The CEBPB-AP-1 (JunB/Fos) Axis Drives Neuroinflammation and Microglial Dysfunction Via TNF Signaling in Ischemic Stroke.

Ischemic stroke triggers a strong neuroinflammatory response, with microglia playing dual roles in both exacerbating tissue damage and promoting repair. The molecular mechanisms regulating microglial activation and polarization remain inadequately defined. In this study, we demonstrate that the transcription factor CEBPB is a key upstream regulator of the AP-1 (JunB-Fos) complex, driving pro-inflammatory transcriptional programs in microglia following transient focal cerebral ischemia (tFCI). Transcriptomic profiling of microglia from tFCI mice revealed significant gene expression changes, particularly enrichment in inflammatory, immune, and cytokine production pathways, and identified Cebpb, Junb, Fos, and Tnf as key hub genes. Mechanistically, CEBPB is upregulated in post-ischemic microglia and directly binds to the Fos promoter to activate AP-1, inducing downstream inflammatory mediators, including IL-1β and TNF-α. Inhibition of AP-1 with the selective inhibitor T-5224 shifted microglia from a pro-inflammatory to an anti-inflammatory phenotype in vitro, decreasing pro-inflammatory cytokine production and enhancing anti-inflammatory mediator release. In vivo, T-5224 treatment in tFCI mice suppressed neuroinflammation, reduced neuronal apoptosis in the striatum and cortex, promoted a restorative microglial phenotype, and improved long-term sensorimotor and cognitive function. These findings establish the CEBPB/AP-1 axis as a critical driver of neuroinflammation in ischemic stroke and highlight it as a promising therapeutic target.