Current and Future Treatments for Persistent Pulmonary Hypertension in the Newborn

[Recent research on inhaled nitric oxide in preterm infants with a gestational age of <34 weeks]

Nitric oxide is a messenger molecule for vasodilation of vascular smooth muscle cells, and inhaled nitric oxide (iNO) can dilate pulmonary blood vessels and reduce pulmonary vascular resistance, thereby reducing pulmonary artery pressure, but with no influence on systemic circulation pressure. Guidelines in China and overseas recommend the use of iNO in full-term infants and late preterm infants, and it has been proved that it has a marked effect on persistent pulmonary hypertension and hypoxic respiratory failure in such infants. However, recent studies have shown that there is an increase in the off-label use of iNO in preterm infants with a gestational age of <34 weeks. This article reviews the research progress on the efficacy, safety, timing, dose, and withdrawal mode of iNO and its combination with vasoactive drugs in the treatment of preterm infants with a gestational age of <34 weeks in China and overseas, so as to provide a reference for clinical application.

Current and emerging pharmacotherapies for the treatment of pulmonary arterial hypertension in infants

INTRODUCTION

Pulmonary hypertension (PH) is a complex condition that encompasses an array of underlying disease processes and affects a diverse population of infants, including those with congenital heart disease, congenital diaphragmatic hernia, persistent PH of the newborn, and those with lung disease such as bronchopulmonary dysplasia. While there are treatments available to adults with PH, limited data exists for infants, especially for the newer medications. Therapies that target the three main pathophysiologic pathways of pulmonary hypertension appear to benefit infants, but which are best for each individual disease process is unclear.

AREAS COVERED

A review of the therapies to treat pulmonary hypertension is covered in this article including the prostacyclin pathway, endothelin pathway, and the nitric oxide pathway. Other adjunctive treatments are also discussed. Findings are based on a PubMed literature search of research papers spanning 1990-2023 and a search of ongoing trials registered with clinicaltrials.gov.

EXPERT OPINION

Overall therapies seem to improve outcomes with most infants with PH. However, given the diverse population of infants with PH, it is imperative to understand the basis for the PH in individual patients and understand which therapies can be applicable. Further research into tailored therapy for the specific populations is warranted.

Inhaled Nitric Oxide Utilization in Congenital Diaphragmatic Hernia Treated With Extracorporeal Life Support: A Propensity Score Analysis

Although used commonly, ability of inhaled nitric oxide (iNO) to improve outcomes in infants with congenital diaphragmatic hernia (CDH) who receive extracorporeal life support (ECLS) remains controversial. We sought to determine the association between pre-ECLS use of iNO and mortality in infants with CDH from the Extracorporeal Life Support Organization (ELSO) Registry. Neonates who underwent ECLS for CDH were identified from the ELSO Registry from 2009 to 2019. Patients were categorized into those treated with iNO versus not prior to initiating ECLS. Patients were then matched 1:1 for case-mix based on pre-ECLS covariates using the propensity score (PS) for iNO treatment. The matched groups were compared for mortality. The matched cohorts were also compared for ELSO-defined systems-based complications as secondary outcomes. There were a total of 3,041 infants with an overall mortality of 52.2% and a pre-ECLS iNO use rate of 84.8%. With 1:1 matching, there were 461 infants with iNO use and 461 without iNO use. Following matching, use of iNO was not associated with a difference in mortality (odds ratio [OR] = 0.805; 95% confidence interval [CI], 0.621-1.042; p = 0.114). Results were similar in unadjusted analyses, and after controlling for covariates in the full cohort of patients and in the 1:1 matched data. Patients receiving iNO had significantly higher odds of renal complications (OR = 1.516; 95% CI, 1.141-2.014; p = 0.004), but no other significant differences were observed among secondary outcomes. ECLS use of iNO in CDH patients was not associated with a difference in mortality. Future randomized controlled studies are needed to delineate the utility of iNO in CDH patients.

Nitric oxide augments signaling for contraction in hypoxic pulmonary arterial smooth muscle—Implications for hypoxic pulmonary hypertension

Introduction: Hypoxic persistent pulmonary hypertension in the newborn (PPHN) is usually treated with oxygen and inhaled nitric oxide (NO), both pulmonary arterial relaxants. But treatment failure with NO occurs in 25% of cases. We previously demonstrated that 72 h exposure to hypoxia, modeling PPHN, sensitized pulmonary artery smooth muscle cells (PASMC) to the contractile agonist thromboxane and inhibited relaxant adenylyl cyclase (AC) activity.

Methods: In this study, we examined the effects of sodium nitroprusside (SNP), as NO donor, on the thromboxane-mediated contraction and NO-independent relaxation pathways and on reactive oxygen species (ROS) accumulation in PASMC. In addition, we examined the effect of the peroxynitrite scavenger 5,10,15,20-Tetrakis (4-sulfonatophenyl)porphyrinato Iron (III) (FeTPPS) on these processes.

Results: Exposure of PASMC to 72 h hypoxia increased total intracellular ROS compared to normoxic control cells and this was mitigated by treatment of cells with either SNP or FeTPPS. Total protein nitrosylation was increased in hypoxic PASMC compared to controls. Both normoxic and hypoxic cells treated with SNP exhibited increased total protein nitrosylation and intracellular nitrite; this was reduced by treatment with FeTPPS. While cell viability and mitochondrial number were unchanged by hypoxia, mitochondrial activity was decreased compared to controls; addition of FeTPPS did not alter this. Basal and maximal mitochondrial metabolism and ATP turnover were reduced in hypoxic PASMC compared to controls. Hypoxic PASMC had higher basal Ca2+, and a heightened peak Ca2+ response to thromboxane challenge compared to controls. Addition of SNP further elevated the peak Ca2+ response, while addition of FeTPPS brought peak Ca2+ response down to control levels. AC mediated relaxation was impaired in hypoxic PASMC compared to controls but was normalized following treatment with FeTPPS. Addition of SNP inhibited adenylyl cyclase activity in both normoxic and hypoxic PASMC. Moreover, addition of the Ca2+ chelator BAPTA improved AC activity, but the effect was minimal.

Discussion: We conclude that NO independently augments contraction and inhibits relaxation pathways in hypoxic PASMC, in part by a mechanism involving nitrogen radical formation and protein nitrosylation. These observations may partially explain impaired effectiveness of NO when treating hypoxic pulmonary hypertension.

Sildenafil Improves Pulmonary Vascular Remodeling in a Rat Model of Persistent Pulmonary Hypertension of the Newborn

ABSTRACT

Persistent pulmonary hypertension of the newborn (PPHN) is characterized by pulmonary arterial remodeling mainly because of apoptosis resistance and excessive proliferation of pulmonary artery smooth muscle cells (PASMCs). Sildenafil is a phosphodiesterase-5 inhibitor. Some reports have shown that sildenafil exerts protective effects against PPHN. However, the function of sildenafil in PPHN and the underlying molecular mechanisms is not clear. Here, we revealed that sildenafil effectively suppressed hypoxia-induced PASMC proliferation and apoptosis inhibition ( P < 0.05). Also, sildenafil obviously reduced ventricular hypertrophy, and inhibited pulmonary vascular remodeling in the PPHN model ( P < 0.05). Moreover, sildenafil treatment significantly attenuated the induction of Notch3 and Hes1 induced by hypoxia treatment ( P < 0.05). Furthermore, overexpression of Notch3 abolished the reduction of PASMC proliferation and promotion of PASMC apoptosis induced by sildenafil under hypoxia ( P < 0.05), whereas knockdown of Notch3 had an opposite effect ( P < 0.05). Together, our study demonstrates that sildenafil shows a potential benefit against the development of PPHN by inhibiting Notch3 signaling, providing a strategy for treating PPHN in the future.

A Review on the Pharmacological Importance of PDE5 and Its Inhibition to Manage Biomedical Conditions

Phosphodiesterase type 5 (PDE5) is a cyclic GMP (cGMP) specific protein. It hydrolyzes the phosphodiesterase linkage and catalyzes the conversion of cGMP to 5’ GMP, which controls different physiological activities of the body. PDE5 is associated with biomedical conditions like neurological disorders, pulmonary arterial hypertension, cardiomyopathy, cancer, erectile dysfunction, and lower urinary tract syndrome. Inhibition of PDE5 has now been proven pharmaceutically effective in a variety of therapeutic conditions. Avanafil, tadalafil, sildenafil, and vardenafil are the most commonly used PDE5 inhibitors (PDE5i) today which are often used for the management of erectile dysfunction, lower urinary tract syndromes, malignancy, and pulmonary arterial hypertension. However, these synthetic PDE5i come with a slew of negative effects. Some of the most common side effects include mild headaches, flushing, dyspepsia, altered color vision, back discomfort, priapism, melanoma, hypotension and dizziness, non-arteritic anterior ischemic optic neuropathy (NAION), and hearing loss. In light of the potential negative effects of this class of medications, there is a lot of room for new, selective PDE5 inhibitors to be discovered. We have found 25 plant botanical compounds effectively inhibiting PDE5 which might be useful in treating a variety of disorders with minimal or no adverse effects.

Critical role of nitric oxide in impeding COVID-19 transmission and prevention: a promising possibility

COVID-19 is a serious respiratory infection caused by a beta-coronavirus that is closely linked to SARS. Hypoxemia is a symptom of infection, which is accompanied by acute respiratory distress syndrome (ARDS). Augmenting supplementary oxygen may not always improve oxygen saturation; reversing hypoxemia in COVID-19 necessitates sophisticated means to promote oxygen transfer from alveoli to blood. Inhaled nitric oxide (iNO) has been shown to inhibit the multiplication of the respiratory coronavirus, a property that distinguishes it from other vasodilators. These findings imply that NO may have a crucial role in the therapy of COVID-19, indicating research into optimal methods to restore pulmonary physiology. According to clinical and experimental data, NO is a selective vasodilator proven to restore oxygenation by helping to normalize shunts and ventilation/perfusion mismatches. This study examines the role of NO in COVID-19 in terms of its specific physiological and biochemical properties, as well as the possibility of using inhaled NO as a standard therapy. We have also discussed how NO could be used to prevent and cure COVID-19, in addition to the limitations of NO.

Association of asymmetric dimethylarginine with the pathological process of persistent pulmonary hypertension of the newborn

OBJECTIVES

To study the change in asymmetric dimethylarginine (ADMA) in the circulation system of full-term infants with persistent pulmonary hypertension of the newborn (PPHN) and its association with treatment response, as well as the possibility of ADMA as a therapeutic target and a marker for treatment response.

METHODS

A prospective study was performed. A total of 30 full-term neonates who were diagnosed with PPHN within 3 days after birth were enrolled as the PPHN group, and the neonates without PPHN, matched for gestational age and age, who were treated or observed in the department of neonatology were enrolled as the control group. Serum samples were collected on days 1, 7, and 14 of treatment. The high-performance liquid chromatography-tandem mass spectrometry was used to measure the serum concentrations of L-arginine, ADMA, and its isomer symmetric dimethylarginine (SDMA).

RESULTS

For the neonates in the control group, the serum concentrations of ADMA and L-arginine continuously increased and the serum concentration of SDMA continuously decreased within the first 14 days of treatment. On days 1 and 14, there was no significant difference in the serum concentration of ADMA between the control and PPHN groups (P>0.05). On day 7, the PPHN group had a significantly higher serum concentration of ADMA than the control group (P<0.05), while there were no significant differences in serum concentrations of SDMA or L-arginine (P>0.05). Moreover, after 7 days of treatment, the PPHN neonates with a systolic pulmonary arterial pressure (sPAP) of >35 mmHg had a significantly higher serum concentration of ADMA than those with an sPAP of ≤35 mm Hg.

CONCLUSIONS

There are continuous increases in the ADMA concentration and the ADMA/SDMA ratio in the circulation system of full-term infants within the first 2 weeks after birth, and this process is accelerated by the pathological process of PPHN, suggesting that ADMA may be involved in the pathologic process of PPHN. A high level of ADMA is associated with the resistance to PPHN treatment, suggesting that inhibition of ADMA might be a potential target of drug intervention to improve the treatment response of PPHN.

Repurposing of the PDE5 Inhibitor Sildenafil for the Treatment of Persistent Pulmonary Hypertension in Neonates

Nitric oxide (NO), an important endogenous signaling molecule released from vascular endothelial cells and nerves, activates the enzyme soluble guanylate cyclase to catalyze the production of cyclic guanosine monophosphate (cGMP) from guanosine triphosphate. cGMP, in turn, activates protein kinase G to phosphorylate a range of effector proteins in smooth muscle cells that reduce intracellular Ca²⁺ levels to inhibit both contractility and proliferation. The enzyme phosphodiesterase type 5 (PDE5) curtails the actions of cGMP by hydrolyzing it into inactive 5'-GMP. Small molecule PDE5 inhibitors (PDE5is), such as sildenafil, prolong the availability of cGMP and therefore, enhance NO-mediated signaling. PDE5is are the first-line treatment for erectile dysfunction but are also now approved for the treatment of pulmonary arterial hypertension (PAH) in adults. Persistent pulmonary hypertension in neonates (PPHN) is currently treated with inhaled NO, but this is an expensive option and around 1/3 of newborns are unresponsive, resulting in the need for alternative approaches. Here the development, chemistry and pharmacology of PDE5is, the use of sildenafil for erectile dysfunction and PAH, are summarized and then current evidence for the utility of further repurposing of sildenafil, as a treatment for PPHN, is critically reviewed.

Incidence of alveolar capillary dysplasia with misalignment of pulmonary veins in infants with unexplained severe pulmonary hypertension: The roles of clinical, pathological, and genetic testing

BACKGROUND

Alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV) is a rare and fatal disorder that occurs in the developing fetal lungs; at birth, infants exhibit an oxygenation disorder accompanied by severe pulmonary hypertension (PH) and have a very short life span. ACDMPV is definitively diagnosed by pathological findings, and infants born with unexplained severe PH may not be properly diagnosed without a biopsy or autopsy.

METHODS

Japanese infants with unexplained severe PH were enrolled in this study. Genetic analyses were performed on DNA extracted from peripheral blood leukocytes. Sanger sequencing or next-generation sequencing was performed by coding exons and introns for FOXF1 in all samples. For individuals without pathogenic exonic variants, multiplex ligation-dependent probe amplification was performed to identify copy number variations (CNVs) in exons, introns, and in the upstream region of FOXF1.

RESULTS

This study included 30 infants who were diagnosed over the course of nine years. Four individuals had the pathogenic variations on the exon 1 of FOXF1, including two frameshift and two missense variations. Pathogenic CNVs were found in another five individuals.

CONCLUSION

In the pathologically proven ACDMPV patients, the ratios of cases with exonic variations, CNVs, and no genetic findings were reported as 45%, 45% and 10%, respectively. We estimate that about 30% (10 (9 + 1) out of 30) of individuals with unexplained severe PH had ACDMPV.

The role of NO in COVID-19 and potential therapeutic strategies

Nitric oxide (NO) is a free radical playing an important pathophysiological role in cardiovascular and immune systems. Recent studies reported that NO levels were significantly lower in patients with COVID-19, which was suggested to be closely related to vascular dysfunction and immune inflammation among them. In this review, we examine the potential role of NO during SARS-CoV-2 infection from the perspective of the unique physical, chemical and biological properties and potential mechanisms of NO in COVID-19, as well as possible therapeutic strategies using inhaled NO. We also discuss the limits of NO treatment, and the future application of this approach in prevention and therapy of COVID-19.

Oral drugs used to treat persistent pulmonary hypertension of the newborn

Introduction:Persistent Pulmonary Hypertension of the Newborn (PPHN) is a life-threatening neonatal condition, mostly treated with inhaled nitric oxide (iNO), intravenous prostaglandins, oral bosentan, sildenafil and tadalafil. However, the utility of non-oral agents is limited in PPHN for their side effects and inconvenient deliveries. Therefore, oral agents such as bosentan, sildenafil and tadalafil are becoming appealing for their satisfactory efficacy, easy mode of administration and acceptable side effects. Areas covered: We conducted a comprehensive search on Pubmed, Scopus, Web of Sciences concerning the use of bosentan, sildenafil and tadalafil to treat PPHN and summarized their efficacy, safety and pharmacokinetics. Expert opinion: Current randomized controlled trials (RCTs) have demonstrated the favorable responses and tolerable side effects of bosentan and sildenafil. Nevertheless, those RCTs are small and only one study has described the pharmacokinetics of sildenafil in neonates. Accordingly, bosentan, sildenafil and tadalafil remain off-label in clinical use. More well-designed RCTs with large samples and long-term follow-up and pharmacometrics studies are needed to demonstrate the efficacy, safety and pharmacokinetics of bosentan, sildenafil and tadalafil in PPHN.

Perinatal cardiopulmonary adaptation to the thin air of the Alto Andino by a native Altiplano dweller, the llama

Most mammals have a poor tolerance to hypoxia, and prolonged O₂ restriction can lead to organ injury, particularly during fetal and early postnatal life. Nevertheless, the llama (Lama Glama) has evolved efficient mechanisms to adapt to acute and chronic perinatal hypoxia. One striking adaptation is the marked peripheral vasoconstriction measured in the llama fetus in response to acute hypoxia, which allows efficient redistribution of cardiac output toward the fetal heart and adrenal glands. This strong peripheral vasoconstrictor tone is triggered by a carotid body reflex and critically depends on α-adrenergic signaling. A second adaptation is the ability of the llama fetus to protect its brain against hypoxic damage. During hypoxia, in the llama fetus there is no significant increase in brain blood flow. Instead, there is a fall in brain O₂ consumption and temperature, together with a decrease of Na⁺-K⁺-ATPase activity and Na⁺ channels expression, protecting against seizures and neuronal death. Finally, the newborn llama does not develop pulmonary hypertension in response to chronic hypoxia. In addition to maintaining basal pulmonary arterial pressure at normal levels the pulmonary arterial pressor response to acute hypoxia is lower in highland than in lowland llamas. The protection against hypoxic pulmonary arterial hypertension and pulmonary contractile hyperreactivity is partly due to increased hemoxygenase-carbon monoxide signaling and decreased Ca²⁺ sensitization in the newborn llama pulmonary vasculature. These three striking physiological adaptations of the llama allow this species to live and thrive under the chronic influence of the hypobaric hypoxia of life at high altitude.

Tadalafil versus linaclotide in gastrointestinal dysfunction and depressive behavior in constipation-predominant irritable bowel syndrome

BACKGROUND

Intestinal GC-C/cGMP pathway may be involved in visceral hypersensitivity and fluid secretion in irritable bowel syndrome (IBS). The guanylcyclase C agonist linaclotide, approved for IBS- constipation, is contraindicated in children as it may cause severe diarrhea. In contrast, drugs increasing cGMP by inhibiting phosphodiesterase 5 (PDE-5) are well tolerated in children with pulmonary hypertension. Accordingly, we investigated whether beneficial effects of linaclotide in IBS might be shared by PDE-5inhibitor tadalafil without the severe diarrhea reported for linaclotide. Since depression is commonly comorbid with IBS and is implicated in its pathophysiology; and since tadalafil is absorbed systemically and crosses blood brain barrier, whereas linaclotide does not, impact of both drugs on behavioral changes in IBS was also investigated.

METHODS

72 rats were divided into 6groups (control naive, control tadalafil, control linaclotide, untreated IBS, IBS tadalafil, and IBS linaclotide-treated). IBS was induced by 0 to 4 °C intragastric saline for 14 days.

RESULTS

Both drugs reduced visceral hypersensitivity and colonic C fos. Tadalafil, and to a greater extent, linaclotide increased colonic cGMP, fecal pellets (8.66 ± 4.6 (IBS),versus14.8 ± 3.3(tadalafil), 20 ± 1.2(linaclotide), fecal water content (29.8 ± 5.5 (IBS), versus 47.83 ± 12.6 (tadalafil), 63.58 ± 11.6 (linaclotide) and reduced intestinal transit time (% distance travelled: 29 ± 6.1(IBS), versus 40.58 + 7.5(tadalafil), 51.83 ± 8.3(linaclotide). Tadalafil, but not linaclotide, increased hippocampal cGMP, and improved behavioral tests scores compared to linaclotide (immobility time: 97.3 ± 12.5 s (IBS) versus 68 ± 12.8(tadalafil), 80 ± 17.06 (linaclotide).

CONCLUSION

Systemic PDE-5 inhibitors might be alternatives to locally acting guanyl cyclase agonists in IBS, inducing less severe diarrhea and more beneficial effects on the associated behavioral changes.

A Comparative Study of Inhaled Nitric Oxide and an Intravenously Administered Nitric Oxide Donor in Acute Pulmonary Hypertension

Purpose

Inhaled nitric oxide (iNO) selectively vasodilates the pulmonary circulation but the effects are sometimes insufficient. Available intravenous (iv) substances are non-selective and cause systemic side effects. The pulmonary and systemic effects of iNO and an iv mono-organic nitrite (PDNO) were compared in porcine models of acute pulmonary hypertension.

Methods

In anesthetized piglets, dose–response experiments of iv PDNO at normal pulmonary arterial pressure (n=10) were executed. Dose–response experiments of iv PDNO (n=6) and iNO (n=7) were performed during pharmacologically induced pulmonary hypertension (U46619 iv). The effects of iv PDNO and iNO were also explored in 5 mins of hypoxia-induced increase in pulmonary pressure (n=2-4).

Results

PDNO (15, 30, 45 and 60 nmol NO kg⁻¹ min⁻¹ iv) and iNO (5, 10, 20 and 40 ppm which corresponded to 56, 112, 227, 449 nmol NO kg⁻¹ min⁻¹, respectively) significantly decreased the U46619-increased mean pulmonary arterial pressure (MPAP) and pulmonary vascular resistance (PVR) to a similar degree without significant decreases in mean arterial pressure (MAP) or systemic vascular resistance (SVR). iNO caused increased levels of methemoglobin. At an equivalent delivered NO quantity (iNO 5 ppm and PDNO 45 nmol kg⁻¹ min⁻¹ iv), PDNO decreased PVR and SVR significantly more than iNO. Both drugs counteracted hypoxia-induced pulmonary vasoconstriction and they decreased the ratio of PVR and SVR in both settings.

Conclusion

Intravenous PDNO was a more potent pulmonary vasodilator than iNO in pulmonary hypertension, with no severe side effects. Hence, this study supports the potential of iv PDNO in the treatment of acute pulmonary hypertension.

Persistent Pulmonary Hypertension of the Newborn: Pathophysiological Mechanisms and Novel Therapeutic Approaches

Persistent pulmonary hypertension of the newborn (PPHN) is one of the main causes of neonatal morbidity and mortality. It is characterized by sustained elevation of pulmonary vascular resistance (PVR), preventing an increase in pulmonary blood flow after birth. The affected neonates fail to establish blood oxygenation, precipitating severe respiratory distress, hypoxemia, and eventually death. Inhaled nitric oxide (iNO), the only approved pulmonary vasodilator for PPHN, constitutes, alongside supportive therapy, the basis of its treatment. However, nearly 40% of infants are iNO resistant. The cornerstones of increased PVR in PPHN are pulmonary vasoconstriction and vascular remodeling. A better understanding of PPHN pathophysiology may enlighten targeted and more effective therapies. Sildenafil, prostaglandins, milrinone, and bosentan, acting as vasodilators, besides glucocorticoids, playing a role on reducing inflammation, have all shown potential beneficial effects on newborns with PPHN. Furthermore, experimental evidence in PPHN animal models supports prospective use of emergent therapies, such as soluble guanylyl cyclase (sGC) activators/stimulators, l-citrulline, Rho-kinase inhibitors, peroxisome proliferator-activated receptor-γ (PPAR-γ) agonists, recombinant superoxide dismutase (rhSOD), tetrahydrobiopterin (BH4) analogs, ω-3 long-chain polyunsaturated fatty acids (LC-PUFAs), 5-HT2A receptor antagonists, and recombinant human vascular endothelial growth factor (rhVEGF). This review focuses on current knowledge on alternative and novel pathways involved in PPHN pathogenesis, as well as recent progress regarding experimental and clinical evidence on potential therapeutic approaches for PPHN.

The prostacyclin analogue treprostinil in the treatment of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a rare but life-threatening disease that progresses rapidly and is currently without a cure. Pharmacological treatments aim to slow down disease progression and to reduce symptoms by targeting the prostacyclin, the endothelin or the nitric oxide pathway. Drugs targeting the prostacyclin pathway have been shown to be favourable for PAH patients by causing vasodilatative, anti-proliferative as well as anti-inflammatory effects, but tend to be underused, partially due to adverse effects and difficulties associated with their intravenous administration. Treprostinil, a stable prostacyclin analogue, was FDA-approved in 2002 to improve exercise capacity in PAH patients and is available in intravenous, subcutaneous, inhaled and oral form. The four different possible ways of administration, a long half-life and its stability at room temperature give treprostinil an advantage over epoprostenol, iloprost and selexipag, the three other FDA-approved drugs targeting the prostacyclin pathway. In clinical trials, treprostinil improved exercise capacity, quality of life (QOL), functional class and clinical status. While the different forms of treprostinil lead to specific complications, its general adverse effects are dizziness, nausea, pain in the jaw and extremities, diarrhoea, flushing and headache. This MiniReview will assess the benefits and drawbacks of treprostinil in the treatment of PAH by examining its specific mechanism of action and pharmacological properties, such as pharmacokinetics, pharmacodynamics, adverse effects and interactions. In addition, we will analyse and discuss results from different clinical trials, comparing treprostinil's four different forms to each other as well as to other drugs targeting the prostacyclin pathway.

Use of sildenafil in an infant with persistent pulmonary hypertension secondary to lung and renal hypoplasia - a case report

Background

Premature preterm rupture of membranes (PPROM) is reported to be associated with high rates of neonatal mortality and morbidity. Sildenafil has been used in infants with persistent pulmonary hypertension of newborn (PPHN) due to congenital diaphragmatic hernia (CDH) and bronchopulmonary dysplasia (BPD). Recently, Sildenafil has been evaluated as an alternative or adjunctive pulmonary vasodilator. This case report illustrates the use of early sildenafil for PPHN and right ventricular dysfunction in an unusual setting of lung and renal hypoplasia.

Case presentation

A male infant was born at 37 weeks with a birth weight of 2840 g. Rupture of membranes developed at approximately 24 weeks of gestational age (GA). Bilateral small kidneys (< 2 standard deviations below average) were detected on ultrasound (US) examination at 30 weeks of gestation. The baby developed pneumothorax and pulmonary hypertensive crisis towards the end of the first day. An echocardiogram showed a dilated right ventricle, moderate right ventricular systolic dysfunction, hypoplastic pulmonary arteries and a large patent ductus arteriosus with bidirectional flow. The patient was sedated, paralyzed, and inhaled nitric oxide was administered to decrease the pulmonary resistance. In anticipation of persistent pulmonary hypertension due to the hypoplastic lungs and small calibre of pulmonary arteries, sildenafil was started on day of life (DOL) 5 at a dosage of 0.25 mg/kg/dose Q8H and gradually increased to 2 mg/kg/dose Q8H on DOL 9. The patient was finally extubated on DOL 7 and weaned off of non-invasive respiratory support on DOL 26. Sildenafil was gradually weaned beginning on DOL 21 and discontinued on DOL 48. Repeat echocardiogram assessment at 3 months showed complete resolution of PHT and right ventricular dilatation.

Conclusions

We describe the early use of sildenafil in treating pulmonary hypertension associated with lung and renal hypoplasia in a non-CDH patient. Following this treatment the patient made a full recovery from right ventricular dysfunction.

Prostanoids and their analogues for the treatment of pulmonary hypertension in neonates

BACKGROUND

Persistent pulmonary hypertension of the newborn (PPHN) is a disease entity that describes a physiology in which there is persistence of increased pulmonary arterial pressure. PPHN is characterised by failure to adapt to a functional postnatal circulation with a fall in pulmonary vascular resistance. PPHN is responsible for impairment in oxygenation and significant neonatal mortality and morbidity. Prostanoids and their analogues may be useful therapeutic interventions due to their pulmonary vasodilatory and immunomodulatory effects.

OBJECTIVES

Primary objective• To determine the efficacy and safety of prostanoids and their analogues (iloprost, treprostinil, and beraprost) in decreasing mortality and the need for extracorporeal membrane oxygenation (ECMO) among neonates with PHSecondary objective• To determine the efficacy and safety of prostanoids and their analogues (iloprost, treprostinil, and beraprost) in decreasing neonatal morbidity (necrotizing enterocolitis (NEC), chronic lung disease (CLD), retinopathy of prematurity (ROP), intraventricular hemorrhage (IVH), periventricular leukomalacia (PVL), length of hospital stay, and duration of mechanical ventilation) and improving neurodevelopmental outcomes among neonates with PHComparisons• Prostanoids and their analogues at any dosage or duration used to treat PPHN versus 'standard treatment without these agents', placebo, or inhaled nitric oxide (iNO) therapy• Prostanoids and their analogues at any dosage or duration used to treat refractory PPHN as an 'add-on' therapy to iNO versus iNO alone SEARCH METHODS: We used the standard search strategy of Cochrane Neonatal to search the Cochrane Central Register of Controlled Trials (CENTRAL; 2018, Issue 9), MEDLINE via PubMed (1966 to 16 September 2018), Embase (1980 to 16 September 2018), and the Cumulative Index to Nursing and Allied Health Literature (CINAHL; 1982 to 16 September 2018). We also searched clinical trials databases, conference proceedings of the Pediatric Academic Societies (1990 to 16 September 2018), and the reference lists of retrieved articles for randomized controlled trials and quasi-randomized trials. We contacted authors who have published in this field as discerned from the reference lists of identified clinical trials and review authors' personal files.

SELECTION CRITERIA

Randomized and quasi-randomized controlled trials evaluating prostanoids or their analogues (at any dose, route of administration, or duration) used in neonates at any gestational age less than 28 days' postnatal age for confirmed or suspected PPHN.

DATA COLLECTION AND ANALYSIS

We used the standard methods of Cochrane Neonatal to conduct a systematic review and to assess the methodological quality of included studies (neonatal.cochrane.org/en/index.html). Three review authors independently assessed the titles and abstracts of studies identified by the search strategy and obtained full-text versions for assessment if necessary. We designed forms for trial inclusion or exclusion and for data extraction. We planned to use the GRADE approach to assess the quality of evidence.

MAIN RESULTS

We did not identify any eligible neonatal trials evaluating prostanoids or their analogues as sole agents in the treatment of PPHN.

AUTHORS' CONCLUSIONS

Implications for practiceCurrently, no evidence shows the use of prostanoids or their analogues as pulmonary vasodilators and sole therapeutic agents for the treatment of PPHN in neonates (age 28 days or less).Implications for researchThe safety and efficacy of different preparations and doses and routes of administration of prostacyclins and their analogues in neonates must be established. Well-designed, adequately powered, randomized, multi-center trials are needed to address the efficacy and safety of prostanoids and their analogues in the treatment of PPHN. These trials should evaluate long-term neurodevelopmental and pulmonary outcomes, in addition to short-term outcomes.

Inhaled Pulmonary Vasodilators and Thoracic Organ Transplantation: Does Evidence Support Its Use and Cost Benefit?

In heart transplantation, pulmonary hypertension and increased pulmonary vascular resistance followed by donor right ventricular dysfunction remain a major cause of perioperative morbidity and mortality. In lung transplantation, primary graft dysfunction remains a major obstacle because it can cause bronchiolitis obliterans and mortality. Pulmonary vasodilators have been used as an adjunct therapy for heart or lung transplantation, mainly to treat pulmonary hypertension, right ventricular failure, and associated refractory hypoxemia. Among pulmonary vasodilators, inhaled nitric oxide is unique in that it is selective in pulmonary circulation and causes fewer systemic complications such as hypotension, flushing, or coagulopathy. Nitric oxide is expected to prevent or attenuate primary graft dysfunction by decreasing ischemia-reperfusion injury in lung transplantation. However, when considering the long-term benefit of these medications, little evidence supports their use in heart or lung transplantation. Current guidelines endorse inhaled vasodilators for managing immediate postoperative right ventricular failure in lung or heart transplantation, but no guidance is offered regarding agent selection, dosing, or administration. This review presents the current evidence of inhaled nitric oxide in lung or heart transplantation as well as comparisons with other pulmonary vasodilators including cost differences in consideration of economic pressures to contain rising pharmacy costs.

The role of nitric oxide signaling in pulmonary circulation of high- and low-altitude newborn sheep under basal and acute hypoxic conditions

Nitric oxide (NO) is the main vasodilator agent that drives the rapid decrease of pulmonary vascular resistance for the respiratory onset during the fetal to neonatal transition. Nevertheless, the enhanced NO generation by the neonatal pulmonary arterial endothelium does not prevent development of hypoxic pulmonary hypertension in species without an evolutionary story at high altitude. Therefore, this study aims to describe the limits of the NO function at high-altitude during neonatal life in the sheep as an animal model without tolerance to perinatal hypoxia. We studied the effect of blockade of NO synthesis with l-NAME in the cardiopulmonary response of lowland (580 m) and highland (3600 m) newborn lambs basally and under an episode of acute hypoxia. We also determined the pulmonary expression of proteins that mediate the actions of the NO vasodilator pathway in the pulmonary vasoactive tone and remodeling. We observed an enhanced nitrergic function in highland lambs under basal conditions, evidenced as a markedly greater increase in basal mean pulmonary arterial pressure (mPAP) and resistance (PVR) under blockade of NO synthesis. Further, acute hypoxic challenge in lowland lambs infused with l-NAME markedly increased their mPAP and PVR to values greater than baseline, whilst in highland animals under NO synthesis blockade, these variables did not show additional increase in response to low PO₂. Highland animals showed increased pulmonary RhoA expression, decreased PSer188-RhoA fraction, increased PSer311-p65-NFқβ fraction and up-regulated smooth muscle α-actin, relative to lowland controls. Taken together our data suggest that NO-mediated vasodilation is important to keep a low pulmonary vascular resistance under basal conditions and acute hypoxia at low-altitude. At high-altitude, the enhanced nitrergic signaling partially prevents excessive pulmonary hypertension but does not protect against acute hypoxia. The decreased vasodilator efficacy of nitrergic tone in high altitude lambs could be in part due to increased RhoA signaling that opposes to NO action in the hypoxic pulmonary circulation.

A Model of Evolutionary Selection: The Cardiovascular Protective Function of the Longevity Associated Variant of BPIFB4

Evolutionary forces select genetic variants that allow adaptation to environmental stresses. The genomes of centenarian populations could recapitulate the evolutionary adaptation model and reveal the secrets of disease resistance shown by these individuals. Indeed, longevity phenotype is supposed to have a genetic background able to survive or escape to age-related diseases. Among these, cardiovascular diseases (CVDs) are the most lethal and their major risk factor is aging and the associated frailty status. One example of genetic evolution revealed by the study of centenarians genome is the four missense Single Nucleotide Polymorphisms (SNPs) haplotype in bactericidal/permeability-increasing fold-containing family B, member 4 (BPIFB4) locus that is enriched in long living individuals: the longevity associated variant (LAV). Indeed, LAV-BPIFB4 is able to improve endothelial function and revascularization through the increase of endothelial nitric oxide synthase (eNOS) dependent nitric oxide production. This review recapitulates the beneficial effects of LAV-BPIFB4 and its therapeutic potential for the treatment of CVDs.