Molecular determinants of thromboinflammatory activation in inflammatory bowel disease

Inflammatory bowel disease (IBD) is consistently associated with an increased risk of venous thromboembolism, particularly during active disease and hospitalization, yet thrombosis in this context extends beyond a transient inflammatory complication. Emerging evidence supports a unifying thromboinflammatory framework in which chronic intestinal inflammation promotes systemic vascular activation. Endothelial dysfunction represents a central interface in this process and is characterized by reduced nitric oxide bioavailability, increased expression of adhesion molecules, angiogenic remodeling, and glycocalyx disruption, collectively shifting the vascular surface toward a proadhesive and procoagulant phenotype. In parallel, dysregulation of coagulation pathways sustains thrombin generation through enhanced tissue factor signaling, elevated procoagulant factors, most consistently factor VIII, impaired endogenous anticoagulant mechanisms including the protein C and antithrombin systems, and features of hypofibrinolysis. Platelet activation further amplifies these disturbances via CD40 ligand (CD40L)-mediated endothelial crosstalk, platelet leukocyte aggregate formation, and imbalance of the von Willebrand factor (VWF)-ADAMTS13 axis, reinforcing a self perpetuating loop between inflammation and coagulation. Although mechanistic plausibility is strong and multiple biomarkers of endothelial and hemostatic activation have been described, much of the current evidence derives from cross sectional or associative studies, with limited prospective validation linking individual pathways to incident thrombotic outcomes in IBD specific cohorts. Taken together, thrombosis in IBD reflects sustained systemic thromboinflammatory dysregulation rather than an isolated complication of flares. Future longitudinal studies integrating vascular biomarkers with adjudicated thrombotic events are essential to refine risk stratification and inform individualized thromboprophylaxis strategies.