NHE1 signaling in Pulmonary Arterial Hypertension

描述（由申请人提供）：肺动脉高压（PH）是一种综合征，世界卫生组织将其细分为5类，包括I组肺动脉高压（PAH），即由毛细血管前肺血管病理引起的PH，以及III组，即由慢性低氧血症引起的PH。PAH的发病机制仍然知之甚少，尽管治疗取得了进展，但PAH导致的死亡率仍然很高。 我们的实验室已经确定了一个新的信号通路，这是必要的发展缺氧诱导的PH在小鼠中。在该通路中，缺氧诱导肺动脉平滑肌细胞（PASMCs）中转录因子HIF-1的激活; HIF-1反过来上调跨膜离子交换剂NHE 1的表达，NHE 1影响PASMC迁移和增殖的变化，这有助于导致PH的病理性肺血管重塑。有趣的是，与正常对照组相比，已发现PAH患者的含氧量正常的PASMCs中HIF-1表达增加。此外，我们的初步研究表明，与对照组相比，PAH模型中PASMCs的NHE 1活性增加。因此，本提案的重点是确定NHE 1信号通路在PAH发生中的作用，以及检测NHE 1抑制剂治疗PAH的疗效。长期目标是，通过阐明有助于PAH发病机制的新途径，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PASMC与正常患者PASMC的体外模型，另一种是比较大鼠（其中PAH是通过Sugen暴露和缺氧联合诱导的）与常氧大鼠的体内模型。在具体目标1中，我们将确定NHE 1表达是否在PAH模型中增加，如果是这样，PAH中NHE 1上调是否依赖于HIF-1。通过NHE 1的过表达和沉默，我们将确定PASMC中的NHE 1水平是否有助于病理性PASMC增殖和迁移。在具体目标2中，我们将确定cariporide（一种特异性NHE 1抑制剂）在我们的大鼠模型中预防和逆转PAH的疗效，以及cariporide在我们的体外模型中对人PASMC功能的影响。 除了确定NHE 1在PAH发病机制中的作用外，本提案的执行还将为候选人提供培训，这将有助于其成为在肺部医学领域进行基础科学研究的医生-科学家的职业目标。

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.