BACKGROUND:Pulmonary hypertension (PH) is a progressive cardiopulmonary disease with a high mortality rate. Although growing evidence has revealed the importance of dysregulated energetic metabolism in the pathogenesis of PH, the underlying cellular and molecular mechanisms are not fully understood. In this study, we focused on ME1 (malic enzyme 1), a key enzyme linking glycolysis to the tricarboxylic acid cycle. We aimed to determine the role and mechanistic action of ME1 in PH.METHODS:Global and endothelial-specific ME1 knockout mice were used to investigate the role of ME1 in hypoxia- and SU5416/hypoxia (SuHx)–induced PH. Small hairpin RNA and ME1 enzymatic inhibitor (ME1*) were used to study the mechanism of ME1 in pulmonary artery endothelial cells. Downstream key metabolic pathways and mediators of ME1 were identified by metabolomics analysis in vivo and ME1-mediated energetic alterations were examined by Seahorse metabolic analysis in vitro. The pharmacological effect of ME1* on PH treatment was evaluated in PH animal models induced by SuHx.RESULTS:We found that ME1 protein level and enzymatic activity were highly elevated in lung tissues of patients and mice with PH, primarily in vascular endothelial cells. Global knockout of ME1 protected mice from developing hypoxia- or SuHx-induced PH. Endothelial-specific ME1 deletion similarly attenuated pulmonary vascular remodeling and PH development in mice, suggesting a critical role of endothelial ME1 in PH. Mechanistic studies revealed that ME1 inhibition promoted downstream adenosine production and activated A_2AR-mediated adenosine signaling, which leads to an increase in nitric oxide generation and a decrease in proinflammatory molecule expression in endothelial cells. ME1 inhibition activated adenosine production in an ATP-dependent manner through regulating malate-aspartate NADH (nicotinamide adenine dinucleotide plus hydrogen) shuttle and thereby balancing oxidative phosphorylation and glycolysis. Pharmacological inactivation of ME1 attenuated the progression of PH in both preventive and therapeutic settings by promoting adenosine production in vivo.CONCLUSIONS:Our findings indicate that ME1 upregulation in endothelial cells plays a causative role in PH development by negatively regulating adenosine production and subsequently dysregulating endothelial functions. Our findings also suggest that ME1 may represent as a novel pharmacological target for upregulating protective adenosine signaling in PH therapy.

中文翻译：

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内皮细胞中苹果酸酶 1 的失活可缓解肺动脉高压

背景：肺动脉高压（PH）是一种进行性心肺疾病，死亡率很高。尽管越来越多的证据表明能量代谢失调在 PH 发病机制中的重要性，但其潜在的细胞和分子机制尚未完全了解。在这项研究中，我们重点关注 ME1（苹果酸酶 1），这是一种将糖酵解与三羧酸循环联系起来的关键酶。我们的目的是确定 ME1 在 PH 中的作用和机制。方法：使用整体和内皮特异性ME1敲除小鼠来研究 ME1 在缺氧和 SU5416/缺氧 (SuHx) 诱导的 PH 中的作用。使用小发夹RNA和ME1酶抑制剂（ME1*）研究ME1在肺动脉内皮细胞中的作用机制。通过体内代谢组学分析鉴定了 ME1 的下游关键代谢途径和介质，并通过体外 Seahorse 代谢分析检查了 ME1 介导的能量变化。在 SuHx 诱导的 PH 动物模型中评估了 ME1* 对 PH 治疗的药理作用。结果：我们发现 PH 患者和小鼠的肺组织中 ME1 蛋白水平和酶活性高度升高，主要是在血管内皮细胞中。ME1的整体敲除可保护小鼠免受缺氧或 SuHx 诱导的 PH 的影响。内皮特异性ME1缺失同样会减弱小鼠肺血管重塑和 PH 发展，表明内皮 ME1 在 PH 中发挥关键作用。机制研究表明，ME1 抑制促进下游腺苷产生并激活 A _2A R 介导的腺苷信号传导，从而导致内皮细胞中一氧化氮生成增加和促炎分子表达减少。 ME1 抑制通过调节苹果酸-天冬氨酸 NADH（烟酰胺腺嘌呤二核苷酸加氢）穿梭，以 ATP 依赖性方式激活腺苷产生，从而平衡氧化磷酸化和糖酵解。 ME1 的药理学灭活通过促进体内腺苷产生来减轻预防性和治疗性肺动脉高压的进展。结论：我们的研究结果表明，内皮细胞中 ME1 的上调通过负调节腺苷产生并随后失调内皮功能，在肺动脉高压的发展中发挥着致病作用。 。我们的研究结果还表明，ME1 可能是 PH 治疗中上调保护性腺苷信号传导的新药理学靶点。