Jaques Belik

Pulmonary hypertension in adult Alk1 heterozygous mice due to oxidative stress

AIMS Mutations in the ALK1 gene, coding for an endothelial-specific receptor of the transforming growth factor-β superfamily, are the underlying cause of hereditary haemorrhagic telangiectasia type 2, but are also associated with familial pulmonary hypertension (PH). We assessed the lung vasculature of mice with a heterozygous deletion of Alk1 (Alk1(+/-)) for disease manifestations and levels of reactive O(2) species (ROS) implicated in both disorders. METHODS AND RESULTS Several signs of PH, including elevated right ventricular (RV) systolic pressure leading to RV hypertrophy, reduced vascular density, and increased thickness and outward remodelling of pulmonary arterioles, were observed in 8- to 18-week-old Alk1(+/-) mice relative to wild-type littermate controls. Higher ROS lung levels were also documented. At 3 weeks, Alk1(+/-) mice were indistinguishable from controls and were prevented from subsequently developing PH when treated with the anti-oxidant Tempol for 6 weeks, confirming a role for ROS in pathogenesis. Levels of NADPH oxidases and superoxide dismutases were higher in adults than newborns, but unchanged in Alk1(+/-) mice vs. controls. Prostaglandin metabolites were also normal in adult Alk1(+/-) lungs. In contrast, NO production was reduced, while endothelial NO synthase (eNOS)-dependent ROS production was increased in adult Alk1(+/-) mice. Pulmonary near resistance arteries from adult Alk1(+/-) mice showed less agonist-induced force and greater acetylcholine-induced relaxation; the later was normalized by catalase or Tempol treatment. CONCLUSION The increased pulmonary vascular remodelling in Alk1(+/-) mice leads to signs of PH and is associated with eNOS-dependent ROS production, which is preventable by anti-oxidant treatment.

Fetal and neonatal effects of maternal drug treatment for depression.

Depression has a female sex predilection with 2 to 3% of the pregnant women population presently requiring treatment with selective serotonin reuptake inhibitors (SSRI). Exposure to SSRIs in late gestation leads to clinical manifestations in as much as 30% of the neonates. These include neurobehavioral, respiratory, gastrointestinal, and somatic symptoms. Among the respiratory manifestations, persistent pulmonary hypertension syndrome is a newly recognized and concerning side effect of SSRI exposure in utero. This causal association has been reproduced in an animal model where fluoxetine administration to pregnant rats induces fetal pulmonary hypertension. The pharmacological effects of SSRI on the fetus and newborn, available treatment, and prevention strategies are discussed in this review.

Isoprostanes in fetal and neonatal health and disease

Isoprostanes are prostaglandin-like bioactive molecules generated via nonenzymatic peroxidation of lipid membrane-derived arachidonic acid by free radicals and reactive oxygen species. Their cognate receptors, biological actions, and signaling pathways are poorly understood. Aside from being sensitive and specific biomarkers of oxidative stress, E- and F-ring isoprostanes have important biological functions and likely mediate many of the disease-related pathological changes for which they are used as indicators. The biochemical pathways involved in isoprostane formation, their pathogenetic relevance to adult disease states, and their biological function are addressed. Developmentally, plasma and tissue content data show that isoprostane levels are highest during fetal and early neonatal life, when compared with adults. As such, the available data suggesting that isoprostanes play an important biological role, as well as possibly actively participate in the regulation of pulmonary vascular tone and the transition from fetal to postnatal life, are here reviewed. Lastly, the association between isoprostanes and certain neonatal clinical conditions is addressed. Although its existence has been recognized for almost 20 years, little is known about the critical importance of isoprostanes during fetal life and immediate neonatal period. This review is an attempt to bridge this knowledge gap.

Persistent pulmonary hypertension of the newborn: recent advances in pathophysiology and treatment

OBJECTIVES Although recognized for decades, little is known about the etiology, physiopathology, and prevention of persistent pulmonary hypertension of the newborn (PPHN), and its treatment remains a major challenge for neonatologists. In this review, the clinical features and physiopathology of the syndrome will be addressed, as well as its general and specific treatments. DATA SOURCE A review was carried out in PubMed, Cochrane Library, and MRei consult databases, searching for articles related to the syndrome and published between 1995 and 2011. DATA SYNTHESIS Risk factors and the physiopathological mechanisms of the syndrome are discussed. The clinical presentation depends on the different factors involved. These are related to the etiology and physiopathology of the different forms of the disease. In addition to the measures used to allow for the decrease in pulmonary vascular resistance after birth, in some instances pulmonary vasodilators will be required. Although inhaled nitric oxide has proved effective, other vasodilators have been recently used, but clinical evidence is still lacking to demonstrate their benefits in the treatment of PPHN. CONCLUSIONS Despite recent technological advances and new physiopathological knowledge of this disease, mortality associated with PPHN remains at 10%. More clinical research and evidence-based experimental results are needed to prevent, treat, and reduce the morbidity/mortality associated with this neonatal syndrome.

Age-dependent endothelial nitric oxide synthase uncoupling in pulmonary arteries of endoglin heterozygous mice

Endoglin is a TGF-beta superfamily receptor critical for endothelial cell function. Mutations in this gene are associated with hereditary hemorrhagic telangiectasia type I (HHT1), and clinical signs of disease are generally more evident later in life. We previously showed that systemic vessels of adult Eng heterozygous (Eng(+/-)) mice exhibit increased vasorelaxation due to uncoupling of endothelial nitric oxide synthase (eNOS). We postulated that these changes may develop with age and evaluated pulmonary arteries from newborn and adult Eng(+/-) mice for eNOS-dependent, acetylcholine (ACh-induced) vasorelaxation, compared with that of age-matched littermate controls. While ACh-induced vasorelaxation was similar in all newborn mice, it was significantly increased in the adult Eng(+/-) vs. control vessels. The vasodilatory responses were inhibited by l-NAME suggesting eNOS dependence. eNOS uncoupling was observed in lung tissues of adult, but not newborn, heterozygous mice and was associated with increased production of reactive O(2) species (ROS) in adult Eng(+/-) vs. control lungs. Interestingly, ROS generation was higher in adult than newborn mice and so were the levels of NADPH oxidase 4 and SOD 1, 2, 3 isoforms. However, enzyme protein levels and NADPH activity were normal in adult Eng(+/-) lungs indicating that the developmental maturation of ROS generation and scavenging cannot account for the increased vasodilatation observed in adult Eng(+/-) mice. Our data suggest that eNOS-dependent H(2)O(2) generation in Eng(+/-) lungs accounts for the heightened pulmonary vasorelaxation. To the extent that these mice mimic human HHT1, age-associated pulmonary vascular eNOS uncoupling may explain the late childhood and adult onset of clinical lung manifestations.

L-ornithine derived polyamines in cystic fibrosis airways.

Increased arginase activity contributes to airway nitric oxide (NO) deficiency in cystic fibrosis (CF). Whether down-stream products of arginase activity contribute to CF lung disease is currently unknown. The objective of this study was to test whether L-ornithine derived polyamines are present in CF airways and contribute to airway pathophysiology. Polyamine concentrations were measured in sputum of patients with CF and in healthy controls, using liquid chromatography-tandem mass spectrometry. The effect of spermine on airway smooth muscle mechanical properties was assessed in bronchial segments of murine airways, using a wire myograph. Sputum polyamine concentrations in stable CF patients were similar to healthy controls for putrescine and spermidine but significantly higher for spermine. Pulmonary exacerbations were associated with an increase in sputum and spermine levels. Treatment for pulmonary exacerbations resulted in decreases in arginase activity, L-ornithine and spermine concentrations in sputum. The changes in sputum spermine with treatment correlated significantly with changes in L-ornithine but not with sputum inflammatory markers. Incubation of mouse bronchi with spermine resulted in an increase in acetylcholine-induced force and significantly reduced nitric oxide-induced bronchial relaxation. The polyamine spermine is increased in CF airways. Spermine contributes to airways obstruction by reducing the NO-mediated smooth muscle relaxation.

Arginase inhibition prevents bleomycin-induced pulmonary hypertension, vascular remodeling, and collagen deposition in neonatal rat lungs.

Arginase is an enzyme that limits substrate L-arginine bioavailability for the production of nitric oxide by the nitric oxide synthases and produces L-ornithine, which is a precursor for collagen formation and tissue remodeling. We studied the pulmonary vascular effects of arginase inhibition in an established model of repeated systemic bleomycin sulfate administration in neonatal rats that results in pulmonary hypertension and lung injury mimicking the characteristics typical of bronchopulmonary dysplasia. We report that arginase expression is increased in the lungs of bleomycin-exposed neonatal rats and that treatment with the arginase inhibitor amino-2-borono-6-hexanoic acid prevented the bleomycin-induced development of pulmonary hypertension and deposition of collagen. Arginase inhibition resulted in increased L-arginine and L-arginine bioavailability and increased pulmonary nitric oxide production. Arginase inhibition also normalized the expression of inducible nitric oxide synthase, and reduced bleomycin-induced nitrative stress while having no effect on bleomycin-induced inflammation. Our data suggest that arginase is a promising target for therapeutic interventions in neonates aimed at preventing lung vascular remodeling and pulmonary hypertension.

Pulmonary vascular and cardiac effects of peroxynitrite decomposition in newborn rats

Evidence implicates oxidative stress as playing a prominent role in the pathogenesis of pulmonary hypertension, to which peroxynitrite anion (ONOO(-)) may make a major contribution. Hypothesizing that removal of ONOO(-) would attenuate chronic neonatal pulmonary hypertension, we examined the effects of a ONOO(-) decomposition catalyst (FeTPPS) on pulmonary arteries in vitro, on primary cultured pulmonary artery smooth muscle cell (PASMC) and cardiomyocyte survival and growth, and on central hemodynamics in rat pups exposed to hypoxia (13% O(2)) for 7 days from birth. Daily FeTPPS (30 mg/kg ip) reduced lung nitrotyrosine content, attenuated vascular remodeling, and normalized pulmonary vascular resistance in hypoxia-exposed animals. FeTPPS attenuated proliferation and increased apoptosis of neonatal PASMCs in vitro. Isolated neonatal pulmonary arteries treated with FeTPPS showed reduced agonist-induced force development and enhanced endothelium-dependent and -independent relaxation, possibly via increased nitrate. However, we observed endothelial dysfunction, enhanced lung tissue phosphodiesterase 5 activity, and biventricular cardiac hypertrophy in air-exposed animals receiving FeTPPS. Further, in contrast to PASMCs, FeTPPS enhanced survival of newborn cardiomyocytes. We conclude that decomposition of ONOO(-) with FeTPPS attenuates chronic hypoxia-induced pulmonary hypertension; however, it may negatively influence the modulation of normal pulmonary arterial relaxation function, cell survival, and growth.

Use of Noninvasive High-Frequency Ventilation in the Neonatal Intensive Care Unit: A Retrospective Review

OBJECTIVE The aim of the article is to review the effectiveness of neonatal noninvasive high-frequency ventilation (NIHFV) in preventing endotracheal mechanical ventilation. STUDY DESIGN Retrospective case series including all 79 instances of NIHFV use at four participating centers between July 2010 and September 2012. RESULTS In 73% of cases, NIHFV was used as rescue after another noninvasive mode, and prophylactically (postextubation) in the remainder. In 58% of cases, infants transitioned to another noninvasive mode, without requiring intubation. There were significant reductions in the mean (SD) number of apneas, bradycardias, or desaturations (over 6 hours) (3.2 [0.4] vs. 1.2 [0.3]; p < 0.001), FiO2 (48 [3] vs. 40 [2]%; p < 0.001) and CO2 levels (74 [6] vs. 62 [4] mm Hg; p = 0.025] with NIHFV. No NIHFV-related complications were noted. CONCLUSIONS NIHFV is a promising NIV mode that may help prevent or delay intubation and deserves further clinical research.

Pantoprazole decreases gastroesophageal muscle tone in newborn rats via rho-kinase inhibition

Proton pump inhibitors reduce gastric acid secretion and are commonly utilized in the management of gastroesophageal reflux disease across all ages. Yet a decrease in lower esophageal sphincter tone has been reported in vitro in rats through an unknown mechanism; however, their effect on the gastroesophageal muscle tone early in life was never studied. Hypothesizing that proton pump inhibitors also reduce gastroesophageal muscle contraction in newborn and juvenile rats, we evaluated the in vitro effect of pantoprazole on gastric and lower esophageal sphincter muscle tissue. Electrical field stimulation and carbachol-induced force were significantly (P < 0.01) reduced in the presence of pantoprazole, whereas the drug had no effect on the neuromuscular-dependent relaxation. When administered in vivo, pantoprazole (9 mg/kg) significantly (P < 0.01) reduced gastric emptying time at both ages. To ascertain the signal transduction pathway responsible for the reduction in muscle contraction, we evaluated the tissue ROCK-2 and CPI-17 activity. Pantoprazole reduced myosin light chain phosphatase MYPT-1, but not CPI-17 phosphorylation of gastric and lower esophageal sphincter tissue, strongly suggesting that it is a ROCK-2 inhibitor. To the extent that these findings can be extrapolated to human neonates, the use of pantoprazole may impair gastric and lower sphincter muscle tone and thus paradoxically exacerbate esophageal reflux. Further studies addressing the effect of proton pump inhibitors on gastroesophageal muscle contraction are warranted to justify its therapeutic use in gastroesophageal reflux disease.