Epilepsy and the immune system: exploring the relationship between neuroinflammation and drug-resistance.

Background: Epilepsy is one of the most common neurological diseases, affecting about 50 million people worldwide. Despite the availability of a wide range of anti seizure medications, about a third of people with epilepsy are drug-resistant. The mechanisms underlying epileptogenesis and drug resistance are still not fully understood, but several clinical and experimental evidences have suggested that neuroinflammation and oxidative stress may play a key role in both processes. Aim: The aim of this research was to analyze serum expression of an extended panel of inflammatory markers (cytokines, soluble receptors and oxidative stress biomarkers) and intracellular expression of proinflammatory cytokines in patients with mesial temporal lobe epilepsy (MTLE) divided according to therapy response (drug-resistant – DR vs. drug-sensitive patients – DS). Materials and methods: Twenty-four patients with MTLE (14 DR and 10 DS) and 12 healthy controls (HC) were enrolled. Blood was collected during the interictal period and immediately processed. For intracellular cytokines detection, peripheral blood mononuclear cells (PBMCs) were isolated, stimulated for 5 hours with the addition of brefeldin A after 2 hours, then fixed, permeabilized, and stained with antibodies against surface receptors and intracellular cytokines, conjugated to different fluorochromes. Samples were finally analyzed with a flow cytometer. Plasma was stored for serum cytokines and oxidative stress biomarkers dosage. Results: DR patients showed a significantly higher percentage of IL-1β and IL6 positive monocytes compared to the DS patients (p=0,016 and p=0,041, respectively). There were no differences in serum cytokines levels between DR and DS patients but, pooling all the patients together, serum levels of IL-8, CCL2 and CCL3 were significantly higher compared to HC (p=0,016, p=0,032 and p=0,032 respectively). Concerning oxidative stress biomarkers, levels of AOPP were significantly higher in epileptic patients compared to HC (p<0,0001), while levels of FRAP and thiols were significantly lower compared to HC (p=0,004 and p