Elsevier

Epilepsy Research

Volume 84, Issue 1, March 2009, Pages 56-66
Epilepsy Research

Effects of SC58236, a selective COX-2 inhibitor, on epileptogenesis and spontaneous seizures in a rat model for temporal lobe epilepsy

https://doi.org/10.1016/j.eplepsyres.2008.12.006Get rights and content

Summary

Inflammation is an important biological process that is activated after status epilepticus and could be implicated in the development of epilepsy. Here we tested whether an anti-inflammatory treatment with a selective cox-2 inhibitor (SC58236) could prevent the development of epilepsy or modify seizure activity during the chronic epileptic phase. SC58236 was orally administered (10 mg/kg) during the latent period for 7 days, starting 4 h after electrically induced SE. Seizures were monitored using EEG/video monitoring until 35 days after SE. Cell death and inflammation were investigated using immunocytochemistry (NeuN and Ox-42). Sprouting was studied using Timm's staining after 1 week and after 4–5 months when rats were chronic epileptic. SC58236 was also administered during 5 days in chronic epileptic rats. Hippocampal EEG seizures were continuously monitored before, during and after treatment. SC58236 effectively reduced PGE2 production but did not modify seizure development or the extent of cell death or microglia activation in the hippocampus. SC58236 treatment in chronic epileptic rats did not show any significant change in seizure duration or frequency of daily seizures. The fact that cox-2 inhibition, which effectively reduced prostaglandin levels, did not modify epileptogenesis or chronic seizure activity suggests that this type of treatment (starting after SE) will not provide an effective anti-epileptogenic or anti-epileptic therapy.

Introduction

In most patients who suffer from human mesial temporal lobe epilepsy (MTLE), the development of epilepsy is an ongoing process. The disease process follows an initial insult (e.g. trauma, complex febrile seizures or status epilepticus) and after a latency period – that may last many years – leads to subsequent spontaneous seizures that might worsen over time, even to a stage that seizures become intractable (Engel, 1996, Sutula and Hermann, 1999). Control of epilepsy has primarily focused on suppressing seizure activity after epilepsy has developed. However it is even more challenging to avoid the development of epilepsy (acquired by an initial event) by preventing or stopping epileptogenesis, the process by which the brain becomes epileptic. Only a few experimental studies have focused on the effect of drugs and the risk of epilepsy after status epilepticus (SE). Chronic treatment with an alpha2 adrenergic agonist did not prevent epileptogenesis although the epilepsy became milder (Pitkanen et al., 2004). Furthermore, treatment during status epilepticus with high doses of diazepam has shown some anti-epileptogenic effects (Pitkanen et al., 2005). However, clinical trials using conventional anti-epileptic drugs (AEDs) have been disappointing and did not reveal an anti-epileptogenic effect (Temkin, 2001). Therefore it is important to test potential new targets which could be used to control the epileptogenic process that occurs after an initial insult.

Effects of drugs on epileptogenesis can be tested in animal models for MTLE in which epilepsy develops after a chemically or electrically induced SE. In our laboratory we use the rat post-SE model in which epilepsy gradually develops after an electrically evoked SE. In a large-scale microarray study we have investigated gene expression in hippocampus (CA3) and entorhinal cortex at different epileptogenic stages. We found many genes that dynamically change their expression at specific time points after SE (Gorter et al., 2006, Gorter et al., 2007). Biological processes such as proteolysis, inflammation, immune and defense response were most conspicuously upregulated in the acute and latent phase and some in the chronic epileptic phase.

Recently, using microarrays we found prominent changes in prostaglandin synthesis and regulation shortly after SE (Fig. 1 and Gorter et al., 2006). An activity-dependent increase of cyclooxygenase-2 (Cox-2) expression has been observed within one day after SE and during the chronic epileptic phase (Gorter et al., 2006). Activation of Cox-2 has also been observed during kindling epileptogenesis (Chen et al., 1995, Tu and Bazan, 2003),. This enzyme is responsible for the activation of prostanoids including PGE2. Increased activity of the prostanoid pathway produces neuroinflammation involving release of cytokines and oxidative stress. Moreover, activation of prostanoids (via Cox-2) can induce glutamate release (Bezzi et al., 1998) and can increase excitability via modulation of potassium channels (Chen and Bazan, 2005). All these conditions could destabilize neuronal network activity. Effects on development of epilepsy have also been studied in genetically modified mice: Cox-2 deficiency decreases the incidence of afterdischarges in a rapid kindling model (Takemiya et al., 2003), while Cox-2 overexpression leads to increased lethality after kainate induced seizures (Kelley et al., 1999). Together these studies suggest that cox-2 inhibitors are possible candidates that merit being investigated since the modification of these targets may counteract the development of the epileptic condition or modify seizure frequency during the chronic epileptic phase.

Section snippets

Experimental animals

Adult male Sprague–Dawley rats (Harlan Netherlands, Horst, The Netherlands) weighing 400–600 g were used in this study which was approved by the University Animal Welfare committee. In total 90 rats were used. The rats were housed individually in a controlled environment (21 ± 1 °C; humidity 60%; lights on 12 h/day; food and water available ad libitum).

Electrode implantation and status epilepticus induction

Rats were anesthetized with an i.p. injection of ketamine (57 mg/kg; Alfasan, Woerden, The Netherlands) and xylazine (9 mg/kg; Bayer AG, Leverkusen,

Severity of status epilepticus

Four hours after electrically induced SE, SC58236 (or vehicle) was administered to the rats under isoflurane anesthesia. Before the anesthesia, all rats exhibited moderate behavioral SE with often continuous head bobbing, regularly interrupted by stage V seizures. Although the behavioral manifestation had become milder after recovery from anesthesia in both groups, the electrographic SE continued for several hours more. SE duration did not significantly differ between the SC-treated and vehicle

Discussion

Cox-2, a key enzyme that plays an important role in inflammation, was extensively upregulated after SE in rat and during the chronic epileptic phase both in rat and human. Treatment with the selective cox-2 inhibitor SC58236 during the latent period did not have a significant effect on seizure development in the rat. Although it effectively reduced PGE2 production, it did not reduce the extent of microglial cell activation, cell death or development of mossy fiber sprouting. Cox-2 inhibition in

Conclusion

In summary, we showed that treatment with the Cox-2 inhibitor SC58236, starting shortly after electrically induced SE, did not have pronounced effects on the extent of neurodegeneration, sprouting or microglial activation. More importantly, Cox-2 inhibition did not lead to a reduced rate of epileptogenesis. Treatment during the chronic epileptic phase also did not lead to a significant change in seizure frequency or duration. The lack of any substantial effects of this selective compound during

Conflict of interest

The authors have no conflicts of interest.

Acknowledgements

We thank Pfizer for providing SC58236. This work was supported by the “Nationaal Epilepsie Fonds” grant NEF 03-03 and 07-19 (JAG), the Hersenstichting and the EU-FP7-project (202167; E. Aronica). We thank Professor F.H. Lopes da Silva for critically reading the manuscript. We thank J.C. Baayen, Free University Amsterdam, for providing the human material.

References (33)

Cited by (99)

  • The holy grail of epilepsy prevention: Preclinical approaches to antiepileptogenic treatments

    2020, Neuropharmacology
    Citation Excerpt :

    Similarly, the transient administration of an anti-HMGB1 monoclonal antibody in mice during epileptogenesis resulted in disease-modifying effects consisting of a significant reduction in spontaneous seizure frequency and improvement of cognitive deficits (Zhao et al., 2017). Furthermore, inhibition of prostaglandin synthesis by blocking COX-2 by celecoxib was reported to cause a significant disease-modifying effect in the pilocarpine rat model (Jung et al., 2006); however, this could not be replicated by other studies with selective COX-2 inhibitors (Holtman et al., 2009; Polascheck et al., 2010). Oxidative stress and brain inflammation are two phenomena that are intimately associated, since they are functionally interconnected and reinforce each other (Ravizza and Vezzani, 2018).

  • Therapeutic role of targeting mTOR signaling and neuroinflammation in epilepsy

    2020, Epilepsy Research
    Citation Excerpt :

    Several animal studies have shown that blockade of COX2 significantly reduces seizure frequency and severity, as well as is neuroprotective against seizure-induced mossy fiber sprouting and neurogenesis (Jung et al., 2006; Ma et al., 2012). However, some studies have shown that inhibition of COX2 worsened chronic seizures and produced adverse effects, suggesting the effects of inhibition are time and model dependent, and could also depend on the type of prostaglandins that are generated following seizures (Holtman et al., 2010, 2009; Kim et al., 2008; Polascheck et al., 2010; Yoshikawa et al., 2006). Clinical trials with Ibuprofen and Aspirin, both COX inhibitors, have shown variable effects.

View all citing articles on Scopus
View full text