Neurosteroids: non-genomic pathways in neuroplasticity and involvement in neurological diseases

Effects of computerized working memory training on neuroplasticity in healthy individuals: A combined neuroimaging and neurotransmitter study

Working memory (WM) is an essential cognitive function that underpins various higher-order cognitive processes. Improving WM capacity through targeted training interventions has emergered as a potential approach for enhancing cognitive abilities. The present study employed an 8-week regimen of computerized WM training (WMT) to investigate its effect on neuroplasticity in healthy individuals, utilizing neuroimaging data gathered both before and after the training. The key metrics assessed included the amplitude of low-frequency fluctuations (ALFF), voxel-based morphometry (VBM), and the spatial distribution correlations of neurotransmitter. The results indicated that post-training, compared to baseline, there was a reduction in ALFF in the medial superior frontal gyrus and an elevation in ALFF in the left middle occipital gyrus within the training group. In comparison to the control group, the training group also exhibited decreased ALFF in the anterior cingulate cortex, angular gyrus, and superior parietal lobule, along with increased ALFF in the postcentral gyrus post-training. VBM analysis revealed a significant increase in gray matter volume (GMV) in the right dorsal superior frontal gyrus after the training period, compared to the initial baseline measurement. Furthermore, the training group showed GMV increases in the dorsal superior frontal gyrus, Rolandic operculum, precentral gyrus, and postcentral gyrus when compared to the control group. In addition, significant associations were identifed between neuroimaging measurements (AFLL and VBM) and the spatial patterns of neurotransmitters such as serotonin (5-HT), dopamine (DA), and N-methyl-D-aspartate (NMDA), providing insights into the underlying neurochemical processes. These findings clarify the neuroplastic changes caused by WMT, offering a deeper understanding of brain plasticity and highlighting the potential advantages of cognitive training interventions.

Neurosteroids: A potential target for neuropsychiatric disorders

Neurosteroids are steroids produced by endocrine glands and subsequently entering the brain, and also include steroids synthesis in the brain. It has been widely known that neurosteroids influence many neurological functions, including neuronal signaling, synaptic adaptations, and neuroprotective effects. In addition, abnormality in the synthesis and function of neurosteroids has been closely linked to neuropsychiatric disorders, such as Alzheimer's disease (AD), schizophrenia (SZ), and epilepsy. Given their important role in brain pathophysiology and disorders, neurosteroids offer potential therapeutic targets for a variety of neuropsychiatric diseases, and that therapeutic strategies targeting neurosteroids probably exert beneficial effects. We therefore summarized the role of neurosteroids in brain physiology and neuropsychiatric disorders, and introduced the recent findings of synthetic neurosteroid analogues for potential treatment of neuropsychiatric disorders, thereby providing insights for further research in the future.

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.

Neuroactive steroids and Parkinson's disease: Review of human and animal studies

The greater prevalence and incidence of Parkinson's disease (PD) in men suggest a beneficial effect of sex hormones. Neuroactive steroids have neuroprotective activities thus offering interesting option for disease-modifying therapy for PD. Neuroactive steroids are also neuromodulators of neurotransmitter systems and may thus help to control PD symptoms and side effect of dopamine medication. Here, we review the effect on sex hormones (estrogen, androgen, progesterone and its metabolites) as well as androstenediol, pregnenolone and dehydroepiandrosterone) in human studies and in animal models of PD. The effect of neuroactive steroids is reviewed by considering sex and hormonal status to help identify specifically for women and men with PD what might be a preventive approach or a symptomatic treatment. PD is a complex disease and the pathogenesis likely involves multiple cellular processes. Thus it might be useful to target different cellular mechanisms that contribute to neuronal loss and neuroactive steroids provide therapeutics options as they have multiple mechanisms of action.

Developmental and adult stress: effects of steroids and neurosteroids

In humans, exposure to early life adversity has profound implications for susceptibility to developing neuropsychiatric disorders later in life. Studies in rodents have shown that stress experienced during early postnatal life can have lasting effects on brain development. Glucocorticoids and sex steroids are produced in endocrine glands and the brain from cholesterol; these molecules bind to nuclear and membrane-associated steroid receptors. Unlike other steroids that can also be made in the brain, neurosteroids bind specifically to neurotransmitter receptors, not steroid receptors. The relationships among steroids, neurosteroids, and stress are multifaceted and not yet fully understood. However, studies demonstrating altered levels of progestogens, androgens, estrogens, glucocorticoids, and their neuroactive metabolites in both developmental and adult stress paradigms strongly suggest that these molecules may be important players in stress effects on brain circuits and behavior. In this review, we discuss the influence of developmental and adult stress on various components of the brain, including neurons, glia, and perineuronal nets, with a focus on sex steroids and neurosteroids. Gaining an enhanced understanding of how early adversity impacts the intricate systems of brain steroid and neurosteroid regulation could prove instrumental in identifying novel therapeutic targets for stress-related conditions.

Advances in steroid research from the pioneering neurosteroid concept to metabolomics: New insights into pregnenolone function

Advances in neuroendocrinology have led to major discoveries since the 19th century, identifying adaptive loops for maintaining homeostasis. One of the most remarkable discoveries was the concept of neurosteroids, according to which the brain is not only a target but also a source of steroid production. The identification of new membrane steroid targets now underpins the neuromodulatory effects of neurosteroids such as pregnenolone, which is involved in functions mediated by the GPCR CB1 receptor. Structural analysis of steroids is a key feature of their interactions with the phospholipid membrane, receptors and resulting activity. Therefore, mass spectrometry-based methods have been developed to elucidate the metabolic pathways of steroids, the ultimate approach being metabolomics, which allows the identification of a large number of metabolites in a single sample. This approach should enable us to make progress in understanding the role of neurosteroids in the functioning of physiological and pathological processes.

Understanding the mechanism of action and clinical effects of neuroactive steroids and GABAergic compounds in major depressive disorder

The pathophysiology of major depressive disorder (MDD) is thought to result from impaired connectivity between key brain networks. Gamma-aminobutyric acid (GABA) is the key inhibitory neurotransmitter in the brain, working primarily via GABA_A receptors, with an important role in virtually all physiologic functions in the brain. Some neuroactive steroids (NASs) are positive allosteric modulators (PAMs) of GABA_A receptors and potentiate phasic and tonic inhibitory responses via activation of synaptic and extrasynaptic GABA_A receptors, respectively. This review first discusses preclinical and clinical data that support the association of depression with diverse defects in the GABAergic system of neurotransmission. Decreased levels of GABA and NASs have been observed in adults with depression compared with healthy controls, while treatment with antidepressants normalized the altered levels of GABA and NASs. Second, as there has been intense interest in treatment approaches for depression that target dysregulated GABAergic neurotransmission, we discuss NASs approved or currently in clinical development for the treatment of depression. Brexanolone, an intravenous NAS and a GABA_A receptor PAM, is approved by the U.S. Food and Drug Administration for the treatment of postpartum depression (PPD) in patients 15 years and older. Other NASs include zuranolone, an investigational oral GABA_A receptor PAM, and PH10, which acts on nasal chemosensory receptors; clinical data to date have shown improvement in depressive symptoms with these investigational NASs in adults with MDD or PPD. Finally, the review discusses how NAS GABA_A receptor PAMs may potentially address the unmet need for novel and effective treatments with rapid and sustained antidepressant effects in patients with MDD.

IUPHAR - invited review - Ibogaine - A legacy within the current renaissance of psychedelic therapy

Ibogaine is a powerful psychoactive substance that not only alters perception, mood and affect, but also stops addictive behaviors. Ibogaine has a very long history of ethnobotanical use in low doses to combat fatigue, hunger and thirst and, in high doses as a sacrament in African ritual contexts. In the 1960's, American and European self-help groups provided public testimonials that a single dose of ibogaine alleviated drug craving, opioid withdrawal symptoms, and prevented relapse for weeks, months and sometimes years. Ibogaine is rapidly demethylated by first-pass metabolism to a long-acting metabolite noribogaine. Ibogaine and its metabolite interact with two or more CNS targets simultaneously and both drugs have demonstrated predictive validity in animal models of addiction. Online forums endorse the benefits of ibogaine as an "addiction interrupter" and present-day estimates suggest that more than ten thousand people have sought treatment in countries where the drug is unregulated. Open label pilot studies of ibogaine-assisted drug detoxification have shown positive benefit in treating addiction. Ibogaine, granted regulatory approval for human testing in a Phase 1/2a clinical trial, joins the current landscape of psychedelic medicines in clinical development.

Early conversion of maternal androgens affects the embryo already in the first week of development

Maternal androgen exposure has potent effects on offspring development. As substantial levels of maternal androgens are deposited in avian egg yolks, avian eggs are frequently used to study maternal effects, with a strong focus on post-natal development. However, the underlying pathways are largely unknown. Since the hormones are taken up during the embryonic phase, and these are rapidly metabolized by avian embryos into metabolites such as etiocholanolone, we studied the effects of yolk androgens (testosterone and androstenedione) and their metabolite etiocholanolone during the first few days of embryonic development. As embryonic heart rate is often used as an indicator of embryonic development, we measured the heart rate from day 3 to day 6 of incubation by using a shell-less culture technique in rock pigeon eggs (Columba livia). Increased androgen exposure increased heart rate, and increased etiocholanolone mimicked this effect, albeit in a small sample size. This indicates that exposure to maternal androgens increases embryonic overall metabolism which may account for the developmental outcomes found in previous studies such as increased growth. Moreover, etiocholanolone is likely to be an important metabolite in a non-genomic pathway underlying the androgen-mediated maternal effect.

Gender and Neurosteroids: Implications for Brain Function, Neuroplasticity and Rehabilitation

Neurosteroids are synthesized de novo in the nervous system; they mainly moderate neuronal excitability, and reach target cells via the extracellular pathway. The synthesis of neurosteroids occurs in peripheral tissues such as gonads tissues, liver, and skin; then, because of their high lipophilia, they cross the blood-brain barrier and are stored in the brain structure. Neurosteroidogenesis occurs in brain regions such as the cortex, hippocampus, and amygdala by enzymes necessary for the in situ synthesis of progesterone from cholesterol. Neurosteroids could be considered the main players in both sexual steroid-induced hippocampal synaptic plasticity and normal transmission in the hippocampus. Moreover, they show a double function of increasing spine density and enhancing long term potentiation, and have been related to the memory-enhancing effects of sexual steroids. Estrogen and progesterone affect neuronal plasticity differently in males and females, especially regarding changes in the structure and function of neurons in different regions of the brain. Estradiol administration in postmenopausal women allowed for improving cognitive performance, and the combination with aerobic motor exercise seems to enhance this effect. The paired association between rehabilitation and neurosteroids treatment could provide a boosting effect in order to promote neuroplasticity and therefore functional recovery in neurological patients. The aim of this review is to investigate the mechanisms of action of neurosteroids as well as their sex-dependent differences in brain function and their role in neuroplasticity and rehabilitation.

Glutamatergic neurotransmission: A potential pharmacotherapeutic target for the treatment of cognitive disorders

In the mammalian brain, glutamate is regarded to be the primary excitatory neurotransmitter due to its widespread distribution and wide range of metabolic functions. Glutamate plays key roles in regulating neurogenesis, synaptogenesis, neurite outgrowth, and neuron survival in the brain. Ionotropic and metabotropic glutamate receptors, neurotransmitters, neurotensin, neurosteroids, and others co-ordinately formulate a complex glutamatergic network in the brain that maintains optimal excitatory neurotransmission. Cognitive activities are potentially synchronized by the glutamatergic activities in the brain via restoring synaptic plasticity. Dysfunctional glutamate receptors and other glutamatergic components are responsible for the aberrant glutamatergic activity in the brain that cause cognitive impairments, loss of synaptic plasticity, and neuronal damage. Thus, controlling the brain's glutamatergic transmission and modifying glutamate receptor function could be a potential therapeutic strategy for cognitive disorders. Certain drugs that regulate glutamate receptor activities have shown therapeutic promise in improving cognitive functions in preclinical and clinical studies. However, several issues regarding precise functional information of glutamatergic activity are yet to be comprehensively understood. The present article discusses the scope of developing glutamatergic systems as prospective pharmacotherapeutic targets to treat cognitive disorders. Special attention has been given to recent developments, challenges, and future prospects.

Chronic MAP4343 reverses escalated alcohol drinking in a mouse model of alcohol use disorder

Alcohol use disorders can be driven by negative reinforcement. Alterations of the microtubule cytoskeleton have been associated with mood regulation in the context of depression. Notably, MAP4343, a pregnenolone derivative known to promote tubulin assembly, has antidepressant properties. In the present study, we tested the hypothesis that MAP4343 may reduce excessive alcohol drinking in a mouse model of alcohol dependence by normalizing affect during withdrawal. Adult male C57BL/6J mice were given limited access to voluntary alcohol drinking and ethanol intake escalation was induced by chronic intermittent ethanol (CIE) vapor inhalation. Chronic, but not acute, administration of MAP4343 reduced ethanol intake and this effect was more pronounced in CIE-exposed mice. There was a complex interaction between the effects of MAP4343 and alcohol on affective behaviors. In the elevated plus maze, chronic MAP4343 tended to increase open-arm exploration in alcohol-naive mice but reduced it in alcohol-withdrawn mice. In the tail suspension test, chronic MAP4343 reduced immobility selectively in Air-exposed alcohol-drinking mice. Finally, chronic MAP4343 countered the plasma corticosterone reduction induced by CIE. Parallel analysis of tubulin post-translational modifications revealed lower α-tubulin acetylation in the medial prefrontal cortex of CIE-withdrawn mice. Altogether, these data support the relevance of microtubules as a therapeutic target for the treatment of AUD.

Many or too many progesterone membrane receptors? Clinical implications

Several receptors for nongenomically initiated actions of progesterone (P4) exist, namely membrane-associated P4 receptors (MAPRs), membrane progestin receptors (mPRs), receptors for neurosteroids [GABA_A receptor (GABA_AR), NMDA receptor, sigma-1 and -2 receptors (S1R/S2R)], the classical genomic P4 receptor (PGR), and α/β hydrolase domain-containing protein 2 (ABHD2). Two drugs related to this field have been approved: brexanolone (Zulresso™) for the treatment of postpartum depression, and ganaxolone (Ztalmy™) for the treatment of CDKL5 deficiency disorder. Both are derivatives of P4 and target the GABA_AR. Several other indications are in clinical testing. CT1812 (Elayta™) is also being tested for the treatment of Alzheimer's disease (AD) in Phase 2 clinical trials, targeting the P4 receptor membrane component 1 (PGRMC1)/S2R complex. In this Review, we highlight emerging knowledge on the mechanisms of nongenomically initiated actions of P4 and its derivatives.

Do neurosteroids have impact on depression and cognitive functions in cases with acromegaly?

OBJECTIVE

Neurosteroids (NSs) are a distinct hormone group and, they are known for their contribution into the status of mood and cognitive functions. Whether they are also involved in the mood disturbances and cognition in acromegaly is not known. Herein we aimed to evaluate the relation of mood status and cognitive functions with the NS levels in cases with acromegaly.

DESIGN

A total of 33 cases with acromegaly composed the acromegaly group (AG) and, 30 age and gender-matched cases without acromegaly composed the control group (CG). The levels of Allopregnanolone (AP), pregnenolone (PRG), 24S-hydroxycholesterol (24OHC), dehydroepiandrosterone (DHEA), dehydroepiandrosterone sulfate (DHEAS), androsterone (ADT), GH and IGF-1 were measured in each group. Beck Depression Inventory (BDI) was used to assess depressive symptoms, whereas an extensive neuropsychological assessment with several neurocognitive tests were carried out for each subject by an experienced psychologist.

RESULTS

Cases with acromegaly had lower 24OHC and DHEA levels (p = 0.002 and p = 0.007, respectively) in comparison to CG. Of the cognitive functions time to complete 1 s Series was significantly higher and, the scores on Switching Verbal Fluency Test, Boston Naming Test (BNT)-semantic and BNT-phonological, the highest learning point of Oktem Verbal Memory Processes Test (VMPT) were significantly lower in cases with acromegaly in comparison to those in controls (p = 0.004, p = 0.01, p < 0.001, p = 0.02 and p = 0.05, respectively). KAS-perseveration errors were higher in CG (p = 0.03). In AG the levels of AP were negatively correlated with the scores on Months backward Test (MBT), Animal Naming Test, Construction, BNT-spontaneous and positively correlated with BNT-incorrect answers; PRG was positively correlated with VMPT-retention scores, ADT was negatively correlated with MBT and 3 s Series scores, DHEAS was positively correlated with VMPT-the highest learning point whereas it was negatively correlated with MBT scores. Additionally, the scores on BDI were positively correlated with DHEA levels in AG.

CONCLUSION

Cognitive changes may be encountered in acromegaly and, neurosteroids may contribute to the changes in certain cognitive functions.

Regulation of phase I and phase II neurosteroid enzymes in the hippocampus of an Alzheimer's disease rat model: A focus on sulphotransferases and UDP-glucuronosyltransferases

Neurosteroids have been associated with neurodegenerative diseases because they are involved in the modulation of neurotransmitter, neurotropic and neuroprotective actions. Emerging evidence suggests that the enzymes responsible for the synthesis of neurosteroids change during the progression of Alzheimer's disease (AD). The present study aimed to assess the changes in phase I and II enzymes involved in the metabolism of neurosteroids of the progestogen, androgenic and estrogenic steroidogenic pathways and the possibility that the neurosteroids are actively converted into the most abundant metabolites (i.e. glucuronides and sulphates). The gene expression for the phase I and II neurosteroid biosynthetic enzymes were studied in the hippocampus of streptozotocin AD rat model. Male Sprague-Dawley rats were randomly divided into control, sham (saline injected into the hippocampus) and 3 and 12 weeks post-STZ administration (STZ-G3w and STZ-G12w, respectively) groups. Behavioral assessments showed memory impairment in both STZ-injected groups, whereas the formation of amyloid-beta was more pronounced in the STZ-12w group. Gene expression of the hippocampus revealed that glucuronidation and sulphation enzymes transcript of the phase I metabolites were upregulated at the late stage of the disease progression (Hsd17b10, Hsd3b1, Akr1c3 and Cyp19a1) except for Sts. The phase II Sult and Ugt enzymes were mostly upregulated in the STZ-G12w rats (Sult1a1, Sult1e1, Ugt1a1, Ugt1a7c, Ugt1a6, Ugt2b35 and Ugt2b17) and normally expressed in the STZ-G3w group (Sult2a2, Sult2a6, Sult2b1, Ugt2b7, Sult4a1 and Ugt1a7c). In conclusion, changes occur in the phase I and II enzymes transcript of the progestogen, androgenic and estrogenic steroidogenic pathways during the progression of AD.

Therapeutic potential of pregnenolone and pregnenolone methyl ether on depressive and CDKL5 deficiency disorders: Focus on microtubule targeting

Pregnenolone methyl-ether (PME) is a synthetic derivative of the endogenous neuroactive steroid pregnenolone (PREG), which is an important modulator of several brain functions. In addition to being the precursor of steroids, PREG acts directly on various targets including microtubules (MTs), the functioning of which is fundamental for the development and homeostasis of nervous system. The coordination of MT dynamics is supported by a plethora of MT-associated proteins (MAPs) and by a specific MT code that is defined by the post-translational modifications of tubulin. Defects associated with MAPs or tubulin post-translational modifications are linked to different neurological pathologies including mood and neurodevelopmental disorders. In this review, we describe the beneficial effect of PME in major depressive disorders (MDDs) and in CDKL5 deficiency disorder (CDD), two pathologies that are joint by defective MT dynamics. Growing evidence indeed suggests that PME, as well as PREG, is able to positively affect the MT-binding of MAP2 and the plus-end tracking protein CLIP170 that are both found to be deregulated in the above mentioned pathologies. Furthermore, PME influences the state of MT acetylation, the deregulation of which is often associated with neurological abnormalities including MDDs. By contrast to PREG, PME is not metabolised into other downstream molecules with specific biological properties, an aspect that makes this compound more suitable for therapeutic strategies. Thus, through the analysis of MDDs and CDD, this work focuses attention on the possible use of PME for neuronal pathologies associated with MT defects.

Normal and Premature Adrenarche

Adrenarche is the maturational increase in adrenal androgen production that normally begins in early childhood. It results from changes in the secretory response to adrenocorticotropin (ACTH) that are best indexed by dehydroepiandrosterone sulfate (DHEAS) rise. These changes are related to the development of the zona reticularis (ZR) and its unique gene/enzyme expression pattern of low 3ß-hydroxysteroid dehydrogenase type 2 with high cytochrome b5A, sulfotransferase 2A1, and 17ß-hydroxysteroid dehydrogenase type 5. Recently 11-ketotestosterone was identified as an important bioactive adrenarchal androgen. Birth weight, body growth, obesity, and prolactin are related to ZR development. Adrenarchal androgens normally contribute to the onset of sexual pubic hair (pubarche) and sebaceous and apocrine gland development. Premature adrenarche causes ≥90% of premature pubarche (PP). Its cause is unknown. Affected children have a significantly increased growth rate with proportionate bone age advancement that typically does not compromise growth potential. Serum DHEAS and testosterone levels increase to levels normal for early female puberty. It is associated with mildly increased risks for obesity, insulin resistance, and possibly mood disorder and polycystic ovary syndrome. Between 5% and 10% of PP is due to virilizing disorders, which are usually characterized by more rapid advancement of pubarche and compromise of adult height potential than premature adrenarche. Most cases are due to nonclassic congenital adrenal hyperplasia. Algorithms are presented for the differential diagnosis of PP. This review highlights recent advances in molecular genetic and developmental biologic understanding of ZR development and insights into adrenarche emanating from mass spectrometric steroid assays.

G protein-coupled estrogen receptor-1 enhances excitatory synaptic responses in the entorhinal cortex

Activation of estrogen receptors is thought to modulate cognitive function in the hippocampus, prefrontal cortex, and striatum by affecting both excitatory and inhibitory synaptic transmission. The entorhinal cortex is a major source of cortical sensory and associational input to the hippocampus, but it is unclear whether either estrogens or progestogens may modulate cognitive function through effects on synaptic transmission in the entorhinal cortex. This study assessed the effects of the brief application of either 17-β estradiol (E2) or progesterone on excitatory glutamatergic synaptic transmission in the female rat entorhinal cortex in vitro. Rats were ovariectomized on postnatal day (PD) 63 and also received subdermal E2 implants to maintain constant low levels of circulating E2 on par with estrus. Electrophysiological recordings from brain slices were obtained between PD70 and PD86, and field excitatory postsynaptic potentials (fEPSPs) reflecting the activation of the superficial layers of the entorhinal cortex were evoked by the stimulation of layer I afferents. The application of E2 (10 nM) for 20 min resulted in a small increase in the amplitude of fEPSPs that reversed during the 30-min washout period. The application of the ERα agonist propylpyrazoletriol (PPT) (100 nM) or the β agonist DPN (1 μM) did not significantly affect synaptic responses. However, the application of the G protein-coupled estrogen receptor-1 (GPER1) agonist G1 (100 nM) induced a reversible increase in fEPSP amplitude similar to that induced by E2. Furthermore, the potentiation of responses induced by G1 was blocked by the GPER1 antagonist G15 (1 μM). Application of progesterone (100 nM) or its metabolite allopregnanolone (1 μM) did not significantly affect synaptic responses. The potentiation of synaptic transmission in the entorhinal cortex induced by the activation of GPER1 receptors may contribute to the modulation of cognitive function in female rats.

Effect of Mindfulness-Based Stress Reduction on dehydroepiandrosterone-sulfate in adults with self-reported stress. A randomized trial

Long‐term stress can lead to long‐term increased cortisol plasma levels, which increases the risk of numerous diseases. Dehydroepiandrosterone (DHEA) and its sulfated form dehydroepiandrosterone‐sulfate (DHEAS), together DHEA(S), have shown to counteract some of the effects of cortisol and may be protective during stress. The program “Mindfulness‐Based Stress Reduction” (MBSR) has shown to have positive effects on stress. The present study examined a possible effect of MBSR on DHEAS in plasma compared to a waiting list and a locally developed stress reduction program (LSR) in people with self‐reported stress. The study was a three‐armed randomized controlled trial conducted in a municipal health care center in Denmark. It included 71 participants with self‐reported stress randomized to either MBSR (n = 24) or LSR (n = 23), or a waiting list (n = 24). Blood samples were collected at baseline and at 12 weeks follow‐up to estimate effects of MBSR on DHEAS. The effect of MBSR on DHEAS was statistically significant compared to both the waiting list and LSR. We found a mean effect of 0.70 µmol/L (95% confidence interval [CI] = 0.18–1.22) higher DHEAS in the MBSR group compared with the waiting list group and a mean effect of 0.54 µmol/L (95% CI = 0.04–1.05) higher DHEAS in the MBSR group compared with the LSR group. Findings indicate an effect on DHEAS of the MBSR program compared to a waiting list and LSR program in people with self‐reported stress. However, we consider our findings hypothesis‐generating and validation by future studies is essential.

The Enigma of the Adrenarche: Identifying the Early Life Mechanisms and Possible Role in Postnatal Brain Development

Dehydroepiandrosterone (DHEA) and its sulfated metabolite (DHEAS) are dynamically regulated before birth and the onset of puberty. Yet, the origins and purpose of increasing DHEA[S] in postnatal development remain elusive. Here, we draw attention to this pre-pubertal surge from the adrenal gland—the adrenarche—and discuss whether this is the result of intra-adrenal gene expression specifically affecting the zona reticularis (ZR), if the ZR is influenced by the hypothalamic-pituitary axis, and the possible role of spino-sympathetic innervation in prompting increased ZR activity. We also discuss whether neural DHEA[S] synthesis is coordinately regulated with the developing adrenal gland. We propose that DHEA[S] is crucial in the brain maturation of humans prior to and during puberty, and suggest that the function of the adrenarche is to modulate, adapt and rewire the pre-adolescent brain for new and ever-changing social challenges. The etiology of DHEA[S] synthesis, neurodevelopment and recently described 11-keto and 11-oxygenated androgens are difficult to investigate in humans owing to: (i) ethical restrictions on mechanistic studies, (ii) the inability to predict which individuals will develop specific mental characteristics, and (iii) the difficulty of conducting retrospective studies based on perinatal complications. We discuss new opportunities for animal studies to overcome these important issues.

Biosynthesis and signalling functions of central and peripheral nervous system neurosteroids in health and disease

Neurosteroids are steroid hormones synthesised de novo in the brain and peripheral nervous tissues. In contrast to adrenal steroid hormones that act on intracellular nuclear receptors, neurosteroids directly modulate plasma membrane ion channels and regulate intracellular signalling. This review provides an overview of the work that led to the discovery of neurosteroids, our current understanding of their intracellular biosynthetic machinery, and their roles in regulating the development and function of nervous tissue. Neurosteroids mediate signalling in the brain via multiple mechanisms. Here, we describe in detail their effects on GABA (inhibitory) and NMDA (excitatory) receptors, two signalling pathways of opposing function. Furthermore, emerging evidence points to altered neurosteroid function and signalling in neurological disease. This review focuses on neurodegenerative diseases associated with altered neurosteroid metabolism, mainly Niemann-Pick type C, multiple sclerosis and Alzheimer disease. Finally, we summarise the use of natural and synthetic neurosteroids as current and emerging therapeutics alongside their potential use as disease biomarkers.

Maternally derived hormones, neurosteroids and the development of behaviour

In a wide range of taxa, there is evidence that mothers adaptively shape the development of offspring behaviour by exposing them to steroids. These maternal effects have major implications for fitness because, by shaping early development, they can permanently alter how offspring interact with their environment. However, theory on parent-offspring conflict and recent physiological studies showing that embryos rapidly metabolize maternal steroids have placed doubt on the adaptive significance of these hormone-mediated maternal effects. Reconciling these disparate perspectives requires a mechanistic understanding of the pathways by which maternal steroids can influence neural development. Here, we highlight recent advances in developmental neurobiology and psychiatric pharmacology to show that maternal steroid metabolites can have direct neuro-modulatory effects potentially shaping the development of neural circuitry underlying ecologically relevant behavioural traits. The recognition that maternal steroids can act through a neurosteroid pathway has critical implications for our understanding of the ecology and evolution of steroid-based maternal effects. Overall, compared to the classic view, a neurosteroid mechanism may reduce the evolutionary lability of hormone-mediated maternal effects owing to increased pleiotropic constraints and frequently influence long-term behavioural phenotypes in offspring.

[Ketamine, psilocybin, and rapid acting antidepressant: new promise for psychiatry?]

The hypothesis of monoaminergic deficiency has long dominated the conceptual framework for the development of new antidepressant strategies, but the limits of conventional antidepressant treatments targeting monoaminergic signaling have motivated the search for new antidepressant pathways. The success of ketamine in the management of depressive disorders has provoked a renewed interest in hallucinogenic substances such as psilocybin targeting the serotonergic signaling 5HT^2A and neurosteroid allosteric modulator of γ-aminobutyric acid (GABAA) receptors such as brexanolone. Unlike conventional treatments, these modulators of glutamatergic, serotonergic and GABAergic systems exert a rapid antidepressant effect ranging from 24hours to a week. Apart from their clinical interest and the fantasized search for a "miracle" molecule that jointly meets the expectations of patients and clinicians, these new targets could lead to the identification of potential new biomarkers for the development of rapid-acting antidepressants and redefine therapeutic strategies in mood disorders.

Serum DBI and biomarkers of neuroinflammation in Alzheimer's disease and delirium

Background

Alzheimer’s disease (AD) patients often express significant behavioral symptoms: for this reason, accessible related biomarkers could be very useful. Neuroinflammation is a key pathogenic process in both AD and delirium (DEL), a clinical condition with behavioral symptoms resembling those of AD.

Methods

A total of n = 30 AD patients were recruited together with n = 30 DEL patients and n = 15 healthy controls (CTRL). Serum diazepam binding inhibitor (DBI), IL-17, IL-6, and TNF-α were assessed by ELISA.

Results

DBI serum levels were increased in AD patients with respect to CTRL (+ 81%), while DEL values were 70% higher than AD. IL-17 was increased in DEL with respect to CTRL (+ 146%), while AD showed dispersed values and failed to reach significant differences. On the other hand, IL-6 showed a more robust increase in DEL with respect to the other two groups (+ 185% and + 205% vs. CTRL and AD, respectively), and TNF-α failed to show any change.

Conclusions

DBI may be a very promising candidate for AD, perhaps marking psychomotor DEL-like symptoms, in view of developing future helping tool for practicing physicians. Furthermore, DBI rise in DEL offers novel cues for a better comprehension of the pathogenesis of this potentially fatal condition.

Sex Hormone Depletion Augments Glucocorticoid Induction of Tau Hyperphosphorylation in Male Rat Brain

Steroid hormones secreted by the gonads (sex steroids) and adrenal glands (glucocorticoids, GC) are known to influence brain structure and function. While levels of sex steroids wane in late adulthood, corticosteroid levels tend to rise in many individuals due to age-related impairments in their feedback on central mechanisms regulating adrenal function. These fluctuations in sex and adrenal steroid secretion may be relevant to age-related neurodegenerative disorders such as Alzheimer's disease (AD) in which hyperphosphorylation of Tau protein is a key pathological event. We here report that both, long-term GC deprivation (by adrenalectomy) and exogenous GC administration with natural or synthetic glucocorticoid receptor ligands (corticosterone and dexamethasone, respectively) induce Tau hyperphosphorylation in the hippocampus and frontocortical regions at epitopes associated with disruption of cytoskeletal and synaptic function. Interestingly, we observed that the changes in Tau induced by manipulation of the GC milieu of male rats were exacerbated by testosterone depletion (by orchiectomy). While this finding supports previous suggestions of a neuroprotective role of male sex hormones, this is the first study to address interactions between adrenal and sex steroids on Tau hyperphosphorylation and accumulation that are known to endanger neuronal function and plasticity. These results are particularly important for understanding the mechanisms that can precipitate AD because, besides being modulated by age, GC are elevated by stress, a phenomenon now established as a trigger of deficits in neural plasticity and survival, cognitive behaviour and AD-like Tau pathology.

[New therapeutic avenues for neurosteroids in psychiatric diseases]

Discovered in the eighties by Pr Baulieu and colleagues, neurosteroids are a class of neuroactive brain-born steroids, which comprises the steroid hormones, their biosynthesis precursors and their metabolites. They can act through genomic as well as non-genomic pathways. Genomic pathways, only triggered by the neurosteroid hormones, are, in the brain, the same as those largely described in the periphery: the binding of these steroid hormones to nuclear receptors leads to transcription regulations. On the other hand, their precursors and metabolites, such as pregnenolone (PREG), dehydroepiandrosterone (DHEA), their respective sulfate esters, pregnenolone sulfate (PREG-S) and DHEA sulfate (DHEA-S) and allopregnanolone (ALLOP), are defined as neurosteroids, but no corresponding nuclear receptors have been identified so far. In fact, they trigger non-genomic pathways which consist in (i) inhibitory ionotropic receptors, (ii) excitatory ionotropic receptors and (iii) the microtubular system. Hence, inhibitory neurosteroids, whose mostly studied representative is ALLOP, positively modulate, or directly activate, the ionotropic GABA-A receptors. In contrast, excitatory neurosteroids, represented by PREG-S, DHEA-S and DHEA, inhibit the GABA-A receptors, and activate, directly or indirectly, through the sigma-1 receptors, the NMDA glutamate receptors. Neurosteroids of the third group, the microtubular neurosteroids, are able to bind microtubule associated proteins, in particular MAP2, to promote microtubule assembly, neurite outgrowth and in fine structural neuroplasticity. So far, PREG, DHEA and progesterone are the three identified microtubular neurosteroids. The pharmacological properties of neurosteroids have led to specific investigations for assessing their therapeutic potentialities in psychiatric diseases, using validated animal models. In some cases, clinical trials were also performed. These studies showed that ALLOP, the main inhibitory neurosteroid, displayed clear-cut anxiolytic-like and antidepressant-like efficacy in animals. It has been subsequently developed as Brexanolone and tested with success in phase III of clinical trials for the treatment of post-partum depression. Although showing pro-cognitive properties in animals, the sulfated neurosteroids, PREG-S and DHEA-S, were, in contrast, never tested in clinical trials, probably due to their poor stability and proconvulsivant side effects. Their respective non-sulfated forms, PREG and DHEA, showed antidepressant and antipsychotic efficacies in clinical trials, but these drugs never reached the phase III of clinical development because their therapeutic uses would have led to an overproduction of active metabolites responsible for intolerable side effects. The alternative strategy which has been selected consists of the development of non-metabolizable synthetic derivatives of these natural steroids, which keep the same neuroactive properties as their parent molecules, but are devoid of any hormonal side effects. An example of such innovative drugs is MAP4343, a synthetic derivative of PREG, which exhibits potent antidepressant-like efficacy in validated animal models. It is currently tested in depressed patients.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

The association between hormones and antipsychotic use: a focus on postpartum and menopausal women

During the postpartum and menopausal periods of women's lives, there is a well-established and significant drop of circulating estrogens. This may be the reason why both these periods are associated with an increased risk for onset or exacerbation of psychiatric disorders. Whether symptoms are mainly affective or mainly psychotic, these disorders are frequently treated with antipsychotic medications, which calls for an examination of the relationship between hormone replacement and antipsychotic agents at these time periods. The aim of this narrative review is to summarize what is known about the association of hormones and antipsychotics in the postnatal period and at menopause. In the review, we focus on estrogen and oxytocin hormones and include, for the most part, only papers published within the last 10 years. Both estradiol and oxytocin have at various times been implicated in the etiology of postpartum disorders, and estrogens, sometimes combined with progesterone, have been tested as potential treatments for these conditions. The role of estradiol as an adjunct to antipsychotics in the prevention of postpartum relapses is currently controversial. With respect to oxytocin, studies are lacking. Psychosis in menopausal and postmenopausal women has been successfully treated with estrogens and selective estrogen-receptor modulators, mainly raloxifene, in addition to antipsychotics. Some symptoms appear to respond better than others. No oxytocin study has specifically targeted postmenopausal women. Because of feedback mechanisms, there is a theoretical danger of therapy with exogenous hormones interfering with endogenous secretion and disturbing the balance among inter-related hormones. When used with antipsychotics, hormones may also affect the metabolism and, hence, the brain level of specific antipsychotics. This makes treatment with antipsychotics plus hormones complicated. Dose, timing and route of intervention may all prove critical to efficacy. While much remains unknown, this literature review indicates that, within standard dose ranges, the combination of hormones and antipsychotics for postnatal and menopausal women suffering severe mental distress can be beneficial, and is safe.

17β-Hydroxysteroid dehydrogenases and neurosteroid metabolism in the central nervous system

17β-Hydroxysteroid dehydrogenases are indispensable for downstream enzyme steps of the neurosteroidogenesis. Neurosteroids are synthesized de novo in neurons and glia from cholesterol transported into mitochondria, or by conversion from proneurosteroids, e. g. dehydroepiandrosterone (DHEA) and pregnenolone, through the same metabolic pathway as revealed in the de novo neurosteroidogenesis. Hormonal steroids generated from endocrine glands are transported into brain from the circulation to exert neuronal activity via genomic pathway, whereas neurosteroids produced in brain cells without genomic targets identified could bind to cell surface targets, e.g., GABA_A or NMDA receptors and elicit antidepressant, anxiolytic, anticonvulsant and anesthetic effects by regulating neuroexcitability. In a broad sense, neurosteroids include hormonal steroids in brain, and they are irrespective of origin playing important roles in brain development including neuroprotection, neurogenesis and neural plasticity. They are also a critical element in cognitive and memory functions. Mitochondrial 17β-HSD10, encoded by the HSD17B10 gene mapping to Xp11.2, is found in various brain regions, essential for the maintenance of neurosteroid homeostasis. Mutations identified in this gene resulted in two distinct brain diseases, namely HSD10 deficiency and MRXS10, of which clinical presentations and pathogenetic mechanisms are quite different. Since elevated levels of 17β-HSD10 was found in brains of Alzheimer's disease patients and AD mouse model, it may also act as an adverse factor in the AD pathogenesis due to an imbalance of neurosteroid metabolism.

Potent inhibitors of equine steroid isomerase EcaGST A3-3

Equine glutathione transferase A3-3 (EcaGST A3-3) belongs to the superfamily of detoxication enzymes found in all higher organisms. However, it is also the most efficient steroid double-bond isomerase known in mammals. Equus ferus caballus shares the steroidogenic pathway with Homo sapiens, which makes the horse a suitable animal model for investigations of human steroidogenesis. Inhibition of the enzyme has potential for treatment of steroid-hormone-dependent disorders. Screening of a library of FDA-approved drugs identified 16 out of 1040 compounds, which at 10 μM concentration afforded at least 50% inhibition of EcaGST A3-3. The most potent inhibitors, anthralin, sennoside A, tannic acid, and ethacrynic acid, were characterized by IC₅₀ values in the submicromolar range when assayed with the natural substrate Δ⁵-androstene-3,17-dione.

Neurosteroid Levels in the Orbital Frontal Cortex of Subjects with PTSD and Controls: A Preliminary Report

Background

Neurosteroids mediate stress signaling and have been implicated in the pathogenesis of post-traumatic stress disorder (PTSD) in both preclinical and clinical studies. Compared to controls, subjects with PTSD exhibit altered neurosteroid levels in peripheral blood and cerebrospinal fluid as well as hypoactivity in the medial orbital frontal cortex (mOFC). Therefore, the aim of this study was to compare neurosteroid levels in the mOFC of subjects with PTSD (n = 18) and controls (n = 35).

Methods

Gray matter was dissected from fresh-frozen mOFC, and levels of the neurosteroids pregnenolone, allopregnanolone, pregnanolone, epiallopregnanolone, epipregnanolone, tetrahydrodeoxycorticosterone, and androsterone were determined by gas chromatography - tandem mass spectrometry (GC/MS/MS).

Results

Analyses of unadjusted levels revealed that males with PTSD had significantly decreased levels of allopregnanolone (p = 0.03) compared to control males and females with PTSD had significantly increased levels of pregnenolone (p = 0.03) relative to control females. After controlling for age, postmortem interval, and smoking status, results showed that males with PTSD had significantly decreased levels of androsterone (t46 = 2.37, p = 0.02) compared to control males and females with PTSD had significantly increased levels of pregnanolone (t46 = -2.25, p = 0.03) relative to control females.

Conclusions

To our knowledge, this is the first report of neurosteroid levels in postmortem brain tissue of subjects with PTSD. Although replication is required in other brain regions and in a larger cohort of subjects, the results suggest a dysregulation of allopregnanolone and androsterone in males with PTSD and pregnanolone in females with PTSD in the mOFC.