ABSTRACT NUMBER: ESOC2026A82 NLRP3 INHIBITION ATTENUATES INFARCT PROGRESSION AND INFLAMMATION ACROSS OCCLUSION, REPERFUSION AND SUBACUTE PHASES IN ISCHEMIC STROKE

Abstract Background and aims Ischemia/reperfusion (I/R) injury drives infarct progression despite rapid recanalization, and sterile inflammation—partly mediated by the NLRP3 inflammasome—amplifies this damage. Although NLRP3 inhibition reduces post-reperfusion injury, it remains unclear whether NLRP3 is already activated during large-vessel occlusion (LVO) and whether its blockade protects continuously across the full ischemic timeline: from penumbral loss under occlusion, through early reperfusion, into the subacute phase. The spatiotemporal dynamics and cellular drivers of NLRP3-mediated neuroinflammation remain insufficiently defined. Methods We used transient and permanent MCAO models in WT and neutrophil-specific NLRP3-KO mice. Animals received the NLRP3 inhibitor MCC950 either prophylactically or therapeutically (1 h / 2 h after occlusion). Infarct volumes, neurological outcome and inflammatory responses were quantified. For translational relevance, pial blood samples were collected from thrombectomy patients before recanalization, enabling analysis of hyperacute NLRP3 signaling in humans. Results NLRP3 expression increased 5-10-fold already during LVO, peaked further after reperfusion. MCC950 significantly reduced infarct volume, IL-1β release, BBB leakage and improved outcomes in both prophylactic and delayed treatment. Neutrophil depletion reproduced part of the neuroprotective effect, indicating a major myeloid contribution. Human hyperacute pial samples confirmed early NLRP3 priming and elevated IL-1β bioactivity before recanalization. Conclusions NLRP3 is rapidly engaged during vessel occlusion and continues to drive injury during reperfusion and the subacute phase. Its pharmacological inhibition preserves penumbral tissue, reduces I/R-driven damage and may extend the therapeutic window before and beyond revascularization. These data support clinical evaluation of NLRP3 blockade as an adjunct to recanalization. Conflict of interest Maximilian Bellut: nothing to disclose