Authors: Arena A., Zimmer T.S., van Scheppingen J., Korotkov A., Anink J.J., Mühlebner A., Jansen F.E., van Hecke W., Spliet W.G., van Rijen P.C., Vezzani A., Baayen J.C., Idema S., Iyer A.M., Perluigi M., Mills J.D., van Vliet E.A., Aronica E. 

Brain Pathol 2018 Oct 10. doi: 10.1111/bpa.12661.

Abstract

Oxidative stress (OS) occurs in brains of patients with epilepsy and coincides with brain inflammation, and both phenomena contribute to seizure generation in animal models. We investigated whether expression of OS and brain inflammation markers co-occurred also in resected brain tissue of patients with epileptogeniccorticalmalformations: hemimegalencephaly (HME), focal cortical dysplasia (FCD) and cortical tubers in tuberous sclerosis complex (TSC). Moreover, we studied molecular mechanisms linking OS and inflammation in an in vitro model of neuronal function. Untangling interdependency and underlying molecular mechanisms might pose new therapeutic strategies for treating patients with drug-resistant epilepsy of differing etiologies. Immunohistochemistry was performed for specific OS markers xCT and iNOS and brain inflammation markers TLR4, COX-2 and NF-κB in cortical tissue derived from patients with HME, FCD IIa, IIb and TSC. Additionally, we studied gene expression of these markers using the human neuronal cell line SH-SY5Y in which OS was induced using H2 O2 . OS markers were increased in dysmorphic neurons, and balloon/giant cells in cortex of patients with FCD IIb or TSC. Expression of OS markers was positively correlated to expression of brain inflammation markers. In vitro, 100 μM, but not 50 μM, of H2 O2 increased expression of TLR4, IL-1β and COX-2. We found that NF-κB signaling was activated only upon stimulation with 100 μM H2 O2leading to upregulation of TLR4 signaling and IL-1β. The NF-κB inhibitor TPCA-1 completely reversed this effect. Our results show that OS positively correlates with neuroinflammation and is particularly evident in brain tissue of patients with FCD IIb and TSC. In vitro, NF-κB is involved in the switch to an inflammatory state after OS. We propose that the extent of OS can predict the neuroinflammatory state of the brain. Additionally, anti-oxidant treatments may prevent the switch to inflammation in neurons thus targeting multiple epileptogenic processes at once.