Metabolism of free and sulfoconjugated DHEA in brain tissue in vivo and in vitro

A new sample preparation method coupled to GC-MS analysis was developed and validated for quantification of sulfate esters of pregnenolone (PREG-S) and dehydroepiandrosterone (DHEA-S) in rat brain. Using a solid-phase extraction recycling protocol, the results show that little or no PREG-S and DHEA-S ( Ͻ 1 pmol/g) is present in rat and mouse brain. These data are in agreement with studies in which steroid sulfates were analyzed without deconjugation. We suggest that the discrepancies between analyses with and without deconjugation are caused by internal contamination of brain extract fractions, supposed to contain steroid sulfates, by lipoidal forms of PREG and DHEA (L-PREG and L-DHEA, respectively). These derivatives can be acylated very efficiently with heptafluorobutyric anhydride and triethylamine, and their levels in rodent brain ( ‫ف‬ 1 nmol/g) are much higher than those of their unconjugated counterparts. They are distinct from fatty acid esters, and preliminary data do not favor structures such as sulfolipids or sterol peroxides. Noncovalent interactions between steroids and proteolipidic elements, such as lipoproteins, could account for some experimental data. Given their abundance in rodent brain, the structural characterization and biological functions of L-PREG and L-DHEA in the central nervous system merit considerable attention. Four years ago, we developed and validated an analytical procedure for measuring trace amounts of neurosteroids in brain tissue by GC-MS (1). This method, which includes solid-phase extraction (SPE) and HPLC as fractionation and purification steps, is very suitable for quantifying simultaneously numerous neurosteroids in small individual regions of the central nervous system (CNS) (2) or peripheral nervous system (3) with high sensitivity and accuracy. Interest was primarily focused on pregnenolone (PREG), dehydroepiandrosterone (DHEA), and their sulfated conjugates (PREG-S and DHEA-S, respectively) and on progesterone (PROG) and allopregnanolone (3 ␣ -hydroxy-5 ␣ -pregnan-20-one).Neurosteroids are synthesized by glial cells and neurons from cholesterol or from blood-borne precursors (4). In particular, PREG-S and DHEA-S are known to be neuroactive, and their major effects are the modulation of several neuronal membrane receptors, such as ␥ -aminobutyric acid (5, 6), N -methyl-d -aspartate (7), and σ receptors, by affecting neuronal excitability and behavior (8, 9). Notably, a physiologic function of PREG-S was suggested by the positive correlation between PREG-S levels in the hippocampus of aged rats and their spatial memory performance (10). However, some studies do not favor the concept that PREG-S and DHEA-S are actually neurosteroids. Indeed, contradictory results have been obtained concerning the presence and activity of the hydroxysteroid sulfotransferase, implied in the sulfation of free steroid.

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“…Other studies have reported a very low hydroxysteroid sulfotransferase activity in rat (17) and human (18) brain.…”

mentioning

confidence: 78%

Novel lipoidal derivatives of pregnenolone and dehydroepiandrosterone and absence of their sulfated counterparts in rodent brain

Lière

Pianos

Eychenne

et al. 2004

Journal of Lipid Research

110

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“…Although much of the research has pointed to the relevant role played by PREGS in enhancing learning and memory functions (see references in the Introduction), there are some discrepancies mostly related to the dose of the steroid, its route of administration (peripheral vs. central), and the behavioral paradigm tested. Results may, indeed, be difficult to interpret in the case of peripheral administration (9, 26) because hydrophilic-acidic compounds such as sulfated steroids poorly cross the blood-brain barrier (27,28). In addition, in studies using foot-shock avoidance-based paradigms, results may not only reflect the specific modulation of memory processes, but also interfering emotional factors: for instance, the ICV administration of PREGS at 0.84-1680 pmol in rats and 1-100 pmol in mice has been found ineffective on retention performances in avoidance learning tasks (7,8), whereas doses of the steroid between 2.4 ϫ 10 Ϫ18 mol and 10 Ϫ14 mol infused into mice amygdala and hippocampus increased retention in the same paradigm (2).…”

Section: Discussionmentioning

confidence: 99%

The synthetic enantiomer of pregnenolone sulfate is very active on memory in rats and mice, even more so than its physiological neurosteroid counterpart: Distinct mechanisms?

Akwa

Ladurelle

Covey

et al. 2001

Proc. Natl. Acad. Sci. U.S.A.

126

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The demonstration that the neurosteroid pregnenolone sulfate (PREGS) is active on memory function at both the physiological and pharmacological levels led to us examining in detail the effects of the steroid on spatial working memory by using a two-trial recognition task in a Y-maze, a paradigm based on the natural drive in rodents to explore a novel environment. Dose-response studies in young male adult Sprague-Dawley rats and Swiss mice, after the postacquisition intracerebroventricular injection of steroid, showed an U-inverted curve for memory performance and indicated a greater responsiveness in rats compared with mice. Remarkably, the synthetic (؊) enantiomer of PREGS not only also displayed promnesiant activity, but its potency was 10 times higher than that of the natural steroid. Intracerebroventricular coadministration experiments with DL-2-amino-5-phosphonovaleric acid, a competitive selective antagonist of the N-methyl-D-aspartate receptor, abolished the memory-enhancing effect of PREGS, but not that of the PREGS enantiomer, evoking enantiomeric selectivity at the N-methyl-D-aspartate receptor and͞or different mechanisms for the promnestic function of the two enantiomers.spatial memory ͉ Y-maze ͉ N-methyl-D-aspartate receptor ͉ 2-amino-5-phosphovaleric acid ͉ rodents S teroids found in the brain, of peripheral origin or locally synthesized (neurosteroids), are known to exert modulatory actions on several functions in the central nervous system. Among them, the neurosteroid pregnenolone sulfate (3␤-hydroxy-5-pregnen-20-one sulfate, PREGS) has been well described as a potent steroidal enhancer of learning and memory processes in rodents (1-6). Of particular interest is the physiological role of PREGS in the hippocampus, which was recently demonstrated for the preservation of age-related spatial memory loss (4). With regards to the mechanism(s) underlying the promnestic action of this endogenous steroid, it is most likely occurring by regulating neurotransmitter receptor function [particularly ␥-aminobutyric acid type A (GABA A ) and N-methyl-D-aspartate (NMDA) receptor activities] in several brain regions (2,3,(7)(8)(9)(10)(11)(12)(13).Particularly relevant to the work here on enantiomeric steroids are the structure-activity data that have demonstrated a marked stereoselectivity for steroid regulation of neurotransmitter receptor function. For example, the endogenous 3␣-hydroxy ring A-reduced steroids, such as the neurosteroid allopregnanolone (3␣-hydroxy-5␣-pregnan-20-one), display potent positive-allosteric modulation of GABA A receptors (14-16) that may explain their anesthetic, anxiolytic, hypnotic, and anticonvulsant effects in animals (17). Conversely, epiallopregnanolone and pregnanolone, the respective 3␤-and 5␤-hydroxy-diastereomers of allopregnanolone (diastereomers having the opposite configuration at only one of multiple chiral centers, in this case at C-3 or C-5, also are known as epimers) are ineffective in potentiating GABA A receptors (18). Cognate evidence for a direct interaction betwe...

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“…The mRNAs encoding the 17␤-HORs isozymes 1, 3, 4 and 5 have also been detected and quantified in human brain and their respective levels showed no significant differences between men and women (Steckelbroeck et al, 2001b;Beyenburg et al, 2000). 17␤-HOR activity has been demonstrated in human fetal brain, in meningiomas (Knapstein et al, 1968;Jenkins and Hall, 1977;Carlson et al, 1994) and in temporal lobe biopsies from men and women suffering from epilepsy, and again, no sex differences were observed (Steckelbroeck et al, 1999b). When human SH-SY5Y neuroblastoma cells are incubated with testosterone, they form large amounts of androstenedione, indicative of catalysis by highly active 17␤-HOR (Wozniak et al, 1998).…”

Section: Steroids In the Aging Nervous System: The Endocrine Glands Amentioning

confidence: 97%

Steroid hormones and neurosteroids in normal and pathological aging of the nervous system

Schumacher

Weill-Engerer

Lière

et al. 2003

Progress in Neurobiology

261

170

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Without medical progress, dementing diseases such as Alzheimer's disease will become one of the main causes of disability. Preventing or delaying them has thus become a real challenge for biomedical research. Steroids offer interesting therapeutical opportunities for promoting successful aging because of their pleiotropic effects in the nervous system: they regulate main neurotransmitter systems, promote the viability of neurons, play an important role in myelination and influence cognitive processes, in particular learning and memory. Preclinical research has provided evidence that the normally aging nervous system maintains some capacity for regeneration and that age-dependent changes in the nervous system and cognitive dysfunctions can be reversed to some extent by the administration of steroids. The aging nervous system also remains sensitive to the neuroprotective effects of steroids. In contrast to the large number of studies documenting beneficial effects of steroids on the nervous system in young and aged animals, the results from hormone replacement studies in the elderly are so far not conclusive. There is also little information concerning changes of steroid levels in the aging human brain. As steroids present in nervous tissues originate from the endocrine glands (steroid hormones) and from local synthesis (neurosteroids), changes in blood levels of steroids with age do not necessarily reflect changes in their brain levels. There is indeed strong evidence that neurosteroids are also synthesized in human brain and peripheral nerves. The development of a very sensitive and precise method for the analysis of steroids by gas chromatography/mass spectrometry (GC/MS) offers new possibilities for the study of neurosteroids. The concentrations of a range of neurosteroids have recently been measured in various brain regions of aged Alzheimer's disease patients and aged non-demented controls by GC/MS, providing reference values. In Alzheimer's patients, there was a general trend toward lower levels of neurosteroids in different brain regions, and neurosteroid levels were negatively correlated with two biochemical markers of Alzheimer's disease, the phosphorylated tau protein and the ␤-amyloid peptides. The metabolism of dehydroepiandrosterone has also been analyzed for the first time in the aging brain from Alzheimer patients and non-demented controls. The conversion of dehydroepiandrosterone to 5-androstene-3␤,17␤-diol and to 7␣-OH-dehydroepiandrosterone occurred in frontal cortex, hippocampus, amygdala, cerebellum and striatum of both Alzheimer's patients and controls. The formation of these metabolites within distinct brain regions negatively correlated with the density of ␤-amyloid deposits.

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Metabolism of free and sulfoconjugated DHEA in brain tissue in vivo and in vitro

Cited by 80 publications

References 9 publications

Novel lipoidal derivatives of pregnenolone and dehydroepiandrosterone and absence of their sulfated counterparts in rodent brain

Novel lipoidal derivatives of pregnenolone and dehydroepiandrosterone and absence of their sulfated counterparts in rodent brain

The synthetic enantiomer of pregnenolone sulfate is very active on memory in rats and mice, even more so than its physiological neurosteroid counterpart: Distinct mechanisms?

Steroid hormones and neurosteroids in normal and pathological aging of the nervous system

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