Change of 7alpha-hydroxy-dehydroepiandrosterone levels in serum of mice treated by cytochrome P450-modifying agents

The Origin of 7α-Hydroxy-Dehydroepiandrosterone and Its Physiological Role: a History of Discoveries

Nearly 60 years has elapsed since the first isolation and identification of 7α-hydroxy-dehydroepiandrosterone, and in that time much information has been gained on its occurrence, metabolism, ontogeny, immunomodulatory activity, cell proliferation, cortisol control in local tissues and neuroactivity. Additional knowledge about this steroid may elucidate its role in obesity, neurodegenerative disturbances such as Alzheimer’s disease, or psychiatric disorders such as schizophrenia or depression. This review aims to provide a comprehensive summary of the available literature on 7α-hydroxy-dehydroepiandrosterone.

Synthesis of 3α-deuterated 7α-hydroxy-DHEA and 7-oxo-DHEA and application in LC-MS/MS plasma analysis

7-Oxygenated metabolites of dehydroepiandrosterone (DHEA) are known for their neuroprotective and immunomodulatory properties. These neuroactive steroids are currently predominately analysed by mass spectrometry, for which the use of internal deuterated standards is necessary. The aim of this study was to synthesize the deuterated derivatives of 7α-hydroxy-DHEA and 7-oxo-DHEA and test them in liquid chromatography-tandem mass spectrometry (LC-MS/MS) in order to enhance the performance characteristics of this method. Here we report the synthesis of 3α deuterium-labelled 7α-hydroxy-DHEA and 7-oxo-DHEA. Deuterium was introduced into the 3α position by reduction of the corresponding 3-ketone with a protected 17-carbonyl group using NaBD4. Our new procedure allows the easier synthesis of deuterated steroid labelled compounds. The use of these deuterated steroids enabled us to improve the human plasma LC-MS/MS analysis of 7α-hydroxy-DHEA and 7-oxo-DHEA in terms of sensitivity, precision and recovery.

The identification and simultaneous quantification of 7-hydroxylated metabolites of pregnenolone, dehydroepiandrosterone, 3beta,17beta-androstenediol, and testosterone in human serum using gas chromatography-mass spectrometry

7-Hydroxy-metabolites of dehydroepiandrosterone (DHEA) and 3beta,17beta-androstenediol (AD) possess immunomodulatory and neuroprotective properties; therefore, the measurement of these steroids in patients with autoimmune diseases or disturbances in the CNS may be of interest. A gas chromatography-mass spectrometry (GC-MS) method for the determination of 7-hydroxy-metabolites of pregnenolone, DHEA, AD, and testosterone including the parent steroids was applied to serum samples from 12 adult men (27-66 years), 13 male adolescents (13-20 years), 5 boys (6-10 years), 15 women in the follicular phase of the menstrual cycle (22-45 years), 17 women in the luteal phase (22-45 years), and 4 girls (6-10 years). The steroids were age and sex dependent, but independent of the menstrual cycle. The ratio of the 7alpha-hydroxy-metabolites to their parent steroids were age dependent, exhibiting an increasing trend (p < 0.0001, ANOVA) from pregnenolone (5%) to AD (20%). The ratio of 7beta- to 7alpha-metabolites ranged from 0.6 to 1. These results are consistent with models suggesting 7alpha-hydroxylation of the parent steroid, conversion to a 7-oxo-steroid and finally to the 7beta-hydroxylated-metabolite. Partial correlations suggested that 7-hydroxylation might reduce the concentration of circulating androgens. Despite the three times lower concentration of AD-metabolites, their antiglucocorticoid, immunomodulatory, and neuroprotective effects may be comparable to that of DHEA based on their reported greater biological activity.

Simultaneous determination of dehydroepiandrosterone and its 7-oxygenated metabolites in human serum by high-resolution gas chromatography--mass spectrometry

A highly sensitive and specific method has been developed for the simultaneous measurement of free (unconjugated) or sulfate-conjugated forms of dehydroepiandrosterone (DHEA), 7alpha-hydroxy-DHEA (7alpha-OH-DHEA), 7beta-hydroxy-DHEA (7beta-OH-DHEA), and 7-oxo-DHEA (7-oxo-DHEA) in human serum. This method is based upon a stable isotope-dilution technique by gas chromatography-selected-ion monitoring mass spectrometry. Free steroids were extracted from serum with an organic solvent and the sulfate-conjugated steroids remained in aqueous phase. Free steroids were purified by solid-phase extraction, while sulfate-conjugated steroids were hydrolyzed by sulfatase and deconjugated steroids were purified by solid-phase extractions. The extracts were treated with O-methylhydroxylamine hydrochloride and were subsequently dimethylisopropylsilylated. The resulting methyloxime-dimethylisopropylsilyl (MO-DMIPS) ether derivatives were quantified by gas chromatography-selected-ion monitoring mass spectrometry in a high-resolution mode. The detection limits of MO-DMIPS ether derivatives of DHEA, 7alpha-OH-DHEA, 7beta-OH-DHEA and 7-oxo-DHEA were 1.0, 0.5, 0.5 and 2.0pg, respectively. Coefficients of variation between samples ranged from 10.6 to 22.9% for free 7-oxygenated DHEA to less than 10% for DHEA and sulfate-conjugated 7-oxygenated DHEA. The concentrations of these steroids were measured in 18 sera samples from healthy volunteers (9 males and 9 females; aged 23-78 years). Free DHEA, 7alpha-OH-DHEA, 7beta-OH-DHEA and 7-oxo-DHEA levels ranged between 0.21-3.55, 0.001-0.194, 0.003-0.481, and 0.000-0.077ng/ml, respectively, and the sulfate-conjugated steroid levels of these metabolites ranged between 253-4681, 0.082-3.001, 0.008-0.903, and 0.107-0.803ng/ml, respectively. The free DHEA-related steroid concentrations were much lower than those previously measured by RIA and low-resolution GC-MS. The present method made it possible to determine simultaneously serum DHEA-related steroid levels with sufficient sensitivity and accuracy.

Simultaneous determination of dehydroepiandrosterone, its 7-hydroxylated metabolites, and their sulfates in rat brain tissues

A method is described for simultaneous assessment of dehydroepiandrosterone (DHEA), its sulfate (DHEAS), and their 7-hydroxylated metabolites in cortex and subcortex of the rat brain. The procedure for determination of unconjugated steroids and DHEAS involved diethyl ether extraction of the homogenized tissue, solvent partition of the dry extract, and final quantification by specific radioimmunoassays. In addition, determination of 7-hydroxy-dehydroepiandrosterone sulfates required solvolysis, followed by high-performance liquid chromatography for separation of 7-hydroxylated metabolites from their precursor. The losses during this process were monitored by measurement of spiked radioactivity of [(3)H]testosterone or [(3)H]dehydroepiandrosterone sulfate. The content of dehydroepiandrosterone sulfate in both brain tissues was of the order of ten(s) nmol/g tissue irrespective its type (cortex or subcortex), while concentrations of other steroids were about 10 times lower in both tissues. In contrast to the ratio of sulfated/unconjugated DHEA, the levels of unconjugated 7-hydroxylated metabolites and their sulfates were close to each other. The reproducibility of the method with respect to coefficients of variation varied from 12 to 25%. An age-related decrease of sulfated dehydroepiandrosterone in the cortex of animals was also observed.

Protection against inflammatory neurodegeneration and glial cell death by 7β-hydroxy epiandrosterone, a novel neurosteroid

It has been demonstrated that neuroprotective effects of dehydroepiandrosterone (DHEA) may be mediated by its 7alpha- and 7beta-hydroxy derivatives. Epiandrosterone is also converted to 7beta-hydroxy epiandrosterone (7beta-OH EPIA) in numerous tissues. The aim of the present study was to establish whether treatment with 7beta-hydroxy epiandrosterone has a neuroprotective effect in animal models of Alzheimer's disease (AD) lesions. Intra-amygdaloid administration of amyloid beta [Abeta(25-35)] increased the number of tau-positive cells in the ipsilateral hippocampus. Intracerebroventricular administration of ethylcholine aziridinium (AF64A) caused cholinergic damage in the septum, and glial lesions in the lateral septal nucleus and in the lateral zones of the hippocampus. These effects were almost completely prevented when animals were treated subcutaneously (b.i.d.) for 10 days with 0.1 mg/kg 7beta-hydroxy epiandrosterone. These findings indicate that 7beta-hydroxy epiandrosterone has powerful cytoprotective effects suggesting that (a) this neurosteroid may have therapeutic potential in various neurodegenerative conditions such as Alzheimer's disease, and (b) 7beta-hydroxy steroids may constitute a novel class of endogenous neuroprotective agents.

Neurosteroid 7-hydroxylation products in the brain

The neurosteroids pregnenolone (PREG) and dehydroepiandrosterone (DHEA) are precursors for both oxidized and hydroxylated metabolites in the brain. Thus, brain production of 7-hydroxylated derivatives is second to that in the liver, and P4507B1-containing hippocampus is the major site for 7 alpha-hydroxylation. Other P450s and/or oxido-reductive mechanisms may be responsible for 7 beta-hydroxylation. In addition to regulating neurosteroid brain levels, when produced, the 7-hydroxylated derivatives of PREG and DHEA were investigated for antiglucocorticoid-mediated neuroprotective potencies, and both 7 alpha- and 7 beta-hydroxy-DHEA were efficient in preventing the nuclear uptake of [3H]dexamethasone-activated glucocorticoid receptor in brain cells. Activation of 7 alpha-hydroxylation by increased close contacts of astrocytes and after glucocorticoid treatment suggested that the regulated production of 7 alpha-hydroxysteroids was a key event for the neuroprotection conferred by neurosteroids.

Involvement of steroids and cytochromes P(450) species in the triggering of immune defenses

In vertebrates the wide variety of cytochromes P(450) (P(450)) is a key for elimination of low molecular weight xenobiotics and for the production and metabolism of steroid hormones. In contrast, xenobiotics of large molecular weight are processed and eliminated after the immune response. The suppression of immune response by native P(450)-produced glucocorticoid (GC) hormones constitutes a first link between P(450) and immunity. In the last decade, mechanisms and molecules responsible for the triggering of immune response were investigated and results showed that many tissues and organs transform native 3beta-hydroxysteroids into 7-hydroxylated metabolites that trigger immunity. Present data suggest that 7-hydroxysteroids are native anti-GCs that block the GC-induced immunosuppression. Because specific P(450) are responsible for the production of 7-hydroxylated steroids resulting into increased immunity, a second link exists between P(450) and immunity. Taken together, these findings support the proposal that P(450) are keys to all of the known defense mechanisms of vertebrates against all xenobiotic forms.

7-Hydroxydehydroepiandrosterone epimers in human serum and saliva. Comparison of gas chromatography-mass spectrometry and radioimmunoassay

Recent reports demonstrated that 7-hydroxylated metabolites of dehydroepiandrosterone (DHEA) possess immunomodulatory and antiglucocorticoid properties. Increased 7alpha-OH-DHEA levels were found in patients with Alzheimer's disease. Hence, measurement of steroids in patients with autoimmune diseases or disturbances in the central nervous system could be of interest. A new sensitive GC-MS method for the determination of 7-hydroxydehydroepiandrosterone epimers was developed and compared with previously developed radioimmunoassays. Besides serum, these steroids were, for the first time, measured in saliva where their concentrations were about five times lower. 7alpha- and 7beta-epimer levels correlated well in both body fluids and they were larger in male.

7 alpha-hydroxy-dehydroepiandrosterone and immune response

In human and murine lymphoid organs, circulating 3 beta-hydroxysteroids, including pregnenolone (PREG), dehydroepiandrosterone (DHEA), and epiandrosterone (EPIA), are 7 alpha-hydroxylated by a cytochrome P450 identified in the hippocampus as P4507B1. Mouse and human lymphoid organs produced different patterns of 3 beta-hydroxysteroid 7 alpha-hydroxylation with the absence of pregnenolone and epiandrosterone hydroxylation in human and mouse, respectively. Both 7 alpha-hydroxy-DHEA and 7 alpha-hydroxy-EPIA triggered a significant increase of antitetanus toxoid and anti-Bordetella pertussis toxins IgGs production in cultures of activated B + T cells derived from human tonsils, whereas both 7 alpha-hydroxy-PREG and 7 alpha-hydroxy-DHEA increased the immune response in mouse. Paracrine action of 7 alpha-hydroxysteroids resulted from their production in cells of the lymphoid organs. Comparison of P4507B1 sequences in rat, human, and two mouse species showed that one amino acid change might explain important differences in KM for 7 alpha-hydroxylation, and suggested that such differences might contribute to the extent of immune response.

Interactions of melatonin with the liver microsomal cytochrome P450 system of rats and humans in vitro and effects on the P450 system and the antioxidative status in rat liver after acute treatment

In vitro melatonin binds to human and rat liver microsomal cytochrome P-450 (P450) according to a type II substrate. The affinity is similar to that of aniline with a general left-shift. Melatonin interferes with model monooxygenase reactions indicative of different P450 forms in humans and rats (in humans according to the lower specific P450 content less pronounced): the strongest inhibition was found for ethoxyresorufin O-deethylation, indicating the binding to P450 1A, the binding to P450 2B (ethoxycoumarin O-deethylation) was less pronounced, the least inhibition was found for P450 3A (ethylmorphine N-demethylation) reaction. The oxidase function was also inhibited: luminol amplified chemiluminescence was more inhibited than the lucigenin amplified one, hydrogen peroxide formation was inhibited at concentrations higher than 10(-4) M, microsomal NADPH/Fe stimulated lipid peroxidation was inhibited at concentrations higher than 10(5) M. In vivo melatonin prolonged hexobarbital sleeping time in rats in a dose dependent manner (ip. co-administration of 1, 5 and 20 mg/kg b.w. melatonin with 100 mg/kg hexobarbital). Immediately after awakening the animals were sacrificed: a small increase in P450 concentrations cannot be explained, no changes in P450 monooxygenase or oxidase activities nor in microsomal lipid peroxidation or GSH status could be observed.

Dexamethasone-induced apoptosis of mouse thymocytes: prevention by native 7alpha-hydroxysteroids

Dehydroepiandrosterone (DHEA) has been shown to decrease the dexamethasone (DEX)-induced apoptosis of thymocytes and to be one of the native 3beta-hydroxysteroids extensively 7alpha-hydroxylated in thymus. This led us to question whether DHEA or 7alpha-hydroxy-DHEA is responsible for the decrease in DEX-induced apoptosis of thymocytes and whether this property is shared with other native 3beta-hydroxysteroids and their 7alpha-hydroxylated metabolites. Treatment of mice with DHEA or 7alpha-hydroxy-DHEA prior to DEX led to a smaller decrease in thymus weight than with DEX alone and to a disappearance of the DEX-induced changes in thymocyte phenotypes. Thymocyte apoptosis induced by DEX treatment was significantly lowered in DHEA- and 7alpha-hydroxy-DHEA-treated thymi, even after 18 h culture with additional 10-6 mol/L DEX. Extensive apoptosis of thymocytes cultured with 10-7 mol/L DEX was brought back to control levels when 10-5 mol/L 7alpha-hydroxy-DHEA or 10-5 mol/L 7alpha-hydroxy-epiandrosterone was added. After use of DHEA and epiandrosterone or pregnenolone, less significant and no significant changes were obtained, respectively. These findings imply that the 7alpha-hydroxylation of 3beta-hydroxysteroids may be a prerequisite for an exquisite regulation of the thymocyte-positive selection driven by the glucocorticoids produced in thymic epithelial cells.

Immunoassay of 7-hydroxysteroids: 2. Radioimmunoassay of 7alpha-hydroxy-dehydroepiandrosterone

High sensitivity radioimmunoassay of 3beta, 7alpha-dihydroxy-5-androsten-17-one (7alpha-OH-DHEA) has been developed and evaluated. The method is based on polyclonal rabbit antisera raised against 19-O-(carboxymethyl)oxime bovine serum albumin conjugate and bridge- and position homologous [(125)I]iodotyrosine methyl ester as a tracer. Sensitivity of the assay amounted to 3.12 fmol (0.95 pg)/tube, precision as a mean intra- and interassay coefficient of variation was 7.1 and 10.6%, respectively, and the average recovery of the analyte added to steroid-free serum was 110%. Out of the steroids occurring in human serum which may interfere with the assay, the only important cross-reactants were dehydroepiandrosterone and 3beta, 7beta-dihydroxy-5-androsten-17-one (7beta-OH-DHEA) with cross-reactivities of 1.95 and 1.16%, respectively. The levels of free (unconjugated) 7alpha-OH-DHEA have been determined in 29 sera from healthy volunteers (23 females and 6 males), and from 48 patients (43 females and 5 males) in which dehydroepiandrosterone and its sulfate (DHEA/S) had been measured for various endocrinopathies. The levels in healthy subjects ranged from 0.21 to 6.57 (mean 2.33+/-1.50) nM, while those of the patients from 0 to 5. 99 (mean 1.46+/-1.52) nM. The levels of 7alpha-OH-DHEA in patients significantly correlated with those of DHEA and its sulfate.

Immunoassay of 7-hydroxysteroids: 1. Radioimmunoassay of 7beta-hydroxy dehydroepiandrosterone

High sensitivity radioimmunoassay of 3beta,7beta-dihydroxy-5-androsten-17-one (7beta-OH-DHEA) has been developed and evaluated. The method is based on polyclonal rabbit antisera raised against its 19-O-(carboxymethyl)oxime bovine serum albumin conjugate and bridge- and position homologous [125I]iodotyrosine methyl ester as a tracer. Alternatively, [3H]tracer has been prepared, which was recognized by the antiserum as well, but the assay sensitivity was lower. The identity of measured immunoreactive material was confirmed by high performance liquid chromatography which separated 7beta-OH-DHEA from its 7alpha-isomer. Using radioiodinated tracer, the sensitivity of the method was 3.48 fmol (1.06 pg) per tube, the mean recovery of standard added to steroid-free serum was 98.5%. Free (unconjugated and not-esterified) 7beta-OH-DHEA amounted in average 5.8% of the total 7beta-OH-DHEA present in human serum. It was measured in 42 normal subjects (28 females and 14 males) and in 92 randomly selected patients with various endocrinopathies. The mean values +/- SD in normals were 2.05 +/- 1.02 nmol l(-1), the broad range of values from undetectable levels to 10.3 nmol l(-1) was found in the patients. Serum levels of free 7beta-OH-DHEA in the patients significantly correlated with DHEA and its sulfate.