Implications of antiinflammatory properties of the anticonvulsant drug levetiracetam in astrocytes

Epilepsy and demyelination: Towards a bidirectional relationship

Demyelination stands out as a prominent feature in individuals with specific types of epilepsy. Concurrently, individuals with demyelinating diseases, such as multiple sclerosis (MS) are at a greater risk of developing epilepsy compared to non-MS individuals. These bidirectional connections raise the question of whether both pathological conditions share common pathogenic mechanisms. This review focuses on the reciprocal relationship between epilepsy and demyelination diseases. We commence with an overview of the neurological basis of epilepsy and demyelination diseases, followed by an exploration of how our comprehension of these two disorders has evolved in tandem. Additionally, we discuss the potential pathogenic mechanisms contributing to the interactive relationship between these two diseases. A more nuanced understanding of the interplay between epilepsy and demyelination diseases has the potential to unveiling the molecular intricacies of their pathological relationships, paving the way for innovative directions in future clinical management and treatment strategies for these diseases.

Changes in the Dentate Gyrus Gene Expression Profile Induced by Levetiracetam Treatment in Rats with Mesial Temporal Lobe Epilepsy

Temporal lobe epilepsy (TLE) is one of the most common forms of focal epilepsy. Levetiracetam (LEV) is an antiepileptic drug whose mechanism of action at the genetic level has not been fully described. Therefore, the aim of the present work was to evaluate the relevant gene expression changes in the dentate gyrus (DG) of LEV-treated rats with pilocarpine-induced TLE. Whole-transcriptome microarrays were used to obtain the differential genetic profiles of control (CTRL), epileptic (EPI), and EPI rats treated for one week with LEV (EPI + LEV). Quantitative RT-qPCR was used to evaluate the RNA levels of the genes of interest. According to the results of the EPI vs. CTRL analysis, 685 genes were differentially expressed, 355 of which were underexpressed and 330 of which were overexpressed. According to the analysis of the EPI + LEV vs. EPI groups, 675 genes were differentially expressed, 477 of which were downregulated and 198 of which were upregulated. A total of 94 genes whose expression was altered by epilepsy and modified by LEV were identified. The RT-qPCR confirmed that LEV treatment reversed the increased expression of Hgf mRNA and decreased the expression of the Efcab1, Adam8, Slc24a1, and Serpinb1a genes in the DG. These results indicate that LEV could be involved in nonclassical mechanisms involved in Ca2+ homeostasis and the regulation of the mTOR pathway through Efcab1, Hgf, SLC24a1, Adam8, and Serpinb1a, contributing to reduced hyperexcitability in TLE patients.

Tiagabine and zonisamide differentially regulate the glial properties in an astrocyte-microglia co-culture model of inflammation

Due to the role of astrocytes and microglia in the pathophysiology of epilepsy and limited studies of antiseizure medication (ASM) effects on glial cells, we studied tiagabine (TGB) and zonisamide (ZNS) in an astrocyte-microglia co-culture model of inflammation. Different concentrations of ZNS (10, 20, 40, 100 µg/ml) or TGB (1, 10, 20, 50 µg/ml) were added to primary rat astrocytes co-cultures with 5-10% (M5, physiological conditions) or 30-40% (M30, pathological inflammatory conditions) microglia for 24 h, aiming to study glial viability, microglial activation, connexin 43 (Cx43) expression and gap-junctional coupling. ZNS led to the reduction of glial viability by only 100 µg/ml under physiological conditions. By contrast, TGB revealed toxic effects with a significant, concentration-dependent reduction of glial viability under physiological and pathological conditions. After the incubation of M30 co-cultures with 20 µg/ml TGB, the microglial activation was significantly decreased and resting microglia slightly increased, suggesting possible anti-inflammatory features of TGB under inflammatory conditions. Otherwise, ZNS caused no significant changes of microglial phenotypes. The gap-junctional coupling was significantly decreased after the incubation of M5 co-cultures with 20 and 50 µg/ml TGB, which can be related to its anti-epileptic activity under noninflammatory conditions. A significant decrease of Cx43 expression and cell-cell coupling was found after the incubation of M30 co-cultures with 10 µg/ml ZNS, suggesting additional anti-seizure effects of ZNS with the disruption of glial gap-junctional communication under inflammatory conditions. TGB and ZNS differentially regulated the glial properties. Developing novel ASMs targeting glial cells may have future potential as an "add-on" therapy to classical ASMs targeting neurons.

Impact of levetiracetam on cognitive impairment, neuroinflammation, oxidative stress, and neuronal apoptosis caused by lipopolysaccharides in rats

Introduction

Neuroinflammation is associated with the elevation of toxic proinflammatory mediators that promote neurodegeneration and subsequently affect cognition. Causes of inflammation in the neuronal cells are believed to initiate various neurodegenerative disorders, mainly Alzheimer's disease. Levetiracetam is a second-generation antiepileptic drug. There is evidence supporting the memory-enhancing effect of levetiracetam from numerous experimental and clinical studies. Therefore, this research focused on finding its protective effects against lipopolysaccharides prompted cognitive impairment and exploring possible mechanisms underlining their neuroprotection.

Methodology

Two doses (100 or 200 mg/kg) of levetiracetam were administrated orally for 30 days. Additionally, four doses (250 µg/kg) of lipopolysaccharide were injected peripherally to induce neurotoxicity. Behavioral tests were carried out using various maze models. At the end of the tests, brain tissues were collected for biochemical evaluations. Cholinergic, neuroinflammatory, apoptosis, and oxidative-related parameters were analyzed in the brain homogenate to explore the possible mechanisms of action of levetiracetam.

Results

In lipopolysaccharide-induced rats, levetiracetam indicated a reduction (p < 0.01) in transfer latency using the elevated plus-maze. An improvement (p < 0.01) in novel and familiar objects exploration time using novel object recognition test. A rise (p < 0.05) in novel arm entries and extended time spent in the novel arm using the Y-maze test. In extension, the levels of acetylcholine (p < 0.001), anti-inflammatory factors (transforming growth factor-β1; p < 0.01 and interleukin-10; p < 0.05), and an antioxidant (catalase; p < 0.01) were elevated in lipopolysaccharide-induced rats after the administration of levetiracetam. In contrast, inflammatory factors (cyclooxygenase-2; p < 0.05, nuclear factor kappa B; p < 0.05, tumor necrosis factor-α; p < 0.01, and interleukin-6 (p < 0.01), apoptosis inducers (BCL2-associated X protein; p < 0.05 and Caspase-3 (p < 0.001), and oxidative stress (malondialdehyde; p < 0.05) were considerably reduced with levetiracetam in lipopolysaccharide-induced rats.

Conclusion

The collective results suggested that levetiracetam may be able to treat neuroinflammatory-related memory loss by enhancing cholinergic activity while reducing neuroinflammation, cellular apoptosis, and oxidative stress.

Role of Impaired Astrocyte Gap Junction Coupling in Epileptogenesis

The gap-junction-coupled astroglial network plays a central role in the regulation of neuronal activity and synchronisation, but its involvement in the pathogenesis of neuronal diseases is not yet understood. Here, we present the current state of knowledge about the impact of impaired glial coupling in the development and progression of epilepsy and discuss whether astrocytes represent alternative therapeutic targets. We focus mainly on temporal lobe epilepsy (TLE), which is the most common form of epilepsy in adults and is characterised by high therapy resistance. Functional data from TLE patients and corresponding experimental models point to a complete loss of astrocytic coupling, but preservation of the gap junction forming proteins connexin43 and connexin30 in hippocampal sclerosis. Several studies further indicate that astrocyte uncoupling is a causal event in the initiation of TLE, as it occurs very early in epileptogenesis, clearly preceding dysfunctional changes in neurons. However, more research is needed to fully understand the role of gap junction channels in epilepsy and to develop safe and effective therapeutic strategies targeting astrocytes.

Inhibition of Microglial Activation by Amitriptyline and Doxepin in Interferon-β Pre-Treated Astrocyte–Microglia Co-Culture Model of Inflammation

Depression may occur in patients with multiple sclerosis, especially during interferon-β (IFN-β) treatment, and therapy with antidepressants may be necessary. Interactions of IFN-β with antidepressants concerning glia-mediated inflammation have not yet been studied. Primary rat co-cultures of astrocytes containing 5% (M5, consistent with “physiological” conditions) or 30% (M30, consistent with “pathological, inflammatory” conditions) of microglia were incubated with 10 ng/mL amitriptyline or doxepin for 2 h, or with 2000 U/mL IFN-β for 22 h. To investigate the effects of antidepressants on IFN-β treatment, amitriptyline or doxepin was added to IFN-β pre-treated co-cultures. An MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay was performed to measure the glial cell viability, immunocytochemistry was performed to evaluate the microglial activation state, and ELISA was performed to measure pro-inflammatory TNF-α and IL-6 cytokine concentrations. Incubation of inflammatory astrocyte–microglia co-cultures with amitriptyline, doxepin or IFN-β alone, or co-incubation of IFN-β pre-treated co-cultures with both antidepressants, significantly reduced the extent of inflammation, with the inhibition of microglial activation. TNF-α and IL-6 levels were not affected. Accordingly, the two antidepressants did not interfere with the anti-inflammatory effect of IFN-β on astrocytes and microglia. Furthermore, no cytotoxic effects on glial cells were observed. This is the first in vitro study offering novel perspectives in IFN-β treatment and accompanying depression regarding glia.

Brivaracetam exhibits mild pro-inflammatory features in an in vitro astrocyte-microglia co-culture model of inflammation

Implications of glia in the pathophysiology of epilepsy raise the question of how these cells besides neurons are responsive to antiseizure medications (ASMs). Understanding ASM effects on glia and glia-mediated inflammation may help to explore astrocytes and microglia as potential targets for alternative anti-epileptogenic therapies. The aim of this study was to investigate the effects of the new generation ASM brivaracetam (BRV) in an astrocyte-microglia co-culture model of inflammation. Primary rat astrocytes co-cultures containing 5%–10% (M5, “physiological” conditions) or 30%–40% (M30, “pathological inflammatory” conditions) of microglia were treated with different concentrations of BRV (0.5, 2, 10, and 20 μg/ml) for 24 h. Glial cell viability was measured by MTT assay. Microglial activation states were analyzed by immunocytochemistry and astroglial connexin 43 (Cx43) expression by Western blot analysis and immunocytochemistry. Gap-junctional coupling was studied via Scrape Loading. Incubation with high, overdose concentration (20 μg/ml) of BRV significantly reduced the glial cell viability under physiological conditions (p &lt; 0.01: **). Treatment with BRV in therapeutic concentrations (0.5 and 2 μg/ml) reduced the resting microglia (p &lt; 0.05: *) and increased the microglial activation under inflammatory conditions (p &lt; 0.01: **). Astroglial Cx43 expression was not affected. The gap-junctional coupling significantly increased only by 0.5 μg/ml BRV under physiological conditions (p &lt; 0.05: *). Our findings suggest mild pro-inflammatory, in vitro features of BRV with regard to microglia morphology. BRV showed no effects on Cx43 expression and only limited effects on gap-junctional coupling. Reduction of glial viability by overdose BRV indicates possible toxic effects.

The correlation of temporal changes of neutrophil-lymphocyte ratio with seizure severity and the following seizure tendency in patients with epilepsy

Background

Changes in the neutrophil-lymphocyte ratio (NLR) has been reported to be associated with epilepsy. Here we aim to investigate the correlation of temporal changes of NLR level with seizure severity and the follow-up seizure attacks in patients with epilepsy (PWE).

Methods

We performed a retrospective analysis of the laboratory data including leukocyte count and NLR within 24 h of acute seizure and during the follow-up period of 5–14 days after acute seizure (NLR1, NLR2, respectively) in 115 PWE, and 98 healthy individuals were included as controls in this study. The correlation of laboratory data with seizure types, etiology of epilepsy, anti-seizure drugs (ASDs), seizure severity, and the follow-up seizure attacks in PWE was studied.

Results

Leukocyte count (P < 0.001) and NLR level (P < 0.001) were found significantly different between PWE and controls. On the other hand, a multivariable logistic regression analysis showed that NLR1 level (OR = 2.992, P = 0.001) and admission leukocyte (OR = 2.307, P = 0.002) were both independently associated with acute epileptic seizures. Especially, higher NLR1 level was significantly associated with status epileptics (P = 0.013) and recurrent seizures after admission (P < 0.001). Furthermore, the multivariable logistic regression analysis indicated that higher NLR1 was a predictor for the tendency of the following recurrent seizure attacks (OR = 1.144, P = 0.002). NLR2 was inversely correlated with ASDs taken (P = 0.011). Levels of NLR1 (r = 0.441, P < 0.001) and NLR2 (r = 0.241, P = 0.009) were both positively correlated with seizure severity.

Conclusions

Seizures were correlated with the alterations of systemic inflammation reflected by leukocyte and NLR. NLR1 and admission leukocyte were both independently associated with acute epileptic seizures. Higher NLR1 was associated with status epilepticus and independently predicted the tendency of the following epileptic seizures. NLR2 was significantly associated with ASDs taken. Besides, NLR may be used as a biomarker for seizure severity.

Seizures and epilepsy in multiple sclerosis, aquaporin 4 antibody-positive neuromyelitis optica spectrum disorder and myelin oligodendrocyte glycoprotein antibody-associated disease

Seizure is one of the manifestations of central nervous system (CNS) inflammatory demyelinating diseases, which mainly include multiple sclerosis (MS), aquaporin 4 antibody-positive neuromyelitis optica spectrum disorder (AQP4-NMOSD) and myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD). "Acute symptomatic seizures secondary to MS / AQP4-NMOSD / MOGAD" occur in the acute phase of the diseases, and are more frequent in MOGAD. In contrast, recurrent non-provoked seizures, mainly attributed to "autoimmune-associated epilepsy", occur in the non-acute phase of the diseases. Seizures in MS / AQP4-NMOSD / MOGAD mostly have a focal-onset. MS patients with concomitant systemic infections, an earlier onset and a higher disease activity are more likely to have seizures, whereas factors such as higher MS severity, the presence of status epilepticus and cortical damage indicate a greater risk of developing epilepsy. In MOGAD, cerebral cortical encephalitis, acute disseminated encephalomyelitis (ADEM)-like phenotypes (predominately ADEM and multiphasic disseminated encephalomyelitis) indicate a higher seizure risk. Multiple relapses with ADEM-like phenotypes predict epilepsy in pediatrics with MOGAD. Pathophysiologically, acute symptomatic seizures in MS are associated with neuronal hyperexcitability secondary to inflammation and demyelination. Chronic epilepsy in MS is largely due to gliosis, neuronal dysfunction and synaptic abnormalities. The mainstay of treatment for seizures secondary to MS / AQP4-NMOSD / MOGAD include immunotherapy along with antiseizure medications. This critical review discusses the most-updated evidence on epidemiology, clinical correlates, and inflammatory mechanisms underlying seizures and epilepsy in MS / AQP4-NMOSD / MOGAD. Treatment cautions including drug-drug interactions and the impact of treatments on the other are outlined. We also highlight pitfalls and challenges in managing such patients and future research perspectives to address unsolved questions.

Effects of Levetiracetam on the Serum C-Reactive Protein in Children With Epilepsy: A Meta-Analysis

This meta-analysis aims to evaluate the effect of levetiracetam on serum C-reactive protein (CRP) in children with epilepsy. Articles published up to April 15, 2021 were searched from Google Scholar databases, PubMed, Science Direct, Springer, Wiely, NIH and Baidu Scholar databases to analyzed the difference of serum CRP in epilepsy children compared to healthy controls, and the effect of levetiracetam on serum CRP in children with epilepsy was also assessed. All the included studies met the inclusion criteria. 103 publications were selected and eight articles were included in this study with sample size n = 246. The serum CRP level in childhood epilepsy was significantly higher than the healthy controls (pooled standardized mean difference (SMD): 6.930, 95% CI: 2.716–11.143, z = 3.22, p < 0.01). A significant level of between-study heterogeneity was found (τ² = 17.911, Chi² = 148.67, df = 3, p < 0.01, I² = 98.0%). Besides, serum CRP level was significantly decreased by the treatment of levetiracetam in childhood epilepsy (pooled SMD: 3.505, 95% CI: 1.638–5.373, z = 3.68, p < 0.01). A significant level of between-study heterogeneity was found (τ² = 4.346, Chi² = 97.17, df = 4, p < 0.01, I² = 95.9%). The funnel plot showed there was no significant publication bias in the meta-analysis. Serum CRP levels are upregulated in childhood epilepsy and reduced by levetiracetam in children with epilepsy.

Levetiracetam Mechanisms of Action: From Molecules to Systems

Epilepsy is a chronic disease that affects millions of people worldwide. Antiepileptic drugs (AEDs) are used to control seizures. Even though parts of their mechanisms of action are known, there are still components that need to be studied. Therefore, the search for novel drugs, new molecular targets, and a better understanding of the mechanisms of action of existing drugs is still crucial. Levetiracetam (LEV) is an AED that has been shown to be effective in seizure control and is well-tolerable, with a novel mechanism of action through an interaction with the synaptic vesicle protein 2A (SV2A). Moreover, LEV has other molecular targets that involve calcium homeostasis, the GABAergic system, and AMPA receptors among others, that might be integrated into a single mechanism of action that could explain the antiepileptogenic, anti-inflammatory, neuroprotective, and antioxidant properties of LEV. This puts it as a possible multitarget drug with clinical applications other than for epilepsy. According to the above, the objective of this work was to carry out a comprehensive and integrative review of LEV in relation to its clinical uses, structural properties, therapeutical targets, and different molecular, genetic, and systemic action mechanisms in order to consider LEV as a candidate for drug repurposing.

Beneficial effects of levetiracetam in streptozotocin-induced rat model of Alzheimer's disease

Alzheimer's disease (AD) is the most common neurodegenerative disorder among the elderly. In the light of increasing AD prevalence and lack of effective treatment, new strategies to prevent or reverse this condition are needed. Levetiracetam (LEV) is a newer antiepileptic drug that is commonly used to treat certain types of seizures. Researches indicated that LEV has several other pharmacological activities, including improvement of cognitive function. In this study, the recovery effects of chronic (28 days) administration of LEV (50, 100, and 150 mg/kg, ip) on cognitive deficits caused by the intracerebroventricular (icv) injection of streptozotocin (STZ), as a model for sporadic AD, were evaluated in rats. We also considered the protective effects of LEV against hippocampal cell loss, oxidative damage, acetylcholinesterase (AChE) activity, neuroinflammation, and tauopathy caused by STZ. LEV (100 and 150 mg/kg) significantly attenuated the STZ-induced learning and memory impairments in the passive avoidance and Morris water maze (MWM) tasks. In addition, LEV suppressed STZ-induced hippocampal neuronal loss, while restored alterations in the redox status (lipid peroxides and glutathione), AChE activity, proinflammatory cytokines (IL-1β, IL-6, TNF-α), and hyperphosphorylation of tau linked to STZ administration. In conclusion, our study demonstrated that LEV alleviated hippocampal cell death and memory deficits in STZ-AD rats, through mitigating oxidative damage, suppression of proinflammatory cytokines expression, and inhibition of abnormal tau hyperphosphorylation.

Anti-inflammatory properties of lacosamide in an astrocyte-microglia co-culture model of inflammation

PURPOSE

Understanding the effects of antiepileptic drugs on glial cells and glia-mediated inflammation is a new approach to future treatment of epilepsy. Little is known about direct effects of the antiepileptic drug lacosamide (LCM) on glial cells. Therefore, we aimed to study the LCM effects on glial viability, microglial activation, expression of gap-junctional (GJ) protein Cx43 as well as intercellular communication in an in vitro astrocyte-microglia co-culture model of inflammation.

METHODS

Primary rat astrocytes co-cultures containing 5% (M5, "physiological" conditions) or 30% (M30, "pathological inflammatory" conditions) of microglia were treated with different concentrations of LCM [5, 15, 30, and 90 μg/ml] for 24 h. Glial cell viability was measured by MTT assay. Immunocytochemistry was performed to analyze the microglial activation state. Western blot analysis was used to quantify the astroglial Cx43 expression. The GJ cell communication was studied via Scrape Loading.

RESULTS

A concentration-dependent incubation with LCM did not affect the glial cell viability both under physiological and pathological conditions. LCM induced a significant concentration-dependent decrease of activated microglia with parallel increase of ramified microglia under pathological inflammatory conditions. This correlated with an increase in astroglial Cx43 expression. Nevertheless, the functional coupling via GJs was significantly reduced after incubation with LCM.

CONCLUSION

LCM has not shown effects on the glial cell viability. The reduced GJ coupling by LCM could be related to its anti-epileptic activity. The anti-inflammatory glial features of LCM with inhibition of microglial activation under inflammatory conditions support beneficial role in epilepsy associated with neuroinflammation.

Pharmacological Investigations in Glia Culture Model of Inflammation

Astrocytes and microglia are the main cell population besides neurons in the central nervous system (CNS). Astrocytes support the neuronal network via maintenance of transmitter and ion homeostasis. They are part of the tripartite synapse, composed of pre- and postsynaptic neurons and perisynaptic astrocytic processes as a functional unit. There is an increasing evidence that astroglia are involved in the pathophysiology of CNS disorders such as epilepsy, autoimmune CNS diseases or neuropsychiatric disorders, especially with regard to glia-mediated inflammation. In addition to astrocytes, investigations on microglial cells, the main immune cells of the CNS, offer a whole network approach leading to better understanding of non-neuronal cells and their pathological role in CNS diseases and treatment. An in vitro astrocyte-microglia co-culture model of inflammation was developed by Faustmann et al. (2003), which allows to study the endogenous inflammatory reaction and the cytokine expression under drugs in a differentiated manner. Commonly used antiepileptic drugs (e.g., levetiracetam, valproic acid, carbamazepine, phenytoin, and gabapentin), immunomodulatory drugs (e.g., dexamethasone and interferon-beta), hormones and psychotropic drugs (e.g., venlafaxine) were already investigated, contributing to better understanding mechanisms of actions of CNS drugs and their pro- or anti-inflammatory properties concerning glial cells. Furthermore, the effects of drugs on glial cell viability, proliferation and astrocytic network were demonstrated. The in vitro astrocyte-microglia co-culture model of inflammation proved to be suitable as unique in vitro model for pharmacological investigations on astrocytes and microglia with future potential (e.g., cancer drugs, antidementia drugs, and toxicologic studies).

Effects of Lamotrigine and Topiramate on Glial Properties in an Astrocyte-Microglia Co-Culture Model of Inflammation

BACKGROUND

Astrocytes and microglia are involved in the pathophysiology of epilepsy and bipolar disorder with a link to inflammation. We aimed to investigate the effects of the antiepileptic and mood-stabilizing drugs lamotrigine (LTG) and topiramate (TPM) on glial viability, microglial activation, cytokine release, and expression of gap-junctional protein connexin 43 (Cx43) in different set-ups of an in vitro astrocyte-microglia co-culture model of inflammation.

METHODS

Primary rat co-cultures of astrocytes containing 5% (M5, representing "physiological" conditions) or 30% (M30, representing "pathological, inflammatory" conditions) of microglia were treated with different concentrations of LTG and TPM for 24 hours. An 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was performed to measure the glial cell viability. The microglial activation state was analyzed by immunocytochemistry. The pro-inflammatory tumor necrosis factor-α (TNF-α) and anti-inflammatory transforming growth factor-ß1 (TGF-ß1) cytokine levels were measured by enzyme-linked immunosorbent assay. The astroglial Cx43 expression was quantified by western blot.

RESULTS

A significant reduction of the glial cell viability after incubation with LTG or TPM was observed in a concentration-dependent manner under all conditions. LTG caused no significant alterations of the microglial phenotypes. Under pathological conditions, TPM led to a significant concentration-dependent reduction of microglial activation. This correlated with increased astroglial Cx43 expression. TNF-α levels were not affected by LTG and TPM. Treatment with higher concentrations of LTG, but not with TPM, led to a significant increase in TGF-ß1 levels in M5 and M30 co-cultures.

CONCLUSIONS

Despite the possible glial toxicity of LTG and TPM, both drugs reduced inflammatory activity, suggesting potential positive effects on the neuroinflammatory components of the pathogenesis of epilepsy and bipolar disorder.

Levetiracetam treatment leads to functional recovery after thoracic or cervical injuries of the spinal cord

Spinal cord injury (SCI) leads to dramatic impairments of motor, sensory, and autonomic functions of affected individuals. Following the primary injury, there is an increased release of glutamate that leads to excitotoxicity and further neuronal death. Therefore, modulating glutamate excitotoxicity seems to be a promising target to promote neuroprotection during the acute phase of the injury. In this study, we evaluated the therapeutic effect of a FDA approved antiepileptic drug (levetiracetam-LEV), known for binding to the synaptic vesicle protein SV2A in the brain and spinal cord. LEV therapy was tested in two models of SCI-one affecting the cervical and other the thoracic level of the spinal cord. The treatment was effective on both SCI models. Treated animals presented significant improvements on gross and fine motor functions. The histological assessment revealed a significant decrease of cavity size, as well as higher neuronal and oligodendrocyte survival on treated animals. Molecular analysis revealed that LEV acts by stabilizing the astrocytes allowing an effective uptake of the excess glutamate from the extracellular space. Overall, our results demonstrate that Levetiracetam may be a promising drug for acute management of SCI.

Connexins as therapeutic targets in neurological and neuropsychiatric disorders

Astrocytes represent the reticular part of the central nervous system; gap junctions formed by connexins Cx43, Cx30- and Cx26 provide for homocellular astrocyte-astrocyte coupling, whereas connexins Cx30, Cx32, Cx43, and Cx47 connect astrocytes and oligodendrocytes. Astroglial networks are anatomically and functionally segregated being homologous to neuronal ensembles. Connexons, gap junctions and hemichannels (unpaired connexons) are affected in various neuropathologies from neuropsychiatric to neurodegenerative diseases. Manipulation of astrocytic connexins modulates the size and outreach of astroglial syncytia thus affecting astroglial homeostatic support. Modulation of astrocytic connexin significantly modifies pharmacological profile of many CNS drugs, which represents an innovative therapeutic approach for CNS disorders; this approach is now actively tested in pre-clinical and clinical studies. Wide combination of connexin modulators with CNS drugs open new promising perspectives for fundamental studies and therapeutic strategies.

Astrocytic Connexin43 Channels as Candidate Targets in Epilepsy Treatment

In epilepsy research, emphasis is put on exploring non-neuronal targets such as astrocytic proteins, since many patients remain pharmacoresistant to current treatments, which almost all target neuronal mechanisms. This paper reviews available data on astrocytic connexin43 (Cx43) signaling in seizures and epilepsy. Cx43 is a widely expressed transmembrane protein and the constituent of gap junctions (GJs) and hemichannels (HCs), allowing intercellular and extracellular communication, respectively. A plethora of research papers show altered Cx43 mRNA levels, protein expression, phosphorylation state, distribution and/or functional coupling in human epileptic tissue and experimental models. Human Cx43 mutations are linked to seizures as well, as 30% of patients with oculodentodigital dysplasia (ODDD), a rare genetic condition caused by mutations in the GJA1 gene coding for Cx43 protein, exhibit neurological symptoms including seizures. Cx30/Cx43 double knock-out mice show increased susceptibility to evoked epileptiform events in brain slices due to impaired GJ-mediated redistribution of K⁺ and glutamate and display a higher frequency of spontaneous generalized chronic seizures in an epilepsy model. Contradictory, Cx30/Cx43 GJs can traffic nutrients to high-energy demanding neurons and initiate astrocytic Ca²⁺ waves and hyper synchronization, thereby supporting proconvulsant effects. The general connexin channel blocker carbenoxolone and blockers from the fenamate family diminish epileptiform activity in vitro and improve seizure outcome in vivo. In addition, interventions with more selective peptide inhibitors of HCs display anticonvulsant actions. To conclude, further studies aiming to disentangle distinct roles of HCs and GJs are necessary and tools specifically targeting Cx43 HCs may facilitate the search for novel epilepsy treatments.

Brivaracetam attenuates pain behaviors in a murine model of neuropathic pain

Background

The antiseizure racetams may provide novel molecular insights into neuropathic pain due to their unique mechanism involving synaptic vesicle glycoprotein 2A. Anti-allodynic effects of levetiracetam have been shown in animal models of neuropathic pain. Here, we studied the effect of brivaracetam, which binds to synaptic vesicle glycoprotein 2A with 20-fold greater affinity, and has fewer off-target effects.

Methods

Mice underwent unilateral sciatic nerve cuffing and were evaluated for mechanical sensitivity using von Frey filaments. Pain behaviors were assessed with prophylactic treatment using levetiracetam (100 or 10 mg/kg) or brivaracetam (10 or 1 mg/kg) beginning after surgery and continuing for 21 days, or with therapeutic treatment using brivaracetam (10 or 1 mg/kg) beginning on day 14, after allodynia was established, and continuing for 28 or 63 days. Spinal cord tissues from the prophylaxis experiment with10 mg/kg brivaracetam were examined for neuroinflammation (Iba1 and tumor necrosis factor), T-lymphocyte (CD3) infiltration, and synaptic vesicle glycoprotein 2A expression.

Results

When used prophylactically, levetiracetam, 100 mg/kg, and brivaracetam, 10 mg/kg, prevented the development of allodynia, with lower doses of each being less effective. When used therapeutically, brivaracetam extinguished allodynia, requiring 10 days with 10 mg/kg, and six weeks with 1 mg/kg. Brivaracetam was associated with reduced neuroinflammation and reduced T-lymphocyte infiltration in the dorsal horn. After sciatic nerve cuffing, synaptic vesicle glycoprotein 2A expression was identified in neurons, activated astrocytes, microglia/macrophages, and T lymphocytes in the dorsal horn.

Conclusion

Synaptic vesicle glycoprotein 2A may represent a novel target for neuropathic pain. Brivaracetam may warrant study in humans with neuropathic pain due to peripheral nerve injury.

Percutaneous delivery of levetiracetam as an alternative to topical nonsteroidal anti-inflammatory drugs: formulation development, in vitro and in vivo characterization

The study focused on formulation of carmellose sodium hydrogels and nonionic microemulsions with 5% and 10% of levetiracetam and investigation of drug concentration influence on their physicochemical characteristics and in-use stability as well as influence of drug concentration and carrier type on in vitro drug release and in vivo antihyperalgesic/antiedematous activity in a rat model of localized (intraplantar) carrageenan-induced inflammation. Hydrogels were pseudoplastic semisolids with thixotropy and pH 7.37-7.58. Microemulsions were low viscous Newtonian nanodispersions of oil droplets (13.11-15.11 nm) in water, with pH 4.01-4.64. Physical stability of the investigated systems was preserved over the 3-month storage under ambient conditions. Levetiracetam release followed zero order and Korsmeyer-Peppas models (R² ≥ 0.99) reflecting the combined effects of drug concentration and carrier viscosity. All levetiracetam-loaded formulations produced significant reduction of hyperalgesia and paw swelling induced by carrageenan (p < 0.001). Their efficacy in exerting antihyperalgesic activity was significantly higher than that observed with the reference 5% ibuprofen hydrogel preparation (up to 6 h) (p < 0.001), while antiedematous activity was comparable with the reference product. No erythema and visible blood vessels were observed in a rat ear test. The study demonstrated percutaneous delivery of levetiracetam as useful and safe therapeutic option for localized inflammatory pain with potential to overcome the insufficient efficacy of topically applied nonsteroidal anti-inflammatory drugs in the form of a hydrogel. Graphical abstract.

Glial Connexins and Pannexins in the Healthy and Diseased Brain

Over the past several decades a large amount of data have established that glial cells, the main cell population in the brain, dynamically interact with neurons and thus impact their activity and survival. One typical feature of glia is their marked expression of several connexins, the membrane proteins forming intercellular gap junction channels and hemichannels. Pannexins, which have a tetraspan membrane topology as connexins, are also detected in glial cells. Here, we review the evidence that connexin and pannexin channels are actively involved in dynamic and metabolic neuroglial interactions in physiological as well as in pathological situations. These features of neuroglial interactions open the way to identify novel non-neuronal aspects that allow for a better understanding of behavior and information processing performed by neurons. This will also complement the "neurocentric" view by facilitating the development of glia-targeted therapeutic strategies in brain disease.

Levetiracetam Reduces Early Inflammatory Response After Experimental Intracerebral Hemorrhage by Regulating the Janus Kinase 2 (JAK2)-Signal Transducer and Activator of Transcription 3 (STAT3) Signaling Pathway

Background

Levetiracetam (LEV) is an antiepileptic drug that promotes recovery of neurological function by alleviating inflammatory reactions. However, it is not known whether it can improve secondary brain injury after intracerebral hemorrhage (ICH). The aim of this study was to determine whether LEV can reduce early inflammatory response after ICH in rats.

Material/Methods

An in vitro model of early inflammation was created by treating microglia cells with lipopolysaccharide (LPS). After exposure to various concentrations of LEV, the expression levels of NF-κB and STAT3 and inflammatory factors such as interleukin (IL)-1β and tumor necrosis factor (TNF)-α in microglia were detected. In vivo, autologous blood was used to induce the rat ICH model. The effects of LEV on post-cerebral hemorrhagic inflammatory response were examined using neurobehavioral tests, FJC staining, brain water content testing, and analysis of protein expression levels of NF-κB, JAK2, STAT3, and inflammatory factors.

Results

LEV treatment significantly reduced the expression of inflammatory factors and protein expression levels of NF-κB and STAT3 in LPS-treated microglia cells (P<0.05). In male Sprague-Dawley (SD) rats, LEV treatment markedly decreased the volume of hematoma and the number of degenerative neurons (P<0.05). It also improved the neurological function and relieved brain edema. The protein expression levels of NF-κB, JAK2, and STAT3 were significantly lower in the ICH+LEV group than in the control group (P<0.05).

Conclusions

Our study suggests that treatment with LEV alleviates early inflammatory responses induced by ICH. Mechanistically, LEV inhibited the JAK2-STAT3 signaling pathway and reduced neuronal injury around the hematoma, and ameliorated brain edema, all of which promoted recovery of nerve function after hemorrhage.

Low-grade inflammation causes gap junction-coupled cell dysfunction throughout the body, which can lead to the spread of systemic inflammation

BACKGROUND AND AIMS

Gap junction-coupled cells form networks in different organs in the body. These networks can be affected by inflammatory stimuli and become dysregulated. Cell signaling is also changed through connexin-linked gap junctions. This alteration affects the surrounding cells and extracellular matrix in organs. These changes can cause the spread of inflammatory substances, thus affecting other network-linked cells in other organs in the body, which can give rise to systemic inflammation, which in turn can lead to pain that can turn into chronic.

METHODS

This is a review based on literature search and our own research data of inflammatory stimuli that can affect different organs and particularly gap-junction-coupled cells throughout the body.

CONCLUSIONS

A remaining question is which cell type or tissue is first affected by inflammatory stimuli. Can endotoxin exposure through the air, water and body start the process and are mast cells the first target cells that have the capacity to alter the physiological status of gap junction-coupled cells, thereby causing breakdown of different barrier systems?

IMPLICATIONS

Is it possible to address the right cellular and biochemical parameters and restore inflammatory systems to a normal physiological level by therapeutic strategies?

Neuroprotective effect of levetiracetam in mouse diabetic retinopathy: Effect on glucose transporter-1 and GAP43 expression

AIMS

Retinopathy is a neurodegenerative complication associating diabetes mellitus. Diabetic retinopathy (DR) is the primary reason of visual loss during early adulthood. DR has a complicated multifactorial pathophysiology initiated by hyperglycaemia-induced ischaemic neurodegenerative retinal changes, followed by vision-threatening consequences. The main therapeutic modalities for DR involve invasive delivery of intravitreal antiangiogenic agents as well as surgical interventions. The current work aimed to explore the potential anti-inflammatory and retinal neuroprotective effects of levetiracetam.

MAIN METHODS

This study was performed on alloxan-induced diabetes in mice (n: 21). After 10 weeks, a group of diabetic animals (n: 7) was treated with levetiracetam (25 mg/kg) for six weeks. Retinal tissues were dissected and paraffin-fixed for examination using (1) morphometric analysis with haematoxylin and eosin (HE), (2) immunohistochemistry (GLUT1, GFAP and GAP43), and (3) RT-PCR-detected expression of retinal inflammatory and apoptotic mediators (TNF-α, IL6, iNOS, NF-κB and Tp53).

KEY FINDINGS

Diabetic mice developed disorganized and debilitated retinal layers with upregulation of the gliosis marker GFAP and downregulation of the neuronal plasticity marker GAP43. Additionally, diabetic retinae showed increased transcription of NF-κB, TNF-α, IL6, iNOS and Tp53. Levetiracetam-treated mice showed downregulation of retinal GLUT1 with relief and regression of retinal inflammation and improved retinal structural organization.

SIGNIFICANCE

Levetiracetam may represent a potential neuroprotective agent in DR. The data presented herein supported an anti-inflammatory role of levetiracetam. However, further clinical studies may be warranted to confirm the effectiveness and safety of levetiracetam in DR patients.

Anti-inflammatory effects induced by pharmaceutical substances on inflammatory active brain astrocytes-promising treatment of neuroinflammation

Background

Pharmaceutical treatment with probable anti-inflammatory substances that attack cells in various ways including receptors, ion channels, or transporter systems may slow down the progression of inflammatory conditions. Astrocytes and microglia are the most prominent target cells for inflammation in the central nervous system. Their responses upon inflammatory stimuli work through the NO/cyclic GMP/protein kinase G systems that can downregulate the ATP-induced Ca²⁺ signaling, as well as G protein activities which alter Na⁺ transporters including Na⁺/K⁺-ATPase pump activity, Toll-like receptor 4 (TLR4), glutamate-induced Ca²⁺ signaling, and release of pro-inflammatory cytokines. The rationale for this project was to investigate a combination of pharmaceutical substances influencing the NO and the G_i/G_s activations of inflammatory reactive cells in order to make the cells return into a more physiological state. The ATP-evoked Ca²⁺ signaling is important maybe due to increased ATP release and subsequent activation of purinergic receptors. A balance between intercellular Ca²⁺ signaling through gap junctions and extracellular signaling mediated by extracellular ATP may be important for physiological function.

Methods

Astrocytes in primary cultures were incubated with lipopolysaccharide in a physiological glucose concentration for 24 h to induce inflammatory reactivity. The probable anti-inflammatory substances sildenafil and 1α,25-Dihydroxyvitamin D3 together with endomorphin-1, naloxone, and levetiracetam, were used in the presence of high glucose concentration in the medium to restore the cells. Glutamate-, 5-HT-, and ATP-evoked intracellular Ca²⁺ release, Na⁺/K⁺-ATPase expression, expression of inflammatory receptors, and release of tumor necrosis factor alpha were measured.

Results

Sildenafil in ultralow concentration together with 1α,25-Dihydroxyvitamin D3 showed most prominent effects on the ATP-evoked intracellular Ca²⁺ release. The μ-opioid agonist endomorphin-1, the μ-opioid antagonist naloxone in ultralow concentration, and the antiepileptic agent levetiracetam downregulated the glutamate-evoked intracellular Ca²⁺ release and TLR4. The combination of the pharmaceutical substances in high glucose concentration downregulated the glutamate- and ATP-evoked Ca²⁺ signaling and the TLR4 expression and upregulated the Na⁺/K⁺-ATPase pump.

Conclusion

Pharmaceutical treatment with the combination of substances that have potential anti-inflammatory effects, which attack different biochemical mechanisms in the cells may exert decisive effects to downregulate neuroinflammation in the nervous system.

The effect of serum levetiracetam concentrations on therapeutic response and IL1-beta concentration in patients with epilepsy

OBJECTIVE

Assessment of the relevance between serum drug concentration to its therapeutic response is a valid monitoring strategy for the clinical efficacy of antiepileptic drugs (AEDs). Levetiracetam (LEV) is a broad spectrum AED with a possible anti-inflammatory effect. We aimed to determine the relationship between LEV concentrations and its therapeutic response, and the effect of LEV on IL1-beta concentrations in patients with epilepsy.

METHODS

Patients on monotherapy (n = 7) or polytherapy (n = 15) with LEV for their seizures management were included. Blood samples of each patient were collected: just before LEV intake, 1 h, 2 h, 4 h and 8 h following the last dose. Serum LEV concentrations were measured by liquid chromatography mass spectrometry and IL1-beta concentrations by chemiluminescent immunometric assay. Concentration to dose (C/D) ratio values was used for analyses. LEV concentrations were compared between responders (≤1 seizure/month) and non-responders (>1 seizure/month) and patients with or without adverse reactions. IL1-beta concentrations before and at 2 h following LEV ingestion were compared in order to detect the effect of the increase in serum LEV concentration on IL1-beta.

RESULTS

Although there was no change in LEV (C/D) ratio or LEV maximum concentration (Cmax)/D ratio of the responders and non-responders, the C/D ratio following 1 h of LEV intake (2.17 ± 0.59 kg.day/L) and Cmax/D ratio (2.25 ± 0.56 kg.day/L) in the patients with adverse effects was significantly higher than for the patients without adverse effects (1.09 ± 0.12 kg.day/L and 1.49 ± 0.14 kg.day/L respectively). A statistically significant decrease was found in the IL1-beta concentration to LEV (C/D) ratio with the increase in LEV concentration in patients on LEV monotherapy.

CONCLUSION

The possible relationship between LEV Cmax and its therapeutic response or IL1-beta concentrations may be an importance indication of LEV antiepileptic efficacy. Consequently, monitoring LEV Cmax values may enhance LEV adherence because patients would be less likely to develop adverse effects.

Effects of levetiracetam on astroglial release of kynurenine-pathway metabolites

BACKGROUND AND PURPOSE

Several preclinical studies have demonstrated the unique profiles of levetiracetam (LEV), inhibits spontaneous absence epilepsy models but does not affect traditional convulsion models; however, the detailed pharmacological mechanisms of action of LEV remain to be clarified.

EXPERIMENTAL APPROACH

We determined the interaction between LEV and IFNγ regarding astroglial release of anti-convulsive (kynurenic acid and xanthurenic acid), pro-convulsive (quinolinic acid) and anti-convulsive but pro-absence (cinnabarinic acid) kynurenine-pathway metabolites from rat cortical primary cultured astrocytes using ultra-HPLC equipped with MS.

KEY RESULTS

IFNγ increased basal astroglial release of cinnabarinic acid and quinolinic acid but decreased that of kynurenic acid and xanthurenic acid. IFNγ enhanced inositol 1,4,5-trisphosphate (IP₃ ) receptor agonist (adenophostin A, AdA)-induced astroglial release of kynurenine-pathway metabolites, without affecting AMPA-induced release. LEV increased basal astroglial release of kynurenic acid and xanthurenic acid without affecting cinnabarinic acid or quinolinic acid. Chronic and acute LEV administration inhibited AMPA- and AdA-induced kynurenine-pathway metabolite release. Upon chronic administration, LEV enhanced stimulatory effects of IFNγ on kynurenic acid and xanthurenic acid, and reduced its stimulatory effects on cinnabarinic acid and quinolinic acid. Furthermore, LEV inhibited stimulatory effects of chronic IFNγ on AdA-induced release of kynurenine-pathway metabolites.

CONCLUSIONS AND IMPLICATIONS

This study demonstrated several mechanisms of LEV: (i) inhibition of AMPA- and AdA-induced astroglial release, (ii) inhibition of IFNγ-induced IP₃ receptor activation and (iii) inhibition of release of cinnabarinic acid and quinolinic acid with activation of that of kynurenic acid induced by IFNγ. These combined actions of LEV may contribute to its unique profile.

Levetiracetam+nonsteroidal anti-inflammatory drug binary systems: A contribution to the development of new solid dosage forms

A study has been carried out of binary solid systems made up of the antiepileptic drug levetiracetam, LEV, and a nonsteroidal anti-inflammatory drug, NSAID, capable of managing the inflammation that accompanies epileptic activity. One aim of this research was to identify eutectic mixtures and co-crystals, which are able to impact positively on their biopharmaceutical properties. The NSAIDs studied are (S)- and (R,S)-ibuprofen, (S)- and (R,S)-naproxen, (R,S)-ketoprofen and (R,S)-flurbiprofen, all class II in the Biopharmaceutical Classification System. A green mechanochemical methodology has been used to prepare binary mixtures with different molar ratios, and the binary solid-liquid phase diagrams established. For LEV+(S)-ibuprofen, formation of a single (1:1) co-crystal was confirmed; this was found to melt incongruently. The co-crystal was found to be stable in accelerated stability tests. For the other systems, interesting eutectic mixtures were identified, which showed enhanced dissolution rates of the NSAID relative to the pure drug. For LEV+(R,S)-ibuprofen, LEV+(S)-naproxen and LEV+(R,S)-naproxen, the eutectic mixture compositions have the effective doses of both components. All the NSAIDs investigated are chiral, and their racemates are racemic compounds. Levetiracetam, the (S)-enantiomer of etiracetam, was not efficient in enantiomer discrimination, as all the racemic compound structures are present as the prepared solid mixtures.

Connexin-Dependent Neuroglial Networking as a New Therapeutic Target

Astrocytes and neurons dynamically interact during physiological processes, and it is now widely accepted that they are both organized in plastic and tightly regulated networks. Astrocytes are connected through connexin-based gap junction channels, with brain region specificities, and those networks modulate neuronal activities, such as those involved in sleep-wake cycle, cognitive, or sensory functions. Additionally, astrocyte domains have been involved in neurogenesis and neuronal differentiation during development; they participate in the “tripartite synapse” with both pre-synaptic and post-synaptic neurons by tuning down or up neuronal activities through the control of neuronal synaptic strength. Connexin-based hemichannels are also involved in those regulations of neuronal activities, however, this feature will not be considered in the present review. Furthermore, neuronal processes, transmitting electrical signals to chemical synapses, stringently control astroglial connexin expression, and channel functions. Long-range energy trafficking toward neurons through connexin-coupled astrocytes and plasticity of those networks are hence largely dependent on neuronal activity. Such reciprocal interactions between neurons and astrocyte networks involve neurotransmitters, cytokines, endogenous lipids, and peptides released by neurons but also other brain cell types, including microglial and endothelial cells. Over the past 10 years, knowledge about neuroglial interactions has widened and now includes effects of CNS-targeting drugs such as antidepressants, antipsychotics, psychostimulants, or sedatives drugs as potential modulators of connexin function and thus astrocyte networking activity. In physiological situations, neuroglial networking is consequently resulting from a two-way interaction between astrocyte gap junction-mediated networks and those made by neurons. As both cell types are modulated by CNS drugs we postulate that neuroglial networking may emerge as new therapeutic targets in neurological and psychiatric disorders.

Dexamethasone and levetiracetam reduce hetero-cellular gap-junctional coupling between F98 glioma cells and glial cells in vitro

Gap junctions (GJs) in astrocytes and glioma cells are important channels for cell-to-cell communication that contribute to homo- and heterocellular coupling. According to recent studies, heterocellular gap-junctional communication (H-GJC) between glioma cells and their surrounding environment enhances glioma progression. Therefore, we developed a new in vitro model to examine H-GJC between glioma cells, astrocytes and microglia. Consequently, F98 rat glioma cells were double-labeled with GJ-impermeable (CM-DiI) and GJ-permeable dye (calcein AM) and were seeded on unlabeled astrocyte-microglia co-cultures. Dual whole cell voltage clamp recordings were carried out on selected cell pairs to characterize the functional properties of H-GJC in vitro. The expression of four types of connexins (Cxs), including Cx32, Cx36, Cx43 and Cx45, and microglial phenotypes were analyzed by immunocytochemistry. The H-GJC between glioma cells and astrocytes/microglia increased after a longer incubation period with a higher number of glioma cells. We provided evidence for the direct GJ coupling of microglia and glioma cells under native in vitro conditions. In addition, we exploited this model to evaluate H-GJC after incubation with levetiracetam (LEV) and/or dexamethasone (DEX). Previous in vitro studies suggest that LEV and DEX are frequently used to control seizure and edema in glioma. Our findings showed that LEV and/or DEX decrease the number of heterocellular coupled cells significantly. In conclusion, our newly developed model demonstrated H-GJC between glioma cells and both astrocytes and microglia. The reduced H-GJC by LEV and DEX suggests a potential effect of both drugs on glioma progression.

Neuroprotection and anti-seizure effects of levetiracetam in a rat model of penetrating ballistic-like brain injury

PURPOSE

We assessed the therapeutic efficacy of FDA-approved anti-epileptic drug Levetiracetam (LEV) to reduce post-traumatic nonconvulsive seizure (NCS) activity and promote neurobehavioral recovery following 10% frontal penetrating ballistic-like brain injury (PBBI) in male Sprague-Dawley rats.

METHODS

Experiment 1 anti-seizure study: 50 mg/kg LEV (25 mg/kg maintenance doses) was given twice daily for 3 days (LEV3D) following PBBI; outcome measures included seizures incidence, frequency, duration, and onset. Experiment 2 neuroprotection studies: 50 mg/kg LEV was given twice daily for either 3 (LEV3D) or 10 days (LEV10D) post-injury; outcome measures include motor (rotarod) and cognitive (water maze) functions.

RESULTS

LEV3D treatment attenuated seizure activity with significant reductions in NCS incidence (54%), frequency, duration, and delayed latency to seizure onset compared to vehicle treatment. LEV3D treatment failed to improve cognitive or motor performance; however extending the dosing regimen through 10 days post-injury afforded significant neuroprotective benefit. Animals treated with the extended LEV10D dosing regimen showed a twofold improvement in rotarod task latency to fall as well as significantly improved spatial learning performance (24%) in the MWM task.

CONCLUSIONS

These findings support the dual anti- seizure and neuroprotective role of LEV, but more importantly identify the importance of an extended dosing protocol which was specific to the therapeutic targets studied.

The effects of topiramate on lipopolysaccharide (LPS)-induced proinflammatory cytokine release from primary rat microglial cell cultures

A growing body of evidence suggests that inflammatory processes and activation of glial cells could contribute to seizures and epileptogenesis. In various animal studies on epilepsy, proinflammatory cytokines have been demonstrated to exert a proconvulsive activity. On the other hand, it is suggested that antiepileptic drugs could modulate immune system activity. The aim of the present study was to investigate whether topiramate, a new generation antiepileptic drug with a complex mechanism of action, could affect the lipopolysaccharide (LPS)-induced release of TNF-α, IL-1β and IL-6 from primary rat microglial cell cultures. Proinflammatory cytokines were measured in supernatants of primary rat microglial cell culture with enzyme-linked immunosorbent assay kits. Additionally, the effect of the drug on LPS-evoked changes in mitochondrial metabolic activity was evaluated with the aid of the MTT test. Topiramate (1, 10, 100μg/ml; 24h incubation) produced a statistically significant decrease in LPS-stimulated IL-1β and IL-6 levels from primary rat microglial cells in a concentration-dependent manner. The drug used at a concentration of 100μg/ml also significantly suppressed TNF-α release. Incubation of microglial cells with topiramate for 24h prevented the LPS-induced increase in their mitochondrial activity. It is suggested that the anti-cytokine action of topiramate could provide an additional mechanism in its antiepileptic activity.

Connexins and their channels in inflammation

Inflammation may be caused by a variety of factors and is a hallmark of a plethora of acute and chronic diseases. The purpose of inflammation is to eliminate the initial cell injury trigger, to clear out dead cells from damaged tissue and to initiate tissue regeneration. Despite the wealth of knowledge regarding the involvement of cellular communication in inflammation, studies on the role of connexin-based channels in this process have only begun to emerge in the last few years. In this paper, a state-of-the-art overview of the effects of inflammation on connexin signaling is provided. Vice versa, the involvement of connexins and their channels in inflammation will be discussed by relying on studies that use a variety of experimental tools, such as genetically modified animals, small interfering RNA and connexin-based channel blockers. A better understanding of the importance of connexin signaling in inflammation may open up towards clinical perspectives.

Ultralow Dose of Naloxone as an Adjuvant to Intrathecal Morphine Infusion Improves Perceived Quality of Sleep but Fails to Alter Persistent Pain: A Randomized, Double-blind, Controlled Study

Supplemental Digital Content is available in the text.

Introduction:

This randomized, cross-over, double-blind, controlled study of continuous intrathecal morphine administration in patients with severe, long-term pain addresses whether the supplementation of low doses of naloxone in this setting is associated with beneficial clinical effects.

Methods:

All of the study subjects (n=11) provided informed consent and were recruited from a subset of patients who were already undergoing long-term treatment with continuous intrathecal morphine because of difficult-to-treat pain. The patients were (in a randomized order) also given intrathecal naloxone (40 ng/24 h or 400 ng/24 h). As control, the patients’ ordinary dose of morphine without any additions was used. The pain (Numeric Rating Scale, NRS) during activity, perceived quality of sleep, level of activity, and quality of life as well as the levels of several proinflammatory and anti-inflammatory cytokines in the blood were assessed. The prestudy pain (NRS during activity) in the study group ranged from 3 to 10.

Results:

A total of 64% of the subjects reported improved quality of sleep during treatment with naloxone at a dose of 40 ng per 24 hours as compared with 9% with sham treatment (P=0.024). Although not statistically significant, pain was reduced by 2 NRS steps or more during supplemental treatment with naloxone in 36% of subjects when using the 40 ng per 24 hours dose and in 18% of the subjects when using naloxone 400 ng per 24 hours dose. The corresponding percentage among patients receiving unaltered treatment was 27%.

Conclusions:

To conclude, the addition of an ultralow dose of intrathecal naloxone (40 ng/24 h) to intrathecal morphine infusion in patients with severe, persistent pain improved perceived quality of sleep. We were not able to show any statistically significant effects of naloxone on pain relief, level of activity, or quality of life.

Therapeutic innovation: Inflammatory-reactive astrocytes as targets of inflammation

This study aimed to test pharmaceutical compounds targeting astrocytes showing inflammatory dysregulation. The primary rat brain cultures were treated with different batches of serum with or without microglia added to make the cells inflammatory-reactive. Lipopolysaccharide (LPS) and tryptase were used as inflammatory inducers. Expression levels of Toll-like receptor 4 (TLR4), Na⁺/K⁺-ATPase, and matrix metalloprotease-13 (MMP-13), as well as actin filament organization, pro-inflammatory cytokines, and intracellular Ca²⁺ release, were evaluated. LPS combined with tryptase upregulated TLR4 expression, whereas Na⁺/K⁺-ATPase expression was downregulated, ATP-evoked Ca²⁺ transients were increased, actin filaments were reorganized and ring structures instead of stress fibers were observed. Other aims of the study were to prevent astrocytes from becoming inflammatory-reactive and to restore inflammatory dysregulated cellular changes. A combination of the μ-opioid antagonist (-)-naloxone in ultra-low concentrations, the non-addictive μ-opioid agonist (-)-linalool, and the anti-epileptic agent levetiracetam was examined. The results indicated that this drug cocktail prevented the LPS- and tryptase-induced inflammatory dysregulation. The drug cocktail could also restore the LPS- and tryptase-treated cells back to a normal physiological level in terms of the analyzed parameters.

Glial dysfunction and persistent neuropathic postsurgical pain

BACKGROUND

Acute pain in response to injury is an important mechanism that serves to protect living beings from harm. However, persistent pain remaining long after the injury has healed serves no useful purpose and is a disabling condition. Persistent postsurgical pain, which is pain that lasts more than 3 months after surgery, affects 10-50% of patients undergoing elective surgery. Many of these patients are affected by neuropathic pain which is characterised as a pain caused by lesion or disease in the somatosensory nervous system. When established, this type of pain is difficult to treat and new approaches for prevention and treatment are needed. A possible contributing mechanism for the transition from acute physiological pain to persistent pain involves low-grade inflammation in the central nervous system (CNS), glial dysfunction and subsequently an imbalance in the neuron-glial interaction that causes enhanced and prolonged pain transmission.

AIM

This topical review aims to highlight the contribution that inflammatory activated glial cell dysfunction may have for the development of persistent pain.

METHOD

Relevant literature was searched for in PubMed.

RESULTS

Immediately after an injury to a nerve ending in the periphery such as in surgery, the inflammatory cascade is activated and immunocompetent cells migrate to the site of injury. Macrophages infiltrate the injured nerve and cause an inflammatory reaction in the nerve cell. This reaction leads to microglia activation in the central nervous system and the release of pro-inflammatory cytokines that activate and alter astrocyte function. Once the astrocytes and microglia have become activated, they participate in the development, spread, and potentiation of low-grade neuroinflammation. The inflammatory activated glial cells exhibit cellular changes, and their communication to each other and to neurons is altered. This renders neurons more excitable and pain transmission is enhanced and prolonged. Astrocyte dysfunction can be experimentally restored using the combined actions of a μ-opioid receptor agonist, a μ-opioid receptor antagonist, and an anti-epileptic agent. To find these agents we searched the literature for substances with possible anti-inflammatory properties that are usually used for other purposes in medicine. Inflammatory induced glial cell dysfunction is restorable in vitro by a combination of endomorphine-1, ultralow doses of naloxone and levetiracetam. Restoring inflammatory-activated glial cells, thereby restoring astrocyte-neuron interaction has the potential to affect pain transmission in neurons.

CONCLUSION

Surgery causes inflammation at the site of injury. Peripheral nerve injury can cause low-grade inflammation in the CNS known as neuroinflammation. Low-grade neuroinflammation can cause an imbalance in the glial-neuron interaction and communication. This renders neurons more excitable and pain transmission is enhanced and prolonged. Astrocytic dysfunction can be restored in vitro by a combination of endomorphin-1, ultralow doses of naloxone and levetiracetam. This restoration is essential for the interaction between astrocytes and neurons and hence also for modulation of synaptic pain transmission.

IMPLICATIONS

Larger studies in clinical settings are needed before these findings can be applied in a clinical context. Potentially, by targeting inflammatory activated glial cells and not only neurons, a new arena for development of pharmacological agents for persistent pain is opened.

Role of inflammation and its miRNA based regulation in epilepsy: Implications for therapy

There is a need to develop innovative therapeutic strategies to counteract epilepsy, a common disabling neurological disorder. Despite the recent advent of additional antiepileptic drugs and respective surgery, the treatment of epilepsy remains a major challenge. The available therapies are largely based on symptoms, and these approaches do not affect the underlying disease processes and are also associated frequently with severe side effects. This is mainly because of the lack of well-defined targets in epilepsy. The discovery that inflammatory mediators significantly contribute to the onset and recurrence of seizures in experimental seizure models, as well as the presence of inflammatory molecules in human epileptogenic tissue, highlights the possibility of targeting specific inflammation related pathways to control seizures that are otherwise resistant to the available AEDs. Emerging studies suggest that miRNAs have a significant role in regulating inflammatory pathways shown to be involved in epilepsy. These miRNAs can possibly be used as novel therapeutic targets in the treatment of epilepsy as well as serve as diagnostic biomarkers of epileptogenesis. This review highlights the immunological features underlying the pathogenesis of epileptic seizures and the possible miRNA mediated approaches for drug resistant epilepsies that modulate the immune-mediated pathogenesis.

Astrocyte roles in traumatic brain injury

Astrocytes sense changes in neural activity and extracellular space composition. In response, they exert homeostatic mechanisms critical for maintaining neural circuit function, such as buffering neurotransmitters, modulating extracellular osmolarity and calibrating neurovascular coupling. In addition to upholding normal brain activities, astrocytes respond to diverse forms of brain injury with heterogeneous and progressive changes of gene expression, morphology, proliferative capacity and function that are collectively referred to as reactive astrogliosis. Traumatic brain injury (TBI) sets in motion complex events in which noxious mechanical forces cause tissue damage and disrupt central nervous system (CNS) homeostasis, which in turn trigger diverse multi-cellular responses that evolve over time and can lead either to neural repair or secondary cellular injury. In response to TBI, astrocytes in different cellular microenvironments tune their reactivity to varying degrees of axonal injury, vascular disruption, ischemia and inflammation. Here we review different forms of TBI-induced astrocyte reactivity and the functional consequences of these responses for TBI pathobiology. Evidence regarding astrocyte contribution to post-traumatic tissue repair and synaptic remodeling is examined, and the potential for targeting specific aspects of astrogliosis to ameliorate TBI sequelae is considered.

Astrocyte uncoupling as a cause of human temporal lobe epilepsy

Glial cells are now recognized as active communication partners in the central nervous system, and this new perspective has rekindled the question of their role in pathology. In the present study we analysed functional properties of astrocytes in hippocampal specimens from patients with mesial temporal lobe epilepsy without (n = 44) and with sclerosis (n = 75) combining patch clamp recording, K(+) concentration analysis, electroencephalography/video-monitoring, and fate mapping analysis. We found that the hippocampus of patients with mesial temporal lobe epilepsy with sclerosis is completely devoid of bona fide astrocytes and gap junction coupling, whereas coupled astrocytes were abundantly present in non-sclerotic specimens. To decide whether these glial changes represent cause or effect of mesial temporal lobe epilepsy with sclerosis, we developed a mouse model that reproduced key features of human mesial temporal lobe epilepsy with sclerosis. In this model, uncoupling impaired K(+) buffering and temporally preceded apoptotic neuronal death and the generation of spontaneous seizures. Uncoupling was induced through intraperitoneal injection of lipopolysaccharide, prevented in Toll-like receptor4 knockout mice and reproduced in situ through acute cytokine or lipopolysaccharide incubation. Fate mapping confirmed that in the course of mesial temporal lobe epilepsy with sclerosis, astrocytes acquire an atypical functional phenotype and lose coupling. These data suggest that astrocyte dysfunction might be a prime cause of mesial temporal lobe epilepsy with sclerosis and identify novel targets for anti-epileptogenic therapeutic intervention.

Role of inflammatory mediators in the pathogenesis of epilepsy

Epilepsy is one of the most common chronic brain disorders worldwide, affecting 1% of people across different ages and backgrounds. Epilepsy is defined as the sporadic occurrence of spontaneous recurrent seizures. Accumulating preclinical and clinical evidence suggest that there is a positive feedback cycle between epileptogenesis and brain inflammation. Epileptic seizures increase key inflammatory mediators, which in turn cause secondary damage to the brain and increase the likelihood of recurrent seizures. Cytokines and prostaglandins are well-known inflammatory mediators in the brain, and their biosynthesis is enhanced following seizures. Such inflammatory mediators could be therapeutic targets for the development of new antiepileptic drugs. In this review, we discuss the roles of inflammatory mediators in epileptogenesis.

Actin filament reorganization in astrocyte networks is a key functional step in neuroinflammation resulting in persistent pain: novel findings on network restoration

In recent years, the importance of glial cell activation in the generation and maintenance of long-term pain has been investigated. One novel mechanism underlying long-lasting pain is injury-induced inflammation in the periphery, followed by microglial activation in the dorsal horn of the spinal cord, which results in local neuroinflammation. An increase in neuronal excitability may follow, with intense signaling along the pain tracts to the thalamus and the parietal cortex along with other cortical regions for the identification and recognition of the injury. If the local neuroinflammation develops into a pathological state, then the astrocytes become activated. Previous studies in which lipopolysaccharide (LPS) was used to induce inflammation have shown that in a dysfunctional astrocyte network, the actin cytoskeleton is reorganized from the normally occurring F-actin stress fibers into the more diffusible, disorganized, ring-form globular G-actin. In addition, Ca(2+) signaling systems are altered, Na(+)- and glutamate transporters are downregulated, and pro-inflammatory cytokines, particularly IL-1β, are released in dysfunctional astrocyte networks. In a series of experiments, we have demonstrated that these LPS-induced changes in astrocyte function can be restored by stimulation of Gi/o and inhibition of Gs with a combination of a μ-receptor agonist and ultralow concentrations of a μ-receptor antagonist and by inhibition of cytokine release, particularly IL-1β, by the antiepileptic drug levetiracetam. These findings could be of clinical significance and indicate a novel treatment for long-term pain.

Influence of drugs on gap junctions in glioma cell lines and primary astrocytes in vitro

Gap junctions (GJs) are hemichannels on cell membrane. Once they are intercellulary connected to the neighboring cells, they build a functional syncytium which allows rapid transfer of ions and molecules between cells. This characteristic makes GJs a potential modulator in proliferation, migration, and development of the cells. So far, several types of GJs are recognized on different brain cells as well as in glioma. Astrocytes, as one of the major cells that maintain neuronal homeostasis, express different types of GJs that let them communicate with neurons, oligodendrocytes, and endothelial cells of the blood brain barrier; however, the main GJ in astrocytes is connexin 43. There are different cerebral diseases in which astrocyte GJs might play a role. Several drugs have been reported to modulate gap junctional communication in the brain which can consequently have beneficial or detrimental effects on the course of treatment in certain diseases. However, the exact cellular mechanism behind those pharmaceutical efficacies on GJs is not well-understood. Accordingly, how specific drugs would affect GJs and what some consequent specific brain diseases would be are the interests of the authors of this chapter. We would focus on pharmaceutical effects on GJs on astrocytes in specific diseases where GJs could possibly play a role including: (1) migraine and a novel therapy for migraine with aura, (2) neuroautoimmune diseases and immunomodulatory drugs in the treatment of demyelinating diseases of the central nervous system such as multiple sclerosis, (3) glioma and antineoplastic and anti-inflammatory agents that are used in treating brain tumors, and (4) epilepsy and anticonvulsants that are widely used for seizures therapy. All of the above-mentioned therapeutic categories can possibly affect GJs expression of astrocytes and the role is discussed in the upcoming chapter.

Levetiracetam Differentially Alters CD95 Expression of Neuronal Cells and the Mitochondrial Membrane Potential of Immune and Neuronal Cells in vitro

Epilepsy is a neurological seizure disorder that affects over 100 million people worldwide. Levetiracetam, either alone, as monotherapy, or as adjunctive treatment, is widely used to control certain types of seizures. Despite its increasing popularity as a relatively safe and effective anti-convulsive treatment option, its mechanism(s) of action are poorly understood. Studies have suggested neuronal, glial, and immune mechanisms of action. Understanding the precise mechanisms of action of levetiracetam would be extremely beneficial in helping to understand the processes involved in seizure generation and epilepsy. Moreover, a full understanding of these mechanisms would help to create more efficacious treatments while minimizing side-effects. The current study examined the effects of levetiracetam on the mitochondrial membrane potential of neuronal and non-neuronal cells, in vitro, in order to determine if levetiracetam influences metabolic processes in these cell types. In addition, this study sought to address possible immune-mediated mechanisms by determining if levetiracetam alters the expression of immune receptor–ligand pairs. The results show that levetiracetam induces expression of CD95 and CD178 on NGF-treated C17.2 neuronal cells. The results also show that levetiracetam increases mitochondrial membrane potential on C17.2 neuronal cells in the presence of nerve growth factor. In contrast, levetiracetam decreases the mitochondrial membrane potential of splenocytes and this effect was dependent on intact invariant chain, thus implicating immune cell interactions. These results suggest that both neuronal and non-neuronal anti-epileptic activities of levetiracetam involve control over energy metabolism, more specifically, mΔΨ. Future studies are needed to further investigate this potential mechanism of action.