the enhanced vasoconstriction in pulmonary hypertension (PH). The intracellular Cl- concentrations ([Cl-]i) determine the driving force for Cl- conductance, thereby the functional consequence of channel activation. We have previously found that the [Cl-]i was increased in pulmonary artery (PA) smooth muscle cells of rats with chronic hypoxic PH (CHPH), which may lead to an increased depolarizing Cl- efflux during channel activation. Yet how the [Cl-]i is regulated in PA is unknown. Here we examined the expression profile in rat PAs of SLC12 family cation-coupled Cl- cotransporters (CCCs) and SLC4 family of Cl/HCO3 anion exchangers (AEs) that have been shown to regulate the intracellular Cl- homeostasis in other tissues. CHPH was induced by exposing rats to 10% O2 for 3 weeks. Conventional and real-time PCR were used to detect and quantify the mRNA expression in endothelium-denuded intralobal PAs. Normoxic PAs expressed all 9 CCCs and both Na+- dependent (SLC4A8) and -independent AEs (SLC4A1-3). SCL12A2 encoding for Na-K-2Cl cotransporter 1 (NKCC1) showed 45- and 12-fold higher expression than NKCC2-encoding SCL12A1 and Na-Cl cotransporter-encoding SLC12A3, respectively. Among the 4 genes that encode for K-Cl cotransporters (KCC) 1-4, the expression of SLC12A4, 6 and 7 was about 100-1000 fold higher than that of SCL12A5. Control PAs also showed higher SLC4A2 and 3 expression than SLC4A1 and 8. In hypoxic PAs, the expression of SCL12A2 encoding for Cl--accumulating NKCC1 was increased (copy number normalized to that of cyclophilin A served as an internal control: 1.23x10-2±.001, n=6 vs. 6.19x10-3±.0002, n=6, p<0.001) while that of SLC12A7 encoding for Cl--extruding KCC4 was reduced (4.92x10-3±.0005, n=6 vs. 1.14x10-2±.002, n=6, p<0.01), consistent with our previous functional findings. This study provides the first characterization of Cl- transporter expression profile and the first evidence of CHPH-associated transcriptional alterations in Cl- transporters in pulmonary arterial smooth muscle.
Author Disclosures: H. Sun: None. O. Paudel: None. J.S. Sham: None.
This research has received full or partial funding support from the American Heart Association
- © 2014 by American Heart Association, Inc.