Anticonvulsant Compounds Research Articles

Calcium Imaging of Neuronal Activity in Drosophila Can Identify Anticonvulsive Compounds.

Although there are now a number of antiepileptic drugs (AEDs) available, approximately one-third of epilepsy patients respond poorly to drug intervention. The reasons for this are complex, but are probably reflective of the increasing number of identified mutations that predispose individuals to this disease. Thus, there is a clear requirement for the development of novel treatments to address this unmet clinical need. The existence of gene mutations that mimic a seizure-like behaviour in the fruit fly, Drosophila melanogaster, offers the possibility to exploit the powerful genetics of this insect to identify novel cellular targets to facilitate design of more effective AEDs. In this study we use neuronal expression of GCaMP, a potent calcium reporter, to image neuronal activity using a non-invasive and rapid method. Expression in motoneurons in the isolated CNS of third instar larvae shows waves of calcium-activity that pass between segments of the ventral nerve cord. Time between calcium peaks, in the same neurons, between adjacent segments usually show a temporal separation of greater than 200 ms. Exposure to proconvulsants (picrotoxin or 4-aminopyridine) reduces separation to below 200 ms showing increased synchrony of activity across adjacent segments. Increased synchrony, characteristic of epilepsy, is similarly observed in genetic seizure mutants: bangsenseless1 (bss1) and paralyticK1270T (paraK1270T). Exposure of bss1 to clinically-used antiepileptic drugs (phenytoin or gabapentin) significantly reduces synchrony. In this study we use the measure of synchronicity to evaluate the effectiveness of known and novel anticonvulsive compounds (antipain, isethionate, etopiside rapamycin and dipyramidole) to reduce seizure-like CNS activity. We further show that such compounds also reduce the Drosophila voltage-gated persistent Na+ current (INaP) in an identified motoneuron (aCC). Our combined assays provide a rapid and reliable method to screen unknown compounds for potential to function as anticonvulsants.

The effects of antiepileptic drugs on the growth of glioblastoma cell lines.

To determine the effects of antiepileptic drug compounds on glioblastoma cellular growth, we exposed glioblastoma cell lines to select antiepileptic drugs. The effects of selected antiepileptic drugs on glioblastoma cells were measured by MTT assay. For compounds showing significant inhibition, cell cycle analysis was performed. Statistical analysis was performed using SPSS. The antiepileptic compounds selected for screening included carbamazepine, ethosuximide, gabapentin, lamotrigine, levetiracetam, magnesium sulfate, oxcarbazepine, phenytoin, primidone, tiagabine, topiramate, valproic acid, and vigabatrin. Dexamethasone and temozolomide were used as a negative and positive control respectively. Our results showed temozolomide and oxcarbazepine significantly inhibited glioblastoma cell growth and reached IC50 at therapeutic concentrations. The other antiepileptic drugs screened were unable to reach IC50 at therapeutic concentrations. The metabolites of oxcarbazepine were also unable to reach IC50. Dexamethasone, ethosuximide, levetiracetam, and vigabatrin showed some growth enhancement though they did not reach statistical significance. The growth enhancement effects of ethosuximide, levetiracetam, and vigabatrin found in the study may indicate that these compounds should not be used for prophylaxis or short term treatment of epilepsy in glioblastoma. While valproic acid and oxcarbazepine were effective, the required dose of valproic acid was far above that used for the treatment of epilepsy and the metabolites of oxcarbazepine failed to reach significant growth inhibition ruling out the use of oral oxcarbazepine or valproic acid as monotherapy in glioblastoma. The possibility of using these compounds as local treatment is a future area of study.

Current Research on Antiepileptic Compounds

Epilepsy affects about 1% of the world’s population. Due to the fact all antiepileptic drugs (AEDs) have some undesirable side effects and about 30% of epileptic patients are not seizure-free with the existing AEDs, there is still an urgent need for the development of more effective and safer AEDs. Based on our research work on antiepileptic compounds and other references in recent years, this review covers the reported work on antiepileptic compounds which are classified according to their structures. This review summarized 244 significant anticonvulsant compounds which are classified by functional groups according to the animal model data, although there are some limitations in the data. This review highlights the properties of new compounds endowed with promising antiepileptic properties, which may be proven to be more effective and selective, and possibly free of unwanted side effects. The reviewed compounds represent an interesting possibility to overcome refractory seizures and to reduce the percentage of patients with a poor response to drug therapy.

Neuroprotective activity of stiripentol with a possible involvement of voltage-dependent calcium and sodium channels.

A growing body of data has shown that recurrent epileptic seizures may be caused by an excessive release of the excitatory neurotransmitter glutamate in the brain. Glutamatergic overstimulation results in massive neuronal influxes of calcium and sodium through N-methyl-D-aspartate (NMDA), α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, and kainic acid glutamate subtype receptors and also through voltage-gated calcium and sodium channels. These persistent and abnormal sodium and calcium entry points have deleterious consequences (neurotoxicity) for neuronal function. The therapeutic value of an antiepileptic drug would include not only control of seizure activity but also protection of neuronal tissue. The present study examines the in vitro neuroprotective effects of stiripentol, an antiepileptic compound with γ-aminobutyric acidergic properties, on neuronal-astroglial cultures from rat cerebral cortex exposed to oxygen-glucose deprivation (OGD) or to glutamate (40 µM for 20 min), two in vitro models of brain injury. In addition, the affinity of stiripentol for the different glutamate receptor subtypes and the interaction with the cell influx of Na(+) and of Ca(2+) enhanced by veratridine and NMDA, respectively, are assessed. Stiripentol (10-100 µM) included in the culture medium during OGD or with glutamate significantly increased the number of surviving neurons relative to controls. Stiripentol displayed no binding affinity for different subtypes of glutamate receptors (IC50 >100 µM) but significantly blocked the entry of Na(+) and Ca(2+) activated by veratridine and NMDA, respectively. These results suggest that Na(+) and Ca(2+) channels could contribute to the neuroprotective properties of sitiripentol.

Genetically epilepsy-prone rats (GEPRs) and DBA/2 mice: Two animal models of audiogenic reflex epilepsy for the evaluation of new generation AEDs.

This review summarizes the current knowledge about DBA/2 mice and genetically epilepsy-prone rats (GEPRs) and discusses the contribution of such animal models on the investigation of possible new therapeutic targets and new anticonvulsant compounds for the treatment of epilepsy. Also, possible chemical or physical agents acting as proconvulsant agents are described. Abnormal activities of enzymes involved in catecholamine and serotonin synthesis and metabolism were reported in these models, and as a result of all these abnormalities, seizure susceptibility in both animals is greatly affected by pharmacological manipulations of the brain levels of monoamines and, prevalently, serotonin. In addition, both genetic epileptic models permit the evaluation of pharmacodynamic and pharmacokinetic interactions among several drugs measuring plasma and/or brain level of each compound. Audiogenic models of epilepsy have been used not only for reflex epilepsy studies, but also as animal models of epileptogenesis. The seizure predisposition (epileptiform response to sound stimulation) and substantial characterization of behavioral, cellular, and molecular alterations in both acute and chronic (kindling) protocols potentiate the usefulness of these models in elucidating ictogenesis, epileptogenesis, and their mechanisms. This article is part of a Special Issue entitled "Genetic and Reflex Epilepsies, Audiogenic Seizures and Strains: From Experimental Models to the Clinic".

Synergistic effect of docosahexaenoic acid on anticonvulsant activity of valproic acid and lamotrigine in animal seizure models.

Add-on therapy is a common strategy to improve efficacy and tolerability of antiepileptic drugs (AEDs). Anticonvulsant potential and appropriate safety of docosahexaenoic acid (DHA) makes it a promising candidate for combination therapy. We evaluated influence of DHA on anticonvulsant activity of AEDs phenytoin, valproate, and lamotrigine in maximal electroshock (MES), pentylenetetrazole (PTZ), and kindling models of epilepsy. The dose-response to DHA was obtained 15min after intracerebroventricular (i.c.v.) injection in PTZ model of clonic seizures in mice, MES model of tonic seizures in mice, and kindling model of complex partial seizures in rats. The dose-response curve of valproate (30min after i.p. injection to mice) in PTZ, phenytoin (60min after i.p. injection to mice) in MES, and lamotrigine (60min after i.p. injection to rats) in kindling models were obtained. Dose-response curves of the AEDs were then achieved in the presence of ED25 of DHA. DHA had no anticonvulsant effect in the MES model. However, it showed a dose-dependent protective effect against PTZ (ED50=0.13μM) and kindled seizures (ED50=1.08mM). DHA at ED25 caused a 3.6-fold increase in potency of valproate as its ED50 value from 117.5 (98.3-135.3) decreased to 32.5(21.6-44.1)mg/kg. Moreover, a 4.9-fold increase in potency of lamotrigine occurred, as its ED50 value from 13.10 (11.50-14.9) decreased to 2.65(0.8-5.6)mg/kg. CompuSyn analysis indicated synergistic anticonvulsant interaction between DHA and both valproate and lamotrigine. Co-administration strategy of the safe and inexpensive anticonvulsant compound DHA with AEDs should be favorably regarded in clinical studies of epilepsy treatment.

Exploring the interaction of SV2A with racetams using homology modelling, molecular dynamics and site-directed mutagenesis.

The putative Major Facilitator Superfamily (MFS) transporter, SV2A, is the target for levetiracetam (LEV), which is a successful anti-epileptic drug. Furthermore, SV2A knock out mice display a severe seizure phenotype and die after a few weeks. Despite this, the mode of action of LEV is not known at the molecular level. It would be extremely desirable to understand this more fully in order to aid the design of improved anti-epileptic compounds. Since there is no structure for SV2A, homology modelling can provide insight into the ligand-binding site. However, it is not a trivial process to build such models, since SV2A has low sequence identity to those MFS transporters whose structures are known. A further level of complexity is added by the fact that it is not known which conformational state of the receptor LEV binds to, as multiple conformational states have been inferred by tomography and ligand binding assays or indeed, if binding is exclusive to a single state. Here, we explore models of both the inward and outward facing conformational states of SV2A (according to the alternating access mechanism for MFS transporters). We use a sequence conservation analysis to help guide the homology modelling process and generate the models, which we assess further with Molecular Dynamics (MD). By comparing the MD results in conjunction with docking and simulation of a LEV-analogue used in radioligand binding assays, we were able to suggest further residues that line the binding pocket. These were confirmed experimentally. In particular, mutation of D670 leads to a complete loss of binding. The results shed light on the way LEV analogues may interact with SV2A and may help with the on-going design of improved anti-epileptic compounds.

Genetic background of mice strongly influences treatment resistance in the 6 Hz seizure model.

The 6 Hz model of focal seizures has been increasingly used to identify anticonvulsant compounds with potential activity against therapy-resistant epilepsy, but the protective response to anticonvulsants in this model could be dependent on experimental conditions and selection of mouse strains. Seizure thresholds in the 6 Hz model were compared in CF-1, NMRI, and C57Bl/6J male mice with two different electrical stimulators (Ugo Basile 5780 and Grass S48). Dose-response curves for phenytoin and levetiracetam were generated in the three strains at 32 and 44 mA current intensities using both devices. Plasma and brain exposure to the two drugs were measured in all three strains. CF-1 mice had the lowest seizure threshold and responded to phenytoin at 32 mA stimulation intensity, but not at 44 mA. NMRI and C57Bl/6J mice had nearly identical threshold values, but NMRI mice responded well to phenytoin at 32 mA and showed limited responsiveness to this drug at 44 mA, whereas C57Bl/6J mice were nearly completely resistant to phenytoin. Furthermore, levetiracetam showed limited efficacy and low potency in CF-1 and C57Bl/6J mice, particularly at 44 mA, whereas in NMRI mice the drug showed much higher potency in all experimental conditions. No obvious difference in the pharmacokinetics of both phenytoin and levetiracetam was detected between the mouse strains that would have explained these unexpected variations in potency. We have also found that the protective effects of both drugs may be influenced by the device type. Collectively these observations clearly indicate that treatment resistance of 6 Hz seizures should be interpreted with strain and experimental conditions in mind. Furthermore, it is important to note that strain differences, much like human genetic differences, may explain why some mice and patients respond to a given treatment and others do not.

Crystal structures of 2-meth-oxy-isoindoline-1,3-dione, 1,3-dioxoisoindolin-2-yl methyl carbonate and 1,3-dioxo-2,3-di-hydro-1H-benzo[de]isoquinolin-2-yl methyl carbonate: three anti-convulsant compounds.

The title compounds, C9H7NO3, (1), C10H7NO5, (2), and C14H9NO5, (3), are three potentially anti-convulsant compounds. Compounds (1) and (2) are isoindoline derivatives and (3) is an iso-quinoline derivative. Compounds (2) and (3) crystallize with two independent mol-ecules (A and B) in their asymmetric units. In all three cases, the isoindoline and benzoiso-quinoline moieties are planar [r.m.s. deviations are 0.021 Å for (1), 0.04 and 0.018 Å for (2), and 0.033 and 0.041 Å for (3)]. The substituents attached to the N atom are almost perpendicular to the mean planes of the heterocycles, with dihedral angles of 89.7 (3)° for the N-O-Cmeth-yl group in (1), 71.01 (4) and 80.00 (4)° for the N-O-C(=O)O-Cmeth-yl groups in (2), and 75.62 (14) and 74.13 (4)° for the same groups in (3). In the crystal of (1), there are unusual inter-molecular C=O⋯C contacts of 2.794 (1) and 2.873 (1) Å present in mol-ecules A and B, respectively. There are also C-H⋯O hydrogen bonds and π-π inter-actions [inter-centroid distance = 3.407 (3) Å] present, forming slabs lying parallel to (001). In the crystal of (2), the A and B mol-ecules are linked by C-H⋯O hydrogen bonds, forming slabs parallel to (10-1), which are in turn linked via a number of π-π inter-actions [the most significant centroid-centroid distances are 3.4202 (7) and 3.5445 (7) Å], forming a three-dimensional structure. In the crystal of (3), the A and B mol-ecules are linked via C-H⋯O hydrogen bonds, forming a three-dimensional structure, which is consolidated by π-π inter-actions [the most significant inter-centroid distances are 3.575 (3) and 3.578 (3) Å].

Determination of 5-(3-Chlorophenyl)-4-hexyl-2,4-dihydro-3H-1,2,4-triazole-3-thione in Mouse Brain Tissue by Microwave-Assisted Extraction and High-Performance Liquid Chromatography with Fluorescence Detection

A sensitive and selective method was developed for the determination of 5-(3-chlorophenyl)-4-hexyl-2,4-dihydro-3H-1,2,4-triazole-3-thione (TP-315), an antiepileptic compound, in the tissue homogenate of mouse brains by microwave-assisted extraction and high performance liquid chromatography with fluorescence detection by use of an external standard. The analyses were performed on a C18 column using a mobile phase consisting of 60% acetonitrile in water. Fluorescence detection was performed at an excitation wavelength of 263 nm and an emission wavelength of 411 nm. The method provided a high extraction yield with recoveries exceeding 90%. The precision values expressed by intra- and inter-day relative standard deviations were lower than 5%. The validated procedure was employed to develop a brain concentration profile after intraperitoneal administration of a single oral dose equal to 300 mg per kg of body weight. The time to the maximum anticonvulsant action of TP-315 in a mouse maximal electroshock-induced seizure test was 30 min after administration.

Determination of a selection of anti-epileptic drugs and two active metabolites in whole blood by reversed phase UPLC-MS/MS and some examples of application of the method in forensic toxicology cases.

Quantitative determination of anti-epileptic drug concentrations is of great importance in forensic toxicology cases. Although the drugs are not usually abused, they are important post-mortem cases where the question of both lack of compliance and accidental or deliberate poisoning might be raised. In addition these drugs can be relevant for driving under the influence cases. A reversed phase ultra-performance liquid chromatography-tandem mass spectrometry method has been developed for the quantitative analysis of the anti-epileptic compounds carbamazepine, carbamazepine-10,11-epoxide, gabapentin, lamotrigine, levetiracetam, oxcarbazepine, 10-OH-carbazepine, phenobarbital, phenytoin, pregabalin, and topiramate in whole blood, using 0.1 mL sample volume with methaqualone as internal standard. Sample preparation was a simple protein precipitation with acetonitrile and methanol. The diluted supernatant was directly injected into the chromatographic system. Separation was performed on an Acquity UPLC® BEH Phenyl column with gradient elution and a mildly alkaline mobile phase. The mass spectrometric detection was performed in positive ion mode, except for phenobarbital, and multiple reaction monitoring was used for drug quantification. The limits of quantification for the different anti-epileptic drugs varied from 0.064 to 1.26 mg/L in blood, within-day and day-to-day relative standard deviations from 2.2 to 14.7% except for phenobarbital. Between-day variation for phenobarbital was 20.4% at the concentration level of 3.5 mg/L. The biases for all compounds were within ±17.5%. The recoveries ranged between 85 and 120%. The corrected matrix effects were 88-106% and 84-110% in ante-mortem and post-mortem whole blood samples, respectively.

Nav1.1 modulation by a novel triazole compound attenuates epileptic seizures in rodents.

Here, we report the discovery of a novel anticonvulsant drug with a molecular organization based on the unique scaffold of rufinamide, an anti-epileptic compound used in a clinical setting to treat severe epilepsy disorders such as Lennox-Gastaut syndrome. Although accumulating evidence supports a working mechanism through voltage-gated sodium (Nav) channels, we found that a clinically relevant rufinamide concentration inhibits human (h)Nav1.1 activation, a distinct working mechanism among anticonvulsants and a feature worth exploring for treating a growing number of debilitating disorders involving hNav1.1. Subsequent structure–activity relationship experiments with related N-benzyl triazole compounds on four brain hNav channel isoforms revealed a novel drug variant that (1) shifts hNav1.1 opening to more depolarized voltages without further alterations in the gating properties of hNav1.1, hNav1.2, hNav1.3, and hNav1.6; (2) increases the threshold to action potential initiation in hippocampal neurons; and (3) greatly reduces the frequency of seizures in three animal models. Altogether, our results provide novel molecular insights into the rational development of Nav channel-targeting molecules based on the unique rufinamide scaffold, an outcome that may be exploited to design drugs for treating disorders involving particular Nav channel isoforms while limiting adverse effects.

Structure Activity Relationships of Novel Antiepileptic Drugs

Despite notable success over years in the discovery and development of new antiepileptic drugs (AEDs), about 30-40% of the patients are resistant to drug treatment. There is a still significant need to develop novel AEDs that demonstrate superior efficacy, broad spectrum of activities and good safety profile. The synaptic vesicle glycoprotein 2A (SV2A), α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPA-R) and voltage-gated potassium channels (KCNQ2/Q3) are clinically validated as new molecular targets for epilepsy. The discovery of SV2A as a target for levetiracetam, 2,3-benzodiazepine GYKI 52466 as a non-competitive AMPA-R antagonist and retigabine as a KCNQ2/Q3 channels activator provided a rational basis to develop novel AEDs. The optimization of SV2A binding affinity of levetiracetam led to the discovery of novel high affinity SV2A ligands that displayed superior efficacy and protective index in animal models of epilepsy. The high-throughput screening (HTS) and medicinal chemistry efforts yielded many non-competitive AMPA-R antagonists of which perampanel was recently approved as a first-in-a new class. The efficacy and lack of sub-type selectivity of retigabine prompted many research efforts to discover several potent and selective KCNQ2/Q3 channel activators of distinct chemical scaffolds that are at various stages of clinical development. Despite the known role of galanin and galanin receptor (Gal-R) in epilepsy over a decade, development of potent and brainpenetrant Gal-R agonists is very challenging. The discovery of selective Gal-R2 positive allosteric modulator, CYM 2503, offers a valuable and an alternative approach. The review focuses on the available structure-activity relationships and preclinical efficacy of novel antiepileptic compounds that are distinct from most of the approved AEDs, specifically SV2A ligands, non-competitive AMPA-R antagonists, KCNQ2/Q3 channels activators and Gal-R modulators.

New In Vitro Phenotypic Assay for Epilepsy: Fluorescent Measurement of Synchronized Neuronal Calcium Oscillations

Research in the epilepsy field is moving from a primary focus on controlling seizures to addressing disease pathophysiology. This requires the adoption of resource- and time-consuming animal models of chronic epilepsy which are no longer able to sustain the testing of even moderate numbers of compounds. Therefore, new in vitro functional assays of epilepsy are needed that are able to provide a medium throughput while still preserving sufficient biological context to allow for the identification of compounds with new modes of action. Here we describe a robust and simple fluorescence-based calcium assay to measure epileptiform network activity using rat primary cortical cultures in a 96-well format. The assay measures synchronized intracellular calcium oscillations occurring in the population of primary neurons and is amenable to medium throughput screening. We have adapted this assay format to the low magnesium and the 4-aminopyridine epilepsy models and confirmed the contribution of voltage-gated ion channels and AMPA, NMDA and GABA receptors to epileptiform activity in both models. We have also evaluated its translatability using a panel of antiepileptic drugs with a variety of modes of action. Given its throughput and translatability, the calcium oscillations assay bridges the gap between simplified target-based screenings and compound testing in animal models of epilepsy. This phenotypic assay also has the potential to be used directly as a functional screen to help identify novel antiepileptic compounds with new modes of action, as well as pathways with previously unknown contribution to disease pathophysiology.

Novel Nicotinic Receptor Agonist Reduces Hyperalgesia and Allodynia of Neuropathic Pain in Diabetic Rats

Diabetic Peripheral Neuropathic Pain (DPNP) has been attributed to abnormal glucose metabolism and oxidative stress. It is among the most common consequence of chronic diabetes and is treated with antiepileptic compounds, antidepressants, and opioids. However, many patients with DPNP experience lack of treatment efficacy and/or adverse secondary effects that impair quality of life. Here we report the identification of a novel agonist targeting neuronal nicotinic Acetylcholine Receptors (nAChRs) that may alleviate neuropathic pain. A new pyrazole analogue, Cris-104, has been observed to produce antinociceptive activity in acute and chronic pain models. In the present study, Cris-104 effects on thermal hyperalgesia and mechanical allodynia were evaluated in a rat DPNP model. Oral administration of Cris-104 (35 mg.kg-1.day-1 for 7 days) induced antinociception as evidenced by reductions in thermal hyperalgesia and mechanical allodynia in DPNP rats. The mechanism of antinociception cannot be attributed to a diabetes-alleviating effect because blood glucose levels were not reduced significantly by the treatment. The analgesia could be mediated by activation of nAChRs since Cris-104 is a specific ligand for the nAChR. In conclusion, Cris-104 is a compound with potential to be used as a pain reliever in patients with DPNP.

EVALUATION OF ANTI EPILEPTIC ACTIVITY OF ETHANOLIC EXTRACT OF MURRAYA KAENIGII ON MES, PTZ INDUCED CONVULSIONS IN RATS

The aim of the study was to evaluate anti epileptic activity of ethanolic extract of M. kaenigii on MES, PTZ Induced convulsions in Rats. After the collection of the plant it was extracted with using ethanol solvent by maceration method. Preliminary Phytochemical analysis was done. Acute toxicity was studied. Assessments of antioxidant activity by assay of superoxide dismutase were done and also different enzyme analysis was studied. Effect of EEMK on ME induced convlusions was done in PHT treated animals. Secondary metabolites including alkaloids, saponins, cardiac glycosides and flavonoids were found to be present in the extract and these could have a wide range of compounds with pharmacological activities including those found in this study. Effect of antioxidant enzymes on MES and PTZ induced convolutions were studied. EEMK significantly inhibited the PTZ-induced convulsion, prolonged the latency for convulsion and decreased mortality. The PTZ kindling model is a widely used screening model for testing anticonvulsive compounds. Results based on the PTZ induced clonic seizures and MES induced generalized clonic-tonic seizures in rats model demonstrated that the ethanol extract of Murraya koenigii - Linn. is effective in reducing the severity of clonic seizures and generalized clonic-tonic seizures. This, therefore, supports the traditional use of the plant in the treatment of epilepsy.

Repression of oxidative stress/reactive metabolite regulated gene expression is associated with conversion of carbamazepine into a hepatotoxicant in LPS and DSS rat models

Idiosyncratic hepatotoxicity accounts for many drug failures in the clinic and is a leading cause for black-boxed and withdrawn drugs. This toxicity has proven difficult to predict preclinically, but correlates with oxidative stress/reactive metabolites (OS/RM). As noted previously for antiepileptic compounds, many drugs causing idiosyncratic adverse drug effects are detected by OS/RM gene expression responses in the rat. In the present study, two immune activation models, low dose lipopolysaccharide (1 mg/kg IV) and 5% dextran sulphate sodium (DSS) in drinking water, were examined to determine if either would convert the non-toxic idiosyncratic toxicant carbamazepine (225 mg/kg) into a rat hepatotoxicant at 24 hours. Using the low dose LPS model, about 1/3 of the carbamazepine-treated rats either showed robust ALT and AST elevations with histopathological evidence of hepatotoxicity, or died. Rats in this LPS/carbamazepine group were subdivided based on ALT values into non-responders, responders or robust responders. Whereas most carbamazepine-induced mRNAs were repressed by LPS across all rats in this group, the OS/ RM genes aflatoxin aldehyde reductase (Afar) and glutathione transferase Ya (Gstya) were repressed only in the robust responder subgroup; it is unclear whether repression of these genes contributes to or results from hepatotoxicity. The OS/RM gene microsomal epoxide hydrolase (mEphx) showed repression across all rats. NAD(P)H: menadione oxidoreductase (Nmor) is an OS/RM-responsive gene that is also induced by LPS, confounding interpretation of its changes. After pretreatment with 5% DSS at 24 hours or for 5 days, using a protocol that reportedly produces increased endotoxin absorption, carbamazepine was not converted to a hepatototoxicant in any rats. Instead, DSS produced a pronounced (2- to 6-fold) and selective potentiation of carbamazepine induction of OS/RM-responsive mRNAs. The lack of repressive effects of DSS on these mRNAs or in converting carbamazepine to a hepatotoxicant was not due to desensitization of endotoxin responses since LPS was at least as effective when administered to DSS-pretreated rats. OS/RM gene repression may contribute to development of hepatotoxicity of carbamazepine in immune activation models.

Modulation of c-Fos and BDNF Protein Expression in Pentylenetetrazole-Kindled Mice following the Treatment with Novel Antiepileptic Compound HHL-6

Brain-derived neurotrophic factor (BDNF) and c-Fos are shown to promote epileptogenesis and are taken as a marker of neuronal activity. The present study investigated the expression of BDNF and c-Fos in mice brain with pentylenetetrazol- (PTZ-) induced generalized seizure and evaluated the effect of novel tryptamine derivative HHL-6 on the expression of these two markers. The subconvulsive dose of PTZ (50 mg/kg) was administered on alternate days in the experimental groups until the seizure scores 4-5 developed in the PTZ-control group. At the end of each experiment, animals were sacrificed, brain samples were collected and cryosectioned, and immunohistochemical analysis of BDNF and c-Fos protein was performed. Data obtained from two sections per mouse (n = 12 animals/group) is presented as means ± S.E.M. The test compound HHL-6 demonstrated a potent anticonvulsant activity in the PTZ-induced seizure in mice. Significant reduction in the BDNF (P < 0.003) and c-Fos (P < 0.01) protein expression was observed in the HHL-6 treated group. Based on these results we suggest that one of the possible mechanisms of HHL-6 to inhibit epileptogenesis might be due to its controlling effect on the cellular and molecular expression of the factors that contribute to the development of epileptogenic plasticity in the CNS.

Encapsulated galanin‐producing cells attenuate focal epileptic seizures in the hippocampus

Encapsulated cell biodelivery (ECB) is a relatively safe approach, since the devices can be removed in the event of adverse effects. The main objectives of the present study were to evaluate whether ECB could be a viable alternative of cell therapy for epilepsy. We therefore developed a human cell line producing galanin, a neuropeptide that has been shown to exert inhibitory effects on seizures, most likely acting via decreasing glutamate release from excitatory synapses. To explore whether ECB of genetically modified galanin-producing human cell line could provide seizure-suppressant effects, and test possible translational prospect for clinical application, we implanted ECB devices bilaterally into the hippocampus of rats subjected to rapid kindling, a model for recurrent temporal lobe seizures. Two clones from a genetically modified human cell line secreting different levels of galanin were tested. Electroencephalography (EEG) recordings and stimulations were performed by electrodes implanted into the hippocampus at the same surgical session as ECB devices. One week after the surgery, rapid kindling stimulations were initiated. Enzyme-linked immunosorbent assay (ELISA) measurements prior to device implantation showed a release of galanin on average of 8.3 ng/mL/24 h per device for the low-releasing clone and 12.6 ng/mL/24 h per device for the high-releasing clone. High-releasing galanin-producing ECB devices moderately decreased stimulation-induced focal afterdischarge duration, whereas low-releasing ECB devices had no significant effect. Our study shows that galanin-releasing ECB devices moderately suppress focal stimulation-induced recurrent seizures. Despite this moderate effect, the study provides conceptual proof that ECB could be a viable alternative approach to cell therapy in humans, with the advantage that the treatment could be terminated by removing these devices from the brain. Thereby, this strategy provides a higher level of safety for future therapeutic applications, in which genetically modified human cell lines that are optimized to produce and release antiepileptic compounds could be clinically evaluated for their seizure-suppressant effects.

ChemInform Abstract: Synthetic Methods, Chemistry, and the Anticonvulsant Activity of Thiadiazoles

AbstractReview: 94 refs.