Assessment of the Anticonvulsant Potency of Ursolic Acid in Seizure Threshold Tests in Mice

AMPK role in epilepsy: a promising therapeutic target?

Epilepsy is a complex and multifaceted neurological disorder characterized by spontaneous and recurring seizures. It poses significant therapeutic challenges due to its diverse etiology and often-refractory nature. This comprehensive review highlights the pivotal role of AMP-activated protein kinase (AMPK), a key metabolic regulator involved in cellular energy homeostasis, which may be a promising therapeutic target for epilepsy. Current therapeutic strategies such as antiseizure medication (ASMs) can alleviate seizures (up to 70%). However, 30% of epileptic patients may develop refractory epilepsy. Due to the complicated nature of refractory epilepsy, other treatment options such as ketogenic dieting, adjunctive therapy, and in limited cases, surgical interventions are employed. These therapy options are only suitable for a select group of patients and have limitations of their own. Current treatment options for epilepsy need to be improved. Emerging evidence underscores a potential association between impaired AMPK functionality in the brain and the onset of epilepsy, prompting an in-depth examination of AMPK's influence on neural excitability and ion channel regulation, both critical factors implicated in epileptic seizures. AMPK activation through agents such as metformin has shown promising antiepileptic effects in various preclinical and clinical settings. These effects are primarily mediated through the inhibition of the mTOR signaling pathway, activation of the AMPK-PI3K-c-Jun pathway, and stimulation of the PGC-1α pathway. Despite the potential of AMPK-targeted therapies, several aspects warrant further exploration, including the detailed mechanisms of AMPK's role in different brain regions, the impact of AMPK under various conditional circumstances such as neural injury and zinc toxicity, the long-term safety and efficacy of chronic metformin use in epilepsy treatment, and the potential benefits of combination therapy involving AMPK activators. Moreover, the efficacy of AMPK activators in refractory epilepsy remains an open question. This review sets the stage for further research with the aim of enhancing our understanding of the role of AMPK in epilepsy, potentially leading to the development of more effective, AMPK-targeted therapeutic strategies for this challenging and debilitating disorder.

Ursolic acid inhibits the synaptic release of glutamate and prevents glutamate excitotoxicity in rats

The present study evaluated the effect of ursolic acid, a natural pentacyclic triterpenoid, on glutamate release in rat cortical nerve terminals (synaptosomes) and its neuroprotection in a kainic acid-induced excitotoxicity rat model. In cortical synaptosomes, ursolic acid produced a concentration-dependent inhibition of evoked glutamate release with a half-maximum inhibition of release value of 9.5 μM, and calcium-free medium and the P/Q -type Ca2+ channel blocker, ω-agatoxin IVA, but not ω-conotoxin GVIA, an N-type Ca2+ channel blocker, prevented the ursoloic acid effect. The molecular docking study indicated that ursolic acid interacted with P/Q-type Ca2+ channels. Ursolic acid also significantly decreased the depolarization-induced activation of Ca2+/calmodulin-dependent protein kinase II (CaMKII) and the subsequent phosphorylation of synapsin I, and the ursolic acid effect on evoked glutamate release was inhibited by the CaMKII inhibitor KN 62 in synaptosomes. In addition, in rats that were intraperitoneally injected with ursolic acid 30 min before kainic acid intraperitoneal injection, cortical neuronal degeneration was attenuated. This effect of ursolic acid in the improvement of kainic acid-induced neuronal damage was associated with the reduction of kainic acid-induced glutamate increase in the cortex of rats; this was characterized by the reduction of glutamate and glutaminase levels and elevation of glutamate dehydrogenase, glutamate transporter 1, glutamate-aspartate transporter, and glutamine synthetase protein levels. These results suggest that ursolic acid inhibits glutamate release from cortical synaptosomes by decreasing P/Q-type Ca2+ channel activity and subsequently suppressing CaMKII and exerts a preventive effect against glutamate neurotoxicity by controlling glutamate levels.

Oleanolic acid and ursolic acid: therapeutic potential in neurodegenerative diseases, neuropsychiatric diseases and other brain disorders

Brain disorders such as neurodegenerative diseases and neuropsychiatric diseases have become serious threatens to human health and quality of life. Oleanolic acid (OA) and ursolic acid (UA) are pentacyclic triterpenoid isomers widely distributed in various plant foods and Chinese herbal medicines. Accumulating evidence indicates that OA and UA exhibit neuroprotective effects on multiple brain disorders. Therefore, this paper reviews researches of OA and UA on neurodegenerative diseases, neuropsychiatric diseases and other brain disorders including ischemic stroke, epilepsy, etc, as well as the potential underlying molecular mechanisms.

New Ketene Dithioacetals Generated from 2-Nitroperchlorobutadiene and Investigation of Their Antibacterial, Antifungal, Anticonvulsant and Antidepressant Activities

The ketene dithioacetal 3 generated from 2-nitroperchlorobutadiene 1 reacted with various heterocyclic amines and aliphatic, aromatic and heterocyclic thiols to produce functionalized new ketene-N,S,S-acetals and S,S,S-acetals 4a-f, 5a-h as heterocyclic dithiolanes. They were separated/purified by chromatographic methods and their exact structure characterization were made clear by spectroscopic methods. These compounds synthesized could act as effective drugs for versatile activity. Evaluation of the antimicrobial effect of the obtained substances determined derivatives 4e and 5h, which have MIC=15.6 μg/mL for the test culture of Mycobacterium luteum bacteria closing to the control drug Vancomycin. The obtained compounds can be proposed as a promising synthetic objects for future molecular design to enhance the antimicrobial action. Ketene dithioacetals 3, 4a, 4b, 4e, 5g (50 mg/kg) exhibited antiseizure effect comparable with reference drug (valproic acid) on the model of pentylenetetrazole-induced convulsions after single oral administration both at 3 h and 24 h. Furthermore, tested dithioacetals possessed prolonged antidepressant activity in forced swim test (FST) considerable decreasing the duration of immobility time compared to reference drug amitriptyline. This is the first study of the investigation of anticonvulsant and antidepressant activities of ketene dithioacetals.

Anticonvulsant Effect of Minocycline on Pentylenetetrazole-Induced Seizure in Mice: Involvement of 5-HT3 Receptor

Minocycline, widely used as an antibiotic, has recently been found to have an anti-inflammatory, neuroprotective and anticonvulsant effects. This study was aimed to investigate the anticonvulsant effect of acute administration of minocycline on pentylenetetrazole (PTZ)-induced seizures considering the possible involvement of 5-HT₃ receptor in this effect. For this purpose, seizures were induced by intravenous PTZ infusion. All drugs were administrated by intraperitoneal (i.p.) route before PTZ injection. Also, 1-(m-chlorophenyl)-biguanide (mCPBG, a 5-HT₃ receptor agonist) and Tropisetron (a 5-HT₃ receptor antagonist) were used 45 minutes before minocycline treatment. Our results demonstrate that acute minocycline treatment (80 and 120 mg/kg) increased the seizure threshold. In addition, the 5-HT₃ antagonist, tropisetron, at doses that had no effect on seizure threshold, augmented the anticonvulsant effect of minocycline (40 mg/kg), while mCPBG (0.2 mg/kg) blunted the anticonvulsant effect of minocycline (80 mg/kg). In conclusion, our findings revealed that the anticonvulsant effect of minocycline is mediated, at least in part, by inhibition of 5-HT₃ receptor.

Phenylalanine-Based AMPA Receptor Antagonist as the Anticonvulsant Agent with Neuroprotective Activity-In Vitro and In Vivo Studies

Trying to meet the multitarget-directed ligands strategy, a series of previously described aryl-substituted phenylalanine derivatives, reported as competitive antagonists of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, were screened in vitro for their free-radical scavenging and antioxidant capacity in two different assays: ferric reducing antioxidant power (FRAP) and oxygen radical absorbance capacity fluorescent (ORAC-FL) assays. The most active antioxidants 1 and 8 were further examined to evaluate their neuroprotective properties in vitro. In this study, compound 1 showed a significant neuroprotective effect against the neurotoxin 6-hydroxydopamine in neuroblastoma SH-SY5Y and IMR-32 cell lines. Both compounds also showed prevention from high levels of reactive oxygen species (ROS) in SH-SY5Y cells. Furthermore, the desired monoamine oxidase B (MAO-B) inhibition effect (IC₅₀ = 278 ± 29 nM) for 1 was determined. No toxic effects up to 100 µM of 1 and 8 against neuroblastoma cells were observed. Furthermore, in vivo studies showed that compound 1 demonstrated significant anticonvulsant potential in 6-Hz test, but in neuropathic pain models its antiallodynic and antihyperalgesic properties were not observed. Concluding, the compound 1 seems to be of higher importance as a new phenylalanine-based lead candidate due to its confirmed promise in in vitro and in vivo anticonvulsant activity.

Protective Effects of Anthocleista djalonensis Extracts against Pentylenetetrazole-Induced Epileptic Seizures and Neuronal Cell Loss: Role of Antioxidant Defense System

Oxidative stress and neurodegeneration are involved in the initiation of epileptogenesis and progression of epileptic seizures. This study was aimed at investigating the anticonvulsant, antioxidant, and neuroprotective properties of active fractions isolated from Anthocleista djalonensis root barks in pentylenetetrazole mouse models of epileptic seizures. Bioactive-guided fractionation of Anthocleista djalonensis (AFAD) extracts using acute pentylenetetrazole (90 mg/kg) induced generalised tonic-clonic seizures, which afforded a potent anticonvulsant fraction (FPool 5). Further fractionation of AFAD was performed by high-performance liquid chromatography, which yielded fifteen subfractions, which were chemically characterised. In addition, AFAD was tested against convulsions or spontaneous kindled seizures induced, respectively, by acute (50 mg/kg) or subchronic (30 mg/kg) injection of pentylenetetrazole. Finally, oxidative stress markers, brain GABA content, and neuronal cell loss were evaluated in AFAD-treated pentylenetetrazole-kindled mice. Administration of AFAD significantly protected mice against acute pentylenetetrazole (90 mg/kg)-induced convulsions. In acute pentylenetetrazole (50 mg/kg)-induced hippocampal and cortical paroxysmal discharges, AFAD significantly decreased the number of crisis, the cumulative duration of crisis, and the mean duration of crisis. Additionally, AFAD significantly decreased the number of myoclonic jerks and improved the seizure score in subchronic pentylenetetrazole-induced kindled seizures. The pentylenetetrazole-induced alteration of oxidant-antioxidant balance, GABA concentration, and neuronal cells in the brain were attenuated by AFAD treatment. This study showed that AFAD protected mice against pentylenetetrazole-induced epileptic seizures possibly through the enhancement of antioxidant defence and GABAergic signalling. These events might be correlated with the amelioration of neuronal cell loss; hence, AFAD could be a potential candidate for the treatment of epilepsy.

The triterpenoid ursolic acid ameliorates stress in Caenorhabditis elegans by affecting the depression-associated genes skn-1 and prdx2

INTRODUCTION

Depression is one of the leading causes of death worldwide. Lower antioxidant concentrations and increased oxidative stress levels contribute to the development of depression. Effective and tolerable medications are urgently needed. Nrf2 and PRDX2 are promising targets in the treatment of oxidative stress and, therefore, promising for the development of novel antidepressants. Ursolic acid (UA), a natural triterpenoid found in various plants is known to exert neuroprotective and antioxidant effects. Skn-1 (which corresponds to human Nrf2) and prdx2 deficient mutants of the nematode Caenorhabditis elegans are suitable models to study the effect of UA on these targets. Additionally, stress assays are used to mimic stress or depressed state.

METHODS

We examined the antioxidant activity of UA in Caenorhabditis elegans wildtype and skn-1- and prdx2-deficient strains by H2DCF-DA and juglone assays as well as osmotic and heat stress assays. Additionally, we analyzed the binding of UA to human PRDX2 and Skn-1 proteins by molecular docking and microscale thermophoresis.

RESULTS

UA exerted strong antioxidant activities. Additionally, induction of stress resistance towards osmotic and heat stress was observed. qRT-PCR revealed that UA upregulated the gene expression of skn-1 and prdx2. Molecular docking studies supported these findings.

CONCLUSION

Our findings implicate that the strong antioxidant activity of UA may exert anti-depressive effects by its interaction with the Skn-1 transcription factor, which is part of a detoxification network, and the antioxidant PRDX2 protein, which protects the organism from the detrimental effects of radical oxygen species.

Identification of Potential Antiseizure Agents in Boswellia sacra using In Vivo Zebrafish and Mouse Epilepsy Models

The resin of the tree Boswellia sacra Flueck. (synonym: B. carterii; Burseraceae), also known as "frankincense", is a traditional remedy used for central nervous system disorders in East Africa. Here we report the evaluation of its antiseizure activity in zebrafish and mouse epilepsy models to identify novel antiseizure compounds. The resin was extracted by solvents of increasing polarity. The hexane extract demonstrated the strongest antiseizure activity and was therefore subjected to bioactivity-guided isolation, which leaded to the isolation of eight terpene derivatives. A new prenylbicyclogermacrene derivative (2) was isolated along with seven other compounds (1, 3-8). Among them, the triterpene β-boswellic acid (5) showed the strongest activity and reduced 90% of pentylenetetrazole (PTZ)-induced seizures at 100 μg/mL. In parallel to B. sacra, a commercial extract of Boswellia serrata was also evaluated and showed moderate bioactivity (45% reduction at 30 μg/mL). The extract of B. serrata was subjected to targeted isolation of other boswellic acid derivatives (9-13), which were evaluated for antiseizure activity in comparison with 5. In the whole series, β-boswellic acid (5) was the most active (60% reduction at 200 μM), and its potency was also confirmed with its purchased standard (S5). Pure nanoparticles of S5 and a commercially formulated extract of B. serrata were tested in a PTZ-kindling mouse seizure model. This notably revealed that the S5 administration reduced seizures by 50% in this mouse model, which was consistent with its detection and quantification in plasma and brain samples. This study and the preclinical evaluation performed indicate that β-boswellic acid, common to various species of Boswellia, has some potential as an antiseizure agent.

Natural Medicines for the Treatment of Epilepsy: Bioactive Components, Pharmacology and Mechanism

Epilepsy is a chronic disease that can cause temporary brain dysfunction as a result of sudden abnormal discharge of the brain neurons. The seizure mechanism of epilepsy is closely related to the neurotransmitter imbalance, synaptic recombination, and glial cell proliferation. In addition, epileptic seizures can lead to mitochondrial damage, oxidative stress, and the disorder of sugar degradation. Although the mechanism of epilepsy research has reached up to the genetic level, the presently available treatment and recovery records of epilepsy does not seem promising. Recently, natural medicines have attracted more researches owing to their low toxicity and side-effects as well as the excellent efficacy, especially in chronic diseases. In this study, the antiepileptic mechanism of the bioactive components of natural drugs was reviewed so as to provide a reference for the development of potential antiepileptic drugs. Based on the different treatment mechanisms of natural drugs considered in this review, it is possible to select drugs clinically. Improving the accuracy of medication and the cure rate is expected to compensate for the shortage of the conventional epilepsy treatment drugs.

Involvement of the Benzodiazepine Site in the Anticonvulsant Activity of Tapinanthus globiferus against Pentylenetetrazole-induced Seizures in Mice

Tapinanthus globiferus is often referred to as an all-purpose herb for the treatment of stroke and epilepsy. The present study investigates the anticonvulsant effect of methanolic leaf extract, active fractions, and lupeol (isolate) of Tapinanthus globiferus in mice as well as the underlying mechanisms. Following phytochemical studies of T. globiferus, preliminary assays were performed to evaluate MLE-induced toxic effect and behavioral changes. The pentylenetetrazol (70 mg/kg, i. p.)-induced seizure was evaluated in mice that were pretreated orally with vehicle 10 mL/kg, MLE (4, 20, or 100 mg/kg), fractions (F1 to F6), lupeol 10 mg/kg or diazepam (3 mg/kg). Methanolic leaf extract preserved neuron viability as well as the relative organ weight, and hematological and biochemical parameters. The behavioral endpoints, neuromuscular coordination, and sensory response parameters revealed a dose-dependent effect of methanolic leaf extract. This extract, active fractions, lupeol, and diazepam potentiated the hypno-sedative effect of the barbiturate and attenuated PTZ-induced acute seizure. This antiseizure effect was completely reversed by flumazenil 2 mg/kg (benzodiazepine site antagonist). Altogether, the benzodiazepine site-mediated anticonvulsant effects of methanolic leaf extract, active fractions, and lupeol corroborate traditional application of T. globiferus against epilepsy.

Ursolic acid: A systematic review of its pharmacology, toxicity and rethink on its pharmacokinetics based on PK-PD model

Ursolic acid (UA) is a natural pentacyclic triterpenoid compound existing in various traditional Chinese medicinal herbs, and it possesses diverse pharmacological actions and some undesirable adverse effects, even toxicological activities. Due to UA's low solubility and poor bioavailability, and its interaction with gut microbiota after oral administration, the pharmacokinetics of UA remain elusive, leading to obscurity in the pharmacokinetics-pharmacodynamics (PK-PD) profile and relationship for UA. Based on literatures from PubMed, Google Scholar, ResearchGate, Web of Science and Wiley Online Library, with keywords of "pharmacology", "toxicology", "pharmacokinetics", "PK-PD" and "ursolic acid", herein we systematically review the pharmacology and toxicity of UA, and rethink on its pharmacokinetics on the basis of PK-PD model, and seek to delineate the underlying mechanisms for the characteristics of pharmacology and toxicology of UA, and for the pharmacokinetic features of UA particularly from the organ tropism and the interactions between UA and gut microbiota, and lay a solid foundation for development of UA-derived therapeutic agents in clinical settings.

Zebrafish-Based Screening of Antiseizure Plants Used in Traditional Chinese Medicine: Magnolia officinalis Extract and Its Constituents Magnolol and Honokiol Exhibit Potent Anticonvulsant Activity in a Therapy-Resistant Epilepsy Model

With the aim to discover interesting lead compounds that could be further developed into compounds active against pharmacoresistant epilepsies, we first collected 14 medicinal plants used in traditional Chinese medicine (TCM) against epilepsy. Of the six extracts that tested positive in a pentylenetetrazole (PTZ) behavioral zebrafish model, only the ethanol and acetone extracts from Magnolia officinalis (M. officinalis) also showed effective antiseizure activity in the ethylketopentenoate (EKP) zebrafish model. The EKP model is regarded as an interesting discovery platform to find mechanistically novel antiseizure drugs, as it responds poorly to a large number of marketed anti-epileptics. We then demonstrated that magnolol and honokiol, two major constituents of M. officinalis, displayed an effective behavioral and electrophysiological antiseizure activity in both the PTZ and the EKP models. Out of six structural analogues tested, only 4-O-methylhonokiol was active and to a lesser extent tetrahydromagnolol, whereas the other analogues (3,3'-dimethylbiphenyl, 2,2'-biphenol, 2-phenylphenol, and 3,3',5,5'-tetra-tert-butyl-[1,1'-biphenyl]-2,2'-diol) were not consistently active in the aforementioned assays. Finally, magnolol was also active in the 6 Hz psychomotor mouse model, an acute therapy-resistant rodent model, thereby confirming the translation of the findings from zebrafish larvae to mice in the field of epilepsy. We also developed a fast and automated power spectral density (PSD) analysis of local field potential (LFP) recordings. The PSD results are in agreement with the visual analysis of LFP recordings using Clampfit software and manually counting the epileptiform events. Taken together, screening extracts of single plants employed in TCM, using a combination of zebrafish- and mouse-based assays, allowed us to identify allyl biphenol as a chemical scaffold for the future development of compounds with potential activity against therapy-resistant epilepsies.

An interaction study of Ocimum sanctum L. and levetiracetam in pentylenetetrazole kindling model of epilepsy

ETHNOPHARMACOLOGICAL RELEVANCE

Ocimum sanctum L. commonly known as tulsi (synonym of Ocimum tenuiflorum L.) is widely used in Ayurveda medicine and is having multitude neuromodulatory effect including the anticonvulsant effect in acute seizure models as per previous studies. In India, it is used for the treatment of epilepsy as traditional medicine. However, its role in chronic seizure model and interaction with newer antiepileptic drugs has not been investigated, which will enhance its translational value.

AIM OF THE STUDY

Current study investigated the effect of Ocimum on chronic seizure model and its interaction with levetiracetam (LEV), a newer antiepileptic drug.

MATERIALS AND METHODS

The adjuvant role of Ocimum sanctum hydroalcoholic extracts (OSHE) 1000 mg/kg along with LEV 300 mg/kg was studied in adult male Wistar rats with mean weight of 227.84 ± 21.68 g using pentylenetetrazole (30 mg/kg, i.p.) kindling (K) (with maximum 24 injections on alternate days and challenge on 7th-day). Along with seizure score, neurobehavioral, brain tissue oxidative stress and histopathology status were assessed. Pharmacokinetic interaction was assessed between LEV and OSHE after 14 days of drug treatment.

RESULTS

K-LEV + OSHE had least seizure score during kindling and on the pentylenetetrazole-challenge test (p=0.031) than other kindling groups. Seizure protection was more in K-LEV + OSHE (85.72%) than others (K-LEV-42.86%, K-OSHE-42.86%, and K-Control-28.58%). Ocimum treated groups had better memory retention potential as evident from Morris water maze (MWM), passive avoidance test but not in an elevated plus maze test. Oxidative-stress was lower in Ocimum treated groups than K-Control group. As per histopathology, K-LEV + OSHE group had the least neuronal degeneration among kindling groups. There was no significant pharmacokinetic interaction between LEV and OSHE, except increased T_max in LEV + OSHE group than LEV alone (p=0.009).

CONCLUSIONS

Ocimum per se and combination with levetiracetam treatment exerted better seizure control, memory retention, oxidative stress reduction, and neuronal structure preservation than kindling control group. There was a very minimal drug interaction between Ocimum and LEV. So, Ocimum as an adjuvant to LEV may be shelpful in enhancing the antiepileptic effect and also in minimizing the adverse effects.

Antioxidant and Anti-inflammatory Mechanisms of Neuroprotection by Ursolic Acid: Addressing Brain Injury, Cerebral Ischemia, Cognition Deficit, Anxiety, and Depression

Ursolic acid (UA) is a pentacyclic triterpene which is found in common herbs and medicinal plants that are reputed for a variety of pharmacological effects. Both as an active principle of these plants and as a nutraceutical ingredient, the pharmacology of UA in the CNS and other organs and systems has been extensively reported in recent years. In this communication, the antioxidant and anti-inflammatory axis of UA's pharmacology is appraised for its therapeutic potential in some common CNS disorders. Classic examples include the traumatic brain injury (TBI), cerebral ischemia, cognition deficit, anxiety, and depression. The pharmacological efficacy for UA is demonstrated through the therapeutic principle of one drug → multitargets → one/many disease(s). Both specific enzymes and receptor targets along with diverse pharmacological effects associated with oxidative stress and inflammatory signalling are scrutinised.