Chemokines regulate the migration and the maturation of dendritic cells (DC) licensed by microbial constituents. We have recently found that the function of DC, including their ability to activate naïve, allogeneic CD4+ T cells, requires the autocrine/pracrine release of the nuclear protein high mobility group box 1 (HMGB1). We show here that human myeloid DC, which rapidly secrete upon maturation induction their own HMGB1, remodel their actin-based cytoskeleton, up-regulate the CCR7 and the CXCR4 chemokine receptors, and acquire the ability to migrate in response to chemokine receptor ligands. The events are apparently causally related: DC challenged with LPS in the presence of HMGB1-specific antibodies fail to up-regulate the expression of the CCR7 and CXCR4 receptors and to rearrange actin-rich structures. Moreover, DC matured in the presence of anti-HMGB1 antibodies fail to migrate in response to the CCR7 ligand CCL19 and to the CXCR4 ligand CXCL12. The blockade of receptor for advanced glycation end products (RAGE), the best-characterized membrane receptor for HMGB1, impinges as well on the up-regulation of chemokine receptors and on responsiveness to CCL19 and CXCL12. Our data suggest that the autocrine/paracrine release of HMGB1 and the integrity of the HMGB1/RAGE pathway are required for the migratory function of DC.

Venous thromboembolism (VTE) and arterial thrombosis (AT) are distinct yet closely related pathological processes. While traditionally considered separate entities, accumulating evidence suggests that they share common risk factors, such as inflammation and endothelial dysfunction (ED). This review explores the parallels and differences between venous and arterial thrombosis, with particular attention to the role of unprovoked VTE and its potential links to atherosclerosis and systemic inflammation. A key focus is the role of ED, which is emerging as a critical factor in thrombogenesis across both the venous and arterial systems. We examine the current methods for clinically detecting ED, including the use of biomarkers and advanced imaging techniques. Additionally, we discuss novel research avenues, such as the potential of endothelial colony-forming cells and other innovative methodologies, to further unravel the complex mechanisms of thrombosis. Finally, we propose future clinical scenarios where targeting endothelial health could pave the way for more effective prevention and treatment strategies in thrombosis management.

Aims Platelets express functional interleukin-1 receptor-1 (IL-1R1) as well as a repertoire of toll-like receptors (TLRs) involved in platelet activation, platelet–leucocyte reciprocal activation, and immunopathology. IL-1R8, also known as single Ig IL-1-related receptor (SIGIRR) or TIR8, is a member of the IL-1R family that negatively regulates responses to IL-1R family members and TLRs. In the present study, we addressed the expression of IL-1R8 in platelets and megakaryocytes and its role in the control of platelet activation during inflammatory conditions and thromboembolism. Methods and results Here, we show by flow cytometry analysis, western blot, confocal microscopy, and quantitative real-time polymerase chain reaction that IL-1R8 is expressed on human and mouse platelets at high levels and on megakaryocytes. IL-1R8-deficient mice show normal levels of circulating platelets. Homotypic and heterotypic (platelet–neutrophil) aggregation triggered by Adenosine DiPhosphate (ADP) and IL-1 or lipopolysaccharide (LPS) was increased in IL-1R8-deficient platelets. IL-1R8-deficient mice showed increased soluble P-selectin levels and increased platelet–neutrophil aggregates after systemic LPS administration. Commensal flora depletion and IL-1R1 deficiency abated platelet hyperactivity and the increased platelet/neutrophil aggregation observed in Il1r8^−/− mice in vitro and in vivo, suggesting a key role of IL-1R8 in regulating platelet TLR and IL-1R1 function. In a mouse model of platelet-dependent pulmonary thromboembolism induced by ADP administration, IL-1R8-deficient mice showed an increased frequency of blood vessel complete obstruction. Conclusion These results show that platelets, which have a large repertoire of TLRs and IL-1 receptors, express high levels of IL-1R8, which plays a non-redundant function as a regulator of thrombocyte activity in vitro and in vivo.

The study of endothelial dysfunction (ED) is crucial to identify the pathogenetic mechanism(s) and provide indications for patient management in cardiovascular diseases. It is currently hindered by the limited availability of patient-specific primary endothelial cells (ECs). Endothelial colony-forming cells (ECFCs) represent an optimal non-invasive tool to overcome this issue. Therefore, we investigated the use of ECFCs as a substrate in thrombogenesis and thrombin generation assay (TGA) to assess ED. Both assays were set up on human umbilical vein endothelial cells (HUVECs) and then tested on ECFCs obtained from healthy donors. To prove the ability of the assays to detect endothelial activation, ECs stimulated with TNFα were compared with unstimulated ECs. EC activation was confirmed by the upregulation of VCAM-1 and Tissue Factor expression. Both assays discriminated between unstimulated and activated HUVECs and ECFCs, as significantly higher platelet deposition and fibrin formation in thrombogenesis assay, and thrombin generation in TGA, were observed when TNFα-activated ECs were used as a substrate. The amount of fibrin and thrombin measured in the two assays were directly correlated. Our results support the combined use of a thrombogenesis assay and TGA performed on patient-derived ECFCs to provide a personalized global assessment of ED relevant to the patient’s hemostatic profile.