Homocysteinylation, a post-translational modification involving the covalent attachment of homocysteine to proteins, has emerged as a critical mechanism linking hyperhomocysteinemia to thrombotic disease. This review focuses on the homocysteinylation of fibrinogen, a key coagulation factor, and its impact on clot structure and function. Evidence indicates that elevated homocysteine levels can induce significant changes in fibrin architecture, promoting the formation of dense, rigid clots with reduced permeability and impaired fibrinolytic susceptibility, thus fostering a prothrombotic environment. However, inconsistencies in reported effects on fiber diameter and polymerization kinetics highlight the need for standardized experimental protocols. Advances in proteomics and high-resolution imaging are expected to clarify the molecular underpinnings of these modifications. Moreover, homocysteinylation intersects with oxidative stress and may serve as a mechanistic bridge between metabolic and vascular dysfunction. Understanding its role not only enhances insight into thrombosis but also opens avenues for biomarker discovery and targeted therapies in cardiovascular and potentially neurological disorders.

Reactive nitrogen species (RNS), particularly peroxynitrite (ONOO⁻), play a central role in post-translational modifications (PTMs) of proteins, including fibrinogen, a key component of the coagulation cascade. This review explores the structural and functional consequences of fibrinogen nitration, with a focus on its impact on clot formation, morphology, mechanical stability, and fibrinolysis. Nitration, primarily targeting tyrosine residues within functional domains of the Aα, Bβ, and γ chains, induces conformational changes, dityrosine crosslinking, and aggregation into high molecular weight species. These modifications result in altered fibrin polymerization, the formation of porous and disorganized clot networks, reduced mechanical resilience, and variable susceptibility to fibrinolysis. Moreover, nitrated fibrinogen may affect interactions with platelets and endothelial cells, although current evidence remains limited. Emerging clinical studies support its role as both a prothrombotic mediator and a potential biomarker of oxidative stress in cardiovascular and inflammatory diseases. Finally, we explore both pharmacological interventions, such as NOX inhibitors, and natural antioxidant strategies at counteracting fibrinogen nitration. Overall, fibrinogen nitration emerges as a critical molecular event linking oxidative stress to thrombotic risk.