KDM4A regulates microglial polarization after ischemic stroke by regulating SPINK5 signaling.

Microglia/macrophage polarization is a crucial factor in inflammatory processes following ischemic stroke (IS). This study explores the molecular mechanisms through which lysine-specific histone demethylase 4 (KDM4A) regulates microglial polarization postischemic stroke. IS models are established in vivo via transient middle cerebral artery occlusion (MCAO) surgery and in vitro via oxygen-glucose deprivation (OGD) treatment. 2,3,5-Triphenyl tetrazolium chloride staining is conducted to determine the infarct size. RT-qPCR is used to determine mRNA expression. Immunofluorescence assay is used to detect the expressions of KDM4A and biomarkers of microglia. Western blot analysis is used to determine the expressions of KDM4A and serine peptidase inhibitor Kazal type 5 (SPINK5). The enrichment of H3K9me3 on the promoter of SPINK5 is determined via chromatin immunoprecipitation assay. Neuronal apoptosis is detected via TUNEL assay. We find that KDM4A is upregulated in IS models. Downregulation of KDM4A mitigates neurological dysfunction, enhances motor capacity, and reduces inflammatory infiltration in vivo while suppressing microglial activation and promoting M2 polarization. Mechanistically, KDM4A reduces the enrichment of H3K9me3 on the SPINK5 promoter, thereby increasing SPINK5 expression. Moreover, overexpression of SPINK5 inhibits M2 microglial polarization and neuronal apoptosis. Overall, KDM4A exacerbates ischemic stroke-induced brain injury by promoting proinflammatory microglial polarization via SPINK5 signaling.