NHE1 signaling in Pulmonary Arterial Hypertension

描述(申请人提供)：肺高压(PH)是一种综合征，世界卫生组织将其细分为五类，包括第一组肺动脉高压(PAH)，它是由于毛细血管前血管的病理而导致的PH；以及第三组，它是由于慢性低氧血症而导致的PH。PAH的发病机制仍然知之甚少，尽管治疗取得了进展，但PAH的死亡率仍然很高。我们的实验室已经发现了一条新的信号通路，这是低氧诱导的小鼠肺高压发生所必需的。在这个途径中，低氧诱导PASMCs转录因子HIF-1的激活，HIF-1反过来上调跨膜离子交换NHE1的表达，从而影响PASMC迁移和增殖的变化，从而导致肺血管重构，从而导致PH。有趣的是，与正常对照组相比，人类PAH患者在常氧状态下的PASMC中HIF-1的表达增加。此外，我们的初步研究表明，与对照组相比，PAH模型的PASMCs中NHE1活性增加。因此，这项建议的重点是确定NHE1信号通路在PAH发生发展中的作用以及测试NHE1抑制剂在治疗PAH中的疗效。我们的长期目标是，通过阐明有助于PAH发病的新途径，我们可能会发现新的治疗靶点。我们将采用两种PAH模型：一种是比较PAH患者和正常患者的PASMCs的体外模型，另一种是通过SUGEN暴露和低氧相结合的方法诱导正常大鼠的PAH的体内比较模型。在特定的目标1中，我们将确定NHE1在PAH模型中的表达是否增加，如果是的话，是否依赖于HIF-1。通过NHE1的过度表达和沉默，我们将确定PASMC中NHE1的水平是否有助于病理性PASMC的增殖和迁移。在特定的目标2中，我们将在我们的体外模型中检测特异性NHE1抑制剂cariporide预防和逆转PAH的有效性，以及cariporide对人PASMC功能的影响。除了确定NHE1在PAH发病机制中的作用外，这项提案的执行还将为候选人提供培训，这将有助于他成为一名在肺部医学领域进行基础科学研究的内科科学家。

DESCRIPTION (provided by applicant): Pulmonary hypertension (PH) is a syndrome which the World Health Organization subdivides into five classes, including Group I pulmonary arterial hypertension (PAH), which is PH due to pathology of the precapillary pulmonary vasculature, and Group III, which is PH due to chronic hypoxemia. The pathogenesis of PAH remains poorly understood and, despite advances in therapy, mortality due to PAH remains high. Our laboratory has identified a novel signaling pathway which is necessary for the development of hypoxia- induced PH in mice. In this pathway, hypoxia induces activation of the transcription factor HIF-1 in pulmonary artery smooth muscle cells (PASMCs); HIF-1 in turn upregulates expression of the transmembrane ion exchanger NHE1, which effects changes in PASMC migration and proliferation that contribute to the pathologic pulmonary vascular remodeling that leads to PH. Interestingly, HIF-1 expression has been found to be increased in normoxic PASMCs from human patients with PAH, in comparison with normal controls. Furthermore, our preliminary studies show that NHE1 activity is increased in PASMCs in PAH models compared to controls. Therefore, the focus of this proposal is to determine the role of the NHE1 signaling pathway in the development of PAH as well as to test the efficacy of NHE1 inhibitors in the treatment of PAH. The long-term goal is that, by elucidating new pathways that contribute to the pathogenesis of PAH, we may discover novel targets for therapy. We will employ two models of PAH: an in vitro model comparing PASMCs from PAH patients to those from normal patients, and an in vivo model comparing rats, in which PAH is induced through the combination of Sugen exposure and hypoxia, to normoxic rats. In Specific Aim 1, we will determine whether NHE1 expression is increased in PAH models and, if so, whether NHE1 upregulation in PAH is dependent upon HIF-1. Through overexpression as well as silencing of NHE1, we will determine whether NHE1 levels in PASMCs contribute to pathologic PASMC proliferation and migration. In Specific Aim 2, we will determine the efficacy of cariporide, a specific NHE1 inhibitor, in the prevention and reversal of PAH in our rat model, as well as the effect of cariporide on human PASMC function in our in vitro model. In addition to determining the role of NHE1 in the pathogenesis of PAH, execution of this proposal will provide training for the candidate that will be instrumental toward his career goal of becoming a physician- scientist performing basic science research in the field of pulmonary medicine.