Induction of autophagy in the porcine corpus luteum of pregnancy following anti-androgen treatment

Experimentally induced androgen deficiency during late pregnancy leads to decreased progesterone synthesis in the porcine corpus luteum (CL), which suggested an onset of functional luteolysis. It was shown that luteal regression in mammals involves not only apoptosis but also autophagy. Therefore, this study aimed to examine whether anti-androgen flutamide treatment during late pregnancy in pigs induces apoptosis and/or autophagy within luteal cells. Flutamide (50 mg/kg b.w.) was administered into pregnant gilts between 83 - 89 (GD90F) or 101 - 107 (GD108F) gestational days (GD). CLs were retrieved on day 90 or 108 of pregnancy (n = 3/each group). Detection of apoptosis was performed by TUNEL assay and assessment of cleaved caspase 3 level. Both assays revealed that luteal rate of apoptosis was unaffected by flutamide treatment either in the GD90F or GD108F groups. Moreover, pro-apoptotic protein Bax was downregulated on GD108. The autophagy was examined by expression of two markers, LC3-II and Lamp1. Flutamide led to greater expression of LC3-II protein form in the GD90F and GD108F groups. Likewise, the mRNA and protein levels of Lamp1 were elevated in both flutamide-treated groups. The activation of autophagy is regulated by Beclin 1 and the increased Beclin 1 mRNA and protein expression was found in the GD90F and GD108F groups. Beclin 1 is a Bcl-2-binding protein, thus Beclin1/Bcl-2 interactions were examined using immunoprecipitation. Beclin 1/Bcl-2 complexes were less abundant following flutamide treatment in both flutamide-exposed groups. In summary, we concluded that androgen deficiency induced autophagy by disrupting Beclin 1/Bcl-2 interplay in the porcine CL during pregnancy. The role of autophagy in luteal regression in pigs requires further evaluation.

HCG-mediated activation of mTORC1 signaling plays a crucial role in steroidogenesis in human granulosa lutein cells

Luteinizing hormone/human chorionic gonadotropin stimulates progesterone biosynthesis in the corpus luteum by activating cyclic adenosine monophosphate/protein kinase A cascade. Recent studies have shown that cyclic adenosine monophosphate-mediated activation of protein kinase A interacts with the mammalian target of rapamycin signaling pathways. Furthermore, the use of mammalian target of rapamycin inhibitors for immunosuppression in transplant patients has shown adverse effects in reproductive functions. This study examined whether the mammalian target of rapamycin pathway plays any role in luteinizing hormone-mediated regulation of progesterone production. Human granulosa lutein cells were isolated from follicular aspirates of women undergoing in vitro fertilization. Cells were cultured for 72 h and treated with human chorionic gonadotropin (50 ng/ml) for different time periods with or without pretreatment with mammalian target of rapamycin complex 1 inhibitor, rapamycin, (20 nM) for 1 h. Expression of steroidogenic enzymes, including steroidogenic acute regulatory protein, cholesterol side chain cleavage enzyme, and 3β-hydroxysteroid dehydrogenase type 1 messenger RNA, were examined by real-time polymerase chain reaction after 6 h of human chorionic gonadotropin treatment. Expressions of phospho-ribosomal protein S6 kinase and cholesterol side chain cleavage enzyme were analyzed after 15 min and 24 h of human chorionic gonadotropin treatment, respectively. Progesterone production was analyzed by an enzyme immunoassay kit after human chorionic gonadotropin (50 ng/ml) or forskolin (10 μM) treatment for 24 h. Treatment with human chorionic gonadotropin increased the expression of downstream targets of mammalian target of rapamycin complex 1, as well as cholesterol side chain cleavage enzyme, 3β-hydroxysteroid dehydrogenase type 1 and steroidogenic acute regulatory protein messenger RNAs. These increases were inhibited by rapamycin pretreatment. Increased progesterone production in response to treatment with human chorionic gonadotropin or forskolin was also blocked by rapamycin pretreatment. Our findings support a role for mammalian target of rapamycin complex 1 in regulating steroidogenesis in human granulosa lutein cells.

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 potential role of endoplasmic reticulum stress in development of ovarian hyperstimulation syndrome

Vascular endothelial growth factor A (VEGFA) is crucial for ovarian angiogenesis, but its excess production induces ovarian hyperstimulation syndrome (OHSS). The aim of this study was to determine whether endoplasmic reticulum (ER) stress regulates VEGFA expression in granulosa cells, and whether its activation is involved in OHSS development. The expression of the spliced form of X-box-binding protein 1 [XBP1(S)], induced by ER stress, in cumulus cells from OHSS patients was higher than that in cumulus cells from non-OHSS patients. The ER stress inducer tunicamycin increased human chorionic gonadotropin-induced VEGFA production in human granulosa cells through the induction of XBP1(S), and pretreatment with the ER stress inhibitor tauroursodeoxycholic acid (TUDCA) abrogated the effect of tunicamycin. In OHSS model rats, TUDCA administration prevented the OHSS development, reducing ovarian VEGFA production. Our findings suggest ER stress upregulates hCG-induced VEGFA production in granulosa cells, indicating that ER stress might be involved in OHSS development.

Differential activation of noncanonical SMAD2/SMAD3 signaling by bone morphogenetic proteins causes disproportionate induction of hyaluronan production in immortalized human granulosa cells

Successful fertilization depends upon proper cumulus-oocyte complex (COC) expansion. Synthesized by hyaluronan synthases (HASs), hyaluronan forms the backbone of the COC matrix and plays a critical role in COC expansion. This study investigated the effects and mechanisms of ovarian BMPs on HAS expression and hyaluronan production in human granulosa cells. Treatment with BMP4, BMP6, BMP7 or BMP15 induced differing levels of noncanonical SMAD2/3, but equal levels of canonical SMAD1/5/8, phosphorylation which were mirrored by differing levels of HAS2 up-regulation and hyaluronan production. The effects of BMP4 and BMP15 on HAS2 mRNA were partially reversed by knockdown of SMAD3, and blocked by knockdown of SMAD2+SMAD3 or SMAD4. BMP4-induced SMAD2/3 phosphorylation and HAS2 mRNA up-regulation were mediated by both BMP and activin/transforming growth factor-β type I receptors. Our results suggest differential activation of noncanonical SMAD2/SMAD3 signaling by BMPs causes disproportionate induction of HAS2 expression and hyaluronan production in immortalized human granulosa cells.

The role of adrenergic activation on murine luteal cell viability and progesterone production

Sympathetic innervations exist in mammalian CL. The action of catecholaminergic system on luteal cells has been the focus of a variety of studies. Norepinephrine (NE) increased progesterone secretion of cattle luteal cells by activating β-adrenoceptors. In this study, murine luteal cells were treated with NE and isoprenaline (ISO). We found that NE increased the viability of murine luteal cells and ISO decreased the viability of luteal cells. Both NE and ISO promoted the progesterone production. Nonselective β-adrenergic antagonist, propranolol reversed the effect of ISO on cell viability but did not reverse the effect of NE on cell viability. Propranolol blocked the influence of NE and ISO on progesterone production. These results reveal that the increase of luteal cell viability induced by NE is not dependent on β-adrenergic activation. α-Adrenergic activation possibly contributes to it. Both NE and ISO increased progesterone production through activating β-adrenergic receptor. Further study showed that CyclinD2 is involved in the increase of luteal cell induced by NE. 3β-Hydroxysteroid dehydrogenase, LHR, steroidogenic acute regulatory protein (StAR), and PGF2α contribute to the progesterone production induced by NE and ISO.

Follicle-stimulating hormone potentiates the steroidogenic activity of chorionic gonadotropin and the anti-apoptotic activity of luteinizing hormone in human granulosa-lutein cells in vitro

Luteinizing hormone (LH) and choriogonadotropin (hCG) are glycoprotein hormones regulating ovarian function and pregnancy, respectively. Since these molecules act on the same receptor (LHCGR), they were traditionally assumed as equivalent in assisted reproduction techniques (ART), although differences between LH and hCG were demonstrated at molecular and physiological level. In this study, we demonstrated for the first time that co-treatment with a follicle-stimulating hormone (FSH) dose in the ART therapeutic range potentiates different LH- and hCG-dependent responses in vitro, measured in terms of cAMP, phospho-CREB, -ERK1/2 and -AKT activation, gene expression, progesterone and estradiol production in human granulosa-lutein cells (hGLC). We show that in the presence of FSH, hCG biopotency is about 5-fold increased, in the presence of FSH, in terms of cAMP activation. Accordingly, CREB phosphorylation and steroid production is increased under hCG and FSH co-treatment. LH effects, evaluated as steroidogenic cAMP/PKA pathway activation, do not change in the presence of FSH, which, however, increases LH-dependent ERK1/2 and AKT, but not CREB phosphorylation, resulting in anti-apoptotic effects. The different modulatory activity of FSH on LH and hCG action in vitro corresponds to their different physiological functions, reflecting proliferative effects exerted by LH during the follicular phase and before trophoblast development, and the high steroidogenic potential of hCG requested to sustain pregnancy from the luteal phase onwards.

BMP4 and BMP7 Suppress StAR and Progesterone Production via ALK3 and SMAD1/5/8-SMAD4 in Human Granulosa-Lutein Cells

Adequate production of progesterone by the corpus luteum is critical to the successful establishment of pregnancy. In animal models, bone morphogenetic protein (BMP) 4 and BMP7 have been shown to suppress either basal or gonadotropin-induced progesterone production, depending on the species examined. However, the effects of BMP4 and BMP7 on progesterone production in human granulosa cells are unknown. In the present study, we used immortalized (SVOG) and primary human granulosa-lutein cells to investigate the effects of BMP4 and BMP7 on steroidogenic acute regulatory protein (StAR) expression and progesterone production and to examine the underlying molecular mechanism. Treatment of primary and immortalized human granulosa cells with recombinant BMP4 or BMP7 decreased StAR expression and progesterone accumulation. In SVOG cells, the suppressive effects of BMP4 and BMP7 on StAR expression were blocked by pretreatment with inhibitors of activin receptor-like kinase (ALK)2/3/6 (dorsomorphin) or ALK2/3 (DMH1) but not ALK4/5/7 (SB-431542). Moreover, small interfering RNA-mediated depletion of ALK3, but not ALK2 or ALK6, reversed the effects of BMP4 and BMP7 on StAR expression. Likewise, BMP4- and BMP7-induced phosphorylation of SMAD 1/5/8 was reversed by treatment with DMH1 or small interfering RNA targeting ALK3. Knockdown of SMAD4, the essential common SMAD for BMP/TGF-β signaling, abolished the effects of BMP4 and BMP7 on StAR expression. Our results suggest that BMP4 and BMP7 down-regulate StAR and progesterone production via ALK3 and SMAD1/5/8-SMAD4 signaling in human granulosa-lutein cells.

Effects of 2,2',4,4'-tetrabromodiphenyl ether (BDE47) on the enzymes of phase I (CYP2B1/2) and phase II (SULT1A and COMT) metabolism, and differences in the action of parent BDE-47 and its hydroxylated metabolites, 5-OH-BDE-47 and 6-OH-BDE47, on steroid secretion by luteal cells

In this study we determined the effects of BDE-47 on the expression and activity of phase I (CYP2B1/2) and phase II (SULT1A and COMT) enzymes, and assessed the actions of BDE-47 and its metabolites on luteal steroidogenesis. Luteal cells collected during early (ELP), middle (MLP) and late (LLP) luteal phase were exposed to BDE-47 (0.5, 25, and 50ng/ml) or metabolites (2.5, 5 and 25ng/ml). BDE-47 decreased CYP2B1/2 activity and expression but had no effect on SULT1A or COMT. BDE-47 exerted a stimulatory action on estrogen secretion in MLP and an inhibitory in LLP, but had no effect on progesterone secretion. 5-OH-BDE-47 and 6-OH-BDE-47 decreased progesterone, but had no effect on estrogen secretion.

CONCLUSIONS

The inhibitory effect of BDE-47 on CYP2B1/2 suggests the possibility of BDE-47 accumulation in the corpus luteum; by affecting steroid secretion and steroidogenesis enzymes, BDE-47 and its metabolites can be responsible for shortening luteal phase.

Recombinant BMP4 and BMP7 increase activin A production by up-regulating inhibin βA subunit and furin expression in human granulosa-lutein cells

CONTEXT

Granulosa cell-derived activins play important roles in the regulation of ovarian functions. To date, there is limited information pertaining to the intracellular regulation, assembly, and secretion of endogenous activin A in human granulosa cells.

OBJECTIVE

The aim of this study was to examine the effects of BMP4 and BMP7 on furin expression and activin A production as well as the underlying mechanisms of action in human granulosa cells.

DESIGN

An established immortalized human granulosa cell line (SVOG) and primary granulosa-lutein cells were used as study models. Expression of inhibin subunits and furin as well as activin A accumulation were examined after exposure to recombinant human BMP4 or BMP7. A BMP type I receptor inhibitor (dorsomorphin), a furin inhibitor (Decanoyl-Arg-Val-Lys-Arg-chloromethylketone), and small interfering RNAs targeting SMAD4 and furin were used to verify the specificity of the effects and investigate potential mechanisms.

SETTING

The study was conducted in an academic center.

MAIN OUTCOME MEASURES

Specific mRNA and protein levels were examined using real time qPCR and Western blot. Activin A levels were measured using enzyme immunoassay.

RESULTS

Treatment with bone morphogenetic protein (BMP) 4 and BMP7 significantly increased furin mRNA and protein, inhibin βA mRNA, and activin A accumulation. Pre-treatment with dorsomorphin or SMAD4 knockdown reversed the stimulatory effects of BMP4 and BMP7 on furin and inhibin βA expression. In addition, furin knockdown or pre-treatment with a furin inhibitor attenuated the BMP4- and BMP7-induced accumulation of activin A.

CONCLUSION

Recombinant BMP4 and BMP7 increase the production of bioactive mature activin A by up-regulating both the production and proteolytic processing of inhibin βA subunit in human granulosa cells. The enhancement of inhibin βA subunit processing is attributable to a SMAD-dependent up-regulation of its proprotein convertase, furin. These findings provide a potential mechanism by which theca cells can regulate neighboring granulosa cells in the ovary.

Effects of recombinant activins on steroidogenesis in human granulosa-lutein cells

CONTEXT

Exerting a broad range of biological effects in various tissues, activins are homo- or heterodimers of activin/inhibin β-subunits (βA, βB, βC, and βE in humans). Although activins A (βAβA), B (βBβB), AB (βAβB), and AC (βAβC) have been demonstrated in the female reproductive system, little is known about their individual functions in the ovary.

OBJECTIVE

To investigate the biological roles and activities of activins in regulating steroidogenesis in human granulosa cells.

DESIGN

Human granulosa-lutein cells obtained from 32 patients undergoing in vitro fertilization were used to investigate the effects of activin A, B, AB, and AC on the expression of steroidogenic enzymes and steroid production.

SETTING

An academic research center.

MAIN OUTCOME MEASURES

mRNA and protein levels were examined by reverse transcription quantitative real-time PCR and Western blot analysis, respectively. The production of estradiol and progesterone was measured by enzyme immunoassay.

RESULTS

P450 aromatase, FSH receptor, and estradiol levels were increased, whereas steroidogenic acute regulatory protein (StAR), LH receptor, and progesterone levels were decreased after treatment with activin A, B, and AB, but not activin AC. FSH or LH induced the production of aromatase/estradiol and StAR/progesterone; however, pretreatment with activin A, B, or AB enhanced the effects of gonadotropins on aromatase/estradiol, but suppressed their effects on StAR/progesterone. Treatment with activin A, B, or AB induced the phosphorylation of SMA- and MAD-related proteins (SMAD2 and 3), whereas activin AC had no such effects. Furthermore, co-culture of activin AC (1-100 ng/mL) with activin A (25 ng/mL) did not alter the effects of activin A on P450 aromatase or StAR mRNA levels.

CONCLUSION

Activin A, B, and AB have similar effects on steroidogenesis in human granulosa cells. In contrast, activin AC is not biologically active and does not act as a competitive antagonist.

Adverse influence of coumestrol on secretory function of bovine luteal cells in the first trimester of pregnancy

Coumestrol is one of a few biologically active substances present in leguminous plants, which are widely used as fodder for ruminants. Depending on the doses, coumestrol acts on the reproductive processes as an estrogen-like factor or antiestrogen to evoke a decrease in ovulation frequency, elongation of estrous cycle duration. The aim of the current investigations was to study the influence of coumestrol on secretory function of luteal cells obtained from first trimester of pregnant cows. Luteal cells (2.5 × 10(5) /mL) from 3rd to 5th, 6th to 8th, and 9th to 12th week of pregnancy were preincubated for 24 h and incubated with coumestrol (1 × 10(-6) M) for successive 48 h and the medium concentrations of progesterone (P4), oxytocin (OT), prostaglandin (PG) E2 and F2α were determined. Moreover, the expression of mRNA for neurophysin-I/oxytocin (NP-I/OT; precursor of OT) and peptidyl-glycine-α-amidating mono-oxygenase (PGA, an enzyme responsible for post-translational OT synthesis) was determined after 8 h of treatment. Coumestrol did not affect P4 secretion but increased the secretion of OT from the cells collected at all stages of gestation studied. Hence, the ratio of P4 to OT was markedly decreased. Simultaneously, coumestrol increased the expression of NP-I/OT mRNA during 9th to 12th weeks of pregnancy, and mRNA for PGA during 3rd to 5th and 9th to 12th weeks of gestation. Furthermore, coumestrol decreased PGE2 secretion from luteal cells in all studied stages of pregnancy, while it affected PGF2α metabolite (PGFM) concentration only from week 3 to 5 of pregnancy. Obtained results suggest that coumestrol impairs secretory function of the corpus luteum (CL) and this way it can affect the maintenance of pregnancy in the cow.

Endocrine disruptors and human corpus luteum: in vitro effects of phenols on luteal cells function

Endocrine disruptors are well known to impair fertility. The aim of the present study was to investigate the effects of bisphenol A (BPA) and nonylphenol (p-NP) on human luteal function in vitro. In particular, in luteal cells isolated from 21 human corpora lutea progesterone, prostaglandin (PG) F2α, PGE2 and vascular endothelial growth factor (VEGF) release, as well as VEGF expression were evaluated. BPA and p-NP negatively affected both luteal steroidogenesis and luteotrophic/ luteolytic factors balance, without influencing VEGF mRNA expression. Actually, BPA and p-NP impaired human luteal cells function in vitro, underlining the already suggested correlation between phenols and reproductive failure.

Estrous cycle-dependent changes of Fas expression in the bovine corpus luteum: influence of keratin 8/18 intermediate filaments and cytokines

BACKGROUND

Fas expression and Fas-induced apoptosis are mechanisms attributed to the selective destruction of cells of the corpus luteum (CL) during luteal regression. In certain cell-types, sensitivity to these death-inducing mechanisms is due to the loss or cleavage of keratin-containing intermediate filaments. Specifically, keratin 8/18 (K8/K18) filaments are hypothesized to influence cell death in part by regulating Fas expression at the cell surface.

METHODS

Here, Fas expression on bovine luteal cells was quantified by flow cytometry during the early (Day 5, postovulation) and late stages (Days 16-18, postovulation) of CL function, and the relationship between Fas expression, K8/K18 filament expression and cytokine-induced cell death in vitro was evaluated.

RESULTS

Both total and cell surface expression of Fas on luteal cells was greater for early versus late stage bovine CL (89% vs. 44% of cells for total Fas; 65% vs.18% of cells for cell surface Fas; respectively, P<0.05, n=6-9 CL/stage). A similar increase in the steady-state concentration of mRNA for Fas, as detected by quantitative real-time polymerase chain reaction, however, was not observed. Transient disruption of K8/K18 filaments in the luteal cells with acrylamide (5 mM), however, had no effect on the surface expression of Fas (P>0.05, n=4 CL/stage), despite evidence these conditions increased Fas expression on HepG2 cells (P<0.05, n= 3 expts). Exposure of the luteal cells to cytokines induced cell death (P<0.05) as expected, but there was no effect of K8/K18 filament disruption by acrylamide (P>0.05) or stage of CL (P>0.05, n= 4 CL/stage) on this outcome.

CONCLUSION

In conclusion, we rejected our null hypothesis that the cell surface expression of Fas does not differ between luteal cells of early and late stage CL. The results also did not support the idea that K8/K18 filaments influence the expression of Fas on the surface of bovine luteal cells. Potential downstream effects of these filaments on death signaling, however, remain a possibility. Importantly, the elevated expression of Fas observed on cells of early stage bovine CL compared to late stage bovine CL raises a provocative question concerning the physiological role(s) of Fas in the corpus luteum, particularly during early luteal development.

Roles of prostaglandin F2alpha and hydrogen peroxide in the regulation of Copper/Zinc superoxide dismutase in bovine corpus luteum and luteal endothelial cells

BACKGROUND

Prostaglandin F2alpha (PGF) induces luteolysis in cow by inducing a rapid reduction in progesterone production (functional luteolysis) followed by tissue degeneration (structural luteolysis). However the mechanisms of action of PGF remain unclear. Reactive oxygen species (ROS) play important roles in regulating the luteolytic action of PGF. The local concentration of ROS is controlled by superoxide dismutase (SOD), the main enzyme involved in the control of intraluteal ROS. Thus SOD seems to be involved in luteolysis process induced by PGF in cow.

METHODS

To determine the dynamic relationship between PGF and ROS in bovine corpus luteum (CL) during luteolysis, we determined the time-dependent change of Copper/Zinc SOD (SOD1) in CL tissues after PGF treatment in vivo. We also investigated whether PGF and hydrogen peroxide (H2O2) modulates SOD1 expression and SOD activity in cultured bovine luteal endothelial cells (LECs) in vitro.

RESULTS

Following administration of a luteolytic dose of PGF analogue (0 h) to cows at the mid-luteal stage, the expression of SOD1 mRNA and protein, and total SOD activity in CL tissues increased between 0.5 and 2 h, but fell below the initial (0 h) level at 24 h post-treatment. In cultured LECs, the expression of SOD1 mRNA was stimulated by PGF (1-10 microM) and H2O2 (10-100 microM) at 2 h (P<0.05). PGF and H2O2 increased SOD1 protein expression and total SOD activity at 2 h (P<0.05), whereas PGF and H2O2 inhibited SOD1 protein expressions and total SOD activity at 24 h (P<0.05). In addition, H2O2 stimulated PGF biosynthesis at 2 and 24 h in bovine LECs. Overall results indicate that, SOD is regulated by PGF and ROS in bovine LECs. SOD may play a role in controlling intraluteal PGF and ROS action during functional and structural luteolysis in cows.

Hyperglycosylated human chorionic gonadotropin does not increase progesterone production by luteinized granulosa cells

CONTEXT

Trophoblast-derived human chorionic gonadotropin (hCG) promotes corpus luteum progesterone (P4) production, and wide ranges of serum P4 levels are noted in various pregnancy outcomes, despite similar hCG concentrations. There are five unique biologically active hCG variants in human pregnancy urine, and previous studies of P4 production in response to hCG have used only preparations containing all isoforms. Understanding exactly which hCG variant is primarily responsible for stimulating corpus luteum steroidogenesis may have great clinical and diagnostic implications, including in the setting of ectopic pregnancy.

OBJECTIVE

Our objective was to delineate the role of the standard and hyperglycosylated (H)-hCG isoforms in stimulating P4 production by luteinized granulosa cells.

DESIGN AND SETTING

Cell culture, ELISA, and fluorometric-based protein assays were done at Duke University Medical Center.

PATIENTS

Patients were anonymous oocyte donors.

INTERVENTION

Cultured luteinized granulosa cells were treated with 0.25, 0.5, and 1.0 ng/ml total hCG, which contains all isoforms, purified standard hCG (37.1 kDa), and purified H-hCG (42.8 kDa).

MAIN OUTCOME MEASURE

P4 produced per total cellular protein (nanograms per microgram) was measured via ELISA and fluorometric protein determination kits.

RESULTS

Both total hCG (P = 0.0003) and purified standard hCG (P < 0.0001) stimulated a dose-dependent increase in P4 production. Purified H-hCG did not change the P4 produced per total cellular protein response (P value not significant).

CONCLUSIONS

Standard hCG stimulated P4 production by cultured granulosa cells and likely supports corpus luteum function via interactions with the LH/hCG receptor. In contrast, H-hCG did not increase P4 production, which indicates a nonsteroidogenic role for this protein during early gestation.

The relationship between follicle development and progesterone receptor membrane component-1 expression in women undergoing in vitro fertilization

OBJECTIVE

To determine the relationship between progesterone receptor membrane component-1 (PGRMC1) expression and the outcome of IVF treatment.

DESIGN

A prospective study in which PGRMC1 messenger RNA (mRNA) levels, methylation status of the Pgrmc1 promoter, and the presence of point mutations within Pgrmc1 were obtained from granulosa (GC)/luteal cells of women undergoing controlled ovarian hyperstimulation (COH).

SETTING

Fertility center/basic science laboratory.

PATIENT(S)

Eighty-five patients undergoing IVF treatment and 10 women who were undergoing COH for the purpose of oocyte donation were included in this study.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

The PGRMC1 measurements were correlated with clinical outcomes, such as number of follicles, number of retrieved oocytes, and ongoing pregnancy rates (PR).

RESULT(S)

The PGRMC1 mRNA levels within GC/luteal cells of 18% of IVF patients were >2.25-fold higher than those of oocyte donors. Individuals with elevated PGRMC1 mRNA levels had 30% fewer large follicles and fewer oocytes retrieved. The elevated PGRMC1 mRNA levels were associated with an increase in the methylation of Pgrmc1 promoter.

CONCLUSION(S)

In patients with elevated PGRMC1 mRNA levels, gonadotropin-induced follicle development is attenuated, although sufficient numbers of follicles develop to allow for ET and subsequent pregnancy.

Stimulation of tube formation mediated through the prostaglandin EP2 receptor in rat luteal endothelial cells

To explore the role of prostaglandin E(2) (PGE(2)) in angiogenesis in the developing corpus luteum, luteal microvascular endothelial-like cells (luteal ECs) were prepared from highly luteinizing ovaries of rats using the percoll density gradient method. The cells abundantly expressed the mRNAs of the endothelial markers CD31 (PECAM-1) and responded to the vascular endothelial growth factor (VEGF) to form in vitro tube structures on Matrigel. Cyclooxygenase (COX) inhibitors significantly suppressed tube formation in luteal ECs, whereas PGE(2) counteracted the COX inhibitor-induced blockage. PGE(2)-induced tube formation was blocked by a cyclic AMP-dependent protein kinase A (PKA) inhibitor, H89. The antagonist against the PGE receptor type 2 (EP2 receptor), AH6809, completely inhibited PGE(2)-induced tube formation and partly suppressed the VEGF-induced tube formation but did not attenuate PGE(2)-induced phosphorylation of both AKT kinase and extracellular signal-regulated kinase 1/2. VEGF significantly enhanced the expression of COX-2 mRNAs detected by real-time RT-PCR and PGE(2) secretion into the media measured by ELISA in luteal ECs. In turn, PGE(2) stimulated VEGF expression. In vitro co-culture of luteal ECs with steroidogenic luteal cells (SLCs) promoted tube formation. Pre-treatment of SLCs with VEGF further enhanced tube formation of ECs, and this effect was blocked by the COX-2 inhibitor. This stimulatory effect was inhibited by treatment with AH6809. These data indicate that PGE(2) exerts a direct stimulatory effect on tube formation mainly via the EP2 receptor/PKA signaling in luteal ECs. Our results suggest the possibility that the endogenous PGE(2) that is produced from luteinizing follicular cells as well as ECs may stimulate luteal angiogenesis.

Activation of PI3K/mTOR signaling pathway contributes to induction of vascular endothelial growth factor by hCG in bovine developing luteal cells

We recently reported that HIF-1α plays a critical role in the regulation of vascular endothelial growth factor (VEGF) expression in the developing letual cells (LCs) and VEGF-dependent angiogenesis is essential for normal luteal development. Although it is believed that hypoxia is the primary inducer of VEGF, recent reports have also shown that human chorionic gonadotrophin (hCG) up-regulates VEGF expression in developing corpus luteum (CL). Therefore the present study was designed to test the induced effects of hCG on the expression of VEGF and HIF-1α in LCs under normoxic and hypoxic conditions. In addition, we also investigated whether the signaling pathways such as phosphatidylinositol 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) and mitogen-activated protein kinase (MAPK) are involved in hCG-induced VEGF in LCs. A significant increase of VEGF mRNA was found in LCs treated with hCG, which was consistent with the changes of HIF-1α protein, even under hypoxic conditions. However, there was no obvious changes of HIF-1α mRNA in hCG-treated LCs between normoxic and hypoxic conditions, indicating hCG induces VEGF expression by increasing transcription of HIF-1α, while hypoxia mainly increases HIF-1α protein stability. When LCs were pretreated with inhibitors, we found that the PI3K/mTOR signaling pathway is required for HIF-1α and VEGF expression induced by hCG, while the MAPK pathway is not required. Together, these results suggest that activation of IP3K/mTOR signaling pathway contributes to the induction of VEGF and HIF-1α in hCG-treated LCs. To our knowledge this will provide a new insight into the important mechanism of hCG/LH-induced VEGF-dependent angiogenesis in the bovine ovary.

Expression of vascular endothelial growth factor A during ligand-induced down-regulation of luteinizing hormone receptor in the ovary

Vascular endothelial growth factor A (VEGF-A) is one of the most important regulators of ovarian angiogenesis. In this study, we examined the temporal relationship between VEGF-A and luteinizing hormone receptor (LHR) mRNA expression during ligand-induced down-regulation of LHR. Immature female rats were treated with pregnant mare's serum gonadotropin followed by 25 IU hCG 56 h later (day 0). On day 5, treatment with hCG (50 IU) to down-regulate LHR showed a temporal decrease in VEGF-A mRNA and protein levels in parallel with decreasing LHR mRNA. This effect was specific since the expression of CYP11A1 mRNA showed no decline. Examination of VEGF-A mRNA expression, using in situ hybridization histochemistry with (35)S-labeled antisense VEGF-A mRNA probe, showed intense signal in the corpora lutea on day 5. Treatment with 50 IU hCG to down-regulate LHR mRNA showed a decline in the intensity of VEGF-A mRNA in the corpora lutea. VEGF-A mRNA expression returned to control level 53 h later when the expression of LHR mRNA also recovered. These results show that the transient down-regulation of VEGF-A mRNA and protein closely parallels the ligand-induced down-regulation of LHR mRNA. The present study establishes a close association between VEGF-A and LHR mRNA expression, suggesting the possibility that VEGF-A-induced vascularization of the ovary is dictated by the expression of LHR and this might play a regulatory role in ovarian physiology.

Growth differentiation factor 9 reverses activin A suppression of steroidogenic acute regulatory protein expression and progesterone production in human granulosa-lutein cells

BACKGROUND

We have reported that growth differentiation factor 9 (GDF9) can enhance activin A (β(A)β(A))-induced inhibin B (αβ(B)) secretion in human granulosa-lutein (hGL) cells, but its effects on steroidogenic acute regulatory protein (StAR), ovarian steroidogenic enzymes, and progesterone production are unknown. We undertook this study to further evaluate GDF9 in this regard.

METHODS

hGL cells from women undergoing in vitro fertilization treatment were cultured with and without small interfering RNA (siRNA) transfection targeted at inhibin α-subunit or GDF9 before treatment with GDF9, activin A, FSH, or combinations. We compared StAR, P450 side-chain cleavage enzyme, and 3β-hydroxysteroid dehydrogenase expression in hGL cells and progesterone levels in culture media after these treatments. mRNA, protein, and hormone levels were assessed with real-time RT-PCR, immunoblotting, and ELISA, respectively. Data were analyzed by ANOVA followed by Tukey's test.

RESULTS

Activin A alone reduced basal and FSH-induced progesterone production by decreasing the expression of StAR protein, which regulates the rate-limiting step in steroidogenesis but not P450 side-chain cleavage enzyme and 3β-hydroxysteroid dehydrogenase. GDF9 attenuated these activin A effects on StAR and progesterone. After transfection of α-subunit siRNA, activin A level increased (P < 0.001), whereas basal and activin A-induced inhibin B levels (with and without GDF9) decreased. Furthermore, the effects of GDF9 in reversing activin A suppression of progesterone production were attenuated (P < 0.001). Transfection of GDF9 siRNA decreased GDF9 as expected and led to lower StAR expression and progesterone secretion than those observed with activin A treatment alone.

CONCLUSION

GDF9 attenuates the suppressive effects of activin A on StAR expression and progesterone production by increasing the expression of inhibin B, which acts as an activin A competitor.

Human chorionic gonadotropin up-regulates expression of myeloid cell leukemia-1 protein in human granulosa-lutein cells: implication of corpus luteum rescue and ovarian hyperstimulation syndrome

CONTEXT

The corpus luteum is a dynamic endocrine structure with periodic development and regression during menstrual cycles. Its lifespan can be prolonged by human chorionic gonadotropin (hCG). However, the signal mechanisms of this phenomenon remain unclear.

OBJECTIVE

Our objective was to investigate the molecular mechanisms of hCG in the maintenance of the viability of granulosa-lutein cells.

DESIGN

Granulosa-lutein cells were obtained from women undergoing in vitro fertilization. We examined the effects of hCG on the survival of cultured granulosa-lutein cells. The signal pathway inducing antiapoptotic protein was investigated.

RESULTS

hCG enhanced viability of granulosa-lutein cells through antiapoptosis but not proliferation, because the apoptotic marker of annexin V was decreased, but the proliferative markers of Ki67 and proliferating cell nuclear antigen were not increased. Myeloid cell leukemia-1 (Mcl-1) protein, but not B-cell lymphoma protein-2 or B-cell lymphoma protein-xL, was significantly induced by hCG and LH. The granulosa-lutein cells secreted vascular endothelial growth factor that induced endothelial permeability. Mcl-1 small interfering RNA increased DNA fragmentation and diminished the antiapoptotic effect of hCG. hCG induced Mcl-1 expression through the LH/hCG receptor, adenylate cyclase, protein kinase A, and cAMP response element-binding protein signal pathway. Flavopiridol inhibited Mcl-1 production, released cytochrome c, and induced apoptosis of granulosa-lutein cells.

CONCLUSIONS

We first demonstrate that hCG prevents apoptosis of granulosa-lutein cells through the induction of Mcl-1 protein via the LH/hCG receptor and a cAMP response element-binding protein-dependent pathway. We may have found the molecular mechanism for luteal rescue during early pregnancy. Mcl-1 prevents apoptosis and increases cell viability but not proliferation as mechanisms for luteal rescue. Mcl-1 is a key molecule of hCG signaling.

Effect of phthalate esters on the secretion of prostaglandins (F2alpha and E2) and oxytocin in cultured bovine ovarian and endometrial cells

The influence of phthalate esters di-2-ethylhexyl phthalate (DEHP) and mono-2-ethylhexyl phthalate (MEHP) on uterine prostaglandin (PGF2alpha and PGE2) and ovarian oxytocin secretion was investigated. Endometrial, granulosa, and luteal cells from cows on days 8-12 of the estrous cycle were treated with DEHP or MEHP (0.1, 1, or 10 ng/mL). We found that DEHP and MEHP stimulated (P < 0.05) secretion of PGF2alpha and inhibited (P < 0.001) secretion of PGE2 from endometrial cells. The ratio of PGF2alpha to PGE2 was markedly altered. The endocrine disrupting chemicals also enhanced secretion of oxytocin (P < 0.05) from ovarian cells. Our results indicated that DEHP and its metabolite MEHP could affect the process of the estrous cycle by impairing secretion of prostaglandin from the uterus and oxytocin from the ovary.

Luteinizing hormone stimulates mammalian target of rapamycin signaling in bovine luteal cells via pathways independent of AKT and mitogen-activated protein kinase: modulation of glycogen synthase kinase 3 and AMP-activated protein kinase

LH stimulates the production of cAMP in luteal cells, which leads to the production of progesterone, a hormone critical for the maintenance of pregnancy. The mammalian target of rapamycin (MTOR) signaling cascade has recently been examined in ovarian follicles where it regulates granulosa cell proliferation and differentiation. This study examined the actions of LH on the regulation and possible role of the MTOR signaling pathway in primary cultures of bovine corpus luteum cells. Herein, we demonstrate that activation of the LH receptor stimulates the phosphorylation of the MTOR substrates ribosomal protein S6 kinase 1 (S6K1) and eukaryotic translation initiation factor 4E binding protein 1. The actions of LH were mimicked by forskolin and 8-bromo-cAMP. LH did not increase AKT or MAPK1/3 phosphorylation. Studies with pathway-specific inhibitors demonstrated that the MAPK kinase 1 (MAP2K1)/MAPK or phosphatidylinositol 3-kinase/AKT signaling pathways were not required for LH-stimulated MTOR/S6K1 activity. However, LH decreased the activity of glycogen synthase kinase 3Beta (GSK3B) and AMP-activated protein kinase (AMPK). The actions of LH on MTOR/S6K1 were mimicked by agents that modulated GSK3B and AMPK activity. The ability of LH to stimulate progesterone secretion was not prevented by rapamycin, a MTOR inhibitor. In contrast, activation of AMPK inhibited LH-stimulated MTOR/S6K1 signaling and progesterone secretion. In summary, the LH receptor stimulates a unique series of intracellular signals to activate MTOR/S6K1 signaling. Furthermore, LH-directed changes in AMPK and GSK3B phosphorylation appear to exert a greater impact on progesterone synthesis in the corpus luteum than rapamycin-sensitive MTOR-mediated events.

The relationship between the production and the anti-gonadotrophic action of prostaglandin F 2 alpha in luteal cells from the marmoset monkey (Callithrix jacchus) in the early and mid-luteal phase

To address the potential luteolytic role for prostaglandin F(2 alpha) (PGF(2 alpha)) in the corpus luteum of the common marmoset monkey (Callithrix jacchus), the ability of marmoset luteal cells, maintained in monolayer culture, to produce PGF(2 alpha) was determined in vitro in the presence and absence of human chorionic gonadotrophin (hCG) and other established pharmacological modulators of PGF(2 alpha) synthesis. We also assessed the effects of the PGF(2 alpha) analogue, cloprostenol, on progesterone output from luteal cells isolated in the early luteal phase versus the mid-luteal phase (days 3 and 14 post ovulation, respectively). Cloprostenol had no effect on progesterone output from luteal cells isolated on day 3 of the luteal phase, whereas it significantly inhibited both basal and hCG-stimulated progesterone synthesis by day 14 luteal cells during the culture period 48-72 h (P<0.001). Intra-luteal PGF(2 alpha) concentrations were 5-fold higher in luteal cells isolated in the early luteal phase than in mid-luteal phase cells (16.5+/-3.5 versus 3.5+/-0.6 pmol/10(5) cells). While PGF(2 alpha) production was unaffected by hCG in vitro, it was decreased by indomethacin (1000 ng/ml) (P<0.05) and stimulated by the calcium ionophore A23187 (10 micromol/l) (P<0.05) in luteal cells from both stages of the luteal phase. Phospholipase A(2) did not influence PGF(2 alpha) production by day 3 luteal cells whereas at 10 IU/ml, it significantly stimulated PGF(2 alpha) production by day 14 luteal cells (P<0.05). Hence, the timing of luteolysis in the common marmoset monkey appears to involve changes in both the luteal cell response to and production of PGF(2 alpha).