Leptin Suppresses Human Chorionic Gonadotropin-Induced Cyclooxygenase-2 Expression and Prostaglandin Production in Cultured Human Granulose Luteal Cells

OBJECTIVE

In a previous study, we demonstrated that high leptin levels at the time of human chorionic gonadotropin (hCG) injection impaired the pregnancy rate for women undergoing in vitro fertilization. In this study we examine leptin's effect on prostaglandin formation and cyclooxygenase (COX) expression induced by hCG in human granulose luteal (GL) cells.

METHODS

Human GL cells were obtained from women undergoing ovarian hyperstimulation. COX expression and microsomal prostaglandin E synthase (mPGES) expression, as well as prostaglandin E(2) (PGE(2)) and prostaglandin F(2alpha) (PGF(2alpha)) production were studied. This was done in both the presence and absence of leptin following hCG stimulation. PGE(2) and PGF(2alpha) were determined by enzyme-linked immunosorbent assay (ELISA). The expressions of COX and mPGES were investigated by using immunocytochemical techniques in addition to Western blotting and reverse transcriptase-polymerase chain reaction (RT-PCR) analysis.

RESULTS

HCG and leptin do not affect COX-1 expression. However, leptin blocked COX-2 and mPGES expression induced by hCG. Moreover, while leptin, in various concentrations, did not affect PGE(2) and PGF(2alpha) levels, it inhibited the elevation of PGE(2) and PGF(2alpha) concentrations in response to hCG.

CONCLUSIONS

The study confirms that the expression of COX-2 is up-regulated by hCG in human GL cells. Leptin suppresses hCG-induced PGE(2) formation through the inhibition of COX-2 and mPGES expression. The preliminary results suggest a potential inhibiting effect of leptin on human GL cells induced by hCG.

A maternal high-fat diet represses the expression of antioxidant defense genes and induces the cellular senescence pathway in the liver of male offspring rats

Maternal high-fat (HF) diet feeding is associated with increased risk of developing metabolism-related diseases in adult offspring, including chronic liver disease. The present study tested the hypothesis that maternal HF diet leads to a decreased antioxidant defense capacity and causes cellular senescence in liver of adult offspring rats, which might increase risk of developing chronic liver disease. Timed-pregnant Sprague Dawley rats were fed a HF diet (45% of energy from fat) or a control (C) diet (16% of energy from fat) during gestation and lactation. The resulting offspring were fed a C diet after weaning to generate 2 offspring groups: C diet-fed offspring of dams fed C diet (C/C) and C diet-fed offspring of dams fed a HF diet (HF/C). At 12 wk of age, male rats were killed and samples were collected for analysis. Maternal HF diet significantly increased plasma TG and hepatic TBARS concentrations and the size of hepatic lipid droplets in offspring rats. The expression of antioxidant defense genes, such as glutathione peroxidase-1, Cu/Zn superoxide dismutase (Sod1), paraoxonase enzymes (Pon1, Pon2, and Pon3), were significantly lower in the liver of HF/C pups than in C/C pups. The expression of Inhibitor of cyclin dependent Kinase 4a (p16INK4a), a marker of cellular senescence, and cyclooxygenase-2 (Cox2), a proinflammatory marker, was significantly higher in the HF/C offspring group than in the C/C offspring group. Western-blot analysis shows that cyclin D1 and phosphorylated retinoblastoma protein were significantly lower in HF/C offspring than in C/C offspring. The results provide the first evidence to our knowledge that maternal HF diet might alter antioxidant defense capacity and program the p16INK4a-dependent cellular senescence in the liver of adult offspring.

Chorionic gonadotrophin regulates CXCR4 expression in human endometrium via E-series prostanoid receptor 2 signalling to PI3K-ERK1/2: implications for fetal-maternal crosstalk for embryo implantation

Murine knock-out models and blastocyst co-culture studies have identified prostaglandin-endoperoxide synthase (PTGS) 2, prostaglandin (PG) E receptor 2 (PTGER2) and the chemokine receptor CXCR4 as important regulators of early pregnancy events. In vitro studies and studies in non-human primates have shown that these proteins are regulated in the endometrium by the early embryonic signal, chorionic gonadotrophin (CG). Here we show that expressions of PTGER2 and CXCR4 are elevated during the mid-secretory phase of the menstrual cycle and decidua of early pregnancy in humans. Using first trimester decidua explants, we show that CG induces expression of PTGS2 and biosynthesis of PGE₂, and expression of PTGER2. Subsequently, PGE₂via PTGER2 induces expression of CXCR4. Using an in vitro model system of Ishikawa endometrial epithelial cells stably expressing PTGER2 and human first trimester decidua explants, we demonstrate that CXCR4 expression is regulated by PTGER2 via the epidermal growth factor receptor (EGFR)-phosphatidylinositol-3-kinase (PI3K)-extracellular signal-regulated kinase (ERK1/2) pathway.Taken together, our data suggest that early embryonic signals may regulate fetal–maternal crosstalk in the human endometrium by inducing CXCR4 expression via the PGE₂–PTGER2-mediated induction of the EGFR, PI3K and ERK1/2 pathways.

Paradoxical stimulation of cyclooxygenase-2 expression by glucocorticoids via a cyclic AMP response element in human amnion fibroblasts

Human amnion fibroblasts produce abundant prostaglandins toward the end of gestation, which is one of the major events leading to parturition. In marked contrast to its well-described antiinflammatory effect, glucocorticoids have been shown to up-regulate cyclooxygenase-2 (COX-2) expression in human amnion fibroblasts. The mechanisms underlying this paradoxical induction of COX-2 by glucocorticoids have not been resolved. Using cultured human amnion fibroblasts, we found that the induction of COX-2 mRNA expression by cortisol was a glucocorticoid receptor (GR)-dependent process requiring ongoing transcription. Upon transfection of a COX-2 promoter-driven reporter gene into the amnion fibroblasts, cortisol stimulated the COX-2 promoter activity. This was abolished by mutagenesis of a cAMP response element (CRE) at -53 to approximately -59bp as well as by cotransfection of a plasmid expressing dominant-negative CRE-binding protein (CREB). The phosphorylation level of CREB-1 was significantly increased by cortisol treatment of the amnion fibroblasts, whereas the effect was attenuated either by the protein kinase A inhibitor H89 or the p38 -MAPK inhibitor SB203580. The induction of the COX-2 promoter activity and the phosphorylation of CREB-1 were also blocked by the GR antagonist RU486. Chromatin immunoprecipitation (ChIP) assay revealed that the binding of CREB-1 to the CRE of the COX-2 promoter was increased by cortisol treatment of the amnion fibroblasts. In conclusion, cortisol, via binding to GR, stimulated COX-2 expression by increasing phosphorylated CREB-1 binding to the CRE of the COX-2 gene. Cortisol may phosphorylate CREB-1 by activating either protein kinase A or p38-MAPK in the amnion fibroblasts.

Mifepristone attenuates human chorionic gonadotropin–induced extracellular signal–regulated kinase 1/2 phosphorylation, cyclooxygenase-2, and prostaglandin E2 production in human granulosa luteal cells

OBJECTIVE

To elucidate the role of RU486 in regulating the function of granulosa luteal cells and its possible involvement in ovarian dysfunction.

DESIGN

An in vitro study.

SETTING

University hospital.

PATIENT(S)

Our subjects were women under the age of 40 who were unable to get pregnant as a result of male-factor infertility.

INTERVENTION(S)

HCG and RU486 were added to cultured granulosa luteal cells; after incubation for 12 hours, the harvested cells were subjected to total mRNA and protein measurements.

MAIN OUTCOME MEASURE(S)

Reverse transcriptase-polymerase chain reaction, immunoblot assay, immunocytochemistry, and enzyme immunoassay were performed.

RESULT(S)

RU486 attenuates hCG-induced cyclooxygenase-2 (COX-2) mRNA and protein expression and extracellular signal-regulated kinase (ERK) 1/2 phosphorylation and decreases the hCG-induced prostaglandin E2 (PGE2) production in a dose-dependent manner. RU486 treatment had no significant effect on COX-1 mRNA expression.

CONCLUSION(S)

Treatments using gonadotropins are able to induce ERK1/2 phosphorylation resulting in increased COX-2 protein expression and prostaglandin synthesis. RU486 attenuates the activation of ERK1/2, decreases the expression of COX-2, and affects PGE2 production by inhibiting hCG-induced COX-2 expression.

Dose-dependent effects of meloxicam administration on cyclooxygenase-1 and cyclooxygenase-2 protein expression in intrauterine tissues and fetal tissues of a sheep model of preterm labor

Meloxicam (MEL), a cyclooxygenase (COX)-2 inhibitor, decreases prostaglandin production and blocks preterm labor in sheep. The objective of this study is to investigate MEL dosage regimens on COX-1, COX-2, and prostaglandin dehydrogenase (PGDH) expression in ovine intrauterine and fetal tissues. Animals in preterm labor received maternal infusions of saline or MEL at maintained high or graded doses (study 1) or acute graded doses (study 2). MEL blocked preterm labor. In study 1, MEL decreased COX-2 expression in the endometrium, myometrium, and amnion but not placenta or fetal tissues. In study 2, COX-2 expression was unchanged. COX-1/PGDH expression was unaffected. While MEL is an effective tocolytic, reductions in COX-2 protein occurred only with maintained MEL exposure. MEL effects are tissue specific and do not affect COX-1 or PGDH expression. Maternal MEL does not affect fetal COX expression in the sheep, possibly contributing to its lack of fetal side effects.

Nanomolar and micromolar effects of 15-deoxy-delta 12,14-prostaglandin J2 on amnion-derived WISH epithelial cells: differential roles of peroxisome proliferator-activated receptors gamma and delta and nuclear factor kappa B

15-Deoxy delta(12,14)-prostaglandin J(2) (15d-PGJ(2)), an activator of peroxisome proliferator-activated receptor (PPAR)-gamma and -delta, is a prostanoid metabolite with anti-inflammatory actions. In intrauterine tissues, proinflammatory cytokines and prostaglandins have been identified as playing key roles in the maintenance of pregnancy and the onset of labor. We investigated and compared the early (<3 h) effects of 15d-PGJ(2) with rosiglitazone (PPAR-gamma ligand) and 2-methyl-4-((4-methyl-2-(4-trifluoromethylphenyl)-1,3-thiazol-5-yl)-methylsulfanyl)phenoxy-acetic acid (GW501516) (PPAR-delta ligand) on interleukin (IL)-1beta-induced prostaglandin and cytokine production by amnion-derived WISH cells. We show that 15d-PGJ(2) exerts differential effects depending on concentration. At low concentrations (<0.1 microM), 15d-PGJ(2) inhibited IL-1beta-stimulated prostaglandin E(2) (PGE(2)) but not cytokine (IL-6/IL-8) production or cyclooxygenase-2 (COX-2) expression. This effect was attenuated by a PPAR-gamma inhibitor [2-chloro-5-nitro-N-phenyl-benzamide (GW9662)], by transfection with a dominant-negative PPAR construct, and was reproduced by the PPAR-gamma ligand rosiglitazone. At higher concentrations (1-10 microM), 15d-PGJ(2) inhibited IL-1beta-stimulated PGE(2) and cytokine production and COX-2 expression, and this effect was not blocked by GW9662. Rosiglitazone at high concentrations (1-10 microM) stimulated PGE(2) production in the absence or presence of the dominant-negative PPAR. The PPAR-delta ligand GW501516 also inhibited IL-1beta-stimulated PGE(2) production but only at high concentrations (1 microM). IL-1beta-induced nuclear factor-kappaB (NF-kappaB) DNA binding activity was significantly inhibited by 15d-PGJ(2) (10 microM) and GW501516 (1 microM) but increased with 10 microM rosiglitazone. We conclude that 1) at low concentrations, 15d-PGJ(2) acts through a PPAR-gamma signaling pathway; b) at higher concentrations, its actions are mediated most likely through other pathways such as activation of PPAR-delta and/or inhibition of NF-kappaB; and 3) rosiglitazone exerts PPAR-independent effects at high concentrations (>1 microM).

The in vivo control of prostaglandin H synthase-2 messenger ribonucleic acid expression in the human amnion at parturition

Prostaglandin H synthase-2 (PGHS-2) activity and mRNA rise in the human amnion at late gestation, contributing to the increase in intrauterine PG production crucial for labor and delivery. In the present investigation we have determined the mechanism that controls amniotic PGHS-2 mRNA levels in vivo at term parturition. Amnion membranes were collected after elective cesarean section (n = 20), and after spontaneous labor (n = 20). PGHS-2 relative gene transcription rates were determined by transcriptional run-on, and PGHS-2 mRNA and heterogeneous nuclear RNA (hnRNA) relative abundance were measured by quantitative real-time RT-PCR. The PGHS-2 mRNA degradation rate was determined by incubating amnion in the presence of the transcription inhibitor 5,6-dichlorobenzimidazole riboside. The dynamics of PGHS-2 hnRNA and mRNA abundance were characterized in 0- to 24-h tissue incubations. The PGHS-2 relative gene transcription rate was a significant (P < 0.05) predictor of PGHS-2 hnRNA and mRNA abundance, and PGHS-2 hnRNA was also a predictor (P < 0.01) of PGHS-2 mRNA levels both before and after labor. Interestingly, even though PGHS-2 gene activity remained unchanged, PGHS-2 mRNA abundance increased with labor and displayed constitutive stability before and after labor. PGHS-2 mRNA levels spontaneously increased by 400% (P < 0.01) upon incubation for 24 h, whereas the transcription rate dropped by 95% during the first 2 h, then rebounded significantly between 6-24 h. Thus, PGHS-2 mRNA abundance is transcriptionally controlled in term amnion. Labor does not increase PGHS-2 gene activity or mRNA stability. The PGHS-2 gene is probably induced before labor by a factor(s) originating in the amnion membrane, and the resulting stable mRNA accumulates progressively in the tissue throughout labor and delivery.

Mechanism of parturition and preterm labor

Preterm birth occurs in 5 to 10 percent of all pregnancies and accounts for 75 percent of neonatal mortality and morbidity, including long-term handicap. Thirty percent of preterm birth may be associated with an underlying infective process, and approximately 50 percent are idiopathic. Preterm birth corresponds to a syndrome with a variety of causes. The factors contributing to preterm birth may vary at different "windows" of gestation. Glucocorticoids seem to have a central role in processes of birth at term and preterm, and alter synthesis and/or activity of key enzymes in prostaglandin synthesis and metabolism as well as increasing corticotropin-releasing hormone output by intrauterine tissues. This new information should facilitate development of improved methods of diagnosis and therapy for patients at risk of preterm labor.

TARGET AUDIENCE

Gynecologists and Family Physicians

LEARNING OBJECTIVES

After completion of this article, the reader will be able to describe potential mechanisms of partition and preterm labor and to list the various substances that can inhibit and promote myometrial contractions.