Fasudil reduces monocrotaline-induced pulmonary arterial hypertension: comparison with bosentan and sildenafil

Dual ETA-ETB receptor antagonism improves metabolic syndrome-induced heart failure with preserved ejection fraction

BACKGROUND

Metabolic syndrome (MetS) is a multifaceted disease associated with heart failure (HF), which affects the vascular system. The endothelin (ET) system is a key player in MetS and HF; therefore, targets for ET receptors are of therapeutic interest.

OBJECTIVES

This study sought to evaluate the effects of macitentan, a dual endothelin receptor antagonist (ERA), in a rat model of MetS-induced heart failure with preserved ejection fraction (HFpEF).

METHODS

We assessed in 12-week-old Zucker fa/fa rats the effects of macitentan (10 mg/kg/day as a food additive for short-term/7- or long-term/90-day treatment) on right ventricular (RV) and left ventricular (LV) function/remodelling (MRI), RV and LV haemodynamics (catheterization) and RV and LV coronary function (myograph).

RESULTS

After 7- and 90-days, untreated Zucker fa/fa rats presented isolated LV diastolic dysfunction (illustrated by elevated LV end-diastolic pressure [EDP] and LV end-diastolic pressure-volume relationship [EDPVR] without changes in LV EDPVR). This was associated with increased collagen deposition and impaired endothelium-dependent coronary artery relaxation. Macitentan 7- and 90-day treatment significantly decreased blood pressure and prevented LV, RV and coronary dysfunctions and long-term treatment reduced LV collagen density. Moreover, 7- and 90-day macitentan treatment significantly reduced cardiac inflammation and reactive oxygen species (ROS) production.

CONCLUSIONS

Dual ERA macitentan improved both LV and RV diastolic dysfunction. This was associated with improved coronary vasodilation, diminished cardiac oxidative stress and improved blood composition. These results suggest that antagonizing the ET system with macitentan is a promising approach to treat HFpEF and its complications.

Mechanism and Treatment of Right Ventricular Failure Due to Pulmonary Hypertension in Children

Pulmonary hypertension (PH) is a progressive disorder characterized by obstructive changes in the pulmonary vasculature, leading to increased pulmonary vascular resistance (PVR), right ventricular (RV) strain, and eventual RV failure (RVF). Despite advancements in medical therapy, PH remains associated with significant morbidity and mortality, particularly in children. RVF is a clinical syndrome resulting from complex structural and functional remodeling of the right heart, leading to inadequate pulmonary circulation, reduced cardiac output, and elevated venous pressure. Management paradigms for pediatric PH diverge significantly from those in adults, particularly due to the predominance of congenital heart disease (CHD) and the dynamic nature of pediatric cardiovascular and pulmonary development. CHD remains a principal driver of PH in children, and its associated pathophysiology demands a nuanced approach. In patients with unrepaired left-to-right shunts, elevated pulmonary blood flow can lead to progressive pulmonary vascular remodeling and increased PVR. The postoperative persistence or progression of PH may occur if irreversible vascular changes have already developed. Current PH treatments primarily focus on reducing PVR, yet distinguishing between therapeutic approaches that target the pulmonary vasculature and those aimed at improving RV function remain challenging. In pediatric patients with progressive PH despite optimal therapy, additional targeted interventions may be necessary to mitigate RV dysfunction and disease progression. This review provides a comprehensive analysis of the mechanisms underlying RVF in PH, incorporating insights from clinical studies in adults and experimental models, while highlighting the unique considerations in children. Furthermore, it explores current pharmacological and interventional treatment strategies, emphasizing the need for novel therapeutic approaches aimed at directly reversing RV remodeling. Given the complexities of RV adaptation in pediatric PH, further research into disease-modifying treatments and innovative interventions is crucial to improving long-term outcomes in affected children.

Role of Xuefu Zhuyu decoction in improving pulmonary vascular remodeling by inhibiting endothelial-to-mesenchymal transition

BACKGROUND

Pulmonary hypertension (PH) is a serious vascular disease characterized by pulmonary vascular remodeling. Xuefu Zhuyu decoction (XFZYD) can potentially improve pulmonary vascular remodeling; however, its mechanism requires further investigation.

METHODS

Rat models of monocrotaline (MCT)-induced PH and chronic thromboembolic pulmonary hypertension (CTEPH) were employed to investigate whether XFZYD has the potential to improve pulmonary vascular remodeling. After 21 days of XFZYD administration, the right ventricular systolic pressure (RVSP), organ indices, and wall thickness of pulmonary arteries of the rats were measured. Considering the possibility of endothelial-to-mesenchymal transition (EndMT), the specific mechanism of XFZYD in improving pulmonary vascular remodeling was further explored. Immunofluorescence, immunohistochemistry, and western blotting were used to detect the expression of EndMT markers, transforming growth factor-β1 (TGF-β1)/Smad pathway-related proteins, hypoxia-inducible factor-1α (HIF-1α), and levels of reactive oxygen species (ROS) in the lung tissues.

RESULTS

XFZYD demonstrated significant efficacy in treating PH, as evidenced by its effects in both the rat models of MCT-induced PH and CTEPH. XFZYD remarkably improved pulmonary vascular remodeling while reducing RVSP and right ventricular hypertrophy. XFZYD has the potential to improve pulmonary vascular remodeling by inhibiting EndMT in the pulmonary vasculature. The underlying mechanism may be closely associated with the inhibition of TGF-β1/Smad and HIF-1α signaling pathways and the reduction of ROS levels in lung tissue by XFZYD.

CONCLUSION

This study indicates that XFZYD may inhibit EndMT by modulating the ROS/HIF-1α/TGF-β1 signaling pathway, thereby improving pulmonary vascular remodeling. These findings provide a theoretical foundation for the clinical application of XFZYD in PH.

Searching for Old and New Small-Molecule Protein Kinase Inhibitors as Effective Treatments in Pulmonary Hypertension-A Systematic Review

Treatment options for pulmonary arterial hypertension (PAH) have improved substantially in the last 30 years, but there is still a need for novel molecules that can regulate the excessive accumulation of pulmonary artery smooth muscle cells (PASMCs) and consequent vascular remodeling. One set of possible candidates are protein kinases. The study provides an overview of existing preclinical and clinical data regarding small-molecule protein kinase inhibitors in PAH. Online databases were searched from 2001 to 2023 according to PRISMA. The corpus included preclinical studies demonstrating alterations in at least one PH-related parameter following chronic exposure to an individual protein kinase inhibitor, as well as prospective clinical reports including healthy adults or those with PAH, with primary outcomes defined as safety or efficacy of an individual small-molecule protein kinase inhibitor. Several models in preclinical protocols (93 papers) have been proposed for studying small-molecule protein kinase inhibitors in PAH. In total, 51 kinase inhibitors were tested. Meta-analysis of preclinical results demonstrated seralutinib, sorafenib, fasudil hydrochloride, and imatinib had the most comprehensive effects on PH with anti-inflammatory, anti-oxidant, and anti-proliferative potential. Fasudil demonstrated more than 70% animal survival with the longest experimental period, while dasatinib, nintedanib, and (R)-crizotinib could deteriorate PAH. The substances targeting the same kinases often varied considerably in their activity, and such heterogeneity may be due to the variety of causes. Recent studies have addressed the molecules that affect multiple networks such as PDG-FRα/β/CSF1R/c-KIT/BMPR2 or FKBP12/mTOR. They also focus on achieving a satisfactory safety profile using innovative inhalation formulations Many small-molecule protein kinase inhibitors are able to control migration, proliferation and survival in PASMCs in preclinical observations. Standardized animal models can successfully reduce inter-study heterogeneity and thereby facilitate successful identification of candidate drugs for further evaluations.

Effect of fasudil on clinical outcomes of pulmonary hypertension: a systematic review and meta-analysis

BACKGROUND

Pulmonary hypertension (PH) is a life-threatening condition with high mortality, categorized into Group 1-5 by distinct etiologies. Fasudil, a potent vasodilator targeting RhoA/Rho kinase pathway, holds promise for diverse PH pathologies. However, a systematic evaluation of its clinical benefits remains elusive.

METHODS

We conducted a systematic search in several databases. Meta-analysis using odds ratio and mean difference was performed, with an assessment of studies' quality and pooled evidences.

RESULTS

Inclusion of 3269 Group-3 PH patients demonstrated that Fasudil increased effective events, forced expiratory volume in one second (FEV1), 6-minute walking distance (6MWD) and arterial partial pressure of oxygen (PaO2), and decreased mean pulmonary artery pressure (mPAP) and pulmonary artery systolic pressure (PASP); Inclusion of 197 Group-2 PH patients suggested that Fasudil increased 6MWD and PaO2, and decreased PASP. Subgroup analysis revealed no significant difference between 30 and 60 mg/day dosages of Fasudil, while administration durations and methods might affect its effectiveness in treating Group-3 PH patients.

CONCLUSIONS

Our study favors the beneficial effects of Fasudil by enhancing FEV1, 6MWD and PaO2, and reducing mPAP and PASP on Group-3 PH patients, suggesting Fasudil as a viable treatment option and highlighting the need for further studies to inform healthcare policies.

PROTOCOL REGISTRATION

www.crd.york.ac.uk/prospero identifier is CRD42022308947.

Pulmonary arterial hypertension nanotherapeutics: New pharmacological targets and drug delivery strategies

Pulmonary arterial hypertension (PAH) is a rare, serious, and incurable disease characterized by high lung pressure. PAH-approved drugs based on conventional pathways are still not exhibiting favorable therapeutic outcomes. Drawbacks like short half-lives, toxicity, and teratogenicity hamper effectiveness, clinical conventionality, and long-term safety. Hence, approaches like repurposing drugs targeting various and new pharmacological cascades and/or loaded in non-toxic/efficient nanocarrier systems are being investigated lately. This review summarizes the status of conventional, repurposed, either in vitro, in vivo, and/or in clinical trials of PAH treatment. In-depth description, discussion, and classification of the new pharmacological targets and nanomedicine strategies with a description of all the nanocarriers that showed promising efficiency in delivering drugs are discussed. Ultimately, an illustration of the different nucleic acids tailored and nanoencapsulated within different types of nanocarriers to restore the pathways affected by this disease is presented.

Development of novel bosentan analogues as endothelin receptor antagonists for pulmonary arterial hypertension

Since decades, bosentan has been in use for the treatment of pulmonary arterial hypertension (PAH). However, chronic exposure to bosentan leads to the development of resistance, tolerance, and serious adverse effects that have restricted its usage in clinical practices. To surmount these limitations, some new bosentan derivatives have been synthesized and evaluated for their therapeutic efficacy in PAH. Molecular docking analyses of all the synthesized derivatives were carried out using the endothelin (ET) receptor. In addition, the inhibitory ability of synthesized derivatives was determined in in vitro assay employing an ET-1 human ELISA kit. Among the synthesized derivatives, three derivatives namely 17d, 16j, and 16h with higher docking scores and lower IC50 values were selected for determination of the magnitude of the binding force between the derivative and ET receptor using molecular dynamics (MD) simulations study. Further, these derivatives were subjected to in vivo studies using monocrotaline (MCT) induced PAH in rat model. Results of in vivo studies inferred that the derivatives exhibit impressive ability to reduce PAH. Besides, its protective role was also evidenced in hemodynamic and right ventricular hypertrophy analyses, histological analysis, cardiac biomarkers, hypoxia-inducible factor 1 alpha (HIF1α) levels, and biochemical studies. Furthermore, gene quantification by quantitative RT-PCR and Western blot analysis was also performed to examine its effect on the expression of key proteins in PAH. Notably, amongst three, derivative 16h exhibited the most encouraging results in molecular docking analysis, in vitro, in vivo, histopathological, biochemical, protein expression, and MD studies. Besides, derivative 16h also showed impressive pharmacokinetic features in ADMET analysis. In conclusion, derivative 16 h could act as a reliable ET receptor antagonist and requires further exploration to attain its therapeutic utility in PAH management.

T18/S19 diphosphorylation of myosin regulatory light chain impairs pulmonary artery relaxation in monocrotaline-induced pulmonary hypertensive rats

Phosphorylation of Ser19 (S19-p) on the myosin regulatory light chain (MLC2) is critical for arterial contraction. It has been shown that elevated RhoA-dependent kinase (ROCK) activity or decreased MLC phosphatase (MLCP) activity leads to further phosphorylation of Thr18 (T18/S19-pp), which has been linked to vasospastic diseases. However, this phenomenon has not yet been studied in the context of pulmonary arterial hypertension (PAH). In the monocrotaline-induced PAH (PAH-MCT) rat model, we observed a significant delay in pulmonary artery (PA) relaxation following high potassium-induced contraction, which persisted even with the use of an L-type calcium channel blocker or in a calcium-free solution. Immunoblot analysis showed increased levels of both S19-p and T18/S19-pp in unstimulated PAs from PAH-MCT rats. Proteomics analysis revealed a reduction in soluble guanylate cyclase (sGC) and protein kinase G (PKG) levels, and immunoblotting confirmed decreased levels of MYPT1 (a component of MLCP) and increased ROCK in PAH-MCT. In the control PAs, the pharmacological inhibition of sGC with ODQ resulted in a prominent delay of relaxation and increased T18/S19-pp as in PAH-MCT. The delayed relaxation and the T18/S19-pp in PAH-MCT were reversed by ROCK inhibitor, Y27632, while not by membrane permeable 8-Br-cGMP. The delayed relaxation and T18/S19-diP in the ODQ-treated control PA were also reversed by Y27632. Taken together, the decreased sGC and MLCP, and increased ROCK increased T18/S19-pp, which leads to the decreased ability of PA to relax in PAH-MCT rats. PA specific inhibition of ROCK or activation of MLCP are expected to serve as potential drugs in the treatment of PAH.

Stable Gastric Pentadecapeptide BPC 157 as Useful Cytoprotective Peptide Therapy in the Heart Disturbances, Myocardial Infarction, Heart Failure, Pulmonary Hypertension, Arrhythmias, and Thrombosis Presentation

In heart disturbances, stable gastric pentadecapeptide BPC 157 especial therapy effects combine the therapy of myocardial infarction, heart failure, pulmonary hypertension arrhythmias, and thrombosis prevention and reversal. The shared therapy effect occurred as part of its even larger cytoprotection (cardioprotection) therapy effect (direct epithelial cell protection; direct endothelium cell protection) that BPC 157 exerts as a novel cytoprotection mediator, which is native and stable in human gastric juice, as well as easily applicable. Accordingly, there is interaction with many molecular pathways, combining maintained endothelium function and maintained thrombocytes function, which counteracted thrombocytopenia in rats that underwent major vessel occlusion and deep vein thrombosis and counteracted thrombosis in all vascular studies; the coagulation pathways were not affected. These appeared as having modulatory effects on NO-system (NO-release, NOS-inhibition, NO-over-stimulation all affected), controlling vasomotor tone and the activation of the Src-Caveolin-1-eNOS pathway and modulatory effects on the prostaglandins system (BPC 157 counteracted NSAIDs toxicity, counteracted bleeding, thrombocytopenia, and in particular, leaky gut syndrome). As an essential novelty noted in the vascular studies, there was the activation of the collateral pathways. This might be the upgrading of the minor vessel to take over the function of the disabled major vessel, competing with and counteracting the Virchow triad circumstances devastatingly present, making possible the recruitment of collateral blood vessels, compensating vessel occlusion and reestablishing the blood flow or bypassing the occluded or ruptured vessel. As a part of the counteraction of the severe vessel and multiorgan failure syndrome, counteracted were the brain, lung, liver, kidney, gastrointestinal lesions, and in particular, the counteraction of the heart arrhythmias and infarction.

Early diagnosis and targeted approaches to pulmonary vascular disease in bronchopulmonary dysplasia

Pulmonary hypertension has emerged as a life-threatening disease in preterm infants suffering from bronchopulmonary dysplasia (BPD). Its development is closely linked to respiratory disease, as vasculogenesis and alveologenesis are closely interconnected. Once clinically significant, BPD-associated pulmonary hypertension (BPD-PH) can be challenging to manage, due to poor reversibility and multiple comorbidities frequently associated. The pulmonary vascular disease process underlying BPD-PH is the result of multiple innate and acquired factors, and emerging evidence suggests that it progressively develops since birth and, in certain instances, may begin as early as fetal life. Therefore, early recognition and intervention are of great importance in order to improve long-term outcomes. Based on the most recent knowledge of BPD-PH pathophysiology, we review state-of-the-art screening and diagnostic imaging techniques currently available, their utility for clinicians, and their applicability and limitations in this specific population. We also discuss some biochemical markers studied in humans as a possible complement to imaging for the detection of pulmonary vascular disease at its early stages and the monitoring of its progression. In the second part, we review pharmacological agents currently available for BPD-PH treatment or under preclinical investigation, and discuss their applicability, as well as possible approaches for early-stage interventions in fetuses and neonates. IMPACT: BPD-associated PH is a complex disease involving genetic and epigenetic factors, as well as environmental exposures starting from fetal life. The value of combining multiple imaging and biochemical biomarkers is emerging, but requires larger, multicenter studies for validation and diffusion. Since "single-bullet" approaches have proven elusive so far, combined pharmacological regimen and cell-based therapies may represent important avenues for research leading to future cure and prevention.

Stable Gastric Pentadecapeptide BPC 157 Therapy for Monocrotaline-Induced Pulmonary Hypertension in Rats Leads to Prevention and Reversal

Background. Monocrotaline selectively injures the lung's vascular endothelium and induces pulmonary arterial hypertension. The stable gastric pentadecapeptide BPC 157 acts as a prototype cytoprotective agent that maintains endothelium, and its application may be a novel therapy. Besides, BPC 157 prevents and reverses thrombosis formation, maintains platelet function, alleviates peripheral vascular occlusion disturbances, and has anti-arrhythmic and anti-inflammatory effects. Monocrotaline-induced pulmonary arterial hypertension in rats (wall thickness, total vessel area, heart frequency, QRS axis deviation, QT interval prolongation, increase in right ventricle systolic pressure and bodyweight loss) can be counteracted with early or delayed BPC 157 therapy. Methods and Results. After monocrotaline (80 mg/kg subcutaneously), BPC 157 (10 μg/kg or 10 ng/kg, days 1-14 or days 1-30 (early regimens), or days 14-30 (delayed regimen)) was given once daily intraperitoneally (last application 24 h before sacrifice) or continuously in drinking water until sacrifice (day 14 or 30). Without therapy, the outcome was the full monocrotaline syndrome, marked by right-side heart hypertrophy and massive thickening of the precapillary artery's smooth muscle layer, clinical deterioration, and sometimes death due to pulmonary hypertension and right-heart failure during the 4th week after monocrotaline injection. With all BPC 157 regimens, monocrotaline-induced pulmonary arterial hypertension (including all disturbed parameters) was counteracted, and consistent beneficial effects were documented during the whole course of the disease. Pulmonary hypertension was not even developed (early regimens) as quickly as the advanced pulmonary hypertension was rapidly attenuated and then completely eliminated (delayed regimen). Conclusions. Thus, pentadecapeptide BPC 157 prevents and counteracts monocrotaline-induced pulmonary arterial hypertension and cor pulmonale in rats.

Promising therapeutic approaches in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a debilitating multifactorial disease characterized by progressive pulmonary vascular remodeling, elevated pulmonary arterial pressure, and pulmonary vascular resistance, resulting in right ventricular failure and subsequent death. Current available therapies do not reverse the disease, resulting in a persistent high morbidity and mortality. Thus, there is an urgent unmet medical need for novel effective therapies to better treat patients with PAH. Over the past few years, enthusiastic attempts have been made to identify novel effective therapies that address the essential roots of PAH with targeting key signaling pathways in both preclinical models and patients with PAH. This review aims to discuss the most emerging and promising therapeutic interventions in PAH pathogenesis.

ROCK Inhibition as Potential Target for Treatment of Pulmonary Hypertension

Pulmonary hypertension (PH) is a cardiovascular disease caused by extensive vascular remodeling in the lungs, which ultimately leads to death in consequence of right ventricle (RV) failure. While current drugs for PH therapy address the sustained vasoconstriction, no agent effectively targets vascular cell proliferation and tissue inflammation. Rho-associated protein kinases (ROCKs) emerged in the last few decades as promising targets for PH therapy, since ROCK inhibitors demonstrated significant anti-remodeling and anti-inflammatory effects. In this review, current aspects of ROCK inhibition therapy are discussed in relation to the treatment of PH and RV dysfunction, from cell biology to preclinical and clinical studies.

Additive protective effects of sacubitril/valsartan and bosentan on vascular remodelling in experimental pulmonary hypertension

AIMS

Although right ventricular (RV) function is an important determinant of morbidity and mortality in patients with pulmonary arterial hypertension (PAH), there is no treatment targeting directly the RV. We evaluate the efficacy of sacubitril/valsartan (LCZ 696) as add-on therapy to bosentan in rats with severe pulmonary hypertension (PH).

METHODS AND RESULTS

Combination therapy of LCZ 696 and bosentan has additive vascular protective effects against the pulmonary vascular remodelling and PH in two preclinical models of severe PH. Compared with monotherapy, co-treatment of LCZ 696 (30 or 68 mg/kg/day for 2 weeks, per os) and bosentan (100 mg/kg/day for 2 weeks, per os) started 7 days after monocrotaline (MCT) injection substantially reduces pulmonary pressures, vascular remodelling, and RV hypertrophy and fibrosis in rats. Consistent with these observations, co-treatment of rats with established PH induced by sugen/hypoxia (SuHx) with LCZ 696 (30 mg/kg/day for 3 weeks, per os) and bosentan (100 mg/kg/day for 3 weeks, per os) started 5 weeks after Sugen injection partially attenuate total pulmonary vascular resistance and cardiovascular structures. We also obtained evidence showing that LCZ 696 has anti-proliferative effect on cultured human pulmonary artery smooth muscle cells derived from patients with idiopathic PAH, an effect that is more pronounced in presence of bosentan. Finally, we found that the plasma levels of atrial natriuretic peptide (ANP) and cyclic guanosine monophosphate (cGMP) are higher in rats co-treated with LCZ 696 (30 mg/kg/day) and bosentan (100 mg/kg/day) than in MCT and SuHx rats treated with vehicle.

CONCLUSION

Dual therapy with LCZ 696 plus bosentan proved significantly superior beneficial effect to LCZ 696 or bosentan alone on vascular remodelling and severity of experimental PH.

Fasudil Dichloroacetate Alleviates SU5416/Hypoxia-Induced Pulmonary Arterial Hypertension by Ameliorating Dysfunction of Pulmonary Arterial Smooth Muscle Cells

Background

Pulmonary arterial hypertension (PAH) is an incurable disease that urgently needs therapeutic approaches. Based on the therapeutic effects of fasudil and dichloroacetate (DCA) on PAH, we aimed to explore the effects and potential mechanism of a new salt, fasudil dichloroacetate (FDCA), in a SU5416 plus hypoxia (SuHx)-induced rat model of PAH.

Methods

The rat model of PAH was established by a single subcutaneous injection of SU5416 (20 mg/kg) followed by hypoxia (10% O₂) exposure for 3 weeks. FDCA (15, 45, or 135 mg/kg i.g. daily) or the positive control, bosentan (100 mg/kg i.g. daily), were administered from the first day after SU5416 injection. After 3-week hypoxia, hemodynamic parameters, and histological changes of the pulmonary arterial vessels and right ventricle (RV) were assessed. Additionally, in vitro, the effects of FDCA (50 μM), compared with equimolar doses of fasudil, DCA, or fasudil+DCA, on the proliferation, migration, and contraction of human pulmonary arterial smooth muscle cell (PASMC) under hypoxia (1% O₂) were evaluated.

Results

FDCA dose-dependently attenuated SuHx-induced PAH, with significant reductions in RV systolic pressure, pulmonary artery wall thickness, pulmonary vessel muscularization, perivascular fibrosis, as well as RV hypertrophy and fibrosis. In vitro, FDCA inhibited hypoxia-induced PASMC proliferation, migration, and contraction to a greater degree than fasudil or DCA alone by restoring mitochondrial function, reducing intracellular Ca²⁺, and inhibiting calcium/calmodulin-dependent kinase (Ca²⁺/CaMK) activity as well as Rho-kinase activity.

Conclusion

FDCA ameliorates hypoxia-induced PASMC dysfunction by inhibiting both Ca²⁺/CaMK and Rho-kinase signaling pathways, as well as maintaining mitochondrial homeostasis, thus alleviating SuHx-induced PAH.

Concealed role of red blood cells in pathogenesis of pulmonary arterial hypertension: Decreased red blood cell nitric oxide generation and effect of Rho-Kinase inhibitor fasudil

BACKGROUND

Pulmonary arterial hypertension (PAH) is a devastating disease characterized with alterations in pulmonary vasculature yielding increased pulmonary arterial resistance. Emerging evidences suggest important regulatory roles of red blood cells (RBCs) on nitric oxide (NO) bioavailability, mainly by modulating their endothelial nitric oxide synthase (eNOS) enzyme activity.

OBJECTIVE

The aim of this pilot study was to evaluate the alterations in RBC eNOS activity and intracellular NO generation in PAH patients and the modulatory effects of Rho-Kinase (ROCK) inhibitors.

METHODS

RBCs were isolated from patients with PAH and age-matched healthy subjects and were analyzed for their eNOS activity and NO generation capacity under the conditions of the presence or absence of ROCK inhibitor, fasudil. Phosphotidylserine (PS) exposure was also defined.

RESULTS

eNOS activity and intracellular NO generation were lower in RBC from PAH patients. ROCK inhibitor increased basal eNOS activity and improved NO generation capacity of RBC of PAH patients to healthy control levels. PS exposure levels were also higher in RBC of PAH patients.

CONCLUSIONS

This study provides first evidences for decreased RBC eNOS activity due to its ROCK mediated negative regulation in PAH patients. Considering increased ROCK activity contribution to progression of PAH, ROCK inhibition influences NO bioavailability through RBC eNOS, in addition to endothelial eNOS.

Targeted Drugs for Treatment of Pulmonary Arterial Hypertension: Past, Present, and Future Perspectives

Pulmonary arterial hypertension (PAH) is a devastating disease that can lead to right ventricular failure and premature death. Although approved drugs have been shown to be safe and effective, PAH remains a severe clinical condition, and the long-term survival of patients with PAH is still suboptimal. Thus, potential therapeutic targets and new agents to treat PAH are urgently needed. In recent years, a variety of related pathways and potential therapeutic targets have been found, which brings new hope for PAH therapy. In this perspective, not only are the marketed drugs used to treat PAH summarized but also the recently developed novel pharmaceutical therapies currently in clinical trials are discussed. Furthermore, the advances in natural products as potential treatment for PAH are also updated.

Pulmonary-arterial-hypertension (PAH)-on-a-chip: fabrication, validation and application

Currently used animal and cellular models for pulmonary arterial hypertension (PAH) only partially recapitulate its pathophysiology in humans and are thus inadequate in reproducing the hallmarks of the disease, inconsistent in portraying the sex-disparity, and unyielding to combinatorial study designs. Here we sought to deploy the ingenuity of microengineering in developing and validating a tissue chip model for human PAH. We designed and fabricated a microfluidic device to emulate the luminal, intimal, medial, adventitial, and perivascular layers of a pulmonary artery. By growing three types of pulmonary arterial cells (PACs)-endothelial, smooth muscle, and adventitial cells, we recreated the PAH pathophysiology on the device. Diseased (PAH) PACs, when grown on the chips, moved of out their designated layers and created phenomena similar to the major pathologies of human PAH: intimal thickening, muscularization, and arterial remodeling and show an endothelial to mesenchymal transition. Flow-induced stress caused control cells, grown on the chips, to undergo morphological changes and elicit arterial remodeling. Our data also suggest that the newly developed chips can be used to elucidate the sex disparity in PAH and to study the therapeutic efficacy of existing and investigational anti-PAH drugs. We believe this miniaturized device can be deployed for testing various prevailing and new hypotheses regarding the pathobiology and drug therapy in human PAH.

Monocrotaline-induced pulmonary arterial hypertension: Time-course of injury and comparative evaluation of macitentan and Y-27632, a Rho kinase inhibitor

Novel pharmacological approaches are needed to improve outcomes of patients with idiopathic pulmonary hypertension. Rho-associated protein kinase (ROCK) inhibitors have shown beneficial effects in preclinical models of pulmonary arterial hypertension (PAH), because of their role in the regulation of pulmonary artery vasoconstrictor tone and remodeling. We compared a ROCK inhibitor, Y-27632, for the first time with the dual endothelin receptor antagonist, macitentan, in a monocrotaline-induced rat pulmonary hypertension model. Different methods (echocardiography, hemodynamics, histology of right ventricle and pulmonary vessels, and circulating biomarkers) showed consistently that 100 mg/kg daily of Y-27632 and 10 mg/kg daily of macitentan slowed the progression of PAH both at the functional and structural levels. Treatments started on day 14 after monocrotaline injection and lasted 14 days. The findings of all experimental methods show that the selective ROCK inhibitor Y-27632 has more pronounced effects than macitentan, but a major limitation to its use is its marked peripheral vasodilating action.

Quantification of regional right ventricular strain in healthy rats using 3D spiral cine dense MRI

Statistical data from clinical studies suggests that right ventricular (RV) circumferential strain (Ecc) and longitudinal strain (Ell) are significant biomarkers for many cardiovascular diseases. However, a detailed and regional characterization of these strains in the RV is very limited. In the current study, RV images were obtained with 3D spiral cine DENSE MRI in healthy rats. An algorithm for surface growing was proposed in order to fit irregular topology. Specifically, a new custom plugin for the DENSEanalysis program, called 3D DENSE Plugin for Crescent Organ, was developed for surface reconstruction and precise segmentation of organs with sharp curvature, such as the murine RV. The RV free wall (RVFW) was divided into three longitudinal thirds (i.e., basal, middle, and apical) with each one partitioned into circumferential fourths (i.e., anterior, anteriorlateral, inferiorlateral and inferior). Peak systolic strains were quantified for each segment and comparisons were performed statistically. The inclusion of a new plugin was able to generate global values for Ecc and Ell that are in good agreement with previous findings using MRI. Despite no regional variation found in the peak Ecc, the peak Ell exhibited regional variation at the anterior side of the RV, which is potentially due to differences in biventricular torsion at the RV insertion point and fiber architecture. These results provide fundamental insights into the regional contractile function of the RV in healthy rat and could act as a normative baseline for future studies on regional changes induced by disease or treatment.

Novel Therapeutic Approaches of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is an uncommon disease characterized progressive remodeling of pulmonary vasculature. Although treatment for PAH have improved in last two decades but the outcome remains fatal. Currently, the therapies for PAH target three well-established pathways the nitric oxide (NO) pathway, endothelin receptors, and prostanoids. There are multiple potential targets for development of newer drugs in PAH which requires meticulous research and clinical trials.

Rho kinase and Na+ /H+ exchanger mediate endothelin-1-induced pulmonary arterial smooth muscle cell proliferation and migration

Excessive production of endothelin‐1 (ET‐1) has been observed in almost all forms of pulmonary hypertension. ET‐1, a highly potent vasoconstrictor, can also potentiate pulmonary arterial smooth muscle cell (PASMC) growth and migration, both of which contribute to the vascular remodeling that occurs during the development of pulmonary hypertension. Increasing evidence indicates that alkalinization of intracellular pH (pH_i), typically due to activation of Na⁺/H⁺ exchange (NHE), is associated with enhanced PASMC proliferation and migration. We recently demonstrated that application of exogenous ET‐1 increased NHE activity in murine PASMCs via a mechanism requiring Rho kinase (ROCK). However, whether ROCK and/or increased NHE activity mediate ET‐1‐induced migration and proliferation in PASMCs remains unknown. In this study, we used fluorescent microscopy in transiently cultured PASMCs from distal pulmonary arteries of the rat and the pH‐sensitive dye, BCECF‐AM, to measure changes in resting pH_i and NHE activity induced by exposure to exogenous ET‐1 (10⁻⁸ mol/L) for 24 h. Cell migration and proliferation in response to ET‐1 were also measured using Transwell assays and BrdU incorporation, respectively. We found that application of exogenous ET‐1 had no effect on NHE1 expression, but increased pH_i, NHE activity, migration, and proliferation in rat PASMCs. Pharmacologic inhibition of NHE or ROCK prevented the ET‐1‐induced changes in cell function (proliferation and migration). Our results indicate that ET‐1 modulates PASMC migration and proliferation via changes in pH_i homeostasis through a pathway involving ROCK.

Pharmacological characterization of a highly selective Rho kinase (ROCK) inhibitor and its therapeutic effects in experimental pulmonary hypertension

Studies on the role of Rho-associated protein kinase (ROCK) in experimental pulmonary artery hypertension (PAH) relies mainly on the use of pharmacological inhibitors. However, interpreting these data is hampered by the lack of specificity of commonly utilized inhibitors. To fill this gap, we have selected and characterized a novel ROCK inhibitor, Compound 3, previously described in a patent. Inhibitory potency of Compound 3 against enzymatic activity of ROCK-1 and 2 (IC₅₀ = 10 ± 3.1 and 7.8 ± 0.5 nM, respectively) was accompanied by a strong vasodilating effect in phenylephrine pre-contracted isolated rat pulmonary artery rings (IC₅₀ = 51.7 ± 9.1 nM) as well as in aortic rings (IC₅₀ = 45.5 ± 1.1 nM). Compound 3 showed a remarkable selectivity towards ROCK 1 and 2 when tested against a large panel (>400) of human kinases. A partial explanation for its selectivity is provided from docking simulations within ROCK-1. Pharmacokinetic studies showed that Compound 3 is suitable for a twice daily administration without significant accumulation upon repeated dosing. In rats with monocrotaline (MCT)-induced pulmonary hypertension, therapy with Compound 3, (1 and 3 mg/kg, s.c., b.i.d.), started 14 days after induction of the disease, attenuated right ventricle systolic pressure (RVSP) increase. Morphometric histological analysis showed that Compound 3, at both doses, counteracted MCT-induced medial thickening of lung distal arterioles with an effect comparable to macitentan (10 mg/kg, p.o., q.d.). Compound 3 is a potent and highly selective ROCK inhibitor that ameliorates hemodynamic parameters and counteracts pulmonary vascular remodeling in experimental PAH.

Fasudil preserves lung endothelial function and reduces pulmonary vascular remodeling in a rat model of end‑stage pulmonary hypertension with left heart disease

Pulmonary hypertension (PH) due to left heart disease (LHD) is a common condition associated with significant morbidity. It contributes to the elevation of pulmonary vascular resistance and mean pulmonary pressure, eventually leading to heart failure and even mortality. The present study aimed to explore the potential efficacy of late and long‑term treatment with a Rho‑kinase (ROCK) signaling inhibitor, namely fasudil, in a rat model of end‑stage PH‑LHD. The PH‑LHD model was established by supracoronary aortic banding, and the effect of fasudil treatment on the progression of PH‑LHD was monitored. After 9 weeks (63 days) of supracoronary aortic banding, a significant increase in mean pulmonary pressure and RV systolic pressure was observed in the rats, associated with increased RhoA/ROCK activity in the lungs. Therapy with fasudil (30 mg/kg/day, intraperitoneal) for 4 weeks from postoperative day 35 reversed the hemodynamic disorder and prevented pulmonary vascular remodeling in rats with PH‑LHD. In addition, the blockade of ROCK signaling by fasudil decreased the protein levels of endothelin‑1 (ET‑1) and the mRNA expression levels of endothelin A receptor and promoted the production of nitric oxide (NO) in rats with PH‑LHD. Furthermore, fasudil inhibited the migration of human pulmonary microvascular endothelial cells and the proliferation of pulmonary artery smooth muscle cells induced by ET‑1. Therefore, this late, long‑term blockade of the ROCK pathway by fasudil may be a promising strategy to reverse hemodynamic dysfunction and impede the development of end‑stage PH‑LHD in patients.

Medical therapies for pulmonary arterial hypertension

Pulmonary Arterial hypertension (PAH) is a chronic and progressive disease characterized by an increase in pulmonary vascular resistance due to severe remodeling of the small pulmonary arteries. In PAH, the endothelial cells fail to maintain their homeostatic balance, with the consequent impaired production of vasodilators and over-expression of vasoconstrictors and proliferators. Current treatment of PAH is based on the discovery of three main pathways of endothelial dysfunction (prostacyclin, nitric oxide and endothelin-1), and includes drugs such as prostacyclin analogs, phosphodiesterase-5 inhibitors and endothelin receptor antagonists (ERAs). Recently approved drugs that act through these classic pathways include riociguat (cyclic GMP stimulator) and macitentan (a tissue specific dual ERA). However, several new drugs and new pathways are under study. New targeted therapies include tyrosine kinase inhibitors, Rho kinase inhibitors and serotonin receptor blockers. There are now ten drugs approved for the treatment of PAH that, alone or in combination, have changed the natural history of this disease. The new drugs will allow us to further modified the patients' life expectancy and move towards a cure.

Adenosine Receptors As Drug Targets for Treatment of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a clinical condition characterized by pulmonary arterial remodeling and vasoconstriction, which promote chronic vessel obstruction and elevation of pulmonary vascular resistance. Long-term right ventricular (RV) overload leads to RV dysfunction and failure, which are the main determinants of life expectancy in PAH subjects. Therapeutic options for PAH remain limited, despite the introduction of prostacyclin analogs, endothelin receptor antagonists, phosphodiesterase type 5 inhibitors, and soluble guanylyl cyclase stimulators within the last 15 years. Through addressing the pulmonary endothelial and smooth muscle cell dysfunctions associated with PAH, these interventions delay disease progression but do not offer a cure. Emerging approaches to improve treatment efficacy have focused on beneficial actions to both the pulmonary vasculature and myocardium, and several new targets have been investigated and validated in experimental PAH models. Herein, we review the effects of adenosine and adenosine receptors (A₁, A_2A, A_2B, and A₃) on the cardiovascular system, focusing on the A_2A receptor as a pharmacological target. This receptor induces pulmonary vascular and heart protection in experimental models, specifically models of PAH. Targeting the A_2A receptor could potentially serve as a novel and efficient approach for treating PAH and concomitant RV failure. A_2A receptor activation induces pulmonary endothelial nitric oxide synthesis, smooth muscle cell hyperpolarization, and vasodilation, with important antiproliferative activities through the inhibition of collagen deposition and vessel wall remodeling in the pulmonary arterioles. The pleiotropic potential of A_2A receptor activation is highlighted by its additional expression in the heart tissue, where it participates in the regulation of intracellular calcium handling and maintenance of heart chamber structure and function. In this way, the activation of A_2A receptor could prevent the production of a hypertrophic and dysfunctional phenotype in animal models of cardiovascular diseases.

Regulation of Pulmonary Vascular Smooth Muscle Contractility in Pulmonary Arterial Hypertension: Implications for Therapy

There are two primary components that produce pulmonary arterial hypertension (PAH); aberrant structural changes (smooth muscle cell proliferation, smooth muscle cell hypertrophy, and the deposition of matrix proteins within the media of pulmonary arterial vessels), and excess vasoconstriction. However, in PAH, the target and aim of all current therapeutic agents is to reduce the contractility of the pulmonary vasculature; prostaglandins, phosphodiesterase inhibitors, guanylate cyclase stimulators, endothelin antagonists, NO inhalation and Rho kinase inhibitors all influence signaling pathways in the pulmonary vascular smooth muscle to decrease vasoconstriction, and hence, pulmonary vascular resistance (PVR). This review will therefore primarily focus on discussing the signaling pathways regulating contractility in pulmonary vascular smooth muscle, the mechanism for current treatments, as well as highlighting potential targets for the development of novel therapies.

Effects of fasudil on pulmonary hypertension in clinical practice

Pulmonary hypertension (PH) is a pathophysiologic disorder that may involve multiple clinical conditions and can complicate the majority of cardiovascular and respiratory diseases. The presence of PH is associated with worse outcomes, but the efficacy of current therapy is still unsatisfactory. Because Rho-kinase (ROCK) plays an important role in the pathogenesis of PH, the ROCK inhibitor fasudil is expected to contribute to PH treatment. In animal models of PH, fasudil reduced pulmonary artery pressure (PAP) and improved survival. Furthermore, the short-term efficacy and safety of fasudil in the treatment of PH are demonstrated in clinical trials. Both PAP and pulmonary vascular resistance in patients with PH are significantly decreased by intravenous or inhaled fasudil without apparent side effect. However, no clinical trial has assessed the long-term efficacy of fasudil in the treatment of PH. Limited data suggest that the mid-term use of fasudil could improve exercise capacity and reduce in-hospital mortality. We also discuss the combined use of fasudil and other drugs for PH treatment. However, these combinations have not yet been evaluated in a clinical trial. According to animal studies, the combination of fasudil with beraprost or sildenafil shows synergistic effects, whereas the combination of fasudil with bosentan has no additional ameliorating effects on PH development.

Statins ameliorate pulmonary hypertension secondary to left ventricular dysfunction through the Rho-kinase pathway and NADPH oxidase

BACKGROUND

Pulmonary hypertension (PH) is a devastating disorder, for which no therapy is curative. It has been reported that pulmonary vascular remodeling, associated with increasing mean pulmonary arterial pressure and upregulated expression of endothelial nitric oxide synthase (eNOS), endothelin-1 (ET-1), RhoA/RhoH-kinase results in the development of PH. Oxidative stress and the RhoA/Rho-kinase pathway are also thought to be involved in the pathophysiology of PH. Statins are 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (HMG-CoA reductase inhibitors) with pleiotropic effects and are potential agents for the treatment of PH. In this study, we investigated the beneficial effects of simvastatin on the development of PH secondary to left ventricular dysfunction.

METHODS

A PH secondary to left ventricular dysfunction model was established in 6-week-old aortic-banded rats. The pulmonary expression of Rho kinase, ET-1, eNOS, p-eNOS, nitrite/nitrate (NOx), cGMP, p47^Phox , and p67^Phox were investigated in the early-treatment group, to which was administered simvastatin (30 mg/kg/day) from days 1 to 42 or the late-treatment group, to which was administered simvastatin (30 mg/kg/day) from days 29 to 42.

RESULTS

Simvastatin attenuated the mean pulmonary artery pressure, pulmonary arteriolar remodeling, plasma brain natriuretic peptide, ET-1, reactive oxygen species, and the NADPH oxidase 2 regulatory subunits, p47^Phox and p67^Phox , and upregulated pulmonary p-eNOS, NOx, and cGMP in both the early- and late-treated groups.

CONCLUSIONS

Inhibiting HMG-CoA reductase may have therapeutic potential for preventing and attenuating the development of PH in left ventricular dysfunction through the Rho-kinase pathway and NADPH oxidase. A translational study in humans is needed to substantiate these findings. Pediatr Pulmonol. 2017;52:443-457. © 2016 Wiley Periodicals, Inc.

Comparison of Macitentan and Bosentan on Right Ventricular Remodeling in a Rat Model of Non-vasoreactive Pulmonary Hypertension

Supplemental Digital Content Is Available in the Text.

We compared the efficacy of macitentan, a novel dual endothelin A/endothelin B receptor antagonist, with that of another dual endothelin receptor antagonist, bosentan, in a rat model of non-vasoreactive pulmonary hypertension (PH) with particular emphasis on right ventricular (RV) remodeling.

Right ventricular failure due to chronic pressure load: What have we learned in animal models since the NIH working group statement?

Right ventricular (RV) failure determines outcome in patients with pulmonary hypertension, congenital heart diseases and in left ventricular failure. In 2006, the Working Group on Cellular and Molecular Mechanisms of Right Heart Failure of the NIH advocated the development of preclinical models to study the pathophysiology and pathobiology of RV failure. In this review, we summarize the progress of research into the pathobiology of RV failure and potential therapeutic interventions. The picture emerging from this research is that RV adaptation to increased afterload is characterized by increased contractility, dilatation and hypertrophy. Clinical RV failure is associated with progressive diastolic deterioration and disturbed ventricular–arterial coupling in the presence of increased contractility. The pathobiology of the failing RV shows similarities with that of the LV and is marked by lack of adequate increase in capillary density leading to a hypoxic environment and oxidative stress and a metabolic switch from fatty acids to glucose utilization. However, RV failure also has characteristic features. So far, therapies aiming to specifically improve RV function have had limited success. The use of beta blockers and sildenafil may hold promise, but new therapies have to be developed. The use of recently developed animal models will aid in further understanding of the pathobiology of RV failure and development of new therapeutic strategies.

Preventive effect of sildenafil on right ventricular function in rats with monocrotaline-induced pulmonary arterial hypertension

The present study aimed to evaluate the preventive effect of sildenafil treatment on pulmonary hypertension (PH) induced by monocrotaline (MCT) in rats. Fifty-four 12-week-old male Sprague-Dawley rats were injected with MCT or saline solution (MCT-injected rats: n=36; saline: n=18). Serial echocardiography and right ventricular systolic pressure (RVSP) measurements via a cardiac catheter were performed at 2, 4 and 6 weeks after the injection. After injection of MCT, rats received oral sildenafil (MCT/sildenafil group: n=18) or no treatment (MCT group: n=18) until undergoing echocardiography and cardiac catheterization. RVSP in the MCT/sildenafil group was lower than that in the MCT group at 4 (P<0.001) and 6 weeks (P<0.001). The septal curvature was improved in the MCT/sildenafil group compared with the MCT group. This finding showed that sildenafil prevented flattening of the interventricular septum because of right ventricular pressure overload. The ratio of peak trans-tricuspid early diastolic wave velocity to active filling with atrial systolic velocity showed that sildenafil improved diastolic function. Tricuspid annular plane systolic excursion and tricuspid annular systolic velocity in the MCT/sildenafil group did not show preserved myocardial contraction after administration of sildenafil. Administration of sildenafil leads to a reduction in RVSP and improvement in cardiac function in rats with PH induced by MCT. The vasodilatory action of sildenafil improves right ventricular diastolic function, but the intrinsic, positive, inotropic effect of sildenafil is minimal.

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.

Lungs at high-altitude: genomic insights into hypoxic responses

Hypobaric hypoxia at high altitude (HA) results in reduced blood arterial oxygen saturation, perfusion of organs with hypoxemic blood, and direct hypoxia of lung tissues. The pulmonary complications in the cells of the pulmonary arterioles due to hypobaric hypoxia are the basis of the pathophysiological mechanisms of high-altitude pulmonary edema (HAPE). Some populations that have dwelled at HA for thousands of years have evolutionarily adapted to this environmental stress; unadapted populations may react with excessive physiological responses that impair health. Individual variations in response to hypoxia and the mechanisms of HA adaptation provide insight into physiological responses. Adaptive and maladaptive responses include alterations in pathways such as oxygen sensing, hypoxia signaling, K+- and Ca2+-gated channels, redox balance, and the renin-angiotensin-aldosterone system. Physiological imbalances are linked with genetic susceptibilities, and nonhomeostatic responses in gene regulation that occur by small RNAs, histone modification, and DNA methylation predispose susceptible humans to these HA illnesses. Elucidation of the interaction of these factors will lead to a more comprehensive understanding of HA adaptations and maladaptations and will lead to new therapeutics for HA disorders related to hypoxic lungs.

Novel therapeutic approaches for pulmonary arterial hypertension: Unique molecular targets to site-specific drug delivery

Pulmonary arterial hypertension (PAH) is a cardiopulmonary disorder characterized by increased blood pressure in the small arterioles supplying blood to lungs for oxygenation. Advances in understanding of molecular and cellular biology techniques have led to the findings that PAH is indeed a cascade of diseases exploiting multi-faceted complex pathophysiology, with cellular proliferation and vascular remodeling being the key pathogenic events along with several cellular pathways involved. While current therapies for PAH do provide for amelioration of disease symptoms and acute survival benefits, their full therapeutic potential is hindered by patient incompliance and off-target side effects. To overcome the issues related with current therapy and to devise a more selective therapy, various novel pathways are being investigated for PAH treatment. In addition, inability to deliver anti-PAH drugs to the disease site i.e., distal pulmonary arterioles has been one of the major challenges in achieving improved patient outcomes and improved therapeutic efficacy. Several novel carriers have been explored to increase the selectivity of currently approved anti-PAH drugs and to act as suitable carriers for the delivery of investigational drugs. In the present review, we have discussed potential of various novel molecular pathways/targets including RhoA/Rho kinase, tyrosine kinase, endothelial progenitor cells, vasoactive intestinal peptide, and miRNA in PAH therapeutics. We have also discussed various techniques for site-specific drug delivery of anti-PAH therapeutics so as to improve the efficacy of approved and investigational drugs. This review will provide gainful insights into current advances in PAH therapeutics with an emphasis on site-specific drug payload delivery.

Existing drugs and agents under investigation for pulmonary arterial hypertension

Pulmonary arterial hypertension is a progressive and debilitating disorder with an associated high morbidity and mortality rate. Significant advances in our understanding of the epidemiology, pathogenesis, and pathophysiology of pulmonary hypertension have occurred over the past several decades. This has allowed the development of new therapeutic options in this disease. Today, our selection of therapeutic modalities is broader, including calcium channel blockers, prostanoids, endothelin receptor antagonists, phosphodiesterase inhibitors, and soluble guanylate cyclase stimulators, but the disease remains fatal. This underscores the need for a continued search for novel therapies. Several potential pharmacologic agents for the treatment of pulmonary arterial hypertension are under clinical development and some promising results with these treatments have been reported. These agents include rho-kinase inhibitors, long-acting nonprostanoid prostacyclin receptor agonists, tyrosine protein kinase inhibitors, endothelial nitric oxide synthase couplers, synthetically produced vasoactive intestinal peptide, antagonists of the 5-HT2 receptors, and others. This article will review several of these promising new therapies and will discuss the current evidence regarding their potential benefit in pulmonary arterial hypertension.

Effects of exercise training on pulmonary vessel muscularization and right ventricular function in an animal model of COPD

BACKGROUND

Right ventricular dysfunction in COPD is common, even in the absence of pulmonary hypertension. The aim of the present study was to examine the effects of high intensity interval training (HIIT) on right ventricular (RV) function, as well as pulmonary blood vessel remodeling in a mouse model of COPD.

METHODS

42 female A/JOlaHsd mice were randomized to exposure to either cigarette smoke or air for 6 hours/day, 5 days/week for 14 weeks. Mice from both groups were further randomized to sedentariness or HIIT for 4 weeks. Cardiac function was evaluated by echocardiography and muscularization of pulmonary vessel walls by immunohistochemistry.

RESULTS

Smoke exposure induced RV systolic dysfunction demonstrated by reduced tricuspid annular plane systolic excursion. HIIT in smoke-exposed mice reversed RV dysfunction. There were no significant effects on the left ventricle of neither smoke exposure nor HIIT. Muscularization of the pulmonary vessels was reduced after exercise intervention, but no significant effects on muscularization were observed from smoke exposure.

CONCLUSIONS

RV function was reduced in mice exposed to cigarette smoke. No Increase in pulmonary vessel muscularization was observed in these mice, implying that other mechanisms caused the RV dysfunction. HIIT attenuated the RV dysfunction in the smoke exposed mice. Reduced muscularization of the pulmonary vessels due to HIIT suggests that exercise training not only affects the heart muscle, but also has important effects on the pulmonary vasculature.

An update on medical therapy for pulmonary arterial hypertension

Over the past 20 years, great progress has been made in the treatment of pulmonary arterial hypertension (PAH). Available therapies target one of three principal pathways: the endothelin (ET), nitric oxide (NO) or the prostacyclin (PGI2) pathway. Evidence shows that current drugs, used either as monotherapy or in different combinations, can improve exercise capacity, clinical symptoms, hemodynamics and even survival in PAH. Unfortunately, the disease remains incurable and the prognosis of the disease is still poor. However, existing and novel potent antiproliferative therapies are being explored, and new agents targeting different and/or additional pathways are likely to become available to clinicians in the near future. Promising candidates include tyrosine kinase antagonists (e.g. imatinib); soluble guanylate cyclase stimulators (riociguat); an oral analog of prostacyclin (selexipag); and a tissue targeting endothelin receptor antagonist (macitentan). Phase II or III trials have either been completed or are underway to evaluate the safety and efficacy of these various therapies.

PKG-1α leucine zipper domain defect increases pulmonary vascular tone: implications in hypoxic pulmonary hypertension

Pulmonary hypertension (PH) is a chronic disease characterized by a progressive increase in vasomotor tone, narrowing of the vasculature with structural remodeling, and increase in pulmonary vascular resistance. Current treatment strategies include nitric oxide therapy and methods to increase cGMP-mediated vasodilatation. cGMP-dependent protein kinases (PKG) are known mediators of nitric oxide- and cGMP-induced vasodilatation. Deletion of PKG-1 in mice has been shown to induce PH, however, the exact mechanisms by which loss of PKG-1 function leads to PH is not known. In a mouse model with a selective mutation in the NH2-terminus leucine zipper protein interaction domain of PKG-1α [leucine zipper mutant (LZM)], we found a progressive increase in right ventricular systolic pressure and right heart hypertrophy compared with wild-type (WT) mice and increased RhoA-GTPase activity in the lungs. When exposed to chronic hypoxia, LZM mice developed modestly enhanced right ventricular remodeling compared with WT mice. Tadalafil, a phosphodiesterase-5 inhibitor that increases cGMP levels, significantly attenuated hypoxia-induced cardiopulmonary remodeling in WT mice but had no effect in LZM mice. We conclude that a functional leucine zipper domain in PKG-1α is essential for maintenance of a low pulmonary vascular tone in normoxia and for cGMP-mediated beneficial effects of phosphodiesterase-5 inhibition in hypoxic cardiopulmonary remodeling.

Fasudil reversed MCT-induced and chronic hypoxia-induced pulmonary hypertension by attenuating oxidative stress and inhibiting the expression of Trx1 and HIF-1α

Antioxidant therapy attenuates pulmonary hypertension (PH). In the present study, we tested the antioxidant effects of fasudil against PH in rats. Monocrotaline (MCT)-induced and chronic hypoxia-induced PH models of rats were established, and the haemodynamic and pathomorphologic results of three different doses of fasudil (10 mg/kg, 30 mg/kg, and 75 mg/kg per day) were subsequently compared with those of bosentan (30 mg/kg per day). Additionally, the protein expressions of thioredoxin-1 (Trx1) and hypoxia inducible factor-1α (HIF-1α), the content of superoxide dismutase (SOD), and the levels of hydrogen peroxide (H2O2), malonyldialdehyde (MDA), and hydroxy radical (·OH) were investigated. Fasudil effectively reduced the right ventricular systolic pressure (RVSP) and alleviated right ventricle (RV) hypertrophy, as well as the histological changes in the pulmonary arterioles. Moreover, fasudil markedly lessened the expression of Trx1 and HIF-1α, up-regulated the concentration of SOD, and lowered the levels of H2O2, MDA, and ·OH. In conclusion, fasudil is a notably attractive potential therapy for PH.

Pulmonary arterial hypertension in adults: novel drugs and catheter ablation techniques show promise? Systematic review on pharmacotherapy and interventional strategies

This systematic review aims to provide an update on pharmacological and interventional strategies for the treatment of pulmonary arterial hypertension in adults. Currently US Food and Drug Administration approved drugs including prostanoids, endothelin-receptor antagonists, phosphodiesterase type-5 inhibitors, and soluble guanylate-cyclase stimulators. These agents have transformed the prognosis for pulmonary arterial hypertension patients from symptomatic improvements in exercise tolerance ten years ago to delayed disease progression today. On the other hand, percutaneous balloon atrioseptostomy by using radiofrequency perforation, cutting balloon dilatation, or insertion of butterfly stents and pulmonary artery catheter-based denervation, both associated with very low rate of major complications and death, should be considered in combination with specific drugs at an earlier stage rather than late in the progression of pulmonary arterial hypertension and before the occurrence of overt right-sided heart failure.

Rho kinases in cardiovascular physiology and pathophysiology: the effect of fasudil

Rho kinase (ROCK) is a major downstream effector of the small GTPase RhoA. ROCK family, consisting of ROCK1 and ROCK2, plays central roles in the organization of actin cytoskeleton and is involved in a wide range of fundamental cellular functions, such as contraction, adhesion, migration, proliferation, and apoptosis. Due to the discovery of effective inhibitors, such as fasudil and Y27632, the biological roles of ROCK have been extensively explored with particular attention on the cardiovascular system. In many preclinical models of cardiovascular diseases, including vasospasm, arteriosclerosis, hypertension, pulmonary hypertension, stroke, ischemia-reperfusion injury, and heart failure, ROCK inhibitors have shown a remarkable efficacy in reducing vascular smooth muscle cell hypercontraction, endothelial dysfunction, inflammatory cell recruitment, vascular remodeling, and cardiac remodeling. Moreover, fasudil has been used in the clinical trials of several cardiovascular diseases. The continuing utilization of available pharmacological inhibitors and the development of more potent or isoform-selective inhibitors in ROCK signaling research and in treating human diseases are escalating. In this review, we discuss the recent molecular, cellular, animal, and clinical studies with a focus on the current understanding of ROCK signaling in cardiovascular physiology and diseases. We particularly note that emerging evidence suggests that selective targeting ROCK isoform based on the disease pathophysiology may represent a novel therapeutic approach for the disease treatment including cardiovascular diseases.

The role of cGMP in the physiological and molecular responses of the right ventricle to pressure overload

Pulmonary arterial hypertension (PAH) is a progressive disease that is associated with a poor prognosis and results in right heart dysfunction. While pulmonary vascular disease is the obvious primary pathological focus, right ventricular hypertrophy (RVH) and right ventricular (RV) dysfunction are major determinants of prognosis in PAH. Our knowledge about the molecular physiology and pathophysiology of RV hypertrophy and failure in response to pressure overload is still limited, and most data are derived from left heart research. However, the molecular mechanisms of left ventricular remodelling cannot be generalized to the RV, because the right and left ventricles differ greatly in their size, shape, architecture and function. Despite the recent advances in diagnosis and treatment of PAH, little is known about the molecular and cellular mechanisms that underlie the transition from compensatory to maladaptive RV remodelling. The cGMP-phosphodiesterase 5 (PDE5) pathway is one of the extensively studied pathways in PAH, but our knowledge about cGMP-PDE5 signalling in RV pathophysiology is still limited. For this purpose, there is need for animal models that can represent changes in the RV that closely mimic the human situation. The availability of an animal model of pressure-overload-induced RVH (e.g. pulmonary artery banding model) provides us with a valuable tool to understand the differences between adaptive and maladaptive RVH and to explore the direct effects of current PAH therapy on the heart. In this report, we discuss myocardial regulatory effects of cGMP-PDE5 signalling in preclinical models of RV pressure overload for understanding the physiological/pathophysiological mechanisms involved in maladaptive RVH.

Antenatal hypoxia and pulmonary vascular function and remodeling

This review provides evidence that antenatal hypoxia, which represents a significant and worldwide problem, causes prenatal programming of the lung. A general overview of lung development is provided along with some background regarding transcriptional and signaling systems of the lung. The review illustrates that antenatal hypoxic stress can induce a continuum of responses depending on the species examined. Fetuses and newborns of certain species and specific human populations are well acclimated to antenatal hypoxia. However, antenatal hypoxia causes pulmonary vascular disease in fetuses and newborns of most mammalian species and humans. Disease can range from mild pulmonary hypertension, to severe vascular remodeling and dangerous elevations in pressure. The timing, length, and magnitude of the intrauterine hypoxic stress are important to disease development, however there is also a genetic-environmental relationship that is not yet completely understood. Determining the origins of pulmonary vascular remodeling and pulmonary hypertension and their associated effects is a challenging task, but is necessary in order to develop targeted therapies for pulmonary hypertension in the newborn due to antenatal hypoxia that can both treat the symptoms and curtail or reverse disease progression.