Hemolysis and free heme signaling in pulmonary hypertension

肺动脉高压(PAH)是一种致命的疾病，伴随着进行性肺血管重构导致 右心肥大和衰竭。在一般情况下，多环芳烃的患病率存在极大的差异 人群(0.001%)和溶血性贫血患者(10-80%)。我们之前公布的数据表明 从未经历过溶血情况的特发性PAH患者，表现出5倍于 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 进步。虽然之前已经报道了游离乙肝的致病特性，但这些研究是 主要集中在与氧化还原和一氧化氮清除相关的游离Hb和游离血红素的胞外功能 活动。因此，在了解溶血介导的机制方面存在着严重的差距。 PAH的细胞内信号转导。事实上，我们的初步数据表明，游离的血红素诱导激活 P38/MK2轴介导的磷酸果糖激酶(PFK)在肺动脉内皮细胞和平滑肌细胞中的表达 导致代谢转向糖酵解。 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， 代谢稳态的关键酶--丙酮酸脱氢酶(PDH)功能障碍 网织红细胞成熟，并负责未成熟网织红细胞的积聚，这些网织红细胞容易患上 破裂。已知的是，PDH不足直接参与了PAH的发病过程 线粒体功能。我们认为PDH失活也是PAH溶血增加的原因。 其他无溶血障碍的患者。 根据我们的初步数据，我们假设PDH不足会增加血管内溶血和 通过刺激PFK激活游离的血红素介导的代谢开关。这种新陈代谢的转变发生在 PDH功能障碍导致肺血管细胞重编程 增殖表型，促进肺血管重构。我们将描述以下内容的重要性 目的：1)阐明血红素介导的信号转导在PAH中的作用。 激活糖酵解开关；2)确定丙酮酸脱氢酶(PDH)在溶血中的作用； 3)检测EC/SMC中血红素介导的信号转导与PDH缺陷之间的串扰 重新编程。 如果成功，这项提议将揭示导致两国之间紧密联系的机制。 溶血条件和多环芳烃，为减轻血红素介导的途径提供了潜在的治疗方法。 有溶血和非溶血背景的多环芳烃。新的目标将在拟议的研究中进行测试，并将 由于缺乏适当的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.