Neurosteroid modulation of embryonic neuronal survival in vitro following anoxia

Hormesis: A potential strategic approach to the treatment of neurodegenerative disease

This review describes neuroprotective effects mediated by pre- and post-conditioning-induced processes that act via the quantitative features of the hormetic dose response. These lead to the development of acquired resilience that can protect neuronal systems from endogenous and exogenous stresses and insult. Particular attention is directed to issues of dose optimization, inter-individual variation, and potential ways to further study and employ hormetic-based preconditioning approaches in medical and public health efforts to treat and prevent neurodegenerative disease.

A tale of two steroids: The importance of the androgens DHEA and DHEAS for early neurodevelopment

DHEA and DHEAS are neuroactive neurosteroids that interact with several major receptor systems in the brain, including sigma (σ), glutamate, and GABA-A receptors. It has been recognized as early as 1952, that the loss of DHEA/DHEAS in adult life is associated with neuropsychiatric disorders (eg schizophrenia, depression). However, the mechanistic role for DHEA/DHEAS in any of these domains remains speculative, not the least because the presence of these androgens in the adrenal gland and brain is largely confined to humans and only some non-human primates. DHEA and DHEAS are dynamically regulated from before birth and before the onset of puberty, and therefore an understanding of the synthesis, regulation, and functions of this important androgen pathway warrants attention. Here, we draw attention to the possible modulating influence of DHEA/DHEAS in early brain development from fetal life to the remarkable increase of these steroids in early childhood - the adrenarche. We propose that the pre-pubertal DHEA/DHEAS surge plays a key role in modulating early brain development, perhaps by prolonging brain plasticity during childhood to allow the pre-adolescent brain to adapt and re-wire in response to new, and ever-changing social challenges. Nonetheless, the aetiology of neurodevelopmental phenomena in relation to DHEA/DHEAS synthesis and action cannot be easily studied in humans due to the obvious ethical restrictions on mechanistic studies, the uncertainty of predicting the future mental characteristics of individuals, and the difficulty of conducting retrospective investigations based on pre-birth and/or neonatal complications. We discuss new opportunities for animal studies to resolve these important questions.

Central intracrine DHEA synthesis in ageing-related neuroinflammation and neurodegeneration: therapeutic potential?

It is a well-known fact that DHEA declines on ageing and that it is linked to ageing-related neurodegeneration, which is characterised by gradual cognitive decline. Although DHEA is also associated with inflammation in the periphery, the link between DHEA and neuroinflammation in this context is less clear. This review drew from different bodies of literature to provide a more comprehensive picture of peripheral vs central endocrine shifts with advanced age—specifically in terms of DHEA. From this, we have formulated the hypothesis that DHEA decline is also linked to neuroinflammation and that increased localised availability of DHEA may have both therapeutic and preventative benefit to limit neurodegeneration. We provide a comprehensive discussion of literature on the potential for extragonadal DHEA synthesis by neuroglial cells and reflect on the feasibility of therapeutic manipulation of localised, central DHEA synthesis.

DHEA in Prenatal and Postnatal Life: Implications for Brain and Behavior

Dehydroepiandrosterone (DHEA) and its sulfated congener (DHEAS) are the principal C₁₉ steroid produced by the adrenal gland in many mammals, including humans. It is secreted in high concentrations during fetal life, but synthesis decreases after birth until, in humans and some other primates, there is a prepubertal surge of DHEA production by the adrenal gland-a phenomenon known as adrenarche. There remains considerable uncertainty about the physiological role of DHEA and DHEAS. Moreover, the origin of the trophic drives that determine the waxing and waning of DHEA synthesis are poorly understood. These gaps in knowledge arise in some measure from the difficulty of understanding mechanistic determinants from observations made opportunistically in humans and primates, and have stimulated a search for other suitable species that exhibit adrenarche- and adrenopause-like changes of adrenal function. DHEA and DHEAS are clearly neuroactive steroids with actions at several neurotransmitter receptors; indeed, DHEA is now known to be also synthesized by many parts of the brain, and this capacity undergoes ontogenic changes, but whether this is dependent or independent of the changes in adrenal synthesis is unknown. In this chapter we review key contributions to this field over the last 50+ years, and speculate on the importance of DHEA for the brain, both during development and for maturation and aging of cerebral function and behavior.

An exploratory pilot investigation of neurosteroids and self-reported pain in female Iraq/Afghanistan-era Veterans

Female Veterans are the most rapidly growing segment of new users of the Veterans Health Administration (VHA), and a significant proportion of female Veterans receiving treatment from VHA primary care providers report persistent pain symptoms. Currently, available data characterizing the neurobiological underpinnings of pain disorders are limited. Preclinical data suggest that neurosteroids may be involved in the modulation of pain symptoms, potentially via actions at gamma-aminobutyric acid (GABA) and N-methyl-D-aspartate (NMDA) receptors. Dehydroepiandrosterone (DHEA) and dehydroepiandrosterone sulfate (DHEAS) are neurosteroids that modulate inhibitory GABA receptors and excitatory NMDA receptors, producing complex neuronal effects. Emerging evidence from male Iraq/Afghanistan-era Veterans suggests that reductions in neurosteroid levels are associated with increased pain symptoms and that neurosteroids may be promising biomarker candidates. The current exploratory study thus examined associations between self-reported pain symptoms in 403 female Iraq/Afghanistan-era Veterans and serum DHEAS and DHEA levels. Serum DHEAS levels were inversely correlated with low back pain in female Veterans (Spearman r = -0.103; p = 0.04). Nonparametric analyses indicate that female Veterans reporting moderate/extreme low back pain demonstrated significantly lower DHEAS levels than those reporting no/little low back pain (|Z| = 2.60; p = 0.009). These preliminary findings support a role for DHEAS in pain physiology of low back pain and the rationale for neurosteroid therapeutics in pain analgesia.

Developmental effects of androgens in the human brain

Neuroendocrine theories of brain development posit that androgens play a crucial role in sex-specific cortical growth, although little is known about the differential effects of testosterone and dehydroepiandrosterone (DHEA) on cortico-limbic development and cognition during adolescence. In this context, the National Institutes of Health Study of Normal Brain Development, a longitudinal study of typically developing children and adolescents aged 4-24 years (n=433), offers a unique opportunity to examine the developmental effects of androgens on cortico-limbic maturation and cognition. Using data from this sample, our group found that higher testosterone levels were associated with left-sided decreases in cortical thickness (CTh) in post-pubertal boys, particularly in the prefrontal cortex, compared to right-sided increases in CTh in somatosensory areas in pre-pubertal girls. Prefrontal-amygdala and prefrontal-hippocampal structural covariance (considered to reflect structural connectivity) also varied according to testosterone levels, with the testosterone-related brain phenotype predicting higher aggression levels and lower executive function, particularly in boys. By contrast, DHEA was associated with a pre-pubertal increase in CTh of several regions involved in cognitive control in both boys and girls. Covariance within several cortico-amygdalar structural networks also varied as a function of DHEA levels, with the DHEA-related brain phenotype predicting improvements in visual attention in both boys and girls. DHEA-related cortico-hippocampal structural covariance, on the other hand, predicted higher scores on a test of working memory. Interestingly, there were significant interactions between testosterone and DHEA, such that DHEA tended to mitigate the anti-proliferative effects of testosterone on brain structure. In sum, testosterone-related effects on the developing brain may lead to detrimental effects on cortical functions (ie, higher aggression and lower executive function), whereas DHEA-related effects may optimise cortical functions (ie, better attention and working memory), perhaps by decreasing the influence of amygdalar and hippocampal afferents on cortical functions.

Calcium-engaged Mechanisms of Nongenomic Action of Neurosteroids

BACKGROUND

Neurosteroids form the unique group because of their dual mechanism of action. Classically, they bind to specific intracellular and/or nuclear receptors, and next modify genes transcription. Another mode of action is linked with the rapid effects induced at the plasma membrane level within seconds or milliseconds. The key molecules in neurotransmission are calcium ions, thereby we focus on the recent advances in understanding of complex signaling crosstalk between action of neurosteroids and calcium-engaged events.

METHODS

Short-time effects of neurosteroids action have been reviewed for GABAA receptor complex, glycine receptor, NMDA receptor, AMPA receptor, G protein-coupled receptors and sigma-1 receptor, as well as for several membrane ion channels and plasma membrane enzymes, based on available published research.

RESULTS

The physiological relevance of neurosteroids results from the fact that they can be synthesized and accumulated in the central nervous system, independently from peripheral sources. Fast action of neurosteroids is a prerequisite for genomic effects and these early events can significantly modify intracellular downstream signaling pathways. Since they may exert either positive or negative effects on calcium homeostasis, their role in monitoring of spatio-temporal Ca2+ dynamics, and subsequently, Ca2+-dependent physiological processes or initiation of pathological events, is evident.

CONCLUSION

Neurosteroids and calcium appear to be the integrated elements of signaling systems in neuronal cells under physiological and pathological conditions. A better understanding of cellular and molecular mechanisms of nongenomic, calcium-engaged neurosteroids action could open new ways for therapeutic interventions aimed to restore neuronal function in many neurological and psychiatric diseases.

Dehydroepiandrosterone protects male and female hippocampal neurons and neuroblastoma cells from glucose deprivation

Dehydroepiandrosterone (DHEA) modulates neurogenesis, neuronal function, neuronal survival and metabolism, enhancing mitochondrial oxidative capacity. Glucose deprivation and hypometabolism have been implicated in the mechanisms that mediate neuronal damage in neurological disorders, and some studies have shown that these mechanisms are sexually dimorphic. It was also demonstrated that DHEA is able to attenuate the hypometabolism that is related to some neurodegenerative diseases, eliciting neuroprotective effects in different experimental models of neurodegeneration. The aim of this study was to evaluate the effect of DHEA on the viability of male and female hippocampal neurons and SH-SY5Y neuroblastoma cells exposed to glucose deprivation. It was observed that after 12h of pre-treatment, DHEA was able to protect SH-SY5Y cells from glucose deprivation for 6h (DHEA 10(-12), 10(-8) and 10(-6)M) and 8h (DHEA 10(-8)M). In contrast, DHEA was not neuroprotective against glucose deprivation for 12 or 24h. DHEA (10(-8)M) also protected SH-SY5Y cells when added together or even 1h after the beginning of glucose deprivation (6h). Furthermore, DHEA (10(-8)M) also protected primary neurons from both sexes against glucose deprivation. In summary, our findings indicate that DHEA is neuroprotective against glucose deprivation in human neuroblastoma cells and in male and female mouse hippocampal neurons. These results suggest that DHEA could be a promising candidate to be used in clinical studies aiming to reduce neuronal damage in people from both sexes.

Programming the brain and behaviour by early-life stress: a focus on neuroactive steroids

Animal studies have amply demonstrated that stress exposure during pregnancy or in early postnatal life can adversely influence brain development and have long-term 'programming' effects on future brain function and behaviour. Furthermore, a growing body of evidence from human studies supports the hypothesis that some psychiatric disorders may have developmental origins. Here, the focus is on three adverse consequences of early-life stress: dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis, heightened anxiety behaviour and cognitive impairments, with review of what is known about the underlying central mechanisms. Neuroactive steroids modulate neuronal activity and play a key role in neurodevelopment. Moreover they can negatively modulate activity of the HPA axis, exert anxiolytic actions and influence cognitive performance. Thus, neuroactive steroids may provide a link between early-life stress and the resultant adverse effects on the brain and behaviour. Here, a role for neuroactive steroids, in particular the 5α-reduced/3α-hydroxylated metabolites of progesterone, testosterone and deoxycorticosterone, is discussed in the context of early-life stress. Furthermore, the impact of early-life stress on the brain's capacity to generate neurosteroids is considered and the evidence for an ability of neuroactive steroids to over-write the negative effects of early-life stress on the brain and behaviour is examined. An enhanced understanding of the influence of early-life stress on brain neurosteroid systems could aid the identification of new targets for developing treatments for stress-related conditions in humans.

Exploratory Investigation of Biomarker Candidates for Suicide in Schizophrenia and Bipolar Disorder

Background: Clozapine and lithium increase neurosteroids in rodents, and both drugs demonstrate antisuicidal actions. We therefore hypothesized that neurosteroid levels may be reduced in patients with schizophrenia or bipolar disorder who completed suicide. Aims: To investigate neurosteroid levels in the parietal cortex and posterior cingulate in schizophrenia and bipolar patients who died by suicide, and compare them with patients with these disorders who died of other causes. Method: Neurosteroid levels were quantified by gas chromatography/mass spectrometry in the parietal cortex and posterior cingulate. Mann–Whitney analyses were conducted in exploratory post hoc analyses to investigate neurosteroids as possible biomarker candidates for suicide. Results: The study showed that pregnenolone was significantly decreased in the parietal cortex in the combined group of patients with schizophrenia or bipolar disorder who died by suicide (n = 13) compared with patients with these disorders who died of other causes (n = 17, p = .02). Pregnenolone levels were also lower in the parietal cortex in the individual group of schizophrenia patients who died by suicide (n = 4) compared with schizophrenia patients who died of other causes (n = 11) p = .04). Conclusion: Pregnenolone alterations may be relevant to the neurobiology of suicide in schizophrenia and bipolar disorder.

Interactive effects of dehydroepiandrosterone and testosterone on cortical thickness during early brain development

Humans and the great apes are the only species demonstrated to exhibit adrenarche, a key endocrine event associated with prepubertal increases in the adrenal production of androgens, most significantly dehydroepiandrosterone (DHEA) and to a certain degree testosterone. Adrenarche also coincides with the emergence of the prosocial and neurobehavioral skills of middle childhood and may therefore represent a human-specific stage of development. Both DHEA and testosterone have been reported in animal and in vitro studies to enhance neuronal survival and programmed cell death depending on the timing, dose, and hormonal context involved, and to potentially compete for the same signaling pathways. Yet no extant brain-hormone studies have examined the interaction between DHEA- and testosterone-related cortical maturation in humans. Here, we used linear mixed models to examine changes in cortical thickness associated with salivary DHEA and testosterone levels in a longitudinal sample of developmentally healthy children and adolescents 4-22 years old. DHEA levels were associated with increases in cortical thickness of the left dorsolateral prefrontal cortex, right temporoparietal junction, right premotor and right entorhinal cortex between the ages of 4-13 years, a period marked by the androgenic changes of adrenarche. There was also an interaction between DHEA and testosterone on cortical thickness of the right cingulate cortex and occipital pole that was most significant in prepubertal subjects. DHEA and testosterone appear to interact and modulate the complex process of cortical maturation during middle childhood, consistent with evidence at the molecular level of fast/nongenomic and slow/genomic or conversion-based mechanisms underlying androgen-related brain development.

Androgen receptor overexpression is neuroprotective in experimental stroke

Male sex is a known risk factor in human stroke. However, the role of the cognate receptor for androgens-the androgen receptor (AR)-in stroke outcome remains unclear. Here, we found that AR mRNA is downregulated in the peri-infarct tissue of gonadally intact male mice subjected to middle cerebral artery occlusion (MCAO) and 6 h reperfusion. We then used genetically engineered mice overexpressing AR in brain (AR-Tg) to compare outcomes from MCAO in intact or castrated males and to evaluate the neuroprotective role of dihydrotestosterone (DHT) replacement in AR-Tg castrates. A further evaluation of AR overexpression in ischemic paradigms was performed using rat PC12 cells transfected with human AR and treated with oxidative and apoptotic stressors. We then studied the role of DHT in cultures overexpressing AR. Our results show (1) ischemia alters the expression of AR by decreasing AR mRNA levels, (2) AR overexpression is protective in vivo against MCAO in intact and castrated AR-Tg mice and in vitro against oxidative and apoptotic stressors in AR-PC12 cells, and (3) DHT does not enhance the protection triggered by AR overexpression in AR-Tg castrated mice nor in AR-PC12 cells.

Antiepileptic action of exogenous dehydroepiandrosterone in iron-induced epilepsy in rat brain

In the study described here, the antiepileptic effect of dehydroepiandrosterone (DHEA) treatment on iron-induced focal epileptiform activity in the rat brain was investigated. DHEA is a neuroactive corticosteroid hormone synthesized both in the adrenal cortex and in the brain. Its antioxidant properties are well known. As oxidative stress seems to play a major role in epileptogenesis in the iron-induced model of posttraumatic epilepsy, it was of interest to examine whether DHEA would exert antiepileptic activity. DHEA at a dose of 30 mg/kg/day administered intraperitoneally for 7, 14, and 21 days to iron-induced epileptic rats prevented epileptiform electrophysiological activity. Morris water maze and open-field tests on iron-induced epileptic rats revealed that DHEA also prevented behavioral alterations related to epileptiform activity. Thus, DHEA attenuated the cognitive defects produced by epileptic activity. Moreover, alterations in epileptogenesis-related biochemical parameters-lipid peroxidation, protein oxidation and Na(+), K(+)-ATPase (sodium pump) activity--were also countered by DHEA.

The 7-hydroxylation of dehydroepiandrosterone in rat brain

Dehydroepiandrosterone (DHEA) is an important neurosteroid with multiple functions in the central nervous system including neuroprotection. How DHEA exerts its neuroprotection function has not been fully elucidated. One possible mechanism is via its active metabolites, 7alpha-OH DHEA and 7beta-OH DHEA. The purpose of this research is to understand how DHEA is metabolized to 7alpha-OH DHEA and 7beta-OH DHEA by brain tissue. DHEA was incubated with rat brain microsomes and mitochondria and the 7alpha-OH DHEA and 7beta-OH DHEA formed by these fractions were analyzed by LC/MS. For the first time, we observed that DHEA could be metabolized to 7alpha-OH DHEA and 7beta-OH DHEA in mitochondria but the formation of 7alpha-OH DHEA and 7beta-OH DHEA demonstrated different enzymatic kinetic properties. Adding NADPH, an essential cofactor, to mitochondria incubation mixtures increased only the formation of 7alpha-OH DHEA, but not that of 7beta-OH DHEA. Addition of estradiol to the incubation mixtures inhibited only the formation of 7alpha-OH DHEA, but not that of 7beta-OH DHEA. Western blot analysis showed that both microsomes and mitochondria contained cytochrome P450 7B. We also found that 7alpha-OH DHEA could be converted to 7beta-OH DHEA by rat brain homogenates. Our data suggest that 7alpha-OH DHEA and 7beta-OH DHEA are formed by different enzymes and that 7beta-OH DHEA can be formed from both DHEA and 7alpha-OH DHEA, although the overall level of 7beta-OH DHEA was very low.

Allopregnanolone levels are reduced in temporal cortex in patients with Alzheimer's disease compared to cognitively intact control subjects

The neurosteroid allopregnanolone has pronounced neuroprotective actions, increases myelination, and enhances neurogenesis. Evidence suggests that allopregnanolone dysregulation may play a role in the pathophysiology of Alzheimer's disease (AD) and other neurodegenerative disorders. Our prior data demonstrate that allopregnanolone is reduced in prefrontal cortex in male patients with AD compared to male cognitively intact control subjects, and inversely correlated with neuropathological disease stage (Braak and Braak). We therefore determined if allopregnanolone levels are also reduced in AD patients compared to control subjects in temporal cortex, utilizing a larger set of samples from both male and female patients. In addition, we investigated if neurosteroids are altered in subjects who are APOE4 allele carriers. Allopregnanolone, dehydroepiandrosterone (DHEA), and pregnenolone levels were determined in temporal cortex postmortem samples by gas chromatography/mass spectrometry, preceded by high performance liquid chromatography (40 subjects with AD/41 cognitively intact control subjects). Allopregnanolone levels are reduced in temporal cortex in patients with AD (median 2.68 ng/g, n=40) compared to control subjects (median 5.64 ng/g, n=41), Mann-Whitney p=0.0002, and inversely correlated with Braak and Braak neuropathological disease stage (Spearman r=-0.38, p=0.0004). DHEA and pregnenolone are increased in patients with AD compared to control subjects. Patients carrying an APOE4 allele demonstrate reduced allopregnanolone levels in temporal cortex (Mann-Whitney p=0.04). In summary, our findings indicate that neurosteroids are altered in temporal cortex in patients with AD and related to neuropathological disease stage. In addition, the APOE4 allele is associated with reduced allopregnanolone levels. Neurosteroids may be relevant to the neurobiology and therapeutics of AD.

Novel dehydroepiandrosterone derivatives with antiapoptotic, neuroprotective activity

DHEA analogues with modifications at positions C3 or C17 were synthesized and evaluated for neuroprotective activity against the neural-crest-derived PC12 cell model of serum deprivation-induced apoptosis. The most potent compounds were the spiro-epoxy derivatives 17beta-spiro[5-androstene-17,2'-oxiran]-3beta-ol (20), (20S)-3beta,21-dihydroxy-17beta,20-epoxy-5-pregnene (23), and (20R)-3beta,21-dihydroxy-17alpha,20-epoxy-5-pregnene (27) with IC(50) values of 0.19 +/- 0.01, 99.0 +/- 4.6, and 6.4 +/- 0.3 nM, respectively. Analogues 20, 23, and 27, up to the micromolar range of concentrations, were unable to activate estrogen receptor alpha and beta (ERalpha and ERbeta) or to interfere with ER-dependent gene expression significantly. In addition, they were unable to stimulate the growth of Ishikawa, MCF-7, and LNCaP cells. Our results suggest that the spiro-epoxyneurosteroid derivatives 20, 23, and 27 may prove to be lead molecules for the synthesis of novel neuroprotective agents.

Neurobiological and neuropsychiatric effects of dehydroepiandrosterone (DHEA) and DHEA sulfate (DHEAS)

DHEA and DHEAS are steroids synthesized in human adrenals, but their function is unclear. In addition to adrenal synthesis, evidence also indicates that DHEA and DHEAS are synthesized in the brain, further suggesting a role of these hormones in brain function and development. Despite intensifying research into the biology of DHEA and DHEAS, many questions concerning their mechanisms of action and their potential involvement in neuropsychiatric illnesses remain unanswered. We review and distill the preclinical and clinical data on DHEA and DHEAS, focusing on (i) biological actions and putative mechanisms of action, (ii) differences in endogenous circulating concentrations in normal subjects and patients with neuropsychiatric diseases, and (iii) the therapeutic potential of DHEA in treating these conditions. Biological actions of DHEA and DHEAS include neuroprotection, neurite growth, and antagonistic effects on oxidants and glucocorticoids. Accumulating data suggest abnormal DHEA and/or DHEAS concentrations in several neuropsychiatric conditions. The evidence that DHEA and DHEAS may be fruitful targets for pharmacotherapy in some conditions is reviewed.

Induction of Akt by endogenous neurosteroids and calcium sequestration in P19 derived neurons

Neuronal cell death caused by pathophysiological over-activation of glutamate receptors and the subsequent CaII overloading, has been implicated in neurodegeneration after stroke, cerebral trauma and epileptic seizures. Recent findings suggest that certain progesterone metabolites (neurosteroids) such as allopregnanolone and dehydroepiandrosterone can protect neuronal cells from such insults. In the present study, murine P19 cells were induced to differentiate into postmitotic neurons expressing specific neuronal markers, including GABA(A) and NMDA receptors. Activation of NMDA receptors in P19-N neurons resulted in excitotoxic cell death, which involved suppression of the phosphorylation of the survival kinase PKB/Akt. Allopregnanolone and DHEA induced a rapid and prolonged phosphorylation of the Akt kinase and they were able to reverse the NMDA-induced suppression of the PI3-K/Akt pathway. The specificity of the neuroprotective effects of these neurosteroids was confirmed by the phosphatidylinositol 3-kinase (PI3-K) inhibitor wortmannin, as well as by the GABA(A) receptor antagonist, bicuculline. The neurotoxic effect of NMDA on P19-N neurons was directly correlated with increased CaII entry, since the addition of EGTA or BAPTA-AM, significantly suppressed the NMDA-induced decrease of phospho-Akt and subsequent neuronal death. These results suggest that neurosteroids are able to act as survival factors on P19-N neurons, promoting the activation of the PI3-K/Akt pathway through a calcium-entry dependent mechanism.

Pregnenolone protects the PC-12 cell line against amyloid beta peptide toxicity but its sulfate ester does not

Pregnenolone (P), the main precursor of the steroids, and its sulfate ester, pregnenolone sulfate (PS), are the major neurosteroids produced in the neural tissue. Many neuroendocrinological studies stressed the neuroprotective role of neurosteroids although it has been suggested that the inhibition of P and PS synthesis can delay neuronal cell death. The potential roles of P and PS in vital neuronal functions and in amyloid beta peptide (Abeta) toxicity are not clearly identified. This work aims to investigate the effects of P and PS on cell viability and Abeta peptide toxicity in a concentration and exposure time-dependent manner in rat PC-12 cells. The cells were treated with 20muM Abeta peptide 25-35 and variable concentrations of P and PS ranging from 0.5muM to 100muM. To examine the effects of steroid treatment on Abeta peptide toxicity, 0.5muM (low) and 50muM (high) neurosteroids were used. The cell viability and lactate dehydrogenase release of cells were evaluated after 24, 48 and 72h. Morphological changes of cells were also examined. The treatment with higher than 1muM concentrations of P and PS significantly decreased the cell viability comparing to untreated cells. At lower concentrations, P and PS had no toxic actions until 72h. The Abeta treatment resulted in a significant decrease in cell viability comparing to untreated cells. P showed a dose-dependent protective effect against Abeta peptide in PC-12 cells. But its sulfate ester did not have the same effect on Abeta peptide toxicity, even it significantly decreased cell viability in Abeta-treated cells. Consequently, the discrepant effects of P and PS on Abeta peptide toxicity may provide insight on the pathogenesis of Alzheimer's disease.

Cerebrospinal fluid dehydroepiandrosterone levels are correlated with brain dehydroepiandrosterone levels, elevated in Alzheimer's disease, and related to neuropathological disease stage

OBJECTIVE

It is currently unknown whether cerebrospinal fluid (CSF) neurosteroid levels are related to brain neurosteroid levels in humans. CSF and brain dehydroepiandrosterone (DHEA) levels are elevated in patients with Alzheimer's disease (AD), but it is unclear whether CSF DHEA levels are correlated with brain DHEA levels within the same subject cohort. We therefore determined DHEA and pregnenolone levels in AD patients (n = 25) and cognitively intact control subjects (n = 16) in both CSF and temporal cortex.

DESIGN

DHEA and pregnenolone levels were determined by gas chromatography/mass spectrometry preceded by HPLC. Frozen CSF and temporal cortex specimens were provided by the Alzheimer's Disease Research Center at Duke University Medical Center. Data were analyzed by Mann-Whitney U test statistic and Spearman correlational analyses.

RESULTS

CSF DHEA levels are positively correlated with temporal cortex DHEA levels (r = 0.59, P < 0.0001) and neuropathological disease stage (Braak and Braak) (r = 0.42, P = 0.007). CSF pregnenolone levels are also positively correlated with temporal cortex pregnenolone levels (r = 0.57, P < 0.0001) and tend to be correlated with neuropathological disease stage (Braak) (r = 0.30, P = 0.06). CSF DHEA levels are elevated (P = 0.032), and pregnenolone levels tend to be elevated (P = 0.10) in patients with AD, compared with cognitively intact control subjects.

CONCLUSIONS

These findings indicate that CSF DHEA and pregnenolone levels are correlated with temporal cortex brain levels of these neurosteroids and that CSF DHEA is elevated in AD and related to neuropathological disease stage. Neurosteroids may thus be relevant to the pathophysiology of AD.

Treatments for spinal cord injury: is there hope in neurosteroids?

In this review, we describe the current therapeutic strategies to find a cure for paralysis. We use the example of DHEA, a neurosteroid normally produced in the developing neural tube, to raise the hypothesis that such a class of molecules, capable of modulating proliferation of committed neural precursors, could serve as an environmental cue in the adult injured spinal cord to promote re-population of CNS lesion with endogenous dormant precursor cells. Such mechanism may be a part of the natural response to heal the injured CNS and promote recovery of function, suggesting that neurosteroid-treatment could be a promising and novel therapeutic avenue for SCI. We will review pertinent biological activities of DHEA supporting this hypothesis, demonstrate that such activities, dependent on an intact sonic-hedgehog pathway, are responsible for the motor and bladder functional recovery observed after DHEA-treatment in the adult injured spinal cord. We will also raise the current limitations to further development of DHEA- or other neurosteroid-treatments as drug candidates, including the urgent need to further document DHEA long-term safety in CNS indications.

3beta-HSD activates DHEA in the songbird brain

Dehydroepiandrosterone (DHEA) is an abundant circulating prohormone in humans, with a variety of reported actions on central and peripheral tissues. Despite its abundance, the functions of DHEA are relatively unknown because common animal models (laboratory rats and mice) have very low DHEA levels in the blood. Over the past decade, we have obtained considerable evidence from avian studies demonstrating that (1) DHEA is an important circulating prohormone in songbirds and (2) the enzyme 3beta-hydroxysteroid dehydrogenase/isomerase (3beta-HSD), responsible for converting DHEA into a more active androgen, is expressed at high levels in the songbird brain. Here, we first review biochemical and molecular studies demonstrating the widespread activity and expression of 3beta-HSD in the adult and developing songbird brain. Studies examining neural 3beta-HSD activity show effects of sex, stress, and season that are region-specific. Second, we review studies showing seasonal and stress-related changes in circulating DHEA in captive and wild songbird species. Third, we describe evidence that DHEA treatment can stimulate song behavior and the growth of neural circuits controlling song behavior. Importantly, brain 3beta-HSD and aromatase can work in concert to locally metabolize DHEA into active androgens and estrogens, which are critical for controlling behavior and robust adult neuroplasticity in songbirds. DHEA is likely secreted by the avian gonads and/or adrenals, as is the case in humans, but DHEA may also be synthesized de novo in the songbird brain from cholesterol or other precursors. Irrespective of its source, DHEA seems to be an important prohormone in songbirds, and 3beta-HSD is a key enzyme in the songbird brain.

Activities of 3beta-HSD and aromatase in slices of developing and adult zebra finch brain

Sex steroids influence the development and function of the songbird brain. Developmentally, the neural circuitry underlying song undergoes masculine differentiation under the influence of estradiol. In adults, estradiol stimulates song behavior and the seasonal growth of song control circuits. There is good reason to believe that these neuroactive estrogens are synthesized in the brain. At all ages, estrogens could act at the lateral ventricle, during migration, or where song nuclei exist or will form. We investigated the activity of two critical steroidogenic enzymes, 3beta-hydroxysteroid dehydrogenase/isomerase (3beta-HSD) and aromatase, using a slice culture system. Sagittal brain slices were collected from juvenile (posthatch day 20) and adult zebra finches containing either the lateral ventricle, where neurons are born, or the telencephalic song nuclei HVC and RA. The slices were incubated with (3)H-dehydroepiandrosterone or (3)H-androstenedione. Activity was determined by isolating certain products of 3beta-HSD (5alpha-androstanedione, 5beta-androstanedione, estrone, and estradiol) and aromatase (estrone and estradiol). Activities of both 3beta-HSD and aromatase were detected in all slices and were confirmed using specific enzyme inhibitors. We found no significant difference in activity between adult males and females in either region for either enzyme. Juvenile female slices containing the lateral ventricle, however, showed greater levels of 3beta-HSD activity than did similar slices from age-matched males. Determination of the activity of these critical steroidogenic enzymes in slice culture has implications for the role of neurosteroids in brain development.

Adrenarche and the evolution of human life history

Adrenarche, the prepubertal onset of adrenal production of dehydroepiandrosterone sulfate (DHEAS), is a distinctive aspect of the human life course. Yet its evolutionary origins remain unexplained. Production of DHEAS is associated with the development of the zona reticularis, a novel histological layer within the adrenal gland, derived from the fetal adrenal gland, and associated with primates more generally. Evidence that DHEAS is a neurosteroid, together with the fact that increases in DHEAS parallel patterns of cortical maturation from approximately age 6 years to the mid-20s, suggests that DHEAS may play an important role in extended brain maturation among humans. DHEAS has demonstrated effects on mood in humans, and acts at neuron receptor sites. I suggest three ways in which DHEAS may play a role in human brain maturation: 1) increasing activity of the amgydala; 2) increasing activity of the hippocampus; and 3) promoting synaptogenesis within the cortex. I propose that associated changes in fearfulness and anxiety, and memory, could act to increase social interaction with nonfamiliar individuals and shape cognitive development. Comparison with the African apes suggests that the timing of adrenarche in chimpanzees may be similar to that in humans, though the full course of age-related changes in DHEAS and their relationship to reproductive and brain maturation are not clear. The role of DHEAS as a physiological mechanism supporting increased brain development, extended life span, and decreased sexual dimorphism is most compatible with Kaplan et al.'s (2000) theory of the evolution of human life history and intergenerational transfers.

Neuroactive steroids are altered in schizophrenia and bipolar disorder: relevance to pathophysiology and therapeutics

Evidence suggests that neuroactive steroids may be candidate modulators of schizophrenia pathophysiology and therapeutics. We therefore investigated neuroactive steroid levels in post-mortem brain tissue from subjects with schizophrenia, bipolar disorder, nonpsychotic depression, and control subjects to determine if neuroactive steroids are altered in these disorders. Posterior cingulate and parietal cortex tissue from the Stanley Foundation Neuropathology Consortium collection was analyzed for neuroactive steroids by negative ion chemical ionization gas chromatography/mass spectrometry preceded by high-performance liquid chromatography. Subjects with schizophrenia, bipolar disorder, nonpsychotic depression, and control subjects were group matched for age, sex, ethnicity, brain pH, and post-mortem interval (n = 14-15 per group, 59-60 subjects total). Statistical analyses were performed by ANOVA with post-hoc Dunnett tests on log transformed neuroactive steroid levels. Pregnenolone and allopregnanolone were present in human post-mortem brain tissue at considerably higher concentrations than typically observed in serum or plasma. Pregnenolone and dehydroepiandrosterone levels were higher in subjects with schizophrenia and bipolar disorder compared to control subjects in both posterior cingulate and parietal cortex. Allopregnanolone levels tended to be decreased in parietal cortex in subjects with schizophrenia compared to control subjects. Neuroactive steroids are present in human post-mortem brain tissue at physiologically relevant concentrations and altered in subjects with schizophrenia and bipolar disorder. A number of neuroactive steroids act at inhibitory GABA(A) and excitatory NMDA receptors and demonstrate neuroprotective and neurotrophic effects. Neuroactive steroids may therefore be candidate modulators of the pathophysiology of schizophrenia and bipolar disorder, and relevant to the treatment of these disorders.

The relevance of neurosteroids to clinical psychiatry: from the laboratory to the bedside

Neurosteroids are important neuroactive molecules with suggested central involvement in several neurophysiological and psychiatric disease processes. The discovery of neurosteroids followed the revelation that the brain exhibited the capacity to synthesize its own steroids in situ and thus be a potential site of steroidogenesis. In contrast to some steroids that exhibit traditional genomic steroid actions, most neurosteroids appear to regulate neuronal function by means of "non-genomic" mechanisms influencing neuronal excitability. Neurosteroids are synthesized either from CNS cholesterol or from peripheral steroid precursors and exhibit a wide range of modulatory effects on neurotransmitter receptor activity, most notably at the gamma-aminobutyric acid A (GABA(A)) receptor. Neurosteroids play an important role in neurodevelopment and neuroprotective effects, many aspects of which may have particular applicability to psychiatric disorders including various gender differences. Neurosteroids appear to be relevant to the pathophysiology and pharmacological treatment of many psychiatric disorders including the most notable mood and anxiety disorders, but also psychotic, childhood, eating, dementia, stress and postpartum disorders. It has been suggested that neurosteroids may become potential targets for pharmacological intervention in the future with further neurosteroid investigation contributing to a more comprehensive understanding of human behavior and psychopathology.

Effects of estrogen and related agents upon methamphetamine-induced neurotoxicity within an impaired nigrostriatal dopaminergic system of ovariectomized mice

Estrogen increases methamphetamine (MA)-induced neurotoxicity within the impaired nigrostriatal dopaminergic (NSDA) system of ovariectomized female mice, as defined by enhanced striatal dopamine (DA) depletion. In this study we compared the effects of a lower dose of estradiol benzoate (EB, 1 microg) with related agents--tamoxifen (TMX, 12.5 microg), testosterone (5 microg) and dehydroepiandrosterone (DHEA, 3 mg) in this paradigm. In experiment 1, ovariectomized mice received an initial treatment with MA. At 1 week after MA, mice were treated with EB, TMX, testosterone, DHEA or oil vehicle and 24 h later a second MA treatment. Striatal DA and 3,4-dihydroxyphenylacetic acid (DOPAC) concentrations in the MA-treated groups were decreased compared to the non-MA-treated control. Neither EB nor any of the other agents tested showed enhanced neurodegenerative or neuroprotective effects against a second MA invasion. To verify that estrogen was capable of showing a neuroprotective effect under a condition of two administrations of MA, in experiment 2, EB was administered either once or twice prior to each of the two MA treatments. EB treatment prior to the first MA invasion or first and second MA protected the NSDA system against DA and DOPAC depletion. These results imply that a lower dose of EB, TMX, testosterone and DHEA cannot exert neurodegenerative or neuroprotective effects in the impaired NSDA model. However, EB administered prior to the introduction of neurotoxicity can protect the NSDA system. This study may provide an understanding of the variations in results on the effects of estrogen upon the NSDA neurodegenerative disorder, Parkinson's disease.

A study of a dendritic marker, microtubule-associated protein 2 (MAP-2), in rats neonatally treated neurosteroids, pregnenolone and dehydroepiandrosterone (DHEA)

Neurosteroids administered during the neonatal period affect the development of several brain systems. We examined the effects of neonatal treatment with pregnenolone and dehydroepiandrosterone (DHEA) on a marker of neuronal dendrites, microtubule-associated protein 2 (MAP-2), in rat brain. Neonatal treatment with pregnenolone and DHEA increased the expression of MAP-2 in the hippocampus and nucleus accumbens but not in the prefrontal cortex, striatum or amygdala in adulthood.

Low and high circulating cortisol levels predict mortality and cognitive dysfunction early after stroke

OBJECTIVE

Elevated cortisol levels are associated with confusion and poor outcome after stroke. Dehydroepiandrosterone sulphate (DS), the most abundant adrenal androgen may act as an anti-glucocorticoid. An altered regulation of these steroids may affect numerous brain functions, including neuronal survival. The purpose of this study was to investigate serum cortisol and DS levels and the cortisol/DS ratio early after stroke and relate our findings to the presence of disorientation and mortality.

DESIGN

Patients with acute ischaemic stroke (n = 88, 56 men and 32 women) admitted to a stroke unit were investigated with repeated clinical assessments and scores for degree of confusion, extent of paresis and level of functioning. Serum cortisol (C) and DS were measured on day 1 and/or day 4. Data for 28-day and 1-year mortality are presented. A control group of 65 age-matched healthy individuals was used. Multivariate analyses of mortality rates in the different tertiles or sixtiles of serum cortisol were performed with logistic regression, adjusting for age, sex, diabetes and level of consciousness.

RESULTS

There was no difference in serum cortisol levels on day 1 for stroke patients when compared with control group values. Initial cortisol levels were significantly higher in the patients with acute disorientation versus orientated patients (P < 0.05). Cortisol levels on day 1 were an independent predictor of 28-day mortality, and patients with low cortisol levels (<270 nmol L(-1)) and increased levels (>550 nmol L(-1)) both had an increased 1-year mortality. DS levels on day 1 were significantly elevated in stroke patients.

CONCLUSION

Hypercortisolism is associated with cognitive dysfunction early after ischaemic stroke. High and low circulating cortisol levels are associated with increased mortality after stroke. DS levels were not associated with clinical outcome.

Dehydroepiandrosterone metabolism by 3beta-hydroxysteroid dehydrogenase/Delta5-Delta4 isomerase in adult zebra finch brain: sex difference and rapid effect of stress

Dehydroepiandrosterone (DHEA) is a precursor to sex steroids such as androstenedione (AE), testosterone (T), and estrogens. DHEA has potent effects on brain and behavior, although the mechanisms remain unclear. One possible mechanism of action is that DHEA is converted within the brain to sex steroids. 3beta-Hydroxysteroid dehydrogenase/Delta5-Delta4 isomerase (3beta-HSD) catalyzes the conversion of DHEA to AE. AE can then be converted to T and estrogen within the brain. We test the hypothesis that 3beta-HSD is expressed in the adult brain in a region- and sex-specific manner using the zebra finch (Taeniopygia guttata), a songbird with robust sex differences in song behavior and telencephalic song nuclei. In zebra finch brain, DHEA is converted by 3beta-HSD to AE and subsequently to estrogens and 5alpha- and 5beta-reduced androgens. 3beta-HSD activity is highest in the diencephalon and telencephalon. In animals killed within 2-3 min of disturbance, baseline 3beta-HSD activity in portions of the telencephalon is higher in females than males. Acute restraint stress (10 min) decreases 3beta-HSD activity in females but not in males, and in stressed animals, telencephalic 3beta-HSD activity is greater in males than in females. Thus, the baseline sex difference is rapidly reversed by stress. To our knowledge, this is the first demonstration of 1) brain region differences in DHEA metabolism by 3beta-HSD, 2) rapid modulation of 3beta-HSD activity, and 3) sex differences in brain 3beta-HSD and regulation by stress. Songbirds are good animal models for studying the regulation and functions of DHEA and neurosteroids in the nervous system.

DHEAS as a new diagnostic tool

Dehydroepiandrosterone sulfate (DHEAS) is a 19-carbon steroid, situated along the steroid metabolic pathway. It is the most abundant circulating steroid hormone in the body and can be converted to either androgens or estrogens. Their physiological and pathological functions have not yet been fully identified. Serum DHEAS concentrations peak at around age 25 years and then decline steadily over the following decades. Due to its long half-life and high concentration in the blood, the levels of DHEAS remain the same 24 h a day. This makes DHEAS a very interesting new diagnostic tool for both scientific research and clinical diagnostics. Moreover, circulating concentrations of DHEAS can be changed by many factors, such as endogenous production, hormone supplementation, many kinds of drugs, and many types of disease states. As research moves forward to better understand the relationships of DHEAS with health and disease, it is essential that studies should be designed to control for the influence of many factors on serum DHEAS concentrations.

The delayed administration of dehydroepiandrosterone sulfate improves recovery of function after traumatic brain injury in rats

The goal of the current study was to test the hypothesis that dehydroepiandrosterone-sulfate (DHEAS), a pro-excitatory neurosteroid, could facilitate recovery of function in male rats after delayed treatment following TBI. DHEAS has been found to play a major role in brain development and aging by influencing the migration of neurons, arborization of dendrites, and formation of new synapses. These characteristics make it suitable as a potential treatment to enhance neural repair in response to CNS injury. In our study, behavioral tests were conducted concurrently with DHEAS administration (0, 5, 10, or 20 mg/kg) starting seven days post-injury (PI). These assays included 10 days of Morris Water Maze testing (MWM; 7d PI), 10 days of Greek-Cross (GC; 21d PI), Tactile Adhesive Removal task (TAR; PI days: 6, 13, 20, 27, 34), and spontaneous motor behavior testing (SMB; PI days: 2, 4, 6, 12, 19, 26, 33). Brain-injured rats showed an improvement in performance in all tasks after 5, 10, or 20 mg/kg DHEAS. The most effective dose of DHEAS in the MWM was 10 mg/kg, while in the GC it was 20 mg/kg, in TAR 5 mg/kg, and all doses, except for vehicle, were effective at reducing injury-induced SMB hyperactivity. In no task did DHEAS-treated animals perform worse than the injured controls. In addition, DHEAS had no significant effects on behavioral performance in the sham-operates. These results can be interpreted to demonstrate that after a 7-day delay, the chronic administration of DHEAS to injured rats significantly improves behavioral recovery on both sensorimotor and cognitive tasks.

Specific binding of dehydroepiandrosterone to the N terminus of the microtubule-associated protein MAP2

The effect of neurosteroids is mediated through their membrane or nuclear receptors. However, no dehydroepiandrosterone (DHEA)-specific receptors have been evidenced so far in the brain. In this paper, we showed by isothermal titration calorimetry that the DHEA specifically binds to the dendritic brain microtubule-associated protein MAP2C with an association constant of 2.7 x 10(7) m-1 and at a molar ratio of 1:1. By partial tryptic digestions and mass spectrometry analysis, we found that the binding involved the N-terminal region of MAP2C. Interestingly, MAP2C displays homologies with 17 beta-hydroxysteroid dehydrogenase 1, an enzyme required for estrogen synthesis. Based on these sequence homologies and on the x-ray structure of the DHEA-binding pocket of 17 beta-hydroxysteroid dehydrogenase 1, we modeled the complex of DHEA with MAP2C. The binding of DHEA to MAP2C involved specific hydrogen bonds that orient the steroid into the pocket. This work suggests that DHEA can directly influence brain plasticity via MAP2C binding. It opens interesting ways for understanding the role of DHEA in the brain.

Dehydroepiandrosterone (DHEA) such as 17beta-estradiol prevents MPTP-induced dopamine depletion in mice

Previous work from our laboratory has shown prevention of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced striatal dopamine (DA) depletion in mice by 17beta-estradiol, progesterone, and raloxifene. Dehydroepiandrosterone (DHEA), a neurosteroid, was shown to have neuroprotective activities in various paradigms of neuronal death but its effect in vivo in mice on MPTP toxicity has not been reported. We investigated the effects of 17beta-estradiol (2 microg/day) and DHEA (3 mg/day) for 5 days before and after an acute treatment of four MPTP (10 mg/kg) injections in male C57Bl/6 mice. Striatal DA concentrations and its metabolites dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) were measured by HPLC. MPTP mice that received 17beta-estradiol or DHEA had striatal DA, DOPAC, and HVA concentrations comparable to intact animals and higher than striatal DA, DOPAC, and HVA levels in saline-MPTP-treated mice. MPTP treatment led to an increase of striatal DA turnover (assessed with the HVA/DA ratio); DHEA and 17beta-estradiol prevented this increase. 17beta-Estradiol did not affect striatal DA and metabolites concentrations in intact mice in this paradigm. Furthermore, in the substantia nigra DHEA and 17beta-estradiol prevented the MPTP-induced dopamine transporter and tyrosine hydroxylase mRNA decreases measured by in situ hybridization. Therefore, DHEA such as 17beta-estradiol is active in preventing the catecholamine-depleting effect of MPTP and our results suggest that this involves neuroprotection of DA neurons.

Synergistic effect of retinoic acid and dehydroepiandrosterone on differentiation of human neuroblastoma cells

Retinoic acid (RA) affects many cell types by either promoting their survival or inducing their differentiation. Dehydroepiandrosterone (DHEA), a precursor for both androgenic and estrogenic steroids and abundantly produced by brain, is known as an inhibitor of cell proliferation. Differentiation of a human neuroblastoma cell line (SK-N-BE) was evaluated measuring growth rate, motility, neurite extension and GAP-43 expression. We report that DHEA enhances the differentiating effect of RA on neuroblastoma cells via a signalling that is not RA receptor-mediated. Instead, we show a differential expression of matrix metalloproteinases: RA enhances the activity of MMP-2, whereas MMP-9 expression is up-regulated by DHEA. The concerted modulation of these proteinases may support the neurite outgrowth observed after co-treatment with the two drugs.

Comparative study of the neuroprotective effect of dehydroepiandrosterone and 17beta-estradiol against 1-methyl-4-phenylpyridium toxicity on rat striatum

The effects of dehydroepiandrosterone, estradiol and testosterone on 1-methyl-4-phenylpyridium (MPP+)-induced neurotoxicity of the nigrostriatal dopaminergic system were examined in rat. They were subjected to a unilateral intrastriatal infusion of the following treatment conditions: MPP+ alone or co-injection of MPP+ plus each hormone. Four days after injection, concentrations of dopamine and their metabolites were determined from the corpus striatum. To corroborate the neurochemical data an immunohistochemical analysis of tyrosine hydroxylase-immunoreactive fibers and acetylcholinesterase histochemistry in the striatum was performed. Moreover, we performed a dose-response study of the three hormones on the high-affinity dopamine transport system in rat striatal synaptosomes. Rats co-injected within the striatum with MPP+ and either dehydroepiandrosterone or estradiol had significantly greater concentrations of dopamine and less tyrosine hydroxylase-immunoreactive fibers and acetylcholinesterase fiber density loss compared with their respective controls. In addition, 4 days after injection, the brain was fixed and cut into coronal sections, and was immunostained with major histocompatibility complex class II antigens for activated microglia, and glial fibrillary acidic protein for activated astrocytes. Dehydroepiandrosterone also attenuated microglial cell activation. In contrast, testosterone showed reductions in dopamine concentrations similar to those obtained by MPP+. The protective effect of dehydroepiandrosterone against the MPP+ neurotoxic dopaminergic system may be produced by its partial prevention of MPP+ inhibition of NADH oxidase activity, whereas the estradiol may function as a neuroprotectant by reducing the uptake of MPP+ into dopaminergic neurons. Our findings we suggest indicate that dehydroepiandrosterone and estradiol by a non-genomic effect may have an important modulatory action, capable of attenuating degeneration within the striatum, and in this way serve as neuroprotectants of the nigrostriatal dopaminergic system.

Preclinical development of neurosteroids as neuroprotective agents for the treatment of neurodegenerative diseases

Recent literature has emphasized the unique role that the neurosteroid subclass of steroids, which includes dehydroepiandrosterone (DHEA) and dehydroepiandrosterone sulfate (DHEAS), play in the developing and adult central nervous system (CNS). Both DHEA and DHEAS are found in abundance in the CNS (Majewska, 1995), and both can be synthesized and metabolized in the brain of many species (Baulieu, 1981, 1998; Corpéchot et al., 1981, 1983; Zwain and Yen, 1999). DHEA and DHEAS have been implicated as potential signaling molecules for neocortical organization during neuronal development, suggesting that they have trophic factor-like activity (neurotrophic or neurotropic) or can interact with various neurotransmitter systems to promote neuronal remodeling (Compagnone and Mellon, 1998; Mao and Barger, 1998). Consistent with a neurotrophic role for these steroids, studies have shown that DHEAS protects certain neuronal populations against neurotoxic insults inflicted by the excitatory amino acid glutamate (Kimonides et al., 1998; Mao and Barger, 1998). This finding suggests that DHEAS may be useful in treating neurodegenerative diseases in which excitotoxicity is believed to be the underlying cause or a major contributor to cell death. Moreover, because DHEA and DHEAS are multifunctional and exhibit a variety of properties in the CNS, including memory consolidation, neuroprotection, and reduction of neurodegeneration (Majewska, 1992, 1995; Lapchak et al., 2000), their potential therapeutic benefits may be extended to include the treatment of other neurodegenerative diseases not directly linked to excitotoxicity.

Dehydroepiandrosterone (DHEA) increases territorial song and the size of an associated brain region in a male songbird

In many species, male territorial aggression is tightly coupled with gonadal secretion of testosterone (T). In contrast, in song sparrows (Melospiza melodia morphna), males are highly aggressive during the breeding (spring) and nonbreeding (autumn and early winter) seasons, but not during molt (late summer). In aggressive nonbreeding song sparrows, plasma T levels are basal (< or = 0.10 ng/ml), and castration has no effect on aggression. However, aromatase inhibitors reduce nonbreeding aggression, indicating a role for estrogen in wintering males. In the nonbreeding season, the substrate for brain aromatase is unclear, because plasma T and androstenedione levels are basal. Aromatizable androgen may be derived from plasma dehydroepiandrosterone (DHEA), an androgen precursor. DHEA circulates at elevated levels in wintering males (approximately 0.8 ng/ml) and might be locally converted to T in the brain. Moreover, plasma DHEA is reduced during molt, as is aggression. Here, we experimentally increased DHEA in wild nonbreeding male song sparrows and examined territorial behaviors (e.g., singing) and discrete neural regions controlling the production of song. A physiological dose of DHEA for 15 days increased singing in response to simulated territorial intrusions. In addition, DHEA treatment increased the volume of a telencephalic brain region (the HVc) controlling song, indicating that DHEA can have large-scale neuroanatomical effects in adult animals. The DHEA treatment also caused a slight increase in plasma T. Exogenous DHEA may have been metabolized to sex steroids within the brain to exert these behavioral and neural effects, and it is also possible that peripheral metabolism contributed to these effects. These are the first results to suggest that exogenous DHEA increases male-male aggression and the size of an entire brain region in adults. The data are consistent with the hypothesis that DHEA regulates territorial behavior, especially in the nonbreeding season, when plasma T is basal.

The influence of hormones and pharmaceutical agents on DHEA and DHEA-S concentrations: a review of clinical studies

Low endogenous levels of dehydroepiandrosterone (DHEA) and/or its sulfoconjugated derivative DHEA-S have been associated with diseases such as lupus, cancer, and diabetes. Circulating concentrations of DHEA and DHEA-S resulting from endogenous production or hormone supplementation may also be relevant in psychiatric illness. Drugs may significantly increase or decrease circulating concentrations of these adrenal androgens by various mechanisms. Some agents, such as dexamethasone, affect the HPA axis by inhibiting ACTH and therefore decrease DHEA and DHEA-S concentrations. Central nervous system agents, including carbamazepine and phenytoin, induce the P450 enzymes that metabolize DHEA and DHEA-S and therefore decrease circulating concentrations of these hormones. Danazol alters the ratio between DHEA and DHEA-S by inhibiting sulfatase. As research moves forward to better understand the relationships of these adrenal androgens with health and disease, it is essential that studies be designed to control for the influence of administered pharmaceuticals on DHEA and DHEA-S.