Limin Hong, Hangfei Wang, Xiyuan Lin, Bo Sun, Xianping Lin, Miao Chen
Reperfusion therapies following stroke can contribute to further brain injury.Inhibition of G9a has been demonstrated to increase BDNF expression, thereby exerting neuroprotective effects. Isoquercetin (ISO) has shown neuroprotective potential, but its molecular mechanisms are not fully known. This study aimed to investigate the role and mechanism of ISO in improving cerebral ischemia-reperfusion injury, in relation to G9a/H3K9me2/BDNF pathway. A rat middle cerebral artery occlusion (MCAO) model and an oxygen-glucose deprivation/reoxygenation (OGD/R) neuronal model were used. Neurological scores, infarct volume, brain water content, neuronal morphology, apoptosis and cell viability were evaluated. Moreover, a G9a overexpression plasmid was constructed to verify mechanism specificity. G9a and H3K9me2 expression levels were assessed by RT-PCR and western blotting. BDNF levels were measured by ELISA, oxidative stress by ROS assays and H3K9me2 enrichment at the BDNF promoter by chromatin immunoprecipitation. Cerebral I/R injury significantly increased G9a and H3K9me2 expression, leading to reduced BDNF levels and enhanced neuronal apoptosis. ISO treatment decreased G9a/H3K9me2 expression, increased BDNF levels, improved neurological function and reduced neuronal damage both in vivo and in vitro. G9a overexpression reversed these protective effects. Isoquercetin alleviates cerebral I/R injury by inhibiting G9a-mediated histone methylation and promoting BDNF expression, highlighting a novel epigenetic mechanism for stroke therapy.