The role of calcium channel mutations in human epilepsy

In Silico drug repurposing pipeline using deep learning and structure based approaches in epilepsy

Due to considerable global prevalence and high recurrence rate, the pursuit of effective new medication for epilepsy treatment remains an urgent and significant challenge. Drug repurposing emerges as a cost-effective and efficient strategy to combat this disorder. This study leverages the transformer-based deep learning methods coupled with molecular binding affinity calculation to develop a novel in-silico drug repurposing pipeline for epilepsy. The number of candidate inhibitors against 24 target proteins encoded by gain-of-function genes implicated in epileptogenesis ranged from zero to several hundreds. Our pipeline has repurposed the medications with most anti-epileptic drugs and nearly half psychiatric medications, highlighting the effectiveness of our pipeline. Furthermore, Lomitapide, a cholesterol-lowering drug, first emerged as particularly noteworthy, exhibiting high binding affinity for 10 targets and verified by molecular dynamics simulation and mechanism analysis. These findings provided a novel perspective on therapeutic strategies for other central nervous system disease.

P/Q type (Cav2.1) Calcium Channel Blocker ω-Agatoxin IVA Alters Cleaved Caspase-3 and BDNF Expressions in the Rat Brain and Suppresses Seizure Activity

High-voltage-gated calcium channels have pivot role in the cellular and molecular mechanisms of various neurological disorders, including epilepsy. Similar to other calcium channels, P/Q-type calcium channels (Cav2.1) are also responsible for vesicle release at synaptic terminals. Up to date, there are very limited reports showing the mechanisms of Cav2.1 in epileptogenesis. In the present study, we investigated the anticonvulsive and neuroprotective effects of ω-agatoxin IVA, a specific Cav2.1 blocker, in a chemical kindling model of epileptogenesis. Righting reflex and inclined plane tests were used to assess motor coordination. Electroencephalography was recorded for electrophysiological monitoring of seizure activity in freely moving rats. Immunohistochemical analyses were performed for brain-derived neurotrophic factor (BDNF) and cleaved caspase-3 expressions in the prefrontal cortex, striatum, hippocampus, and thalamic nucleus. ω-Agatoxin IVA injected into the right lateral ventricle significantly prolonged the onset of seizures in a dose-dependent manner. In addition, repeated intraperitoneal administrations of ω-agatoxin IVA significantly suppressed the development of kindling and epileptic discharges without altering motor coordination. In addition, ω-agatoxin IVA significantly increased BDNF expressions, and decreased cleaved caspase-3 expressions in the brain when compared to PTZ + saline group. Our current study emphasizes the significance of the inhibition of P/Q type calcium channels by ω-agatoxin IVA, which suppresses the development of epileptogenesis and provides a new potential pathway for epilepsy treatment.

Hypoparathyroidism Revealed by Unsuccessful Anti-epileptic Therapy

Pediatric hypoparathyroidism is an uncommon endocrine disease that can be either isolated or syndromic. It occurs when the secretion of parathormone is insufficient to maintain normal levels of ionized calcium. Patients with hypoparathyroidism can exhibit cerebral calcifications and metabolic disorders, and the severity of such features is inversely correlated with hypocalcemia. We report a case of a 13-year-old patient who was initially diagnosed with epilepsy by another medical team two years before her admission to our hospital and who was subjected to oral valproate therapy. The anti-epileptic therapy proved to be unsuccessful even with increasing doses. The diagnosis was corrected when we performed adequate biological investigations. This case is underlying the importance of the electrolytes profile, especially the serum phosphocalcic test, in the management of patients with new onset or recurrent epileptic seizures.

Recent Progress in the Development of New Antiepileptic Drugs with Novel Targets

Background

Epilepsy is a chronic neurological disorder that affects approximately 50-70 million people worldwide. Epilepsy has a significant economic and social burden on patients as well as on the country. The recurrent, spontaneous seizure activity caused by abnormal neuronal firing in the brain is a hallmark of epilepsy. The current antiepileptic drugs provide symptomatic relief by restoring the balance of excitatory and inhibitory neurotransmitters. Besides, about 30% of epileptic patients do not achieve seizure control. The prevalence of adverse drug reactions, including aggression, agitation, irritability, and associated comorbidities, is also prevalent. Therefore, researchers should focus on developing more effective, safe, and disease-modifying agents based on new molecular targets and signaling cascades.

Summary

This review overviews several clinical trials that help identify promising new targets like lactate dehydrogenase inhibitors, c-jun n-terminal kinases, high mobility group box-1 antibodies, astrocyte reactivity inhibitors, cholesterol 24-hydroxylase inhibitors, glycogen synthase kinase-3 beta inhibitors, and glycolytic inhibitors to develop a new antiepileptic drug.

Key messages

Approximately 30% of epileptic patients do not achieve seizure control. The current anti-seizure drugs are not disease modifying, cure or prevent epilepsy. Lactate dehydrogenase inhibitor, cholesterol 24-hydroxylase inhibitor, glycogen synthase kinase-3 beta inhibitors, and mTOR inhibitors have a promising antiepileptogenic effect.

A neurodevelopmental disorder caused by a dysfunctional CACNA1A allele

P/Q-type Ca²⁺ flux into nerve terminals via Ca_V2.1 channels is essential for neurotransmitter release at neuromuscular junctions and nearly all central synapses. Mutations in CACNA1A, the gene encoding Ca_V2.1, cause a spectrum of pediatric neurological disorders. We have identified a patient harboring an autosomal-dominant de novo frameshift-causing nucleotide duplication in CACNA1A (c.5018dupG). The duplicated guanine precipitated 43 residues of altered amino acid sequence beginning with a glutamine to serine substitution in Ca_V2.1 at position 1674 ending with a premature stop codon (Ca_V2.1 p.Gln1674Serfs*43). The patient presented with episodic downbeat vertical nystagmus, hypotonia, ataxia, developmental delay and febrile seizures. In patch-clamp experiments, no Ba²⁺ current was observed in tsA-201 cells expressing Ca_V2.1 p.Gln1674Serfs*43 with β₄ and α₂δ-1 auxiliary subunits. The ablation of divalent flux in response to depolarization was likely attributable to the inability of Ca_V2.1 p.Gln1674Serfs*43 to form a complete channel pore. Our results suggest that the pathology resulting from this frameshift-inducing nucleotide duplication is a consequence of an effective haploinsufficiency.

Calcium Homeostasis, Transporters, and Blockers in Health and Diseases of the Cardiovascular System

Calcium is a highly positively charged ionic species. It regulates all cell types' functions and is an important second messenger that controls and triggers several mechanisms, including membrane stabilization, permeability, contraction, secretion, mitosis, intercellular communications, and in the activation of kinases and gene expression. Therefore, controlling calcium transport and its intracellular homeostasis in physiology leads to the healthy functioning of the biological system. However, abnormal extracellular and intracellular calcium homeostasis leads to cardiovascular, skeletal, immune, secretory diseases, and cancer. Therefore, the pharmacological control of calcium influx directly via calcium channels and exchangers and its outflow via calcium pumps and uptake by the ER/SR are crucial in treating calcium transport remodeling in pathology. Here, we mainly focused on selective calcium transporters and blockers in the cardiovascular system.

Mutations in the Voltage Dependent Calcium Channel CACNA1A (P/Q type alpha 1A subunit) Causing Neurological Disorders - An Overview

Background

The voltage-dependent calcium channel α1 subunit (CACNA1A) gene plays a major role in neuronal communication. Mutation in this gene results in altered Ca²⁺ ion influx that modify the neurotransmitter release resulting in the development of various neurological disorders like hemiplegic migraine with cortical spreading depression, epilepsy, episodic ataxia type 2, and spinocerebellar ataxia type 6.

Objective

This review aimed in portraying the frequent mutations in CACNA1A gene causing hemiplegic migraine with cortical spreading depression, epilepsy, episodic ataxia type 2 and spinocerebellar ataxia type 6.

Methodology

A systematic search has been adopted in various databases using the keywords "Calcium channel," "migraine," "epilepsy," "episodic ataxia," and "spinocerebellar ataxia" for writing this review that collectively focuses on mutations in the CACNA1A gene causing the common neurological diseases from 1975 to 2019.

Conclusion

Every type of mutation has its own signature in gene functioning and understanding them might aid knowing more in disease progression.

Calcium channelopathies and intellectual disability: a systematic review

BACKGROUND

Calcium ions are involved in several human cellular processes including corticogenesis, transcription, and synaptogenesis. Nevertheless, the relationship between calcium channelopathies (CCs) and intellectual disability (ID)/global developmental delay (GDD) has been poorly investigated. We hypothesised that CCs play a major role in the development of ID/GDD and that both gain- and loss-of-function variants of calcium channel genes can induce ID/GDD. As a result, we performed a systematic review to investigate the contribution of CCs, potential mechanisms underlying their involvement in ID/GDD, advancements in cell and animal models, treatments, brain anomalies in patients with CCs, and the existing gaps in the knowledge. We performed a systematic search in PubMed, Embase, ClinVar, OMIM, ClinGen, Gene Reviews, DECIPHER and LOVD databases to search for articles/records published before March 2021. The following search strategies were employed: ID and calcium channel, mental retardation and calcium channel, GDD and calcium channel, developmental delay and calcium channel.

MAIN BODY

A total of 59 reports describing 159 cases were found in PubMed, Embase, ClinVar, and LOVD databases. Variations in ten calcium channel genes including CACNA1A, CACNA1C, CACNA1I, CACNA1H, CACNA1D, CACNA2D1, CACNA2D2, CACNA1E, CACNA1F, and CACNA1G were found to be associated with ID/GDD. Most variants exhibited gain-of-function effect. Severe to profound ID/GDD was observed more for the cases with gain-of-function variants as compared to those with loss-of-function. CACNA1E, CACNA1G, CACNA1F, CACNA2D2 and CACNA1A associated with more severe phenotype. Furthermore, 157 copy number variations (CNVs) spanning calcium genes were identified in DECIPHER database. The leading genes included CACNA1C, CACNA1A, and CACNA1E. Overall, the underlying mechanisms included gain- and/ or loss-of-function, alteration in kinetics (activation, inactivation) and dominant-negative effects of truncated forms of alpha1 subunits. Forty of the identified cases featured cerebellar atrophy. We identified only a few cell and animal studies that focused on the mechanisms of ID/GDD in relation to CCs. There is a scarcity of studies on treatment options for ID/GDD both in vivo and in vitro.

CONCLUSION

Our results suggest that CCs play a major role in ID/GDD. While both gain- and loss-of-function variants are associated with ID/GDD, the mechanisms underlying their involvement need further scrutiny.

Posttranslational modifications & lithium's therapeutic effect-Potential biomarkers for clinical responses in psychiatric & neurodegenerative disorders

Several neurodegenerative diseases and neuropsychiatric disorders display aberrant posttranslational modifications (PTMs) of one, or many, proteins. Lithium treatment has been used for mood stabilization for many decades, and is highly effective for large subsets of patients with diverse neurological conditions. However, the differential effectiveness and mode of action are not fully understood. In recent years, studies have shown that lithium alters several protein PTMs, altering their function, and consequently neuronal physiology. The impetus for this review is to outline the links between lithium's therapeutic mode of action and PTM homeostasis. We first provide an overview of the principal PTMs affected by lithium. We then describe several neuropsychiatric disorders in which PTMs have been implicated as pathogenic. For each of these conditions, we discuss lithium's clinical use and explore the putative mechanism of how it restores PTM homeostasis, and thereby cellular physiology. Evidence suggests that determining specific PTM patterns could be a promising strategy to develop biomarkers for disease and lithium responsiveness.

Identification of epilepsy-associated neuronal subtypes and gene expression underlying epileptogenesis

Epilepsy is one of the most common neurological disorders, yet its pathophysiology is poorly understood due to the high complexity of affected neuronal circuits. To identify dysfunctional neuronal subtypes underlying seizure activity in the human brain, we have performed single-nucleus transcriptomics analysis of >110,000 neuronal transcriptomes derived from temporal cortex samples of multiple temporal lobe epilepsy and non-epileptic subjects. We found that the largest transcriptomic changes occur in distinct neuronal subtypes from several families of principal neurons (L5-6_Fezf2 and L2-3_Cux2) and GABAergic interneurons (Sst and Pvalb), whereas other subtypes in the same families were less affected. Furthermore, the subtypes with the largest epilepsy-related transcriptomic changes may belong to the same circuit, since we observed coordinated transcriptomic shifts across these subtypes. Glutamate signaling exhibited one of the strongest dysregulations in epilepsy, highlighted by layer-wise transcriptional changes in multiple glutamate receptor genes and strong upregulation of genes coding for AMPA receptor auxiliary subunits. Overall, our data reveal a neuronal subtype-specific molecular phenotype of epilepsy.

The pathophysiology of epilepsy is unclear. Here, the authors present single-nuclei transcriptomic profiling of human temporal lobe epilepsy from patients. They identified epilepsy-associated neuronal subtypes, and a panel of dysregulated genes, predicting neuronal circuits contributing to epilepsy.

Partial Activation of TrkB Receptors Corrects Interneuronal Calcium Channel Dysfunction and Reduces Epileptogenic Activity in Neocortex following Injury

Decreased GABAergic inhibition due to dysfunction of inhibitory interneurons plays an important role in post-traumatic epileptogenesis. Reduced N-current Ca2+ channel function in GABAergic terminals contributes to interneuronal abnormalities and neural circuit hyperexcitability in the partial neocortical isolation (undercut, UC) model of post-traumatic epileptogenesis. Because brain-derived neurotrophic factor (BDNF) supports the development and maintenance of interneurons, we hypothesized that the activation of BDNF tropomyosin kinase B (TrkB) receptors by a small molecule, TrkB partial agonist, PTX BD4-3 (BD), would correct N channel abnormalities and enhance inhibitory synaptic transmission in UC cortex. Immunocytochemistry (ICC) and western blots were used to quantify N- and P/Q-type channels. We recorded evoked (e)IPSCs and responses to N and P/Q channel blockers to determine the effects of BD on channel function. Field potential recordings were used to determine the effects of BD on circuit hyperexcitability. Chronic BD treatment 1) upregulated N and P/Q channel immunoreactivity in GABAergic terminals; 2) increased the effects of N or P/Q channel blockade on evoked inhibitory postsynaptic currents (eIPSCs); 3) increased GABA release probability and the frequency of sIPSCs; and 4) reduced the incidence of epileptiform discharges in UC cortex. The results suggest that chronic TrkB activation is a promising approach for rescuing injury-induced calcium channel abnormalities in inhibitory terminals, thereby improving interneuronal function and suppressing circuit hyperexcitability.

Compound heterozygous CACNA1H mutations associated with severe congenital amyotrophy

Neuromuscular disorders encompass a wide range of conditions often associated with a genetic component. In the present study, we report a patient with severe infantile-onset amyotrophy in whom two compound heterozygous variants in the gene CACNA1H encoding for Ca_v3.2 T-type calcium channels were identified. Functional analysis of Ca_v3.2 variants revealed several alterations of the gating properties of the channel that were in general consistent with a loss-of-channel function. Taken together, these findings suggest that severe congenital amyoplasia may be related to CACNA1H and would represent a new phenotype associated with mutations in this gene.

Activation of small conductance calcium-activated potassium channels suppresses seizure susceptibility in the genetically epilepsy-prone rats

Small conductance calcium-activated potassium (SK) channels dampen neuronal excitability by contributing to slow afterhyperpolarization (AHP) that follows a series of action potentials, and therefore may represent an intrinsic inhibitory mechanism to prevent seizures. We have previously reported that susceptibility to acoustically evoked seizures was associated with downregulation of SK1 and SK3 subtypes of SK channels in the inferior colliculus of the moderated seizure severity strain of the genetically epilepsy-prone rats (GEPR-3s). Here, we evaluated the effects of 1-ethyl-2-benzimidazolinone (1-EBIO), a potent activator of SK channels, on acoustically evoked seizures in both male and female adult GEPR-3s at various time points post-treatment. Systemic administration of 1-EBIO at various tested doses suppressed seizure susceptibility in both male and female GEPR-3s; however, the complete seizure suppression was only observed following administration of relatively higher doses of 1-EBIO in females. These findings indicate that activation of SK channels results in anticonvulsive action against generalized tonic-clonic seizures in both male and female GEPR-3s, with males exhibiting higher sensitivity than females.

P/Q-type and T-type voltage-gated calcium channels are involved in the contraction of mammary and brain blood vessels from hypertensive patients

AIM

Calcium channel blockers are widely used in cardiovascular diseases. Besides L-type channels, T- and P/Q-type calcium channels are involved in the contraction of human renal blood vessels. It was hypothesized that T- and P/Q-type channels are involved in the contraction of human brain and mammary blood vessels.

METHODS

Internal mammary arteries from bypass surgery patients and cerebral arterioles from patients with brain tumours with and without hypertension were tested in a myograph and perfusion set-up. PCR and immunohistochemistry were performed on isolated blood vessels.

RESULTS

The P/Q-type antagonist ω-agatoxin IVA (10^-8  mol L^-1 ) and the T-type calcium blocker mibefradil (10^-7  mol L^-1 ) inhibited KCl depolarization-induced contraction in mammary arteries from hypertensive patients with no effect on blood vessels from normotensive patients. ω-Agatoxin IVA decreased contraction in cerebral arterioles from hypertensive patients. L-type blocker nifedipine abolished the contraction in mammary arteries. PCR analysis showed expression of P/Q-type (Ca_v 2.1), T-type (Ca_v 3.1 and Ca_v 3.2) and L-type (Ca_v 1.2) calcium channels in mammary and cerebral arteries. Immunohistochemical labelling of mammary and cerebral arteries revealed the presence of Ca_v 2.1 in endothelial and smooth muscle cells. Ca_v 3.1 was also detected in mammary arteries.

CONCLUSION

P/Q- and T-type Ca_v are present in human internal mammary arteries and in cerebral penetrating arterioles. P/Q- and T-type calcium channels are involved in the contraction of mammary arteries from hypertensive patients but not from normotensive patients. Furthermore, in cerebral arterioles P/Q-type channels importance was restricted to hypertensive patients might lead to that T- and P/Q-type channels could be a new target in hypertensive patients.

Genome-Wide DNA Methylation Patterns Analysis of Noncoding RNAs in Temporal Lobe Epilepsy Patients

Temporal lobe epilepsy (TLE) is the most common form of adult epilepsy and frequently evolving drug resistance. Although there is growing consensus that noncoding ribonucleic acids (ncRNAs) are modulators of TLE, the knowledge about the deoxyribonucleic acid (DNA) methylation patterns of ncRNAs in TLE remains limited. In the current study, we constructed DNA methylation profiles from 30 TLE patients and 30 healthy controls for ncRNAs, primarily focusing on long ncRNAs (lncRNAs) and microRNAs (miRNAs), by reannotating data of DNA methylation BeadChip. Statistics analyses have revealed a global hypermethylation pattern in miRNA and lncRNA gene in TLE patients. Bioinformatic analyses have found aberrantly methylated miRNAs and lncRNAs are related to ion channel activity, drug metabolism, mitogen-activated protein kinase (MAPK) signaling pathway, and neurotrophin signaling pathway. Aberrantly methylated ncRNA and pathway target might be involved in TLE development and progression. The methylated and demethylated ncRNAs identified in this study provide novel insights for developing TLE biomarkers and potential therapeutic targets.

The genetic relationship between epilepsy and hemiplegic migraine

Epilepsy and migraine are common diseases of the nervous system and share genetic and pathophysiological mechanisms. Familial hemiplegic migraine is an autosomal dominant disease. It is often used as a model of migraine. Four genes often contain one or more mutations in both epilepsy and hemiplegic migraine patients (ie, CACNA1A, ATP1A2, SCN1A, and PRRT2). A better understanding of the shared genetics of epilepsy and hemiplegic migraine may reveal new strategic directions for research and treatment of both the disorders.

Epileptic seizure, as the first symptom of hypoparathyroidism in children, does not require antiepileptic drugs

OBJECTIVE

Patients with hypoparathyroidism exhibit metabolic disorders (hypocalcemia) and brain structural abnormalities (brain calcifications). Currently, studies have determined whether antiepileptic drug (AED) treatment is required for epileptic seizures in children with hypoparathyroidism.

METHOD

This study aims to evaluate the data of two medical centers in Beijing based on the diagnosis of epileptic seizures as the first symptom of hypoparathyroidism in children.

RESULT

A total of 42 patients were included and assigned into AED and non-AED treatment groups in a 1:2 matched case-control study. Results show that the seizure outcome after 1 year of AED treatment is not significantly different from that of the control. In the subgroup analysis of patients with subcortical calcifications, the seizure outcome is still not significantly different from that of the control.

CONCLUSION

Thus, AED treatment cannot improve the seizure outcomes in children with parathyroid disorder, even in such cases as suspected structural seizure caused by subcortical calcifications. Clinicians must take adequate considerations on the use of AEDs in these patients. Epileptic seizures, as the first symptom of hypoparathyroidism in children, do not require epilepsy drugs.

Review: Cav2.3 R-type Voltage-Gated Ca2+ Channels - Functional Implications in Convulsive and Non-convulsive Seizure Activity

Background:

Researchers have gained substantial insight into mechanisms of synaptic transmission, hyperexcitability, excitotoxicity and neurodegeneration within the last decades. Voltage-gated Ca²⁺ channels are of central relevance in these processes. In particular, they are key elements in the etiopathogenesis of numerous seizure types and epilepsies. Earlier studies predominantly targeted on Ca_v2.1 P/Q-type and Ca_v3.2 T-type Ca²⁺ channels relevant for absence epileptogenesis. Recent findings bring other channels entities more into focus such as the Ca_v2.3 R-type Ca²⁺ channel which exhibits an intriguing role in ictogenesis and seizure propagation. Ca_v2.3 R-type voltage gated Ca²⁺ channels (VGCC) emerged to be important factors in the pathogenesis of absence epilepsy, human juvenile myoclonic epilepsy (JME), and cellular epileptiform activity, e.g. in CA1 neurons. They also serve as potential target for various antiepileptic drugs, such as lamotrigine and topiramate.

Objective:

This review provides a summary of structure, function and pharmacology of VGCCs and their fundamental role in cellular Ca²⁺ homeostasis. We elaborate the unique modulatory properties of Ca_v2.3 R-type Ca²⁺ channels and point to recent findings in the proictogenic and proneuroapoptotic role of Ca_v2.3 R-type VGCCs in generalized convulsive tonic–clonic and complex-partial hippocampal seizures and its role in non-convulsive absence like seizure activity.

Conclusion:

Development of novel Ca_v2.3 specific modulators can be effective in the pharmacological treatment of epilepsies and other neurological disorders.

Absence-like seizures and their pharmacological profile in tottering-6j mice

We previously showed that recessive ataxic tottering-6j mice carried a base substitution (C-to-A) in the consensus splice acceptor sequence linked to exon 5 of the α1 subunit of the Cav2.1 channel gene (Cacna1a), resulting in the skipping of exon 5 and deletion of part of the S4-S5 linker, S5, and part of the S5-S6 linker in domain I of the α1 subunit of the Cav2.1 channel. However, the electrophysiological and pharmacological consequences of this mutation have not previously been investigated. Upon whole-cell patch recording of the recombinant Cav2.1 channel in heterologous reconstitution expression systems, the mutant-type channel exhibited a lower recovery time after inactivation of Ca(2+) channel current, without any change in peak current density or the current-voltage relationship. Tottering-6j mice exhibited absence-like seizures, characterized by bilateral and synchronous 5-8 Hz spike-and-wave discharges on cortical and hippocampal electroencephalograms, concomitant with sudden immobility and staring. The pharmacological profile of the seizures was similar to that of human absence epilepsy; the seizures were inhibited by ethosuximide and valproic acid, but not by phenytoin. Thus, the tottering-6j mouse is a useful model for studying Cav2.1 channel functions and Cacna1a-related diseases, including absence epilepsy.