Advances in therapeutic interventions for patients with pulmonary arterial hypertension

Combination Therapy with Oral Treprostinil for Pulmonary Arterial Hypertension. A Double-Blind Placebo-controlled Clinical Trial

Rationale: Oral treprostinil improves exercise capacity in patients with pulmonary arterial hypertension (PAH), but the effect on clinical outcomes was unknown.

Objectives: To evaluate the effect of oral treprostinil compared with placebo on time to first adjudicated clinical worsening event in participants with PAH who recently began approved oral monotherapy.

Methods: In this event-driven, double-blind study, we randomly allocated 690 participants (1:1 ratio) with PAH to receive placebo or oral treprostinil extended-release tablets three times daily. Eligible participants were using approved oral monotherapy for over 30 days before randomization and had a 6-minute-walk distance 150 m or greater. The primary endpoint was the time to first adjudicated clinical worsening event: death; hospitalization due to worsening PAH; initiation of inhaled or parenteral prostacyclin therapy; disease progression; or unsatisfactory long-term clinical response.

Measurements and Main Results: Clinical worsening occurred in 26% of the oral treprostinil group compared with 36% of placebo participants (hazard ratio, 0.74; 95% confidence interval, 0.56–0.97; P = 0.028). Key measures of disease status, including functional class, Borg dyspnea score, and N-terminal pro–brain natriuretic peptide, all favored oral treprostinil treatment at Week 24 and beyond. A noninvasive risk stratification analysis demonstrated that oral treprostinil–assigned participants had a substantially higher mortality risk at baseline but achieved a lower risk profile from Study Weeks 12–60. The most common adverse events in the oral treprostinil group were headache, diarrhea, flushing, nausea, and vomiting.

Conclusions: In participants with PAH, addition of oral treprostinil to approved oral monotherapy reduced the risk of clinical worsening.

Clinical trial registered with www.clinicaltrials.gov (NCT01560624).

Effects of Different Types of Exercise Training on Pulmonary Arterial Hypertension: A Systematic Review

Pulmonary arterial hypertension (PAH) represents a chronic progressive disease characterized by high blood pressure in the pulmonary arteries leading to right heart failure. The disease has been a focus of medical research for many years due to its worse prognosis and limited treatment options. The aim of this study was to systematically assess the effects of different types of exercise interventions on PAH. Electronic databases were searched until July 2019. MEDLINE database was used as the predominant source for this paper. Studies with regards to chronic physical activity in adult PAH patients are compared on retrieving evidence on cellular, physiological, and psychological alterations in the PAH setting. Twenty human studies and 12 rat trials were identified. Amongst all studies, a total of 628 human subjects and 614 rats were examined. Regular physical activity affects the production of nitric oxygen and attenuates right ventricular hypertrophy. A combination of aerobic, anaerobic, and respiratory muscle training induces the strongest improvement in functional capacity indicated by an increase of 6 MWD and VO₂peak. In human studies, an increase of quality of life was found. Exercise training has an overall positive effect on the physiological and psychological components of PAH. Consequently, PAH patients should be encouraged to take part in regular exercise training programs.

Evaluation of a collaborative care program for pulmonary hypertension patients: a multicenter randomized trial

Background Pulmonary hypertension is a rare, chronic and life-threatening group of diseases. Recent advances in pulmonary hypertension management prolong survival and improve quality-of-life. However, highly complex drug therapy enhances the risk of drug-related problems. Objective To assess the impact of involving clinical pharmacists in the collaborative care of pulmonary hypertension patients. Setting Ten French University Hospital Pneumology departments, all members of the French Network for Pulmonary Hypertension. Methods This prospective multicenter randomized controlled trial included incident pulmonary hypertension patients who were followed-up for 18 months. Randomization using an adapted Zelen method allocated patients to collaborative care (n = 41) or usual care groups (n = 51). A collaborative care program involving clinical pharmacists was developed through a close partnership between with physicians, nurses and pharmacists. Besides usual care, the program includes regular one-to-one interviews between the pharmacist and the patient. These interviews had following objectives: to perform an exhaustive medication history review; to identify the patient' needs, knowledge and skills; to define educational objectives and to provide patients with relevant information when needed. Following each interview, a standardized report form containing the pharmacist's recommendations was provided to physicians and nurses and discussed collaboratively. An ancillary economic analysis was performed. Main outcome measure Number of drug-related problems and their outcomes. Results The number of drug-related problems was not significantly different between groups (1.6 ± 1.5 vs. 1.9 ± 2.4; p = 0.41). More problems were resolved in the collaborative care group than in the usual care group (86.5% vs. 66.7%, p = 0.01). Time to clinical worsening, therapeutic adherence, satisfaction or quality-of-life were not statistically different between groups. Collaborative care decreased costs of drug-related hospitalizations. Conclusion Including clinical pharmacists in the multidisciplinary care of hospitalized patients with pulmonary hypertension improved the outcome of drug-related problems and reduced the costs of related hospitalization. However, we observed no efficacy on medication errors, clinical outcomes or medication adherence. Clinical Trial Registration ClinicalTrials.gov Identifier NCT01038284.

Apoptosis signal-regulating kinase 1 inhibition in in vivo and in vitro models of pulmonary hypertension

Pulmonary arterial hypertension, group 1 of the pulmonary hypertension disease family, involves pulmonary vascular remodelling, right ventricular dysfunction and cardiac failure. Oxidative stress, through activation of mitogen-activated protein kinases is implicated in these changes. Inhibition of apoptosis signal-regulating kinase 1, an apical mitogen-activated protein kinase, prevented pulmonary arterial hypertension developing in rodent models. Here, we investigate apoptosis signal-regulating kinase 1 in pulmonary arterial hypertension by examining the impact that its inhibition has on the molecular and cellular signalling in established disease. Apoptosis signal-regulating kinase 1 inhibition was investigated in in vivo pulmonary arterial hypertension and in vitro pulmonary hypertension models. In the in vivo model, male Sprague Dawley rats received a single subcutaneous injection of Sugen SU5416 (20 mg/kg) prior to two weeks of hypobaric hypoxia (380 mmHg) followed by three weeks normoxia (Sugen/hypoxic), then animals were either maintained for three weeks on control chow or one containing apoptosis signal-regulating kinase 1 inhibitor (100 mg/kg/day). Cardiovascular measurements were carried out. In the in vitro model, primary cultures of rat pulmonary artery fibroblasts and rat pulmonary artery smooth muscle cells were maintained in hypoxia (5% O₂) and investigated for proliferation, migration and molecular signalling in the presence or absence of apoptosis signal-regulating kinase 1 inhibitor. Sugen/hypoxic animals displayed significant pulmonary arterial hypertension compared to normoxic controls at eight weeks. Apoptosis signal-regulating kinase 1 inhibitor decreased right ventricular systolic pressure to control levels and reduced muscularised vessels in lung tissue. Apoptosis signal-regulating kinase 1 inhibition was found to prevent hypoxia-induced proliferation, migration and cytokine release in rat pulmonary artery fibroblasts and also prevented rat pulmonary artery fibroblast-induced rat pulmonary artery smooth muscle cell migration and proliferation. Apoptosis signal-regulating kinase 1 inhibition reversed pulmonary arterial hypertension in the Sugen/hypoxic rat model. These effects may be a result of intrinsic changes in the signalling of adventitial fibroblast.

Pulmonary artery denervation for pulmonary arterial hypertension

Pulmonary arterial hypertension remains a progressive, life-limiting disease despite optimal medical therapy. Pulmonary artery denervation has arisen as a novel intervention in the treatment of pulmonary arterial hypertension, and other forms of pulmonary hypertension, with the aim of reducing the sympathetic activity of the pulmonary circulation. Pre-clinical studies and initial clinical trials have demonstrated that the technique can be performed safely with some positive effects on clinical, haemodynamic and echocardiographic markers of disease. The scope of the technique in current practice remains limited given the absence of well-designed, large-scale, international randomised controlled clinical trials. This review provides an overview of this exciting new treatment modality, including pathophysiology, technical innovations and recent trial results.

Thrombocytopenia During Prostacyclin Analogue Therapies of Pulmonary Arterial Hypertension-Possible Pathomechanisms and Implications

Pulmonary arterial hypertension is a quite rare, but problematic disease in everyday cardiologists' practice. Prostanoids are the most important group of drugs used in this disease. One of the biggest problems encountered during treatment with analogs of prostacyclin is thrombocytopenia. Based on hematological guidelines we suggest common therapeutic schemes depending on the number of platelets or the severity of bleeding conducting the therapy.

Pulmonary hypertension in low- and middle-income countries with focus on sub-Saharan Africa

Pulmonary hypertension (PH) is a devastating, progressive disease with increasingly debilitating symptoms and usually shortened overall life expectancy. This article reviews the global epidemiology of PH with focus on low- and middle-income countries (LMICs) and sub-Sahara African in particular. Although left ventricular heart disease is the most common cause globally, the main contributing risk factors in LMICs are chronic infectious diseases especially human immunodeficiency virus (HIV) and schistosomiasis. Other important risk factors of PH are rheumatic heart disease, untreated congenital heart disease (CHD), and sickle cell disease. Despite existing epidemiological data of PH risk factors suggesting a high prevalence in sub-Saharan Africa (SSA), the available literature is limited. International registries in LMICs like the pan African pulmonary hypertension cohort (PAPUCO) study are essential to provide information about the causes, treatment, outcome, and the natural course of PH in Africa and other parts of the world. In addition, there is a need to track diagnostic and management practices in order to develop suitable algorithms to diagnose PH in LMICs.

Immunotherapy of Endothelin-1 Receptor Type A for Pulmonary Arterial Hypertension

BACKGROUND

Pulmonary arterial hypertension (PAH) is a chronic fatal disease. The treatment of PAH is less than ideal and the control is far from satisfactory worldwide. Vaccination provides a promising approach for treatment of PAH.

OBJECTIVES

This study sought to find a vaccine against endothelin-1 (ET-1) receptor type A (ETAR) for treating PAH.

METHODS

The ETRQβ-002 vaccine was screened and the specific antibodies against epitope ETR-002 belonging to the second extracellular loop of ETAR (including the polyclonal and monoclonal antibody) were produced. The effect of the antibodies on Ca²⁺-dependent signal transduction events was investigated. In vivo, ETRQβ-002 vaccine was used to vaccinate monocrotaline (MCT)- and Sugen/hypoxia-induced pulmonary hypertension animals. The monoclonal antibody (mAb) against ETR-002 was also injected into the PAH animals. The effect of ETRQβ-002 vaccine on pulmonary hypertension and remodeling of pulmonary arterioles and right ventricle (RV) was carefully evaluated. Further, the possible immune-mediated damage was detected in normal vaccinated animals.

RESULTS

ETR-002 peptide has perfect immunogenicity and ETRQβ-002 vaccine could induce strong antibody production. In vitro, the anti-ETR-002 antibody bound to ETAR and inhibited Ca²⁺-dependent signal transduction events, including extracellular signal-regulated kinase phosphorylation and elevation of intracellular Ca²⁺ concentration induced by ET-1. In vivo, both ETRQβ-002 vaccine and the mAb significantly decreased the RV systolic pressure up to 20 mm Hg and 10 mm Hg in MCT-exposed rats and Sugen/hypoxia-exposed mice, respectively. Also, ETRQβ-002 vaccine/mAb obviously ameliorated pathological remodeling of pulmonary arterioles and hypertrophy of the RV in PAH animals. Additionally, no significant immune-mediated damage was detected in vaccinated animals.

CONCLUSIONS

ETRQβ-002 vaccine/mAb attenuated remodeling of pulmonary arterioles and RV in MCT- and Sugen/hypoxia-induced PAH animals and decreased RV systolic pressure effectively through diminishing the pressure response and inhibiting signal transduction initiated by ET-1. ETRQβ-002 vaccine/mAb may provide a novel and promising method for PAH treatment.

Psychometric Validation of a Japanese Version of the emPHasis-10 Questionnaire, a Patient-Reported Outcome Measure for Pulmonary Hypertension - Multicenter Study in Japan

Background: The emPHasis-10 questionnaire is a disease-specific patient-reported outcome assessment of quality of life (QOL) in pulmonary hypertension (PH). The aim of this study was to psychometrically validate a linguistically validated Japanese version of the emPHasis-10. Methods and Results: Japanese patients with PH (age ≥18 years) and no change in functional status, or initiation or change in PH-specific treatment during the past 3 months were recruited from 5 institutions from August 2018 to July 2019. A set of questionnaires was administered twice. The validity and reliability of the emPHasis-10 were assessed using the data of 76 patients. On concurrent validity analysis, a moderate-to-strong correlation was seen with the total score of all 5 external criteria (the Minnesota Living with Heart Failure modified for PH [MLHFQ-PH], Hospital Anxiety and Depression Scale, Dyspnea-12 questionnaire, European Quality of Life-5 Dimensions questionnaire [EQ-5D], and 6-min walk test), with a notably strong correlation with the MLHFQ-PH (0.77) and EQ-5D (-0.64). On known-group validity, a linear increasing trend of the emPHasis-10 score was observed across 4 World Health Organization functional status groups (Jonckheere-Terpstra test, 1-sided, P<0.001). Intraclass correlation coefficient for test-retest reliability was 0.86, and the Cronbach's α for internal consistency was 0.89. Conclusions: The Japanese emPHasis-10 questionnaire is psychometrically valid to evaluate QOL in Japanese PH patients in a clinical setting.

Regulatory effects of Prohibitin 1 on proliferation and apoptosis of pulmonary arterial smooth muscle cells in monocrotaline-induced PAH rats

BACKGROUND

Pulmonary arterial hypertension (PAH) is a severe pulmonary vascular disease characterized by unbalanced proliferation and apoptosis of pulmonary arterial smooth muscle cells (PASMCs). Prohibitin 1 (PHB1) is known for its significant anti-proliferative activity. However, the role of PHB1 in PASMCs and PAH have not been elucidated.

METHODS

Monocrotaline (MCT 60 mg/kg) was used to build a PAH model in SD rats. Right ventricular systolic pressure (RVSP) and right ventricle (RV) hypertrophy were measured. Morphology of pulmonary vessels was observed by Hematoxylin-Eosin (HE) staining. Expression of PHB1 in pulmonary arteries and PASMCs was determinated by immunoblot and immunofluorescence. Cell proliferation was detected by CCK8 and EDU when PASMCs were stimulated by PDGF-BB (20 ng/mL). Furthermore, siRNA for PHB1 and Akt inhibitor were conducted to investigate the mechanism behind the role of PHB1 and AKT signaling pathway in PASMCs proliferation and apoptosis.

RESULTS

The protein expression of PHB1 in PAH rats lung tissue was significantly up-regulated accompanied by elevated RVSP and enhanced RV hypertrophy. Immunohistochemistry showed that PHB1 was mainly localized in the pulmonary vascular smooth muscle layer. PDGF-BB significantly up-regulated the expression of PHB1 in rat primary PASMCs in a time- and dose-dependent manner. After PHB1 knock down, PASMCs proliferation was significantly suppressed while apoptosis was significantly recovered. Meanwhile the level of proliferating cell nuclear antigen (PCNA) and P-Akt were significantly down-regulated. Perifosine (Akt inhibitor) also significantly inhibit proliferation of PASMCs.

CONCLUSION

PHB1 contributes to pulmonary vascular remodeling by accelerating proliferation of PASMCs which involves AKT phosphorylation.

Connexin-43 is a promising target for pulmonary hypertension due to hypoxaemic lung disease

The mechanisms underlying pulmonary hypertension (PH) are complex and multifactorial, and involve different cell types that are interconnected through gap junctional channels. Although connexin (Cx)-43 is the most abundant gap junction protein in the heart and lungs, and critically governs intercellular signalling communication, its contribution to PH remains unknown. The focus of the present study is thus to evaluate Cx43 as a potential new target in PH.Expressions of Cx37, Cx40 and Cx43 were studied in lung specimens from patients with idiopathic pulmonary arterial hypertension (IPAH) or PH associated with chronic hypoxaemic lung diseases (chronic hypoxia-induced pulmonary hypertension (CH-PH)). Heterozygous Cx43 knockdown CD1 (Cx43^+/-) and wild-type littermate (Cx43^+/+) mice at 12 weeks of age were randomly divided into two groups, one of which was maintained in room air and the other exposed to hypoxia (10% oxygen) for 3 weeks. We evaluated pulmonary haemodynamics, remodelling processes in cardiac tissues and pulmonary arteries (PAs), lung inflammation and PA vasoreactivity.Cx43 levels were increased in PAs from CH-PH patients and decreased in PAs from IPAH patients; however, no difference in Cx37 or Cx40 levels was noted. Upon hypoxia treatment, the Cx43^+/- mice were partially protected against CH-PH when compared to Cx43^+/+ mice, with reduced pulmonary arterial muscularisation and inflammatory infiltration. Interestingly, the adaptive changes in cardiac remodelling in Cx43^+/- mice were not affected. PA contraction due to endothelin-1 (ET-1) was increased in Cx43^+/- mice under normoxic and hypoxic conditions.Taken together, these results indicate that targeting Cx43 may have beneficial therapeutic effects in PH without affecting compensatory cardiac hypertrophy.

Mitochondria in the Pulmonary Vasculature in Health and Disease: Oxygen-Sensing, Metabolism, and Dynamics

In lung vascular cells, mitochondria serve a canonical metabolic role, governing energy homeostasis. In addition, mitochondria exist in dynamic networks, which serve noncanonical functions, including regulation of redox signaling, cell cycle, apoptosis, and mitochondrial quality control. Mitochondria in pulmonary artery smooth muscle cells (PASMC) are oxygen sensors and initiate hypoxic pulmonary vasoconstriction. Acquired dysfunction of mitochondrial metabolism and dynamics contribute to a cancer-like phenotype in pulmonary arterial hypertension (PAH). Acquired mitochondrial abnormalities, such as increased pyruvate dehydrogenase kinase (PDK) and pyruvate kinase muscle isoform 2 (PKM2) expression, which increase uncoupled glycolysis (the Warburg phenomenon), are implicated in PAH. Warburg metabolism sustains energy homeostasis by the inhibition of oxidative metabolism that reduces mitochondrial apoptosis, allowing unchecked cell accumulation. Warburg metabolism is initiated by the induction of a pseudohypoxic state, in which DNA methyltransferase (DNMT)-mediated changes in redox signaling cause normoxic activation of HIF-1α and increase PDK expression. Furthermore, mitochondrial division is coordinated with nuclear division through a process called mitotic fission. Increased mitotic fission in PAH, driven by increased fission and reduced fusion favors rapid cell cycle progression and apoptosis resistance. Downregulation of the mitochondrial calcium uniporter complex (MCUC) occurs in PAH and is one potential unifying mechanism linking Warburg metabolism and mitochondrial fission. Mitochondrial metabolic and dynamic disorders combine to promote the hyperproliferative, apoptosis-resistant, phenotype in PAH PASMC, endothelial cells, and fibroblasts. Understanding the molecular mechanism regulating mitochondrial metabolism and dynamics has permitted identification of new biomarkers, nuclear and CT imaging modalities, and new therapeutic targets for PAH. © 2020 American Physiological Society. Compr Physiol 10:713-765, 2020.

Berberine alleviates pulmonary hypertension through Trx1 and β-catenin signaling pathways in pulmonary artery smooth muscle cells

Pulmonary arterial hypertension (PAH) is closely associated with profound vascular remodeling, especially pulmonary arterial medial hypertrophy and muscularization, due to aberrant proliferation of pulmonary artery smooth muscle cells (PASMCs). Berberine, a drug commonly used to treat inflammation, may be a novel therapeutic option for PAH by improving pulmonary artery remodeling. The present study investigated whether berberine affected Trx1/β-catenin expression and/or activity and whether it could reduce the development of pulmonary hypertension in an experimental rat model and proliferation in human PASMCs (HPASMCs). The results showed that increased proliferation in hypoxia-induced healthy PASMCs or PAH PASMCs was associated with a significant increase in Trx1 and β-catenin expression. Treatment with the Trx1-specific inhibitor PX-12 significantly reduced pulmonary arterial pressure and vascular remodeling, as well as improved in vivo cardiac function and right ventricular hypertrophy, in Su/Hox-induced PAH rats. Berberine reversed right ventricular systolic pressure and right ventricular hypertrophy and decreased pulmonary vascular remodeling in the rats. Furthermore, berberine had an antiproliferative effect on hypoxia-induced HPASMC proliferation in a manner likely mediated by inhibiting Trx1 and its target gene β-catenin expression. Our work will help elucidate novel strategies for PAH treatment involving the traditional Chinese medicine berberine, and Trx1/β-catenin may be a promising therapeutic target.

Diagnostic delay in pulmonary arterial hypertension: Insights from the Australian and New Zealand pulmonary hypertension registry

BACKGROUND AND OBJECTIVE

Early diagnosis of PAH is clinically challenging. Patterns of diagnostic delay in Australian and New Zealand PAH populations have not been explored in large-scale studies. We aimed to evaluate the magnitude, risk factors and survival impact of diagnostic delay in Australian and New Zealand PAH patients.

METHODS

A cohort study of PAH patients from the PHSANZ Registry diagnosed from 2004 to 2017 was performed. Diagnostic interval was the time from symptom onset to diagnostic right heart catheterization as recorded in the registry. Factors associated with diagnostic delay were analysed in a multivariate logistic regression model. Survival rates were compared across patients based on the time to diagnosis using Kaplan-Meier method and Cox regression.

RESULTS

A total of 2044 patients were included in analysis. At diagnosis, median age was 58 years (IQR: 43-69), female-to-male ratio was 2.8:1 and majority of patients were in NYHA FC III-IV (82%). Median diagnostic interval was 1.2 years (IQR: 0.6-2.7). Age, CHD-PAH, obstructive sleep apnoea and peripheral vascular disease were independently associated with diagnostic interval of ≥1 year. No improvement in diagnostic interval was seen during the study period. Longer diagnostic interval was associated with decreased 5-year survival.

CONCLUSION

PAH patients experience significant diagnostic interval, which has not improved despite increased community awareness. Age, cardiovascular and respiratory comorbidities are significantly associated with longer time to diagnosis. Mortality rates appear higher in patients who experience longer diagnostic interval.

Key inflammatory pathways underlying vascular remodeling in pulmonary hypertension

Independent of the underlying cause, pulmonary hypertension (PH) remains a devastating condition that is characterized by limited survival. Cumulating evidence indicates that in addition to a dysbalance of mediators regulating vascular tone and growth factors promoting vascular remodeling, failure to resolve inflammation and altered immune processes play a pivotal role in the development and progression of PH. Here, we highlight the role of key inflammatory pathways in the pathobiology of vascular remodeling and PH, and discuss potential therapeutic interventions that may halt disease progression or even reverse pulmonary vascular remodeling. Perivascular inflammation is present in all forms of PH, and inflammatory pathways involve numerous mediators and cell types including macrophages, neutrophils, T cells, dendritic cells, and mast cells. Dysfunctional bone morphogenic protein receptor 2 (BMPR2) signaling and dysregulated immunity enable the accumulation of macrophages and other inflammatory cells in obliterative vascular lesions. Regulatory T cells (Tregs) were shown to be of particular relevance in the control of inflammatory responses. Key cytokines/chemokines include interleukin-6, functioning via classic or trans-signaling, macrophage migratory inhibitory factor (MIF), but also other mediators such as neutrophil-derived myeloperoxidase. The expanding knowledge on this topic has resulted in multiple opportunities for sophisticated therapeutic interventions.

Clinical outcomes stratified by baseline functional class after initial combination therapy for pulmonary arterial hypertension

Background

Initial combination therapy with ambrisentan and tadalafil reduced the risk of clinical failure events for treatment-naïve participants with pulmonary arterial hypertension (PAH) as compared to monotherapy. Previous studies in PAH have demonstrated greater treatment benefits in more symptomatic participants.

Methods

AMBITION was an event-driven, double-blind study in which participants were randomized 2:1:1 to once-daily initial combination therapy with ambrisentan 10 mg plus tadalafil 40 mg, ambrisentan 10 mg plus placebo, or tadalafil 40 mg plus placebo. In this pre-specified subgroup analysis, we compared the efficacy data between those with functional class (FC) II vs. FC III symptoms at baseline.

Results

This analysis included 500 participants in the previously defined primary analysis set (n = 155 FC II, n = 345 FC III). Comparing combination therapy to pooled monotherapy, the risk of clinical failure events was reduced by 79% (hazard ratio, 0.21 [95% confidence interval: 0.071, 0.63]) for FC II patients and 42% (hazard ratio, 0.58 [95% confidence interval: 0.39, 0.86]) for FC III patients. In a post-hoc analysis, the risk of first hospitalization for worsening PAH was also reduced by combination therapy, particularly for FC II patients (0 combination vs. 11 [14%] pooled monotherapy). Adverse events were frequent but comparable between the subgroups.

Conclusions

Treatment benefit from initial combination therapy appeared at least as great for FC II as for FC III participants. Hospitalizations for worsening PAH were not observed in FC II participants assigned to combination. The present data support an initial combination strategy for newly diagnosed patients even when symptoms are less severe.

Funded by Gilead Sciences, Inc. and GlaxoSmithKline; AMBITION ClinicalTrials.gov number, NCT01178073.

Supplementary information

Supplementary information accompanies this paper at 10.1186/s12931-019-1180-1.

Clinical Outcomes and Treatment Options in Patients With Pulmonary Hypertension Who Received Pulmonary Hypertension-Specific Drugs - Single-Center Case Series

Background: Recent progress in the development of pulmonary hypertension (PH)-specific pharmaceutical agents has improved mortality and morbidity remarkably. Today, these PH-specific drugs have become a standard treatment for PH. Methods and Results: We herein summarize the treatment options and longitudinal clinical outcomes of 21 patients with PH who received PH-specific drugs at the present institution. Sixteen patients began treatment with a single PH-specific drug; 9 of them needed additional PH-specific drugs, but the other 7 were still taking the same drug at the last follow-up. Five patients began treatment with a combination of 2 or 3 PH-specific drugs, and their drugs were not discontinued. Most patients (17/21) were taking a phosphodiesterase type 5 (PDE5) inhibitor at the last follow-up. During the 6.5±4.4 years' follow-up, 5 patients died, but only 1 death was related to PH. At 5 and 10 years, the estimated PH-related death-free and lung transplantation-free survival rate was 100% (95% CI: 100-100%) and 87.5% (95% CI: 38.7-98.1%), respectively. The estimated 5- and 10-year estimated overall survival rates were 77.9% (95% CI: 50.8-91.3%) and 68.2% (95% CI: 37.4-86.2%), respectively. Conclusions: PDE5 inhibitors played a central role in the treatment options. The long-term prognosis of PH was favorable at the present institution.

CD146-HIF-1α hypoxic reprogramming drives vascular remodeling and pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a vascular remodeling disease of cardiopulmonary units. No cure is currently available due to an incomplete understanding of vascular remodeling. Here we identify CD146-hypoxia-inducible transcription factor 1 alpha (HIF-1α) cross-regulation as a key determinant in vascular remodeling and PAH pathogenesis. CD146 is markedly upregulated in pulmonary artery smooth muscle cells (PASMCs/SMCs) and in proportion to disease severity. CD146 expression and HIF-1α transcriptional program reinforce each other to physiologically enable PASMCs to adopt a more synthetic phenotype. Disruption of CD146-HIF-1α cross-talk by genetic ablation of Cd146 in SMCs mitigates pulmonary vascular remodeling in chronic hypoxic mice. Strikingly, targeting of this axis with anti-CD146 antibodies alleviates established pulmonary hypertension (PH) and enhances cardiac function in two rodent models. This study provides mechanistic insights into hypoxic reprogramming that permits vascular remodeling, and thus provides proof of concept for anti-remodeling therapy for PAH through direct modulation of CD146-HIF-1α cross-regulation.

Vascular remodelling contributes to the development of pulmonary hypertension (PH). Here Luo and colleagues find that increases in CD146 levels drive vascular remodelling in PH through a cross-talk with hypoxia inducible factor (HIF) signalling, and show that inhibition of CD146 can attenuate disease progression.

Nitric Oxide-Independent Soluble Guanylate Cyclase Activation Improves Vascular Function and Cardiac Remodeling in Sickle Cell Disease

Sickle cell disease (SCD) is associated with intravascular hemolysis and oxidative inhibition of nitric oxide (NO) signaling. BAY 54-6544 is a small-molecule activator of oxidized soluble guanylate cyclase (sGC), which, unlike endogenous NO and the sGC stimulator, BAY 41-8543, preferentially binds and activates heme-free, NO-insensitive sGC to restore enzymatic cGMP production. We tested orally delivered sGC activator, BAY 54-6544 (17 mg/kg/d), sGC stimulator, BAY 41-8543, sildenafil, and placebo for 4-12 weeks in the Berkeley transgenic mouse model of SCD (BERK-SCD) and their hemizygous (Hemi) littermate controls (BERK-Hemi). Right ventricular (RV) maximum systolic pressure (RVmaxSP) was measured using micro right-heart catheterization. RV hypertrophy (RVH) was determined using Fulton's index and RV corrected weight (ratio of RV to tibia). Pulmonary artery vasoreactivity was tested for endothelium-dependent and -independent vessel relaxation. Right-heart catheterization revealed higher RVmaxSP and RVH in BERK-SCD versus BERK-Hemi, which worsened with age. Treatment with the sGC activator more effectively lowered RVmaxSP and RVH, with 90-day treatment delivering superior results, when compared with other treatments and placebo groups. In myography experiments, acetylcholine-induced (endothelium-dependent) and sodium-nitroprusside-induced (endothelium-independent NO donor) relaxation of the pulmonary artery harvested from placebo-treated BERK-SCD was impaired relative to BERK-Hemi but improved after therapy with sGC activator. By contrast, no significant effect for sGC stimulator or sildenafil was observed in BERK-SCD. These findings suggest that sGC is oxidized in the pulmonary arteries of transgenic SCD mice, leading to blunted responses to NO, and that the sGC activator, BAY 54-6544, may represent a novel therapy for SCD-associated pulmonary arterial hypertension and cardiac remodeling.

Anti-inflammatory nutrition with high protein attenuates cardiac and skeletal muscle alterations in a pulmonary arterial hypertension model

Pulmonary arterial hypertension (PAH) is characterized by remodelling of the pulmonary arteries and right ventricle (RV), which leads to functional decline of cardiac and skeletal muscle. This study investigated the effects of a multi-targeted nutritional intervention with extra protein, leucine, fish oil and oligosaccharides on cardiac and skeletal muscle in PAH. PAH was induced in female C57BL/6 mice by weekly injections of monocrotaline (MCT) for 8 weeks. Control diet (sham and MCT group) and isocaloric nutritional intervention (MCT + NI) were administered. Compared to sham, MCT mice increased heart weight by 7%, RV thickness by 13% and fibrosis by 60% (all p < 0.05) and these were attenuated in MCT + NI mice. Microarray and qRT-PCR analysis of RV confirmed effects on fibrotic pathways. Skeletal muscle fiber atrophy was induced (P < 0.05) by 22% in MCT compared to sham mice, but prevented in MCT + NI group. Our findings show that a multi-targeted nutritional intervention attenuated detrimental alterations to both cardiac and skeletal muscle in a mouse model of PAH, which provides directions for future therapeutic strategies targeting functional decline of both tissues.

Oral treprostinil in transition or as add-on therapy in pediatric pulmonary arterial hypertension

Treprostinil, a prostacyclin analogue, is approved for the treatment of pulmonary arterial hypertension (PAH) in adults. Transition from parenteral to oral treprostinil has been successfully accomplished in adults with PAH but not in children. In this multicenter study, pediatric patients treated with parenteral (Cohort 1) or inhaled (Cohort 2) treprostinil were transitioned to oral treprostinil. Prostacyclin-naïve individuals on background oral PAH therapy received oral treprostinil as add-on therapy (Cohort 3). Successful transition was oral treprostinil dose maintenance through week 24. Patients were monitored for adverse events (AEs), 6-min walk distance (6MWD), PAH symptoms, World Health Organization (WHO) Functional Class (FC), cardiac magnetic resonance imaging (cMRI), cardiopulmonary exercise testing (CPET), and quality of life through 24 weeks. A total of 32 patients were enrolled in the study; 23 (72%) were girls (mean age = 12.2 years). All patients were on background oral PAH therapy. Overall, patients (96.9%) maintained transition to oral treprostinil; one patient (Cohort 1) transitioned to oral treprostinil, then back to parenteral after experiencing syncope and WHO FC change from II to III. Cohorts 1, 2, and 3 received a final mean oral treprostinil dose of 5.6, 3.3, and 4.5 mg t.i.d., respectively. All cohorts had variable changes in 6MWD, cMRI, and CPET. Overall, 12 serious AEs were reported. All patients had drug-related AEs including headache (81%), diarrhea (69%), nausea (66%), vomiting (66%), and flushing (56%). Pediatric patients maintained transition to oral treprostinil with preservation of exercise capacity and WHO FC. Prostanoid-related AEs were most common and similar to those reported in adults.

EXPRESS: Long term study of oral treprostinil to treat pulmonary arterial hypertension: dosing, tolerability, and pharmacokinetics

Oral treprostinil may be an option for low- and intermediate-risk patients with pulmonary arterial hypertension, a rare lung vascular disease. This open-label extension study collected data on participants who completed previously reported, placebo-controlled oral treprostinil studies. Eligible participants had completed the prospective parent studies and took increasing doses of oral treprostinil twice daily; some later transitioned to three times daily dosing. Investigators measured 6-minute walk distance at Month 12 as the sole efficacy measure but collected adverse events throughout the study. A single center measured pharmacokinetics in 13 subjects who changed dosing from twice daily to three times daily. Eight hundred and ninety-four participants enrolled and 71% completed one year of therapy, with a median total daily dose of 7 mg and a median 6-minute walk distance increase of 22 m (interquartile range, −14 to 67 m). Subjects achieving higher doses had larger increases in 6-minute walk distance; 42% of participants completed three years of therapy. Adverse events were typical for prostacyclin class therapy, but prostacyclin-type adverse events may have been better tolerated with three times daily dosing in 105 participants. In 13 participants transitioned to three times daily dosing with pharmacokinetic measurements before and after, trough drug levels were higher with three times daily dosing. Oral treprostinil is associated with modest but durable, dose-responsive effects on exercise tolerance for those who remained on therapy at one year in this prospective, uncontrolled study. Three times daily dosing was associated with higher trough levels and better tolerability. The recently completed Freedom-EV study will provide further insights into the utility of oral treprostinil (https://clinicaltrials.gov/show/NCT01560624 ).

Sirtuin 1 regulates pulmonary artery smooth muscle cell proliferation: role in pulmonary arterial hypertension

OBJECTIVE

Energy metabolism shift from oxidative phosphorylation toward glycolysis in pulmonary artery smooth muscle cells (PASMCs) is suggested to be involved in their hyperproliferation in pulmonary arterial hypertension (PAH). Here, we studied the role of the deacetylase sirtuin1 (SIRT1) in energy metabolism regulation in PASMCs via various pathways including activation of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), master regulator of mitochondrial biogenesis.

APPROACH AND RESULTS

Contents of PGC-1α and its downstream targets as well as markers of mitochondrial mass (voltage-dependent anion channel and citrate synthase) were diminished in human PAH PASMCs. These cells and platelet-derived growth factor-stimulated rat PASMCs demonstrated a shift in cellular acetylated/deacetylated state, as evidenced by the increase of the acetylated forms of SIRT1 targets: histone H1 and Forkhead box protein O1. Rat and human PASMC proliferation was potentiated by SIRT1 pharmacological inhibition or specific downregulation via short-interfering RNA. Moreover, after chronic hypoxia exposure, SIRT1 inducible knock out mice displayed a more intense vascular remodeling compared with their control littermates, which was associated with an increase in right ventricle pressure and hypertrophy. SIRT1 activator Stac-3 decreased the acetylation of histone H1 and Forkhead box protein O1 and strongly inhibited rat and human PASMC proliferation without affecting cell mortality. This effect was associated with the activation of mitochondrial biogenesis evidenced by higher expression of mitochondrial markers and downstream targets of PGC-1α.

CONCLUSION

Altered acetylation/deacetylation balance as the result of SIRT1 inactivation is involved in the pathogenesis of PAH, and this enzyme could be a promising therapeutic target for PAH treatment.

Beraprost Upregulates KV Channel Expression and Function via EP4 Receptor in Pulmonary Artery Smooth Muscle Cells Obtained from Rats with Hypoxia-Induced Pulmonary Hypertension

The reduced expression and function of voltage-dependent potassium (KV) channels have been involved in the pathogenesis of hypoxia-induced pulmonary hypertension (HPH), leading to pulmonary vasoconstriction and vascular remodeling, while the upregulation of KV channels is of therapeutic significance for pulmonary hypertension. Beraprost sodium (BPS) has been shown to be effective in patients with pulmonary hypertension. However, the effect of BPS on O2-sensitive KV channels in pulmonary artery smooth muscle cells (PASMCs) remains unclear. In the present study, the effect of BPS on rats with HPH was observed, and the influence of BPS on the expression and function of O2-sensitive KV channels in PASMCs was investigated. The results revealed that BPS reduced mean pulmonary artery pressure, suppressed right ventricular hypertrophy, and attenuated the remodeling of pulmonary arteries in rats exposed to discontinuous hypoxia for 4 weeks (8 h/day). This was accompanied with the significantly upregulated expression of KV channel α-subunits (KV1.2, KV1.5 and KV2.1) and O2-sensitive voltage-gated K+ (KV) channel current (IK(V)) in small pulmonary arteries in HPH model rats, as well as in hypoxia-induced PASMCs. Furthermore, in vitrostudies have revealed that the upregulation of BPS on O2-sensitive KV channels was significantly inhibited after treatment with prostaglandin E2 receptor subtype EP4 antagonist GW627368X. Taken together, these results suggest that BPS attenuates the development of HPH through the upregulation of O2-sensitive KV channels, which was probably via the EP4 receptor-related pathway.

Mesenchymal stem/stromal cell therapy for pulmonary arterial hypertension: Comprehensive review of preclinical studies

Pulmonary arterial hypertension (PAH) is a disease characterized by progressive pulmonary vascular remodeling, resulting in right-sided heart failure and premature death. Current available therapies for PAH have limited efficacy, and new therapeutic strategies need to be developed. Mesenchymal stem/stromal cells (MSCs) may offer a novel therapeutic approach to PAH. Since the first report in 2006, a number of preclinical studies have demonstrated a potential therapeutic effect of this approach, with attenuated hemodynamic and histological progression of PAH, in animal models of PAH. However, there remain several issues that should be addressed for this approach to be clinically successful. With the aim to highlight such issues, this review clarifies existing knowledge on MSC therapy for PAH in preclinical studies, including types of PAH animal models used for MSC therapy, MSC sources, and administration protocol (route, cell dose, and timing of administration). This review thereafter summarizes thoroughly and discusses the mechanism underpinning MSC therapy for PAH. For clinical success of MSC therapy, insufficient evidence of safety (e.g. critical risk of pulmonary embolism) and therapeutic efficacy of MSCs on established PAH with severe vascular remodeling, as well as further optimization of the MSC administration protocol, are considered as remaining issues to be addressed. In terms of the efficacy, it is controversial whether angiogenic cytokines, which are considered as one of the therapeutic mechanisms of MSC, have beneficial effect for human PAH. To address these issues, further preclinical data using more clinically-relevant animal models of PAH, such as SU5416 model, should be accumulated, whereas most preclinical studies have been conducted using monocrotaline-induced PAH model. While MSC therapy has a great potential to become a novel therapy in PAH, continuing careful preclinical research is warranted for clinical success in PAH.

The Liver in Circulatory Disturbances

Liver diseases frequently coexist with heart disease. The causes of coexistent heart and liver disease are categorized into four groups: (1) heart disease affecting the liver, (2) liver disease affecting the heart, (3) cardiac and hepatic manifestations of a common cause, and (4) coexistent heart and liver disease with distinct causes. Discerning the cause of cardiac and liver dysfunction is important in the management of these conditions, particularly when considering surgical intervention or heart or liver transplantation.

ADAPTATION AND VALIDATION OF THE CAMBRIDGE PULMONARY HYPERTENSION OUTCOME REVIEW (CAMPHOR) FOR CROATIA

Pulmonary hypertension (PH) is a chronic disease which severely impairs quality of life (QoL). The Cambridge Pulmonary Hypertension Outcome Review (CAMPHOR) is the first disease-specific tool to assess patient-reported symptoms, functioning and QoL in PH patients. The aim of this study was to adapt and validate the CAMPHOR for use in Croatia. The adaptation process involved three stages: translation (bilingual and lay panel), cognitive debriefing interviews with patients and psychometric validation. For the latter stage, a postal survey was conducted with 50 patients to examine the reliability and validity of the adapted scale. All three scales of the Croatian CAMPHOR demonstrated excellent internal consistency (Symptoms = 0.93; Activity limitations = 0.94; QoL = 0.92) and test-retest reliability correlations (Symptoms = 0.90; Activity limitations = 0.95; QoL = 0.90). Predicted correlations with the SF-36 scales provided evidence for construct validity of the CAMPHOR scales. Evidence for known group validity was shown by the ability of the scales to distinguish between participants based on patient-perceived general health and disease severity. The Croatian version of the CAMPHOR is a valid and reliable tool for use in clinical routine and clinical research.

EXPRESS: Switching to riociguat: A potential treatment strategy for the management of CTEPH and PAH

Currently, five classes of drug are approved for the treatment of pulmonary arterial hypertension (PAH): phosphodiesterase 5 inhibitors (PDE5i); endothelin receptor antagonists; prostacyclin analogs; the IP receptor agonist selexipag; and the soluble guanylate cyclase (sGC) stimulator riociguat. For patients with inoperable or persistent/recurrent chronic thromboembolic pulmonary hypertension (CTEPH), riociguat is currently the only approved pharmacotherapy. Despite the development of evidence-based guidelines on appropriate use of specific drugs, in clinical practice patients are often prescribed PAH-targeted therapies off label or at inadequate doses.

PDE5i are the most often prescribed class of drugs as initial therapy, either alone or in combination with other drug classes. However, a proportion of patients receiving PAH therapies do not reach or maintain treatment goals. As PDE5i and riociguat target different molecules in the nitric oxide-sGC-cyclic guanosine monophosphate (NO-sGC-cGMP) signaling pathway, for patients with PAH without an initial or sustained response to PDE5i, there is a biological rationale for switching to riociguat. However, robust data from randomized controlled trials on the safety and efficacy of switching are lacking, as is formal guidance for clinicians. Here we review studies of sequential combination therapy, and trial data and case studies that have investigated switching between PAH-approved therapies, particularly from PDE5i to riociguat in patients with PAH with an insufficient response to PDE5i, and in patients with CTEPH who were receiving off-label treatment. These studies summarize the current evidence and practical real-life experience on the concept of switching treatments.

Clinical and hemodynamic benefit of macitentan and riociguat upfront combination in patients with pulmonary arterial hypertension

In this open-label study, we evaluated the effect of upfront macitentan and riociguat combination in newly diagnosed pulmonary arterial hypertension (PAH) patients. In 15 consecutive PAH patients, we collected clinical and hemodynamic data at baseline, visit 1 (median 4 months) and visit 2 (median 12 months). Survival and transplantation status were analyzed over 36 months. Statistical analysis included student t-test and 95% confidence interval (CI) ( t-statistic or Clopper-Pearson). Kaplan-Meier was used to estimate survival rate. There were 11/15 women (mean age 56 years), in World Health Organization (WHO) functional class (FC) III ( n = 14) or IV ( n = 1). The 6 min walk distance increased from 281.6 m (baseline) to 315.7 m (visit 1) and visit 2 (313.9 m), representing a 34- and 32-m change ( P < 0.05), respectively, associated with Borg score improvements. Brain natriuretic peptide decreased: 318.2 pg/mL (baseline) to 122.0 pg/mL (visit 1) and 98.6 pg/mL (visit 2) ( P < 0.05). WHO FC improved in eight patients (53%, 95% CI 27%-79%). Pulmonary vascular resistance (9.2 to 5.7 Wood Units) and mean pulmonary artery pressure (47.3 to 38.9 mmHg) decreased; cardiac index increased (2.3 to 3.0 L/min/m²) (baseline to visit 2, all P < 0.05). All patients had intermediate and high risk score (baseline); at 1-year follow-up, dual therapy led to reduction to low risk score in 7/15 (47%) patients. There were no unexpected or serious side effects. Three patients died due to unrelated causes; one patient received a lung transplant. Transplant-free survival rate (36 months) was 85%. Preliminary evidence is provided for effectiveness of initial macitentan and riociguat combination therapy in PAH.

Modulators of Transient Receptor Potential (TRP) Channels as Therapeutic Options in Lung Disease

The lungs are essential for gas exchange and serve as the gateways of our body to the external environment. They are easily accessible for drugs from both sides, the airways and the vasculature. Recent literature provides evidence for a role of Transient Receptor Potential (TRP) channels as chemosensors and essential members of signal transduction cascades in stress-induced cellular responses. This review will focus on TRP channels (TRPA1, TRPC6, TRPV1, and TRPV4), predominantly expressed in non-neuronal lung tissues and their involvement in pathways associated with diseases like asthma, cystic fibrosis, chronic obstructive pulmonary disease (COPD), lung fibrosis, and edema formation. Recently identified specific modulators of these channels and their potential as new therapeutic options as well as strategies for a causal treatment based on the mechanistic understanding of molecular events will also be evaluated.

Metabolic Alterations in Cardiopulmonary Vascular Dysfunction

Cardiovascular diseases (CVD) are the leading cause of death worldwide. CVD comprise a range of diseases affecting the functionality of the heart and blood vessels, including acute myocardial infarction (AMI) and pulmonary hypertension (PH). Despite their different causative mechanisms, both AMI and PH involve narrowed or blocked blood vessels, hypoxia, and tissue infarction. The endothelium plays a pivotal role in the development of CVD. Disruption of the normal homeostasis of endothelia, alterations in the blood vessel structure, and abnormal functionality are essential factors in the onset and progression of both AMI and PH. An emerging theory proposes that pathological blood vessel responses and endothelial dysfunction develop as a result of an abnormal endothelial metabolism. It has been suggested that, in CVD, endothelial cell metabolism switches to higher glycolysis, rather than oxidative phosphorylation, as the main source of ATP, a process designated as the Warburg effect. The evidence of these alterations suggests that understanding endothelial metabolism and mitochondrial function may be central to unveiling fundamental mechanisms underlying cardiovascular pathogenesis and to identifying novel critical metabolic biomarkers and therapeutic targets. Here, we review the role of the endothelium in the regulation of vascular homeostasis and we detail key aspects of endothelial cell metabolism. We also describe recent findings concerning metabolic endothelial cell alterations in acute myocardial infarction and pulmonary hypertension, their relationship with disease pathogenesis and we discuss the future potential of pharmacological modulation of cellular metabolism in the treatment of cardiopulmonary vascular dysfunction. Although targeting endothelial cell metabolism is still in its infancy, it is a promising strategy to restore normal endothelial functions and thus forestall or revert the development of CVD in personalized multi-hit interventions at the metabolic level.

EXPRESS: Preserving right ventricular function in patients with pulmonary arterial hypertension: single centre experience with a cardiac magnetic resonance imaging-guided treatment strategy

The feasibility and usefulness of routine cardiac magnetic resonance imaging (CMR) in the management of idiopathic pulmonary arterial hypertension (IPAH) is unknown. The aims of the study were: 1) to study whether a decrease in CMR‐derived right ventricular ejection fraction (RVEF) coincides with clinical deterioration; 2) to determine whether RVEF is responsive to early escalation of pulmonary arterial hypertension (PAH)‐specific therapy. This was a prospective study including 30 incident IPAH patients. Patients underwent right heart catheterization and CMR at regular follow‐up visits (baseline, four, eight, 12, 24 months; no right heart catheterization at eight months). New York Heart Association (NYHA) functional class II patients started with monotherapy (endothelin receptor antagonist or phosphodiesterase‐5‐inhibitor) and NYHA III patients with combination therapy (endothelin receptor antagonist plus phosphodiesterase‐5‐inhibitor). In the case of a deterioration in RVEF of more than 3% compared with the previous measurement, PAH‐specific therapy was added (i.e. treatment escalation). In 11 patients without signs of clinical deterioration, a greater than 3% decrease in RVEF occurred. After treatment escalation, RVEF significantly improved (average improvement of 7%, p = 0.009) whereas right ventricle volumes, N‐terminal pro‐brain natriuretic peptide and six‐minute walking distance remained stable. Clinical worsening did not occur after escalating therapy. Throughout the study, four patients presented with clinical worsening, despite a stable RVEF. Three of these four patients had a baseline RVEF <35%. In IPAH patients presenting with an early decrease in RVEF but otherwise stable disease, progressive right ventricle failure and subsequent clinical worsening did not occur when therapy was escalated. Nevertheless, clinical worsening did occur in patients with a low baseline RVEF.

Therapeutic options to treat mustard gas poisoning - Review

Among the blistering (vesicant) chemical warfare agents (CWA), sulfur mustard is the most important since it is known as the "King of chemical warfare agents". The use of sulfur mustard has caused serious damages in several organs, especially the eyes, skin, respiratory, central and peripheral nervous systems after short and long term exposure, incapacitating and even killing people and troops. In this review, chemical properties, mechanism of actions and their effects on each organ, clinical manifestations, diagnostic evaluation of the actions triage, and treatment of injuries have been described.

Characterization and regulation of wild-type and mutant TASK-1 two pore domain potassium channels indicated in pulmonary arterial hypertension

Key points

The TASK‐1 channel gene (KCNK3) has been identified as a possible disease‐causing gene in heritable pulmonary arterial hypertension (PAH).

In the present study, we show that novel mutated TASK‐1 channels, seen in PAH patients, have a substantially reduced current compared to wild‐type TASK‐1 channels.

These mutated TASK‐1 channels are located at the plasma membrane to the same degree as wild‐type TASK‐1 channels.

ONO‐RS‐082 and alkaline pH 8.4 both activate TASK‐1 channels but do not recover current through mutant TASK‐1 channels.

We show that the guanylate cyclase activator, riociguat, a novel treatment for PAH, enhances current through TASK‐1 channels but does not recover current through mutant TASK‐1 channels.

Abstract

Pulmonary arterial hypertension (PAH) affects ∼15–50 people per million. KCNK3, the gene that encodes the two pore domain potassium channel TASK‐1 (K2P3.1), has been identified as a possible disease‐causing gene in heritable PAH. Recently, two new mutations have been identified in KCNK3 in PAH patients: G106R and L214R. The present study aimed to characterize the functional properties and regulation of wild‐type (WT) and mutated TASK‐1 channels and determine how these might contribute to PAH and its treatment. Currents through WT and mutated human TASK‐1 channels transiently expressed in tsA201 cells were measured using whole‐cell patch clamp electrophysiology. Localization of fluorescence‐tagged channels was visualized using confocal microscopy and quantified with in‐cell and on‐cell westerns. G106R or L214R mutated channels were located at the plasma membrane to the same degree as WT channels; however, their current was markedly reduced compared to WT TASK‐1 channels. Functional current through these mutated channels could not be restored using activators of WT TASK‐1 channels (pH 8.4, ONO‐RS‐082). The guanylate cyclase activator, riociguat, enhanced current through WT TASK‐1 channels; however, similar to the other activators investigated, riociguat did not have any effect on current through mutated TASK‐1 channels. Thus, novel mutations in TASK‐1 seen in PAH substantially alter the functional properties of these channels. Current through these channels could not be restored by activators of TASK‐1 channels. Riociguat enhancement of current through TASK‐1 channels could contribute to its therapeutic benefit in the treatment of PAH.

The TASK‐1 channel gene (KCNK3) has been identified as a possible disease‐causing gene in heritable pulmonary arterial hypertension (PAH).

In the present study, we show that novel mutated TASK‐1 channels, seen in PAH patients, have a substantially reduced current compared to wild‐type TASK‐1 channels.

These mutated TASK‐1 channels are located at the plasma membrane to the same degree as wild‐type TASK‐1 channels.

ONO‐RS‐082 and alkaline pH 8.4 both activate TASK‐1 channels but do not recover current through mutant TASK‐1 channels.

We show that the guanylate cyclase activator, riociguat, a novel treatment for PAH, enhances current through TASK‐1 channels but does not recover current through mutant TASK‐1 channels.

Insights on the epigenetic mechanisms underlying pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH), characterized by localized increased arterial blood pressure in the lungs, is a slow developing long-term disease that can be fatal. PAH is characterized by inflammation, vascular tone imbalance, pathological pulmonary vascular remodeling, and right-sided heart failure. Current treatments for PAH are palliative and development of new therapies is necessary. Recent and relevant studies have demonstrated that epigenetic processes may exert key influences on the pathogenesis of PAH and may be promising therapeutic targets in the prevention and/or cure of this condition. The aim of the present mini-review is to summarize the occurrence of epigenetic-based mechanisms in the context of PAH physiopathology, focusing on the roles of DNA methylation, histone post-translational modifications and non-coding RNAs. We also discuss the potential of epigenetic-based therapies for PAH.