Anticonvulsive and Neuroprotective Effects of Eupafolin in Rats Are Associated with the Inhibition of Glutamate Overexcitation and Upregulation of the Wnt/β-Catenin Signaling Pathway

The role of glutamate receptors and transporters in epilepsy: evidence from animal studies

Epilepsy encompasses a group of chronic brain disorders characterized by recurrent, hypersynchronous activity of neuronal clusters, with epileptic seizures being the primary manifestation of these disorders. The objective of epilepsy treatment is to prevent seizures with minimum adverse side effects. However, approximately 30 % of patients do not respond to available medications. One proposed mechanism of epileptogenesis is glutamate excitotoxicity. When released in excess or not appropriately removed from the synaptic cleft, glutamate hyperactivates receptors, causing a biochemical cascade, which culminates in seizures and cell death. The use of animal models is essential for uncovering potential epileptogenic pathways, understanding the role of receptors and transporters in excitotoxicity, and screening effective antiepileptic treatments. This review examines studies that investigate the role of glutamate transporters and receptors in excitotoxicity and epileptogenesis using animal models. For this, we searched through both PubMed/Medline and ScienceDirect databases. After applying the inclusion and exclusion criteria, 26 (twenty-six) studies were selected for analysis. The studies addressed key glutamate transporter family of excitatory amino acid transporters (EAATs) EAAT1, EAAT2, and EAAT3, responsible for glutamate clearance, as well as AMPA receptor subunits GluA1 and GluA2, NMDA receptor subunits GluN1, GluN2a, and GluN2b, and the metabotropic receptors mGluR5 and mGluR2/3. Results showed that the dysregulation of these transporters and receptors is associated to seizure induction and excitotoxic damage, pointing to their fundamental role in the mechanisms of excitotoxicity and epileptogenesis. These findings highlight the potential of targeting glutamate transporters and receptors to stabilize glutamate homeostasis as an intervention in epilepsy management.

Interplay of epilepsy and long-term potentiation: implications for memory

The interplay between long-term potentiation (LTP) and epilepsy represents a crucial facet in understanding synaptic plasticity and memory within neuroscience. LTP, a phenomenon characterized by a sustained increase in synaptic strength, is pivotal in learning and memory processes, particularly in the hippocampus. This review delves into the intricate relationship between LTP and epilepsy, exploring how alterations in synaptic plasticity mechanisms akin to those seen in LTP contribute to the hyperexcitable state of epilepsy. This state is conceptualized as a dysregulation between LTP and LTD (Long-term depression), leading to pathologically enhanced synaptic efficacy. Additionally, the role of neuroinflammation in both LTP and epilepsy is examined, highlighting how inflammatory mediators can influence synaptic plasticity. The dual role of neuroinflammatory pathways, enhancing or inhibiting LTP, is a focal area of ongoing research. The significance of various signaling pathways, including the MAPK, mTOR, and WNT/β-catenin pathways, in the modulation of synaptic plasticity and their relevance in both LTP and epilepsy. These pathways are instrumental in memory formation, consolidation, and epileptogenesis, illustrating a complex interaction between cellular mechanisms in the nervous system. Lastly, the role of calcium signaling in the relationship between LTP and epilepsy is scrutinized. Aberrant calcium signaling in epilepsy leads to an enhanced, yet pathologically altered, LTP. This dysregulation disrupts normal neural pathways, potentially leading to cognitive dysfunction, particularly in memory encoding and retrieval. The review emphasizes the need for targeted interventions in epilepsy that address cognitive functions alongside seizure control.

Wnt Signaling Modulators Exhibit Neuroprotective Effects via Combating Astrogliosis and Balancing Synaptic Density at Early and Late Stage Temporal Lobe Epilepsy

Temporal Lobe Epilepsy (TLE) is a severe neurological condition characterized by recurrent seizures that often do not respond well to available anti-seizure medications. TLE has been associated with epileptogenesis, a process that starts during the latent period following a neurologic insult and is followed by chronic phase. Recent research has linked canonical Wnt signaling to the pathophysiology of epileptogenesis and TLE. Our previous study demonstrated differential regulation of canonical Wnt signaling during early and late stage post status epilepticus (SE) induction. Building on these findings, our current study utilized Wnt modulators: GSK-3β inhibitor 6-bromoindirubin-3'-oxime (6-Bio) and disheveled inhibitor niclosamide and investigated their impact on canonical Wnt signaling during the early (30 days) and later stages (60 days) following SE induction. We assessed several parameters, including seizure frequency, astrogliosis, synaptic density, and neuronal counts in hippocampal tissue. We used immunohistochemistry and Nissl staining to evaluate gliosis, synaptic density, and neuronal counts in micro-dissected hippocampi. Western blotting was used to examine the expression of proteins involved in canonical Wnt/β-catenin signaling, and real-time PCR was conducted to analyze their relative mRNA expression. Wnt modulators, 6-Bio and Niclosamide were found to reduce seizure frequency and various other parameters including behavioral parameters, hippocampal morphology, astrogliosis and synaptic density at different stages of TLE.

NRICM101 prevents kainic acid-induced seizures in rats by modulating neuroinflammation and the glutamatergic system

Taiwan Chingguan Yihau (NRICM101) is a Traditional Chinese medicine (TCM) formula used to treat coronavirus disease 2019; however, its impact on epilepsy has not been revealed. Therefore, the present study evaluated the anti-epileptogenic effect of orally administered NRICM101 on kainic acid (KA)-induced seizures in rats and investigated its possible mechanisms of action. Sprague-Dawley rats were administered NRICM101 (300 mg/kg) by oral gavage for 7 consecutive days before receiving an intraperitoneal injection of KA (15 mg/kg). NRICM101 considerably reduced the seizure behavior and electroencephalographic seizures induced by KA in rats. NRICM101 also significantly decreased the neuronal loss and glutamate increase and increased GLAST, GLT-1, GAD67, GDH and GS levels in the cortex and hippocampus of KA-treated rats. In addition, NRICM101 significantly suppressed astrogliosis (as determined by decreased GFAP expression); neuroinflammatory signaling (as determined by reduced HMGB1, TLR-4, IL-1β, IL-1R, IL-6, p-JAK2, p-STAT3, TNF-α, TNFR1 and p-IκB levels, and increased cytosolic p65-NFκB levels); and necroptosis (as determined by decreased p-RIPK3 and p-MLKL levels) in the cortex and hippocampus of KA-treated rats. The effects of NRICM101 were similar to those of carbamazepine, a well-recognized antiseizure drug. Furthermore, no toxic effects of NRICM101 on the liver and kidney were observed in NRICM101-treated rats. The results indicate that NRICM101 has antiepileptogenic and neuroprotective effects through the suppression of the inflammatory cues (HMGB1/TLR4, Il-1β/IL-1R1, IL-6/p-JAK2/p-STAT3, and TNF-α/TNFR1/NF-κB) and necroptosis signaling pathways (TNF-α/TNFR1/RIP3/MLKL) associated with glutamate level regulation in the brain and is innocuous. Our findings highlight the promising role of NRICM101 in the management of epilepsy.

An innovative UPLC-MS/MS method for the quantitation and pharmacokinetics of eupafolin in rat plasma

In this experiment, a rapid and highly sensitive ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) technology was established and validated for the quantitation and pharmacokinetic analysis of eupafolin in rat plasma, utilizing licochalcone B as internal standard (IS). After liquid-liquid extraction of the analyte samples by ethyl acetate, chromatographic separation was achieved using a UPLC HSS T3 column under gradient elution conditions, with the mobile phase consisting of acetonitrile and water (with 0.1 % formic acid). Eupafolin was quantified by multiple reaction monitoring (MRM) in electrospray positive-ion mode (ESI+), employing the mass transition m/z 315.2 → 300.3 for eupafolin and m/z 285.4 → 270.3 for IS. Eupafolin demonstrated excellent linear relationship (r > 0.99) over the concentration range of 1.25-1250 ng/mL, with the lower limit of quantification (LLOQ) of the UPLC-MS/MS assay determined as 1.25 ng/mL. Method validation followed the bioanalytical method validation criteria outlined by the FDA. The accuracy of eupafolin ranged from 86.7 % to 111.2 %, and the precision was less than 12 %. The matrix effect was observed at 92.8 %-98.6 %, while the recoveries exceeded 83.2 %. The established UPLC-MS/MS assay was successfully employed for the pharmacokinetic evaluation of eupafolin in rats. The half-lives (t1/2z) were determined to be 1.4 ± 0.4 h and 2.5 ± 1.4 h for intravenous and oral administration, respectively. Notably, the bioavailability of eupafolin was relatively low (8.3 %). The optimized UPLC-MS/MS technology showed highly sensitive, selective, and effective, rendering it suitable for the pharmacokinetics of eupafolin in preclinical practice.

Sodium Houttuyfonate Prevents Seizures and Neuronal Cell Loss by Maintaining Glutamatergic System Stability in Male Rats with Kainic Acid-Induced Seizures

The present study evaluated the antiseizure and neuroprotective effects of sodium houttuyfonate (SH), a derivative of Houttuynia cordata Thunb. (H. cordata), in a kainic acid (KA)- induced seizure rat model and its underlying mechanism. Sprague Dawley rats were administered normal saline, SH (50 or 100 mg/kg), or carbamazepine (300 mg/kg) by oral gavage for seven consecutive days before the intraperitoneal administration of KA (15 mg/kg). SH showed antiseizure effects at a dose of 100 mg/kg; it prolonged seizure latency and decreased seizure scores. SH also significantly decreased neuronal loss in the hippocampi of KA-treated rats, which was associated with the prevention of glutamate level increase, the upregulation of glutamate reuptake-associated proteins (excitatory amino acid transporters 1-3), glutamate metabolism enzyme glutamine synthetase, the downregulation of the glutamate synthesis enzyme glutaminase, and significant alterations in the expression of AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid receptor) and NMDA (N-methyl-D-aspartic acid receptor) receptor subunits in the hippocampus. Furthermore, the effects of SH were similar to those of the antiseizure drug carbamazepine. Therefore, the results of the present study suggest that SH has antiseizure effects on KA-induced seizures, possibly through the prevention of glutamatergic alterations. Our findings suggest that SH is a potential alternative treatment that may prevent seizures by preserving the normal glutamatergic system.

Canonical Wnt activator Chir99021 prevents epileptogenesis in the intrahippocampal kainate mouse model of temporal lobe epilepsy

The Wnt signaling pathway mediates the development of dentate granule cell neurons in the hippocampus. These neurons are central to the development of temporal lobe epilepsy and undergo structural and physiological remodeling during epileptogenesis, which results in the formation of epileptic circuits. The pathways responsible for granule cell remodeling during epileptogenesis have yet to be well defined, and represent therapeutic targets for the prevention of epilepsy. The current study explores Wnt signaling during epileptogenesis and for the first time describes the effect of Wnt activation using Wnt activator Chir99021 as a novel anti-epileptogenic therapeutic approach. Focal mesial temporal lobe epilepsy was induced by intrahippocampal kainate (IHK) injection in wild-type and POMC-eGFP transgenic mice. Wnt activator Chir99021 was administered daily, beginning 3 h after seizure induction, and continued up to 21-days. Immature granule cell morphology was quantified in the ipsilateral epileptogenic zone and the contralateral peri-ictal zone 14 days after IHK, targeting the end of the latent period. Bilateral hippocampal electrocorticographic recordings were performed for 28-days, 7-days beyond treatment cessation. Hippocampal behavioral tests were performed after completion of Chir99021 treatment. Consistent with previous studies, IHK resulted in the development of epilepsy after a 14 day latent period in this well-described mouse model. Activation of the canonical Wnt pathway with Chir99021 significantly reduced bilateral hippocampal seizure number and duration. Critically, this effect was retained after treatment cessation, suggesting a durable antiepileptogenic change in epileptic circuitry. Morphological analyses demonstrated that Wnt activation prevented pathological remodeling of the primary dendrite in both the epileptogenic zone and peri-ictal zone, changes in which may serve as a biomarker of epileptogenesis and anti-epileptogenic treatment response in pre-clinical studies. These findings were associated with improved object location memory with Chir99021 treatment after IHK. This study provides novel evidence that canonical Wnt activation prevents epileptogenesis in the IHK mouse model of mesial temporal lobe epilepsy, preventing pathological remodeling of dentate granule cells. Wnt signaling may therefore play a key role in mesial temporal lobe epileptogenesis, and Wnt modulation may represent a novel therapeutic strategy in the prevention of epilepsy.

Gypenoside XVII Reduces Synaptic Glutamate Release and Protects against Excitotoxic Injury in Rats

Excitotoxicity is a common pathological process in neurological diseases caused by excess glutamate. The purpose of this study was to evaluate the effect of gypenoside XVII (GP-17), a gypenoside monomer, on the glutamatergic system. In vitro, in rat cortical nerve terminals (synaptosomes), GP-17 dose-dependently decreased glutamate release with an IC50 value of 16 μM. The removal of extracellular Ca2+ or blockade of N-and P/Q-type Ca2+ channels and protein kinase A (PKA) abolished the inhibitory effect of GP-17 on glutamate release from cortical synaptosomes. GP-17 also significantly reduced the phosphorylation of PKA, SNAP-25, and synapsin I in cortical synaptosomes. In an in vivo rat model of glutamate excitotoxicity induced by kainic acid (KA), GP-17 pretreatment significantly prevented seizures and rescued neuronal cell injury and glutamate elevation in the cortex. GP-17 pretreatment decreased the expression levels of sodium-coupled neutral amino acid transporter 1, glutamate synthesis enzyme glutaminase and vesicular glutamate transporter 1 but increased the expression level of glutamate metabolism enzyme glutamate dehydrogenase in the cortex of KA-treated rats. In addition, the KA-induced alterations in the N-methyl-D-aspartate receptor subunits GluN2A and GluN2B in the cortex were prevented by GP-17 pretreatment. GP-17 also prevented the KA-induced decrease in cerebral blood flow and arginase II expression. These results suggest that (i) GP-17, through the suppression of N- and P/Q-type Ca2+ channels and consequent PKA-mediated SNAP-25 and synapsin I phosphorylation, reduces glutamate exocytosis from cortical synaptosomes; and (ii) GP-17 has a neuroprotective effect on KA-induced glutamate excitotoxicity in rats through regulating synaptic glutamate release and cerebral blood flow.

Differential changes in Wnt7 and Dkk1 levels in astrocytes exposed to glutamate or TNFα

Wnt signaling plays an important role in adult brain function, and its dysregulation has been implicated in the loss of neuronal homeostasis. Despite the existence of many studies on the participation of the Wnt pathway in adult neurons, its regulation in astrocytes has been scarcely explored. Several reports point to the presence of Wnt ligands in astrocytes and their possible impact on neuronal plasticity or neuronal death. We aimed to analyze the effect of the neurotransmitter glutamate and the inflammatory cytokine TNFα on the mRNA and protein levels of the canonical Wnt agonist Wnt7a and the antagonist Dkk1 in cultured astrocytes. Primary astrocyte cultures from rat cerebral cortices were exposed to glutamate or TNFα. Wnt7a and Dkk1 expression was analyzed by RT-qPCR and its protein abundance and distribution was assessed by immunofluorescence. We found high basal expression and protein levels of Wnt7a and Dkk1 in unstimulated astrocytes and overproduction of Dkk1 mRNA induced by the two stimuli. These results reveal the astrocytic source of the canonical Wnt ligands Wnt7a and Dkk1, whose levels are differentially regulated by glutamate and TNFα. Astrocytes are a significant source of Wnt ligands, the production of which can be differentially regulated under excitatory or proinflammatory conditions, thereby impacting neuronal function.

Therapeutic Potential of Natural Compounds from Herbs and Nutraceuticals in Alleviating Neurological Disorders: Targeting the Wnt Signaling Pathway

As an important signaling pathway in multicellular eukaryotes, the Wnt signaling pathway participates in a variety of physiological processes. Recent studies have confirmed that the Wnt signaling pathway plays an important role in neurological disorders such as stroke, Alzheimer's disease, and Parkinson's disease. The regulation of Wnt signaling by natural compounds in herbal medicines and nutraceuticals has emerged as a potential strategy for the development of new drugs for neurological disorders. Purpose: The aim of this review is to evaluate the latest research results on the efficacy of natural compounds derived from herbs and nutraceuticals in the prevention and treatment of neurological disorders by regulating the Wnt pathway in vivo and in vitro. A manual and electronic search was performed for English articles available from PubMed, Web of Science, and ScienceDirect from the January 2010 to February 2023. Keywords used for the search engines were "natural products,″ "plant derived products,″ "Wnt+ clinical trials,″ and "Wnt+,″ and/or paired with "natural products″/″plant derived products", and "neurological disorders." A total of 22 articles were enrolled in this review, and a variety of natural compounds from herbal medicine and nutritional foods have been shown to exert therapeutic effects on neurological disorders through the Wnt pathway, including curcumin, resveratrol, and querctrin, etc. These natural products possess antioxidant, anti-inflammatory, and angiogenic properties, confer neurovascular unit and blood-brain barrier integrity protection, and affect neural stem cell differentiation, synaptic formation, and neurogenesis, to play a therapeutic role in neurological disorders. In various in vivo and in vitro studies and clinical trials, these natural compounds have been shown to be safe and tolerable with few adverse effects. Natural compounds may serve a therapeutic role in neurological disorders by regulating the Wnt pathway. This summary of the research progress of natural compounds targeting the Wnt pathway may provide new insights for the treatment of neurological disorders and potential targets for the development of new drugs.

Protective effect of Salvia plebeia R. Br ethanol extract on UVB-induced skin photoaging in vitro and in vivo

BACKGROUND

UV exposure is one of the primary factors responsible for photoaging, causing the increase in matrix metalloproteinases (MMPs) and the reduction in collagen. Salvia plebeia R. Br (SP), as an herbaceous plant, contains abundant flavonoids and possesses excellent anti-inflammatory and antioxidant activities. This study aimed to investigate the photoprotective effects of SP on UVB-induced photodamage in immortalized human keratinocytes (HaCaTs) and Kunming mice, as well as its main active components such as homoplantaginin (HP).

METHODS

CCK-8 was applied to detect the cell viability in UVB-irradiated or non-irradiated HaCaTs. Commercial kits were used to evaluate the levels of ROS, MDA, SA-β-Gal, MMP-1, and IL-6. The expression of MAPK and TGF-β/Smad pathways was detected by western blot. HE and Masson's trichrome staining were performed to examine the epidermis thickness and collagen degradation of Kunming mice.

RESULTS

Our results found that SP and HP notably decreased UVB-induced ROS, MDA, and SA-β-Gal production, and inhibited MMP-1 and IL-6 secretion by inhibiting the MAPK signaling pathway. In addition, SP and HP significantly promoted type I procollagen synthesis by activation of TGF-β/Smad pathway. Consistently, the in vivo experiments also indicated that SP and HP had a photoprotective effect, which significantly reversed UVB-induced epidermis thickness and collagen degradation.

CONCLUSION

This study demonstrated that SP effectively could protect skin from UVB-induced photoaging, while HP acted as the active substance in SP. All these findings provided a new strategy for skin photoaging treatment.

Inhibition of Synaptic Glutamate Exocytosis and Prevention of Glutamate Neurotoxicity by Eupatilin from Artemisia argyi in the Rat Cortex

The inhibition of synaptic glutamate release to maintain glutamate homeostasis contributes to the alleviation of neuronal cell injury, and accumulating evidence suggests that natural products can repress glutamate levels and associated excitotoxicity. In this study, we investigated whether eupatilin, a constituent of Artemisia argyi, affected glutamate release in rat cortical nerve terminals (synaptosomes). Additionally, we evaluated the effect of eupatilin in an animal model of kainic acid (KA) excitotoxicity, particularly on the levels of glutamate and N-methyl-D-aspartate (NMDA) receptor subunits (GluN2A and GluN2B). We found that eupatilin decreased depolarization-evoked glutamate release from rat cortical synaptosomes and that this effect was accompanied by a reduction in cytosolic Ca2+ elevation, inhibition of P/Q-type Ca2+ channels, decreased synapsin I Ca2+-dependent phosphorylation and no detectable effect on the membrane potential. In a KA-induced glutamate excitotoxicity rat model, the administration of eupatilin before KA administration prevented neuronal cell degeneration, glutamate elevation, glutamate-generating enzyme glutaminase increase, excitatory amino acid transporter (EAAT) decrease, GluN2A protein decrease and GluN2B protein increase in the rat cortex. Taken together, the results suggest that eupatilin depresses glutamate exocytosis from cerebrocortical synaptosomes by decreasing P/Q-type Ca2+ channels and synapsin I phosphorylation and alleviates glutamate excitotoxicity caused by KA by preventing glutamatergic alterations in the rat cortex. Thus, this study suggests that eupatilin can be considered a potential therapeutic agent in the treatment of brain impairment associated with glutamate excitotoxicity.

Transcriptome Profiling of the Hippocampal Seizure Network Implicates a Role for Wnt Signaling during Epileptogenesis in a Mouse Model of Temporal Lobe Epilepsy

Mesial temporal lobe epilepsy (mTLE) is a life-threatening condition characterized by recurrent hippocampal seizures. mTLE can develop after exposure to risk factors such as febrile seizure, trauma, and infection. Within the latent period between exposure and onset of epilepsy, pathological remodeling events occur that contribute to epileptogenesis. The molecular mechanisms responsible are currently unclear. We used the mouse intrahippocampal kainite model of mTLE to investigate transcriptional dysregulation in the ipsilateral and contralateral dentate gyrus (DG), representing the epileptogenic zone (EZ) and peri-ictal zone (PIZ). DG were analyzed after 3, 7, and 14 days by RNA sequencing. In both the EZ and PIZ, transcriptional dysregulation was dynamic over the epileptogenic period with early expression of genes representing cell signaling, migration, and proliferation. Canonical Wnt signaling was upregulated in the EZ and PIZ at 3 days. Expression of inflammatory genes differed between the EZ and PIZ, with early expression after 3 days in the PIZ and delayed expression after 7-14 days in the EZ. This suggests that critical gene changes occur early in the hippocampal seizure network and that Wnt signaling may play a role within the latent epileptogenic period. These findings may help to identify novel therapeutic targets that could prevent epileptogenesis.

The recycling of AMPA receptors/GABAa receptors is related to neuronal excitation/inhibition imbalance and may be regulated by KIF5A

BACKGROUND

Excitation/inhibition imbalance (E/I imbalance), which involves an increase of alpha-amino-3-hydroxy-5-methyl-4-isoxazole (AMPA) receptors (AMPARs) and decrease of gamma-aminobutyric acid type A (GABA) type A receptors (GABAaRs) on the neuron surface, has been documented in the pathogenesis of seizures. Notably, it has been established that both the glutamate receptor subunit 2 (GluR2) of AMPARs and beta 2/3 subunits of GABAaRs (Gabrb2+3) participate in the recycling mechanism mediated by the kinesin heavy chain isoform 5A (KIF5A), which determines the number of neuron surface receptors. However, it remains unclear whether receptor recycling is involved in the pathogenesis of seizures.

METHODS

Twelve adult male Sprague-Dawley rats were randomly allocated to the normal control (Ctl) group (n=6) and the pentylenetetrazol (PTZ)-induced seizure (Sez) group (n=6). The rats in the Ctl group were treated with saline. The rats in the Sez group received an intraperitoneal injection of PTZ at an initial dose of 40 mg/kg. Primary cultured neurons were obtained from newborn rats (24-hour-old). The neurons were exposed to magnesium-free (Mg2+-free) extracellular fluid for 3 hours to establish the seizure model in vitro. We detected the electrophysiology of the seizure model, the expression levels of KIF5A, GluR2, and Gabrb2+3, the recycling ratio of GluR2 and Gabrb2+3, the interaction between KIF5A and GluR2, and the interaction between KIF5A and Gabrb2+3.

RESULTS

In the Sez group, the expression of GluR2 on the cell surface was increased and the expression of Gabrb2+3 on the cell surface was decreased. The amplitude and frequency of action potentials were significantly increased in the Mg2+-free group. The amplitude and decay time of AMPAR-mediated miniature excitatory postsynaptic currents were increased in the Mg2+-free group. The amplitude and decay time of miniature inhibitory postsynaptic currents were decreased in the Mg2+-free group. The recycling ratio of GluR2 was increased and the recycling ratio of Gabrb2+3 was decreased in the Mg2+-free group. The interaction between KIF5A and GluR2 was increased, and the interaction between KIF5A and Gabrb2+3 was decreased in the seizure model in vivo and in vitro.

CONCLUSIONS

The recycling of AMPA receptors/GABAa receptors is related to E/I imbalance and may be regulated by KIF5A.