Aspirin and fibrin clot modulation in vascular pharmacology: Fibrinogen acetylation, disease context, and translational uncertainty.

Fibrin clot architecture is increasingly recognized as a determinant of thrombotic phenotype and a potentially modifiable endpoint in vascular pharmacology. Aspirin is established as an antiplatelet agent through irreversible cyclooxygenase-1 acetylation and thromboxane A₂ suppression. Beyond this canonical pathway, aspirin has been proposed to modulate fibrin clot properties through nonenzymatic Nε-lysine acetylation of fibrinogen. Experimental studies in purified, recombinant, and selected ex vivo systems suggest effects on fibrin polymerization, factor XIIIa-dependent cross-linking, clot permeability, viscoelasticity, and fibrinolysis, with aspirin-sensitive lysines identified across fibrinogen chains. However, clinical relevance remains uncertain. At clinically relevant exposure, fibrinogen acetylation appears generally low, and contemporary low-dose aspirin does not consistently increase acetylation or modify clot phenotype despite effective platelet thromboxane suppression. Disease-related modifications, including glycation, carbamylation, oxidation, and nitration, may further reshape fibrin structure and influence aspirin responsiveness. This review examines the biochemical rationale, experimental evidence, disease-context dependency, and limitations of aspirin-mediated fibrinogen acetylation as a proposed extra-platelet mechanism. Its biological significance will require quantitative evidence of site occupancy, residue-specific function, physiological aspirin exposure, standardized clot assays, and integration with disease-specific modifiers of fibrin phenotype.