Receptor binding and electrophysiological effects of dehydroepiandrosterone sulfate, an antagonist of the GABAA receptor

Neurosteroids and their potential as a safer class of general anesthetics

Neurosteroids (NS) are a class of steroids that are synthesized within the central nervous system (CNS). Various NS can either enhance or inhibit CNS excitability and they play important biological roles in brain development, brain function and as mediators of mood. One class of NS, 3α-hydroxy-pregnane steroids such as allopregnanolone (AlloP) or pregnanolone (Preg), inhibits neuronal excitability; these endogenous NS and their analogues have been therapeutically applied as anti-depressants, anti-epileptics and general anesthetics. While NS have many favorable properties as anesthetics (e.g. rapid onset, rapid recovery, minimal cardiorespiratory depression, neuroprotection), they are not currently in clinical use, largely due to problems with formulation. Recent advances in understanding NS mechanisms of action and improved formulations have rekindled interest in development of NS as sedatives and anesthetics. In this review, the synthesis of NS, and their mechanism of action will be reviewed with specific emphasis on their binding sites and actions on γ-aminobutyric acid type A (GABAA) receptors. The potential advantages of NS analogues as sedative and anesthetic agents will be discussed.

Analysis of the Effects of Pentose Phosphate Pathway Inhibition on the Generation of Reactive Oxygen Species and Epileptiform Activity in Hippocampal Slices

The pentose phosphate pathway (PPP) is one of three major pathways involved in glucose metabolism, which is regulated by glucose-6-phosphate dehydrogenase (G6PD) controls NADPH formation. NADPH, in turn, regulates the balance of oxidative stress and reactive oxygen species (ROS) levels. G6PD dysfunction, affecting the PPP, is implicated in neurological disorders, including epilepsy. However, PPP's role in epileptogenesis and ROS production during epileptic activity remains unclear. To clarify these points, we conducted electrophysiological and imaging analyses on mouse hippocampal brain slices. Using the specific G6PD inhibitor G6PDi-1, we assessed its effects on mouse hippocampal slices, examining intracellular ROS, glucose/oxygen consumption, the NAD(P)H level and ROS production during synaptic stimulation and in the 4AP epilepsy model. G6PDi-1 increased basal intracellular ROS levels and reduced synaptically induced glucose consumption but had no impact on baselevel of NAD(P)H and ROS production from synaptic stimulation. In the 4AP model, G6PDi-1 did not significantly alter spontaneous seizure frequency or H2O2 release amplitude but increased the frequency and peak amplitude of interictal events. These findings suggest that short-term PPP inhibition has a minimal impact on synaptic circuit activity.

Neurosteroids as positive and negative allosteric modulators of ligand-gated ion channels: P2X receptor perspective

Neurosteroids are steroids synthesized de novo in the brain from cholesterol in an independent manner from peripheral steroid sources. The term "neuroactive steroid" includes all steroids independent of their origin, and newly synthesized analogs of neurosteroids that modify neuronal activities. In vivo application of neuroactive steroids induces potent anxiolytic, antidepressant, anticonvulsant, sedative, analgesic and amnesic effects, mainly through interaction with the γ-aminobutyric acid type-A receptor (GABA_AR). However, neuroactive steroids also act as positive or negative allosteric regulators on several ligand-gated channels including N-methyl-d-aspartate receptors (NMDARs), nicotinic acetylcholine receptors (nAChRs) and ATP-gated purinergic P2X receptors. Seven different P2X subunits (P2X1-7) can assemble to form homotrimeric or heterotrimeric ion channels permeable for monovalent cations and calcium. Among them, P2X2, P2X4, and P2X7 are the most abundant within the brain and can be regulated by neurosteroids. Transmembrane domains are necessary for neurosteroid binding, however, no generic motif of amino acids can accurately predict the neurosteroid binding site for any of the ligand-gated ion channels including P2X. Here, we will review what is currently known about the modulation of rat and human P2X by neuroactive steroids and the possible structural determinants underlying neurosteroid-induced potentiation and inhibition of the P2X2 and P2X4 receptors.

Progesterone: A Steroid with Wide Range of Effects in Physiology as Well as Human Medicine

Progesterone is a steroid hormone traditionally linked with female fertility and pregnancy. In current reproductive medicine, progesterone and its analogues play crucial roles. While the discovery of its effects has a long history, over recent decades, various novel actions of this interesting steroid have been documented, of which its neuro- and immunoprotective activities are the most widely discussed. Discoveries of the novel biological activities of progesterone have also driven research and development in the field of progesterone analogues used in human medicine. Progestogen treatment has traditionally and predominately been used in maintaining pregnancy, the prevention of preterm labor, various gynecological pathologies, and in lowering the negative effects of menopause. However, there are also various other medical fields where progesterone and its analogues could find application in the future. The aim of this work is to show the mechanisms of action of progesterone and its metabolites, the physiological and pharmacological actions of progesterone and its synthetic analogues in human medicine, as well as the impacts of its production and use on the environment.

Fenfluramine modulates the anti-amnesic effects induced by sigma-1 receptor agonists and neuro(active)steroids in vivo

Fenfluramine (N-ethyl-α-methl-3-(trifluoromethyl)phenethylamine) is an anti-seizure medication (ASM) particularly effective in patients with Dravet syndrome, a severe treatment-resistant epileptic encephalopathy. Fenfluramine acts not only as neuronal serotonin (5-HT) releaser but also as a positive modulator of the sigma-1 receptor (S1R). We here examined the modulatory activity of Fenfluramine on the S1R-mediated anti-amnesic response in mice using combination analyses. Fenfluramine and Norfenfluramine, racemate and isomers, were combined with either the S1R agonist (PRE-084) or the S1R-acting neuro(active)steroids, pregnenolone sulfate (PREGS), Dehydroepiandrosterone sulfate (DHEAS), or progesterone. We report that Fenfluramine racemate or (+)-Fenfluramine, in the 0.1-1 mg/kg dose range, attenuated the dizocilpine-induced learning deficits in spontaneous alternation and passive avoidance, and showed low-dose synergies in combination with PRE-084. These effects were blocked by the S1R antagonist NE-100. Dehydroepiandrosterone sulfate or PREGS attenuated dizocilpine-induced learning deficits in the 5-20 mg/kg dose range. Co-treatments at low dose between steroids and Fenfluramine or (+)-Fenfluramine were synergistic. Progesterone blocked Fenfluramine effect. Finally, Fenfluramine and (+)-Fenfluramine effects were prevented by the 5-HT1A receptor antagonist WAY-100635 or 5-HT2A antagonist RS-127445, but not by the 5-HT1B/1D antagonist GR 127935 or the 5-HT2C antagonist SB 242084, confirming a 5-HT1A and 5-HT2A receptor involvement in the drug effect on memory. We therefore confirmed the positive modulation of Fenfluramine racemate or dextroisomer on S1R and showed that, in physiological conditions, the drug potentiated the low dose effects of neuro(active)steroids, endogenous S1R modulators. The latter are potent modulators of the excitatory/inhibitory balance in the brain, and their levels must be considered in the antiepileptic action of Fenfluramine.

The Sulfated Steroids Pregnenolone Sulfate and Dehydroepiandrosterone Sulfate Inhibit the α1β3γ2L GABAA Receptor by Stabilizing a Novel Nonconducting State

The GABAA receptor is inhibited by the endogenous sulfated steroids pregnenolone sulfate (PS) and dehydroepiandrosterone sulfate (DHEAS). It has been proposed in previous work that these steroids act by enhancing desensitization of the receptor. Here, we have investigated the modulatory effects of the steroids on the human α1β3γ2L GABAA receptor. Using electrophysiology and quantitative model-based data analysis, we show that exposure to the steroid promotes occupancy of a nonconducting state that retains high affinity to the transmitter but whose properties differ from those of the classic, transmitter-induced desensitized state. From the analysis of the inhibitory actions of two combined steroids, we infer that PS and DHEAS act through shared or overlapping binding sites. SIGNIFICANCE STATEMENT: Previous work has proposed that sulfated neurosteroids inhibit the GABAA receptor by enhancing the rate of entry into the desensitized state. This study shows that the inhibitory steroids pregnenolone sulfate and dehydroepiandrosterone sulfate act through a common interaction site by stabilizing a distinct nonconducting state.

Gut feelings: the microbiota-gut-brain axis on steroids

The intricate connection between central and enteric nervous systems is well established with emerging evidence linking gut microbiota function as a significant new contributor to gut-brain axis signaling. Several microbial signals contribute to altered gut-brain communications, with steroids representing an important biological class that impacts central and enteric nervous system function. Neuroactive steroids contribute pathologically to neurological disorders, including dementia and depression, by modulating the activity of neuroreceptors. However, limited information is available on the influence of neuroactive steroids on the enteric nervous system and gastrointestinal function. In this review, we outline how steroids can modulate enteric nervous system function by focusing on their influence on different receptors that are present in the intestine in health and disease. We also highlight the potential role of the gut microbiota in modulating neuroactive steroid signaling along the gut-brain axis.

Exploring the Impact of the Microbiome on Neuroactive Steroid Levels in Germ-Free Animals

Steroid hormones are essential biomolecules for human physiology as they modulate the endocrine system, nervous function and behaviour. Recent studies have shown that the gut microbiota is directly involved in the production and metabolism of steroid hormones in the periphery. However, the influence of the gut microbiota on levels of steroids acting and present in the brain (i.e., neuroactive steroids) is not fully understood. Therefore, using liquid chromatography–tandem mass spectrometry, we assessed the levels of several neuroactive steroids in various brain areas and the plasma of germ-free (GF) male mice and conventionally colonized controls. The data obtained indicate an increase in allopregnanolone levels associated with a decrease in those of 5α-androstane-3α, 17β-diol (3α-diol) in the plasma of GF mice. Moreover, an increase of dihydroprogesterone and isoallopregnanolone in the hippocampus, cerebellum, and cerebral cortex was also reported. Changes in dihydrotestosterone and 3α-diol levels were also observed in the hippocampus of GF mice. In addition, an increase in dehydroepiandrosterone was associated with a decrease in testosterone levels in the hypothalamus of GF mice. Our findings suggest that the absence of microbes affects the neuroactive steroids in the periphery and the brain, supporting the evidence of a microbiota-mediated modulation of neuroendocrine pathways involved in preserving host brain functioning.

Photoaffinity labeling identifies an intersubunit steroid-binding site in heteromeric GABA type A (GABAA) receptors

Allopregnanolone (3α5α-P), pregnanolone, and their synthetic derivatives are potent positive allosteric modulators (PAMs) of GABA_A receptors (GABA_ARs) with in vivo anesthetic, anxiolytic, and anti-convulsant effects. Mutational analysis, photoaffinity labeling, and structural studies have provided evidence for intersubunit and intrasubunit steroid-binding sites in the GABA_AR transmembrane domain, but revealed only little definition of their binding properties. Here, we identified steroid-binding sites in purified human α1β3 and α1β3γ2 GABA_ARs by photoaffinity labeling with [³H]21-[4-(3-(trifluoromethyl)-3H-diazirine-3-yl)benzoxy]allopregnanolone ([³H]21-pTFDBzox-AP), a potent GABA_AR PAM. Protein microsequencing established 3α5α-P inhibitable photolabeling of amino acids near the cytoplasmic end of the β subunit M4 (β3Pro-415, β3Leu-417, and β3Thr-418) and M3 (β3Arg-309) helices located at the base of a pocket in the β⁺-α^- subunit interface that extends to the level of αGln-242, a steroid sensitivity determinant in the αM1 helix. Competition photolabeling established that this site binds with high affinity a structurally diverse group of 3α-OH steroids that act as anesthetics, anti-epileptics, and anti-depressants. The presence of a 3α-OH was crucial: 3-acetylated, 3-deoxy, and 3-oxo analogs of 3α5α-P, as well as 3β-OH analogs that are GABA_AR antagonists, bound with at least 1000-fold lower affinity than 3α5α-P. Similarly, for GABA_AR PAMs with the C-20 carbonyl of 3α5α-P or pregnanolone reduced to a hydroxyl, binding affinity is reduced by 1,000-fold, whereas binding is retained after deoxygenation at the C-20 position. These results provide a first insight into the structure-activity relationship at the GABA_AR β⁺-α^- subunit interface steroid-binding site and identify several steroid PAMs that act via other sites.

Dehydroepiandrosterone (DHEA) and its Sulphate (DHEAS) in Alzheimer's Disease

BACKGROUND

Neurosteroids Dehydroepiandrosterone (DHEA) and Dehydroepiandrosterone Sulphate (DHEAS) are involved in many important brain functions, including neuronal plasticity and survival, cognition and behavior, demonstrating preventive and therapeutic potential in different neuropsychiatric and neurodegenerative disorders, including Alzheimer's disease.

OBJECTIVE

The aim of the article was to provide a comprehensive overview of the literature on the involvement of DHEA and DHEAS in Alzheimer's disease.

METHODS

PubMed and MEDLINE databases were searched for relevant literature. The articles were selected considering their titles and abstracts. In the selected full texts, lists of references were searched manually for additional articles.

RESULTS

We performed a systematic review of the studies investigating the role of DHEA and DHEAS in various in vitro and animal models, as well as in patients with Alzheimer's disease, and provided a comprehensive discussion on their potential preventive and therapeutic applications.

CONCLUSION

Despite mixed results, the findings of various preclinical studies are generally supportive of the involvement of DHEA and DHEAS in the pathophysiology of Alzheimer's disease, showing some promise for potential benefits of these neurosteroids in the prevention and treatment. However, so far small clinical trials brought little evidence to support their therapy in AD. Therefore, large-scale human studies are needed to elucidate the specific effects of DHEA and DHEAS and their mechanisms of action, prior to their applications in clinical practice.

Inhibition of cytochrome P450c17 reduces spinal astrocyte activation in a mouse model of neuropathic pain via regulation of p38 MAPK phosphorylation

We have recently demonstrated that the neurosteroid-metabolizing enzyme, cytochrome P450c17 is increased in spinal astrocytes contributing to the development of mechanical allodynia in chronic constriction injury (CCI)-induced neuropathic mice. However, the mechanisms by which spinal P450c17 modulates pathological changes in astrocytes remain unclear. In this study we investigated whether P450c17 modulates astrocyte activation and whether this process is mediated by spinal p38 mitogen-activated protein kinase phosphorylation ultimately leading to the development of mechanical allodynia in CCI mice. Sciatic nerve injury induced a significant increase in glial fibrillary acidic protein (GFAP) expression in the superficial dorsal horn (SDH, laminae I-II) and nucleus proprius (NP, laminae III-IV) regions of the spinal cord dorsal horn. Repeated daily (from days 0-3 post-surgery) intrathecal administration of the P450c17 inhibitor, ketoconazole (10 nmol) significantly inhibited the CCI-induced increase in GFAP-immunoreactivity, but had no effect on the CCI-induced increase in Iba-1-immunoreactivity. In addition, intrathecal administration of ketoconazole significantly inhibited the CCI-induced increase in p38 phosphorylation, while the levels of ERK and JNK phosphorylation remained unchanged. The CCI-induced development of mechanical allodynia was attenuated by administration of either ketoconazole (10 nmol) or the p38 MAPK inhibitor, SB203580 (5 nmol). Administration of a sub-effective dose of SB203580 (0.5 nmol) potentiated the pharmacological effect of ketoconazole (1 nmol) on spinal GFAP-immunostaining, as well as, the development of mechanical allodynia following CCI. Collectively these data suggest that spinal P450c17 activates astrocytes via p38 phosphorylation, ultimately leading to the development of mechanical allodynia in a model of peripheral neuropathy.

Cortisol and DHEA in development and psychopathology

Dehydroepiandrosterone (DHEA) and cortisol are the most abundant hormones of the human fetal and adult adrenals released as end products of a tightly coordinated endocrine response to stress. Together, they mediate short- and long-term stress responses and enable physiological and behavioral adjustments necessary for maintaining homeostasis. Detrimental effects of chronic or repeated elevations in cortisol on behavioral and emotional health are well documented. Evidence for actions of DHEA that offset or oppose those of cortisol has stimulated interest in examining their levels as a ratio, as an alternate index of adrenocortical activity and the net effects of cortisol. Such research necessitates a thorough understanding of the co-actions of these hormones on physiological functioning and in association with developmental outcomes. This review addresses the state of the science in understanding the role of DHEA, cortisol, and their ratio in typical development and developmental psychopathology. A rationale for studying DHEA and cortisol in concert is supported by physiological data on the coordinated synthesis and release of these hormones in the adrenal and by their opposing physiological actions. We then present evidence that researching cortisol and DHEA necessitates a developmental perspective. Age-related changes in DHEA and cortisol are described from the perinatal period through adolescence, along with observed associations of these hormones with developmental psychopathology. Along the way, we identify several major knowledge gaps in the role of DHEA in modulating cortisol in typical development and developmental psychopathology with implications for future research.

Effects of chronic alcohol consumption on neuronal function in the non-human primate BNST

Alterations in hypothalamic-pituitary-adrenal axis function contribute to many of the adverse behavioral effects of chronic voluntary alcohol drinking, including alcohol dependence and mood disorders; limbic brain structures such as the bed nucleus of the stria terminalis (BNST) may be key sites for these effects. Here, we measured circulating levels of several steroid hormones and performed whole-cell electrophysiological recordings from acutely prepared BNST slices of male rhesus monkeys allowed to self-administer alcohol for 12 months or a control solution. Initial comparisons revealed that BNST neurons in alcohol-drinking monkeys had decreased membrane resistance, increased frequency of spontaneous inhibitory postsynaptic currents (sIPSCs) with no change in spontaneous excitatory postsynaptic currents (sEPSCs). We then used a combined variable cluster analysis and linear mixed model statistical approach to determine whether specific factors including stress and sex hormones, age and measures of alcohol consumption and intoxication are related to these BNST measures. Modeling results showed that specific measures of alcohol consumption and stress-related hormone levels predicted differences in membrane conductance in BNST neurons. Distinct groups of adrenal stress hormones were negatively associated with the frequency of sIPSCs and sEPSCs, and alcohol drinking measures and basal neuronal membrane properties were additional positive predictors of inhibitory, but not excitatory, PSCs. The amplitude of sEPSCs was highly positively correlated with age, independent of other variables. Together, these results suggest that chronic voluntary alcohol consumption strongly influences limbic function in non-human primates, potentially via interactions with or modulation by other physiological variables, including stress steroid hormones and age.

Acute Effects of Oral Dehydroepiandrosterone on Counterregulatory Responses During Repeated Hypoglycemia in Healthy Humans

We tested the hypothesis that acute administration of oral dehydroepiandrosterone (DHEA) during episodes of repeated hypoglycemia can prevent the development of hypoglycemia-associated neuroendocrine and autonomic failure in healthy humans. Twenty-seven individuals (16 men, 11 women) participated in two separate randomized, single-blind, 2-day protocols. Day 1 consisted of morning and afternoon 2-h hypoglycemic clamps (2.9 mmol/L) with 800 mg of DHEA or placebo administered before each clamp. Day 2 consisted of a single 2-h hypoglycemic clamp (2.9 mmol/L) following either DHEA (1,600 mg) or placebo. A 3-tritiated glucose was used to determine glucose kinetics during hypoglycemia on day 2. Antecedent hypoglycemia with placebo resulted in significant reductions of epinephrine, norepinephrine, glucagon, growth hormone, cortisol, endogenous glucose production, and lipolytic and symptom responses. During hypoglycemia on day 2, DHEA prevented blunting of all neuroendocrine, autonomic nervous system (ANS), metabolic, and symptom counterregulatory responses following hypoglycemia on day 1. In summary, DHEA can acutely preserve a wide range of key neuroendocrine, ANS, and metabolic counterregulatory homeostatic responses during repeated hypoglycemia. We conclude that DHEA may have acute effects to protect against hypoglycemia-associated neuroendocrine and autonomic failure in healthy humans.

Effects of acute and chronic administration of neurosteroid dehydroepiandrosterone sulfate on neuronal excitability in mice

Background

Neurosteroid dehydroepiandrosterone sulfate (DHEAS) has been associated with important brain functions, including neuronal survival, memory, and behavior, showing therapeutic potential in various neuropsychiatric and cognitive disorders. However, the antagonistic effects of DHEAS on γ-amino-butyric acid_A receptors and its facilitatory action on glutamatergic neurotransmission might lead to enhanced brain excitability and seizures and thus limit DHEAS therapeutic applications. The aim of this study was to investigate possible age and sex differences in the neuronal excitability of the mice following acute and chronic DHEAS administration.

Methods

DHEAS was administered intraperitoneally in male and female adult and old mice either acutely or repeatedly once daily for 4 weeks in a 10 mg/kg dose. To investigate the potential proconvulsant properties of DHEAS, we studied the effects of acute and chronic DHEAS treatment on picrotoxin-, pentylentetrazole-, and N-methyl-D-aspartate-induced seizures in mice. The effects of acute and chronic DHEAS administration on the locomotor activity, motor coordination, and body weight of the mice were also studied. We also investigated the effects of DHEAS treatment on [³H]flunitrazepam binding to the mouse brain membranes.

Results

DHEAS did not modify the locomotor activity, motor coordination, body weight, and brain [³H]flunitrazepam binding of male and female mice. The results failed to demonstrate significant effects of single- and long-term DHEAS treatment on the convulsive susceptibility in both adult and aged mice of both sexes. However, small but significant changes regarding sex differences in the susceptibility to seizures were observed following DHEAS administration to mice.

Conclusion

Although our findings suggest that DHEAS treatment might be safe for various potential therapeutic applications in adult as well as in old age, they also support subtle interaction of DHEAS with male and female hormonal status, which may underline observed sex differences in the relationship between DHEAS and various health outcomes.

Novel dehydroepiandrosterone troche supplementation improves the serum androgen profile of women undergoing in vitro fertilization

Dehydroepiandrosterone (DHEA) is the most abundant steroid hormone in the circulation and has potent multifunctional activity. Epidemiological evidence suggests that levels of serum DHEA decrease with advancing age, and this has been associated with onset or progression of various age-related ailments, including cognitive decline and dementia, cardiovascular disease, and obesity. Consequently, these findings have sparked intense research interest in DHEA supplementation as an "antiaging" therapy. Currently, DHEA is being used by 25% of in vitro fertilization (IVF) clinicians as an adjuvant in assisted reproductive programs, yet the therapeutic benefit of DHEA is unclear. Here, we examined the use of novel DHEA-containing oral troches in patients undertaking IVF and investigated the impact of these troches on their serum androgen profile. This retrospective study determined the androgen profile of 31 IVF patients before (baseline) and after DHEA supplementation (with DHEA). Baseline serum measurements of testosterone (total and free), DHEA sulfate (DHEAS), sex hormone-binding globulin (SHBG), and androstenedione were made before and after supplementation. Each patient received DHEA troches containing 25 mg of micronized DHEA, and troches were administered sublingually twice daily for a period of no greater than 4 months. Adjuvant treatment with DHEA boosted the serum concentration of a number of androgen-related analytes, including total and free testosterone, androstenedione, and DHEAS, while serum SHBG remained unchanged. Supplementation also significantly increased the free-androgen index in IVF patients. Interestingly, the increase in serum analyte concentration following DHEA supplementation was found to be dependent on body mass index (BMI), but not individual age. Patients with the lowest BMI (<20.0 kg/m(2)) tended to have lower testosterone and DHEAS, but higher SHBG and androstenedione levels in comparison with other BMI groups postsupplementation. However, patients in the highest BMI group (>30.0 kg/m(2)) tended to have lower androgen responses following DHEA supplementation, but these were not statistically different from the corresponding baseline level. This method of DHEA administration results in a similar enhancement of testosterone, DHEAS, and androstenedione levels in comparison with other methods of administration. Furthermore, we showed that BMI significantly influences DHEA uptake and metabolism, and that BMI should be carefully considered during dosage calculation to ensure a significant and robust androgen-profile boost.

Inhibition of the GABAA Receptor by Sulfated Neurosteroids: A Mechanistic Comparison Study between Pregnenolone Sulfate and Dehydroepiandrosterone Sulfate

The γ-aminobutyric acid type A receptor (GABAAR) is negatively modulated by two structurally similar neurosteroids, pregnenolone sulfate (PS) and dehydroepiandrosterone sulfate (DHEAS). This study attempted to ascertain the molecular mechanisms of inhibition of the GABA-ergic current by neurosteroids. We demonstrated that the presence of the γ subunit in GABAAR enhances the efficacy of DHEAS without altering its binding affinity. A saturating concentration of DHEAS blocked approximately 75 % of currents mediated by GABAAR, which is composed of human α1, β1, and γ2S subunits, whereas the inhibition was only 35 % in GABAAR containing only α1 and β1 subunits. The IC50 values of DHEAS with and without the γ subunit were almost identical. In contrast to DHEAS, neither the affinity nor the efficacy of PS was altered by the γ subunit. When Val256 of α1 subunit was mutated to Ser, the mutant channel became resistant to inhibition by both DHEAS and PS. PS exerted its inhibitory effect by enhancing the desensitization kinetics of GABAAR possibly through promoting the interaction between the M2-M3 linker and extracellular loop 7/loop 2. Mutant α1, containing double Cys in loop 2/loop 7 and the M2-M3 linker, formed disulfide bonds three times as much fast, when treated with saturating GABA+PS, compared with GABA alone or with GABA+DHEAS. We demonstrated that PS, but not DHEAS, mediates GABA-ergic inhibition by promoting collisions between the structural elements involved in receptor desensitization, i.e., loop 2, loop 7, and the M2-M3 linker, thus following different inhibitory mechanisms.

Dehydroepiandrosterone, its metabolites and ion channels

This review is focused on the physiological and pathophysiological relevance of steroids influencing the activities of the central and peripheral nervous systems with regard to their concentrations in body fluids and tissues in various stages of human life like the fetal development or pregnancy. The data summarized in this review shows that DHEA and its unconjugated and sulfated metabolites are physiologically and pathophysiologically relevant in modulating numerous ion channels and participate in vital functions of the human organism. DHEA and its unconjugated and sulfated metabolites including 5α/β-reduced androstane steroids participate in various physiological and pathophysiological processes like the management of GnRH cyclic release, regulation of glandular and neurotransmitter secretions, maintenance of glucose homeostasis on one hand and insulin insensitivity on the other hand, control of skeletal muscle and smooth muscle activities including vasoregulation, promotion of tolerance to ischemia and other neuroprotective effects. In respect of prevalence of steroid sulfates over unconjugated steroids in the periphery and the opposite situation in the CNS, the sulfated androgens and androgen metabolites reach relevance in peripheral organs. The unconjugated androgens and estrogens are relevant in periphery and so much the more in the CNS due to higher concentrations of most unconjugated steroids in the CNS tissues than in circulation and peripheral organs. This article is part of a Special Issue entitled "Essential role of DHEA".

DHEA and cognitive function in the elderly

The adrenal prohormone dehydroepiandrosterone (DHEA) and its sulphate conjugate (DHEAS) steadily decrease with age by 10% per decade reaching a nadir after the age of 80. Both DHEA and DHEAS (DHEA/S) exert many biological activities in different tissues and organs. In particular, DHEA and DHEAS are produced de novo in the brain, hence their classification as neurosteroids. In humans, the brain-to-plasma ratios for DHEA and DHEAS are 4-6.5 and 8.5, respectively, indicating a specific neuroendocrine role for these hormones. DHEA/S stimulates neurite growth, neurogenesis and neuronal survival, apoptosis, catecholamine synthesis and secretion. Together with antioxidant, anti-inflammatory and anti-glucocorticoid properties, it has been hypothesized a neuroprotective effect for DHEA/S. We conducted an accurate research of the literature using PubMed. In the period of time between 1994 and 2013, we selected the observational human studies testing the relationship between DHEA/S and cognitive function in both sexes. The studies are presented according to the cross-sectional and longitudinal design and to the positive or neutral effects on different domains of cognitive function. We also analysed the Clinical Trials, available in the literature, having cognitive domains as the main or secondary outcome. Although the cross-sectional evidence of a positive association between DHEA/S and cognitive function, longitudinal studies and RCTs using DHEA oral treatment (50mg/day) in normal or demented adult-older subjects, have produced conflicting and inconsistent results. In summary, the current data do not provide clear evidence for the usefulness of DHEA treatment to improve cognitive function in adult-older subjects. This article is part of a Special Issue entitled 'Essential role of DHEA'.

Depression, Anxiety, and Anger in Patients with Polycystic Ovary Syndrome

INTRODUCTION

Polycystic Ovary Syndrome (PCOS) is a syndrome of heterogeneous nature, affecting multiple systems, particularly the endocrine system. We propose to investigate the possible relationships among hormonal changes, levels of anxiety, depression, and anger in patients with PCOS.

METHOD

Forty-four female patients with PCOS and 44 body mass index (BMI )-matched healthy women participated in this study. We measured the sociodemographic features, some serum hormonal levels (insulin, gonadotropins, prolactin, dehydroepiandrosterone sulfate (DHEAS), thyroid-stimulating hormone (TSH), triiodothyronine (T3), thyroxine (T4), 17 OH-progesterone, and total and free testosterone), and some other biochemical parameters of the participants. Also, all participants completed the Trait Anger-Anger Expression Scale (STAS), Beck Depression, and Beck Anxiety Inventories. We evaluated the psychiatric scale scores obtained from PCOS patients and control subjects. We used the independent-samples t-test for parametric data to evaluate normal distribution, and Mann-Whitney U-test was used for both abnormally distributed and nonparametric data. We used Pearson correlation analysis to evaluate the potential connection between the two groups' data.

RESULTS

The mean ages of the patients with PCOS and control subjects who participated in this study were 27.3±5.6 and 27.4±6.1 years, respectively. The measures of BMI, insulin, luteinizing hormone (LH), DHEAS, and total testosterone serum levels in the patient group were significantly higher than in the control group (p<.05). There was a statistically significant positive correlation between Beck anxiety scores and serum DHEAS levels (Pearson r=.4366, P=.0001). We found significant differences between the two groups in terms of trait anger, anger control, outward and inward anger, anxiety level, and depression scores (P<.05).

CONCLUSION

Anxiety symptoms indicate a stronger relationship compared to depression with DHEAS serum levels via the autonomic nervous system, considering the gamma-aminobutyric acid (GABA)-antagonistic effect of DHEAS. Obesity, hirsutism, and infertility may reduce self-confidence and create depressive symptoms in patients with PCOS. In addition, changes in hormonal levels may lead to anxiety directly. Possibly, depressive symptoms are a secondary reflection of these changes.

Reactive oxygen species initiate a metabolic collapse in hippocampal slices: potential trigger of cortical spreading depression

Excessive accumulation of reactive oxygen species (ROS) underlies oxidative damage. We find that in hippocampal slices, decreased activity of glucose-based antioxidant system induces a massive, abrupt, and detrimental change in cellular functions. We call this phenomenon metabolic collapse (MC). This collapse manifested in long-lasting silencing of synaptic transmission, abnormal oxidation of NAD(P)H and FADH2 associated with immense oxygen consumption, and massive neuronal depolarization. MC occurred without any preceding deficiency in neuronal energy supply or disturbances of ionic homeostasis and spread throughout the hippocampus. It was associated with a preceding accumulation of ROS and was largely prevented by application of an efficient antioxidant Tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl). The consequences of MC resemble cortical spreading depression (CSD), a wave of neuronal depolarization that occurs in migraine, brain trauma, and stroke, the cellular initiation mechanisms of which are poorly understood. We suggest that ROS accumulation might also be the primary trigger of CSD. Indeed, we found that Tempol strongly reduced occurrence of CSD in vivo, suggesting that ROS accumulation may be a key mechanism of CSD initiation.

Dehydroepiandrosterone (DHEA) blocks the increase in food intake caused by neuropeptide Y (NPY) in the Zucker rat

Recent studies have demonstrated that neuropeptide Y (NPY) reduced the neural production of dehydroepiandrosterone (DHEA) in frog hypothalamic explants. The objective of this study was to assess if DHEA can block the NPY induced increase in food intake in lean and obese Zucker rats. Rats were given one of the following four treatments: sterile water/dimethylsulfoxide (DMSO), NPY/DMSO, water/DHEA, and NPY/DHEA. Immediately after administration of their respective treatment, rats were exposed to macronutrients for 4 h and food intake was monitored. NPY caused a significant increase in total calories consumed compared to control. Co-administration of DHEA along with NPY blocked this NPY dependent effect. These results suggest that DHEA blocks the over-eating in satiated rats induced by NPY. Measurement of changes in regional hypothalamic and raphe monoamine neurotransmitters known to affect food intake suggested a possible role of serotonin fluctuations in the ventromedial hypothalamus (VMH) guiding this behaviour.

Serum dehydroepiandrosterone (DHEA) and DHEA-sulfate (S) levels in medicated patients with major depressive disorder compared with controls

BACKGROUND

There is accumulating evidence regarding gender differences in clinical symptoms or response to antidepressants in patients with depression. However, less attention has been given to sex differences in the underlying biological mechanisms of depression. The adrenal androgens, dehydroepiandrosterone (DHEA) and its sulfate derivative (DHEA-S), play a critical role in controlling affect, mood, and anxiety. Changes in serum adrenal androgen levels have been reported in conditions pertaining to stress as well as in psychiatric disorders. The objective of the present study was to investigate differences in serum levels of adrenal androgens in male and female patients with major depressive disorder (MDD).

METHODS

Participants included 90 inpatients with MDD at the psychiatric ward of Juntendo University Koshigaya Hospital who were receiving antidepressants. Serum levels of DHEA and DHEA-S were assessed at the time of admission. Matched controls (based on sex and age) included 128 healthy individuals. First, data from male and female MDD patients and controls were compared. Second, correlations between serum hormone levels and scores on the Hamilton Rating Scale for Depression (HAM-D) of patients with MDD were assessed by gender. In addition, effects of various factors on adrenal androgens were analyzed using multiple regression analysis.

RESULTS

Serum DHEA levels were significantly increased in both male and female MDD patients compared with controls. Serum levels of DHEA-S in male patients were significantly decreased compared with male controls, whereas no significant differences were seen in female patients and controls. No significant correlations among adrenal androgens were observed in male patients with MDD, whereas significant positive correlations were found in both male and female controls. No significant correlations were seen between adrenal androgens and HAM-D scores in male or female patients. Multiple regression analysis showed that both hormones were affected by the age at onset of depression.

LIMITATIONS

All subjects in the present study were on antidepressant medications.

CONCLUSIONS

Elevated levels of serum DHEA may be associated with the biological pathophysiology of depression, as DHEA administration has been found to be effective for the treatment of depression. Findings of differential changes in DHEA-S levels in men compared with women may suggest distinct characteristics of these hormones between men and women with depression. However, DHEA/DHEA-S may be a poor indicator for evaluating severity of depression.

Active sulforhodamine 101 uptake into hippocampal astrocytes

Sulforhodamine 101 (SR101) is widely used as a marker of astrocytes. In this study we investigated labeling of astrocytes by SR101 in acute slices from the ventrolateral medulla and the hippocampus of transgenic mice expressing EGFP under the control of the astrocyte-specific human GFAP promoter. While SR101 efficiently and specifically labeled EGFP-expressing astrocytes in hippocampus, we found that the same staining procedure failed to label astrocytes efficiently in the ventrolateral medulla. Although carbenoxolone is able to decrease the SR101-labeling of astrocytes in the hippocampus, it is unlikely that SR101 is taken up via gap-junction hemichannels because mefloquine, a blocker for pannexin and connexin hemichannels, was unable to prevent SR101-labeling of hippocampal astrocytes. However, SR101-labeling of the hippocampal astrocytes was significantly reduced by substrates of organic anion transport polypeptides, including estron-3-sulfate and dehydroepiandrosterone sulfate, suggesting that SR101 is actively transported into hippocampal astrocytes.

Reduced brain levels of DHEAS in hepatic coma patients: significance for increased GABAergic tone in hepatic encephalopathy

Increased neurosteroids with allosteric modulatory activity on GABA(A) receptors such as 3α-5α tertrahydroprogesterone; allopregnanolone (ALLO), are candidates to explain the phenomenon of "increased GABAergic tone" in hepatic encephalopathy (HE). However, it is not known how changes of other GABA(A) receptor modulators such as dehydroepiandrosterone sulfate (DHEAS) contribute to altered GABAergic tone in HE. Concentrations of DHEAS were measured by radioimmunoassay in frontal cortex samples obtained at autopsy from 11 cirrhotic patients who died in hepatic coma and from an equal number of controls matched for age, gender, and autopsy delay intervals free from hepatic or neurological diseases. To assess whether reduced brain DHEAS contributes to increased GABAergic tone, in vitro patch clamp recordings in rat prefrontal cortex neurons were performed. A significant reduction of DHEAS (5.81±0.88 ng/g tissue) compared to control values (9.70±0.79 ng/g, p<0.01) was found. Brain levels of DHEAS in patients with liver disease who died without HE (11.43±1.74 ng/g tissue), and in a patient who died in uremic coma (12.56 ng/g tissue) were within the control range. Increasing ALLO enhances GABAergic tonic currents concentration-dependently, but increasing DHEAS reduces these currents. High concentrations of DHEAS (50 μM) reduce GABAergic tonic currents in the presence of ALLO, whereas reduced concentrations of DHEAS (1 μM) further stimulate these currents. These findings demonstrate that decreased concentrations of DHEAS together with increased brain concentrations of ALLO increase GABAergic tonic currents synergistically; suggesting that reduced brain DHEAS could further increase GABAergic tone in human HE.

Dehydroepiandrosterone sulphate: action and mechanism in the brain

Dehydroepiandrosterone sulphate (DHEAS) is synthesised from dehydroepiandrosterone by the enzyme sulphotransferase. DHEAS is one of the most important neurosteroids in the brain. The concentration of DHEAS in the brain is sometimes higher than peripheral system. At the cellular level, DHEAS has been shown to modulate a variety of synaptic transmission, including cholinergic, GABAergic dopaminergic and glutamatergic synaptic transmission. In addition to the effect on the release of a number of neurotransmitters, DHEAS could also modulate the activity of postsynaptic receptors. DHEAS has been found to have multiple important effects on brain functions, such as memory enhancing, antidepressant and anxiolytic effects, and may have relationships with many brain diseases.

Cis-isomerism and other chemical requirements of steroidal agonists and partial agonists acting at TRPM3 channels

BACKGROUND AND PURPOSE

The transient receptor potential melastatin-3 (TRPM3) channel forms calcium-permeable, non-selective, cationic channels that are stimulated by pregnenolone sulphate (PregS). Here, we aimed to define chemical requirements of this acute steroid action and potentially reveal novel stimulators with physiological relevance.

EXPERIMENTAL APPROACH

We used TRPM3 channels over-expressed in HEK 293 cells, with intracellular calcium measurement and whole-cell patch-clamp recording techniques.

KEY RESULTS

The stimulation of TRPM3 channels was confined to PregS and closely related steroids and not mimicked by other major classes of steroids, including progesterone. Relatively potent stimulation of TRPM3-dependent calcium entry was observed. A sulphate group positioned at ring A was important for strong stimulation but more striking was the requirement for a cis (beta) configuration of the side group, revealing previously unrecognized stereo-selectivity and supporting existence of a specific binding site. A cis-oriented side group on ring A was not the only feature necessary for high activity because loss of the double bond in ring B reduced potency and loss of the acetyl group at ring D reduced efficacy and potency. Weak steroid stimulators of TRPM3 channels inhibited effects of PregS, suggesting partial agonism. In silico screening of chemical libraries for non-steroid modulators of TRPM3 channels revealed the importance of the steroid backbone for stimulatory effects.

CONCLUSIONS AND IMPLICATIONS

Our data defined some of the chemical requirements for acute stimulation of TRPM3 channels by steroids, supporting the existence of a specific and unique steroid binding site. Epipregnanolone sulphate was identified as a novel TRPM3 channel stimulator.

Neurosteroids and GABA-A Receptor Function

Neurosteroids represent a class of endogenous steroids that are synthesized in the brain, the adrenals, and the gonads and have potent and selective effects on the GABAA-receptor. 3α-hydroxy A-ring reduced metabolites of progesterone, deoxycorticosterone, and testosterone are positive modulators of GABA(A)-receptor in a non-genomic manner. Allopregnanolone (3α-OH-5α-pregnan-20-one), 5α-androstane-3α, 17α-diol (Adiol), and 3α5α-tetrahydrodeoxycorticosterone (3α5α-THDOC) enhance the GABA-mediated Cl(-) currents acting on a site (or sites) distinct from the GABA, benzodiazepine, barbiturate, and picrotoxin binding sites. 3α5α-P and 3α5α-THDOC potentiate synaptic GABA(A)-receptor function and activate δ-subunit containing extrasynaptic receptors that mediate tonic currents. On the contrary, 3β-OH pregnane steroids and pregnenolone sulfate (PS) are GABA(A)-receptor antagonists and induce activation-dependent inhibition of the receptor. The activities of neurosteroid are dependent on brain regions and types of neurons. In addition to the slow genomic action of the parent steroids, the non-genomic, and rapid actions of neurosteroids play a significant role in the GABA(A)-receptor function and shift in mood and memory function. This review describes molecular mechanisms underlying neurosteroid action on the GABA(A)-receptor, mood changes, and cognitive functions.

The neurosteroid dehydroepiandrosterone (DHEA) and its metabolites alter 5-HT neuronal activity via modulation of GABAA receptors

Dehydroepiandrosterone (DHEA) and its metabolites, DHEA-sulphate (DHEA-S) and androsterone, have neurosteroid activity. In this study, we examined whether DHEA, DHEA-S and androsterone, can influence serotonin (5-HT) neuronal firing activity via modulation of γ-aminobutryic acid (GABA(A)) receptors. The firing of presumed 5-HT neurones in a slice preparation containing rat dorsal raphe nucleus was inhibited by the GABA(A) receptor agonists 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridinyl-3-ol (THIP) (25 μM) and GABA (100 μM). DHEA (100 and 300 μM) and DHEA-S (1, 10 and 100 μM) caused a rapid and reversible attenuation of the response to THIP. DHEA (100 μM) and DHEA-S (100 μM) also attenuated the effect of GABA. Androsterone (10 and 30 μM) markedly enhanced the inhibitory response to THIP (25 μM). The effect was apparent during androsterone administration but persisted and even increased in magnitude after drug wash-out. The data indicate that GABA(A) receptor-mediated regulation of 5-HT neuronal firing is sensitive to negative modulation by DHEA and its metabolite DHEA-S is sensitive to positive modulation by the metabolite androsterone. The effects of these neurosteroids on GABA(A) receptor-mediated regulation of 5-HT firing may underlie some of the reported behavioural and psychological effects of endogenous and exogenous DHEA.

The influence of the membrane on neurosteroid actions at GABA(A) receptors

Modern views of anesthetic neurosteroid interaction with the GABA(A) receptor conceptualize steroid ligands interacting with a protein binding site on the receptor. It has generally been assumed that the steroid interaction/binding site is contained in an extracellular domain of the receptor, and that steroid interactions are of high potency, evidenced by the low aqueous ligand concentrations required to achieve potentiation of channel function. We have been considering implications of the observations that steroids are quite lipophilic and that recently identified putative steroid binding sites are in transmembrane domains of the receptor. Accordingly, we expect that both the effective plasma membrane steroid concentration and steroid pharmacophore properties will contribute to steady-state potency and to the lifetime of steroid actions following removal of free aqueous steroid. Here we review our recent studies that address the evidence that membrane partitioning and intracellular accumulation are non-specific contributors to the effects of anesthetic steroids at GABA(A) receptors. We compare and contrast the profile of anesthetic steroids with that of sulfated steroids that negatively regulate GABA(A) receptor function. These studies give rise to the view that the inherent affinity of anesthetic steroid for GABA(A) receptors is very low; low effective aqueous concentrations are accounted for by lipid partitioning. This yields a very different picture of the interaction of neurosteroids with the GABA(A) receptor than that of steroid interactions with classical intracellular steroid receptors, which exhibit inherently high affinity. These considerations have practical implications for actions of endogenous neurosteroids. Lipophilicity will tend to promote autocrine actions of neurosteroids at GABA(A) receptors within cells that synthesize neurosteroids, and lipophilic retention will limit intercellular diffusion from the source of steroid synthesis. Lipophilicity and steroid access to the receptor binding sites also must be considerations in drug design if drugs are to effectively reach the target GABA(A) receptor site.

Dehydroepiandrosterone sulfate and cognitive function in the elderly: The InCHIANTI Study

DHEA and its sulfate derivative (DHEAS) decline with age. The decline in DHEAS levels has been associated with many physiological impairments in older persons including cognitive dysfunction. However, data regarding the possible relationship between DHEAS and cognition are scant. We investigated whether DHEAS levels are associated with presence and development of lower cognitive function measured by the Mini Mental State Examination (MMSE) in older men and women. One thousand and thirty-four residents aged > or =65 yr of the InCHIANTI Study with data available on DHEAS and MMSE were randomly selected. MMSE was administered at baseline and 3 yr later. Among these, 841 completed a 3-yr follow-up. Parsimonious models obtained by backward selection from initial fully-adjusted models were used to identify independent factors associated with MMSE and DHEAS. The final analysis was performed in 755 participants (410 men and 345 women) with MMSE score > or =21. A significant age-related decline of both DHEAS levels (p<0.001) and MMSE score (p<0.001) was found over the 3-yr follow-up. At enrolment, DHEAS was significantly and positively associated with MMSE score, independently of age and other potential confounders (beta+/-SE 0.003+/-0.001, p<0.005). Low baseline DHEAS levels were predictive of larger decline of MMSE and this relationship was significant after adjusting for covariates (beta+/-SE -0.004+/-0.002, p<0.03). Our data show a significant and positive association between DHEAS and cognitive function, assessed by MMSE test. Low DHEAS levels predict accelerated decline in MMSE score during the 3-yr follow-up period.

Relationships among plasma dehydroepiandrosterone and dehydroepiandrosterone sulfate, cortisol, symptoms of dissociation, and objective performance in humans exposed to underwater navigation stress

BACKGROUND

A growing body of research has provided evidence that dehydroepiandrosterone (DHEA) and dehydroepiandrosterone sulfate (DHEAS) are involved in an organism's response to stress and that it may provide beneficial behavioral and neurotrophic effects.

METHODS

This study investigated plasma DHEA and DHEAS, cortisol, psychological symptoms of dissociation, and military performance in 41 healthy active duty subjects enrolled in the military Combat Diver Qualification Course (CDQC).

RESULTS

Baseline values of DHEA and DHEAS were significantly and positively predictive of superior performance in the underwater navigation exam; in addition, DHEA and DHEAS were significantly and negatively related to stress-induced symptoms of dissociation during performance of the task. Similarly, participants who reported fewer symptoms of dissociation exhibited superior military performance and increased levels of DHEA after the test.

CONCLUSIONS

These data provide prospective, empiric evidence that DHEA and DHEAS are associated with superior stress tolerance, fewer symptoms of dissociation, and superior, objectively assessed, military performance.

Intrathecal injection of the neurosteroid, DHEAS, produces mechanical allodynia in mice: involvement of spinal sigma-1 and GABA receptors

BACKGROUND AND PURPOSE

The neurosteroid, dehydroepiandrosterone sulphate (DHEAS) and its non-sulphated form, DHEA, are considered as crucial endogenous modulators of a number of important physiological events. Evidence suggests that DHEAS and DHEA modulate central nervous system-related functions by activating sigma-1 receptors and/or allosterically inhibiting gamma-aminobutyric acid receptor type A (GABA(A)) receptors. As both the sigma-1 receptor and the GABA(A) receptor play important roles in spinal pain transmission, the present study was designed to examine whether intrathecally injected DHEAS or DHEA affect nociceptive signalling at the spinal cord level.

EXPERIMENTAL APPROACH

We first determined whether intrathecal (i.t.) DHEA or DHEAS injection was able to affect nociceptive thresholds to peripheral mechanical stimulation and subsequently examined whether this effect was mediated by sigma-1 or the GABA(A) receptors.

KEY RESULTS

The i.t. DHEAS injection dose-dependently decreased the nociceptive threshold to mechanical stimulation, thus producing mechanical allodynia. Moreover, this DHEAS-induced mechanical allodynia was significantly reduced by administration of the sigma-1 receptor antagonist, BD-1047 or the GABA(A) receptor agonist, muscimol. Conversely, i.t. DHEA had no effect on mechanical sensitivity. However, when i.t. DHEA was combined with the GABA(A) receptor antagonist bicuculline, DHEA dose-dependently produced mechanical allodynia similar to that of DHEAS. This effect was blocked by BD-1047 and by muscimol.

CONCLUSIONS AND IMPLICATIONS

These findings indicate that i.t. injection of DHEAS produces mechanical allodynia and that the development of this mechanical allodynia is mediated by sigma-1 and GABA(A) receptors. The findings of this study raise several interesting questions for further investigations into the mechanisms underlying neurosteroid modulation of spinal pain transmission.

Photoperiodic modulation of adrenal gland function in the rhesus macaque: effect on 24-h plasma cortisol and dehydroepiandrosterone sulfate rhythms and adrenal gland gene expression

In temperate zones, day length changes markedly across the year, and in many mammals these photoperiodic variations are associated with physiological adaptations. However, the influence of this environmental variable on human behavior and physiology is less clear, and the potential underlying mechanisms are unknown. To address this issue, we examined the effect of changing photoperiods on adrenal gland function in ovariectomized female rhesus macaques (Macaca mulatta), both in terms of steroid hormone output and in terms of gene expression. The animals were sequentially exposed to the following lighting regimens, which were designed to simulate photoperiods associated with winter, spring/autumn and summer respectively: 8 h light:16 h darkness (short days), 12 h light:12 h darkness and 16 h light:8 h darkness (long days). Remote 24-h serial blood sampling failed to disclose any effect of photoperiod on mean or peak plasma levels of cortisol or dehydroepiandrosterone sulfate. However, there was a marked phase-advancement of both hormonal rhythms in short days, which was reflected as a similar phase-advancement of the daily motor activity rhythm. Gene microarray analysis of the adrenal gland transcriptome revealed photoperiod-induced differences in the expression of genes associated with homeostatic functions, including: development, lipid synthesis and metabolism, and immune function. Taken together, the results indicate that in primates, both circadian adrenal physiology and gene expression are influenced by seasonal changes in day length, which may have implications for adrenal-regulated physiology and behavior.

Discriminative stimulus effects of ethanol, pregnanolone, and dehydroepiandrosterone (DHEA) in rats administered ethanol or saline as adolescents

Adolescent alcohol use may produce long-term changes in the receptors and neurosteroids that putatively mediate alcohol's effects and consequently contribute to alcohol abuse and dependence as an adult. To test this possibility, ethanol (0.18-1.8 g/kg) and two neurosteroids, pregnanolone (1-10 mg/kg) and dehydroepiandrosterone (DHEA, 1-100 mg/kg), were administered alone and in combination to adult, male Long-Evans rats discriminating 1 g/kg ethanol (15% v/v) under a fixed ratio (FR) 20 schedule of food presentation after adolescent treatment with 15 injections of ethanol (n = 9, 2 g/kg, 20% v/v) or saline (n = 7). When compared as adults, ethanol-treated adolescents (as opposed to saline-treated adolescents) had higher percentages of ethanol-lever responding at doses smaller than the training dose, and higher response rates after both control and ethanol injections. Neither pregnanolone nor DHEA substituted for ethanol in either adolescent-treated group up to doses that substantially decreased response rates. When administered with ethanol, 1 and 3.2 mg/kg of pregnanolone enhanced the discriminative stimulus effects of small ethanol doses more in saline-treated adolescents than in ethanol-treated adolescents. Unlike pregnanolone, 32 and 100 mg/kg of DHEA attenuated the discriminative stimulus effects of ethanol modestly in both adolescent-treated groups. These results in adult rats suggest that adolescent ethanol administration can enhance the discriminative stimulus effects of small ethanol doses and affect the capacity of pregnanolone, but not DHEA, to interact with ethanol's discriminative stimulus effects.

Genome-wide analysis of DHEA- and DHT-induced gene expression in mouse hypothalamus and hippocampus

Dehydroepiandrosterone (DHEA) is the most abundant steroid in humans and a multi-functional neuroactive steroid that has been implicated in a variety of biological effects in both the periphery and central nervous system. Mechanistic studies of DHEA in the periphery have emphasized its role as a prohormone and those in the brain have focused on effects exerted at cell surface receptors. Recent results demonstrated that DHEA is intrinsically androgenic. It competes with DHT for binding to androgen receptor (AR), induces AR-regulated reporter gene expression in vitro, and exogenous DHEA administration regulates gene expression in peripheral androgen-dependent tissues and LnCAP prostate cancer cells, indicating genomic effects and adding a level of complexity to functional models. The absence of information about the effect of DHEA on gene expression in the CNS is a significant gap in light of continuing clinical interest in the compound as a hormone replacement therapy in older individuals, patients with adrenal insufficiency, and as a treatment that improves sense of well-being, increases libido, relieves depressive symptoms, and serves as a neuroprotective agent. In the present study, ovariectomized CF-1 female mice, an established model for assessing CNS effects of androgens, were treated with DHEA (1mg/day), dihydrotestosterone (DHT, a potent androgen used as a positive control; 0.1mg/day) or vehicle (negative control) for 7 days. The effects of DHEA on gene expression were assessed in two regions of the CNS that are enriched in AR, hypothalamus and hippocampus, using DNA microarray, real-time RT-PCR, and immunohistochemistry. RIA of serum samples assessed treatment effects on circulating levels of major steroids. In hypothalamus, DHEA and DHT significantly up-regulated the gene expression of hypocretin (Hcrt; also called orexin), pro-melanin-concentrating hormone (Pmch), and protein kinase C delta (Prkcd), and down-regulated the expression of deleted in bladder cancer chromosome region candidate 1 (Dbccr1) and chitinase 3-like 3 (Chi3l3). Two-step real-time RT-PCR confirmed changes in the expression of three genes (Pmch, Hcrt and Prkcd) using the same RNA sample employed in the microarray experiment. Immunohistochemistry showed augmentation of prepro-hypocretin (pHcrt) neuropeptide protein expression by DHEA and DHT in hypothalamus, consistent with the localization of orexin neurons. In hippocampus, DHT down-regulated the expression of Prkcd, while DHEA did not have significant effects. RIA results supported the view that DHEA-induced effects were mediated through AR. The current study identified neurogenomic effects of DHEA treatment on a subset of genes directly implicated in the regulation of appetite, energy utilization, alertness, apoptosis, and cell survival. These changes in gene expression in the CNS represent a constellation of effects that may help explain the diverse benefits attributed to replacement therapy with DHEA. The data also provide a new level of detail regarding the genomic mechanism of action of DHEA in the CNS and strongly support a central role for the androgen receptor in the production of these effects. More broadly, the results may be clinically significant because they provide new insights into processes that appear to mediate the diverse CNS effects attributed to DHEA.

Effects of mirtazapine on dehydroepiandrosterone-sulfate and cortisol plasma concentrations in depressed patients

BACKGROUND

Among the neuroactive steroids, dehydroepiandrosterone sulfate (DHEA-S) is at least in part produced in the adrenal gland and is therefore under the control of the hypothalamic-pituitary-adrenocortical (HPA)-system. In the present study, the impact of mirtazapine on DHEA-S and cortisol (COR) levels was investigated in relation to clinical response in depressed patients.

METHODS

A total of 23 inpatients suffering from a major depressive episode (DSM-IV criteria) underwent 5-week treatment with mirtazapine (45 mg/day). Plasma samples were taken weekly at 0800 h and quantified for COR and DHEA-S levels.

RESULTS

Mirtazapine significantly reduced both COR and DHEA-S concentrations, but had no impact on the COR/DHEA-S ratio. The percentage decrease of DHEA-S, but not that of COR was significantly and positively correlated with the percentage reduction in the sum score of the Hamilton Depression Rating Scale at week 5, suggesting a relationship between DHEA-S reduction and clinical efficacy of mirtazapine. There was a significant positive correlation between the decline in COR and DHEA-S levels.

CONCLUSIONS

Apparently, the decrease in COR and DHEA-S concentrations conjointly reflects an attenuating impact of mirtazapine on HPA axis activity, thereby decreasing the adrenal secretion of COR and DHEA-S.

DHEA lessens depressive-like behavior via GABA-ergic modulation of the mesolimbic system

Alterations in the levels of dehydroepiandrosterone (DHEA) in the brain can allosterically modulate gamma-aminobutyric-acid-type-A (GABA(A)R), N-methyl-D-aspartate (NMDAR), and Sigma-1 (sigma 1R) receptors. In humans, DHEA has antidepressive effects; however, the mechanism is unknown. We examined whether alterations in DHEA also occur in an animal model of depression, the Flinders-sensitive-line (FSL) rats, with the intention of determining the brain site of DHEA action and its antidepressant mechanism. We discovered that DHEA levels were lower in some brain regions involved with depression of FSL rats compared to Sprague-Dawley (SD) controls. Moreover, DHEA (1 mg/kg IP for 14 days)-treated FSL rats were more mobile in the forced swim test than FSL controls. In the NAc and VTA, significant changes were observed in the levels of the delta-subunit of GABA(A), but not of sigma 1R mRNA, in FSL rats compared to SD rats. The delta-subunit controls the sensitivity of the GABA(A)R to the neurosteroid. Indeed, treatment (14 days) of FSL rats with the GABA(A) agonist muscimol (0.5 mg/kg), together with DHEA (a negative modulator of GABA(A)), reversed the effect of DHEA on immobility in the swim test. Perfusion of DHEA sulfate (DHEAS) (3 nM and 30 nM for 14 days) into the VTA and NAc of FSL rats improved their performance in the swim test for at least 3 weeks post-treatment. Our results imply that alterations in DHEA are involved in the pathophysiology of depression and that the antidepressant action of DHEA is mediated via GABA(A)Rs in the NAc and VTA.

Modulation of neurotransmitter systems by dehydroepiandrosterone and dehydroepiandrosterone sulfate: mechanism of action and relevance to psychiatric disorders

Dehydroepiandrosterone (DHEA) is synthesized in the brain and several studies have shown that this steroid is a modulator of synaptic transmission. The effect of DHEA, and its sulfate ester DHEAS, on glutamate and GABA neurotransmission has been extensively studied but some effects on other neurotransmitter systems, such as dopamine, serotonin and nitric oxide, have also been reported. This review summarizes studies showing the effect of DHEA and DHEAS on neurotransmitter systems at different levels (metabolism, release, reuptake, receptor activation), as well as the activation of voltage-gated ion channels and calcium homeostasis, showing the variety of effects that these steroids exert on those systems, allowing the discussion of its mechanisms of action and its relevance to psychiatric disorders.

Effects of methylphenidate and bupropion on DHEA-S and cortisol plasma levels in attention-deficit hyperactivity disorder

We evaluated plasma levels of DHEA-S and cortisol before and after treating ADHD patients with one of two medications: methylphenidate (n = 12) or bupropion (n = 10). Boys with ADHD (combined type) were evaluated with the Korean ADHD rating scale (K-ARS) and the computerized ADHD diagnostic system (ADS). All assessments were measured at baseline and repeated after 12 weeks. There were significant clinical improvements in both treatment groups as measured by K-ARS and ADS. DHEA-S levels increased from baseline to endpoint, but cortisol levels did not change significantly. This study suggests that both methylphenidate and bupropion increase plasma levels of DHEA-S in boys with ADHD.

The neurosteroids dehydroepiandrosterone sulfate and pregnenolone sulfate inhibit the UNC-49 GABA receptor through a common set of residues

Neurosteroids are endogenous neuromodulators that bind and allosterically regulate GABA(A) receptors. Residues were recently identified in the first transmembrane domain (M1) of GABA(A) receptor subunits that are important for neurosteroid modulation. We are studying the inhibition of GABA(A) receptors by sulfated neurosteroids. One of these neurosteroid, pregnenolone sulfate (PS), depends on six identified M1 residues to inhibit the UNC-49 GABA receptor, a homomeric GABA receptor from Caenorhabditis elegans that is homologous to the mammalian GABA(A) receptor. Here, we investigate the inhibition of the UNC-49 GABA receptor by another sulfated neurosteroid, dehydroepiandrosterone sulfate (DHEAS). DHEAS is identical to PS except that it contains a carbonyl oxygen instead of an acetyl group at C17 on the steroid D ring. UNC-49 mutations that affect PS inhibition had broadly parallel effects on DHEAS, suggesting the two neurosteroids act through similar mechanisms. However, certain M1 mutations affected DHEAS differently than PS. Considering that first, the D ring contains the only structural difference between PS and DHEAS, and second, the strongest chemical and steric effects of a mutation are likely to be felt in the local environment of the altered residues, this result implies that the steroid D ring may contact M1 near the mutated residues. This possibility is interesting because current models of neurosteroid interactions with GABA(A) receptors, based on pregnane steroids, suggest that the steroid A ring binds M1, whereas the D ring binds M4. Our findings suggest that there may be considerable diversity in the way different classes of neurosteroids interact with GABA(A) receptors.

The relevance of neuroactive steroids in schizophrenia, depression, and anxiety disorders

1. Neuroactive steroids are steroid hormones that exert rapid, nongenomic effects at ligand-gated ion channels. There is increasing awareness of the possible role of these steroids in the pathology and manifestation of symptoms of psychiatric disorders. The aim of this paper is to review the current knowledge of neuroactive steroid functioning in the central nervous system, and to assess the role of neuroactive steroids in the pathophysiology and treatment of symptoms of schizophrenia, depression, and anxiety disorders. Particular emphasis will be placed on GABAA receptor modulation, given the extensive knowledge of the interactions between this receptor complex, neuroactive steroids, and psychiatric illness. 2. A brief description of neuroactive steroid metabolism is followed by a discussion of the interactions of neuroactive steroids with acute and chronic stress and the HPA axis. Preclinical and clinical studies related to psychiatric disorders that have been conducted on neuroactive steroids are also described. 3. Plasma concentrations of some neuroactive steroids are altered in individuals suffering from schizophrenia, depression, or anxiety disorders compared to values in healthy controls. Some drugs used to treat these disorders have been reported to alter plasma and brain concentrations in clinical and preclinical studies, respectively. 4. Further research is warranted into the role of neuroactive steroids in the pathophysiology of psychiatric illnesses and the possible role of these steroids in the successful treatment of these disorders.