5-HT/GABA interaction in epilepsy

Coronaridine congeners induce anticonvulsant activity in rodents by hippocampal mechanisms involving mainly potentiation of GABAA receptors

The coronaridine congeners catharanthine and 18-methoxycoronaridine (18-MC) display sedative, anxiolytic, and antidepressant properties by acting on mechanisms involving GABAergic and/or monoaminergic transmissions. Here, we expanded their pharmacological properties by studying their anticonvulsant activity in male and female mice using the pentylenetetrazole (PTZ)-induced seizure test. To determine potential neurochemical mechanisms, the effect of congeners on monoamine content and kainic acid (KA)-induced epileptiform discharge was studied in the hippocampus. The behavioral results showed that coronaridine congeners induce acute anticonvulsant activity in a dose-dependent but sex-independent manner. Repeated treatment with a subthreshold dose (20 mg/kg) of each congener produced anticonvulsant activity in a sex-independent manner, but was significantly higher in male mice when compared to its acute effect. Using a behaviourally relevant regimen, we found that PTZ increased dopamine metabolites and serotonin tissue content. Coronaridine congeners, which induced distinct effects on monoamines, blunted the effect of PTZ instead of potentiating it, suggesting the existence of another mechanism in their anticonvulsant activity. The electrophysiological results indicated that both congeners inhibit KA-induced epileptiform discharges in hippocampal slices. A key aspect of this study is that the activity of both congeners was observed only in the presence of GABA, supporting the notion that hippocampal GABAAR potentiation plays an important role. Our study showed that coronaridine congeners induce acute anticonvulsant activity in a sex-independent manner. However, a comparatively higher susceptibility was observed in male mice after repeated treatment. The underlying hippocampal mechanisms mainly involve GABAAR potentiation, whereas monoamines play a minor role in the anticonvulsive action.

Advances in the study of gut microbes in pediatric epilepsy

Epilepsy a prevalent childhood neurological disorder, arises from chronic brain dysfunction caused by oversynchronized firing of neurons. Frequent seizures often lead to both physical and intellectual damage in children, seriously affecting their growth and development, life and health. Recent research studies have shown that the intestinal microbes in pediatric epilepsy is significantly different from that of healthy children, characterised by changes in the abundance of specific microbe communities and a reduction in diversity. These alterations may influence epileptic seizures through various pathways, including the microbiota-gut-brain axis by modulating neurotransmitters metabolism, affecting gut barrier function and immune responses, and directly impacting brain activity via the vagus nerves. This review highlights the alterations in gut microbes and their metabolites in epileptic children, analyzes their impact on seizures, and explores potential associations.

Electroencephalographic profile of Salvia amarissima Ortega and amarisolide A in the absence and presence of PTZ-induced seizures in mice

Salvia amarissima Ortega is a plant used in traditional medicine to treat CNS's affections. Despite its depressant properties in anxiety and fibromyalgia, there is no scientific evidence about its capability to control seizure activity. This study aimed to investigate the effects of the S. amarissima aqueous extract (SAAE) and its metabolite amarisolide A (AMA) on the electrocorticographic (ECoG) activity. The ECoG profiles were previously and concurrently analyzed to the pentylenetetrazole (85 mg/kg, i.p.)-induced seizure behavior after thirty min of the administration of several doses of the SAAE (1, 10, 30, and 100 mg/kg, i.p.) and two doses of AMA (0.5 and 1 mg/kg, i.p.). A dosage of AMA (1 mg/kg,i.p.) was selected to explore a possible mechanism of action by using antagonists of inhibitory receptors such as GABAA (picrotoxin, 1 mg/kg, i.p.) or 5-HT1A of serotonin (WAY100635, 1 mg/kg, i.p.). Significant changes in the frequency bands and the spectral power were observed after the treatment alone. Additionally, SAAE and AMA produced significant and dose-dependent anticonvulsant effects by reducing the incidence and severity of seizures and increasing latency or survival. Both antagonists prevented the effects of AMA in the severity score of seizures and survival during the tonic-clonic seizures. In conclusion, our preclinical data support that S. amarissima possesses anticonvulsant properties, in part due to the presence of amarisolide A, mediated by different inhibitory mechanisms of action. Our scientific evidence suggests that this Salvia species and amarisolide A are potential neuroprotective alternatives to control seizures in epilepsy therapy.

An update on the role of Hippo signaling pathway in ischemia-associated central nervous system diseases

The most frequent reason of morbidity and mortality in the world, cerebral ischemia sets off a chain of molecular and cellular pathologies that associated with some central nervous system (CNS) disorders mainly including ischemic stroke, Alzheimer's disease (AD), Parkinson's disease (PD), epilepsy and other CNS diseases. In recent times, despite significant advancements in the treatment of the pathological processes underlying various neurological illnesses, effective therapeutic approaches that are specifically targeted to minimizing the damage of such diseases remain absent. Hippo signaling pathway, characterized by enzyme linked reactions between MSTI/2, LAST1/2, and YAP or TAZ proteins, controls cell division, survival, and differentiation, as well as being engaged in a variety of biological activities, such as the development and transformation of the nervous system. Recently, accumulating studies demonstrated that Hippo pathway takes part in the processes of ischemic stroke, AD, PD, etc., including but not limited to oxidative stress, inflammatory response, blood-brain barrier damage, mitochondrial disorders, and neural cells death. Thus, it's crucial to understand the molecular basis of the Hippo signaling pathway for determining potential new therapeutic targets against ischemia-associated CNS diseases. Here, we discuss latest advances in the deciphering of the Hippo signaling pathway and highlight the therapeutic potential of targeting the pathway in treating ischemia-associated CNS diseases.

Fenfluramine: a plethora of mechanisms?

Developmental and epileptic encephalopathies are rare, treatment-resistant epilepsies with high seizure burden and non-seizure comorbidities. The antiseizure medication (ASM) fenfluramine is an effective treatment for reducing seizure frequency, ameliorating comorbidities, and potentially reducing risk of sudden unexpected death in epilepsy (SUDEP) in patients with Dravet syndrome and Lennox-Gastaut syndrome, among other rare epilepsies. Fenfluramine has a unique mechanism of action (MOA) among ASMs. Its primary MOA is currently described as dual-action sigma-1 receptor and serotonergic activity; however, other mechanisms may be involved. Here, we conduct an extensive review of the literature to identify all previously described mechanisms for fenfluramine. We also consider how these mechanisms may play a role in the reports of clinical benefit in non-seizure outcomes, including SUDEP and everyday executive function. Our review highlights the importance of serotonin and sigma-1 receptor mechanisms in maintaining a balance between excitatory (glutamatergic) and inhibitory (γ-aminobutyric acid [GABA]-ergic) neural networks, and suggests that these mechanisms may represent primary pharmacological MOAs in seizures, non-seizure comorbidities, and SUDEP. We also describe ancillary roles for GABA neurotransmission, noradrenergic neurotransmission, and the endocrine system (especially such progesterone derivatives as neuroactive steroids). Dopaminergic activity underlies appetite reduction, a common side effect with fenfluramine treatment, but any involvement in seizure reduction remains speculative. Further research is underway to evaluate promising new biological pathways for fenfluramine. A better understanding of the pharmacological mechanisms for fenfluramine in reducing seizure burden and non-seizure comorbidities may allow for rational drug design and/or improved clinical decision-making when prescribing multi-ASM regimens.

Anxiolytic and anticonvulsant effect of Ibuprofen derivative through GABAergic neuromodulation in adult Zebrafish

Anxiety and epilepsy affect millions of people worldwide, and the treatment of these pathologies involves the use of Benzodiazepines, drugs that have serious adverse effects such as dependence and sedation, so the discovery of new anxiolytic and antiepileptic drugs are necessary. Many routes for synthesizing ibuprofen derivatives have been developed, and these derivatives have shown promising pharmacological effects. Therefore, this study aims to evaluate its anxiolytic and anticonvulsant effect against the adult Zebrafish animal model of Ibuprofen (IBUACT) and its interaction with the GABAergic receptor through in silico studies. The light/dark preference test (Scototaxis test) was used to evaluate the anxiolytic behavior of adult Zebrafish acutely treated with IBUACT and Diazepam, and their anticonvulsant effects were investigated through the pentylenetetrazol (PTZ)-induced seizure model. Animals treated with IBUACT showed anxiolytic behavior similar to Diazepam, and pretreatment with flumazenil reversed this behavior. PTZ-induced seizures were delayed by IBUACT in all three stages and were shown to bind strongly in the Diazepam region of GABAA. In addition, this work presents evidence of new pharmacological applications of ibuprofen derivative in pathologies of the central nervous system (CNS), opening the horizon for new studies.Communicated by Ramaswamy H. Sarma.

Identifying microbe-disease association based on graph convolutional attention network: Case study of liver cirrhosis and epilepsy

The interactions between the microbiota and the human host can affect the physiological functions of organs (such as the brain, liver, gut, etc.). Accumulating investigations indicate that the imbalance of microbial community is closely related to the occurrence and development of diseases. Thus, the identification of potential links between microbes and diseases can provide insight into the pathogenesis of diseases. In this study, we propose a deep learning framework (MDAGCAN) based on graph convolutional attention network to identify potential microbe-disease associations. In MDAGCAN, we first construct a heterogeneous network consisting of the known microbe-disease associations and multi-similarity fusion networks of microbes and diseases. Then, the node embeddings considering the neighbor information of the heterogeneous network are learned by applying graph convolutional layers and graph attention layers. Finally, a bilinear decoder using node embedding representations reconstructs the unknown microbe-disease association. Experiments show that our method achieves reliable performance with average AUCs of 0.9778 and 0.9454 ± 0.0038 in the frameworks of Leave-one-out cross validation (LOOCV) and 5-fold cross validation (5-fold CV), respectively. Furthermore, we apply MDAGCAN to predict latent microbes for two high-risk human diseases, i.e., liver cirrhosis and epilepsy, and results illustrate that 16 and 17 out of the top 20 predicted microbes are verified by published literatures, respectively. In conclusion, our method displays effective and reliable prediction performance and can be expected to predict unknown microbe-disease associations facilitating disease diagnosis and prevention.

Serotonin receptors in epilepsy: novel treatment targets?

Despite the availability of over 30 antiseizure medications (ASMs), there is no “one size fits it all,” so there is a continuing search for novel ASMs. There are divergent data demonstrating that modulation of distinct serotonin (5‐hydroxytryptamine, 5‐HT) receptors subtypes could be beneficial in the treatment of epilepsy and its comorbidities, whereas only a few ASM, such as fenfluramine (FA), act via 5‐HT. There are 14 different 5‐HT receptor subtypes, and most epilepsy studies focus on one or a few of these subtypes, using different animal models and different ligands. We reviewed the available evidence of each 5‐HT receptor subtype using MEDLINE up to July 2021. Our search included medical subject heading (MeSH) and free terms of each “5‐HT subtype” separately and its relation to “epilepsy or seizures.” Most research underlines the antiseizure activity of 5‐HT_{1A,1D,2A,2C,3} agonism and 5‐HT₆ antagonism. Consistently, FA, which has recently been approved for the treatment of seizures in Dravet syndrome, is an agonist of 5‐HT_1D,2A,2C receptors. Even though each study focused on a distinct seizure/epilepsy type and generalization of different findings could lead to false interpretations, we believe that the available preclinical and clinical studies emphasize the role of serotonergic modulation, especially stimulation, as a promising avenue in epilepsy treatment.

Use of Zebrafish Models to Boost Research in Rare Genetic Diseases

Rare genetic diseases are a group of pathologies with often unmet clinical needs. Even if rare by a single genetic disease (from 1/2000 to 1/more than 1,000,000), the total number of patients concerned account for approximatively 400 million peoples worldwide. Finding treatments remains challenging due to the complexity of these diseases, the small number of patients and the challenge in conducting clinical trials. Therefore, innovative preclinical research strategies are required. The zebrafish has emerged as a powerful animal model for investigating rare diseases. Zebrafish combines conserved vertebrate characteristics with high rate of breeding, limited housing requirements and low costs. More than 84% of human genes responsible for diseases present an orthologue, suggesting that the majority of genetic diseases could be modelized in zebrafish. In this review, we emphasize the unique advantages of zebrafish models over other in vivo models, particularly underlining the high throughput phenotypic capacity for therapeutic screening. We briefly introduce how the generation of zebrafish transgenic lines by gene-modulating technologies can be used to model rare genetic diseases. Then, we describe how zebrafish could be phenotyped using state-of-the-art technologies. Two prototypic examples of rare diseases illustrate how zebrafish models could play a critical role in deciphering the underlying mechanisms of rare genetic diseases and their use to identify innovative therapeutic solutions.