Pulmonary arterial hypertension (PAH) is a progressive vascular disease with a high mortality rate. It is characterized by an occlusive vascular remodeling due to a pro-proliferative and ...antiapoptotic environment in the wall of resistance pulmonary arteries (PAs). Proliferating cells exhibit a cancer-like metabolic switch where mitochondrial glucose oxidation is suppressed, whereas glycolysis is up-regulated as the major source of adenosine triphosphate production. This multifactorial mitochondrial suppression leads to inhibition of apoptosis and downstream signaling promoting proliferation. We report an increase in pyruvate dehydrogenase kinase (PDK), an inhibitor of the mitochondrial enzyme pyruvate dehydrogenase (PDH, the gatekeeping enzyme of glucose oxidation) in the PAs of human PAH compared to healthy lungs. Treatment of explanted human PAH lungs with the PDK inhibitor dichloroacetate (DCA) ex vivo activated PDH and increased mitochondrial respiration. In a 4-month, open-label study, DCA (3 to 6.25 mg/kg b.i.d.) administered to patients with idiopathic PAH (iPAH) already on approved iPAH therapies led to reduction in mean PA pressure and pulmonary vascular resistance and improvement in functional capacity, but with a range of individual responses. Lack of ex vivo and clinical response was associated with the presence of functional variants of
and
that predict reduced protein function. Impaired function of these proteins causes PDK-independent mitochondrial suppression and pulmonary hypertension in mice. This first-in-human trial of a mitochondria-targeting drug in iPAH demonstrates that PDK is a druggable target and offers hemodynamic improvement in genetically susceptible patients, paving the way for novel precision medicine approaches in this disease.
Pulmonary arterial hypertension (PAH) is a heterogeneous disorder with high mortality.
We conducted a comprehensive study of plasma metabolites using ultraperformance liquid chromatography mass ...spectrometry to identify patients at high risk of early death, to identify patients who respond well to treatment, and to provide novel molecular insights into disease pathogenesis.
Fifty-three circulating metabolites distinguished well-phenotyped patients with idiopathic or heritable PAH (n=365) from healthy control subjects (n=121) after correction for multiple testing (P<7.3e-5) and confounding factors, including drug therapy, and renal and hepatic impairment. A subset of 20 of 53 metabolites also discriminated patients with PAH from disease control subjects (symptomatic patients without pulmonary hypertension, n=139). Sixty-two metabolites were prognostic in PAH, with 36 of 62 independent of established prognostic markers. Increased levels of tRNA-specific modified nucleosides (N2,N2-dimethylguanosine, N1-methylinosine), tricarboxylic acid cycle intermediates (malate, fumarate), glutamate, fatty acid acylcarnitines, tryptophan, and polyamine metabolites and decreased levels of steroids, sphingomyelins, and phosphatidylcholines distinguished patients from control subjects. The largest differences correlated with increased risk of death, and correction of several metabolites over time was associated with a better outcome. Patients who responded to calcium channel blocker therapy had metabolic profiles similar to those of healthy control subjects.
Metabolic profiles in PAH are strongly related to survival and should be considered part of the deep phenotypic characterization of this disease. Our results support the investigation of targeted therapeutic strategies that seek to address the alterations in translational regulation and energy metabolism that characterize these patients.
Two coding variants in the apolipoprotein L1 (APOL1) gene (termed G1 and G2) are strongly associated with increased risk of nondiabetic kidney disease in people of recent African ancestry. The ...mechanisms by which the risk variants cause kidney damage, although not well-understood, are believed to involve injury to glomerular podocytes. The intracellular localization and function of APOL1 in podocytes remain unclear, with recent studies suggesting possible roles in the endoplasmic reticulum (ER), mitochondria, endosomes, lysosomes, and autophagosomes. Here, we demonstrate that APOL1 also localizes to intracellular lipid droplets (LDs). While a large fraction of risk variant APOL1 (G1 and G2) localizes to the ER, a significant proportion of wild-type APOL1 (G0) localizes to LDs. APOL1 transiently interacts with numerous organelles, including the ER, mitochondria, and endosomes. Treatment of cells that promote LD formation with oleic acid shifted the localization of G1 and G2 from the ER to LDs, with accompanying reduction of autophagic flux and cytotoxicity. Coexpression of G0 APOL1 with risk variant APOL1 enabled recruitment of G1 and G2 from the ER to LDs, accompanied by reduced cell death. The ability of G0 APOL1 to recruit risk variant APOL1 to LDs may help explain the recessive pattern of kidney disease inheritance. These studies establish APOL1 as a bona fide LD-associated protein, and reveal that recruitment of risk variant APOL1 to LDs reduces cell toxicity, autophagic flux, and cell death. Thus, interventions that divert APOL1 risk variants to LDs may serve as a novel therapeutic strategy to alleviate their cytotoxic effects.
Inhibition of p38 reduces the proliferation and migration of pulmonary artery fibroblasts and cytokine release from these cells in vitro (3-5), all of which are key elements of pulmonary vascular ...remodeling. The main criticisms of preclinical studies focus on the fidelity of animal models with regard to disease in humans, and the failure to apply the same methodological rigor required in clinical studies (specifically, blinding, randomization, and a priori sample size calculations). Welsh DJ, Peacock AJ, MacLean M, Harnett M. Chronic hypoxia induces constitutive p38 mitogen-activated protein kinase activity that correlates with enhanced cellular proliferation in fibroblasts from rat pulmonary but not systemic arteries.
Objectives This study sought to understand the prevalence and clinical relevance of iron deficiency in patients with idiopathic pulmonary arterial hypertension (IPAH). Background Iron availability ...influences the pulmonary vascular response to hypoxia in humans and may be significant in the pathogenesis of IPAH. Methods Iron deficiency, defined by raised levels of soluble transferrin receptor (sTfR), was investigated in 98 patients with IPAH. Hepcidin and erythropoietin (EPO) levels were also measured. The effect of bone morphogenetic protein (BMP) receptor knockdown on BMP-6–stimulated hepcidin production was assessed in human hepatoma HepG2 cells. Relationships between sTfR and exercise capacity, functional class, and all-cause mortality were analyzed. Results Circulating sTfR levels were raised in 63% of IPAH patients, indicating significant iron deficiency. Consistent with this, iron, ferritin, and transferrin saturation levels were reduced and red cell distribution width increased, without overt anemia. Hepcidin correlated inversely with sTfR and positively with increasing ferritin. Hepcidin was inappropriately raised in IPAH independent of the inflammatory marker interleukin-6. EPO levels were also raised and correlated inversely with hepcidin. BMP receptor-type 2 ( BMPR2 ) knockdown in HepG2 cells increased BMP-6–stimulated hepcidin expression. sTfR increased with World Health Organization functional class (p < 0.05), correlated negatively with exercise capacity (p = 0.027), and values >28.1 nmol/l independently predicted survival (p = 0.011). Conclusions Iron deficiency is common in IPAH patients and associated with disease severity and poor clinical outcome. Inappropriately raised hepcidin levels, which impair iron absorption from the gut, may be a factor.
OBJECTIVE—Inflammation and dysregulated angiogenesis are features of endothelial dysfunction in pulmonary hypertension. Neutrophil extracellular traps (NETs), produced by dying neutrophils, ...contribute to pathogenesis of numerous vascular disorders but their role in pulmonary hypertension has not been studied. We sought evidence of (NETs) formation in pulmonary hypertension and investigated the effect of NETs on endothelial function.
APPROACH AND RESULTS—Plasma and lung tissues of patients with pulmonary hypertension were analyzed for NET markers. The effects of NETs on endothelial function were studied in vitro and in vivo. Patients with chronic thromboembolic pulmonary hypertension and idiopathic pulmonary hypertension showed elevated plasma levels of DNA, neutrophil elastase, and myeloperoxidase. NET-forming neutrophils and extensive areas of NETosis were found in the occlusive plexiform lesions and vascularized intrapulmonary thrombi. NETs induced nuclear factor κB–dependent endothelial angiogenesis in vitro and increased vascularization of matrigel plugs in vivo. Angiogenic responses were associated with increased release of matrix metalloproteinase-9, heparin-binding epidermal growth factor–like growth factor, latency-associated peptide of the transforming growth factor β1, and urokinase-type plasminogen activator, accompanied by increased endothelial permeability and cell motility. NETs-induced responses depended on myeloperoxidase/H2O2-dependent activation of Toll-like receptor 4/nuclear factor κB signaling. NETs stimulated the release of endothelin-1 in HPAECs (human pulmonary artery endothelial cells) and stimulated pulmonary smooth muscle cell proliferation in vitro.
CONCLUSIONS—We are the first to implicate NETs in angiogenesis and provide a functional link between NETs and inflammatory angiogenesis in vitro and in vivo. We demonstrate the potential pathological relevance of this in 2 diseases of disordered vascular homeostasis, pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension.
Pulmonary arterial hypertension (PAH) is a severe disorder of lung vasculature that causes right heart failure. Homoeostatic effects of flow-activated transcription factor Krüppel-like factor 2 ...(KLF2) are compromised in PAH. Here, we show that KLF2-induced exosomal microRNAs, miR-181a-5p and miR-324-5p act together to attenuate pulmonary vascular remodelling and that their actions are mediated by Notch4 and ETS1 and other key regulators of vascular homoeostasis. Expressions of KLF2, miR-181a-5p and miR-324-5p are reduced, while levels of their target genes are elevated in pre-clinical PAH, idiopathic PAH and heritable PAH with missense p.H288Y KLF2 mutation. Therapeutic supplementation of miR-181a-5p and miR-324-5p reduces proliferative and angiogenic responses in patient-derived cells and attenuates disease progression in PAH mice. This study shows that reduced KLF2 signalling is a common feature of human PAH and highlights the potential therapeutic role of KLF2-regulated exosomal miRNAs in PAH and other diseases associated with vascular remodelling.
In addition to N-terminal pro-brain natriuretic peptide (NT-proBNP), red cell distribution width (RDW), growth differentiation factor (GDF)-15, interleukin (IL)-6 and creatinine are all potential ...circulating prognostic biomarkers in pulmonary arterial hypertension (PAH).
To establish the relative prognostic utility of these biomarkers in patients with idiopathic PAH (IPAH) and to identify independent prognostic markers in this disease.
Circulating RDW, GDF-15, IL-6, creatinine and NT-proBNP levels were determined in 139 patients with IPAH (mean follow-up 4.0±2.4 years) and 40 age- and sex-matched healthy volunteers. Coincident clinical data and baseline haemodynamic measurements were also analysed.
All the biomarkers except creatinine correlated with a 6 min walk distance (6MWD; p<0.05), and all but NT-proBNP correlated with WHO functional class (p<0.01). GDF-15, creatinine and NT-proBNP correlated with mean right atrial pressures and cardiac index. RDW outperformed other biomarkers in receiver operating characteristic (ROC) analysis (area under the curve 0.820). Sensitive (>80%) ROC-derived cut-off points of RDW (15.7%, p=0.001), GDF-15 (779 pg/ml, p<0.001), IL-6 (2.5 pg/ml, p=0.019), creatinine (80.5 μmol/l, p=0.010) and NT-proBNP (491 fmol/ml, p<0.001), all predicted survival in patients with IPAH over time. All the plasma biomarkers analysed predicted survival in Cox regression analysis, as did clinical and haemodynamic parameters. However, only RDW predicted survival independently of NT-proBNP and 6MWD.
Circulating RDW, GDF-15, IL-6, creatinine and NT-proBNP levels are all related to disease severity and may be used to predict survival in patients with IPAH. RDW added significant prognostic value to measurements of NT-proBNP and exercise capacity and may prove valuable in a multiple biomarker approach to disease stratification.
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