Maladaptive Right Ventricular Research Articles

Metabolic changes contribute to maladaptive right ventricular hypertrophy in pulmonary hypertension beyond pressure overload: an integrative imaging and omics investigation

Right ventricular (RV) failure remains the strongest determinant of survival in pulmonary hypertension (PH). We aimed to identify relevant mechanisms, beyond pressure overload, associated with maladaptive RV hypertrophy in PH. To separate the effect of pressure overload from other potential mechanisms, we developed in pigs two experimental models of PH (M1, by pulmonary vein banding and M2, by aorto-pulmonary shunting) and compared them with a model of pure pressure overload (M3, pulmonary artery banding) and a sham-operated group. Animals were assessed at 1 and 8 months by right heart catheterization, cardiac magnetic resonance and blood sampling, and myocardial tissue was analyzed. Plasma unbiased proteomic and metabolomic data were compared among groups and integrated by an interaction network analysis. A total of 33 pigs completed follow-up (M1, n = 8; M2, n = 6; M3, n = 10; and M0, n = 9). M1 and M2 animals developed PH and reduced RV systolic function, whereas animals in M3 showed increased RV systolic pressure but maintained normal function. Significant plasma arginine and histidine deficiency and complement system activation were observed in both PH models (M1&M2), with additional alterations to taurine and purine pathways in M2. Changes in lipid metabolism were very remarkable, particularly the elevation of free fatty acids in M2. In the integrative analysis, arginine–histidine–purines deficiency, complement activation, and fatty acid accumulation were significantly associated with maladaptive RV hypertrophy. Our study integrating imaging and omics in large-animal experimental models demonstrates that, beyond pressure overload, metabolic alterations play a relevant role in RV dysfunction in PH.

Abstract 11774: Right Ventricular Function and Myocardial Blood Volume Analyses by Convolutional Neural Network in Experimental Pulmonary Hypertension

Introduction: Survival of patients with pulmonary hypertension (PH) is highly dependent on the right ventricular (RV) function. Despite the association of various factors with adaptive or maladaptive RV phenotypes, the contribution of microvascular density to RV adaptation to pressure overload remains unclear. Hypothesis: This study aimed to evaluate the RV myocardial blood volume and its role in the RV adaptation to pressure overload. Methods: Both the University Animal Care Committee and the federal authorities for animal research of the Regierungsprasidium Giessen (Hessen, Germany) approved the study protocol. The study used adult Wistar-Kyoto rats and Sprague-Dawley rats to induce PH using SuHx and monocrotaline (MCT), respectively. Echocardiography, in vivo contrast-μCT, and invasive hemodynamic measurements were performed. The researchers used an artificial intelligence (AI)-based convolutional neural network (CNN) approach to reconstruct, segment, and analyze the cardiac μCT images. The RV functional reserve was evaluated during mCT acquisition and dobutamine stress test, and metabolomics analysis was performed. Results: The data showed that SuHx rats developed maladaptive cardiac function and RV-PA uncoupling. MCT rats exhibited adaptive RV function at days 14 and 21, but maladaptive function at day 35, which was associated with RV-PA uncoupling and reduced RV functional reserve. Impaired PKA-CREB signaling pathway was also found to be associated with the reduced RV functional reserve in the MCT rats. In both PH models, the absolute RV blood volume significantly increased with the development of RV hypertrophy, but the relative blood volume decreased, which was associated with maladaptive RV function Conclusions: This study is the first to demonstrate the use of AI CNN in post-processing of μCT-derived cardiac images from experimental PH models. Additionally, a single-beat PV loop was established for the first time in a rat model of PH by combining non-invasive and invasive techniques. The findings suggest that RV maladaptive function in rat models of PH is characterized by capillary rarefaction, impaired RV reserve in response to dobutamine infusion, which is associated with impaired PKA-CREB signaling pathway in the RV.

Transcriptional profiling unveils molecular subgroups of adaptive and maladaptive right ventricular remodeling in pulmonary hypertension

Right ventricular (RV) function is critical to prognosis in all forms of pulmonary hypertension. Here we perform molecular phenotyping of RV remodeling by transcriptome analysis of RV tissue obtained from 40 individuals, and two animal models of RV dysfunction of both sexes. Our unsupervised clustering analysis identified ‘early’ and ‘late’ subgroups within compensated and decompensated states, characterized by the expression of distinct signaling pathways, while fatty acid metabolism and estrogen response appeared to underlie sex-specific differences in RV adaptation. The circulating levels of several extracellular matrix proteins deregulated in decompensated RV subgroups were assessed in two independent cohorts of individuals with pulmonary arterial hypertension, revealing that NID1, C1QTNF1 and CRTAC1 predicted the development of a maladaptive RV state, as defined by magnetic resonance imaging parameters, and were associated with worse clinical outcomes. Our study provides a resource for subphenotyping RV states, identifying state-specific biomarkers, and potential therapeutic targets for RV dysfunction.

Down-regulation of the mitochondrial fusion protein Opa1/Mfn2 promotes cardiomyocyte hypertrophy in Su5416/hypoxia-induced pulmonary hypertension rats

BackgroundMaladaptive right ventricular (RV) remodeling is the most important pathological feature of pulmonary hypertension (PH), involving processes such as myocardial hypertrophy and fibrosis. A growing number of studies have shown that mitochondria-associated endoplasmic reticulum membranes (MAMs) are involved in various physiological and pathological processes, such as calcium homeostasis, lipid metabolism, inflammatory response, mitochondrial dynamics, and autophagy/mitophagy. The abnormal expression of MAMs-related factors is closely related to the occurrence and development of heart-related diseases. However, the role of MAM-related factors in the maladaptive RV remodeling of PH rats remains unclear. Methods and resultsWe first obtained the transcriptome data of RV tissues from PH rats induced by Su5416 combined with hypoxia treatment (SuHx) from the Gene Expression Omnibus (GEO) database. The results showed that two MAMs-related genes (Opa1 and Mfn2) were significantly down-regulated in RV tissues of SuHx rats, accompanied by significant up-regulation of cardiac hypertrophy-related genes (such as Nppb and Myh7). Subsequently, using the SuHx-induced PH rat model, we found that the downregulation of mitochondrial fusion proteins Opa1 and Mfn2 may be involved in maladaptive RV remodeling by accelerating mitochondrial dysfunction. Finally, at the cellular level, we found that overexpression of Opa1 and Mfn2 could inhibit hypoxia-induced mitochondrial fission and reduce ROS production in H9c2 cardiomyocytes, thereby retarded the progression of cardiomyocyte hypertrophy. ConclusionsThe down-regulation of mitochondrial fusion protein Opa1/Mfn2 can accelerate cardiomyocyte hypertrophy and then participate in maladaptive RV remodeling in SuHx-induced PH rats, which may be potential targets for preventing maladaptive RV remodeling.

Abstract P2008: Contractile Adaptation Of The Right Ventricular Myocardium In Pulmonary Hypertension

Introduction: Pulmonary hypertension (PH) is characterized by increased right ventricular (RV) afterload inducing notable biomechanical remodeling in the RV free wall (RVFW) myocardium. While changes in the passive behavior of the RVFW have been studied, its contractile adaptations in PH remain to be investigated. Methods: Two sugen-hypoxia models were developed by injecting SU5416 into Sprague Dawley (SD) and Fischer (CDF) rats (n=4 each) and placing them in a hypoxia chamber for 3 weeks, followed by 1 week of normoxia. Wild-type rats (n=4), injected with vehicle and kept in normoxia, were used as controls. Right heart catheterization was perfomed at week 4. RVFW samples were skinned in 10% Triton. Samples were activated at pCa 4.5. Mechanical tests were performed isometrically at 20% stretch. Circumferential and longitudinal stresses were summed to report ensemble stress. Results: RV systolic pressure and stroke volume showed significant increase and decrease in both PH groups, respectively, compared to controls (Figs. 1A, B). While increases in initial stress, representing the passive behavior, did not reach significance in either PH group (Fig. 1C), total stress, representing the combined passive and active behavior, increased significantly only in CDF-PH group (Fig. 1D), known to exhibit a more maladaptive RV remodeling compared to SD-PH. Select stresses are shown in Figs. 1E, F. Conclusions: While elevated passive stresses in the RVFW are commonly reported in PH, the measurement of contractile stresses is essential to properly assess the adaptation of the RV. Further studies are needed to determine the role of passive vs. active stresses in the outcome of RV remodeling.

Differential angiogenic response contributes to sexual dimorphism in right ventricular adaptation in male and female Fischer CDF rats subjected to pulmonary artery banding model

Background: Female sex has been associated with better right ventricular (RV) adaptation and survival in patients with elevated RV afterload; however, the mechanisms underlying these differences remain unclear. Therefore, we studied the mechanisms underlying sex differences in RV remodeling and development of RHF using the rat pulmonary artery banding (PAB) model. Methods: Adult male and female Fischer CDF rats were subjected to PAB or sham surgery and echocardiography was performed at 1- or 2-weeks post-PAB to evaluate RV structure and function. RV systolic pressure (RVSP) was measured using a pressure catheter and Fulton Index (RV/ left ventricle + septum) was measured to evaluate RV hypertrophy (RVH). To explore the mechanisms, a focused PCR array was performed to assess the expression of angiogenic genes in the RV of male and female rats subjected to sham or PAB procedure. RV endothelial cells (RVECs) were isolated from Fischer CDF rats and effects of female sex hormones on angiogenic ability of RVECs was assessed using Matrigel network formation assay. We also assessed the role of sphingosine kinase-1 (Sphk1) inhibitor, PF-543, in mediating the effects of female sex hormones on angiogenic potential of RVECs. Results: At 1- and 2-week post-PAB, RVSP and RVH were significantly elevated in PAB rats compared to control rats; however, no differences were observed between male and female rats. Cardiomyocyte surface area (330 vs 234 mm2, p<0.05) and fibrosis (6.96 vs 4.58%, p<0.05) were both significantly higher in male compared to female rats. RV end-diastolic diameter was also increased in male rats compared to female rats (3.33 vs 2.05 mm; p<0.05). On the contrary, RV function was preserved in female rats as indicated by higher cardiac index and fractional area change compared to male rats. Up-regulation of angiogenic genes, including Sphk1, was observed in the RV of female rats compared to male rats at 2 weeks post-PAB. Estradiol treatment increased network forming ability of RVEC isolated from Fischer CDF rats and this effect was inhibited by PF-543. Conclusions: Female Fischer CDF rats develop adaptive RV remodeling in response to PAB compared to mal-adaptive RV remodeling in male rats. Moreover, the better RV adaptation in female rats involves increased RV angiogenesis and these effect may be mediated through Sphk1. Research Nova Scotia, Dalhousie University This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Prognostic role of pulmonary impedance estimation to predict right ventricular dysfunction in pulmonary hypertension

The effect of pulmonary hypertension (PH) on right ventricular (RV) afterload is commonly defined by elevation of pulmonary artery (PA) pressure or pulmonary vascular resistance (PVR). In humans however, one-third to half of the hydraulic power in the PA is contained in pulsatile components of flow. Pulmonary impedance (Zc) expresses opposition of the PA to pulsatile blood flow. We evaluate pulmonary Zc relationships according to PH classification using a cardiac magnetic resonance (CMR)/right heart catheterization (RHC) method. Prospective study of 70 clinically indicated patients referred for same-day CMR and RHC [60±16years; 77% females, 16 mPAP <25mmHg (PVR <240dynes.s.cm-5 /mPCWP <15mmHg), 24 pre-capillary (PrecPH), 15 isolated post-capillary (IpcPH), 15 combined pre-capillary/post-capillary (CpcPH)]. CMR provided assessment of PA flow, and RHC, central PA pressure. Pulmonary Zc was expressed as the relationship of PA pressure to flow in the frequency domain (dynes.s.cm-5 ). Baseline demographic characteristics were well matched. There was a significant difference in mPAP (P<0.001), PVR (P=0.001), and pulmonary Zc between mPAP<25mmHg patients and those with PH (mPAP <25mmHg: 47±19 dynes.s.cm-5 ; PrecPH 86±20dynes.s.cm-5 ; IpcPH 66±30dynes.s.cm-5 ; CpcPH 86±39dynes.s.cm-5 ; P=0.05). For all patients with PH, elevated mPAP was found to be associated with raised PVR (P<0.001) but not with pulmonary Zc (P=0.87), except for those with PrecPH (P<0.001). Elevated pulmonary Zc was associated with reduced RVSWI, RVEF, and CO (all P<0.05), whereas PVR and mPAP were not. Raised pulmonary Zc was independent of elevated mPAP in patients with PH and more strongly predictive of maladaptive RV remodelling than PVR and mPAP. Use of this straightforward method to determine pulmonary Zc may help to better characterize pulsatile components of RV afterload in patients with PH than mPAP or PVR alone.

Clinical phenotyping of plasma thrombospondin-2 reveals relationship to right ventricular structure and function in pulmonary hypertension.

Converging evidence from proteogenomic analyses prioritises thrombospondin-2 (TSP2) as a potential biomarker for idiopathic or heritable pulmonary arterial hypertension (PAH). We aimed to assess TSP2 levels in different forms of pulmonary hypertension (PH) and to define its clinical phenotype. Absolute concentrations of TSP2 were quantified in plasma samples from a prospective single-centre cohort study including 196 patients with different forms of PH and 16 disease controls (suspected PH, but normal resting pulmonary haemodynamics). In an unbiased approach, TSP2 levels were related to 152 clinical variables. Concentrations of TSP2 were increased in patients with PH versus disease controls (p<0.001 for group comparison). The discriminatory ability of TSP2 levels to distinguish between patients and controls was superior to that of N-terminal pro-brain natriuretic peptide (p=0.0023 for comparison of areas under the curve). Elevation of TSP2 levels was consistently found in subcategories of PAH, in PH due to lung disease and due to left heart disease. Phenotypically, TSP2 levels were robustly related to echocardiographic markers that indicate the right ventricular (RV) response to chronically increased afterload with increased levels in patients with impaired systolic function and ventriculoarterial uncoupling. Focusing on PAH, increased TSP2 levels were able to distinguish between adaptive and maladaptive RV phenotypes (area under the curve 0.87, 95% CI 0.76-0.98). The study indicates that plasma TSP2 levels inform on the presence of PH and associate with clinically relevant RV phenotypes in the setting of increased afterload, which may provide insight into processes of RV adaptability.

Abstract 13499: Unravelling the Pathophysiology of Right Ventricular Maladaptive Hypertrophy in Chronic Pulmonary Hypertension Through Imaging and Omics

Introduction: Right ventricular (RV) failure is the strongest determinant of survival in chronic pulmonary hypertension (PH), but its pathophysiological mechanisms remain unclear. Hypothesis: In addition to RV pressure overload, compounds liberated from the pulmonary vascular damage (identifiable by omics) may exert a detrimental effect on RV function in PH. Methods: Four different experimental models of RV pressure overload in 48 Yucatan pigs were developed: chronic postcapillary PH by pulmonary veins banding (M1); chronic PH by aorto-pulmonary shunting (M2); RV pressure overload by PA banding (thus without PH) (M3); and sham procedure (M0). Animals were evaluated at 1, 5 and 8 months after surgery by right heart catheterization, cardiac magnetic resonance (CMR), and blood/histological sampling. Unsupervised proteomic and metabolomic analyses were performed and compared among experimental groups and to the severity of RV dysfunction. Results: A total of 33 pigs completed follow-up (M1,n=8; M2,n=6; M3,n=10; and M0,n=9). As expected, M1&amp;M2-animals developed chronic PH, whereas M3-animals had severely increased RV systolic pressure without PH (Table). M3-pigs developed more severe RV hypertrophy (significantly higher mass on CMR and cardiomyocyte area on histology), but maintained normal function. In contrast, M1&amp;M2 animals developed RV systolic disfunction and increased myocardial apoptosis in M1. Plasma metabolomic and proteomic patterns differed among groups, highlighting greater inflammation and taurine/arginine deficiency in PH models (M1&amp;M2), coagulation disturbances in M1, and predominant lipidomic changes in M3. Key proteins/metabolites from coagulation, complement system and apolipoproteins pathways significantly associated with RV performance. Conclusion: Maladaptive RV hypertrophy in PH is associated with significant changes in plasma proteins and metabolites. Their identification may help to identify potential targets.

Melatonin activates the Mst1-Nrf2 signaling to alleviate cardiac hypertrophy in pulmonary arterial hypertension

Among pulmonary arterial hypertension (PAH) patients, right ventricular (RV) functioning has been considered a major determining factor for cardiac capacity and survival. However, despite the recognition of the clinical importance for preserving RV functioning, no effective treatments are currently available for RV failure. This study aims to suggest one such possible treatment, through investigating the cardio-protective capabilities of the anti-oxidant, melatonin (Mel), for treating adverse RV remodeling in PAH, along with its underlying mechanisms. Arginine vasopressin induced neonatal rat cardiomyocyte hypertrophy in vitro; in vivo, PAH was induced in rats through intraperitoneal monocrotaline (MCT) injections, and Mel was administered intraperitoneally 24 h prior to MCT. Mel reduced rat cardiomyocyte hypertrophy and mitochondrial oxidative stress in vitro by activating the Mst1-Nrf2 pathway, which were all reversed upon siRNA knockdown of Mst1. Likewise, in vivo, Mel pre-treatment significantly ameliorated MCT-induced deterioration in cardiac function, RV hypertrophy, fibrosis and dilation. These beneficial effects were also associated with Mst1-Nrf2 pathway up regulation and its associated reduction in oxidative stress, as evidenced by the decrease in RV malondialdehyde content. Notably, results from Mel treatment were similar, or even superior, to those obtained from N-acetyl cysteine (NAC), which has already been-confirmed as an anti-oxidative treatment for PAH. By contrast, co-treatment with the Mst1 inhibitor XMU-MP-1 reversed all of those Mel-associated beneficial effects. Our findings thus identified Mel as a potent cardio-protective agent against the onset of maladaptive RV remodeling, through enhancement of the anti-oxidative response via Mst1-Nrf2 pathway activation.

Right Heart Failure in Mice Upon Pressure Overload Is Promoted by Mitochondrial Oxidative Stress

We sought to unravel pathomechanisms of the transition of maladaptive right ventricular (RV) remodeling to right heart failure (RHF) upon pressure overload. Exposure of C57BL/6J and C57BL/6N mice to pulmonary artery banding disclosed a tight relation of structural remodeling with afterload, but a dissociation from RV systolic function. Reduced release of mitochondrial reactive oxygen species in C57BL/6J mice prevented the development of RHF. In patients with left heart failure, increased oxidative damage in RV sections was associated with severely impaired RV function. In conclusion, reactive oxygen species are involved in the transition of maladaptive RV remodeling to RHF.

Structural and Hemodynamic Changes of the Right Ventricle in PH-HFpEF.

One of the most important diagnostic challenges in clinical practice is the distinction between pulmonary hypertension (PH) due to primitive pulmonary arterial hypertension (PAH) and PH due to left heart diseases. Both conditions share some common characteristics and pathophysiological pathways, making the two processes similar in several aspects. Their diagnostic differentiation is based on hemodynamic data on right heart catheterization, cardiac structural modifications, and therapeutic response. More specifically, PH secondary to heart failure with preserved ejection fraction (HFpEF) shares features with type 1 PH (PAH), especially when the combined pre- and post-capillary form (CpcPH) takes place in advanced stages of the disease. Right ventricular (RV) dysfunction is a common consequence related to worse prognosis and lower survival. This condition has recently been identified with a new classification based on clinical signs and progression markers. The role and prevalence of PH and RV dysfunction in HFpEF remain poorly identified, with wide variability in the literature reported from the largest clinical trials. Different parenchymal and vascular alterations affect the two diseases. Capillaries and arteriole vasoconstriction, vascular obliteration, and pulmonary blood fluid redistribution from the basal to the apical district are typical manifestations of type 1 PH. Conversely, PH related to HFpEF is primarily due to an increase of venules/capillaries parietal fibrosis, extracellular matrix deposition, and myocyte hypertrophy with a secondary “arteriolarization” of the vessels. Since the development of structural changes and the therapeutic target substantially differ, a better understanding of pathobiological processes underneath PH-HFpEF, and the identification of potential maladaptive RV mechanisms with an appropriate diagnostic tool, become mandatory in order to distinguish and manage these two similar forms of pulmonary hypertension.

Transcriptomic Analysis of Right Ventricular Adaptation and Failure in a Novel Ovine Model of Pulmonary Hypertension

<h3>Purpose</h3> Right ventricular failure (RVF) is a large contributor to morbidity and mortality in pulmonary hypertension (PH). Molecular understanding of RVF may facilitate identification of novel drug and device therapy targets. Using our previously published large animal model of PH-RVF, we performed RNA-seq analysis of RV tissues sampled from healthy sheep, PH sheep, and PH sheep that received mechanical circulatory support (MCS). <h3>Methods</h3> We assessed RV gene expression in adult sheep prior to and after completion of a previously described PH model. Three PH sheep subsequently underwent acute MCS for 3-6 hours. Right ventricular (RV) free wall tissues were collected prior to PA banding and at termination of MCS (pre-PH vs post-PH, N=3 each). One subject experienced severe maladaptive RVF and expired prior to MCS. This maladaptive characterization was based on its mixed venous saturation below 30% and several liters of ascites and pleural effusion found at necropsy. The pre-PH and post-PH RV tissue samples were analyzed for gene expression profile with RNAseq and studied with over-representation analysis to elucidate enriched pathways. <h3>Results</h3> RNAseq identified 358 genes with differential expression between pre-PH and post-PH tissue samples (p < 0.01, >2-fold change). Enrichment analysis showed that these genes were related to cardiomyocyte muscularization and proliferation, indicating adaptation to RV loading. The maladaptive RV sample, even when compared to the other PH sheep that received MCS, demonstrated markedly reduced expression of metabolic genes, especially in fatty acid oxidation. <h3>Conclusion</h3> RV load stress coincides with differential expression of genes related to cardiomyocyte muscularization and proliferation. Observations of reduced expression of fatty acid oxidation genes in a maladaptive subject with RVF warrants further investigation. The role of mechanical support on RV gene expression needs to be further studied in longer-term settings.

PARP1-PKM2 Axis Mediates Right Ventricular Failure Associated With Pulmonary Arterial Hypertension

The authors show that increased poly(adenosine diphosphate-ribose) polymerase 1 (PARP1) and pyruvate kinase muscle isozyme 2 (PKM2) expression is a common feature of a decompensated right ventricle in patients with pulmonary arterial hypertension and animal models. The authors find invitro that overactivated PARP1 promotes cardiomyocyte dysfunction by favoring PKM2 expression and nuclear function, glycolytic gene expression, activation of nuclear factor κB-dependent proinflammatory factors. Pharmacologic and genetic inhibition of PARP1 or enforced tetramerization of PKM2 attenuates maladaptive remodeling improving right ventricular (RV) function in multiple rodent models. Taken together, these data implicate the PARP1/PKM2 axis as a critical driver of maladaptive RV remodeling and a new promising target to directly sustain RV function inpatients with pulmonary arterial hypertension.

Abstract 11091: Failure of Right Ventricular Adaptation to Pressure Overload Due to a Profound Deficiency in Adenylate Kinase 1 and Impaired Ventricular Energetics

Introduction: Interindividual heterogeneity in the ability of the right ventricular (RV) to adapt to pressure overload in pulmonary hypertension (PH) is likely influenced by genetic determinants. We took advantage of strain-dependent, maladaptive RV remodeling in Fischer compared to Sprague-Dawley (SD) rats to define the molecular and genetic mechanisms that predispose to development of RV failure in PH. Methods/Results: In the SU5416/hypoxia(SUHx) PH model, Fischer rats exhibited RV failure and 100% mortality by 5-weeks, whereas SD rats showed preserved RV function and 88% survival beyond 9 weeks (p&lt;0.0001). In vivo oxidative metabolism, assessed by [ 11 C]acetate PET, was increased in Fischer rats at 4 weeks (p&lt;0.05), associated with impaired RV efficiency compared to SD (work metabolic index: 58±12 vs 102±20 mmHg·mL/cm 2 , respectively; p&lt;0.001), but no differences were observed in mitochondrial complex activity in permeabilized RV cardiac fibers. Adenylate Kinase 1 (AK1) was among the top ten differentially expressed genes between Fischer and SD rats by unbiased transcriptomic analysis, with markedly lower expression in the RV of Fischer rats (FC:3.36, P&lt;0.05). Profound AK1 deficiency was confirmed by proteomics and validated by Western blotting (&gt;10-fold reduction, P&lt;0.001). Fischer rats also exhibited evidence of hemolysis, recapitulating the hemolytic phenotype seen in patients with rare AK1 coding region mutations. While whole genome sequencing failed to reveal any coding region mutations in Fischer rats, there was a unique variant in a highly conserved upstream flanking region. AK1 levels were also reduced in the RV of PH patients with decompensated RV function and right heart failure. Conclusion: Fischer rats with AK1 deficiency have inefficient energetics likely related to reduced ATP shuttling from the mitochondria to the contractile fibers, which represents a novel mechanism for RV failure in response to chronic increases in afterload.

Abstract 10231: Parp1-Pkm2 Axis Mediates Right Ventricular Failure Associated with Pulmonary Arterial Hypertension

Introduction: Right ventricular (RV) function is the poor prognosis factor in pulmonary arterial hypertension (PAH) patients. Inflammation, oxidative DNA damage, and glycolysis are key triggering pathways that induce cardiomyocytes (CM) dysfunction. Oxidative DNA damage-dependent Poly (ADP ribose) Polymerase 1 (PARP1) activation was documented to promote glycolysis and inflammation through nuclear retention of Pyruvate Kinase Muscle isozyme 2 (PKM2). Despite PARP1/PKM2 axis is involved in many pathologies, their role in RV failure (RVF) remains unclear. We hypothesized that sustained PARP1 activation induces nuclear PKM2 localization, cardiac inflammation, and myocytes apoptosis resulting in transition from compensated (cRV) to decompensated RV (dRV). Methods and Results: We found that PARP1/PKM2 expression/activity (IF, WB) is upregulated in dRV patients (died of RVF, n=11) compared to cRV patients (CI&gt;2.2, n=12) and control donors (n=19). Similar findings were seen in two rat models of RVF (monocrotaline, PA banding). In vitro , we confirmed that oxidative DNA damage (ET-1+H 2 O 2 ) as well as inflammatory stress (ET-1+LPS) induced nuclear expression of PARP1/PKM2 (IF, WB) leading to inflammation (NF-κB nuclear translocation) and CM death (TUNEL). These effects were prevented by treatment with PARP1 inhibitor (ABT-888, Olaparib) or enforced cytosolic retention of PKM2 (TEPP-46, DASA-58). Cardiomyocytes isolated from neonatal Parp1 deficient mice were resistant to myocyte dysfunction (PKM2 nuclear upregulation, NF-κB nuclear translocation, TUNEL) induced by oxidative DNA damage (ET-1+H 2 O 2 ). In vivo , Olaparib (10mg/kg) as well as TEPP-46 (25mg/kg) prevented RVF (CO, hypertrophy, fibrosis, inflammation, DNA damage, apoptosis) induced by PAB in rats (n=8~12 per group). Moreover, we confirmed that global Parp1 loss-of-function confers protection against PAB induced-RVF (CO, hypertrophy, fibrosis, inflammation, DNA damage, apoptosis, n=10 per group). (All p&lt;0.05) Conclusions: We demonstrated for the first time that PARP1/PKM2 axis is a critical signal pathway RV decompensation. Targeting PARP1/PKM2 axis may represent a promising avenue for tackling maladaptive RV remodeling and pulmonary circulation, simultaneously.

SEX DIFFERENCES IN RIGHT (-SIDED) HEART FAILURE IN PULMONARY ARTERY BANDING MODEL ARE ASSOCIATED WITH DIFFERENTIAL RIGHT VENTRICULAR ANGIOGENESIS

SEX DIFFERENCES IN RIGHT (-SIDED) HEART FAILURE IN PULMONARY ARTERY BANDING MODEL ARE ASSOCIATED WITH DIFFERENTIAL RIGHT VENTRICULAR ANGIOGENESIS

α7 Nicotinic acetylcholine receptor mediates right ventricular fibrosis and diastolic dysfunction in pulmonary hypertension.

Right ventricular (RV) fibrosis is a key feature of maladaptive RV hypertrophy and dysfunction and is associated with poor outcomes in pulmonary hypertension (PH). However, mechanisms and therapeutic strategies to mitigate RV fibrosis remain unrealized. Previously, we identified that cardiac fibroblast α7 nicotinic acetylcholine receptor (α7 nAChR) drives smoking-induced RV fibrosis. Here, we sought to define the role of α7 nAChR in RV dysfunction and fibrosis in the settings of RV pressure overload as seen in PH. We show that RV tissue from PH patients has increased collagen content and ACh expression. Using an experimental rat model of PH, we demonstrate that RV fibrosis and dysfunction are associated with increases in ACh and α7 nAChR expression in the RV but not in the left ventricle (LV). In vitro studies show that α7 nAChR activation leads to an increase in adult ventricular fibroblast proliferation and collagen content mediated by a Ca2+/epidermal growth factor receptor (EGFR) signaling mechanism. Pharmacological antagonism of nAChR decreases RV collagen content and improves RV function in the PH model. Furthermore, mice lacking α7 nAChR exhibit improved RV diastolic function and have lower RV collagen content in response to persistently increased RV afterload, compared with WT controls. These finding indicate that enhanced α7 nAChR signaling is an important mechanism underlying RV fibrosis and dysfunction, and targeted inhibition of α7 nAChR is a potentially novel therapeutic strategy in the setting of increased RV afterload.

17β-Estradiol and estrogen receptor α protect right ventricular function in pulmonary hypertension via BMPR2 and apelin.

Women with pulmonary arterial hypertension (PAH) exhibit better right ventricular (RV) function and survival than men; however, the underlying mechanisms are unknown. We hypothesized that 17β-estradiol (E2), through estrogen receptor α (ER-α), attenuates PAH-induced RV failure (RVF) by upregulating the procontractile and prosurvival peptide apelin via a BMPR2-dependent mechanism. We found that ER-α and apelin expression were decreased in RV homogenates from patients with RVF and from rats with maladaptive (but not adaptive) RV remodeling. RV cardiomyocyte apelin abundance increased in vivo or in vitro after treatment with E2 or ER-α agonist. Studies employing ER-α-null or ER-β-null mice, ER-α loss-of-function mutant rats, or siRNA demonstrated that ER-α is necessary for E2 to upregulate RV apelin. E2 and ER-α increased BMPR2 in pulmonary hypertension RVs and in isolated RV cardiomyocytes, associated with ER-α binding to the Bmpr2 promoter. BMPR2 is required for E2-mediated increases in apelin abundance, and both BMPR2 and apelin are necessary for E2 to exert RV-protective effects. E2 or ER-α agonist rescued monocrotaline pulmonary hypertension and restored RV apelin and BMPR2. We identified what we believe to be a novel cardioprotective E2/ER-α/BMPR2/apelin axis in the RV. Harnessing this axis may lead to novel RV-targeted therapies for PAH patients of either sex.

CILP1 as a biomarker for right ventricular maladaptation in pulmonary hypertension.

The aim of our study was to analyse the protein expression of cartilage intermediate layer protein (CILP)1 in a mouse model of right ventricular (RV) pressure overload and to evaluate CILP1 as a biomarker of cardiac remodelling and maladaptive RV function in patients with pulmonary hypertension (PH).Pulmonary artery banding was performed in 14 mice; another nine mice underwent sham surgery. CILP1 protein expression was analysed in all hearts using Western blotting and immunostaining. CILP1 serum concentrations were measured in 161 patients (97 with adaptive and maladaptive RV pressure overload caused by PH; 25 with left ventricular (LV) hypertrophy; 20 with dilative cardiomyopathy (DCM); 19 controls without LV or RV abnormalities)In mice, the amount of RV CILP1 was markedly higher after banding than after sham. Control patients had lower CILP1 serum levels than all other groups (p<0.001). CILP1 concentrations were higher in PH patients with maladaptive RV function than those with adaptive RV function (p<0.001), LV pressure overload (p<0.001) and DCM (p=0.003). CILP1 showed good predictive power for maladaptive RV in receiver operating characteristic analysis (area under the curve (AUC) 0.79). There was no significant difference between the AUCs of CILP1 and N-terminal pro-brain natriuretic peptide (NT-proBNP) (AUC 0.82). High CILP1 (cut-off value for maladaptive RV of ≥4373 pg·mL-1) was associated with lower tricuspid annular plane excursion/pulmonary artery systolic pressure ratios (p<0.001) and higher NT-proBNP levels (p<0.001).CILP1 is a novel biomarker of RV and LV pathological remodelling that is associated with RV maladaptation and ventriculoarterial uncoupling in patients with PH.