Treatment for pulmonary arterial hypertension-associated right ventricular dysfunction

The thromboxane receptor antagonist NTP42 promotes beneficial adaptation and preserves cardiac function in experimental models of right heart overload

Background

Pulmonary arterial hypertension (PAH) is a progressive disease characterized by increased pulmonary artery pressure leading to right ventricular (RV) failure. While current PAH therapies improve patient outlook, they show limited benefit in attenuating RV dysfunction. Recent investigations demonstrated that the thromboxane (TX) A₂ receptor (TP) antagonist NTP42 attenuates experimental PAH across key hemodynamic parameters in the lungs and heart. This study aimed to validate the efficacy of NTP42:KVA4, a novel oral formulation of NTP42 in clinical development, in preclinical models of PAH while also, critically, investigating its direct effects on RV dysfunction.

Methods

The effects of NTP42:KVA4 were evaluated in the monocrotaline (MCT) and pulmonary artery banding (PAB) models of PAH and RV dysfunction, respectively, and when compared with leading standard-of-care (SOC) PAH drugs. In addition, the expression of the TP, the target for NTP42, was investigated in cardiac tissue from several other related disease models, and from subjects with PAH and dilated cardiomyopathy (DCM).

Results

In the MCT-PAH model, NTP42:KVA4 alleviated disease-induced changes in cardiopulmonary hemodynamics, pulmonary vascular remodeling, inflammation, and fibrosis, to a similar or greater extent than the PAH SOCs tested. In the PAB model, NTP42:KVA4 improved RV geometries and contractility, normalized RV stiffness, and significantly increased RV ejection fraction. In both models, NTP42:KVA4 promoted beneficial RV adaptation, decreasing cellular hypertrophy, and increasing vascularization. Notably, elevated expression of the TP target was observed both in RV tissue from these and related disease models, and in clinical RV specimens of PAH and DCM.

Conclusion

This study shows that, through antagonism of TP signaling, NTP42:KVA4 attenuates experimental PAH pathophysiology, not only alleviating pulmonary pathologies but also reducing RV remodeling, promoting beneficial hypertrophy, and improving cardiac function. The findings suggest a direct cardioprotective effect for NTP42:KVA4, and its potential to be a disease-modifying therapy in PAH and other cardiac conditions.

Role of IL-33 receptor (ST2) deletion in diaphragm contractile and mitochondrial function in the Sugen5416/hypoxia model of pulmonary hypertension

Pulmonary arterial hypertension (PAH) is a progressive disease of the pulmonary vasculature that leads to right ventricular failure. Skeletal muscle maladaptations limit physical activity and may contribute to disease progression. The role of alarmin/inflammatory signaling in PAH respiratory muscle dysfunction is unknown. We hypothesized that diaphragm mitochondrial and contractile functions are impaired in SU5416/hypoxia-induced pulmonary hypertension due to increased systemic IL-33 signaling. We induced pulmonary hypertension in adult C57Bl/6 J (WT) and ST2 (IL1RL1) gene ablated mice by SU5416/hypoxia (SuHx). We measured diaphragm fiber mitochondrial respiration, inflammatory markers, and contractile function ex vivo. SuHx reduced coupled and uncoupled permeabilized myofiber respiration by ∼40 %. During coupled respiration with complex I substrates, ST2^-/- attenuated SuHx inhibition of mitochondrial respiration (genotype × treatment interaction F[1,67] = 3.3, p = 0.07, η² = 0.04). Flux control ratio and coupling efficiency were not affected by SuHx or genotype. A higher substrate control ratio for succinate was observed in SuHx fibers and attenuated in ST2^-/- fibers (F[1,67] = 5.3, p < 0.05, η² = 0.07). Diaphragm TNFα, but not IL-33 or NFkB, was increased in SuHx vs. DMSO in both genotypes (F[1,43] = 4.7, p < 0.05, η² = 0.1). Diaphragm force-frequency relationships were right-shifted in SuHx vs. WT (F[3,440] = 8.4, p < 0.05, η² = 0.0025). There was no effect of ST2^-/- on the force-frequency relationship. Force decay during a fatigue protocol at 100 Hz, but not at 40 Hz, was attenuated by SuHx vs. DMSO in both genotypes (F[1,41] = 5.6, p < 0.05, η² = 0.11). SuHx mice exhibit a modest compensation in diaphragm contractility and mitochondrial dysfunction during coupled respiration; the latter partially regulated through ST2 signaling.

Anesthetic protocol for right ventricular dysfunction management in heart transplantation: systematic review, development and validation

BACKGROUND

Right Ventricular Dysfunction (RVD) is the most frequent intraoperative hemodynamic complication in Heart Transplantation (HTx). RVD occurs in 0.04-1.0% of cardiac surgeries with cardiotomy and in 20-50% of HTx, with mortality up to 75%. No consensus has been established for how anesthesiologists should manage RVD, with management methods many times remaining unvalidated.

METHODS

We conducted a systematic review, following PRISMA guidelines, to create an anesthetic protocol to manage RVD in HTx, using databases that include PubMed and Embase, until September 2018 based on inclusion and exclusion criteria. The articles screening for the systematic review were done two independent reviewers, in case of discrepancy, we consulted a third independent reviewer. Based on the systematic review, the anesthetic protocol was developed. The instrument selected to perform the validation of the protocol was AGREE II, for this purpose expert anesthetists were recruited to do this process. The minimum arbitration score for domains validation cutoff of AGREE II is arbitered to 70%. This study was registered at PROSPERO (115600).

RESULTS

In the systematic review, 152 articles were included. We present the protocol in a flowchart with six steps based on goal-directed therapy, invasive monitoring, and transesophageal echocardiogram. Six experts judged the protocol and validated it.

CONCLUSION

The protocol has been validated by experts and new studies are needed to assess its applicability and potential benefits on major endpoints.

The left atrium and the right ventricle: two supporting chambers to the failing left ventricle

Heart failure (HF) is mainly caused by left ventricular (LV) impairment of function, hence detailed assessment of its structure and function is a clinical priority. The frequent involvement of the left atrium (LA) and the right ventricle (RV) in the overall cardiac performance has recently gained significant interest with specific markers predicting exercise intolerance and prognosis being proposed. The LA and RV are not anatomically separated from the LV, while the LA controls the inlet the RV shares the interventricular septum with the LV. Likewise, the function of the two chambers is not entirely independent from that of the LV, with the LA enlarging to accommodate any rise in filling pressures, which could get transferred to the RV via the pulmonary circulation. In the absence of pulmonary disease, LA and RV function may become impaired in patients with moderate-severe LV disease and raised filling pressures. These changes can often occur irrespective of the severity of systolic dysfunction, thus highlighting the important need for critical assessment of the function of the two chambers. This review evaluates the pivotal role of the left atrium and right ventricle in the management of HF patients based on the available evidence.

Tsantan Sumtang attenuated chronic hypoxia-induced right ventricular structure remodeling and fibrosis by equilibrating local ACE-AngII-AT1R/ACE2-Ang1-7-Mas axis in rat

ETHNOPHARMACOLOGICAL RELEVANCE

Tsantan Sumtang, which consists of Choerospondias axillaris (Roxb.) Burtt et Hill, Myristica fragrans Houtt and Santalum album L, is a traditional and common prescription of Tibetan medicine. Tsantan Sumtang originates from Four Tantra with properties of nourishing heart and has been used as a folk medicine for cardiovascular diseases and heart failure in Qinghai, Tibet and Inner Mongolia. Our previous studies found that Tsantan Sumtang showed beneficial effects on right ventricular structure in hypoxia rats, while the underling mechanism remains unclear.

AIM OF THE STUDY

To elucidate the underlying mechanisms of Tsantan Sumtang attenuated right ventricular (RV) remodeling and fibrosis of chronic hypoxia-induced pulmonary arterial hypertension (HPAH) rats.

MATERIALS AND METHODS

Fifty male Sprague Dawley (SD) rats (170 ± 20 g) were randomly divided into control group, hypoxia group, and hypoxia + Tsantan Sumtang groups (1.0 g· kg^-1·day^-1, 1.25 g· kg^-1·day^-1, 1.5 g ·kg^-1·day^-1). Rats in the hypoxia group and hypoxia + Tsantan Sumtang groups were maintained in a hypobaric chamber by adjusting the inner pressure and oxygen content to simulate an altitude of 4500 m for 28 days. The mean pulmonary arterial pressure (mPAP), right ventricle hypertrophy index (RVHI), the ratio of RV weight to tibia length (TL) (RV/TL), heart rate (HR) and RV systolic pressure (RVSP) was determined. Histomorphological assay of RV structure was evaluated by hematoxylin and eosin (HE) staining. RV tissue fibrosis was assessed by collagen proportion area (CPA), collagen I, collagen III and hydroxyproline content. CPA was obtained by picro-sirius red staining (PSR). The expression of collagen I and collagen III were detected by immunohistochemistry and western blotting. The hydroxyproline content was detected by alkaline hydrolysis. In addition, the level of angiotensin II (AngII) and angiotensin 1-7 (Ang1-7) in RV tissue was tested by enzyme-linked immune sorbent assay (ELISA). Protein expression of angiotensin-converting enzyme (ACE), AngII, AngII type 1 receptor (AT1R), angiotensin-converting enzyme 2 (ACE2), Mas receptor (Mas) were determined by immunohistochemistry and western blotting. mRNA level of ACE, AT1R, ACE2, Mas were tested by qPCR. The chemical profile of Tsantan Sumtang was revealed by UHPLC-Q-Exactive hybrid quadrupole-orbitrap mass analysis.

RESULTS

Our results showed that RVHI, RV/TL and RVSP were significantly increased in HPAH rat. Furthermore, levels of collagen I, collagen III and hydroxyproline were up-regulated in RV tissue under hypoxia. We found that RV hypertrophy and fibrosis were associated with increased expression of ACE, AngII, AT1R as well as decreased expression of ACE2, Ang1-7 and Mas. RV remodeling and fibrosis were attenuated after Tsantan Sumtang administration by up-regulating ACE2 and Mas level as well as down-regulating ACE, AngII and AT1R levels in RV tissue. 35 constituents in Tsantan Sumtang were identified.

CONCLUSION

Tsantan Sumtang attenuated RV remodeling and fibrosis in rat exposed to chronic hypoxia. The pharmacological effect of Tsantan Sumtang was based on equilibrating ACE-AngII-AT1R and ACE2-Ang1-7-Mas axis of RV tissue in HPAH rat.

Serum parathyroid hormone levels in patients with chronic right heart failure

Parathyroid hormone (PTH) is a novel cardiovascular biomarker which is particularly useful for detection and assessment of heart failure (HF). However, previous studies examining PTH in heart failure have primarily focused on left HF; thus, the relationship between PTH and right HF remains unclear. The aim of the present study was to evaluate the serum PTH levels in patients with chronic right HF. A total of 154 patients with chronic right HF were enrolled in the present study. A binary logistic regression analysis model was used to assess the independent predictive value of PTH levels in chronic right HF. Partial correlative analysis was used to demonstrate the relevance of PTH levels on the parameters of assessment of right heart function. A multiple linear regression analysis model was used to evaluate the independent factors of PTH levels in patients with right HF. The results showed that the serum PTH levels in the right HF group were significantly higher compared with the control group. After adjusting for predictors of right HF, serum PTH levels were associated with right HF with an odds ratio of 1.066 (95% confidence interval: 1.030-1.102, P<0.001. Serum PTH levels were independently correlated with plasma N-terminal pro-B-type natriuretic peptide levels, right ventricular end-diastolic diameter and severity of lower extremity edema (all P<0.05). Therefore, based on the results of the present study, PTH may be a useful biomarker for detection and assessment of right HF.

Right heart failure in pulmonary hypertension: Diagnosis and new perspectives on vascular and direct right ventricular treatment

Adaptation of right ventricular (RV) function to increased afterload-known as RV-arterial coupling-is a key determinant of prognosis in pulmonary hypertension. However, measurement of RV-arterial coupling is a complex, invasive process involving analysis of the RV pressure-volume relationship during preload reduction over multiple cardiac cycles. Simplified methods have therefore been proposed, including echocardiographic and cardiac MRI approaches. This review describes the available methods for assessment of RV function and RV-arterial coupling and the effects of pharmacotherapy on these variables. Overall, pharmacotherapies for pulmonary hypertension have shown beneficial effects on various measures of RV function, but it is often unclear if these are direct RV effects or indirect results of afterload reduction. Studies of the effects of pharmacotherapies on RV-arterial coupling are limited and mostly restricted to experimental models. Simplified methods to assess RV-arterial coupling should be validated and incorporated into routine clinical follow-up and future clinical trials. LINKED ARTICLES: This article is part of a themed issue on Risk factors, comorbidities, and comedications in cardioprotection. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.1/issuetoc.

In-silico assessment of the effects of right ventricular assist device on pulmonary arterial hypertension using an image based biventricular modeling framework

Pulmonary arterial hypertension (PAH) is a heart disease that is characterized by an abnormally high pressure in the pulmonary artery (PA). While right ventricular assist device (RVAD) has been considered recently as a treatment option for the end-stage PAH patients, its effects on biventricular mechanics are, however, largely unknown. To address this issue, we developed an image-based modeling framework consisting of a biventricular finite element (FE) model that is coupled to a lumped model describing the pulmonary and systemic circulations in a closed-loop system. The biventricular geometry was reconstructed from the magnetic resonance images of two PAH patients showing different degree of RV remodeling and a normal subject. The framework was calibrated to match patient-specific measurements of the left ventricular (LV) and RV volume and pressure waveforms. An RVAD model was incorporated into the calibrated framework and simulations were performed with different pump speeds. Results showed that RVAD unloads the RV, improves cardiac output and increases septum curvature, which are more pronounced in the PAH patient with severe RV remodeling. These improvements, however, are also accompanied by an adverse increase in the PA pressure. These results suggest that the RVAD implantation may need to be optimized depending on disease progression.

Long non-coding RNA CASC2 suppresses pulmonary artery smooth muscle cell proliferation and phenotypic switch in hypoxia-induced pulmonary hypertension

Background

In this study, we aimed to investigate whether and how lncRNA CASC2 was involved in hypoxia-induced pulmonary hypertension (PH)-related vascular remodeling.

Methods

The expression of lncRNAs or mRNAs was detected by qRT-PCR, and western blot analysis or immunochemistry was employed for detecting the protein expression. Cell number assay and EdU (5-ethynyl-2′-deoxyuridine) staining were performed to assess cell proliferation. Besides, flow cytometry and wound healing assay were employed for assessments of cell apoptosis and cell migration, respectively. Rat model of hypoxic PH was established and the hemodynamic measurements were performed. Hematoxylin and eosin (HE) and Masson′s trichrome staining were carried out for pulmonary artery morphometric analysis.

Results

The expression of lncRNA CASC2 was decreased in hypoxia-induced rat pulmonary arterial tissues and pulmonary artery smooth muscle cells (PASMCs). Up-regulation of lncRNA CASC2 inhibited cell proliferation, migration yet enhanced apoptosis in vitro and in vivo in hypoxia-induced PH. Western blot analysis and immunochemistry showed that up-regulation of lncRNA CASC2 greatly decreased the expression of phenotype switch-related marker α-SMA in hypoxia-induced PH. Furthermore, it was indicated by the pulmonary artery morphometric analysis that lncRNA CASC2 suppressed vascular remodeling of hypoxia-induced rat pulmonary arterial tissues.

Conclusion

LncRNA CASC2 inhibited cell proliferation, migration and phenotypic switch of PASMCs to inhibit the vascular remodeling in hypoxia-induced PH.

Electronic supplementary material

The online version of this article (10.1186/s12931-019-1018-x) contains supplementary material, which is available to authorized users.

The Role of G Protein-Coupled Receptors in the Right Ventricle in Pulmonary Hypertension

Pressure overload of the right ventricle (RV) in pulmonary arterial hypertension (PAH) leads to RV remodeling and failure, an important determinant of outcome in patients with PAH. Several G protein-coupled receptors (GPCRs) are differentially regulated in the RV myocardium, contributing to the pathogenesis of RV adverse remodeling and dysfunction. Many pharmacological agents that target GPCRs have been demonstrated to result in beneficial effects on left ventricular (LV) failure, such as beta-adrenergic receptor and angiotensin receptor antagonists. However, the role of such drugs on RV remodeling and performance is not known at this time. Moreover, many of these same receptors are also expressed in the pulmonary vasculature, which could result in complex effects in PAH. This manuscript reviews the role of GPCRs in the RV remodeling and dysfunction and discusses activating and blocking GPCR signaling to potentially attenuate remodeling while promoting improvements of RV function in PAH.

Blood Outgrowth and Proliferation of Endothelial Colony Forming Cells are Related to Markers of Disease Severity in Patients with Pulmonary Arterial Hypertension

In pulmonary arterial hypertension (PAH), lung-angioproliferation leads to increased pulmonary vascular resistance, while simultaneous myocardial microvessel loss contributes to right ventricular (RV) failure. Endothelial colony forming cells (ECFC) are highly proliferative, angiogenic cells that may contribute to either pulmonary vascular obstruction or to RV microvascular adaptation. We hypothesize ECFC phenotypes (outgrowth, proliferation, tube formation) are related to markers of disease severity in a prospective cohort-study of 33 PAH and 30 healthy subjects. ECFC were transplanted in pulmonary trunk banded rats with RV failure. The presence of ECFC outgrowth in PAH patients was associated with low RV ejection fraction, low central venous saturation and a shorter time to clinical worsening (5.4 months (0.6–29.2) vs. 36.5 months (7.4–63.4), p = 0.032). Functionally, PAH ECFC had higher proliferative rates compared to control in vitro, although inter-patient variability was high. ECFC proliferation was inversely related to RV end diastolic volume (R² = 0.39, p = 0.018), but not pulmonary vascular resistance. Tube formation-ability was similar among donors. Normal and highly proliferative PAH ECFC were transplanted in pulmonary trunk banded rats. While no effect on hemodynamic measurements was observed, RV vascular density was restored. In conclusion, we found that ECFC outgrowth associates with high clinical severity in PAH, suggesting recruitment. Transplantation of highly proliferative ECFC restored myocardial vascular density in pulmonary trunk banded rats, while RV functional improvements were not observed.

Treatment of exercise pulmonary hypertension improves pulmonary vascular distensibility

Exercise pulmonary hypertension (ePH) is an underappreciated form of exertional limitation. Despite normal resting pulmonary artery pressures, patients with ePH demonstrate early pulmonary vascular changes with reduced pulmonary arterial compliance (PAC) and vascular distensibility (α). Recent data suggest that targeted vasodilator therapy may improve hemodynamics in ePH, but it is not well-known whether such medications alter pulmonary vascular distensibility. Thus, we sought to evaluate if vasodilator therapy improved α a marker of early pulmonary vascular disease in ePH. Ten patients performed supine exercise right heart catheterization (exRHC) with bicycle ergometer to peak exercise. Patients diagnosed with ePH were treated with pulmonary vasodilators. A repeat symptom-limited exercise RHC was performed at least six months after therapy. Patients with ePH had evidence of early pulmonary vascular disease, as baseline PAC and α were reduced. After pulmonary vasodilator therapy, a number of peak exercise hemodynamics statistically improved, including a decrease of total pulmonary resistance and pulmonary vascular resistance, while cardiac output increased. Importantly, vasodilator therapy partially reversed the pathogenic decreases of α at the time of repeat exRHC. Pulmonary vascular distensibility, α, a marker of early pulmonary vascular disease, improves in ePH after therapy with pulmonary vasodilators.

Modeling Pulmonary Hypertension: A Pig Model of Postcapillary Pulmonary Hypertension

Pulmonary hypertension (PH) is a pathophysiological condition defined as an increase in mean pulmonary arterial pressure ≥25 mmHg at rest assessed by right heart catheterization.Based on hemodynamic criteria, precapillary PH is characterized by a mean pulmonary capillary wedge pressure ≤15 mmHg as opposed to the postcapillary PH by >15 mmHg. Postcapillary PH is one of the most common forms of PH, often caused by left ventricular dysfunction and heart failure.In this chapter, we describe protocols for creating a large animal model of postcapillary PH. It is induced by open chest surgery (lateral thoracotomy) to band the pulmonary veins. The model is characterized by low mortality, relatively easy surgical procedure with well reproducible results, and pulmonary and cardiac remodeling at the structural, functional, and molecular levels. The presence of right ventricular (RV) remodeling is of significant importance since right heart failure is the main cause of death in patients suffering from PH. One of the advantages of the model described in this chapter is that both adaptive and maladaptive forms of RV remodeling can be observed during the progression of the disease. This can help understand the progressive pathophysiology of RV failure in humans. Besides the description of the model, a detailed guidance of the RV functional assessment in pigs for both invasive (heart catheterization) and noninvasive (echocardiography) approaches is provided.

Steps forward in the treatment of pulmonary arterial hypertension: latest developments and clinical opportunities

Pulmonary arterial hypertension (PAH) is a chronic disease that results in narrowing of the small pre-capillary pulmonary arteries leading to elevation of pulmonary artery pressure and pulmonary vascular resistance, subsequent right ventricular failure, and if unchecked, death. Advances in the treatment of PAH over the last two decades have markedly improved survival. These improvements reflect a combination of changes in treatments, improved patient care strategies, and varying disease phenotypes in the PAH population. Currently approved therapies for PAH are directed at the recognized abnormalities within the pulmonary vasculature and include endothelin receptor antagonists, phosphodiesterase-5 inhibitors, soluble guanylate cyclase stimulators, and prostacyclin pathway agents. Most of these drugs have been approved on the basis of short-term trials that mainly demonstrated improvements in exercise capacity. More recently, long-term, event-driven trials of novel drugs have been performed, demonstrating new efficacy parameters. There have also been exciting advances in the understanding of right heart failure pathophysiology in PAH that have the potential to inspire the development of right ventricular targeted therapy and continued discoveries in the heterogeneity of disease and response to treatment has great potential for developing more 'personalized' therapeutic options. In this article, we review the current available data regarding the management of PAH, with an emphasis on the pharmacologic therapies and discussion of novel therapeutic directions for the treatment of this fatal disease.

Pharmacokinetics of drugs for pediatric pulmonary hypertension

BACKGROUND

Over the past few years, several drugs, each with a different mechanism, have been developed for the treatment of pulmonary hypertension (PH) and are now prescribed in the clinical setting. While the optimal doses of these drugs in adults have been determined, the optimal dose in children, however, is unclear. The aim of this study was therefore, to measure blood drug levels and analyze the pharmacokinetics of two such drugs in children.

METHODS

From April 2010 to May 2015, we prospectively enrolled 23 children with PH for treatment with bosentan and/or tadalafil. Twenty children were treated with bosentan and 19 received tadalafil. Sixteen children were given both drugs. Blood samples were collected after 2 weeks of treatment, and blood drug levels measured using high-performance liquid chromatography.

RESULTS

For both drugs, the peak plasma concentration was lower and the half-life was shorter than the known values in adults. The blood trough level of bosentan significantly correlated with its dose, but no such correlation was seen for tadalafil. For both drugs, no correlation was observed between age and blood drug levels.

CONCLUSIONS

Oral dosing with bosentan and tadalafil in children may not achieve therapeutic blood concentration. Thus, the optimal dosing must be established individually while monitoring blood drug level.

Detrimental Impact of Vasopressin V2 Receptor Antagonism in a SU5416/Hypoxia/Normoxia-Exposed Rat Model of Pulmonary Arterial Hypertension

BACKGROUND

The expression of vasopressin type 2 receptor (V2R) in the lung, and the long-term effects of tolvaptan, a selective V2R antagonist, on pulmonary circulation and right ventricular (RV) remodeling in a pulmonary arterial hypertension (PAH) rat model were evaluated.

METHODS AND RESULTS

Six-week-old male Sprague-Dawley rats were injected subcutaneously with 20 mg/kg of SU5416 and were exposed to hypoxia for 3 weeks followed by re-exposure to normoxia for 7 weeks. These rats showed signs of RV failure and upregulation of V2R and cAMP in the lung tissue at 10 weeks after SU5416 injection. They were then treated with either 0.05% tolvaptan in diet (SUHx+Tolv) or normal diet (SUHx) during 5-10 weeks of SU5416 injection. Normal control rats (Cont) were also used for comparison. SUHx+Tolv had significantly higher pulmonary arterial pressure, more progressive pulmonary arterial remodeling, and more severe myocyte hypertrophy and interstitial myocardial fibrosis in the right ventricle compared with SUHx despite achieving successful preload reduction.

CONCLUSIONS

Chronic vasopressin V2R antagonism may contribute to the worsening of PAH and the development of RV remodeling.

Novel Therapeutic Strategies for Reducing Right Heart Failure Associated Mortality in Fibrotic Lung Diseases

Fibrotic lung diseases carry a significant mortality burden worldwide. A large proportion of these deaths are due to right heart failure and pulmonary hypertension. Underlying contributory factors which appear to play a role in the mechanism of progression of right heart dysfunction include chronic hypoxia, defective calcium handling, hyperaldosteronism, pulmonary vascular alterations, cyclic strain of pressure and volume changes, elevation of circulating TGF-β, and elevated systemic NO levels. Specific therapies targeting pulmonary hypertension include calcium channel blockers, endothelin (ET-1) receptor antagonists, prostacyclin analogs, phosphodiesterase type 5 (PDE5) inhibitors, and rho-kinase (ROCK) inhibitors. Newer antifibrotic and anti-inflammatory agents may exert beneficial effects on heart failure in idiopathic pulmonary fibrosis. Furthermore, right ventricle-targeted therapies, aimed at mitigating the effects of functional right ventricular failure, include β-adrenoceptor (β-AR) blockers, angiotensin-converting enzyme (ACE) inhibitors, antioxidants, modulators of metabolism, and 5-hydroxytryptamine-2B (5-HT2B) receptor antagonists. Newer nonpharmacologic modalities for right ventricular support are increasingly being implemented. Early, effective, and individualized therapy may prevent overt right heart failure in fibrotic lung disease leading to improved outcomes and quality of life.

Advancing knowledge of right ventricular pathophysiology in chronic pressure overload: Insights from experimental studies

The right ventricle (RV) has to face major changes in loading conditions due to cardiovascular diseases and pulmonary vascular disorders. Clinical experience supports evidence that the RV better compensates for volume than for pressure overload, and for chronic than for acute changes. For a long time, right ventricular (RV) pathophysiology has been restricted to patterns extrapolated from left heart studies. However, the two ventricles are anatomically, haemodynamically and functionally distinct. RV metabolic properties may also result in a different behaviour in response to pathological conditions compared with the left ventricle. In this review, current knowledge of RV pathophysiology is reported in the setting of chronic pressure overload, including recent experimental findings and emerging concepts. After a time-varying compensated period with preserved cardiac output despite overload conditions, RV failure finally occurs, leading to death. The underlying mechanisms involved in the transition from compensatory hypertrophy to maladaptive remodelling are not completely understood.

Up-regulation of hexokinase1 in the right ventricle of monocrotaline induced pulmonary hypertension

Background

Pulmonary arterial hypertension (PAH) is a proliferative arteriopathy associated with a glycolytic shift during heart metabolism. An increase in glycolytic metabolism can be detected in the right ventricle during PAH. Expression levels of glycolysis genes in the right ventricle during glycolysis that occur in monocrotaline (MCT)-induced pulmonary hypertension (PH) remain unknown.

Methods

PH was induced by a single subcutaneous injection of MCT (50 mg/kg) into rats, eventually causing right heart failure. Concurrently, a control group was injected with normal saline. The MCT-PH rats were randomly divided into three groups according to MCT treatment: MCT-2 week, 3 week, and 4 week groups (MCT-2w, 3w, 4w). At the end of the study, hemodynamics and right ventricular hypertrophy were compared among experimental groups. Expression of key glycolytic candidate genes was screened in the right ventricle.

Results

We observed an increase in mean pulmonary arterial pressure, right ventricular systolic pressure and right ventricular hypertrophy index three weeks following MCT injection. Alterations in the morphology and structure of right ventricular myocardial cells, as well as the pulmonary vasculature were observed. Expression of hexokinase 1 (HK1) mRNA began to increase in the right ventricle of the MCT-3w group and MCT-4w group, while the expression of lactate dehydrogenase A (LDHA) was elevated in the right ventricle of the MCT-4w group. Hexokinase 2(HK2), pyruvate dehydrogenase complex α1 (PDHα1), and LDHA mRNA expression showed no changes in the right ventricle. HK1 mRNA expression was further confirmed by HK1 protein expression and immunohistochemical analyses. All findings underlie the glycolytic phenotype in the right ventricle.

Conclusions

There was an increase in the protein and mRNA expression of hexokinase-1 (HK1) three and four weeks after the injection of monocrotaline in the right ventricle, intervention of HK1 may be amenable to therapeutic intervention.