Dose response of luteinized porcine granulosa cells in vitro to prolactin: dependency on pre-exposure to human chorionic gonadotrophin

The diverse mechanism of action of dichlorodiphenyldichloroethylene (DDE) and methoxychlor in ovarian cells in vitro

Dichlorodiphenyldichloroethylene (DDE), the most stable metabolite of the organochlorine insecticide dichlorodiphenyltrichloroethane (DDT), and the DDT analog methoxychlor can have adverse effects on reproduction. These chemicals have been identified as having estrogenic activity. The aim of the current study was to examine the effects of dichlorodiphenyldichloroethylene (DDE), methoxychlor, and estradiol-17 beta on steroidogenesis and FSH responsiveness in ovarian cells in vitro. Experiments were performed on a primary culture of porcine granulosa cells and a culture of Chinese hamster ovary (CHO) cells, the latter stably transfected with the FSH receptor (CHO-FSH-R). DDE (10 microM) and estradiol-17 beta (0.1 microM) but not methoxychlor (10 microM), increased proliferation of the granulosa cells. DDE (100 and 10 microM, respectively) decreased FSH-stimulated cAMP synthesis in the granulosa and CHO-FSH-R cells. DDE also decreased progesterone synthesis in the granulosa cells. Methoxychlor (10 microM) inhibited progesterone synthesis in the granulosa cells, but it did not affect the generation of cAMP in either type of cells studied. However, methoxychlor inhibited estradiol-17 beta-stimulated progesterone synthesis in the granulosa cells. We conclude that DDE primarily inhibited the generation of cAMP, while methoxychlor suppressed progesterone synthesis through a mechanism distal to cAMP generation. The present results indicate that DDE and methoxychlor are not limited to a mimicking of the endocrine effects of estradiol-17 beta in cultured ovarian cells. Therefore, a non-estrogenic component of the endocrine disrupting activities of DDE and methoxychlor must be considered in evaluating their reproductive toxicity.

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.

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.

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

We investigated the regulation of steroidogenesis in a cell line of porcine granulosa origin, JC-410. Cells responded to the protein kinase-A activators, cholera toxin and forskolin, with increased accumulation of intracellular cAMP. Histochemically, cells were shown to contain 3beta-HSD, the enzyme which converts pregnenolone to progesterone. The JC-410 cells produced progesterone and responded to the protein kinase-A activators with an increase in progesterone synthesis. Progesterone levels were also increased by 25-hydroxycholesterol, pregnenolone, estradiol and androstenedione. Follicle-stimulating hormone and luteinizing hormone had no effect on cAMP or progesterone accumulation. Androstenedione was required for the synthesis of estradiol by JC-410 cells. Steady-state levels of mRNA for the steroidogenic enzymes 3beta-HSD and P450scc were increased by treatment with cholera toxin, whereas P450arom was not changed. These cells express the steroidogenic enzymes genes in a similar fashion to primary cultures of porcine granulosa cells. The JC-410 cells may represent a valuable model to study second messenger regulation and the molecular mechanisms involved in steroidogenesis in granulosa cells.

Prolactin (PRL) and its receptor: actions, signal transduction pathways and phenotypes observed in PRL receptor knockout mice

PRL is an anterior pituitary hormone that, along with GH and PLs, forms a family of hormones that probably resulted from the duplication of an ancestral gene. The PRLR is also a member of a larger family, known as the cytokine class-1 receptor superfamily, which currently has more than 20 different members. PRLRs or binding sites are widely distributed throughout the body. In fact, it is difficult to find a tissue that does not express any PRLR mRNA or protein. In agreement with this wide distribution of receptors is the fact that now more than 300 separate actions of PRL have been reported in various vertebrates, including effects on water and salt balance, growth and development, endocrinology and metabolism, brain and behavior, reproduction, and immune regulation and protection. Clearly, a large proportion of these actions are directly or indirectly associated with the process of reproduction, including many behavioral effects. PRL is also becoming well known as an important regulator of immune function. A number of disease states, including the growth of different forms of cancer as well as various autoimmune diseases, appear to be related to an overproduction of PRL, which may act in an endocrine, autocrine, or paracrine manner, or via an increased sensitivity to the hormone. The first step in the mechanism of action of PRL is the binding to a cell surface receptor. The ligand binds in a two-step process in which site 1 on PRL binds to one receptor molecule, after which a second receptor molecule binds to site 2 on the hormone, forming a homodimer consisting of one molecule of PRL and two molecules of receptor. The PRLR contains no intrinsic tyrosine kinase cytoplasmic domain but associates with a cytoplasmic tyrosine kinase, JAK2. Dimerization of the receptor induces tyrosine phosphorylation and activation of the JAK kinase followed by phosphorylation of the receptor. Other receptor-associated kinases of the Src family have also been shown to be activated by PRL. One major pathway of signaling involves phosphorylation of cytoplasmic State proteins, which themselves dimerize and translocate to nucleus and bind to specific promoter elements on PRL-responsive genes. In addition, the Ras/Raf/MAP kinase pathway is also activated by PRL and may be involved in the proliferative effects of the hormone. Finally, a number of other potential mediators have been identified, including IRS-1, PI-3 kinase, SHP-2, PLC gamma, PKC, and intracellular Ca2+. The technique of gene targeting in mice has been used to develop the first experimental model in which the effect of the complete absence of any lactogen or PRL-mediated effects can be studied. Heterozygous (+/-) females show almost complete failure to lactate after the first, but not subsequent, pregnancies. Homozygous (-/-) females are infertile due to multiple reproductive abnormalities, including ovulation of premeiotic oocytes, reduced fertilization of oocytes, reduced preimplantation oocyte development, lack of embryo implantation, and the absence of pseudopregnancy. Twenty per cent of the homozygous males showed delayed fertility. Other phenotypes, including effects on the immune system and bone, are currently being examined. It is clear that there are multiple actions associated with PRL. It will be important to correlate known effects with local production of PRL to differentiate classic endocrine from autocrine/paracrine effects. The fact that extrapituitary PRL can, under some circumstances, compensate for pituitary PRL raises the interesting possibility that there may be effects of PRL other than those originally observed in hypophysectomized rats. The PRLR knockout mouse model should be an interesting system by which to look for effects activated only by PRL or other lactogenic hormones. On the other hand, many of the effects reported in this review may be shared with other hormones, cytokines, or growth factors and thus will be more difficult to study. (ABSTRACT TRUNCATED)

3β-hydroxy-5-ene Steroid dehydrogenase gene expression regulation in porcine granulosa cells : Differential effect of FSH and LH on gene transcription

The objective of this study was to investigate the effect of the tumor-promoting phorbol ester phorbol 12-myristate 13-acetate (PMA) on FSH- and LH-induced 3β-HSD-gene expression in cultured porcine granulosa cells. FSH and LH induced a dose dependent increase in the accumulation of 3β-HSD mRNA, measured by Northern blot. A 1.6- to 1.8-fold increase (p<0.01) was observed with 10 ng/mL of FSH or LH. Maximal levels of 2.5- to 2.9-fold increases, relative to control, were reached at 30 and 100 ng/mL of the gonadotropins. When granulosa cells were treated with PMA (100 nM) just before the addition of FSH, the 3β-HSD rnRNA levels induced by 10 or 30 ng/mL of FSH were inhibited or partially inhibited, respectively. PMA did not inhibit elevated levels of 3β-HSD mRNA induced by FSH at concentrations of 100, 300, and 1000 ng/mL. Alternatively, PMA added just before LH, inhibited LH-stimulated 3β-HSD mRNA levels at all doses of LH tested (10, 30, 100, 300, and 1000 ng/mL). The protein kinase A-stimulators, dibutyryl-cAMP (cAMP) (0.5 mM) and forskolin (10 nM), also elevated the 3β-HSD-gene transcription, 3.5- and 4.0-fold respectively. PMA prevented the stimulation of the 3β-HSD-gene transcription when it was added just before cAMP or forskolin. We concluded that stimulation of PKC by PMA appears to have inhibited the gonadotropin-induced increase in 3β-HSD mRNA levels by preventing cAMP-activated 3β-HSD-gene transcription. The data also suggest that the effect of PMA appears to be more specific for regulation of LH-stimulated intracellular signals than those of FSH. This effect may indicate a site of differential regulation of FSH and LH on the stimulation of 3β-HSD-gene transcription.

3β-hydroxy-5-ene steroid dehydrogenase gene expression regulation in porcine granulosa cells. I: FSH- and LH-mediated transcriptional activation

In this report we examined the effect of FSH and LH, on the steady state levels of 3β-5-hydroxy-5-ene steroid dehydrogenase (3β-HSD) mRNA and on the 3β-HSD-gene transcriptional activation in porcine cultured granulosa cells. Exposure of granulosa cells to 100 ng/ml FSH or LH for 8 h, elevated to 3.0 and 2.5-fold respectively the levels of 3β-HSD mRNA measured by Northern blot analyses. The withdrawal of FSH and LH induced a rapid decay of the 3β-HSD levels, reaching the control values after 2 h. Re-addition of FSH and LH after 4 h withdrawal elevated the levels of 3β-HSD mRNA to 4.8 and 5.3-fold respectively. Addition of actinomycin D, to granulosa cells previously treated with FSH or LH, induced a rapid decay in the levels of 3β-HSD mRNA, reaching the control values after 2 h, with an estimated half life 1.3 and 1.2 h respectively. FSH and LH stimulated the 3β-HSD-gene transcription, measured by nuclear run-on assays, by 1.7 and 1.9-fold respectively. Addition of cholera toxin (10 ng/ml) or forskolin (10NM: ) stimulated the 3β-HSD-gene transcription by 2.15 and 2.4-fold respectively. We conclude that gonadotropins positively regulate 3β-HSD transcriptional activation and appear to have no effect on the 3β-HSD mRNA stability.

Alterations in 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) mRNA accumulation induced by beta-adrenergic stimulation in cultured porcine granulosa cells

1. In primary cultures of porcine granulosa cells incubation with isoproterenol (10(-7)-10(-5) M) produced a dose-dependent increase in 3 beta-HSD mRNA, 3 beta-HSD content and progesterone production which ranged from 1.5- to 5-fold. 2. These effects were completely blocked by alprenolol. Terbutaline (10(-6) M) increased 3 beta-HSD mRNA, 3 beta-HSD content and progesterone production (1.5- to 3-fold), an effect which could be prevented by alprenolol. 3. Treatment with dobutamine (10(-6) M) produced no significant change in 3 beta-HSD mRNA accumulation. 4. The results suggest that beta-adrenergic agonists have the capacity to regulate transcription and translation of 3 beta-HSD mRNA in granulosa cells and this effect is mediated by the beta 2 adrenergic receptor.