Prevention of status epilepticus-induced brain edema and neuronal cell loss by repeated treatment with high-dose levetiracetam

Changes in the Dentate Gyrus Gene Expression Profile Induced by Levetiracetam Treatment in Rats with Mesial Temporal Lobe Epilepsy

Temporal lobe epilepsy (TLE) is one of the most common forms of focal epilepsy. Levetiracetam (LEV) is an antiepileptic drug whose mechanism of action at the genetic level has not been fully described. Therefore, the aim of the present work was to evaluate the relevant gene expression changes in the dentate gyrus (DG) of LEV-treated rats with pilocarpine-induced TLE. Whole-transcriptome microarrays were used to obtain the differential genetic profiles of control (CTRL), epileptic (EPI), and EPI rats treated for one week with LEV (EPI + LEV). Quantitative RT-qPCR was used to evaluate the RNA levels of the genes of interest. According to the results of the EPI vs. CTRL analysis, 685 genes were differentially expressed, 355 of which were underexpressed and 330 of which were overexpressed. According to the analysis of the EPI + LEV vs. EPI groups, 675 genes were differentially expressed, 477 of which were downregulated and 198 of which were upregulated. A total of 94 genes whose expression was altered by epilepsy and modified by LEV were identified. The RT-qPCR confirmed that LEV treatment reversed the increased expression of Hgf mRNA and decreased the expression of the Efcab1, Adam8, Slc24a1, and Serpinb1a genes in the DG. These results indicate that LEV could be involved in nonclassical mechanisms involved in Ca2+ homeostasis and the regulation of the mTOR pathway through Efcab1, Hgf, SLC24a1, Adam8, and Serpinb1a, contributing to reduced hyperexcitability in TLE patients.

Treatment of Status Epilepticus after Traumatic Brain Injury Using an Antiseizure Drug Combined with a Tissue Recovery Enhancer Revealed by Systems Biology

We tested a hypothesis that in silico-discovered compounds targeting traumatic brain injury (TBI)-induced transcriptomics dysregulations will mitigate TBI-induced molecular pathology and augment the effect of co-administered antiseizure treatment, thereby alleviating functional impairment. In silico bioinformatic analysis revealed five compounds substantially affecting TBI-induced transcriptomics regulation, including calpain inhibitor, chlorpromazine, geldanamycin, tranylcypromine, and trichostatin A (TSA). In vitro exposure of neuronal-BV2-microglial co-cultures to compounds revealed that TSA had the best overall neuroprotective, antioxidative, and anti-inflammatory effects. In vivo assessment in a rat TBI model revealed that TSA as a monotherapy (1 mg/kg/d) or in combination with the antiseizure drug levetiracetam (LEV 150 mg/kg/d) mildly mitigated the increase in plasma levels of the neurofilament subunit pNF-H and cortical lesion area. The percentage of rats with seizures during 0-72 h post-injury was reduced in the following order: TBI-vehicle 80%, TBI-TSA (1 mg/kg) 86%, TBI-LEV (54 mg/kg) 50%, TBI-LEV (150 mg/kg) 40% (p < 0.05 vs. TBI-vehicle), and TBI-LEV (150 mg/kg) combined with TSA (1 mg/kg) 30% (p < 0.05). Cumulative seizure duration was reduced in the following order: TBI-vehicle 727 ± 688 s, TBI-TSA 898 ± 937 s, TBI-LEV (54 mg/kg) 358 ± 715 s, TBI-LEV (150 mg/kg) 42 ± 64 (p < 0.05 vs. TBI-vehicle), and TBI-LEV (150 mg/kg) combined with TSA (1 mg/kg) 109 ± 282 s (p < 0.05). This first preclinical intervention study on post-TBI acute seizures shows that a combination therapy with the tissue recovery enhancer TSA and LEV was safe but exhibited no clear benefit over LEV monotherapy on antiseizure efficacy. A longer follow-up is needed to confirm the possible beneficial effects of LEV monotherapy and combination therapy with TSA on chronic post-TBI structural and functional outcomes, including epileptogenesis.

Early preclinical plasma protein biomarkers of brain trauma are influenced by early seizures and levetiracetam

OBJECTIVE

We used the lateral fluid percussion injury (LFPI) model of moderate-to-severe traumatic brain injury (TBI) to identify early plasma biomarkers predicting injury, early post-traumatic seizures or neuromotor functional recovery (neuroscores), considering the effect of levetiracetam, which is commonly given after severe TBI.

METHODS

Adult male Sprague-Dawley rats underwent left parietal LFPI, received levetiracetam (200 mg/kg bolus, 200 mg/kg/day subcutaneously for 7 days [7d]) or vehicle post-LFPI, and were continuously video-EEG recorded (n = 14/group). Sham (craniotomy only, n = 6), and naïve controls (n = 10) were also used. Neuroscores and plasma collection were done at 2d or 7d post-LFPI or equivalent timepoints in sham/naïve. Plasma protein biomarker levels were determined by reverse phase protein microarray and classified according to injury severity (LFPI vs. sham/control), levetiracetam treatment, early seizures, and 2d-to-7d neuroscore recovery, using machine learning.

RESULTS

Low 2d plasma levels of Thr231 -phosphorylated tau protein (pTAU-Thr231 ) and S100B combined (ROC AUC = 0.7790) predicted prior craniotomy surgery (diagnostic biomarker). Levetiracetam-treated LFPI rats were differentiated from vehicle treated by the 2d-HMGB1, 2d-pTAU-Thr231 , and 2d-UCHL1 plasma levels combined (ROC AUC = 0.9394) (pharmacodynamic biomarker). Levetiracetam prevented the seizure effects on two biomarkers that predicted early seizures only among vehicle-treated LFPI rats: pTAU-Thr231 (ROC AUC = 1) and UCHL1 (ROC AUC = 0.8333) (prognostic biomarker of early seizures among vehicle-treated LFPI rats). Levetiracetam-resistant early seizures were predicted by high 2d-IFNγ plasma levels (ROC AUC = 0.8750) (response biomarker). 2d-to-7d neuroscore recovery was best predicted by higher 2d-S100B, lower 2d-HMGB1, and 2d-to-7d increase in HMGB1 or decrease in TNF (P < 0.05) (prognostic biomarkers).

SIGNIFICANCE

Antiseizure medications and early seizures need to be considered in the interpretation of early post-traumatic biomarkers.

Levetiracetam Suppresses the Infiltration of Neutrophils and Monocytes and Downregulates Many Inflammatory Cytokines during Epileptogenesis in Pilocarpine-Induced Status Epilepticus Mice

Acute brain inflammation after status epilepticus (SE) is involved in blood-brain barrier (BBB) dysfunction and brain edema, which cause the development of post-SE symptomatic epilepsy. Using pilocarpine-induced SE mice, we previously reported that treatment with levetiracetam (LEV) after SE suppresses increased expression levels of proinflammatory mediators during epileptogenesis and prevents the development of spontaneous recurrent seizures. However, it remains unclear how LEV suppresses neuroinflammation after SE. In this study, we demonstrated that LEV suppressed the infiltration of CD11b+CD45high cells into the brain after SE. CD11b+CD45high cells appeared in the hippocampus between 1 and 4 days after SE and contained Ly6G+Ly6C+ and Ly6G-Ly6C+ cells. Ly6G+Ly6C+ cells expressed higher levels of proinflammatory cytokines such as IL-1β and TNFα suggesting that these cells were inflammatory neutrophils. Depletion of peripheral Ly6G+Ly6C+ cells prior to SE by anti-Ly6G antibody (NIMP-R14) treatment completely suppressed the infiltration of Ly6G+Ly6C+ cells into the brain. Proteome analysis revealed the downregulation of a variety of inflammatory cytokines, which exhibited increased expression in the post-SE hippocampus. These results suggest that Ly6G+Ly6C+ neutrophils are involved in the induction of acute brain inflammation after SE. The proteome expression profile of the hippocampus treated with LEV after SE was similar to that after NIMP-R14 treatment. Therefore, LEV may prevent acute brain inflammation after SE by suppressing inflammatory neutrophil infiltration.

Regulation of Inflammation-Related Genes through Fosl1 Suppression in a Levetiracetam-Treated Pilocarpine-Induced Status Epilepticus Mouse Model

Levetiracetam (LEV) suppresses the upregulation of proinflammatory molecules that occurs during epileptogenesis after status epilepticus (SE). Based on previous studies, LEV likely helps prevent the onset of epilepsy after insults to the brain, unlike other conventional anti-epileptic drugs. Recently, we discovered that the increase in Fosl1 expression that occurs after lipopolysaccharide (LPS) stimulation is suppressed by LEV and that Fosl1 inhibition suppresses inflammation in BV-2 microglial cells. These data indicate that Fosl1 is an important target of LEV and a key factor in preventing epilepsy onset. In this study, we examined the effects of LEV on Fosl1 expression and neuroinflammation in vivo. During epileptogenesis, the post-SE upregulation of hippocampal levels of Fosl1 and many inflammatory factors were suppressed by LEV. Fosl1 expression showed a characteristic pattern different from that of the expression of Fos, an immediate-early gene belonging to the same Fos family. At 2 days after SE, Fosl1 was predominantly expressed in astrocytes but was rarely detected in microglia, whereas Fos expression was distributed in various brain cell types. The expression of A2 astrocyte markers was similar to that of Fosl1 and was significantly suppressed by LEV. These results suggest that LEV may regulate astrocyte reactivity through regulation of Fosl1.

Levetiracetam Mechanisms of Action: From Molecules to Systems

Epilepsy is a chronic disease that affects millions of people worldwide. Antiepileptic drugs (AEDs) are used to control seizures. Even though parts of their mechanisms of action are known, there are still components that need to be studied. Therefore, the search for novel drugs, new molecular targets, and a better understanding of the mechanisms of action of existing drugs is still crucial. Levetiracetam (LEV) is an AED that has been shown to be effective in seizure control and is well-tolerable, with a novel mechanism of action through an interaction with the synaptic vesicle protein 2A (SV2A). Moreover, LEV has other molecular targets that involve calcium homeostasis, the GABAergic system, and AMPA receptors among others, that might be integrated into a single mechanism of action that could explain the antiepileptogenic, anti-inflammatory, neuroprotective, and antioxidant properties of LEV. This puts it as a possible multitarget drug with clinical applications other than for epilepsy. According to the above, the objective of this work was to carry out a comprehensive and integrative review of LEV in relation to its clinical uses, structural properties, therapeutical targets, and different molecular, genetic, and systemic action mechanisms in order to consider LEV as a candidate for drug repurposing.

FosL1 Is a Novel Target of Levetiracetam for Suppressing the Microglial Inflammatory Reaction

We previously showed that the antiepileptic drug levetiracetam (LEV) inhibits microglial activation, but the mechanism remains unclear. The purpose of this study was to identify the target of LEV in microglial activity suppression. The mouse microglial BV-2 cell line, cultured in a ramified form, was pretreated with LEV and then treated with lipopolysaccharide (LPS). A comprehensive analysis of LEV targets was performed by cap analysis gene expression sequencing using BV-2 cells, indicating the transcription factors BATF, Nrf-2, FosL1 (Fra1), MAFF, and Spic as candidates. LPS increased AP-1 and Spic transcriptional activity, and LEV only suppressed AP-1 activity. FosL1, MAFF, and Spic mRNA levels were increased by LPS, and LEV only attenuated FosL1 mRNA expression, suggesting FosL1 as an LEV target. FosL1 protein levels were increased by LPS treatment and decreased by LEV pretreatment, similar to FosL1 mRNA levels. The FosL1 siRNA clearly suppressed the expression of TNFα and IL-1β. Pilocarpine-induced status epilepticus increased hippocampus FosL1 expression, along with inflammation. LEV treatment significantly suppressed FosL1 expression. Together, LEV reduces FosL1 expression and AP-1 activity in activated microglia, thereby suppressing neuroinflammation. LEV might be a candidate for the treatment of several neurological diseases involving microglial activation.

Therapeutic Effects of Time-Limited Treatment with Brivaracetam on Posttraumatic Epilepsy after Fluid Percussion Injury in the Rat

Mounting evidence suggests the synaptic vesicle glycoprotein 2A (SV2A) targeted by levetiracetam may contribute to epileptogenesis. Levetiracetam has shown anti-inflammatory, antioxidant, neuroprotective, and possible antiepileptogenic effects in brain injury and seizure/epilepsy models, and a phase 2 study has signaled a possible clinical antiepileptogenic effect. Brivaracetam shows greater affinity and specificity for SV2A than levetiracetam and broader preclinical antiseizure effects. Thus, we assessed the antiepileptogenic/disease-modifying potential of brivaracetam in an etiologically realistic rat posttraumatic epilepsy model optimized for efficient drug testing. Brivaracetam delivery protocols were designed to maintain clinical moderate-to-high plasma levels in young (5-week-old) male Sprague-Dawley rats for 4 weeks. Treatment protocols were rapidly screened in 4-week experiments using small groups of animals to ensure against rigorous testing of futile treatment protocols. The antiepileptogenic effects of brivaracetam treatment initiated 30 minutes, 4 hours, and 8 hours after rostral parasagittal fluid percussion injury (rpFPI) were then compared with vehicle-treated controls in a fully powered blind and randomized 16-week validation. Seizures were evaluated by video-electrocorticography using a 5-electrode epidural montage. Endpoint measures included incidence, frequency, duration, and spread of seizures. Group sizes and recording durations were supported by published power analyses. Three months after treatment ended, rats treated with brivaracetam starting at 4 hours post-FPI (the best-performing protocol) experienced a 38% decrease in overall incidence of seizures, 59% decrease in seizure frequency, 67% decrease in time spent seizing, and a 45% decrease in the proportion of spreading seizures that was independent of duration-based seizure definition. Thus, brivaracetam shows both antiepileptogenic and disease-modifying properties after rpFPI. SIGNIFICANCE STATEMENT: The rpFPI model, which likely incorporates epileptogenic mechanisms operating after human head injury, can be used to efficiently screen investigational treatment protocols and assess antiepileptogenic/disease-modifying effects. Our studies 1) support a role for SV2A in epileptogenesis, 2) suggest that brivaracetam and other drugs targeting SV2A should be considered for human clinical trials of prevention of post-traumatic epilepsy after head injury, and 3) provide data to inform the design of treatment protocols for clinical trials.

Selected Molecular Targets for Antiepileptogenesis

The term epileptogenesis defines the usually durable process of converting normal brain into an epileptic one. The resistance of a significant proportion of patients with epilepsy to the available pharmacotherapy prompted the concept of a causative treatment option consisting in stopping or modifying the progress of epileptogenesis. Most antiepileptic drugs possess only a weak or no antiepileptogenic potential at all, but a few of them appear promising in this regard; these include, for example, eslicarbazepine (a sodium and T-type channel blocker), lamotrigine (a sodium channel blocker and glutamate antagonist) or levetiracetam (a ligand of synaptic vehicle protein SV2A). Among the approved non-antiepileptic drugs, antiepileptogenic potential seems to reside in losartan (a blocker of angiotensin II type 1 receptors), biperiden (an antiparkinsonian drug), nonsteroidal anti-inflammatory drugs, antioxidative drugs and minocycline (a second-generation tetracycline with anti-inflammatory and antioxidant properties). Among other possible antiepileptogenic compounds, antisense nucleotides have been considered, among these an antagomir targeting microRNA-134. The drugs and agents mentioned above have been evaluated in post-status epilepticus models of epileptogenesis, so their preventive efficacy must be verified. Limited clinical data indicate that biperiden in patients with brain injuries is well-tolerated and seems to reduce the incidence of post-traumatic epilepsy. Exceptionally, in this regard, our own original data presented here point to c-Fos as an early seizure duration, but not seizure intensity-related, marker of early epileptogenesis. Further research of reliable markers of early epileptogenesis is definitely needed to improve the process of designing adequate antiepileptogenic therapies.

Involvement of the Microglial Aryl Hydrocarbon Receptor in Neuroinflammation and Vasogenic Edema after Ischemic Stroke

Microglia are activated after ischemic stroke and induce neuroinflammation. The expression of the aryl hydrocarbon receptor (AhR) has recently been reported to elicit cytokine expression. We previously reported that microglial activation mediates ischemic edema progression. Thus, the purpose of this study was to examine the role of AhR in inflammation and edema after ischemia using a mouse middle cerebral artery occlusion (MCAO) model. MCAO upregulated AhR expression in microglia during ischemia. MCAO increased the expression of tumor necrosis factor α (TNFα) and then induced edema progression, and worsened the modified neurological severity scores, with these being suppressed by administration of an AhR antagonist, CH223191. In THP-1 macrophages, the NADPH oxidase (NOX) subunit p47phox was significantly increased by AhR ligands, especially under inflammatory conditions. Suppression of NOX activity by apocynin or elimination of superoxide by superoxide dismutase decreased TNFα expression, which was induced by the AhR ligand. AhR ligands also elicited p47phox expression in mouse primary microglia. Thus, p47phox may be important in oxidative stress and subsequent inflammation. In MCAO model mice, P47phox expression was upregulated in microglia by ischemia. Lipid peroxidation induced by MCAO was suppressed by CH223191. Taken together, these findings suggest that AhR in the microglia is involved in neuroinflammation and subsequent edema, after MCAO via p47phox expression upregulation and oxidative stress.

Knockout of Transient Receptor Potential Melastatin 4 Channel Mitigates Cerebral Edema and Neuronal Injury After Status Epilepticus in Mice

This study aimed to evaluate whether the knockout of transient receptor potential melastatin 4 (TRPM4) could reduce cerebral edema and improve neurologic outcome in a mouse model of status epilepticus (SE). Wild-type (WT) (n = 61) and Trpm4-/- mice (n = 61) with behavioral seizures induced by lithium (10 mEq/kg) and pilocarpine (30-40 mg/kg) were terminated 2.5 hours after the onset of SE. After SE, 28 WT-SE and 27 Trpm4-/--SE mice were observed for 28 days and assessed for survival and cognitive function; the others were killed after 24 hours, 72 hours, or 7 days, and evaluated for cerebral edema and histological injury. In comparison to WT-SE mice, the mortality and cognitive deficit for Trpm4-/--SE mice following SE after 28 days were significantly ameliorated. Trpm4-/--SE mice also showed less water content and cerebral edema assessed by magnetic resonance imaging, and decreased blood-brain barrier breakdown after SE. Moreover, Trpm4 deficiency significantly mitigated neuronal loss, cellular necrosis and apoptosis in the hippocampus and piriform cortex and mitigated astrocytosis and microgliosis. In conclusion, this study suggests that Trmp4 may represent a new target for improving outcomes after SE.

Levetiracetam and N-Cadherin Antibody Alleviate Brain Pathology Without Reducing Early Epilepsy Development After Focal Non-convulsive Status Epilepticus in Rats

Focal non-convulsive status epilepticus (fNCSE) is a neurological condition characterized by a prolonged seizure that may lead to the development of epilepsy. Emerging experimental evidence implicates neuronal death, microglial activation and alterations in the excitatory and inhibitory synaptic balance as key features in the pathophysiology following fNCSE. We have previously reported alterations in the excitatory adhesion molecule N-cadherin in rats with fNCSE originating from the hippocampus that subsequently also develop spontaneous seizures. In this study, fNCSE rats were treated intraperitoneally with the conventional anti-epileptic drug levetiracetam in combination with intraparenchymal infusion of N-cadherin antibodies (Ab) for 4 weeks post-fNCSE. The N-cadherin Ab was infused into the fornix and immunohistochemically N-cadherin Ab-stained neurons were detected within the dorsal hippocampal structures as well as in superjacent somatosensory cortex. Continuous levetiracetam treatment for 4 weeks post-fNCSE reduced microglia activation, including cell numbers and morphological changes, partly decreased neuronal cell loss, and excitatory post-synaptic scaffold protein PSD-95 expression in selective hippocampal structures. The additional treatment with N-cadherin Ab did not reverse neuronal loss, but moderately reduced microglial activation, and further reduced PSD-95 levels in the dentate hilus of the hippocampus. Despite the effects on brain pathology within the epileptic focus, neither monotherapy with systemic levetiracetam nor levetiracetam in combination with local N-cadherin Ab administration, reduced the amount of focal or focal evolving into bilateral convulsive seizures, seizure duration, or interictal epileptiform activity during 1 month of continuous electroenephalogram recordings within the hippocampus after fNCSE. Behavioral tests for spatial memory, anxiety, social interaction and anhedonia did not detect gross behavioral differences between fNCSE rats with or without treatment. The results reveal the refractory features of the present rodent model of temporal lobe epilepsy following fNCSE, which supports its clinical value for further therapeutic studies. We identify the persistent development of epilepsy following fNCSE, in spite of partly reduced brain pathology within the epileptic focus.

Systematic evaluation of rationally chosen multitargeted drug combinations: a combination of low doses of levetiracetam, atorvastatin and ceftriaxone exerts antiepileptogenic effects in a mouse model of acquired epilepsy

Epileptogenesis, the gradual process that leads to epilepsy after brain injury or genetic mutations, is a complex network phenomenon, involving a variety of morphological, biochemical and functional brain alterations. Although risk factors for developing epilepsy are known, there is currently no treatment available to prevent epilepsy. We recently proposed a multitargeted, network-based approach to prevent epileptogenesis by rationally combining clinically available drugs and provided first proof-of-concept that this strategy is effective. Here we evaluated eight novel rationally chosen combinations of 14 drugs with mechanisms that target different epileptogenic processes. The combinations consisted of 2-4 different drugs per combination and were administered systemically over 5 days during the latent epileptogenic period in the intrahippocampal kainate mouse model of acquired temporal lobe epilepsy, starting 6 h after kainate. Doses and dosing intervals were based on previous pharmacokinetic and tolerability studies in mice. The incidence and frequency of spontaneous electrographic and electroclinical seizures were recorded by continuous (24/7) video linked EEG monitoring done for seven days at 4 and 12 weeks post-kainate, i.e., long after termination of drug treatment. Compared to vehicle controls, the most effective drug combination consisted of low doses of levetiracetam, atorvastatin and ceftriaxone, which markedly reduced the incidence of electrographic seizures (by 60%; p<0.05) and electroclinical seizures (by 100%; p<0.05) recorded at 12 weeks after kainate. This effect was lost when higher doses of the three drugs were administered, indicating a synergistic drug-drug interaction at the low doses. The potential mechanisms underlying this interaction are discussed. We have discovered a promising novel multitargeted combination treatment for modifying the development of acquired epilepsy.

Characterization and treatment of spontaneous recurrent seizures following nerve agent-induced status epilepticus in mice

PURPOSE

To develop and characterize a mouse model of spontaneous recurrent seizures following nerve agent-induced status epilepticus (SE) and test the efficacy of existing antiepileptic drugs.

METHODS

SE was induced in telemeterized male C57Bl6/J mice by soman exposure, and electroencephalographic activity was recorded for 4-6 weeks. Mice were treated with antiepileptic drugs (levetiracetam, valproic acid, phenobarbital) or corresponding vehicles for 14 d after exposure, followed by 14 d of drug washout. Survival, body weight, seizure characteristics, and histopathology were used to characterize the acute and chronic effects of nerve agent exposure and to evaluate the efficacy of treatments in mitigating or preventing neurological effects.

RESULTS

Spontaneous recurrent seizures manifested in all survivors, but the number and frequency of seizures varied considerably among mice. In untreated mice, seizures became longer over time. Moderate to severe histopathology was observed in the amygdala, piriform cortex, and CA1. Levetiracetam provided modest improvements in neurological parameters such as reduced spike rate and improved histopathology scores, whereas valproic acid and phenobarbital were largely ineffective.

CONCLUSIONS

This model of post-SE spontaneous recurrent seizures differs from other experimental models in the brief latency to seizure development, the occurrence of seizures in 100 % of exposed animals, and the lack of damage to CA4/dentate gyrus. It may serve as a useful tool for rapidly and efficiently screening novel therapies that would be effective against severe epilepsy cases.

Anti-Epileptogenic Effects of Antiepileptic Drugs

Generally, the prevalence of epilepsy does not exceed 0.9% of the population and approximately 70% of epilepsy patients may be adequately controlled with antiepileptic drugs (AEDs). Moreover, status epilepticus (SE) or even a single seizure may produce neurodegeneration within the brain and SE has been recognized as one of acute brain insults leading to acquired epilepsy via the process of epileptogenesis. Two questions thus arise: (1) Are AEDs able to inhibit SE-induced neurodegeneration? and (2) if so, can a probable neuroprotective potential of particular AEDs stop epileptogenesis? An affirmative answer to the second question would practically point to the preventive potential of a given neuroprotective AED following acute brain insults. The available experimental data indicate that diazepam (at low and high doses), gabapentin, pregabalin, topiramate and valproate exhibited potent or moderate neuroprotective effects in diverse models of SE in rats. However, only diazepam (at high doses), gabapentin and pregabalin exerted some protective activity against acquired epilepsy (spontaneous seizures). As regards valproate, its effects on spontaneous seizures were equivocal. With isobolography, some supra-additive combinations of AEDs have been delineated against experimental seizures. One of such combinations, levetiracetam + topiramate proved highly synergistic in two models of seizures and this particular combination significantly inhibited epileptogenesis in rats following status SE. Importantly, no neuroprotection was evident. It may be strikingly concluded that there is no correlation between neuroprotection and antiepileptogenesis. Probably, preclinically verified combinations of AEDs may be considered for an anti-epileptogenic therapy.

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.

Functional characterization of novel bumetanide derivatives for epilepsy treatment

Temporal lobe epilepsy (TLE) is the most common type of focal epilepsies, affecting approximately 35 million people worldwide. Despite the introduction of numerous novel antiepileptic drugs during the last decades, the proportion of patients with therapy-resistant TLE is still high. As an impaired cellular chloride homeostasis appears involved in disease pathophysiology, bumetanide, an antagonist to Na-K-Cl cotransporters, gained interest as potential therapeutic option. However, bumetanide induces a strong diuretic effect and displays poor penetration across the blood-brain barrier (BBB). To reduce these unwanted effects, we modified the already described BUM690 by exchanging the allyl-into a trifluoro-ethyl group to yield BUM532. Furthermore, we exchanged the nitrogen for oxygen in the trifluoro-ethyl group to yield BUM97. In the intrahippocampal kainic acid mouse model of TLE BUM532 ± phenobarbital (PB), bumetanide ± PB and PB alone significantly reduced hippocampal paroxysmal discharges (HPDs) but not spike trains. By contrast, treatment with BUM97 suppressed HPDs as well as spike trains dose-dependently, more pronounced compared to the other tested compounds and exerted a synergistic anticonvulsant effect with PB. Moreover, at higher doses BUM97 achieved long-lasting reduction of spike trains. In pentylenetetrazole-induced acute seizures only BUM532 combined with a sub-effective dose of PB increased the seizure threshold. No diuretic effects were observed at any dose of the three derivatives. Our data demonstrate the successful optimization of the pharmacological profile of bumetanide and the potential of the improved derivative BUM97 for the treatment of therapy-resistant TLE, in particular in combinatorial drug regimens with a GABA mimetic.

Suppressive effects of levetiracetam on neuroinflammation and phagocytic microglia: A comparative study of levetiracetam, valproate and carbamazepine

We previously reported that treatment with levetiracetam (LEV) after status epilepticus (SE) termination by diazepam (DZP) prevents the development of spontaneous recurrent seizures. LEV suppresses increased expression levels of proinflammatory mediators during epileptogenesis after SE, but how LEV acts in neuroinflammatory processes is not yet known. In this study, we examined the effects of LEV on neuroinflammation and phagocytic microglia in vivo and in vitro and compared the effects of LEV with those of representative antiepileptic drugs valproate (VPA) and carbamazepine (CBZ). Repeated treatment with LEV for 30 days after the termination of pilocarpine-induced SE by DZP almost completely prevented the incidence of spontaneous recurrent seizures, while administration of VPA or CBZ showed no effect on the seizures. LEV clearly suppressed phagocytosis of mononuclear phagocytes, and cytokine expression was observed 2 days after SE. VPA attenuated neuroinflammation only, and CBZ showed no effect on changes after SE. Treatment with LEV significantly suppressed BV-2 microglial activation, which was defined by morphological changes, phagocytic activity and cytokine expression. By contrast, VPA and CBZ did not affect BV-2 microglial activity. In summary, LEV directly suppresses excess microglial phagocytosis during epileptogenesis, which might prevent the occurrence of spontaneous recurrent seizures after SE.

The holy grail of epilepsy prevention: Preclinical approaches to antiepileptogenic treatments

A variety of acute brain insults can induce epileptogenesis, a complex process that results in acquired epilepsy. Despite advances in understanding mechanisms of epileptogenesis, there is currently no approved treatment that prevents the development or progression of epilepsy in patients at risk. The current concept of epileptogenesis assumes a window of opportunity following acute brain insults that allows intervention with preventive treatment. Recent results suggest that injury-induced epileptogenesis can be a much more rapid process than previously thought, suggesting that the 'therapeutic window' may only be open for a brief period, as in stroke therapy. However, experimental data also suggest a second, possibly delayed process ("secondary epileptogenesis") that influences the progression and refractoriness of the epileptic state over time, allowing interfering with this process even after onset of epilepsy. In this review, both methodological issues in preclinical drug development and novel targets for antiepileptogenesis will be discussed. Several promising drugs that either prevent epilepsy (antiepileptogenesis) or slow epilepsy progression and alleviate cognitive or behavioral comorbidities of epilepsy (disease modification) have been described in recent years, using diverse animal models of acquired epilepsy. Promising agents include TrkB inhibitors, losartan, statins, isoflurane, anti-inflammatory and anti-oxidative drugs, the SV2A modulator levetiracetam, and epigenetic interventions. Research on translational target validity and on prognostic biomarkers that can be used to stratify patients (or experimental animals) at high risk of developing epilepsy will hopefully soon lead to proof-of-concept clinical trials with the most promising drugs, which will be essential to make prevention of epilepsy a reality. 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'.

Neuroprotective effects of levetiracetam, both alone and combined with propylparaben, in the long-term consequences induced by lithium-pilocarpine status epilepticus

Status epilepticus (SE) is a neurological condition that frequently induces severe neuronal injury in the hippocampus, subsequent epileptogenesis and pharmacoresistant spontaneous recurrent seizures (SRS). The repeated administration of LEV (a broad-spectrum antiepileptic drug) during the post-SE period does not prevent the subsequent development of SRS. However, this treatment reduces SE-induced neurodegeneration in the hippocampus. Conversely, propylparaben (PPB) is a widely used antimicrobial that blocks voltage-dependent Na⁺ channels, induces neuroprotection and reduces epileptiform activity in vitro. The present study attempted to determine if the neuroprotective effects induced by LEV are augmented when combined with a sub-effective dose of PPB. Long-term SE-induced consequences (hyperexcitability, high glutamate release, neuronal injury and volume loss) were evaluated in the hippocampus of rats. LEV alone, as well as combined with PPB, did not prevent the occurrence of SRS. However, animals treated with LEV plus PPB showed high prevalence of low frequency oscillations (0.1-4 Hz and 8-90 bands, p < 0.001) and low prevalence of high frequency activity (90-250 bands, p < 0.001) during the interictal period. In addition, these animals presented lower extracellular levels of glutamate, decreased rate of neurodegeneration and a similar hippocampal volume compared to the control conditions. This study's results suggest that LEV associated with PPB could represent a new therapeutic strategy to reduce long-term consequences induced by SE that facilitate pharmacoresistant SRS.

Astroglial role in the pathophysiology of status epilepticus: an overview

Status epilepticus is a medical emergency with elevated morbidity and mortality rates, and represents a leading cause of epilepsy-related deaths. Though status epilepticus can occur at any age, it manifests more likely in children and elderly people. Despite the common prevalence of epileptic disorders, a complete explanation for the mechanisms leading to development of self-limited or long lasting seizures (as in status epilepticus) are still lacking. Apart from neurons, research evidence suggests the involvement of immune and glial cells in epileptogenesis. Among glial cells, astrocytes represent an ideal target for the study of the pathophysiology of status epilepticus, due to their key role in homeostatic balance of the central nervous system. During status epilepticus, astroglial cells are activated by the presence of cytokines, damage associated molecular patterns and reactive oxygen species. The persistent activation of astrocytes leads to a decrease in glutamate clearance with a corresponding accumulation in the synaptic extracellular space, increasing the chance of neuronal excitotoxicity. Moreover, major alterations in astrocytic gap junction coupling, inflammation and receptor expression, facilitate the generation of seizures. Astrocytes are also involved in dysregulation of inhibitory transmission in the central nervous system and directly participate in ionic homeostatic alterations during status epilepticus. In the present review, we focus on the functional and structural changes in astrocytic activity that participate in the development and maintenance of status epilepticus, with special attention on concurrent inflammatory alterations. We also include potential astrocytic treatment targets for status epilepticus.

Progression of vasogenic edema induced by activated microglia under permanent middle cerebral artery occlusion

Brain edema is a severe complication that accompanies ischemic stroke. Increasing evidence shows that inflammatory cytokines impair tight junctions of the blood-brain barrier, suggesting the involvement of microglia in brain edema. In this study, we examined the role of microglia in the progression of ischemic brain edema using mice with permanent middle cerebral artery occlusion. The intensity of T2-weighted imaging (T2WI) in the cerebral cortex and the striatum was elevated 3 h after occlusion and spread to peripheral regions of the ischemic hemisphere. Merged images of 2,3,5-triphenyl tetrazolium chloride staining and T2WI revealed the exact vasogenic edema region, which spread from the ischemic core to outside the ischemic region. Microglia were strongly activated in the ischemic region 3 h after occlusion and, notably, activated microglia were observed in the non-ischemic region 24 h after occlusion. Pretreatment with minocycline, an inhibitor of microglial activation clearly suppressed not only vasogenic edema but also infarct formation. We demonstrated in this study that vasogenic edema spreads from the ischemic core to the peripheral region, which can be elicited, at least in part, by microglial activation induced by ischemia.

Glibenclamide ameliorates cerebral edema and improves outcomes in a rat model of status epilepticus

Glibenclamide (GBC), a sulfonylurea receptor 1 blocker, emerges recently as a promising neuron protectant in various neurological disorders. This study aimed to determine whether GBC improves survival and neurological outcome of status epilepticus (SE). Male Sprague-Dawley rats successfully undergoing SE for 2.5 h (n = 134) were randomly assigned to GBC or vehicle group. Rats in the GBC group received a loading dose of 10 μg/kg of GBC, followed by 1.2 μg/6 h for 3 days, while same dose of vehicle was used as control. The 28-day survival rate in the GBC group (11/23) was significantly higher than that in the vehicle group (8/36). In addition, the frequency and duration of spontaneous recurrent seizures in SE rats were profoundly reduced by GBC but not by vehicle treatment. Moreover, cognitive impairment was observed in the SE rats at day 28, which was reversed by GBC treatment. Meanwhile, cerebral edema, as well as neuronal loss, was decreased in several brain areas in the GBC group. Additionally, on the molecular basis, the subunits of sulfonylurea receptor 1/transient receptor potential M4 (SUR1-TRPM4) heterodimer were both strongly upregulated after SE but partly suppressed by GBC treatment. Furthermore, gene knockdown of Trpm4 in SE rats reduced BBB disruption and neuronal loss, similar to the inhibitory effects with GBC treatment. Taken together, GBC treatment markedly improved survival and neurologic outcomes after SE. The salutary effects of GBC were correlated to the alleviation of cerebral edema and reduction in neurological injury via down-regulation of SUR1-TRPM4 channel.

Network evolution in mesial temporal lobe epilepsy revealed by diffusion tensor imaging

OBJECTIVE

The objective of the present study is to identify novel, time-indexed imaging biomarkers of epileptogenesis in mesial temporal lobe epilepsy (MTLE).

METHODS

We used high-resolution brain diffusion tensor imaging (DTI) of the translationally relevant methionine sulfoximine (MSO) brain infusion model of MTLE. MSO inhibits astroglial glutamine synthetase, which is deficient in the epileptogenic hippocampal formation of patients with MTLE. MSO-infused (epileptogenic) rats were compared with phosphate-buffered saline (PBS)-infused (nonepileptogenic) rats at early (3-4 days) and late (6-9 weeks) time points during epileptogenesis.

RESULTS

The epileptogenic rats exhibited significant changes in DTI-measured fractional anisotropy (FA) in numerous brain regions versus nonepileptogenic rats. Changes included decreases and increases in FA in regions such as the entorhinal-hippocampal area, amygdala, corpus callosum, thalamus, striatum, accumbens, and neocortex. The FA changes evolved over time as animals transitioned from early to late epileptogenesis. For example, some areas with significant decreases in FA early in epileptogenesis changed to significant increases late in epileptogenesis. Finally, the FA changes significantly correlated with the seizure load.

SIGNIFICANCE

Our results suggest (1) that high-resolution DTI can be used for early identification and tracking of the epileptogenic process in MTLE, and (2) that the process identified by DTI is present in multiple brain areas, even though infusion of MSO is restricted to the unilateral entorhinal-hippocampal region.

Down-regulated expression of aquaporin-4 in the cerebellum after status epilepticus

Status epilepticus (SE) is a common neurological condition associated with high rates of mortality and permanent brain injury. SE usually leads to neuronal death which may be accompanied by edema, epileptogenesis and learning impairment. Aquaporin-4 (AQP4), is a transmembrane water channel protein in the neuropil of the central nervous system that has an important role in water transport in the brain; AQP4 expression is altered in many pathological conditions such as changes in the blood- brain barrier and/or astrocytic activation, including seizures. AQP4 was shown to be downregulated in the piriform cortex and the hippocampus after SE. Although it is normally expressed at a high level in the cerebellum, little is known about AQP4 levels in the cerebellum following SE. We addressed this in the present study in a mouse model of pilocarpine-induced SE. We found that AQP4 expression was reduced from 3 h to 3 days after SE, with the levels recovering on day 7. Moreover, mice in the acute post-SE stages exhibited impaired motor coordination and learning. These results indicate that cerebellar damage following SE involves changes in AQP4 expression.

Levetiracetam treatment influences blood-brain barrier failure associated with angiogenesis and inflammatory responses in the acute phase of epileptogenesis in post-status epilepticus mice

Our previous study showed that treatment with levetiracetam (LEV) after status epilepticus (SE) termination by diazepam might prevent the development of spontaneous recurrent seizures via the inhibition of neurotoxicity induced by brain edema events. In the present study, we determined the possible molecular and cellular mechanisms of LEV treatment after termination of SE. To assess the effect of LEV against the brain alterations after SE, we focused on blood-brain barrier (BBB) dysfunction associated with angiogenesis and brain inflammation. The consecutive treatment of LEV inhibited the temporarily increased BBB leakage in the hippocampus two days after SE. At the same time point, the LEV treatment significantly inhibited the increase in the number of CD31-positive endothelial immature cells and in the expression of angiogenic factors. These findings suggested that the increase in neovascularization led to an increase in BBB permeability by SE-induced BBB failure, and these brain alterations were prevented by LEV treatment. Furthermore, in the acute phase of the latent period, pro-inflammatory responses for epileptogenic targets in microglia and astrocytes of the hippocampus activated, and these upregulations of pro-inflammatory-related molecules were inhibited by LEV treatment. These findings suggest that LEV is likely involved in neuroprotection via anti-angiogenesis and anti-inflammatory activities against BBB dysfunction in the acute phase of epileptogenesis after SE.

Xenograft of human umbilical mesenchymal stem cells from Wharton's jelly as a potential therapy for rat pilocarpine-induced epilepsy

We evaluated the effects of intra-hippocampal transplantation of human umbilical mesenchymal stem cells (HUMSCs) on pilocarpine-treated rats. Sprague-Dawley rats were divided into the following three groups: (1) a normal group of rats receiving only PBS, (2) a status epilepticus (SE) group of rats with pilocarpine-induced SE and PBS injected into the hippocampi, and (3) a SE+HUMSC group of SE rats with HUMSC transplantation. Spontaneous recurrent motor seizures (SRMS) were monitored using simultaneous video and electroencephalographic recordings at two to four weeks after SE induction. The results showed that the number of SRMS within two to four weeks after SE was significantly decreased in SE+HUMSCs rats compared with SE rats. All of the rats were sacrificed on Day 29 after SE. Hippocampal morphology and volume were evaluated using Nissl staining and magnetic resonance imaging. The results showed that the volume of the dorsal hippocampus was smaller in SE rats compared with normal and SE+HUMSCs rats. The pyramidal neuron loss in CA1 and CA3 regions was more severe in the SE rats than in normal and SE+HUMSCs rats. No significant differences were found in the hippocampal neuronal loss or in the number of dentate GABAergic neurons between normal and SE+HUMSCs rats. Compared with the SE rats, the SE+HUMSCs rats exhibited a suppression of astrocyte activity and aberrant mossy fiber sprouting. Implanted HUMSCs survived in the hippocampus and released cytokines, including FGF-6, amphiregulin, glucocorticoid-induced tumor necrosis factors receptor (GITR), MIP-3β, and osteoprotegerin. In an in vitro study, exposure of cortical neurons to glutamate showed a significant decrease in cell viability, which was preventable by co-culturing with HUMSCs. Above all, the expression of human osteoprotegerin and amphiregulin were significantly increased in the media of the co-culture of neurons and HUMSCs. Our results demonstrate the therapeutic benefits of HUMSC transplantation for the development of epilepsy, which are likely due to the ability of the cells to produce neuroprotective and anti-inflammatory cytokines. Thus, HUMSC transplantation may be an effective therapy in the future.