Cyclooxygenase-1 as a Potential Therapeutic Target for Seizure Suppression: Evidences from Zebrafish Pentylenetetrazole-Seizure Model

Rotenone exposure causes features of Parkinson`s disease pathology linked with muscle atrophy in developing zebrafish embryo

Parkinson's disease (PD) is associated with both genetic and environmental factors; however, sporadic forms of PD account for > 90 % of cases, and PD prevalence has doubled in the past 25 years. Depending on the importance of the environmental factors, various neurotoxins are used to induce PD both in vivo and in vitro. Unlike other neurodegenerative diseases, PD can be induced in vivo using specific neurotoxic chemicals. However, no chemically induced PD model is available because of the sporadic nature of PD. Rotenone is a pesticide that accelerates the induction of PD and exhibits the highest toxicity in fish, unlike other pesticides. Therefore, in this study, we aimed to establish a model exhibiting PD pathologies such as dysfunction of DArgic neuron, aggregation of ɑ-synuclein, and behavioral abnormalities, which are known features of PD pathology, by rotenone exposure at an environmentally relevant concentration (30 nM) in developing zebrafish embryos. Our results provide direct evidence for the association between PD and muscle degeneration by confirming rotenone-induced muscle atrophy. Therefore, we conclude that the rotenone-induced model presents non-motor and motor defects with extensive studies related to muscle atrophy.

Co-exposure to microplastic and plastic additives causes development impairment in zebrafish embryos

Since the run off of microplastic and plastic additives into the aquatic environment through the disposal of plastic products, we investigated the adverse effects of co-exposure to microplastics and plastic additives on zebrafish embryonic development. To elucidate the combined effects between microplastic mixtures composed of microplastics and plastic additives in zebrafish embryonic development, polystyrene (PS), bisphenol S (BPS), and mono-(2-ethylhexyl) phthalate (MEHP) were chosen as a target contaminant. Based on non-toxic concentration of each contaminant in zebrafish embryos, microplastic mixtures which is consisted of binary and ternary mixed forms were prepared. A strong phenotypic toxicity to zebrafish embryos was observed in the mixtures composed with non-toxic concentration of each contaminant. In particular, the mixture combination with ≤ EC10 values for BPS and MEHP showed a with a strong synergistic effect. Based on phenotypic toxicity to zebrafish embryos, change of transcription levels for target genes related to cell damage and thyroid hormone synthesis were analyzed in the ternary mixtures with low concentrations that were observed non-toxicity. Compared with the control group, cell damage genes linked to the oxidative stress response and thyroid hormone transcription factors were remarkably down-regulated in the ternary mixture-exposed groups, whereas the transcriptional levels of cyp1a1 and p53 were significantly up-regulated in the ternary mixture-exposed groups (P < 0.05). These results demonstrate that even at low concentrations, exposure to microplastic mixtures can cause embryonic damage and developmental malformations in zebrafish, depending on the mixed concentration-combination. Consequently, our findings will provide data to examine the action mode of zebrafish developmental toxicity caused by microplastic mixtures exposure composed with microplastics and plastic additives.

A Narrative Review of the Published Pre-Clinical Evaluations: Multiple Effects of Arachidonic Acid, its Metabolic Enzymes and Metabolites in Epilepsy

Arachidonic acid (AA), an important polyunsaturated fatty acid in the brain, is hydrolyzed by a direct action of phospholipase A2 (PLA2) or through the combined action of phospholipase C and diacylglycerol lipase, and released into the cytoplasm. Various derivatives of AA can be synthesized mainly through the cyclooxygenase (COX), lipoxygenase (LOX) and cytochrome P450 (P450) enzyme pathways. AA and its metabolic enzymes and metabolites play important roles in a variety of neurophysiological activities. The abnormal metabolites and their catalytic enzymes in the AA cascade are related to the pathogenesis of various central nervous system (CNS) diseases, including epilepsy. Here, we systematically reviewed literatures in PubMed about the latest randomized controlled trials, animal studies and clinical studies concerning the known features of AA, its metabolic enzymes and metabolites, and their roles in epilepsy. The exclusion criteria include non-original studies and articles not in English.

Chemically-induced epileptic seizures in zebrafish: A systematic review

The use of zebrafish as a model organism is gaining evidence in the field of epilepsy as it may help to understand the mechanisms underlying epileptic seizures. As zebrafish assays became popular, the heterogeneity between protocols increased, making it hard to choose a standard protocol to conduct research while also impairing the comparison of results between studies. We conducted a systematic review to comprehensively profile the chemically-induced seizure models in zebrafish. Literature searches were performed in PubMed, Scopus, and Web of Science, followed by a two-step screening process based on inclusion/exclusion criteria. Qualitative data were extracted, and a sample of 100 studies was randomly selected for risk of bias assessment. Out of the 1058 studies identified after removing duplicates, 201 met the inclusion criteria. We found that the most common chemoconvulsants used in the reviewed studies were pentylenetetrazole (n = 180), kainic acid (n = 11), and pilocarpine (n = 10), which increase seizure severity in a dose-dependent manner. The main outcomes assessed were seizure scores and locomotion. Significant variability between the protocols was observed for administration route, duration of exposure, and dose/concentration. Of the studies subjected to risk of bias assessment, most were rated as low risk of bias for selective reporting (94%), baseline characteristics of the animals (67%), and blinded outcome assessment (54%). Randomization procedures and incomplete data were rated unclear in 81% and 68% of the studies, respectively. None of the studies reported the sample size calculation. Overall, these findings underscore the need for improved methodological and reporting practices to enhance the reproducibility and reliability of zebrafish models for studying epilepsy. Our study offers a comprehensive overview of the current state of chemically-induced seizure models in zebrafish, highlighting the common chemoconvulsants used and the variability in protocol parameters. This may be particularly valuable to researchers interested in understanding the underlying mechanisms of epileptic seizures and screening potential drug candidates in zebrafish models.

Zebrafish as an Innovative Tool for Epilepsy Modeling: State of the Art and Potential Future Directions

This article discusses the potential of Zebrafish (ZF) (Danio Rerio), as a model for epilepsy research. Epilepsy is a neurological disorder affecting both children and adults, and many aspects of this disease are still poorly understood. In vivo and in vitro models derived from rodents are the most widely used for studying both epilepsy pathophysiology and novel drug treatments. However, researchers have recently obtained several valuable insights into these two fields of investigation by studying ZF. Despite the relatively simple brain structure of these animals, researchers can collect large amounts of data in a much shorter period and at lower costs compared to classical rodent models. This is particularly useful when a large number of candidate antiseizure drugs need to be screened, and ethical issues are minimized. In ZF, seizures have been induced through a variety of chemoconvulsants, primarily pentylenetetrazol (PTZ), kainic acid (KA), and pilocarpine. Furthermore, ZF can be easily genetically modified to test specific aspects of monogenic forms of human epilepsy, as well as to discover potential convulsive phenotypes in monogenic mutants. The article reports on the state-of-the-art and potential new fields of application of ZF research, including its potential role in revealing epileptogenic mechanisms, rather than merely assessing iatrogenic acute seizure modulation.

Evaluation of 5-[(Z)-(4-nitrobenzylidene)]-2-(thiazol-2-ylimino)-4-thiazolidinone (Les-6222) as Potential Anticonvulsant Agent

It was determined that the studied 5-[(Z)-(4-nitrobenzylidene)]-2-(thiazol-2-ylimino)-4-thiazolidinone (Les-6222) affects the cyclooxygenase pathway of the arachidonic acid cascade, the markers of damage to neurons on models of PTZ kindling. In the model of chronic epileptogenesis in mice (pentylenetetrazole kindling), a 4-thiazolidinone derivative showed high anticonvulsant activity, which is weaker than the effect of sodium valproate and higher than Celecoxib. The mentioned compound has a pronounced anti-inflammatory effect in the brain on the background of the PTZ kindling, reliably inhibiting COX-1 and COX-2. The predominant inhibition of COX-2 by 44.5% indicates this enzyme’s high selectivity of Les-6222. According to the molecular docking study results, the studied compound revealed the properties of COX-1/COX-2 inhibitor and especially 5-LOX/FLAP. The decreasing content of 8-isoprostane in the brain of mice of the Les-6222 group indicates a beneficial effect on cell membranes in the background of oxidative stress during the long-term administration of PTZ. In addition, Les-6222 significantly decreased the content of neuron-specific enolase, indicating neuroprotective properties in the background of chronic epileptogenesis. The obtained results experimentally substantiate the feasibility of further developing Les-6222 as a promising anticonvulsant agent.

Thiamine alleviates cognitive impairment and epileptogenesis by relieving brain inflammation in PTZ-induced kindling rat model

OBJECTIVE

Epileptogenesis, the process by which the brain becomes epileptic, is related to neuroinflammation, hyperexcitability cognitive deficits. Evidence suggests that improving brain inflammation can inhibit the epileptogenesis process and help the emergence of new drugs for the treatment of epilepsy. Therefore, the PTZ kindling model of epilepsy was utilized to assess the neuroprotective role of thiamine in epileptogenesis.

METHODS

Male rats were exposed to PTZ-induced kindling and pretreated with low thiamine (25 mg/kg) or high thiamine (50 mg/kg). Cyclooxygenase (COX-1 and COX-2), interleukin 1-beta (IL-1β), tumor necrosis factor-alpha (TNF-α), and nuclear factor-κB (NF-κB) concentrations in the brain were analyzed using biochemical assays. Cognitive function was evaluated using the passive avoidance test.

RESULTS

Thiamine ameliorated epileptogenesis and enhanced the rats' performance in the passive avoidance test. Also, thiamine significantly decreased the level of neuroinflammatory mediators in the brain induced by PTZ.

CONCLUSION

These results provide evidence that thiamine alleviates PTZ-induced neuroinflammation and cognitive impairments.

How to Find Candidate Drug-targets for Antiepileptogenic Therapy?

Although over 25 antiepileptic drugs (AEDs) have become currently available for clinical use, the incidence of epilepsy worldwide and the proportions of drug-resistant epilepsy among them are not significantly reduced during the past decades. Traditional screens for AEDs have been mainly focused on their anti-ictogenic roles, and their efficacies primarily depend on suppressing neuronal excitability or enhancing inhibitory neuronal activity, almost without the influence on the epileptogenesis or with inconsistent results from different studies. Epileptogenesis refers to the pathological process of a brain from its normal status to the alterations with the continuous prone of unprovoked spontaneous seizures after brain insults, such as stroke, traumatic brain injury, CNS infectious, and autoimmune disorders, and even some specific inherited conditions. Recently growing experimental and clinical studies have discovered the underlying mechanisms for epileptogenesis, which are multi-aspect and multistep. These findings provide us a number of interesting sites for antiepileptogenic drugs (AEGDs). AEGDs have been evidenced as significantly roles of postponing or completely blocking the development of epilepsy in experimental models. The present review will introduce potential novel candidate drug-targets for AEGDs based on the published studies.

Evaluation of Anticonvulsant Activity of Dual COX-2/5-LOX Inhibitor Darbufelon and Its Novel Analogues

Neuroinflammation is an integral part of epilepsy pathogenesis and other convulsive conditions, and non-steroidal anti-inflammatory drugs (NSAIDs) present a potent tool for the contemporary search and design of novel anticonvulsants. In the present paper, evaluation of the anticonvulsant activity of the potential NSAID dual COX-2/5-LOX inhibitor darbufelone methanesulfonate using an scPTZ model in mice in dose 100 mg/kg is reported. Darbufelone possesses anticonvulsant properties in the scPTZ model and presents interest for in-depth studies as a possible anticonvulsant multi-target agent with anti-inflammatory activity. The series of 4-thiazolidinone derivatives have been synthesized following the analogue-based drug design and hybrid-pharmacophore approach using a darbufelone matrix. The synthesized derivatives showed a significant protection level for animals in the scPTZ model and are promising compounds for the design of potential anticonvulsants with satisfactory drug-like parameters.

Perillyl alcohol decreases the frequency and severity of convulsive-like behavior in the adult zebrafish model of acute seizures

This research aimed to assess the effect of perillyl alcohol (PA) on convulsive behavior in vivo using adult zebrafish (Danio rerio, both sexes). The seizures were induced with pentylenetetrazole (PTZ) intraperitoneally at 170 mg/kg, and diazepam (DZP) was used as the control anticonvulsant (2 mg/kg, oral); PA was tested at 10, 50, and 100 mg/kg orally. The groups had ten animals per group (total n = 60), observed for 10 minutes after seizure induction. We manually appraised typical seizure phenotypes for quantification and used an animal tracking software (Toxtrac) to assess the motor parameters. Next, we sought to find a mechanism of action for PA anticonvulsant activity in silico using a structure-based activity prediction server and molecular docking. The results show that PTZ induced seizure-like behavior in all untreated animals with hyperlocomotion episodes, seizure itself, posture loss, and immobility. DZP inhibited the seizures in all animals of the positive control group. PA, in turn, inhibited the occurrence of seizures in a dose-dependent manner, with frequencies of 90%, 70%, and 40% (for 10, 50, and 100 mg/kg, respectively). The PA treatments also decreased several seizure endpoints in a dose-dependent manner. Also, the difference of the group treated with highest dose of PA was statistically significant compared with the negative control group for all the endpoints assessed (p < 0.05, Kruskal-Wallis). The in silico analyses suggested that PA can affect the GABAergic system, which might be involved in its anticonvulsant activity, but other mechanisms cannot be ruled out. Overall, our results suggest an anticonvulsant potential in perillyl alcohol.

Pharmacological appraisal of ligustrazine based cyclohexanone analogs as inhibitors of inflammatory markers

The targeting of pro-inflammatory enzymes becomes a therapeutic intervention when acute inflammation is proliferating in pathological conditions. This research is intended to carry out an evaluation of inhibiting and inducing enzymes with inflammatory associations with 28 cyclohexanone analogs based on the ligustrazine. Tests were undertaken with inhibitor screening assay kits using a range of synthetic compounds to investigate how they could inhibit the activity of cyclooxygenase (COX) enzymes, secretory phospholipase A₂ (sPLA₂), and lipoxygenase (LOX) enzyme. Significant and similar inhibitory activities against sPLA₂ with were noted with synthetic compounds which included 1f and 1g (IC₅₀ = 2.2 μM). The optimal inhibitory activity regarding LOX enzyme was shown with compounds 1d (IC₅₀ = 8.1 μM) and 1e (IC₅₀ = 7.5 μM). Additionally, the compounds 1b, 1d, 1e, 2n, and 2o were shown to be significant inhibitors of COX-1 activity with IC₅₀ values 0.09 to 0.7 μM. The outcomes of assays for COX inhibition demonstrated that the same compounds had a further strong inhibitive influence on the COX-2 enzyme, and certain compounds such as 1d, 1e, and 2n demonstrated enhanced potency compared with positive controls.

An update of cyclooxygenase (COX)-inhibitors in epilepsy disorders

INTRODUCTION

Neuroinflammation has a critical role in brain disorders. Cyclooxygenase (COX) is one of the principal drug targets for the reduction of neuroinflammation; however, studies have yielded mixed results for COX-inhibitors in the treatment of diverse acute and chronic models of epilepsy.

AREAS COVERED

The article covers the effects of COX-inhibitors in epilepsy disorders. A considerable emphasis has been placed on the antiepileptic and 'disease-modifying' properties of COX-1 and COX-2 inhibitors in various preclinical epilepsy models.

EXPERT OPINION

The effect of COX-inhibitors on epilepsy is inconclusive. Studies have indicated beneficial effects in preclinical models; however, proconvulsant or no effects have also been observed. These molecules may have a bidirectional role with early neuroprotective and delayed neurotoxic effects. Further systematic preclinical studies to establish the use of COX-inhibitors in epilepsy are necessary.

A Systematic Review on Non-mammalian Models in Epilepsy Research

Epilepsy is a common neurological disorder characterized by seizures which result in distinctive neurobiological and behavioral impairments. Not much is known about the causes of epilepsy, making it difficult to devise an effective cure for epilepsy. Moreover, clinical studies involving epileptogenesis and ictogenesis cannot be conducted in humans due to ethical reasons. As a result, animal models play a crucial role in the replication of epileptic seizures. In recent years, non-mammalian models have been given a primary focus in epilepsy research due to their advantages. This systematic review aims to summarize the importance of non-mammalian models in epilepsy research, such as in the screening of anti-convulsive compounds. The reason for this review is to integrate currently available information on the use and importance of non-mammalian models in epilepsy testing to aid in the planning of future studies as well as to provide an overview of the current state of this field. A PRISMA model was utilized and PubMed, Springer, ScienceDirect and SCOPUS were searched for articles published between January 2007 and November 2017. Fifty-one articles were finalized based on the inclusion/exclusion criteria and were discussed in this review. The results of this review demonstrated the current use of non-mammalian models in epilepsy research and reaffirmed their potential to supplement the typical rodent models of epilepsy in future research into both epileptogenesis and the treatment of epilepsy. This review also revealed a preference for zebrafish and fruit flies in lieu of other non-mammalian models, which is a shortcoming that should be corrected in future studies due to the great potential of these underutilized animal models.

The role of inflammation in the development of epilepsy

Epilepsy, a neurological disease characterized by recurrent seizures, is often associated with a history of previous lesions in the nervous system. Impaired regulation of the activation and resolution of inflammatory cells and molecules in the injured neuronal tissue is a critical factor to the development of epilepsy. However, it is still unclear as to how that unbalanced regulation of inflammation contributes to epilepsy. Therefore, one of the goals in epilepsy research is to identify and elucidate the interconnected inflammatory pathways in systemic and neurological disorders that may further develop epilepsy progression. In this paper, inflammatory molecules, in neurological and systemic disorders (rheumatoid arthritis, Crohn’s, Type I Diabetes, etc.) that could contribute to epilepsy development, are reviewed.

Understanding the neurobiology of inflammation in epileptogenesis will contribute to the development of new biomarkers for better screening of patients at risk for epilepsy and new therapeutic targets for both prophylaxis and treatment of epilepsy.

A crystallographic and theoretical study of an (E)-2-Hydroxyiminoethanone derivative: prediction of cyclooxygenase inhibition selectivity of stilbenoids by MM-PBSA and the role of atomic charge

We recently reported that the hydroxyiminoethanone derivative, (E)-OXM, behaves as a highly selective COX-1 inhibitor (COX-1 SI = 833), and also an interesting scaffold with unique characteristics. In the current study, a comprehensive crystallographic and computational study was performed to elucidate its conformational stability and pharmacological activity. Its conformational energy was studied at the B3LYP/6-311G** level of theory and compared to the single-crystal X-ray diffraction data. In addition, computational studies of three structurally different stilbenoid derivatives used as selective COX-1 or COX-2 inhibitors were undertaken to predict their COX selectivity potentials. Flexible docking was performed for all compounds at the active site of both COX-1 and COX-2 enzymes by considering some of the key residues as flexible during the docking operation. In the next step, molecular dynamic simulation and binding free energy calculations were performed by MM-PBSA. Final results were found to be highly dependent on the atomic charges of the inhibitors and the choice of force field used to calculate the atomic charges. The binding conformation of the hydroxyiminoethanone derivative is highly correlated with the type of COX isoform inhibited. Our predictive approach can truly predict the cyclooxygenase inhibition selectivity of stilbenoid inhibitors.

Syntaxin 1B Mediates Berberine's Roles in Epilepsy-Like Behavior in a Pentylenetetrazole-Induced Seizure Zebrafish Model

Epilepsy is a neuronal dysfunction syndrome characterized by transient and diffusely abnormal discharges of neurons in the brain. Previous studies have shown that mutations in the syntaxin 1b (stx1b) gene cause a familial, fever-associated epilepsy syndrome. It is unclear as to whether the stx1b gene also correlates with other stimulations such as flashing and/or mediates the effects of antiepileptic drugs. In this study, we found that the expression of stx1b was present mainly in the brain and was negatively correlated with seizures in a pentylenetetrazole (PTZ)-induced seizure zebrafish model. The transcription of stx1b was inhibited by PTZ but rescued by valproate, a broad-spectrum epilepsy treatment drug. In the PTZ-seizure zebrafish model, stx1b knockdown aggravated larvae hyperexcitatory swimming and prompted abnormal trajectory movements, particularly under lighting stimulation; at the same time, the expression levels of the neuronal activity marker gene c-fos increased significantly in the brain. In contrast, stx1b overexpression attenuated seizures and decreased c-fos expression levels following PTZ-induced seizures in larvae. Thus, we speculated that a deficiency of stx1b gene expression may be related with the onset occurrence of clinical seizures, particularly photosensitive seizures. In addition, we found that berberine (BBR) reduced larvae hyperexcitatory locomotion and abnormal movement trajectory in a concentration-dependent manner, slowed down excessive photosensitive seizure-like swimming, and assisted in the recovery of the expression levels of STX1B. Under the downregulation of STX1B, BBR's roles were limited: specifically, it only slightly regulated the levels of the two genes stx1b and c-fos and the hyperexcitatory motion of zebrafish in dark conditions and had no effect on the overexcited swimming behavior seen in conjunction with lighting stimulation. These findings further demonstrate that STX1B protein levels are negatively correlated with a seizure and can decrease the sensitivity of the photosensitive response in a PTZ-induced seizure zebrafish larvae; furthermore, STX1B may partially mediate the anticonvulsant effect of BBR. Additional investigation regarding the relationship between STX1B, BBR, and seizures could provide new cues for the development of novel anticonvulsant drugs.

Measuring drug absorption improves interpretation of behavioral responses in a larval zebrafish locomotor assay for predicting seizure liability

INTRODUCTION

Unanticipated effects on the central nervous system are a concern during new drug development. A larval zebrafish locomotor assay can reveal seizure liability of experimental molecules before testing in mammals. Relative absorption of compounds by larvae is lacking in prior reports of such assays; having those data may be valuable for interpreting seizure liability assay performance.

METHODS

Twenty-eight reference drugs were tested at multiple dose levels in fish water and analyzed by a blinded investigator. Responses of larval zebrafish were quantified during a 30min dosing period. Predictive metrics were calculated by comparing fish activity to mammalian seizure liability for each drug. Drug level analysis was performed to calculate concentrations in dose solutions and larvae. Fifteen drug candidates with neuronal targets, some having preclinical convulsion findings in mammals, were tested similarly.

RESULTS

The assay has good predictive value of established mammalian responses for reference drugs. Analysis of drug absorption by larval fish revealed a positive correlation between hyperactive behavior and pro-convulsive drug absorption. False negative results were associated with significantly lower compound absorption compared to true negative, or true positive results. The predictive value for preclinical toxicology findings was inferior to that suggested by reference drugs.

DISCUSSION

Disproportionately low exposures in larvae giving false negative results demonstrate that drug exposure analysis can help interpret results. Due to the rigorous testing commonly performed in preclinical toxicology, predicting convulsions in those studies may be more difficult than predicting effects from marketed drugs.