Cox-2 inhibition can lead to adverse effects in a rat model for temporal lobe epilepsy

doi:10.1016/j.eplepsyres.2010.06.011

Epilepsy Research

Volume 91, Issue 1, September 2010, Pages 49-56

https://doi.org/10.1016/j.eplepsyres.2010.06.011 Get rights and content

Summary

Purpose

Status epilepticus (SE) leads to upregulation of pro-inflammatory proteins including cyclooxygenase-2 (cox-2) which could be implicated in the epileptogenic process and epileptic seizures. Recent studies show that cox-2 can regulate expression of P-glycoprotein (P-gp) during epileptogenesis and epilepsy. P-gp could cause pharmacoresistance by reducing brain entry of anti-epileptic drugs such as phenytoin (PHT). Here we have investigated the effects of cox-2 inhibition on epileptogenesis, spontaneous seizures and PHT treatment in a rat model for temporal lobe epilepsy (TLE).

Methods

A 3-day treatment with the cox-2 inhibitor SC-58236 (SC) was started 1 day before electrically induced SE. Chronic epileptic rats were treated with SC for 14 days, which was followed by a 7-day period of SC/PHT combination treatment. Seizure activity was monitored continuously using electroencephalography.

Results

SC treatment did not affect SE duration, but led to an increased number of rats that died during the first 2 weeks after SE. Cox-2 inhibition during the chronic period led to an increased number of seizures in the 2nd week of treatment in 50% of the rats. SC/PHT treatment reduced seizures significantly for only 2 days.

Conclusions

Both SC treatment that started before SE and the 14-day treatment in chronic epileptic rats led to adverse effects in the TLE rat model. Despite a temporal reduction in seizure frequency with SC/PHT treatment, SC does not seem to be a suitable approach for anti-epileptogenic or anti-epileptic therapy.

Introduction

There is ample evidence that temporal lobe epilepsy and the development of epilepsy (epileptogenesis) are associated with inflammatory processes in the brain (Gorter et al., 2006, Vezzani and Granata, 2005). Inflammatory mediators are abundantly present in brain tissue from animals during the epileptogenic (latent) period and during the chronic epileptic phase as well as in resected human hippocampal tissue from medical intractable epileptic patients (Gorter et al., 2006, Jamali et al., 2006, Ravizza et al., 2008). Inhibition of inflammation may therefore provide a new therapeutic strategy for (pharmacoresistant) epilepsy. Moreover, it may even be possible to prevent the development of epilepsy. A potential target for anti-inflammatory treatment in epilepsy is cyclooxygenase-2 (cox-2). Several studies have shown neuroprotective effects of cox-2 inhibition (Hewett et al., 2006, Iadecola et al., 2001, Kunz and Oliw, 2001). However, in a recent study we could not confirm a neuroprotective effect when we used the highly specific cox-2 inhibitor SC-58236 (SC) that was administered after the status epilepticus (SE) in a rat model for temporal lobe epilepsy. More importantly, the SC treatment was not anti-epileptogenic and did not produce an anticonvulsive effect when administered to chronic epileptic rats (Holtman et al., 2009). Interestingly, in a subsequent study in which we started to apply the cox-2 inhibitor before the induction of SE, we were able to prevent the upregulation of P-glycoprotein (P-gp), a protein that is involved in the transport of many compounds including several anti-epileptic drugs (AEDs) (van Vliet et al., 2010).

Since this SC treatment protocol prevents the normally SE-induced P-gp upregulation, we reasoned that timing of the cox-2 inhibition could be crucial for an effective reduction of inflammation and an anti-epileptogenic effect. Therefore we tested the effects of this cox-2 inhibition protocol on early epileptogenesis in rats in which SE was electrically induced. Moreover, since P-gp expression after a 2-week SC treatment in chronic epileptic rats could be reduced to levels similar to control expression (van Vliet et al., 2010), we also tested the effects of SC on seizure activity in chronic epileptic rats in the absence and presence of phenytoin (PHT), an AED that is a substrate for P-gp. In a previous study we detected that PHT brain levels are increased in SC-treated rats after PHT administration vs. vehicle-treated rats (van Vliet et al., 2010), a phenomenon that can be expected if this AED is a substrate for P-gp. Since PHT treatment in untreated chronic epileptic rats does not lead to complete seizure reduction (van Vliet et al., 2006), we expected that PHT administration in SC-treated rats, in which P-gp expression has been shown to be reduced compared to untreated epileptic rats (van Vliet et al., 2010), would lead to improved seizure control.

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. The rats were housed individually in a controlled environment (21 ± 1 °C; humidity 60%; lights on 08:00 a.m.–8:00 p.m.; food and water available ad libitum).

Electrode implantation and status epilepticus (SE) induction

In order to record hippocampal EEG and to induce SE, insulated stainless steel electrodes were implanted in the left dentate gyrus and angular bundle respectively, as

Effects of SC-58236 pretreatment on SE duration and epileptogenesis

SE-duration in the SC-treated group did not differ significantly from vehicle-treated animals: 11.3 ± 1.3 h (SC treatment) compared to 9.7 ± 0.2 h (vehicle treatment) (Fig. 1(A)). An example of PED activity during SE is shown in Fig. 5(A). SE severity was scored according to the behavior the animals showed during SE. In the SC-treated group, 4 out of 9 animals experienced severe SE, whereas 2 out of 9 from the vehicle-treated group experienced severe SE, which was not significantly different. SE may

Discussion

The findings in this study indicate that treatment with the cox-2 inhibitor SC-58236 starting before SE led to adverse effects with more rats dying within the first 2 weeks after SE. Moreover, 2 week SC treatment in chronic epileptic rats with daily frequent seizures led to an increase of seizures in 3 out of 6 rats during the 2nd week of treatment. Subsequent combined SC/PHT treatment transiently improved seizure control. Below we discuss the significance of these findings.

Conclusion

Cox-2 inhibition with SC-58236 had severe side effects with increased mortality after SE as well as after 2-week chronic treatment. The results indicate that extreme care must be taken in case of chronic cox-2 inhibition in relation with the disease process itself. Whether the effects of chronic cox-2 inhibition on seizure activity is unique for SC-58236 or also occur when other cox-2 inhibitors are used, needs to be investigated. In any case, these data do no support a cox-2 inhibition

Acknowledgements

We thank Pfizer for providing SC-58236. We also thank M.C. De Rijke and W.E. Dieters (Epilepsy Institute in The Netherlands Foundation, Heemstede, The Netherlands) for analysis of phenytoin in plasma.

This work was supported by the “Nationaal Epilepsie Fonds” grant 07-19 (JAG), The Netherlands Organisation for Scientific Research (NWO) grant 863.08.017 (Veni) (EAvV) and EU FP7 project NeuroGlia, grant agreement no. 202167 (EA).

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Cox-2 inhibition can lead to adverse effects in a rat model for temporal lobe epilepsy

Summary

Purpose

Methods

Results

Conclusions

Introduction

Section snippets

Experimental animals

Electrode implantation and status epilepticus (SE) induction

Effects of SC-58236 pretreatment on SE duration and epileptogenesis

Discussion

Conclusion

Acknowledgements

Brain Res.

Neurosci. Lett.

Epilepsy Res.

Neurobiol. Dis.

Brain Res.

Electroencephalogr. Clin. Neurophysiol.

Neurobiol. Dis.

Epilepsy Res.

Exp. Neurol.

Neuropharmacology

Neuropharmacology

Seizure-induced up-regulation of P-glycoprotein at the blood-brain barrier through glutamate and cyclooxygenase-2 signaling

Mol. Pharmacol.

Septotemporal variation of the supragranular projection of the mossy fiber pathway in the dentate gyrus of normal and kindled rats

Hippocampus