Regulation of Prostaglandin Endoperoxide H Synthase 1 and 2 by Estradiol and Progesterone in Nonpregnant Ovine Myometrium and Endometrium in Vivo

Abstract

PG endoperoxide H synthase-2 (PGHS-2) messenger RNA (mRNA) and protein levels are increased dramatically in ovine myometrium and endometrium during both glucocorticoid-induced premature labor and spontaneous term labor. In this study, we examined estradiol and progesterone regulation in vivo of PGHS-1 and PGHS-2 expression at both mRNA and protein levels using a nonpregnant ovariectomized sheep model. We determined the differential distribution of PGHS-2 and PGHS-1 in ovine myometrium and endometrium with immunocytochemistry. Twenty ovariectomized ewes were treated with saline (n = 5) or estradiol infused i.v. for 2 days (50 microg/day; n = 5) or an intravaginal progesterone sponge for 10 days (containing 0.3 g progesterone; n = 5) or an intravaginal progesterone sponge for 10 days with estradiol (50 microg/day) administered on days 9 and 10 with the progesterone sponge still in place (EP; n = 5). PGHS-1 and -2 mRNA and protein were measured by Northern and Western blot analyses, respectively. PGHS-2 mRNA and protein abundance increased significantly in myometrium after estradiol treatment (P < 0.01). In contrast, progesterone was a more potent stimulator than estradiol of PGHS-2 protein abundance in endometrium (P < 0.01). PGHS-1 concentration did not change after estradiol and/or progesterone administration (P > 0.05). PGHS-2 was immunolocalized in myometrial cells and endometrial glandular epithelial cells, whereas immunoreactive PGHS-1 was located in the myometrial cells, endothelial and smooth muscle cells of blood vessels, as well as epithelial cells of glands and stromal cells in endometrium. Estradiol-dependent activation of PGHS-2 gene expression resulted in increased PGHS-2 levels in sheep myometrium in vivo. Progesterone did not have any effect on PGHS-2 gene expression in the myometrium. In contrast, progesterone was a more potent stimulator of endometrial PGHS-2 abundance than estradiol. Estradiol and progesterone did not regulate PGHS-1 expression in either endometrium or myometrium. The distribution and differential regulation of PGHS-1 and -2 in myometrium and endometrium are consistent with the differential functions of both enzymes.

Regulation of the prostaglandin enzymatic system by estradiol and progesterone in nonpregnant sheep cervix

“…We have repeatedly shown that COX1 is constitutively expressed in pregnant and nonpregnant uterine tissues (Zhang et al 1996, Wu et al 1999. COX2 is an inducible enzyme that responds to inflammatory cytokines, growth factors (Diaz et al 1992, Hempel et al 1994, and steroid hormones (Wu et al 1997(Wu et al 2004a(Wu et al , 2005b and is increased in intrauterine tissues, including the cervix during premature and spontaneous term labor (Wu et al 1999(Wu et al , 2004a(Wu et al , 2005a. Therefore, COX2 is the focal point of our present study.…”

“…number: NP04) demonstrated in our previous study (Wu et al 1997). A rabbit polyclonal antibody for human mPTGES1 (Cayman Chemical Com, Ann Arbor, MI, USA) was used at 1:500 dilution and incubated at 4 8C for 20 h. A rabbit polyclonal antibody for bovine PTGFS kindly provided by Dr Watanabe (University of East Asia, Yamaguchi, Japan) was used at 1:500 dilution at 4 8C for 20 h. The primary antibodies used for immunocytochemistry were the same antibodies used for western analysis.…”

“…A few studies have characterized in vivo regulation of COX2 in rat ovary (Sirois et al 1992) by human chorionic gonadotropin and in nonpregnant and pregnant sheep uterus by E 2 and progesterone (Charpigny et al 1997, Wu et al 2004a, 2005a, 2005b. Results from our and others' previous studies demonstrated that progesterone could induce COX2 expression (Charpigny et al 1997, Wu et al 1997 and activated prostaglandin production (Louis et al 1976) in nonpregnant and pregnant sheep uterus (Wu et al 2005a). However, the regulation of cervical COX2, PTGFS, and mPTGES in vivo by progesterone and E 2 has not been determined in any species.…”

“…Progesterone sponges were purchased from Carter Holt Harvey Plastic Products (Hamilton, New Zealand) to produce plasma concentrations ranging from 1.5 to 2 ng/ml (data provided by the manufacturer). The dose of E 2 used produces physiological increments in plasma E 2 concentrations, which stimulated uterine COX2 and estrogen receptor mRNA and protein expression (our pilot study, Wu et al 1996Wu et al , 1997. Two days of estrogen and ten days of progesterone treatment were chosen to simulate the physiological estrous cycle in vivo.…”

Up-regulation of rat myometrial phospholipases Cβ1 and Cβ3 correlates with increased term sensitivity to carbachol and oxytocin

“…At term, the increased expression of Gq and PLC 1 and PLC 3 due to progesterone withdrawal and oestrogen increase respectively may underlie the enhancement of uterine responsiveness to uterotonic factors. In myometrium, the expression of many proteins including OTR, connexin-43, cyclo-oxygenase 2 and Gi2 protein was shown to be regulated at the transcriptional level by oestradiol (Larcher et al 1995, Lefebvre et al 1995, Cohen-Tannoudji et al 1995, Wu et al 1997). Whether or not oestradiol controls the expression of PLC 1 and PLC 3 at the transcriptional or post-transcriptional level remains to be determined.…”