Endothelial-specific Ezh2 deficiency exacerbates blood-brain barrier dysfunction and neuroinflammation in sepsis-associated encephalopathy

Sepsis-associated encephalopathy (SAE) is a frequent yet insufficiently understood form of acute brain dysfunction driven by systemic inflammation and neurovascular injury. Here, we identify endothelial Enhancer of Zeste Homolog 2 ( Ezh2 ) as a key epigenetic regulator that maintains blood-brain barrier (BBB) integrity and restrains neuroinflammatory responses during sepsis. Using constitutive and inducible endothelial-specific Ezh2 knockout mice, we demonstrate that loss of Ezh2 disrupts neurovascular unit organization at baseline, characterized by reduced tight junction protein expression, diminished glucose transporter levels, altered vascular morphology, and impaired astrocytic endfoot coverage. Following cecal ligation and puncture, Ezh2 -deficient mice exhibited markedly increased mortality, exacerbated cerebral edema, and severe albumin extravasation, indicating profound BBB breakdown. Neuropathological analyses revealed region-dependent neuronal degeneration and apoptosis across cortex, midbrain, and hippocampus, accompanied by reactive gliosis and microglial activation. The absence of Ezh2 further promoted robust leukocyte infiltration, including neutrophils and CD4⁺/CD8⁺ T cells, into the cortex, basal ganglia, and choroid plexus, consistent with dysregulated peripheral-central nervous system (CNS) immune communication. Transcriptomic profiling identified upregulation of inflammatory, cytokine, and cell death pathways alongside downregulation of synaptic, metabolic, and neuronal maturation programs, providing a mechanistic molecular landscape linking endothelial epigenetic dysfunction to CNS vulnerability. Collectively, these findings reveal that endothelial Ezh2 acts as a protective neurovascular gatekeeper that limits systemic inflammatory penetration into the CNS and mitigates neuroimmune activation during sepsis. This work establishes an epigenetic axis coupling BBB dysfunction to neuroinflammation in SAE and suggests that endothelial-targeted epigenetic modulation may represent a therapeutic strategy for limiting CNS injury in systemic inflammatory disorders. Endothelial Ezh2 Regulates Neuroinflammation and Neuronal Apoptosis in Sepsis. This Graphic Abstract illustrates the experimental workflow and key findings regarding the role of endothelial-specific Ezh2 in the brain during sepsis. The study utilizes two genetic mouse models: Ezh2 fl/fl ; Tek-Cre for conditional endothelial Ezh2 knockout ( Ezh2 cKO) and Ezh2 fl/fl ; Tek-CreERT2 for tamoxifen-inducible endothelial Ezh2 knockout ( Ezh2 iKO). These models allow for the specific deletion of Ezh2 in endothelial cells, which form the crucial BBB. Sepsis is induced via the Cecal Ligation and Puncture (CLP) procedure. Following CLP, various brain regions, including the cortex, midbrain, and hippocampus, are harvested for RNA extraction and Next-Generation Sequencing (NGS) to identify differentially expressed genes. Subsequent bioinformatics analysis, including volcano plots, Gene Ontology (GO) enrichment, KEGG pathway analysis, heatmaps, and protein-protein interaction (PPI) networks, reveals significant alterations in gene expression related to inflammation, neuronal death, and BBB integrity in Ezh2 -deficient mice compared to controls. The findings indicate that endothelial Ezh2 plays a critical protective role in maintaining BBB function, mitigating neuroinflammation, and preventing neuronal apoptosis during sepsis