Comprehensive Multi-Parameter Characterisation of Circulating Extracellular Vesicles from Rivaroxaban-Treated VTE Patients Reveals Reduced Inflammation and Ameliorated Endothelial Dysfunction

Venous Thromboembolism (VTE) remains a significant cause of morbidity and mortality worldwide. Rivaroxaban, a direct oral factor Xa inhibitor, mediates anti-inflammatory and cardiovascular-protective effects besides its well-established anticoagulant properties, however, these remain poorly characterized. Extracellular vesicles (EVs) are important circulating messengers regulating a myriad of biological and pathological processes and may be highly relevant to the pathophysiology of VTE as they reflect alterations in platelet and endothelial biology. However, the effects of Rivaroxaban on circulating pro-inflammatory EVs in VTE patients remain unknown. We hypothesized that rivaroxaban's anti-inflammatory properties are reflected upon differential molecular profiles of circulating EVs.

Single-episode VTE patients anticoagulated with 20 mg Rivaroxaban or warfarin at a target INR of 2.0-3.0, respectively, who had commenced therapy no sooner than 3 months previously were recruited following informed written consent at the Mater Misericordiae University Hospital, Dublin, Ireland. Patient data including age, sex, BMI, prevalent risk factors and comorbidities were collected. Patients on warfarin therapy had a time in therapeutic range of at least 55% and an INR in target range at time of blood sampling. Exclusion criteria included known pro-inflammatory conditions, active malignancy, recurrent VTE, antiphospholipid syndrome, bleeding or platelet function disorders, use of anti-platelet drugs, and thrombocytopenia.

To address the hypothesis, we firstly used a combination of Nanoparticle Tracking Analysis (NTA) and flow cytometry to comprehensively characterise differences in the concentration and size of small (0-200 nm) and large (200-1000 nm) circulating EVs, respectively. Statistical analysis revealed a trend towards reduced levels of circulating small and large EVs in Rivaroxaban-treated VTE patients compared with matched warfarin controls. Moreover, small and large EVs measured in the patients plasma correlated strongly and highly significantly (r=0.804, p<0.0001), indicating a concomitant decrease in both populations. As circulating EVs are considered pro-coagulant and pro-inflammatory, these results may point towards an ameliorated baseline pro-inflammatory state of VTE patients anticoagulated with Rivaroxaban. To further uncover Rivaroxaban-mediated alterations, we next compared proteomic profiles of circulating EVs. We robustly quantified over 300 vesicular proteins. Statistical analysis of the protein expression level using a student's t-test with a false discovery rate of 5% and a minimal fold change of 0.1 identified differential protein expression of a tightly regulated cluster of proteins involved in negative feedback regulation of inflammatory and coagulation pathways in Rivaroxaban-treated patients, which may in part contribute to the superior outcomes of Rivaroxaban-treated patients seen in recent clinical trials. Furthermore, we recently established that Rivaroxaban potentially ameliorates endothelial dysfunction in a cohort of non-valvular atrial fibrillation patients. Therefore, we aimed to also assess circulating markers of endothelial activation (Intercellular Adhesion Molecule 1 [ICAM-1] and Tissue Factor Pathway Inhibitor [TFPI]). Intriguingly, Rivaroxaban-treated patients exhibited an increase in plasma TFPI levels with a simultaneous decrease in soluble ICAM-1, potentially pointing towards ameliorated endothelial dysfunction in Rivaroxaban-treated VTE patients relative to warfarin.

Collectively, we established that EV proteomic signatures are powerful biological sensors of Rivaroxaban's anti-inflammatory potential. Moreover, Rivaroxaban therapy may ameliorate endothelial dysfunction relative to warfarin. These findings are of translational relevance towards characterizing the anti-inflammatory and cardiovascular-protective mechanisms associated with Rivaroxaban therapy.