The Novel Effect of Immunomodulator-Glatiramer Acetate on Epileptogenesis and Epileptic Seizures

Abstract

Background/Aims: Immunological mechanisms can be triggered as a response to central nervous system insults and can lead to seizures. In this study an investigation was made to determine if glatiramer acetate (GA), an immunomodulator currently used in the treatment of multiple sclerosis, could protect rats from pilocarpine-induced seizures and chronic epilepsy. Methods: Two groups of adult male Sprague-Dawley rats, experimental (GA) and control, were used in the study. The systemic IL-1α and IL-1β levels at baseline were checked as well as status epilepticus (SE), and the spontaneous recurrent seizure (SRS) stage by enzyme-linked immunosorbent assay. The GA group was given GA (150 μg/kg, ip) and the control group was given a saline injection prior to pilocarpine-induced seizures. Seizure susceptibility, severity and mortality were evaluated, using Racine seizure classification and hippocampal damage was evaluated by Nissl staining. The GA group received GA (150 μg/kg/day, ip) daily after SE, and the chronic spontaneous seizures were evaluated by long-term video recording, and mossy fiber sprouting was evaluated by Timm staining. The IL-1α and IL-1β levels were correlated with seizure activities. The TNF-α level in the hippocampus was determined at the SRS stage by immunohistochemistry. The effect of GA on ionic currents and action potentials (APs) in NG108-15 differentiated neurons was investigated using patch-clamp technology. Results: It was found that latency to severe seizures was significantly longer in the GA (p < 0.01) group, which also had SE of shorter duration and less frequent SRS (p < 0.01). GA attenuated acute hippocampal neuron loss and chronic mossy fiber sprouting in the CA3 and the SRS-reduction correlated with the reduction of IL-1α, but not with IL-1β or TNF-α levels. Mechanistically, GA reduced the peak amplitude of voltage-gated Na⁺ current (I_Na), with a negative shift in the inactivation curve of I_Na and reduced the amplitude of APs along with decreased firing of APs. Conclusion: GA might serve as a neuroexcitability modulator which attenuates pilocarpine-induced acute and chronic excitotoxicity. Sodium channel attenuation was partially independent of the immunomodulatory effect.