PB1101 - Assessing the Antithrombotic Effects of Isoquercetin in Sickle Cell Disease

Tuesday, June 27, 2023

18:30 – 19:30 ET

Room: Exhibition

Presenting Author(s)

BP

Bindu Parachalil Gopalan, MSc, PhD

PhD
Sickle Cell Branch, National Heart, Lung, and Blood Institute, National Institutes of Health
Bethesda, Maryland, United States

Co-Author(s)

ML

Maria A. Lizarralde-Iragorri

PhD
Sickle Cell Branch, National Heart, Lung, and Blood Institute, National Institutes of Health
Bethesda, Maryland, United States
MH

Mai Hill

RN, MHSA
National Heart, Lung and Blood Institute, National Institutes of Health
Bethesda, Maryland, United States
BM

Brenda Merriweather

RN, MSN
National Heart, Lung and Blood Institute, National Institutes of Health
Bethesda, Maryland, United States
JB

Jennifer Brooks

RN
National Heart, Lung and Blood Institute, National Institutes of Health
Bethesda, Maryland, United States
RP

Ruth Pierre Charles

DSc,PA-C
National Heart, Lung and Blood Institute, National Institutes of Health
Bethesda, Maryland, United States
RV

Rafael Villasmil

M.Sc., C.Cy
FlowCytometry Core Facility, National Eye Institute, National Institutes of Health
Bethesda, Maryland, United States
NJ

Neal Jeffries

PhD
Office of Biostatistics Research, National Heart, Lung, and Blood Institute, National Institutes of Health
Bethesda, Maryland, United States
AS

Arun S. Shet

MD, PhD
Sickle Cell Branch, National Heart, Lung, and Blood Institute, National Institutes of Health
Bethesda, Maryland, United States

Background: Sickle Cell Disease (SCD) resulting from a single point mutation in the beta hemoglobin gene is associated with a hypercoagulable state, chronic inflammation, and increased risk of venous thrombosis and stroke.

Aims: Abnormal intravascular tissue factor (TF) expression partly mediates the sickle hypercoagulable state. Therefore, we tested whether the antithrombotic effects of flavonoid quercetins in vitro would be translatable in vivo to patients with SCD.

Methods: Platelet-free plasma (PFP) was prepared using citrate-anticoagulated blood from SCD subjects participating in a randomized clinical trial (NCT04514510). Patients received either fixed-dose isoquercetin (1000mg/day for 28 days) or an identically formulated placebo (n=22 in both study groups). Extracellular vesicles (EVs) isolated from PFP by centrifugation were quantified and characterized by flow cytometry. EV-associated TF procoagulant activity was measured by fluorometric FXa generation. Platelet-dependent thrombin generation was assessed indirectly using thrombin-stimulated healthy donor platelets suspended in PFP from SCD patients. Thrombo-elastography (TEG), and agonist-induced platelet aggregation were also performed. Comparisons between the treatment groups were performed using either the two-sample t-test or the Mann-Whitney U test.

Results: Neither the number of TF+EVs nor the number of cell-derived EVs was reduced in response to isoquercetin treatment (Table 1). EV-associated TF procoagulant activity was ~30-fold higher in SCD patients compared to levels previously published in healthy individuals and was not appreciably reduced after isoquercetin treatment (IQ = 665±155 fM vs placebo = 826±185 fM; p=0.37). TEG and low-dose collagen-induced platelet aggregation revealed changes in the appropriate direction suggesting antithrombotic efficacy attributable to isoquercetin treatment. In preliminary experiments, platelet-dependent thrombin generation was significantly lower in the IQ group compared to the placebo group (n = 10; p= < 0.01) (fig 1).

Conclusion(s): Short-term, fixed-dose isoquercetin exhibited modest antithrombotic effects in patients with SCD mediated via inhibition of platelet-dependent thrombin generation.