Experimental Models for the Discovery of Novel Anticonvulsant Drugs: Focus on Pentylenetetrazole-Induced Seizures and Associated Memory Deficits

The Traf2 and NcK interacting kinase inhibitor NCB-0846 suppresses seizure activity involving the decrease of GRIA1

Epilepsy, one of the most common neurological disorders, is characterized by spontaneous recurrent seizures. Temporal lobe epilepsy (TLE) is one of the most common medically intractable seizure disorders. Traf2-and NcK-interacting kinase (TNIK) has recently attracted attention as a critical modulation target of many neurological and psychiatric disorders, but its role in epilepsy remains unclear. In this study, we hypothesized the involvement of TNIK in epilepsy and investigated TNIK expression in patients with intractable TLE and in a pilocarpine-induced rat model of epilepsy by western blotting, immunofluorescence, and immunohistochemistry. A pentylenetetrazole (PTZ)-induced epilepsy rat model was used to determine the effect of the TNIK inhibitor NCB-0846 on behavioral manifestations of epilepsy. Coimmunoprecipitation (Co-IP)/mass spectrometry (MS) was used to identify the potential mechanism. Through Co-IP, we detected and confirmed the main potential TNIK interactors. Subcellular fractionation was used to establish the effect of NCB-0846 on the expression of the main interactors in postsynaptic density (PSD) fractions. We found that TNIK was primarily located in neurons and decreased significantly in epilepsy model rats and TLE patients compared with controls. NCB-0846 delayed kindling progression and decreased seizure severity. Co-IP/MS identified 63 candidate TNIK interactors in rat hippocampi, notably CaMKII. Co-IP showed that TNIK might correlate with endogenous GRIA1, SYN2, PSD-95, CaMKIV, GABRG1, and GABRG2. In addition, the significant decrease in GRIA1 in hippocampal total lysate and PSDs after NCB-0846 treatment might help modify the progression of PTZ kindling. Our results suggest that TNIK contributes to epileptic pathology and is a potential antiepileptic drug target.

Sinapic Acid Mitigates Pentylenetetrazol-induced Acute Seizures By Modulating the NLRP3 Inflammasome and Regulating Calcium/calcineurin Signaling: In Vivo and In Silico Approaches

Sinapic acid (SA) is a naturally occurring carboxylic acid found in citrus fruits and cereals. Recent studies have shown that SA has potential anti-seizure properties due to its anti-inflammatory, antioxidant, and anti-apoptotic effects. The present study investigated the neuroprotective role of SA at two different dosages in a pentylenetetrazol (PTZ)-induced acute seizure model. Mice were divided into six groups: normal control, PTZ, SA (20 mg/kg), SA (20 mg/kg) + PTZ, SA (40 mg/kg), and SA (40 mg/kg) + PTZ. SA was orally administered for 21 days, followed by a convulsive dose of intraperitoneal PTZ (50 mg/kg). Seizures were estimated via the Racine scale, and animals were behaviorally tested using the Y-maze. Brain tissues were used to assess the levels of GABA, glutamate, oxidative stress markers, calcium, calcineurin, (Nod)-like receptor protein-3 (NLRP3), interleukin (IL)-1β, apoptosis-associated speck-like protein (ASC), Bcl-2-associated death protein (Bad) and Bcl-2. Molecular docking of SA using a multistep in silico protocol was also performed. The results showed that SA alleviated oxidative stress, restored the GABA/glutamate balance and calcium/calcineurin signaling, downregulated NLRP3 and apoptosis, and improved recognition and ambulatory activity in PTZ-treated mice. In silico results also revealed that SA strongly interacts with the target proteins NLRP3 and ASC. Overall, the results suggest that SA is a promising antiseizure agent and that both doses of SA are comparable, with 40 mg/kg SA being superior in normalizing glutathione, calcium and IL-1β, in addition to calcineurin, NLRP3, ASC and Bad.

Synthesis, characterization, and biological study of new synthetic opioid hemorphin-4 peptides containing sterically restricted nonnatural amino acids

Some new hemorphin-4 analogs with structures of Xxx-Pro-Trp-Thr-NH2 and Tyr-Yyy-Trp-Thr-NH2, where Xxx is 2-amino-3-(4-hydroxy-2,6-dimethylphenyl)propanoic acid or 2-amino-3-(4-dibenzylamino-2,6-dimethylphenyl)propanoic acid, and Yyy is (2S,4S)-4-amino-pyrrolidine-2-carboxylic acid, were synthesized and characterized by electrochemical and spectral analyses. In vivo anticonvulsant and antinociceptive activities of peptide derivatives were studied after intracerebroventricular injection in mice. The therapeutic effects of the modified peptides on seizures and pain in mice were evaluated to provide valuable insights into the potential applications of the novel compounds. Electrochemical characterization showed that the compounds behave as weak protolytes and that they are in a soluble, stable molecular form at physiological pH values. The antioxidant activity of the peptides was evaluated with voltammetric analyses, which were confirmed by applying the 2,2-Diphenyl-1-picrylhydrazyl method. The compounds showed satisfactory results regarding their structural stability, reaching the desired centers for the manifestation of biological activity without hydrolysis processes at 37°C and physiological pH. Dm-H4 and H4-P1 exhibited 100% and 83% potency to suppress the psychomotor seizures in the 6-Hz test compared to 67% activity of H4. Notably, only the H4-P1 had efficacy in blocking the tonic component in the maximal electroshock test with a potency comparable to H4. All investigated peptides containing unnatural conformationally restricted amino acids showed antinociceptive effects. The analogs Db-H4 and H4-P1 showed the most pronounced and long-lasting effect in both experimental models of pain induced by thermal and chemical stimuli. Dm-H4 produced a dose-dependent thermal antinociception and H4-P2 inhibited only formalin-induced pain behavior.

The Discovery of Novel Agents against Staphylococcus aureus by Targeting Sortase A: A Combination of Virtual Screening and Experimental Validation

Staphylococcus aureus (S. aureus), commonly known as "superbugs", is a highly pathogenic bacterium that poses a serious threat to human health. There is an urgent need to replace traditional antibiotics with novel drugs to combat S. aureus. Sortase A (SrtA) is a crucial transpeptidase involved in the adhesion process of S. aureus. The reduction in virulence and prevention of S. aureus infections have made it a significant target for antimicrobial drugs. In this study, we combined virtual screening with experimental validation to identify potential drug candidates from a drug library. Three hits, referred to as Naldemedine, Telmisartan, and Azilsartan, were identified based on docking binding energy and the ratio of occupied functional sites of SrtA. The stability analysis manifests that Naldemedine and Telmisartan have a higher binding affinity to the hydrophobic pockets. Specifically, Telmisartan forms stable hydrogen bonds with SrtA, resulting in the highest binding energy. Our experiments prove that the efficiency of adhesion and invasion by S. aureus can be decreased without significantly affecting bacterial growth. Our work identifies Telmisartan as the most promising candidate for inhibiting SrtA, which can help combat S. aureus infection.

Additive Anticonvulsant Profile and Molecular Docking Analysis of 5,5'-Diphenylhydantoin Schiff Bases and Phenytoin

Four 5,5'-diphenylhydantoin Schiff bases possessing different aromatic species (SB1-SB4) were recently synthesized and characterized using spectroscopic and electrochemical tools. The present study aimed to ascertain the anticonvulsant activity of the novel phenytoin derivatives SB1-Ph, SB2-Ph, SB3-Ph, and SB4-Ph, containing different electron-donor and electron-acceptor groups, and their possible mechanism of action. The SB2-Ph exhibited the highest potency to suppress the seizure spread with ED50 = 8.29 mg/kg, comparable to phenytoin (ED50 = 5.96 mg/kg). While SB2-Ph did not produce neurotoxicity and sedation, it decreased locomotion and stereotypy compared to control. When administered in combination, the four Schiff bases decreased the phenytoin ED50 by more than 2× and raised the protective index by more than 7× (phenytoin+SB2-Ph). The strongest correlation between in-vivo and docking study results was found for ligands' interaction energies with kappa and delta receptors. These data, combined with the worst interaction energies of our ligands with the mu receptor, suggest that the primary mechanism of their action involves the kappa and delta receptors, where the selectivity to the kappa receptor leads to higher biological effects. Our findings suggest that the four Schiff bases might be promising candidates with potential applications as a safe and effective adjuvant in epilepsy.

Ameliorative effects of Albizia adianthifolia aqueous extract against pentylenetetrazole-induced epilepsy and associated memory loss in mice: Role of GABAergic, antioxidant defense and anti-inflammatory systems

Albizia adianthifolia (Schumach.) (Fabaceae) is a medicinal herb used for the treatment of epilepsy and memory impairment. This study aims to investigate the anticonvulsant effects of Albizia adianthifolia aqueous extract against pentylenetetrazole (PTZ)-induced spontaneous convulsions in mice; and determine whether the extract could mitigate memory impairment, oxidative/nitrergic stress, GABA depletion and neuroinflammation. Ultra-high performance liquid chromatography/mass spectrometry analysis was done to identify active compounds from the extract. Mice were injected with PTZ once every 48 h until kindling was developed. Animals received distilled water for the normal group and negative control groups, doses of extract (40, 80, or 160 mg/kg) for the test groups and sodium valproate (300 mg/kg) for the positive control group. Memory was measured using Y maze, novel object recognition (NOR) and open field paradigms, while the oxidative/nitrosative stresses (MDA, GSH, CAT, SOD and NO), GABAergic transmission (GABA, GABA-T and GAD) and neuro-inflammation (TNF-α, IFN-γ, IL- 1β, and IL-6) were determined. Brain photomicrograph was also studied. Apigenin, murrayanine and safranal were identified in the extract. The extract (80-160 mg/kg) significantly protected mice against seizures and mortality induced by PTZ. The extract significantly increased the spontaneous alternation and the discrimination index in the Y maze and NOR tests, respectively. PTZ kindling induced oxidative/nitrosative stress, GABA depletion, neuroinflammation and neuronal cells death was strongly reversed by the extract. The results suggest that the anticonvulsant activity of Albizia adianthifolia extract is accompanied by its anti-amnesic property, and may be supported by the amelioration of oxidative stress, GABAergic transmission and neuroinflammation.

Ameliorative Effect of Ethanolic Extract of Moringa oleifera Leaves in Combination with Curcumin against PTZ-Induced Kindled Epilepsy in Rats: In Vivo and In Silico

The ameliorative effect of ethanolic extract of M. oleifera (MOEE) leaves in combination with curcumin against seizures, cognitive impairment, and oxidative stress in the molecular docking of PTZ-induced kindled rats was performed to predict the potential phytochemical effects of MOEE and curcumin against epilepsy. The effect of pretreatment with leaves of M. oleifera ethanolic extracts (MOEE) (250 mg/kg and 500 mg/kg, orally), curcumin (200 mg/kg and 300 mg/kg, orally), valproic acid used as a standard (100 mg/kg), and the combined effect of MOEE (250 mg/kg) and curcumin (200 mg/kg) at a low dose on Pentylenetetrazole was used for (PTZ)-induced kindling For the development of kindling, individual Wistar rats (male) were injected with pentyletetrazole (40 mg/kg, i.p.) on every alternate day. Molecular docking was performed by the Auto Dock 4.2 tool to merge the ligand orientations in the binding cavity. From the RCSB website, the crystal structure of human glutathione reductase (PDB ID: 3DK9) was obtained. Curcumin and M. oleifera ethanolic extracts (MOEE) showed dose-dependent effects. The combined effects of MOEE and curcumin leaves significantly improved the seizure score and decreased the number of myoclonic jerks compared with a standard dose of valproic acid. PTZ kindling induced significant oxidative stress and cognitive impairment, which was reversed by pretreatment with MOEE and curcumin. Glutathione reductase (GR) is an enzyme that plays a key role in the cellular control of reactive oxygen species (ROS). Therefore, activating GR can uplift antioxidant properties, which leads to the inhibition of ROS-induced cell death in the brain. The combination of the ethanolic extract of M. oleifera (MOEE) leaves and curcumin has shown better results than any other combination for antiepileptic effects by virtue of antioxidant effects. As per the docking study, chlorogenic acid and quercetin treated with acombination of curcumin have much more potential.

Animal Models of Hypertension (ISIAH Rats), Catatonia (GC Rats), and Audiogenic Epilepsy (PM Rats) Developed by Breeding

Research into genetic and physiological mechanisms of widespread disorders such as arterial hypertension as well as neuropsychiatric and other human diseases is urgently needed in academic and practical medicine and in the field of biology. Nevertheless, such studies have many limitations and pose difficulties that can be overcome by using animal models. To date, for the purposes of creating animal models of human pathologies, several approaches have been used: pharmacological/chemical intervention; surgical procedures; genetic technologies for creating transgenic animals, knockouts, or knockdowns; and breeding. Although some of these approaches are good for certain research aims, they have many drawbacks, the greatest being a strong perturbation (in a biological system) that, along with the expected effect, exerts side effects in the study. Therefore, for investigating the pathogenesis of a disease, models obtained using genetic selection for a target trait are of high value as this approach allows for the creation of a model with a "natural" manifestation of the pathology. In this review, three rat models are described: ISIAH rats (arterial hypertension), GC rats (catatonia), and PM rats (audiogenic epilepsy), which are developed by breeding in the Laboratory of Evolutionary Genetics at the Institute of Cytology and Genetics (the Siberian Branch of the Russian Academy of Sciences).

Rodent Models of Audiogenic Epilepsy: Genetic Aspects, Advantages, Current Problems and Perspectives

Animal models of epilepsy are of great importance in epileptology. They are used to study the mechanisms of epileptogenesis, and search for new genes and regulatory pathways involved in the development of epilepsy as well as screening new antiepileptic drugs. Today, many methods of modeling epilepsy in animals are used, including electroconvulsive, pharmacological in intact animals, and genetic, with the predisposition for spontaneous or refractory epileptic seizures. Due to the simplicity of manipulation and universality, genetic models of audiogenic epilepsy in rodents stand out among this diversity. We tried to combine data on the genetics of audiogenic epilepsy in rodents, the relevance of various models of audiogenic epilepsy to certain epileptic syndromes in humans, and the advantages of using of rodent strains predisposed to audiogenic epilepsy in current epileptology.

The role of interleukin-17 in epilepsy

Epilepsy is a common neurological disorder that seriously affects human health. It is a chronic central nervous system dysfunction caused by abnormal discharges of neurons. About 50 million patients worldwide are affected by epilepsy. Although epileptic symptoms of most patients are controllable, some patients with refractory epilepsy have no response to antiseizure medications. It is necessary to investigate the pathogenesis of epilepsy and identify new therapeutic targets for refractory epilepsy. Epileptic disorders often accompany cerebral inflammatory reactions. Recently, the role of inflammation in the onset of epilepsy has increasingly attracted attention. The activation of both innate and adaptive immunity plays a significant role in refractory epilepsy. According to several clinical studies, interleukin-17, an essential inflammatory mediator linking innate and adaptive immunity, increased significantly in the body liquid and epileptic focus of patients with epilepsy. Experimental studies also indicated that interleukin-17 participated in epileptogenesis through various mechanisms. This review summarized the current studies about interleukin-17 in epilepsy and aimed at finding new therapeutic targets for refractory epilepsy.

Aquatic Freshwater Vertebrate Models of Epilepsy Pathology: Past Discoveries and Future Directions for Therapeutic Discovery

Epilepsy is an international public health concern that greatly affects patients’ health and lifestyle. About 30% of patients do not respond to available therapies, making new research models important for further drug discovery. Aquatic vertebrates present a promising avenue for improved seizure drug screening and discovery. Zebrafish (Danio rerio) and African clawed frogs (Xenopus laevis and tropicalis) are increasing in popularity for seizure research due to their cost-effective housing and rearing, similar genome to humans, ease of genetic manipulation, and simplicity of drug dosing. These organisms have demonstrated utility in a variety of seizure-induction models including chemical and genetic methods. Past studies with these methods have produced promising data and generated questions for further applications of these models to promote discovery of drug-resistant seizure pathology and lead to effective treatments for these patients.

Pentylenetetrazole-induced seizures cause impairment of memory acquisition and consolidation in zebrafish (Danio rerio)

Epilepsy is characterized by the occurrence seizures, and the high prevalence of epilepsy-associated comorbidities affects the quality of patients' life. We investigated the effects of pentylenetetrazole (PTZ) exposure in zebrafish cognitive performance on inhibitory avoidance test. The animals were exposed to the 7.5mM PTZ for 10minutes, in the acquisition (before training) and in the consolidation memory phases (after training). In the acquisition phase, the animals were submitted to PTZ-induced seizures and trained in periods of 1, 24, or 48hours after exposure, and 24hours after training were tested. In the consolidation phase, animals were trained and exposed to PTZ 10minutes after training and were tested 24hours later. Control groups in periods of 1, 24, or 48hours before or 10minutes after training showed a significantly increased latency to enter the dark compartment. The latencies between training and test sessions did not differ in PTZ groups of animals exposed and trained 1 and 24hours or exposed to PTZ 10minutes after training. At 48hours, animals exposed to PTZ showed an increased latency to enter the dark compartment. Animals exposed to PTZ and trained 1h after increased the traveled distance, when compared to the control group. Traveled distance did not differ in animals that were exposed to PTZ and trained 24 and 48hours, or 10minutes after training. Our findings indicate that PTZ causes a cognitive deficit in the pre-and post-training phase, allowing us to explore the influence of seizures at different memory phases.

Seizure Susceptibility and Sleep Disturbance as Biomarkers of Epileptogenesis after Experimental TBI

Objectives: We investigated whether seizure susceptibility increases over weeks−months after experimental traumatic brain injury (TBI), and whether seizure susceptibility in rats predicts the development of post-traumatic epilepsy (PTE) or epileptiform activity. We further investigated whether rats develop chronic sleep disturbance after TBI, and whether sleep disturbance parameters—alone or in combination with pentylenetetrazol (PTZ) test parameters—could serve as novel biomarkers for the development of post-traumatic epileptogenesis. Methods: TBI was induced in adult male Sprague-Dawley rats with lateral fluid-percussion injury. Sham-operated experimental controls underwent craniectomy without exposure to an impact force. Seizure susceptibility was tested with a PTZ test (30 mg/kg, intraperitoneally) on day (D) 30, D60, D90, and D180 after TBI (n = 28) or sham operation (n = 16) under video electroencephalogram (vEEG). In the 7th post-injury month, rats underwent continuous vEEG monitoring to detect spontaneous seizures and assess sleep disturbances. At the end of the experiments, rats were perfused for brain histology. Results: In the TBI group, the percentage of rats with PTZ-induced seizures increased over time (adjusted p < 0.05 compared with D30). Combinations of three PTZ test parameters (latency to the first epileptiform discharge (ED), number of EDs, and number of PTZ-induced seizures) survived the leave-one-out validation for differentiating rats with or without epileptiform activity, indicating an area under the receiver operating curve (AUC) of 0.743 (95% CI 0.472−0.992, p = 0.05) with a misclassification rate of 36% on D90, and an AUC of 0.752 (95% CI 0.483−0.929, p < 0.05) with a misclassification rate of 32% on D180. Sleep analysis revealed that the number of transitions to N3 or rapid eye movement (REM) sleep, along with the total number of transitions, was increased in the TBI group during the lights-on period (all p < 0.05). The sleep fragmentation index during the lights-on period was greater in the TBI rats than in sham-operated rats (p < 0.05). A combination of sleep parameters showed promise as diagnostic biomarkers of prior TBI, with an AUC of 0.792 (95% CI 0.549−0.934, p < 0.01) and a misclassification rate of 28%. Rats with epilepsy or any epileptiform activity had more transitions from N3 to the awake stage (p < 0.05), and the number of N3−awake transitions differentiated rats with or without epileptiform activity, with an AUC of 0.857 (95% CI 0.651−1.063, p < 0.01). Combining sleep parameters with PTZ parameters did not improve the biomarker performance. Significance: This is the first attempt to monitor the evolution of seizure susceptibility over months in a well-described rat model of PTE. Our data suggest that assessment of seizure susceptibility and sleep disturbance can provide diagnostic biomarkers of prior TBI and prognostic biomarkers of post-traumatic epileptogenesis.

Male rats are more vulnerable to pentylenetetrazole-kindling model but females have more spatial memory-related deficits

Epilepsy is the most common neurological condition worldwide and is largely associated with memory impairment, both in human as well as animal models. Furthermore, differences in seizure onset and severity have already been observed between the sexes. The induction of epilepsy through multiple systemic injections of pentylenetetrazole (PTZ), a protocol known as chemical kindling, is a well-established tool for studies regarding epileptogenesis, as well as the efficacy of antiseizure medication. The aim of this study was to compare possible sex-related differences in seizure severity, memory, neuronal damage as well as the effects of the estrous cycle on seizure severity. Male (n = 10) and Female (n = 11) animals received 30 mg/kg i.p. injections three days a week for 6 weeks and, after the last application, were tested for short and long-term memory. Control, Male (n = 8) and Female (n = 5) groups did not receive PTZ injections. Although PTZ did not promote important changes into the estrous cycle phases throughout the entire experiment, female animals presented lower seizure scores but had both short and long-term memory impairments associated with cell loss in the hippocampus and anterior cingulate area. Male rats presented higher seizure scores associated with pronounced cell loss, but only long-term memory deficits. Our results demonstrate that the PTZ kindling protocol results in higher seizure scores with increased vulnerability in male rats, but female rats displayed more intense memory deficits.

Animal Models of Epilepsy: A Phenotype-oriented Review

Epilepsy is a serious neurological disorder characterized by abnormal, recurrent, and synchronous discharges in the brain. Long-term recurrent seizure attacks can cause serious damage to brain function, which is usually observed in patients with temporal lobe epilepsy. Controlling seizure attacks is vital for the treatment and prognosis of epilepsy. Animal models, such as the kindling model, which was the most widely used model in the past, allow the understanding of the potential epileptogenic mechanisms and selection of antiepileptic drugs. In recent years, various animal models of epilepsy have been established to mimic different seizure types, without clear merits and demerits. Accordingly, this review provides a summary of the views mentioned above, aiming to provide a reference for animal model selection.

Synthesis and characterization of new 5,5′-dimethyl- and 5,5′-diphenylhydantoin-conjugated hemorphin derivatives designed as potential anticonvulsant agents

Herein, the synthesis and characterization of some novel N-modified hybrid analogues of hemorphins containing a C-5 substituted hydantoin residue as potential anticonvulsants and for the blockade of sodium channels are presented.

Anticonvulsant activity of β-caryophyllene in association with pregabalin in a seizure model in rats

Epilepsy is a common chronic neurological disease. The hallmark of epilepsy is recurrent, unprovoked seizures. Unfortunately, drug resistance is frequent in patients with epilepsy, and therefore improved therapeutic strategies are needed. In the present study, we tested the effect of pregabalin in association with beta-caryophyllene, an FDA-approved food additive and naturally occurring agonist of cannabinoid receptor subtype 2 against pentylenetetrazol (PTZ)-induced seizures in rats. In addition, selected neurochemical parameters were evaluated in the cerebral cortex. Adult male Wistar rats received beta-caryophyllene (100 mg/kg), pregabalin (40 mg/kg) or their combination before PTZ (60 mg/kg). Appropriated vehicle-treated control groups were included for each treatment. Animals were monitored by video-EEG and the latency to myoclonic seizures, latency to tonic-clonic seizures, tonic-clonic seizure duration and overall seizure score were measured. Glial fibrillary acidic protein (GFAP) release, erythroid-related factor 2 (Nrf2), c-fos and 3-nitrotyrosine (3-NT) levels were evaluated in the frontal cortex. We found that beta-caryophyllene plus pregabalin increased the latency to PTZ-induced myoclonic and tonic-clonic seizures and decreased the tonic-clonic seizure duration and overall seizure score. Interestingly, lower levels of GFAP, c-Fos and 3-NT were observed in animals receiving beta-caryophyllene and pregabalin treatments. Our results suggest a possible synergic effect of beta-caryophyllene plus pregabalin against PTZ induced-seizures.

Preclinical investigation of β-caryophyllene as a therapeutic agent in an experimental murine model of Dravet syndrome

Dravet Syndrome (DS) is caused by mutations in the Scn1a gene encoding the α1 subunit of the sodium channel Nav1.1, which results in febrile seizures that progress to severe tonic-clonic seizures and associated comorbidities. Treatment with cannabidiol has been approved for the management of seizures in DS patients, but it appears to be also active against associated comorbidities. In this new study, we have investigated β-caryophyllene (BCP), a cannabinoid with terpene structure that appears to also have a broad-spectrum profile, as a useful therapy against both seizuring activity and progression of associated comorbidities. This has been studied in heterozygous conditional knock-in mice carrying a missense mutation (A1783V) in Scn1a gene expressed exclusively in neurons of the Central Nervous System (Syn-Cre/Scn1a^WT/A1783V), using two experimental approaches. In the first approach, an acute treatment with BCP was effective against seizuring activity induced by pentylenetetrazole (PTZ) in wildtype (Scn1a^WT/WT) and also in Syn-Cre/Scn1a^WT/A1783V mice, with these last animals having a greater susceptibility to PTZ. Such benefits were paralleled by a BCP-induced reduction in PTZ-induced reactive astrogliosis (labelled with GFAP) and microgliosis (labelled with Iba-1) in the prefrontal cortex and the hippocampal dentate gyrus, which were visible in both wildtype (Scn1a^WT/WT) and Syn-Cre/Scn1a^WT/A1783V mice. In the second approach, both genotypes were treated repeatedly with BCP to investigate its effects on several DS comorbidities. Thus, BCP corrected important behavioural abnormalities of Syn-Cre/Scn1a^WT/A1783V mice (e.g. delayed appearance of hindlimb grasp reflex, induction of clasping response, motor hyperactivity, altered social interaction and memory impairment), attenuated weight loss, and slightly delayed premature mortality. Again, these benefits were paralleled by a BCP-induced reduction in reactive astrogliosis and microgliosis in the prefrontal cortex and the hippocampal dentate gyrus typical of Syn-Cre/Scn1a^WT/A1783V mice. In conclusion, BCP was active in Syn-Cre/Scn1a^WT/A1783V mice against seizuring activity (acute treatment) and against several comorbidities (repeated treatment), in both cases in association with its capability to reduce glial reactivity in areas related to these behavioural abnormalities. This situates BCP in a promising position for further preclinical evaluation towards a close translation to DS patients.

A zebrafish-centric approach to antiepileptic drug development

Danio rerio (zebrafish) are a powerful experimental model for genetic and developmental studies. Adaptation of zebrafish to study seizures was initially established using the common convulsant agent pentylenetetrazole (PTZ). Larval PTZ-exposed zebrafish exhibit clear behavioral convulsions and abnormal electrographic activity, reminiscent of interictal and ictal epileptiform discharge. By using this model, our laboratory developed simple locomotion-based and electrophysiological assays to monitor and quantify seizures in larval zebrafish. Zebrafish also offer multiple advantages for rapid genetic manipulation and high-throughput phenotype-based drug screening. Combining these seizure assays with genetically modified zebrafish that represent Dravet syndrome, a rare genetic epilepsy, ultimately contributed to a phenotype-based screen of over 3500 drugs. Several drugs identified in these zebrafish screens are currently in clinical or compassionate-use trials. The emergence of this 'aquarium-to-bedside' approach suggests that broader efforts to adapt and improve upon this zebrafish-centric strategy can drive a variety of exciting new discoveries.

Glucosamine promotes seizure activity via activation of the PI3K/Akt pathway in epileptic rats

CONTEXT

Glucosamine is an amino monosaccharide with a small molecular weight and has a protective effect against various neurological diseases including multiple sclerosis and encephalomyelitis. Interestingly, low-dose glucosamine has exhibited anti-epilepsy activity. Recent studies have shown that the activation of the protein kinase B (Akt) signaling pathway may promote epilepsy. Glucosamine can increase the level of Akt phosphorylation in the brain tissue, which may aggravate epilepsy. Hence, we speculate that a higher dose of glucosamine may aggravate epilepsy via AKT signaling.

OBJECTIVE

To investigate the effect of glucosamine on the behavior and electrophysiology of epileptic rats through PI3K/Akt pathway.

METHODS

Glucose (2.0 g/kg) and glucosamine (0, 0.5, 1.0, and 2.0 g/kg) were added to 2 mL of drinking water, respectively. An acute seizure rat model of lithium-pilocarpine and PTZ-kindling were constructed to observe the effects of different doses of glucosamine on epileptic behavior and hippocampal electrical activity. Meanwhile, the changes in Akt were detected by western blot.

RESULTS

Epileptic seizures were induced by a single dose of pilocarpine or PTZ and 2.0 g/kg of glucosamine significantly prolonged the duration and severity of epileptic seizures, enhanced hippocampal electrical activity energy density, and increased phosphorylated AKT levels. A glucosamine dose of 2.0 g/kg also significantly increased the total onset energy density. Furthermore, 2.0 g/kg glucosamine facilitated the development of the chronic PTZ-kindling process.

CONCLUSIONS

Glucosamine may exacerbate acute and chronic epileptic seizures via activation of the PI3K/Akt pathway in rats with experimental epilepsy.

Ameliorating effects of histamine H3 receptor antagonist E177 on acute pentylenetetrazole-induced memory impairments in rats

Histamine H3 receptors (H3Rs) are involved in several neuropsychiatric diseases including epilepsy. Therefore, the effects of H3R antagonist E177 (5 and 10 mg/kg, intraperitoneal (i.p.)) were evaluated on acute pentylenetetrazole (PTZ)-induced memory impairments, oxidative stress levels (glutathione (GSH), malondialdehyde (MDA), catalase (CAT), and superoxide dismutase (SOD)), various brain neurotransmitters (histamine (HA), acetylcholine (ACh), γ-aminobutyric acid (GABA)), and glutamate (Glu), acetylcholine esterase (AChE) activity, and c-fos protein expression in rats. E177 (5 and 10 mg/kg, i.p.) significantly prolonged step-through latency (STL) time in single-trial passive avoidance paradigm (STPAP), and shortened transfer latency time (TLT) in elevated plus maze paradigm (EPMP) (all P < 0.05). Moreover, and in the hippocampus of PTZ-treated animals, E177 mitigated abnormal levels of AChE activity, ACh and HA (all P < 0.05), but failed to modify brain levels of GABA and Glu. Furthermore, E177 alleviated hippocampal oxidative stress by significantly decreasing the elevated levels of MDA, and increasing the abnormally decreased level of GSH (all P < 0.05). Furthermore, E177 reduced elevated levels of hippocampal c-fos protein expression in hippocampal tissues of PTZ-treated animals (all P < 0.05). The observed results propose the potential of H3R antagonist E177 with an added advantage of avoiding cognitive impairment, emphasizing the H3Rs as a prospective target for future pharmacological management of epilepsy with associated memory impairments.

Neuropathological Characterization of a Dravet Syndrome Knock-In Mouse Model Useful for Investigating Cannabinoid Treatments

Dravet syndrome (DS) is an epileptic syndrome caused by mutations in the Scn1a gene encoding the α1 subunit of the sodium channel Nav1.1, which is associated with febrile seizures that progress to severe tonic-clonic seizures and associated comorbidities. Treatment with cannabidiol has been approved to reduce seizures in DS, but it may also be active against these comorbidities. The aim of this study was to validate a new mouse model of DS having lower mortality than previous models, which may serve to further evaluate therapies for the long-term comorbidities. This new model consists of heterozygous conditional knock-in mice carrying a missense mutation (A1783V) in Scn1a gene expressed exclusively in neurons of the CNS (Syn-Cre/Scn1a^WT/A1783V). These mice have been used here to determine the extent and persistence of the behavioral deterioration in different postnatal days (PND), as well as to investigate the alterations that the disease produces in the endocannabinoid system and the contribution of inflammatory events and impaired neurogenesis in the pathology. Syn-Cre/Scn1a^WT/A1783V mice showed a strong reduction in hindlimb grasp reflex at PND10, whereas at PND25, they presented spontaneous convulsions and a greater susceptibility to pentylenetetrazole-induced seizures, marked hyperactivity, deficient spatial working memory, lower levels of anxiety, and altered social interaction behavior. These differences disappeared at PND40 and PND60, except the changes in social interaction and anxiety. The analysis of CNS structures associated with these behavioral alterations revealed an elevated glial reactivity in the prefrontal cortex and the dentate gyrus. This was associated in the dentate gyrus with a greater cell proliferation detected with Ki67 immunostaining, whereas double-labeling analyses identified that proliferating cells were GFAP-positive suggesting failed neurogenesis but astrocyte proliferation. The analysis of the endocannabinoid system of Syn-Cre/Scn1a^WT/A1783V mice confirmed reductions in CB₁ receptors and MAGL and FAAH enzymes, mainly in the cerebellum but also in other areas, whereas CB₂ receptors became upregulated in the hippocampus. In conclusion, Syn-Cre/Scn1a^WT/A1783V mice showed seizuring susceptibility and several comorbidities (hyperactivity, memory impairment, less anxiety, and altered social behavior), which exhibited a pattern of age expression similar to DS patients. Syn-Cre/Scn1a^WT/A1783V mice also exhibited greater glial reactivity and a reactive response in the neurogenic niche, and regional changes in the status of the endocannabinoid signaling, events that could contribute in behavioral impairment.

Anticonvulsant effect of pterostilbene and its influence on the anxiety- and depression-like behavior in the pentetrazol-kindled mice: behavioral, biochemical, and molecular studies

RATIONALE

Pterostilbene is the 3,5-dimethoxy derivative of resveratrol with numerous beneficial effects including neuroprotective properties. Experimental studies revealed its anticonvulsant action in the acute seizure tests.

OBJECTIVES

The purpose of the present study was to evaluate the effect of pterostilbene in the pentetrazol (PTZ)-induced kindling model of epilepsy in mice as well as to assess some possible mechanisms of its anticonvulsant action in this model.

METHODS

Mice were repeatedly treated with pterostilbene (50-200 mg/kg) and its effect on the development of seizure activity in the PTZ kindling was estimated. Influence of pterostilbene on the locomotor activity and anxiety- and depression-like behavior in the PTZ-kindled mice was also assessed. To understand the possible mechanisms of anticonvulsant activity of pterostilbene, γ-aminobutyric acid (GABA) and glutamate concentrations in the prefrontal cortex and hippocampus of the PTZ-kindled mice were measured using LC-MS/MS method. Moreover, mRNA expression of BDNF, TNF-α, IL-1β, IL-6, GABRA1A, and GRIN2B was determined by RT-qPCR technique.

RESULTS

We found that pterostilbene at a dose of 200 mg/kg considerably reduced seizure activity but did not influence the locomotor activity and depression- and anxiety-like behavior in the PTZ-kindled mice. In the prefrontal cortex and hippocampus, pterostilbene reversed the kindling-induced decrease of GABA concentration. Neither in the prefrontal cortex nor hippocampus pterostilbene affected mRNA expression of IL-1β, IL-6, GABRA1A, and GRIN2B augmented by PTZ kindling. Pterostilbene at a dose of 100 mg/kg significantly decreased BDNF and TNF-α mRNA expression in the hippocampus of the PTZ-kindled mice.

CONCLUSIONS

Although further studies are necessary to understand the mechanism of anticonvulsant properties of pterostilbene, our findings suggest that it might be considered a candidate for a new antiseizure drug.

Structure-activity relationship study on new hemorphin-4 analogues containing steric restricted amino acids moiety for evaluation of their anticonvulsant activity

In the present study, several new analogues of hemorphin-4, modified with unnatural conformationally restricted amino acids followed the structure Aaa-Tyr-Xxx-Trp-Thr-NH₂, where Aaa is the low-molecular-weight lipophilic adamantyl building block, and Xxx is Ac5c (1-aminocyclopentanecarboxylic acid) or Ac6c (1-aminocyclohexane carboxylic acid) was synthesized, characterized and investigated for anticonvulsant activity in three seizure tests, the maximal electroshock test (MES), 6-Hz psychomotor seizure test and timed intravenous pentylenetetrazole infusion (ivPTZ) test. The acute neurological toxicity was determined using the rota-rod test. The new synthetic neuropeptide analogues were prepared by solid-phase peptide synthesis-Fmoc chemistry and were evaluated in three doses of 1, 3 and 5 µg, respectively, administered intracerebroventricularly in male ICR mice. The physicochemical properties of these peptide analogues were evaluated as pKa and pI values were calculated using potentiometry. The IR spectrum of the compounds was recorded and the characteristic lines of both adamantane moiety and the peptide backbone were registered in the wavelength range from 4000 to 400 cm^-1. The hexapeptide Ang IV was used as a positive control. From the six synthesized peptide analogues, the P4-5 was the most active at doses of 1 and 3 µg in the three seizure tests. The order of potency of other peptides was as follows: P4 > P4-3 = P4-4 > P4-2 > Ang IV in MES, P4-4 ≥ P4-1 > P4-3 > P4-2 > P4 > Ang IV in 6-Hz test and P4-4 = P4-3 > P4-2 = P4 > Ang IV in ivPTZ test. None of the peptides displayed neurotoxicity in the rota-rod test. Docking study results suggest that direct H-bonding and ionic interactions between our synthetic ligands and residues, responsible for coordination of Zn²⁺ along with hydrophobic interactions between our ligands and IRAP active site are the most important for the ligand binding. The results propose that incorporation of adamantane and cycloalkane building blocks in the peptide chain of the hemorphin-4 scaffold is important for the potential high biological activity.

Rational design of new multitarget histamine H3 receptor ligands as potential candidates for treatment of Alzheimer's disease

Design and development of multitarget-directed ligands (MTDLs) has become a very important approach in the search of new therapies for Alzheimer's disease (AD). In our present research, a number of xanthone derivatives were first designed using a pharmacophore model for histamine H₃ receptor (H₃R) antagonists/inverse agonists, and virtual docking was then performed for the enzyme acetylcholinesterase. Next, 23 compounds were synthesised and evaluated in vitro for human H₃R (hH₃R) affinity and inhibitory activity on cholinesterases. Most of the target compounds showed hH₃R affinities in nanomolar range and exhibited cholinesterase inhibitory activity with IC₅₀ values in submicromolar range. Furthermore, the inhibitory effects of monoamine oxidases (MAO) A and B were investigated. The results showed low micromolar and selective human MAO B (hMAO B) inhibition. Two azepane derivatives, namely 23 (2-(5-(azepan-1-yl)pentyloxy)-9H-xanthen-9-one) and 25 (2-(5-(azepan-1-yl)pentyloxy)-7-chloro-9H-xanthen-9-one), were especially very promising and showed high affinity for hH₃R (K_i = 170 nM and 100 nM respectively) and high inhibitory activity for acetylcholinesterase (IC₅₀ = 180 nM and 136 nM respectively). Moreover, these compounds showed moderate inhibitory activity for butyrylcholinesterase (IC₅₀ = 880 nM and 394 nM respectively) and hMAO B (IC₅₀ = 775 nM and 897 nM respectively). Furthermore, molecular docking studies were performed for hH₃R, human cholinesterases and hMAO B to describe the mode of interactions with these biological targets. Next, the two most promising compounds 23 and 25 were selected for in vivo studies. The results showed significant memory-enhancing effect of compound 23 in dizocilpine-induced amnesia in rats in two tests: step-through inhibitory avoidance paradigm (SIAP) and transfer latency paradigm time (TLPT). In addition, favourable analgesic effects of compound 23 were observed in neuropathic pain models. Therefore, compound 23 is a particularly promising structure for further design of new MTDLs for AD.