Limited Ability to Activate Protein C Confers Left Atrial Endocardium A Thrombogenic Phenotype: A Role in Cardioembolic Stroke?

Background and Purpose—Atrial fibrillation is the most important risk factor for cardioembolic stroke. Thrombi form in the left atrial appendage rather than in the right. The causes of this different thrombogenicity are not well-understood. The goal herein was to compare the activation of the anticoagulant protein C and the thrombomodulin and endothelial protein C receptor/activated protein C receptor expression on the endocardium between right and left atria. Methods—We harvested the atria of 6 monkeys (Macaca fascicularis) and quantified their ability to activate protein C ex vivo and we measured the thrombomodulin and endothelial protein C receptor expression by immunofluorescence. Results—We found the ability to activate protein C decreased by half (P 0.028) and there was lower expression of thrombomodulin in the left atrial endocardium than the right (52.5 19.9 and 72.1 18.8 arbitrary intensity units, mean standard deviation; P 0.028). No differences were detected in endothelial protein C receptor expression. Conclusions—Impaired protein C activation on the left atrial endocardium attributable to low thrombomodulin expression may explain its higher thrombogenicity and play a role in cardioembolic stroke

sPLA2-V inhibits EPCR anticoagulant and antiapoptotic properties by accommodating lysophosphatidylcholine or PAF in the hydrophobic groove

The endothelial protein C receptor (EPCR) plays an important role in cardiovascular disease by binding protein C/activated protein C (APC). EPCR structure contains a hydrophobic groove filled with an unknown phospholipid needed to perform its function. It has not been established whether lipid exchange takes place in EPCR as a regulatory mechanism of its activity. Our objective was to identify this phospholipid and to explore the possibility of lipid exchange as a regulatory mechanism of EPCR activity driven by the endothelially expressed secretory group V phospholipase A2 (sPLA2-V). We identified phosphatidylcholine (PCh) as the major phospholipid bound to human soluble EPCR (sEPCR). PCh in EPCR could be exchanged for lysophosphatidylcholine (lysoPCh) and platelet activating factor (PAF). Remarkably, lysoPCh and PAF impaired the protein C binding ability of sEPCR. Inhibition of sPLA2-V, responsible for lysoPCh and PAF generation, improved APC binding to endothelial cells. EPCR-dependent protein C activation and APC antiapoptotic effect were thus significantly enhanced. In contrast, endothelial cell supplementation with sPLA2-V inhibited both APC generation and its antiapoptotic effects. We conclude that APC generation and function can be modulated by changes in phospholipid occupancy of its endothelial cell receptor

A randomized, double-blind, placebo-controlled, phase 2b Study to evaluate the safety and efficacy of recombinant human soluble thrombomodulin, ART-123, in patients with sepsis and suspected disseminated intravascular coagulation

Objectives: To determine the safety and efficacy of recombinant thrombomodulin (ART-123) in patients with suspected sepsis-associated disseminated intravascular coagulation. design: Phase 2b, international, multicenter, double-blind, randomized, placebo-controlled, parallel group, screening trial. setting: Two hundred and thirty-three ICUs in 17 countries. patients: All adult patients admitted with sepsis and suspected disseminated intravascular coagulation as assessed using a modified International Society on Thrombosis and Hemostasis score. interventions: Patients were randomized to receive IV ART-123 (0.06 mg/kg/d) for 6 days or placebo, in addition to standard of care. The primary endpoint was reduction in mortality. Secondary endpoints included reversal of overt disseminated intravascular coagulation and reduction in disease severity. Measurements and main results: A total of 750 patients were randomized, nine of whom did not receive the allocated treatment so that 371 patients received ART-123 and 370 received placebo. There were no meaningful differences between the two groups in any of the baseline variables. Twenty-eight-day mortality was 17.8% in the ART-123 group and 21.6% in the placebo group (Cochran-Mantel-Haenszel two-sided p value of 0.273 in favor of ART-123, which met the predefined statistical test for evidence suggestive of efficacy). There were no statistically significant differences in event-free and alive days between the two groups. d-dimer, prothrombin fragment F1.2 and TATc concentrations were lower in the ART-123 group than in the placebo group. There were no differences between the two groups in organ function, inflammatory markers, bleeding or thrombotic events or in the development of new infections. In post hoc analyses, greatest benefit from ART-123 was seen in patients with at least one organ system dysfunction and an international normalized ratio greater than 1.4 at baseline. conclusions: ART-123 is a safe intervention in critically ill patients with sepsis and suspected disseminated intravascular coagulation. The study provided evidence suggestive of efficacy supporting further development of this drug in sepsis-associated coagulopathy including disseminated intravascular coagulation. Future study should focus on using ART-123 in the subgroup of patients most likely to respond to this agent. Copyright © 2013 by the Society of Critical Care Medicine and Lippincott Williams & Wilkins.SCOPUS: ar.jinfo:eu-repo/semantics/publishe