Role of Rho kinase and Na+/H+ exchange in hypoxia‐induced pulmonary arterial smooth muscle cell proliferation and migration

• Published in: Physiological reports Vol. 4; no. 6; pp. e12702 - n/a
• Main Authors: Walker, Jasmine, Undem, Clark, Yun, Xin, Lade, Julie, Jiang, Haiyang, Shimoda, Larissa A.
• Format: Journal Article
• Language: English
• Published: United States John Wiley & Sons, Inc 01-03-2016; John Wiley and Sons Inc
• Subjects: Amides - pharmacology; Amiloride; Amiloride - analogs & derivatives; Amiloride - pharmacology; Animals; Blood Pressure; Cation Transport Proteins - antagonists & inhibitors; Cation Transport Proteins - deficiency; Cation Transport Proteins - genetics; Cation Transport Proteins - metabolism; Cell adhesion & migration; Cell growth; Cell Hypoxia; Cell migration; Cell Movement - drug effects; Cell proliferation; Cell Proliferation - drug effects; Cells, Cultured; Disease Models, Animal; Enzyme Activation; Homeostasis; Hydrogen-Ion Concentration; Hypertension; Hypertension, Pulmonary - enzymology; Hypertension, Pulmonary - etiology; Hypertension, Pulmonary - pathology; Hypertension, Pulmonary - physiopathology; Hypoxia; Hypoxia - complications; Hypoxia - enzymology; Hypoxia - pathology; Hypoxia - physiopathology; Male; Mice, Inbred C57BL; Mice, Knockout; Muscle, Smooth, Vascular - drug effects; Muscle, Smooth, Vascular - enzymology; Muscle, Smooth, Vascular - pathology; Muscle, Smooth, Vascular - physiopathology; Myocytes, Smooth Muscle - drug effects; Myocytes, Smooth Muscle - enzymology; Myocytes, Smooth Muscle - pathology; Na+/H+-exchanging ATPase; Original Research; Pathogenesis; Physiology; Protein Kinase Inhibitors - pharmacology; Pulmonary arteries; Pulmonary artery; Pulmonary Artery - enzymology; Pulmonary Artery - pathology; Pulmonary Artery - physiopathology; Pulmonary Circulation; Pulmonary hypertension; Pyridines - pharmacology; Rats, Wistar; Regulatory Pathways; remodeling; Rho-associated kinase; rho-Associated Kinases - metabolism; Rodents; Signal Transduction; Smooth Muscle; Sodium-Hydrogen Exchanger 1; Sodium-Hydrogen Exchangers - antagonists & inhibitors; Sodium-Hydrogen Exchangers - genetics; Sodium-Hydrogen Exchangers - metabolism; vascular; Vascular Remodeling - drug effects; vascular; remodeling; Pulmonary hypertension
• ISSN: 2051-817X; 2051-817X
• DOI: 10.14814/phy2.12702

Abnormal proliferation and migration of pulmonary arterial smooth muscle cells (PASMCs) are hallmark characteristics of vascular remodeling in pulmonary hypertension induced by chronic hypoxia. In this study, we investigated the role of the Na+/H+ exchanger (NHE) and alterations in intracellular pH (pHi) homeostasis in meditating increased proliferation and migration in PASMCs isolated from resistance‐sized pulmonary arteries from chronically hypoxic rats or from normoxic rats that were exposed to hypoxia ex vivo (1% or 4% O2, 24–96 h). We found that PASMCs exposed to either in vivo or ex vivo hypoxia exhibited greater proliferative and migratory capacity, elevated pHi, and enhanced NHE activity. The NHE inhibitor, ethyl isopropyl amiloride (EIPA), normalized pHi in hypoxic PASMCs and reduced migration by 73% and 45% in cells exposed to in vivo and in vitro hypoxia, respectively. Similarly, EIPA reduced proliferation by 97% and 78% in cells exposed to in vivo and in vitro hypoxia, respectively. We previously demonstrated that NHE isoform 1 (NHE1) is the predominant isoform expressed in PASMCs. The development of hypoxia‐induced pulmonary hypertension and alterations in PASMC pHi homeostasis were prevented in mice deficient for NHE1. We found that short‐term (24 h) ex vivo hypoxic exposure did not alter the expression of NHE1, so we tested the role of Rho kinase (ROCK) as a possible means of increasing NHE activity. In the presence of the ROCK inhibitor, Y‐27632, we found that pHi and NHE activity were normalized and migration and proliferation were reduced in PASMCs exposed to either in vivo (by 68% for migration and 22% for proliferation) or ex vivo (by 43% for migration and 17% for proliferation) hypoxia. From these results, we conclude that during hypoxia, activation of ROCK enhances NHE activity and promotes PASMC migration and proliferation.
Pulmonary arterial smooth muscle cell (PASMC) migration and proliferation contribute to vascular remodeling in hypoxia‐induced pulmonary hypertension. The enhanced proliferative and migratory capacity of PASMCs from chronically hypoxic rats can be reversed with inhibition of Na+/H+ exchange or Rho kinase.