Acute effects of aceclofenac, COX-2 inhibitor, on penicillin-induced epileptiform activity

A Narrative Review of the Published Pre-Clinical Evaluations: Multiple Effects of Arachidonic Acid, its Metabolic Enzymes and Metabolites in Epilepsy

Arachidonic acid (AA), an important polyunsaturated fatty acid in the brain, is hydrolyzed by a direct action of phospholipase A2 (PLA2) or through the combined action of phospholipase C and diacylglycerol lipase, and released into the cytoplasm. Various derivatives of AA can be synthesized mainly through the cyclooxygenase (COX), lipoxygenase (LOX) and cytochrome P450 (P450) enzyme pathways. AA and its metabolic enzymes and metabolites play important roles in a variety of neurophysiological activities. The abnormal metabolites and their catalytic enzymes in the AA cascade are related to the pathogenesis of various central nervous system (CNS) diseases, including epilepsy. Here, we systematically reviewed literatures in PubMed about the latest randomized controlled trials, animal studies and clinical studies concerning the known features of AA, its metabolic enzymes and metabolites, and their roles in epilepsy. The exclusion criteria include non-original studies and articles not in English.

Electrophysiologic and anti-inflammatorial effects of cyclooxygenase inhibition in epileptiform activity

The aim of our study is to investigate the electrophysiological and anti-inflammatory effects of diclofenac potassium on epileptiform activity, which is the liquid form of diclofenac, and frequently used clinically for inflammatory process by inhibiting cyclooxygenase enzyme (COX). Wistar rats aged 2-4 months were divided into Epilepsy, Diazepam, Diclofenac potassium, and Diazepam+diclofenac potassium groups. Diazepam and diclofenac potassium were administered intraperitoneally 30 min after the epileptiform activity was created with penicillin injected intracortically under anesthesia. After the electrophysiological recording was taken in the cortex for 125 min, interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) were evaluated by the ELISA in the serums. No change was observed between the groups in serum IL-1β, IL-6, and TNF-α values. It was observed that the co-administration of diclofenac potassium and diazepam at 51-55, 56-60, 61-65, 111-115, and 116-120 min was more effective in reducing spike amplitude than diclofenac potassium alone (p < 0.05). Single-dose diclofenac potassium did not have an anti-inflammatory effect in epileptiform activity but both diazepam and diclofenac potassium reduced the epileptiform activity.

An involvement of COX and 5-LOX pathways in the penicillin- and pentylenetetrazole (PTZ)-induced epilepsy models

This study aimed to examine the relationship between epilepsy and COX/5-LOX inflammation pathways in the penicillin and pentylenetetrazole (PTZ)-induced epilepsy models. For this purpose, 42 albino male Wistar rats were used in this study. In the penicillin and PTZ-induced epilepsy models, epileptiform activity was induced by injection of penicillin (500 IU, i.c.) and PTZ (35 mg/kg, i.p., three times a week), respectively. Licofelone (20 mg/kg, i.p.), a dual inhibitor of COX/5-LOX, and esculetin (20 mg/kg, i.p.), a 5-LOX inhibitor, were given. In the penicillin-induced epilepsy model, ECoG activity was recorded for 180 min. In the PTZ-induced epilepsy model, both ECoG activity was recorded, and behavioral parameters were performed. In the penicillin groups, both licofelone and esculetin decreased the mean spike frequency and amplitude during the experiments. In the PTZ groups, licofelone (20 mg/kg, i.p.) was more effective than esculetin (20 mg/kg, i.p.). Licofelone showed its protective effects both in ECoG activity and in behavioral parameters. Esculetin was less effective when compared to licofelone. The electrophysiological and behavioral data from the present study indicated that inflammation pathways might have a crucial role in controlling epileptiform activity in rats. Licofelone might be a valuable candidate in advanced studies.

Acute treatment with dexketoprofen reduces penicillin induced epileptiform activity in wistar albino rats (dexketoprofen in penicillin induced seizure model)

AIM

Dexketoprofen trometamol is one of the most commonly used anti-inflammatory analgesic agents for pain control. This study aims to investigate the effect of dexketoprofen on penicillin-induced epileptiform activity in rats.

METHOD

In this study, 28 male Wistar rats weighing 220-240 g were used. Tripolar electrodes were implanted under urethane anesthesia. Epileptiform activity was induced by micro-injection of 500 units (IU) penicillin into the rats' left somatomotor cortex. Dexketoprofen (5, 25, and 50 mg/kg) was administrated intraperitoneally after 30 min of penicillin injection. Epileptiform activity was evaluated by electrocorticography (ECoG).

RESULTS

The low dose of dexketoprofen administration (5 mg/kg) reduced the mean spike frequency of epileptiform activity 60 min after its injection. However, 25 and 50 mg/kg dexketoprofen significantly reduced the mean spike frequency 30 min after the dexketoprofen injection compared to the control group (p < 0.05). The amplitudes of epileptiform discharges in all groups were unaffected (p > 0.05).

CONCLUSION

This study revealed that dexketoprofen had a significant anti-seizure effect when applied at 5 mg/kg, 25 mg/kg, and 50 mg/kg (especially at 25 and 50 mg/kg), in the penicillin-induced seizure model. The obtained data revealed that dexketoprofen might play an essential role against epileptic seizures.

Novel roles of ER stress in repressing neural activity and seizures through Mdm2- and p53-dependent protein translation

Seizures can induce endoplasmic reticulum (ER) stress, and sustained ER stress contributes to neuronal death after epileptic seizures. Despite the recent debate on whether inhibiting ER stress can reduce neuronal death after seizures, whether and how ER stress impacts neural activity and seizures remain unclear. In this study, we discovered that the acute ER stress response functions to repress neural activity through a protein translation-dependent mechanism. We found that inducing ER stress promotes the expression and distribution of murine double minute-2 (Mdm2) in the nucleus, leading to ubiquitination and down-regulation of the tumor suppressor p53. Reduction of p53 subsequently maintains protein translation, before the onset of translational repression seen during the latter phase of the ER stress response. Disruption of Mdm2 in an Mdm2 conditional knockdown (cKD) mouse model impairs ER stress-induced p53 down-regulation, protein translation, and reduction of neural activity and seizure severity. Importantly, these defects in Mdm2 cKD mice were restored by both pharmacological and genetic inhibition of p53 to mimic the inactivation of p53 seen during ER stress. Altogether, our study uncovered a novel mechanism by which neurons respond to acute ER stress. Further, this mechanism plays a beneficial role in reducing neural activity and seizure severity. These findings caution against inhibition of ER stress as a neuroprotective strategy for seizures, epilepsies, and other pathological conditions associated with excessive neural activity.

One-third of epilepsy patients respond poorly to current anti-epileptic drugs. Thus, there is an urgent need to characterize cellular behavior during seizures, and the corresponding molecular mechanisms in order to develop better therapies. Seizures are known to induce ER stress but how the ER stress response functions to modulate seizure activity is unknown. Our study provides evidence to demonstrate a novel and beneficial role for the ER stress response in reducing neural activity and seizure severity. Mechanistically, we found that these beneficial effects are mediated by elevated protein translation, which is triggered by the activation of Mdm2-p53 signaling, during the early ER stress response. Our findings suggest that therapeutic attempts to reduce ER stress in epilepsies may result in worsening seizure activity and therefore caution against inhibition of ER stress as a neuroprotective strategy for epilepsies.

An update of cyclooxygenase (COX)-inhibitors in epilepsy disorders

INTRODUCTION

Neuroinflammation has a critical role in brain disorders. Cyclooxygenase (COX) is one of the principal drug targets for the reduction of neuroinflammation; however, studies have yielded mixed results for COX-inhibitors in the treatment of diverse acute and chronic models of epilepsy.

AREAS COVERED

The article covers the effects of COX-inhibitors in epilepsy disorders. A considerable emphasis has been placed on the antiepileptic and 'disease-modifying' properties of COX-1 and COX-2 inhibitors in various preclinical epilepsy models.

EXPERT OPINION

The effect of COX-inhibitors on epilepsy is inconclusive. Studies have indicated beneficial effects in preclinical models; however, proconvulsant or no effects have also been observed. These molecules may have a bidirectional role with early neuroprotective and delayed neurotoxic effects. Further systematic preclinical studies to establish the use of COX-inhibitors in epilepsy are necessary.

The COX-2/prostanoid signaling cascades in seizure disorders

Introduction：A robust neuroinflammatory response is a prevalent feature of multiple neurological disorders, including epilepsy and acute status epilepticus. One component of this neuroinflammatory reaction is the induction of cyclooxygenase-2 (COX-2), synthesis of several prostaglandins and endocannabinoid metabolites, and subsequent activation of prostaglandin and related receptors. Neuroinflammation mediated by COX-2 and its downstream effectors has received considerable attention as a potential target class to ameliorate the deleterious consequences of neurological injury. Areas covered: Here we describe the roles of COX-2 as a major inflammatory mediator. In addition, we discuss the receptors for prostanoids PGE₂, prostaglandin D2, and PGF_2α as potential therapeutic targets for inflammation-driven diseases. The consequences of prostanoid receptor activation after seizure activity are discussed with an emphasis on the utilization of small molecules to modulate prostanoid receptor activity. Expert opinion: Limited clinical trial experience is supportive but not definitive for a role of the COX signaling cascade in epileptogenesis. The cardiotoxicity associated with chronic coxib use, and the expectation that COX-2 inhibition will influence the levels of endocannabinoids, leukotrienes, and lipoxins as well as the prostaglandins and their endocannabinoid metabolite analogs, is shifting attention toward downstream synthases and receptors that mediate inflammation in the brain.