Methyl-CpG-Binding Domain Protein 3 Promotes Seizures by Recruiting Methyltransferase DNMT1 to Enhance TREM2 Methylation.

Epilepsy represents a hazardous neurological disorder, underpinned by a pathophysiological process that is yet to be fully understood. Here, we aimed to elucidate the effect of methyl-CpG-binding domain protein 3 (MBD3) on hippocampal neuronal damage in epileptic mice by targeting the phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) pathway. The expression of MBD3 was determined by Western blot in a hippocampal neuronal culture (HNC) epileptic model established using the low Mg2+ECF culture method. The interaction between MBD3 and DNA methyltransferase 1 (DNMT1) was determined via co-immunoprecipitation and mass spectrometry analysis. Bisulfite modification and sequencing was performed to evaluate the degree of methylation of triggering receptor expressed on myeloid cells 2 (TREM2). The viability and apoptosis of hippocampal neurons were detected by CCK-8 and TUNEL assays, respectively. Finally, the effect of MBD3 was verified in vivo. MBD3 was highly expressed in the HNC model of epilepsy, with its interaction with DNMT1 found to promote the hypermethylation of TREM2 at site cg25748868. Additionally, decreased TREM2 and inhibited PI3K/Akt pathway was observed in the HNC epileptic model. Simultaneous inhibition of MBD3 and DNMT1 decreased the methylation level at cg25748868, up-regulated TREM2 expression, and activated the PI3K/Akt pathway, thereby arresting neuronal damage. Inhibition of MBD3 reduced the level of epileptic seizures, down-regulated cg25748868 methylation, activated TREM2-mediated signaling pathways, and alleviated hippocampal neuronal damage in the acute seizure mouse models. The present study unveiled that MBD3 and DNMT1 synergistically enhanced hypermethylation of cg25748868 in TREM2, and promoted the onset of epilepsy via inhibition of the PI3K/Akt pathway.