Stroke emboli from patients with atrial fibrillation enriched with neutrophil extracellular traps.

BACKGROUND: Recent literature has demonstrated remarkable heterogeneity in the composition of acute ischemic stroke (AIS) emboli, which may impact susceptibility to therapy.

OBJECTIVES: In this study, we explored differences in proteomic composition of retrieved embolic material from patients with stroke with and without atrial fibrillation (AF) (AF+ and AF-, respectively).

METHODS: The full proteome of retrieved thromboembolic material from 24 patients with AIS was obtained by mass spectrometry. Known marker proteins were assigned groups representing broad classes of embolus components: red blood cells, platelets, neutrophils, eosinophils, histones, complement, and other clotting-associated proteins (eg, fibrinogen). Relative protein abundances were compared between AF+ and AF- samples. Functional implications of differences were explored with gene set enrichment analysis and Gene Ontology enrichment analysis and visualization tool.

RESULTS: One hundred sixty-six proteins were differentially expressed between AF+ and AF- specimens. Eight out of the 15 neutrophil proteins ( P  < .05; fold change, >2) and 4 of the 14 histone proteins were significantly enriched in AF+ emboli ( P  < .05; fold change, >2). Gene set enrichment analysis revealed a significant representation of proteins from published neutrophil extracellular trap (NET) proteomic gene sets. The most significantly represented functional Gene Ontology pathways in patients with AF involved neutrophil activation and degranulation ( P  < 1 × 10-7 ).

CONCLUSION: The present analysis suggests enrichment of NETs in emboli of patients with stroke and AF. NETs are a significant though understudied structural component of thrombi. This work suggests not only unique stroke biology in AF but also potential therapeutic targets for AIS in this population.