Circulating immunoreactive endothelin-1 in children with pulmonary hypertension. Association with acute hypoxic pulmonary vasoreactivity

Increased Endothelin-1 Is Associated With Morbidity in Single Ventricle Heart Disease in Children Undergoing Fontan Palliation

BACKGROUND

Endothelin-1 (ET1) is a potent vasoconstrictor and stimulator of pulmonary artery smooth muscle cell proliferation. We previously demonstrated that failure to suppress ET1 is associated with morbidity in infants with single ventricle heart disease (SVHD) undergoing stage 2 palliation.

OBJECTIVES

The aim of this study is to evaluate whether persistent failure to suppress ET1 is associated with impaired recovery among children with SVHD undergoing the stage 3 (Fontan) operation.

METHODS

A prospective cohort study that includes 84 children with SVHD undergoing stage 3 palliation and 50 controls. Samples for ET1 analysis were collected at preoperation (systemic and pulmonary vein), 2, 24, and 48 hours postoperation for SVHD cases and a single timepoint for controls. Primary outcomes were Fontan pressure and systemic oxygen saturation at 24 hours postoperation.

RESULTS

SVHD cases showed higher ET1 in the systemic vein than pulmonary vein (1.0 vs 0.7 pg/mL, P < 0.001) and lower systemic vein levels than controls (1.0 vs 1.4 pg/mL, P = 0.001). Among cases, ET1 concentration peaked at 2 hours postoperation, decreased by 24 hours, and was stable but not back to baseline by 48 hours. Adjusting for clinical covariates, higher preoperative ET1 was associated with higher 24-hour Fontan pressure. Higher 24-hour postoperative ET1 was associated with lower systemic oxygen saturation at 24 hours postoperation, higher 24-hour Fontan pressure, more pleural drainage, and longer length of stay.

CONCLUSIONS

SVHD children with higher peri-operative ET1 experience more post-stage 3 morbidity. Failure to suppress ET1 may be a modifiable risk factor for intolerance of SVHD palliation.

Gender differences in genotypic distribution of endothelin-1 gene and endothelin receptor A gene in pulmonary hypertension associated with rheumatic mitral valve disease

INTRODUCTION

The female gender is a risk factor for idiopathic pulmonary arterial hypertension. However, it is unknown whether females with rheumatic mitral valve disease are more predisposed to develop pulmonary hypertension compared to males.

AIM

We aimed to investigate whether there was a difference in genotypic distribution of endothelin-1 (ET-1) and endothelin receptor A (ETA) genes between female and male patients of pulmonary hypertension associated with rheumatic mitral valve disease (PH-MVD).

METHODS

We compared prevalence of ET-1 gene (Lys198Asn) and ETA gene (His323His) polymorphisms according to gender in 123 PH-MVD subjects and 123 healthy controls.

RESULTS

The presence of mutant Asn/Asn and either mutant Asn/Asn or heterozygous Lys/Asn genotypes of Lys198Asn polymorphism when compared to Lys/Lys in females showed significant association with higher risk (odds ratio [OR] 4.5; p =0.007 and OR 2.39; p =0.02, respectively). The presence of heterozygous C/T and either mutant T/T or heterozygous C/T genotypes of His323His polymorphism when compared to wild C/C genotype in females showed a significant association with higher risk (OR 1.96; p =0.047 and OR 2.26; p =0.01, respectively). No significant difference was seen in genotypic frequencies in males between PH-MVD subjects and controls. Logistic regression analysis showed that mutant genotype Asn/Asn (p =0.007) and heterozygous genotype Lys/Asn of Lys198Asn polymorphism (p =0.018) were independent predictors of development of PH in females.

CONCLUSIONS

ET-1 and ETA gene polymorphisms were more prevalent in females than males in PH-MVD signifying that females with rheumatic heart disease may be more susceptible to develop PH.

Increased Circulating Endothelin 1 Is Associated With Postoperative Hypoxemia in Infants With Single-Ventricle Heart Disease Undergoing Superior Cavopulmonary Anastomosis

Background Inadequate pulmonary vascular growth results in morbidity for many children with single-ventricle heart disease (SVHD). Endothelin 1 (ET1) is a potent vasoconstrictor and stimulator of pulmonary artery smooth muscle proliferation. Circulating ET1 levels and their association with outcomes have not been studied during early SVHD palliation. We aimed to define circulating levels of ET1 in patients with SVHD undergoing stage 2 palliation and evaluate their relationship to postoperative hypoxemia. We hypothesized that patients with SVHD with higher ET1 concentration would have a greater post-stage 2 hypoxemia. Methods and Results Prospective cohort study of 55 subjects with SVHD undergoing stage 2 palliation and 50 controls. Samples for ET1 analysis were collected at preoperation (systemic and pulmonary vein) and 2, 24, and 48 hours postoperation for cases and a single time point for controls. The primary outcome was percentage of first 48 postoperative hours with clinically significant hypoxemia (saturation, <70%). ET1 concentration was lower in preoperative cases than controls (2.2 versus 2.7 pg/mL; P=0.0015) and in the pulmonary vein than systemic vein (1.7 versus 2.2 pg/mL; P<0.001). ET1 level increased by 2 hours postoperation and trended back to baseline by 48 hours. Higher preoperative pulmonary vein ET1 and 2 hours postoperative ET1 were associated with larger hypoxemia burden (10.6% versus 2.7% [P=0.0081]; and 7.6% versus 3.2% [P=0.01], respectively). Multivariable testing demonstrated ET1 concentration and cardiopulmonary bypass time were associated with hypoxemia, whereas catheterization measurements and clinical variables were not. Conclusions Infants with SVHD with higher perioperative ET1 concentration experience more post-stage 2 hypoxemia. ET1 activity may be a modifiable risk factor of pulmonary vascular inadequacy for stage 2 palliation.

The role of miR-543 in human cancerous and noncancerous diseases

MicroRNA (miRNA) is a noncoding single-stranded RNA molecule that can regulate the posttranscriptional expression level of a gene by binding to the 3'-untranslated region (3'-UTR) of the target messenger RNA. miR-543 is a kind of miRNA, which plays an important role in the occurrence and development of various human cancerous and noncancerous diseases. miR-543 directly or indirectly regulates a large number of downstream target genes and plays an important role in cellular components, biological processes, and molecular functions. In addition, many studies have verified the regulatory mechanism, physiological role, biological function, and prognostic value of miR-543. Therefore, this article reviews the papers published in the past decade and elaborates on the research progress of miR-543 from the aspects of physiology and pathology, especially in cancerous and other noncancerous diseases. In particular, we pay attention to the expression patterns, direct targets, biological functions, related pathways, and prognostic value of miR-543 reported in experimental articles. And by comparing similar research articles, we point out existing controversies in this field to date, so as to facilitate further research in the future.

PKCβ and reactive oxygen species mediate enhanced pulmonary vasoconstrictor reactivity following chronic hypoxia in neonatal rats

Reactive oxygen species (ROS), mitochondrial dysfunction, and excessive vasoconstriction are important contributors to chronic hypoxia (CH)-induced neonatal pulmonary hypertension. On the basis of evidence that PKCβ and mitochondrial oxidative stress are involved in several cardiovascular and metabolic disorders, we hypothesized that PKCβ and mitochondrial ROS (mitoROS) signaling contribute to enhanced pulmonary vasoconstriction in neonatal rats exposed to CH. To test this hypothesis, we examined effects of the PKCβ inhibitor LY-333,531, the ROS scavenger 1-oxyl-2,2,6,6-tetramethyl-4-hydroxypiperidine (TEMPOL), and the mitochondrial antioxidants mitoquinone mesylate (MitoQ) and (2-(2,2,6,6-tetramethylpiperidin-1-oxyl-4-ylamino)-2-oxoethyl)triphenylphosphonium chloride (MitoTEMPO) on vasoconstrictor responses in saline-perfused lungs (in situ) or pressurized pulmonary arteries from 2-wk-old control and CH (12-day exposure, 0.5 atm) rats. Lungs from CH rats exhibited greater basal tone and vasoconstrictor sensitivity to 9,11-dideoxy-9α,11α-methanoepoxy prostaglandin F_2α (U-46619). LY-333,531 and TEMPOL attenuated these effects of CH, while having no effect in lungs from control animals. Basal tone was similarly elevated in isolated pulmonary arteries from neonatal CH rats compared with control rats, which was inhibited by both LY-333,531 and mitochondria-targeted antioxidants. Additional experiments assessing mitoROS generation with the mitochondria-targeted ROS indicator MitoSOX revealed that a PKCβ-mitochondrial oxidant signaling pathway can be pharmacologically stimulated by the PKC activator phorbol 12-myristate 13-acetate in primary cultures of pulmonary artery smooth muscle cells (PASMCs) from control neonates. Finally, we found that neonatal CH increased mitochondrially localized PKCβ in pulmonary arteries as assessed by Western blotting of subcellular fractions. We conclude that PKCβ activation leads to mitoROS production in PASMCs from neonatal rats. Furthermore, this signaling axis may account for enhanced pulmonary vasoconstrictor sensitivity following CH exposure.NEW & NOTEWORTHY This research demonstrates a novel contribution of PKCβ and mitochondrial reactive oxygen species signaling to increased pulmonary vasoconstrictor reactivity in chronically hypoxic neonates. The results provide a potential mechanism by which chronic hypoxia increases both basal and agonist-induced pulmonary arterial smooth muscle tone, which may contribute to neonatal pulmonary hypertension.

Outcomes of pulmonary vascular disease in infants conceived with non-IVF fertility treatment and assisted reproductive technologies at 1 year of age

BACKGROUND

Assisted reproductive technologies (ARTs) have been associated with the development of endothelial dysfunction.

OBJECTIVE

To determine potential differences in outcomes associated with pulmonary vascular disease in infants born to mothers receiving any infertility treatment including ART and non-IVF fertility treatments (NIFTs).

DESIGN/METHODS

The sample was derived from an administrative database containing detailed information on infant and maternal characteristics for live-born infants in California (2007-2012) with gestational age (GA) 22 to 44 weeks. Cases were defined as infants with ICD-9 code for pulmonary vascular disease (PVD) and records for ART/NIFT. Controls were randomly selected at a 1:4 ratio. The primary outcome was 1-year mortality. Crude and adjusted odds ratio (OR) with 95% confidence interval (CI) were calculated.

RESULTS

We identified 159 cases and 636 controls. Mothers that utilized ART/NIFT were older, to be of the Caucasian race, to have pre-eclampsia, private insurance, and education >12 years (P < .001). Cases compared to controls were more premature, had lower birth weights, and were more often the product of a multiple gestation pregnancy (P < .001). Cases had a higher 1-year mortality (18.2% vs 9.1%; OR: 2.2; 95% CI: 1.4, 3.6), more severe PVD (86.2% vs 72.3%; OR: 2.4; 95% CI: 1.5, 3.9), and a longer hospital stay (66.7 ± 73.0 vs 32.5 ± 47.2 days; P < .001) than controls. However, when adjusting for GA these differences become statistically insignificant.

CONCLUSION

Children born following ART/NIFT with PVD had increased mortality compared to infants with PVD but without ART/NIFT. The primary driver of this relationship is prematurity.

Interleukin-1 Receptor Antagonist Protects Newborn Mice Against Pulmonary Hypertension

Pulmonary hypertension secondary to bronchopulmonary dysplasia (BPD-PH) represents a major complication of BPD in extremely preterm infants for which there are currently no safe and effective interventions. The abundance of interleukin-1 (IL-1) is strongly correlated with the severity and long-term outcome of BPD infants and we have previously shown that IL-1 receptor antagonist (IL-1Ra) protects against murine BPD; therefore, we hypothesized that IL-1Ra may also be effective against BPD-PH. We employed daily injections of IL-1Ra in a murine model in which BPD/BPD-PH was induced by antenatal LPS and postnatal hyperoxia of 65% O₂. Pups reared in hyperoxia for 28 days exhibited a BPD-PH-like disease accompanied by significant changes in pulmonary vascular morphology: micro-CT revealed an 84% reduction in small vessels (4-5 μm diameter) compared to room air controls; this change was prevented by IL-1Ra. Pulmonary vascular resistance, assessed at day 28 of life by echocardiography using the inversely-related surrogate marker time-to-peak-velocity/right ventricular ejection time (TPV/RVET), increased in hyperoxic mice (0.27 compared to 0.32 in air controls), and fell significantly with daily IL-1Ra treatment (0.31). Importantly, in vivo cine-angiography revealed that this protection afforded by IL-1Ra treatment for 28 days is maintained at day 60 of life. Despite an increased abundance of mediators of pulmonary angiogenesis in day 5 lung lysates, namely vascular endothelial growth factor (VEGF) and endothelin-1 (ET-1), no difference was detected in ex vivo pulmonary vascular reactivity between air and hyperoxia mice as measured in precision cut lung slices, or by immunohistochemistry in alpha-smooth muscle actin (α-SMA) and endothelin receptor type-A (ET_A) at day 28. Further, on day 28 of life we observed cardiac fibrosis by Sirius Red staining, which was accompanied by an increase in mRNA expression of galectin-3 and CCL2 (chemokine (C-C motif) ligand 2) in whole hearts of hyperoxic pups, which improved with IL-1Ra. In summary, our findings suggest that daily administration of the anti-inflammatory IL-1Ra prevents the increase in pulmonary vascular resistance and the pulmonary dysangiogenesis of murine BPD-PH, thus pointing to IL-1Ra as a promising candidate for the treatment of both BPD and BPD-PH.

Pulmonary artery smooth muscle cell HIF-1α regulates endothelin expression via microRNA-543

Pulmonary artery smooth muscle cells (PASMCs) express endothelin (ET-1), which modulates the pulmonary vascular response to hypoxia. Although cross-talk between hypoxia-inducible factor-1α (HIF-1α), an O₂-sensitive transcription factor, and ET-1 is established, the cell-specific relationship between HIF-1α and ET-1 expression remains incompletely understood. We tested the hypotheses that in PASMCs 1) HIF-1α expression constrains ET-1 expression, and 2) a specific microRNA (miRNA) links HIF-1α and ET-1 expression. In human (h)PASMCs, depletion of HIF-1α with siRNA increased ET-1 expression at both the mRNA and protein levels ( P < 0.01). In HIF-1α^-/- murine PASMCs, ET-1 gene and protein expression was increased ( P < 0.0001) compared with HIF-1α^+/+ cells. miRNA profiles were screened in hPASMCs transfected with siRNA-HIF-1α, and RNA hybridization was performed on the Agilent (Santa Clara, CA) human miRNA microarray. With HIF-1α depletion, miRNA-543 increased 2.4-fold ( P < 0.01). In hPASMCs, miRNA-543 overexpression increased ET-1 gene ( P < 0.01) and protein ( P < 0.01) expression, decreased TWIST gene expression ( P < 0.05), and increased ET-1 gene and protein expression, compared with nontargeting controls ( P < 0.01). Moreover, we evaluated low passage hPASMCs from control and patients with idiopathic pulmonary arterial hypertension (IPAH). Compared with controls, protein expression of HIF-1α and Twist-related protein-1 (TWIST1) was decreased ( P < 0.05), and miRNA-543 and ET-1 expression increased ( P < 0.001) in hPASMCs from patients with IPAH. Thus, in PASMCs, loss of HIF-1α increases miRNA-543, which decreases Twist expression, leading to an increase in PASMC ET-1 expression. This previously undescribed link between HIF-1α and ET-1 via miRNA-543 mediated Twist suppression represents another layer of molecular regulation that might determine pulmonary vascular tone.

Diagnosis, Evaluation and Treatment of Pulmonary Arterial Hypertension in Children

Pulmonary Hypertension (PH), the syndrome of elevated pressure in the pulmonary arteries, is associated with significant morbidity and mortality for affected children. PH is associated with a wide variety of potential underlying causes, including cardiac, pulmonary, hematologic and rheumatologic abnormalities. Regardless of the cause, for many patients the natural history of PH involves progressive elevation in pulmonary arterial resistance and pressure, right ventricular dysfunction, and eventually heart failure. In recent years, a number of pulmonary arterial hypertension (PAH)-targeted therapies have become available to reduce pulmonary artery pressure and improve outcome. A growing body of evidence in both the adult and pediatric literature demonstrates enhanced quality of life, functional status, and survival among treated patients. This review provides a description of select etiologies of PH seen in pediatrics and an update on the most recent data pertaining to evaluation and management of children with PH/PAH. The available evidence for specific classes of PAH-targeted therapies in pediatrics is additionally discussed.

Regulation, signalling and functions of hormonal peptides in pulmonary vascular remodelling during hypoxia

Hypoxic state affects organism primarily by decreasing the amount of oxygen reaching the cells and tissues. To adjust with changing environment organism undergoes mechanisms which are necessary for acclimatization to hypoxic stress. Pulmonary vascular remodelling is one such mechanism controlled by hormonal peptides present in blood circulation for acclimatization. Activation of peptides regulates constriction and relaxation of blood vessels of pulmonary and systemic circulation. Thus, understanding of vascular tone maintenance and hypoxic pulmonary vasoconstriction like pathophysiological condition during hypoxia is of prime importance. Endothelin-1 (ET-1), atrial natriuretic peptide (ANP), and renin angiotensin system (RAS) function, their receptor functioning and signalling during hypoxia in different body parts point them as disease markers. In vivo and in vitro studies have helped understanding the mechanism of hormonal peptides for better acclimatization to hypoxic stress and interventions for better management of vascular remodelling in different models like cell, rat, and human is discussed in this review.

Enhanced NO-dependent pulmonary vasodilation limits increased vasoconstrictor sensitivity in neonatal chronic hypoxia

Augmented vasoconstrictor reactivity is thought to play an important role in the development of chronic hypoxia (CH)-induced neonatal pulmonary hypertension. However, whether this response to CH results from pulmonary endothelial dysfunction and reduced nitric oxide (NO)-mediated vasodilation is not well understood. We hypothesized that neonatal CH enhances basal tone and pulmonary vasoconstrictor sensitivity by limiting NO-dependent pulmonary vasodilation. To test this hypothesis, we assessed the effects of the NO synthase (NOS) inhibitor N^ω-nitro-l-arginine (l-NNA) on baseline pulmonary vascular resistance (PVR) and vasoconstrictor sensitivity to the thromboxane mimetic U-46619 in saline-perfused lungs (in situ) from 2-wk-old control and CH (12-day exposure, 0.5 atm) Sprague-Dawley rats. Basal tone was defined as that reversed by exogenous NO (spermine NONOate). CH neonates displayed elevated right ventricular systolic pressure (in vivo) and right ventricular hypertrophy, indicative of pulmonary hypertension. Perfused lungs from CH rats demonstrated greater baseline PVR, basal tone, and U-46619-mediated vasoconstriction compared with control rats in the absence of l-NNA. l-NNA markedly increased baseline PVR and reactivity to U-46619 in lungs from CH neonates, further augmenting vasoconstrictor sensitivity compared with control lungs. Exposure to CH also enhanced NO-dependent vasodilation to arginine vasopressin, pulmonary expression of NOS III [endothelial NOS (eNOS)], and eNOS phosphorylation at activation residue Ser¹¹⁷⁷ However, CH did not alter lung nitrotyrosine levels, a posttranslational modification reflecting [Formula: see text] scavenging of NO. We conclude that, in contrast to our hypothesis, enhanced basal tone and agonist-induced vasoconstriction after neonatal CH is limited by increased NO-dependent pulmonary vasodilation resulting from greater eNOS expression and phosphorylation at activation residue Ser¹¹⁷⁷NEW & NOTEWORTHY This research is the first to demonstrate enhanced nitric oxide-dependent vasodilation that limits increased vasoconstrictor reactivity in neonatal pulmonary hypertension. These results suggest that augmented vasoconstriction in this setting reflects changes in smooth muscle reactivity rather than a reduction in nitric oxide-dependent pulmonary vasodilation.

Pathophysiological Trends During Withdrawal of Life Support: Implications for Organ Donation After Circulatory Death

BACKGROUND

Donation after circulatory death (DCD) provides an alternative pathway to deceased organ transplantation. Although clinical DCD lung, liver, and kidney transplantation are well established, transplantation of hearts retrieved from DCD donors has reached clinical translation only recently. Progress has been limited by concern regarding the viability of DCD hearts. The aim of this study was to document the pathophysiological changes that occur in the heart and circulation during withdrawal of life (WLS) support.

METHODS

In a porcine asphyxia model, we characterized the hemodynamic, volumetric, metabolic, biochemical, and endocrine changes after WLS for up to 40 minutes. Times to circulatory arrest and electrical asystole were recorded.

RESULTS

After WLS, there was rapid onset of profound hypoxemia resulting in acute pulmonary hypertension and right ventricular distension. Concurrently, progressive systemic hypotension occurred with a fall in left atrial pressure and little change in left ventricular volume. Mean times to circulatory arrest and electrical asystole were 8 ± 1 and 16 ± 2 minutes, respectively. Hemodynamic changes were accompanied by a rapid fall in pH, and rise in blood lactate, troponin-T, and potassium. Plasma noradrenaline and adrenaline levels rose rapidly with dramatic increases in coronary sinus levels indicative of myocardial release.

CONCLUSIONS

These findings provide insight into the nature and tempo of the damaging events that occur in the heart and in particular the right ventricle during WLS, and give an indication of the limited timeframe for the implementation of potential postmortem interventions that could be applied to improve organ viability.

Endothelin receptor antagonists for persistent pulmonary hypertension in term and late preterm infants

BACKGROUND

Endothelin, a powerful vasoconstrictor, is one of the mediators in the causation of persistent pulmonary hypertension of the newborn (PPHN). Theoretically, endothelin receptor antagonists (ETRA) have the potential to improve the outcomes of infants with PPHN.

OBJECTIVES

To assess the efficacy and safety of ETRA in the treatment of PPHN in full-term, post-term and late preterm infants.To assess the efficacy and safety of selective ETRAs (which block only the ETA receptors) and non-selective ETRAs (which block both ETA and ETB receptors) separately.

SEARCH METHODS

CENTRAL (Cochrane Central Register of Controlled Trials), MEDLINE, EMBASE and CINAHL databases were searched until December 2015.

SELECTION CRITERIA

Randomised, cluster-randomised or quasi-randomised controlled trials were eligible.

DATA COLLECTION AND ANALYSIS

Two review authors independently searched the literature, selected the studies, assessed the risk of bias and extracted the data. A fixed-effect model was used for meta-analysis. We used the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach to assess the quality of evidence.

MAIN RESULTS

Two randomised controlled trials of ETRA met the inclusion criteria. Both studies utilized oral Bosentan. The first study was done in a setting where inhaled nitric oxide (iNO) therapy was not available. Forty-seven infants (≥ 34 weeks' gestation) were randomised to receive either Bosentan or placebo. The second study was a multicentre study where iNO therapy was the standard of care for PPHN. Twenty-one infants were randomised to receive either 'iNO plus Bosentan' or 'iNO plus placebo'.In the first study, there was no significant difference in the incidence of death before hospital discharge between the Bosentan and placebo groups (1/23 vs 3/14; RR 0.20, 95% CI 0.02 to 1.77; RD -0.17, 95% CI -0.40 to 0.06). A higher proportion of infants in the Bosentan group showed improvement in oxygenation index (OI) at the end of therapy (21/24 vs 3/15; RR 4.38, 95% CI 1.57 to 12.17; RD 0.68, 95% CI 0.43 to 0.92; number needed to treat for a beneficial outcome (NNTB) 1.5). The duration of mechanical ventilation was lower in the Bosentan group (4.3 ± 0.9 vs 11.5 ± 0.6 days; MD -7.20, 95% CI -7.64 to -6.76). There was no significant difference in adverse neurological outcomes at six months (0/23 vs 4/14; RR 0.07, 95% CI 0.00 to 1.20; RD -0.29, 95% CI -0.52 to -0.05). The study suffered from a high risk of attrition bias since 8/23 infants in the placebo group were excluded from various analyses. Since the protocol for the study could not be accessed, the study suffered from unclear risk of reporting bias.In the second study, there was no significant difference in the incidence of treatment failure needing extracorporeal membrane oxygenation (ECMO) between the 'iNO plus Bosentan' vs 'iNO plus placebo' groups (1/13 vs 0/8; RR 1.93, 95% CI 0.09 to 42.35; RD 0.08, 95% CI -0.14 to 0.30). There was no significant difference in the median time to wean from iNO ('iNO plus Bosentan': 3.7 days (95% CI 1.17 to 6.95); 'iNO plus placebo': 2.9 days (95% CI 1.26 to 4.23); P = 0.34). There were no significant differences in the OI 0, 3, 5, 12, 24, 48 and 72 hours of treatment between the groups. There were no significant differences in the time to complete weaning from mechanical ventilation (median 10.8 days (CI 3.21 to 12.21) versus 8.6 days (CI 3.71 to 9.66); P = 0.24). The study had unequal distribution to the Bosentan group (N = 13) and the placebo group (N = 8). The methods used for generating random sequence numbers and allocation concealment were unclear, resulting in unclear risk of selection bias.Both studies reported that Bosentan was well tolerated and no major adverse effects were noted. Data from the two studies was not pooled given the heterogenous nature of the clinical settings and the modalities used for the treatment of PPHN.Overall, the quality of evidence was considered low, given the small sample size of the included studies, the numerical imbalance between the groups due to randomisation and attrition, and unclear risk of bias on some of the important domains.

AUTHORS' CONCLUSIONS

There is inadequate evidence to support the use of ETRAs either as stand-alone therapy or as adjuvant to inhaled nitric oxide in PPHN. Adequately powered RCTs are needed.

Hypoxia-inducible factor-1α, vascular endothelial growth factor, inducible nitric oxide synthase, and endothelin-1 expression correlates with angiogenesis in congenital heart disease

In Taiwan, the average prevalence of congenital heart disease (CHD) is 13.08/1000 live births. Most children with CHD die before the age of 5 years; therefore, identifying treatment methods to extend the life of CHD patients is an important issue in clinical practice. The objective of this study is to evaluate the roles of hypoxia-inducible factor-1α (HIF-1α), vascular endothelial growth factor (VEGF), inducible nitric oxide synthase (iNOS), endothelin-1 (ET-1), and CD34 in CHD autopsy cases in comparison with autopsy cases without CHD. The study included 19 autopsy cases, which were divided into the following four groups: acyanotic CHD (n = 11), cyanotic CHD (n = 3), CHD associated with chromosomal abnormalities (n = 3), and complex CHD (n = 2). Heart specimens obtained from 10 autopsy cases without CHD were included as controls. Our results indicated that high percentages of HIF-1α (100%), VEGF (89.5%), iNOS (78.9%), and ET-1 (84.2%) expressions were observed in CHD autopsy cases and this was found to be significant. HIF-1α induced by hypoxia could play a potential role in relating downstream gene expressions in CHD patients. Upregulation of VEGF by HIF-1α could play an important role in triggering angiogenesis to protect myocardial cell survival in a hypoxic microenvironment. Therefore, HIF-1α could be a significant prognosis marker in CHD and be a prospective candidate in the development of target therapy in cardiovascular diseases.

Treatment-related biomarkers in pulmonary hypertension

Significant advances in the treatment of pulmonary arterial hypertension (PAH) over the last two decades have led to the introduction of multiple classes of oral therapy, but the disease remains devastating for many patients. Disease progression, in spite of oral monotherapy, is a major problem, and alternative therapy, such as infusion of prostacyclins, is cumbersome and carries considerable potential morbidity. Use of combination oral therapy, including drugs from both the endothelin receptor antagonist and phosphodiesterase-5 inhibitor classes, has increased, and there is some evidence to support this approach. Given the multiple options now available in pulmonary hypertension (PH) therapy, biomarkers to guide treatment decisions could be helpful. Here, we review the evidence for and against the clinical use of molecular biomarkers relevant to PH pathogenesis, emphasizing assayable markers that may also inform more rational selection of agents that influence pathways targeted by treatment. We emphasize the interactive nature of changes in mediators and messengers, such as endothelin-1, prostacyclin, brain natriuretic peptide (which has demonstrated biomarker utility), nitric oxide derivatives, and cyclic guanosine monophosphate, which play important roles in processes central to progression of PAH, such as vascular remodeling, vasoconstriction, and maladaptive right ventricular changes, and are relevant to its therapy. Accordingly, we propose that the identification and use of a molecular biomarker panel that assays these molecules in parallel and serially might, if validated, better inform unique patient phenotypes, prognosis, and the rational selection and titration of combination oral and other therapy in individual patients with PH/PAH.

Prenatal programming of pulmonary hypertension induced by chronic hypoxia or ductal ligation in sheep

Pulmonary hypertension of the newborn is caused by a spectrum of functional and structural abnormalities of the cardiopulmonary circuit. The existence of multiple etiologies and an incomplete understanding of the mechanisms of disease progression have hindered the development of effective therapies. Animal models offer a means of gaining a better understanding of the fundamental basis of the disease. To that effect, a number of experimental animal models are being used to generate pulmonary hypertension in the fetus and newborn. In this review, we compare the mechanisms associated with pulmonary hypertension caused by two such models: in utero ligation of the ductus arteriosus and chronic perinatal hypoxia in sheep fetuses and newborns. In this manner, we make direct comparisons between ductal ligation and chronic hypoxia with respect to the associated mechanisms of disease, since multiple studies have been performed with both models in a single species. We present evidence that the mechanisms associated with pulmonary hypertension are dependent on the type of stress to which the fetus is subjected. Such an analysis allows for a more thorough evaluation of the disease etiology, which can help focus clinical treatments. The final part of the review provides a clinical appraisal of current treatment strategies and lays the foundation for developing individualized therapies that depend on the causative factors.

Update on pediatric pulmonary arterial hypertension. Differences and similarities to adult disease

Children and adults with pulmonary arterial hypertension (PAH) have similarities and differences in their background characteristics, hemodynamics, and clinical manifestations. Regarding genetic background, mutations in BMPR2-related pathways seem to be pivotal; however, it is likely that other modifier genes and bioactive mediators have roles in the various forms of PAH in children and adults. In pediatric PAH, there are no clear sex differences in incidence, age at onset, disease severity, or prognosis but, as compared with adults, syncope incidence, pulmonary vascular resistance, and mean pulmonary artery pressure are higher, and vasoreactivity to acute drug testing is more frequent, among children. Nevertheless, the pharmacokinetic effects of 3 major pulmonary vasodilators appear to be similar in children and adults with PAH. This review focuses on the specific pathophysiologic features of PAH in children.

Endothelial GATA-6 deficiency promotes pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a chronic and progressive disease characterized by pulmonary vasculopathy with elevation of pulmonary artery pressure, often culminating in right ventricular failure. GATA-6, a member of the GATA family of zinc-finger transcription factors, is highly expressed in quiescent vasculature and is frequently lost during vascular injury. We hypothesized that endothelial GATA-6 may play a critical role in the molecular mechanisms underlying endothelial cell (EC) dysfunction in PAH. Here we report that GATA-6 is markedly reduced in pulmonary ECs lining both occluded and nonoccluded vessels in patients with idiopathic and systemic sclerosis-associated PAH. GATA-6 transcripts are also rapidly decreased in rodent PAH models. Endothelial GATA-6 is a direct transcriptional regulator of genes controlling vascular tone [endothelin-1, endothelin-1 receptor type A, and endothelial nitric oxide synthase (eNOS)], pro-inflammatory genes, CX3CL1 (fractalkine), 5-lipoxygenease-activating protein, and markers of vascular remodeling, including PAI-1 and RhoB. Mice with the genetic deletion of GATA-6 in ECs (Gata6-KO) spontaneously develop elevated pulmonary artery pressure and increased vessel muscularization, and these features are further exacerbated in response to hypoxia. Furthermore, innate immune cells including macrophages (CD11b(+)/F4/80(+)), granulocytes (Ly6G(+)/CD45(+)), and dendritic cells (CD11b(+)/CD11c(+)) are significantly increased in normoxic Gata6-KO mice. Together, our findings suggest a critical role of endothelial GATA-6 deficiency in development and disease progression in PAH.

Cyclic guanosine monophosphate signalling pathway in pulmonary arterial hypertension

During the last decade, it emerged that cyclic guanosine monophosphate (cGMP) is a novel drug target for the treatment of pulmonary arterial hypertension (PAH). cGMP regulates many cellular functions, ranging from contractility to growth, of relevance to the disease. Generated from guanylyl cyclases in response to natriuretic peptides or nitric oxide (NO), cGMP transduces its effects through a number of cGMP effectors, including cGMP-regulated phosphodiesterases and protein kinases. Furthermore, the cGMP concentration is modulated by cGMP-degrading phosphodiesterases. Data to date demonstrate that increasing intracellular cGMP through stimulation of GCs, inhibition of PDEs, or both is a valid therapeutic strategy in drug development for PAH. New advances in understanding of cGMP are unravelled, as well as the pathobiology of PAH. cGMP remains an attractive future PAH drug target. This review makes a more detailed examination of cGMP signalling with particular reference to PAH.

Endothelin receptor antagonists for the treatment of pulmonary artery hypertension

AIMS

The demonstration that endothelin production is upregulated in pulmonary artery hypertension (PAH) served as the rationale for developing endothelin-receptor antagonists (ERAs) as a treatment for PAH. This article reviews the primary studies demonstrating efficacy of ERAs in PAH.

MAIN METHODS

Multicenter, placebo-controlled trials and open-label extension studies.

KEY FINDINGS

Two orally active ERAs are currently approved for the treatment of PAH - the dual receptor antagonist bosentan, and the more selective ET(A) receptor antagonist ambrisentan-based on multicenter randomized clinical trials demonstrating efficacy and safety. Long-term experience with both agents supports maintenance of therapeutic effects in most patients. Adverse effects, including altered liver function and edema may occur and require careful monitoring.

SIGNIFICANCE

Despite failure to demonstrate efficacy of ERAs in other cardiopulmonary conditions, ERAs have a major role in the treatment algorithm for PAH.

Adult congenital heart disease and pulmonary arterial hypertension: the Texas Adult Congenital Heart Program experience

Congenital heart disease (CHD) is a common structural defect of the heart or major blood vessels. Patients with adult congenital heart disease (ACHD) have medical needs that are distinct from those of pediatric patients with CHD, and the transition into adult health care is important for management of the patient with ACHD. A large proportion of patients with CHD develop diseases and complications associated with the long-term stress of intracardiac shunts. Pulmonary arterial hypertension (PAH) is a significant complication of some CHD lesions. The treatment of these patients remains challenging due to their combined heart and lung disease, and multidisciplinary care is ofen necessitated for a variety of secondary conditions. A number of treatment options are available for the management of PAH associated with CHD, including prostanoids, phosphodiesterase type-5 inhibitors, and endothelin receptor antagonists. This article discusses the diagnosis and management of such ACHD patients with PAH.

Physiology of endothelin and the kidney

Since its discovery in 1988 as an endothelial cell-derived peptide that exerts the most potent vasoconstriction of any known endogenous compound, endothelin (ET) has emerged as an important regulator of renal physiology and pathophysiology. This review focuses on how the ET system impacts renal function in health; it is apparent that ET regulates multiple aspects of kidney function. These include modulation of glomerular filtration rate and renal blood flow, control of renin release, and regulation of transport of sodium, water, protons, and bicarbonate. These effects are exerted through ET interactions with almost every cell type in the kidney, including mesangial cells, podocytes, endothelium, vascular smooth muscle, every section of the nephron, and renal nerves. In addition, while not the subject of the current review, ET can also indirectly affect renal function through modulation of extrarenal systems, including the vasculature, nervous system, adrenal gland, circulating hormones, and the heart. As will become apparent, these pleiotropic effects of ET are of fundamental physiologic importance in the control of renal function in health. In addition, to help put these effects into perspective, we will also discuss, albeit to a relatively limited extent, how alterations in the ET system can contribute to hypertension and kidney disease.

Pulmonary arterial hypertension: a comparison between children and adults

The characteristics of pulmonary arterial hypertension (PAH), including pathology, symptoms, diagnosis and treatment are reviewed in children and adults. The histopathology seen in adults is also observed in children, although children have more medial hypertrophy at presentation. Both populations have vascular and endothelial dysfunction. Several unique disease states are present in children, as lung growth abnormalities contribute to pulmonary hypertension. Although both children and adults present at diagnosis with elevations in pulmonary vascular resistance and pulmonary artery pressure, children have less heart failure. Dyspnoea on exertion is the most frequent symptom in children and adults with PAH, but heart failure with oedema occurs more frequently in adults. However, in idiopathic PAH, syncope is more common in children. Haemodynamic assessment remains the gold standard for diagnosis, but the definition of vasoreactivity in adults may not apply to young children. Targeted PAH therapies approved for adults are associated with clinically meaningful effects in paediatric observational studies; children now survive as long as adults with current treatment guidelines. In conclusion, there are more similarities than differences in the characteristics of PAH in children and adults, resulting in guidelines recommending similar diagnostic and therapeutic algorithms in children (based on expert opinion) and adults (evidence-based).

Regulation of blood pressure and salt homeostasis by endothelin

Endothelin (ET) peptides and their receptors are intimately involved in the physiological control of systemic blood pressure and body Na homeostasis, exerting these effects through alterations in a host of circulating and local factors. Hormonal systems affected by ET include natriuretic peptides, aldosterone, catecholamines, and angiotensin. ET also directly regulates cardiac output, central and peripheral nervous system activity, renal Na and water excretion, systemic vascular resistance, and venous capacitance. ET regulation of these systems is often complex, sometimes involving opposing actions depending on which receptor isoform is activated, which cells are affected, and what other prevailing factors exist. A detailed understanding of this system is important; disordered regulation of the ET system is strongly associated with hypertension and dysregulated extracellular fluid volume homeostasis. In addition, ET receptor antagonists are being increasingly used for the treatment of a variety of diseases; while demonstrating benefit, these agents also have adverse effects on fluid retention that may substantially limit their clinical utility. This review provides a detailed analysis of how the ET system is involved in the control of blood pressure and Na homeostasis, focusing primarily on physiological regulation with some discussion of the role of the ET system in hypertension.

Inhibition of endothelin-1 and hypoxia-induced pulmonary pressor responses in the rat by a novel selective endothelin-A receptor antagonist, di-n-butylaminocarbamyl-L-leucyl-D-tryptophanyl-D-4-chloro-Phe

Pulmonary hypertension is a kind of disease associated with a very high rate of mortality, and there are not many effective drugs for the treatment. Today, endothelin (ET)-1 receptor antagonists were proved to be effective in the treatment of pulmonary hypertension. Aiming at developing new endothelin-A receptor (ETA) antagonist for treatment of pulmonary hypertension, di-n-butylaminocarbamyl-L-leucyl-D-tryptophanyl-D-4-chloro-Phe, named GF063, was synthesized at base of selective ETA receptor antagonist BQ485 and selected for the further pharmacological characterization. The preliminary pharmacodynamics of GF063 was evaluated by radioligand receptor binding assay and test of antivasoconstriction effects in vitro and in vivo. The integrative pharmacodynamics was evaluated in hypoxia-induced rat pulmonary hypertension. In vitro, GF063 bound to ETA receptor with 100,000-fold higher affinity than to ETB receptor. GF063 concentration dependently inhibited contraction of isolated rat aortic ring induced by ET-1 and shifted the cumulative concentration-contraction response curve to right with no change in the maximal response. In vivo, GF063 inhibited the increase of mean systemic arterial pressure induced by ET-1 in anesthetized rat. In hypoxia-induced rat pulmonary hypertension model, pretreatment with GF063 (40 mg/kg, s.c.) significantly decreased pulmonary artery pressure and right ventricular hypertrophy, also significantly inhibited the increase of ET-1 level in lung, improved hemodynamics, and alleviated the wall thickness of pulmonary vessels. This study indicated that GF063, as a selective ETA receptor antagonist, could inhibit vasoconstriction effects in vivo and in vitro, could prevent pulmonary hypertension induced by hypoxia, and may have great potential to be developed as a new drug of antipulmonary hypertension.

Pulmonary vascular disease related to hemodynamic stress in the pulmonary circulation

Hemodynamic stress in the pulmonary vessel is directly linked to the development of vascular remodeling and dysfunction, ultimately leading to pulmonary hypertension. Recently, some advances have been made in our molecular understanding of the exogenous upstream stimuli that initiate hemodynamic pertubations as well as the downstream vasoactive effectors that control these responses. However, much still remains unknown regarding how these complex signaling pathways connect in order to result in these characteristic pathophysiological changes. This chapter will describe our current understanding of and needed areas of research into the clinical, physiological, and molecular changes associated with pressure/volume overload in the pulmonary circulation.

Plasma C-reactive protein and endothelin-1 level in patients with chronic obstructive pulmonary disease and pulmonary hypertension

Pulmonary hypertension is a frequent complication of chronic obstructive pulmonary disease (COPD) and associated with a worse survival and increased risk of hospitalization for exacerbation of COPD. However, little information exists regarding the potential role of systemic inflammation in pulmonary hypertension of COPD. The purpose of the present study was to investigate the degree of C-reactive protein (CRP) and endothelin-1 (ET-1) levels in COPD patient with and without pulmonary hypertension. The levels of CRP and ET-1 were investigated in 58 COPD patient with pulmonary hypertension and 50 patients without pulmonary hypertension. Pulmonary hypertension was defined as a systolic pulmonary artery pressure (Ppa) ≥35 mmHg assessed by Doppler echocardiography. Plasma CRP and ET-1 levels were significantly higher in patients with pulmonary hypertension than in patients without hypertension. There were significant positive correlations between the plasma ET-1 level and CRP level in the whole study groups. For COPD patients, systolic Ppa correlated significantly with plasma CRP levels and plasma ET-1 levels. These findings support a possibility that CRP and ET-1 correlate to pulmonary hypertension in COPD patients.

Rho kinase modulates postnatal adaptation of the pulmonary circulation through separate effects on pulmonary artery endothelial and smooth muscle cells

At birth, pulmonary vasodilation occurs concomitant with the onset of air-breathing life. Whether and how Rho kinase (ROCK) modulates the perinatal pulmonary vascular tone remains incompletely understood. To more fully characterize the separate and interactive effects of ROCK signaling, we hypothesized that ROCK has discrete effects on both pulmonary artery (PA): 1) endothelial cell (PAEC) nitric oxide (NO) production and contractile state; and 2) smooth muscle cell tone independent of endothelial NO synthase (eNOS) activity. To test these hypotheses, NO production and endothelial barrier function were determined in fetal PAEC under baseline hypoxia and following exposure to normoxia with and without treatment with Y-27632, a specific pharmacological inhibitor of ROCK. In acutely instrumented, late-gestation ovine fetuses, eNOS was inhibited by nitro-l-arginine infusion into the left PA (LPA). Subsequently, fetal lambs were mechanically ventilated (MV) with 100% oxygen in the absence (control period) and presence of Y-27632. In PAEC, treatment with Y-27632 had no effect on cytosolic calcium but did increase normoxia-induced NO production. Moreover, acute normoxia increased PAEC barrier function, an effect that was potentiated by Y-27632. In fetal lambs, MV during the control period had no effect on LPA flow. In contrast, MV after Y-27632 increased LPA flow and fetal arterial P(O)₂ (Pa(O₂)) and decreased PA pressure. In conclusion, ROCK activity modulates vascular tone in the perinatal pulmonary circulation via combined effects on PAEC NO production, barrier function, and smooth muscle tone. ROCK inhibition may represent a novel treatment strategy for neonatal pulmonary vascular disease.

Surgical Treatment of Pulmonary Arterial Hypertension

Significant advances in the treatment of pulmonary arterial hypertension have occurred in the last several years. The decision to refer a patient for transplantation requires a dynamic approach. Candidate selection and timing of referral to transplant centers is critical for success, particularly with current allocation protocols that do not take into account the severity of illness. Though long-term success is tempered by chronic allograft dysfunction and infection, considerable improvements in outcomes have established lung transplantation for pulmonary arterial hypertension as an efficacious and life-prolonging treatment. However, transplantation should be reserved for patients who have failed the best available medical therapy. Ideally, transplantation occurs when the clinically deteriorating patient has enough reserve to survive long enough to be transplanted but is not debilitated enough to jeopardize the graft. There is significant uncertainty with regard to this ideal.

B-type natriuretic peptide and C-terminal-pro-endothelin-1 for the prediction of severely impaired peak oxygen consumption

OBJECTIVE

To assess the utility of B-type natriuretic peptide (BNP) and C-terminal-pro-endothelin-1 (CT-proET-1) to predict a severely impaired peak oxygen consumption (peak VO(2), < 14 mL kg(-1) min(-1)) in patients referred for cardiopulmonary exercise testing.

DESIGN

Cross-sectional study.

SETTING

Tertiary care center.

METHODS

Peak VO(2), BNP and CT-proET-1 were assessed in 141 consecutive patients referred for cardiopulmonary exercise testing.

RESULTS

B-type natriuretic peptide [median (interquartile range) 48 (38-319) vs. 33 (15-86) pg mL(-1); P = 0.002] and CT-proET-1 [87 (76-95) vs. 60 (52-74) pmol L(-1); P < 0.001] were higher in patients with a peak VO(2) < 14 mL kg(-1) min(-1) (n = 30) than in those with a peak VO(2) > or = 14 mL kg(-1) min(-1) (n = 111). CT-pro-ET-1 had a higher area under the receiver-operator-characteristics curve (AUC) to predict a peak VO(2) < 14 mL kg(-1) min(-1) than BNP (0.79 vs. 0.68; P = 0.04). The optimal BNP cut-off of 37.2 pg mL(-1) had a sensitivity of 80% and a specificity of 56%. The optimal CT-proET-1 cut-off of 74.4 pmol L(-1) had a sensitivity of 80% and specificity of 76%. A five-item score composed of body mass index, diabetes, forced expiratory volume within the first second, alveolo-arterial oxygen pressure difference, and BNP had an AUC of 0.88 to predict a peak VO(2) < 14 mL kg(-1) min(-1). Adding CT-proET-1 to the score resulted in an AUC of 0.92.

CONCLUSIONS

C-terminal-pro-endothelin-1 is superior to BNP for the prediction of a peak VO(2) < 14 mL kg(-1) min(-1) in patients referred for CPET. A score incorporating body mass index, diabetes status, spirometry, blood gases, BNP and CT-proET-1 improves the prediction of a peak VO(2) < 14 mL kg(-1) min(-1) based on single biomarkers.

Pulmonary arterial hypertension in children: a medical update

Pulmonary arterial hypertension (PAH) is a life-threatening disease characterized by a progressive pulmonary vasculopathy with ensuing right heart failure if left untreated. In the 1980's, prior to the current treatment era, idiopathic pulmonary arterial hypertension (IPAH) carried a poor prognosis with a 10 month median survival for children after diagnosis. However, in 1995 continuous intravenous epoprostenol was approved for the treatment of severe PAH, improving hemodynamics, quality of life, exercise capacity, functional class and survival. In the past decade there have been further advances in the treatment of PAH; however, there is still no cure. While much of the groundbreaking clinical research has been performed in adults, children have also seen the benefits of PAH novel therapies. The target population among pediatric patients is expanding with the recent recognition of pulmonary hypertension as a risk factor for sickle cell disease patients. With rapid advances, navigating the literature becomes challenging. A comprehensive review of the most recent literature over the past year on available and emerging novel therapies as well as an approach to target pediatric populations provides insights into the management of pediatric PAH patients.

Upregulation of vascular calcium channels in neonatal piglets with hypoxia-induced pulmonary hypertension

Inhibition of voltage-gated, L-type Ca(2+) (Ca(L)) channels by clinical calcium channel blockers provides symptomatic improvement to some pediatric patients with pulmonary arterial hypertension (PAH). The present study investigated whether abnormalities of vascular Ca(L) channels contribute to the pathogenesis of neonatal PAH using a newborn piglet model of hypoxia-induced PAH. Neonatal piglets exposed to chronic hypoxia (CH) developed PAH by 21 days, which was evident as a 2.1-fold increase in pulmonary vascular resistance in vivo compared with piglets raised in normoxia (N). Transpulmonary pressures (DeltaPtp) in the corresponding isolated perfused lungs were 20.5 +/- 2.1 mmHg (CH) and 11.6 +/- 0.8 mmHg (N). Nifedipine reduced the elevated DeltaPtp in isolated lungs of CH piglets by 6.4 +/- 1.3 mmHg but only reduced DeltaPtp in lungs of N piglets by 1.9 +/- 0.2 mmHg. Small pulmonary arteries from CH piglets also demonstrated accentuated Ca(2+)-dependent contraction, and Ca(2+) channel current was 3.94-fold higher in the resident vascular muscle cells. Finally, although the level of mRNA encoding the pore-forming alpha(1C)-subunit of the Ca(L) channel was similar between small pulmonary arteries from N and CH piglets, a profound and persistent upregulation of the vascular alpha(1C) protein was detected by 10 days in CH piglets at a time when pulmonary vascular resistance was only mildly elevated. Thus chronic hypoxia in the neonate is associated with the anomalous upregulation of Ca(L) channels in small pulmonary arteries in vivo and the resulting abnormal Ca(2+)-dependent resistance may contribute to the pathogenesis of PAH.

Pulmonary arterial hypertension in children: a medical update

PURPOSE OF REVIEW

With rapid advances in the understanding and treatment of pulmonary arterial hypertension, navigating the pediatric literature becomes challenging. A comprehensive review of the most recent literature over the past year on available and emerging novel therapies as well as an approach to target pediatric populations will provide insight into the current management of pediatric pulmonary hypertension patients.

RECENT FINDINGS

Recent therapeutic advances have significantly improved the prognosis for children with pulmonary arterial hypertension. Pediatric pulmonary arterial hypertension continues to be a serious condition, however, which is extremely challenging to manage. There are also new target groups, such as those with sickle cell disease, congenital diaphragmatic hernia and Eisenmenger syndrome who may be candidates for treatments previously used for idiopathic pulmonary arterial hypertension patients.

SUMMARY

The data in children are often limited to case reports as many of those described here. Thus, the reader needs to be cautious about the interpretation of such small uncontrolled studies. While many of these data support the rationale for using novel agents for children with pulmonary arterial hypertension, further controlled and well designed studies are necessary to assess the true impact of these agents on various subgroups of children with pulmonary arterial hypertension.

Pathogenic mechanisms of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a complex disease that causes significant morbidity and mortality and is clinically characterized by an increase in pulmonary vascular resistance. The histopathology is marked by vascular proliferation/fibrosis, remodeling, and vessel obstruction. Development of PAH involves the complex interaction of multiple vascular effectors at all anatomic levels of the arterial wall. Subsequent vasoconstriction, thrombosis, and inflammation ensue, leading to vessel wall remodeling and cellular hyperproliferation as the hallmarks of severe disease. These processes are influenced by genetic predisposition as well as diverse endogenous and exogenous stimuli. Recent studies have provided a glimpse at certain molecular pathways that contribute to pathogenesis; these have led to the identification of attractive targets for therapeutic intervention. We will review our current understanding of the mechanistic underpinnings of the genetic and exogenous/acquired triggers of PAH. The resulting imbalance of vascular effectors provoking pathogenic vascular changes will also be discussed, with an emphasis on common and overarching regulatory pathways that may relate to the primary triggers of disease. The current conceptual framework should allow for future studies to refine our understanding of the molecular pathogenesis of PAH and improve the therapeutic regimen for this disease.

Maturational changes in the regulation of pulmonary vascular tone by nitric oxide in neonatal rats

Nitric oxide (NO) is an important regulator of vasomotor tone in the pulmonary circulation. We tested the hypothesis that the role NO plays in regulating vascular tone changes during early postnatal development. Isolated, perfused lungs from 7- and 14-day-old Sprague-Dawley rats were studied. Baseline total pulmonary vascular resistance (PVR) was not different between age groups. The addition of KCl to the perfusate caused a concentration-dependent increase in PVR that did not differ between age groups. However, the nitric oxide synthase (NOS) inhibitor N(omega)-nitro-L-arginine augmented the K(+)-induced increase in PVR in both groups, and the effect was greater in lungs from 14-day-old rats vs. 7-day-old rats. Lung levels of total endothelial, inducible, and neuronal NOS proteins were not different between groups; however, the production rate of exhaled NO was greater in lungs from 14-day-old rats compared with those of 7-day-old rats. Vasodilation to 0.1 microM of the NO donor spermine NONOate was greater in 14-day lungs than in 7-day lungs, and lung levels of both soluble guanylyl cyclase and cGMP were greater at 14 days than at 7 days. Vasodilation to 100 microM of the cGMP analog 8-(4-chlorophenylthio)guanosine-3',5'-cyclic monophosphate was greater in 7-day lungs than in 14-day lungs. Our results demonstrate that the pulmonary vascular bed depends more on NO production to modulate vascular tone at 14 days than at 7 days of age. The observed differences in NO sensitivity may be due to maturational increases in soluble guanylyl cyclase protein levels.

[Pulmonary arterial hypertension in collagenoses: clinical features, epidemiology, pathogenesis, diagnosis and treatment]

Pulmonary arterial hypertension (PAH) is a severe vasculopathy, which is characterised by progressive narrowing and obliteration of the pulmonary arterioles and increased endothelin-1 levels. The increase of vascular resistance in the lung vessels leads to chronic pressure overload and to right heart failure, if untreated. PAH often occurs in association with rheumatic-inflammatory diseases (e.g., in 15% of patients with systemic sclerosis (SSc), especially in the limited form or in CREST patients) and determines their prognosis: in advanced stages, untreated patients die within a short period. Therefore all SSc patients, particularly the newly diagnosed ones, should be screened for PAH with echocardiography. If PAH is suspected, a right heart catheter should be performed, and if PAH is confirmed, adequate treatment should be initiated. While few years ago lung transplantation was the only option for patients with severe PAH, in recent years enormous progress was seen in drug treatment. Today prostanoids (Ventavis) and the endothelin receptor antagonist bosentan (Tracleer) are available for patients with PAH in WHO/NYHA stage III: they have substantially improved the prognosis of PAH in the last years. Since few months, also the phosphodiesterase inhibitor sildenafil (Revatio) is available. The combination of drugs with different mode of action will likely further improve the prognosis of PAH patients.

Efficacy of an endothelin-A receptor antagonist in heart transplantation from asphyxiated canine non-heart-beating donors

OBJECTIVE

Hypoxic perfusion before arrest, an indeterminate period of warm ischemia, and subsequent reperfusion are major causes of cardiac allograft dysfunction in non-heart-beating donors (NHBDs). The present study was undertaken to elucidate the cardioprotective effects of ET(A) receptor antagonist FR139317 for hearts obtained from asphyxiated NHBDs in a canine transplantation model.

METHODS

Hypoxic cardiac arrest was induced in 17 donor dogs. FR139317 (10 mg/kg) was given to 7 of the dogs over a period of 10 min before disconnecting the ventilator. The hearts were preserved with FR 139317-supplemented cardioplegic solution (FR group). The remaining 10 did not receive FR 139317 at any time during the experiment (control group). Orthotopic transplantation was performed after a mean myocardial ischemic time of 4h.

RESULTS

During the agonal period, the highest systolic pulmonary artery pressure in the FR group was lower than that in the control group (47 +/- 14 vs. 58 +/- 27 mmHg). All animals in the FR group were weaned from cardiopulmonary bypass, whereas only five of the controls were weaned, two of which were identified to have dominant right ventricular failure. After transplantation, recovery rates of the left ventricular end-systolic pressure-volume ratio (E(max)) and the maximum first derivative of pressure measured over time (max dP/dt) were not significantly different between the groups, but recovery rates of the cardiac index, left ventricular minimum dP/dt and exponential time constant of LV relaxation (tau) in the FR group were higher than those in the control group.

CONCLUSIONS

The ET(A) receptor antagonist FR 139317 reduced pressure overload on the right ventricle by decreasing the peak pulmonary artery pressure before donor arrest. Cardioprotective effects of this agent for heart transplantation from NHBDs are manifested by preserved diastolic properties of the left ventricle.

Long-term oral bosentan treatment in patients with pulmonary arterial hypertension related to congenital heart disease: a 2-year study

OBJECTIVE

To evaluate the long-term clinical and exercise effect of chronic oral administration of the non-selective endothelin receptor antagonist bosentan in patients with pulmonary arterial hypertension (PAH) related to congenital heart disease (CHD).

DESIGN

Extension of a preceding prospective non-randomised open clinical study on bosentan treatment in PAH related to CHD.

SETTING

A tertiary referral centre for cardiology.

PATIENTS

19 of the original 21 patients of mean (standard deviation (SD)) age 22 (3) years (13 with Eisenmenger syndrome) in World Health Organization (WHO) class II-IV and having a mean (SD) oxygen saturation of 87 (2) %.

INTERVENTION

Patients received bosentan treatment for 2.4 (0.1) years and underwent clinical and exercise evaluation at baseline, 16 weeks and 2 years of treatment, with haemodynamic assessment at baseline and 16 weeks.

RESULTS

All patients remained stable with sustained subjective clinical and WHO class improvement (p<0.01) at 16 weeks and 2 years of treatment without significant side effects or changes in oxygen saturation. After the initial 16-week improvement (p<0.05) in peak oxygen consumption and exercise duration at treadmill test, and walking distance and Borg dyspnoea index at 6-min walk test, all exercise parameters appeared to return to their baseline values at 2 years of follow-up.

CONCLUSIONS

Long-term bosentan treatment in patients with PAH related to CHD is safe and induces clinical stability and improvement, but the objective exercise values appear to slowly return to baseline. Larger studies on long-term endothelin receptor antagonism including quality of life assessment are needed to evaluate the therapeutic role of bosentan in this population.

Pulmonary arterial hypertension

Pulmonary arterial hypertension is a disease of the small pulmonary arteries characterized by vascular narrowing and increased pulmonary vascular resistance, which eventually leads to right ventricular failure. Vasoconstriction, vascular proliferation, remodeling of the pulmonary vessels, and thrombosis are all contributing factors to the increased vascular resistance seen in this disease. Pulmonary arterial hypertension develops as a sporadic disease (idiopathic), as an inherited disorder (familial), or in association with certain conditions (collagen vascular diseases, portal hypertension, human immunodeficiency virus infection, congenital systemic-to-pulmonary shunts, ingestion of drugs or dietary products, or persistent fetal circulation). The pathogenesis of pulmonary arterial hypertension is a complicated, multifactorial process. It seems doubtful that any one factor alone is sufficient to activate the necessary pathways leading to the development of this disease. Rather, clinically apparent pulmonary arterial hypertension most likely develops after a second insult occurs in an individual who is already susceptible owing to genetic factors, environmental exposures, or acquired disorders. Currently, there is no cure for pulmonary arterial hypertension but several novel therapeutic options are now available that can improve symptoms and increase survival.

Role of endothelins and nitric oxide in the pulmonary circulation of perinatal lambs during hyperoxia and hypoxia

Endothelins (ET) have opposite vascular effects mediated through different receptors: ET(A) receptors mediating vasoconstriction and ET(B) receptors mediating vasoconstriction as well as vasodilation. The role of ET in acute hypoxic pulmonary vasoconstriction (HPV) was studied after dual ET receptor blockade with bosentan and nitric oxide (NO) synthase inhibition with nitro-L-arginine (L-NA). We started from the hypothesis that ET antagonism may inhibit HPV but, if not, would do so after NO synthase inhibition. HPV was evaluated in anesthetized lambs, with an intact pulmonary circulation, by the increase in the mean pulmonary artery pressure (Ppa) minus occluded Ppa (Ppao) gradient in response to hypoxia (inspiratory oxygen fraction of 0.1) at different levels of pulmonary flow (multipoint pressure/flow relationships). ET receptor antagonism decreased pulmonary and systemic vascular tone both in hyperoxia and hypoxia. ET antagonism had no effect on HPV. NO synthase inhibition increased pulmonary vascular tone more in hypoxia than in hyperoxia so that HPV was enhanced. After L-NA, bosentan still decreased pulmonary vascular tone in hypoxia but did not affect the magnitude of HPV. The present results suggest that ET and NO are involved in the regulation of basal pulmonary vascular tone. Furthermore, the vasodilator effect of bosentan persisted in the presence of NO synthase inhibition, suggesting a non NO-dependent vasodilator mechanism. The results from these experiments are in agreement with the idea that ET do not play a major role in HPV in the perinatal lamb, even when it is enhanced by NO synthase inhibition.

Response to bosentan in children with pulmonary hypertension

OBJECTIVE

To describe an early experience of treating 40 children with the dual endothelin receptor antagonist bosentan, which is known to be safe and effective in adults with pulmonary hypertension (PH).

DESIGN

In this retrospective, observational study the UK Service for Pulmonary Hypertension for children treated 40 children with bosentan, 20 with idiopathic pulmonary arterial hypertension (IPAH) (mean age 8.03 years, range 1.2-17) and 20 with PH associated with other conditions (congenital heart disease, parenchymal lung or connective tissue disease, or HIV). Their mean age was 8.3 years (range 0.6-16 years).

PATIENTS

39 patients were in World Health Organization (WHO) class III and IV, and all had shown recent deterioration. In IPAH the mean pulmonary vascular resistance (PVR) was 21.7 units.m2 (range 5.6-42.8). In secondary PH the mean PVR was 18 units.m2 (range 4.9-49). No child had a positive response to vasodilator testing with nitric oxide.

INTERVENTIONS

Bosentan was given as first line treatment to 25. Nine were given intravenous epoprostenol. Children were treated for a mean of 12.7 months (range 2-24 months).

MAIN OUTCOME MEASURES

Response to treatment was judged by WHO functional class, six minute walk test, weight, ECG and echocardiographic findings, and need to add additional treatment.

RESULTS

Bosentan was well tolerated. In the IPAH group 19 (95%) stabilised with bosentan treatment but 12 (60%) patients needed combined treatment with epoprostenol. In secondary PH, WHO class, six minute walk test, and weight gain improved significantly.

CONCLUSION

Bosentan helped stabilise children with IPAH but intravenous epoprostenol was also needed by 60%. Children with secondary PH improved.

Effects of Long-Term Bosentan in Children With Pulmonary Arterial Hypertension

OBJECTIVES

This study investigated the long-term outcome of children with pulmonary arterial hypertension (PAH) treated with bosentan therapy, with or without concomitant prostanoid therapy.

BACKGROUND

Bosentan, an oral endothelin ET(A)/ET(B) receptor antagonist, improves hemodynamics and exercise capacity in adults with PAH; however, limited data are available on its long-term effects in children.

METHODS

In this retrospective study, 86 children with PAH (idiopathic, associated with congenital heart or connective tissue disease) started bosentan with or without concomitant intravenous epoprostenol or subcutaneous treprostinil therapy. Hemodynamics, World Health Organization (WHO) functional class, and safety data were collected.

RESULTS

At the cutoff date, 68 patients (79%) were still treated with bosentan, 13 (15%) were discontinued, and 5 (6%) had died. Median exposure to bosentan was 14 months. In 90% of the patients (n = 78), WHO functional class improved (46%) or was unchanged (44%) with bosentan treatment. Mean pulmonary artery pressure and pulmonary vascular resistance decreased (64 +/- 3 mm Hg to 57 +/- 3 mm Hg, p = 0.005 and 20 +/- 2 U x m2 to 15 +/- 2 U x m2, p = 0.01, respectively; n = 49). Kaplan-Meier survival estimates at one and two years were 98% and 91%, respectively. The risk for worsening PAH was lower in patients in WHO functional class I/II at bosentan initiation than in patients in WHO class III/IV at bosentan initiation.

CONCLUSIONS

These data suggest that bosentan, an oral endothelin ET(A)/ET(B) receptor antagonist, with or without concomitant prostanoid therapy, is safe and efficacious for the treatment of PAH in children.

Endothelin-1 in congenital heart disease

Endothelin-1 (ET-1) is a 21-amino acid polypeptide produced primarily by vascular endothelial cells. First discovered in 1988 as a potent vasoconstrictor, it has subsequently been appreciated to participate in several biologic activities, including vascular smooth muscle proliferation, fibrosis, cardiac and vascular hypertrophy, and inflammation. Increasing data demonstrate alterations in ET-1 signaling in newborns, infants, and children with congenital heart defects that are associated with alterations in pulmonary blood flow. This review outlines the pathophysiologic role of the ET-1 cascade in the development of altered pulmonary vascular tone and reactivity that occurs with congenital heart disease and its repair, following the use of cardiopulmonary bypass. In addition, therapeutic implications for the use of novel ET receptor antagonists will be emphasized.