Corticosterone Injection Impairs Follicular Development, Ovulation and Steroidogenesis Capacity in Mice Ovary

Minor changes to circulating steroid hormones in female rats after perinatal exposure to diethylstilbestrol or ketoconazole

Current chemical test strategies lack sensitive markers for detecting female reproductive toxicity caused by endocrine disrupting chemicals (EDCs). In search of a potentially sensitive readout, the steroidogenic disrupting effects of the well-known EDCs ketoconazole (KTZ) and diethylstilbestrol (DES) were investigated in vitro and on circulating steroid hormones in perinatally exposed female Sprague-Dawley rats. Twenty-one steroid hormones were analysed using LC-MS/MS in plasma from female rat offspring at postnatal day (PD) 6, 14, 22, 42 and 90. Most circulating steroid hormone levels increased with age except for estrone (E1), estradiol (E2) and backdoor pathway androsterone (ANDROST), which decreased after PD 22. Perinatal exposure to DES did not affect circulating steroid hormone levels at any dose or age compared to controls. KTZ exposure resulted in dose-dependent increase of corticosterone (CORTICO) at PD 6 and PD 14, with statistical significance only at PD 14. In the in vitro gold standard H295R steroidogenesis assay, twenty-one steroid hormones were measured instead of only T and E2. DES had subtle effects on steroidogenesis, whereas KTZ decreased most steroid hormones, but increased CORTICO, progesterone (P4), estriol (E3) initially (around 0.1-1 µM) before decreasing. Our data suggests that circulating steroidomic profiling may not be a sensitive readout for EDC-induced female reproductive toxicity. Further studies are needed to associate H295R assay steroidomic profiles with in vivo profiles, especially in target tissues such as adrenals or gonads. Expanding the H295R steroidogenic assay to include a comprehensive steroidomic profile may enhance its regulatory applicability.

Activation of P2X7 Receptor Mediates the Abnormal Ovulation Induced by Chronic Restraint Stress and Chronic Cold Stress

Chronic stress has become a major problem that endangers people's physical and mental health. Studies have shown that chronic stress impairs female reproduction. However, the related mechanism is not fully understood. P2X7 receptor (P2X7R) is involved in a variety of pathological changes induced by chronic stress. Whether P2X7R is involved in the effect of chronic stress on female reproduction has not been studied. In this study, we established a chronic restraint stress mouse model and chronic cold stress mouse model. We found that the number of corpora lutea was significantly reduced in the two chronic stress models. The number of corpora lutea indirectly reflects the ovulation, suggesting that chronic stress influences ovulation. P2X7R expression was significantly increased in ovaries of the two chronic stress models. A superovulation experiment showed that P2X7R inhibitor A-438079 HCL partially rescued the ovulation rate of the two chronic stress models. Further studies showed that activation of P2X7R signaling inhibited the cumulus expansion and promoted the expression of NPPC in granulosa cells, one key negative factor of cumulus expansion. Moreover, sirius red staining showed that the ovarian fibrosis was increased in the two chronic stress models. For the fibrosis-related factors, TGF-β1 was increased and MMP2 was decreased. In vitro studies also showed that activation of P2X7R signaling upregulated the expression of TGF-β1 and downregulated the expression of MMP2 in granulosa cells. In conclusion, P2X7R expression was increased in the ovaries of the chronic restraint-stress and chronic cold-stress mouse models. Activation of P2X7R signaling promoted NPPC expression and cumulus expansion disorder, which contributed to the abnormal ovulation of the chronic stress model. Activation of P2X7R signaling is also associated with the ovarian fibrosis changes in the chronic stress model.

Premeiotic deletion of Eif2s2 causes oocyte arrest at the early diplotene stage and apoptosis in mice

Eukaryotic translation initiation factor 2 subunit 2 (EIF2S2), a subunit of the heterotrimeric G protein EIF2, is involved in the initiation of translation. Our findings demonstrate that the depletion of Eif2s2 in premeiotic germ cells causes oocyte arrest at the pachytene and early diplotene stages at 1 day postpartum (dpp) and 5 dpp, respectively, and eventually leads to oocyte apoptosis and failure of primordial follicle formation. Further studies reveal that Eif2s2 deletion downregulates homologous recombination-related and mitochondrial fission-related protein levels, and upregulates the integrated stress response-related proteins and mRNA levels. Consistently, Eif2s2 deletion significantly decreases the expression of dictyate genes and compromises mitochondrial function, characterized by elongated shapes, decreased ATP levels and mtDNA copy number, along with an excessive accumulation of reactive oxygen species (ROS) and mitochondrial superoxide. Furthermore, DNA damage response and proapoptotic protein levels increase, while anti-apoptotic protein levels decrease in Eif2s2-deleted mice. An increase in oocytes with positive cleaved-Caspase-3 and TUNEL signals, alongside reduced Lamin B1 intensity, further indicates oocyte apoptosis. Collectively, Eif2s2 deletion in premeiotic germ cells causes oocyte meiotic arrest at the early diplotene stage by impairing homologous recombination, and eventually leads to oocyte apoptosis mainly through the downregulation of mitochondrial fission-related proteins, ROS accumulation and subsequent DNA damage.

Neurotensin agonist PD149163 modulates lipopolysaccharide induced inflammation and oxidative stress in the female reproductive system of mice

Inflammation-mediated reproductive health problems in females have become an emerging concern. The present investigation was aimed to elucidate the efficacy of the PD149163, agonist of the type I neurotensin receptor, in preventing/ameliorating the lipopolysaccharide (LPS) induced inflammation of the female reproductive system of the mice. Female Swiss Albino Mice (8 weeks old) were maintained in three groups (6/group): Group I as Control, Group II and Group III were exposed to intraperitoneal (i.p) LPS (1 mg/kg bw) for 5 days followed by treatment with PD149163 (100 μg/kg BW i.p.) to Group III (LPS + PD) for 28 days. After termination of the experiment on 29th day, plasma levels of inflammatory cytokines, LH, FSH, estradiol, corticosterone, oxidative stress effects in the ovary and histopathological study of the ovary and uterine horn were done. LPS-induced inflammation of the ovary and uterine horn was ameliorated/prevented by PD149163 as reflected in the reduced histopathological scores, significant elevation of the plasma anti-inflammatory cytokine IL-10 and decrease of the pro inflammatory cytokines TNF-α and IL-6. Significant decrease of lipid peroxide, increase of antioxidant defense enzymes, Superoxide dismutase and Catalase in the ovary indicated reduction of oxidative stress. The plasma levels of the reproduction related hormones and corticosterone were restored. PD149163 acts as an anti-inflammatory and anti-oxidative agent in modulation of inflammation in the female reproductive system (ovary & uterine horn). These findings suggest that the therapeutic potential of the analogs of neurotensin including PD149163 should be explored for the treatment of the female reproductive health issues.

Differential susceptibility of male and female germ cells to glucocorticoid-mediated signaling

While physiologic stress has long been known to impair mammalian reproductive capacity through hormonal dysregulation, mounting evidence now suggests that stress experienced prior to or during gestation may also negatively impact the health of future offspring. Rodent models of gestational physiologic stress can induce neurologic and behavioral changes that persist for up to three generations, suggesting that stress signals can induce lasting epigenetic changes in the germline. Treatment with glucocorticoid stress hormones is sufficient to recapitulate the transgenerational changes seen in physiologic stress models. These hormones are known to bind and activate the glucocorticoid receptor (GR), a ligand-inducible transcription factor, thus implicating GR-mediated signaling as a potential contributor to the transgenerational inheritance of stress-induced phenotypes. Here, we demonstrate dynamic spatiotemporal regulation of GR expression in the mouse germline, showing expression in the fetal oocyte as well as the perinatal and adult spermatogonia. Functionally, we find that fetal oocytes are intrinsically buffered against changes in GR signaling, as neither genetic deletion of GR nor GR agonism with dexamethasone altered the transcriptional landscape or the progression of fetal oocytes through meiosis. In contrast, our studies revealed that the male germline is susceptible to glucocorticoid-mediated signaling, specifically by regulating RNA splicing within the spermatogonia, although this does not abrogate fertility. Together, our work suggests a sexually dimorphic function for GR in the germline, and represents an important step towards understanding the mechanisms by which stress can modulate the transmission of genetic information through the germline.

Influence of refeeding on production, blood biochemistry parameters, and reproduction in underfed Kacang goat does

This research aimed to investigate the effect of refeeding on production, blood biochemical parameters, and reproduction in underfed Kacang goat does. Twelve 2-3-year-old Kacang goats scored (body condition score [BCS]: 1-1.5) with poor body condition but appeared healthy, gave normal births 3-4 months before but no longer nursing their youngs, and anestrus were used in this study. The experiment consisted of 110 days with 14 days of adaptation period and 96 days of feeding treatment and data collection. After the adaptation period, the animals were divided into two groups (A and B), with six animals each. During the first 40 days (underfeeding period), they were fed with kangkong (Ipomoea reptans) straw at a level of 2% of body weight (BW). For the following 56 days (refeeding period), each animal in group A was fed at the level of 4% BW per day while group B was fed at the level of 5% BW per day consisting of 50% kangkong straw and 50% concentrate. Feed intake, average daily gain, body condition, and estrus were assessed in the period of underfeeding and refeeding. Blood samples were collected at the end of the underfeeding and refeeding period for blood biochemical parameter analyses. During the underfeeding period, the animals were anestrous and had poor body condition (BCS: 1.17-1.33) and high serum levels of cortisol, progesterone, and estradiol. Refeeding resulted in a significant increase in BCS (2.75-3.0), restoring estrous cycle, and reduced serum cortisol and progesterone level (p < 0.05). The Kacang goats had good compensatory growth. It could be concluded that refeeding at the level of 4-5% BW would restore undernourished goats' clinical condition, productivity, and reproductive performance after 8 weeks of refeeding.

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.

The Corticosterone–Glucocorticoid Receptor–AP1/CREB Axis Inhibits the Luteinizing Hormone Receptor Expression in Mouse Granulosa Cells

Under stress conditions, luteinizing hormone (LH)-mediated ovulation is inhibited, resulting in insufficient oocyte production and excretion during follicular development. When the body is stressed, a large amount of corticosterone (CORT) is generated, which will lead to a disorder of the body’s endocrine system and damage to the body. Our previous work showed that CORT can block follicular development in mice. Since LH acts through binding with the luteinizing hormone receptor (Lhcgr), the present study aimed to investigate whether and how corticosterone (CORT) influences Lhcgr expression in mouse ovarian granulosa cells (GCs). For this purpose, three-week-old ICR female mice were injected intraperitoneally with pregnant mare serum gonadotropin (PMSG). In addition, the treatment group was injected with CORT (1 mg/mouse) at intervals of 8 h and the control group was injected with the same volume of methyl sulfoxide (DMSO). GCs were collected at 24 h, 48 h, and 55 h after PMSG injection. For in vitro experiments, the mouse GCs obtained from healthy follicles were treated with CORT alone, or together with inhibitors against the glucocorticoid receptor (Nr3c1). The results showed that the CORT caused a downregulation of Lhcgr expression in GCs, which was accompanied by impaired cell viability. Moreover, the effect of the CORT was mediated by binding to its receptor (Nr3c1) in GCs. Further investigation revealed that Nr3c1 might regulate the transcription of Lhcgr through inhibiting the expression of Lhcgr transcription factors, including AP1 and Creb. Taken together, our findings suggested a possible mechanism of CORT-induced anovulation involving the inhibition of Lhcgr expression in GCs by the CORT–Nr3c1–AP1/Creb axis.

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.

Effects of RAC1 on Proliferation of Hen Ovarian Prehierarchical Follicle Granulosa Cells

Simple Summary

The growth and development of ovary follicles is an intricate, highly organized process involving many local intra-ovarian factors. Ras-related C3 botulinum toxin substrate1 (RAC1) is speculated to be associated with prehierarchical follicle development of hen ovaries. The current study initially revealed RAC1 mRNA to be expressed in varied-size follicles and stroma and its expression levels in the prehierarchical follicles of 1.0–3.9 mm, 6.0–6.9 mm and 7.0–8.0 mm in diameter were remarkably higher than the other groups. Moreover, RAC1 protein was mainly expressed in the oocytes and granulosa cells (GC), as well as in stromal tissues of the follicles. To understand the exact roles of the RAC1 gene in regulation of follicular GC proliferation and differentiation, siRNA interference and overexpression of the RAC1 gene were conducted. Our experiments demonstrated that the RAC1 gene can significantly promote the expression of mRNA and proteins of FSHR, CCND2, CYP11A1, PCNA and StAR genes in GC and directly elevate the proliferation of GC in vitro. These results indicated RAC1 played a crucial role in regulation of GC proliferation and differentiation and steroidogenesis during the development of prehierarchical follicles. This study provided a base for elucidating the molecular mechanisms underlying the biological effect of RAC1 on the hen ovary follicle growth and development.

Abstract

RAC1 belongs to the small G protein Rho subfamily and is implicated in regulating gene expression, cell proliferation and differentiation in mammals and humans; nevertheless, the function of RAC1 in growth and development of hen ovarian follicles is still unclear. This study sought to understand the biological effects of RAC1 on granulosa cell (GC) proliferation and differentiation of hen ovarian prehierarchical follicles. Firstly, our results showed expression levels of RAC1 mRNA in the follicles with diameters of 7.0–8.0 mm, 6.0–6.9 mm and 1.0–3.9 mm were greater than other follicles (p < 0.05). The RAC1 protein was mainly expressed in oocyte and its around GCs and stromal tissues of the prehierarchical follicles by immunohistochemistry. Further investigation revealed the RAC1 gene remarkably enhanced the mRNA and protein expression levels of FSHR (a marker of follicle selection), CCND2 (a marker of cell-cycle progression and GC differentiation), PCNA (a marker of GC proliferation), StAR and CYP11A1 (markers of GC differentiation and steroidogenesis) (p < 0.05). Furthermore, our data demonstrated siRNA interference of RAC1 significantly reduced GC proliferation (p < 0.05), while RAC1 gene overexpression enhanced GC proliferation in vitro (p < 0.05). Collectively, this study provided new evidence that the biological effects of RAC1 on GC proliferation, differentiation and steroidogenesis of chicken ovary follicles.