Role of Rho kinase and Na+/H+ exchange in hypoxia-induced pulmonary arterial smooth muscle cell proliferation and migration.
Role of Rho kinase and Na+/H+ exchange in hypoxia-induced pulmonary arterial smooth muscle cell proliferation and migration.
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DOI：
10.14814/phy2.12702
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发表时间：
2016-03
影响因子：
2.5
通讯作者：
Shimoda LA
中科院分区：
文献类型：
--
作者：
Walker J;Undem C;Yun X;Lade J;Jiang H;Shimoda LA
肺动脉平滑肌细胞(PASMCs)的异常增殖和迁移是慢性低氧性肺动脉高压血管重构的显著特征。在这项研究中，我们研究了Na+/H+交换器(NHE)和细胞内pH(Phi)稳态的变化在慢性低氧大鼠或暴露于体外低氧(1%或4%O2，24-96小时)的阻力大鼠肺动脉分离的PASMCs增殖和迁移增加中的作用。我们发现，无论是体内还是体外缺氧，PASMC都表现出更强的增殖和迁移能力，PHI升高，NHE活性增强。NHE抑制剂乙基异丙基阿米洛利(EIPA)使低氧PASMCs的PHI正常化，并使暴露于体内和体外低氧的细胞迁移分别减少73%和45%。同样，EIPA使暴露于体内和体外缺氧的细胞的增殖分别减少了97%和78%。我们先前证明NHE异构体1(NHE1)是PASMCs表达的主要异构体。在缺乏NHE1的小鼠中，低氧诱导的肺动脉高压的发展和PASMC pH I动态平衡的改变被阻止。我们发现，短期(24小时)体外低氧暴露不会改变NHE1的表达，因此我们测试了Rho激酶(ROCK)作为一种可能的增加NHE活性的手段的作用。在ROCK抑制剂Y-27632存在的情况下，我们发现PASMCs在体内(迁移减少68%，增殖减少22%)和体外缺氧(迁移减少43%，增殖减少17%)下，PHI和NHE活性恢复正常，迁移和增殖减少。根据这些结果，我们认为在低氧条件下，ROCK的激活增强了NHE活性，促进了PASMC的迁移和增殖。
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 pH i 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.