Epileptic Encephalopathies as Neurodegenerative Disorders

Epileptic encephalopathies and progressive neurodegeneration

Developmental encephalopathies (DE), epileptic encephalopathies (EE) and developmental and epileptic encephalopathies (DEE) are overlapping neurodevelopmental disorders characterized by early-onset, often severe epileptic seizures, developmental delay, or regression and have multiple etiologies. Classical nosology in child neurology distinguished progressive and nonprogressive conditions. A progressive course with global cognitive worsening in DEE is usually attributed to severe seizures and electroencephalographic abnormalities whose deleterious effects interfere with developmental processes both in an apparently healthy brain and in an anatomically compromised one. Next generation sequencing and functional studies have helped identifying and characterizing clinical conditions, each with a broad spectrum of clinical and anatomic severity corresponding to a variable level of neurodegeneration, such that both a rapidly progressive course and considerably milder phenotypes with no obvious deterioration can be configured with mutations in the same gene. In this mini review, we present examples of genetic DEE that draw connections between neurodevelopmental and neurodegenerative disorders.

Integrated virtual screening, molecular modeling and machine learning approaches revealed potential natural inhibitors for epilepsy

Epilepsy, a prevalent chronic disorder of the central nervous system, is typified by recurrent seizures. Present treatments predominantly offer symptomatic relief by managing seizures, yet fall short of influencing epileptogenesis. This study endeavored to identify novel phytochemicals with potential therapeutic efficacy against S100B, an influential protein in epileptogenesis, through an innovative application of machine learning-enabled virtual screening. Our study incorporated the use of multiple machine learning algorithms, including Support Vector Machine (SVM), k-Nearest Neighbors (kNN), Naive Bayes (NB), and Random Forest (RF). These algorithms were employed not only for virtual screening but also for essential feature extraction and selection, enhancing our ability to distinguish between active and inactive compounds. Among the tested machine learning algorithms, the RF model outshone the rest, delivering an impressive 93.43 % accuracy on both training and test datasets. This robust RF model was leveraged to sift through the library of 9,000 phytochemicals, culminating in the identification of 180 potential inhibitors of S100B. These 180 active compounds were than docked with the active site of S100B proteins. The results of our study highlighted that the 6-(3,12-dihydroxy-4,10,13-trimethyl-7,11-dioxo-2,3,4,5,6,12,14,15,16,17-decahydro-1H cyclopenta[a] phenanthren -17-yl)-2-methyl-3-methylideneheptanoic acid, rhinacanthin K, thiobinupharidine, scopadulcic acid, and maslinic acid form significant interactions within the binding pocket of S100B, resulting in stable complexes. This underscores their potential role as S100B antagonists, thereby presenting novel therapeutic possibilities for epilepsy management. To sum up, this study's deployment of machine learning in conjunction with virtual screening not only has the potential to unearth new epilepsy therapeutics but also underscores the transformative potential of these advanced computational techniques in streamlining and enhancing drug discovery processes.

Involvement of mTOR pathway in neurodegeneration in NSF-related developmental and epileptic encephalopathy

Membrane fusion is mediated by soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins. During neurotransmitter exocytosis, SNARE proteins on a synaptic vesicle and the target membrane form a complex, resulting in neurotransmitter release. N-ethylmaleimide-sensitive factor (NSF), a homohexameric ATPase, disassembles the complex, allowing individual SNARE proteins to be recycled. Recently, the association between pathogenic NSF variants and developmental and epileptic encephalopathy (DEE) was reported; however, the molecular pathomechanism of NSF-related DEE remains unclear. Here, three patients with de novo heterozygous NSF variants were presented, of which two were associated with DEE and one with a very mild phenotype. One of the DEE patients also had hypocalcemia from parathyroid hormone deficiency and neuromuscular junction impairment. Using PC12 cells, a neurosecretion model, we show that NSF with DEE-associated variants impaired the recycling of vesicular membrane proteins and vesicle enlargement in response to exocytotic stimulation. In addition, DEE-associated variants caused neurodegenerative change and defective autophagy through overactivation of the mammalian/mechanistic target of rapamycin (mTOR) pathway. Treatment with rapamycin, an mTOR inhibitor or overexpression of wild-type NSF ameliorated these phenotypes. Furthermore, neurons differentiated from patient-derived induced pluripotent stem cells showed neurite degeneration, which was also alleviated by rapamycin treatment or gene correction using genome editing. Protein structure analysis of NSF revealed that DEE-associated variants might disrupt the transmission of the conformational change of NSF monomers and consequently halt the rotation of ATP hydrolysis, indicating a dominant negative mechanism. In conclusion, this study elucidates the pathomechanism underlying NSF-related DEE and identifies a potential therapeutic approach.

Nuclear and Cytoplasmatic Players in Mitochondria-Related CNS Disorders: Chromatin Modifications and Subcellular Trafficking

Aberrant mitochondrial phenotypes are common to many central nervous system (CNS) disorders, including neurodegenerative and neurodevelopmental diseases. Mitochondrial function and homeostasis depend on proper control of several biological processes such as chromatin remodeling and transcriptional control, post-transcriptional events, vesicle and organelle subcellular trafficking, fusion, and morphogenesis. Mutation or impaired regulation of major players that orchestrate such processes can disrupt cellular and mitochondrial dynamics, contributing to neurological disorders. The first part of this review provides an overview of a functional relationship between chromatin players and mitochondria. Specifically, we relied on specific monogenic CNS disorders which share features with mitochondrial diseases. On the other hand, subcellular trafficking is coordinated directly or indirectly through evolutionarily conserved domains and proteins that regulate the dynamics of membrane compartments and organelles, including mitochondria. Among these “building blocks”, longin domains and small GTPases are involved in autophagy and mitophagy, cell reshaping, and organelle fusion. Impairments in those processes significantly impact CNS as well and are discussed in the second part of the review. Hopefully, in filling the functional gap between the nucleus and cytoplasmic organelles new routes for therapy could be disclosed.

Biochemical aspects and therapeutic mechanisms of cannabidiol in epilepsy

Epilepsy is a chronic neurological disease characterized by recurrent epileptic seizures. Studies have shown the complexity of epileptogenesis and ictogenesis, in which immunological processes and epigenetic and structural changes in neuronal tissues have been identified as triggering epilepsy. Cannabidiol (CBD) is a major active component of the Cannabis plant and the source of CBD-enriched products for the treatment of epilepsy and associated diseases. In this review, we provide an up-to-date discussion on cellular and molecular mechanisms triggered during epilepsy crises, and the phytochemical characteristics of CBD that make it an attractive candidate for controlling rare syndromes, with excellent therapeutic properties. We also discuss possible CBD anticonvulsant mechanisms and molecular targets in neurodegenerative disorders and epilepsy. Based on these arguments, we conclude that CBD presents a biotecnological potential in the anticonvulsant process, including decreasing dependence on health care in hospitals, and could make the patient's life more stable, with regard to neurological conditions.

Survival of a male patient harboring CASK Arg27Ter mutation to adolescence

Background

CASK is an X‐linked gene in mammals and its deletion in males is incompatible with life. CASK heterozygous mutations in female patients associate with intellectual disability, microcephaly, pontocerebellar hypoplasia, and optic nerve hypoplasia, whereas CASK hemizygous mutations in males manifest as early infantile epileptic encephalopathy with a grim prognosis. Here, we report a rare case of survival of a male patient harboring a CASK null mutation to adolescent age.

Methods

Trio whole exome sequencing analysis was performed from blood genomic DNA. Magnetic resonance imaging (MRI), magnetic resonance spectroscopy (MRS), and electroencephalogram (EEG) analyses were performed to determine anomalies in brain development, metabolite concentrations, and electrical activity, respectively.

Results

Trio‐WES analysis identified a de novo c.79C>T (p.Arginine27Ter) mutation in CASK causing a premature translation termination at the very N‐terminus of the protein. The 17‐years, and 11‐month‐old male patient displayed profound intellectual disability, microcephaly, dysmorphism, ponto‐cerebellar hypoplasia, and intractable epilepsy. His systemic symptoms included overall reduced somatic growth, dysautonomia, ventilator and G tube dependence, and severe osteopenia. Brain MRI revealed a severe cerebellar and brain stem hypoplasia with progressive cerebral atrophy. EEG spectral analysis revealed a global functional defect with generalized background slowing and delta waves dominating even in the awake state.

Conclusion

This case study is the first to report survival of a male patient carrying a CASK loss‐of‐function mutation to adolescence and highlights that improved palliative care could extend survival. Moreover, the genomic position encoding Arg27 in CASK may possess an increased susceptibility to mutations.

Clinical approach to neurodegenerative disorders in childhood: an updated overview

Neurodegenerative disorders include a group of severe diseases that share a core including a gradual loss of previously acquired motor, sensory and cognitive functions. In pediatric age, the main diagnostic issues are the discrimination between the loss of previously acquired competencies and the lack of achievement of specific developmental milestones. An ideal classification of these disorders could be based on the combination of genetic, clinical and neuroimaging features. Diagnostic workup should be organized with a special attention to the few diseases with an available and effective therapeutic treatment. The present paper reports a proposal of classification that is based on the prominently involved structure and summarizes the hallmarks for clinical approach and therapeutic management.

Altered inhibitory synapses in de novo GABRA5 and GABRA1 mutations associated with early onset epileptic encephalopathies

We performed next generation sequencing on 1696 patients with epilepsy and intellectual disability using a gene panel with 480 epilepsy-related genes including all GABAA receptor subunit genes (GABRs), and we identified six de novo GABR mutations, two novel GABRA5 mutations (c.880G>T, p.V294F and c.1238C>T, p.S413F), two novel GABRA1 mutations (c.778C>T, p.P260S and c.887T>C, p.L296S/c.944G>T, p.W315L) and two known GABRA1 mutations (c.335G>A, p.R112Q and c.343A>G, p.N115D) in six patients with intractable early onset epileptic encephalopathy. The α5(V294F and S413F) and α1(P260S and L296S/W315L) subunit residue substitutions were all in transmembrane domains, while the α1(R112Q and N115R) subunit residue substitutions were in the N-terminal GABA binding domain. Using multidisciplinary approaches, we compared effects of mutant GABAA receptor α5 and α1 subunits on the properties of recombinant α5β3γ2 and α1β3γ2 GABAA receptors in both neuronal and non-neuronal cells and characterized their effects on receptor clustering, biogenesis and channel function. GABAA receptors containing mutant α5 and α1 subunits all had reduced cell surface and total cell expression with altered endoplasmic reticulum processing, impaired synaptic clustering, reduced GABAA receptor function and decreased GABA binding potency. Our study identified GABRA5 as a causative gene for early onset epileptic encephalopathy and expands the mutant GABRA1 phenotypic spectrum, supporting growing evidence that defects in GABAergic neurotransmission contribute to early onset epileptic encephalopathy phenotypes.

Cannabidiol for epilepsy: a new indication for an old drug

Medicinal cannabis, and cannabidiol in particular, has garnered much attention in the media and medical community as a possible therapeutic for multiple conditions including epilepsy. Although the use of cannabis has been reported for centuries, evidence in its usefulness in the treatment of epilepsy has been mainly anecdotal. This review discusses emerging research on cannabidiol in the treatment of severe pediatric epilepsies, including Dravet syndrome and Lennox Gastaut syndrome. We discuss the data from both open-label and Phase III trials and report a consistently significant reduction in seizures but also concomitant drug interactions and adverse effects. Future directions of research are considered to determine the full therapeutic potential of this old, but new, class of compounds.