Stable changes in global DNA- methylation in reactive astrocytes from animals exposed to experimental temporal lobe epilepsy (TLE)

GOMEZ DD, ROSSI A, MURTA V, D`ALESSIO L, RAMOS AJ

Congreso; Reunión conjunta SAI-SAIC-AAFE-Nanomed; 2021

Neuron-centric literature considers epilepsy as the result of an alteration of excitatory/inhibitory balance; however a growing body of evidence shows the glial role in this disease. Usually TLE patients refer a initial precipitating event (IPE), followed by a silent period of latency before initiating chronic seizures. We hypothesize that IPE releases DAMP that produce the alteration of astroglial proinflammatory and homeostatic genes during the latency period, and that long lasting effects are due to epigenetic cues. In the present work we used the Lithium-Pilocarpine model of TLE (Li-Pi Model) in male Wistar rats that were analyzed at 3, 7, 21 or 35 days post-status epilepticus (DPSE). Status epilepticus mimics the IPE events in humans. In vitro, astrocyte enriched culture were exposed to DAMP (HMGB-1) or PAMP (LPS) to induce a proinflammatory burst that imitates an in vivo IPE. Using immunohistochemistry, quantitative image analysis and RT-PCR, we observed that animals presented a long-lasting increase in global methylation in astrocytes (from 7 to 35DPSE) and coexisted with an increase in the DNMT3a/DNMT1 mRNA expression. A concomitant reduction of homoestatic astroglial Kir4.1 and glutamine synthetase (GS) expression were also observed during the latency period. In vitro, acute exposure to DAMP or PAMP was able to recapitulate the in vivo profile, by producing long-lasting increased global methylation, reactive gliosis and decreased expression of homeostatic genes in the astroglial cultures. The increased global methylation in astrocytes was also confirmed in hippocampal sections resected from TLE patients. We conclude that long-lasting astroglial alterations during the latency period induce a profound disbalance in neuronal homeostasis and K+ buffering that contributes to increased neuronal excitability. The altered pro-epileptogenic astroglial profile is sustained by increased global methylation of these genes. Supported by PICT 2017-2203 and 2019-0851.