Silencing of Long Non-coding RNA GAS5 Suppresses Neuron Cell Apoptosis and Nerve Injury in Ischemic Stroke Through Inhibiting DNMT3B-Dependent MAP4K4 Methylation

Ischemic stroke is associated with various physiological and pathological processes including neuronal apoptosis. Growth-arrest-specific transcript 5 (GAS5), a long non-coding RNA (lncRNA), has been recently reported to affect ischemic stroke-induced neuron apoptosis, while its mechanisms remain largely undefined. Through in silico analysis, GAS5 was predicted to interact with the promoter of MAP4K4. The aim of the present study was therefore to investigate the possible role of GAS5 in the progression of ischemic stroke via regulation of mitogen-activated protein kinase kinase kinase kinase 4 (MAP4K4) methylation. The expression of MAP4K4 was found to be lowly expressed in the clinical samples collected from 55 patients. MAP4K4 was suggested to be methylated in an in vitro model of oxygen-glucose deprivation (OGD)-treated mouse primary cortical neurons, while its overexpression could inhibit OGD-induced neuronal apoptosis. A series of dual-luciferase reporter, RIP, RNA pull-down, ChIP MSP, and BSP assays confirmed that GAS5 significantly induced MAP4K4 methylation and downregulated MAP4K4 expression through the recruitment of DNA methyltransferase 3B (DNMT3B). An in vivo ischemic stroke model was developed using middle cerebral artery occlusion (MCAO). Upregulation of GAS5 promoted OGD-induced neuronal apoptosis in the in vitro model and increased cerebral infarction size and neurological score in the in vivo model by reducing MAP4K4 expression. Collectively, the present study highlights that silencing GAS5 may inhibit neuronal apoptosis and improve neurological function in ischemic stroke by suppressing DNMT3B-mediated MAP4K4 methylation, which contributes to better understanding of the pathologies of ischemic stroke and development of novel therapeutic options for this disease.