Hemolysis and free heme signaling in pulmonary hypertension

肺动脉高压（PAH）是一种致死性疾病，伴有进行性肺血管重塑， 右心肥大和衰竭。PAH的患病率在一般人群中存在极大差异， 人群（0.001%）和溶血性贫血患者（10-80%）。我们之前公布的数据显示 从未经历过溶血性疾病的特发性PAH患者， 血浆中游离血红蛋白（Hb）水平和游离Hb水平与PAH进展显著相关。 在临床前PAH模型中也观察到溶血增加，并与疾病相关 进展虽然先前已经报道了游离Hb的致病特性，但这些研究是 主要集中在游离血红蛋白和游离血红素细胞外功能有关的氧化还原和一氧化氮清除 活动因此，在理解溶血介导的细胞因子的机制方面存在着关键的差距。 PAH的细胞内信号传导。事实上，我们的初步数据表明，游离血红素诱导激活 磷酸果糖激酶（PFK）通过p38/MK2轴在肺动脉内皮细胞和平滑肌细胞中的作用 导致代谢向糖酵解转变。 另一个重要的问题是为什么PAH患者的溶血增加？我们最近发现， 丙酮酸脱氢酶（PDH）是代谢稳态中的关键酶， 网织红细胞成熟，并负责积聚未成熟的网织红细胞，这些未成熟的网织红细胞易受 破裂已知PDH功能不全通过损害正常的 线粒体功能我们认为PDH失活也是PAH溶血增加的原因 没有其他溶血性疾病的患者。 根据我们的初步数据，我们假设PDH不足会增加血管内溶血， 通过刺激PFK激活游离血红素介导的代谢开关。这种代谢转变发生在 PDH功能障碍的背景导致肺血管细胞重编程， 增殖表型和促进肺血管重建。我们将阐述 本研究旨在探讨血红素介导的信号通路在PAH发病中的作用，其目的如下：1）阐明血红素介导的信号通路在PAH发病中的作用， 2）确定丙酮酸脱氢酶（PDH）在溶血中的作用; 和3）检查EC/SMC中血红素介导的信号传导与HH缺陷之间的串扰 重新编程 如果成功的话，这个提议将揭示负责与一个或多个组织之间强关联的机制。 溶血性疾病和PAH，提供了潜在的治疗，减弱血红素介导的途径， 具有溶血和非溶血背景的PAH。新的目标将在拟议的研究中进行测试， 由于缺乏足够的PAH治疗选择而需要的先进治疗方法。

Pulmonary arterial hypertension (PAH) is a fatal disease with progressive lung vascular remodeling leading to right heart hypertrophy and failure. There is an extreme disparity between the prevalence of PAH in the general population (0.001%) and patients with hemolytic anemias (10-80%). Our previously published data indicate that idiopathic PAH patients, which have never experienced hemolytic conditions, exhibited 5-fold increase in free hemoglobin (Hb) levels in plasma, and free Hb levels significantly correlated with PAH progression. Increased hemolysis has also been observed in pre-clinical PAH models and correlated with a disease progression. While the pathogenic properties of free Hb have been previously reported, these studies were mainly focused on free Hb and free heme extracellular functions related to redox and nitric oxide scavenging activities. Therefore, there is a critical gap in understanding the mechanisms of hemolysis-mediated intracellular signaling in PAH. Indeed, our preliminary data demonstrated that free heme induces activation of phosphofructokinase (PFK) via p38/MK2 axis in pulmonary artery endothelial cells and smooth muscle cells resulting in a metabolic switch toward glycolysis. Another important question is why PAH patients have increased hemolysis? We recently discovered that the dysfunction of pyruvate dehydrogenase (PDH), a critical enzyme in metabolic homeostasis, impairs reticulocyte maturation, and responsible for the accumulation of immature reticulocytes that are susceptible to rupture. PDH insufficiency is known to be directly involved in PAH pathogenesis by compromising normal mitochondrial function. We propose that PDH inactivation is also responsible for increased hemolysis in PAH patients that have no hemolytic disorders otherwise. Based on our preliminary data, we hypothesize that PDH insufficiency increases intravascular hemolysis and activates free heme-mediated metabolic switch through stimulation of PFK. This metabolic shift occurred on the background of PDH dysfunction results in reprogramming of pulmonary vascular cells toward highly proliferative phenotype and promoted pulmonary vascular remodeling. We will delineate the importance of heme-mediated pathways in PAH in the following aims: 1) To elucidate the role of heme-mediated signaling in the activation of a glycolytic switch; 2) To determine the role of pyruvate dehydrogenase (PDH) in hemolysis; and 3) To examine the crosstalk between heme-mediated signaling and PDH deficiency in EC/SMC reprogramming. If successful, this proposal will uncover the mechanisms responsible for a strong association between hemolytic conditions and PAH, provide the potential treatments for attenuating heme-mediated pathways in PAH with hemolytic and non-hemolytic background. New targets will be tested in the proposed studies and will advance therapeutic approaches that are needed due to the lack of adequate PAH treatment options.