Human ischemic stroke thrombi contain an NLRP3-associated neutrophil inflammatory network with histological evidence consistent with inflammasome assembly, which appears to reflect local thrombus biology rather than clinical disease severity.
NLRP3 was detected in all 34 human ischemic stroke thrombi analyzed.
NLRP3 correlated with neutrophil abundance, NETosis, HMGB1, and GSDMD independently of fibrin content.
A majority of CD66B-positive neutrophils within the thrombi exhibited ASC immunoreactivity.
The thrombus inflammatory signature encompassed markers of both NETosis and pyroptosis, forming an interconnected network.
Neither NLRP3 nor the broader inflammatory thrombus signature was associated with stroke severity, infarct extent, or functional outcome.
Human cerebral thrombi are described as biologically active immunothrombotic structures with evidence of NLRP3 inflammasome involvement.
This research suggests that blood clots (thrombi) that cause ischemic strokes are not simply passive blockages but are biologically active structures containing an organized inflammatory response. By examining clots removed from 34 stroke patients during mechanical thrombectomy procedures, the researchers found that every clot contained NLRP3, a protein that acts as a sensor for cellular stress and danger signals and triggers inflammation. Within these clots, immune cells called neutrophils appeared to be actively undergoing two forms of inflammatory cell death — NETosis (where neutrophils release web-like DNA structures) and pyroptosis (a form of explosive, inflammatory cell death) — and these processes were interconnected with the NLRP3 signaling pathway. The study found that the levels of NLRP3 and related inflammatory markers within the clots were tightly linked to each other but were not connected to how severe the patient's stroke was, how large the resulting brain injury was, or how well the patient recovered. This means the inflammatory activity detected appears to be a feature of the clot itself, rather than a reflection of how badly the patient was affected by the stroke. This research suggests that stroke-causing clots have their own internal inflammatory biology driven by neutrophils and the NLRP3 inflammasome system. Understanding this clot-specific inflammatory network could open new avenues for developing treatments that target the clot's inflammatory properties, though this study was observational and did not test any interventions. The finding that this inflammation did not track with clinical outcomes also raises questions about when and how such processes might become clinically relevant.
Bellut M, Strootmann M, Essig F, Stoll G, Vogt M, Guggenberger K, et al.. (2026). NLRP3 Marks an Inflammatory Neutrophil-NETosis-Pyroptosis Network in Human Ischemic Stroke Thrombi.. Cells. https://doi.org/10.3390/cells15171597