Pregnancy Increases Ovine Uterine Artery Endothelial Cyclooxygenase-1 Expression*

Abstract

During normal pregnancy, and especially in the third trimester, both uterine blood flow and prostacyclin production by ovine uterine arteries are dramatically increased. We sought to determine if this is due, in part, to an increase in cyclooxygenase (COX) expression in the uterine artery endothelium. In this study we compared COX expression in uterine artery endothelium from nonpregnant and third-trimester pregnant (110-142 days' gestation) ewes. COX-2 expression was not detectable by Western blotting in uterine artery endothelium or vascular smooth muscle (VSM). In contrast, COX-1 expression was clearly observed in uterine artery. Immunohistochemical localization of COX-1 was endothelium > VSM, with both cell types showing an increase in COX-1 during the third trimester of pregnancy. COX-1 protein and messenger RNA (mRNA) levels were also detectable in collagenase dispersed endothelial cells, with expression of COX-1 in uterine artery endothelial cells dramatically increased during the third trimester of pregnancy at both the level of protein (346.4 +/- 28% of nonpregnant controls, P < 0.0005) and mRNA (51.04 +/- 7.98-fold of nonpregnant controls, P < 0.001). We conclude that the pregnancy-induced increases in prostacyclin production by uterine arteries is largely due to a dramatic increase in expression of COX-1 mRNA and associated protein predominantly occurring in the uterine artery endothelium and, to a lesser extent, in the VSM.

Endothelial Vasodilator Production by Uterine and Systemic Arteries. IV. Cyclooxygenase Isoform Expression During the Ovarian Cycle and Pregnancy in Sheep1

“…This theory is supported by the proportionally greater PGI 2 production by uterine arteries from pregnant versus nonpregnant ewes during incubation in the presence of excess arachidonic acid, the substrate for COX [11]. Previously we have shown, in freshly isolated uterine artery endothelial cells from pregnant and nonpregnant sheep, that COX-1 expression is elevated at the level of both protein and mRNA in pregnancy [16]. However, since pregnancy is a state of both high estrogen and progesterone, it is possible that either or both of these steroid hormones are responsible for this response [2,[17][18][19].…”

“…During dissection, the PBS was removed from the dish and replaced three times. The methods for the preparation of the intact or endotheliumdenuded uterine or omental arterial segments, or direct mechanical isolation of endothelial protein for SDS-PAGE electrophoresis and Western immunoblotting, were reported by and validated previously in this laboratory [14,16,[35][36][37]. Additional arterial segments were either subjected to collagenase dispersion or fixed for immunohistochemistry, as described below.…”

“…The protocol for SDS-PAGE on 7.5% gels as well as subsequent Western immunoblot analysis, as described previously [14,16,[35][36][37], was performed for 6 sheep in each of the OVEX, follicular-phase (FOL), and luteal-phase (LUT) groups and for 8 pregnant (PREG) sheep. COX-1-specific antiserum (Cayman Chemical Company, Ann Arbor, MI) was utilized at a dilution of 1:3000 overnight at room temperature, and a secondary antibody (sheep antimouse Fab2-horseradish peroxidase conjugate; Amersham; now Amersham Pharmacia Biotech, Piscataway, NJ) was used at 1:5000 dilution for 1 h. A positive control for COX-1, ram seminal vesicle (RSV), was included on each blot.…”

Maternal Vascular Physiology in Preeclampsia

“…29 It is likely that this is because of a pregnancymediated upregulation of cyclooxygenase enzyme activity in endothelial cells, which has been previously reported in pregnant ewes. 30 Pregnancy-mediated changes in cyclooxygenase expression in vascular tissues have not been reported. In preeclampsia, PGI 2 metabolites are decreased, 31 and this is evident in various vascular beds, plasma, and urine from patients with preeclampsia.…”

Endothelial Cell Confluence Regulates Cyclooxygenase-2 and Prostaglandin E2 Production That Modulate Motility

“…Cyclooxygenase-1, found in many tissues, typically is constitutively expressed, although it and not cyclooxygenase-2 is induced in uterine endothelial cells in the third trimester of pregnancy when PGI 2 levels and blood flow increase (6). Cyclooxgenase-2 typically is absent from endothelial cells and white blood cells but accumulates to high levels in endothelial cells over several hours in response to IL-1␤ (7), lipopolysaccharide (8), phorbol myristate acetate (8), TNF␣ (9), and oxidized phospholipids (10).…”