Mass spectrometric assay and physiological-pharmacological activity of androgenic neurosteroids

Carbon-chain length determines the binding affinity and inhibitory strength of per- and polyfluoroalkyl substances on human and rat steroid 5α-reductase 1 activity

Per- and polyfluoroalkyl substances (PFAS) are widely used synthetic chemicals that persist in the environment and bioaccumulate in animals and humans. There is growing evidence that PFAS exposure adversely impacts neurodevelopment and neurological health. Steroid 5α-reductase 1 (SRD5A1) plays a key role in neurosteroidogenesis by catalyzing the conversion of testosterone or pregnenolone to neuroactive steroids, which influence neural development, cognition, mood, and behavior. This study investigated the inhibitory strength and binding interactions of 18 PFAS on human and rat SRD5A1 activity using enzyme assays, molecular docking, and structure-activity relationship analysis. Results revealed that C9-C14 PFAS carboxylic acid at 100 μM significantly inhibited human SRD5A1, with IC50 values ranged from 10.99 μM (C11) to 105.01 μM (C14), and only one PFAS sulfonic acid (C8S) significantly inhibited human SRD5A1 activity, with IC50 value of 8.15 μM. For rat SRD5A1, C9-C14 PFAS inhibited rat SRD5A1, showing the similar trend, depending on carbon number of the carbon chain. PFAS inhibit human and rat SRD5A1 in a carbon chain length-dependent manner, with optimal inhibition around C11. Kinetic studies indicated PFAS acted through mixed inhibition. Molecular docking revealed PFAS bind to the domain between NADPH and testosterone binding site of both SRD5A1 enzymes. Inhibitory potency correlated with physicochemical properties like carbon number of the carbon chain. These findings suggest PFAS may disrupt neurosteroid synthesis and provide insight into structure-based inhibition of SRD5A1.

Neuroactive Steroids, Toll-like Receptors, and Neuroimmune Regulation: Insights into Their Impact on Neuropsychiatric Disorders

Pregnane neuroactive steroids, notably allopregnanolone and pregnenolone, exhibit efficacy in mitigating inflammatory signals triggered by toll-like receptor (TLR) activation, thus attenuating the production of inflammatory factors. Clinical studies highlight their therapeutic potential, particularly in conditions like postpartum depression (PPD), where the FDA-approved compound brexanolone, an intravenous formulation of allopregnanolone, effectively suppresses TLR-mediated inflammatory pathways, predicting symptom improvement. Additionally, pregnane neurosteroids exhibit trophic and anti-inflammatory properties, stimulating the production of vital trophic proteins and anti-inflammatory factors. Androstane neuroactive steroids, including estrogens and androgens, along with dehydroepiandrosterone (DHEA), display diverse effects on TLR expression and activation. Notably, androstenediol (ADIOL), an androstane neurosteroid, emerges as a potent anti-inflammatory agent, promising for therapeutic interventions. The dysregulation of immune responses via TLR signaling alongside reduced levels of endogenous neurosteroids significantly contributes to symptom severity across various neuropsychiatric disorders. Neuroactive steroids, such as allopregnanolone, demonstrate efficacy in alleviating symptoms of various neuropsychiatric disorders and modulating neuroimmune responses, offering potential intervention avenues. This review emphasizes the significant therapeutic potential of neuroactive steroids in modulating TLR signaling pathways, particularly in addressing inflammatory processes associated with neuropsychiatric disorders. It advances our understanding of the complex interplay between neuroactive steroids and immune responses, paving the way for personalized treatment strategies tailored to individual needs and providing insights for future research aimed at unraveling the intricacies of neuropsychiatric disorders.

The role of neurosteroids in posttraumatic stress disorder and alcohol use disorder: A review of 10 years of clinical literature and treatment implications

Rates of alcohol use disorder (AUD) are increasing in men and women and there are high rates of concurrent posttraumatic stress disorder (PTSD) and AUD. AUD and PTSD synergistically increase symptomatology and negatively affect treatment outcomes; however, there are very limited pharmacological treatments for PTSD/AUD. Neurosteroids have been implicated in the underlying neurobiological mechanisms of both PTSD and AUD and may be a target for treatment development. This review details the past ten years of research on pregnenolone, progesterone, allopregnanolone, pregnanolone, estradiol, testosterone and dehydroepiandrosterone/dehydroepiandrosterone-sulfate (DHEA/DHEA-S) in the context of PTSD and AUD, including examination of trauma/alcohol-related variables, such as stress-reactivity. Emerging evidence that exogenous pregnenolone, progesterone, and allopregnanolone may be promising, novel interventions is also discussed. Specific emphasis is placed on examining the application of sex as a biological variable in this body of literature, given that women are more susceptible to both PTSD diagnoses and stress-related alcohol consumption.

Preclinical and clinical pharmacology of brexanolone (allopregnanolone) for postpartum depression: a landmark journey from concept to clinic in neurosteroid replacement therapy

This article describes the critical role of neurosteroids in postpartum depression (PPD) and outlines the landmark pharmacological journey of brexanolone as a first-in-class neurosteroid antidepressant with significant advantages over traditional antidepressants. PPD is a neuroendocrine disorder that affects about 20% of mothers after childbirth and is characterized by symptoms including persistent sadness, fatigue, dysphoria, as well as disturbances in cognition, emotion, appetite, and sleep. The main pathology behind PPD is the postpartum reduction of neurosteroids, referred to as neurosteroid withdrawal, a concept pioneered by our preclinical studies. We developed neurosteroid replacement therapy (NRT) as a rational approach for treating PPD and other conditions related to neurosteroid deficiency, unveiling the power of neurosteroids as novel anxiolytic-antidepressants. The neurosteroid, brexanolone (BX), is a progesterone-derived allopregnanolone that rapidly relieves anxiety and mood deficits by activating GABA-A receptors, making it a transformational treatment for PPD. In 2019, the FDA approved BX, an intravenous formulation of allopregnanolone, as an NRT to treat PPD. In clinical studies, BX significantly improved PPD symptoms within hours of administration, with tolerable side effects including headache, dizziness, and somnolence. We identified the molecular mechanism of BX in a neuronal PPD-like milieu. The mechanism of BX involves activation of both synaptic and extrasynaptic GABA-A receptors, which promote tonic inhibition and serve as a key target for PPD and related conditions. Neurosteroids offer several advantages over traditional antidepressants, including rapid onset, unique mechanism, and lack of tolerance upon repeated use. Some limitations of BX therapy include lack of aqueous solubility, limited accessibility, hospitalization for treatment, lack of oral product, and serious adverse events at high doses. However, the unmet need for synthetic neurosteroids to address this critical condition supersedes these limitations. Recently, we developed novel hydrophilic neurosteroids with a superior profile and improved drug delivery. Overall, approval of BX is a major milestone in the field of neurotherapeutics, paving the way for the development of novel synthetic neurosteroids to treat depression, epilepsy, and status epilepticus.

Allosteric Modulation of Muscarinic Receptors by Cholesterol, Neurosteroids and Neuroactive Steroids

Muscarinic acetylcholine receptors are membrane receptors involved in many physiological processes. Malfunction of muscarinic signaling is a cause of various internal diseases, as well as psychiatric and neurologic conditions. Cholesterol, neurosteroids, neuroactive steroids, and steroid hormones are molecules of steroid origin that, besides having well-known genomic effects, also modulate membrane proteins including muscarinic acetylcholine receptors. Here, we review current knowledge on the allosteric modulation of muscarinic receptors by these steroids. We give a perspective on the research on the non-genomic effects of steroidal compounds on muscarinic receptors and drug development, with an aim to ultimately exploit such knowledge.

Factors not considered in the study of drug-resistant epilepsy: Psychiatric comorbidities, age, and gender

In basic research and clinical practice, the control of seizures has been the most important goal, but it should not be the only one. There are factors that remain poorly understood in the study of refractory epilepsy such as the age and gender of patients and the presence of psychiatric comorbidities. It is known that in patients with drug-resistant epilepsy (DRE), the comorbidities contribute to the deterioration of the quality of life, increase the severity, and worsen the prognosis of epilepsy. Some studies have demonstrated that patients diagnosed with a co-occurrence of epilepsy and psychiatric disorders are more likely to present refractory seizures and the probability of seizure remission after pharmacotherapy is reduced. The evidence of this association suggests the presence of shared pathogenic mechanisms that may include endocrine disorders, neuroinflammatory processes, disturbances of neurotransmitters, and mechanisms triggered by stress. Additionally, significant demographic, clinical, and electrographic differences have been observed between women and men with epilepsy. Epilepsy affects the female gender in a greater proportion, although there are no studies that report whether refractoriness affects more females. The reasons behind these sex differences are unclear; however, it is likely that sex hormones and sex brain differences related to chromosomal genes play an important role. On the other hand, it has been shown in industrialized countries that prevalence of DRE is higher in the elderly when compared to youngsters. Conversely, this phenomenon is not observed in developing regions, where more cases are found in children and young adults. The correct identification and management of these factors is crucial in order to improve the quality of life of the patients.

Factors not considered in the study of drug-resistant epilepsy: Psychiatric comorbidities, age, and gender

In basic research and clinical practice, the control of seizures has been the most important goal, but it should not be the only one. There are factors that remain poorly understood in the study of refractory epilepsy such as the age and gender of patients and the presence of psychiatric comorbidities. It is known that in patients with drug-resistant epilepsy (DRE), the comorbidities contribute to the deterioration of the quality of life, increase the severity, and worsen the prognosis of epilepsy. Some studies have demonstrated that patients diagnosed with a co-occurrence of epilepsy and psychiatric disorders are more likely to present refractory seizures and the probability of seizure remission after pharmacotherapy is reduced. The evidence of this association suggests the presence of shared pathogenic mechanisms that may include endocrine disorders, neuroinflammatory processes, disturbances of neurotransmitters, and mechanisms triggered by stress. Additionally, significant demographic, clinical, and electrographic differences have been observed between women and men with epilepsy. Epilepsy affects the female gender in a greater proportion, although there are no studies that report whether refractoriness affects more females. The reasons behind these sex differences are unclear; however, it is likely that sex hormones and sex brain differences related to chromosomal genes play an important role. On the other hand, it has been shown in industrialized countries that prevalence of DRE is higher in the elderly when compared to youngsters. Conversely, this phenomenon is not observed in developing regions, where more cases are found in children and young adults. The correct identification and management of these factors is crucial in order to improve the quality of life of the patients.

Neurosteroid replacement therapy for catamenial epilepsy, postpartum depression and neuroendocrine disorders in women

Neurosteroids are involved in the pathophysiology of many neuroendocrine disorders in women. This review describes recent advancements in pharmacology of neurosteroids and emphasizes the benefits of neurosteroid replacement therapy for the management of neuroendocrine disorders such as catamenial epilepsy (CE), postpartum depression (PPD) and premenstrual brain conditions. Neurosteroids are endogenous modulators of neuronal excitability. A variety of neurosteroids are present in the brain including allopregnanolone (AP), allotetrahydro-deoxycorticosterone and androstanediol. Neurosteroids interact with synaptic and extrasynaptic GABA_A receptors in the brain. AP and related neurosteroids, which are positive allosteric modulators of GABA_A receptors, are powerful anticonvulsants, anxiolytic, antistress and neuroprotectant agents. In CE, seizures are most often clustered around a specific menstrual period in women. Neurosteroid withdrawal-linked plasticity in extrasynaptic receptors has been shown to play a key role in catamenial seizures, anxiety and other mood disorders. Based on our extensive research spanning two decades, we have proposed and championed neurosteroid replacement therapy as a rational strategy for treating disorders marked by neurosteroid-deficiency, such as CE and other related ovarian or menstrual disorders. In 2019, AP (renamed as brexanolone) was approved for treating PPD. A variety of synthetic neurosteroids are in clinical trials for epilepsy, depression and other brain disorders. Recent advancements in our understanding of neurosteroids have entered a new era of drug discovery and one that offers a high therapeutic potential for treating complex brain disorders.

Brain structural and neuroendocrine basis of sex differences in epilepsy

This chapter reviews the current information about sex differences in epilepsy and potential mechanisms underlying sex differences in seizure susceptibility and epilepsy. The susceptibility to and occurrence of seizures are generally higher in men than women. There is gender-specific epilepsies such as catamenial epilepsy, a neuroendocrine condition in which seizures are most often clustered around the perimenstrual or periovulatory period in adult women. Structural differences in cerebral morphology, the structural and functional circuits may render men and women differentially vulnerable to seizure disorders and epileptogenic processes. Changes in seizure sensitivity are evident at puberty, pregnancy, and menopause, often attributed to circulating steroid hormones and neurosteroids as well as neuroplasticity in receptor systems. An improved understanding of the sexual dimorphism in neural circuits and the neuroendocrine basis of sex differences or resistance to protective drugs is essential to develop sex-specific therapies for seizure conditions.

Sex hormones and proteins involved in brain plasticity

It is well known that peripheral sex steroid hormones cross the blood-brain barrier and control a broad spectrum of reproductive behaviors. However, their role in other essential brain functions was investigated since the 1980s, when the accumulation of pregnenolone and dehydroepiandrosterone in the brain of mammalian species was determined. Since then, numerous studies have demonstrated the participation of sex hormones in brain plasticity processes. Sex hormones through both genomic and non-genomic mechanisms of action are capable of inducing gene transcription or activating signaling cascades that result in the promotion of different physiological and pathological events of brain plasticity, such as remodeling or formation of dendritic spines, neurogenesis, synaptogenesis or myelination. In this chapter, we will present the effects of sex hormones and proteins involved in brain plasticity.

Neurosteroids and neuropathic pain management: Basic evidence and therapeutic perspectives

Complex mechanisms involved in neuropathic pain that represents a major health concern make its management complicated. Because neurosteroids are bioactive steroids endogenously synthesized in the nervous system, including in pain pathways, they appear relevant to develop effective treatments against neuropathic pain. Neurosteroids act in paracrine or autocrine manner through genomic mechanisms and/or via membrane receptors of neurotransmitters that pivotally modulate pain sensation. Basic studies which uncovered a direct link between neuropathic pain symptoms and endogenous neurosteroid production/regulation, paved the way for the investigations of neurosteroid therapeutic potential against pathological pain. Concordantly, antinociceptive properties of synthetic neurosteroids were evidenced in humans and animals. Neurosteroids promote peripheral analgesia mediated by T-type calcium and gamma-aminobutyric acid type A channels, counteract chemotherapy-induced neuropathic pain and ameliorate neuropathic symptoms of injured spinal cord animals by stimulating anti-inflammatory, remyelinating and neuroprotective processes. Together, these data open interesting perspectives for neurosteroid-based strategies to manage/alleviate efficiently neuropathic pain.

Neuroactive steroid levels and cocaine use chronicity in men and women with cocaine use disorder receiving progesterone or placebo

BACKGROUND AND OBJECTIVES

Neuroactive steroids (NAS) may play a role in addiction, with observed increases in response to acute stress and drug use, but decreases with chronic substance use, suggesting that NAS neuroadaptations may occur with chronic substance use. However, levels of NAS in addicted individuals have not been systematically examined. Here, we evaluated a panel of NAS in men and women with cocaine use disorder (CUD) who participated in a clinical laboratory study of progesterone.

METHODS

Forty six CUD individuals were enrolled in a randomized placebo-controlled laboratory study to evaluate progesterone effects on levels of various NAS. On day 5 of a 7-day inpatient treatment regimen of 400 mg/day progesterone (15M/8F) or placebo (14M/9F), plasma levels of NAS known to be downstream of progesterone (allopregnanolone, pregnanolone), and NAS not in the progesterone synthesis pathway (androstanediol, testosterone, dehydroepiandrosterone [DHEA] and the NAS precursor, pregnenolone) were analyzed using highly sensitive gas chromatography/mass spectrometry (GC/MS). The relationship between each of the NAS and chronicity of cocaine use was also assessed.

RESULTS

Progesterone versus placebo significantly increased the GABAergic NAS allopregnanolone and pregnanolone in both CUD men and women. Levels of pregnenolone, testosterone, its GABAergic metabolite androstanediol, and the non-GABAergic DHEA were unaffected by progesterone treatment, and testosterone and androstanediol levels were significantly higher in men than women. Importantly, lower pregnenolone and androstanediol levels were associated with greater years of cocaine use.

SCIENTIFIC SIGNIFICANCE

GABAergic NAS that are upstream from the progesterone synthesis pathway appear susceptible to chronic effects of cocaine use. (Am J Addict 2019;28:16-21).

Neurosteroid Metabolites of Gonadal Steroid Hormones in Neuroprotection: Implications for Sex Differences in Neurodegenerative Disease

Gonadal steroid hormones are neurotrophic and neuroprotective. These effects are modulated by local metabolism of the hormones within the brain. Such control is necessary to maintain normal function, as several signaling pathways that are activated by gonadal steroid hormones in the brain can also become dysregulated in disease. Metabolites of the gonadal steroid hormones—particularly 3α-hydroxy, 5α-reduced neurosteroids—are synthesized in the brain and can act through different mechanisms from their parent steroids. These metabolites may provide a mechanism for modulating the responses to their precursor hormones, thereby providing a regulatory influence on cellular responses. In addition, there is evidence that the 3α-hydroxy, 5α-reduced neurosteroids are neuroprotective in their own right, and therefore may contribute to the overall protection conferred by their precursors. In this review article, the rapidly growing body of evidence supporting a neuroprotective role for this class of neurosteroids will be considered, including a discussion of potential mechanisms that may be involved. In addition, we explore the hypothesis that differences between males and females in local neurosteroid production may contribute to sex differences in the development of neurodegenerative disease.

Sex differences in the anticonvulsant activity of neurosteroids

Epilepsy is one of the leading causes of chronic neurological morbidity worldwide. Acquired epilepsy may result from a number of conditions, such as brain injury, anoxia, tumors, stroke, neurotoxicity, and prolonged seizures. Sex differences have been observed in many seizure types; however, some sex-specific seizure disorders are much more prevalent in women. Despite some inconsistencies, substantial data indicates that sensitivity to seizure stimuli differs between the sexes. Men generally exhibit greater seizure susceptibility than women, whereas many women with epilepsy experience a cyclical occurrence of seizures that tends to center around the menstrual period, which has been termed catamenial epilepsy. Some epilepsy syndromes show gender differences with female predominance or male predominance. Steroid hormones, endogenous neurosteroids, and sexually dimorphic neural networks appear to play a key role in sex differences in seizure susceptibility. Neurosteroids, such as allopregnanolone, reflect sex differences in their anticonvulsant activity. This Review provides a brief overview of the evidence for sex differences in epilepsy and how sex differences influence the use of neurosteroids in epilepsy and epileptogenesis. © 2016 Wiley Periodicals, Inc.

Effects of Fungicides on Rat's Neurosteroid Synthetic Enzymes

Exposure to environmental endocrine disruptors may interfere with nervous system's activity. Fungicides such as tebuconazole, triadimefon, and vinclozolin have antifungal activities and are used to prevent fungal infections in agricultural plants. In the present study, we studied effects of tebuconazole, triadimefon, and vinclozolin on rat's neurosteroidogenic 5α-reductase 1 (5α-Red1), 3α-hydroxysteroid dehydrogenase (3α-HSD), and retinol dehydrogenase 2 (RDH2). Rat's 5α-Red1, 3α-HSD, and RDH2 were cloned and expressed in COS-1 cells, and effects of these fungicides on them were measured. Tebuconazole and triadimefon competitively inhibited 5α-Red1, with IC50 values of 8.670 ± 0.771 × 10-6 M and 17.390 ± 0.079 × 10-6 M, respectively, while vinclozolin did not inhibit the enzyme at 100 × 10-6 M. Triadimefon competitively inhibited 3α-HSD, with IC50 value of 26.493 ± 0.076 × 10-6 M. Tebuconazole and vinclozolin weakly inhibited 3α-HSD, with IC50 values about 100 × 10-6 M, while vinclozolin did not inhibit the enzyme even at 100 × 10-6 M. Tebuconazole and triadimefon weakly inhibited RDH2 with IC50 values over 100 × 10-6 M and vinclozolin did not inhibit this enzyme at 100 × 10-6 M. Docking study showed that tebuconazole, triadimefon, and vinclozolin bound to the steroid-binding pocket of 3α-HSD. In conclusion, triadimefon potently inhibited rat's neurosteroidogenic enzymes, 5α-Red1 and 3α-HSD.

The neuroendocrine basis of sex differences in epilepsy

Epilepsy affects people of all ages and both genders. Sex differences are well known in epilepsy. Seizure susceptibility and the incidence of epilepsy are generally higher in men than women. In addition, there are gender-specific epilepsies such as catamenial epilepsy, a neuroendocrine condition in which seizures are most often clustered around the perimenstrual or periovulatory period in adult women with epilepsy. Changes in seizure sensitivity are also evident at puberty, pregnancy, and menopause. Sex differences in seizure susceptibility and resistance to antiseizure drugs can be studied in experimental models. An improved understanding of the neuroendocrine basis of sex differences or resistance to protective drugs is essential to develop targeted therapies for sex-specific seizure conditions. This article provides a brief overview of the current status of sex differences in seizure susceptibility and the potential mechanisms underlying the gender differences in seizure sensitivity.

Clinical Potential of Neurosteroids for CNS Disorders

Neurosteroids are key endogenous molecules in the brain that affect many neural functions. We describe here recent advances in US National Institutes of Health (NIH)-sponsored and other clinical studies of neurosteroids for CNS disorders. The neuronal GABA-A receptor chloride channel is one of the prime molecular targets of neurosteroids. Allopregnanolone-like neurosteroids are potent allosteric agonists as well as direct activators of both synaptic and extrasynaptic GABA-A receptors. Hence, neurosteroids can maximally enhance synaptic phasic and extrasynaptic tonic inhibition. The resulting chloride current conductance generates a form of shunting inhibition that controls network excitability, seizures, and behavior. Such mechanisms of neurosteroids are providing innovative therapies for epilepsy, status epilepticus (SE), traumatic brain injury (TBI), fragile X syndrome (FXS), and chemical neurotoxicity. The neurosteroid field has entered a new era, and many compounds have reached advanced clinical trials. Synthetic analogs have several advantages over natural neurosteroids for clinical use because of their superior bioavailability and safety trends.

Variation in AKR1C3, which encodes the neuroactive steroid synthetic enzyme 3α-HSD type 2 (17β-HSD type 5), moderates the subjective effects of alcohol

RATIONALE

Animal models suggest that neuroactive steroids contribute to alcohol's acute effects. We previously reported that a common nonsynonymous polymorphism, AKR1C3 2 in the gene encoding the enzyme 3α-HSD2/17β-HSD5, and a synonymous single nucleotide polymorphism (SNP), rs248793, in SRD5A1, which encodes 5α-reductase, were associated with alcohol dependence (AD).

OBJECTIVES

The aim of the study was to investigate whether these polymorphisms moderate subjective effects of alcohol in humans and whether AKR1C3 2 affects neuroactive steroid synthesis.

METHODS

Sixty-five Caucasian men (34 lighter and 31 heavier drinkers; mean age 26.2 years) participated in a double-blind laboratory study where they consumed drinks containing no ethanol or 0.8 g/kg of ethanol. Breath alcohol, heart rate (HR), and self-reported alcohol effects were measured at 40-min intervals, and genotype was examined as a moderator of alcohol's effects. Levels of the neuroactive steroid 5α-androstane-3α,17β-diol and its precursors, 3α,5α-androsterone and dihydrotestosterone, were measured at study entry using GC/MS.

RESULTS

Initially, carriers of the AD-protective AKR1C3 2 G allele had higher levels of 5α-androstane-3α,17β-diol relative to the precursor 3α,5α-androsterone than C allele homozygotes. AKR1C3 2 G allele carriers exhibited greater increases in heart rate and stimulant and sedative effects of alcohol than C allele homozygotes. The genotype effects on sedation were observed only in heavier drinkers. The only effect of the SRD5A1 SNP was to moderate HR. There were no interactive effects of the two SNPs.

CONCLUSIONS

The observed effects of variation in a gene encoding a neuroactive steroid biosynthetic enzyme on the rate of 17β-reduction of androsterone relative to androstanediol and on alcohol's sedative effects may help to explain the association of AKR1C3 2 with AD.

Neurosteroid 3α-androstanediol efficiently counteracts paclitaxel-induced peripheral neuropathy and painful symptoms

Painful peripheral neuropathy belongs to major side-effects limiting cancer chemotherapy. Paclitaxel, widely used to treat several cancers, induces neurological symptoms including burning pain, allodynia, hyperalgesia and numbness. Therefore, identification of drugs that may effectively counteract paclitaxel-induced neuropathic symptoms is crucial. Here, we combined histopathological, neurochemical, behavioral and electrophysiological methods to investigate the natural neurosteroid 3α-androstanediol (3α-DIOL) ability to counteract paclitaxel-evoked peripheral nerve tissue damages and neurological symptoms. Prophylactic or corrective 3α-DIOL treatment (4 mg/kg/2days) prevented or suppressed PAC-evoked heat-thermal hyperalgesia, cold-allodynia and mechanical allodynia/hyperalgesia, by reversing to normal, decreased thermal and mechanical pain thresholds of PAC-treated rats. Electrophysiological studies demonstrated that 3α-DIOL restored control values of nerve conduction velocity and action potential peak amplitude significantly altered by PAC-treatment. 3α-DIOL also repaired PAC-induced nerve damages by restoring normal neurofilament-200 level in peripheral axons and control amount of 2’,3’-cyclic-nucleotide-3’-phosphodiesterase in myelin sheaths. Decreased density of intraepidermal nerve fibers evoked by PAC-therapy was also counteracted by 3α-DIOL treatment. More importantly, 3α-DIOL beneficial effects were not sedation-dependent but resulted from its neuroprotective ability, nerve tissue repairing capacity and long-term analgesic action. Altogether, our results showing that 3α-DIOL efficiently counteracted PAC-evoked painful symptoms, also offer interesting possibilities to develop neurosteroid-based strategies against chemotherapy-induced peripheral neuropathy. This article shows that the prophylactic or corrective treatment with 3α-androstanediol prevents or suppresses PAC-evoked painful symptoms and peripheral nerve dysfunctions in rats. The data suggest that 3α-androstanediol-based therapy may constitute an efficient strategy to explore in humans for the eradication of chemotherapy-induced peripheral neuropathy.

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.

Variation in genes encoding the neuroactive steroid synthetic enzymes 5α-reductase type 1 and 3α-reductase type 2 is associated with alcohol dependence

BACKGROUND

Studies of alcohol effects in rodents and in vitro implicate endogenous neuroactive steroids as key mediators of alcohol effects at GABA(A) receptors. We used a case-control sample to test the association with alcohol dependence (AD) of single nucleotide polymorphisms in the genes encoding two key enzymes required for the generation of endogenous neuroactive steroids: 5α-reductase, type I (5α-R), and 3α-hydroxysteroid dehydrogenase, type 2 (3α-HSD), both of which are expressed in human brain.

METHODS

We focused on markers previously associated with a biological phenotype. For 5α-R, we examined the synonymous SRD5A1 exon 1 SNP rs248793, which has been associated with the ratio of dihydrotestosterone to testosterone. For 3α-HSD, we examined the nonsynonymous AKR1C3 SNP rs12529 (H5Q), which has been associated with bladder cancer. The SNPs were genotyped in a sample of 1,083 non-Hispanic Caucasians including 552 controls and 531 subjects with AD.

RESULTS

The minor allele for both SNPs was more common among controls than subjects with AD: SRD5A1 rs248793 C-allele (χ(2)(1) = 7.6, p = 0.006) and AKR1C3 rs12529 G-allele (χ(2)(1) = 14.6, p = 0.0001). There was also an interaction of these alleles such that the "protective" effect of the minor allele at each marker for AD was conditional on the genotype of the second marker.

CONCLUSIONS

We found evidence of an association with AD of polymorphisms in two genes encoding neuroactive steroid biosynthetic enzymes, providing indirect evidence that neuroactive steroids are important mediators of alcohol effects in humans.

Altered levels of circulating GABAergic 5α/β-reduced pregnane and androstane steroids in schizophrenic men

The role of GABAergic pathways in the pathophysiology of schizophrenia is generally accepted. Therefore, the information concerning alterations of the steroid metabolome associated with the disease and/or its treatment is of interest with regard to the pathophysiology of the disease. Hence, we assessed 18 serum steroids and steroid polar conjugates in a group of drug-naive patients (13 adult men) and after 6-months therapy by atypical antipsychotics and age-matched controls (19 men) using gas chromatography-mass spectrometry analysis. This study, for the first time, demonstrates the altered circulating GABAergic steroids in schizophrenic men as well as the effect of the therapy with two types of atypical antipsychotics. The GABAergic androsterone (3α5α) and etiocholanolone (3α5β) are reduced in schizophrenic men but the therapy with atypical antipsychotics reinstates their levels. This reinstatement could be of importance when considering that the GABAergic substances generally improve the well-being of patients. In addition to the unconjugated androsterone, being the most abundant GABAergic steroid in men, most of the other GABAergic steroids also tended to decrease in the patients. By contrast, the conjugated 5β-pregnanolone isomers were elevated in the patients. In conclusion, although schizophrenia status in adult men is associated with unfavorable alterations in neuroactive steroids, the treatment with antipsychotics could at least partly reinstate their circulating levels.

Effects of valproate and carbamazepine monotherapy on neuroactive steroids, their precursors and metabolites in adult men with epilepsy

Only limited data is available concerning the role of unconjugated Δ(5) C19-steroids and almost no data exists regarding the neuroactive C21 and C19 3α-hydroxy-5α/β-metabolites in men with epilepsy. To evaluate the alterations in serum neuroactive steroids and related substances in adult men with epilepsy on valproate and carbamazepine monotherapy, we have measured 26 unconjugated steroids, 18 steroid polar conjugates, gonadotropins and sex hormone binding globulin (SHBG) in 6 and 11 patients on valproate and carbamazepine monotherapy, respectively, and in 19 healthy adult men, using the GC-MS and immunoassays. Decreased testosterone, free androgen index, free testosterone, androstenediol, 5α-androstane-3α,17β-diol (androstanediol), androsterone, epiandrosterone, DHEA, 7β-hydroxy-DHEA, and DHEAS levels were associated with epilepsy per se. Valproate (VPA) therapy increased 5α-dihydrotestosterone, androsterone, epiandrosterone, DHEA, DHEAS, and 7β-hydroxy-DHEA levels. Decrease in pregnenolone and 17-hydroxypregnenolone were associated with epilepsy with no effect of antiepileptic drugs (AEDs). Alternatively, the increase in progesterone levels was linked to epilepsy and VPA further increased progesterone levels. Reduced steroid 20α-hydroxy-metabolites and cortisol were connected with epilepsy without an effect of AEDs. Carbamazepine induced only slight decrease in isopregnanolone, 5α,20α-tetrahydroprogesterone, and androstanediol levels.

The testosterone-derived neurosteroid androstanediol is a positive allosteric modulator of GABAA receptors

Testosterone modulates seizure susceptibility, but the underlying mechanisms are obscure. Recently, we demonstrated that testosterone affects seizure activity via its conversion to neurosteroids in the brain. Androstanediol (5alpha-androstan-3alpha,17beta-diol) is an endogenous neurosteroid synthesized from testosterone. However, the molecular mechanism underlying the seizure protection activity of androstanediol remains unclear. Here, we show that androstanediol has positive allosteric activity as a GABA(A) receptor modulator. In whole-cell recordings from acutely dissociated hippocampus CA1 pyramidal cells, androstanediol (but not its 3beta-epimer) produced a concentration-dependent enhancement of GABA-activated currents (EC(50) of 5 microM). At 1 microM, androstanediol produced a 50% potentiation of GABA responses. In the absence of GABA, androstanediol has moderate direct effects on GABA(A) receptor-mediated currents at high concentrations. Systemic doses of androstanediol (5-100 mg/kg), but not its 3beta-epimer, caused dose-dependent suppression of behavioral and electrographic seizures in mouse hippocampus kindling, which is a model of temporal lobe epilepsy. The ED(50) value for antiseizure effects of androstanediol was 50 mg/kg, which did not produce sedation/motor toxicity. At high (2x ED(50)) doses, androstanediol produced complete seizure protection that lasted for up to 3 h after injection. The estimated plasma concentrations of androstanediol producing 50% seizure protection in the kindling model (10.6 microM) are within the range of concentrations that modulate GABA(A) receptors. These studies suggest that androstanediol could be a neurosteroid mediator of testosterone actions on neuronal excitability and seizure susceptibility via its activity as a GABA(A) receptor modulator and that androstanediol may play a key role in men with epilepsy, especially during the age-related decline in androgen levels.

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.

The role of neurosteroids in the pathophysiology and treatment of catamenial epilepsy

Catamenial epilepsy is a multifaceted neuroendocrine condition in which seizures are clustered around specific points in the menstrual cycle, most often around perimenstrual or periovulatory period. Generally, a twofold or greater increase in seizure frequency during a particular phase of the menstrual cycle could be considered as catamenial epilepsy. Based on this criteria, recent clinical studies indicate that catamenial epilepsy affects 31-60% of the women with epilepsy. Three types of catamenial seizures (perimenstrual, periovulatory and inadequate luteal) have been identified. However, there is no specific drug available today for catamenial epilepsy, which has not been successfully treated with conventional antiepileptic drugs. Elucidation of the pathophysiology of catamenial epilepsy is a prerequisite to develop specific targeted approaches for treatment or prevention of the disorder. Cyclical changes in the circulating levels of estrogens and progesterone play a central role in the development of catamenial epilepsy. There is emerging evidence that endogenous neurosteroids with anticonvulsant or proconvulsant effects could play a critical role in catamenial epilepsy. It is thought that perimenstrual catamenial epilepsy is associated with the withdrawal of anticonvulsant neurosteroids. Progesterone and other hormonal agents have been shown in limited trials to be moderately effective in catamenial epilepsy, but may cause endocrine side effects. Synthetic neurosteroids, which enhance the tonic GABA-A receptor function, might provide an effective approach for the catamenial epilepsy therapy without producing hormonal side effects.

Studies on neurosteroids XXIV. Determination of neuroactive androgens, androsterone and 5alpha-androstane-3alpha,17beta-diol, in rat brain and serum using liquid chromatography-tandem mass spectrometry

The development and validation of liquid chromatography-electrospray ionization-tandem mass spectrometric (LC-ESI-MS/MS) methods that enable the quantification of neuroactive androgens, androsterone (5alpha-androstan-3alpha-ol-17-one, 3alpha,5alpha-A) and 5alpha-androstane-3alpha,17beta-diol (3alpha,5alpha-Adiol), in the rat brain and serum are presented. The androgens were extracted with methanol-acetic acid, purified using solid-phase extraction cartridges, derivatized with an ESI-active reagent, isonicotinoyl azide (INA), and then subjected to LC-ESI-MS/MS. The quantifications were based on selected reaction monitoring mode using the characteristic transitions of the INA derivatives. The methods allowed the reproducible and accurate quantification of the brain and serum neuroactive androgens using a 100 mg or 100 microL sample; the intra- and inter-assay relative standard deviations were below 3.6%, and the percentage accuracy values were 97.1-103.7% for both androgens. The animal study using the methods suggests that most of 3alpha,5alpha-Adiol found in the brain is derived from the periphery, while 3alpha,5alpha-A is not only transported from the periphery into the brain, but also synthesized in the brain by the oxidation of 3alpha,5alpha-Adiol. The androgens in the rats intraperitoneally administered finasteride, a 5alpha-reductatse inhibitor, were also measured; this treatment significantly reduced the brain 3alpha,5alpha-A and 3alpha,5alpha-Adiol levels and increased only the brain level of androstenedione, the precursor of 3alpha,5alpha-A.