Brivaracetam attenuates pain behaviors in a murine model of neuropathic pain

The impact of brivaracetam on cognitive processes and anxiety in various experimental models

BACKGROUND

Memory deficits and anxiety symptoms are undesirable effects that occur in epilepsy patients. They may be associated with the pathophysiology of the disease but also with anticonvulsant therapy. Brivaracetam (BRV) is one of the newest antiseizure drugs. It acts as a ligand for synaptic vesicle glycoprotein 2A (SV2A), which may play a significant role in cognitive processes. Although BRV has a favorable safety profile, its central side effects remain unclear. Hence, this study aimed to evaluate the effect of BRV on various types of memory and anxiety in rats.

METHODS

BRV was given to adult male Wistar rats (n = 80) via gastric tube as a single dose (6 mg/kg or 20 mg/kg) or chronically (6 mg/kg). The effect of the drug on spatial memory was evaluated in the Morris water maze (MWM), fear-learning by passive avoidance (PA), and recognition memory with novel object recognition (NOR). The elevated plus maze (EPM) was used to assess anxiety-like behaviors.

RESULTS

The impact of BRV on memory is dose-dependent and mainly high doses may alter retrieval memory and fear-learning. Sub-chronic administration also impaired retrieval and spatial memory in animals. Moreover, chronic BRV may increase anxiety levels in rats but did not affect recognition memory.

CONCLUSIONS

BRV may cause transient memory deficits as well as anxiety disturbances. However, the results are varied and depend on the type of memory, used dose, and duration of administration.

Modulating Hyperpolarization-Activated Cation Currents through Small Molecule Perturbations: Magnitude and Gating Control

The hyperpolarization-activated cation current (Ih) exhibits a slowly activating time course of the current (Ih) when the cell membrane is hyperpolarized for an extended duration. It is involved in generating electrical activity in various excitable cells. Numerous structurally distinct compounds or herbal drugs have the potential to impact both the magnitude and gating kinetics of this current. Brivaracetam, a chemical analog of levetiracetam known to be a ligand for synaptic vesicle protein 2A, could directly suppress the Ih magnitude. Carisbamate, an anticonvulsant agent, not only inhibited the Ih amplitude but also reduced the strength of voltage-dependent hysteresis (Hys(V)) associated with Ih. Cilobradine, similar to ivabradine, inhibited the amplitude of Ih; however, it also suppressed the amplitude of delayed-rectifier K+ currents. Dexmedetomidine, an agonist of α2-adrenergic receptor, exerted a depressant action on Ih in a concentration-dependent fashion. Suppression of Ih amplitude was observed when GAL-021, a breathing control modulator, was present at a concentration exceeding 30 μM. Lutein, one of the few xanthophyll carotenoids, was able to suppress the Ih amplitude as well as to depress Hys(V)'s strength of Ih. Pirfenidone, a pyridine derivative known to be an anti-fibrotic agent, depressed the Ih magnitude in a concentration- and voltage-dependent fashion. Tramadol, a synthetic centrally active analgesic, was shown to reduce the Ih magnitude, independent of its interaction with opioid receptors. Various herbal drugs, including ent-kaurane-type diterpenoids from Croton tonkinensis, Ganoderma triterpenoids, honokiol, and pterostilbene, demonstrated efficacy in reducing the magnitude of Ih. Conversely, oxaliplatin, a platinum-based chemotherapeutic compound, was observed to effectively increase the Ih amplitude. Collectively, the regulatory effects of these compounds or herbal drugs on cellular function can be partly attributed to their perturbations on Ih.

Investigating anti-inflammatory and immunomodulatory properties of brivaracetam and lacosamide in experimental autoimmune encephalomyelitis (EAE)

PURPOSE

Inflammation plays a role in drug-resistant epilepsy (DRE). We have previously reported an increased proportion of CD4 T cells displaying a pro-inflammatory profile in the peripheral blood of adults with DRE. Specific anti-epileptic drugs (AEDs) exhibit immunomodulatory properties that could increase the risk of infections but also contribute to their beneficial impact on DRE and other neurological diseases. The impact of novel generation AEDs on the profile of immune cells and on neuroinflammatory processes remains unclear.

METHODS

We compared the influence of brivaracetam and lacosamide on the activation of human and murine peripheral immune cells in vitro and in vivo in active experimental autoimmune encephalomyelitis (EAE), a common mouse model of central nervous system inflammation.

RESULTS

We found that brivaracetam and lacosamide at 2.5 μg/ml did not impair the survival and activation of human immune cells, but a higher dose of 25 μg/ml decreased mitogen-induced proliferation of CD8 T cells in vitro. Exposure to high doses of brivaracetam, and to a lesser extent lacosamide, reduced the proportion of CD25⁺ and CD107a⁺ CD8⁺ human T cells in vitro, and the frequency of CNS-infiltrating CD8⁺ T cells at EAE onset and CD11b⁺ myeloid cells at peak in vivo. Prophylactic administration of brivaracetam or lacosamide did not delay EAE onset but significantly improved the clinical course in the chronic phase of EAE compared to control.

CONCLUSION

Novel generation AEDs do not impair the response to immunization with MOG peptide but improve the course of EAE, possibly through a reduction of neuroaxonal damage.

Potential novel therapeutic strategies for neuropathic pain

Purpose

To explore the potential therapeutic strategies of different types of neuropathic pain (NP) and to summarize the cutting-edge novel approaches for NP treatment based on the clinical trials registered on ClinicalTrials.gov.

Methods

The relevant clinical trials were searched using ClinicalTrials.gov Dec 08, 2022. NP is defined as a painful condition caused by neurological lesions or diseases. All data were obtained and reviewed by the investigators to confirm whether they were related to the current topic.

Results

A total of 914 trials were included in this study. They were divided into painful diabetic neuropathy (PDN), postherpetic neuralgia (PHN), sciatica (SC), peripheral nerve injury-related NP (PNI), trigeminal neuralgia (TN), chemotherapy-induced NP (CINP), general peripheral NP (GPNP) and spinal cord injury NP (SCI-NP). Potential novel therapeutic strategies, such as novel drug targets and physical means, were discussed for each type of NP.

Conclusion

NP treatment is mainly dominated by drug therapy, and physical means have become increasingly popular. It is worth noting that novel drug targets, new implications of conventional medicine, and novel physical means can serve as promising strategies for the treatment of NP. However, more attention needs to be paid to the challenges of translating research findings into clinical practice.

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.

MiR-204-5p Alleviates Neuropathic Pain by Targeting BRD4 in a Rat Chronic Constrictive Injury Model

Purpose

The pathogenesis of neuropathic pain is complex, and previous studies have found that microRNAs are important regulators of neuropathic pain and are associated with the progression of neuropathic pain. This study aims to explore the level and role of miR-204-5p in the chronic constrictive injury (CCI) model of rats.

Patients and Methods

The CCI rat model was constructed to evaluate paw withdrawal threshold (PWT), paw withdrawal latency (PWL), the expressions of miR-204-5p, and the contents of inflammatory factors in the model. Overexpression of miR-204-5p in rat spinal cord was induced by intrathecal injection of miR-204-5p mimics. PWT and PWL were used to estimate mechanical and thermal pain thresholds. IL-6 and TNF-α were determined by ELISA. Luciferase reporter gene was conducted to verify the targeting relationship between miR-204-5p and BRD4.

Results

miR-204-5p was abnormally down-regulated in the CCI group. The thresholds of mechanical and thermal pain stimulation in the CCI group were lower, and the levels of inflammatory factors were higher than those in the sham group. Overexpression of miR-204-5p alleviated PWT, PWL and inflammatory factors. Besides, the luciferase reporter gene showed that BRD4 was a target gene of miR-204-5p.

Conclusion

These results suggested that miR-204-5p may alleviate neuropathic pain and inflammation through targeted regulation of BRD4 expression.

The Integrated Effects of Brivaracetam, a Selective Analog of Levetiracetam, on Ionic Currents and Neuronal Excitability

Brivaracetam (BRV) is recognized as a novel third-generation antiepileptic drug approved for the treatment of epilepsy. Emerging evidence has demonstrated that it has potentially better efficacy and tolerability than its analog, Levetiracetam (LEV). This, however, cannot be explained by their common synaptic vesicle-binding mechanism. Whether BRV can affect different ionic currents and concert these effects to alter neuronal excitability remains unclear. With the aid of patch clamp technology, we found that BRV concentration dependently inhibited the depolarization-induced M-type K⁺ current (I_K(M)), decreased the delayed-rectifier K⁺ current (I_K(DR)), and decreased the hyperpolarization-activated cation current in GH3 neurons. However, it had a concentration-dependent inhibition on voltage-gated Na⁺ current (I_Na). Under an inside-out patch configuration, a bath application of BRV increased the open probability of large-conductance Ca²⁺-activated K⁺ channels. Furthermore, in mHippoE-14 hippocampal neurons, the whole-cell I_Na was effectively depressed by BRV. In simulated modeling of hippocampal neurons, BRV was observed to reduce the firing of the action potentials (APs) concurrently with decreases in the AP amplitude. In animal models, BRV ameliorated acute seizures in both OD-1 and lithium-pilocarpine epilepsy models. However, LEV had effects in the latter only. Collectively, our study demonstrated BRV’s multiple ionic mechanism in electrically excitable cells and a potential concerted effect on neuronal excitability and hyperexcitability disorders.

SUR1, newly expressed in astrocytes, mediates neuropathic pain in a mouse model of peripheral nerve injury

BACKGROUND

Neuropathic pain following peripheral nerve injury (PNI) is linked to neuroinflammation in the spinal cord marked by astrocyte activation and upregulation of interleukin 6 (IL-6), chemokine (C-C motif) ligand 2 (CCL2) and chemokine (C-X-C motif) ligand 1 (CXCL1), with inhibition of each individually being beneficial in pain models.

METHODS

Wild type (WT) mice and mice with global or pGfap-cre- or pGFAP-cre/ERT2-driven Abcc8/SUR1 deletion or global Trpm4 deletion underwent unilateral sciatic nerve cuffing. WT mice received prophylactic (starting on post-operative day [pod]-0) or therapeutic (starting on pod-21) administration of the SUR1 antagonist, glibenclamide (10 µg IP) daily. We measured mechanical and thermal sensitivity using von Frey filaments and an automated Hargreaves method. Spinal cord tissues were evaluated for SUR1-TRPM4, IL-6, CCL2 and CXCL1.

RESULTS

Sciatic nerve cuffing in WT mice resulted in pain behaviors (mechanical allodynia, thermal hyperalgesia) and newly upregulated SUR1-TRPM4 in dorsal horn astrocytes. Global and pGfap-cre-driven Abcc8 deletion and global Trpm4 deletion prevented development of pain behaviors. In mice with Abcc8 deletion regulated by pGFAP-cre/ERT2, after pain behaviors were established, delayed silencing of Abcc8 by tamoxifen resulted in gradual improvement over the next 14 days. After PNI, leakage of the blood-spinal barrier allowed entry of glibenclamide into the affected dorsal horn. Daily repeated administration of glibenclamide, both prophylactically and after allodynia was established, prevented or reduced allodynia. The salutary effects of glibenclamide on pain behaviors correlated with reduced expression of IL-6, CCL2 and CXCL1 by dorsal horn astrocytes.

CONCLUSION

SUR1-TRPM4 may represent a novel non-addicting target for neuropathic pain.