Characterization of ovarian carbonyl reductase gene expression during ovulation in the gonadotropin-primed immature Rat

Comparative Transcriptomics Reveal Key Sheep (Ovis aries) Hypothalamus LncRNAs that Affect Reproduction

The diverse functions of long noncoding RNAs (lncRNAs), which execute their functions mainly through modulating the activities of their target genes, have been have been widely studied for many years (including a number of studies involving lncRNAs in the ovary and uterus). Herein, for the first time, we detect lncRNAs in sheep hypothalami with FecB++ through RNA Sequencing (RNA-Seq) and identify a number of known and novel lncRNAs, with 622 and 809 found to be differentially expressed in polytocous sheep in the follicular phase (PF) vs. monotocous sheep in the follicular phase (MF) and polytocous sheep in the luteal phase (PL) vs. monotocous sheep in the luteal phase (ML), respectively. Then, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were performed based on the predicted target genes. The most highly enriched GO terms (at the molecular function level) included carbonyl reductase (NADPH), 15-hydroxyprostaglandin dehydrogenase (NADP+), and prostaglandin-E2 9-reductase activity in PF vs. MF, and phosphatidylinositol-3,5-bisphosphate binding in PL vs. ML was associated with sheep fecundity. Interestingly, the phenomena of valine, leucine, and isoleucine degradation in PL vs. ML, and valine, leucine, and isoleucine biosynthesis in PF vs. MF, were present. In addition, the interactome of lncRNA and its targets showed that MSTRG.26777 and its cis-targets ENSOARG00000013744, ENSOARG00000013700, and ENSOARG00000013777, and MSTRG.105228 and its target WNT7A may participate in the sheep reproductive process at the hypothalamus level. Significantly, MSTRG.95128 and its cis-target Forkhead box L1 (FOXG1) were shown to be upregulated in PF vs. MF but downregulated in PL vs. ML. All of these results may be attributed to discoveries of new candidate genes and pathways related to sheep reproduction, and they may provide new views for understanding sheep reproduction without the effects of the FecB mutation.

From Follicular Development and Ovulation to Ovarian Cancers: An Unexpected Journey

Follicular development and ovulation are complex development processes that are regulated by multiple, interacting pathways and cell types. The oocyte, cumulus cells, granulosa cells, and theca cells communicate to impact follicular development and ovulation. Many hormones and cytokines control intracellular regulatory networks and transcription factors, some of which are cell type specific. Molecular biology approaches and mutant mouse models have contributed immensely to our knowledge of what genes and signaling cascades impact each stage of follicular development and ovulation, and how the alteration of gene expression profiles and the activation of specific signaling pathways can impact ovarian cancer development in ovarian surface epithelial cells as well as granulosa cells. This chapter explores how pathways controlling normal follicle development and ovulation can be diverted to abnormal development.

Regulation of the ovarian oxidative status by leptin during the ovulatory process in rats

Leptin exerts both stimulatory and inhibitory effects on the ovulatory process. In this study, we investigated whether these opposite effects involve changes in the oxidative status in response to different levels of leptin. To this end, we performed bothin vivoandin vitroassays using ovaries of immature rats primed with gonadotropins to induce ovulation. Superoxide dismutase (SOD) and catalase (CAT) activity, lipid peroxidation, glutathione (GSH) content, and reactive oxygen species (ROS) were studied as oxidative damage-related parameters. The expression of BCL2, BAX, and caspase 3 were measured by western blot as apoptosis-related biomarkers. The acute treatment with leptin, which inhibits ovulation, decreased SOD activity and increased active caspase 3 expression. No differences were found in CAT activity, lipid peroxidation, or total GSH. In contrast, the daily administration of leptin, which induces ovulation, decreased GSH content, ROS levels, and Bax and active caspase 3 expression, but caused no changes in other parameters. In addition, the daily administration of leptin induced follicular growth, measured by the number of antral follicles in ovarian sections. Using ovarian explant cultures, we found increased BCL2 expression and decreased SOD activity at low and high concentrations of leptin respectively. Thus, leptin can modulate the oxidative status of the ovarian tissue, during the ovulatory process, by acting on different targets according to its circulating levels. At low concentration, leptin seems to play a protective role against the oxidative stress, whereas at high concentrations, this protein seems to be involved in cell death.

20β-hydroxysteroid dehydrogenase gene promoter: potential role for cyclic AMP and xenobiotic responsive elements

Teleostean 20β-hydroxysteroid dehydrogenase (20β-HSD) is involved in final oocyte maturation and steroid hormone metabolism. It has structural and functional similarities to mammalian carbonyl reductases that are involved in the metabolism of endogenous carbonyl and xenobiotic compounds. To understand the transcriptional regulation of 20β-HSD, here we report the cloning of 20β-HSD promoter from two fish species, rainbow trout and air-breathing catfish. Analysis of the promoter motifs, in silico identified the presence of several sites for transcription factor binding including cAMP, xenobiotic and steroid hormone responsive elements. Luciferase reporter assays with progressive deletion constructs demonstrated that 20β-HSD type B of trout has no promoter activity while 20β-HSD type A of trout and catfish 20β-HSD promoters showed basal promoter activity. A TATA box flanked by a CAAT box is important for basal transcription. Deletion of cAMP responsive element in the promoter decreased basal promoter activity significantly. Reporter assays with forskolin and IBMX, drugs that increase intracellular cAMP induced the promoter activity over the basal level. Intriguingly, β-nafthoflavone, an arylhydrocarbon receptor ligand, induced the 20β-HSD promoter activity and is further evidenced by the induction of 20β-HSD expression in the livers of catfish, in vivo. These results demonstrate for the first time that 20β-HSD expression is not only modulated by cAMP but also by xenobiotics and further studies may provide significance to the ubiquitous distribution and broad substrate specificity of this enzyme.

The water permeability channels aquaporins 1-4 are differentially expressed in granulosa and theca cells of the preovulatory follicle during precise stages of human ovulation

CONTEXT

Changes in vascular permeability and expansion of the fluid-filled antrum are major events in the LH-induced ovulatory process.

OBJECTIVES

Our objective was to investigate the presence and expression levels of aquaporins (AQPs) in the granulosa and theca cell compartments of the follicle during defined phases of human ovulation.

DESIGN AND SETTING

We conducted a prospective experimental study at the Department of Obstetrics and Gynaecology at a university hospital.

PARTICIPANTS

Twenty-eight women underwent laparoscopic sterilization and at the same time follicle retrieval at four periovulatory phases.

MAIN OUTCOME MEASURES

mRNA levels of AQP1-4 were measured in separated granulosa and theca cells from preovulatory phase, early ovulatory (EO) phase, late ovulatory phase, and postovulatory phase. Immunohistochemistry was done for AQP1-4 in intact human follicles.

RESULTS

All four AQPs were expressed in both the theca and granulosa cells during ovulation. In granulosa cells, AQP1 levels increased in the late ovulatory and postovulatory phases. Expression of AQP2-3 followed a similar pattern with a marked increase in the EO phase, whereas AQP4 levels decreased from preovulatory to the EO phase. The presence of AQP1-4 in the human follicle was verified by immunohistochemistry.

CONCLUSIONS

The results show for the first time the presence of AQP1-4 in human follicles during ovulation. The marked early rise in expression of AQP2 and AQP3 suggests a role during the process leading to follicular rupture, and the late rise of AQP1 suggests a role in corpus luteum formation.

New evidences for the involvement of 20beta-hydroxysteroid dehydrogenase in final oocyte maturation of air-breathing catfish

20beta-hydroxysteroid dehydrogenase (20beta-HSD) synthesizes 17alpha,20beta-dihdroxy-4-pregnen-3-one, the steroid required for resumption of prophase-I arrested oocytes in teleosts. Though 20beta-HSD cDNAs have been cloned from few fish species, its role in final oocyte maturation (FOM) is still questionable. To study the role of 20beta-HSD in FOM more explicitly, we cloned and characterized 20beta-HSD from ovary of air-breathing catfish, Clarias gariepinus. Interestingly, Escherichia coli expressed recombinant proteins, both full-length and an N-terminal truncated proteins catalyzed the reduction of steroids and xenobiotics, however there was significant difference between them. Semi-quantitative RT-PCR and Western blots demonstrated the presence of 20beta-HSD transcript and protein in various tissues with relatively higher level in gonads, gill, kidney and brain. A positive correlation of 20beta-HSD expression was observed in different phases of ovarian cycles. Immunocytochemical/immunofluoroscence analysis with specific antibody identified presence of 20beta-HSD in follicular layer of ovary. Real-time RT-PCR and Western blotting showed an induction of 20beta-HSD expression during human chorionic gonadotropin (hCG)-induced oocyte maturation, in vitro and in vivo. Concomitantly, a rise in 20beta-HSD enzyme activity was also noticed. Specific inhibitors of carbonyl reductase inhibited not only recombinant protein catalytic activity but also hCG-induced oocyte maturation in a dose-dependent manner as evidenced by blocking of germinal vesicle break down. These results together provide new evidences for the involvement of 20beta-HSD in the FOM/meiotic maturation.

Carbonyl Reductases and Pluripotent Hydroxysteroid Dehydrogenases of the Short-chain Dehydrogenase/reductase Superfamily

Carbonyl reduction of aldehydes, ketones, and quinones to their corresponding hydroxy derivatives plays an important role in the phase I metabolism of many endogenous (biogenic aldehydes, steroids, prostaglandins, reactive lipid peroxidation products) and xenobiotic (pharmacologic drugs, carcinogens, toxicants) compounds. Carbonyl-reducing enzymes are grouped into two large protein superfamilies: the aldo-keto reductases (AKR) and the short-chain dehydrogenases/reductases (SDR). Whereas aldehyde reductase and aldose reductase are AKRs, several forms of carbonyl reductase belong to the SDRs. In addition, there exist a variety of pluripotent hydroxysteroid dehydrogenases (HSDs) of both superfamilies that specifically catalyze the oxidoreduction at different positions of the steroid nucleus and also catalyze, rather nonspecifically, the reductive metabolism of a great number of nonsteroidal carbonyl compounds. The present review summarizes recent findings on carbonyl reductases and pluripotent HSDs of the SDR protein superfamily.

Low expression of COX-2, reduced cumulus expansion, and impaired ovulation in SULT1E1-deficient mice

The SULT1E1-encoded estrogen sulfotransferase (EST) catalyzes sulfation of estrogen, resulting in its inactivation. Reduced fertility observed in SULT1E1 knockout (KO) female mice has previously been attributed to the deleterious effect of chronic exposure to high levels of circulating estrogen on placental function. We herein suggest that, in addition to placental dysfunction, this phenotype demonstrates that an excess of estrogen impairs ovulation. The role of SULT1E1 in ovulation is suggested by the substantially low ovulatory response in hCG-treated SULT1E1 KO mice; a similar effect was observed when 17beta-estradiol was administered to wild-type (WT) females. The normal rate of ovulation in SULT1E1 KO females may be restored by PGE2. Along this line, ovaries of human Chorionic Gonadotropin (hCG)-treated SULT1E1 KO mice expressed low levels of cyclooxygenase-2 (COX-2) and its downstream TSG6; moreover, their ovaries contained a reduced number of expanded cumuli. Our results demonstrate, for the first time, that estrogen inactivation may allow the expression of COX-2 and subsequent cumulus expansion, enabling normal ovulation. Our findings may be applied to novel treatments of human ovulatory failure.

Regulation of the Rhox5 Homeobox Gene in Primary Granulosa Cells: Preovulatory Expression and Dependence on SP1/SP3 and GABP1

Homeobox genes encode transcription factors that regulate embryonic development and postnatal events. Rhox5 (previously called Pem), the founding member of a homeobox gene cluster that we recently identified on the X chromosome, is selectively expressed in granulosa cells in the ovary and other somatic-cell types in other reproductive organs. In this report, we investigate its regulation in granulosa cells in the rat ovary. We found that Rhox5 expression in the ovary is governed by the Rhox5 distal promoter and is expressed at least as early as Day 5 postpartum. Rhox5 mRNA levels are regulated during the ovarian cycle, peaking before ovulation. Deletion analysis revealed a 25-nt element essential for distal promoter transcription in primary granulosa cells. This distal promoter element contains two ETS and one SP1 transcription-factor family binding sites that mutagenesis analysis indicated were essential for high-level transcription. This element was both necessary and sufficient for transcription, because it activated transcription when placed upstream of a heterologous minimal promoter. Cold competition and electrophoretic mobility shift assay studies demonstrated that SP1, SP3, and the ETS family transcription factor GABP bound this element. Dominant-negative forms of GABP and SP3 repressed distal promoter expression in primary rat granulosa, showing that these factors are crucial for Rhox5 expression. Cotransfection of dominant-negative mutants indicated that Rhox5 expression in granulosa cells is regulated by the c-Jun N-terminal protein kinase (JNK, MAPK8) and RAS pathways, which are known to be upstream of ETS family transcription factors. The discovery that Rhox5 expression in granulosa cells is regulated by MAPK pathways and ETS and SP1 family members provides an opportunity to understand how these regulatory pathways and factors collaborate to regulate gene expression during the ovarian cycle.

Development and application of a rat ovarian gene expression database

The pituitary gonadotropins play a key role in follicular development and ovulation through the induction of specific genes. To identify these genes, we have constructed a genome-wide rat ovarian gene expression database (rOGED). The database was constructed from total RNA isolated from intact ovaries, granulosa cells, or residual ovarian tissues collected from immature pregnant mare serum gonadotropin (PMSG)/human chorionic gonadotropin-treated rats at 0 h (no PMSG), 12 h, and 48 h post PMSG, as well as 6 and 12 h post human chorionic gonadotropin. The total RNA was used for DNA microarray analysis using Affymetrix Rat Expression Arrays 230A and 230B (Affymetrix, Santa Clara, CA). The microarray data were compiled and used for display of individual gene expression profiles through specially developed software. The final rOGED provides immediate analysis of temporal gene expression profiles for over 28,000 genes in intact ovaries, granulosa cells, and residual ovarian tissue during follicular growth and the preovulatory period. The accuracy of the rOGED was validated against the gene profiles for over 20 known genes. The utility of the rOGED was demonstrated by identifying six genes that have not been described in the rat periovulatory ovary. The mRNA expression patterns and cellular localization for each of these six genes (estrogen sulfotransferase, synaptosomal-associated protein 25 kDa, runt-related transcription factor, calgranulin B, alpha1-macroglobulin, and MAPK phosphotase-3) were confirmed by Northern blot analyses and in situ hybridization, respectively. The current findings demonstrate that the rOGED can be used as an instant reference for ovarian gene expression profiles, as well as a reliable resource for identifying important yet, to date, unknown ovarian genes.

Immature rats show ovulatory defects similar to those in adult rats lacking prostaglandin and progesterone actions

Gonadotropin-primed immature rats (GPIR) constitute a widely used model for the study of ovulation. Although the equivalence between the ovulatory process in immature and adult rats is generally assumed, the morphological and functional characteristics of ovulation in immature rats have been scarcely considered. We describe herein the morphological aspects of the ovulatory process in GPIR and their response to classical ovulation inhibitors, such as the inhibitor of prostaglandin (PG) synthesis indomethacin (INDO) and a progesterone (P) receptor (PR) antagonist (RU486). Immature Wistar rats were primed with equine chorionic gonadotropin (eCG) at 21, 23 or 25 days of age, injected with human chorionic gonadotropin (hCG) 48 h later, and sacrificed 16 h after hCG treatment, to assess follicle rupture and ovulation. Surprisingly, GPIR showed age-related ovulatory defects close similar to those in adult rats lacking P and PG actions. Rats primed with eCG at 21 or 23 days of age showed abnormally ruptured corpora lutea in which the cumulus-oocyte complex (COC) was trapped or had been released to the ovarian interstitum, invading the ovarian stroma and blood and lymphatic vessels. Supplementation of immature rats with exogenous P and/or PG of the E series did not significantly inhibit abnormal follicle rupture. Otherwise, ovulatory defects were practically absent in rats primed with eCG at 25 days of age. GPIR treated with INDO showed the same ovulatory alterations than vehicle-treated ones, although affecting to a higher proportion of follicles. Blocking P actions with RU486 increased the number of COC trapped inside corpora lutea and decreased ovulation. The presence of ovulatory defects in GPIR, suggests that the capacity of the immature ovary to undergo the coordinate changes leading to effective ovulation is not fully established in Wistar rats primed with eCG before 25 days of age.

Metallothionein-1 messenger RNA transcription in steroid-secreting cells of the rat ovary during the periovulatory period

An increase in metallothionein 1 (MT-1) mRNA was detected in the ovaries of immature Wistar rats that were primed with s.c. injection of 10 IU eCG followed 48 h later by 10 IU hCG s.c. to initiate the ovulatory process. Ovarian RNA was extracted at 0, 2, 4, 8, 12, 24, 72, 144, and 288 h after the primed animals were injected with hCG. These extracts were used for reverse transcription polymerase chain reaction (RT-PCR) differential display and Northern analyses that yielded complementary gene fragments for MT-1. Expression of MT-1 mRNA increased significantly by 24 h after hCG treatment and reached a peak at 144 h after hCG. In contrast, a disintegrin and metalloproteinase with thrombospondin motifs and a tissue inhibitor of metalloproteinase 1, which were also detected by the RT-PCR differential display procedure, reached a peak at 12 h after hCG and returned to control levels in the ovaries by 72 h after hCG. In situ hybridization indicated that most of the MT-1 mRNA was expressed in the vicinity of the theca interna of preovulatory follicles and in the lutein granulosa of postovulatory follicles. Thus, MT-1 mRNA expression is primarily in the vicinity of steroid-secreting areas of the ovary. The substantial increase in MT-1 mRNA expression might be important in protecting the ovarian tissues from oxidative stress generated by ovarian inflammatory events during the ovulatory process and luteinization.

Temporal and spatial patterns of ovarian gene transcription following an ovulatory dose of gonadotropin in the rat

In recent years, there have been a number of efforts to identify genes that are expressed in mature ovarian follicles in response to an ovulatory dose of LH or its homologue hCG. This review keys on 20 ovulation-specific genes that we have identified by the molecular procedure known as differential display. The objective is to use this sampling of genes to illustrate the diversity in the temporal and spatial patterns of expression of genes in the ovary following the stimulus of this gonadal target tissue by a single glycoprotein hormone. The specific genes that are surveyed include 5-aminolevulinate synthase; early growth response protein-1; gamma-glutamylcysteine synthetase; cyclooxygenase-2; epiregulin; pituitary adenylate cyclase-activating polypeptide; tumor necrosis factor-stimulated gene-6; regulator of G-protein signaling protein-2; adrenodoxin; steroidogenic acute regulatory protein; 3alpha-hydroxysteroid dehydrogenase; CD63, a disintegrin and metalloproteinase with thrombospondin motifs; tissue inhibitor of metalloproteinase-1; carbonyl reductase, a G-protein-coupled receptor; pancreatitis-associated protein-III; glutathione S-transferase; and metallothionein-1. The ovulatory expression of these different genes is predominantly within the granulosa layer of mature follicles. However, there were also instances of expression in the thecal and stromal tissue of the ovary, as well as in vascular endothelial cells and in luteal tissue. The overwhelming impression is that the molecular events of ovulation are far more complex, and therefore more highly ordered, than originally imagined.

Ovarian Carbonyl Reductase-Like 20β-Hydroxysteroid Dehydrogenase Shows Distinct Surge in Messenger RNA Expression During Natural and Gonadotropin-Induced Meiotic Maturation in Nile Tilapia1

Meiotic maturation in fish is accomplished by maturation-inducing hormones. 17alpha,20beta-Dihydroxy-4-pregnen-3-one (17alpha,20beta-DP) was identified as the maturation-inducing hormone of several teleosts, including Nile tilapia. A cDNA encoding 20beta-hydroxysteroid dehydrogenase (20beta-HSD), the enzyme that converts 17alpha-hydroxyprogesterone to 17alpha,20beta-DP, was cloned from the ovarian follicle of Nile tilapia. Genomic Southern analysis indicated that 20beta-HSD probably exists as a single copy in the genome. The Escherichia coli-expressed cDNA product oxidized both carbonyl and steroid compounds, including progestogens, in the presence of NADPH. Carbonyl reductase-like 20beta-HSD is broadly expressed in various tissues of tilapia, including ovary, testis, and gill. Northern blot and reverse transcription polymerase chain reaction analyses during the 14-day spawning cycle revealed that the expression of 20beta-HSD in ovarian follicles is low from Day 0 to Day 8 after spawning and is not detectable on Day 11. Distinct expression was evident at Day 14, the day of spawning. In males, 20beta-HSD expression was observed continually in mature testes but not in immature testes of 30-day-old fish. In vitro incubation of postvitellogenic immature follicles (corresponding to Day 11 after spawning) with hCG induced the expression of 20beta-HSD mRNA transcripts within 1-2 h, followed by the final meiotic maturation of oocytes. In tissues such as gill, muscle, brain, and pituitary, however, hCG treatment did not induce any changes in the levels of mRNA transcripts. Actinomycin D blockade of hCG-induced 20beta-HSD expression and final oocyte maturation demonstrated the involvement of transcriptional factors. The carbonyl reductase-like 20beta-HSD plays an important role in the meiotic maturation of tilapia gametes.

Ovulation: new dimensions and new regulators of the inflammatory-like response

Ovulation is a complex process that is initiated by the lutenizing hormone surge and is controlled by the temporal and spatial expression of specific genes. This review focuses on recent endocrine, biochemical, and genetic information that has been derived largely from the identification of new genes that are expressed in the ovary, and from knowledge gained by the targeted deletion of genes that appear to impact the ovulation process. Two main areas are described in most detail. First, because mutant mouse models indicate that appropriate formation of the cumulus matrix is essential for successful ovulation, genes expressed in the cumulus cells and those that control cumulus expansion are discussed. Second, because mice null for the progesterone receptor fail to ovulate and are ideal models for dissecting the critical events downstream of progesterone receptor, genes expressed in mural granulosa cells that regulate the expression of novel proteases are described.

Teleost ovarian carbonyl reductase-like 20beta-hydroxysteroid dehydrogenase: potential role in the production of maturation-inducing hormone during final oocyte maturation

17alpha,20beta-Dihydroxy-4-pregnen-3-one is the major oocyte maturation-inducing hormone of several teleost species. Gonadotropin-induced increase in ovarian 20beta-hydroxysteroid dehydrogenase activity is essential for the synthesis of maturation-inducing hormone. Cloning and expression studies suggest that ayu (Plecoglossus altivelis) ovarian carbonyl reductase can function as 20beta-hydroxysteroid dehydrogenase. The amino acid sequence deduced from the isolated cDNA had 276 amino acid residues and shared approximately 60% homology with mammalian and teleostean carbonyl reductases. The sequence data search showed that the ayu cDNA clone belongs to the short-chain dehydrogenase/reductase family. The clear lysate prepared from Escherichia coli harboring the cDNA catalyzed the production of maturation-inducing hormone. Its identification was confirmed by two-dimensional, thin-layer chromatography followed by recrystallization. Purification of the E. coli-expressed cDNA product revealed that it possessed both carbonyl reductase and steroid dehydrogenase activities, and 17alpha-hydroxyprogesterone, the endogenous immediate precursor of maturation-inducing hormone, was one of the preferred substrates. Furthermore, Northern blot analysis denoted that the transcripts are present both in fully grown, immature ovarian follicles and at higher levels in mature ovarian follicles. These results demonstrate that the carbonyl reductase of ayu ovary is involved in the production of maturation-inducing hormone, and they provide evidence for a novel physiological role of this enzyme in the final maturation of oocytes. Based on its functional properties, the enzyme can be referred to as carbonyl reductase-like 20beta-hydroxysteroid dehydrogenase.

Effects of carbamazepine on the first ovulation in gonadotropin-primed immature female rats

1. The effects of carbamazepine (CBZ) and its possible mechanisms on the first ovulation were investigated in immature female rats. The first ovulation was induced by administration of equine chorionic gonadotropin (eCG) at 0800 h at 26 days of age. 2. A single s.c. injection of 360 mg x kg(-1) CBZ at 1300 h on the first pro-oestrus (day 28) completely inhibited the first ovulation on the morning of day 29. A marked elevation in 13, 14-dihydro-prostaglandin F2alpha (13, 14H2-PGF2alpha) forming capacity, a sensitive indicator of luteinizing hormone (LH) surge, was not detected in the CBZ-treated group at 0800 h on day 29 (72 h after eCG treatment). The elevation in serum LH levels at 57 h after eCG treatment was not observed in the CBZ-treated group, either. The blocking of the first ovulation and 13, 14H2-PGF2alpha forming capacity were recovered by an i.p. injection of human CG on day 28 in all animals. 3. However, the first ovulation was not blocked by repeated injections of 360 mg x kg(-1) CBZ at 1300 h once daily for 3 days (days 26 - 28). The repeated injections of CBZ caused a great fall (64% decrease) in the serum levels of CBZ at 4 h after the final CBZ injection as compared with the case of a single injection of CBZ and resulted in a delay for 5 h the occurrence of LH surge, which is normally observed around 57 h after eCG injection. 4. A significant increase in the activity of microsomal CBZ catabolism by the repeated injections of CBZ was quantitatively verified by the HPLC analysis. But, the activity of CBZ metabolism in the single injected-animals showed almost similar levels to that in the control. 5. The present results demonstrated that a single injection of CBZ blocks the ovulation by inhibiting LH surge but that the failure of the inhibition of ovulation by repeated injections of CBZ is due to a decrease in serum CBZ levels mediated through CBZ-induced hepatic enzyme induction.

3alpha-hydroxysteroid dehydrogenase messenger RNA transcription in the immature rat ovary in response to an ovulatory dose of gonadotropin

The ovulatory process in mammals involves a substantial increase in the metabolism of steroids and eicosanoids in response to a surge in LH or to an injection of hCG into experimental animals. This study provides evidence that the ovulatory stimulus causes induction of the gene for 3alpha-hydroxysteroid dehydrogenase (3alpha-HSD), an enzyme that belongs to several oxidoreductase superfamilies that affect steroid and eicosanoid metabolism. Immature Wistar rats were primed with 10 IU eCG s.c., and 48 h later the 12-h ovulatory process was initiated by 10 IU hCG s.c. Ovarian RNA was extracted at 0, 2, 4, 8, 12, and 24 h after injecting the animals with hCG. The RNA extracts were used for reverse transcription-polymerase chain reaction (PCR) differential display to detect gene expression in the stimulated ovarian tissue. One of the PCR primer sets differentially amplified a cDNA fragment that is 52.3% homologous with a 3alpha-HSD gene in rat liver. Northern analyses revealed that maximum transcription was at 8 h after the animals had been treated with hCG. The Northerns also indicated that the 3alpha-HSD cDNA probe cross-hybridized with as many as six different bands of mRNA on the blots. In situ hybridization localized 3alpha-HSD mRNA in the granulosa and thecal layers of mature follicles and in newly formed corpora lutea at 24 h after the ovulatory stimulus. In conclusion, gene(s) for 3alpha-HSD are transcribed in ovarian follicles in response to an ovulatory dose of gonadotropin. A possible function of the oxidoreductase enzyme that is translated from the 3alpha-HSD mRNA may be to reduce the toxic aldehyde and ketone components of the steroids and eicosanoids that accumulate in the mammalian ovary at the time of ovulation.

Characterization of multiple Chinese hamster carbonyl reductases

Carbonyl reductase (CR) is an enzyme which can catalyze the oxidoreduction of various carbonyl compounds in the presence of NAD(P)H. With the PCR method, using primers carrying the conserved nucleotide sequence among mammalian CRs, we isolated three different cDNAs (CHCR1, CHCR2 and CHCR3) which encode a unique carbonyl reductase from the Chinese hamster. The PCR products of CHCR1 and CHCR2 were clearly isolated with Bpu1102I, BspEI and XmaI restriction enzymes. The nucleotide-sequence of CHCR3 was completely different from those of CHCR1 and CHCR2. The predicted double-wound betaalphabetaalpha-structures of the CHCRs suggests the presence of a typical NADP(+)-binding motif and is similar to the corresponding region of 3alpha,20beta-hydroxysteroid dehydrogenase and mouse lung tetrameric carbonyl reductase. The deduced amino acid sequence of CHCR1 showed a high homology to CHCR2 (>96%) and the other mammalian CRs (>81%). However, CHCR3 showed a high homology to human CBR3 (>86%) and a relatively lower homology to the other CHCRs (<76%). Bacterial recombinant CHCRs showed typical carbonyl reductase activities towards 4-benzoylpyridine, 4-nitrobenzaldehyde and pyridine 4-carboxyaldehyde. These three CRs showed not only 3-keto reductase of steroids, but also 20-keto reductase. However, these CRs did not show any activity of 17-keto reductase activity. Both CHCR1 and CHCR2 have prostaglandin 9-keto reductase and 15-hydroxyprostaglandin dehydrogenase activities towards PGE(2) and PGF(2alpha) from the analyses of enzymatic reaction products. The results of Western blotting and RT-PCR suggest these CHCRs have a tissue-dependent-distribution in the Chinese hamster.

Carbonyl reductase

Carbonyl reductase (secondary-alcohol:NADP(+) oxidoreductase, EC 1.1. 1.184) belongs to the family of short chain dehydrogenases/reductases (SDR). Carbonyl reductases (CBRs) are NADPH-dependent, mostly monomeric, cytosolic enzymes with broad substrate specificity for many endogenous and xenobiotic carbonyl compounds. They catalyze the reduction of endogenous prostaglandins, steroids, and other aliphatic aldehydes and ketones. They also reduce a wide variety of xenobiotic quinones derived from polycyclic aromatic hydrocarbons. CBR reduces the anthracycline anticancer drugs, daunorubicin(dn) and doxorubicin (dox) to their C-13 hydroxy metabolites, changing the pharmacological properties of these drugs. Emerging data on CBRs over the last several years is generating new insights on the potential involvement of CBRs in a variety of cellular and molecular reactions associated with drug metabolism, detoxication, drug resistance, mutagenesis, and carcinogenesis.

Expression of tumor necrosis factor-stimulated gene-6 in the rat ovary in response to an ovulatory dose of gonadotropin

Current evidence supports the hypothesis that the biochemical events of mammalian ovulation are analogous to an acute inflammatory reaction. This study reveals that tumor necrosis factor-stimulated gene-6 (TSG-6), which encodes a member of the superfamily of hyaluronan-binding proteins that is specifically translated in inflammatory reactions, is expressed in ovarian follicles that have been induced to ovulate. Immature Wistar rats were primed with 10 IU equine CG s.c.; and 48 h later, the 12-h ovulatory process was initiated by 10 IU human CG (hCG), s.c.. Ovarian RNA was extracted at 0, 2, 4, 8, 12, and 24 h after the primed animals were injected with hCG. The RNA extracts were used for RT-PCR differential display of amplified complementary DNAs (cDNAs) that represented gene expression in the stimulated ovarian tissue. Northern analysis of one of the differentially amplified cDNAs confirmed that it was part of a gene that was substantially up-regulated at 4-8 h after the ovaries had been stimulated by hCG. Subcloning and sequence analysis revealed that the cDNA matched the gene for TSG-6. In situ hybridization indicated that the TSG-6 messenger RNA was primarily located in the cumulus mass and the antral granulosa cells of large ovarian follicles. In conclusion, the data show that expression of TSG-6 is an integral part of the cascade of inflammatory-like changes that occur in an ovulatory follicle in response to a trophic hormone that couples with luteinizing hormone/hCG receptors.

Expression of regulator of G-protein signaling protein-2 gene in the rat ovary at the time of ovulation

The ovulatory process in mammals begins when an endogenous surge in LH circulates to the ovary and couples with receptors in the plasma membranes of granulosa cells in mature ovarian follicles. This study provides evidence that the ovulatory stimulus includes induction of the gene for regulator of G-protein signaling protein-2 (RGS2). Immature Wistar rats were primed with 10 IU eCG s.c., and 48 h later the 12-h ovulatory process was initiated by 10 IU hCG (a homolog of LH) s.c. Ovarian RNA was extracted at 0, 2, 4, 8, 12, and 24 h after injecting the animals with hCG. The RNA extracts were used for reverse transcription-polymerase chain reaction differential display to detect gene expression in the stimulated ovarian tissue. Two of the amplified cDNAs that were upregulated within 2 h after the ovaries had been stimulated by hCG were homologous to segments of the mouse gene for RGS2. In situ hybridization indicated that the RGS2 mRNA was expressed in the granulosa layer of mature follicles. In conclusion, the gene for RGS2, which is known to regulate membrane signaling pathways, is transcribed in ovarian follicles in response to an ovulatory dose of gonadotropin.

Induction of early growth response protein-1 gene expression in the rat ovary in response to an ovulatory dose of human chorionic gonadotropin

Granulosa cells in a mature ovarian follicle have an abundance of LH/hCG receptors that respond rapidly to an ovulatory surge in gonadotropins. Within minutes, membrane signal transduction sets in motion metabolic changes that lead to follicular rupture. This study provides evidence that the initial ovarian response to such an ovulatory stimulus includes induction of the immediate-early transcription factor gene for early growth response protein-1 (Egr-1). Immature Wistar rats were primed with 10 IU equine CG (eCG), sc, and 48 h later the 12-h ovulatory process was initiated by 10 IU hCG, sc. Ovarian RNA was extracted at 0, 0.5, 1, 2, 4, 8, 12, and 24 h after the primed animals were injected with hCG. The RNA extracts were used for RT-PCR differential display for random detection of gene expression in the stimulated ovarian tissue. Northern analysis of one of the differentially amplified complementary DNAs confirmed that it was part of a gene that was significantly up-regulated within 1 h after the ovaries had been stimulated by hCG. Maximum transcription was at 4 h after hCG, and expression declined to 0 h control levels by 24 h after hCG. Subcloning and sequence analysis revealed that the complementary DNA matched the gene for Egr-1. In situ hybridization indicated that the Egr-1 messenger RNA was in the granulosa layer of mature follicles. Western blotting confirmed the temporal pattern of Egr-1 expression detected by differential display, Northern analysis and in situ hybridization. The Egr-1 protein is approximately 84 kDa. In conclusion, the data show that expression of the zinc finger transcription factor Egr-1 is an early event in the cascade of inflammatory-like changes that occur in an ovulatory follicle in response to a trophic hormone.

Ovarian expression of a disintegrin and metalloproteinase with thrombospondin motifs during ovulation in the gonadotropin-primed immature rat

Mammalian ovulation is a dynamic process that requires degradation of the collagenous connective tissue in the thecal layers of a mature follicle. In this reverse transcription-polymerase chain reaction differential display study, gonadotropin-primed immature rats were used to detect ovarian expression of a relatively new type of disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS-1) that is known to cleave extracellular matrix in acutely inflamed tissues. Immature Wistar rats were primed with 10 IU eCG s. c., and the temporal pattern of expression of the ADAMTS-1 gene was delineated by extracting ovarian RNA at 0, 2, 4, 8, 12, and 24 h after induction of ovulation by injecting the primed animals with 10 IU hCG s.c. The differential display data, Northern analyses, and in situ hybridization micrographs all showed significant up-regulation of ADAMTS-1 gene expression by 8 h after hCG administration. The in situ data indicated that the ADAMTS-1 mRNA was in the granulosa layer of mature follicles. Expression reached a peak at 12 h and remained elevated at 24 h after hCG. ADAMTS-1 gene expression was impaired by the antiprogesterone agent epostane, but this inhibition could be overcome by exogenous progesterone. ADAMTS-1 expression was not affected when ovulation was blocked by treatment of the animals with the anti-eicosanoid agent indomethacin. In conclusion, the temporal pattern of expression of this gene, and its apparent regulation by progesterone, suggests that ADAMTS-1 has a significant role in the inflammatory events of the ovulatory process.