Dual ETA/ETB blockade with macitentan improves both vascular remodeling and angiogenesis in pulmonary arterial hypertension

The biased apelin receptor agonist, MM07, reverses Sugen/hypoxia-induced pulmonary arterial hypertension as effectively as the endothelin antagonist macitentan

Introduction: Pulmonary arterial hypertension (PAH) is characterised by endothelial dysfunction and pathological vascular remodelling, resulting in the occlusion of pulmonary arteries and arterioles, right ventricular hypertrophy, and eventually fatal heart failure. Targeting the apelin receptor with the novel, G protein-biased peptide agonist, MM07, is hypothesised to reverse the developed symptoms of elevated right ventricular systolic pressure and right ventricular hypertrophy. Here, the effects of MM07 were compared with the clinical standard-of-care endothelin receptor antagonist macitentan. Methods: Male Sprague-Dawley rats were randomised and treated with either normoxia/saline, or Sugen/hypoxia (SuHx) to induce an established model of PAH, before subsequent treatment with either saline, macitentan (30 mg/kg), or MM07 (10 mg/kg). Rats were then anaesthetised and catheterised for haemodynamic measurements, and tissues collected for histopathological assessment. Results: The SuHx/saline group presented with significant increases in right ventricular hypertrophy, right ventricular systolic pressure, and muscularization of pulmonary arteries compared to normoxic/saline controls. Critically, MM07 was as at least as effective as macitentan in significantly reversing detrimental structural and haemodynamic changes after 4 weeks of treatment. Discussion: These results support the development of G protein-biased apelin receptor agonists with improved pharmacokinetic profiles for use in human disease.

Pulmonary arterial hypertension drugs can partially restore altered angiogenic capacities in bmpr2-silenced human lung microvascular endothelial cells

Mutations in the bone morphogenetic protein receptor type 2 (bmpr2) gene and signaling pathway impairment are observed in heritable and idiopathic pulmonary arterial hypertension (PAH). In PAH, endothelial dysfunction is currently handled by drugs targeting the endothelin-1 (ET-1), nitric oxide (NO), and prostacyclin (PGI2) pathways. The role of angiogenesis in the disease process and the effect of PAH therapies on dysregulated angiogenesis remain inconclusive. We aim to investigate in vitro whether (i) bmpr2 silencing can impair angiogenic capacity of human lung microvascular endothelial cells (HLMVECs) and (ii) PAH therapies can restore them. The effects of macitentan (ET-1), tadalafil (NO), and selexipag (PGI2), on BMPRII pathway activation, endothelial barrier function, and angiogenesis were investigated in bmpr2-silenced HLMVECs. Stable bmpr2 silencing resulted in impaired migration and tube formation in vitro capacity. Inhibition of ET-1 pathway was able to partially restore tube formation in bmpr2-silenced HLMVECs, whereas none of the therapies was able to restore endothelial barrier function, no deleterious effects were observed. Our findings highlight the potential role of BMPRII signaling pathway in driving pulmonary endothelial cell angiogenesis. In addition, PAH drugs display limited effects on endothelial function when BMPRII is impaired, suggesting that innovative therapeutic strategies targeting BMPRII signaling are needed to better rescue endothelial dysfunction in PAH.

Macitentan in the Young-Mid-term Outcomes of Patients with Pulmonary Hypertensive Vascular Disease treated in a Pediatric Tertiary Care Center

BACKGROUND

Pulmonary hypertension (PH) is a severe hemodynamic condition with high morbidity and mortality. Approved targeted therapies are limited for pediatric subjects, and treatments are widely adopted from adult algorithms. Macitentan is a safe and effective drug used for adult PH, but data on pediatric patients are limited. In this prospective single-center study, we investigated mid- and long-term effects of macitentan in children with advanced pulmonary hypertensive vascular disease.

METHODS

Twenty-four patients were enrolled in the study for treatment with macitentan. Efficacy was determined by echo parameters and brain natriuretic peptide levels (BNP) at 3 months and 1 year. For detailed analysis, the entire cohort was subgrouped into patients with congenital heart disease-related PH (CHD-PH) and non-CHD-PH patients, respectively.

RESULTS

Mean age of the patients was 10.7 ± 7.6 years; median observation period was 36 months. Twenty of 24 patients were on additional sildenafil and/or prostacyclins. Two of 24 patients discontinued because of peripheral edema. Within the entire cohort, BNP levels and all echo measures such as right ventricular systolic pressure (RVSP), right ventricular end-diastolic diameter (RVED), tricuspid annular plane systolic excursion (TAPSE), pulmonary velocity time integral (VTI), and pulmonary artery acceleration time (PAAT) improved significantly after 3 months (p ≤ 0.01), whereas in the long term significant improvement persisted for BNP levels (-16%), VTI (+14%) and PAAT (+11%) (p < 0.05). By subgroup analysis, non-CHD PH patients showed significant improvements in BNP levels (-57%) and all echo measures (TAPSE +21%, VTI +13%, PAAT +37%, RVSP -24%, RVED -12%) at 3 months (p ≤ 0.01), whereas at 12 months, improvements persisted (p < 0.05) except for RVSP and RVED (nonsignificant). In CHD-PH patients, none of the measures changed (nonsignificant). 6-MWD (distance walked in 6 minutes) slightly increased but was not statistically evaluated.

CONCLUSION

Data presented herein account for the largest cohort of severely affected pediatric patients receiving macitentan. Overall, macitentan was safe and associated with significant beneficial effects and sustained positive signals after 1 year, albeit in the long term disease progression remains a major concern. Our data suggest limited efficacy in CHD-related PH, whereas favorable outcomes were mainly driven by improvements in patients with PH not related to CHD. Larger studies are needed to verify these preliminary results and to prove efficacy of this drug in different pediatric PH entities.

Exploring the failing right ventricle in pulmonary hypertension by CMR: An in vivo study utilising Macitentan

Cardiac magnetic resonance (CMR) imaging is used to assess the right ventricle (RV) of pulmonary hypertensive (PH) patients and more recently to track changes in response to therapy. We wished to investigate if repeat CMRs could be used to assess ventricular changes in the Sugen 5416 hypoxic (Su/Hx) rat model of PH treated with the dual endothelin receptor antagonist Macitentan. Male Sprague Dawley Su/Hx rats were dosed for 3 weeks with either vehicle or Macitentan (30 mg/kg) daily, control rats received only vehicle. All rats underwent three CMR scans; before treatment, 2 weeks into treatment, and end of the study. A separate group of Su/Hx and control rats, treated as above, underwent terminal hemodynamic measurements. Using terminal and CMR measurements, Macitentan was found to lower RV systolic pressure pulmonary artery remodeling and increase RV ejection fraction but not change RV hypertrophy (RVH). Repeat CMRs determined that Su/Hx rats treated with Macitentan had significantly reversed RVH via reducing RV mass as well as reducing elevated left ventricular eccentricity index; reductions in RV mass were also observed in Su/Hx vehicle rats exposed to normoxic conditions. We have demonstrated that repeat CMRs can be used to assess the volume and structural changes in the ventricles of the Su/Hx rat model. Using repeat CMRs has allowed us to build a more complete picture of the response of the RV and the left ventricle to treatment. It is unknown if these effects are a consequence of direct action on the RV or secondary to improvements in the lung vasculature.

Macitentan attenuates cardiovascular remodelling in infant rats with chronic lung disease

Background

Cardiovascular impairment contributes to increased mortality in preterm infants with chronic lung disease. Macitentan, an endothelin-1 receptor antagonist, has the potential to attenuate pulmonary and cardiovascular remodelling.

Methods

In a prospective randomized placebo-controlled intervention trial, Sprague–Dawley rats were exposed to 0.21 or 1.0 fraction of inspired oxygen (FiO2) for 19 postnatal days. Rats were treated via gavage with placebo or macitentan from days of life 5 to 19. Alveoli, pulmonary vessels, α-smooth muscle actin content in pulmonary arterioles, size of cardiomyocytes, right to left ventricular wall diameter ratio, and endothelin-1 plasma concentrations were assessed.

Results

FiO2 1.0 induced typical features of chronic lung disease with significant alveolar enlargement (p = 0.012), alveolar (p = 0.048) and pulmonary vessel rarefaction (p = 0.024), higher α-smooth muscle actin content in pulmonary arterioles (p = 0.009), higher right to left ventricular wall diameter ratio (p = 0.02), and larger cardiomyocyte cross-sectional area (p < 0.001). Macitentan treatment significantly increased pulmonary vessel count (p = 0.004) and decreased right to left ventricular wall diameter ratios (p = 0.002). Endothelin-1 plasma concentrations were higher compared to placebo (p = 0.015). Alveolar number and size, α-smooth muscle actin, and the cardiomyocyte cross-sectional area remained unchanged (all p > 0.05).

Conclusion

The endothelin-1 receptor antagonist macitentan attenuated cardiovascular remodelling in an infant rat model for preterm chronic lung disease. This study underscores the potential of macitentan to reduce cardiovascular morbidity in preterm infants with chronic lung disease.

Exercise intolerance in pulmonary arterial hypertension: insight into central and peripheral pathophysiological mechanisms

Exercise intolerance is a cardinal symptom of pulmonary arterial hypertension (PAH) and strongly impacts patients' quality of life (QoL). Although central cardiopulmonary impairments limit peak oxygen consumption (V' O2peak ) in patients with PAH, several peripheral abnormalities have been described over the recent decade as key determinants in exercise intolerance, including impaired skeletal muscle (SKM) morphology, convective O2 transport, capillarity and metabolism indicating that peripheral abnormalities play a greater role in limiting exercise capacity than previously thought. More recently, cerebrovascular alterations potentially contributing to exercise intolerance in patients with PAH were also documented. Currently, only cardiopulmonary rehabilitation has been shown to efficiently improve the peripheral components of exercise intolerance in patients with PAH. However, more extensive studies are needed to identify targeted interventions that would ultimately improve patients' exercise tolerance and QoL. The present review offers a broad and comprehensive analysis of the present literature about the complex mechanisms and their interactions limiting exercise in patients and suggests several gaps in knowledge that need to be addressed in the future for a better understanding of exercise intolerance in patients with PAH.

Application of [18F]FLT-PET in pulmonary arterial hypertension: a clinical study in pulmonary arterial hypertension patients and unaffected bone morphogenetic protein receptor type 2 mutation carriers

Pulmonary arterial hypertension is a heterogeneous group of diseases characterized by vascular cell proliferation leading to pulmonary vascular remodelling and ultimately right heart failure. Previous data indicated that 3′-deoxy-3′-[18F]-fluorothymidine (¹⁸FLT) positron emission tomography (PET) scanning was increased in pulmonary arterial hypertension patients, hence providing a possible biomarker for pulmonary arterial hypertension as it reflects vascular cell hyperproliferation in the lung. This study sought to validate ¹⁸FLT-PET in an expanded cohort of pulmonary arterial hypertension patients in comparison to matched healthy controls and unaffected bone morphogenetic protein receptor type 2 mutation carriers. ¹⁸FLT-PET scanning was performed in 21 pulmonary arterial hypertension patients (15 hereditary pulmonary arterial hypertension and 6 idiopathic pulmonary arterial hypertension), 11 unaffected mutation carriers and 9 healthy control subjects. In-depth kinetic analysis indicated that there were no differences in lung ¹⁸FLT k3 phosphorylation among pulmonary arterial hypertension patients, unaffected bone morphogenetic protein receptor type 2 mutation carriers and healthy controls. Lung ¹⁸FLT uptake did not correlate with haemodynamic or clinical parameters in pulmonary arterial hypertension patients. Sequential ¹⁸FLT-PET scanning in three patients demonstrated uneven regional distribution in ¹⁸FLT uptake by 3D parametric mapping of the lung, although this did not follow the clinical course of the patient. We did not detect significantly increased lung ¹⁸FLT uptake in pulmonary arterial hypertension patients, nor in the unaffected bone morphogenetic protein receptor type 2 mutation carriers, as compared to healthy subjects. The conflicting results with our preliminary human ¹⁸FLT report may be explained by a small sample size previously and we observed large variation of lung ¹⁸FLT signals between patients, challenging the application of ¹⁸FLT-PET as a biomarker in the pulmonary arterial hypertension clinic.

Long-term chronic intermittent hypoxia: a particular form of chronic high-altitude pulmonary hypertension

In some subjects, high-altitude hypobaric hypoxia leads to high-altitude pulmonary hypertension. The threshold for the diagnosis of high-altitude pulmonary hypertension is a mean pulmonary artery pressure of 30 mmHg, even though for general pulmonary hypertension is ≥25 mmHg. High-altitude pulmonary hypertension has been associated with high hematocrit findings (chronic mountain sickness), and although these are two separate entities, they have a synergistic effect that should be considered. In recent years, a new condition associated with high altitude was described in South America named long-term chronic intermittent hypoxia and has appeared in individuals who commute to work at high altitude but live and rest at sea level. In this review, we discuss the initial epidemiological pattern from the early studies done in Chile, the clinical presentation and possible molecular mechanism and a discussion of the potential management of this condition.

Oxidative Stress, Kinase Activity and Inflammatory Implications in Right Ventricular Hypertrophy and Heart Failure under Hypobaric Hypoxia

High altitude (hypobaric hypoxia) triggers several mechanisms to compensate for the decrease in oxygen bioavailability. One of them is pulmonary artery vasoconstriction and its subsequent pulmonary arterial remodeling. These changes can lead to pulmonary hypertension and the development of right ventricular hypertrophy (RVH), right heart failure (RHF) and, ultimately to death. The aim of this review is to describe the most recent molecular pathways involved in the above conditions under this type of hypobaric hypoxia, including oxidative stress, inflammation, protein kinases activation and fibrosis, and the current therapeutic approaches for these conditions. This review also includes the current knowledge of long-term chronic intermittent hypobaric hypoxia. Furthermore, this review highlights the signaling pathways related to oxidative stress (Nox-derived O₂^.- and H₂O₂), protein kinase (ERK5, p38α and PKCα) activation, inflammatory molecules (IL-1β, IL-6, TNF-α and NF-kB) and hypoxia condition (HIF-1α). On the other hand, recent therapeutic approaches have focused on abolishing hypoxia-induced RVH and RHF via attenuation of oxidative stress and inflammatory (IL-1β, MCP-1, SDF-1 and CXCR-4) pathways through phytotherapy and pharmacological trials. Nevertheless, further studies are necessary.

Endurance exercise training in pulmonary hypertension increases skeletal muscle electron transport chain supercomplex assembly

Pulmonary hypertension is associated with pronounced exercise intolerance (decreased V ċ O₂ max) that can significantly impact quality of life. The cause of exercise intolerance in pulmonary hypertension remains unclear. Mitochondrial supercomplexes are large respiratory assemblies of individual electron transport chain complexes which can promote more efficient respiration. In this study, we examined pulmonary hypertension and exercise-induced changes in skeletal muscle electron transport chain protein expression and supercomplex assembly. Pulmonary arterial hypertension was induced in rats with the Sugen/Hypoxia model (10% FiO₂, three weeks). Pulmonary arterial hypertension and control rats were assigned to an exercise training protocol group or kept sedentary for one month. Cardiac function and V ċ O₂ max were assessed at the beginning and end of exercise training. Red (Type 1—oxidative muscle) and white (Type 2—glycolytic muscle) gastrocnemius were assessed for changes in electron transport chain complex protein expression and supercomplex assembly via SDS- and Blue Native-PAGE. Results showed that pulmonary arterial hypertension caused a significant decrease in V ċ O₂ max via treadmill testing that was improved with exercise (P < 0.01). Decreases in cardiac output and pulmonary acceleration time due to pulmonary arterial hypertension were not improved with exercise. Pulmonary arterial hypertension reduced expression in individual electron transport chain complex protein expression (NDUFB8 (CI), SDHB (CII), Cox IV (CIV), but not UQCRC2 (CIII), or ATP5a (CV)) in red gastrocnemius muscle. Both red gastrocnemius and white gastrocnemius electron transport chain expression was unaffected by exercise. However, non-denaturing Blue Native-PAGE analysis of mitochondrial supercomplexes demonstrated increases with exercise training in pulmonary arterial hypertension in the red gastrocnemius but not white gastrocnemius muscle. Pulmonary arterial hypertension-induced exercise intolerance is improved with exercise and is associated with muscle type specific alteration in mitochondrial supercomplex assembly and expression of mitochondrial electron transport chain proteins.

Endothelin-1 Downregulates Sulfur Dioxide/Aspartate Aminotransferase Pathway via Reactive Oxygen Species to Promote the Proliferation and Migration of Vascular Smooth Muscle Cells

The regulatory mechanisms for proliferation and migration of vascular smooth muscle cells have not yet been clear. The present study was designed to investigate whether and how endothelin-1 (ET-1) impacted the generation of endogenous sulfur dioxide (SO₂) in rat vascular smooth muscle cell (VSMC) proliferation and migration. Primary VSMCs and purified aspartate aminotransferase (AAT) protein were used in this study. We found that in the presence of ET-1, the expression of PCNA and Ki-67 was upregulated and the migration of VSMCs was promoted, while the AAT activity and SO₂ levels in VSMCs were reduced without any changes in AAT1 and AAT2 expression. SO₂ supplementation successfully prevented the ET-1-facilitated expression of PCNA and Ki-67 and the migration of VSMCs. Interestingly, ET-1 significantly increased reactive oxygen species (ROS) production in association with SO₂/AAT pathway downregulation in VSMCs compared with controls, while the ROS scavenger N-acetyl-L-cysteine (NAC) and the antioxidant glutathione (GSH) significantly abolished the ET-1-stimulated downregulation of the SO₂/AAT pathway. Moreover, the AAT activity was reduced in purified protein after the treatment for 2 h. However, NAC and GSH blocked the hydrogen peroxide-induced AAT activity reduction. In conclusion, our results suggest that ET-1 results in the downregulation of the endogenous SO₂/AAT pathway via ROS generation to enhance the proliferation and migration of VSMCs.

Puerarin protects pulmonary arteries from hypoxic injury through the BMPRII and PPARγ signaling pathways in endothelial cells

BACKGROUND

Recent evidence indicates that Puerarin has a protective effect on pulmonary arteries. In the present study, we aimed to investigate whether Puerarin could protect pulmonary arterial endothelial cells from hypoxic injury and determine its potential targets.

METHODS

In our study, human pulmonary arterial endothelial cells (HPAECs) were injured by hypoxic (1% O2) incubation. Cell viability was detected by a cell counting kit (CCK8). The production of nitric oxide (NO) was detected by Griess reagent and endothelin-1 (ET-1) was detected by the ELISA method. Oxidative stress was measured by a fluorescence microscope via the fluorescent probe DCFH-DA. Western blotting was employed for studying the mechanism.

RESULTS

The results show that Puerarin protects HPAECs from hypoxia-induced apoptosis and slightly improves cell viability. Puerarin increases NO and decreases ET-1 to prevent the imbalance between vasoactive substances induced by hypoxia in HPAECs. Puerarin also inhibits the oxidative stress induced by hypoxia. The results from the Western blot show that Puerarin activates the BMPRII/Smad and PPARγ/PI3K/Akt signaling pathways.

CONCLUSION

In conclusion, Puerarin protects HPAECs from hypoxic injury through the inhibition of oxidative stress and the activation of the BMPRII and PPARγ signaling pathways. This work provides insight into the development of Puerarin as a treatment for hypoxic pulmonary hypertension.

Clinical value of non-coding RNAs in cardiovascular, pulmonary, and muscle diseases

Although a majority of the mammalian genome is transcribed to RNA, mounting evidence indicates that only a minor proportion of these transcriptional products are actually translated into proteins. Since the discovery of the first non-coding RNA (ncRNA) in the 1980s, the field has gone on to recognize ncRNAs as important molecular regulators of RNA activity and protein function, knowledge of which has stimulated the expansion of a scientific field that quests to understand the role of ncRNAs in cellular physiology, tissue homeostasis, and human disease. Although our knowledge of these molecules has significantly improved over the years, we have limited understanding of their precise functions, protein interacting partners, and tissue-specific activities. Adding to this complexity, it remains unknown exactly how many ncRNAs there are in existence. The increased use of high-throughput transcriptomics techniques has rapidly expanded the list of ncRNAs, which now includes classical ncRNAs (e.g., ribosomal RNAs and transfer RNAs), microRNAs, and long ncRNAs. In addition, splicing by-products of protein-coding genes and ncRNAs, so-called circular RNAs, are now being investigated. Because there is substantial heterogeneity in the functions of ncRNAs, we have summarized the present state of knowledge regarding the functions of ncRNAs in heart, lungs, and skeletal muscle. This review highlights the pathophysiologic relevance of these ncRNAs in the context of human cardiovascular, pulmonary, and muscle diseases.

Inhibition of miR-495 Improves Both Vascular Remodeling and Angiogenesis in Pulmonary Hypertension

BACKGROUND AND AIMS

Pulmonary hypertension (PH) is a chronic progressing vascular disease characterized by pulmonary arteriole remodeling and loss of pulmonary microvasculature. The aim of this study was to investigate a potential role for the miR-495 in PH pathogenesis and to explore its therapeutic potential in PH.

METHODS

Male C57BL/6J mice were injected with SU5416 weekly during 3 weeks of exposure to 10% oxygen to cause PH. We first tested the effects of adeno-associated virus 9 (AAV9) delivery which was specifically designed to block miR-495 in the lungs of the PH model. Then, the biological function of miR-495 was analyzed in cultured pulmonary arterial endothelial cells (PAECs) under hypoxic condition.

RESULTS

The inhibition of miR-495 improves hemodynamics and vascular remodeling in PH. At the same time, these effects were associated with increases in angiogenic transcription factor VEZF1 and marked upregulation of other angiogenic genes such as Angpt-1 and IGF1. In vitro, cultured mouse PAECs were transfected with miR-495 inhibitor or miR-495 mimics. Both the flow cytometry results and CCK8 assay showed that miR-495 inhibitor increased the percentage of cells in the G2/M+S phase, and the wound healing assays indicated that the migration capacity of PAECs transfected with miR-495 inhibitor was increased compared to the inhibitor-NC cells.

CONCLUSIONS

Our results indicate that AAV9-TuD-miR-495 delivery improves hemodynamic and pulmonary vascular structural changes in PH mice.

Pulmonary arterial hypertension in systemic sclerosis: Diagnosis and treatment according to the European Society of Cardiology and European Respiratory Society 2015 guidelines

Scleroderma (systemic sclerosis) is an autoimmune connective tissue disease which presents endothelial dysfunction and fibroblast dysregulation, resulting in vascular and fibrotic disorders. Pulmonary hypertension is frequent in patients with systemic sclerosis: the natural evolution of the disease can induce the development of different forms of pulmonary hypertension, representing one of the main causes of death. Among the different forms of pulmonary hypertension in systemic sclerosis, pulmonary arterial hypertension is the most frequent one (rate of occurrence is estimated between 7% and 12%). This pulmonary vascular complication should be treated with a combination of drugs that is able to counteract endothelial dysfunction, antagonizing the endothelin-1 system and replacing prostaglandin I2 and nitric oxide activity. A correct diagnosis is mandatory, because it is possible only for pulmonary arterial hypertension to use specific drugs that are able to control the symptomatic condition and the evolution of the disease. According to the most recent guidelines, for the patients with systemic sclerosis, also without pulmonary hypertension symptoms, echocardiography screening for the detection of pulmonary hypertension is recommended. Pulmonary arterial hypertension screening programs in systemic sclerosis patients is able to identify milder forms of the disease, allowing earlier management and better long-term outcome.

Vascular Adaptation of the Right Ventricle in Experimental Pulmonary Hypertension

Optimal right ventricular (RV) function in pulmonary hypertension (PH) requires structural and functional coupling between the RV cardiomyocyte and its adjacent capillary network. Prior investigations have indicated that RV vascular rarefaction occurs in PH, which could contribute to RV failure by reduced delivery of oxygen or other metabolic substrates. However, it has not been determined if rarefaction results from relative underproliferation in the setting of tissue hypertrophy or from actual loss of vessels. It is also unknown if rarefaction results in inadequate substrate delivery to the RV tissue. In the present study, PH was induced in rats by SU5416-hypoxia-normoxia exposure. The vasculature in the RV free wall was assessed using stereology. Steady-state metabolomics of the RV tissue was performed by mass spectrometry. Complementary studies were performed in hypoxia-exposed mice and rats. Rats with severe PH had evidence of RV failure by decreased cardiac output and systemic hypotension. By stereology, there was significant RV hypertrophy and increased total vascular length in the RV free wall in close proportion, with evidence of vessel proliferation but no evidence of endothelial cell apoptosis. There was a modest increase in the radius of tissue served per vessel, with decreased arterial delivery of metabolic substrates. Metabolomics revealed major metabolic alterations and metabolic reprogramming; however, metabolic substrate delivery was functionally preserved, without evidence of either tissue hypoxia or depletion of key metabolic substrates. Hypoxia-treated rats and mice had similar but milder alterations. There is significant homeostatic vascular adaptation in the right ventricle of rodents with PH.

EXPERIENCE OF USING THE NON­SELECTIVE ENDOTHELIN RECEPTOR ANTAGONIST MACITENTAN IN PATIENTS WITH PULMONARY ARTERIAL HYPERTENSION

Aim. To present the results of treatment with macitentan of patients included in the clinical trial SERAPHIN in Almazov National Medical Research Centre and define target therapy of pulmonary arterial hypertension (PAH) in real clinical practice.

Material and methods. The article presents the results of the 151 patients with PAH followed­up in Almazov National Medical Research Centre from 2009 to 2016.

Results. Five­year survival of PAH patients included in the register of Almazov National Medical Research Centre reached 77% for idiopathic PAH, 52% for PAH associated with systemic scleroderma, 81% for PAH associated with non­repaired congenital heart disease, 82% for patients with repaired congenital shunts and 100% for PAH associated with human immunodeficiency virus infection. The group that received PAH specific monotherapy consisted of 47% (n=71) of patients among which phosphodiesterase type 5 inhibitor (PDE­5i) sildenafil was undoubtedly the most prescribed drug — 74% (n=53). The group that received combined PAH specific therapy consisted of 66 (44%) patients: 48 patients received various two­component therapy, 18 patients — threecomponent therapy with endothelin receptor antagonist in combination with PDE­5i and prostanoids. 11 patients with PAH were included in SERAPHIN study of which 9 patients had been already receiving generic PDE­5i therapy. In macitentan group, a statistically significant increase in the 6­minute walk distance (+50 meters) and a decrease in hemodynamic parameters such as mean right atrial pressure (­2,3 mm Hg) and pulmonary vascular resistance (­445 dyn­sec/cm5) were observed after 6 months. No patient had a clinically significant increase in liver transaminases or a decrease in hemoglobin levels.

Conclusion. Improvement of prognosis in PAH patients according to the register of the Centre is connected both with early detection of the disease, thanks to the development of specialized healthcare, and more frequent use of combination therapy. Macitentan proved its long­term efficacy and safety as monotherapy and in combination with PDE­5i.