Showing papers on "Steroid biosynthesis published in 2003"
TL;DR: The various polymeric states of PBR might be part of a cycle mediating cholesterol uptake and release into the mitochondria, with PBR functioning as a cholesterol exchanger against steroid product(s) arising from cytochrome P450 action.
334 citations
TL;DR: This chapter describes the imaging mitochondrial function in intact cells, which has set the mitochondrion center stage as a key player in major aspects of modern cell biology and medicine.
Abstract: Publisher Summary This chapter describes the imaging mitochondrial function in intact cells. Mitochondria play a central role in cell life and cell death. Mitochondria not only generate ATP, the major currency used by cells in energy-requiring processes, but also house a range of synthetic enzymes, including enzymes involved in heme and steroid biosynthesis. Mitochondria are intimately involved in shaping the spatiotemporal characteristics of intracellular [Ca 2+ ] c signaling, and they house several proteins that play a key role in the regulation of programmed cell death, or apoptosis. The discovery that proteins critically involved in the initiation and regulation of apoptotic cell death are housed within mitochondria and may be released, either accidentally as a consequence of cell injury or in a regulated fashion at the onset of programmed cell death, has set the mitochondrion center stage as a key player in major aspects of modern cell biology and medicine.
229 citations
TL;DR: The use of recombinant receptors as a means of primary screening of environmental samples for estrogenicity and antiestrogenicity is discussed, which avoids species and seasonal variation in receptor response to ligand binding, a recognized problem of earlier bioassays.
Abstract: A wide range of organic contaminant compounds prevalent in the aquatic environment has been shown to exhibit hormone-disrupting activity. The actual potency of such compounds are low compared with endogenous hormones, such as 17beta-estradiol, but may still produce detrimental biological effects. Induced hormone levels are routinely measured using commercial testing kits, though these fail to relate to actual effects. Field and laboratory studies on the biological effects of environmental estrogens have, in the past, largely relied on assays of vitellogenin (vtg) induction in male fish, reduced growth in testes formation, and intersex incidence. Here, we critically review the current and potential application of molecular techniques in assessing the adverse biological reproductive effects of endocrine-disrupting chemicals in aquatic organisms. The role of fish (estrogen, androgen, and progestogen) hormone receptors and invertebrate (ecdysone) hormone receptor, egg production (vtg and chorion) proteins, steroid biosynthesis enzymes (aromatase, sulfotransferase, and hydroxysteroid dehydrogenase), DNA damage, apoptosis, and their potential development as biomarkers are discussed in turn. In each case, the sequences characterized are presented and homologies across species are highlighted. Molecular methods of gauging vtg and zona radiata (ZR) expression and protein concentrations have included immunoassay and reverse transcription polymerase chain reaction (RT-PCR). Suggestions for the isolation for key gene expression products (aromatase, ZR, and vtg, for instance), from a wider range of fish species using degenerate primers, are given. Endocrine disruption in invertebrates has received less attention compared with fish, partly because the knowledge regarding invertebrate endocrinology is limited. Here we review and suggest alternate isolation strategies for key players in the imposex induction process: vitellin (Vn), aromatase, and Ala-Pro-Gly-Trp (APGW) amide neurohormone. Current molecular-level techniques rely on ligand-binding assays, enzyme-linked immunosorbent assay (ELISA), and, more recently, gene expression. In the future, more reliance will be placed on the development of gene expression assays using reporter systems combined with cross-species PCR-based or polyclonal antibody-based assays. We discuss the use of recombinant receptors as a means of primary screening of environmental samples for estrogenicity and antiestrogenicity, which avoids species and seasonal variation in receptor response to ligand binding, a recognized problem of earlier bioassays. Most exciting is the potential that microarray and proteomics approaches have to offer. Such techniques are now used routinely in medical research to identify specific genes and proteins affected by treatment with endocrine disruptors, including estradiol. The technique has yet to be used to screen aquatic organisms, but it has the potential to implicate previously unsuspected estradiol-sensitive genes that may later become molecular markers of endocrine disruption.
176 citations
TL;DR: The cloning of the first bacterial steroid biosynthesis gene, cas, encoding the cycloartenol synthase (Cas) of S. aurantiaca is described, indicating a close evolutionary relationship between myxobacterial and eukaryotic steroids biosynthesis.
Abstract: Summary
Steroids, such as cholesterol, are synthesized in almost all eukaryotic cells, which use these triterpenoid lipids to control the fluidity and flexibility of their cell membranes. Bacteria rarely synthesize such tetracyclic compounds but frequently replace them with a different class of triterpenoids, the pentacyclic hopanoids. The intriguing mechanisms involved in triterpene biosynthesis have attracted much attention, resulting in extensive studies of squalene-hopene cyclase in bacteria and (S)-2,3-oxidosqualene cyclases in eukarya. Nevertheless, almost nothing is known about steroid biosynthesis in bacteria. Only three steroid-synthesizing bacterial species have been identified before this study. Here, we report on a variety of sterol-producing myxobacteria. Stigmatella aurantiaca is shown to produce cycloartenol, the well-known first cyclization product of steroid biosynthesis in plants and algae. Additionally, we describe the cloning of the first bacterial steroid biosynthesis gene, cas, encoding the cycloartenol synthase (Cas) of S. aurantiaca. Mutants of cas generated via site-directed mutagenesis do not produce the compound. They show neither growth retardation in comparison with wild type nor any increase in ethanol sensitivity. The protein encoded by cas is most similar to the Cas proteins from several plant species, indicating a close evolutionary relationship between myxobacterial and eukaryotic steroid biosynthesis.
167 citations
TL;DR: It is proposed that LRH-1 plays an important role as a competence factor in regulating aromatase, and thus estrogen biosynthesis, in ovary.
141 citations
TL;DR: This review addresses environmental influences on sex determination and differentiation in fishes and focuses on two classes of examples where the key environmental cues are of clear ecological relevance, the effects appear especially likely to be important as a normal part of the life history, and where there is evidence suggesting the sexual patterns observed represent adaptations that increase individual fitness.
Abstract: Van Valen (1973) characterized evolution as the control of development by ecology. Sex determination in fishes provides some clear examples of this “control” in operation. Teleost fishes show a remarkable variety of sex determination and differentiation patterns. These range from systems in which sex is determined by sex chromosomes, as in birds and mammals, to simultaneous hermaphrodites that alternate spawning as a female and male on a second to second basis. This extraordinary flexibility may result from a combined lack of developmental constraint on reproductive structures in many lineages and selection for sexual lability in the face of environmental unpredictability. This review addresses environmental influences on sex determination and differentiation in fishes. There is a variety of documented environmental influences on sex determination (ESD) in fishes. We focus here on two classes of examples where the key environmental cues are of clear ecological relevance, the effects appear especially likely to be important as a normal part of the life history, and where there is evidence suggesting the sexual patterns observed represent adaptations that increase individual fitness. These classes are sex determination that is controlled by social interactions (behavioral sex determination [BSD]) (Crews 1993) and temperaturedependent sex determination (TSD). Sex determination controlled by social influences can occur before or after sexual maturation but appears to maximize the expected reproductive success of individuals in both cases. Here we first address BSD and then TSD in fishes. For each pattern of sex determination, we discuss selection pressures that appear to favor these patterns, examples of each, and what is known regarding the underlying physiological mechanisms. For more comprehensive and general reviews of patterns and mechanisms of sex determination in fishes, the reader is referred to several excellent reviews (Nakamura et al. 1998; Baroiller et al. 1999; Baroiller and D’Cotta 2001; Piferrer 2001). The major focus in studies of physiological mediation of teleost sex determination is what is referred to by endocrinologists as the hypothalamo-pituitary-gonadal (HPG) axis (Fig. 1). This axis consists primarily of hypothalamic neurosecretory neurons producing gonadotropin-releasing hormone (GnRH), gonadotropins produced in and released from the pituitary gland (GtH I and GtH II), and the gonad as the major site of steroid biosynthesis with its steroid metabolizing enzymes, steroid hormone receptors, and a variety of other proteins that mediate steroid hormone action. One steroid biosynthetic enzyme that has been a particularly fruitful focus in correlative and manipulative studies of vertebrate sex determination is cytochrome P-450 aromatase. This enzyme catalyzes the conversion of androgens to estrogens (primarily testosterone to estradiol-17 ). Aromatase expression correlates with female determination in a variety of vertebrates, and aromatasespecific antagonists can block female development in fishes, amphibians, reptiles, and birds (Elbrecht and Smith 1992; Lance and Bogart 1992; Crews et al. 1994; Wennstrom and Crews 1995; Kitano et al. 1999; D’Cotta et al. 2001). Estradiol-17 plays a central role in female reproductive physiology in fishes, whereas the androgen 11-ketotestosterone (11-KT) is crucial to gamete maturation and the expression of secondary sexual characteristics in males (Borg 1994; Brantley et al. 1993). Importantly, testosterone levels often do not differ between male and female fishes or are higher in females (Borg 1994). Because of the central role of aromatase in the biosynthesis of estrogens, it will be a focus in consideration of mechanisms by which environmental information leads to sex determination responses. More generally, our understanding of vertebrate sexual function indicates the HPG axis plays the key role in transducing environmental information into gonadal determination, differentiation, and maturation events. A general theme of this review is where and how this transduction may occur in the HPG axis.
119 citations
TL;DR: The present studies demonstrate that the specialized DNA polymerase kappa (polkappa) is uniquely and preferentially expressed in the adrenal cortex and testis of the mouse, as well as in a variety of other tissues.
74 citations
TL;DR: It is suggested that the high level of steroid biosynthesis in R2C cells is a result of the constitutive expression of the components involved in the uptake of cholesterol esters, their conversion to free cholesterol, and its mobilization to the inner mitochondrial membrane (StAR).
Abstract: The rat R2C Leydig tumor cell line is constitutively steroidogenic in nature, while the mouse MA-10 Leydig tumor cell line synthesizes large amounts of steroids only in response to hormonal stimulation. Earlier studies showed abundant cAMP-independent steroid production and constitutive expression of steroidogenic acute regulatory (StAR) protein in R2C cells. The objective of the current study was to identify possible genetic alterations in the R2C cell line responsible for rendering it a constitutively steroidogenic cell line, especially those that might have altered its cholesterol homeostatic mechanisms. Measurement of the levels of cholesterol esters and free cholesterol, precursors for steroidogenesis, indicated that R2C mitochondria were fourfold enriched in free cholesterol content compared with MA-10 mitochondria. In addition to the previously demonstrated increased expression of StAR protein, we show that R2C cells possess marginally enhanced protein kinase A activity, exhibit higher capacity to take up extracellular cholesterol esters, and express much higher levels of scavenger receptor-type B class 1 (SR-B1) and hormone sensitive lipase (HSL). These observations suggest that the high level of steroid biosynthesis in R2C cells is a result of the constitutive expression of the components involved in the uptake of cholesterol esters (SR-B1), their conversion to free cholesterol (HSL), and its mobilization to the inner mitochondrial membrane (StAR).
72 citations
TL;DR: An alternating expression of proteins related to cell survival in endometria from PCOSE may potentially be associated with the disruption of their endometrial cell cycle.
52 citations
TL;DR: The assembly of various transcription factors forming protein-DNA complexes appears to be the key step in CYP11A1 transcription, which controls the first and rate-limiting step of steroid biosynthesis.
Abstract: Steroid hormones are important physiological regulators that control our glucose and salt balance, as well as sexual characteristics. The synthesis of steroid hormones is under tight control; disturbed secretion of steroids often leads to diseases. The mechanism controlling the secretion of steroids, namely steroidogenesis, has been the focus of intensive studies. CYP11A1 controls the first and rate-limiting step of steroid biosynthesis. It is expressed in the adrenal cortex and gonads, under the control of pituitary hormones, through the cAMP-signaling pathway. The promoter of the CYP11A1 gene contains sequences that bind to transcription factor SF-1, which plays an important role in the tissue-specific and hormonally regulated expression of steroidogenic genes. Detailed transcriptional analysis documents the importance of SF-1 in activating CYP11A1 in vitro and in vivo. Other factors like c-Jun are also involved. The assembly of various transcription factors forming protein-DNA complexes appears to be the key step in CYP11A1 transcription.
46 citations
TL;DR: The mother and the brother have been demonstrated to be carriers of deletion mutation through restriction enzyme analysis, and the first report of the molecular genetic study of 17alpha-hydroxylase/17,20-lyase deficiency in mainland China with a novel compound heterozygous mutation.
TL;DR: CYP17 accommodates the stereochemically unnatural ent-progesterone better than CYP21, and these compounds may be effective inhibitors of steroid biosynthesis.
TL;DR: Ginkgolide B (GKB) is a purified component of Ginkgo biloba leaf extracts that reduces the mRNA, protein, and ligand-binding levels of the adrenal peripheral-type benzodiazepine receptor (PBR), a mitochondrial cholesterol-binding protein, leading to decreased corticosteroid synthesis as mentioned in this paper.
01 Jan 2003
TL;DR: In this paper, Ginkgolide B (GKB), a purified component of Ginkgo biloba leaf extracts, reduces the mRNA, protein, and ligand-binding levels of the adrenal peripheral-type benzodiazepine receptor (PBR), a mitochondrial cholesterol-binding protein, leading to decreased corticosteroid synthesis.
Abstract: Treatment of rats and adrenocortical cells with ginkgolide B (GKB), a purified component of Ginkgo biloba leaf extracts, reduces the mRNA, protein, and ligand-binding levels of the adrenal peripheral-type benzodiazepine receptor (PBR), a mitochondrial cholesterol-binding protein, leading to decreased corticosteroid synthesis. In the Y I adrenocortical cell line, GKB reduced both PBR levels and cyclic AMP-induced steroid formation. In these cells, GKB, but not various steroids and vitamins, reduced the expression of a reporter gene driven by the DNA sequence -624/-513 relative to the transcription start site of the PBR encoding gene. GKB treatment did not affect the SV40 promoter and increased the cytochrome P450 17α-hydroxylase gene promoter driven expression of the reporter gene. Electrophoretic mobility shift assays (EMSAs) indicated the presence of a functional transcriptional element bound to the -624/-513 DNA fragment. This GKB-induced inhibition of PBR was mediated by an interaction with a transcription factor that binds to the -636/-616 PBR-promoter region. Deletion or mutation of this sequence eliminated the DNA-protein interaction and the inhibitory effect of GKB on PBR gene transcription. This DNA-binding protein could be detected in nuclear extracts of rat brain, liver, and testis, but not kidney. It is also present in the human adrenal glands. However, the inhibitory effect following GKB treatment could be seen only in the adrenal glands. These results demonstrate that the GKB-activated inhibition of glucocorticoid production is due to a specific transcriptional suppression of the adrenal PBR gene and suggest that GKB might serve as a pharmacological tool to control excess glucocorticoid formation.
TL;DR: A combination of intersex phenotype and dysmorphology suggests that an error in a transcription factor may be an alternative to hydroxylation redox partner deficit as causative of the condition.
TL;DR: A novel CYP17 mutation is found from the molecular analysis of a Korean patient with primary amenorrhea with a 46,XX karyotype, and hypokalemic hypertension, which might account for the patient's clinical manifestations of 17α-hydroxylase/17,20-lyase deficiency.
Abstract: Mutations in the CYP17 gene impair steroid biosynthesis in the adrenals and gonads and often cause 17α-hydroxylase/17,20-lyase deficiency, leading to amenorrhea, sexual infantilism, and hypokalemic low aldosterone hypertension. Several CYP17 mutations resulting in 17α-hydroxylase/17,20-lyase deficiency have been reported previously. In the present study, we found a novel CYP17 mutation from the molecular analysis of a Korean patient with primary amenorrhea with a 46,XX karyotype, and hypokalemic hypertension. We sequenced all 8 exons of the CYP17 gene that were amplified from patient's genomic DNA using polymerase chain reaction (PCR) and found a compound heterozygous mutation in the CYP17 structural gene; a 1-base deletion and a 1-base transversion (TAC→AA) at codon 329, leading to the production of a truncated protein (1-417 amino acids), and a 3-base deletion (TCC, either 350-351 or 351-352 codon) in the other allele. Restriction enzyme digestion analysis of patient's and parental DNA showed that the 1-base deletion and the 3-base deletion are inherited from mother and father, respectively. Here we conclude that these novel compound heterozygous mutations might account for the patient's clinical manifestations of 17α-hydroxylase/17,20-lyase deficiency. Copyright 2003 Elsevier, Inc. All rights reserved.
TL;DR: Possession of the A2 variant of CYP17 may predispose to an increased risk of RPL with a gene dosage effect, and this polymorphism was investigated by PCR/restriction fragment length polymorphism using DNA from peripheral lymphocytes.
Abstract: The CYP17 gene encodes the enzyme cytochrome P450c17a, which mediates both 17a-hydroxylase and 17,20-lyase activity in the steroid biosynthesis pathway. A TfiC polymorphism in the 5¢ promoter region of CYP17 has been described. To examine the association between recurrent pregnancy loss (RPL) and a polymorphism in CYP17, a case‐control study of 117 cases with RPL and 164 controls was conducted. This polymorphism was investigated by PCR/restriction fragment length polymorphism using DNA from peripheral lymphocytes. The TfiC transition in the variant allele (A2) creates a new recognition site for the restriction enzyme MspA1, which permits designation of the wildtype allele (A1) and A2. Women with the A2 allele of CYP17 had an increased risk of RPL [A1/A1 genotype (reference); A1/A2 genotype: odds ratio (OR), 1.68; 95% confidence interval (CI), 0.94‐3.01; A2/A2 genotype: OR, 2.37; 95% CI, 1.16‐4.83; P trend, 0.016]. Additionally, there was a similar tendency for the increased risk of primary RPL [A1/A1 genotype (reference); A1/A2 genotype: OR, 2.14; 95% CI, 1.14‐4.01; A2/A2 genotype: OR, 2.50; 95% CI, 1.16‐5.41; P trend, 0.015]. These results suggest that possession of the A2 variant of CYP17 may predispose to an increased risk of RPL with a gene dosage effect.
TL;DR: Investigation of the mouse PAP7 gene found that it is mainly localized in the trans-Golgi apparatus and mitochondria in mouse tumor Leydig cells, in agreement with its proposed function in targeting the PKA isoenzyme to organelles rich in PBR, i.e. mitochondria.
TL;DR: The data demonstrate, for the first time in invertebrates, a potent role of cGMP in the negative control of ovarian steroidogenesis and suggest a possible co-regulation with NO.
Abstract: Previous investigations in the female blowfly Phormia regina have shown that 3-isobutyl-1-methylxanthine (IBMX), a broad spectrum inhibitor of phosphodiesterases (PDEs), fails to mimic the steroidogenic effects of cAMP on ovaries, although it efficiently increases the concentrations of this second messenger. In this study, experiments carried out to clear up this contradiction demonstrated that IBMX, besides its effect on cAMP, also increased cGMP concentrations in blowfly ovary and that these two cyclic nucleotides controlled ovarian steroidogenesis antagonistically. In particular, a selective inhibitor of cGMP-specific PDEs, unlike IBMX, had a very strong negative effect on ovarian steroidogenesis. Moreover, a cGMP analog was able to inhibit steroid biosynthesis in previtellogenic and vitellogenic ovaries, thus affecting basal and acute steroidogenesis respectively. Our observations also demonstrated that cGMP was always present in blowfly ovary, reaching its maximal levels at the end of vitellogenesis, in close correlation with the physiological decrease in ovarian steroidogenesis. Experiments using an inhibitor of protein kinase G clearly indicated that the effects of cGMP were mediated by this enzyme. On the contrary, these effects did not seem to involve cGMP-regulated PDEs or ion channels. Our results also indicated that ovarian cGMP concentrations were not controlled by brain factors, suggesting a probable involvement of paracrine/autocrine factors. Nitric oxide (NO) appeared to be a good candidate for such a control, because an NO donor was able to stimulate ovarian cGMP concentrations and to drastically decrease ovarian ecdysteroid biosynthesis in blowflies. These data thus demonstrate, for the first time in invertebrates, a potent role of cGMP in the negative control of ovarian steroidogenesis and suggest a possible co-regulation with NO.
Journal Article•
TL;DR: The data provide no evidence for an association between prostate cancer risk and the CYP17 gene polymorphism and the distribution of this polymorphism in the Turkish population and its association with prostate cancer and benign prostatic hyperplasia.
Abstract: Steroid hormones, especially androgens, are believed to play a key role in the etiology of prostate cancer. Therefore, polymorphisms in genes involved in the androgen metabolism may affect the risk of prostate cancer. One such gene is CYP17, which encodes the cytochrome P450c17alpha enzyme that mediates both 17alpha-hydroxylase and 17,20-lyase in the steroid biosynthesis pathway. A polymorphism in the 5'-promoter region of the CYP17 gene has been associated with increased risk for prostate cancer. The T to C transition in the risk allele creates a new recognition site for the restriction enzyme MspA1. In this study we investigated the distribution of this polymorphism in the Turkish population and its association with prostate cancer and benign prostatic hyperplasia. Genotype frequencies in the patients with prostate cancer or prostatic hyperplasia and the control group were not significantly different. Our data provide no evidence for an association between prostate cancer risk and the CYP17 gene polymorphism.
TL;DR: Results suggest that NP exhibited clearly estrogenic activity on the three chemicals in oocyte steroid biosynthesis, as compared to BPA treatment, which increased the androgen, while estrogen synthesis was slightly inhibited.
Abstract: In this study, fully vitellogenic oocytes of the longchin goby (Chasmichthys dolichognathus) were exposed to in vitro xenoestrogens such as diethylstilbestrol (DES), bisphenol A (BPA) and nonylphenol (NP) at concentrations of 100 ng/ml in the presence of [3H]17α-hydroxyprogesterone as precursor. The major metabolites produced in vitro are progestogens [17α-hydroxy,20α-dihydroprogesterone (17α20αOHP) and 17α-hydroxy,20β-dihydroprogesterone (17α20βOHP)], androgens [androstenedione (A4) and testosterone (T)] and estrogens [estrone (E1) and estradiol-17β (E2)]. Comparative activities of these chemicals in oocyte steroid biosynthesis showed as follows: NP treatment resulted in clear stimulation of estrogen production, while the opposite occurred in DES treated incubation. Treatment with DES resulted in a higher synthesis of 17α20αOHP. BPA treatment increased the androgen, while estrogen synthesis was slightly inhibited. These results suggest that NP exhibited clearly estrogenic activity on the three chemicals.
Journal Article•
TL;DR: In this article, Stigmatella aurantiaca is shown to produce cycloartenol, the well-known first cyclization product of steroid biosynthesis in plants and algae.
Abstract: Steroids, such as cholesterol, are synthesized in almost all eukaryotic cells, which use these triterpenoid lipids to control the fluidity and flexibility of their cell membranes. Bacteria rarely synthesize such tetracyclic compounds but frequently replace them with a different class of triterpenoids, the pentacyclic hopanoids. The intriguing mechanisms involved in triterpene biosynthesis have attracted much attention, resulting in extensive studies of squalene‐hopene cyclase in bacteria and (S)‐2,3‐oxidosqualene cyclases in eukarya. Nevertheless, almost nothing is known about steroid biosynthesis in bacteria. Only three steroid‐synthesizing bacterial species have been identified before this study. Here, we report on a variety of sterol‐producing myxobacteria. Stigmatella aurantiaca is shown to produce cycloartenol, the well‐known first cyclization product of steroid biosynthesis in plants and algae. Additionally, we describe the cloning of the first bacterial steroid biosynthesis gene, cas, encoding the cycloartenol synthase (Cas) of S. aurantiaca. Mutants of cas generated via site‐directed mutagenesis do not produce the compound. They show neither growth retardation in comparison with wild type nor any increase in ethanol sensitivity. The protein encoded by cas is most similar to the Cas proteins from several plant species, indicating a close evolutionary relationship between myxobacterial and eukaryotic steroid biosynthesis.
TL;DR: This study is the first to clarify the complete steroidogenic pathways in the gonads of a diandric protogynous species throughout its life, when combined with the results of the steroidogenesis in the ovarian follicles.
Abstract: The wrasse, Pseudolabrus sieboldi, is a diandric protogynous labrid fish. Spawning is performed by a terminal phase (TP) male and an initial phase (IP) female between 6:00 and 9:00 h daily during two-month-long spawning season. In the present study, to investigate the roles of steroid hormones in the diurnal spermatogenesis of the P. sieboldi TP male, all steroid hormones produced in the testis were identified and the synthetic pathways of these steroids were determined. Furthermore, the circulating levels of the major steroids produced were analyzed throughout a day at 3-hour intervals during spawning season. In the testis, 11-ketotestosterone (11-KT), estradiol-17β (E2), 17,20β-dihydoxy-4-pregnane-3-one (17,20β-P) and 17,20β,21-trihydroxy-4-pregnen-3-one (20β-S) were synthesized as the major metabolites. In vitro steroid biosynthesis experiments showed similar results to the circulation profiles of the major steroids. This study is the first to clarify the complete steroidogenic pathways in the gonads of a diandric protogynous species throughout its life, when combined with the results of the steroidogenesis in the ovarian follicles. This is also the first report of a clear diurnal rhythm of the steroid production corresponding to the spermatogenic process in the testis of a male teleost.
TL;DR: In this article, the authors investigated the role of TR3 orphan receptor transcription factor in the progression of atherosclerosis in the human vascular and inflammatory cells and found that TR3 prevented excessive SMC proliferation.
Abstract: Summary
1. Atherosclerosis is a multifactorial, inflammatory disease of the arterial vessel wall that is promoted by various well-defined risk factors. Although numerous genes, expressed in different vascular and inflammatory cells, have been implicated in this disease, it is widely appreciated that most of the genes and gene products vital for initiation and progression of atherosclerosis are unknown.
2. We follow two strategies in an attempt to make up for the void of essential knowledge. First, we study candidate genes that have not been implied in human atherosclerosis before, notably the differentiation factor activin A.
3. Second, we performed a genome-wide search by differential display reverse transcription–polymerase chain reaction. This study indicated potential involvement of the TR3 orphan receptor transcription factor in smooth muscle cell (SMC) (patho)physiology.
4. To reveal functional involvement of these proteins in SMC during atherosclerosis, we performed experiments with mouse models, adjusted either to the characteristics of a secreted protein or to that of an intracellular transcription factor.
5. The secreted protein activin A was studied in mice infected systemically with recombinant adenoviral vehicles, resulting in predominant hepatic expression and subsequent high protein levels in the circulation.
6. To study the role of TR3 in atherosclerosis, we generated transgenic mice in which promoter sequences were applied that direct expression of the transgenes to SMC of the arterial tree.
7. Two approaches were taken to induce the formation of SMC-rich lesions: (i) activation of femoral artery SMC by placement of a loosly fitting cuff; and (ii) ligation of the carotid artery.
8. The aim of the present review is to illustrate the different approaches that can be taken to assess the potential relevance of genes in atherosclerosis in carefully selected mouse models.
9. Based on the results described, we propose that both activin A and TR3 prevent excessive SMC proliferation.
TL;DR: The results suggest that within the traditional view that vertebrate biosynthetic pathway activity and end-products are phylogenetically conserved, there is likely to be considerably species- and/or genus-specific variation in the production of androgens and steroid conjugates in vertebrates.
TL;DR: The use of gene expression analyses together with evaluation of SAT weights is a promising tool as an early and sensitive marker of antiandrogen action, but more work is needed on the choice of time frame as well as the selection of genes to monitor.
Abstract: BACKGROUND: The Hershberger assay for antiandrogens and modifiers of steroid biosynthesis uses surgically-castrated rats. We described an adaptation of the assay using the GnRH inhibitor Antarelix in place of surgical castration [Ashby J, Lefevre PA, Deghenghi R, Wallis N. Regulatory Toxicology and Pharmacology 34:188–203, 2001], and concomitantly described changes in expression of the androgen-dependent prostatic genes PBP C3, TRPM-2, and ODC as a possible complement to gravimetric analysis of the sex accessory tissues (SAT) [Nellemann C, Vinggaard AM, Dalgaard M, Hossaini A, Larsen J-J. Toxicology 163:29–38, 2001]. METHODS: The present study describes the results of combining these two modifications into a single assay. During the course of these experiments it was shown that SD rats gave similar results to AP rats and that the higher stimulatory dose of testosterone propionate (TP) used in our experiments gave stronger assay responses to FLU than the lower dose of TP used by some earlier investigators. The potent antiandrogen flutamide (FLU) and the weak antiandrogen DDE were used to evaluate this modified assay. RESULTS: For all parameters studied (SAT weights and changes in expression of the 3 prostatic genes) FLU gave the expected positive results. The weak antiandrogen DDE gave variable and mainly non-reproducible responses. Use of DDE as a weak antiandrogen accelerated assessment of the new assay. CONCLUSIONS: Possible reasons for this failure to detect DDE are discussed, and it is concluded that the modified assay is unsuitable for use in its present form. The use of gene expression analyses together with evaluation of SAT weights is a promising tool as an early and sensitive marker of antiandrogen action, but more work is needed on the choice of time frame as well as the selection of genes to monitor. Birth Defects Res B 68:344–354, 2003. © 2003 Wiley-Liss, Inc.
TL;DR: The assembly of various transcription factors forming protein-DNA complexes appears to be the key step in CYP11A1 transcription, which controls the first and rate-limiting step of steroid biosynthesis.
Abstract: Steroid hormones are important physiological regulators that control our glucose and salt balance, as well as sexual characteristics. The synthesis of steroid hormones is under tight control; disturbed secretion of steroids often leads to diseases. The mechanism controlling the secretion of steroids, namely steroidogenesis, has been the focus of intensive studies.CYP11A1 controls the first and rate-limiting step of steroid biosynthesis. It is expressed in the adrenal cortex and gonads, under the control of pituitary hormones, through the cAMP-signaling pathway. The promoter of theCYP11A1 gene contains sequences that bind to transcription factor SF-1, which plays an important role in the tissue-specific and hormonally regulated expression of steroidogenic genes. Detailed transcriptional analysis documents the importance of SF-1 in activatingCYP11A1 in vitro and in vivo. Other factors like c-Jun are also involved. The assembly of various transcription factors forming protein-DNA complexes appears to be the key step inCYP11A1 transcription.
TL;DR: It is suggested that even mild forms of hyperandrogenism must be considered seriously and dysregulations of the steroidogenic pathway and ovarian abnormalities must be evaluated carefully to determine the risk of FOH/PCOS.
Abstract: To describe the presence of dysregulations in steroid biosynthesis and the risk of functional ovarian hyperandrogenism (FOH) and polycystic ovary syndrome (PCOS)-like development in children with hyperandrogenism, 28 girls were studied. Adrenal steroidogenic profile was defined by basal and ACTH-stimulated levels of 17OHP, cortisol, DHEAS and androstenedione, and delta precursor/delta product ratios. Ovarian hyperandrogenism was defined by 17OHP response to LHRH stimulation, and pelvic ultrasonography (US) was performed to evaluate ovarian morphology. Basal and ACTH-stimulated hormonal results revealed non-classical 21-hydroxylase deficiency-like status in one patient (3.6%), and 21-hydroxylase deficiency heterozygote carrier-like state in four patients (14.3%), while the other 23 patients (82.1%) had functional adrenal hyperandrogenism (FAH). Among these patients with FAH, 47.83% had FOH; when these patients were evaluated by pelvic US, 30.4% had morphological changes which were not concordant with their age. We suggest that even mild forms of hyperandrogenism must be considered seriously and dysregulations of the steroidogenic pathway and ovarian abnormalities must be evaluated carefully to determine the risk of FOH/PCOS.
TL;DR: The long-term (more than 12 months) effect of simvastatin or pravastatin on patients with hypercholesterolaemia was investigated by a cross-over design, and the adrenal sensitivity to angiotensin II (AII) was estimated by determining the plasma aldosterone : AII ratio at the end of the treatment period.
Abstract: The adrenal gland requires a continuous supply of cholesterol for the biosynthesis of steroids including aldosterone. Cholesterol can be derived from de novo synthesis by the adrenal gland and uptake of plasma lipoproteins. Simvastatin and pravastatin are 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors widely used for the treatment of hypercholesterolaemia by inhibition of cholesterol synthesis in the liver. Simvastatin, but not pravastatin, also affects cholesterol synthesis in the adrenal gland [1]. Therefore, the effect of simvastatin on steroid biosynthesis may be different from that of pravastatin. The renin-angiotensin-aldosterone (R-A-A) axis is the primary hormonal modulator of blood pressure and fluid homeostasis in humans. However, there is little information about the effect of HMG-CoA reductase inhibitors on the R-A-A axis [2]. This study investigated the long-term (more than 12 months) effect of simvastatin or pravastatin on patients with hypercholesterolaemia by a cross-over design, and estimated the adrenal sensitivity to angiotensin II (AII) by determining the plasma aldosterone : AII ratio [3] at the end of the treatment period.
Two male and six female patients with hypercholesterolaemia (age 53 ± 12 years, weight 60 ± 4 kg) gave informed written consent. The study was approved by the Review Board of Jichi Medical School. The patients received simvastatin 5 mg or pravastatin 10 mg once daily for 12 or more months in the first treatment period. The HMG-CoA reductase inhibitor regimen was then changed to the alternative for the next 12 or more months in the second treatment period. At the end of each treatment period, furosemide (20 mg) was injected intravenously after overnight fasting to elevate the endogenous AII concentration. Blood samples were obtained just before and 120 min after furosemide injection, and the plasma concentrations of AII, aldosterone, ACTH and potassium were measured. The patients were recumbent for at least 30 min before blood sampling. AII, aldosterone and ACTH were determined by radioimmunoassay methods [4–6]. Urine was collected during the 24 h before furosemide injection, and the urinary excretions of sodium and potassium were also determined. The patients were asked to adhere to their usual dietary habits throughout the study period. No other drugs which influence the R-A-A axis were given during the entire treatment period. Nonsteroidal anti-inflammatory drugs or diuretics were also prohibited for 2 weeks before furosemide injection. Statistical analysis was performed by paired t-test and analysis of variance (anova). The Bonferroni/Dunn test was used as a post hoc test.
Plasma total cholesterol concentration was reduced by a similar extent by the HMG-CoA reductase inhibitors [mean (95% CI) mg dl−1: basal 254 (234, 275), simvastatin 194 (179, 210), pravastatin 208 (192, 224)]. Plasma aldosterone concentration during simvastatin treatment was lower than that during pravastatin treatment, but it did not reach statistical significance. Plasma AII increased (anova: time, P = 0.0008) and serum potassium decreased (anova: time, P = 0.0003) while plasma aldosterone and ACTH did not change after furosemide injection. The plasma aldosterone : AII ratio after simvastatin treatment was smaller than that after pravastatin treatment (anova: group, P = 0.0413) (Figure 1). The plasma aldosterone : AII ratio decreased after furosemide injection. The reduction in the ratio was significant for simvastatin [difference; mean (95% CI) −3.60 (−6.27, 0.93)], but was not significant for pravastatin [difference (95% CI) −7.57 (−17.16, 2.02)]. However, because the reduction for pravastatin was larger than that of simvastatin, the aldosterone : AII ratio of the two trials did not differ significantly at 120 min after furosemide injection. There were no significant differences between the treatments in 24 h urine volume [mean (95% CI) ml day−1: simvastatin 2080 (1,614, 2545), pravastatin 1820 (1,427, 2214)] or urinary excretion of sodium [mean (95% CI) mmol day−1: simvastatin 12.0 (7.5, 16.5), pravastatin 11.0 (7.1, 14.8)] and potassium [mean (95% CI) mmol day−1: simvastatin 4.2 (2.6, 5.8), pravastatin 3.3 (2.4, 4.1)] before furosemide injection.
Figure 1
Plasma aldosterone : AII ratio before and 120 min after furosemide injection. Mean ± SD, n = 8. S: simvastatin, P: pravastatin.
Adrenal sensitivity to AII, as measured by the plasma aldosterone : AII ratio [3], was significantly lower during simvastatin treatment than during pravastatin treatment in this study. Simvastatin, a lipophilic agent, is easily taken up into various tissues including the adrenal gland. In contrast, pravastatin, a hydrophilic agent, does not easily penetrate the organs except for the liver. These physicochemical profiles partly explain the differences in the inhibition of cholesterol synthesis in the adrenal gland [1] and the adrenal sensitivity to AII shown in this study. Plasma potassium concentration was significantly decreased after furosemide injection, which may be caused by the drug-related massive potassium excretion in the urine. Although plasma AII concentration was elevated following furosemide, plasma aldosterone concentration did not significantly change, resulting in decreased adrenal sensitivity to AII. As aldosterone biosynthesis is regulated not only by AII and ACTH, but also by potassium [7], we think that the decrease in plasma potassium opposed steroid synthesis by the elevated AII concentration. A previous study showed that plasma aldosterone decreases after long-term (9 months) treatment with simvastatin [2]. It is also reported that three patients experienced symptomatic hypotension during simvastatin therapy [8]. The mechanism was unknown, but the episode might be related to the suppression of aldosterone production by simvastatin. Taken together, we think that aldosterone synthesis by AII is potentially impaired by simvastatin, but the simvastatin-related suppression of aldosterone production may only be evident under critical situations, which require sufficient supply of aldosterone to maintain body functions.
Patent•
23 Sep 2003
TL;DR: In this article, the identification of an antagonist to the peripheral-type benzodiazepine receptor (PBR) has been investigated and the use of the PBR antogonist to block receptor function to treat and prevent PBR-related diseases and conditions has been proposed.
Abstract: The invention relates to the identification of an antagonist to the peripheral-type benzodiazepine receptor (PBR) The PBR is known to have a large role in many important processes of the body, such as steroid biosynthesis processes of the adrenal glands and gonads, mitochondrial respiration, apoptosis and cell proliferation PBR is also implicated in such medical concerns as cancer progression, ischemia-reperfusion injury, Alzheimer's disease and diseases with elevated steroid levels The present invention is directed to the use of the PBR antogonist to block receptor function to treat and prevent PBR-related diseases and conditions