Prostaglandin F2α upregulates Slit/Robo expression in mouse corpus luteum during luteolysis

Unraveling the role of lipid droplets and perilipin 2 in bovine luteal cells

Steroidogenic tissues contain cytosolic lipid droplets that are important for steroidogenesis. Perilipin 2 (PLIN2), a structural coat protein located on the surface of lipid droplets in mammalian cells, plays a crucial role in regulating lipid droplet formation and contributing to various cellular processes such as lipid storage and energy homeostasis. Herein, we examine the role that PLIN2 plays in regulating progesterone synthesis in the bovine corpus luteum. Utilizing gene array databases and Western blotting, we have delineated the expression pattern of PLIN2 throughout the follicular to luteal transition. Our findings reveal the presence of PLIN2 in both ovarian follicular and steroidogenic luteal cells, demonstrating an increase in its levels as follicular cells transition into the luteal phase. Moreover, the depletion of PLIN2 via siRNA enhanced progesterone production in small luteal cells, whereas adenovirus-mediated overexpression of both PLIN2 and Perilipin 3 (PLIN3) induced an increase in cytosolic lipid droplet accumulation and decreased hormone-induced progesterone synthesis in these cells. Lastly, in vivo administration of the luteolytic hormone prostaglandin F2α resulted in an upregulation of PLIN2 mRNA and protein expression, accompanied by a decline in serum progesterone. Our findings highlight the pivotal role of PLIN2 in regulating progesterone synthesis in the bovine corpus luteum, as supported by its dynamic expression pattern during the follicular to luteal transition and its responsiveness to luteotropic and luteolytic hormones. We suggest PLIN2 as a potential therapeutic target for modulating luteal function.

PGF2alpha Inhibits 20alpha-HSD Expression by Suppressing CK1alpha-induced ERK and SP1 Activation in the Corpus Luteum of Pregnant Mice

Prostaglandin F2α (PGF2α) is a luteolytic hormone that promotes parturition in mammals at the end of pregnancy by reducing progesterone secretion from the corpus luteum (CL). In rodents and primates, PGF2α rapidly converts progesterone to 20α-hydroxyprogesterone (20α-OHP) by promoting 20α-hydroxysteroid dehydrogenase (20α-HSD) expression. However, the specific mechanism of 20α-HSD regulation by PGF2α remains unclear. Casein Kinase 1α (CK1α) is a CK1 family member that regulates a variety of physiological functions, including reproductive development. Here, we investigated the effects of CK1α on pregnancy in female mice. Our experiments showed that CK1α is expressed in mouse CL, and its inhibition enhanced progesterone metabolism, decreased progesterone levels, and affected mouse embryo implantation. Further, CK1α mediated the effect of PGF2α on 20α-HSD in mouse luteal cells in vitro. Our results are the first to show that CK1α affects the 20α-HSD mRNA level by affecting the ERK signalling pathway to regulate the expression of the transcription factor SP1. These findings improve our understanding of PGF2α regulation of 20α-HSD.

Prostaglandin F2α regulates mitochondrial dynamics and mitophagy in the bovine corpus luteum

Prostaglandins are arachidonic acid-derived lipid mediators involved in numerous physiological and pathological processes. PGF2α analogues are therapeutically used for regulating mammalian reproductive cycles and blood pressure, inducing term labor, and treating ocular disorders. PGF2α exerts effects via activation of calcium and PKC signaling, however, little is known about the cellular events imposed by PGF2α signaling. Here, we explored the early effects of PGF2α on mitochondrial dynamics and mitophagy in the bovine corpus luteum employing relevant and well characterized in vivo and in vitro approaches. We identified PKC/ERK and AMPK as critical protein kinases essential for activation of mitochondrial fission proteins, DRP1 and MFF. Furthermore, we report that PGF2α elicits increased intracellular reactive oxygen species and promotes receptor-mediated activation of PINK-Parkin mitophagy. These findings place the mitochondrium as a novel target in response to luteolytic mediator, PGF2α. Understanding intracellular processes occurring during early luteolysis may serve as a target for improving fertility.

Hand2os1 Regulates the Secretion of Progesterone in Mice Corpus Luteum

The corpus luteum plays a key role in pregnancy maintenance and estrous cycle regulation by secreting progesterone. Hand2os1 is an lncRNA located upstream of Hand2, with which a bidirectional promoter is shared and is involved in the regulation of cardiac development and embryo implantation in mice. The aim of this study was to investigate the expression and regulation of Hand2os1 in the ovaries. Here, we used RNAscope to detect differential expression of Hand2os1 in the ovaries of cycling and pregnant mice. Hand2os1 was specifically detected in luteal cells during the proestrus and estrus phases, showing its highest expression in the corpus luteum at estrus. Additionally, Hand2os1 was strongly expressed in the corpus luteum on day 4 of pregnancy, but the positive signal progressively disappeared after day 8, was detected again on day 18, and gradually decreased after delivery. Hand2os1 significantly promoted the synthesis of progesterone and the expression of StAR and Cyp11a1. The decreased progesterone levels caused by Hand2os1 interference were rescued by the overexpression of StAR. Our findings suggest that Hand2os1 may regulate the secretion of progesterone in the mouse corpus luteum by affecting the key rate-limiting enzyme StAR, which may have an impact on the maintenance of pregnancy.

Slit/Robo signaling regulates Leydig cell steroidogenesis

BACKGROUND

First identified as a regulator of neuronal axon guidance, Slit/Robo signaling has since been implicated in additional physiologic and pathologic processes, such as angiogenesis, organogenesis and cancer progression. However, its roles in the regulation of testis function have been little explored.

METHODS

Immunohistochemistry and RT-qPCR analyses were performed to detect the expression of Slit/Robo signaling effectors in the adult mouse testis. To identify the roles and mechanisms of Slit/Robo signaling in the regulation of steroidogenesis, RT-qPCR, immunoblotting and hormone measurements were carried out using Leydig cells (primary cultures and the MA10 cell line) treated with exogenous SLIT ligands, and testes from Robo1-null mice.

RESULTS

Slit1, -2 and -3 and Robo1 and -2 expression was detected in the adult mouse testis, particularly in Leydig cells. In vitro treatment of Leydig cells with exogenous SLIT ligands led to a decrease in the expression of the steroidogenic genes Star, Cyp11a1, and Cyp17a1. SLIT2 treatment decreased the phosphorylation of the key steroidogenic gene regulator CREB, possibly in part by suppressing AKT activity. Furthermore, SLIT2 treatment reduced the responsiveness of MA10 cells to luteinizing hormone by decreasing the expression of Lhcgr. Consistent with these in vitro results, an increase in testicular Star mRNA levels and intra-testicular testosterone concentrations were found in Robo1-null mice. Finally, we showed that the expression of the Slit and Robo genes in Leydig cells is enhanced by testosterone treatment in vitro, by an AR-independent mechanism.

CONCLUSION

Taken together, these results suggest that Slit/Robo signaling represents a novel mechanism that regulates Leydig cell steroidogenesis. It may act in an autocrine/paracrine manner to mediate negative feedback by testosterone on its own synthesis. Video Abstract.

Differential expression profiles of long noncoding RNAs and mRNAs in human bone marrow mesenchymal stem cells after exposure to a high dosage of dexamethasone

Background

Abnormalities in apoptosis, cell cycle, proliferation, and differentiation of human bone marrow mesenchymal stem cells (hBMSCs) significantly impact bone metabolism and remodeling, resulting in various skeletal disorders. Long-term exposure to a high dosage of dexamethasone (Dex) induces apoptosis and inhibits the proliferation of mesenchymal stromal cells (MSCs), which are probable primary causes of various skeletal disorders. However, to date, the exact mechanisms of action of Dex on hBMSCs have not been fully elucidated.

Methods

To explore the effects of Dex on apoptosis, cell cycle, proliferation, senescence, osteogenic and adipogenic differentiation of hBMSCs at the various exposure times and concentrations, Hoechst 33342/PI staining, flow cytometry, crystal violet assay, β-galactosidase (β-GAL) activity assay, alizarin red S (ARS) staining assay, and Oil Red O (ORO) staining assay were performed. A microarray assay was used to identify differentially expressed lncRNAs and mRNAs in 10^− 6 mol/L Dex-treated hBMSCs, and a bioinformatics analysis was conducted to further explore the role of these differentially expressed lncRNAs and mRNAs in the coding and noncoding (CNC) network. Furthermore, the microarray results were validated using quantitative real-time PCR (qRT-PCR) analysis.

Results

Over the range of 10⁻⁸, 10⁻⁷, and 10⁻⁶ mol/L, Dex induced apoptosis, arrest of the cell cycle, inhibition of osteogenic differentiation, and promotion adipogenic differentiation of the hBMSCs in a dose-dependent manner. In addition, 10⁻⁶ mol/L Dex significantly induced apoptosis, suppressed proliferation, and increased the senescence of hBMSCs in a time-dependent manner. Interestingly, this time-dependent effect of Dex on the apoptosis of hBMSCs plateaued at the 7th day and decreased from the 8th day to the 10th day, while Dex treatment increased senescence of the hBMSCs on the 6th day. Furthermore, the microarray analysis identified a total of 137 differentially expressed mRNAs (90 upregulated and 47 downregulated) and 90 differentially expressed lncRNAs (61 upregulated and 29 downregulated) in hBMSCs after exposure to 10⁻⁶ mol/L Dex. The differentially expressed mRNAs and lncRNAs were associated with the regulation of cell apoptosis, proliferation, and cell cycle. Meanwhile, several signaling pathways involved in these processes, including the mTOR signaling pathway, Ras signaling pathway, HIF-1 signaling pathway, NF-kappa B signaling pathway, and TGF-beta signaling pathway, also were identified through the interaction net in the significant pathways (Path-Net) analysis. Furthermore, the CNC network further identified 78 core regulatory genes involved in the regulation of apoptosis. Additionally, qRT-PCR was used to confirm the identity of the key differentially expressed mRNAs and lncRNAs found to be closely associated with cell apoptosis to confirm the reliability of the microarray dataset.

Conclusions

In summary, the effect of Dex on apoptosis, cell cycle, proliferation, and osteogenic differentiation and adipogenic differentiation of the hBMSCs depended on exposure time and concentration. Continuous exposure to 10⁻⁶ mol/L of Dex for 7 days may be a suitable protocol for inducing the apoptosis of hBMSCs. Under this protocol, differentially expressed lncRNAs and mRNAs associated with apoptosis, cell cycle, and proliferation were identified, providing a new research direction for further studies.

Supplementary information

The online version contains supplementary material available at 10.1186/s13287-020-02040-8.

Slit2 Protects Hearts Against Ischemia-Reperfusion Injury by Inhibiting Inflammatory Responses and Maintaining Myofilament Contractile Properties

Background

The secreted glycoprotein Slit2, previously known as an axon guidance cue, has recently been found to protect tissues in pathological conditions; however, it is unknown whether Slit2 functions in cardiac ischemia-reperfusion (IR) injury.

Methods

Langendorff-perfused isolated hearts from Slit2-overexpressing (Slit2-Tg) mice and C57BL/6J mice (background strain) were subjected to 20 min of global ischemia followed by 40 min of reperfusion. We compared Slit2-Tg with C57BL/6J mice in terms of left ventricular function and infarct size of post-IR hearts along with tissue histological and biochemical assessments (mRNA and protein expression, phosphorylation status, and myofilament contractile properties).

Results

Slit2 played cardioprotective roles in maintaining contractile function and reducing infarct size in post-IR hearts. IR increased the expression of the Slit2 receptor Robo4 and the membrane receptor Slamf7, but these increases were suppressed by Slit2 overexpression post IR. This suppression was associated with inhibition of the nuclear translocation of NFκB p65 and reductions in IL-1β and IL-18 release into perfusates. Furthermore, Slit2 overexpression attenuated the increases in myofilament-associated PKCs and phosphorylation of cTnI at Ser43 in the post-IR myocardium. The myofilament calcium sensitivity and actomyosin MgATPase activity were preserved in the post-IR Slit2 myocardium.

Conclusion

Our work demonstrates that Slit2 inhibits inflammatory responses and maintains myofilament contractile properties, thus contributing, at least in part, to the prevention of structural and functional damage during IR.

Mitogen-activated protein kinase kinase kinase 8 (MAP3K8) mediates the LH-induced stimulation of progesterone synthesis in the porcine corpus luteum

Progesterone (P4) synthesized by the corpus luteum (CL) plays a key role in the establishment and maintenance of pregnancy. The LH signal is important for luteinisation and P4 synthesis in pigs. In a previous study, we demonstrated that mitogen-activated protein kinase kinase kinase 8 (MAP3K8) regulates P4 synthesis in mouse CL, but whether the function and mechanism of MAP3K8 in the pig is similar to that in the mouse is not known. Thus, in the present study we investigated the effects of MAP3K8 on porcine CL. Abundant expression of MAP3K8 was detected in porcine CL, and, in pigs, MAP3K8 expression was higher in mature CLs (or those of the mid-luteal phase) than in regressing CLs (late luteal phase). Further functional studies in cultured porcine luteal cells showed that P4 synthesis and the expression of genes encoding the key enzymes in P4 synthesis are significantly reduced when MAP3K8 is inhibited with the MAP3K8 inhibitor Tpl2 kinase inhibitor (MAP3K8i, 10μM). After 12-24h treatment of luteal cells with 100ngmL-1 LH, MAP3K8 expression and P4 secretion were significantly upregulated. In addition, the 10μM MAP3K8 inhibitor blocked the stimulatory effect of LH on P4 synthesis and extracellular signal-regulated kinase (ERK) 1/2 phosphorylation in porcine luteal cells. The LH-induced increases in MAP3K8 phosphorylation and expression, ERK1/2 phosphorylation and P4 synthesis were all blocked when protein kinase A was inhibited by its inhibitor H89 (20 μM) in porcine luteal cells. In conclusion, MAP3K8 mediates the LH-induced stimulation of P4 synthesis through the PKA/mitogen-activated protein kinase signalling pathway in porcine CL.

The Role of Apoptotic Signaling in Axon Guidance

Navigating growth cones are exposed to multiple signals simultaneously and have to integrate competing cues into a coherent navigational response. Integration of guidance cues is traditionally thought to occur at the level of cytoskeletal dynamics. Drosophila studies indicate that cells exhibit a low level of continuous caspase protease activation, and that axon guidance cues can activate or suppress caspase activity. We base a model for axon guidance on these observations. By analogy with other systems in which caspase signaling has non-apoptotic functions, we propose that caspase signaling can either reinforce repulsion or negate attraction in response to external guidance cues by cleaving cytoskeletal proteins. Over the course of an entire trajectory, incorrectly navigating axons may pass the threshold for apoptosis and be eliminated, whereas axons making correct decisions will survive. These observations would also explain why neurotrophic factors can act as axon guidance cues and why axon guidance systems such as Slit/Robo signaling may act as tumor suppressors in cancer.

Prostaglandin F2α Facilitates Hepatic Glucose Production Through CaMKIIγ/p38/FOXO1 Signaling Pathway in Fasting and Obesity

Gluconeogenesis is drastically increased in patients with type 2 diabetes and accounts for increased fasting plasma glucose concentrations. Circulating levels of prostaglandin (PG) F_2α are also markedly elevated in diabetes; however, whether and how PGF_2α regulates hepatic glucose metabolism remain unknown. Here, we demonstrated that PGF_2α receptor (F-prostanoid receptor [FP]) was upregulated in the livers of mice upon fasting- and diabetic stress. Hepatic deletion of the FP receptor suppressed fasting-induced hepatic gluconeogenesis, whereas FP overexpression enhanced hepatic gluconeogenesis in mice. FP activation promoted the expression of gluconeogenic enzymes (PEPCK and glucose-6-phosphatase) in hepatocytes in a FOXO1-dependent manner. Additionally, FP coupled with G_q in hepatocytes to elicit Ca²⁺ release, which activated Ca²⁺/calmodulin-activated protein kinase IIγ (CaMKIIγ) to increase FOXO1 phosphorylation and subsequently accelerate its nuclear translocation. Blockage of p38 disrupted CaMKIIγ-induced FOXO1 nuclear translocation and abrogated FP-mediated hepatic gluconeogenesis in mice. Moreover, knockdown of hepatic FP receptor improved insulin sensitivity and glucose homeostasis in ob/ob mice. FP-mediated hepatic gluconeogenesis via the CaMKIIγ/p38/FOXO1 signaling pathway, indicating that the FP receptor might be a promising therapeutic target for type 2 diabetes.

Progesterone down-regulates SLIT/ROBO expression in mouse corpus luteum

BACKGROUND

Progesterone produced by the corpus luteum (CL) is essential for preparation, implantation and maintenance of gestation. Furthermore, progesterone plays a protective role against luteolysis in rodents. It has been reported that Slit/Robo family members expressed in the CL and involved in prostaglandin F_2α (PGF_2α) induced luteolysis. However, the interactions between progesterone and Slits/Robos in CL are not clear. This study was designed to examine whether or not luteolysis is regulated by the interaction of progesterone and Slits/Robos in mouse CL.

METHODS

In the current study, we used Real-time PCR to identify the effect of progesterone on Slit2/Robo1 expression in cultured luteal cells in vitro, and the exogenous progesterone injection on mouse luteolysis and Slit/Robo expression in vivo was studied via Real-time PCR and Western bolt.

RESULTS

Our in vitro experiment revealed that 1μM progesterone significantly decreased Slit2/Robo1 mRNA levels at 6h, 12h and 24h. Our in vivo experiment showed that the mRNA and protein levels of Slit2 and Robo1 decreased significantly 7days after progesterone supplement.

CONCLUSION

These findings indicate that progesterone maintains CL function and resists luteolysis possibly through down-regulating Slit/Robo signaling pathway in the CL.

Regulation of inflammation by lipid mediators in oral diseases

Lipid mediators (LM) of inflammation are a class of compounds derived from ω-3 and ω-6 fatty acids that play a wide role in modulating inflammatory responses. Some LM possess pro-inflammatory properties, while others possess proresolving characteristics, and the class switch from pro-inflammatory to proresolving is crucial for tissue homeostasis. In this article, we review the major classes of LM, focusing on their biosynthesis and signaling pathways, and their role in systemic and, especially, oral health and disease. We discuss the detection of these LM in various body fluids, focusing on diagnostic and therapeutic applications. We also present data showing gender-related differences in salivary LM levels in healthy controls, leading to a hypothesis on the etiology of inflammatory diseases, particularly Sjögren's syndrome. We conclude by enumerating open areas of research where further investigation of LM is likely to result in therapeutic and diagnostic advances.

The role of GPR1 signaling in mice corpus luteum

Chemerin, a chemokine, plays important roles in immune responses, inflammation, adipogenesis, and carbohydrate metabolism. Our recent research has shown that chemerin has an inhibitory effect on hormone secretion from the testis and ovary. However, whether G protein-coupled receptor 1 (GPR1), the active receptor for chemerin, regulates steroidogenesis and luteolysis in the corpus luteum is still unknown. In this study, we established a pregnant mare serum gonadotropin-human chorionic gonadotropin (PMSG-hCG) superovulation model, a prostaglandin F2α (PGF2α) luteolysis model, and follicle and corpus luteum culture models to analyze the role of chemerin signaling through GPR1 in the synthesis and secretion of gonadal hormones during follicular/luteal development and luteolysis. Our results, for the first time, show that chemerin and GPR1 are both differentially expressed in the ovary over the course of the estrous cycle, with highest levels in estrus and metestrus. GPR1 has been localized to granulosa cells, cumulus cells, and the corpus luteum by immunohistochemistry (IHC). In vitro, we found that chemerin suppresses hCG-induced progesterone production in cultured follicle and corpus luteum and that this effect is attenuated significantly by anti-GPR1 MAB treatment. Furthermore, when the phosphoinositide 3-kinase (PI3K) pathway was blocked, the attenuating effect of GPR1 MAB was abrogated. Interestingly, PGF2α induces luteolysis through activation of caspase-3, leading to a reduction in progesterone secretion. Treatment with GPR1 MAB blocked the PGF2α effect on caspase-3 expression and progesterone secretion. This study indicates that chemerin/GPR1 signaling directly or indirectly regulates progesterone synthesis and secretion during the processes of follicular development, corpus luteum formation, and PGF2α-induced luteolysis.

New insights into implication of the SLIT/ROBO pathway in the prehierarchical follicle development of hen ovary

The SLIT/Roundabout (ROBO) pathway is involved in follicle development of mammalian ovary, and 2 secreted hormones activin A and inhibin A have potential roles in modulation of the SLIT/ROBO system, but the related actions remain poorly understood in bird. The aims of the present study were to examine the spatial and temporal expression of the SLIT ligand genes (SLIT1, SLIT2, and SLIT3) and their receptor ROBO1, ROBO2, ROBO3, and ROBO4 genes in various-sized prehierarchical follicles during hen ovary development and the effects of activin A and inhibin A on the expression of these genes in the cultured hen follicles. Our result demonstrated that the transcripts of the 3 SLIT genes were highly expressed in the developing follicles and expression patterns of the SLIT transcripts were different from those of ROBO genes detected by real-time quantitative reverse transcriptase PCR. Both SLIT and ROBO transcripts were predominantly expressed in oocytes and granulosa cells from the prehierarchichal follicles examined by in situ hybridization. The localization for SLIT and ROBO proteins was revealed by immunohistochemistry similar to the spatial distribution of their transcript. In cultured follicles (4 to 8 mm in diameter), the expression levels of SLIT and ROBO members are hormonally regulated by activin A (10 ng/mL) and/or inhibin A (20 ng/mL) after treatment for 24 h. However, the expression of only SLIT2, SLIT3, and ROBO3 mRNA presented a directly opposite response to activin A and inhibin A hormones. These results indicate that SLIT/ROBO pathway is implicated in the prehierarchical follicular development of the hen ovary by an intrafollicular autocrine and/or paracrine action, and is influenced by activin A and inhibin A hormones.

Stem cells, progenitor cells, and lineage decisions in the ovary

Exploring stem cells in the mammalian ovary has unleashed a Pandora's box of new insights and questions. Recent evidence supports the existence of stem cells of a number of the different cell types within the ovary. The evidence for a stem cell model producing mural granulosa cells and cumulus cells is strong, despite a limited number of reports. The recent identification of a precursor granulosa cell, the gonadal ridge epithelial-like cell, is exciting and novel. The identification of female germline (oogonial) stem cells is still very new and is currently limited to just a few species. Their origins and physiological roles, if any, are unknown, and their potential to produce oocytes and contribute to follicle formation in vivo lacks robust evidence. The precursor of thecal cells remains elusive, and more compelling data are needed. Similarly, claims of very small embryonic-like cells are also preliminary. Surface epithelial cells originating from gonadal ridge epithelial-like cells and from the mesonephric epithelium at the hilum of the ovary have also been proposed. Another important issue is the role of the stroma in guiding the formation of the ovary, ovigerous cords, follicles, and surface epithelium. Immune cells may also play key roles in developmental patterning, given their critical roles in corpora lutea formation and regression. Thus, while the cellular biology of the ovary is extremely important for its major endocrine and fertility roles, there is much still to be discovered. This review draws together the current evidence and perspectives on this topic.