Interferon regulatory factor-1–expressing astrocytes are epigenetically controlled and exacerbate TBI-associated pathology in mice

Astrocyte heterogeneity is closely associated with the pathophysiology of traumatic brain injury (TBI), particularly in the development of cerebral edema, which is a major contributor to morbidity and mortality in patients with TBI. However, little is known about how certain astrocyte subpopulations contribute to the development of cerebral edema after acute brain injury. Using multiomics approaches, we identified a proinflammatory interferon regulatory factor-1-positive (IRF1⁺) astrocyte cluster that correlates with clinical severity and outcomes in patients with TBI. Mechanistically, IRF1 in astrocytes binds to promoters of inflammatory cytokine genes, driving neurotoxicity and disrupting endothelial tight junction integrity. Using <i>Aldh1l1</i>^CreERT2; <i>Irf1</i>^flox/flox mice, we demonstrated that astrocyte-specific deletion of <i>Irf1</i> mitigates astrocyte-mediated pathogenic activities, ameliorates blood-brain barrier (BBB) disruption, and reduces cerebral edema after TBI. Moreover, enhanced IRF1 activity in astrocytes facilitates the recruitment of CD8⁺ T cells by releasing C-X-C motif chemokine ligand 10 (CXCL10), which exacerbates BBB disruption and cerebral edema. Furthermore, we identified tet methylcytosine dioxygenase 3 (TET3)-mediated DNA hydroxymethylation as a key epigenetic mechanism that up-regulates IRF1 expression in astrocytes, thereby activating proinflammatory transcriptional programs. Finally, we developed an IRF1 antagonist, 8003-3282, which effectively reduces inflammation, preserves BBB integrity, alleviates cerebral edema, and improves neurological outcomes in a TBI mouse model. These findings highlight IRF1⁺ astrocytes as critical mediators of TBI-associated pathology and suggest that targeting this astrocyte cluster may represent a promising therapeutic strategy to mitigate inflammation, BBB damage, and cerebral edema in TBI.