Hyperacute Interleukin-1β Production and Neutrophil Extracellular Trap Formation in the Cerebral Circulation of Stroke Patients with Large Vessel Occlusion

Objective: Cerebral ischemia remains a major cause of disability, and the contribution of the hyperacute immune response is increasingly recognized. The aim of this study was to investigate the local inflammatory response in the affected brain of stroke patients with large vessel occlusion during the hyperacute phase of stroke. Methods: To decipher the role of myeloid immune cells in stroke-induced inflammation, we performed an unsupervised multiomics analysis of innate immune pathways in ischemic blood obtained directly from the occluded middle cerebral artery in 54 patients undergoing mechanical recanalization. Paired nonischemic arterial blood served as an internal control. Results: Stroke triggered a local hyperacute activation of classical monocytes and neutrophils in the ischemic cerebral vasculature, with interleukin (IL)-1β emerging as a key mediator of inflammation. Elevated plasma adenosine triphosphate levels and inflammasome priming in intravascular monocytes were associated with IL-1β production within the occluded middle cerebral artery within 4.5 hours of stroke onset. IL-1β release coincided with increased neutrophil-attracting chemokines (C-X-C motif chemokine ligand 1 [CXCL1], IL-8). Locally activated neutrophils formed neutrophil extracellular traps (NETs) within the ischemic vasculature, a hallmark of thromboinflammation. Postmortem analyses revealed NET deposition within ischemic brain parenchyma. Interpretation: These findings indicate increased IL-1β expression and enhanced NET formation within the cerebral circulation in stroke caused by large vessel occlusion, suggesting that these mechanisms might contribute to early stroke pathophysiology and represent potential targets for immunomodulatory strategies. ANN NEUROL 2026.