Vagus Nerve Stimulation Inhibits DNA and RNA Methylation in a Rat Model of Pilocarpine-Induced Temporal Lobe Epilepsy.

INTRODUCTION: Vagus nerve stimulation (VNS) represents a clinically approved neuromodulatory intervention for managing refractory epilepsy. VNS exhibits antiepileptogenic effects in animal models; the molecular and cellular mechanisms driving these effects have yet to be fully elucidated. Epigenetic alterations, including DNA and RNA methylation, are implicated in the pathogenesis of epilepsy. This study was designed to examine whether VNS inhibits DNA/RNA methylation in temporal lobe epilepsy. METHODS: A rat model of temporal lobe epilepsy induced by intraperitoneal injection of lithium chloride-pilocarpine was used. Naïve control group, Pilo groups (8 and 12 weeks after pilocarpine respectively), VNS group (VNS stimulation for 4w and 8w respectively), and Sham group (VNS off control group, with VNS implanted but not turned on for 4w and 8w respectively). The rats were monitored by video-EEG. DNMT1 (DNA methyltransferase-1), DNMT3A (methyltransferase-3A), 5-hmC (5-hydroxymethyl-cytosine), 5-mC (5-methyl-cytosine), METTL3 (RNA methyltransferase like 3), METTL14 (RNA methyltransferase like 14) were quantified via immunohistochemistry and Western blot. RESULTS: Pilocarpine-induced epileptic animals were characterized by overexpression of 5-mC, DNMT1, DNMT3A, METTL3, and METTL14, and a decrease of 5-hmC. Compared to the Pilo group, VNS significantly inhibited the overexpression of 5-mC, DNMT1, DNMT3A, METTL3, and METTL14, reduced the downregulation of 5-hmC, and attenuated spontaneous recurrent seizures (SRSs). CONCLUSIONS: We conclude that VNS reduces the number of SRSs in a rat model of epilepsy, concurrently reducing the expression of 5-mC, DNMT1, DNMT3A, METTL3, and METTL14, as well as the increase of 5-hmC. These findings suggest that epigenetic modifications, specifically the suppression of DNA and RNA methylation, could constitute a potential target of VNS-mediated antiepileptic effects.