Antagonism of Histamine H3 receptors Alleviates Pentylenetetrazole-Induced Kindling and Associated Memory Deficits by Mitigating Oxidative Stress, Central Neurotransmitters, and c-Fos Protein Expression in Rats

SRF Facilitates Transcriptional Inhibition of Gem Expression by m6A Methyltransferase METTL3 to Suppress Neuronal Damage in Epilepsy

A bioinformatics analysis was conducted to screen for relevant expression datasets of the transcription factor SRF knockout mice. The aim was to investigate the relationship between SRF and m6A-related genes, predict how SRF regulates the m6A modification of GEM genes mediated by METTL3, and explore potential molecular mechanisms associated with neurotrauma. Disease gene databases such as GeneCards, DisGeNET, and Phenolyzer, and transcription factor databases TFDB and TRRUST, were used to obtain epilepsy-related genes and transcription factors. The intersection was then selected. Expression data of SRF knockout epilepsy mice were obtained from the GEO database and used to filter differentially expressed genes. Important module genes related to the disease were selected through WGCNA co-expression analysis. The intersection between these genes and the differentially expressed genes was performed, followed by PPI network analysis and GO/KEGG enrichment analysis. Furthermore, the core genes were selected using the cytoHubba plugin of the Cytoscape software. Differential expression analysis was performed on m6A-related factors in the GEO dataset, and the relationship between SRF and m6A-related factors and core genes was analyzed. The m6A binding sites of SRF with the METTL3 promoter and target gene Gem were predicted using the AnimalTFDB and SRAMP websites, respectively. We found that the transcription factor SRF may be a key gene in epilepsy during neuronal development. Further WGCNA analysis showed that 129 module genes were associated with SRF knockout epilepsy, and these differentially expressed genes were mainly enriched in the neuroactive ligand-receptor interaction pathway. The final results indicate that knocking out SRF may inhibit the transcription of METTL3, thereby inhibiting the m6A modification of Gem and leading to upregulation of Gem expression, thereby playing an important role in neuronal damage. Knocking out the SRF gene may inhibit the transcription of m6A methyltransferase METTL3, thereby inhibiting the m6A modification of GEM genes mediated by METTL3, promoting GEM gene expression, and leading to the occurrence of epilepsy-related neuron injury. Further investigation revealed that SRF overexpression can potentially enhance the transcription of METTL3, thus promoting m6A modification of GEM, resulting in downregulation of GEM expression. This process regulates oxidative stress in epileptic mouse neurons, suppresses inflammatory responses, and mitigates associated damage. Additionally, an in vitro neuronal epileptic model was established, and experimental techniques such as qRT-PCR and WB were employed to assess the expression of SRF, METTL3, and GEM in hippocampal tissues and neurons. The experimental results were consistent with our predictions, demonstrating that overexpression of SRF can inhibit the development of epilepsy-related neuronal damage. This study reveals that knockout of the SRF gene may suppress the transcription of m6A methyltransferase METTL3, thereby inhibiting m6A modification of the GEM gene mediated by METTL3 and subsequently promoting the expression of the GEM gene, leading to the occurrence of epilepsy-related neuronal damage.

Targeting Microglia in Neuroinflammation: H3 Receptor Antagonists as a Novel Therapeutic Approach for Alzheimer's Disease, Parkinson's Disease, and Autism Spectrum Disorder

Histamine performs dual roles as an immune regulator and a neurotransmitter in the mammalian brain. The histaminergic system plays a vital role in the regulation of wakefulness, cognition, neuroinflammation, and neurogenesis that are substantially disrupted in various neurodegenerative and neurodevelopmental disorders. Histamine H3 receptor (H3R) antagonists and inverse agonists potentiate the endogenous release of brain histamine and have been shown to enhance cognitive abilities in animal models of several brain disorders. Microglial activation and subsequent neuroinflammation are implicated in impacting embryonic and adult neurogenesis, contributing to the development of Alzheimer's disease (AD), Parkinson's disease (PD), and autism spectrum disorder (ASD). Acknowledging the importance of microglia in both neuroinflammation and neurodevelopment, as well as their regulation by histamine, offers an intriguing therapeutic target for these disorders. The inhibition of brain H3Rs has been found to facilitate a shift from a proinflammatory M1 state to an anti-inflammatory M2 state, leading to a reduction in the activity of microglial cells. Also, pharmacological studies have demonstrated that H3R antagonists showed positive effects by reducing the proinflammatory biomarkers, suggesting their potential role in simultaneously modulating crucial brain neurotransmissions and signaling cascades such as the PI3K/AKT/GSK-3β pathway. In this review, we highlight the potential therapeutic role of the H3R antagonists in addressing the pathology and cognitive decline in brain disorders, e.g., AD, PD, and ASD, with an inflammatory component.

Barbaloin Protects Pentylenetetrazol-Induced Cognitive Deficits in Rodents via Modulation of Neurotransmitters and Inhibition of Oxidative-Free-Radicals-Led Inflammation

BACKGROUND

Epilepsy is defined by an excessive level of activity in the neurons and coordinated bursts of electrical activity, resulting in the occurrence of seizure episodes. The precise cause of epileptogenesis remains uncertain; nevertheless, the etiology of epilepsy may involve neuroinflammation, oxidative stress, and malfunction of the neurotransmitter system.

OBJECTIVE

The goal of this investigation was to assess barbaloin's protective properties with respect to pentylenetetrazol (PTZ)-)-induced cognitive deficits in rats via antioxidative, anti-inflammatory, and neurotransmitter-modulating effects.

METHODS

Wistar rats were subjected to PTZ [40 mg/kg (i.p.)], which induced cognitive decline. Behavior assessment using a kindling score, open-field test (OFT), novel object recognition test (NORT), and assays for superoxide dismutase (SOD), reduced glutathione (GSH), catalase (CAT), malondialdehyde (MDA), acetylcholinesterase (AChE), caspase-3, nitric oxide (NO), interleukins-1β (IL-1β), tumor necrosis factor-α (TNF-α), IL-6, nuclear factor kappa-B (NF-κB), Bcl-2 and Bax, and neurotransmitter levels [GABA, DA, NE, and serotonin (5-HT)] were performed.

RESULTS

The treatment of rats with barbaloin resulted in behavior improvement and significant changes in the levels of GSH, SOD, CAT, MDA, AChE, NO, IL-6, IL-1β, TNF-α, NF-κB, caspase-3, Bcl-2, and Bax compared to the PTZ control group. Barbaloin treatment resulted in notable changes in neurotransmitter levels (GABA, NE, 5-HT, DA) compared to the PTZ group.

CONCLUSIONS

The ongoing study has gathered evidence indicating that the injection of barbaloin has resulted in significant improvements in cognitive performance in rats. This is achieved by inhibiting oxidative stress, enhancing the activity of natural antioxidant enzymes, reducing cytokine levels, and increasing the levels of neurotransmitters in the brain. These results were detected in comparison to a PTZ control and can be attributed to the potent anti-inflammatory and antioxidant capabilities of barbaloin, which could be linked to its neuroprotective properties. Barbaloin may potentially increase cognitive decline and boost neuronal survival by altering the expression of Bax, caspase-3, Bcl-2.

Discovery of Novel Steroid-Based Histamine H3 Receptor Antagonists/Inverse Agonists

Steroid-based histamine H3 receptor antagonists (d-homoazasteroids) were designed by combining distinct structural elements of HTS hit molecules. They were characterized, and several of them displayed remarkably high affinity for H3 receptors with antagonist/inverse agonist features. Especially, the 17a-aza-d-homolactam chemotype demonstrated excellent H3R activity together with significant in vivo H3 antagonism. Optimization of the chemotype was initiated with special emphasis on the elimination of the hERG and muscarinic affinity. Additionally, ligand-based SAR considerations and molecular docking studies were performed to predict binding modes of the molecules. The most promising compounds (XXI, XXVIII, and XX) showed practically no muscarinic and hERG affinity. They showed antagonist/inverse agonist property in the in vitro functional tests that was apparent in the rat in vivo dipsogenia test. They were considerably stable in human and rat liver microsomes and provided significant in vivo potency in the place recognition and novel object recognition cognitive paradigms.

Ameliorative effects of vanillin against pentylenetetrazole-induced epilepsy and associated memory loss in mice: The role of Nrf2/HO-1/NQO1 and HMGB1/RAGE/TLR4/NFκB pathways

BACKGROUND

Epilepsy is a severe neurological disorder associated with substantial morbidity and mortality. Vanillin (Van) is a natural phenolic aldehyde with beneficial pharmacological properties. This study investigated the neuroprotective effects of Van in epilepsy and elucidated its mechanism of action.

METHODS

Swiss albino mice were divided into the following five groups: "normal group", 0.9 % saline; "pentylenetetrazole (PTZ) group", intraperitoneal administration of 35 mg/kg PTZ on alternate days up to 42 days; and "PTZ + Van 20", "PTZ + Van 40", and "PTZ + sodium valproate (Val)" groups received PTZ injections in conjunction withVan 20 mg, Van 40 mg/kg, and Val 300 mg/kg, respectively. Behavioural tests and hippocampal histopathological analysis were performed in all groups. The Nrf2/HO-1/NQO1 and HMGB1/RAGE/TLR4/NFκB pathways, oxidative stress, neuro-inflammation, and apoptotic markers were analysed. Furthermore, brain acetylcholinesterase (AChE) activity and levels of dopamine (DA), gamma-aminobutyric acid GABA, and serotonin 5-HT were assessed.

RESULTS

Van prolonged seizure manifestations and improved electroencephalogram (EEG)criteriain conjunction with 100 mg/kg PTZ once daily. Van administration increased Nrf2/HO-1/NQO1 levels, with subsequent attenuation of malondialdehyde (MDA) and nitric oxide (NO) levels with elevated glutathione (GSH) levels and intensified superoxide dismutase (SOD) and catalase activities. Van reduced the gene and protein expression of HMGB1/RAGE/TLR4/NFκB and decreased the levels of inflammatory and apoptotic markers. In addition, Van reduced AChE activity, and elevated glial fibrillary acidic proteins (GFAP) increased neurotransmitter and brain-derived neurotrophic factors (BDNF).

CONCLUSION

By increasing Nrf2/HO-1/NQO1 levels and downregulating the HMGB1/RAGE/TLR4/ NFκB pathway, Van offered protection in PTZ-kindled mice with subsequent attenuation in lipid peroxidation, upregulation in antioxidant enzyme activities, and reduction in inflammation and apoptosis.

Stem bark chloroform extract of Bombax costatum Pellegr. & Vuillet exhibit anticonvulsant and neuroprotective effects in pentylenetetrazole-induced seizures in rats

AIM OF THE STUDY

The study aimed at evaluating the potentials of stem bark extracts of Bombax costatum (B. costatum) on seizure, pentylenetetrazole (PTZ) induced kindling and associated changes in wistar albino rats.

MATERIALS AND METHODS

Phase 1 evaluated which extract of B. costatum (chloroform, ethanol and n-hexane) is most effective in preventing seizure in acute PTZ-induced (85mg/kg) seizure in rats. Phase 2 evaluated the potentials of stem bark chloroform extract of B. costatum in PTZ-kindled rats at a dose 250 and 500mg/kg in comparison to diazepam. As its effects on memory, oxidative stress markers, neurotransmitters and brain histology were evaluated. Phase 3 determined the probable curative effects of B. costatum on fully kindled rats.

RESULTS

In phase 1, Chloroform extract of B. coststum 500mg/kg is the most effective (P<0.05) in preventing seizure as compared to ethanol and n-hexane extracts. In phase 2, chloroform extract of B. costatum delayed the development of kindling, improved kindling associated cognitive impairment and alterations of glutamate and gamma-aminobutyric acid (GABA). Further, it attenuated oxidative stress besides the maintenance of neuronal architecture of the hippocampus.

CONCLUSION

Conclusively, chloroform stem bark extract of B. costatum antagonizes PTZ-induced seizure progression, protects against kindling induced cognitive impairment and oxidative stress. Additionally, it also increases the brain level of GABA at high dose and prevented against kindling-induced hippocampal disruptions. Hence, this justifies its use traditionally in the treatment of epileptic seizures.

Geniposide and asperuloside alter the COX-2 and GluN2B receptor expression after pilocarpine-induced seizures in mice

Asperuloside (ASP) and geniposide (GP) are iridoids that have shown various biological properties, such as reduction of inflammation, oxidative stress, and neuroprotection. The aim of this study was to investigate the mechanism of action of ASP and GP through the experimental model of pilocarpine-induced seizures. Mice were treated daily with saline, valproic acid (VPA), GP (5, 25, or 50 mg/kg), or ASP (20 or 40 mg/kg) for 8 days. Pilocarpine (PILO) treatment was administered after the last day of treatment, and the epileptic behavior was recorded for 1 h and analyzed by an adapted scale. Afterward, the hippocampus and blood samples were collected for western blot analyses, ELISA and comet assay, and bone marrow to the micronucleus test. We evaluated the expression of the inflammatory marker cyclooxygenase-2 (COX-2), GluN2B, a subunit of the NMDA receptor, pGluR1, an AMPA receptor, and the enzyme GAD-1 by western blot and the cytokine TNF-α by ELISA. The treatments with GP and ASP were capable to decrease the latency to the first seizure, although they did not change the latency to status epilepticus (SE). ASP demonstrated a genotoxic potential analyzed by comet assay; however, the micronuclei frequency was not increased in the bone marrow. The GP and ASP treatments were capable to reduce COX-2 and GluN2B receptor expression after PILO exposure. This study suggests that GP and ASP have a protective effect on PILO-induced seizures, decreasing GluN2B receptor and COX-2 expression.

Valproic Acid Attenuated PTZ-induced Oxidative Stress, Inflammation, and Apoptosis in the SH-SY5Y Cells via Modulating the TRPM2 Channel

Valproic acid (VPA) is one of the most widely used antiepileptic drugs. The protective role of VPA and the role of the TRPM2 channel in this mechanism in developing neuronal damage due to increased pentylenetetrazol (PTZ)-induced neurotoxicity in SH-SY5Y cells were not clarified. Here, we investigated the role of VPA via modulation of TRPM2 channel on cell death and oxidative neurotoxicity in SH-SY5Y cells. The SH-SY5Y cell toxicity model was constructed by treating SH-SY5Y cells with PTZ. The VPA and TRPM2 channel antagonist N-(p-amylcinnamoyl) anthranilic acid (ACA) were added to prevent neurotoxicity in PTZ-induced SH-SY5Y cells. The role of the VPA and TRPM2 channel was evaluated using an ELISA kit and patch-clamp. Primarily, antioxidant (GSH and GSH-Px) and oxidative stress (MDA and ROS) levels and inflammatory factors (IL-1β, IL-6, and TNF-α) in cells were determined by ELISA kits. Then, TRPM2 channel activation in cells was detected using both the ELISA kit and patch-clamp methods. In addition, apoptosis and cell viability levels in cells were determined by performing PARP1, caspase-3, caspase-9, and CCK-8 assays by ELISA kits. Our results showed that the TRPM2 channel is vital in damage formation in PTZ-induced cells. Furthermore, we observed that VPA attenuated PTZ-induced neurotoxicity by suppressing cells' oxidative stress and inflammation, and reducing TRPM2 channel activation. In our study, in which the protective effect of VPA and the role of the TRPM2 channel in PTZ-induced SH-SY5Y cells were investigated for the first time, we can conclude that VPA treatment and TRPM2 channel blockade can suppress PTZ-induced neurotoxicity.

Anti-kindling effect of Ginkgo biloba leaf extract and L-carnitine in the pentylenetetrazol model of epilepsy

Epilepsy is one of the most common serious brain disorders, affecting about 1% of the population all over the world. Ginkgo biloba extract (GbE) and L-carnitine (LC) reportedly possess the antioxidative activity and neuroprotective potential. In this report, we investigated the possible protective and therapeutic effects of GbE and LC against pentylenetetrazol (PTZ)-induced epileptic seizures in rat hippocampus and hypothalamus. Adult male albino rats were equally divided into eight groups: control, GbE (100 mg/kg), LC (300 mg/kg), PTZ (40 mg/kg), protective groups (GbE + PTZ and LC + PTZ), and therapeutic groups (PTZ + GbE and PTZ + LC). The oxidative stress, antioxidant, and neurochemical parameters, viz., malondialdehyde (MDA), nitric oxide (NO), reduced glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), acetylcholine esterase (AchE), dopamine (DA), norepinephrine (NE), and serotonin (5-HT), in the hippocampal and hypothalamic regions have been evaluated. PTZ injection leads to an increase in the seizure score, the levels of MDA and NO, and to a decrease in the activity of GSH, SOD, CAT, and GPx. Besides, monoamine neurotransmitters, DA, NE, and 5-HT, were depleted in PTZ-kindled rats. Furthermore, PTZ administration caused a significant elevation in the activity of AchE. Hippocampal and hypothalamic sections from PTZ-treated animals were characterized by severe histopathological alterations and, intensely, increased the ezrin immunolabeled astrocytes. Pre- and post-treatment of PTZ rats with GbE and LC suppressed the kindling acquisition process and remarkably alleviated all the aforementioned PTZ-induced effects. GbE and LC have potent protective and therapeutic effects against PTZ-induced kindling seizures via the amelioration of oxidative/antioxidative imbalance, neuromodulatory, and antiepileptic actions.

R-α-Lipoic Acid Conjugated to d-α-Tocopherol Polyethylene Glycol 1000 Succinate: Synthesis, Characterization, and Effect on Antiseizure Activity

α-Lipoic acid (LA), a dithiol micronutrient, acts as a vital cofactor in various cellular catabolic reactions and is also known as a universal antioxidant. The therapeutic efficacy of LA is compromised by a poor aqueous solubility as well as a short half-life. In the present study, LA was conjugated to d-α-tocopherol polyethylene glycol succinate (TPGS) using carbodiimideacid-alcohol coupling reaction. The synthesized conjugate (TPGS-LA) was characterized using ¹H and ¹³C nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FT-IR), UV-vis spectroscopy, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The TPGS-LA conjugate was demonstrated to be biocompatible and to have better anticonvulsion activity as compared to native LA in pentylenetetrazol (PTZ)-induced convulsions in zebrafish. Moreover, zebrafish larvae pretreated with TPGS-LA conjugate demonstrated a significant (p < 0.05) reduction of protein carbonylation levels and downregulation of c-fos expression during seizures as compared to native LA. Conclusively, the present findings demonstrate that the TPGS-LA conjugate can be a promising approach for the delivery of LA.

Betahistine Attenuates Seizures, Neurodegeneration, Apoptosis, and Gliosis in the Cerebral Cortex and Hippocampus in a Mouse Model of Epilepsy: A Histological, Immunohistochemical, and Biochemical Study

Epilepsy is a prevalent and chronic neurological disorder marked by recurring, uncontrollable seizures of the brain. Chronic or repeated seizures produce memory problems and induce damage to different brain regions. Histamine has been reported to have neuroprotective effects. Betahistine is a histamine analogue. The current research investigated the effects of convulsions on the cerebral cortex and hippocampus of adult male albino mice and assessed the possible protective effect of betahistine. Four groups of 40 adult male mice were organized: control, betahistine (10 mg/kg/day), pentylenetetrazole (PTZ) (40 mg/kg/ on alternate days), and Betahistine-PTZ group received betahistine 1 h before PTZ. PTZ induced a substantial rise in glutamate level and a considerable decrease in histamine level. Structural changes in the cerebral cortex and cornu ammonis (CA1) of the hippocampus were detected in the pattern of neuron degeneration. Some neurons were shrunken with dark nuclei, and others had faintly stained ones. Focal accumulation of neuroglial cells and ballooned nerve cells of the cerebral cortex were also detected. Cleaved caspase-3, glial fibrillary acidic protein, and ionized calcium-binding adaptor molecule 1 showed substantial increases, while synaptophysin expression was significantly reduced. Interestingly, these changes were less prominent in mice pretreated with betahistine. In conclusion, betahistine had shown neuroprotective properties against brain damage induced by convulsions.

Histamine H3 receptor antagonists - Roles in neurological and endocrine diseases and diabetes mellitus

Human histamine H3 receptor (H3R) was initially described in the brain of rat in 1983 and cloned in 1999. It can be found in the human brain and functions as a regulator of histamine synthesis and release. H3 receptors are predominantly resident in the presynaptic region of neurons containing histamine, where they modulate the synthesis and release of histamine (autoreceptor) or other neurotransmitters such as dopamine, norepinephrine, gamma-aminobutyric acid (GABA), glutamate, acetylcholine and serotonin (all heteroreceptors). The human histamine H3 receptor has twenty isoforms of which eight are functional. H3 receptor expression is seen in the cerebral cortex, neurons of the basal ganglia and hippocampus, which are important for process of cognition, sleep and homoeostatic regulation. In addition, histamine H3R antagonists stimulate insulin release, through inducing the release of acetylcholine and cause significant reduction in total body weight and triglycerides in obese subjects by causing a feeling of satiety in the hypothalamus. The ability of histamine H3R antagonist to reduce diabetes-induced hyperglycaemia is comparable to that of metformin. It is reasonable therefore, to claim that H3 receptor antagonists may play an important role in the therapy of disorders of cognition, the ability to sleep, oxidative stress, inflammation and anomaly of glucose homoeostasis. A large number of H3R antagonists are being developed by pharmaceutical companies and university research centres. As examples of these new drugs, this review will discuss a number of drugs, including the first histamine H3R receptor antagonist produced.

The 3-iodothyronamine (T1AM) and the 3-iodothyroacetic acid (TA1) indicate a novel connection with the histamine system for neuroprotection

The 3-iodothyronamine (T1AM) and 3-iodothryoacetic acid (TA1), are endogenous occurring compounds structurally related with thyroid hormones (THs, the pro-hormone T4 and the active hormone T3) initially proposed as possible mediators of the rapid effects of T3. However, after years from their identification, the physio-pathological meaning of T1AM and TA1 tissue levels remains an unsolved issue while pharmacological evidence indicates both compounds promote in rodents central and peripheral effects with mechanisms which remain mostly elusive. Pharmacodynamics of T1AM includes the recognition of G-coupled receptors, ion channels but also biotransformation into an active metabolite, i.e. the TA1. Furthermore, long term T1AM treatment associates with post-translational modifications of cell proteins. Such array of signaling may represent an added value, rather than a limit, equipping T1AM to play different functions depending on local expression of targets and enzymes involved in its biotransformation. Up to date, no information regarding TA1 mechanistic is available. We here review some of the main findings describing effects of T1AM (and TA1) which suggest these compounds interplay with the histaminergic system. These data reveal T1AM and TA1 are part of a network of signals involved in neuronal plasticity including neuroprotection and suggest T1AM and TA1 as lead compounds for a novel class of atypical psychoactive drugs.

Central histaminergic signalling, neural excitability and epilepsy

Epilepsy is a common neurological disorder characterized by repeated and spontaneous epileptic seizures and is not well controlled by current medication. Traditional theory suggests that epilepsy results from an imbalance of excitatory glutamate neurons and inhibitory GABAergic neurons. However, new evidence from clinical and preclinical research suggests that histamine in the CNS plays an important role in the modulation of neural excitability and in the pathogenesis of epilepsy. Many histamine receptor ligands have achieved curative effects in animal epilepsy models, among which the histamine H₃ receptor antagonist pitolisant has shown anti-epileptic effects in clinical trials. Recent studies, therefore, have focused on the potential action of histamine receptors to control and treat epilepsy. In this review, we summarize the findings from animal and clinical epilepsy research on the role of brain histamine and its receptors. We also identify current gaps in the research and suggest where further studies are most needed.

miR-485 inhibits histone deacetylase HDAC5, HIF1α and PFKFB3 expression to alleviate epilepsy in cellular and rodent models

We investigated the role of microRNA (miR)-485 and its downstream signaling molecules on mediating epilepsy in cellular and rat models. We established a cellular epilepsy model by exposing hippocampal neurons to magnesium and a rat model by treating ICR mice with lithium chloride (127 mg/kg) and pilocarpine (30 mg/kg). We confirmed that miR-485 could bind and inhibit histone deacetylase 5 (HDAC5) and then measured expression of miR-485 and in mice and cells. Cells were transfected with overexpression or knockdown of miR-485, HDAC5, hypoxia-inducible factor-1alpha (HIF1α), or 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 enzyme (PFKFB3) to verify their roles in apoptosis, oxidative stress, and inflammation in epileptic hippocampal neurons. Binding relationship between miR-485, HDAC5, HIF1α, and PFKFB3 was verified. Oxidative stress and inflammation marker levels in epilepsy model mice were assessed. miR-485 was downregulated and HDAC5 was upregulated in cell and animal model of epilepsy. Seizure, neuronal apoptosis, oxidative stress (increased SOD and GSH-Px expression and decreased MDA and 8-OHdG expression) and inflammation (reduced IL-1β, TNF-α, and IL-6 expression) were reduced by miR-485 in epileptic cells. HIF1α and PFKFB3 expression was reduced by HDAC5 knockdown in cells, which was recapitulated in vivo. Thus, miR-485 alleviates neuronal damage and epilepsy by inhibiting HDAC5, HIF1α, and PFKFB3.

Histamine H3 receptor and cholinesterases as synergistic targets for cognitive decline: Strategies to the rational design of multitarget ligands

The role of histamine and acetylcholine in cognitive functions suggests that compounds able to increase both histaminergic and cholinergic neurotransmissions in the brain should be considered as promising therapeutic options. For this purpose, dual inhibitors of histamine H₃ receptors (H₃ R) and cholinesterases (ChEs) have been designed and assessed. In this context, this paper reviews the strategies used to obtain dual H₃ R/ChEs ligands using multitarget design approaches. Hybrid compounds designed by linking tacrine or flavonoid motifs to H₃ R antagonists were obtained with high affinity for both targets, and compounds designed by merging the H₃ R antagonist pharmacophore with known anticholinesterase molecules were also reported. These reports strongly suggest that key modifications in the lipophilic region (including a second basic group) seem to be a strategy to reach novel compounds, allied with longer linker groups to a basic region. Some compounds have already demonstrated efficacy in memory models, although the pharmacokinetic and toxicity profile should be considered when designing further compounds. In conclusion, the key features to be considered when designing novel H₃ R/ChEs inhibitors with improved pharmacological profile were herein summarized.

Discovery of Potential, Dual-Active Histamine H3 Receptor Ligands with Combined Antioxidant Properties

In an attempt to find new dual acting histamine H₃ receptor (H₃R) ligands, we designed a series of compounds, structurally based on previously described in our group, a highly active and selective human histamine H₃ receptor (hH₃R) ligand KSK63. As a result, 15 obtained compounds show moderate hH₃R affinity, the best being the compound 17 (hH₃R K_i = 518 nM). Docking to the histamine H₃R homology model revealed two possible binding modes, with key interactions retained in both cases. In an attempt to find possible dual acting ligands, selected compounds were tested for antioxidant properties. Compound 16 (hH₃R K_i = 592 nM) showed the strongest antioxidant properties at the concentration of 10⁻⁴ mol/L. It significantly reduced the amount of free radicals presenting 50–60% of ascorbic acid activity in the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, as well as showed antioxidative properties in the ferric reducing antioxidant power (FRAP) assay. Despite the yet unknown antioxidation mechanism and moderate hH₃R affinity, 16 (QD13) constitutes a starting point for the search of potential dual acting H₃R ligands-promising tools for the treatment of neurological disorders associated with increased neuronal oxidative stress.

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.

Efficacy of Cicuta virosa medicinal preparations against pentylenetetrazole-induced seizures

Epileptic seizures are characterized by imbalanced inhibition-excitation cycle that triggers biochemical alterations responsible for jeopardized neuronal integrity. Conventional antiepileptic drugs (AEDs) have been the mainstay option for treatment and control; however, symptomatic control and potential to exacerbate the seizure condition calls for viable alternative to these chemical agents. In this context, natural product-based therapies have accrued great interest in recent years due to competent disease management potential and lower associated adversities. Cicuta virosa (CV) is one such herbal remedy that is used in traditional system of medicine against myriad of disorders including epilepsy. Homeopathic medicinal preparations (HMPs) of CV were assessed for their efficacy in pentylenetetrazole (PTZ)-induced acute and kindling models of epilepsy. CV HMPs increased the latency and reduced the duration of tonic-clonic phase in acute model while lowering the kindling score in the kindling model that signified their role in modulating GABAergic neurotransmission and potassium conductance. Kindling-induced impairment of cognition, memory, and motor coordination was ameliorated by the CV HMPs that substantiated their efficacy in imparting sustained neuronal fortification. Furthermore, biochemical evaluation showed attenuated oxidative stress load through reduced lipid peroxidation and strengthened free radical scavenging mechanism. Taken together, CV HMPs exhibited promising results in acute and kindling models and must be further assessed through molecular and epigenomic studies.

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.

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.