Neurosteroids and epilepsy

Neurosteroids and neurological disorders

Neurosteroids play an important role as endogenous neuromodulators that are locally produced in the central nervous system and rapidly change the excitability of neurons and the activation of microglial cells and astrocytes. Here we review the mechanisms of synthesis, metabolism, and actions of neurosteroids in the central nervous system. Neurosteroids are able to play a variety of roles in the central nervous system under physiological conditions by binding to membrane ion channels and receptors such as gamma-aminobutyric acid type A receptors, Nmethyl- D-aspartate receptors, L- and T-type calcium channels, and sigma-1 receptors. In addition, numerous neurological disorders, including persistent neuropathic pain, multiple sclerosis, and seizures, have altered the levels of neurosteroids in the central nervous system. Thus, we review how local synthesis and metabolism of neurosteroids are modulated in the central nervous system and describe the role of neurosteroids under pathological conditions. Furthermore, we discuss whether neurosteroids may play a role as a new therapeutic for the treatment of neurological disorders.

Hypotheses of pathophysiological mechanisms in epileptic encephalopathies: A review

INTRODUCTION

Epileptic encephalopathy (EE) is a serious clinical issue that manifests as part of developmental and epileptic encephalopathy (DEE), particularly in childhood epilepsy. In EE, neurocognitive functions and behavior are impaired by intense epileptiform electroencephalogram (EEG) activity. Hypotheses of pathophysiological mechanisms behind EE are reviewed to contribute to an effective solution for EE.

REVIEW

Current hypotheses are as follows: 1) neuronal dysfunction based on genetic abnormalities that may affect neurocognitive functions and epilepsy separately; 2) impairment of synaptic homeostasis during sleep that may be responsible for DEE/EE with spike-and-wave activation in sleep; 3) abnormal subcortical regulation of the cerebral cortex; 4) abnormal cortical metabolism and hemodynamics with impairment of the neural network including default mode network; 5) neurotransmitter imbalance and disordered neural excitability; 6) the effects of neuroinflammation that may be caused by epileptic seizures and in turn aggravate epileptogenesis; 7) the interaction between physiological and pathological high-frequency EEG activity; etc. The causal relationship between epileptiform EEG activity and neurocognitive dysfunctions is small in DEE based on genetic abnormalities and it is largely unestablished in the other hypothetical mechanisms.

CONCLUSION

We have not yet found answers to the question of whether the single-central or multiple derangements are present and what seizures and intense epileptiform EEG abnormalities mean in EE. We need to continue our best efforts in both aspects to elucidate the pathophysiological mechanisms of DEE/EE and further develop epilepsy treatment and precision medicine.

The Role of Glial Cells in the Pathophysiology of Epilepsy

Epilepsy is a chronic neurological disorder marked by recurrent seizures, significantly impacting individuals worldwide. Current treatments are often ineffective for a third of patients and can cause severe side effects, necessitating new therapeutic approaches. Glial cells, particularly astrocytes, microglia, and oligodendrocytes, are emerging as crucial targets in epilepsy management. Astrocytes regulate neuronal homeostasis, excitability, and synaptic plasticity, playing key roles in maintaining the blood-brain barrier (BBB) and mediating neuroinflammatory responses. Dysregulated astrocyte functions, such as reactive astrogliosis, can lead to abnormal neuronal activity and seizure generation. They release gliotransmitters, cytokines, and chemokines that may exacerbate or mitigate seizures. Microglia, the innate immune cells of the CNS, contribute to neuroinflammation, glutamate excitotoxicity, and the balance between excitatory and inhibitory neurotransmission, underscoring their dual role in seizure promotion and protection. Meanwhile, oligodendrocytes, primarily involved in myelination, also modulate axonal excitability and contribute to the neuron-glia network underlying seizure pathogenesis. Understanding the dynamic interactions of glial cells with neurons provides promising avenues for novel epilepsy therapies. Targeting these cells may lead to improved seizure control and better clinical outcomes, offering hope for patients with refractory epilepsy.

Role of cholesterol in modulating brain hyperexcitability

Cholesterol is a critical molecule in the central nervous system, and imbalances in the synthesis and metabolism of brain cholesterol can result in a range of pathologies, including those related to hyperexcitability. The impact of cholesterol on disorders of epilepsy and developmental and epileptic encephalopathies is an area of growing interest. Cholesterol cannot cross the blood-brain barrier, and thus the brain synthesizes and metabolizes its own pool of cholesterol. The primary metabolic enzyme for brain cholesterol is cholesterol 24-hydroxylase (CH24H), which metabolizes cholesterol into 24S-hydroxycholesterol (24HC). Dysregulation of CH24H and 24HC can affect neuronal excitability through a range of mechanisms. 24HC is a positive allosteric modulator of N-methyl-D-aspartate (NMDA) receptors and can increase glutamate release via tumor necrosis factor-α-dependent pathways. Increasing cholesterol metabolism can lead to dysfunction of excitatory amino acid transporter 2 and impair glutamate reuptake. Finally, overstimulation of NMDA receptors can further activate metabolism of cholesterol, leading to a vicious cycle of overactivation. All of these mechanisms increase extracellular glutamate and can lead to hyperexcitability. For these reasons, the cholesterol pathway represents a new potential mechanistic target for antiseizure medications. CH24H inhibition has been shown to decrease seizure behavior and improve survival in multiple animal models of epilepsy and could be a promising new mechanism of action for the treatment of neuronal hyperexcitability and developmental and epileptic encephalopathies.

Causal associations of ischemic stroke, metabolic factors, and related medications with epilepsy: a Mendelian randomization study

Background

Earlier researches have demonstrated that ischemic stroke, metabolic factors, and associated medications may influence the risk of epilepsy. Nevertheless, the causality between these elements and epilepsy remains inconclusive. This study aims to examine whether ischemic stroke, metabolic factors, and related medications affect the overall risk of epilepsy.

Methods

We used single nucleotide polymorphisms associated with ischemic stroke, hypothyroidism, hypertension, blood glucose levels, high cholesterol, serum 25-Hydroxyvitamin D levels, testosterone, HMG CoA reductase inhibitors, and beta-blocking agents as instrumental variables in a Mendelian randomization technique to investigate causality with epilepsy. Multiple sensitivity methods were performed to evaluate pleiotropy and heterogeneity.

Results

The IVW analysis revealed positive associations between ischemic stroke (OR = 1.29; p = 0.020), hypothyroidism (OR = 1.05; p = 0.048), high blood pressure (OR = 1.10; p = 0.028), high cholesterol (OR = 1.10; p = 0.024), HMG CoA reductase inhibitors (OR = 1.19; p = 0.003), beta-blocking agents (OR = 1.20; p = 0.006), and the risk of epilepsy. Conversely, blood glucose levels (OR = 0.79; p = 0.009), serum 25-Hydroxyvitamin D levels (OR = 0.75; p = 0.020), and testosterone (OR = 0.62; p = 0.019) exhibited negative associations with the risk of epilepsy. Sensitivity analyses confirmed the robustness of these findings (p > 0.05).

Conclusion

Our research suggests that ischemic stroke, hypothyroidism, high blood pressure, high cholesterol, HMG CoA reductase inhibitors, and beta-blockers may increase the risk of epilepsy, whereas serum 25-Hydroxyvitamin D levels and blood glucose levels may reduce the risk.

An overview of ganaxolone as a treatment for seizures associated with cyclin-dependent kinase-like 5 deficiency disorder

INTRODUCTION

Cyclin-dependent kinase-Like 5 (CDKL5) deficiency disorder (CDD) is a rare neurodevelopmental condition commonly characterized by drug-resistant, refractory epilepsy, and seizures beginning in infancy. Most patients use multiple drugs, yet seizures remain difficult to control. So far, no conventional anti-seizure medications have been proven to be effective in individuals with CDD, in well-conducted studies.

AREAS COVERED

In this review, the authors assess the pharmacokinetics, early studies and appraise a recent study investigating the efficacy and safety of the oral suspension of ganaxolone (3α-hydroxy-3β-methyl-5α-pregnan-20-one) as an adjunctive therapy to treat seizures in CDD. The authors also discuss the impact of this drug on non-seizure outcomes.

EXPERT OPINION

Ganaxolone is a neuroactive 3β-methylated synthetic analogue of the potent agonist of gamma-aminobutyric acid type A receptors, allopregnanolone. Ganaxolone is the only drug that has been studied in a robust randomized controlled trial and been proven to be effective in this population.

Subthreshold Cannabidiol Potentiates Levetiracetam in the Kainic Acid Model of Temporal Lobe Epilepsy: A Pilot Study

Refractoriness to antiseizure medications is still a major concern in the pharmacotherapy of epilepsy. For this reason, we decided to evaluate the combination of levetiracetam and cannabidiol, administered at a subthreshold dose, to limit the possible adverse effects of this phytocannabinoid. We administered levetiracetam (300 mg/kg/day, via osmotic minipumps), cannabidiol (120 mg/kg/day, injected once a day subcutaneously), or their combination for one week in epileptic rats. Saline-treated epileptic rats were the control group. Animals were monitored with video electroencephalography the week before and after the treatment. No changes were found in the controls. Levetiracetam did not significantly reduce the total seizure number or the overall seizure duration. Still, the overall number of seizures (p < 0.001, Duncan's new multiple range test) and their total duration (p < 0.01) increased in the week following treatment withdrawal. Cannabidiol did not change seizures when administered as a single drug. Instead, levetiracetam combined with cannabidiol resulted in a significant reduction in the overall number and duration of seizures (p < 0.05), when comparing values measured during treatment with both pre- and post-treatment values. These findings depended on changes in convulsive seizures, while non-convulsive seizures were stable. These results suggest that cannabidiol determined a remarkable potentiation of levetiracetam antiseizure effects at a subthreshold dose.

The present and future of seizure detection, prediction, and forecasting with machine learning, including the future impact on clinical trials

Seizures have a profound impact on quality of life and mortality, in part because they can be challenging both to detect and forecast. Seizure detection relies upon accurately differentiating transient neurological symptoms caused by abnormal epileptiform activity from similar symptoms with different causes. Seizure forecasting aims to identify when a person has a high or low likelihood of seizure, which is related to seizure prediction. Machine learning and artificial intelligence are data-driven techniques integrated with neurodiagnostic monitoring technologies that attempt to accomplish both of those tasks. In this narrative review, we describe both the existing software and hardware approaches for seizure detection and forecasting, as well as the concepts for how to evaluate the performance of new technologies for future application in clinical practice. These technologies include long-term monitoring both with and without electroencephalography (EEG) that report very high sensitivity as well as reduced false positive detections. In addition, we describe the implications of seizure detection and forecasting upon the evaluation of novel treatments for seizures within clinical trials. Based on these existing data, long-term seizure detection and forecasting with machine learning and artificial intelligence could fundamentally change the clinical care of people with seizures, but there are multiple validation steps necessary to rigorously demonstrate their benefits and costs, relative to the current standard.

The Emerging Role of Neurosteroids: Novel Drugs Brexanalone, Sepranolone, Zuranolone, and Ganaxolone in Mood and Neurological Disorders

This review investigates the potential of neurosteroids, including brexanolone, zuranolone, sepranolone, and ganaxalone, as therapeutic agents for a range of mood and neurological disorders. Notably, these disorders encompass postpartum depression, post-traumatic stress disorder (PTSD), major depressive disorder (MDD), epilepsy, and Alzheimer's disease. Brexanolone and zuranolone have emerged as frontrunners in the treatment of postpartum depression, offering rapid relief from debilitating symptoms. Their mechanism of action involves modulation of the gamma-aminobutyric acid (GABA) system, which plays a pivotal role in mood regulation. Clinical trials have demonstrated their efficacy, heralding a potential breakthrough in addressing this often-overlooked condition. In the context of PTSD and MDD, neurosteroids have demonstrated significant promise. Their positive allosteric modulation of GABA-A receptors translates into improved mood stabilization and reduced symptoms. This novel approach represents a departure from conventional treatments and could offer newfound hope for individuals grappling with these disorders. Beyond mood disorders, neurosteroids, especially ganaxalone, exhibit potential in the realm of epilepsy management. Ganaxalone's capacity to control seizures is attributed to its GABAergic activity, which helps restore the delicate balance of neurotransmission in epileptic brains. Moreover, neurosteroids have revealed neuroprotective properties in Alzheimer's disease models. By influencing the GABAergic system, they mitigate excitotoxicity, a hallmark of Alzheimer's pathology. This neuroprotection opens a novel avenue for slowing neurodegeneration, although further research and clinical validation are essential. In conclusion, this review underscores the substantial therapeutic promise of neurosteroids in mood and neurological disorders. Their modulation of the GABA system emerges as a central mechanism of action, emphasizing the importance of GABAergic signaling in these conditions. The path forward entails continued investigation and clinical trials to fully unlock the potential of neurosteroids, offering hope for enhanced treatments in these challenging clinical domains.

A systematic review and meta-analysis on efficacy and safety of Ganaxolone in epilepsy

INTRODUCTION

Ganaxolone has exhibited potential in managing seizures for epilepsy. This systematic review and meta-analysis aim to assess both the safety and efficacy of Ganaxolone for refractory epilepsy.

METHODS

A thorough search of electronic databases was conducted to identify relevant randomized controlled trials involving patients with drug-resistant focal epilepsy and CDKL5 deficiency disorder. Efficacy and safety outcomes were extracted from the selected studies. Cochrane Review Manager was utilized for data synthesis and analysis, with risk ratios and mean differences calculated to evaluate the efficacy and safety profile of Ganaxolone.

RESULTS

The meta-analysis included a total of five randomized controlled trials. Ganaxolone exhibited significant efficacy in reducing seizure frequency by at least 50% from baseline [RR 0.90 (95% CI: 0.83, 0.98), p = 0.02]. However, the results did not reach significance for reducing 28-day seizure frequency [Mean Difference -1.45 (95% CI: -3.39, 0.49), p = 0.14]. Ganaxolone exhibited a positive safety profile, with no statistically significant occurrence of adverse events [RR 1.30 (95% CI: 0.93, 1.83), p = 0.12] and adverse events leading to discontinuation of the study drug [RR 1.01 (95% CI: 0.42, 2.39), p = 0.99] compared to placebo.

CONCLUSION

Ganaxolone presents itself as a viable therapeutic option for refractory epilepsy, showing efficacy in reducing seizure frequency and exhibited a favorable safety profile.

PROSPERO REGISTRATION NUMBER

CRD42023434883.

Multiomic analysis implicates nuclear hormone receptor signalling in clustering epilepsy

Clustering Epilepsy (CE) is an epileptic disorder with neurological comorbidities caused by heterozygous variants of the X chromosome gene Protocadherin 19 (PCDH19). Recent studies have implicated dysregulation of the Nuclear Hormone Receptor (NHR) pathway in CE pathogenesis. To obtain a comprehensive overview of the impact and mechanisms of loss of PCDH19 function in CE pathogenesis, we have performed epigenomic, transcriptomic and proteomic analysis of CE relevant models. Our studies identified differential regulation and expression of Androgen Receptor (AR) and its targets in CE patient skin fibroblasts. Furthermore, our cell culture assays revealed the repression of PCDH19 expression mediated through ERα and the co-regulator FOXA1. We also identified a protein-protein interaction between PCDH19 and AR, expanding upon the intrinsic link between PCDH19 and the NHR pathway. Together, these results point to a novel mechanism of NHR signaling in the pathogenesis of CE that can be explored for potential therapeutic options.

Evaluation of Midazolam-Ketamine-Allopregnanolone Combination Therapy against Cholinergic-Induced Status Epilepticus in Rats

Status epilepticus (SE) is a life-threatening development of self-sustaining seizures that becomes resistant to benzodiazepines when treatment is delayed. Benzodiazepine pharmacoresistance is thought in part to result from internalization of synaptic GABAA receptors, which are the main target of the drug. The naturally occurring neurosteroid allopregnanolone is a therapy of interest against SE for its ability to modulate all isoforms of GABAA receptors. Ketamine, an N-methyl-D-aspartate (NMDA) receptor antagonist, has been partially effective in combination with benzodiazepines in mitigating SE-associated neurotoxicity. In this study, allopregnanolone as an adjunct to midazolam or midazolam-ketamine combination therapy was evaluated for efficacy against cholinergic-induced SE. Adult male rats implanted with electroencephalographic (EEG) telemetry devices were exposed to the organophosphorus chemical (OP) soman (GD) and treated with an admix of atropine sulfate and HI-6 at 1 minute after exposure followed by midazolam, midazolam-allopregnanolone, or midazolam-ketamine-allopregnanolone 40 minutes after seizure onset. Neurodegeneration, neuronal loss, and neuroinflammation were assessed 2 weeks after GD exposure. Seizure activity, EEG power integral, and epileptogenesis were also compared among groups. Overall, midazolam-ketamine-allopregnanolone combination therapy was effective in reducing cholinergic-induced toxic signs and neuropathology, particularly in the thalamus and hippocampus. Higher dosage of allopregnanolone administered in combination with midazolam and ketamine was also effective in reducing EEG power integral and epileptogenesis. The current study reports that there is a promising potential of neurosteroids in combination with benzodiazepine and ketamine treatments in a GD model of SE. SIGNIFICANCE STATEMENT: Allopregnanolone, a naturally occurring neurosteroid, reduced pathologies associated with soman (GD) exposure such as epileptogenesis, neurodegeneration, and neuroinflammation, and suppressed GD-induced toxic signs when used as an adjunct to midazolam and ketamine in a delayed treatment model of soman-induced status epilepticus (SE) in rats. However, protection was incomplete, suggesting that further studies are needed to identify optimal combinations of antiseizure medications and routes of administration for maximal efficacy against cholinergic-induced SE.

A review on linking stress, depression, and insulin resistance via low-grade chronic inflammation

Stress is a disturbance in homeostasis caused by psychological, physiological, or environmental factors. Prolonged reactions to chronic stress can be detrimental, resulting in various metabolic abnormalities, referred to as metabolic syndrome (MS). There is a reciprocal increased risk between MS and major depressive disorder. Recent studies established an association between inflammation and insulin signaling in type 2 diabetes mellitus with depression. In the present review, we discuss chronic low-grade inflammation, pathways of insulin resistance, and brain glucose metabolism in the context of neuroinflammation and depression. Specific attention is given to psychotropic drugs such as bupropion, mirtazapine, and nefazodone, anti-inflammatory drugs like Celecoxib (COX-2 inhibitor), Etanercept, adalimumab, IL-4Ra antagonist, Anti-IL- 17A antibody (Ixekizumab) and lifestyle modifications including exercise, dietary changes, and sleep hygiene. These therapeutic solutions offer potential in treating depression by targeting metabolic conditions like insulin resistance and inflammatory pathways. The article further explains the significance of a nutrition and antioxidants-rich diet, emphasizing the role of omega-3 fatty acids, vitamin D, zinc, and polyphenols, to improve immunity and activate anti-inflammatory signaling pathways.

Low glycemic index diet restrains epileptogenesis in a gender-specific fashion

Dietary restriction, such as low glycemic index diet (LGID), have been successfully used to treat drug-resistant epilepsy. However, if such diet could also counteract antiepileptogenesis is still unclear. Here, we investigated whether the administration of LGID during the latent pre-epileptic period, prevents or delays the appearance of the overt epileptic phenotype. To this aim, we used the Synapsin II knockout (SynIIKO) mouse, a model of temporal lobe epilepsy in which seizures manifest 2-3 months after birth, offering a temporal window in which LGID may affect epileptogenesis. Pregnant SynIIKO mice were fed with either LGID or standard diet during gestation and lactation. Both diets were maintained in weaned mice up to 5 months of age. LGID delayed the seizure onset and induced a reduction of seizures severity only in female SynIIKO mice. In parallel with the epileptic phenotype, high-density multielectrode array recordings revealed a reduction of frequency, amplitude, duration, velocity of propagation and spread of interictal events by LGID in the hippocampus of SynIIKO females, but not mutant males, confirming the gender-specific effect. ELISA-based analysis revealed that LGID increased cortico-hippocampal allopregnanolone (ALLO) levels only in females, while it was unable to affect ALLO plasma concentrations in either sex. The results indicate that the gender-specific interference of LGID with the epileptogenic process can be ascribed to a gender-specific increase in cortical ALLO, a neurosteroid known to strengthen GABAergic transmission. The study highlights the possibility of developing a personalized gender-based therapy for temporal lobe epilepsy.

Quantitative and Qualitative Analysis of Neurotransmitter and Neurosteroid Production in Cerebral Organoids during Differentiation

In the human brain, neurophysiological activity is modulated by the movement of neurotransmitters and neurosteroids. To date, the similarity between cerebral organoids and actual human brains has been evaluated using comprehensive multiomics approaches. However, a systematic analysis of both neurotransmitters and neurosteroids from cerebral organoids has not yet been reported. Here, we performed quantitative and qualitative assessments of neurotransmitters and neurosteroids over the course of cerebral organoid differentiation. Our multiomics approaches revealed that the expression levels of neurotransmitter-related proteins and RNA, including neurosteroids, increase as cerebral organoids mature. We also found that the electrophysiological activity of human cerebral organoids increases in tandem with the expression levels of both neurotransmitters and neurosteroids. Our study demonstrates that the expression levels of neurotransmitters and neurosteroids can serve as key factors in evaluating the maturity and functionality of human cerebral organoids.

New GABA-Targeting Therapies for the Treatment of Seizures and Epilepsy: I. Role of GABA as a Modulator of Seizure Activity and Recently Approved Medications Acting on the GABA System

γ-Aminobutyric acid (GABA) is the most prevalent inhibitory neurotransmitter in the mammalian brain and has been found to play an important role in the pathogenesis or the expression of many neurological diseases, including epilepsy. Although GABA can act on different receptor subtypes, the component of the GABA system that is most critical to modulation of seizure activity is the GABAA-receptor-chloride (Cl-) channel complex, which controls the movement of Cl- ions across the neuronal membrane. In the mature brain, binding of GABA to GABAA receptors evokes a hyperpolarising (anticonvulsant) response, which is mediated by influx of Cl- into the cell driven by its concentration gradient between extracellular and intracellular fluid. However, in the immature brain and under certain pathological conditions, GABA can exert a paradoxical depolarising (proconvulsant) effect as a result of an efflux of chloride from high intracellular to lower extracellular Cl- levels. Extensive preclinical and clinical evidence indicates that alterations in GABAergic inhibition caused by drugs, toxins, gene defects or other disease states (including seizures themselves) play a causative or contributing role in facilitating or maintaning seizure activity. Conversely, enhancement of GABAergic transmission through pharmacological modulation of the GABA system is a major mechanism by which different antiseizure medications exert their therapeutic effect. In this article, we review the pharmacology and function of the GABA system and its perturbation in seizure disorders, and highlight how improved understanding of this system offers opportunities to develop more efficacious and better tolerated antiseizure medications. We also review the available data for the two most recently approved antiseizure medications that act, at least in part, through GABAergic mechanisms, namely cenobamate and ganaxolone. Differences in the mode of drug discovery, pharmacological profile, pharmacokinetic properties, drug-drug interaction potential, and clinical efficacy and tolerability of these agents are discussed.

Shank3 deletion in PV neurons is associated with abnormal behaviors and neuronal functions that are rescued by increasing GABAergic signaling

BACKGROUND

Phelan-McDermid syndrome (PMS) is a neurodevelopmental disorder characterized by developmental delay, intellectual disability, and autistic-like behaviors and is primarily caused by haploinsufficiency of SHANK3 gene. Currently, there is no specific treatment for PMS, highlighting the need for a better understanding of SHANK3 functions and the underlying pathophysiological mechanisms in the brain. We hypothesize that SHANK3 haploinsufficiency may lead to alterations in the inhibitory system, which could be linked to the excitatory/inhibitory imbalance observed in models of autism spectrum disorder (ASD). Investigation of these neuropathological features may shed light on the pathogenesis of PMS and potential therapeutic interventions.

METHODS

We recorded local field potentials and visual evoked responses in the visual cortex of Shank3∆11-/- mice. Then, to understand the impact of Shank3 in inhibitory neurons, we generated Pv-cre+/- Shank3Fl/Wt conditional mice, in which Shank3 was deleted in parvalbumin-positive neurons. We characterized the phenotype of this murine model and we compared this phenotype before and after ganaxolone administration.

RESULTS

We found, in the primary visual cortex, an alteration of the gain control of Shank3 KO compared with Wt mice, indicating a deficit of inhibition on pyramidal neurons. This alteration was rescued after the potentiation of GABAA receptor activity by Midazolam. Behavioral analysis showed an impairment in grooming, memory, and motor coordination of Pv-cre+/- Shank3Fl/Wt compared with Pv-cre+/- Shank3Wt/Wt mice. These deficits were rescued with ganaxolone, a positive modulator of GABAA receptors. Furthermore, we demonstrated that treatment with ganaxolone also ameliorated evocative memory deficits and repetitive behavior of Shank3 KO mice.

LIMITATIONS

Despite the significant findings of our study, some limitations remain. Firstly, the neurobiological mechanisms underlying the link between Shank3 deletion in PV neurons and behavioral alterations need further investigation. Additionally, the impact of Shank3 on other classes of inhibitory neurons requires further exploration. Finally, the pharmacological activity of ganaxolone needs further characterization to improve our understanding of its potential therapeutic effects.

CONCLUSIONS

Our study provides evidence that Shank3 deletion leads to an alteration in inhibitory feedback on cortical pyramidal neurons, resulting in cortical hyperexcitability and ASD-like behavioral problems. Specifically, cell type-specific deletion of Shank3 in PV neurons was associated with these behavioral deficits. Our findings suggest that ganaxolone may be a potential pharmacological approach for treating PMS, as it was able to rescue the behavioral deficits in Shank3 KO mice. Overall, our study highlights the importance of investigating the role of inhibitory neurons and potential therapeutic interventions in neurodevelopmental disorders such as PMS.

Trajectories of Allopregnanolone and Allopregnanolone to Progesterone Ratio across the Six Subphases of Menstrual Cycle

Background: Allopregnanolone is one of the most studied neuroactive steroids; yet, despite its relevance to neuropsychiatric research, it is not known how it, as well as its ratio to progesterone, varies across all six subphases of the menstrual cycle. Two enzymes—5α-dihydroprogesterone and 5α-reductase—convert progesterone to allopregnanolone, and, based on immunohistochemical studies in rodents, the activity of 5α-reductase is considered the rate-limiting step in the formation of allopregnanolone. It is not clear, however, whether the same phenomenon is observed across to the menstrual cycle, and, if so, at what point this takes place. Methods: Thirty-seven women completed the study during which they attended eight clinic visits across one menstrual cycle. We analyzed their allopregnanolone and progesterone serum concentrations using ultraperformance liquid chromatography–tandem mass spectrometry, and we implemented a validated method to realign the data from the original eight clinic study visits, following which we imputed the missing data. Hence, we characterized allopregnanolone concentrations, and the ratio of allopregnanolone:progesterone at six menstrual cycle subphases: (1) early follicular, (2) mid-follicular, (3) periovulatory, (4) early luteal, (5) mid-luteal, and (6) late luteal. Results: There were significant differences in allopregnanolone levels between (1) early follicular and early luteal, (2) early follicular and mid-luteal, (3) mid-follicular and mid-luteal, (4) periovulatory and mid-luteal, and (5) mid-luteal and late luteal. We detected a sharp drop in allopregnanolone:progesterone ratio in the early luteal subphase. Within the luteal subphase, the ratio was the lowest in the mid-luteal subphase. Conclusions: Allopregnanolone concentrations are the most distinct, relative to the other subphases, in the mid-luteal subphase. The shape of the allopregnanolone trajectory across the cycle is similar to that of progesterone; however, the proportion of the two neuroactive steroid hormones is drastically different due to enzymatic saturation, which takes place at the start of the early luteal subphase, but continuing through, and peaking, in the mid-luteal subphase. Hence, the estimated activity of 5α-reductase decreases, but does not cease, at any point across the menstrual cycle.

1400 W, a selective inducible nitric oxide synthase inhibitor, mitigates early neuroinflammation and nitrooxidative stress in diisopropylfluorophosphate-induced short-term neurotoxicity rat model

Organophosphate nerve agent (OPNA) exposure induces acute and long-term neurological deficits. OPNA exposure at sub-lethal concentrations induces irreversible inhibition of acetylcholinesterase and cholinergic toxidrome and develops status epilepticus (SE). Persistent seizures have been associated with increased production of ROS/RNS, neuroinflammation, and neurodegeneration. A total of 1400W is a novel small molecule, which irreversibly inhibits inducible nitric oxide synthase (iNOS) and has been shown to effectively reduce ROS/RNS generation. In this study, we investigated the effects of 1400W treatment for a week or two weeks at 10 mg/kg or 15 mg/kg per day in the rat diisopropylfluorophosphate (DFP) model. 1400W significantly reduced the number of microglia, astroglia, and NeuN+FJB positive cells compared to the vehicle in different regions of the brain. 1400W also significantly reduced nitrooxidative stress markers and proinflammatory cytokines in the serum. However, neither of the two concentrations of 1400W for two weeks of treatment had any significant effect on epileptiform spike rate and spontaneous seizures during the treatment period in mixed sex cohorts, males, or females. No significant sex differences were found in response to DFP exposure or 1400W treatment. In conclusion, 1400W treatment at 15 mg/kg per day for two weeks was more effective in significantly reducing DFP-induced nitrooxidative stress, neuroinflammatory and neurodegenerative changes.

Status Epilepticus in Older Adults: Diagnostic and Treatment Considerations

Status epilepticus (SE) is one of the leading life-threatening neurological emergencies in the elderly population, with significant morbidity and mortality. SE presents unique diagnostic and therapeutic challenges in the older population given overlap with other causes of encephalopathy, complicating diagnosis, and the common occurrence of multiple comorbid diseases complicates treatment. First-line therapy involves the use of rescue benzodiazepine in the form of intravenous lorazepam or diazepam, intramuscular or intranasal midazolam and rectal diazepam. Second-line therapies include parenteral levetiracetam, fosphenytoin, valproate and lacosamide, and underlying comorbidities guide the choice of appropriate medication, while third-line therapies may be influenced by the patient's code status as well as the cause and type of SE. The standard of care for convulsive SE is treatment with an intravenous anesthetic, including midazolam, propofol, ketamine and pentobarbital. There is currently limited evidence guiding appropriate therapy in patients failing third-line therapies. Adjunctive strategies may include immunomodulatory treatments, non-pharmacological strategies such as ketogenic diet, neuromodulation therapies and surgery in select cases. Surrogate decision makers should be updated early and often in refractory episodes of SE and informed of the high morbidity and mortality associated with the disease as well as the high probability of subsequent epilepsy among survivors.

Seizure-induced overexpression of NPY induces epileptic tolerance in a mouse model of spontaneous recurrent seizures

Epileptic seizures result in pronounced over-expression of neuropeptide Y (NPY). In vivo and in vitro studies revealed that NPY exerts potent anticonvulsive actions through presynaptic Y2 receptors by suppressing glutamate release from principal neurons. We now investigated whether seizure-induced over-expression of NPY contributes to epileptic tolerance induced by preceding seizures. We used a previously established animal model based on selective inhibition of GABA release from parvalbumin (PV)-containing interneurons in the subiculum in mice. The animals present spontaneous recurrent seizures (SRS) and clusters of interictal spikes (IS). The frequency of SRS declined after five to six weeks, indicating development of seizure tolerance. In interneurons of the subiculum and sector CA1, SRS induced over-expression of NPY that persisted there for a prolonged time despite of a later decrease in SRS frequency. In contrast to NPY, somatostatin was not overexpressed in the respective axon terminals. Contrary to interneurons, NPY was only transiently expressed in mossy fibers. To demonstrate a protective function of endogenous, over-expressed NPY, we injected the selective NPY-Y2 receptor antagonist JNJ 5207787 simultaneously challenging the mice by a low dose of pentylenetetrazol (PTZ, 30 or 40 mg/kg, i.p.). In control mice, neither PTZ nor PTZ plus JNJ 5207787 induced convulsions. In mice with silenced GABA/PV neurons, PTZ alone only modestly enhanced EEG activity. When we injected JNJ 5207787 together with PTZ (either dose) the number of seizures, however, became significantly increased. In addition, in the epileptic mice CB1 receptor immunoreactivity was reduced in terminal areas of basket cells pointing to reduced presynaptic inhibition of GABA release from these neurons. Our experiments demonstrate that SRS result in overexpression of NPY in hippocampal interneurons. NPY overexpression persists for several weeks and may be related to later decreasing SRS frequency. Injection of the Y2 receptor antagonist JNJ 5207787 prevents this protective action of NPY only when release of the peptide is triggered by injection of PTZ and induces pronounced convulsions. Thus, over-expressed NPY released “on demand” by seizures may help terminating acute seizures and may prevent from recurrent epileptic activity.

GABA tonic currents and glial cells are altered during epileptogenesis in a mouse model of Dravet syndrome

Dravet Syndrome (DS) is a rare autosomic encephalopathy with epilepsy linked to Na_v1.1 channel mutations and defective GABAergic signaling. Effective therapies for this syndrome are lacking, urging a better comprehension of the mechanisms involved. In a recognized mouse model of DS, we studied GABA tonic current, a form of inhibition largely neglected in DS, in brain slices from developing mice before spontaneous seizures are reported. In neurons from the temporal cortex (TeCx) and CA1 region, GABA tonic current was reduced in DS mice compared to controls, while in the entorhinal cortex (ECx) it was not affected. In this region however allopregnanonole potentiation of GABA tonic current was reduced in DS mice, suggesting altered extrasynaptic GABA_A subunits. Using THIP as a selective agonist, we found reduced δ subunit mediated tonic currents in ECx of DS mice. Unexpectedly in the dentate gyrus (DG), a region with high δ subunit expression, THIP-evoked currents in DS mice were larger than in controls. An immunofluorescence study confirmed that δ subunit expression was reduced in ECx and increased in DG of DS mice. Finally, considering the importance of neuroinflammation in epilepsy and neurodevelopmental disorders, we evaluated classical markers of glia activation. Our results show that DS mice have increased Iba1 reactivity and GFAP expression in both ECx and DG, compared to controls. Altogether we report that before spontaneous seizures, DS mice develop significant alterations of GABA tonic currents and glial cell activation. Understanding all the mechanisms involved in these alterations during disease maturation and progression may unveil new therapeutic targets.

Epilepsy: expert opinion on emerging drugs in phase 2/3 clinical trials

INTRODUCTION

Despite the existence of over 30 anti-seizure medications (ASM), including 20 over the last 30 years, a third of patients with epilepsy remain refractory to treatment, with no disease-modifying or preventive therapies until very recently. The development of new ASMs with new mechanisms of action is therefore critical. Recent clinical trials of new treatments have shifted focus from traditional common epilepsies to rare, genetic epilepsies with known mechanistic targets for treatment and disease-specific animal models.

AREAS COVERED

ASMs in phase 2a/b-3 clinical trials target cholesterol, serotonin, sigma-1 receptors, potassium channels and metabotropic glutamate receptors. Neuroinflammation, protein misfolding, abnormal thalamocortical firing, and molecular deficiencies are among the targeted pathways. Clinically, the current phase 2a/b-3 agents hold promise for variety of epilepsy conditions, from developmental epileptic encephalopathies (Dravet Syndrome, Lennox-Gastaut syndrome, CDKL5 and PCDH19, Rett's Syndrome), infantile spasms, tuberous sclerosis as well as focal and idiopathic generalized epilepsies and acute rescue therapy for cluster seizures.

EXPERT OPINION

New delivery mechanisms increase potency and site-specificity of existing drugs. Novel mechanisms of action involve cholesterol degradation, mitochondrial pathways, anti-inflammation, and neuro-regeneration. Earlier identification of genetic conditions through genetic testing will allow for earlier use of disease specific and disease-modifying therapies.

Ganaxolone treatment for epilepsy patients: from pharmacology to place in therapy

Introduction: Nonsulfated neurosteroids can provide phasic and tonic inhibition through activation of synaptic and extra-synaptic γ-aminobutyric acid (GABA)A receptors, exhibiting a greater potency for the latter. These actions occur by interacting with modulatory sites that are distinct from those bound by benzodiazepines and barbiturates. Ganaxolone (GNX) is a synthetic analog of the endogenous neurosteroid allopregnanolone and a member of a novel class of neuroactive steroids called epalons.Areas covered: The authors review the pharmacology of GNX, summarize the main clinical evidence about its antiseizure efficacy and tolerability, and suggest implications for clinical practice and future research.Expert opinion: The clinical development of GNX is mainly oriented to target unmet needs and focused on status epilepticus and rare genetic epilepsies that have few or no treatment options.The availability of oral and intravenous formulations allows reaching adult and pediatric patients in acute and chronic care settings. Further evidence will complement the understanding of the potentialities of GNX and possibly lead to indications for use in clinical practice.

Protocadherin 19 Clustering Epilepsy and Neurosteroids: Opportunities for Intervention

Steroids yield great influence on neurological development through nuclear hormone receptor (NHR)-mediated gene regulation. We recently reported that cell adhesion molecule protocadherin 19 (encoded by the PCDH19 gene) is involved in the coregulation of steroid receptor activity on gene expression. PCDH19 variants cause early-onset developmental epileptic encephalopathy clustering epilepsy (CE), with altered steroidogenesis and NHR-related gene expression being identified in these individuals. The implication of hormonal pathways in CE pathogenesis has led to the investigation of various steroid-based antiepileptic drugs in the treatment of this disorder, with mixed results so far. Therefore, there are many unmet challenges in assessing the antiseizure targets and efficiency of steroid-based therapeutics for CE. We review and assess the evidence for and against the implication of neurosteroids in the pathogenesis of CE and in view of their possible clinical benefit.

Age dependent effects of Retigabine on absence seizure in WAG/Rij rats; an experimental study

Retigabine (RTG, Ezogabine, DC23129) is the first neuronal potassium channel opener in the treatment of epilepsy and exerts its effects through the activation of neuronal KCNQ2/3 potassium channels; in higher doses, it acts also on sodium and voltage-gated calcium channels. The aim of this study was to investigate possible age-dependent therapeutic effects of RTG on spike-and-wave discharges (SWD) in an animal model of absence epilepsy using WAG/Rij rats. In this study, 6- and 12-month-old WAG/Rij rats were used. For both age categories, three sub-groups that consisted of one control group (n=7) by the administration of 20% DMSO (control) and two study groups by the administration of 5 mg/kg (n=7) and 15 mg/kg RTG (n=7) were designed. EEG electrodes were placed onto the skull of anaesthetized animals; and baseline EEG was recorded for one hour after a recovery period from surgery. Then, the pre-determined two distinct doses of RTG and 20% DMSO were administered as a solvent via intraperitoneal injections, and EEG was recorded for 3 hours. After injection, both doses of RTG increased the total SWD number and duration of SWD in the first and second hours in 12-month-old rats. These parameters were elevated compared to 6-month-old rats. Age-dependent effects of RTG were observed in SWD activity. Pro-epileptic effects in middle-aged WAG/Rij rats were demonstrated in both RTG doses. Differences in the distribution of KCNQ2/3 channels and switch of GABAergic system from inhibitory to excitatory with age might contribute to increased SWD activity in middle-aged rats.

The pilocarpine model of mesial temporal lobe epilepsy: Over one decade later, with more rodent species and new investigative approaches

Fundamental work on the mechanisms leading to focal epileptic discharges in mesial temporal lobe epilepsy (MTLE) often rests on the use of rodent models in which an initial status epilepticus (SE) is induced by kainic acid or pilocarpine. In 2008 we reviewed how, following systemic injection of pilocarpine, the main subsequent events are the initial SE, the latent period, and the chronic epileptic state. Up to a decade ago, rats were most often employed and they were frequently analysed only behaviorally. However, the use of transgenic mice has revealed novel information regarding this animal model. Here, we review recent findings showing the existence of specific neuronal events during both latent and chronic states, and how optogenetic activation of specific cell populations modulate spontaneous seizures. We also address neuronal damage induced by pilocarpine treatment, the role of neuroinflammation, and the influence of circadian and estrous cycles. Updating these findings leads us to propose that the rodent pilocarpine model continues to represent a valuable tool for identifying the basic pathophysiology of MTLE.

Relationship between Delta Rhythm, Seizure Occurrence and Allopregnanolone Hippocampal Levels in Epileptic Rats Exposed to the Rebound Effect

Abrupt withdrawal from antiepileptic drugs is followed by increased occurrence of epileptic seizures, a phenomenon known as the “rebound effect”. By stopping treatment with levetiracetam (LEV 300 mg/kg/day, n = 15; vs. saline, n = 15), we investigated the rebound effect in adult male Sprague-Dawley rats. LEV was continuously administered using osmotic minipumps, 7 weeks after the intraperitoneal administration of kainic acid (15 mg/kg). The effects of LEV were determined by comparing time intervals, treatments, and interactions between these main factors. Seizures were evaluated by video-electrocorticographic recordings and power band spectrum analysis. Furthermore, we assessed endogenous neurosteroid levels by liquid chromatography-electrospray-tandem mass spectrometry. LEV significantly reduced the percentage of rats experiencing seizures, reduced the seizure duration, and altered cerebral levels of neurosteroids. In the first week of LEV discontinuation, seizures increased abruptly up to 700% (p = 0.002, Tukey’s test). The power of delta band in the seizure postictal component was related to the seizure occurrence after LEV withdrawal (r² = 0.73, p < 0.001). Notably, allopregnanolone hippocampal levels were positively related to the seizure occurrence (r² = 0.51, p = 0.02) and to the power of delta band (r² = 0.67, p = 0.004). These findings suggest a role for the seizure postictal component in the rebound effect, which involves an imbalance of hippocampal neurosteroid levels.

Reliability of additional reported seizure manifestations to identify dissociative seizures

PURPOSE

Descriptions of seizure manifestations (SM), or semiology, can help localize the symptomatogenic zone and subsequently included brain regions involved in epileptic seizures, as well as identify patients with dissociative seizures (DS). Patients and witnesses are not trained observers, so these descriptions may vary from expert review of seizure video recordings of seizures. To better understand how reported factors can help identify patients with DS or epileptic seizures (ES), we evaluated the associations between more than 30 SMs and diagnosis using standardized interviews.

METHODS

Based on patient- and observer-reported data from 490 patients with diagnoses documented by video-electoencephalography, we compared the rate of each SM in five mutually exclusive groups: epileptic seizures (ES), DS, physiologic seizure-like events (PSLE), mixed DS and ES, and inconclusive testing.

RESULTS

In addition to SMs that we described in a prior manuscript, the following were associated with DS: light triggers, emotional stress trigger, pre-ictal and post-ictal headache, post-ictal muscle soreness, and ictal sensory symptoms. The following were associated with ES: triggered by missing medication, aura of déjà vu, and leftward eye deviation. There were numerous manifestations separately associated with mixed ES and DS.

CONCLUSIONS

Reported SM can help identify patients with DS, but no manifestation is pathognomonic for either ES or DS. Patients with mixed ES and DS reported factors divergent from both ES-alone and DS-alone.

5-HT/GABA interaction in epilepsy

Epilepsy is a neurological condition characterized by synchronous neuronal oscillations (seizures) in the electroencephalogram. Seizures are classified in focal or generalized (depending on the brain territory interested during seizures), and in convulsive and/or not convulsive (depending on the presence or not of involuntary movements). The current pharmacological treatments are mainly based on GABA modulation although different neurotransmitters are also involved in epilepsy, including serotonin. However despite much extensive progress in the understanding of epilepsy mechanisms, still, a percentage of people with epilepsy are pharmaco-resistant calling for the need for new therapeutic targets. Here we review preclinical and human evidence showing that serotonin modulates epilepsy that this likely happens via a major modulation/interaction with GABA.

Neurosteroids and Focal Epileptic Disorders

Neurosteroids are a family of compounds that are synthesized in principal excitatory neurons and glial cells, and derive from the transformation of cholesterol into pregnenolone. The most studied neurosteroids—allopregnanolone and allotetrahydrodeoxycorticosterone (THDOC)—are known to modulate GABA_A receptor-mediated transmission, thus playing a role in controlling neuronal network excitability. Given the role of GABA_A signaling in epileptic disorders, neurosteroids have profound effects on seizure generation and play a role in the development of chronic epileptic conditions (i.e., epileptogenesis). We review here studies showing the effects induced by neurosteroids on epileptiform synchronization in in vitro brain slices, on epileptic activity in in vivo models, i.e., in animals that were made epileptic with chemoconvulsant treatment, and in epileptic patients. These studies reveal that neurosteroids can modulate ictogenesis and the occurrence of pathological network activity such as interictal spikes and high-frequency oscillations (80–500 Hz). Moreover, they can delay the onset of spontaneous seizures in animal models of mesial temporal lobe epilepsy. Overall, this evidence suggests that neurosteroids represent a new target for the treatment of focal epileptic disorders.

Inhibiting Epileptiform Activity in Cognitive Disorders: Possibilities for a Novel Therapeutic Approach

Cognitive impairment is a common and seriously debilitating symptom of various mental and neurological disorders including autism, attention deficit hyperactivity disorder, multiple sclerosis, epilepsy, and neurodegenerative diseases, like Alzheimer's disease. In these conditions, high prevalence of epileptiform activity emerges as a common pathophysiological hallmark. Growing body of evidence suggests that this discrete but abnormal activity might have a long-term negative impact on cognitive performance due to neuronal circuitries' remodeling, altered sleep structure, pathological hippocampo-cortical coupling, and even progressive neuronal loss. In animal models, epileptiform activity was shown to enhance the formation of pathological amyloid and tau proteins that in turn trigger network hyperexcitability. Abolishing epileptiform discharges might slow down the cognitive deterioration. These findings might provide basis for therapeutic use of antiepileptic drugs in neurodegenerative cognitive disorders. The aim of our review is to describe the data on the prevalence of epileptiform activity in various cognitive disorders, to summarize the current knowledge of the mechanisms of epileptic activity in relation to cognitive impairment, and to explore the utility of antiepileptic drugs in the therapy of cognitive disorders. We also propose future directions for drug development and novel therapeutic interventions targeting epileptiform discharges in these disorders.

Characterization of seizure susceptibility in Pcdh19 mice

OBJECTIVE

PCDH19-related epilepsy is characterized by a distinctive pattern of X-linked inheritance, where heterozygous females exhibit seizures and hemizygous males are asymptomatic. A cellular interference mechanism resulting from the presence of both wild-type and mutant PCDH19 neurons in heterozygous patients or mosaic carriers of PCDH19 variants has been hypothesized. We aim to investigate seizure susceptibility and progression in the Pchd19 mouse model.

METHODS

We assessed seizure susceptibility and progression in the Pcdh19 mouse model using three acute seizure induction paradigms. We first induced focal, clonic seizures using the 6-Hz psychomotor test. Mice were stimulated with increasing current intensities and graded according to a modified Racine scale. We next induced generalized seizures using flurothyl or pentylenetetrazol (PTZ), both γ-aminobutyric acid type A receptor function inhibitors, and recorded latencies to myoclonic and generalized tonic-clonic seizures.

RESULTS

Pcdh19 knockout and heterozygous females displayed increased seizure susceptibility across all current intensities in the 6-Hz psychomotor test, and increased severity overall. They also exhibited shorter latencies to generalized seizures following flurothyl, but not PTZ, seizure induction. Hemizygous males showed comparable seizure incidence and severity to their wild-type male littermates across all paradigms tested.

SIGNIFICANCE

The heightened susceptibility observed in Pcdh19 knockout females suggests additional mechanisms other than cellular interference are at play in PCDH19-related epilepsy. Further experiments are needed to understand the variability in seizure susceptibility so that this model can be best utilized toward development of future therapeutic strategies for PCDH19-related epilepsy.

Antiseizure potential of the ancient Greek medicinal plant Helleborus odorus subsp. cyclophyllus and identification of its main active principles

ETHNOPHARMACOLOGICAL RELEVANCE

Ethnopharmacological data and ancient texts support the use of black hellebore (Helleborus odorus subsp. cyclophyllus, Ranunculaceae) for the management and treatment of epilepsy in ancient Greece.

AIM OF THE STUDY

A pharmacological investigation of the root methanolic extract (RME) was conducted using the zebrafish epilepsy model to isolate and identify the compounds responsible for a potential antiseizure activity and to provide evidence of its historical use. In addition, a comprehensive metabolite profiling of this studied species was proposed.

MATERIALS AND METHODS

The roots were extracted by solvents of increasing polarity and root decoction (RDE) was also prepared. The extracts were evaluated for antiseizure activity using a larval zebrafish epilepsy model with pentylenetetrazole (PTZ)-induced seizures. The RME exhibited the highest antiseizure activity and was therefore selected for bioactivity-guided fractionation. Isolated compounds were fully characterized by NMR and high-resolution tandem mass spectrometry (HRMS/MS). The UHPLC-HRMS/MS analyses of the RME and RDE were used for dereplication and metabolite profiling.

RESULTS

The RME showed 80% inhibition of PTZ-induced locomotor activity (300 μg/ml). This extract was fractionated and resulted in the isolation of a new glucopyranosyl-deoxyribonolactone (1) and a new furostanol saponin derivative (2), as well as of 20-hydroxyecdysone (3), hellebrin (4), a spirostanol glycoside derivative (5) and deglucohellebrin (6). The antiseizure activity of RME was found to be mainly due to the new furostanol saponin (2) and hellebrin (4), which reduced 45% and 60% of PTZ-induced seizures (135 μM, respectively). Besides, the aglycone of hellebrin, hellebrigenin (S34), was also active (45% at 7 μM). To further characterize the chemical composition of both RME and RDE, 30 compounds (A7-33, A35-37) were annotated based on UHPLC-HRMS/MS metabolite profiling. This revealed the presence of additional bufadienolides, furostanols, and evidenced alkaloids.

CONCLUSIONS

This study is the first to identify the molecular basis of the ethnopharmacological use of black hellebore for the treatment of epilepsy. This was achieved using a microscale zebrafish epilepsy model to rapidly quantify in vivo antiseizure activity. The UHPLC-HRMS/MS profiling revealed the chemical diversity of the extracts and the presence of numerous bufadienolides, furostanols and ecdysteroids, also present in the decoction.

Novel 3-Substituted-2, 3-Dihydro-2-Thioxoquinazolin-4-(1H)-one derivative as Anticonvulsants: Synthesis, Molecular Docking and Pharmacological Screening

Background:

According to the World Health Organization, 50 million people worldwide are suffering from epilepsy, making it one of the most common neurological diseases globally. 2,3 disubstituted quinazolinone-4-one derivatives endowed with various pharmacological activity, particularly having anticonvulsant action.

Objectives:

The aim of this study was to synthesize 3-Substituted-2,3-Dihydro-2-thioxoquinazolin- 4-(1H)-one derivative and evaluate for anticonvulsant activity and neurotoxicity in order to find an efficient, compound with lesser side effects.

Methods:

A novel series of 3-[4-(2-amino-5, 6-dihydro-4(substituted phenyl)-4H-1, 3-oxazin /thiazin-6yl) phenyl]-2, 3-dihyro-2-thioxoquinazolin-4(1H)-one derivatives (4a-4p) were synthesized. The structures of the synthesized compounds were assigned on the basis of spectral data (UV, IR, 1HNMR, 13CNMR and MS) and performed anticonvulsant activity against maximal electroshock test and Subcutaneous Pentylenetetrazole model. Neurotoxicity was assessed using a rotarod apparatus test. The molecular docking study was performed to assess their binding affinities towards Gamma-Aminobutyric Acid type A receptor. A quantitative estimate of drug-likeness was also performed, which calculates the molecular properties and screen the molecules based on drug-likeness rules.

Results:

Compounds 4b, 4e, 4j and 4m have shown the highest anticonvulsant activity against tonic seizure with decreased mean duration of tonic hind leg extension of 8.31, 7.35, 8.61 and 8.99 s, respectively in maximal electroshock model and increased onset time clonic convulsion duration of 94.45, 96.65, 93.51 and 91.86 s in Subcutaneous Pentylenetetrazole model. Molecular docking study revealed a better binding affinity with Gamma-Aminobutyric Acid type A receptor.

Conclusion:

The compound 4b and 4e emerged out as the pilot molecule with a better anticonvulsant activity without any neurotoxicity. The obtained results showed that compounds 4b and 4e could be useful as a template for future design, optimization, and investigation to produce more active analogs.

Screening for Efficacious Anticonvulsants and Neuroprotectants in Delayed Treatment Models of Organophosphate-induced Status Epilepticus

Organophosphorus (OP) compounds are deadly chemicals that exert their intoxicating effects through the irreversible inhibition of acetylcholinesterase (AChE). In addition to an excess of peripheral ailments, OP intoxication induces status epilepticus (SE) which if left untreated may lead to permanent brain damage or death. Benzodiazepines are typically the primary therapies for OP-induced SE, but these drugs lose efficacy as treatment time is delayed. The CounterACT Neurotherapeutic Screening (CNS) Program was therefore established by the National Institutes of Health (NIH) to discover novel treatments that may be administered adjunctively with the currently approved medical countermeasures for OP-induced SE in a delayed treatment scenario. The CNS program utilizes in vivo EEG recordings and Fluoro-JadeB (FJB) histopathology in two established rat models of OP-induced SE, soman (GD) and diisopropylfluorophosphate (DFP), to evaluate the anticonvulsant and neuroprotectant efficacy of novel adjunct therapies when administered at 20 or 60 min after the induction of OP-induced SE. Here we report the results of multiple compounds that have previously shown anticonvulsant or neuroprotectant efficacy in other models of epilepsy or trauma. Drugs tested were ganaxolone, diazoxide, bumetanide, propylparaben, citicoline, MDL-28170, and chloroquine. EEG analysis revealed that ganaxolone demonstrated the most robust anticonvulsant activity, whereas all other drugs failed to attenuate ictal activity in both models of OP-induced SE. FJB staining demonstrated that none of the tested drugs had widespread neuroprotective abilities. Overall these data suggest that neurosteroids may represent the most promising anticonvulsant option for OP-induced SE out of the seven unique mechanisms tested here. Additionally, these results suggest that drugs that provide significant neuroprotection from OP-induced SE without some degree of anticonvulsant activity are elusive, which further highlights the necessity to continue screening novel adjunct treatments through the CNS program.

Interactions of Aromatase and Seladin-1: A Neurosteroidogenic and Gender Perspective

Aromatase and seladin-1 are enzymes that have major roles in estrogen synthesis and are important in both brain physiology and pathology. Aromatase is the key enzyme that catalyzes estrogen biosynthesis from androgen precursors and regulates the brain’s neurosteroidogenic activity. Seladin-1 is the enzyme that catalyzes the last step in the biosynthesis of cholesterol, the precursor of all hormones, from desmosterol. Studies indicated that seladin-1 is a downstream mediator of the neuroprotective activity of estrogen. Recently, we also showed that there is an interaction between aromatase and seladin-1 in the brain. Therefore, the expression of local brain aromatase and seladin-1 is important, as they produce neuroactive steroids in the brain for the protection of neuronal damage. Increasing steroid biosynthesis specifically in the central nervous system (CNS) without affecting peripheral hormone levels may be possible by manipulating brain-specific promoters of steroidogenic enzymes. This review emphasizes that local estrogen, rather than plasma estrogen, may be responsible for estrogens’ protective effects in the brain. Therefore, the roles of aromatase and seladin-1 and their interactions in neurodegenerative events such as Alzheimer’s disease (AD), ischemia/reperfusion injury (stroke), and epilepsy are also discussed in this review.

Stem cells: A path towards improved epilepsy therapies

Despite the immense growth of new anti-seizure drugs (ASDs), approximately one-third of epilepsy patients remain resistant to current treatment options. Advancements in whole genome sequencing technology continues to identify an increasing number of epilepsy-associated genes at a rate that is outpacing the development of in vivo animal models. Patient-derived induced pluripotent stem cells (iPSCs) show promise in providing a platform for modeling genetic epilepsies, high throughput drug screening, and personalized medicine. This is largely due to the ease of collecting donor cells for iPSC reprogramming, and their ability to be maintained in vitro, while preserving the patient's genetic background. In this review, we summarize the current state of iPSC research in epilepsy and closely related syndromes, discuss the growing need for high-throughput drug screening (HTS), and review the use of stem cell technology for the purpose of autologous transplantation for epilepsy stem cell therapy. Although the use of iPSC technology, as it applies to ASD discovery, is in its infancy, we highlight the significant progress that has been made in phenotype and assay development to facilitate systematic HTS for personalized medicine. This article is part of the special issue entitled 'New Epilepsy Therapies for the 21st Century - From Antiseizure Drugs to Prevention, Modification and Cure of Epilepsy'.

Allopregnanolone augments epileptiform activity of an in-vitro mouse hippocampal preparation in the first postnatal week

In the immature brain the neurotransmitter γ-amino butyric acid (GABA) mediates a membrane depolarization and can contribute to both, inhibition and excitation. Therefore the consequences of a positive modulation of GABA(A) receptors by neurosteroids on epileptiform activity are hard to predict. In order to analyze whether neurosteroids attenuate or exaggerate epileptiform activity in the immature brain, we investigated the effect of the neurosteroid allopregnanolone on epileptiform activity in an in-toto hippocampus preparation of early postnatal mice (postnatal days 4-7) using field potential recordings. These in-vitro experiments revealed that 0.5 μmol/L allopregnanolone had no effect on ictal-like epileptiform activity, but increased the occurrence of interictal epileptiform events. The allopregnanolone-induced enhancement of interictal epileptiform activity could be blocked by a selective inhibition of synaptic GABA_A receptors. In contrast, allopregnanolone had no effect on interictal epileptiform activity upon enhanced extrasynaptic GABAergic activity. Patch-clamp experiments demonstrated that allopregnanolone prolonged the decay of GABAergic postsynaptic currents, but had no effect on tonic GABAergic currents. We conclude from these results that allopregnanolone can enhance excitability in the immature hippocampus viaprolonged synaptic GABAergic currents. This potential effect of neurosteroids on brain excitability should be considered if they are applied as anticonvulsants to premature or early postnatal babies.

Neurosteroid regulation of GABAA receptors: A role in catamenial epilepsy

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

Impact of strain, sex, and estrous cycle on gamma butyrolactone-evoked absence seizures in rats

Childhood absence epilepsy (CAE) is the most common pediatric epilepsy syndrome and is characterized by typical absence seizures (AS). AS are non-convulsive epileptic seizures characterized by a sudden loss of awareness and bilaterally generalized synchronous 2.5-4 Hz spike and slow-wave discharges (SWD). Gamma butyrolactone (GBL) is an acute pharmacological model of AS and induces bilaterally synchronous SWDs and behavioral arrest. Despite the long use of this model, little is known about its strain and sex-dependent features. We compared the dose-response profile of GBL-evoked SWDs in three rat strains (Long Evans, Sprague-Dawley, and Wistar), and examined the modulatory effects of estrous cycle on SWDs in female Wistar rats. We evaluated the number of seizures, the cumulative time seizing, and the average seizure duration as a function of dose, strain, and sex/estrous phase. Long Evans rats displayed the greatest sensitivity to GBL, followed by Wistar rats, and then by Sprague-Dawley rats. GBL-evoked SWDs were modulated by estrous cycle in female rats, with the lowest sensitivity to GBL occurring during metestrus. Wistar rats showed the greatest variability as a function of dose, and the least variability within dose; these features make this strain desirable for interventional studies. Moreover, our finding that the SWD response to GBL differs as a function of estrous cycle underscores the importance of cycle monitoring in studies examining female animals using this model. Together, these strain and sex-dependent findings provide guidance for future studies.

Aromatase inhibition by letrozole attenuates kainic acid-induced seizures but not neurotoxicity in mice

Evidence shows neurosteroids play a key role in regulating epileptogenesis. Neurosteroids such as testosterone modulate seizure susceptibility through its transformation to metabolites which show proconvulsant and anticonvulsant effects, respectively. Reduction of testosterone by aromatase generates proconvulsant 17-β estradiol. Alternatively, testosterone is metabolized into 5α-dihydrotestosterone (5α-DHT) by 5α-reductase, which is then reduced by 3α-hydroxysteroid oxidoreductase enzyme (3α-HSOR) to form anticonvulsant metabolite 3α-androstanediol (3α-Diol), a potent GABAA receptor modulating neurosteroid. The present study evaluated whether inhibition of aromatase inhibitor letrozole protects against seizures and neuronal degeneration induced by kainic acid (KA) (10 mg/kg, i.p.) in Swiss albino mice. Letrozole (1 mg/kg, i.p.) administered one hour prior to KA significantly increased the onset time of seizures and reduced the% incidence of seizures. Pretreatment with finasteride, a selective inhibitor of 5α-reductase and indomethacin, a selective inhibitor of 3α-hydroxysteroid oxidoreductase enzyme (3α-HSOR), reversed the protective effects of letrozole in KA-induced seizures in mice. Microscopic examination using cresyl violet staining revealed that letrozole did not modify KA-induced neurotoxicity in the CA1, CA3 and DG region of the hippocampus. Letrozole treatment resulted in the reduced levels of 17-β estradiol and elevated the levels of 5α-dihydrotestosterone (DHT) and 3α-Diol in the hippocampus. Finasteride and indomethacin attenuated letrozole-induced elevations of 5α-DHT and 3α-Diol. Our results indicate the potential anticonvulsant effects of letrozole against KA-induced seizures in mice that might be mediated by inhibiting aromatization of testosterone to 17β-estradiol, a proconvulsant hormone and by redirecting the synthesis to anticonvulsant metabolites, 5α-DHT and 3α-Diol. Acute aromatase inhibition, thus, might be used as an adjuvant in the treatment of status epilepticus and can be pursued further.

Neurosteroids in Schizophrenia: Pathogenic and Therapeutic Implications

Neurosteroids are a group of important endogenous molecules affecting many neural functions in the brain. Increasing evidence suggests a possible role of these neurosteroids in the pathology and symptomatology of schizophrenia (SZ) and other mental disorders. The aim of this review is to summarize the current knowledge about the neural functions of neurosteroids in the brain, and to evaluate the role of the key neurosteroids as candidate modulators in the etiology and therapeutics of SZ. The present paper provides a brief introduction of neurosteroid metabolism and distribution, followed by a discussion of the mechanisms underlying neurosteroid actions in the brain. The content regarding the modulation of the GABAA receptor is elaborated, given the considerable knowledge of its interactions with other neurotransmitter and neuroprotective systems, as well as its ameliorating effects on stress that may play a role in the SZ pathophysiology. In addition, several preclinical and clinical studies suggested a therapeutic benefit of neurosteroids in SZ patients, even though the presence of altered neurosteroid pathways in the circulating blood and/or brain remains debatable. Following treatment of antipsychotic drugs in SZ, therapeutic benefits have also been linked to the regulation of neurosteroid signaling. Specifically, the neurosteroids such as pregnenolone and dehydroepiandrosterone affect a broad spectrum of behavioral functions through their unique molecular characteristics and may represent innovative therapeutic targets for SZ. Future investigations in larger cohorts with long-term follow-ups will be required to ascertain the neuropsychopharmacological role of this yet unexploited class of neurosteroid agents.

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

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

Reduced steroidogenesis in patients with PCDH19-female limited epilepsy

Patients affected by protocadherin 19 (PCDH19)-female limited epilepsy (PCDH19-FE) present a remarkable reduction in allopregnanolone blood levels. However, no information is available on other neuroactive steroids and the steroidogenic response to hormonal stimulation. For this reason, we evaluated allopregnanolone, pregnanolone, and pregnenolone sulfate by liquid chromatographic procedures coupled with electrospray tandem mass spectrometry in 12 unrelated patients and 15 age-matched controls. We also tested cortisol, estradiol, progesterone, and 17OH-progesterone using standard immunoassays. Apart from estradiol and progesterone, all the considered hormones were evaluated in basal condition and after stimulation with adrenocorticotropic hormone (ACTH). A generalized decrease in blood levels of almost all measured neuroactive steroids was found. When considering sexual development, cortisol and pregnenolone sulfate basal levels were significantly reduced in postpubertal girls affected by PCDH19-FE. Of interest, ACTH administration did not recover pregnenolone sulfate serum levels but restored cortisol to control levels. In prepubertal girls with PCDH19-FE, by challenging adrenal function with ACTH we disclosed defects in the production of cortisol, pregnenolone sulfate, and 17OH-progesterone, which were not apparent in basal condition. These findings point to multiple defects in peripheral steroidogenesis associated with and potentially relevant to PCDH19-FE. Some of these defects could be addressed by stimulating adrenocortical activity.

Increased hair cortisol and antecedent somatic complaints in children with a first epileptic seizure

OBJECTIVE

Stress is the most frequent seizure-precipitating factor reported by patients with epilepsy, while stressful life events may increase seizure susceptibility in humans. In this study, we investigated the relations between both biological and behavioral measures of stress in children with a first epileptic seizure (hereafter called seizure). We hypothesized that hair cortisol, a biomarker of chronic stress reflecting approximately 3months of preceding exposure, might be increased in children with a first seizure. We also employed standardized questionnaires to examine presence of stress-related behavioral markers.

METHODS

This was a cross-sectional clinical study investigating stress-related parameters in children with a first seizure (First Epileptic Seizure Group (FESG), n=22) in comparison to healthy children without seizures (Control Group, n=29). Within 24h after a first seizure, hair samples were collected from children for the determination of cortisol. In parallel, perceived stress and anxiety and depressive symptoms were examined with appropriate self- and parent-completed questionnaires, and history of stressful life events during the past year was recorded. Emotional and behavioral problems were also assessed by parent-reported validated and widely-used questionnaires.

RESULTS

Higher hair cortisol measurements were observed in the FESG than control children (7.5 versus 5.0pg/mg respectively, p=0.001). The former were more likely to complain of somatic problems than the latter (59.8 vs. 55.4 according to DSM-oriented Scale, p=0.021); however, there were no differences in perceived stress and anxiety or depressive symptoms between the two groups. Using ROC analysis of hair cortisol measurements for predicting disease status, the maximum sensitivity and specificity were observed for a cut-off point of 5.25pg/mg.

SIGNIFICANCE

Increased hair cortisol indicates chronic hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis prior to the first seizure. This might have contributed to the epileptogenesis process and may help explain the higher incidence of antecedent somatic complaints in the first seizure group.