The molecular targets of approved treatments for pulmonary arterial hypertension

Challenges and opportunities in targeting epigenetic mechanisms for pulmonary arterial hypertension treatment

Pulmonary arterial hypertension (PAH) is a devastating disorder characterized by elevated pulmonary vascular resistance and pulmonary artery pressure, resulting from a multitude of etiological factors. If left untreated, PAH progressively leads to right heart failure and is associated with high mortality. The etiology of PAH is multifactorial, encompassing both congenital genetic predispositions and acquired secondary influences. Epigenetics, which refers to the regulation of gene expression through chromosomal alterations that do not involve changes in the DNA sequence, has garnered significant attention in PAH research. This includes mechanisms such as DNA methylation, histone modification, and RNA modification. Aberrant epigenetic modifications have been closely linked to the dysregulated proliferation and apoptosis of pulmonary artery smooth muscle cells and endothelial cells, suggesting that these alterations may serve as pivotal drivers of the pathophysiological changes observed in PAH. This review examines the potential impact of epigenetic alterations on the pathogenesis of PAH, highlighting their promise as therapeutic targets. Furthermore, we explore emerging therapeutic strategies and compounds aimed at modulating these epigenetic markers, and discusses their potential applications in both preclinical models and clinical trials. As our understanding of epigenetics deepens, it holds the potential to unlock novel avenues for the precise, individualized treatment of PAH, offering a new frontier in the fight against this debilitating disease.

Empagliflozin Attenuates Pulmonary Arterial Remodeling Through Peroxisome Proliferator-Activated Receptor Gamma Activation

The loss of peroxisome proliferator-activated receptor gamma (PPARγ) exacerbates pulmonary arterial hypertension (PAH), while its upregulation reduces cell proliferation and vascular remodeling, thereby decreasing PAH severity. SGLT2 inhibitors, developed for type 2 diabetes, might also affect signal transduction in addition to modulating sodium-glucose cotransporters. Pulmonary arterial smooth muscle cells (PASMCs) isolated from patients with idiopathic pulmonary arterial hypertension (IPAH) were treated with three SGLT2 inhibitors, canagliflozin (Cana), dapagliflozin (Dapa), and empagliflozin (Empa), to investigate their antiproliferative effects. To assess the impact of Empa on PPARγ, luciferase reporter assays and siRNA-mediated PPARγ knockdown were employed to examine regulation of the γ-secretase complex and its downstream target Notch3. Therapy involving daily administration of Empa was initiated 21 days after inducing hypoxia-induced PAH in mice. Empa exhibited significant antiproliferative effects on fast-growing IPAH PASMCs. Empa activated PPARγ to prevent formation of the γ-secretase complex, with specific impacts on presenilin enhancer 2 (PEN2), which plays a crucial role in maintaining γ-secretase complex stability, thereby inhibiting Notch3. Similar results were obtained in lung tissue of chronically hypoxic mice. Empa attenuated pulmonary arterial remodeling and right ventricle hypertrophy in a hypoxic PAH mouse model. Moreover, PPARγ expression was significantly decreased and PEN2, and Notch3 levels were increased in lung tissue from PAH patients compared with non-PAH lung tissue. Empa reverses vascular remodeling by activating PPARγ to suppress the γ-secretase-Notch3 axis. We propose Empa as a PPARγ activator and potential therapeutic for PAH.

An overview of conventional and investigational phosphodiesterase 5 inhibitors for treating erectile dysfunction and other conditions

INTRODUCTION

There is a rising concern about developing innovative, efficacious PDE5I molecules that provide better safety, efficacy, and tolerability with less adverse effects. Innovative PDE5I with dual targets have also been defined in the literature. Additionally, some of PDE5I are able to selectively inhibit other enzymes such as histone deacetylase, acetylcholine esterase, and cyclooxygenase or act as nitric oxide donors. This review presents knowledge concerning the advanced trends and perspectives in using PDE5I in treatment of ED and other conditions.

AREAS COVERED

Pre-clinical and early clinical trials that investigated the safety, efficacy, and tolerability of novel PDE5I such as Udenafil, Mirodenafil, Lodenafil, Youkenafil, Celecoxib, and TPN729 in treatment of ED and other conditions.

EXPERT OPINION

Preclinical and limited early clinical studies of the new molecules of PDE5I have demonstrated encouraging results; however, safety, efficacy, and tolerability are still issues that necessitate further long-term multicenter clinical studies to ensure justification of their uses in treatment of ED and other conditions. Progress in molecular delivery techniques and tailored patient-specific management and additional therapeutic technology will dramatically improve care for ED and other conditions. The dream of ED and many other conditions becoming more effectively managed may be feasible in the near future.

The Princeton IV Consensus Recommendations for the Management of Erectile Dysfunction and Cardiovascular Disease

The Princeton Consensus (Expert Panel) Conference is a multispecialty collaborative symposium dedicated to optimizing sexual function and preserving cardiovascular health. The Fourth Princeton Consensus Conference was convened on March 10-11, 2023, at the Huntington Medical Research Institutes in Pasadena, California. Princeton panels I to III addressed the clinical management of men with erectile dysfunction (ED) who also had cardiovascular disease. Thirteen years since Princeton III, Princeton IV builds on previous foundations in several key areas. Mounting evidence supports the need for providers to treat men with ED as being at risk for cardiac events until proven otherwise. Algorithms for the diagnosis and treatment of ED are updated with new recommendations for coronary artery calcium scoring for advanced cardiovascular risk stratification. Optimization of oral phosphodiesterase type 5 inhibitors in the treatment of men with ED and cardiovascular disease is thoroughly explored, including recent evidence of potential cardioprotective effects of these drugs.

Urolithin A Protects against Hypoxia-Induced Pulmonary Hypertension by Inhibiting Pulmonary Arterial Smooth Muscle Cell Pyroptosis via AMPK/NF-κB/NLRP3 Signaling

Recent studies confirmed that pyroptosis is involved in the progression of pulmonary hypertension (PH), which could promote pulmonary artery remodeling. Urolithin A (UA), an intestinal flora metabolite of ellagitannins (ETs) and ellagic acid (EA), has been proven to possess inhibitory effects on pyroptosis under various pathological conditions. However, its role on PH remained undetermined. To investigate the potential of UA in mitigating PH, mice were exposed to hypoxia (10% oxygen, 4 weeks) to induce PH, with or without UA treatment. Moreover, in vitro experiments were carried out to further uncover the underlying mechanisms. The in vivo treatment of UA suppressed the progression of PH via alleviating pulmonary remodeling. Pyroptosis-related genes were markedly upregulated in mice models of PH and reversed after the administration of UA. In accordance with that, UA treatment significantly inhibited hypoxia-induced pulmonary arterial smooth muscle cell (PASMC) pyroptosis via the AMPK/NF-κB/NLRP3 pathway. Our results revealed that UA treatment effectively mitigated PH progression through inhibiting PASMC pyroptosis, which represents an innovative therapeutic approach for PH.

Switching from Beraprost to Selexipag in the Treatment of Pulmonary Arterial Hypertension: Insights from a Phase IV Study of the Japanese Registry (The EXCEL Study: EXChange from bEraprost to seLexipag Study)

Pulmonary arterial hypertension (PAH) remains a significant challenge in cardiology, necessitating advancements in treatment strategies. This study explores the safety and efficacy of transitioning patients from beraprost to selexipag, a novel selective prostacyclin receptor agonist, within a Japanese cohort. Employing a multicenter, open-label, prospective design, 25 PAH patients inadequately managed on beraprost were switched to selexipag. Key inclusion criteria included ongoing beraprost therapy for ≥3 months, a diagnosis of PAH confirmed by mean pulmonary artery pressure (mPAP) ≥ 25 mmHg, and current treatment with endothelin receptor antagonists and/or phosphodiesterase type 5 inhibitors. Outcomes assessed were changes in hemodynamic parameters (mPAP, cardiac index, pulmonary vascular resistance) and the 6 min walk distance (6-MWD) over 3-6 months. The study found no statistically significant changes in these parameters post-switch. However, a subset of patients, defined as responders, demonstrated improvements in all measured hemodynamic parameters, suggesting a potential benefit in carefully selected patients. The transition was generally well-tolerated with no serious adverse events reported. This investigation underscores the importance of personalized treatment strategies in PAH, highlighting that certain patients may benefit from switching to selexipag, particularly those previously on higher doses of beraprost. Further research is needed to elucidate the predictors of positive response to selexipag and optimize treatment regimens for this complex condition.

Molecular recognition and activation of the prostacyclin receptor by anti-pulmonary arterial hypertension drugs

The prostacyclin (PGI2) receptor (IP) is a Gs-coupled receptor associated with blood pressure regulation, allergy, and inflammatory response. It is a main therapeutic target for pulmonary arterial hypertension (PAH) and several other diseases. Here we report cryo-electron microscopy (cryo-EM) structures of the human IP-Gs complex bound with two anti-PAH drugs, treprostinil and MRE-269 (active form of selexipag), at global resolutions of 2.56 and 2.41 angstrom, respectively. These structures revealed distinct features governing IP ligand binding, receptor activation, and G protein coupling. Moreover, comparison of the activated IP structures uncovered the mechanism and key residues that determine the superior selectivity of MRE-269 over treprostinil. Combined with molecular docking and functional studies, our structures provide insight into agonist selectivity, ligand recognition, receptor activation, and G protein coupling. Our results provide a structural template for further improving IP-targeting drugs to reduce off-target activation of prostanoid receptors and adverse effects.

The nitric oxide-soluble guanylate cyclase-cGMP pathway in pulmonary hypertension: from PDE5 to soluble guanylate cyclase

The nitric oxide (NO)-soluble guanylate cyclase (sGC)-cyclic guanosine monophosphate (cGMP) pathway plays a key role in the pathogenesis of pulmonary hypertension (PH). Targeted treatments include phosphodiesterase type 5 inhibitors (PDE5i) and sGC stimulators. The sGC stimulator riociguat is approved for the treatment of pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH). sGC stimulators have a dual mechanism of action, enhancing the sGC response to endogenous NO and directly stimulating sGC, independent of NO. This increase in cGMP production via a dual mechanism differs from PDE5i, which protects cGMP from degradation by PDE5, rather than increasing its production. sGC stimulators may therefore have the potential to increase cGMP levels under conditions of NO depletion that could limit the effectiveness of PDE5i. Such differences in mode of action between sGC stimulators and PDE5i could lead to differences in treatment efficacy between the classes. In addition to vascular effects, sGC stimulators have the potential to reduce inflammation, angiogenesis, fibrosis and right ventricular hypertrophy and remodelling. In this review we describe the evolution of treatments targeting the NO-sGC-cGMP pathway, with a focus on PH.

Princeton IV consensus guidelines: PDE5 inhibitors and cardiac health

BACKGROUND

In 1999, 1 year after the approval of the first oral phosphodiesterase type 5 (PDE5) inhibitor for the treatment of erectile dysfunction (ED), the first Princeton Consensus Conference was held to address the clinical management of men with ED who also had cardiovascular disease. These issues were readdressed in the second and third conferences. In the 13 years since the last Princeton Consensus Conference, the experience with PDE5 inhibitors is more robust, and recent new data have emerged regarding not only safety and drug-drug interactions, but also a potential cardioprotective effect of these drugs.

AIM

In March 2023, an interdisciplinary group of scientists and practitioners met for the fourth Princeton Consensus Guidelines at the Huntington Medical Research Institutes in Pasadena, California, to readdress the cardiovascular workup of men presenting with ED as well as the approach to treatment of ED in men with known cardiovascular disease.

METHOD

A series of lectures from experts in the field followed by Delphi-type discussions were developed to reach consensus.

OUTCOMES

Consensus was reached regarding a number of issues related to erectile dysfunction and the interaction with cardiovascular health and phosphodiesterase-5 inhibitors.

RESULTS

An algorithm based on recent recommendations of the American College of Cardiology and American Heart Association, including the use of computed tomography coronary artery calcium scoring, was integrated into the evaluation of men presenting with ED. Additionally, the issue of nitrate use was further considered in an algorithm regarding the treatment of ED patients with coronary artery disease. Other topics included the psychological effect of ED and the benefits of treating it; the mechanism of action of the PDE5 inhibitors; drug-drug interactions; optimizing use of a PDE5 inhibitors; rare adverse events; potential cardiovascular benefits observed in recent retrospective studies; adulteration of dietary supplements with PDE5 inhibitors; the pros and cons of over-the-counter PDE5 inhibitors; non-PDE5 inhibitor therapy for ED including restorative therapies such as stem cells, platelet-rich plasma, and shock therapy; other non-PDE5 inhibitor therapies, including injection therapy and penile prostheses; the issue of safety and effectiveness of PDE5 inhibitors in women; and recommendations for future studies in the field of sexual dysfunction and PDE5 inhibitor use were discussed.

CLINICAL IMPLICATIONS

Algorithms and tables were developed to help guide the clinician in dealing with the interaction of ED and cardiovascular risk and disease.

STRENGTHS AND LIMITATIONS

Strengths include the expertise of the participants and consensus recommendations. Limitations included that participants were from the United States only for this particular meeting.

CONCLUSION

The issue of the intersection between cardiovascular health and sexual health remains an important topic with new studies suggesting the cardiovascular safety of PDE5 inhibitors.

High-Soluble-Fiber Diet Attenuates Hypoxia-Induced Vascular Remodeling and the Development of Hypoxic Pulmonary Hypertension

BACKGROUND

Hypoxic pulmonary hypertension is a difficult disease to manage that is characterized by sustained elevation of pulmonary vascular resistance and pulmonary artery pressure due to vasoconstriction, perivascular inflammation, and vascular remodeling. Consumption of soluble-fiber is associated with lower systemic blood pressure, but little is known about its ability to affect the pulmonary circulation.

METHODS

Mice were fed either a low- or high-soluble-fiber diet (0% or 16.9% inulin) and then exposed to hypoxia (FiO2, 0.10) for 21 days to induce pulmonary hypertension. The impact of diet on right ventricular systolic pressure and pulmonary vascular resistance was determined in vivo or in ex vivo isolated lungs, respectively, and correlated with alterations in the composition of the gut microbiome, plasma metabolome, pulmonary inflammatory cell phenotype, and lung proteome.

RESULTS

High-soluble-fiber diet increased the abundance of short-chain fatty acid-producing bacteria, with parallel increases in plasma propionate levels, and reduced the abundance of disease-related bacterial genera such as Staphylococcus, Clostridioides, and Streptococcus in hypoxic mice with parallel decreases in plasma levels of p-cresol sulfate. High-soluble-fiber diet decreased hypoxia-induced elevations of right ventricular systolic pressure and pulmonary vascular resistance. These changes were associated with reduced proportions of interstitial macrophages, dendritic cells, and nonclassical monocytes. Whole-lung proteomics revealed proteins and molecular pathways that may explain the effect of soluble-fiber supplementation.

CONCLUSIONS

This study demonstrates for the first time that a high-soluble-fiber diet attenuates hypoxia-induced pulmonary vascular remodeling and the development of pulmonary hypertension in a mouse model of hypoxic pulmonary hypertension and highlights diet-derived metabolites that may have an immuno-modulatory role in the lung.

Prostaglandin and prostaglandin receptors: present and future promising therapeutic targets for pulmonary arterial hypertension

BACKGROUND

Pulmonary arterial hypertension (PAH), Group 1 pulmonary hypertension (PH), is a type of pulmonary vascular disease characterized by abnormal contraction and remodeling of the pulmonary arterioles, manifested by pulmonary vascular resistance (PVR) and increased pulmonary arterial pressure, eventually leading to right heart failure or even death. The mechanisms involved in this process include inflammation, vascular matrix remodeling, endothelial cell apoptosis and proliferation, vasoconstriction, vascular smooth muscle cell proliferation and hypertrophy. In this study, we review the mechanisms of action of prostaglandins and their receptors in PAH.

MAIN BODY

PAH-targeted therapies, such as endothelin receptor antagonists, phosphodiesterase type 5 inhibitors, activators of soluble guanylate cyclase, prostacyclin, and prostacyclin analogs, improve PVR, mean pulmonary arterial pressure, and the six-minute walk distance, cardiac output and exercise capacity and are licensed for patients with PAH; however, they have not been shown to reduce mortality. Current treatments for PAH primarily focus on inhibiting excessive pulmonary vasoconstriction, however, vascular remodeling is recalcitrant to currently available therapies. Lung transplantation remains the definitive treatment for patients with PAH. Therefore, it is imperative to identify novel targets for improving pulmonary vascular remodeling in PAH. Studies have confirmed that prostaglandins and their receptors play important roles in the occurrence and development of PAH through vasoconstriction, vascular smooth muscle cell proliferation and migration, inflammation, and extracellular matrix remodeling.

CONCLUSION

Prostacyclin and related drugs have been used in the clinical treatment of PAH. Other prostaglandins also have the potential to treat PAH. This review provides ideas for the treatment of PAH and the discovery of new drug targets.

Aloperine protects pulmonary hypertension via triggering PPARγ signaling and inhibiting calcium regulatory pathway in pulmonary arterial smooth muscle cells

Previous studies have reported the beneficial role of Aloperine (ALO), an active vasodilator purified from the seeds and leaves of the herbal plant Sophora alopecuroides L., on experimental pulmonary hypertension (PH); however, detailed mechanisms remain unclear. In this study, monocrotaline-induced PH (MCT-PH) rat model and primarily cultured rat distal pulmonary arterial smooth muscle cells (PASMCs) were used to investigate the mechanisms of ALO on experimental PH, pulmonary vascular remodeling, and excessive proliferation of PASMCs. Results showed that first, ALO significantly prevented the disease development of MCT-PH by inhibiting right ventricular systolic pressure (RVSP) and right ventricular hypertrophy indexed by the Fulton Index, normalizing the pulmonary arterials (PAs) remodeling and improving the right ventricular function indexed by transthoracic echocardiography. ALO inhibited the excessive proliferation of both PAs and PASMCs. Then, isometric tension measurements showed vasodilation of ALO on precontracted PAs isolated from both control and MCT-PH rats via activating the KCNQ channel, which was blocked by specific KCNQ potassium channel inhibitor linopirdine. Moreover, by using immunofluorescence staining and nuclear/cytosol fractionation, we further observed that ALO significantly enhanced the PPARγ nuclear translocation and activation in PASMCs. Transcriptome analyses also revealed activated PPARγ signaling and suppressed calcium regulatory pathway in lungs from MCT-PH rats treated with ALO. In summary, ALO could attenuate MCT-PH through both transient vasodilation of PAs and chronic activation of PPARγ signaling pathway, which exerted antiproliferative roles on PASMCs and remodeled PAs.NEW & NOTEWORTHY Aloperine attenuates monocrotaline-induced pulmonary hypertension (MCT-PH) in rats by inhibiting the pulmonary vascular remodeling and proliferation of pulmonary arterial smooth muscle cells (PASMCs). In mechanism, Aloperine not only exerts a transient KCNQ-dependent vasodilation in precontracted pulmonary arteries (PAs) from both control and MCT-PH rats but also activates PPARγ nuclear translocation and signaling transduction in PASMCs, which chronically inhibits the calcium regulatory pathway and proliferation of PASMCs.

Current Status of Endothelin Receptor Antagonists in Pulmonary Arterial Hypertension: A Combined Study Results and Pharmacology-Based Review

Pulmonary arterial hypertension (PAH) affects a wide range of people globally and has a poor prognosis despite many advancements in available treatment options. Among the available treatments, endothelin receptor antagonists (ERA) are among the most widely used drugs. These drugs have been evaluated in scientific trials. We included free full texts in the English language from the last ten years and reviewed them. We are writing this review to amalgamate the pharmacological aspects and the previous studies on ERAs to demonstrate a comprehensive overview of the current status of ERAs for PAH treatment. We focused on the structure, pharmacodynamics, pharmacokinetics, and efficacy and safety of the three most widely used ERAs: Bosentan, Ambrisentan, and Macitentan. These drugs have different receptor affinities, bioavailability, excretion routes, and different levels of safety profiles. There are three available studies, the RCT, the ARIES series, and the SERAPHIN studies, for assessing the safety and efficacy of Bosentan, Ambrisentan, and Macitentan, respectively. All the studies and some additional studies for combination therapy have proven all three drugs effective in treating PAH. The side effects (SE) varied from headache and hepatic enzyme elevation to worsening the PAH status of varied severities. Although these studies provided valuable insight into the role of ERAs, there is still enough scope for more studies on ERAs, both as monotherapy and combination therapy for PAH.

The role of riociguat in combination therapies for pulmonary arterial hypertension

Effective clinical decision-making in initial treatment selection and switching or escalations of therapy for pulmonary arterial hypertension (PAH) depends on multiple factors including the patient's risk profile. Data from clinical trials suggest that switching from a phosphodiesterase-5 inhibitor (PDE5i) to the soluble guanylate cyclase stimulator riociguat may provide clinical benefit in patients not reaching treatment goals. In this review, we cover the clinical evidence for riociguat combination regimens for patients with PAH and discuss their evolving role in upfront combination therapy and switching from a PDE5i as an alternative to escalating therapy. Specifically, we review current evidence which suggests or provides a hypothesis for 1) the potential use of riociguat plus endothelin receptor antagonist combinations for upfront combination therapy in patients with PAH at intermediate to high risk of 1-year mortality and 2) the benefits of switching to riociguat from a PDE5i in patients who are not achieving treatment goals with PDE5i-based dual combination therapy and at intermediate risk.

Acute Vasoreactivity Testing and Outcomes in Pulmonary Arterial Hypertension: A Call for Increased Testing

BACKGROUND

Pulmonary arterial hypertension (PAH) has a progressive, unremitting clinical course. Vasoreactivity testing (VdT) during right heart catheterisation (RHC) identifies a subgroup with excellent long-term response to calcium channel blockade (CCB). Reporting on these patients is limited. Established in 2011, the Pulmonary Hypertension Society of Australia and New Zealand (PHSANZ) registry offers the opportunity to assess the frequency of VdT during RHC, treatment and follow up of PAH patients.

METHODS

Registry data from 3,972 PAH patients with index RHC revealed 1,194 VdT appropriate patients. Data was analysed in three groups: 1) VdT+CCB+: VdT positive, CCB treated; 2) VdT+CCB-: VdT positive, no CCB prescribed, 3) VdT-/noVdT: VdT negative, or VdT not tested. Data was reviewed for adherence to guidelines, clinical response (World Health Organization functional class [WHO FC], 6-minute-walk-distance [6MWD], RHC), and outcomes (survival or lung transplantation).

RESULTS

Patients included had idiopathic (IPAH=1,087), heritable (HPAH=67) and drug or toxin-induced PAH (DPAH=40). A VdT was performed in 22% (268/1,194), with incomplete data in 26% (70/268); 28% (55/198) were VdT+. Analysis group allocation was: VdT+CCB+ (33/55), VdT+CCB- (22/55), VdT- (143)/noVdT (996). From patients with 1-year data VdT+CCB+ and VdT-/noVdT patients improved WHO FC, 6MWD and cardiac index (CI); VdT+CCB- data remained similar. Within the VdT+CCB+ group, 30% (10/33) were long-term CCB responders with a 100% 5-year survival; non-responders had a 61% survival at 5.4 years. Long-term responders were younger at diagnosis (40 yrs vs 54 yrs).

CONCLUSION

Use of VdT testing and documentation is poor in this contemporary patient cohort. Nonetheless, survival in VdT+CCB+ patients from the PHSANZ registry is excellent, supporting guidelines promoting VdT testing. Strategies to promote the use of VdT are warranted.

Pyrazole-containing pharmaceuticals: target, pharmacological activity, and their SAR studies

Pyrazole is a five-membered heterocycle bearing two adjacent nitrogen atoms. Both pharmaceutical agents and natural products with pyrazole as a nucleus have exhibited a broad spectrum of biological activities. In the last few decades, more than 40 pyrazole-containing drugs have been approved by the FDA for the treatment of a broad range of clinical conditions including celecoxib (anti-inflammatory), CDPPB (antipsychotic), difenamizole (analgesic), etc. Owing to the unique physicochemical properties of the pyrazole core, pyrazole-containing drugs may exert better pharmacokinetics and pharmacological effects compared with drugs containing similar heterocyclic rings. The purpose of this paper is to provide an overview of all the existing drugs bearing a pyrazole nucleus that have been approved or in clinical trials, involving their pharmacological activities and SAR studies.

Novel and robust treatment of pulmonary hypertension with netrin-1 and netrin-1-derived small peptides

Limited medical therapies have been implemented for the treatment of the devastating cardiorespiratory disease of pulmonary hypertension (PH) while none of which is sufficiently effective to stop or regress development of PH. We have previously shown that netrin-1, an axon-guiding protein during development, protects against ischemia reperfusion injury induced myocardial infarction via modest and stable production of nitric oxide (NO) and attenuation of oxidative stress. Since NO deficiency and oxidative stress-mediated vascular remodeling play important roles in the pathogenesis of PH, our present study investigated therapeutic effects on PH of netrin-1 and its derived small peptides. Infused into mice for 3 weeks during exposure to hypoxia, netrin-1 and netrin-1 derived small peptides V1, V2 or V3 substantially alleviated pathophysiological and molecular features of PH, as indicated by abrogated increases in mean pulmonary artery pressure (mPAP) and right ventricular systolic pressure (RVSP), attenuated right ventricular hypertrophy, diminished vascular remodeling of medial thickening and upregulation in smooth muscle alpha-actin (SMA) and proliferative cell nuclear antigen (PCNA), and alleviated perivascular and peribronchial fibrosis reflected by collagen deposition. NO bioavailability was substantially improved by treatment with netrin-1 and netrin-1 derived small peptides, while hypoxia induced increases in total superoxide production and eNOS uncoupling activity were all attenuated. These dual mechanisms of increasing NO bioavailability and decreasing oxidative stress at the same time, underlie robust protective effects on PH of netrin-1 and its derived small peptides, which are different from existing medications that primarily target NO signaling alone. Our data for the first time demonstrate intriguing findings that netrin-1 and netrin-1 derived small peptides can be used as novel and robust therapeutics for the treatment of PH.

Applications of the ultrasound-guided nerve block technique for nonanalgesic effects

The nerve block technique guided by ultrasound has been able to accurately block tiny nerves throughout the body in recent years. It has been increasingly used to treat multisystem diseases or analgesia in surgical patients, but the latter accounted for the vast majority of cases. The nonanalgesic effect of nerve blocks is also in wide demand. After searching ultrasound-guided nerve block works on the PubMed database, we systematically summarized the current clinical application of the nerve block technique and the unique role and related mechanism of nerve block in the prevention and treatment of multi-system diseases or symptoms, including disorders of the circulatory and respiratory systems, postoperative cognitive dysfunction, immune function, posttraumatic stress disorder, and postoperative digestive system, to put forward the potential prospective application in future and serve as a reference for future research of nerve block therapy in these diseases mentioned.

Study to Explore the Association of the Renin-Angiotensin System and Right Ventricular Function in Mechanically Ventilated Patients

Background: Right ventricular (RV) dysfunction is associated with pulmonary vasoconstriction in mechanically ventilated patients. Enhancing the activity of angiotensin-converting enzyme 2 (ACE2), a key enzyme of the renin-angiotensin system (RAS), using recombinant human ACE2 (rhACE2) could alleviate RAS-mediated vasoconstriction and vascular remodeling. Methods: This prospective observational study investigated the association between concentrations of RAS peptides (Ang II or Ang(1–7)) and markers of RV function, as assessed by echocardiography (ratio of RV to left ventricular end-diastolic area, interventricular septal motion, and pulmonary arterial systolic pressure (PASP)). Results: Fifty-seven mechanically ventilated patients were enrolled. Incidence rates of acute cor pulmonale (ACP) and pulmonary circulatory dysfunction (PCD) were consistent with previous studies. In the 45 evaluable participants, no notable or consistent changes in RAS peptides concentration were observed over the observation period, and there was no correlation between Ang II concentration and either PASP or RV size. The model of the predicted posterior distributions for the pre- and post-dose values of Ang II demonstrated no change in the likelihood of PCD after hypothetical dosing with rhACE2, thus meeting the futility criteria. Similar results were observed with the other RAS peptides evaluated. Conclusions: Pre-defined success criteria for an association between PCD and the plasma RAS peptides were not met in the mechanically ventilated unselected patients.

Riociguat in children with pulmonary arterial hypertension: The PATENT-CHILD study

Riociguat, a soluble guanylate cyclase stimulator, is approved for treatment of adults with pulmonary arterial hypertension (PAH). The safety, tolerability, and pharmacokinetics (PK) of oral riociguat in a pediatric population with PAH was assessed in PATENT-CHILD (NCT02562235), a multicenter, single-arm, 24-week, open-label, Phase 3 study. Patients aged 6-17 years in World Health Organization functional class (WHO-FC) I-III treated with stable endothelin receptor antagonists and/or prostacyclin analogs received riociguat equivalent to 0.5-2.5 mg three times daily in adults, as either oral pediatric suspension or tablets, based on bodyweight. Primary outcomes were safety, tolerability, and PK of riociguat. Twenty-four patients (mean age 12.8 years), 18 of whom were in WHO-FC II, were enrolled. Adverse events (AEs), mostly mild or moderate, were reported in 20 patients (83%). Four patients (17%) experienced a serious AE; all resolved by study end and two (8%) were considered study-drug related. Hypotension was reported in three patients and hemoptysis in one (all mild/moderate intensity). Riociguat plasma concentrations in pediatric patients were consistent with those published in adult patients. From baseline to Week 24, mean ± standard deviation increase in 6-minute walking distance was 23 ± 69 m (n = 19), and mean decrease in NT-proBNP was -66 ± 585 pg/ml (n = 14). There was no change in WHO-FC. Two patients experienced clinical worsening events of hospitalization for right heart failure. PK results confirmed a suitable riociguat dosing strategy for pediatric patients with PAH. The data suggest an acceptable safety profile with potential efficacy signals.

Artemisinin and Its Derivate Alleviate Pulmonary Hypertension and Vasoconstriction in Rodent Models

Background

Pulmonary arterial hypertension (PAH) is a complex pulmonary vasculature disease characterized by progressive obliteration of small pulmonary arteries and persistent increase in pulmonary vascular resistance, resulting in right heart failure and death if left untreated. Artemisinin (ARS) and its derivatives, which are common antimalarial drugs, have been found to possess a broad range of biological effects. Here, we sought to determine the therapeutic benefit and mechanism of ARS and its derivatives treatment in experimental pulmonary hypertension (PH) models.

Methods

Isolated perfused/ventilated lung and isometric tension measurements in arteries were performed to test pulmonary vasoconstriction and relaxation. Monocrotaline (MCT) and hypoxia+Su5416 (SuHx) were administered to rats to induce severe PH. Evaluation methods of ARS treatment and its derivatives in animal models include echocardiography, hemodynamics measurement, and histological staining. In vitro, the effect of these drugs on proliferation, viability, and hypoxia-inducible factor 1α (HIF1α) was examined in human pulmonary arterial smooth muscle cells (hPASMCs).

Results

ARS treatment attenuated pulmonary vasoconstriction induced by high K⁺ solution or alveolar hypoxia, decreased pulmonary artery (PA) basal vascular tension, improved acetylcholine- (ACh-) induced endothelial-dependent relaxation, increased endothelial nitric oxide (NO) synthase (eNOS) activity and NO levels, and decreased levels of NAD(P)H oxidase subunits (NOX2 and NOX4) expression, NAD(P)H oxidase activity, and reactive oxygen species (ROS) levels of pulmonary arteries (PAs) in MCT-PH rats. NOS inhibitor, L-NAME, abrogated the effects of ARS on PA constriction and relaxation. Furthermore, chronic application of both ARS and its derivative dihydroartemisinin (DHA) attenuated right ventricular systolic pressure (RVSP), Fulton index (right ventricular hypertrophy), and vascular remodeling of PAs in the two rat PH models. In addition, DHA inhibited proliferation and migration of hypoxia-induced PASMCs.

Conclusions

In conclusion, these results indicate that treatment with ARS or DHA can inhibit PA vasoconstriction, PASMC proliferation and migration, and vascular remodeling, as well as improve PA endothelium-dependent relaxation, and eventually attenuate the development and progression of PH. These effects might be achieved by decreasing NAD(P)H oxidase generated ROS production and increasing eNOS activation to release NO in PAs. ARS and its derivatives might have the potential to be novel drugs for the treatment of PH.

The Potential Application and Promising Role of Targeted Therapy in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a rare yet serious progressive disorder that is currently incurable. This female-predominant disease unfolds as a pan-vasculopathy that affects all layers of the vessel wall. Five classes of pharmacological agents currently exist to target the three major cellular signaling pathways identified in PAH but are incapable of effectively reversing the disease progression. While several targets have been identified for therapy, none of the current PAH specific therapies are curative and cost-effective as they fail to reverse vascular remodeling and do not address the cancer-like features of PAH. Our purpose is to review the current literature on the therapeutic management of PAH, as well as the molecular targets under consideration for therapy so as to shed light on the potential role and future promise of novel strategies in treating this high-mortality disease. This review study summarizes and discusses the potential therapeutic targets to be employed against PAH. In addition to the three major conventional pathways already used in PAH therapy, targeting PDGF/PDGFR signaling, regulators in glycolytic metabolism, PI3K/AKT pathways, mitochondrial heat shock protein 90 (HSP90), high-mobility group box-1 (HMGB1), and bromodomain and extra-terminal (BET) proteins by using their specific inhibitors, or a pharmacological induction of the p53 expression, could be attractive strategies for treating PAH.

Comparison of Healthcare Encounters and Drug Persistence in Patients With Pulmonary Arterial Hypertension Receiving Oral Selexipag, Inhaled Iloprost, or Parenteral Treprostinil: A Retrospective Database Analysis

Background: Agents targeting the prostacyclin (PGI2) pathway are important in managing pulmonary arterial hypertension (PAH). No head-to-head clinical trials have compared outcomes between the 3 different PGI2-pathway drugs most commonly available in countries with advanced healthcare: oral selexipag, inhaled iloprost, and parenteral (subcutaneous or intravenous) treprostinil. Objectives: To conduct retrospective database analyses to describe characteristics of patients with PAH initiating therapy with these agents and compare the rate and risk of healthcare facility encounters and drug persistence. Methods: Data were obtained from the Optum™ Clinformatics® Data Mart and Truven™ Health Analytics® MarketScan® Commercial Claims and Encounters databases from July 1, 2008, to September 30, 2020 (Optum™), or October 31, 2020 (Truven™). Patients were categorized into index-drug cohorts based on first pharmacy claims for selexipag, inhaled iloprost, or parenteral treprostinil. Eligible patients were ≥18 years of age with ≥1 ICD-9-CM or ICD-10-CM diagnosis code indicating pulmonary hypertension and no diagnosis code suggesting Group 3-5 pulmonary hypertension. Rates of hospitalization (inpatient admissions), emergency room visits, or outpatient visits per person-year were calculated. Drug persistence was measured as time to discontinuation of index drug. Multivariable analyses were performed to compare outcomes with selexipag vs inhaled iloprost and parenteral treprostinil, adjusting for baseline characteristics using inverse probability of treatment weighting. Results: Overall, 583 patients were included in the Optum™ sample and 482 in the Truven™ sample. Mean (SD) age was 61.7 (14.5) and 49.3 (11.3) years, respectively; 74.4% and 75.7% of patients, respectively, were women. In the pooled samples, after adjustment for baseline characteristics, selexipag had a lower risk than inhaled iloprost or parenteral treprostinil for hospitalization (relative rate ratio [95% CI], 0.40 [0.22, 0.75], and 0.26 [0.17, 0.39]) and outpatient visits (0.66 [0.56, 0.78] and 0.76 [0.66, 0.88]). Trends toward lower risk of emergency room visits did not attain statistical significance. Drug discontinuation risk was 16% and 36% lower with selexipag vs parenteral treprostinil and inhaled iloprost, respectively. Conclusions: In real-world use, selexipag appears to be associated with lower rates of hospitalization and outpatient visits than inhaled iloprost or parenteral treprostinil. Further research is required to identify factors underlying these differences.

Comprehensive Review on Novel Targets and Emerging Therapeutic Modalities for Pulmonary Arterial Hypertension

Pulmonary Arterial Hypertension (PAH) is the progressive increase in mean pulmonary arterial pressure (mPAP) (≥ 20 mmHg at rest). Current treatment strategies include the drugs targeting at nitric oxide pathway, endothelin receptors, prostaglandin receptors, thromboxane receptors and phosphodiesterase inhibitors, which provides the symptomatic relief. Despite of these treatments, the mortality amongst the PAH patients remains high due to non-reversal of the condition. This review primarily covers the introduction of PAH and the current treatments of the disease. This is followed by the newer disease targets expressed in the pathobiology of the disease like Rho Kinase Pathway, Vasoactive Intestinal Peptide Pathway, Receptor Tyrosine Kinases, Serotonin signalling pathway, Voltage-gated potassium (Kv) channel pathway. Newer formulation strategies for targeting at these specific receptors were covered and includes nano formulations like liposomes, Micelles, Polymeric Nanoparticles, Solid Lipid Nanoparticles (SLN), Bioresorbable stents, NONOates, Cell-Based Therapies, miRNA therapy for PAH. Novel targets were identified for their role in the pathogenesis of the PAH and needs to be targeted with new molecules or existing molecules effectively. Nanosystems have shown their potential as alternative carriers on the virtue of their better performance than traditional drug delivery systems.

Epigenetic Mechanisms as Emerging Therapeutic Targets and Microfluidic Chips Application in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a disease that progress over time and is defined as an increase in pulmonary arterial pressure and pulmonary vascular resistance that frequently leads to right-ventricular (RV) failure and death. Epigenetic modifications comprising DNA methylation, histone remodeling, and noncoding RNAs (ncRNAs) have been established to govern chromatin structure and transcriptional responses in various cell types during disease development. However, dysregulation of these epigenetic mechanisms has not yet been explored in detail in the pathology of pulmonary arterial hypertension and its progression with vascular remodeling and right-heart failure (RHF). Targeting epigenetic regulators including histone methylation, acetylation, or miRNAs offers many possible candidates for drug discovery and will no doubt be a tempting area to explore for PAH therapies. This review focuses on studies in epigenetic mechanisms including the writers, the readers, and the erasers of epigenetic marks and targeting epigenetic regulators or modifiers for treatment of PAH and its complications described as RHF. Data analyses from experimental cell models and animal induced PAH models have demonstrated that significant changes in the expression levels of multiple epigenetics modifiers such as HDMs, HDACs, sirtuins (Sirt1 and Sirt3), and BRD4 correlate strongly with proliferation, apoptosis, inflammation, and fibrosis linked to the pathological vascular remodeling during PAH development. The reversible characteristics of protein methylation and acetylation can be applied for exploring small-molecule modulators such as valproic acid (HDAC inhibitor) or resveratrol (Sirt1 activator) in different preclinical models for treatment of diseases including PAH and RHF. This review also presents to the readers the application of microfluidic devices to study sex differences in PAH pathophysiology, as well as for epigenetic analysis.

Effect of Calamintha officinalis on Vascular Contractility and Angiotensinconverting Enzyme-2

AIMS

The study aimed to assess the antihypertensive activity of Calamintha officinalis.

BACKGROUND

Calamintha officinalis (CO) is a medicinal and aromatic herb as well as an antihypertensive plant that is widely used for its medicinal properties in several regions.

OBJECTIVE

This study aimed to evaluate the effect of the aqueous extract of Calamintha officinalis (AECO) on vasorelaxant activity and arterial blood pressure under normal and hypertensive states in rats. Additionally, the effect of AECO on vascular angiotensin-converting enzyme 2 (ACE-2) was assessed.

METHODS

In the current study, AECO (100 mg/Kg) was prepared, and its antihypertensive ability was assessed in L-N^G-Nitro arginine methyl ester (L-NAME)-induced hypertensive rats. Blood pressure and heart rate were recorded for 6 h for the acute experiment and during seven days for the subchronic treatment.

RESULTS

The results indicated that AECO reduced the systolic, diastolic, and mean arterial blood pressure in hypertensive rats. In addition, the study showed that AECO exerts a vasorelaxant ability through the sGC-cGMP induction pathway, vascular cyclooxygenase pathway, and the opening of K+ channels. However, AECO had no inhibitory effect on aortic ACE-2.

CONCLUSION

The study illustrates the beneficial action of AECO as an antihypertensive and vasorelaxant agent.

Clinical characteristics and prognosis analysis of idiopathic and hereditary pulmonary hypertension patients with ACVRL1 gene mutations

Pulmonary arterial hypertension is a kind of heart and lung vascular disease with low incidence and poor prognosis. Genetic variants are the important factors of pulmonary arterial hypertension. The mutations of activin receptor-like kinase-1 (ACVRL1) could cause pulmonary arteriole obstruction and occlusion in pulmonary arterial hypertension patients. The ACVRL1 gene mutation and clinical characteristics of Chinese idiopathic or hereditary pulmonary hypertension (IPAH/HPAH) patients are still unclear. This study aimed to retrospectively study the mutation characteristics of ACVRL1 gene in Chinese IPAH/HPAH patients and its effect on clinical prognosis. We analyzed the clinical, functional, hemodynamic and mutation characteristics of 12 IPAH/HPAH patients with ACVRL1 mutations and compared with 94 IPAH/HPAH patients (27 patients carried bone morphogenetic protein receptor type 2 (BMPR2) mutations and 67 without mutations). All ACVRL1 mutations of 12 patients were single nucleotide missense mutations. The ratio of male to female in 12 patients was 1:1. The diagnosis age of ACVRL1 mutation patients was younger than that of BMPR2 mutation patients (13.6 ± 11.3 years vs. 16.0 ± 12.9 years) but higher than that of patients without mutations (13.6 ± 11.3 years vs. 8.8 ± 8.5 years, p = 0.006). IPAH/HPAH patients with ACVRL1 mutation have rapid disease progresses, high overall mortality rate (approximately 50%) and no response to the acute pulmonary vasodilation test. In conclusion, this is the first study to analyze the ACVRL1 gene mutation and clinical characteristics of Chinese IPAH/HPAH patients. It is beneficial to screen ACVRL1 gene mutation for IPAH/HPAH patients to facilitate genetic counseling and early prevention and treatment.

Endogenous Hemoprotein-Dependent Signaling Pathways of Nitric Oxide and Nitrite

Interdisciplinary research at the interface of chemistry, physiology, and biomedicine have uncovered pivotal roles of nitric oxide (NO) as a signaling molecule that regulates vascular tone, platelet aggregation, and other pathways relevant to human health and disease. Heme is central to physiological NO signaling, serving as the active site for canonical NO biosynthesis in nitric oxide synthase (NOS) enzymes and as the highly selective NO binding site in the soluble guanylyl cyclase receptor. Outside of the primary NOS-dependent biosynthetic pathway, other hemoproteins, including hemoglobin and myoglobin, generate NO via the reduction of nitrite. This auxiliary hemoprotein reaction unlocks a "second axis" of NO signaling in which nitrite serves as a stable NO reservoir. In this Forum Article, we highlight these NO-dependent physiological pathways and examine complex chemical and biochemical reactions that govern NO and nitrite signaling in vivo. We focus on hemoprotein-dependent reaction pathways that generate and consume NO in the presence of nitrite and consider intermediate nitrogen oxides, including NO2, N2O3, and S-nitrosothiols, that may facilitate nitrite-based signaling in blood vessels and tissues. We also discuss emergent therapeutic strategies that leverage our understanding of these key reaction pathways to target NO signaling and treat a wide range of diseases.

Selonsertib in adults with pulmonary arterial hypertension (ARROW): a randomised, double-blind, placebo-controlled, phase 2 trial

BACKGROUND

Data obtained in human lung tissue and preclinical models suggest that oxidative stress and increased apoptosis signal-regulating kinase 1 (ASK1) activity might have a prominent role in the pathobiology of pulmonary arterial hypertension (PAH). The purpose of this study was to determine the efficacy, safety, and tolerability of the ASK1 inhibitor selonsertib compared with placebo in patients with PAH.

METHODS

We did a randomised, double-blind, placebo-controlled, phase 2 trial at 46 centres located in Canada, France, Germany, Italy, the Netherlands, Spain, the UK, and the USA. Participants were aged 18-75 years and had an established diagnosis of idiopathic or hereditary PAH, or PAH associated with connective tissue disease, drugs or toxins, human immunodeficiency virus, or repaired congenital heart defects. Patients were stratified by PAH aetiology and background therapy, and randomly assigned (1:1:1:1) using an interactive voice-response or web-response system to placebo or selonsertib 2 mg, 6 mg, or 18 mg administered orally once daily. Both placebo and selonsertib were in tablet form. The primary efficacy endpoint was change in pulmonary vascular resistance, measured by right heart catheterisation, from baseline to week 24 in the full analysis set. Pair-wise comparisons between each of the selonsertib groups and the placebo group were made with a stratified Wilcoxon (van Elteren) rank sum test for participants without major protocol deviations who received at least one dose of study drug. This trial is registered with ClinicalTrials.gov, NCT02234141.

FINDINGS

Between Dec 3, 2014, and Nov 13, 2015, 151 patients were enrolled and randomly assigned. Of 150 participants who received selonsertib or placebo, 134 (89%) completed 24 weeks of the randomly assigned treatment; all were on background PAH therapy (138 [92%] on combination therapy). 90 (60%) patients were in functional class II and 60 (40%) in functional class III. Mean baseline pulmonary vascular resistance was 772 (SD 334) dyn·s/cm⁵. Change in pulmonary vascular resistance was 6·0 dyn·s/cm⁵ (SD 28·0; n=31) for placebo, and 35·0 (35·4) dyn·s/cm⁵ (n=35; p=0·21 vs placebo) for 2 mg selonsertib, -28·0 (30·2) dyn·s/cm⁵ (n=34; p=0·27 vs placebo) for 6 mg selonsertib, and -21·0 (37·9) dyn·s/cm⁵ (n=36; p=0·60 vs placebo) for 18 mg selonsertib. The most frequent adverse events were headache (17 [15%]), abnormal dreams (eight [7%]), nausea (seven [6%]), and diarrhoea (seven [6%]) in the selonsertib groups, and headache (six [16%]), nausea (five [14%]), and diarrhoea (two [5%]) in the placebo group. Serious adverse events occurred in 23 (20%) of 113 selonsertib-treated patients and seven (19%) of 37 patients who received placebo.

INTERPRETATION

Selonsertib once daily for 24 weeks did not lead to a significant reduction in pulmonary vascular resistance or to clinical improvement in patients with PAH, but appeared to be safe and well tolerated. Although these data do not support the clinical use of selonsertib in PAH, further study of the potential of targeting the ASK1-p38 pathway in PAH is warranted.

FUNDING

Gilead Sciences.

Riociguat: Clinical research and evolving role in therapy

Riociguat is a first-in-class soluble guanylate cyclase stimulator, approved for the treatment of adults with pulmonary arterial hypertension (PAH), inoperable chronic thromboembolic pulmonary hypertension (CTEPH), or persistent or recurrent CTEPH after pulmonary endarterectomy. Approval was based on the results of the phase III PATENT-1 (PAH) and CHEST-1 (CTEPH) studies, with significant improvements in the primary endpoint of 6-minute walk distance vs placebo of +36 m and +46 m, respectively, as well as improvements in secondary endpoints such as pulmonary vascular resistance and World Health Organization functional class. Riociguat acts as a stimulator of cyclic guanosine monophosphate synthesis rather than as an inhibitor of cGMP metabolism. As with other approved therapies for PAH, riociguat has antifibrotic, antiproliferative and anti-inflammatory effects, in addition to vasodilatory properties. This has led to further clinical studies in patients who do not achieve a satisfactory clinical response with phosphodiesterase type-5 inhibitors. Riociguat has also been evaluated in patients with World Health Organization group 2 and 3 pulmonary hypertension, and other conditions including diffuse cutaneous systemic sclerosis, Raynaud's phenomenon and cystic fibrosis. This review evaluates the results of the original clinical trials of riociguat for the treatment of PAH and CTEPH, and summarises the body of work that has examined the safety and efficacy of riociguat for the treatment of other types of pulmonary hypertension.

Platelets, extracellular vesicles and coagulation in pulmonary arterial hypertension

Pulmonary arterial hypertension is a rare disease of the pulmonary vasculature, characterised pathologically by proliferation, remodelling and thrombosis in situ. Unfortunately, existing therapeutic interventions do not reverse these findings and the disease continues to result in significant morbidity and premature mortality. A number of haematological derangements have been described in pulmonary arterial hypertension which may provide insights into the pathobiology of the disease and opportunities to explore new therapeutic pathways. These include quantitative and qualitative platelet abnormalities, such as thrombocytopaenia, increased mean platelet volume and altered platelet bioenergetics. Furthermore, a hypercoagulable state and aberrant negative regulatory pathways can be observed, which could contribute to thrombosis in situ in distal pulmonary arteries and arterioles. Finally, there is increasing interest in the role of extracellular vesicle autocrine and paracrine signalling in pulmonary arterial hypertension, and their potential utility as biomarkers and novel therapeutic targets. This review focuses on the potential role of platelets, extracellular vesicles and coagulation pathways in the pathobiology of pulmonary arterial hypertension. We highlight important unanswered clinical questions and the implications of these observations for future research and pulmonary arterial hypertension-directed therapies.

Inhibition of the Proliferation of Human Lung Fibroblasts by Prostacyclin Receptor Agonists is Linked to a Sustained cAMP Signal in the Nucleus

Idiopathic pulmonary fibrosis is a chronic and progressive fibrotic lung disease, and current treatments are limited by their side effects. Proliferation of human lung fibroblasts in the pulmonary interstitial tissue is a hallmark of this disease and is driven by prolonged ERK signalling in the nucleus in response to growth factors such as platelet-derived growth factor (PDGF). Agents that increase cAMP have been suggested as alternative therapies, as this second messenger can inhibit the ERK cascade. We previously examined a panel of eight Gα_s-cAMP-coupled G protein-coupled receptors (GPCRs) endogenously expressed in human lung fibroblasts. Although the cAMP response was important for the anti-fibrotic effects of GPCR agonists, the magnitude of the acute cAMP response was not predictive of anti-fibrotic efficacy. Here we examined the reason for this apparent disconnect by stimulating the Gα_s-coupled prostacyclin receptor and measuring downstream signalling at a sub-cellular level. MRE-269 and treprostinil caused sustained cAMP signalling in the nucleus and complete inhibition of PDGF-induced nuclear ERK and fibroblast proliferation. In contrast, iloprost caused a transient increase in nuclear cAMP, there was no effect of iloprost on PDGF-induced ERK in the nucleus, and this agonist was much less effective at reversing PDGF-induced proliferation. This suggests that sustained elevation of cAMP in the nucleus is necessary for efficient inhibition of PDGF-induced nuclear ERK and fibroblast proliferation. This is an important first step towards understanding of the signalling events that drive GPCR inhibition of fibrosis.

From Celecoxib to a Novel Class of Phosphodiesterase 5 Inhibitors: Trisubstituted Pyrazolines as Novel Phosphodiesterase 5 Inhibitors with Extremely High Potency and Phosphodiesterase Isozyme Selectivity

A ligand-based approach involving systematic modifications of a trisubstituted pyrazoline scaffold derived from the COX2 inhibitor, celecoxib, was used to develop novel PDE5 inhibitors. Novel pyrazolines were identified with potent PDE5 inhibitory activity lacking COX2 inhibitory activity. Compound d12 was the most potent with an IC₅₀ of 1 nM, which was three times more potent than sildenafil and more selective with a selectivity index of >10,000-fold against all other PDE isozymes. Sildenafil inhibited the full-length and catalytic fragment of PDE5, while compound d12 only inhibited the full-length enzyme, suggesting a mechanism of enzyme inhibition distinct from sildenafil. The PDE5 inhibitory activity of compound d12 was confirmed in cells using a cGMP biosensor assay. Oral administration of compound d12 achieved plasma levels >1000-fold higher than IC₅₀ values and showed no discernable toxicity after repeated dosing. These results reveal a novel strategy to inhibit PDE5 with unprecedented potency and isozyme selectivity.

Evolution of randomized, controlled studies of medical therapy in chronic thromboembolic pulmonary hypertension

Although pulmonary endarterectomy (PEA) is the treatment of choice for chronic thromboembolic pulmonary hypertension (CTEPH), many patients have inoperable disease, and some have persistent or recurrent pulmonary hypertension (PH) after surgery. Alternative options (balloon pulmonary angioplasty (BPA) and PH-targeted medical therapy) are, therefore, required. Studies of medical therapies for CTEPH have evolved since Aerosolized Iloprost Randomized (AIR), the first randomized, controlled study of a PH-targeted therapy (inhaled iloprost) to include patients with CTEPH. Key learnings from these studies include the need to evaluate CTEPH separately from other types of PH, the importance of prospective operability adjudication as part of the protocol, and the need for sufficient duration to allow treatment benefits to become apparent. The 16-week Chronic Thromboembolic Pulmonary Hypertension Soluble Guanylate Cyclase-Stimulator Study 1 (CHEST-1) study was the first to operationalize these learnings, demonstrating a significant mean improvement in 6-minute walk distance (+46 m) and improvements in hemodynamic endpoints with riociguat versus placebo. Findings from previous studies will inform the design of future studies to address key issues related to combination medical therapy. Data on combinations of macitentan with phosphodiesterase type 5 inhibitors or oral prostanoids are available from MERIT, the first study to allow such regimens. No data on combinations including riociguat, the only licensed medical therapy for CTEPH, are available. Studies are also needed for multimodality treatment, including medical therapy plus BPA, and medical therapy as a bridge to PEA in selected operable patients. To address these issues and improve patient outcomes, it is vital that we learn from current studies to improve future trial design.

Prognostic value of late gadolinium enhancement mass index in patients with pulmonary arterial hypertension

PURPOSE

Dysfunction of the right ventricle (RV) is an important determinant of survival in patients with pulmonary arterial hypertension (PAH). The presence of late gadolinium enhancement (LGE) in cardiac magnetic resonance (CMR) at RV insertion points (RVIPs) has been found in majority of PAH patients and was associated with parameters of RV dysfunction. We hypothesize, that more detailed quantification of LGE may provide additional prognostic information.

MATERIAL AND METHODS

Twenty-eight stable PAH patients (mean age 49.9 ​± ​15.9 years) and 12 healthy subjects (control group, 44.8 ​± ​13.5 years) were enrolled into the study. Septal LGE mass was quantified at the RVIPs and subsequently indexed by subject's body surface area. Mean follow-up time of this study was 16.6 ​± ​7.5 months and the clinical end-point (CEP) was defined as death or clinical deterioration.

RESULTS

Median LGE mass index (LGEMI) at the RVIPs was 2.75 ​g/m2 [1.41-4.85]. We observed statistically significant correlations between LGEMI and hemodynamic parameters obtained from right heart catheterization - mPAP (r ​= ​0.61, p ​= ​0.001); PVR (r ​= ​0.52, p ​= ​0.007) and from CMR - RVEF (r ​= ​-0.54, p ​= ​0.005); RV global longitudinal strain (r ​= ​0.42, p ​= ​0.03). Patients who had CEP (n ​= ​16) had a significantly higher LGEMI (4.49 [2.75-6.17] vs 1.67 [0.74-2.7], p ​= ​0.01); univariate Cox analysis confirmed prognostic value of LGEMI. Furthermore, PAH patients with LGEMI higher than median had worse prognosis in Kaplan-Meier analysis (log-rank test, p ​= ​0.0006).

CONCLUSIONS

The body surface indexed mass of LGE at RV septal insertion points are suggestive of RV hemodynamic dysfunction and could be a useful non-invasive marker of PAH prognosis.

Soluble Guanylate Cyclase Stimulators and Activators

When Furchgott, Murad, and Ignarro were honored with the Nobel prize for the identification of nitric oxide (NO) in 1998, the therapeutic implications of this discovery could not be fully anticipated. This was due to the fact that available therapeutics like NO donors did not allow a constant and long-lasting cyclic guanylyl monophosphate (cGMP) stimulation and had a narrow therapeutic window. Now, 20 years later, the stimulator of soluble guanylate cyclase (sGC), riociguat, is on the market and is the only drug approved for the treatment of two forms of pulmonary hypertension (PAH/CTEPH), and a variety of other sGC stimulators and sGC activators are in preclinical and clinical development for additional indications. The discovery of sGC stimulators and sGC activators is a milestone in the field of NO/sGC/cGMP pharmacology. The sGC stimulators and sGC activators bind directly to reduced, heme-containing and oxidized, heme-free sGC, respectively, which results in an increase in cGMP production. The action of sGC stimulators at the heme-containing enzyme is independent of NO but is enhanced in the presence of NO whereas the sGC activators interact with the heme-free form of sGC. These highly innovative pharmacological principles of sGC stimulation and activation seem to have a very broad therapeutic potential. Therefore, in both academia and industry, intensive research and development efforts have been undertaken to fully exploit the therapeutic benefit of these new compound classes. Here we summarize the discovery of sGC stimulators and sGC activators and the current developments in both compound classes, including the mode of action, the chemical structures, and the genesis of the terminology and nomenclature. In addition, preclinical studies exploring multiple aspects of their in vitro, ex vivo, and in vivo pharmacology are reviewed, providing an overview of multiple potential applications. Finally, the clinical developments, investigating the treatment potential of these compounds in various diseases like heart failure, diabetic kidney disease, fibrotic diseases, and hypertension, are reported. In summary, sGC stimulators and sGC activators have a unique mode of action with a broad treatment potential in cardiovascular diseases and beyond.

Riociguat treatment in patients with pulmonary arterial hypertension: Final safety data from the EXPERT registry

OBJECTIVE

The soluble guanylate cyclase stimulator riociguat is approved for the treatment of adult patients with pulmonary arterial hypertension (PAH) and inoperable or persistent/recurrent chronic thromboembolic pulmonary hypertension following Phase 3 randomized trials. The EXPosurE Registry RiociguaT in patients with pulmonary hypertension (EXPERT) study was designed to monitor the long-term safety of riociguat in clinical practice.

METHODS

EXPERT was an international, multicenter, prospective, uncontrolled, non-interventional cohort study of patients treated with riociguat. Patients were followed for at least 1 year and up to 4 years from enrollment or until 30 days after stopping riociguat treatment. Primary safety outcomes were adverse events (AEs) and serious adverse events (SAEs) coded using Medical Dictionary for Regulatory Activities preferred terms and System Organ Classes version 21.0, collected during routine clinic visits (usually every 3-6 months) and collated via case report forms.

RESULTS

In total, 326 patients with PAH were included in the analysis. The most common AEs in these patients were dizziness (11.7%), right ventricular (RV)/cardiac failure (10.7%), edema/peripheral edema (10.7%), diarrhea (8.6%), dyspnea (8.0%), and cough (7.7%). The most common SAEs were RV/cardiac failure (10.1%), pneumonia (6.1%), dyspnea (4.0%), and syncope (3.4%). The exposure-adjusted rate of hemoptysis/pulmonary hemorrhage was 2.5 events per 100 patient-years.

CONCLUSION

Final data from EXPERT show that in patients with PAH, the safety of riociguat in clinical practice was consistent with clinical trials, with no new safety concerns identified and a lower exposure-adjusted rate of hemoptysis/pulmonary hemorrhage than in the long-term extension of the Phase 3 trial in PAH.

Endothelial Dysfunction in Pulmonary Hypertension: Cause or Consequence?

Pulmonary arterial hypertension (PAH) is a rare, complex, and progressive disease that is characterized by the abnormal remodeling of the pulmonary arteries that leads to right ventricular failure and death. Although our understanding of the causes for abnormal vascular remodeling in PAH is limited, accumulating evidence indicates that endothelial cell (EC) dysfunction is one of the first triggers initiating this process. EC dysfunction leads to the activation of several cellular signalling pathways in the endothelium, resulting in the uncontrolled proliferation of ECs, pulmonary artery smooth muscle cells, and fibroblasts, and eventually leads to vascular remodelling and the occlusion of the pulmonary blood vessels. Other factors that are related to EC dysfunction in PAH are an increase in endothelial to mesenchymal transition, inflammation, apoptosis, and thrombus formation. In this review, we outline the latest advances on the role of EC dysfunction in PAH and other forms of pulmonary hypertension. We also elaborate on the molecular signals that orchestrate EC dysfunction in PAH. Understanding the role and mechanisms of EC dysfunction will unravel the therapeutic potential of targeting this process in PAH.

Discovery of Novel Pyrazolo[3,4-b] Pyridine Derivatives with Dual Activities of Vascular Remodeling Inhibition and Vasodilation for the Treatment of Pulmonary Arterial Hypertension

Current pulmonary arterial hypertension (PAH) therapeutic strategies mainly focus on vascular relaxation with less emphasis on vascular remodeling, which results in poor prognosis. Hence, dual pathway regulators with vasodilation effect via soluble guanylate cyclase (sGC) stimulation and vascular remodeling regulation effect by AMP-activated protein kinase (AMPK) inhibition provide more advantages and potentialities. Herein, we designed and synthesized a series of novel pyrazolo[3,4-b] pyridine derivatives based on sGC stimulator and AMPK inhibitor scaffolds. In vitro, 2 exhibited moderate vasodilation activity and higher proliferation and migration suppressive effects compared to riociguat. In vivo, 2 significantly decreased right ventricular systolic pressure (RVSP), attenuated pulmonary artery medial thickness (PAMT), and right ventricular hypertrophy (RVH) in hypoxia-induced PAH rat models (i.g.). Given the unique advantages of significant vascular remodeling inhibition and moderate vascular relaxation based on the dual pathway regulation, we proposed 2 as a promising lead for anti-PAH drug discovery.

Pulmonary Hypertension: A Brief Guide for Clinicians

Pulmonary hypertension (PH) is classified into 5 clinical subgroups: pulmonary arterial hypertension (PAH), PH due to left-sided heart disease, PH due to chronic lung disease, chronic thromboembolic PH (CTEPH), and PH with an unclear and/or multifactorial mechanisms. A range of underlying conditions can lead to these disorders. Overall, PH affects approximately 1% of the global population, and over half of patients with heart failure may be affected. Cardiologists are therefore likely to encounter PH in their practice. Routine tests in patients with symptoms and physical findings suggestive of PH include electrocardiography, chest radiography, and pulmonary function tests. Transthoracic echocardiography is used to estimate the probability of PH. All patients with suspected or confirmed PH, without confirmed left-sided heart or lung diseases, should have a ventilation-perfusion scan to exclude CTEPH. Right-sided heart catheterization is essential for accurate diagnosis and classification. All patients with PAH or CTEPH must be referred to a specialist center. Surgical pulmonary endarterectomy is the treatment of choice for eligible patients with CTEPH. Targeted treatments (phosphodiesterase type 5 inhibitors, soluble guanylate cyclase stimulators, endothelin receptor antagonists, prostacyclin analogues, and prostacyclin receptor agonists) are licensed for patients with PAH. The soluble guanylate cyclase stimulator riociguat is the only licensed targeted therapy for patients with inoperable or persistent/recurrent CTEPH. Management of PH resulting from left-sided heart disease primarily involves treatment of the underlying condition.

Efficacy and safety of riociguat in combination therapy for patients with pulmonary arterial hypertension (PATENT studies)

Many patients with pulmonary arterial hypertension do not achieve treatment goals with monotherapy, and therefore combination therapy is becoming the standard of care. The soluble guanylate cyclase stimulator riociguat is licensed for the treatment of pulmonary arterial hypertension; here we present findings from patients who were receiving combined riociguat plus endothelin receptor antagonists or non-intravenous prostanoids in the randomized, placebo-controlled PATENT-1 study and its open-label extension (PATENT-2). Moreover, we include new data from patients receiving early sequential combination therapy (three to six months of endothelin receptor antagonist treatment) or long-term background endothelin receptor antagonist therapy (>6 months). Patients were randomized to riociguat 2.5 mg–maximum (N = 131 pretreated patients) and placebo (N = 60 pretreated patients). Riociguat improved 6-min walking distance (PATENT-1 primary endpoint), functional capacity, and hemodynamics after 12 weeks in pretreated patients. The placebo-corrected changes in 6-min walking distance were +24 m in endothelin receptor antagonist-pretreated patients and +106 m in the small group of prostanoid-pretreated patients. In the early sequential combination and long-term background endothelin receptor antagonist groups, the placebo-corrected changes in 6-min walking distance were +65 m (95% CI: 17 to 113 m) and +13 m (95% CI: –8 to 33 m), respectively. In conclusion, these data suggest that early sequential combination of an endothelin receptor antagonist plus riociguat is a feasible treatment option. Both early sequential therapy and long-term background endothelin receptor antagonist plus riociguat were well tolerated in the PATENT studies.

Stem cell therapy for COVID-19 and other respiratory diseases: Global trends of clinical trials

Respiratory diseases, including coronavirus disease 2019 and chronic obstructive pulmonary disease (COPD), are leading causes of global fatality. There are no effective and curative treatments, but supportive care only. Cell therapy is a promising therapeutic strategy for refractory and unmanageable pulmonary illnesses, as proved by accumulating preclinical studies. Stem cells consist of totipotent, pluripotent, multipotent, and unipotent cells with the potential to differentiate into cell types requested for repair. Mesenchymal stromal cells, endothelial progenitor cells, peripheral blood stem cells, and lung progenitor cells have been applied to clinical trials. To date, the safety and feasibility of stem cell and extracellular vesicles administration have been confirmed by numerous phase I/II trials in patients with COPD, acute respiratory distress syndrome, bronchial dysplasia, idiopathic pulmonary fibrosis, pulmonary artery hypertension, and silicosis. Five routes and a series of doses have been tested for tolerance and advantages of different regimes. In this review, we systematically summarize the global trends for the cell therapy of common airway and lung diseases registered for clinical trials. The future directions for both new clinical trials and preclinical studies are discussed.

Bioequivalence and Tolerability of Ambrisentan: A Pharmacokinetic Study in Mexican Healthy Male Subjects

BACKGROUND

Pulmonary arterial hypertension (PAH) is a disease characterized by a progressive rise in pulmonary vascular resistance. Ambrisentan is an oral, propanoic acid based-endothelin receptor antagonist (ERA), selective for the endothelin type-A receptor, which is approved for the treatment of PAH. The Colombia National Food and Drug Surveillance Institute regulatory criteria require demonstrating that the proposed generic product is bioequivalent to its reference-listed drug to obtain marketing approval.

OBJECTIVES

The purpose of this study was to test the bioequivalence, pharmacokinetics, and tolerability of ambrisentan 10 mg tablets.

METHODS

In this open-label, randomized, oral single-dose, two-way crossover bioequivalence study, 26 Mexican adult healthy male subjects received either the generic product of ambrisentan 10 mg or the reference product Volibris^® (ambrisentan) 10 mg tablets during each study period under fasting conditions. There was a 7-day washout period between each dosing. Ambrisentan concentrations in plasma samples were quantified using a validated ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS) method. Blood samples were collected up to 72 h post-dose in each study period. The primary end points were maximum plasma concentration (C_max) and area under the plasma concentration-time (AUC_0-t) curve between 0 and 72 h for ambrisentan.

RESULTS

The ratios (90% CI) of geometric mean for ambrisentan were 104.3% (97.12-111.98%) and 100.2% (95.56-104.72%). These pharmacokinetic parameter values lie within the INVIMA-specified bioequivalence limits of 80%-125%. Nervous system disorders were the most common adverse events (AEs). All AEs were mild to moderate in nature and were resolved after follow-up or pharmacologic treatment. Both products were safe and well tolerated.

CONCLUSIONS

The test product ambrisentan 10 mg tablets is bioequivalent to the reference product Volibris^® (ambrisentan) 10 mg tablets. Both treatments were well tolerated in the Mexican male population of this study.

TRIAL REGISTRATION

COFEPRIS National Clinical Trials Registry number 183300410B0367/2018.

Hoeper M, Hofbeck M, Hohenfrost-Schmidt W, Jurevičienė E, Gumbienè L, Kabitz HJ, Klose H, Köhler T, Konstantinides S, Köestenberger M, Kozlik-Feldmann R, Kramer HH, Kropf-Sanchen C, Lammers A, Lange T, Meyn P, Miera O, Milger-Kneidinger K, Neidenbach R, Neurohr C, Opitz C, Perings C, Remppis BA, Riemekasten G, Scelsi L, Scholtz W, Simkova I, Skowasch D, Skride A, Stähler G, Stiller B, Tsangaris I, Vizza CD, Vonk Noordegraaf A, Wilkens H, Wirtz H, Diller GP, Grünig E, Rosenkranz S. Pulmonary Hypertension in Adults with Congenital Heart Disease: Real-World Data from the International COMPERA-CHD Registry

INTRODUCTION

Pulmonary hypertension (PH) is a common complication in patients with congenital heart disease (CHD), aggravating the natural, post-operative, or post-interventional course of the underlying anomaly. The various CHDs differ substantially in characteristics, functionality, and clinical outcomes among each other and compared with other diseases with pulmonary hypertension.

OBJECTIVE

To describe current management strategies and outcomes for adults with PH in relation to different types of CHD based on real-world data.

METHODS AND RESULTS

COMPERA (Comparative, Prospective Registry of Newly Initiated Therapies for Pulmonary Hypertension) is a prospective, international PH registry comprising, at the time of data analysis, >8200 patients with various forms of PH. Here, we analyzed a subgroup of 680 patients with PH due to CHD, who were included between 2007 and 2018 in 49 specialized centers for PH and/or CHD located in 11 European countries. At enrollment, the patients´ median age was 44 years (67% female), and patients had either pre-tricuspid shunts, post-tricuspid shunts, complex CHD, congenital left heart or aortic disease, or miscellaneous other types of CHD. Upon inclusion, targeted therapies for pulmonary arterial hypertension (PAH) included endothelin receptor antagonists, PDE-5 inhibitors, prostacyclin analogues, and soluble guanylate cyclase stimulators. Eighty patients with Eisenmenger syndrome were treatment-naïve. While at inclusion the primary PAH treatment for the cohort was monotherapy (70% of patients), with 30% of the patients on combination therapy, after a median observation time of 45.3 months, the number of patients on combination therapy had increased significantly, to 50%. The use of oral anticoagulants or antiplatelets was dependent on the underlying diagnosis or comorbidities. In the entire COMPERA-CHD cohort, after follow-up and receiving targeted PAH therapy (n = 511), 91 patients died over the course of a 5-year follow up. The 5-year Kaplan-Meier survival estimate for CHD associated PH was significantly better than that for idiopathic PAH (76% vs. 54%; p < 0.001). Within the CHD associated PH group, survival estimates differed particularly depending on the underlying diagnosis and treatment status.

CONCLUSIONS

In COMPERA-CHD, the overall survival of patients with CHD associated PH was dependent on the underlying diagnosis and treatment status, but was significantly better as than that for idiopathic PAH. Nevertheless, overall survival of patients with PAH due to CHD was still markedly reduced compared with survival of patients with other types of CHD, despite an increasing number of patients on PAH-targeted combination therapy.

MicroRNA Nanotherapeutics for Lung Targeting. Insights into Pulmonary Hypertension

In this review, the potential future role of microRNA-based therapies and their specific application in lung diseases is reported with special attention to pulmonary hypertension. Current limitations of these therapies will be pointed out in order to address the challenges that they need to face to reach clinical applications. In this context, the encapsulation of microRNA-based therapies in nanovectors has shown improvements as compared to chemically modified microRNAs toward enhanced stability, efficacy, reduced side effects, and local administration. All these concepts will contextualize in this review the recent achievements and expectations reported for the treatment of pulmonary hypertension.

[Experience with Selexipag to Treat Pulmonary Arterial Hypertension]

Aim To present an own experience in using a medication selexipag in patients with pulmonary arterial hypertension (PAH) included into the V. A. Almazov National Medical Research Center registry and participating in the GRIPHON and GRIPHON OL clinical studies.Material and methods 26 patients with PAH were included into this study since 2010: 20 patients with idiopathic PAH, 4 patients with PAH associated with systemic scleroderma, and 2 patients with corrected congenital heart defects. At the time of randomization, 19 patients had been receiving therapy with phosphodiesterase type 5 inhibitors for at least one month. Among the patients treated with selexipag (n=14), 4 patients reached a high individual maintenance dose (1200-1600 µg b.i.d.), 4 patients reached a medium dose (600-1000 µg b.i.d.), and 6 patients reached a low dose (200-400 µg b.i.d.).Results The selexipag therapy exerted a positive effect on secondary endpoints, specifically, on changes in the functional class of pulmonary hypertension, serum concentration of NT-proBNP, and physical working capacity of patients. Adverse events associated with the selexipag treatment, which resulted in termination of study participation, were observed in one patient.Conclusion To achieve the main goal of drug therapy, low risk of death with selexipag it is critical to observe the titration schedule and to aim at reaching the highest individual maintenance dose.

Current and future treatments of pulmonary arterial hypertension

Therapeutic options for pulmonary arterial hypertension (PAH) have increased over the last decades. The advent of pharmacological therapies targeting the prostacyclin, endothelin, and NO pathways has significantly improved outcomes. However, for the vast majority of patients, PAH remains a life-limiting illness with no prospect of cure. PAH is characterised by pulmonary vascular remodelling. Current research focusses on targeting the underlying pathways of aberrant proliferation, migration, and apoptosis. Despite success in preclinical models, using a plethora of novel approaches targeting cellular GPCRs, ion channels, metabolism, epigenetics, growth factor receptors, transcription factors, and inflammation, successful transfer to human disease with positive outcomes in clinical trials is limited. This review provides an overview of novel targets addressed by clinical trials and gives an outlook on novel preclinical perspectives in PAH. LINKED ARTICLES: This article is part of a themed issue on Risk factors, comorbidities, and comedications in cardioprotection. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.1/issuetoc.

Newer approaches and novel drugs for inhalational therapy for pulmonary arterial hypertension

Introduction: Pulmonary arterial hypertension (PAH) is a progressive disease characterized by remodeling of small pulmonary arteries leading to increased pulmonary arterial pressure. Existing treatments acts to normalize vascular tone via three signaling pathways: the prostacyclin, the endothelin-1, and the nitric oxide. Although over the past 20 years, there has been considerable progress in terms of treatments for PAH, the disease still remains incurable with a disappointing prognosis.Areas covered: This review summarizes the pathophysiology of PAH, the advantages and disadvantages of the inhalation route, and assess the relative advantages various inhaled therapies for PAH. The recent studies concerning the development of controlled-release drug delivery systems loaded with available anti-PAH drugs have also been summarized.Expert opinion: The main obstacles of current pharmacotherapies of PAH are their short half-life, stability, and formulations, resulting in reducing the efficacy and increasing systemic side effects and unknown pathogenesis of PAH. The pulmonary route has been proposed for delivering anti-PAH drugs to overcome the shortcomings. However, the application of approved inhaled anti-PAH drugs is limited. Inhalational delivery of controlled-release nanoformulations can overcome these restrictions. Extensive studies are required to develop safe and effective drug delivery systems for PAH patients.