cyclic-gmp and Persistent-Fetal-Circulation-Syndrome

Effective ventilation of the lungs is essential in mediating pulmonary vasodilation at birth to allow effective gas exchange and an increase in systemic oxygenation. Unsuccessful transition prevents the increase in pulmonary blood flow after birth resulting in hypoxemia and persistent pulmonary hypertension of the newborn (PPHN). Management of neonates with PPHN includes ventilation of the lungs with supplemental oxygen to correct hypoxemia. Optimal oxygenation should meet oxygen demand to the tissues and avoid hypoxic pulmonary vasoconstriction (HPV) while preventing oxidative stress. The optimal target for oxygenation in PPHN is not known. Animal models have demonstrated that PaO

Topics: Animals; Antioxidants; Cyclic GMP; Disease Models, Animal; Humans; Infant, Newborn; Infant, Premature; Lung; Mice; Oxidative Stress; Oxygen; Persistent Fetal Circulation Syndrome; Rats; Reactive Oxygen Species; Respiration, Artificial; Vasoconstriction

Topics: Cyclic GMP; Endothelium, Vascular; Fetus; Humans; Infant, Newborn; Lung; Nitric Oxide; Persistent Fetal Circulation Syndrome

At birth, a marked decrease in pulmonary vascular resistance allows the lung to establish gas exchange. Persistent pulmonary hypertension of the newborn (PPHN) occurs when this normal adaptation of gas exchange does not occur. We review animal models used to study the pathogenesis and treatment of PPHN. Both acute models, such as acute hypoxia and infusion of vasoconstrictors, and chronic models of PPHN created both before and immediately after birth are described. Inhaled nitric oxide is an important emerging therapy for PPHN. We review nitric oxide receptor mechanisms, including soluble guanylate cyclase, which produces cGMP when stimulated by nitric oxide, and phosphodiesterases, which control the intensity and duration of cGMP signal transduction. A better understanding of these mechanisms of regulation of vascular tone may lead to safer use of nitric oxide and improved clinical outcomes.

Topics: Animals; Constriction, Pathologic; Cyclic GMP; Disease Models, Animal; Humans; Hypertension, Pulmonary; Hypoxia; Infant, Newborn; Ligation; Nitric Oxide Synthase; Persistent Fetal Circulation Syndrome; Pulmonary Artery; Vasodilation

To examine the role of endogenous nitric oxide (NO) and endothelin-1 (ET-1) in the pathogenesis of persistent pulmonary hypertension of the newborn (PPHN) and to determine whether inhaled NO, currently under investigation as a new therapy for PPHN, affects plasma concentrations of these vasoactive mediators.. Circulating ET-1 and cyclic guanosine monophosphate (cGMP) concentrations were measured by radioimmunoassay in 15 healthy term newborn infants and 46 newborn infants with PPHN enrolled in a randomized, controlled trial of inhaled NO. These concentrations were followed up longitudinally and compared between the NO and the conventionally treated group.. Concentrations of ET-1 were significantly higher and cGMP concentrations significantly lower in infants with PPHN compared with healthy newborn infants (median ET-1, 28 vs 11 pmol/L; p = 0.0001; median cGMP, 35 vs 61 pmol/ml; p = 0.0001, respectively). ET-1 concentrations showed an upward trend at 1 and 24 hours of treatment and a subsequent decline at recovery in both subgroups of patients, with the most pronounced decrease in the NO group. cGMP concentrations increased significantly only in the NO group, with a peak at 1 hour of treatment (median, 61 pmol/ml). As the dose of NO decreased, cGMP concentrations declined. In contrast, conventionally treated infants manifested no change in cGMP concentrations from baseline until recovery, when a significant decrease was noted (median decrease of 13 pmol/ml; p = 0.002). We did not find a significant difference between ET-1 and cGMP concentrations in infants who required extracorporeal membrane oxygenation compared with those who did not.. PPHN is associated with increased ET-1 and decreased cGMP plasma concentrations, which may contribute to the pathogenesis of the disease. Inhaled NO appears to modulate these mediators during the disease process, suggesting an interaction between ET-1 and NO in vivo.

Topics: Administration, Inhalation; Cyclic GMP; Endothelin-1; Female; Humans; Infant, Newborn; Male; Nitric Oxide; Persistent Fetal Circulation Syndrome

Persistent pulmonary hypertension of the newborn (PPHN) features hypoxemia, pulmonary vasoconstriction, and impaired cardiac inotropy. We previously reported low basal and stimulated cAMP in hypoxic pulmonary artery smooth muscle cells (PASMCs). We now examine pulmonary arterial adenylyl cyclase (AC) activity and regulation in hypoxic PPHN. PPHN was induced in newborn swine by normobaric hypoxia (fraction of inspired oxygen 0.10) for 72 h and compared with age-matched normoxic controls. We studied relaxation of pulmonary arterial (PA) rings to AC activator forskolin and cGMP activator sodium nitroprusside (SNP) by isometric myography, ATP content, phosphodiesterase activity, AC content, isoform expression, and catalytic activity in presence or absence of Gαs-coupled receptor agonists, forskolin, or transnitrosylating agents in human and neonatal porcine PASMCs and HEK293T stably expressing AC isoform 6, after 72 h hypoxia (10% O

Topics: Adenylyl Cyclases; Animals; Animals, Newborn; Cell Line; Cyclic GMP; Down-Regulation; HEK293 Cells; Humans; Hypertension, Pulmonary; Hypoxia; Muscle Relaxation; Myocytes, Smooth Muscle; Nitroprusside; Persistent Fetal Circulation Syndrome; Pulmonary Artery; Swine

In the pulmonary vasculature, cGMP levels are regulated by soluble guanylate cyclase (sGC) and phosphodiesterase 5 (PDE5). We previously reported that lambs with persistent pulmonary hypertension of the newborn (PPHN) demonstrate increased reactive oxygen species (ROS) and altered sGC and PDE5 activity, with resultant decreased cGMP. The objective of this study was to evaluate the effects of hydrocortisone on pulmonary vascular function, ROS, and cGMP in the ovine ductal ligation model of PPHN. PPHN lambs were ventilated with 100% O(2) for 24 h. Six lambs received 5 mg/kg hydrocortisone every 8 h times three doses (PPHN-hiHC), five lambs received 3 mg/kg hydrocortisone followed by 1 mg·kg(-1)·dose(-1) times two doses (PPHN-loHC), and six lambs were ventilated with O(2) alone (PPHN). All groups were compared with healthy 1-day spontaneously breathing lambs (1DSB). O(2) ventilation of PPHN lambs decreased sGC activity, increased PDE5 activity, and increased ROS vs. 1DSB lambs. Both hydrocortisone doses significantly improved arterial-to-alveolar ratios relative to PPHN lambs, decreased PDE5 activity, and increased cGMP relative to PPHN lambs. High-dose hydrocortisone also increased sGC activity, decreased PDE5 expression, decreased ROS, and increased total vascular SOD activity vs. PPHN lambs. These data suggest that hydrocortisone treatment in clinically relevant doses improves oxygenation and decreases hyperoxia-induced changes in sGC and PDE5 activity, increasing cGMP levels. Hydrocortisone reduces ROS levels in part by increasing SOD activity in PPHN lambs ventilated with 100% O(2.) We speculate that hydrocortisone increases cGMP by direct effects on sGC and PDE5 expression and by attenuating abnormalities induced by oxidant stress.

Topics: Animals; Animals, Newborn; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Guanylate Cyclase; Humans; Hydrocortisone; Hyperoxia; Infant, Newborn; Oxidative Stress; Oxygen; Persistent Fetal Circulation Syndrome; Pulmonary Artery; Reactive Oxygen Species; Receptors, Cytoplasmic and Nuclear; Sheep; Soluble Guanylyl Cyclase; Superoxide Dismutase

Although inhaled NO (iNO) therapy is often effective in treating infants with persistent pulmonary hypertension of the newborn (PPHN), up to 40% of patients fail to respond, which may be partly due to abnormal expression and function of soluble guanylate cyclase (sGC). To determine whether altered sGC expression or activity due to oxidized sGC contributes to high pulmonary vascular resistance (PVR) and poor NO responsiveness, we studied the effects of cinaciguat (BAY 58-2667), an sGC activator, on pulmonary artery smooth muscle cells (PASMC) from normal fetal sheep and sheep exposed to chronic intrauterine pulmonary hypertension (i.e., PPHN). We found increased sGC α(1)- and β(1)-subunit protein expression but lower basal cGMP levels in PPHN PASMC compared with normal PASMC. To determine the effects of cinaciguat and NO after sGC oxidation in vitro, we measured cGMP production by normal and PPHN PASMC treated with cinaciguat and the NO donor, sodium nitroprusside (SNP), before and after exposure to 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, an sGC oxidizer), hyperoxia (fraction of inspired oxygen 0.50), or hydrogen peroxide (H(2)O(2)). After treatment with ODQ, SNP-induced cGMP generation was markedly reduced but the effects of cinaciguat were increased by 14- and 64-fold in PPHN fetal PASMC, respectively (P < 0.01 vs. controls). Hyperoxia or H(2)O(2) enhanced cGMP production by cinaciguat but not SNP in PASMC. To determine the hemodynamic effects of cinaciguat in vivo, we compared serial responses to cinaciguat and ACh in fetal lambs after ductus arteriosus ligation. In contrast with the impaired vasodilator response to ACh, cinaciguat-induced pulmonary vasodilation was significantly increased. After birth, cinaciguat caused a significantly greater fall in PVR than either 100% oxygen, iNO, or ACh. We conclude that cinaciguat causes more potent pulmonary vasodilation than iNO in experimental PPHN. We speculate that increased NO-insensitive sGC may contribute to the pathogenesis of PPHN, and cinaciguat may provide a novel treatment of severe pulmonary hypertension.

Topics: Animals; Benzoates; Cells, Cultured; Cyclic GMP; Disease Models, Animal; Female; Fetus; Guanylate Cyclase; Humans; Hydrogen Peroxide; Infant, Newborn; Isoenzymes; Myocytes, Smooth Muscle; Nitric Oxide; Nitroprusside; Oxadiazoles; Persistent Fetal Circulation Syndrome; Pregnancy; Pulmonary Artery; Pulmonary Circulation; Quinoxalines; Receptors, Cytoplasmic and Nuclear; Sheep; Soluble Guanylyl Cyclase; Vascular Resistance; Vasodilation; Vasodilator Agents

In the pulmonary vasculature, phosphodiesterase-5 (PDE5) degrades cGMP and inhibits nitric oxide-mediated, cGMP-dependent vasorelaxation. We previously reported that ventilation with 100% O2 increased PDE5 activity in pulmonary arteries (PAs) of pulmonary hypertension lambs (PPHN) more than in control lambs. In the present study, PA smooth muscle cells (PASMCs) from PPHN lambs had increased basal PDE5 activity, decreased cGMP-responsiveness to NO, and increased mitochondrial matrix oxidant stress compared to control PASMC. Hyperoxia (24 h) increased PDE5 activity and mitochondrial matrix oxidant stress above baseline to a similar degree in PPHN and control PASMC. Mitochondrially targeted catalase decreased PDE5 activity at baseline and after hyperoxia in PPHN PASMC. Similarly, catalase treatment of PPHN lambs ventilated with 100% O2 decreased PDE5 activity and increased cGMP in PA. We conclude that baseline PDE5 activity and oxidative stress is increased in PPHN PASMC, and scavenging H2O2 is sufficient to block oxidant-mediated increases in PDE5 activity in PPHN.

Topics: Animals; Animals, Newborn; Catalase; Cells, Cultured; Cyclic GMP; Disease Models, Animal; Embryo, Mammalian; Female; Gene Expression Regulation; Goats; Humans; Immunoassay; Infant, Newborn; Mitochondria; Myocytes, Smooth Muscle; Nitric Oxide; Oxidative Stress; Oxygen; Persistent Fetal Circulation Syndrome; Polyethylene Glycols; Pregnancy; Pulmonary Artery; Reactive Oxygen Species

The aim of the study was to examine the relationship between the plasma concentration of cyclic guanosine monophosphate (cGMP) and pulmonary pressure and hypoxia defined by oxygenation index (OI) in newborn infants with severe persistent pulmonary hypertension (PPHN) on inhaled nitric oxide (NO). In this prospective study, 18 newborn infants having Doppler ultrasound-diagnosed PPHN and treated with NO were investigated. The ratio of pulmonary artery to systemic artery pressure (PAP/SAP) and OI was assessed before treatment and at 0.5, 1, 12, and 24 h from the beginning of NO. At these time points, plasma concentrations of cGMP could be determined in 11 patients. The association of birth asphyxia as assessed by Apgar 1 min and 5 min and plasma cGMP before the NO treatment was examined. The initial median plasma concentration of cGMP was 37.3 pmol/ml (IQR 13.3-79.6). After the start of NO, cGMP increased significantly within 60 min (p = 0.003) and peaked at 12 h. Initial plasma cGMP was associated with Apgar score (1 and 5 min). OI decreased within 30 min of NO and PAP/SAP within 60 min. Persistent high PAP/SAP after 1 h of NO was associated with low cGMP concentration (r = 0.70, p = 0.02). We conclude that a significant increase in plasma cGMP is already evident after 60 min of NO therapy. This effect is accompanied by changes in oxygenation index and in pulmonary artery pressure. Initial plasma concentrations of cGMP were associated with hypoxia assessed as Apgar score.

Topics: Apgar Score; Asphyxia Neonatorum; Blood Pressure; Cyclic GMP; Female; Humans; Infant, Newborn; Kinetics; Male; Nitric Oxide; Oxygen; Persistent Fetal Circulation Syndrome; Prospective Studies; Pulmonary Artery

We investigated the pulmonary vascular effects of E4021, a potent inhibitor of cGMP-specific phosphodiesterase, in control late-gestation fetal lambs, and in newborn lambs with persistent pulmonary hypertension (PPHN) after prenatal ligation of the ductus arteriosus. E4021 alone significantly relaxed fifth-generation pulmonary arteries isolated from control fetal lambs, an effect completely blocked after inhibition of nitric oxide synthase (NOS). In contrast, E4021 did not relax pulmonary arteries isolated from hypertensive lambs. Pretreatment with E4021 (10(-7) M) significantly enhanced relaxations to the NO donor S-nitrosyl-acetyl-penicilamine (SNAP) in arteries from both control and hypertensive lambs. In control, fully instrumented fetal lambs, infusions of E4021 (31 microgram/min) selectively dilated the pulmonary circulation, an effect again blocked after inhibition of NO synthase. Further studies were performed in newborn lambs with PPHN to study the vascular effects of E4021 alone, and in combination with inhaled NO. E4021 alone (1 to 100 microgram/kg/min) decreased pulmonary artery pressure (Ppa) in a dose-dependent fashion, and had minimal effect on systemic pressure. At the highest dose (100 microgram/kg/min), the dilation was selective for the pulmonary circulation. In subsequent protocols, E4021 (10 microgram/kg/min) significantly decreased Ppa and pulmonary vascular resistance (PVR), but these pulmonary vascular effects were not enhanced after NO inhalation at 0.5 or 5 ppm. We speculate that the lack of enhancement was due to the dramatic effects of E4021 alone. Potent, specific phosphodiesterase inhibitors such as E4021 may prove to be useful in the treatment of PPHN.

Topics: Analysis of Variance; Animals; Animals, Newborn; Cyclic GMP; Disease Models, Animal; Dose-Response Relationship, Drug; Female; Fetus; Humans; Infant, Newborn; Infusions, Intravenous; Nitric Oxide; Persistent Fetal Circulation Syndrome; Phosphodiesterase Inhibitors; Piperidines; Pregnancy; Pulmonary Artery; Pulmonary Circulation; Quinazolines; Sheep; Statistics, Nonparametric; Vasodilation

Nitric oxide (NO) relaxes vascular smooth muscle by increasing the intracellular concentration of cGMP. In the pulmonary circulation, cGMP is inactivated by specific phosphodiesterases (PDE5). Dipyridamole, a clinically approved drug, has inhibitory activity against PDE5 and has been reported to augment the response to inhaled NO in persistent pulmonary hypertension of the newborn (PPHN). We wished to determine whether dipyridamole alone, or in combination with NO, can be used to treat a newborn lamb model of PPHN. In newborn lambs with PPHN, dipyridamole infused at 0.02 mg/kg/min for 45 min alone, or in combination with 5 ppm of inhaled NO for the final 15 min, significantly decreased pulmonary and systemic blood pressure, decreased pulmonary vascular resistance, and increased pulmonary blood flow. There was no significant difference between the pulmonary vascular effects of 5 ppm NO alone compared with the effects of NO combined with dipyridamole. In control lambs, the 45-min infusion of dipyridamole did not change pulmonary pressure whereas systemic pressure decreased by 28 +/- 3%. These systemic effects in control lambs persisted 90 min after discontinuing the dipyridamole infusion. Systemic arteries isolated from both control and PPHN lambs were significantly more sensitive to dipyridamole than pulmonary arteries. We conclude that dipyridamole has significant hemodynamic effects in both the pulmonary and systemic circulations of newborn lambs with pulmonary hypertension as well as in the systemic circulation of newborn control lambs. The pronounced effects of dipyridamole on the systemic circulation limits its utility as an adjunct to inhaled NO in the treatment of PPHN.

Topics: Animals; Animals, Newborn; Cyclic GMP; Dipyridamole; Disease Models, Animal; Female; Hemodynamics; Humans; In Vitro Techniques; Infant, Newborn; Mesenteric Arteries; Nitric Oxide; Persistent Fetal Circulation Syndrome; Phosphodiesterase Inhibitors; Pregnancy; Pulmonary Artery; Pulmonary Circulation; Sheep

Acute hypoxia causes pulmonary hypertension in the fetus and newborn that is contrasted by systemic hypotension or normotension. To better understand the role of nitric oxide (NO) in this specific pulmonary vascular response, we determined the acute effects of decreased oxygenation on NO production in ovine fetal pulmonary and systemic (mesenteric) endothelial cells. NO was assessed by measuring cGMP accumulation in fetal vascular smooth muscle (VSM) cells during co-culture incubations of endothelium and VSM (40 s) in the presence of the phosphodiesterase inhibitor isobutylmethylxanthine. Changes in cGMP were dependent on the endothelium and on NO synthase and guanylate cyclase activity. At high O2 (680 mm Hg), basal NO was detectable and NO increased 6- to 10-fold with bradykinin or A23187. In pulmonary endothelium, basal NO fell 58% at pO2 = 150 mm Hg and 51% at 40 mm Hg versus 680 mm Hg, while NO with bradykinin fell 56% and 63%, respectively. NO with A23187, however, was unchanged at 150 mm Hg, but it fell 56% at 40 mm Hg. In contrast, in systemic endothelium basal and stimulated NO production were not altered at lower O2. Findings were similar using pulmonary or systemic detector VSM cells, and exogenous L-arginine had no effect. Thus, decreased O2 acutely attenuates NO production specifically in fetal pulmonary endothelial cells. This process is not related to changes in O2 or L-arginine availability as substrates for NO synthase; alternatively, it may be partially mediated by specific effects of O2 on pulmonary endothelial cell calcium homeostasis.

Topics: 1-Methyl-3-isobutylxanthine; Amino Acid Oxidoreductases; Animals; Bradykinin; Calcimycin; Cells, Cultured; Cyclic GMP; Disease Models, Animal; Endothelium, Vascular; Female; Guanylate Cyclase; Humans; Hypoxia; Infant, Newborn; Lung; Mesenteric Arteries; Muscle, Smooth, Vascular; Nitric Oxide; Nitric Oxide Synthase; Nitroprusside; Oxygen; Persistent Fetal Circulation Syndrome; Pregnancy; Pulmonary Artery; Sheep