Cortisol is a suppressor of apoptosis in bovine corpus luteum

Progesterone modulates HSD11B1-mediated cortisol production in luteinized bovine granulosa cells

Progesterone (P4) and cortisol production increase in luteinized granulosa cells (LGCs) during the periovulatory period, but their interaction is not well established. Therefore, we investigated their interaction in cultured bovine LGCs. Granulosa cells were collected from follicles of 2-5 mm in diameter and cultured in DMEM/F-12 supplemented with 10% fetal calf serum for up to 14 days. P4 production and the expression of steroidogenic acute regulatory protein (STAR), cholesterol side-chain cleavage enzyme (CYP11A1), and 3β-hydroxysteroid dehydrogenase type 1 (HSD3B1) rapidly increased until day 10 and remained high thereafter. No de novo production of cortisol from P4 was detected during the culture period. The expression of 11β-hydroxysteroid dehydrogenase type 1 (HSD11B1), which converts cortisone to cortisol, increased dramatically on day two, decreased until day 8, and remained relatively constant. To investigate how P4 and cortisol influence each other's production, LGCs were treated with trilostane (a P4 synthesis inhibitor), nomegestrol acetate (NA, a synthetic progestogen), P4, and/or cortisol for 24 h on days 6 and 12 of culture. Trilostane suppressed P4 and STAR expression while elevating HSD11B1 and HSD3B1 expression and cortisol production. Concomitant treatment with NA or P4 dose-dependently decreased cortisol production and HSD11B1 and HSD3B1 expression but elevated STAR expression in both days 6 and 12. Conversely, cortisol treatment increased HSD11B1 and HSD3B1 expression and decreased STAR expression without influencing P4 production. These results indicate that progestogens suppress cortisol production by modulating HSD11B1 expression and that progestogens and cortisol differentially regulate STAR, HSD3B1, and HSD11B1 expression in bovine LGCs.

Glucocorticoids and Their Receptor Isoforms: Roles in Female Reproduction, Pregnancy, and Foetal Development

Alterations in the hypothalamic-pituitary-adrenal (HPA) axis and associated changes in circulating levels of glucocorticoids are integral to an organism's response to stressful stimuli. Glucocorticoids acting via glucocorticoid receptors (GRs) play a role in fertility, reproduction, placental function, and foetal development. GRs are ubiquitously expressed throughout the female reproductive system and regulate normal reproductive function. Stress-induced glucocorticoids have been shown to inhibit reproduction and affect female gonadal function by suppressing the hypothalamic-pituitary-gonadal (HPG) axis at each level. Furthermore, during pregnancy, a mother's exposure to prenatal stress or external glucocorticoids can result in long-lasting alterations to the foetal HPA and neuroendocrine function. Several GR isoforms generated via alternative splicing or translation initiation from the GR gene have been identified in the mammalian ovary and uterus. The GR isoforms identified include the splice variants, GRα and GRβ, and GRγ and GR-P. Glucocorticoids can exert both stimulatory and inhibitory effects and both pro- and anti-inflammatory functions in the ovary, in vitro. In the placenta, thirteen GR isoforms have been identified in humans, guinea pigs, sheep, rats, and mice, indicating they are conserved across species and may be important in mediating a differential response to stress. Distinctive responses to glucocorticoids, differential birth outcomes in pregnancy complications, and sex-based variations in the response to stress could all potentially be dependent on a particular GR expression pattern. This comprehensive review provides an overview of the structure and function of the GR in relation to female fertility and reproduction and discusses the changes in the GR and glucocorticoid signalling during pregnancy. To generate this overview, an extensive non-systematic literature search was conducted across multiple databases, including PubMed, Web of Science, and Google Scholar, with a focus on original research articles, meta-analyses, and previous review papers addressing the subject. This review integrates the current understanding of GR variants and their roles in glucocorticoid signalling, reproduction, placental function, and foetal growth.

Morphologic, Steroidogenic, and Transcriptomic Assessment of the Corpus Luteum in Holstein Cows after Spontaneous or Hormone-Induced Ovulation

There is evidence that replacing the gonadotropin-releasing hormone (GnRH) with porcine luteinizing hormone (pLH) to synchronize ovulation prior to artificial insemination (AI) increased pregnancy per AI in dairy cows without affecting blood progesterone (P₄) concentrations. Whether morphologic, steroidogenic, and transcriptomic differences exist among corpora lutea (CL) formed after ovulation induced by GnRH and pLH is unclear. Our main objective, therefore, was to compare CL characteristics between GnRH- and pLH-induced CL. In 24 non-lactating Holstein cows, ovulations were spontaneous (Spont-Ov) or induced with 100 µg GnRH, 25 mg pLH, or 1 mg estradiol benzoate (EB), with CL excised 12 d after ovulation. In pLH- versus GnRH-treated cows, the duration of elevated LH (above baseline) was prolonged (10 versus 6 h, respectively, p < 0.01), but CL dimensions, pixel intensity of CL images, proportions of steroidogenic and non-steroidogenic luteal cells, and mean plasma LH did not significantly differ. Post-ovulation mean plasma P₄ (ng/mL) did not differ among Spont-Ov (3.0) pLH (3.1) or GnRH (3.0) cows but were lower in EB cows (2.0). In vitro P₄ concentration was greater in luteal explants of pLH-treated cows than in all other groups (combined means, 16.0 vs. 12.3 µg/mL, p < 0.02). Relative abundance of mRNA for oxytocin receptor (OXTR) was 2-fold higher (p < 0.01) in CL of pLH vs. GnRH cows and highest in Spont-Ov CL. In summary, pLH-treated cows had a longer LH peak, and greatest luteal tissue concentrations and in vitro production of P₄. We inferred that increased P₄ concentrations at the ovarian-uterine level in pLH-treated cows could have promoted embryo development and increased pregnancy per AI.

Dysregulation of steroid metabolome in follicular fluid links phthalate exposure to diminished ovarian reserve of childbearing-age women

The widespread use of phthalates (PAEs) has drawn increasing attention due to their endocrine disruption and reproductive toxicity, while the steroid metabolome is essential for follicular development. However, the mechanism by which PAE exposure affects ovarian reserve through the steroid metabolome remains unclear. This study recruited 264 childbearing-age women in Tianjin (China) from April 2019 to August 2020 in a cross-sectional design. Target metabolome analysis of 16 steroids was performed in follicular fluid (FF) to compare diminished ovarian reserve (DOR) against normal ovarian reserve (NOR) women and differential steroids were identified using binary logistic analyses. Further analysis of eleven PAE metabolites (mPAEs) in FF was conducted, and the retrieved oocyte number (RON) representing ovarian reserve was counted. Multiple linear regression and quantile-based g-computation (qgcomp) models were used to associate individual mPAEs and mPAE mixture with the DOR-related differential steroids in FF. Mediation analysis was used to discuss the mediating effect of DOR-related steroids on the association between mPAEs and RON. Androstenedione (A4), corticosterone (CORT), cortisol (COR) and cortisone were significantly down-regulated in FF from women with DOR. Nine mPAEs with detection frequencies greater than 60% and median concentrations of 0.02-4.86 ng/mL were incorporated into statistical models. Negative associations with COR and CORT were found for mono-ethyl phthalate (mEP), mono-(2-ethyl-5-oxohexyl) phthalate (mEOHP), and mono-2-ethylhexyl phthalate (mEHP). A positive association with cortisone was found for mEOHP, mEHP, monobutyl phthalate (mBP), and mono (2-isobutyl) phthalate (miBP). The qgcomp and mediation analyses revealed that mEP and mEOHP not only significantly contributed to the decline of COR and CORT in the mixed exposure but also indirectly reduced RON through the mediating effects of COR and CORT. In conclusion, PAE exposure may decrease ovarian reserve by downregulating COR and CORT.

Assessing chronic stress in wild mammals using claw-derived cortisol: a validation using European badgers (Meles meles)

Measuring stress experienced by wild mammals is increasingly important in the context of human-induced rapid environmental change and initiatives to mitigate human-wildlife conflicts. Glucocorticoids (GC), such as cortisol, mediate responses by promoting physiological adjustments during environmental perturbations. Measuring cortisol is a popular technique; however, this often reveals only recent short-term stress such as that incurred by restraining the animal to sample blood, corrupting the veracity of this approach. Here we present a protocol using claw cortisol, compared with hair cortisol, as a long-term stress bio-indicator, which circumvents this constraint, where claw tissue archives the individual's GC concentration over preceding weeks. We then correlate our findings against detailed knowledge of European badger life history stressors. Based on a solid-phase extraction method, we assessed how claw cortisol concentrations related to season and badger sex, age and body-condition using a combination of generalized linear mixed models (GLMM) (n = 668 samples from 273 unique individuals) followed by finer scale mixed models for repeated measures (MMRM) (n = 152 re-captured individuals). Claw and hair cortisol assays achieved high accuracy, precision and repeatability, with similar sensitivity. The top GLMM model for claw cortisol included age, sex, season and the sex*season interaction. Overall, claw cortisol levels were significantly higher among males than females, but strongly influenced by season, where females had higher levels than males in autumn. The top fine scale MMRM model included sex, age and body condition, with claw cortisol significantly higher in males, older and thinner individuals. Hair cortisol was more variable than claw; nevertheless, there was a positive correlation after removing 34 outliers. We discuss strong support for these stress-related claw cortisol patterns from previous studies of badger biology. Given the potential of this technique, we conclude that it has broad application in conservation biology.

Corticosterone stage-dependently inhibits progesterone production presumably via impeding the cAMP-StAR cascade in granulosa cells of chicken preovulatory follicles

Stress can suppress reproduction capacity in either wild or domestic animals, but the exact mechanism behind it, especially in terms of steroidogenesis, remains under-investigated so far. Considering the important roles of progesterone in avian breeding, we investigated the modulation of corticosterone on progesterone production in cultured granulosa cells of chicken follicles at different developmental stages. Using enzyme immunoassays, our study showed that corticosterone could only inhibit progesterone synthesis in granulosa cells from F5-6, F4, and F3 follicles, but not F2 and F1 follicles. Coincidentally, both quantitative real-time PCR and western blotting revealed that corticosterone could downregulate steroidogenic acute regulatory protein (StAR) expression, suggesting the importance of StAR in corticosterone-related actions. Using the dual-luciferase reporter system, we found that corticosterone can potentially enhance, rather than inhibit, the activity of StAR promoter. Of note, combining high-throughput transcriptomic analysis and quantitative real-time PCR, phosphodiesterase 10A (PDE10A), protein kinase cAMP-dependent type II regulatory subunit alpha (PRKAR2A) and cAMP responsive element modulator (CREM) were identified to exhibit the differential expression patterns consistent with cAMP blocking in granulosa cells from F5-6, F4, and F3, but not F2 and F1 follicles. Afterward, the expression profiles of these genes in granulosa cells of distinct developmental-stage follicles were examined by quantitative real-time PCR, in which all of them expressed correspondingly with progesterone levels of granulosa cells during development. Collectively, these findings indicate that corticosterone can stage-dependently inhibit progesterone production in granulosa cells of chicken preovulatory follicles, through impeding cAMP-induced StAR activity presumptively.

Apoptosis, autophagic cell death, and necroptosis: different types of programmed cell death in bovine corpus luteum regression

In mammals, the corpus luteum (CL) is a transient organ that secretes progesterone (P4). In the absence of pregnancy, the CL undergoes regression (luteolysis), which is a crucial preparation step for the next estrous cycle. Luteolysis, initiated by uterine prostaglandin F_2α (PGF) in cattle, is usually divided into two phases, namely functional luteolysis characterized by a decline in P4 concentration and structural luteolysis characterized by the elimination of luteal tissues from the ovary. Programmed cell death (PCD) of luteal cells, including luteal steroidogenic cells (LSCs) and luteal endothelial cells (LECs), plays a crucial role in structural luteolysis. The main types of PCD are caspase-dependent apoptosis (type 1), autophagic cell death (ACD) via the autophagy-related gene (ATG) family (type 2), and receptor-interacting protein kinase (RIPK)-dependent programmed necrosis (necroptosis, type 3). However, these PCD signaling pathways are not completely independent and interact with each other. Over the past several decades, most studies on luteolysis have focused on apoptosis as the principal mode of bovine luteal cell death. Recently, ATG family members were reported to be expressed in bovine CL, and their levels increased during luteolysis. Furthermore, the expression of RIPKs, which are crucial mediators of necroptosis, is reported to increase in bovine CL during luteolysis and is upregulated by pro-inflammatory cytokines in bovine LSCs and LECs. Therefore, apoptosis, ACD, and necroptosis may contribute to bovine CL regression. In this article, we present the recent findings regarding the mechanisms of the three main types of PCD and the contribution of these mechanisms to luteolysis.

Corticosterone triggers anti-proliferative and apoptotic effects, and downregulates the ACVR1-SMAD1-ID3 cascade in chicken ovarian prehierarchical, but not preovulatory granulosa cells

The coordinated proliferation and apoptosis of granulosa cells plays a critical role in follicular development. To identify the exact mechanisms of how stress-driven glucocorticoid production suppresses reproduction, granulosa cells were isolated from chicken follicles at different developmental stages and then treated with corticosterone. Using CCK-8, EDU and TUNEL assays, we showed that corticosterone could trigger both anti-proliferative and pro-apoptotic effects in granulosa cells from 6 to 8 mm follicles only, while depicting no influence on granulosa cells from any preovulatory follicles. High-throughput transcriptomic analysis identified 1362 transcripts showing differential expression profiles in granulosa cells from 6 to 8 mm follicles after corticosterone treatment. Interestingly, Kyoto Encyclopedia of Genes and Genomes enrichment analysis revealed that 17 genes were enriched in the TGF-β signaling pathway, and 13 showed differential expression patterns consistent with corticosterone-induced effects. The differential expression profiles of these 13 genes were examined by quantitative real-time PCR in cultured chicken ovarian granulosa cells at diverse developmental stages following corticosterone challenge for a short (8 h) or long period (24 h). After 24 h of treatment, INHBB, FST, FMOD, NOG, ACVR1, SMAD1 and ID3 were the genes that responded consistently with corticosterone-induced proliferative and apoptotic events in all granulosa cells detected. However, only ACVR1, SMAD1 and ID3 could initiate coincident expression patterns after being treated for 8 h, suggesting their significance in corticosterone-mediated actions. Collectively, these findings indicate that corticosterone can inhibit proliferation and cause apoptosis in chicken ovarian prehierarchical, but not preovulatory granulosa cells, through impeding ACVR1-SMAD1-ID3 signaling presumptively.

Loss of luteal sensitivity to luteinizing hormone underlies luteolysis in cattle: A hypothesis

By virtue of the secretion of progesterone (P4), corpus luteum (CL) is important not only for normal cyclicity but also for conception and continuation of pregnancy in female mammals. Luteolysis (also called luteal regression) is defined as loss of the capacity to synthesize and secrete P4 followed by the demise of the CL. There is strong evidence that sequential pulses of prostaglandin F2α (PGF) secreted from the uterus near the end of luteal phase induces luteolysis in farm animals. Loss of luteal sensitivity to luteinizing hormone (LH) at the end of menstrual cycle has been reported to be critical for initiation of luteolysis in primates, however this has not been investigated in farm animals. A closer observation of the published real-time profiles of circulating hormones (P4, LH, and PGF) and their inter-relationships around the time of the beginning of spontaneous luteolysis in cattle revealed- 1) A natural pulse of PGF causes a transient P4 suppression lasting a couple of hours followed by a rebound in P4 concentration, 2) The P4 secretions that occur in response to LH pulses before the beginning of luteolysis (i.e., preluteolysis) either fail or do so to a lesser extent during luteolysis indicating a loss of sensitivity to LH, and 3) The loss of sensitivity coincides with the beginning of luteolysis (i.e., transition), and apparently luteolysis does not initiate until there is loss of sensitivity to LH. The CL is sensitive to LH during preluteolysis, and the LH-stimulated P4-dependent and/or independent local survival mechanisms maintain the steroidogenic capability and viability of the CL until the very end of preluteolysis. Luteolysis does not appear to initiate with the PGF pulse(s) that occur during this period. With the loss of sensitivity to LH at the transition, however, a progressive decline in P4 begins initiating luteolysis. Also, the survival mechanisms become compromised making the CL less viable. The uterine PGF pulses that occur after the beginning of luteolysis induces increase in the local luteolytic factors, which contribute to further luteolysis, more importantly, structural luteolysis with ultimate demise of the CL. Therefore, I hypothesize that the loss of luteal sensitivity to LH underlies luteolysis in cattle. The hypothesis not only unifies the basic mechanism of luteolysis in a farm animal and primates but also provides a perspective to view luteolysis as a process rather than a factor-mediated event. A novel unified working model for luteolysis in a farm animal and primates is described. A better understanding of the luteal physiology including how responsiveness to LH diminishes in aging CL would help in the development of novel strategies in modulating CL structure-function to improve and/or control fertility in humans as well as in animals.

Effects of cortisol on prostaglandin F2α secretion and expression of genes involved in the arachidonic acid metabolic pathway in equine endometrium - In vitro study

Glucocorticoids (GCs) are known to play an important role in maintaining basal and stress-related homeostasis by interacting with endocrine mediators and prostaglandins (PGs). Although a growing body of evidence shows that GCs exert their regulatory action at a multitude of sites in the reproductive axis through corticosteroid receptors, little is known about the direct role of cortisol, an active form of GCs, in the equine endometrium. Thus, the study aimed to determine the effect of cortisol on PGF_2α synthesis in the endometrial tissue and cells in vitro. In Exp.1, the immunolocalization and the expression of the glucocorticoid receptor (GCR) in the endometrium throughout the estrous cycle were established. In Exp. 2 and 3, the effects of cortisol on PGF_2α secretion and transcripts associated with the arachidonic acid (AA) cascade in endometrial tissues, and cells were defined. Endometrial tissues obtained from the early, mid, and late luteal phases and the follicular phase of the estrous cycle were exposed to cortisol (100, 200, and 400 nM) for 24 h. Endometrial epithelial and stromal cells (early phase of estrous cycle) were exposed to cortisol (100 nM) for 24 h. Then, PGF_2α secretion and transcripts associated with the AA cascade (PLA2G2A, PLA2G4A, PTGS2, and PGFS) were assessed. GCR was expressed in the cytoplasm and the nucleus in the luminal and glandular epithelium as well as in the stroma. Endometrial GCR protein abundance was up-regulated at the late luteal phase compared to the mid-luteal phase of the estrous cycle. Cortisol dose-dependently decreased PGF_2α secretion, PLA2G2A and PLA2G4A transcripts in endometrial tissues. Additionally, cortisol treatment decreased PGF_2α secretion from endometrial epithelial and stromal cells. Moreover, it affected PLA2G2A, PLA2G4A, and PTGS2 transcripts in endometrial stromal cells. These findings suggest that cortisol suppresses the synthesis of PGF_2α by affecting the AA cascade in the equine endometrium during the estrous cycle.

Effect of natural pre-luteolytic prostaglandin F2α pulses on the bovine luteal transcriptome during spontaneous luteal regression

The pulsatile pattern of prostaglandin F2alpha (PGF) secretion during spontaneous luteolysis is well-documented, with multiple pulses of exogenous PGF necessary to induce regression using physiologic concentrations of PGF. However, during spontaneous regression, the earliest pulses of PGF are small and not associated with detectable changes in circulating progesterone (P4), bringing into question what, if any, role these early, subluteolytic PGF pulses have during physiologic regression. To investigate the effect of small PGF pulses, luteal biopsies were collected throughout natural luteolysis in conjunction with bihourly blood samples to determine circulating P4 and PGF metabolite to retrospectively assign biopsies to early and later regression. Whole transcriptome analysis was conducted on CL biopsies. Early PGF pulses altered the luteal transcriptome, inducing differential expression of 210 genes (Q < 0.05) during early regression, compared to 4615 differentially expressed genes during later regression. In early regression, few of these differentially expressed genes were directly associated with luteolysis, rather there were changes in local steroid and glutathione metabolism. Most (94%) differentially expressed genes from early regression were also differentially expressed during later regression, with 98% of these continuing to be altered in the same direction compared to CL at a similar stage of the cycle that had not yet been exposed to PGF. Thus, early, subluteolytic PGF pulses impact the luteal transcriptome, though not by altering steroidogenesis or causing direct inhibition of cellular function. Rather, small pulses alter pathways resulting in removal of cellular support systems, which may sensitize the CL to later pulses of PGF.

The effects of luteinizing hormone as a suppression factor for apoptosis in bovine luteal cells in vitro

The fate of the corpus luteum, a transient endocrine gland formed and degraded during an oestrous cycle, is decided by various physiological factors, such as luteinizing hormone (LH). As a stimulator of progesterone, LH is known to maintain corpus luteum functional and structural integrity by inhibiting apoptosis, a programmed cell death. Therefore, we aim to investigate its action during the mid-luteal phase hypothesized that LH suppresses the death mechanism of bovine luteal steroidogenic cells (LSC) by analysing the expression of proteins involved. Cultured bovine LSC obtained from corpus luteum were treated for 24 hr with recombinant TNF and IFNG in the presence or absence of LH. The result showed that LH proved to have a protective effect by increased cell viability (p < .05) and prevented DNA fragmentation (p < .05), as demonstrated by the WST-1 colorimetric assay and TUNEL assay. Expression analysis of mRNA and protein levels showed that LH altered the expression of BCL2 (p < .05), CASP3 (p < .05), FAS (p < .05), and BAX (p < .05) to support cell survival. In conclusion, our study suggests that LH prolongs the corpus luteum life span through the anti-apoptotic mechanism by increasing cell viability and suppressing apoptosis-related genes and protein expression.

Effects of body condition score and estrus phase on blood metabolites and steroid hormones in Saanen goats in the tropics

Background and Aim:

Body condition scores (BCSs) assessment can be a potential management tool for the improvement of animal performance. The study investigated whether blood metabolic (protein, glucose, blood urea nitrogen, and cholesterol) and steroid hormonal (progesterone, estrogen, and cortisol) parameters are affected by the BCS and estrous status in Saanen goat.

Materials and Methods:

Blood samples were collected from three groups of mature, dry, and non-pregnant female goats with different BCSs: 2-2.9 (BCS 2), 3-3.9 (BCS 3), and 4-4.9 (BCS 4) on a BCS scale ranged from 1 to 5. Blood serum was collected (n = 160) to determine the blood metabolic profile and steroid hormone levels, depending on the follicular status.

Results:

The results demonstrate a variation in the serum metabolite and hormone (glucose, BUN, protein, estrogen, and cortisol) levels at different BCSs and at different phases of the estrous cycle. The hormonal profiles were significantly different (p<0.05) between the estrous cycle phases. The results suggest that BCSs were associated with blood metabolic profiles and steroid hormone levels.

Conclusion:

As it can be concluded, an association between steroid hormone levels and the phases of the estrous cycle existed in Saanen goats.

The proliferative effect of cortisol on bovine endometrial epithelial cells

BACKGROUND

Bovine endometrial epithelial cells (BEECs) undergo regular regeneration after calving. Elevated cortisol concentrations have been reported in postpartum cattle due to various stresses. However, the effects of the physiological level of cortisol on proliferation in BEECs have not been reported. The aim of this study was to investigate whether cortisol can influence the proliferation properties of BEECs and to clarify the possible underlying mechanism.

METHODS

BEECs were treated with different concentrations of cortisol (5, 15 and 30 ng/mL). The mRNA expression of various growth factors was detected by quantitative reverse transcription-polymerase chain reaction (qPCR), progression of the cell cycle in BEECs was measured using flow cytometric analysis, and the activation of the Wnt/β-catenin and phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) signaling pathways was detected with Western blot and immunofluorescence.

RESULTS

Cortisol treatment resulted in upregulated mRNA levels of vascular endothelial growth factor (VEGF) and connective tissue growth factor (CTGF); however, it had no influence on transforming growth factor-beta1 (TGF-β1). Cortisol (15 ng/mL) accelerated the cell cycle transition from the G0/G1 to the S phase. Cortisol upregulated the expression of β-catenin, c-Myc, and cyclinD1 and promoted the phosphorylation of PI3K and AKT.

CONCLUSIONS

These results demonstrated that cortisol may promote proliferation in BEECs by increasing the expression of some growth factors and activating the Wnt/β-catenin and PI3K/AKT signaling pathways.

The effects of dexamethasone administered during pregnancy on the postpartum spiny mouse ovary

Excessive exposure to glucocorticoids can alter ovarian function by modulating oogenesis, folliculogenesis and steroidogenesis. The aim of the present study was to examine the effects of dexamethasone (DEX) administered during pregnancy on folliculogenesis and corpus luteum development in the postpartum spiny mouse ovary. DEX (125 μg kg^-1 body weight per day) was applied to pregnant spiny mouse from day 20 of gestation to parturition. The obtained ovaries were fixed and used for immunohistochemistry and TEM analysis. The expression of proteins related to apoptosis (caspase-3, Bax, Bcl-2) and autophagy (Beclin1, Lamp1) as well as PCNA and GR receptors were evaluated by western-blot. In comparison with DEX-treated group a higher percentage of TUNEL positive granulosa and luteal cells was observed in the control group. These data were consistent with changes in caspase-3 and Bax expression, which increased in the control and decreased after DEX exposure. In turn, the proliferation index and PCNA expression were higher in the DEX-treated group. Moreover, the higher level of Beclin1, Lamp1, anti-apoptotic Bcl-2 protein and GR was observed in the DEX-treated females than in the control group. Beclin1 and Lamp1 were strongly expressed in luteal cells which exhibited an autophagic ultrastructure. Surprisingly, DEX augmented the number of ovarian follicles and corpora lutea, which resulted in a significant increase in ovarian weight. These findings suggest that DEX exerts anti-apoptotic action on granulosa layer and stimulates follicular maturation. Moreover, DEX induces autophagy in luteal cells promoting cell survival rather than cell death, which can prolong the corpus luteum life span.

Programmed necrosis - a new mechanism of steroidogenic luteal cell death and elimination during luteolysis in cows

Programmed necrosis (necroptosis) is an alternative form of programmed cell death that is regulated by receptor-interacting protein kinase (RIPK) 1 and 3-dependent, but is a caspase (CASP)-independent pathway. In the present study, to determine if necroptosis participates in bovine structural luteolysis, we investigated RIPK1 and RIPK3 expression throughout the estrous cycle, during prostaglandin F2α (PGF)-induced luteolysis in the bovine corpus luteum (CL), and in cultured luteal steroidogenic cells (LSCs) after treatment with selected luteolytic factors. In addition, effects of a RIPK1 inhibitor (necrostatin-1, Nec-1; 50 μM) on cell viability, progesterone secretion, apoptosis related factors and RIPKs expression, were evaluated. Expression of RIPK1 and RIPK3 increased in the CL tissue during both spontaneous and PGF-induced luteolysis (P < 0.05). In cultured LSCs, tumor necrosis factor α (TNF; 2.3 nM) in combination with interferon γ (IFNG; 2.5 nM) up-regulated RIPK1 mRNA and protein expression (P < 0.05). TNF + IFNG also up-regulated RIPK3 mRNA expression (P < 0.05), but not RIPK3 protein. Although Nec-1 prevented TNF + IFNG-induced cell death (P < 0.05), it did not affect CASP3 and CASP8 expression. Nec-1 decreased both RIPK1 and RIPK3 protein expression (P < 0.05). These findings suggest that RIPKs-dependent necroptosis is a potent mechanism responsible for bovine structural luteolysis induced by pro-inflammatory cytokines.

Cellular and molecular mechanisms involved in placental separation in the bovine: A review

Retention of fetal membranes (RFM), where the fetal placenta is not expelled within 8-12 hr after calving, lowers bovine productivity and fertility, resulting in significant economic loss to the dairy industry. Several risk factors that predispose an individual to RFM are known, but a unifying pathogenesis remains elusive due to its multifactorial etiology. Fetal membrane separation and expulsion after parturition involves structural and immunological changes of the bovine placentome that are governed predominantly by steroid hormones and the prostaglandin milieu of late pregnancy and parturition. Maturation of the placentome, a gradual and concerted event of late gestation, is likely initiated by the up-regulation of fetal major histocompatibility complex class I in the interplacentomal region-which increases the apoptosis of binucleate and other trophoblastic cells, the degradation of collagen in the extracellular matrix by matrix metalloproteinases, and an influx of phagocytic leukocytes. Shear force further distorts the crypt architecture of the mature placentomes when they are forced against the fetus during the second stage of labor. Cotyledon dehiscence from the caruncular crypts is completed following fetal expulsion as a result of acute shrinkage of the cotelydonary villi as well as reduced perfusion to the caruncle; the secundinae is expelled by uterine contractions. A better understanding of placentomal maturation, intra-partum, and immediate postpartum changes of the placentome should help develop strategies for the treatment and prevention of RFM. The present review proposes a model of placentome maturation and separation of fetal membranes in the dairy cow.

Role of Glucocorticoids in Cystic Ovarian Disease: Expression of Glucocorticoid Receptor in the Bovine Ovary

The aim of this study was to characterize the expression of glucocorticoid receptor (GR) in the components of normal bovine ovary and in animals with cystic ovarian disease (COD). Changes in the protein and mRNA expression levels were determined in control cows and cows with COD by immunohistochemistry and real-time PCR. GR protein expression in granulosa cells was higher in cysts from animals with spontaneous COD and adrenocorticotropic hormone-induced COD than in tertiary follicles from control animals. In theca interna cells, GR expression was higher in cysts from animals with spontaneous COD than in tertiary follicles from control animals. The increase in GR expression observed in cystic follicles suggests a mechanism of action for cortisol and its receptor through the activation/inactivation of specific transcription factors. These factors could be related to the pathogenesis of COD in cattle.

Glucocorticoid metabolism in the bovine cumulus-oocyte complex matured in vitro

Glucocorticoid action in target organs is regulated by relative activities of 11β-HSD type 1 (HSD11B1) that mainly converts cortisone to active cortisol and type 2 (HSD11B2) that inactivates cortisol to cortisone. HSD11Bs have been shown to be expressed in the ovary of various species. However, little is known about the expression and activity of HSD11Bs in the bovine cumulus-oocyte complex (COC). In the present study, we investigated the expression and activities of HSD11Bs in in vitro-matured (IVM) bovine COCs. Bovine COCs were matured in M199 supplemented with or without FSH and FCS. The expression of HSD11B1 and HSD11B2 was measured by using quantitative RT-PCR in denuded oocytes (DO) and cumulus cells (CC). Reductive and oxidative activities of HSD11Bs were determined by radiometric conversion assay using labeled cortisol, cortisone or dexamethasone in intact COCs, DO or CC in the presence or absence of 11-keto-progesterone (11kP), a selective inhibitor of HSD11B2. The presence of HSD11Bs in the oocyte was examined by immunofluorescence microscopy. Oocytes exclusively expressed HSD11B2 and its expression and activity were largely unchanged during IVM. CC, on the other hand, exclusively expressed HSD11B1 and its expression and activity were upregulated as IVM progressed. As a result, the net glucocorticoid metabolism shifted from inactivation to activation towards the end of IVM. These results indicate that the bovine COC is capable of modulating local glucocorticoid concentration and, by doing so, may create an environment that is favorable to ovulating oocyte for maturation, fertilization and subsequent development.

Effect of cortisol on bovine oocyte maturation and embryo development in vitro

Glucocorticoids (GCs) are important mediators of key cellular events. Herein, we investigated the effect of adding cortisol to the IVM medium on the acquisition of developmental competency in bovine oocytes. Cortisol (0.01, 0.1, or 1 μg/mL) had no effect on cleavage rates or cell numbers of resulting blastocysts; however, supplementation with 0.1 μg/mL during IVM increased blastocyst rates of in vitro-fertilized bovine oocytes as compared to untreated controls (41 ± 10% vs. 21 ± 1.2%, P < 0.05, respectively). This concentration was chosen to assess changes in the relative expression of potential GC target genes. Oocytes matured in the presence of cortisol and their corresponding cumulus cells did not show changes in expression for genes analyzed as compared to untreated controls. Notably, blastocysts from oocytes matured in cortisol-supplemented medium expressed higher relative levels of glucose transporter 1 (GLUT1), fatty acid synthase (FASN), and heat shock protein 70 (HSP70). This study supports a role for cortisol in the acquisition of bovine oocyte competence. This is evidenced by increased blastocyst development rates and presumably related to elevated embryonic transcripts with roles in glucose and lipid metabolism, as well as the cellular response to stress.

Toxicity Assessment of 4-Methyl-1-cyclohexanemethanol and Its Metabolites in Response to a Recent Chemical Spill in West Virginia, USA

The large-scale chemical spill on January 9, 2014 from coal processing and cleaning storage tanks of Freedom Industries in Charleston affected the drinking water supply to 300,000 people in Charleston, West Virginia metropolitan, while the short-term and long-term health impacts remain largely unknown and need to be assessed and monitored. There is a lack of publically available toxicological information for the main contaminant 4-methyl-1-cyclohexanemethanol (4-MCHM). Particularly, little is known about 4-MCHM metabolites and their toxicity. This study reports timely and original results of the mechanistic toxicity assessment of 4-MCHM and its metabolites via a newly developed quantitative toxicogenomics approach, employing proteomics analysis in yeast cells and transcriptional analysis in human cells. These results suggested that, although 4-MCHM is considered only moderately toxic based on the previous limited acute toxicity evaluation, 4-MCHM metabolites were likely more toxic than 4-MCHM in both yeast and human cells, with different toxicity profiles and potential mechanisms. In the yeast library, 4-MCHM mainly induced chemical stress related to transmembrane transport and transporter activity, while 4-MCHM metabolites of S9 mainly induced oxidative stress related to antioxidant activity and oxidoreductase activity. With human A549 cells, 4-MCHM mainly induced DNA damage-related biomarkers, which indicates that 4-MCHM is related to genotoxicity due to its DNA damage effect on human cells and therefore warrants further chronic carcinogenesis evaluation.

Oocyte environment: follicular fluid and cumulus cells are critical for oocyte health

Bidirectional somatic cell-oocyte signaling is essential to create a changing intrafollicular microenvironment that controls primordial follicle growth into a cohort of growing follicles, from which one antral follicle is selected to ovulate a healthy oocyte. Such intercellular communications allow the oocyte to determine its own fate by influencing the intrafollicular microenvironment, which in turn provides the necessary cellular functions for oocyte developmental competence, which is defined as the ability of the oocyte to complete meiosis and undergo fertilization, embryogenesis, and term development. These coordinated somatic cell-oocyte interactions attempt to balance cellular metabolism with energy requirements during folliculogenesis, including changing energy utilization during meiotic resumption. If these cellular mechanisms are perturbed by metabolic disease and/or maternal aging, molecular damage of the oocyte can alter macromolecules, induce mitochondrial mutations, and reduce adenosine triphosphate production, all of which can harm the oocyte. Recent technologies are now exploring transcriptional, translational, and post-translational events within the human follicle with the goal of identifying biomarkers that reliably predict oocyte quality in the clinical setting.

Intrafollicular cortisol levels inversely correlate with cumulus cell lipid content as a possible energy source during oocyte meiotic resumption in women undergoing ovarian stimulation for in vitro fertilization

OBJECTIVE

To determine whether follicular fluid (FF) cortisol levels affect cumulus cell (CC) lipid content during oocyte meiotic resumption, and whether CCs express genes for glucocorticoid action.

DESIGN

Prospective cohort study.

SETTING

Academic medical center.

PATIENT(S)

Thirty-seven nonobese women underwent ovarian stimulation for in vitro fertilization (IVF).

INTERVENTION(S)

At oocyte retrieval, FF was aspirated from the first follicle (>16 mm in size) of each ovary and pooled CCs were collected.

MAIN OUTCOME MEASURE(S)

Follicular fluid cortisol and cortisone analysis was performed with the use of liquid chromatography-tandem mass spectrometry. CCs were stained with lipid fluorescent dye Bodipy FL C16 to determine lipid content with the use of confocal microscopy. Quantitative real-time polymerase chain reaction was used to detect CC gene expression of 11β-hydroxysteroid dehydrogenase (11β-HSD) types 1 and 2, glucocorticoid receptor (NR3C1), lipoprotein lipase (LPL), and hormone-sensitive lipase (HSL).

RESULT(S)

Adjusting for maternal age, FF cortisol levels negatively correlated with CC lipid content and positively correlated with numbers of total and mature oocytes. CCs expressed genes for 11β-HSD type 1 as the predominant 11β-HSD isoform, NR3C1, LPL, and HSL.

CONCLUSION(S)

FF cortisol levels may regulate CC lipolysis during oocyte meiotic resumption and affect oocyte quality during IVF.

Characterization of the human cumulus cell transcriptome during final follicular maturation and ovulation

Cumulus expansion and oocyte maturation are central processes in ovulation. Knowledge gained from rodent and other mammalian models has revealed some of the molecular pathways associated with these processes. However, the equivalent pathways in humans have not been thoroughly studied and remain unidentified. Compact cumulus cells (CCs) from germinal vesicle cumulus oocyte complexes (COCs) were obtained from patients undergoing in vitro maturation (IVM) procedures. Expanded CCs from metaphase 2 COC were obtained from patients undergoing IVF/ICSI. Global transcriptome profiles of the samples were obtained using state-of-the-art RNA sequencing techniques. We identified 1746 differentially expressed (DE) genes between compact and expanded CCs. Most of these genes were involved in cellular growth and proliferation, cellular movement, cell cycle, cell-to-cell signaling and interaction, extracellular matrix and steroidogenesis. Out of the DE genes, we found 89 long noncoding RNAs, of which 12 are encoded within introns of genes known to be involved in granulosa cell processes. This suggests that unique noncoding RNA transcripts may contribute to the regulation of cumulus expansion and oocyte maturation. Using global transcriptome sequencing, we were able to generate a library of genes regulated during cumulus expansion and oocyte maturation processes. Analysis of these genes allowed us to identify important new genes and noncoding RNAs potentially involved in COC maturation and cumulus expansion. These results may increase our understanding of the process of oocyte maturation and could ultimately improve the efficacy of IVM treatment.

A role for glucocorticoids in stress-impaired reproduction: beyond the hypothalamus and pituitary

In addition to the well-characterized role of the sex steroid receptors in regulating fertility and reproduction, reproductive events are also mediated by the hypothalamic-pituitary-adrenal axis in response to an individual's environment. Glucocorticoid secretion in response to stress contributes to the well-characterized suppression of the hypothalamic-pituitary-gonadal axis through central actions in the hypothalamus and pituitary. However, both animal and in vitro studies indicate that other components of the reproductive system are also regulated by glucocorticoids. Furthermore, in the absence of stress, it appears that homeostatic glucocorticoid signaling plays a significant role in reproduction and fertility in all tissues comprising the hypothalamic-pituitary-gonadal axis. Indeed, as central regulators of the immune response, glucocorticoids are uniquely poised to integrate an individual's infectious, inflammatory, stress, nutritional, and metabolic status through glucocorticoid receptor signaling in target tissues. Endocrine signaling between tissues regulating the immune and stress response and those determining reproductive status provides an evolutionary advantage, facilitating the trade-off between reproductive investment and offspring fitness. This review focuses on the actions of glucocorticoids in tissues important for fertility and reproduction, highlighting recent studies that show glucocorticoid signaling plays a significant role throughout the hypothalamic-pituitary-gonadal axis and characterizing these effects as permissive or inhibitory in terms of facilitating reproductive success.

Ovarian localization of 11β-hydroxysteroid dehydrogenase (11βHSD): effects of ACTH stimulation and its relationship with bovine cystic ovarian disease

Cystic ovarian disease (COD) is an important cause of infertility in cattle, and ACTH has been involved in regulatory mechanisms related to ovarian function associated with ovulation, steroidogenesis, and luteal function. Here, we examined the localization of 11β-hydroxysteroid dehydrogenase type 1 (11βHSD1) and 11βHSD2 proteins in the ovary of healthy cows and animals with spontaneous and ACTH-induced COD and the in vitro response of the follicular wall exposed to ACTH. After stimulation by ACTH, we documented changes in 11βHSD expression and cortisol secretion by the follicular wall of large antral and follicular cysts. Follicular cysts showed a higher constitutive expression of both enzymes, whereas ACTH induced an increase in 11βHSD1 in tertiary follicles and follicular cysts and a decrease in 11βHSD2 in follicular cysts. Moderate expression of 11βHSD1 was observed by immunohistochemistry in granulosa of control animals, with an increase (P < 0.05) from primary to secondary, tertiary, and atretic follicles. The level of immunostaining in theca interna was lower than that in granulosa. The expression of 11βHSD2 was lower in the granulosa of primary follicles than in that of secondary, tertiary, and atretic follicles and was lower in the theca interna than in the granulosa. In ACTH-induced and spontaneously occurring follicular cysts, differences from controls were observed only in the expression of 11βHSD1 in the granulosa, being higher (P < 0.05) than in tertiary follicles. These findings indicate that follicular cysts may be exposed to high local concentrations of active glucocorticoids and indicate a local role for cortisol in COD pathogenesis and in regulatory mechanisms of ovarian function.

Effect of cortisol on neurophysin I/oxytocin and peptidyl glycine-alpha-amidating mono-oxygenase mRNA expression in bovine luteal and granulosa cells

Cortisol stimulates the synthesis and secretion of oxytocin (OT) from bovine granulosa and luteal cells, but the molecular mechanisms of cortisol action remain unknown. In this study, granulosa cells or luteal cells from days 1-5 and 11-15 of the oestrous cycle were incubated for 4 or 8 h with cortisol (1 x 10(-5), 1 x 10(-7) M). After testing cell viability and hormone secretion (OT, progesterone, estradiol), we studied the effect of cortisol on mRNA expression for precursor of OT (NP-I/OT) and peptidyl glycine-alpha-amidating mono-oxygenase (PGA). The influence of RU 486 (1 x 10(-5) M), a progesterone receptor blocker and inhibitor of the glucocorticosteroid receptor (GR), on the expression for both genes was tested. Cortisol increased the mRNA expression for NP-I/OT and PGA in granulosa cells and stimulated the expression for NP-I/OT mRNA in luteal cells obtained from days 1-5 and days 11-15 of the oestrous cycle. Expression for PGA mRNA was increased only in luteal cells from days 11-15 of the oestrous cycle. In addition, RU 486 blocked the cortisol-stimulated mRNA expression for NP-I/OT and PGA in both types of cells. These data suggest that cortisol affects OT synthesis and secretion in bovine ovarian cells, by acting on the expression of key genes, that may impair ovary

Luteoprotective roles of luteinizing hormone are mediated by not only progesterone production but also glucocorticoid conversion in bovine corpus luteum

Luteinizing hormone (LH) is known as a key regulator of corpus luteum (CL) function, but the luteoprotective mechanisms of LH in the maintenance of bovine CL function are not well understood. The current study investigated if LH increases cell viability and induces cortisol conversion, and if the luteoprotective action of LH is mediated by stimulating the local production and action of progesterone (P4) and/or cortisol. Cultured bovine luteal cells obtained at the mid-luteal stage (Days 8-12 of the estrous cycle) were treated for 24 hr with LH (10 ng/ml) with/without onapristone (OP, a specific P4 receptor antagonist; 100 µM), cortisone (1 µM), and aminoglutethimide (AGT, a specific inhibitor of cytochrome P450 side-chain cleavage; 100 µM). LH with and without OP significantly increased the mRNA and protein expressions of 11β-hydroxysteroid dehydrogenase (HSD11B) 1, but did not affect the mRNA or protein expression of HSD11B2. These treatments also significantly increased HSD11B1 activity. Cell viability was significantly increased by LH alone or by LH in combination with cortisone and OP. LH in combination with OP or AGT significantly decreased cell viability as compared to LH alone. The overall results suggest that LH stimulates not only P4 production but also HSD11B1 expression, thereby increasing the cortisol concentration in the bovine CL, and that LH prevents cell death through these survival pathways. LH may consequently support CL function during the luteal phase in cattle.

Dexamethasone-induced eosinopenia is associated with lower progesterone production in cattle

Eosinophilic cells accumulate in the capillaries of the bovine Graafian follicle shortly before ovulation and in the early developing corpus luteum (CL). Suppressing the migration of these eosinophilic cells by dexamethasone allowed us to evaluate their possible function in the CL development. Brown Swiss cows (n = 10) were randomly subdivided into two groups (n = 5). Every group was used once as control group and once as experimental group with two oestrous cycles between each treatment. Eighteen hours (h) after oestrus synchronization, dexamethasone or saline was given. Ovulation was induced 24 h later with gonadotropin-releasing hormone. Another injection of dexamethasone or saline was given 12 h later. Eosinophilic cells in the blood were counted daily until day 7 after the first dexamethasone injection. The collection of ovaries took place at days 1, 2 and 5. Gene expression, protein concentration and location of angiogenic factors, chemokines, insulin-like growth factor 1 (IGF1) and eosinophilic cells were studied. No eosinophilic cells were found in the CL of the treatment group. Blood progesterone decreased significantly in the dexamethasone group from day 8 to 17. The protein concentration of FGF2 increased significantly in CL tissue at day 2 and VEGFA decreased. Local IGF1 gene expression in the CL was not regulated. We assume from our data that the migration of eosinophilic cells into the early CL is not an essential, but an important stimulus for angiogenesis during early CL development in cattle.

Animal-level factors affecting ovarian function in Bos indicus heifers treated to synchronize ovulation with intravaginal progesterone-releasing devices and oestradiol benzoate

The primary objective of this study was to investigate the impact of animal-level factors including energy balance and environmental/management stress, on the ovarian function of Bos indicus heifers treated to synchronize ovulation. Two-year-old Brahman (BN) (n = 30) and BN-cross (n = 34) heifers were randomly allocated to three intravaginal progesterone-releasing device (IPRD) treatment groups: (i) standard-dose IPRD [Cue-Mate(®) (CM) 1.56 g; n = 17]; (ii) half-dose IPRD [0.78 g progesterone (P(4)); CM 0.78 g; n = 15]; (iii) half-dose IPRD + 300 IU equine chorionic gonadotrophin at IPRD removal (CM 0.78 g + G; n = 14); (iv) and a control group, 2× PGF(2α) [500 μg prostaglandin F(2α) (PGF(2α))] on Day -16 and -2 (n = 18). Intravaginal progesterone-releasing device-treated heifers received 250 μg PGF(2α) at IPRD insertion (Day -10) and IPRD removal (Day -2) and 1 mg oestradiol benzoate on Day -10 and -1. Heifers were managed in a small feedlot and fed a defined ration. Ovarian function was evaluated by ultrasonography and plasma P(4) throughout the synchronized and return cycles. Energy balance was evaluated using plasma insulin-like growth factor 1 (IGF-I) and glucose concentrations. The impact of environmental stressors was evaluated using plasma cortisol concentration. Heifers that had normal ovarian function had significantly higher IGF-I concentrations at commencement of the experiment (p = 0.008) and significantly higher plasma glucose concentrations at Day -2 (p = 0.040) and Day 4 (p = 0.043), than heifers with abnormal ovarian function. There was no difference between the mean pre-ovulatory cortisol concentrations of heifers that ovulated or did not ovulate. However, heifers that ovulated had higher cortisol concentrations at Day 4 (p = 0.056) and 6 (p = 0.026) after ovulation than heifers that did not ovulate.

Effects of cortisol on pregnancy rate and corpus luteum function in heifers: an in vivo study

To determine whether glucocorticoids affect the function of the bovine corpus luteum (CL) during the estrous cycle and early pregnancy, we examined the effects of exogenous cortisol or reduced endogenous cortisol on the secretion of progesterone (P4) and on pregnancy rate. In preliminary experiments, doses of cortisol and metyrapone (an inhibitor of cortisol synthesis) were established (n=33). Cortisol in effective doses of 10 mg blocked tumor necrosis factor-induced prostaglandin F(2α) secretion as measured by its metabolite (PGFM) concentrations in the blood. Metyrapone in effective doses of 500 mg increased the P4 concentration. Thus, both reagents were then intravaginally applied in the chosen doses daily from Day 15 to 18 after estrus (Day 0) in noninseminated heifers (n=18) or after artificial insemination (n=36). Pregnancy was confirmed by transrectal ultrasonography between Days 28-30 after insemination. Plasma concentrations of P4 were lower in cortisol-treated heifers than in control heifers on Days 17 and 18 of the estrous cycle (P<0.05). However, the interestrus intervals were not different between control and cortisol-treated animals (P>0.05). Moreover, metyrapone increased P4 and prolonged the CL lifespan in comparison to control animals (P<0.05). Interestingly, in inseminated heifers, cortisol increased the pregnancy rate (75%) compared with control animals (58%), whereas metyrapone reduced the pregnancy rate to 16.7% (P<0.05). The overall results suggest that cortisol, depending on the physiological status of heifers (pregnant vs. nonpregnant), modulates CL function by influencing P4 secretion. Cortisol may have a positive influence on CL function during early pregnancy, leading to support of embryo implantation and resulting in higher rates of pregnancy in heifers.

Are glucocorticoids auto- and/or paracrine factors in early bovine embryo development and implantation?

We determined the transcript content of three genes involved in the metabolism of glucocorticoids (GC) in bovine in vitro fertilized embryos (2-blastomere stage until hatched blastocyst), trophoblast as well as the oviduct (Day 2-4 of the estrous cycle) and endometrium (Day 16 of the cycle and pregnancy). Since mRNA expression of the glucocorticoid receptor and two enzymes responsible for GC production (11β-HSD1 and 2) was demonstrated in the embryos in all pre-implantation stages as well as in the endometrium and oviduct, it is suggested that GC may serve as auto-/paracrine factors in the development of bovine pre-implantation embryos.

Downregulation of both gene expression and activity of Hsp27 improved maturation of mouse oocyte in vitro

BACKGROUND

Heat shock protein 27 (Hsp27), a member of the small heat shock protein family, is an apoptosis regulator. Our previous proteomic study showed that Hsp27 mainly expressed in human oocyte, and that Hsp27 expression was downregulated in the ovaries derived from women with the polycystic ovary syndrome (PCOS), a well known endocrinal disorder with abnormal apoptotic activity and folliculogenesis. However, the exact effects of Hsp27 downregulation on oocyte development have not yet been clarified.

METHODS

The expression of Hsp27 gene was downregulated in the mouse oocytes cultured in vitro using siRNA adenovirus infection, while the activity of Hsp27 was decreased by microinjection of polyclonal Hsp27 antibody into the cytoplasm of germinal vesicle (GV) oocytes. Oocyte maturation rate was evaluated by morphological observation. Early stage of apoptosis was determined using Annexin-V staining analysis and some critical apoptotic factors and cytokines were also monitored at both mRNA level by real time RT-PCR and protein expression level by immunofluorescence and western blot.

RESULTS

Hsp27 expressed at high level in maturing oocytes. Infection with AdshHsp27, and microinjection of Hsp27 antibody into GV oocytes, resulted in the improved oocyte development and maturation. Germinal vesicle breakdown (GVBD) rates were significantly increased in two AdshHsp27-treated groups (88.7%, 86.0%) and Hsp27 antibody-injected group (77.0%) when compared with control (76.2% in AdGFP, 64.4% in IgG-injected), respectively. In addition, the rates of metaphase II (MII) development in two AdshHsp27-treated groups (73.8%, 76.4%) and Hsp27 antibody-injected group (67.3%) were higher than that in the controls (59.6% in AdGFP, 55.1% in IgG-injected). We also found that the rates of early stage of apoptosis in Hsp27 downregulated groups (46.5% and 45.6%) were higher than that in control group (34.1%) after 8 h of IVM. Similarly, downregulation of Hsp27 caused a significantly enhanced the expression of apoptotic factors (caspase 8, caspase 3) and cytokines (bmp 15 and gdf 9).

CONCLUSIONS

Downregulation of Hsp27 improved the maturation of mouse oocytes, while increased early stage of apoptosis in oocytes by inducing the activation of extrinsic, caspase 8-mediated pathway.

The expression of the nuclear receptors NR5A1 and NR5A2 and transcription factor GATA6 correlates with steroidogenic gene expression in the bovine corpus luteum

The corpus luteum (CL) is the major site of progesterone (P4) production during the luteal phase of the estrous cycle in cattle. To better understand the molecular mechanisms underlying P4 production, we compared the mRNA and protein expression profiles of key components of the steroidogenic pathway (StAR, CYP11A, and 3beta-HSD) during the bovine CL luteal phase with that of several transcription factors (NR5A1, NR5A2, GATA4, GATA6) known for their roles in the control of steroidogenic gene expression. In the bovine CL, StAR, CYP11A, and 3beta-HSD mRNA and protein levels remained constant at the mid and late luteal phases but markedly declined at the regressed luteal stage. NR5A1 and NR5A2 exhibited a similar pattern with a significant decrease in expression at the regressed luteal stage. Both GATA4 and GATA6 mRNA and proteins could be detected in bovine CL; GATA6 levels, however, were generally higher. Although GATA4 expression did not change during the luteal phase, GATA6 showed a marked decrease at the regressed luteal stage, like NR5A1, NR5A2, and the other steroidogenic markers. Thus, we suggest that NR5A1, NR5A2, and GATA6, but not GATA4, contribute to the transcriptional regulation of steroidogenic gene expression, and hence P4 production, in the bovine CL. Furthermore, we have demonstrated the association of NR5A1 and NR5A2 with the bovine StAR promoter in the mid-luteal CL using chromatin immunoprecipitation, suggesting that these factors have definitive roles in the regulation of StAR gene transcription in vivo.

Prolactin signaling through the short isoform of the mouse prolactin receptor regulates DNA binding of specific transcription factors, often with opposite effects in different reproductive issues

BACKGROUND

It has been well established that prolactin (PRL) signals through the long form of its receptor (PRL-RL) and activates the Jak/Stat pathway for transcription of PRL target genes. However, signaling pathways mediated through the short PRL-R isoform (PRL-RS) remains controversial. Our recent finding that PRL signaling through PRL-RS represses two transcription factors critical for follicular development lead us to examine other putative PRL/PRL-RS target transcription factors in the decidua and ovary, two well-known target tissues of PRL action in reproduction.

METHODS

In this investigation we used mice expressing PRL-RS on a PRL-R knockout background and a combo protein/DNA array to study the transcription factors regulated by PRL through PRL-RS only.

RESULTS

We show that PRL activation of the PRL-RS receptor either stimulates or inhibits the DNA binding activity of a substantial number of transcription factors in the decidua as well as ovary. We found few transcription factors to be similarly regulated in both tissues, while most transcription factors are oppositely regulated by PRL in the decidua and ovary. In addition, some transcription factors are regulated by PRL only in the ovary or only in the decidua. Several of these transcription factors are involved in physiological pathways known to be regulated by PRL while others are novel.

CONCLUSION

Our results clearly indicate that PRL does signal through PRL-RS in the decidua as well as the ovary, independently of PRL-RL, and activates/represses transcription factors in a tissue specific manner. This is the first report showing PRL/PRL-RS regulation of specific transcription factors. Many of these transcription factors were not previously known to be PRL targets, suggesting novel physiological roles for this hormone.

Anti-apoptotic roles of prostaglandin E2 and F2alpha in bovine luteal steroidogenic cells

Production of prostaglandins (PGs) and expression of their receptors have been demonstrated in bovine corpus luteum (CL). The aim of the present study was to determine whether PGE2 and PGF2alpha have roles in bovine luteal steroidogenic cell (LSC) apoptosis. Cultured bovine LSCs obtained at the midluteal stage (Days 8-12 of the cycle) were treated for 24 h with PGE2 (0.001-1 microM) and PGF2alpha (0.001-1 microM). Prostaglandin E2 (1 microM) and PGF2alpha (1 microM) significantly stimulated progesterone (P4) production and reduced the levels of cell death in the cells cultured with or without tumor necrosis factor alpha (TNF)/interferon gamma (IFNG), in the presence and absence of FAS ligand (P < 0.05). Furthermore, DNA fragmentation induced by TNF/IFNG was observed to be suppressed by PGE2 and PGF2alpha. Prostaglandin E2 and PGF2alpha also attenuated mRNA expression of caspase 3 and caspase 8, as well as caspase 3 activity (P < 0.05) in TNF/IFNG-treated cells. FAS mRNA and protein expression were decreased only by PGF2alpha (P < 0.05). A specific P4 receptor antagonist (onapristone) attenuated the apoptosis-inhibitory effects of PGE2 and PGF2alpha in the absence of TNF/IFNG (P < 0.05). A PG synthesis inhibitor (indomethacin) reduced cell viability in PGE2- and PGF2alpha-treated cells (P < 0.05). A specific inhibitor of cyclooxygenase (PTGS), PTGS2 (NS-398), also reduced cell viability, whereas an inhibitor of PTGS1 (FR122047) did not affect it. The overall results suggest that PGE2 and PGF2alpha locally play luteoprotective roles in bovine CL by suppressing apoptosis of LSCs.