The role of endothelin in oxygen-induced contraction of the ductus arteriosus in rabbit and rat fetuses

Using omics to breathe new life into our understanding of the ductus arteriosus oxygen response

The ductus arteriosus (DA) connects the aorta to the pulmonary artery (PA), directing placentally oxygenated blood away from the developing lungs. High pulmonary vascular resistance and low systemic vascular resistance facilitate shunting of blood in utero from the pulmonary to the systemic circulation through the widely patent DA, thereby optimizing fetal oxygen (O₂) delivery. With the transition from fetal (hypoxia) to neonatal (normoxia) oxygen conditions, the DA constricts while the PA dilates. This process often fails in prematurity, promoting congenital heart disease. Impaired O₂-responsivness in the DA promotes persistent ductus arteriosus (PDA), the most common form of congenital heart disease. Knowledge of DA oxygen sensing has greatly advanced in the past few decades, however we still lack a complete understanding of the sensing mechanism. The genomic revolution of the past two decades has facilitated unprecedented discovery in every biological system. This review will demonstrate how multiomic integration of data generated from the DA can breathe new life into our understanding of the DA's oxygen response.

Patent ductus arteriosus and oxidative stress in preterm infants: a narrative review

The role of oxygen, reactive oxygen species (ROS), and isoprostanes (IsoPs) in regulating patency and closure of patent ductus arteriosus (PDA) have been studied in preterm infants. Also the possible correlation between a hemodynamically significant PDA and its pharmacological treatment with oxidative stress has been investigated. The National Library of Medicine (MEDLINE) database was searched without time limits. Available data demonstrate that free radicals are not always harmful and that ROS and IsoPs play a relevant role in DA closure. On the other hand, a hemodynamically significant PDA can cause oxidative stress and this can partially explain its association with other complications of prematurity related to oxidative stress, such as bronchopulmonary dysplasia (BPD), intraventricular haemorrhage (IVH), and necrotizing enterocolitis (NEC). Some drugs used for pharmacological closure, such as ibuprofen, also have antioxidant effects, and the closure of PDA can restore a proper tissue oxygenation and the balance between pro-oxidant and antioxidant factors. These data support the importance of the relationship between PDA and oxidative stress whose understanding increase our awareness when we approach this prematurity complication in the clinical practice. Further studies might assess the reliability of ROS as possible biomarkers of the risk of developing a hsPDA.

Effects of prophylactic oral ibuprofen on the closure rate of patent ductus arteriosus in premature infants

The aim of this study was to investigate the effects of prophylactic oral ibuprofen on the closure rate of patent ductus arteriosus (PDA).This was a retrospective study and data on infants born before 36 weeks were collected. The prophylactic group was treated with ibuprofen (10, 5, and 5 mg/kg) from days 1 to 3 after birth, respectively. The conventional group was treated with the same dose of ibuprofen from days 4 to 6 once they were echocardiographically confirmed with PDA on day 3 after birth. The placebo group was treated with 5% glucose.The closure rate of PDA in the prophylactic group significantly increased on day 7 compared with the placebo group (P = .02), but showed no difference compared with the conventional group (P = .12). Serum NT-proBNP in the prophylactic and conventional groups decreased compared with the placebo group (P = .03 vs P = .07).Prophylactic oral ibuprofen can increase the closure rate of PDA in premature infants; however, it showed no significant advantages compared with conventional treatment. Serum NT-proBNP can be used to observe PDA treatment responses in premature infants.

Pulmonary arterial hypertension in pregnancy

Pulmonary hypertension is a medical condition characterized by elevated pulmonary arterial pressure and secondary right heart failure. Pulmonary arterial hypertension is a subset of pulmonary hypertension, which is characterized by an underlying disorder of the pulmonary arterial vasculature. Pulmonary hypertension can also occur secondarily to structural cardiac disease, autoimmune disorders, and toxic exposures. Although pregnancies affected by pulmonary hypertension and pulmonary arterial hypertension are rare, the pathophysiology exacerbated by pregnancy confers both high maternal and fetal mortality and morbidity. In light of new treatment modalities and the use of a multidisciplinary approach to care, maternal outcomes may be improving.

Mouse aortic muscle cells respond to oxygen following cytochrome P450 3A13 gene transfer

We have previously shown that a cytochrome P450 (CYP450) hemoprotein from the 3A subfamily CYP3A13 for the mouse, serves as the sensor in the contraction of the ductus arteriosus in response to increased oxygen tension. In addition, we have identified endothelin-1 (ET-1) as the effector for this response. Here, we examined whether Cyp3a13 gene transfer confers oxygen sensitivity to cultured muscle cells from mouse aorta. Coincidentally, we determined whether the same hemoprotein is normally present in the vessel. Cyp3a13-transfected aortic cells responded to oxygen, whereas no significant response was seen in native cells or in cells transfected with an empty vector. Furthermore, this oxygen effect was curtailed by the ET-1/ETA receptor antagonist BQ-123. We also found that CYP3A13 occurs naturally in aortic tissue and its isolated muscle cells in culture. We conclude that CYP3A13 is involved in oxygen sensing, and its action in the transfected muscle cells of the aorta, as in the native cells of the ductus, takes place through a linkage to ET-1. However, the response of aortic muscle to oxygen, conceivably entailing the presence of CYP3A13 at some special site, is not seen in the native situation, and may instead unfold upon transfection of the parent gene.

Mechanisms for ductus arteriosus closure

Closure of the ductus arteriosus at birth is a complex phenomenon being conditioned by antenatal events and progressing in preprogrammed steps. Functional at first, narrowing of the vessel is determined by 2 overlapping processes--removal of the prostaglandin E(2)-based relaxation sustaining prenatal patency and activation of a constrictor mechanism by the natural rise in blood oxygen tension. Two schemes have been proposed for oxygen action--one involving a cytochrome P450 hemoprotein (sensor)/endothelin-1 (effector) complex and the other a set of voltage-gated K(+) channels. These proposals, however, are not mutually exclusive. Structural closure follows the constriction through a remodeling process initiated antenatally with the development of intimal cushions and completed postnatally by a host of humoral and mechanical stimuli. Research in this area has already provided clinical applications. Nevertheless, management of premature infants with persistent ductus remains troublesome and calls for an alternative approach to the prostaglandin E(2) inhibitors now in use. Studies in progress on the oxygen-sensing system may lead to a definitive solution for this problem.

Ontogeny of chicken ductus arteriosus response to oxygen and vasoconstrictors

The present study aimed to characterize the contractile reactivity of the chicken ductus arteriosus (DA) from the last stage of prenatal development and throughout the perinatal period. Isolated DA rings from 15-day, noninternally-pipped 19-day, and externally-pipped 21-day embryos were studied using myograph techniques. On embryonic day 15, the chicken DA did not respond to O(2) (0 to 21%), norepinephrine (NE), or phenylephrine (Phe) but contracted in response to high-K(+) solution, the inhibitor of voltage-gated channels 4-aminopyridine, U-46619, and endothelin (ET)-1. These responses increased with advancing incubation age. Contractile responses to O(2), NE, and Phe were present in the 19- and 21-day embryo. Oxygen-induced contraction was restricted to the pulmonary side of the DA and was augmented by the nitric oxide synthase inhibitor N(omega)-nitro-l-arginine methyl ester and the soluble guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one and reduced by the peptidic ET(A) and ET(B)-receptor antagonist PD-142,893. Transmural electrical stimulation of nerves, the nonselective cyclooxygenase (COX) inhibitor indomethacin, the COX-1 inhibitor valeryl salicylate, the COX-2 inhibitor nimesulide, the inhibitor of ATP-sensitive K(+) channels glibenclamide, and the inhibitor of Ca(2+)-activated K(+) channels tetraethylammonium did not cause contraction of the DA rings at any age. We conclude that transition to ex ovo life is accompanied by dramatic changes in chicken DA reactivity. At 0.7 incubation, excitation-contraction and pharmacomechanical coupling for several contractile agonists are already present, whereas the constrictor effects of O(2) and cathecolamines appear later in development and are located in the pulmonary side of the DA.