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.

[Antipsychotic Treatment of Alcohol Withdrawal Syndrome with Focus on Delirium Tremens: a Systematic Review]

BACKGROUND

Delirium tremens (DT) is a common complication of alcohol withdrawal. Pharmacological treatment of hospitalized patients with DT is important in addiction medicine but also in other medical disciplines where DT can occur as a complication of hospitalization. Patients suffering from DT require treatment with benzodiazepines (short-acting benzodiazepines for elderly patients to reduce accumulation), and in cases of psychotic symptoms, treatment with antipsychotics. Benzodiazepines are a first-line treatment for DT. A specific guideline for the use of antipsychotics has yet to be developed. This review discusses the current guidelines and literature on the antipsychotic treatment options in DT.

AIM

Systematic presentation of relevant antipsychotics for the treatment of DT.

METHODS

A systematic literature search was conducted using Scopus and PubMed. The last search was conducted on May 22nd 2022. Original articles and reviews on antipsychotic treatment in alcohol withdrawal and DT were included in this review. Further, international guidelines were also considered. The review was registered using the PROSPERO database (https://www.crd.york.ac.uk/prospero/); CRD42021264611.

RESULTS

Haloperidol is mainly recommended for use in the intensive care unit. There is little literature on the use of atypical antipsychotics to treat DT. Treatment with antipsychotics always should be combined with benzodiazepines, and physicians should watch out for complications like neuroleptic malignant syndrome, QTc interval prolongation, extrapyramidal symptoms and withdrawal seizures resulting from lowering the threshold for seizures.

CONCLUSION

Antipsychotic treatment should depend on the experience of the physician. Beside haloperidol, no other clear recommendations are available.

Experimental Investigations of Monomethyl and Dimethyl Fumarate in an Astrocyte-Microglia Co-Culture Model of Inflammation

INTRODUCTION

Multiple sclerosis (MS) is the most common chronic inflammatory, demyelinating disease of the central nervous system. Dimethyl fumarate (DMF) and monomethyl fumarate (MMF) belong to the disease-modifying drugs in treatment of MS. There is evidence that astrocytes and microglia are involved in MS pathology, but few studies are available about MMF and DMF effects on astrocytes and microglia. The aim of this study was to investigate the effects of MMF and DMF on microglial activation and morphology as well as potential effects on glial viability, Cx43, and AQP4 expressions in different set-ups of an in vitro astrocyte-microglia co-culture model of inflammation.

METHODS

Primary rat glial co-cultures of astrocytes containing 5% (M5, mimicking "physiological" conditions) or 30% (M30, mimicking "pathological, inflammatory" conditions) of microglia were treated with different concentrations of MMF (0.1, 0.5, and 2 μg/mL) or DMF (1.5, 5, and 15 μM) for 24 h. Viability, proliferation, and cytotoxicity of glial cells were examined using MTT assay. Immunocytochemistry was performed to analyze the microglial phenotypes. Connexin 43 (Cx43) and aquaporin 4 (AQP4) expressions were quantified by immunoblot analysis.

RESULTS

Treatment with different concentrations of MMF or DMF for 24 h did not change the glial cell viability in M5 and M30 co-cultures. Microglial phenotypes were not altered by DMF under physiological M5 conditions, but treatment with higher concentration of DMF (15 μM) induced microglial activation under inflammatory M30 conditions. Incubation with different concentrations of MMF had no effects on microglial phenotypes. The Cx43 expression in M5 and M30 co-cultures was not changed significantly by immunoblot analysis after incubation with different concentrations of DMF or MMF for 24 h. The AQP4 expression was significantly increased in M5 co-cultures after incubation with 5 μm DMF. Under the other conditions, AQP4 expression was not affected by DMF or MMF.

DISCUSSION

In different set-ups of the astrocyte-microglia co-culture model of inflammation, MMF has not shown significant effects. DMF had only limited effects on microglia phenotypes and AQP4 expression. In summary, mechanisms of action of fumarates probably do not involve direct effects on microglia phenotypes as well as Cx43 and AQP4 expression.

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 < 0.01: **). Treatment with BRV in therapeutic concentrations (0.5 and 2 μg/ml) reduced the resting microglia (p < 0.05: *) and increased the microglial activation under inflammatory conditions (p < 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 < 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.

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.

Ammonia induced microglia activation was associated with limited effects on connexin 43 and aquaporin 4 expression in an astrocyte-microglia co-culture model

Background

Hepatic encephalopathy (HE) is a neurological complication resulting from acute or chronic liver disease. Hyperammonemia leading to astrocyte swelling and cerebral edema in combination with neuroinflammation including microglia activation, mainly contribute to the pathogenesis of HE. However, little is known about microglia and their inflammatory response, as well as their influence on astrocytic channels and astrocyte swelling under hyperammonemia.

Objective

To investigate the effects of ammonia on the microglial activation and morphology in different set-ups of an in vitro astrocyte-microglia co-culture model. Further, potential effects on glial viability, connexin 43 (Cx43) and aquaporin 4 (AQP4) expression were tested.

Methods

Primary rat glial co-cultures of astrocytes containing 5% (M5, representing "physiological" conditions) or 30% (M30, representing "pathological" conditions) of microglia were incubated with 3 mM, 5 mM, 10 mM and 20 mM ammonium chloride (NH4Cl) for 6 h and 24 h in order to mimic the conditions of HE. An MTT assay was performed to measure the viability, proliferation and cytotoxicity of cells. The microglial phenotypes were analyzed by immunocytochemistry. The expression of Cx43 and AQP4 were quantified by immunoblot analysis.

Results

A significant reduction of glial viability was observed in M30 co-cultures after incubation with 20 mM NH4Cl for 6 h, whereas in M5 co-cultures the viability remained unchanged. Microglial activation was detected by immunocytochemistry after incubation with 3 mM, 5 mM and 10 mM NH4Cl for 6 h and 24 h in M5 as well as in M30 co-cultures. The Cx43 expression was slightly increased in M30 co-cultures after 6 h incubation with 5 mM NH4Cl. Also, the AQP4 expression was slightly increased only in M5 co-cultures treated with 10 mM NH4Cl for 6 h. Under the other conditions, Cx43 and AQP4 expression was not affected by NH4Cl.

Conclusions

The novel aspect of our study was the significant microglial activation and decrease of viability after NH4Cl incubation in different set-ups of an in vitro astrocyte-microglia co-culture model, contributing to better understanding of pathophysiological mechanisms of HE. Hyperammonemia led to limited effects on Cx43 and AQP4 expression, the relevance of these minimal changes should be viewed with caution.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12868-021-00628-1.