Long-term swimming exercise attenuates right ventricular hypertrophy via modulating meta-inflammation in monocrotaline-induced pulmonary hypertensive rats.

Pulmonary arterial hypertension (PAH) is a complex disease characterized by elevated pulmonary vascular resistance, resulting in right ventricular (RV) hypertrophy and, eventually, failure, which remains the primary cause of mortality in PAH patients. While current PAH therapies primarily target vascular abnormalities, most fail to address RV dysfunction. Therefore, improving RV function is a critical treatment goal. Exercise has emerged as an effective intervention for PAH, but the specific impact of swimming exercise on this disease and its associated pathological changes has been less extensively studied. In this study, we investigated the effects of swimming training (60 min/day, 5 days/week for 4 weeks) on monocrotaline (MCT; 60 mg/kg, i. p.)-induced PAH in rats. Our findings demonstrate that swimming significantly attenuates RV hypertrophy and reduces mean pulmonary arterial pressure (MPAP), mitigating the detrimental effects of PAH. Furthermore, we observed structural remodeling in the right ventricle, including increased myocardial necrosis, collagen deposition, and fibrosis-related protein expression. Swimming exercise training was found to reduce these pathological changes, suggesting a protective effect on the right ventricle. Mechanistically, our study revealed the crucial role of meta-inflammation in PAH and the anti-PAH effects of exercise. Swimming training attenuated macrophage accumulation, reduced serum inflammatory cytokines, and improved systemic and RV insulin sensitivity, highlighting its potential to modulate meta-inflammatory processes. In summary, our study suggests that swimming training exerts a beneficial effect on RV function and hypertrophy in MCT-induced PAH rats by targeting meta-inflammation. These results underscore the potential value of exercise-based rehabilitation as a complementary therapy for PAH patients.

ECG patterns to predict pulmonary arterial hypertension in patients with severe tricuspid regurgitation.

INTRODUCTION: Echocardiographic evaluation of tricuspid regurgitation (TR) velocity is a key measure in screening for pulmonary hypertension. Based on its value and additional features of right ventricle overload patients are classified into low, intermediate or high probability of pulmonary hypertension which transfers into decisions of further invasive evaluation. However, in the presence of severe TR echocardiography underestimates pulmonary artery pressure and therefore pulmonary hypertension may be overlooked in some patients. Accordingly, in the present study we aimed to assess the role of electrocardiography in predicting the presence of pulmonary arterial hypertension (PAH) in patients with severe TR. RESULTS: We analysed 83 consecutive patients with severe TR who were diagnosed in our centre between February 2008 and 2021 and who underwent right heart catheterization. Of them 58 had PAH while 25 had isolated TR (iTR). We found that the following ECG criteria supported the diagnosis of PAH as opposed to the diagnosis of iTR: R:SV1 > 1.0, max RV1 or 2 + max S I or aVL -SV1 > 6 mm, SI/RI > 1 in I. For these parameters using ROC analysis we found that the optimal thresholds suggesting the presence of pulmonary hypertension were: R:SV1 > 1.5 (AUC = 0.74, p = 0.0004, sensitivity 57.1%,specificity of 85%), max RV1 or 2 + max S I or aVL - SV1 > 3 mm (AUC = 0.76, p < 0.0001, sensitivity 91.4%, specificity of 60%) and for SI:RI > 0.71 (AUC = 0.79, p < 0.0001, sensitivity 82.5%,specificity of 70.8%). Presence of atrial fibrillation predicted iTR with 76% sensitivity and 81% specificity. CONCLUSIONS: ECG analysis can improve the diagnostic process for patients with severe TR. The presence of atrial fibrillation facilitates the diagnosis of isolated tricuspid regurgitation (iTR), while increased values of R:SV1, R:SI, and increased max RV1 or 2 + max SI or aVL - SV1 favor the diagnosis of TR secondary to PAH.

Electrocardiographic Z-axis QRS-T voltage-time-integral in patients with typical right bundle branch block - Correlation with echocardiographic right ventricular size and function.

BACKGROUND: Right bundle branch block (RBBB) can be benign or associated with right ventricular (RV) functional and structural abnormalities. Our aim was to evaluate QRS-T voltage-time-integral (VTI) compared to QRS duration and lead V1 R' as markers for RV abnormalities. METHODS: We included adults with an ECG demonstrating RBBB and echocardiogram obtained within 3 months of each other, between 2010 and 2020. VTIQRS and VTIQRST were obtained for 12 standard ECG leads, reconstructed vectorcardiographic X, Y, Z leads and root-mean-squared (3D) ECG. Age, sex and BSA-adjusted linear regressions were used to assess associations of QRS duration, amplitudes, VTIs and lead V1 R' duration/VTI with echocardiographic tricuspid annular plane systolic excursion (TAPSE), RV tissue Doppler imaging S', basal and mid diameter, and systolic pressure (RVSP). RESULTS: Among 782 patients (33% women, age 71 ± 14 years) with RBBB, R' duration in lead V1 was modestly associated with RV S', RV diameters and RVSP (all p ≤ 0.03). QRS duration was more strongly associated with RV diameters (both p < 0.0001). AmplitudeQRS-Z was modestly correlated with all 5 RV echocardiographic variables (all p ≤ 0.02). VTIR'-V1 was more strongly associated with TAPSE, RV S' and RVSP (all p ≤ 0.0003). VTIQRS-Z and VTIQRST-Z were among the strongest correlates of the 5 RV variables (all p < 0.0001). VTIQRST-Z.√BSA cutoff of ≥62 µVsm had sensitivity 62.7% and specificity 65.7% for predicting ≥3 of 5 abnormal RV variables (AUC 0.66; men 0.71, women 0.60). CONCLUSION: In patients with RBBB, VTIQRST-Z is a stronger predictor of RV dysfunction and adverse remodeling than QRS duration and lead V1 R'.

Pattern of Right Ventricular Changes in Patients with Uncomplicated Systemic Hypertension at a Tertiary Centre in Southwest Nigeria.

BACKGROUND AND AIMS: Hypertension is an independent risk factor for cardiovascular complications. The effect of systemic hypertension on the right ventricle (RV) has received less attention probably due to its complex structure and location. The aim of the study was to assess the effect of systemic hypertension on the structure and function of the right ventricle using transthoracic echocardiography. METHOD: One hundred hypertensives and 100 healthy controls were recruited into the study. Transthoracic echocardiography was used to measure RV wall thickness (RVWT) in diastole, RV internal dimensions in diastole, tricuspid annular plane systolic excursion (TAPSE), right ventricular filling velocities (TE and TA), and RV systolic excursion velocity (RVSm). These measurements were repeated on the left ventricle. RESULTS: There was significantly thicker RV wall (0.51 + 0.08cm vs 0.44+0.08cm; p=0.001) in the hypertensive group and higher frequency of RV hypertrophy (48.45% vs 18.75%; p<0.001). Tricuspid annular plane systolic excursion (TAPSE) and the tricuspid annular peak systolic excursion velocity (TSm) were significantly lower in the hypertensive group (2.34+0.45cm vs 2.50+0.36cm; p=0.008, and 11.70+3.03cm/s vs 12.60+2.93cm/s p=0.039, respectively), though no participant had abnormal TAPSE. Tricuspid E/A ratio was lower in the hypertensive group (1.13+ 0.33 vs 1.24+0.27; p=0.011). The tricuspid E/A ratio had positive correlation with mitral E/A ratio. CONCLUSION: Right ventricular structural and functional changes are found in systemic hypertension, even in the absence of other systemic complications. These changes could have been mediated by ventricular interdependence and altered humoral factors.

CONTEXTES ET OBJECTIFS: L'hypertension artérielle est un facteur de risque indépendant pour les complications cardiovasculaires. L'effet de l'hypertension artérielle systémique sur le ventricule droit (VD) a reçu moins d'attention probablement en raison de sa structure complexe et de son emplacement. L'objectif de l'étude était d'évaluer l'effet de l'hypertension artérielle systémique sur la structure et la fonction du ventricule droit en utilisant l'échocardiographie transthoracique. MÉTHODE: Cent hypertendus et 100 témoins en bonne santé ont été recrutés dans l'étude. L'échocardiographie transthoracique a été utilisée pour mesurer l'épaisseur de la paroi du VD (EPVD) en diastole, les dimensions internes du VD en diastole, l'excursion plane systolique annulaire tricuspide (TAPSE), les vitesses de remplissage ventriculaire droit (TE et TA), et la vitesse d'excursion systolique ventriculaire droit (RVSm). Ces mesures ont été répétées sur le ventricule gauche. RÉSULTATS: Il y avait une paroi du VD significativement plus épaisse (0,51 ± 0,08 cm vs 0,44 ± 0,08 cm ; p=0,001) dans le groupe hypertendu et une fréquence plus élevée d'hypertrophie ventriculaire droite (48,45% vs 18,75% ; p<0,001). L'excursion plane systolique annulaire tricuspide (TAPSE) et la vitesse maximale systolique annulaire tricuspide (TSm) étaient significativement plus basses dans le groupe hypertendu (2,34 ± 0,45 cm vs 2,50 ± 0,36 cm ; p=0,008, et 11,70 ± 3,03 cm/s vs 12,60 ± 2,93 cm/s p=0,039, respectivement), bien qu'aucun participant n'ait eu de TAPSE anormal. Le rapport E/A tricuspide était plus bas dans le groupe hypertendu (1,13 ± 0,33 vs 1,24 ± 0,27 ; p=0,011). Le rapport E/A tricuspide avait une corrélation positive avec le rapport E/A mitral. CONCLUSION: Des modifications structurales et fonctionnelles du ventricule droit sont retrouvées dans l'hypertension artérielle systémique, même en l'absence d'autres complications systémiques. Ces changements pourraient avoir été médiés par l'interdépendance ventriculaire et des facteurs humoraux modifiés. MOTS-CLÉS: Hypertension ; Échocardiographie ; Hypertrophie ventriculaire droite ; Dysfonction diastolique ventriculaire droit.

Circ-Ntrk2 acts as a miR-296-5p sponge to activate the TGF-ß1/p38 MAPK pathway and promote pulmonary hypertension and vascular remodelling.

BACKGROUND: Circular RNAs (circRNAs), a novel class of non-coding RNAs, play an important regulatory role in pulmonary arterial hypertension (PAH); however, the specific mechanism is rarely studied. In this study, we aimed to discover functional circRNAs and investigate their effects and mechanisms in hypoxia-induced pulmonary vascular remodelling, a core pathological change in PAH. METHODS: RNA sequencing was used to illustrate the expression profile of circRNAs in hypoxic PAH. Bioinformatics, Sanger sequencing, and quantitative real-time PCR were used to identify the ring-forming characteristics of RNA and analyse its expression. Then, we established a hypoxia-induced PAH mouse model to evaluate circRNA function in PAH by echocardiography and hemodynamic measurements. Moreover, microRNA target gene database screening, fluorescence in situ hybridisation, luciferase reporter gene detection, and western blotting were used to explore the mechanism of circRNAs. RESULTS: RNA sequencing identified 432 differentially expressed circRNAs in mouse hypoxic lung tissues. Our results indicated that circ-Ntrk2 is a stable cytoplasmic circRNA derived from Ntrk2 mRNA and frequently upregulated in hypoxic lung tissue. We further found that circ-Ntrk2 sponges miR-296-5p and miR-296-5p can bind to the 3'-untranslated region of transforming growth factor-ß1 (TGF-ß1) mRNA, thereby attenuating TGF-ß1 translation. Through gene knockout or exogenous expression, we demonstrated that circ-Ntrk2 could promote PAH and vascular remodelling. Moreover, we verified that miR-296-5p overexpression alleviated pulmonary vascular remodelling and improved PAH through the TGF-ß1/p38 MAPK pathway. CONCLUSIONS: We identified a new circRNA (circ-Ntrk2) and explored its function and mechanism in PAH, thereby establishing potential targets for the diagnosis and treatment of PAH. Furthermore, our study contributes to the understanding of circRNA in relation to PAH.

Lack of right ventricular hypertrophy is associated with right heart failure in patients with left ventricular failure.

Presence of right heart failure (RHF) is associated with a worse prognosis in patients with left ventricular failure (LVF). While the cause of RHF secondary to LVF is multifactorial, an increased right ventricular (RV) afterload is believed as the major cause of RHF. However, data are scarce on the adaptive responses of the RV in patients with LVF. Our aim was to understand the relationship of right ventricular hypertrophy (RVH) with RHF and RV systolic and diastolic properties in patients with LVF. 55 patients with a left ventricular ejection fraction of 40% or less were included in the present study. A comprehensive two-dimensional transthoracic echocardiographic examination was done to all participants. 12 patients (21.8%) had RHF, and patients with RHF had a significantly lower right ventricular free wall thickness (RVFWT) as compared to patients without RHF (5.3 ± 1.7 mm vs. 6.6 ± 0.9 mm, p = 0.02) and the difference remained statistically significant after adjusting for confounders (Δx̅:1.34 mm, p = 0.002). RVFWT had a statistically significant correlation with tricuspid annular plane systolic excursion (r = 0.479, p < 0.001) and tricuspid annular lateral systolic velocity (r = 0.360, p = 0.007), but not with the indices of the RV diastolic function. None of the patients with concentric RVH had RHF, while 22.2% of patients with eccentric RVH and 66.7% of patients without RVH had RHF (p < 0.01 as compared to patients with concentric RVH). In patients with left ventricular systolic dysfunction, absence of RVH was associated with worse RV systolic performance and a significantly higher incidence of RHF.

Perk heterozygosity ameliorates chronic hypoxia-induced pulmonary hypertension and right ventricular hypertrophy in male rats.

BACKGROUND: Pulmonary hypertension (PH) is a rare and deadly disease characterized by remodeling of the pulmonary vasculature and increased pulmonary artery pressure. hypobaric pulmonary hypertension (HPH) is clinically classified as group 4 of pulmonary hypertension and has a poor prognosis . Previous reports showed that HPH was associated with increased endoplasmic reticulum (ER) stress. The protein kinase R-like endoplasmic reticulum kinase (PERK) is an ER-associated stress protein. However, to date, its physiological effects on HPH and RVF development remains unknown. This study aimed to assess PERK's role in HPH and RV function using in vivo experimental model. METHODS: Perk-knockout male Sprague-Dawley rats were generated and were housed in either a hypobaric chamber or in a normoxic environment. After stimulation for 4 weeks, the hemodynamic parameters of the rats were measured. The heart and lungs were harvested for pathological observation. Blood was collected for the detection of inflammatory indexes. The right ventricle tissue was collected to assess phosphorylated-AKT, ROCK1, ET1, and MMP2 protein expression. RESULTS: WE FIRSTLY GENERATED PERK+/− RATS,: Under normal conditions, Perk+/- rats showed no changes in mPAP(mean pulmonary artery pressure), RVHI(Right ventricular hypertrophy index), cardiomyocyte size and interstitial fibrosis, and pulmonary vascular remodeling. However, in response to chronic hypoxia, Perk+/- rats exhibited decreased in mPAP, RVHI, ventricular fibrosis, and lung remodeling compared to wild-type rats. Perk+/- rats also showed lower expression of phosphor-AKT, ROCK1, ET1, and MMP2 protein in response to chronic hypoxia. CONCLUSIONS: These findings suggest that Perk heterozygosity protects against HPH and Perk may be a suitable target for treating HPH.

Sildenafil prevents right ventricular hypertrophy and improves heart rate variability in rats with pulmonary hypertension secondary to experimental diabetes.

Chronic treatment with sildenafil (SILD) is an effective protector on the development of cardiovascular complications of pulmonary hypertension (PH) and diabetes. However, to date, no studies have evaluated the effect of SILD on cardiopulmonary pathophysiology during PH secondary to type 1 diabetes. AIM: The present study aimed to evaluate the beneficial effects of chronic SILD treatment on pulmonary arterial pressure, right ventricular hypertrophy (RVH) and cardiac autonomic dysfunction in rats with PH secondary to diabetes. METODOLOGY: Male Sprague Dawley rats were randomly distributed into the control group (saline), diabetic group (60 mg/kg with streptozotocin), SILD-treated control group (20 mg/kg) and SILD-treated diabetic group. RESULTS: After 8 weeks the type 1 diabetic animals presented PH, endothelial dysfunction of the pulmonary arteries, electrocardiographic alterations, RVH and overexpression of phosphodiesterase type 5 in the heart. In type 1 diabetic animals, SILD treatment prevented the development of PH, endothelial dysfunction and RVH. SILD treatment also prevented alterations in the corrected QT period and heart rate variability and prevented overexpression of phosphodiesterase type 5. CONCLUSION: Our results indicate for the first time that SILD treatment prevents pulmonary arterial endothelial dysfunction, pulmonary hypertension, right ventricular hypertrophy and improves heart rate variability in type 1 diabetic rats.

Up-regulation of circRNA_0068481 promotes right ventricular hypertrophy in PAH patients via regulating miR-646/miR-570/miR-885.

CircRNA-0068481 and several miRNAs are important in the pathogenesis of right ventricular hypertrophy (VH), while the inhibition of eye absent transcriptional coactivator and phosphatase 3 (EYA3) was proved to reverse vascular remodelling in rats. In this study, we tried to study the diagnostic value and mechanistic role of circRNA_0068481 in the diagnosis of RVH in PAH patients. qPCR was done to measure circRNA-0068481, miR-646, miR-750, miR-885 and EYA3 mRNA expression. Luciferase assay was done to explore the regulatory relationship between circRNA-0068481/EYA3 and the miRNAs. Western blot was done to measure EYA3 expression in AC16 cells. The expression of circRNA-0068481, miR-646 and miR-570 showed a considerable capability to diagnose RVH in PAH patients. The luciferase activity of circRNA-0068481 was remarkably suppressed by miR-646, miR-570 or miR-885. The luciferase signal of EYA3 was also inhibited by miR-646, miR-570 and miR-885. Up-regulation of circRNA-0068481 expression in AC16 significantly decreased miR-646, miR-570 and miR-885 expression, and up-regulated EYA3 expression, whereas circRNA-0068481 down-regulation significantly increased miR-646, miR-570 and miR-885 expression, and repressed EYA3 expression. CircRNA_0068481 sponged several miRNAs including miR-646, miR-570 and miR-885. These miRNAs were all found to target the expression of EYA3 mRNA, which is involved in the onset of right ventricular hypertrophy. Therefore, it can be concluded that the up-regulation of circRNA_0068481 can predict the diagnosis of right ventricular hypertrophy in pulmonary arterial hypertension patients.

Cystamine Treatment Fails to Prevent the Development of Pulmonary Hypertension in Chronic Hypoxic Rats.

INTRODUCTION: Pulmonary hypertension is characterized by vasoconstriction and remodeling of pulmonary arteries, leading to right ventricular hypertrophy and failure. We have previously found upregulation of transglutaminase 2 (TG2) in the right ventricle of chronic hypoxic rats. The hypothesis of the present study was that treatment with the transglutaminase inhibitor, cystamine, would inhibit the development of pulmonary arterial remodeling, pulmonary hypertension, and right ventricular hypertrophy. METHODS: Effect of cystamine on transamidase activity was investigated in tissue homogenates. Wistar rats were exposed to chronic hypoxia and treated with vehicle, cystamine (40 mg/kg/day in mini-osmotic pumps), sildenafil (25 mg/kg/day), or the combination for 2 weeks. RESULTS: Cystamine concentration-dependently inhibited TG2 transamidase activity in liver and lung homogenates. In contrast to cystamine, sildenafil reduced right ventricular systolic pressure and hypertrophy and decreased pulmonary vascular resistance and muscularization in chronic hypoxic rats. Fibrosis in the lung tissue decreased in chronic hypoxic rats treated with cystamine. TG2 expression was similar in the right ventricle and lung tissue of drug and vehicle-treated hypoxic rats. DISCUSSION/CONCLUSIONS: Cystamine inhibited TG2 transamidase activity, but cystamine failed to prevent pulmonary hypertension, right ventricular hypertrophy, and pulmonary arterial muscularization in the chronic hypoxic rat.

Interleukin-17 aggravates right ventricular remodeling via activating STAT3 under both normoxia and hypoxia.

OBJECTIVE: Proinflammatory cytokine interleukin 17 (IL-17) is involved in ventricular remodeling, mainly of the left ventricle. This study was designed to explore the role of IL-17 played in the pathogenesis of right ventricular hypertrophy (RVH), aiming to provide a novel treatment target or diagnostic biomarker options for improving the care of RVH patients. METHODS: C57BL/6 mice were maintained in 10% O2 chamber or room air for four weeks. Right ventricular hypertrophy index (RVHI), RV/body weight ratio, pulmonary arteriolar remodeling determined by percent media thickness (%MT), and the cardiomyocyte diameter of RV were evaluated. Mice were treated with exogenous recombinant mouse IL-17 (rmIL-17, 1 µg per dose twice a week) for four weeks. H9c2 cardiomyocytes were cultured and treated with IL-17 (10 ng/mL) and STAT3 inhibitor (10 ng/mL) either under normoxia (21% O2, 5% CO2, 74% N2) or under hypoxia (3% O2, 5% CO2, 92% N2). Cardiomyocyte viability was assessed by Cell counting kit 8 (CCK-8) assay. The mRNA level was detected by RT-PCR, where as the protein expression was measured by Western blot, immunohistochemistry, and immunofluorescent analyses. RESULTS: In vivo experiments showed that IL-17 did not affect the pulmonary artery under normoxia, after treatment with rmIL-17, %MT was not changed, while RVHI and the RV/body weight ratio were increased, indicating that IL-17 directly induced right ventricular hypertrophy. In a time-course study, the mice were exposed to hypoxia for 0, 1, 2, 3, 4 weeks, respectively. We found that the expression of IL-17 was gradually upregulated in RV tissue in a time-dependent manner after one week of hypoxia exposure, especially at the third and fourth week. Cardiomyocyte hypertrophy and apoptosis were observed after the exposure of the mice to hypoxia for four weeks, rmIL-17 further aggravated the hypoxia-induced cardiomyocyte hypertrophy and apoptosis. The expression of p-STAT3 in the IL-17-deficient mice was lower than in the wild-type mice. In vitro, IL-17 inhibited cardiomyocyte viability and induced cardiomyocyte apoptosis via STAT3 under both normoxic and hypoxic conditions. CONCLUSIONS: These findings support a role for IL-17 as a mediator in the pathogenesis RVH, which might be considered as a potential novel anti-inflammation therapeutic strategy or diagnostic biomarker for RVH.

Echocardiographic follow-up to right ventricular modifications in secondary pulmonary hypertension to diabetes in rats.

Clinical studies suggest that diabetes is a risk factor in the development of pulmonary arterial hypertension. The increase in blood pressure in the pulmonary area is characterized by the increase in the afterload and hypertrophy of the right ventricle. The objective of this study was to conduct a longitudinal follow-up of the morphological and functional changes in the right ventricle in a rat model with pulmonary arterial hypertension secondary to diabetes. Male Sprague Dawley rats were randomly divided into a control group (saline solution) and a diabetic group (60 mg/kg with streptozotocin). For 12 weeks, an echocardiography for longitudinal (in vivo) image analysis of the pulmonary pressure was performed at the same time as the evaluation of myocardial remodeling and right ventricular. After this period, the pulmonary pressure was measured by means of a pulmonary artery catheterization, and the presence of hypertrophy was determined by means of the Fulton index. The plasma concentration of brain natriuretic peptide was measured by means of the ELISA technique. It was found that the diabetic rats showed an increase in pressure in the pulmonary arteries, an increase in the Fulton index, and an increase in brain natriuretic peptide. The echocardiographic follow-up showed that the diabetic rats presented an increase in the pulmonary artery from the fourth week, while hypertrophy and right ventricular systolic dysfunction occurred until the twelfth week. In conclusion, pulmonary arterial hypertension induced by experimental diabetes generated hypertrophy and systolic dysfunction of the right ventricle.

New Insights into Pulmonary Hypertension: A Role for Connexin-Mediated Signalling.

Pulmonary hypertension is a serious clinical condition characterised by increased pulmonary arterial pressure. This can lead to right ventricular failure which can be fatal. Connexins are gap junction-forming membrane proteins which serve to exchange small molecules of less than 1 kD between cells. Connexins can also form hemi-channels connecting the intracellular and extracellular environments. Hemi-channels can mediate adenosine triphosphate release and are involved in autocrine and paracrine signalling. Recently, our group and others have identified evidence that connexin-mediated signalling may be involved in the pathogenesis of pulmonary hypertension. In this review, we discuss the evidence that dysregulated connexin-mediated signalling is associated with pulmonary hypertension.

Role of Hypoxia-Inducible Factors in Regulating Right Ventricular Function and Remodeling during Chronic Hypoxia-induced Pulmonary Hypertension.

Pulmonary hypertension (PH) and right ventricular (RV) hypertrophy frequently develop in patients with hypoxic lung disease. Chronic alveolar hypoxia (CH) promotes sustained pulmonary vasoconstriction and pulmonary artery (PA) remodeling by acting on lung cells, resulting in the development of PH. RV hypertrophy develops in response to PH, but coronary arterial hypoxemia in CH may influence that response by activating HIF-1α (hypoxia-inducible factor 1α) and/or HIF-2α in cardiomyocytes. Indeed, other studies show that the attenuation of PH in CH fails to prevent RV remodeling, suggesting that PH-independent factors regulate RV hypertrophy. Therefore, we examined the role of HIFs in RV remodeling in CH-induced PH. We deleted HIF-1α and/or HIF-2α in hearts of adult mice that were then housed under normoxia or CH (10% O2) for 4 weeks. RNA-sequencing analysis of the RV revealed that HIF-1α and HIF-2α regulate the transcription of largely distinct gene sets during CH. RV systolic pressure increased, and RV hypertrophy developed in CH. The deletion of HIF-1α in smooth muscle attenuated the CH-induced increases in RV systolic pressure but did not decrease hypertrophy. The deletion of HIF-1α in cardiomyocytes amplified RV remodeling; this was abrogated by the simultaneous loss of HIF-2α. CH decreased stroke volume and cardiac output in wild-type but not in HIF-1α-deficient hearts, suggesting that CH may cause cardiac dysfunction via HIF-dependent signaling. Collectively, these data reveal that HIF-1 and HIF-2 act together in RV cardiomyocytes to orchestrate RV remodeling in CH, with HIF-1 playing a protective role rather than driving hypertrophy.

Mesenchymal Stem Cell Extracellular Vesicles Reverse Sugen/Hypoxia Pulmonary Hypertension in Rats.

Mesenchymal stem cell extracellular vesicles attenuate pulmonary hypertension, but their ability to reverse established disease in larger animal models and the duration and mechanism(s) of their effect are unknown. We sought to determine the efficacy and mechanism of mesenchymal stem cells' extracellular vesicles in attenuating pulmonary hypertension in rats with Sugen/hypoxia-induced pulmonary hypertension. Male rats were treated with mesenchymal stem cell extracellular vesicles or an equal volume of saline vehicle by tail vein injection before or after subcutaneous injection of Sugen 5416 and exposure to 3 weeks of hypoxia. Pulmonary hypertension was assessed by right ventricular systolic pressure, right ventricular weight to left ventricle + septum weight, and muscularization of peripheral pulmonary vessels. Immunohistochemistry was used to measure macrophage activation state and recruitment to lung. Mesenchymal stem cell extracellular vesicles injected before or after induction of pulmonary hypertension normalized right ventricular pressure and reduced right ventricular hypertrophy and muscularization of peripheral pulmonary vessels. The effect was consistent over a range of doses and dosing intervals and was associated with lower numbers of lung macrophages, a higher ratio of alternatively to classically activated macrophages (M2/M1 = 2.00 ± 0.14 vs. 1.09 ± 0.11; P < 0.01), and increased numbers of peripheral blood vessels (11.8 ± 0.66 vs. 6.9 ± 0.57 vessels per field; P < 0.001). Mesenchymal stem cell extracellular vesicles are effective at preventing and reversing pulmonary hypertension in Sugen/hypoxia pulmonary hypertension and may offer a new approach for the treatment of pulmonary arterial hypertension.

FHL-1 is not involved in pressure overload-induced maladaptive right ventricular remodeling and dysfunction.

AIMS: The cytoskeletal signaling protein four and-a-half LIM domains 1 (FHL-1) has recently been identified as a novel key player in pulmonary hypertension as well as in left heart diseases. In this regard, FHL-1 has been implicated in dysregulated hypertrophic signaling in pulmonary arterial smooth muscle cells leading to pulmonary hypertension. In mice, FHL-1-deficiency (FHL-1-/-) led to an attenuated hypertrophic signaling associated with a blunted hypertrophic response of the pressure-overloaded left ventricle (LV). However, the role of FHL-1 in right heart hypertrophy has not yet been addressed. METHODS AND RESULTS: We investigated FHL-1 expression in C57Bl/6 mice subjected to chronic biomechanical stress and found it to be enhanced in the right ventricle (RV). Next, we subjected FHL-1-/- and corresponding wild-type mice to pressure overload of the RV by pulmonary arterial banding for various time points. However, in contrast to the previously published study in LV-pressure overload, which was confirmed here, RV hypertrophy and hypertrophic signaling was not diminished in FHL-1-/- mice. In detail, right ventricular pressure overload led to hypertrophy, dilatation and fibrosis of the RV from both FHL-1-/- and wild-type mice. RV remodeling was associated with impaired RV function as evidenced by reduced tricuspid annular plane systolic excursion. Additionally, PAB induced upregulation of natriuretic peptides and slight downregulation of phospholamban and ryanodine receptor 2 in the RV. However, there was no difference between genotypes in the degree of expression change. CONCLUSION: FHL-1 pathway is not involved in the control of adverse remodeling in the pressure overloaded RV.

Taurine prevents cardiomyocyte apoptosis by inhibiting the calpain-1/cytochrome c pathway during RVH in broilers.

The calpain-1-activated apoptotic pathway plays a key role in right ventricular hypertrophy (RVH). Taurine has been shown to attenuate apoptosis by inhibiting calpain activity. This experiment aimed to determine whether taurine could prevent RVH by inhibiting the calpain-1/cytochrome c apoptotic pathway. The broilers were given 1% taurine dissolved in drinking water and were raised at 10 °C ~ 12 °C from day 21 to day 42. At 21 d, 28 d, 35 d and 42 d, the right ventricular (RV) tissues were collected. Increased RVH index, angiotensin II, norepinephrine and atrial natriuretic peptide mRNA expression were reduced by taurine in the broiler RVs. Taurine obviously inhibited cardiomyocyte apoptosis via maintaining the mitochondrial membrane potential and decreased the activation of caspase-9 and caspase-3 in the broiler RVs. The antioxidant assay demonstrated that taurine enhanced the activities of superoxide dismutase, total antioxidant capacity and glutathione peroxidase and the glutathione/glutathione disulfide ratio. Western blot results revealed that taurine also downregulated the expression of calpain-1 and cytosolic cytochrome c while upregulating the expression of Bcl-2/Bax and mitochondrial cytochrome c in broiler cardiomyocytes during RVH. In summary, we found that taurine could enhance cardiomyocyte antioxidant ability and further prevented cardiomyocyte apoptosis by inhibiting the calpain-1/cytochrome c pathway during RVH in broilers.

Inferior Right Ventricular Wall Thickness by Echocardiogram: A Novel Method of Assessing Hypertrophy in Neonates and Infants.

An established echocardiographic (echo) standard for assessing the newborn right ventricle (RV) for hypertrophy has not been thoroughly developed. This is partially due to the RV's complex architecture, which makes quantification of RV mass by echo difficult. Here, we retrospectively evaluate the thickness of the inferior RV wall (iRVWT) by echo in neonates and infants with normal cardiopulmonary physiology. Inferior RVWT was defined at the medial portion of the inferior wall of the RV at the mid-ventricular level, collected from a subxiphoid, short axis view. iRVWT was indexed to body surface area (BSA) to the 0.5 power and normalized to iLVWT to explore the best normalization method. Ninety-eight neonates and 32 infants were included in the final analysis. Mean age for neonates and infants was 2 days and 59 days, respectively. Mean ± SD for neonate and infant end-diastole iRVWT was 2.17 ± 0.35 mm and 1.79 ± 0.28 mm, respectively. There was no residual relationship between the index iRVWT and BSA (r = 0.03, p = NS). In the infant cohort, the iRVWT was significantly lower and iLVWT was significantly higher compared to neonate, consistent with known physiologic changes of RV and LV mass. Thus, iRVWT may serve as a reliable and accurate proxy for RV mass and the parameter warrants further evaluation.

Cardiac remodelling in a swine model of chronic thromboembolic pulmonary hypertension: comparison of right vs. left ventricle.

KEY POINTS: Right ventricle (RV) function is the most important determinant of survival and quality of life in patients with chronic thromboembolic pulmonary hypertension (CTEPH). The changes in right and left ventricle gene expression that contribute to ventricular remodelling are incompletely investigated. RV remodelling in our CTEPH swine model is associated with increased expression of the genes involved in inflammation (TGFß), oxidative stress (ROCK2, NOX1 and NOX4), and apoptosis (BCL2 and caspase-3). Alterations in ROCK2 expression correlated inversely with RV contractile reserve during exercise. Since ROCK2 has been shown to be involved in hypertrophy, oxidative stress, fibrosis and endothelial dysfunction, ROCK2 inhibition may present a viable therapeutic target in CTEPH. ABSTRACT: Right ventricle (RV) function is the most important determinant of survival and quality of life in patients with chronic thromboembolic pulmonary hypertension (CTEPH). The present study investigated whether the increased cardiac afterload is associated with (i) cardiac remodelling and hypertrophic signalling; (ii) changes in angiogenic factors and capillary density; and (iii) inflammatory changes associated with oxidative stress and interstitial fibrosis. CTEPH was induced in eight chronically instrumented swine by chronic nitric oxide synthase inhibition and up to five weekly pulmonary embolizations. Nine healthy swine served as a control. After 9 weeks, RV function was assessed by single beat analysis of RV-pulmonary artery (PA) coupling at rest and during exercise, as well as by cardiac magnetic resonance imaging. Subsequently, the heart was excised and RV and left ventricle (LV) tissues were processed for molecular and histological analyses. Swine with CTEPH exhibited significant RV hypertrophy in response to the elevated PA pressure. RV-PA coupling was significantly reduced, correlated inversely with pulmonary vascular resistance and did not increase during exercise in CTEPH swine. Expression of genes associated with hypertrophy (BNP), inflammation (TGFß), oxidative stress (ROCK2, NOX1 and NOX4), apoptosis (BCL2 and caspase-3) and angiogenesis (VEGFA) were increased in the RV of CTEPH swine and correlated inversely with RV-PA coupling during exercise. In the LV, only significant changes in ROCK2 gene-expression occurred. In conclusion, RV remodelling in our CTEPH swine model is associated with increased expression of genes involved in inflammation and oxidative stress, suggesting that these processes contribute to RV remodelling and dysfunction in CTEPH and hence represent potential therapeutic targets.

Inhaled combination of sildenafil and rosiglitazone improves pulmonary hemodynamics, cardiac function, and arterial remodeling.

Currently, dual- or triple-drug combinations comprising different vasodilators are the mainstay for the treatment of pulmonary arterial hypertension (PAH). However, the patient outcome continues to be disappointing because the existing combination therapy cannot restrain progression of the disease. Previously, we have shown that when given as a monotherapy, long-acting inhaled formulations of sildenafil (a phosphodiesterase-5 inhibitor) and rosiglitazone (a peroxisome proliferator receptor-γ agonist) ameliorate PAH in rats. Thus, with a goal to develop a new combination therapy, we prepared and characterized poly(lactic-co-glycolic acid) (PLGA)-based long-acting inhalable particles of sildenafil and rosiglitazone. We then assessed the efficacy of the combinations of sildenafil and rosiglitazone, given in plain forms or as PLGA particles, in reducing mean pulmonary arterial pressure (mPAP) and improving pulmonary arterial remodeling and right ventricular hypertrophy (RVH) in Sugen 5416 plus hypoxia-induced PAH rats. After intratracheal administration of the formulations, we catheterized the rats and measured mPAP, cardiac output, total pulmonary resistance, and RVH. We also conducted morphometric studies using lung tissue samples and assessed the degree of muscularization, the arterial medial wall thickening, and the extent of collagen deposition. Compared with the plain drugs, given via the pulmonary or oral route as a single or dual combination, PLGA particles of the drugs, although given at a longer dosing interval compared with the plain drugs, caused more pronounced reduction in mPAP without affecting mean systemic pressure, improved cardiac function, slowed down right heart remodeling, and reduced arterial muscularization. Overall, PLGA particles of sildenafil and rosiglitazone, given as an inhaled combination, could be a viable alternative to currently available vasodilator-based combination therapy for PAH.