Expression of 5alpha-reductase and 3alpha-hydroxisteroid oxidoreductase in the hippocampus of patients with chronic temporal lobe epilepsy

Human Microglia Synthesize Neurosteroids to Cope with Rotenone-Induced Oxidative Stress

We obtained evidence that mouse BV2 microglia synthesize neurosteroids dynamically to modify neurosteroid levels in response to oxidative damage caused by rotenone. Here, we evaluated whether neurosteroids could be produced and altered in response to rotenone by the human microglial clone 3 (HMC3) cell line. To this aim, HMC3 cultures were exposed to rotenone (100 nM) and neurosteroids were measured in the culture medium by liquid chromatography with tandem mass spectrometry. Microglia reactivity was evaluated by measuring interleukin 6 (IL-6) levels, whereas cell viability was monitored by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. After 24 h (h), rotenone increased IL-6 and reactive oxygen species levels by approximately +37% over the baseline, without affecting cell viability; however, microglia viability was significantly reduced at 48 h (p < 0.01). These changes were accompanied by the downregulation of several neurosteroids, including pregnenolone, pregnenolone sulfate, 5α-dihydroprogesterone, and pregnanolone, except for allopregnanolone, which instead was remarkably increased (p < 0.05). Interestingly, treatment with exogenous allopregnanolone (1 nM) efficiently prevented the reduction in HMC3 cell viability. In conclusion, this is the first evidence that human microglia can produce allopregnanolone and that this neurosteroid is increasingly released in response to oxidative stress, to tentatively support the microglia's survival.

Neurosteroids: A novel promise for the treatment of stroke and post-stroke complications

Stroke is the primary reason for death and disability worldwide, with few treatment strategies to date. Neurosteroids, which are natural molecules in the brain, have aroused great interest in the field of stroke. Neurosteroids are a kind of steroid that acts on the nervous system, and are synthesized in the mitochondria of neurons or glial cells using cholesterol or other steroidal precursors. Neurosteroids mainly include estrogen, progesterone (PROG), allopregnanolone, dehydroepiandrosterone (DHEA), and vitamin D (VD). Most of the preclinical studies have confirmed that neurosteroids can decrease the risk of stroke, and improve stroke outcomes. In the meantime, neurosteroids have been shown to have a positive therapeutic significance in some post-stroke complications, such as epilepsy, depression, anxiety, cardiac complications, movement disorders, and post-stroke pain. In this review, we report the historical background, modulatory mechanisms of neurosteroids in stroke and post-stroke complications, and emphasize on the application prospect of neurosteroids in stroke therapy.

Expression in Escherichia Coli, Purification, and Functional Reconstitution of Human Steroid 5α-Reductases

The potent androgen 5α-dihydrotestosterone irreversibly derives from testosterone via the activity of steroid 5α-reductases (5αRs). The major 5αR isoforms in most species, 5αR1 and 5αR2, have not been purified to homogeneity. We report here the heterologous expression of polyhistidine-tagged, codon-optimized human 5αR1 and 5αR2 cDNAs in Escherichia coli. A combination of the nonionic detergents Triton X-100 and Nonidet P-40 enabled solubilization of these extremely hydrophobic integral membrane proteins and facilitated purification with affinity and cation-exchange chromatography methods. For functional reconstitution, we incorporated the purified isoenzymes into Triton X-100-saturated dioleoylphosphatidylcholine liposomes and removed excess detergent with polystyrene beads. Kinetic studies indicated that the 2 isozymes differ in biochemical properties, with 5αR2 having a lower apparent Km for testosterone, androstenedione, progesterone, and 17-hydroxyprogesterone than 5αR1; however, 5αR1 had a greater capacity for steroid conversion, as reflected by a higher Vmax than 5αR2. Both enzymes preferred progesterone as substrate over other steroids, and the catalytic efficiency of purified reconstituted 5αR2 exhibited a sharp pH optimum at pH 5. Intriguingly, we found that the prostate-cancer drug-metabolite 3-keto-∆ 4-abiraterone is metabolized by 5αR1 but not 5αR2, which may serve as a structural basis for isoform selectivity and inhibitor design. The functional characterization results with the purified reconstituted isoenzymes paralleled trends obtained with HEK-293 cell lines stably expressing native 5αR1 and 5αR2. Access to purified human 5αR1 and 5αR2 will advance studies of these important enzymes and might help to clarify their contributions to steroid anabolism and catabolism.

Gelsemine and koumine, principal active ingredients of Gelsemium, exhibit mechanical antiallodynia via spinal glycine receptor activation-induced allopregnanolone biosynthesis

Gelsemine, the principal active alkaloid from Gelsemium sempervirens Ait., and koumine, the most dominant alkaloids from Gelsemium elegans Benth., produced antinociception in a variety of rodent models of painful hypersensitivity. The present study explored the molecular mechanisms underlying gelsemine- and koumine-induced mechanical antiallodynia in neuropathic pain. The radioligand binding and displacement assays indicated that gelsemine and koumine, like glycine, were reversible and orthosteric agonists of glycine receptors with full efficacy and probably acted on same binding site as the glycine receptor antagonist strychnine. Treatment with gelsemine, koumine and glycine in primary cultures of spinal neurons (but not microglia or astrocytes) concentration dependently increased 3α-hydroxysteroid oxidoreductase (3α-HSOR) mRNA expression, which was inhibited by pretreatment with strychnine but not the glial inhibitor minocycline. Intrathecal injection of gelsemine, koumine and glycine stimulated 3α-HSOR mRNA expression in the spinal cords of neuropathic rats and produced mechanical antiallodynia. Their spinal mechanical antiallodynia was completely blocked by strychnine, the selective 3α-HSOR inhibitor medroxyprogesterone acetate (MPA), 3α-HSOR gene silencer siRNA/3α-HSOR and specific GABA_A receptor antagonist isoallopregnanolone, but not minocycline. All the results taken together uncovered that gelsemine and koumine are orthosteric agonists of glycine receptors, and produce mechanical antiallodynia through neuronal glycine receptor/3α-HSOR/allopregnanolone/GABA_A receptor pathway.

Neurosteroid regulation of GABAA receptors: A role in catamenial epilepsy

The female reproductive hormones progesterone and estrogen regulate network excitability. Fluctuations in the circulating levels of these hormones during the menstrual cycle cause frequent seizures during certain phases of the cycle in women with epilepsy. This seizure exacerbation, called catamenial epilepsy, is a dominant form of drug-refractory epilepsy in women of reproductive age. Progesterone, through its neurosteroid derivative allopregnanolone, increases γ-aminobutyric acid type-A receptor (GABAR)-mediated inhibition in the brain and keeps seizures under control. Catamenial seizures are believed to be a neurosteroid withdrawal symptom, and it was hypothesized that exogenous administration of progesterone to maintain its levels high during luteal phase will treat catamenial seizures. However, in a multicenter, double-blind, phase III clinical trial, progesterone treatment did not suppress catamenial seizures. The expression of GABARs with reduced neurosteroid sensitivity in epileptic animals may explain the failure of the progesterone clinical trial. The expression of neurosteroid-sensitive δ subunit-containing GABARs is reduced, and the expression of α4γ2 subunit-containing GABARs is upregulated, which alters the inhibition of dentate granule cells in epilepsy. These changes reduce the endogenous neurosteroid control of seizures and contribute to catamenial seizures.

Intracrine Regulation of Estrogen and Other Sex Steroid Levels in Endometrium and Non-gynecological Tissues; Pathology, Physiology, and Drug Discovery

Our understanding of the intracrine (or local) regulation of estrogen and other steroid synthesis and degradation expanded in the last decades, also thanks to recent technological advances in chromatography mass-spectrometry. Estrogen responsive tissues and organs are not passive receivers of the pool of steroids present in the blood but they can actively modify the intra-tissue steroid concentrations. This allows fine-tuning the exposure of responsive tissues and organs to estrogens and other steroids in order to best respond to the physiological needs of each specific organ. Deviations in such intracrine control can lead to unbalanced steroid hormone exposure and disturbances. Through a systematic bibliographic search on the expression of the intracrine enzymes in various tissues, this review gives an up-to-date view of the intracrine estrogen metabolisms, and to a lesser extent that of progestogens and androgens, in the lower female genital tract, including the physiological control of endometrial functions, receptivity, menopausal status and related pathological conditions. An overview of the intracrine regulation in extra gynecological tissues such as the lungs, gastrointestinal tract, brain, colon and bone is given. Current therapeutic approaches aimed at interfering with these metabolisms and future perspectives are discussed.

Allopregnanolone levels and depressive symptoms during pregnancy in relation to single nucleotide polymorphisms in the allopregnanolone synthesis pathway

Allopregnanolone, a neurosteroid whose levels rise throughout gestation, putatively stabilizes antenatal mood. The present study aimed to investigate associations of plasma allopregnanolone to antenatal depressive symptoms, as well as to genetic and obstetric factors. Allopregnanolone plasma levels from 284 pregnant women were measured around gestational week 18. Haplotype tag single nucleotide polymorphisms in the aldo-keto reductase family 1, members C2 and C4 (AKR1C2, AKR1C4), and steroid 5 alpha-reductase 1 and 2 (SRD5A1, and SRD5A2) genes were genotyped in a larger sample of pregnant women (n=1351). The Edinburgh Postnatal Depression Scale (EPDS) was administered via web-questionnaires in gestational weeks 17 and 32. Demographic and obstetric data was retrieved from web-questionnaires and medical records. There was no association between allopregnanolone levels and depressive symptoms. Furthermore, no associations between allopregnanolone level and synthesis pathway genotypes were found after accounting for multiple comparisons. However, exploratory analyses suggested that the women who were homozygous for the minor allele of the AKR1C2 polymorphism rs1937863 had nominally lower allopregnanolone levels and lower depression scores in gestational week 17, but also the highest increase in depression scores between week 17 and 32. Additionally, higher body mass index was associated with lower allopregnanolone levels. The results do not support second trimester plasma allopregnanolone as a mood stabilizing factor. However, we speculate that AKR1C2 variation may alter the susceptibility to depressive symptoms through effects on central allopregnanolone synthesis. Another implication of this study is that the relationship between neuroactive steroids and obesity in pregnancy deserves to be investigated.

Novel therapeutic approaches for disease-modification of epileptogenesis for curing epilepsy

This article describes the recent advances in epileptogenesis and novel therapeutic approaches for the prevention of epilepsy, with a special emphasis on the pharmacological basis of disease-modification of epileptogenesis for curing epilepsy. Here we assess animal studies and human clinical trials of epilepsy spanning 1982-2016. Epilepsy arises from a number of neuronal factors that trigger epileptogenesis, which is the process by which a brain shifts from a normal physiologic state to an epileptic condition. The events precipitating these changes can be of diverse origin, including traumatic brain injury, cerebrovascular damage, infections, chemical neurotoxicity, and emergency seizure conditions such as status epilepticus. Expectedly, the molecular and system mechanisms responsible for epileptogenesis are not well defined or understood. To date, there is no approved therapy for the prevention of epilepsy. Epigenetic dysregulation, neuroinflammation, and neurodegeneration appear to trigger epileptogenesis. Targeted drugs are being identified that can truly prevent the development of epilepsy in at-risk people. The promising agents include rapamycin, COX-2 inhibitors, TRK inhibitors, epigenetic modulators, JAK-STAT inhibitors, and neurosteroids. Recent evidence suggests that neurosteroids may play a role in modulating epileptogenesis. A number of promising drugs are under investigation for the prevention or modification of epileptogenesis to halt the development of epilepsy. Some drugs in development appear rational for preventing epilepsy because they target the initial trigger or related signaling pathways as the brain becomes progressively more prone to seizures. Additional research into the target validity and clinical investigation is essential to make new frontiers in curing epilepsy.

5α-Reductase Inhibition Prevents the Luteal Phase Increase in Plasma Allopregnanolone Levels and Mitigates Symptoms in Women with Premenstrual Dysphoric Disorder

Changes in neurosteroid levels during the luteal phase of the menstrual cycle may precipitate affective symptoms. To test this hypothesis, we stabilized neurosteroid levels by administering the 5α-reductase inhibitor dutasteride to block conversion of progesterone to its neurosteroid metabolite allopregnanolone in women with premenstrual dysphoric disorder (PMDD) and in asymptomatic control women. Sixteen women with prospectively confirmed PMDD and 16 control women participated in one of two separate randomized, double-blind, placebo-controlled, cross-over trials, each lasting three menstrual cycles. After one menstrual cycle of single-blind placebo, participants were randomized to receive, for the next two menstrual cycles, either double-blind placebo or dutasteride (low-dose 0.5 mg/day in the first eight PMDD and eight control women or high-dose 2.5 mg/day in the second group of women). All women completed the daily rating form (DRF) and were evaluated in clinic during the follicular and luteal phases of each menstrual cycle. Main outcome measures were the DRF symptoms of irritability, sadness, and anxiety. Analyses were performed with SAS PROC MIXED. In the low-dose group, no significant effect of dutasteride on PMDD symptoms was observed compared with placebo (ie, symptom cyclicity maintained), and plasma allopregnanolone levels increased in women with PMDD from follicular to the luteal phases, suggesting the absence of effect of the low-dose dutasteride on 5α-reductase. In contrast, the high-dose group experienced a statistically significant reduction in several core PMDD symptoms (ie, irritability, sadness, anxiety, food cravings, and bloating) on dutasteride compared with placebo. Dutasteride had no effect on mood in controls. Stabilization of allopregnanolone levels from the follicular to the luteal phase of the menstrual cycle by blocking the conversion of progesterone to its 5α-reduced neurosteroid metabolite mitigates symptoms in PMDD. These data provide preliminary support for the pathophysiologic relevance of neurosteroids in this condition.

Gelsemium analgesia and the spinal glycine receptor/allopregnanolone pathway

Gelsemium, a small genus of flowering plant from the family Loganiaceae, comprises five species including the popular Gelsemium sempervirens Ait. and Gelsemium elegans Benth., which are indigenous to North America and China/East Asia, respectively. Approximately 120 alkaloids have been isolated and identified from Gelsemium, with the predominant indole alkaloids including gelsemine, koumine, gelsemicine, gelsenicine, gelsedine, sempervirine, koumidine, koumicine and humantenine. Gelsemine is the principal active alkaloid in G. sempervirens Ait., and koumine and gelsemine are the most and second-most dominant alkaloids in G. elegans Benth. Gelsemium extract and its active alkaloids serve a variety of biological functions, including neurobiological, immunosuppressive and antitumor effects, and have traditionally been used to treat pain, neuralgia, anxiety, insomnia, asthma, respiratory ailments and cancers. This review focuses on animal-based studies of Gelsemium as a pain treatment and its mechanism of action. In contrast to morphine, when administered intrathecally and systemically, koumine, gelsemine and gelsenicine have marked antinociception in inflammatory, neuropathic and bone cancer pains without inducing antinociceptive tolerance. Gelsemium and its active alkaloids may produce antinociception by activating the spinal α3 glycine/allopregnanolone pathway. The results of this review support the clinical use of Gelsemium and suggest that its active alkaloids may be developed to treat intractable and other types of pain, preferably after chemical modification. However, Gelsemium is a known toxic plant, and its toxicity limits its appropriate dosage and clinical use. To avoid or decrease the side/toxic effects of Gelsemium, an individual monomer of highly potent alkaloids must be selected, or alkaloids that exhibit greater α3 glycine receptor selectivity may be discovered or modified.

Gender-specific association of variants in the AKR1C1 gene with dimensional anxiety in patients with panic disorder: additional evidence for the importance of neurosteroids in anxiety?

BACKGROUND

Neurosteroids are synthesized both in brain and peripheral steroidogenic tissue from cholesterol or steroidal precursors. Neurosteroids have been shown to be implicated in neural proliferation, differentiation, and activity. Preclinical and clinical studies also suggest a modulatory role of neurosteroids in anxiety-related phenotypes. However, little is known about the contribution of genetic variants in genes relevant for the neurosteroidogenesis to anxiety disorders.

METHODS

We performed an association analysis of single nucleotide polymorphisms (SNPs) in five genes related to the neurosteroidal pathway with emphasis on progesterone and allopregnanolone biosynthesis (steroid-5-alpha-reductase 1A (SRD5A1), aldo-keto reductase family 1 C1-C3 (AKR1C1-AKR1C3) and translocator protein 18 kDA (TSPO) with panic disorder (PD) and dimensional anxiety in two German PD samples (cases N = 522, controls N = 1,115).

RESULTS

Case-control analysis for PD and SNPs in the five selected genes was negative in the combined sample. However, we detected a significant association of anticipatory anxiety with two intronic SNPs (rs3930965, rs41314625) located in the gene AKR1C1 surviving correction for multiple testing in PD patients. Stratification analysis for gender revealed a female-specific effect of the associations of both SNPs.

CONCLUSIONS

These results suggest a modulatory effect of AKR1C1 activity on anxiety levels, most likely through changes in progesterone and allopregnanolone levels within and outside the brain. In summary, this is the first evidence for the gender-specific implication of the AKR1C1 gene in the expression of anticipatory anxiety in PD. Further analyses to unravel the functional role of the SNPs detected here and replication analyses are needed to validate our results.

Allopregnanolone modulation of HPA axis function in the adult rat

RATIONALE

GABAergic neuronal circuits regulate neuroendocrine stress response, and the most potent positive endogenous modulator of GABAA receptor function is allopregnanolone. This neurosteroid acts in a nongenomic manner to selectively increase the inhibitory signal meditated by GABAA receptors; in addition, it also induces long-lasting changes in the expression of specific GABAA receptor subunits in various brain regions, with consequent changes in receptor function.

OBJECTIVE

The objective of this review is to summarize our findings on emotional state and stress responsiveness in three animal models in which basal brain concentrations of allopregnanolone differ. It is postulated that individual differences in allopregnanolone levels can influence general resilience.

RESULTS

The results showed that there is an apparent correlation between endogenous levels of brain allopregnanolone and basal and stress-stimulated HPA axis activity.

CONCLUSION

The relationship between endogenous brain levels of allopregnanolone and HPA axis activity and function sustains the therapeutic potential of this neurosteroid for the treatment of stress-associated disorders.

5α-reductase type I expression is downregulated in the prefrontal cortex/Brodmann's area 9 (BA9) of depressed patients

RATIONALE

The implications of the neurosteroid 3α-hydroxy-5α-pregnan-20-one [allopregnanolone (Allo)] in neuropsychiatric disorders have been highlighted in several recent clinical investigations. For instance, Allo levels are decreased in the cerebrospinal fluid (CSF) of patients with posttraumatic stress disorder (PTSD) and major unipolar depression. Neurosteroidogenic antidepressants [i.e., selective brain steroidogenic stimulants (SBSSs)], including fluoxetine and analogs, correct this decrease in a manner that correlates with improved depressive symptoms. Allo positively and allosterically modulates GABA action at postsynaptic and extrasynaptic GABAA receptors. It is synthesized in both the human and rodent brain cortices by principal glutamatergic pyramidal neurons from progesterone by the sequential action of 5α-reductase type I (5α-RI), which is the rate-limiting step enzyme in Allo biosynthesis, and 3α-hydroxysteroid dehydrogenase (3α-HSD), which converts 5α-dehydroprogesterone into Allo.

HYPOTHESIS

We thus hypothesized that decreased CSF levels of Allo in depressed patients could reflect a brain dysfunction of 5α-RI.

METHODS

In a pilot study of samples from six patients per group [six depressed patients and six nonpsychiatric subjects (NPS)], we studied the expression of 5α-RI messenger RNA (mRNA) in prefrontal cortex Brodmann's area 9 (BA9) and cerebellum from depressed patients obtained from the Maryland Brain Collection at the Maryland Psychiatric Research Center (Baltimore, MD) that were age-matched with NPS.

RESULTS

The levels of 5α-RI mRNA were decreased from 25 ± 5.8 in NPS to 9.1 ± 3.1 fmol/pmol neuronal specific enolase (NSE) (t1,10 = 2.7, P = 0.02) in depressed patients. These differences are absent in the cerebellum of the same patients. The levels of neurosteroids were determined in the prefrontal cortex BA9 of depressed patients obtained from the Stanley Foundation Brain Bank Neuropathology Consortium, Bethesda (MD). The BA9 levels of Allo in male depressed patients failed to reach statistical difference from the levels of NPS (1.63 ± 1.01 pg/mg, n = 8, in NPS and 0.82 ± 0.33 pg/mg, n = 5, in nontreated depressed patients). However, depressed patients who had received antidepressant treatment (three patients SSRI and one TCA) exhibited increased BA9 Allo levels (6.16 ± 2.5 pg/mg, n = 4, t1,9 = 2.4, P = 0.047) when compared with nontreated depressed patients.

CONCLUSIONS

Although in a small number of patients, this finding is in-line with previous reports in the field that have observed an increase of Allo levels in CSF and plasma of depressed patients following antidepressant treatment. Hence, the molecular mechanisms underlying major depression may include a GABAergic neurotransmission deficit caused by a brain Allo biosynthesis downregulation, which can be normalized by SBSSs.

Cognitive effects of testosterone and finasteride administration in older hypogonadal men

Serum concentrations of neuroactive androgens decline in older men and, in some studies, low testosterone is associated with decreased cognitive function and incidence of depression. Existing studies evaluating the effect of testosterone administration on cognition in older men have been largely inconclusive, with some studies reporting minor to moderate cognitive benefit, while others indicate no cognitive effect. Our objective was to assess the cognitive effects of treating older hypogonadal men for 1 year with a supraphysiological dose of testosterone, either alone or in combination with finasteride (a type II 5α-reductase inhibitor), in order to determine whether testosterone produces cognitive benefit and whether suppressed dihydrotestosterone influences cognition. Sixty men aged ≥60 years with a serum testosterone concentration of ≤300 ng/dL or bioavailable testosterone ≤70 ng/dL and no evidence of cognitive impairment received testosterone-enanthate (125 mg/week) versus vehicle, paired with finasteride (5 mg/day) versus placebo using a 2×2 factorial design. Testosterone caused a small decrease in depressive symptoms as assessed by the Geriatric Depression Scale and a moderate increase in visuospatial memory as assessed by performance on a recall trial of the Rey-Osterrieth Complex Figure Test. Finasteride caused a small increase in performance on the Benton Judgment of Line Orientation test. In total, major improvements in cognition were not observed either with testosterone or finasteride. Further studies are warranted to determine if testosterone replacement may improve cognition in other domains.

Neurosteroids and their role in sex-specific epilepsies

Neurosteroids are involved in sex-specific epilepsies. Allopregnanolone and related endogenous neurosteroids in the brain control excessive neuronal excitability and seizure susceptibility. Neurosteroids activate GABA-A receptors, especially extrasynaptic αγδ-GABA-A receptor subtypes that mediate tonic inhibition and thus dampen network excitability. Our studies over the past decade have shown that neurosteroids are broad-spectrum anticonvulsants and confer seizure protection in various animal models. Neurosteroids also exert antiepileptogenic effects. There is emerging evidence on a critical role for neurosteroids in the pathophysiology of the sex-specific forms of epilepsies such as catamenial epilepsy, a menstrual cycle-related seizure disorder in women. Catamenial epilepsy is a neuroendocrine condition in which seizures are clustered around specific points in the menstrual cycle, most often around the perimenstrual or periovulatory period. Apart from ovarian hormones, fluctuations in neurosteroid levels could play a critical role in this gender-specific epilepsy. Neurosteroids also regulate the plasticity of synaptic and extrasynaptic GABA-A receptors in the hippocampus and other regions involved in epilepsy pathology. Based on these studies, we proposed a neurosteroid replacement therapy for catamenial epilepsy. Thus, neurosteroids are novel drug targets for pharmacotherapy of epilepsy.

Neurosteroid interactions with synaptic and extrasynaptic GABA(A) receptors: regulation of subunit plasticity, phasic and tonic inhibition, and neuronal network excitability

RATIONALE

Neurosteroids are steroids synthesized within the brain with rapid effects on neuronal excitability. Allopregnanolone, allotetrahydrodeoxycorticosterone, and androstanediol are three widely explored prototype endogenous neurosteroids. They have very different targets and functions compared to conventional steroid hormones. Neuronal γ-aminobutyric acid (GABA) type A (GABA(A)) receptors are one of the prime molecular targets of neurosteroids.

OBJECTIVE

This review provides a critical appraisal of recent advances in the pharmacology of endogenous neurosteroids that interact with GABA(A) receptors in the brain. Neurosteroids possess distinct, characteristic effects on the membrane potential and current conductance of the neuron, mainly via potentiation of GABA(A) receptors at low concentrations and direct activation of receptor chloride channel at higher concentrations. The GABA(A) receptor mediates two types of inhibition, now characterized as synaptic (phasic) and extrasynaptic (tonic) inhibition. Synaptic release of GABA results in the activation of low-affinity γ2-containing synaptic receptors, while high-affinity δ-containing extrasynaptic receptors are persistently activated by the ambient GABA present in the extracellular fluid. Neurosteroids are potent positive allosteric modulators of synaptic and extrasynaptic GABA(A) receptors and therefore enhance both phasic and tonic inhibition. Tonic inhibition is specifically more sensitive to neurosteroids. The resulting tonic conductance generates a form of shunting inhibition that controls neuronal network excitability, seizure susceptibility, and behavior.

CONCLUSION

The growing understanding of the mechanisms of neurosteroid regulation of the structure and function of the synaptic and extrasynaptic GABA(A) receptors provides many opportunities to create improved therapies for sleep, anxiety, stress, epilepsy, and other neuropsychiatric conditions.

Role of hormones and neurosteroids in epileptogenesis

This article describes the emerging evidence of hormonal influence on epileptogenesis, which is a process whereby a brain becomes progressively epileptic due to an initial precipitating event of diverse origin such as brain injury, stroke, infection, or prolonged seizures. The molecular mechanisms underlying the development of epilepsy are poorly understood. Neuroinflammation and neurodegeneration appear to trigger epileptogenesis. There is an intense search for drugs that truly prevent the development of epilepsy in people at risk. Hormones play an important role in children and adults with epilepsy. Corticosteroids, progesterone, estrogens, and neurosteroids have been shown to affect seizure activity in animal models and in clinical studies. However, the impact of hormones on epileptogenesis has not been investigated widely. There is emerging new evidence that progesterone, neurosteroids, and endogenous hormones may play a role in regulating the epileptogenesis. Corticosterone has excitatory effects and triggers epileptogenesis in animal models. Progesterone has disease-modifying activity in epileptogenic models. The antiepileptogenic effect of progesterone has been attributed to its conversion to neurosteroids, which binds to GABA-A receptors and enhances phasic and tonic inhibition in the brain. Neurosteroids are robust anticonvulsants. There is pilot evidence that neurosteroids may have antiepileptogenic properties. Future studies may generate new insight on the disease-modifying potential of hormonal agents and neurosteroids in epileptogenesis.

Sex dependent influence of a functional polymorphism in steroid 5-α-reductase type 2 (SRD5A2) on post-traumatic stress symptoms

A non-synonymous, single nucleotide polymorphism (SNP) in the gene coding for steroid 5-α-reductase type 2 (SRD5A2) is associated with reduced conversion of testosterone to dihydrotestosterone (DHT). Because SRD5A2 participates in the regulation of testosterone and cortisol metabolism, hormones shown to be dysregulated in patients with PTSD, we examined whether the V89L variant (rs523349) influences risk for post-traumatic stress disorder (PTSD). Study participants (N = 1,443) were traumatized African-American patients of low socioeconomic status with high rates of lifetime trauma exposure recruited from the primary care clinics of a large, urban hospital. PTSD symptoms were measured with the post-traumatic stress symptom scale (PSS). Subjects were genotyped for the V89L variant (rs523349) of SRD5A2. We initially found a significant sex-dependent effect of genotype in male but not female subjects on symptoms. Associations with PTSD symptoms were confirmed using a separate internal replication sample with identical methods of data analysis, followed by pooled analysis of the combined samples (N = 1,443, sex × genotype interaction P < 0.002; males: n = 536, P < 0.001). These data support the hypothesis that functional variation within SRD5A2 influences, in a sex-specific way, the severity of post-traumatic stress symptoms and risk for diagnosis of PTSD.

Sex and hormonal influences on seizures and epilepsy

Epilepsy is the third most common chronic neurological disorder. Clinical and experimental evidence supports the role of sex and influence of sex hormones on seizures and epilepsy as well as alterations of the endocrine system and levels of sex hormones by epileptiform activity. Conversely, seizures are sensitive to changes in sex hormone levels, which in turn may affect the seizure-induced neuronal damage. The effects of reproductive hormones on neuronal excitability and seizure-induced damage are complex to contradictory and depend on different mechanisms, which have to be accounted for in data interpretation. Both estradiol and progesterone/allopregnanolone may have beneficial effects for patients with epilepsy. Individualized hormonal therapy should be considered as adjunctive treatment in patients with epilepsy to improve seizure control as well as quality of life.

Expression of P450c17 in the human fetal nervous system

P450c17 catalyzes steroid 17α-hydroxylase and 17,20 lyase activities. P450c17 is expressed in human fetal and postnatal adrenals and gonads and in the developing mouse nervous system, but little is known about its expression in the human nervous system. We obtained portions of 9-, 10-, and 11-wk gestation human fetuses and delineated the pattern of expression of P450c17 in their peripheral nervous systems by immunocytochemistry using the P450c17 antiserum previously used to characterize P450c17 in the mouse brain. P450c17 was readily detected in the dorsal root ganglia (DRG) and spinal cord. Neural structures were identified with antisera to the cytoskeletal protein neural cell adhesion molecule; DRG were identified with antisera to the neuronal transcription factor BRN3A and neurotrophin receptor tropomyosin-receptor-kinase B. The identification of P450c17 was confirmed using commercial antisera directed against different domains of P450c17 and by using antisera immunodepleted with authentic human P450c17. We also found expression of the P450 cholesterol side-chain cleavage enzyme (P450scc) in the spinal cord and DRG. Expression of P450scc is limited to cell bodies; unlike P450c17, we never detected P450scc in fiber tracts. Catalysis by P450c17 requires electron donation from P450 oxidoreductase (POR). Dual-label immunohistochemistry detected P450c17 and POR colocalized in DRG bundles, but some fibers containing P450c17 lacked POR. These data suggest that neurosteroids synthesized via these two enzymes may act in the developing human nervous system. The expression of P450c17 in structures lacking POR means that P450c17 may not be steroidogenic in those locations, suggesting that P450c17 may have additional functions that do not require POR.

5α-Reduced glucocorticoids: a story of natural selection

5α-Reduced glucocorticoids (GCs) are formed when one of the two isozymes of 5α-reductase reduces the Δ(4-5) double bond in the A-ring of GCs. These steroids are largely viewed inert, despite the acceptance that other 5α-dihydro steroids, e.g. 5α-dihydrotestosterone, retain or have increased activity at their cognate receptors. However, recent findings suggest that 5α-reduced metabolites of corticosterone have dissociated actions on GC receptors (GRs) in vivo and in vitro and are thus potential candidates for safer anti-inflammatory steroids. 5α-Dihydro- and 5α-tetrahydro-corticosterone can bind with GRs, but interest in these compounds had been limited, since they only weakly activated metabolic gene transcription. However, a greater understanding of the signalling mechanisms has revealed that transactivation represents only one mode of signalling via the GR and recently the abilities of 5α-reduced GCs to suppress inflammation have been demonstrated in vitro and in vivo. Thus, the balance of parent GC and its 5α-reduced metabolite may critically affect the profile of GR signalling. 5α-Reduction of GCs is up-regulated in liver in metabolic disease and may represent a pathway that protects from both GC-induced fuel dyshomeostasis and concomitant inflammatory insult. Therefore, 5α-reduced steroids provide hope for drug development, but may also act as biomarkers of the inflammatory status of the liver in metabolic disease. With these proposals in mind, careful attention must be paid to the possible adverse metabolic effects of 5α-reductase inhibitors, drugs that are commonly administered long term for the treatment of benign prostatic hyperplasia.

Role of anticonvulsant and antiepileptogenic neurosteroids in the pathophysiology and treatment of epilepsy

This review highlights the role of major endogenous neurosteroids in seizure disorders and the promise of neurosteroid replacement therapy in epilepsy. Neurosteroids are endogenous modulators of seizure susceptibility. Neurosteroids such as allopregnanolone (3α-hydroxy-5α-pregnane-20-one) and allotetrahydrodeoxycorticosterone (3α,21-dihydroxy-5α-pregnan-20-one) are positive modulators of GABA-A receptors. Aside from peripheral tissues, neurosteroids are synthesized within the brain, mostly in principal neurons. Neurosteroids potentiate synaptic GABA-A receptor function and also activate δ-subunit-containing extrasynaptic GABA-A receptors that mediate tonic currents and thus may play an important role in neuronal network excitability and seizure susceptibility. Our studies over the past decade have shown that neurosteroids are broad-spectrum anticonvulsants and confer seizure protection in various animal models. They protect against seizures induced by GABA-A receptor antagonists, 6-Hz model, pilocarpine-induced limbic seizures, and seizures in kindled animals. Unlike benzodiazepines, tolerance does not occur to their actions during chronic administration. Our recent studies provide compelling evidence that neurosteroids may have antiepileptogenic properties. There is emerging evidence that endogenous neurosteroids may play a key role in the pathophysiology of catamenial epilepsy, stress-sensitive seizure conditions, temporal lobe epilepsy, and alcohol-withdrawal seizures. It is suggested that neurosteroid replacement with natural or synthetic neurosteroids may be useful in the treatment of epilepsy. Synthetic analogs of neurosteroids that are devoid of hormonal side effects show promise in the treatment of diverse seizure disorders. Agents that stimulate endogenous production of neurosteroids may also be useful for treatment of epilepsy.

Neurosteroids: endogenous role in the human brain and therapeutic potentials

This chapter provides an overview of neurosteroids, especially their impact on the brain, sex differences and their therapeutic potentials. Neurosteroids are synthesized within the brain and rapidly modulate neuronal excitability. They are classified as pregnane neurosteroids, such as allopregnanolone and allotetrahydrodeoxycorticosterone, androstane neurosteroids, such as androstanediol and etiocholanolone, and sulfated neurosteroids such as pregnenolone sulfate. Neurosteroids such as allopregnanolone are positive allosteric modulators of GABA-A receptors with powerful anti-seizure activity in diverse animal models. Neurosteroids increase both synaptic and tonic inhibition. They are endogenous regulators of seizure susceptibility, anxiety, and stress. Sulfated neurosteroids such as pregnenolone sulfate, which are negative GABA-A receptor modulators, are memory-enhancing agents. Sex differences in susceptibility to brain disorders could be due to neurosteroids and sexual dimorphism in specific structures of the human brain. Synthetic neurosteroids that exhibit better bioavailability and efficacy and drugs that enhance neurosteroid synthesis have therapeutic potential in anxiety, epilepsy, and other brain disorders. Clinical trials with the synthetic neurosteroid analog ganaxolone in the treatment of epilepsy have been encouraging. Neurosteroidogenic agents that lack benzodiazepine-like side effects show promise in the treatment of anxiety and depression.

Neurosteroid biosynthesis: enzymatic pathways and neuroendocrine regulation by neurotransmitters and neuropeptides

Neuroactive steroids synthesized in neuronal tissue, referred to as neurosteroids, are implicated in proliferation, differentiation, activity and survival of nerve cells. Neurosteroids are also involved in the control of a number of behavioral, neuroendocrine and metabolic processes such as regulation of food intake, locomotor activity, sexual activity, aggressiveness, anxiety, depression, body temperature and blood pressure. In this article, we summarize the current knowledge regarding the existence, neuroanatomical distribution and biological activity of the enzymes responsible for the biosynthesis of neurosteroids in the brain of vertebrates, and we review the neuronal mechanisms that control the activity of these enzymes. The observation that the activity of key steroidogenic enzymes is finely tuned by various neurotransmitters and neuropeptides strongly suggests that some of the central effects of these neuromodulators may be mediated via the regulation of neurosteroid production.

Steroidogenic acute regulatory protein expression and pregnenolone synthesis in rat astrocyte cultures

Neurosteroids are steroids synthesised by brain cells. The molecular mechanism of neurosteroidogenesis from cholesterol has not yet been revealed. We studied the potential role of the steroidogenic acute regulatory (StAR) protein in neurosterodogenesis by using rat brain astrocytes. The novelty of the study is that regulation of StAR is described in primary cultures from embryonic mesencephalon and cerebellum regions of the brain. Dibutyryl cyclic AMP (dbcAMP) treatment increased StAR protein expression in astrocyte cultures. This was observed in immunoblots of mitochondrial fractions and by immunocytochemistry. Dual-labelling showed that the cyclic AMP-induced increase in StAR immunofluorescence was localised to mitochondria. In addition, mitochondrial cytochrome P450-side chain cleavage enzyme was demonstrated with a specific antibody, indicating the potential for pregnenolone production in these cells. Radioimmunoassay on ether-extracted conditioned media of control and dbcAMP treated cells demonstrated pregnenolone production by mesencephalic and cerebellar astrocyte cultures. Furthermore, 24-h pregnenolone levels, in the presence of inhibitors of further pregnenolone metabolism, were significantly increased by dbcAMP exposure. A murine StAR promoter-luciferase fusion plasmid was activated by dbcAMP in transiently transfected mesencephalic and cerebellar astrocytes. These novel results indicate that cyclic AMP signalling can regulate StAR expression and pregnenolone production in brain astrocytes, and provide additional insight into the role of StAR in neurosteroidogenesis.

Finasteride induced depression: a prospective study

Background

Finasteride is a competitive inhibitor of 5 alpha-reductase enzyme, and is used for treatment of benign prostatic hyperplasia and androgenetic alopecia. Animal studies have shown that finasteride might induce behavioral changes. Additionally, some cases of finasteride-induced depression have been reported in humans. The purpose of this study was to examine whether depressive symptoms or anxiety might be induced by finasteride administration.

Methods

One hundred and twenty eight men with androgenetic alopecia, who were prescribed finasteride (1 mg/day) were enrolled in this study. Information on depressed mood and anxiety was obtained by Beck Depression Inventory (BDI), and Hospital Anxiety and Depression Scale (HADS). Participants completed BDI and HADS questionnaires before beginning the treatment and also two months after it.

Results

Mean age of the subjects was 25.8(± 4.4) years. At baseline, mean BDI and HADS depression scores were 12.11(± 7.50) and 4.04(± 2.51), respectively. Finasteride treatment increased both BDI (p < 0.001) and HADS depression scores significantly (p = 0.005). HADS anxiety scores were increased, but the difference was not significant (p = 0.061).

Conclusion

This preliminary study suggests that finasteride might induce depressive symptoms; therefore this medication should be prescribed cautiously for patients with high risk of depression. It seems that further studies would be necessary to determine behavioral effects of this medication in higher doses and in more susceptible patients.

Steroids in intractable childhood epilepsy: Clinical experience and review of the literature

Steroids and adrenocorticotrophic hormone (ACTH) have been used for the treatment of infantile spasms for several years. However, the use of steroids in the treatment of epilepsy beyond infantile spasms has been limited to only a few studies. We report the experience with steroids in 32 children with intractable epilepsy, not including West syndrome. In 47% there was a decrease in seizure frequency, 25% became seizure free, 11% had a seizure reduction of >50% and 11% had a seizure reduction of <50%. Our study confirms the conclusions of few previous reports of effective adjunctive steroid treatment for children with intractable epilepsy. The possible side effects, however, especially during prolonged therapy remain an important concern.

Attenuating 5alpha-pregnane-3alpha-ol-20-one formation in the hippocampus of female rats increases pentylenetetrazole-induced seizures

Progesterone has antiseizure effects, which may be due to the actions of its 5alpha-reduced metabolite, 5alpha-pregnan-3alpha-ol-20-one (3alpha,5alpha-THP). Whether metabolism of progesterone to 3alpha,5alpha-THP in the hippocampus is essential for its antiseizure effects was investigated. In Experiment 1, ovariectomized rats were administered subcutaneous progesterone (500 microg) or vehicle (sesame oil), followed 1 hour later by subcutaneous administration of an inhibitor of the 5alpha-reductase enzyme, finasteride (50 mg/kg), or vehicle (90% sesame oil, 10% ethanol). Administration of progesterone increased the latency to, and decreased the number of, tonic seizures and increased hippocampal 3alpha,5alpha-THP levels, compared with vehicle. Administration of finasteride with progesterone attenuated progesterone's antiseizure effects and decreased levels of 3alpha,5alpha-THP in the hippocampus. Finasteride administration alone did not alter ictal behavior or 3alpha,5alpha-THP levels compared with vehicle. In Experiment 2, ovariectomized rats were administered subcutaneous progesterone (500 microg) or vehicle (sesame oil), followed 1 hour later by bilateral infusions of finasteride (10 microg) or vehicle (beta-cyclodextran) into the hippocampus. Administration of finasteride to the hippocampus of progesterone-primed rats significantly increased ictal activity and decreased hippocampal 3alpha,5alpha-THP levels, compared with progesterone administration alone. These data suggest that formation of 3alpha,5alpha-THP in the hippocampus is important for progesterone's antiseizure effects.

Anxiety levels and neurosteroid synthesis in the brains of prenatally stressed male rats

This report presents studies of the effects of immobilization stress applied to pregnant female rats during the last third of pregnancy on anxiety levels and neurosteroid synthesis in brain structures of adult offspring. Neurosteroid synthesis was assessed in terms of changes in the activity of 5alpha-reductase, the enzyme which converts progesterone into active metabolites. Prenatal stress results in a significant decrease in the level of anxiety and an increase in movement activity among adult males. Stressed rats showed increases in progesterone-5alpha-reductase activity in the hypothalamus, hippocampus, and frontal cortex. These results provide evidence that changes in the behavior of adult male rats due to stress in the prenatal period of development may be due to the formation of active progesterone metabolites in the brain.

Neurosteroid biosynthesis in the human brain and its clinical implications

This paper summarizes the current knowledge concerning the biosynthesis of neurosteroids in the human brain, the enzymes mediating these reactions, their localization, and the putative effects of neurosteroids. The presence of the steroidogenic enzymes cytochrome P450(SCC), aromatase, 5alpha-reductase, 3alpha-hydroxysteroid dehydrogenase, and 17beta-hydroxysteroid dehydrogenase in the human brain has now been firmly established by molecular biological and biochemical studies. Their presence in the cerebral cortex and in the subcortical white matter indicates that various cell types, either neurons or glial cells, are involved in the biosynthesis of neuroactive steroids in the brain. The following functions are attributed to specific neurosteroids: modulation of GABA(A), N-methyl-d-aspartate (NMDA), nicotinic, muscarinic, serotonin (5-HT(3)), kainate, glycine and sigma receptors, neuroprotection and induction of neurite outgrowth, dendritic spines, and synaptogenesis. We still do not know whether and how the steroidogenic enzymes are involved in the pathophysiology of the nervous system. The first clinical investigations in humans produced evidence for an involvement of neuroactive steroids in conditions such as fatigue during pregnancy, premenstrual syndrome, postpartum depression, catamenial epilepsy, and depressive disorders. Further and improved knowledge of the biochemical pathways of neurosteroidogenesis and their actions on the brain may enable new perspectives in the understanding of the physiology of the human brain as well as in the pharmacological treatment of its disturbances.

The implications of 7-dehydrosterol-7-reductase deficiency (Smith-Lemli-Opitz syndrome) to neurosteroid production

Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive, multiple malformation/mental retardation syndrome with an estimated incidence among individuals of European ancestry of 1 in 20000 to 1 in 30000. It is caused by inactivity of the enzyme 7-dehydrosterol-delta(7)-reductase, which catalyses the terminal transformation in cholesterol synthesis. Patients show not only an increased level of 7-dehydrocholesterol in blood and tissues, but also increased 8-dehydrocholesterol because of the presence of an active delta(8)-delta(7) isomerase. A major consequence of these biochemical abnormalities is the alteration of normal embryonic and fetal somatic development causing postnatal abnormalities of growth, learning, language and behavior. While deficient cholesterol during early development is the primary cause of central nervous system (CNS) abnormalities and retardation, we questioned whether neurosteroids could also be involved since they can have a profound influence on behavioral characteristics. Disordered neurosteroidogenesis would be expected in SLOS and could be caused by a deficiency in classical neurosteroid synthesis secondary to cholesterol deficiency, or by synthesis from 7- and 8-dehydrocholesterol of novel neurosteroids with delta(7) or delta(8) unsaturation which may have altered activity compared with conventional neurosteroids. In particular we sought analogues of dehydroepiandrosterone sulfate, pregnenolone sulfate and the pregnanolone epimers. We targeted urine from post-pubertal females, as this type of sample would be most likely to yield identifiable amounts of the pregnanolone metabolites of progesterone. Analysis by GC/MS of urinary steroids excreted by post-pubertal females confirmed the presence of neurosteroid-like compounds in SLOS patient's urine. Even though the new neuroactive steroids identified were unlikely to have been formed in the brain, it is likely that mechanisms for their synthesis are operable in this organ.

Gender differences in the regulation of 3 alpha-hydroxysteroid dehydrogenase in rat brain and sensitivity to neurosteroid-mediated stress protection

The enzyme 3 alpha-hydroxysteroid dehydrogenase (3 alpha-HSD) is involved in the generation of neuroactive steroids through ring-A-reduction of hormonal precursors. We examined the developmental regulation of, gender differences in, and effects of hormonal manipulations on the expression of 3 alpha-HSD in the rat hippocampus. High levels of 3 alpha-HSD mRNA were found on postnatal day 7, coinciding with the stress hyporesponsive period in the rat. Gender differences in 3 alpha-HSD expression were documented during puberty, but not in adulthood. Adrenalectomy and gonadectomy, and supplementation with individual steroid hormones influenced 3 alpha-HSD expression in a gender-specific mode. We also demonstrate that the manifestation of behavioral and endocrine consequences of early life stress depends on the individual's gender and gonadal status. Males are liable to aftereffects of neonatal maternal deprivation, regardless of their adult gonadal status. In females, however, anxiogenic aftereffects of neonatal stress become apparent only after gonadectomy. These data suggest that (i) transient increase of neurosteroid biosynthesis may contribute to stress hyporesponsiveness during early infancy; (ii) gonadal steroids regulate 3 alpha-HSD expression in the hippocampus in a sex-specific mode; (iii) physiological sex steroid secretions in females may mask behavioral consequences of adverse early life events, and (iv) concomitant treatment with the neurosteroid THP counteracts behavioral and endocrine dysregulation induced by neonatal stress in both genders.

Cognitive changes associated with supplementation of testosterone or dihydrotestosterone in mildly hypogonadal men: a preliminary report

This study prospectively examined changes in cognition in hypogonadal men given testosterone (T) or older hypogonadal men given dihydrotestosterone (DHT) gel. A battery of cognitive tests assessing verbal and spatial memory, language, and attention was administered at baseline (prior to medication) and again at days 90 and 180 of treatment for men receiving T gel and at baseline and days 30 and 90 of treatment for men receiving DHT gel. For men receiving T gel, circulating total T and estradiol (E(2)) were significantly raised compared with baseline, and a significant improvement in verbal memory was observed. For men receiving DHT gel, serum DHT levels increased and T levels decreased significantly compared with baseline, and a significant improvement in spatial memory was observed. The results suggest that beneficial changes in cognition can occur in hypogonadal men using T replacement levels and DHT treatment, and these changes in cognition can be reliably measured during a relative steady-state dose level. Further, our results suggest that aromatization of T to E(2) may regulate verbal memory in men, whereas nonaromatizable androgens may regulate spatial memory.

Allopregnanolone serum levels and expression of 5 alpha-reductase and 3 alpha-hydroxysteroid dehydrogenase isoforms in hippocampal and temporal cortex of patients with epilepsy

In the human central nervous system, progesterone is rapidly metabolised to 5 alpha-dihydroprogesterone which subsequently is further reduced to allopregnanolone (AP). These conversions are catalysed by 5 alpha-reductase and 3 alpha-hydroxysteroid dehydrogenase (3 alpha-HSD). Although different isoforms of both enzymes have been identified in the brain, our knowledge of their expression in the human brain remains limited. The aim of the present study was to investigate the mRNA expression of 5 alpha-reductase 1 as well as 3 alpha-HSD 1, 2, 3 and 20 alpha-HSD in brain tissue from patients with pharmacoresistant temporal lobe epilepsy (TLE). Specimens were derived from either the hippocampus or the temporal lobe cortex and from the tumor-free approach corridor tissue of patients with brain tumors. Quantification of different mRNAs was achieved by real time PCR. In addition, we provide data on simultaneous evaluation of serum AP concentrations. We could demonstrate that 3 alpha-HSD 1 was not expressed in the hippocampus and temporal lobe of patients with TLE. In the hippocampus and temporal lobe, the expression levels of 3 alpha-HSD 2 were about 20% of that in liver tissue, those of 3 alpha-HSD 3 about 7% and those of 20 alpha-HSD about 2%, respectively. In patients with TLE, expression of 3 alpha-HSD 2 was significantly higher in the hippocampus than in temporal lobe cortex tissue (P<0.006). AP concentrations did not correlate significantly with the mRNA expression levels of 5 alpha-reductase 1, 3 alpha-HSD 2 and 3 and 20 alpha-HSD in any of the patient groups under investigation. In conclusion, the present study demonstrates mRNA expression of 5 alpha-reductase 1 and 3 alpha-HSD 2 and 3 and 20 alpha-HSD in the hippocampus and temporal lobe of epileptic patients. These findings provide further molecular biological evidence for the formation and metabolism of neuroactive steroids in the human brain.

Stress-induced deoxycorticosterone-derived neurosteroids modulate GABA(A) receptor function and seizure susceptibility

Stress affects seizure susceptibility in animals and humans, but the underlying mechanisms are obscure. Here, we provide evidence that GABA(A) receptor-modulating neurosteroids derived from deoxycorticosterone (DOC) play a role in stress-related changes in seizure control. DOC, an adrenal steroid whose synthesis is enhanced during stress, undergoes sequential metabolic reduction by 5alpha-reductase and 3alpha-hydroxysteroid oxidoreductase to form 5alpha-dihydrodeoxycorticosterone (DHDOC) and allotetrahydrodeoxycorticosterone (THDOC), a GABA(A) receptor-modulating neurosteroid with anticonvulsant properties. Acute swim stress in rats significantly elevated plasma THDOC concentrations and raised the pentylenetetrazol (PTZ) seizure threshold. Small systemic doses of DOC produced comparable increases in THDOC and PTZ seizure threshold. Pretreatment with finasteride, a 5alpha-reductase inhibitor that blocks the conversion of DOC to DHDOC, reversed the antiseizure effects of stress. DOC also elevated plasma THDOC levels and protected mice against PTZ, methyl-6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate, picrotoxin, and amygdala-kindled seizures in mice (ED50 values, 84-97 mg/kg). Finasteride reversed the antiseizure activity of DOC (ED50, 7.2 mg/kg); partial antagonism was also obtained with indomethacin (100 mg/kg), an inhibitor of 3alpha-hydroxysteroid oxidoreductase. Finasteride had no effect on seizure protection by DHDOC and THDOC, whereas indomethacin partially reversed DHDOC but not THDOC. DHDOC, like THDOC, potentiated GABA-activated Cl- currents in cultured hippocampal neurons (< or =1 microm) and directly activated GABA(A) receptor currents (> or =1 microm), compatible with a role for DHDOC in the antiseizure activity of DOC. DOC is a mediator of the physiological effects of acute stress that could contribute to stress-induced changes in seizure susceptibility through its conversion to neurosteroids with modulatory actions on GABA(A) receptors including THDOC and possibly also DHDOC.

Messenger RNA of steroid 21-hydroxylase (CYP21) is expressed in the human hippocampus

21-hydroxylase converts progesterone to 11-deoxycorticosterone and 17-hydroxyprogesterone to 11-deoxycortisol, the substrates which are required for the production of the main adrenal steroids, corticosterone, aldosterone, and cortisol. As 21-hydroxylase activity has been detected in rodent and fetal human brain, we studied whether and to what extent 21-hydroxylase mRNA is expressed in hippocampal tissue specimens from patients undergoing epilepsy surgery (n=42). 21-hydroxylase mRNA was detected in the hippocampus with an expression 10 000 times lower than in adrenal gland tissue. There was no significant difference in expression levels between women (9.5+/-2.7 arbitrary units (aU); mean+/-SEM) and men (8.0+/-2.2 aU); however, mRNA concentrations in the hippocampus of children (n=4, 1.8+/-0.5 aU) were considerably lower than in adults (n=38, 8.6+/-1.7 aU). The expression of 21-hydroxylase mRNA in the hippocampus suggests that this human brain area has the enzymatic capability to convert progesterone to 11-deoxycorticosterone and 17-hydroxyprogesterone to 11-deoxycortisol.

Neuroactive steroids and seizure susceptibility

There is increasing clinical and experimental evidence that hormones, in particular sex steroid hormones, influence neuronal excitability and other brain functions. The term 'neuroactive steroids' has been coined for steroids that interact with neurotransmitter receptors. One of the best characterized actions of neuroactive steroids is the allosteric modulation of GABA(A)-receptor function via binding to a putative steroid-binding site. Since neuroactive steroids may interact with a variety of other membrane receptors, excitatory as well as inhibitory, they may have an impact on the excitability of specific brain regions. Neuronal excitability is enhanced by estrogen, whereas progesterone and its metabolites exert anticonvulsant effects. Testosterone and corticosteroids have less consistent effects on seizure susceptibility. Apart from these particular properties, neuroactive steroids may regulate gene expression via progesterone receptors. Based on their molecular properties, these compounds appear to have a promising therapeutical profile for the treatment of different neuropsychiatric diseases including epilepsy. This review focuses on the effects of neuroactive steroids on neuronal excitability and their putative impact on the physiology of epileptic disorders.

Androgen receptor mRNA expression in the human hippocampus

The androgen receptor (AR) plays a central role in mediating androgen action. Since the hippocampus is a target of steroid modulation, we studied the expression of AR mRNAs in hippocampal tissue specimens from patients undergoing epilepsy surgery (n=42). AR mRNA expression was in the same order of magnitude than in prostate tissue, known for its high expression of AR. AR mRNA concentrations showed no significant difference in AR mRNA expression between men (49.3+/-8.0 arbitrary units (aU); mean+/-SEM) and women (54.3+/-11.2 aU) and no sex-specific hippocampal lateralization pattern was observed. No relationship could be detected between duration of epilepsy, individual seizure frequency, age of the patients and the expression levels of AR. The high expression of AR in the hippocampus suggests that this human brain area is an important target for androgen action.

Expression of mRNAs encoding for 17beta-hydroxisteroid dehydrogenase isozymes 1, 2, 3 and 4 in epileptic human hippocampus

Sex steroid hormones exert important influences on neuroendocrine and behavioural brain function. As neuroactive steroids they are able to modify neuronal excitability. Unbalanced synthesis may thus be implicated in pathophysiological conditions, such as epilepsy, migraine, depression and anxiety. In sex steroid metabolism, 17beta-hydroxisteroid dehydrogenases (17beta-HSDs) play a crucial role in catalyzing the final steps of androgen and estrogen biosynthesis. The hippocampus appears to be a major target area of neurosteroidal action. The expression of 17beta-HSD isozymes has not yet been studied in human hippocampus. Therefore, we investigated the expression of 17beta-HSD 1, 2, 3 and 4 mRNAs in hippocampal tissue specimens obtained at neurosurgery from 42 patients with pharmacoresistant temporal lobe epilepsy. A competitive RT-PCR assay was used to quantify the mRNA transcript level. 17beta-HSD 1 mRNA concentrations were 10000 fold lower in the hippocampus compared to placental tissue, whereas 17beta-HSD 3 mRNA concentrations were 50 fold lower than in testis and 17beta-HSD 4 concentrations were in the same order of magnitude as in liver. 17beta-HSD 2 mRNA was not expressed. 17beta-HSD 1, 3 and 4 mRNA concentrations in the hippocampus showed no significant differences between men and women and there were no significant differences in expression levels of these enzymes between patients with Ammon's horn sclerosis (AHS) and those with histopathologically normal hippocampus associated with extrahippocampal lesions. No significant correlation could be detected between duration of epilepsy, individual seizure frequency and expression levels of 17beta-HSDs. In conclusion, the present study is the first to demonstrate mRNA expression of 17beta-HSD 1, 3 and 4 in the epileptic human hippocampus. Together with data on 5alpha-reductase 1, 3alpha-hydroxisteroid oxidoreductase 2 and cytochrome P450scc, previously shown to be expressed in the human hippocampus also, our data provide further evidence for the existence of sex steroid formation and metabolism in this specific brain area.