Recent advances in the pathogenesis and treatment of persistent pulmonary hypertension of the newborn

Serum pentraxin 3 levels in term neonates with persistent pulmonary hypertension

BACKGROUND

Persistent pulmonary hypertension of the neonate (PPHN) is a serious disorder. The long pentraxin 3 (PTX3) plays an important role in angiogenesis, cell proliferation, tissue repair and cell regulation. The present study aims to assess the diagnostic and clinical value of PTX3 in PPHN.

METHODS

The present case-control 60 full-term neonates diagnosed with PPHN by echocardiography within 72 hours of birth. In addition, there were 30 age and sex-matched healthy neonates who served as controls. All participants were subjected to careful history taking and complete clinical examination, Laboratory investigations included complete blood count, C-reactive protein (CRP), blood culture and PTX3 level. Radiological investigations included plain X- ray and two-dimensional transthoracic echocardiography (TTE).

RESULTS

Comparison between patients and controls revealed that patients had significantly higher CRP (6.12±2.18 versus 3.69±1.25 mg/dl, p < 0.001) and PTX3 levels (2.07±0.67 versus 0.96±0.21, p < 0.001) when compared with controls. Patients with associated PDA had significantly higher PTX3 levels when compared with patients without (2.58±0.5 versus 2.02±0.51 ng/ml, p = 0.002). Also, patients with associated PFO had significantly higher PTX3 levels when compared with patients without (2.12±1.05 versus 2.05±0.46, p = 0.002). ROC curve analysis identified good performance of CRP and PTX3 levels in diagnosis of PPHN with PTX3 showing better performance.

CONCLUSIONS

There is a significant association between serum PTX3 levels and PPHN particularly those with associated PDA or PFO.

The Role of Sildenafil in Treating Brain Injuries in Adults and Neonates

Sildenafil is a recognized treatment for patients suffering from erectile dysfunction and pulmonary hypertension. However, new evidence suggests that it may have a neuroprotective and a neurorestorative role in the central nervous system of both adults and neonates. Phosphodiesterase type 5-the target of sildenafil-is distributed in many cells throughout the body, including neurons and glial cells. This study is a comprehensive review of the demonstrated effects of sildenafil on the brain with respect to its function, extent of injury, neurons, neuroinflammation, myelination, and cerebral vessels.

Chorioamnionitis, Inflammation and Neonatal Apnea: Effects on Preterm Neonatal Brainstem and on Peripheral Airways: Chorioamnionitis and Neonatal Respiratory Functions

Background: The present manuscript aims to be a narrative review evaluating the association between inflammation in chorioamnionitis and damage on respiratory centers, peripheral airways, and lungs, explaining the pathways responsible for apnea in preterm babies born by delivery after chorioamnionitis. Methods: A combination of keywords and MESH words was used, including: "inflammation", "chorioamnionitis", "brainstem", "cytokines storm", "preterm birth", "neonatal apnea", and "apnea physiopathology". All identified papers were screened for title and abstracts by the two authors to verify whether they met the proper criteria to write the topic. Results: Chorioamnionitis is usually associated with Fetal Inflammatory Response Syndrome (FIRS), resulting in injury of brain and lungs. Literature data have shown that infections causing chorioamnionitis are mostly associated with inflammation and consequent hypoxia-mediated brain injury. Moreover, inflammation and infection induce apneic episodes in neonates, as well as in animal samples. Chorioamnionitis-induced inflammation favors the systemic secretion of pro-inflammatory cytokines that are involved in abnormal development of the respiratory centers in the brainstem and in alterations of peripheral airways and lungs. Conclusions: Preterm birth shows a suboptimal development of the brainstem and abnormalities and altered development of peripheral airways and lungs. These alterations are responsible for reduced respiratory control and apnea. To date, mostly animal studies have been published. Therefore, more clinical studies on the role of chorioamninitis-induced inflammation on prematurity and neonatal apnea are necessary.

Association between genetic variations in carbamoyl-phosphate synthetase gene and persistent neonatal pulmonary hypertension

Persistent pulmonary hypertension of the new-borns (PPHN) is one of the main etiologies of morbidity as well as mortality in neonates. Previous studies found that genetic polymorphisms in urea cycle enzymes are associated with PPHN. Few of the genetic polymorphisms in neonates have been recognized with PPHN. We aimed to find out the prevalence of the CPS-I gene polymorphism and to correlate the genotype with the serum nitric oxide (NO) levels in Egyptian neonates with idiopathic PPHN. We included neonates diagnosed with PPH (n = 150) while the control group included healthy neonates with matched age and sex (n = 100). The CPS-I gene polymorphism: A/C, trans-version substitution, rs4399666 genotype was identified using TaqMan-based quantitative PCR. The results revealed that the CPS-I A/C rs4399666 gene polymorphism and lower serum NO levels were significantly associated with idiopathic PPHN in neonates. In addition, serum NO level was significantly associated with an rs4366999 A/C variant gene in idiopathic PPHN (p = 0.001). Univariable regression analysis demonstrated that there was a significant association between CPS-I A/C rs4399666 CC and increased risk of PPHN (odd ratio, 95% CI of 1.8 (0.78 to 1.75), p-value = 0.04).Conclusion: We concluded that mutant CPS-I A/C rs4399666 minor variant especially the homozygous CC genotype is frequently distributed among the PPHN group. This demonstrates that the presence of mutant CPS-I rs4399666 does not necessarily predispose to the development of PPHN in neonates, but nonetheless, if the C allele is inherited in the homozygous CC genotype, it is associated with a higher risk of PPHN. What is Known: • Prior studies found that polymorphisms in urea cycle enzyme genes are associated with PPHN. • Association between CPS-1 gene polymorphisms is significantly associated with PPHN. What is New: • The prevalence of CPS-1, A/C trans-version substitution, rs4399666 gene polymorphism in Egyptian neonates presented with idiopathic PPHN. • Mutant CPS-I A/C rs4399666 especially the homozygous CC genotype is more frequently distributed among PPHN, and it is significantly associated with low serum nitric oxide level.

The newborn sheep translational model for pulmonary arterial hypertension of the neonate at high altitude

Chronic hypoxia during gestation induces greater occurrence of perinatal complications such as intrauterine growth restriction, fetal hypoxia, newborn asphyxia, and respiratory distress, among others. This condition may also cause a failure in the transition of the fetal to neonatal circulation, inducing pulmonary arterial hypertension of the neonate (PAHN), a syndrome that involves pulmonary vascular dysfunction, increased vasoconstrictor tone and pathological remodeling. As this syndrome has a relatively low prevalence in lowlands (~7 per 1000 live births) and very little is known about its prevalence and clinical evolution in highlands (above 2500 meters), our understanding is very limited. Therefore, studies on appropriate animal models have been crucial to comprehend the mechanisms underlying this pathology. Considering the strengths and weaknesses of any animal model of human disease is fundamental to achieve an effective and meaningful translation to clinical practice. The sheep model has been used to study the normal and abnormal cardiovascular development of the fetus and the neonate for almost a century. The aim of this review is to highlight the advances in our knowledge on the programming of cardiopulmonary function with the use of high-altitude newborn sheep as a translational model of PAHN.

Effectiveness of oral sildenafil for neonates with persistent pulmonary hypertension of newborn (PPHN): a prospective study in a tertiary care hospital

INTRODUCTION

The prevalence of persistent pulmonary hypertension of newborn (PPHN) has been estimated 1.9/1000 live births. Although the efficacy of inhaled nitric oxide and extracorporeal membrane oxygenation in PPHN is well established but it is difficult to administer and monitor in resource limited countries. Owing to this, other treatment options need to be evaluated.

METHOD

This is a prospective observational study conducted in the Pediatric Cardiology Department, NICVD, Karachi, from February 2020 to October 2020 after the approval from the Institutional Ethical Review Committee. All the neonates referred to our Unit were screened by echocardiography (echo) and those who fulfilled the inclusion criteria were included. Echo were done before starting sildenafil and after 72 h to assess the pressure gradient across tricuspid valve and right to left or bidirectional shunt across patent ductus arteriosus , patent foramen ovale , or both. Sildenafil was started with a dose of 1 mg/kg/dose thrice a day and increased to 2 mg/kg/dose after 48 h if partial pressure of oxygen (PO₁] did not increase. In neonates who did not respond to increased dose of Sildenafil were added on oral Bosentan 1 mg/kg/dose twice a day.

RESULTS

Total 82 newborns were enrolled. Fifty-two patients improved after 48 h so were continued on same treatment. Sildenafil dose was increased in 30 (37.9%) patients whose PO₂ did not increase to at least 10% from baseline after 48 h of starting treatment. Three patients expired within 48-72 h. Out of 27 remaining patients, only four responded whereas 23 patients did not show any improvement. In these patients, Bosentan was supplemented along with sildenafil.

CONCLUSION

The results of our study show effectiveness of oral Sildenafil in treating PPHN. The overall improvement observed in the patients was overwhelming. Combination of Sildenafil with Bosentan is beneficial in patients who did not respond on Sildenafil alone.

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.

Melatonin long-lasting beneficial effects on pulmonary vascular reactivity and redox balance in chronic hypoxic ovine neonates

Pulmonary arterial hypertension of the neonate (PAHN) is a pathophysiological condition characterized by maladaptive pulmonary vascular remodeling and abnormal contractile reactivity. This is a multifactorial syndrome with chronic hypoxia and oxidative stress as main etiological drivers, and with limited effectiveness in therapeutic approaches. Melatonin is a neurohormone with antioxidant and vasodilator properties at the pulmonary level. Therefore, this study aims to test whether a postnatal treatment with melatonin during the neonatal period improves in a long-lasting manner the clinical condition of PAHN. Ten newborn lambs gestated and born at 3600 m were used in this study, five received vehicle and five received melatonin in daily doses of 1 mg kg^-1 for the first 3 weeks of life. After 1 week of treatment completion, lung tissue and small pulmonary arteries (SPA) were collected for wire myography, molecular biology, and morphostructural analyses. Melatonin decreased pulmonary arterial pressure the first 4 days of treatment. At 1 month old, melatonin decreased the contractile response to the vasoconstrictors K⁺ , TX₂ , and ET-1. Further, melatonin increased the endothelium-dependent and muscle-dependent vasodilation of SPA. Finally, the treatment decreased pulmonary oxidative stress by inducing antioxidant enzymes and diminishing pro-oxidant sources. In conclusion, melatonin improved vascular reactivity and oxidative stress at the pulmonary level in PAHN lambs gestated and born in chronic hypoxia.

Gestational Hypoxia and Programing of Lung Metabolism

Gestational hypoxia is a risk factor in the development of pulmonary hypertension in the newborn and other sequela, however, the mechanisms associated with the disease remain poorly understood. This review highlights disruption of metabolism by antenatal high altitude hypoxia and the impact this has on pulmonary hypertension in the newborn with discussion of model organisms and human populations. There is particular emphasis on modifications in glucose and lipid metabolism along with alterations in mitochondrial function. Additional focus is placed on increases in oxidative stress and the progression of pulmonary vascular disease in the newborn and on the need for further exploration using a combination of contemporary and classical approaches.

Pentraxin 3: A Potential Novel Predictor for Neonatal Pulmonary Hypertension

BACKGROUND:

Persistent pulmonary hypertension of the newborn (PPHN) is a serious neonatal problem which has a high mortality rate even with advanced modes of mechanical ventilation. Pentraxin 3 is one of the long pentraxins, which plays an essential role in regulation of cell proliferation and angiogenesis.

AIM:

This study aims to assess serum pentraxin 3 levels in neonates with pulmonary arterial hypertension and compare them in those who have other congenital heart diseases and healthy neonates. Also, we intended to evaluate serum levels of CRP as a mediator of inflammation in the studied groups.

METHODS:

The study is a case-control study. Cases were recruited from El Galaa Teaching Hospital, classified into three groups; each group had thirty cases. The first one: cases with pulmonary hypertension (PHT), the second one: cases with congenital heart diseases (CHD) without pulmonary hypertension and the third group included healthy neonates. All participants were subjected to full history taking and full clinical examination. Diagnosis of congenital heart disease and pulmonary hypertension was made according to echocardiographic findings by pediatric cardiologist using echocardiography machine. Laboratory investigations included measurement of serum pentraxin 3, Routine CBC, CRP.

RESULTS:

This study found that the mean serum pentraxin 3 in PHT neonates was significantly higher than that of the control and CHD neonates (p ≤ 0.001, p = 0.02 respectively). Also, the mean Pentraxin3 of the CHD neonates was significantly higher than that of the control (p = 0.06). Also, the mean CRP of the PHT neonates was significantly higher than that of the control (p = 0.01). Regression analysis showed that Pentraxin3 was the main predictor of PAP (P = 0.01).

CONCLUSION:

Serum pentraxin 3 is significantly elevated in neonates with pulmonary hypertension, so measurement of pentraxin 3 levels in neonates may be valuable as a predictor for pulmonary hypertension in neonates.

Dynamic changes of pulmonary arterial pressure in perinatal neonates with pulmonary and extrapulmonary acute lung injury/respiratory distress syndrome

This study aims to explore the dynamic changes of pulmonary arterial pressure (PAP) and its clinical significance in prenatal neonates with pulmonary and extra-pulmonary acute lung injury/respiratory distress syndrome (ALI/ARDS).A prospective study was conducted in the Neonate Intensive Care Unit (NICU) between May 2015 and April 2017. A total of 78 prenatal neonates with ALI/ARDS were selected and divided into 2 groups: pulmonary group (n = 37) and extra-pulmonary group (n = 41). These neonates were further divided into 3 groups according to the OSI index: mild, moderate, and severe groups. The dynamic changes of PAP were observed in these neonates. In the moderate and severe groups, PAP was significantly higher in neonates with pulmonary ALI/ADDS (ALI/ARDSp) than in neonates with extrapulmonary ALI/ARDS(ALI/ARDSexp) (62.5 ± 5.4 vs 68.0 ± 6.5, 54.7 ± 5.9 vs 64.2 ± 4.9; t = 3.264, 3.123; P = .004,.039). Furthermore, PAP was higher in neonates with ALI/ADDSp in the severe group, compared with those in the moderate group (t = 2.420, P < .05). There was significant difference among the 3 subgroups of neonates with ALI/ADDSexp (F = 60.100, P = .000). PAP was positively correlated with the OSI index (r = 0.823). The overall dynamic PAP monitoring results revealed that PAP was higher in the pulmonary group than that in the extrapulmonary group, and this exhibited a gradually decreasing trend as the condition of the subject improved.PAP in perinatal neonates with ALI/ARDS increases in varying degrees, and its extent was related to the severity of the illness. PAP was significantly higher in neonates with ALI/ADDSp than in neonates with ALI/ADDSexp. This can be used as a monitoring indicator for the severity of illness.

The role of nitric oxide in the cardiopulmonary response to hypoxia in highland and lowland newborn llamas

KEY POINTS

Perinatal hypoxia causes pulmonary hypertension in neonates, including humans. However, in species adapted to hypoxia, such as the llama, there is protection against pulmonary hypertension. Nitric oxide (NO) is a vasodilatator with an established role in the cardiopulmonary system of many species, but its function in the hypoxic pulmonary vasoconstrictor response in the newborn llama is unknown. Therefore, we studied the role of NO in the cardiopulmonary responses to acute hypoxia in high- and lowland newborn llamas. We show that high- compared to lowland newborn llamas have a reduced pulmonary vasoconstrictor response to acute hypoxia. Protection against excessive pulmonary vasoconstriction in the highland llama is mediated via enhancement of NO pathways, including increased MYPT1 and reduced ROCK expression as well as Ca2+ desensitization. Blunting of pulmonary hypertensive responses to hypoxia through enhanced NO pathways may be an adaptive mechanism to withstand life at high altitude in the newborn llama.

ABSTRACT

Llamas are born in the Alto Andino with protection against pulmonary hypertension. The physiology underlying protection against pulmonary vasoconstrictor responses to acute hypoxia in highland species is unknown. We determined the role of nitric oxide (NO) in the cardiopulmonary responses to acute hypoxia in high- and lowland newborn llamas. The cardiopulmonary function of newborn llamas born at low (580 m) or high altitude (3600 m) was studied under acute hypoxia, with and without NO blockade. In pulmonary arteries, we measured the reactivity to potassium and sodium nitroprusside (SNP), and in lung we determined the content of cGMP and the expression of the NO-related proteins: BKCa, PDE5, PSer92-PDE5, PKG-1, ROCK1 and 2, MYPT1, PSer695-MYPT1, PThr696-MYPT1, MLC20 and PSer19-MLC20. Pulmonary vascular remodelling was evaluated by morphometry and based on α-actin expression. High- compared to lowland newborn llamas showed lower in vivo pulmonary arterial pressor responses to acute hypoxia. This protection involved enhanced NO function, as NO blockade reverted the effect and the pulmonary arterial dilatator response to SNP was significantly enhanced in highland neonates. The pulmonary expression of ROCK2 and the phosphorylation of MLC20 were lower in high-altitude llamas. Conversely, MYPT1 was up-regulated whilst PSer695-MYPT1 and PThr695-MYPT1 did not change. Enhanced NO-dependent mechanisms were insufficient to prevent pulmonary arterial remodelling. Combined, the data strongly support that in the highland newborn llama reduced ROCK, increased MYPT1 expression and Ca2+ desensitization in pulmonary tissue allow an enhanced NO biology to limit hypoxic pulmonary constrictor responses. Blunting of hypoxic pulmonary hypertensive responses may be an adaptive mechanism to life at high altitude.

Factors relating caesarean section to persistent pulmonary hypertension of the newborn

BACKGROUND

Several studies have clearly demonstrated a significantly higher incidence of persistent pulmonary hypertension of the newborn (PPHN) in neonates delivered by caesarean section (CS) compared to those delivered vaginally. The pathophysiological factors underlying the link between CS and PPHN are still poorly understood. In this review, we describe the mechanisms that could explain the association between CS delivery and subsequent PPHN, as well as potential preventive measures.

DATA SOURCES

A literature search was conducted by electronic scanning of databases such as PubMed and Web of Science using the key words "persistent pulmonary hypertension of the newborn", "caesarean section", "iatrogenic prematurity", "oxidative stress", "late preterm", "labor" and "vasoactive agents".

RESULTS

Iatrogenic prematurity, higher rates of late preterm delivery and lack of physiological changes of labor play an important role in the association between CS and PPHN. CS delivery also results in limited endogenous pulmonary vasodilator synthesis and lower levels of protective anti-oxidants in the neonates. In addition, CS delivery exposes infants to a higher risk of respiratory distress syndrome and its concomitant increase in endothelin-1 levels, which might indirectly lead to a higher risk of developing PPHN. We believe that neonates delivered by CS are exposed to a combination of these pathophysiological events, culminating in an endpoint of respiratory distress, hypoxia, acidosis, and delayed transition and thereby increased risks of PPHN. The use of antenatal corticosteroids prior to elective CS in late preterm deliveries, promoting accurate informedconsent process, delaying elective CS to 39 weeks of gestation or beyond and antenatal maternal anti-oxidant supplementation could potentially mitigate the effects of CS delivery and minimize CS-related PPHN.

CONCLUSIONS

The link between CS delivery and PPHN is complex. In view of the rising rates of CS worldwide, there is an urgent need to further explore the mechanisms linking CS to PPHN and experimentally test therapeutic options in order to allow effective targeted interventions.

How to assess hemodynamic status in very preterm newborns in the first week of life?

BACKGROUND

Assessing hemodynamic status in preterm newborns is an essential task, as many studies have shown increased morbidity when hemodynamic parameters are abnormal. Although oscillometric monitoring of arterial blood pressure (BP) is widely used due to its simplicity and lack of side effects, these values are not always correlated with microcirculation and oxygen delivery.

OBJECTIVES

This review focuses on different tools for the assessment of hemodynamic status in preterm newborns. These include the measurement of clinical (BP, capillary refill time and urinary output (UO)) or biological parameters (lactate analysis), functional echocardiography, and near-infrared spectroscopy (NIRS). We describe the concepts and techniques involved in these tools in detail, and examine the interest and limitations of each type of assessment.

CONCLUSIONS

This review highlights the complementarities between the different parameters used to assess hemodynamic status in preterm newborns during the first week of life. The analysis of arterial BP measured by oscillometric monitoring must take into account other clinical data, in particular capillary refill time and UO, and biological data such as lactate levels. Echocardiography improves noninvasive hemodynamic management in newborns but requires specific training. In contrast, NIRS may be useful in monitoring the clinical course of infants at risk of, or presenting with, hypotension. It holds the potential for early and noninvasive identification of silent hypoperfusion in critically ill preterm infants. However, more data are needed to confirm the usefulness of this promising tool in significantly changing the outcome of these infants.

Pulmonary Hypertension Therapy and a Systematic Review of Efficacy and Safety of PDE-5 Inhibitors

Pulmonary hypertension (PH) is a syndrome that is of growing concern to pediatricians worldwide. Recent data led to concerns about the safety of phosphodiesterase type 5 (PDE5) inhibitors in children and a US Food and Drug Administration safety advisory. Our objective is to provide insight into therapies for PH in children and to systematically review the comparative effectiveness and safety of PDE5 inhibitors in the management of pediatric patients with PH. We searched the following databases through February 2015: Medline, Embase, SCOPUS, and the Cochrane Central Register of Controlled Trials. We included studies that examined PDE5 inhibitor use in children with PH. Allowed comparators were either no medication or other classes of medication for management of PH. Study inclusion was via a 2-stage process with 2 reviewers and a predesigned form. Of 1270 papers identified by the literature search, 21 were included: 8 randomized controlled trials and 13 observational studies (9 retrospective, 4 prospective). There is strong evidence that PDE5 inhibitor use improves echocardiography measurements, cardiac catheterization parameters, and oxygenation compared with baseline or placebo in pediatric patients with PH. Evidence suggests that low- and moderate-dose sildenafil are safe regimens for children. There are a relatively small number of randomized controlled trials that address use of PDE5 inhibitors in pediatric patients with PH. PDE5 inhibitors are effective agents for cardiovascular and oxygenation end points in pediatric PH and important components of a multimodal pharmacotherapeutic approach to this growing challenge. Additional studies are needed to define optimal PH therapy in childhood.

Altered cardiovascular function at birth in growth-restricted preterm lambs

BACKGROUND

Cardiovascular dysfunction at birth may underlie poor outcomes after fetal growth restriction (FGR) in neonates. We compared the cardiovascular transition between FGR and appropriately grown (AG) preterm lambs and examined possible mechanisms underlying any cardiovascular dysfunction in FGR lambs.

METHODS

FGR was induced in ewes bearing twins at 0.7 gestation; the twin was used as an internal control (AG). At 0.8 gestation, lambs were delivered and either euthanized with their arteries isolated for in vitro wire myography, or ventilated for 2 h. At 60 min, inhaled nitric oxide (iNO) was administered in a subgroup for 30 min. Molecular assessment of the nitric oxide (NO) pathway within lung tissue was conducted.

RESULTS

FGR lambs had lower left ventricular output and cerebral blood flow (CBF) and higher systemic vascular resistance compared with AG lambs. INO administration to FGR lambs rapidly improved cardiovascular and systemic hemodynamics but resulted in decreased CBF in AG lambs. Isolated arteries from FGR lambs showed impaired sensitivity to NO donors, but enhanced vasodilation to Sildenafil and Sodium nitroprusside, and altered expression of components of the NO pathway.

CONCLUSION

Cardiovascular dysfunction at birth may underlie the increased morbidity and mortality observed in preterm FGR newborns. Impaired NO signaling likely underlies the abnormal vascular reactivity.

Sildenafil Improves Brain Injury Recovery following Term Neonatal Hypoxia-Ischemia in Male Rat Pups

Term asphyxiated newborns remain at risk of developing brain injury despite available neuropreventive therapies such as hypothermia. Neurorestorative treatments may be an alternative. This study investigated the effect of sildenafil on brain injury induced by neonatal hypoxia-ischemia (HI) at term-equivalent age. Neonatal HI was induced in male Long-Evans rat pups at postnatal day 10 (P10) by left common carotid ligation followed by a 2-hour exposure to 8% oxygen; sham-operated rat pups served as the control. Both groups were randomized to oral sildenafil or vehicle twice daily for 7 consecutive days. Gait analysis was performed on P27. At P30, the rats were sacrificed, and their brains were extracted. The surfaces of both hemispheres were measured on hematoxylin and eosin-stained brain sections. Mature neurons and endothelial cells were quantified near the infarct boundary zone using immunohistochemistry. HI caused significant gait impairment and a reduction in the size of the left hemisphere. Treatment with sildenafil led to an improvement in the neurological deficits as measured by gait analysis, as well as an improvement in the size of the left hemisphere. Sildenafil, especially at higher doses, also caused a significant increase in the number of neurons near the infarct boundary zone. In conclusion, sildenafil administered after neonatal HI may improve brain injury recovery by promoting neuronal populations.

2-AMINOETHYLDIPHENYLBORINATE MODIFIES THE PULMONARY CIRCULATION IN PULMONARY HYPERTENSIVE NEWBORN LAMBS WITH PARTIAL GESTATION AT HIGH ALTITUDE

Calcium signaling through store operated channels (SOC) is involved in hypoxic pulmonary hypertension. We determined whether a treatment with 2-aminoethyldiphenylborinate (2-APB), a compound with SOC blocker activity, reduces pulmonary hypertension and vascular remodeling. Twelve newborn lambs exposed to perinatal chronic hypoxia were studied, 6 of them received a 2-APB treatment and the other 6 received vehicle treatment, for 10 days in both cases. Throughout this period, we recorded cardiopulmonary variables and on day 11 we evaluated the response to an acute hypoxic challenge. Additionally, we assessed the vasoconstrictor and vasodilator function in isolated pulmonary arteries as well as their remodeling in lung slices. 2-APB reduced pulmonary arterial pressure at the third and tenth days, cardiac output between the fourth and eighth days, and pulmonary vascular resistance at the tenth day of treatment. The pulmonary vasoconstrictor response to acute hypoxia was reduced by the end of treatment. 2-APB also decreased maximal vasoconstrictor response to the thromboxane mimetic U46619 and endothelin-1 and increased maximal relaxation to 8-Br-cGMP. The maximal relaxation and potency to phosphodiesterase-5 and Rho-kinase inhibition with sildenafil and fasudil respectively, were also increased. Finally, 2-APB reduced the medial and adventitial layers' thickness, the expression of α-actin and the percentage of Ki67+ nuclei of small pulmonary arteries. Taken together, our results indicate that 2-APB reduces pulmonary hypertension, vasoconstrictor responses and pathological remodeling in pulmonary hypertensive lambs. We conclude that SOC targeting may be a useful strategy for the treatment of neonatal pulmonary hypertension, however, further testing of specific blockers is needed.

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.

Pharmacological models and approaches for pathophysiological conditions associated with hypoxia and oxidative stress

Hypoxia is the failure of oxygenation at the tissue level, where the reduced oxygen delivered is not enough to satisfy tissue demands. Metabolic depression is the physiological adaptation associated with reduced oxygen consumption, which evidently does not cause any harm to organs that are exposed to acute and short hypoxic insults. Oxidative stress (OS) refers to the imbalance between the generation of reactive oxygen species (ROS) and the ability of endogenous antioxidant systems to scavenge ROS, where ROS overwhelms the antioxidant capacity. Oxidative stress plays a crucial role in the pathogenesis of diseases related to hypoxia during intrauterine development and postnatal life. Thus, excessive ROS are implicated in the irreversible damage to cell membranes, DNA, and other cellular structures by oxidizing lipids, proteins, and nucleic acids. Here, we describe several pathophysiological conditions and in vivo and ex vivo models developed for the study of hypoxic and oxidative stress injury. We reviewed existing literature on the responses to hypoxia and oxidative stress of the cardiovascular, renal, reproductive, and central nervous systems, and discussed paradigms of chronic and intermittent hypobaric hypoxia. This systematic review is a critical analysis of the advantages in the application of some experimental strategies and their contributions leading to novel pharmacological therapies.

Changes in mean arterial blood pressure during sildenafil use in neonates with meconium aspiration syndrome or sepsis

The aim of this study was to evaluate changes in mean blood pressure (MBP) in late preterm and term newborns with meconium aspiration syndrome (MAS) or sepsis who, in addition to inhaled nitric oxide (iNO), received enteral sildenafil for treatment of persistent pulmonary hypertension of the newborn. Data on sildenafil dosing, MBP, and vasopressor/inotrope use were collected for 72 hours after initiation of sildenafil. Groups were compared between "low dose" (<3 mg·kg·d) versus "high dose" (≥ 3 mg·kg·d) and "early" (<7 postnatal days) versus "late" (≥ 7 postnatal days) administration of sildenafil. Seventeen patients were identified. Ten and 7 patients received "low-dose" and "high-dose" sildenafil, respectively, and 8 and 9 patients were started on sildenafil "early" and "late," respectively. At the doses used, sildenafil treatment of infants with MAS and sepsis was not associated with changes in MBP. In addition, vasopressor/inotropic support was weaned in all groups. During the first 72 hours of enteral sildenafil administration in neonates with pulmonary hypertension of the newborn secondary to MAS or sepsis, no significant decrease in MBP or increase in vasopressor/inotrope requirement occurred.

Endothelin 1 in healthy foals and in foals affected by neonatal diseases

In newborn babies, endothelin 1 (ET-1), a potent vasoconstrictor, increases during septicemia and severe respiratory syndromes. Because equine neonatal sepsis (ENS) and perinatal asphyxia syndrome (PAS) are major causes of morbidity and mortality in newborn foals and because no information on the concentration of ET-1 in healthy and sick foals has been reported yet, the aims of this study were (1) to define the serum concentration of Big ET-1 in healthy neonatal foals during the first week of age; (2) to preliminarily explore the diagnostic and prognostic role of Big ET-1 during ENS and PAS. Six healthy and 23 sick foals affected by ENS and/or PAS were enrolled in the study. In healthy foals, Big ET-1 concentration increased in the first hours of life until 24 hours after birth, and it remained constant during the first 3 days, then gradually decreased becoming significantly lower from Day 4 onward (P < 0.05). In sick foals, only 26.1% of animals showed higher values of Big ET-1 than controls at admission, and no difference between surviving and nonsurviving foals was found. Because in nonsurviving foals, Big ET-1 remained over the maximum value recorded in clinically healthy horses or, when normal at admission, increased over time; this study suggested that repeated measurement of Big ET-1 during hospitalization may be helpful in monitoring the course of the disease. In conclusion, possible prognostic information may be obtained by repeated analysis of Big ET-1 during hospitalization, but further studies are needed.

Buffered l-ascorbic acid, alone or bound to KMUP-1 or sildenafil, reduces vascular endothelium growth factor and restores endothelium nitric oxide synthase in hypoxic pulmonary artery

Ascorbic acid bound to KMUP-1 and sildenafil were examined for their antioxidant effects on vascular endothelium growth factor (VEGF) and endothelium nitric oxide synthase (eNOS) in hypoxic pulmonary artery (PA). Inhaled KMUP-1 and oral sildenafil released NO from eNOS. The effect of buffered l-ascorbic acid, alone and bound to KMUP-1 or sildenafil, for treating pulmonary arterial hypertension (PAH) is unclear. In this study, the antioxidant capacity of ascorbic acid increased the beneficial effects of KMUP-1 on PAH. KMUP-1A and sildenafil-A (5 mg/kg/d) were administered to hypoxic PAH rats. Pulmonary artery blood pressure, and VEGF, Rho kinase II (ROCK II), eNOS, soluble guanylate cyclase (sGC-α), and protein kinase G expression in lung tissues were measured to link PAH and right ventricular hypertrophy. Hypoxic rats had higher pulmonary artery blood pressure, greater PA medial wall thickness and cardiac weight, and a higher right ventricle/left ventricle + septum [RV/(LV+S)] ratio than normoxic rats. Oral KMUP-1A or sildenafil-A for 21 days in hypoxia prevented the rarefaction of eNOS in immunohistochemistry (IHC), reduced the IHC of VEGF in PAs, restored eNOS/protein kinase G/phosphodiesterase 5A; unaffected sGC-α and inactivated ROCK II expression were also found in lung tissues. In normoxic PA, KMUP-1A/Y27632 (10μM) increased eNOS and reduced ROCK II. ROCK II/reactive oxidative species was increased and eNOS was reduced after long-term hypoxia for 21 days. KMUP-1A or Y27632 blunted ROCK II in short-term hypoxic PA at 24 hours. l-Ascorbic acid + l-sodium ascorbate (40, 80μM) buffer alone directly inhibited the IHC of VEGF in hypoxic PA. Finally, KMUP-1A or sildenafil-A reduced PAH and associated right ventricular hypertrophy.

Molecular physiopathogenetic mechanisms and development of new potential therapeutic strategies in persistent pulmonary hypertension of the newborn

Persistent pulmonary hypertension of the newborn (PPHN) is a cyanogenic plurifactorial disorder characterized by failed postnatal drop of pulmonary vascular resistance and maintenance of right-to-left shunt across ductus arteriosus and foramen ovale typical of intrauterine life. The pathogenesis of PPHN is very complex and can result from functional (vasoconstriction) or structural (arteriolar remodeling, reduced pulmonary vessels density) anomalies of pulmonary circulation. Etiopathogenetic factors heterogeneity can strongly condition therapeutical results and prognosis of PPHN that is particularly severe in organic forms that are usually refractory to selective pulmonary vasodilator therapy with inhaled nitric oxide. This paper reports the more recent acquisitions on molecular physiopathogenetic mechanisms underlying functional and structural forms of PPHN and illustrates the bases for adoption of new potential treatment strategies for organic PPHN. These strategies aim to reverse pulmonary vascular remodeling in PPHN with arteriolar smooth muscle hypertrophy and stimulate pulmonary vascular and alveolar growth in PPHN associated with lung hypoplasia.In order to restore lung growth in this severe form of PPHN, attention is focused on the results of studies of mesenchymal stem cells and their therapeutical paracrine effects on bronchopulmonry dysplasia, a chronic neonatal lung disease characterized by arrested vascular and alveolar growth and development of pulmonary hypertension.

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.

Ventilation/perfusion mismatch during lung aeration at birth

At birth, the transition to newborn life is triggered by lung aeration, which stimulates a large increase in pulmonary blood flow (PBF). Current theories predict that the increase in PBF is spatially related to ventilated lung regions as they aerate after birth. Using simultaneous phase-contrast X-ray imaging and angiography we investigated the spatial relationships between lung aeration and the increase in PBF after birth. Six near-term (30-day gestation) rabbits were delivered by caesarean section, intubated and an intravenous catheter inserted, before they were positioned for X-ray imaging. During imaging, iodine was injected before ventilation onset, after ventilation of the right lung only, and after ventilation of both lungs. Unilateral ventilation increased iodine levels entering both left and right pulmonary arteries (PAs) and significantly increased heart rate, iodine ejection per beat, diameters of both left and right PAs, and number of visible vessels in both lungs. Within the 6th intercostal space, the mean gray level (relative measure of iodine level) increased from 68.3 ± 11.6 and 70.3 ± 7.5%·s to 136.3 ± 22.6 and 136.3 ± 23.7%·s in the left and right PAs, respectively. No differences were observed between vessels in the left and right lungs, despite the left lung not initially being ventilated. The increase in PBF at birth is not spatially related to lung aeration allowing a large ventilation/perfusion mismatch, or pulmonary shunting, to occur in the partially aerated lung at birth.

Angiotensin II type 2 receptor ligand PD123319 attenuates hyperoxia-induced lung and heart injury at a low dose in newborn rats

Intervening in angiotensin (Ang)-II type 2 receptor (AT2) signaling may have therapeutic potential for bronchopulmonary dysplasia (BPD) by attenuating lung inflammation and preventing arterial hypertension (PAH)-induced right ventricular hypertrophy (RVH). We first investigated the role of AT2 inhibition with PD123319 (0.5 and 2 mg·kg(-1)·day(-1)) on the beneficial effect of AT2 agonist LP2-3 (5 μg/kg twice a day) on RVH in newborn rats with hyperoxia-induced BPD. Next we determined the cardiopulmonary effects of PD123319 (0.1 mg·kg(-1)·day(-1)) in two models: early treatment during continuous exposure to hyperoxia for 10 days and late treatment starting on day 6 in rat pups exposed postnatally to hyperoxia for 9 days, followed by a 9-day recovery period in room air. Parameters investigated included lung and heart histopathology, fibrin deposition, vascular leakage, and differential mRNA expression. Ten days of coadministration of LP2-3 and PD123319 abolished the beneficial effects of LP2-3 on RVH in experimental BPD. In the early treatment model PD123319 attenuated cardiopulmonary injury by reducing alveolar septal thickness, pulmonary influx of inflammatory cells, including macrophages and neutrophils, medial wall thickness of small arterioles, and extravascular collagen III deposition, and by preventing RVH. In the late treatment model PD123319 diminished PAH and RVH, demonstrating that PAH is reversible in the neonatal period. At high concentrations PD123319 blocks the beneficial effects of the AT2-agonist LP2-3 on RVH. At low concentrations PD123319 attenuates cardiopulmonary injury by reducing pulmonary inflammation and fibrosis and preventing PAH-induced RVH but does not affect alveolar and vascular development in newborn rats with experimental BPD.

Antenatal hypoxia and pulmonary vascular function and remodeling

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

Therapeutic hypercapnia prevents inhaled nitric oxide-induced right-ventricular systolic dysfunction in juvenile rats

Chronic pulmonary hypertension in the neonate and infant frequently presents with right-ventricular (RV) failure. Current clinical management may include protracted treatment with inhaled nitric oxide (iNO), with the goal of reducing RV afterload. We have previously reported that prolonged exposure to iNO causes RV systolic dysfunction in the chronic hypoxia-exposed juvenile rat, which was prevented by a peroxynitrite decomposition catalyst. Given that inhalation of CO2 (therapeutic hypercapnia) may limit oxidative stress and upregulated cytokine expression in the lung and other organs, we hypothesized that therapeutic hypercapnia would attenuate cytokine-mediated nitric oxide synthase (NOS) upregulation, thus limiting peroxynitrite generation. Sprague-Dawley rat pups were exposed to chronic hypoxia (13% O2) from postnatal day 1 to 21, while receiving iNO (20 ppm) from day 14 to 21, with or without therapeutic hypercapnia (10% CO2). Therapeutic hypercapnia completely normalized RV systolic function, RV hypertrophy, and remodeling of pulmonary resistance arteries in animals exposed to iNO. Inhaled nitric oxide-mediated increases in RV peroxynitrite, apoptosis, and contents of tumor necrosis factor (TNF)-α, interleukin (IL)-1α, and NOS-2 were all attenuated by therapeutic hypercapnia. Inhibition of NOS-2 activity with 1400 W (1 mg/kg/day) prevented iNO-mediated upregulation of peroxynitrite and led to improved RV systolic function. Blockade of IL-1 receptor signaling with anakinra (500 mg/kg/day) decreased NOS-2 content and had similar effects compared to NOS-2 inhibition on iNO-mediated effects, whereas blockade of TNF-α signaling with etanercept (0.4 mg/kg on alternate days) had no effects on these parameters. We conclude that therapeutic hypercapnia prevents the adverse effects of sustained exposure to iNO on RV systolic function by limiting IL-1-mediated NOS-2 upregulation and consequent nitration. Therapeutic hypercapnia also acts synergistically with iNO in normalizing RV hypertrophy, vascular remodeling, and raised pulmonary vascular resistance secondary to chronic hypoxia.

Hypoxic pulmonary hypertension of the newborn

Hypoxic pulmonary hypertension of the newborn is characterized by elevated pulmonary vascular resistance and pressure due to vascular remodeling and increased vessel tension secondary to chronic hypoxia during the fetal and newborn period. In comparison to the adult, the pulmonary vasculature of the fetus and the newborn undergoes tremendous developmental changes that increase susceptibility to a hypoxic insult. Substantial evidence indicates that chronic hypoxia alters the production and responsiveness of various vasoactive agents such as endothelium-derived nitric oxide, endothelin-1, prostanoids, platelet-activating factor, and reactive oxygen species, resulting in sustained vasoconstriction and vascular remodeling. These changes occur in most cell types within the vascular wall, particularly endothelial and smooth muscle cells. At the cellular level, suppressed nitric oxide-cGMP signaling and augmented RhoA-Rho kinase signaling appear to be critical to the development of hypoxic pulmonary hypertension of the newborn.

Risk factors and outcomes of persistent pulmonary hypertension of the newborn in neonatal intensive care unit of Al-minya university hospital in egypt

Background:

Persistent pulmonary hypertension of the newborn (PPHN) result from the failure of the normal fetal-to-neonatal circulatory transition is associated with substantial infant mortality and morbidity.

Objective:

To estimate the possible risk factors and assess the outcome of these cases.

Materials and Methods:

Prospective study was performed enrolling all full-term and post-term newborn admitted to the NICU from January 2009 to April 2012, All neonates were subjected to complete history and physical examination, laboratory data including a complete blood count, arterial blood gases, blood glucose, serum electrolytes, and blood culture to exclude sepsis. Cases with PPHN had a continuous pulse oximeter, blood pressure and electrocardiography monitoring. Chest X-ray and echocardiogarphy were carried out to verify shunt and exclude structural congenital heart disease.

Results:

Out of the studied 640 infants, 32 infants (5%) developed PPHN, Meconium aspiration, birth asphyxia, hyaline membrane diseases, neonatal septicemia, post-term birth being large for gestational age, cesarean section, maternal overweight, and diabetes mellitus were associated with an elevated risk for PPHN. All neonates treated with O₂, 10 neonates with Mg sulphate, 16 with oral sildenafil and 12 with mechanical ventilation. After 6 months follow-up, 12 (37.54%) improved and followed-up without sequelae, 4 (12.5%) developed some neurodevelopmental impairment, 8 (25%) died, 3 (9.3%) developed chronic lungs diseases, 2 (6.2%) developed hearing defects and another 3 (9.3%) missed follow-up.

Conclusion:

PPHN was found in 5% of the studied population. Meconium aspiration, birth asphyxia, neonatal septicemia, post-term were associated with an elevated risk for PPHN. As this is a unit based study, a comprehensive countrywide survey on PPHN in Egypt is recommended to determine any regional differences in disease incidence.

Agonists of MAS oncogene and angiotensin II type 2 receptors attenuate cardiopulmonary disease in rats with neonatal hyperoxia-induced lung injury

Stimulation of MAS oncogene receptor (MAS) or angiotensin (Ang) receptor type 2 (AT2) may be novel therapeutic options for neonatal chronic lung disease (CLD) by counterbalancing the adverse effects of the potent vasoconstrictor angiotensin II, consisting of arterial hypertension (PAH)-induced right ventricular hypertrophy (RVH) and pulmonary inflammation. We determined the cardiopulmonary effects in neonatal rats with CLD of daily treatment during continuous exposure to 100% oxygen for 10 days with specific ligands for MAS [cyclic Ang-(1-7); 10-50 μg·kg(-1)·day(-1)] and AT2 [dKcAng-(1-7); 5-20 μg·kg(-1)·day(-1)]. Parameters investigated included lung and heart histopathology, fibrin deposition, vascular leakage, and differential mRNA expression in the lungs of key genes involved in the renin-angiotensin system, inflammation, coagulation, and alveolar development. We investigated the role of nitric oxide synthase inhibition with N(ω)-nitro-l-arginine methyl ester (25 mg·kg(-1)·day(-1)) during AT2 agonist treatment. Prophylactic treatment with agonists for MAS or AT2 for 10 days diminished cardiopulmonary injury by reducing alveolar septum thickness and medial wall thickness of small arterioles and preventing RVH. Both agonists attenuated the pulmonary influx of inflammatory cells, including macrophages (via AT2) and neutrophils (via MAS) but did not reduce alveolar enlargement and vascular alveolar leakage. The AT2 agonist attenuated hyperoxia-induced fibrin deposition. In conclusion, stimulation of MAS or AT2 attenuates cardiopulmonary injury by reducing pulmonary inflammation and preventing PAH-induced RVH but does not affect alveolar and vascular development in neonatal rats with experimental CLD. The beneficial effects of AT2 activation on experimental CLD were mediated via a NOS-independent mechanism.

The consequences of chorioamnionitis: preterm birth and effects on development

Preterm birth is a major cause of perinatal mortality and long-term morbidity. Chorioamnionitis is a common cause of preterm birth. Clinical chorioamnionitis, characterised by maternal fever, leukocytosis, tachycardia, uterine tenderness, and preterm rupture of membranes, is less common than subclinical/histologic chorioamnionitis, which is asymptomatic and defined by inflammation of the chorion, amnion, and placenta. Chorioamnionitis is often associated with a fetal inflammatory response. The fetal inflammatory response syndrome (FIRS) is defined by increased systemic inflammatory cytokine concentrations, funisitis, and fetal vasculitis. Clinical and epidemiological studies have demonstrated that FIRS leads to poor cardiorespiratory, neurological, and renal outcomes. These observations are further supported by experimental studies that have improved our understanding of the mechanisms responsible for these outcomes. This paper outlines clinical and experimental studies that have improved our current understanding of the mechanisms responsible for chorioamnionitis-induced preterm birth and explores the cellular and physiological mechanisms underlying poor cardiorespiratory, neural, retinal, and renal outcomes observed in preterm infants exposed to chorioamnionitis.

Intrauterine inflammation alters cardiopulmonary and cerebral haemodynamics at birth in preterm lambs

Intrauterine inflammation is associated with preterm birth and poor long-term cardiopulmonary outcomes. We aimed to determine the effect of intrauterine inflammation on the cardiopulmonary and cerebral haemodynamic transition at birth, and the response to subsequent haemodynamic challenge. Fetal instrumentation was performed at ∼112 days gestation (term is 147 days) for measurement of cardiopulmonary and cerebral haemodynamics. At 118 days, inflammation was induced by intra-amniotic administration of lipopolysaccharide (LPS; n = 7); controls (n = 5) received intra-amniotic saline. At 125 days lambs were delivered and mechanically ventilated. Arterial blood gases, pulmonary and systemic arterial blood pressures and flows were measured during the perinatal period. At 10 min a haemodynamic challenge was administered by increasing positive end-expiratory pressure. During the first 10 min after birth, LPS-exposed lambs had higher pulmonary vascular resistance and lower pulmonary blood flow and left ventricular output than controls. Carotid arterial blood flow was higher in LPS-exposed lambs than controls between 3 and 7 min after delivery, and cerebral oxygen delivery was higher at 5 min. During the haemodynamic challenge, pulmonary blood flow and left ventricular output were reduced in controls but not in LPS-exposed lambs; a transient reduction in brachiocephalic arterial pressure occurred in LPS-exposed lambs but not in controls. Intrauterine inflammation altered the cardiopulmonary and cerebral haemodynamic transition at birth and reduced the cardiopulmonary response to a haemodynamic challenge after birth. The transient reduction in brachiocephalic arterial pressure suggests intrauterine inflammation may alter cerebrovascular control following an increase in positive end-expiratory pressure.

Ambrisentan reduces pulmonary arterial hypertension but does not stimulate alveolar and vascular development in neonatal rats with hyperoxic lung injury

Ambrisentan, an endothelin receptor type A antagonist, may be a novel therapeutic agent in neonatal chronic lung disease (CLD) by blocking the adverse effects of the vasoconstrictor endothelin-1, especially pulmonary arterial hypertension (PAH)-induced right ventricular hypertrophy (RVH). We determined the cardiopulmonary effects of ambrisentan treatment (1-20 mg·kg(-1)·day(-1)) in neonatal rats with CLD in 2 models: early treatment during continuous exposure to hyperoxia for 10 days and late treatment starting on day 6 in rat pups exposed postnatally to hyperoxia for 9 days, followed by a 9-day recovery period in room air. Parameters investigated included survival, lung and heart histopathology, right ventricular function, fibrin deposition, and differential mRNA expression in the lungs. In the early treatment model, we investigated the role of nitric oxide synthase (NOS) inhibition with N(ω)-nitro-L-arginine methyl ester (L-NAME; 25 mg·kg(-1)·day(-1)) during ambrisentan treatment. In the early treatment model, ambrisentan improved survival with reduced lung fibrin and collagen III deposition, arterial medial wall thickness, and RVH. These changes were not affected by L-NAME administration. Ambrisentan did not reduce the influx of macrophages and neutrophils or prevent reduced irregular elastin expression. In the late treatment model, ambrisentan diminished PAH, RVH, and right ventricular peak pressure, demonstrating that RVH is reversible in the neonatal period. Alveolarization and vascularization were not affected by ambrisentan. In conclusion, ambrisentan prolongs survival and reduces lung injury, PAH, and RVH via a NOS-independent mechanism but does not affect inflammation and alveolar and vascular development in neonatal rats with CLD.

Furegrelate, a thromboxane synthase inhibitor, blunts the development of pulmonary arterial hypertension in neonatal piglets

The development of pulmonary arterial hypertension (PAH) in pediatric patients has been linked to the production of the arachidonic acid metabolite, thromboxane A₂ (TxA₂). The present study evaluated the therapeutic effect of furegrelate sodium, a thromboxane synthase inhibitor, on the development of PAH in a neonatal piglet model. Three-day-old piglets were exposed to 21 days of normoxia (N; 21% F_IO₂) or chronic hypoxia (CH; 10% F_IO₂). A third group of piglets received the oral TxA₂ synthase inhibitor, furegrelate (3 mg/kg, 2 or 3 times daily) at the induction of CH. In vivo hemodynamics confirmed a 2.55-fold increase of the pulmonary vascular resistance index (PVRI) in CH piglets (104±7 WU) compared to N piglets (40±2 WU). The CH piglets treated twice daily with furegrelate failed to show improved PVRI, but furegrelate three times daily lowered the elevated PVRI in CH piglets by 34% to 69±5 WU and ameliorated the development of right ventricular hypertrophy. Microfocal X-ray computed tomography (CT) scanning was used to estimate the diameter-independent distensibility term, α (% change in diameter per Torr). Pulmonary arterial distensibility in isolated lungs of CH piglets (α=1.0±0.1% per Torr) was lower than that of N piglets (α=1.5±0.1% per Torr) indicative of vascular remodeling. Arterial distensibility was partially restored in furegrelate-treated CH piglets (α =1.2±0.1% per Torr) and microscopic evidence showing muscularization of small pulmonary arteries also was less prominent in these animals. Finally, isolated lungs of furegrelate-treated piglets showed lower basal and vasodilator-induced transpulmonary pressures compared to CH animals. These findings suggest that pharmacological inhibition of TxA₂ synthase activity by furegrelate blunts the development of hypoxia-induced PAH in an established neonatal piglet model primarily by preserving the structural integrity of the pulmonary vasculature.

Inhaled epoprostenol therapy for pulmonary hypertension: Improves oxygenation index more consistently in neonates than in older children

The purpose of this study was to determine the efficacy of inhaled epoprostenol for treatment of acute pulmonary hypertension (PH) in pediatric patients and to formulate a plan for a prospective, randomized study of pulmonary vasodilator therapy in this population. Inhaled epoprostenol is an effective treatment for pediatric PH. A retrospective chart review was conducted of all pediatric patients who received inhaled epoprostenol at a tertiary care hospital between October 2005 and August 2007. The study population was restricted to all patients under 18 years of age who received inhaled epoprostenol for greater than 1 hour and had available data for oxygenation index (OI) calculation. Arterial blood gas values and ventilator settings were collected immediately prior to epoprostenol initiation, and during epoprostenol therapy (as close to 12 hours after initiation as possible). Echocardiograms were reviewed during two time frames: Within 48 hours prior to therapy initiation and within 96 hours after initiation. Of the 20 patients in the study population, 13 were neonates, and the mean OI for these patients improved during epoprostenol administration (mean OI before and during therapy was 25.6±16.3 and 14.5±13.6, respectively, P=0.02). Mean OI for the seven patients greater than 30 days of age was not significantly different during treatment (mean OI before and during therapy was 29.6±15.0 and 25.6±17.8, P=0.56). Improvement in echocardiographic findings (evidence of decreased right-sided pressures or improved right ventricular function) was demonstrated in 20% of all patients. Inhaled epoprostenol is an effective therapy for the treatment of selected pediatric patients with acute PH. Neonates may benefit more consistently from this therapy than older infants and children. A randomized controlled trial is needed to discern the optimal role for inhaled prostanoids in the treatment of acute PH in childhood.

Voltage-dependent anion channel-2 interaction with nitric oxide synthase enhances pulmonary artery endothelial cell nitric oxide production

Increased pulmonary artery endothelial cell (PAEC) endothelium-dependent nitric oxide synthase (eNOS) activity mediates perinatal pulmonary vasodilation. Compromised eNOS activity is central to the pathogenesis of persistent pulmonary hypertension of the newborn (PPHN). Voltage-derived anion channel (VDAC)-1 was recently demonstrated to bind eNOS in the systemic circulation. We hypothesized that VDAC isoforms modulate eNOS activity in the pulmonary circulation, and that decreased VDAC expression contributes to PPHN. In PAECs derived from an ovine model of PPHN: (1) there is eNOS activity, but not expression; and (2) VDAC1 and -2 proteins are decreased. Immunocytochemistry, coimmunoprecipitation, and in situ proximity ligation assays in human PAECs (hPAECs) demonstrate binding between eNOS and both VDAC1 and -2, which increased upon stimulation with NO agonists. The ability of agonists to increase the eNOS/VDAC interaction was significantly blunted in hypertensive, compared with normotensive, ovine PAECs. Depletion of VDAC2, but not VDAC1, blocked the agonist-induced increase in eNOS activity in hPAECs. Overexpression of VDAC2 in hypertensive PAECs increased eNOS activity. Binding of VDAC2 enhances eNOS activity in the pulmonary circulation, and diminished VDAC2 constrains eNOS in PAECs derived from fetal lambs with chronic intrauterine pulmonary hypertension. We speculate that decreases in VDAC2 may contribute to the limited eNOS activity that characterizes pulmonary hypertension.

Persistent pulmonary hypertension of non cardiac cause in a neonatal intensive care unit

Parenchymal lung diseases are the main cause of persistent pulmonary hypertension of the newborn (PPHN). We aimed to assess the non cardiac conditions associated to PPHN in the newborn and the survival rate over the last 15 years, at our center. A retrospective chart review of the neonates admitted for PPHN from 1996 to 2010 was performed. New therapies were introduced in 2003, and the survival rates between two periods (1996–2002 and 2003–2010) were compared. Out of 6750 newborns, 78 (1.1%) had the diagnosis of PPHN of non cardiac cause. The most prevalent causes were associated to pulmonary hypoplasia (30.7%), infection (24.3%), and aspiration syndromes (15.3%). Many other causes were identified in 33.3%. The overall survival rate was 68%. There was a significant difference on survival rates between the two periods (1996–2002 = 63.8% and 2003–2010 = 71.4%, P = 0.04). Our study showed a myriad of non cardiac aetiologies for PPHN of the newborn, most of them related to lung disease or lung hypoplasia. We observed an improvement in survival rate since 2003, which was associated to the use of new therapies.

A comprehensive approach to the prevention of bronchopulmonary dysplasia

The current bronchopulmonary dysplasia (BPD) is seen in infants born extremely premature, with less severe respiratory distress syndrome (RDS) and who received prenatal steroids-"new BPD". The pathophysiology of BPD is based on an impairment of lung maturation with prenatal and postnatal multi-hit insults and genetic susceptibility. This multifactorial pathophysiology of BPD suggests that no single "magic bullet" will prevent it. Thus, to avoid BPD we need to implement a complex and comprehensive strategy. This strategy is based on ventilatory and non-ventilatory measures. The ventilatory route allows an individualized endotracheal intubation approach. Early lung recruitment with nasal respiratory support (nasal continuous positive airway pressure [NCPAP] or nasal intermittent positive pressure ventilation [NIPPV] / synchronized NIPPV [SNIPPV]) and the INSURE (intubation, surfactant and early extubation) approach are discussed. Initial treatment with NCPAP did not reduce the rate of BPD compared to endotracheal ventilation and surfactant administration. While NIPPV/SNIPPV may have short-term advantages over NCPAP, the effect on BPD needs to be further studied. During hospitalization the respiratory goals should aim for adequate oxygenation, permissive hypercapnia, and gentle ventilation. However, these goals were found to have short-term benefits but did not reduce significantly the rate of BPD. Selective use of a short course of low dose corticosteroids can be considered after the first or second week of life in infants who are unable to be weaned from the ventilator and are at high risk for BPD. Non-ventilatory measures include early nutritional support with fluid restriction, caffeine and consideration of vitamin A. Hemodynamic significant patent ductus arteriosus (PDA) may be associated with BPD, but medical or surgical treatment of PDA were not shown to decrease BPD. Each component and the strategy as a whole needs to be further studied in large randomized prospective studies or by meta-analyses, especially in the target population of extremely premature infants who are the most prone to BPD.

Attenuated vasodilatation in lambs with endogenous and exogenous activation of cGMP signaling: role of protein kinase G nitration

Pulmonary vasodilation is mediated through the activation of protein kinase G (PKG) via a signaling pathway involving nitric oxide (NO), natriuretic peptides (NP), and cyclic guanosine monophosphate (cGMP). In pulmonary hypertension secondary to congenital heart disease, this pathway is endogenously activated by an early vascular upregulation of NO and increased myocardial B-type NP expression and release. In the treatment of pulmonary hypertension, this pathway is exogenously activated using inhaled NO or other pharmacological agents. Despite this activation of cGMP, vascular dysfunction is present, suggesting that NO-cGMP independent mechanisms are involved and were the focus of this study. Exposure of pulmonary artery endothelial or smooth muscle cells to the NO donor, Spermine NONOate (SpNONOate), increased peroxynitrite (ONOO(-) ) generation and PKG-1α nitration, while PKG-1α activity was decreased. These changes were prevented by superoxide dismutase (SOD) or manganese(III)tetrakis(1-methyl-4-pyridyl)porphyrin (MnTMPyP) and mimicked by the ONOO(-) donor, 3-morpholinosydnonimine N-ethylcarbamide (SIN-1). Peripheral lung extracts from 4-week old lambs with increased pulmonary blood flow and pulmonary hypertension (Shunt lambs with endogenous activation of cGMP) or juvenile lambs treated with inhaled NO for 24 h (with exogenous activation of cGMP) revealed increased ONOO(-) levels, elevated PKG-1α nitration, and decreased kinase activity without changes in PKG-1α protein levels. However, in Shunt lambs treated with L-arginine or lambs administered polyethylene glycol conjugated-SOD (PEG-SOD) during inhaled NO exposure, ONOO(-) and PKG-1α nitration were diminished and kinase activity was preserved. Together our data reveal that vascular dysfunction can occur, despite elevated levels of cGMP, due to PKG-1α nitration and subsequent attenuation of activity.

16q24.1 microdeletion in a premature newborn: usefulness of array-based comparative genomic hybridization in persistent pulmonary hypertension of the newborn

OBJECTIVE

Report of a 16q24.1 deletion in a premature newborn, demonstrating the usefulness of array-based comparative genomic hybridization in persistent pulmonary hypertension of the newborn and multiple congenital malformations.

DESIGN

Descriptive case report.

SETTING

Genetic department and neonatal intensive care unit of a tertiary care children's hospital.

INTERVENTIONS

None.

PATIENT

We report the case of a preterm male infant, born at 26 wks of gestation. A cardiac malformation and bilateral hydronephrosis were diagnosed at 19 wks of gestation. Karyotype analysis was normal, and a 22q11.2 microdeletion was excluded by fluorescence in situ hybridization analysis. A cesarean section was performed due to fetal distress. The patient developed persistent pulmonary hypertension unresponsive to mechanical ventilation and nitric oxide treatment and expired at 16 hrs of life.

MEASUREMENTS AND MAIN RESULTS

An autopsy revealed partial atrioventricular canal malformation and showed bilateral dilation of the renal pelvocaliceal system with bilateral ureteral stenosis and annular pancreas. Array-based comparative genomic hybridization analysis (Agilent oligoNT 44K, Agilent Technologies, Santa Clara, CA) showed an interstitial microdeletion encompassing the forkhead box gene cluster in 16q24.1. Review of the pulmonary microscopic examination showed the characteristic features of alveolar capillary dysplasia with misalignment of pulmonary veins. Some features were less prominent due to the gestational age.

CONCLUSIONS

Our review of the literature shows that alveolar capillary dysplasia with misalignment of pulmonary veins is rare but probably underreported. Prematurity is not a usual presentation, and histologic features are difficult to interpret. In our case, array-based comparative genomic hybridization revealed a 16q24.1 deletion, leading to the final diagnosis of alveolar capillary dysplasia with misalignment of pulmonary veins. It emphasizes the usefulness of array-based comparative genomic hybridization analysis as a diagnostic tool with implications for both prognosis and management decisions in newborns with refractory persistent pulmonary hypertension and multiple congenital malformations.

Phosphodiesterase 4 inhibition attenuates persistent heart and lung injury by neonatal hyperoxia in rats

Phosphodiesterase (PDE) 4 inhibitors are potent anti-inflammatory drugs with antihypertensive properties, and their therapeutic role in bronchopulmonary dysplasia (BPD) is still controversial. We studied the role of PDE4 inhibition with piclamilast on normal lung development and its therapeutic value on pulmonary hypertension (PH) and right ventricular hypertrophy (RVH) in neonatal rats with hyperoxia-induced lung injury, a valuable model for premature infants with severe BPD. The cardiopulmonary effects of piclamilast treatment (5 mg·kg(-1)·day(-1)) were investigated in two models of experimental BPD: 1) daily treatment during continuous exposure to hyperoxia for 10 days; and 2) late treatment and injury-recovery in which pups were exposed to hyperoxia or room air for 9 days, followed by 9 or 42 days of recovery in room air combined with treatment started on day 6 of oxygen exposure until day 18. Prophylactic piclamilast treatment reduced pulmonary fibrin deposition, septum thickness, arteriolar wall thickness, arteriolar vascular smooth muscle cell proliferation and RVH, and prolonged survival. In the late treatment and injury-recovery model, hyperoxia caused persistent aberrant alveolar and vascular development, PH, and RVH. Treatment with piclamilast in both models reduced arteriolar wall thickness, attenuated RVH, and improved right ventricular function in the injury recovery model, but did not restore alveolarization or angiogenesis. Treatment with piclamilast did not show adverse cardiopulmonary effects in room air controls in both models. In conclusion, PDE4 inhibition attenuated and partially reversed PH and RVH, but did not advance alveolar development in neonatal rats with hyperoxic lung injury or affect normal lung and heart development.