Regulation of cyclooxygenase-2 induction in the mouse uterus during decidualization. An event of early pregnancy

Lupus activity in pregnancy

Pregnancy in a woman with systemic lupus erythematosus (SLE) can be complicated by both lupus activity and pregnancy mishaps. The majority of recent studies found an increase in lupus activity during pregnancy, perhaps exacerbated by hormonal shifts required to maintain pregnancy. Increased lupus activity, in turn, prompts an elevated risk for poor pregnancy outcomes, including stillbirth, preterm birth, low birth weight, and preeclamspsia. Fortunately, the majority of pregnancies in women with SLE are successful. However, the interaction between pregnancy and SLE activity can lead to complications for both mother and baby.

Acute, chronic and withdrawal effects of the cannabinoid receptor agonist WIN55212-2 on the sequential activation of MAPK/Raf-MEK-ERK signaling in the rat cerebral frontal cortex: short-term regulation by intrinsic and extrinsic pathways

The cannabinoids (CB) modulate the extracellular signal-regulated kinase (ERK), leading to various forms of plasticity in the brain. Little is known, however, on the in vivo short- and long-term activation and regulation of the components of mitogen-activated protein kinase (MAPK)/ERK signaling by CB. The CB agonist WIN55212-2 (8 mg/kg) increased the immunodensities of phosphorylated c-Raf-1 (42%), MEK1/2 (63%), ERK1 (24%), and ERK2 (28%) in the rat cerebral frontal cortex. These effects were antagonized by SR141716A (rimonabant, 10 mg/kg), a selective CB(1) receptor antagonist. Repeated WIN55212-2 treatment (2-8 mg/kg for 5 days) resulted in tachyphylaxis to the acute activation of Raf-MEK-ERK signaling. Acute WIN55212-2 also induced a hypothermic effect in rats, which was reduced after repeated administration (tolerance). Treatment with SR141716A after chronic WIN55212-2 resulted in the expected cannabinoid withdrawal syndrome, without concomitant alterations in the phosphorylation state of c-Raf-1, MEK1/2, or ERK1/2. Pretreatment with SL327 (20 mg/kg, a MEK1/2 inhibitor) increased the basal phosphorylation of c-Raf-1 (40%) and MEK1/2 (74%; feedback regulation) and fully prevented the up-regulation of ERK1/2 (23-31%) induced by WIN55212-2. Pretreatment with MK801 (1 mg/kg, a NMDA receptor antagonist) effectively blocked the up-regulation c-Raf-1 (41%), MEK1/2 (57%) and ERK1/2 (25-30%) induced by the CB agonist. The main findings demonstrate that the acute stimulation of CB(1) receptors in the frontal cortex results in the sequential phosphorylation of Raf-MEK-ERK cascade, in which c-Raf-1 activation (rate-limiting process) plays a crucial role. Moreover, the in vivo stimulating effect of WIN55212-2 on Raf-MEK-ERK signaling is under the extrinsic regulation of an excitatory glutamatergic mechanism.

Effects of opiate drugs on Fas-associated protein with death domain (FADD) and effector caspases in the rat brain: regulation by the ERK1/2 MAP kinase pathway

This study was designed to assess the effects of opiate treatment on the expression of Fas-associated protein with death domain (FADD) in the rat brain. FADD is involved in the transmission of Fas-death signals that have been suggested to contribute to the development of opiate tolerance and addiction. Acute treatments with high doses of sufentanil and morphine (mu-agonists), SNC-80 (delta-agonist), and U50488H (kappa-agonist) induced significant decreases (30-60%) in FADD immunodensity in the cerebral cortex, through specific opioid receptor mechanisms (effects antagonized by naloxone, naltrindole, or nor-binaltorphimine). The cannabinoid CB1 receptor agonist WIN 55,212-2 did not alter FADD content in the brain. Chronic (5 days) morphine (10-100 mg/kg), SNC-80 (10 mg/kg), or U50488H (10 mg/kg) was associated with the induction of tachyphylaxis to the acute effects. In morphine- and SNC-80-tolerant rats, antagonist-precipitated (2 h) or spontaneous withdrawal (24-48 h) induced a new and sustained inhibition of FADD (13-50%). None of these treatments altered the densities of caspases 8/3 (including the active cleaved forms) in the brain. Pretreatment of rats with SL 327 (a selective MEK1/2 inhibitor that blocks ERK activation) fully prevented the reduction of FADD content induced by SNC-80 in the cerebral cortex (43%) and corpus striatum (29%), demonstrating the direct involvement of ERK1/2 signaling in the regulation of FADD by the opiate agonist. The results indicate that mu- and delta-opioid receptors have a prominent role in the modulation of FADD (opposite to that of Fas) shortly after initiating treatment. Opiate drugs (and specifically the delta-agonists) could promote survival signals in the brain through inhibition of FADD, which in turn is dependent on the activation of the antiapoptotic ERK1/2 signaling pathway.

Regulation of intracellular cyclooxygenase levels by gene transcription and protein degradation

Cyclooxygenases-1 and -2 (COX-1 and -2) catalyze the committed step in prostaglandin formation. Each isozyme subserves different biological functions. This is, at least in part, a consequence of differences in patterns of COX-1 and COX-2 expression. COX-1 is induced during development, and COX-1 mRNA and COX-1 protein are very stable. These latter properties can explain why COX-1 protein levels usually remain constant in those cells that express this isozyme. COX-2 is usually expressed inducibly in association with cell replication or differentiation. Both COX-2 mRNA and COX-2 protein have short half-lives relative to those of COX-1. Therefore, COX-2 protein is typically present for only a few hours after its synthesis. Here we review and develop the concepts that (a) COX-2 gene transcription can involve at least six different cis-acting promoter elements interacting with trans-acting factors generated by multiple, different signaling pathways, (b) the relative contribution of each cis-acting COX-2 promoter element depends on the cell type, the stimulus and the time following the stimulus and (c) a unique 27 amino acid instability element located just upstream of the C-terminus of COX-2 targets this isoform to the ER-associated degradation system and proteolysis by the cytosolic 26S proteasome.

Differential regulation of endocannabinoid synthesis and degradation in the uterus during embryo implantation

Preimplantation embryo development to the blastocyst stage and uterine differentiation to the receptive state are prerequisites for embryo implantation. Burgeoning evidence suggests that endocannabinoid signaling is critical to early pregnancy events. Anandamide (N-arachidonoylethanolamine) and 2-AG (2-arachidonoylglycerol) are two major endocannabinoids that bind to and activate G-protein coupled cannabinoid receptors CB1 and CB2. We have previously shown that a physiological tone of anandamide is critical to preimplantation events in mice, since either silencing or amplification of anandamide signaling causes retarded development and oviductal retention of embryos via CB1, leading to deferred implantation and compromised pregnancy outcome. Whether 2-AG, which also influences many biological functions, has any effects on early pregnancy remains unknown. Furthermore, mechanisms by which differential uterine endocannabinoid gradients are established under changing pregnancy state is not clearly understood. We show here that 2-AG is present at levels one order of magnitude higher than those of anandamide in the mouse uterus, but with similar patterns as anandamide, i.e. lower levels at implantation sites and higher at interimplantation sites. We also provide evidence that region- and stage-specific uterine expression of N-acylphosphatidylethanolamine-specific phospholipase D (NAPE-PLD) and fatty acid amide hydrolase (FAAH), and sn-1-diacylglycerol (DAG) lipase alpha (DAGLalpha) and monoacylglycerol lipase (MAGL) for synthesis and hydrolysis of anandamide and 2-AG, respectively, creates endocannabinoid gradients conducive to implantation. Our genetic evidence suggests that FAAH is the major degrading enzyme for anandamide, whereas COX-2, MAGL and to some extent COX-1 participate in metabolizing 2-AG in the pregnant uterus. The results suggest that aberrant functioning of these pathways impacting uterine anandamide and/or 2-AG levels would compromise pregnancy outcome.

Nitration of p38 MAPK in the placenta: association of nitration with reduced catalytic activity of p38 MAPK in pre-eclampsia

Peroxynitrite, a potent pro-oxidant formed from the interaction of superoxide and nitric oxide, has been widely reported to be nitrating tyrosine residues in proteins resulting in the formation of nitrotyrosine. Biological nitration of tyrosine, a footprint of oxidative injury, has been found to occur in various pathological states including pre-eclampsia, a leading cause of maternal mortality and increased perinatal mortality. Oxidative stress is a major contributor to endothelial dysfunction in pre-eclampsia. Previously, we have demonstrated increased nitrotyrosine immunostaining in placental villous vascular endothelium, surrounding vascular smooth muscle and villous stroma from pre-eclamptic or diabetic pregnancies. Immunoprecipitation (IP) with antinitrotyrosine antibodies followed by immunoblot analysis identified increased nitration of phospho-p38 mitogen-activated protein kinase (MAPK) in the pre-eclamptic placenta. The catalytic activity of p38 MAPK and concentration of phospho-p38 MAPK was also found to be reduced in placentae from pre-eclamptic pregnancies. Comparison of peptide masses of a 42-kDa protein obtained by mass spectrometry with masses of a theoretical tryptic digest of p38 MAPK that was modified by phosphorylation and nitration identified the protein to be p38 MAPK.

Expression of cyclooxygenase-1 and -2 in the porcine endometrium during the oestrous cycle and early pregnancy

Cyclooxygenase (COX) is the rate-limiting enzyme that catalyses the initial step in prostaglandins (PGs) production. In the present studies, endometrial COX-1 and COX-2 expression throughout the oestrous cycle and early pregnancy was analysed in pigs using real-time reverse transcriptase-polymerase chain reaction (RT-PCR), Western blot and immunohistochemistry. There were no changes in messenger RNA (mRNA) and protein expression for COX-1 in cyclic pigs. In pregnant animals, mRNA levels of this enzyme increased on days 22-25 (p < 0.001). However, no upregulation of COX-1 protein was detected. Quantification of COX-2 mRNA expression during the oestrous cycle revealed significant increases on days 10-12 and 14 (p < 0.001 and p < 0.01 vs days 2-4, respectively). Protein levels were also increased on day 14 when compared with days 2-12 and 18-20 after oestrus. In pregnant animals, the patterns of both COX-2 mRNA and protein expression were similar. Messenger RNA levels were higher on days 16 and 22-25 (p < 0.01 vs day 10). Moreover, the protein content tended to increase on days 16 and 22-25. COX-1 and COX-2 were localized in the luminal and glandular epithelium as well as in the uterine stroma. In contrast to COX-1, a positive immunostaining reaction for COX-2 was detected only on days 12-16 after ovulation and on days 14-16 of pregnancy. In conclusion, these results indicate specific patterns of COX-1 and COX-2 expression in the porcine endometrium throughout the oestrous cycle and early pregnancy. COX-2 rather than COX-1 seems to be the primary enzyme responsible for modulated PGs production at the time of luteolysis in cyclic and during implantation in pregnant animals.

The kinase p38 regulates peroxisome proliferator activated receptor-gamma in human trophoblasts

Deficiency of either the mitogen-activated protein kinase p38 or the nuclear receptor PPARgamma results in disrupted vasculogenesis and abnormal development of the murine placenta. In addition, PPARgamma regulates differentiation of human trophoblasts. Here we tested the hypothesis that p38 plays an important role in the regulation of PPARgamma in primary human trophoblasts. We initially confirmed that cultured trophoblasts derived from normal term human placentas express p38 as well as its functional phosphorylated form. Whereas PPARgamma did not alter p38 expression, p38 inhibitors diminished the transcriptional activity of PPARgamma in primary trophoblasts. In addition, inhibition of p38 resulted in marked attenuation of PPARgamma-stimulated hCG production by cultured trophoblast. Our data support an effect of p38 on PPARgamma protein stability because p38 inhibition led to reduced expression of PPARgamma protein without a significant effect on PPARgamma mRNA, and this reduction was blocked by the protease inhibitor MG-132. Together, these data indicate that p38 regulates PPARgamma expression and activity in term human trophoblasts. Cross talk between p38 and PPARgamma signaling may play a role in modulating differentiation and function of the human placenta.

Identification of transcription factors at the site of implantation in the later stages of murine pregnancy

Despite medical advances, preterm delivery continues to complicate 12% of all births in the United States and is a major cause of neonatal deaths. One of the reasons that preterm labor continues to be a significant problem is that very little is understood about the factors involved in normal labor. Many investigators have studied parturition in the mouse and defined essential pathways for normal labor. Prostaglandins play an essential role in mouse labor and are important in human labor as well. We examined the 23 transcription factors from pregnant mouse uterus that change expression after the induction of cyclooxygenase-1, the enzyme that catalyzes the first committed step in prostaglandin synthesis. Usingin situhybridization, we have identified three of these transcription factors, Hoxa10, Hoxa11 and GILZ as being expressed in the decidua and regulated at the end of pregnancy. Both Hoxa10 and Hoxa11 are known to be critical for implantation, but very little is known about their roles in late gestation. GILZ has not previously been identified in the gravid uterus. In summary, we have identified three transcription factors that are regulated in the decidua at the end of pregnancy, suggesting a role in detachment of the fetus and placenta.

Sphingosine-1-Phosphate Receptor Expression and Signaling Correlate with Uterine Prostaglandin-Endoperoxide Synthase 2 Expression and Angiogenesis During Early Pregnancy1

Signaling mechanisms coordinating uterine angiogenesis and tissue remodeling during decidualization are not completely understood. Prostanoid signaling is thought to play a functionally important role in each of these events. In the present study, we demonstrate that the subfamily of G-protein-coupled receptors that binds and becomes activated by the terminal signaling lipid in the sphingolipid pathway, sphingosine-1-phosphate (S1P), were expressed during uterine decidualization. Three of the five known S1P receptors, termed endothelial differentiation genes (Edg; Edg1, Edg3, and Edg5) were upregulated in the uterine deciduum from Day of Pregnancy (DOP) 4.5 to 7.5, while Edg6 and Edg8 expression remained unchanged. Consistent with angiogenesis in general during decidualization, we believe EDG1 and EDG5 to be regulated by the embryo because no microvascular expression for these receptors was observed in oil-induced deciduomas. Observed expression of EDG1 and EDG5 showed a similar expression pattern to that previously reported for prostaglandin-endoperoxide synthase 2 (PTGS2), transitioning from the sublumenal stromal compartment in the antimesometrial pole (DOP 5) to the microvasculature of the mesometrial pole (DOP 7). Furthermore, these two receptors colocalized with PTGS2 at three additional sites at the maternal:fetal interface throughout pregnancy. Treatment of cultured predecidualized stromal cells with S1P resulted in upregulation of Ptgs2 mRNA and PTGS2 protein, but not the downstream enzyme prostacyclin synthase. These combined results suggest the existence of a link between the sphingolipid and prostanoid signaling pathways in uterine physiology, and that, based on their expression pattern, S1P receptors function to coordinate uterine mesometrial angiogenesis during the implantation phase of early gestation.

Functional role of NF-IL6beta and its sumoylation and acetylation modifications in promoter activation of cyclooxygenase 2 gene

NF-IL6β regulates gene expression and plays function roles in many tissues. The EGF-regulated cyclooxygenase-2 (cox-2) expression is mediated through p38^MAPK signaling pathway and positively correlates with NF-IL6β expression in A431 cells. NF-IL6β coordinated with c-Jun on cox-2 transcriptional activation by reporter and small interfering RNA assays. NF-IL6β could directly bind to CCAAT/enhancer-binding protein (C/EBP) and cyclic AMP-response element (CRE) sites of the cox-2 promoter by in vitro-DNA binding assay. The C/EBP site was important for basal and, to a lesser extent, for EGF-regulated cox-2 transcription, while the CRE site was a more specific response to EGF inducibility of cox-2 gene. SUMO1 expression attenuated EGF- and NF-IL6β-induced cox-2 promoter activities. NF-IL6β was found to be sumoylated by in vivo- and in vitro-sumoylation assays, and the SUMO1-NF-IL6β (suNF-IL6β) lost its ability to interact with p300 in in vitro-binding assay. NF-IL6β was also acetylated by p300, and acetylation of NF-IL6β enhanced the cox-2 promoter activity stimulated by NF-IL6β itself. In vivo-DNA binding assay demonstrated that EGF stimulated the recruitment of p300 and NF-IL6β to the cox-2 promoter, yet promoted the dissociation of SUMO1-modificated proteins from the promoter. These results indicated that NF-IL6β plays a pivotal role in the regulation of basal and EGF-induced cox-2 transcription.

Lipid signaling in embryo implantation

A reciprocal interaction between the implantation-competent blastocyst and the receptive uterus is required for successful implantation. Although various molecular pathways are known to participate in this cross-talk, a comprehensive understanding of the implantation process is still missing. Gene expression studies and genetically engineered mouse models have provided evidence that lipid mediators serve as important signaling molecules in coordinating the series of events during early pregnancy including preimplantation embryo formation and development, implantation and postimplantation growth. This review focuses on the roles of two groups of lipid mediators, prostaglandins (PGs) and endocannabinoids, during early pregnancy. Our laboratory has shown that while PGs generated by the cPLA2-cyclooxygenase (COX) system are essential to ovulation, fertilization, and implantation, endocannabinoids are important for synchronizing preimplantation embryo development with uterine receptivity for implantation. A better understanding of these molecular signaling pathways is hoped to generate new strategies to correct implantation failure and improve pregnancy rates in women.

Functional characterization of prostaglandin transporter and terminal prostaglandin synthases during decidualization of human endometrial stromal cells

BACKGROUND

Decidualization of endometrial stromal cells is essential for successful implantation and pregnancy. Prostaglandins (PG) have been shown to be required for the initiation and maintenance of decidualization in animal models. The transport of PG across the plasma membrane is mediated by carriers such as prostaglandin transporter (PGT). Our recent data have shown the expression of human PGT (hPGT) in the endometrium during the menstrual cycle. The objective of the present study was to characterize hPGT in decidualized stromal cells.

METHODS AND RESULTS

Human endometrial stromal cells were treated with a combination of cAMP and medroxyprogesterone acetate to induce decidualization. Decidualization was confirmed by morphological differentiation and increased secretion of prolactin. A large increase in hPGT mRNA level, as measured by real-time PCR analysis, was observed in decidual cells compared with control. Similarly, a 2-fold up-regulation of hPGT and 3-12-fold increase in PG biosynthetic enzymes were obtained at the protein level. Decidual cells exhibited a higher isotopic PGE2 uptake and greater intracellular PG levels than control.

CONCLUSIONS

The higher uptake of PG by decidual cells is highly likely to be mediated via hPGT. PGT is a newly identified regulator of PG action at the cellular level and likely contributes to the regulation of PG action in female reproductive processes.

The abortifacient effects from the seeds of Coix lachryma-jobi L. var. ma-yuen Stapf

This study evaluated the abortifacient effects of the extracts of seeds of Coix lachryma-jobi L. var. ma-yuen Stapf (adlay) in pregnant rats. Pregnant rats were treated with oral administration of adlay seed extracts on d 6 of pregnancy and their fetuses were examined for growth and malformations on d 20 of pregnancy. Following oral administration of 1 g/kg body weight of water extracts but not methanolic extracts, fetal resorptions were significantly increased and mortality of postimplantation was increased. There were no significant differences in the uterine and fetal weight compared to control. Fetal malformations were not observed in the adlay seed extracts-treated pregnant rats. The contractile activity of uteri isolated from rats on d 20 of pregnancy was assessed. The spontaneous uterine contractions were significantly enhanced in rats treated with water extracts of adlay seeds (1 g/kg body weight). Immunoblotting of uteri from rats treated with water extracts of adlay seeds demonstrated an induction of cyclooxygenase-2 (COX-2) protein expression. The water extracts of adlay seeds also enhanced extracellular signal-regulated protein kinase (ERK) 1/2 phosphorylation and protein kinase C (PKC)-alpha translocation from cytosolic to particulate fractions in uteri. These results indicate that the water extracts of adlay seeds are capable of inducing embryotoxicity and enhancing uterine contractility during pregnancy. The enhanced activities of PKC-alpha, ERK1/2, and COX-2 may contribute to these responses.

Possible Pathophysiological Roles of Mitogen-Activated Protein Kinases (MAPKs) in Endometriosis

PROBLEM

Endometriosis accompanies local inflammatory reactions in the peritoneal cavity. We examined the phosphorylation of mitogen-activated protein kinases (MAPKs), i.e. extracellular signal-regulated kinase (ERK), p38 MAPK (p38) and c-Jun N-terminal kinase (JNK) in endometriotic stromal cells, and their possible pathophysiological roles in endometriosis in relation to proinflammatory substances.

METHOD OF STUDY

Endometriotic stromal cells were isolated from endometriomas and were cultured for the experiments. Phosphorylation of MAPKs in endometriotic stromal cells treated with interleukin (IL)-1beta, tumor necrosis factor (TNF)alpha and H(2)O(2) were examined by Western blot analysis. Effects of PD98059, SB202190 and SP600125 (inhibitors of ERK, p38 and JNK, respectively) on IL-1beta-induced secretion of IL-6 and IL-8, and on IL-1beta-induced expression of cyclo-oxygenase-2 (COX-2) in endometriotic cells were studied. In addition, eutopic endometrial tissues were collected, and the phosphorylation rate of p38 in eutopic endometrial tissues and endometriotic tissues were determined.

RESULTS

IL-1beta, TNFalpha and H(2)O(2) stimulated the phosphorylation of ERK, p38 and JNK, while the total amounts of proteins of the respective MAPKs were virtually the same compared with those in the unstimulated controls. Both SB202190 and SP600125 suppressed IL-1beta-induced secretion of IL-6 and IL-8, and PD98059 suppressed IL-1beta-induced secretion of IL-8. Both SB202190 and PD98059 suppressed IL-1beta-induced expression of COX-2 in endometriotic cells. The p38 phosphorylation rates in the endometriotic tissues were significantly higher than those in the eutopic endometrial tissues of the same patients.

CONCLUSIONS

Given the current theory that inflammatory changes are involved in the progression of endometriosis, MAPKs could play as pivotal intracellular signal transducers in endometriotic cells, and thus have a pathophysiological role in the disease.

Signal transduction pathways regulating cyclooxygenase-2 expression: potential molecular targets for chemoprevention

Expression of cyclooxygenase-2 (COX-2) has been reported to be elevated in human colorectal adenocarcinoma and other tumors, including those of breast, cervical, prostate, and lung. Genetic knock-out or pharmacological inhibition of COX-2 has been shown to protect against experimentally-induced carcinogenesis. Results from epidemiological and laboratory studies indicate that regular intake of selective COX-2 inhibitors reduces the risk of several forms of human malignancies. Thus, it is conceivable that targeted inhibition of abnormally or improperly elevated COX-2 provides one of the most effective and promising strategies for cancer chemoprevention. The COX-2 promoter contains a TATA box and binding sites for several transcription factors including nuclear factor-kappaB (NF-kappaB), nuclear factor for interleukin-6/CCAAT enhancer-binding protein (NF-IL6/C/EBP) and cyclic AMP response element (CRE) binding protein. Upregulation of COX-2 is mediated by a variety of stimuli including tumor promoters, oncogenes, and growth factors. Stimulation of either protein kinase C (PKC) or Ras signaling enhances mitogen-activated protein kinase (MAPK) activity, which, in turn, activates transcription of cox-2. Celecoxib, the first US FDA approved selective COX-2 inhibitor, initially developed for the treatment of adult rheumatoid arthritis and osteoarthritis, has been reported to reduce the formation of polyps in patients with familial adenomatous polyposis. This COX-2 specific inhibitor also protects against experimentally-induced carcinogenesis, but the underlying molecular mechanisms are poorly understood. The present review covers the signal transduction pathways responsible for regulating COX-2 expression as novel molecular targets of chemopreventive agents with celecoxib as a specific example.

Decidualization of the human endometrial stromal cell: an enigmatic transformation

Changes in human endometrium are essential to allow the establishment of pregnancy. These changes are induced in vivo by progesterone, and include appearance within the tissue of a specific uterine natural killer cell, characterized by an abundant expression of CD56. Changes also occur in the stromal cells, which undergo a characteristic decidualization reaction. Decidualized stromal cells are derived from the fibroblast-like cells within the endometrium, which maintain their progesterone receptors in the presence of progesterone. Prolonged exposure to progesterone induces a rounded cell characterized by release of prolactin and insulin-like growth factor binding protein-1 (IGFBP-1), and expression of tissue factor. Additional changes include the secretion of interleukin (IL)-15, vascular endothelial growth factor, and surface expression of zinc dependent metalloproteinases such as CD10 and CD13. In vitro, elevated intracellular cAMP as well as progesterone is necessary for decidualization. In vivo, these conditions may be provided by progesterone from the corpus luteum, by prostaglandin E, a stimulator of adenyl cyclase, and relaxin, which has recently been shown to be a phosphodiesterase inhibitor. Given the co-distribution of uterine natural killer cells and decidualized stromal cells, a mutual interaction might provide the correct regulatory environment for successful implantation, and penetration of the maternal blood vessels by trophoblastic cells.

Differential Localization of Prostaglandin E Synthase Isoforms in Human Placental Cell Types

Increased prostaglandin E(2)(PGE(2)) synthesis involves multiple enzymes and two isoforms of the terminal enzyme of this biosynthetic pathway, PGE synthase (PGES), were recently identified. Cytosolic PGES (cPGES) is identical to the Hsp90 chaperone, p23, and is reportedly functionally coupled to constitutive PG endoperoxide H synthase-1 (PGHS-1). Microsomal PGES (mPGES), on the other hand, is inducible by proinflammatory cytokines such as IL-1beta. We have studied the cellular localization of both enzyme isoforms in human placenta at term and early gestation (10 weeks). Cytosolic PGES was immunolocalized to the fibroblasts and macrophages in villous stroma, whereas mPGES was localized in the extravillous trophoblasts (EVTs) as well as macrophages in both term and early gestation tissues. Microsomal PGES was also observed in cytotrophoblasts (CTs), but not in syncytiotrophoblasts (STs), in early gestation. Apoptotic early gestational STs were heavily stained with cPGES. We also investigated the cellular localization of cPLA(2)and PGHS-2 in early gestation and at term. Cytosolic PLA(2)was immunolocalized to the stroma and STs at term, but was only observed in CTs in early gestation. PGHS-2, on the other hand, was immunolocalized to both extravillous and STs in early gestation and at term. Our results suggest that mPGES could play a role in trophoblast invasion via its association with EVTs in the basal plate, whereas cPGES could be involved in apoptosis or repair mechanisms.

Nuclear prostaglandin receptors: role in pregnancy and parturition?

The key regulatory role of prostanoids [prostaglandins (PGs) and thromboxanes (TXs)] in the maintenance of pregnancy and initiation of parturition has been established. However, our understanding of how these events are fine-tuned by the recruitment of specific signaling pathways remains unclear. Whereas, initial thoughts were that PGs were lipophilic and would easily cross cell membranes without specific receptors or transport processes, it has since been realized that PG signaling occurs via specific cell surface G-protein coupled receptors (GPCRs) coupled to classical adenylate cyclase or inositol phosphate signaling pathways. Furthermore, specific PG transporters have been identified and cloned adding a further level of complexity to the regulation of paracrine action of these potent bioactive molecules. It is now apparent that PGs also activate nuclear receptors, opening the possibility of novel intracrine signaling mechanisms. The existence of intracrine signaling pathways is further supported by accumulating evidence linking the perinuclear localization of PG synthesizing enzymes with intracellular PG synthesis. This review will focus on the evidence for a role of nuclear actions of PGs in the regulation of pregnancy and parturition.

Comparison of nonselective cyclo-oxygenase (COX) inhibitor and selective COX-2 inhibitors on preimplantation loss, postimplantation loss and duration of gestation: an experimental study

Comparison of effect of three cyclo-oxygenase (COX) inhibitors, indomethacin, nimesulide and celecoxib, on the following were assessed: preimplantation loss, postimplantation loss and duration of gestation in Wistar rats. Indomethacin (2.5 and 10 mg/kg), nimesulide (10 and 40 mg/kg) and celecoxib (10 and 40 mg/kg) were administered by gavage daily from days 1-7 for preimplantation loss studies and from day 13 to completion of gestation for postimplantation and duration of gestation studies. Number of animals in each group was six. Preimplantation loss was calculated by subtracting number of implantation sites from number of luteal spots and postimplantation loss was calculated by noting the difference between implantation sites and pups delivered. The higher doses of the three drugs were shown to increase significantly the preimplantation loss, while all the doses of three drugs produced a significant increase in postimplantation loss. Number of animals crossing upper limit of 23-day normal gestation period in Wistar rats was increased in the higher doses. At comparable dose levels, there was no significant difference among the three drugs.

Differential G protein-coupled cannabinoid receptor signaling by anandamide directs blastocyst activation for implantation

Mammalian fertility absolutely depends on synchronized development of the blastocyst to the stage when it is competent to implant, and the uterus to the stage when it is receptive to implantation. However, the molecular basis for the reciprocal interaction between the embryo and the uterus remains largely unexplored. One potentially important mechanism involves signaling between an evolutionarily conserved G protein-coupled protein cannabinoid receptor, CB1, that is expressed at high levels on the surface of the trophectoderm and anandamide (N-arachi-donoylethanolamine), an endocannabinoid ligand found to be produced at higher levels by the uterus before implantation and then down-regulated at the time of implantation. Using genetic, pharmacological, and physiological approaches, we show here that anandamide within a very narrow range regulates blastocyst function and implantation by differentially modulating mitogen-activated protein kinase signaling and Ca2+ channel activity via CB1 receptors. Anandamide at a low concentration (7 nM) induces extracellular regulated kinase phosphorylation and nuclear translocation in trophectoderm cells without influencing Ca2+ channels, and renders the blastocyst competent for implantation in the receptive uterus. In contrast, anandamide at a higher concentration (28 nM) inhibits Ca2+ channel activity and blastocyst competency for implantation without influencing mitogen-activated protein kinase signaling. Besides uncovering a potentially important regulatory mechanism for synchronizing blastocyst and uterine competency to implantation, this observation has high clinical relevance, because elevated levels of anandamide induce spontaneous pregnancy loss in women.

Induction of p38 mitogen-activated protein kinase-mediated apoptosis is involved in outgrowth of trophoblast cells on endometrial epithelial cells in a model of human trophoblast-endometrial interactions

During embryo implantation in species with hemochorial placentation, such as the mouse and human, trophoblast cells of the attached blastocyst penetrate the luminal epithelium of the endometrium before invasion into the endometrial stroma. Signs of apoptosis were demonstrated in luminal endometrial epithelial cells (EEC) adjacent to the trophoblast cells; however, the signaling mechanisms leading to apoptosis in EEC remain unclear. Because mitogen-activated protein kinases (MAPK) were shown to mediate apoptosis in several model systems and found to be activated in the uterus during decidualization, the possible involvement of MAPK during trophoblast-EEC interactions was studied. By coculturing BeWo human trophoblast spheroids with RL95-2 human EEC monolayers to mimic the blastocyst-endometrial interaction, we found that most spheroids rapidly attached to EEC monolayers and then progressively expanded, with marked dislodgment of EEC adjacent to the spreading trophoblast cells. Immunoblotting analysis showed that both p38 MAPK and extracellular signal-regulated kinase (ERK) were activated in EEC after coculture. However, only SB203580 (a p38 MAPK inhibitor), but not PD98059 (an ERK inhibitor), inhibited trophoblast outgrowth on EEC monolayers through the suppression of p38 MAPK activation in EEC. Furthermore, trophoblast expansion caused prominent EEC apoptosis at the spheroid-EEC interface, as detected by annexin V labeling and valyl-alanyl-aspartyl-[O-methyl]-fluoromethylketone (which binds activated caspases) staining, and SB203580 significantly decreased the percentage of apoptotic cells. Our results, based on a model of human trophoblast-EEC interactions, establish that trophoblast cells cause activation of p38 MAPK in EEC and, consequently, induce apoptosis and displacement of EEC, a process that may facilitate implantation.

Prenatal effects of DuP-697-the irreversible, highly selective cyclooxygenase-2 inhibitor

DuP-697 (5-bromo-2-(4-fluorophenyl)-3-[4-(methylsulfonyl)phenyl]-thiophene), like celecoxib and rofecoxib, is a vicinal diaryl heterocycle highly selective cyclooxygenase-2 (COX-2) inhibitor. The aim of the study was to evaluate prenatal tolerability of DuP-697. The drug was administered orally in Tween 80 water suspension once a day to pregnant Wistar rats, on Days 7-18 of gestation. The initial dose, similar to the rat antipyretic dose, was set at 0.05 mg/kg. The middle dose, 3.5 mg/kg, corresponded to the rat anti-inflammatory and analgesic dose. The high dose was set at 35.0 mg/kg. Control animals received Tween 80 water suspension. On Day 21 of gestation, fetuses were delivered by laparotomy and double stained with alcian blue and alizarin red S or examined using the Wilson technique. Intrauterine growth retardation occurred in the groups exposed to the middle and highest dose of DuP-697. Minimal reactive and degenerative hepatic changes were found in both drug-exposed and control groups. Skeletal malformations were seen occasionally in all drug-treated and control groups. A significant increase in skeleton variations, such as delayed and asymmetrical ossification, was observed in fetuses exposed to the highest drug dose when compared with the control. These changes were not increased (P<0.1) in the middle drug-dose group. The experimentally-derived NOAEL for developmental toxicity was 0.05 mg/kg, and the corresponding LOAEL was 3.5 mg/kg.

Pivotal role of attractin in cell survival under oxidative stress in the zitter rat brain with genetic spongiform encephalopathy

Accumulation of reactive oxygen species (ROS), which is generated during energy metabolism, is a cause of physiological aging, neuropathogenesis and numerous diseases, such as Parkinson's and Alzheimer's diseases. Zitter rat is an autosomal recessive mutant, characterized by spongiform degeneration and hypomyelination in the brain, and the phenotype has been suggested to be involved in oxidative stress by the accumulation of ROS. To determine the relation between neurodegeneration of the zitter rat and Attractin (Atrn) gene expression, which was identified as a gene responsible for the zitter, we established fibroblast cells from the zitter rat (Fz) and the Wistar tremor control (WTC) rat (Fw), and transduced Fz cells with the Atrn gene (Fz/Atrn). In the Fz/Atrn cells, accumulation of ROS was repressed, and cell survival against oxidative stress was enhanced to the same level as in Fw cells. Interestingly, phosphorylation of ERK was significantly increased in Fz/Atrn cells by H(2)O(2) stimulus, similarly to Fw cells. Furthermore, activation of ERK was confirmed in the brains of WTC and zitter rats by Western blot analysis and immunohistochemistry. These observations suggested that lack of Atrn gene expression induced neurodegeneration by a decrease in active ERK through an intracellular signaling via oxidative stress.

Significant neuroprotection against ischemic brain injury by inhibition of the MEK1 protein kinase in mice: exploration of potential mechanism associated with apoptosis

MEK1/2 is a serine/threonine protein kinase that phosphorylates and activates extracellular signal-responsive kinase (ERK)1/2. In the present study we explored the role of MEK1/2 in ischemic brain injury using a selective MEK1/2 inhibitor, SL327, in mice. C57BL/6 mice were subjected to a 30-min occlusion of the middle cerebral artery (MCAO) followed by reperfusion. Western blot analysis demonstrated the immediate activation of MEK/ERK after reperfusion (within the first 10 min) in the ischemic brain; this activation was dose dependently blocked by SL327 (10-100 mg/kg, i.p.). A single dose of SL327 (100 mg/kg) administered 15 min before or 25 min after the onset of ischemia resulted in 63.6% (n = 18, p < 0.001) and 50.7% (n = 18, p < 0.01) reduction in infarct size, respectively, compared with vehicle-treated mice. Similarly, SL327 significantly reduced neurological deficits 1 to 3 days after reperfusion (n = 12, p < 0.01). The salutary effect of SL327-induced neuroprotection was independent of mitochondrial cytochrome c release or caspase-8-mediated apoptosis; however, SL327 markedly suppressed the levels of active caspase-3 and DNA fragmentation (as a measure of apoptosis) after ischemia/reperfusion. Our data suggest that the inhibition of MEK1/2 results in neuroprotection from reperfusion injury and that this protection may be associated with the reduction in apoptosis.

Peroxisome proliferator-activated receptor-beta signaling contributes to enhanced proliferation of hepatic stellate cells

BACKGROUND & AIMS

The peroxisome proliferator-activated nuclear receptors (PPAR-alpha, PPAR-beta, and PPAR-gamma), which modulate the expression of genes involved in energy homeostasis, cell cycle, and immune function, may play a role in hepatic stellate cell activation. Previous studies focused on the decreased expression of PPAR-gamma in hepatic stellate cell activation but did not investigate the expression and role of the PPAR-alpha and -beta isotypes. The aim of this study was to evaluate the expression of the different PPARs during hepatic stellate cell activation in vitro and in situ and to analyze possible factors that might contribute to their expression. In a second part of the study, the effect of a PPAR-beta agonist on acute liver injury was evaluated.

METHODS

The effects of PPAR isotype-specific ligands on hepatic stellate cell transition were evaluated by bromodeoxyuridine incorporation, gel shifts, immunoprecipitation, and use of antisense PPAR-beta RNA-expressing adenoviruses. Tumor necrosis factor alpha-induced PPAR-beta phosphorylation and expression was evaluated by metabolic labeling and by using specific P38 inhibitors.

RESULTS

Hepatic stellate cells constitutively express high levels of PPAR-beta, which become further induced during culture activation and in vivo fibrogenesis. No significant expression of PPAR-alpha or -gamma was found. Stimulation of the P38 mitogen-activated protein kinase pathway modulated the expression of PPAR-beta. Transcriptional activation of PPAR-beta by L165041 enhanced hepatic stellate cell proliferation. Treatment of rats with a single bolus of CCl(4) in combination with L165041 further enhanced the expression of fibrotic markers.

CONCLUSIONS

PPAR-beta is an important signal-transducing factor contributing to hepatic stellate cell proliferation during acute and chronic liver inflammation.

COX-2 inhibitors and their role in gynecology

This review summarizes current knowledge about the roles of cyclooxygenases and prostaglandins in reproductive medicine. With the development of COX-2 specific inhibitors, new therapeutic options are available to obstetricians and gynecologists, offering better-tolerated alternatives to conventional NSAIDs. The analgesic effectiveness of COX-2 specific inhibitors is well established, and they are already in use in a range of painful conditions. Both celecoxib and valdecoxib are indicated for the treatment of primary dysmenorrhea, and may be effective in postoperative pain, including hysterectomy, and pain associated with endometriosis. There is also speculation that COX-2 specific inhibitors may be effective tocolytic agents without the risks to the fetus seen with conventional NSAIDs. The role of COX-2 in oncogenesis is also under investigation, and COX-2 specific inhibitors may eventually be used in the prevention and treatment of gynecologic malignancies.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians Learning Objectives: After completion of this article, the reader will be able to describe the two types of cylooxygenase enzymes (COX), to list the effects and side effects of NSAIDs and COX-2 medications, and to outline the various changes in COX expression during pregnancy.

Anti-implantation effects of indomethacin and celecoxib in rats

Pregnant Wistar rats were used to investigate the anti-implantation effect of cyclooxygenase (COX) inhibitors, indomethacin (nonselective COX-1/COX-2 inhibitor) and celecoxib (specific COX-2 inhibitor). Indomethacin at doses of 2.5 and 5 mg/kg/day and celecoxib at doses of 40, 80, and 160 mg/kg/day were orally administered once daily to each group (n = 8) on Days 3-5 of pregnancy (Day 1 = sperm detection). Indomethacin and celecoxib at anti-implantation dosages were further investigated for the effects on changes in endometrial vascular permeability in pregnant rats and uterine decidualization in pseudopregnant rats. The results demonstrated that indomethacin at a dose of 5 mg/kg/day as well as celecoxib at doses of 80 and 160 mg/kg/day could significantly reduce the proportion of pregnant rats. At the anti-implantation dosages, they exhibited no significant effect on proportion of rats with blue dye sites in the endometrial vascular permeability study, but they could significantly reduce the uterine decidualization. From these findings, the anti-implantation effect of the two COX inhibitors may principally be from decidualization defects, and COX inhibitors should, therefore, be used with caution in childbearing age women. On the other hand, specific COX-2 inhibitors with their good gastric safety profile may have a potential role in nonhormonal postcoital contraception.

Control of growth and differentiation of the endometrium: the role of tissue interactions

Early work with neonatal mice showed that estrogen receptor-negative uterine epithelium responded to estrogen treatment. Since the underlying mesenchymal cells were estrogen receptor-positive, it was suggested that these cells mediated the hormonal response through elaboration of a paracrine factor. Cell culture work showed that mesenchymal cells produced soluble factors that stimulate uterine epithelium, but hormonal regulation was absent or minimal. The paracrine hypothesis of estrogen action has been proved by the use of tissue recombinant studies in which epithelium from estrogen receptor-alpha knockout mice was combined with wild-type mesenchyme; estrogen stimulated the ER alpha-negative epithelium if the underlying stromal cells were receptor-positive. Also, it is hypothesized that there is a reciprocal paracrine interaction during stimulation with progesterone and estrogen. Accordingly, under progesterone dominance, the epithelium elaborates factors that direct the underlying stroma to proliferate when estrogen is administered. Although this hypothesis needs further testing, it has been shown that the uterine epithelium is required for stromal responsiveness to hormones. The question arises: What are the factors that mediate the effects of the steroid hormones in the uterus? Several peptide growth factors are regulated by estrogen and/or progesterone. Use of knockout animals will allow a determination of the role that these factors play in the uterus. However, ablation of many of these growth factor genes has proved lethal to the newborn animals, making it impossible to study hormonal effects using standard techniques. Tissue xenograft and tissue recombination studies offer a means of defining the role of specific growth factors in uterine physiology.

Possible involvement of p38 mitogen-activated protein kinase in decidual function in parturition

We designed the present study to elucidate the molecular mechanism for parturition, focusing on p38 mitogen-activated protein kinase (p38). The kinase activity of p38 in mouse uterus was gestation stage-dependent, and was markedly increased on day 19 of gestation and during labor. Immunohistochemical examination with anti-phospho p38 antibody revealed that activated p38 was predominantly localized in decidual stromal cells stained with anti-prolactin antibody. In human primary cultured decidual cells, a p38 inhibitor, SB202190, significantly inhibited both prostaglandin F(2alpha) production and COX-2 expression induced by stimulation with IL-1beta. These results suggest that the p38 signaling pathway is involved in decidual function at the late stage of gestation and may contribute to parturition.

Differential regulation of IL-1beta and TNF-alpha RNA expression by MEK1 inhibitor after focal cerebral ischemia in mice

Activation of the extracellular-signal-responsive kinase (ERK 1/2) by MAP kinase/ERK kinase (MEK1/2) following ischemia/reperfusion in the brain has been associated with cell death since inhibition of MEK1/2 provides neuroprotection in cerebral ischemia injury. Since inflammation has been implicated in ischemic brain injury, the present study investigated whether MEK1/2 modifies expression of two key inflammatory cytokines, IL-1beta and TNFalpha, that have been shown to exacerbate ischemic brain injury. A mouse model of transient cerebral ischemia was deployed to test the effect of selective MEK1/2 inhibitor (SL327) on infarct size and cytokine expression. SL327 (100 mg/kg, i.p.) administered 15 min prior to ischemia resulted in 64% reduction in infarct size over controls (n = 8, P < 0.01). Under the same condition, SL327 significantly reduced peak expression of IL-1beta mRNA (59% reduction compared to vehicle, P < 0.01, n = 4) but not TNF-alpha mRNA. A parallel reduction in IL-1beta protein (67%, P < 0.05, n = 6) was also observed using ELISA analysis. These data suggest that the neuroprotective effect of MEK1/2 inhibition may be mediated by suppression of IL-1beta. The study also demonstrates for the first time that these two cytokines are differentially regulated by kinase mediated signaling pathways.