title: Developmental changes in prostacyclin synthesis are conserved in cultured pulmonary endothelium and vascular smooth muscle.
abstract: Prostacyclin (PGI2) is a key mediator of pulmonary vascular and parenchymal function during late fetal and early postnatal life, and its synthesis in intrapulmonary arteries increases markedly during that period. The rate-limiting enzyme in PGI2 synthesis in the developing lung is cyclooxygenase (COX). To understand better the mechanisms underlying the developmental increase in PGI2 synthesis, we evaluated PGI2 production in early-passage, cultured pulmonary artery endothelial cells (PAEC) and pulmonary vascular smooth-muscle cells (VSM) from fetal and newborn lambs. In arterial segments, PGI2 synthesis was sevenfold greater in intact arteries from newborn than from fetal lambs, and it was 12-fold greater in endothelium-denuded newborn than in fetal arteries, indicating that the developmental increase occurs in both the endothelium and medial layer. Similarly, basal PGI2 production was three-fold greater in newborn than in fetal PAEC, and 2.5-fold greater in newborn than in fetal pulmonary VSM cells. Calcium ionophore (A23187)-stimulated and arachidonic acid-stimulated PGI2 synthesis were also greater in newborn than in fetal PAEC and VSM, revealing a developmental upregulation in COX enzymatic activity in both cell types. Immunoblot analysis showed that this is due to greater COX-1 protein expression in newborn than in fetal vascular cells; COX-2 protein expression was not detected. In addition, COX-1 messenger RNA (mRNA) abundance was greater in newborn than in fetal PAEC, and this was not due to a difference in COX-1 mRNA stability. Thus, the developmental upregulation of PGI2 synthesis is conserved in early-passage PAEC and pulmonary VSM, and is related to a maturational increase in COX-1 gene expression. Further studies with the cultured cell model will enable determination of the factors that directly regulate COX-1 expression in the developing pulmonary vasculature.
authors.affiliation: Department of Pediatrics, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, USA. PSHAUL@MEDNET.SWMED.EDU
authors.forename: P W
authors.initials: PW
authors.lastname: Shaul
authors.forename: M C
authors.initials: MC
authors.lastname: Pace
authors.forename: Z
authors.initials: Z
authors.lastname: Chen
authors.forename: T S
authors.initials: TS
authors.lastname: Brannon
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D016718:Arachidonic Acid / Q000494:pharmacology; D000001:Calcimycin / Q000494:pharmacology; D002478:Cells, Cultured; D051545:Cyclooxygenase 1; D004730:Endothelium, Vascular / Q000196:embryology / Q000201:enzymology* / Q000254:growth & development; D011464:Epoprostenol / Q000096:biosynthesis*; D015870:Gene Expression; D015151:Immunoblotting; D007527:Isoenzymes / Q000235:genetics; D024510:Muscle Development; D009131:Muscle, Smooth, Vascular / Q000196:embryology / Q000201:enzymology* / Q000254:growth & development; D011451:Prostaglandin-Endoperoxide Synthases / Q000235:genetics / Q000378:metabolism*; D011651:Pulmonary Artery / Q000196:embryology / Q000201:enzymology* / Q000254:growth & development*; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012756:Sheep
chemical_list: D007527:Isoenzymes; D012333:RNA, Messenger; D016718:Arachidonic Acid; D000001:Calcimycin; D011464:Epoprostenol; D051545:Cyclooxygenase 1; D011451:Prostaglandin-Endoperoxide Synthases