Histone lactylation exacerbates cerebral ischemia-reperfusion injury via NSUN2-mediated epigenetic activation of astrocytic neuroinflammation

Objective This study investigates how histone lactylation regulates NOP2/Sun RNA methyltransferase family member 2 (NSUN2)-mediated 5-methylcytosine (m5C) modification and promotes astrocyte-driven neuroinflammation in cerebral ischemia – reperfusion (I/R) injury.Methods A middle cerebral artery occlusion – reperfusion (MCAO/R) model was used to induce I/R injury. Mice were treated with NSUN2 knockdown/overexpression or the lactate dehydrogenase inhibitor oxamate. In vitro, oxygen – glucose deprivation/reperfusion (OGD/R) models were established in C8-D1A astrocytes and BV2 microglia. Neurological function, infarct volume assessed by 2,3,5-triphenyltetrazolium chloride (TTC) staining, and histopathology were evaluated. NSUN2 expression, histone lactylation [pan-lysine lactylation (Pan-Kla), histone H3 lysine 18 lactylation (H3K18la)], m5C levels, lactate concentration, and inflammatory cytokines were measured using reverse transcription quantitative PCR (RT-qPCR), Western blotting, ELISA, and immunofluorescence. Chromatin immunoprecipitation followed by qPCR (ChIP-qPCR) was used to verify H3K18la binding to the NSUN2 promoter.Results I/R injury significantly increased neurological deficits, m5C levels, and NSUN2 expression (p < 0.05). NSUN2 knockdown alleviated brain injury (p < 0.05). In OGD/R-exposed astrocytes, oxamate reduced lactate levels, suppressed histone lactylation, downregulated NSUN2 expression, and decreased m5C modification and proinflammatory cytokine release (all p < 0.05). Lactate reduction also attenuated I/R injury in vivo, while NSUN2 overexpression reversed these protective effects (p < 0.05).Conclusion Histone lactylation transcriptionally activates NSUN2, promoting m5C-dependent astrocytic neuroinflammation and exacerbating cerebral I/R injury. Targeting the lactate – H3K18la – NSUN2 axis may offer a promising therapeutic strategy for ischemic stroke.