Circulating Microparticles, Blood Cells, and Endothelium Induce Procoagulant Activity in Sepsis Through Phosphatidylserine Exposure

Abstract

Sepsis is invariably accompanied by altered coagulation cascade; however, the precise role of phosphatidylserine (PS) in inflammation-associated coagulopathy in sepsis has not been well elucidated. We explored the possibility of exposed PS on microparticles (MPs), blood cells, as well as on endothelium, and defined its role in procoagulant activity (PCA) in sepsis. PS-positive MPs and cells were detected by flow cytometry, while PCA was assessed with clotting time, purified coagulation complex, and fibrin formation assays. Plasma levels of PS MPs derived from platelets, leukocytes (including neutrophils, monocytes, and lymphocytes), erythrocytes, and endothelial cells were elevated by 1.49-, 1.60-, 2.93-, and 1.53-fold, respectively, in septic patients. Meanwhile, PS exposure on blood cells was markedly higher in septic patients than in controls. Additionally, we found that the endothelial cells (ECs) treated with septic serum in vitro exposed more PS than with healthy serum. Isolated MPs/blood cells from septic patients and cultured ECs treated with septic serum in vitro demonstrated significantly shortened coagulation time, greatly enhanced intrinsic/extrinsic FXa generation, and increased thrombin formation. Importantly, confocal imaging of MPs or septic serum-treated ECs identified binding sites for FVa and FXa to form prothrombinase, and further supported fibrin formation in the area where PS exposure was abundant. Pretreatment with lactadherin blocked PS on MPs/blood cells/ECs, prolonged coagulation time by at least 25%, reduced FXa/thrombin generation, and inhibited fibrin formation by approximately 85%. Our findings suggest a key role for PS exposed on MPs, blood cells, and endothelium in augmenting coagulation in sepsis. Therefore, therapies targeting PS may be of particular importance.

Bubble-Induced Endothelial Microparticles Promote Endothelial Dysfunction

“…Several studies in vitro have confirmed that EMPs could mediate endothelial dysfunction, such as decline of angiopoiesis, vasorelaxation, nitric oxide production, proliferation and migration [8, 18, 26]. In our study, a pure population of bubble-induced EMPs was used and endothelial activity and function were injured after co-incubation with them.…”

Diagnosis and management of the antiphospholipid syndrome

“…79–81 Endothelial cell activation transforms the normally anticoagulant endothelial surface to a procoagulant phenotype. 82 Activated endothelial cells demonstrate increased expression of adhesion molecules (E-selectin, VCAM-1, ICAM-1), 74, 83, 84 von Willebrand Factor 85 , tissue factor (TF), 86 and proinflammatory cytokines, 87 decreased levels of endothelial cell-derived nitric oxide 88 and release microparticles with pro-inflammatory and procoagulant properties 89 , 90, 91 Monocyte activation may also be of importance in the pathogenesis of APS. Early studies demonstrated that anti-β2GPI antibodies activate monocytes in an annexin A2-dependent manner through a pathway involving Toll-like receptor 4 (TLR4) in lipid rafts.…”

Bubbles Induce Endothelial Microparticle Formation via a Calcium-Dependent Pathway Involving Flippase Inactivation and Rho Kinase Activation

“…MPs harboring endothelial-associated molecules were identified both in vitro and in vivo and therefore, were called endothelial MPs (EMPs) [7]. Increasing evidence suggests that EMPs not only constitute an emerging marker of endothelial injury, but can also be considered as important mediators capable of regulating a variety of biological functions, including inflammation, coagulation, angiogenesis and thrombosis [8, 9]. Thus EMPs appear to serve as both markers and hazards in vascular pathology [10-14].…”