Regulation of steroidogenesis in jc-410, a stable cell line of porcine granulosa origin

Establishment of A Reversibly Inducible Porcine Granulosa Cell Line

Granulosa cells (GCs) are the key components of ovarian follicles for regulating oocyte maturation. Previous established GC lines have allowed prolonged proliferation, but lost some physiological features owing to long-term immortalization. This study was to establish an induced immortal porcine GC line with reversible proliferation status by the tetracycline inducible (Tet-on) 3G system. Our conditional immortal porcine GCs (CIPGCs) line steadily propagated for at least six months and displayed primary GC morphology when cultured in the presence of 50 ng/mL doxycycline [Dox (+)]. Upon Dox withdrawal [Dox (–)], Large T-antigen expression, reflected by mCherry fluorescence, gradually became undetectable within 48 h, accompanied by less proliferation and size increase. The levels of estradiol and progesterone, and the expression of genes associated with steroid production, such as CYP11A1 (cytochrome P450 family 11), 3β-HSD (3β-hydroxysteroid dehydrogenase), StAR (steroidogenic acute regulatory protein), and CYP19A1 (cytochrome P450 family 19 subfamily a member 1), were all significantly higher in the Dox (–) group than Dox (+) group. The CIPGCs could switch into a proliferative state upon Dox induction. Interestingly, the expression of StAR and CYP19A1 in the CIPGCs (–Dox) was significantly increased by adding porcine follicular fluid (PFF) to mimic an ovary follicle environment. Moreover, PFF priming the CIPGCs in Dox (–) group resulted in similar estradiol production as that of primary GC, and enabled this cell line to respond to gonadotrophins in estradiol production. Collectively, we have established an inducible immortal porcine GC line, which offers a unique and valuable model for future research on the regulation of ovarian functions.

Pregnenolone co-treatment partially restores steroidogenesis, but does not prevent growth inhibition and increased atresia in mouse ovarian antral follicles treated with mono-hydroxy methoxychlor

Mono-hydroxy methoxychlor (mono-OH MXC) is a metabolite of the pesticide, methoxychlor (MXC). Although MXC is known to decrease antral follicle numbers, and increase follicle death in rodents, not much is known about the ovarian effects of mono-OH MXC. Previous studies indicate that mono-OH MXC inhibits mouse antral follicle growth, increases follicle death, and inhibits steroidogenesis in vitro. Further, previous studies indicate that CYP11A1 expression and production of progesterone (P4) may be the early targets of mono-OH MXC in the steroidogenic pathway. Thus, this study tested whether supplementing pregnenolone, the precursor of progesterone and the substrate for HSD3B, would prevent decreased steroidogenesis, inhibited follicle growth, and increased follicle atresia in mono-OH MXC-treated follicles. Mouse antral follicles were exposed to vehicle (dimethylsulfoxide), mono-OH MXC (10 μg/mL), pregnenolone (1 μg/mL), or mono-OH MXC and pregnenolone together for 96 h. Levels of P4, androstenedione (A), testosterone (T), estrone (E1), and 17β-estradiol (E2) in media were determined, and follicles were processed for histological evaluation of atresia. Pregnenolone treatment alone stimulated production of all steroid hormones except E2. Mono-OH MXC-treated follicles had decreased sex steroids, but when given pregnenolone, produced levels of P4, A, T, and E1 that were comparable to those in vehicle-treated follicles. Pregnenolone treatment did not prevent growth inhibition and increased atresia in mono-OH MXC-treated follicles. Collectively, these data support the idea that the most upstream effect of mono-OH MXC on steroidogenesis is by reducing the availability of pregnenolone, and that adding pregnenolone may not be sufficient to prevent inhibited follicle growth and survival.

Role of sex hormones in the modulation of cholangiocyte function

Over the last years, cholangiocytes, the cells that line the biliary tree, have been considered an important object of study for their biological properties which involves bile formation, proliferation, injury repair, fibrosis and angiogenesis. Cholangiocyte proliferation occurs in all pathologic conditions of liver injury where it is associated with inflammation and regeneration. During these processes, biliary cells start to secrete different cytokines, growth factors, neuropeptides and hormones which represent potential mechanisms for cross talk with other liver cells. Several studies suggest that hormones, and in particular, sex hormones, play a fundamental role in the modulation of the growth of this compartment in the injured liver which functionally conditions the progression of liver disease. Understanding the mechanisms of action and the intracellular pathways of these compounds on cholangiocyte pathophysiology will provide new potential strategies for the management of chronic liver diseases. The purpose of this review is to summarize the recent findings on the role of sex hormones in cholangiocyte proliferation and biology.

Hydroxysteroid Dehydrogenases in Bovine and Porcine Granulosa Cells Convert Zearalenone into its Hydroxylated Metabolites α-Zearalenol and β-Zearalenol

The enzymes 3alpha- and 3beta-hydroxysteroid dehydrogenase (3alpha- and 3beta-HSD) play a pivotal role in synthesis of various steroid hormones including oestradiol and testosterone. The structure of the mycotoxin zearalenone resembles many characteristics of steroids and binds to oestrogen receptors as an agonist. Consequently, it is suggested that zearalenone is also a substrate for 3alpha-HSD and 3beta-HSD. 3alpha-HSD and 3beta-HSD isoforms are expressed in the liver and kidney but also in many steroidogenic tissues. It was the aim of the present study to demonstrate the presence of these enzymes in granulosa cells, which were obtained from bovine and porcine ovaries, and to investigate whether zearalenone is a substrate for these enzymes. The results show a species-specific expression pattern in the granulosa cells of both species. Moreover, it was demonstrated that zearalenone when added to the culture medium, is converted into alpha-zearalenol and beta-zearalenol. Corresponding to the apparent expression profile, in porcine granulosa cells predominantly alpha-zearalenol was formed, whereas bovine granulosa cells preferentially converted zearalenone into beta-zearalenol. This is the first report demonstrating the extrahepatic biotransformation of zearalenone in target tissues.

Pharmacological inhibition of phosphodiesterase 4 triggers ovulation in follicle-stimulating hormone-primed rats

Phosphodiesterases (PDEs) are a family of enzymes that hydrolyze cyclic nucleotides to render them biologically inactive. As such, these enzymes are critical regulators of signal transduction pathways that use cyclic nucleotides as second messengers. PDE4 is one such member that has been identified in ovarian tissue and purported to have a role in the regulation of gonadotropin action. In the present study, selective PDE4 inhibitors enhanced intracellular signaling in a human LH receptor-expressing granulosa cell line. In vivo, PDE4 inhibition in FSH-primed rats resulted in ovulation, indicating that the PDE4 inhibitors can substitute for LH and human chorionic gonadotropin (hCG) in this process. Moreover, when coadministered with a subeffective dose of hCG, PDE4 inhibitors acted synergistically to enhance the ovulation response. Inhibitors of PDE3 or PDE5 had no ovulatory effect under similar conditions. Oocytes that were ovulated after PDE4 inhibition could be fertilized in vitro at a rate similar to that of oocytes from hCG-induced ovulation. Moreover, such oocytes were fully capable of being fertilized in vivo and developing into normal live pups. These results indicate that small molecule PDE4 inhibitors may be orally active alternatives to hCG as part of a fertility treatment regimen.

Ovarian granulosa cell lines

The ovary is a complex endocrine gland responsible for production of sex steroids and is the source of fertilizable ova for reproduction. It also produces various growth factors, transcription factors and cytokines that assist in the complex signaling pathways of folliculogenesis. The ovary possesses two primary steroidogenic cell types. The theca cells (and to a lesser extent, the stroma) are responsible for androgen synthesis, and the granulosa cells are responsible for conversion of androgens to estrogens, as well as progesterone synthesis. These cells undergo a transformation in the luteal phase of the menstrual cycle, converting them from estrogen producing, to predominantly progesterone producing cells. Understanding the molecular mechanisms regulating these cells is essential in understanding the regulation of steroidogenesis and reproduction. Creation of appropriate in vitro cell model systems can provide important tools for the study of ovarian function. This has led to the development of ovarian steroidogenic cell lines in several laboratories. Developing theca cell lines has met with limited success. Conversely, numerous human and animal granulosa cell lines have been developed. This review will discuss the existing granulosa cell lines and their characteristics.

Protein kinase Ciota enhances the transcriptional activity of the porcine P-450 side-chain cleavage insulin-like response element

IGF-I enhances steroidogenesis in granulosa cells by stimulating the expression of the rate-limiting steroidogenic enzyme, cytochrome P-450 side-chain cleavage (P-450(scc)). This effect is mediated through an IGF response element (IGFRE) that binds polypyrimidine tract-binding protein (PTB)-associated splicing factor (PSF) and Sp1. Sp1 is essential for activation of the IGFRE, and PSF functions as a repressor. We investigated mechanisms of modulation of the IGFRE by the atypical protein kinase C (PKC)iota in a porcine stable granulosa cell line, JC-410. PKCiota was found in nuclear extracts, and levels were increased by IGF-I after 24 and 48 h of treatment. Immunoprecipitation experiments demonstrated that PSF and PKCiota associated with each other in nuclear extracts from JC-410 cells. Transient transfection with expression plasmids of kinase-active and kinase-deficient PKCiota isoforms enhanced transcriptional activity of the IGFRE regardless of kinase catalytic activity. Depletion of PKCiota protein by small interfering RNA suppressed basal IGFRE activity but did not prevent IGF-I stimulation of the IGFRE. We conclude that PKCiota enhances transcriptional activity of the porcine P-450(scc) IGFRE independently of kinase activity by a mechanism involving protein-protein interaction with PSF.

Effects of progestins on progesterone synthesis in a stable porcine granulosa cell line: control of transcriptional activity of the cytochrome p450 side-chain cleavage gene

The purpose of the present study was to examine the effects of progestins on progesterone synthesis and expression of the cytochrome P450 cholesterol side-chain cleavage gene (P450(scc)) in a stable porcine granulosa cell line, the JC-410. Cells were incubated for 48 h with the synthetic progestogen-levornorgestrel with or without RU486 (progesterone and glucocorticoid receptor antagonist) or RWJ26819 (progesterone agonist without affinity to glucocorticoid receptors). Both levonorgestrel and RU486 enhanced progesterone accumulation in a dose-dependent manner. RU486 did not antagonize the effects of levonorgestrel, and RWJ26819 had no effect on progesterone production in cultured JC-410 cells. Progesterone and levonorgestrel increased steady state P450(scc) mRNA levels after 3-6 h of treatment. Progesterone and RU486 at 0.1, 1, and 10 microM increased the transcription rate of P450(scc) transiently expressed in JC-410 cells after 18 h of incubation; 30 microM had no effect, and 100 microM suppressed transcription. Levonorgestrel did not affect transcription of the P450(scc) gene, and RWJ26819 reduced its transcription. Progesterone and RU486 significantly decreased the number of cells and total protein content after 72 and 24 h of incubation, respectively. Levonorgestrel had no effect, whereas RWJ26819 increased (24 h) but subsequently reduced (72 h) cell number and protein content. The present results indicate that progestins are capable of directly modulating progesterone biosynthesis in porcine JC-410 granulosa cells. These effects may be exerted in part through the regulation of P450(scc) gene expression. Ostensible differences exist between progesterone and its synthetic analogues in the control of progesterone secretion in the stable porcine granulosa cell line in vitro.

Characterization of regulatory elements of ovine follicle-stimulating hormone (FSH) receptor gene: the role of E-box in the regulation of ovine FSHreceptor expression

Expression and activation of follicle-stimulating hormone receptor (FSHR) in the granulosa and Sertoli cells are required for normal development of the ovarian follicles and germ cells. However, little is known regarding the mechanisms by which FSHR expression is regulated. We fused an ovine FSHR promoter to a luciferase gene to understand the promoter regulation in two gonadal cell lines. Deletion studies revealed that the strongest promoter was at -200 to +163 relative to the transcription start site. One of cis-elements protected from DNase I digestion was mapped to between +32 and +54 of the 174-base pair (bp) minimal promoter. Electrophoretic mobility shift assay with a 26-bp probe (+32 to +57) and nuclear extracts from Sertoli (15P1) and granulosa (JC-410) cell lines demonstrated a sequence-specific DNA-protein complex. Southwestern analysis detected a 43-kDa protein bound to the 26-bp probe. Gel supershift with upstream stimulatory factor 1 and 2 (USF-1/2) antibodies revealed that the DNA-protein complex contained these two transcription factors. Mutation within the E-box of the promoter abolished the sequence-specific binding and the minimal promoter activity but also greatly reduced the transcription of the proximal promoters by 49%-70%. These data suggest that the USF-1/2 binding to the promoter is required for the expression of the ovine FSHR in the gonadal cells.

Generation of stable cell lines by spontaneous immortalization of primary cultures of porcine granulosa cells

We report the generation of stable cell lines obtained by spontaneous immortalization of primary cultures of porcine granulosa cells. Three hundred stable cell lines were obtained from three independent immortalization trials. Two of these cell lines retained the steroidogenic capabilities characteristic of granulosa cells, such as de novo synthesis of progesterone and conversion of androstenedione into estradiol-17beta. All the stable cell lines expressed the P450arom and 3betaHSD genes, confirming their granulosa origin. Moreover, the steroidogenic stable granulosa cells also expressed StAR and P450scc genes. Stable cells were developed in cultures using Medium 199 supplemented with 5% newborn calf serum (NBCS). The surviving cells overcame the senescent phase and entered a stage of continuous growth for over one hundred generations. No stable colonies were obtained from cultures grown in MEM or DMEM or media supplemented with 10% NBCS or 5 and 10% fetal calf serum (FCS). Medium 199 is a formulation richer in nutrients compared to MEM or DMEM and the cell growth capability of NBCS is lower than that of FCS, probably due to deficiency of growth factors. We speculate that spontaneous immortalization of granulosa cells may be facilitated by using a rich culture formulation supplemented with low concentrations of serum deficient in growth factors. We have validated the stable cell lines for studying the effect of hormonal steroids on granulosa cell steroidogenesis and the expression of the steroidogenic genes. Therefore, we believe that they are useful models to study the molecular mechanism involved in granulosa cell differentiation and steroidogenesis.

Activation of extracellular-regulated kinase pathways in ovarian granulosa cells by the novel growth factor type 1 follicle-stimulating hormone receptor. Role in hormone signaling and cell proliferation

Follicle-stimulating hormone (FSH) regulated growth and function of the ovarian follicle was previously thought to be mediated solely through activation of G(s)-coupled receptors. In this study, we show for the first time that this function is predominantly mediated through the alternatively spliced and novel growth factor type 1 receptor (oFSH-R3) that is also present in the ovary. Immortalized granulosa cells lacking endogenous FSH receptors, when transfected with either oFSH-R3 cDNA (JC-R3) or the G(s)-coupled oFSH-R1 (JC-R1), expressed the corresponding glycosylated receptor. In JC-R3 or JC-R1 cells labeled with bromodeoxyuridine or [(3)H]thymidine, FSH stimulated the cells to progress through S-phase and divide. The growth promoting effect of recombinant FSH in JC-R3 cells was preceded by the rapid activation of ERK1 and ERK2. This effect was hormone-specific and transient. In JC-R3 cells inhibitors like calphostin C, PD98059, Ag 18, or calcium chelators EGTA or 1,2-bis(O-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid/AM inhibited both mitogen-activated protein kinase activation and bromodeoxyuridine incorporation. FSH induced phosphorylation of the FSH-R3 receptor was blocked by pretreating cells with calphostin C. There was no cAMP induction by FSH in JC-R3 cells. The cAMP independent growth promoting effect of FSH is mediated by activation of Ca(2+) and mitogen-activated protein kinase-dependent pathways. Thus, alternative splicing of a G-protein coupled receptor creates the expression of a novel receptor motif that can mediate a widely recognized function of the glycoprotein hormone.

Dichlorodiphenyldichloroethylene potentiates the effect of protein kinase A pathway activators on progesterone synthesis in cultured porcine granulosa cells

The insecticide dichlorodiphenyltrichloroethane (DDT) and its major metabolite p,p'-dichlorodiphenyldichloroethylene (DDE) have been implicated as endocrine-modulating chemicals. The DDT metabolite p, p'-DDE has been found contaminating human tissues and follicular fluid because of dietary exposure. We investigated the effects of DDE on progesterone synthesis in a stable porcine granulosa cell line, JC-410, and in primary cultures of porcine granulosa cells. Progesterone synthesis was not affected by 0.1-100 ng/ml DDE in the JC-410 cells. However, 10 ng/ml DDE increased 8-bromo-cAMP (8-Br-cAMP)-stimulated progesterone synthesis 0.4-fold (P < 0.05) over the levels observed with 1 mM 8-Br-cAMP alone. The effect of cholera toxin (CT) on progesterone synthesis was increased 0.7-fold (P < 0.05) by 10 ng/ml DDE over the value observed with 30 ng/ml CT alone. In primary cultures of porcine granulosa cells, 10 ng/ml DDE potentiated CT-stimulated progesterone synthesis 1.2-fold over the value observed with CT alone. In the JC-410 cells, 1 and 10 ng/ml DDE increased CT-stimulated cytochrome P450-cholesterol side-chain cleavage (P450(scc)) mRNA levels 0.3- and 0.4-fold, respectively, over the values obtained with CT alone. Neither basal nor CT-stimulated cAMP levels were changed by DDE. We conclude that DDE affects granulosa cell response to protein kinase A activators by altering the expression of the P450(scc) gene.

Steroid regulation of progesterone synthesis in a stable porcine granulosa cell line: a role for progestins

The objective of this investigation was to determine the effect of steroid hormones on the synthesis of progesterone in a stable porcine granulosa cell line, JC-410. We also examined the effect of steroid hormones on expression of the genes encoding the steroidogenic enzymes, cytochrome P450-cholesterol side chain cleavage (P450scc) and 3beta-hydroxy-5-ene steroid dehydrogenase (3beta-HSD). We observed that 48 h exposure of the JC-410 cells to estradiol-17beta (estradiol), androstenedione, 5alpha-dihydrotestosterone, levonorgestrel, and 5-cholesten-3beta, 25-diol (25-hydroxycholesterol) resulted in stimulation of progesterone synthesis. 25-Hydroxycholesterol augmented progesterone synthesis stimulated by estradiol, 5alpha-dihydrotestosterone, levonorgestrel and 8-bromoadenosine 3':5'-cyclic monophosphate (8-Br-cAMP). This increase in progesterone synthesis was additive with estradiol, 5alpha-dihydrotestosterone and levonorgestrel, and synergistic with 8-Br-cAMP. Cholera toxin, progesterone, levonorgestrel and androstenedione increased P450scc mRNA levels, whereas estradiol had no effect. Cholera toxin, progesterone and levonorgestrel increased 3beta-HSD mRNA levels, but estradiol and androstenedione had no effect. The results were interpreted to mean that estrogens, androgens and progestins regulate progesterone synthesis in the JC-410 cells. The effect of androgens appears to be mediated by stimulation of P450scc gene expression while progestins stimulate both P450scc and 3beta-HSD gene expression. Our results support the concept that progesterone is an autocrine regulator of its own synthesis in granulosa cells.