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Background: Obese and overweight body habitus are common among patients undergoing right heart catheterization for suspected pulmonary hypertension, but previous studies have described only patients with severe obesity. This study examined the effect of body habitus on intracardiac pressures, thermodilution cardiac output (TDCO), indirect Fick (iFick) cardiac output (CO), and pulmonary vascular resistance (PVR) in subjects with normal cardiopulmonary hemodynamics. Methods: A retrospective analysis was conducted on healthy volunteers and patients referred for right heart catheterization for dyspnea of unknown origin with normal hemodynamics. Of the 65 subjects (53 ± 14 years; 51% female), 31% were normal weight, 49% were overweight, and 20% had obesity, as defined by a body mass index of 30-39.9 kg/m2. Mixed venous oxygen saturations and intracardiac pressures were compared across body mass index categories. Agreement between iFick CO calculated by 3 formulae, and TDCO and PVR was examined. Results: No differences in intracardiac pressures were observed, but mixed venous oxygen saturations were lower in the obese group. iFick CO underestimated TDCO, particularly with the LaFarge formula, with a systematic difference of 0.33 L/min for every 1 L/min increase in CO. This difference was largest in the obese group—on average by 23% ± 10%, translating to an overestimation of PVR by 34% ± 16% on average. Conclusions: In individuals without severe obesity, intracardiac pressures are not different, but mixed venous oxygen saturations are lower. Obesity confounds estimations of CO and PVR by iFick methods, which could result in inappropriate hemodynamic classification. These data can inform best practices in hemodynamic assessment of populations with obesity. Résumé: Introduction: Les habitus corporels liés à l'obésité et à l'embonpoint sont fréquents chez les patients qui subissent un cathétérisme du cœur droit en raison d'une suspicion d'hypertension pulmonaire, mais les études antérieures n'ont porté que sur les patients atteints d'une obésité sérieuse. La présente étude portait sur les répercussions des habitus corporels sur les pressions intracardiaques, le débit cardiaque obtenu par thermodilution (DCTD), le débit cardiaque (DC) calculé selon le principe indirect de Fick (iFick) et la résistance vasculaire pulmonaire (RVP) chez les sujets ayant une hémodynamie cardiopulmonaire normale. Méthodes: Nous avons mené une analyse rétrospective auprès de volontaires en bonne santé et de patients orientés pour un cathétérisme cardiaque droit en raison de dyspnée d'origine inconnue, mais qui avaient une hémodynamie normale. Au sein de 65 sujets (53 ± 14 ans; 51 % de femmes), 31 % avaient un poids normal, 49 % faisaient de l'embonpoint et 20 % souffraient d'obésité d'après l'indice de masse corporelle entre 30-39,9 kg/m2. Nous avons comparé les saturations veineuses mixtes en oxygène et les pressions intracardiaques de toutes les catégories d'indice de masse corporelle. Nous avons examiné la concordance entre le calcul du DC selon le principe iFick au moyen de 3 formules, ainsi que le DCTD et la RVP. Résultats: Les pressions intracardiaques n'ont montré aucune différence, mais les saturations veineuses mixtes en oxygène étaient plus faibles chez les sujets obèses. Le DC calculé selon le principe iFick a démontré une sous-estimation du DCTD, particulièrement lors du calcul au moyen de la formule LaFarge, qui a révélé une différence systématique de 0,33 L/min à chaque augmentation du DC de 1 L/min. Cette différence qui était plus importante chez les sujets obèses (en moyenne de 23 % ± 10 %, se traduisait en moyenne par une surestimation de la RVP de 34 % ± 16 %). Conclusions: Chez les individus non atteints d'une obésité sérieuse, les pressions intracardiaques ne sont pas différentes, mais les saturations veineuses mixtes en oxygène sont plus faibles. L'obésité fait remettre en cause les estimations du DC et de la RVP par les méthodes iFick, lesquelles pourraient donner lieu à une classification hémodynamique erronée. Ces données peuvent permettre d’établir des pratiques exemplaires lors de l’évaluation hémodynamique des populations atteintes d'obésité.

The von Hippel-Lindau (VHL) protein binds and degrades hypoxia-inducible factors (HIF) hydroxylated by prolyl-hydroxylases under normoxia. Although originally described as a tumor suppressor, there is growing evidence that VHL may paradoxically promote tumor growth. The significance of its described interactions with many other proteins remains unclear. We found that VHL interacts with p53, preventing its tetramerization, promoter binding and expression of its target genes p21, PUMA, and Bax. VHL limited the decrease in proliferation and increase in apoptosis caused by p53 activation, independent of prolyl-hydroxylation and HIF activity, and its presence in tumors caused a resistance to p53-inducing chemotherapy in vivo. We propose that VHL has both anti-tumor function, via HIF degradation, and a new pro-tumor function via p53 target (p21, PUMA, Bax) inhibition. Because p53 plays a critical role in tumor biology, is activated by many chemotherapies, and because VHL levels vary among different tumors and its function can even be lost by mutations in some tumors, our results have important clinical applications. KEY MESSAGES: VHL and p53 physically interact and VHL inhibits p53 activity by limiting the formation of p53 tetramers. VHL attenuates the expression of p53 target genes in response to p53 stimuli. The inhibition of p53 by VHL is independent of HIF and prolyl-hydroxylation.

Early right heart failure (RHF) remains a major source of morbidity and mortality after left ventricular assist device (LVAD) implantation, yet efforts to predict early RHF have proven only modestly successful. Pharmacologic unloading of the left ventricle may be a risk stratification approach allowing for assessment of right ventricular and hemodynamic reserve.We performed a multicenter, retrospective analysis of patients who had undergone continuous-flow LVAD implantation from October 2011 to April 2020. Only those who underwent vasodilator testing with nitroprusside during their preimplant right heart catheterization were included (n = 70). Multivariable logistic regression was used to determine independent predictors of early RHF as defined by Mechanical Circulatory Support-Academic Research Consortium.Twenty-seven patients experienced post-LVAD early RHF (39%). Baseline clinical characteristics were similar between patients with and without RHF. Patients without RHF, however, achieved higher peak stroke volume index (SVI) (30.1 ± 8.8 vs 21.7 ± 7.4 mL/mPeak SVI with nitroprusside administration was independently associated with post-LVAD early RHF while resting hemodynamics were not. Vasodilator testing may prove to be a strong risk stratification tool when assessing LVAD candidacy though additional prospective validation is needed.

Chemotherapy-induced cardiotoxicity (CIC) is a common clinical problem that compromises effective anticancer therapies. Many chemotherapeutics (including anthracyclines, such as doxorubicin) induce the proapoptotic transcription factor p53 in the tumor and nonspecifically in the heart, promoting heart failure. Although inhibition of p53 shows benefit in preclinical heart failure models, it would not be an attractive adjuvant therapy for CIC, because it would prevent tumor regression. A p53-targeting therapy that would decrease chemotherapy-induced apoptosis in the myocardium and, at the same time, enhance apoptosis in the tumor would be ideal. Here, we propose that differences in oxygen tension between the myocardium and the tumor could provide a platform for redox-dependent tissue-specific therapies. We show by coimmunoprecipitation and mass spectrometry that the redox-regulated pyruvate kinase muscle 2 (PKM2) directly binds with p53 and that the redox status of cysteine-423 of tetrameric (but not monomeric) PKM2 is critical for the differential regulation of p53 transcriptional activity. Tetrameric PKM2 suppresses p53 transcriptional activity and apoptosis in a high oxidation state but enhances them in a low oxidation one. We show that the oxidation state (along with cysteine-423 oxidation) is higher in the heart compared to the tumor of the same animal. Treatment with TEPP-46 (a compound that stabilizes tetrameric PKM2) suppressed doxorubicin-induced cardiomyocyte apoptosis, preventing cardiac dysfunction, but enhanced cancer cell apoptosis and tumor regression in the same animals in lung cancer models. Thus, our work suggests that redox-dependent differences in common proteins expressed in the myocardium and tumor can be exploited therapeutically for tissue selectivity in CIC.

Pulmonary arterial hypertension (PAH) is a complex disease leading to right ventricular (RV) failure and death, because of a proliferative vascular remodeling that obstructs the lumen of resistance pulmonary arteries (PA). Despite tremendous investments from the scientific community and industry over the past 20 years, the disease remains deadly.1 Currently approved therapies act mainly as vasodilators that cannot reverse the disease or improve survival, while they are offered at a prohibitive cost for many patients.1 Is the field in crisis? Kuhn2 described scientific crisis as a state where there is loss of confidence in the current paradigm while alternative, more attractive theories emerge and social pressures push toward a new outlook and proposed that these conditions promote a paradigm shift. The PAH community is losing confidence in the current paradigm, ie, the use of vasodilators as therapy for PAH, a disease in which vasoconstriction plays only a minor role. Yet, more drugs from the same families (endothelin receptor antagonists, activators of the NO/cGMP axis, or prostacyclin analogues) continue to be developed, tested, and approved. Although these drugs may also affect apoptotic and proliferation mechanisms, their primary mode of action is vasodilation. The proproliferative and antiapoptotic environment within the PA wall can be explained by a myriad of molecular abnormalities discovered in preclinical research, many of which show translational promise as targets for novel therapies.1 But none has been approved, and only a small fraction enters clinical trials.1 Translation to early-phase trials is a challenging stage in drug development, and many bottlenecks have been identified.1 Instead of intensifying efforts to develop novel drugs that target the foundation of PAH’s pathology, the development of vasodilators remains attractive for industry. Although vasoconstriction is not an important factor for most PAH patients, it contributes to a small degree …

Pulmonary arterial hypertension (PAH) is a complex obliterative vascular disease. It remains deadly despite an explosion of basic research over the past 20 years that identified myriads of potential therapeutic targets, few of which have been translated into early phase trials. Despite the agreement over the past decade that its pathogenesis is based on an antiapoptotic and proproliferative environment within the pulmonary arterial wall, and not vasoconstriction, all the currently approved therapies were developed and tested in PAH because of their vasodilatory properties. Numerous potential therapies identified in preclinical research fail to be translated in clinical research. Here we discuss 7 concepts that might help address the "translational gap" in PAH. These include: a need to approach the "pulmonary arteries-right ventricle unit" comprehensively and develop right ventricle-specific therapies for heart failure; the metabolic and inflammatory theories of PAH that put many "diverse" abnormalities under 1 mechanistic roof, allowing the identification of more effective targets and biomarkers; the realization that PAH might be a systemic disease with primary abnormalities in extrapulmonary tissues including the right ventricle, skeletal muscle, immune system, and perhaps bone marrow, shifting our focus toward more systemic targets; the realization that many heritable components of PAH have an epigenetic basis that can be therapeutically targeted; and novel approaches like cell therapy or devices that can potentially improve access to transplanted organs. This progress marks the entrance into a new and exciting stage in our understanding and ability to fight this mysterious deadly disease.

Rationale: Right ventricular (RV) failure is a major cause of morbidity and mortality in pulmonary hypertension, but its mechanism remains unknown. Myocyte enhancer factor 2 (Mef2) has been implicated in RV development, regulating metabolic, contractile, and angiogenic genes. Moreover, Mef2 regulates microRNAs that have emerged as important determinants of cardiac development and disease, but for which the role in RV is still unclear. Objective: We hypothesized a critical role of a Mef2-microRNAs axis in RV failure. Methods and Results: In a rat pulmonary hypertension model (monocrotaline), we studied RV free wall tissues from rats with normal, compensated, and decompensated RV hypertrophy, carefully defined based on clinically relevant parameters, including RV systolic and end-diastolic pressures, cardiac output, RV size, and morbidity. Mef2c expression was sharply increased in compensating phase of RVH tissues but was lost in decompensation phase of RVH. An unbiased screening of microRNAs in our model resulted to a short microRNA signature of decompensated RV failure, which included the myocardium-specific miR-208, which was progressively downregulated as RV failure progressed, in contrast to what is described in left ventricular failure. With mechanistic in vitro experiments using neonatal and adult RV cardiomyocytes, we showed that miR-208 inhibition, as well as tumor necrosis factor-α, activates the complex mediator of transcription 13/nuclear receptor corepressor 1 axis, which in turn promotes Mef2 inhibition, closing a self-limiting feedback loop, driving the transition from compensating phase of RVH toward decompensation phase of RVH. In our model, serum tumor necrosis factor-α levels progressively increased with time while serum miR-208 levels decreased, mirroring its levels in RV myocardium. Conclusions: We describe an RV-specific mechanism for heart failure, which could potentially lead to new biomarkers and therapeutic targets.

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 SIRT3 and UCP2 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.

The aim of this study was to assess the association between peripheral arterial tonometry (PAT) and two more traditional measures of endothelial function – flow-mediated dilation (FMD) and its hyperemic stimulus, hyperemic peak velocity time integral (VTI). We related three vascular function measures (natural log transformed PAT, FMD, and VTI) from 304 patients (mean age 48.9 ± 12.5 years), including 105 with coronary artery disease (CAD). Using linear regression, we studied the relationships between lnPAT, FMD, and VTI, and compared differences in these parameters in those with and without CAD. Although FMD and lnPAT both had a correlation with VTI (Pearson’s r = 0.119, p = 0.039 and r = 0.167, p = 0.004, respectively), lnPAT had no correlation with FMD ( r = −0.0471, p = 0.414). lnPAT was also lower in patients with CAD compared to controls (mean 0.51 ± 0.19 versus 0.65 ± 0.26, respectively, p < 0.0001). In multivariate analysis, VTI remained associated with lnPAT (standardized β = 0.1369, p = 0.04). Among this group of subjects with and without CAD, lnPAT was found to be unrelated to FMD but correlated with VTI. This would suggest that lnPAT is a measure of microvascular function. Although it is unrelated to FMD, lnPAT is decreased in patients with pre-existing cardiovascular disease. Further studies are required to determine if this can be used clinically as a tool for cardiac risk stratification and prediction of CAD.

Background— Sildenafil was recently approved for the treatment of pulmonary arterial hypertension. The beneficial effects of phosphodiesterase type 5 (PDE5) inhibitors in pulmonary arterial hypertension are thought to result from relatively selective vasodilatory and antiproliferative effects on the pulmonary vasculature and, on the basis of early data showing lack of significant PDE5 expression in the normal heart, are thought to spare the myocardium. Methods and Results— We studied surgical specimens from 9 patients and show here for the first time that although PDE5 is not expressed in the myocardium of the normal human right ventricle (RV), mRNA and protein are markedly upregulated in hypertrophied RV (RVH) myocardium. PDE5 also is upregulated in rat RVH. PDE5 inhibition (with either MY-5445 or sildenafil) significantly increases contractility, measured in the perfused heart (modified Langendorff preparation) and isolated cardiomyocytes, in RVH but not normal RV. PDE5 inhibition leads to increases in both cGMP and cAMP in RVH but not normal RV. Protein kinase G activity is suppressed in RVH, explaining why the PDE5 inhibitor–induced increase in cGMP does not lead to inhibition of contractility. Rather, it leads to inhibition of the cGMP-sensitive PDE3, explaining the increase in cAMP and contractility. This is further supported by our findings that, in RVH protein kinase A, inhibition completely inhibits PDE5-induced inotropy, whereas protein kinase G inhibition does not. Conclusions— The ability of PDE5 inhibitors to increase RV inotropy and to decrease RV afterload without significantly affecting systemic hemodynamics makes them ideal for the treatment of diseases affecting the RV, including pulmonary arterial hypertension.

Introduction: Pulmonary arterial hypertension (PAH) is often associated with interstitial lung disease, like idiopathic pulmonary fibrosis (IPF). IPF pulmonary fibroblasts have a very similar pro-proliferative and anti-apoptotic phenotype similar to PAH vascular smooth muscle cells (SMC). As this phenotype is often associated with a cancer-like mitochondrial suppression, we hypothesized that a common mitochondria abnormality may underlie both PAH and IPF. We speculated that the loss of the mitochondrial deacetylase Sirt3, which we recently showed promotes PAH, will also promote IPF. Results: SIRT3 expression was decreased in human IPF-PH lungs (transplant recipients, n=7) and in Sirt3 wild type (Sirt3WT)+ bleomycin BLEO lungs (n=15 for each) and fibroblasts compared to healthy lungs (unused transplant tissue, n=3) and Sirt3WT. Sirt3 knockout (Sirt3KO) fibroblasts, like Sirt3WT+BLEO, had decreased mitochondrial function assessed by decreased pyruvate dehydrogenase activity, decreased respiration (Seahorse Assay) and increased mitochondrial membrane potential (TMRM dye in live cell imaging). Sirt3KO and Sirt3WT+BLEO fibroblasts had increased collagen production and smooth muscle actin expression (immunoblot). All of these findings are very similar to those in pulmonary artery SMCs from the same Sirt3KO animals, which develop spontaneous PAH. In vivo, Sirt3KO mice treated with BLEO developed worse IPF than Sirt3WT+BLEO (dynamic resistance 2±0.5 vs 1.4±0.2cmH2O.s/mL, dynamic elastance 20±3 vs 38±10cmH2O/mL). Intra-tracheal delivery of an adenovirus overexpressing SIRT3 improved both Sirt3KO+BLEO and Sirt3WT+BLEO compared to GFP-only adenovirus. We have previously showed that the same virus reverses PAH in rodents. Conclusion: Sirt3 downregulation plays an important role in the development of IPF. While the exact mechanisms by which Sirt3 is downregulated remains to be established, this work opens new perspectives for the treatment of IPF. Given the frequent overlap of IPF and pulmonary hypertension in the same patients, our data suggest the intriguing possibility that they both represent aspects of an “overlap syndrome”, which may benefit from similar therapeutic approaches, despite the differences in the “cell of origin”.

Introduction: In Pulmonary Arterial Hypertension (PAH), a “cancer-like” mitochondrial suppression in pulmonary vascular cells underlies in part the apoptosis resistance that characterizes the proliferative vascular remodeling. There is emerging evidence that a similar mitochondrial suppression is present in extra-pulmonary tissues like the skeletal muscle or circulating cells in PAH. We speculated that this may be due to a circulating factor. In cancer, such factors may underlie muscle wasting (cancer cachexia). In worms, there is evidence that “mitokines” secreted by one organ can “condition” other organs remotely by suppressing mitochondria. We hypothesized that Prohibitin (PHB-1; a protein increased both in the tumor and in the serum of cancer patients) maybe a candidate mitokine in PAH. Results: To determine whether the pulmonary circulation responds to endogenously produced PHB-1, we studied a rat tumor xenotransplant model with CRL-2335 breast cancer cells. Rats with tumors exhibited higher PA pressures compared to rats without tumors (mPAP=12±1mmHg vs 20±2mmHg, n=18) and this increase correlated with tumor size. Importantly, this increase in PA pressures was not due to thromboembolism and was associated with increased muscularization of resistance PAs. PHB-1 levels were increased in the PAs and serum of rats with tumors compared to controls and in the culture media of CRL2335 compared to normal cells. PASMCs exposed to Recombinant (Rec)PHB-1 displayed inhibited pyruvate dehydrogenase, increased mitochondrial membrane potential (TMRM live cell imaging 37±0.5AFU vs 53±1.2AFU), decreased mitochondrial respiration and suppressed apoptosis, mimicking the PAH phenotype. Preliminary data suggested that RecPHB-1 activates the plasma membrane receptor ErbB2, which is translocated into the mitochondria (immunoblot on isolated mitochondria and immunostaining) where it acts as a negative regulator of mitochondrial function. Conclusion: The pulmonary circulation may be responsive to endogenous circulating mitochondrial inhibitors originating from extra-pulmonary tissues. PHB-1 may be a potential mitokine in PAH.

Introduction: Pulmonary arterial hypertension (PAH) and idiopathic pulmonary fibrosis (IPF) are deadly diseases that often require lung transplantation. Preclinical evidence suggests that mitochondrial suppression underlies the pro-proliferative and anti-apoptotic phenotype of pulmonary artery smooth muscle cells and pulmonary fibroblasts, respectively. Two therapies to improve mitochondrial function are a) dichloroacetate (DCA), an activator of pyruvate dehydrogenase (PDH), the gate-keeping enzyme for glucose oxidation, and b) 4-phenylbutyrate (4-PBA), an inhibitor of endoplasmic reticulum stress, a response that suppresses mitochondrial function during cellular stress. Although these drugs can be studied in vitro or in animals, their metabolic effects on the whole human lung may only by studied through ex vivo lung perfusion (EVLP). Methods: We used a custom-made EVLP system to study explanted, diseased human lungs of patients undergoing lung transplant for PAH (n=2), or IPF (n=4). The bronchi were connected to a ventilator, while a pump-driven system perfused the pulmonary artery (PA) with modified Krebs-Henseleit buffer or STEEN solution™ in recirculation. Lung biopsies were collected to measure mitochondrial respiration (using a Seahorse analyzer) and PDH activity at baseline, and after drug intervention with DCA or 4-PBA for 1 hour. Results: In the PAH lungs, hypoxic pulmonary vasoconstriction, a validated marker of lung health, was absent. However administrating the prostacyclin analogue treprostinil reduced PA pressure by 31.6% (at a level of flow corresponding to the patient’s cardiac output), confirming abnormal but present vasoreactivity in the model. DCA caused a 61.1% increase in oxygen consumption, and a 34-fold increase in PDH activity. In IPF lungs, PBA increased oxygen consumption by 62.0%. Conclusions: EVLP is a feasible model to study the direct effects of drugs on diseased human lungs. Since before-after biopsies are not possible in clinical trials, this is a valuable model to facilitate translation of preclinical therapies to clinical trials. Our results show, for the first time in human lungs, that the metabolic remodeling of the PAH and IPF can be reversed by clinically available small molecules like DCA and 4-PBA.

> “As you set out for Ithaka, hope the voyage is a long one, full of adventure, full of discovery. > > Keep Ithaka always in your mind. Arriving there is what you are destined for… > > But do not hurry the journey at all. Better if it lasts for years, so you are old by the time you reach the island, > > wealthy with all you have gained on the way, not expecting Ithaka to make you rich… > > And if you find her poor, Ithaka won’t have fooled you. > > Wise as you will have become, so full of experience, you will have understood by then > > what these Ithakas mean.” > > from Ithaka, by C.P. Cavafy1 Pulmonary arterial hypertension (PAH) is a relatively rare but fatal disease. However, with the advances in diagnostic tools and our organized approach (most tertiary-care centers now have PAH programs), we now know that PAH is more common than we thought even 15 years ago, although precise estimates of global incidence and prevalence are lacking. PAH is projected to become a 5-billion-dollar industry by the end of this decade,2 as most of the approved 3 classes of therapies (phosphodiesterase type 5 inhibitors/cGMP modulators, endothelin antagonists, and prostacyclin analogues) are expensive. The vast majority of clinical trials with these drugs have been short (≤6 months) and have not included mortality as a primary end point, and there is no prospective evidence that these therapies can prolong life or reverse the progression of the disease. On the other hand, it seems that they can improve symptoms or decrease hospitalizations.3 The ultimate treatment remains lung transplantation, and there are currently no therapies to treat the major complication of the disease, that is, right ventricular failure. Yet, there are myriads of promising therapies at the preclinical stage.3 Like in many other …

Background Clear-cell renal cell carcinoma (ccRCC) exhibits suppressed mitochondrial function and preferential use of glycolysis even in normoxia, promoting proliferation and suppressing apoptosis. ccRCC resistance to therapy is driven by constitutive hypoxia-inducible factor (HIF) expression due to genetic loss of von Hippel-Lindau factor. In addition to promoting angiogenesis, HIF suppresses mitochondrial function by inducing pyruvate dehydrogenase kinase (PDK), a gatekeeping enzyme for mitochondrial glucose oxidation. Objective To reverse mitochondrial suppression of ccRCC using the PDK inhibitor dichloroacetate (DCA). Design, setting, and participants Radical nephrectomy specimens from patients with ccRCC were assessed for PDK expression. The 786-O ccRCC line and two animal models (chicken in ovo and murine xenografts) were used for mechanistic studies. Outcome measurements and statistical analysis Mitochondrial function, proliferation, apoptosis, HIF transcriptional activity, angiogenesis, and tumor size were measured in vitro and in vivo. Independent-sample t -tests and analysis of variance were used for statistical analyses. Results PDK was elevated in 786-O cells and in ccRCC compared to normal kidney tissue from the same patient. DCA reactivated mitochondrial function (increased respiration, Krebs cycle metabolites such as α-ketoglutarate [cofactor of factor inhibiting HIF], and mitochondrial reactive oxygen species), increased p53 activity and apoptosis, and decreased proliferation in 786-O cells. DCA reduced HIF transcriptional activity in an FIH-dependent manner, inhibiting angiogenesis in vitro. DCA reduced tumor size and angiogenesis in vivo in both animal models. Conclusions DCA can reverse the mitochondrial suppression of ccRCC and decrease HIF transcriptional activity, bypassing its constitutive expression. Its previous clinical use in humans makes it an attractive candidate for translation to ccRCC patients. Patient summary We show that an energy-boosting drug decreases tumor growth and tumor blood vessels in animals carrying human kidney cancer cells. This generic drug has been used in patients for other conditions and thus could be tested in kidney cancer that remains incurable.

ObjectivesThe right ventricle fails quickly after increases in its afterload (ie, pulmonary hypertension) compared with the left ventricle (ie, systemic hypertension), resulting in significant morbidity and mortality. We hypothesized that the poor performance of the hypertrophied right ventricle is caused, at least in part, by a suboptimal mitochondrial/metabolic remodeling.Methods/ResultsWe studied mitochondrial membrane potential, a surrogate for mitochondrial function, in human (n = 11) and rat hearts with physiologic (neonatal) and pathologic (pulmonary hypertension) right ventricular hypertrophy in vivo and in vitro. Mitochondrial membrane potential is higher in the normal left ventricle compared with the right ventricle but is highest in the hypertrophied right ventricle, both in myocardium and in isolated cardiomyocytes (P < .01). Mitochondrial membrane potential correlated positively with the degree of right ventricular hypertrophy in vivo and was recapitulated in phenylephrine-treated neonatal cardiomyocytes, an in vitro model of hypertrophy. The phenylephrine-induced mitochondrial hyperpolarization was reversed by VIVIT, an inhibitor of the nuclear factor of activated T lymphocytes, a transcription factor regulating the expression of several mitochondrial enzymes during cardiac development and hypertrophy. The clinically used drug dichloroacetate, known to increase the mitochondria-based glucose oxidation, reversed both the phenylephrine-induced mitochondrial hyperpolarization and nuclear factor of activated T lymphocytes (NFAT) activation. In Langendorff perfusions, dichloroacetate increased rat right ventricular inotropy in hypertrophied right ventricles (P < .01) but not in normal right ventricles, suggesting that mitochondrial hyperpolarization in right ventricular hypertrophy might be associated with its suboptimal performance.ConclusionsThe dynamic changes in mitochondrial membrane potential during right ventricular hypertrophy are chamber-specific, associated with activation of NFAT, and can be pharmacologically reversed leading to improved contractility. This mitochondrial remodeling might provide a framework for development of novel right ventricle–specific therapies.

SummarySuppression of mitochondrial function promoting proliferation and apoptosis suppression has been described in the pulmonary arteries and extrapulmonary tissues in pulmonary arterial hypertension (PAH), but the cause of this metabolic remodeling is unknown. Mice lacking sirtuin 3 (SIRT3), a mitochondrial deacetylase, have increased acetylation and inhibition of many mitochondrial enzymes and complexes, suppressing mitochondrial function. Sirt3KO mice develop spontaneous PAH, exhibiting previously described molecular features of PAH pulmonary artery smooth muscle cells (PASMC). In human PAH PASMC and rats with PAH, SIRT3 is downregulated, and its normalization with adenovirus gene therapy reverses the disease phenotype. A loss-of-function SIRT3 polymorphism, linked to metabolic syndrome, is associated with PAH in an unbiased cohort of 162 patients and controls. If confirmed in large patient cohorts, these findings may facilitate biomarker and therapeutic discovery programs in PAH.