Neutrophil extracellular traps induce endothelial damage and exacerbate vasospasm in traumatic brain injury

Cerebral vasospasm (CVS) critically exacerbates secondary brain injury following traumatic brain injury (TBI). Understanding the underlying mechanisms is essential for developing targeted interventions. <b>Methods:</b> We developed a comprehensive murine multimodal imaging platform to evaluate CVS cerebral perfusion, and blood-brain barrier (BBB) integrity, integrating <i>in vivo</i> multiphoton microscopy, magnetic resonance angiography, carotid Doppler ultrasound, and laser speckle contrast imaging with molecular assays and functional assessments. Additionally, we comprehensively analyze single-cell RNA (TBI vs Sham) and bulk-RNA data (NETs-treated vs Control), delineating NETs-driven endothelial injury signatures. Finally, we explored the roles of PAD4^-/-, TLR4 inhibition and TREM1 blockade in blocking NETs-induced endothelial injury and CVS, validating key therapeutic targets. <b>Results:</b> Our findings reveal that neutrophil extracellular traps (NETs) stimulate endothelial cells, promoting intracellular accumulation of TREM1, which forms a stable complex with NF-κB. This complex synergistically amplifies TLR4-mediated inflammatory responses, constituting a novel mechanism by which NETs aggravate endothelial injury and vasospasm after TBI. Preclinical interventions aimed at inhibiting NET formation or blocking TREM1 signaling significantly reduced neuroinflammation, cerebral edema, and CVS. <b>Conclusions:</b> These findings identify TREM1 as a promising therapeutic target and illuminate a NET-driven crosstalk between vascular dysfunction and inflammatory cascades in the context of TBI, offering novel translational insights for mitigating secondary brain injury.