In vivo constriction of the fetal and neonatal ductus arteriosus by a prostanoid EP4-receptor antagonist in rats

A novel role for PGE2-EP4 in the developmental programming of the mouse ductus arteriosus: consequences for vessel maturation and function

The ductus arteriosus (DA) is a vascular shunt that allows oxygenated blood to bypass the developing lungs in utero. Fetal DA patency requires vasodilatory signaling via the prostaglandin E2 (PGE2) receptor EP4. However, in humans and mice, disrupted PGE2-EP4 signaling in utero causes unexpected patency of the DA (PDA) after birth, suggesting another role for EP4 during development. We used EP4-knockout (KO) mice and acute versus chronic pharmacological approaches to investigate EP4 signaling in DA development and function. Expression analyses identified EP4 as the primary EP receptor in the DA from midgestation to term; inhibitor studies verified EP4 as the primary dilator during this period. Chronic antagonism recapitulated the EP4 KO phenotype and revealed a narrow developmental window when EP4 stimulation is required for postnatal DA closure. Myography studies indicate that despite reduced contractile properties, the EP4 KO DA maintains an intact oxygen response. In newborns, hyperoxia constricted the EP4 KO DA but survival was not improved, and permanent remodeling was disrupted. Vasomotion and increased nitric oxide (NO) sensitivity in the EP4 KO DA suggest incomplete DA development. Analysis of DA maturity markers confirmed a partially immature EP4 KO DA phenotype. Together, our data suggest that EP4 signaling in late gestation plays a key developmental role in establishing a functional term DA. When disrupted in EP4 KO mice, the postnatal DA exhibits signaling and contractile properties characteristic of an immature DA, including impairments in the first, muscular phase of DA closure, in addition to known abnormalities in the second permanent remodeling phase.NEW & NOTEWORTHY EP4 is the primary EP receptor in the ductus arteriosus (DA) and is critical during late gestation for its development and eventual closure. The "paradoxical" patent DA (PDA) phenotype of EP4-knockout mice arises from a combination of impaired contractile potential, altered signaling properties, and a failure to remodel associated with an underdeveloped immature vessel. These findings provide new mechanistic insights into women who receive NSAIDs to treat preterm labor, whose infants have unexplained PDA.

Prostaglandin E2 Receptor EP4 Inhibition Contracts Rat Ductus Arteriosus

BACKGROUND

Patent ductus arteriosus (PDA) is common in premature infants. Cyclooxygenase inhibitors such as indomethacin, which inhibit prostaglandin E2(PGE2) synthesis, are currently the sole treatments for patients with PDA. Their efficacy are, however, frequently limited, and adverse effects are problematic. Because the PGE2-specific receptor EP4 selectively expresses in rat ductus arteriosus (DA), it is hypothesized that EP4 inhibition would promote DA closure with fewer side-effects.

METHODS AND RESULTS

A new chemical compound EP4 antagonist, RQ-15986 (renamed from CJ-042794), was used. Whether RQ-15986 selectively contracted the DA was examined by measuring the isometric tension of rat DA ex vivo at embryonic day 19 (e19) and e21. RQ-15986 at a dose of 10-6mol/L increased the isometric tension of the DA up to 44.8±6.2% and 69.1±12.9% to the maximal KCl-induced tension at e19 and e21 respectively. The effect of RQ-15986 on rat DA in vivo was also tested by using a rapid whole-body freezing method. RQ-15986 inhibited PGE1-induced DA dilatation in neonatal rats. Furthermore, RQ-15986 contracted the DA in a dose-dependent manner, and the constriction was greater at e21 than at e19. Moreover, RQ-15986 did not contract the aorta or the marginal artery of the colon.

CONCLUSIONS

EP4 inhibition contracts rat DA with fewer side-effects. EP4 inhibition is a promising alternative strategy to treat patients with PDA.

Increase of prostaglandin E2 in the reversal of fetal ductal constriction after polyphenol restriction

OBJECTIVE

Anti-inflammatory substances that inhibit the synthesis of prostaglandins, such as non-steroidal anti-inflammatory drugs (NSAIDs) and polyphenol-rich foods, can cause constriction of the fetal ductus arteriosus. This study aimed to test the hypothesis that reversal of fetal ductal constriction after maternal restriction of polyphenol-rich foods, in the third trimester of pregnancy, is accompanied by increased plasma levels of prostaglandin E2 (PGE2).

METHODS

This was a controlled clinical trial of women with singleton pregnancy ≥ 28 weeks undergoing fetal echocardiography. The intervention group included pregnancies with diagnosis of fetal ductal constriction and not exposed to NSAIDs. The control group consisted of third-trimester normal pregnancies. Both groups answered a food frequency questionnaire to assess the amount of total polyphenols in their diet, underwent Doppler echocardiographic examination and had blood samples collected for analysis of plasma levels of PGE2. Intervention group participants received dietary guidance to restrict the intake of polyphenol-rich foods. The assessments were repeated after 2 weeks in both groups.

RESULTS

Forty normal pregnancies were assessed in the control group and 35 with fetal ductal constriction in the intervention group. Mean maternal age (26.6 years) and mean body mass index (30.12 kg/m² ) were similar between the two groups. Intragroup analysis showed that dietary guidance reduced the median consumption of polyphenols (from 1234.82 to 21.03 mg/day, P < 0.001), increasing significantly the plasma concentration of PGE2 (from 1091.80 to 1136.98 pg/mL, P < 0.05) in the intervention group after 2  weeks. In addition, Doppler echocardiography showed reversal of fetal ductal constriction in the intervention group. No significant changes were observed in the control group.

CONCLUSIONS

Dietary intervention for maternal restriction of polyphenol-rich foods in the third trimester of pregnancy is accompanied by increase in plasma levels of PGE2 and reversal of fetal ductal constriction. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Transcriptional profiling of the ductus arteriosus: Comparison of rodent microarrays and human RNA sequencing

DA closure is crucial for the transition from fetal to neonatal life. This closure is supported by changes to the DA's signaling and structural properties that distinguish it from neighboring vessels. Examining transcriptional differences between these vessels is key to identifying genes or pathways responsible for DA closure. Several microarray studies have explored the DA transcriptome in animal models but varied experimental designs have led to conflicting results. Thorough transcriptomic analysis of the human DA has yet to be performed. A clear picture of the DA transcriptome is key to guiding future research endeavors, both to allow more targeted treatments in the clinical setting, and to understand the basic biology of DA function. In this review, we use a cross-species cross-platform analysis to consider all available published rodent microarray data and novel human RNAseq data in order to provide high priority candidate genes for consideration in future DA studies.

Role of prostaglandin E2 in bronchoconstriction-triggered cough response in guinea pigs

A feature of cough variant asthma is a heightened cough response to bronchoconstriction. The mediators of this response are unknown. This study was designed to elucidate the role of lipid mediators in bronchoconstriction-triggered cough response in an experimental animal model. We examined the influence of bronchoconstriction on cell components and mediators including prostaglandin E₂ (PGE₂) in bronchoalveolar lavage fluid (BALF). We studied the cough response to bronchoconstriction (CRB) by measuring the correlation between the increase in enhanced pause (Penh), an index of bronchoconstriction, and cough counts induced by methacholine (Mch) inhalation in conscious guinea pigs. We then examined the effects of intraperitoneal pretreatment with 16, 16-dimethyl-prostaglandin E₂ (dm-PGE₂) on CRB and cough counts. The total number of cells and cell components in the BALF were not influenced by bronchoconstriction. While levels of PGE₂, prostaglandin I₂, and cysteinyl leukotrienes were significantly increased, levels of prostaglandin D₂, thromboxane B₂, and substance P in the BALF were not. Dm-PGE₂ significantly decreased the Mch-induced increase in Penh. Following bronchoconstriction by additional Mch inhalation, dm-PGE₂ produced an increase in CRB and cough counts in a dose-dependent manner. Additionally, the heightened CRB following dm-PGE₂ treatment was suppressed by pretreatment with PGE₂ receptor (E-prostanoid EP) -1 and EP-3 antagonists in a dose-dependent manner, but not by EP-2 and EP-4 antagonists. The EP-1 antagonist also decreased cough counts. These results suggest that PGE₂ acts as an exacerbating factor for bronchoconstriction-triggered cough. EP1 and EP3 may provide new therapeutic targets for cough variant asthma.

Prostaglandin E-mediated molecular mechanisms driving remodeling of the ductus arteriosus

The ductus arteriosus (DA), a fetal arterial connection between the pulmonary arteries and aorta, normally closes after birth. Persistent DA patency usually has life-threatening consequences. In certain DA-dependent congenital heart diseases, however, patient survival depends on maintaining DA patency. Complete closure of the DA involves both functional closure, induced by muscle contraction, and anatomical closure, achieved through morphological and molecular remodeling. Anatomical closure of the DA is associated with the formation of intimal thickening, which is characterized by deposition of extracellular matrix in the subendothelial region, sparse elastic fiber formation, and migration of medial smooth muscle cells into the subendothelial space. In addition, fetal molecular remodeling that is suitable for postnatal muscle contraction has been observed in the DA. After the second trimester, high concentration of prostaglandin E2 (PGE2) causes the DA to dilate through the remainder of the fetal period. Emerging evidence from studies using pharmacological approaches and genetically modified mice suggests that, in addition to its vasodilatory effect, this chronic exposure to PGE2 promotes DA-specific anatomical and molecular remodeling through EP4, one of four receptor subtypes for PGE2. Signals that are downstream of PGE2-EP4, such as cyclic AMP (cAMP)-protein kinase A (PKA), exchange protein activated by cAMP (Epac), phospholipase C, and Wnt/β-catenin, may be involved in the regulation of intimal thickening, elastogenesis, and contraction-related genes. Understanding the physiological role of PGE2 in DA remodeling could enable more effective regulation of PDA, both in isolation and in the context of congenital cardiac anomalies.

Prenatal effects of maternal consumption of polyphenol-rich foods in late pregnancy upon fetal ductus arteriosus

Fetal circulation has characteristic features, being morphologically and functionally different from extrauterine circulation. The ductus arteriosus plays a fundamental role in directing the blood flow to fetal inferior body parts. Basically, the ductus arteriosus directs 80-85% of the right ventricular output arising from the superior vena cava, coronary sinus, and a small part from the inferior vena cava to descending aorta. Its histological structure is made up predominantly by a thick muscular layer, differently from the aorta and the pulmonary artery, which increases with gestational age. The fibers have a circumferential orientation, especially at the external layers, facilitating and making effective ductal constriction. These factors may generate lumen alterations which may cause fetal and neonatal complications, such as heart failure, hydrops, neonatal pulmonary hypertension, and even death. Classically, maternal administration of indomethacin and/or other antiinflammatory drugs interfere in prostaglandins metabolism, causing ductal constriction. However, many cases of fetal ductal constriction, as well as of persistent neonatal pulmonary artery hypertension, remain without an established etiology, being referred as "idiopathic." In recent years, a growing body of evidence has shown that herbs, fruits, nuts, and a wide diversity of substances commonly used in daily diets have definitive effects upon the metabolic pathway of inflammation, with consequent inhibition of prostaglandins synthesis. This antiinflammatory action, especially of polyphenols, when ingested during the third trimester of pregnancy, may influence the dynamics of fetal ductus arteriosus flow. The goal of this review is to present these new observations and findings, which may influence dietary orientation during pregnancy.

Prostaglandin E-prostanoid4 receptor mediates angiotensin II-induced (pro)renin receptor expression in the rat renal medulla

Angiotensin II (Ang II) stimulates (pro)renin receptor (PRR) expression in the renal collecting duct, triggering the local renin response in the distal nephron. Our recent study provided evidence for involvement of cyclooxygenase-2-prostaglandin E2 pathway in Ang II-dependent stimulation of PRR expression in the collecting duct. Here, we tested the role of E-prostanoid (EP) subtypes acting downstream of cyclooxygenase-2 in this phenomenon. In primary rat inner medullary collecting duct cells, Ang II treatment for 12 hours induced a 1.8-fold increase in the full-length PRR protein expression. To assess the contribution of EP receptor, the cell was pretreated with specific EP receptor antagonists: SC-51382 (for EP1), L-798106 (for EP3), L-161982 (for EP4), and ONO-AE3-208 (ONO, a structurally distinct EP4 antagonist). The upregulation of PRR expression by Ang II was consistently abolished by L-161982 and ONO and partially suppressed by SC-51382 but was unaffected by L-798106. The PRR expression was also significantly elevated by the EP4 agonist CAY10598 in the absence of Ang II. Sprague-Dawley rats were subsequently infused for 1 or 2 weeks with vehicle, Ang II alone, or in combination with ONO. Ang II infusion induced parallel increases in renal medullary PRR protein and renal medullary and urinary renin activity and total renin content, all of which were blunted by ONO. Both tail cuff plethysmography and telemetry demonstrated attenuation of Ang II hypertension by ONO. Overall, these results have established a crucial role of the EP4 receptor in mediating the upregulation of renal medullary PRR expression and renin activity during Ang II hypertension.

Managing the patent ductus arteriosus in the premature neonate: a new look at what we thought we knew

Over recent years, the clinical approach to patency of the ductus arteriosus in the premature neonate has been the subject of intensive reevaluation. What had once been considered inherently obvious is no longer to be taken for granted. In this review we will focus on some of the controversies surrounding various aspects of the pharmacologic treatment regimens for patent ductus arteriosus closure. The pros and cons of prophylactic vs therapeutic indomethacin, of early vs late therapy, of high- vs low-dose indomethacin, of single vs multiple courses of treatment, and of ibuprofen vs indomethacin will be considered. In addition, the possibility that patency of the ductus arteriosus is merely a physiological manifestation of extreme prematurity, and thus does not necessarily need to be therapeutically closed, has become a viable approach in some cases. As such, we will examine echocardiographic and biochemical criteria aimed at determining the clinical and hemodynamic significance of ductal shunting, and thereby of the need to treat. Finally, we speculate on potential therapeutic directions for the future, including individualized treatment regimens and multidrug treatment cocktails for those who fail initial monodrug therapy.

Basics and dynamics of neonatal and pediatric pharmacology

Understanding the role of ontogeny in the disposition and actions of medicines is the most fundamental prerequisite for safe and effective pharmacotherapeutics in the pediatric population. The maturational process represents a continuum of growth, differentiation, and development, which extends from the very small preterm newborn infant through childhood, adolescence, and to young adulthood. Developmental changes in physiology and, consequently, in pharmacology influence the efficacy, toxicity, and dosing regimen of medicines. Relevant periods of development are characterized by changes in body composition and proportion, developmental changes of physiology with pathophysiology, exposure to unique safety hazards, changes in drug disposition by major organs of metabolism and elimination, ontogeny of drug targets (e.g., enzymes, transporters, receptors, and channels), and environmental influences. These developmental components that result in critical windows of development of immature organ systems that may lead to permanent effects later in life interact in a complex, nonlinear fashion. The ontogeny of these physiologic processes provides the key to understanding the added dimension of development that defines the essential differences between children and adults. A basic understanding of the developmental dynamics in pediatric pharmacology is also essential to delineating the future directions and priority areas of pediatric drug research and development.

Prostanoid receptor antagonists: development strategies and therapeutic applications

Identification of the primary products of cyclo-oxygenase (COX)/prostaglandin synthase(s), which occurred between 1958 and 1976, was followed by a classification system for prostanoid receptors (DP, EP(1), EP(2) ...) based mainly on the pharmacological actions of natural and synthetic agonists and a few antagonists. The design of potent selective antagonists was rapid for certain prostanoid receptors (EP(1), TP), slow for others (FP, IP) and has yet to be achieved in certain cases (EP(2)). While some antagonists are structurally related to the natural agonist, most recent compounds are 'non-prostanoid' (often acyl-sulphonamides) and have emerged from high-throughput screening of compound libraries, made possible by the development of (functional) assays involving single recombinant prostanoid receptors. Selective antagonists have been crucial to defining the roles of PGD(2) (acting on DP(1) and DP(2) receptors) and PGE(2) (on EP(1) and EP(4) receptors) in various inflammatory conditions; there are clear opportunities for therapeutic intervention. The vast endeavour on TP (thromboxane) antagonists is considered in relation to their limited pharmaceutical success in the cardiovascular area. Correspondingly, the clinical utility of IP (prostacyclin) antagonists is assessed in relation to the cloud hanging over the long-term safety of selective COX-2 inhibitors. Aspirin apart, COX inhibitors broadly suppress all prostanoid pathways, while high selectivity has been a major goal in receptor antagonist development; more targeted therapy may require an intermediate position with defined antagonist selectivity profiles. This review is intended to provide overviews of each antagonist class (including prostamide antagonists), covering major development strategies and current and potential clinical usage.

Changing expression of cyclooxygenases and prostaglandin receptor EP4 during development of the human ductus arteriosus

Programmed proliferative degeneration of the human fetal ductus arteriosus (DA) in preparation for its definite postnatal closure has a large developmental variability and is controlled by several signaling pathways, most prominently by prostaglandin (PG) metabolism. Numerous studies in various mammalian species have shown interspecies and developmental differences in ductal protein expression of cyclooxygenase (COX) isoforms and PG E receptor subtypes (EP1-4). We examined COX1, COX2, and EP4 receptor protein expression immunohistochemically in 57 human fetal autopsy DA specimens of 11-38 wk of gestation. According to their histologic maturity, specimens were classified into four stages using a newly designed maturity score that showed that histologic maturity of the DA was not closely related to gestational age. COX1 expression was found in all DA regions and rose steadily during development. COX2 staining remained weak throughout gestation. EP4 receptor staining increased moderately during gestation and was limited to the intima and media. In conclusion, histologic maturity classification helps to address developmentally regulated processes in the fetal DA. Concerning prostaglandin metabolism our findings are in line with animal studies, which assigned COX1 the predominant role in the DA throughout gestation. EP4 receptor presumably plays a key role for active patency of the human DA in the third trimester.