α2δ-1 Signaling Drives Cell Death, Synaptogenesis, Circuit Reorganization, and Gabapentin-Mediated Neuroprotection in a Model of Insult-Induced Cortical Malformation

α2δ1-mediated maladaptive sensory plasticity disrupts adipose tissue homeostasis following spinal cord injury

Spinal cord injury (SCI) increases the risk of cardiometabolic disorders, including hypertension, dyslipidemia, and insulin resistance. Not only does SCI lead to pathological expansion of adipose tissue, but it also leads to ectopic lipid accumulation in organs integral to glucose and insulin metabolism. The pathophysiological changes that underlie adipose tissue dysfunction after SCI are unknown. Here, we find that SCI exacerbates lipolysis in epididymal white adipose tissue (eWAT). Whereas expression of the α2δ1 subunit of voltage-gated calcium channels increases in calcitonin gene-related peptide-positive dorsal root ganglia neurons that project to eWAT, conditional deletion of the gene encoding α2δ1 in these neurons normalizes eWAT lipolysis after SCI. Furthermore, α2δ1 pharmacological blockade through systemic administration of gabapentin also normalizes eWAT lipolysis after SCI, preventing ectopic lipid accumulation in the liver. Thus, our study provides insight into molecular causes of maladaptive sensory processing in eWAT, facilitating the development of strategies to reduce metabolic and cardiovascular complications after SCI.

Cigarette smoke triggers calcium overload in mouse hippocampal neurons via the ΔFOSB-CACNA2D1 axis to impair cognitive performance

A growing body of evidence shows that cigarette smoking impairs cognitive performance. The 'Calcium Hypothesis' theory of neuronopathies reveals a critical role of aberrant calcium signaling in compromised cognitive functions. However, the underlying implications of abnormalities in calcium signaling in the neurotoxicity induced by cigarette smoke (CS) have not yet been identified. CACNA2D1, an important auxiliary subunit involved in the composition of voltage-gated calcium channels (VGCCs), was reported to affect the calcium signaling in neurons by facilitating VGCCs-mediated Ca²⁺ influx. ΔFOSB, an alternatively-spliced product of the Fosb gene, is an activity-dependent transcription factor induced robustly in the brain in response to environmental stimuli such as CS. Interestingly, our preliminary bioinformatics analysis revealed a significant co-expression between ΔFOSB and CACNA2D1 in brain tissues of patients with neurodegenerative diseases characterized by progressive cognitive decline. Therefore, we hypothesized that the activation of the ΔFOSB-CACNA2D1 axis in response to CS exposure might cause dysregulation of calcium homeostasis in hippocampal neurons via VGCCs-mediated Ca²⁺ influx, thereby contributing to cognitive deficits. To this end, the present study established a CS-induced mouse model of hippocampus-dependent cognitive impairment, in which the activation of the ΔFOSB-CACNA2D1 axis accompanied by severe calcium overload was observed in the mouse hippocampal tissues. More importantly, ΔFOSB knockdown-/overexpression-mediated inactivation/activation of the ΔFOSB-CACNA2D1 axis interdicted/mimicked CS-induced dysregulation of calcium homeostasis followed by severe cellular damage in HT22 mouse hippocampal neurons. Mechanistically speaking, a further ChIP-qPCR assay confirmed the physical interaction between transcription factor ΔFOSB and the Cacna2d1 gene promoter, suggesting a direct transcriptional regulation of the Cacna2d1 gene by ΔFOSB. Overall, our current work aims to deliver a unique insight into the neurotoxic mechanisms induced by CS to explore potential targets for intervention.

Cortical Parvalbumin-Positive Interneuron Development and Function Are Altered in the APC Conditional Knockout Mouse Model of Infantile and Epileptic Spasms Syndrome

Infantile and epileptic spasms syndrome (IESS) is a childhood epilepsy syndrome characterized by infantile or late-onset spasms, abnormal neonatal EEG, and epilepsy. Few treatments exist for IESS, clinical outcomes are poor, and the molecular and circuit-level etiologies of IESS are not well understood. Multiple human IESS risk genes are linked to Wnt/β-catenin signaling, a pathway that controls developmental transcriptional programs and promotes glutamatergic excitation via β-catenin's role as a synaptic scaffold. We previously showed that deleting adenomatous polyposis coli (APC), a component of the β-catenin destruction complex, in excitatory neurons (APC cKO mice, APCfl/fl x CaMKIIαCre) increased β-catenin levels in developing glutamatergic neurons and led to infantile behavioral spasms, abnormal neonatal EEG, and adult epilepsy. Here, we tested the hypothesis that the development of GABAergic interneurons (INs) is disrupted in APC cKO male and female mice. IN dysfunction is implicated in human IESS, is a feature of other rodent models of IESS, and may contribute to the manifestation of spasms and seizures. We found that parvalbumin-positive INs (PV+ INs), an important source of cortical inhibition, were decreased in number, underwent disproportionate developmental apoptosis, and had altered dendrite morphology at P9, the peak of behavioral spasms. PV+ INs received excessive excitatory input, and their intrinsic ability to fire action potentials was reduced at all time points examined (P9, P14, P60). Subsequently, GABAergic transmission onto pyramidal neurons was uniquely altered in the somatosensory cortex of APC cKO mice at all ages, with both decreased IPSC input at P14 and enhanced IPSC input at P9 and P60. These results indicate that inhibitory circuit dysfunction occurs in APC cKOs and, along with known changes in excitation, may contribute to IESS-related phenotypes.SIGNIFICANCE STATEMENT Infantile and epileptic spasms syndrome (IESS) is a devastating epilepsy with limited treatment options and poor clinical outcomes. The molecular, cellular, and circuit disruptions that cause infantile spasms and seizures are largely unknown, but inhibitory GABAergic interneuron dysfunction has been implicated in rodent models of IESS and may contribute to human IESS. Here, we use a rodent model of IESS, the APC cKO mouse, in which β-catenin signaling is increased in excitatory neurons. This results in altered parvalbumin-positive GABAergic interneuron development and GABAergic synaptic dysfunction throughout life, showing that pathology arising in excitatory neurons can initiate long-term interneuron dysfunction. Our findings further implicate GABAergic dysfunction in IESS, even when pathology is initiated in other neuronal types.

Blood-Brain Barrier-Associated Proteins Are Elevated in Serum of Epilepsy Patients

Blood-brain barrier (BBB) dysfunction emerges as one of the mechanisms underlying the induction of seizures and epileptogenesis. There is growing evidence that seizures also affect BBB, yet only scarce data is available regarding serum levels of BBB-associated proteins in chronic epilepsy. In this study, we aimed to assess serum levels of molecules associated with BBB in patients with epilepsy in the interictal period. Serum levels of MMP-9, MMP-2, TIMP-1, TIMP-2, S100B, CCL-2, ICAM-1, P-selectin, and TSP-2 were examined in a group of 100 patients who were seizure-free for a minimum of seven days and analyzed by ELISA. The results were compared with an age- and sex-matched control group. Serum levels of MMP-9, MMP-2, TIMP-1, TIMP-2 and S100B were higher in patients with epilepsy in comparison to control group (p < 0.0001; <0.0001; 0.001; <0.0001; <0.0001, respectively). Levels of CCL-2, ICAM-1, P-selectin and TSP-2 did not differ between the two groups. Serum levels of MMP-9, MMP-2, TIMP-1, TIMP-2 and S100B are elevated in patients with epilepsy in the interictal period, which suggests chronic processes of BBB disruption and restoration. The pathological process initiating epilepsy, in addition to seizures, is probably the factor contributing to the elevation of serum levels of the examined molecules.

Neuronal Loss of the Glutamate Transporter GLT-1 Promotes Excitotoxic Injury in the Hippocampus

GLT-1, the major glutamate transporter in the mammalian central nervous system, is expressed in presynaptic terminals that use glutamate as a neurotransmitter, in addition to astrocytes. It is widely assumed that glutamate homeostasis is regulated primarily by glutamate transporters expressed in astrocytes, leaving the function of GLT-1 in neurons relatively unexplored. We generated conditional GLT-1 knockout (KO) mouse lines to understand the cell-specific functions of GLT-1. We found that stimulus-evoked field extracellular postsynaptic potentials (fEPSPs) recorded in the CA1 region of the hippocampus were normal in the astrocytic GLT-1 KO but were reduced and often absent in the neuronal GLT-1 KO at 40 weeks. The failure of fEPSP generation in the neuronal GLT-1 KO was also observed in slices from 20 weeks old mice but not consistently from 10 weeks old mice. Using an extracellular FRET-based glutamate sensor, we found no difference in stimulus-evoked glutamate accumulation in the neuronal GLT-1 KO, suggesting a postsynaptic cause of the transmission failure. We hypothesized that excitotoxicity underlies the failure of functional recovery of slices from the neuronal GLT-1 KO. Consistent with this hypothesis, the non-competitive NMDA receptor antagonist MK801, when present in the ACSF during the recovery period following cutting of slices, promoted full restoration of fEPSP generation. The inclusion of an enzymatic glutamate scavenging system in the ACSF conferred partial protection. Excitotoxicity might be due to excess release or accumulation of excitatory amino acids, or to metabolic perturbation resulting in increased vulnerability to NMDA receptor activation. Previous studies have demonstrated a defect in the utilization of glutamate by synaptic mitochondria and aspartate production in the synGLT-1 KO in vivo, and we found evidence for similar metabolic perturbations in the slice preparation. In addition, mitochondrial cristae density was higher in synaptic mitochondria in the CA1 region in 20–25 weeks old synGLT-1 KO mice in the CA1 region, suggesting compensation for loss of axon terminal GLT-1 by increased mitochondrial efficiency. These data suggest that GLT-1 expressed in presynaptic terminals serves an important role in the regulation of vulnerability to excitotoxicity, and this regulation may be related to the metabolic role of GLT-1 expressed in glutamatergic axon terminals.

The Calcium Channel α2δ1 Subunit: Interactional Targets in Primary Sensory Neurons and Role in Neuropathic Pain

Neuropathic pain is mainly triggered after nerve injury and associated with plasticity of the nociceptive pathway in primary sensory neurons. Currently, the treatment remains a challenge. In order to identify specific therapeutic targets, it is necessary to clarify the underlying mechanisms of neuropathic pain. It is well established that primary sensory neuron sensitization (peripheral sensitization) is one of the main components of neuropathic pain. Calcium channels act as key mediators in peripheral sensitization. As the target of gabapentin, the calcium channel subunit α2δ1 (Cavα2δ1) is a potential entry point in neuropathic pain research. Numerous studies have demonstrated that the upstream and downstream targets of Cavα2δ1 of the peripheral primary neurons, including thrombospondins, N-methyl-D-aspartate receptors, transient receptor potential ankyrin 1 (TRPA1), transient receptor potential vanilloid family 1 (TRPV1), and protein kinase C (PKC), are involved in neuropathic pain. Thus, we reviewed and discussed the role of Cavα2δ1 and the associated signaling axis in neuropathic pain conditions.

In silico Screening and Behavioral Validation of a Novel Peptide, LCGA-17, With Anxiolytic-Like Properties

The aim of the study was to develop better anxiolytics and antidepressants. We focused on GABA_A receptors and the α2δ auxiliary subunit of V-gated Ca²⁺ channels as putative targets because they are established as mediators of efficacious anxiolytics, antidepressants, and anticonvulsants. We further focused on short peptides as candidate ligands because of their high safety and tolerability profiles. We employed a structural bioinformatics approach to develop novel tetrapeptides with predicted affinity to GABA_A receptors and α2δ. In silico docking studies of one of these peptides, LCGA-17, showed a high binding score for both GABA_A receptors and α2δ, combined with anxiolytic-like properties in a Danio rerio behavioral screen. LCGA-17 showed anxiolytic-like effects in the novel tank test, the light–dark box, and the social preference test, with efficacy comparable to fluvoxamine and diazepam. In binding assays using rat brain membranes, [³H]-LCGA-17 was competed more effectively by gabapentinoid ligands of α2δ than ligands of GABA_A receptors, suggesting that α2δ represents a likely target for LCGA-17. [³H]-LCGA-17 binding to brain lysates was unaffected by competition with ligands for GABA_B, glutamate, dopamine, serotonin, and other receptors, suggesting specific interaction with α2δ. Dose-finding studies in mice using acute administration of LCGA-17 (i.p.) demonstrated anxiolytic-like effects in the open field test, elevated plus maze, and marble burying tests, as well as antidepressant-like properties in the forced swim test. The anxiolytic effects were effectively blocked by bicuculline. Therefore, LCGA-17 is a novel candidate anxiolytic and antidepressant that may act through α2δ, with possible synergism by GABA_A receptors.

Pathology-selective antiepileptic effects in the focal freeze-lesion rat model of malformation of cortical development

Malformations of cortical development (MCD) represent a group of rare diseases with severe clinical presentation as epileptic and pharmacoresistant encephalopathies. Morphological studies in tissue from MCD patients have revealed reduced GABAergic efficacy and increased intracellular chloride concentration in neuronal cells as important pathophysiological mechanisms in MCD. Also, in various animal models, alterations of GABAergic inhibition have been postulated as a predominant factor contributing to perilesional hyperexcitability. Along with this line, the NKCC1 inhibitor bumetanide has been postulated as a potential drug for treatment of epilepsy, mediating its antiepileptic effect by reduction of the intracellular chloride and increased inhibitory efficacy of GABAergic transmission. In the present study, we focused on the focal freeze-lesion model of MCD to compare antiepileptic drugs with distinct mechanisms of action, including NKCC1 inhibition by bumetanide. For this purpose, we combined electrophysiological and optical methods in slice preparations and assessed the properties of seizure like events (SLE) induced by 4-aminopyridine. In freeze-lesioned but not control slices, SLE onset was confined to the perilesional area, confirming that this region is hyperexcitable and likely triggers pathological activity. Bumetanide selectively reduced epileptic activity in lesion-containing slices but not in slices from sham-treated control rats. Moreover, bumetanide caused a shift in the SLE onset site away from the perilesional area. In contrast, effects of other antiepileptic drugs including carbamazepine, lacosamide, acezatolamide and zonisamide occurred mostly independently of the lesion and did not result in a shift of the onset region. Our work adds evidence for the functional relevance of chloride homeostasis in the pathophysiology of microgyrus formation as represented in the focal freeze-lesion model. Further studies in different MCD models and human tissue will be required to validate the effects across different MCD subtypes and species and to assess the translational value of our findings.

Phenotypic Characterization and Brain Structure Analysis of Calcium Channel Subunit α2δ-2 Mutant (Ducky) and α2δ Double Knockout Mice

Auxiliary α2δ subunits of voltage-gated calcium channels modulate channel trafficking, current properties, and synapse formation. Three of the four isoforms (α2δ-1, α2δ-2, and α2δ-3) are abundantly expressed in the brain; however, of the available knockout models, only α2δ-2 knockout or mutant mice display an obvious abnormal neurological phenotype. Thus, we hypothesize that the neuronal α2δ isoforms may have partially specific as well as redundant functions. To address this, we generated three distinct α2δ double knockout mouse models by crossbreeding single knockout (α2δ-1 and -3) or mutant (α2δ-2/ducky) mice. Here, we provide a first phenotypic description and brain structure analysis. We found that genotypic distribution of neonatal litters in distinct α2δ-1/-2, α2δ-1/-3, and α2δ-2/-3 breeding combinations did not conform to Mendel's law, suggesting premature lethality of single and double knockout mice. Notably, high occurrences of infant mortality correlated with the absence of specific α2δ isoforms (α2Δ-2 > α2δ-1 > α2δ-3), and was particularly observed in cages with behaviorally abnormal parenting animals of α2δ-2/-3 cross-breedings. Juvenile α2δ-1/-2 and α2δ-2/-3 double knockout mice displayed a waddling gate similar to ducky mice. However, in contrast to ducky and α2δ-1/-3 double knockout animals, α2δ-1/-2 and α2δ-2/-3 double knockout mice showed a more severe disease progression and highly impaired development. The observed phenotypes within the individual mouse lines may be linked to differences in the volume of specific brain regions. Reduced cortical volume in ducky mice, for example, was associated with a progressively decreased space between neurons, suggesting a reduction of total synaptic connections. Taken together, our findings show that α2δ subunits differentially regulate premature survival, postnatal growth, brain development, and behavior, suggesting specific neuronal functions in health and disease.

Gabapentin Inhibits Multiple Steps in the Amyloid Beta Toxicity Cascade

Oligomeric β-amyloid peptide (Aβ) is one of the main neurotoxic agents of Alzheimer's disease (AD). Oligomers associate to neuronal membranes, forming "pore-like" structures that cause intracellular calcium and neurotransmitter dyshomeostasis, leading to synaptic failure and death. Through molecular screening targeting the C terminal region of Aβ, a region involved in the toxic properties of the peptide, we detected an FDA approved compound, gabapentin (GBP), with neuroprotective effects against Aβ toxicity. At micromolar concentrations, GBP antagonized peptide aggregation over time and reduced the Aβ absorbance plateau to 28% of control. In addition, GBP decreased Aβ association to membranes by almost half, and the effects of Aβ on intracellular calcium in hippocampal neurons were antagonized without causing effects on its own. Finally, we found that GBP was able to block the synaptotoxicity induced by Aβ in hippocampal neurons, increasing post-synaptic currents from 1.7 ± 0.9 to 4.2 ± 0.7 fC and mean relative fluorescence intensity values of SV2, a synaptic protein, from 0.7 ± 0.09 to 1.00 ± 0.08. The results show that GBP can interfere with Aβ-induced toxicity by blocking multiple steps, resulting in neuroprotection, which justifies advancing toward additional animal and human studies.

Phospholipase Cβ3 in the hippocampus may mediate impairment of memory by long-term blockade of orexin 1 receptors assessed by the Morris water maze

Orexin-A is an endogenous peptide with receptors throughout the brain. According to some recent research, learning and memory are affected by the central administration of orexin; however, no study so far has investigated the long-term inhibition of the orexinergic system. The present study has evaluated the effect of pretraining administration of orexin 1 receptor (OXR1) antagonist, SB-334867, on the acquisition of memory. The Morris water maze (MWM) task was used for training and trial purposes in all groups. Memory performance was analyzed by measuring escape latency, traveled distance, and time spent in the target quadrant. Moreover, the effect of SB-334867 on phospholipase Cβ3 (PLCβ3) levels in the CA1 region of hippocampus slices was examined. Hippocampus slices were prepared using an immunohistochemistry (IHC) approach. SB-334867 (20 mg/kg) increased escape latency in SB-treated rats compared to SB-vehicle group (P < 0.01). SB-treated rats spent less time in the target quadrant compared to the SB-vehicle group (P < 0.001). Distance traveled in the target quadrant was significantly more in SB-treated rats compared to the SB-vehicle group (P < 0.001). Furthermore, SB-334867 decreased PLCβ3 levels in the CA1 of the hippocampus (P < 0.01 and P < 0.05, respectively). Put together, our results suggest that the long-term inhibition of OXR1 plays a prominent role in spatial learning and memory, probably by attenuating PLCβ3 in CA1 neurons.

Putative roles of SLC7A5 (LAT1) transporter in pain

Large amino acid transporter 1 (LAT1), also known as SLC7A5, is an essential amino acid transporter that forms a heterodimeric complex with the glycoprotein cell-surface antigen heavy chain (4F2hc (CD98, SLC3A2)). Within nociceptive pathways, LAT1 is expressed in the dorsal root ganglia and spinal cord. Although LAT1 expression is upregulated following spinal cord injury, little is known about LAT1 in neuropathic pain. To date, only circumstantial evidence supports LAT1/4F2hc's role in pain. Notably, LAT1's expression and regulation link it to key cell types and pathways implicated in pain. Transcriptional regulation of LAT1 expression occurs via the Wnt/frizzled/β-catenin signal transduction pathway, which has been shown to be involved in chronic pain. The LAT1/4F2hc complex may also be involved in pain pathways related to T- and B-cells. LAT1's expression induces activation of the mammalian target of rapamycin (mTOR) signaling axis, which is involved in inflammation and neuropathic pain. Similarly, hypoxia and cancer induce activation of hypoxia-inducible factor 2 alpha, promoting not only LAT1's expression but also mTORC1's activation. Perhaps the strongest evidence linking LAT1 to pain is its interactions with key voltage-gated ion channels connected to nociception, namely the voltage-gated potassium channels Kv1.1 and Kv1.2 and the voltage-gated sodium channel Nav1.7. Through functional regulation of these channels, LAT1 may play a role in governing the excitatory to inhibitory ratio which is altered in chronic neuropathic pain states. Remarkably, the most direct role for LAT1 in pain is to mediate the influx of gabapentin and pregabalin, two first-line neuropathic pain drugs, that indirectly inhibit high voltage-activated calcium channel auxiliary subunit α2δ-1. In this review, we discuss the expression, regulation, relevant signaling pathways, and protein interactions of LAT1 that may link it to the development and/or maintenance of pain. We hypothesize that LAT1 expressed in nociceptive pathways may be a viable new target in pain.

The adenosine A1 receptor agonist WAG 994 suppresses acute kainic acid-induced status epilepticus in vivo

Status epilepticus (SE) is a neurological emergency characterized by continuous seizure activity lasting longer than 5 min, often with no recovery between seizures (Trinka et al., 2015). SE is refractory to benzodiazepine and second-line treatments in about 30% cases. Novel treatment approaches are urgently needed as refractory SE is associated with mortality rates of up to 70%. Robust adenosinergic anticonvulsant effects have been known for decades, but translation into seizure treatments was hampered by cardiovascular side effects. However, the selective adenosine A1 receptor agonist SDZ WAG 994 (WAG) displays diminished cardiovascular side effects compared to classic A1R agonists and was safely administered systemically in human clinical trials. Here, we investigate the anticonvulsant efficacy of WAG in vitro and in vivo. WAG robustly inhibited high-K⁺-induced continuous epileptiform activity in rat hippocampal slices (IC₅₀ = 52.5 nM). Importantly, WAG acutely suppressed SE in vivo induced by kainic acid (20 mg/kg i.p.) in mice. After SE was established, mice received three i.p. injections of WAG or diazepam (DIA, 5 mg/kg). Interestingly, DIA did not attenuate SE while the majority of WAG-treated mice (1 mg/kg) were seizure-free after three injections. Anticonvulsant effects were retained when a lower dose of WAG (0.3 mg/kg) was used. Importantly, all WAG-treated mice survived kainic acid induced SE. In summary, we report for the first time that an A1R agonist with an acceptable human side-effect profile can acutely suppress established SE in vivo. Our results suggest that WAG stops or vastly attenuates SE while DIA fails to mitigate SE in this model.

Beneficial "Pharmaceutical Pleiotropy" of Gabapentinoids in Spinal Cord Injury: A Case for Refining Standard-of-Care

Spinal cord injury results in devastating neurological deficits accompanied by lifelong disability and significant economic burden. While the development of novel compounds or cell-based interventions for spinal cord injury is unquestionably worthwhile, a complementary approach examines current standards of care and the degree to which these can be optimized to benefit long-term neurological function. Numerous classes of drugs, already in use in the acute phase of spinal cord injury, are intriguing because they (1) readily cross the blood-spinal cord barrier to modulate activity in the central nervous system and (2) are administered during a window of time in which neuroprotection, and even some repair, are feasible. Here, we review a rare case of convergent lines of evidence from both preclinical and human studies to support the early administration of a class of drug (ie, gabapentinoids) to both foster motor recovery and reduce the severity of neuropathic pain.

Prolonged prophylactic effects of gabapentin on status epilepticus-induced neocortical injury

Long-term consequences of status epilepticus (SE) occur in a significant proportion of those who survive the acute episode. We developed an in vivo model of acute focal neocortical SE (FSE) to study long-term effects on local cortical structure and function and potential strategies to mitigate adverse consequences of SE. An acute 2 h episode of FSE was induced in anesthetized mice by epidural application of gabazine +4-aminopyridine over sensorimotor neocortex. Ten and 30 days later, the morphological and functional consequences of this single episode of FSE were studied using immunocytochemical and electrophysiological techniques. Results, focused on cortical layer V, showed astrogliosis, microgliosis, decreased neuronal density, and increased excitatory synapses, along with increased immunoreactivity for thrombospondin 2 (TSP2) and α2δ-1 proteins. In addition, neocortical slices, obtained from the area of prior focal seizure activity, showed abnormal epileptiform burst discharges along with increases in the frequency of miniature and spontaneous excitatory postsynaptic currents in layer V pyramidal cells, together with decreases in both parvalbumin immunoreactivity (PV-IR) and the frequency of miniature inhibitory postsynaptic currents in layer V pyramidal cells. Treatment with an approved drug, gabapentin (GBP) (ip 100 mg/kg/day 3 × /day for 7 days following the FSE episode), prevented the gliosis, the enhanced TSP2- and α2δ-1- IR and the increased excitatory synaptic density in the affected neocortex. This model provides an approach for assessing adverse effects of FSE on neocortical structure and function and potential prophylactic treatments.

Repurposed molecules for antiepileptogenesis: Missing an opportunity to prevent epilepsy?

Prevention of epilepsy is a great unmet need. Acute central nervous system (CNS) insults such as traumatic brain injury (TBI), cerebrovascular accidents (CVA), and CNS infections account for 15%-20% of all epilepsy. Following TBI and CVA, there is a latency of days to years before epilepsy develops. This allows treatment to prevent or modify postinjury epilepsy. No such treatment exists. In animal models of acquired epilepsy, a number of medications in clinical use for diverse indications have been shown to have antiepileptogenic or disease-modifying effects, including medications with excellent side effect profiles. These include atorvastatin, ceftriaxone, losartan, isoflurane, N-acetylcysteine, and the antiseizure medications levetiracetam, brivaracetam, topiramate, gabapentin, pregabalin, vigabatrin, and eslicarbazepine acetate. In addition, there are preclinical antiepileptogenic data for anakinra, rapamycin, fingolimod, and erythropoietin, although these medications have potential for more serious side effects. However, except for vigabatrin, there have been almost no translation studies to prevent or modify epilepsy using these potentially "repurposable" medications. We may be missing an opportunity to develop preventive treatment for epilepsy by not evaluating these medications clinically. One reason for the lack of translation studies is that the preclinical data for most of these medications are disparate in terms of types of injury, models within different injury type, dosing, injury-treatment initiation latencies, treatment duration, and epilepsy outcome evaluation mode and duration. This makes it difficult to compare the relative strength of antiepileptogenic evidence across the molecules, and difficult to determine which drug(s) would be the best to evaluate clinically. Furthermore, most preclinical antiepileptogenic studies lack information needed for translation, such as dose-blood level relationship, brain target engagement, and dose-response, and many use treatment parameters that cannot be applied clinically, for example, treatment initiation before or at the time of injury and dosing higher than tolerated human equivalent dosing. Here, we review animal and human antiepileptogenic evidence for these medications. We highlight the gaps in our knowledge for each molecule that need to be filled in order to consider clinical translation, and we suggest a platform of preclinical antiepileptogenesis evaluation of potentially repurposable molecules or their combinations going forward.

No prevention or cure of epilepsy as yet

Approximately 20% of all epilepsy is caused by acute acquired injury such as traumatic brain injury, stroke and CNS infection. The known onset of the injury which triggers the epileptogenic process, early presentation to medical care, and a latency between the injury and the development of clinical epilepsy present an opportunity to intervene with treatment to prevent epilepsy. No such treatment exists and yet there has been remarkably little clinical research during the last 20 years to try to develop such treatment. We review possible reasons for this, possible ways to rectify the situations and note some of the ways currently under way to do so. Resective surgical treatment can achieve "cure" in some patients but is sparsely utilized. In certain "self-limiting" syndromes of childhood and adolescence epilepsy remits spontaneously. In a proportion of patients who become seizure free on medications or with dietary treatment, seizure freedom persists when treatment is discontinued. We discuss these situations which can be considered "cures"; and note that at present we have little understanding of mechanism of such cures, and cannot therefore translate them into a treatment paradigm targeting a "cure" of epilepsy. 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'.