Dual actions of phorbol ester on cytochrome P450 cholesterol side-chain cleavage messenger ribonucleic acid accumulation in porcine granulosa cells

In earlier studies in cultures of porcine granulosa cells prepared from small antral follicles, steroidogenesis-related loci were inhibited by treatment for 48 h with 12-O-tetradecanoyl-phorbol-13-acetate (TPA), a potent activator of protein kinase C (PKC). In the present investigation, cells were incubated in serum-free medium for 48 h, with various agents present during the last 2-24 h. With TPA at 30 ng/ml, the FSH-stimulated cAMP accumulation was markedly enhanced at all time points. FSH increased the concentration of cytochrome P450 cholesterol side-chain cleavage (P450scc) mRNA throughout the 24-h incubation. At 4 and 8 h, TPA increased the accumulation of P450scc mRNA, having an additive effect with FSH. However, at 24 h, TPA markedly suppressed the FSH-induced increased in P450scc mRNA. Pretreatment of cells with FSH did not shorten the time required for TPA to become inhibitory. The stimulatory effect of 8-bromo-cAMP on P450scc mRNA also was augmented by TPA at 4 h, but significant inhibition was not observed at 24 h. The concentration of glyceraldehyde-3-phosphate dehydrogenase mRNA, intended to be used for correction of gel loading, was stably increased by both cAMP and TPA. These effects of TPA suggest multiple actions of PKC(s) on the regulation of P450scc expression and other endpoints in ovarian granulosa cells.

Characterization of placental transcriptional activation of the human gene for P450scc

Steroid hormones, which are ubiquitous regulators of physiologic processes, are produced primarily in the adrenals, gonads, and placenta. Each steroidogenic cell type produces different steroids due to cell-specific expression of various steroidogenic enzymes, but all steroidogenesis is initiated by P450scc, the mitochondrial enzyme that converts cholesterol to pregnenolone. We previously showed the unique segments of the P450scc promoter that are responsible for basal and cAMP-induced expression of this gene in the placenta are not employed for expression in the adrenal (C.C.D. Moore, D.W. Hum, and W.L. Miller, Mol. Endocrinol. 6, 2045-2058, 1992). We now show that sequences between -142 and -153 exhibit placental-specific activator activity. Sequences between -131 and -155 can confer activator activity to a 32-bp promoter from the thymidine kinase gene of herpes simplex virus in an orientation-independent fashion. Two protein complexes, termed IV and VII, interact specifically with DNA from -131 to -155. Mutating bases -142 to -151 abolishes formation of complex VII and partially inhibits complex IV, suggesting that the proteins forming these complexes bind neighboring segments of DNA. Mutating only two cytosines at bases 141 and 142 also eliminates the formation of complex VII and reduces the transcriptional activity of the activator by about 75-80%, indicating that complex VII is important for placental expression of P450scc. The sequence from -140 to -149 on the antisense strand resembles an NF-kappa B binding site. Antibodies to NF-kappa B subunit p50, but not to p52, p65, or c-Rel, will supershift some but not all of complex IV, whereas none of these antibodies interact with complex VII. A consensus NF-kappa B oligonucleotide does not form complex IV, suggesting that p50 interacts with the protein component, but not the DNA component of complex IV. Photoaffinity UV cross-linking yielded single bands of cross-linked DNA-protein complexes at approximately 85 kD for complex IV and approximately 70 kD for complex VII, indicating that separate proteins form complexes IV and VII. Southwestern blotting identified a single protein of 55 kD forming complex VII but did not identify the protein forming complex IV. Bandshifts and Southwestern blots with nuclear extracts from steroidogenic human placental JEG-3 cells and human adrenal NCI-H295 cells show that this 55-kD protein is found in placental but not adrenal cells. This 55-kD nuclear protein appears to be a trans-acting factor necessary for placental but not adrenal expression of P450scc.

Expression of messenger ribonucleic acid encoding cytochrome P450 side-chain cleavage, cytochrome p450 17 alpha-hydroxylase, and cytochrome P450 aromatase in bovine follicles during the first follicular wave

The objective of the present study was to investigate changes in the expression of messenger RNAs (mRNAs) encoding cytochrome P450 side-chain cleavage (P450scc), cytochrome P450 17 alpha-hydroxylase (P450c17), and cytochrome P450 aromatase (P450arom) at different stages of the first follicular wave of the bovine estrous cycle. Groups of heifers (three to five per group) were ovariectomized on the day of initiation of the first follicular wave (as determined by ultrasonography, day 0) or on days 2, 4, 6, 8, and 10 after initiation of the first follicular wave following estrus. Expression of mRNAs encoding P450scc, P450c17, and P450arom was detected by in situ hybridization and quantified by image analysis. P450scc mRNA was localized to theca interna cells of large preantral follicles and also to granulosa cells of follicles 4 mm or greater in diameter. mRNA for P450c17 was localized exclusively to theca interna cells, whereas P450arom mRNA was localized to granulosa cells of follicles 4 mm or greater in diameter. There were changes in mRNA levels for all three enzymes in thecal and/or granulosa cells at different times of the first follicular wave. Before identification of the dominant follicle (i.e. on days 0 and 2), there was no change in expression of P450scc and P450c17 mRNAs, whereas expression of P450arom mRNA was higher on day 2 than on day 0. Maximal mRNA levels for all three enzymes were observed on day 4. By day 6, P450scc and P450c17 mRNA levels were reduced compared to those on day 4, whereas P450arom mRNA levels remained elevated. On day 8, mRNA levels for all three enzymes were reduced. After initiation of the second follicular wave (day 10), dominant follicles from the first wave were at an advanced stage of atresia. P450scc and P450arom mRNAs were undetectable in granulosa cells, and very low levels of P450scc and P450c17 mRNAs were observed in theca interna cells. Before identification of the dominant follicle, mRNA levels for all three enzymes were similar within a cohort of follicles. Therefore, expression of these enzymes may not be associated with the mechanism of selection of the dominant follicle during a follicular wave.

Perspectives in steroid hydroxylase gene expression: novel sites of expression during embryonic development

CYP17 is not expressed in adult mouse adrenal glands but is expressed in a subset of fetal adrenocortical cells, indicating the potential to produce both corticosterone and cortisol during murine embryogenesis. CYP11A is expressed in the fetal adrenal but also in developing hindgut, which will form the colon, and in cells located beneath the skin of the embryo. Novel sites of expression of CYP17 and CYP11A in the mouse embryo suggest potential physiological roles for local production of steroids in diverse organs systems during development.

Regulation of expression of steroidogenic enzymes in Leydig cells

The Leydig cell of the testis is the only cell in the male that has the capacity to synthesize testosterone from cholesterol. Testosterone is critical during fetal development for male sexual differentiation, and postnatally for initiation and maintenance of spermatogenesis and the expression of the male secondary sex characteristics. The biosynthesis of testosterone requires the activities of four enzymes, cholesterol side-chain cleavage enzyme (P450scc), 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase (3 beta HSD), 17 alpha-hydroxylase/C17-20 lyase (P450(17 alpha)), and 17-ketosteroid reductase. The expression of these enzymes appears to be regulated by different mechanisms. The recent isolation of the mouse cDNAs and structural genes that encode these enzymes has enabled us to begin to investigate the regulation of their expression at the molecular level. This review discusses the regulation by cAMP and steroids of three enzymes in Leydig cells, P450scc, P450(17 alpha), and 3 beta HSD, as well as characterization of the promoters of the mouse genes that encode P450scc and P450(17 alpha).

Protein kinase C inhibition of in vitro FSH-induced differentiation in pig granulosa cells

In granulosa cells, growth factor IGF I plays a major role in both growth and differentiation, acting through an autocrine/paracrine mechanism, and its production is regulated by FSH, via cyclic AMP (cAMP). As protein kinase C is also involved in granulosa cell function, we investigated the possibility that its activation could balance the positive effects of FSH. Using pig granulosa cells cultured in vitro, we studied the effects of protein kinase C activation by tetradecanoylphorbol acetate (TPA) on IGF I mRNA level. We also checked morphological modifications, cAMP production and steroidogenesis at the P450 side chain cleavage mRNA and progesterone levels. Our data demonstrate that protein kinase C activation antagonizes the in vitro FSH-induced differentiation, particularly morphological modifications and accumulation of IGF I mRNA. These inhibitory effects on FSH responses suggest that there could be a balance between protein kinase A and protein kinase C pathways in regulating differentiation in pig granulosa cells.

Concentrations of cytochrome P450 cholesterol side-chain cleavage enzyme and 3 beta-hydroxysteroid dehydrogenase during prostaglandin F2 alpha-induced luteal regression in cattle

Prostaglandin F2 alpha (PGF2 alpha)-induced regression of the corpus luteum causes both plasma progesterone concentrations and luteal concentrations of mRNA encoding the steroidogenic enzyme 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) to fall in parallel. To investigate the hypothesis that a decline in the concentrations of mRNA encoding steroidogenic enzymes causes plasma progesterone to fall, the luteal concentrations of the enzymes 3 beta-HSD and cytochrome P450 cholesterol side-chain cleavage were measured during induced luteolysis. Holstein heifers were treated with PGF2 alpha (25 mg Lutalyse) on Day 6 or Day 7 of the oestrous cycle and corpora lutea were collected 0 h, 2 h, 12 h, and 24 h later (n = 6, 4, 4, and 4 respectively). Analyses of the steroidogenic enzymes were carried out by Western immunoblotting. The luteal concentrations of both steroidogenic enzymes did not decrease over the 24-h period. It is concluded that, although the concentrations of mRNA encoding steroidogenic enzymes may decline in response to PGF2 alpha, this does not lead to a sufficiently rapid reduction in the concentrations of the enzymes to precede, and thus cause, the decline in plasma progesterone concentrations. Thus, the mechanism for the initial decline in plasma progesterone concentrations during luteolysis is still not known.

Induction of rat granulosa cell steroidogenic enzyme activities and their messenger ribonucleic acids by a splenocyte-derived factor

We have previously identified and purified a splenocyte-derived factor (PSF) that stimulates the accumulation of progesterone and 20 alpha-dihydroprogesterone (20 alpha-OH-P) in rat ovarian granulosa cells independently of FSH. In the present study, time course experiments comparing the response to PSF with that to FSH revealed that PSF-stimulated progesterone accumulation was slower than that of FSH, but PSF-stimulated 20 alpha-OH-P accumulation had a time course similar to that of FSH. To determine the basis for the slower progesterone response to PSF, the effect of these two agents on each step of the steroidogenic pathway was assessed. First, to examine whether PSF-stimulated cholesterol mobilization was limiting, cultured granulosa cells were treated with 22(R)-hydroxycholesterol. While both FSH- and PSF-stimulated progesterone and 20 alpha-OH-P accumulation approximately doubled, the overall time courses did not change indicating that cholesterol availability was not the factor limiting the response to PSF. Next, PSF and FSH induction of steroidogenic enzyme activities and messenger RNAs were compared. While FSH-stimulated cytochrome P450 side chain cleavage enzyme (SCC) activity rapidly increased (peaking at 2 days) and then slowly declined, PSF-stimulated SCC activity gradually increased over 5 days to approximately 35% of the maximal activity stimulated by FSH. PSF also induced slower increases in P450scc mRNA levels than did FSH. In addition, PSF stimulated 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) activity more slowly than did FSH, but after 3 days of culture, PSF-stimulated activity was significantly higher than that induced by FSH.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of corticotropin and steroidogenic enzyme mRNAs in human fetal adrenal cells by corticotropin, angiotensin-II and transforming growth factor beta 1

Using cultured human fetal adrenal cells, we have investigated the basal secretion of cortisol and dehydroepiandrosterone sulfate (DHAS) and the effect of corticotropin (ACTH), angiotensin-II (A-II) and transforming growth factor beta 1 (TGF beta 1) on the secretion of these steroids and on the mRNA levels of ACTH receptor (ACTHR), cytochrome P-450scc (cholesterol side-chain cleavage), P450 17 alpha (17 alpha-hydroxylase/17-20 lyase) and 3 beta-HSD (3 beta-hydroxysteroid dehydrogenase). The basal DHAS/cortisol ratio declined progressively between 12.5 and 21 weeks. ACTH treatment enhanced the secretion of cortisol and to a lesser extent that of DHAS, and increased the steroidogenic response to an acute stimulation with ACTH. These changes were associated with increased mRNA levels of ACTHR and of the steroidogenic enzymes. A-II treatment also increased the secretion of both DHAS and cortisol, but less than ACTH, enhanced the responsiveness to ACTH and increased ACTHR, P450scc and P450 17 alpha mRNA levels. In contrast, TGF beta 1 alone or together with ACTH decreased DHAS secretion, but not cortisol secretion. Moreover, TGF beta 1 had no effect on ACTHR and P450scc mRNA levels, decreased by about 50% the mRNA levels of P450 17 alpha both in the absence or presence of ACTH, but enhanced the stimulatory effects of ACTH on 3 beta-HSD mRNA. These results, along with those previously reported, suggest that both A-II and TGF beta may play a role in fetal adrenal function. In addition, they show that the effects of both peptides are qualitatively different from, even sometimes opposite to, those previously reported in bovine and ovine adrenal cells.

Regulation by retinoids of luteinizing hormone/chorionic gonadotropin receptor, cholesterol side-chain cleavage cytochrome P-450, 3 beta-hydroxysteroid dehydrogenase/delta (5-4)-isomerase and 17 alpha-hydroxylase/C17-20 lyase cytochrome P-450 messenger ribonucleic acid levels in the K9 mouse Leydig cell line

Vitamin A is a potent regulator of testicular function. We have reported that retinol (R) and retinoic acid (RA) induced a down regulation of luteinizing hormone/human chorionic gonadotropin (LH/CG) binding sites in K9 Leydig cells. In the present study we evaluated the effect of R and RA on LH/CG receptors, cholesterol side-chain cleavage cytochrome P-450 (P-450 scc), 17 alpha-hydroxylase/C17-20 lyase (P-450 17 alpha) and 3 beta-hydroxysteroid dehydrogenase (3 beta HSD) mRNA levels in K9 mouse Leydig cells. To validate K9 cells as a model for studying Leydig cell steroidogenesis at the molecular level, we first investigated the effect of hCG on mRNA levels of the steroidogenic enzymes. P-450 scc, 3 beta HSD and P-450 17 alpha were expressed constitutively. The addition of 10 ng/ml hCG enhanced mRNA levels for the three genes within 2 h. Maximal accumulation of P-450 scc, P-450 17 alpha and 3 beta HSD mRNA in treated cells represents a 2.5-, 8.5- and 4-fold increase over control values, respectively. P-450 17 alpha expression reached a maximum by 4 h and then declined rapidly to return to control value by 24 h. The pattern of LH/CG receptor mRNAs in K9 cells was very similar to that of MA10 Leydig cells and showed six transcripts of 1.1, 1.6, 1.9, 2.6, 4.2 and 7.0 kb. Treatment of cells with R or RA resulted in a time- and dose-dependent decrease in all six species.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence of a steroidogenic enzyme gene dose effect on adrenal gene expression in hereditary rabbit congenital adrenal hyperplasia

We previously reported the gene deletion encoding cytochrome P-450 cholesterol side-chain cleavage enzyme (P-450SCC, resulting in complete elimination of the adrenal gene expression and causing congenital adrenal hyperplasia in the rabbit. Using the rabbit congenital adrenal hyperplasia model, we investigated the wild type (wt) P-450SCC gene dose effect on gene expression in three P-450SCC genotype animals [wt/wt, wt/mutant (mt), mt/mt] identified by Southern blot analysis. Northern blots using a rabbit P-450SCC cDNA probe revealed no detectable P-450SCC mRNA in individual adrenals of animals with congenital adrenal hyperplasia (mt/mt) and approximately half or slightly less than half the levels of the mRNA in the pooled adrenals of five heterozygous (wt/mt) newborn animals compared with the mRNA levels in the pooled adrenals of five homozygous normal (wt/wt) newborn animals. Identical P-450SCC mRNA levels were found individual adrenals of adult animals with regard to the P-450SCC genotype, although at a higher expression level than in the newborn animals of the same genotype. Control Northern blots using human CPY21-B cDNA and cytoplasmic actin cDNA probes confirmed the accuracy and integrity of RNA. Western immunoblotting using anti-ovine P-450SCC antibody revealed decreased P-450SCC protein in the adrenals of wt/mt animals at approximately half the level of the P-450SCC protein in the adrenals of the wt/wt animals. Baseline and ACTH-stimulated serum corticosterone (B) levels in vivo were similar between the age-matched wt/mt and wt/wt animals, whereas ACTH-stimulated B levels in adult animals were higher than those in the newborn animals irrespective of P-450SCC genotype.(ABSTRACT TRUNCATED AT 250 WORDS)

Corticosterone regulates cell proliferation and cytochrome P450 cholesterol side-chain cleavage enzyme messenger ribonucleic acid expression in primary cultures of fetal rat adrenals

Glucocorticoids are known to inhibit growth in many different cell types. Although corticosterone is secreted by the adrenal cortex, its direct effect on the growth of different zones is poorly determined. We studied the effects of corticosterone on cell proliferation and cytochrome P450 cholesterol side-chain cleavage enzyme (P450scc; the rate-limiting step in adrenal steroidogenesis) messenger RNA (mRNA) accumulation in primary cultures of fetal rat adrenals. Adrenocortical cells, grown in the absence of ACTH for 3 weeks, possess typical features of zona glomerulosa cells. These cells differentiate into fasciculata-type cells and undergo biphasic proliferation when stimulated with ACTH. The primary antimitogenic phase of 24 h is followed by rapidly increased bromodeoxyuridine incorporation after 72 h of ACTH treatment. If the treatment is continued, the proliferation decreases again, but remains higher than the proliferation of the untreated cells. Undifferentiated zona glomerulosa-type cells secrete very low amounts of corticosterone. The 10% basal proliferation was not affected if exogenous corticosterone was added. However, if corticosterone was combined with ACTH for 3 days, it blocked the stimulatory growth effect of ACTH dose dependently. Etomidate, an inhibitor of steroidogenic enzymes, completely blocked corticosterone secretion. In our cultures it inhibited 50% of the proliferation of the zona glomerulosa-type cells. However, its effect was totally opposite in long term ACTH-treated cultures; in these fasciculata-type cells, etomidate stimulated the proliferation rate 3-fold. P450scc gene expression was low in undifferentiated zona glomerulosa-like cells. ACTH stimulation increased P450scc mRNA expression 10-fold. Exogenous corticosterone inhibited ACTH-induced P450scc mRNA accumulation by 50%, whereas etomidate doubled it. Our data suggest that a low corticosterone concentration supports the proliferation of undifferentiated zona glomerulosa-type cells, whereas a high corticosterone concentration inhibits the proliferation of differentiated zona fasciculata-type cells. In addition, a high corticosterone concentration may inhibit steroidogenesis by reducing P450scc expression. Thus, corticosterone may be an important modulator of adrenocortical cell proliferation and steroidogenesis in different zones of the adrenal cortex.

Insulin-like growth factor-I increases expression of the porcine P-450 cholesterol side chain cleavage gene through a GC-rich domain

The promoter/regulatory region of the porcine P-450 cholesterol side chain cleavage (P450scc) gene was cloned from a porcine genomic library. This gene contains a GC-rich region (-130-100) that mediates insulin-like growth factor I (IGF-I) and cAMP stimulation of gene expression in porcine granulosa cells. Stimulation of gene expression by cAMP occurs in 6 h, while IGF-I stimulation occurs in 24-48 h. This region is also responsive to insulin but not fibroblast growth factor. The effects of IGF-I and cAMP on gene expression in porcine granulosa cells are additive. In Y1 adrenal cells, the same region is responsive to cAMP but not to IGF-I. Gel shift assays using an oligonucleotide of this region and nuclear extract protein from porcine granulosa and Y1 adrenal cells identified three DNA-protein complexes (C1-C3). The binding activity of the complexes did not change with IGF-I or forskolin treatment of granulosa cells. Mutational analysis results were consistent with IGF-I regulating gene expression through the C2 DNA protein complex. Moreover, this complex binds differently in gel shift assay to mutant oligonucleotides with porcine and Y1 and nuclear extract protein. We conclude that IGF-I stimulates porcine P450scc gene expression through a distinct, cell-specific protein complex binding to a GC-rich domain.

Protein kinase C second messenger system mediates the antisteroidogenic effects of prostaglandin F2 alpha in the ovine corpus luteum in vivo

Experiment I was designed to determine the optimal dose of phorbol 12-myristate 13-acetate (PMA) that inhibited progesterone production when infused into the ovarian artery. The most efficacious dose of PMA was 2 mumol. Experiment II was designed to determine whether activation of protein kinase C (PKC) inhibited progesterone production without initiating luteolysis. Ewes received ovarian arterial infusions of 4 alpha-phorbol (2 mumol, n = 4), PMA (2 mumol, n = 8), or prostaglandin F2 alpha (PGF2 alpha; 1 mumol, n = 5). Concentrations of progesterone in serum decreased by 3 h in PMA-treated ewes and by 5 h in PGF2 alpha treated ewes (p < 0.05). By 48 h, serum levels of progesterone in PMA-treated ewes had returned to control values; but in PGF2 alpha-treated ewes they remained low for the duration of the experiment. Luteal weights and progesterone contents at 48 h were similar in 4 alpha-phorbol- and PMA-treated ewes but were decreased in PGF2 alpha-treated ewes (p < 0.05). Experiment III was designed to determine whether PGF2 alpha or PKC activation induced oligonucleosome formation or influenced mRNA levels for cytochrome P450sec or 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase (3 beta-HSD). Ewes received treatments as in experiment II, and CL were collected at 3, 12, or 24 h (n = 3-4 per group). Luteal weights were decreased (p < 0.05) and oligonucleosome formation was increased (p < 0.05) in PGF2 alpha-treated ewes compared to controls or to PMA-treated ewes by 12 h.(ABSTRACT TRUNCATED AT 250 WORDS)

No mutation in cytochrome P450 side chain cleavage in a patient with congenital lipoid adrenal hyperplasia

Molecular basis of lipoid adrenal hyperplasia (lipoid CAH) in a Japanese patient was investigated. A 46XY Japanese female patient was clinically diagnosed as having lipoid CAH based on her clinical history of adrenal crisis at birth and the low basal concentrations of cortisol, aldosterone, adrenal androgens and testosterone in serum. In vitro studies of testicular mitochondrial enzymes confirmed a specific impairment of cholesterol side chain cleavage (SCC) activity. However, in spite of the virtual reduction of SCC activity, the amounts of immunodetectable P450scc, adrenodoxin reductase, and adrenodoxin in testicular mitochondria were almost same as those of normal testis. Furthermore, the size of each protein was similar to that of normal testis. Enzymatic amplification of the complementary DNA encoding P450scc from the patient's testis RNA and its nucleotide analysis by direct sequencing revealed no mutation. These results indicate that defective P450scc is not the lesion in this patient, confirming a previous report showing no P450scc mutations in patients with lipoid CAH. The exact lesion causing lipoid CAH in this patient is currently unknown.

A modified form of the cytochrome P450scc precursor: a new approach in studies on protein import into mitochondria

Recombinant DNA was constructed providing hypersynthesis of a hybrid protein with a MRGSH6GIR sequence preceding the NH2-terminus of the bovine cytochrome P450scc precursor (6His-pP450scc) in Escherichia coli cells. A large-scale procedure for isolation and purification of this protein was elaborated. 6His-pP450scc was imported into isolated rat liver mitochondria and processed to the mature-sized form. As a similar procedure can be applied to other proteins the results of this work offer new opportunities in studies of protein import into mitochondria.

Development of cytochrome P-450 side chain cleavage mRNA levels in neonatal ovaries of normal and hypogonadal (hpg) mice

Cytochrome P-450 side chain cleavage (P-450scc) is vital for biosynthesis of gonadal steroids. In this study changes in P-450scc mRNA levels and cholesterol side-chain cleavage (CSCC) enzyme activity have been measured during development in the ovary of the normal mouse and the hypogonadal (hpg) mouse which lacks circulating gonadotrophins. Levels of P-450scc mRNA were measured using a semi-quantitative reverse transcription-polymerase chain reaction technique for which part of the 5' sequence of a mouse P-450scc cDNA was sequenced. On the day of birth P-450scc mRNA was present at low levels in the mouse ovary. Thereafter there was no change in P-450scc mRNA levels for 5 days after which time levels increased significantly to reach a peak around day 10. Activity of CSCC showed a similar pattern of development although activity was not detectable on days 1 and 3. In the hpg mouse P-450scc mRNA levels were normal on day 1 but did not increase thereafter up to 15 days. These results show that there is gonadotrophin-independent expression of P-450scc mRNA in the mouse ovary at birth when only primordial follicles and stromal tissue are present. As the ovary develops after 5 days changes in P-450scc mRNA levels become gonadotrophin-dependent and coincide with maturation of secondary follicles.

Steroidogenic cytochrome P450 enzyme messenger ribonucleic acids and follicular fluid steroids in individual follicles during preovulatory maturation in the pig

Changes in follicular concentrations of steroidogenic cytochrome P450 enzyme mRNAs were determined during preovulatory maturation. RNA was isolated from 59 individual follicles dissected from 18 pigs during altrenogest-synchronized preovulatory follicular maturation: at Day 1 (pre-follicular phase), Day 3 (early follicular phase), Day 5 (mid-follicular phase), and Day 7 (late follicular phase, 24-36 h after the onset of the LH surge). Follicular fluid was aspirated for steroid RIA. RNA was also isolated from pooled granulosa cells, theca tissue, and luteal tissue. RNA was analyzed by Northern and slot-blot procedures using cDNA probes to human aromatase cytochrome P450 (P450arom), porcine 17 alpha-hydroxylase cytochrome P450 (P450(17) alpha), and porcine cholesterol side-chain cleavage cytochrome P450 (P450scc). P450arom mRNA was expressed in both granulosa and theca interna cells but was not detectable in luteal tissue from Day 13 of the estrous cycle. Follicular P450arom mRNA concentration tended to increase between Days 1 and 5 and decreased (p < or = 0.05) by 92% between Days 5 and 7. Follicular fluid estradiol-17 beta concentration increased 17-fold between Days 1 and 5 and then decreased (p < or = 0.05) by 96% between Days 5 and 7. P450(17) alpha mRNA was present in theca interna but was not detected in granulosa cells or luteal tissue. Follicular P450(17) alpha mRNA concentrations did not differ significantly among days, but the content per follicle increased (p < 0.05) between Days 1 and 5 and decreased (p < 0.05) between Days 5 and 7.(ABSTRACT TRUNCATED AT 250 WORDS)

Peroxisome proliferators and retinoids affect JEG-3 choriocarcinoma cell function

To examine the hypothesis that nutritional signals regulate trophoblast cell function, JEG-3 choriocarcinoma cells were treated with drugs that stimulate peroxisome proliferator-activated receptors (PPARs). These receptors are thought to mediate in part the effects of lipidic nutrients on gene expression. Because PPARs are modulated by interactions with retinoid-X receptors, we also examined the actions of the peroxisome proliferators in the presence of retinoids. Clofibric acid, a known peroxisome proliferator, suppressed JEG-3 cell growth in association with increases in the tumor suppressor p53 protein and its messenger RNA (mRNA). It reduced CG secretion and CG alpha and CG beta mRNAs in growing cells. However, clofibric acid did not induce peroxisome proliferation in the JEG-3 cells, as assessed by electron microscopy and immunostaining for catalase, a peroxisomal enzyme, or alter levels of mRNAs for peroxisomal proteins, sterol carrier protein-X/sterol carrier protein-2 and acyl-Coenzyme-A oxidase. The mitochondrial cholesterol side-chain cleavage enzyme, cytochrome P450scc, was modestly increased in some experiments. All-trans-retinoic acid and 9-cis-retinoic acid increased CG secretion and CG alpha and CG beta mRNAs, but clofibric acid blunted these stimulatory effects. WY 14,643, another peroxisome proliferator, also reduced CG gene expression without increasing mRNAs encoding peroxisomal proteins or altering P450scc mRNA. The mRNA for a human PPAR, NUC1, was demonstrated in JEG-3 cells, and NUC1 mRNA was shown to be upregulated by 8-bromo-cAMP. We conclude 1) that JEG-3 cells express a PPAR and are subject to regulation by PPAR stimulators; 2) that PPAR stimulation in JEG-3 cells does not promote peroxisome proliferation; and 3) that peroxisome proliferators and retinoids differentially regulate JEG-3 cell endocrine activities. We suggest from these findings that JEG-3 cells possess mechanisms to respond to nutrient cues.

Steady-state concentrations of messenger ribonucleic acid encoding cytochrome P450 side-chain cleavage and 3 beta-hydroxysteroid dehydrogenase/delta 5,delta 4 isomerase in ovine corpora lutea during the estrous cycle

The objective of these experiments was to determine the pattern of mRNA expression for cytochrome P450 side-chain cleavage (P450scc) and 3 beta-hydroxysteroid dehydrogenase/delta 5,delta 4 isomerase (3 beta-HSD) during luteinization of the follicle and in ovine luteal tissue on Days 3, 6, 9, 12, and 15 of the estrous cycle. Mean concentration of mRNA for P450scc was not different in follicles collected 4 or 24 h after the onset of estrus but increased (p < 0.05) 3-fold by 48 h (corpus hemorrhagicum). With the methods used, mRNA for 3 beta-HSD was not detected until after ovulation and formation of the corpus hemorrhagicum (48 h after onset of estrus). In luteal tissue, mean concentration of mRNA for P450scc increased from Days 3 to 9 (p < 0.05) and had decreased (p < 0.05) by Day 15. Mean concentration of mRNA for P450scc was higher (p < 0.05) in small luteal cells on Day 9 than on Day 15, with values on Days 6 and 12 being intermediate. In large luteal cells, mean concentrations of P450scc mRNA increased (p < 0.05) between Days 6 and 12 and then decreased (p < 0.05) on Day 15. Mean concentration of mRNA for 3 beta-HSD was not different (p = 0.33) in luteal tissue on any day examined. In small luteal cells, mean concentrations of mRNA for 3 beta-HSD decreased between Days 6 and 15 (p < 0.05) while in large luteal cells, mean concentrations decreased (p < 0.05) between Days 12 and 15.(ABSTRACT TRUNCATED AT 250 WORDS)

Vasoactive intestinal peptide-induced expression of cytochrome P450 cholesterol side-chain cleavage and 17 alpha-hydroxylase enzyme activity in hen granulosa cells

Experiments were conducted to determine whether vasoactive intestinal peptide (VIP) can regulate expression of cytochrome P450 side-chain cleavage (P450scc) and P450 17 alpha-hydroxylase (P450 17 alpha-OH) mRNA levels and enzyme activity in granulosa cells from nonhierarchal (6-8-mm) follicles. Initial studies demonstrated that immunoreactive VIP is localized within the theca (but not granulosa) layer of both resting (< 0.5-mm follicles) and 6-8-mm follicles, thus providing a potential paracrine mechanism of action for VIP. While short-term (3 h) incubation of granulosa cells with VIP (0.001-1.0 microM) failed to stimulate progesterone production from 6-8-mm follicle granulosa cells, a 4-h culture period in the presence of VIP resulted in increased cyclic AMP (cAMP) accumulation, and a 24-h culture period resulted in progesterone synthesis and increased P450scc mRNA levels; control levels of each endpoint measurement were not altered within the period observed. By contrast, culture with the growth factor transforming growth factor alpha (TGF alpha) in the presence of VIP (1 microM) prevented increases in P450scc mRNA levels and progesterone production. Similar effects of VIP and TGF alpha in the presence of VIP were demonstrated for P450 17 alpha-OH mRNA levels and enzyme activity. Finally, there was an additive effect of VIP (0.1 microM) plus recombinant human (rh) FSH (100 mIU) on the initiation of progesterone production in cultured 6-8-mm follicle granulosa cells compared to the addition of VIP or rhFSH alone.(ABSTRACT TRUNCATED AT 250 WORDS)

The mitochondrial environment is required for activity of the cholesterol side-chain cleavage enzyme, cytochrome P450scc

Steroidogenesis is initiated by the conversion of cholesterol to pregnenolone by mitochondrial cytochrome P450scc [cholesterol, reduced-adrenal-ferredoxin:oxygen oxidoreductase (side-chain-cleaving); EC 1.14.15.6]. Several subsequent steroidal conversions occur in the endoplasmic reticulum (ER), but the last step in the production of glucocorticoids and mineralocorticoids again occurs in the mitochondria. Although cellular compartmentalization of steroidogenic enzymes appears to be a feature of all steroidogenic pathways, some reports indicate that cholesterol can be converted to pregnenolone outside the mitochondria. To investigate whether P450scc can function outside the mitochondria, we constructed vectors producing P450scc and various fusion enzymes of P450scc with electron-transport proteins and directed their expression to either the ER or the mitochondria. Whether targeted to mitochondria or to the ER, plasmid vectors encoding P450scc and fusion proteins of P450scc with either mitochondrial or microsomal electron-transport proteins produced immunodetectable protein. When expressed in mitochondria, all of these constructions converted 22-hydroxycholesterol to pregnenolone, but when expressed in the ER none of them produced pregnenolone. These results show that P450scc can function only in the mitochondria. Furthermore, it appears to be the mitochondrial environment that is required, rather than the specific mitochondrial electron-transport intermediates.

Ontogeny of expression of the genes for steroidogenic enzymes P450 side-chain cleavage, 3 beta-hydroxysteroid dehydrogenase, P450 17 alpha-hydroxylase/C17-20 lyase, and P450 aromatase in fetal mouse gonads

It is well known that fetal androgens are required for male sexual differentiation, and it is thought that fetal ovaries are not steroidogenically active. However, molecular details, such as which steroidogenic enzymes are present in fetal testes and which enzymes are absent in fetal ovaries, have not been established. The pattern of expression of the genes that encode four of the steroidogenic enzymes necessary for androgen and estrogen production was examined during fetal development in mouse gonads. Messenger RNA (mRNA) expression for cholesterol side-chain cleavage (P450scc), 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4-isomerase (3 beta HSD), P450 17 alpha-hydroxylase/C17-20 lyase (P450c17), and P450 aromatase (P450arom) was determined before ovaries and testes were distinguishable (13 days postconception) and during sexual differentiation (15, 17, and 20 days postconception) using reverse transcriptase-polymerase chain reactions (RT-PCR). A PCR assay for Sry was used to determine gender on day 13. P450scc, 3 beta HSD, and P450c17 transcripts were detected at all ages in fetal testes, indicating that mRNAs for the steroidogenic enzymes that are required to convert cholesterol to androgens are present in the male gonad even before sexual differentiation. P450arom mRNA was detected in several fetal testes on day 17, but consistently observed on day 20. The expression of P450arom suggests the potential of fetal and neonatal testes to convert androgens to estrogens. In contrast, although 3 beta HSD mRNA was detected in several of the ovaries examined, the detection of P450scc, P450c17, and P450arom transcripts was rare. These data suggest that the absence of fetal ovarian steroid hormone production is the result of lack of expression of at least three of the steroidogenic enzymes, P450scc, P450c17, and P450arom.

Dexamethasone potentiates IGF-I actions in porcine granulosa cells

To understand better interactions between glucocorticoids and insulin-like growth factor I (IGF-I) in the ovary, we studied the effects of dexamethasone on IGF-I stimulation of P-450 cholesterol side-chain cleavage enzyme (P-450scc) mRNA concentrations in porcine granulosa cells. Dexamethasone potentiated IGF-I-stimulated P-450scc mRNA concentrations and progesterone production in granulosa cell cultures. Time-course and dose-response studies showed that maximal enhancement occurred at a 1-microM dexamethasone concentration after 48 h of treatment. This potentiation was prevented by the glucocorticoid receptor antagonist RU-38486, 17 beta-hydroxy-11 beta-[-4-dimethyl-aminophenyl]estra-4,9,-dien-3-one (RU-486). We investigated mechanisms for this potentiation by performing IGF-I binding studies in porcine granulosa cells. Dexamethasone increased IGF-I binding, and Scatchard analysis showed this enhanced binding was caused by an increase in receptor concentration. Northern blot hybridization using a rat type I IGF-I receptor gene riboprobe showed that although dexamethasone alone did not increase IGF-I receptor mRNA concentrations, it did prevent a decrease in receptor mRNA concentrations caused by IGF-I. In addition, we used synthetic primers from conserved regions of the rat type I IGF-I receptor gene with total RNA from porcine granulosa cells and polymerase chain reaction to isolate a 615-base pair porcine type I IGF-I receptor cDNA clone. Ribonuclease protection assay results were similar to those found with the rat IGF-I receptor riboprobe. We conclude that dexamethasone potentiates IGF-I actions on steroidogenesis in the porcine ovary.

Regulation of steroid hydroxylase gene expression in the ovine fetal adrenal gland at 0.4 gestation

This study was designed to test the hypothesis that ACTH from the fetal pituitary is a major regulator of adrenocortical steroid hydroxylase gene expression in the ovine fetus at 0.4 (60-70 days) of gestation. Pregnant ewes at 0.4 gestation received intravenous infusions of dexamethasone (0.76 mg/h, n = 13) for 48 h. The rationale for this regime was that some of the infused dexamethasone would cross the placenta and act on the fetal pituitary to suppress ACTH release. Control animals received infusions of saline (0.38 ml/h, n = 12) for 48 h. At the end of the infusion period, the animals were killed, umbilical vessel blood taken for ACTH and cortisol analyses, and the fetal adrenal glands taken for assessment of P-450scc, P-450(17 alpha) and P-450c21 levels using the techniques of hybridization histochemistry and RNase protection assay. Dexamethasone treatment decreased maternal and fetal concentrations of ACTH to 29 +/- 10 and < 20 pg/ml, respectively and cortisol concentrations to 3.5 +/- 0.6 and 3.2 +/- 0.8 nmol/l respectively. The adrenal glands from the dexamethasone-treated fetuses exhibited significantly lower levels of mRNA for P-450scc (11% of control) and P-450(17 alpha) (2% of control). These results suggest that ACTH is a major regulator of steroid hydroxylase gene expression and subsequent cortisol biosynthesis in vivo in the ovine fetus at 0.4 gestation.

Regulatory mechanisms of cAMP-dependent and cell-specific expression of human steroidogenic cytochrome P450scc (CYP11A1) gene

Cytochrome P450scc (CYP11A1) is the enzyme that catalyzes the side-chain cleavage reaction of cholesterol, the first and rate-limiting reaction in the biosynthesis of steroid hormones in the adrenal cortex. DNase-I-footprinting analysis using nuclear extracts from the bovine adrenal cortex and the 5' upstream regulatory region (nucleotides -1697 to -1523) of the CYP11A1 gene, which is mainly required for response to cAMP [Inoue, H., Watanabe, N., Higashi, Y. & Fujii-Kuriyama, Y. (1991) Eur. J. Biochem. 195, 563-569], revealed that some protein factors bound to that region. One of the sequences protected by the binding factors is a cAMP-responsive-element (CRE)-like sequence, which is known to be recognized by CRE-binding protein (CREB) or its related proteins, and another is a sequence designated Ad4 which is bound by a tissue-specific factor, Ad4-binding protein (Ad4BP). The region containing the two closely arranged DNA sequences showed a high level of cAMP responsive and cell-specific expression when it was fused to the basal promoters. Introduction of point mutations in these sequences demonstrated that the CREB/ATF factors and Ad4BP bound to the sequences showed synergistic enhancer effects on cAMP-responsive and cell-specific expression of the CYP11A1 gene.

Tyrosine kinase inhibitor AG18 arrests follicle-stimulating hormone-induced granulosa cell differentiation: use of reverse transcriptase-polymerase chain reaction assay for multiple messenger ribonucleic acids

A sensitive assay of multiple mRNAs by reverse transcriptase-polymerase chain reaction was adopted to study the hormonally regulated expression of steroidogenic enzymes in primary rat granulosa cells in culture. As little as 15-60 ng total RNA prepared from cultured cells were reverse transcribed in the presence of pd(T)6, and polymerase chain reaction was conducted in the presence of specific oligonucleotide pairs designed to identify cDNAs of steroidogenic enzymes. In combination with Northern blot analysis of cholesterol side-chain cleavage cytochrome P450 (P450scc) message, it is shown that a novel protein kinase inhibitor, tyrphostin AG18, arrests the FSH-induced accumulation of P450scc mRNA. This inhibition is dose dependent (IC50, 15 microM) and reversible. The addition of 80 microM AG18 to cells containing high levels of P450scc mRNA caused a rapid decline of the cytochrome message (t 1/2, 5 h), similar to the effect of 30 micrograms/ml alpha-amanitin. However, concomitant addition of the two drugs did not accelerate the mRNA degradation process, suggesting that AG18 does not affect message stabilization. Tyrphostin AG18 did not affect mRNA species that are not FSH inducible, such as the ribosomal protein L19, or the constitutively expressed low levels of steroid 5 alpha-reductase mRNA. Moreover, even the extremely high levels of P450scc mRNA in granulosa-lutein cells, being cAMP independent and terminally differentiated a few hours after LH surge, were not affected by the addition of AG18 in culture. In contrast, two additional key and FSH-inducible steroidogenic enzymes, i.e. aromatase cytochrome P450 and 3 beta-hydroxysteroid dehydrogenase-I, were inhibited by AG18 at their mRNA levels. These results suggest that an as yet undetermined tyrosine kinase pathway is involved in the cAMP-dependent signal transduction pathway of FSH action, so that the presence of AG18 does not allow FSH induction of gene expression to occur.

Human cultured adrenal fasciculata-reticularis cells are targets for angiotensin-II: effects on cytochrome P450 cholesterol side-chain cleavage, cytochrome P450 17 alpha-hydroxylase, and 3 beta-hydroxysteroid-dehydrogenase messenger ribonucleic acid and proteins and on steroidogenic responsiveness to corticotropin and angiotensin-II

In the present study we have examined the effects of ACTH and angiotensin-II (A-II) on cultured human adult fasciculata-reticularis-specific functions. When cells were cultured in a chemically defined medium, the mRNA levels of cholesterol side-chain cleavage enzyme (P450scc), 17 alpha-hydroxylase/17,20-lyase (P45017 alpha), and 3 beta-hydroxysteroid dehydrogenase (3 beta HSD) progressively declined, so that by day 6 of culture, less than 20% of those observed in freshly isolated cells were present. ACTH and A-II, in a dose- and time-dependent manner, enhanced the mRNA levels of the three enzymes and the protein levels of P45017 alpha and 3 beta HSD, but not protein levels of P450scc. At maximal concentrations, the effects of ACTH on P450scc mRNA levels and P45017 alpha mRNA and protein levels were significantly greater than those induced by A-II, but the effects of both hormones on 3 beta HSD mRNA and protein were similar. At maximal concentrations, the effects of ACTH and A-II were additive only on 3 beta HSD mRNA and protein. The cortisol production of cells pretreated with ACTH or A-II was significantly higher than that of control cells, but the effects of ACTH were greater than those of A-II. Moreover, the acute steroidogenic responses to ACTH or A-II of cells pretreated with either hormone, were significantly higher than those of control cells. In conclusion, the present results demonstrate that human adult adrenal fasciculata-reticularis cells are targets for A-II, because 1) A-II acutely stimulates cortisol secretion and causes a long term increase in P450scc, P45017 alpha, and 3 beta HSD mRNA levels; 2) the steroidogenic responsiveness of A-II-pretreated cells to both ACTH and A-II was increased; and 3) the positive effects of A-II alone or in association with ACTH on steroidogenic enzyme gene expression are opposite those previously reported on bovine and ovine adrenal cells.

Recombinant murine tumor necrosis factor-alpha inhibits cholesterol side-chain cleavage cytochrome P450 and insulin-like growth factor-I gene expression in rat Leydig cells

The purpose of the present study was to evaluate the effects of murine recombinant tumor necrosis factor-alpha (TNF-alpha) on rat Leydig cell function. In primary cultures of Leydig cells, we found that in the presence of hCG (10 ng/ml), testosterone levels were markedly elevated, 69.3 +/- 3.1 ng/10(6) cells/h (mean + SE). TNF-alpha in a concentration of 1 ng/ml markedly inhibited testosterone biosynthesis (a 69% reduction; p < 0.01) and 100 ng/ml of TNF-alpha almost completely inhibited testosterone formation (p < 0.001). TNF-alpha (10 ng/ml) inhibited hCG (0.1, 1 and 10 ng/ml)-induced testosterone formation by 63%, 67% and 61%, respectively. TNF-alpha (10 ng/ml) also markedly inhibited 8-bromo cAMP-induced testosterone formation from 76 +/- 9 ng/10(6) cells/h to 4.9 ng/10(6) cells/h. This indicates that the major effect of TNF-alpha is at steps beyond LH receptor site. To further evaluate the site(s) of action of TNF-alpha, we evaluated its effect on the conversion of precursor steroids to testosterone. We found that the addition of 20-hydroxy-cholesterol could not reverse inhibitory effects of TNF-alpha on hCG-induced testosterone formation. TNF-alpha had no effect on the conversions of pregnenolone, 17-OH-pregnenolone, DHEA and androstenedione to testosterone. This indicates that the major effect of TNF-alpha is at the key steroidogenic enzyme, P450scc. We reported previously that human recombinant TNF-alpha had no effect on hCG-induced testosterone formation but did enhance the inhibitory effects of human recombinant IL-1beta. In the present study, we demonstrated that both murine TNF-alpha and human IL-1beta were potent inhibitors of hCG-induced testosterone formation. IL-1beta alone in concentrations of 0.1, 1 and 10 ng/ml inhibited testosterone formation by 45%, 62% and 91%, respectively, in the presence of TNF-alpha (10 ng/ml), IL-1beta in a concentration as low as 0.1 ng/ml completely blocked hCG-induced testosterone formation. We next evaluated the effect of TNF-alpha on P450scc gene expression. There was no constitutively expressed P450scc mRNA in Leydig cells after 24 h in culture. In response to hCG, there was a 33-fold increase in the P450scc mRNA level. Both TNF-alpha and IL-1beta inhibited hCG-induced expression of P450scc mRNA. Finally, the effect of TNF-alpha on IGF-I gene expression was investigated since IGF-I enhances Leydig cell androgen formation and IGF-I gene is expressed in high levels in Leydig cells. TNF-alpha inhibited both large (7.4 kb) and small species (0.8-1.2 kb) IGF-I mRNA levels in a dose-dependent manner. In conclusion, murine TNF-alpha is a potent inhibitor of Leydig cell function. TNF-alpha inhibited both P450scc and IGF-I mRNA gene expression.

Ontogeny of steroidogenic enzyme expression in the porcine conceptus

This study examined fetal steroidogenic enzyme expression and function during pregnancy in the pig. Northern and Western analyses were performed to detect the cytochrome P450 enzyme 17 alpha-hydroxylase/17-20 lyase (P450c17) and that for cholesterol side-chain cleavage (P450scc), as well as 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) expression in several porcine fetal tissues. The data demonstrate higher steroidogenic enzyme expression in the fetal adrenal glands and testes than in the placenta at all stages of development examined. Although steroidogenic enzyme expression was maintained throughout gestation in both the fetal adrenals and the testes, adrenal P450c17 expression was higher in the early and late stages when compared with the intermediate stages of fetal development. The stimulation of fetal adrenal steroidogenic enzyme expression in the later stage fetuses was accompanied by increased expression of P450c17 in both the fetal testes and placenta. The expression of 3 beta-HSD by porcine fetal testes was low compared with that of the fetal adrenal gland at all stages of development. Adrenal explants and cultured cells secreted cortisol and androstenedione but much lower amounts of corticosterone, dehydroepiandrosterone and aldosterone. Secretion of cortisol and androstenedione by adrenal explants was maintained by ACTH for 5 days of culture but declined in controls. In cultured porcine fetal adrenal cells, ACTH and angiotensin II stimulated the secretion of multiple steroids. Porcine fetal testis explants and cultured cells secreted testosterone, dehydroepiandrosterone and androstenedione, but were only moderately responsive to trophic stimulation by LH. In general, the data suggest that the fetal adrenal glands and the fetal testes have the potential to contribute significantly to the production of steroids during pregnancy in pigs.

Differential regulation of cholesterol side-chain cleavage (P450scc) and aromatase (P450arom) enzyme mRNA expression by gonadotrophins and cyclic AMP in human granulosa cells

The co-ordinated biosynthesis of progesterone and oestradiol in the human ovary is critical for reproductive cyclicity and eventual pregnancy. The crucial regulatory enzymes for progesterone and oestradiol biosynthesis in granulosa cells are the cholesterol side-chain cleavage (P450scc) and aromatase (P450arom) enzymes respectively. We utilized the cDNA sequences encoding P450arom and P450scc to examine the roles of FSH and LH, and their intracellular second messenger, cyclic AMP (cAMP), in regulating steroidogenic gene expression. Mature granulosa cells (aspirated before the onset of the endogenous LH surge) and granulosa lutein cells (obtained after an ovulatory dose of human chorionic gonadotrophin) were cultured for 4 days with FSH, LH or dibutyryl cAMP (dbcAMP). After the period of culture, total RNA was extracted from granulosa cells and Northern analyses were performed utilizing 32P-labelled cDNAs encoding P450arom and P450scc. Spent culture media were analysed for steroid and cAMP content. Both FSH and LH strongly stimulated P450arom mRNA expression and oestradiol production in mature granulosa cells. On the other hand, P450scc mRNA expression and progesterone biosynthesis were weakly induced by FSH; maximal synthesis occurred only in the presence of LH. With both gonadotrophins at equivalent concentrations, LH generated a 30-fold higher level of cAMP than FSH. Furthermore, the differential effects of FSH and LH on P450 mRNA expression were reproduced by the presence of low and high concentrations of dbcAMP respectively. LH (and high levels of dbcAMP) increased P450arom mRNA expression in mature granulosa cells but inhibited its accumulation in granulosa lutein cells. In contrast, it stimulated P450scc mRNA expression and progesterone synthesis in both mature granulosa and granulosa lutein cells. Therefore, FSH/low cAMP levels stimulated P450arom gene expression and oestradiol production, while LH/high cAMP levels maximally induced P450scc gene expression and function, in a development-related manner consistent with steroid production in vivo. These findings support the hypothesis that one set of genes (like P450arom) in human granulosa cells is regulated by FSH/low cAMP levels and another (like P450scc) by LH/high cAMP levels.

Actions of two different cAMP-responsive sequences and an enhancer of the human CYP11A1 (P450scc) gene in adrenal Y1 and placental JEG-3 cells

We have characterized three cis-acting elements of the human CYP11A1 gene. A proximal cAMP-responsive sequence (P-CRS) functioned in both adrenal Y1 and placental JEG-3 cells. An upstream cAMP-responsive sequence (U-CRS) and an enhancer, localized by transfections of deleted gene segments linked to a reporter gene to bases -1621 to -1503 and -1931 to -1822, respectively, functioned in Y1 but not JEG-3 cells. Both regions bind proteins only from Y1 cells as identified by footprinting analysis. U-CRS contains the TCAAGGTCA sequence that binds the nuclear receptor family of proteins. The cAMP-dependent transcription mediated by U-CRS, but not by P-CRS, was abolished in a cell line deficient in cAMP-dependent protein kinase. Therefore, P-CRS and U-CRS use different effectors to mediate cAMP response. Gel mobility shift, competition, and antibody supershift experiments showed that nucleotides -117 to -94, which contributed to P-CRS activity in transfection experiments, bound weakly to Sp1-like proteins. This feature is shared by many proximal regulatory elements of steroidogenic genes. Therefore, steroidogenic genes could be coordinately regulated through common regulatory elements such as P-CRS, U-CRS, and cell type-selective enhancers.

Transcriptional activation of cytochrome P450 side chain cleavage enzyme expression during trophoblast cell differentiation

The purpose of this study was to investigate P450scc expression during trophoblast differentiation. Biochemical characteristics of P450scc protein and mRNA identified in rat trophoblast tissues were similar to those identified in the rat adrenal gland. Furthermore, P450scc was localized to trophoblast giant cells. This observation prompted an examination of progesterone biosynthesis and P450scc expression in Rcho-1 cells. Rcho-1 cells were derived from a transplantable rat choriocarcinoma, their differentiation can be regulated, and they have the capacity to express the trophoblast giant cell phenotype. Progesterone was produced by Rcho-1 cells and increased approximately 100-fold as the cells progressed from proliferation to differentiation. P450scc protein and mRNA accumulation also increased during trophoblast differentiation. P450scc expression within the Rcho-1 cell line was restricted to trophoblast giant cells. To further investigate the regulation of P450scc expression during trophoblast differentiation, we examined a plasmid construct, containing 894 base pairs of DNA 5' upstream from the P450scc transcriptional start site linked to a human growth hormone reporter gene, following stable transfection into Rcho-1 cells. The transfected P450scc regulatory DNA permitted the expression of human growth hormone which paralleled expression of the endogenous P450scc gene. In conclusion, transcriptional activation of the P450scc gene accompanies trophoblast giant cell differentiation.

Steroidogenic factor-1 binding and transcriptional activity of the cholesterol side-chain cleavage promoter in rat granulosa cells

The cholesterol side-chain cleavage cytochrome P450 (CYP11A; P450scc) gene is expressed in rat ovarian follicles in response to gonadotropins (FSH/LH) and cAMP. To identify functional regions within the rat P450scc promoter, 894 basepairs (bp) of 5'-flanking sequence and 5'-deletions (at -379, -101, -73, and -38 bp) were linked to the human GH reporter gene and transfected into cultured rat granulosa cells. cAMP inducibility of the rat promoter was localized to a region (between -73/-38 bp) that contains one of two AGGT/CC/TA motifs, designated SCC1 (-51/-43 bp) and SCC2 (-79/-71 bp), within the rat promoter. One of the nuclear proteins in granulosa cells that binds to SCC1 was identified as the orphan receptor, steroidogenic factor-1 (SF-1). In contrast, multiple protein-DNA complexes formed with SCC2, only one of which was clearly identified as SF-1. Nuclear extract binding was sequence specific; SCC1 bound SF-1 more strongly than did SCC2. Thus, the two AGGT/CC/TA motifs of the rat promoter appear to differ structurally and functionally. Furthermore, because the expression of SF-1 mRNA precedes hormonal/cAMP induction of P450scc mRNA and is not regulated in vitro by cAMP, the functional role of SF-1 in transcriptional regulation of the P450scc gene, including its induction by cAMP, is not entirely clear and is probably dependent on other factors and/or the modification (phosphorylation?) of SF-1.

Changes in levels of messenger ribonucleic acid for cytochrome P450 side-chain cleavage and 3 beta-hydroxysteroid dehydrogenase during prostaglandin F2 alpha-induced luteolysis in cattle

Regression of the CL causes a dramatic decrease in plasma progesterone levels. To test the hypothesis that the decrease in progesterone involves the down-regulation of mRNA encoding the steroidogenic enzymes, cytochrome P450 side-chain cleavage (P450scc) and/or 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD), levels of plasma progesterone and luteal mRNA for P450scc and 3 beta-HSD were measured and correlated during induced luteolysis. Holstein heifers (n = 25) were injected with 25 mg prostaglandin F2 alpha (PGF2 alpha) on Day 6 or 7 of the estrous cycle (Day 0 = estrus) to induce luteal regression. To determine acute changes in plasma progesterone during luteolysis, jugular blood samples were obtained from 5 heifers hourly for 12 h, beginning immediately before injection of PGF2 alpha, and assayed for progesterone by RIA. A significant decrease in plasma progesterone levels was observed as early as 1 h after the PGF2 alpha injection (3.62 vs. 2.72 ng/ml, p < 0.05). Progesterone levels continued to decline with time through 12 h after administration of PGF2 alpha. The other 20 animals were ovariectomized at 0 (n = 6), 2 (n = 4), 12 (n = 4), or 24 (n = 6) h after PGF2 alpha. Levels of P450scc and 3 beta-HSD mRNA were determined in extracts of total luteal RNA by ribonuclease (RNase) protection assay. By 2 h after PGF2 alpha, 3 beta-HSD mRNA levels had decreased by about 40% as compared with levels at time 0 (p < 0.05), and a further significant decrease occurred between 2 and 12 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Steroidogenic adrenocortical cell lines produced by genetically targeted tumorigenesis in transgenic mice

Studies of adrenal steroidogenesis have been facilitated by the availability of immortalized mouse adrenocortical Y-1 cells. We sought to make new, alternative mouse steroidogenic cell lines by genetically targeted tumorigenesis. Transgenic mice were constructed expressing both the SV40 T-antigen and a bacterial neomycin-resistance gene under the control of the promoter for the human P450 cholesterol side-chain cleavage (P450scc) gene, which encodes the first and rate-limiting enzyme in steroidogenesis. Two female transgenic mice expressed T-antigen in various nonsteroidogenic tissues but generated tumors only in the adrenals, suggesting adrenal tumor formation was an early event. Ovarian tissues, which, unlike the adrenal, do not make steroids in fetal or early postnatal life, did not develop tumors. Cell lines derived from the adrenal tumors were resistant to the neomycin analog G418. Clonal sublines are stable, growing easily in monolayers with a doubling time of 24-60 h. The cell lines secrete progesterone and 11-deoxycorticosterone, indicating these cells express the P450scc system, 3 beta-hydroxysteroid dehydrogenase, and 21-hydroxylase activity. However the 21-hydroxylase activity was not mediated by P450c21, as the cells lacked P450c21 mRNA. The cells did not secrete any 11-hydroxylated steroids, although they contained P450c11 beta mRNA. Both the secretion of progesterone and the abundance of P450scc mRNA increase in response to 8-bromo-cAMP, but not to ACTH or angiotensin II. In addition to expression of steroidogenic enzyme mRNAs, one cell line also expresses mouse renin-1 mRNA, making these cells useful for studies of the role of adrenal renin in regulating adrenal steroidogenesis. These findings represent an approach in transgenic mice to develop highly differentiated adrenal cell lines.

Neurosteroid biosynthesis: genes for adrenal steroidogenic enzymes are expressed in the brain

To determine if neurosteroids (steroids synthesized in the brain) are produced by enzymes found in steroidogenic tissues, we determined if mRNA for five steroidogenic enzymes could be detected in brain tissues or cultured cells. We detected mRNAs for adrenodoxin, P450scc (cholesterol side-chain cleavage enzyme) and P450c11 beta (11 beta-hydroxylase) but not for P450c17 (17 alpha-hydroxylase/17,20 lyase) or P450c11AS (aldosterone synthase) in rat brains and cultures of rat glial cells. P450scc mRNA abundance in brain or primary glial cultures was approximately 0.01% of that found in the adrenal, but more P450scc mRNA was detected in C6 glial cells. Both P450scc and P450c11 beta mRNAs were most abundant in the cortex, but there were region-specific differences for both mRNAs, and sex-specific differences for P450c11 beta mRNA. P450scc mRNA was equally abundant in mixed glial cultures containing both astrocytes and oligodendrocytes as in astrocyte-enriched cultures, and P450scc immunoreactivity co-localized with GFAP immunoreactivity in cultured astrocytes. P450c11 beta mRNA was not detected in the mixed primary glial cultures for the C6 glioma cell line that synthesize P450scc mRNA, suggesting that glial cells do not synthesize P450c11 beta mRNA. Thus some of the same enzymes involved in steroidogenesis in classic endocrine tissues are found in a cell-specific and region-specific fashion in the brain. Neurosteroids may be derivatives of known classic steroids, and/or may function through non-classic steroid hormone receptors, such as GABAA, N-methyl-D-aspartate, and corticosterone receptors.

Regulation of expression of the 3 beta-hydroxysteroid dehydrogenases of human placenta and fetal adrenal

The appropriate expression of 3 beta-hydroxysteroid dehydrogenase/delta 5-->4-isomerase (3 beta-HSD) is vital for mammalian reproduction, fetal growth and life maintenance. Several isoforms of 3 beta-HSD, the products of separate genes, have been identified in various species including man. Current investigations are targeted toward defining the processes that regulate the levels of specific isoforms in various steroidogenic tissues of man. High levels of expression of 3 beta-HSD were observed in placental tissues. It has been generally considered that the multinucleated syncytiotrophoblastic cells are the principal sites of 3 beta-HSD expression and, moreover, that 3 beta-HSD expression is intimately associated with cyclic AMP-promoted formation of syncytia. Herein we report the presence of 3 beta-HSD immunoreactive and mRNA species in uninucleate cytotrophoblasts in the chorion laeve, similar to that in syncytia but not cytotrophoblast placenta. In vitro, 3 beta-HSD levels in chorion laeve cytotrophoblasts were not increased with time nor after treatment with adenylate cyclase activators, whereas villous cytotrophoblasts spontaneously demonstrated progressive, increased 3 beta-HSD expression. Moreover, 3 beta-HSD synthesis appeared to precede morphologic syncytial formation. Thus high steroidogenic enzyme expression in placenta is not necessarily closely linked to formation of syncytia. Both Western immunoblot and enzymic activity analyses also indicated that the 3 beta-HSD expressed in these cytotrophoblastic populations was the 3 beta-HSD type I gene product (M(r), 45K) and not 3 beta-HSD type II (M(r), 44K) expressed in fetal testis. In cultures of fetal zone and definitive zone cell of human fetal adrenal, 3 beta-HSD expression was not detected until ACTH was added. ACTH, likely acting in a cyclic AMP-dependent process, induced 3 beta-HSD type II activity and mRNA expression. The higher level of 3 beta-HSD mRNA in definitive zone compared with fetal zone cells was associated with parallel increases in cortisol secretion relative to dehydroepiandrosterone sulfate formation.

Mechanisms of action for an androgen-mediated autoregulatory process in rat thecal-interstitial cells

In rat thecal-interstitial cells (TIC), treatment with the synthetic androgen mibolerone has led to the documentation of an autoregulatory process for androgen production. In the present study, accumulated evidence has provided insight into the mechanisms of mibolerone action that control this process. Investigations using the nonsteroidal antiandrogen hydroxyflutamide were conducted to characterize mibolerone's mode of action. Hydroxyflutamide had differential effects on hCG action, the 1-microM dose stimulating hCG-induced androsterone synthesis by 27% and the 10-microM concentration decreasing the androgen levels by 84%. In addition, treatment with 1 microM hydroxyflutamide was effective in partially reversing the inhibitory action of mibolerone on hCG-stimulated androsterone production. Thus, the data indicated that mibolerone's mode of action may be mediated, at least in part, via the androgen receptor. The possibility that mibolerone had multiple sites of action prompted studies on the effectiveness of this androgen to alter various signaling pathways. Treatment with increasing concentrations (0.01-100 nM) of the phorbol ester 12-0-tetradecanoylphorbol 13-acetate (TPA), which activates protein kinase C, resulted in a 75% decrease in hCG-stimulated androgen production at a dose of 100 nM TPA. Treatment with mibolerone (100 nM) was unable to alter the action of TPA on androgen synthesis when doses of 1 and 10 nM TPA were employed. It was also found that Ca2+ can serve as a mediator of mibolerone action. Treatment with a 0.01-microM dose of A23187, a Ca2+ ionophore known to increase intracellular Ca2+, was ineffective in altering hCG-stimulated androsterone synthesis. The concurrent treatment of mibolerone (100 nM) and A23187 (0.01 microM) resulted in the potentiation of mibolerone's inhibitory effects on hCG-stimulated androgen production, thereby suggesting that mibolerone can stimulate Ca2+ influx. Additional studies revealed that the administration of a 1-microM dose of the L-type Ca2+ channel blocker verapamil to TIC cultures was able to partially block the inhibitory effect of mibolerone on androgen synthesis. Evidence for an additional site of mibolerone action was revealed through an analysis of the mRNA levels of P450scc and P450(17) alpha enzymes. Although hCG and insulin-like growth factor I treatment resulted in 20- and 32-fold increases in the amount of P450scc and P450(17) alpha mRNA, respectively, the addition of mibolerone (100 nM) reduced only P450(17) alpha mRNA levels by 91%. Overall, the evidence indicates that mibolerone has multiple sites of action in exerting its regulatory effect on androgen synthesis.

Differential regulation of steroidogenic enzymes during differentiation optimizes testosterone production by adult rat Leydig cells

The postnatal differentiation of rat Leydig cells may be subdivided into three stages based on morphology and steroid production. The purpose of this study was to clarify the developmental mechanisms underlying increased testosterone production by measuring steady state levels of the mRNAs for three steroidogenic enzymes in isolated Leydig cells at each stage of differentiation. These include Leydig cell progenitors on day 21, immature Leydig cells on day 35, and adult Leydig cells on day 90. The steroidogenic enzymes were 1) cholesterol side-chain cleavage enzyme (CSCC), 2) 17 alpha-hydroxylase (P450-17 alpha), and 3) 3 alpha-hydroxysteroid dehydrogenase (3 alpha HSD). We report that levels of CSCC and P450-17 alpha mRNAs increase, whereas 3 alpha HSD mRNA levels decline during the course of Leydig cell differentiation. The levels of 3 alpha HSD mRNA were high in progenitor Leydig cells that appeared to contain little smooth endoplasmic reticulum and decreased in cells as smooth endoplasmic reticulum developed and other enzyme mRNAs increased. These observations suggest that the factors that regulate 3 alpha HSD mRNA levels are startlingly different from those that regulate the mRNA levels of CSCC and P450-17 alpha. We conclude that the progressive increase in the capacity of differentiating Leydig cells to produce testosterone can be explained in part by an increase in the activity of enzymes that synthesize testosterone (CSCC and P450-17 alpha) and a decrease in the activity of an enzyme that metabolizes testosterone and its precursors (3 alpha HSD).

Temporal and spatial localization of steroidogenic enzymes in premenopausal human ovaries: in situ hybridization and immunohistochemical study

In situ hybridization and immunohistochemical localization of cytochrome P450 cholesterol side-chain cleavage (P450scc), 3 beta-hydroxysteroid dehydrogenase (3 beta HSD), cytochrome P450 17 alpha-hydroxylase (P450c17) and cytochrome P450 aromatase (P450arom) was performed in 50 morphologically normal human premenopausal ovaries, and correlated these findings with their endometrial phase. In general, mRNA expression of these enzymes examined by in situ hybridization were in good agreement with immunolocalization examined by immunohistochemistry. Expression of P450scc, 3 beta HSD and P450c17 was observed in large-sized preantral follicles, consisting of more than five layers of granulosa cells, preovulatory follicles, corpora lutea, and some degenerating corpora lutea and atretic follicles in all endometrial phases. Several follicles and/or corpora lutea positive for these enzymes were observed in the same ovary. Expression of P450arom was generally observed in only one follicle (antral or preovulatory follicle) or corpus luteum per case in mid proliferative to premenstrual phase, and was not observed in menstrual to early proliferative phase. These findings indicated that (1) expression of steroidogenic enzymes was associated with the continual human ovarian process including follicular development and atresia, and (2) especially, P450arom expression may occur only in a selected antral follicle and may have an important role in dominant follicular development.

Differential regulation of the CYP11A1 (P450scc) and ferredoxin genes in adrenal and placental cells

The regulation of the genes encoding cholesterol side-chain cleavage enzyme (P450scc) and ferredoxin, two components in the first step of steroid synthetic pathways, was studied by RNA analyses of endogenous and transfected genes. cAMP rather than calcium was the major secondary messenger that stimulated expression of both P450scc and ferredoxin genes in human placental JEG-3 cells. The effect of cAMP on P450scc expression was abolished by cycloheximide in JEG-3 cells, but it was superinduced in mouse adrenal Y1 cells. For ferredoxin expression, both reagents have synergistic effect in Y1 and JEG-3 cells. To test the mechanism of regulation, DNA segments containing regulatory elements of the P450scc and ferredoxin genes were connected to reporter genes and analyzed in cotransfection experiments. The results showed that the proximal cAMP-responsive sequences of both P450scc and ferredoxin genes were stimulated by cAMP early in both Y1 and JEG-3 cells, requiring no new protein synthesis. This indicates a common mechanism for the regulated expression of both genes. P450scc possessed an additional upstream cAMP-responsive sequence that also responded to cAMP induction in a different manner from the proximal element. The presence of additional upstream regulatory elements makes it possible for the P450scc gene to be further regulated.

Sodium restriction increases aldosterone biosynthesis by increasing late pathway, but not early pathway, messenger ribonucleic acid levels and enzyme activity in normotensive rats

To determine whether changes in dietary sodium intake modify the early and/or late pathways of aldosterone biosynthesis, we studied in Sprague-Dawley rats the effect of sodium restriction on early (conversion of cholesterol to pregnenolone) and late (conversion of corticosterone to aldosterone) pathway activity and on the mRNA levels for the enzymes regulating these steps. Sodium restriction increased basal and angiotensin-II-stimulated aldosterone output from isolated zona glomerulosa cells by 5- to 9-fold. This increase in aldosterone output did not appear to be due to changes in the conversion of cholesterol to pregnenolone or in the mRNA levels of the early pathway enzyme, cholesterol side-chain cleavage cytochrome P-450. In contrast, sodium restriction increased the conversion of corticosterone to aldosterone 10-fold and increased by over 10-fold the mRNA levels of the late pathway enzyme aldosterone synthase. Sodium restriction had no effect on zona glomerulosa levels of 11 beta-hydroxylase mRNA. In two other normotensive rats, Dahl salt-resistant and Wistar Kyoto, sodium restriction again specifically increased aldosterone synthase mRNA without altering 11 beta-hydroxylase or cholesterol side-chain cleavage cytochrome P-450 mRNA levels. Thus, it appears that sodium restriction specifically increases late pathway aldosterone synthase mRNA levels, resulting in an increase in enzyme levels, followed by an increase in late pathway activity and an increase in aldosterone output.

Cellular aspects of corpus luteum function in the primate

The primate corpus luteum produces progesterone for a period of 14-16 days, at which time, in non-fertile cycles, steroidogenesis ceases and the tissue regresses. Studies completed in this laboratory have established that while luteinizing hormone (LH) is necessary to maintain luteal steroidogenesis, changes in LH secretion are not causal to luteolysis. The studies presented here demonstrate that luteal cell synthetic capacity, as reflected in steady-state levels of messenger ribonucleic acid (mRNA) encoding steroidogenic enzymes, is maximal shortly after ovulation and steadily declines thereafter, independently of progesterone and LH secretion. In addition, the loss of luteal mRNA expression for steroidogenic enzymes following LH withdrawal occurs 24 h after the decline in progesterone levels. Finally, the detection of mRNA encoding vascular endothelial growth factor within the corpus luteum throughout the luteal phase in the subhuman primate may provide the first identification of a potential secreted, non-steroidal factor responsible for the vast degree of angiogenesis that occurs within the corpus luteum.

Expression of steroidogenic enzyme messenger ribonucleic acids and corticosteroid production in aldosterone-producing and "nonfunctioning" adrenal adenomas

"Nonfunctioning" adrenal adenomas are often diagnosed in patients without recognizable clinical symptoms of adrenocortical hyperfunction. The objective of this study was to determine directly the steroidogenic activity of such adenomas (n = 12) and compare them histologically and functionally to normal human adrenals (n = 6) and aldosterone-producing adenomas (n = 15). The histological appearances of nonfunctioning and aldosterone-producing adenomas were surprisingly similar. Nonfunctioning adrenal adenomas expressed all mRNAs of P450scc, P450c17, P450c21, adrenodoxin, and adrenodoxin reductase with relative levels comparable to those found in normal adrenals. Consistent with their hormone-producing nature, these adenomas had cortisol and aldosterone contents as high as those in normal adrenal tissues, a significantly (P < 0.05) increased 17-hydroxyprogesterone content, and a disproportionally low expression of P450c21 mRNA compared to aldosterone-producing adenomas. Cells isolated from both aldosterone-producing and nonfunctioning adrenal adenomas exhibited highly ACTH-sensitive cortisol and aldosterone production, suggesting again the presence of both zona glomerulosa-like and zona fasciculata-like steroidogenesis in these adenoma tissues. These results indicate that so-called nonfunctioning adrenal adenomas are not without steroidogenic activity. Therefore, the assumption that adrenal adenomas are entirely nonfunctioning in the absence of recognizable hormonal hyperfunction may not be correct.

Interaction of insulin-like growth factor-II and estradiol directs steroidogenesis in the human fetal adrenal toward dehydroepiandrosterone sulfate production

We examined the regulation of steroid production in fetal zone cells from midgestation (16-21 weeks) human fetal adrenal glands to elucidate the mechanism by which these cells secrete large quantities of dehydroepiandrosterone sulfate (DHAS) and little cortisol in response to ACTH. Our underlying hypothesis is that estrogen and insulin-like to ACTH. Our underlying hypothesis is that estrogen and insulin-like growth factor-II (IGF-II) modulate the steroidogenic response of fetal zone cells to ACTH, driving steroid production toward DHAS rather than cortisol. We also hypothesize that the effects of IGF-II and estrogen on steroidogenesis are achieved by modulating the expression of key enzymes in the steroidogenic pathway. Basal cortisol secretion by cultured fetal zone cells was below the limit of assay sensitivity (< 0.54 pmol/10(5) cells.24 h), whereas basal DHAS secretion was 210.8 +/- 41.0 pmol/10(5) cells.24 h (mean +/- SE). ACTH-(1-24) increased the secretion of cortisol to 228.96 +/- 6.75 pmol/10(5) cells.24 h and that of DHAS to 2039.8 +/- 121.7 pmol/10(5) cells.24 h. Neither IGF-II nor estradiol (E2) affected basal (no added ACTH) steroid secretion by fetal zone cells. IGF-II increased ACTH-stimulated cortisol and DHAS secretion by fetal zone cells in a dose-dependent fashion. In contrast, E2 at high concentrations (1-10 mumol/L) decreased ACTH-stimulated cortisol production to basal levels, but increased ACTH-stimulated DHAS production 1.5- to 2-fold. Combinations of IGF-II (100 ng/mL) and E2 (1 mumol/L) increased ACTH-stimulated cortisol and DHAS secretion by 1.5- to 2-fold compared with control values. However, compared with cultures exposed to IGF-II alone, inclusion of E2 decreased ACTH-stimulated cortisol secretion by about 60% and increased ACTH-stimulated DHAS secretion by about 50%. IGF-II increased the abundance of ACTH-stimulated mRNAs encoding cholesterol side-chain cleavage cytochrome P450 (P450scc), 17 alpha hydroxylase/17,20 lyase P450 (P450c17), and 3 beta-hydroxysteroid dehydrogenase (3 beta HSD). In addition, IGF-II increased the abundance of mRNA encoding P450c17 under basal conditions, but did not affect the basal expression of P450scc or 3 beta HSD. E2 had no effect on basal expression of these steroidogenic enzymes, but increased the abundance of ACTH-stimulated mRNA encoding P450scc and P450c17. The abundance of mRNA encoding 3 beta HSD was not affected by E2. The effect of IGF-II and E2 in combination on steroidogenic enzyme mRNA abundance was not different from that of IGF-II alone. These data indicate that IGF-II increases ACTH-stimulated steroid production in fetal zone cells by increasing the expression of key steroidogenic enzymes.(ABSTRACT TRUNCATED AT 400 WORDS)

Regulation of P450 cholesterol side-chain cleavage messenger ribonucleic acid expression and progesterone production in hen granulosa cells

Previous studies have shown that granulosa cells from hen follicles < 8 mm in diameter are steroidogenically inactive. We have proposed that cytochrome P450 cholesterol side-chain cleavage (P450scc) enzyme activity within the granulosa layer is first expressed at the time the follicle is selected into the preovulatory hierarchy. The present studies were conducted to evaluate the actions of FSH and of the growth factors epidermal growth factor (EGF), transforming growth factor alpha (TGF alpha), and insulin-like growth factor I (IGF-I) in regulating levels of P450scc mRNA and initiating progesterone production in cultured granulosa cells from 6- to 8-mm follicles. Levels of P450scc mRNA were elevated, and progesterone production initiated, in granulosa cells cultured for 16 h and 8 h, respectively, in serum-free medium containing recombinant human (rh) FSH or the cAMP analog, 8-bromo-cAMP. While both EGF and TGF alpha blocked the ability of rhFSH to increase P450scc mRNA levels and initiate progesterone production, IGF-I failed to alter P450scc mRNA levels or progesterone production in either the presence or absence of rhFSH. Results from these studies indicate that, as in mammals, FSH is a primary factor that mediates the initiation of steroidogenesis in hen granulosa cells at the time of follicle selection. Furthermore, we propose that EGF and TGF alpha are, at least in part, responsible for preventing premature differentiation of granulosa cells in ovarian follicles that have not yet been selected into the preovulatory hierarchy.

Regulation of expression of the CYP11A (P450scc) gene in bovine ovarian luteal cells by forskolin and phorbol esters

This study examines the transcriptional regulation of the bovine CYP11A (P450scc) gene by activators of protein kinase A and protein kinase C in bovine ovarian luteal cells. Cells were transfected with reporter gene constructs containing deletion mutations of the 5'-flanking region of the bovine CYP11A gene linked to the minimal beta-globin gene. A construct containing -118/-101 base pairs of CYP11A sequence retains the same degree of stimulation by forskolin and inhibition by co-treatment with phorbol 12-myristate 13-acetate as larger constructs. This sequence contains two putative binding sites for nuclear proteins, an AP1-like sequence and an overlapping GA box element. Gel shift analysis using nuclear extracts of bovine ovarian luteal cells demonstrated that both the wild-type -118/-101-base pair sequence and a consensus GC box bound Sp1 or Sp1-like proteins. Mutation of the GA box element completely suppressed stimulation by forskolin. Absence of binding using the same mutated sequence correlated with the reporter gene transcription results. Mutation of the AP1-like site had little effect on forskolin induction of phorbol 12-myristate 13-acetate inhibition. These results indicate that both stimulation by forskolin and inhibition by phorbol esters are mediated by the same GA box element, which binds Sp1 or an Sp1-like protein.

Regulation of CYP11A gene expression in bovine ovarian granulosa cells in primary culture by cAMP and phorbol esters is conferred by a common cis-acting element

Production and secretion of steroid hormones throughout the ovarian cycle occurs in a highly episodic and coordinated fashion that requires precise and finely tuned regulatory mechanisms. The regulation of ovarian steroidogenesis by the gonadotropin follicle stimulating hormone (FSH) and luteinizing hormone (LH) as well as by other factors occurs, at least in part, at the level of expression of the genes encoding steroidogenic enzymes. The present study is aimed at the elucidation of regulatory mechanisms by which cyclic adenosine monophosphate (cAMP) and protein kinase C regulate cytochrome P450scc (CYP11A) gene expression in bovine granulosa cells in primary culture. As a first step we characterized the bovine granulosa cell cultures with regard to regulation of P450scc activity and mRNA levels upon treatment with forskolin and/or the phorbol ester TPA. Forskolin, a potent stimulator of cAMP generation, increased both progesterone secretion and P450scc mRNA levels. In contrast, treatment with TPA alone decreased both basal progesterone production and P450scc mRNA accumulation. Co-treatment with forskolin and TPA decreased progesterone and P450scc mRNA levels as compared to forskolin treatment alone. The possibility that TPA interfered with the forskolin-stimulated cAMP production could be excluded because simultaneous treatment of granulosa cells with TPA and forskolin potentiated the formation of cAMP. In order to identify regulatory sequences within the 5' flanking region of the bovine CYP11A gene, chimeric DNA constructs comprizing regions of the CYP11A gene fused to a beta-globin-derived reporter gene were transfected into granulosa cells in primary culture.(ABSTRACT TRUNCATED AT 250 WORDS)

Protein kinase C is a tonic negative regulator of steroidogenesis and steroid hydroxylase gene expression in Y1 adrenal cells and functions independently of protein kinase A

The role of protein kinase C (PKC) in the regulation of basal steroidogenesis and steroid hydroxylase gene expression in Y1 adrenocortical cells was investigated. Treatment of Y1 cells with either staurosporine or calphostin C, inhibitors of PKC, increases steroid hormone production up to 7-fold. Induction of P450-cholesterol side chain cleavage enzyme (SCC) mRNA expression parallels induction of steroidogenesis by the PKC inhibitors. Staurosporine increases expression of a transiently transfected SCC promoter--human growth hormone construct in Y1 cells, indicating that PKC regulates expression of SCC mRNA at the level of transcription. Treatment with staurosporine increases expression of mRNA for two additional steroid synthetic enzymes, P450-11 beta-hydroxylase and 3 beta-hydroxysteroid dehydrogenase. These data indicate that PKC acts as a tonic negative regulator of basal steroidogenesis in Y1 cells by suppressing expression of mRNA encoding the steroid synthetic enzymes. Protein kinase A (PKA) and PKC have reciprocal effects on steroidogenesis and expression of the steroid synthetic enzymes in Y1 cells. However, the results of this study demonstrate that these signaling pathways are not interdependent. Steroid production by Y1 cells treated with (Bu)2cAMP and calphostin C together is equal to the sum of steroid production after treatment with either agent alone. Pretreatment of Y1 cells with Rp-8-Bromo-cAMP, a specific inhibitor of PKA, prevents induction of steroidogenesis by (Bu)2cAMP, but not by staurosporine, indicating that PKC is not dependent on PKA activity. In addition, induction of SCC mRNA expression by staurosporine, in Y1 cells which are defective in activation of PKA (Y1 kin-8), is equivalent to induction in Y1 cells. These data indicate that PKA and PKC regulate basal steroidogenesis through independent effects on expression of the steroid synthetic enzymes.