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Query: UMLS:C0338671 (Steroids)
 9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Butyltins are widely used biocides and accumulate in the food chain. Tributyltin is an imposex-inducing endocrine disrupter in animals. Imposex is characterized by the development of additional male sex organs on females. In a previous study, we identified tributyltin as an inhibitor of human cytochrom P450 aromatase activity. The present work focuses on the impact of butyltins on human androgen metabolism. Activation of androgens is mediated by two human 5alpha-reductase isoenzymes. 5alpha-Reductase type 1 was completely inhibited by tributyltin chloride (IC50=19.9 microM) and dibutyltin dichloride (IC50=32.9 microM), whereas 5alpha-reductase type 2 was only inhibited by tributyltin chloride (IC50=10.8 microM). Both isoenzymes were not affected by tetrabutyltin or monobutyltin indicating that at least two butyl groups bound to the positively charged Sn are required for the interaction of butyltins with the enzymes. Tributyltin inhibited 5alpha-reductase type 1 competitively whereas an irreversible inhibition was evident for the type 2 isoenzyme. In contrast to the distinct effects on 5alpha-reductases, reductive brain 17beta-hydroxysteroid dehydrogenase activity was not inhibited by any butyltin. Insufficient activation of androgens is responsible for developmental disorders of the male reproductive system such as hypospadias. At pharmacologic levels butyltins might contribute to the onset of developmental disorders of the male reproductive system. At present, however, it is unknown whether these levels are reached after acute or chronic exposure to butyltins.
Steroids 2002 Sep
PMID:Effects of butyltins on human 5alpha-reductase type 1 and type 2 activity. 1223 Nov 21

CYP19 (P450arom) catalyzes the aromatization reaction of C19 steroids leading to estrogens. While readily expressed in insect cells, the human P450arom has been a difficult P450 to express in Escherichia coli at useful levels. In the present study, we replaced the N-terminal sequence in human CYP19 with the corresponding sequences of other microsomal P450s (CYP2C11 and CYP17) that are efficiently expressed in E. coli. Although the N-terminal replacement alone was not sufficient for the expression, human P450arom was successfully expressed up to the level of 240nmol/l culture by the combination of the N-terminal replacement and the induction of cold stress response by 1 microg/ml chloramphenicol. Membrane fractions containing the expressed P450arom catalyzed aromatization of androstenedione with a specific activity of 4.9 nmol/min/nmol P450. Our results are important to provide large quantities of human P450arom as an active form for structure-function studies.
Steroids 2003 Feb
PMID:Expression of human aromatase (CYP19) in Escherichia coli by N-terminal replacement and induction of cold stress response. 1260 12

Steroids are known as important factors on the route of oocytes development and cumulus oocyte complexes (COC) as well as follicular granulosa cells (GC) are suggested to be themselves involved in steroidogenesis. The aim of this study was to characterize such a local sex steroidogenic system during in vitro maturation (IVM) of bovine COCs according to the production of estradiol (E), testosterone (T) and progesterone (P). The expression of two steroid-converting key-enzymes was measured in parallel by quantitative RT-PCR. Furthermore, possible effects of the environmental pollutant tri-butyltin (TBT) were elucidated for the first time on bovine COC and GC in vitro concerning that steroidogenic system. During IVM of bovine COCs concentrations of P increased continuously, corresponding with steady-state levels of 3-beta-hydroxy-steroid-dehydrogenase (HSD) transcripts. In contrast, E together with P450 aromatase mRNA (ARO) increased in the first hours of IVM but declining thereafter, whereas T reached almost balanced levels. However, TBT showed only slight effects during IVM of COC. In cultured GC, LH caused highest P- and E-production within 24h and treatment with 50pM TBT induced a significant decrease of E in contrast to 100pM TBT and the control. These results indicate, that (1) COCs were able to modulate their steroidogenic environment in vitro and that (2) TBT may possibly influence or disturb steroidogenesis in the cows reproductive tract shown here for GC.
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PMID:Steroidogenesis during in vitro maturation of bovine cumulus oocyte complexes and possible effects of tri-butyltin on granulosa cells. 1271 Oct 15

Twelve 17-(2'-oxazolyl)- and 17-(2'-thiazolyl)-androsta-5,16-diene derivatives were designed and synthesized from 3 beta-acetoxy-pregna-5,16-dien-20-one (1b) as inhibitors of 17 alpha-hydroxylase-C(17,20)-lyase (P450(17 alpha)). Potent inhibitors of this enzyme could be of value as treatment of prostate cancer. Two substituents (methyl and phenyl) were introduced either at their 4'- or 5'-position in order to investigate their structure-activity relationship. Due to the 16,17-double bond, 17-thiazoles were generally obtained in low yield. The pharmacological results showed that the compounds containing 17-(2'-oxazolyl) (14c) and 17-(2'-thiazolyl) (8c) (41.5%) demonstrated reasonable inhibition against P450(17 alpha). Their 3-acetate (13c and 7c) were less potent than their 3-OH counterparts. The introduction of a phenyl or methyl group generally decreased inhibitory activity. Surprisingly, 17-(5'-methyl-2'-thiazolyl) (12a) was the most potent compound in this series and was almost as potent as L-39, which has good antitumor activity.
Steroids 2003 Sep
PMID:Novel P450(17alpha) inhibitors: 17-(2'-oxazolyl)- and 17-(2'-thiazolyl)-androstene derivatives. 1295 65

This paper collates and reviews a number of clinical cases published over the last 20 years that we believe describe a novel steroid disorder associated with genital ambiguity. The authors of the original papers were unable to diagnose their patients conclusively. Females with the disorder are frequently masculinized and males feminized. The central feature of steroid biosynthesis is overproduction of pregnenolone and progesterone, which results in elevated concentrations of these steroids in plasma and exaggerated response to ACTH. Equivalent urinary data show elevated excretion of 5-pregnene-3beta,20alpha-diol (the major pregnenolone metabolite) and pregnanediol. Another notable feature of the metabolome is the relatively high plasma concentrations of the analytes for 21-hydroxylase deficiency (17-hydroxyprogesterone) and 17-hydroxylase deficiency (corticosterone). Correspondingly, metabolites of these steroids are prominent in urine. Circulating cortisol was generally normal but had blunted response to ACTH. Taken together these features pointed to an apparent relative deficiency of 21- and 17-hydroxylation, but no mutations have been found in the enzymes responsible for these transformations in cases where it has been investigated. The simultaneous presence of mutated genes on two chromosomes is also extremely unlikely. Until more is known of this interesting condition, and the genetic cause (presumed) is known, we propose naming it apparent pregnene hydroxylation deficiency (APHD). The metabolome is similar to that of isolated 17,20-lyase deficiency with which it has been confused. In fact, diminished (but not isolated) lyase activity is probably a significant factor in some patients. We believe that the attenuated steroid hydroxylation could be associated with deficiency of the required co-factors and modulators of hydroxylation such as P450 reductase and cytochrome b5. Post-translational modifications of the hydroxylases such as phosphorylation/dephosphorylation have also been suggested as influential in directionally regulating steroid synthesis. Some patients with the disorder have no dysmorphology apart from genital malformations while others have skeletal abnormalities attributed to Antley-Bixler syndrome. Whether we are looking at different conditions, or a severity continuum is not known. It is possible that the presence of this metabolome may become a required feature for diagnosis of Antley-Bixler syndrome. 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.The virilization of female patients with APHD probably results from a transient hyperandrogenism prior to birth.
Steroids 2003 Oct
PMID:Apparent pregnene hydroxylation deficiency (APHD): seeking the parentage of an orphan metabolome. 1462 2

Cytochrome P450 (P450) monooxygenases play a role in target tissue metabolic activation of xenobiotics and/or endogenous compounds, such as vasoactive molecules or hormones. Indeed, tissue-specific metabolism of steroids is important in a variety of organs, including thymus, and may alter tissue-specific functions. Steroids have been shown to regulate thymus growth and function, but surprisingly little is known about expression of the responsible enzyme systems in thymus tissue, nor is the thymus-specific biotransformation of testosterone known. We therefore investigated gene and protein expression, total protein content, and enzyme activity of major P450 isoforms and other key steroid-metabolizing enzymes in thymus tissue of adult and fetal rats. We detected 6 beta-hydroxytestosterone (HT), 7 alpha-HT, 16 alpha-HT, 2 alpha-HT, and androstenedione to be major testosterone metabolites in the adult thymus. The high production of 7 alpha-HT and 16 alpha-HT correlated well with the gene and protein expression of CYP2A1/2 and CYP2B1/2 in thymus of adult animals. When compared with fetal thymic tissue, CYP2A1/2, 17beta-hydroxysteroid dehydrogenase isoform 1 (17 beta-HSDH1) and the androgen receptor were 8-, 3-, and 3-fold more highly expressed in adult rats, whereas 17 beta-HSDH2, 17 beta-HSDH3, and 5 alpha-reductase were reduced to 12%, 0%, and 32% of those in fetal thymus. In conclusion, we demonstrated that rat thymus expresses a variety of cytochrome P450 monooxygenases and other steroid-metabolizing enzymes, and it successfully metabolizes testosterone. Changes of the underlying steroid-metabolizing enzyme systems may aid in understanding the role of androgens in altering biological functions of the thymus.
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PMID:Androgen metabolism in thymus of fetal and adult rats. 1515 60

Aromatase (P450arom, CYP19) catalyzes the aromatization reaction that converts androgens to estrogens. Although human P450arom has been readily purified from placenta, its hydrophobic properties and instability has hampered detailed characterization. Utilizing a N-terminal replacement (MARQSFGRGKL, derived from CYP2C11), we successfully modified this unstable enzyme into stable forms. Based on a known polymorphism, we created two constructs, NmA264C and NmA264R having cysteine or arginine at position 264. The recombinant P450arom NmA264R was expressed in Escherichia coli (350-400 nmol/L culture) primarily by coexpression with molecular chaperones GroES/GroEL while NmA264C was expressed (240 nmol/L culture) only in the presence of chloramphenicol. Although NmA264C was recovered only in the membrane fraction, approximately 14% of NmA264R was recovered in the cytosolic fraction, suggesting that NmA264R is more hydrophilic than NmA264C. NmA264R was highly purified to the specific content 13.6 nmol P450/mg protein. Purified P450arom NmA264R converted androstenedione to estrone with Vmax 12.4 nmol/(min nmol) and Km) 0.26 microM, and testosterone to estradiol with Vmax 52.2 nmol/(min nmol) and Km 10.9 microM. Because of the increased stability of NmA264R, we could unambiguously determine properties of human P450arom by optical and electron paramagnetic resonance spectroscopy. The purified protein was a typical low-spin form, which was converted to a high-spin form when androstenedione was added. The rhombicity of substrate-bound forms was higher than that reported for other P450s, an interesting characteristic of human P450arom. The highly stable and active P450arom NmA264R sets the stope for detailed structure/function analyses of this important member of the P450 superfamily.
Steroids 2004 Apr
PMID:Characterization of stable human aromatase expressed in E. coli. 1518 89

Cytochrome P450 BioI (CYP107H1) from Bacillus subtilis is involved in the early stages of biotin synthesis. Previous studies have indicated that BioI can hydroxylate fatty acids and may also perform an acyl bond cleavage reaction [Green, A. J., Rivers, S. L., Cheesman, M., Reid, G. A., Quaroni, L. G., Macdonald, I. D. G., Chapman, S. K., and Munro, A. W. (2001) J. Biol. Inorg. Chem. 6, 523-533. Stok, J. E., and De Voss, J. J. (2000) Arch. Biochem. Biophys. 384, 351-360]. Here we show novel binding features of P450 BioI--specifically that it binds steroids (including testosterone and progesterone) and polycyclic azole drugs with similar affinity to that for fatty acids (K(d) values in the range 0.1-160 microM). Sigmoidal binding curves for titration of BioI with azole drugs suggests a cooperative process in this case. BioI as isolated from Escherichia coli is in a mixed heme iron spin state. Alteration of the pH of the buffer system affects the heme iron spin-state equilibrium (higher pH increasing the low-spin content). Steroids containing a carbonyl group at the C(3) position induce a shift in heme iron spin-state equilibrium toward the low-spin form, whereas fatty acids produce a shift toward the high-spin form. Electron paramagnetic resonance (EPR) studies confirm the heme iron spin-state perturbation inferred from optical titrations with steroids and fatty acids. Potentiometric studies demonstrate that the heme iron reduction potential becomes progressively more positive as the proportion of high-spin heme iron increases (potential for low-spin BioI = -330 +/- 1 mV; for BioI as purified from E. coli (mixed-spin) = 228 +/- 2 mV; for palmitoleic acid-bound BioI = -199 +/- 2 mV). Extraction of bound substrate-like molecule from purified BioI indicates palmitic acid to be bound. Differential scanning calorimetry studies indicate that the BioI protein structure is stabilized by binding of steroids and bulky azole drugs, a result confirmed by resonance Raman studies and by analysis of disruption of BioI secondary and tertiary structure by the chaotrope guanidinium chloride. Molecular modeling of the BioI structure indicates that a disulfide bond is present between Cys250 and Cys275. Calorimetry shows that structural stability of the protein was altered by addition of the reductant dithiothreitol, suggesting that the disulfide is important to integrity of BioI structure.
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PMID:Thermodynamic and biophysical characterization of cytochrome P450 BioI from Bacillus subtilis. 1544 31

We previously reported that tributyltin chloride (TBT) and triphenyltin chloride (TPT) powerfully suppressed human chorionic gonadotropin- and 8-bromo-cAMP-stimulated testosterone production in pig Leydig cells at concentrations that were not cytotoxic [Nakajima Y, Sato Q, Ohno S, Nakajin S. Organotin compounds suppress testosterone production in Leydig cells from neonatal pig testes. J Health Sci 2003;49:514-9]. This study investigated the effects of these organotin compounds on the activity of enzymes involved in testosterone biosynthesis in pig testis. At relatively low concentrations of TPT, 17beta-hydroxysteroid dehydrogenase (17beta-HSD; IC(50)=2.6microM) and cytochrome P450 17alpha-hydroxylase/C(17-20) lyase (IC(50)=117microM) activities were inhibited, whereas cholesterol side-chain cleavage cytochrome P450 and 3beta-HSD/Delta(4)-Delta(5) isomerase activities were less sensitive. Overall, TPT was more effective than TBT. TPT also inhibited both ferredoxin reductase and P450 reductase activities at concentrations over 30microM; however, TBT had no effect, even at 100microM. The IC(50) values of TPT were estimated to be 25.7 and 22.8microM for ferredoxin reductase and P450 reductase, respectively. The inhibitory effect of TPT (30microM) on microsomal 17beta-HSD activity from pig testis was eliminated by pretreatment with the reducing agents dithiothreitol (1mM) and dithioerythritol (1mM). On the other hand, TPT (0.03microM) or TBT (0.1microM) exposure suppressed the testosterone production from androstenedione in pig Leydig cells indicating that these organotins inhibit 17beta-HSD activity in vivo as well as in vitro, and the IC(50) values of TPT and TBT for 17beta-HSD activity were estimated to be 48 and 114nM, respectively. Based on these results, it appears possible that the effects of TBT and TPT are largely due to direct inhibition of 17beta-HSD activity in vivo.
Steroids 2005 Aug
PMID:Triphenyltin and Tributyltin inhibit pig testicular 17beta-hydroxysteroid dehydrogenase activity and suppress testicular testosterone biosynthesis. 1589 6

Tributyltin, an environmental pollutant, affected adrenal steroid hormone biosynthesis by two modes of action. Treatment of bovine adrenal cultured cells with 10-100 nM tributyltin for 48 h suppressed cortisol and androstenedione secretion, but induced the accumulation of 17alpha-hydroxyprogesterone and deoxycortisol, indicating that the P450(C21) and P450(11beta) activities were specifically suppressed. Direct inhibition of the enzymatic activities due to tributyltin was not observed in isolated organelles of untreated cells at concentrations less than 10 microM. Western blotting experiments using specific antibodies against steroidogenic enzymes showed that treatment with 1-100 nM tributyltin caused a decrease in cellular P450(C21) and P450(11beta) protein levels, and real-time PCR experiments showed that the decrease in protein content was attributable to decreases in mRNA of the enzymes. Tributyltin at concentrations higher than 100 nM suppressed all steroid biosynthesis in the adrenal cells. This suppression was closely correlated to the decrease in steroidogenic acute regulatory protein. Since nanomolar concentrations of tributyltin disturbed steroidogenesis in mammalian cells, there is the possibility that steroid hormone synthesis in polluted wild animals is affected by this compound.
Steroids 2005 Dec 15
PMID:Tributyltin disturbs bovine adrenal steroidogenesis by two modes of action. 1603 56


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