PB1394 - Prothrombotic mechanisms associated with enhanced venous thrombosis in sickle cell trait

Tuesday, June 25, 2024

13:45 – 14:45 ICT

Room: Exhibition Hall

Co-Author(s)

Steven P. Grover, PhD

Research Assistant Professor
Division of Hematology and Blood Research Center, University of North Carolina, Chapel Hill
Chapel Hill, North Carolina, United States
FT

Fatima Trebak

Postdoc
UNC Blood Research Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
Chapel Hill, North Carolina, United States
AI

Anton Ilich

Postdoctoral Research Associate
UNC Blood Research Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
Chapel Hill, North Carolina, United States
YP

Yuriy Prokopenko

Postdoctoral Research Associate
UNC Blood Research Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
Chapel Hill, North Carolina, United States
KS

Karnsasin Seanoon

Postdoc
UNC Blood Research Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
Chapel Hill, North Carolina, United States
CM

Chatphatai Moonla

Postdoc
UNC Blood Research Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
Chapel Hill, North Carolina, United States
MK

Malgorzata Kasztan

Assistant Professor
University of Alabama at Birmingham
Birmingham, Alabama, United States
NK

Nigel S. Key

Professor
Division of Hematology, Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
Chapel Hill, North Carolina, United States

Presenting Author(s)

RP

Rafal Pawlinski

Professor
Division of Hematology, Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
Chapel Hill, North Carolina, United States

Background: Individuals with sickle cell trait (SCT) are heterozygous carriers of the sickle beta-globin gene. SCT is a risk factor for venous thrombosis (VT). We previously demonstrated that sickling of SCT red blood cells (RBCs) contributes to enhanced VT in humanized SCT mice that was attenuated by Senicapoc, an anti-sickling agent.

Aims: To identify procoagulant mechanisms by which RBC sickling contributes to enhanced VT in SCT.

Methods: Human SCT RBCs were exposed to sodium metabisulfite for 10 minutes to induce sickling and maintained at pO2 10mm Hg in a hypoxia chamber to mimic conditions within a venous clot. RBCs were then either fixed for imaging flow cytometry to detect phosphatidylserine or used intact for coagulation assays in the hypoxia chamber.
VT was induced by complete occlusion of the inferior vena cava (IVC stasis) in humanized, control mice expressing two copies of normal beta-globin (AA) or heterozygous for mutated sickle beta-globin (AS). Anti-FXIIa or control IgG antibody (10mg/kg) were administered intravenously 1 hour before stasis.

Results: As shown in Figure 1A-C, sickled SCT RBCs express phosphatidylserine distributed over the cell surface. This is associated with shortening of the Russell Viper Venom time, indicative of phosphatidylserine-dependent prothrombinase activity (Figure 1D).
The weight of thrombi formed 24 hours after IVC stasis was significantly increased (p < 0.01) in AS mice (n=8) compared to AA controls (n=7). To determine if the enhancement of VT observed in AS mice was FXIIa-dependent, mice were pretreated with inhibitory anti-FXIIa or control IgG antibody. Compared to IgG-treated AS mice (33.6mg +/- 2.4; n=4) pre-treatment with anti-FXIIa antibody reduced clot weight (29.3 +/- 5.9; n=5) but didn’t reach statistical significance. However, prolongation of the aPTT strongly correlated with thrombus weight (Figure 2).

Conclusion(s): Procoagulant changes associated with sickled RBCs likely promote the enhanced tendency to VT in SCT.