Therapeutic potential of microglial SMEK1 via regulation of H3 lysine 9 lactylation in cerebral ischemia-reperfusion injury

Immune responses and neuroinflammation occurring after acute ischemic stroke (AIS) are closely related to brain injury. Histone lactylation is a metabolic stress-related histone modification that participates in the pathogenesis of various diseases. However, the role of histone regulation in cerebral ischemic stroke remains unknown. In this study, a transient middle cerebral artery occlusion (tMCAO/R) model and an oxygen–glucose deprivation and reoxygenation (OGD/R) model were used to simulate in vivo/in vitro ischemia–reperfusion injury. The underlying mechanism of microglial histone lactylation was investigated using microglia-specific SMEK1-overexpressing mice and BV2 cells. The results showed that lactate overload resulted in elevated histone lactylation after AIS. Decreased SMEK1 expression in microglia after ischemic stroke was associated with increased lactate levels and subsequent neuroinflammation. Microglia-specific SMEK1 deficiency in microglia after ischemia can promote lactate production by inhibiting the pyruvate dehydrogenase kinase 3-pyruvate dehydrogenase (PDK3-PDH) pathway. Specifically, H3 lysine 9 lactylation (H3K9la) activated Ldha and Hif-1α transcription in microglia and promoted glycolysis. SMEK1-overexpressing mice exhibited better neurologic recovery after ischemic stroke than control mice. Mechanistically, we provided new evidence that microglial histone lactylation promoted glycolysis in ischemia‒reperfusion injury and elucidated the potential role of SMEK1 as an upstream regulatory molecule in histone lactylation after cerebral ischemia. According to our results, microglial SMEK1 may be potential therapeutic targets for AIS. Comparative gene expression profiling analysis of RNA-seq data for BV2 cells and its KD derivatives (LV1 and NL)