Cytochrome b5: novel roles in steroidogenesis

MiR-223 inhibits proliferation and steroid hormone synthesis of ovarian granulosa cell via the AKT signaling pathway by targeting CRIM1 in chicken

Within the poultry industry, hens' reproductive performance is of great economic significance. The development and growth of follicles is a key aspect of hen egg production, and ovarian follicle growth and development are closely associated with granulosa cells (GCs) proliferation and the synthesis of steroid hormones. It has been confirmed by numerous studies that microRNAs (miRNAs) play important roles in the steroid hormone synthesis and proliferation of GCs. In this study, we examined the main miRNAs influencing hens' ability to reproduce, identified the miR-223 that is mainly expressed in atretic follicles based on sequencing, and investigated its role in GCs. Then, we used miR-223 mimic and inhibitor to knockdown or overexpress miR-223 expression. The result showed that miR-223 significantly inhibits both the steroid hormone synthesis and the proliferation of GCs. Subsequently, the results of the dual luciferase reporter experiment and bioinformatics prediction demonstrated that cysteine rich transmembrane BMP regulator 1 (CRIM1) was a downstream target gene of miR-223, and overexpression of miR-223 prevented CRIM1 expression. The function of CRIM1 was further investigated, and we observed a significant reduction in the synthesis of steroid hormones and the proliferation of GCs after transfection with CRIM1 siRNA. The opposite function of miR-223 was observed for CRIM1 in our study. Additionally, we demonstrated the involvement of the miR-223/CRIM1 axis in GCs through modulation of the AKT signaling pathway. Our data demonstrate the pivotal role of the miR-223 in the proliferation and steroid hormone synthesis of chicken GCs, which helps to explain how non-coding RNA (ncRNA) affects chicken reproductive function.

Regulating Effect of Cytochrome b5 Overexpression on Human Breast Cancer Cells

Imbalance in the cellular redox system is thought to be associated with the induction and progression of breast cancers, and heme proteins may regulate the redox balance. Cytochrome b₅ (Cyt b₅) is a small mitochondrial heme protein. Its function and regulating mechanism in breast cancer remain unknown. In this study, we elucidated the level of endogenous oxidative stress in breast cancer cells, MCF-7 cells (hormone receptor-positive cells) and MDA-MB-231 cells (triple-negative cells), and investigated the difference in Cyt b₅ content. Based on the low content of Cyt b₅ in MDA-MB-231 cells, the overexpression of Cyt b₅ was found to regulate the oxidative stress and apoptosis cascades, including ERK1/2 and Akt signaling pathways. The overexpressed Cyt b₅ MDA-MB-231 cells were shown to exhibit decreased oxidative stress, less phosphorylation of ERK1/2 and Akt, and less cleavage of caspases 3 and 9 upon treatment with H₂O₂, as compared to those of normal MDA-MB-231 cells. Moreover, the overexpressed Cyt b₅ most likely functioned by interacting with its protein partner, Cyt c, as suggested by co-immunoprecipitation studies. These results indicated that Cyt b₅ has different effects on breast cancer cells of different phenotypes, which provides useful information for understanding the multiple roles of Cyt b₅ and provides clues for clinical treatment.

Isolated 17, 20 Lyase Deficiency Secondary to a Novel CYB5A Variant: Comparison of Steroid Metabolomic Findings with Published Cases Provides Diagnostic Guidelines and Greater Insight into Its Biological Role

OBJECTIVE

The objective of this study was to report CYB5A deficiency, to discuss the contribution of steroid metabolomics to diagnosis and interpretation, and to highlight the presence of testicular microlithiasis.

METHODS

Two siblings with ambiguous genitalia at birth were later found to carry novel CYB5A variants, with resulting isolated 17, 20 lyase deficiency. We compared urine steroid data obtained between birth and adulthood with that from other cases.

RESULTS

Neonatal urine steroid profiles show a relative increase of 16-hydroxylated pregnenolone metabolites. Thereafter, there are no distinguishing features until puberty, when sex steroid deficiency drives gonadotrophin production, resulting in marked increases of 17-hydroxyprogesterone metabolites derived from the gonads. This excess may be revealed pre-pubertally by gonadotrophin stimulation testing. Novel findings are first, a considerable capacity for DHEA synthesis in the neonatal period compared to childhood and adulthood, suggesting that DHEAS production is much less dependent on CYB5A at birth; second, no consistent change in "backdoor pathway" intermediates; third, side chain cleavage of cortisol is largely unaffected, supporting the existence of a different lyase not dependent on CYB5A; fourth, increased 17-hydroxyprogesterone metabolites and very low androgen metabolites are diagnostic post-pubertally.

CONCLUSION

This is the fourth disease-causing variant in CYB5A in isolated 17, 20 lyase deficiency and the first associated with testicular microlithiasis. Establishing a biochemical diagnosis pre-pubertally should now be possible using urine steroid profiling, supported by synacthen and gonadotrophin stimulation testing. We recommend liquid chromatography-mass spectrometry/mass spectrometry rather than immunoassay for serum steroid analysis, early methaemoglobin measurement and surveillance should testicular microlithiasis be detected.

Redox metabolism for improving whole-cell P450-catalysed terpenoid biosynthesis

The growing preference for producing cytochrome P450-mediated natural products in microbial systems stems from the challenging nature of the organic chemistry approaches. The P450 enzymes are redox-dependent proteins, through which they source electrons from reducing cofactors to drive their activities. Widely researched in biochemistry, most of the previous studies have extensively utilised expensive cell-free assays to reveal mechanistic insights into P450 functionalities in presence of commercial redox partners. However, in the context of microbial bioproduction, the synergic activity of P450- reductase proteins in microbial systems have not been largely investigated. This is mainly due to limited knowledge about their mutual interactions in the context of complex systems. Hence, manipulating the redox potential for natural product synthesis in microbial chassis has been limited. As the potential of redox state as crucial regulator of P450 biocatalysis has been greatly underestimated by the scientific community, in this review, we re-emphasize their pivotal role in modulating the in vivo P450 activity through affecting the product profile and yield. Particularly, we discuss the applications of widely used in vivo redox engineering methodologies for natural product synthesis to provide further suggestions for patterning on P450-based terpenoids production in microbial platforms.

Adrenal androgens, adrenarche, and zona reticularis: A human affair?

In humans, reticularis cells of the adrenal cortex fuel the production of androgen steroids, constituting the driver of numerous morphological changes during childhood. These steps are considered a precocious stage of sexual maturation and are grouped under the term "adrenarche". This review describes the molecular and enzymatic characteristics of the zona reticularis, along with the possible signals and mechanisms that control its emergence and the associated clinical features. We investigate the differences between species and discuss new studies such as genetic lineage tracing and transcriptomic analysis, highlighting the rodent inner cortex's cellular and molecular heterogeneity. The recent development and characterization of mouse models deficient for Prkar1a presenting with adrenocortical reticularis-like features prompt us to review our vision of the mouse adrenal gland maturation. We expect these new insights will help increase our understanding of the adrenarche process and the pathologies associated with its deregulation.

The multiple roles of coenzyme Q in cellular homeostasis and their relevance for the pathogenesis of coenzyme Q deficiency

Coenzyme Q (CoQ) is a redox active lipid that plays a central role in cellular homeostasis. It was discovered more than 60 years ago because of its role as electron transporter in the mitochondrial respiratory chain. Since then it has become evident that CoQ has many other functions, not directly related to bioenergetics. It is a cofactor of several mitochondrial dehydrogenases involved in the metabolism of lipids, amino acids, and nucleotides, and in sulfide detoxification. It is a powerful antioxidant and it is involved in the control of programmed cell death by modulating both apoptosis and ferroptosis. CoQ deficiency is a clinically and genetically heterogeneous group of disorders characterized by the impairment of CoQ biosynthesis. CoQ deficient patients display defects in cellular bioenergetics, but also in the other pathways in which CoQ is involved. In this review we will focus on the functions of CoQ not directly related to the respiratory chain, and on how their impairment is relevant for the pathophysiology of CoQ deficiency. A better understanding of the complex set of events triggered by CoQ deficiency will allow to design novel approaches for the treatment of this condition.

Sub-fertility in crossbred bulls: deciphering testicular level transcriptomic alterations between zebu (Bos indicus) and crossbred (Bos taurus x Bos indicus) bulls

BACKGROUND

The incidence of poor semen quality and sub-fertility/infertility is higher in crossbred as compared to Zebu males. Several attempts have been made to understand the possible reasons for higher incidence of fertility problems in crossbred males, at sperm phenotype, proteome and genome level but with variable results. Since the quality of the ejaculated spermatozoa is determined by the testicular environment, assessing the testicular transcriptome between these breeds would help in identifying the possible mechanisms associated with infertility in crossbred bulls. However, such information is not available. We performed global transcriptomic profiling of testicular tissue from crossbred and Zebu bulls using Agilent Bos taurus GXP 8X60k AMADID: 29411 array. To the best of our knowledge, this is the first study comparing the testicular mRNAs between crossbred and Zebu bulls.

RESULTS

Out of the 14,419 transcripts detected in bovine testis, 1466 were differentially expressed between crossbred and Zebu bulls, in which 1038 were upregulated and 428 were downregulated in crossbred bulls. PI4KB and DPY19L2 genes, reported to be involved in sperm capacitation and acrosome formation respectively, were among the top 10 downregulated transcripts in crossbred testis. Genes involved in ubiquitination and proteolysis were upregulated, while genes involved in cell proliferation, stem cell differentiation, stem cell population maintenance, steroidogenesis, WNT signalling, protein localization to plasma membrane, endocannabinoid signalling, heparin binding, cAMP metabolism and GABA receptor activity were downregulated in crossbred testis. Among the 10 genes validated using qPCR, expression of CCNYL, SOX2, MSMB, SPATA7, TNP1, TNP2 and CRISP2 followed the same trend as observed in microarray analysis with SPATA7 being significantly downregulated and transition proteins (TNP1, TNP2) being significantly upregulated in crossbred bulls.

CONCLUSIONS

Abundant proteolysis by ubiquitination and downregulation of WNT signaling, cell proliferation, differentiation and steroidogenesis might be associated with higher incidence of poor semen quality and/or sub-fertility/infertility in crossbred bulls as compared to Zebu bulls. Downregulation of SPATA7 (Spermatogenesis Associated 7) and upregulation of transition proteins (TNP1 and TNP2) in crossbred bull testis might be associated with impaired spermatogenesis processes including improper chromatin compaction in crossbred bulls.

From electrochemistry to enzyme kinetics of cytochrome P450

This review is an attempt to describe advancements in the electrochemistry of cytochrome P450 enzymes (EC 1.14.14.1) and to study molecular aspects and catalytic behavior of enzymatic electrocatalysis. Electroanalysis of cytochrome P450 demonstrates how to translate theoretical laws and equations of classical electrochemistry for the calculation of the kinetic parameters of enzymatic reactions and then translation of kinetic parameters to interpretation of drug-drug interactions. The functional significance of cytochrome P450s (CYPs) includes the metabolism of drugs, foreign chemicals, and endogenic compounds. The pharmaceutical industry needs sensitive and cost-effective systems for screening new drugs and investigation of drug-drug interactions. The development of different types of CYP-based biosensors is now in great demand. This review also highlights the characteristics of electrode processes and electrode properties for optimization of the cytochrome P450 electroanalysis. Electrochemical cytochrome P450-biosensors are the most studied. In this review, we analyzed electrode/cytochrome P450 systems in terms of the mechanisms underlying P450-catalyzed reactions. Screening of potential substrates or inhibitors of cytochromes P450 by means of electrodes were described.

Properties of purified CYP2R1 in a reconstituted membrane environment and its 25-hydroxylation of 20-hydroxyvitamin D3

Recent studies indicate that CYP2R1 is the major 25-hydroxylase catalyzing the first step in vitamin D activation. Since the catalytic properties of CYP2R1 have been poorly studied to date and it is a membrane protein, we examined the purified enzyme in a membrane environment. CYP2R1 was expressed in E. coli and purified by nickel affinity- and hydrophobic interaction-chromatography and assayed in a reconstituted membrane system comprising phospholipid vesicles plus purified human NADPH-P450 oxidoreductase. CYP2R1 converted vitamin D3 in the vesicle membrane to 25-hydroxyvitamin D3 [25(OH)D3] with good adherence to Michaelis-Menten kinetics. The kinetic parameters for 25-hydroxylation of vitamin D3 by the two major vitamin D 25-hydroxylases, CYP2R1 and CYP27A1, were examined in vesicles under identical conditions. CYP2R1 displayed a slightly lower k_cat than CYP27A1 but a much lower K_m for vitamin D3, and thus an overall 17-fold higher catalytic efficiency (k_cat/K_m), consistent with CYP2R1 being the major vitamin D 25-hydroxylase. 20-Hydroxyvitamin D3 [20(OH)D3], the main product of vitamin D3 activation by an alternative pathway catalyzed by CYP11A1, was metabolized by CYP2R1 to 20,25-dihydroxyvitamin D3 [20,25(OH)₂D3], with catalytic efficiency similar to that for the 25-hydroxylation of vitamin D3. 20,25(OH)₂D3 retained full, or somewhat enhanced activity compared to the parent 20(OH)D3 for the inhibition of the proliferation of melanocytes and dermal fibroblasts, with a potency comparable to 1,25-dihydroxyvitamin D3 [1,25(OH)₂D3]. The 20,25(OH)₂D3 was also able to act as an inverse agonist on retinoic acid-related orphan receptor α, like its parent 20(OH)D3. Thus, the major findings of this study are that CYP2R1 can metabolize substrates in a membrane environment, the enzyme displays higher catalytic efficiency than CYP27A1 for the 25-hydroxylation of vitamin D, it efficiently hydroxylates 20(OH)D3 at C25 and this product retains the biological activity of the parent compound.

Use of Phenoxyaniline Analogues To Generate Biochemical Insights into the Interactio n of Polybrominated Diphenyl Ether with CYP2B Enzymes

Human hepatic cytochromes P450 (CYP) are integral to xenobiotic metabolism. CYP2B6 is a major catalyst of biotransformation of environmental toxicants, including polybrominated diphenyl ethers (PBDEs). CYP2B substrates tend to contain halogen atoms, but the biochemical basis for this selectivity and for species specific determinants of metabolism has not been identified. Spectral binding titrations and inhibition studies were performed to investigate interactions of rat CYP2B1, rabbit CYP2B4, and CYP2B6 with a series of phenoxyaniline (POA) congeners that are analogues of PBDEs. For most congeners, there was a <3-fold difference between the spectral binding constants (K_S) and IC₅₀ values. In contrast, large discrepancies between these values were observed for POA and 3-chloro-4-phenoxyaniline. CYP2B1 was the enzyme most sensitive to POA congeners, so the Val-363 residue from that enzyme was introduced into CYP2B4 or CYP2B6. This substitution partially altered the protein-ligand interaction profiles to make them more similar to that of CYP2B1. Addition of cytochrome P450 oxidoreductase (POR) to titrations of CYP2B6 with POA or 2'4'5'TCPOA decreased the affinity of both ligands for the enzyme. Addition of cytochrome b₅ to a recombinant enzyme system containing POR and CYP2B6 increased the POA IC₅₀ value and decreased the 2'4'5'TCPOA IC₅₀ value. Overall, the inconsistency between K_S and IC₅₀ values for POA versus 2'4'5'TCPOA is largely due to the effects of redox partner binding. These results provide insight into the biochemical basis of binding of diphenyl ethers to human CYP2B6 and changes in CYP2B6-mediated metabolism that are dependent on POA congener and redox partner identity.

Role of cytochrome b5 in the modulation of the enzymatic activities of cytochrome P450 17α-hydroxylase/17,20-lyase (P450 17A1)

Cytochrome b5 (cyt b5) is a small hemoprotein that plays a significant role in the modulation of activities of an important steroidogenic enzyme, cytochrome P450 17α-hydroxylase/17,20-lyase (P450 17A1, CYP17A1). Located in the zona fasciculata and zona reticularis of the adrenal cortex and in the gonads, P450 17A1 catalyzes two different reactions in the steroidogenic pathway; the 17α-hydroxylation and 17,20-lyase, in the endoplasmic reticulum of these respective tissues. The activities of P450 17A1 are regulated by cyt b5 that enhances the 17,20-lyase reaction by promoting the coupling of P450 17A1 and cytochrome P450 reductase (CPR), allosterically. Cyt b5 can also act as an electron donor to enhance the 16-ene-synthase activity of human P450 17A1. In this review, we discuss the many roles of cyt b5 and focus on the modulation of CYP17A1 activities by cyt b5 and the mechanisms involved.

Electrochemistry of cytochrome P450 17α-hydroxylase/17,20-lyase (P450c17)

Within the superfamily of cytochrome P450 enzymes (P450s), there is a small class which is functionally employed for steroid biosynthesis. The enzymes in this class appear to have a small active site to accommodate the steroid substrates specifically and snuggly, prior to the redox transformation or hydroxylation to form a product. Cytochrome P450c17 is one of these and is also a multi-functional P450, with two activities, the first 17α-hydroxylation of pregnenolone is followed by a subsequent 17,20-lyase transformation to dehydroepiandrosterone (DHEA) as the dominant pathways to cortisol precursors or androgens in humans, respectively. How P450c17 regulates these two redox reactions is of special interest. There is a paucity of direct electrochemical studies on steroidogenic P450s, and in this mini-review we provide an overview of these studies with P450c17. Historical consideration as to the difficulties in obtaining reliable electrochemistry due to issues of handling proteins on an electrode, together with advances in the electrochemical techniques are addressed. Recent work using Fourier transformed alternating current voltammetry is highlighted as this technique can provide both catalytic information simultaneously with the underlying redox transfer with the P450 haem.

A new dawn for androgens: Novel lessons from 11-oxygenated C19 steroids

The abundant adrenal C19 steroid 11β-hydroxyandrostenedione (11OHA4) has been written off as a dead-end product of adrenal steroidogenesis. However, recent evidence has demonstrated that 11OHA4 is the precursor to the potent androgenic 11-oxygenated steroids, 11-ketotestosterone and 11-ketodihydrotestosterone, that bind and activate the human androgen receptor similarly to testosterone and DHT. The significance of this discovery becomes apparent when considering androgen dependent diseases such as castration resistant prostate cancer and diseases associated with androgen excess, e.g. congenital adrenal hyperplasia and polycystic ovary syndrome. In this review we describe the production and metabolism of 11-oxygenated steroids. We subsequently discuss their androgenic activity and highlight the putative role of these androgens in disease states.

A Comprehensive Evaluation of Steroid Metabolism in Women with Intrahepatic Cholestasis of Pregnancy

Intrahepatic cholestasis of pregnancy (ICP) is a common liver disorder, mostly occurring in the third trimester. ICP is defined as an elevation of serum bile acids, typically accompanied by pruritus and elevated activities of liver aminotransferases. ICP is caused by impaired biliary lipid secretion, in which endogenous steroids may play a key role. Although ICP is benign for the pregnant woman, it may be harmful for the fetus. We evaluated the differences between maternal circulating steroids measured by RIA (17-hydroxypregnenolone and its sulfate, 17-hydroxyprogesterone, and cortisol) and GC-MS (additional steroids), hepatic aminotransferases and bilirubin in women with ICP (n = 15, total bile acids (TBA) >8 μM) and corresponding controls (n = 17). An age-adjusted linear model, receiver-operating characteristics (ROC), and multivariate regression (a method of orthogonal projections to latent structure, OPLS) were used for data evaluation. While aminotransferases, conjugates of pregnanediols, 17-hydroxypregnenolone and 5β-androstane-3α,17β-diol were higher in ICP patients, 20α-dihydropregnenolone, 16α-hydroxy-steroids, sulfated 17-oxo-C19-steroids, and 5β-reduced steroids were lower. The OPLS model including steroids measured by GC-MS and RIA showed 93.3% sensitivity and 100% specificity, while the model including steroids measured by GC-MS in a single sample aliquot showed 93.3% sensitivity and 94.1% specificity. A composite index including ratios of sulfated 3α/β-hydroxy-5α/β-androstane-17-ones to conjugated 5α/β-pregnane-3α/β, 20α-diols discriminated with 93.3% specificity and 81.3% sensitivity (ROC analysis). These new data demonstrating altered steroidogenesis in ICP patients offer more detailed pathophysiological insights into the role of steroids in the development of ICP.

Effect of n-3 and n-6 Polyunsaturated Fatty Acids on Microsomal P450 Steroidogenic Enzyme Activities and In Vitro Cortisol Production in Adrenal Tissue From Yorkshire Boars

Dysregulation of adrenal glucocorticoid production is increasingly recognized to play a supportive role in the metabolic syndrome although the mechanism is ill defined. The adrenal cytochrome P450 (CYP) enzymes, CYP17 and CYP21, are essential for glucocorticoid synthesis. The omega-3 and omega-6 polyunsaturated fatty acids (PUFA) may ameliorate metabolic syndrome, but it is unknown whether they have direct actions on adrenal CYP steroidogenic enzymes. The aim of this study was to determine whether PUFA modify adrenal glucocorticoid synthesis using isolated porcine microsomes. The enzyme activities of CYP17, CYP21, 11β-hydroxysteroid dehydrogenase type 1, hexose-6-phosphate dehydrogenase (H6PDH), and CYP2E1 were measured in intact microsomes treated with fatty acids of disparate saturated bonds. Cortisol production was measured in a cell-free in vitro model. Microsomal lipid composition after arachidonic acid (AA) exposure was determined by sequential window acquisition of all theoretical spectra-mass spectrometry. Results showed that adrenal microsomal CYP21 activity was decreased by docosapentaenoic acid (DPA), docosahexaenoic acid (DHA), eicosapentaenoic acid, α-linolenic acid, AA, and linoleic acid, and CYP17 activity was inhibited by DPA, DHA, eicosapentaenoic acid, and AA. Inhibition was associated with the number of the PUFA double bonds. Similarly, cortisol production in vitro was decreased by DPA, DHA, and AA. Endoplasmic enzymes with intraluminal activity were unaffected by PUFA. In microsomes exposed to AA, the level of AA or oxidative metabolites of AA in the membrane was not altered. In conclusion, these observations suggest that omega-3 and omega-6 PUFA, especially those with 2 or more double bonds (DPA, DHA, and AA), impede adrenal glucocorticoid production.

Heterologous expression of fungal cytochromes P450 (CYP5136A1 and CYP5136A3) from the white-rot basidiomycete Phanerochaete chrysosporium: Functionalization with cytochrome b5 in Escherichia coli

Cytochromes P450 from the white-rot basidiomycete Phanerochaete chrysosporium, CYP5136A1 and CYP5136A3, are capable of catalyzing oxygenation reactions of a wide variety of exogenous compounds, implying their significant roles in the metabolism of xenobiotics by the fungus. It is therefore interesting to explore their biochemistry to better understand fungal biology and to enable the use of fungal enzymes in the biotechnology sector. In the present study, we developed heterologous expression systems for CYP5136A1 and CYP5136A3 using the T7 RNA polymerase/promoter system in Escherichia coli. Expression levels of recombinant P450s were dramatically improved by modifications and optimization of their N-terminal amino acid sequences. A CYP5136A1 reaction system was reconstructed in E. coli whole cells by coexpression of CYP5136A1 and a redox partner, NADPH-dependent P450 reductase (CPR). The catalytic activity of CYP5136A1 was significantly increased when cytochrome b5 (Cyt-b5) was further coexpressed with CPR, indicating that Cyt-b5 supports electron transfer reactions from NAD(P)H to CYP5136A1. Notably, P450 reaction occurred in E. coli cells that harbored CYP5136A1 and Cyt-b5 but not CPR, implying that the reducing equivalents required for the P450 catalytic cycle were transferred via a CPR-independent pathway. Such an "alternative" electron transfer system in CYP5136A1 reaction was also demonstrated using purified enzymes in vitro. The fungal P450 reaction system may be associated with sophisticated electron transfer pathways.

Mechanistic Scrutiny Identifies a Kinetic Role for Cytochrome b5 Regulation of Human Cytochrome P450c17 (CYP17A1, P450 17A1)

Cytochrome P450c17 (P450 17A1, CYP17A1) is a critical enzyme in the synthesis of androgens and is now a target enzyme for the treatment of prostate cancer. Cytochrome P450c17 can exhibit either one or two physiological enzymatic activities differentially regulated by cytochrome b5. How this is achieved remains unknown. Here, comprehensive in silico, in vivo and in vitro analyses were undertaken. Fluorescence Resonance Energy Transfer analysis showed close interactions within living cells between cytochrome P450c17 and cytochrome b5. In silico modeling identified the sites of interaction and confirmed that E48 and E49 residues in cytochrome b5 are essential for activity. Quartz crystal microbalance studies identified specific protein-protein interactions in a lipid membrane. Voltammetric analysis revealed that the wild type cytochrome b5, but not a mutated, E48G/E49G cyt b5, altered the kinetics of electron transfer between the electrode and the P450c17. We conclude that cytochrome b5 can influence the electronic conductivity of cytochrome P450c17 via allosteric, protein-protein interactions.

Advances in the analytical methodologies: Profiling steroids in familiar pathways-challenging dogmas

The comprehensive evaluation of the adrenal steroidogenic pathway, given its complexity, requires methodology beyond the standard techniques currently employed. Advances in LC-MS/MS, coupled with in vitro cell models that produce all the steroid metabolites of the mineralo-, glucocorticoid and androgen arms, present a powerful approach for the comprehensive evaluation of adrenal steroidogenesis in response to compounds of interest including bioactives, drug treatments and endocrine disrupting compounds. UHPLC-MS/MS analysis of steroid panels in forskolin, angiotensin II and K(+) stimulated H295R cells provides a snapshot of their effect on intermediates and end products of adrenal steroidogenesis. The impact of full steroid panel evaluations by LC- and GC-MS/MS extends to clinical profiling with the characterization of normal pediatric steroid reference ranges in sexual development and of disease-specific profiles improving diagnosis and sub classification. Comprehensive analyses of steroid profiles may potentially improve patient outcomes together with the application of treatments specifically suited to clinical subgroups. LC-MS/MS and GC-MS/MS applications in the analyses of comprehensive steroid panels are demonstrated in clinical conditions such as congenital adrenal hyperplasia in newborns requiring accurate diagnoses and in predicting metabolic risk in polycystic ovary syndrome patients. Most notable perhaps is the impact of LC-MS/MS evaluations on our understanding of the basic biochemistry of steroidogenesis with the detection of the long forgotten adrenal steroid, 11β-hydroxyandrostenedione, at significant levels. The characterization of its metabolism to androgen receptor ligands in the LNCaP prostate cancel cell model, specifically within the context of recurring prostate cancer, lends new perspectives to old dogmas. We demonstrate that UHPLC-MS/MS has enabled the analyses of novel metabolites of the enzymes, SRD5A, 11βHSD and 17βHSD, in LNCaP cells. Undoubtedly, the continuous advances in the analytical methodologies used for steroid profiling and quantification will give impetus to the unraveling of the remaining enigmas, old and new, of both hormone biosynthesis and metabolism.

Cytochrome b5 modulates multiple reactions in steroidogenesis by diverse mechanisms

Cytochrome b5 (cyt-b5) is a relatively small haemoprotein which plays an important role in the regulation of mammalian steroidogenesis. This unique protein has the ability to modulate the activity of key steroidogenic enzymes via a number of diverse reaction mechanisms. Cyt-b5 can augment the 17,20-lyase activity of CYP17A1 by promoting the interaction of CYP17A1 and POR; enhance the 16-ene-synthase activity of CYP17A1 by acting as an electron donor; and enhance the activity of 3βHSD by increasing the affinity of 3βHSD for its cofactor NAD(+). We review the modulation of CYP17A1 and 3βHSD activity by cyt-b5 and discuss the reaction mechanisms associated with each activity. The physiological importance of cyt-b5 in regulating mammalian steroidogenesis is presented and the impact of inactivating cyt-b5 mutations are reviewed. This article is part of a Special Issue entitled 'Steroid/Sterol signaling'.

Effect of Cytochrome b5 Content on the Activity of Polymorphic CYP1A2, 2B6, and 2E1 in Human Liver Microsomes

Human cytochrome b5 (Cyt b5) plays important roles in cytochrome P450 (CYP)-mediated drug metabolism. However, the expression level of Cyt b5 in normal human liver remains largely unknown. The effect of Cyt b5 on overall CYP activity in human liver microsomes (HLM) has rarely been reported and the relationship between Cyt b5 and the activity of polymorphic CYP has not been systematically investigated. In this study, we found that the median value of Cyt b5 protein was 270.01 pmol/mg from 123 HLM samples, and 12- and 19-fold individual variation was observed in Cyt b5 mRNA and protein levels, respectively. Gender and smoking clearly influenced Cyt b5 content. In addition, we found that Cyt b5 protein levels significantly correlated with the overall activity of CYP1A2, 2B6, and 2E1 in HLM. However, when the CYP activities were sorted by single nucleotide polymorphisms (SNP), the effect of Cyt b5 protein on the kinetic parameters varied greatly. There were significant correlations between Cyt b5 content and V_max and CL_int of CYP1A2 wild-types (3860GG, 2159GG, and 5347CC) as well as homozygous mutants (163AA and 3113GG). In contrast to V_max and CL_int, the K_m of CYP2B6 516GG and 785AA genotypes was inversely associated with Cyt b5 content. Correlations between Cyt b5 content and V_max and CL_int of CYP2E1 -1293GG, -1293GC, 7632TT, 7632TA, -333TT, and -352AA genotypes were also observed. In conclusion, Cyt b5 expression levels varied considerably in the Chinese cohort from this study. Cyt b5 had significant impact on the overall activity of CYP1A2, 2B6, and 2E1 in HLM and the effects of Cyt b5 protein on polymorphic CYP1A2, 2B6, and 2E1 activity were SNP-dependent. These findings suggest that Cyt b5 plays an important role in CYP-mediated activities in HLM and may possibly be a contributing factor for the individual variation observed in CYP enzyme activities.

Steroidogenic enzyme profile in an androgen-secreting adrenocortical oncocytoma associated with hirsustism

Hirsutism induced by hyperandrogenism can be associated with polycystic ovary syndrome, 21-hydroxylase (OH) deficiency or androgen-secreting tumors, including ovarian and adrenal tumors. Adrenal androgen-secreting tumors are frequently malignant. Adrenal oncocytomas represent rare causes of hyperandrogenism. The aim of the study was to investigate steroidogenic enzyme expression and steroid secretion in an androgen-secreting adrenal oncocytoma in a young woman presenting with hirsutism. Hyperandrogenism was diagnosed on the basis of elevated plasma Δ4-androstenedione and testosterone levels. Pelvic ultrasound was normal, CT scanning revealed a right adrenal mass. Androgens were assessed in adrenal and ovarian vein samples and proved a right adrenal origin. Adrenalectomy normalized androgen levels and the adrenal tumor was diagnosed as an oncocytoma. Real time-PCR, immunohistochemistry and cell culture studies were performed on tumor explants to investigate the steroid secretion profile. Among enzymes required for cortisol synthesis, 17α-OH and 3β-hydroxysteroid dehydrogenase 2 (3β-HSD2) were highly expressed whereas 21-OH and 11β-OH were weakly produced at the mRNA and/or protein levels. Enzymes involved in testosterone production, 17β-HSD5 and 17β-HSD3, were also detected. ACTH receptor was present in the tissue. Cortisol, Δ4-androstenedione and testosterone secretions by cultured cells were increased by ACTH. These results provide the first demonstration, to our knowledge, of abnormal expression profile of steroidogenic enzymes in an adrenocortical oncocytoma. Our results also indicate that Δ4-androstenedione hypersecretion resulted from high 17α-OH and 3β-HSD2 expression in combination with low expression of 21-OH and 11β-OH. Testosterone production was ascribed to occurrence of 17β-HSD5 and 17β-HSD3. Finally, our results indicate that androgen secretion was stimulated by ACTH.

Mechanistic basis of electron transfer to cytochromes p450 by natural redox partners and artificial donor constructs

Cytochromes P450 (P450s) are hemoproteins catalyzing oxidative biotransformation of a vast array of natural and xenobiotic compounds. Reducing equivalents required for dioxygen cleavage and substrate hydroxylation originate from different redox partners including diflavin reductases, flavodoxins, ferredoxins and phthalate dioxygenase reductase (PDR)-type proteins. Accordingly, circumstantial analysis of structural and physicochemical features governing donor-acceptor recognition and electron transfer poses an intriguing challenge. Thus, conformational flexibility reflected by togging between closed and open states of solvent exposed patches on the redox components was shown to be instrumental to steered electron transmission. Here, the membrane-interactive tails of the P450 enzymes and donor proteins were recognized to be crucial to proper orientation toward each other of surface sites on the redox modules steering functional coupling. Also, mobile electron shuttling may come into play. While charge-pairing mechanisms are of primary importance in attraction and complexation of the redox partners, hydrophobic and van der Waals cohesion forces play a minor role in docking events. Due to catalytic plasticity of P450 enzymes, there is considerable promise in biotechnological applications. Here, deeper insight into the mechanistic basis of the redox machinery will permit optimization of redox processes via directed evolution and DNA shuffling. Thus, creation of hybrid systems by fusion of the modified heme domain of P450s with proteinaceous electron carriers helps obviate the tedious reconstitution procedure and induces novel activities. Also, P450-based amperometric biosensors may open new vistas in pharmaceutical and clinical implementation and environmental monitoring.

Placental estrogen suppresses cyclin D1 expression in the nonhuman primate fetal adrenal cortex

We have previously shown that estrogen selectively suppresses growth of the fetal zone of the baboon fetal adrenal cortex, which produces the C19-steroid precursors, eg, dehydroepiandrosterone sulfate, which are aromatized to estrogen within the placenta. In the present study, we determined whether fetal adrenal expression of cell cycle regulators are altered by estrogen and thus provide a mechanism by which estrogen regulates fetal adrenocortical development. Cyclin D1 mRNA levels in the whole fetal adrenal were increased 50% (P < .05), and the number of cells in the fetal adrenal definitive zone expressing cyclin D1 protein was increased 2.5-fold (P < .05), whereas the total number of cells in the fetal zone and fetal serum dehydroepiandrosterone sulfate levels were elevated 2-fold (P < .05) near term in baboons in which fetal serum estradiol levels were decreased by 95% (P < .05) after maternal administration of the aromatase inhibitor letrozole and restored to normal by concomitant administration of letrozole plus estradiol throughout second half of gestation. However, fetal adrenocortical expression of cyclin D2, the cyclin-dependent kinase (Cdk)-2, Cdk4, and Cdk6, and Cdk regulatory proteins p27(Kip1) and p57(Kip2) were not changed by letrozole or letrozole plus estradiol administration. We suggest that estrogen controls the growth of the fetal zone of the fetal adrenal by down-regulating cyclin D1 expression and thus proliferation of progenitor cells within the definitive zone that migrate to the fetal zone. We propose that estrogen restrains growth and function of the fetal zone via cyclin D1 to maintain estrogen levels in a physiological range during primate pregnancy.

Regulation of cytochrome b5 expression by miR-223 in human liver: effects on cytochrome P450 activities

PURPOSE

Cytochrome b5 (b5) is a hemoprotein that transfers electrons to several enzymes to fulfill functions in fatty acid desaturation, methemoglobin reduction, steroidogenesis, and drug metabolism. Despite the importance of b5, the regulation of b5 expression in human liver remains largely unknown. We investigated whether microRNA (miRNA) might be involved in the regulation of human b5.

METHODS

Twenty-four human liver specimens were used for correlation analysis. In silico analysis and luciferase assay were performed to determine whether the predicted miRNAs functionally target to b5. The miR-223 was overexpressed into HepG2 cells infected with adenovirus expressing human cytochrome P450.

RESULTS

In human livers, the b5 protein levels were not positively correlated with the b5 mRNA levels, and miR-223 levels were inversely correlated with the b5 mRNA levels or the translational efficiencies. The luciferase assay showed that miR-223 functionally binds to the element in the 3′-untranslated region of b5 mRNA. The overexpression of miR-223 significantly reduced the endogenous b5 protein level and the mRNA stability in HepG2 cells. Moreover, the overexpression of miR-223 significantly reduced CYP3A4-catalyzed testosterone 6β-hydroxylation activity and CYP2E1-catalyzed chlorzoxazone 6-hydroxylase activity but not CYP1A2-catalyzed 7-ethoxyresorufin O-deethylase activity.

CONCLUSIONS

miR-223 down-regulates b5 expression in the human liver, modulating P450 activities.

Higher androgen bioactivity is associated with excessive erythrocytosis and chronic mountain sickness in Andean Highlanders: a review

Populations living at high altitudes (HA), particularly in the Peruvian Central Andes, are characterised by presenting subjects with erythrocytosis and others with excessive erythrocytosis (EE)(Hb>21 g dl(-1) ). EE is associated with chronic mountain sickness (CMS), or lack of adaptation to HA. Testosterone is an erythropoietic hormone and it may play a role on EE at HA. The objective of the present review was to summarise findings on role of serum T levels on adaptation at HA and genes acting on this process. Men at HA without EE have higher androstenedione levels and low ratio androstenedione/testosterone than men with EE, suggesting low activity of 17beta-hydroxysteroid dehydrogenase (17beta-HSD), and this could be a mechanism of adaptation to HA. Higher conversion of dehydroepiandrosterone to testosterone in men with EE suggests nigher 17beta-HSD activity. Men with CMS at Peruvian Central Andes have two genes SENP1, and ANP32D with higher transcriptional response to hypoxia relative to those without. SUMO-specific protease 1 (SENP1) is an erythropoiesis regulator, which is essential for the stability and activity of hypoxia-inducible factor 1 (HIF-1α) under hypoxia. SENP1 reverses the hormone-augmented SUMOylation of androgen receptor (AR) increasing the transcription activity of AR.In conclusion, increased androgen activity is related with CMS.