Showing papers on "Pregnenolone published in 1995"
TL;DR: In three unrelated individuals with this disorder, steroidogenic acute regulatory protein, which enhances the mitochondrial conversion of cholesterol into pregnenolone, was mutated and nonfunctional, providing genetic evidence that this protein is indispensable normal adrenal and gonadal steroidogenesis.
Abstract: Congenital lipoid adrenal hyperplasia is an autosomal recessive disorder that is characterized by impaired synthesis of all adrenal and gonadal steroid hormones In three unrelated individuals with this disorder, steroidogenic acute regulatory protein, which enhances the mitochondrial conversion of cholesterol into pregnenolone, was mutated and nonfunctional, providing genetic evidence that this protein is indispensable normal adrenal and gonadal steroidogenesis
976 citations
TL;DR: It is demonstrated that progesterone is not simply a sex steroid, and a new therapeutic approach is suggested to promote myelin repair in male mice after cryolesion of the sciatic nerve.
Abstract: Progesterone is shown here to be produced from pregnenolone by Schwann cells in peripheral nerves. After cryolesion of the sciatic nerve in male mice, axons regenerate and become myelinated. Blocking either the local synthesis or the receptor-mediated action of progesterone impaired remyelination. Administration of progesterone or its precursor, pregnenolone, to the lesion site increased the extent of myelin sheath formation. Myelination of axons was also increased when progesterone was added to cultures of rat dorsal root ganglia. These observations indicate a role for locally produced progesterone in myelination, demonstrate that progesterone is not simply a sex steroid, and suggest a new therapeutic approach to promote myelin repair.
446 citations
TL;DR: The results suggest that DHEA S and PREG S control the NMDA response via sigma 1 receptors and that progesterone may act as a sigma antagonist.
Abstract: N-Methyl-D-aspartate (NMDA, 200 microM) evokes the release of [3H]norepinephrine ([3H]NE) from preloaded hippocampal slices. This effect is potentiated by dehydroepiandrosterone sulfate (DHEA S), whereas it is inhibited by pregnenolone sulfate (PREG S) and the high-affinity sigma inverse agonist 1,3-di(2-tolyl)guanidine, at concentrations of > or = 100 nM. Neither 3 alpha-hydroxy-5 alpha-pregnan-20-one nor its sulfate ester modified NMDA-evoked [3H]NE overflow. The sigma antagonists haloperidol and 1-[2-(3,4-dichlorophenyl)-ethyl]-4-methylpiperazine, although inactive by themselves, completely prevented the effects of DHEA S, PREG S, and 1,3-di(2-tolyl)guanidine on NMDA-evoked [3H]NE release. Progesterone (100 nM) mimicked the antagonistic effect of haloperidol and 1-[2-(3,4-dichlorophenyl)ethyl]-4-methyl-piperazine. These results indicate that the tested steroid sulfate esters differentially affected the NMDA response in vitro and suggest that DHEA S acts as a sigma agonist, that PREG S acts as a sigma inverse agonist, and that progesterone may act as a sigma antagonist. Pertussis toxin, which inactivates the Gi/o types of guanine nucleotide-binding protein (Gi/o protein) function, suppresses both effects of DHEA S and PREG S. Since sigma 1 but not sigma 2 receptors are coupled to Gi/o proteins, the present results suggest that DHEA S and PREG S control the NMDA response via sigma 1 receptors.
424 citations
TL;DR: Steroidogenic acute regulatory protein (StAR) appears to mediate the rapid increase in pregnenolone synthesis stimulated by tropic hormones and StAR mRNA levels are regulated by cAMP.
Abstract: Steroidogenic acute regulatory protein (StAR) appears to mediate the rapid increase in pregnenolone synthesis stimulated by tropic hormones. cDNAs encoding StAR were isolated from a human adrenal cortex library. Human StAR, coexpressed in COS-1 cells with cytochrome P450scc and adrenodoxin, increased pregnenolone synthesis > 4-fold. A major StAR transcript of 1.6 kb and less abundant transcripts of 4.4 and 7.5 kb were detected in ovary and testis. Kidney had a lower amount of the 1.6-kb message. StAR mRNA was not detected in other tissues including placenta. Treatment of granulosa cells with 8-bromo-adenosine 3',5'-cyclic monophosphate for 24 hr increased StAR mRNA 3-fold or more. The structural gene encoding StAR was mapped using somatic cell hybrid mapping panels to chromosome 8p. Fluorescence in situ hybridization placed the StAR locus in the region 8p11.2. A StAR pseudogene was mapped to chromosome 13. We conclude that StAR expression is restricted to tissues that carry out mitochondrial sterol oxidations subject to acute regulation by cAMP and that StAR mRNA levels are regulated by cAMP.
377 citations
Journal Article•
TL;DR: Comparing the effects of a variety of agents on CYP3A expression in primary cultures of hepatocytes from rats, rabbits, and humans, maintained under nearly identified conditions on Matrigel found striking interspecies differences in response to CYP2A inducers.
Abstract: We previously demonstrated that induction of hepatic cytochrome P4503A (CYP3A) immunoreactive protein is a response in rats, but not rabbits, treated with the antiglucocorticoid, pregnenolone 16 alpha-carbonitrile and in rabbits, but not rats, treated with rifampicin. These striking interspecies differences in response to CYP3A inducers prompted us to compare the effects of a variety of agents on CYP3A expression in primary cultures of hepatocytes from rats, rabbits, and humans, maintained under nearly identified conditions on Matrigel. We used treatment with dexamethasone, the most effective inducer of CYP3A mRNA and CYP3A immunoreactive protein in cultures of rat hepatocytes, to define the 100% response. As expected from their effects in vivo, incubations of cultures with medium containing pregnenolone 16 alpha-carbonitrile or rifampicin induced CYP3A mRNA to high levels exclusively in rat hepatocytes or rabbit hepatocytes, respectively. Pregnenolone 16 alpha-carbonitrile treatment also did not induce CYP3A immunoreactive protein in rabbit hepatocytes, although rifampicin treatment did increase CYP3A immunoreactive protein levels in rat hepatocyte cultures. Additions of phenobarbital to the cultures induced CYP3A mRNA and CYP3A immunoreactive protein to a greater extent in rabbit hepatocytes (94-108% of the dexamethasone response) than in rat hepatocytes (38-57% of the dexamethasone response). In primary cultures of human hepatocytes, dexamethasone and phenobarbital treatments induced CYP3A mRNA (> or = 4.4- and 1.9-fold, respectively, over the amounts of CYP3A mRNA in incubated control cultures).(ABSTRACT TRUNCATED AT 250 WORDS)
242 citations
TL;DR: It is suggested that cytochrome b5 plays a role in regulating the activities of P450c17 to optimize the balance between sex hormone synthesis and glucocorticoid synthesis, and in human testes which contains a high b5/P450 ratio, 17 alpha-hydroxyprogesterone can serve as an intermediate in testosterone production.
216 citations
TL;DR: The expression and characterization of a human EST distinct from other human STs which sulfate estrogens indicates that this ST may be important in both the metabolism of estrogens and in the regulation of their activities.
212 citations
TL;DR: Beta-sitosterol reduces the gonadal steroid biosynthetic capacity through effects on cholesterol availability or the activity of the side chain cleavage enzyme P450SCC, which could be a contributing factor to the reproductive dysfunction observed in fish exposed to BKME.
210 citations
TL;DR: It is demonstrated that progesterone is not simply a sex steroid, and a new therapeutic approach is suggested to promote myelin repair in male mice after cryolesion of the sciatic nerve.
Abstract: Progesterone is shown here to be produced from pregnenolone by Schwann cells in peripheral nerves. After cryolesion of the sciatic nerve in male mice, axons regenerate and become myelinated. Blocking either the local synthesis or the receptor-mediated action of progesterone impaired remyelination. Administration of progesterone or its precursor, pregnenolone, to the lesion site increased the extent of myelin sheath formation. Myelination of axons was also increased when progesterone was added to cultures of rat dorsal root ganglia. These observations indicate a role for locally produced progesterone in myelination, demonstrate that progesterone is not simply a sex steroid, and suggest a new therapeutic approach to promote myelin repair.
206 citations
TL;DR: In this article, the selective expression of a 3β-hydroxysteroid dehydrogenase/Δ5-Δ4 isomerase (3β-HSD) isoform in rat brain was reported.
202 citations
TL;DR: The finding that fewer than 150 molecules of PS significantly enhanced post-training memory processes when injected into the amygdala establishes PS as the most potent memory enhancer yet reported and the amygdala as themost sensitive brain region for ME by any substance yet tested.
Abstract: Immediate post-training, stereotactically guided, intraparenchymal administration of pregnenolone sulfate (PS) into the amygdala, septum, mammillary bodies, or caudate nucleus and of PS, dehydroepiandrosterone sulfate, and corticosterone into the hippocampus was performed in mice that had been weakly trained in a foot-shock active avoidance paradigm. Intrahippocampal injection of PS resulted in memory enhancement (ME) at a lower dose than was found with dehydroepiandrosterone sulfate and corticosterone. Intraamygdally administered PS was approximately 10(4) times more potent on a molar basis in producing ME than when PS was injected into the hippocampus and approximately 10(5) times more potent than when injected into the septum or mammillary bodies. ME did not occur on injection of PS into the caudate nucleus over the range of doses tested in the other brain structures. The finding that fewer than 150 molecules of PS significantly enhanced post-training memory processes when injected into the amygdala establishes PS as the most potent memory enhancer yet reported and the amygdala as the most sensitive brain region for ME by any substance yet tested.
TL;DR: The experiments suggest that the brain, like adrenals and gonads, is a steroidogenic organ which produces allopregnanolone as one of its own most important physiologically relevant steroids.
Abstract: Coupling high performance liquid chromatography with gas chromatography-mass fragmentography has made it possible to simultaneously measure subpicomolar concentrations of allopregnanolone and its precursors, pregnenolone, progesterone and 5 alpha-dihydroprogesterone (5 alpha-DHP) in various brain areas. Allopregnanolone was measured in the brain of adrenalectomized/castrated (ADX/CX) rats in nanomolar concentrations long after peripheral sources of allopregnanolone were removed. A partial decrease (approximately 30%) in the content of allopregnanolone was found in the brains of ADX/CX rats compared to sham-operated rats. Moreover, the content of allopregnanolone in brains of sham-operated as well as ADX/CX rats was nonuniformly distributed (olfactory bulb > striatum > cortex > hippocampus) and was one to two orders of magnitude higher than in plasma or liver. Infusion of pregnenolone sulfate in ADX/CX rats elicited a fourfold increase in 5 alpha-DHP and progesterone content and a seven- to eightfold increase in the content of allopregnanolone in brain but not in liver or plasma. Furthermore, the content of allopregnanolone in brain increased to the same extent in both sham-operated and ADX/CX rats following pregnenolone sulfate infusion. The 5 alpha-reductase inhibitor, (17 beta)17[[bis(1-methylethyl)amino]carbonyl] androstane-3,5-diene-3-carboxylic acid (SKF 105111), reduced the brain content of allopregnanolone and blocked the increased formation of allopregnanolone in brain following pregnenolone sulfate infusion. The results clearly demonstrate that the synthesis of allopregnanolone from 5 alpha-DHP and progesterone occurs in the brain and that a significant amount of allopregnanolone is synthesized locally in brain from its precursors. These experiments suggest that the brain, like adrenals and gonads, is a steroidogenic organ which produces allopregnanolone as one of its own most important physiologically relevant steroids.
TL;DR: In this article, pregnenolone sulfate, progesterone and some of its main reduced metabolites were tested for anxiolytic properties in rats using the burying behavior paradigm.
TL;DR: The results suggest that the brain produces pregnenolone from cholesterol in adult male Japanese quails, and most accumulation of pregnanolone in the brain may be independent of the peripheral endocrine gland system.
TL;DR: Using NADPH-cytochrome P-450 reductase as electron donor the homogeneous pig CYP17 was shown to catalyse the conversion of delta 5, as well as delta 4, steroids (pregnenolone and progesterone respectively) predominantly into the corresponding 17 alpha-hydroxylated products.
Abstract: Using NADPH-cytochrome P-450 reductase as electron donor the homogeneous pig 17 alpha-hydroxylase-17,20-lyase (CYP17) was shown to catalyse the conversion of delta 5, as well as delta 4, steroids (pregnenolone and progesterone respectively) predominantly into the corresponding 17 alpha-hydroxylated products. The latter were then cleaved by the lyase (desmolase) activity of the enzyme into androgens. Cytochrome b5 stimulated both these activities, but its most noticeable effect was on the formation of delta 16-steroids, which compulsorily required the presence of cytochrome b5. These results on the pig enzyme confirm the original findings [Nakajin, Takahashi, Shinoda and Hall (1985) Biochem. Biophys. Res. Commun. 132, 708-713]. The human CYP17 expressed in Escherichia coli [Imai, Globerman, Gertner, Kagawa and Waterman (1993) J. Biol. Chem. 268, 19681-19689] was also purified to homogeneity and was found to catalyse the hydroxylation of pregnenolone and progesterone without requiring cytochrome b5. Like the pig CYP17, the human CYP17 also catalysed the cytochrome b5-dependent direct cleavage of pregnenolone into the delta 5,16-steroid, but unlike it the human enzyme did not cleave progesterone at all. 17 alpha-Hydroxypregnenolone was, however, cleaved into the corresponding androgen but only in the presence of cytochrome b5. 17 alpha-Hydroxyprogesterone was a poor substrate for the human CYP17; although it was converted into androstenedione in the presence of cytochrome b5 its K(m) was 5 times higher and Vmax. 2.6 times lower than those for the hydroxylation of progesterone. The endocrinological and mechanistic implications of these results are discussed.
TL;DR: A recently identified protein termed Steroidogenic Acute Regulatory protein (StAR) has the necessary properties of enhancing steroidogenesis, rapid cAMP inducibility and rapid cycloheximide sensitivity that characterize the long-sought acute regulator of steroidogenesis.
TL;DR: A model where the interaction of DBI with PBR, at the outer/inner membrane contact sites, is the signal transducer of hormone-stimulated and constitutive steroidogenesis at the mitochondrial level is proposed.
TL;DR: The results of immunohistochemical and Western immunoblotting analyses confirm the previous findings of pregnenolone biosynthesis and suggest the presence of a P450scc-like substance in both neuronal and glial cells of the quail brain.
TL;DR: The spatial and temporal expression patterns of P450c17 and aldosterone synthase mRNA, which differ from those of cholesterol side-chain cleavage cytochrome P450 and adrenodoxin, suggest that multiple factors must be required to program cell type- and species-specific expression of these steroid hydroxylases during embryonic development.
Abstract: Corticosterone is the major circulating glucocorticoid in adult mice and rats, and this is explained, in part, by the absence of 17 alpha-hydroxylase cytochrome P450 (P450c17) in adrenal glands of these rodents. During embryonic development, however, we discovered transient expression of P450c17 in a subset of adrenocortical cells in the fetal mouse adrenal. This differs from cholesterol side-chain cleavage cytochrome P450 and adrenodoxin, which are expressed continuously in most fetal adrenocortical cells from onset of expression at embryonic days 11-12 (E11-12) until term. Adrenal P450c17 transcripts are detectable in situ at E12.5 and increase in abundance from E12.5 to E14.5. Transcripts are then lost between E16.5 and term (E18.5) and are undetectable in situ in adrenal glands of adult mice. These results are consistent with the presence of pregnenolone 17 alpha-hydroxylase activity in adrenal homogenates of fetal but not adult mice. By using polymerase chain reaction, we determined that murine fetal...
TL;DR: The activation of CYP3A1 gene transcription by glucocorticoids may involve proteins already bound to the controlling element in the CYP5′-flanking sequences fused to a chloramphenicol acetyltransferase reporter plasmid through a mechanism in which GR in the presence of hormone does not bind directly to CYP 3A1 DNA.
TL;DR: The molecular cloning and functional characterization of a full-length complementary DNA for estrogen sulfotransferase from mouse testis are reported and suggest complex regulatory mechanisms in its expression under normal and pathophysiological conditions.
Abstract: Sulfation represents a major pathway for the inactivation of steroid hormones such as estrogens and is catalyzed by a group of enzymes called sulfotransferases. Aberrant regulation of an estrogen sulfotransferase has been demonstrated previously in the livers of obese and diabetogenic C57BL/KsJ-db/db strain mice. In this paper, we report the molecular cloning and functional characterization of a full-length complementary DNA for estrogen sulfotransferase from mouse testis. The mouse estrogen sulfotransferase complementary DNA encodes 295 amino acids. It shares 88%, 77%, 75%, and 68% identity in amino acid sequence with the rat liver, human liver, guinea pig adrenal, and bovine placental estrogen sulfotransferase, respectively. The mouse enzyme was expressed as a glutathione-S-transferase fusion protein in Escherichia coli. The fusion protein was affinity purified, and milligram quantities of pure enzyme were obtained after cleavage of the fusion protein with thrombin. The expressed enzyme exhibits a high substrate specificity toward estrogens, including estradiol and estrone. Neither dehydroepiandrosterone, pregnenolone, testosterone, nor a simple phenolic compound, 4-nitrophenol appears to be a substrate. Northern hybridization indicates that messenger RNA (1.3 kilobases) for the estrogen sulfotransferase is expressed exclusively in the testes in control C57BL/KsJ mice. However, both the messenger RNA and protein are dramatically induced in the livers of obese and diabetogenic C57BL/KsJ-db/db mice. In contrast to the liver, the constitutive expression of the enzyme in the testis is not affected by the db/db genotype. These results recapitulate the species-specific nature in the tissue distribution of estrogen sulfotransferase and suggest complex regulatory mechanisms in its expression under normal and pathophysiological conditions.
01 Oct 1995-Comparative Biochemistry and Physiology Part C: Pharmacology, Toxicology and Endocrinology
TL;DR: The steroid biosynthetic capacity of white sucker ovarian follicles undergoing vitellogenesis was examined to determine if reductions in steroid production contribute to the reduced circulating steroid levels found during this stage of reproduction.
TL;DR: It is concluded that neurosteroids regulate the morphology and/or GFAP distribution of astrocytes in hippocampal slice cultures from adult rats.
Abstract: Recent evidence indicates that astroglia may be involved in the synthesis of endogenous neurosteroids. The extension of glial fibrillary acidic protein (GFAP)-immunoreactive astroglial cell processes was assessed in hippocampal slice cultures from adult gonadectomized male rats under the influence of the neurosteroids dehydroepiandrosterone, dehydroepiandrosterone sulfate, dehydroepiandrosterone estereate, pregnenolone, pregnenolone sulfate, and pregnenolone oleate. The effects of neurosteroids were compared to those induced by the gonadal steroids testosterone, 17 beta-estradiol and progesterone. Astrocytes in hippocampal slice cultures had a morphology that was indistinguishable from that observed in the hippocampus fixed in situ. Castration of adult male rats resulted in a significant decrease in the extension of GFAP-immunoreactive processes, both in tissues fixed in situ and in slice cultures. In contrast, incubation of slice cultures from gonadectomized animals with pregnenolone, pregnenolone sulfate, 17 beta-estradiol, and testosterone enhanced the extension of GFAP-immunoreactive processes. While other steroids tested did not affect this parameter, dehydroepiandrosterone and its sulfate and estereate derivatives induced the transformation of astroglial cells into hypertrophic and highly GFAP immunoreactive cells with the morphological characteristics of reactive astroglia. We conclude that neurosteroids regulate the morphology and/or GFAP distribution of astrocytes in hippocampal slice cultures from adult rats.
TL;DR: E2 production by follicles was shown to depend largely on aromatase activity, while T production by hair follicles appeared to be depend partly on SPH-induced pregnenolone production, followed by a further increase or a slight decrease during the migratory nucleus stage.
TL;DR: A novel integrated mechanism by which ammonia-induced activation of PBRs leads to elevated levels of pregnenolone-derived neurosteroids which are known to enhance GABA-ergic neurotransmission may play a pivotal role in pathogenesis of HE.
TL;DR: Prenatal diagnosis correctly identified both an unaffected XX fetus and an affected XY fetus and Immunocytochemistry and Western blotting showed that the affected placental tissue contained P450scc protein, confirming that P 450scc is intact in these patients.
Abstract: Congenital lipoid adrenal hyperplasia (lipoid CAH) is a rare genetic disorder of adrenal and gonadal steroidogenesis of unknown cause in which cholesterol cannot be converted to pregnenolone. As a result, affected individuals can make no steroid hormones, so that all affected newborns are phenotypic females, irrespective of karyotype. We studied two pregnancies in a family with two previously affected children by examining fetal karyotype, genital ultrasonography, and amniotic fluid steroid concentrations and by performing ACTH tests on family members. Prenatal diagnosis correctly identified both an unaffected XX fetus and an affected XY fetus. In the affected pregnancy, amniotic fluid concentrations of progesterone and pregnenolone were 30% and 50% of normal, respectively, but concentrations of 17 alpha-hydroxypregnenolone, 17 alpha-hydroxyprogesterone, cortisol, dehydroepiandrosterone, androstenedione, and estriol were either extremely low or undetectable, suggesting that these detected steroids were do...
TL;DR: It is possible to suggest that the increase in the brain content of ALLO, rather than 5α-DHP, mediates the effect of PREG sulfate on dizocilpine- or CPPene-induced cognition deficit.
Abstract: Pregnenolone (PREG) is metabolized in brain to progesterone (PROG), 5 alpha-dihydroprogesterone (5 alpha-DHP) and allopregnanolone (ALLO). Infusion of adrenalectomized/castrated rats with PREG sulfate prevented the cognition deficit elicited by the ionotropic glutamate receptor antagonists, dizocilpine and CPPene. Using a new gas chromatographic/mass-spectrometric method, we demonstrated that PREG sulfate infusion markedly increased the PREG, PROG, 5 alpha-DHP and ALLO brain content. The increase in 5 alpha-DHP and ALLO, but not PREG or PROG content and the antagonism of dizocilpine amnesia observed by injecting rats with PREG sulfate was reversed by inhibiting the conversion of PROG to 5 alpha-DHP with the 5 alpha-reductase blocker SKF 105111. We and others have shown that ALLO potently modulate GABAA receptor function whereas 5 alpha-DHP fails to induce rapid changes in neurotransmitter receptor function. Thus it is possible to suggest that the increase in the brain content of ALLO, rather than 5 alpha-DHP, mediates the effect of PREG sulfate on dizocilpine- or CPPene-induced cognition deficit.
TL;DR: The findings indicate that sex hormones directly affect rat adrenocortical secretion, mainly by acting on the rate-limiting step of steroidogenesis (i.e. the conversion of cholesterol to PREG); moreover, they suggest that testosterone is also able depress the activity of the enzymes operating distally to cholesterol side-chain cleavage.
TL;DR: The data pertaining to the role of brain P450 in the synthesis and degradation of neurosteroids is examined to answer the following questions: Does P450scc in the brain contribute significantly to the synthesis of GABAA receptor active steroids?
TL;DR: Evidence is provided that mitochondrial P450 systems indeed function as a significant source of oxygen radicals in steroidogenic cells and a correlation between the effects previously observed in living cells and in reconstituted systems is revealed.