Carbenoxolone reduces cyclic nucleotides level, destabilizes maturation promoting factor and induces meiotic exit from diplotene arrest in rat cumulus oocytes complexes cultured in vitro

Selenium-based metabolic oligosaccharide engineering strategy for quantitative glycan detection

Metabolic oligosaccharide engineering (MOE) is a classical chemical approach to perturb, profile and perceive glycans in physiological systems, but probes upon bioorthogonal reaction require accessibility and the background signal readout makes it challenging to achieve glycan quantification. Here we develop SeMOE, a selenium-based metabolic oligosaccharide engineering strategy that concisely combines elemental analysis and MOE,enabling the mass spectrometric imaging of glycome. We also demonstrate that the new-to-nature SeMOE probes allow for detection, quantitative measurement and visualization of glycans in diverse biological contexts. We also show that chemical reporters on conventional MOE can be integrated into a bifunctional SeMOE probe to provide multimodality signal readouts. SeMOE thus provides a convenient and simplified method to explore the glyco-world.

BPA interferes with granulosa cell development and oocyte meiosis in mouse preantral follicles

Bisphenol A (BPA) is an established environmental endocrine disruptor and can interfere with the development of female germ cells. However, the underlying mechanisms are still unclear. We investigated the effects of BPA on granulosa cell development and meiosis of oocytes using in vitro culture system of mouse preantral follicles. Preantral follicles from D14 mouse ovary were treated with 10 μg/mL BPA in vitro for 11 days. The adherent area of follicles was measured. On D11, cumulus cell expansion was observed. The meiosis recovery rate was calculated. Western blot detected P53, proliferating cell nuclear antigen (PCNA), estrogen receptor α (ERα), and cyclin B1. ELISA measured estrogen and progesterone levels. Immunofluorescence detected Cx37 on oocyte membrane. Gap junction communication was assessed. We found that BPA significantly promoted the expressions of PCNA and ERα in granulosa cells and the secretion of estrogen and progesterone by granulosa cells on D10 and significantly increased the attachment area of the follicles on D8 and D10. However, it reduced the expansion of cumulus cells, Cx37 expression, and the gap junction communication between cumulus cells and oocytes on D11. BPA promoted the recovery of oocytes from meiosis, interrupted the expression of cyclin B1 protein in arrested germinal vesicle breakdown (GVBD) oocytes, and reduced the in vitro maturation rate of oocytes. These GVBD oocytes were live without apoptosis or death. Conclusively, BPA disturbs the development of granulosa cells and the meiosis progression of oocytes by decreasing gap junction communication between oocytes and the granulosa cells as well as regulating cyclin B1 expression in GVBD oocytes.

Cilostamide, a phosphodiesterase 3A inhibitor, sustains meiotic arrest of rat oocytes by modulating cyclic adenosine monophosphate level and the key regulators of maturation promoting factor

Cilostamide, a phosphodiesterase 3A (Pde3A) inhibitor, is known to increase intraoocyte cyclic adenosine monophosphate (cAMP) level which is involved in sustaining meiotic arrest of the oocytes. To explore the mechanisms involved in the cilostamide-mediated meiotic arrest of the oocytes, the present study describes the effects of cilostamide on cAMP level and related factors involved in maturation of the oocytes at its different meiotic stages; diplotene, metaphase I (MI) and metaphase II (MII). The oocytes from these three stages were collected from rat ovary and incubated with 10 µM cilostamide for 3 h in CO₂ incubator. The levels of cAMP, cyclic guanosine monophosphate (cGMP) and the key players of maintaining meiotic arrest during oocyte maturation; Emi2, Apc, Cyclin B1, and Cdk1, were analyzed in diplotene, MI and MII stages. Pde3A was found to be expressed at all three stages but with the lowest level in MI oocyte. As compared to the control sets, the cAMP concentration was found to be highest in MII whereas cGMP was highest in the diplotene stage of cilostamide-treated group. The treated group showed declined reactive oxygen species level as compared with the control counterparts. Relatively increased levels of the Emi2, Cyclin B1, and phosphorylated thr161 of Cdk1 versus declined levels of phosphorylated thr14/tyr15 of Cdk1 in diplotene and MII stage oocytes are known to be involved in maintaining meiotic arrest and all these factors were found to undergo similar pattern of change due to the treatment with cilostamide. The findings thus suggest that cilostamide treatment promotes meiotic arrest by Pde3A inhibition led increase of both cAMP and cGMP level vis-a-vis modulation of the related regulatory factors such as Emi2, CyclinB1, and phosphorylated status of Cdk1 in diplotene and MII stage oocytes. Such a mechanism of meiotic arrest could allow the oocyte to prepare itself for meiotic maturation and thereby to improve oocyte quality.

Cyclic nucleotide phosphodiesterase inhibitors: possible therapeutic drugs for female fertility regulation

Cyclic nucleotide phosphodiesterases (PDEs) are group of enzymes responsible for the hydrolysis of cyclic adenosine 3', 5' monophosphate (cAMP) and cyclic guanosine 3', 5' monophosphate (cGMP) levels in wide variety of cell types. These PDEs are detected in encircling granulosa cells or in oocyte with in follicular microenvironment and responsible for the decrease of cAMP and cGMP levels in mammalian oocytes. A transient decrease of cAMP level initiates downstream pathways to cause spontaneous meiotic resumption from diplotene arrest and induces oocyte maturation. The nonspecific PDE inhibitors (caffeine, pentoxifylline, theophylline, IBMX etc.) as well as specific PDE inhibitors (cilostamide, milrinone, org 9935, cilostazol etc.) have been used to elevate cAMP level and inhibit meiotic resumption from diplotene arrest and oocyte maturation, ovulation, fertilization and pregnancy rates both in vivo as well as under in vitro culture conditions. The PDEs inhibitors are used as powerful experimental tools to demonstrate cyclic nucleotide mediated changes in ovarian functions and thereby fertility. Indeed, non-hormonal nature and reversible effects of nonspecific as well as specific PDE inhibitors hold promise for the development of novel therapeutic drugs for female fertility regulation.

Cilostamide and rolipram prevent spontaneous meiotic resumption from diplotene arrest in rat oocytes cultured in vitro

The involvement of specific phosphodiesterases (PDEs) in the modulation of cAMP and thereby spontaneous meiotic resumption remains poorly understood. This work aims to evaluate the effects of cilostamide and rolipram (PDE 3A and PDE 4D inhibitors) on spontaneous meiotic resumption from diplotene arrest in rat oocytes cultured in vitro. For this purpose, diplotene-arrested cumulus oocyte complexes (COCs) were collected from rat ovary. The COCs and denuded oocytes were exposed to various concentrations of cilostamide (0.0, 2.5, 5.0 and 10 μM) and rolipram (0, 10, 50 and 100 μM) for various times (0, 3, 5, 7, 14, 16, 18, 20, 22 and 24 h). Cilostamide inhibited spontaneous meiotic resumption in a concentration- and time-dependent manner in COCs and denuded oocytes. Although rolipram showed inhibition of spontaneous meiotic resumption up to some extent, cilostamide was more potent to prevent spontaneous meiotic resumption in both COCs and denuded oocytes. Cilostamide significantly reduced PDE 3A expression, increased cAMP level and prevented spontaneous meiotic resumption in COCs and denuded oocytes. Although rolipram inhibited PDE 4D expression in cumulus cells, increased cAMP level but was not sufficient to prevent spontaneous meiotic resumption. We conclude that both drugs prevent spontaneous resumption from diplotene-arrest through PDE 3A/PDE 4D-cAMP mediated pathway. However, as compare to rolipram, cilostamide was more potent in preventing spontaneous resumption from diplotene-arrest in rat oocytes cultured in vitro. Thus, cilostamide could be used as a potential candidate for the development of female contraceptive drug in future.

Role of granulosa cell mitogen-activated protein kinase 3/1 in gonadotropin-mediated meiotic resumption from diplotene arrest of mammalian oocytes

In mammals, preovulatory oocytes are encircled by several layers of granulosa cells (GCs) in follicular microenvironment. These follicular oocytes are arrested at diplotene arrest due to high level of cyclic nucleotides from encircling GCs. Pituitary gonadotropin acts at the level of encircling GCs and increases adenosine 3',5'-cyclic monophosphate (cAMP) and guanosine 3',5'-cyclic monophosphate (cGMP) and activates mitogen-activated protein kinase 3/1 (MAPK3/1) signaling pathway. The MAPK3/1 disrupts the gap junctions between encircling GCs and oocyte. The disruption of gap junctions interrupts the transfer of cyclic nucleotides to the oocyte that results a drop in intraoocyte cAMP level. A transient decrease in oocyte cAMP level triggers maturation promoting factor (MPF) destabilization. The destabilized MPF finally triggers meiotic resumption from diplotene arrest in follicular oocyte. Thus, MAPK3/1 from GCs origin plays important role in gonadotropin-mediated meiotic resumption from diplotene arrest in follicular oocyte of mammals.

Activity of MPF and expression of its related genes in mouse MI oocytes exposed to cadmium

Research has revealed that cadmium can disrupt ovarian function; however, few reports have focused on MI oocytes meiotic progression, especially the activity of maturation promoting factor (MPF) and its related genes (Cdk1, Ccnb1, and Cdc25b) expression. In this study, GV oocytes cultured in vitro for 0, 6, and 9 hours with five groups (control and doses of 0.05, 0.5, 2.5, and 5 μM Cd). At the same dose of cadmium but different exposure time: compared with 0h, Periodic changes in MPF activity were changed and continuously increased over time. The mRNA and protein expression of each MPF-related gene in different cadmium dose groups were changed compared with that of 0h. At the same exposure time but different dose of cadmium: compared with control group, MPF activity, mRNA and protein expressions of each MPF-related gene in all the cadmium exposure groups were increased at 9h after exposure. Cadmium maintains the high MPF activity in mouse MI oocytes during its meiotic process and disturbs the periodic change of MPF activity; meanwhile, cadmium exposure promotes the syntheses of MPF-related gene, which may be one of the molecular mechanisms for the maintenance of high MPF activity, and ultimately prevents the meiotic progression in oocytes.