Drp1 Phosphorylation Is Indispensable for Steroidogenesis in Leydig Cells

EGFR-ERK1/2 signaling and mitochondrial dynamics in seasonal ovarian steroidogenesis of the muskrats (Ondatra zibethicus)

The dynamic systems of mitochondria, including mitochondrial fusion and fission, are essential for ovarian endocrine and follicular development. Meanwhile, ERK1/2 signaling is an important mechanism mediating altered mitochondrial dynamics and steroidogenesis. The purpose of this study was to investigate the seasonal changes in ovarian steroidogenesis concerning EGFR-ERK1/2 signaling and mitochondrial dynamics of the muskrats (Ondatra zibethicus). The results showed that follicular development in the muskrats remained in the tertiary follicular stage during the non-breeding season, accompanied by a significant decrease in serum and ovarian concentrations of 17β-estradiol and progesterone from the breeding season to the non-breeding season. EGF, EGFR, ERK1/2, p-ERK1/2, and mitochondrial dynamics regulators were mainly localized in granulosa cells and theca cells of muskrats during the breeding and non-breeding seasons. The mRNA levels of Egfr, Erk1/2, Mfn1/2, Opa1, Drp1, and steroidogenic enzymes in the ovaries were remarkably higher during the breeding season. The 17β-estradiol concentrations in the serum and ovaries as well as the relative levels of Mfn1/2, Opa1, and Drp1 were positively associated with each other. Furthermore, transcriptomic analysis of the ovaries revealed that differentially expressed genes might be linked to steroid biosynthesis, estrogen signaling pathway, and mitochondrial membrane-related pathways. In conclusion, these results suggest that the up-regulation of mitochondrial dynamics regulators during the breeding season is closely associated with enhanced ovarian steroidogenesis in the muskrats, which may be regulated by upstream EGFR-ERK1/2 signaling.

The mitochondrial protease PARL is required for spermatogenesis

Mitochondrial function plays an important role in the maintenance of male fertility. However, the mechanisms underlying mitochondrial defect-related infertility remain mostly unclear. Here we show that a deficiency of PARL (Parl-/-), a mitochondrial protease, causes complete arrest of spermatogenesis during meiosis I. PARL deficiency led to severe downregulation of proteins of respiratory chain complex IV in testes that did not occur in other tested organs, causing a deficit in complex IV activity and ATP production. Furthermore, Parl-/- testes showed an almost complete loss of HSD17B3, a protein of the sER responsible for the last step in testosterone synthesis. While testosterone production appeared to be restored by overexpression of HSD17B12, loss of the canonical testosterone synthesis led to an upregulation of luteinizing hormone (LH) and of LH-regulated responses. These results suggest an important impact of the downstream regulation of mitochondrial defects that manifest in a cell-type-specific manner and extend beyond mitochondria.

Drp1 regulated PINK1-dependent mitophagy protected duck follicular granulosa cells from acute heat stress injury

The mitochondrial quality control system is crucial in maintaining cellular homeostasis during environmental stress. Granulosa cells are the main cells secreting steroid hormones, and mitochondria are the key organelles for steroid hormone synthesis. The impact of the mitochondrial quality control system on granulosa cells' steroid hormone synthesis and survival under heat stress is still unclear. Here, we showed that acute heat stress induces mitochondrial damage and significantly increases the number of mitophagy-like vesicles in the cytoplasm of duck ovary granulosa cells at the ultra-structural level. Meanwhile, we also found heat stress significantly increased mitochondrial fission and mitophagy-related protein expression levels both in vivo and in vitro. Furthermore, by confocal fluorescence analysis, we discovered that LC3 was distributed spot-like manner near the nucleus in the heat treatment group, and the LC3 spots and lysosomes were colocalized with Mito-Tracker in the heat treatment group. We further detected the mitophagy-related protein in the cytoplasm and mitochondria, respectively. Results showed that the PINK1 protein was significantly increased both in cytoplasm and mitochondria, while the LC3-Ⅱ/LC3-Ⅰ ratio increase only occurred in mitochondrial. In addition, the autophagy protein induced by acute heat treatment was effectively inhibited by the mitophagy inhibitor CysA. Finally, we demonstrated that the alteration of cellular mitophagy by siRNA interference with Drp1 and PINK1 inhibited the steroid synthesis of granulosa cells and increased cell apoptosis. Study provides strong evidence that the Drp1 regulated PINK1-dependent mitophagy pathway protects follicular granulosa cells from acute heat stress-induced injury.

ID3 regulates progesterone synthesis in bovine cumulus cells through modulation of mitochondrial function

DNA binding inhibitory factor 3 (ID3) has been shown to have a key role in maintaining proliferation and differentiation. It has been suggested that ID3 may also affect mammalian ovarian function. However, the specific roles and mechanisms are unclear. In this study, the expression level of ID3 in cumulus cells (CCs) was inhibited by siRNA, and the downstream regulatory network of ID3 was uncovered by high-throughput sequencing. The effects of ID3 inhibition on mitochondrial function, progesterone synthesis, and oocyte maturation were further explored. The GO and KEGG analysis results showed that after ID3 inhibition, differentially expressed genes, including StAR, CYP11A1, and HSD3B1, were involved in cholesterol-related processes and progesterone-mediated oocyte maturation. Apoptosis in CC was increased, while the phosphorylation level of ERK1/2 was inhibited. During this process, mitochondrial dynamics and function were disrupted. In addition, the first polar body extrusion rate, ATP production and antioxidation capacity were reduced, which suggested that ID3 inhibition led to poor oocyte maturation and quality. The results will provide a new basis for understanding the biological roles of ID3 as well as cumulus cells.

Loss of SUMO-specific protease 2 causes isolated glucocorticoid deficiency by blocking adrenal cortex zonal transdifferentiation in mice

SUMOylation is a dynamic posttranslational modification, that provides fine-tuning of protein function involved in the cellular response to stress, differentiation, and tissue development. In the adrenal cortex, an emblematic endocrine organ that mediates adaptation to physiological demands, the SUMOylation gradient is inversely correlated with the gradient of cellular differentiation raising important questions about its role in functional zonation and the response to stress. Considering that SUMO-specific protease 2 (SENP2), a deSUMOylating enzyme, is upregulated by Adrenocorticotropic Hormone (ACTH)/cAMP-dependent Protein Kinase (PKA) signalling within the zona fasciculata, we generated mice with adrenal-specific Senp2 loss to address these questions. Disruption of SENP2 activity in steroidogenic cells leads to specific hypoplasia of the zona fasciculata, a blunted reponse to ACTH and isolated glucocorticoid deficiency. Mechanistically, overSUMOylation resulting from SENP2 loss shifts the balance between ACTH/PKA and WNT/β-catenin signalling leading to repression of PKA activity and ectopic activation of β-catenin. At the cellular level, this blocks transdifferentiation of β-catenin-positive zona glomerulosa cells into fasciculata cells and sensitises them to premature apoptosis. Our findings indicate that the SUMO pathway is critical for adrenal homeostasis and stress responsiveness.

Bitter Taste Receptors and Endocrine Disruptors: Cellular and Molecular Insights from an In Vitro Model of Human Granulosa Cells

Endocrine disrupting chemicals (EDCs) are compounds that interfere with the synthesis, transport and binding action of hormones responsible for reproduction and homeostasis. Some EDCs compounds are activators of Taste bitter Receptors, a subclass of taste receptors expressed in many extraoral locations, including sperm and follicular somatic cells. This makes TAS2Rs attractive molecules to study and investigate to shed light on the effect of EDCs on female reproduction and fertility. This study aims to assess the effect of selected EDCs [namely Biochanin A (BCA), caffeine, Daidzein, Genistein and Isoflavone] on hGL5, an immortalized cell line exhibiting characteristics coherent with primary follicular granulosa cells. After demonstrating that this model expresses all the TAS2Rs (TAS2R3, TAS2R4, TAS2R14, TAS2R19, TAS2R43) specifically expressed by the primary human granulosa cells, we demonstrated that BCA and caffeine significantly affect mitochondrial footprint and intracellular lipid content, indicating their contribution in steroidogenesis. Our results showed that bitter taste receptors may be involved in steroidogenesis, thus suggesting an appealing mechanism by which these compounds affect the female reproductive system.

Neuromedin S Regulates Steroidogenesis through Maintaining Mitochondrial Morphology and Function via NMUR2 in Goat Ovarian Granulosa Cells

Neuromedin S (NMS) plays various roles in reproductive regulation, while the mechanism by which NMS regulates ovarian steroidogenesis remains unclear. In the current study, we confirmed the enhancement role of NMS in steroidogenesis in goat ovarian granulosa cells (GCs). To further explore the specific mechanism, we conducted a knockdown of NMUR2 in GCs followed by treatment with NMS and determined the effects of NMS treatment on mitochondrial morphology and function. The results found that NMS treatment increased the production of estrogen and up-regulated the expression of STAR, CYP11A1, 3BHSD, and CYP19A1, while the effects of NMS treatment were blocked by the knockdown of NMUR2 in goat GCs. Moreover, NMS treatment enhanced the fusion of mitochondria and up-regulated the expression of OPA1, MFN1, and MFN2, and increased mitochondrial membrane potential, the activity of respiratory chain enzymes and ATP production by maintaining a low expression level of mitochondrial unfolded protein response markers. The effects of NMS treatment on mitochondria were reversed by NMUR2 knockdown and NMS cotreatment. The possible mechanism of the results above was revealed by NMS treatment activating the Hippo pathway effector YAP1 and then managing the expression of phosphorylation PPARGC1A (Ser571). Together, these data showed that NMS promoted the fusion of mitochondria and protected mitochondrial function from mitochondrial unfolded protein response possibly via the NMUR2/YAP1/PPARGC1A pathway, thereby affecting the steroidogenesis of goat GCs. By elaborating the potential mechanism of NMS in regulating estrogen production in goat GCs, our results can serve as the mechanism reference for follicular growth and development.

Grim-19 plays a key role in mitochondrial steroidogenic acute regulatory protein stability and ligand-binding properties in Leydig cells

Grim-19 (gene associated with retinoid-IFN-induced mortality 19), the essential component of complex I of mitochondrial respiratory chain, functions as a noncanonical tumor suppressor by controlling apoptosis and energy metabolism. However, additional biological actions of Grim-19 have been recently suggested in male reproduction. We investigated here the expression and functional role of Grim-19 in murine testis. Testicular Grim-19 expression was detected from mouse puberty and increased progressively thereafter, and GRIM-19 protein was observed to be expressed exclusively in interstitial Leydig cells (LCs), with a prominent mitochondrial localization. In vivo lentiviral vector-mediated knockdown of Grim-19 resulted in a significant decrease in testosterone production and triggered aberrant oxidative stress in testis, thus impairing male fertility by inducing germ cell apoptosis and oligozoospermia. The control of testicular steroidogenesis by GRIM-19 was validated using the in vivo knockdown model with isolated primary LCs and in vitro experiments with MA-10 mouse Leydig tumor cells. Mechanistically, we suggest that the negative regulation exerted by GRIM-19 deficiency-induced oxidative stress on steroidogenesis may be the result of two phenomena: a direct effect through inhibition of phosphorylation of steroidogenic acute regulatory protein (StAR) and subsequent impediment to StAR localization in mitochondria and an indirect pathway that is to facilitate the inhibiting role exerted by the extracellular matrix on the steroidogenic capacity of LCs via promotion of integrin activation. Altogether, our observations suggest that Grim-19 plays a potent role in testicular steroidogenesis and that its alterations may contribute to testosterone deficiency-related disorders linked to metabolic stress and male infertility.

Linking mitochondrial dynamics and fertility: promoting fertility by phoenixin through modulation of ovarian expression of GnRH receptor and mitochondrial dynamics proteins DRP-1 and Mfn-2

Obesity is linked to reproductive disorders. Novel neuropeptide phoenixin demonstrated many therapeutic actions. In this study, we aim to evaluate phoenixin’s potential effect in obesity-induced infertility through modulating mitochondrial dynamics. Ninety adult female rats were divided to 4 groups: (I), fed with normal pellet diet; (II), given phoenixin; (III), fed with high-fat diet. Rats that developed obesity and infertility were divided to 2 groups: (III-A), received no further treatment; (III-B), given phoenixin. Our results showed that phoenixin treatment in obese infertile rats significantly decreased serum levels of insulin and testosterone and ovarian levels of dynamin-related protein1(Drp1),reactive oxygen species ROS, TNF-α, MDA, and caspase-3. Phoenixin treatment also significantly increased serum estrogen progesterone, LH, and FSH together with ovarian levels of GnRH receptor (GnRHR), mitofusin2(Mfn2), mitochondrial transmembrane potential (ΔΨm), and electron transport chain (ETC) complex-I significantly when compared with obese group. Ovarian histopathological changes were similarly improved by phoenixin. Our data demonstrate phoenixin’s role in improving obesity-induced infertility.

1-Nitropyrene disrupts testosterone biogenesis via AKAP1 degradation promoted mitochondrial fission in mouse Leydig cell

Previous study found 1-NP disrupted steroidogenesis in mouse testis, but the underlying mechanism remained elusive. The current work aims to explore the roles of ROS-promoted AKAP1 degradation and excessive mitochondrial fission in 1-NP-induced steroidogenesis disruption in MLTC-1 cells. Transmission electron microscope analysis found 1-NP promoted excessive mitochondrial fission. Further data showed 1-NP disrupted mitochondrial function. pDRP1 (Ser637), a negative regulator of mitochondrial fission, was reduced in 1-NP-treated MLTC-1 cells. Mechanistically, 1-NP caused degradation of AKAP1, an upstream regulator of pDRP1 (Ser637). MG132, a proteasome inhibitor, attenuated 1-NP-induced AKAP1 degradation and downstream pDRP1 (Ser637) reduction, thereby ameliorating 1-NP-downregulated steroidogenesis. Further analysis found that cellular ROS was elevated and NOX4, HO-1 and SOD2 were upregulated in 1-NP-exposed MLTC-1 cells. NAC, a well-known commercial antioxidant, alleviated 1-NP-induced excessive ROS and oxidative stress. 1-NP-induced AKAP1 degradation and subsequent downregulation of pDRP1 (Ser637) were prevented by NAC pretreatment. Moreover, NAC attenuated 1-NP-resulted T synthesis disturbance in MLTC-1 cells. The present study indicates that ROS mediated AKAP1 degradation and subsequent pDRP1 (Ser637) dependent mitochondrial fission is indispensable in 1-NP caused T synthesis disruption. This study provides a new insight into 1-NP-induced endocrine disruption, and offers theoretical basis in public health prevention.

Evidence of a role for cAMP in mitochondrial regulation in ovarian granulosa cells

In the ovary, proliferation and differentiation of granulosa cells (GCs) drive follicular growth. Our immunohistochemical study in a non-human primate, the Rhesus monkey, showed that the mitochondrial activity marker protein cytochrome c oxidase subunit 4 (COX4) increases in GCs in parallel to follicle size, and furthermore, its intracellular localization changes. This suggested that there is mitochondrial biogenesis and trafficking, and implicates the actions of gonadotropins, which regulate follicular growth and ovulation. Human KGN cells, i.e. granulosa tumour cells, were therefore used to study these possibilities. To robustly elevate cAMP, and thereby mimic the actions of gonadotropins, we used forskolin (FSK). FSK increased the cell size and the amount of mitochondrial DNA of KGN cells within 24 h. As revealed by MitoTracker™ experiments and ultrastructural 3D reconstruction, FSK treatment induced the formation of elaborate mitochondrial networks. H89, a protein kinase A (PKA) inhibitor, reduced the network formation. A proteomic analysis indicated that FSK elevated the levels of regulators of the cytoskeleton, among others (data available via ProteomeXchange with identifier PXD032160). The steroidogenic enzyme CYP11A1 (Cytochrome P450 Family 11 Subfamily A Member 1), located in mitochondria, was more than 3-fold increased by FSK, implying that the cAMP/PKA-associated structural changes occur in parallel with the acquisition of steroidogenic competence of mitochondria in KGN cells. In summary, the observations show increases in mitochondria and suggest intracellular trafficking of mitochondria in GCs during follicular growth, and indicate that they may partially be under the control of gonadotropins and cAMP. In line with this, increased cAMP in KGN cells profoundly affected mitochondrial dynamics in a PKA-dependent manner and implicated cytoskeletal changes.

Drp1 Expression and Phosphorylation in Steroidogenic Corpus Luteum during the Estrous Cycle in Rat Ovaries

In response to luteinizing hormone (LH), a higher concentration of progesterone (P4) is produced in luteal cells of corpus luteum (CL). Mitochondria are an essential cellular organelle in steroidogenesis. The specific engagement of the concept regarding mitochondrial shaping with early stages of steroidogenesis was suggested in reproductive endocrine cells. Although the specific involvement of GTPase dynamin-related protein 1 (Drp1) with steroidogenesis has been demonstrated in luteal cells of bovine CL in vitro, its actual relationship with ovarian steroidogenesis during the estrous cycle remains unknown. In this study, while Fis1 and Opa1 protein levels did not show significant changes during the estrous cycle, Drp1, Mfn1, and Mfn2 proteins exhibited relatively lower levels at proestrus than at estrus or diestrus. 3β-HSD showed higher levels at proestrus than at estrus or diestrus. In addition, Drp1 phosphorylation (s637) was higher in proestrus than in estrus or diestrus. Immune-positive cells for Drp1, pDrp1 (s637), and 3β-HSD were all localized in the cytoplasm of luteal cells in the CL. The immune-positive cells for 3β-HSD were more frequently seen in the CL at proestrus than at estrus or diestrus. Immunoreactivity for Drp1 in luteal cells at proestrus was weaker than that at estrus or diestrus. However, pDrp1 (s637) immune-positive cells were mostly detected in luteal cells at proestrus. These results imply that steroidogenesis (P4 production) in the CL is closely related to phosphorylation of Drp1 at serine 637. Taken together, this study presents evidence that Drp1 phosphorylation at serine 637 is an important step in steroidogenesis in the CL.

Prohibitin-1 plays a regulatory role in Leydig cell steroidogenesis

Mitochondria are essential for steroidogenesis. In steroidogenic cells, the initiation of steroidogenesis from cholesterol occurs on the matrix side of the inner mitochondrial membrane by the enzyme P450scc. This requires cholesterol import from the cytoplasm through the outer mitochondrial membrane, facilitated by the StAR protein. The subsequent steps leading to P450scc remain elusive. Here we report that the male transgenic mice that expressed a mutant form of a mitochondrial protein prohibitin-1 (PHB1^Tyr114Phe) from the Fabp-4 gene promoter displayed smaller testes, higher testosterone, and lower gonadotropin levels compared with PHB1-expressing and wild-type mice. A subsequent analysis of the testis and Leydig cells from the mice revealed that PHB1 played a previously unknown regulatory role in Leydig cell steroidogenesis. This includes a role in coordinating cell signaling, cholesterol homeostasis, and mitochondrial biology pertaining to steroidogenesis. The implications of our finding are broad as the initial stages of steroidogenesis are indistinguishable across steroidogenic cells.

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Tyr114Phe-PHB-1 transgenic male mice reveal PHB-1’s role in testosterone production

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PHB-1 coordinates steroidogenic signaling and events in testosterone biosynthesis

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Tyr114 residue in PHB-1 plays a regulatory role in testosterone production

Epimedium promotes steroidogenesis by CREB activation-mediated mitochondrial fusion in endosulfan treated leydig cells

Epimedium, is used traditionally in Chinese medicine to treat infertility problems. In this study, we establish the cell model to elucidate the protective effect of epimedium against ES by analyzing the molecular relationship between mitochondrial dynamics and steroidogenesis and to explore the molecular mechanism focusing on mitochondria function relating to fertility. ES induced ROS accumulation in mitochondria and the epimedium treatment significantly reduced the ROS accumulation. Furthermore, mitochondria morphology was restored to elongated shape following epimedium treatment. Epimedium treatment promoted dynamin-associated protein 1 (Drp1)-mediated steroidogenesis pathway by upregulating PKA, CREB, Drp1, and StAR protein expression in response to ES exposure in Leydig cells. Moreover, it was also identified that, CREB plays an important role in epimedium activation in Drp1-mediated steroidogenesis signaling pathway by increasing, phospho-CREB expression in nucleus. Testosterone level is decreased in ES-exposed cells; however, the testosterone level was increased after epimedium treatment. In conclusion, epimedium treatment improved mitochondria function in ES-exposed Leydig cells and activated downstream Drp1-dependent steroidogenesis by CREB mediated signaling pathway.

The antioxidant and anti-apoptotic potential of Pleurotus eryngii extract and its chitosan-loaded nanoparticles against doxorubicin-induced testicular toxicity in male rats

This study was conducted to evaluate the protective role of Pleurotus eryngii extract (PE) and Pleurotus eryngii extract-loaded chitosan nanoparticles (PE-CSNP) against doxorubicin (DOX)-induced testicular toxicity in rats. Male rats were divided into six groups: control (DMSO/ethanol), PE (200 mg/kg PE), PE-CSNP (30 mg/kg PE-CSNP), DOX (10 mg/kg DOX, a single dose, i.p), DOX+PE (10 mg/kg DOX+200 mg/kg PE) and DOX+PE-CSNP (10 mg/kg DOX+30 mg/kg PE-CSNP). PE and PE-CSNP were administered by oral gavage every other day for 21 days. DOX-treated rats showed histopathological impairment compared with the control group. There was an increase in the apoptotic index, caspase 3 (CASP3), BCL2-associated X apoptosis regulator (BAX), dynamin-related protein 1 (DRP1) expression and total oxidative status (TOS) in the DOX group, while mitofusin-2 (MFN2), total antioxidative status (TAS) and serum testosterone levels of the DOX group reduced when compared with the other groups. PE and PE-CSNP treatments provided significant protection against DOX-induced oxidative stress by reducing TOS levels and increasing TAS levels. CASP3, BAX, apoptotic index and DRP1-MFN2 expressions were restored by PE and PE-CSNP. However, the PE-CSNP showed higher antioxidant and anti-apoptotic efficacy compared with PE. Thus, our results provide evidence that CSNP and PE could synergistically have a potent antioxidant and anti-apoptotic therapy against DOX-induced testicular damage in male rats.

The Expanding Role of Mitochondria, Autophagy and Lipophagy in Steroidogenesis

The fundamental framework of steroidogenesis is similar across steroidogenic cells, especially in initial mitochondrial steps. For instance, the START domain containing protein-mediated cholesterol transport to the mitochondria, and its conversion to pregnenolone by the enzyme P450scc, is conserved across steroidogenic cells. The enzyme P450scc localizes to the inner mitochondrial membrane, which makes the mitochondria essential for steroidogenesis. Despite this commonality, mitochondrial structure, number, and dynamics vary substantially between different steroidogenic cell types, indicating implications beyond pregnenolone biosynthesis. This review aims to focus on the growing roles of mitochondria, autophagy and lipophagy in cholesterol uptake, trafficking and homeostasis in steroidogenic cells and consequently in steroidogenesis. We will focus on these aspects in the context of the physiological need for different steroid hormones and cell-intrinsic inherent features in different steroidogenic cell types beyond mitochondria as a mere site for the beginning of steroidogenesis. The overall goal is to provide an authentic and comprehensive review on the expanding role of steroidogenic cell-intrinsic processes in cholesterol homeostasis and steroidogenesis, and to bring attention to the scientific community working in this field on these promising advancements. Moreover, we will discuss a novel mitochondrial player, prohibitin, and its potential role in steroidogenic mitochondria and cells, and consequently, in steroidogenesis.

Melatonin Protects Against Mdivi-1-Induced Abnormal Spindle Assembly and Mitochondrial Superoxide Production During Porcine Oocyte Maturation

Mitochondrial division inhibitor 1 (Mdivi-1) reportedly provides a close connection between oocyte maturation and mitochondrial function in pigs. N-acetyl-5-methoxy-tryptamine (melatonin) is known to be a representative antioxidant with the ability to rehabilitate meiotic maturation of porcine oocytes. However, the ability of melatonin to recover Mdivi-1-mediated disruption of spindle formation during meiotic maturation of porcine oocytes during in vitro maturation (IVM) has not been studied. Here, we first investigated changes in mitochondrial length, such as fragmentation and elongation form, in mature porcine oocytes during IVM. Mature oocytes require appropriate mitochondrial fission for porcine oocyte maturation. We identified a dose-dependent reduction in meiotic maturation in porcine oocytes following Mdivi-1 treatment (50, 75, and 100 μM). We also confirmed changes in mitochondrial fission protein levels [dynamin-related protein 1 phosphorylation at serine 616 (pDRP1-Ser616) and dynamin-related protein 1 (DRP1)], mitochondrial membrane potential, and ATP production in 75 μM Mdivi-1-treated oocytes. As expected, Mdivi-1 significantly reduced mitochondrial function and DRP1 protein levels and increased spindle abnormalities in porcine oocytes. In addition, we confirmed that melatonin restores abnormal spindle assembly and reduces meiotic maturation rates by Mdivi-1 during porcine oocyte maturation. Interestingly, the expression levels of genes that reduce DNA damage and improve tubulin formation were enhanced during porcine meiotic maturation. Taken together, these results suggest that melatonin has direct beneficial effects on meiotic maturation through tubulin formation factors during porcine oocyte maturation.

Triptolide Induces Leydig Cell Apoptosis by Disrupting Mitochondrial Dynamics in Rats

Triptolide is widely used in the clinical treatment of various diseases. Side effects, including reproductive toxicity to male patients, limit its application. However, no detailed mechanisms or potential intervention targets have been reported. In this study, we show that triptolide activated the mitochondrial apoptosis pathway in rat testicular Leydig cells and induced apoptosis both in vivo and in vitro, which may cause hypoleydigism and impair spermatogenesis. Mechanistically, triptolide-induced dynamin-related protein 1 (Drp1) overexpression, which interfered with mitochondrial dynamic stability to activate the mitochondrial apoptosis pathway. Mdivi-1, a selective Drp1 inhibitor, partially reversed the mitochondrial dynamic disturbance and rat testicular Leydig cell apoptosis induced by triptolide. Inhibiting Drp1 over-activation may be a new strategy for mitigating the reproductive toxicity of triptolide.

Neuropeptide Y Induces Cardiomyocyte Hypertrophy via Attenuating miR-29a-3p in Neonatal Rat Cardiomyocytes

BACKGROUND

Neuropeptide Y (NPY) has been well known to induce Cardiomyocyte Hypertrophy (CH), which is possibly caused by disruption of cardiac cell energy balance. As mitochondria is losely related to energy metabolism, in this study, we investigated the changes in mitochondrial Dynamics-related protein (Drp1) expression under the action of NPY. miRNA-29a, a endogenous noncoding small molecule RNA which is involved in many cardiac diseases, by using a bioinformatics tool, we found a potential binding site of miRNA-29a on the Drp1 mRNA, and suggesting that miRNA-29a might play a regulatory role.

OBJECTIVE

To investigate the role of miR-29a-3p in the process of NPY-induced CH, and further explore it's predicted relationship with Drp1.

METHODS

The expression levels of miR-29a-3p and Atrial Natriuretic Peptide (ANP) were performed by the method of fluorescence quantitative PCR, in addition, expression of Drp1 in treated and control groups were performed by western blot analysis.] Results: We found NPY leads to the CH and up-regulation of ANP expression levels. We also found significant up-regulation of Drp1 expression and down-regulation of miR-29a-3p expression in NPY-treated cells. The decrease in miR-29a-3p expression may lead the increase expression level of Drp1. We found that the expression of ANP increased after NPY treatment. When Drp1 protein was silenced, the high expression of ANP was inhibited.

CONCLUSION

In this study, we found up-regulation of Drp1 in cells treated with NPY. Drp1 mRNA is a predicted target for miR-29a-3p, and the expression of Drp1 was attenuated by miR-29a-3p. Therefore, NPY leads to down-regulation of miR-29a-3p expression, up-regulation of Drp1 expression, and NPY leads to CH. Correspondingly, miR-29a-3p can counteract the effects of NPY. This may be a new way, which could be used in diagnosis and treatment plan for CH.

Growing Up Under Constant Light: A Challenge to the Endocrine Function of the Leydig Cells

The factors influencing Leydig cell maturity and the acquisition of functional capacity are incompletely defined. Here we analyzed the constant light (LL) influence on Leydig cells' endocrine function during reproductive maturation. Rats were exposed to LL from P21 to P90. Data were collected at juvenile (P35), peri/pubertal (P42, P49), and adult (P90) stages of life. The results proved the effect of LL on rats' physiology by changing of bimodal voluntary activity pattern into free-running. Additionally, the peripheral clock in Leydig cells changed in LL condition, indicating disturbed rhythm: the positive element (Bmal1) increased in pre-/pubertal but decreased in the adult period, while negative elements (Per2 and Reverba) were increased. The effects of LL were most prominent in puberty: pituitary genes encoding gonadotropic hormones (Cga, Lhb, Fshb) decreased; serum corticosterone increased, while serum androgens and mass of testicular and sex accessory organs reduced; markers of Leydig cells maturity/differentiation (Insl3, Lhcgr) and steroidogenesis-related genes (Scarb1, Star, Cyp11a1, Cyp17a1) decreased; the steroidogenic and energetic capacity of the Leydig cell mitochondria decreased; the mtDNA copy number reduced, and mitochondrial dynamics markers changed: fusion decreased (Opa1 and Mfn2), and mitophagy increased (Pink1). In adults, the negative effect of LL on mitochondrial function and steroidogenic capacity persists in adult Leydig cells while other parameters reached control values. Altogether, the results indicate that LL slows down Leydig cells' maturation by reducing the endocrine and energy capacity of cells leading to the delay of reproductive development.

Dependence of Leydig Cell's Mitochondrial Physiology on Luteinizing Hormone Signaling

Knowledge about the relationship between steroidogenesis and the regulation of the mitochondrial bioenergetics and dynamics, in steroidogenic cells, is not completely elucidated. Here we employed in vivo and ex vivo experimental models to analyze mitochondrial physiology in Leydig cells depending on the different LH-cAMP environments. Activation of LH-receptor in rat Leydig cells ex and in vivo triggered cAMP, increased oxygen consumption, mitoenergetic and steroidogenic activities. Increased mitoenergetic activity i.e., ATP production is achieved through augmented glycolytic ATP production and a small part of oxidative phosphorylation (OXPHOS). Transcription of major genes responsible for mitochondrial dynamics was upregulated for Ppargc1a (regulator of mitogenesis and function) and downregulated for Drp1 (main fission marker), Prkn, Pink1 and Tfeb (mitophagy markers). Leydig cells from gonadotropin-treated rats show increased mitogenesis confirmed by increased mitochondrial mass, increased mtDNA, more frequent mitochondria observed by a transmission electron microscope and increased expression of subunits of respiratory proteins Cytc/CYTC and COX4. Opposite, Leydig cells from hypogonadotropic-hypogonadal rats characterized by low LH-cAMP, testosterone, and ATP production, reduced markers of mitogenesis and mitofusion (Mfn1/2, Opa1) associated with reduced mtDNA content. Altogether results underline LH-cAMP signaling as an important regulator of mitochondrial physiology arranging mitochondrial dynamics, bioenergetic and steroidogenic function in Leydig cells.

Clock-Controlled Mitochondrial Dynamics Correlates with Cyclic Pregnenolone Synthesis

Neurosteroids are steroids synthetized in the nervous system, with the first step of steroidogenesis taking place within mitochondria with the synthesis of pregnenolone. They exert important brain-specific functions by playing a role in neurotransmission, learning and memory processes, and neuroprotection. Here, we show for the first time that mitochondrial neurosteroidogenesis follows a circadian rhythm and correlates with the rhythmic changes in mitochondrial morphology. We used synchronized human A172 glioma cells, which are steroidogenic cells with a functional core molecular clock, to show that pregnenolone levels and translocator protein (TSPO) are controlled by the clock, probably via circadian regulation of mitochondrial fusion/fission. Key findings were recapitulated in mouse brains. We also showed that genetic or pharmacological abrogation of fusion/fission activity, as well as disturbing the core molecular clock, abolished circadian rhythms of pregnenolone and TSPO. Our findings provide new insights into the crosstalk between mitochondrial function (here, neurosteroidogenesis) and circadian cycles.

Luteinizing hormone regulates the phosphorylation and localization of the mitochondrial effector dynamin-related protein-1 (DRP1) and steroidogenesis in the bovine corpus luteum

The corpus luteum is an endocrine gland that synthesizes and secretes progesterone. Luteinizing hormone (LH) activates protein kinase A (PKA) signaling in luteal cells, increasing delivery of substrate to mitochondria for progesterone production. Mitochondria maintain a highly regulated equilibrium between fusion and fission in order to sustain biological function. Dynamin-related protein 1 (DRP1), is a key mediator of mitochondrial fission. The mechanism by which DRP1 is regulated in the ovary is largely unknown. We hypothesize that LH via PKA differentially regulates the phosphorylation of DRP1 on Ser616 and Ser637 in bovine luteal cells. In primary cultures of steroidogenic small luteal cells (SLCs), LH, and forskolin stimulated phosphorylation of DRP1 (Ser 637), and inhibited phosphorylation of DRP1 (Ser 616). Overexpression of a PKA inhibitor blocked the effects of LH and forskolin on DRP1 phosphorylation. In addition, LH decreased the association of DRP1 with the mitochondria. Genetic knockdown of the DRP1 mitochondria receptor, and a small molecule inhibitor of DRP1 increased basal and LH-induced progesterone production. Studies with a general Dynamin inhibitor and siRNA knockdown of DRP1 showed that DRP1 is required for optimal LH-induced progesterone biosynthesis. Taken together, the findings place DRP1 as an important target downstream of PKA in steroidogenic luteal cells.